| 摘要 |
<p>A pneumatic cylinder-piston door operator is connected to an air supply by a solenoid actuated valve. A linkage connects the piston rod to the door. A control circuit selectively energizes the solenoid valve in response to momentary actuation of switches including control and safety switches. The mechanical linkage includes a drive arm tube which is pivotally interconnected to a mounting bracket and to the piston rod. A flexible rod of a smaller diameter is releasably interconnected within the drive arm as an extended cantilever by a plug releasably secured therein. The drive arm tube has a pair of oppositely spaced threaded openings lying in the plane of movement through the center of the tube. Safety switches include a threaded mounting element mounted in the one, or both, of the threaded openings with a suitable lock nut to permit selective adjustment of the position of the corresponding switch actuator with respect to the flexible rod. Thus, any opposing force on the door or linkage results in an increased deflection in the common plane to activate the appropriate switch at a selected force level. 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 and pull cord actuator. A stop limits the travels of the actuator and prevents overtravel of the switch to maintain a long switch life.</p> |
