Motors: expansible chamber type – With correlated control of motive fluid and locking means – By electrical control means
Patent
1995-11-02
1998-03-17
Nguyen, Hoang
Motors: expansible chamber type
With correlated control of motive fluid and locking means
By electrical control means
91 43, 91 44, 91 45, F15B 1526
Patent
active
057274428
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention pertains to a safety device at hydraulic piston-cylinder units, in particular for monitoring locking cylinders of, for example, operating tools mounted on a dredger bucket boom, whereby a sensor for monitoring the piston position is provided at the hydraulic piston-cylinder unit, which sensor is electrically coupled with a monitoring circuit for triggering an alarm system in the case of an incorrect piston position.
It is particularly essential in locking cylinders that the correct position of the locking means, which are actuated with the hydraulic piston-cylinder unit, is dependably maintained in the locking position and that it is also monitored whether they move out of their locking position due to the operating movement of the operating tool.
A monitoring device of the above-noted kind is known, for instance, from U.S. Pat. No. 5,049,027 which provides a micro-switch which is closed only when the locking cylinder is retracted and then causes a control lamp to light up. That prior art configuration has the disadvantage that the locking cylinders can be freely actuated while the control system need not be taken into consideration.
The invention is based on the object to provide a safety device of the above-noted kind in which free actuation of the locking cylinders is prevented, i.e. that the cylinders must be consciously unlocked so as to attain a release of the operating tools.
2. Summary of the Invention
This object is solved, in accordance with the invention, in that the sensor is coupled with an electrically actuated locking valve coupled to the monitoring circuit for triggering the hydraulic piston-cylinder unit. It is thus necessary to actuate the electrically actuated locking valve through the monitoring circuit before the locking cylinder is actuated, because the locking valve serves the purpose to hold the locking cylinder in its new adjusted position after the adjustment, whereby that locking valve is only opened for adjusting the locking cylinder. It is further assured that the sensor also checks the control circuit for the locking valve.
It is advantageous if a push switch for overriding the monitoring circuit is provided for actuating the locking valve. Only after the push switch has been pushed is an adjustment possible of the locking cylinder by corresponding actuation thereof. Finally, it is also possible to provide the monitoring circuit with a relay switch triggered by the sensor for triggering the alarm system, which makes it possible in a simple manner to turn on alarm circuits quickly through the monitoring circuit.
It may be stated, in summary, that the safety device serves the purpose of forcing the operator to use two hands for locking and unlocking the locking cylinder, i.e. that the locking valve is opened with one hand and the locking cylinder is then actuated with the other hand. It is thus impossible for a grab bucket to be exchanged while the grab bucket boom is actuated; the latter leads to an increased accident risk to persons at the construction site, because it is possible for the operating tool to be received on the boom which the locking cylinder has not been inserted into a corresponding opening, but the tool is only held by clamping.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram of an hydraulic circuit for a mounting tool at a grab bucket boom at which a locking cylinder with a safety device is provided;
FIG. 2 is a diagram of an electrical circuit for a monitoring device of the locking cylinder;
FIG. 3 is a front view of a locking cylinder; and
FIG. 4 is a side view of the locking cylinder as seen in the direction of the arrow A in FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Numeral 1 refers to an hydraulic piston-cylinder unit which, in the exemplary embodiment, forms the locking cylinder of a coupling device for operating tools at a grab bucket boom. The hydraulic piston-cylinder unit 1 can be arrested in the desired position via a locking cylinder. A sensor 3 for monitoring t
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patent: 5468042 (1995-11-01), Heinrichs et al.
Emergemcy & Fail Safe Circuits, Hydraulic Pneumatic Power, J.E. Graham, May 1969.
Greenberg Laurence A.
Lerner Herbert L.
Nguyen Hoang
Stemer Werner H.
Wimmer Hartstahl Ges.mbH & Co. KG
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