GB2331590A

GB2331590A - Laser-based device for checking geometry

Info

Publication number: GB2331590A
Application number: GB9821788A
Authority: GB
Inventors: Paul Coetsier; Olivier Sausay
Original assignee: Muller Bem S A
Current assignee: Muller Bem S A
Priority date: 1997-10-08
Filing date: 1998-10-07
Publication date: 1999-05-26
Anticipated expiration: 2018-10-07
Also published as: GB9821788D0; FR2769365B1; GB2331590B; FR2769365A1

Abstract

A device for checking vehicle geometry comprises at least one laser beam emitting means 4. The laser beam emitting means 4 is mounted in an optical block 1 carrying a beam splitter plate 13 mounted adjustably so as to define an optical square.

Description

2331590 LASER-BASED DEVICE FOR CHECKING GEOMETRY The invention relates to

a device for checking vehicle geometry, of the type comprising at least one laser beam emitting means.

French patent application, publication number FR 2451020 describes an apparatus for checking parallelism comprising, for each of the front wheels, a horizontal arm supported by the corresponding wheel and inside which is arranged a laser emitter associated with a-beam splitter plate capable of subdividing the laser ray into a first horizontal ray lying in the direction of the initial ray emitted and reflected at right angles from a first mirror transversely in front of the vehicle, and a second ray reflected at right angles from a second mirror, towards a third mirror carried by the corresponding back wheel. The first ray strikes a first receiver mounted facing the first mirror on the end of the arm carried by the other front wheel and the second laser ray strikes a second receiver mounted on the same arm. The apparatus furthermore comprises an electronic computer programmed so as automatically to determine the angular values relating to the parallelism of the front and back wheels as well as the set back from the information recorded on the receivers.

The construction of such an apparatus requiring numerous optical components is relatively expensive and the relative adjusting of the optical components with respect to one another requires very precise adjustments and machining.

One purpose of the invention is to provide a laser-based device for geometrical checking which is of simple and inexpensive construction and can be adjusted in the factory as regards the optical part.

1 i Another purpose of the invention is to provide a device for checking geometry in which the calibration is performed solely by mechanical adjustment without any intervention on the optical elements of the device.

The subject of the invention is a device for checking vehicle geometry, of the type comprising at least one means of emitting a laser beam, characterized in that the laser beam emitting means is mounted in an optical block carrying a beam splitter plate mounted adjustably so as to define an optical square.

Other preferred characteristics of a device in accordance with the present invention include the following:

is e the beam reflected by the beam splitter plate passes through a focusing means defining a light plane; the means for focusing defining a light plane consists of a cylindrical bar of glass or material of index comparable to the index of glass; the beam splitter plate is integral with a metal hinge which can be deformed so as to carry out adjustment; the metal hinge is formed by a narrowed part of a plate bent at an angle of around 45', fixed at one end to the optical block and adjustable by means of screws for pressing thereon; e the optical block comprises a means of adjusting the position of the optical block on a calibration bench; e the means for adjusting position is fashioned so as to perform adjustment by pivoting about an axis; 2 the adjusting means comprises in combination an orifice of larger diameter than that of a clamping screw and a bore for fitting onto a pin, or a cylindrical stud; the device comprises at least one measurement sMe with an orifice for the passage of a plane laser beam and a mirror for reflecting this plane laser beam onto the said measurement scale; the device comprises at least one measurement scale which receives the laser beam emitted by a means for emitting a laser beam.

is The invention will be better understood by virtue of the description which follows, given by way of non-limiting example with reference to the appended drawings in which: Figure 1, diagrammatically represents a partial exploded perspective view of a device according to the invention. Figure 2, diagrammatically represents a partial sectional view through a horizontal mid-plane of a device according to the invention.

Figure 3, diagrammatically represents a view from above of a first embodiment of the invention during calibration.

Figure 4, diagrammatically represents a view from above of a second embodiment of the invention during calibration.

Figure 5, diagrammatically represents a view from above of a third embodiment of the invention during calibration.

In Figures 1 and 2, elements which are identical or functionally equivalent are labelled with identical references.

In Figure 1, an optical block I in the form of a right-angled parallelepiped with a 45" canted corner 2 receives in a through bore 3 3 opening out into the oblique canted comer 2 a laser diode 4 able to emit a laser ray substantially along the axis of the bore 3.

The laser diode 4 is immobilized by a press screW 5 which is substantially perpendicular to the axis of the bore 3. The optical block 1 also includes a bore 6 parallel to the bore 3 able to receive a cylindrical lens 7 consisting of a cylindrical bar made of glass or of material of index comparable to glass.

The cylindrical lens 7 constitutes a focusing means defining a light plane from an input light ray. A small plate 10 includes a fixing part 10a and a positionally adjustable part 10b bent substantially at 45 with respect to the part 10a.

The optical block 1 includes two tappings 8 and 9 enabling the part 10a to be fixed by means of clamping screws and appropriate washers 11 and 12. The positionally adjustable part 1 Ob carries a beam splitter plate 13 mounted in an adjustable manner by means of press screws 14 and 15.

During adjustment by means of the screws 14 and 15, a narrowed central part 16 of the small plate 10 can be deformed so as to adjust the position of the beam splitter plate 13 in order to define an optical square comprising two perpendicular light rays, of which the first lies on the axis of emission of the laser diode 4 and the second is perpendicular to this axis at the point of impact of the first ray on the beam splitter plate 13.

4 In Figure 2, the laser diode 4 emits a light ray L2which is split by the beam splitter plate 13 into two light rays L.2 lying on the axis of L,, and L3which is perpendicular to the axis of L2Because the perpendicular ray L3passes through the cylindrical lens 7, on exiting the cylindrical lens 7 the ray L3 forms a light plane which can define on a target C such as a scale a trace of light allowing a measurement.

The optical block 1 also includes two bores 17 and 18; the bore 17 is a through-bore allowing passage of a means of adjustment and of fixing by clamping, whilst the bore 18 is a bore mating with a stud or with a positioning pin fixed to a support box.

With reference to Figures 3 to 5, elements which are identical or functionally equivalent are labelled with identical references.

In Figure 3, a first embodiment of the device comprises two dogs or supports 19a, 19b for fixing to a vehicle wheel, these being mounted on a calibration support E, comprising two braced parallel crossmembers.

The first dog 19a carries a box 20a containing an optical block described with reference to Figures 1 and 2. The box 20a is shuttered in such a way as to prevent the emission of the ray L2. The dog or support 19b carries a box for supporting a reflecting mirror R. The box 20a carries a graduated scale 21 comprising an orifice 22 allowing passage of the light plane L.3, in such a way that this light plane L3 strikes the mirror R and is reflected as a luminous beam L4which will strike the graduated scale 21, thereby indicating a value representative of the total parallelism of the wheel pair on which the supports 19a and 19b are mounted.

To carry out mechanical calibration of this device, the optical block 1 positioned by virtue of the bore 18 engaged with a pin or a stud integral with the box 20a can be displaced angularly accordint to a small angle of adjustment. For this purpose, a screw of smaller diameter than that of the bore 17 is engaged in the bore 17 and the optical block 1 is displaced angularly about the axis defined by the bore 18 until the trace of light defined by L4 strikes the scale 21 at the zero of the scale. The position of the optical block 1 is then locked by tightening the screw passing through the bore 17. The only adjustment to be made thus during calibration is a mechanical adjustment via a pivoting motion about the axis 18.

In Figure 4, dogs 19a, 19b are mounted on a calibration bench E2 comprising two parallel crossmembers with three braces. The rear of the bench E2 carries two scales 23a, 23b intended to be fixed to an axle of a vehicle other than the axle to which the dogs 19a, 19b are fixed. The laser beam issuing from the laser diode 4a is subdivided into two rays L2, L3. Ray L2 strikes the scale 23a, whilst ray L.3 is reflected off the mirror R as a reflected ray L4which will strike the scale 21.

Another laser diode 4b mounted in the box 20b behind the reflecting mirror R emits a light ray L, which will strike the graduated scale 23b on the other axle. The light beams L2, L, are point light beams which can be likened to a ray, that is to say which exhibit a very small divergence spot which does not fall outside the surface of the graduated measurement scales 23a, 23b. The beams L3 and L4 are plane light beams so that the image formed on the graduated scale 21 is a vertical straight line segment.

6 Owing to the use of the optical block 1, this embodiment of the invention also exhibits a separation between optical precision adjustment performed in the factory during manufacture and mechanical calibration adjustment by means of the pair of bores 17 and 18.

In Figure 5, the third embodiment of the invention comprises scales 23a and 23b intended to be mounted on an axle other than the axle for mounting the dogs 19a and 19b. Each box 20a or 20b comprises an 10 optical block 1 of the kind described with reference to Figures 1 and 2.

The difference with the other two embodiments consists in the absence of a reflecting mirror R: each box 20a or 20b comprises a measurement scale 24a or 24b drilled at 25a or 25b respectively, for the passage of a light beam L3. The light beam L3 issuing from a diode 4a of an optical block 1 passes through an aperture 25a so as to strike the scale 24b integral with the box 20b intended to be fixed to the opposite wheel: whilst the light ray L3 passing through the aperture 25b will strike the measurement scale 24a of the box 20a. The paths emerging from the boxes 20a or 20b are comparable to the optical paths of the laser beams emerging from the boxes of the second embodiment of the device described in document FR 2 451020.

By comparison with this document, the number of optical components has been appreciably reduced and the cost of production much diminished. The optical block 1 fully equipped with the elements 2 to 16 can be manfactured and adjusted in the factory and dispatched in fast mode by virtue of its low bulk: the optical block 1 thus equipped constitutes an interchangeable component which can be fixed permanently 7 in boxes 20, this fixing requiring only mechanical calibration such as described with reference to Figures 3 to 8.

The invention described with reference to thr& particular ernbodiments is in no way limiting thereof, but on the contrary covers any modification of form and any variant embodiment within the framework and spirit of the invention.

In particular, the invention also covers the variant according to 10which the scales 23a, 23b of Figures 4 and 5 are alignment reference scales, and separate scales for checking geometry are provided for mounting on the back axle of the vehicle.

8 1 1 1 1

Claims

1. Device for checking vehicle geometry, of the type comprising at least one means (4, 4a, 4b) of emitting a laser beam (In), characterized in that the laser beam emitting means (4, 4a, 4b) is mounted in an optical block (1) carrying a beam splitter plate (13) mounted adjustably (10, 14, 15, 16) so as to define an optical square Q_., 1,3).

2. Device according to Claim 1, characterized in that the beam(I.3) reflected by the beam splitter plate (13) passes through a focusing means (7) defining a light plane (L3).

3. Device according to Claim 2, characterized in that the means for focusing defining a light plane consists of a cylindrical bar (7) of glass or material of index comparable to the index of glass.

4. Device according to one of the preceding claims, characterized in that the beam splitter plate (13) is integral with a metal hinge (16) which can be deformed so as to carry out adjustment.

5. Device according to Claim 4, characterized in that the metal hinge (16) is formed by a narrowed part of a plate (10) bent at an angle of around 45', fixed (11, 12) at one end to the optical block (1) and adjustable by means of screws (14, 15) for pressing thereon.

6. Device according to one of the preceding claims, characterized in that the optical block (1) comprises a means (17, 18) of adjusting the position of the optical block (1) on a calibration bench.

9

7. Device according to Claim 6, characterized in that the means (17, 18) for adjusting position is fashioned so as to perform adjustment by pivoting about an axis.

1

8. Device according to Claim 7, characterized in that the adjusting means (17, 18) comprises in combination an orifice (17) of larger diameter than that of a clamping screw and a bore (18) for fitting onto a pin, or a cylindrical stud.

9. Device according to one of the preceding claims, characterized in that the device comprises at least one measurement scale (21) with an orifice (22) for the passage of a plane laser beam (L3) and a mirror (R) for the passage of a plane laser beam (L3) and a mirror (R) for reflecting this plane laser beam (L4) onto the said measurement scale (21).

10. Device according to one of the preceding claims, characterized in that the device comprises at least one measurement scale (23a, 23b, 24a, 25b) which receives the laser beam emitted by a means (4a, 4b) for emitting a laser beam (L2, L3, L5).

11. A device for checking vehicle geometry constructed adapted and arranged to operate substantially as hereinbefore described with reference to the accompanying drawings.