Patent ID: 6928815

Claim:
A master cylinder having a master piston slidably received in a cylinder bore, with a plurality of annular grooves formed around an inner wall of said cylinder bore, comprising: an annular seal member having an annular groove of U-shaped cross section formed on one end face thereof, said seal member being placed in such a manner that the annular groove of U-shaped cross section is opened forward in said cylinder bore; and a substantially annular seal retainer placed in front of said seal member for restricting at least axial movement of said seal member, said seal retainer including a substantially annular lifted wall portion formed to extend axially into the annular groove of said seal member, and a substantially annular step portion formed on an inner periphery of said lifted wall portion, for contacting an open end face of the annular groove of said seal member, said seal retainer being reduced in diameter by radial pressing force produced when said seal retainer is received in said cylinder bore, and restored when the pressing force is released, wherein said annular grooves includes an annular transfer groove and an annular hold groove having a larger diameter than said annular transfer groove, formed in parallel with each other toward one open end of said cylinder bore, and wherein said seal member is placed in said annular hold groove, and said seal retainer is received from the other open end of said cylinder bore to be placed in said annular transfer groove, with said seal retainer reduced in diameter, and wherein said seal retainer is transferred from said annular transfer groove to said annular hold groove, and said seal retainer is restored in such a state that said lifted wall portion extends into the annular groove of said seal member.