GB2024999A

GB2024999A - Pressure Regulators

Info

Publication number: GB2024999A
Application number: GB7923465A
Authority: GB
Original assignee: TRINITY PUMPS Ltd
Current assignee: TRINITY PUMPS Ltd
Priority date: 1978-07-08
Filing date: 1979-07-05
Publication date: 1980-01-16
Also published as: GB2024999B

Abstract

A differential piston 4 having a profiled waist or intermediate portion 5 defined between two portions of different radius is slidably mounted on a spindle 6 within a housing having inlet and outlet ports 2, 3. The piston is urged by a spring assembly 2 to allow communication between the inlet and outlet ports through an annular control port formed between the waisted portion of the piston and the interior of the housing. The action of an incoming high pressure fluid at the waisted portion and against the piston portion of greater radius displaces the piston against the action of the spring assembly to maintain a substantially constant pressure and hence flow in a branch line connected to the outlet port 3. Means are provided for adjusting the spring assembly and thereby the operating range of the regulator. <IMAGE>

Description

SPECIFICATION Pressure Regulators The present invention concerns pressure regulators for reducing and regulating pressure in branch lines connected to main pressure lines, the pressure in the main lines being too high for direct application.

According to the present invention a pressure regulator comprises a housing, a piston slideable in the housing, a pair of annular chambers in the housing about the piston, one of the chambers having an inlet for a fluid at high pressure, the other chamber having an outlet for the fluid, an annular control port formed between cooperating portions of the piston and housing and providing communication between the chambers, the piston presenting an increased surface area to the fluid within said other chamber such that fluid entering said other chamber acts to urge the piston into a position to close the control port, and adjustabie spring means acting on the piston to oppose said fluid action to maintain the control port in an open condition consistent with a required pressure at the outlet from said other chamber.

The invention will be described, by way of example, with reference to the accompanying drawings; in which: Fig. 1 is a sectional view of an embodiment of a pressure regulator; and Fig. 2, comprising 2a and 2b, is a view of a modified end of the regulator shown in Fig. 1.

A pressure regulator comprises a housing 1 having inlet and outlet ports 2 and 3 respectively with a hollow piston 4 slidable within the bore of the housing. One end of the piston 4, the upper end as shown in the drawing, is of a smaller diameter than the opposite lower end. The two end portions are joined by an integral waist 5 having a bore therethrough to receive a spindle 6 which extends coaxially the length of the housing.

The bore of the housing is profiled to cooperate with the piston. An annular inlet chamber 7 communicates with the inlet port 2. The chamber 7 is arranged off-centre with respect to the axis of the piston whereby to produce a swirl flow path for fluid entering the chamber through the inlet 2.

An outlet chamber 8 communicates with the outlet port 3 and is separated from the inlet chamber by an inwardly directed flange or lip 9 which can engage a face 10 on the piston.

The upper and lower ends of the piston are in sliding, sealing engagement with cylindrical portions of the bore. Preferably, the cylindrical portions are formed by liners 11, 12 conveniently formed from stainless steel, to reduce wear and friction. The liner 11 is positioned between a lip 13 and an end cap 14. The liner 12 is positioned between a similar lip 1 5 and a sandwich plate 1 6 which is secured by countersunk screws 1 7 to the housing. A second larger end cap 1 8 is in turn secured to the sandwich plate 1 6 and the housing by a stud, plain washer, spring washer and nut assemblies 1 9.

A seal ring assembly 20 is located about the ends of the piston to cooperate with the stainless steel liners. Each assembly comprises an elastomeric O-ring, suitably a rubber O-ring surrounded by a plastics ring, the preferred plastics material being PTFE.

A spring assembly 21 is located within the larger diameter end of the piston. Conveniently the assembly comprises coaxial inner and outer coil springs 22 and 23 respectively. The springs are accommodated and positioned between stepped faces on the piston and stepped faces on a spring cap 24 which is supported by an adjustable nut 25 in threaded engagement with a thread at the end of the spindle 6. A locknut 26 is also provided on the threaded end of the spindle. The adjacent end of the spindle 6 is located in central socket in the end face of the end cap 1 8. This end face is further provided with openings 27 which are concealed beneath a resiliently deformable end cover 28.

The opposite end of the spindle is also threaded and is located in a bore in end cap 14. A lock nut 29 on the spindle bears against the inner face of the end cap and the end of the spindle protruding through the end cap 14 is secured by screw collar 30 with a tension pin 31 extending through aligned diametrical apertures in the spindle and the collar. The end cap 14 is secured to the housing by stud, plain washer, spring washer and nut assemblies 32 and the end cap is also provided with openings 33 which are concealed beneath a resiliently deformable end cover 34. A channel 35 formed on the inner face of the end cap communicates with the openings.

The waist 5 of the piston is profiled as shpwn in the drawing. Thus, in moving in a direction from the smaller diameter end of the piston to the larger diameter end the waist has an inwardly sloping surface 36 which is radiused at its base to merge smoothly with an outwardly sloping surface 37. The waist is profiled so as to present a smooth continuous surface to the fluid.

Preferably, the surfaces 36 and 37 are inclined at 45 to the longitudinal axis of the regulator.

In its inoperative condition the piston 4 is urged by the spring assembly 21 into an end position at which the end of the smaller diameter portion abuts against the inner face of the end cap 1 4. In this position of the piston the face 10 slides out of engagement with the flange 9 to provide an annular control port between the chambers 7 and 8. When the inlet port is coupled to a high pressure line the incoming high pressure fluid swirls around in the chamber 7 and passes into the outlet chamber 8 through the annular port formed between the separated face 10 and the flange 9. The fluid entering the chamber 8 tends to react on the faces 36 and 37 in opposite directions. The reaction at the face 36 tends to urge the piston towards the end cap 14 while the reaction at the face 37 tends to urge the piston in the opposite direction towards the end cap 18.

The smooth profile of the waist avoids any abrupt movement of the piston and the effective operating area of the piston is given by the annulus between the radii r1 and r2 where r, is the radius of the sealing face of the flange 9 and r2 is the radius of the sealing face of the liner 12. The piston will achieve a stable balance or equilibrium position at which the pressure on the piston is such as to maintain a substantially constant gap at the annular port between the chambers 7 and 8. The extent of this gap is determined by the tension of the spring assembly and this can be set by appropriate adjustment of the nut 25 on the spindle. The spring lengths and loads can be calculated and selected for different operating inlet and outlet pressures.As examples, the spring assembly at the left hand side of the drawing is for a low output regulator while that at the right hand side of the drawing is for a high output regulator. The low output regulator can receive an inlet pressure range from 140 to 240 p.s.i. with an outlet pressure setting range from 80 to 120 p.s.i. Such a regulator is suitable for a nominal flow of 100 gallons per minute. Corresponding figures for the high output regulator with the same inlet pressure range can be 110 to 134 p.s.i. outlet range and a nominal flow of 200 gailons/minute.

The spring assembly in Fig. 1 comprises two coaxial coil springs. Clearly, the assembly can be modified to include more than two springs and thereby increase the operating pressure range of the regulator. For example, a third coil spring could be accommodated in the larger diameter end of the piston and the regulator could then operate an-an outlet pressure in the region of 1 50 p.s.i.

It is to be noted that d gap 38 is provided between the faces of the piston and the liners at the side of each sealing ring assembly directed towards the respective chambers 7 and 8. The gaps enable the pressure fluid passing through the housing to scour away any dirt or debris which might otherwise damage the seals or increase their frictional resistance. The portions of the piston at the opposite sides of the sealing ring assemblies are in substantially sliding engagement with the liners to prevent lateral movement or play.

Seepage-of fluid can occur around the ends of the piston which could result in undesirable pressure build-ups. Any such seepage can escape through the openings 27 and 33 in the respective end caps 18 and 14.

Figs. 2a and 2b show'a modification for adjusting the pressure of the springs, Fig. 2b being a view at right angles to Fig. 2a.

The upper end cap 14 in Fig. 1 is modified in Figs. 2a and 2b whereby the piston rod 6 is slidable in the end cap. For this purpose, the bore in the end cap to receive the piston rod 6 is lined with a bush 50 to permit sliding movement of the piston rod. The end of the piston rod protruding beyond the end cap is threaded and received in threaded boss 51 which is fixedly secured to the base of a U-shaped member 52. The piston rod is secured by a locknut 53. The opposite end of the piston rod 6 is extended to maintain support within the end cap 18.

The U-shaped member 52 is arranged between two substantially identical inverted U-shaped members 54 which are mounted on four pillars 55 on the end cap 14. The members 54, pillars 55 and the end cap are secured to the housing 1 by studs or bolts (not shown).

Two spaced apart plates 56 are fixedly secured to the upper ends of the members 54, the plates passing between the limbs of the U-shaped member 52, and constituting a support for a cam follower 57. The cam follower 57 is carried on a spindle 58 which is journalled in the plates 56.

A spindle 59 passes through aligned bores at the free ends of the limbs of the U-shaped member 52 and a cam 60 is mounted on the spindle 59 to engage the cam follower 57. The cam is actuated and moved to turn about the spindle 59 by means of a lever or handle 61. In the illustrated embodiment the cam is movable between three operative positions as indicated and at which the cam surface is notched and profiled to match the curvature of the cam follower. Operation of the cam effects a jacking action on the piston rod 6 to change the tension of the spring assembly and thereby the operating pressure of the regulator.

Examples of the use of the described regulator are for reducing and regulating the pressure in branch lines of foam and water fire-fighting sytems and airfield crash tenders where the main operating pressure is too high for direct application.

Claims

1. A pressure regulator comprising a housing, a piston slideable in the housing, a pair of annular chambers in the housing about the piston, one of the chambers having an inlet for-a fluid at high pressure, the other chamber having an outlet for the fluid, an annular control port formed between cooperating portions of the piston and the housing and providing communication between the chambers, the piston presenting an increased surface area to the fluid within said other chamber such that fluid entering said other chamber acts to urge the piston into a position to close the control port, and adjustable spring means acting on the piston to oppose said fluid action to maintain the control port in an open condition consistent with a required pressure at the outlet from said other chamber.

2. A pressure regulator as claimed in claim 1 in which the piston has a first portion within said one chamber joined to a second portion within said other chamber by a waist portion presenting a smooth continuous surface to the fluid, the diameter of the first portion being smaller than the diameter of the second portion.

3. A pressure regulator as claimed in claim 2 in which the diameter of the waist portion decreases progressively from the respective first and second piston portions.

4. A pressure regulator as claimed in claim 2 or 3 including a spindle passing axially through the piston and journalled in the opposite ends of the housing.

5. A pressure regulator as claimed in claim 4 in which the spring means comprises a spring assembly located within the second portion of the piston between an end of said second portion adjacent the waist portion and a cap on the spindle.

6. A pressure regulator as claimed in claim 5 in which the cap is displaceable axially along the spindle to vary the tension of the spring assembly.

7. A pressure regulator as claimed in claim 5 including jacking means mounted on one end of the housing and coupled to the spindle to axially displace the spindle to vary the tension of the spring assembly.

8. A pressure regulator as claimed in claim 5, 6 or 7 in which the spring assembly comprises two or more coaxial coil springs.

9. A pressure regulator substantially as herein described with reference to and as illustrated in Fig. 1 of the accompanying drawings.

10. A pressure regulator substantially as herein described with reference to and as illustrated in Fig. 1 when modified by the arrangement in Fig. 2 of the accompanying drawings.