GB2037922A

GB2037922A - Pipe Joint Structure

Info

Publication number: GB2037922A
Application number: GB7939063A
Authority: GB
Original assignee: Hymatic Clamps International Ltd
Current assignee: Hymatic Clamps International Ltd
Priority date: 1978-11-11
Filing date: 1979-11-12
Publication date: 1980-07-16
Also published as: GB2037922B

Abstract

A joint structure between two tubes (10, 11) of an exhaust system comprises part-spherical end portions (12, 13) of the tubes sandwiched between an internal support (14) and a band (17) which embraces the end portions. The band can be tightened to secure the tubes rigidly to one another in a selected angular relation. <IMAGE>

Description

SPECIFICATION Joint Structure and Internal Combustion Engine with Exhaust System Comprising the Joint Structure Description of Invention This invention relates to a joint structure primarily for use in an exhaust system associated with an internal combustion engine.

In U.S. Patent 2,323,823, there is disclosed a joint structure for use in the exhaust system of an aircraft engine. The structure is intended to provide a gas-tight connection between two tubes of the exhaust system whilst freely permitting relative angular movement of the tubes. The tubes are formed with adjacent end portions having part-spherical surfaces. A spacer is disposed inside the end portions of the tubes to limit mutual approach of the tubes and a band embraces external surfaces of the end portions to maintain them in the required relative position, that is as close together as is permitted by the spacer.

In the joint structure disclosed in U.S. Patent 2,323,823, neither of the end portions of the tubes is sandwiched between the spacer and the band. The spacer engages each end portion in an annular region and the band engages the end portions in respective further regions which lie between the annular regions of contact between the spacer and tubes. Thus, the spacer does not provide direct support for those parts of the tubes which are directly engaged by the band. The band is tightened sufficiently to prevent excessive escape of gasses through the joint structure but not sufficiently to make the joint structure rigid.

The tubes remain free to undergo reiativeengular movement and are properly supported by means other than the joint structure.

The exhaust systems of motor road vehicles generally comprise a plurality of tubes joined endto-end to convey exhaust gasses from the engine to the rear of the vehicle. The number of positions at which the exhaust system is supported from a body of the vehicle is small. Brackets which connect the exhaust system with the vehicle body provide paths through which noise and other vibration can be transmitted to the body.

Furthermore, by reducing the number of mounting brackets, the cost of the exhaust system and of fitting the exhaust system is reduced.

Accordingly, in the exhaust system of a motor road vehicle, the joints between the tubes are required to be rigid so that the tubes can provide mutual support for one another. The joint structure disclosed in the aforesaid U.S. Patent is unsuitable for this purpose. If the band could be tightened sufficiently to make the structure rigid, the band could not conveniently be secured in its tightly embracing relation with the tubes.

Furthermore, tightening of the band sufficiently to render the structure rigid would cause deformation of the end portions of the tubes where these are not directly supported internally.

According to a first aspect of the present invention, there is provided a structure comprising two tubes, a band embracing respective adjacent end portions of said tubes and a support engaged with internal surfaces of the end portions, wherein the band has two terminal portions which are adjacent to each other and means for applying force to said terminal portions to contract the band and hold same contracted, each of said internal surfaces of the end portions is of partspherical form, the support has complimentary part-spherical surfaces engaged with the internal surfaces of the end portions, the external surface of each end portion is also part-spherical, is concentric with the internal surface of the end portion and is engaged by a complimentary partspherical internal surface of the band, whereby each end portion is sandwiched between the band and the support and the support limits radially inward deformation of each end portion when the band is tightened.

By a band, we mean an elongate element which extends from a selected position around the tubes to or almost to the selected position and has a length (measured circumferentially of the tubes) and a width (measured longitudinally of the tubes) which are both substantially larger than the radial thickness of the element.

The band is preferably flexible, relative to the internal support. The band may have a radial thickness which is substantially less than the radial thickness of the support.

According to a second aspect of the invention, there is provided the combination of an internal combustion engine and an exhaust system which includes a structure according to the first aspect of the invention, wherein the tubes are arranged to convey hot exhaust gases discharged from the engine.

An example of an embodiment of the invention will now be described with reference to the accompanying drawings wherein.~ Figure 1 shows an end elevation of a clamp comprised by a joint structure; Figure 2 shows a plan view of the clamp; and Figure 3 shows on an enlarged scale a partial cross-section of the joint structure, the crosssection being in the plane Ill-Ill indicated in Figure 1.

The joint structure illustrated in Figure 3 comprises two tubes, 10 and 1 1 respectively which preferably have circular transverse crosssections and the same diameter. The tube 10 has an outwardly flared end portion 12 which presents part-spherical, concentric internal and external surfaces. The diameter of the tube increases gradually along the end portion 10 from its junction with the cylindrical portion of the tube towards the end of the tube. The tube 11 has a similar end portion 13 situated near to the end portion 12 but separated therefrom by a gap. The external surfaces of the end portions 1 2 and 1 3 have the same radius of curvature and, preferably, the same centre of curvature.

The joint structure further comprises a support for the end portions 12 and 13, this support being in the form of a ring 14 having a radially outwardly projecting rib 15 which lies in the gap between the end portions 12 and 13. On each side of the rib 1 5, the ring presents a partspherical surface having substantially the same radius of curvature as the internal surfaces of the end portions 12 and 13. These surfaces of the ring are engaged with the end portions to support same against inward collapse.

The tubes 10 and 1 1 are joined together by a clamp 16 which is also shown in Figures 1 and 2.

The clamp comprises a generally annular band 17 having terminal portions which are adjacent to each other and are spaced apart by a gap 18. On each of the terminal portions of the band 1 7, there is secured by welding an abutment in the form of a respective housing 19 which projects radially outwardly from the band and defines an aperture to receive an adjustable fastener in the form of a bolt 20. By means of the bolt, force can be applied to the terminal portions of the band 1 7 to contract the band. In the assembled joint structure, the bolt maintains the band in a contracted condition.

The band 17 has an internal surface which is substantially part-spherical and has the same radius of curvature as the external surfaces of the end portions 12 and 13. The band has a width, as measured along the axes of the tubes 10 and 1 1, sufficient to enable the band to overlap with both of the end portions 12 and 13.

Prior to assembly of the joint structure, the bolt 20 is slack and the radius of the band 17 is somewhat greater than the radius of curvature of the external surfaces of the end portions 12 and 13. The ring 14 and the clamp 16 are assembled with one of these end portions and then the other end portion is introduced between the ring and the clamp. Both of the end portions 1 2 and 1 3 are brought into abutting relation with the rib 15 at at least one position around the axis of the ring. The bolt 20 is then tightened to reduce the gap 18 and draw the band 17 into tightly embracing relation with the end portions 12 and 13. This may close the gap 18. Alternatively, the gap may still be present when the bolt has been tightened to the required degree.

The band 17 is sufficiently flexible to enable it to be drawn readily into tightly embracing relation with the end portions 12 and 13. The support 14 is relatively inflexible and therefore provides sufficiently firm support for the end portions of the tubes to limit radially inwardly deformation of these when the band is tightened. As can be seen clearly in Figure 3, the radial thickness of the band 17 is substantially less than that of the support 14. The support is further stiffened against radial deformation by the presence of the rib 1 5.

The rib 1 5 enables the position of the support 14 inside the tubes to be controlled during assembly of the joint so that the areas of contact between the support and end portions 12 and 13 of the tubes lie directly radially inwardly of the areas of contact between the band 17 and the end portions 12 and 13. The end portions are thus sandwiched between the band and the support.

As illustrated in Figure 3, the respective axes 21 and 22 of the tubes 10 and 1 1 may be inclined to each other. In this case, at the side of the joint structure at which the end portions 12 and 13 engage the rib 15, the band 17 extends almost from the cylindrical portion of the tube 10 to the cylindrical portion of the tube 11. It will be understood that at the opposite side of the structure (not illustrated) the edges of the band 1 7 will be spaced somewhat further from the cylindrical portions of the tubes.

The joint structure forms a part of an exhaust system associated with an internal combustion engine of a road vehicle. The exhaust system further includes one or more xpansion chambers (not shown) and hot exhaust gasses flow from the engine through the expansion chambers and the tubes 10 and 1 1 to the rear of the vehicle where the gasses are discharged into the atmosphere.

The clamp 16 remains slack whilst the components of the exhaust system are assembled together on the vehicle. Whilst the clamp is slack, the joint structure is not rigid and the tubes can be adjusted to the positions which they are required to occupy. The band 17 is then tightened until the joint structure becomes rigid and relative angular movement of the tubes is prevented. The metal-to-metal contact at the part-spherical interfaces is generally sufficient to prevent leakage of exhaust gasses from the joint structure. However to eliminate any slight leakage which may occur, a sealant may be applied to one or more of the mating surfaces of the joint structure prior to tightening of the clamp.

If the tubes 10 and 1 1 are in coaxial relation, the band 17 is spaced somewhat from the cylindrical portion of each of the tubes 10 and 1 1 and thus overlaps with a part only of each of the end portions 12 and 13. In a case where the radius of curvature of the external surfaces of the end portions 12 and 13 is 31.8 millimetre, the developed width of the band 17 is typically 28.6 millimetre. These dimensions are suitable in a structure for joining tubes having an outside diameter of 53.8 millimetres.

Claims

1. A structure comprising two tubes, a band embracing respective adjacent end portions of the tubes and a support engaged with internal surfaces of the end portions, wherein the band has two terminal portions which are adjacent to each other and means for applying force to said terminal portions to contract the band and hold same contracted, each of said internal surfaces of the end portions is of part-sphericalform, the support has complimentary part-spherical surfaces engaged with the internal surfaces of the end portions, the external surface of each end portion is also part-spherical, is concentric with the internal surface of the end portion and is engaged by a complimentary part-spherical internal surface of the band, whereby each end portion is sandwiched between the band and the support and the support limits radially inward deformation of each end portion when the band is tightened.

2.A structure according to Claim 1 wherein said end portions of the tubes are spaced apart and there is on the support a radially projecting formation disposed in the space between the ends of the tubes.

3. A structure according to Claim 1 or Claim 2 wherein the band is flexible, relative to the support.

4. A structure according to Claim 1 or Claim 2 wherein the radial thickness of the band is less than the radial thickness of the support.

5. A structure according to any preceding claim wherein all of said part-spherical surfaces have a common centre of curvature.

6. A structure according to any preceding claim wherein said means for applying force to said terminal portions includes two abutments secured one on each terminal portion of the band and an adjustable fastener engaged with said abutments.

7. A structure according to Claim 6 wherein each abutment is in the form of a hollow housing and the fastener is a bolt which extends through the housings.

8. A structure according to any preceding claim wherein there is a gap between said terminal portions of the band, at least prior to tightening of the band on the end portions of the tubes.

9. In combination, an internal combustion engine and an exhaust system which includes a joint structure according to any preceding claim, wherein said tubes of the joint structure are arranged to convey hot exhaust gasses discharged from the engine.

10. In or for an exhaust system of an internal combustion engine, a joint structure substantially as herein described with reference to and as shown in the accompanying drawings.