| 摘要 |
<p>The apparatus comprises a piston 1 movable by a rod 3 in a cylinder 2 which has at each end a pressure relief valve 5. Sleeves 12, which each comprise an annular groove 15 and an axial slot 13, are rotatable about the cylinder 2 to align the slot with one of a series of apertures 11. As the piston 2 is moved to the left (as shown) the air pressure builds up and is partly relieved by the valve 5. When the piston passes the aperture aligned with the slot 13 the air in front of the piston rushes via the bypass groove and slot to the rear of the piston. Two such units may be linked in tandem. <IMAGE></p> |
