SK94895A3 - Device for testing of coins or flat objects - Google Patents

Abstract

Two optical barriers (L1,L2) are sepd. by a distance (L) along a track inclined at an angle (theta) to the horizontal (H). The coin (M) rolling down the track starts a timing operation at the first barrier and terminates it at the second. From the durations of occultation at the two barriers and of transit between them, the length of a chord (B) of the rolling coin at a max. distance from its edge equal to the distance (h) of the barriers from the track is calculated on the assumption of approximately constant acceleration. <IMAGE>

Description

Technical field

The invention relates to a device for testing the authenticity of a coin or other flat object of the type mentioned in the preamble of claim 1.

Such coin testing devices are suitable, for example, for identifying coins in payphones, vending machines, energy counters, etc.

BACKGROUND OF THE INVENTION

A coin testing device of the type mentioned in the preamble of claim 1 is known from French patent FR 1,605,182. The two light barriers are located along the coin channel and the time interval the coin needs to pass from the first light barrier to the second light barrier, and the time interval during which the coin covers the second light barrier is compared to predetermined reference values. Such a measurement implicitly constitutes a determination of the length of the coin string. In order to avoid different initial velocities, it is necessary to have a stop which can be actuated by a relay and which stops the coin inserted and subsequently releases the coin channel for the coin.

DE 2,015,058 C2 discloses a coin testing device in which there is a stop for releasing the coin channel, a magnet holding the coin according to its specific properties, and two light barriers for determining the speed of the coin after it has passed through the magnet. There is no measure to take into account the acceleration of the coin on the way from one light barrier to another. To further increase the reliability of coin detection, two additional light barriers are placed in front of the braking magnet, by means of which the speed of the coin can be determined before entering the magnetic pole of the magnet.

A coin testing apparatus with coin diameter determination by means of two light barriers is known from EP 119, 936 A1. The coin rolls over the coin channel and at the same time undergoes constant acceleration. The average velocity is calculated from two time intervals during which the coin obscures two light barriers and is used to correct the effect of acceleration to determine the diameter.

It is known from EP 483,451 A1 to use the arithmetic mean of the times during which a coin rolling over a coin channel obscures two light barriers to determine the length of the coin string.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION The object of the present invention is to provide a coin testing device in which the length of the test coin string can be determined, independently of the initial conditions, in a simple and accurate manner.

Said aim is achieved according to the invention by the features of claim 1.

Overview of the figures in the drawing

An exemplary embodiment of the invention is explained in more detail below with reference to the drawing of a single figure. The figure shows a device for testing the authenticity of coins or stamps or other flat objects.

DETAILED DESCRIPTION OF THE INVENTION

The device has a coin channel K known per se, two light barriers L1 and L2 and electronic means E for recording and evaluating the electrical signals emitted by the light barriers L1 and L2. In the region from the coin entry to the first light barrier, the coin channel is designed and secured with energy absorbing elements in such a way that there is normally no possibility for the coin M to bounce or jump between two light barriers L1 and L2. In the region between the two light barriers L1 and L2, the coin channel is designed as an inclined plane SE which is inclined with respect to the horizontal H at an angle Θ. On the inclined plane SE between the two light barriers L1 and L2, the coin M moves downward with a constant acceleration resulting from the force of gravity and the frictional forces. Movement can be rolling with and without gliding, gliding without rolling or a combination of rolling and gliding. The light barriers L1 and L2 are located above the inclined plane SE at a predetermined equal height ha with a predetermined distance L relative to one another. The distance traveled by the coin M on the SE plane in relation to time t is determined by coordinate x (t). The zero points χθ at _{Q of the} coordinate axis x and time t are selected such that χθ = 0 at _Q = 0 when coin M begins to shield the first light barrier L1.

The coin M has a mass m, a radius R and a moment of inertia I. The moment of inertia I is related to the axis of rotation passing through the center of gravity of the coin M. As is known, for a homogeneous coin,

ABOUT ,

1 = 5 mR. The length of the chord running parallel to the inclined plane SE at height h, the coin M is denoted as B. The center of gravity of the coin M moves at v (t). The coin M rotates around its center of gravity at an angular velocity of CO (t). The energy E of the coin M is composed of the potential energy Ep _Ot , the kinetic energy E _k £ _{n of the} center of gravity and the rotational energy E _ro1 - in relation to its center of gravity:

E = Ep _Ot + E _kin + E _rot = mg Sine (L + B - x) + | mv ² + Hoj ² (1) where g stands for gravitational acceleration.

At time t _Q = 0, the velocity v of the coin M has a value in _Q and its angular velocity ω is a value of ω ₀ , so the expression

Ε (χθ = 0) = mgsin0 (L + B) + _Q ² + IMV 1 I _'0 ² (2) is true.

The law of conservation of energy provides an equation

-xmg sine + jmv ² + | Ιω ² = | mv0 ² +> IW0 ²

If the coin rolls without sliding, v = Ro) is true. Thus, by deriving equation (3), a constant acceleration of two mg sine is obtained over time t ^and l = --- = -----—- (4) dt m + R ² I

Integration yields _ mg sine x (t) = 1 and _x t ² + vQt = ---------— t ² + vQt (5)

2 (m + R ² )

When the coin M of the roll over the coin channel is gradually obscured by two light barriers L1 and L2. I.e., time marks the end of the first light-shielding barrier of L1 time t ₂ the top shield part of the light barrier L2 at the _{3 'end} of shielding the second light barrier L 2 to give the following equation (6), (7), (8):

^{Β = + in} O ^t l (6)

L = i _ai t ₂ ² + in _Q t ₂ (7)

L = La + B _x ² + t ₃ t in _{the 3} (8)

Solving this system of equations (6), (7), (8) gives (t ₂ - t ₃ ) t _x ² + (t3 ² - t2 ² ) t ₁

B = L (9) (t ₃ ² - ie ² ) t ₂ - (t ₃ - t 1) t ₂ ² a

^ť l ^{+ t} 2 “ ^t 3 ^and l = ^2L --- 3 <

(t ₃ - ie) t ₂ - (t ₃ - t 1) t ₂

The formula (9) for determining the length of the chord B of the coin M does not contain any members which depend on its initial velocity νθ, its initial angular velocity C ₀ or on any of the physical constants. The length of the chord B is obtained exclusively from the predetermined distance L of the two light barriers L1 and L2 and the times t _x , t ₂ and t ₃ which are measured, while the timeline is selected such that t _Q = 0. times t _lz t ₂ and t ₃ thus actually correspond to time differences. The radius R of the coin M can be calculated from the length of the chord B and the height h according to the formula

B ² + 4h ² _R = ----------- (11) 8h

The acceleration of the coin M can likewise be calculated from the times, t ₂ and t _3, by the formula (10). Assuming that the coin M rolls without sliding, the ratio of the moment of inertia I to the mass m of the coin M can be determined by formulas (4), (10) and (11):

(12)

I g ² sin ©

If the coin M slides without rolling, its rotational energy disappears and the constant acceleration a ₂ dv and ₀ = ---- = gsinO dt is similarly obtained by the solution x (t). = Ia ₂ t ² + vQt = jgsinOt ² + vQt (14)

As will be appreciated, the determination of the length of the chord B can, as before, be determined by the formula (9) from the times ie, t ₂ and t ₃ . In addition, the formula (9) for determining the length of the chord B is also applicable when the coin M of the roll and the slide slides, provided that the acceleration and its center of gravity are approximately constant from time t ₀ to time t ₃ . L1 and L2 barriers.

The measurement of the times t _Q , ie, t ₂ and t ₃ , can be performed with high precision by known methods. In a first embodiment of the coin testing device, the signals transmitted by the light barriers L1 and L2 are fed via separate lines to the two microprocessor inputs so that the distance of the two light barriers L1 and L2 can be fixed as desired. In a preferred embodiment, the distance L is selected to be greater than the chord B of the largest coin to be measured. In this case, the two light barriers L1 and L2 are never shielded simultaneously, so that the output signals of the two light barriers L1 and L2 can be fed to a common input of the microprocessor. As the coin M crosses the light barriers L1 and L2 in both embodiments, two pulses are applied sequentially to the microprocessor. The rising edge of the first pulse starts the measurement of time, thus setting t _Q = Ον to the microprocessor. The other three edges of the two pulses then determine three times, ie, t ₂ and t ₃ . Using the formula (9), the microprocessor then calculates the length of the chord B of the coin M, which serves as at least one decision criterion for accepting or rejecting the coin M.

Of course, the specified formulas may be transformed or in all cases even replaced by an approximation formula, so that rounding errors can be avoided, if possible, when the calculation is performed by a microprocessor.

The advantage of the described device is that neither the initial velocity νθ, nor the initial angular velocity nor the actual acceleration and the coin M on its path from the first light barrier to the second are included in the determination of the length of the chord B. coins, e.g. by a magnet, it is not necessary in the coin channel in front of the first L1 light barrier. The length of the chord B of the coin M may be determined by the formula (9) to an accuracy of the order of one thousandth. The proposed coin testing device is therefore perfectly suitable for use in a machine that is to accept coins of different sizes and different currencies.

The moment of inertia I of the coin M depends on the nature and number of alloys from which the coin M is made. If the coin M consists of several alloys, the moment of inertia I also depends on the geometrical arrangement of the various alloys in the coin M. The ratio of moment of inertia to mass I / m is therefore another variable that characterizes coin M. , the I / m ratio can be used as a decision criterion in accepting or rejecting the coin M, thereby making it unnecessary to incorporate a conductive sensor to determine the alloy composition in the coin testing device.

The device may also have additional sensors to measure other characteristics, such as the thickness of the coins to be tested, and which then similarly serve as a decision criterion for accepting or rejecting the M coin.

Claims (7)

PATENT CLAIMS A device for testing the authenticity of coins (M), money stamps or other flat objects with a coin channel (K) and electronic means (E), in which the coin (M) to be tested passes on a track inclined to the horizontal (H) ) at an angle Θ, two light barriers (L1, L2) which are located at the same height (h) to the track and which have a distance (L) relative to each other, characterized in that during the passage of the coin (M) ) records the time t _Q the beginning of the shielding of the first light barrier (LI), the end time shielding the first light barrier (LI), the time t ₂ the start of shielding the second light barrier (L2) and the time t ₃ the end shield of the second light barrier (L2) and calculate the length coin (M) coins (M) from these four times t _Q , t 1, t ₂ , t ₃ , provided that the coin (M) is approximately constant acceleration and from the time t _Q the first light barrier shielding (L1) to time t ₃ con c the shielding of the second light barrier (L2), and the length of the string (B) serves as a decision criterion for accepting or rejecting the coin (M). Device according to claim 1, characterized in that the length of the chord (B) is calculated using the formula (t ₂ - t ₃ ) t · ^ ² + (t 3 ² - t ^{2 2} ) ie B - L 'χ (t ₃ ² - t ^{1 2} ) t 2 - (t ₃ - t ₁ ) t ₂ ² where the zero point of time measurement is fixed at t _Q = 0. Device according to claim 1 or 2, characterized in that the acceleration a is determined and serves as a decision criterion for accepting or rejecting the coin (M). Device according to Claim 3, characterized in that the acceleration and the coin (M) are determined as ^fc 1 ⁺ t ₂ - ^ 3 3. η - 2 L ^- '· (t ₃ ² - tx ² ) t 2 - (t ₃ - t ₁ ) t ₂ ² Device according to any one of claims 1 to 4, characterized in that the ratio of moment of inertia I to the weight m of the coin (M) is determined and serves as a decision criterion for accepting or rejecting the coin (M). Apparatus according to claim 5, characterized in that the ratio of the moment of inertia I and the weight m of the coin (M) is determined using the relation GR ² sin8 - --- r ² ma B ² + 4h ² where R = --------, g stands for gravitational acceleration 8h and the acceleration α is calculated according to claim 4. A coin testing device (M) according to any one of claims 1 to 6, characterized in that it accepts coins (M) of different names.