GB2254443A

GB2254443A - Gauge for indicating the misalignment of the wheels of road vehicles

Info

Publication number: GB2254443A
Application number: GB9106232A
Authority: GB
Inventors: Frank Edward Sanville
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-03-23
Filing date: 1991-03-23
Publication date: 1992-10-07
Anticipated expiration: 2011-03-23
Also published as: GB2254443B; GB9106232D0

Abstract

The gauge is a flexible mat in two layers lying one on top of the other each having grooved and ridged mating surfaces arranged so as to restrict relative sliding to one direction. The gauge is placed in front of a wheel of a vehicle with the grooves of the mating surfaces at right angles to the vehicle motion. When the vehicle is driven over the gauge and if the wheel is misaligned the upper layer will slide over the other and thereby indicate the extent of misalignment. Either solid or liquid lubricant is provided for the mating surfaces. <IMAGE>

Description

GAUGE FOR INDICATING ERROR IN THE ALIGNMENT OF THE WHEELS OF ROAD VEHICLES This invention is a device for indicating and measuring misalignment of the road wheels of vehicles especially the wheels used for steering by responding to the force exerted on the road by a misaligned wheel.

According to the invention there is provided a gauge for indicating and measuring misalignment of a road wheel of a vehicle comprising a flexible mat in two layers lying one on the other with grooved and ridged mating surfaces arranged to restrict relative sliding of the two layers to only one direction.

For a better understanding of the invention and to show how it may be used, reference is made to the accompanying drawings where some reference numbers are repeated when a feature is duplicated or appears in more than one figure.

Figure 1 represents a misaligned tyred wheel resting on the road.

Figure 2 is a plan view of the lower of the two layers of the gauge showing the grooved and ridged surface uppermost.

Figure 3 is part of the side view of one embodiment of the said gauge showing the engagement of features of the mating surfaces of both layers.

Figures 4 and 5 show parts of the side views of other embodiments of the said gauge having conforming mating surfaces.

Figures 6, 7 and 8 show parts of side views of other embodiments of the said gauge having conforming and identical mating surfaces.

Figure 9 is a plan view of part of the said gauge showing detail of the measuring scale and index mark.

Figure 10 is a plan view of the said gauge showing the relative locations of the measuring scales and index marks.

Figure 1 is a plan view as seen from the vehicle, 1 is a line parallel to the direction of travel and the arrow head shows that the vehicle is moving as if up the paper. Line 2 represents the plane of rotation of the misaligned wheel. Lines 1 and 2 would coincide if there were no misalignment. Outline 3 is the footprint of the tyre on the road and 4 is the outline of the tyre itself. As the vehicle moves in the sense shown, the diagram of figure 1 remains fixed because it is seen from the vehicle, and the road surface appears to move down the paper. As the tyre rolls on the road, a point A on the road at the entry of the footprint advances through the footprint to the exit point B.At the same time, the point on the tyre starting from point A on the road tends to move through the footprint in the plane of the wheel to point B' but friction forces between the tyre tread and the road tend to keep points B and B' together. This conflict causes excessive tread wear and the same conflict is exploited in this invention.

If, in the illustration just considered, the wheel is rolling not on the road but on a flexible mat made in two layers one sliding on the other but restrained to move in one direction and that direction is at rightangles to the vehicle movement, relative motion of the two layers is an indicator of wheel misalignment. Referring again to figure 1, point A on the tyre makes contact with the point on the mat directly underneath it, the same points remain in contact while they are within the footprint because of friction between the tyre and mat. The mat is able to yield under the friction force and the upper layer slides over the lower layer through the distance BB'.

The angle of misalignment of the wheel is given by the ratio BB'/AB. It may also be represented more conventionally by toe-in (or toe-out), CD, as a ratio with the mean diameter of the tyre, DE.

In practice, measurement of misalignment by rolling the wheel through only one footprint is not sufficiently sensitive. In this gauge, the relative transverse motion of the layers of the mat, which shows error, is proportional to distance rolled by the wheel on the mat. Therefore the indication may be enhanced by making the mat equal to several footprints in length.

For example, from the maker's instructions for a typical car, the mean diameter of the tyre, DE, is 470mm, the footprint, AB, is 156mm long, and the greatest permitted misalignment is given as 3mm toe-out, CD. Thus the ratio is effectively specified as 3/470 = 0-0064. The corresponding value of displacement, BB' = 0-0064.156 = imam. This value of transverse displacement is too small for convenience of observation, but it could be increased threefold to a practical value by having the mat three footprints in length or about 0 5m.

The mating surfaces of the two layers of the mat may have any form of cooperating ridges and grooves if relative motion is thereby restricted to only one direction. Figure 3 shows a ridged surface on the lower layer engaging with grooves in the upper layer without fitting exactly. Figures 4 and 5 show two forms of improved embodiment where in each case the mating surfaces conform, that is to say there is no space anywhere between the surfaces when they are in contact with each other. Figures 6,7 and 8 show other embodiments of the invention where the mating surfaces conform and are identical.

Identical profiles of grooves and ridges lead to advantage in manufacture by allowing both layers of the mat to be made in the same mould or forming tool.

To facilitate measurement of alignment error, a notch 8, as shown in figures 9 and 10, is provided at the end of the upper layer 5.

The notch 8 discloses part of the upper surface of the lower layer 6 whereon are printed or indented scale divisions 9 with a zero at the centre 10. An index mark 11 is provided as a projecting ridge on the side of the notch 8. By initially setting the index mark 11 on the upper layer against the zero 10 of the scale on the lower layer, subsequent relative movement may be measured against the scale 9.

In embodiments of the invention where the two layers of the mat are identical, the notch 8 in the upper layer is matched by a similar notch 8' in the lower layer. Notches 8 and 8' may extend to the edge of the mat as shown by the dashed outlines 9 and 9'.

Lubrication between the mating surfaces of the mat is required to minimise wear by abrasion in spite of the low interface stress in this application. It is not necessary to provide for a low coefficient of friction, only for the friction force generated between the mating surfaces to be less than the friction force between the road and tyre of the other wheel on the same axis and less than the friction force generated between the road and the bottom surface of the lower layer and less than the friction force between the tyre and the top surface of the upper layer of the mat. Whichever embodiment of the invention is used there is an integral coating of solid lubricant such as polytetrafluorethylene on the mating surfaces of either or both of the layers of the mat. Alternatively, the lubricant may be applied as a separate coating of solid lubricant or as a coating of grease or oil. Because the lubrication requirements of the gauge are not rigourous, materials such as glycerine, liquid detergents or soap may be used as lubricant.

Claims

CLAIMS 1. A gauge for indicating and measuring misalignment of a road wheel of a vehicle comprising a flexible mat in two layers lying one on the other with grooved and ridged mating surfaces arranged to restrict relative sliding of the two layers to only one direction. 2. A gauge as claimed in claim 1 having conforming mating surfaces. 3. A gauge as claimed in claims 1 or 2 having identical mating surfaces. 4. A gauge as claimed in claims 1,2 or 3 having a coating of solid lubricant integral with one or both mating surfaces. 5. A gauge as claimed in claims 1,2 or 3 having lubricant applied as a separate layer between the mating surfaces. 6. A gauge as claimed in claims 1,2,3 or 4 incorporating means to indicate and measure relative motion between the two layers of the mat. 7. A gauge substantially as heretofore described with reference to the accompanying drawings. Amendments to the claims have been filed as follows CLAIMS

1. A gauge for indicating and measuring misalignment of a road wheel of a vehicle comprising a flexible mat in two layers lying one on top of the other with grooved and ridged mating surfaces on opposing upper and lower surfaces of the two layers arranged to restrict relative sliding of the two layers to only one direction.

2. A gauge as claimed in claim 1 having conforming mating surfaces.

3. A gauge as claimed in claims 1 or 2 having identical mating surfaces.

4. A gauge as claimed in claims 1, 2 or 3 having a coating of solid lubricant integral with one or both mating surfaces,

5. A gauge as claimed in claims 1, 2 or 3 having lubricant applied as a separate layer between the mating surfaces.

6. A gauge as claimed in claims 1, 2, 3 or 4 incorporating means to indicate or measure relative motion between the two layers of the mat.

7. A gauge as claimed in claim 6 wherein said means comprises an index mark integral with one of the said layers and cooperating with a scale on the other of the said layers.

8. A gauge substantially as heretofore described with reference to the accompanying drawings.