This method teaches how to recover and reuse a powder of a thermally degradable material which is used in a selective laser sintering (SLS) process. To recycle such a laser-sinterable powder successfully in a SLS machine it is protected against degradation by cooling the hot bed while layer-upon-layer (layer-wise) of powder is being sintered, seriatim, to form successive slices fused together to form an article of arbitrary shape (part). The process requires maintaining the powder which has more than 80% of the number of particles <53 .mu.m as a quiescent bed which is nevertheless porous enough to permit flowing a cooling gas downwardly through the bed without disrupting its surface. Since each slice is formed at the surface, and the part, as it is formed, is supported in a well-insulated bed, the powder adjacent the slice is at a much higher temperature than powder in the rest of the bed, which, but for the cooling gas, would get overheated. Overheated powder not only degrades but is fused to the surfaces of the hot part forming a "growth" which makes the part unusable for its intended purpose. The process allows one to recycle the unused powder from the bed to extinction, economically. If the powder, when hot, is also sensitive to oxygen, an inert gas is used as the cooling gas.

This invention relates to a novel method of recovering recyclable unsintered but "used" powder from a `part` bed of a Selective Laser Sintering.RTM. (SLS.RTM.) machine operated in such a manner as to allow unsintered powder to remain in such near-pristine condition as to form a sintered part which is essentially indistinguishable from one formed by sintering "virgin" powder. By "virgin" powder we refer to powder which has never been exposed to the laser-environment of a SLS machine.
More particularly this invention is directed to the recovery and reuse of powder which is difficult to recycle because it is either, thermally or thermooxidatively degradable ("TOD") in the environment of the part bed.
Still more particularly this invention is directed to the recovery and recycle of a TOD synthetic resinous semi-crystalline or substantially crystalline powder which has a two-tier particle size distribution in a critically defined particle size range, most of which particles are "fines" smaller than 53.mu.m, the remaining being smaller than 180.mu.m (referred to as "large particles"). The powder is stripped of substantially all too-large particles (termed "rocks") larger than 180.mu.m (80 mesh, U.S. Standard Sieve Series). By "substantially all" we mean that at least 95% of the number of "rocks" in the powder are removed.
The two-tier distribution of the sizes of the particles free of substantially all rocks allows (i) the powder to be freely flowable even when hot, particularly at near the powder's softening temperature T.sub.s ; and, (ii) the formation of a "quiescent part bed" through which cooling gas may be flowed without disrupting the bed, making it possible to control the temperature profile of the bed.
By "freely flowable" we refer to a mass of small particles, the major portion of which, and preferably all of which have a sphericity of at least 0.5, and preferably from 0.7 to 0.9 or higher, so that the mass tends to flow steadily and consistently as individual particles. Though such flow is conventionally considered a characteristic of a powder which flows through an orifice slightly larger than the largest particle, such flow (through an orifice) is of less importance than the ability of a tailored SLS powder to be picked up in the nip of a rotating roller and transported by it as an elongated fluent mass of individual particles urged along by the roller. A freely flowable powder has the critical property of being able to be urged as a dynamic elongated mass, referred to as a "rolling bank" of powder, by the rotating roller even when the powder is at a temperature near T.sub.s.
To form a sintered part in a SLS machine, an initial slice is sintered from powder held in the part bed at near T.sub.s but well below T.sub.c. By "near T.sub.s " we refer to "near the softening point", a temperature within about 5.degree. C. of T.sub.s, that is T.sub.s .+-.5, preferably T.sub.s .+-.2.
By "softening point" we refer to T.sub.s, at which a powder's storage modulus (G'.sub.s) has decreased substantially from its value of G, at room temperature. At or above T.sub.s the storage modulus G'.sub.s of a sintered slice of the powder is low enough so as not to let it "curl". The sintered layer will curl when the initial slice sintered by the laser, heats the uppermost, newly-spread layer of powder, which is spread over the hot sintered part, more than the lower portion (referred to as "differential heating") of the bed, and the newly spread layer is below T.sub.s. The importance of countering curl is most critical when the first slice and the subsequent initial slices are formed.
By a "quiescent bed" we refer to one upon the surface of which the particles are not active, that is, do not move sufficiently to affect the sintering of each layer spread upon a preceding slice sintered in the part bed. The bed is not disrupted by the downward flow of gas, so that the bed appears to be static.
To be useful as a laser-sinterable powder, a powder must have unique characteristics which allow it to be sinterd to form a part which is visually essentially indistinguishable from a similar dimensioned part which is not sintered. At the same time, the part formed is required to have "clean" surfaces, free of "growth". The term "growth" refers to particles so tightly adhered to the surface as to be removed satisfactorily only with a machining step. Such growth makes a sintered part unfit for the purpose at hand, namely to function as a prototype for a compression molded part. Such a powder into which specific physical characteristics have been inculcated to ensure its performance in a SLS machine is referred to as a "designed" or "tailored" SLS powder. Such a powder is disclosed in concurrently filed copending patent application Ser. No. 07/980,004. A tailored powder is preferably of an unblended synthetic resinous material such as Nylons 6, 11 and 12, polybutylene terephthalate, wax, polycarbonate, etc. having physical properties defined herebelow, which powder provides an absorption coefficient in a range suitable for the particular laser used.
A sintered article (or "part") formed by laser-sintering the tailored powder, though porous, has the precise dimensions of the shape desired, that is, .+-.125.mu.m. By the term "porous" we refer to a density in the range from 60%-95% (void fraction from 0.4 to as low as 0.05), typically from 60%-80% of the density (void fraction 0.4-0.2) of an isotropically (say, compression) molded article which is deemed to be fully dense. Under critically defined conditions, one may produce a "near-fully dense" part from the tailored SLS powders referred to above.
The term "near-fully dense" refers to a slightly porous article which has a density in the range from 80%-95% (void fraction from 0.2 to as low as 0.05), typically from 85%-90% of the density (void fraction 0.15-0.1) of a compression molded article which is deemed to be fully dense.
The usual, common and realistic goal in the practical operation of a SLS machine is to sinter a mass of primary particles of a synthetic resin, typically nylon 6, 11, 12, polycarbonate or wax, to produce a "look-alike" prototype. The term "prototype" refers to an article which has identical inside and outside dimensions as the original. In the particular instance where the tailored powder is to produce a "near-fully dense" part, the goal is to produce a "working" prototype. A working prototype may be used under comparable conditions as the original except for those where strength near ultimate elongation is required. However, as indicated hereinabove, the prerequisite for forming a working prototype is the use of a powder with unique properties specifically tailored for its end use, which powder is the subject matter of the aforementioned sister application.
The prototype is formed by selectively laser-sintering a powder in the SLS machine which uses a laser beamed upon a target area where the part is produced. A powder dispenser system deposits a "layer" of powder from a "powder feed bed" or "feed bed" onto a "part bed" which is the target area. The term "layer" is used herein to refer to a predetermined depth (or thickness) of deposited powder before it is sintered. A layer of powder is confined by vertically spaced apart horizontal planes, no more than about 250 .mu.m apart, preferably no more than 180 .mu.m apart.
A laser control mechanism operates to direct and move the laser beam and to modulate it, so as selectively to sinter only the powder disposed within defined boundaries, to produce the desired "slice" of the part. The term "slice" is used herein to refer to a sintered portion of a deposited layer. The control mechanism operates selectively to sinter sequential layers of powder, producing a completed part comprising a plurality of slices sintered together. The defined boundaries of each slice corresponds to respective cross-sectional regions of the part. Preferably, the control mechanism includes a computer--e.g. a CAD/CAM system to determine the defined boundaries for each slice. That is, given the overall dimensions and configuration of the part, the computer determines the defined boundaries for each slice and operates the laser control mechanism in accordance with the defined boundaries for each slice. Alternatively, the computer can be initially programmed with the defined boundaries for each slice.
A part is produced by depositing a first portion of sinterable powder onto a target surface of the part bed, scanning the aim of a laser over the target surface, and sintering a first layer of the first portion of powder on the target surface to form the first slice. The powder is sintered by operating the directed laser beam within the boundaries defining the first slice, at a high enough energy to sinter the powder. The first slice corresponds to a first cross-sectional region of the part.
A second portion of powder is deposited onto the first sintered slice and the aim of the laser beam scanned over the first sintered slice. A second layer of the second portion of powder is sintered by operating the laser beam within the boundaries defining the second slice. Formation of the second sintered slice also integrally joins the first and second slices into a cohesive mass. Successive layers of powder are deposited onto the previously sintered slices, each layer being sintered in turn to form a slice.
Repetition of the foregoing steps results in the formation of a laser-sintered article lying in a "part bed" of powder which continually presents the target surface. If the particles of powder at the boundaries of each layer are overheated sufficiently to be melted, unmelted particles immediately outside the boundaries adhere to the molten particles within, and the sharp definition of the surface of the sintered article is lost. Without sharp definition at the boundaries, the article cannot be used as a prototype.
It is therefore essential that the particles of powder adjacent the surfaces of the article to be formed, resist being strongly adhered to those surfaces. When particles are not so strongly adhered they are referred to as "fuzz" because fuzz is easily dislodged from the surface, manually, and the dislodged particles retain most of their individual identities. A method for sintering a shaped "part" of arbitrary shape from powder in a SLS machine is disclosed in U.S. Pat. Nos. 4,247,508 to Housholder; 4,863,538 and 5,132,143 to Deckard; 4,938,816 to Beaman et al; and, 4,944,817 to Bourell et al, the disclosure of each of which is incorporated by reference thereto as if fully set forth herein. It will be evident that the thrust of the foregoing disclosures is to form a sintered part on a bed of powder using a directed laser beam.
The references taught using a down-draft of air to control the temperature of the powder (see the '143 patent, col 4, lines 16-27) by adjusting the air temperature to above the softening point of the powder, but below the temperature at which significant sintering will occur (bridging cols 6 and 7). Air was used to heat the surface of the bed of powder, not cool it. Further, there is no suggestion how this could be accomplished with a powder having at least 80% of the total number of particles present as "fines"<53.mu.m. Such fines from 1.mu.m-53.mu.m have a relatively high tapped density in a bed which one would expect to provide excellent particle-to-particle heat transfer, and also to generate a high enough pressure drop to require a high-pressure gas source, with the expected result that the bed would be disrupted when gas is flowed downwardly through it.
Though the concept of recovering and recycling unsintered powder from the bed is not a novel one, the ability to recover and reuse a powder which is TOD, is. There was no indication in the `143 patent as to what might be the physical condition of the used but unsintered powder, particularly if it was TOD, and no recognition of the fact that, after being sintered, the very hot part is susceptible to thermal distortion because it rests in an effectively insulated bed of powder which is then continuously heated not only with the incoming air but also with the radiating sintered part. Further, there was no recognition that hot air, at the temperature required, on the surfaces of a synthetic resinous material, would lead to thermooxidative degradation.
Most of all there is no suggestion that the used powder might be recovered in particulate form, or used for any purpose whatsoever. There is no stated concern about recycling unsintered powder, no mention of what considerations affected the definition of the surfaces of the sintered part, and no clear indication of what was referred to as "sintering" with a laser beam.
"Sintering" is defined by the heating of the powder to a temperature which causes viscous flow only at contiguous boundaries of its particles, with at least some portion of substantially all particles remaining solid. Such sintering causes coalescence of particles into a sintered solid mass the bulk density of which is increased compared to the bulk density of the powder particles before they were sintered.
The SLS machine uses a directed infra-red laser beam having a wavelength of 10.6.mu.m upon a target area where the part is produced, and lasers having other wavelengths may be used if desired. Conventionally, when powders are sintered under conditions which are likely to generate flammable byproducts, the SLS process is operated in an oxygenstarved nitrogen atmosphere, which means that enough N.sub.2 is flowed into the sintering chamber to maintain a concentration of O.sub.2 lower than will support combustion, usually less than about 5%. At the end of each sintering cycle, the flow of N.sub.2 is shut off, and the door of the sintering chamber is opened. For obvious economic reasons, no more N.sub.2 is used than is necessary to negate the possibility of a fire.
Since only a minor fraction by weight of the particles in the part bed are incorporated in the sintered part, that is "used", the remaining used but unsintered particles should be recyclable through the SLS machine. Stated differently, if the "unsintered" particles from the part bed are freely flowable and essentially indistinguishable from virgin particles, it should be possible to reuse the unsintered powder from the part bed.
As of the present time, it has been difficult to reuse "unsintered" recovered powder of any of several synthetic resinous materials to form a part with demanding specifications for density and surface finish, because the individual particles of powder are either thermally or oxidatively degraded, or both, that is "thermooxidatively degraded". Even if the particles themselves are not degraded, overheating the part bed to T.sub.c, the temperature at which the particles agglomerate ("clump"), causes high enough interparticle bonding that clumps recovered from the part bed are not friable enough to regenerate a freely flowable mass of powder. Therefore the used powder cannot be reused, the cost being attributed to the part formed.
The goal of the invention is to produce a sintered part from used but unsintered powder (referred to as "recyclable" or "re-usable" powder); and to provide a method for operating a SLS machine so that one can recycle powder from the part bed, without noticeable prejudice to the physical properties of the newly sintered part containing only recycled powder, relative to the properties of a part sintered from only virgin powder.
More specifically, the recyclable powder is just as freely flowable as the virgin sinterable powder at a temperature near T.sub.s and becomes sticky at the same "sticky" or "caking" temperature T.sub.c as the virgin powder. This caking temperature T.sub.c may be as little as about 2.degree. C. to 25.degree. C. above T.sub.s. The difference between T.sub.c and T.sub.s is referred to as the "window of sinterability" or "T-window", but will be referred to hereinafter as the "SLS-window".
By "sticky" or "caking" we infer that the force required to separate contiguous particles has exceeded an acceptable limit for the purpose at hand. The caking temperature T.sub.c is reached when the critical storage modulus (G'.sub.c) of the powder has been reached or exceeded. The storage modulus is a property of the powder akin to a material's tensile strength and can be measured directly with a Rheometrics dynamic mechanical analyzer.
The temperature at which the powder is freely flowable may be as low as desired, except that if the too-cool powder is distributed over a newly-sintered and very hot slice, the slice will "curl". By "curl" we refer to the sintered layer becoming non-planar, one or more portions or corners of the sintered layer rising more than about 50.mu.m above the surface of the last (uppermost) slice in the horizontal x-y-plane.
A slice will curl when there is a too-large mismatch between the temperature of the initial slice sintered by the laser and the bed of powder on which it lies; or, between powder freshly spread over a just-sintered slice and the temperature at the upper interface of the slice and the freshly spread powder. Such a mismatch is the result of differential heating. The importance of countering curl is most critical when the first slice is formed. If the first slice curls, the roller spreading the next layer of powder over the slice will push the slice off the surface of the part bed.
If the powder is transported from the feed bed to the part bed in which a hot slice is embedded, and the temperature at the interface T.sub.i between the hot upper surface of the slice and the freshly spread powder is high enough to raise the temperature of the freshly spread powder above T.sub.s, this powder cannot be rollingly distributed over the hot slice because the powder sticks and smears over the hot slice. The indication is that the slice is too hot.
If the powder in the feed bed is too cool, that is, so cool that the equilibrium temperature on the surface of the hot, embedded slice is such that the temperature of the freshly spread powder is below T.sub.s, the slice will curl.
The slice will not curl when the powder spread over it reaches an equilibrium temperature at the interface, and the equilibrium temperature is at or above T.sub.s. The precise temperature T.sub.i at the interface is difficult to measure, but to form successive slices cohesively sintered together, the temperature of the powder at the interface must be above T.sub.s, but below the powder's "sticky point" or "caking temperature" T.sub.c at which the powder will not flow.
The difficulty of rolling out a softened powder in a rolling bank dictates that the feed bed be maintained at as low a temperature a.sub.s will assure free flow over the surface of the part bed. Therefore the powder is usually stored in the feed bed at a temperature well below T.sub.s and transferred from the feed bed to the part bed at a temperature in the range from 2.degree. C. to 40.degree. C. below, more preferably from 5.degree.-20.degree. C. below the powder's T.sub.c at which the powder will not flow at all. When the powder which is at near T.sub.s is spread over a just-sintered slice, the powder quickly reaches or exceeds T.sub.s but is below T.sub.c, so that the powder lies in the window of sinterablity.
The window of sinterability may be determined in a different procedure, recognizing that immediately after the initial slice is formed, the slice is much hotter than the powder on which it rests. Therefore a relatively cool powder, as much as about 40.degree. C., but more typically about 20.degree. C. below its T.sub.s, may be spread over the hot slice and the interface temperature raises the temperature of the powder to near T.sub.s. As the powder is spread evenly over the hot slice it is to remain cool enough to be spread, but soon thereafter, due to heat transfer at the interface, must reach or exceed T.sub.s, or the just-sintered slice will curl; that is, the temperature of the powder must enter the "window of sinterability". This window may be measured by running two DSC (differential scanning calorimetry) curves on the same sample of powder, sequentially, with a minimum of delay between the two runs, one run heating the sample past its melting point, the other run, cooling the sample from above its melting point until it recrystallizes. The difference between the onset of melting in the heating curve, Tm, and the onset of supercooling in the cooling curve, Tsc, is a measure of the width of the window of sinterability. (see FIG. 6).
The upper limit of this SLS-window is defined by T.sub.c at which the powder softens so much that it will not flow. The lower limit of the window is the perceptible change in the property of the powder as seen in the cooling curve.
For this reason, an essential property of a recovered, recyclable powder is that it have an acceptably wide window to be laser-sinterable, that is, freely flowable at a temperature from about 25.degree. C. and as little as about 2.degree. C. below T.sub.c ; more typically, it is about 5.degree. C.-15.degree. C. below T.sub.c. When such a powder is recycled to a SLS machine, one is able to form a solid porous part of arbitrary shape, the void fraction of the part depending upon the particle size distribution of the powder.
The temperature at which the powder is freely flowable may be as low as desired except that if the temperature at which the powder is transferred to the part bed is too cool, that is, as little as 2.degree. C. to 20.degree. C below the powder's softening point T.sub.s, the sintered slice will "curl".
At the start of a sintering cycle it is best to maintain the temperature of the feed bed near T.sub.s because the temperature of the part bed is maintained near T.sub.s. However, as the mass of the sintered slices accumulates in the part bed the mass provides a large heat sink which transfers heat to each layer of powder freshly spread over the hot mass, thus allowing a relatively cool powder, as much as 30.degree. C, more typically 20.degree. C, lower than T.sub.s to be transferred from the feed bed, yet come to equilibrium at T.sub.s so that, when sintered, the slice will not curl. It is critical that the powder be "freely flowable" at a temperature in the SLS-window so that upon being spread upon the last sintered slice, it will not curl; or, upon formation of a slice from the freshly spread powder, the slice will not curl.
It will now be realized that the cooler the powder (below T.sub.s) the higher the risk of curling; and the hotter the powder (above T.sub.s) the higher the risk of caking. A powder is not freely flowable when the temperature at which it is held or distributed exceeds its T.sub.s. The powder cakes and does not flow at all when the caking temperature is reached. At the caking temperature, G'.sub.s decreases to G'.sub.c, where G'.sub.c represents the powder's critical storage modulus. This caking temperature is also referred to as the "G'.sub.c temperature".
It is therefore essential that a powder which has been held at its T.sub.s or slightly higher but below its T.sub.c, be recoverable in particulate form from the part bed and that the recovered powder be freely flowable at or near T.sub.s. Even so, there is no guaranty that the polymer chains near the surface of the used particles will be in essentially the same condition as those in particles of virgin powder. The condition of the polymer chains determines not only the temperature at which, but also the temperature range over which the critical viscosity required for fusing the particles is reached.
It is possible to transfer powder from the feed bed to the part bed at above the softening temperature of a powder if the impaired flowability allows one to do so, and the risk of operating closer to the caking temperature is acceptable. It will now be evident that an essential property of the tailored powder is that it be freely flowable in the "SLS window". This window is different for different materials, and ranges from about 2.degree. C. to about 25.degree. C.; more typically, it is about 5.degree. C.-5.degree. C. With such a powder one is able to form a solid near-fully dense article when the powder is sintered in a SLS machine.
The temperature at which G'.sub.s is measured is not narrowly critical provided the G'.sub.c temperature offers an adequately large SLS-window. A powder becomes sticky enough so as not to be freely flowable at its "sticky temperature" or caking temperature, when its G'.sub.s decreases to a critical G'.sub.c, where G'.sub.s represents the powder's storage modulus. The storage modulus is a property of the powder akin to a material's tensile strength. The difference between G'.sub.s and G'.sub.c is referred to as the "G'-window" which also defines the "window of sinterability". Most desirable laser-sinterable powders have an unexpected common characteristic, namely that their G'.sub.c dictates their laser-sinterability, and this property is narrowly defined in the range from 1.times.10.sup.6 dynes/cm.sup.2 to 3.times.10.sup.6 dynes/cm.sup.2.
For a crystalline powder, the softening point T.sub.m is its melting point Tm. Therefore G'.sub.s and G'.sub.c essentially identical and there is no G'-window.
For an amorphous powder, its softening point is its initial glass transition temperature Tg. An amorphous powder offers a very large window of sinterability, but because its viscosity decreases too slowly as temperature increases and approaches the G'.sub.c limit of the SLS-window, the melt viscosity is still too high. That is, the melt viscosity is too high to allow requisite interchain diffusion at the boundaries of the particles without melting the entire particle. Therefore an amorphous powder is difficult to sinter to a near-fully dense part, and sintered parts formed have a void fraction in the range from 0.4 to 0.2. This infers that the condition of the unsintered powder in the bed is difficult to control.
Powders which are best suited for recovery and recycling are semi-crystalline powders such as nylon and polybutylene terephthalate (PBT) which provide signs of crystalline order under X-ray examination, and show a crystalline melting point as well as a glass transition temperature. Because the crystallinity is largely controlled by the number and distribution of branches along the chain, the crystallinity varies, bulky side chains or very long chains each resulting in a reduction of the rate of crystallization. Preferred polymers have a crystallinity in the range from 10% to 90%, more preferably from 15% to 60%. Powders which produce the least porous sintered parts are semi-crystalline powders having a crystallinity in the range from 50% to 90%.
By a "semi-crystalline polymer" is meant a resin which has at least 10% crystallinity as measured by thermal gravimetric analysis, preferably from about 25%-70%, and most preferably from about 60-90% as measured by differential scanning calorimetry.
Powder which is rolled out on to the part bed is not only preferably heated in the feed bed to a temperature at which a sintered slice will not curl, but the powder is also heated in the part bed due to heat dissipated from the sintered part. If the powder is over-heated in the part bed, it loses some, if not all of the physical properties which make the virgin powder suitable. For example, over-heated powder is no longer freely flowable.
Further, overheated particles tend to be thermooxidatively degraded as is typically evidenced by their change in color (a white powder will turn brown) and loss of tensile strength. It was not known that the presence of a very small quantity of oxygen, as little as 0.5%, in contact with particles in the part bed, was sufficient to degrade them.
It was found that in normal operation of a SLS machine using a synthetic resinous material there was sufficient thermooxidative degradation that the unsintered powder from the part bed could not be re-used for sintering another part of the same quality as one sintered from the virgin powder.
Although we have experimentally processed many synthetic resinous powders in the SLS machine, we have found that none is recyclable unless the part bed is kept from overheating after the sintered part is formed. We now understand, and have set forth below, what critical processing steps are required to recycle once-used powder a second time, or even several times, in a SLS machine.
Since it has now become evident that a semi-crystalline organic polymer is the powder of choice if it is to provide the high definition of surface ("lack of growth") which a prototype made from a tailored powder provides, it is even less economical to run a SLS machine without recycling the previously used but unsintered powder than it was when an amorphous powder was used.
In copending patent application Ser. No. 727,746 filed by Shimandle on Jul. 10, 1991, now U.S. Pat. No. 5,185,108, it was taught that to produce a sintered article of wax having a void fraction (porosity) of 0.1, a two-tier weight distribution of wax particles was necessary. Despite the relatively low temperature at which the part bed is maintained, there is no indication that any portion of the used powder from the sintered bed could be reused. Neither was there any indication that the `746`s two-tier distribution of particle sizes was beneficial for any reason other than that it provided the densest packing of the particles.
It has now been found that the rate of heat transfer into the mass of a small particle, which rate is higher than that into the mass of a large particle, dictates that the desired sinterable powder be deliberately tailored in a two-tier particle size distribution. The ranges of sizes in the two-tier distribution of particles used in the novel process is different from the ranges of the two-tier distribution of Shimandle et al's wax powder. Quite unexpectedly, despite the numerical predominance of particles smaller than 53.mu.m, the few "large particles"<53.mu.m in the two-tier distribution of particles in the powder used in this novel process, (i) imbue the powder with free-flowability near Ts; (ii) provide a bed with sufficient porosity to permit downflow of low pressure inert gas through it, thus permitting the formation of a sintered part, whether large or small; and (iii) allow a predetermined temperature profile to be maintained in the vertical plane of the part bed, irrespective of the density of the sintered part formed; with the result that, undesirable "growth" on the part is essentially negated, and the unsintered powder is recoverable and reusable.
It was thus found that using a laser-sinterable powder defined by two critical quantifiable physical properties, namely (i) a desirable "SLS- window", and, (ii) a narrowly defined particle size range in a two-tier size distribution, was a prerequisite to recoverability and reusability of the unsintered powder.
The unexpected effect of using the tailored powder with a defined SLS-window is supported by evidence of the sinterability of the powder in this window. The SLS-window is directly correlatable to the powder's fundamental properties defined by its G'.sub.c temperature.
A tailored powder with preferred properties: (a) is a freely-flowable semi-crystalline powder at near T.sub.s having at least 10%, preferably at least 25%, crystallinity measured by differential scanning calorimetry; (b) a major portion by weight of the powder, and preferably essentially all the powder having a sphericity in the range from greater than 0.5 to 0.9, and a two-tier particle size distribution of primary particles having an average diameter smaller from than 180.mu.m, with substantially no particles >180.mu.m, provided further that the number average ratio of particles smaller than 53.mu.m is greater than 80%, preferably greater than 90%, and most preferably greater than 95%, the remaining particles being in the size range from 53.mu.m to 180.mu.m; a layer of the powder no more than 250.mu.m deep absorbs essentially all infra-red energy at the 10.6.mu.m wavelength beamed therethrough, and absorbs more than 50% of that energy in a layer no more than 180.mu.m thick;
(c) a SLS window in the range from 2.degree. C. to 25.degree. C. below T.sub.s ; PA1 (d) a melt viscosity in the range from 100-10.sup.4 poise (10-1000 Pa-sec) when the temperature of the powder being sintered exceeds T.sub.c in less time than is required to melt contiguous large particles >53.mu.m; PA1 (e) a critical storage modulus G'.sub.c in the range from 1.times.10.sup.6 Pa to 3.times.10.sup.6 Pa; and, PA1 (f) forms a sintered part in a bed which, during operation sintering a part, has a temperature profile defined by sequential positive and negative temperature gradients in the vertical plane of the bed when a layer thereof, less than 250.mu.m thick near the surface, is at a temperature in the range from 5.degree. C. to 20.degree. C. below T.sub.s. PA1 (a) a major portion by weight of the powder, and preferably essentially all the powder has a sphericity in the range from greater than 0.5 to 0.9, and a two-tier size distribution of primary particles in which the number of particles smaller than 53.mu.m is greater than 80%, preferably >90%, most preferably >95%, the remaining particles being no larger than 180.mu.m, that is, with a powder with substantially no particles (that is <5%) larger than 180.mu.m; provided further that a layer of said powder no more than 250.mu.m deep absorbs essentially all infra-red energy at the 10.6.mu.m wavelength beamed therethrough, and absorbs more than 50% of said energy in a layer no more than 180.mu.m thick; PA1 (b) a crystallinity in the range from 10% to 90%, preferably from 15% to 60%, a number average molecular weight in the range from about 30,000 to 500,000, preferably 60,000-300,000, and a molecular weight distribution M.sub.w /M.sub.n in the range from 1 to 5, preferably from 1.2 to 3; PA1 (c) a "SLS-window" in the temperature range from 2.degree. C.-25.degree. C. between the softening temperature T.sub.s of the powder and its "caking temperature" T.sub.c, such that the powder has a "flow time" of <20 sec for 100 g in a funnel test (ASTM D1895-61T) at a temperature near T.sub.s in a range from 70.degree. C. to 220.degree. C., but below the powder's T.sub.c ; PA1 (d) a melt viscosity in the range from 100-10.sup.4 poise (10-1000 Pa-sec) when the temperature of the powder being sintered exceeds T.sub.c in less time than is required to melt contiguous large particles >53.mu.m; PA1 (e) the powder forms a `part bed` in which the temperature profile is defined by sequential positive and negative temperature gradients through the part bed when the uppermost slice is less than 250.mu.m thick and at a temperature in the range from 5.degree. C. to 20.degree. C., preferably from 8.degree.-5.degree. C., below that at which the powder softens; that is, the gradient from the upper surface of the bed to the maximum temperature of powder in the horizontal plane through a zone of maximum temperature is positive, the temperature increasing at from 0.2.degree. C./cm (0.5.degree. C./in) to 2.degree. C./cm (5.degree. C./in) of vertical depth, and the maximum temperature of the powder being no higher than the caking temperature T.sub.c of the powder; and, from the maximum temperature to the bottom of the bed is negative, the temperature decreasing at from 0.2.degree. C./cm (0.5.degree. C./in) to 2.degree. C./cm (5.degree. C./in).
The unexpected effect of using the tailored powder with defined particle size in a SLS machine is supported by evidence of the "coolability" of the hot bed despite its narrowly defined porosity range, without which coolability the necessary temperature profile in the part bed could not be maintained. An identifying characteristic of a novel, hot `part bed` at near T.sub.s of the powder, is that the bed is porous and fluffy enough to permit the flow therethrough of cooling gas at superatmospheric pressure in the range from 1 cm of Hg-2 psig, typically 105-120 kPa with a pressure drop in the range from 3-12 kPa, typically 5-7 kPa, through a bed 30-38 cm deep. This characteristic allows one to maintain a specified temperature profile in the bed which profile avoids overheating the unsintered powder, and avoids distorting the sintered part not only as it is formed slice-wise, but also after the part is formed, and the part lies removably embedded in the heated part bed.
Though the importance of a two-tier particle size weight distribution was disclosed with respect specifically to wax particles in the copending '746 application, it was not then realized that the ranges of particle sizes in each tier of the two-tier distribution controlled both, the density of the sintered part, and the sinterability of the powder. Neither was it known that the distribution of particle sizes in a two-tier distribution was as critical as the viscosity characteristics of the material as a function of temperature.
Because the SLS-window is critically defined by the requirements of the SLS process, the part bed (and sometimes the powder bed) must be indirectly heated to negate the proclivity of the sintered layer to "curl". If the part bed temperature, at least near its surface, is near T.sub.s, the risk of curling is lowest when the feed bed temperature is high enough to allow powder delivered to the part bed to enter the SLS-window quickly, before the just-sintered slice can curl. To minimize the curling of a slice as it lies on a part bed, it has been discovered that a critical temperature profile is to be maintained in the bed, with a slight but narrowly specified temperature gradient on either side of a horizontal zone through the portion of the bed occupied by the sintered part, referred to as the "hot" zone.
The gradient in a part bed in a SLS machine operating effectively, is first positive, that is, the temperature increases to a maximum, then the gradient is negative, that is the temperature decreases from the maximum. The upper temperature gradient in the upper portion of the bed is positive, that is the temperature increases until it reaches a maximum temperature T.sub.max in the hot zone. The lower temperature gradient in the lower portion of the bed is negative, that is the temperature decreases from T.sub.max in the hot zone to the bottom of the bed.
More specifically, the temperature in the upper portion of the bed progressively increases as one moves downward from the upper surface of the bed to T.sub.max in the vertical plane; then progressively decreases as one moves downward from T.sub.max to the bottom surface of the part bed, which surface is in contact with the bed-supporting piston.
The gradient in a conventional SLS machine without controlled gas cooling of the part bed, in each direction is typically more than 2.degree. C./cm (5.degree. C./in). Such a gradient was found to be too high to provide an acceptable risk of either thermooxidative degradation of the powder, or, of distortion of the sintered part.
These considerations lead to temperature limits in the feed and part beds which limits define the G'-window or T-window, namely, (i) the temperature at which the part bed is maintained, and the temperature profile therein, and (ii) the temperature at which the feed bed is maintained.
In turn, the temperature at which the part bed is maintained is defined by (a) a lower (minimum) part bed temperature below which curling is so pronounced as to negate any reasonable probability of effecting a layer-wise fusion of plural vertically contiguous layers; and, (b) an upper (maximum) temperature at which interparticle viscosity in the part bed makes it so "sticky" as to fuzz (obfuscate) the predetermined boundaries of the part to be made. All sintered powder between vertically spaced apart lateral planes in the part bed is solidified sufficiently to have mechanical strength. The remaining unsintered powder remains freely flowable.

Method of recovering recyclable unsintered powder from the part bed of a selective laser-sintering machine


A vibration extraction processing unit extracts a deflection component synchronous with a rotation from a clock signal of a non-contact sensor so as to correct a clock jitter. A clock generating unit generates a clock signal of any format frequency preliminarily set up according to the clock signal from the vibration extraction processing unit. A sector correction processing unit measures an error due to the frequency deflection so as to correct the writing start position for the format pattern signal of each sector containing a servo frame signal stored in a memory according to the measured error. Writing processing units read out the corrected format pattern signal from the memory according to a synchronous signal corresponding to a single turn of a disc and a format frequency clock signal and then writes into a disc medium face.

1. Field of the Invention
The present invention relates to a servo track writing device for recording a format pattern including a servo frame in a magnetic disc drive unit and a method thereof and more particularly to a servo track writing device for recording a format pattern including a servo frame by generating a clock signal from a disc scale by means of a non-contact sensor and a method thereof.
2. Description of the Related Arts
When a servo frame pattern is recorded into a magnetic disc of a hard disc drive using a device conventionally known as a servo track writer (STW) at the manufacturing stage, a reference clock is necessary for achieving synchronism between a write position in the circumferential direction on a disc medium plane and a write signal.
According to an ordinary method, the clock signal is written directly into the disc medium using a reference head which is a specialized magnetic head and then, the reference clock is generated by reading this signal for reference.
According to this method, an assembled disc enclosure case needs to have a hole for inserting the reference head and thus, a servo frame signal must be written in a clean room for dust protection.
Further, because the reference head needs to be often replaced because of its consumption, it has a problem of low production efficiency. To solve these problems, a device which generates a clock using a non-contact sensor is considered.
However, when a clock is generated using the non-contact sensor, the frequency of the reference clock is fixed by the revolution numbers of an encoder bonded to a disc face as a seal and the disc. Consequently, even if circuit processing for ordinary frequency conversion is carried out, nothing but a clock which is produced by multiplication by an integer or dividing by an integer of the reference clock can be obtained and therefore, there is such an inconvenience that an arbitrary clock frequency (format frequency) required for writing of the servo frame pattern cannot be set up freely.
Further, the clock itself changes due to unevenness of the density of the clock pattern formed on the encoder scale, a deflection of the rotation of a disc or the like. Further, when the disc enclosure is vibrated a clock jitter occurs. Consequently, physical sector starting positions on a disc face can deflect in the radius direction and therefore, there is such a problem that the time of each sector also deflects more largely as compared to a case where there is no rotation deflection or vibration.

Servo track writing device and method thereof


A print head protection device is used with an inkjet printer having a print head adapted for elevating. A roller is mounted upstream of the print heads and above the process path a predetermined distance. A cover on the roller outer surface contacts the sheet lead edge if sheet curl exceeds a set curl range. The cover will cause rotation of the roller by engaging the sheet. A rotary encoder is mounted for synchronous rotation with the roller. The rotary encoder generates a signal in response to rotation of the roller, raising the print head to preclude damage. Alternately, the sheet can be discarded.

Digital printing machines can take on a variety of configurations. One common process is that of electrostatographic printing, which is carried out by exposing a light image of an original document to a uniformly charged photoreceptive member to discharge selected areas. A charged developing material is deposited to develop a visible image. The developing material is transferred to a medium sheet (paper) and heat fixed.
Another common process is that of direct to paper ink jet printing systems. In ink jet printing, tiny droplets of ink are sprayed onto the paper in a controlled manner to form the image. Other processes are well known to those skilled in the art. The primary output product for a typical digital printing system is a printed copy substrate such as a sheet of paper bearing printed information in a specified format.
The output sheet can be printed on one side only, known as simplex, or on both sides of the sheet, known as duplex printing. In order to duplex print, the sheet is fed through a marking engine to print on the first side, then the sheet is inverted and fed through the marking engine a second time to print on the reverse side. The apparatus that turns the sheet over is called an inverter.
FIG. 1 shows a state-of-the-art inkjet digital printing machine 20. Printer 20 includes a marking module or engine 22 having an ink jet print head or multiple print heads 23, disposed centrally on the marking engine 22, and facing downward. Printer 20 has a media path 24 along which the media sheet 34 moves, and a media path entrance 26 where sheets are fed into the printer by a media sheet feeder (not shown). Printer 20 also has a media path exit 28 where sheets leave the printer and are fed into a finisher (not shown). Printer 20 has an inverter 30 to turn the sheet over for duplex printing. A media sheet 34 leaving the inverter 30 follows arrow 32 back to the marking engine 22 for printing on the reverse side. Arrows 26 and 28 also indicate the process path direction, which is downstream from entrance 26 toward exit 28.
In cut sheet printing devices, under certain conditions, the lead-edge of the paper can curl up and have potential for separating from the marking transport and contact the print head. A sheet with out-of-spec flatness can occur when a duplexed sheet has a heavy ink image on the trail edge of side 1, which then becomes the lead edge when inverted and curls towards Side 2. This is most severe when the paper is thin, and the cross-process direction image is parallel to the grain direction of the paper (Example: letter size paper, grain-long, long-edge-feed).
In direct-to-paper ink jet marking engines, an ink jet print head is mounted such that the face (where the ink nozzles are located) is mounted a fixed distance from the surface of the media. The gap is typically 1 mm or less. Because the paper curl height can be several millimeters, it poses a risk to the print head because it can hit the print head face plate when it passes through the nominally thin gap that the print heads are spaced from the media.
Ink jet print heads are very delicate and can easily be damaged if the face of the print head is contacted by the media which is passing nearby. The print heads are also very expensive. Thus, it is very important to minimize any risk of damaging these print heads.
Accordingly, there is a need to provide a print head protection device for inkjet printers that will detect media sheet curl and take remedial action to prevent print head damage.
There is a further need to provide a print head protection device for inkjet printers of the type described and that will match the high production rate of a digital printing machine.
There is a yet further need to provide a print head protection device for inkjet printers of the type described and that is mechanically simple and robust, thereby minimizing cost.

Print head protection device for inkjet printers


A water absorptive material comprising a fibrous substrate impregnated with a water absorptive, water insoluble polymer, wherein the polymer is intertwined and interlocked with fibers of the fibrous substrate, and the use of such water absorptive material to form a water control zone to prevent water egress from the water control zone into adjacent ground or water ingress into the water control zone from adjacent ground.

Commonly owned and related U.S. Pat. No. 5,614,269 discloses a method of making a water absorptive article comprising a water absorptive, water insoluble polymer and discloses the use of such a water absorptive article to protect cable, such as fiber optic cable, from water from the ingress of moisture and water into the cable. As explained in U.S. Pat. No. 5,614,269 ingress of water into cable is a substantial and persistent problem in the cable industry. Such ingress often results from changes in ambient conditions which cause differences in vapor pressure between the inside and the outside of a cable jacket. Consequently, moisture tends to diffuse in a unidirectional manner from the outside of the cable to the inside of the cable, resulting in an undesirably high moisture level inside the cable. High levels of condensed moisture inside a cable sheath system may have a detrimental effect on the transmission characteristics of a metallic conductor cable.
Furthermore, water may enter the cable as a result of damage to the cable which perforates the external water barrier elements. For example, animal attacks and mechanical impacts often create openings in the sheath system of the cable, which allows water to enter the cable. Once inside the cable sheath system, the water tends to move longitudinally along the cable into splice closures, if not controlled.
In another field, water flow through ground (meaning "earth") can pose problems, if not controlled. Water naturally percolates through the ground and such percolation is normally desirable because it purifies water. Rain water normally percolates through the surface of the ground and eventually flows into the local ground water system.
It is desirable to prevent percolation of water through ground in some instances. For example, it is desirable to prevent water egress from waste disposal sites into the adjacent ground and water ingress into waste disposal sites from the adjacent ground to avoid contamination of the local ground water by toxins in the waste disposal site. A landfill is a specific example of such a waste disposal site.
Bentonite clay has been used to block water flow into and out of waste disposal sites, but bentonite clay tends to migrate during use, leaving water permeable areas, and is heavy and therefore expensive to transport.
Accordingly, in addition to controlling water ingress into cables, there is also a need to control water flow through the ground, and there is a particular need to control water egress from a waste disposal site into the adjacent ground and water ingress from the adjacent ground into the waste disposal site.

System and method for controlling water flow through ground with a geotextile comprising water absorbing material


A detection system for measuring one or more conditions within an area. At least one fiber optic cable transmits light wherein the at least one fiber optic cable defines a plurality of nodes arranged to measure the one or more conditions. A control system communicates with the at least one fiber optic cable such that scattered light and a time of flight record is transmitted from the at least one fiber optic cable to the control system. The control system includes a detection algorithm operable to identify a portion of the scattered light associated with each of the plurality of nodes. When determining an alert, the control system transmits data associated with a presence and magnitude of the one or more conditions at each of the plurality of nodes and, in return, receives a notification based on the data transmitted to the cloud computing environment.

Embodiments of this disclosure relate generally to a fiber optic detection system for detecting conditions within a space and, more particularly, to a fiber optic detection system to detect and identify a source location of smoke or other airborne pollutants in a space.
Although conventional smoke detection systems and high sensitivity smoke detection systems utilizing airflow can detect the presence of smoke or other airborne pollutants, delays often occur in the detection of the smoke or other airborne pollutants. Also, the conventional smoke detection systems and high sensitivity smoke detection systems utilizing airflow can identify the presence of smoke at the detector but do not identify the source location of the smoke or other airborne pollutants.
High sensitivity smoke detection systems based on fiber optics can detect the presence of smoke or other airborne pollutants in real-time. These known high sensitivity smoke detection systems with fiber optics typically use a primary detection node for whole area detection and a secondary node, commonly referred to as a localization or collimated node, for localization based on a spatial index relative the density of the smoke or the airborne pollutant. Although the spatial and temporal evolution of the pattern of the smoke or pollutant is a way to detect smoke or the pollutant and identify the source location, improved capabilities are needed to identify the type of fire or pollutant and to eliminate nuisances caused by detection of non-hazardous conditions or other conditions that may be distinguishable from conditions that would be required (e.g. by building code or other regulation) or desirable to trigger an alarm.

Spatial and temporal pattern analysis for integrated smoke detection and localization


A voltage controlled oscillator includes a resonator configured to resonate with an initial oscillation frequency during starting period of oscillation and a steady oscillation frequency during a steady state oscillation. The resonator includes a film bulk acoustic resonator having a series resonance frequency higher than the steady oscillation frequency. A negative resistance circuit configured to drive the resonator, has a positive increment for reactance in the steady state oscillation compared with reactance in the starting period.

1. Field of the Invention
The present invention relates to a voltage controlled oscillator using a film bulk acoustic resonator and, more particularly, to a voltage controlled oscillator having a variable oscillation frequency, a communication apparatus and a frequency synthesizer using the same.
2. Description of the Related Art
In recent years, the market for a wireless communication system including a mobile phone and the like, has expanded, and at the same time, mobile communications services have been increasingly sophisticated. Moreover, it is expected that a local area network (LAN) system will rapidly become widespread in coming years. In these wireless communication systems, a radio frequency (RF) band of 2 GHz, 5 GHz, or more, is generally used.
In the RF band wireless communication systems, frequency synthesizers are used which are capable of oscillating in frequency bands required in the respective systems. The use of a quartz oscillator makes it possible to generate a highly precise reference frequency. However, a voltage controlled oscillator (VCO) is generally used in an RF band where the quartz oscillator cannot directly oscillate. Although a VCO alone cannot generate a highly precise frequency, frequency precision of a VCO or a frequency synthesizer is provided by implementing feedback control using a phase locked loop (PLL) circuit so as to generate integer or fracture times the frequency of a quartz oscillator. However, a VCO using a quartz oscillator normally provides a frequency band around 5 to 30 MHz, and even the highest frequency band of approximately 100 MHz at most.
Requirements for a VCO used in a frequency synthesizer include a wide tunability of an oscillation frequency so as to cover enough frequency range, and a low phase noise characteristic, as well as compactness and low power consumption.
A phase noise is an index to characterize dispersion of an oscillation frequency. The lower phase noise indicates that the oscillation frequency is closer to a single frequency, that is, almost ideal. The phase noise of a VCO, through frequency conversion by a frequency mixer, adversely affects the spectrum of signals in transmitting and receiving. In an orthogonal frequency division multiplex (OFDM) system, which is used for a wireless LAN system, an asymmetrical digital subscriber line (ADSL), a digital terrestrial television and the like, the lower the phase noise of a VCO, the higher the quality of signals. Accordingly, in principle, the quantity of information for transmitting and receiving can be increased.
A phase noise is caused by a thermal noise, flicker noise (1/f noise) and the like, inside an oscillator circuit. The noises emerge, as a momentary shift in the oscillation frequency, at an output node of the oscillator circuit. In order to reduce a phase noise in an oscillator, it is effective to increase the quality factor (Q value) of a resonator used in an oscillator circuit.
As a resonator exhibiting a high Q value in an RF band of GHz frequency or more, a film bulk acoustic resonator (FBAR) has been proposed recently and has collected attention. Currently, as resonators used in RF communication systems, bulk (ceramic) dielectric resonators or surface acoustic wave (SAW) devices have been used. As compared with the currently used resonators, the FBAR is suitable for miniaturization, and also for higher frequency applications. On the basis of the above reasons, a high frequency filter using an FBAR has already been commercially manufactured. Moreover, there is a proposal to use an FBAR of an aluminum nitride (AlN) as a resonator of VCO (see A. P. S. Khanna, et al., "A 2 GHz Voltage Tunable FBAR Oscillator," IEEE MTT Symposium Digest, pp. 717–720, 2003).
Moreover, there is a proposal in which, in order to achieve a wide oscillation frequency tunability, a detection circuit is added to detect the transition of an oscillating operation from an initial state into a steady state, and a load capacitance in a resonator is connected to improve tunability of the oscillation frequency. (refer to Japanese Patent Laid-Open No. 2002-344242).
Furthermore, there is another proposal employing a wide-band frequency synthesizer in a wireless communication system, in which a wide frequency tunability is realized by means of selecting a VCO from a plurality of VCOs having different frequency bands (refer to Japanese Patent Laid-Open No. 2002-314414).
The VCO disclosed in Japanese Patent Laid-Open No. 2002-344242 is a quartz oscillator and therefore inapplicable in a GHz frequency band. In addition, the VCO requires an additional detection circuit for an oscillation signal and, therefore, is not suitable for miniaturization. Moreover, according to A. P. S. Khanna, et al., a prototype of a VCO using an AlN FBAR with an oscillation frequency of 2 GHz has achieved an extremely low phase noise (C/N). However, only a value of approximately 0.1% can be achieved for a frequency tunability. Further, in Japanese Patent Laid-Open No. 2002-314414, the frequency synthesizer is constructed by using an LC oscillator having inductors and capacitors for a resonator. Therefore, the circuitry becomes large and phase noise reduction is difficult.
As described above, currently, a VCO using a FBAR which is suitable for miniaturization and capable to oscillate a frequency range over GHz has not yet reached a point of providing a needed frequency tunablilty. Therefore, there have been few disclosed frequency synthesizers with a VCO using a FBAR.

Voltage controlled oscillator, frequency synthesizer and communication apparatus


The present invention provides a liquid container which has a check valve for preventing a flow of outside air into its inside and which is capable of maintaining the performance of the check valve constant. An ink pack (25) includes a bag portion (36), which holds an outlet portion by heat-welding. An internal space (S) is formed in the bag portion (36), and ink is contained therein. The outlet portion has a first flow path forming component (41). A first recess portion (47) is recessed from the one side surface (41a) of the first flow path forming component (41). First and second ink flow paths (46, 51), which communicate with the internal space (S), extend from a bottom surface (47a) of this first recess portion (47). A valve seat (53) is formed in a projecting shape so as to surround the second ink flow path (51). A laminate film (36a) sealingly closes the first recess portion (47). Thus, a valve body accommodating chamber (55) is formed. The valve body accommodating chamber (55) accommodates a first valve body (58). The valve body (58) and the valve seat (53) form a first valve device (59).

The present invention relates to a liquid container, a component for forming a liquid container, and a method for producing a liquid container.
Conventionally, an ink jet recording apparatus has been widely used as a liquid ejecting apparatus, which ejects liquid to a target. In greater detail, this ink jet recording apparatus comprises a carriage, a recording head mounted on the carriage, and an ink cartridge containing ink as liquid. Printing is carried out on a recording medium by ejecting ink from nozzles formed on the recording head while moving the carriage relative to the recording medium and providing ink to the recording head from the ink cartridge.
Moreover, in such an ink jet recording apparatus, in order to reduce the load on a carriage, or to make the apparatus compact and thin, there is a structure, in which an ink cartridge is not mounted on a carriage (a so-called off-carriage type). Such an ink cartridge typically includes an ink pack containing ink, and a case accommodating the ink pack.
Conventionally, an ink pack 180 with an outlet portion 181 shown in FIG. 25 is known as such an ink pack (For example, see Japanese Patent Application Publication No. 2002-192739). In detail, this outlet portion 181 is held in an opening of a bag portion 182 of the ink pack 180 in a manner being sandwiched, and discharges the ink contained in the bag portion 182. This outlet portion 181 is provided with a first tube body 183, and a second tube body 184.
An annular rubber packing 185, and a first valve body 187 capable of sealingly closing an opening of the rubber packing 185 by a biasing force of a coil-shaped spring component 186 are provided inside the first tube body 183. When an ink inlet tube 188 connected to an ink supply tube (not show) is inserted into the outlet portion 181, a first valve body 187 is pressed and moved by the ink inlet tube 188, and then the opening of the rubber packing 185 is opened.
In addition, in the state where the ink inlet tube 188 is not inserted into the outlet portion 181, the first valve body 187 abuts and sealingly closes the opening of the rubber packing 185 so that the ink in the ink pack 180 does not leak to the outside.
The second tube body 184 is fixed by press-fitting into the first tube body 183. A valve body accommodating chamber 191 is defined by the second tube body 184 and the first tube body 183. This valve body accommodating chamber 191 movably accommodates a disc-shaped second valve body 192. This second valve body 192 abuts a valve seat 193 provided in the second tube body 184 so as to sealingly close a tube path of the outlet portion 181. On the other hand, when the pressure of the ink in the ink pack increases, the second valve body 192 moves away from the valve seat 193 so as to open the path of the outlet portion 181. Thus, this second valve body 192 and the seat 193 construct a valve device 194, this valve device 194 functions as a check valve, which allows the flow of ink only from an inside of the ink pack 180 to the outside.
In order to supply ink from the ink pack 180 having the outlet portion 181 as constructed above to a recording head, an ink inlet tube 188 is first inserted into the outlet portion 181, then the pressure of the ink in the ink pack 180 is increased by pressing the bag portion 182 or the like. As a result, the second valve body 192 moves away from the valve seat 193, and the ink in the ink pack 180 is supplied to the recording head through the outlet portion 181 and an ink supply tube.
The ink pack 180 having the outlet portion 181 as mentioned above has the following advantages: That is, for example, even if a user forcedly moves the first valve body 187 with a screw driver, etc., the valve device 194 functions as a check valve. Accordingly, this can prevent leakage of the ink in the ink pack 180 to the outside because the movement of the first valve body 187 by such user's operation causes ink in the interior of the first tube body 183 to attempt to flow into the inside of the ink pack 180 but this relatively strong or quick reverse flow of ink instantaneously move the second valve body 192 to seat on the valve seat 193. Also, this can prevent the outside air and so on associated with such relatively strong or quick reverse flow from flowing into the ink pack 180, to thereby maintain the degassed rate or cleanliness of the ink in the ink pack 180.
In addition, the valve device 194 functioning as a check valve may permit a slight or slow reverse flow which does not cause the entry of the outside air and so on into the ink pack 180, and which would be occasionally caused, for example, during printing.
The outlet portion 181 is required to maintain high performance of the valve device 194 functioning as a check valve, and therefore to improve airtightness of the valve body accommodating chamber 191. As one of methods for improving airtightness of the valve body accommodating chamber 191, heat-crimping is used to fix the first tube body 183 and the second tube body 184 in a tight fit state to form the valve body accommodating chamber 191.
However, since recent tendency is directed toward a case in which both of the first tube body 183 and second tube body 184 are formed of synthetic resin or the like such as plastic, and since both of the first tube body 183 and the second tube body 184, in this case, are rigid, the aforementioned method suffers from a possibility that unevenness in dimension of the first and second tube bodies 183 and 184, and thus unevenness in airtightness of the valve body accommodating chamber 191 tends to appear. This deteriorates the performance of the second valve body 192 as a check valve.
The present invention aims at solving the above problem, and its object is to provide a liquid container, a component for forming a liquid container, and a method for producing the liquid container capable of maintaining constant performance of a check valve disposed in the liquid container.
Another object of the present invention is to provide a liquid container having a check valve that can more reliably prevents the flow of outside air or the like into its inside.
Yet another object of the present invention is to ease injection of ink into a liquid container having a check valve.

Liquid container, component for forming liquid container, and method for producing liquid container


A portable, expandable laser golf training device that can be placed on the ground to provide alignment. The present invention can supply a plurality of light beams produced by lasers or other light sources, switchable on and off, that can be projected along the ground both in the direction of play and perpendicular to it. In a folded configuration, the device can project in four directions creating a pair of axis lines running at right angles to each other. In an expanded configuration, one of the major axis lines can be separated into two parallel lines for putting alignment by sliding the halves of the device apart. The device can be used by placing it on the ground in front of the golfer (between the golfer's feet and the ball. Two lines project outward perpendicular to the direction of play, and two or four lines project into and away from the direction of play. These lines provide alignment for the golfer. Various combinations of beams on or off can be selected by a selector switch under control of the user. The device can contain a rechargeable battery.

1. Field of the Invention
The present invention relates generally to the field of light-aided sport improvement devices and more particularly to a laser golf or other sport alignment device and method.
2. Description of the Prior Art
There are numerous devices known in the art that place a laser or other light source somewhere on or near a golf club. For example, U.S. Pat. No. 6,007,436 teaches a laser system that helps align the golfer's feet in relation to the ball. U.S. Pat. No. 5,029,868 describes a practice high intensity light source mounted on a golf club. US 2005/0261072 describes a golf club alignment device with one or two laser units connected to a golf club. U.S. Pat. No. 5,435,562 teaches a golf club having a laser generating diode and laser reflecting prism. U.S. Pat. No. 5,042,815 describes a grid-like reference system for obtaining a properly aligned golf stance. U.S. Pat. No. 5,467,991 teaches a self-contained portable unit attachable to the shaft of a golf club that supplies a beam of light. U.S. Pat. No. 5,165,691 discloses a laser golf putter assembly mounted on the putter club. U.S. Pat. No. 5,738,595 describes a hand-held laser pointing device. U.S. Pat. No. 5,818,036 describes a laser aided practice putting device. U.S. Pat. No. 5,452,897 teaches a laser putter alignment system with a mirrored surface on the ball-striking surface of the putter club. U.S. Pat. No. 6,213,887 teaches an apparatus for practicing golf using a laser aiming device. U.S. Pat. No. 7,134,966 describes a golf putt training device using a light apparatus positioned behind the ball. U.S. Pat. No. 7,118,488 discloses a training putter with a laser line projecting device. U.S. Pat. No. 6,672,972, U.S. Pat. No. 5,467,992 and U.S. Pat. No. 7,207,896 teach hat-mounted laser golf devices. U.S. Pat. No. 7,160,198 teaches a golf club swing training system. U.S. Pat. No. 6,383,087 discloses a golf putting alignment system using lasers for determining the aiming tendencies of a golfer. U.S. Pat. No. 6,767,291 teaches a putting device that includes lasers mounted on a putter. U.S. Pat. No. 5,810,674 discloses a golf club with light sources. U.S. Pat. No. 5,759,110 teaches a swing training device with a light beam along the longitudinal axis of the golf club.
All of these and other prior art methods suffer from either having a light source attached to the moving golf club or not projecting a beam where the golfer needs it most. It would be advantageous to have a laser golf alignment system and method that can place right angle beams on the ground in the direction of ball travel and perpendicular to that direction. It would also be advantageous to be able to project two separated beams in the direction of ball travel for putting.


A console assembly for an automobile is provided. The console assembly includes a console and a cable. The console has at least one cavity for receiving objects. The at least one cavity is illuminated by the cable containing an electroluminescent (EL) tape.

In an automobile, a console assembly has various utilities. For instance, the console assembly can be utilized for installing accessories such as music systems, display screens, or for placing objects such as cups, bottles, glasses and mugs. The objects may be placed in cavities such as cup-holders in the console assembly. In the absence of proper light, such as during night time, it may be difficult for an occupant of the automobile to locate the cup-holders to place the objects.
Hence, there is a need for illuminating the cavities in the console assembly. Further, the means for illuminating may also improve the visual appearance of the interior of the automobile.


An apparatus and method for reducing errors in a battery powered sensing circuit uses two pull-up resistors. The first resistor has a value selected to minimize battery drain and the second resistor has a value selected to reduce dendrite or other parasitic parallel resistance. The resistors are selectively connected to the circuit based on a predetermined sequence and/or time interval.

Dendrites are microscopic crystalline structures that form between parallel conductors, for example, on a printed circuit board surface between two copper traces that have different voltage potentials. The dendrites develop over a long period of time and may eventually extend from trace-to-trace. These structures are electrically conductive, and when extending from trace to trace form a short circuit. Dendrite structures are caused by the voltage difference acting on surface contaminants on the printed circuit board. A more detailed discussion of dendrite is found in, Metal Migration in Encapsulated Modules and Time-to-Fail Model as a Function of the Environment and Package Properties, Givlio DiGiacomo, IEEE Proceedings, 1982, incorporated herein by reference.
Dendrites, or other materials, can create a parallel parasitic resistance in various electronic devices, causing short circuits or other malfunctions under certain operating parameters. For example, in a wireless security system, sensors communicate with a system controller via RF-transmitted message packets. Each sensor includes a transmitter (typically an integrated circuit or chip) that is connected to other circuitry on a small printed circuit board. Although located in an enclosed package, the sensor circuit board is exposed to environmental contaminants, and dendrites or other materials may accumulate on the sensor circuit board.
Additionally, dendrites or other parasitic parallel resistance agents may form in other areas of the sensor circuit. For example, dendrite-induced short circuits may develop within the sensor. For example, window screen sensors are susceptible to the development of parallel parasitic resistances. Parasitic parallel resistances may also develop between the external contacts of the transmitter.
During operation, conditions exist that are conducive to dendrites forming short circuits on the sensor circuit board and at remotely wired detector sensors. These short circuits may appear to the transmitter as a change in condition, when no actual change in condition has occurred. The transmitter then sends incorrect information to the system controller. Therefore, there is a need for preventing or eliminating dendrite short circuits on the sensor circuit board and at remotely wired detector sensors. Additionally, there is a need to eliminate or overcome other types of parasitic parallel resistances within the sensor system.
Implementing a short circuit reduction feature must be balanced with other important design considerations in a wireless security system. The sensors of the wireless security system are typically battery powered. For convenience and reliability purposes, the sensor and transmitter circuitry are designed to minimize energy consumption and extend the battery life. Additionally, certifying organizations, such as Underwriters Laboratories, require minimum periods for which the batteries must power the sensor.
In order to meet the low energy consumption goal, the battery-powered sensor and transmitter systems are typically operated a low currents. These low-current operating conditions are conducive to dendrite-induced short circuits and other types of parasitic parallel resistance malfunctions. Operating the circuits at higher currents would tend to reduce the parasitic parallel resistance problems, but also reduce battery life. Therefore, there is a conflict in the need to extend battery life and to prevent malfunctions induced by parasitic parallel resistance.

Apparatus and method for reducing errors in a battery operated sensing circuit


An absorbent brief, or diaper, including a liquid-permeable layer, a liquid-impervious layer, and an absorbent layer sandwiched between the liquid-permeable and liquid-impervious layers, the absorbent layer having a dispersion channel extending through the absorbent layer to the liquid-impervious layer for providing unobstructed liquid flow.

1. Field of the Invention
The present invention relates generally to personal hygiene products. More particularly, it relates to an absorbent brief structure, for example a diaper, and to means for reducing the tendency of the brief to leak during evacuation of a large volume of liquid over a short period of time.
2. Brief Description of the Prior Art
Incontinence, or the inability to control excretory functions, is a common condition, particularly in infants and the elderly. Every child and, according to recent studies, as many as one-third of older adults have some problem with urinary incontinence, which among older persons is more common among those who are housebound or have cognitive or functional impairments.
Incontinence among the elderly may have severe consequences. For example, incontinent individuals may restrict their physical or social activities and may exhibit a preoccupation with toileting functions. Incontinence also can cause psychological reactions, can result in considerable expense for cleaning, and can precipitate institutionalization or even death.
Although many older incontinent persons could be cured, many tend to view their condition merely as embarrassing, and prefer to rely on self-devised strategies to minimize urine loss. These strategies typically include the use of absorbent briefs or pads.
Absorbent briefs, also known as adult diapers, are well known for use by incontinent persons. These briefs typically include a first or inner layer made of a liquid-permeable material, a second or outer layer made of a liquid-impervious material, and an absorbent layer sandwiched between the inner and outer layers. The inner layer, which is generally worn next to the body, allows liquid to penetrate therethrough to the absorbent layer. The outer layer provides a barrier that prevents liquid from penetrating through the brief, e.g., to bedding, clothing, or the like. Although such absorbent briefs provide satisfactory use in many instances, these briefs often leak, particularly in or around the crotch area, in the case of a large liquid evacuation over a short period of time.
Various structures for absorbent briefs and pads have been suggested for improving absorption of quick, large volume, liquid evacuations, and for reducing the associated leaking. One suggestion is merely to increase the volume of the absorbent layer. Another suggestion is to use a material having a greater absorbency (assuming the same volume). The former increases the volume of the brief and may become awkward, uncomfortable or embarrassing to the user (e.g., unsightly). The latter may be too expensive.
U.S Pat. No. 4,678,464 relates to an absorbent structure (e.g., a diaper, a sanitary pad, an incontinence pad or the like) that contains a loosely compacted cellulosic fibrous batt having two reservoirs and a connecting channel formed by compressing the fibrous batt. The base of each reservoir is formed by a densified fibrous region, and the fibrous base of the channel is of a higher density than the immediate surrounding areas, except for the reservoirs.


Associating and/or disassociating a mobile point-of-sale scanner device with a particular shopper. Shoppers may be identified, for example, using biometrics or by scanning a loyalty card. As an example of using biometrics, the shopper's fingerprint may be scanned as a trigger of the scanner is activated to scan an item's barcode. The fingerprint is preferably transmitted, along with the scanned barcode, to a server or other device for comparison to previously-stored information. The scanner is then automatically associated with the shopper to whom the fingerprint corresponds. In another embodiment, scanned loyalty card information is preferably transmitted (optionally, along with a scanned barcode), such that the scanner is then automatically associated with the shopper to whom the loyalty card corresponds. Disassociating the scanner from a shopper is preferably triggered using a sensor (such as a light) that forms part of the scanner device, whereby the sensor is activated when the shopper releases the scanner device. A timer may be used to filter out accidental activation of the sensor.

The present invention relates generally to point-of-sale scanner devices, and more particularly, to use of such devices for automatically associating and disassociating a scanner device with a shopper in an on-demand manner.
A so-called "shopping buddy" application allow shoppers to roam about a retail store or other environment with an information-transmitting device, gathering various types of information.
In one approach, a shopper goes to an in-store kiosk where a number of scanners are available. The shopper provides identifying information through the kiosk, and the shopping buddy application then assigns one of the available scanners to the shopper. Typically, a light flashes to indicate to the shopper which of the scanners he/she is to use. When a large number of scanners are available, it may be time-consuming and/or cumbersome for the shopper to locate the assigned scanner.
In another approach, a tablet-sized computing device is mounted on a shopping cart. The computing device may be equipped with a barcode scanner. The shopper provides identifying information to the computing device, and can then use the scanner to read barcodes on items as they are placed into the shopping cart.

International Business Machines Corporation


A vapor condenser includes a conduit defining a passage for guidingly communicating a vapor stream in a vapor flow direction from an inlet at a first location to a second location, a first heat exchanger between the first and second locations for open heat exchange between the vapor and a first coolant, the first coolant flowing in a direction that is counter to the vapor flow direction, and a second heat exchanger between the first and second locations for open heat exchange between the vapor and a second coolant. The vapor condenser automatically controls the flow rate of coolant in the first heat exchanger in response to changes in the density of the vapor in the vapor stream entering the conduit. Control of the flow rate of coolant is maintained, for example, by controlling the flow rate of individual dispersal devices, such as nozzles, or by controlling the number of nozzles operating.

Many commercial and industrial processes generate as by-products large amounts of vapor, such as steam, during operation. As is the case with the by-products of any commercial or industrial process, the vapor produced must eventually be released for disposal in the surrounding environment.
One disposal method is to exhaust the vapor stream directly to the ambient environment. This method, however, has come under increased scrutiny by federal, state, and local regulatory authorities, leading to legal restrictions being placed on the disposal of vapor in this manner. Most commonly, a permit is required to exhaust vapor streams to the ambient environment. Sometimes, such a permit is difficult to obtain.
Even if a permit is obtained to exhaust the vapor by-products of an industrial process to the ambient environment, the physical requirements of such an exhaust system often create additional problems. For example, the exhaust stack may interfere with the motion of other machinery, such as an overhead crane. Additionally, the process generating the vapor to be exhausted may be located a great distance from an external wall, requiring an extensive system of duct work to be installed.
Alternatively, the vapor stream by-products could be released within the plant where the commercial or industrial process is being practiced. However, such a disposal method may result in a dangerous environment for the employees working in the surrounding area of the plant, unless the vapor content or density of the vapor stream is somehow limited before the stream is released into the plant surroundings.


The present invention relates to a review control method of a video cassette recorder capable of controlling a review operation without noises on a screen in switching from a play mode into a review mode.

1. Field of the Invention
The present invention relates to a review control method of a video cassette recorder, in particular, for implementing a review operation without noises on a screen in switching from a play mode into a review mode.
2. Description of the Related Art
A video cassette recorder uses a capstan 7 and a pinch roller 9 to run a tape at a regulated rate. The capstan 7 performs loading/unloading under the force of the capstan motor 8, and provides a force for running the tape. The pinch roller 9 is closely contacted with the capstan 7, and functions to pull the tape in a specific running direction. In addition to the foregoing components, a tension belt 4 can be included as a component that is used for running the tape. The tension belt 4 is used to uniformly maintain a tension applied to the tape in a running mode such as a play mode for regenerating the tape while running the same.
In a conventional video cassette recorder having the foregoing configuration, a configuration of mechanical modes is as shown in FIG. 1.
In a play mode PLAY, the pinch roller 9 maintains a compressed state, and a tension band brake 5 has an operation state On. A supply reel brake 13 and a turning-up reel brake 15 are released having off states Off to help forward running of the tape. FIG. 2 illustrates the components in such a play mode PLAY.
In a review mode REV, the tension band brake 5 switches into a released off state Off from the play mode PLAY, and the turning-up reel brake 15 is turned on into an operating or on state to help review. FIG. 3 illustrates the components in such a review mode REV.
As shown above, the pinch roller 9 has the compressed state in all ranges of the play mode PLAY and the review mode REV. A video cassette tape with such a configuration tends to have noises due to droop of the tape when switching from the play mode PLAY to the review mode REV.
Therefore, the conventional video cassette recorder performs operation processes as shown in FIG. 4 in order to solve the problems as set forth above.
When a key is inputted for switching to the review mode REV during operation in the play mode PLAY, a control unit (not shown) reverses a loading motor (not shown) while rotating forward the capstan motor 8 continuously at a basic rate so as to be positioned in a loading end mode L/D END where the pinch roller 9 has a decompressed off state Off. When positioned in the loading end mode L/D END in this operation, the capstan motor 8 and the loading motor are stopped. This operation state is shown in a range A in FIG. 4.
Then, the capstan motor 8 is reversed at a predetermined amount. This operation moves an idle roller 10 toward a supply reel 3. Then, the capstan motor 8 is stopped.
After the capstan motor 8 is stopped and the loading motor is forward rotated into the review mode REV, the capstan motor 8 is reversed to carry out the review operation. This operation state is shown in a range B in FIG. 4.
In the foregoing operation, the supply reel brake 13 switches from an off state into an on state and then returns to the off state in order to prevent the tape from being unwound from the supply reel 3. Switching the turning-up reel brake 15 from the off state into the on state is necessary to stabilize a running path of the tape by applying back tension to the tape in the review operation.
In other words, the taped is drooped while the tension band brake 5 is switched from an on operation into an off operation in switching of the conventional video cassette from the play mode PLAY into the review node REV. The drooping of the tape is controlled by continuously forward rotating the capstan motor 8 on the loading end mode L/D END where the pinch roller 9 has the off state Off.
However, the review control method of the conventional video cassette recorder operating in such a manner brings about the following problems.
The turning-up reel brake 15 is necessarily switched into the on state in the range of the play mode PLAY and the review mode REV in order to progress the review mode. The brake torque of the turning-up reel brake 15 acts as the load on the turning-up reel 1 as soon as the turning-up reel brake 15 is on. Therefore, the rotation torque of the tinning-up reel 3 decreases as much as the brake torque acting as above. If the forward torque of a friction clutch 12 is not sufficiently larger than the load torque of the turning-up reel brake 15 due to such actions, the tape is unwound (the turning-up reel is incapable of rotating) after the pinch roller 9 in the range A in FIG. 4 and noises due to the tape drooping take place from a time point, when the pinch roller 9 is off, in the range B.
If the forward torque of the clutch 12 is set high to solve the foregoing problem, the capstan motor 8 is barely stopped at a correct position Moreover, a clutch friction member is abraded to lower the reliability of a product.

Review control method of video cassette recorder


The invention relates to a display element, an element drive method, and an information display system having the element, and has an object to provide a display element capable of stably acting even if a received electric power reduces, a method for driving the element, and an information display system having the element. The system comprises: a display section having laminated display layers; a wireless transmitting/receiving section for receiving electric waves containing the display data of the display layers; a driving voltage generating circuit for generating drive voltages to drive the display layers from the electric waves received; and a control section for simultaneously driving the display layers of the number which is determined on the basis of the receiving situations of the electric waves.

1. Field of the Invention
The present invention relates to a display element, a method for driving the same, and an information display system including the same.
2. Description of the Related Art
Recently, development of electronic paper is active in enterprises and universities. Promising applications of electronic paper include electronic books first of all, sub-displays of mobile terminals, and display portions of IC card. Writing of electronic paper on a wireless basis is studied as a promising applied technique of electronic paper. Existing interfaces available for wireless writing include wireless LANs, Bluetooth (a registered trademark), and contactless IC card systems. When a wireless LAN or Bluetooth is used, electronic paper must be provided with a battery. In the case of a contactless IC card system, data in an IC card are read and written using electric waves transmitted from a reader/writer as a temporary power source. Since the field strength is several tens of milliwatt, the use of a contactless IC card system can make it possible to provide a wireless and battery-less driving system in which electronic paper is written for display without providing it with a battery.
Display elements advantageously used in electronic paper include display elements using a cholesteric liquid crystal. Display elements using a cholesteric liquid crystal allows a reduction in power consumption which is a prerequisite for a wireless and battery-less driving system because they have memory characteristics to allow display to be held semi-permanently. Display elements using a cholesteric liquid crystal also have excellent characteristics, i.e., high color display characteristics which allow vivid display of colors, high contrast, and high resolution. A cholesteric liquid crystal can be obtaining by adding a relatively large amount (several tens %) of a chiral additive (chiral material) to a nematic liquid crystal, and it is therefore sometimes called a chiral nematic liquid crystal. A cholesteric liquid crystal forms a cholesteric phase in which molecules of the nematic liquid crystal are helically (spirally) aligned.
A display element using a cholesteric liquid crystal displays is enabled for display by controlling the state of alignment of liquid crystal molecules. States of alignment of a cholesteric liquid crystal include a planer state in which incident light is reflected and a focal conic state in which incident light is transmitted. Those states exist with stability even when there is no electric field. A liquid crystal layer in the focal conic state transmits light, and a liquid crystal layer in the planar state selectively reflects light having particular wavelengths in accordance with the helical pitch of liquid crystal molecules.
FIG. 12A schematically shows a configuration of a common liquid crystal display element, and FIG. 12B schematically shows a configuration of a liquid crystal display element using a cholesteric liquid crystal. As shown in FIG. 12A, a common liquid crystal display element has one liquid crystal display layer 101 in which pixels of red (R), green (G), and blue (B) are arranged side by side. On the contrary, as shown in FIG. 12B, a liquid crystal display element using a cholesteric liquid crystal generally has a structure formed by stacking three liquid crystal display layers 101R, 101G, and 101B in which pixels of the colors R, G, and B are provided, respectively. The liquid crystal display layers 101R, 101G, and 101B are enabled for display of the colors R, G, and B by varying the helical pitch of liquid crystal molecules. A liquid crystal display element using a cholesteric liquid crystal has an aperture ratio which is about three times greater than that of a common liquid crystal display element. A liquid crystal display element using a cholesteric liquid crystal is therefore capable of color display with high brightness because it has light utilization efficiency (reflectance) that is about three times higher than that of a common liquid crystal display element.
Patent Document 1: Japanese Utility Model No. 3089912
Patent Document 2: JP-A-2003-66413
Patent Document 3: JP-A-2002-108308
However, a liquid crystal display element for color display using a cholesteric liquid crystal suffers from a significant increase in power consumption when display is rewritten because it has a structure formed by stacking three monochromatic liquid crystal display elements and requires a driving voltage of ten and a few V or more. In the case of a wireless and battery-less driving system using feeble electric waves as power, an increase in a communication distance results in a reduction in receiving power. Therefore, a liquid crystal display element employing a wireless and battery-less driving system has a problem in that it is liable to operational failures attributable to shortage of power.

Display element, method for driving the same, and information display system including the same