IE50204B1

IE50204B1 - A capacitive coin detector

Info

Publication number: IE50204B1
Application number: IE2110/80A
Authority: IE
Original assignee: Gnt Automatic As
Priority date: 1979-10-18
Filing date: 1980-10-10
Publication date: 1986-03-05
Also published as: SE8007291L; MX149388A; IE802110L; PT71922B; GB2062327A; NO153384C; DK440879A; GB2062327B; AR221182A1; DK148010B; BE885741A; ES496023A0; NO153384B; DK148010C; FI72397B; NO803113L; JPS5696393A; DE3038988A1; SE450303B; NL8005658A

Abstract

In a capacitive coin detector capacitor electrodes (3, 4) connected to an electric circuit for detecting capacitance variation during the passage of a coin (5), are arranged on a rearwardly inclined wall (1) of a sloping coin chute having a coin support rail (2). One or more first electrodes (4) are located on the wall (1) in such a manner that the edge of a coin (5) in the chute overlaps said electrode a little or not at all, dependent on its size. A further electrode (3) is located to be closer to the centre of the coin path and has a considerable area. In this manner the capacitive coupling between the electrodes (3 and 4) via the coin (5) is substantially determined by the coin overlap of the first electrode(s) (4). With the first electrodes (4) located at the upper edge of the coin, the coin diameter can be directly checked. When they are located at the lower edge of the coin in a coin chute, where the coin support rail forms an angle of less than 90 DEG with the wall, it is possible to check the coin thickness.

Description

The present invention relates to a capacitive coin detector for checking coins in a coin-operated apparatus, comprising a coin passage having a rearwardly inclined wall provided with capacitor electrodes covered by a dielectric material, said electrodes being connected to an electric circuit for detecting any capacitance varia tion during the passage of a coin.

In a coin detector of the said type as disclosed by Danish Patent specification No. Io8.335 coins inserted lo pass down through a substantially vertical coin passage past two closely spaced opposing capacitor electrodes with the effect that a pulse is generated in the connected electric circuit as the coin passes the electrodes. This prior art construction allows only detection of the passa15 ge of some coin or other through the apparatus but does not make it possible to determine the dimensions of the coin.

It is known to check the diameter of coins in a coin chute by means of electromagnetic or photoelectric 2o sensors arranged at certain distances from the coin support rail. It is further known to check the diameter electrically as during its passage along the coin chute the coin establishes electrical connection between a conductive chute bottom and conductive strips provided on a rear25 wardly inclined chute wall of insulating material, said strips having such a width and being arranged at such distances from the chute bottom that contact is made when the coin diameter is between predetermined acceptable minimum and maximum values. Since the operation of such 3o a detector is based on the establishment of electric contact, the conductive strips are required to have a certain length to ensure that contact is made.

Besides, it is known to employ a V-shaped bottom in a coin chute having a rejection slot in the chute wall with the effect that too thin coins sink so deep into the chute that they will drop through the slot.

The object of the present invention is to provide a capacitive coin detector of the aforesaid type by means of which it is possible to check one or more coin dimensions.

The invention provides a capacitive coin detector for checking coins in a coin-operated apparatus, comprising a coin passage having a rearwardly inclined wall provided with capacitor electrodes covered by a dielectric material, the electrodes being connected to an electrical circuit for detecting any capacitance variation due to the presence of a coin, the coin passage being in the form of an inclined coin chute having a coin support rail along which coins may roll in contact with the said wall, in vtoich at least one electrode has an edge substantially parallel to the coin support rail, the said edge delimiting the electrode in a direction towards the path of a coin in the chute and being intended to be located substantially on a level with the edge of a coin, and a further electrode is provided closer to the centre of the coin path, the said further electrode having an area substantially greater than that of the said at least one electrode.

As a coin rolls along the coin chute in contact with the wall thereof there is provided a positive capacitive coupling between the coin and the said further electrode, which has a considerable surface area. If the coin has such a dimension that it overlaps part of the first electrode past the said delimiting edge, there is provided between the coin and the first electrode a capacitive coupling dependent on this overlapping which is small in relation to the aforesaid capacitive coupling and which will substantially determine the amplitude of the coin-recording signal transferred by the electrical circuit connected to the electrodes. It should be noted in this connection that the detecting circuit may be arranged so that only signal amplitudes above a certain level are recorded. If the coin does not overlap the first electrode it follows that no capacitive coupling is provided at this place and consequently no recording of the coin. 8y virtue of the capacitive mode of operation of the device it is possible to ensure positive recording even with a short electrode dimension lengthwise of the coin chute.

In an embodiment of the coin detector according to the invention a first and a second electrode have a lower edge parallel to the coin support rail, said edges being located at levels above the coin support rail sub- _ stantially equal to the smallest acceptable coin diameter and the smallest unacceptable excess diameter, respectively. This design allows the coin detector to determine directly the diameter range of a given coin. If no capacitive coupling is established between the coin and the first electrode, or if a coupling is established between the coin and the second electrode, the coin diameter is under the permitted lower limit and over the permitted upper limit, respectively. If a coupling is lo established between the coin and only the first electrode, the coin diameter is within the permitted limits.

In another embodiment of the coin detector according to the invention the coin support rail forms an angle with the wall of the coin chute which is less than 9o°, and a first and a second electrode have an upper edge substantially parallel to the coin support rail, said edges beinq located at levels in the coin chute substantially equal to the position in the coin chute of the lower edge of a coin having the maximum acceptable thickness 2o and the maximum unacceptable undersized coin thickness, respectively. Consequently as the coins will roll in a path which is further down in the chute the thinner the coins, it becomes possible to record coins in response to their thickness. If no capacitive coupling is established between a coin and the said first electrode, or if a coupling is established between a coin and the said second electrode, the coin thickness is either above the permitted maximum thickness or below the permitted minimum thickness. In case of a coupling between the coin and only the 3o first electrode, the coin thickness is within the permitted limits.

In yet another embodiment of the coin detector according to the invention a plurality of pairs of the first and second electrodes are arranged in succession along the coin chute with the said delimiting edge located in accordance with the diameter and/or thickness of coins of various sizes. Since each pair of electrodes need only be relatively short in length it follows that a coin de50204 Ιο 2ο 3ο tector for checking a plurality of coin diameters and. coin thicknesses can be given a very compact design.’ In order to simplify the electric circuit, the further electrode may advantageously be common to more pairs of first and second electrodes. Subject to employment of sequential control, the output signal from the common further electrode is passed to a common amplifier and signal level detector circuit.

” The invention will now be described in more detail with reference to the accompanying drawing, in which Fig. 1 is a schematic view of an embodiment of the coin detector according to the invention, Fig. 2 is a frontal view of a coin chute for a detector according to the invention for diameter detection, Fig. 3 is a sectional view of same taken along the line 3-3 of Fig. 2, Fig. 4 is a frontal view of a coin chute for a detector according to the invention for detection of coin thickness.

Fig. 5 is a cross-sectional view of same taken along the line 5-5 of Fig. 4, and Fig. 6 is a frontal view of a coin chute wall to be used for detecting diameter and thickness of three coin sizes.

Referring to the drawing Fig. 1 shows a coin chute comprising a rearwardly inclined wall 1 and a bottom 2. The wall 1 is made of an electrically insulating material and has two metal surfaces or areas 3 and 4 covered by a not shown insulating layer. By way of example, the wall 1 may be a printed circuit board and the surfaces 3 and 4 may be copper coatings on the surfaces of the printed circuit board. The insulating layer may be a protective lacquer or tape, e.g. of polytetrafluoroethylene. Fig. 1 shows a metal disk 5, e.g. a coin, which is resting on the chute bottom 2 and partly Covers or overlaps the surfaces’ 3 and 4 on the wall 1. This establishes a capacitive coupling between the surfaces 3 and 4, the surface 3 and the coin 5 forming a capacitor Cl in conductive connection with a capacitor C2 which is formed by the surface 4 and the overlapping portion of the coin 5.

From a generator 6 an alternating voltage of 2oo kHz, for example, is supplied to the surface 4 and transferred by the two capacitors C2 and Cl to an amplilo fier 7 connected to the surface 3, the output signal of said amplifier being passed to a signal level detector 8 which provides an output signal on a terminal 9. The capacitor Cl formed by the coin and the surface 3 is much larger than the capacitor C2 formed by the coin and the surface 4, for which reason it is mainly the size of the capacitor C2 which determines the amplitude of the output signal from the amplifier 7. As will be readily appreciated, the size of the capacitor C2 depends on how much of the area of the surface 4 is covered by the coin 5. After 2o removing the coin 5, no signal will be transferred from the generator 6 to the amplifier 7, and the level detector 8 will provide no output signal on the terminal 9.

In the embodiment of the coin detector for detecting the diameter illustrated in Figs. 2 and 3 there are shown parts similar to those in Fig. 1 and identical reference numerals have been used. Hence, the board 1 is provided with coatings or electrodes 3 and 4 covered by a dielectric layer lo, as will appear from Tig. 3. In addition to the electrodes 3 and 4 there is provided an addi3o tional electrode 11 to which, as to the electrode 4, there is sequentially applied an alternating voltage by the gene rator 6 (Fig. 1). The electrodes 4 and 11 have a lower edge parallel to the chute bottom 2, said edges being positioned in relation to a predetermined size of a coin in such a manner that when a coin passes the coin chute there is either made no capacitive coupling at all, or established coupling between the electrode 3 and the electrode 4 or between the electrode 3 and both electrodes 4 and 11 dependent on coin size. If no capacitive coupling is established between the electrodes 3 and 4, the coin diameter is under the acceptable diameter limit. In case of a coupling between the electrode 3 and both the elec5 trode 4 and the electrode 11, the coin diameter is above the permitted limit. If there is capacitive coupling only between the electrodes 3 and 4, the coin diameter is within the acceptable limits.

In the embodiment of a coin detector for detecting lo coin thickness illustrated in Figs. 4 and 5 there are shown parts similar to those in the foregoing figures and identical reference numerals have been used suffixed by an apostrophe. In this embodiment the chute bottom 2' forms an angle with the rear wall, said angle being less than 9o°. A coin 5' rolling along the coin chute, therefore, will sink deeper into the chute the thinner the coin For this reason the electrodes 4' and 11' are arranged adjacent the chute bottom to enable them to detect the location of the lower edge of a coin. Similar to the fore2o going embodiment the upper edge of the electrodes 4' and 11' are arranged in such a manner that the coin thickness will determine whether there is established a capacitive coupling between the electrode 3' and the electrodes 4' and 11'. Hence, if there is established a capacitive coupling between the electrode 3' and the electrode 11', the coin thickness is under the acceptable limit. In case of no coupling between the electrodes 3' and 4', the thickness of the coin is above the acceptable limit. Should coupling be established between the electrodes 3' and 4' 3o but not between the electrodes 3' and 11', the thickness of the coin is within the acceptable limits.

Fig. 6 shows a coin chute wall suitable for detection of diameter and thickness of three different coin sizes. The wall consists of a printed circuit board with common electrodes 3 and 3' for detection of diameter and thickness, respectively, of the three coin sizes. The electrodes 4 and 11 and 4' and 11', respectively, for each of the three coin sizes are arranged in relation to each other and to the chute bottom'in such a manner that when the latter is joined with the chute wall, it is possible to £ense sequentially from the electrodes 3 and 3' a signal to signify whether the diameter and thickness of an inserted coin of one of the three coin sizes for which the detector is designed are within or outside the permis sible limits. It will be appreciated that the alternating voltage is supplied sequentially from the generator 6 (Fig. 1) to the electrodes 4,11 and 4',11'. Owing to the lo capacitive mode of action and sequential control, the electrodes need only have a small dimension lengthwise of the coin chute and may be spaced closely, which means that the overall coin chute may be made with a small extent only.

Claims

1. A capacitive coin detector for checking coins in a coin-operated apparatus, comprising a coin passage having a rearwardly inclined wall provided with capacitor electrodes covered by a dielectric material, the electrodes being connected to an electrical circuit for detecting any capacitance variation due to the presence of a coin, the coin passage being in the fora of an inclined coin chute having a coin support rail along which coins may roll in contact with the said wall, in which at least one electrode has an edge substantially parallel to the coin support rail, the said edge delimiting the electrode in a direction towards the path of a coin in the chute and being intended to be located substantially on a level with the edge of a coin, and a further electrode is provided closer to the centre of the coin path, the said further electrode having an area substantially greater than that of the said at least one electrode.

2. A capacitive coin detector as claimed in claim 1, including a pair of electrodes each having a lower edge substantially parallel to the coin support rail, the said edges being located at levels above the coin support rail substantially equal to the smallest acceptable coin diameter and the smallest unacceptable excess diameter, respectively.

3. A capacitive coin detector as claimed in claim 1 or 2, in which the coin support rail forms an angle with the said wall of the coin chute which is less than 30°, the detector including a pair of electrodes each having an upper edge substantially parallel to the coin support rail, the said edges being located at levels in the coin chute substantially equal to the position in the coin chute of the lower edge of a coin having the maximum acceptable thickness and the maximum unacceptable undersized 5 coin thickness, respectively.

4. A capacitive coin detector as claimed in claim 2 or 3, in which a plurality of pair of electrodes are arranged in succession along the coin chute, with the said delimiting edges located in accordance with the diameter and/or thickness of 10 coins of various sizes.

5. A capacitive coin detector as claimed in claim 4, in which the further electrode is common to a plurality of the pairs of electrodes.

6. A capacitive coin detector substantially as described with IS reference to, and as shown in, Figure 1, Figures 2 and 3, Figures 4 and 5, or Figure 6 of the accompanying drawings.