| 摘要 |
838,603. Machinery safety devices. PIONEER OILSEALING & MOULDING CO. Ltd. June 11, 1958 [March 13, 1957], No. 8220/57. Class 80 (4). A safety-arrangement for an hydraulically operated machine controlled by a valve to connect the machine either to hydraulic pressure or exhaust comprises a reversible electric motor or solenoid thrust unit M for actuating the valve under control of relays operated by photoelectric cells so that when a beam of light across an access area is interrupted the relays operate to effect movement of the valve to exhaust. Two light sources LL and LR are shown which act directly or through a system of mirrors on to photo-electric cells PCL and PCR, respectively, which control through amplifiers AL, AR, relays ALR and ARR operating switch contacts ALR1 and ARR1 in series with a main relay MR, stop switches PB3, PB4 and start switches PB1, PB2. The main relay MR actuates a holding-switch contact MR1 and motor contacts MR2, MR3. Limit switch contacts LS1 and LS2 are provided in series with contacts MR2 and MR3 and are adapted to be opened when the valve has been fully actuated to one position or the other. If the light beams are not interrupted the contacts ALR1 and ARR1 are held closed and on closure of either of start switches PB1 or PB2 the main relay MR is energized to close contacts MR1 and MR3 which results in the motor opening the control valve to the pressure supply, the motor being stopped when limit switch LS2 is opened. Any interruption of the light beams results in one or other of the contacts ALR1 or ARR1 being opened to de-energize main relay MR. This causes closing of contact MR2 to reverse the direction of the motor to open the control valve to exhaust when the limit switch LS1 opens to stop the motor. |
