GB2085537A

GB2085537A - Improvements in pipe couplings

Info

Publication number: GB2085537A
Application number: GB8032572A
Authority: GB
Original assignee: Fujii Kinzoku Kako Co Ltd; Fuji Metal Manufacturing Co Ltd
Current assignee: Fujii Kinzoku Kako Co Ltd; Fuji Metal Manufacturing Co Ltd
Priority date: 1980-10-09
Filing date: 1980-10-09
Publication date: 1982-04-28
Also published as: GB2085537B

Abstract

A compression pipe coupling comprising a main body (4) having an externally threaded portion (1), a nut (8), a front sleeve (11) having a recessed portion (10) in its rear end, and a rear sleeve (13) having a projecting portion (12) at its front end. To prevent the front edges of the sleeves from cutting into the surface of the pipe (25) to be connected to another member and so weakening the pipe, the recessed portion (10) and the projecting portion (12) slope at the same angle each in the form of a tapered surface (18, 19), and the rear surface of a flange (22) on the rear sleeve (13) and the top wall inner surface of the nut (8) also slope at the same angle, each providing a tapered surface (20, 21). <IMAGE>

Description

SPECIFICATION Improvements in pipe couplings The present invention relates to pipe couplings, and more particularly to compression pipe couplings.

British Patent No. 978,343 discloses a conventional pipe coupling of this type which comprises a hollow main body having two ends, at least one of the ends having an externally threaded portion and a tapered portion on its inner surface; a cap nut having an internally threaded portion engageable with the externally threaded portion of the main body and a pipe passing bore formed in the center of its top wall; a front sleeve provided on its outer surface with a tapered portion having a smaller angle of inclination than the tapered portion of the main body and a sphero-concave portion formed in its rear end centrally thereof; and a rear sleeve disposed to the rear of the front sleeve and provided at its front end with a sphero-convex portion fittable in the concave portion of the front sleeve. The convex portion is slightly smaller than the concave portion in radius.The rear sleeve has a rear end engageable with the top wall inner surface of the nut, and these surfaces have an angular relationship to each other opening radially inward.

Throughout the specification and the appended claims, the term "front" refers to the forward side with respect to the direction of advance of a nut when it is tightened, and the term "rear" to the reverse side.

When the nut is advanced on the main body of the conventional pipe coupling, the rear sleeve which is pushed by the nut from behind strikes the front sleeve first, the front and rear sleeves then advance together, and the front sleeve comes into contact with the main body. Because the spheroconvex portion of the rear sleeve is slightly smaller in radius than the sphero-concave portion of the front sleeve, and further because the rear surface of the rear sleeve and the top wall inner surface of the nut have an angular relationship opening radially inward, the rear sleeve thereafter rolls or gyrates until this angular relationship has been nullified, forcing the front edge of the rear sleeve to bite into the pipe.The gyration of the rear sleeve further advances the front sleeve and brings its front end into a tight wedging relationship between the main body tapered portion and the pipe. Although the front edge biting into the pipe appears to always maintain an extremely strong fluid tight connection between the rear sleeve and the pipe, the following failures will result. The rear sleeve, when sharply biting into the pipe with its front edge by gyration, forms an annular groove in the outer surface of the pipe, reducing the wall thickness of the pipe at the grooved portion. Accordingly when the conventional coupling is subjected to vibrations during use, a concentrated stress will build up in the thin portion to cause cracking, or if it is used in a corrosive atmosphere as in a coastal area, the thin portion will develop stress corrosion cracking.

According to the present invention there is provided a pipe coupling comprising a hollow main body having two ends, at least one of the ends having an externally threaded portion and a tapered portion on its inner surface; a cap nut having an internally threaded portion engageable with the externally threaded portion of the main body and a pipe passing bore formed in the centre of itsuop wall; a front sleeve provided on its outer surface with a tapered portion having a smaller angle of inclination than the tapered portion of the main body and a recessed portion formed in its rear end centrally thereof; and a rear sleeve disposed to the rear of the front sleeve and provided at its front end with a projecting portion fittable in the recessed portion of the front sleeve, wherein each of the recessed portion of the front sleeve and the projecting portion of the rear sleeve has a tapered face, the tapered faces extending obliquely straight at the same angle of inclination in longitudinal section, the rear sleeve having a flange engageable with the inner surface of the top wall of the nut, each of the rear surface of the flange and the top wall surface being in the form of a tapered face, the tapered faces extending obliquely straight at the same angle of inclination in longitudinal section.

In addition to the above feature, the coupling of this invention has another feature that the nut has a bore for passing the pipe therethrough which bore has a radius larger than the outside radius of the pipe approximately by the wall thickness of the rear sleeve, and that the rear sleeve has an extension projecting rearward from the pipe passing bore of the nut for accurately guiding the pipe into the coupling and also for permitting the nut to be unscrewed smoothly even when the pipe is bent at a portion thereof in the rear of the coupling.

Two embodiments of this invention will be described below with reference to the drawings.

Fig. 1 is a view in longitudinal section showing a pipe coupling embodying the invention, with a pipe inserted therein and a nut slightly tightened; Figs. 2 to 5 are fragmentary enlarged views of Fig. 1 showing the nut as it is progressively advanced from a loosened position to its clamping position; and Fig. 6 is a sectional view corresponding to Fig. 5 and showing another pipe coupling embodying the invention.

With reference to Fig. 1 , a pipe coupling comprises a hollow main body 4 having two ends 1, at least one of the ends having an externally threaded portion 2 and a tapered portion 3 on its inner surface; a cap nut 8 having an internally threaded portion 5 engageable with the externally threaded portion 2 of the main body 4 and a pipe passing bore 7 formed in the center of its top wall 6; a front sleeve 11 provided on its outer surface with a tapered portion 9 having a smaller angle of inclination than the tapered portion 3 of the main body 4 and a recessed portion 10 formed in its rear end centrally thereof; and a rear sleeve 13 disposed to the rear of the front sleeve 1 1 and provided at its front end with a projecting portion 12 fittable in the recessed portion 10 of the front sleeve 11.The recessed portion 10 of the front sleeve 11 and the projecting portion 12 of the rear sleeve 13 have tapered faces 18 and 19, respectively, which extend obliquely straight at the same angle of inclination in longitudinal section.

The rear sleeve 13 has a flange 22 adapted for abutting contact with the inner surface of the top wall 6 of the nut 8. The rear surface of the flange 22 and the top wall inner surface 6 are each in the form of a tapered face 20 (21). These tapered faces 20 and 21 extend obliquely straight at the same angle of inclination in longitudinal section.

The tapered portion 3 of the coupling main body 4 has an angle of inclination of about 200, while the tapered portion 9 of the front sleeve 11 has an angle of inclination of 100 to 150. The tapered faces 18 and 19 of the recessed portion 10 of the front sleeve 11 and the projecting portion 12 of the rear sleeve 13 each have an angle of inclination of about 350 to 460. The tapered face 20 of the flange 22 of the rear sleeve 13 and the tapered face 21 of the nut 8 each have an angle of inclination of 700 to 850. Although not limitative, these angles are preferable.

The pipe passing bore 7 of the nut 8 has a radius larger than the outside radius of a pipe 25 by an amount approximately equal to the wall thickness of the rear sleeve 13. The rear sleeve 13 has an extension 13A projecting rearward from the bore 7 of the nut and having a length which is preferably about 1/4 the entire length of the sleeve 13.

The main body 4 includes a center portion 23 having a flange 24 on its outer side and an inward annular projection 26 formed on its inner side and projecting radially inward by an amount corresponding to the wall thickness of the pipe 25 to be connected.

The nut 8, front sleeve 11 and rear sleeve 13 to be provided on the left end 1 of the main body 4 are not shown in Fig. 1.

Figs. 2 to 5 show how a pipe is connected to another member (not shown) by the coupling of this invention.

A pipe 25 is inserted into the main body 4 until it is brought into abutting contact with the inward annular projection 26, through the bore 7 of the nut 8 while being guided by the extension 13A of the rear sleeve 13 projecting rearward from the cap 8. In this stage, the main body 4, front sleeve 11, rear sleeve 13 and nut 8 have play relative to one another (see Fig. 2).

When the nut 8 is then advanced, the tapered inner face 21 of the top wall 6 of the nut 8 abuts the tapered face 20 of the flange 22 of the rear sleeve 13 to advance the sleeve 13, whereby the projecting portion 12 of the sleeve 13 is intimately fitted into the recessed portion 10 of the front sleeve 11. The nut 8 now advances the front sleeve 11 with the rear sleeve 13, forcing the front end 17 of the sleeve 11 against the tapered portion 3 of the main body 4 (see Fig. 3).

With a further advance of the nut 8, the front end 17 of the front sleeve 11 is constricted radially inward since the tapered portion of the sleeve 11 has a smaller angle of inclination than the tapered portion 3 of the main body 4.

Consequently the sleeve end 17 tightly presses the pipe 25 in face-to-face contact therewith (see Fig. 4).

The nut 8, when further tightened up, causes the tapered face 1 9 of the rear sleeve 1 3 to slide along the tapered face 18 of the front sleeve 11, with the result that the part of the rear sleeve 13 extending forward from the flange 22 and including the projecting portion 12 is constricted to tightly press the pipe 25 in face-to-face contact therewith (see Fig. 5). This is accomplished because the tapered faces 18 and 19 extend obliquely straight at the same angle of inclination when seen in longitudinal section, and because the flange 22 on the sleeve 13 and the nut top wall 6 have the tapered rear face 20 and the tapered inner face 21, respectively, which extend obliquely straight at the same angle. In this way, the pipe is installed in place by the coupling of this invention.In this state, the main body 4 and the front sleeve 11 are clamped together in face-toface contact with each other at the tapered portions 3 and 9, while both the front sleeve 11 and the rear sleeve 13 are held compressed at their front ends against the pipe 25 in face-to-face therewith, thus providing a fluid tight connection at all times, without forming any annular groove in the outer surface of the pipe by the gyration of the rear sleeve unlike the conventional coupling. This eliminates the likelihood that a concentrated stress will cause cracking or stress corrosion cracking in the pipe. Additionally the extension 13A of the rear sleeve 1 3 serves to mitigate the vibration or impact to be concentrated on the portion of the pipe which has been deformed plastically by the constriction of the rear sleeve 13.The pipe connected to another member by the coupling may sometimes be bent from behind the coupling, for example, at an angle of 600 to 900.

When the rear sleeve 13 is not provided with the extension 13A projecting rearward from the nut 8, the pipe 25 will then be bent at a portion immediately behind the nut 8, making it impossible to unscrew the nut 8 and therefore to remove the pipe 25 from the coupling. This is very disadvantageous for maintenance. With the presence of the extension 1 3A, the nut 8 can be unscrewed.

Fig. 6 shows another pipe coupling of this invention as installed in place. The coupling comprises a front sleeve 31 formed in the inner surface of its front end portion with an annular cutout 14 approximately L-shaped in longitudinal section to provide a forward projection 15 and also with an annular groove 16 positioned at a small distance from the cutout 14 to the rear thereof and approximately V-shaped in longitudinal section to form a pipe clamping annular portion 27 between the cutout 14 and the groove 16. The coupling has a rear sleeve 33 which is not provided with the above-mentioned extension 13A, so that a nut 8 has a pipe passing bore 28 whose diameter is approximately equal to the outside diameter of the pipe 25 to be connected. Throughout Figs. 1 to 6, like parts are referred to by like reference numerals.

When the nut 8 is advanced, the front end of the front sleeve 31 is constricted radially inward, with the result that the front sleeve 31 in line contact with the main body 4 is brought into intimate face-to-face contact with the body 4, and the pipe clamping annular portion 27 between the L-shaped annular cutout 14 and the V-shaped annular groove 16 is pressed tightly against the pipe 25 in face-to-face contact therewith, since the tapered portion 9 of the front sleeve 31 has a smaller angle of inclination than the tapered portion 3 of the main body 4, and also owing to the provision of the cutout 14 and the groove 1 6.

Although the pipe coupling shown in Fig. 1 is straight and symmetrical, the present invention can be embodied as L-shaped and T-shaped pipe couplings and also as pipe couplings having one end adapted for attachment to walls.

Claims

1. A pipe coupling comprising a hollow main body having two ends, at least one of the ends having an externally threaded portion and a tapered portion on its inner surface; a cap nut having an internally threaded portion engageable with the externally threaded portion of the main body and a pipe passing bore formed in the centre of its top wall; a front sleeve provided on its outer surface with a tapered portion having a smaller angle of inclination than the tapered portion of the main body and a recessed portion formed in its rear end centrally thereof; and a rear sleeve disposed to the rear of the front sleeve and provided at its front end with a projecting portion fittable in the recessed portion of the front sleeve, wherein each of the recessed portions of the front sleeve and the projecting portion of the rear sleeve has a tapered face, the tapered faces extending obliquely straight at the same angle of inclination in longitudinal section, the rear sleeve having a flange engageable with the inner surface of the top wall of the nut, each of the rear surface of the flange and the top wall surface being in the form of a tapered face, the tapered faces extending obliquely straight at the same angle of inclination in longitudinal section.

2. A pipe coupling according to claim 1, wherein the bore of the nut for passing a pipe therethrough has a radius larger than the outside radius of the pipe approximately by the wall thickness of the rear sleeve, and the rear sleeve has an extension projecting rearward from the pipe passing bore of the nut for accurately guiding the pipe into the coupling and for permitting the nut to be unscrewed smoothly even when the pipe is bent at a portion thereof in the rear of the coupling.

3. A pipe coupling according to claim 1 or 2, wherein the front sleeve is formed in the inner surface of its front end portion with an annular cutout approximately L-shaped in longitudinal section to provide a forward projection and with an annular groove positioned at a small distance from the cutout to the rear thereof and approximately V-shaped in longitudinal section to form a pipe clamping annular portion between the cutout and the groove.

4. A pipe coupling according to any of claims 1 to 3, wherein the tapered faces of the recessed portion of the front sleeve and the projecting portion of the rear sleeve have an angle of inclination of 350 to 460, and the tapered face of the nut have an angle of inclination of 700 to 850.

5. A pipe coupling substantially as hereinbefore described with reference to the accompanying drawings.

6. Any novel subject matter or combination including novel subject matter herein disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.