Hydraulically operated self-closing two-way seat-type valve

Claim 1

In a hydrualically operated self-closing two-way valve, particularly a built-in valve, comprising a housing (15) having an inner opening and a valve seat at said inner opening; a piston-shaped loacking body (12) received in said opening and cooperating with said valve seat and having a guide portion (12a) and a seat portion (21), said guide portion being of greater diameter than that of said seat portion; a cover (1) mounted on said housing and having a recess; a hydraulically loadable actuating piston (3) received in said recess and being operative for actuating said locking body, said actuating piston being of diameter greater than that of said guide portion (12a), said actuating piston having, at a side thereof which faces away from said closing body, a piston-shaped extension (5) which is guided in said cover and limits in said cover a chamber (9), said locking body having between said guide portion and said seat portion a ring-shaped surface (60), said actuating piston having at a side thereof facing away from said locking body, a circular surface (62), said ring-shaped surface and said circular surface being loaded with a pump pressure, said actuating piston further having at a side thereof facing said locking body a surface (63) which is selectively loadable with a pump pressure or a low pressure, the improvement comprising: (a) said actuating piston having at the side thereof facing said locking body an additional piston-shaped extension (4) which is connected to said locking body in a locking fashion; (b) a separation wall (6) formed between said piston and said locking body, said additional extension being guided in said separation wall; (c) said additional extension limiting between said locking body and said separation wall and said chamber (9) a further chamber (20a) which is loaded with the pressure lower than the pump pressure; (d) said piston-shaped extension and said additional extension being of the same diameter and having a common axial bore (52) also extending through said piston; and (e) said additional extension having radial bores (53) connected to said axial bore while said axial bore and said radial bores connect said further chamber (20a) with said chamber (9).