Abstract:
A check valve comprises a valve body defining a valve opening and a pair of valve elements mounted so as to be movable from a closed position in which they close the valve opening to prevent fluid flow through the opening to an open position in which they permit fluid flow through the opening. The valve further comprises a one piece bridge element having first and second end portions mounted to the valve housing on opposite sides of the valve opening and an intermediate portion extending between the end portions. The intermediate portion acts as a stop for the valve elements in their open position. A shaft mounting the valve elements for pivotal movement between their open and closed positions, is supported in the end portions of the bridge element. Fasteners for attaching the bridge element to the valve housing overlap the ends of the valve shaft thereby retaining it in the bridge element.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to check valves. 
       BACKGROUND 
       [0002]    Check valves are valves that allow fluid flow in one direction therethrough and prevent flow in the opposite direction. They are widely used in a range of applications, for example in air conditioning systems, for example in an aircraft system. 
         [0003]    Check valves commonly include one or more valve elements or flappers located at an opening in a valve body. The flappers are hingedly supported relative to the valve body such that in a closed position they lie across and close the opening, preventing fluid flow through the opening in one direction. However, under the pressure of a fluid (gas or liquid) on one side of the check valve, the flappers rotate from their closed positions so as to allow the fluid to flow through the valve in the opposite direction. 
         [0004]    Typical check valves often have one or more physical stops, which limit the angle to which the flappers may open. When the flappers move from the closed to the open position, the flappers hit the stop or stops, thereby preventing the flappers from opening further. In a known arrangement, the stop is provided by a pin which is mounted to posts arranged on opposite sides of the valve housing and which extends across the opening at a distance therefrom. One such arrangement is shown in EP-A-2034224. 
       SUMMARY 
       [0005]    From one aspect, the present disclosure provides a check valve comprising a valve body defining a valve opening and a pair of valve elements mounted so as to be movable from a closed position, in which they close the valve opening to prevent fluid flow through the opening, to an open position in which they permit fluid flow through the opening. A valve shaft mounts the valve elements for pivotal movement between their open and closed positions, The check valve further comprises a one piece bridge element having first and second end portions mounted to the valve housing on opposite sides of the valve opening and an intermediate portion extending across the valve opening. The intermediate portion acts a stop for the valve elements in their open position. The valve shaft is supported in the end portions of the bridge element. 
         [0006]    The use of a one piece bridge element both to support the valve shaft and to provide a stop for the valve elements is beneficial in that it significantly simplifies the earlier arrangements in which multiple parts had to be assembled, which added to the valve&#39;s complexity and its weight, which is a major concern particularly in aircraft applications. 
         [0007]    The bridge element may be made in any convenient manner. It may, for example be moulded, forged or cast. However, in certain embodiments it may be formed from a sheet material, for example sheet metal. This may allow the bridge element to be formed very simply, for example by cutting out an appropriately shaped element from a sheet of material and bending the element to the appropriate shape. 
         [0008]    The particular material used for the bridge element will depend on the intended application of the valve, for example depending on the valve operating conditions, (pressure, temperature and fluid flow rate). It may be metallic, for example formed of a stainless steel material, or, if it is intended for higher temperature applications, from a nickel steel. 
         [0009]    The bridge element may be either stiff or deformable, for example flexible, depending on, for example, the material used to make it, the thickness of the material and so on. 
         [0010]    The bridge element may be formed with any convenient shape. It may for example be formed such that the intermediate portion extends straight between the end portions. However, in order to reduce the height of the valve at its peripheral regions (which may be desirable in certain installations where only limited space is available), the intermediate portion may extend upwardly from the end regions towards its centre. Thus the intermediate portion could, for example, comprise a plurality, for example two, straight portions meeting at an apex portion. In a particular embodiment, however, the intermediate portion is arcuate in shape, for example having the shape of an arc of a circle, with a generally constant radius of curvature. Such arrangements also have the effect that it is possible to raise the point of impact of the valve elements on the intermediate portion, which will reduce the reaction forces acting on the valve shaft. An arcuate shape may, in certain embodiments, also permit the choice of an optimal impact point with a minimal increase in part weight. For example it may be possible to produce a check valve family with different impact heights, but similar overall geometry. 
         [0011]    While the valve elements may engage with a relatively large section of the intermediate portion of the bridge element, it may be desirable to have the valve elements engage at a relatively small impact area. Accordingly, the intermediate portion may be provided with one or more lateral projections for engaging the valve elements. Typically these will be aligned on opposite sides of the intermediate portion to avoid bending moments being generated in the intermediate portion. 
         [0012]    The intermediate portion of the bridge element may be narrower in width than the end portions of the bridge element. This may allow for a weight saving in the valve construction. 
         [0013]    The valve shaft may be retained in the bridge element in a number of ways. 
         [0014]    In one embodiment, the valve shaft may be retained by means of fasteners attaching the bridge element to the valve housing. This allows the fasteners to perform a dual function and means that the valve shaft may, for example, be of a constant diameter, without the need to provide any retention features on the shaft. 
         [0015]    The fastener may therefore project upwardly to such an extent that it overlaps the adjacent end of the valve shaft, preventing it from moving out of the bridge element. 
         [0016]    The end portions of the bridge element may each comprise a base limb for mounting to the valve housing and an upright limb for receiving the end of the valve shaft. The end portions may therefore be generally L shaped. 
         [0017]    The base limb may therefore receive the fastener (such as a screw, bolt, nut or stud, for example) which attaches the bridge element to the valve housing. 
         [0018]    In a particular embodiment, a bolt and nut arrangement is used, with a portion of the bolt extending above the nut to prevent valve shaft from moving out of the bridge element. Such an arrangement may be advantageous in that the shaft, as it abuts the bolt, may damage the bolt thread, thereby preventing the nut from unscrewing from the bolt and separating from the bolt in use. This may prevent the nut and bolt from separating and falling into the system, thereby potentially preventing damage to downstream system components. 
         [0019]    In an alternative arrangement, the valve shaft may be provided with at least one reduced diameter or reduced cross sectional area end portion which is retained in a respective end portion of the bridge element. In one embodiment, reduced diameter or cross sectional area end portions are provided at both ends of the shaft and the bridge element made flexible or deformable to allow insertion of the end portions of the shaft in the bridge end portions. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    A non-limiting exemplary embodiment of a check valve in accordance with this disclosure will now be described with reference to the accompanying drawings in which: 
           [0021]      FIG. 1  shows a perspective view of a first embodiment of check valve in accordance with the disclosure; 
           [0022]      FIG. 2  shows a side elevation of the check valve of  FIG. 1 ; 
           [0023]      FIG. 3  shows a top view of the valve of  FIG. 1 ; 
           [0024]      FIG. 4  shows a vertical sectional view through the valve of  FIG. 1  taken along the line A-A shown in  FIG. 3 ; 
           [0025]      FIG. 5  shows a side elevation of the valve of  FIG. 1  with the valve elements in an open position; 
           [0026]      FIG. 6  shows an enlarged view of the region A shown in  FIG. 4 ; 
           [0027]      FIG. 7  shows a perspective view of a second embodiment of check valve in accordance with this disclosure; and 
           [0028]      FIG. 8  shows a detail of a third embodiment of check valve in accordance with this disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    With reference to  FIGS. 1 to 6 , a first embodiment of check valve  2  generally comprises a valve housing  4 , a pair of valve elements or flappers  6 , a bridge element  8  and a valve shaft  10 . 
         [0030]    The valve housing  4  in this embodiment is generally circular in shape and defines a generally circular valve opening through which a fluid may flow in one direction, namely from the bottom to the top in the sense of the Figures (although it will be appreciated that the valve housing may be installed in any orientation in use). The valve housing is provided with a plurality of, in this particular case four, apertures  12  around its periphery to allow it to be installed in a duct, pipe or any other fluid flow path. 
         [0031]    The valve opening is divided into two generally D-shaped openings by a web  14  of the housing ( FIG. 4 ). Each D-shaped opening is provided with a seat which receives a respective valve element  6  when the valve element is in its closed position, as illustrated in  FIGS. 1 to 4 . 
         [0032]    Each valve element  6  is also generally D-shaped and has a pair of lugs  16  at one edge thereof. Each lug  16  has a bore  18 . The bores  18  receive the valve shaft  10  around which the valve elements  6  pivot. As can be seen from  FIG. 1  for example, the lugs  16  of the respective valve elements  6  are arranged towards the ends of the shaft  10 , leaving a central region  20  of the shaft exposed. However, this is not a limiting arrangement and other lug arrangements may be envisaged. For example each valve element might have three or more lugs  16 , the lugs  16  of the respective valve elements alternating on the shaft  10 . 
         [0033]    The valve shaft  10  in this embodiment is a rod of constant diameter. 
         [0034]    The valve shaft  10  is supported at its ends  24  in the bridge element  8 . The bridge element  8  is a one piece element having opposed end portions  26 , and an intermediate portion  28 . The bridge element  8  is advantageously made from a sheet metal material so that it can be bent to the appropriate shape. 
         [0035]    The end portions  26  of the bridge element are generally L-shaped in vertical section, having a base limb  32  and an upright limb  34 . The ends  24  of the valve shaft  10  are received in aligned bores  36  formed in the respective upright limbs  34 . The base limbs  32  are provided with respective bores  38  which receive a fastener  40  (in this example a bolt) for attaching the bridge element  8  to the valve housing  4 . The fastener  40  also passes through a bore  42  provided in the valve housing  4 . The fastener  40  is secured by a suitable element such as a nut  44 . 
         [0036]    As can be seen for example from  FIG. 6 , the fastener  40  is of such a length that when received through the openings  42 ,  38  in the valve housing  4  and the base limb  32 , it extends vertically to a height h 1  which is such that it overlaps the end  24  of the valve shaft  10 . The valve shaft  10  will therefore be retained in the bridge element between the respective fasteners  40 . This avoids the need for providing any special retention mechanism on the valve shaft  10 , thereby simplifying its manufacture. 
         [0037]    In this embodiment the nut  44  is chosen to be of such a height h 2  that it does not overlap the end  24  of the valve shaft  10 . However, in other embodiments, the nut  44  may overlap the end of the valve shaft  10 , thereby acting to retain the valve shaft  10 . However, the former arrangement is more compact. 
         [0038]    As can be seen from  FIG. 1  for example, the intermediate portion  28  of the bridge element  8  is narrower than the end portions  26  of the bridge element  8 . This represents a weight saving in the bridge element, while at the same time allowing for adequate support for the valve shaft  10 . 
         [0039]    The intermediate portion  28  of the bridge element  8  is, in this embodiment, arcuate in shape, having a generally constant radius of curvature. This is thought to provide good stress distribution in the bridge element  8  during impact of the valve elements  6 . 
         [0040]    As can be seen from  FIG. 6 , the bridge element  8  acts as a stop for the valve elements  6  when they are in their open position. To provide a relatively small contact area for each valve element  6 , the bridge element  8  is provided with a pair of stop projections  46 . These are aligned so as to avoid introducing bending moments on the central area of the bridge element  8 . Of course, the bridge arm may be made without the projections  46 , but these projections advantageously determine the area of impact and contact with the valve element  6  and allow the opening angle of the valve elements to be managed without significant weight increase. 
         [0041]    It will be appreciated that the shape of the bridge element  8  means that it is possible to provide the stops  46  a significant distance above the valve housing  4 . This means that the reaction forces acting on the valve shaft  10  during impact are reduced compared to a lower stop position. At the same time, the reduced height end portions  26  of the bridge element  8  allow the valve to be installed in relatively compact areas. 
         [0042]    To assemble the check valve  2 , the valve elements  6  may first be mounted on the valve shaft  10  which is then mounted in the bridge element  8 . This sub assembly is then positioned on the valve housing  4  and the fasteners  40  inserted through the openings  40 ,  38  in the valve housing and the end portions  26  of the bridging element  8 . The nuts  44  can be slid under the ends  24  of the valve shaft  10 , and the vertical limb  34  of the end portion  26  prevents rotation of the nut as the fastener  40  is tightened. When fully inserted, the fasteners  40  will overlap the ends of the valve shaft thereby retaining the valve shaft  10 . 
         [0043]    In use, when the valve  2  is subjected to a flow of fluid in a flow direction X ( FIG. 2 ), the valve elements  6  will be pivoted away from the valve opening, thereby allowing fluid flow through the valve  2  in that direction. However, fluid flow in the opposite, checked direction will cause the valve elements  6  to pivot closed, thereby preventing flow through the valve  2 . 
         [0044]    The various elements of the valve  2  may be made from any material appropriate to the intended use of the valve  2 . For example, the various elements will typically be formed from a metallic material, for example steel. However, in other applications, other materials may be used. 
         [0045]    Turning now to  FIG. 7 , a second check valve  102  in accordance with the invention is disclosed. 
         [0046]    The general structure of the check valve  102  is the same as that of the check valve  2  of  FIGS. 1 to 6 , except for the shape of the bridge element  8 . In this embodiment, the bridge element  104  has an intermediate portion  106  formed with two straight portions  108  joining at a generally flat apex portion  110 . The remaining structure is the same and need not therefore be described further. 
         [0047]    In a further variation of this construction, multiple straight portions may be provided on either side of the apex portion, so the bridge element  104  may have a generally “hip roof” shape. 
         [0048]    Turning to  FIG. 8 , a detail of a third embodiment is shown. 
         [0049]    In this embodiment, each end of the valve shaft  200  is formed with a reduced diameter end section  202 . This reduced diameter section  202  is received in a corresponding opening  204  in the end portion  206  of the bridge element  208 . The valve shaft  200  is therefore trapped between the end portions  206  of the bridge element  208 . In this embodiment, the bridge element  208  should be deformable, advantageously elastically deformable, to the extent that the end portions  206  may be moved apart sufficiently to allow the end sections  202  of the valve shaft  200  to be inserted into the openings  204 . 
         [0050]    This embodiment therefore does not rely upon the fasteners  210  which attach the bridge element  208  to the valve housing retaining the valve shaft  200 . This means that shorter fasteners  210 , for example bolts as illustrated, may be used compared to the embodiments of  FIGS. 1 to 7 . It also means that smaller openings  204  may potentially be provided in the end portions  206  of the bridge element  208 , which may increase the strength thereof. 
         [0051]    It will be understood that the above description is of a non-limiting example and that various changes and modifications may be made thereto without departing from the scope of the disclosure. 
         [0052]    For example, a further embodiment may be a hybrid of the embodiments of  FIGS. 1 to 7  and  FIG. 8 . In such an embodiment, the valve shaft may be provided with a reduced cross sectional area at just one end, allowing it to be inserted through an opening in one end portion of the bridge element for engagement with and retention by an opening in the other end portion of the bridge element as shown in  FIG. 8 , with the other end of the valve shaft being retained by a fastener in the manner shown in  FIG. 6 . 
         [0053]    The Summary section above indicates various alternative or additional features which may be employed. Also, if desired, a spring element may be provided which biases the valve elements  6  towards their closed position, meaning that the valve elements  6  will only move open in the event of a predetermined pressure differential across the valve  2 . In such a case, the valve shaft may be provided with location features for the springs.