DEVICE AND METHOD FOR OBTAINING MECHANICAL CHARACTERISTICS OF COINS

Abstract: Device for obtaining mechanical characteristics of coins, comprised of an element which is elastically deformable by the weight of coins during their passage on said element. The deformation of said element will depend on the weight of the coins and their position on the length of said element. The elastically deformable element is provided with sensors in order to obtain an electric signal inherent to the mechanical characteristic searched in the coin. From the impact produced by the drop of the coins on said beam a parameter representative of the mechanical elasticity of the coin is determined by means of frequency analysis, by proceeding to the measurement of higher harmonics of the impact signal.

Description: The invention relates to a device for obtaining mechanical characteristics of coins having the features of the pre-characterising portion of claim 1. Such a device is known from EP 0 360 506 A3, wherein means for producing an impact signal caused from the falling coins are formed as a microphone. The microphone is positioned to detect acoustic vibrations of a coin after striking a hard surface upon which the coin is falling after entering the device. An output from the microphone is applied to signal processor means to produce a dynamic signal analysis of the coin vibrations. The microphone not only detects the vibrations of the coin but also other noises and the produced signal do not respond to the vibrations only. EP 0 318 229 A2 discloses a coin validation apparatus comprising a microphone also positioned to detect acoustic vibrations of the coin after falling to a hard striking surface. That apparatus further comprises an electronic circuit capable of comparing data from said coin with stored data representative to a set of standard coins. The sound emitted by the coin will contain information about the resonant modes, whose relative amplitudes will change with time after the coin has been struck. This apparatus do not comprise any elastically deformable element. Selectors, in which the impact of the coins is analysed, have been described, for example, in the Swiss patents numbers 645.201 and 647.608, in the Spanish patent 514.234 and in the British patent 2173624. The measurements of the impact of the coins is not precise, as the impact brings about irregular effects which are not very repetitive, depending on the condition of the edge of the coin, the angle of incidence, the types of materials of coins and the anvil or sensor plate which receives the impact, etc. Selectors which measure the weight of the coins have been described in the Swiss patents 624.500, the British patent 2010559 and the French patent 2335005. The Swiss patent 624.500, refers to a coin verification device for automatic vending machines based on the measurement of the weight of the coins by means of a weighing device or electronic scale. The British patent 2.010.559 refers to an apparatus for detecting the value of a coin, in combination with coin dimension detector mechanisms includes a weight sensor made up of a mobile plate with a phototransistor incorporated which detects the position of this plate. To determine the weight of the coin it is necessary for the coin to be retained. The French patent 2335005 refers to a coin controlling device, which includes a mechanical weighing device in the form of a roman scale which checks if the coin is of the minimum weight. The device which is the subject of the present invention, corresponds to the latter of the above mentioned sensors which is based on the measurement of the weight of the coins. The device subject of the invention weighs the coins by detecting the deformations tolerated by an elastically deformable element, on which the coins fall. In the Swiss patent 624.500 the weight of the coins is measured by detecting the displacement of a mobile element, on which the coins fall. In the device subject of the invention there is no such mobile element, but rather a deformable elastic element. The weight sensor used is different. In comparation with the British patent 2010559, the detector subject of the present invention does not need to retain the coin in order to measure its weight. In other words, with a static measurement, the device subject of the invention realizes a dynamic measurement. On the other hand, the element with which the weight of the coins is effected, is of a completely different nature. Finally, the device subject of the invention uses a weighing element which is different from that of the French patent 2.335.005, which on the other hand, only checks if the coin possesses the minimum weight, that is to say, it detects the possible lack of weight but not the correct weight of the coin. Nor does it provide electric signals for later checks and comparisons. The present invention incorporates a device as defined in the appended claim 1 for ascertaining mechanical characteristics of coins, applicable to coin selectors, which enables the identification of coins on the basis of detecting the deformations tolerated by a deformable elastic element, preferably of a metallic substance on which the coin rolls, the deformations produced on this element will depend on the weight of the coin and on the position of the coin at each stage in relation to the deformable element. To measure the deformations of the deformable element any of the direct or indirect procedures, applicable to the measurement of deformations on materials, may be used. According to the invention, the elastically deformable element is composed of a beam with at least one of its ends embedded. This beam determines the route along which the coin will roll, bringing about the deformation of the beam to an extend which will depend on the weight of the coin and on its position in relation to the point of incasement of the beam. The beam also includes a measurer of deformations. This device will form part of a coin selector and the deformable elastic element will define a path along which the coins will pass on their way through the selector. The aforementioned may be made up of an elastic strip which is embedded at one end and the other overhanging. The measurer of deformations may consist of an extensometer gage attached to the metallic strip, near its incasement. This measurer may also consist of a displacement sensing device which measures the deflection of the point of maximum deformation on the beam. The strip which defines the elastically deformable element may be attached at its free end. By way of variation, the beam or elastic band may be embedded at both ends. In addition to the beam which defines the elastically deformable element, an upper stretch may be included which will define the route along which the coins will roll, and a lower stretch which will serve as an anchorage for the body of the selector. At the very least, the first stretch mentioned will have a slight inclination so as to induce the rolling of the coins. The signal obtained from the impact and rolling of the coin on the elastically deformable element, the subject of the invention, includes two fields which are clearly distinguishable by the different activation caused in both (frequency fields), one of these fields corresponds to the moment of impact of the coin on the elastically deformable element and the other corresponds to the variable signal which is produced during the rolling of the coin along the aforementioned element and which depends on the weight of the coin and its position throughout. The measurement procedure is based on the degree of impact of the coin on the deformable elastic element in order to determine, by means of a specific frequency analysis, a parameter which is representative of the mechanical elasticity of the coin. For this purpose a measurement of the upper harmonics of the impact signal is made, the content of this measurement representing the mechanical elasticity of the coin. The invention therefore uses frequency analysis techniques with the aim of analysing the resonance frequencies in relation to the type of impact. If the coin is high in elasticity, the frequencies tend to be proportionately more active than if the coin is of low elasticity, in which case the coin acts like a shock absorber. Therefore, analysing the harmonic content of the signal produced by the impact, it is possible to obtain a measurement which is representative of the elasticity of the coin. To carry out a measurement of the frequency occurring on impact, a parameter depending on the mechanical elasticity of the coins is used and stored in the coin selector memory and used later to identify the coins, together with other parameters representative of, for example, weight, alloy, dimensions, etc. The frequency analysis of the impact described can be carried out by means of a circuit which includes: an amplifier, responsible for increasing the level of the signal supplied to the impact sensor; an analogue band-pass filter circuit, tuned to the normal frequency of the sought after elasticity, an analogue-digital converter and a microprocesor. The analogue filter may be of a fixed or variable band-pass frequency depending on whether one or various frequency ranges are involved. Furthermore, as an alternative to the analogue filter, it is possible to use digital filtering, incorporated in the microprocessor used in the coin selector. If one should wish to incorporate a measurement of characteristic vibrations present during the rolling or displacement of the coin along the beam, it is possible to use a circuit similar to the one previously described. As an alternative, it is also possible to use a single analogue filter, obtaining different frequency tuning during variable tuning or line switching techniques (usually tuning capacitors) controlled by the processor. The characteristics of the invention as they are presented in the claims, are more easily understood from the following description, made with reference to the attached drawings in which a possible form of procedure shown, offered by way of example but by no means meant to be limiting. Figure 1 shows a schematic drawing of a device for ascertaining mechanical characteristics of coins, made up of a beam embedded at one extreme. Figure 2 shows a diagram of the force of the coin on the beam submitted to flexion. Figure 3 corresponds to a possible circuit which can provide currents which are proportional to the deformation of the elastically deformable element. Figure 4 is a diagram of the electric signal derived from the deformations of the elastically deformable element during the rolling of the coin. Figure 5 shows a perspective of a possible effect on the deformable elastic element. Figure 6 shows a lower plan of the element in figure 5. Figure 7 shows a frontal elevation of the internal part of a coin selector which includes the deformable elastic element of figures 5 and 6. Figure 8 offers a perspective of the performance of figure 7. Figures 9 and 10 show a lateral elevation, of other effects of the elastically deformable element. Figures 11 and 12 correspond to other graphs, which represent the frequency content of the impact of two coins, of the same dimensions, but of different elasticity, the graph of figure 11 corresponds to a legal tender coin and figure 12 to a leas fake. Figure 13 is a block diagram of a circuit which allows the process to be carried out. In figure 1 the deflections marked number 1, indicate the route followed by coin, for example, within the coin selector. A stretch of this route is defined by the device which is the subject of the invention and incorporates an elastically deformable beam (2) which is incased at one extreme (3) and overhanging. This beam, along which the coins (4) will roll, may be of a metallic plate. As a coin (4) rolls along the embedded plate (2) a deformation is produced. This deformation will reach a maximum value when the coin (4) arrives at the free end (5) of the plate or beam (2), at which time the plate will be in a position represented by the dotted lines and reference numbered 2a. The maximum deformation corresponds to the deflection (6). The deformation of line 5, will always be in relation to the weight of the coin (4) and to its position throughout the length of the beam (2). To measure these deformations it is possible to use extensometric gages (7) attached near the incasement of the beam. without this technique necessarily excluding other possible procedures or systems of measuring deformations in the plate. Hence, for example, the measurement of the deformations may be done by displacement capacitors (without contact) in their multiple variations (inductive, capacitive, etc.). When the plate or beam (2) is in a totally horizontal position, the force produced by the coin and hence producing the flexion, will be its own weight (F = m x g). If the plate is at an angle with the horizontal position, as seen in figure 2, the force provoking the flexion will be made up of the weight of the coin, in the normal direction of the plate (F = m x g x cos a). In order to measure the deformation produced, it will be sufficient to attach an extensometer gage on the base of the plate, near the incasement, which is the most sensitive area. The gage may be arranged using auxiliary resistances or other gages, on a Wheatstone bridge assembly (half or complete). Using any of the typical signal conditioning circuits for Wheatstone bridges, it is possible to obtain, at the circuit exit, an electric current related to the deformation experienced by the incased plate, as illustrated in figure 3. With a methodical analysis of this electric current, various mechanical characteristics of the coins could be determined. For example, it could be possible to determine the volume of the coins, obtaining the principal component of the resulting electric signal. This signal will increase gradually until the coin goes beyond the end of the plate (2) at which time it will return to the value indicated prior to the passing of the coin. Figure 4 represents the electric current obtained as the coin passes; t0 and t1 corresponding to the beginning and end of the roll of the coin along the plate (2). In this way it is also possible to calculate the volume of the coin by carrying out a frequency analysis of the electric signal obtained as, in addition to the principal component, (proportional to the weight of the coin), it is possible to find the correct frequency for the plate-coin unit. These frequencies will vary,depending on the coins inserted. Finally, if the coin has a poligonal edge or the circular edge is ridged or fluted, it is possible to extract from the electric signal obtained, a component generated by the small vibrations produced by the edge of the coin as it rolls along the plate, therefore obtaining information about the shape of the coin. Plate (2) may be supported at the free end or even encased at both ends, hence obtaining optimum flexion when the coin is halfway along the plate. Plate (2) also allows shock absorbing material to be attached with the aim of filtering from the sensor, components of the electric signal obtained which are of a higher frequency than the basic and which are no longer required. If the coin (4) should fall on sheet (2), it is possible to position a shock absorbing block in front of this sheet so as to deenergise the coin. The beam or strip will preferably be of metal, although it could also be made from non metallic materials, such as a composite base which is shock absorbing. The beam represented in figure 5 and 6 comprises the upper route, reference marked 10, which defines the coin pathway, and a lower route number 11, which operated as an anchorage area for the beam to the body or housing unit of the selector. The upper route (10) takes on the shape of flat C, the extreme ends 12 and 13 being of different length. Prolongation number 13 extends, from its free transversal edge to a first section (14) which is bent at 180° to the prolongation (13), and to a second section bent outwards at an angle slightly more than 90°, which defines the lower route (11). This portion has a series of holes (15) to allow the passing of rivets or anchorage elements of the beam to the body of the selector. The prolongation 12 and 13 run at a certain inclination, downwards from the control stretch. The central stretch of the beam will have a sensor or measurer of deformations (16) attached to the lower part. Figures 7 and 8 show the internal part of a coin selector in which the beam, shown in figures 5 and 6, is mounted. Figures 7 reprents the stretch along which a coin (4), inserted into the selector,will follow. In front of the beam (10) is an anvil (18) on which the coin will fall and which serves as a shock absorbing element against the impact vibrations. In this case, the sensor 16 incorporated in the beam (10), will detect only the deformations originating on the beam as a result of the rolling or displacement of the coin along the beam. As can be seen from figure (8), the selector body has a lower stopper (19) and upper stopper (20) which limit the possibilities of oscillations or movements of the beam (10). The remaining components shown in figures 7 and 8 correspond to those of a traditional selector. In the case of figure (9), the upper stretch of the beam is reference marked 10a and the lower stretch 11a. These two stretches are straight and converge on each other, remaining joined for an intermediate stretch (21) which is a prolongation and forms part of the tracts 10a and 11a, being perpendicular to the latter. Tract 10a will run along, as in the case of figures 1 to 6, at an inclination so as to facilitate the rolling of the coins 4. The sensor 16 is attached to the external surface of the intermediate stretch 21. The beam unit illustrated in figure 9 adopts a general form C. None of the extreme ends of the tract (10a), which make up the rolling pathway, are incased. The incasement is defined by the C base or lower tract 11a. Finally, figure 10 represents a configuration of the beam in the form approximately of T. The upper tract 10b and the lower tract 11b are straight and converge as in the case of figure 9 and continue joined for the length of the intermediate tract 21b which forms part of the lower tract 11b and is independent from the upper tract 10b which determines the rolling pathway for coins (4). The intermediate tract 21b coincides at an intermediate point on the upper tract 10b, to which it is joined. In this case, none of the extremes of the ramp 10b are incased. As in the case of figure 9, the lower tract 11b defines the incasement or attachment zones. The sensor 16 is attached to the external surface of the intermediate tract 21b. the signal obtained with this is symmetrical, with respect to the moment at which the coin passes over the intermediate tract 21b. Figure 4 corresponds to a diagram of the electric signal which ensues from the deformations of the elastically deformable element, shown in figure 1, in the form of beam 2 incased at one end, during the impact and rolling of the coin (4). The electrical current obtained is also shown in this diagram, where the references t₀ and t₁ correspond to the moment of commencement and completion of the rolling of the coin on the beam which makes up the deformable elastic element. The detailed analysis of the signal represented in figure 4 enables one to clearly distinguish two perfectly differentiated fields by the dissimilar activation of both. Firstly, the signals produced by the deformation experienced in the beam, which constitutes the deformable elastic element, are detected at the moment of impact of the coin on the beam, precisely up to the moment when the rolling is about to begin. These signals correspond to the graph in figure 4, to those observed near the moment tO, the moment of impact, immediately before the commencement of the rolling. Once the coin begins to roll along the beam, the signals corresponding to the impact (instant tO) terminate and the vibrations which the coin beam unit produce begin to be activated by the rolling of the coin. The duration of these vibrations extends to the instant t1, in which the coin rolls along the sensored beam. The invention uses the first signals referred to, which in the graph of figure 4 correspond to those observed around the instant tO. By means of frequency analysis techniques the frequencies corresponding to the resonance in relation to the type of impact are analysed, hence determining a parameter which is representative of the mechanical elasticity of the coin. For this purpose, as already indicated, the upper harmonics of the impact signal are measured, the content of this measurement being representative of the mechanical elasticity of the coin. These characteristics can be seen in the graph of figures 11 and 12 in the first of which the frequency content of a legal tender coin is shown and in the graph of figure 12 the frequency content of a coin of the same size but made of lead. The main difference between these graphs is detected in the spectrum near the frequency, indicated by the point f₁, corresponding to the moment of impact of the coin on the elastically deformable element. As already indicated previously, a new parameter will be considered when carrying out a measurement of the frequency contents present on impact, depending on the mechanical elasticity of the coin, for their storage in the coin selector memory and their later help in identification, together with other parameters representative of the weight, alloy, dimensions, etc. Figure 13 corresponds to a block diagram of a circuit applicable to the frequency analysis of the impact previously described. In this circuit, reference mark 4 indicates a coin which will impact on the elastically deformable element, to which the impact sensor 7, figure 1, is related. The level of the signal delivered by sensor 7 is amplified by a block amplifier 22. Following, is an analogue band-pass filter circuit (23) the tuning of which is centred on the characteristic frequency f O of the elasticity sought after. After the filter is an analogue to digital converter 24, which will send the digital signal to a microprocessor (25) for processing, the filter (23) may be of fixed or variable pass-band frequency, depending on whether one or various ranges of frequency are involved. The memory (26), in which the parameters corresponding to different legal tender coins will be stored and which will assist in identification of the same, is connected to the microprocessor. A digital filter can be used as an alternative to the analogue filter (23), incorporated in the microprocessor used in the coin selector. When wishing to incorporate a measurement of the characteristic vibrations present during the rolling of the coin along the beam, in other words between the instants t₀ and t₁ of figure 4, a circuit similar to that described in reference to figure 13 can be used, with the link reference marked 27. Reference 28 indicates the admission/rejection and control of signal.

Claims: Device for obtaining the mechanical characteristics of coins, comprising an elastic element which may be deformed by the effect of the weight of the coins (4) and which is made up of a beam (2) fixed at one end, at least (3), where in the beam (2) is defining a rolling path along which the coins (4) travel, comprising a sensor (7) for producing a first signal representative of the deformation of the beam (2) to an extent which depends on the weight of the coin (4) and of its position in relation to the point of fixation of the beam (2) and further comprising means for producing an impact signal caused from the falling coins, characterised in that the elastic element is arranged so that the coins (4) will fall on it and that the sensor (7) is used to receive the impact signal as well as the first signal representative of the deformation of the elastic element, wherein the analysis of the high frequencies generated by the falling coins (4) on the elastic element determines a parameter representative of the mechanical elasticity of the coins (4). Device according to claim 1, characterized in that said beam (2) is made up of an elastic strip preferably of a metallic strip which is fixed at one extreme and the other overhanging. Device according to claim 2, characterized in that the sensor (7) consists of at least one extensometric gage attached to the elastic strip (2), near its point of fixation (3). Device according to claim 2, characterized in that the sensor (7) consists of at least one displacement sensing device attached to the elastic strip near its point of fixation (3). Device according to claim 2, characterized in that the elastic strip or beam (2) is supported at its free end. Device according to claim 1, characterized in that the beam (2) which is preferably made up of a metallic strip is fixed at both ends. Device according to claim 1, characterized in that said beam (2) comprises an upper tract (10), which defines the rolling path for the coins, and a lower tract (11) which defines an anchoring zone for the unit to the body or housing unit of the selector; with the first tract running at an inclination in order to provoke the rolling of the coins. Device according to claim 7, characterized in that the upper tract (10) adopts a configuration in the form of flat C, the arms (12 and 13) of which are of different length, the longer prolongation (13) extending to a first section (14) which is bent at 180° under itself, and a second section bending outwards at an angle of slightly more than 90°, hence defining the lower anchorage tract (11), with the sensor (16) being attached underneath the central arm of the upper tract (10). Device according to claim 7, characterized in that the upper and lower tract (10a and 11a)are straight and converging, remaining joinend by their divergent extremes via an intermediate stretch (21) which is a prolongation of both tracts(10a and 11a), making up one single piece and is perpendicular to the lower anchorage tract (11a), the sensor (16)being attached laterally to the intermediate stretch (21). Device according to claim 7, characterized in that the upper and lower tracts (10b and 11b) are straight and converge and remain joined for a straight intermediate stretch which is a prolongation of the lower tract (11b), with which it forms an angle of 90°, coming together and joining underneath at an intermediate point of the upper stretch (10b), the sensor (16) being attached laterally to the intermediate Device according to one of the claims 1 to 10, characterized in that the electric signal obtained at the moment of impact of the coin, is amplified (22) in order to increase its level, then being passed through an analogue band-pass filter (23) circuit, the tuning of which is centred on the characteristic frequency of the elasticity sought after, the analogue signal being immediately converted into digital (24) so as to be sent to a microprocessor (25,26) for analysis.

Inventors: ECHAPARE IBARROLA JESUS, PINA INSAUSTI JOSE LUIS, ECHAPARE, IBARROLA, JESUS, PINA INSAUSTI, JOSE, LUIS, ECHAPARE, Ibarrola, Jesús, PINA INSAUSTI, José, Luis
Applicants: AZKOYEN IND SA, AZKOYEN INDUSTRIAL, S.A.
Application year: 1991
Main classification: G07F3
IPC codes: G07D5