| 摘要 |
A pneumatic cylinder-piston door operator is connected to an air supply by a solenoid actuated valve. A control circuit selectively energizes the solenoid valve in response to momentary actuation of switches including control and safety switches. For refrigeration unit installation, the switch contacts are formed with one contact having a pimpled surface and the other contact having a serrated surface to provide a reliably electrical connection. For the manual control switches, a micro-switch is mounted in a suitable enclosure with appropriate gaskets to minimize the effect of adverse environmental conditions. A spring-loaded plunger is mounted within the housing and provided with an external push-button or pull cord actuator.
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