GB2129892A

GB2129892A - Pipe compression fitting

Info

Publication number: GB2129892A
Application number: GB08322016A
Authority: GB
Inventors: Roland Skarud
Original assignee: Wirsbo Bruks AB
Current assignee: Uponor Wirsbo AB
Priority date: 1982-10-28
Filing date: 1983-08-16
Publication date: 1984-05-23
Also published as: GB8322016D0

Abstract

The pipe fitting olive 9 is provided with a longitudinal split 12 which is of such a width that it will completely close in use. Also disclosed is an olive 9a formed of a cross-linked plastics material which is resiliently or permanently deformable in use and which is harder than the plastics pipe and preferably not quite as hard as the fitting 4 with which it is to be applied. <IMAGE>

Description

SPECIFICATION Pipe fitting This invention relates to pipe fittings and has particular reference to olives for pipe fittings.

Pipe fittings, such as those for use with copper pipe are well known to include, in addition to a nipple and co-operating nut, a ring having outer chamferred circumferential edges which fit the tube to be conjoined and is deformed on pressure generated between the nut and the nipple thereby to seal the nipple to the pipe. Olives of this type are not generally useful for use with pipes of softer materials such as linear and cross-linked polyethylene because it is, in practice, difficult to insert the olive onto the exterior surface of the plastics pipe.

Pipe fittings for use with linear or cross-linked polyethylene tubes are also known which are of the above general type but which additionally include a pipe liner formed as part of the nipple which is inserted within the end of the plastics pipe. Such arrangements have heretofore incorporated an olive with a broad split often angled to the axis of the nipple, the broad split being radially contracted by the axial pressure exerted by the interaction of the nut and nipple.

Pipe fittings of this latter type have been perfectly satisfactory for use with cross-linked polyethylenic tubes. Our co-pending European Application No. 80304008.8 describes and claims a tube or pipe which is basically of a laminated construction. In a specific example described in the above referred to European Application, there is provided, an inner pipe formed of cross-linked polyethylene, an intermediate layer of polyvinyl alcohol designed to reduce or substantially eliminate gaseous diffusion into the tube and an outer layer of protected material extruded thereover.The use of pipe fittings in which the nipple has a large angled split in conjunction with laminated pipes of the type described above, provide a considerable problem since unlike the unitary cross-linked polyethylenic pipes of substantial uniform (uniform crosssection) the laminated layers are such that on application to such a pipe, a degree of creep occurs whereby the angled ends of the olive, on clamping to secure the fitting, serve to clamp a small amount of the outer coating of the pipe between the ends of the olive, thereby allowing a relaxation of the clamping pressure of the pipe to the nipple in the area of the split in the olive. This allows, with repeated cycling, the possibility of a leakage path which causes corresponding failure of the union.

According to one aspect of the present invention, therefore, there is provided a pipe fitting olive comprising a split annulus chamferred at its outer peripheral edges for engagement with cooperating surfaces in a pipe fitting; characterised in that the circumferential width of the split is such as to close completely in use, and in that the clamping of the olive onto the pipe is effected by deformation of the olive, particularly at its peripheral edges. In a preferred embodiment the olive is formed of a copper containing anealable material which readily deforms in response to pressure. The split is preferably parallel to the axis of the annulus and generally has a width of less than 1 mm.

In a second aspect of the invention there is provided a pipe fitting olive formed of a permanently, or resiliently deformable plastics material, the material being selected such that it is harder than the plastics material of the pipe to which it is to be applied in use, and no harder than the material of the fitting with which it is to be applied, and in that optionally the olive is formed as a continuous annulus.

The fittings of the present invention, while they may be applied to all pipes, are particularly suitable for linear and cross-linked plastics, especially polyethylene pipes. In fittings provided for use with plastics pipes the nipple portion includes pipe liner adapted to fit in the end of the plastics pipe in order to provide a suitable surface for cooperation with the radially deformed olive.

The invention will now be described, by way of illustration only, with reference to the accompanying drawings wherein Figure 1 shows in part cross-section a pipe union incorporating a nipple showing to its left hand side an olive of the invention and to its right hand side an olive according to the prior art, and in Figure 2 an annular olive of a plastics material according to the second aspect of the invention.

The type of union shown generally in Figure 1 is provided with a nipple 4 of brass. Nipple 4 comprises a body having a longitudinal axis about which is disposed a through bore 13. Intermediate to ends of the bore 13, a circumferential surface of the nipple 4 includes a spanner engaging surface 6. Adjacent each side of the spanner engaging surface 6 are a pair of threaded portions 5 adapted in use to cooperate with a thread 3 disposed on the internal surface of the nut 1.

The nipple 4 further includes re-entrant 8 adapted in use to accommodate the ends of a cross-linked polyethylene tube. Extending outwardly from the body of the nipple 4 and about the through bore 13 is a pipe liner 4 which in use is disposed within the end of the plastics tube with a corrugated surface for better sealing with the internal pipe bore.

The nut 1 is formed with a bore 2 which is adapted to be readily accommodated about the outer surface of the plastics pipe. The internal surface of the nut disposed parallel to the axis thereof is provided with thread 3, and adjacent to thread 3 disposed remote from the forward face of the nut is an olive engaging surface 7 adapted to act upon the olive in use.

The olive 9 formed of annealable brass material provided with a split 12 which is just under 1 mm wide. When the thread 3 of the nut 1 is engaged with the thread 5 of the nipple body 4 and tightened thereupon, the olive engaging surface 7 on the nut and the olive engaging surface 14 on the nipple are forced onto the peripheral circumferential edges of the olive 9 and initially act to close the split 12 so that the edges thereof are in abutment. This acts merely incidentally to tighten the pipe disposed thereunder onto the liner 4 and is in itself insufficient to provide a sealing joint. Further axial pressure acts to deform the olive by pressing its outer chamfered periphery into the tube thereby deforming the tube and forcing the same into contact with the liner. This provides an excellent seal to the liner 4 while leaving no portion of the tube unsupported.If the nut is subsequently withdrawn from the nipple the split 12 will tend to open a little, or indeed can be opened by gently inserting the end of a screwdriver, for example, and the joint can be readily disassembled. Indeed, in some circumstances the olive can be reused.

This is in contra-distinction to the prior art olive shown at 10 where, however, much pressure is exerted by virtue of the axial pressure applied between the nut and the nipple, the broad split 1 1 cannot completely close and hence cannot prevent a leakage path from developing.

With reference to Figure 2 an olive, 9a, is also provided which may replace the olive 9 of Figure 1. The olive 9a is formed of a cross-linked plastics material having a hardness adjusted such that it is harder than the plastics pipe to which it is to be applied, but obviously softer than the brass of the nipple valve. In this particular instance the plastics material is cross-linked polyethylene having carefully controlled hardness characteristics such that it is not brittle but is to some extent resiliently deformable. This can be controlled by carefully controlling the conditions and additives for cross-linking in the manufacture of the olive.The internal diameter of the olive 9a is just in excess of the external diameter of the pipe to which it is to be applied, and accordingly this may be slid over the pipe particularly if a lubricating solution is applied to the end of the pipe to assist this process. When axial pressure is applied by the fitting as previously described the edges of the olive 9a resiliently deform into the pipe thereby forcing the pipe into contact with the surface 4a of the fitting. It will be appreciated that in the present invention the plastics olive has a hardness intermediate that of the fitting and pipe to which the fitting is to be applied. This is in contradistinction to the situation which pertains olives for copper pipes wherein the olive is primarily deformed into the copper pipe. If such an arrangement were utilized with plastics pipe of course no significant pressure could be applied to the surface 4a of course as it would be absorbed by the olive.

The invention, therefore, relates not only to novel olives for use particularly with plastics pipe unions, but also to such unions specifically adapted to utilize such olives, and to water systems incorporating such a sealing system.

Claims

1. A pipe fitting olive formed of a permanently, or resiliently, glue formable plastics material, the material being selected such that it is harder than the plastics material of the pipe to which it is to be applied in use, and no harder than the material of the fitting with which it is to be applied.

2. According to Claim 1 formed as a continuous annulus.

3. A pipe fitting olive comprising a split annulus chamfered at its outer peripheral edges for engagement with cooperating surfaces in the pipe fitting; characterised in that the circumferential width of the split is such as to close completely in use, the clamping of the olive onto the pipe is effected by deformation of the olive, particularly at its peripheral edges.

4. The pipe fitting olive substantially as hereinbefore set forth with reference to, and as illustrated in, Figure 1 or Figure 2 of the accompanying drawings.