Field of the invention

The present invention relates to coin recognition apparatus for recognition of acceptable coins.

Prior art

There are numerous applications where coin operated apparatus are used to for example open doors or gates for entering a convenience facility or a location such as an amusement park or a showroom. Other application can include but not limited to activating a vending machine or a gaming machine etc.

The use of such apparatus for various needs and at various locations with different types and sizes of coins, and with different materials requires a multitude of solutions in order to satisfy the different needs and solve the associated problems. Most applications of coin recognition and coin acceptance apparatus are generally price sensitive and many low priced apparatus are mechanically based. These however suffer from frequent failures due to many moving parts and consequently they need frequent service and maintenance. Additionally these mechanical devices are normally designed and arranged to accept a single or at best a limited number of coin types.

Traditionally all such apparatus are designed such that the inserted coin rolls through the coin chute on its edge, and this results in that the coin does not roll in a straight line but rather has a wobbly path as it rolls through the chute. The degree of diversion from a straight line is very much dependent on the width of the coin chute. The wider the chute, the more the coin wobbles. However, if the coin chute is made narrow, there is a risk that some inserted coins get stuck in the chute putting the apparatus out of service which in turn leads to loss of functionality and revenues. One of the main challenges with identifying a wobbly coin is how to ensure accuracy of the coin sensing and recognition if the coin is sensed while on the move. A solution to this problem can be to force the coin into a stationary position before it is recognized. This results in a slow response and requires some mechanism for setting the coin in motion after sensing, which results in additional moving parts with consequent reliability reduction and increased maintenance needs.

The sensing and recognition means in electronically based coin acceptors is traditionally performed by inductive circuits involving multiples of coils mounted with precision along the path of the coin. The required coil driving circuitry also poses a problem of power consumption as well as expensive design. Other means of recognition have been proposed in the prior art based on optical sensors using light emitting means. US4089400A discloses a coin testing device comprising a coin inlet, a downwardly sloping coin chute defining a path for travel of the coins, an array of light emitting means, such as LEDs, and light sensitive means, such as phototransistors, disposed in association with the coin chute for sensing various parameters, such as the diameter and the thickness of the coin moving along the chute. The device includes processing means configured to estimate the parameters of the coins based on the output from the light sensitive means, and to determining whether the coin is acceptable or not based on the estimated parameter. There are several disadvantages with this device, such as a need for a large number of LED/phototransistor pairs for each coin type, different sensor pairs are needed for different coin types, it is additionally difficult to upgrade with new types of coins due to the complex arrangement of sensors.

US6929110B2 discloses an electronic coin acceptor comprising a coin chute having a track on which the coin is rolling on its edge, two pairs of optical transmitter and receiver to create beams arranged to measure the diameter of the coin. The coin diameter is estimating by measuring the time it takes for the coin to transverse the beam and exaggerating the distance travelled in order to achieve a good accuracy. This device needs to be calibrated for certain coins and it requires new adjustments to upgrade with new types of coins.

GB1597940A teaches to use a support rail where part of the length is covered by electrically conducting material while other sections are covered by insulating material and one strip of conductive material is located at the back of the wall parallel to the support rail. The arrangement is such that one can recognize a coin with a diameter between the smallest and largest acceptable length. This device can only recognize metallic coins, and needs to be specifically calibrated for certain coin diameters. To upgrade with new types of coins requires new arrangement.

US2002074209A1 discloses a coin sorting device that uses two cameras (preferably CCD cameras) that produce grayscale images of the upper and lower surfaces of the coin. The images are transmitted to a processor. The processor compares the images with predetermined reference data, which represent a plurality of known coin types. The processor calculates a maximum correlation between each of the images and the predetermined reference data and determines a type of coin in response. The coin sorting device may also be provided with an additional coin discriminator arranged to detect the passage of a coin inductively, thereby identifying certain physical property of the coin, such as size, diameter, thickness, electrical conductivity and magnetic permeability. The output from the inductive coin discriminator is supplied to the processor, which will use this information in addition to the images provided by the cameras. This device is expensive and requires elaborate signal processing of the images. JP2005202586A discloses a coin diameter detector by a line sensor. The sensor comprises a CCD sensor including a plurality of photodiodes arranged on one side of the coin passage carrying the coin. The passage is formed by a pair of guide rails and a light source arranged on the other side of the coin passage and emitting light toward the CCD line sensor. The diameter of the coin present between the CCD line sensor and the light source is detected based on the level of the light emitted from the light source and received by the CCD line sensor. This device uses a sensor covering the entire lateral direction of the passage.

Problems will arise when coins travel down the passage close to the edges of the guide rails on either side as this can lead to false signals as the light is affected by the guide rails walls leading to misinterpreted signals by the CCD line sensor. Another limitation of this device is that it cannot distinguish between different shapes of coins.

US2011151759A1 discloses a coin sorting device including an outer diameter detection sensor arranged to determine the diameter of the coin. The outer diameter detection sensor includes a light emitting section and a light receiving section. The outer diameter detection sensor detects the maximum length of the light receiving section that is blocked with one coin crosses as the diameter of the coin. The device also includes an upper-side and a lower- side image detection section, each including a CCD area sensor that detects an image of the coin. The device includes a control apparatus configured to determine whether the diameter detection data correspond with reference data for the diameter by a predetermined degree of coincident, in order to determine whether the coin is false. Then, the control apparatus compares reference pattern data for the images with pattern data from the upper-side and a lower-side image detection section, and detects whether or not the pattern data agree by a predetermined degree of coincident, in order to determine whether the coin is false. This coin sorting device is expensive and requires elaborate signal processing of the images.

Object and summary of the invention

It is an object of the present invention to at least partly overcome the above problems, and to provide an improved coin recognition apparatus.

This object is achieved by a coin recognition apparatus as defined in claim 1.

The apparatus is characterized in that the image sensor is configured to produce a sequence of images of a coin while the coin is sliding on the coin chute, and the processing means is configured to estimate a sequence of increasing and decreasing parameter values based on the contours of the coin in the sequence of images, and to determine whether the coin is acceptable or not based on the estimated sequence of increasing and decreasing parameter values. The parameter can be the diameter of the coin or a part of the diameter of the coin.

According to an embodiment of the invention, the image sensor is configured to produce a number for images for each coin sliding on the coin chute, and the number of images is more than 50 images, and preferably more than 200 images. The large number of images increases the accuracy of the estimation of the parameter.

According to an embodiment of the invention, the processing means is configured to estimate a peak value of the parameter based on the estimated sequence increasing and decreasing parameter values, to compare the estimated peak value of the parameter with defined intervals of acceptable values of the parameter, and to generate an acceptance signal when the peak value is within the defined interval.

According to an embodiment of the invention, the image sensor is disposed relative the coin chute so that a part of the coin chute is in the view of the light sensitive element of the image sensor, and the sensor is adapted to produces the said sequence of images of the coin while the coin is passing the part of the coin chute. For example, the part of the coin chute in the view of the sensor is made of transparent material and the image sensor is disposed below the part of the coin chute to avoid dirt to reach the sensor. According to an embodiment of the invention, the coin chute is inclined with respect to a horizontal plane about two orthogonal axes. Further, the coin chute is provided with a guiding rail disposed along the length of the chute to support and guide the coins when they slide on the coin chute. By that it is ensured that the coins have a defined position with respect to the coin chute, and accordingly with respect to the part of the coin chute in the view of the image sensor, the while sliding along the chute. Thus, estimation of the parameter is facilitated.

According to an embodiment of the invention, the coin chute comprises a first portion having a first end disposed in connection to the coin inlet for receiving the coin, and a second portion arranged angled relative to the first portion, and a coin damping member is provided at a second end of the first part arranged for damping the movements of coin in order to avoid wobbling and bouncing of the coin as it enters the second portion of the chute, thereby facilitating accurate estimation of the coin parameter as the coin slides past the part of the chute in the view of the image sensor.

According to an embodiment of the invention, the coin damping member comprises a thin rubber sheet situated between two metal plates arranged for preventing bouncing of the coin as it hits the damping element.

I n most coin acceptance apparatus, a rejected coin return box is used. This requires that the coin is directed to one of two paths, the accepted coin path or the rejected coin path. This is normally solved by some mechanical means with moving parts to open the gate to the two the paths. Moving parts almost always leads to reduced reliability, increased maintenance and higher costs. The second problem related to this two path issue is the need to quickly (in matters of seconds or parts of a second) recognize the inserted coin and determine its fate, which in turn imposes special speed and accuracy requirements on the sensing means and recognition methods used. Once again, these requirements also lead to higher cost and in many cases also demand that the coin is stationary during the recognition process and until the gate of the determined path is opened.

According to an embodiment of the invention, the processing means is configured to generate an acceptance signal upon detecting a coin with an acceptable physical parameter, the coin chute has coin discharge end, and the apparatus comprises a collection box arranged at the discharge end of the coin chute for collecting all coins traveled on the coin chute. By that it eliminates the need for any moving parts due to no rejected coin collection box and consequently no return chute.

Brief description of the drawings

The invention will now be explained more closely by the description of different embodiments of the invention and with reference to the appended figures. Fig. 1 shows the coin recognition apparatus in accordance with an embodiment of the present invention.

Fig. 2 graphically shows the overall shape of the contour of the complete sequence of images of the part of the coin visible in the sensing region for a round coin.

Fig. 3 graphically shows the overall shape of the contour of the complete sequence of images of the coin when the whole coin is visible in the sensing region for a round coin.

Fig. 4 illustrates the first of the two orthogonal inclinations (a) of the chute and the position of the coin viewed from the side (in the direction of the coin slide) as it slides on the guiding rail of the coin chute past the sensing region. Fig. 5 illustrates the second of the two orthogonal inclinations (β) of the chute and the position of the coin viewed from the front as it slides on the guiding rail of the coin chute past the sensing region.

Fig. 6 shows the position of the image sensor with respect to the guiding rail of the coin chute and the minimum preferred diameter of an acceptable coin according to an embodiment of the invention.

Fig. 7 shows the shape of overall shape of the contour of the complete sequence of images of the part of the coin visible in the sensing region for round coins of different diameters.

Fig. 8 schematically shows the structure of the damping element according an embodiment of the invention. Fig. 9 shows the shape of overall shape of the contour of the complete sequence of images of the part of the coin visible in the sensing region for coins of different shapes.

All the figures are schematic and generally only show parts which are necessary in order to elucidate the invention, whereas other parts may be omitted or merely suggested.

Detailed description of preferred embodiments of the invention

The invention will now be described more fully hereinafter with reference to the accompanying figures, in which certain embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout the description. As seen in figure 1, a coin recognition apparatus 10 in accordance with the present invention includes a coin inlet 20 located in front of the top part of a downwardly sloping coin chute 3, and an image sensor comprising a light source 4 and a light sensitive element 2 positioned in the lower part of the coin chute across the path of the sliding coin 1 and mounted directly on a control circuit 6. In a preferred embodiment the image sensor is configured to produce a sequence of images of the coin as it passes in view of the light sensitive element while sliding on the said coin chute and that the light sensitive element is a high speed high resolution sensor preferably a CCD (charge coupled device) sensor. However other technologies can be used for example CMOS based image sensors. It is known to a person skilled in the art that CCD sensors convert light into electric charge and process it into electronic signals whereby every pixel's charge is transferred through the output node to be converted to voltage, buffered, and sent off-chip as an analog signal.

The sequence of images produced as a coin slides past the sensor are shown graphically in figure 2, where each line 50 represents one image and the height of the line represents the part of the coin visible at the specific time of the coin passing the sensor view. In an embodiment, the tip of the lines forming the contour 51 of the lines in the sequence of images is used to estimate the diameter of the coin.

It will be obvious to a skilled person that if both edges of the coin are in the view of the sensor at all times as shown in figure 3, then the maximum width of the contour of the lines will represent the diameter of the coin. It is well known in the mathematical field of numerical analysis that to provide a reliable and accurate estimate of a number of data points, obtained by sampling, which represent the values of a function for a limited number of values of the independent variable. It is often required to interpolate (i.e. estimate) the value of that function for an intermediate value of the independent variable. This may be achieved by a curve fitting process of constructing a curve, or a mathematical function that best fit to the said series of data points, subject to constraints. Curve fitting may involve interpolation, where an exact fit to the data is required, or smoothing, in which a "smooth" function is constructed that approximately fits the data. The resulting curve then represents the contour of the sequence of the images of the coin. The process of interpolating and obtaining the contour of the sequence of images is programmed into the control circuit.

It is therefore the intention of this invention to produce a large number of images of the coin as it slides past the image sensor, thereby providing a better opportunity to achieve more exact estimation of the coin parameters such as the diameter of the coin based on the contour of the sequence of images. In one embodiment more than 50 images of the coin passing through the sensor are produced and preferably more than 200 images are produced. A person skilled in the art will realize the number of images will vary depending on the size of the coin, the speed of the image sensor and the speed of the coin through the shoot. For example a coin of the size of the five Swedish crone may result in as many images as 700, while a one Swedish crone coin may result in 400 images.

It will be obvious to a skilled person that although a large number of images will be produced, not all images need to be used in the recognition process, if the sole purpose of the coin recognition is to estimate the coin diameter. In this situation it may be sufficient to use less than 10 images of the total sequence of images to recognize a coin.

The image sensor must be able to produce the said preferably sequence of more than 200 images during the time it takes for the complete coin to slide past it. The available time T depends on the velocity of the coin as well as its diameter and is given by:

Diameter of the coin (D)

Velocity of the coin (V)

It is therefore necessary to control the velocity of the sliding coin so that it allows the image sensor to produce the preferred number of said sequence of images within the available time T for a coin with the smallest acceptable diameter. However, the velocity must not lead to a situation whereby a coin stops sliding on the coin chute and does not exit into the collection box 60. It is therefore the purpose of the embodiment of inclining the coin chute with respect to a horizontal plane about two orthogonal axes to provide the necessary control of the velocity and position of the sliding coin on the coin chute. The first angle of inclination a as shown in figure 4 is in the direction of the length of the coin chute to force the coin to slide downwards along the length of the chute. The said angle a is between 30 degrees and 80 degrees to the horizontal and preferably between 40 degrees and 55 degrees to the horizontal. The second angle of inclination β as shown in figure 5 is in the direction of the width of the coin chute to force the coin to slide against the guiding rail 6 of the chute, thereby ensuring a fixed and predetermined path for the sliding coin. This embodiment provides a known point on the edge of the coin and thereby fixing one end of the contour of the sequence of images produced by the sensor. This one degree of freedom allows a more reliable estimation of the coin diameter and reduces the error by half compared to a case whereby both ends need to be measured and estimated. The angle β is between 30 degrees and 80 degrees to the horizontal and preferably between 40 degrees and 55 degrees to the horizontal.

One of the objectives of this present invention is to use the same coin recognition apparatus for a many types of coins with a large variation of the diameter and with different shapes. However, the length of the light emitting source and of the light sensitive element is limited for cost and practical reasons. An embodiment of the present invention is to position the sensor elements a fixed distance x away from the guiding rail of the coin chute, whereby x is arranged to be smaller than the diameter of the smallest coin that will be accepted by the apparatus as illustrated in figure 6. In this way, the sequence of produced images will only show the part of the coin that is larger than x. To ensure proper recognition, the minimum coin diameter must be larger than x preferably larger than 1.5x. The advantage of this embodiment is that any coin with a diameter between (1.5x) to diameters of (x+L) where L is the length of the light sensitive element can be recognized.

A further parameter affecting the velocity control is the friction force between the surface of the coin chute and the surface of the sliding coin. The smoothness of the surfaces as well as contact area and weight of the coin sliding along the chute are factors affecting the said friction. It is the intention of the present invention to recognize coins of different diameters and consequently of different weights as well as coins made of non-metallic materials for example plastic tokens. To avoid large variation of the velocity and prevent objects from sliding, the surface of the coin chute can be grooved; thereby different objects made of other materials than metals such as plastic tokens can also easily slide along the chute.

An objective of the present invention is to provide a coin recognition apparatus with no moving parts apart from the coin in order to reduce cost and provide an extremely reliable and maintenance free apparatus. In an embodiment all coins are kept regardless of whether the coin is accepted or not whereby the maintenance free objective is satisfied.

The objective of extremely reliable recognition is provided by having a coin chute that comprises a first portion having a first end disposed in connection to the coin inlet for receiving the coin, and a second portion arranged angled relative to the first portion, and a coin damping member is provided at a second end of the first part arranged for damping the movements of coin in order to avoid wobbling and bouncing of the coin as it enters the second portion of the chute and slides on the guiding rail 7 of the chute. The wobble free bounce free sliding coin can thereby be accurately recognized as it slides past the part of the chute in the view of the image sensor. The said coin damping member 8 is preferably comprised of a thin between 1-2 mm thick rubber sheet 80 situated between two metal plates arranged for preventing bouncing of the coin as it hits the damping element as shown in figure 8, whereby one of the metal plates forms part of the coin chute.

As outlined above, the control algorithm used to perform the coin recognition may be embodied as computer-executable instructions distributed and used in the form of a computer-program product including a computer-readable medium storing such instructions such as a microcontroller. By way of example, computer-readable medium may comprise computer storage media and communication media. As is well known to a person skilled in the art, computer storage media includes volatile and non-volatile, removable and nonremovable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices. Further, it is known to the skilled person that communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media.

The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims. For example although the above description was considering round coins the present invention can also be used to recognize other shapes of coins. It is obvious to a person skilled in the art to use the invention to identify coins with different shapes using the total form of the contour produced from the sequence of images as can be seen in figure 9.