Prior Art

[0001] V-clamps are used for coupling circular flanges formed at the ends of two pipes to be interconnected.

[0002] US 2,941 ,823 discloses such a clamp which includes a clamping band and two separate semicircular segments of generally V-shape cross-section surrounded by the clamping band. The ends of the clamping band are formed with loops which surround a pair of trunnions through which a tightening screw extends.

[0003] When the clamp is tightened, friction between the trunnions and the band loops tends to bend the screw as the trunnions move toward the centre of the clamp.

[0004] Moreover, clamping forces exerted on the pipe connection are unevenly distributed along the circumference, with the highest force occurring underneath the screw and the lowest force at the opposite location. Summary of the Invention

[0005] It is an object of the present invention to provide a V-clamp which avoids the above deficiencies. To this end, the V-clamp of the invention comprises at least one segment of generally V-shape cross-section adapted to surround said pipe flanges, a clamping band surrounding said at least one segment, loops provided at both ends of the clamping band, a pair of trunnions surrounded by said loops, and a tightening screw extending through said trunnions. The at least one segment of generally V-shape cross-section has two inclined surfaces configured to interact with the flanges such that a radial force exercised by the clamping band is at least partially transformed into an axial force pressing the flanges against each other.

[0006] According to one aspect of the invention, the V-clamp further comprises a supporting structure provided at an end portion of the at least one segment at a position underneath the screw, wherein the supporting structure is configured to take up a part of the radial force via a surface other than the inclined surfaces when the radial force exceeds a threshold value. The part of the radial force bearing on the surface other than the inclined surfaces does not contribute to a further elastic deformation of the end portion of the segment concerned. Accordingly, the deformation and hence the bending stress acting on the screw is reduced. Moreover, an increase of a static friction due to increased deformation is avoided. Consequently, the transmission of tension forces to parts if the clamping band remote from the screw and the trunnions can be improved as compared to conventional devices.

[0007] Preferably, the V-clamp includes a plurality of separate segments equally spaced circumferentially, most preferably three segments.

[0008] The inventors further propose that the supporting structure includes at least one spacer disposed between at least one end of the at least one segment and the pipe flanges. A simple spacer can reliably stop further deformation and the threshold can be easily set by adapting the radial thickness of the spacer. The number of additional parts can be kept small if the supporting structure includes a single spacer element. In other embodiments of the invention, the spacer includes two separate spacer elements each between radially outer surfaces of the pipe flanges and an end of the at least one segment.

[0009] In further embodiments of the invention, the supporting structure includes a notch formed in a connecting portion between the two inclined surfaces of the least one segment of generally V-shape cross-section. This embodiment is particularly advantageous as it avoids additional components that might result in an increased complexity of the assembly.

Drawings

[000 0] Embodiments of the invention will be described below in more detail with reference to the drawings, in which:

Fig. 1 is a perspective view of a pipe connection with a V-clamp according to a first embodiment of the invention;

Fig. 2 is a radial section of the pipe connection of Fig. 1 ;

Fig. 3 is a detail of a view of an axial section of the pipe connection of Fig.

1 and 2 in a configuration with low radial load;

Fig. 4 is the view of the pipe connection of Fig. 3 in a tightened condition with high radial load;

Fig. 5 is a detail of an axial section of a pipe connection according to a second embodiment of the invention with a supporting structure formed as a notch; and Fig. 6 is a radial section of the pipe connection according to a third embodiment of the invention with a supporting structure formed as a single spacer.

Embodiments

[0001 1] Fig. 1 is a perspective view a pipe connection with a V-clamp according to a first embodiment of the invention. The V-clamp illustrated in Figs 1 to 3 includes three segments 10, 11 and 12 of generally V-shape cross-section adapted to surround the adjacent flanges 13, 14 (Fig. 2) of two pipes 24, 27 to be coupled by the clamp. The segments 10-12 are equally spaced around the pipe flanges 13, 14 and are surrounded by a clamping band 15 that is formed at both ends with loops 16, 17 which receive a pair of trunnions 18, 19. A tightening screw 20 extends through each loop 16, 17. In the non-tightened condition shown in Fig. 1 , the segments 10-12 are mutually spaced by gaps 21 , 22, 23.

[00012] As illustrated in Fig. 2, the clamping band surrounds a major part of more than 80 or 90% of the circumference of the pipe flanges 13, 14. When the clamp is tightened by means of the screw 20, the gaps 21 ...23 are reduced and the segments 10 - 12 are pressed radially onto the flanges 13, 14 to clamp the two pipes 24, 25 together. A radial force is exerted onto the segments 10 - 12.

[00013] As illustrated in Fig. 3, the segments 1 1 - 13 include two inclined inner surfaces bearing on corresponding lateral surfaces of the flanges 13, 14 which are inclined at an angle similar to that of the inner surfaces of the segments 10 -12, respectively. A gasket 28 is arranged between the opposing axial end faces of the flanges 13, 14. Due to the inclination, a part of the radial force exercised by the clamping band is at least partially transformed into an axial force pressing the flanges 13, 14 against each other and compressing the gasket 28.

[00014] Returning to Fig. 2, the radial clamping force transmitted by the clamping band 15 is not homogeneous over the circumference of the clamp. Due to geometrical constraints, the clamping force shows a maximum underneath the trunnions 18, 19. Moreover, inevitable static friction results in a decrease of the radial clamping force with increasing distance to the screw 20 and the trunnions 18, 19. Moreover, the elasticity of the system, i.e. the ratio of a radial movement of a certain point on one of the segments 10 - 12 and the radial force exerted on that point, is not homogeneous over the length of the segments 10 - 12 but rather increases towards the ends thereof.

[00015] The trunnions 18, 19 are placed in proximity to the ends of the segments 10, 12 such that the region of maximum force coincides with a region of maximum elasticity. Consequently, the deformation of the segments 10, 12 is particularly large in the end portions of the segments 10, 12 underneath the trunnions. The latter holds for conventional clamps, whereas it holds for clamps according to the invention only as long as the radial clamping forces do not exceed a threshold value, as described in further detail below.

[00016] The coincidence of high elasticity and high force at the end portions of the segments 10, 12 underneath the trunnions 18, 19 leads to relatively large bending deformations in these end portions of the segments 10, 12. This has various problematic consequences.

[00017] Firstly, the static friction between the clamping band 15 and the outer surfaces of the segments 10, 12 increases with increasing curvature of the outer surfaces. Increased static friction impairs the transmission of the clamping force to portions remote from the screw 20, i.e. to the 6-o-clock position at the bottom of Fig. 2.

[00018] Secondly, the bending deformation of the end portions of the segments 10, 12 results in an inward swivelling motion of the loops 16, 17. As a result of this swivelling motion, a static friction between the outer surfaces of the trunnions 18, 19 and the inner surfaces of the loops 16, 17 transmits a torque onto the trunnions, which in turn leads to a bending stress of the screw 20. The amount of bending depends on the angle of the inward swivelling motion of the loops 16, 17, which in turn depends on the amount of radial deformation of the end portion of the segments 10, 12. The inventors have found that this bending stress is one important reason for failure of conventional V-clamps.

[00019] According to the invention, the clamp is provided with a supporting structure. In the embodiment of Figs. 1 and 3, the supporting structure is comprised of two spacers 25a, 25b at end portions the two segments 10, 12 arranged underneath the screw 20.

[00020] In the range of small clamping forces illustrated in Fig. 3, the spacers 25a, 25b do not influence the distribution of the clamping forces at all. The radial thickness of the spacers 25a, 25b is smaller than the radial width of a gap between the radially outer rims of the flanges 13, 14 and the inner bottom surface 29 of the segments 10 - 12 on the unloaded state. However, with increasing clamping force, the width of the gap between the radially outer rims of the flanges 13, 14 and the inner bottom surface 29 decreases until it coincides with the thickness of the spacers 25a, 25b, which then bottoms down onto the flanges 13, 14 and stops any further deformation of the segment 10.

[00021] The force required for the spacers 25a, 25b to abut both the flanges 13, 14 and the bottom surface 29 is defined as the threshold force and can be suitably set by varying the thickness of the spacers 25a, 25b and the elasticity of the material used for the segments 10 - 12. The threshold force is set such that it is reached at a value of the tightening torque of the screw 20 which is smaller than the target tightening torque.

[00022] A further increase in the radial clamping force beyond the threshold value acting on the segment 10 in the high-force configuration of Fig. 4 would be directly taken up by the rims of the flanges 13, 14 via the bottom surface 29 of the segments 10, 12 and therefore does not result in a further increase of the axial force clamping the two pipes 24, 25 together. The supporting structure formed by the spacers 25a, 25b therefore takes up a part of the radial force via a surface 29 other than the inclined surfaces 30, 31 when the radial force exceeds the threshold value.

[00023] As described above, the supporting structure according to the invention limits the bending deformation of the end portions of the segments 10, 12 arranged underneath the screw 20 and the trunnions 18, 19. Consequently, the problematic consequences of an excessive bending deformation, i.e. the reduced force transmission to a portion of the clamping band 15 remote from the screw 20 and the bending stress acting on the screw 20, can be limited or reduced as well. The improved force transmission results in a higher clamping force and consequently better sealing properties in the portions remote from the screw 20, for a given torque of the screw. As compared to conventional V-clamps, the presence of the supporting structure reduces the axial clamping force immediately underneath the trunnions 18, 19. However, the threshold force can be set such that it is still sufficient. [00024] Figures 5 and 6 show further embodiments of the invention. The following description is limited to differences from the embodiment of Figs. 1 - 4, whereas the reader is referred to the above description of the embodiment of Figs. 1 - 4 for features which are unchanged. The same reference numbers are used for features with the same or similar functions in order to highlight the similarities.

[00025] In the embodiment of Fig. 5, the supporting structure is formed as a protrusion 25c on the bottom surface 29 in end portions of the segments 10, 12 arranged underneath the trunnions 18, 19. The protrusion 25c in the inner surface 29 is the result of a notch embossed in an outer surface of the segments 10 - 12. The radial thickness of the protrusion 25c, by which it protrudes over the bottom surface 29, is set such that it bottoms down onto the radially outer rims of the flanges 13, 14 when the clamping force reaches the threshold value. For the ease of manufacturing and assembly, protrusions 25c may be provided at both end portions of all segments even if those protrusions 25c which are not placed underneath the trunnions 18, 19 will never abut to the flanges 13, 14 and therefore will not have any function.

[00026] In the embodiment of Fig. 6, the supporting structure is formed as a single spacer member 25, which covers the gap 21 and is fitted under the end portions of the segments 10, 12.

[00027] The invention is not limited to the specific combination of features described above and disclosed in the accompanying drawings. The skilled person will be able to find other combinations or sub-combinations of features in order to adapt the invention as defined in the claims to the intended use. In particular, it is possible to provide supporting structures combining notches as described in relation to Fig. 5 with spacers as disclosed in the embodiments of Figs. 1 - 4 and 6.

Reference Numbers

10...12 segments

13, 14 flanges

15 clamping band

16, 17 loops

18, 19 trunnions

20 tightening screw

21...23 gaps

25a, 25b spacers

25c protrusion

26, 27 pipes

28 gasket

29 bottom surface

30 inclined surface

31 inclined surface