GB2210467A - Alignment gauge - Google Patents

Abstract

An optical wheel alignment gauge comprising a viewing and target unit, and a separate mirror unit (12), the viewing and target unit including an adjustable viewing and target assembly, the mirror unit including a mirror (27) in which, in use, a reflection of the target of the viewing and target assembly can be viewed through the viewing component of the assembly, and, each unit incorporating releasable clamping means (13-18) for detachably mounting the unit on the rim of a respective wheel. <IMAGE>

Description

ALIGNMENT GAUGE The present invention relates to an alignment gauge for measuring the angle, in a generally horizontal plane, between pairs of wheels on opposite sides respectively of a vehicle.

Such alignment gauges are most often used to determine the alignment of the steered wheels of a road vehicle, the parameter measured usually being referred to as the "toe-in/toe-out" measurement of the steering geometry of the vehicle. A known alignment gauge makes use of two physically separate units which are associated in use with the two wheels of the pair of wheels whose alignment is to be measured. One unit incorporates an adjustable, periscope viewing and target assembly, while the other unit incorporates a mirror. Both units are free standing, and each includes abutment probes which are placed in abutment with the wheel rims of the two wheels in question so that each unit is aligned with the plane of rotation of its respective wheel.An operator looking through the periscope of the periscope viewing and target assembly rotates the assembly about a substantially vertical axis relative to the remainder of its unit to align a datum line of the assembly with a reflection from the mirror of the other unit of a datum mark on the target of the viewing and target assembly.

The viewing and target assembly includes a calibrated scale from which the angle between the two wheels can be read when the image of the datum line and the datum mark are in alignment when viewed through the periscope.

Such alignment gauges are eminently satisfactory for use in a wide variety of environments and require a minimum degree of operator skill. However, since the units are free standing the use of such a gauge is restricted to floor level operations where the floor is suitably smooth and generally horizontal, and cannot be utilised, for example, where the vehicle is elevated on an hydraulic lift, since hydraulic lifts generally do not incorporate laterally extending platforms upon which the units of the known gauge can be positioned.

It is an object of the present invention to provide an alignment gauge which is not dependent upon the surface supporting the vehicle for its operation.

In accordance with the present invention there is provided an optical wheel alignment gauge comprising a viewing and target unit, and a separate mirror unit, the viewing and target unit including an adjustable viewing and target assembly, the mirror unit including a mirror in which, in use, a reflection of the target of the viewing and target assembly can be viewed through the viewing component of the assembly, and, each unit incorporating releasable clamping means for detachably mounting the unit on the rim of a respective wheel.

Throughout this specification the term "wheel rim" is intended to denote that portion of a vehicle wheel which is affixed to a hub of the vehicle, and supports the tyre of the vehicle. Thus in general terms a vehicle wheel is considered to comprise a wheel rim and a tyre encircling the wheel rim.

Preferably each unit incorporates locking pivot means whereby the remainder of the unit can be adjusted relative to the clamping means about an axis parallel to the rotational axis of the wheel in use.

Desirably the releasable clamping means of each unit is adjustable to accommodate a range of wheel rim diameters.

One example of the invention is illustrated in the accompanying drawings wherein: Figure 1 is a perspective view of the mirror unit of an alignment gauge; Figure 2 is a front elevational view of the unit of Figure 1; Figure 3 is a front elevational view of the viewing and target assembly of the viewing and target unit of the gauge; and Figures 4 and 5 are a rear elevational view and a plan view respectively of the assembly shown in Figure 3.

Referring to the drawings, the alignment gauge comprises a viewing and target unit 11, and a mirror unit 12.

The units 11, 12 are separate from one another, and each includes a releasable clamping means whereby the unit can be clamped to the rim of a respective vehicle wheel. Since the releasable clamping means of the units are the same then only one will be described.

Each releasable clamping means includes a die-cast aluminium, or aluminium alloy clamp plate 13 carrying three wheel rim gripping elements 14, 15, 16. The elements 14-16 protrude from one face of the plate 13 at right angles thereto, the position of the element 16 relative to the plate being adjustable along the length of an elongate slot 17 in the plate. The plate 13 is formed with two rectilinear rows of apertures 17a, 17b parallel to the slot 17 and spaced both vertically and horizontally therefrom. The element 14 is associated with the row 17a of apertures while the element 15 is associated with the row 17b. Considering the rows 17a, 17b to be vertically orientated, then the apertures of each row are aligned in a horizontal direction.

Moreover, although spaced vertically from the rows 17a, 17b the slot 17 is disposed in a horizontal direction mid-way between the rows 17a, 17b and thus when the elements 14 and 15 are engaged in corresponding apertures of their respective rows 17a, 17b then the elements 14, 15, 16 define the apices of an isosceles triangle the base of which is the imaginary line joining the elements 14, 15.

Each of the elements 14-16 is generally in the form of a cylindrical rod, the elements 14, 15 having end regions of reduced width for engagement in their respective apertures and being counter bored and threaded to receive screw clamping arrangements whereby the elements 14 and 15 are clamped to the plate 13 in any of the selected apertures of their respective rows 17a, 17b. The diameter of the element 16 is greater than the width of the slot 17, but the element 17 has an end region formed with a pair of parallel flat surfaces whereby the end region is slidably received in the slot 17. Rotatably mounted on the plate 13 for rotation about an axis parallel to the plane of the plate 13 is a screw adjuster 18.The screw adjuster 18 is held against axial movement relative to the plate 13, but can rotate relative thereto, and includes a screw-threaded shank which passes through a corresponding screw-threaded bore in the element 16 whereby rotation of the adjuster 18 relative to the plate 13 results in movement of the element 16 lengthwise of the slot 17.

At its end remote from the plate 13 each element 16-18 includes a wheel engagement insert, different inserts being available to suit different types of wheel rim.

Generally centrally disposed on the plate 13, and projecting at right-angles to the plane of the plate 13 from the face thereof opposite the elements 14-16 is a pivot post 19. The pivot post 19 is fixed relative to the plate 13, and supports a triangular pivot plate 21 which conveniently is a die-casting formed from the same material as the plate 13. Adjacent one apex the plate 21 includes an integral cylindrical boss 22 having its axis perpendicular to the plane of the plate 21. The post 19 of the plate 13 is received in the boss 22 so that the plate 21 can pivot about the post 19 relative to the plate 13. The boss 22 is formed with a cross drilling which is internally screw-threaded and receives a locking member 23.Effectively the locking member 23 is a screw-threaded bolt which can be tightened onto the post 19 to resist angular movement of the boss 22, and therefore the plate 21, about the post 19.

Adjacent its other two apices the plate 21 is formed with integral upstanding lugs 24 each of which contains a through bore having its axis parallel to the plane of the plate 21. The bores of the bosses 24 are co-axial and receive one end region of an elongate, tubular, aluminium support member 25. Thus the support member 25 extends with its axis parallel to the planes of the plates 21 and 13, and the axial position of the support member 25 relative to the plate 21 can be adjusted by sliding the support member 25 relative to the bosses 24. The wall of each boss 24 is formed with a cross drilling which is screw-threaded and receives a locking member 26 which can be screwed down to grip the support member 25 and thus prevent axial movement of the support member 25 relative to the plate 21.

As mentioned previously each of the units 11, 12 incorporates a clamping means as described above, the two units being mirror images of one another, and differing significantly only in the equipment carried at the end of the respective support member 25 remote from the respective plate 21.

Each clamping means is attached to its respective wheel rim in the following manner. The element 16 is positioned proximate the mid-point of its slot 17, and the elements 14 and 15 are located in apertures of their respective rows 17a, 17b selected in accordance with the diameter of the wheel rim to which the respective unit is to be clamped. Assuming that the wheel rim is a conventional pressed steel wheel rim then the inserts chosen for the elements 14-16 will have plain cylindrical ends, the inserts of the elements 14, 15 will be engaged with the radially inwardly presented face of the outer peripheral flange of the wheel rim and the adjuster 18 of the element 16 will be rotated to move the element 16 away from the elements 14, 15 until the insert of the element 16 similarly engages the radially inwardly presented face of the peripheral flange of the rim.Thereafter, a small degree of rotation of the adjuster 18 will cause the inserts of all three elements 14, 15, 16 to bear tightly against the radially inwardly presented face of the outer peripheral flange of the wheel rim, at three circumferentially spaced points around the flange, thus fixing the plate 13, and therefore the respective unit 11 or 12, to the wheel rim. Thereafter, each plate 21 will be moved angularly with respect to its plate 13 about the respective post 19 to position the respective support member 25 horizontallv. The support members 25

are each provided with a spirit levels to tacilitate horizontal positioning thereof. The support members 25 are locked in a horizontal orientation by tightening the screw device 23 of each plate 21.

It will be recognised that the distance between the free end of the insert of each element 14-16 and the plane of the plate 13 is the same, and thus provided that the free ends of the inserts seat against the wheel rim then the plane of the plate 13 will be parallel to the plane of the wheel rim, and thus parallel to the plane of rotation of the wheel. Since each pivot post 19 is perpendicular to the plane of its respective plate 13 and each support member 25 is parallel to the plane of its respective plate 21, then the longitudinal axis of each support member 25 will be parallel to the plane of rotation of the respective wheel to which it is clamped.Thus with a unit 11 clamped to one wheel and a unit 12 clamped to the opposite wheel then the angle defined between the two horizontally extending support members 25 is equal to the angle defined between the planes of rotation of the two wheels.

In the unit 11, at the end of the support member 25 remote from the plate 21, there is provided a viewing and target assembly 26 whereas in the unit 12, at the end of the support member 25 remote from the plate 21 there is provided a plane mirror 27. The nature and operation of the mirror, and the viewing and target assembly is conventional, and need not be described in detail. A similar mirror, and viewing and target assembly is to be found in, for example, the Dunlop optical alignment gauge AGO/40.

When the support member 25 of the unit 12 is positioned horizontally, the mirror 27 thereof is positioned with its plane disposed vertically, and parallel to a plane containing the axis of the support bar 25. The viewing and target assembly 26 of the unit 11 is aligned laterally with the mirror 27 of the unit 12, and includes a periscope arrangement 28 through which a reflection in the mirror 27 of a datum triangle 31 on a vertically disposed target 29 of the assembly 26 can be viewed.The periscope arrangement 28 is angularly movable, about a vertically disposed axis, relative to the respective support member 25 to permit angular adjustment of the periscope assembly 28 so that a datum line carried by the periscope assembly 28 can be aligned, in the sight picture visible through the periscope arrangement 28, with the reflection of the datum triangle 31 which also appears in the sight picture of the periscope arrangement 28. An elongate limb 32 extends from the periscope arrangement 28 and carries, at its free end, a small lens element 33 which, during angular movement of the periscope arrangement 28, moves relative to a scale 35 carried on a fixed portion 34 of the viewing and target assembly 26.

Initially, before the alignment gauge is utilised, the apparatus is calibrated and "zeroed" by clamping the plates 13 of the units together so that their planes are parallel. Thereafter, the datum line is aligned with the reflection of the datum triangle in the sight picture of the periscope arrangement and the scale 35 and/or a reference mark on the lens 33 are adjusted such that the reference mark on the lens 33 coincides with a zero mark on the scale 35. In use therefore when the units 11 and 12 are carried by respective wheels of the vehicle and the datum line is aligned with the reflection of the datum triangle in the sight picture of the periscope arrangement 28 then the angular displacement of the planes of rotation of the two wheels can be read from the scale 35 by noting the position of the reference mark on the lens 33 in relation to the scale 35.This reading is a measure of the "toe-in" or "toe-out" of the two wheels in question. For convenience the scale 35 is calibrated in degrees and minutes on either side of a zero position, "toe-in" being represented to one side of the zero and "toe-out" being represented to the opposite side of the zero. In the United Kingdom it is usual to refer to "toe-in" and "toe-out" in fractions of an inch rather than degrees and minutes, and thus for convenience the limb 32 carries a simple conversion calculator 36 for converting the scale reading in degrees and minutes to a measurement in fractions of an inch and/or millimetres.

It will be recognised that since the units 11, 12 are supported directly from the wheels whose alignment is being measured then operation of the alignment gauge is not dependent upon the surface upon which the vehicle is supported, and the gauge can be used equally well whether the vehicle is supported at ground level, or is elevated on a vehicle lift. Moreover since the units are each clamped to their respective wheel rim there is no risk of accidental displacement of a unit relative to its wheel rim during operation, as could occur with the known, free standing arrangements.

Naturally in order to facilitate initial setting up of the gauge the mirror and the viewing and target assembly are adjustable in position on their respective support members 25. For convenience all of the various locking devices of both units are arranged to be capable of manual operation without the need for tools.

Where the gauge is to be used on vehicles having alloy wheels then it is more convenient to provide the elements 14-16 with inserts having hooked free ends and to engage the hooked free ends on the outer periphery of the wheel rim. In such an arrangement, to achieve firm clamping, the adjusters 28 will be rotated to move the elements 16 towards the elements 14, 15 since their inserts are gripping on the outer surface of the rim, rather than on a radially inwardly presented surface.

Each of the inserts is conveniently screw-threaded, and is received in a blind bore of predetermined depth in its respective element. Thus since the inserts are each of the same length then screwing them into their elements 14-16 until they engage the blind ends of the bores in the elements ensures that the distance between the free end, or the operative hook portion, of each insert and the plane of its respective plate 13 is constant. If desired inserts having a hook portion at one end and a plain portion at the opposite end can be provided so that the change from pressed steel wheel rims to alloy rims can be effected simply by reversing the inserts in their respective elements.

Claims (8)

1. An optical wheel alignment gauge comprising a viewing and target unit, and a separate mirror unit, the viewing and target unit including an adjustable viewing and target assembly, the mirror unit including a mirror in which, in use, a reflection of the target of the viewing and target assembly can be viewed through the viewing component of the assembly, and, each unit incorporating releasable clamping means for detachably mounting the unit on the rim of a respective wheel.

2. A gauge as claimed in claim 1 wherein each unit incorporates locking pivot means whereby the remainder of the unit can be adjusted relative to the clamping means about an axis parallel to the rotational axis of the wheel in use.

3. A gauge as claimed in claim 1 or claim 2 wherein the releasable clamping means of each unit is adjustable to accommodate a range of wheel rim diameters.

4. A gauge as claimed in anyone of claims 1 to 3 wherein each unit includes an elongate element arranged, when its respective clamping means is secured to the respective wheel to project beyond the periphery of the wheel and to carry at its end remote from the clamping means either the mirror or the viewing and target assembly.

5. A gauge as claimed in claim 4 wherein each elongate element is provided with level indicator means for indicating a horizontal orientation of the element.

6. A gauge as claimed in claim 4 or claim 5 wherein the spacing between wheel axis and the mirror and the viewing and target assembly is adjustable.

7. A gauge as claimed in anyone of claims 1 to 6 wherein the mirror and the viewing and target assembly are adjustable in orientation about axes transverse to the wheel axes.

8. An optical wheel alignment gauge substantially as hereinbefore described with reference to the accompanying drawings.