Copolymers are formed by suspension polymerization of monomers, including one or more styrenic monomers, and one or more acrylic monomers. The monomers can be polymerized in the presence of polymeric seeds. The polymerization can be carried out in the presence of one or more blowing agents, producing polymers that can be expanded. The methods are useful, for example, in forming expandable polymeric particles. The expandable polymer particles are useful in processes such as forming patterns for lost foam molding techniques.

The present invention is directed to processes for forming styrenic copolymers. In particular, the present invention is directed to processes for forming copolymers of styrenic and acrylic monomers. The invention is further directed to processes for forming expandable and expanded styrenic-acrylic copolymers.
Styrenic polymers have a wide variety of applications, including the formation of expanded polystyrene which can be used to make a variety of products. Processes for forming styrenic polymers include emulsion polymerization, suspension polymerization, and the use of particular suspensions or emulsion aids.
Polymer particles are useful in applications such as the formation of expanded resins, for example, expanded polystyrene. Expanded polystyrene and other expanded resins can be prepared from expandable polymeric particles made by contacting the polymeric particles with a volatile compound known as a xe2x80x9cblowing agentxe2x80x9d or xe2x80x9cexpanding agentxe2x80x9d. Such agents include aliphatic hydrocarbons such as butane, pentanes, hexanes, and halogenated hydrocarbons such as trichloromethane, trichlorofluoromethane, and methyl chloride. The particles in contact with the expanding agent may be expanded by heating, or by exposure to reduced pressure as in a vacuum. The size and size distribution of the expanded particles will depend upon the size and size distribution of the expandable particles.
Expanded and expandable polymeric resins have applications in packaging, consumer products, and in materials processing. Examples of materials processing applications for expanded polymeric resins include so-called xe2x80x9clost foam castingxe2x80x9d, also called xe2x80x9cevaporative pattern castingxe2x80x9d. In lost foam casting, molten metal is poured into a pattern made of expanded polymeric material, i.e. a foam, coated with a refractory material surrounded and supported by unbounded sand. The foam is decomposed by the heat of the molten metal and replaced by the metal.
However, parts cast of metals such as iron, using expanded polystyrene foams, may have an unacceptable amount of surface defects and/or folds. The use of foams made of styrenic/acrylic copolymers can improve the quality of foam molds and metal parts made using such molds. Expandable resin compositions made of styrene-acrylic copolymers are described in U.S. Pat. No. 5,403,866.
A need remains for new and/or improved processes for forming styrenic copolymers.
One aspect of the present invention is a method for forming a styrenic copolymer. The method includes providing polymeric seeds in an aqueous medium; combining with the polymeric seeds, in the aqueous medium, a suspending agent and one or more surfactants in a ratio of about 1:175 or less to the weight of suspending agent, to form a seed mixture; providing a monomer mixture comprising from about 50 to about 90 percent by weight of one or more acrylic monomers, from about 10 to about 50 weight percent of one or more styrenic monomers, and one or more initiators; combining the monomer mixture with one or more expanding agents to form a reaction mixture; combining the seed mixture with about 100 to about 2500 weight percent of the reaction mixture, based on the weight of the seeds in the seed mixture, of the seed mixture to form a polymerization mixture; and heating the polymerization mixture to a polymerization temperature to effect formation of the copolymer.
In preferred embodiments, the total amount of one or more acrylic monomers in the monomer mixture is about 85 weight percent or less. In highly preferred embodiments, the total amount of styrenic and acrylic monomers in the monomer mixture includes from about 50 to about 85 percent by weight of one or more acrylic monomers, and from about 15 to about 50 percent by weight of one or more styrenic monomers.
In certain highly preferred embodiments, the styrenic monomers in the monomer mixture include at least one of styrene or alpha-methyl styrene.
In other highly preferred embodiments, the acrylic monomers in the monomer mixture include at least one of methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethyl hexyl methacrylate, n-butyl acrylate, n-hexyl acrylate, and 2-ethyl hexyl acrylate.
In some embodiments, the polymeric seeds comprise, as polymerized units, one or more styrenic monomers.
In some embodiments, the polymeric seeds comprise, as polymerized units, one or more non-styrenic monomers, such as, for example, acrylic monomers.
In some embodiments, the polymeric seeds comprise, as polymerized units, styrenic monomers and non-styrenic monomers.
In certain preferred embodiments, the polymeric seeds comprise, as polymerized units, methyl acrylate.
A further aspect of the invention is a process for preparing a pattern for use in making metal castings. The method includes providing styrenic copolymer particles having diameters from about 150 to about 600 microns; pre-expanding the particles by subjecting the particles to atmospheric steam to obtain a density of about 0.5 to about 2.0 pounds per cubic foot; and molding the particles into the desired pattern having a density of about 2.0 pounds per cubic foot or less.
Another aspect of the present invention is a pattern for use in molding molten metal, formed from a styrenic copolymer by molding into a desired pattern styrenic copolymer particles having diameters from about 150 to about 600 microns, the particles having been pre-expanded by subjecting the particles to atmospheric steam to obtain a density of about 0.5 to about 2.0 pounds per cubic foot. In preferred embodiments, the pattern has a density of about 2.0 pounds per cubic foot or less.
These and other aspects of the invention will become apparent to those skilled in the art in view of the following disclosures and the appended claims.
The present invention provides methods for forming styrenic copolymers. Monomers to be polymerized are provided in the form of a reaction mixture. The reaction mixture can be combined with small polymer particles referred to as xe2x80x9cseedsxe2x80x9d.
Seeds for use in the methods described herein may be styrenic or non-styrenic. Also, the seeds may be copolymeric. For example, the seeds may include copolymers of styrenic monomers and acrylic monomers such as methyl methacrylate. The seeds may include acrylic monomers such as methyl methacrylate, and may be, for example, acrylic homopolymers such as polymethylmethacrylate. Moreover, mixtures of two or more types of styrenic and/or non-styrenic seeds may be used.
The use of polymeric seeds in forming the styrenic copolymers can allow the formation of polymeric particles having narrower size distributions than are obtained using some conventional processes. The formation of styrenic polymers by incorporation of polymeric seeds is described in U.S. patent application Ser. No. 09/473,606, the disclosure of which is hereby incorporated herein by reference in its entirety.
Polymeric seeds can be prepared using methods known to those skilled in the art, including conventional emulsion or suspension polymerization methods, such as those disclosed in Odian, Principles of Polymerization, pp. 319-339 and pp. 287-288, John Wiley and Sons, Inc. (1982); or methods disclosed in U.S. Pat. Nos. 4,336,173; 4,459,378; and 2,673,194. The disclosures of each of the patents and publications referred to herein are hereby incorporated herein by reference in their entirety.
The polymer seeds are preferably provided in an aqueous seed suspension, as described hereinbelow. The styrenic monomers in the reaction mixture can be the same as or different from those polymerized in the seeds, and the ratios of monomers in the reaction mixture can be the same as or different from the ratios of polymerized monomers in the seeds. The total amount of styrenic monomers in the reaction mixture when combined with the seeds is preferably at least about 100 weight percent, more preferably at least about 200 weight percent, still more preferably at least about 300 weight percent, and even more preferably at least about 400 weight percent, based on the weight of the seeds. In some embodiments, higher weight percentages of styrenic monomers may be used, such as 1000 weight percent, 2000 weight percent or more.
The reaction mixture contains one or more styrenic monomers, one or more polymerization initiators, and optional additives known for use in suspension polymerization processes. Styrenic monomers that can be polymerized in the reaction mixture according to the processes of the invention include alpha-methyl styrene, paramethyl styrene, para-t-butyl styrene, monochlorostyrene, and dichlorostyrene. Preferred styrenic monomers include styrene and alpha-methyl styrene, and styrene is more preferred.
The amount of styrenic monomers in the reaction mixture prior to combining with the seed suspension is preferably about 50 weight percent or less, more preferably about 45 weight percent or less, even more preferably about 40 weight percent or less, and still more preferably about 35 weight percent or less. In preferred embodiments, the reaction mixture contains about 30 weight percent or less of styrenic monomers, such as about 25, 20, or 15 weight percent.
Initiators suitable for polymerization of styrenic monomers are well known to those skilled in the art. Preferred initiators include benzoyl peroxide, tertiary butyl perbenzoate, and tertiary amyl 2-ethylhexyl peroxycarbonate. The amount of initiator in the reaction mixture is generally at least about 0.05 weight percent, typically at least about 0.1 weight percent, and frequently at least about 0.15 weight percent, based on the total weight of all monomers in the reaction mixture. It is preferred to use as little initiator as can be used to achieve an acceptable polymerization yield. Generally, the amount of initiator in the reaction mixture is about 0.6 weight percent or less, typically about 0.55 weight percent or less, and frequently about 0.5 weight percent or less.
The reaction mixture also contains one or more acrylic monomers copolymerizable with styrenic monomers. xe2x80x9cAcrylic monomersxe2x80x9d, as used herein, means acrylic and methacrylic esters such as, for example, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, and ethyl methacrylate. Preferably, the acrylic monomers include methyl methacrylate. The amount of acrylic monomer is preferably at least about 50 weight percent, more preferably at least about 55 weight percent, even more preferably at least about 60 weight percent, and still more at least about 65 weight percent, based on the total weight of all monomers in the reaction mixture. In certain highly preferred embodiments, the reaction mixture can contain about 70 weight percent or more acrylic monomers, such as about 75, 80, or 85 weight percent.
In addition to the seeds, a seed suspension also contains water, a suspending agent, and a surfactant. The order of placing seeds, suspending agent, and surfactant into the water is not critical. Thus, for example, the suspending agent and surfactant can be added to water that contains the seeds, or the seeds can be added to water containing suspending agent and surfactant. Preferred suspending agents are inorganic salts such as phosphates, having minimal to moderate water solubility. Exemplary suitable suspending agents are described in U.S. Pat. No. 2,673,194, already incorporated herein by reference. Preferred suspending agents include tricalcium phosphate, hydroxyapatite, and magnesium phosphate. Tricalcium phosphate (xe2x80x9cTCPxe2x80x9d) is highly preferred. The amount of suspending agent is typically at least about 0.3 weight percent, based on the total weight of the dispersion, more typically at least about 0.4 weight percent, even more typically at least about 0.5 weight percent. The dispersion can also contain optional additives known to those skilled in the art, such as anti-foaming agents. Suitable antifoaming agents are known to those skilled in the art, and are commercially available from manufacturers including Henkel Corporation, Ambler, Pa. (sold under the name Foamaster) and Dow Corning Corporation, Midland, Mich.
Preferred surfactants for use in a seed suspension are anionic surfactants, such as sodium dodecylbenzene sulfonate, sodium lauryl ether sulfonate, sodium lauryl sulfate, and sodium laureth sulfate. Sodium dodecylbenzene sulfonate is highly preferred. The amount of surfactant required is less than that typically used in forming an emulsion, and can be determined by one skilled in the art, without undue experimentation, based upon the composition of the suspending agent. For example, when the suspending agent is tricalcium phosphate, the preferred weight ratio of surfactant to tricalcium phosphate is about 1:175 or less, more preferably about 1:300 or less.
In preferred embodiments, the seed suspension is placed into a reactor and the reaction mixture is added to the seed suspension. Also preferably, the reaction mixture is added to the seed suspension gradually. Gradual addition of the reaction mixture to the seed suspension can be accomplished by pumping, such as, for example, using a metered pump, or by other controlled methods known to those skilled in the art.
Alternatively, aliquots of reaction mixture can be added batchwise to the seed suspension intermittently, such as, for example, every 30 minutes. Each aliquot is preferably added over about 5 to 10 minutes. The amount of reaction mixture in each aliquot will depend, in part, on the quantity of seeds in the reactor. Typically, a weight of reaction mixture equal to about xc2xc the weight of seeds in the reactor can be added to the reactor over about a 30-minute period.
The reaction mixture is heated to an appropriate polymerization temperature for the monomer composition and ratio being used, which can be determined by one skilled in the art. If a seed suspension is used, the reaction mixture is preferably heated to an appropriate polymerization temperature for the monomers before being combined with the seed suspension. In addition to the monomer composition, the appropriate polymerization temperature is also dependent, in part, upon the amount and composition of initiators present. For example, if benzoyl peroxide (xe2x80x9cBPOxe2x80x9d) is used as an initiator, the appropriate polymerization temperature for styrenic monomers is generally from about 80xc2x0 C. to about 95xc2x0 C. If desired, a second initiator having a higher activation temperature may be used, and the temperature of the reaction mixture may be increased after the polymerization reaction is mostly complete, such as, for example, about 85 percent complete, to a higher temperature referred to as the xe2x80x9cfinishing temperaturexe2x80x9d. The second initiator may be included in the reaction mixture when the mixture is prepared, or may be added after polymerization of the monomers has started. For styrenic monomers with tertiary amyl 2-ethylhexyl peroxycarbonate (TAEC) initiator, the finishing temperature is preferably from about 114xc2x0 C. to about 118xc2x0 C. For styrenic monomers with tertiary butyl perbenzoate initiator, the finishing temperature is preferably from, about 123xc2x0 C. to about 129xc2x0 C.
For making expandable copolymers, the reaction mixture and/or the seeds preferably contain one or more blowing agents. The term xe2x80x9cblowing agentxe2x80x9d, as used herein, means a substance capable of inducing expansion or foaming of a polymeric material. Blowing agents can be included in the polymerization mixture when it is expected that the polymer is to be expanded. For example, expanded polystyrene can be formed using polystyrene that has been formed by polymerization of monomers in the presence of a blowing agent. Alternatively, if desired, a blowing agent can be imbibed by the polymer after polymerization is complete.
Preferred blowing agents have boiling points below the softening point of the polymer, and are in the gaseous or liquid state at ordinary room temperatures (about 20-28xc2x0 C.). Also preferably, the blowing agent is only partially soluble in the polymer. However, in some embodiments, the blowing agent may be capable of being absorbed by the polymer. Suitable blowing agents include hydrocarbons and halogenated hydrocarbons such as, for example, propane, butane, normal pentane, iso-pentane, heptane, hexanes including iso-hexane, propylene, butylene, neopentane, 1-pentene, cyclobutane, cyclopentane, and difluoromethane. Pentanes are preferred, and a mixture of pentanes is highly preferred. Particularly preferred is a mixture of n-pentane, iso-pentane and cyclopentane, and a preferred ratio is 70% n-pentane, 15% iso-pentane, and 15% cyclopentane.
A blowing agent can be added to the reaction mixture at any time. One or more blowing agents can be dissolved in the styrenic monomers prior to combination of the monomers with the seed suspension, and it is believed that dissolution of the blowing agent in the styrenic monomers provides for improved dispersion of the blowing agent in the polymer, as compared to addition of the blowing agent to the reactor after combination of the monomers with the seed suspension. The improved dispersion of the blowing agent in the polymer may result in improved performance of the polymer during use in some applications.
Alternatively, blowing agents can be added to the reactor separately at any time. In some embodiments, a portion of the blowing agent can be dissolved in the styrenic monomers and a portion can be added to the reactor separately. Selection of the preferred manner of adding the blowing agent may be accomplished by one skilled in the art, and will depend in part upon desired properties of the polymer. Generally, the earlier in the process of the reaction the blowing agent is added, the slower the reaction will proceed and the lower will be the molecular weight of the polymer. However, the inventors have discovered that one or more blowing agents can be added to the seed suspension and the suspension containing the blowing agent maintained at a temperature of about 80xc2x0 C. to about 105xc2x0 C. for several hours, e.g., 2, 3, or 4 hours. Preferably the seed suspension is then allowed to reach the desired reaction temperature, including cooling or heating as necessary, before the reaction mixture is combined with the seed mixture. While it is not intended that the invention be bound by any particular theory, it is believed that maintaining the seed suspension and blowing agent at an elevated temperature for several hours allows the blowing agent to impregnate the seeds and provides an increased reaction rate. Polymeric seeds impregnated by a blowing agent can be referred to as xe2x80x9cexpandablexe2x80x9d polymeric seeds. Expandable polymeric seeds can be used in the processes disclosed herein, in place of conventional polymeric seeds.
For applications requiring an expanded polymer, styrenic copolymers having a blowing agent dispersed therein can be stored until needed, and expanded by heating to a temperature above the boiling point of the blowing agent and above the glass transition temperature (Tg) of the polymer containing the blowing agent.
For some applications, styrenic copolymers formed according to the methods herein may be partially expanded to form xe2x80x9cprepuffxe2x80x9d. xe2x80x9cPrepuffxe2x80x9d, as used herein means polymeric particles or beads having expanding agents incorporated therein and having been partially expanded but capable of being further expanded. Prepuff may be aged, then heated using, for example, steam, to form a molded article. Exemplary methods for forming molded articles using styrenic copolymers and suitable for use with styrenic copolymers prepared using the methods described herein, are described in Ingram et al., xe2x80x9cPolystyrene and Related Thermoplastic Foamsxe2x80x9d, Plastic Foams, Part II, Chapter 10, pp. 531-581, (Marcel Dekker, 1973); and Ingram et al., xe2x80x9cExpandable Polystyrene Processesxe2x80x9d, Addition and Condensation Polymerization Processes, Chapter 33, pp. 531-535 (American Chemical Society 1969), the disclosures of each of which are hereby incorporated herein by reference in their entirety.
In some embodiments, a pre-swelling mixture can be used, as described in U.S. patent application Ser. No. 09/473,606, already incorporated herein by reference.
The term xe2x80x9cswellingxe2x80x9d as used herein, including as used with respect to xe2x80x9cpreswellingxe2x80x9d, is not intended to imply any mechanism, but refers only to an increase in size of the polymeric seeds and/or growth in size of a polymeric particle.
In embodiments of the invention wherein a seed suspension is used, the rate of combination of the reaction mixture with the seed suspension can be controlled, for example, by using a pump. As mentioned, preferably the reaction mixture is added to the seed suspension, the seed suspension having been placed into a reaction vessel. When a pre-swelling mixture is used, the pre-swelling mixture is placed into the reaction vessel, containing the seed suspension, and the reaction mixture is then added. The rate of pumping the reaction mixture into the reactor can be varied intermittently. Such variation can include temporarily halting pumping or decreasing the rate. A regular pattern of variation can be referred to as a xe2x80x9cprofilexe2x80x9d, for example, a pump profile. A pump profile would result if a graphic representation were made of pumping rate as a function of time. For example, a suitable pump profile may resemble stairs, and may be referred to as a xe2x80x9cstepxe2x80x9d profile. Other suitable pump profiles include linear profiles and xe2x80x9csecond order profilesxe2x80x9d, wherein a graphic representation of pump rate as a function of time would approximate a plot of a second-order mathematical function; regular batch additions of reaction mixture; and power law function profiles. In some embodiments, an external control such as a computer program may be used to control the pump rate, and the program may include parameters such as the amount of monomer theoretically present in the reactor at a given time. A feedback apparatus, such as a flow meter, may be used to help in controlling the rate of pumping the mixtures into the reactor. Generally, it is preferred that the amount of monomer in the reactor be about 30 weight percent or less, based on the total weight of the monomer plus polymer, including original polymeric seed plus any polymer formed during reaction, in the reactor, substantially throughout the reaction until all of the monomer has been added to the reactor. More preferably, the amount of monomer is about 20 weight percent or less.
Additives that may be present in the reaction mixture include waxes. The use of waxes in polymerization processes is known to those skilled in the art. Suitable waxes for use in the processes of the invention include microcrystalline waxes and Fisher-Tropsch waxes having appropriate melting points. It has been discovered that some waxes, when added in particulate form, may form regions of wax that are larger in volume than the initial size of individual wax particles. The formation of large regions of wax may be undesirable for some applications. While it is not intended that the invention be bound by any particular theory, it is believed that waxes may provide nucleation sites for the formation of cells when the polymer includes a blowing agent and is later expanded.
In some embodiments, styrenic copolymers formed according to the invention comprise polymeric particles having a core and a shell. The core of such a polymeric particle comprises a polymeric seed. The shell comprises, as polymerized units, from about 50 to about 85 weight percent one or more acrylic monomers, and from about 15 to about 50 weight percent of one or more styrenic monomers.
A general procedure for forming styrenic copolymers according to the processes disclosed herein, including a polymerization cycle and a finishing cycle, follows. A suspension containing deionized water, polymer seeds, a suspending agent, a surfactant, and an antifoaming agent is placed within an appropriately-sized reactor, and heated to an elevated temperature sufficient to effect the beginning of polymerization. Generally, the volume of the monomer emulsion tank reactor is at least about 1.5 times, preferably at least about 2 times, the total final volume of all reaction components. Preferably the suspension is heated to about 35xc2x0 C., more preferably about 40xc2x0 C. A reaction mixture including one or more styrenic monomers, one or more acrylic monomers, one or more initiators and optionally one or more blowing agents, is added.
A separate initiator mixture may be used and, if used, preferably includes one or more initiators dissolved in a styrenic monomer. A particularly preferred initiator mixture includes styrene containing a peroxide initiator dissolved therein, such as benzoyl peroxide. The separate initiator mixture is added to the suspension gradually, preferably using a pump, over about 5-20 minutes, preferably about 10-15 minutes. The combined mixture, which includes the reaction mixture and optional initiator mixture, and suspension are held at the elevated temperature for at least about 45 minutes, preferably at least about 50 minutes, more preferably at least about 60 minutes, even more preferably at least about 70 minutes and still more preferably at least about 80 minutes. If desired, one or more samples of the combined mixture and suspension may be removed, preferably after about 1 hour of heating, for analysis such as molecular weight determination, residual monomer content analysis, or microscopy.
A reaction mixture including one or more styrenic monomers, one or more acrylic monomers, one or more initiators and optionally one or more blowing agents, is added to the seed suspension, to form a polymerization mixture. The reaction mixture is preferably added gradually, e.g., using a pump. Preferably, the reaction mixture is initially added at a rate of about 0.5 lbs./min or more, more preferably about 0.6 lbs./min or more, even more preferably about 0.66 lbs./min or more. Preferably, for about one hour, the rate of addition of the reaction mixture to the seed suspension is less than about 1 lbs./min. If the reaction mixture is added too rapidly during about the first hour, the forming polymer may coagulate. After about one hour, the rate may be increased to about 1 lbs./min or more, preferably about 1.20 lbs./min or more, and more preferably about 1.22 lbs./min.
A finishing mixture is preferably then added. The finishing mixture includes deionized water, a suspending agent, and one or more surfactants. After the finishing mixture has been added, the reaction vessel containing the combined polymerization mixture and finishing mixture is sealed and purged with an inert gas, preferably nitrogen. Preferably, the inert gas is added to pressurize the vessel to 5 psig nitrogen. The combined mixtures are agitated for about 30 minutes. The agitation rate is not critical, and one skilled in the art can determine an appropriate agitation rate to ensure adequate mixing. Any remaining reaction mixture not yet added to the reaction vessel is then added gradually but preferably at an increased rate, such as about 1.5 lbs./min or more.
If desired, a reaction mixture excluding the blowing agents may be added to the seed suspension to form a polymerization mixture, which is then polymerized to form polymer beads. The beads can then be isolated and optionally screened to remove undersized, oversized, and/or clustered beads. The screened beads can then be re-suspended in water and impregnated with one or more blowing agents. Such a procedure may be referred to as a xe2x80x9ctwo-stepxe2x80x9d process, to refer to the addition of an additional step of removing and screening the polymer beads before proceeding with addition of a blowing agent.
After the addition of the reaction mixture to the vessel is completed, the vessel contents are heated relatively quickly, preferably at a rate of about 0.5xc2x0 C./min or more, more preferably about 1xc2x0 C./min or more, and preferably not higher than about 3xc2x0 C./min, to a temperature of about 113-116xc2x0 C. While the vessel is being heated, the pressure of the vessel is monitored. The pressure preferably does not increase above about 125 psig. If the pressure rises to about 135 psig, the temperature should be reduced by about 6-10xc2x0 C., e.g., to about 108xc2x0 C. The vessel is maintained at the increased temperature for about 7 hours. The vessel is then cooled to about 38xc2x0 C. or less, and the contents are transferred to a vessel such as a batch-out tank. Because a substantial amount of foaming may have occurred, it is preferred that as little foam as possible be transferred with the vessel contents.
The transferred contents are acidified to a pH of about 2.0 or less. A product is then recovered from the acidified vessel contents by drying. Drying may be accomplished using a conventional drying instrument known for use in drying polymeric materials. The product will be in the form of particles. If desired, the particles can be screened. The particles may then be stored, or may be used to form a molded part. Storage conditions are not critical, and the particles may be stored at room temperature in a closed container. Molded parts made from the compositions disclosed herein may be used to form patterns for use in lost foam processes using molten metals such as iron.
Lost foam molding processes are described, for example, in Expandable Patteni Casting, Vol. 1 (American Foundrymen""s Society, 1994), and in U.S. Pat. Nos. 4,028,285; 4,113,672; 3,755,209; 3,975,327; 4,281,067; and 4,286,071, the disclosures of each of which are hereby incorporated herein by reference in their entirety.
For use in lost foam molding processes, styrenic copolymers prepared according to the methods described herein and in the form of particles having diameters of at least about 100 microns are preferred. Also, it is generally preferred to use polymeric particles having diameters of about 600 microns or less in lost foam molding processes. Preferably, the copolymeric particles have molecular weights of at least-about 150,000, and more preferably at least about 170,000. Also preferably, the copolymeric particles have molecular weights of about 350,000 or less, more preferably about 320,000 or less, and even more preferably about 300,000 or less.

Processes for forming styrenic copolymers


The present invention generally relates to an air control module unit for a portable pneumatic tool, more particularly, to an air control module unit that actuates a valve stem inside an air inlet block of the air inlet module by a correspondent air bleed valve in the air actuation module. The air control module unit for a portable pneumatic tool comprising: an air inlet module, which has at least one valve stem inside an air inlet block, the air inlet block having plug screws on both ends towards the valve stem and one plug screw on the intersectional direction of the valve stem with at least one air inlet port opening for hooking up the compressed air; an air actuation module having a bleed valve inside the valve block; a plurality of flexible air hoses with a plurality of dimensions and being prepared for connecting the air inlet module and air actuation module; and a plurality of hose connectors and rubber seats with a plurality of types for connecting the air inlet module and the air operation module.

1. Field of the Invention
The present invention generally relates to an air control module unit for portable pneumatic tools, more particularly, to an air control module unit that actuates a valve stem inside an air inlet block of an air inlet module by an air bleed valve in an air actuation module.
2. Description of the Prior Art
The prior art "Portable Pneumatic Tool assembled with Module Units" U.S. Pat. No. 6,149,356, with the concept to divide the portable pneumatic tools in basically four modules, i.e. air inlet module, air actuation module, air directional module, and air operation module, which are connected by air hoses in between, then, installed inside the clam shell housings, as shown in FIG. 12 and FIG. 13. The housings can be two symmetric half shells (clam shell) or several partially cutaway shells made of sheet metal forming or composite material injection molding. It has the benefits to build the portable pneumatic tools economically and pursues to apply this invention to build the tool more flexible and ergonomic.
As shown in FIG. 14, which is a sectional drawing showing an air actuation valve of the prior art, and the air actuation valve 3 consists of a valve block 31, a valve stem 32, two hose connectors 33, one spring 35, and one plug screw 34, in order to allow sufficient flow of compressed air passing by and enter the operation module, the prior art cannot be minimized to ideal compact dimensions to meet the satisfaction and comfort of the hand held housing design.
However, while applying the up-mentioned prior art to build portable pneumatic tools, especially pistol grip type of air tools, the inventor has found the drawbacks thereof.
Since the air passage of the prior art should be big enough to allow sufficient compressed air go through while keeping the hand held portion of the housing to fit the palm grip comfortably, but all efforts have been done in vain while installing the air actuation module into the hand grip portion of the half shell housings, the inventor has then developed and invented the present new air control module unit to actuate the valve stem inside the air inlet block of the air inlet module remotely by air bleed valve in the air actuation module. The air actuation module is functioned by air bleed valve and correspondent air bleed hose which are all in miniature dimensions. The air inlet module and air actuation module are separated and connected remotely by air hoses in between. This mechanism will make the hand held portion retains only the air actuation module, air bleed hose, and air hoses for leading the compressed air to the operation module and easy to make the half shell housings fit the palm grip ergonomically. It will not only provide the great interchangeability of the air control module units for most of portable pneumatic tools to reduce production and inventory cost and making tool service and assembly faster and easier, but also allow more versatility for assembling with additional electro-mechanical devices and sensors with digital displays, etc. for various requirements of functions and applications.
Therefore the inventor has developed the new structure of the air control module unit to solve the problems mentioned above and will be described as follows.

Air control module unit for portable pneumatic tool


A technique is provided which enables proper correction of optical characteristics in accordance with change in ambient temperature.

1. Field of the Invention
The present invention relates to an optical beam scanning device which causes a luminous flux from a light source to scan a photoconductive surface of a photoconductor in the main scanning direction, and particularly a technique to realize improvement in optical characteristics.
2. Description of the Related Art
Traditionally, for an optical beam scanning device which shapes a luminous flux from a light source into a predetermined sectional shape and causes the luminous flux to scan in a predetermined direction, there is known a technique of providing a lens or diffractive optics with negative power that passes luminous fluxes from plural light sources in a pre-deflection optical system, thereby changing the beam spacing in a direction of restraining color shift which occurs in an image forming apparatus having the optical beam scanning device when a temperature change occurs (JP-A-2005-221870).
Also, there is known a technique of providing a diffractive optics which corrects chromatic aberration of magnification in a pre-deflection optical system, thus preventing the length of a scanning line in the main scanning direction from being varied by a change in wavelength (JP-A-2006-171117).
Moreover, a configuration is known in which a scanning optical device having a refraction surface and a diffraction surface is provided in a post-deflection optical system, the radius of curvature in the sub scanning direction on at least one refraction surface of the scanning optical device is continuously changed from the optical axis toward outside in accordance with the main scanning direction, and the diffraction power in the sub scanning direction of at least one diffraction surface is continuously changed from the optical axis toward outside in accordance with the main scanning direction (JP-A-2002-221681).
However, in the technique descried in the JP-A-2005-221870, the number of lenses arranged in the pre-deflection optical system must be increased.
Also, in the techniques described in JP-A-2006-171117 and JP-A-2002-221681, since correction of color shift due to thermal expansion of the image forming apparatus is considered with respect to the sub scanning direction, there is a problem that color shift occurs due to a temperature rise in the image forming apparatus.

Optical beam scanning device restraining beam position error due to temperature change with diffraction grating and image forming apparatus using the same

Abstract: An optical beam scanning device capable of causing a luminous flux from a light source to scan a photoconductive surface of each of plural photoconductors in a main scanning direction, includes: a polygon mirror 80 which reflects and deflects an incident luminous flux by plural reflection surfaces arrayed in a direction of rotation, and thereby causes the incident luminous flux to scan in the main scanning direction; and a post-deflection optical system A which includes plural optical devices and which guides the luminous flux reflected and deflected by each of the plural reflection surfaces in the polygon mirror 80, to a photoconductive surface of a photoconductor to which the luminous flux should be guided. Of the plural optical devices forming the post-deflection optical system A, in at least one optical device on which a principal ray of the luminous flux which should be guided to each of the plural photoconductors becomes incident at different incident positions from each other in a sub scanning direction orthogonal to the main scanning direction, a diffraction grating is formed at least on one of an incident surface and an exit surface of the luminous flux in the optical device.


The semiconductor light emitting device includes a semiconductor substrate (1), a first conductivity type first cladding layer (2) deposited on the semiconductor substrate (1), an active layer (4) deposited on the first cladding layer (2), and the second conductivity type second cladding layer (6) deposited on the active layer (4). The first and the second cladding layers (2, 6) are made of the II/VI-compound semiconductors including at least one kind of II group elements such as Zn, Hg, Cd, Mg and at least one kind of VI group elements such as S, Se, Te. The lattice mismatching .DELTA.a/a (%) between at least one of the first cladding layer (2) and the second cladding layer (6) and the substrate is set within the range of -0.9%.ltoreq..DELTA.a/a.ltoreq.0.5% (reference symbols a and a.sub.c represent the lattice constant of the semiconductor substrate and the lattice constant of at least either of the first and second cladding layers, and .DELTA.a is obtained from .DELTA.a=a.sub.c -a).

1. Fields of the Invention
The present invention relates to a semiconductor light emitting device in which at least an active layer and a cladding layer on a substrate are made of II/VI-compound semiconductors.
2. Related Art
Since it is requested that an optical disc and a magneto-optical disc is recorded and/or reproduced with high density and high resolution, a demand for a semiconductor laser which emits green or blue laser light is more and more increased.
II/VI-compound semiconductors made of II group elements such as Zn, Hg, Cd, Mg and VI group elements such as S, Se, Te are promising as materials to form semiconductor light emitting devices such as the semiconductor lasers, light emitting diodes or the like. In particular, ZnMgSSe mixed crystal can be grown on a GaAs substrate and is suitable for a guiding layer and a cladding layer used when a blue semiconductor laser is fabricated (see "Electronics Letters 28 (1992) p. 1798").
When this kind of a II/VI-compound semiconductor light emitting device such as ZngSSe compound semiconductor is formed as the cladding layer, the GaAs substrate and the ZnSe substrate are used as semiconductor substrate on which the cladding layer and the active layer are epitaxially grown because they are excellent in crystallinity and are now commercially available on the market. In this case, in order that the semiconductor light emitting device can emit laser light with a desired short wavelength highly efficiently, the cladding layer that is eptaxially grown on the GaAs substrate directly or via a buffer layer should be formed as a compound semiconductor layer with an excellent crystallinity.
Therefore, semiconductor light emitting devices have hitherto been considered that a lattice constant of the cladding layer is strictly agreed with that of the GaAs substrate. For this reason, values x and values y of Zn.sub.x Mg.sub.1-x S.sub.y Se.sub.1-y cladding layer should be selected very strictly so that compositions cannot be selected substantially with freedom and that composition should be selected strictly. Thus, the semiconductor light emitting devices cannot be fabricated satisfactorily.
Moreover, in the II/VI-compound semiconductor light emitting devices, a p-type electrode obtained when a semiconductor laser using an electrode formed on the opposite side of the substrate, particularly, n-type substrate is fabricated generates much heat and luminous intensity is therefore deteriorated.

Method of fabricating of light emitting device with controlled lattice mismatch


Sheets are separated one-by-one from their stack placed in a holder by a sheet feed roller and a separation member provided in an inclined separation plate. The separation member can be a flat metal plate, and possibly includes a base portion, arm portions extending from the base portion, separation protrusions provided on the arm portions and capable of contacting a sheet, and elastic legs extending from the base portion. The arm portions, the separation protrusions, and the elastic legs can be arranged along a sheet feeding direction. The inclined separation plate may be provided with window holes on a central portion with respect to a direction perpendicular to the sheet feeding direction. The window holes can allow each separation protrusion or two or more separation protrusions to protrude toward the front surface of the inclined separation plate. Bridge portions can be provided between adjacent window holes. The bridge portions may strengthen the bending stiffness of the inclined separation plate in the direction perpendicular to the sheet feeding direction, and thus the separation protrusions are allowed to protrude only by a specified amount as designed.

1. Technical Field
Aspects of the invention relate to a sheet feeder capable of separating sheets one-by-one from a stack of the sheets in a holder by a sheet feed roller and a separation member having elasticity.
2. Related Art
Image recording apparatuses such as a printer, a copier, a facsimile machine, generally include a sheet feeder that separates cut sheets (recording sheets) one-by-one and feeds them to an image recording unit.
In Japanese Laid-Open Patent Publication No. 2002-173240, cut sheets are accommodated substantially horizontally in an open-top box shaped cassette body, inclined separation face plates are provided at established intervals in a sheet width direction and on a downstream side of the cassette body with respect to a sheet feeding direction, and a sheet feed roller is provided in an upper portion of the cassette body and rotates while pressing a surface of an uppermost sheet of the stack. The sheets are separated one-by-one from the stack by the sheet feed roller in cooperation with the inclined separation faceplates, and fed via a U-turn path (a U-shaped conveying path) toward an image recording unit disposed in the upper portion of the cassette body.
Japanese Laid-Open Patent Publication No. 2004-149297 discloses a sheet feeder having an inclined wall designed to place a stack of sheets diagonally downward, a bottom plate provided in a lower portion of the inclined wall and having an obtuse angle with respect to the inclined wall and extending in a sheet width direction, and a sheet feed roller that feeds an uppermost sheet of a stack held between the bottom plate and the inclined wall by pressing against the sheet. The bottom plate is provided with a sheet separating portion made of a stainless steel. The sheet separating portion is comprised of protrusions that are arranged at established intervals in a sheet feeding direction, arm portions that support the protrusions at both sides, and a base portion that supports the arm portions continuously. The protrusions are set to protrude by a specific amount from long holes formed along the sheet feeding direction in a metal holder fixed to the bottom plate. When an uppermost sheet is pressed and fed by the sheet feed roller, the uppermost sheet presses the protrusions at its lower edge, the protrusions move down from the long holes of the holder due to the deformation of the arm portions by elasticity. However, sheets except for the uppermost sheet are held down by the protrusions protruding from the long holes and thus the uppermost sheet only is separated and fed.
However, in the structure disclosed in Japanese Laid-Open Patent Publication No. 2002-173240, a large gap exists between a position where the inclined separation face plate is provided and a position where the inclined separation face plate is not provided, and a sheet being fed is likely to be creased at its end portion. On the other hand, if the sheet separating portion formed of metal sheet disclosed in Japanese Laid-Open Patent Publication No. 2004-149297 is provided at the inclined separation face plates located on the downstream side of the cassette body disclosed in Japanese Laid-Open Patent Publication No. 2002-173240, the holder may be deformed due to a pressing force generated when the sheet is fed by the sheet feed roller, the protrusions may greatly protrude from the long holes in the holder, the sheet may be strongly rubbed by the protrusions and a surface of the sheet may be easily damaged.
Especially when glossy paper, suitable for photo image recording, is fed from a stack of a few glossy papers held in a deep cassette capable of holding a number of sheets toward a U-turn path having small radius of curvature, the glossy paper may be strongly rubbed by the protrusions because the paper is inherently hard to bend and returns to its flat state. As a result, a surface (recorded surface) of the glossy paper may be easily damaged. Furthermore, if the protrusions are shaped in the form of a claw, scratches on the surface of the sheet may appear and be deep.


An equipment with pivoting handles. The equipment includes a support and a pivoting handle that are assembled by at least one pivot pin, the pivoting handle being able to rest on at least one surface of the support. The handle includes at least one bearing surface and the equipment includes at least one pad of elastic material arranged to be compressed against the support by the bearing surface when the handle is resting on the surface of the support. The equipment may be applied for example to suspended equipment for aircraft consoles.

The invention relates to an equipment with a pivoting handle, and in particular to a suspended equipment for an aircraft console. The equipment has to be able to be fitted into a system and removed from this system, for example to be updated or replaced. In the preferred case of an aircraft console, the equipment installed on the console is advantageously mounted locked suspended via its front face on the console and has a pivoting handle to make it easier to install.
Once the equipment has been installed in a system, the pivoting handle is folded back. When an operator wishes to extract this equipment from the system, particularly from a system with significant constraints on small size, he often finds the handle jammed, and extraction is then often performed with damage to the equipment and to any nearby equipment that might be present in the same system, by using tools of the lever type in order to access the handle. There are many reasons why the handle might jam, for example a tight space constraint forcing various equipments to be fitted into one and the same system in the most compact way possible, or alternatively misalignment leading to the handle jamming as it is installed in the system.

Equipment with a pivoting handle, in particular to be suspended in an aircraft console


Systems and methods for selectively forwarding full header information in email messages are presented. When, an email message is received by a user, and the user chooses to forward the received email message, an option is provided to the user to either include the full header information of the received email in the forwarded email, or to not include the full header information of the received email in the forwarded email.

In many email systems, when a user receives an email message, the user is provided an option that permits the user to read the received email message. Typically, if the user chooses to read the received email message, then the received email message is displayed to the user in an email read window. In many email systems, when a recipient receives an email message, much of the standard header information is generally hidden from the recipient. Thus, a recipient often only sees a sender's name and/or email address, a subject line, and names and/or email addresses of other recipients if, for example, the email message is courtesy copied (cc) to other recipients or sent to multiple recipients.
From the email read window, the user is usually provided a number of options including the option to delete the email message, reply to the email message, print the email message, or forward the email message to a third person. When the user chooses to forward the received email message to a third person, the full header information of the received email message is normally removed, and a truncated header is placed in the message. The truncated header typically includes the name and email address of the original sender of the message, the subject line, the date of forwarding, and the person forwarding the email. Thus, the truncated header removes much of the information that is originally present in the full header information (e.g., return path, intermediate hops, date, time, content class, content type, subject, object linking and embedding (OLE) protocols used, multi-purpose Internet mail extensions (MIME), date sent, message identifier (ID), attachments, thread topic, thread index, transport neutral encapsulated format (TNEF) information, thread index, sender name, sender email address, reply-to address, content-transfer-encoding information, date received, time received, recipient names, recipient email addresses, attachment type, file name of attachment, etc.). The truncation of much of the full header, therefore, simplifies the header information.
Unfortunately, the truncated header is insufficient for certain purposes, such as reporting email abuse or tracing email for security purposes. Thus, when a recipient of an email wishes to report email abuse or wishes to trace an email, a systems administrator or security personnel typically needs the full header information of the received email.
For these types of situations where the full header information is needed, different options for viewing the email message are selected until the full header information is visible. Once the full header information is visible, the user typically has no other option but to copy the full header information into a buffer, and manually paste the full header information into an email message to send to security personnel or a systems administrator.
The manual cutting and pasting of the full header information is an inconvenient process that is also prone to human error. There is, therefore, a need in the art to address this deficiency.

System and method for forwarding full header information in email messages

AT&T Delaware Intellectual Property, Inc.


Methods and systems for autonomously steering a moving vehicle are disclosed. A processor determines a longitudinal velocity, a longitudinal acceleration, a lateral acceleration, and a yaw rate of the vehicle. The processor estimates, based on the longitudinal velocity, lateral acceleration, and yaw rate of the vehicle, a change in lateral velocity over time. The processor estimates, based on the change in the lateral velocity over time, the yaw rate, a distance between the front axle of the vehicle and a center of gravity of the vehicle, and a distance between the rear axle of the vehicle and the center of gravity of the vehicle, a lateral front velocity of the vehicle and a lateral rear velocity of the vehicle. Using calculations, a state estimation model for the vehicle is updated by the processor using a lateral acceleration bias. The updated state estimation model is used to autonomously steer the vehicle.

In recent years, transportation methods have changed substantially. This change is due in part to a concern over the limited availability of natural resources, a proliferation in personal technology, and a societal shift to adopt more environmentally friendly transportation solutions. These considerations have encouraged the development of a number of new flexible-fuel vehicles, hybrid-electric vehicles, and electric vehicles.
While these vehicles appear to be new they are generally implemented as a number of traditional subsystems that are merely tied to an alternative power source. In fact, the design and construction of the vehicles is limited to standard frame sizes, shapes, materials, and transportation concepts. Among other things, these limitations fail to take advantage of the benefits of new technology, power sources, and support infrastructure.
Contemporary methods of estimating the state of a vehicle typically focuses on main vehicle states estimation, such as longitudinal/lateral velocity and acceleration. Such methods are focused on lower-level chassis control, e.g., traction control, stability control, etc. Typically, the states of the system are a bicycle model lateral velocity and yaw rate.

Vehicle control system using nonlinear dynamic model states and steering offset estimation


A dock bracket assembly has a rod supporting bracket and a rod receiving bracket with a N-shaped slot for receiving a section bracket rod, due to the slot. The bracket rod is used with the slot either side of adjoining sections of a dock being constructed.

Every boat owner, with a property having water frontage desires, to have a dock. With the dock, the boat owner has control of the time and place for putting the boat in the water. With such control, the boat owner can greatly increase the enjoyment that comes with owning a boat.
Construction of a dock is a major project. Much work in the water is required. The special tools and equipment required to support this work in the water add greatly to the cost of producing a dock. Any device, which reduces the cost or simplifies the construction of a dock, can provide many great advantages.
Likewise, there is an advantage for the owner of a marina which services a number of boats to have at least one dock. As the number of docks increases, cost savings and efficiency of construction become more important.
In order to reduce the cost of building a dock, it is very desirable to reduce the required time in the water. No efficient way of accomplishing, this reduction of time in the water now required for dock construction, is available.
Docks are customarily made in sections and held together with clamps. With different clamps, it is required for safety and efficiency to assemble the dock in the water. However, if safety and efficiency can be maintained with great reductions in the assembly process and water, great advantages are obtained.
If the dock is assembled without entering the water, it is required to hold a dock section in a vertical position for a period of time as it is attached to an adjoining section of a dock. Since the dock section is so large, a strong wind can substantially interfere with the dock section in that position. The dock brackets of the prior art cannot withstand such pressure.


A remote client interface to manipulate OLAP and other reports is described. A Web client or other thin client may access an intelligence server via an intermediate network server. The network server may translate between HTML or other code supplied by the client, in order to access a database serviced by the intelligence server in all its functionality. For instance, a user may clink onto a linkable URL to access a stored report run against the remote database, and perform operations on that report, such as doing a table pivot, page down, running totals or averages, or other functions. Multiple users may access the report and other data resources using different interfaces.

The deployment of large scale databases in commercial organizations and others has led to improvements in sales forecasting, inventory control, and other strategic predictions. One prevailing technique is to run analytic reports against databases, for instance online analytic processing (OLAP)-compliant databases, to identify trends and other significant information.
However, the use of such engines may not be convenient or user friendly. For instance, many OLAP-based intelligence engines may require a manager or other user to be seated in front of a workstation equipped with a standard query language (SQL) or other database-compatible software package in order to initiate, view, modify, or store reports. Productivity might be improved if the users of such systems could obtain easier and less cumbersome access to the query engines, reports and other outputs. Other problems exist.

System and method for remote manipulation of analytic reports


A circuit for operating a polyphase dc motor includes first circuitry for determining when the back emf of the floating driving coils crosses zero. A first counter counts a time period between a first set of zero crossings, and a second counter is loaded with the count reached by the first counter. The second counter counts a time period between a subsequently occurring set of zero crossings. If the second counter reaches zero before the occurrence of a third zero crossing, a warning signal is generated. A method for determining if a deceleration rate of a polyphase dc motor exceeds a predetermined threshold includes measuring a first period between a first set of zero crossings of the back emf of the floating driving coils, and comparing the measurement of the first period with a subsequent period between a subsequent set of zero crossings. If the subsequent period is larger than the first period by a predetermined amount a warning signal is produced. The first period is measured by counting up from zero at a first predetermined rate from a first zero crossing until a second zero crossing occurs. The comparison of the measurement of the first period with a subsequent period is done by counting down at a second predetermined rate from the count reached in the up count when the second zero crossing occurred. And the warning signal is produced if the down count reaches a zero before a third zero crossing occurs.

1. Field of the Invention
This invention pertains to improvements in motor driving and controlling circuitry, and more particularly, to an improved circuit and method for detecting deceleration rates of a brushless, sensorless, dc motor, or the like, and for providing warnings or other responses in response to a breach of a desired deceleration rate profile.
2. Description of the Prior Art
Although the present invention pertains to polyphase dc motors, in general, it finds particular application in conjunction with three phase dc motors, particularly of the brushless, sensorless type. Three phase brushless, sensorless dc motors are becoming especially popular, due to their reliability, low weight, and accuracy.
Motors of this type can typically be thought of as having a stator with three coils connected in a "Y" configuration, although actually, a larger number of stator coils are usually employed with multiple motor poles. Typically, in such applications, eight pole motors are used having twelve stator windings and four N-S magnetic sets on the rotor, resulting in four electrical cycles per revolution of the rotor. The stator coils, however, can be analyzed in terms of three "Y" connected coils, connected in three sets of four coils, each physically separated by 90.degree.. In operation, the coils are energized in sequences in each of which a current path is established through two coils of the "Y", with the third coil left floating. The sequences are arranged so that as the current paths are changed, or commutated, one of the coils of the current path is switched to float, and the previously floating coil is switched into the current path. Moreover, the sequence is defined such that when the floating coil is switched into the current path, current will flow in the same direction in the coil which was included in the prior current path. In this manner, six commutation sequences are defined for each electrical cycle in a three phase motor.
In the past, during the operation of a such polyphase dc motor, it has been recognized that maintaining a known position of the rotor is an important concern. There have been various ways by which this was implemented. The most widely used way, for example, was to start the motor in a known position, then develop information related to the instantaneous or current position of the rotor. One source of such instantaneous position information was developed as a part of the commutation process, and involved identifying the floating coil, and monitoring its back emf, that is, the emf induced into the coil as it moves through the magnetic field provided by the stator.
When the voltage of the floating coil crossed zero (referred to in the art as "a zero crossing"), the position of the rotor was assumed to be known. Upon the occurrence of this event, the rotor coil commutation sequence was incremented to the next phase, and the process repeated. The assumption that the zero crossing accurately indicated the rotor position was generally if the motor was functioning properly.
As brushless, sensorless dc motors become more and more in demand, they are being increasingly used in such applications as in disk drives for use in computer applications, such as floppy disk, hard disk, CD ROM, and other similar applications. One of the main advantages provided by such brushless, sensorless motors is the absence of brush elements. This reduces the number of parts in the motor, reduces the mean time between failure of a particular motor, and has no sparking or other undesirable spurious emf generation properties.
In addition, brushless, sensorless motors are finding widespread use in robotics applications. This is due, in part, to the above listed advantages of such motors. It can be seen, furthermore, that the absence of brushes in the motors used in robotics arms, for example, enables their use in hazardous or explosive environments, in contrast to prior art devices.
In any such application, however, many factors exist that may produce an undesirable deceleration of the motor. For example, in the disk drive applications described, motor bearings may seize and cause the motor to decelerate. In disk drives that may be employed, for instance, in lap top computers, a bump or jar to the computer may cause the heads of the disk drive to bind, resulting in an undesired frictional force on the disk and causing an undesirable deceleration of the motor itself.
In robotics applications, a robot arm may encounter an unexpected object or an object in an unexpected place along the path of its travel. This may cause an undesirable deceleration of the motor, and, if no corrective steps are taken, may result in the current within the motor coils increasing to the point of damaging or destroying the motor. Alternatively, the robot arm may damage the object with which it comes in to contact. This is particularly disadvantageous in such applications as automotive assembly, and the like, in which relatively expensive objects may be seriously damaged by unintended contact with the robot arm.

Circuit and method for detecting deceleration rates of a polyphase DC motor


The present invention provides a level conversion circuit. The circuit is as follows: A cathode of a first equivalent diode is connected to a reference voltage, and an anode of the first equivalent diode is separately connected to a gate of a first switching transistor and a first end of a first capacitor; a second end of the first switching transistor and a first end of a second switching transistor are connected together; a second end of the second capacitor is separately connected to a cathode of a second equivalent diode and a gate of the second switching transistor; and a second end of the second switching transistor is grounded, and an anode of the second equivalent diode is connected to a reference voltage.

In a pipeline analog-to-digital converter, a level conversion circuit is usually used to implement conversion between a high level signal and a low level signal. With an increasingly high requirement for a speed indicator of the pipeline analog-to-digital converter, improving a speed of the level conversion circuit becomes one means of improving a speed of the pipeline analog-to-digital converter.
As shown in FIG. 1, a level conversion circuit used in the prior art includes a PMOS (P-type metal-oxide-semiconductor) transistor T1, a PMOS transistor T2, an NMOS (N-type metal-oxide-semiconductor) transistor T3, an NMOS transistor T4, and a phase inverter, where both a source of T1 and a source of T2 are connected to a power supply positive electrode AVDD, a drain of T1 is connected to a gate of T2, a gate of T1 is connected to a drain of T2, a gate of T3 is connected to an output end clk of a square wave generation circuit, a source of T3 is connected to a source of T4 and is grounded, a drain of T3 is connected to the drain of T1, a gate of T4 is connected to the gate of T3 by using the phase inverter, and a drain of T4 is connected to the drain of T2 and is used as an output end clkout of the level conversion circuit for connecting to a load. A specific working principle is as follows: It is assumed that a value of AVDD is 2 V, a lowest voltage value of a signal output by the square wave generation circuit is 0 V, and a highest voltage value is 1 V. When clk=0 V, a gate voltage of T3 is 0 V, and T3 is cut off, whereas a gate voltage of T4 is converted into 1 V by using the phase inverter and therefore T4 is conducted. In this case, clkout=0 V. In this case, T1 is conducted because a gate voltage of T1 is less than a source voltage of T1; T2 is cut off because a gate voltage of T2 is AVDD=2 V. When clk=1 V, T3 is conducted because the gate voltage of T3 is greater than a source voltage of T3, and T4 is cut off. A drain voltage of T3 and the gate voltage of T2 are 0. T2 is conducted because the gate voltage of T2 is less than a source voltage of T2. In this case, clkout=AVDD=2 V, and T1 is cut off. In this way, level signal conversion is completed.
However, in the foregoing implementation process, when clk changes from zero to a highest voltage, states of T1, T2, and T3 change in the following sequence: first T3 is conducted, then T2 can be conducted, and finally T1 changes from a conducted state to a cut-off state. That is, in a process in which T3 changes from a cut-off state to a conducted state, a status in which both T3 and T1 are conducted exists. Therefore, the drain voltage of T3 cannot immediately change to 0 V but instead, gradually changes from an intermediate value of AVDD to 0 V. As a result, a conducting speed of T2 slows down, and further a speed at which clkout changes from 0 to AVDD becomes slow. That is, a conversion speed of the level conversion circuit is decreased.


A method for removing impurities from a mother liquor comprising a carboxylic acid, a metal catalyst, impurities by (a) evaporating the mother liquor comprising a carboxylic acid, the metal catalyst, impurities, water and a solvent in a first evaporator zone to produce a vapor stream and a concentrated mother liquor stream; (b) evaporating the concentrated mother liquor stream in a second evaporator zone to form a solvent rich stream and a super concentrated mother liquor stream; (c) separating organic impurities with a water-solvent solution from the super concentrated mother liquor in a solid-liquid separation zone to form an aqueous stream and a second aqueous stream; (d) mixing in a mixing zone water and optionally and extraction solvent with the aqueous stream and second aqueous stream to form an aqueous mixture; and (e) adding an extraction solvent to the aqueous mixture in an extraction zone to form an extract stream and a raffinate stream.

Terephthalic acid is commercially produced by oxidation of paraxylene in the presence of a catalyst, such as, for example, Co, Mn, Br and a solvent. Terephthalic acid used in the production of polyester fibers, films, and resins must be further treated to remove impurities present due to the oxidation of paraxylene.
Terephthalic acid (TPA) is an intermediate in the production of polyesters for plastics and fiber applications. Commercial processes for the manufacture of TPA are based on the heavy-metal catalyzed oxidation of p-xylene, generally with a bromide promoter in acetic acid solvent. Due to the limited solubility of TPA in acetic acid under practical oxidation conditions, a slurry of TPA crystals is formed in the oxidation reactor. Typically, the TPA crystals are withdrawn from the reactor and separated from the reaction mother liquor using conventional solid-liquid separation techniques. The mother liquor, which contains most of the catalyst and promoter used in the process, is recycled to the oxidation reactor. Aside from the catalyst and promoter, the mother liquor also contains dissolved TPA and many by-products and impurities. These by-products and impurities arise partially from minor impurities present in the p-xylene feed stream. Other impurities arise due to the incomplete oxidation of p-xylene resulting in partially oxidized products. Still other by-products result from competing side reactions in the oxidation of p-xylene to terephthalic acid.
The solid TPA crystals obtained by solid-liquid separation are generally washed with fresh solvent to displace the major portion of the mother liquor and then dried to remove most of the acetic acid solvent. The dried, crude TPA crystals are contaminated with impurities that were present in the mother liquor since these impurities are co-precipitated with the TPA crystals. Impurities are also present due to occlusion in the TPA crystal structure and due to incomplete removal of the mother liquor by the fresh solvent wash.
Many of the impurities in the mother liquor that are recycled are relatively inert to further oxidation. Such impurities include, for example, isophthalic acid, phthalic acid and trimellitic acid. Impurities, which undergo further oxidation are also present, such as, for example, 4-carboxybenzaldehyde, p-toluic acid and p-tolualdehyde. The concentration of oxidation inert impurities tends to accumulate in the mother liquor. The concentration of these inert impurities will increase in the mother liquor until an equilibrium is reached whereby the amount of each impurity contained in the dry TPA product balances its rate of formation or addition to the oxidation process. The normal level of impurities in crude TPA makes it unsuitable for direct use in most polymer applications.
Traditionally, crude TPA has been purified either by conversion to the corresponding dimethyl ester or by dissolution in water with subsequent hydrogenation over standard hydrogenation catalysts. More recently, secondary oxidative treatments have been used to produce polymer-grade TPA. Irrespective of the method used to purify TPA to render it suitable for use in polyester manufacture, it is desirable to minimize the concentrations of impurities in the mother liquor and thereby facilitate subsequent purification of TPA. In many cases, it is not possible to produce a purified, polymer-grade TPA unless some means for removing impurities from the mother liquor is utilized.
One technique for impurity removal from a recycle stream commonly used in the chemical processing industry is to draw out or "purge" some portion of the recycle stream. Typically, the purge stream is simply disposed of or, if economically justified, subjected to various treatments to remove undesired impurities while recovering valuable components. One example is U.S. # 4,939,297 herein incorporated by reference. The amount of purge required for control of impurities is process-dependent; however, a purge amount equal to 10-40% of the total mother liquor is usually sufficient for TPA manufacture. In the production of TPA, the level of mother liquor purge necessary to maintain acceptable impurity concentrations, coupled with the high economic value of the metal catalyst and solvent components of the mother liquor, make simple disposal of the purge stream economically unattractive. Thus, there is a need for a process that recovers essentially all of the expensive metal catalysts and acetic acid contained in the mother liquor while removing a major portion of the impurities present in the purge stream. The metal catalyst should be recovered in an active form suitable for reuse by recycling to the p-xylene oxidation step.
This invention is a marked improvement over a typical purge process. Some of the advantages are:                1) enhanced operability and reliability due to reduction in plugging potential;        2) reduction in overall energy usage.
The invention enhances the impurity removal efficacy of the process, and the operability of the process compared to the existing processes.

This patent is subject to a terminal disclaimer.

Extraction process for removal of impurities from mother liquor in the synthesis of carboxylic acid


A random access method and apparatus, the method comprising: a terminal device sending a first message to a network device, the first message including a random access preamble and uplink information; the random access preamble occupies at least one first symbol in the time domain, and the uplink information occupies at least one second symbol in the time domain, the one first symbol comprises a first cyclic prefix (CP) and at least one first information segment, and the one second symbol comprises a second CP and at least one second information segment. The random access method and apparatus of an implementation of the present disclosure may reduce signaling overhead during random access.

Random access is the most basic function that a cellular system has, which makes it possible to establish a communication connection between a terminal device and a network device. In a new radio (NR) system (or called 5G system or 5G network), a four-step random access procedure similar to that of Long Term Evolution (LTE) is adopted, however, the signaling overhead of the traditional four-step random access procedure is relatively large.
Therefore, how to reduce the signaling overhead of a random access procedure is an urgent problem to be solved.

GUANGDONG OPPO MOBILE TELECOMMUNICATIONS CORP., LTD.


‘LIRSS’ is a distinctive variety of Liriope muscari which is characterized by a foliage variegation pattern with white-colored leaf striations that are significantly wider than the green-colored leaf striations, giving plants a general silver appearance.

The present invention relates to a new and distinct perennial variety of Liriope muscari, which has been given the variety denomination of 'LIRSS'. Its market class is that of an ornamental flowering perennial. 'LIRSS' is intended for use in landscaping and also in garden containers. Liriope muscari, commonly called "lilyturf", is an evergreen perennial native to China and Japan that forms clumps of dark green grass-like leaves with light lavender flower spikes that appear in summer. Its consistent size and performance through its hardiness range make it an ideal choice for specimen, borders and mass plantings in any filtered sun to shady, low maintenance landscape or container.
Parentage: In April 2007, a basal shoot with a higher degree of white striations was discovered growing from an unnamed variegated Liriope muscari stock plant (unpatented) at a wholesale nursery in Oakville, New South Wales, Australia. The instant mutation was isolated from the mother plant by way of dividing the plant's crown and said mutation was potted into a nursery container for further observation. The resulting plant was further grown and asexually propagated through five generations from April 2007 until January 2011, at which time it was determined that the characteristics for which the instant mutation was originally isolated were uniform and stable. The new plant was given the name 'LIRSS'
Asexual Reproduction: 'LIRSS' was first asexually propagated by dividing the root-bearing, rhizomatous propagules of the plant (i.e. "division cloning") in April of 2007 at a wholesale nursery in Oakville, New South Wales, Australia and has since been asexually propagated through five subsequent generations. The distinctive characteristics of the inventive 'LIRSS' variety are stable from generation to generation; clones of the variety produced by asexual reproduction maintain the distinguishing characteristics of the original plant.


An abrasive product includes a plurality of abrasive particles and a resin cured with a polythiol group. A method of preparing the abrasive product includes contacting the plurality of abrasive particles with a curable composition that includes a resin and a polythiol group, and curing the curable composition to produce the abrasive product. A method of abrading a work surface includes applying an abrasive product to a work surface in an abrading motion to remove a portion of the work surface. A curable composition includes a formaldehyde resin and a polythiol group. A formaldehyde resin is crosslinked by a polythiol group. A method of crosslinking the formaldehyde resin includes reacting the polythiol group with the formaldehyde resin.

Many abrasive products include abrasive particles in a binder, for example, abrasive particles bound to paper in sandpaper, or a bonded abrasive article such as a grinding wheel, formed of abrasive particles and a binder.
Desirable characteristics for such binders include binding strength, toughness, flexibility, ease of curing, ease of additive incorporation such as colorants, minimal cost, and the like. Abrasive binders having one or more such characteristics can exhibit longer abrading lifetime, better abrading performance, decreased random scratch formation on a workpiece due to particle movement, and the like.
Numerous binders have been employed or attempted in abrasive products, for example, phenolic resins, aminoplast resins having pendant α, β-unsaturated carbonyl groups, urethane resins, epoxy resins, urea-formaldehyde resins, isocyanurate resins, melamine-formaldehyde resins, acrylate resins, acrylated isocyanurate resins, acrylated urethane resins, acrylated epoxy resins, bismaleimide resins, hide glue, cellulosics, latices, casein, soy proteins, sodium alginate, polyvinyl alcohol, polyvinylacetate, polyacrylester, and polyethylene vinylacetate, polystyrene-butadiene, mixtures thereof, and the like.
However, there is still a need in the art for abrasive binders with improved properties.

High-performance resin for abrasive products


The present invention provides an adaptive Y/C separation circuit for video signal processing that is capable of correcting previous color discrepancy in separating the luminance (Y) and chrominance (C) signals from the color video signals. In the process, the correlation of video signals on referencing scanning lines is analyzed by transposing the chrominance signals onto a two-dimensional UV plane. A correlation coefficient is obtained through the analysis for adjusting the video signals in the direction of the actual chrominance level, thus separating the luminance and chrominance signals with relatively low cost circuit implementation.

1. Field of the Invention
The present invention relates to an adaptive Y/C separation circuit for video signal processing, in particular to a circuit that is able to automatically separate the luminance (Y) and chrominance (C) signals from the color video signals on referencing scanning lines, such that the real luminance and chrominance signals can be separated using relatively simple circuit implementation.
2. Description of Related Arts
In general, the luminance (Y) signals and the chrominance (C) signals overlap each other in composite color video signals. FIG. 7 shows a frequency spectrum of a composite color television signal with the chrominance signal (Y) completely overlapped by the luminance signal (C). The conventional means of high pass filter (HPF), low pass filter (LPF) and band pass filter (BPF) to separate the Y signal and the C signal cannot extract these two signals in whole, whilst some luminance signal component still remains in the filtered chrominance signal, or some chrominance signal component remains in the filtered luminance signal, but the filtered luminance signal lacks certain components to correspond to the chrominance signal. This discrepancy in Y/C separation often leads to blurring of the output picture and color distortion, resulting in degradation of the picture resolution.
One of the solutions often used to solve the above Y/C separation discrepancy problem is a two-dimensional separation circuit, where the Y/C signals on adjacent scanning lines, that is current scanning line, the one immediately preceding and the one immediately following (Vn+1, Vn, Vn−1), are sampled from the color video signals through a two-stage delay circuit (D1, D2), and then signals on either two out of three scanning lines that demonstrate closer values are picked out and subtracted from each other to extract the chrominance signal component (C). Since the chrominance signals on two adjacent lines (Y+C, Y−C) are 180 degrees out of phase, the luminance signal component (Y) is taken out after the subtraction, leaving the chrominance signal (C). The C signal is further subtracted from the original signal (Y+C) to obtain the luminance signal (Y). Using this technique, the color discrepancy can thus be effectively controlled.
However, the Y signals used for computation of the chrominance signal are not equal on adjacent scanning lines, so there is a small amount of the Y signal component remaining in the resultant C signal. The color discrepancy is conspicuous when the luminance output experiences large variation. Then the idea of vertical correlation to control the mixing ratio of signals on adjacent scanning lines was introduced. In FIG. 10, the signals on three adjacent scanning lines are produced through the cascaded delay circuit (D1, D2). The main difference with the previous example is that a vertical correlation circuit (80) is introduced, as shown by the dotted line portion in the diagram. Through the correlation analyzer (81) for computing the vertical correlation of chrominance signals on three adjacent scanning lines, the correlation coefficients are input to two mixers (73, 74) for ratio mixing. Through two comb filters (71, 72) the filtered luminance signal can be used for adjustment of the mixing ratio in accordance with the vertical correlation, such that the chrominance signal is able to come close to the actual chrominance level, thus improving the picture resolution.
However, since the vertical correlation circuit (80) only employs unidirectional vector computation to find the variance between the luminance signals on adjacent scanning lines, the resultant value is still unable to meet the low discrepancy criterion. One way to solve the problem is to increase the number of referencing scanning lines from three to five, and another way is to introduce the analysis of two adjacent frames which requires a frame buffer (F), as shown in FIG. 11. A three-dimensional separation circuit is needed for the analysis of two frames. The biggest disadvantage of a three-dimensional separation circuit is the massive amount of data that are needed for the computation of the picture frames. With such a large amount of processing data the related circuit design gets very complicated and also is not very cost effective for commercial use.


There is provided a portable packet switched wireless voice messaging device capable of transmitting and receiving a digital voice signal. The device includes a microphone for inputting a voice message, an encoder for encoding the voice message, a memory for storing the encoded message, a data compressor with variable compression ratio for compressing the encoded message in accordance with a data compression mode selected by the user and a transmitting circuit for transmitting the compressed data with information indicating the mode selected. The device also includes a receiving circuit for receiving an incoming message data which has been compressed in a transmitting side, a detector for detecting the compression mode used in the transmitting side, a data decompressor for decompressing the incoming message data in accordance with the detected mode, a memory for storing the decompressed data, a decoder for decoding the decompressed data and a speaker for reproducing a voice message in accordance with the decoded voice message signal provided by the decoder. The user can select a data compression mode depending upon the importance of his voice message to be transmitted.

1. Field of the Invention
This invention relates to a two-way wireless messaging system for transmitting and receiving messages. More particularly, this invention relates to a wireless voice messaging system for transmitting and receiving encoded voice signals which are subject to variable data compression.
2. Background
Personal communication systems for enabling users to communicate with each other have become popular in the recent years. While in the past such systems have generally been realized using analog technology, it is desirable to instead use digital processing in order to use limited frequency resources more efficiently as well as reduce signal distortion and degradation and thus improve the overall quality of the voice signal.
In general, in a digital cellular telephone system for transmitting and receiving digital voice signals, an input voice signal is digitized and encoded to speech parameters. A variety of speech encoding/decoding methods have been known for processing digital voice signals. For example, MBE (Multi Band Excitation), SBE (Single Band Excitation), SBC (Sub-Band Coding), Harmonic Coding, LPC (Linear Predictive Coding), DCT (Discrete Cosine Transform), MDCT (Modified DCT) and FFT (Fast Fourier Transform) have been known as such a encoding/decoding method. In addition, CELP (Code Excited Linear Prediction), VSELP (Vector Sum Excited Linear Prediction), PSI-CELP (Pitch Synchronous Innovation - CELP) and RPE-LTP (Regular Pulse Excitation - Long Term Prediction) have also become known as a speech encoding method for digital cellular telephone system.
Such a digital cellular telephone system is called a circuit switched communication and two or more users can interactively communicate with each other in realtime. During the interactive communication, a signal channel is physically established exclusively for the communicating users. The cellular telephone system is relatively expensive because the users are charged for the exclusive use of the signal channel, for example, per minute basis. Even when a user just wants to talk for a short period to send a simple voice message, the service takes a high charge for using a cellular network in conjunction with PSTN (Public Switch Telephone Network).
Unlike a cellular telephone system for a realtime communication, packet switched communication systems are also known. Packet switched communication systems are considered as non-realtime communication systems. One of the non-realtime communication systems is a one-way pager which is capable of receiving a text-based short message. A two-way pager terminal is also known for providing limited transmitting capability as well as receiving capability of a text-based short message. For the non-realtime communication system, there is no need to establish an exclusive signal channel between the communicating users. Therefore, the charge for the system is based on the amount of data transmitted, for example, per byte basis. However, such a pager system cannot transmit a voice message.

Voice messaging system having user-selectable data compression modes


An aquatic exercise device which is to be used within a body of water such as a pool has an element which can be engaged by the foot or hand of an individual, which element is linked to a piston-cylinder combination so that as the user engagement element is moved by the user the piston rides in the cylinder. At the head end of the cylinder there is an opening which provides communication between the cylinder chamber and the water environment. As the piston moves back and forth water is either pushed out of the chamber through that opening or drawn into the chamber through that opening. The size of the opening, which may be selected by the user, determines the degree of resistance to the user's movement against the user engagement element.

This invention relates in general to an exercise device that is immersed in water.
It is well known that exercising in an aquatic environment is beneficial to the person doing the exercise because the resistance of the water aids in promoting muscle tone and the buoyancy of the individual relative to the water reduces the likelihood of muscle strain. Exercising in an aquatic environment is invigorating and motivating, in part because of the coolness of the pool water and in part because of the comfort due to the buoyancy of the water. An example of an aquatic exercise device is shown in U.S. Pat. No. 5,033,735 issued Jul. 23, 1991.
The value or utility of an exercise device is usually a function of it being adaptable to the needs of the individual user. Accordingly, it is an object of this invention to provide an aquatic exercise device which provides a user selectable level of resistance to the exercise motion.
In order to obtain widespread use of any given exercise device, it is important that it be relatively inexpensive, easy to use and to assemble, require minimum maintenance, be easy to install and remove and can be adapted to be used in a wide variety of environments.
Accordingly, it is further purpose of this invention to provide the user selected variable resistance function in the context of an inexpensive, simple device which requires minimum maintenance and is easy to install and remove.