GB2238838A - Pipe coupling - Google Patents

Abstract

A coupling for connecting two pipes 10, 12 in an engine exhaust system comprises a rigid intermediate tube 14 to be inserted between the two pipes 10, 12 and having one pant of a flexible ball joint at each end for coupling the intermediate tube to the respective pipes, the pivotal centres of the two ball joints 16 and 18, when assembled, being spaced from one another. <IMAGE>

Description

PIPE COUPLING The present invention relates to a pipe coupling for use in vehicle exhaust systems and in particular is intended for connecting a catalytic converter to an engine down pipe.

Flexible ball joints have previously been proposed for connecting two pipes in an exhaust system in which a convex part-spherical sealing collar is compressed by a spring between a flange on one pipe and a concave partspherical seat on the other pipe. The collar is formed, for example of a wire mesh with a copper cladding.

The joint is not locked tight and the pipes are permitted a small degree of pivotal movement relative to one another without leakage. Though such a ball joint permits pivoting of one pipe relative to the other, it does not accommodate forces tending to cause axial misalignment of the pipes.

To accommodate such axial misalignment, there have been proposed constructions of flexible exhaust piping. One such construction employs convoluted stainless steel tubing but this is not sufficiently flexible in practice and also disturbs the gas flow conditions in the exhaust system. An alternative construction relies on a braided tube and though this is more flexible it is more costly to manufacture.

With a view to mitigating the foregoing disadvantages, the present invention provides a coupling for connecting two pipes in an engine exhaust system which comprises a rigid intermediate tube to be inserted between the two pipes and having one part of a flexible ball joint at each end for coupling the intermediate tube to the respective pipes, the pivotal centres of the two ball joints, when assembled, being spaced from one another.

The part-spherical seats of the ball joints may be formed either on the pipes to be connected to one another or on the intermediate tube, the flange against which the sealing collar may be compressed being formed in each case on the other part of the ball joint.

According to a second aspect of the invention, there is provided an exhaust system including a down pipe connected to a catalytic converter by means of a coupling which comprises a rigid intermediate tube connected to the down pipe and the catalytic converter by means of respective flexible ball joints having pivotal centres spaced from one another.

By using two ball joints in this manner, it is possible to accommodate axial misalignment between the pipes without resorting to flexible tubing.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a section through a coupling in accordance with a first embodiment of the invention, and Figure 2 is a similar section through an alternative embodiment of the invention.

In Figure 1, the lower end 10 of the down pipe of an engine is to be connected to the section of pipe designated 12, which is the inlet pipe of a catalytic converter (not shown). During use, engine movement can cause the axes of the pipes 10 and 12 to tilt relative to one another and can also cause the axes to be offset from one another. In order to avoid undue stresses on the pipes, the coupling used between them should remain flexible during use and accommodate such misalignment.

Conventionally, the pipes 10 and 12 are joined to one another either through a ball joint or a through short length of flexible tubing. As described earlier, a single ball joint cannot accommodate offset between the axes of the pipes and in only tolerant of tilting.

Flexible tubing, on the other hand, is expensive.

In the present invention, a short length of rigid pipe 14 is used to connect the pipes 10 and 12. At each end, the pipe 14 is connected by a flexible ball joint, 16 and 18 respectively, to the pipes 10 and 12. The ball joints are herein termed "flexible" because they can bend even after installation to distinguish them from joints which are locked tight when in use and serve only to provide alignment tolerance during installation.

Each flexible ball joint comprises a flared seat on one pipe, a flange on the other pipe and a collar interposed between the flange and the seat. The two pipes are urged towards one another by springs, applying a predetermined tension across the joint, but the tension, while sufficient to maintain a gas tight seal, does not inhibit flexing of the ball joint. Typically, the collar is formed of a wire mesh coated with copper cladding, so that the collar has a limited degree of compressibility to adapt to the shape of the abutment surfaces on the flange and on the flared seat.

In the case of the embodiment shown in Figure 1, the flared seats 16a and 18a are formed on the pipes 10 and 12 while the flanges 16b and 18b are formed on the intermediate tube 14. The embodiment of Figure 2, on the other hand, has flared seats 16a' and 18a' on the intermediate tube 14' and flanges 16b' and 18b' on the pipes 10' and 12'. The collars are designated 16c and 18c in both Figures.

In both embodiments, the arrangement for applying a tensioning force to the two flexible ball joints is common to both joints. In the case of the embodiment in Figure 1, clamping rings 26 and 28 are fitted to the pipes 10 and 12 behind the flared seats 16a and 18a through which clamping bolts 20 are passed. The clamping bolts illustrated in the drawings are purposely designed, rapid assembly, bolts which are the subject of a separate application for a patent filed on the same day as the present application.

The head 34 of the bolt 30 in Figure 1 can be slid over the shank 32 of the bolt and is held in place by a pin 36, which can be a split pin or a rolled steel pin. The shank 32 has a circumferential groove 38 for receiving a U-shaped retainer plate 42 which is at a fixed distance from the threaded end 40 of the shank. A tensioning spring 44 is fitted over the shank and is compressed between a washer and nut 46 fitted to the threaded end of the bolt 30 and the clamping ring 28.

The catalytic converter, in the case of the embodiment of Figure 1, is supplied complete with the intermediate tube 14, and the clamping bolts 30. At least two clamping bolts 30 are required but only one is shown in the drawings. The flange 16b of one of the ball joints has ear pieces through which the bolts 30 pass, with clearance and tube 14 is held in place by the tension of the springs 44 acting through the plates 42.

During installation, the ball joint 16 is assembled and the ends of the shanks 32 are fed through the holes in the clamping collar. The heads 34 are then slipped onto the bolts 30 and the pins 36 are inserted to lock the heads permanently in position. Once the heads 34 are in position, the plates 42 are pulled out of the grooves 38 thus allowing the spring 44 to expand and to apply a preset tension across both the ball joints 16 and 18.

The nut 46 is supplied fully tightened and is provided mainly for maintenance purposes. The nut 46 can be loosened to separate the joints and if then re-tightened fully, the tension in the spring 44 will be not be changed.

Some movement of the bolt needs to occur to accommodate flexing in the exhaust system and to permit such movement, the bolts must pass with clearance through the holes in the clamping rings 26, 28 and in the flange 16.

It further assists movement to provided curved seating surfaces on the heads 34 of the bolts 30 and on the clamping ring 26.

In order to accommodate both axial offset and flexing, the rolling centres of the two ball joints must be spaced apart from one another. This requirement can be met if both ball joints are concave towards each other, as in Figure 1, if they are both concave in the same direction, or if they are convex towards each other, as in Figure 2.

In the case of the embodiment of Figure 2, there are fewer components required as there is no need for clamping rings. A flange may if desired, be provided so that the intermediate tube may be supplied attached to the catalytic converter and held loosely in place during use. Alternatively, however, the groove 38' may be formed adjacent the spring 44 as shown in Figure 2. The embodiment of Figure 2 is sufficiently similar to that of Figure 1 not to require further explanation and to assist comparison the same reference numerals have been used in both drawings to designate corresponding components but a prime has been added to the numerals in the case of the second embodiment.

Claims (5)

1. A coupling for connecting two pipes in an engine exhaust system which comprises a rigid intermediate tube to be inserted between the two pipes and having one part of a flexible ball joint at each end for coupling the intermediate tube to the respective pipes, the pivotal centres of the two ball joints, when assembled, being spaced from one another.

2. A coupling as claimed in claim 1, wherein the part-spherical seats of the ball joints are formed on the pipes to be connected to one another, and wherein the flanges against which the sealing collars may be compressed are formed on the intermediate tube.

3. An exhaust system including a down pipe connected to a catalytic converter by means of a coupling which comprises a rigid intermediate tube connected to the down pipe and the catalytic converter by means of respective flexible ball joints having pivotal centres spaced from one another.

4. An exhaust system as claimed in claim 3, wherein a common spring tensioning means is provided to maintain a compression force across both the ball joints.

5. An exhaust system having a coupling constructed substantially as herein described with reference to and as illustrated in the accompanying drawings.