Abstract:
A pipe coupling has an enlarged end for receiving a pipe end and a flange apertured for supporting coupling bolts; a tightening ring is placed around the pipe end and includes a slanted radially inner surface cooperating with a gripping ring; a slide ring is placed about the pipe end to be engaged by an end of the gripper ring; the enlarged end has a seal cavity with an inner slanted surface for engaging a seal ring; the gripper ring has two pairs of teeth extending radially inwardly to different extents with the axially inner pair being of greater length than the outer pair.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to pipe couplings where the pipe is made from plastic such as polyolefin, polyvinyl chloride or ductile iron or similar materials that are at least slightly deformable under localized pressure. In particular, this invention relates to an improved gripper ring for use in couplings where a sealing ring is compressed by a portion of a ring member when the coupling is installed. Specifically, the gripper ring is provided with a plurality of annular teeth which extend radially inwardly to different distances relative to the axis of the coupling and pipe end being coupled.  
         BACKGROUND OF THE INVENTION  
         [0002]    In many fluid handling systems, couplings for pipe ends are employed in constructing the system and the prior art has proposed a variety of different coupling structures to enable users to install the systems with secure couplings or joints between pipe ends. In some of these designs, a portion of the flow path is obstructed by the coupling mechanism and this is undesirable as the obstruction causes premature wear on the pipe particularly where the fluid being carried includes solid materials. In other arrangements, the labor required to establish the coupling is excessive due to the number of parts that must be used to assure a leak proof connection. In still other systems, where the couplings are located, for example, under vehicle thoroughfares, the stability of the coupling is adversely affected by heavy traffic leading eventually to leakage or failure of the coupling.  
           [0003]    In view of these difficulties, there is a need for a secure, leak free pipe coupling that can be easily and quickly installed, has few parts and provides a clear flow path through the coupling.  
         SUMMARY OF THE INVENTION  
         [0004]    The coupling of the present invention, in one form, includes a sleeve having enlarged ends for receiving a pipe end. The sleeve includes two or more apertured flanges at each end for receiving a tightening bolt. The interior of the sleeve may include a seat for the end of the pipe and a wall portion that is slanted relative to the axis of the sleeve to serve as a seat for a seal member. The sealing elements of the coupling include a slide ring, a gripper ring and a locking ring. The locking ring includes apertures for receiving the tightening bolts and has a radially inner surface that is slanted axially and engages an outer slanted surface of the gripper ring. The slide ring and gripper ring each have mutually abutting ends with the opposite end of the slide ring engaging a flexible seal ring or annular gasket to compress the gasket into sealing engagement with adjacent surfaces of the coupling. The gripper ring has a plurality of radially inwardly extending annular edges or teeth members, the radial extent of which differ from adjacent edges or teeth members to improve the gripping action of the gripper ring when the tightening bolts are tightened to urge the gripper ring axially toward the slide ring and seal member.  
           [0005]    With this structure, the action of the teeth will penetrate the surface of the pipe being coupled when moved by the tightening bolts to effectively lock the position of the slide ring against the seal member.  
           [0006]    The foregoing and other advantages of the invention will become apparent as consideration is given to the following description and the accompanying drawings, in which: 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is section view of one end of a pipe coupling according to the present invention;  
         [0008]    [0008]FIG. 2 is a detailed view in section of a portion of the gripper ring;  
         [0009]    [0009]FIG. 3 is a detailed view in section of the gripper ring engaging the surface of a pipe end; and  
         [0010]    [0010]FIG. 4 is a detailed view in section similar to FIG. 3 but showing a variation of the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0011]    Referring to the drawings, wherein like numerals designate corresponding parts throughout the several views, in FIG. 1 there is shown a sectional view of a coupling  10  for two pipe ends one of which is shown at  12  inserted into a coupling sleeve  14 . It will be understood that this view is symmetrical about the center of sleeve  14  and only the left end elements of the coupling  10  are illustrated, the opposite end being identical.  
         [0012]    The coupling sleeve  14  is provided with an enlarged end  16  which includes a slanted interior wall  18  and the pipe end seat  20 . Externally of the end  16  are provided two or more flanges  32  which are apertured to receive tightening bolts as described below. The coupling  10  further includes a tightening ring  22  which surrounds a gripper ring  26 , one end of which abuts a slide ring  36  which, in turn, abuts for compression purposes a resilient seal ring  38 , one side of which abuts the slanting wall  18  of the sleeve end  16 .  
         [0013]    The tightening ring  22  has two or more bores  28  for receiving tightening bolts  30  so that the bolts will each extend through a bore  28  and through the aperture in the flange  32 . Preferably, the bolts have an anchoring portion or catch  34  to facilitate engagement between the tightening ring  22  and the flanges  32  of the sleeve  14 . With this arrangement, tightening of the nuts  52  on the threaded ends of the bolts  30  secure the elements together and assure a fluid tight seal as described below.  
         [0014]    The radially interior surface  24  of the tightening ring  22  is slanted to cooperate with a complementary surface  48  on the gripper ring  26 . The end of the gripper ring  26  opposite the slanted surface  48  is preferably flat or planar, as shown in FIGS.  2 - 4 , to provide a stable engagement with the planar surface  49  of the slide ring  36 . To improve the compression of the seal ring  38 , the opposite side  51  of the slide ring  38  is slanted substantially to the same degree as the opposite wall  18  of the sleeve  14 . The surface  51  and the wall  18  together define a cavity for the seal ring  38  with the wall  18  being movable toward the slide ring  36  when the nuts  52  are tightened on the end of bolts  30 . Thus, once the resilient seal ring  38  is compressed between surface  51  and  18 , the radial expansion of the seal ring  38  due to the orientation of the surfaces  51  and  18  will assure leak proof operation of the seal ring  38 .  
         [0015]    According to the present invention, the chance that the compressive force of the coupling on the seal ring  38  will be decreased is minimized by the construction of the gripper ring  26 . Such a diminution of the force compressing the seal ring  38  may be due to vibrations imposed on the coupling where the pipe is buried under a roadway which is subjected to heavy traffic. Over time, such continued vibrations can result in wear on the connecting flanges  32  and the catch  34  or even in loosening of the threads of the nuts  52 . Of course, other environmental conditions may also result in a tendency for the compressive force imposed by the tightened bolts  30  to decrease such as extreme temperature changes either externally or due to the temperature changes of the material being carried through the pipe  12 . To counteract these effects, the present invention provides a unique set of annular gripping edges or teeth  40 ,  42 ,  44  and  46  on the radially inner surface  41  of the gripper ring  26 . A shown in FIG. 2, each tooth is provided with a radially extending surface  44   a  and a slanted backup surface  44   b  which extends at an angle from the inner edge  47 . Of primary importance is the different heights to which the teeth extend with the teeth adjacent the axially outer end of the gripper ring  26  as at  40  and  42  extending radially inwardly from the surface  41  of the body of the ring  26 . As shown in FIGS.  2 - 4 , the inner teeth  44  and  46  differ in height slightly from the axially outer teeth  40  and  42 . Preferably, this difference in the radial extents will be on the order of 0.0200 in. However, this will have a major impact on the gripping force exerted by the ring  26  once it engages the surface of the pipe  12  being coupled as will be evident from FIGS. 3 and 4 to which reference is now made below.  
         [0016]    With the coupling established as shown in FIG. 1, an operator will commence tightening and securing the coupling by tightening the nuts  52  on the bolts  30 . Initially, this will result in sliding movement of the gripper ring  26  and the slide ring  36  over the surface of the pipe  12  to result in a compression of the O-ring  38 . Continued tightening of the nuts  52  will, however, cause the force exerted by the surface  24  of the tightening ring  22  to be transmitted to the surface  48  of the gripper ring  26  and where the pipe is polyethylene or polyvinyl chloride material, the central teeth  44  and  46  will commence penetration of the surface of the pipe  58  as shown in FIG. 3. Continued tightening of the nuts  52  will cause the outer teeth sets  40  and  42  to also penetrate the surface of the pipe  58 . Where the gripper ring  26  is made of the coated steel or ductile iron, and the pipe  58  is of a plastic material as described above, penetration on the order of about 0.04 inches for the central teeth  44  and  46  will be effected while the penetration of about 0.02 inches for the outer teeth  40  and  42  of the gripper ring will be effected.  
         [0017]    Where the pipe  60  is a metal such as ductile iron, the penetration of the teeth  44  and  46  of the gripper ring will be substantially shallower then is the case with a plastic pipe  58 . Typically, a penetration for the larger teeth  44  and  46  will be on the order of about 0.01 to 0.02 in. In most cases, the shorter teeth  40  and  42  will not penetrate the surface of the iron pipe  60 . This should be acceptable in almost all applications as the ductile iron pipe will not exhibit the effects of the traffic induced vibrations to the same extent as the plastic pipe  58 .  
         [0018]    There are several advantages to use of a gripper ring  26  having at least two sets of teeth of different radial heights. Firstly, one type of the gripper ring need be manufactured to achieve secure gripping in either a plastic or a ductile iron pipe. Secondly, once the teeth of the gripper ring  26  are embedded in the surface of the pipe, substantially uniform compression of the resilient O-ring seal  38  will be assured over a wide range of conditions.  
         [0019]    Having described the invention, it will be apparent to those skilled in this art that various modifications can be made to the invention with departing from the spirit and scope of the invention.