| 摘要 |
A bolster travels, with a first set of wheels propelled by a first pneumatic motor, along a first pair of rails into and out of a press and, with a second set of wheels propelled by a second pneumatic motor, along a second pair of rails laid at right angles with the first rail pair. The first set of wheels are mounted to the bolster body via hydraulic lift jacks for up-and-down movement into and out of engagement with the rails. The first and second pneumatic motors communicate with a source of air under pressure via first and second pilot-operated selector valves respectively. The lift jacks communicate with a hydraulic pump, driven from the pressurized air source, via a third pilot-operated selector valve. For pilot-operating the first, second and third selector valves there are provided manual control valves and sensors, the latter being actuated automatically to produce pneumatic signals representative of various working conditions of the bolster. The pneumatic output signals of the control valves and the sensors are processed by additional valves and logic devices and applied to the pilot ports of the three selector valves for correctly controlling the travel of the bolster along the first and second pairs of rails. Also provided are indicators, operated pneumatically by the sensors, for visually indicating the operating conditions of the bolster.
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