Valve cartridge including an actuator which closes the valve with a predetermined pressure and stop means comprising spaced apart lugs

A valve cartridge for a tap includes a housing 32 having inlet member 54, outlet member 52 and screw thread 34. Cavity 36 extends axially through housing 32 within which is a piston 38 which moves axially against piston seal 44 to open and close the tap. A flow chamber 40 is provided at the end of housing 32 and includes a first seal 42 for sealing against a valve seat in the tap. Piston 38 can be moved axially by either a rotatable spindle 46 or, a solenoid and push rod. Piston 38 is moved axially without any rotation. Coupling member 84 couples spindle 46 to piston 38 and rotates relative to the piston 38 and the spindle. When spindle 46 is turned a predetermined number of revolutions the coupling 84 causes piston 38 to abut piston seal 44, any further rotation of spindle 46 causes rotation of the coupling member 84 without effecting the axial position of piston 38. Ratchet members 92, 94, slip past housing splines 102 when the predetermined number of revolution or force is reached. This limits the sealing pressure of the piston 38 against the piston seal 44 irrespective of the number of turns made of spindle 46. Stops 64 limits maximum opening and prevents check valve 70 from being forced into sealing contact with inlet member 54.