Safety device for a jacking system including a plurality of jacks designed for simultaneous operation
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United States of America Patent
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Mar 20, 1990
Grant Date -
N/A
app pub date -
Feb 9, 1988
filing date -
Feb 10, 1987
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A safety device for a jacking system comprising a plurality of jacks which are designed for simultaneous operation, at least one table supported on the jacks, and a mechanism connecting the jacks for their simultaneous operation. Each jack is provided with a hydraulic or pneumatic cylinder for moving the jack to raise and lower the table, a pawl and rack mechanism which is normally held in its engaged position for holding the table in its raised position, and an AC solenoid connected to the pawl and rack mechanism for moving it to its disengaged position to allow the table to be lowered. The device includes a resistor connected in series to the solenoid. An integrating circuit is connected in parallel to the resistor, includes a capacitor and produces an electrical signal indicating any failure of the pawl and rack mechanism to be moved to its disengaged position. A relay is connected in parallel to the capacitor for operation in response to the signal to stop any lowering motion of the cylinder.
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