| 摘要 |
<p>A portable one-hand-operable, hydraulic punching machine is disclosed which comprises at least two pumps driven by an electric motor, and a single-acting, spring-return cylinder driven by one of the pumps for a variety of punching operations such as cutting, perforating, and wrenching. The machine has a pump housing and a cylinder housing disposed end to end, with a partition therebetween in which there are formed a fluid supply passageway for supplying a hydraulic fluid under pressure from one pump to the cylinder fluid chamber, a fluid return passageway for returning the fluid from the cylinder fluid chamber to the pump fluid chamber, and a spool chamber open to the return passageway. In order to hold the return passageway closed during cylinder extension, and to open the same for cylinder contraction a return valve is provided which includes a spool reciprocably received in the spool chamber. Normally holding the return passageway open under spring pressure, the valve spool closes the return passageway upon delivery of the fluid under pressure into the spool chamber by the other pump in the pump fluid chamber. A relief valve is provided for bleeding off excess pressure from the spool chamber into the cylinder fluid chamber.</p> |
