Pump control mechanism

Claim 1

A swash plate type pump comprising in combination a body, a rotor within the body having formed therein a plurality of equiangularly spaced cylinders, a plurality of pistons occupying the cylinders respectively, an angularly adjustable cam plate with which the pistons co-act, a servo piston for moving the cam plate between opposite inclinations relative to the axis of rotation of the rotor, a pump stroke controlling member, valve means connected to said member for controlling the position of the servo piston, an abutment on said member, a pivoted lever operatively connected to said member, a part rockable relative to the lever against the action of resilient means, control means for setting said member, said control means being operatively connected to said part, a further piston subjected to the output pressure of the pump, an arm connected to the piston to co-act with the abutment in reducing the stroke of the pump against the action of said resilient means, when the pump output pressure pressure exceeds a predetermined pressure with the cam plate of the pump set at one inclination to the axis of rotation of the rotor, and a further lever connected to the piston so as to coact with the abutment in reducing the stroke of the pump against the action of said resilient means, when the pump output pressure exceeds said predetermined pressure when the cam plate of the pump set at the opposite inclination to the axis of rotation of the rotor.