Importance

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Abstract

A hydraulic arrangement is described comprising a lifting cylinder 10 for a lifting arm 12 pivotably mounted on a vehicle. A hose 22 selectively connects a working chamber 10a of the lifting cylinder 10 to a supply 16 and a return 18 line to raise and lower the lifting arm, respectively. A safety check valve 46 is connected between the hose 22 and the working chamber 10a to maintain the working chamber under pressure and avoid collapse of the lifting arm 12 in the event of rupturing of the hose 22. An accumulator 70 is connectable to the working chamber 10 of the lifting cylinder 10 by way of the safety check valve 46 to provide ride control. A solenoid 50 overrides the operation of the safety check valve 46 while the hose 22 is isolated from both the supply 16 and the return 18 line to allow fluid to flow in both directions between the accumulator 70 and the working chamber 10a to cause the lifting cylinder to act as a spring supporting the weight of the lifting arm. A pressure switch 82 prevents overriding of the operation of the safety check valve 46 if the pressure in the hose 22 should drop below a threshold.

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First Claim