GB2255611A - Composite arm and clamp assembly - Google Patents

Abstract

A composite arm such a radius arm (14) for a motor vehicle axle is secured to a clamp (17) which comprises U-section upper and lower clamp members (22 and 21). During assembly an external compressive load is applied to the clamp members to generate a clamping load on the arm. Adjacent flanges are secured together by rivets (35) whilst the compressive load is maintained to prevent lateral movement between adjacent flanges and retain the clamping loads. A sleeve (31) of resilient plastics may be interposed between the clamp members (22, 21) and the arm (14). <IMAGE>

Description

A COMPOSITE ARM AND CLAMP ASSEMBLY AND A METHOD OF ASSEMBLING SAME The invention relates to a composite arm and clamp assembly and a method of assembling same. Particularly, but not exclusively, it relates to composite arm and clamp assemblies of the kind used as radius/torque arms in a motor vehicle suspension or as leaf springs.

It is known to use two clamp members and bolts tensioned to provide a clamping load. This represents a clamping arrangement which has been used with metal leaf springs for several decades but when applied to a composite arm and clamp assembly it has the disadvantage that the bolts have to be tightened in a specific order and to a specified torque and have to be check tightened after allowing for settlement.

According to one aspect of the invention there is provided a composite arm and clamp assembly,

the clamp comprising two U-section clamp members, each clamp member having a base portion to apply a clamping load to the arm and a pair of side flanges, the side flanges of one clamp member flanking the arm and each side flange of the other clamp member extending away from the arm and abutting the adjacent flange of said one clamp member, and retaining means to resist lateral movement between the adjacent flanges and retain the clamping loads.

According to another aspect of the invention there is provided a method of assembling a composite arm and a clamp,

the clamp comprising two U-section clamp members, each clamp member having a base portion for applying a clamping load to the arm and a pair of side flanges, the side flanges of one clamp member flanking the arm and each side flange of the other clamp member extending away from the arm and abutting the adjacent flange of said one clamp member, the method comprising the steps of applying a predetermined compressive load to the clamp members to generate the clamping loads and applying retaining means to ' adjacent flanges to resist lateral movement thereof whilst the compressive load is maintained.

Other aspects of this invention will be apparent from the dependent claims and from the following description which is by way of example and is with reference to the accompanying drawings, of which: Figure 1 is a side elevation of part of a motor vehicle chassis and axle showing a composite arm and clamp assembly according to the invention; Figure 2 is a side elevation of part of the composite arm and the clamp assembly shown in Figure 1; Figure 3 is a view on arrow A in Figure 2; and Figure 4 is perspective CAD view on arrow B in Figures 2 and 3.

Referring to Figure 1, a vehicle chassis 11 is partially supported by an axle 12 through a coil spring 13. The axle is located in the fore and aft direction by a radius arm 14 which also acts as a torque arm to resist braking and driving torque on the axle. The axle 12 comprises an axle tube 15 having a pair of flanges 16 welded to it. The flanges 16 flank a clamp 17 which is secured to the radius arm 14 adjacent one of its ends. At the other end of the radius arm there is a rubber bushed eye 18 by which the arm is secured to the chassis 11.

Referring to Figures 2 to 4, the radius arm 14 is of laminated composite construction comprising resin reinforced with glass fibres and is of substantially uniform rectangular cross section.

The clamp 17 comprises two U-section clamp members 21 and 22 joined at one end and formed from a single stamping. One clamp member 21, the lower as seen in Figure 2, has a base portion 23 and a pair of side flanges 24 which flank the arm 14 and extend beyond it.

The other clamp member 22, the upper as seen in Figure 2, also has a base portion 25 and a pair of side flanges 26 which extend away from the arm and abut the respective adjacent flange of the lower clamp member 21.

In the end region where the clamp members 21 and 22 are joined there is a reinforcing rib 27 to support load from a tube section 28 which is secured to the clamp members at a curved interconnecting portion 29 by welding. The side flanges 24 of the lower clamp member 21 extend towards the end region and also support the tube section 28.

At end regions opposite the interconnecting portion 29 the flanges 24 and 26 and the base portions 23 and 25 of the clamp members 21 and 22 are joggled outwards to accommodate a sleeve 31 of a resilient plastics material (eg polyurethane or nylon) which is interposed between the clamp members and the arm 14.

Between the sleeve 31 and the interconnecting portion 29 the clamp members 21 and 22 directly abut the arm 14 which has a thickened end portion 32 adjacent the tube section 28.

Rivets 33 and 34 which extend through the arm transverse to the base portions 23 and 25 secure the clamp 17 to the arm 14.

Whilst both the rivets 33 and 34 and the thickened arm portion 32 serve to ensure that the clamp 17 and arm 14 are correctly located and secured together, the primary means of securing is a clamping load which is applied by the respective base portion 23 and 25 of each clamp member to the arm 14 through the resilient plastics sleeve 31. These clamping loads are retained by preventing lateral movement between the adjacent abutting flanges 24 and 26. As seen in Figures 2 to 4, retaining means to resist such lateral movement are provided in the form of rivets 35 and a cross tube 37 which extends through the flanges of both clamp members and is secured by welding.

To assemble the clamp 17 to the radius arm 14 the base portions 23 and 25 are, before assembly, spaced apart to allow entry of the thicked end portion 32. The clamp members 21 and 22 are then moved together, the resilient plastics sleeve 31 having previously been located on the arm. This operation plastically deforms the clamp in the region of the interconnecting portion 29.

The assembly method continues by applying a predetermined compressive load to the clamp members 21 and 22 to generated the clamping loads on the arm 14 through the sleeve 31 and, whilst the compressive load is maintained, securing the adjacent flanges 24 and 26 by the rivets 35. The cross tube 36 is also preferably secured whilst the compressive load is maintained. The rivets 33 and 34 are subsequently installed.

To ensure an accurate fit for the rivets 35 and the cross tube 36, their respective holes are preferably finish bored whilst the compressive load is maintained. Several alternatives are envisaged. The 'holes could be drilled through whilst the load is maintained or the holes in the flanges of one or both members could be pre-punched undersize and finish reamed whilst the load is maintained.

Alternatively, the holes in one of the flanges could be finished to size before the assembly operation and the remaining holes drilled or finish reamed whilst the load is maintained.

Figures 2 to 4 show conventional cold headed rivets 35.

Alternative tensile fasteners are envisaged and may be preferable where there is insufficient space between the side flanges 26 of the upper clamp member 22 for a rivetting anvil. Such fasteners may comprise the type which utilises a headed pin retained by a swaged collar such as is available as a proprietary item from the Huck Manufacturing Co.

Where stresses permit, the rivets 35 may be omitted and the cross tube 36 alone used to secure adjacent flanges.

Alternatively or additionally the flanges may be secured together by welding, eg, resistance spot welding or seam welding at the outer peripheries of the flanges. Where welding is the sole retaining means for the flanges, this is done whilst the compressive load is maintained. However, it is not necessary to perform all the methods of securing the flanges together whilst maintaining the compressive load, provided that at least one of the retaining means is in place to prevent relative movement of the flanges when the compressive load is removed.

In a modification (not shown) the thickened end portion of the radius arm is omitted. In this case the base portions are spaced apart only just sufficient for the insertion of the arm and the interconnecting portion is not subsequently plastically deformed.

For installation on the vehicle, the cross tube 36 and the tube section 28 are aligned with holes in the flanges 16 on the axle 12 and through bolts installed.

The arm may have alternative cross-sections and the clamp members have a complementary profile at their base portions.

The arm may not be uniform over its length. Alternative fibres may be used, e.g. carbon or Kevlar (Trade Mark).

Claims (29)

1. A composite arm and clamp assembly,

the clamp comprising two U-section clamp members, each clamp member having a base portion to apply a clamping load to the arm and a pair of side flanges, the side flanges of pne clamp member flanking the arm and each side flange of the other clamp member extending away from the arm and abutting the adjacent flange of said one clamp member, and retaining means to resist lateral movement between the adjacent flanges and retain the clamping loads.

2. An assembly according to Claim 1 wherein a resilient plastics material is interposed between the clamp members and the arm.

3. An assembly according to Claim 1 or Claim 2 wherein the clamp members are joined at an end thereof.

4. An assembly according to Claim 3 wherein the clamp members are formed from one stamping.

5. An assembly according to Claim 3 or Claim 4 wherein a tube section is secured to the members at said one end.

6. An assembly according to any of Claims 3 to 5 wherein the arm has a thickened portion adjacent said one end.

7. An assembly according to any of Claims 3 to 6 wherein the arm is secured to the clamp members by fasteners extending through the arm transverse to the base portions.

8. An assembly according to any preceding claim wherein a cross tube is secured between the flanges of said other clamp member.

9. An assembly according to Claim 8 wherein the cross tube extends through the flanges of both clamp members.

10. An assembly according to Claim 9 wherein the retaining means comprises the cross tube.

11. An assembly according to any preceding claim wherein the retaining means comprises tensile fasteners.

12. An assembly according to any preceding claim wherein the retaining means comprises welding between adjacent flanges.

13. A method of assembling a composite arm and a clamp, the clamp comprising two U-section clamp members, each clamp member having a base portion for applying a clamping load to the arm and a pair of side flanges, the side flanges of one clamp member flanking the arm and each side flange of the other clamp member extending away from the arm and abutting the adjacent flange of said one clamp member, the method comprising the steps of applying a predetermined compressive load to the clamp members to generate the clamping loads and applying retaining means to adjacent flanges to resist lateral movement thereof whilst the compressive load is maintained.

14. A method according to Claim 13 wherein a resilient plastics material is interposed between the clamp members and the arm.

15. A method according to Claim 13 or Claim 14 wherein the clamp members are joined at an end thereof.

16. A method according to Claim 15 wherein the clamp members are formed from one stamping.

17. A method according to Claim 15 or Claim 16 wherein a tube section is secured to the members at said one end.

18. A method according to any of Claims 15 to 17 wherein the arm has a thickened portion adjacent said one end.

19. A method according to Claim 18 wherein the base portions, before assembly, are spaced apart to allow entry of said thickened portion and after assembly the clamp members are moved together to positively locate the arm in the clamp.

20. A method according to any of Claims 15 to 19 wherein the arm is secured to the clamp members by fasteners extending through the arm transverse to the base portions.

21. A method according to any of Claims 13 to 20 wherein a cross tube is secured between the flanges of said other clamp member.

22. A method according to Claim 21 wherein the cross tube extends through the flanges of both clamp members.

23. A method according to Claim 22 wherein the retaining means comprises the cross tube.

24. A method according to Claim 23 wherein the flanges are finish bored for the cross tube after the predetermined compressive load is applied.

25. A method according to any of Claims 13 to 24 wherein the retaining means comprises tensile fasteners.

26. A method according to Claim 25 wherein the flanges are finish bored for the fasteners after the predetermined compressive load is applied.

27. A method according to any of Claims 13 to 26 wherein the retaining means comprises welding between adjacent flanges.

28. A composite arm and clamp assembly substantially as described herein with reference to the accompanying drawings.

29. A method of assembling a composite arm and a clamp substantially as described herein with reference to the accompanying drawings.