Valves

A valve including a valve housing providing a chamber accommodating at least part or a valve member, said chamber forming at least part of a first or high pressure side of said valve, a valve port leading from said chamber to a second or low-pressure side of said valve, a valve seat around the valve port, said valve member having a seating surface co-operating with the valve seat and the valve member being displaceable, along an axis passing through said port, respectively (a) in a first direction, to move said seating surface into said chamber and away from said valve seat and (b) in a second, opposite direction, to move said seating surface towards said valve seat, the valve member having a bore extending axially from the high pressure end thereof and forming a cylinder sealingly slidable, in said first and second directions, on a piston fixed within said valve housing, to define therewith a further chamber, biasing means being provided biasing said valve member in said second direction towards its closed position, said further chamber in either case communicating with the low pressure side of the valve, whereby the effective area of said valve member acted on by the fluid pressure difference between said first and second sides of said valve is substantially reduced as compared with the area encompassed by said valve seat, and wherein said piston has a base part or a supporting insert providing an outer periphery received in an internal recess or groove provided around a bore which extends axially into the valve housing from a high pressure end thereof and which bore at least partially defines said chamber accommodating the valve member, said internal recess or groove being disposed at a location remote from said valve seat, the valve housing having one or more longitudinal slits therethrough extending from the high pressure end of the valve housing, (i.e. the end remote from said valve seat) adjacent said internal groove or recess and extending through the location of said internal groove or recess, the material of the valve housing being sufficiently resilient to allow the wall of the valve housing to be flexed outwardly sufficiently to allow said base part or insert to pass within said bore in the valve housing from said high pressure end thereof to the axial position of said internal groove or recess and to allow the wall of the valve housing thereafter to spring back around said base part or insert to locate said base part or insert in said internal groove or recess.

A valve including a valve housing providing a chamber accommodating at least part of a valve member, said chamber forming at least part of a first or high pressure side of said valve, a valve port leading from said chamber to a second or low-pressure side of said valve, a valve seat around the valve port, said valve member having a seating surface co-operating with the valve seat and the valve member being displaceable, along an axis passing through said port, respectively (a) in a first direction, to move said seating surface into said chamber and away from said valve seat and (b) in a second, opposite direction, to move said seating surface towards said valve seat, the valve member having a bore extending axially from the high pressure end thereof and forming a cylinder sealingly slidable, in said first and second directions, on a piston fixed within said valve housing, to define therewith a further chamber, biasing means being provided biasing said valve member in said second direction towards its closed position, said further chamber in either case communicating with the low pressure side of the valve, whereby the effective area of said valve member acted on by the fluid pressure difference between said first and second sides of said valve is substantially reduced as compared with the area encompassed by said valve seat, and wherein said piston has a base part or supporting insert providing an outer periphery received in an internal recess or groove provided around a bore which extends axially into the valve housing from a high pressure end thereof and which bore at least partially defines said chamber accommodating the valve member, said internal recess or groove being disposed at a location remote from said valve seat, wherein the base part or supporting insert is designed for resilient inward flexing to allow it to be inserted in the bore in the valve housing from said high pressure end thereof to spring into said groove when the base part or insert is at the longitudinal position of said internal groove or recess, thereby to retain said piston in place.