Hydraulic tank reservoir pressure and vacuum stabilizer system

Claim 1

In an hydraulic system comprising a sealed reservoir tank, and a displacement-type hydraulic element in communication with said tank for receiving hydraulic fluid from and returning hydraulic fluid to said sealed reservoir tank; a stabilizer means for changing the volume of the sealed reservoir tank in response to fluid requirements of the displacement type hydraulic element, the stabilizer means comprising an accordion type air bag having walls defining a variable volume chamber, at least one of said walls being movable and having its outer surface in communication with the interior of said sealed reservoir tank, said air bag being formed with sufficient resiliency to resist complete collapsing by the pressure generated from the weight of hydraulic fluid in the sealed reservoir when said sealed reservoir is filled, vent means for providing ingress and egress of ambient atmospheric air into and out of the variable volume chamber allowing substantially atmospheric pressure to be maintained in the sealed tank; the stabilizer means further comprising an elongated tube extending from the vent means, said tube being rigid and having one or more passages establishing communication between the inside of the tube and the inside of the variable volume chamber, said elongated tube having a portion thereof extending outwardly of said tank, roof means supported over said portion, said roof means being formed to direct air entering therein upwardly and then downwardly into said tube whereby movement of solid particles into the stabilizer means is minimized.