Abstract:
The fluid flow check valve uses a flexure plate or plates to accommodate the valve disk&#39;s axial motion required to open and close the valve. The flexure plate also limits the disk&#39;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  
         [0001]    This invention relates to axially movable members, and in particular to valves and in particular nozzle-style check valves.  
         BACKGROUND OF THE INVENTION  
         [0002]    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.  
           [0003]    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.  
           [0004]    Disadvantages with this conventional check valve include bearing friction (which increases due to contamination), reducing the effective spring force and decreasing the valve&#39;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.  
         SUMMARY OF THE INVENTION  
         [0005]    This invention seeks to overcome problems with the prior art.  
           [0006]    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.  
           [0007]    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.  
           [0008]    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.  
           [0009]    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.  
           [0010]    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&#39;properties.  
           [0011]    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&#39;s dynamic response. The wide available range of closure forces result in a valve with faster dynamic response than in the prior art.  
           [0012]    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.  
           [0013]    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.  
           [0014]    These and other aspects of the invention are described in the detailed description of the invention and claimed in the claims that follow. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    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:  
         [0016]    [0016]FIG. 1. is a side (lateral) view, partly in section, of a valve incorporating improvements according to the invention, with the valve open;  
         [0017]    [0017]FIG. 1A is a detail, partly in section, showing the mounting of the flexure plates elements  34  and  42  in FIG. 1, in the valve disk support housing, element  20  in FIG. 1.  
         [0018]    [0018]FIGS. 2A and 2B are respectively axial views showing detail of the front and back flexure plates, elements  34  and  42  in FIG. 1;  
         [0019]    [0019]FIG. 3 is the view shown in FIG. 1, with the valve closed;  
         [0020]    [0020]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  
         [0021]    [0021]FIG. 5 is the view shown in FIG. 4, with the valve closed.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0022]    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.  
         [0023]    Referring to the figures, the valve  10  comprises a valve body  12  whose interior defines a fluid passageway  14 , a valve seat  16  formed on the valve body  12  in the fluid passageway  14 , a valve disk  18 , a valve disk support housing  20 , and compression spring  22 . The annular space between the housing  20  and the valve body  12  forms a diffuser area  24 . The valve disk support housing  20  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. Valve disk support housing  20  is known in the art for check valves, and serves to support the valve components within the fluid passageway  14  without unduly hindering fluid flow. Normal fluid flow  26  is in the axial direction  28 , and the valve disk  18  moves axially when the valve  10  opens or closes. A lateral direction  30  is any direction perpendicular to the axial direction  28 . The valve  10  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.  
         [0024]    The valve disk support housing  20  is mounted to the inner wall of the valve body  14  by struts  32  or other conventional means. The valve  10  is preferably made as two separate parts (i.e. the valve body  12  and the disk support housing  20 ) to allow easy manufacturing in small sizes, and allow machining of all internal surfaces.  
         [0025]    As illustrated for example in FIG. 1, a front flexure plate  34  (FIG. 2A) is mounted to the back, or down stream side, of the valve disk  18  by means of a valve disk bolt  36 . A back flexure plate  42  (FIG. 2B) is mounted at a fixed distance as determined by the length of the outer spacers  50  so it contacts valve disk support housing  20  at the back of an annular groove  40  within the valve disk support housing  20 . The pair of flexure plates  34  and  42  may be held within an annular groove  40  through a lockup ring  54 .  
         [0026]    Inner spacer rods  46  are attached to the flexure plates  34 ,  42 , as for example with nuts as shown, near the inner diameters  38 ,  48  and maintain a fixed axial distance between the flexure plates&#39; inner diameters  38 ,  48 . Similarly, outer spacer rods  50  are attached to the flexure plates  34 ,  42  as for example with a pair of nuts, near their outer diameters  44 ,  52  and maintain a fixed axial distance between the outer diameters  44 ,  52 . Referring to FIG. 1A, a lockup ring  54  holds the flexure plates  34 ,  42  in place in the groove  40  in the valve disk support housing  20 . Alternatively, the front and back flexure plates  34 ,  42  can be mounted in the valve disk support housing  20  by attaching one or both to the valve disk support housing  20  at the flexure plate outer diameter or diameters  44 ,  52 . No outer spacer rods  50  are needed if both flexure plates  34 , 42  are so attached to the valve disk support housing  20   
         [0027]    Both front and back flexure plates  34 ,  42  are mounted co-axially with the valve disk  18  and compression spring  22 . Their axis is parallel to the flow direction  26  and axial direction  28 . The flexure plates&#39; flat faces, shown in detail in FIG. 2, are therefore perpendicular to the flow direction  26 . The compression spring  22  is located (or mounted) in the hollow center of the flexure plate  42  and abuts against the inner portion of the flexure plate  34 . The compression spring  22  is centered by a circular recess  49  in the valve disk support  20  and by a circular hub  37  in the backside of the front flexure disc  18 .  
         [0028]    The flexure plates  34 ,  42  allow the axial motion of the valve disk  18  necessary to open and close the valve  10 . The flexure plates  34 ,  42  also minimize lateral  30  movement of the valve disk  18  so the valve disk  18  will align properly with the valve seat  16  when the valve  10  closes.  
         [0029]    The flexure plates  34 ,  42  are preferably flat plates cut from sheet metal, as shown in FIGS. 2A and 2B. FIGS. 2A and 2B show the front plate  34  as having a hollow center  56  to accommodate the valve disk bolt  36  and the back plate  42  also having a hollow center  58  to accommodate passage of the compression spring. The back plate  42  can have a solid center  58  if no passage for the compression spring  22  or other components is required. The front flexure plate  34  may be attached to the disk  18  by a valve disk bolt  36  or by other suitable means.  
         [0030]    Referring to FIGS. 2A and 2B, the flexure plate  34 ,  42  is a flat spring made by machining cuts  60   a ,  60   b  through the flat plate. Each cut  60   a ,  60   b  is along a spiral or spiral-like path from near the flexure plate outer diameter  44 ,  52  to near the flexure plate inner diameter  38 ,  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 cut  60   a ,  60   b . 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 the cuts  62   a ,  62   b  of coinciding cuts are equal. The flexure plates  34 ,  42  can have fewer or more than the 6 cuts  60   a ,  60   b  shown. 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 a cut  60   a ,  60   b , a hole  64   a ,  66   a ,  64   b ,  66   b  can be cut to relieve local stresses and facilitate machining the cut  60   a ,  60   b . Holes  68   a ,  68   b , near the inner and outer diameters  38 ,  48 ,  44 ,  52  of the flexure plates  34 ,  42  may be used for so attaching the flexure plates  34 ,  42  inner and outer spacer rods  46 ,  50 .  
         [0031]    [0031]FIG. 1 shows the valve  10  in the open position. The front flexure plate  34  is flat, while the back flexure plate  42  is axially extended by the differential pressure force across the valve disk overcoming the compression spring  22  and any spring force in the flexure plates. The inner spacers  46 , being longer relative to the outer spacers  50 , force the back flexure plate  42  into extension. When fluid flow is normal, the flow creates a differential pressure force across the valve disk  18 , which is sufficient to compress the compression spring  22  and extend the back flexure plate  42 , maintaining the valve  10  open.  
         [0032]    When the fluid flow decelerates and becomes too low or reverses, it does not produce sufficient differential pressure force across the valve disk  18  to maintain the valve  10  open. The valve disk  18  therefore moves axially  28  towards the closed position and seals against the valve seat  16 , as shown in FIG. 3. In this closed position, the back flexure plate  42  is now flat, and the front flexure plate  34  is axially extended.  
         [0033]    The configuration of the flexure plates  34 ,  42  can be varied by varying the lengths of the spacer rods  46  relative to  50  thereby varying the flexure plate assembly length, closure force and tilting stiffness. Tilting means rotation of the valve disk about a lateral  30  axis. In the embodiment shown in FIGS. 1 and 3, the inner spacer rods  46  are twice the length of the outer spacer rods. The outer spacer rods&#39;  50  length is the same as the distance the valve disk  18  travels as it moves from fully open to closed.  
         [0034]    A further preferred embodiment is shown in FIGS. 4 and 5, which show the valve  10  open and closed respectively. The length of the inner and outer spacer rods  46 ,  50  and the valve travel distance are all equal. The front and back flexure plates  34 ,  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.  
         [0035]    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 flexure plates  34 ,  42 , the stiffness of the axial spring  22 , if any, the configuration of the flexure plates  34 ,  42  and the valve  10  closing travel distance. The opening and closure forces, for the two embodiments can be calculated as follows:  
         [0036]    [0036]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)  
         [0037]    [0037]FIG. 3: Fclose=Fcse−½Fplate,  
         [0038]    [0038]FIG. 4: Fopen=Fcsc  
         [0039]    [0039]FIG. 5: Fclose=Fcse−2Fplate  
         [0040]    Where:  
         [0041]    Fopen=total spring force (flexure plates and compression spring) when valve fully open  
         [0042]    Fclose=total spring force when valve fully closed  
         [0043]    Fcsc=fully compressed compression spring force when the valve is opened  
         [0044]    Fcse=extended compression spring force when the valve is closed  
         [0045]    Fcsc&gt;Fcse  
         [0046]    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).  
         [0047]    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 inner spacer rods  46  relative to the length of the outer spacer rods  50  will increase the effective closing force exerted by the compression spring  22 . Conversely, decreasing the length of the inner spacer rods  46  relative to the length of the outer spacer rods  50  will decrease the effective closing force exerted by the compression spring  22 .  
         [0048]    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.  
         [0049]    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).  
         [0050]    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.  
         [0051]    A further, preferred embodiment is to stack more than one flexure plate in one or both of the front and back locations  34 ,  42 . These stacked plates provide greater lateral stiffness, as would be required for a heavy valve disk.  
         [0052]    In a further preferred embodiment, there is only one flexure plate or stack of flexure plates. If the front flexure plate  34  or plates in the embodiments described above provide or provides for sufficient lateral stiffness and spring forces, no back flexure plate  42  is necessary.  
         [0053]    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.  
         [0054]    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.  
         [0055]    While the flexure plates  34 ,  42  are shown attached by their outer peripheries to the support housing  20 , they could also be attached to the support housing  20  by their inner portions, for example by a shaft extending from the support housing  20 , and the outer periphery of the flexure plate  34  then connected to the outer periphery of the disk  18 .  
         [0056]    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.  
         [0057]    In the embodiment shown in FIGS. 4 and 5, a wave spring may advantageously be used for the compression spring.  
         [0058]    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.