Patent Number: 6,305,486

Title: Hydrostatic drive and steering system for a utility vehicle

Abstract: A hydrostatic drive for a utility vehicle includes a prime mover (engine) which drives a variable rate hydrostatic pump. In a two-wheel drive system, the hydraulic fluid flow from the pump is split evenly and directed to the rear wheel motors. This flow turns the rear wheel motors and then exits the wheel motors where it is directed back to the pump. In a four-wheel drive system the flow from the pump is split evenly between the front wheel motors. The flow exiting the front motors is directed to the rear wheel motors on the opposite sides of the vehicles. This flow turns the rear motors and then is directed back to the pump. Direction and speed of the vehicle is regulated by an operator-controlled actuator which controls the direction and displacement of the hydrostatic pump. A neutral valve is interconnected between the pump and the motors. The neutral valve is movable between a first position at which fluid flow output from the pump bypasses the motors and is redirected to the pump, and a second position at which the output flow from the pump is directed to the hydraulic motors. The neutral valve allows the pump to be disengaged from the motors so the vehicle can be easily pushed by hand. The hydrostatic drive also includes a flow control valve interconnected between the pump and the motors and being adapted to bypass fluid flow around the motors until the rate of flow from the pump reaches a predetermined level. The flow control valve operates to expand the neutral region and add to the controllability of the vehicle. The vehicle also has a hydrostatic steering system.

Inventors: Polzin; Keith M. (Tea, SD), Van Voorst; Gene A. (Inwood, IA)

Assignee: Koyker Manufacturing Company

International Classification: B60K 17/34 (20060101); B60K 17/356 (20060101); B60K 17/10 (20060101); B60K 017/356 ()

Expiration Date: 10/23/2018