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A hydraulic system for propelling a vehicle, and with the system arranged with a pump and vehicle drive motors and valves and pilot lines. The operator can select an all-wheel drive or a lesser number of wheel drives. Also, there is a system automatic response to certain conditions of vehicle drive,

A hydraulic system for propelling a vehicle, and with the system arranged with a pump and vehicle drive motors and valves and pilot lines. The operator can select an all-wheel drive or a lesser number of wheel drives. Also, there is a system automatic response to certain conditions of vehicle drive, whereupon the system activates to alter the drive to the various vehicle wheels, including changing from a four-wheel drive mode to a two-wheel drive mode. Further, the operator can override the system's own activation and thereby establish the two-wheel drive mode desired.

대표청구항 ▼

[ What is claimed is:] [7.] In a hydraulic system for traction drive of a vehicle, a main hydraulic line presenting an endless hydraulic flow circuit, a rotatably reversible hydraulic pump fluid-flow connected in said circuit, a first and a second hydraulically powered ground wheel drive motor with

[ What is claimed is:] [7.] In a hydraulic system for traction drive of a vehicle, a main hydraulic line presenting an endless hydraulic flow circuit, a rotatably reversible hydraulic pump fluid-flow connected in said circuit, a first and a second hydraulically powered ground wheel drive motor with each fluid-flow connected in said circuit and with both said motors being fluid-flow connected in parallel in said circuit, a hydraulic selector valve hydraulically connected in said circuit to be operatively interposed between said motors for controlling the flow of hydraulic fluid from said pump to said second one of said motors, the improvement comprising:a fluid-flow check valve fluid-flow connected in said circuit and operatively interposed between said pump and said second motor and arranged to operatively block fluid flow from said pump to said second motor,a portion of said circuit being interposed to fluid-flow extend from a location intermediate said selector valve and said second motor to a location intermediate said check valve and said second motor for bypassing hydraulic flow relative to said pump,an additional fluid-flow valve fluid-flow connected in said portion of said circuit and arranged to selectively operatively block the bypassing hydraulic flow relative to said second motor,a first hydraulic fluid-flow pilot connection fluid-flow connected with said check valve and with said circuit at a first site which is intermediate said pump and said second motor, and being arranged for fluid-flow opening of said check valve in response to fluid pressure in said circuit at said first site, anda second hydraulic fluid-flow pilot connection fluid-flow connected with said additional valve and with said circuit at a second site which is intermediate said pump and said check valve for fluid-flow opening of said additional valve in response to fluid pressure in said circuit at said second site.