GB2247503A

GB2247503A - Axially flanged tension band pipe coupling

Info

Publication number: GB2247503A
Application number: GB9117416A
Authority: GB
Inventors: Robert Lohr
Original assignee: Rasmussen GmbH
Current assignee: Norma Germany GmbH
Priority date: 1990-08-27
Filing date: 1991-08-12
Publication date: 1992-03-04
Also published as: FR2666133A1; ITTO910660A0; SE9102447D0; SE9102447L; ITTO910660A1; DE4027032C1; IT1249998B; GB9117416D0

Description

k i A Pipe Coupling This invention relates to a coupling for

interconnecting the ends of two pipes. More particularly, but not exclusively, the invention also relates to a pipe coupling for coaxially connecting smooth end sections of two pipes, the coupling having a flexible, approximately C-shaped bent sheet steel tension band and two substantially radially outwardly orientated clamping jaws made of a thicker steel than the tension band, wherein the one end section of the tension band is secured to the one clamping jaw and the other end section is secured to the other clamping jaw, and having tightening screws which are each guided through a group of mutually aligned holes in the end sections of the tension band and of the clamping jaws, wherein the clamping jaws extend axially over the width of the tension band and in the centre of the radially outer edge thereof each has a first recess to permit compensation for differences in diameter of the pipes.

A pipe coupling of this kind is known from EP 0057373 AI in which coupling the clamping jaw members are in the form of flat plates and their radially. outer edges are provided with an approximately Vshaped recess. The end sections of the tension band are sub-divided into axially. disposed flaps which are spaced apart by sections extending from the ends of the tension bands in the peripheral direction. The flaps rest on one side of the mutually facing surfaces of the two clamping members and are provided with holes. These holes receive bushings which are formed for tightening screws to pass therethrough by the protuberance of the edges of the holes provided in the clamping members. The bushings are to prevent damage to the holes in the flaps and to permit a screwthread to be formed in the holes of the clamping members, which holes are provided for the tightening screws to pass therethrough. If a pipe coupling of this kind is to be used to connect pipes with very different diameters, e. g. thick-walled pipes, the end sections of which are inserted into each other for connection, or pipes with very large diameters, the ends of which are to be connected on contact, the clamping members are bent by the application of very high tension forces in their plane, about an axis which is vertical to this plane, so that there is a danger of the clamping members tearing in the region of the tip of the V-shaped recess, since that recess as a result exhibits a considerable notch effect. If end sections of exhaust pipes which are inserted inside each other are to be connected, wherein it is possible to do without a sealing sleeve between the coupling and the pipes, the tension band does not rest totally on the peripheral surface of the pipe of the smaller diameter, because in the region of the pipe of the smaller diameter, the clamping members extend throughout inclinedly to the longitudinal axis of the pipe, and the tension band presses against the per ipheral surface of the pipe of the smaller diameter, with only the one peripheral edge thereof. Therefore, the tension band exerts only a relatively small clamping force on the pipe of the smaller diameter. A pipe coupling of this kind could not therefore maintain the connection when greater axial traction forces are exerted on the pipes. Moreover, there is a danger that the holes in the end sections of the relatively thin tension band will tear, if large tension forces are exerted.

The aim of the invention is to provide a pipe coupling of the kind in question which permits greater tension forces to be exerted, and which withstands greater axial traction exerted on the pipes, without the clamping jaws tearing in the bending region and without the holes tearing in the end sections of the tension band.

According to the invention in a first aspect, there is provided a coupling for interconnecting the ends of two pipes, comprising a tension band having two ends and adapted to encircle the pipes in the region of the interconnection; and a pair of radially outwardly extending clamping members each comprising a pair of generally U-profile end members interconnected in a central region by a web and each having a throughM&40. rus going bore, the webs being spaced by --ds from the upper and lower 4!;W edges of the end members; wherein the ends of the tension band are gripped between the limbs of the U-shaped profiles of the respective clamping members and, in use of the coupling, the clamping members are disposed facing one another with pairs of the through-going bores mutually aligned so that tension bolts or screws may be inserted into the aligned pairs of bores to draw the end members of the clamping members i i i 1 j J closer together and thereby apply tension to the tension band, the arrangement being such that the webs act as flexure joints to accommodate differences between the peripheries of the pipes being coupled.

According to second aspect of the invention, the problems of the known couplings are solved in that the clamping jaws are bent into a Ushaped configuration, wherein their limbs project somewhat radially outwardly, the one end section of the tension band being bent around the limb of the one clamping jaw and the other end section of the tension band being bent around the limb of the other clamping jaw, wherein the limbs enclosed by the end sections are adjacent to each other and the end sections of the tension band are each clamped between the limbs of the clamping jaws. The first recess of each clamping jaw is formed in the radially outer edges of the two limbs and the clamping jaws have in the centre of their radially inner curvature a hole which forms a second recess, wherein the first and second recesses of the clamping jaw are separated by an axialy extending crosspiece.

With this embodiment, the clamping jaws withstand very great tensional forces, because owing to the fact that they fold together they are twice as thick as the sheet steel of which they are made. It is possible to do without the bushings which engage into the holes of the tenston band. Yet, the material of the tension bands is sufficiently thick to cut screwthreads, if so desired, in the holes of the one clamping jaw.

Since each end section of the tension band has two coaxial lead-in holes for each tightening screw, and also is clamped between the limbs of one of the clamping jaws, there is no longer any. danger of the lead-in holes becoming torn, particularly if the pipe coupling is allowed to be tightened to such an extent that the mutually facing surfaces of the ends of the tension band are pressed together by the clamping jaws, so that an additional clamping force is exerted on the end sections of the tension band. The recesses in the two longitudinal edges of the clamping jaws and the web or crosspiece extending longitudinally between the clamping jaws are advantageous in that the web or crosspiece acts like a flexural hinge, but nonetheless is not subject to any notch effect. In the second recess, the clamping jaws also freely accommodate a step formed by varying p1pe diameters, and the clamping members can push the tension band axially beyond the second recess, with a large part of its surface area against the pipes, or against a rubber sleeve which may be interposed, resulting in better friction contact between the tension band, on the one hand, and the pipes or rubber sleeve, on the other hand.

The ends of the tension band are preferably designed so that they are continuously (axially) transverse with respect to the tension band. As opposed to ripping open the ends of the tension band by cuts in the ends which extend in the peripheral direction of the tension band, the end sections of the tension band are formed so that they are continuously transverse to or axial to the tension band, and this is advantageous because there is no danger of the flaps tearing, such as resulted in previous couplings when cuts were formed in the peripheral direction at the ends of the tension band, and also there is no danger of the tenslon band tearing in the peripheral region between the flaps when greater tensional forces are exerted.

In addition, the webs or crosspieces are preferably bowed or curved in the peripheral direction in each clamping member, so that the concave sides of the curvatures on the side of the one clamping member are facing the others of the other clamping member. In this way., curved webs or crosspieces can extend approximately in the transverse direction of the tension band or in the axial direction of the pipes, so that the tension band, after having been tightened about the end section of a pipe of greater diameter, can also be tightened in the region of the smaller pipe more easily having a large part of its surface bearing against the pipes, so that both pipes are firmly clamped by the tension band.

The region of the ends of the tension band which cover the webs or crosspieces and the recesses can be curved like the webs or crosspieces, in order to make it easier for the tension band to be adapted 1 i i 1 1 i to the periphery of pipes of different diameter outside the transition step between the circumference of the one pipe and the circumference of the other pipe.

It is thus favourable if the radially Inner bends of the clamping members have at least one other hole on both sides of the recess. This results in a reduction to the cross-section in the region of the curvatures of the clamping members, so that they can be bent more easily into the U-shape. In addition, these holes are advantageous because they ensure greater surface pressure between the curvatures and the tension band and thus ensure a yet firmer hold of the tension band on the periphery of the pipes or of rubber sleeves which may be disposed between the tension band and the pipes.

Preferred embodiments of the invention and further developments thereof are described hereinafter with the aid of the accompanying drawings wherein:

Figure 1 shows a view in perspective of the clamping region of a pipe coupling according to the invention, Figure 2 shows the axial section II-II according to Figure 1 where two pipes inserted into each other are coupled together, Figure 3 shows a clamping member of the pipe coupling according to Figure 1 prior to deflection into the Ushape, Figure 4 shows a Plan view of the clamping region of the pipe coupling according to the invention according to Figure 2, and Figure 5 shows the same view as in Figure 2 of a slightly dif f erent pipe coupling according to the invention for two abutting pipes which are to be connected.

The pipe coupling according to Figures 1 to 4 is used to coaxially A Lf connect preferably smooth end sections, to be inserted into each other, of two pipes I and 2 forming e.g. an exhaust pipe. The pipe coupling includes an approximately C-shaped sheet steel tension band, two U-shaped, generally radially outwardly orientated clamping members in the form of jaws 4 and 5 made of a thicker sheet steel than the tension band 3 and two tightening screws 6 and 7 which are only shown in the illustration by broken lines, and which each have a head with multiple sides in the embodiment shown.

The tension band 3 has two similar end sections 8 and 9, of which each end section 8, 9 has four through-holes 10, pairs of which are in alignment with each other. One end section 8 is bent about one limb 11 of the two limbs 11, 12 of the clamping jaw 4 and the other end section 9 is bent around one limb 13 of the two limbs 13, 14 of the other clamping jaw 5. The limbs 11, 13 which are thus embraced by the end sections 8, 9 are adjacent each other. The end sections 8, 9 are each clamped between limbs 11, 12 and 13, 14 of the clamping jaws 4, 5 and - up to the holes 10 are formed so that they are continuously (axially) transverse to the tension band 3.

The clamping jaws 4 and 5 are made from flat sheet steel as shown in Figure 3, are bent into a U-shaped configuration and their longitudinal axes extend over the width of the tension band 3. In the centre of their radially outer edge they each have a second recess 17 or 18. The second recesses 17 and 18 each form a central aperture which has, prior to the clamping jaw being bent over about the central longitudinal axis 19, four bevelled or rounded corners, as shown in Figure 3 for the second recess 17 of the one clamping jaw 4. In each clamping jaw 4 and 5, the first recess 15 and 16 is separated from the second recess 17 or 18 by an axially extending web in the form of crosspiece 20 or 21, wherein each crosspiece 20 or 21 is formed by identical pairs of crosspieces 20a, 20b and 21a, 21b.

The clamping jaws 4, 5 also have four holes 22 and 23 arranged in alignment in pairs, wherein the holes 23 are provided with screwthreads 1 f - 7 for engagement with the tightening screws 6 and 7. Instead of the screwthreaded holes 23 it is possible to use holes without screwthreads, if tightening nuts are used to tighten the tightening screws 6, 7.

In each of the clamping jaws, the crosspieces 20 and 21 are curved to provide concave sides on one clamping jaw 4 facing correspondingly concave sides of the other clamping jaw 5. The regions of the end sections 8, 9 of the tension band 3 which overlap the crosspieces 20, 21 and the recesses 15, 17 or 16, 18 are also curved like the crosspieces 20, 21.

Also, the radially inner curvatures or edges of the clamping jaws have on both sides of the second recess 17 or 18 at least one other hole, and preferably two holes 24 as shown i.e. a total of four holes 24. The other holes 24 are circular; before the clamping jaws 4, 5 are bent into the Ushaped configuration they form approximately semi-circular recesses in the radially inner edges or curvatures of the clamping jaws 4, 5. These recesses or holes 24 facilitate the bending operation of the flat sheet steel pieces of Figure 3 about the longitudinal axis 19 into the Ushaped configuration shown in Figures 1, 2 and 4. Moreover, they increase the surface contact between the clamping jaws 4, 5, on the one hand, and the tension band 3, on the other hand, in the regions of the radially inner curvatures of the clamping jaws 4, 5 which are adjacent the tension band 3.

After the end sections of the pipes I and 2 have been inserted into each other, and after the tension band 3 has been wrapped around the two pipes I and 2, the tightening screws 6 and 7 are inserted into the holes 10 and 23 and tightened. Alternatively, it is also possible, after the tightening screws 6 and 7 have been inserted into the holes 10 and 23 to introduce the pipe I into the pipe coupling before the tightening screws 6 and 7 are f ully tightened. The pipe 2 is in that case inserted into pipe I and the tightening screws 6 and 7 are then tightened. In both cases, the tension band 3 is drawn more closely around the pipe 2 than about the pipe 1, as shown in Figures 2 and 4. If necessary, the tension band 3 can be tightened around the pipe 2 to such an extent that a large part of the surface area of the facing surfaces of the end sections 8, 9 of the tension band 3 are disposed against one another in the region of the pipe 2. In each case, however, in the region of the pipe I there is a spacing, as shown in Figure 4. In the region of the stepped transition between the two pipes I and 2, the crosspieces 20 and 21 which consist of the crosspieces 20a and 20b and 21a and 21b act like flexural joints, so that the regions of the clamping jaws 4, 5 which are adjacent the axial ends of the crosspieces 20, 21 press the tension band 3 to that it is coaxial with the pipes I and 2, whereby curvature of the crosspieces 20, 21 and the curvatures of the end sections 8, 9 of the tension band 3 is ensured in the region of the crosspieces 20, 21 and the clamping jaws 4, 5 are mutually parallel in their regions which are axial on both sides of the crosspieces 20, 21 and through which pass the tightening screws 6, 7. In this way, the tension band 3 presses, with a large part of its surface area, against pipes I and 2 on both sides of the diameter graduation region of the pipes I and 2, so that a fixed friction contact between the tension band 3 and the pipes 1, 2 results, which ensures high axial tractional loadability of the pipes I and 2, without the pipes 1, 2 sliding apart. At the same time, there is no danger of the recesses 15 and 16 tearing, because the crosspieces 20, 21 essentially have bending forces imposed upon them, and very great tensional forces can be exerted without the end sections 8, 9 of the tension band 3 tearing and/or without tearing occurring in the region of the tightening screws 6, 7. The recesses 17 and 18 receive the graduation region of the pipes 1, 2, without the crosspieces 20, 21 pressing the tension band 3 against the radially outer edge at the end of pipe I and being exposed there to a notch effect. Moreover, the edge regions of the clamping jaws 4, 5 disposed on either side of the holes 24 exert great surface pressure on the tension band, whereby the friction contact between the tension band 3, on the one hand, and the pipes 1, 2, on the other hand, is yet further improved. Moreover, the holes 24 facilitate bending of the clamping jaws 4, 5 from the flat shape illustrated in Figure 3 about the axis 19 into the U-shaped configuration.

The pipe coupling according to Figure 5 differs from that in tk 4 1 1 Figures I to 4 simply by the fact that a rubber sleeve 25 is arranged between the tension band 3 and the pipes 1, 2, and the pipes I and 2 are to be connected at their ends on contact, but have slightly different diameters, due to manufacturing tolerances for example. The rubber sleeve 25 therein engages the resulting radially inwardly projecting, perpipheral groove 26 between the mutually facing front ends of the pipes I and 2, and is used to seal the gap between the pipes I and 2. The tension band 3 can also have generally radially inwardly projecting flanges 27 and 28 at the axial ends thereof, which each rest on the pipes I and 2 when the pipe coupling is tightened. The mode of operation is otherwise generally the same as with the embodiment according to Figures 1 to 4.

A further variation can consist in the gap between the mutually facing surfaces of the end section 8 and 9 of the tension band 3 being bridged by a flap welded to the inside of the tension band 3 (e.g. by spot welding).

1

Claims

1. A coupling for interconnecting the ends of two pipes, comprising a tension band having two ends and adapted to encircle the pipes in the region of the interconnection; and a pair of radially outwardly extending clamping members each comprising a pair of generally U-profile end members interconnected in a central region by a web and each having a through-going bore, the webs being spaced b)Z from the upper and lower edges of the end members, wherein the ends of the tension band are gripped between the limbs of the U-shaped profiles of the respective clamping members and, in use of the coupling, the clamping members are disposed facing one another with pairs of the through-going bores mutually aligned so that tension bolts or screws may be inserted into the aligned pairs of bores to draw the end members of the clamping members closer together and thereby apply tension to the tension band, the arrangement being such that the webs act as flexure joints to accommodate difference between the peripheries of the pipes being coupled.

2. A pipe coupling for coaxially connecting smooth end sections of two pipes, the coupling having a flexible approximately C-shaped bent sheet metal tension band and two substantially radially outwardly orientated clamping jaws made of a thicker sheet steel than the tension band, wherein the one end of the tension band is secured to the one clamping member and the other end is secured to the other clamping member, and having tightening screws which are each guided through a group of mutually aligned holes in the ends of the tension band and of the clamping member wherein the clamping member extends axially over the width of the tension band and in the centre of the radially outer edge thereof each has a first recess to permit equalisation of differences in the diameters of the pipes, wherein the clamping members are bent into a Ushaped configuration, wherein the limbs thereof project somewhat radially outwardly, one end of the tension band being bent around the limb of the one clamping member and the other end of the tension band being bent around the limb of the other clamping member, wherein the limbs 1 1 1 1 1 enclosed by the ends are adjacent to each other and the ends of the tension band are each clamped between the limbs of the clamping members; the first recess of each clamping jaw being formed in the radially outward edges of the two limbs and the clamping members having in the centre of their radially inner portions a hole which forms a second recess wherein the first and second recesses in each clamping member are separated by an axially extending web.

3. A pipe coupling according to Claim 1 or claim 2, wherein the ends of the tension band are formed so that they are continuously (axially) transverse with respect to the tension band.

4. A pipe coupling according to any. preceding claim, wherein the webs of each clamping member are curved in the peripheral extent, so that the concave sides of the curvatures on the one clamping member are facing those of the other clamping jaw.

5. A pipe coupling according to Claim 3, wherein regions of the end of the tension band cover the webs and the recesses, said end regions being curved in the vicinity of the webs generally to conform thereto.

6. A pipe coupling according to any of Claims 2 to 5, wherein the radially inner portions of the clamping jaws have, on both sides of the second recess, at least one other hole.

7. A pipe coupling generally as herein described, with reference to or as illustrated in the accompanying drawings.

8. Any novel combination or sub-combination disclosed and/or illustrated herein.

Published 1992 at The Patent Office- Concepi Houst. Cardiff Road Newport. Gwent NP9 I F.H Further copies ma-% be obtained Ii -port. NPI 7HZ. Printed by M -y Crii. Kein Sales Branch. Unit 6 Nine Mile Point. Cwmfelinfach. Cross Keys- '\ek, ultiplex techniques lid. St Mai