GB2470276A

GB2470276A - Clamp for pipe couplings

Info

Publication number: GB2470276A
Application number: GB1007880A
Authority: GB
Inventors: Stephan Vogler
Original assignee: Straub Werke AG
Current assignee: Straub Werke AG
Priority date: 2009-05-13
Filing date: 2010-05-12
Publication date: 2010-11-17
Anticipated expiration: 2030-05-12
Also published as: GB201007880D0; CH701049A1; GB2470276B; DE102010019864A1; CH701049B1

Abstract

A clamp having an outside and an inside, in particular for frictional coupling of plastic pipes or tubes, comprising a clamp band 4 which surrounds a pipe to be coupled over a major part of its circumference and preferably consists of sheet metal. The end regions of the clamp band 4 are in the form of loops 4a, 4b bent over towards the inside of the clamp and having free ends 4e, 4. The free ends 4e, 4f of the loops 4a, 4b are connected, via at least one coupling point 4c, 4d, to the circumference of the clamp band 4. The free end 4e, 4f of the loop projects beyond the coupling point 4c, 4d by at least 5% of the circumference.

Description

I

Clamp for pipe couplings The invention relates to a clamp having an outside and an inside, in particular for frictional coupling of plastic pipes or tubes, comprising a clamp band which sur- rounds a pipe to be connected over a major part of its circumference and prefera-bly consists of sheet metal and whose end regions are in the form of loops bent over towards the inside of the clamp and having free ends, the free ends of the loops being connected, at at least one coupling point, to the circumference of the clamp band.

A multiplicity of different pipe couplings are known and are also used for the fric-tional coupling of plastic pipes. For example, EP 0 205 896 Bi discloses a pipe coupling which has a metallic housing and a sealing collar arranged therein and having a C-shaped cross-section. Anchoring rings provided with teeth are sup-is ported axially and radiaUy over plate-like discs in the corner of the housing. On tensioning the housing, firstly the sealing lips of the sealing collar are pressed against the lateral surface of the plastic pipes and secondly the teeth of the an-choring elements penetrate into this lateral surface of the plastic pipes. Thus, firstly the pipes are sealed and secondly a strong coupling of the pipes is achieved. These pipe couplings are, however, relatively complicated and sec- ondly are limited in the diameter range of the plastic pipes. In order to avoid col- lapsing of the plastic pipes due to the tensioning, metallic support rings are in-serted into the pipe ends.

EP 1141 607 BI describes a pipe coupling for plastic pipes, in which, by introduc-tion of a fluid passed into a collar surrounding the pipe, the plastic pipes are pressed radially inwards against a coupling socket connecting the pipes to one another and inserted into the pipe ends. However, this solution is very compli-cated in that it requires technical aids, such as pumps and the like, for applying the pressure in the fluid.

Instead of the collars, attempts have already been made to press the pipes ra-dially against the coupling sockets by means of clamp bands, Owing to the high resultant forces, relatively high material thicknesses of the clamp bands to be used are required for this purpose. Since such pipe couplings are very exposed to weathering and/or a corrosive atmosphere, these clamp bands are generally pro-duced from stainless (chromium nickel) steel for corrosion protection reasons.

The material costs are therefore very high. Moreover, when fastening the loop ends, there is the danger of crevice corrosion, in particular in the case of welded joints.

DE 100 48 955 Al discloses a clamp band in which the ends of the loops are bent io over inwards and fastened by bent-over flaps projecting radially outwards and passing through slots. Instead of the flaps, pot-like projections which are intro-duced in an interlocking manner into a hole of the opposite region can also serve for coupling. All these couplings must absorb practically the total tangential prestressing forces.

WO 2007/060563 describes a clamp or pipe collar in which the loops are bent over flat in an inward direction and the free ends of the loops are fastened by in- terlocking (press-fit/joint) couplings. In this solution too, these couplings must ab-sorb practically the total prestressing forces.

US 2008 /0040897 Al discloses clamps for round or angular articles, in which the loops are likewise bent over inwards. The fastening of the loops is recessed somewhat (by about 12° or about 3% of the circumference) relative to the free end of the loops. This is said to signify an improvement compared with the prior art mentioned and also shown figuratively in this document and comprising tongues which are bent over outwards. On overloading the tongue by tensile forces occur-ring during operation, it is said that the coupling point at the free ends of the tongue are not torn or sheared off as in the case of the prior art but the inside of S the tongue is pressed radially against the article to be clamped.

It is the object of the invention to provide a clamp which permits the application of high clamping forces in combination with small material thickness.

According to the invention, this is achieved if the free end of the ioop projects be-yond the coupling point by at least 5% of the circumference. On tensioning of the clamp band, this region projecting beyond the coupling point in the crcumferential direction, as besides also the region of the clamp band between the loops, will be pressed radially against the pipe. As a result of the contact friction of the lateral surface of the pipe, this region projecting beyond the coupling point can absorb a part of the tensile forces occurring at the tongue. This leads to a considerable relief of the coupling point of the tongues.

A further improvement and optimization of the force conditions is achieved if the free end of the loop projects beyond the coupling point by about 10% of the cir- cumference. By relieving the coupling point of the tongues, it is possible to man-age with a minimum material thickness of the clamp band.

The coupling point is preferably in the form of interlocking couplings. Interlocking couplings result in considerable advantages with regard to corrosion resistance in comparison with welded joints (e.g. point welding or seam welding).

A particularly expedient solution consists in forming the coupling point as press-fit/joint couplings ("clinches"). Such press-fit/joint couplings permit in particular very high shear forces.

The press-fit/joint couplings are advantageously in the form of circular holes in the clamp band and pot-like protuberances engaging the holes in the end region of the loops in an interlocking manner. As a result of the circular shape of the holes and of the protuberances engaging these in an interlocking manner, the danger of notching is relatively low.

Depending on the size of the forces occurring on clamping or during operation of the pipe line, it is expedient to provide a plurality of coupling points arranged side by side in the axial direction. The safety factor can be determined or defined by the number of coupling points.

In order to achieve a uniform distribution of the forces over the total pipe circum-ference, it is advantageous to arrange an inlay bridging the gap between the loops on the inside of the loops which is directed towards the pipes to be coupled.

This inlay expediently extends from the coupling point of one loop to the coupling loop of the other, opposite loop.

Plastic pipes have a relatively low stability to resultant pressure from outside. In order to avoid compression, a support sleeve is therefore advantageously ar-ranged on an inside of the plastic pipes or tubes to be coupled. This support io sleeve simultaneously forms the coupling socket of the two plastic pipes to be coupled to one another.

In order to achieve good coupling of the plastic pipes with the support sleeve dur-ing clamping of the pipes, the support sleeve is expediently provided on its outside with profiles. Such profiles permit interlocking engagement and prevent the pipes from "slipping out".

The profiles are advantageously in the form of stamped formations. Such stamped formations may be, for example, in the form of raised teeth or scales.

Since the support sleeves are in most cases produced as turned parts, it is expe-dient for the profiles to be formed as all-round ribs.

The support sleeve should be made equally deep in the two plastic pipes to be coupled to one another. In order to ensure this and to facilitate the use, it is expe-dient if the support sleeve has an all-round collar in its middle region. This collar serves as an axial stop on introduction of the support sleeve.

In the mounting process, it is advantageous if a support sleeve is pushed by ap-proximately half its length into the free end of a first pipe to be coupled and that region of the support sleeve which projects axially beyond the first pipe is inserted into the free end of a second pipe to be coupled with the first pipe and then two clamps, according to one of the abovementioned embodiments, are pushed over the pipe ends and tightened.

Further developments of the invention are given in the figures and in the depend-ent patent claims.

The list of reference numerals is part of the disclosure.

The invention is explained in more detail by way of example with reference to fig- ures. The figures are described in relation to one another and as a whole. Identi-cal reference numerals mean identical components, and reference numerals with different indices indicate functionally identical or similar components.

Fig. 1 shows a pipe coupling having a clamp according to the invention, partly in longitudinal section, Fig. 2 shows a cross-section through the pipe coupling shown in fig. 1, along the line II -II, Fig. 3 shows the clamp band of a clamp, corresponding to fig. 2, on a larger scale, Fig. 4 shows the clamp band corresponding to fig. 3, in a perspective diagram, Fig. 5 shows a further embodiment of a clamp, having a one-part clamp band.

Fig. I shows two plastic pipes 1, 2 which are tightly coupled to one another by means of two clamp bands 3, 4 according to the invention. The clamp bands 3, 4 shown are of identical design.

As is evident from the cross-section of the clamp band 3 or 4, shown in fig. 2, the clamp band 3 or 4 has, at its ends, two loops 3a, 3b and 4a, 4b respectively, bent over towards the inside. Coupling points 3c, 3d and 4c, 4d are arranged in the region of the overlap of the loops 3a, 3b and 4a, 4b, respectively. The coupling points 3c, 3d and 4c, 4d are preferably formed without welding as press-fit/joint couplings. In technical terms, this type of coupling is also known neutrally as "clinching" or is known by the trade name "tox clinching". Here, preferably circular holes are punched out in one part and pot-Hke elevations are pushed out in the other part, which are then pressed in an interlocking manner into the holes on coupflng. This type of coupling is distinguished by a very high corrosion resis-tance compared with weld joints. The free ends 3e, 3f and 4e, 4f project beyond the coupling points 3c, 3d and 4c, 4d, respectively, by about 10% of the circum-ference, ie. by an angle of arc of about 30°. This ensures that the coupling point is substantially relieved by the contact friction between the inside of the loop 3a, 3b and 4a, 4b and the pipe I or 2 to be coupled.

Holed bolts 5 are inserted into the loops 3a, 4a, and threaded bolts 6 into the loops 3b, 4b. By means of a lock screw 7 connecting the holed bolts 5 and the threaded bolts 6, the clamp bands 3, 4 can be tightened over the circumference of the plastic pipes 1, 2. The clamp bands 3, 4 are provided in the region of the loops 3a, 3b; 4a, 4b with slots 3g, 4g which serve for the passage of the threaded shaft of the lock screw 7 or of the screw head. A gap 3h or 4h which is bridged by an inlay 9 preferably consisting of a steel band is present between the two loops 3a, 3b; 4a, 4b. The inlay 9 extends over both coupling points 3c, 3d and 4c, 4d and is preferably fastened at one end, for example by spot welding, to the clamp band 3 and 4, respectively.

As is evident in particular from the longitudinal section through the ppe coupling, shown in fig. 1, a support sleeve 8 is inserted into the free ends of the plastic pipes 1, 2. The support sleeve 8 has a plurality of functions. Thus, t firstly seals off the pipe gap between the two plastic pipes 1, 2. Moreover, the pipe sleeve prevents the plastic pipes 1, 2 from collapsing on tightening of the clamp bands 3, 4. In its cylindrical end regions, the support sleeve is provided with profiles 8a, for example ribs or the like. On tightening of the clamp bands 3, 4, these profiles 8a are pressed into the inner wall of the pipe and thus permit an axial frictional con- nection between the plastic pipes 1, 2. The support sleeve (8) shown has an all-round collar (8b) in its middle region.

In the diagram of the clamp band 3 in fig. 3, which is on a larger scae compared with fig. 2, the free ends 3e, 3f which project beyond coupling points 3c, 3d by the angle a at the circumference are clearly evident. The angle a is preferably about 300, i.e. the free ends 3e, 3f which project beyond the coupling points extend ap-proximately over 1/10 of the circumference of a circle.

As is evident in particular from the perspective diagram of a clamp band 4 in fig. 4, a plurality of coupling points 4d are arranged side by side, when viewed in the ax-ial direction, The number of coupling points 4d depends on the width of clamp band 4 or on the load occurring during operation.

The longitudinal section through a further embodiment of a clamp according to the invention, which appears in fig. 5, likewise shows two plastic pipes 11, 12 which are coupled to one another by means of a support sleeve 18 inserted into the pipe ends. A pipe butt joint 10 exists between the two plastic pipes 11, 12 arranged a distance apart. The support sleeve 18 is provided in its cylindrical end regions with profiles 18a and, in its middle region, likewise has a collar 18b which, when the support sleeve 18 is inserted into the ends of the plastic pipes 11, 12, serves as an axial stop.

In contrast to the embodiment shown in fig. 1, in which two separate clamp bands 3, 4 are tightened over the plastic pipes 1, 2, the two clamp bands together are in the form of a one-part clamp band 13 in fig. 5. The clamp band 13 has approxi-mately the same width as the total length of the support sleeve 18. Because the clamp 13 also seals the pipe butt joint 10 between the plastic pipes 11, 12 from the outside, firstly dirt is prevented from penetrating from the outside into the pipe butt joint 10 and secondly medium in the pipeline which diffuses into the pipe wall of the plastic pipes 11, 12 can emerge at the end face of the plastic pipes 11, 12.

List of reference numerals I P'astic pipe 2 P'astic pipe 3 Clamp band 3a Loop 3b Loop 3c CoupUng point 3d Coupling point 3e Free end 3f Free end 3g Slot 3h Gap 4 Clamp band 4a Loop 4b Loop 4c Coupling point 4d Coupling point 4e Free end 4f Free end 4g Sot 4h Gap 5 Hoed boot 6 Threaded bo't 7 Lock screw 8 Support sleeve 8a Profile 8b Collar 9 Inlay Pipe butt joint 11 Plastic pipe 12 Plastic pipe 13 Clamp band 18 Support s'eeve 18a Proffle 18b Coflar

Claims

Claims: 1. Clamp having an outside and an inside, in particular for frictional coupling of plastic pipes or tubes, comprising a clamp band which surrounds a pipe to be coupled over a major part of its circumference and preferably consists of sheet metal and whose end regions are in the form of loops bent over to-wards the inside of the clamp and having free ends, the free ends of the loops being connected, at at least one coupling point, to the circumference of the clamp band, wherein the free end of the loop projects beyond the cou-pling point by at least 5% of the circumference.
2. Clamp according to Claim 1, wherein the free end of the loop projects be-yond the coupling point by about 10% of the circumference.
3. Clamp according to Claim 1 or 2, wherein the coupling point is in the form of interlocking couplings.
4. Clamp according to Claim 3, wherein the coupling point is in the form of press-fit/joint couplings ("clinches").
5. Clamp according to Claim 4, wherein the press-fit/joint couplings are in the form of circular holes in the clamp band and pot-like protuberances engaging the holes in the end region of the loops in an interlocking manner.
6. Clamp according to any of Claims 3 to 5, wherein a plurality of coupling points arranged side by side in the axial direction are provided.
7. Clamp according to any of the preceding claims, wherein an inlay bridging a gap between the loops is arranged on the inside of the loops which is di-rected towards the pipes to be coupled.
8. Clamp according to Claim 7, wherein the inlay extends from the coupling point of one loop to the coupling point of the other, opposite loop.
9. Clamp according to any of the preceding claims, wherein a support sleeve is arranged on an inside of the plastic pipes or tubes to be coupled.
10. Clamp according to Claim 9, wherein the support sleeve has profiles on its outside,
11. Clamp according to Claim 10, wherein the profiles are in the form of stamped formations.
12. Clamp according to Claim 10, wherein the profiles are in the form of al'-round ribs.13 Clamp according to any of Claims 9 to 12, wherein the support sleeve has an allround collar in its middle region.14. Clamp according to any of the preceding claims, wherein the clamp band extends over a pipe butt joint and those ends of the plastic pipes which are adjacent to the pipe butt joint, 15. Method for coupling pipes using a cflamp according to any of the preceding claims, wherein a support sleeve is pushed by approximately haff its length into the free end of a first pipe to be connected and that region of the sup port sleeve which projects axially beyond the first pipe is inserted into the free end of a second pipe to be coupled to the first pipe, and then one or two clamp bands according to any of the preceding claims are pushed over the ends of the pipes and are tightened.