Hydraulic lash adjuster

Claim 1

A hydraulic lash adjuster comprising: an outer tubular member having a closed upper end serving as a lash adjuster upper end; an inner tubular member disposed concentrically within said outer tubular member and having an outward flange at which it is secured to said outer tubular member; a source of fluid under pressure; a first reservoir defined between said inner and outer tubular members and in fluid communication with said source of fluid under pressure; a movable plunger slidably mounted on said inner tubular member, said movable plunger being tubular and having an open upper end and a closed lower end serving as a lash adjuster lower end; a stationary plunger slidably mounted in said movable plunger, said stationary plunger being tubular and having an open upper end and a closed lower end covered by an end wall; an opening provided to said open upper end of said stationary plunger; a second reservoir formed in the inside of said stationary plunger and in fluid communication through said opening with said first reservoir; a communication port formed in said end wall of said stationary plunger; a high pressure chamber defined between said movable plunger and said stationary plunger and in fluid communication with said second reservoir through said communication port; a check valve provided to said communication port to permit fluid flow only in one direction from said second reservoir to said high pressure chamber; a cuplike partition member having an upper end wall interposed between said open upper end of said stationary plunger and said upper end of said outer tubular member and a circumferential wall surrounding said upper ends of said stationary and movable plungers; biasing means disposed in said high pressure chamber for urging said stationary plunger together with said partition member against said upper end of said outer tubular member while urging said movable plunger away from said outer tubular member; said upper end of said outer tubular member being covered by an end wall formed with a concentric air vent; a radial air venting groove formed in an upper surface of said upper end wall of said partition member for providing communication between said first reservoir and said concentric air vent; a first axial air vent formed in said upper end wall of said partition member for providing communication between said first reservoir and said radial air venting groove; and a second axial air vent formed in said upper end wall of said partition member for providing said second reservoir and said radial air venting groove.