Hydraulic circuit for activating a clutch and a throttle valve used in the circuit

Abstract

A hydraulic circuit is disclosed for activating a clutch as well as a throttle valve which is used in the circuit. The hydraulic circuit includes a hydraulic actuator which is connected to a source of pressurized fluid to alternatively activate the clutch. Connected between the source of pressurized fluid in the actuator is a control valve and a pressure-responsive throttle valve. The control valve is basically an on/off valve which controls the flow of fluid to the clutch actuator or from the clutch actuator to a reservoir. The throttle valve, on the other hand, is arranged in series with the control valve and is responsive to fluid pressure on its downstream side to cause increased throttling of the fluid as the fluid pressure to the actuator increases. Such a circuit is beneficial in preventing the clutch from snatching as it is being engaged.

We claim: 
     
       1. A hydraulic circuit for activating a clutch, said circuit comprising: (a) actuator means for activating said clutch;   (b) a source of pressurized fluid;   (c) a conduit connecting said source of pressurized fluid to said actuator means;   (d) a control valve positioned across said conduit for controlling the flow of pressurized fluid therethrough; and   (e) a pressure-responsive throttle valve positioned across said conduit and arranged in series with said control valve, said throttle valve having a fluid flow path across a spool valve located therein, said spool valve having a first passageway permitting relatively unrestricted fluid flow across said spool valve and a second passageway restricting fluid flow across said spool valve.[.relative to said first position.]..Iadd., .Iaddend.wherein a shifting .Iadd.of flow .Iaddend.from said first to said second .[.position.]. .Iadd.passageway .Iaddend.occurs solely in response to a predetermined fluid pressure on the downstream side of said spool valve with said flow path being maintained across said second passageway as long as fluid pressure downstream of said spool valve equals or exceeds said predetermined fluid pressure.   
     
     
       2. The hydraulic circuit of claim 1 wherein said control valve is an on/off valve. 
     
     
       3. The hydraulic circuit of claim 2 wherein said control valve is a four-way, two position valve which is movable between a first position in which said source of pressurized fluid is connected to said actuator means via said throttle valve and a second position in which said source of pressurized fluid is directly connected to a hydraulic brake which brakes a power take-off shaft. 
     
     
       4. A hydraulic circuit for activating both a clutch and a brake associated with a power take-off shaft, said clutch having a plurality of interacting drive plates and driven plates, said hydraulic circuit comprising: (a) a hydraulic piston positioned in said clutch for frictionally causing said drive plates to contact said driven plates;   (b) a source of pressurized fluid;   (c) a first conduit connecting said source of pressurized fluid to said hydraulic piston;   (d) a second conduit connecting said brake to a fluid reservoir;   (e) a four-way, two position control valve positioned across both said first and second conduits, said control valve being movable between a first position wherein pressurized fluid is directed both from said source to said hydraulic piston and from said brake to said reservoir, and a second position wherein pressurized fluid is directed both from said source to said brake and from said hydraulic piston to said reservoir; and   (f) a two-way two position throttle valve positioned across said first conduit between said control valve and said hydraulic piston, said throttle valve including a valve body having a through bore formed therein which is intersected by a transverse bore, said through bore being connected at one end to said control valve and at an opposite end to said hydraulic piston, .[.and a flow passage connecting said through bore to one end of said transverse bore,.]. a spool valve positioned in said transverse bore having a pair of spaced apart grooves formed in the periphery thereof, one of said grooves being larger than said other groove, and a spring positioned in said transverse bore and acting on one end of said spool valve for urging said spool valve to a first position wherein said larger groove is aligned with said through bore to permit unrestricted fluid flow from said control valve to said hydraulic piston, and .[.when a rise in pressure occurs in said through bore, it is conveyed through said flow passage.]. .Iadd.a flow passage connecting said through bore to one end of said transverse bore for conveying a rise in pressure in said through bore .Iaddend.to an end of said spool valve opposite said spring to force said spool valve against said spring thereby aligning said smaller groove with said through bore to throttle fluid flow from said control valve to said hydraulic piston.