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Leak detection pump with integral vent seal

  • US 5,474,050 A
  • Filed: 01/13/1995
  • Issued: 12/12/1995
  • Est. Priority Date: 01/13/1995
  • Status: Expired due to Term
First Claim
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1. An automotive vehicle comprising an internal combustion engine and a fuel system for said engine which comprises a fuel tank for storing volatile liquid fuel for the engine and an evaporative emission control system which comprises a collection canister that in cooperative combination with head space of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected until periodically purged by means of a canister purge valve to an intake manifold of the engine for entrainment with induction flow of combustible mixture into combustion chamber space of the engine and ensuing combustion in said combustion chamber space, valve means comprising a vent valve via which said evaporative emission space is selectively communicated to atmosphere, said vehicle further comprising means, including pump means, for distinguishing between integrity and non-integrity of said evaporative emission control system, under conditions conducive to obtaining a reliable distinction between such integrity and non-integrity, against leakage of volatile fuel vapor from that portion thereof which includes said tank, said canister, said valve means, and said canister purge valve, said pump means comprising a positive displacement reciprocating pump having a walled housing comprising an air pumping chamber space having a movable wall, a non-movable wall that separates said air pumping chamber space from a walled enclosure containing said vent valve, said housing further comprising a first port communicating the interior of said enclosure to said evaporative emission space and a second port communicating the interior of said enclosure to atmosphere, said pump further comprising a mechanical spring that acts on said movable wall in a sense urging said movable wall toward contracting the volume of said air pumping chamber space, said pump further comprising a first one-way valve means arranged to allow air to pass through said second port from atmosphere and enter, but not exit, said air pumping chamber space, a second one-way valve means arranged to allow air to exit, but not enter, said air pumping chamber space and pass through said first port to said evaporative emission space, means effective while said valve means is closed to prevent communication of said evaporative emission space to atmosphere and while said canister purge valve is closed to prevent communication of said evaporative emission space to said intake manifold for repeatedly causing said movable wall to execute an intake stroke that expands the volume of said air pumping chamber space against force exerted thereon by said mechanical spring, causing the opening of said first one-way valve means in the process so that air fills said air pumping chamber space to create a measured charge volume of air at given pressure, and that imparts energy to said spring for the subsequent execution of a compression stroke that contracts the volume of said air pumping chamber space by extracting energy from said spring to compress said measured charge volume of air to pressure greater than such given pressure, causing the opening of said second one-way valve means in the process so that a portion of the air in said air pumping chamber space is forced into said evaporative emission space during a compression stroke, said first and second ports having respective points of communication with the interior of said enclosure, characterized in that,(1) both when said vent valve is open and when said vent valve is closed, one of said first and second one-way valve means is disposed in operative association with a first set of one or more through-holes in said non-movable wall through which said one of said first and second one-way valve means controls the passage of air between said air pumping chamber space and one of said first and second ports,(2) in that when said vent valve is closed, the other of said first and second one-way valve means is disposed in operative association with a second set of one or more through-holes in said non-movable wall through which said other of said first and second one-way valve means controls the passage of air between said air pumping chamber space and the other of said first and second ports, and(3) in that when said vent valve is open, said other of said first and second one-way valve means is disposed out of operative association with said second set of one or more through-holes so that air is capable of passing both into and out of said air pumping chamber space through said second set of one or more through-holes.

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