Externally adjustable load plus pump control assembly

Claim 1

In a pump control assembly for moving a swash plate of a variable displacement pump between maximum and minimum discharge displacement positions, said assembly having first means for controlling the position of the swash plate, said first means having an actuating means connected to the swash plate and a valve member having first and second end portions, said valve member being movable between a first position at which a pump discharge pressure signal is in communication with the actuating means and a second position at which said pump discharge pressure signal is blocked from communication with the actuating means and the actuating means in in communication with a drain, said first end portion of the valve member having an end substantially continuously exposed to the pump discharge pressure signal and being responsive thereto for biasing the valve member toward one of the first and second positions, the improvement comprising: a spring connected to said valve member; means for selectively adjusting the preload on the spring for selectively adjusting the minimum pump discharge pressure; piston means for increasing the load on the spring for increasing the pump discharge pressure in response to a load pressure signal exceeding a preselected pressure level; and an adjustable stop means for selectively adjusting the maximum force exerted on the the spring by the piston means.