Automatic draining back flow preventer

  • US 5,228,471 A
  • Filed: 05/18/1992
  • Issued: 07/20/1993
  • Est. Priority Date: 05/18/1992
  • Status: Expired due to Term
First Claim
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1. In automatic draining back flow prevention apparatus, the combination comprising:

  • a) tubular body means having main passage structure between flow entrance and exit ports,b) the body means having first and second side ports communicating with said passage structure,c) first and second diaphragms carried by the body means to exposed to flow in said passage means,d) a stopper in said passage means cooperating with said first diaphragm to pass forward fluid flow while said first diaphragm flexes to block exit flow of fluid through the first side port, and to block back flow of fluid through said main passage means when said diaphragm moves to unblock exit flow of fluid through said first side port,e) the second diaphragm moving to block exit flow through the second side port in response to said forward flow of fluid through the main passage means, and movable to allow drainage flow of fluid through the second side port during at least one of the following conditions;

    i) when the stopper and first diaphragm block back flow of fluid through the main passage means, andii) when the stopper and first diaphragm are at rest,f) the first diaphragm having a medial through opening to pass the flow, there being a disc in said body means exposed to said passage means, the disc located directly above said first diaphragm, there being spring means carried by said body means for urging the stopper against the diaphragm to hold the diaphragm engaged against the disc at which time said diaphragm through opening is blanked by the stopper and by the disc in the absence of forward flow pressure exerted on the diaphragm, there being at least one through opening through the disc to pass said pressure to a portion of the diaphragm spaced from said diaphragm medial through opening to effect said flexing of the first diaphragm and to pass said forward flow, said through opening through the disc being blanked by the diaphragm when the diaphragm is held engaged against the disc by the stopper, the stopper bridging said through openings in the disc and diaphragm.

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