Abstract:
An improved valve assembly having an integral single piece housing ( 1 ) having an inlet ( 15 ), an outlet and defining an inwardly extending wall forming a valve seat ( 3 ); a valve member ( 4 ) moveable within the housing ( 1 ) between a closed position and an open position and a seal ( 11 ) to form a fluid tight seal between the valve member ( 4 ) and the valve seat ( 3 ) when the valve member is in the closed position. The seal ( 11 ) also acting to retain the valve member ( 4 ) within the housing ( 1 ) and in which the housing defining end portions which extend axially away from the valve member ( 4 ) at any position of the valve member between the open and closed positions.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a valve assembly and particularly to a check valve. 
     BACKGROUND OF THE INVENTION 
     Patent specification U.S. Pat. No. 4,862,913 describes a check valve having a valve body confining a valve element. Such valves are intended to be installed into the end of a conduit to inhibit retrograde, i.e. reverse, flow of fluid within the conduit. To ensure that fluid cannot by-pass the valve, a sufficiently strong seal must be formed between the valve body and the conduit. This is achieved by making the valve body slightly larger in diameter than the conduit and forming the conduit from a resiliently flexible material. Consequently, this arrangement is unsuitable for use in systems where the fluids used are corrosive and/or of high temperatures and/or pressures. Additionally it is difficult to integrate these devices into compression fitted systems as the valve&#39;s proximity to the end of the conduit leads to damage of the valve when the ferrule is compressed, and also because the conduit is liable to significantly deform when the ferrule is tightened compromising the effectiveness of the seal at the joint. Another example of an insert check valve is part number #110 manufactured by Smart Products Inc. of 675 Jarvis Drive, Morgan Hill, Calif. 95037 USA http://www.smartproducts.com. 
     Patent specification U.S. Pat. No. 6,981,512 relates to a biased-ball check valve assembly. The central position of the valve ball relative to the conduit&#39;s ends lends itself more easily for adaptation with compression fitting systems. However, the ball valve does not provide the necessary protection against reverse flow where precise control of fluid flow is required, such as in gas manifolds and systems for the control of supply/removal of reagents/products in chemical reactors. 
     SUMMARY OF THE INVENTION 
     According to the invention there is provided a check valve comprising: an integral single piece housing having an inlet proximate its first end and an outlet proximate its second end, between said inlet and outlet the housing defining an inwardly extending wall forming a valve seat; a valve member moveable within the housing between a closed position and an open position; and a seal to form a fluid tight seal between the valve member and the valve seat when the valve member is in the closed position, said seal also acting as means to retain the valve member within the housing; wherein the check valve comprises means to bias the valve member towards the closed position, and the housing defines end portions which extend axially away from the valve member at any position of the valve member between the open and closed positions. 
     The invention enables valves to be formed from as few as four separate components which significantly reduces manufacturing cost. Furthermore, the valve can be connected into a system using conventional compression fittings using standard compression fittings and occupies no more space than a plain straight length of pipe work without the valve mechanism being vulnerable to damage during connection of the piping to a pipe fitting. Alternatively the valve can be assembled within a pipefitting. 
     It is preferred that the valve member comprises retaining means which retains the seal. This may be arranged such that when valve member is in the closed position the seal engages the seal retaining means and prevents removal of the valve member through the inlet of the housing. Using the seal to retain the valve member reduces the number of components simplifying and reducing cost of manufacture. 
     The valve member may be retained within the housing such as to have a portion housed at an outlet side of the valve seat and a portion housed at the inlet side of the valve seat, preferably arranged so that the means to retain a seal is housed at the outlet side and the means to retain the biasing means housed at the inlet side. 
     The valve member, which may be formed from a single piece, may define an enlarged portion retaining the seal and a stem retaining the bias means. Preferably the bias means is a spring, e.g. a helical spring, retained over the stem of the valve member. 
     The seat wall may be tapered such as to define a portion of the housing having a narrowing inner diameter 
     In a preferred embodiment the bias means is retained over a stem of the valve member and between a flange defined by the valve member and the inlet side of the valve seat. In this embodiment said end portions are adapted to be inserted into a compression fitting, a push fit fitting or a solder weld fitting. 
     For the purposes of this specification the terms ‘tube’ and ‘tubular’ include hollow longitudinal members having circular, variable or other cross sections. 
     Preferably seal-retaining means is included for holding the seal so that the seal can be forced into engagement with the retaining means during assembly of the valve and, when thus retained, prevents removal of the valve member from the housing. 
     According to a second aspect of the invention there is provided a method of assembling a check valve comprising a housing, a valve member movable between a closed position and an open position, a seal and seal-retaining-means for holding the seal in a position to form a fluid tight seal between the valve member and the housing when the valve member is in the closed position, and a means to bias the valve member towards the closed position; the method comprising the steps of:
         a) locating the valve member and means to bias the valve member within the housing;   b) using a guide to guide the seal into a position where it is retained by the seal-retaining means; and   c) removing the guide.       

     In a preferred embodiment the seal is passed over and guided along the guide, which may takes the form of a rod and held in axial alignment relative to the valve member, into a recess between shoulder on the valve member. A tool may be used to assist the insertion of the seal. Preferably the tool passes substantially around and slides over the guide. The tool may also be provided with means to locate against the valve member such as by a spigot and corresponding recess provided by the guide and valve member. 
     A limiter may be used to prevent the seal from being pushed beyond the recess. The limiter may be provided by the tool and adapted so as to engage with the housing when the seal is in position. The valve member may also be held in position within the housing a stop which may also be provided with a limiter. The tool and stop can be used in combination to assemble the valve without the need for judgement to ensure the seal is accurately placed, thereby increasing assembly speed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described by way of example with reference to the following figures in which: 
         FIG. 1A  is a cross sectional side elevation of a tube for holding a valve member; 
         FIG. 1B  is a side elevation of a valve member and spring adapted to reside in the tube; 
         FIG. 1C  is a top elevation of the valve member; 
         FIGS. 2A ,  2 B and  2 C are partial cross section views showing stages of assembly of a check valve; 
         FIG. 3  is a partial cross-section transparency of the assembled check valve in a closed position connected at either end to compression fittings; 
         FIGS. 4A &amp; 4B  are top elevation transparencies of a pipe fitting housing a check valve in two possible orientations; 
         FIG. 5  is a cross section of a further alternative embodiment in which the housing takes the form of a gas bottle adaptor; and 
         FIG. 6  is a cross section perspective of a block housing a number of conduits each having a check valve. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1A ,  1 B and  1 C illustrates a tubular conduit  1  made from a single piece of metal such as stainless steel having a substantially uniform outer diameter. The tube bore has a first portion  1 A extending from an inlet of the tube at the bottom end as shown on  FIG. 1A . The first portion  1 A ends at a radial step  2  defining an opening of reduced diameter as compared with the conduit portion  1 A. This opening communicates with a second bore portion  1 B having a widening diameter so as to define a conical valve seat  3 . The second portion  1 B leads into a third bore portion  1 C having a diameter greater than that of the first portion  1 A. The third portion  1 C of the bore leads to an outlet at the top of the tube as shown on  FIG. 1A . 
     The first and third portions  1 A,  1 C extend sufficiently far from the step  2  and seat  3  respectively so to allow end parts of the tube as indicated by broken lines  1 D to be inserted into a compression fitting. 
     The various diameters of the bore and seat/step features can be formed by machining out, e.g. boring or counterboring a solid metal rod or tube. 
     Referring to  FIGS. 1B and 1C  there is shown a valve member  4 . The valve member  4  has a flange  6  and a head  7  at opposite ends of a stem  5 . The head  7  includes an enlarged part  7 A, an intermediate part  7 C and spigot  7 E. Between parts  7 A and  7 C lies a groove  7 B formed by approaching conical shoulders which acts as a retainer for an O-ring seal (not shown in  FIG. 1 ). On the other side of the part  7 C, a tapered part  7 D leads into the spigot  7 E. A helical spring  8  sits over the stem  5  and against the flange  6 . 
     During assembly of the valve as illustrated in  FIGS. 2A ,  2 B and  2 C, the valve member  4  is placed head first into the inlet of the conduit  1  and moved to position such that the spring  8  is held and compressed between the flange  6  and step  2  with the head  7  protruding past the seat  3  and into the third portion  1 C as shown in  FIG. 2A . The maximum diameter of the head is marginally smaller than the opening of the valve seat  2  so that it can pass through the latter during assembly. 
     The valve member  4  is moved to and maintained in this position with the aid of backstop  9 . The backstop  9  comprises a shaft portion  9 A having a diameter similar to that of the flange  6  so as to provide good support for the valve member  4 , and a stop  9 B spaced from the free end of the shaft  9 A such that the stop  9 B abuts against the end of the conduit  1  when the valve member  4  is in the required location. The position is as shown in  FIG. 2A   
     Whilst the valve member  4  is held in this position, a guide rod  10  is inserted into the outlet of the tube  1 . A recess  10 A in the end of the guide rod  10  receives the spigot  7 E so as to hold the guide rod in axial alignment with the valve member  4 . An O-ring seal  11 , formed from resiliently flexible plastics material, is located over the free end of the guide rod  10 . The position is now as shown in  FIG. 2B . Using a tool  12 , the O-ring is pushed along the guide rod  10  onto the head  7 . It is then stretched by the action of the tool  12 , over the intermediary portion as shown in  FIG. 2C , and retained in groove  7 B. During this action the O-ring may be squashed between the part  7 C and the bore  1 C, this is shown exaggerated in  FIG. 2C . The insertion tool  12  has a shaft  12 A with a bore which allows the shaft  12 A to be passed with a sliding fit over guide  10  and into portion  1 C behind the O-ring  11 . 
     To prevent the tool  12  from accidentally pushing the O-ring beyond the groove  7 B and onto the enlarged portion  7 A or stem  5 , the tool  12  is provided with a limiter  12 B which is located at a position spaced from the free end of the shaft  12 A such as to engage with the end of the conduit  1  when the O-ring is between the shoulders  7 B. With the O-ring  11  now in place, the tool  12 , guide  10  and back stop  9  are removed from the tube  1  allowing the spring  8  to extend causing the head  7  to move into the portion  1 B and the O-ring  11  to be compressed between the shoulders of the groove  7 B and seat  3  effecting a fluid tight seal and preventing the valve head  7  from passing back through the opening in the valve seat  3 . 
     It will be understood that, for the limiter  12 A and stop  9 B to perform their functions, the length of the shafts  9 A,  12 A and positions of the stops  9 B  12 B must be selected corresponding to the length of the conduit  1 , valve member  4  and relative position of the seat  2  within the conduit  1 . 
     In  FIG. 3  the conduit  1  with assembled valve is shown connected to compression fittings  13 . Compression nuts  13 A and two part ferrules each comprising a front ferrule  14 A and back ferrule/olive  14 B (though a single part ferrule may equally be used) are passed over each end of the tube  1 . The first and second ends are inserted into the fitting  13  so as to abut against seats  13 B and then the compression nuts are tightened about the tube such that the front ferrule  14 A deforms and crimps the tube causing a fluid tight seal and slight deformation of the tube. The deformation is not visible in the figure but it can be seen that the first and third portions  1 A,  1 C are sufficiently long that that the ferrules can be tightened about their ends without causing deformation in the region of the valve member  4  or O-ring  11 . 
     In use, pressure from fluid flow from the inlet, indicated by arrow  15  urges the valve member  4  to move in the direction of fluid flow, compressing the spring  8  and opening the valve. When fluid flow from the inlet subsides, the spring will causes the O-ring  11  to re-engage with the seat  3  re-effecting the seal. 
     In an alternative embodiment, the conduits could also be joined by other means such as push fit fittings and solder joints. In the latter case, the distance of the valve member  4  from the ends of the conduit may reduce any damage that could be caused to the components from the application of heat used to solder the joint. 
       FIGS. 4A and 4B  illustrate alternative embodiments of the invention in which the valve as described above is incorporated into a pipe fitting. In each case arrows  15  indicate direction of intended fluid flow. The fitting  100  defines external screw threads  500  at one end and has compression fitting nut  400  at the other end. The body of the fitting  100  defines a bore for housing the check valve and allowing the passage of fluid through the fitting. The bore defines portions  100 A in which spring  8  is housed, narrowing portion  100 B and portion  100 C in which the head of the valve member is housed. As with the previous embodiments, the internal wall of the bore defines a step  200  and a valve seat  300 . The seal  11  and valve member  4  are assembled within the pipe fitting using the method previously described. Portion  100 C leads into wider bore portion  100 D by way of step  100 E. Portion  100 D is sized to receive piping into and for connection with the compression fitting  400 . Step  100 E limit the extent of insertion of piping so as protect the valve member  4  from over insertion.  FIG. 4B  illustrates a fitting which is similar but in which portions  100 A,  100 C and step  200  and seat  300  have been formed in alternative positions to allow the valve member to be held in a reverse orientation. 
       FIG. 5  illustrates an embodiment in which the valve assembly is housed within a bull nose bottle adapter. Such adaptors are commonly used for the connection of gas cylinders to pipe systems. In a variation to the above examples the first portion  100 A communicates with a wider bore  100 F which in turn communicates with a widest portion  100 G which extends to the inlet. Portion  100 F is formed with threaded internal wall  100 H. Portion  100 A is of sufficient length to house spring  8  and flange  6  (shown ghosted) when the valve member  4  is in the closed position. Also shown is a retainer  600  having an outer threaded wall and a flange portion  600 A which extends axially from the inner diameter portion of the retainer  600 . 
     The method of assembly follows that substantially as described above with the addition that once the seal  11  has been mounted onto head  7 , retainer  600  is inserted flange  600 A first into the inlet, brought to portion  100 F and rotated so that the outer threaded wall of the retainer  600  engages with the corresponding thread  100 H of portion  100 F drawing the retainer  600  towards portion  100 A and securing it against portion  100 F. The thickness of the retainer wall  600  is such that when secured, flange  600 A protrudes into portion  100 A. The retainer  600  is of use where the valve is used in systems operating at high pressures (e.g. 200 bar and over) to prevent dislodgement of the poppet. 
     It is envisaged that the above described method and valve arrangement could equally be adapted into housings forming other types of pipe fittings such as push fit fittings. 
       FIG. 6  illustrates a further embodiment of the invention in which a series of bores  700 A, in this embodiment six bores, are formed within a block or plate structure  700 . Each bore  700 A extends from a top surface of the block to bottom surface (as oriented in the illustration) and defines a valve seat  300  and step  200  about which a valve member  4  is held (shown without ‘O’ ring attached). Block or plate  700  is intended to be used in conjunction with a second component (not shown) adapted to be placed against block  700  and having passages which communicate with passageways  700 A one-to-one so as to form an extension thereto. Alternatively the component may define a more complex relationship e.g. so to provide communication between multiple passages  700 A or to a plenum so as to form a manifold structure. Grooves  700 B formed in the top surface of block  700  may be used to retain seals in order to provide a fluid tight seal between block  700  and the further component. 
     It is believed that the illustrated embodiments provides a check valve suitable for situations where it is required to provide a high reliability seal against reverse flow even in systems where the fluids used are corrosive and at high temperatures and pressures. 
     It is emphasised that the illustrated embodiments are described only by way of example and that many variations are possible within the scope of the accompanying claims. For example, the valve member and conduit/housing may be made from materials other than metal, though a metal conduit/housing would be preferable where it to be deformed by a compression fitting. The housing and bores may be formed by moulding techniques. In a further alternative the guide may be provided with a spigot or other protrusion and the valve member be provided with a recess instead of the reverse arrangement described. In another variation, the seal may be adapted to be held on the fixed valve housing rather than the movable valve stem. In such an arrangement, a tool, equivalent to the tool  12  would be used to manipulate the seal into its operational position where it is retained on the valve housing, seals against the valve member, and prevents withdrawal thereof during operation.