Patent GB-738912-A (GB)
Title: Apparatus for testing and measuring vehicle wheel alignment
IPC: G01B11/275
Filed: 1953-07-24
Abstract: 738,912. Optical gauging apparatus. MULLER, F. July 24, 1953 [July 28, 1952; Jan. 5, 1953], No. 20663/53. Class 106 (2). An apparatus for measuring the alignment of vehicle wheels, Fig. 5. comprises a telescope 531 provided with crossthreads, a member 534 bearing vertical and horizontal scales, and means 512 adapted to be attached or positioned with respect to a wheel to be tested so as to cause the calibrations of the member 534 and the cross-threads of the telescope 531 to co-operate and give an indication of the alignment condition of the wheel or wheels being tested. In Figs. 1 and 3, each front wheel 511 of a vehicle has a mirror unit 512 pivotally mounted on a pin 542 extending from a plate 518 secured by screw means 520 to the wheel of the car in such a manner that the mirror 512 may be brought into a plane at right-angles to the axis of the wheel, the mirror being pivoted on the pin 542 so that it remains in the position to which it is set. Each mirror unit 512 comprises a central mirror 622 and two side mirrors 623 displaced rearwardly by 20 degrees. Facing each mirror unit is a reading plate 534 with horizontal and vertical scales. Each gauging unit H supports a vertical telescope 531. Below each telescope is an adjustable projector 533 enabling the reflection in the mirror unit 512, of the reading plate 534, to be viewed through the telescope 531. The gauging units H are joined by a U-shaped tube 521 mounted on three legs 522 and 525. Method of operation. The wheels 511 are lifted slightly and each mirror 512 is adjusted until the image of the scales on the plate 534, as viewed through the associated telescope, are stationary while the wheel is rotating. Each mirror 512 is then in a plane perpendicular to the axis of the wheel. The wheels are then lowered and the mirrors are arranged such that their upper and lower edges are horizontal. The gauging units H are next moved through guiding means 526 until the distance between each reading-plate 534 and its associated mirror 512 is such that one graduation of the said scales corresponds to the wheel being adjusted to the extent of one step or graduation in the scale of measurement in use. The two telescopes 531 are arranged such that their crossthreads are parallel to the scales of the respective reading plates 534. The steering-wheel is now turned until one wheel is such that the vertical thread of the associated telescope coincides with the vertical scale on the plate 534. The toe-in of the wheels is then measured by reading the horizontal scale of the other reading plate 534 through the other telescope 531. To determine the caster of a wheel, for instance the left wheel 511, the wheels are turned right or left until a side mirror 623 of the left wheel 511 is in such a position that the vertical line of the telescope and the plate 534 coincide. The line corresponding to the horizontal of the cross-threads of the right telescope 531, then indicates a deflection on the horizontal scale of the right-hand plate 534, other than the camber measurement, which may be used to determine caster, inclination of the steering knuckle pivot and king-pin inclination from a special table. Setting up measuring apparatus to check alignment characteristics of front and rear automobile wheels. To check the alignment of the front and rear wheels the measuring apparatus B, Fig. 6, comprises a U-shaped rod 17 standing on legs 20, 21 and 22, and supporting at each end a plate 18. On each plate 18 is slidably mounted a unit C comprising a vertical telescope 25 and a reflector so arranged that the optical axis of the apparatus is along the line n. Pivoted to each unit C is an optical element which, when swung into the vertical position causes the optical axis of the apparatus to change to the axis p. Two units E are also provided, each supporting a plate 34 having horizontal and vertical graduations, there being a horizontal rod 35 adjustable in length extending from each unit as shown. To adjust the setting of the measuring apparatus B, C the vehicle wheels 11, 12 are arranged parallel to the central plane m of the vehicle. The alignment of the units C is then checked by observing through each telescope 25 along the axis n a scale on the opposite unit C. Adjustments are made until the optical axis n is common to both units. The apparatus B, C is then arranged such that the optical axis n is approximately at right-angles to the plane m. The optical elements are then moved to change the optical axis to the line p. Each unit E is then brought close to the gauging unit C such that the zero line on the plate 34 lies in the vertical plane through the line p. The adjustable rod 35 on each unit E is then set at such a length that it abuts a certain part of the vehicle, preferably the lower central rim portion of the front wheel. Each adjusting element E is then moved to the corresponding rear wheel and placed in such a manner that the rod 35 abuts the same rim portion of the rear wheels. In order to properly set the measuring apparatus B, C, the latter is moved, e.g. by swinging the apparatus about the legs 20, 21 and 22 until the same graduations on both horizontal scales of the two adjusting units E is observed. When this is the case, the optical cross-wise disposed axis n of the measuring apparatus will be at right angles to the central longitudinal plane m of the vehicle.