WO2007012121A1

WO2007012121A1 - Stressed valve manufacturing method

Info

Publication number: WO2007012121A1
Application number: PCT/AU2006/001046
Authority: WO
Inventors: Stuart Maxwell
Original assignee: Global Valve Technology Limited
Priority date: 2005-07-26
Filing date: 2006-07-26
Publication date: 2007-02-01

Abstract

This invention relates generally to the manufacture of a product in the form of a valve. The general steps involved in manufacture of the valve (10) are as follows: (1). The valve (10) is formed in its initial configuration which is in a substantially unstressed condition; and (2). The valve in its initial configuration is at least partially inverted to provide the valve (10) in its operative and stressed condition.

Description

STRESSED VALVE MANUFACTURING METHOD

FIELD OF THE INVENTION

The present invention relates broadly to a method of manufacturing a product such as a valve or seal. The invention further relates to the manufactured product itself.

BACKGROUND OF THE INVENTION

Figure 1 is a schematic diagram taken from Australian Standard 2845:1 of a dual check valve of the prior art. The check valve is for example used domestically at a water meter to prevent reverse flow into the mains water supply. The prior art check valve 1 comprises a main housing 2 containing a pair of non-return valves 3 and 4 arranged in series adjacent one another. The non-return valves 3 and 4 are identical in construction having a poppet valve element 5 coaxially mounted on a spindle or shaft 6 for sliding and reciprocating movement. The poppet 5 is urged via a compression spring 7 into sealing engagement with an inner annular surface of a poppet housing 8. In other applications the check valve will include one only of the non-return valves.

This water meter check valve of the prior art suffers from at least the following drawbacks:

1. The non-return valves of the check valve are fabricated from multiple components;

2. the non-return valve relies upon seals and relatively accurate machining or moulding for effective closure; and

3. the relatively complex nature of this check valve means that it is susceptible to failure and requires maintenance or frequent replacement.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided a method of manufacturing a product, said method comprising the steps of: forming an initial configuration of the product in a substantially unstressed condition; and inverting at least part of the initial product to provide the product in an operative and stressed condition.

Preferably the step of inverting the initial product involves turning said at least part of the initial product inside out. More preferably inversion of said at least part of the initial product imparts stress to said part which is transmitted to other parts of the product which are thus post-stressed in the operative and stressed condition. Even more preferably this inversion step is performed manually.

Preferably the step of forming the initial configuration of the product involves moulding or casting it into the initial configuration. More preferably the moulding or casting involves forming an opening in the initial product, said opening being closed on inversion of the initial product. Alternately the opening is formed independent of the step of moulding or casting. The product may also be formed in its initial configuration by machining, bonding, gluing or other forms of fabrication.

Preferably the step of moulding or casting the product into its initial configuration involves forming biasing means in said at least part of the initial product. More preferably the step of moulding or casting the product involves forming recesses associated with the biasing means in said at least part of the initial product.

Preferably the step of inverting the initial product involves turning part of the initial product inside out so that biasing means projecting outwardly from said at least part of the initial product are in the product directed inwardly. More preferably said inversion of the initial product results in said at least part of the initial product enveloping the other parts.

Preferably the step of forming the initial configuration of the product involves specifically shaping said at least part of the initial product to determine the stress imparted to said part and thus transmitted to the other parts. More preferably said at least part of the product is shaped cylindrical but with a longitudinal taper which dictates the stress imparted to this cylindrical part on its inversion to the operative and stressed condition. Even more preferably the opening is configured, either alone or in combination with the said at least one part, to vary the stress imparted to said at least part of the initial product on its inversion. According to another aspect of the invention there is provided a product which in its operative condition comprises a stressed part which is formed by inverting at least part of an initial configuration of the product having been formed in a substantially unstressed condition.

Preferably the product comprises a housing connected to the stressed part which includes one or more moveable elements. More preferably the moveable elements are each in the form of a closure or sealing element.

Preferably the product is a valve wherein the housing is shaped generally cylindrical. More preferably the closure elements of the valve together, in the operative and stressed condition, form a dome or pyramid shaped valve element connected to and located coaxially with the housing. Still more preferably the closure elements are separated by one or more collapsible slits formed at or adjacent an apex of the valve element.

Alternately the housing is in cross-section shaped generally square or rectangular and there is a single closure element formed by a single slit. Preferably the single closure element is substantially planar in the form of a closure flap.

In another embodiment the valve comprises a tensioning element connected to the stressed part which includes one or more moveable valve elements. In this embodiment the tensioning element includes a ring member formed integral with the valve and configured to lock into retaining engagement with the stressed part for biased closure of the valve elements.

According to a further aspect of the invention there is provided a method of manufacturing a valve, said method comprising the steps of: forming an initial configuration of the valve in a substantially unstressed condition; and deflecting at least part of the initial valve to impart stress to a remaining part of the valve which is retained in an operative and stressed position.

Preferably the initial configuration of the valve includes a plurality of housing segments and the deflection step involves bending of the housing segments inwardly of the valve. More preferably this step of bending the housing segments is effected during installation of the valve in a valve casing wherein the deflected housing segments together form a housing or skirt of the valve. According to yet another aspect of the invention there is provided a valve which in its operative condition comprises a stressed part which is formed by deflecting at least part of an initial configuration of the valve having been formed in a substantially unstressed condition, the deflected part being locked in position to retain the stressed part in the operative and stressed condition.

Preferably the valve also comprises one or more biasing elements each connected to the valve housing and arranged on closure of the valve to contact the valve elements for sealing closure at relatively low differential pressures. More preferably the biasing element is in the form of a lug connected to and projecting inwardly of the valve housing, the lug being aligned with a corresponding recess in the valve housing. Even more preferably the lug at least in part deflects into the recess on opening of the valve.

Preferably the valve is retained normally closed with a closure pressure dictated by forces induced in the stressed part from deflection or inversion of the product in its initial unstressed configuration. More preferably the closing pressure of the valve in the operative and normally closed condition provides closure of the valve up to a minimum differential pressure. Even more preferably the minimum differential pressure is relatively low and between 3.5 to 15 kPa.

Preferably the product is of a unitary design and at least in part formed of a resiliently flexible material. More preferably the product is moulded in one piece from a plastic or thermoplastic or elastomeric material such as silicone or rubber.

Alternately the product is a seal.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to achieve a better understanding of the nature of the present invention preferred embodiments of a method of manufacturing a product, together with the product itself, will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a schematic diagram of a prior art dual check valve;

Figure 2 shows various views of a product formed in its initial configuration; Figure 2a shows various views of a variation of the product of figure 2 in its initial configuration;

Figure 3 shows various views of the product of figure 2 in its operative and stressed condition;

Figure 4a shows various views of another embodiment of the product formed in its initial configuration;

Figure 4b shows various views of the product of figure 4a shown open and closed in its operative condition;

Figures 5a and 5b show various perspective and sectional views of a valve in each of its initial and stressed/operative configurations, respectively,

Figures 6a to 6c schematically depict a sequence of steps for inverting and stressing a valve according to another embodiment of the invention;

Figures 7a to 7c schematically show a valve in its initial and stressed/operative configurations; and

Figure 8 are detailed views of an enlarged section of the product of figure 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiment of the invention relates to the manufacture of a product in the form of a valve. However, it should be appreciated that the invention extends to the manufacture of other products, such as seals, which involve process steps as broadly defined by this specification. The invention also relates to the product itself which is not to solely be limited to the valve of the preferred embodiment but extends to other products which requiring induced stressing or loading in anticipation of their subsequent use or application.

Figures 2 and 3 should assist in better understanding the general steps involved in manufacture of a product, in this example a valve 10, namely:

1. the product is formed in its initial configuration such as that shown in figure 2 which is in a substantially unstressed condition; and 2. the product in its initial configuration is at least partially inverted to provide the valve 10 in its operative and stressed condition as illustrated in figure 3.

The initial configuration of the valve 10 is in this example moulded from a plastic or elastomeric material using either a compression moulding, vacuum moulding or injection moulding technique. The product is moulded in appropriate tooling, such as a die or mould having a cavity for injection of the elastomeric compound. The tool or die (not shown) may also include a feature or insert which forms an opening in the initial product. The opening of this example is in the form of the pair of perpendicular intersecting slits 12A and 12B. As shown in figure 2 the initial product includes a circumferential skirt 14 formed continuous with a dome-shaped valve member 16. The skirt 14 is slightly concave and angled radially inwardly. The slits 12A/B in this example are slightly exposed or opened in this unstressed condition of the product in its initial configuration.

As shown in figure 2a the product may be formed without the slit(s) which are cut or otherwise formed in a supplementary step. The broken line detail of figure 2a shows where the slits of this embodiment are to be cut prior to inversion of the initial product. The product may be formed in its initial configuration by other techniques including injection moulding, transfer moulding, die casting, pressure or other forms of fabrication such as gluing and bonding.

In figure 3 the initial product has been at least in part inverted to provide the valve 10 of this example. The skirt 14 is inverted or turned inside out from its initial configuration to envelope the dome-shaped valve member 16 in the operative condition. Inversion of the skirt 14 imparts the stresses to the skirt 14 which are transmitted to the valve member 16. In this embodiment the stresses imparted to the skirt 14 tension or induce a bending moment in the valve member 16.

The pair of slits 12A/B divide the valve member 16 into four generally triangular-shaped quadrants or valve elements 18A to 18D, respectively. The tension or induced bending moment in each of the valve elements such as 18A urges or biases them into abutment with each other for effective closure and sealing of the slits 12A/B. The sealing or closure force provided by the valve member 16 or valve elements 18A to 18D will be dictated by a range of factors including: 1. the material from which the product is manufactured where, for example, greater stresses may be imparted for materials having a relatively high modulus of elasticity;

2. the initial configuration of for example the skirt 14 which may be specifically designed to attain predetermined stresses on inversion;

3. the extent to which for example the skirt 14 is inverted and stressed;

4. the size of the opening or slits which in this case will assume a greater sealing or closure force when the slit in its initial configuration is narrowed.

The closure or sealing force provided by the product or in this example valve 10 will also depend on the particular design of the product in its operative and stressed or loaded conditions. As best shown in figure 3, the valve 10 of this embodiment includes an internal annular recess 20 where the skirt 14 adjoins the valve member 16. This annular recess 20 influences the force or differential pressure required to open or unseal the valve member 16.

The valve 10 of this embodiment includes a continuous and generally square-shaped annular recess 20 which defines a web or bending element such as 22 about which the valve member 16 deforms to open. In this example the annular recess 20 and corresponding square-shaped web 22 is in the form of a hinge about which respective of the valve elements 18 A to 18D fold. The stresses imparted to the skirt after inversion are transmitted to the hinge 22 for preloaded closure of the valve elements 18 A to 18D. The valve of this general construction is a water valve including an elastomeric or resiliently flexible hinge as disclosed in the applicant's international patent application no. PCT/AU2005/001762. The disclosure of this international patent application is to be considered included herein by way of reference.

Figure 4a illustrates another embodiment of the valve 10 in its as moulded state. For ease of reference and to avoid repetition, components of this embodiment which generally correspond to the preceding embodiments have been designated with the same reference numeral. The step of moulding or casting this embodiment into its initial condition involves forming biasing elements in the form of lugs such as 24, projecting outwardly from the skirt 14, and also recesses such as 26 associated with the lugs 24 in the skirt 14. As shown in figure 4b, after inverting the skirt 14 the lugs 24 are directed inwardly to contact the valve member 16. Also, the skirt 14 envelopes the valve member 16. This ensures sealing closure of the valve 10 at low differential pressures (see lower section c-c). When the valve opens the lugs 24 at least in part deflect into the associated recesses such as 26 allowing the valve 10 to open to its maximum extent (see upper section C-C).

Figures 5a and 5b show a valve 50 taken from a sports ball. The sports ball valve 50 is generally of a similar construction to that disclosed in the applicant's international patent application no. PCT/AU2004/000329 and its national equivalents. The disclosure of this patent family is by way of reference to be considered included herein. The sports ball valve 50 comprises a mounting element or membrane 52 of a disc shape connected to a generally conical or bulbous shaped valve element 54 via an isolation zone 56. The isolation zone 56 is formed by a narrowed or necked portion of the valve 50. The valve 50 includes an elongate passageway 57 extending into a collapsible aperture or slit (not shown) at the valve element 54.

In this embodiment and as best shown in figure 5a, the sports ball valve 50 includes an annular recess or channel 58 formed about an outer surface of the bulbous valve element 54. The channel 58 is in cross-section in the general shape of a trapezium. The valve 50 also comprises a tensioning element 60 connected to and extending axially downward from the bulbous valve element 54. The tensioning element 60 includes a ring member 62 connected to the valve element 54 via a resiliency flexible sleeve 64. The ring member 62 is shaped complementary to the channel 58 so that it locks into the channel 58 on inversion of the flexible sleeve 64. The ring member 62 applies a tension force or hoop stress to the valve element 54 to bias the collapsible slit of the valve 50 closed.

Figures 6a to 6c show a variant of the sports ball valve 50 of figures 5a and 5b. For ease of reference and to avoid repetition, like components of the valves 50 have been designated with the same reference numeral. In this embodiment the tensioning element 60 is generally cup- shaped and located about midway along the valve 50. The tensioning element 60 includes a ring member 62 which is circular in cross-section and substantially resembles an O-Ring. The tensioning element 60 also includes a resilien y flexible cup-shaped member 64 which on inversion provides locking of the O-Ring member 62 into an annular channel 58 in the valve element 54. The O-Ring member provides a tension force or hoop stress to the valve element 54 in the same manner as the preceding embodiment. The valve 50 of this embodiment may also include a protrusion or shoulder 66 formed about the neck of the isolation zone 56. This shoulder 66 is designed to abut or be squeezed by the flexible member 64 on its inversion.

The sports ball valves 50 are thus fabricated in a substantially unstressed condition in an initial configuration as shown in figures 5a and 6a/b. The tensioning element 60 and in particular the flexible sleeve or cup-shaped member 64 is then inverted to engage with and impart stress to the valve element 54 to bias it closed.

Figures 7a to 7c illustrate a valve 70 of yet another embodiment of the invention. The valve 70 of this particular example is a water valve 70 and as such is a variation of the valves of figures 2 to 4. In this example the valve 70 generally comprises a plurality of housing segments or in this case quadrants 72A to 72D extending outwardly from the valve 70 at an acute angle in an unstressed condition. The quadrants 72A to 72D are designed to be deflected or bent inwardly to impart stresses to the remainder of the valve 70. The stresses are directed to the dome shaped valve member 74 to bias or urge it closed. The valve 70 locates within a cylindrical housing (not shown) which effects deflection of the quadrants 72A to 72D which together form the circumferential skirt 76. The general steps in manufacturing the valve 70 are thus as follows:

(i) the valve 70 is fabricated in a substantially unstressed condition as shown in figures 7a and 7b; and

(ii) the unstressed valve 70 in the initial configuration is installed in a housing whereby the quadrants 72A to 72D are deflected to stress the valve member to promote closure of the valve as shown in figure 7c.

The valves 10 of these embodiments can be specifically designed to only open at a minimum differential pressure. In its application as a water meter valve it should remain closed up to a differential pressure of 7 kPa. The valve in this application is oriented in its operative condition with the dome-shaped valve member 16 directed in a downstream direction. By maintaining closure of the valve up until a differential pressure of 7 kPa, there is no risk of leakage of fluid at differential pressures less than 7 kPa. This particular design of the valve 10 can thereafter, that is at differential pressures greater than 7 kPa, be opened with minimal stresses being imparted to the valve. This characteristic is made possible by the hinged design of the valve as disclosed in more detail in the applicant's international patent application no. PCT/AU2005/001762.

The product or in this case valve 10 may as shown in figure 8 include additional features to promote effective closure and sealing. Figure 8 shows four variants of different configurations for abutting or mating surfaces defined by the slits such as 12A/B of the valve member 16. The arrangements shown on the left hand side of figure 8 do not interlock but rather provide an increased contact surface for improved sealing on closure of the valve elements 18A to 18D. The alternate arrangements shown on the right hand side of figure 8 provide partial interlocking of abutting surfaces of the valve elements 18A to 18D. These alternate configuration may require an additional force or differential pressure to disengage and permit flow in a forward or downstream direction. The preferred configuration is that which is akin to a labyrinth seal. It is envisaged that the various configuration illustrated in figure 8 would be included in the tool or die for moulding together with the slits such as 12A/B of the valve lO.

Now that several preferred embodiments of the method and product have been described, it will be apparent to those skilled in the art that the invention at least in the preferred embodiments has the following advantages:

1. The product or valve in its operative condition has an induced stress which for example is effective in maintaining closure up until a minimum differential pressure;

2. The product or valve can be tailored or designed to suit specific operating parameters for opening at predetermined pressures;

3. The product is relatively simple in construction and at least in the preferred embodiment is of a unitary or one-piece construction; and

4. The method of manufacture lends itself to a range of materials and products where an induced stress is required in the product in its operative condition.

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modification other than those specifically described. For example, the product need not be of a one-piece construction but may be fabricated from more than one component. The elastomeric material will depend largely on the application although it is expected that silicone rubber or a derivative thereof will be used in the application of the valve to water flow lines. The slits of this example need not be formed during moulding but rather may be cut or otherwise formed independent of the moulding process. The inversion or deflection of the product may be different to that described where for example the valve member or valve elements themselves may be inverted or deflected inwardly of the skirt to induce stresses within the valve element(s) themselves which are biased closed.

All such variations and modifications are to be considered within the scope of the present invention the nature of which is to be determined from the foregoing description.

Claims

1. A method of manufacturing a product, said method comprising the steps of: forming an initial configuration of the product in a substantially unstressed condition; and inverting at least part of the initial product to provide the product in an operative and stressed condition.

2. A method of manufacturing as defined in claim 1 wherein the step of inverting the initial product involves turning said at least part of the initial product inside out.

3. A method of manufacturing as defined in either of claims 1 or 2 wherein inversion of said at least part of the initial product imparts stress to said part which is transmitted to other parts of the product which are thus post-stressed in the operative and stressed condition.

4. A method of manufacturing as defined in any one of the preceding claims wherein the inversion step is performed manually.

5. A method of manufacturing as defined in any one of the preceding claims wherein the step of forming the initial configuration of the product involves moulding or casting it into the initial configuration.

6. A method of manufacturing as defined in claim 5 wherein the step of moulding or casting involves forming an opening in the initial product, said opening being closed on inversion of the initial product.

7. A method of manufacturing as defined in claim 5 wherein an opening is formed independent of the step of moulding or casting.

8. A method of manufacturing as defined in any one of claims 1 to 4 wherein the product is formed in its initial configuration by machining, bonding, gluing or other forms of fabrication.

9. A method of manufacturing as defined in any one of claims 5 to 7 wherein the step of moulding or casting the product into its initial configuration involves forming biasing means in said at least part of the initial product.

10. A method of manufacturing as defined in claim 9 wherein the step of moulding or casting the product involves forming recesses associated with the biasing means in said at least part of the initial product.

11. A method of manufacturing as defined in either of claims 9 or 10 wherein the step of inverting the initial product involves turning part of the initial product inside out so that biasing means projecting outwardly from said at least part of the initial product are in the product directed inwardly.

12. A method of manufacturing as defined in claim 11 wherein said inversion of the initial product results in said at least part of the initial product enveloping the other parts.

13. A method of manufacturing as defined in any one of the preceding claims wherein the step of forming the initial configuration of the product involves specifically shaping said at least part of the initial product to determine the stress imparted to said part and thus transmitted to the other parts.

14. A method of manufacturing as defined in claim 13 wherein said at least part of the product is shaped cylindrical but with a longitudinal taper which dictates the stress imparted to this cylindrical part on its inversion to the operative and stressed condition.

15. A method of manufacturing as defined in either of claims 6 or 7 wherein the opening is configured, either alone or in combination with the said at least one part, to vary the stress imparted to said at least part of the initial product on its inversion.

16. A product which in its operative condition comprises a stressed part which is formed by inverting at least part of an initial configuration of the product having been formed in a substantially unstressed condition.

17. A product as defined in claim 16 also comprising a housing connected to the stressed part which includes one or more moveable elements.

18. A product as defined in claim 17 wherein the movable elements are each in the form of a closure or sealing element.

19. A product as defined in either of claims 17 or 18 wherein the product is a valve and the housing is shaped generally cylindrical.

20. A product as defined in claim 19 wherein the closure elements of the valve together, in the operative and stressed condition, form a dome or pyramid shaped valve element connected to and located coaxially with the housing.

21. A product as defined in claim 20 wherein the closure elements are separated by one or more collapsible slits formed at or adjacent an apex of the valve element.

22. A product as defined in claim 17 wherein the housing is in cross-section shaped generally square or rectangular and there is a single closure element formed by a single slit.

23. A product as defined in claim 22 wherein the single closure element is substantially planar in the form of a closure flap.

24. A product as defined in any one of claims 19 to 21 wherein the valve comprises a tensioning element connected to the stressed part which includes the one or more moveable valve elements.

25. A product as defined in claim 24 wherein the tensioning element includes a ring member formed integral with the valve and configured to lock into retaining engagement with the stressed part for biased closure of the valve elements.

26. A method of manufacturing a valve, said method comprising the steps of: forming an initial configuration of the valve in a substantially unstressed condition; and deflecting at least part of the initial valve to impart stress to a remaining part of the valve which is retained in an operative and stressed position.

27. A method of manufacturing as defined in claim 26 wherein the initial configuration of the valve includes a plurality of housing segments and the deflection step involves bending of the housing segments inwardly of the valve.

28. A method of manufacturing as defined in claim 27 wherein the step of bending the housing segments is effected during installation of the valve in a valve casing wherein the deflected housing segments together form a skirt of the valve.

29. A valve which in its operative condition comprises a stressed part which is formed by deflecting at least part of an initial configuration of the valve having been formed in a substantially unstressed condition, the deflected part being locked in position to retain the stressed part in the operative and stressed condition.

30. A valve as defined in claim 29 also comprising one or more biasing elements each connected to the valve housing and arranged on closure of the valve to contact the valve elements for sealing closure at relatively low differential pressures.

31. A valve as defined in claim 30 wherein the biasing element is in the form of a lug connected to and projecting inwardly of the valve housing, the lug being aligned with a corresponding recess in the valve housing.

32. A valve as defined in claim 31 wherein the lug at least in part deflects into the recess on opening of the valve.

33. A valve as defined in any one of claims 29 to 32 wherein the valve is retained normally closed with a closure pressure dictated by forces induced in the stressed part from deflection or inversion of the product in its initial unstressed configuration.

34. A valve as defined in claim 33 wherein the closing pressure of the valve in the operative and normally closed condition provides closure of the valve up to a minimum differential pressure.

35. A valve as defined in claim 34 wherein the minimum differential pressure is relatively low and between 3.5 to 15 kPa.

36. A product as defined in any one of claims 16 to 25 being of a unitary design and at least in part formed of a resiliency flexible material.

37. A product as defined in claim 36 wherein the product is moulded in one piece from a plastic or thermoplastic or elastomeric material.

38. A product as defined in either of claims 36 or 37 wherein the product is a valve.

39. A product defined in either of claims 36 or 37 wherein the product is a seal.

40. A valve as defined in any one of claims 29 to 35 being of a unitary design and at least in part formed of a resiliently flexible material.

41. A valve as defined in claim 40 wherein the product is moulded in one piece from a plastic or thermoplastic or elastomeric material.