| 摘要 |
The external part of the rear chamber of the cylinder (1) is closed by two concentric annular valves (8, 11), the inner valve (11) being axially traversed by the rod (3) of the piston (2). The outer outlet valve (8) is stressed by spring (9) to be pressed onto a seat (7) provided at that end of the cylinder (1) which is traversed by the rod (3) for as long as the pressure in the rear part of the cylinder (1) does not reach a value which has been fixed in advance. The inner inlet valve is stressed by spring (13) to be pressed onto a seat (12) of the first valve (8) for as long as the pressure in this rear part is higher than another value which has been fixed in advance. Passage cross-sections for these valves are thus produced and are of maximum size, due to the fact that they are in the peripheral region of the cylinder. <IMAGE>
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