Patents by Inventor David R. Walker
David R. Walker has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Publication number: 20020114597Abstract: Some optical transmission fibers, such as LEAF and EFEAF, have a positive dispersion slope too great to be fully compensated for by a dispersion compensation fiber (DCF). To achieve improved dispersion compensation for such transmission fibers, the signals may be passed through a non-dispersion shifted fiber (NDSF) as well as through a DCF.Type: ApplicationFiled: December 26, 2000Publication date: August 22, 2002Applicant: NORTEL NETWORKS LIMITEDInventors: Robert K. Brimacombe, David R. Walker
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Patent number: 6136077Abstract: An apparatus which absorbs gas that has been discharged from a pipe at a high velocity and which releases the gas to the atmosphere at a reduced velocity and with relatively low noise. The apparatus includes a container which has a container interior, a container inlet through which the gas enters the container interior, and a container outlet, preferably located at the top of the container, through which the gas is released to the atmosphere. The container further includes a container expanded section and a container main section. The container expanded section, which acts to reduce the velocity of the gas, is located intermediate the container inlet and the container main section and has an inner surface cross-sectional area which expands from the container inlet to the container main section. The container also includes deflector vanes for diverting the flow of the gas within the container interior towards the container outlet.Type: GrantFiled: November 5, 1998Date of Patent: October 24, 2000Inventor: David R. Walker
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Patent number: 5854805Abstract: A laser machining (including marking) method that employs a diode laser pumped solid state laser is controlled by a computer that contains a program for the interaction of the laser beam with a workpiece. The pumping of the laser is synchronised with the action of the beam in a series of active machining periods alternating with inactive non-machining periods. In order to avoid overheating of the active element, the duty cycle of these periods is maintained below a chosen value and no active period is allowed to exceed a selected percentage of the thermal time constant of the active element.Type: GrantFiled: March 21, 1997Date of Patent: December 29, 1998Assignee: Lumonics Inc.Inventors: John Reid, David R. Walker
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Patent number: 5812569Abstract: The energy of a series of output pulses of a solid state laser pumped by a diode array and triggered by a Q-switch is stabilized and rendered independent of the repetition rate by interrupting the pumping to allow the energy stored in the laser active element to fall at the commencement of an interval between a pair of Q-switch trigger signals that is longer than the interval corresponding to the chosen repetition rate. Before the second of this pair of Q-switch trigger signals occurs, the pumping is recommenced for a duration and at an input level that restore the stored energy to the value required for generating output pulses of the laser at the desired energy level.Type: GrantFiled: March 21, 1997Date of Patent: September 22, 1998Assignee: Lumonics, Inc.Inventors: David R. Walker, Philip D. Barton, Robert G. Parker
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Patent number: 5592327Abstract: A regenerative amplifier includes a resonant cavity having a gain medium and a spectral filter located in the cavity. A source is provided to pump the gain medium and thereby raise it to an excited state. Elements are also provided for creating laser seed pulses which are then injected into the resonant cavity, these elements preferably include in part a mode-locked oscillator having a wavelength substantially the same as that at which the gain medium can support amplification of the energy of the injected pulse. In a preferred embodiment the gain medium is Ti:Sapphire for both the amplifier and oscillator. Also, in the preferred embodiment the seed pulse from the oscillator is stretched in time by multiplicative factors sufficient to ensure that upon amplification, the seed pulse power density remains below the self-focusing threshold of the material through which the pulse is passed.Type: GrantFiled: December 29, 1995Date of Patent: January 7, 1997Assignee: Clark-MXR, Inc.Inventors: Edward F. Gabl, David R. Walker, Yang Pang
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Patent number: 5572358Abstract: A regenerative amplifier includes a resonant cavity having a gain medium and a spectral filter located in the cavity. A source is provided to pump the gain medium and thereby-raise it to an excited state. Elements are also provided for creating laser seed pulses which are then injected into the resonant cavity, these elements preferably include in part a mode-locked oscillator having a wavelength substantially the same as that at which the gain medium can support amplification of the energy of the injected pulse. In a preferred embodiment the gain medium is Ti:Sapphire for both the amplifier and oscillator. Also, in the preferred embodiment the seed pulse from the oscillator is stretched in time by multiplicative factors sufficient to ensure that upon amplification, the seed pulse power density remains below the self-focusing threshold of the material through which the pulse is passed.Type: GrantFiled: December 16, 1994Date of Patent: November 5, 1996Assignee: Clark-MXR, Inc.Inventors: Edward F. Gabl, David R. Walker, Yang Pang
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Patent number: 5520780Abstract: A newspaper de-inking system and process require much less water than conventional de-inking systems and which require much lower capital expenditure. The system removes ink from newspaper pulp in a continuous process using one or more extractors each of which performs a de-inking operation equivalent to 6 or more stages of a conventional de-inking process using reactor tanks. Water and heat are conserved still further by employing an evaporator to separate pure water from the extractor effluent and by recycling the purified water to the extractor and to other components of the system. A particularly preferred extractor employs a counterflow single-screw conveyor the flights of which have slots formed therethrough which extend counter to the direction of screw rotation. The slots permit efficient extraction using relatively little de-inking solution and at the same time obviate the need to periodically reverse the direction of screw rotation to unclog the slots.Type: GrantFiled: November 30, 1993Date of Patent: May 28, 1996Assignee: dxResources CorporationInventor: David R. Walker
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Patent number: 5476550Abstract: A counterflow single-screw extractor includes a screw conveyor having a helical scroll formed from arcuate flight sections each having a plurality of elongated slots extending away from the direction of screw rotation and permitting the flow of effluent through the product and the flights in a manner controlled by the size, number, and orientation of the slots. The slots permit efficient extraction using relatively little extraction medium and at the same time permit a single-screw extractor to be used without having to periodically reverse the direction of screw rotation to unclog the slots and by the pitch of the screw conveyor. The inventive arrangement permits the use of a multi-section extractor employing different extraction media and/or different extraction media wash rates in different sections of the extractor.Type: GrantFiled: March 7, 1995Date of Patent: December 19, 1995Assignee: dxResources CorporationInventor: David R. Walker
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Patent number: 5409541Abstract: A counterflow single-screw extractor includes a screw conveyor having a helical scroll formed from arcuate flight sections each having a plurality of elongated slots extending away from the direction of screw rotation and permitting the flow of effluent through the product and the flights in a manner controlled by the size, number, and orientation of the slots. The slots permit efficient extraction using relatively little extraction medium and at the same time permit a single-screw extractor to be used without having to periodically reverse the direction of screw rotation to unclog the slots and by the pitch of the screw conveyor. The inventive arrangement permits the use of a multi-section extractor employing different extraction media and/or different extraction media wash rates in different sections of the extractor.Type: GrantFiled: November 30, 1993Date of Patent: April 25, 1995Assignee: dxResources CorporationInventor: David R. Walker
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Patent number: 5326538Abstract: The present invention relates to a closed sterilization system including an infeed device for receiving the toxic product, first preparing means for rendering the toxic or infectious product suitable for sterilization, sterilization means for sterilizing the product, combustion means for incinerating the sterilized product, and conveying means for conveying the sterilized product from the sterilizing means into the combustion means. The system further includes a first isolating means positioned between the first preparing means and the inlet of the sterilizing means for isolating the product in the sterilizing means from the product in the first preparing means. Second isolation means are also positioned between the outlet of the sterilizing means and the conveying means for isolating the sterilized product from the product in sterilizing means.Type: GrantFiled: March 13, 1991Date of Patent: July 5, 1994Assignee: Serawaste Systems CorporationInventor: David R. Walker
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Patent number: 5285581Abstract: A dryer assembly dries waste materials to a predetermined moisture level. The dryer includes a drum having an inlet where waste materials and hot gasses are simultaneously introduced, and an outlet where dried materials and hot vapors are transferred out of the dryer. The drum presents a plurality of preheat baffles in which the material is heated by but does not contact the gasses, thereby avoiding premature combustion of the material. Baffle sections located downstream of preheat baffles uniformly distribute material downstream into a primary drying section of the drum, where the material is mixed with the gasses to uniformly dry the material to the predetermined moisture level. The primary drying section includes alternating baffle sections which dry the material and which recycle material that is not yet dried back into the preceding baffle sections, respectively.Type: GrantFiled: October 30, 1991Date of Patent: February 15, 1994Assignee: Combustion Design CorporationInventor: David R. Walker
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Patent number: 5137545Abstract: A vapor clarification system includes a suction box and a plurality of fans located on top of the suction box. The fans withdraws a moisture-laden stream from the suction box and centrifugally accelerates it, producing a clarified vapor stream and a secondary vapor stream that is heavily laden with particulate matter. The secondary vapor stream leaving each fan passes through a cyclone, where particulate matter falls out of the vapor stream. The partially clarified vapor stream leaving the cyclone is returned to the suction box and re-accelerated in the fans. By placing the fans on top of the suction box, there is a reduction in the temperature drop occurring in the vapor stream which exits the fans; this in turn reduces condensation and improves the efficiency of the system. Primary cyclones are preferably disposed within the suction box, and secondary cyclones may be placed outside of the suction box.Type: GrantFiled: April 19, 1990Date of Patent: August 11, 1992Assignee: Combustion Design CorporationInventor: David R. Walker
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Patent number: 5114684Abstract: An in-line microwave applicator has an electromagnetic energy wave generating unit which transmits waves, particularly microwaves, dispersing from a longitudinal axis. The dispersing waves are interrupted by microwave diverters which cause the wave lengths to be transmitted through holes from the first chamber to a second surrounding chamber. The second surrounding chamber has interior walls which are reflective to the microwaves and may have a spiral rib to enhance reflectivity. Product for heating is passed through the second chamber to be irradiated by microwaves exiting the holes from the first chamber. The holes are generally elongate in shape and can be surrounded with microwave transparent material to prevent material from falling through. The microwave diverters can be protrusions extending from the holes into the inner chamber by increasing amounts as the distance from the microwave energy generating unit increases.Type: GrantFiled: December 13, 1990Date of Patent: May 19, 1992Assignee: SeraWaste Systems CorporationInventor: David R. Walker
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Patent number: 5080581Abstract: A dryer assembly dries waste materials to a predetermined moisture level. The dryer includes a drum having an inlet where waste materials and hot gasses are simultaneously introduced, and an outlet where dried materials and hot vapors are transferred out of the dryer. The drum presents a plurality of preheat baffles in which the material is heated by but does not contact the gasses, thereby avoiding premature combustion of the material. Baffle sections located downstream of preheat baffles uniformly distribute material downstream into a primary drying section of the drum, where the material is mixed with the gasses to uniformly dry the material to the predetermined moisture level. The primary drying section includes alternating baffle sections which dry the material and which recycle material that is not yet dried back into the preceding baffle sections, respectively.Type: GrantFiled: April 19, 1990Date of Patent: January 14, 1992Assignee: Combustion Design CorporationInventor: David R. Walker
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Patent number: 5054405Abstract: Waste materials are efficiently and completely incinerated in a gasification unit with a minimum amount of fly ash while ensuring complete sterilization of residual materials. The gasification unit includes a refractory liner which is stepped to define primary, secondary, and tertiary combustion chambers where waste materials are completely incinerated. A fan is adapted to draw combustion air past the outer surface of the refractory liner to initially heat the combustion air while simultaneously cooling the refractory liner. The fan is further adapted to force combustion air under pressure into a preheating chamber in which the combustion air is preheated before passing into the primary and secondary combustion chambers. Turbulence in the combustion chambers, brought about through equalization of air pressure in the preheating chamber, is effected through the provision of tangential air inlets in the walls of the refractory liner.Type: GrantFiled: November 2, 1990Date of Patent: October 8, 1991Assignee: Serawaste Systems CorporationInventor: David R. Walker
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Patent number: 5052313Abstract: A waste treatment system conditions waste materials for combustion by uniformly drying them to a predetermined moisture level and subsequently incinerating the dried materials in a burner which effects complete combustion of even high moisture content fuels. The system includes the burner, a dryer assembly, and a system of fans which clarifies vapors withdrawn from the dryer and which returns at least part of these vapors to the burner. The system mixes exhaust gasses from the burner and recycled vapors returned by the fans to produce gasses of a suitable temperature for drying the materials. The waste materials and the gasses are then introduced into the dryer, which is designed to use the gasses to dry the material uniformly to the predetermined moisture level without burning them prematurely. The dried materials are then conveyed to the burner, where they are burned to produce more exhaust gasses for drying additional materials. The residual ash in the burners is nontoxic and is suitable for burying.Type: GrantFiled: April 19, 1990Date of Patent: October 1, 1991Assignee: Combustion Design CorporationInventor: David R. Walker
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Patent number: 4824574Abstract: A novel water softening membrane and process for making the same is described. The membrane can be prepared by treating a polyamide reverse osmosis membrane with a strong mineral acid followed by treatment with a rejection enhancing agent. The resulting membrane at transmembrane pressures of 50 psi can attain a magnesium sulfate rejection with a 0.2 percent aqueous solution of more than 90 percent with a water flux of more than 15 gallons per square foot per day.Type: GrantFiled: June 13, 1988Date of Patent: April 25, 1989Assignee: The Dow Chemical CompanyInventors: John E. Cadotte, David R. Walker
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Patent number: 4812270Abstract: A novel water softening membrane and process for making the same is described. The membrane can be prepared by treating a polyamide reverse osmosis membrane with a strong mineral acid followed by treatment with a rejection enhancing agent. The resulting membrane at transmembrane pressures of 50 psi can attain a magnesium sulfate rejection with a 0.2 percent aqueous solution of more than 90 percent with a water flux of more than 15 gallons per square foot per day.Type: GrantFiled: June 13, 1988Date of Patent: March 14, 1989Assignee: Filmtec CorporationInventors: John E. Cadotte, David R. Walker
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Patent number: 4765897Abstract: A novel water softening membrane and process for making the same is described. The membrane can be prepared by treating a polyamide reverse osmosis membrane with a strong mineral acid followed by treatment with a rejection enhancing agent. The resulting membrane at transmembrane pressures of 50 psi can attain a magnesium sulfate rejection with a 0.2 percent aqueous solution of more than 90 percent with a water flux of more than 15 gallons per square foot per day.Type: GrantFiled: April 28, 1986Date of Patent: August 23, 1988Assignee: The Dow Chemical CompanyInventors: John E. Cadotte, David R. Walker