Coin Sorter With Automatic Bag-Switching or Stopping

The present invention relates generally to coin sorting and counting systems and, more particularly, to coin sorting and counting systems of the type which use a resilient disc rotating beneath a stationary sorting head for sorting coins of mixed denominations.

It is a primary object of the present invention to provide an improved coin sorting and counting system which is capable of sorting coins in mixed denominations and discharging only a prescribed number of coins of any selected denomination at any selected exit location. In this connection, a related object of the invention is to provide such a system which provides a separate count of each coin denomination prior to the sorting of the coins.

Another related object of the invention is to provide a coin counting and sorting system which is capable of monitoring the precise position of each separate coin from the time that coin passes a fixed counting station until the coin is sorted and discharged. Thus, one specific object of the invention is to provide such a system which permits any desired coin to be stopped, or diverted from one path to another, at any desired location after that coin has been counted but before it has been discharged from the system.

A particularly important object of one embodiment of the invention is to provide a coin counting and sorting system which provides automatic bag-switching for any desired coin denomination(s) combined with precise bag stopping at each bag station.

Another important object of this invention is to provide such an improved coin sorting and counting system which is capable of operating continuously, without stopping, while discharging successive batches of any desired number of coins of any desired denomination or denominations.

It is a further object of this invention to provide an improved coin counting and sorting system which is capable of providing precise bag stopping without the use of any movable members in the sorting head.

Yet another object of the invention is to provide such a system which is capable of initiating deceleration of the rotating disc as the last coin is a prescribed batch of coins approaches its discharge point. In this connection, a related object of one specific embodiment of the invention is to alter the path of the coins of at least one denomination before the next successive coin following the last coin in a prescribed batch has passes a fixed path-altering station beneath the sorting head.

A still further object of this invention is to provide such an improved coin sorting and counting system which does not discharge any coins in excess of the desired number for each denomination, even when coins of the same denomination are next to each other as they move through the sorter.

It is still another object of this invention to provide such an improved coin sorting an counting system which eliminates the need for coins sensors outside the periphery of the station sorting head.

A still further object of the invention is to provide such an improved coin sorting and counting system which eliminates the need for retractable or movable coin-sensing elements for use in counting the coins.

Other objects and advantages of the invention will be apparent from the following detailed description and the accompanying drawings.

In accordance with the present invention, the foregoing objectives are realized by providing a coin sorting and counting system which comprises a rotatable disc having a resilient surface for receiving mixed denomination coins and imparting rotational movement to the coins; means for rotating the disc; a stationary sorting head having a contoured surface spaced slightly away from the generally parallel to the resilient surface of said rotatable disc, the sorting head including means for queuing the coins on the disc into a single file of coins, and a guiding edge which engages selected edges of the coins in the single file and guides the coins along a prescribed path where the positions of the non-engaged edges of the coins are determined by the diameters of the respective coins; a counting station along the prescribed path for separately counting each coin denomination before the coins are sorted; and a sorting station spaced circumferentially from the counting station, in the direction of coin movement, for discriminating among coins of different denominations and selecting coins of different denominations for discharge from the rotating disc at different locations around the periphery of the sorting head.

FIG. 1 is perspective view of a coin counting and sorting system embodying the present invention, with portions thereof broken away to show the internal structure;

FIG. 2 is an enlarged horizontal section taken generally along the line 2--2 in FIG. 1 to show the configuration of the underside of the sorting head or guide plate;

FIG. 3 is an enlarged section taken generally along line 3--3 in FIG. 2;

FIG. 4 is an enlarged section taken generally along line 4-3 in FIG. 2;

FIG. 5 is an enlarged section taken generally along line 5--5 in FIG. 2;

FIG. 6 is an enlarged section taken generally along line 6--6 in FIG. 2;

FIG. 7 is an enlarged section taken generally along line 7--7 in FIG. 2;

FIG. 8 is an enlarged section taken generally along line 8--8 in FIG. 2;

FIG. 9 is an enlarged section taken generally along line 9--9 in FIG. 2;

FIG. 10 is an enlarged section taken generally along line 10--10 in FIG. 2;

FIG. 11 is an enlarged section taken generally along line 11--11 in FIG. 2;

FIG. 12 is an enlarged section taken generally along line 12--12 in FIG. 2;

FIG. 13 is an enlarged section taken generally along line 13--13 in FIG. 2;

FIG. 14 is an enlarged section taken generally along line 14--14 in FIG. 2, and illustrating a coin in the exit channel with the movable element in that channel in its retracted position;

FIG. 15 is the same section shown in FIG. 14 with the movable element in its advanced position;

FIG. 16 is an enlarged perspective view of a preferred drive system for the rotatable disc in the system of FIG. 1;

FIG. 17 is a perspective view of a portion of the coin sorter of FIG. 1, showing two of the six coin discharge and bagging stations and certain of the components included in those stations;

FIG. 18 is an enlarged section taken generally along line 18--18 in FIG. 17 and showing additional details of one of the coin discharge and bagging station;

FIG. 19 is a block diagram of a microprocessor-based control system for use in the coin counting and sorting system of FIGS. 1-18;

FIGS. 20A and 20B, combined, form a flow chart of a portion of a program for controlling the operation of the microprocessor included in the control system of FIG. 19;

FIG. 21 is a fragmentary section of a modification of the sorting head of FIG. 2;

FIG. 22 is an enlarged section taken generally along line 22--22 in FIG. 21;

FIG. 23 is an enlarged section taken generally along line 23--23 in FIG. 21;

FIG. 24 is a bottom plan view of another modified sorting head for use in the coin counting and sorting system of FIG. 1, and embodying the present invention;

FIG. 25 is an enlarged section taken generally along line 25--25 in FIG. 24;

FIG. 26 is the same section shown in FIG. 25 with a larger diameter coin in place of the coin shown in FIGS. 24 and 25;

FIG. 27 is an enlarged section taken generally along line 27--27 in FIG. 24;

FIG. 28 is the same section shown in FIG. 27 with a smaller diameter coin in place of the coin shown in FIGS. 24 and 27;

FIG. 29 is a bottom plan view of another modified sorting head for use in the coin counting and sorting system of FIG. 1, and embodying the present invention of FIG. 24;

FIG. 30 is an enlargement of the upper right-hand portion of FIG. 29;

FIG. 31 is a section taken generally along line 31--31 in FIG. 30;

FIG. 32 is a fragmentary bottom plan view of a modified coin-counting area for the sorting head of FIG. 29;

FIG. 33 is a section taken generally along line 33--33 in FIG. 32;

FIG. 34 is a fragmentary bottom plan view of still another modified coin-counting area for the sorting head of FIG. 29;

FIG. 35 is a section taken generally along line 35--35 in FIG. 34;

FIG. 36 is a fragmentary bottom plan view of yet another modified coin-counting area for the sorting head of FIG. 24; and

FIG. 37 is a timing diagram illustrating the operation of the counting area shown in FIG. 36.

While the invention is susceptible to various modifications and alternative forms, certain specific embodiments thereof having been shown by way of example in the drawings and will be described in detail. It should be understood, however, that it is not intended to limit the invention to the particular forms described, but, on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Turning now to the drawings and referring first to FIG. 1, a hopper 10 receives coins of mixed denominations and feeds them through central openings in an annular sorting head or guide plate 12. As the coins pass through these openings, they are deposited on the top surface of a rotatable disc 13. This disc 13 is mounted for rotation on a stub shaft (not shown) and driven by an electric motor 14. The disc 13 comprises a resilient pad 16, preferably made of a resilient rubber or polymeric material, bonded to the top surface of a solid metal disc 17.

As the disc 13 is rotated, the coins deposited on the top surface thereof tend to slide outwardly over the surface of the pad due to centrifugal force. As the coins move outwardly, those coins which are lying flat on the pad enter the gap between the pad surface and the guide plate 12 because the underside of the inner periphery of this plate is spaced above the pad 16 by a distance which is about the same as the thickness of the thickest coin.

As can be seen most clearly in FIG. 2, the outwardly moving coins initially enter an annular recess 20 formed in the underside of the guide plate 12 and extending around a major portion of the inner periphery of the annular guide plate. The outer wall 21 of the recess 20 extends downwardly to the lowermost surface 22 of the guide plate (see FIG. 3), which is spaced from the top surface of the pad 16 by a distance which is slightly less, e.g., 0.010 inch, than the thickness of the thinnest coins. Consequently, the initial radial movement of the coins is terminated when they engage the wall 21 of the recess 20, through the coins continue to move circumferentially along the wall 21 by the rotational movement of the pad 16. Overlapping coins which only partially enter the recess 20 are stripped apart by a notch 20a formed in the top surface of the recess 20 along its inner edge (see FIG. 4).

The only portion of the central opening of the guide plate 12 which does not open directly into the recess 20 is that sector of the periphery which is occupied by a land 23 whose lower surface is at the same elevation as the lowermost surface 22 of the guide plate. The upstream end of the land 23 forms a ramp 23a (FIG. 5), which prevents certain coins stack on top of each other from reaching the ramp 24. When two or more coins are stacked on top of each other, they may be pressed into the resilient pad 16 even within the deep peripheral recess 20. Consequently, stacked coins can be located at different radial positions within the channel 20 as they approach the land 23. When such a pair of stacked coins has only partially entered the recess 20, they engage the ramp 23a on the leading edge of the land 23. The ramp 23a presses the stacked coins downwardly into the resilient pad 16, which retards the lower coin while the upper coin continues to be advanced. Thus, the stacked coin are stripped apart so that they can be recycled and once again enter the recess 20, this time in a single layer.

When a stacked pair of coins has moved out into the recess 20 before reaching the land 23, the stacked coins engage the inner spiral wall 26. The vertical dimension of the wall 26 is slightly less than the thickness of the thinnest coin, so the lower coin in a stacked pair passes beneath the wall and is recycled while the upper coin in the stacked pair is cammed outwardly along the wall 26 (see FIGS. 6 and 7). Thus, the two coins are stripped apart with the upper coin moving along the guide wall 26, while the lower coin is recycled.

As coins within the recess 20 approach the land 23, those coins move outwardly around the land 23 and engage a ramp 24 leading into a recess 25 which is an outward extension of the inner peripheral recess 20. The recess 25 is preferably just slightly wider than the diameter of the coin denomination having the greatest diameter. The top surface of the major portion of the recess 25 is spaced away from the top of the pad 16 by a distance that is less than the thickness of the thinnest coin so that the coins are gripped between the guide plate 12 and the resilient pad 16 as they are rotated through the recess 25. Thus, coins which move into the recess 25 are all rotated into engagement with the outwardly spiralling inner wall 26, and then continue to move outwardly through the recess 25 with the inner edges of all the coins riding along the spiral wall 26.

As can be seen in FIGS. 6-8, a narrow band 25a of the top surface of the recess 25 adjacent its inner wall 26 is spaced away from the pad 16 by approximately the thickness of the thinnest coin. This ensures that coins of all denominations (but only the upper coin is a stacked or shingled pair) are securely engaged by the wall 26 as it spirals outwardly. The rest of the top surface of the recess 25 tapers downwardly from the band 25a to the outer edge of the recess 25. This taper causes the coins to be tilted slightly as they move through the recess 25, as can be seen in FIGS. 6-8, thereby further ensuring continuous engagement of the coins with the outwardly spiraling wall 26.

The primary purpose of the outward spiral formed by the wall 26 is to space apart the coins so that during normal steady-state operation of the sorter, successive coins will not be touching each other. As will be discussed below, this spacing of the coins contributes to a high degree of reliability in the counting of the coins.

Rotation of the pad 16 continues to move the coins along the wall 26 until those coins engage a ramp 27 sloping downwardly from the recess 25 to a region 22a of the lowermost surface 22 of the guide plate 12 (see FIG. 9). Because the surface 22 is located even closer to the pad 16 than the recess, the effect of the ramp 27 is to further depress the coins into the resilient pad 16 as the coins are advanced along the ramp by the rotating disc. This causes the coins to be even more firmly gripped between the guide plate surface region 22a and the resilient pad 16, thereby securely holding the coins in a fixed radial position as they continue to be rotated along the underside of the guide plate by the rotating disc.

As the coins emerge from the ramp 27, the coins enter a referencing and counting recess 30 which still presses all coin denominations firmly against the resilient pad 16. The outer edge of this recess 30 forms an inwardly spiralling wall 31 which engages and precisely positions the outer edges of the coins before the coins reach the exit channels which serve as means for discriminating among coins of different denominations according to their different diameters.

The inwardly spiralling wall 31 reduces the spacing between successive coins, but only a minor extent so that successive cons remain spaced apart. The inward spiral closes any spaces between the wall 31 and the outer edges of the coins so that the outer edges of all the coins are eventually located at a common radial position, against the wall 31, regardless of where the outer edges of those coins were located when they initially entered the recess 30.

At the downstream end of the referencing recess 30, a ram 32 (FIG. 13) slopes downwardly from the top surface of the referencing recess 30 to region 22b of the lowermost surface 22 of the guide plate. Thus, at the downstream end of the ramp 32 the coins are gripped between the guide plate 12 and the resilient pad 16 with the maximum compressive force. This ensures that the coins are held securely in the radial position initially determined by the wall 31 of the referencing recess 30.

Beyond the referencing recess 30, the guide plate 12 forms series of exit channels 40, 41, 42, 43, 44 and 45 which function as selecting means to discharge coins of different denominations at different circumferential locations around the periphery of the guide plate. Thus, the channels 40-45 are spaced circumferentially around the outer periphery of the plate 12, with the innermost edges of successive pairs of channels located progressively farther away from the common radial location of the outer edges of all coins for receiving and ejecting coins in order of increasing diameter. In the particular embodiment illustrated, the six channels 40-45 are positioned and dimensioned to eject only dimes (channels 40 and 41), nickels (channels 42 and 43) and quarters (channel 44 and 45). The innermost edges of the exit channels 40-45 are positioned so that the inner edge of a coin of only one particular denomination can enter each channel; the coins of all other denominations reaching a given exit channel extend inwardly beyond the innermost edge of that particular channel so that those coins cannot enter the channel and, therefore, continue on to the next exit channel.

For example, the first two exit channels 40 an 41 (FIGS. 2 and 14) are intended to discharge only dimes, and thus the innermost edges 40a and 41a of these channels are located at a radius that is spaced inwardly from the radius of the referencing wall 31 by a distance that is only slightly greater than the diameter of a dime. Consequently, only dimes can enter the channels 40 and 41. Because the outer edges of all denominations of coins are located at the same radial position when they leave the referencing recess 30, the inner edges of the nickels and quarters all extend inwardly beyond the innermost edge 40a of the channel 40, thereby preventing these coins from entering that particular channel. This is illustrated in FIG. 2 which shows a dime D captured in the channel 40, while nickels N and quarters Q bypass the channel 40 because their inner edges extend inwardly beyond the innermost edge 40a of the channel so that they remain gripped between the guide plate surface 22b and the resilient pad 16.

Of the coins that each channel 42 and 43, the inner edges of only the nickels are located close enough to the periphery of the guide plate 12 to enter those exit channels. The inner edges of the quarters extend inwardly beyond the innermost edge of the channels 42 and 43 so that they remain gripped between the guide plate and the resilient pad. Consequently, the quarters are rotated past the channel 41 and continue on to the next exit channel. This is illustrated in FIG. 2 which shows nickels N captured in the channel 42, while quarters Q bypass the channel 42 because the inner edges of the quarters extend inwardly beyond the innermost edge 42a of the channel.

Similarly, only quarters can enter the channels 44 and 45, so that any larger coins that might be accidentally loaded into the sorter are merely recirculated because they cannot enter any of the exit channels.

The cross-sectional profile of the exit channels 40-45 is shown most clearly in FIG. 14, which is a section through the dime channel 40. Of course, the cross-sectional configurations of all the exit channels are similar; they vary only in their widths and their circumferential and radial positions. The width of the deepest portion of each exit channel is smaller than the diameter of the coin to be received and ejected by that particular exit channel, and the stepped surface of the guide plate adjacent the radially outer edge of each exit channel presses the outer portions of the coins received by that channel into the resilient pad so that the inner edges of those coins are tilted upwardly into the channel (see FIG. 14). The exit channels extend outwardly to the periphery of the guide plate so that the inner edges of the channels guide the tilted coins outwardly and eventually eject those coins from between the guide plate 12 and the resilient pad 16.

The first dime channel 40, for example, has a width which is less than the diameter of the dime. Consequently, as the dime is moved circumferentially by the rotating disc, the inner edge of the dime is tilted upwardly against the inner wall 40a which guides the dime outwardly until it reaches the periphery of the guide plate 12 and eventually emerges from between the guide plate and the resilient pad. At this point the momentum of the coin causes it to move away form the sorting head into an arcuate guide which directs the coin toward a suitable receptacle, such as a coin bag or box.

As coins are discharged from the six exit channels 40-45, the coins are guided down toward six corresponding bag stations BS by six arcuate guide channels 50, as shown in FIGS. 17 and 18. Only tow of the six bag stations BS are illustrated in FIG. 17, and one of the stations is illustrated in FIG. 18.

As the coins leave the lower ends of the guide channels 50, they enter corresponding cylindrical guide tubes 51 which are part of the bag stations BS. The lower ends of these tubes 51 flare outwardly to accommodate conventional clamping-ring arrangements for mounting coin bags B directly beneath the tubes 51 to receive coins therefrom.

As can be seen in FIG. 18, each clamping-ring arrangement includes a support bracket 71 below which the corresponding coin guide tube 51 is supported in such a way that the inlet to the guide tube is aligned with the outlet of the corresponding guide channel. A clamping ring 72 having a diameter which is slightly larger than the diameter of the upper portions of the guide tubes 51 is slidably disposed on each guide tube. This permits a coin bag B to be releasably fastened to the guide tube 51 by positioning the mouth of the bag over the flared end of the tube and then sliding the clamping ring down until it fits tightly around the bag on the flared portion of the tube, as illustrated in FIG. 18. Releasing the coin bag merely requires the clamping ring to be pushed upwardly onto the cylindrical section of the guide tube. The clamping ring is preferably made of steel, and a plurality of magnets 73 are disposed on the underside of the support bracket 71 to hold the ring 72 in its released position while a full coin bag is being replaced with an empty bag.

Each clamping-ring arrangement is also provided with a bag interlock switch for indicating the presence of absence of a coin bag at each bag station. In the illustrative embodiment, a magnetic red switch 74 of the "normally-closed" type is disposed beneath the bracket 71 of each clamping-ring arrangement. The switch 74 is adapted to be activated when the corresponding clamping ring 72 contacts the magnets 73 and thereby conducts the magnetic field generated by the magnets 73 into the vicinity of the switch 74. This normally occurs when a previously clamped full coin bag is released and has not yet been replaced with an empty coin bag. A similar mechanism is provided for each of the other bag stations BS.

As described above, two different exit channels are provided for each coin denomination. Consequently, each coin denomination can be discharged at either of two different locations around the periphery of the guide plate 12, i.e., at the outer ends of the channels 40 and 41 for the dimes, at the outer ends of the channels 43 and 44 for the nickels, and at the outer ends of the channels 45 and 46 for the quarters. In order to select one of the two exit channels available for each denomination, a controllably actuatable shunting device is associated with the first of each of the three pairs of similar exit channels 40-41, 42-43 and 44-45. When one of these shunting devices is actuated, it shunts coins of the corresponding denomination from the first to the second of the two exit channels provided for that particular denomination.

Turning first to the pair of exit channels 40 and 41 provided for the dimes, a vertically movable bridge 80 is positioned adjacent the inner edge of the first channel 40, at the entry end of that channel. This bridge 80 is normally held in its raised, retracted position by means of a spring 81 (FIG. 14), as will be described in more detail below. When the bridge 80 is in this raised position, the bottom of the bridge is flush with the top wall of the channel 40, as shown in FIG. 14, so that dimes D enter the channel 40 and are discharged through the channel in the normal manner.

When it is desired to shunt dimes past the first exit channel 40 to the second exit channel 41, a solenoid S.sub.D (FIGS. 14, 15 and 19) is energized to overcome the force of the spring 81 and lower the bridge 80 to its advanced position. In this lowered position, shown in FIG. 15, the bottom of the bridge 80 is flush with the lowermost surface 22b of the guide plate 12, which has the effect of preventing dimes D from entering the exit channel 40. Consequently, the quarters are rotated past the exit channel 40 by the rotating disc, sliding across the bridge 80, and enter the second exit channel 41.

To ensure that precisely the desired number of dimes are discharged through the exit channel 40, the bridge 80 must be interposed between the last dime for any prescribed batch and the next successive dime (which is normally the first dime for the next batch). To facilitate such interposition of the bridge 80 between two successive dimes, the dimension of the bridge 80 in the direction of coin movement is relatively short, and the bridge is located along the edges of the coins, where the space between successive coins is at a maximum. The fact that the exit channel 40 is narrower than the coins also helps ensure that the outer edge of a coin will not enter the exit channel while the bridge is being moved from its retracted position to its advanced position. In fact, with the illustrative design, the bridge 80 can be advanced after a dime has already partially entered the exit channel 40, overlapping all or part of the bridge, and the bridge will still shunt the dime to the next exit channel 41.

Vertically movable bridges 90 and 100 (FIG. 2) located in the first exit channels 42 and 44 for the nickels and quarters, respectively, operate in the same manner as the bridge 80. Thus, the nickel bridge 90 is located along the inner edge of the first nickel exit channel 42, at the entry end of that exit channel. The bridge 90 is normally held in its raised, retracted position by mans of a spring. In this raised position the bottom of the bridge 90 is flush with the top wall of the exit channel 42, so that nickels enter the channel 42 and are discharged through that channel. When it is desired to divert nickels to the second exit channel 43, a solenoid S.sub.N (FIG. 19) is energized to overcome the force of the spring and lower the bridge 90 to its advanced position, where the bottom of the bridge 60 is flush with the lowermost surface 22b of the guide plate 12. When the bridge 90 is in this advanced position, the bridge prevents any coins from entering the first exit channel 42. Consequently, the nickels slide across the bridge 90, continue on to the second exit channel 43 and are discharged therethrough. The quarter bridge 100 (FIG. 2) and its solenoid S.sub.Q (FIG. 19) operate in exactly the same manner. The edges of all the bridges 80, 90 and 100 are preferably chamfered to prevent coins from catching on these edges.

The details of the actuating mechanism for the bridge 80 are illustrated in FIGS. 14 and 15. The bridges 90 and 100 have similar actuating mechanisms, and thus only the mechanism for the bridge 80 will be described. The bridge 80 is mounted on the lower end of a plunger 110 which slides vertically through a guide bushing 111 threaded into a hole bored into the guide plate 12. The bushing 111 is held in place by a locking nut 112. A smaller hole 113 is formed in the lower portion of the plate 12 adjacent the lower end of the bushing 111, to provide access for the bridge 80 into the exit channel 40. The bridge 80 is normally held in its retracted position by the coil spring 81 compressed between the locking nut 112 and a head 114 on the upper end of the plunger 110. The upward force of the spring 81 hold the bridge 80 against the lower end of the bushing 111.

To advance the plunger 110 to its lowered position within the exit channel 40 (FIG. 15), the solenoid coil is energized to push the plunger 110 downwardly with a force sufficient to overcome the upward force of the spring 81. The plunger is held in this advanced position as long as the solenoid coil remains energized, and is returned to its normally raised position by the spring 81 as soon as the solenoid is de-energized.

Solenoids S.sub.N ad S.sub.Q control the bridge 90 and 100 in the same manner described above in connection with the bridge 80 and the solenoid S.sub.D.

In accordance with one aspect of the present invention, each coin denomination is separately counted at a counting station along the lower surface of the guide plate, before the coins are sorted. The counted coins are then sorted at sorting stations spaced circumferentially from the counting station in the direction of coin movement. By counting the various coin denominations prior to sorting, the present invention provides ample time for actuation of a movable control member for affecting the movement of one or more coin denominations at some point between the counting station and the coin-discharge locations. Movement of any given coin from its counting sensor to the point where its movement is affected by the control member can be monitored with a high degree of precision. Thus, movement of the control member can be timed to affect the coin movement, downstream of the counting sensors, to ensure that no coin following the last coin within any desired batch (defined by a prescribed count) are discharged at a selected bag station. Even the response time of the movable control member can be taken into account so that the control member actually moves to affect the coin movement at precisely the desired instant.

In the particular embodiment of the invention illustrated in FIGS. 2-15, the control members comprise the shunting bridges 80, 90 and 100, and the coins are counted as they move through the referencing recess 30. As the coins move along the wall 31 of the recess, the outer edges of all coin denominations are at the same radial position at any given angular location along the edge. Consequently, the inner edges of coins of different denominations are offset form each other at any given angular location, due to the different diameters of the coins (see FIG. 2). These offset inner edges of the coins are used to separately count each coin before it leaves the referencing recess 30.

As can be seen in FIGS. 2 and 10-12, three coin sensors S.sub.1, S.sub.2 and S.sub.3 in the form of insulated electrical contact pins are mounted in the upper surface of the recess 30. The outermost sensor S.sub.1 is positioned so that it is contacted by all three coin denominations, the middle sensor S.sub.2 is positioned so that it is contacted only by the nickels and quarters, and the innermost sensor S.sub.3 is positioned so that it is contacted only by the quarters. An electrical voltage is applied to each sensor so that when a coin contacts the pin and bridges across its insulation, the voltage source is connected to ground via the coin and the metal head surrounding the insulated sensor. The grounding of the sensor during the time interval when it is contacted by the coin generates an electrical pulse which is detected by a counting system connected to the sensor. The pulses produced by coins contacting the three sensors S.sub.1, S.sub.2 and S.sub.3 will be referred to herein as pulses P.sub.1, P.sub.2 an P.sub.3, respectively, and the accumulated counts of those pulses in the counting system will be referred to as counts C.sub.1, C.sub.2, C.sub.3, respectively.

As a coin traverses one of the sensors, intermittent contact can occur between the coin and the sensor because of the contour of the coin surface. Consequently, the output signal from the sensor can consist of a series of short pulses rather than a single wide pulse, which is a common problem referred to as "contact bounce." This problem can be overcome by simply detecting the first pulse and then ignoring subsequent pulses during the time interval required for one coin to cross the sensor. Thus, only one pulse is detected for each coin that contacts the sensor.

The outer sensor S.sub.1 contacts all three coin denominations, so the actual dime count C.sub.D is determined by subtracting C.sub.2 (the combined quarter and nickel count) from C.sub.1 (the combined count of quarters, nickels and dimes). The middle sensor S.sub.2, contacts both the quarters an the nickels, so the actual nickel count C.sub.N is determined by subtracting C.sub.3 (the quarter count) from C.sub.2 (the combined quarter and nickel count). Because the innermost sensor S.sub.3 contacts only quarters, the count C.sub.3 is the actual quarter count C.sub.Q.

Another counting technique uses the combination of (1) the presence of a pulse P.sub.1 from the sensor S.sub.1 and (2) the absence of a pulse P.sub.2 from the sensor S.sub.2 to detect the presence of a dime. A nickel is detected by the combination of (1) the presence of a pulse P.sub.2 from the sensor S.sub.2 an (2) the absence of pulse P.sub.3 from sensor S.sub.3, and a quarter is detected by the presence of a pulse P.sub.3 from the sensor S.sub.3. The presence or absence of the respective pulses can be detected by a simple logic routine which can be executed by either hardware or software.

To permit the simultaneous counting of prescribed batches of coins of each denomination using the first counting technique described above, i.e., the subtraction algorithm, counts C.sub.2 and C.sub.3 must be simultaneously accumulated over two different time periods. For example, count C.sub.3 is the actual quarter count C.sub.Q, which normally has its own operator-selected limit C.sub.QMAX. While the quarter count C.sub.Q (=C.sub.3) is accumulating toward its own limit C.sub.QMAX, however, the nickel count C.sub.N (=C.sub.2 -C.sub.3) might reach its limit C.sub.NMAX and be reset to zero to start the counting of another batch of nickels. For accurate computation of C.sub.N following its reset to zero, the count C.sub.3 must also be reset at the same time. The count C.sub.3, however, is still needed for the ongoing count of quarters; thus the pulses P.sub.3 are supplied to a second counter C'.sub.3 which counts the same pulses P.sub.3 that are counted by the first counter C.sub.3 but is reset each time the counter C.sub.2 is reset. Thus, the two counters C.sub.3 and C'.sub.3 count the same pulses P.sub.3, but can be reset to zero at different times.

The same problem addresses above also exists when the count C.sub.1 is reset to zero, which occurs each time the dime count C.sub.D reaches its limit C.sub.MAX. That is, the count C.sub.2 is needed to compute both the dime count C.sub.D and the nickel count C.sub.N, which are usually reset at different times. Thus, the pulses P.sub.2 are supplied to two different counters C.sub.2 and C.degree..sub.2. The first counter C.sub.2 is reset to zero only when the nickel count C.sub.N reaches its C.sub.NMAX, and the second counter is reset to zero each time C.sub.1 is reset to zero when C.sub.D reaches its limit C.sub.DMAX.

Whenever one of the counts C.sub.D, C.sub.N or C.sub.Q reaches its limit, a control signal is generated to initiate a bag-switching or bag-stop function.

For the bag-switching function, the control signal is used to actuate the movable shunt within the first of the two exit channels provided for the appropriate coin denomination. This enables the coin sorter to operate continuously (assuming that each full coin bag is replaced with an empty bag before the second bag for that same denomination is filled) because there is no need to stop the sorter either to remove full bags or to remove excess coins from the bags.

For a bag-stop function, the control signal preferably stops the drive for the rotating disc and at the same time actuates a brake for the disc. The disc drive can be stopped either by de-energizing the drive motor or by actuating a clutch which de-couples the drive motor from the disc. An alternative bag-stop system uses a movable diverter within a coin-recycling slot located between the counting sensors and the exit channels. Such a recycling diverter is described, for example, in U.S. Pat. No. 4,564,036 issued Jan. 14, 1986, for "Coin Sorting System With Controllable Stop."

Referring now to FIG. 19, there is shown an upper level block diagram of an illustrative microprocessor-based control system 200 for controlling the operation of a coin sorter incorporating the counting and sorting system of this invention. The control system 200 includes a central processor unit (CPU) 201 for monitoring and regulating the various parameters involved in the coin sorting/counting and bag-stopping and switching operations. The CPU 201 accepts signals from (1) the bag-interlock switches 74 which provide indications of the positions of the bag-clamping rings 72 which are used to secure coin bags B to the six coin guide tubes 51, to indicate whether or not a bag is available to receive each coin denomination (2) the three coin sensors S.sub.1 -S.sub.3, (3) an encoder sensor E.sub.5 and (4) three coin-tracking counters CTC.sub.D, CTC.sub.N and CTC.sub.Q. The CPU 201 produces output signals to control the three shunt solenoids S.sub.D, S.sub.N and S.sub.Q, the main drive motor M.sub.1, an auxiliary drive motor M.sub.2, a brake B and the three coin-tracking counters.

A drive system for the rotating disc, for use in conjunction with the control system of FIG. 19, is illustrated in FIG. 16. The disc is normally driven by a main a-c. drive motor M.sub.1 which is coupled directly to the coin-carrying disc 13 through a speed reducer 210. To stop the disc 13, a brake B is actuated at the same time the main motor M.sub.1 is de-energized. To permit precise monitoring of the angular movement of the disc 13, the outer peripheral surface of the disc carries an encoder in the form of a large number of uniformly spaced indicia 211 (either optical or magnetic) which can be sensed by an encoder sensor 212. In the particular example illustrated, the disc has 720 indicia 211 so that the sensor 212 produces an output pulse for every 0.5.degree. of movement of the disc 13.

The pulses from the encoder sensor 212 are supplied to the three coin-tracking down counters CTD.sub.D, CTC.sub.N and CTC.sub.Q for separately monitoring the movement of each of the three coin denominations between fixed points on the sorting head. The outputs of these three counters CTC.sub.D, CTC.sub.N and CTC.sub.Q can then be used to separately control the actuation of the bag-switching bridges 80, 90 and 100 and/or the drive system. For example, when the last dime in a prescribed bath has been detected by the sensors S.sub.1 -S.sub.3, the dime-tracking counter CTC.sub.D is preset to count the movement of a predetermined number of the indicia 211 on the disc periphery past the encoder sensor 212. This is a way of measuring the movement of the last dime through an angular displacement that brings that last dime to a position where the bag-switching bridge 80 should be actuated to interpose the bridge between the last dime and the next successive dime.

In the sorting head of FIG. 2, a dime must traverse an angle of 20.degree. to move from the position where it has just cleared the last counting sensor S.sub.1 to the position where it has just cleared the bag-switching bridge 80. At a disc speed of 250 rpm, the disc turns--and the coin moves--at a rate of 1.5.degree. per millisecond. A typical response time for the solenoid that moves the bridge 80 to 6 milliseconds (4 degrees of disc movement), so the control signal to actuate the solenoid should be transmitted when the last dime is 4 degrees form its bridge-clearing position. In the case where the encoder has 720 indicia around the circumference of the disc, the encoder sensor produces a pulse for ever 0.5.degree. of disc movement. Thus the coin-tracking counter CTC.sub.D for the dime is preset to 32 when the last dime is sensed, so that the counter CTC.sub.D counts down to zero, and generates the required control signal, when the dime has advanced 16.degree. beyond the last sensor S.sub.1. This ensures that the bridge 80 will be moved just after it has been cleared by the last dime, so that the bridge 80 will be interposed between the last dime and the next successive dime.

In order to expand the time interval available for any of the bag-switching bridges to be interposed between the last coin in a prescribed batch and the next successive coin of that same denomination, control means may be provided for reducing the speed of the rotating disc 13 as the last coin in a prescribed batch is approaching the bridge. Reducing the speed of the rotating disc in this brief time interval has little effect on the overall throughput of the system, and yet it significantly increases the time interval available between the instant when the trailing edge of the last coin clears the bridge and the instant when the leading edge of the next successive coin reaches the bridge. Consequently, the timing of the interposing movement of the bridge relative to the coin flow past the bridge becomes less critical and, therefore, it becomes easier to implement and more reliable in operation.

Reducing the speed of the rotating disc is preferably accomplished by reducing the speed of the motor which drives the disc. Alternatively, this speed reduction can be achieved by actuation of a brake for the rotating disc, or by a combination of brake actuation and speed reduction of the drive motor.

One example of a drive system for controllably reducing the speed of the disc 13 is illustrated in FIG. 16. This system includes an auxiliary d-c. motor M.sub.2 connected to the drive shaft of the main drive motor M.sub.1 through a timing belt 213 and an overrun clutch 214. The speed of the auxiliary motor M.sub.2 is controlled by a drive control circuit 215 through a current sensor 216 which continuously monitors the armature current supplied to the auxiliary motor M.sub.2. When the main drive motor M.sub.1 is de-energized, the auxiliary d-c. motor M.sub.2 can be quickly accelerated to its normal speed while the main motor M.sub.1 is decelerating. The output shaft of the auxiliary motor turns a gear which is connected to a larger gear through the timing belt 213, thereby forming a speed reducer for the output of the auxiliary motor M.sub.2. The overrun clutch 214 is engaged only when the auxiliary motor M.sub.2 is energized, and serves to prevent the rotational speed of the disc 13 from decreasing below a predetermined level while the disc is being driven by the auxiliary motor.

Returning to FIG. 19, when the prescribed number of coins of a prescribed denomination has been counted for a given coin batch, the controller 201 produces control signals which energize the brake B and the auxiliary motor M.sub.2 and de-energize the main motor M.sub.1. The auxiliary motor M.sub.2 rapidly accelerates to its normal speed, while the main motor M.sub.1 decelerates. When the speed of the main motor is reduced to the speed of the overrun clutch 214 driven by the auxiliary motor, the brake overrides the output of the auxiliary motor, thereby causing the armature current of the auxiliary motor to increase rapidly. When this armature current exceeds a preset level, it initiates de-actuation of the brake, which is than disengaged after a short time delay. After the brake is disengaged, the armature current of the auxiliary motor drops rapidly to a normal level needed to sustain the normal speed of the auxiliary motor. The disc then continues to be driven by the auxiliary motor alone, at a reduced rotational speed, until the encoder sensor 212 indicates that the last coin in the batch has passed the position where that coin has cleared the bag-switching bridge in the first exit slot for that particular denomination. At this point the main drive motor is re-energized, and the auxiliary motor is de-energized.

Referring now to FIG. 20, there is shown a flow chart 220 illustrating the sequence of operations involved in utilizing the bag-switching system of the illustrative sorter of FIG. 1 in conjunction with the microprocessor-based system discussed above with respect to FIG. 19.

The subroutine illustrated in FIG. 20 is executed multiple times in every millisecond. Any given coin moves past the coin sensors at a rate of about 1.5.degree. per millisecond. Thus, several milliseconds are required for each coin to traverse the sensors, and so the subroutine of FIG. 20 is executed several times during the sensor-traversing movement of each coin.

The first six steps 300-305 in the subroutine of FIG. 20 determine whether the interrupt controller has received any pulses from the three sensors S.sub.1 -S.sub.3. If the answer is affirmative for any of the three sensors, the corresponding count C.sub.1, C.sub.2, C'.sub.2, C.sub.3 and C'.sub.3 is incremented by one. Then at step 306 the actual dime count C.sub.D is computed by subtracting count C'.sub.2 and C.sub.1. The resulting value C.sub.D is then compared with the current selected limit value C.sub.DMAX at step 307 to determine whether the selected number of dimes has passed the sensors. If the answer is negative, the subroutine advances to step 308 where the actual nickel count C.sub.N is computed by subtracting count C'.sub.3 from C.sub.2. The resulting value C.sub.N is then compared with the selected nickel limit value C.sub.NMAX at step 309 to determine whether the selected number of nickels has passed the sensors. A negative answer at step 309 advances the program to step 310 where the quarter count C.sub.Q (=C.sub.3) is compared with C.sub.DMAX to determine whether the selected number of quarters has been counted.

When one of the actual counts C.sub.D, C.sub.N or C.sub.Q reaches the corresponding limit C.sub.DMAX, C.sub.NMAX or C.sub.QMAC, an affirmative answer is produced at step 311, 312 or 313.

An affirmative answer at step 311 indicates that the selected number of dimes has been counted, and thus the bridge 80 in the first exit slot 40 for the dime must be actuated so that it diverts all dimes following the last dime in the completed batch. To determine when the last dime has reached the predetermined position where it is desired to transmit the control signal that initiates actuation of the solenoid S.sub.D, step 311 presets the coin-tracking counter CTC.sub.D to a value P.sub.D. The counter CTC.sub.D then counts down from P.sub.D in response to successive pluses from the encoder sensor ES as the last dime is moved from the last sensor S.sub.3 toward the bridge 80. To control the speed of the dime so that it is moving at a known constant speed during the time interval when the solenoid S.sub.D is being actuated, step 314 turns off the main drive motor M1 and turns on the auxiliary d-c. drive motor M2 and the brake B. This initiates the sequence of operations described above, in which the brake B is engaged while the main drive motor M1 is decelerating an then disengaged while the auxiliary motor M2 drives the disc 13 so that the last dime is moving at a controlled constant speed as it approaches and passes the bridge 80.

To determine whether the solenoid S.sub.D must be energized or de-energized, step 315 of the subroutine determines whether the solenoid S.sub.D is already energized. An affirmative response at step 315 indicates that it is bag B that contains the preset number of coins, and thus the system proceeds to step 316 to determine whether bag A is available. If the answer is negative, indicating that bag B is not available, than there is no bag available for receiving dimes and the sorter must be stopped. Accordingly, the system proceeds to step 317 where the auxiliary motor M2 is turned off and the brake B is turned on to stop the disc 13 after the last dime is discharged into bag B. The sorter cannot be re-started again until the bag-interlock switches for the dime bags indicate that the full bag has been removed and replaced with an empty bag.

An affirmative answer at step 316 indicates that bag A is available, and thus the system proceeds to step 318 to determine whether the coin-tracking counter CTC.sub.D has reached zero, i.e., whether the OVFL.sub.D signal is on. The system reiterates this query until OVFL.sub.D is on, and then advances to step 319 to generate a control signal to de-energize the solenoid S.sub.D so that the bridge 80 is moved to its retracted (upper) position. This causes all the dimes for the next coin batch to enter the first exit channel 40 so that they are discharged into bag A.

A negative answer at step 315 indicates the full bag is bag A rather than bag B, and thus the system proceeds to step 320 to determine whether bag B is available. If the answer is negative, it means that neither bag A nor bag B is available to receive the dimes, and thus the sorter is stopped by advancing to step 317. An affirmative answer at step 320 indicates that bag B is, in fact, available, and thus the system proceeds to step 321 to determine when the solenoid S.sub.D is to be energized, in the same manner described above for step 318. Energizing the solenoid S.sub.D causes the bridge 80 to be advanced to its lower position so that all the dimes for the next batch are shunted past the first exit channel 40 to the second exit channel 41. The control signal for energizing the solenoid is generated at step 321 when step 320 detects that OVFL.sub.D is on.

Each time the solenoid S.sub.D is either energized at step 322 or de-energized at step 319, the subroutine resets the counters C.sub.1 and C'.sub.2 at step 323, and turns off the auxiliary motor M2 and the brake B and turns on the main drive motor M1 at step 324. This initializes the dime-counting portion of the system to begin the counting of a new batch of dimes.

It can thus be seen that the sorter can continue to operate without interruption, as long as each full bag of coins is removed and replaced with an empty bag before the second bag receiving the same denomination of coins has been filled. The exemplary sorter is intended for handling coin mixtures of only dimes, nickels and quarters, but it will be recognized that the arrangement described for these three coins in the illustrative embodiment could be modified for any other desired coin denominations, depending upon the coin denominations in the particular coin mixtures to be handled by the sorter.

An alternative coin-sensor arrangement is illustrated in FIGS. 21-23. In this arrangement that portion of the top surface of the referencing recess 30 that contains the counting sensors S.sub.1 -S.sub.3 is stepped so that each sensor is offset from the other two sensors in the axial (vertical) direction as well a the radial (horizontal) direction. Thus, the steps 300 and 301 form three coin channels 302, 303 and 304 of different widths and depths. Specifically, the deepest channel 302 is also the narrowest channel, so that it can receive only dimes; the middle channel 303 is wide enough to receive nickels but not quarters; and the shallowest channel 304 is wide enough to receive quarters. The top surfaces of all three channels 302-304 are close enough to the pad 16 to press all three coin denominations into the pad.

The three counting sensors S.sub.1, S.sub.2 and S.sub.3 are located within the respective channels 302, 202 and 304 so that each sensor is engaged by only one denomination of coin. For example, the sensor S.sub.1 engages the dimes in the channel 302, but cannot be reached by nickels or quarters because the channel 302 is too narrow to receive coins larger than dimes. Similarly, the sensor S.sub.2 is spaced radially inwardly from the inner edges of the dimes so that it engages only nickels in the channel 303. The sensor S.sub.3 engages quarters in the channel 304, but is spaced radially inwardly from both the nickels and the dimes.

It will be appreciated from the foregoing description of the sensor arrangement of FIGS. 21-23 that this arrangement permits direct counting of the various coin denominations, without using the subtraction algorithm or the pulse-processing logic described above in connection with the embodiment of FIGS. 2-15.

FIGS. 24-28 show another modification of the sorting head of FIGS. 2-15 to permit the counting and sorting of coins of six different exit channels 40'-45', one for each of six different denominations, rather than a pair of exit channels for each denomination.

In the counting system of FIGS. 24-28, the six sensors S.sub.1 S.sub.6 are spaced apart from each other in the radial direction so that one of the sensors is engaged only by half dollars, and each of the other sensors is engaged by a different combination of coin denominations. For example, a illustrated in FIGS. 25 and 26, the sensor S.sub.4, engages not only quarters (FIG. 25) but also all larger coins (FIG. 26), while missing all coins smaller than the quarter. FIGS. 27 and 28 illustrate the sensor S.sub.2 engaging a penny (FIG. 27) but missing a dime (FIG. 28).

The entire array of sensors produces a unique combination of signals for each different coin denomination, as illustrated by the following table where a "1" represents engagement with the sensor and a "0" represents non-engagement with the sensor:

By analyzing the combination of signals produced by the six sensors S.sub.1 -S.sub.6 in response to the passage of any coin thereover, the denomination of that coin is determined immediately, and the actual count for that denomination can be incremented directly without eh sue of any subtraction algorithm. Also, this sensor arrangement minimizes the area of the sector that must be dedicated to the sensors on the lower surface of the sorting head.

The analysis of the signals produced by the six sensors S.sub.1 -S.sub.6 in response to any given coin can be simplified by detecting only that portion of each combination of signals that is unique to one denomination of coin. As can be seen from the above table, these unique portions are P.sub.1 =0 and P.sub.2 =1 for the dime, P.sub.2 =0 and P.sub.3 =1 for the penny, P.sub.3 =0 and P.sub.4 =1 for the nickel, P.sub.4 =0 and P.sub.5 =1 for the quarter, P.sub.5 =0 and P.sub.6 =1 for the dollar, and P.sub.6 =1 for the half dollar.

As an alternative to the signal-processing system described above, the counts C.sub.1 -C.sub.6 of the pulses P.sub.1 -P.sub.6 from the six sensors S.sub.1 -S.sub.6 in FIGS. 24-28 may be processed as follows to yield actual counts C.sub.D, C.sub.P, C.sub.N, C.sub.Q, C.sub.S and C.sub.H of dimes, pennies, nickels, quarters, dollars and half dollars:

C.sub.D =C.sub.1 -C.sub.2

C.sub.P =C.sub.2 -C.sub.3

C.sub.N =C.sub.3 -C.sub.4

C.sub.Q =C.sub.4 -C.sub.5

C.sub.S =C.sub.5 -C.sub.6

C.sub.H =C.sub.6

FIGS. 29-31 illustrate a six-denominations sorting head using yet another coin-sensors arrangement. In this arrangement the sensors S.sub.1 -S.sub.6 are located at the upstream end of the referencing recess 30, in the outer wall 31 of that recess. Because the coins leave the outwardly spiralling channel 25 with the inner edges of all coin denominations at a common radius, the outer edges of the coins are offset from each other according to the diameters (denominations) of the coins. Consequently, coins of different denominations engage the inwardly spiralling wall 31 at different circumferential positions, and the six sensors S.sub.1 -S.sub.6 are located at different circumferential positions so that each sensor is engaged by a different combination of denominations.

The end result of the sensor arrangement of FIGS. 29-31 is the same as that of the sensor arrangement of FIGS. 24-28. That is, the sensor S.sub.1 is engaged by six denominations, sensor S.sub.2 is engaged by five denominations, sensor S.sub.3 is engaged by four denominations, sensor S.sub.4 is engaged by three denominations, sensor S.sub.5 is engaged by two denominations, and sensor S.sub.6 is engaged by only one denomination. The counts C.sub.1 -C.sub.6 of the pulses P.sub.1 -P.sub.6 from the six sensors S.sub.1 -S.sub.6 may be processed in the same manner described above for FIGS. 24-28 to yield actual counts C.sub.D, C.sub.P, C.sub.N, C.sub.Q, C.sub.S and C.sub.H.

As shown in FIG. 31, the sensors used in the embodiment of FIGS. 29-31 may be formed as integral parts of the outer wall 31 of the recess 30. Thus, the insulated contact pins may be installed in the metal plate used to form the sorting head before the various contours are formed by machining the surface of the plate. Then when the recess 30 is formed in the plate, the cutting tool simply cuts through a portion of each contact pin just as though it were part of the plate.

Still another coin sensor arrangement is shown in FIGS. 32 and 33. In this arrangement only two sensors are used to detect all denominations. One of the sensors S.sub.1, is located in the wall that guides the coins while they are being sensed, and the other sensor S.sub.2 is spaced radially away from the sensor S.sub.1 by a distance that is less than the diameter of the smallest coin to be sensed by S.sub.2. Every coin engages both sensors S.sub.1 and S.sub.2, but the time interval between the instant of initial engagement with S.sub.2 and the instant of initial engagement with S.sub.1 varies according to the diameter of the coin. A large-diameter coin engages S.sub.2 earlier (relative to the engagement with S.sub.1) than a small-diameter coin. Thus, by measuring the time interval between the initial contacts with the two sensors S.sub.1 and S.sub.2 for any given coin, the diameter of that coin can be determined.

Alternatively, the encoder on the periphery of the disc 13 can be used to measure the angular displacement a of each coin from the time it initially contacts the sensor S.sub.1 until it initially contacts the sensor S.sub.2. This angular displacement a increases as the diameter of the coin increases; so the diameter of each coin can be determined for the magnitude of the measured angular displacement. This denomination-sensing technique is insensitive to variations in the rotational speed of the disc because it is based on the position of the coin, not its speed.

FIGS. 34 and 35 show a modified form of the two-sensor arrangement of FIGS. 32 and 33. In this case the sensor S.sub.1 engages the flat side of the coin rather than the edge of the coin. Otherwise the operation is the same.

Another modified counting arrangement is shown in FIG. 36. This arrangement uses a single sensor S.sub.1 which is spaced away from the coin-guiding wall 31 by a distance that is less than the diameter of the smallest coin. Each coin denomination traverses the sensor S.sub.1 over a unique range of angular displacement b, which can be accurately measured by the encoder on the periphery of the disc 13, as illustrated by the timing diagram in FIG. 37. The counting of pulses from the encoder sensor 212 is started when the leading edge of a coin first contacts the sensor S.sub.1, and the counting is continued until the trailing edge of the coin clears the sensor. As mentioned previously, the sensor will not usually produce a uniform flat pulse, but there is normally a detectable rise or fall in the sensor output signal when a coin first engages the sensor, and again when the coin clears the sensor. Because each coin denomination requires a unique angular displacement b to traverse the sensor, the number of encoder pulses generated during the sensor-traversing movement of the coin provides a direct indication of the size, and therefore the denomination, of the coin.