Hand-held press tool appliance for connection of pipes etc. has regulating valve which remains closed when hydraulic pump fails and system pressure is below switch-off pressure

摘要

The appliance has a drive motor (19), a hydraulic pump (22), and a hydraulic motor (20) to actuate a press tool. A hydraulic system contains a regulator valve (45), which forms a connection to a hydraulic reservoir (21) when the pump fails. The valve does not open when the pump fails, if and as long as, the pressure in the system is above a pre-set intermediate hydraulic pressure below switch-off pressure. The valve has a piston (47), which is held in closing position against the action of a valve spring (59), when the pump is operating.