GB2063785A - Vehicle suspensions - Google Patents

Abstract

The trailing link (15) of a pneumatic semi-trailer suspension of the kind described in UK Patent Specification No 1,219,911 is articulated to the chassis (11) by a bracket (31) of inverted U-shape. Lugs (18) project from opposite sides of the link (15) and are received between respective pairs of flanges (17) of the bracket. A bolt (19) passes through aligned bores in each pair of flanges (17) and the lug (18) therebetween and washers or shims on the bolt (19) can be exchanged between opposite sides of the lug (18) to adjust the point of articulation of the limb (15) to the chassis (11). <IMAGE>

Description

SPECIFICATION Vehicle suspensions The present invention relates to an improved vehicle suspension, and more particularly to an improved means for connecting to the vehicle chassis a free end of a suspension linkage arm or spring at a point spaced along the chassis from the position where said arm or spring is connected to an axle.

Axle suspensions for semi-trailers or for the rear axles of heavy vehicles essentially comprise a spring between the axle and chassis and means retaining the spring in an upright attitude so that the permitted relative movement of the axle and chassis against the action of the spring is generally vertical.

In one well known construction a stack of leaf springs extends longitudinally of the chassis, being connected at its opposite ends to the chassis and intermediate its ends to the axle. Another type of suspension is exemplified by British Patent Specification No 1219911, wherein an air spring is substituted for the leaf springs, being located in a generally upright attitude by a forwardly extending trailing link, a rearwardly-extending suspension damper and a laterally extending Panhard rod.

In all such suspensions the accurate location to the chassis of a free end of a leafspring stack, a trailing link, a damper or a Panhard rod (all such elements or equivalents thereof being hereinafter designated 'suspension arms or springs') is extremely critical.

Even a very small error can have a serious effect on the angular relationship of the axle to the chassis which at best will cause uneven wear of the tyres or at worst will render the vehicle unsafe.

Hitherto the trailing link suspension damper and Panhard rod of a pneumatic suspension have been articulated to brackets welded to the chassis of the vehicle. As described in British Patent Specification No. 1,219,911 spherical joints can be used. These allow some angular movement, but the position of each element longitudinally or laterally of the chassis is fixed. It is very difficult to achieve perfect accuracy of the final position of a welded-on bracket but such accuracy has been essential to provide a serviceable vehicle, such as a semi-trailer. The task has therefore required skilled labour and strict quality control with a high proportion of rejects.

Similar considerations apply in the case of leaf-spring suspensions. Here the expedient has been adopted of connecting the axle to the chassis at a point spaced along the chassis from the axle by means of a two-part strut, the two parts being in screw-threaded engagement and the arrangement being such that by rotating one part relative to the other the effective length of the strut can be adjusted.

This solution is not readily applicable to pneumatic suspensions because the trailing link, for example, is of box-girder construction and to interpose in its length a threaded-rod section would represent a costly and difficult modification which would, moreover, weaken the assembly.

A principal object of the present invention is to provide a cheap, simple and versatile adjustment facility applicable both to pneumatic suspensions and to leaf-spring suspensions, in the latter case offering a superior facility to that currently available.

In accordance with the present invention there is provided a vehicle suspension wherein a free end portion of a suspension arm or spring (as herein defined) is connected to the vehicle chassis by means of a bolt passing through a bore in said portion parallel with the chassis and through at least one flange of a bracket secured to the chassis, there being a clearance along the bolt between said flange and said portion which is taken up by a shim or shims on the bolt, the arrangement being such that the addition or removal of shims can be used to alter the position of said portion relative to the chassis.

Preferably said portion of each suspension arm or spring is one of two similar lugs extending transversely from opposite sides of said free end portion, each lug being connected to the chassis by a similar bracket, bolt and shims assembly, the arrangement being such that by a different arrangement of shims on the two bolts associated with each arm or spring the angular orientation of the arm or spring with respect to the chassis can be adjusted.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a side view of a semi-trailer suspension, and Figure 2 is a detail view on an enlarged scale taken on the line ll-ll of Fig. 1.

The semi-trailer suspension illustrated in Fig. 1 is of a kind known from British Patent Specification No 1,219,911 in which an air spring 10 is interposed between the chassis 11 of a semi-trailer and an axle 1 2. The suspension includes a linkage 1 3 below the axle 1 2 which is connected at its rear end to the chassis 11 by a suspension damper 1 4 and which has a forwardly extending trailing link 1 5 articulated at its leading end to the chassis 11 by a spherical bearing 30 which permits limited angular movement of the link 1 5 relative to an associated bracket 31.Conventionally, two systems such as shown in Fig. 1 support the same axle 1 2 is spaced positions along its length near to the opposite sides of the semi-trailer and to the wheels (not shown) at the opposite ends of the axle 1 2 and a Panhard rod extends laterally of each system to the chassis.

In according with the present invention the leading end of each link 1 5 is articulated to the chassis 11 by a bracket 31 of inverted Ushape the two limbs 16 of which are spaced transversely of the chassis a distance slightly greater than the thickness of the leading end of the associated ink 1 5. Each limb 1 6 of the bracket has a pair of downwardly extending flanges 17, the flanges of each bracket being spaced-apart a distance longitudinally of the chassis 11 slightly greater than the thickness of an associated lug 1 8 projecting transversely from the leading end of the link 1 5.

A pair of lugs 18 project transversely from opposite sides of the leading end of each link 1 5 and each is formed with a bore which can be aligned with coaxial bores in the two flanges 1 7 of each bracket limb 1 6 and a bolt 1 9 passed through the bores in the flanges and lugs to secure them together. The portion of each bolt 1 9 between the associated flanges 1 7 exposed from the associated lugs 18 is occupied by a plurality of washers or shims 20 which take up the clearance and prevent movement of a lug 1 8 between the associated flanges 17 when a nut 21 is tightened onto the bolt 1 9.

To assemble the suspension linkage the brackets 31 having the limbs 1 6 are welded to the chassis 11, but this need not be with the degree of accuracy previously required for welding the brackets to the chassis. Each link 1 5 is lifted up between the two limbs 1 6 of the associated bracket 31 until each of its lugs 18 passes between an associated pair of flanges 1 7 and then bolts 1 9 are passed through the aligned bores to secure the arm to the bracket.

To compensate for any error in the positioning of a bracket 31 longitudinally of the chassis 11 one or more of the shims 20 may be removed from one side of the associated lug 18 and positioned on its other side, by withdrawing and re-inserting the bolt 19, thus shifting the position of the lug 1 8 longitudinally of the chassis 11. If the position longitudinally of the chassis 11 of the brackets 31 associated with one link 1 5 is different from that of the other bracket associated with the other link 1 5 the arrangement of a similar number of shims 20 on one side of both lugs 18 of one link different from the number of shims on the corresponding sides of the two lugs of the other link will compensate for this.

By this means the final position of each link 1 5 associated with an axle 1 2 can be adjusted after the brackets 31 have been welded to the chassis 11. The position of the axle 1 2 can be predetermined and then the shims 20 re-arranged so that the link 1 5 can be secured to the brackets with the axle in that position.

In a modification of the invention all of the flanges 1 7 nearer to the air spring 10 are dispensed with. Each limb 1 6 of each bracket 31 has only one flange 17 on the side of the associated lug 18 nearer the fifth wheel.

Shims are located on the bolts 1 9 between the lugs 1 8 and the sole associated flange 17, the head of the bolt and the nut on the bolt engaging the lug 18 and flange 1 7 respectively.

Claims (4)

1. A vehicle suspension wherein a free end portion of a suspension arm or spring (as herein defined) is connected to the vehicle chassis by means of a bolt passing through a bore in said portion parallel with the chassis and through at least one flange of a bracket secured to the chassis, there being a clearance along the bolt between said flange and said portion which is taken up by a shim or shims on the bolt, the arrangement being such that the addition or removal of shims can be used to alter the position of said portion relative to the chassis.

2. A suspension as claimed in Claim 1, wherein said portion of each suspension arm of spring is one of two similar lugs extending transversely from opposite sides of said free end portion, each lug being connected to the chassis by a similar bracket, bolt and shims assembly, the arrangement being such that by a different arrangement of shims on the two bolts associated with each arm or spring the angular orientation of the arm or spring with respect to the chassis can be adjusted.

3. A suspension as claimed in Claim 1 or Claim 2 and of the kind described and iilus- trated in the Complete Specification of Patent No 1,219,911.

4. A semi-trailer suspension substantially as herein decribed with reference to and as illustrated in the accompanying drawings.