Abstract:
A coupling for joining pipe segments together is disclosed. The coupling is derived from a standard fitting and has a housing with a socket and an expanded region adjacent to the socket. Three shoulders are positioned within the expanded region. A sealing member and two support washers are positioned within the expanded region, each engaging a shoulder. A retainer is positioned in the expanded region between the two support washers. A lip, positioned at the end of the expanded region, extends radially inwardly and captures the sealing member, washers and retainer within the coupling. The retainer has a plurality of radial teeth angularly oriented to engage a pipe and prevent its removal from the coupling. One of the washers is kept in spaced relation from the other washer by a shoulder to prevent contact with the retainer upon assembly which may otherwise inhibit the teeth engaging the pipe.

Description:
RELATED APPLICATION  
       [0001]    This application is a continuation-in-part of U.S. application Ser. No. 10/123,607, filed Apr. 16, 2002, which is a continuation-in-part of U.S. application Ser. No. 10/007,951, filed Dec. 3, 2001, which is based on and claims priority of U.S. Provisional Application No. 60/262,820, filed Jan. 19, 2001. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates to couplings for pipes and especially to mechanical couplings derived from standard fittings which effect a strong, reliable joint with a fluid-tight seal without the need for brazing or soldering.  
         BACKGROUND OF THE INVENTION  
         [0003]    The construction of piping networks requires couplings that can form fluid-tight joints between pipe ends which can withstand external mechanical forces, as well as internal fluid pressure and reliably maintain the integrity of the joint. Many forms of joints are known, such as brazed or soldered joints, threaded joints, welded joints and joints effected by mechanical means.  
           [0004]    For example, copper tubing, which is used extensively throughout the world to provide water service in homes, businesses and industry, is typically joined by means of couplings which are soldered to the pipe ends to effect a connection.  
           [0005]    The use of copper tubing for piping networks is so widespread that standard tubing sizes have been established in various countries. For example, in the U.S., there is the ASTM Standard; in Germany, the DIN Standard; and in the United Kingdom, the British Standard (BS). Chart 1 below shows a portion of the range of nominal diameters of the various standard copper tubes listed above.  
                                 CHART 1                           Standard Outer Copper Tube Outer Diameters                ASTM   DIN   BS                       ½″   15 mm   15 mm           ¾″   22 mm   22 mm           1″   28 mm   28 mm           1.25″   35 mm   35 mm           1.5″   42 mm   42 mm           2″   54 mm   54 mm                      
 
           [0006]    Naturally, there are standard pipe fittings such as elbows (45° and 90°), tees and straight segments matched for use with the standard tube diameters. These standard fittings are defined in the U.S. by ASME Standard B16.22a-1998, Addenda to ASME B16.22-1995 entitled “Wrought Copper and Copper Alloy Solder Joint Pressure Fittings” dated 1998 and hereby incorporated by reference. The standard fittings have open ends with inner diameters sized to accept the outer diameter of a particular standard tube in mating contact for effecting a soldered joint.  
           [0007]    In addition to the standard fittings described above, other components, such as valves, strainers, adapters, flow measurement devices and other components which may be found in a pipe network, will have a coupling which is compatible with the standard pipe, and it is understood that the term “coupling”, when used herein, is not limited to a standard elbow, tee or other fitting but includes the open end of any component useable in a piping network which serves to couple the component to the pipe end.  
           [0008]    A soldered joint is effected between a standard diameter tube end and its associated standard fitting by first cleaning the surfaces to be joined, typically with an abrasive such as a wire brush or steel wool, to remove any contaminants and the oxide layer which forms on the surfaces. Next, the cleaned surfaces are coated with a flux material, usually an acid flux, which further disrupts the oxide layer (especially when heated) and permits metal to metal contact between the fitting, the pipe end and the solder. The pipe end is next mated with the fitting thereby bringing the cleaned, flux coated surfaces into contact. The fitting and pipe end are then heated to the melting temperature of the solder, and the solder is applied to the interface between the tube and the fitting. The solder melts, flows between the surfaces of the pipe end and the fitting via capillary action and upon cooling and solidifying forms the solder joint. Excess flux is removed from the outer surfaces to prevent further acid etching of the pipe near the joint.  
           [0009]    While the soldered joint provides a strong, fluid-tight connection between pipe end and fitting, it has several disadvantages. Many steps are required to make the soldered joint, thus, it is a time consuming and labor intensive operation. Some skill is required to obtain a quality, fluid-tight joint. Furthermore, the solder often contains lead, and the flux, when heated, can give off noxious fumes, thus, exposing the worker to hazardous substances which can adversely affect health over time. The joint is typically heated with an open gas flame which can pose a fire hazard, as well as a personal burn hazard.  
           [0010]    To overcome these disadvantages, many attempts have been made to create mechanical couplings which do not require solder or flame to effect a strong, fluid-tight joint. Such mechanical couplings often use an over-sized opening accommodating an O-ring for sealing purposes and an annular retainer interposed between the outer diameter of the pipe end and the inner diameter of the coupling to mechanically hold the parts together. The retainer often has radially extending teeth which dig into the facing surfaces of the coupling and the pipe end to resist extraction of the pipe end from the coupling after engagement.  
           [0011]    While these mechanical couplings avoid the above identified problems associated with soldered joints, they can suffer from one or more of the following disadvantages. To be effective, the retainer requires sufficient space within the coupling. Thus, the couplings tend to be oversized relatively to the pipes they are intended to receive, and if existing standard couplings are to be adapted for use with such a mechanical system, it is usually necessary to adapt a larger size standard fitting to a smaller size standard pipe. This is more expensive than adapting the standard fitting appropriate to the standard pipe in what is known as a “size-on-size” fitting. For example, a standard ¾ inch pipe fitting may be used to couple a ½ inch standard copper pipe in a mechanical system (not “size-on-size”). Furthermore, the retainer may not provide adequate pull-out strength, and the pipe end could be inadvertently separated from the coupling, for example, during a pressure spike within the pipe, caused by a sudden closing of a valve (the “water hammer effect”) which places the joint under increased tension.  
           [0012]    The retainer also does not help keep the pipe end coaxial with the coupling upon insertion, allowing the pipe end to tip and deform the retainer and gouge the inside surface of the coupling or an elastomeric seal, such as an O-ring. In such a mechanical joint, there is furthermore little or no resistance to axial rotation of the pipe relatively to the coupling (i.e., relative rotation of the pipe and coupling about the longitudinal axis of the pipe). Thus, valves or other items mounted on the pipe will tend to rotate. Mechanical joints with retainers also tend to have little resistance to bending, allowing the pipe too much angular free play and permitting the pipe to “walk” out of the joint under repeated reversed bending loads. Excessive free play also tends to disengage the teeth on one side of the retainer and deform the teeth on the other side, weakening the joint. Furthermore, use of an enlarged section to accommodate the retainer may cause energy loss impeding fluid flow if the fluid is forced to flow into a coupling having a larger cross-sectional area. In general, when mechanical couplings are designed to overcome the aforementioned inherent disadvantages, they tend to suffer from a high part count, making them relatively complex and expensive.  
           [0013]    There is clearly a need for a mechanical pipe coupling which avoids the disadvantages of both soldered pipe fittings, as well as prior art mechanical fittings described above, and which can be derived from existing standard fittings and used with pipes appropriate to the standard fitting in a “size-on-size” association rather than using a larger size fitting to couple smaller diameter pipes together.  
         SUMMARY OF THE INVENTION  
         [0014]    The invention concerns a pipe coupling housing having a socket with an inner diameter sized to receive a pipe and an outer diameter. The pipe coupling housing comprises an expanded region positioned adjacent to one end of the socket. The expanded region has an inner diameter and an outer diameter larger than the inner and outer diameters of the socket respectively. The expanded region also has an end defining an opening for receiving the pipe. A first shoulder is positioned between the socket and the expanded region. A second shoulder is positioned intermediate between the first shoulder and the opening. A third shoulder is positioned adjacent to the opening, and a lip is positioned at the opening in spaced relation to the third shoulder. The lip projects substantially radially inwardly. The functions of the various features of the housing are described below in the context of the pipe coupling.  
           [0015]    The pipe coupling is sealingly engageable with a pipe. The pipe coupling comprises a housing as described above and further includes a sealing member positioned in the expanded region to effect a seal between the pipe coupling and the pipe. The sealing member engages the first shoulder which prevents the sealing member from moving further into the coupling housing when a pipe is received in the socket. A first support washer is positioned in the expanded region adjacent to the sealing member. The first support washer engages the second shoulder which acts as a stop preventing further motion of the first support washer toward the sealing member. A retainer is positioned within the expanded region adjacent to the first support washer. The retainer has a circumferential rim and a plurality of teeth projecting inwardly therefrom. A second support washer is positioned within the expanded region between the third shoulder and the opening. The second support washer engages the third shoulder and remains in spaced apart relation away from the first support washer over a distance at least equal to the width of the retainer rim. A lip is positioned at the opening in spaced relation to the third shoulder. The lip projects substantially radially inwardly to engage the second support washer and retain it between the third shoulder and the opening.  
           [0016]    The invention also includes a method of manufacturing a pipe coupling housing. The method comprises the steps of:  
           [0017]    (A) providing or forming a fitting having a socket;  
           [0018]    (B) expanding a portion of the socket into an expanded region having a larger inner diameter than the socket, the first expanded region defining an opening;  
           [0019]    (C) forming a first shoulder between the socket and the expanded region;  
           [0020]    (D) forming a second shoulder between the first shoulder and the opening; and  
           [0021]    (E) forming a third shoulder between the second shoulder and the opening.  
           [0022]    The coupling may be assembled using the housing by inserting into the expanded region the sealing member, the retainer and the support washers and then forming the lip that captures these internal components within the expanded region.  
           [0023]    Preferably, the fitting provided is one that is readily available and manufactured according to a standard, such as ASME Standard B16.22a-1998. This standard includes fittings having sockets sized to receive copper pipe having a nominal diameter between ½ inch and 2 inches inclusive. Other standards may also be considered, for example, standards wherein the socket is sized to receive copper pipe having a nominal diameter between 15 mm and 54 mm inclusive. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    [0024]FIG. 1 is a partial longitudinal sectional view of a pipe coupling housing according to the invention;  
         [0025]    [0025]FIG. 1A is a partial longitudinal sectional view of an alternate embodiment of a pipe coupling housing according to the invention;  
         [0026]    [0026]FIG. 2 is a longitudinal sectional view of a pipe coupling according to the invention; and  
         [0027]    [0027]FIG. 3 is an exploded perspective view of a pipe coupling in the form of an elbow fitting according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0028]    [0028]FIG. 1 shows a pipe coupling housing  10  according to the invention. Housing  10  is preferably formed from a readily available standard pipe fitting and has a socket  12  with an inner diameter  14  sized to receive a pipe. Socket  12  also has an outer diameter  16 . An expanded region  18  is positioned adjacent to one end of the socket  12 . The expanded region  18  has an end  20  opposite the socket  12  that defines an opening  22  for receiving the pipe. A pipe stop  24  is positioned adjacent to the opposite end of socket  12 . Pipe stop  24  is formed by a surface  26  that projects substantially radially inwardly to engage the pipe received within the socket. The stop  24  may extend substantially continuously around the circumference of the housing as shown in FIG. 1, or it may comprise one or more discrete surfaces  28  as illustrated in FIG. 1A.  
         [0029]    With reference again to FIG. 1, the expanded region  18  has an inner diameter  30  and an outer diameter  32  , both of which are larger, respectively, than the inner and outer diameters  14  and  16  of socket  12 . A first shoulder  34  is positioned between the socket  12  and the expanded region  18 . A second shoulder  36  is positioned within the expanded region  18  intermediate between the first shoulder  34  and the opening  22 . Preferably, second shoulder  36  is formed by a dimple  38  projecting substantially radially inwardly of the housing  10 . Dimple  38  may extend substantially continuously around the expanded region  18  or it may be discontinuous as shown in FIG. 1A. FIG. 1 shows a third shoulder  40  positioned adjacent to opening  22 , and a lip  42 , positioned at the opening  22  in spaced relation to the third shoulder. Lip  42  projects radially inwardly of the coupling  10 . The functions of the various aforementioned features of the housing  10  are described below in the context of the pipe coupling and its components.  
         [0030]    [0030]FIG. 2 is a longitudinal sectional view of a pipe coupling  44  according to the invention. Coupling  44  comprises housing  10  and further includes a sealing member  46  positioned within expanded region  18 . Sealing member  46  engages first shoulder  34  and effects a seal between the outer surface  48  of a pipe  50  (shown in broken line received within the coupling) and the pipe coupling housing. Engagement between the sealing member  46  and the first shoulder  34  prevents the sealing member from being dislodged from the expanded region  18  upon insertion of pipe  50  into the socket  12 . Preferably, sealing member  46  is a pressure responsive seal having a lobe or gland  52  that is pressurized by the fluid within the pipe  50 , the pressure further forcing the gland  52  against the pipe outer surface  48  thereby effecting a fluid tight seal. Pressure responsive sealing members are advantageous because they provide a fluid tight seal without the need for significant interference between the sealing member  46  and the pipe  50 , thus lowering the insertion force necessary to engage the pipe  50  with the coupling  44 .  
         [0031]    A first support washer  54  is positioned within the expanded region adjacent to the sealing member  46 . First support washer  54  preferably engages or is engageable with the sealing member  46  to prevent its extrusion outwardly toward the opening  22  of coupling housing  10  when it is subjected to high fluid pressure within the pipe  50 . The first support washer  54  has an outer diameter  56  that allows it to engage the second shoulder  36 , thus fixing the washer&#39;s position within the expanded region  18 . Preferably, the first support washer  54  also has an inner diameter  58  that is substantially equal to the socket inner diameter  14 , allowing the first support washer to engage and support the pipe  50  received within the socket  12 . Preferably, the first support washer is made from stainless steel to prevent corrosion although beryllium copper alloys, as well as high strength engineering plastics are also feasible. It is also feasible to attach seal  46  to support washer  54 .  
         [0032]    A retainer  60  is positioned within the expanded region  18  adjacent to the first support washer  54 . Retainer  60  preferably comprises a circumferential rim  62  sized to fit substantially coaxially within the expanded region  18 , and a plurality of teeth  64  projecting from the rim  62 . Preferably, teeth  64  extend angularly inwardly toward the socket  12 . The teeth  64  are designed to engage the outer surface  48  of pipe  50  when it is received within the housing  10 . The angular orientation of the teeth  64  cause them to be “self jamming” in that they dig into the pipe surface  48  in response to outward motion (caused by internal pressure or external loads) to prevent withdrawal of the pipe from the coupling  44 . This is particularly advantageous for plain end pipe as shown in FIG. 2. Engagement of the teeth  64  with the pipe  50  may be enhanced by the incorporation of circumferential grooves  78  around the pipe  50  as shown in FIG. 3. The grooves provide purchase for the teeth, increasing their ability to prevent withdrawal of the pipe from the coupling. Preferably, the retainer is made from stainless steel to prevent corrosion although beryllium copper alloys are also feasible. Engineering plastics are also feasible and may be used with plastic pipe and plastic fittings.  
         [0033]    As shown in FIG. 2, a second support washer  66  is positioned within the expanded region  18 . Second support washer  66  engages the third shoulder  40  which keeps the second support washer in spaced apart relation away from the first support washer  54  over a distance at least equal to the width of rim  62 . It is found advantageous to maintain this separation between the support washers so as to avoid imposing contact forces between the second support washer  66  and the teeth  64  upon assembly of the coupling. Such contact forces operate to deflect the teeth  64  and relieve the preload between them and the pipe surface  48 . Relief of the preload, if allowed to occur, inhibits the ability of the retainer to prevent withdrawal of the pipe  50  from the coupling  44 , thus, reducing the maximum pressure at which the coupling maintains a fluid tight seal.  
         [0034]    It is advantageous to construct the second support washer  66  from a circumferential flange  68  and a collar  70 . Circumferential flange  68  is sized to engage the third shoulder  40  while the collar  70  is oriented transversely to the flange, preferably co-axially with the socket  12 . Collar  70  preferably has an inner diameter  72  substantially equal to the inner diameter  14  of the socket  12  and can thereby provide alignment and support to the pipe  50  upon engagement with the coupling  44 . As shown on the right side of FIG. 2, collar  70  may project inwardly to engage and support teeth  64  when they are deflected to the right by motion of pipe  50  to the right. Support of the teeth by the collar increases the force required to withdraw the pipe from the coupling, thus increasing the maximum pressure which the coupling can withstand. As shown on the left side of FIG. 2, collar  70  may also project outwardly from the coupling to increase the total distance over which pipe  50  is directly supported by the coupling  44 , thus providing greater bending stiffness to the joint formed between the coupling and the pipe. Preferably, the second support washer is made from stainless steel to prevent corrosion although beryllium copper alloys, as well as high strength engineering plastics are also feasible.  
         [0035]    Lip  42  surrounds and defines opening  22 , the lip being positioned in spaced apart relation with the third shoulder  40  so that the second support washer  66  may be captured between the lip and the third shoulder. Lip  42  projects substantially radially inwardly to engage and capture the second support washer  66 . Preferably lip  42  comprises a portion of expanded region  18  that is turned inwardly after the sealing member  46 , first support washer  54 , retainer  60  and second support washer  66  are positioned within the expanded region.  
         [0036]    [0036]FIG. 3 shows an exploded view of a coupling  44  according to the invention in the form of an elbow fitting  76 , it being understood that the coupling may take any of various practical forms including Tee fittings, reducers and may also be used on components such as valves, strainers and the like to couple the components to pipes as well as pipes to pipes. As described above, elbow fitting  76  is preferably formed from a standard fitting, for example ASME Standard B16.22a-1998. The expanded region  18  is adjacent to the socket  12 , the first shoulder  34  is engaged by the sealing member  46 , the first support washer  54  engages the second shoulder  36 , the retainer  60  is positioned adjacent to the first support washer  54 , the second support washer  66  engages the third shoulder  40  and is kept in spaced apart relation from the first support washer  54  over a distance at least equal to the width of the rim  62 . Lip  42 , shown in broken line, extends substantially radially inwardly to capture the aforementioned components within the expanded region  18 . Lip  42  defines opening  22  that receives pipe  50 , the pipe in this example having the aforementioned grooves  78  to provide purchase to teeth  64  of the retainer.  
         [0037]    In manufacturing the coupling according to the invention, it is preferred to begin with a commonly available standard fitting such as those made according to ASME Standard B16.22a-1998 for wrought copper fittings. These fittings are especially appropriate for use to couple to pipes having a nominal diameter between ½ inch and 2 inches inclusive. Other standards are also available, for example British or German DIN standards that specify fittings appropriate for copper pipe having a nominal diameter between 15 mm and 54 mm inclusive. It is also feasible to form the fitting by various techniques. Cast and forged fittings are preferred for certain types of valves and other fittings, and such castings or forgings are compatible with the coupling housing design and internal components as described previously.  
         [0038]    The method of manufacture according to the invention includes the steps of providing or forming the fitting, preferably a fitting manufactured to comply with a standard such as ASME Standard B 16.22a-1998, and then expanding a portion of the socket to form the expanded region. The expansion is preferably accomplished by die forming the existing fitting although other techniques, such as hydro-forming and spinning are also feasible.  
         [0039]    The aforementioned die forming techniques may also be used to form the first shoulder between the socket and the expanded region as well as the second shoulder between the first shoulder and the opening and the third shoulder between the second shoulder and the opening. Once all of the shoulders have been formed the sealing member, the first support washer, the retainer and the second support washer are inserted into the expanded region and the lip is formed, preferably by rolling the free edge of the expanded region over so that the lip extends substantially radially inwardly of the coupling.  
         [0040]    Couplings according to the invention provide a mechanical pipe coupling which can form a reliable fluid-tight joint without the hazards associated with brazing, welding or soldering while taking advantage of existing standard fittings in a size-on-size relationship with standard pipe to achieve significant economical advantage.