Vehicle-mounted spray apparatus

Claim 1

Apparatus comprising a hydraulic pump, a variable speed input drive connected to said pump, control means associated with said pump anD adjustable to different positions, the delivery rate of said pump changing when the speed of said input drive changes and said control means are in a fixed position and also changing when the speed of said input drive is constant and said control means are adjusted in first and second directions, a hydraulic motor connected to be driven by the delivery of said pump, a second pump connected to be driven by said motor and operable when driven to discharge liquid under pressure, and a series of spray nozzles connected to receive the liquid discharged from said second pump and adapted to be selectively opened or closed, the discharge pressure of said second pump changing when the delivery rate of said hydraulic pump changes and a certain number of said nozzles are open and also changing when the delivery rate of said hydraulic pump is constant and a different number of nozzles are open, the improvement in said apparatus comprising, a reversible fluid-operated actuator connected to adjust said control mmeans, a source of pressure fluid at constant pressure and acting on said actuator to bias said control means in said first direction, the discharge pressure of said second pump acting on said actuator to bias said control means in said second direction whereby said control means seek a position in which said actuator is balanced by said constant pressure and said discharge pressure and in which the discharge pressure is at a substantially constant magnitude determined by the magnitude of said constant pressure, and means selectively operable to adjust the magnitude of said constant pressure.