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Electro/pneumatic proportional valve

  • US 4,638,837 A
  • Filed: 11/13/1984
  • Issued: 01/27/1987
  • Est. Priority Date: 11/13/1984
  • Status: Expired due to Fees
First Claim
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1. An electrically actuated proportional valve for outputting a fluid at a pressure proportional to at least one continuously variable component of an electrical signal comprising:

  • an enclosed housing defining an internal chamber, said housing having an inlet port for receiving a pressurized fluid, an outlet port, and vent port;

    a piston disposed in said internal chamber operative to assume a first position and displaceable in response to a fluid pressure applied to one side of said piston;

    first valve means, opened in response to said piston being in said first position to connect said outlet port to said vent port and closed in response to said piston being displaced from said first position;

    second valve means closed in response to said piston being in said first position and opened in response to said piston being displaced from said first position to connect said outlet port with said inlet port, said second valve in said open state also applying a fluid pressure to the side of said piston opposite said one side to balance the position of said piston such that the fluid pressure at the outlet port is proportional to the fluid pressure applied to said one side of the piston; and

    electrically actuated pilot valve means responsive to the electrical signal for applying a fluid to said one side of said piston having a fluid pressure proportional to the value of the variable component of said electrical signal, said fluid pressure displacing said piston and opening said second valve means to produce a pressure applied to the other side of said piston and at said outlet port proportional to the value of the variable component of said electrical signal.

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