Patents by Inventor John Frederick Harkness

John Frederick Harkness 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).

  • Liquid-sensing apparatus and method
    Patent number: 5691466
    Abstract: A device for detecting the presence of liquid in a flow of gas has a heated temperature sensor mounted on a heated member in thermal contact with the gas and an unheated temperature sensor in thermal contact with the gas, but thermally isolated from the heated temperature sensor. Liquid in the gas flow evaporates by absorbing heat from the heated member and therefore reduces the temperature of the heated temperature sensor. The reduction in temperature is used to detect the presence of liquid. The device is suitable for detecting liquid at the output of an evaporator in a heat transfer system, and may be used as part of a control system which reduces the flow of refrigerant through the evaporator when liquid is detected at the output, so avoiding damage caused by liquid entering the compressor of the heat transfer system.
    Type: Grant
    Filed: June 26, 1996
    Date of Patent: November 25, 1997
    Assignee: J.T.L. Systems Ltd.
    Inventors: John Michael Walmsley Lawrence, John Frederick Harkness