Patents by Inventor Robert K. Hoffman

Robert K. Hoffman 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: 4640309
    Abstract: A pilot-operated poppet valve with integral flow control, the latter being adjustable and direction sensitive to provide free or metered flow. Pressure actuated slidable metering seats having integral lip seals are disposed at load ports and are responsive to pressure therein to move relative to adjustable needles between a metering position and a spaced free flow position. The poppet valves include piston seals consisting of cup-shaped elastomeric elements with a central domed bumper structure disposed freely at the piston head.
    Type: Grant
    Filed: August 15, 1985
    Date of Patent: February 3, 1987
    Assignee: Parker Hannifin Corporation
    Inventors: Robert K. Hoffman, Mark A. Kavanaugh, David C. Franson
  • Patent number: 4353290
    Abstract: A pneumatic circuit includes a source of fluid pressure 11, a selector valve 12, a control valve 14, and a power cylinder 15. The control valve 14 includes main valves 35 and 45 and a pilot interlock valve 27. The main valves 35 and 45 include a main inlet port 36, a main exhaust port 38, and cylinder ports 37 and 47. The pilot interlock valve 27 includes a pilot inlet port 28, an interlock port 30, and a signal port 29 which communicates with signal chambers 39 and 49. The control valve 14 is mounted on a motor vehicle transmission, and a mechanical actuator 16 moves between an extended position when the transmission is out of the neutral position and a retracted position when the transmission is in the neutral position. When the actuator 16 is in the extended position, the pilot interlock valve 27 is retained in an interlocked position to maintain the pressure condition existing in the signal chambers 39 and 49.
    Type: Grant
    Filed: November 26, 1979
    Date of Patent: October 12, 1982
    Assignee: Parker-Hannifin Corporation
    Inventors: Robert K. Hoffman, Mark A. Kavanaugh
  • Patent number: 4243072
    Abstract: A valve selectively supplies air pressure to two pneumatic devices on the transmission housing of a motor vehicle. The selector valve includes a stationary base mounted on the top of the gearshift lever of the vehicle. First and second valve plates are mounted for individual movement between two positions relative to the base to selectively connect and disconnect an air pressure source with the two pneumatic devices. Cooperating engaging surfaces on the first and second valve plates insure proper sequencing of the selector valve by the operator.
    Type: Grant
    Filed: December 26, 1978
    Date of Patent: January 6, 1981
    Assignee: Parker-Hannifin Corporation
    Inventors: Robert K. Hoffman, Mark A. Kavanaugh
  • Patent number: 4112968
    Abstract: A drain valve for a compressed air system automatically discharges liquid separated from system air from a container in which the separated liquid is trapped when the trapped liquid activates the drain valve. A spring biases the valve element of the drain valve to an open position to drain the trapped liquid during system shut-down and is positioned in an outlet passage of the container so that the spring is accessible for replacement without dissassembly of the drain valve. A float in the container is responsive to the level of trapped liquid to open communication between the system pressure and a chamber on the upper side of a diaphragm type valve actuator to offset the system pressure in a chamber on the lower side of the valve actuator so that the spring and the pressure on the upper side of the valve actuator acting on the valve element moves the valve element to its open position for discharging the trapped liquid.
    Type: Grant
    Filed: May 3, 1977
    Date of Patent: September 12, 1978
    Assignee: Parker-Hannifin Corporation
    Inventors: Robert K. Hoffman, David C. Franson
  • Patent number: 4082107
    Abstract: A drain valve for a compressed air system automatically discharges liquid separated from system air from a container in which the separated liquid is trapped when the trapped liquid activates the drain valve. A spring biases the valve element of the drain valve to an open position to drain the trapped liquid during system shut-down and is positioned in an outlet passage of the container so that the spring is accessible for replacement without disassembly of the drain valve. A float in the container is responsive to the level of trapped liquid to open communication between the system pressure and a chamber on the upper side of a diaphragm type valve actuator to offset the system pressure in a chamber on the lower side of the valve actuator so that the spring and the pressure on the upper side of the valve actuator acting on the valve element moves the valve element to its open position for discharging the trapped liquid.
    Type: Grant
    Filed: May 4, 1977
    Date of Patent: April 4, 1978
    Assignee: Parker-Hannifin Corporation
    Inventors: Robert K. Hoffman, David C. Franson