GB2264543A - Compression fitting for soft pipes with split frustoconical gripper ring - Google Patents

Abstract

A pipe fitting has a body member 10, said body member 10 defining a socket portion 11 into which the end of a pipe (14, Fig 3) may be inserted, the socket portion 11 having a thread formation 12 for engagement of a correspondingly threaded thrust nut 20, a sealing ring 30 and a gripper ring 35 being disposed coaxially of the socket portion 11 between the end 15 thereof and a frustoconical abutment surface 22 of the thrust nut 20, the sealing ring 30 being located between the end 15 of the socket portion 11 and the gripper ring 35, the gripper ring 35 being of frustoconical configuration and split, the ends of the split gripper ring 35 overlapping, the outer periphery 37 of the gripper ring 35 being arranged to engage the abutment surface 22 of the thrust nut 20, the gripper ring 35 and abutment surface 22 of the thrust nut 20 being of opposite inclination. <IMAGE>

Description

PIPE FITTINGS PIPE FITTINGS The present invention relates to pipe fittings and in particular to compression fittings for pipes made of relatively soft materials.

In conventional compression fittings for pipes, a ring is located on the pipe and is compressed into tigllt engagement with the pipe between opposed frustocoriical faces on screw threaded fastening means. With pipes made of soft materials such as lead or plastics, compression of the ring will merely deform the pipe and the joint will be of low tensile strength. The strength of the joint may be improved by using a strengthening liner which is inserted into the end of the pipe to which the fitting is attached. However the soft material is liable to extrude between the compressed ring and liner when subject to tensile loads.

In accordance with GB 2186934 A, it has been proposed to provide an end fitting including a gripper ring which, upon tightening of the screw threaded fastening means will cut into the pipe. This will provide a joint with improved tensile strength. In order that the pipe is not unduly weakened where it is cut into by the gripper ring, penetration of the gripper ring must be controlled relatively accurately. As a consequence, pipe fittings of this type must be sized fairly accurately with respect to the diameter of pipe with which they are to be used.

Typically, fittings of this type are limited to use on pipes varying in diameter by up to 1 mm. As a result, different fittings have to be provided for imperial and metric ranges of pipes.

The present invention provides a pipe fitting for pipes made of soft materials which can accommodate greater variations in the diameters of the pipes with which tile fittings may be used.

According to one aspect of the present invention a pipe fitting comprises a body member, said body member defining a socket portion into which the end of a pipe may be inserted, the socket portion having a thread formation for engagement of a correspondingly threaded thrust nut, a sealing ring and a gripper ring being disposed coaxially of the socket portion between the end thereof and a frustoconical abutment surface of the thrust nut, the sealing ring being located between the end of the socket portion and the gripper ring, the gripper ring being of frustoconical configuration and split, the ends of the split gripper ring overlapping, the outer periphery of the gripper ring being arranged to engage the abutment surface of the thrust nut, the gripper ring and abutment surface of the thrust nut being of opposite inclination.

With the pipe fitting of the present invention, when a tube is located in the bore of the socket portion and the thrust nut is tightened up, the outer periphery of the gripper ring will first ride down the frustoconical abutment surface of the thrust nut, until the inner periphery of the gripper ring engages the pipe. Further tightening of the thrust nut will then tend to distort the gripper ring flattening it in a plane normal to tlie axis of the pipe, causing the inner periphery of the gripper ring to cut into the wall of the pipe thereby producing a joint of high tensile strength. The sealing ring is compressed between the end of the socket portion and gripper ring to produce a fluid tight seal.By vlsillg a split gripper ring and frustoconical abutment surface on the thrust nut, the pipe fittings disclosed above can be used for pipes varying in diameter by up to 5 mm.

In accordance with the preferred embodiment of the invention, the frustoconical abutment surface of the thrust nut is inclined at from 20 to 40 degrees to the axis of the joint while the faces of the frustoconical gripper ring are inclined at from 30 to 60 degrees to the axis of the joint.

The sealing ring is preferably made of elastomeric material of tubular configuration and has a sleeve around its outer periphery to prevent binding of the elastomeric material with the threads of the thrust nut and also to constrain the seal to expand inwardly on to the pipe when the seal is compressed axially An embodiment of the invention is now described by way of example only with reference to the accompanying drawings in which: Figure 1 illustrates a cross section, a pipe fitting in accordance with the present invention; Figure 2 is a large view of the gripper ring of the pipe fitting illustrated in Figure 1, and Figure 3 illustrates in cross section an assembled joint using the pipe fitting illustrated in Figure 1.

The pipe fitting illustrated in the accompanying drawings, comprises of body member 10 which defines a socket portion 11 with external screw thread 12. The socket portion 11 has a bore 13 into which a pipe 14 may be inserted. A frustoconical leading portion 15 is provided to bore 13.

A thrust nut 20 has an internal screw thread 21 for engagement of thread 12 of the body member 10. A frustoconical abutment surface 22 is provided at the end of thrust nut 20 remote from thread 2S, the frustoconical abutment surface 22 being inclined at an angle of 25 degrees to the axis of the thrust nut 20.

A tubular rubber sealing ring 30 has a frustoconical end portion 31 corresponding to the frustoconical leading portion 15 of bore 13. A support sleeve 32 formed from rigid plastics material engages around the outer periphery of the sealing ring 30.

A split frustoconical gripper ring 35 is located between the sealing ring 30 and the thrust nut 20, the frustoconical gripper ring 35 being oppositely inclined to the abutment surface 22, so that its inner periphery 36 abuts the sealing ring 30 while its outer periphery 37 engages the abutment surface 22. As illustrated in Figure 2, the ends of the gripper ring 35 overlap to provide a continuous ring which may be expanded or contracted to accommodate varying diameters of tube.

The pipe fitting is pre-assembled with the thrust nut 20 hand tightened onto the socket formation 11, so that the sealing ring 30 with support sleeve 32 about its outer periphery and gripper ring 35 are located axially and radially therebetween. A pipe 14 may then be inserted through the coupling parts into the bore 13 of the body portion 10, the gripper ring 35 and sealing ring 30 expanding, if necessary, to accommodate oversize pipes.

The thrust nut 20 is then tightened up so that the outer periphery 37 of gripper ring 35 will first ride down the frustoconical abutment surface 22 of thrust nut 20, causing the gripper ring 35 to reduce in diameter until its inner periphery 36 engages the pipe 14. Further tightening of the thrust nut 20 will then cause the outer periphery 37 of gripper ring 35 to move axially towards body member 10, causing the gripper ring 35 to flatten in a plane normal to the axis of the pipe 14. Flattening of the gripper ring 35 in this manner, will cause its inner periphery 36 to cut into the wall of the pipe 14 thereby providing a joint of high tensile strength.Flattening of the gripper ring 35 will also compress the sealing ring 30, causing frustoconical portion 31 to ride down the frustoconical leading portion 15 of bore 13 and also causing the sealing ring 30 to expand inwardly, outward expansion being prevented by support sleeve 32, thereby providing a seal between the body member 10 and the pipe 14.

Pipe fittings of the type disclosed above may be used to couple two or more lengths of pipe together or to connect pipes to components such as valves, sensors, etc. When used to couple two or more pipes made of soft material, the body member will define an appropriate number of socket portions and each fitting may be as described above. To connect a pipe made from soft material to one made of hard material, for example a lead or plastic pipe to a copper pipe, the coupling may comprise of fitting as described above for the lead or plastic pipe and a conventional compression fitting for the copper pipe.

The pipe fitting described above may be used with a pipe liner, to strengthen the end of the pipe to which the fitting is attached, this is particularly applicable when the coupling is used with thin wall pipes. Although in the pipe fitting described above with reference to the accompanying drawings, the socket portion is threaded externally and the thrust nut is threaded internally, the socket portion may alternatively be provided with an internal thread and the thrust nut with a corresponding external thread.

While the pipe fitting disclosed above is particularly suitable for pipes made of soft materials such as lead or plastics, it may be used with harder materials where, for example, a joint of high tensile strength is required for high pressure application In order to ensure that the gripper ring will cut into the pipe when the fitting is tightened, the gripper ring or at least the inner periphery thereof should be made of material harder than that of the pipe.

When undersized pipes are being connected to the fitting, a support liner may be provided between the pipe and bore of the socket portion of the fitting, in order to produce a more rigid joint.

Claims (9)

1. A pipe fitting comprising a body member, said body member defining a socket portion into which the end of a pipe may be inserted, the socket portion having a thread formation for engagement of a correspondingly threaded thrust nut, a sealing ring and a gripper ring being disposed coaxially of the socket portion between the end thereof and a frustoconical abutment surface of the thrust nut, the sealing ring being located between the end of the socket portion and the gripper ring, the gripper ring being of frustoconical configuration and split, the ends of the split gripper ring overlapping, the outer periphery of the gripper ring being arranged to engage the abutment surface of the thrust nut, the gripper ring and abutment surface of the thrust nut being of opposite inclination.

2. A pipe fitting according to Claim 1 in which the frustoconical abutment surface of the nut is inclined at an angle of from 200 to 400 to its axis.

3. A pipe fitting according to Clainm 1 or 2 in which the faces of the frustoconical gripper ring are inclined at an angle of 300 to 600 to its axis.

4. A pipe fitting according to any one of the preceding claims in which the sealing ring is made of elastomeric material and is of tubular configuration.

5. A pipe fitting according to Claim 4 in which the sealing ring has a frustoconical end portion which is adapted to engage in a corresponding frustoconical recess in the end of the socket portion of the body member.

6. A pipe fitting according to any one of the preceding claims in which a support ring engages the external diameter of the sealing ring.

7. A pipe fitting according to any one of the preceding claims in which a pipe liner is located in the end of the pipe to which the fitting is attached.

8. A pipe fitting according to any one of the preceding claims in which a support liner is provided in the bore of the socket portion to close a gap between the bore of the socket portion of the fitting and the pipe.

9. A pipe fitting substantially as described herein with reference to and as shown in Figures 1 to 3 of the accompanying drawings.