WO2005108005A1

WO2005108005A1 - Measuring instrument and method to determine the position of a point on the edge of a plate-shaped object

Info

Publication number: WO2005108005A1
Application number: PCT/BE2005/000071
Authority: WO
Inventors: Alex Van Den Bossche
Original assignee: Krypton Electronic Engineering N.V.
Priority date: 2004-05-10
Filing date: 2005-05-10
Publication date: 2005-11-17
Also published as: BE1016010A3

Abstract

The invention concerns a measuring instrument to determine the position of a point which is situated on the edge (3) of a plate-shaped object (4), such as a glass plate, by means of a three-dimensional position measuring system, characterised in that it comprises a stop element (1) which is to be placed against said edge (3) and which is fixed to a marking element (10) which can be perceived by said position measuring system, whereby this stop element (10) is situated between two supporting elements (2) which must be placed against said edge (3) as well and which can be moved in relation to the stop element (1). Further, the invention also concerns a method for using the measuring instrument.

Description

MEASURING INSTRUMENT AND METHOD TO DETERMINE THE POSITION OF A POINT ON THE EDGE OF A PLATE-SHAPED OBJECT The invention concerns a measuring instrument to determine the position of a point which is situated on the edge of a plate-shaped object, such as a glass plate, by means of a position measuring system, such as for example an optical measuring system. According to the state of the art, the edge of a plate-shaped object is measured by means of a measuring instrument as described in international patent application WO 98/48241. Such a measuring instrument is provided with a measuring pin having a point which is placed against the edge of the plate-shaped object in order to determine its position. This does not provide any accurate measuring results when the plate- shaped object has for example a somewhat rounded edge, as is the case for example with car windows, or when the plate-shaped object is very thin. In such cases, it is very difficult to place the measuring pin of the measuring instrument precisely on the edge of the object. The invention aims to provide a measuring instrument which makes it possible to measure the position of a point on the edge of a plate-shaped object with very great precision. To this aim, the measuring instrument comprises a stop element which must be placed against said edge and which is fixed to a marker element which is perceptible through said optical measuring system, whereby this stop element is situated between two supporting elements which must be placed against said edge as well, and which can be freely moved in relation to the stop element. Practically, said stop element can be moved in a direction which is perpendicular to a line of junction between said supporting elements. In an advantageous manner, the distance between said stop element and each of said supporting elements is practically equal. According to a preferred embodiment of the measuring instrument according to the invention, it contains a holder onto which said supporting elements are fixed, whereby said stop element is mounted in a floating manner in relation to the holder. According to an interesting embodiment of the measuring instrument according to the invention, said stop element and said marker element are provided on one and the same support, whereby this support has a bearing face which is to rest on said plate-shaped object. The invention also concerns a method to determine the position of a point on the edge of a plate-shaped object by means of an optical measuring system, whereby two supporting elements which are fixed to each other are placed against said edge and a stop element is moved up to against this edge as well in a direction which is perpendicular to a line of junction between said supporting elements and which is parallel to the surface of said plate-shaped object in the vicinity of said edge. Next, the position of a marking element which is fixed to the stop element is perceived with the optical measuring system, and the position of said point is determined on the basis of said perceived position. Further, the invention concerns a method to determine the deviations of the edge of a plate-shaped object in relation to a computer model of this object by means of said measuring instrument, whereby three said measuring instruments are fixed against said edge, whereby the position of the marking elements of these measuring instruments is measured and an expected deflection of the edge is determined on the basis of said computer model and the measured positions of these marking elements. According to this method, a fourth measuring instrument is placed against a point of said edge, and the position of the latter point is determined in order to compare this position with its expected position according to the expected deflection of the edge. Other particularities and advantages of the invention will become clear from the following description of a few embodiments of the measuring instrument and the methods according to the invention; this description is given as an example only and does not restrict the scope of the claimed protection in any way; the figures of reference used hereafter refer to the accompanying figures. Figure 1 is a schematic diagram of the edge of a plate-shaped object with two supporting elements and a stop element. Figure 2 is a schematic view in perspective of a support of the measuring instrument according to the invention. Figure 3 is a schematic longitudinal section of a measuring instrument according to the invention, according to line III-1II from figures 5 to 14. Figure 4 is a schematic longitudinal section according to line IV-IV in figures 5 to 14 of this measuring instrument. Figure 5 is a schematic bottom view of a support and a basic part of a holder of the measuring instrument according to the invention. Figure 6 is a schematic side view of a support of the measuring instrument according to the invention. Figure 7 is a schematic top view of a support of the measuring instrument according to the invention. Figure 8 is a schematic side view of a first part of the holder of the measuring instrument according to the invention. Figure 9 is a schematic bottom view of the first part of the holder from figure 8. Figure 10 is a schematic top view of the first part of the holder from figure 8. Figure 11 is a schematic side view of a second part of the holder of the measuring instrument according to the invention. Figure 12 is a schematic side view according to line XII-XII of figure 1 1 of said second part of the holder. Figure 13 is a schematic side view of a third part of the holder of the measuring instrument according to the invention. Figure 14 is a schematic top view of the third part from figure 13. In the different drawings, the same figures of reference refer to identical or analogous elements. The invention in general concerns a measuring instrument to determine the position of a point on the edge of a plate-shaped object. Although the invention can be applied to any plate-shaped object whatsoever, it is particularly interesting for the automobile industry, where it is used to measure the edge of windows of a car or the edge of metal plates of the coachwork of a vehicle. In the following description, said plate-shaped object will thus consist, by way of example, of a glass plate forming for example a car window. Figure 1 schematically represents the working principle of the measuring instrument according to the invention. This measuring instrument comprises a stop element 1 and two supporting elements 2 which are placed against the edge 3 of a glass plate 4. The stop element 1, which is situated in the middle between the supporting elements 2, can be moved in the direction of arrow 5 in relation to the supporting elements 2 which thus rest against the edge 3 on either side of the stop element 1. The stop element 1 can be moved in particular in a direction situated in a plane which is parallel to the glass plate 4 near the point 8 of the edge 3 to be measured and which is perpendicular to the straight line 6 connecting the contact points 7 between the supporting elements 2 and the edge 3 of the glass plate 4. This straight line 6 thus forms a chord of the curve described by the edge 3 between said contact points 7. When the edge 3 describes a curve with a slight curvature, we may assume that the contact point 8 between the stop element 1 and the edge 3 is practically situated at right angles to said straight line 6. Thus, the curvature of the edge 3 to be measured is preferably smaller than that of a circle having a diameter which is equal to the distance between the supporting elements 2. Normally, the edge of a car window will meet this demand. According to a preferred embodiment of the measuring instrument according to the invention, the distance between said supporting elements 2 is in the order of magnitude of 12 mm. The supporting elements 2 and the stop element 1 are then formed for example of little rods having a circular section with a diameter of almost 3 mm. In such a configuration, said line of junction 6 is almost parallel to a straight line connecting the axes of the supporting elements 2 in a plane which is parallel to the surface of the glass plate 4 near the point 8 of the edge 3 to be measured. When the position of the point 8 of the edge 3 is to be measured by means of an optical measuring system, a marking element, such as for example an LED, is fixed in relation to the stop element 1. The exact position of the marking element in relation to the stop element 1 is hereby determined. Of course it is possible, in a variant of this embodiment of the measuring instrument, to provide several marking elements which are fixed in relation to the stop element 1. When for example three marking elements which are not situated in a straight line are fixed to the stop element 1, the position of the measuring instrument, and thus of the stop element 1 can always be univocally determined. In order to measure the position of a point 8 of the edge 2 of the glass plate 4, the stop element 1 is thus placed against this point 8, whereby the supporting elements 2 rest against the edge 3 on either side of the stop element 1. Next, the position of the marking element is perceived by means of the optical measuring system, whereby, on the basis of this perception and the known relative position of the marking element in relation to the stop element 1 , the position of the point 8 to be measured is calculated. The optical measuring system hereby comprises one or several cameras which perceive the marking element, whereby the exact three-dimensional position of the marking element is determined on the basis of this perception, in a manner known as such. The optical measuring system preferably comprises two, three or several linear cameras or one, two or several matrix cameras, or a combination of both. Figures 2 to 14 schematically represent a concrete embodiment of a measuring instrument according to the invention, and of the different parts thereof. Figure 2, figure 6 and figure 7 schematically represent a support 9 onto which are provided a stop element 1 and a marking element 10. This support 9 comprises a rectangular plate 1 1 whereby the stop element 1 is mounted on the bottom side thereof. This stop element 1 consists of a cylindrical rod with a circular section which extends almost perpendicular to the bottom side of the plate 1 1. Further, the support 9 has a cylindrical fixing element 12 on the top side of the plate 1 1 whose longitudinal axis is perpendicular to the latter. On the free end 13 of the fixing element 12, opposite to said plate 1 1 , said marking element is fixed. This marking element 10 consists for example of a light emitting diode (LED) and it thus has a fixed position in relation to the stop element 1. Further, figure 2 represents two supporting elements 2 by means of a dot and dash line. These supporting elements 2 consist of a rod with a circular section and they each extend through a corresponding recess 14 which is provided in said plate 11 of the support 9. The recesses 14 form a longitudinal slot whose width practically corresponds to the diameter of the supporting elements 2 and they extend along either side of the stop element 1 in a direction which is perpendicular to the line of junction between the supporting elements 2. This line of junction is almost parallel to the straight line 6 from figure 1. Thus, the supporting elements 2 are guided through said recesses 14, in the direction of the arrow 5 represented in figure 1, when they are moved in relation to the stop element 1. Further, a third recess 14' is provided in the plate 1 1 which has practically the same dimensions and orientation as the recesses 14 through which said supporting elements 2 extend. In this third recess 14' is situated the free end of a guiding rod 15. Consequently, the support 9 with the stop element 1 can be moved in the longitudinal direction of the recesses 14 and 14' in relation to the supporting elements 2 and the guiding rod 15. These supporting elements 2 and the guiding rod 15 hereby extend parallel to the stop element 1. The bottom side of said plate 1 1 is provided with three supporting points 16, which are not situated in a straight line, which determine what is called a bearing face which extends perpendicular to the axis of the stop element 1. When the stop element 1 is placed against the edge 3 of a glass plate 4, said supporting points 16 rest on the surface of this glass plate 4 in such a manner that the stop element 1 extends almost perpendicular to said surface. Said support 9 is mounted in a holder 17 as is schematically represented in figures 3 and 4. In the specific embodiment of the measuring instrument according to the invention as represented, this holder 17 comprises three parts 18, 19 and 20. A first part 18 of the holder 17 is also represented in figures 5 and 8 up to 10 and has a flat, plate-shaped base 21 on which said supporting elements 2 and the guiding rod 15 are provided in a fixed manner. In particular, the latter extend at right angles to the surface of the base 21 which is directed to said support 9. The support 9 is directed with the top side, upon which said fixing element 12 is provided, to said base 21. The fixing element 12 hereby extends through a corresponding recess 22 in the base 21, such that the free end 13 of the fixing element 12 can be perceived on the side of the base opposite to the latter which is directed towards said support 9. The recess 22 is made longitudinal, in order to make it possible for the fixing element 12 to make the same movement in relation to this first part 18 of the holder 17 as the support 9 in relation to the supporting elements 2. Thus, the support 9 can move together with the stop element 1 in relation to the holder 17 in a direction which is perpendicular to the plane in which the longitudinal axis of said supporting elements 2 is situated. Further, the support 9 with the stop element 1 is mounted in a floating manner in relation to the holder 17 by means of three cylindrical pins 23 as represented in figure 5. One far end of these pins is anchored in said first part 18, whereas the other far end thereof extends in a recess 24 provided to that end in the side edges of said plate 1 1 of the support 9. The dimensions of the recesses 24 are selected such that the support 9 can move almost freely in the longitudinal direction of said recesses 14 without being hampered by the presence of the pins 23 in the recesses 24. These recesses 24 also open in the bottom side of the support 9. Further, said second part 19 of the holder 17 is represented in figures

11 and 12. This second part 19 is made U-shaped and thus has a base 26 from which two legs 27 extend. Via this base 26, said second part 19 is fixed to said first part 18 as represented in figures 3 and 4. The legs 27 have an almost perpendicular angle, such that they extend as of said base 26, partly, almost parallel to said supporting elements 2, and extend with their free end, partly, at right angles to and under the supporting elements 2. Near said base 21 is provided a cylindrical recess 28 in each of said legs 27 with a common central axis 29. Further, on the free end of each of the legs 27 is provided a cylindrical recess 30, whereby the recess 30 of the one leg 27 is situated in the extension of the other leg 27. Between the legs 27 is mounted a third part 20 of the holder 17. This third part 20 is represented in figures 13 and 14 and comprises a longitudinal plate of which one far end 31 is provided with a corrugated surface, whereas its other far end 32 is covered with a buffer 33, made for example of rubber. Between both far ends 31 and 32, this third part 20 of the holder 17 has a buckle. At the height of this buckle is provided a cylindrical bore 34. In the holder 17 of the measuring instrument, this bore 34 extends between said recesses 30 and in the prolongation thereof. A hub element extends through the bore 34 and the recesses 30 to thus form a hinge. In this manner, said third part 20 can rotate in relation to the second part 19, whereby said buffer 33 extends opposite to the support 9. Further, a draw spring 35 is fixed between the third part 20 and the second part 19 of the holder 17 which makes sure that, between said buffer 33 and the bottom side of the support 9, a plate-shaped object can be clamped. More particularly, this spring 35 makes sure that the measuring instrument can be clamped around the edge of a glass plate 4, as represented in figures 3 and 4. As will become clear from these figures, the glass plate 4 is clamped between said supporting points 16 and the buffer 33 in the holder 17, whereby the edge 3 of the glass plate rests against the stop element 1 and the supporting elements 2. Between the top side of the support 9 and the bottom side of the base 21 of said first part 18 of the holder 17 is mounted a spring element 25, more particularly a spiral spring. This spring element 25 makes sure that the support 9 is pushed against the surface of the glass plate 4 on the one hand, and that, when the supporting elements 2 are placed against the edge 3 of the glass plate 4, the support 9 with the stop element 1 is pushed against this edge 3 as well. As the support 9 is mounted in a floating manner in the holder 17, this guarantees that said bearing face, which is determined by the supporting points 16, is always parallel to the surface of the glass plate 4 near the point of the edge 3 to be measured, when the measuring instrument rests on the glass plate 4 via the supporting points 16. Consequently, the axis of the stop element 1 is perpendicular to this surface. The above-described measuring instrument is particularly interesting to determine deviations of the edge of a plate-shaped object, such as a glass plate forming a car window, in relation to a computer model of this object. In a first step, three measuring instruments are hereby fixed to the edge of the glass plate. The position of the corresponding marking elements is then determined by means of an optical measuring system. On the basis of this measured position of the marking elements and the deflection of the edge of the glass plate according to the computer model, an expected deflection of the edge of the glass plate is calculated, and thus the position of the glass plate can be determined. In other words, a coordinate system is selected for the optical measuring system, such that the position of the points which are determined by means of the measuring instruments are situated on the curve which corresponds to the edge of the glass plate according to the computer model. When a measuring instrument according to the invention is provided to a following point on the edge of the glass plate, the position of the point is calculated on the basis of the measured position of the marking element of this measuring instrument. The use of the measuring instrument according to the invention can thus for example also be applied to a glass plate which moves while the above- mentioned measurements are carried out. Naturally, the invention is not restricted to the above-described concrete embodiment of the measuring instrument and the methods according to the invention. Thus, the supporting points 16 of said support 9 are not necessarily present, and the bottom side of the support 9 itself can form said bearing face. The supporting points 16 can have different shapes and dimensions and they may consist for example of little spherical balls which are partly countersunk in the bottom side of the support 9. As already mentioned above, in a variant of the preceding embodiment of the measuring instrument, for example two marking elements 10 or three or more marking elements 10 which are not situated in a straight line can be fixed to the fixing element 12. When the position of each of these marking elements 10 in relation to the stop element 1 is known, the exact position of the stop element 1 and thus of the point concerned on the edge 3 of the plate-shaped object 4 will consequently be calculated by measuring the position of these marking elements 10 by means of a three- dimensional measuring system, such as an optical measuring system. The measuring instrument and the methods according to the invention can also be used together with all sorts of three-dimensional position measuring systems. Such a position measuring system can for example make use of cameras or laser beams with what is called a "laser tracker" for optical measuring systems, or of ultrasonic sound waves when the position of the marking element is acoustically determined. Thus, said marking element consists for example of what is called a corner mirror comprising three orthogonal mirror surfaces ("corner cube"), a reflector ("cat- eye"), a mirror, an LED or any element whatsoever which can be perceived by the corresponding three-dimensional position measuring system.

Claims

1. Measuring instrument to determine the position of a point which is situated on the edge (3) of a plate-shaped object (4), such as a glass plate, by means of a position measuring system, characterised in that it comprises a stop element (1) which is to be placed against said edge (3) and which is fixed to a marking element (10) which can be perceived by said position measuring system, whereby this stop element (1) is situated between two supporting elements (2) which must be placed against said edge (3) as well and which can be moved in relation to the stop element (1).

2. Measuring instrument according to claim 1, characterised in that said stop element (1) can be moved in a direction which is perpendicular to a line of junction between said supporting elements (2).

3. Measuring instrument according to claim 1 or 2, characterised in that the distance between said stop element (1) and each of said supporting elements (2) is almost equal.

4. Measuring instrument according to any of claims 1 to 3, characterised in that it comprises a holder (17) to which said supporting elements (2) are fixed, whereby said stop element (1) is mounted in a floating manner in relation to the holder (17).

5. Measuring instrument according to any of claims 1 to 4, characterised in that said stop element (1) and said marking element (10) are provided on one and the same support (9), whereby this support (9) has a bearing face which must rest on said plate-shaped object (4).

6. Measuring instrument according to claim 5, characterised in that said bearing face is determined by at least three supporting points (16) which are not situated in a straight line.

7. Measuring instrument according to claim 5 or 6, characterised in that said stop element (1) comprises a rod which extends almost perpendicular to the bearing face of said support (9).

8. Measuring instrument according to any of claims 5 to 7, characterised in that said support (9) is mounted in a floating manner in relation to said holder (17).

9. Measuring instrument according to any of claims 5 to 8, characterised in that means are provided which make it possible to fix said plate-shaped object (4) in a detachable manner between said support (9) and said holder (17).

10. Measuring instrument according to any of claims 5 to 9, characterised in that said support (9) is connected to said holder (17) via a spring element (25) in order to push said stop element (1) against the edge (3) of the plate- shaped object (4) when said supporting elements (2) are placed against this edge (3).

1 1. Method to determine the position of a point on the edge (3) of a plate-shaped object (4) by means of a three-dimensional position measuring system, characterised in that two supporting elements (2) which are fixed to each other are placed against said edge (3) and a stop element (1) is moved as well up to this edge (3) in a direction which is perpendicular to a line of junction between said supporting elements (2) and which is parallel to the surface of said plate-shaped object (4) near said edge (3), whereby the position of a marking element (10) which is fixed to the stop element (1) is then perceived with the position measuring system, and the position of said point is determined on the basis of said perceived position.

12. Method to determine the deviations of the edge (3) of a plate- shaped object (4) in relation to a computer model of this object (4) by means of the measuring instrument according to any of claims 1 to 10, whereby three such measuring instruments are fixed to said edge (3), whereby the position of the marking elements (10) of these measuring instruments is measured and an expected deflection of the edge (3) is determined on the basis of said computer model and the measured positions of these marking elements (10), whereby a fourth measuring instrument is provided against a point of said edge (3) and the position of this latter point is determined so as to compare this position to the expected position thereof according to the expected deflection of the edge (3).