GB1597940A

GB1597940A - Coin detector for checking the diameter of coins in a coin operated device

Info

Publication number: GB1597940A
Application number: GB1439978A
Authority: GB
Original assignee: GNT Automatic AS
Current assignee: GNT Automatic AS
Priority date: 1977-04-12
Filing date: 1978-04-12
Publication date: 1981-09-16
Also published as: IE780717L; IE46533B1; PT67894B; ES468697A1; PT67894A; DK160277A

Description

(54) COIN DETECTOR FOR CHECKING THE DIAMETER OF COINS IN A COIN OPERATED DEVICE (72) We, GNT AUTOMatic A/S, a Danish body corporate of Telefonvej 6, DK2860 Soborg, Denmark, 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:- The present invention relates to a coin detector for checking the diameter of at least one coin size in a coin operated device comprising a longitudinally sloping coin chute including a coin support rail between front and back walls which are backwardly inclined transversely of the longitudinal direction of the chute.

In order to prevent to the greatest possible extent incorrect coins, such as coins from other countries, coin imitations, tokens and other discs of metal or other material being used in coin operated devices, such as coin operated telephones and vending machines, it is known to prescribe a number of criteria e.g. in respect of dimensions and electrical, magnetic and mechanical properties to be satisfied if an inserted coin is to be accepted and collected for operating the device. Thus, it is known to carry out the checking of the diameter in a longitudinally sloping coin chute, the forwardly inclined front wall of which being provided with an opening of a size such that too small coins will fall out to be rejected while coins of the correct size will continue without hindrance and too large coins are sorted out by means of a similar upstream located arrangement.Obviously a check of diameter according to this principle becomes quite extensive, in particular if a plurality of different types of coins are to be checked in the same unit.

Furthermore it is known to carry out a detection of coins of different sizes in one and the same coin chute by means of electromagnetic or photoelectric sensing elements spaced from the coin track or a stop means therein corresponding to the individual coin sizes. However, a sufficiently accurate check of the diameter of the individual coins by means of such sensing elements results usually in an unduly high power consumption unless quite complex power saving circuit is used.

The object of the invention is to provide a coin detector of the kind indicated above which is able to check electrically the diameter of coins with a high degree of accuracy without too large coins being trapped in the coin chute and if desirable may check a plurality of coin sizes in the same coin chute while being mechanically simple and compact.

According to the invention a coin detector comprising a longitudinally sloping coin chute including a coin support rail between front and back walls which are backwardly inclined transversely of the longitudinal direction of the chute, is characterised in that the coin support rail along at least part of its length within the chute is made of or provided with a covering of electrically conductive material while at least the backwardly inclined back wall is made of electrically insulating material, that at least one strip of conductive material is located on the back wall parallel to the coin support rail such that the bottom edge of the strip has a distance to the coin support rail equal to the smallest acceptable diameter of a coin to be accepted and that a spacer of insulating material extends into the coin chute further from the back wall than the conductive strip and is located along said strip such that the bottom edge of said spacer has a distance to the coin support rail equal to the greatest acceptable diameter of said coin and that the coin support rail and the conductive strip form parts of an electrical detection circuit adapted to provide an acceptance output signal when a coin of acceptable diameter makes contact between the strip and coin support rail.

Thereby is obtained that a coin while rolling down the coin chute will lean against the inclined back wall and if it has a diameter greater than the distance from the coin support rail to the bottom edge of the conductive strip and smaller than the distance from the coin support rail to the insulating spacer will form contact between the coin support rail and the conductive strip which contact formation is used as input signal to the electrical detection circuit. Accordingly, the detection circuit will only deliver an acceptance signal when the diameter of the coin is within the defined interval. It is seen that too small coins can not reach the strip and form contact while too large coins are prevented from contact ing the strip due to the insulating spacer.

No particular mechanical stop means are therefore required to sort out too large coins. The acceptance signal provided by the detection circuit is applied to an electrically operated coin cashing mechanism preferably together with further acceptance signals to indicate if several other criteria for control of the coin are fulfilled.

In an embodiment of the invention a plurality of sets of conductive strips and insulating spacers are located one after another along the coin chute at different distances from the coin support rail for the control of a plurality of coin sizes. Each individual set of conductive strip and insulating spacer need only to have a relatively short length so that a coin detector for the control of a plurality of coin diameters can have relatively small dimensions such that it is advantageous also to applications with limited available space such as in coin operated telephones.

In order to always ensure that coins of correct size while rolling along the coin chute contact the conductive strip it is advantageous according to the invention that the angle between the coin support rail and back wall is smaller than 90". Then the coin will always move towards the back wall carrying the conductive strip.

In a simple embodiment of the invention the conductive strip is a metal plate secured to the back wall said metal plate being covered partly by the insulating spacer. In a further embodiment of the invention the conductive strip is a metal plate secured to the bottom edge of the spacer perpendicular to the back wall, the thickness of said metal plate being equal to the acceptable interval of coin diameter. This embodiment is very simple to produce and adjust and enables a high acuracy of the checking of diameter.

Because of the movement of the coin in the coin chute and its relatively small weight the contact formation in itself to the conductive strip is rather incomplete and consists mainly of a plurality of very short pulses. A reliable indication of the contact formation is obtainable, however, when the electrical detection circuit according to the invention is a voltage sensitive semiconductor device requiring a very small control current, such as a C-MOS flip-flop.

This is particularly important when the available voltage in the circuit to be closed by the coin is low such as it is often the case in a coin operated telephone.

In an embodiment of the invention for use in coin operated telephones the circuit into which the conductive strip and coin support rail are connected is galvanically isolated from the connecting leads of the telephone. This is desirable for example due to the monitoring of the telephone cables by leakage control because in the opposite case direct contact may be estab lished between the connecting leads of the telephone and metal parts which directly or indirectly may contact other things.

In order to obtain a more reliable contact formation by the coin the circuit into which the conductive strip and coin support rail are connected may be supplied by an auxiliary voltage derived from the line voltage of the telephone. When a cashing relay is used in the coin operated device the said auxiliary voltage may be provided by an extra winding on the cashing relay the exitation current thereof being pulsed.

The invention will now be described in more detail with reference to the accompanying drawing, in which: Fig. 1 is a longitudinal section along the line I-I of Figure 2 of an embodiment of a coin detector according to the invention adapted to check the diameters of three coin sizes, Fig. 2 is a cross-section of the coin detector of Figure 1 along the line 11-11, Fig. 3 is a variant of the embodiment of Figure 2, Fig. 4 is a diagram of an electrical detection circuit forming part of the coin detector, and Fig. 5 is a modified embodiment of the detection circuit.

Referring to the drawing Figures 1 and 2 show a longitudinally sloping backwardly inclined coin chute consisting of a front wall 1, a back wall 2 and a bottom 3. The back wall 2 is made of an electrically insulating material while the bottom 3 forming a support rail for coins inserted into the coin chute consists of or is provided with a covering of conductive material. The angle r between the back wall and bottom wall is preferably slightly less than 90" to ensure that the coins during their rolling movement abut on the back wall 2.

Strips 4 of electrically conductive material forming electrodes are fixed to the inside of the back wall 2 such that the bottom edges of the strips are parallel to the support rail and are disposed in distances thereto equal to the minimum acceptable diameter of coins 5 which are intended to be accepted by the coin detector. Spacers 6 of electrically insulating material are mounted on the conductive strips 4, said spacers being positioned such that the bottom edges thereof are parallel to the coin support rail and in distances thereto equal to the maximum acceptable diameter of said coins which are intended to be accepted by the detector.

A variant of the embodiment of Figure 2 is shown in Figure 3 in which the electrode strip 4 is L-shaped around the spacer 6. Thereby the thickness of the electrode strip corresponds to the acceptable interval of coin diameters for the particular coin size. Because of the simple adjustment of the conductive strip and the spacer on the back wall this embodiment permits a particularly accurate and selective checking of coin diameter.

As shown in Figure 1 a plurality of sets of conductive electrode strips and covering spacers may be placed a short distance apart so that the checking of the diameter of several coin sizes may take place on a relatively short section of one and the same coin chute, coins and tokens of wrong diameter merely passing without giving rise to any detection. It is to be understood that Figure 1 shows only a part of the coin chute which usually contains further detection devices for checking other properties of the coins and the coin material. Upstream of the diameter detector preferably a releasable stop means (not shown) is provided so that the coins will pass the detector with an appropriate low velocity whereby the movement of the coin becomes a true rolling on the coin support rail 3.

In operation of the device a voltage is applied across the coin support rail and the electrode strip 4 and when a conductive coin of correct size touches the electrode 4 contact closure is established. The contact function, however, is rather incomplete due to the movement and relatively small weight of the coin such that only a series of very short pulses are provided. To enable utilization of the said pulses for reliable detection of a coin of correct size and further measures for cashing or rejection of the coin the coin support track 3 and electrode strip 4 form part of a detection circuit, shown in Figure 4. This Figure shows a voltage sensitive semi-conductor device in the form of a C-MOS flip-flop 7 to which a DC voltage is applied through leads 8 and 9. In case of a coin operated telephone the said leads may be the connecting leads of the telephone.The electrode 4 is connected to the positive lead 8 through a current limiting resistor 19 and to a control input 10 of the flip-flop 7. A capacitor 11 is used for noise suppression and prevents thereby erroneous triggering of the flip-flop 7.

A capacitor 11 is used for noise suppression and prevents thereby erroneous triggering of the flip-flop 7. When a coin of correct size forms contact between the coin support rail and the electrode 4 an acceptance signal may be applied to a device positioned further downstream of the coin chute for cashing a coin of correct diameter.

As previously indicated the acceptance of the coin will usually be dependant on the concurrent receipt of acceptance signals from other detection devices. The flip-flop 7 is bistable. The acceptance signal at output 12 is supplied to a control circuit (not shown) of the coin operated telephone which circuit, when an acceptance signal is supplied thereto, resets the flip-flop 7 after an appropriate delay by supplying to a reset input (not shown) of the flip-flop 7 a resetting signal.

A circuit as described with reference to Figure 4 is required for each coin size intended to be accepted.

Since it is often undesirable in coin operated telephones -- i.e. because of monitoring the telephone cables by leakage con trol - to have direct contact between the connecting leads of the telephone and and metal parts which directly or indirectly may be contacted by other objects the detection circuit may advantageously be carried out as shown in Figure 5. An auxiliary voltage is applied to the coin support rail 3 and electrode strip 4, said auxiliary voltage being provided in a manner known per se and is selected of such magnitude that safe contact formation is provided by the coin, The generated contact pulses are coupled by a transformer 13 to the control input 10 of a C-MOS flip-flop 7 of the same kind as shown in Figure 4. The operation of the circuit of Figure 5 is otherwise the same as that of the circuit of Figure 4.

When the checking of diameter is carried out in a coin operated telephone including a cashing relay for cashing coins from an external storage of unsorted coins, the said relay may be used to generate the auxiliary voltage which is applied across the coin support rail 3 and electrode 4 in Figure 5.

To economize on current the cashing magnet is controlled, when energized, by pulses of a duration and frequency imparting sufficient holding force to the magnet. The auxiliary voltage for the checking of diameter may then be provided by rectifying the voltage generated in an extra winding of the relay.

It is to be noted that the described circuits are of particular importance in connection with coin operated telephones because the available voltage and current are very small so that the circuit must have only a small power consumption. When the checking of diameter is carried out in coin operated devices such as vending machines in which the current consumption is not essential other circuit elements having a higher power consumption may of course be used for providing the acceptance signal.

WHAT WE CLAIM IS: 1. A coin detector for checking the diameter of at least one coin size in a coin operated device comprising a longitudinally sloping coin chute including a coin support rail between front and back walls which are backwardly inclined transversely of the longitudinal direction of the chute, characterized in that the coin support rail along at least part of its length within the chute is made of or provided with a covering of electrically conductive material while at least the backwardly inclined back wall is made of electrically insulating material, that at least one strip of conductive material is located on the back wall parallel to the coin support rail such that the bottom edge of the strip has a distance to the coin support rail equal to the smallest acceptable diameter of a coin to be accepted and that a spacer of insulating material extends into the coin chute further from the back wall than the conductive strip and is located along said strip such that the bottom edge of said spacer has a distance to the coin support rail equal to the greatest acceptable diameter of said coin and that the coin support rail and the conductive strip form parts of an electrical detection circuit adapted to provide an acceptance output signal when a coin of acceptable diameter makes contact between the strip and coin support rail.

2. A coin detector as in claim 1, characterized in that a plurality of sets of conductive strips and insulating spacers are located one after another along the coin chute at different distances from the coin support rail for checking a plurality of coin sizes.

3. A coin detector as in claim 1 or 2, characterized in that the angle between the coin support rail and back wall is smaller than 90".

4. A coin detector as in any of the preceding claims, characterized in that the conductive strip is a metal plate secured to the back wall said metal plate being covered partly by the insulating spacer.

5. A coin detector as in any of claims 1-3, characterized in that the conductive strip includes a metal plate.

secured at the bottom edge of the spacer perpendicular to the back wall, the thickness of said metal plate being equal to the acceptable interval of coin diameters.

6. A coin detector as in claim 1 for use in a coin operated telephone, characterized in that the electrical detection circuit is a voltage sensitive semi-conductor device requiring a very small control current, such as a C-MOS flipfiop.

7. A coin detector as in claim 6, characterized in that the circuit into which the conductive strip and coin support rail are connected is galvanically isolated from the connecting leads of the telephone.

8. A coin detector as in claim 7, characterized in that the circuit into which the conductive strip and coin support rail are connected is supplied by an auxiliary voltage derived from the line voltage of the telephone.

9. A coin detector as in claim 8 wherein a cashing relay is used, characterized in that said auxiliary voltage is provided by an extra winding on the cashing relay, the exitation current thereof being pulsed.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. be used for providing the acceptance signal. WHAT WE CLAIM IS:

1. A coin detector for checking the diameter of at least one coin size in a coin operated device comprising a longitudinally sloping coin chute including a coin support rail between front and back walls which are backwardly inclined transversely of the longitudinal direction of the chute, characterized in that the coin support rail along at least part of its length within the chute is made of or provided with a covering of electrically conductive material while at least the backwardly inclined back wall is made of electrically insulating material, that at least one strip of conductive material is located on the back wall parallel to the coin support rail such that the bottom edge of the strip has a distance to the coin support rail equal to the smallest acceptable diameter of a coin to be accepted and that a spacer of insulating material extends into the coin chute further from the back wall than the conductive strip and is located along said strip such that the bottom edge of said spacer has a distance to the coin support rail equal to the greatest acceptable diameter of said coin and that the coin support rail and the conductive strip form parts of an electrical detection circuit adapted to provide an acceptance output signal when a coin of acceptable diameter makes contact between the strip and coin support rail.