초록 ▼

In the field of fluid power control, there is a need for a control scheme that supplies working fluid under pressure to a load in the event of failure of power supplies to control apparatus associated with the circuit. The disclosure relates to a control circuit 10 in which output pressure from a pu

In the field of fluid power control, there is a need for a control scheme that supplies working fluid under pressure to a load in the event of failure of power supplies to control apparatus associated with the circuit. The disclosure relates to a control circuit 10 in which output pressure from a pump 11 is fed to a control piston 13 therefor via a pressure compensator 17. The pressure compensator 17 is biased to disconnect the supply of fluid at outlet pressure when this pressure is below a threshold value, and permit such supply when the outlet pressure exceeds the threshold value determined by the biassing force on the pressure compensator. A proportional control valve 16 may be employed further to counteract the biassing of the pressure compensator 17, whereby to control the threshold pressure at which the compensator 17 operates to feed fluid at control pressure to the piston 13. The invention is of particular use in control circuits eg. for cooling pumps and cooling fans.

대표청구항 ▼

[ We claim:] [1.] A fluid power control circuit, comprising:a pump, connectable to supply fluid at outlet pressure to a load;an adjustable control device capable of supplying control fluid in the circuit;a biased fluid-actuated adjuster for adjusting the output of the pump; anda pressure-actuated di

[ We claim:] [1.] A fluid power control circuit, comprising:a pump, connectable to supply fluid at outlet pressure to a load;an adjustable control device capable of supplying control fluid in the circuit;a biased fluid-actuated adjuster for adjusting the output of the pump; anda pressure-actuated directional controller for operatively supplying fluid at outlet pressure to the adjuster, wherein:i) the directional controller is biased to disconnect fluid at outlet pressure from the adjuster;ii) fluid at outlet pressure acts on the directional controller to counter said bias; andiii) control fluid in the circuit acts on the directional controller to counter said bias, in such away that fluid at outlet pressure is supplied to the adjuster, thereby tending to overcome its bias, when the aggregate effect of fluid at outlet pressure and control fluid on the directional controller exceeds its bias, so that in the absence of power for the adjustable control device the fluid-actuated adjuster adopts a position determined by its bias.