GB1590117A

GB1590117A - Device for indicating vehicle wheel alignment

Info

Publication number: GB1590117A
Application number: GB2488176A
Authority: GB
Original assignee: SPQR ENG Ltd
Current assignee: SPQR ENG Ltd
Priority date: 1977-09-15
Filing date: 1977-09-15
Publication date: 1981-05-28

Description

(54) DEVICE FOR INDICATING VEHICLE WHEEL ALIGNMENT (71) We, S.P.Q.R. ENGINEERING LIMITED, a Company registered under the laws of Great Britain of Rowlands Castle, Hampshire, PO9 6AT, do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to motor car accessories and is particularly concerned with a device for indicating misalignment of the steerable road wheels of a vehicle.

In order to minimize "scrubbing" between the tyres of the steerable road wheels of a vehicle and the road surface it is necessary to ensure that these wheels are correctly aligned or "tracked". This means that to make an appropriate averaging allowance for the disposition and movement of the vehicle suspension and steerable movement of the wheels over a range of vehicle speeds it is usually found that the wheels must "toe in" or "toe out" by an amount advised by the vehicle manufacturer.

Usually tracking adjustment is carried out with the aid of an optical instrument using a part of the wheel such as its rim, as a datum.

Such instruments are expensive, require expert operation and in any event can be used to determine only the amount of "toe in" or "toe out" and not directly the amount of scrub. Other instruments are known which respond directly to the scrubbing action between the tyre and the road and which can be used to track the wheels accurately to minimise such action. Such instruments are however very expensive and require expert operation to reproduce accurate results. Furthermore it is usual to check the alignment of one wheel relative to the other which introduces the possibility of error since each wheel should, for optimum results, be separately aligned relative to the body of the vehicle.

It is accordingly an object of the present invention to provide a simple to operate and inexpensive device for indicating misalignment of a steerable road wheel of a vehicle by responding directly to the scrubbing action between tyre and road.

According to the present invention there is provided a device capable of responding to scrubbing action between the tyre of a single wheel of a vehicle and a road surface in order to indicate any misalignment of that wheel relative to the vehicle comprising a base plate to be located in advance of and with its longitudinal dimension aligned with the rolling path of the tyre, a slide disposed on the base plate and movable transversely relative thereto in response to said scrubbing action, indicator means pivoted on the base plate and having an indicator arm associated with a scale on the base plate the means being engaged directly with the slide to be so that the means Is deflected in response to said movement in either direction from a mean position and to maintain said deflection after the tyre has passed over the device.

The above and other aspects of the present invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 shows in plan one form of the device; Fig. 2 is a similar view of the device indicating scrubbing.

Fig. 3 is a view in the direction of the arrow A in Fig. 2.

Fig. 4 is a plan view with parts cut away of part of a modified device.

Fig. 5 is a section on the line V-V of Fig. 4 and Fig. 6 is a section on the line Vl-VI of Fig.

4.

Referring to Figs. 1 to 3 of the drawings a base plate 1 of resilient plastics material has opposed ends 2 and 3 thickened and formed with guide slots 4 and 5 to receive a rectangular slide 6 as a close sliding fit. The base 1 is cut away at 7 to receive a pointer 8 having an indicator arm 9, a boss 10 and a drive arm 11 of shorter length than the arm 9 formed with a slot 12. The drive arm 11 moves in an extension 7a of the cut-away 7.

The boss 10 is pivoted on a pin 13 carried by the base plate 1 and a pin 14 carried by the slide 6 engages in the slot 12. The base plate 1 carries an outwardly extending part la carrying a scale 15, the pointer being central on this scale when the slide 6 is in a mean position on the base plate 1 Figs. 4 to 6 show a modified arrangement in which, where applicable, like reference numerals have been used for like parts. The base plate 1 has its opposed ends 2 and 3 formed with a chamferred face 21 to facilitate rolling of the vehicle wheel and the scale 15 is marked on the upper surface of a platform 22 extending the entire length of the device.The upper surface 23 of the base 1 is formed with a number of longitudinally extending rectangular slots 24 separated by walls 25 which extend between the ends 2 and 3 and in the region of the cut-away 7 similar, but shorter, slots 24a and walls 25a are arranged on each side of the cut-away.

Plastics rollers 26 are disposed loosely In each slot and have a diameter slightly greater than the depth of the slot. The rollers are, as shown in Fig. 4, disposed centrally of their slots when the slide 6 is in its mean position relative to the base 1 and the pointer 8 is indicating zero. At intervals along their length the walls 25 are formed with grooves 27 accommodating push rods 28 extending at right angles to the slots 24 between the rollers 26 of adjacent pairs of slots 24 to maintain spacing of the rollers 26. The slide 6 is supported on the rollers 26 clear of the upper surface 23 of the base 1.

It will be understood that with this arrangement as the slide 6 moves transversely relative to the base 1 during scrubbing movement of a vehicle tyre thereon, the rollers 26 act as rotating bearings between the slide and the base so minimising friction between these parts and ensuring that the resistance to movement of the slide 6 is maintained substantially constant.

The width of the slots 24 is arranged to accommodate the entire range of movement of the pointer 8 between maximum "toe in" and maximum "toe out" of the rollers 26 and maintained in their correct relative positions by the push rods 28 which slide longitudinally of their lengths through the grooves 27 in the walls 25.

As shown in Fig. 6, the push rods 28 have a lateral dimension less than the rollers 26 so that they do not impose a frictional drag upon the slide 6 and they may be of round or square cross-sectional shape.

As shown in Fig. 4, an extension 7a of the cut-away 7 is formed with a recess 7b extending transversely of the device to facilitate assembly and engagement of the pin 14 in the slot 12.

It will be understood that operation of the device of Figs. 4 to 6 is the same as that referred to above but it has been found that the provision of the rollers 26 increases accuracy with repetitive operations.

It will also be understood that the alterna tive form of indicator shown at 16 in Fig. 1 could be employed with the arrangement of Figs. 4 to 6.

In use the device is located in advance of and in alignment with one of the steerable road wheels of the vehicle when the latter are in the "straight ahead" position. Ideally, it is disposed in advance of the wheel a distance of at least one wheel circumference and the vehicle is then pushed to roll the wheel over the slide.

If the tyre scrubs the slide will be deflected in one or other direction from its mean position; the extent being indicated by the pointer 9 on the scale 15. The track of the vehicle is then adjusted to provide minimum (preferably zero) scrubbing on repeating the test and it will be understood that it is not necessary to measure the actual "toe in" or "toe out" of the wheel.

With some vehicle suspensions it may be desirable to repeat the test on the other steerable road wheel but with most vehicles checking one wheel is enough since the lateral force exerted by scrubbing is transferred from wheel to wheel. Allowing the wheel to roll for one revolution before engagement with the slide ensures that the suspension is returned to a normal condition after rearward movement of the vehicle.

WHAT WE CLAIM IS: 1. A device capable of responding to scrubbing action between the tyre of a single wheel of a vehicle and a road surface in order to indicate any misalignment of that wheel relative to the vehicle comprising a base plate to be located in advance of and with its longitudinal dimension aligned with the rolling path of the tyre, a slide disposed on the base plate and movable transversely relative thereto in response to said scrubbing action, indicator means pivoted on the base plate and having an indicator arm associated with a scale on the base plate the means being engaged directly with the slide to be so that the means is deflected in response to said movement in either direction from a mean position and to maintain said deflection after the tyre has passed over the device.

2. A device according to claim 1 in which the slide is retained in guide slots in the base plate.

3. A device according to claim 1 or claim 2 in which the base plate has a longitudinal side edge cut away to receive the indicator means said means having a drive arm formed with a slot to receive a pin carried by the slide.

4. A device according to any one of the preceding claims in which the slide runs on rollers extending longitudinally in slots formed in the upper surface of the base plate.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

1 carries an outwardly extending part la carrying a scale 15, the pointer being central on this scale when the slide 6 is in a mean position on the base plate 1 Figs. 4 to 6 show a modified arrangement in which, where applicable, like reference numerals have been used for like parts. The base plate 1 has its opposed ends 2 and 3 formed with a chamferred face 21 to facilitate rolling of the vehicle wheel and the scale 15 is marked on the upper surface of a platform 22 extending the entire length of the device. The upper surface 23 of the base 1 is formed with a number of longitudinally extending rectangular slots 24 separated by walls 25 which extend between the ends 2 and 3 and in the region of the cut-away 7 similar, but shorter, slots 24a and walls 25a are arranged on each side of the cut-away.

5. A device according to claim 4 in

which the slots are separated by walls having transverse grooves at intervals along their lengths and push rods are disposed within the grooves to extend between the rollers of adjacent slots in order to maintain the rollers in their desired relative positions during movement of the slide relative to the base plate.

6. A device capable of responding to scrubbing action between a vehicle tyre and a road surface substantially as herein described with reference to Figs. 1, 2 and 3 or Figs. 4, 5 and 6 of the accompanying drawings.