NZ533836A - Improvements in pressure relief valves - Google Patents

Abstract

A filter 40 for a pressure relief valve includes a filter material to create, in use, a filter barrier between an interior of the pressure relief valve and ambient air. The filter 40 has a releasable coupling for fixing part of the filter in position on a seat 48 mounted on the valve body. The coupling allows the filter 40 to be moved from the seat 48 in the event that the filter becomes blocked.

Description

533836 No: 533836 Date: 29 June 2004 NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION IMPROVEMENTS IN PRESSURE RELIEF VALVES WE, MERCER STAINLESS LIMITED a New Zealand company of Corbett Street, Bell Block, New Plymouth, New Zealand do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:- SPEC 1731 l;\l i ELLfcCTur'.L. ;;:F.TV or !\i 7 2 3 JU.j ZM 21 JUNE 2005 2 TITLE OF INVENTION Improvements in Pressure Relief Valves BACKGROUND TO THE INVENTION This invention relates to improvements in pressure relief valves.

In our New Zealand patent specification 331111 there is disclosed a pressure relief valve. This valve has proved to be commercially very successful.

Broadly, the valve has a body with a valve element moveable within the body. Movement of the valve element can bring an inlet port into communication with an outlet port. The valve element is, however, moveable for a distance, while still maintaining the sealing effect, before communication between the inlet and outlet ports occurs.

The pressure relief valve of NZ 331111 has been particularly useful with road transport tankers (e.g. those used in the dairy industry for transporting milk) as the pressure relief valve provides tank protection both for negative and positive pressures. Thus, the valve is able to allow air or liquid to move in or out of the tank during performance of typical operations such as filling, emptying and clean in place. Furthermore, it provides a venting function when there are temperature changes in either the product or air in the tank.

SPEC 1731 21 JUNE 2005 There has been identified a need to be able to transport in milk transporters, on the road, products such as processed milk, thereby leading to a requirement to ensure that there is no ingress of contaminated air flow through the valve and into the tank. The problem with providing such a filter is that it must be of a type which does not negate the valve protection in the event that the filter blocks as it is important that the valve continue to protect the tank in negative pressure situations.

SUMMARY OF THE INVENTION An object of the present invention has been to provide a filter which can be used in conjunction with a pressure relief valve but one which does not tend to negate the valve protection in the event that the filter blocks.

Broadly according to one aspect of the present invention there is provided a filter for a pressure relief valve including a filter material of a physical size and shape to, in use of the filter in a pressure relief valve, create a filter barrier between the interior of a pressure relief valve and ambient air, said filter having a releasable coupling for fixing a part of the filter in position with a seat mounted with the valve whereby said releasable coupling can permit said part of the filter to be moved from said seat in the event of the filter being blocked to a degree that in a negative or positive pressure situation the pressure relief valve is inhibited from correct operation.

INTELLECTUAL PROPERTY OFFICE OF N.Z. 2 0 DEC 2006 RECEIVED SPEC 1731 21 JUNE 2005 4 Preferably the filter is of a tubular form. More preferably the tubular form has an end with which the stretchable coupling is engaged. Preferably the end of the tubular form with which the releasable coupling is engaged is of less cross-sectional area than the other end.

Preferably the tubular form is substantially of truncated conical shape.

In a preferred embodiment the end of greater cross-sectional area includes fixing means for fixedly clamping the end of the filter in place.

In a second broad aspect of the invention there is provided a pressure relief valve incorporating a filter as described in the first broad aspect.

The valve can include a second filter which is of a perforated mesh and located adjacent the filter to remove larger air borne particles.

Preferably the filter is located with a bell shaped cover fitted to the pressure relief valve.

In the preferred form the pressure relief valve is of the type described and claimed in New Zealand, patent specification 331111.

SPEC 1731 21 JUNE 2005 BRIEF DESCRIPTION OF THE DRAWINGS In the following more detailed description of a preferred form of a filter, according to the present invention, reference will be made to the accompanying drawings in which:- Figures 1 is a cross-sectional view of a commercial form of the pressure relief valve of New Zealand patent specification 331111 in conjunction with the filter according to the present invention, Figure 2 is a partial cut away perspective view of the arrangement shown in Figure 1, and Figure 3 is a sectioned elevation view of the filter.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION The filter, according to the present invention, is primarily intended for use with a pressure relief valve of the type described and claimed in New Zealand patent 331 111. However, the filter is envisaged as being usable with other pressure relief valves of the general type where a valve element is moveable to provide communication between the interior of a vessel and atmosphere in response to varying positive and negative pressure conditions.

SPEC 1731 21 JUNE 2005 6 Therefore, while the disclosure in New Zealand patent specification 331111 is herein incorporated by specific reference, it will be appreciated by those skilled in the art that the filter is not intended solely for use with the pressure relief valve disclosed in NZ 331111.

As shown in the drawing, the pressure relief valve 10 has a so-called inlet end 11, which is mounted by a screw thread collar 12 to a threaded mount 13 mounted with the wall of a vessel or tank T.

The inlet 11 is formed by the open end of a tubular sleeve 14. The other end of the sleeve 14 is closed at the end opposite by a wall 1 5. One or more apertures 16 are formed in the sleeve 14. These apertures 16 form the outlets which communicate with the inlet 11 when the valve element 17 (referred to below) is in the position shown in the drawing.

The first valve element 17 is slidably located in sleeve 14. As disclosed in NZ 331111, this primary valve element 17 includes one or more spring loaded secondary valve elements 18.

Extending from the first valve element 1 7 is a stem 19, which extends through a sealed bush 20 in wall 15. The upper end of stem 19 engages with a piston 21, which is slidingly engaged in a chamber formed by housing 42. A spring 23 is SPEC 1731 21 JUNE 2005 7 engaged between the piston 21 and wall 15. An inlet port 24 opens into the chamber 29.

All of the foregoing is in accordance with the pressure relief valve described in NZ 331111 and the pressure valve is operable in accordance with the disclosure in that patent specification.

Also shown in the accompanying drawing is a clean in place arrangement, which comprises a plurality (preferably two) of clean in place couplings 25 mounted by wall 1 5. Each coupling 25 has a spray ball 26 located in the area between wall 1 5, sleeve 14 and the moveable valve element 17. The other spray ball 16 is adjacent housing 22. Via a straight adaptor 27 a CIP connection hose 28 connects the CIP couplings 25. CIP fluid is supplied to the CIP system via an elbow adaptor 29.

A centre bearer 30 is mounted with and extends peripherally out from wall 1 5. This bearer 30 supports a plurality of pairs of upper and lower spacer rods 31 and 32. Stepped ends of the rods engage in openings in the bearer 30. The ends of the rods are welded in place.

The lower ends of the lower spacer rods 32 are threaded and nuts 33 are threaded thereon to locate a lower annular disc 34 through which the lower ends of the lower spacer rods 32 engage. A lower O-ring seal 35 provides a seal between the inner circumferential edge of disc 34 and the outer wall surface of sleeve 14.

SPEC 1731 21 JUNE 2005 8 To the upper ends of the upper spacer rods 31 there is fitted and fixed an upper annular disc 36. An upper O-ring seal 37 is located between the inner circumferential edge of disc 36 and the outer wall surface of housing 22.

A bell shaped cover 39 is removably attached to the upper disc 36. This is facilitated by knobs 38 having threaded shafts which engage in tapped bores in upper disk 36.

A filter 40 encircles the whole of the aforementioned assembly. The filter 40 is of a flared configuration (i.e. generally truncated conical shape) with the narrower and upper end coupled to the upper disc 36 by a resilient O-ring 41. The O-ring 41 can be fastened in place on the filter by being sewn into a hem in the filter material or have a tape 46 sewn over it. The lower and wider end of the filter 40 engages about a lower filter dish 42, which is supported by the lower disc 34 as shown.

The filter 40 is made of any filter material suitable for the end purpose. Thus for example it can be EU-5 filter material. In such a configuration the dense smooth clean air side of the material is innermost and the seam is on the outside.

A perforated mesh disc 43 is located between the interface of the floor of the lower filter dish 42 and the lower disc 34. The mesh disc 43 has at its outer edge a wall 44, which is spaced from the lower peripheral surface of the filter 40. As shown, this SPEC 1731 21 JUNE 2005 9 perforated mesh disc 43 supports and locates a secondary perforated filter 45 which, at its upper end, abuts with the inner surface of the cover 39.

The purpose of the perforated secondary filter 45 is to remove larger air borne particles. Finer particles, which might pass through the secondary filter will be filtered by the primary filter 40.

The primary filter 40 is clamped (see Figure) by a stainless steel clamp 47 at its lower end. The clamp 47, as shown, extends about the periphery of the lower end. A reinforcing annular element 49 can be incorporated in the lower end of the filter (see Figure 2). Because of the stretchable medium in the form of the filter O-ring 41 fitted to the top of the primary filter 40 the filter 40 can be drawn away from the seat 48 (in the edge of disc 36) with which the top end of the filter engages. Thus the filter 40 can be sucked off seat 48 at the top end of the filter sufficient to relieve the tank T in a situation where the filter 40 might be one hundred percent (100%) blocked.

It is envisaged that a differential pressure device can be fitted into the filter 40 to indicate that the filter 40 has been sucked off its top seat. This differential pressure device could alternatively indicate that the filter 40 is approaching a blocked state.

In normal operation of the pressure relief valve the filters 40 and 45 will carry out their normal filtering operation and the pressure relief valve will operate normally.

SPEC1731 21 JUNE 2005 However, in the event that the primary filter 40 is fully blocked or has reached a blocked state sufficient to adversely impact on the normal operation of the pressure relief valve the filter 40 can become sucked off its top seat sufficient to relieve the tank in a negative pressure situation. In a pressure situation the filter 40 would also be forced, by say liquid moving from tank T, to move from its seat 46 thereby resulting in tank content moving through the valve 10 and creating a mess in the valve but nevertheless ensuring that relief to the tank is provided.

The truncated conical shape of filter 40 makes it easier to install and allows the smaller end area to be influenced by the vacuum pulling it off its seat if required. Also, the filter will, it is believed, tend to block from the bottom up as it retains liquid.

The present invention thus provides a filter for a pressure relief valve, which can function to prevent ingress of contaminated airflow through the valve and into the tank. The filter does not interfere with the normal operation of the valve. However, in the event that the filter becomes blocked it can, in either a negative or positive pressure situation, automatically move to ensure fluid movement through the valve can nevertheless occur.

SPEC1731 21 JUNE 2005 11

Claims (21)

WHAT WE CLAIM IS;-

1. A filter for a pressure relief valve the filter including a filter material of a physical size and shape to, in use of the filter in a pressure relief valve, create a filter barrier between the interior of a pressure relief valve and ambient air, said filter having a releasable coupling for fixing a part of the filter in position with a seat mounted with the valve whereby said releasable coupling can permit said part of the filter to be moved from said seat in the event of the filter being blocked to a degree that in a negative or positive pressure situation the pressure relief valve is inhibited from correct operation.

2. The filter as claimed in claim 1 wherein the filter is of a tubular form.

3. The filter as claimed in claim 2 wherein the tubular form has an end with which the releasable coupling is engaged.

4. The filter as claimed in claim 3 wherein the end of the tubular form with which the releasable coupling is engaged is of less cross-sectional area than the other end.

5. The filter as claimed in claim 4 wherein the end of greater cross-sectional area includes fixing means for fixedly clamping the end of the filter in place. SPEC 1731 INTELLECTUAL PROPERTY OFFICE OF N.Z. 2 0 DEC 2006 d F r P i \/ P n 1 JUNE 2005

6. 12 The filter as claimed in claim 5 wherein the fixing means is an adjustable clamp which extends about the periphery of the filter.

7. The filter as claimed in claim 6 wherein an annular reinforcing element is incorporated with the greater cross-sectional end of the filter.

8. The filter as claimed in any one of claims 1 to 7 wherein the releasable coupling is a resilient O-ring.

9. The filter as claimed in claim 8 wherein the O-ring is fastened to the filter.

10. The filter as claimed in claim 9 wherein the O-ring is fastened to the filter by being sewn in a hem or covered by a tape sewn onto the filter.

11. The filter as claimed in any one of claims 1 to 10 wherein the filter is of substantially truncated conical shape.

12. The filter as claimed in any one of claims 1 to 11 wherein the filter material is EU-5 filter material.

13. A pressure relief valve incorporating a filter as claimed in any one of claims 1 to 12. SPEC 1731 21 JUNE 2005

14. 13 The valve as claimed in claim 13 wherein the valve includes a second filter which is of a perforated mesh and located adjacent the filter.

1 5. The valve as claimed in claim 13 or 14 wherein the filter is located within a bell shaped cover fitted to the valve.

16. The valve as claimed in claim 13, 14 or 15 wherein the valve includes an annular seat with which the releasable coupling of the filter is engaged.

1 7. The valve as claimed in any one of claims 13 to 16 further including a filter dish to which a part of the filter is fixedly attached.

18. The valve as claimed in claim 14 wherein the second filter is mounted by a mesh filter dish coupled to a part of a body of the valve.

19. The valve as claimed in any one of claims 13 to 18 wherein the pressure relief valve is of the type described and claimed in New Zealand, patent specification 331 111.

20. A filter as claimed in claim 1 substantially as herein described with reference to the accompanying drawings. SPEC 1731 21 JUNE 2005

21. 14 A pressure relief valve as claimed in claim IB substantially as herein described with reference to the accompanying drawings. MERCER STAINLESS LIMITED By its Attorney DON HOPKINS & ASSOCIATES PER: INTELLECTUAL '-'.JF^'FiTY OFFICE 0! 2o ?!'•« rr, SPEC 1731 21 JUNE 2005