# US 5,347,973 A · Vacuum relief valve > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,347,973 A - Document ID: US5347973A - Status: Granted - Kind: A - Application number: 08/082,750 - Filed: 1993-06-25 - Granted: 1994-09-20 - Earliest claimed: 1993-06-25 - Assignees: Walker Design, Inc. - Inventors: Robert A. Walker, Jr. - Web page: https://patentgrep.com/patent/US5347973A ## CPC - F02M 35/10236: {Overpressure or vacuum relief means; Burst protection} - F01M 13/023: {Control valves in suction conduit} - F02M 25/06: adding lubricant vapours - F02M 35/10222: {Exhaust gas recirculation [EGR]; Positive crankcase ventilation [PCV]; Additional air admission, lubricant or fuel vapour admission} - F01M 13/04: having means for purifying air before leaving crankcase, e.g. removing oil - F02B 1/04: with fuel-air mixture admission into cylinder - Y02T 10/12: Improving ICE efficiencies - F02M: SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF - F01M: LUBRICATING OF MACHINES OR ENGINES IN GENERAL; LUBRICATING INTERNAL COMBUSTION ENGINES; CRANKCASE VENTILATING - F02B: INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL (gas-turbine plants F02C; hot-gas or combustion-product positive-displacement engine plants F02G) - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A vacuum relief valve for use with internal combustion engines is provided. The valve is connected to the breathing tubes of an engine on one side and to the air induction system of the engine on the opposite side. Under certain conditions during engine operation, the induction system has a tendency to reduce the pressure within the crankcase creating a partial vacuum. The vacuum relief valve is interposed between the induction system and the crankcase and control or limits the amount of partial vacuum thus created to a maximum of seven inches of vacuum or less. This is accomplished by providing means for limiting the size of a passageway through the valve and thereby limit the amount of suction that can be communicated by the induction system to the crankcase. In one embodiment, a spring biased piston is used to control the size of the passageway. Other valving mechanisms are also contemplated. An auxiliary pathway to atmosphere is also incorporated into the valve so that the breather tubes can be vented when the passageway through the valve is partially or fully closed. ## Claims ### Claim 1 A vacuum limiting valve for use in cooperation with an air-oil separator comprising a housing having a passageway extending therethrough, a conduit extending transversely of the passageway communicating with the passageway, said conduit being open at one end and closed at the opposite end; a piston located within the conduit, said piston being movable between a plurality of positions within the conduit for adjusting the effective size of the passageway; and means for biasing the piston in a first open position adjacent the open end whereby a decrease in air pressure of a pre-determined magnitude in the passageway pulls the piston toward the closed end of the conduit thereby limiting the size of or completely closing the passageway and opening a pathway to atmosphere through said open end. ### Claim 2 A valve according to claim I wherein an air-filter is located over the open end of the conduit. ### Claim 3 (depends on 2) A valve according to claim 2 wherein the biasing means is a compression spring. ### Claim 4 (depends on 3) A valve according to claim 3 wherein the compression spring is helical and extends between the closed end of the conduit and the base of the piston. ### Claim 5 (depends on 4) A valve according to claim 4 wherein the piston completely blocks the passageway when the spring is fully compressed. ### Claim 6 (depends on 5) A valve according to claim 5 wherein the inlet to the housing is connected to a breather cap and the outlet from the housing is connected to an induction system of an internal combustion engine. ### Claim 7 A vacuum relief valve for use in cooperation with an air-oil separator comprising a housing having a passageway extending therethrough, a conduit extending transversely of the passageway communicating with the passageway, said conduit being closed at both ends; a piston located within the conduit, said piston being movable between a plurality of positions from a fully open position to a fully closed position within the conduit for adjusting the effective size of the passageway; means for biasing the piston in a fully open position whereby an air pressure drop in the passageway of a pre-determined magnitude pulls the piston toward the fully closed position in the conduit thereby limiting the size of or completely closing the passageway; and adjustable vent means communicating with the passageway for providing a pathway to atmosphere. ### Claim 8 (depends on 7) A valve according to claim 7 wherein a normally closed auxiliary port opening to atmosphere is located between an inlet to the housing and the piston. ### Claim 9 (depends on 8) A valve according to claim 8 wherein the biasing means is a compression spring. ### Claim 10 (depends on 9) A valve according to claim 9 wherein the compression spring is helical and extends between one of the fully closed ends of the conduit and the base of the piston. ### Claim 11 (depends on 10) A valve according to claim 10 wherein the piston completely blocks the passageway when the spring is fully extended. ### Claim 12 (depends on 11) A valve according to claim 11 wherein the inlet to the housing is connected to an engine breather cap and the outlet from the housing is connected to an induction system of an internal combustion engine. ### Claim 13 (depends on 12) A valve according to claim 12 wherein a hinged cap is provided on said vent means, said cap being caused to open as the piston closes.