Pipe Joint

This invention relates to a pipe joint which finds particular application as a repair coupling in non-metallic plastic pipe systems, but which may also be used to advantage in other applications, for example as a union between pipe sections of an originating pipe layout.

The need for a reliable repair coupling for fiberglass-reinforced thermosetting resin pipe has been long felt. One basic problem is that in a run of pipe it may not be possible for the sections adjacent a fracture easily to be moved back to allow insertion of a joint. The present invention provides, inter alia, a coupling which can telescope, thereby providing a facility whereby it may be used to form a joint between adjacent pipe sections without the need to provide substantial movement of the sections in order to install the coupling and make the joint.

Broadly stated, the invention provides in one of its aspects, means for providing a joint between adjacent sections of non-metallic pipe (particularly fiber-reinforced thermosetting resin pipe) comprising a pair of tubular sleeve members adapted to be bonded to the respective ends of the pipe sections, an external peripheral seal member carried by each sleeve member, a tubular body member into opposite ends of which the respective sleeve members are adapted to telescope, with the seal members sealingly engaging the inner surface of said body member, and externally threaded adaptor members adapted to fit on the respective pipe sections adjacent said sleeve members for threaded engagement with threads formed on the opposite ends of the body member so as to provide thrust restraint precluding withdrawal of the sleeve members from the body member.

In accordance with a further and independent aspect of the invention, in means providing a joint between adjacent sections of non-metallic pipe as aforesaid, at least one of the sleeve members may have a greater tendency to expand in response to increases in internal pipe pressure than the body member, whereby a seal between said members may be tightened in response to such increases in pressure.

Additional features and advantages of the invention will be apparent from the ensuing description and claims read in conjunction with the accompanying drawing.

The single drawing FIGURE is a longitudinal section through an exemplary form of pipe joint made in accordance with the invention.

The drawing illustrates, by way of example only, one form of pipe joint 10 in accordance with the invention, for connecting adjacent sections 12 and 14 of plastic pipe, which may comprise high-pressure fiber-reinforced thermosetting resin pipe.

Joint 10 includes a pair of plastic sleeve members 16 and 18, which may also be of fiber-reinforced thermosetting resin, and which are internally tapered and bounded (by any suitable bonding means known in the art) to correspondingly tapered end portions of the respective pipe sections. Sleeve members 16 and 18 have non-tapered outer surfaces, each formed adjacent one end, with a groove receiving a seal member comprising an O-ring seal 20, 22 of rubber or like sealing material. The location of the groove and seal is, in each case, preferably such as to align the seal substantially with the end (i.e., extremity) of the respective pipe section where the thickness of the pipe wall is at its smallest.

Joint 10 further includes an outer tubular body member 24, which may be of fiber-reinforced resin wound on a mandel or the like to provide a smooth inner surface, the diameter of which is such that sleeve members 16 and 18 may telescope into and out of opposite ends of the body member 24, with seals 20 and 22 sealingly engaging portions of its inner surface disposed inwardly from the ends. The opposite end portions of body member 24 have internal tapered threads 26, 28 for receiving complementary external tapered threads 30, 32 formed on tubular adaptor members 34, 36, which are slidingly received on the respective pipe sections 12 and 14 adjacent sleeve members 16 and 18. Adaptor members 34 and 36 which may also be made of fiber-reinforced plastic, provide thrust restraint for the joint when threaded into the body member, precluding withdrawal of the sleeve members 16 and 18 therefrom.

According to an important feature of the invention, sleeve members 16 and 18 may have a greater tendency (at least in the regions of seals 20, 22) than body member 24 to expand in response to increases in internal pipe pressure, so that as internal pipe pressure increases, seals 20 and 22 may be pressed into tighter engagement with the inner surface of the body member to enhance the sealing effect. For example, body member 24 may have a greater stiffness than the sleeve members, thereby having a greater resistance to expansion. Factors contributing towards the required expansion differential may for example include; a differential in wall thickness between the sleeve members and body member; the positioning of the seals at the ends of the pipe sections where the pipe wall thickness is at its smallest; and the use of different materials or different manufacturing techniques for the sleeve members and the body member. For example, the sleeve members and body member may have fiber-reinforcement of different orientation. Thus, the fibers in both the sleeve members and the body member may be wound predominantly at about 54.degree., with the body member also including some 90.degree. windings to increase its stiffness. Alternatively, the body member may include wound reinforcement, while the sleeve members may be centrifugally cast, in known manner, with chopped-fiber reinforcement. In all cases, differential expansion of the sleeve members and body member may be adapted to increase the sealing effect of the joint with internal pipe pressure increases, so as to make the joint suitable for withstanding high internal pipe pressures of up to, or exceeding 5,000 psi.

A joint as described and illustrated may be used to provide in situ repair of a fractured pipe, for example, by cutting away the fractured pipe portion, suitably tapering the adjacent pipe section ends (to take sleeve members 16 and 18), freely sliding the adaptor members 34, 36 onto the respective pipe sections, bonding on the sleeve members, telescoping body member 24, over one of the sleeve members along the one pipe section (it may be necessary to somewhat misalign the pipe sections to accommodate this), moving the body member back into place over the other sleeve member and, finally, threading the adaptor members into place.

The illustrated joint may also be supplied in pre-assembled form with lengths of pipe constituting pipe sections 12 and 14 already bounded-in as shown in the drawing. This arrangement provides a convenient telescoping joint which may, for example, be inserted into line pipe by means of additional couplings or the like at the outer ends of the respective pipe sections 12 and 14.

Additionally, since the joint does not require rotation of a pipe section for its installation, it may also be used to good effect as a union in the originating installation of a pipe layout. In this capacity the joint allows a pipe to be layed from opposite ends towards the center, with the subject joint forming in the final connection. The joint also allows tee-sections and the like to be inserted in existing line pipe, and its ability, in use, to accommodate relative movement of the pipe sections and body member makes it suitable for use as an expansion joint. The joint may be made in different sizes, and is considered particularly suitable for pipes in the 2 inch to 4 inch diameter range, though these dimensions are not deemed limiting.

It will be appreciated from the foregoing that the invention provides a pipe joint suitable for diverse applications particularly in the field of fiber-reinforced plastic pipe systems. The subject joint has relatively simple design, manufacture, and installation characteristics and may be used to good effect to withstand internal pipe pressure.

While only a preferred embodiment of the invention has been described herein in detail, the invention is not limited thereby and modifications may be made within the scope of the attached claims. For example, while body member 24 is illustrated as being rectilinear, it may also be curved, as in an elbow fitting or branched, as in a tee.