US 5,331,856 A · Pressure devices

Abstract

A pressure indication device comprises a housing including a bore in which is received a slidable piston. The piston has two end faces, one of which is for connection to a source of fluid at higher pressure and the other of which is for connection to a source of fluid at lower pressure. The device produces an indication when the pressure differential reaches a predetermined value. In an inoperative position of the piston, a portion of the upstream face co-operates with the bore to provide a face seal which reduces leakage between the bore and the piston and which also reduces the effective area of the upstream face. In addition, a labyrinth seal is provided between the bore and the piston. When the predetermined pressure is reached, the piston moves, and as it does so, the effective area of the upstream face is increased. This causes increasingly rapid movement of the piston so providing a very positive indication that predetermined pressure has been reached and so overcoming any tendency of the piston to stick or move only very gradually as the predetermined pressure is reached.

Claims11

Dependent claims

A device for indicating when a pressure differential between fluid at a higher pressure and a fluid at a lower pressure reaches a predetermined value, comprising:

a housing;
a bore formed within the housing and having first and second ends;
a piston slidable within the bore;
a first port leading to the first end of the bore and for connection to a source of fluid at high pressure;
a first face on the piston, located towards the first end of the bore and having an area acted on by the higher pressure fluid and having a first portion and a second portion surrounded by the first portion;
a second face on the piston, directed oppositely to the first face, located towards the second end of the bore, and having an area acted on by the lower pressure fluid;
and
a sealing surface provided on the housing and engaging the first portion of the first face, when the piston is in an inoperative position, to form a face seal inhibiting fluid flow between the first and second ends of the bore and to reduce the area of the first face acted on by the higher pressure fluid, the second portion of the first face of the piston projecting past the sealing surface toward the first end of the bore when the piston is in the inoperative position, the piston moving in the bore at the predetermined value to break the face seal and increase the area of the first face acted on by the higher pressure fluid.

5 more elements

Dependencies are inferred from the claim text.

Pressure devices

Life of this patent

Pressure devices

Life of this patent

Abstract

Claims11