A hydraulic vehicle jack including a novel release valve is disclosed. The jack is of the type having a high pressure cylinder, a ram partially extensible from and retractable into the cylinder,Butterfly Valves and a high pressure pump for forcing fluid from a reservoir into the cylinder to extend the jack. When it is desired to lower the jack, the release valve needle is turned so as to withdraw a needle tip from fluid-flow-halting engagement with a valve seat.Needle Valves This needle tip is formed in the shape of a cone having an altitude of a dimension greater than the cone base radius. When the needle tip is withdrawn from its position against the valve seat,BALL VALVES a small but precisely defined fluid-flow-permitting orifice is created. Valve lowering action then occurs over an extended time period which permits the jack operator to precisely control or halt valve lowering action as desired.  A hydraulic vehicle jack comprising, in combination, a hydraulic fluid reservoir, a high pressure cylinder, a ram partially extensible from and retractable into the cylinder, a high pressure pump in fluid communication with the reservoir and with the cylinder to force fluid from the reservoir under high pressure into the cylinder to extend the ram, and a shiftable release valve for controlling fluid flow from the high pressure cylinder back to the reservoir, the valve comprising an insert defining a fluid passage between the chamber and the reservoir and a valve seat defined in the passage, and a release needle carried axially in the insert by mating insert and needle threads for screw motion toward and away from a valve seat, the needle including a seat-engaging surface, the surface being described by a geometric cone having an altitude of greater dimension than the maximum cone radius, whereby to provide precise control of fluid flow through the annular orifice created between the valve conical surface and the insert seat as the valve is opened.

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