| 摘要 |
In a vertically storing dock leveler having a platform which is stored in an upright position, a control circuit which enables retention of the platform in position in response to power failure, and which compensates for possible operator error or inattentiveness during power failure. A normally closed main solenoid valve can be opened only by pressing a lower switch to lower the platform. During normal operation, the valve will remain open to enable the platform to float, but when the platform is to be raised, or electrical power is removed, the valve is closed. As a result, after the platform is raised, the pressure in the main lift cylinder is maintained, and the platform stays at its upright position. Also, during an electrical power interruption, the deck is prevented from falling.
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