Abstract: A piston pump having a flexible rolling membrane which seals the piston from the cylinder wherein the piston is designed to include an upper portion which is spaced inwardly from the cylinder wall so as to form a cavity which communicates through channels and seals carried by the lower portion of the piston in such a manner that the lower portion of the flexible membrane is depressed between the upper portion of the piston face and the cylinder walls during an intake stroke as the cavity is subjected to a decreased pressure and which decreased pressure is removed from the membrane during a discharge stroke of the piston. In the preferred embodiment, the membrane is secured to the upper surface of the piston by a cup-shaped element which protects the membrane from materials within the cylinder.

Abstract: A combination pressure regulator and manual on-off valve for liquid spraying apparatus. A tubular member 31 has a lower end 31b which forms a valve seat which cooperates with a first valve member 32 actuated by a lever 35. The latter has a lug 35b which acts as a resilient attaching blade. The intermediate member further comprises a portion 31e, the periphery of which is in contact with the wall of a bore 23. A diaphragm 37 is clamped against portion 31e by means of a tubular screw 39. The diaphragm is solid with a second valve member 38.

Abstract: The fluid forced by a pump 1 through a conduit 2 towards a point of use such as a spraying bar 6, passes through a gate valve 7 which generates a pressure drop. The higher pressure P0 and the lower pressure P1 thus determined act on a diaphragm 10 which carries a flap valve member cooperating with a seat 18 formed at the inner end of a discharge tube 15-5 which returns the liquid to the tank from which it is pumped. An auxiliary diaphragm 17 acts in the reverse direction. As soon as the pressure difference P0 - P1 exceeds a given value, the flap valve member 14 closes. It is easily demonstrated that under such conditions the delivery pressure P1 is proportional to the pressure drop P1-P0, irrespective of the flow rate through the nozzles of the sprayer bar 6. If 1 is driven at a constant speed, P1 therefore remains constant.The invention is particularly applicable to agricultural sprayers.