FIELD OF THE INVENTION 
       [0001]    The invention is concerned with a method and apparatus for determining vehicle wheel alignment. 
       BACKGROUND OF INVENTION 
       [0002]    There is presently no cost effective compact solution for the motorist to check vehicle wheel alignment toe angle. Commercial gauges are very expensive and most laser optical versions are based on the method described in GB1395882. They all use a basic principle of calibration to the parallel plane and rely on maintaining this calibration when used to check a vehicle&#39;s wheels deviation from the parallel plane. 
         [0003]    All existing laser optical methods use two planar gauges, consisting of long spans that are single strong parts, to maintain calibration. They are heavy and difficult to store. These spans are the main obstacle to providing the benefit of a compact solution for home storage. Splitting of the spans creates a fundamental problem with existing methods because span parts cannot be relied on to fit together with the same straightness every time thus creating a high risk of a user using un-calibrated apparatus and getting inaccurate results. Commercial gauges are also prone to easy mis-calibration, being pre-calibrated by placing gauges face to face. Over this short distance any small misjudgement is multiplied many times when gauges are moved far apart on a vehicle. Some more expensive gauges use a rig to hold gauges further apart to minimise this risk. This is better but does not provide a low cost, compact solution. 
         [0004]    The spans require further components to access the plane of the wheels and devices at one end to facilitate the intended method. Some stand on the floor and are provided with vertical arms and others are arranged for hanging on or clamping to the wheels. Height, width and level adjustment require separate technical features. 
       STATEMENTS OF INVENTION 
       [0005]    According to the present invention there is provided a method for determining the alignment of a pair of vehicle wheels, comprising positioning a beam projecting device consecutively on each wheel, in the same angular relationship to the wheel, and projecting a beam to a receptor which is located in a predetermined angular relationship to the other wheel, utilising said projecting device and/or said receptor to determine the angle between said beams and relating said angle to the alignment of the pair of wheels, the receptor being maintained in the same position for each beam projection. 
         [0006]    The present invention also provides apparatus for determining the alignment of a pair of wheels comprising an elongate member provided with a plurality of laterally extending means for contacting the wheel at spaced apart positions therebetween, said elongate member comprising at least two elongate parts and means for connecting said parts to the other in longitudinal relationship. 
         [0007]    Preferably, the connecting means include means for adjusting the length of the elongate member and/or the distance between wheel contact means. 
         [0008]    The present invention further provides apparatus for determining the alignment of a pair of wheels comprising an elongate member provided with a plurality of laterally extending means for contacting the wheel at spaced apart positions therebetween, said elongate member being provided with a pair of leg members for supporting said elongate member in an elevated position. 
         [0009]    Preferably, leg connection means are provided to secure the leg members to the elongate member. 
         [0010]    Preferably, the leg connection means permit the leg members to be secured to the elongate member at different separations therealong. 
         [0011]    Preferably, the leg connection means permits the leg members to angularly adjust at said connection to the elongate member. 
         [0012]    Preferably, the connecting means are transversely adjustable with regard to the elongate member. 
         [0013]    Preferably, the contact means extend transversely on opposite sides of the elongate member. 
         [0014]    Preferably, the contacting means are provided on the leg members. 
         [0015]    Preferably, the contacting means are in the form of transversely extending pins, transversely extending collars or collars having transversely extending sections. 
         [0016]    Accordingly, the present invention provides the general motorist with the benefits of compact, low cost apparatus to quickly, simply and accurately check the toe angle of the pair of vehicle wheels. 
         [0017]    The sectional span feature makes it compact for storage and portable should the motorist have to travel to suitable level ground, a necessity for an accurate toe angle check. 
         [0018]    There is no possibility of the sectional span maintaining any degree of accuracy as a result of periodic calibration in comparison to the single part strong spans of known methods and apparatus. 
         [0019]    Use of varying force on connecting links is sufficient to make span parts lock together with different overall straightness. However in the case of the present invention the span will rapidly lock together and can be used immediately to perform an accurate toe angle check with no concern about prior calibration. The method automatically compensates at every use for even the smallest changes in the overall straightness of the span, as compared with the previous use. 
         [0020]    The sectional span feature can be made telescopic by the use of different size tubes that have suitable locking means. 
         [0021]    The method of the invention also automatically achieves a superior state of calibration, with the apparatus adjusted to suit wheel size, in situ on the vehicle. It is superior due to the great distance between the devices, overcoming the problem of easy mis-calibration with known methods. Any small mis-adjustment remains small. 
         [0022]    The method of the invention can be used independently of the sectional span features and the new prop mounted design of the present invention. Thus, the method can be used on known apparatus for single part spans and will provide the feature of superior calibration. 
         [0023]    The present invention allows the use of a new single, reversible planar gauge with a small remote device, eliminating the possibility of a user placing an uncalibrated pair of gauges onto a vehicle and obtaining incorrect results. The remote device incorporates said pivoting laser that provides quick adjustment between working height and folding for compact storage, as well as easy fine adjustment of the laser level, removing any need for adjustable feet. The remote unit is placed at a specified distance from a wheel, allowing a simple scale on the laser target unit to display results accurately on any size of car, impossible with existing methods that all work at the width of the vehicle. Vehicles are of different widths but a scale can only be accurate at a specified distance. An actuated angle calculator, preferably with an exaggerated scale for easy reading, can be incorporated to allow the unit to be placed at any convenient distance. 
         [0024]    The present invention uses a span with prop legs which radically overcomes the size and technical complexity of known methods and apparatus. A rigid span will have two props installed with anti-slip feet, utilising gravity to hold the span against the wheel. The prop span provides easy height adjustment and, with adjustable connections, provides level and vertical angular adjustment of any device mounted at the end of the span. 
         [0025]    The present invention provides new planar reference devices in the form of planar contact collars that tolerate rotation and are movable along the span to suit wheel size. Pairs of collars of different dimensions will suit tyre wall reference or wheel rim reference and both can be supplied to offer full flexibility. Props incorporating planar contact collars may be provided so that two identical parts provide all the features which are required. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The accompanying drawings are as follows:— 
           [0027]      FIGS. 1 and 2  illustrate a prior art calibration method; 
           [0028]      FIGS. 3 and 4  further illustrate the prior art method; 
           [0029]      FIGS. 5 and 6  illustrate a method and apparatus in accordance with the present invention; 
           [0030]      FIGS. 7 to 12  show planar reference devices which can be used with the method and apparatus of the present invention; 
           [0031]      FIGS. 13 to 16  show various combinations, mounted to a wheel, of use in the present invention; 
           [0032]      FIG. 17  shows how laser level adjustment is achieved in a method according to the present invention; and 
           [0033]      FIGS. 18 and 19  show alternative options of actuated angle calculators which may be used in the method and apparatus of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]    The present invention will now be described, by way of examples only, with reference to the accompanying drawings. 
         [0035]      FIG. 1  illustrates the separate process of calibrating an existing pair of gauges  1  and  2  with device ends, laser/target  3  and mirror  4 . Gauges are placed with planar reference pins  5  contacting face to face to set zero. Laser  6  goes from device  3  to mirror  4  reflects back to target on  3  and is adjusted to line up laser dot  7  with zero line  8 . 
         [0036]      FIG. 2  shows how existing methods are prone to easy mis-calibration. Any small misjudgement in calibration method from  FIG. 1  is multiplied many times when gauges are moved apart to the size of a vehicle. Although wheels  9  and  10  are parallel, the gauges show laser dot  7  is not still at zero line  8  as it should be. 
         [0037]      FIG. 3  shows how existing gauges work. Wheels  9  and  10 , on axle  11  are aligned in the forward direction toe out. The bold arrow indicates the forward direction. The dotted lines  12  represent the planes at which gauges read zero and are parallel if existing gauges are accurately calibrated. Solid lines  13  represent the planes of the wheels to which gauges measure. The sum of angles A and B is the correct angular measurement of the wheels deviation from parallel. 
         [0038]      FIG. 4  shows the same toe out wheels from  FIG. 3  and how a small misjudgement in existing gauges calibration process ( FIG. 1 ) is multiplied ( FIG. 2 ). As a result, gauge zero lines  12  are not parallel. Wheel plane lines  13  are the same, angles A and B are increased and will produce an inaccurate result. 
         [0039]      FIG. 5  shows a method of the present invention. A reversible planar gauge is mounted to wheel  9 . The mirror  17  is in a forward perspective of the wheels. A level bubble will assist levelling the gauge. The remote unit  30  has a fold up laser/target unit  18  that emits a laser beam from the zero line  23  on scale  19 . It is placed on the ground on the opposite side of the vehicle at a specified distance from wheel  10 . The laser is turned on and the unit position is physically adjusted so that the laser  20  is reflected straight back on itself  21  from mirror  17 . Laser dot  22  is in line with zero line  23 . Laser level is adjusted by pivoting features of the laser/target unit and mirror. 
         [0040]    Referring to  FIG. 6 , the planar gauge is now moved to the second wheel  10  and placed using the reverse planar reference points  16 , to the same level as when on wheel  9 . The state of alignment is now clearly and accurately indicated by laser dot  22  on the scale  19 . An actuated angle calculator can replace the scaled target. This is placed at a suitable distance, but is not required to be placed at a specific distance, from wheel  10 . 
         [0041]    To create a single reversible planar gauge the span must have planar reference points with the ability to be swapped or rotated from side to side or ideally have dual points installed equally on both sides of the span. This is the only technical feature required to make any existing or new style of apparatus into a reversible gauge. 
         [0042]      FIG. 7  shows a design combining traditional planar reference pins  26  for contacting the wheel rims with a flexible clip  25  that allows snap on fitting and adjustment along the span  14  as well as contact pin  26  around the span for the reversible gauge.  FIG. 8  shows an alternative dual pin design ideal for the reversible gauge. 
         [0043]      FIG. 9  shows a new technical feature for planar reference points. The pins are replaced by a circular collar  27 . Made from suitable material it can snap onto the span bar  14  and being of a circular design keeps the span evenly spaced from the planar contact point eliminating any rotational effect from adjusting the height and level of a span. It provides dual sided points ideal for a reversible gauge. Collar  27  has a radius suitable to contact the wheel rims and maintain clearance of any other part of the gauge from contacting any other part of the wheel or tyre and is narrow to suit accurate location on the edges of the wheel rims.  FIG. 10  shows collar  16 , the smaller radius being suitable to contact the tyre wall and maintain clearance of any other part of the gauge from contacting any other part of the wheel or tyre but is wider to suit accurate location on the tyre wall.  FIG. 11  shows how just a section of the collars can be used to form blades  28  that function more like the pins in  FIGS. 8 and 9  but still maintain a degree of rotational tolerance.  FIG. 12  shows an alternative dual blade design ideal for the reversible gauge. The new planar reference devices can be independent components, connected to the props, or incorporated into the props to form a single part. Collars and blades can be of any suitable dimensions that testing may dictate. 
         [0044]      FIG. 13  shows a side view of the planar gauge mounted to a wheel. The new sectional span  14  incorporates the compacting feature, having more than one part that lock together rigidly for use and then unlock for compact storage. Male and female parts screw together connections meet requirements and allow an optional extension for larger vehicles. Different size tubes with suitable locking means can be provided to use telescopic compacting. The span is mounted against the wheel using the new method of props  15  standing on the ground G. The props lean into the wheel to utilise gravity. Directly fixed props provide this benefit, but an adjustable connection at  25  will provide adjustment of a pivoting nature and/or adjustment along the span. Separate props require their own clip on connection  25 . A bubble level  24  and mirror  17  are installed at one end. The planar contact devices  16  are of a collar design to reference to the tyre walls and are separate from the props  15 . 
         [0045]      FIG. 14  shows an arrangement similar to  FIG. 13  but with the collars  16  incorporated into the props  15  to form a single part. 
         [0046]      FIG. 15  shows an arrangement similar to  FIG. 13  but with the narrow wheel rim contact collars  27  separate from the props  15 . 
         [0047]      FIG. 16  shows an arrangement similar to  FIG. 15  but with the collars  27  incorporated into the props  15 . Any combination of separate or combined props and planar reference devices can be used. 
         [0048]      FIG. 17  shows how a pivoting mounting at  32  of the laser/target unit  18  to remote base  30  allows level adjustment of laser  20 . Pivoting between span  14  at collar part  16  allows vertical angular adjustment of mirror  17  to level the reflected laser  21 . Parts  31  are unit feet of which three provide stability. 
         [0049]      FIG. 18  shows an actuated angle calculator incorporated into the remote unit as it would appear in the final stage of the alignment check shown by  FIG. 6 . No scale is used on laser/target unit  18 , just a central zero line  23 . The laser/target unit is mounted to a carrier  41  which is pivotally connected beneath at point  42  to the larger base  34 . The carrier has an actuator arm  35  with a pointer  36  that points at an adjacent scale  37 . The pointer is set to zero on the scale before use. On completion of a toe angle check any mis-alignment will again be indicated by laser dot  22  not being on zero line  23 . The actuator  35  is moved rotating the laser/target unit, indicated by arrows  43 , when laser dot  22  is back on zero line  23 , the pointer will now indicate a result on the scale  37 . 
         [0050]      FIG. 19  shows how a movement exaggerator will allow a larger easy read scale  38 . The laser/target unit is removed on this diagram to clearly show the carrier  41 . A geared connection  39  between carrier  41  and actuator arm  35  which now has its own pivoting connection to the base at point  40  allows greater movement of the pointer against rotation of the carrier thus allowing the larger, easier to read results scale  38 . 
         [0051]    The laser/target unit  18  can alternatively be installed on the planar gauge and the mirror on the remote unit. In this embodiment an actuated angle calculator can be installed on the planar gauge or on the remote unit. The checking process can be in a forward or rearward perspective of the wheels and on alternative sides of the vehicle. Calibration can be on either wheel. Labelling of the scale will differ depending on combination used.
A method for determining the alignment of a pair of vehicle wheels includes the steps of positioning a beam projecting device consecutively on each wheel, in the same angular relationship to the wheel, and projecting a beam to a receptor, which is located in a predetermined angular relationship the other wheel. The projecting device, the receptor or both is utilized to determine the angle between the beams and the angle is related to the alignment of the pair of wheels; the receptor being maintained in the same position for each beam projection.