The invention relates to a cup-shaped hydraulic piston (10) made from rolled sheet metal, which comprises an open end (12), a side wall (16) with a cylindrical outer surface (18) and an inner surface (22), as well as a piston head (14). The side wall (16) at its outer surface (18) is provided with an annular groove (20) in a portion adjoining the open end (12). To ensure a lightweight style of construction combining high stability with ease of manufacture, the part of the inner surface (22) adjoining the open end (12) and extending axially over the annular groove (20) has a cylindrical shape, and the thickness of the side wall (16) decreases monotonically from the portion (24) of the inner surface (22) up to the piston head (14).
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation of International Application No. PCT/EP02/08887 filed Aug. 8, 2002, the disclosures of which are incorporated herein by reference, which claims priority to Russian Patent Application No. 2001-122026 filed Aug. 8, 2001, the disclosures of which are incorporated herein by reference.
By forging a metal material, there is formed a dustproof boot 20 in which a side of an opening end portion 20b formed with a groove 34 for a dustproof boot is provided with a diameter smaller than that of a side of a piston main body 20a, and a total thereof is provided with a substantially uniform wall thickness, thereafter, by carrying out ironing from a front end of the opening end portion 20b to the piston main body side, the recess groove 34 for the dustproof boot can be formed by providing a build-up portion 20c at the opening end portion.
