| 摘要 |
<p>A concrete pump has two cylinders (1, 2) in which pistons (7, 8) are forced forward by water pressure. A valve (5) connects the cylinders alternately to the concrete discharge (3) and suction (6). A water valve (13) admits the water alternately into the space (9, 10) behind the each piston. Two other cylinders (23, 24) coaxial with the operating cylinders contain pistons (21, 22) attached to the operating pistons (7, 8) by rods (19, 20). The space (29, 31) behind each auxiliary piston is connected to the space (9, 10) behind the corresponding main piston. The spaces (25, 26) in front of the auxiliary pistons are connected together. This gives a hydraulic coupling which uses the forward thrust of one piston to retract the other one. Such a coupling is more reliable than a mechanical connection between the pistons.</p> |
