Abstract:
A novel gasket includes at least one gripping element embedded in an annular member for forming a seal between two tubulars. For tubulars having socket and spigot ends, the gripping element includes teeth for gripping an outer surface of the spigot end and a blunt tooth for contacting a front wall of the socket end. The blunt tooth rolls along the front wall during relative movement between the tubulars and can include a contacting face of a specialized geometry to adjust contact dynamics and/or roughened surfaces to increase the frictional contact between the blunt tooth and the front wall. The embedded element can also include at least four teeth arranged such that no more than two teeth normally grip the outer surface of the spigot end. One or more teeth can also include a transverse groove to enhance penetration into the outer surface of the spigot end.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to devices for locking joints for tubular members. More particularly, the present invention relates to gaskets for sealing and locking a socket end of one tubular to a spigot end of another tubular.  
         [0003]     2. Description of the Prior Art  
         [0004]     Pipes joined in telescoping relationship typically have a spigot end of one pipe inserted into the socket end of the engaging pipe. The socket end has an opening large enough to receive the spigot end of the enclosed pipe. A gasket is inserted in the socket end of the enclosing pipe and prevents leakage of fluid from the joint by forming a seal between the two pipes. In many applications, a fluid under pressure flows through the pipes. This fluid pressure can produce a separating force, known as joint separating end thrust, that can cause the pipes to separate at the joint.  
         [0005]     One method of locking the joint between two pipes involves configuring as sealing gasket as a restraining mechanism. For example, a resilient sealing gasket can be provided with a number of circumferentially spaced apart metal inserts. These metal inserts include teeth that are adapted to penetrate an outer surface of a pipe spigot end. Upon installation, the teeth bite into the pipe spigot end to prevent the pipe spigot end from sliding out of the socket end. As is known, the dimensions of the pipe spigot and socket ends, while conforming to industry standards, can vary during manufacture. The ability of the gasket to seal and lock the joint, however, can be adversely affected by such dimensional variations. Thus, there is a persistent need for sealing and restraining gaskets that can accommodate pipes having such dimensional variations. Moreover, there is a persistent need for gaskets that lock or retain a joint without unduly compromising the structure of the pipe (e.g., excessive penetration). The present invention addresses these and other needs of the prior art.  
       SUMMARY OF THE INVENTION  
       [0006]     In one aspect, the present invention provides a retention and sealing device for joints between tubulars. In one embodiment, the device is used to join a first tubular having a socket end with a second tubular having a spigot end. The exemplary device includes a resilient annular member having a sealing portion for forming a seal between the first tubular and the second tubular and at least one gripping element embedded in the resilient member. The gripping element, which is formed of a relatively hard material, includes a plurality of teeth projecting radially inward relative to the socket for gripping an outer surface of the spigot end and a blunt tooth extending axially forward relative to the socket for contacting a front wall of the socket. The blunt tooth adapted to contact and roll along the front wall during relative movement between the first and second tubulars. The terms radially inward(ly) and radially outward(ly) are used with reference to the axial centerline of the tubulars (i.e., meaning pointing toward or away from the tubular centerline, respectively). The terms axially forward refers to a direction toward the end of the tubular and term axially rearward refers to a direction toward the middle of the tubular.  
         [0007]     In certain embodiments, the blunt tooth can include features and elements for enhancing the rolling contact between the blunt tooth and the front wall of the socket end. For instance, the blunt tooth can have a contacting face of a specialized geometry (e.g. convex, concave, flat, etc.) to selectively adjust the location of initial contact, contact pressure, or other parameter (e.g., contact dynamics). Additionally, a roughened surface on the blunt tooth can be used to increase the frictional contact between the blunt tooth and the front wall. Suitable roughness can be obtained by using an irregular surface formed by grit blasting, chemical etches, spline protrusions, knurled protrusions, impregnated grit, composite constructions, bonded elements, and coated elements.  
         [0008]     In embodiments, the embedded element can also include arrangements to enhance the locking function provided by the gripping elements, facilitate assembly, improve product life and improve performance, etc. For instance, the embedded element can include least four teeth arranged such that no more than two teeth grip the outer surface of the spigot end when the spigot end is inserted into the socket end. For instance, at least three can lie along a common arc. Additionally, the embedded element can include a ridge extending radially outwardly from the embedded element to limit the movement of the blunt tooth along the front face. In certain embodiments, at least one tooth includes a transverse groove that enhances the tooth&#39;s ability to penetrate into the outer surface of the spigot.  
         [0009]     It should be understood that examples of the more important features of the invention have been summarized rather broadly in order that detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0010]     Other objects and advantages of the present invention will become apparent to those skilled in the art from the following description of the invention taken in conjunction with the accompanying drawing in which like numerals indicate like elements and in which:  
         [0011]      FIG. 1  illustrates a cross-sectional view of a jointed between an enclosing pipe and a mating pipe that uses a gasket made in accordance with one embodiment of the present invention;  
         [0012]      FIG. 2  illustrates an end view of a gasket made in accordance with one embodiment of the present invention;  
         [0013]      FIG. 3  illustrates a methodology for arranging inwardly projecting teeth according to one embodiment of the present invention;  
         [0014]      FIG. 4  illustrates the motion of a gasket insert made in accordance with one embodiment of the present invention during use; and  
         [0015]      FIG. 5  illustrates an isometric view of a gasket insert made in accordance with one embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]     The present invention relates to devices and methods providing rugged and cost-effective gasket arrangements for pipe joints. The present invention is susceptible to embodiments of different forms. There are shown in the drawings, and herein will be described in detail, specific embodiments of the present invention with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that illustrated and described herein. As used herein, the terms radially inward(ly) and radially outward(ly) are used with reference to the axial centerline of the tubulars (i.e., meaning pointing toward or away from the tubular centerline). The terms axially forward means in a direction toward the end of the tubular and term axially rearward means in a direction toward the middle of the tubular. Further, no particular geometry, material, or other technical limitation is implied by the term “gasket.” Rather, as used herein, this term merely refers to a device for providing at least a seal at a discontinuity in a flow path of a fluid.  
         [0017]     Referring now to  FIG. 1 , there is shown a joint formed by a first enclosing pipe  10  having a bell end  12  and second pipe  14  having a spigot end  16 . To make up a joint, the second pipe  14  is pushed into the bell end  12  of the enclosing pipe  10 . Conventionally, the inner surface of pipe bell end  12  has a retainer groove  18  bounded by a front wall  20 , a retainer wall  22 , a circumferential compression rib  24  that projects radially inwardly from a sealing wall  26 , and a throat portion  28  that terminates at the front wall  20 . Moreover, the inner surface can also include a shoulder  30  formed adjacent the retainer wall  22 .  
         [0018]     A gasket  50  made in accordance with one embodiment of the present invention locks together the pipes  10  and  14  and also provides a fluid seal at the joint. As will become apparent, the gasket  50  includes elements and features that co-act with the pipes  10  and  14  in a manner that preserves the integrity of the joint by accommodating relative motion between the pipes  10  and  14 .  
         [0019]     Referring now to  FIGS. 1 and 2 , in one embodiment the gasket  50  includes a resilient body  51  provided with a plurality of relatively hard segments  52 . The segments  52 , which can be formed of a suitable metal, are circumferentially arrayed in a spaced-apart fashion within the body of the gasket  50 . In one embodiment, the segments  52  are firmly vulcanized into radial grooves in gasket  50 . The segment  52  can also be embedded into the gasket by bonding, encapsulation, over-molding, mechanical cooperation, or by one of many other suitable methods. The number of segments  52  inserted into the gasket  50  can vary depending upon the anticipated fluid pressure at the joint and the size of the pipes involved. The segments  52  can be suitably machined, investment cast, extruded, forged, or by other suitable manufacturing methods. The segment  52  can include one or more features for enhancing the integrity of the joint between pipes  10  and  14 . While the features are described below as being provided on one segment  52 , it should be understood that each feature can be utilized separately as well as in conjunction with one another.  
         [0020]     In one embodiment, the segment  52  has three teeth  54 ,  56  and  58  pointed radially inwardly such that the teeth  54 ,  56  and  58  can bite into an outer surface of the spigot end  16  when the spigot end  16  is inserted into the pipe bell end  12 . The segment  52  can include a fourth tooth  60  also adapted to bite into the outer surface of the spigot end  16 . The teeth  54 - 60  can be equally spaced or asymmetrically spaced relative to one another. Merely for convenience, the three teeth  54 ,  56  and  58  will be referred to as rearwardly positioned and the fourth tooth  60  will be referred to as forwardly positioned. In one embodiment, the forward tooth  60  will be located “inside” a circle described by the common arc A of the three rearward teeth  54 - 58 . It is believed that positioning the forward tooth  60  “inside” the boundary of the common arc, or relatively “removed” away from the spigot  16 , can reduce the insertion force required to assemble the joint. It will be appreciated that when a plurality of teeth are arranged along a common arc, only two teeth can contact a flat surface at any given time (of course, excluding factors such as teeth penetration and deformation). In some embodiments, more than four teeth can be used. In such embodiments, each subsequent forwardly positioned tooth would also be located inside the common arc of the rearwardly positioned teeth such that each subsequent forward tooth would be more removed from the spigot than the preceding tooth.  
         [0021]     Referring now to  FIG. 3 , another method of defining the relative positioning of four (or more) teeth  54 - 60  is to consider orienting the segment  52  such that a line can be drawn between the two middle teeth  56 , 58 . A declination angle d of the forward tooth  60  is “greater” than a declination angle e of the rearward tooth  58 . For instance, the angle of declination e for the rearward tooth  58  can be defined as at least 3 degrees but less than 10 degrees while the forward angle of declination d would be greater than 10 degrees but no more than about 15 degrees. Subsequent teeth rearward and/or forward would be aligned in compliance with the angles of declination defined above.  
         [0022]     The segment  52  can also include a nose  64  projecting generally axially toward the wall  20 . The nose  64  has a blunt end  66  configured to engage the wall  20 . In particular, the blunt end  66  is constructed as to primarily roll on the wall  20  as opposed to biting into or sliding on the wall  20 . Rolling friction between the blunt end  66  and the wall  20  can be enhanced by roughening the surface of the blunt end  66 , such as by providing knurls  68  on the blunt end  66 . Other methods of roughening include grit blasting, chemical etching, spline protrusions, grit impregnation, composite constructions, bonded or coated elements, etc.  
         [0023]     Referring now to  FIGS. 1 and 4 , during use, the hydraulic pressure of the fluid flowing in the pipes  10  and  14  can create a thrust force that can cause the joints to separate joint separating end thrust). When present, the joint separating end thrust will cause the blunt nose  66  to contact the front wall  20 . Once joint separating end thrust initiates contact between the blunt face and the front wall  20 , the frictional interference forces are relatively static, as long as the joint separating end thrust is maintained in a static state. Frictional forces transition from static to dynamic rotational rolling forces as the segment  52  rotates (generally shown with arrow B) in response to increasing joint separating end thrust. Typically, the nose  66  of the segment  52  will have a defined contact surface area C 1  with the front wall  20 . Continued increasing joint separating end thrust will result in the rotation of the segment  52  as shown with arrow B. Each increment of rotation on the part of the segment  52  will result in a change in the contact surfaces between the front wall  20  and blunt nose  66 . An incremental rotation is shown with segment  52 A in phantom lines with an associated new contact point C 2 . Contact point C 2  now acts as a new fulcrum or pivot point for rotation as shown by arrow B′. Thus, as the segment  52  rotates, the contact surface areas of the blunt nose  66  and the front wall  20  continually changes. Each additional increment of rotation will establish yet a new set of contact surfaces and pivot points between the blunt nose  66  and the front wall  20 .  
         [0024]     The segment  52  can also include a ridge  70  that operates as a mechanical stop to prevent excessive movement of the segment  52  during cases of extreme variations in the dimensions of the pipes  10  and  14 . The blunt ridge  70  projects radially further outward than the nose  64  and ensures that the contact point between the blunt nose  60  and the front wall  20  does not migrate in such a way as to contact the most radially outward surface  72  of the socket or pipe bell end  12 . The blunt ridge  70  includes resilient encapsulation  74  that provides a cushion between the blunt ridge  70  and the most radially outward surface  72  of the socket or pipe bell end  12 —should they come in contact with each other. The encapsulation  74  may be confined to intermittent areas over segment  52 —or be continuous around gasket OD.  
         [0025]     In some embodiments, one or more recesses can be provided in the segment  52  to accommodate material than deforms upon the application of the forces and pressures inherent during use. For example, a recess or pocket  76  is provided between the blunt ridge  70  and the blunt nose  64 . The recessed pocket  76  can be continuous or intermittent at the blunt ridge  70 . In one embodiment, the volume of the recess  76  is approximately equal to the volume of the blunt ridge  70 . This volumetric relationship between ridge  70  and the recess  76  gives the encapsulation  72  covering the blunt ridge  70  a place to flow into during contact—a form of void volume fill. It should be understood that fractional relationship between the volumes of the ridge  70  and the recess  76  can also be suitable in many applications. In any case, this recessed pocket  76  provides an element of flexibility and/or adjustment due to minor pipe shifting, surging, hammer, et cetera.  
         [0026]     Also, the segment  52  further includes a scallop  78  formed on an outer rearward surface  79 . Conventionally the gasket body  51  can include a sealing or bulb portion  53  that provides a fluid barrier between the pipe  10  and second pipe  14 . For instance, the bulb portion  53  forms a seal between the inner wall  26  of the pipe  10  and the outer surface of the spigot end  16 . The scallop  78 , as will be discussed in greater detail below, can reduce the compressive forces on the bulb portion  53  and thereby reduce the risk that the bulb portion  53  bursts or otherwise fails during use.  
         [0027]     The gasket  50  can also include a groove  77  formed on an outer circumferential diameter adjacent the ridge  70 . The groove  77  is adapted to receive the shoulder  30  of the pipe bell end  12 . The groove  68  is sized such that the gasket  50  can pivot at least partially around the shoulder  30  when the spigot end  16  is moving into or out of pipe bell end  12 .  
         [0028]     Referring now to  FIGS. 1 and 5 , there is isometrically shown another segment  80  made in accordance with one embodiment with the present invention. The segment  80  includes a plurality of teeth  82 ,  84 ,  86  and  88  and a blunt nose  90 . As described earlier, the teeth  82 - 88  extend radially inward toward the spigot  16 . The teeth  82 - 88  include at least one groove  92  passing through each tooth  82 - 88 . The groove  92  is transversely oriented relative to the radially inward extending teeth  82 - 88 . By splitting the teeth  82 - 88 , the groove  92  provides a focused contact point between the teeth  82 - 88  and the spigot  16 . The focused contact points allow teeth to penetrate faster and deeper into the spigot or other mating surface for any set of conditions as compared convention teeth that have a more distributed loading of pressure. The groove can be constructed from many geometric forms including half-round, dovetailed, trapezoid, square, rectangular, etc. The groove  92  also provides a haven for swaged and displaced material as teeth  82 - 88  bite into the spigot  16 , which allows the teeth  82 - 88  to allow enhanced penetration. Likewise, the blunt face  90  also includes at least one groove  96  that is transversely oriented relative to the axially extending blunt face  90 . The groove  94  splits the blunt face  90  and provides a focused contact point between the blunt face  90  and the front wall  20 . The focused contact point provides increased frictional interference forces by focusing contact loads over a smaller surface area. The groove  94  can be constructed from many geometric forms including half-round, dovetailed, trapezoid, square, rectangular, etc. This will focus the biting penetration and provide deeper and faster penetration.  
         [0029]     In still other embodiments, the nose can be formed as an acutely pointed tooth having at least one face or the other or both faces defining the tooth to be non-linear surfaces instead of a flat surface. The purpose of at least one non-linear surface defining the faces of the tooth results in a deeper and/or faster bite penetration of the tooth into the front wall  20  for any given set of parameters. Moreover, it should also be appreciated that the groove can be applied to a tooth designed to bite into the front wall  20 . Non-linear surfaces include various convex and/or concave combinations. Non-linear surfaces include ground surfaces, hollow grounding, and various other methods of achieving arcuate convex and/or concave surfaces defining the tooth. Adjusting the geometry of the blunt nose  66  can adjust the contact points between the blunt face, adjust contact pressure, and other behavior characteristics. It should be appreciated, therefore, that the contact dynamics between the blunt nose  66  and the front wall  20  can be adjusted (e.g., optimized or otherwise controlled) by altering the geometry of the blunt nose  66 .  
         [0030]     Referring now to  FIG. 1 , during installation, the gasket  50  is fitted into the pipe end  12  of the enclosing pipe  10 . The second pipe  14  is then inserted into the pipe end  12 . As the spigot end  16  of the second pipe  14  enters the gasket  50 , one or more of the teeth  54 ,  56  and  58  contact the outer surface of the spigot end  16 . The forwardly positioned tooth  69  (if present) is recessed and, therefore, does not impede the movement of the spigot end  16  into the pipe  10 . As the spigot end  16  engages the teeth  54 ,  56  and  58 , the segment  52  rotates about the shoulder  30  such that the bulb portion  53  is squeezed between the inner surface  26  and the segment surface  79 . Advantageously, the scallop  78  minimizes the stresses imposed on the gasket  50  during insertion. Undue stress on the gasket during insertion can result in unnecessarily elevated insertion force—and may dislodge the gasket. The recessed scallop reduces insertion force by reducing stress introduced to the gasket—thus reducing incidence of dislodgment and/or displacement of gasket during assembly. Further, the rotation of the segment  52  can cause one or more of the rearward teeth to disengage from the spigot end  16  and the forward tooth  60  to engage the spigot end  16 . Thus, it should be appreciated that the segment  52  can be constructed such that a selected or predetermined number of teeth can be made to engage the spigot end  16  regardless of the rotational orientation of the segment  52 . Once the second pipe is fully inserted into the enclosing pipe  10 , installation or joint make up is substantially complete.  
         [0031]     As noted earlier, during use or operation, the hydraulic pressure of the fluid flowing through the joint can produce joint separating end thrust that can cause the spigot end  16  to slide out of the pipe  10 . This sliding action causes one or more of the teeth  54 - 60  to bite or penetrate into the spigot end  16 . As noted earlier, the particular teeth that have engaged the spigot end  16  can depend on the rotational orientation of the segment  52 . Thus, the sliding motion of the spigot end  16  draws the gasket  52  axially outward until the blunt nose  66  engages the front wall  20 . The blunt  66 , upon engaging the front wall  20 , allows the segment  52  to rotate in a controlled manner and also modulates the radial movement of the segment  52 . Also, the blunt ridge  70  engages the surface  72  during excessive radial movement of the segment  52  and thereby prevents the blunt nose  66  from riding up to the surface  72 .  
         [0032]     While the invention has been described in the environment of a pipe joint in which the bell end of the enclosing pipe has a compression rib  24 , the gasket will also perform its sealing function with a bell configuration such as that shown in U.S. Pat. No. 2,953,398 which does not have a compression rib. Further, it should be understood that the teachings of the present invention can be also applied to mechanical joints other than those utilizing socket-spigot ends such as for example flanged joints. That is, the present invention may be utilized in any mechanical arrangement wherein the relative movement of two tubulars (or other fluid conduits) can compromise a fluid seal there between. Further, whereas the present invention has been described with respect to specific embodiments thereof, it should be understood that the invention is not limited thereto as many modifications thereof may be made. It is, therefore, contemplated to cover by the present application any and all such modifications as fall within the true spirit and scope of the appended claims.