Reinforced surgical drapes are utilized in combination with a thermal treatment system including a basin recessed in a top surface of a system housing to ensure sterility of a sterile medium and to reduce drape costs. A reinforced surgical drape typically includes a primary drape layer of relatively thin construction that may puncture or tear under stress and at least one reinforcing layer selectively attached to drape portions receiving stress during use to prevent the drape from puncturing or tearing. Each reinforcing layer includes at least one segment that may either reinforce substantially the entire drape or the stressed drape portions. Alternatively, a surgical drape may be reinforced by disposing at least one drape over another drape placed on a thermal treatment system. The multiple drape embodiment enables immediate generation of a sterile field above a previously used or damaged drape, and further enables reuse of an underlying drape since an overlying drape provides the sterile field. The reinforced and multiple drapes may further be utilized in substantially the same manner described above in thermal treatment systems having single or multiple basins for warming, cooling and/or congealing the sterile medium.

1. Technical Field
The present invention pertains to improvements in methods and apparatus for heating or cooling sterile surgical liquids and collecting surgical sterile slush. In particular, the present invention is an improvement of the methods and apparatus disclosed in U.S. Pat. Nos. 4,393,659 (Keyes et al), 4,934,152 (Templeton), 5,163,299 (Faries, Jr. et al), 5,331,820 (Faries, Jr. et al), 5,333,326 (Faries, Jr. et al), 5,457,962 (Faries, Jr. et al), 5,522,095 (Faries, Jr. et al), 5,524,643 (Faries, Jr. et al) and copending U.S. patent application Ser. Nos. 08/810,025, filed Mar. 4, 1997 and entitled "Surgical Drape For Use in Forming and Collecting Surgical Slush" and 08/810,104, filed Feb. 25, 1997 and entitled "Surgical Drape For Use With Surgical Slush Machines Having an Automatic Dislodgement Mechanism". The disclosures in those patents and copending applications are expressly incorporated herein by reference in their entireties.
2. Discussion of the Prior Art
The above-referenced Keyes et al patent (U.S. Pat. No. 4,393,659) discloses a surgical slush producing system having a cabinet with a heat transfer basin at its top surface. A refrigeration mechanism in the cabinet takes the form of a closed refrigeration loop including: an evaporator in heat exchange relation to the outside surface of the heat transfer basin; a compressor; a condenser; and a refrigeration expansion control, all located within the cabinet. A separate product basin is configured to be removably received in the heat transfer basin. Spacers, in the form of short cylindrical stubs or buttons, are arranged in three groups spaced about the heat transfer basin and projecting into the heat transfer basin interior to maintain a prescribed space between the two basins. During use, that space contains a thermal transfer liquid, such as alcohol or glycol, serving as a thermal transfer medium between the two basins. A sterile drape, impervious to the thermal transfer medium, is disposed between the product basin exterior and the liquid thermal transfer medium to preserve the sterile nature of the product basin. Surgically sterile liquid, such as sodium chloride solution, is placed in the product basin and congeals on the side of that basin when the refrigeration unit is activated. A scraping tool is utilized to remove congealed sterile material from the product basin side to thereby form a slush of desired consistency within the product basin. Some users of the system employ the scraping tool to chip the solid pieces from the basin side.
As noted in the above-referenced Templeton patent (U.S. Pat. No. 4,934,152), the Keyes et al system has a number of disadvantages. In particular, the separate product basin must be removed and re-sterilized after each use. Additionally, the glycol or other thermal transfer medium is highly flammable or toxic and, in any event, complicates the procedure. The Templeton patent (U.S. Pat. No. 4,934,152) discloses a solution to these problems by constructing an entirely new apparatus whereby the product basin is eliminated in favor of a sterile drape impervious to the sterile surgical liquid, the drape being made to conform to the basin and directly receive the sterile liquid. Congealed liquid is scraped or chipped from the sides of the conformed drape receptacle to form the desired surgical slush.
The Faries, Jr. et al patent (U.S. Pat. No. 5,163,299) notes that scraping congealed liquid from the drape is undesirable in view of the potential for damage to the drape, resulting in a compromise of sterile conditions. As a solution to the problem, the Faries, Jr. et al patent (5,163,299) proposes that the drape be lifted or otherwise manipulated by hand to break up the congealed liquid adhering to the drape. Although this hand manipulation is somewhat effective, it is not optimal, and often is inconvenient and constitutes an additional chore for operating room personnel.
The Faries, Jr. et al patent (U.S. Pat. No. 5,331,820) resolves the problem of manual manipulation of the drape by providing several techniques to automatically remove the congealed liquid adhering to the drape without endangering the integrity of the drape. For example, one such technique includes providing a flat disk or plate at the bottom of the basin under the drape, wherein the plate is moved in an up and down manner to disengage the congealed liquid from the drape. The plate may be attached to a mechanism below the basin, or to the drape itself as disclosed in the Faries, Jr. et al patent (U.S. Pat. No. 5,457,962).
The Templeton patent (U.S. Pat. No. 4,934,152) further discloses an electrical heater disposed at the bottom of the basin to convert the sterile slush to warmed liquid, or to heat additional sterile liquid added to the basin. Templeton describes the need for such warm sterile liquid as occurring after a surgical procedure is completed to facilitate raising the body cavity of the surgery patient back to its normal temperature by contact with the warmed liquid. However, there are a number of instances during a surgical procedure when it is desirable to have simultaneous access to both warmed sterile liquid and sterile surgical slush. Accordingly, the Faries, Jr. et al patents (U.S. Pat. Nos. 5,333,326 and 5,522,095) disclose a manner in which to simultaneously provide both surgical slush and warmed surgical liquid during a surgical procedure by utilizing a machine having multiple basins with each basin either producing surgical slush or heating a sterile liquid. This machine typically utilizes a single surgical drape that forms a drape receptacle within each basin to collect sterile slush and heated sterile liquid produced by the machine in the respective basins.
The above-described apparatus may stand some improvement. In particular, sterile surgical drapes used with thermal treatment systems (e.g., systems that warm, cool or congeal sterile liquid) are made of a certain thickness to assure that areas of the drape that are stressed during use are not torn or punctured in order to maintain, and avoid compromising, the sterile field. Stress may be applied to the drape, for example, from forces exerted when placing and/or removing the drape from a thermal treatment system, manually or automatically manipulating the drape to dislodge congealed sterile medium as described above, and/or collecting the sterile liquid or slush within a drape container (i.e., forces exerted onto the drape by the weight of the sterile liquid or slush). Although thick drapes resist tearing and puncture, such thick drapes are relatively expensive to manufacture, and are also expensive to store and ship because they are bulky and heavy due to thicker material required for their construction. These thick drapes are also less malleable, thereby degrading drape handling for various aspects of a surgical procedure, such as installation of the drape on a thermal treatment system. By way of example, if sterile liquid impermeability and sterile field protection are the only considerations, the drape may be made of much thinner material, thereby being lighter, more malleable and less costly to manufacture. However, additional strength is required to prevent tearing or puncture of the drape from stress created by manipulation during slush formation, or even proper placement and removal in warming and cooling applications as described above. Thus, there exists a need in the art for drapes of relatively thin construction to reduce drape costs and enhance drape malleability and handling, while being of sufficient strength to withstand stress applied to the drape during normal use.
Further, it is desirable that the above-described apparatus provide a manner in which to reinforce surgical sterile drapes during a surgical procedure such that an immediate sterile field may be created above a previously used and/or damaged surgical drape disposed on a thermal treatment system. In particular, such a manner is needed when a surgical drape ruptures or is otherwise damaged during a surgical procedure. The damaged drape compromises sterility of the sterile liquid or slush and may contaminate the entire surgical procedure, thereby requiring an immediate replacement drape and sterile liquid to avoid risk of injury to a patient. Although the damaged drape and contaminated liquid or slush may be removed for disposal and replacement, this process requires additional time that may be crucial during a surgical procedure.
Moreover, several of the drapes disclosed in the above mentioned patents and copending applications include specialized features to enhance various aspects of thermal treatment system operation. For example, the above-mentioned Faries, Jr. et al patent (U.S. Pat. No. 5,457,962) discloses a surgical drape having a plate that engages a dislodgement mechanism disposed within a thermal treatment system basin wherein the plate in combination with the dislodgement mechanism manipulates the drape to dislodge congealed sterile medium adhered to the drape. However, since the plate substantially increases drape costs, it is desirable to determine a cost efficient manner to reuse these plate drapes to forego the expense of purchasing a new plate drape for each use of the thermal treatment system during surgical procedures. Similarly, drapes including other specialized features, such as the bladder drapes disclosed in copending application Ser. No. 08/810,025 and the sensor drapes disclosed in the Faries, Jr. et al patent (U.S. Pat. No. 5,524,643), tend to have relatively high costs, and it is desirable to determine cost efficient manners to reuse these specialized drapes to forego the expense of repurchasing these expensive drapes for each use of the thermal treatment system during surgical procedures.
In addition, some surgical drapes include specific enhancements to overcome anomalies when used with thermal treatment systems. For example, the above-mentioned copending application Ser. No. 08/810,104 is directed toward enhancing dislodgement of congealed sterile medium formed within a thermal treatment system basin having a dislodgement mechanism. The dislodgement mechanism typically includes a reciprocating plate to manipulate the drape and dislodge congealed sterile medium adhered to the drape. In particular, that copending application is directed toward preventing a drape disposed over the thermal treatment system and within the basin from being drawn beneath the dislodgement mechanism reciprocating plate. Since the dislodgement mechanism becomes ineffective (i.e., does not effectively manipulate a drape) once a drape is drawn beneath the reciprocating plate, the copending application discloses several techniques for preventing the drape from being drawn beneath the reciprocating plate. One such technique includes constructing surgical drapes of materials having a coefficient of friction in a particular range such that a drape may adhere to the basin walls and withstand being drawn under the reciprocating plate. A further technique disclosed in the copending Ser. No. 08/810,104 application proposes attaching securing and other devices to the drape to secure the drape to the thermal treatment system and prevent the drape from being drawn beneath the reciprocating plate. However, it is desirable to alleviate the above described and other surgical drape anomalies without substantially modifying or providing additional components for the drape that increase drape costs.

Reinforced surgical drapes for use with thermal treatment systems


There is provided a vacuum switching assembly for switching an AC or DC current. The vacuum switching assembly comprises a vacuum switch. The vacuum switch includes: first and second electrodes (20, 22) located in a vacuum tight enclosure, the vacuum tight enclosure containing a gas or gas mixture, the first and second electrodes (20, 22) defining opposed electrodes being separated by a gap, each of the first and second electrodes (20,22) being connectable to a respective electrical circuit carrying an AC or DC voltage; and a pressure controller (36) configured to control an internal pressure of the vacuum tight enclosure, wherein the pressure controller (36) is configured to selectively switch the internal pressure of the vacuum tight enclosure between: a first vacuum level that permits formation and maintenance of a glow discharge in the vacuum tight enclosure to allow a current to flow between the first and second electrodes (20, 22) via the glow discharge so as to turn on the vacuum switch; and a second vacuum level that inhibits formation and maintenance of a glow discharge in the vacuum tight enclosure to prevent a current from flowing between the first and second electrodes (20, 22) via the glow discharge so as to turn off the vacuum switch.

The operation of multi-terminal high voltage direct current (HVDC) transmission and distribution networks involves load and fault/short-circuit current switching operations. The availability of switching components to perform such switching permits flexibility in the planning and design of HVDC applications such as parallel HVDC lines with a tap-off line or a closed loop circuit.
A known solution for load and fault/short-circuit current switching is the use of semiconductor-based switches, which are typically used in point-to-point high power HVDC transmission. The use of semiconductor-based switches results in faster switching and smaller values of let-through fault current. The disadvantages of using such switches however include high forward losses, sensitivity to transients and the lack of tangible isolation when the devices are in their off-state.
Another known solution for load and fault/short-circuit current switching is a vacuum interrupter. The operation of the vacuum interrupter relies on the mechanical separation of electrically conductive electrodes to open the associated electrical circuit. Such a vacuum interrupter is capable of allowing high magnitude of continuous AC current with a high short-circuit current interrupting capability.
The conventional vacuum interrupter however exhibits poor performance in interrupting DC current because of the absence of current zero. Although it is feasible to use the conventional vacuum interrupter to interrupt low DC currents up to a few hundred amperes due to the instability of an arc at low currents, such a method is not only unreliable but is also incompatible with the levels of current typically found in HVDC applications.


A two sided thermal printing system includes a sheet which is specially coated on both sides for two sided thermal printing. A first side of the sheet has a dye receiving first coating for heat flowable dye transfer thermal printing via a dye bearing web in a transfer printing step. An opposing second side of the sheet has a second coating containing a heat activated dye material for forming, in situ, a dye image by direct thermal printing in an in situ printing step. The sheet portion, exclusive of the second coating, has a sufficient thickness and thermal resistance for inhibiting heat transfer therethrough during the transfer printing step on the first side to prevent activation of the dye material in the second coating on the second side.

Various printing systems are known for recording (printing) character (text) or graphic (picture) images on a recording medium (receiver sheet) such as a paper or polymer sheet. These include:
(1) liquid ink printing systems as used in printing presses; PA1 (2) two-sheet pressure transfer inert ink printing systems as used in mechanical print head, stylus (pen) and like printers (pressure printers); PA1 (3) two-sheet heat transfer flowable dye printing systems as used in thermal print head, stylus (pen), laser and like printers (thermal printers); PA1 (4) two-sheet pressure transfer reactive dye printing systems as used in pressure printers; PA1 (5) one-sheet in situ pressure reactive dye printing systems as used in pressure printers; and PA1 (6) one-sheet in situ heat reactive dye printing systems as used in thermal printers, such as telephone transmission facsimile printers (FAX machines). PA1 (2) Two-sheet pressure transfer inert ink printing systems typically have an inert one-component colorant, formed of a pigment or dye containing liquid or paste, selectively transferred by printer pressure from a carrier medium (transfer sheet) such as a dye bearing ribbon (donor web) to a receiving medium (receiver sheet) to form images thereon. PA1 (3) Two-sheet heat transfer flowable dye printing systems typically have a heat sensitive one-component colorant, formed of a pigment or dye containing meltable, e.g., waxy, solid ink or a diffusible (sublimable) dye such as an anthraquinone dye, selectively transferred by thermal printer heat ( e.g., Joule heat) from a transfer sheet such as a donor web to a receiver sheet to form images thereon. PA1 (4) Two-sheet pressure transfer reactive dye printing systems typically have a pressure sensitive two-component particulate colorant, formed of a colorless or lightly (pale) colored dye precursor (leuco dye) such as crystal violet lactone (hereinafter CVL), i.e., 3,3-bis (4-dimethylamino phenyl)-6-dimethylamino phthalide, or malachite green lactone (hereinafter MGL), i.e., 3,3-bis (p-methylamino phenyl) phthalide, and a color developer such as bisphenol A, i.e., 4,4'-isopropylidene diphenol. Particles of one component are dispersed in a coating on a transfer sheet and particles of the other component are dispersed in a facing coating on a receiver sheet. At least one of the components is, or is contained in, a liquid, e.g., enclosed in pressure rupturable microcapsules, and is selectively transferred by printer pressure from its coating into reactive contact with the other component in the other coating to develop the dye precursor to color state and form images on the receiver sheet coating. PA1 (5) One-sheet in situ pressure reactive dye printing systems typically have a pressure sensitive two-component colorant, formed of particles of the dye precursor such as CVL, and particles of the color developer such as bisphenol A, dispersed in a coating on a receiver sheet, yet maintained out of reactive contact with each other. At least one of the components is, or is contained in, a liquid, e.g., enclosed in pressure rupturable microcapsules, and is selectively transferred by printer pressure into reactive contact with the other component to develop the dye precursor to color state and form, in situ, images in the receiver sheet coating. PA1 (6) One-sheet in situ heat reactive dye printing systems typically have a heat sensitive two-component colorant formed of particles of the dye precursor such as CVL, and particles of the color developer such as bisphenol A, dispersed in a coating on a receiver sheet for heat reactive contact. At least one of the components is, or is contained in, a meltable substance, e.g., bisphenol A, and is selectively melted and transferred at a given activation temperature by thermal printer heat ( e.g., Joule heat) into reactive contact with the other component, e.g., CVL, to develop the dye precursor to color state and form, in situ, images in the receiver sheet coating.
These printing systems and hybrid variations thereof are illustrated by the following prior art references [1] to [41].
References [1] to [12] concern identical two sided printing systems, and in one case a one sided transfer printing system.
[1] Grupe U.S. Pat. No. 2,333,172, issued Nov. 2, 1943; [2] Rockefeller, Jr. U.S. Pat. No. 3,329,088, issued Jul. 4, 1967; and [3] Dahlgren U.S. Pat. No. 4,208,963, issued Jun. 24, 1980, commonly disclose identical system liquid ink printing of both sides of a web.
Japanese Patent Document (English Abstract) [4] JP 4,555/90 to Imamura, dated Jan. 9, 1990, discloses a one sided two-sheet pressure transfer inert ink system in which printer pressure transfers an ink character from an ink ribbon to a roller which transfers it to the back side of a photosensitive sheet carrying an already exposed, but still undeveloped, image on its front side.
Japanese Patent Document (English Abstract) [5] JP 139,465/86 to Hamada, dated Jun. 26, 1986, discloses a pair of ink ribbons and associated print heads on opposed sides of a paper sheet for respective identical system printing on both sides of the sheet. It is unclear whether the ribbons are of the pressure transfer inert ink, or heat transfer flowable dye, type.
Japanese Patent Documents (English Abstracts) [6] JP 69,071/82 to Moriguchi, dated Apr. 27, 1982; [7] JP 202,863/86 to Watanabe, dated Sep. 8, 1986; and [8] JP 183,865/88 to Noaki, dated Jul. 19, 1988, commonly disclose a pair of ink ribbons and associated thermal print heads on opposed sides of a recording sheet for respective identical system heat transfer flowable dye printing on both sides of the sheet.
Japanese Patent Documents (English Abstracts) [9] JP 3,765/86 to Shimizu, dated Jan. 9, 1986 ([9] Shimizu JP '765); [10] JP 192,572/86 to Teraichi, dated Aug. 27, 1986 ([10] Teraichi JP '572); and [11] JP 113,571/87 to Teraichi, dated May 25, 1987 ([11] Teraichi JP '571), commonly disclose a pair of thermal heads on opposed sides of a paper sheet for respective identical system thermal printing on both sides of the sheet. The type of image recording performed is not indicated.
Japanese Patent Document (English Abstract) [12] JP 8,688/83 to Murakami, dated Jan. 18, 1983 ([12] Murakami JP '688), discloses a pair of thermal print heads on opposed sides of a paper sheet which is heat sensitive on both sides for respective identical system thermal printing on both such sides. The nature of the heat sensitive sides of the sheet is not indicated.
References [13] to [15] concern heat flowable dye transfer printing systems.
[13] Hotta et al. U.S. Pat. No. 4,541,830, issued Sep. 17, 1985 ([13] Hotta), discloses a two-sheet heat transfer flowable dye printing system having a transfer sheet bearing a sublimable dye which is flow transferred by a thermal head or laser beam to a receiver sheet to form images thereon. The dye may be one which sublimes below 100 degrees C. (column 5). The receiver sheet may be active clay coated paper.
[14] Long U.S. Pat. No. 4,804,977, issued Feb. 14, 1989 ([14] Long), which is assigned to the same assignee as the present invention, is similar to [13] Hotta. The receiver sheet may be a substrate of paper or of polyethylene terephthalate (hereinafter PET) film, with a receiving coating, e.g., of polycarbonate, which absorbs and retains the transferred dye images to give a bright hue and prevent subsequent dye wandering.
[15] Kawakami et al. U.S. Pat. No. 5,114,904, issued May 19, 1992, is to the same effect as [13] Hotta. The dye may be a sublimable or hot melt transfer dye. The receiver sheet may be a substrate of paper, polypropylene resin synthetic paper, e.g., of 150 micron (0.006 inch) thickness, or an inorganic sheet, with a receiving coating, e.g., of 5 micron (0.0002 inch) thickness, containing a dye permeating lubricant silicone resin, a high softening point and high glass transition point thermoplastic polymer resin, and a powdered inorganic filler.
References [16] to [20] concern pressure reactive dye transfer and in situ printing systems.
[16] Green et al. U.S. Pat. No. 2,730,456, issued Jan. 10, 1956 ([16] Green '456), discloses a two-sheet pressure transfer reactive dye printing system having a transfer sheet with a coating of microcapsules enclosing a liquid such as a water immiscible oil, carrying a dye precursor such as CVL or MGL, and a receiver sheet with a facing coating of a color developer such as an acid clay-like material. Printing pressure rupture of the microcapsules causes the liquid carrying the precursor dye to flow into reactive contact with the color developer to change the dye precursor to color state and form marks on the receiver sheet.
[17] Green et al. U.S. Pat. No. 2,730,457, issued Jan. 10, 1956, is to the same effect as [16] Green '456, but also discloses a one-sheet in situ pressure reactive dye printing system formed of a receiver sheet with a coating including both the microcapsules of the liquid containing the dye precursor such as CVL or MGL, and particles of the acid clay-like material. Microcapsule rupture causes the liquid carrying the dye precursor to contact and react with adjacent color developer particles in the same coating to form color marks. The disclosure describes the dye precursor as an electron donor compound having a double bond system, and the color developer as an electron acceptor which is acid relative thereto, the electron donor compound being converted to a more highly polar conjugated form giving it a distinctive color, upon reaction with the color developer.
[18] Sullivan U.S. Pat. No. 3,244,548, issued Apr. 5, 1966 ([18] Sullivan), is to the same effect as [16] Green '456, but uses a phenolic substance such as phenol, di- and tri-hydroxy phenols and 1- and 2-naphthol (columns 1 and 6-7) as color developer for the dye precursor, e.g., CVL or MGL (column 16). Many dye precursors are disclosed (columns 1, 5 and 12-24).
[19] Farnham et al. U.S. Pat. No. 3,244,550, issued Apr. 5, 1966 ([19] Farnham '550), is to the same effect as [18] Sullivan, disclosing many dye precursors (columns 18-30) including CVL (column 23) and MGL (column 22), plus biphenols (columns 3, 5 and 18-30) including bisphenol A (column 11) as color developers.
[20] Angleman U.S. Pat. No. 3,968,299, issued Jul. 6, 1976, discloses a two-sheet pressure transfer reactive dye printing system, with multiple component coatings on both sides of a pair of interchangeable transfer and receiver sheets, but operating like the system of [16] Green '456.
References [21] to [23] are mainly pertinent as concerning heat dependent, reversibly reactive dye development systems. [21] Farnham et al. U.S. Pat. No. 3,560,229, issued Feb. 2, 1971 ([21] Farnham '229), is to the same effect as [18] Sullivan, disclosing many dye precursors (columns 3-15) including CVL and MGL (column 7), and phenolic substances (columns 15-32) including bisphenol A (column 19) as color developers. It further discloses (column 37), inter alia, that if a dye precursor is dissolved in a certain type glycol ether, a permanent color forms on heating to about 150 degrees C., whereas if it is dissolved in a certain type phenol compound of low vapor pressure, which phenol compound is either liquid at room temperature or dissolved in certain organic solvents, a color forms at room temperature which disappears on heating to about 130 degrees C. and reversibly reappears on cooling back to room temperature.
[22] Igarashi U.S. Pat. No. 4,138,357, issued Feb. 6, 1979 ([22] Igarashi), discloses a one-sheet in situ heat reactive dye recording system formed of a receiver sheet with a coating of a reversibly color changing mixture of an electron donating color former such as CVL or MGL (column 2), i.e., a dye precursor, and a meltable special oxy benzoic acid ester (i.e., a hydroxy benzoate and thus a phenolic compound) having a melting point (mp) of about 50-200 degrees C. as electron accepting compound (columns 3-5), i.e., a color developer. On heating to melt the color developer, the mixture forms a color, and on cooling to crystallize the color developer, it returns to colorless state. In a given example (Example 1), a mixture of CVL and propyl p-oxy benzoate in a weight ratio of 1:100, coated on a paper sheet, changes from 0.09 optical density (colorless state) at normal temperature to 1.02 optical density (color state) when heated to 150 degrees C.
[23] Ito U.S. Pat. No. 4,940,689, issued Jul. 10, 1990, discloses a one-sheet in situ heat and electric current reactive recording cell. The cell is formed as a multilayer receiver sheet with an internal color forming layer of an oxidation-reduction dye such as CVL or MGL (column 3), and an electrolyte such as an aliphatic quaternary ammonium salt, in an insulating polymer medium which can dissolve the dye and electrolyte and which is liquid-solid transformable on heating and cooling. The dye reversibly changes from colorless to color state by applying heat to liquify the color forming layer and then electric current to induce an oxidation-reduction reaction of the dye.
References [24] to [33] concern heat reactive dye in situ printing systems.
[24] Baum U.S. Pat. No. 3,539,375, issued Nov. 10, 1970 ([24] Baum), discloses a one-sheet in situ heat reactive dye printing system formed of a receiver sheet with a heat activated image forming coating of a matrix of polyvinyl alcohol (hereinafter PVA) containing a mixture of CVL as dye precursor, and a solid phenol compound as acidic material, i.e., color developer, which liquifies and/or vaporizes at the usual thermographic temperatures of 150-200 degrees C., such as bisphenol A, mp 156 degrees C. (columns 3-4). Many phenol compounds and their melting points, ranging from a low of 86, to a high of 184, degrees C., are disclosed (columns 1-6). The coating has, by weight, 1-15% CVL, 45-94% phenol compound and 5.40% PVA. Heat activates the coating to develop an image by liquifying and/or vaporizing the phenol compound for reactive contact with the CVL. In a given example (Example I), a paper sheet is coated with a layer of 3% CVL and 67% bisphenol A (both of 1.3 micron particle size) in 30% PVA.
[25] Blose et al. U.S. Pat. No. 3,674,535, issued Jul. 4, 1972, is to the same effect as [24] Baum, with the image forming coating having a filler such as clay, a lubricant such as zinc stearate and a nontacky wax, e.g., of mp 140-143 degrees C., to inhibit sticking of the coating material to the thermal print head which liquifies and/or vaporizes the phenol compound such as bisphenol A for color developing the CVL.
[26] Hatano et al. U.S. Pat. No. 3,920,510, issued Nov. 18, 1975, is to the same effect as [24] Baum, with the dye precursor being a specific type fluoran compound (columns 2-18). In the use example (Example 18), a paper sheet is coated with, by weight (calculated), 3% 2-p-chloroanilino-3-methyl-6-dimethylamino fluoran as dye precursor and 67% bisphenol A as phenol compound, i.e., color developer, in 30% PVA as matrix.
[27] Oeda et al. U.S. Pat. No. 4,168,845, issued Sep. 25, 1979 ([27] Oeda), is to the same effect as [24] Baum, with the image forming coating having particles of the dye precursor such as CVL or MGL (column 2), and of the color developer such as bisphenol A (column 3), at least one of which are meltable particles providing a meltable color forming material. Oil absorption pigment particles of silicon dioxide, diatomaceous earth, etc., are added to absorb the melted color forming material to prevent its sticking to the thermal print head. Besides other additives, 10-40% of the solid content coating weight may be a binder such as PVA, gum arabic, starch, etc.
[28] Marginean U.S. Pat. No. 4,287,264, issued Sep. 1, 1981 ([28] Marginean '264), is to the same effect as [24] Baum. The receiver sheet has an image forming coating of PVA as carrier (binder, matrix) containing a mixture of a color forming amount of a finely divided homogeneous basic 3,3-bisaryl phthalane derivative such as CVL as dye precursor, and a color developing amount of a finely divided solid phenol derivative such as bisphenol A as acidic phenolic color developer, which at thermal printing temperature is at least partly fluidizable and capable of a color forming reaction with the dye precursor. An anti sticking amount of a functional filler is added to prevent the fluidized color developer from sticking to the thermal print head. A coating composition may have, by weight, 2-30% CVL, 16-36% bisphenol A, and 2-60% functional filler, e.g., zinc di-n-butyl dithiocarbamate (hereinafter butyl zimate), relative to the total solids in the composition. A given coating on a paper sheet (Example I) has, by weight, 3% CVL and 27% bisphenol A (both of 1-3 micron particle size), 30% PVA and 40% butyl zimate, and optionally talc.
[29] Marginean et al. U.S. Pat. No. 4,289,535, issued Sep. 15, 1981 ([29] Marginean '535), is cumulative to [28] Marginean '264. The PVA carrier of [28] Marginean '264 is replaced by a carrier composition of a substantially water soluble anionic polysaccharide gum such as gum arabic (about 16-50%) and a stability enhancing amount of sucrose benzoate (about 3-10%) as binder-carrier. This forms an image forming coating with the finely divided solid (1-3 micron particle size) chromogenous basic 3,3-bisaryl phthalane derivative such as 6-dimethylamino-3,3-bis (p-dimethylamino phenyl) phthalide, i.e., CVL (column 8), or 3,3-bis (p-dimethylamino phenyl) phthalide, i.e., MGL (column 6), as dye precursor, and finely divided solid (1-3 micron particle size) phenol derivative such as bisphenol A as color developer. The color developer is at least partially fluidizable at the printing temperature. Also includable are a functional filler (about 2-12%) such as zinc di-n-butyl dithiocarbamate, i.e. butyl zimate, and a pressure sensitivity eliminating agent such as a micronized polyolefin, or micronized modified (fluorinated) polyolefin, of 1,000 to 2,000 molecular weight (mol. wt.) and 240-700 degrees F. (116-371 degrees C.) mp to prevent pressure color development as occurs with pressure reactive dye printing systems. A preferred coating has, by weight, about 9-30% CVL, 16-36% bisphenol A, 16-50% gum arabic, 3-10% sucrose benzoate, 2-12% zinc zimate, and 2-12% high mol. wt. polyethylene or fluorinated polyethylene of about 240-700 degrees F. (116-371 degrees C.) mp. A given coating applied to a paper sheet (Example I) has, by weight, 11.10% CVL, 33.53% bisphenol A, 32.96% gum arabic, 6.07% sucrose benzoate, 8.17% butyl zimate, and 8.17% high mol. wt. polyethylene of above 500 degrees F. (260 degrees C.) mp.
[30] Yamato U.S. Pat. No. 4,399,188, issued Aug. 16, 1983 ([30] Yamato), discloses a one-sheet in situ heat reactive dye printing system formed of a receiver sheet with an image forming coating of a colorless or pale colored chromogenic fluoran type dye such as 3-diethylamino-6-methyl-7-anilino fluoran, and a specific type p-hydroxy benzoic acid ester (i.e., a first phenolic compound) of about 60-120 degrees C. mp as color developer, such as p-hydroxy benzoic acid ethyl ester or benzyl ester, plus a phenol substance (i.e., a second phenolic compound) of above 90 degrees C. mp, i.e., other than bisphenol A (Reference Example 1-a), such as 4,4'-butylene-bis (3-methyl-6-tertiary butyl phenol), which when used with said benzoic acid ester lowers the degree of yellowing on storage of the receiver sheet. A suitable formulation contains, by weight, per part of the fluoran type dye, 3-10 parts of said benzoic acid ester (first phenolic compound), 1-5 parts of the phenolic substance (second phenolic compound), 1-20 parts of an inorganic or organic filler such as kaolin, diatomaceous earth, talc, etc., plus 1-20%, per total solid content, of a binder such as PVA, starch, etc., and optional additives including a releasing agent such as a metal salt of a fatty acid, e.g., zinc stearate. Triphenylmethane phthalide type dyes such as CVL, rhodamine type dyes, spiropyran type dyes and leuco auramine type dyes are unsuitable in the formulation containing said benzoic acid ester as the color formed upon heating tends to discolor with the lapse of time. Thus, if CVL were used as dye precursor in this low melting point hydroxy benzoic acid ester containing coating, it would apparently function reversibly like the coating of [22] Igarashi which contemplates CVL and a similar hydroxy benzoic acid ester as phenolic compound, i.e., color developer.
[31] Wiklof et al. U.S. Pat. No. 4,604,635, issued Aug. 5, 1986 ([31] Wiklof), discloses a one-sheet in situ heat reactive dye printing system formed of a receiver sheet with an image forming inner coating of a leuco dye or metallic salt as dye precursor and an acidic material as color developer capable of coloring the leuco dye or metallic salt when heat is applied. A protective outer coating of a cured silicone resin on the inner coating contacts the thermal print head to prevent sticking thereto of the image forming coating ingredients. The silicone resin amount should not exceed 10 pounds per 3,000 sq. ft. of the receiver sheet (substrate) or the outer coating thickness will be too large to permit effective heating of the inner coating.
[32] Marginean et al. U.S. Pat. No. 4,675,705, issued Jun. 23, 1987 ([32] Marginean '705), is cumulative to [29] Marginean '535. The image forming coating has (by weight) a color forming amount (5-25%) of finely divided solid (1-3 micron particle size) colorless or pale colored chromogenic fluoran dye as dye precursor such as 6'-(cyclohexyl-methyl-amino) 3'-methyl-2'-(phenylamino)-spiro (isobenzo-fluoran-1-(3H),9,9(H) xanthene)-3-one. It also has a color developing amount (15-25%) of a finely divided solids combination of benzyl paraben, i.e., benzyl p-hydroxy benzoate, and a halogenated derivative of bisphenol A such as tetrabromo bisphenol A, in a 2-4:1 ratio of benzyl paraben to said halogenated derivative, as color developer, and which at the printing temperature is at least partially fluidizable and capable of a color forming reaction with the dye precursor. The fluoran dyes used as dye precursor (columns 1-2) differ from the fluoran dyes of [30] Yamato. The dye precursor and color developer are distributed in a carrier (binder) of substantially water soluble anionic polysaccharide gum (10-25%) such as gum arabic and a stability enhancing amount (1-10%) of sucrose benzoate. The composition may have additives such as an image stabilizing amount (5-10%) of an image stabilizer such as dimethyl terephthalate, and a filler such as calcium carbonate, titanium dioxide, aluminum hydrate, zinc stearate, waxes and zeolites. A given 1-3 micron particle size solids coating formulation applied to a paper sheet (Example) has, by weight, 7.36% 6'-(cyclohexyl-methyl-amino)-3'-methyl-2'-(phenylamino)-spiro (isobenzo-fluoran-1-(3H),9,9(H) xanthene)-3-one, 16.20% benzyl paraben, 5.42% tetrabromo bisphenol A, 20.20% gum arabic, 1.67% sucrose benzoate, 7.09% dimethyl terephthalate, 26.26% calcium carbonate, 0.92% titanium dioxide, 4.58% aluminum hydrate, 1.66% zinc stearate, 4.76% paraffin wax, and 3.50% zeolite.
[33] Yoshida et al. U.S. Pat. No. 5,061,677, issued Oct. 29, 1991, discloses a one sheet in situ heat reactive dye printing system formed of a receiver sheet protected against plasticizer and oil penetration. It includes a paper substrate of 40-100 micron (0.0016-0.004 inch) thickness, having on its front side an opaque inner layer, an image forming middle layer of a dye precursor and a color developer, and a protective outer layer for contacting the thermal print head and which has high smoothness for increased heat conduction efficiency. A plasticizer and oil penetration preventing back layer is disposed on the back side of the substrate as the opaque inner layer on its front side has an affinity for plasticizers and oils. The protective outer layer has a binder such as PVA, a filler such as calcium carbonate and a lubricant such as zinc stearate. The image forming middle layer has binders such as methyl cellulose and PVA, a dye precursor such as CVL, a color developer such as 4,4'-thiobis (2-methyl phenol), and optionally a thermally fusible substance such as a higher fatty acid amide, e.g., stearic amide, a wax, a higher fatty acid or ester, etc. The opaque inner layer has a binder such styrene-butadiene copolymer latex, with light scattering fine particles, up to 10 micron size, of a styrene-acryl copolymer that imparts opacity to the laminate. The back layer is formed of a binder such as PVA and a filler such as calcium carbonate.
References [34] to [41] concern hybrid or dual printing systems.
[34] Ueyama U.S. Pat. No. 4,688,057, issued Aug. 18, 1987 ([34] Ueyama), discloses a hybrid heat sensitive, simultaneous recording and transferring medium formed as a heat sensitive sheet of a substrate with a conventional heat sensitive color forming coating on its front side and a heat sensitive transferring ink coating on its back side. The sheet is overlaid on a plain paper receiver sheet with the ink coating contacting the paper sheet for printing letters thereon, in the manner of a donor web in contact with a paper sheet in a heat transfer flowable dye printing system. The color forming coating has a dye precursor such as CVL and a color developer such as bisphenol A in a binder such as PVA, starch, and the like, and optionally an auxiliary agent such as clay, talc and the like. The ink coating has three different waxes of mutually differing properties, an extender pigment such as calcium carbonate, clay, barium sulfate, talc and the like, and a coloring agent (ink), all in specified proportions, and optionally a softening agent such as an oil. Apparently, the thermal print head contacts the heat sensitive color forming coating and the heat sensitive ink coating contacts the paper sheet for simultaneously printing images in situ in the color forming coating and duplicate images on the paper sheet by ink transfer from the ink coating. Thus, the print head heat is conducted through the color forming coating and the substrate to transfer ink from the ink coating on the back side of the receiver sheet to the paper sheet.
[35] IBM Technical Disclosure Bulletin, Vol. 24, No. 1A, June 1981 to Kuntzleman et al., proposes coating the front side of a paper sheet with an energizable leuco dye combination, followed by the printing thereof by a write head, and then coating the back side of the sheet with such leuco dye combination, followed by the printing thereof by another write head. The type energizable leuco dye combination is not indicated. This proposal is akin to the initially noted printing systems of [9] Shimizu Jp '765, [10] Teraichi JP '572, [11] Teraichi JP '571 and [12] Murakami JP '688 (English Abstracts), but in view of [34] Ueyama, if a sheet with a heat reactive in situ image forming coating on its front side and also on its back side were printed by a thermal head on one side, the heat from the head would be conducted through the facing coating and the substrate, and also form duplicate images in the coating on the back side.
[36] Kubo et al. U.S. Pat. No. 4,500,896, issued Feb. 19, 1985 ([36] Kubo), discloses a hybrid heat sensitive two-sheet sequential heat transfer flowable dye printing system and heat transfer reactive dye printing system. It is formed of a two-layer transfer sheet and a one layer receiver sheet, to transfer in turn two different colors at two different temperatures from the transfer sheet to the receiver sheet. The transfer sheet is formed of a substrate having on its front side an inner layer of a meltable or sublimable solid ink of a first color and a meltable leuco compound discoloring agent that are melted or activated at a high temperature of 80-150 degrees C., overcoated with an outer layer of a colorless leuco compound of a second color such as CVL or MGL (column 5) as dye precursor that is melted or flow activated at a low temperature of 60-100 degrees C. The high temperature is at least 20 degrees C. higher than the low temperature. The receiver sheet is formed of a substrate having a developer layer of a leuco compound color developer such as bisphenol A, mp 156 degrees C. (column 6), in facing contact with the leuco compound outer layer of the transfer sheet. A thermal head acting on the back side of the transfer sheet operates at the low temperature to conduct heat through the transfer sheet substrate, inner layer and outer layer for melt transfer of the leuco compound from the outer layer to the leuco compound developer in the receiver sheet developer layer to form images of the second color thereon without activating the solid ink or discoloring agent in the inner layer of the transfer sheet. The thermal head then operates at the high temperature to conduct heat through the transfer sheet substrate, inner layer and outer layer for melt transfer of the ink from the inner layer to the receiver sheet developer layer to form images of the first color thereon, and at the same time for melt activation of the discoloring agent in the transfer sheet inner layer to prevent the leuco compound from forming the second color with the color developer in the receiver sheet developer layer.
The solid ink is formed of a fusible substance such as a wax, plus a colorant such as carbon black, crystal violet lactone (colored type), etc. (columns 3-4). The discoloring agent is an alcohol such as stearyl alcohol, propylene glycol, etc., capable when melted of preventing the leuco compound from forming a color with the color developer (columns 4-5). The color developer is a phenolic compound, an organic acid, or an ester or salt thereof, including those of indicated melting points ranging from a low of 50, to a high of 200, degrees C. (columns 6-7). The given layers may have a binder such as PVA, etc. (columns 5-6). The discoloring agent appears to function like the hydroxy benzoic acid esters of [22] Igarashi and [30] Yamato.
[37] Sato U.S. Pat. No. 4,940,993, issued Jul. 10, 1990 ([37] Sato); [38] Hakkaku et al. U.S. Pat. No. 4,962,386, issued Oct. 9, 1990 ([38] Hakkaku '386); and [39] Hakkaku U.S. Pat. No. 5,101,222, issued Mar. 31, 1992 ([39] Hakkaku '222), commonly disclose a hybrid one-sheet in situ heat reactive dye printing system formed of a transparent receiver sheet having transparent heat sensitive layers on its front and back sides for developing three color images by a thermal recording head. Yellow and magenta images are formed sequentially on the front side, and then the sheet is turned upside down to form a cyan image on its back side. The sheet is recorded by the head in three steps, in the first step also undergoing photo fixation of the yellow image by a light source. The sheet has a polyester film substrate, e.g., of PET, coated on its front side by an inner magenta layer that forms an image by high heat level head operation, and an outer light fixable yellow layer that forms an image by low heat level head operation, in turn being fixed by exposure to the light source to stabilize it against further development. The substrate is coated on its back side by a cyan layer that forms an image by high heat level head operation.
In the first step, the sheet moves past the head and light source to form and fix the outer layer yellow image on the front side. The low heat level of the head does not develop the inner magenta layer. In the second step, the sheet returns to the starting point and moves past the head to form the inner layer magenta image, the high heat level of the head not influencing the now stabilized outer yellow layer. Then, the sheet is turned upside down, returns to the starting point, and moves past the head to form the cyan image in the back side layer by operating the head at high heat level. While the outer yellow layer must be low heat reactive to avoid also developing the inner magenta layer, it is not stable at the low heat level of the head, and must be photo fixed before operating the head at the high heat level needed to develop the inner magenta layer.
[40] Washizu et al. U.S. Pat. No. 4,956,251, issued Sep. 11, 1990 ([40] Washizu), discloses a hybrid one-sheet in situ heat reactive dye printing system for sequentially color developing three color layers, i.e., yellow, magenta and cyan, akin to [37] Sato, [38] Hakkaku '386 and [39] Hakkaku '222. As exemplified (columns 20-25), the transparent receiver sheet has a PET film substrate coated on its front side with a high temperature heat reactive inner magenta layer of a magenta dye precursor (leuco dye) and a color developer, and a low temperature heat reactive and photo fixable outer yellow layer of a diazonium compound (diazo dye) and a diazo coupler. The substrate is coated on its back side with a high temperature heat reactive cyan layer of a cyan dye precursor (leuco dye) and a color developer. The outer yellow layer is developed by low temperature print head induced coupling reaction of the diazo dye and diazo coupler, followed by photo-fixing with particular wave length light. The inner magenta layer and the back side cyan layer are developed in sequence thereafter by high temperature print head heat induced reaction, but are not developed at the low temperature used to develop the outer yellow layer. The disclosure sets forth many diazo compounds (columns 6-9), diazo couplers (columns 9-10), leuco compounds including CVL and MGL, as dye precursors (column 5), color developers including phenol compounds, organic acids or metal salts thereof, e.g., of 50-250 degrees C. mp, such as in a weight ratio of 0.3-160 parts color developer per part dye precursor (column 11), layer forming binders such as PVA (columns 14-15), and fillers (columns 12-13).
[41] Kobayashi et al. U.S. Pat. No. 5,115,255, issued May 19, 1992 ([41] Kobayashi), discloses a thermal printer for use exchangeably with a two-sheet heat transfer flowable dye printing system or a one-sheet in situ heat reactive dye printing system. The two-sheet system of an ink bearing donor web as transfer sheet and plain paper as receiver sheet is physically replaced in the printer by the one-sheet system of a receiver sheet having a heat reactive dye color image layer (column 4), and the controls are reset (column 6), for one-sheet in situ reactive dye printing.
This most recent hybrid teaching, [41] Kobayashi, confirms the lack of availability of a two sided thermal printing system providing for both the receiving of a heat transfer printed image on one side of a sheet and the in situ printing of a different image on the other side of the same sheet.
As is clear from the foregoing, two differing systems of thermal printing currently exist for printing images on recording media such as paper sheets. One system is the one sheet in situ heat reactive thermal printing system, or simply the direct dye development thermal printing system, and the other system is the two-sheet heat transfer flowable dye thermal printing system, or simply the dye transfer thermal printing system.
In practice, in the direct dye development thermal printing system, a sheet of thermally reactive material as receiver sheet is conducted past a thermal print head to generate images directly therein by modulating (selectively energizing) the head, with respect to energizing time (pulse width) and heat level (Joule heat) per image pixel element, or simply pixel (e.g., of 0.003 inch pixel height and 0.003 inch pixel width, aspect ratio). In the dye transfer thermal printing system, the head is similarly modulated to transfer dye from a dye bearing carrier (dye transfer web, donor web) as transfer sheet to a dye receiving medium as receiver sheet, e.g., a paper sheet. These print heads are typically formed of a plurality of resistor elements such that when a given resistor element is energized it produces heat. In the direct thermal printing system, the heat causes direct formation of an in situ image in the sheet of thermally reactive material. In the dye transfer thermal printing system, the heat causes transfer of dye from the dye transfer web to the dye receiving sheet. In the printers of these systems, a rotating platen and other conveying means are normally used to move the thermally reactive sheet, or the dye receiving sheet together with the dye transfer web, past the head during printing. Associated motors are operated in such manner that the head modulation, platen rotation and operation of the other conveying means produce a series of pixel elements of correct aspect ratio on the given sheet.
More particularly, the direct thermal printing system uses a thermally reactive sheet having a coating of heat activated dye material particles that directly release or change pigmentation in situ on applying heat thereto, e.g., to change or develop directly in situ a leuco dye from colorless to color state. Coatings of this type are used commercially in facsimile systems (FAX machines). For instance, coated paper (FAX paper) is fed through a printing nip between a thermal print head and a platen, usually under slight compression, and the head is modulated as the FAX paper advances through the nip to form an image directly in situ by selective thermal activation of the dye material particles in the coating. These FAX papers typically, but not necessarily, are below 0.002 inch thickness (including the dye material coating) to permit intimate contact at low nip compression between the head and thermally activated dye material coating on the paper for efficient heat transfer to achieve direct color image development.
In the dye transfer thermal printing system, a dye transfer web bears the pigmentation, and the dye is selectively transferred from the web to a recording receiver sheet, using a thermal print head similar in construction to that of the direct thermal printing system, and an associated platen forming a printing nip with the head, typically under slight compression. The dye carried on the transfer web, which may be a wax based pigment or a heat diffusible (sublimable) dye, is selectively transferred to the receiver sheet to form the image by controlled modulation of the head.
In the wax based system, which is comparatively inexpensive and in which the print head operates at lower thermal levels for transfer of the wax based dye, plain (uncoated) paper of about 0.002 to 0.003 inch thickness is used. However, the transferred images are of comparatively poor clarity due to the uneven surface character of the uncoated paper on which the wax based dye is deposited. This is traceable to the surface discontinuities of plain paper. For maximum clarity and uniformity of the transferred images, the nip pressure must be kept uniform, and the receiver sheet recording surface must be uniformly smooth.
In the diffusible dye system, dye is deposited from a dye transfer web onto a special dye receiving coating disposed on a substantially thicker member as receiver sheet, e.g., coated paper, of about 0.005 to 0.009 inch thickness (including the coating). The density or darkness of the printed color dye is a function of the heat energy delivered from the individual resistor elements of the thermal head to the dye transfer web as transfer sheet. Thermal dye transfer printers of the diffusible dye system type offer the advantage of true "continuous tone" dye density transfer. This is achieved by selectively varying the energy applied to each resistor element of the head, to provide a variable dye density image pixel in the receiver sheet coating.
The dye diffusion process creates a more stable image but requires a substantially greater amount of heat to accomplish diffusion transfer than is needed for other types of thermal printing. The receiver sheet for the dye diffusion process may have several layers. Typically, a paper material substrate is coated on both sides with a layer of soft polymeric material such as polyethylene or polypropylene. The dye receiving side of the soft layer coated substrate is typically coated with a water based antistatic agent to permit solvent coating thereon of an outer dye receiving layer providing a dye receiving surface. The dye receiving layer is typically formed of high heat deflection material such as polycarbonate, solvent coated onto the soft layer on one side of the substrate, while the soft layer on the opposite side of the substrate remains exposed.
The multilayer composite formed with coatings on both sides of the substrate, is generally sufficient in thickness to withstand the higher level of heat required for thermal transfer of the diffusible dye from the web to the dye receiving layer on one side of the substrate. The soft layer on the opposite side of the substrate contributes to the stability of the composite and its ability to withstand the higher heat level needed for dye transfer.
It is desirable to provide a two sided thermal printing system formed of a sheet substrate having a front side coated with a heat transfer flowable dye receiving coating serving as a receiver sheet for thermal printer heat transferred first desired color images, transferred from an extraneous dye transfer source in a transfer printing step, and a back side coated with a heat sensitive, in situ heat reactive dye coating serving as a counterpart receiver sheet for thermal printer formed, in situ, second desired color images, unrelated to the transferred first color images, and formed by heat activation in an in situ printing step, such that the reactive dye coating is not activated to form in situ images under the attendant heat applied during the transfer printing step.
In particular, it is desirable to print on both sides of a sheet by dye transfer thermal printing on the front side thereof, e.g., using a multicolor transfer web having a successive series of different color dye areas for repeated thermal transfer printing of graphic color images on a same area on the front side, and by direct thermal printing on the opposing back side thereof, e.g., using a heat activated dye coating on the back side for printing text information thereon, without activating the dye coating on the back side during dye transfer printing on the front side.


A control system for a power conversion system, composed of at least one voltage source type converter and a transformer. The control system includes, a circuit for detecting line-to-line voltages of an AC power source, an instantaneous phase detecting circuit for detecting instantaneously a phase angle of a phase voltage of the AC power source based on the line-to-line voltages of the AC power source, a circuit for detecting AC currents outputted from the power conversion system, a first coordinate transformation circuit for converting AC currents into an active current detected value and a reactive current detected value in a coordinate determined by a phase voltage vector of the AC power source using the phase angle, a current control circuit for generating output signals based on a current control result, a second coordinate transformation circuit for converting the output signals of the current control circuit into two-phase signals in a static coordinate system using the phase angle, a pulse width modulation control circuit for generating pulse width modulated signals, based on a pulse width modulation control result, and a circuit for generating gate pulses based on the pulse width modulated signals.

1. Field of the Invention
This invention relates to a control system for a power conversion system, and more particularly to a control system for a power conversion system composed of voltage source type power converters which can continue its operation without generating overcurrents when the voltage waveform of an AC power source is distorted greatly due to a fault in the AC power source system.
2. Description of the Related Art
Hereinafter, in the drawings, like reference numerals designate identical or corresponding parts throughout the several views, but it is noticed that a part with a reference numeral not in parentheses is different from a part with the same reference numeral in parentheses.
FIG. 8 is a block diagram showing the construction of a conventional main circuit of a power conversion system. In FIG. 8, 1 is an AC power source, 2 is a first transformer, 3 is a second transformer, 4 is a first converter, 5 is a second converter, 6 is a capacitor, and 7 is a DC power source or a load. 8-19 are self-turn-off devices, such as, gate turn-off thyristors (hereinafter, referred to simply as GTO) composing first converter 4, 20-31 are diodes respectively connected in anti-parallel with GTOs 8-19, 32-43 are self-turn-off devices, such as, GTOs composing second converter 5, and 44-55 are diodes respectively connected in anti-parallel with GTOs 32-43.
FIG. 9 is a block diagram showing the construction of a conventional control system for the power conversion system shown in FIG. 8. In FIG. 9, 1 corresponds to AC power source 1 in FIG. 8, 4,5 is a voltage source type power converter corresponding to converters 4 and 5 in FIG. 8, and 2,3 is a transformer corresponding to transformers 2 and 3 in FIG. 8. Furthermore, 6 and 7 correspond respectively capacitor 6 and DC power source or load 7 in FIG. 8.
Further, 56 is a line-to-line voltage detector for detecting three line-to-line voltages of three-phase AC power source 1, and 65 is a phase locked loop (PLL) which generates a voltage phase value .theta. of AC power source 1, obtained by removing the distortion included in the voltage waveform of AC power source 1. 59 is a current control circuit for controlling output currents of converter 4,5. The output currents of converter 4,5 are detected by a current detector 68 and the detected three-phase currents are converted into two-phase currents by a three-phase to two-phase converter 69. The converted two-phase currents are inputted to a coordinate transformation circuit 70, which converts the two-phase currents into current values on a coordinate having the same phase as that of a voltage vector of AC power source 1 using voltage phase value .theta. of AC power source 1 computed by phase locked loop 65. Such current values are composed of an active current detected value 66 and a reactive current detected value 67 and are inputted to current control circuit 59. As current command values for current control circuit 59, an active current command value 72 and a reactive current command value 73 are inputted to current control circuit 59. 71 is a coordinate transformation circuit which converts output signals of current control circuit 59 into two-phase signals on a static coordinate system using voltage phase value .theta. computed by phase locked loop 65. The converted two-phase signals are inputted to a two-phase to polar coordinate transformation circuit 61 which computes an amplitude and a phase angle from the two-phase signals. The computed phase angle is inputted to a triangular wave generator 62 which generates triangular wave signals corresponding to the computed phase angle of 0.degree. to 360.degree.. The computed amplitude is inputted to a cross point detector 63 which detects cross points of the computed amplitude and the triangular wave signals and generates pulse width modulated signals for turning ON or OFF the GTOs in converter 4,5. The pulse width modulated signals are inputted to a gate pulse generator 64 which generates gate pulses for actually turning ON or OFF the GTOs in converter 4,5 based on the pulse width modulated signals. Here, two-phase to polar coordinate transformation circuit 61, triangular wave generator 62 and cross point detector 63 compose a pulse width modulation control means.
FIGS. 10 to 12 are waveform diagrams for explaining the operation of the conventional control system shown in FIG. 9. Hereinafter, the operation of the conventional control system shown in FIG. 9 is described with reference to FIGS. 10 to 12.
FIG. 10 shows waveforms of the voltage detected values of AC power source 1 through the outputs of two-phase to polar coordinate transformation circuit 61 and triangular wave generator 62. In FIG. 10, (1) is a UV-phase line-to-line voltage of AC power source 1, (2) is a VW-phase line-to-line voltage of AC power source 1, and (3) is a WU-phase line-to-line voltage of AC power source 1. It is assumed that at a time t1 two lines of the U-phase and V-phase are grounded and thereby a U-phase voltage and a V-phase voltage become zero. After time t1, UV-phase line-to-line voltage (1) becomes zero, and VW-phase line-to-line voltage (2) and WU-phase line-to-line (3) become the voltages whose amplitudes are 1/.sqroot.3 times those before time t1, respectively. (4) and (5) are two-phase AC voltage signals converted from three-phase line-to-line voltages of AC power source 1 and are used in phase locked loop 65 for detecting voltage phase angle .theta.. As phase locked loop 65 is provided with a filter having a considerably long time constant enough to eliminate the distortion included in the detected AC voltages, two-phase AC voltage signals (4) and (5) do not change practically their waveforms after time t1. (6) and (7) are output signals of current control circuit 59. (8) is an amplitude signal of two-phase to polar coordinate transformation circuit 61. (9) is one of triangular wave signals outputted from triangular wave generator 62 obtained by converting the phase angle signal from two-phase to polar coordinate transformation circuit 61 into triangular waves
(10) is a UV-phase voltage of converter 4,5 and (11) is a U-phase current of AC power source 1. These are explained later in detail with reference to FIG. 11
Next, with reference to FIG. 11, the operation of the control system shown in FIG. 9 is described from two-phase to polar coordinate transformation circuit 61 and triangular wave generator 62 through converter 4,5. In FIG. 11, in cross point detector 63, output signal (9) of triangular wave generator 62 is compared with amplitude output signal (8) of two-phase to polar coordinate transformation circuit 61. While the phase angle is in the range of 0.degree.-180.degree., when signal (8) is larger than signal (9), GTO 8 and GTO 15 in converter 4 are in the ON state and a positive DC voltage is applied to a secondary U-phase winding of transformer 2. When it is detected that signal (8) becomes smaller than signal (9), GTO 8 is turned OFF and GTO 14 is turned ON, and then the voltage applied to the secondary U-phase winding of transformer 2 becomes zero Next, while the phase angle is in the range of 180.degree.-360.degree., when signal (8) becomes larger than signal (9) GTO 15 is turned OFF and GTO 9 is turned ON, and thereby a negative DC voltage is applied to the secondary U-phase winding of transformer 2. When it is detected that signal (8) becomes smaller than signal (9), GTO 14 is turned OFF and GTO 8 is turned ON, and then the voltage applied to the secondary U-phase winding of transformer 2 becomes zero. Then, GTOs 8, 9, 14 and 15 are ON-OFF controlled the same as described above, the waveform of the voltage at the secondary U-phase winding of transformer 2 becomes as shown in (12). (13) is a U-phase output voltage of converter 5 and is applied to a secondary U-phase winding of transformer 3. U-phase output voltage (13) of converter 5 is obtained, similarly as described above, by turning OK and OFF GTOs 32, 33, 38 and 39 in converter 5 based on the comparison result of a triangular wave snot shown) lagged of the phase angle from triangular wave (9) by 30.degree. which is generated from triangular generator 62 with amplitude output signal (8).
Here, a primary winding of transformer 3 is of a zigzag connection. That is, a U-phase primary winding is composed of a series connection of a first winding positively coupled to a U-phase secondary winding by a turn ratio of 1/.sqroot.3 and a second winding negatively coupled to a V-phase secondary winding by a turn ratio of 1/.sqroot.3. (14) is a voltage induced in the first winding, that is, U-phase primary winding positively coupled to U-phase secondary winding in transformer 3, and the amplitude of voltage (14) is 1/.sqroot.3 times that of voltage (13). Similarly, (15) is a voltage induced in the second winding, that is, U-phase primary winding negatively coupled to V-phase secondary winding in transformer 3. Accordingly, a voltage induced in U-phase primary winding of transformer 3 is the sum of voltages (14) and (15). In U-phase primary winding of transformer 2, a voltage equal to voltage (12) is induced. Therefore, a sum of voltages induced in U-phase primary windings of transformers 2 and 3 is the sum of voltages (12), (14) and (15) and is shown by a voltage (16). Voltage (16) is a voltage obtained by composing the output voltages of converters 4 and 5 by transformers 2 and 3 and is referred to as a U-phase converter voltage. Similarly, (17) is a V-phase converter voltage. (10) is UV-phase converter voltage which is equal to the difference between U-phase converter voltage (16) and V-phase converter voltage (17). (18) is a UV-phase voltage of AC power source 1. U-phase current (11) flows which is determined by the relation of the difference between UV-phase converter voltage (10) and UV-phase power source voltage (18) (UV-phase line-to-line voltage (1) of AC power source 1) and the impedances of transformers 2 and 3.
FIG. 12 is a waveform diagram showing the relation among voltages of AC power source 1, voltages of converters 4 and 5, and currents flowing in AC power source 1.
In FIG. 12, (18) is UV-phase power source voltage (UV-phase line-to-line voltage (1) of AC power source 1), (20) is a VW-phase power source voltage (VW-phase line-to-line voltage (2) of AC power source 1), and (22) is a WU-phase power source voltage (WU-phase line-to-line voltage (3) of AC power source 1). (10) is UV-phase converter voltage, (19) is a VW-phase converter voltage, and (21) is a WU-phase converter voltage. Further, (11) is U-phase current, (23) is a V-phase current, and (24) is a W-phase current.
If at time t1, two lines of the U-phase and V-phase are grounded, thereby U-phase voltage and V-phase voltage become zero. After time t1, UV-phase power source voltage (18) becomes zero, and VW-phase power source voltage (20) and WU-phase power source voltage (22) become the voltages whose amplitudes are 1/.sqroot.3 times those before time t1, respectively. Output voltages (10), (19) and (21) of converters 4 and 5 can not follow the sudden change of these voltages and U-phase current (11), V-phase current (23) and W-phase current (24) become in the overcurrent state, respectively.
As described above, according to the conventional control system for a power conversion system, voltages of AC power source 1 are detected and are supplied to phase locked loop 65, which reduces the distortion included in the voltage waveforms of AC power source 1 and computes a voltage phase based on the AC voltages of less distortion. Converters 4 and 5 are controlled based on this voltage phase computed by phase locked loop 65. Therefore, when a fault, such as a line-to-ground fault, occurs in the AC power source system, it is impossible to detect the voltage phase thereof instantaneously by the affect of the filter with a large time constant included in phase locked loop 65. As a result, it is impossible to suppress the overcurrent caused by the sudden change of the voltages and thereby it is not able to continue the operation of the power conversion system.

Control system for power conversion system


A virtual image display system includes a reflective mode spatial light modulator, a light source for illuminating the spatial light modulator, and an optics arrangement for directing a predetermined portion of the light from the light source into the spatial light modulator and for directing certain portions of the light reflected from the spatial light modulator to a desired viewing area. The optics arrangement includes an overall polarizing beam splitter. The polarizing beam splitter has three layers of materials. The first layer is a layer of polarizing beam splitting material configured to reflect light of a first polarization and transmit light of a second polarization. The second layer is another layer of polarizing beam splitting material. The third layer is a layer of material positioned between the first and second layers of polarizing beam splitting materials. The first, second, and third layers of materials act together to form the overall polarizing beam splitter.

The present invention relates generally to polarizing beam splitters and more specifically to a polarizing beam splitter for use in a liquid crystal spatial light modulator display system.
In the display industry, there is continuous pressure to produce virtual display systems with improved contrast ratios. This is a particular concern for display systems in which a liquid crystal spatial light modulator is illuminated by a light source to produce the viewable image. In many configurations of this type of virtual display system, a polarizing beam splitter is used as a main component of the optics for directing light from the light source through the system. In cases where the viewing area of the display is in line with the light source, the efficiency at which the polarizing beam splitter directs light of different polarizations through the system is critical in determining the contrast ratio of the system. U.S. Pat. No. 5,596,451 issued on Jan. 21, 1997 and entitled MINIATURE IMAGE GENERATOR INCLUDING OPTICS ARRANGEMENT, which is incorporated herein by reference, describes in detail several embodiments of such a system. For illustrative purposes, a prior art system of this type will be briefly described herein with reference to FIG. 1.
FIG. 1 illustrates a virtual image display system indicated by reference numeral 10. System 10 includes a light source 12 and a polarizer 14 for directing polarized light into a polarizing beam splitter (PBS) 16 as indicated by arrow 18. In this example, the light indicated by arrow 18 represents S-polarized light. PBS 16 reflects S-polarized light 18 into a reflective, liquid crystal spatial light modulator (SLM) 20. SLM 20 modulates the light by controllably changing the polarization of the light directed into SLM 20 thereby forming a pattern of modulated light that is reflected back into PBS 16. This pattern of modulated light from SLM 20 includes both S-polarized light as indicated by arrow 22 and P-polarized light as indicated by arrow 24. The S-polarized portion of the pattern of modulated light indicated by arrow 22 is reflected by PBS 16 back toward the light source and wasted as indicated by arrow 26. The P-polarized portion of the pattern of modulated light indicated by arrow 24 is allowed to pass through PBS 16 as indicated by arrow 28.
System 10 further includes a quarter wave plate 30 and a reflective magnifier 32. The combination of quarter wave plate 30 and reflective magnifier 32 changes the P-polarized portion of the modulated light indicated by arrow 28 into S-polarized light and reflects it back into PBS 16 as indicated by arrow 34. Since the pattern of light indicated by arrow 34 is now S-polarized light, PBS 16 reflects this pattern of light into a viewing area 36 as indicated by arrow 38 allowing this light to be viewed by a viewer.
As illustrated in FIG. 1, system 10 forms a viewable image by using SLM 20 to modulate the polarization of the light directed into PBS 16. However, because this configuration positions light source 12 in direct line with viewing area 36, the contrast ratio of the system is reduced by any of the S-polarized light indicated by arrow 18 from light source 12 which leaks through PBS 16 as indicated by dashed arrow 40. For currently available polarizing beam splitters which are designed to work over a broad spectrum of light wavelengths and over a broad range of angles of incidence, this leakage indicated by arrow 40 can be substantial.
The above described problem of leakage of light through the polarizing beam splitter has proved to make it very difficult to provide a practical color display system with a high contrast ratio using the configuration described above. This is because conventional polarizing beams splitters designed to work over a wide spectrum of light wavelengths and over a broad range of angles of incidence are not 100 percent effective and allow a substantial amount of leakage through the polarizing beam splitter. Therefore, it is desirable to provide a more efficient polarizing beam splitter which reduces this leakage problem. The present invention provides a polarizing beam splitter that works over a wide spectrum of light wavelengths and over a broad range of angles of incidence while substantially reducing or eliminating the leakage of light through the polarizing beam splitter compared to conventional polarizing beam splitters.

Display system including a polarizing beam splitter


A repetitive data processing method for a solid state drive is provided. The solid state drive includes a non-volatile memory. The repetitive data processing method includes the following steps. Firstly, a write data is received. The write data contains plural codewords. Then, an encoding operation is performed on the plural codewords sequentially, thereby generating plural error correction codes sequentially. If at least two consecutive error correction codes of the plural error correction codes are identical to a first error correction code, the solid state drive confirms that the write data contains a repetitive data and enabling a repetitive data management mechanism.

As is well known, a solid state drive (SSD) is a data storage device that uses a non-volatile memory to store data. After data are written to the non-volatile memory, the data are still retained in the solid state drive even if no electric power is supplied to the non-volatile memory.
FIG. 1 is a schematic functional block diagram illustrating the architecture of a conventional solid state drive. As shown in FIG. 1, the solid state drive 10 comprises a control circuit 110, a buffer 120 and a non-volatile memory 130. For example, the buffer 130 is a dynamic random access memory (DRAM), and the non-volatile memory 130 is a NAND flash memory.
The control circuit 110 is in communication with a host 12 through an external bus 20. Consequently, commands and data can be exchanged between the control circuit 110 and the host 12. For example, the external bus 20 is a USB bus, an SATA bus, a PCIe bus, an M.2 bus, a U.2 bus, or the like.
In the solid state drive 10, the control circuit 110 is connected with the non-volatile memory 130 through an internal bus. According to a write command from the host 12, a write data from the host 12 is stored into the non-volatile memory 130 by the control circuit 110. Alternatively, according to a read command from the host 12, the control circuit 110 acquires a read data from the non-volatile memory 130 and transmits the read data to the host 12.
The control circuit 110 further comprises a flash translation layer (FTL) 114. The flash translation layer 114 contains a logical-to-physical table 115. The logical-to-physical table 115 is also referred as a L2P table. The control circuit 110 can manage the data in the non-volatile memory 130 through the L2P table 115. For updating the L2P table 115 in real time, the L2P table 115 is usually stored in a volatile memory. For example, the contents of the L2P table 115 are stored in a static random access memory (SRAM) or a dynamic random access memory (DRAM) that is included in the control circuit 110. Alternatively, the contents of the L2P table 115 are stored in the buffer 120 that is disposed outside the control circuit 110.
For example, when the host 12 issues a write command, the control circuit 110 receives a write data and a logical address. The write data is temporarily stored in the buffer 120 by the control circuit 110. After the write data in the buffer 120 is encoded by an error correction (ECC) circuit 112 of the control circuit 110, the write data is converted into an encoded write data. Then, the encoded write data is stored into a physical address of the non-volatile memory 130 by the control circuit 110. Moreover, the mapping relationships between the logical address and the physical address are recorded into the L2P table 115 of the flash translation layer 114 by the control circuit 110. For example, the logical address is a logical allocation address, and the physical address is a physical allocation address.
When the host 12 issues a read command, the control circuit 110 receives a logical address. Firstly, the control circuit 110 confirms the physical address corresponding to the logical address according to the contents of the L2P table 115 of the flash translation layer 114. Then, the encoded read data stored in the physical address of the non-volatile memory 130 is transmitted to the control circuit 110 and temporarily stored in the buffer 120. After the encoded read data in the buffer 120 is decoded by the ECC circuit 112, a read data is generated. Then, the read data is transmitted to the host 12 by the control circuit 110.
FIG. 2 schematically illustrates the mapping relationships between the logical address and the physical address recorded in the L2P table of the conventional solid state drive. As shown in the L2P table 115, the non-volatile memory 130 contains n physical addresses PA_0˜PA_n−1.
The logical address LA_70 corresponds to the physical address PA_1. When the host 12 issues a write data corresponding to the logical address LA_70, the write data is encoded into an encoded write data and the encoded write data is stored into the physical address PA_1 of the non-volatile memory 130.
The logical address LA 120 corresponds to the physical address PA_2. When the host 12 issues a write data corresponding to the logical address LA 120, the write data is encoded into an encoded write data and the encoded write data is stored into the physical address PA_2 of the non-volatile memory 130.
The logical address LA_55 corresponds to the physical address PA_4. When the host 12 issues a write data corresponding to the logical address LA_55, the write data is encoded into an encoded write data and the encoded write data is stored into the physical address PA_4 of the non-volatile memory 130.
The logical address LA_60 corresponds to the physical address PA_n−1. When the host 12 issues a write data corresponding to the logical address LA_60, the write data is encoded into an encoded write data and the encoded write data is stored into the physical address PA_n−1 of the non-volatile memory 130.
In the L2P table 115, the physical addresses PA_0, PA_3 and PA_5 have no corresponding logical addresses. That is, no data are stored in the physical addresses PA_0, PA_3 and PA_5 of the non-volatile memory 130.
As mentioned above, all of the write data issued from the host 12 are stored into the non-volatile memory 130 of the conventional solid state drive 10.
In some specified situations, the host 12 continuously issues repetitive data as the write data. The contents of the repetitive data are identical.
When the host 12 continuously issues repetitive data as the write data, the repetitive data are also stored into the non-volatile memory 130 of the conventional solid state drive 10. Consequently, the non-volatile memory 130 needs to have sufficient space to store the plural identical data. In addition, the process of writing the repetitive data into the non-volatile memory 130 may increase the program time of the solid state drive 10.

Repetitive data processing method for solid state drive

SOLID STATE STORAGE TECHNOLOGY CORPORATION


A method of enhancing yield of semiconductor integrated circuit includes determining multiple experimental values, each experimental value corresponding to a distance from a side of a hole to an opposing side of a shape surrounding the hole, forming test patterns representing each of the experimental values on a wafer and calculating experimental value-based systematic fault rates from the test patterns; converting the experimental value-based systematic fault rates of the hole into the experimental value-based systematic fault rates, calculating a length of a side of the hole for which a distance between the side of the hole and the opposing side of the shape corresponds to each of experimental values, and calculating a systematic fault rate of the hole using the experimental value-based systematic fault rates per unit hole length and the length of the sides of the hole calculated for the respective experimental values in the desired layout.

1. Field of the Invention
The invention relates to a method and system for enhancing the yield of semiconductor integrated circuit devices.
2. Description of the Related Art
With the rapid increase in the technological level and complexity of semiconductor circuit design, interest in Design For Manufacturability (DFM) is increasing. In particular, the development of a recommended rule for DFM methods is necessary in order to enhance semiconductor yields. The recommended rule has a value calculated from that of a minimum design rule by a predetermined amount.
In detail, the design of the layout of a semiconductor integrated circuit device depends on a minimum design rule value (or ground rule value). The minimum design rule value represents the limit of resolution in current photolithographic processing, and in particular, refers to the minimum space interval, the minimum overlap area or the like between various masks or within a mask used to manufacture the semiconductor integrated circuit device. However, when the related art technology fails to satisfy the minimum design rule value, the yield can only be rapidly enhanced by using a recommended rule value that is slightly higher than the minimum design rule value in the layout design of a semiconductor integrated circuit device.

Method and system for enhancing yield of semiconductor integrated circuit devices using systematic fault rate of hole


A method and an apparatus for monitoring the maximum distance between two objects, in particular between a child and its guardian, with the aid of two transceivers, the first of which periodically transmits status messages of a particular transmission power to the second, wherein an alarm is triggered in the second transceiver if the reception of the status messages decrease, and wherein a statement of the transmission power is concomitantly transmitted in each status message, are distinguished by the fact that the transmission power to be used for the next status message is determined by comparing the reception power with the transmission power stated in a status message and is transmitted back to the first transceiver in a confirmation message.

The present invention relates to a method and device for monitoring the maximum distance between two objects, in particular, between a child and its guardian, with the help of two transceivers, of which the first periodically transmits status messages of a certain transmission power to the second, wherein an alarm is triggered in the second transceiver when the reception of the status messages decreases, and wherein information on the transmission power is also transmitted in each status message.
A method and a device of this type are known from U.S. Pat. No. 5,963,130. Because the communications between the transceivers is limited to periodic messages with intermediate pauses, energy consumption reduces. U.S. Pat. No. 5,963,130 shows, in detail, a child-monitoring device wherein the parent station evaluates the reception field strength of the polling reply of the child station and compares it with a threshold. When the value falls below the threshold, a power control command is integrated in the next polling query and transmitted to the child station. The child station then increases its reply transmission power and integrates into its reply message performance information that it is now transmitting at high power. The transmission power specified by the child station in its reply is used to trigger the range alarm: if the reply had been transmitted with high transmission power, the alarm is immediately triggered. The performance control command transmitted from the parent station to the child station thus always depends on only the reception field strength and its comparison with the fixed threshold. The principle of such a reception field strength evaluation does not allow detecting whether a weak reception field strength is to be traced to low transmission power or to a large distance.
For everyday, practical use of an object range monitoring device, in particular, for monitoring children for unintentional separation, running off, kidnapping, etc., a robust detector of when a maximum distance has been exceeded that is not susceptible to noise under any circumstances is indispensable, and all of this for minimal energy consumption. The invention sets the goal of creating a method and a device of the type mentioned above that satisfies these requirements.

Method and apparatus for monitoring the maximum distance between two objects


A beater weight assembly for a drum pedal comprises an adjustable main weight member as well as add-on weights selectively affixed to the main weight member. The main weight member is carried by the beater shaft. By adjusting the position and amount of the weight, the distribution of weight acting on the rotary element is altered to affect the balance point of the stroke of the beater element as well as rotational forces influencing the character of the beater stroke. The add-on weights may be affixed to the main weight member without removing the main weight member from the beater shaft.

1. Field of the Invention
The present invention relates to a pedal assembly used to strike a drum and, more particularly, to an accessory used on such a drum pedal assembly to adjust a weight characteristic of the pedal assembly.
2. Description of Prior Art
The prior art has provided a wide variety of drum pedal assemblies. Generally, these pedal assemblies comprise a frame element 1 clamped to a drum hoop, a rotary element 2 rotatably supported by the frame element 1, a pedal element 3 secured to the frame element 1 and connected to the rotary element 2 by a linkage element 4 and a cam element 5, a retraction assembly 6 secured to the rotary element 2 and a beater element 6 adjustably secured to the rotary element 2 by a beater mount 7 thereon. See FIG. 1. All these elements work together for the purpose of axially rotating the beater element in and out of a strike position whereby a drum head is actuated.
Due to the wide range of musical styles, techniques and personal needs, the prior art has provided means to adjust or redistribute the weight of the drum beater. However, these adjustments lack the versatility necessary during use.
One adjustment offered by the prior art is that of beater extension which adjusts the radial distance between the head of the beater element and the axis of the rotary element whereby the arc circumference of the beater stroke as well as the inertia and torque acting on the beater element is affected. This adjustment is provided by the beater mount and is accomplished by securing the beater element at different points along the length of the stem.
The problem with this adjustment is that by increasing beater extension, the increase in arc circumference, inertia and torque results in a loss of speed but an increase of power and swing due to added momentum. Likewise, by decreasing beater extension, the decrease in arc circumference, inertia and torque results in an increase of speed but a loss of power and swing due to reduced momentum. For these reasons, it is difficult to achieve a satisfying combination of speed, power and swing.
Another adjustment offered by the prior art is that of beater angle which adjusts the stroking distance or throw of the beater element. This adjustment is accomplished by adjusting either the position of the beater mount or the rest position of the rotary element by means of the retraction element.
The problem with this adjustment is that when the beater angle is adjusted to provide a longer stroke, the increased stroking distance results in an increased degree of resistance by the retraction element when the beater reaches strike position. This problem requires additional applied pressure to the pedal element in order to compensate.
Another adjustment offered by the prior art is that of the retraction element which comprises a biasing spring eccentrically secured to the rotary element. This adjustment is accomplished by adjusting the torque of the biasing spring whereby the attack and response of the beater element is affected.
The problem with this adjustment is that by increasing the torque of the biasing spring to acquire a quicker attack and response there is added resistance to the pedal element. This problem also requires additional applied pressure to the pedal element in order to compensate.
Numerous attempts have been made to provide beater weights affixed to the rotary element of the beater shaft to improve the power of the hit by adding mass/weight to the beater. However, these beater weights are limited because they lack adjustability in the amount of weight applied to the beater without a complete disassembly of the weight assembly.
Due to these inherent problems found in the prior art and in answer to the need for improvement, the present invention is now disclosed.


A fiber processing machine includes two oppositely rotated, tangentially cooperating first and second clothed rolls, wherein the first roll is an upstream roll and the second roll is a downstream roll as viewed in a travelling direction of fiber material being entrained by the rolls on fiber-advancing portions thereof. The rolls have a generally horizontal axis of rotation and together define opposite first and second converging gaps. A first carrier is disposed in the first converging gap and partially extends over a circumferential portion of the first and second rolls. A mote knife is mounted on the first carrier and bounds a waste discharge opening situated circumferentially along one of the rolls. The first carrier has a carrier part partially covering the fiber-advancing portion of the first roll; and an additional curved carrier part extends along a circumference of the second roll. The additional curved carrier part defines an air intake gap with the second roll. There is also provided a second carrier disposed in the second converging gap; the second carrier has curved carrier parts extending over portions of circumferences of the first and second rolls.

1. Field of the Invention
This invention relates to an apparatus for separating waste from fiber material, such as cotton fiber, as it is being advanced by a clothed roller in a fiber processing machine, such as a cleaner or a card. The apparatus is of the type wherein a carrier is arranged in a generally triangular space (bight or converging gap) defined by two- closely cooperating, oppositely rotated rolls (provided with a sawtooth or pin clothing). The carrier has curved edge surfaces which cover one part of the circumference of both cooperating rolls.
2. Background Art
In a known apparatus, in the lower bight formed by a clockwise rotating first (upstream) and a counterclockwise rotating second (downstream) roll a carrier is positioned and an adjustable guide element is provided at the outlet side of a curved cover following the circumference of the second roll. In the zone of the cover situated at the first roll, the latter entrains no fiber material so that the cover functions there only as a shroud.

Fiber waste separator including carriers, movable covers, and suction hood


In a drive unit for a switching element, a drive circuit changes the switching element between an on-state and an off-state, by controlling a potential difference between a reference terminal, which is one of a pair of ends of a current path of the switching element, and an opening-closing control terminal of the switching element. A determination section determines, if an on-operation command or an off-operation command is inputted as an operation signal for the switching element, whether or not the potential difference has reached a specific value toward which the potential difference shifts, in response to one of the operation commands, with respect to a threshold value by which the switching element is turned on. A forcible processing section removes charge for turning on the switching element from the opening-closing control terminal, if the determination section determines that the potential difference has not reached the specific value.

1. Technical Field
The present invention relates to a drive unit for a switching element which is a target to be driven (hereinafter, referred to as "target switching element"). The target switching element is a voltage control type switching element. The drive unit changes the target switching element between an on-state and an off-state, by controlling a potential difference between a reference terminal, which is one of a pair of ends of a current path of the target switching element, and an opening and closing control terminal of the switching element.
2. Related Art
For example, JP-A-2012-34450 discloses a configuration which includes a function of determining whether or not a voltage (gate voltage) between the gate and the emitter of an IGBT (Insulated gate bipolar transistor), which is the target switching element, is an intermediate voltage, which is higher than a threshold voltage by which the IGBT is turned on but is lower than a voltage applied to the gate when the IGBT is turned. According to this configuration, the IGBT can be forcibly turned off, if the gate voltage remains an intermediate voltage even though the IGBT is being turned on or off.
However, the above technique has the following disadvantages. First, when the IGBT is being turned off, in addition to the problem that the gate voltage may remain at the intermediate voltage, it is also a problem that the gate voltage may remain at a voltage higher than the intermediate voltage. Second, when the IGBT is being turned on, in addition to the problem that the gate voltage remains the intermediate voltage, it is a problem that the IGBT is not completely turned on.