AU2002301985B1

AU2002301985B1 - Pressure control valve

Info

Publication number: AU2002301985B1
Application number: AU2002301985A
Authority: AU
Inventors: Walter George Morrison
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-05-06
Filing date: 2002-11-14
Publication date: 2003-02-13
Anticipated expiration: 2022-11-14

Description

Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT

APPLICANTS:

Invention Title: Walter George MORRISON and Jean Hilary MORRISON PRESSURE CONTROL VALVE The following statement is a full description of this invention, including the best method of performing it known to me: "PRESSURE CONTROL VALVE" Technical field This invention relates to a pressure control valve.

The invention has particular but not exclusive application to a pressure control valve which delivers a relatively constant pressure at the valve outlet when the pressure at the valve inlet reaches or exceeds the constant output pressure.

Background of Invention Pressure control valves are known, as are so-called constant pressure valves which purport to deliver a constant output pressure for varying input pressures.

However some known constant pressure valves deliver a constant pressure only within a specified range of varying input pressures. Thus a constant pressure valve which may deliver a relatively constant output pressure of 300 KPA for varying input pressure within a range of from 300-500KPA, may deliver an output pressure considerably in excess of 300KPA if the input pressure were to increase to 1000KPA.

One such valve is the subject of Australian patent 602199 wherein outlet pressure is controlled by the biasing effect of a spring acting against a piston the face of which has applied to it the pressure at the valve outlet. The outlet pressure overcomes the force exerted by the spring to move the piston away from the outlet and into engagement with a valve seat proximate the valve inlet to close off a bore extending through the piston for providing fluid communication between the inlet and the outlet.

Summary of Invention The present invention aims to provide an alternative to known pressure control valves which purport to deliver a constant outlet pressure. This invention in one aspect resides broadly in a pressure control valve including:an inlet; an outlet; a valve body between the inlet and the outlet; a piston having opposed smaller and larger ends each having a circumferentially extending piston wall, the piston being slideably received within the valve body and having a bore therethrough; a porting assembly for providing a closable fluid passageway between the inlet and the bore, and biasing means for biasing the piston against the pressure at the outlet towards a first position proximate the outlet from a second position proximate the inlet; wherein in the first position fluid communication is made between the inlet and the outlet via the porting assembly and the bore, and in the second position fluid communication between the inlet and the outlet is prevented by the circumferentially extending piston wall of the smaller end of the piston cooperating with the porting assembly to close the fluid passageway between the inlet and the bore.

In another aspect this invention resides broadly in a method of controlling the outlet pressure of a valve having an inlet, an outlet, a valve body between the inlet and the outlet, a piston having opposed smaller and larger ends and being slideably received within the valve body and having a bore therethrough, and a porting assembly for providing a closable fluid passageway between the inlet and the bore, the method including:biasing the piston against the pressure at the outlet towards a first position proximate the outlet from a second position proximate the inlet, whereby in the first position fluid communication is made between the inlet and the outlet via the porting assembly and the bore, and in the second position fluid communication between the inlet and the outlet is prevented by the circumferentially extending piston wall of the smaller end of the piston cooperating with the porting assembly to close the fluid passageway between the inlet and the bore.

It is preferred that the larger end of the piston is exposed to the pressure at the outlet.

It is also preferred that the valve body includes a chamber in fluid communication with the inlet via at least one aperture.

It is also preferred that the inlet and outlet comprise respective discrete members releasably connected to the valve body and that the chamber forms part of the valve body.

It is also preferred that the smaller end of the piston is received within the chamber when in the second position and that the porting assembly includes the at least one aperture and first sealing means for preventing fluid communication between the aperture and the chamber when the piston is in the second position.

It is also preferred that the valve includes second sealing means for preventing fluid communication between the inlet and the outlet other than via the bore.

It is also preferred that the chamber is cylindrical, the fluid communication between the inlet and the chamber is via a plurality of apertures disposed circumferentially about the chamber, and the first and second sealing means respectively include a pair of sealing rings spaced upstream and downstream of the apertures, the sealing rings being positioned by a lantern ring or the like juxtaposing the apertures.

It is also preferred that the chamber includes a plate member removable therefrom to provide an opening for the positioning of the lantern ring and sealing rings therein.

It is also preferred that the predetermined pressure is a function of the bias provided by the biasing means.

It is also preferred that the biasing means is a coil spring bearing on a seat on the valve body to bias the piston towards the first position against the action of the outlet pressure.

It is preferred that the spring is replaceable to vary the bias. The bias can also be varied by packing out the seat.

Description of Drawings In order that this invention may be more easily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention, wherein:- FIG 1 is a cross-sectional elevation illustrating a preferred embodiment of the pressure control valve in accordance with the present invention; FIGS 2A, 2B and 2C illustrate the sequential closing of the Sealing rings in the chamber proximate the inlet of the pressure control valve seen in FIG 1, and FIG 3 is a representative side view of the piston for the purposes of illustrating a difference between the pressure control valve in accordance with the present invention and a known pressure control valve.

Description of Preferred Embodiment of Invention As is best seen in FIG 1, pressure control valve 10 has an inlet 11 and an outlet 12 each of which can be screwed to connect to valve body 13 which is located between the inlet 11 and the outlet 12. Piston 14 has opposed smaller and larger ends 15,16 each having a circumferential surface, the piston being slideably received within the valve body 13 in respective stepped bores 17,18 in the valve body. Piston 14 has a bore 19 extending from one end 15 to the other end 16. As will be subsequently described, a porting assembly having apertures 20 provides a closable fluid passageway between inlet and bore 19. Biasing means in the form of compression spring 26 is seated on seat 27 in valve body 13 and biases piston 14 against the pressure at outlet 12 towards a first position (as seen in FIG 1) proximate outlet 12 from a second position (as seen in FIG 2C) proximate inlet 11. In the first position (FIG fluid communication is established between inlet 11 and outlet 12 via the apertures 20 and bore 19. In the second position (FIG 2C), fluid communication between inlet 11 and outlet 12 is prevented by the circumferentially extending piston wall of the smaller end 15 of piston 14 cooperating with the porting assembly to close the fluid passageway between inlet 11 and bore 19.

Valve body 13 is formed at one end with a chamber 21 in fluid communication with inlet 11 via a number of circumferentially disposed apertures 20, and as can be seen sequentially in FIGS 2A, 2B and 2C, the smaller end 15 of the piston 14 is received within chamber 21 when in the second position. The porting assembly also includes first sealing means in the form of sealing ring 22 which, when engaged by the circumferentially extending piston wall of the smaller end 15 of piston 14, prevents fluid communication between apertures 20 and chamber 21 when the piston 14 is in the second position (FIG 2C). Second sealing means in the form of sealing ring 23 prevents fluid communication between inlet 11 and outlet 12 other than via bore 19, ie it prevents leakage along the stepped bore 17,18 of valve body 13. Sealing rings 22,23 are held in place within cylindrical chamber 21 by a lantern ring 24 which is positioned within chamber 21 by removing a plate member 25 threaded to the end of the chamber and which when re-assembled holds the sealing rings 22,23 and lantern ring 24 in position within chamber 21 with lantern ring 24 in position juxtaposing the circumferentially disposed apertures 20 and with the sealing rings 22,23 upstream and downstream of apertures 20 respectively. Apertures 28 in lantern ring 24 are illustrated in FIGS 2A -and 2B and provide a closable fluid passage into chamber 21 from apertures It will thus be appreciated that pressure control valve 10 in accordance with this invention includes an inlet 11; an outlet 12; a valve body 13 between the inlet 11 and the outlet 12; a piston 14 having opposed smaller and larger ends 15,16 each having a circumferentially extending piston wall, the piston 14 being slideably received within the valve body 13 and having a bore 19 therethrough; a porting assembly 20,22 for providing a fluid passageway between the inlet 11 and the bore 12, and biasing means 26 for biasing the piston 14 against the pressure at the outlet 12 towards a first position (FIG 1) proximate the outlet 12 from a second position (FIG 2C) proximate the inlet 11; wherein in the first position (FIG 1) fluid communication is made between the inlet 11 and the outlet 12 via the porting assembly 20,22 and the bore 19, and in the second position (FIG 2C) fluid communication between the inlet 11 and the outlet 12 is prevented by the circumferentially extending piston wall of the smaller end 15 of the piston 14 cooperating with the porting assembly 20,22 to close the fluid passageway between the inlet 11 and the bore 19.

During operation as seen sequentially in FIGS 2A, 2B and 2C, in the second position (FIG 2A which corresponds with the position of piston 14 as illustrated in FIG 1) with the large end 16 of piston 14 proximate outlet 12, the circumferentially extending piston wall of the small end 16 of piston 14 engages with sealing ring 23 downstream of circumferential apertures 20 to prevent leakage of fluid into the stepped bore 17,18 of valve body 13 and in this position fluid communication between inlet 11 and outlet 12 is via apertures 20, chamber 21 and bore 19. Pressure at outlet 12 is applied to the face at the large end 16 of piston 14 and has the effect of moving piston 14 against the force of compression spring 26 in the direction of inlet 11. The interim position of piston 14 in its movement between the two positions described above is seen in FIG 2B.

As piston 14 moves further towards the inlet the circumferentially extending piston wall of the small end 15 of piston 14 also engages with sealing ring 22 upstream of circumferential apertures 20 to close fluid communication between apertures 20 and chamber 21, thereby closing the fluid communication between inlet 11 and outlet 12.

In use therefore, the present invention will be appreciated as providing a method of controlling the outlet pressure at a valve 10 having an inlet 11, an outlet 12, a valve body 13 between the inlet 11 and the outlet 12, a piston 14 having opposed smaller and larger ends 15,16 and being slideably received within the valve body 13 and having a bore 19 therethrough, and a porting assembly 20,22 for providing a closable fluid passageway between the inlet 11 and the bore 19, in which the method includes biasing the piston 14 against the pressure at the outlet 12 towards a first position (FIG 1) proximate the outlet 12 from a second position (FIG 2C) proximate the inlet 1 1, whereby in the first position fluid communication is made between the inlet 11 and the outlet 12 via the porting assembly 20,22 and the bore 19, and in the second position fluid communication between the inlet 11 and the outlet 12 is prevented by the circumferentially extending piston wall of the smaller end 15 of the piston 14 cooperating with the porting assembly 20,22 to close the fluid passageway between the inlet 11 and the bore 19.

The above explanation of the operation of the valve controlling the pressure at the outlet has not made reference to the effect caused by the pressure acting on the face area of the piston at the inlet end. An analysis of this effect and its significance in relation to the present invention will now be provided with brief reference to FIG 3 which is a side view of piston 14 showing the respective faces of the larger and smaller ends 16,15 and bore 19 being shown in dotted outline, with the radius of bore 19 being and the radius of the smaller end 15 being (r t) where is the thickness of the wall of the smaller end 15 of piston 14.

It will be appreciated that piston 14 is in effect a differential piston and that although the respective areas of the faces of the larger end of the piston and the samaller end are considerably different, the pressure of the fluid acting on the face of smaller end will generate a force which combines with the force exerted by spring 26 in overcoming the opposing force generated in the opposite direction by the pressure at the outlet acting on the face of the larger end 16 of piston 14. In general terms with respect to a valve of this type, when fluid communication between inlet and outlet is interrupted by closure of the fluid path upon movement of the piston towards the inlet away from the outlet, the forces which to that point have been overcome by the force generated by the outlet pressure acting on the face of the larger (ie the combined force generated by the spring and by the inlet pressure acting on face of the small end), is suddenly reduced to the force generated by the spring alone.

Thus as seen in FIG 3, this differential force is equal to the inlet pressure (P) multiplied by the area of the smaller end 15 of piston 14 [7t(r t) 2 7tr 2 in accordance with the equation F P [7r(r t) 2 2 P7t(2rt t 2 This variation in the force which counters that generated on the face of the larger piston end 16 can have an effect on the stability of the outlet pressure, both in terms of its constancy and also, if the force F above is sufficiently large, in terms of valve chatter or stutter. In other words, the larger the force F, the less stable the outlet pressure and the greater the likelihood of valve chatter. Put differently, for a given inlet pressure and piston bore diameter, the smaller the wall thickness of the tube constituting the smaller end of the piston, the more constant the outlet pressure and the less likely that the valve will chatter.

It will therefore be readily appreciated that the valve of the present invention has some distinct advantages over known valves and particularly over the valve disclosed in Australian patent 602199. In order to provide effective closure in a valving arrangement where sealing is provided by a tube abutting a valve seat, it is important that the wall of the tube have sufficient thickness to prevent leakage across the width when the valve seat is engaged. Moreover, the wall must be relatively thick to prevent the valve seat wearing out after relatively little usage. On the other hand, in the present invention where the closure is provided by the sliding action of the periphery of the tube engaging a surrounding sealing ring, the above limitations imposed on the thickness of the tube do not apply.

This is of considerable significance because the force F as calculated in the equation above is subject to a square law. Typically in a valving arrangement as illustrated in 602199, for an inlet pressure of about 300KPA, and a valve with a piston having a bore of 10 mm diameter, the wall thickness must be at least 2-3 mm to provide an effective seal on the seat and to prevent rapid wear of that seat. By way of contrast, the wall thickness in the present invention is limited only by the requirement for the wall to withstand the inlet pressure and for similar dimensions as referred to above, the wall thickness need be no more than 0.5 mm. A valve having a 10 mm bore with a wall thickness of 0.5 mm at the smaller end of the piston will have a pressure differential F which is 4.57 less than that of the same valve with a wall thickness of 2 mm. This comparative factor will increase to 7.43 if the wall thickness increases to 3 mm. Should the wall thickness in accordance with the present invention be as low as 0.3 mm, the relative comparative factors increase from 4.57 to 7.77 for the present invention compared with a 2 mm wall thickness, and from 7.43 to 12.62 when compared with a 3 mm wall thickness.

Furthermore, the wear on the sealing ring seal is considerably less than the wear on the valve seat, leading to longer valve life.

Furthermore, ease of assembly is greatly facilitated by the simple method in the present invention of accessing the chamber in which the sealing rings are located, by means of the removable end plate, thereby leading to enhanced ease of manufacture and reduced cost.

It will of course be realised that whilst the above has been given by way of an illustrative example of this invention, all such and other modifications and variations hereto, as would be apparent to persons skilled in the art, are deemed to fall within the broad scope and ambit of this invention as is herein set forth.

Claims

1. A pressure control valve including:- an inlet; an outlet; a valve body between the inlet and the outlet; a piston having opposed smaller and larger ends each having a circumferentially extending piston wall, the piston being slideably received within the valve body and having a bore therethrough; a porting assembly for providing a closable fluid passageway between the inlet and the bore, and biasing means for biasing the piston against the pressure at the outlet towards a first position proximate the outlet from a second position proximate the inlet; wherein in the first position fluid communication is made between the inlet and the outlet via the porting assembly and the bore, and in the second position fluid communication between the inlet and the outlet is prevented by the circumferentially extending piston wall of the smaller end of the piston cooperating with the porting assembly to close the fluid passageway between the inlet and the bore.

2. A pressure control valve as claimed in claim 1, wherein the larger end of the piston is exposed to the pressure at the outlet.

3. A pressure control valve as claimed in claim 1, wherein the valve body includes a chamber in fluid communication with the inlet via at least one aperture.

4. A pressure control valve as claimed in claim 1, wherein the inlet and outlet comprise respective discrete members releasably connected to the valve body and the chamber forms part of the valve body.

5. A pressure control valve as claimed in claim 3, wherein the smaller end of the piston is received within the chamber when in the second position and the porting assembly includes the at least one aperture and first sealing means for preventing fluid communication between the aperture and the chamber when the piston is in the second position.

6. A pressure control valve as claimed in claim 5, and including second sealing means for preventing fluid communication between the inlet and the outlet other than via the bore.

7. A pressure control valve as claimed in claim 6, wherein the chamber is cylindrical, the fluid communication between the inlet and the chamber is via a plurality of apertures disposed circumferentially about the chamber, and the first and second sealing means respectively include a pair of sealing rings spaced upstream and downstream of the apertures, the sealing rings being positioned by a lantern ring or the like juxtaposing the apertures.

8. A pressure control valve as claimed in claim 7, wherein the chamber includes a plate member removable therefrom to provide an opening for the positioning of the lantern ring and sealing rings therein.

9. A pressure control valve as claimed in claim 1, wherein the outlet pressure is a function of the bias provided by the biasing means.

A pressure control valve as claimed in claim 9, wherein the biasing means is a coil spring bearing on a seat on the valve body to bias the piston towards the first position against the action of the outlet pressure.

11. A pressure control valve as claimed in claim -10, wherein the spring is replaceable to vary the bias.

12. A pressure control valve as claimed in claim 10, wherein the bias is varied by packing out the seat.

13. A method of controlling the outlet pressure of a valve having an inlet, an outlet, a valve body between the inlet and the outlet, a piston having opposed smaller and larger ends and being slideably received within the valve body and having a bore therethrough, and a porting assembly for providing a closable fluid passageway between the inlet and the bore, the method including:- biasing the piston against the pressure at the outlet towards a first position proximate the outlet from a second position proximate the inlet whereby in the first position fluid communication is made between the inlet and the outlet via the porting assembly and the bore, and in the second position fluid communication between the inlet and the outlet is prevented by the circumferentially extending piston wall of the smaller end of the piston cooperating with the porting assembly to close the fluid passageway between the inlet and the bore.

14. A pressure control valve substantially as described with reference to the embodiments illustrated in the drawings. WALTER GEORGE MORRISON and JEAN HILARY MORRISON by PIZZEYS PATENT AND TRADE MARK ATTORNEYS