| 摘要 |
PURPOSE:To make a shell into lightweightiness as well as to lessen a reducing amount on a pressure receiving surface without necessitating a special seal member, by forming a rib being extendes inward on an inner circumferential surface of the shell, while making the rib range over both wall surfaces of the shell in succession. CONSTITUTION:At an opposed position in the radial direction of an inner circumferential surface 5 of a front shell 2, a pair of ribs 15 being extended inward are solidly formed up, and one end in an axial direction of these ribs 15 continuously ranges over a wall surface 4 of the front shell 2 as one body, while the other end extends as far as a position beyond a wall surface 6 of a rear shell 3. In addition, in the rear shell 3, a slit 16 into which these ribs 15 are inserted is formed therein. A power piston 22 is made up in a disc form as whole, and in order to avoid interfering with the said paired ribs 15, a slit 23 is formed just like in case of the rear shell 3. And, the inside of a shell 1 is partitioned into a constant pressure chamber 25 in which suction pressure is usually introduced and a variable pressure chamber 26 by means of a seal member 24 and a valve body 20 on the circumference of the power piston 22. |
