EP0119936A1 - Optical method and apparatus to determine the dimensions of a relatively moving object, in particular a coin in a vending machine - Google Patents

Abstract

The coin (1) rolls on a track (6-7) with a triangular profile with a straight flank and an oblique flank, into which it sinks as a function of its thickness. The time difference between the beginnings (or ends) of occultation of the upper cells (3a, 3b) determines the average speed and the duration of this occultation we deduce the length of the rope (PQ) at the higher level (Y -Y '). Knowing the average speed, the cell (3c) of the second level (Z-Z ') makes it possible to determine the corresponding rope (RS). From (PQ) and (RS) we deduce the heights (h1, h2) above the running surface (X-X ') and we can then calculate the diameter and the thickness of the part. More simply, we can compare electronically (PQ) and (RS) to recorded values to reject (1) or accept it and possibly save its value.

Description

The subject of the present invention is an optical method suitable for determining the dimensions of a moving object relative to the device itself, and it is more particularly applicable to the case of coins engaged in a prepayment device, such as a vending machine.

We know that these devices are required to sort the coins they receive, first to eliminate and return those that do not correspond to what the user of the device should have introduced (coins '' another value than that required, false coins or tokens, etc.), but sometimes also to distinguish between several types of coins likely to be accepted until the total of their individual values represents the sum required for the operation of the device. We therefore had to design various devices to automatically perform such sorting (and which are often associated with others suitable for testing the metal of the part).

In particular, it has been imagined to circulate the part to be examined in a corridor comprising a very slightly inclined wall against which it slides while rolling on a track which, seen in cross section, comprises a series of steps going down towards the wall, so as to pass it in front of a substantially vertical row of suitably lit photocells. The cells thus detect the diameter of the part and the level of the step on which it rolls, which is characteristic of its thickness. However, this system requires a fairly large number of cells and its accuracy is limited by the spacing of these in the row. as well as the finesse of the steps of the track.

The present invention aims to make it possible to establish a particularly simple optical process requiring only a small number of cells and by means of which the diameter and thickness of a coin can be determined and / or checked extremely precisely. introduced into a device of the kind in question. But it should be understood that it can also apply to all cases posing similar problems.

According to the invention a method for determining or verifying the dimensional characteristics of a flat object, and more particularly of a coin, which is rolled on an inclined track so as to make it pass in front of at least a normally lighted main photocell, but the illumination of which it blocks in passing, this cell being situated at a determined level above the track, is characterized in that by using a section track in the form of notch with a first plane parallel to the plane of the object and a second plane whose general profile makes with the first a determined angle, there is on the path of this object an auxiliary photocell located at a different level from that ( Y-Y ') of the main cell and in that one deduces from the signals of this auxiliary cell, taking into account the speed of the object, a signal representative of the diameter of the latter for a determined depth of penetration of this object in the notch, the signals thus taken from the main cell and the auxiliary cell allowing either to calculate the diameter and the thickness of the object, or with recorded data, to check if it enters a planned category and, if there are several, in which

• Fig. 1 est une vue schématique en élévation montrant une pièce de monnaie qui roule sur une piste pour passer devant deux cellules électriques successives situées au même niveau.
• Fig. 2 est une vue en plan correspondant à fig. 1.
• Fig. 3 est une représentation graphique des signaux de sortie des deux cellules dans le cas où la pièce se déplace à vitesse constante.
• Fig. 4 est une vue semblable à celle de fig. 3, mais correspondant au cas d'un mouvement uniformément accéléré de la pièce de monnaie.
• Fig. 5 est une coupe montrant schématiquement une pièce de monnaie roulant dans une entaille constituée par un flanc droit et un flanc oblique.
• Fig. 6 est une vue schématique montrant la pièce de monnaie de fig. 5 un peu avant qu'elle ne passe en face de trois cellules disposées à deux niveaux différents en vue d'identifier son diamètre et son épaisseur.
• Fig. 7 et 8 sont des vues semblables à celle de fig. 5, mais correspondant à des pièces d'épaisseurs différentes.
• Fig. 9 est une représentation graphique des signaux de sortie des trois cellules de fig. 6.
• Fig. 10 montre comment on peut calculer le diamètre de la pièce en fonction des réponses de ces trois cellules.
• Fig. 11 est une coupe montrant une réalisation pratique possible du dispositif schématisé en fig. 5 et 6.

The appended drawing, given by way of example, will make it possible to understand the invention, the characteristics which it presents and the advantages which it is capable of providing:

• Fig. 1 is a schematic elevation view showing a coin rolling on a track to pass in front of two successive electrical cells located at the same level.
• Fig. 2 is a plan view corresponding to FIG. 1.
• Fig. 3 is a graphical representation of the output signals of the two cells in the case where the part is moving at constant speed.
• Fig. 4 is a view similar to that of FIG. 3, but corresponding to the case of a uniformly accelerated movement of the coin.
• Fig. 5 is a section schematically showing a coin rolling in a notch constituted by a straight flank and an oblique flank.
• Fig. 6 is a schematic view showing the coin of FIG. 5 a little before it passes in front of three cells arranged at two different levels in order to identify its diameter and thickness.
• Fig. 7 and 8 are views similar to that of FIG. 5, but corresponding to parts of different thicknesses.
• Fig. 9 is a graphic representation of the output signals of the three cells of FIG. 6.
• Fig. 10 shows how the diameter of the part can be calculated according to the responses of these three cells.
• Fig. 11 is a section showing a possible practical embodiment of the device shown diagrammatically in FIG. 5 and 6.

In the schematic representation of fig. 1 and 2, the reference 1 designates a coin of diameter d located in a vertical mean plane and which rolls at a constant speed on a surface or track 2 following a rectilinear path X-X ', its guidance, its retention in the aforementioned plan and its advance being provided by means not shown, but easy to imagine. It is thus caused to pass between a photoelectric cell 3a and a light source 4a which illuminates the latter. Therefore, the output of the cell affects the ABCDEF profile shown in fig. 3. At time t is _the detection of the front edge of the coin 1 and time t _2a that its rear edge. If one knows its uniform speed of displacement v, the expression (t ₂ a - t _1a ) / v corresponds to the length of segment or chord PQ-determined on the circular profile of the part by its intersection with the horizontal plane YY 'in which cell 3a is located. If we call this length 1, and if we designate by h the vertical distance between the planes XX 'and Y-Y', we easily find that the diameter d of the part 1 is given by the formula (1 ² + 4h ² ) / 4h.

In practice, the speed of movement v of the part 1 is not a known parameter. To determine it, an auxiliary photoelectric cell 3b is used, also located in the plane Y-Y ', but at a certain distance from cell 3a. The response of this cell to the passage of the room is indicated by the line A'B'C'D'E'F 'in fig. 3. We understand that the chronometric offset ^t _lb - t _la is representative of the speed sought and that if 1 ^T we call m the distance which separates the two cells 3a and 3b, we can write ^{v = m} / ( ^t _lb - You're here).

• - soit calculer le diamètre d de la pièce 1 avec une précision qui ne dépend que de la finesse de détection des cellules ;
• - soit à tout le moins comparer la valeur du segment PQ à une ou plusieurs valeurs de référence enregistrées dans sa mémoire, pour décider si la pièce 1 doit être acceptée ou rejetée et, dans le premier cas, pour envoyer à un totalisateur approprié l'indication de la valeur relevée, comme cela est nécessaire dans les appareils exigeant pour leur fonctionnement l'introduction successive de plusieurs pièces de monnaie.

It follows from the above that if the signals or outputs of cells 3a and 3b are sent to a suitably programmed microcomputer 5, the latter can:

• - either calculate the diameter d of the part 1 with an accuracy which only depends on the fineness of detection of the cells;
• - or at the very least compare the value of the PQ segment with one or more reference values stored in its memory, to decide whether the piece 1 should be accepted or rejected and, in the first case, to send the appropriate totalizer indication of the value read, as is necessary in devices requiring for their operation the successive introduction of several coins.

However, it has been assumed above that the part 1 is moving in a uniform movement. In practice, this is rarely the case. This movement is in fact ensured by gravity by suitably inclining the path X _- X 'on the rolling surface 2 (and of course inclining the plane YY' in which the cells are located correspondingly). As a result, the movement of the part tends to take place with constant acceleration, C'D 'then being a little shorter than CD, as shown in fig. 4. But one can easily eliminate this source of error by appealing to the concept of average speed, valid in the case of a uniformly accelerated movement and according to which the displacement carried out between two determined instants is equal to the time which separates those- ci multiplied by the average of the instantaneous speeds at each of them. In the case considered, the speed is equal to m / t _lb - tla) when passing in front of the first cell and to m / (t _2b - t2a) in front of the second. It is easy to program the microcomputer 5 so that it calculates the average of these two values and uses it to determine the diameter of the part. The two cells 3a and 3b then play the same role.

However, the foregoing explanations leave aside an important factor for the sorting operation of the pieces, namely the thickness of the pieces.

To determine the thickness, provision is made to roll the part 1 no longer on a flat surface or track, but in a rectilinear notch comprising (fig. 5) a flank vertical 6 and an inclined blank 7. It can be seen that the height p of the rolling path XX '(FIG. 6) of the part above the bottom of the groove is directly proportional to the thickness of the latter. For a thinner piece (fig. 7) the path in question is located lower, while for a 1 "thicker piece (fig. 8) it is higher.

Furthermore, a third photoelectric cell 3c is located along the length of the groove, situated in a horizontal plane ZZ 'different from that YY' of cells 3a and 3b. The height of this plane above the rolling path XX 'of the part 1 has been referenced h ₂ , the height of the plane YY' here being designated by h _l .

This cell also responds to the passage of the room 1 by sending corresponding signals to the microcomputer 5. As an indication, it has been indicated in FIG. 9 the shape of all three signals thus received by the computer, namely ABCDEF for the first cell 3a, A'B'C'D'E'F 'for the second 3b, and A "B" C "D "E" F "for the third 3c, assuming the three cells arranged in elevation as shown in fig. 6. The speed of the part being measured by cells 3a and 3b, this third cell "C allows for its part to measure the segment or rope RS as a function of this speed.

If the part 1 rolls well on the path X-X 'provided for it, the microcomputer must deduce from the signals from cell 3c a diameter strictly equal to that calculated from those received from cells 3a and 3b. If this is not the case, it is because the part follows a different path located below or above X-X ', so that it does not have the expected thickness.

Of course, to achieve correct operation, we must again take into account the possible acceleration of the part when it passes in front of the cells. This is easily obtained by placing cell 3c between the cells 3a and 3b in the longitudinal direction and equidistant from them. The cell 3c is then in an area where the instantaneous speed of the part is equal to its average speed between the first two cells.

It should also be noted that the device described with reference to FIG. 6 can function correctly even if the plane Y-Y 'passes substantially through the center 0 of the part. Indeed, if then cells 3a and 3b are practically unaffected by small variations in the insertion of the part into the notch 6-7, the third cell 3c, located at a clearly different level, is so sufficient to identify the part in question.

Still referring to fig. 6, it can also be noted that in cases where it can be considered that the speed of the part is constant and is known, it is possible to dispense with cell 3b, cell 3a sufficient to determine the length of the cord PQ.

If it is simply necessary to eliminate the parts which do not conform to a given model, the observation of the identity or non-identity of the diameters determined from the respective levels Y-Y 'and Z-Z' is then sufficient. If, as is the case with certain ticket distributors, the device in question must successively receive several different parts in order to function, the device can then send to the microcomputer 5 signals indicating the length of the segments PQ and RS, which 'he measured. The microcomputer compares this data with that stored in its memory and decides whether the document can be accepted or not. If not, it rejects it and if so it sends the representation of its value to an appropriate totalizer capable of triggering the prepayment device when the total forecast is reached.

However, we may also wish to know the real diameter of the parts despite the greater or lesser height of the 8 0119936 level of their running path in the notch 6-7.

Fig. 10 shows that the calculation of the diameter of the circle representative of the piece 1 (or 1 ′ or 1 ", figs. 7 and 8) is perfectly possible from the signals received from the cells, without having to worry about the height rolling path of the part considered. Indeed, if we call here 1 ₁ the length of the cord PQ measured by cells 3a and 3b, and 1 ₂ that of the cord RS determined by the third cell 3c, we can easily see that if they are arranged symmetrically with respect to a vertical axis, taking care to keep them at the spacing h _l - h ₂ from the horizontal planes YY 'and Z-Z', the four points PQRS clearly define a single circumference whose we can calculate the diameter when we know 1 ₁ , 1 ₂ , h _l and ^h _{2. In} order not to unnecessarily complicate the present, we will not detail this calculation which does not involve any major difficulty. based on the similarity of the triangles defined by the oblique QS chord and its extension t until the vertical axis UU 'intersects in T and a third triangle defined in turn by this axis U-U', by the perpendicular OV which, starting from the center 0, ends in the middle of the oblique chord QS , and by the oblique segment VT. This calculation does not exceed the possibilities of a suitably programmed microcomputer. Once the diameter of the part is known, it is easy to calculate its thickness, if desired, by determining the height of the center 0 above one of the segments PQ and RS, by adding to the value thus found the height of the plane of this segment above that of the entry of notch 6-7, then subtracting the radius of the part from the total. From the value of this depression, the desired thickness is deduced.

Fig. It very schematically indicates how a device according to the invention can be produced in practice. We see at 8 a slightly inclined wall and on which the part 1 slides in the known way. The cells such as 3a and 3c are mounted in perforations of the wall 8. This constitutes the right flank 6 of the notch lower whose oblique flank 7 is connected to another wall 9 which defines with the previous 8 the corridor in which circulate the parts introduced into the device. This corridor is closed at the top by an upper strip 10. Opposite the cells are the light emitters, here 3a for cell 3a and 4c for that 3c.

These emitters can be photo-diodes, the cells being photo-transistors on their side. But of course, one could use any other type of equivalent element, in particular incandescent point bulbs with lenses and diaphragms suitably calibrated in cases where one wishes to obtain a particularly high precision. It would still be possible to use devices integrating transmitters and receivers on the same side of the corridor (barcode reader type).

It goes without saying that in some cases at least one of the planes Y-Y 'and Z-Z' may be above the center of the room. The spacing between cells 3a and 3b can vary.

Claims (5)

1. Method for determining or verifying the dimensional characteristics of a flat object, and more particularly of a coin, which is rolled on an inclined track so as to make it pass in front of at least one photocell main electric normally illuminated, but whose illumination it blocks in passing, this cell being located at a determined level above the track, characterized in that by using a track with a notch-shaped section with a first flank parallel to the plane of the object and a second flank whose general profile makes with the first a determined angle, there is on the path of this object (l) an auxiliary photoelectric cell (3c) located at a level (Z- Z ') different from that (Y-Y') of the main cell (3a, 3b) and in that one deduces from the output signals of this auxiliary cell (3c), taking into account the speed of the object ( 1), a signal (RS) representative of the diameter thereof for a depth of depth determined cement of this object in the notch (6-7), the signals thus taken from the main cell (3a, 3b) and the auxiliary cell (3c) allowing either to calculate the diameter and the thickness of l 'object, either by comparison with recorded data, to check if it falls into a planned category and, if there are several, in which. 2. Method according to claim 1, characterized in that in the section of the notch (6-7) forming a running track the oblique flank (7) is provided uniformly rectilinear. 3. Method according to claim 1, characterized in that in order to overcome the obligation to know the speed of movement of the object on the track as well as the fact that this speed can be uniformly accelerated, provision is made , in the manner known per se, two successive main cells (3a; 3b) arranged at the same level at a spacing determined from one another and which make it possible to calculate the average speed of said object, and in that the auxiliary cell (3c) is placed longitudinally between the two main ones (3a, 3b) and equidistant from them. 4. Method according to any one of the preceding claims, characterized in that the responses of the cells are sent to a microcomputer which calculates the diameter and the thickness of the object. 5. Device for measuring or checking the dimensions of a cylindrical object, characterized in that it is established for the implementation of the method according to any one of the preceding claims.

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