| 摘要 |
The method for control of the loss of support of a hydraulic loading platform, operated by a double acting actuator (20), consists in immediately detecting the sudden appearance of oil flow in the pipework (42) joining the two actuator chambers (22,23). The lower chamber is isolated from the upper chamber and from the hydraulic levelling circuit as soon as this oil flow is detected. The control (50) comprises a valve (54), normally separated from its seat, mounted in an internally threaded sleeve (40) located between the lower chamber outlet pipe (22) and the actuator supply pipe (41). The valve maintains isolation of the lower chamber from the upper chamber whilst the pressure difference between the two chambers remains above a pre-determined value. An adjustable spring holds the valve off its seat. Communication between the upper and lower chambers and the hydraulic levelling circuit is re-established as soon as the pressure difference between the two chambers falls below a pre-determined value.
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