GB1588739A

GB1588739A - Pipe couplings

Info

Publication number: GB1588739A
Application number: GB4112177A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1977-10-04
Filing date: 1977-10-04
Publication date: 1981-04-29
Also published as: JPS5454325A; JPS5756632B2; DE2754055A1; DE2754055C2

Description

(54) PIPE COUPLINGS (71) We, 'LUCKS INDUSTRIES LIMITED, a British Company of Great King Street, Birmingham, B19 2XF, England, do hereby declare this invention for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by 'the following statement : This invention relates to pipe couplings and is particularly, though not exclusively, concerned with high pressure pipe couplings.

In high pressure pipe couplings, it is commonly the practice to provide a coupling comprising a coupling body including an externally screw-threaded sleeve into the bore of which an end of the pipe fits. The pipe coupling, further includes an 0-ring, a båck-up washer, an anti-extrusion washer, a split collet and a securing nut. The 0being, back-up washer and anti-extrusion washer are engaged in the bore and are disposed around the end portion of the pipe. The nut engages with the external screw-threading on the sleeve of the body of the coupling and has an internal frusto-conical surface which engages with a complementary frustoconical surface on the collet so that, when the nut is tightened, the collet is urged against the end of the externally screwthreaded sleeve. This retains the 0being, the back-up washer and the anti-extrusion washer in position. The collet generally has an internal surface which is serrated so that when the nut is tightened the serrated internal surface of the collet bites into the surface of the pipe and so prevents the pipe from being forced out of the coupling under pressure in service. The anti-extrusion washer prevents the O-ring from being extruded- into the clearances inwardly and outwardly of the back-up washer by pressure within the pipe coupling in use.

The disadvantage of such a pipe coupling is that it consists of.no'less than five parts which have to be'individually inserted on to the pipe before ,the end of the pipe is inserted into the coupling and these five parts have to be in the correct order and disposition for the coupling to operate correctly. With unskilled labour, it is quite easy to assemble the parts in the wrong order or disposition with the result that the seal will not be. effective.

It is an object of the present invention to provide a pipe coupling which is virtually impossible to assemble, incorrectly.

According to the present invention, there is provided a pipe coupling comprising a coupling body having an externally screwthreaded sleeve provided with a bore into which an end of a pipe can be fitted, and and assembly of a nut, a collet, a back-up washer, an anti-extrusion washer, a member engaging the nut and the collet 'for retaining the collet in engagement with the nut, means for retaining the back-up washer in engagement with the collet, and means for securing the anti-extrusion washer to the back-up washer.

With a pipe coupling of the above type, it is merely necessary for a fitter to slide the above-mentioned' assembly of nut, collet, back-up washer and anti-extrusion washer and a separate 0being on to the end of-the pipe and then insert the end of the pipe into the sleeve and tighten up the nut onto the sleeve to secure the pipe to the coupling body and there is very little or no risk that the pipe coupling will be assembled wrongly.

In one embodiment, the member for retaining the collet in engagement with the nut engages against an end face of the collet and against an integral surface in the nut.

The back-up'washer may be a snap-fit engagement with the collet and may be formed of a plastics material, e.g. nylon.

Alternatively, the back-up washer may be formed of metal.

The means securing the anti-extrusion washer to the back-up washer may -be an adhesive or it may be a portion integral with both the washers.

Embodiments of the present invention will now be described, by- way of example, with reference to the accompanying drawings, in which: Fig. 1 is an axial section through one embodiment of pipe coupling according to the present invention, and Fig. 2 is an axial section through parts of a second embodiment of pipe coupling according to the present invention.

Referring now to Fig. 1 of the drawing, the pipe coupling illustrated therein comprises a coupling (body 1 including an externally screw-threaded sleeve 2 having an internal bore 3 into which an end portion of a pipe 4 is fitted. The coupling also comprises an assembly of a nut 5, a collet 6, a sleeve or back-up washer 7, an antiextrusion washer 8, and a separate O-ring 9. The nut 5 is of a size to engage with the screw-threading externally of the sleeve 2 and is provided internally with a frustoconical surface 10 which tapers inwardly away from the screw threading. The collet 6 is formed of metal and is split axially (not shown). The collet 6 has a frustoconical external surface 11 which corresponds to the frusto-conical surface 10.

The collet 6 is also provided with a serrated internal surface 12. At its end opposite to that at which the surface 12 is provided, the collet 6 has an internal annular recess 13 defined by an abutment surface 14 and an internal annular rib 15.

The abutment surface 14 extends radially outwardly with respect to the axis of the collet 6. The back-up washer 7 is in the form of a continuous annular sleeve formed of nylon. The external surface of the back-up washer 7 is provided with a recess 16 therein which is complementary in shape to that of the rib 15, and a rib 17. The back-up washer 7 is engaged, in a snap-fit manner, with the collet 6 to be carried thereby with the rib 15 engaging in the recess 16 and the rib 17 e'ngaging in the recess 13 with one axial end of the back-up washer 7 abuting against the abutment surface 14. The opposite axial end of the back-up washer 7 has the antiextrusion washer 8 secured thereto through a neck portion integral with both washers 7 and 8. Thus, the back-up washer 7 and the anti-extrusion washer 8 are produced simultaneously in the same moulding. The collet 6 is retained within the nut 5 by means of a nylon retainer ring 20 which engages against the collet 6 and against part of the screw-threading in the nut 5 so as to retain the collet 6 in position with the frusto-conical surface 11 engaging the frusto-conical surface 10.

As mentioned above, the nut 5, collet 6, back-up washer 7 and anti-extrusion washer 8 are produced as a sub-assembly so that, in effect, there are only three separate parts ,to the pipe coupling, namely the sub-assembly, the coupling body 1 and the 0being 9.

In order to assemble the pipe coupling, it is merely necessary for a fitter to insert the end of the pipe 4 into the pipe coupling 1 after first having engaged O-ring 9 and the aforementioned assembly over the end of the pipe 4. The fitter then merely screws the nut 5 on to the sleeve 2 to complete the coupling. As will be readily apparent, the O-ring 9 is deformed to seal around the periphery of the end portion of the pipe 4 and the internal surface of the bore 3 in the sleeve 2. The pipe 4 is prevented from being forced out of the bore 3 because the serrated surface 12 bites into the surface of the pipe 4 when the nut 5 is tightened due to the wedging action obtained between the two frustoconical surfaces 10 and 11 and the ability of the collet 6 to compress inwardly because it is split.

In the above-described pipe coupling, it will be apparent that there is a minimum possibility of the parts being assembled in the wrong order because of the provision of the nut 5, collet 6, back-up washer 7 and anti-extrusion washer 8 as a separate assembly with one other component, namely the O-ring 9.

Referring now to Fig. 2, a back-up washer 27 formed of metal is provided in place of the nylon back-up washer 7. In this embodiment, the back-up washer 27 is not integrally formed with the antiextrusion washer but has a separate metal anti-extrusion washer 28 adhesively secured thereto by, for example, a composition sold under the trade mark LOCKTITE.

The metal back-up washer 27 and antiextrusion washer 28 can be used in pipe coupling arrangements where a nylon back-up washer is not suitable. In order to assemble the back-up washer 27 with the collet 6, it is necessary to open up the collet 6, as permlitted Iby Ithe split therein, in order to engage the ribs with the respective recesses.

It will be appreciated that it may be necessary to provide a variety of different types of O-ring 9 to suit the particular pressure temperature and fluid characteristics for which the pipe coupling is intended.

WHAT WE CLAIM IS:- 1. A pipe coupling comprising a coupling body having an externally screwthreaded sleeve provided with a bore into which an end of a pipe can be fitted, and an assembly of a nut, a collet, a back-up washer, an anti-extrusion washer, a member engaging the nut and the collet for retaining the collet in engagement with the nut, means for retaining the back-up washer in engagement with the collet, and

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. with reference to the accompanying drawings, in which: Fig. 1 is an axial section through one embodiment of pipe coupling according to the present invention, and Fig. 2 is an axial section through parts of a second embodiment of pipe coupling according to the present invention. Referring now to Fig. 1 of the drawing, the pipe coupling illustrated therein comprises a coupling (body 1 including an externally screw-threaded sleeve 2 having an internal bore 3 into which an end portion of a pipe 4 is fitted. The coupling also comprises an assembly of a nut 5, a collet 6, a sleeve or back-up washer 7, an antiextrusion washer 8, and a separate O-ring 9. The nut 5 is of a size to engage with the screw-threading externally of the sleeve 2 and is provided internally with a frustoconical surface 10 which tapers inwardly away from the screw threading. The collet 6 is formed of metal and is split axially (not shown). The collet 6 has a frustoconical external surface 11 which corresponds to the frusto-conical surface 10. The collet 6 is also provided with a serrated internal surface 12. At its end opposite to that at which the surface 12 is provided, the collet 6 has an internal annular recess 13 defined by an abutment surface 14 and an internal annular rib 15. The abutment surface 14 extends radially outwardly with respect to the axis of the collet 6. The back-up washer 7 is in the form of a continuous annular sleeve formed of nylon. The external surface of the back-up washer 7 is provided with a recess 16 therein which is complementary in shape to that of the rib 15, and a rib 17. The back-up washer 7 is engaged, in a snap-fit manner, with the collet 6 to be carried thereby with the rib 15 engaging in the recess 16 and the rib 17 e'ngaging in the recess 13 with one axial end of the back-up washer 7 abuting against the abutment surface 14. The opposite axial end of the back-up washer 7 has the antiextrusion washer 8 secured thereto through a neck portion integral with both washers 7 and 8. Thus, the back-up washer 7 and the anti-extrusion washer 8 are produced simultaneously in the same moulding. The collet 6 is retained within the nut 5 by means of a nylon retainer ring 20 which engages against the collet 6 and against part of the screw-threading in the nut 5 so as to retain the collet 6 in position with the frusto-conical surface 11 engaging the frusto-conical surface 10. As mentioned above, the nut 5, collet 6, back-up washer 7 and anti-extrusion washer 8 are produced as a sub-assembly so that, in effect, there are only three separate parts ,to the pipe coupling, namely the sub-assembly, the coupling body 1 and the 0being 9. In order to assemble the pipe coupling, it is merely necessary for a fitter to insert the end of the pipe 4 into the pipe coupling 1 after first having engaged O-ring 9 and the aforementioned assembly over the end of the pipe 4. The fitter then merely screws the nut 5 on to the sleeve 2 to complete the coupling. As will be readily apparent, the O-ring 9 is deformed to seal around the periphery of the end portion of the pipe 4 and the internal surface of the bore 3 in the sleeve 2. The pipe 4 is prevented from being forced out of the bore 3 because the serrated surface 12 bites into the surface of the pipe 4 when the nut 5 is tightened due to the wedging action obtained between the two frustoconical surfaces 10 and 11 and the ability of the collet 6 to compress inwardly because it is split. In the above-described pipe coupling, it will be apparent that there is a minimum possibility of the parts being assembled in the wrong order because of the provision of the nut 5, collet 6, back-up washer 7 and anti-extrusion washer 8 as a separate assembly with one other component, namely the O-ring 9. Referring now to Fig. 2, a back-up washer 27 formed of metal is provided in place of the nylon back-up washer 7. In this embodiment, the back-up washer 27 is not integrally formed with the antiextrusion washer but has a separate metal anti-extrusion washer 28 adhesively secured thereto by, for example, a composition sold under the trade mark LOCKTITE. The metal back-up washer 27 and antiextrusion washer 28 can be used in pipe coupling arrangements where a nylon back-up washer is not suitable. In order to assemble the back-up washer 27 with the collet 6, it is necessary to open up the collet 6, as permlitted Iby Ithe split therein, in order to engage the ribs with the respective recesses. It will be appreciated that it may be necessary to provide a variety of different types of O-ring 9 to suit the particular pressure temperature and fluid characteristics for which the pipe coupling is intended. WHAT WE CLAIM IS:-

1. A pipe coupling comprising a coupling body having an externally screwthreaded sleeve provided with a bore into which an end of a pipe can be fitted, and an assembly of a nut, a collet, a back-up washer, an anti-extrusion washer, a member engaging the nut and the collet for retaining the collet in engagement with the nut, means for retaining the back-up washer in engagement with the collet, and

means for securing the anti-extrusion washer to the back-up washer.

2. A pipe coupling as claimed in claim 1, wherein said member for retaining the collet in engagement with the nut engages against an end face of the collet and against an internal surface in the nut.

3. A pipe coupling as claimed in claim 1 or 2, wherein the back-up washer is a snap-fit engagement with the collet.

4. A pipe coupling as claimed in any preceding claim, wherein the means securing the anti-extrusion washer to the back-up washer is an adhesive.

5. A pipe coupling as claimed in any one of claims 1 to 3, wherein the means securing the anti-extrusion washer to the back-up washer is a portion integral with both of the washers.

6. A pipe coupling substantially as hereinbefore described with reference to Figure 1 or Figure 2 of the accompanying drawings.