US20020189688A1 - Valve and assembly for axially movable members - Google Patents

Abstract

The fluid flow check valve uses a flexure plate or plates to accommodate the valve disk's axial motion required to open and close the valve. The flexure plate also limits the disk's motion in any lateral direction, so the valve disk will align properly with the valve seat and seal when it closes. The flexure plate is a flat, axial spring, made by cutting or otherwise manufacturing spiral cuts in a round, sheet metal disk. Valve qualities such as closing force, size and rigidity to lateral disk motion can be modified by varying the number and configuration of the plates, and by modifying plate characteristics. The compactness of the flexural plate design allows for a shorter valve length and cost as well as increased opportunity for flow optimisation.

Description

FIELD OF THE INVENTION
• This invention relates to axially movable members, and in particular to valves and in particular nozzle-style check valves.[0001]
BACKGROUND OF THE INVENTION
• In a conventional nozzle-style check valve, valve closure is spring assisted. When the flow decelerates the springs pushes a circular disk into the valve seat preventing reverse flow and valve slam. Normal flow pushes the disc backwards and fully opens the valve. In this type of design, flow accelerates in the seat area around the valve seat, enabling valve opening while locally lowering the static reducing pressure. The annular diffuser is subsequently used to gradually recover this pressure with minimum losses.[0002]
• The circular disk is mounted on a shaft, which in turn is mounted in a bearing or bearings. These bearings are mounted in the shaft guidance. The bearings permit the axial movement of the disk, while limiting lateral disk movement. The disk will therefore align with the valve seat and seal properly when closing. An axial compression spring assists in closing the valve.[0003]
• Disadvantages with this conventional check valve include bearing friction (which increases due to contamination), reducing the effective spring force and decreasing the valve's dynamic response, the length of the valve body necessary to house the shaft and bearings, and cost of the shaft-bearing-shaft guidance assembly.[0004]
SUMMARY OF THE INVENTION
• This invention seeks to overcome problems with the prior art.[0005]
• Therefore, according to a first aspect of the invention, there is provided a valve, comprising a valve body defining a fluid passageway, with a valve seat in the fluid passageway, a valve disk support mounted within the valve body, a front flexure plate mounted on the valve disk support, a valve disk secured to the front flexure plate and disposed within the valve body, the valve disk having a front side and a back side, the valve disk being movable axially within the valve body, the valve being closed when the front side of the valve disk contacts the valve seat, and the front flexure plate being axially extendable to accommodate axial valve disk movement while limiting lateral valve disk movement.[0006]
• According to a further aspect of the invention, there is provided an assembly for supporting an axially movable member, in which the axially movable member is supported by front and back flexure plates, and the front and back flexure plates are spaced such that each is axially extended when the other is flat.[0007]
• According to a further aspect of the invention, there is provided an assembly for supporting an axially movable member, the assembly comprising a housing defining a passageway, a support mounted within the housing, a flexure plate mounted on the support, an axially movable member secured to the front flexure plate and disposed within the housing, A compression spring mounted between the support and the axially movable member to bias the axially movable member in one axial direction, and the flexure plate being axially extendable to accommodate axial movement of the axially movable member while limiting lateral movement of the axially movable member.[0008]
• The flexure plates are preferably flat axial springs fabricated by machining spiral cuts in flat, circular or annular plates. The flexure plates permit the required axial movement of the valve disk, while sufficiently restricting lateral valve disk movement. Their operation is frictionless and they are less expensive to produce than a shaft, bearings and shaft guidance.[0009]
• In a further aspect of the invention, different numbers of flexure plates can be used in front and back locations by stacking the flexure plates. Adding more flexure plates will increase the lateral stiffness, as would be required for a heavy valve disk. The number of flexure plates will also affect the axial stiffness and thus the rating of the required compression spring. Changing the number and shape of the spiral cuts can vary the flexure plates'properties.[0010]
• The configuration of the flexure plates can be adjusted by changing the length of the inner spacer rods relative to the outer spacer rods, which fix the axial distance between the front and back flexure plates. Adjusting the configuration can also be a means of sizing the axial stiffness of the flexure plate assembly and compression spring to achieve a wide variety of effective spring stiffnesses as required for varying valve opening and closing conditions, i.e. the valve's dynamic response. The wide available range of closure forces result in a valve with faster dynamic response than in the prior art.[0011]
• These configurations allow the design of a short, hence more compact, valve body with a lower non-dimensional pressure loss coefficient than prior art, typically 0.85.[0012]
• In a further aspect of the invention, depending on the particular flow conditions, the flexure plates provide sufficient closure force and an axial compression spring is unnecessary.[0013]
• These and other aspects of the invention are described in the detailed description of the invention and claimed in the claims that follow.[0014]
BRIEF DESCRIPTION OF THE DRAWINGS
• There will now be described preferred embodiments of the invention, with reference to the drawings, by way of illustration only and not with the intention of limiting the scope of the invention, in which like numerals denote like elements and in which:[0015]
• FIG. 1. is a side (lateral) view, partly in section, of a valve incorporating improvements according to the invention, with the valve open;[0016]
• FIG. 1A is a detail, partly in section, showing the mounting of the[0017]flexure plates elements34 and42 in FIG. 1, in the valve disk support housing,element20 in FIG. 1.
• FIGS. 2A and 2B are respectively axial views showing detail of the front and back flexure plates,[0018]elements34 and42 in FIG. 1;
• FIG. 3 is the view shown in FIG. 1, with the valve closed;[0019]
• FIG. 4 is a side (lateral) view, partly in section, of a valve incorporating improvements according to the invention, alternative embodiment, with the valve open; and[0020]
• FIG. 5 is the view shown in FIG. 4, with the valve closed.[0021]
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
• In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word in the sentence are included and that items not specifically mentioned are not excluded. The use of the indefinite article “a” in the claims before an element means that one of the elements is specified, but does not specifically exclude others of the elements being present, unless the context clearly requires that there be one and only one of the elements.[0022]
• Referring to the figures, the[0023]valve10 comprises avalve body12 whose interior defines afluid passageway14, avalve seat16 formed on thevalve body12 in thefluid passageway14, avalve disk18, a valvedisk support housing20, andcompression spring22. The annular space between thehousing20 and thevalve body12 forms adiffuser area24. The valvedisk support housing20 forms the inner boundary of the flow diffuser so that fluid pressure loss at the valve seat is partially recovered in accordance with known diffuser principles. Valvedisk support housing20 is known in the art for check valves, and serves to support the valve components within thefluid passageway14 without unduly hindering fluid flow.Normal fluid flow26 is in theaxial direction28, and thevalve disk18 moves axially when thevalve10 opens or closes. Alateral direction30 is any direction perpendicular to theaxial direction28. Thevalve10 will have other conventional parts, as is well known to a person in the art. Only features required for an understanding of the invention are shown and described.
• The valve[0024]disk support housing20 is mounted to the inner wall of thevalve body14 bystruts32 or other conventional means. Thevalve10 is preferably made as two separate parts (i.e. thevalve body12 and the disk support housing20) to allow easy manufacturing in small sizes, and allow machining of all internal surfaces.
• As illustrated for example in FIG. 1, a front flexure plate[0025]34 (FIG. 2A) is mounted to the back, or down stream side, of thevalve disk18 by means of avalve disk bolt36. A back flexure plate42 (FIG. 2B) is mounted at a fixed distance as determined by the length of theouter spacers50 so it contacts valvedisk support housing20 at the back of anannular groove40 within the valvedisk support housing20. The pair offlexure plates34 and42 may be held within anannular groove40 through alockup ring54.
• [0026]Inner spacer rods46 are attached to theflexure plates34,42, as for example with nuts as shown, near theinner diameters38,48 and maintain a fixed axial distance between the flexure plates'inner diameters38,48. Similarly,outer spacer rods50 are attached to theflexure plates34,42 as for example with a pair of nuts, near theirouter diameters44,52 and maintain a fixed axial distance between theouter diameters44,52. Referring to FIG. 1A, alockup ring54 holds theflexure plates34,42 in place in thegroove40 in the valvedisk support housing20. Alternatively, the front andback flexure plates34,42 can be mounted in the valvedisk support housing20 by attaching one or both to the valvedisk support housing20 at the flexure plate outer diameter ordiameters44,52. Noouter spacer rods50 are needed if bothflexure plates34,42 are so attached to the valvedisk support housing20
• Both front and[0027]back flexure plates34,42 are mounted co-axially with thevalve disk18 andcompression spring22. Their axis is parallel to theflow direction26 andaxial direction28. The flexure plates' flat faces, shown in detail in FIG. 2, are therefore perpendicular to theflow direction26. Thecompression spring22 is located (or mounted) in the hollow center of theflexure plate42 and abuts against the inner portion of theflexure plate34. Thecompression spring22 is centered by acircular recess49 in thevalve disk support20 and by a circular hub37 in the backside of thefront flexure disc18.
• The[0028]flexure plates34,42 allow the axial motion of thevalve disk18 necessary to open and close thevalve10. Theflexure plates34,42 also minimize lateral30 movement of thevalve disk18 so thevalve disk18 will align properly with thevalve seat16 when thevalve10 closes.
• The[0029]flexure plates34,42 are preferably flat plates cut from sheet metal, as shown in FIGS. 2A and 2B. FIGS. 2A and 2B show thefront plate34 as having ahollow center56 to accommodate thevalve disk bolt36 and theback plate42 also having a hollow center58 to accommodate passage of the compression spring. Theback plate42 can have a solid center58 if no passage for thecompression spring22 or other components is required. Thefront flexure plate34 may be attached to thedisk18 by avalve disk bolt36 or by other suitable means.
• Referring to FIGS. 2A and 2B, the[0030]flexure plate34,42 is a flat spring made bymachining cuts60a,60bthrough the flat plate. Each cut60a,60bis along a spiral or spiral-like path from near the flexure plateouter diameter44,52 to near the flexure plateinner diameter38,48. The shape of the spiral path is the same (in the figure shown they are the same, this is not necessarily always the case) for each cut60a,60b. The spiral cuts are spaced evenly around the plate (in the figure shown they are the same, this is not necessarily always the case), so the radial angles between thecuts62a,62bof coinciding cuts are equal. Theflexure plates34,42 can have fewer or more than the 6cuts60a,60bshown. The spiral path shape can be different than that shown, although the path shape should be the same for all coinciding cuts in front and back flexure plate. At each end of acut60a,60b, ahole64a,66a,64b,66bcan be cut to relieve local stresses and facilitate machining thecut60a,60b.Holes68a,68b, near the inner andouter diameters38,48,44,52 of theflexure plates34,42 may be used for so attaching theflexure plates34,42 inner andouter spacer rods46,50.
• FIG. 1 shows the[0031]valve10 in the open position. Thefront flexure plate34 is flat, while theback flexure plate42 is axially extended by the differential pressure force across the valve disk overcoming thecompression spring22 and any spring force in the flexure plates. Theinner spacers46, being longer relative to theouter spacers50, force theback flexure plate42 into extension. When fluid flow is normal, the flow creates a differential pressure force across thevalve disk18, which is sufficient to compress thecompression spring22 and extend theback flexure plate42, maintaining thevalve10 open.
• When the fluid flow decelerates and becomes too low or reverses, it does not produce sufficient differential pressure force across the[0032]valve disk18 to maintain thevalve10 open. Thevalve disk18 therefore moves axially28 towards the closed position and seals against thevalve seat16, as shown in FIG. 3. In this closed position, theback flexure plate42 is now flat, and thefront flexure plate34 is axially extended.
• The configuration of the[0033]flexure plates34,42 can be varied by varying the lengths of thespacer rods46 relative to50 thereby varying the flexure plate assembly length, closure force and tilting stiffness. Tilting means rotation of the valve disk about a lateral30 axis. In the embodiment shown in FIGS. 1 and 3, theinner spacer rods46 are twice the length of the outer spacer rods. The outer spacer rods'50 length is the same as the distance thevalve disk18 travels as it moves from fully open to closed.
• A further preferred embodiment is shown in FIGS. 4 and 5, which show the[0034]valve10 open and closed respectively. The length of the inner andouter spacer rods46,50 and the valve travel distance are all equal. The front andback flexure plates34,42 are always identically axially displaced. This embodiment provides for the shortest flexure plate assembly, hence this configuration allows for the design of the most compact valve, at the expense of reduced resistance to prevent tilting of the valve disk and increased axial stiffness of the flexure plate assembly.
• A wide range of valve closure forces is available as there are several valve components that can be adjusted. The valve closure forces depend upon the stiffness of the[0035]flexure plates34,42, the stiffness of theaxial spring22, if any, the configuration of theflexure plates34,42 and thevalve10 closing travel distance. The opening and closure forces, for the two embodiments can be calculated as follows:
• FIG. 1: Fopen=Fcsc−½Fplate (thus providing, a low opening force while at the same time providing high resistance against tilting of the disc, which are the two main advantages of this configuration)[0036]
• FIG. 3: Fclose=Fcse−½Fplate,[0037]
• FIG. 4: Fopen=Fcsc[0038]
• FIG. 5: Fclose=Fcse−2Fplate[0039]
• Where:[0040]
• Fopen=total spring force (flexure plates and compression spring) when valve fully open[0041]
• Fclose=total spring force when valve fully closed[0042]
• Fcsc=fully compressed compression spring force when the valve is opened[0043]
• Fcse=extended compression spring force when the valve is closed[0044]
• Fcsc>Fcse[0045]
• Fplate=force to fully extend one flexure plate or a stack of flexure plates (front or back) for an assembly where front and back plates are identical (the same plate thickness, and number and shape of the spiral cuts).[0046]
• Therefore, in these two embodiments, the spring forces are greater for the valve fully open than for fully closed. The force from a flexure plate or compression spring is proportional to distance it is extended or compressed. Therefore increasing the length of the[0047]inner spacer rods46 relative to the length of theouter spacer rods50 will increase the effective closing force exerted by thecompression spring22. Conversely, decreasing the length of theinner spacer rods46 relative to the length of theouter spacer rods50 will decrease the effective closing force exerted by thecompression spring22.
• In the case of use of front and back guide plates, both guide plates provide lateral support for the valve disk. The inside-diameter spacers distribute the tilting momentum of the disk over the front and back guide plates. Minimum tilting resistance is provided when inner and outer spacer rods have the same length. The longer the relative difference between inner and outer spacer rods, the larger the tilting resistance provided by the guide plates. Maximum tilting resistance is achieved when the back flexure plates are flat when the valve is in closed position.[0048]
• This can be achieved at minimum assembly length when the inner spacer rod length (IDL) is twice as long as the outer spacer rod length (ODL) and when the outside diameter spacer length (ODL) is equal to the valve stroke(s).[0049]
• The axial stiffness of the flexure guide plate assembly can be modified by making the length (IDL) of the inner spacers longer than the length (ODL) of the outer spacers. The maximum length of the inner spacers is IDL=2×ODL. In this way, two different guide plates can be assembled with minimum (FIGS. 1 and 3) and maximum (FIGS. 4 and 5) lateral stiffness. In FIG. 1, IDL=2×s=2×ODL, so that the total valve stroke requires {fraction (1/4 )} of the load required for the embodiment shown in FIG. 4. In FIG. 4, IDL=1×s=ODL, thus is more compact.[0050]
• A further, preferred embodiment is to stack more than one flexure plate in one or both of the front and[0051]back locations34,42. These stacked plates provide greater lateral stiffness, as would be required for a heavy valve disk.
• In a further preferred embodiment, there is only one flexure plate or stack of flexure plates. If the[0052]front flexure plate34 or plates in the embodiments described above provide or provides for sufficient lateral stiffness and spring forces, noback flexure plate42 is necessary.
• In a further possible embodiment, the valve disk support may be located upstream of the valve seat, with the valve disk on the downstream side. In this configuration, the slight axial tension caused by extension of the flexure plate may be used to provide the forces that bias the valve disk against the valve seat.[0053]
• The valve described here may also be operated as a control valve in which the valve opening and closing is controlled externally, and not dependent on fluid flow changes.[0054]
• While the[0055]flexure plates34,42 are shown attached by their outer peripheries to thesupport housing20, they could also be attached to thesupport housing20 by their inner portions, for example by a shaft extending from thesupport housing20, and the outer periphery of theflexure plate34 then connected to the outer periphery of thedisk18.
• Further, the use of two flexure plates, one being extended when the other is not, and the use of one flexure plate in combination with a compression spring, also has novel application to applications that do not include valves. These embodiments are generally applicable to any axially movable member, where axial extension with limited lateral movement is desirable.[0056]
• In the embodiment shown in FIGS. 4 and 5, a wave spring may advantageously be used for the compression spring.[0057]
• A person skilled in the art could make immaterial changes to the exemplary embodiments described here without departing from the essence of the invention that is intended to be covered by the scope of the claims that follow.[0058]

Claims (20)

I claim:

1. A valve, comprising:

a valve body defining a fluid passageway, with a valve seat in the fluid passageway;

a valve disk support assembly mounted within the valve body;

a front flexure plate mounted on the valve disk support assembly;

a valve disk secured to the front flexure plate and disposed within the valve body, the valve disk having a front side and a back side, the valve disk being movable axially within the valve body, the valve being closed when the front side of the valve disk contacts the valve seat; and

the front flexure plate being axially extendable to accommodate axial valve disk movement while limiting lateral valve disk movement.

2. The valve ofclaim 1 in which the valve disk is biased against the valve seat in the absence of flow in the fluid passageway.

3. The valve ofclaim 3 further comprising a back flexure plate mounted on the valve disk support assembly parallel to the front flexure plate, and spaced by spacers from the front flexure plate, the back flexure plate being axially extendable and cooperating with the front flexure plate to accommodate axial valve disk movement while limiting lateral valve disk movement.

4. The valve ofclaim 1 in which the front flexure plate comprises a flat disk with spiral cuts.

5. The valve ofclaim 3 in which each of the front and back flexure plates comprises a flat disk with spiral cuts.

6. The valve ofclaim 3 in which the back flexure plate has a solid center.

7. The valve ofclaim 3 in which the front and back flexure plates are spaced such that each is axially extended when the other is flat.

8. The valve ofclaim 3 in which the front and back flexure plates are spaced by outer spacer rods attached near the periphery of the front and back flexure plates.

9. The valve ofclaim 8 in which the front and back flexure plates are spaced by inner spacer rods attached near inner diameters of the flexure plates.

10. The valve ofclaim 9 in which the inner spacers have a length IDL, the outer spacers have a length ODL, the valve disk has a stroke s, and IDL=2s=2ODL.

11. The valve ofclaim 9 in which the inner spacers have a length IDL, the outer spacers have a length ODL, the valve disk has a stroke s, and IDL=s=ODL.

12. The valve ofclaim 3 in which each of the front and back flexure plates are attached at their respective peripheries to the valve disk support housing.

13. The valve ofclaim 1 further comprising a compression spring mounted co-axially with the front flexure plate between the valve disk support housing and front flexure plate, the compression spring acting to bias the valve disk against the valve seat.

14. The valve ofclaim 3 further comprising a compression spring mounted co-axially with the front and back flexure plates between the valve disk support and front flexure plate, and the compression spring passing through the back flexure plate, the compression spring acting to bias the valve disk against the valve seat.

15. The valve ofclaim 1 further comprising plural flexure plates stacked together with the front flexure plate, each of the plural flexure plates being axially extendable to accommodate axial valve disk movement while limiting lateral valve disk movement.

16. An assembly for supporting an axially movable member, the assembly comprising:

a housing defining a passageway;

a support assembly mounted within the housing;

a front flexure plate mounted on the support assembly;

a back flexure plate mounted on the support parallel to and spaced from the front flexure plate by spacer members;

an axially movable member secured to the front flexure plate and disposed within the disk support housing;

each of the front flexure plate and back flexure plate being axially extendable to accommodate axial movement of the axially movable member while limiting lateral movement of the axially movable member; and

the front and back flexure plates being spaced such that each is axially extended when the other is flat.

17. The assembly ofclaim 16 in which each of the front and back flexure plates comprises a flat disk with spiral cuts.

18. The assembly ofclaim 16 further in combination with a compression spring mounted between the support and the axially movable member to bias the axially movable member in one axial direction.

19. An assembly for supporting an axially movable member, the assembly comprising:

a housing defining a passageway;

a support mounted within the housing;

a flexure plate mounted on the support;

an axially movable member secured to the front flexure plate and disposed within the housing;

a compression spring mounted between the support and the axially movable member to bias the axially movable member in one axial direction; and

the flexure plate being axially extendable to accommodate axial movement of the axially movable member while limiting lateral movement of the axially movable member.

20. The assembly ofclaim 19 in which the flexure plate is a flat disk with spiral grooves.

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