GB2189302A

GB2189302A - Pipe couplings

Info

Publication number: GB2189302A
Application number: GB08709175A
Authority: GB
Inventors: Pierre Barbe
Original assignee: Pont a Mousson SA
Current assignee: Pont a Mousson SA
Priority date: 1986-04-16
Filing date: 1987-04-16
Publication date: 1987-10-21
Also published as: FR2597569A1; DE8705276U1; NL193502C; IT1208870B; IT8767315A0; LU86846A1; GB8709175D0; NL8700743A; BE1000113A5; CH672013A5; ATA79887A; FR2597569B1; GB2189302B; AT394259B; NL193502B

Abstract

Coupling for pipes, in particular for pipes of synthetic materials, comprising a body 1 through which a passage (5) extends, whereof one part is tapped at (12), a nut 2, through which a passage (18) also extends, comprising a hexagonal terminal flange 30 and an external screw-thread (32) adapted for being screwed into the tap (12) of the body 1 and a metal ring 3 which is able to be deformed radially inwards. Before fitting the coupling, the ring 3 is trapped by one of its ends by the nut 2 in order to form a nut-ring arrangement 2-3 which is screwed into the body 1. <IMAGE>

Description

SPECIFICATION Coupling for pipes The present invention relates to a coupling for pipes and more particularly a coupling to be used with pipes consisting of synthetic materials such as for example, polyvinyl chloride (PVC), high density polyethylene etc The couplings normally used with pipes consisting of synthetic materials are generally formed from a body, a nut which is screwed onto the body, a split attachment ring ensuring that the pipe is retained in the coupling and a packing arranged between the body and the end of the pipe. Sometimes, a compression ring is interposed between the attachment ring and the packing.This type of coupling has the drawback of tending to cause the pipe to twist during the formation of the coupling by screwing and above all of comprising several independent components to be put in position, the position of each of these components having to be respected in orderthatthecoupling ensures its function correctly.

Acoupling is also known which can be used for pipes consisting of soft material, such as pipes consisting of plastics material, comprising a tubular body having a projecting shoulder on the inside, a nut through which a hole passes from one end to the other and which is provided with an annularflange directed towards the axis of the nut and a tubular sleeve of plastics material, through which an axial hole passes, which is housed in the nut. The attachment of the pipe in the coupling is achieved by means of the sleeve of plastics material which encompasses the pipe, the tightening of the sleeve around the pipe being ensured at the time of screwing of the nut onto the body ofthe coupling.If this type of coupling does not tend to cause the pipe to twist during the formation of the coupling by screwing, it has the drawback of not ensuring an adequate attachment between the coupling and the pipe.

In fact, since the pipe and the sleeve both consist of plastics material, the frictional forces between these two members are reduced, the plastics materials having low coefficients of friction and the pipe may be separated from the coupling underthe effect of a slight pulling action.

The object of the present invention is to remedy these drawbacks by providing a coupling which is easy to fit and ensuring a solid attachment of the pipe.

To this end, the invention relates to a coupling for pipes, in particular for pipes consisting of synthetic materials, of the type comprising a body through which a passage extends whereof one part is tapped, a nut, through which a passage also extends, comprising a hexagonal terminal flange and an external screw-thread adapted for screwing in the tap ofthe body and a metal ring which is able to be deformed radially towards the inside, this ring, before the assembly of the coupling, being fixed by the nut by one of its endsengaged in the end ofthe passage in the nut, opposite the flange, in order to form a nut/ring assembly.

Furtherfeatures and advantages of the invention will become apparent from the ensuing description, referring to the accompanying drawings which are given solely byway of example, in which: Figure 1 is a diametral sectional view of a coupling according to the invention to which the end of a pipe is connected; Figure2 is a diametral sectional view of a coupling body constituting part of the coupling; Figure 3 is a diametral sectional view of a nut constituting a second part of the coupling; Figure 4 is a diametral sectional view of a ring constituting a third part ofthe coupling; Figure 5 is a view from the left of the ring illustrated in Figure 4;; Figure 6 is a diametral sectional view showing the nut and the ring pre-assembled beforethefitting of the coupling; Figure 7 is a dia metral sectional view showing the relative positions of the body, of the nut and of the ring atthe beginning offitting ofthecoupling; Figure 8 is a diametral sectional view of a second embodiment ofthe coupling according to the invention; The coupling for pipes consisting of synthetic materials according to the invention, illustrated in Figure 1, is composed of a body 1, of a nut 2 and of a ring 3.

The body 1, illustrated in Figure 2, is a part of revolution about an axis X-X. Extending from one end of itto the other is an inner passage 5 which comprises two cylindrical bores 6 and 8, the diameter of the bore 8 being greaterthan that ofthe bore 6. The bore 8 opens out on the outside of the body 1 by a divergentfrustoconical bore 9. Provided in the bore 6 is an annular narrow portion 7whereof the side situated adjacent the bore 8 forms a shoulder 10 perpendicular to the axis X-X. The connection ofthe bores 6 and 8forms a second shoulder 11 perpendicularto the axis X-X.

Finally, a tap 12 is provided in the bore 8, over approximately half its length, on the side opposite the frustoconical bore 9.

The outside of the body 1 comprises, on the side where the bore 6 opens out, a screw-threaded cylindrical part 13, connected by a shoulder 14 directed outwards to a hexagonal part 15,followed by a terminal cylindrical part 16.

The nut 2, illustrated in Figure 3, is a part of revolution about the axis X-X. One of its ends comprises a flat, radial surface 17 perpendicularto the axis X-X. Passing through the nut 2 from one end to the other is an inner passage 18 which comprises in succession,from the end surface 17:: - a convergentfrustoconical bore 19 whereof the half-angle at the apex is comprised between 200 and 450and preferably has a value of 30"; - a cylindrical bore 20 of diameter Dl; - a cylindrical bore 21 of diameter D2 greaterthan D1, connected to the bore 20 by a radial shoulder 22, perpendicularto the axis X-X; - a convergentfrustoconical bore 23, of the same half-angle at the apex as the firstfrustoconical bore 19; - a cylindrical bore 24 of diameter D3 less than Dl;; - a cylindrical bore 25 much longerthan the preceding bores, of diameter D4 less than D3, connected to the cylindrical bore 24 by a radial shoulder perpendiculartothe axisX-X. The diameter D4 is slighly greaterthan that of the pipeT to be connected. Provided in the cylindrical surface of the bore 25 is a frustoconical groove 27, which convergestowardsthe end opposite the end surface 17,whereofthe corners are rounded, for housing a packing; - a divergentfrustoconical bore 28, opening out on the outside of the nut 2.

The outer surface of the nut 2 comprises a cylindrical body 29, of slightly smaller outer diameterthan the inner diameter ofthe bore 8 ofthe body 1 and a hexagonal terminal flange 30 connected to the body 29 by an external radial shoulder 31. A screw-thread 32 adapted to be screwed into the tap 12 of the body 1 is provided externally on the part ofthe body adjacentthe terminal surface 17, over roughly one third of the length of this body. A groove 33 of substantially square cross section having rounded corners is cut in the body 29, approximately half way along the length ofthe latter.

0-rings 34 and 35 are housed respectively in the grooves 27 and 33 ofthe nut 2.

The ring 3, illustrated in Figures4and 5, is a partof revolution aboutthe axis X-X and is made of metal. It is defined by two flatterminal surfaces 36 and 37, perpendicularto the axis X-X. The ring 3 comprises a longitudinal slit 38, parallel to the axis X-X, limited by two faces parallel to a diametral plane. A passage 39 into which circular attachment claws 40 project, passes longitudinally from one end of the ring 3to the other. In the embodiment illustrated in Figure 4, these claws 40, of which there are three, are identical and equidistant They are defined, at one side, by a flatface 41 perpendicular to the axis X-X, at the other side by a frustoconical surface 42 on the axisX-X which converges towardsthe terminal surface 37.

The diameter defined by the point of the claws 40 is greater than the outer diameter ofthe pipe Tto be connected.

The outer surface of the ring 3 comprises in succession, from the terminal surface 36 to the terminal surface 37, a first cylindrical part 43 of diameter D5, extending over approximately half the length ofthe ring 3, a convergentfrustoconical surface44, a second cylindrical part 45 of diameter D6 less than D5, a divergentfrustoconical surface46, a third cylindrical part 47 of short length, of diameter D7 greaterthan D6 and less than D5 and a divergent frustoconical surface 48 having the same conicity as the surface 44.

The frustoconical surfaces 44 and 48 of the ring 3 have the same conicity as the frustoconical bores 19 and 23 of the passage 18 of the nut 2.

The diameter D7 of the cylindrical part 47 of the ring 3 is greater than the inner diameters D1, D2, D3 of the cylindrical bores 20,21 and 23 of the passage 18 of the nut 2. The diameter D5 of the cylindrical part 43 of the ring 3 is greaterthan the inner diameter Dl ofthe cylindrical bore 20 of the passage 18 of the nut 2. In addition, the differences of the diameters D7 and D3 on the one hand, D5 and D1 on the other hand, are equal: D7-D3=D5-D1.

Before fitting the coupling, the nut 2 and the ring 3 are pre-assembled. Forthis,the ring 3 is squeezed in order to move the parallel faces limiting the longitudinal slot38 closertogether and to make the diameter D7 of the cylindrical part 47 of the ring 3 less than the diameters D1 and D2 ofthe cylindrical bores 20 and 21 ofthe nut 2. It is then possible to introduce the end of diameter D7 of the ring 3 into the end of diameter D1 ofthe nut 2 in orderthatthe cylindrical parts 45 and 47 of the ring and the cylindrical bores 20 and 21 of the nut correspond respectively to each other.

When the pressure exerted on the ring 3 in orderto squeeze it is released, owing its elasticity the ring tends to resume its initial diameter and remains trapped by the nut 2 since the diameter D7 ofthe cylindrical part 47 of the ring 3 is greaterthan the diameter D1 of the cylindrical bore 20 of the nut 2.

The diameter defined by the point of the claws 40 is slightly greaterthan the outer diameter of the pipe T to be connected. The nut 2 and the ring 3 thus form a nut-ring arrangement 2-3 comprising O-rings 34 and 35. This arrangement, illustrated in Figure 6 is solidly assembled and cannot be disconnected underthe effectoftraction tending to separate the ring 3from the nut 2, the frustoconical surface 46 of the ring abuting against the shoulder 22 of the passage 18 of the nut 2. Fitting of this coupling (see Figure 7) takes place in the following manner.The nut-ring arrangement 2-3 is introduced into the passage Sin the body 1,the ring 3 at the front ,and several threads of the screw-thread 32 of the nut 2 are engaged in the tap 12 in the body 1. The pipeT, whereof the end has been previously chamfered, is introduced into the passage 18 in the nut 2, then into the passage 39 in the ring 3, until its end abuts against the shoulder 10 ofthe body 1. The nut 2 is then screwed into the body 1, which causes an axial displacement of the nut-ring arrangement 2-3 until the end surface 36 of the ring 3 abuts against the shoulder 11 of the body 1.Then only the nut 2 continues to move axially and, as it progresses, underthe action of its frustoconical bores 19 and 23 which bear on the corresponding frustoconical surfaces 44 and 48 ofthe ring 3, the latter recloses on itself, by virtue ofthe longitudinal slit 38, which causes the penetration of the claws 40 into the outer surface ofthe pipe. Screwing ofthe nut 2 continues until its outer shoulder 31 abuts against the end of the part 16 of the body 1. When the coupling is fitted, the cylindrical bores 20 and 24 of the nut 2 bear on the corresponding cylindrical surfaces 43 and 47 of the ring 3. The fitted coupling is shown in Figure 1.

Dismantling of the coupling takes place very simply by unscrewing the nut 2. When the latter has withdrawn sufficiently, the cylindrical surfaces 43 and 47 of the ring 3 are disengaged from the corresponding bores 20 and 24 of the nut 2 and on account of its elasticity the latter returns to its initial shape, so thatthe coupling can be used again.

The coupling to which the invention relates is used in particularforconnecting a pipe of synthetic material to a branching cockfitted on a water supply pipe. The coupling is fixed to the cock by the screw-threaded cylindrical part 13 of its body 1.

This coupling may also be used for connecting two pipes of synthetic material to each other as illustrated in Figure 8. In this case, it comprises a body 50 which is symmetrical with respect to a central shoulder 49 on which the ends of the pipes to be connected and two nut-ring arrangements 2-3 abut, on either side of thins shoulder.

If the pipeTto be connected consistsofflexible synthetic material, an inner ring is introduced into the latter in order to give it sufficient rigidity and thus to facilitate the penetration of claws 40 in its outer surface.

The coupling to which the invention relates, has the following advantages: - although constituted by five parts, namely a body,anut,a ring and2O-rings,forfittingthis coupling requires only the assembly of two parts: the body and the nut-ring arrangement provided with its 0-rings; this advantage is appreciable when it is a question of connecting a pipe to a branching cockmounted on an underground pipeline,the operation taking place in a trench; -there is no risk of error the time of fitting of the coupling, sincethe nut-ring arrangement,which is pre-assembled at the factory, can only be introduced in one way into the body of the coupling;; the two frustoconical bores 19 and 23 in the nut and thetwo corresponding surfaces44and48ofthe ring,whichform cooperating ramps, provide cylindrical and not conical tightening ofthe ring on the pipe, the result of which isto keep the tightening torque necessaryatthetimeofscrewing ofthe nut into the body constant; - since the differences between the diameters (D7 D3) on the one hand, (D5 - Dl) on the other hand, are equal,tighteningofthering onthe pipe is uniform overthe entire length of the latter, which provides equal penetration of each of the teeth into the surface of the pipe;; - at the time of screwing of the nut into the body, the pipe is not set in rotation since the ring 3, in contact with the pipe, itself carries out no rotary movement owing to the fact that it is in abutment with a shoulder of the body; - claws of the ring only begin to penetrate the outer surface of the pipe when it is immobilised axially in abutment against the shoulder 11 of the body, which prevents any relative axial movement ofthe ring with respect to the pipe, able to cause stripping ofthe latter; -the end of screwing of the nut is known without ambiguity since it is determined by the abutment of its hexagonal flange 30 with the end of the body; ; - the frustoconical bore 28 of the nut makes it possible to restore the round shape of the pipe to be connected, the latter possibly having been deformed at the time of its storage on a reel.

Claims

1. Coupling for pipes, in particularfor pipes of synthetic material, of the type comprising a body through which a passage extends, in which passage a tap is provided, a nut, through which a passage also extends, comprising a hexagonal terminal flange and an external screw-thread adapted to screw into the tap in the body, and a ring which is split longitudinallyand ableto be deformed radially inwards, through which a passage extends, which, before fitting of the coupling, is trapped by the nut by one of its ends engaged in the end of the passage of the nut opposite the flange, in order to form a nut-ring arrangement, wherein the screwing of the nut into the body first of all causes the abutment ofthe end surface of the ring, opposite the end, against a shoulder of the body, then the penetration ofthe ring inside the nut in order to cause cylindrical surfaces and, provided on the outer surface ofthe ring to cooperate respectively with cylindrical bores and provided in the passage ofthe nut.

2. Coupling according to Claim 1,wherein provided in the passage of the body on the axis X-X are two shoulders, perpendicularto the axis X-X, abutting on which are the end ofthe pipe Tto be connected and the end surface of the ring respectively.

3. Coupling according to Claim 1,whereinthe outer surface of the nut on the axis X-X comprises a cylindrical body, provided in the surface of which are a screw-thread and a groove housing an O-ring, which bears on the surface of a cylindrical bore provided in the passage of the body.

4. Coupling according to Claims 1 and 3 wherein the passage in the nut comprises in succession, from the annular end surface opposite the flange, a convergentfrustoconical bore, a cylindrical bore of diameter D1, a cylindrical bore of diameter D2 greater than Dl, connected to the bore by a radial shoulder, a convergentfrustoconical bore, a cylindrical bore of diameter D3 less than Do, a cylindrical bore whereof the diameter D4 is less than D3 and slightly greaterthan the outer diameter ofthe pipeTto be connected and a divergentfrustoconical bore.

5. Coupling according to Claim 4, wherein provided in the surface of the cylindrical bore of the passage in the nut is a frustoconical groove diverging towards the annular end face, and housed in which is an O-ring.

6. Coupling according to Claim 1,wherein provided in the passage of the ring are identical, circular claws, whereof the inner diameter is slightly greater than the outer diameter of the pipe Tto be connected, defined at one end by flat, radial faces, perpendicularto the axis X-X, at the other end by frustoconical surfaces converging towards the end surfaceofthe ring.

7. Coupling according to Claim 6, wherein the outer surface ofthe ring comprises in succession from the surface, to the surface, a first cylindrical part of diameter D5, a convergent,frustoconical surface, a second cylindrical part of diameter D6 less than D5, a divergentfrustoconical surface, a third cylindrical part, of diameter D7 less than D5 and greaterthan D6, connected to the end surface by a convergent frustoconical surface ofthe same conicity as the surface.

8. Coupling according to Claim 6,wherein the frustoconical surfaces of the ring converge in the same direction as the frustoconical bores ofthe nut and have the same half-angle at the apex as these bores, the value of this half-angle at the apex being between 200 and 450 and preferably equal to 30 .

9. Coupling according to Claim 6 wherein the diameter D7 of the cylindrical part of the ring is greater than the respective diameters Dl, D2 and D3 ofthe cylindrical bores of the passage of the nut.

10. Coupling according to Claim 6, wherein the diameter D5 of the cylindrical part ofthe ring is greaterthan the diameter D1 of the cylindrical bore ofthe passage of the nut.

11. Coupling according to Claims 9 and 10, wherein the differences between the diameters (D7 D3) on the one and (D5 - D1 ) on the other hand are equal.

12. Coupling for pipes substantially as hereinbefore described with reference to any one of the accompanying drawings.