GB2238097A

GB2238097A - Clamping bolts

Info

Publication number: GB2238097A
Application number: GB8925843A
Authority: GB
Inventors: Michael John Southwell; Keith Ransom
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1989-11-15
Filing date: 1989-11-15
Publication date: 1991-05-22
Also published as: GB8925843D0

Abstract

A clamping bolt is described having a shank 132, and a threaded end 140 for receiving a nut 146. The end of the shank remote from the threaded end 140 has a cross bore for receiving a pin 136 to enable a head 134 to be retained on the shank 132, and a releasable temporary retainer 142 is engageable in a groove 138 in the shank at a preset distance from the threaded end 140 of the shank 132 for enabling a spring 144 fitted over the shank to be tensioned prior to fitting of the head onto to the shank of the bolt. Alternatively, the groove 138 may be replaced by a shoulder on the shank 132. The temporary retainer 142 holds the bolt in position with the spring 144 compressed while the head 134 is secured to the shank 132 by means of the pin 136, and then the temporary retainer 142 is removed. Two or more bolts are employed around the clamping rings 126, 128 to hold the flared ends 116a, 116a of the pipes 110, 112 to the ball joint parts 116c, 118c. <IMAGE>

Description

CLAMPING BOLTS The present invention relates to clamping bolts for connecting together two components and applying a predetermined clamping force between the two components.

One application for the clamping bolts of the invention is in the assembly of pipe joints in an exhaust system of a motor vehicle where some movement is to be permitted between the two pipes. For example, flexible ball joints are known in which a collar made of a wire mesh coated with a copper cladding must be retained between a flange on one pipe and a part-spherical seat on the other by the use of a spring clamping device.

The present invention seeks to provide a clamping bolt suitable for use in such an application which simplifies assembly.

According to the present invention, there is provided a clamping bolt having a shank, and a threaded end for receiving a nut, wherein the end of the shank remote from the threaded end has a cross bore for receiving a pin to enable a head to be retained on the shank, and in that releasable abutment means are formed on the shank at a preset distance from the threaded end of the shank for enabling a spring fitted over the shank to be tensioned prior to fitting of the head onto to the shank of the bolt.

In use, prior to fitting of the head to the shank, a spring can be fited over the shank from the head end of the bolt and, after the spring has been compressed, the releasable abutment means may be used to retain the spring in compression without fitting the head onto the shank.

Assembly of the clamping bolt involves no more than slipping the head onto the shank, securing the head in position on the shank by the insertion of a pin, and releasing the abutment means.

Conveniently, the releasable abutment means may comprise a circumferential groove in the shank and a removable Ushaped retainer plate which may be fitted into the groove to act as an abutment plate.

The "head" of the bolt may, in practice, form part of one of the components to be clamped together. For example, to fit a down pipe onto an engine manifold, the manifold may have a bore for receiving the end of the shank and a cross bore may be formed in the manifold for receiving a pin to hold the end of the clamping bolt after it has been passed through a flange on the down pipe.

Once the head has been fitted to the shank, it is not intended that it should be removed but it can serve to prevent the shank from rotating so that a nut fitted to the threaded end of the shank may be unscrewed.

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 which uses a clamping bolt of the invention, and Figure 2 is a section through the coupling between the manifold and the down pipe of an engine which employs an alternative clamping bolt of the invention.

In Figure 1, the lower end 110 of a down pipe of an engine is to be connected to the section of pipe designated 112, which is the inlet pipe of a catalytic converter (not shown). During use, engine movement can cause the axes of the pipes 110 and 112 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 110 and 112 are joined to one another either through a ball joint or a through short length of flexible tubing. 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.

The coupling shown in Figure 1 is described and claimed in a copending Patent Application 89 25T 1,2 filed on the same day as the present application which uses a clamping bolt of the present invention. A short length of rigid pipe 114 is used to connect the pipes 110 and 112. At each end, the pipe 114 is connected by a flexible ball joint, 116 and 118 respectively, to the pipes 110 and 112. 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.

Clamping rings 126 and 128 are fitted to the pipes 110 and 112 behind the flared seats 116a and 118a through which clamping bolts 120 are passed.

The head 134 of the bolt 130 can be slid over the shank 132 of the bolt and is held in place by a pin 136, which can be a split pin or a rolled steel pin. The shank 132 has a circumferential groove 138 for receiving a Ushaped retainer plate 142 which is at a fixed distance from the threaded end 140 of the shank. A tensioning spring 144 is fitted over the shank and is compressed between a washer and nut 146 fitted to the threaded end of the bolt 130 and the clamping ring 128.

The catalytic converter is supplied complete with the intermediate tube 114, and the clamping bolts 130. At least two clamping bolts 130 are required but only one is shown in the drawings. The flange 116b of one of the ball joints has ear pieces through which the bolts 130 pass, with clearance and tube 114 is held in place by the tension of the springs 144 acting through the plates 142.

During installation, the ball joint 116 is assembled and the ends of the shanks 132 are fed through the holes in the clamping collar. The heads 134 are then slipped onto the bolts 130 and the pins 136 are inserted to lock the heads permanently in position. Once the heads 134 are in position, the plates 142 are pulled out of the grooves 138 thus allowing the spring 144 to expand and to apply a preset tension across both the ball joints 116 and 118.

The nut 146 is supplied fully tightened and is provided mainly for maintenance purposes. The nut 146 can be loosened to separate the joints and if then re-tightened fully, the tension in the spring 44 will 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 126, 128 and in the flange 116. It further assists movement to provided curved seating surfaces on the heads 134 of the bolts 130 and on the clamping ring 126.

In Figure 2, an exhaust manifold 10 is joined to a pair of down pipe conduits 12a and 12 by a flexible ball joint sealed by a collar 14. The two conduits 12a and 12b are brought together at their upper end within a stainless steel attachment 16. The attachment 16 has two sockets for receiving the conduits 12a and 12b which are D-shaped when view in plan and arranged back to back to define a full circle with a dividing wall 16c extending along a diameter.

The attachment 16 also has a flange 16d formed with holes for receiving clamping bolts 20 of the present invention which hold the down pipe conduits 12a and 12b against the exhaust manifold 10.

The lower end of the manifold 10 when viewed from the direction of the down pipe is likewise divided into two by a diametrically extending dividing wall 10a aligned with the wall 16c of the attachment 16 and spaced from it by only a small clearance.

In the arrangement shown in Figure 2, which forms the subject of a separate Patent Application (Agent's reference P/2178) filed on the same day as the present application, a single flexible ball joint secures both down pipe conduits 12a and 12b to the manifold 10. To this end, the manifold 10 has at its lower end a shoulder lOb against which there is seated the collar 14. The latter is formed of a slightly compressible material, preferably a wire mesh clad with a layer of copper. The collar 14 is compressed between the shoulder on the exhaust manifold and a part spherical seat 16a defined by the attachment 16 and maintains a gas tight seal while permitting the down pipe conduits 12a and 12b to move relative to the exhaust manifold 10.

The attachment 16 and the manifold 10 are not firmly clamped together but resiliently held against one another by means of springs 24 fitted around the two clamping bolts 20. Each clamping bolt 20 has an end 20a which can be received in a blind bore 22 in the manifold. A steel pin 24 traverses the blind bore 22 and a through cross bore 20d in the end 20a to prevent withdrawal of the end 20a from the blind bore 22. In this way, the manifold itself acts as the head of the clamping bolt 20 which is fixed to the shank by the pins 24. The pins 24 also in this case define a pivot axis about which the attachment 16 may rock relative to the manifold. The aligned axes of the two pins 24 are arranged to lie on a central axis of the part spherical surface 16a at right angles to the partition walls 10a and 16c.

To assemble the flexible ball joint, the bolts 20 and springs 24 are pre-assembled on the attachment flange 16d and the springs are held compressed by means of Ushaped clamping plates (not shown) engaging between the flanges 16d and the ends 20a of the clamping bolts 20.

After the ends 20a have been retained in the manifold by insertion of the pins 24, the clamping plates can be withdrawn, leaving the springs correctly tensioned. The nut 20b can later be unscrewed for servicing.

Claims

1. A clamping bolt having a shank, and a threaded end for receiving a nut, wherein the end of the shank remote from the threaded end has a cross bore for receiving a pin to enable a head to be retained on the shank, and in that releasable abutment means are formed on the shank at a preset distance from the threaded end of the shank for enabling a spring fitted over the shank to be tensioned prior to fitting of the head onto to the shank of the bolt.

2. A clamping bolt as claimed in Claim 1, wherein the releasable abutment means comprises a circumferential groove in the shank and a removable U-shaped retainer plate capable of being fitted into the groove to act as an abutment plate.

3. A clamping bolt constructed, arranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.