Patent Abstract:
A check valve comprises a valve housing defining a valve opening, a pair of mounting posts arranged on opposed sides of the valve opening and a hinge pin mounted between the mounting posts. A pair of flapper elements are pivotably mounted to the hinge pin for rotation relative to the housing between an open position in which they permit fluid flow through the valve opening and a closed position in which they prevent fluid flow through the valve opening. The valve further comprises a stop mounted between the mounting posts above the hinge pin and extending across the valve opening such that the flapper elements will contact the stop in their open positions. The stop is a coil spring.

Full Description:
FOREIGN PRIORITY 
       [0001]    This application claims priority to European Patent Application No. 16461502.3 filed Jan. 14, 2016, the entire contents of which is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present disclosure relates to check valves. 
       BACKGROUND 
       [0003]    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 aircraft air conditioning systems. 
         [0004]    Check valves commonly include a pair of valve elements or flappers located at an opening in a valve housing. The flappers are hingedly supported on a hinge pin mounted to the valve housing for rotation between a closed position in which they lie across and close the opening, preventing fluid flow through the opening in one direction and an open position in which, 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. 
         [0005]    In known check valve arrangements, a stop is provided to limit the rotational movement of the flapper elements as they open. Typically, the stop comprises a stop pin which is mounted to posts arranged on opposed sides of the valve housing opening. The stop pin is spaced from the opening such that when the flappers open, they engage the stop pin. 
         [0006]    The flapper elements may impact the stop pin with some considerable force, meaning that the flapper elements must be sufficiently robust to withstand the impact forces and avoid becoming overstressed which might lead to failure of the flapper element. This may mean that the flapper elements may have to be relatively heavy, which may have implications for example in aircraft applications. 
         [0007]    The present disclosure relates to a check valve which includes a modified stop construction. 
       SUMMARY 
       [0008]    There is disclosed herein a check valve which comprises a valve housing defining a valve opening, a pair of mounting posts arranged on opposed sides of the valve opening and a hinge pin mounted between the mounting posts. A pair of flapper elements is pivotably mounted to the hinge pin for rotation relative to the housing between an open position in which they permit fluid flow through the respective valve openings and a closed position in which they prevent fluid flow through the valve openings. A stop is mounted between the mounting posts above the hinge pin and extending across the valve opening such that the flapper elements will contact the stop in their open positions. The stop is a coil spring. 
         [0009]    In certain embodiments, the coil spring may be a wire spring. 
         [0010]    In other embodiments, the coil spring may be a machined spring. 
         [0011]    The flapper elements and the coil spring may be configured such that the flapper elements engage the stop in a medial region of the coil spring. 
         [0012]    The coil spring may have a variable diameter, with the diameter in the medial region being larger than the diameter in the end regions of the coil spring. In another arrangement, the coil spring may only be provided with turns in a medial region. 
         [0013]    In either of the above arrangements, the flapper elements may have a planar upper surface region for engaging the medial region of the coil spring. 
         [0014]    In other embodiments, the coil spring may have a constant diameter. The flapper elements have a raised medial region, for example a convexly curved medial region for engaging the medial region of the coil spring. 
         [0015]    The ends of the coil spring may be received within respective bores such as to be rotatable in the bores about the spring axis. 
         [0016]    The ends of the coil spring may be received in the respective bores with so as to be rotatable transversely with respect to the spring axis. 
         [0017]    In one arrangement, the end of the coil spring may be rounded and be received within a rounded, flaring bore recess. 
         [0018]    In an alternative arrangement, the end of the coil spring may be formed with a transverse groove having a rounded base, and the bore is provided with a pin extending vertically thereacross, the pin being received within the groove. 
         [0019]    The disclosure also extends to a method of assembling a check valve as described above, the method comprising axially compressing the coil spring, positioning the coil spring between the mounting posts and releasing the coil spring such that it moves into engagement with the mounting posts. 
         [0020]    Some embodiments of the disclosure will now be described by way of example only with reference to the accompanying drawings in which: 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0021]      FIG. 1  shows a perspective view of a first embodiment of check valve in accordance with this disclosure; 
           [0022]      FIG. 2  shows a central vertical cross section through the check valve of  FIG. 1 ; 
           [0023]      FIG. 3  shows a side view of the check valve of  FIG. 1 ; 
           [0024]      FIG. 4  shows a sectional view along the line B-B of  FIG. 3 ; 
           [0025]      FIG. 5  shows a perspective view of a second embodiment of check valve in accordance with this disclosure; 
           [0026]      FIG. 6  shows a sectional view through the check valve of  FIG. 5 , along a line corresponding to the line B-B of  FIG. 4 ; 
           [0027]      FIG. 7  shows a perspective view of a third embodiment of check valve in accordance with this disclosure; 
           [0028]      FIG. 8  shows a sectional view through the check valve of  FIG. 7 , along a line corresponding to the line B-B of  FIG. 4 ; 
           [0029]      FIG. 9  shows a perspective view of a fourth embodiment of check valve in accordance with this disclosure; 
           [0030]      FIG. 10  shows a sectional view through the check valve of  FIG. 9 , along a line corresponding to the line B-B of  FIG. 4 ; 
           [0031]      FIG. 11  shows a part sectional view of a detail of a fifth embodiment of check valve in accordance with this disclosure; and 
           [0032]      FIG. 12  shows a part sectional view of a detail of a sixth embodiment of check valve in accordance with this disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    A first embodiment of check valve  2  in accordance with this disclosure is illustrated in  FIGS. 1 to 4 . 
         [0034]    The check valve  2  comprises a valve housing  4  for mounting in a pipe, duct or the like. The valve housing  4  comprises a valve opening  6  in the form of a pair of generally D-shaped openings  6  which are separated by a central web  8  of the valve housing  4 . 
         [0035]    A pair of mounting posts  10  extend upwardly from the valve housing  4 . The mounting posts  10  may be integrally formed, for example cast, with the valve housing  4 . Alternatively, the mounting posts  10  may be separately formed from the valve housing  4  and mounted thereto by suitable means. 
         [0036]    A hinge pin  12  is mounted between the mounting posts  10  above the central web  8 . As shown, the hinge pin  12  is a unitary pin, but it may be formed in one or more parts suitably joined together. The hinge pin  12  may be retained to the mounting posts  10  in any convenient manner. 
         [0037]    The valve openings  6  are closed by a pair of generally D-shaped flapper elements  14  which are pivotally mounted to the hinge pin  12  by mounting lugs  16 . Each flapper element  14  has 4 mounting lugs  16 , the mounting lugs  16  of the respective flapper elements being arranged in an alternating fashion on the hinge pin  12 . 
         [0038]    The flapper elements  14  are received in a recess  18  formed in one face  20  of the valve housing  4 , the recess  18  having a peripheral flange (not shown) against which the periphery of the flapper elements  14  seat in the closed position. The hinge end  22  of each flapper element  14  also seats against the valve housing web  8  in the closed position, so that the flapper elements  14  close the valve openings  6 . As described so far, the construction of the check valve is conventional. 
         [0039]    The check valve  2  is further provided with a stop  24  mounted between the mounting posts  10 . In this embodiment, the stop  24  is in the form of a wire coil spring  24  having a constant coil diameter D along its length. The coil spring  24  has mounting sections  26  at its ends, aligned along the longitudinal axis A of the coil spring  24 . The end sections  26  are received in bores  28  formed in the upper ends of the mounting posts  10 . The bores  28  are sized to be just slightly larger in diameter than the diameter of the coil spring wire in the end sections  26  of the coil spring  24  such that the coil spring end sections  26  may rotate about the longitudinal axis A of the spring  24  in the bores  28  thereby reducing the likelihood of irregular wear of the components. 
         [0040]    In this embodiment, the flapper elements  14  are generally plate like, but, as can be seen from  FIG. 4 , the upper surface  30  of the flapper element  14  (i.e. that facing away from the valve opening  6  when the flapper element  14  is closed) is convexly curved. In this embodiment, the upper surface  30  is smoothly curved over the entire width of the flapper element, but this is not essential, and it may be that only a medial section  32  of the upper surface  30  is so formed. 
         [0041]    The effect of the curvature of the flapper element upper surface  30  is seen in  FIG. 4 . The curvature means that the flapper element  14  does not contact the coil spring  24  along the entire length of the coil spring  24 , but only in a medial section  34  thereof. This means that the coil spring  24  is able better to deflect upon impact of the flapper element  14 , thereby better dissipating the impact energy. It will be appreciated that as the coil deflects, a central turn of the coil spring  24  will deflected first, after which turns adjacent the central turn will engage the flapper element upper surface  30 . The energy of the impact force is therefore converted into deflection and movement of the respective turns of the coil spring  24 . The damping effect will be best where the impact is asymmetrical (i.e. where one flapper element  14  impacts the coil spring  24  before the other. However, this is what mostly will happen in practice. 
         [0042]    In a variation of this arrangement, instead of a curved upper surface  30 , the medial section  32  of the upper surface  30  of the flapper element may simply be raised with respect to the laterally adjacent sections of the upper surface to create the desired engagement. 
         [0043]    A second embodiment of the disclosure will now be described with reference to  FIGS. 5 and 6 . 
         [0044]    The general construction of the check valve  102  of the second embodiment is similar to that of the first embodiment, so only the differences between the check valve  102  of this embodiment and the check valve  2  of the first embodiment will be discussed. 
         [0045]    In this embodiment, the stop is also in the form of a coil spring  124 . However, the coil diameter D of the spring  124  varies along its length, being a maximum in the medial region  134  of the coil spring and reducing toward the end regions  126  of the coil spring. 
         [0046]    This construction simplifies the construction of the flapper element  114  in that its upper surface  130  may be planar as shown, contact between the flapper element  114  and the medial section  134  of the coil spring  124  being assured by virtue of the varying diameter of the coil spring  124 . 
         [0047]    A third embodiment of the disclosure will now be described with reference to  FIGS. 7 and 8 . 
         [0048]    The general construction of the check valve  202  of the third embodiment is also similar to that of the first embodiment, so only the differences between the check valve  202  of this embodiment and the check valve  2  of the first embodiment will be discussed 
         [0049]    In this embodiment, the stop is also in the form of a coil spring  224 . In this embodiment, turns  222  are only provided in a medial region  234  of the coil spring  224 , with the coil spring  224  having elongated end mounting regions  226 . The coil diameter D of the medial region  234  is constant. 
         [0050]    The flapper element  214  is similar to that of the second embodiment, having a planar upper engagement surface  230 . The provision of coils turns only in the medial region  234  of the coil spring  234 , however, ensures that there is contact with the flapper elements  214  only in that medial region  234 . 
         [0051]    A fourth embodiment of the disclosure will now be described with reference to  FIGS. 9 and 10 . 
         [0052]    The general construction of the check valve  302  of the third embodiment is also similar to that of the first embodiment, so only the differences between the check valve  302  of this embodiment and the check valve  2  of the first embodiment will be discussed. 
         [0053]    In contrast to the first embodiment, the stop  324  in this embodiment is formed as a machined spring  324 . Machined springs are coil springs in which instead of the turns of the coil being made from wire, the turns are machined out of a tubular blank. 
         [0054]    In this embodiment, the spring diameter D is constant along the length of the spring  324 . The end regions  326  of the spring  324  are received in pockets  328  formed in the mounting posts  310 . 
         [0055]    As in the first embodiment, the upper surface  330  of the flapper element  314  is convexly curved so as to ensure contact of a medial region  332  of the flapper element  314  with the medial section  334  of the spring  324 . The upper surface  330  of the flapper element  314  may be shaped appropriately to provide the requisite area of contact with the spring  324 . 
         [0056]    Compared to a wire spring, a machined spring  324  may provide a better contact between the flapper element  314  and the spring  324 , depending on the shape of the upper surface  330  of the flapper element  314 . The spring  324  may be machined to provide the appropriate lateral resilience by controlling the width and thickness of the coil. 
         [0057]    In the various embodiments described above, the spring ends  26 ,  126 ,  226 ,  326  are received in bores or pockets in the mounting posts. The sizing of the spring ends and the bores or pockets will allow the spring ends to rotate about the spring axis A to prevent uneven wear on the spring or mounting posts. 
         [0058]    Lateral deflection of the springs will shorten the length of the spring length by a relatively insignificant distance compared to its side deflection. However, after the spring deflects laterally, the spring ends  26 ,  126 ,  226 ,  326  will no longer be coaxial with the central, deflected region of the spring. This will create a bending force on the mounting bores for the spring ends, which may cause stresses which can damage the mounting posts. 
         [0059]    In further embodiments of the disclosure, therefore, the mounting of the springs may be modified so as to permit rotation of the spring ends relative to the spring mountings. 
         [0060]    A first such modification is shown in  FIG. 11 . In this embodiment, the end regions  426  of a coil spring  424  (which may have either a constant or a varying coil diameter as shown in any of  FIGS. 1 to 8 ) is formed with a rounded end  440 . The rounded end  440  is received within a flaring closed bore  442  formed in the mounting post  410 . The closed bore  442  has a rounded base portion  444  having a radius of curvature slightly larger than that of the rounded end  440  of the coil spring  424 . It further has a flared mouth portion  446  which opens onto the inner surface  448  of the mounting post  410 . A gap  450  is thereby created between the spring end  440  and the flared pocket portion  446 , which will allow the end regions to rotate out of the spring axis A for example in a direction D in a plane extending transversely, for example perpendicularly, to the longitudinal axis A of the spring when impacted by the flapper elements  414 . This will act to avoid potentially damaging bending stresses being transmitted into the mounting post  410 . 
         [0061]    A second such modification is shown in  FIG. 12 . In this embodiment, the end regions  526  of a machined spring  524  are received within respective bores  528  in the mounting posts  510 . A clearance  530  is provided between the bore  528  and the end region  526 . 
         [0062]    Each end region  526  is provided with a transverse groove  540  extending diametrically across its free end. As can be seen, the groove  540  has a curved or rounded base  542 . 
         [0063]    A pin  544  is fixedly mounted within vertically aligned bores in the mounting posts  510 . The pin  544  is in this embodiment circular in cross section and has an outer surface whose diameter is slightly smaller than the radius of curvature of the groove base  542 . This, together with the clearance  530  will allow the ends  526  of the spring  524  to rotate in a direction E around the pin axis F, i.e. transversely to the longitudinal axis of the spring  524 , when the spring  524  is impacted by a flapper element. This arrangement also prevents bending stresses being transmitted into the mounting posts  510 . 
         [0064]    Other arrangements which provide a rotatable joint at the spring mounting also fall within the scope of this disclosure. 
         [0065]    The assembly of the various embodiments of check valve described above is very simple. To install the stop spring  24 , etc., all that is required is that the spring  24  be compressed lengthwise, suitably positioned between the bores or pockets in the mounting posts  10  and then released. The resilience of the spring  24  will retain it in the mounting posts without any additional retaining element being necessary. This is advantageous from a safety and reliability point of view. 
         [0066]    It will be appreciated that various modifications may be made to the embodiments discussed above without departing from the scope of the disclosure. For example, it would be possible in other embodiments to vary both the diameter of the spring and curve the engaging surface of the flapper element.

Technology Classification (CPC): 5