Abstract:
The present invention relates to an alternative pipe coupling apparatus, to conventional tapered screw threads usually used to join ends of pipe sections to fixtures. The invention utilizes a bayonet style interlocking arrangement having a male element and a female element which join together and are opposingly biased against one another by a spring-like retaining ring to ensure an appropriate rigid and leak-proof connection between two elements.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an apparatus for pipe fitting which prevents leakage and ensures a rigid connection between either a section of pipe and a fitting, for example a valve body, or even between separate pipe sections themselves. More specifically the present invention relates to an alternative to conventional tapered screw threads usually used to join ends of pipe sections to fittings and, in particular, a bayonet style interlocking arrangement having a male element and a female element which join together and are opposingly biased against one another by a spring-like retaining ring to ensure an appropriate rigid and leak-proof connection between two elements.  
       BACKGROUND OF THE INVENTION  
       [0002]     The use of taper-threaded pipe and fittings is standard practice in the construction of small diameter (generally, ¼ inch through 2 inch) piping systems. The tapered screw thread gives rise, as the joint is tightened, to interference between the pipe and fitting that acts to prevent leakage and assure a rigid connection.  
         [0003]     Lengths of pipe and associated fittings may be screwed together “by hand” until the imaginary conical pitch surfaces of the male and female threads meet. Further tightening, ranging from one half to one full pitch of the thread is then necessary to create sufficient interference between the threads to complete assembly of the joint. Although this method of construction provides a strong mechanical connection and one that can be made leak-tight, it has shortcomings that make its use troublesome in certain situations.  
         [0004]     The geometry of taper pipe threads is governed by a pair of gauges, a ring gauge for male threads and a plug gauge for female threads. An acceptable thread is one that falls between one turn short of the gauge plane and one turn beyond the gauge plane, an axial span of two times the thread pitch. As a result, the overall length of a piping assembly can vary over a span of four times the pitch of the thread (2 times the pitch for the male thread, 2 times for the female) for every joint.  
         [0005]     For example, the pitch of U.S. standard 1 inch pipe thread is 0.087 of an inch, the variability in length of an assembly of 1 inch pipe and fittings, therefore, is 0.087 of an inch×4 equals 0.35 of an inch per joint, this without considering the probability of further variation arising from tightening of the joints.  
         [0006]     The high degree of uncertainty in predicting the completed length of piping assemblies poses a serious problem in situations wherein a piping a subassembly must meet mating connections at fixed positions within a piping system.  
         [0007]     A further problem is encountered when a taper thread fitting, for instance a valve, is to be assembled into a piping system so that the stem will reside in a certain position when the assembly is completed. To accomplish this, the fully tightened condition must be achieved just as the stem arrives in the desired position. Unfortunately, with conventional taper threaded pipe and fittings, the coincidence of full pipe “makeup” and proper positioning is entirely happenstance.  
         [0008]     Fittings are customarily over-tightened in an effort to achieve a desired orientation, resulting in possible damage including stripping of the threads. Under-tightening invites leakage and inadvertent repositioning (usually loosening) of the fitting through normal use.  
         [0009]     Assembly of taper-thread piping requires the application of considerable torque to achieve sound joints. Application of the necessary torque can be detrimental to other components of the system that must provide a reaction to oppose the applied torque. Furthermore, applying this torque requires use of large tools that are difficult to maneuver in confined areas.  
         [0010]     Also cutting pipe threads in a section of pipe, or in a fitting requires a substantial amount of material, i.e., the wall thickness of the pipe must be sufficient to allow for thread cutting without significant weakening of the pipe. In certain cases where thin walled pipe could be used, for example in relative lower pressure systems, a heavier gauge, and more expensive, pipe must be used solely for the purpose of supporting the thread cutting.  
       OBJECT AND SUMMARY OF THE INVENTION  
       [0011]     Wherefore, it is an object of the present invention to overcome the above mentioned shortcomings and drawbacks associated with the prior art.  
         [0012]     Another object of the present invention is to provide an alternative pipe and fitting coupling to conventional screw thread type connections.  
         [0013]     A further object of the present invention is to provide a male element and a female element which interlock by means of a biased, bayonet style interlocking arrangement which maintains a rigid and leakproof pipe and fixture coupling.  
         [0014]     Yet another object of the present invention is to provide the alternative coupling device with a consistent overlap at the interface between the pipe and fittings, in order that the length of piping assemblies can be more accurately predicted.  
         [0015]     A still further object of the present invention is to provide an easily manipulatable coupling mechanism for attaching pipe and fittings which is economically manufactured and cost effective.  
         [0016]     The present invention also relates to a coupling apparatus comprising a receiving element defining an axial bore having an annular groove; a retaining ring supported in the annular groove; an insertion element having a radially extending projection for engaging the retaining ring in the annular groove; the insertion element being axially inserted into the axial bore, at least partially passing through the retaining ring and the radially extending projection being received in the annular groove; and wherein the receiving element and the insertion element are rotated relative to one another and the radially extending projection is biased by the retaining ring to cause an end of the insertion element to bear on an inner surface in the axial bore of the receiving element.  
         [0017]     The present invention also relates to a coupling apparatus for joining a pipe and a fitting along a central axis, the coupling apparatus comprising a male portion formed on the pipe and a female portion formed on the other of the pipe and the fitting; the male portion comprising an outer surface supporting a first projection and a second projection extending substantially perpendicular from the outer surface; the female portion having an axial bore defined by an inner wall about the main axis, and an annular groove formed in the inner wall; a retaining split ring supported in the annular groove of the female portion, the retaining split ring comprising a first arm and a second arm being joined to one another at respective first ends, and the first and second arms having respective spaced apart second ends; a first notch provided in the first arm and a second notch provided in the second arm of the retaining split ring permit passage of the first and second projections of the male portion past the retaining split ring and into the annular groove in the female element whereupon relative rotation between the male and female portions rotates the first and second projections in the annular groove and forces the first and second projections against the first and second arms of the split ring to bias an end of the male portion against a surface of the inner wall of the female portion.  
         [0018]     The present invention utilizes a method of creating leak-tight joints between tubing (including pipe) and fittings that does not rely on the use of screw threads. The male element, a pipe or a tube having one or more perpendicular projections thereon, is inserted into and held fast to a female element fitting receivably accepting the male element, and via a bayonet-style interlocking arrangement the male and female elements are interlockingly secured. The ability to forego the use of pipe threads enables a thinner walled, or lighter gauge, pipe as well as lighter gauge fittings to be used in appropriate circumstances.  
         [0019]     The coupling is made by inserting the male element end of a pipe into the female element of a fitting, and applying a slight relative twist between both elements that causes the male and female elements to rotate in relation to one another until locking projections on the male element encounter detents in a special retaining ring of the female element. Leak-proof sealing is provided by an o-ring, or other elastic sealing device, placed in a groove within the female element. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     The invention will now be described, by way of example, with reference to the accompanying drawings in which:  
         [0021]      FIG. 1A  illustrates a planar front view of the female element of the coupling apparatus in a fitting;  
         [0022]      FIG. 1B  shows a cross-sectional side view of the female element of the coupling apparatus;  
         [0023]      FIG. 2A  is a side view of the male element of the coupling apparatus;  
         [0024]      FIG. 2B  illustrates a planar front view of the male element of the coupling apparatus;  
         [0025]      FIG. 3A  illustrates retaining ring  41 ;  
         [0026]      FIG. 3B  shows a bottom view of retaining ring  41 ;  
         [0027]      FIG. 3C  illustrates a top view of retaining ring  41 ;  
         [0028]      FIG. 3D  illustrates a side elevational view of retaining ring  41 ;  
         [0029]      FIG. 4A  shows retaining ring  41  in three-quarter perspective view in an unbiased position before installation;  
         [0030]      FIG. 4B  shows after the installation in a biased position within annular groove  25  of the female element  1  (shown in ghost lines);  
         [0031]      FIG. 5A  illustrates the pipe coupling assembly and fitting during initial axial insertion and assembly of the coupling; and  
         [0032]      FIG. 5B  shows the pipe coupling assembly and fitting after insertion and rotational interlocking of the relative male and female elements of the coupling. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0033]      FIGS. 1A, 1B  and  2 A and  2 B illustrate the female and male elements  7 ,  27  of the coupling apparatus  1 , respectively. As is generally known in the art, in order to join a length of pipe or tubing, such as a tee, coupling, elbow or a valve body, it is necessary to provide one end of a pipe or tube with a male element, while providing the opposing end of a fitting, with a respective female element.  
         [0034]     Thus, by way of example, in order to join or couple a pipe and a tee, elbow, coupling or valve body together, the male element  27  of a pipe or tube  3  is connected with the female element  7  of a fitting, such as a coupling, tee, elbow or valve body  13 .  
         [0035]     In most cases a single length of pipe or tubing supports a male element  27  disposed on either end, to mate with female elements of a fitting. As this aspect of pipe fitting and design is relatively conventional in the art, and further realizing that the respective male and female parts of the coupling to be described in detail below could be utilized on the same or separate articles to be joined, whether the article is a pipe, valve or fitting, no further discussion is provided with respect thereto.  
         [0036]     Turning to  FIG. 1A and 1B , the female element  7  of the coupling  1  will be described. By way of example, the female element  7  of the coupling  1  is formed as a bore  9  in a valve body  13  of hexagonal cross-section (arbitrarily chosen for this illustration, as the invention may be applied to any device or fitting). The female element consists of an inner lip  15  against which the square cut end  29  of the male element  27  will eventually abut. A face sealing element  16  may also be provided between the lip  15  and end  29  to seal this connection. The bore  9  is generally defined by an inner wall  17  which extends between the inner lip  15  and an opening  11  to the female element  7 . Along the inner wall  17  is formed a generally circumferential seal groove  21 . The seal groove  21  is circumferentially positioned along the wall  17  between the lip  15  and the opening  11 , and within the seal groove  21  is positioned a gasket or seal  23  for radially contacting an outer surface  4  of the pipe  3  supporting the male element  27  when inserted in the female element  7 . The seal  23  effectively provides a leak-proof radial seal between the outer surface  4  of the pipe  3 , and the inner wall  17  of the female element  7 .  
         [0037]     Also formed in the inner wall  17  is an annular groove  25 , spaced from the seal groove  21  and the lip  15  and adjacent and substantially defining the opening  11  of the female element  7 . The annular groove  25  is defined by a back side  28  and a front side  26 , the front side  26  being substantially adjacent the opening  11  to the bore  9 , and wherein the front side  26  essentially defines the opening  11  to the bore  9 . The front side  26  has an innermost diameter which is greater than an innermost diameter of the back side  28 , this allows both the insertion of the retaining ring  41 , as well as the passage of the male element  27 , through the groove  25  and facilitates the retention and support of the ring  41  and male element  27  therein, a further discussion of which is provided below.  
         [0038]     The opening  11  to the bore  9 , which is essentially defined by the innermost diameter of the front side  26  of the groove  25 , is configured to have a slightly smaller diameter than the bottom of the annular groove  25  and a slightly larger diameter than the innermost diameter of the back side  28 . This structure of the opening  11  assists in axially and radially securing the separate retaining ring  41  to be confined in the annular groove  25  in bore  9 . A further description of the retaining ring  41  is provided below.  
         [0039]      FIG. 2A and 2B  depict the pipe or tube  3  having the male element  27  of the coupling device  1 . The tube  3  has a squarely cut end  29 , which will abut with the lip  15  once the separate elements are coupled. The male element  27  features at least one and preferably two projections  31 ,  33 , more than two could be contemplated, adjacent, but spaced an axial distance d from the square cut end  29  of the tube  3 . Most preferably the two projections  31 ,  33  comprise a first and a second diametrically opposed and radially extending projections  31 ,  33  from the outer wall  4  of the tube  3 . These projections  31 ,  33 , extend a radial distance less than the innermost diameter of the front side  26  of the female element, so they will fit past the front side  26  and into the annular groove  25 .  
         [0040]     This structure ensures that the projections will fit radially inside the annular groove  25  when the male and female elements  27 ,  7  are axially engaged, and in a manner such that the projections  31 ,  33  will rotate within the annular groove  25  when the male and female parts  27 ,  7  are relatively radially rotated with respect to one another to fully engage the coupling  1 . The projections  31 ,  33  also contact the retaining ring  41  which provides a biasing force to secure the coupling  1 , a further discussion of which is provided below.  
         [0041]      FIG. 3A  illustrates retaining ring  41 .  FIGS. 3B-3D  show the retaining ring  41  in a front view with auxiliary top, bottom and right hand side views respectively.  FIGS. 4A and 4B  show retaining ring  41  in three-quarter perspective view before and after installation in the annular groove  25  (shown in ghost lines) of the female part  1 .  
         [0042]     With reference to  FIG. 3A , the front view of retaining ring  41 : the continuity of ring  41  is interrupted by a space  43  which in conjunction with a diametrically opposing jog  45  divides the retaining ring  41  into two independently functioning “limbs”, i.e., a first limb  47  and a second limb  49 , that define planes “a” and “b” in the top view of  FIG. 3C . The first and second limbs  47 ,  49  of the retaining ring  41  have respective first and second free ends  48 ,  50  defined by two formed tabs  51 ,  53  that project perpendicularly from the free ends of the limbs  47 ,  49  in opposing directions. In other words, each tab  51 ,  53  has a bend portion and an end portion where the tab is bent from the end of each limb  47 ,  49  to extend axially relative to the radial circumference of the retaining ring  41 .  
         [0043]     The first and second limbs  47 ,  49  of retaining ring  41  also each have a respective entry slot  55  and  57 , that allow respective first and second projections  31 ,  33  of the male element  27  to pass through retaining ring  41  when the male element  27  is inserted into the female element  7 . Also, a respective detent slot  59 ,  61  is formed in limbs  47 ,  49  to secure the male element  27  fast against further rotation after assembly and coupling of the male and female elements is complete. A first hole  63  and a second hole  65  are formed in limbs  47  and  49 , respectively, near the free ends  48 ,  50  of the limbs  47 ,  49 , substantially adjacent the space  43 . Holes  63 ,  65  aid with the installation, or removal, of retaining ring  41  in the annular groove  25  by permitting use of a pliers-type tool with matching projections (not shown) that fit into the holes  63 ,  65  to manipulate the retaining ring  41 .  
         [0044]     Observing  FIGS. 4A and 4B , this shows retaining ring  41  as if the free ends  48 ,  50  of the first and second limbs  47 ,  49  had been drawn together (by the aforementioned installation tool, or other device) in preparation for installation in the annular groove  25  of the female element  7 .  FIG. 4B  depicts retaining ring  41  sprung into groove  25 , the outer diameter of annular groove  25  being indicated with dashed lines.  
         [0045]     When installed in groove  25 , the first and second limbs  47 ,  49  of the retaining ring  41  are elastically distorted into essentially helical curves crossing the width of the annular groove  25  in opposing manners, in other words and by way of description, relative to the jog  45  between the first and second limbs  47 ,  49 , the first limb  47  axially spans the annular groove  25  from the back side  28  to the front side  26  and the second limb  49  axially spans the annular groove  25  from the front side  26  to the back side  28 . With reference to  FIG. 4B , it is to be noted that the first limb  47  has a first knee portion  44  at jog  45  wherein the first limb  47  bears against the back side  28  of groove  25  (away from the viewer) as does the first tab  51  at the free end of the first limb  47 . The second limb  49  has a second knee portion  46  at jog  45  which bears against the front side  26  of groove  25  (toward the viewer) and the second tab  53  at the free end of the second limb  49  also bears against the front side  26  of the groove  25 .  
         [0046]     After the seal  23  has been installed in seal groove  21  of the female element  7 , the retaining ring  41  is inserted in the annular groove  25  using the aforementioned special tool to seat the retaining ring  41  in the groove  25 . When retaining ring  41  is properly seated within the annular groove  25 , the female element  7  may be swaged, for instance at the indented area shown in  FIG. 1A  adjacent annular groove  25  in order to prevent retaining ring  41  from rotating when the male and female elements  27 ,  7  are engaged and twisted. (The swage may be made before installation if sufficient clearance is provided).  
         [0047]      FIGS. 5A and 5B  illustrate the engagement and securing of the coupling apparatus  1  during assembly.  FIG. 5A  shows the cross section female element  7  of the valve body  13  after the first pipe or tube  3  having the male element  27  has been axially inserted into the bore  9  of the female element  7 . As the male element  27  is being inserted into bore  9 , the first and second projections  31 ,  33  pass freely through the respective first and second entry slots  55 ,  57  in the retaining ring  41 . The forward progress of the pipe or tube  3  stops when the square cut end  29  comes into contact with the inner lip  15  at the end of bore  9  essentially completing a first step of the two-step process of coupling the tube and fitting. It is to be appreciated that a face sealing element  16 , for example an elastomer washer or O-ring, may be inserted or fitted between the square cut end  29  and the inner lip  15  in order to provide a substantially leak tight seal between these two elements.  
         [0048]     Further, in regards to the above described first step, the distance “d”, axially locating the first and second projections  31 ,  33  of the male element  27  with relation to the square cut end  29  is chosen so as to avoid initial interference between projections  3  and retaining ring  41  or contact between the projections  31 ,  33  with surface  28  of the annular groove  25  when the pipe or tube  3  is axially inserted into the female element  7  in this first step.  
         [0049]     The second step of the coupling assembly comprises the twisting i.e., rotation about the axis A, of the pipe or tube  3  relative to the valve body  5 , (a clockwise rotation as shown by the arrow in  FIG. 5B ). During the relative rotation, the first and second projections  31 ,  33  of the male element  27  are situated between the retaining ring  41  and the back side  28  of the annular groove  25 . As rotation continues the projections  31 ,  33  begin to interfere with the rear (right hand facing) surfaces of the limbs  47 ,  49  which forces pipe end  29  towards lip  15  of the female element  5 . The interference between projections  31 ,  33  and the limbs  47 ,  49  elastically deforms the respective first and second limbs  47 ,  49  of the retaining ring  41  and thus, as the rotation continues even further, the projections  31 ,  33  are pushed or biased inwards (to the right in  FIGS. 5A and 5B ) by the arms  47  and  49  so that the square cut end  29  of the male end  27  is forced strongly against the inner lip  15  at the end of bore  9 .  
         [0050]     By this rotation, the projections  31 ,  33  force the free ends  48 ,  50  of each of the first and second limbs,  47 ,  49 , as well as the second knee  46  of jog  45  relative to the second limb  49 , against the front side  26  of groove  25  of female element  7 . By way of further explanation, in addition to the second knee  46 , the bent portion of tab  51  is pushed against front side  26  while the end portion of tab  53  is also pushed against front side  26 . A load is imposed on front side  26  by these three contact points as the rotation of the projections  31 ,  33  continues to distort limbs  47 ,  49 . The distortion of the limbs  47 ,  49  in turn provides an axially inward biasing force (a force to the right in  FIG. 5A and 5B ) on the projections  31 ,  33  pushing the square cut end  29  of male element  27  strongly against the inner lip  15  at the end of the bore  9 .  
         [0051]     Complete assembly of the coupling  1  is accomplished when first and second projections  31 ,  33  of the male element  27  encounter the respective first and second detent notches  59  and  61  in retaining ring  41 . The action of the detent notches  59 ,  61  with the projections  31 ,  33  serves to prevent over-rotation during assembly and also hold the male and female elements  27 ,  7  fast, unless substantial torque is applied to release the projections  31 ,  33  from the respective detents  59 ,  61 .  
         [0052]     Of course, the device can also be designed to assemble in the counterclockwise direction and disassemble in the clockwise direction, if desired, and the relative difficulty of uncoupling the device can be varied through attention to the proportions of projections  31 ,  33  and detent slots  59 ,  61 .  
         [0053]     Since certain changes may be made in the above described invention without departing from the spirit and scope of the invention herein involved, it is intended that all of the subject matter of the above description or shown in the accompanying drawings shall be interpreted merely as examples illustrating the inventive concept herein and shall not be construed as limiting the invention.