Abstract: An hydraulic apparatus for the storage of energy is provided having pump means driven by a source of energy, a pressure line receiving pressure fluid from said pump means, means in said line for maintaining a constant pressure therein from said pump means, at least one pressure reservoir connected to said pressure line receiving fluid pressure therefrom and returning fluid pressure thereto and a restrictor means in said pressure line between the pump means and reservoir restricting flow in said line to maintain a predetermined constant pressure therein.

Abstract: A drive system for a utility vehicle, such as a fork-lift truck, comprises a hydrostatic transmission whose pump is driven by an electric shunt-wound motor having a field winding so energized, under the control of a potentiometer responsive to the fluid pressure in the transmission, that the field current varies inversely with transmitted torque over at least a portion of the speed range of the vehicle. The automatic potentiometer control exerted by the fluid pressure may be overridden by a manually operable lever. The same potentiometer can be used to vary the motor speed in response to the output pressure of another pump which is driven by the electric motor and coupled with the fork-lifting mechanism of the vehicle.