Patents by Inventor David F. Johnston

David F. Johnston 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).

  • Patent number: 6628568
    Abstract: A system and method for verification of acoustic horn performance is disclosed. This system and method includes a pressure detecting mechanism that converts at least one vibratory sound energy pulse, which is followed by at least one vacuum pulse or at least one negative pressure pulse, into a signal that is proportional to a level of sound energy, and the pressure detecting mechanism is operable to be connected to an acoustic horn. There is a measurement device that measures a value that correlates to the signal that is proportional to a level of sound energy and is electrically connected to the pressure detecting mechanism.
    Type: Grant
    Filed: March 19, 2002
    Date of Patent: September 30, 2003
    Assignee: BHA Group Holdings, Inc.
    Inventors: Michael M. Mahler, David F. Johnston, Terry L. Farmer
  • Publication number: 20030179650
    Abstract: A system and method for verification of acoustic horn performance is disclosed. This system and method includes a pressure detecting mechanism that converts at least one vibratory sound energy pulse, which is followed by at least one vacuum pulse or at least one negative pressure pulse, into a signal that is proportional to a level of sound energy, and the pressure detecting mechanism is operable to be connected to an acoustic horn. There is a measurement device that measures a value that correlates to the signal that is proportional to a level of sound energy and is electrically connected to the pressure detecting mechanism.
    Type: Application
    Filed: March 19, 2002
    Publication date: September 25, 2003
    Applicant: BHA Group Holdings, Inc.
    Inventors: Michael M. Mahler, David F. Johnston, Terry L. Farmer
  • Patent number: 6611440
    Abstract: An apparatus and method for controlling voltage applied to an electrostatic precipitator is disclosed. This apparatus includes a pulsating, direct current, voltage mechanism that is operable to receive power from a single phase, alternating current voltage source, and a spiral wound filter capacitor, wherein the pulsating, direct current, voltage mechanism is electrically connected in parallel to the spiral wound filter capacitor and the spiral wound filter capacitor is electrically connected in parallel to the electrostatic precipitator. Optionally, a resistor is present to lower the transient voltage rating of the spiral wound filter capacitor. A switching mechanism may be utilized to apply differing amounts of capacitance and inductance in order to apply a range of voltage waveforms to the electrostatic precipitator to potentially maximize particulate collection efficiency for the electrostatic precipitator.
    Type: Grant
    Filed: March 19, 2002
    Date of Patent: August 26, 2003
    Assignee: BHA Group Holdings, Inc.
    Inventors: David F. Johnston, Michael M. Mahler, Terry L. Farmer, Robert Edgar Hummell, III
  • Patent number: 6540812
    Abstract: An improved method and system is provided to control the rapping process used to clean the internal collection plates and discharge electrodes of electrostatic precipitators. The system obtains the performance characteristics of a first rapper and calculates a rapper lift value. The system then obtains performance characteristic data from two or more additional rappers and calculates rapper lift values for each of the rappers. Finally, the system compares the rapper lift value of each additional rapper and adjusts its performance characteristics so that it substantially approximates the performance characteristics of the first rapper.
    Type: Grant
    Filed: July 6, 2001
    Date of Patent: April 1, 2003
    Assignee: BHA Group Holdings, Inc.
    Inventors: Terry L. Farmer, David F. Johnston, Sven Richter, Michael M. Mahler
  • Publication number: 20030010203
    Abstract: An improved method and system is provided to control the rapping process used to clean the internal collection plates and discharge electrodes of electrostatic precipitators. The system obtains the performance characteristics of a first rapper and calculates a rapper lift value. The system then obtains performance characteristic data from two or more additional rappers and calculates rapper lift values for each of the rappers. Finally, the system compares the rapper lift value of each additional rapper and adjusts its performance characteristics so that it substantially approximates the performance characteristics of the first rapper.
    Type: Application
    Filed: July 6, 2001
    Publication date: January 16, 2003
    Applicant: BHA Group Holdings, Inc.
    Inventors: Terry L. Farmer, David F. Johnston, Sven Richter, Michael M. Mahler
  • Patent number: 5950441
    Abstract: Method and apparatus for controlling an evaporative gas conditioning system utilizes a controller for controlling the rate at which liquid is introduced into a conditioning chamber, thereby closely controlling the rate at which temperature within the conditioning chamber is adjusted to a desired temperature. Nozzle characteristics of a plurality of different nozzle types are stored in a memory associated with the controller, so that when existing nozzles are replaced with a different nozzle type, an operator can select the new nozzle type, and data stored in memory will be retrieved to permit efficient control of the system without the necessity for manual reconfiguration. Additionally, spray nozzles for spraying water into the conditioning chamber of the system are organized into banks of nozzles, and the banks of nozzles are controlled to maintain optimum water flow through each nozzle, and to evenly distribute the water into the conditioning chamber.
    Type: Grant
    Filed: October 10, 1997
    Date of Patent: September 14, 1999
    Assignee: BHA Group Holdings, Inc.
    Inventors: Anand Mahableshwarkar, Michael M. Mahler, David F. Johnston, Robert Hummell
  • Patent number: 5890369
    Abstract: Method and apparatus for controlling an evaporative gas conditioning system utilizes a controller for controlling the rate at which liquid is introduced into a conditioning chamber, thereby closely controlling the rate at which temperature within the conditioning chamber is adjusted to a desired temperature. Nozzle characteristics of a plurality of different nozzle types are stored in a memory associated with the controller, so that when existing nozzles are replaced with a different nozzle type, an operator can select the new nozzle type, and data stored in memory will be retrieved to permit efficient control of the system without the necessity for manual reconfiguration. Additionally, spray nozzles for spraying water into the conditioning chamber of the system are organized into banks of nozzles, and the banks of nozzles are controlled to maintain optimum water flow through each nozzle, and to evenly distribute the water into the conditioning chamber.
    Type: Grant
    Filed: September 17, 1998
    Date of Patent: April 6, 1999
    Assignee: BHA Group Holdings, Inc.
    Inventors: Anand Mahableshwarkar, Michael M. Mahler, David F. Johnston, Robert Hummell
  • Patent number: 5705923
    Abstract: A method and apparatus for varying an electrically variable current limiting reactor (VICLR) ( 16) are provided in cooperation with an electrostatic precipitator automatic voltage control system. The inductance of VICLR (16) is varied by altering the DC current in control winding (66) of VICLR (16). A power source (10) connects serially to an inverse parallel SCR1 and SCR2, to VICLR (16), and to a TR set comprising a transformer (18) and rectifier (20) which supply power to precipitator (22). System electrical characteristics on both sides of the TR set are monitored. Computer (40) uses these monitored values to continuously calculate form factor and fractional conduction values. Step-down transformer (60) is connected to solid state relay (62) which is in turn connected to full wave bridge rectifier (64). Rectifier (64) is connected to control winding (66) of VICLR (16). Solid state relay (62) is also connected to computer (40).
    Type: Grant
    Filed: November 22, 1994
    Date of Patent: January 6, 1998
    Assignee: BHA Group, Inc.
    Inventors: David F. Johnston, Michael McCall Mahler, Timothy Gerald Lawrence
  • Patent number: 5515262
    Abstract: An electrically variable current limiting reactor which is usable in association with a power supply for an electrostatic precipitator is disclosed herein. The current limiting reactor is capable of having the inductance value thereof varied responsive to system operation conditions. Most particularly the inductance of the current limiting reactor can be modified responsive to the form factor of the sinusoidal AC input current to the power supply transformer. Additionally the inductance of the current limiting reactor can be controlled responsive to the fractional conduction of the full wave rectified current waveform at the output of the full wave rectifier of the power supply. Other conditions can be monitored to control the inductance value of the current limiting reactor such as physical system parameters. An automatic operating control may modify the inductance of the current limiting reactor responsive to the current entering the primary of the transformer of the power supply.
    Type: Grant
    Filed: December 7, 1994
    Date of Patent: May 7, 1996
    Assignees: Hitran Corporation, BHS Group, Inc.
    Inventors: David F. Johnston, Peter T. Bircsak
  • Patent number: 5374809
    Abstract: An induction heating device includes a handle having a hollow interior and two opposite ends, a wrist connected to one end of the handle, a U-shaped pole piece having two spaced apart ends, a tank circuit including an induction coil wrapped around the pole piece and a capacitor connected to the induction coil, a head connected to the wrist and including a housing for receiving the U-shaped pole piece, the two spaced apart ends of the pole piece extending outwardly beyond the housing, and a power source connected to the tank circuit. When the tank circuit is energized and a susceptor is placed in juxtaposition to the ends of the U-shaped pole piece, the susceptor is heated by induction heating due to a magnetic flux passing between the two ends of the pole piece.
    Type: Grant
    Filed: May 12, 1993
    Date of Patent: December 20, 1994
    Assignee: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
    Inventors: Robert L. Fox, Samuel D. Johnson, Carl E. Copeland, Robert H. Coultrip, W. Morris Phillips, David F. Johnston, Robert J. Swaim, James R. Dinkins
  • Patent number: 5350902
    Abstract: An induction heating device includes a handle having a hollow interior and two opposite ends, a wrist connected to one end of the handle, a U-shaped pole piece having two spaced apart ends, a tank circuit including an induction coil wrapped around the pole piece and a capacitor connected to the induction coil, a head connected to the wrist and including a housing for receiving the U-shaped pole piece, the two spaced apart ends of the pole piece extending outwardly beyond the housing, and a power source connected to the tank circuit. When the tank circuit is energized and a susceptor is placed in juxtaposition to the ends of the U-shaped pole piece, the susceptor is heated by induction heating due to a magnetic flux passing between the two ends of the pole piece.
    Type: Grant
    Filed: May 12, 1993
    Date of Patent: September 27, 1994
    Assignee: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
    Inventors: Robert L. Fox, Copeland, Carl E., Robert J. Swaim, Robert H. Coultrip, David F. Johnston, W. Morris Phillips, Samuel D. Johnson, James R. Dinkins, John D. Buckley
  • Patent number: 5173867
    Abstract: A multiple rapper control (10) for an electrostatic precipitator for monitoring and individually controlling each of a plurality of rappers based on computer (12) stored rapper characteristics including the voltage type, the voltage level, the pre-set electrical input current, the minimum increment between energization cycles, and the maximum duration of energization. Each rapper is connected to a TRIAC switch device (20) linked to a computer (14) and a power control means (16) to vary the input power to each rapper supplied from a power source (18). Current detecting means (22) is bi-directionally connected to the computer (14) and is connected to the power control means (16) to sense and measure the peak electrical input current to each rapper. A preselected logic sequence stored in the computer (12) controls power to each rapper. Optional polarity reversal means (37) eliminate undesirable magnetization of rapper components.
    Type: Grant
    Filed: July 27, 1990
    Date of Patent: December 22, 1992
    Assignee: BHA Group, Inc.
    Inventors: David F. Johnston, Michael M. Mahler, Verne J. Pickren
  • Patent number: 5068811
    Abstract: Form factor measurement and fault detection equipment to determine proper sizing of electrical components and efficiency of an electrostatic precipitator (22) by calculating a system form factor from either primary voltage or current. A power source (10) connects serially to an inverse parallel SCR1 and SCR2, to a current limiting reactor (16), and to a T/R set comprising a transformer (18) and rectifier (20) which supply power to precipitator (22). A current transformer (26) senses input current between the reactor (16) and T/R set (18,20) to signal an input scaling and signal conditioner (28) connected to a current meter (34), a voltage meter (39) and a computer (40) having a display monitor (42). The computer (40) is also connected to an SCR control circuit (24) of SCR1 and SCR2. The appropriate electrical characteristic is converted to both its RMS value and average value and then sent to the computer (40).
    Type: Grant
    Filed: July 27, 1990
    Date of Patent: November 26, 1991
    Assignee: BHA Group, Inc.
    Inventors: David F. Johnston, Terry L. Farmer
  • Patent number: 4891591
    Abstract: The invention is a nonintrusive method of monitoring the cure of a polymeric material using an electromagnetic field to sense a change of resistance of the polymeric material in the electromagnetic field that occurs during curing. This change of resistance is used to vary the impedance of an alternating voltage power supply that produces the electromagnetic field and which change of impedance is measured periodically or continuously to monitor the cure of said polymeric material.Apparatus for practicing the method of this invention may include a nonintrusive sensing head 11 providing an inner, electromagnetic core 12 within an open ended outer pot 14 formed of magnet material, the open end 17 of the pot core 14 being positioned from a selected area of the surface of a sheet 27 of the polymeric material.
    Type: Grant
    Filed: February 16, 1988
    Date of Patent: January 2, 1990
    Assignee: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
    Inventors: David F. Johnston, Robert L. Fox
  • Patent number: 4860149
    Abstract: A method and apparatus for controlling power to a preciptator 27. After each spark the power to the precipitator is reduced to zero, increased along a fast ramp 15 for a fixed period of time and then increased along a slow ramp 17 until a spark occurs. The fast and slow ramp data is computed and stored (memory 48) and then retrieved after each spark. The data retrieved is the data corresponding to the firing angle at the last spark. Apparatus is provided (selector 51 and memory 52) for dividing (frequency divider 45) the retrieved slow ramp data by a number to select the number of sparks per minute. Also the AC current and the AC voltage in the power to the precipitator are detected and the RMS values are obtained (32 and 34) and compared 35 and if the difference is above a predetermined value the power is disconnected (relay 36 and contacts 23 and 24).
    Type: Grant
    Filed: May 14, 1986
    Date of Patent: August 22, 1989
    Assignee: The United States of America as represented by the United States National Aeronautics and Space Administration
    Inventor: David F. Johnston
  • Patent number: 4605424
    Abstract: A method and apparatus for controlling power to a precipitator 27. After each spark the power to the precipitator is reduced to zero, increased along a fast ramp 15 for a fixed period of time and then increased along a slow ramp 17 until a spark occurs. The fast and slow ramp data is computed and stored (memory 48) and then retrieved after each spark. The data retrieved is the data corresponding to the firing angle at the last spark. Means are provided (selector 51 and memory 52) for dividing (frequency divider 45) the retrieved slow ramp data by a number to select the number of sparks per minute. Also the AC current and the AC voltage in the power to the precipitator are detected and the RMS values are obtained (32 and 34) and compared 35 and if the difference is above a predetermined value the power is disconnected (relay 36 and contacts 23 and 24).
    Type: Grant
    Filed: June 28, 1984
    Date of Patent: August 12, 1986
    Inventor: David F. Johnston
  • Patent number: 4521659
    Abstract: This device for inductively heating and fusing thermoplastics includes an alternating current passing through a tank circuit, the inductor member of the tank circuit being wrapped around a curved pole piece of a ferromagnetic material. The magnetic flux arising within the inductor coil member flows to the ends of the pole piece and into a screen placed between the materials to be joined. The flux induces a current in the screen, and heat is generated to melt the thermoplastics together. Because only 30-150 watts of power are passed through the tank circuit, a wire which will remain cool under operational wattage may be selected, making air or fluid cooling unnecessary.
    Type: Grant
    Filed: June 24, 1983
    Date of Patent: June 4, 1985
    Assignee: The United States of America as represented by the Administrator of the National Aeronautics & Space Administration
    Inventors: John D. Buckley, Robert J. Swaim, Robert L. Fox, David F. Johnston
  • Patent number: 4483073
    Abstract: A measuring device for use with hi-jump standards to aid jumpers in determining their in-run starting points approaching the high jump in practice or in competition. The device includes a base member having a 0 to 180 degree scale, whose end points are parallel with the cross-bar, together with a swivable arm that can be set at the desired angle. The arm includes a measuring tape attachment point so that once the angle is set, a measuring tape can be used to determine the exact starting point. The device can be integrally formed with a standard or be separately attachable to a standard.
    Type: Grant
    Filed: July 29, 1982
    Date of Patent: November 20, 1984
    Inventor: David F. Johnston
  • Patent number: 4470595
    Abstract: A compact, lightweight, portable device designed to be removably placed on the end of a pole vaulting pole to permit pole vault cross bars to be replaced without the need of a separate replacing device. The device is comprised of a cylindrical body having a bottom portion defining a pole receiving cavity and a top V-shaped portion for engaging a pole vault cross bar.
    Type: Grant
    Filed: January 15, 1982
    Date of Patent: September 11, 1984
    Inventor: David F. Johnston
  • Patent number: 4468024
    Abstract: A pivot end plug or end cap for vaulting poles designed to provide an eccentric portion at the pivoting bottom end of the pole as it pivots within the plant box. The eccentric portion of the end plug causes the bottom of the vaulting pole to move rearwardly away from the front wall of the plant box thereby permitting a greater forward penetration of the pole and the vaulter into the pit area.
    Type: Grant
    Filed: July 29, 1982
    Date of Patent: August 28, 1984
    Inventor: David F. Johnston