Hydrostatic transmission check valves with automatic unloading

Abstract

Hydrostatic transmission having a crossover which is provided with check valves. The check valves are automatically controlled by a series of power chambers that respond to different hydrostatic pressures.

What is claimed is: 
     
       1. In a vehicle having an engine, .[.and traction wheels with.]. a hydraulic transmission.Iadd., .Iaddend..[.and.].  a hydraulically actuated implement means operatively connected therebetween .Iadd., a fluid charge pump driven by said engine and communicatively connecting said transmission to a fluid source, said transmission having .[.including.]. a pump and motor, first conduit means connecting the pump outlet with the motor inlet and second conduit means connecting the motor outlet with the pump inlet so that the pump supplies fluid under pressure to drive the motor, and a variable angle swash plate mechanism in the pump operable for varying the transmission ratio of the transmission and for controlling direction of fluid flow between pump and motor according to desired vehicle movement .[.and a fluid charge pump driven by the engine and communicatively connected to a fluid source,.]. the combination therewith of automatic.[.,.]. valving means communicatively interconnectable between said charge pump and the first and second conduit means .[.interconnecting said pump and motor.]. and operable in one position for porting fluid flow from said charge pump selectively to the first and second of said conduit means, and in another position for by-passing fluid between the said first and second conduit means, said automatic valve means including housing means having first and second power chamber means .[., said first power chamber being controlled by pressurized fluid from.]. .Iadd.selectively fluidly communicative with .Iaddend.said charge pump means .[., said second power chamber being controlled by.]. .Iadd.and .Iaddend.said pump and motor means, .[.whereby.]. .Iadd.and spool means responsive to .Iaddend.pressure changes in said power chamber means .[.cause movement of said valve device means resulting in communicatively.]. .Iadd.for selectively .Iaddend.connecting .[.or disconnecting.]. said charge pump means .Iadd.and said transmission, .Iaddend.and said pump and motor means. 
     
     
       2. The assembly of claim 1 wherein said .[.automatic valving means housing.]. means includes; a central bore means which carries a spring loaded sliding pin means. 
     
     
       3. The assembly of claim 2 wherein said central bore means is multi-diametered and said pin means extends into said first and second power chambers. 
     
     
       4. The assembly of claim 3 wherein said first and second power chambers are separated by .[.a sliding.]. means .[...]. .Iadd.slidably carried in said central bore for selectively separating said chambers in response to said pin means and the pressure in said chambers. .Iaddend. 
     
     
       5. The assembly of claim 4 wherein said central bore means includes a first bore means slidingly carrying said pin means, a second bore means which includes said first power chamber and a third bore means which is said second power chamber; and said sliding means is spring loaded to a position between said first and second power chambers in said third bore means. 
     
     
       6. In a vehicle having an engine .[.and traction wheels with.]. .Iadd., .Iaddend.a hydraulic transmission .[.and.]. .Iadd.having a pump and motor, .Iaddend.a hydraulically actuated implement means operatively connected therebetween .[.including a pump and motor.]. first conduit means connecting the pump outlet with the motor inlet and second conduit means connecting the motor outlet with the pump inlet so that the pump supplies fluid under pressure to drive the motor, and a variable angle swash plate mechanism in .[.the.]. .Iadd.said .Iaddend.pump operable for varying the transmission ratio of .[.the.]. .Iadd.said .Iaddend.transmission and for controlling direction of fluid flow between pump and motor according to desired vehicle movement, and a fluid charge pump driven by the engine and communicatively .[.connected.]. .Iadd.connecting said transmission .Iaddend.to a fluid source, the combination therewith of automatic.[.,.]. valving means communicatively interconnectable between said charge pump and the first and second conduit means .[.interconnecting said pump and motor.]. and operable in one position for porting fluid flow from said charge pump selectively to the first and second of said conduit means, and in another position for bypassing fluid between the said first and second conduit means, said automatic valve means including a housing means having a central bore means of first, second and third diameter area means, .[.said first area carrying.]. a sliding spring loaded pin means .Iadd.carried in said first area means and .Iaddend.capable of extending into said second and third area means, a spring loaded valve ball means carried in said third area means, thereby creating adjacent power chamber means in said second and third diameter areas.