Patent Description:
An apparatus in which coils are provided for a banknote stage and detect entry of a piece of metal has been disclosed (e.g., refer to PTL <NUM>). In addition, an apparatus in which banknotes are set upright, for which coils are provided, and that detects entry of a piece of metal has been disclosed (e.g., refer to PTL <NUM>).

<CIT> and <CIT> disclose a sheet processing apparatuses with a feeding section which comprises a plurality of detection coils for the detection of foreign objects.

In PTL <NUM> and PTL <NUM>, however, signals output from coils might change due to an effect of an environment, and a piece of metal might not be accurately detected. The effect of the environment is, for example, an effect of surrounding temperature. There is a technique for correcting the effect of surrounding temperature using a temperature sensor, a reference coil, or the like, but the number of parts increases in this case.

The present invention, therefore, aims to provide a technique for improving the accuracy of detecting entry of a foreign object while suppressing an increase in the number of parts.

A sheet processing apparatus of the present invention according to claim <NUM> comprises: a plurality of coils that are provided in a feeding section which feeds a sheet that has been taken in into a transport path and that generate magnetic fields; and a control section that determines, on a basis of differential values between signals output from the plurality of coils, whether a foreign object has entered the feeding section.

A foreign-object entry determination method of the present invention according to claim <NUM> comprises:
generating magnetic fields from a plurality of coils provided in a feeding section that feeds a sheet that has been taken in into a transport path; calculating differential values between signals output from the plurality of coils; and determining, on a basis of the differential values, whether a foreign object has entered the feeding section.

According to the present invention, it is made possible to improve the accuracy of detecting entry of a foreign object while suppressing an increase in the number of parts. Brief Description of Drawings.

An embodiment of the present invention will be described hereinafter with reference to the drawings. A sheet processing apparatus will be described using banknotes as an example of sheets. The sheets, however, are not limited to banknotes, and may be securities such as notes or checks, instead. In addition, the sheets need not be composed of paper, but may be a material other than paper shaped in the form of sheets or a material other than paper pasted on paper and formed in the shape of sheets. The material other than paper is, for example, a resin. In the drawings, components are schematically illustrated in order to facilitate understanding. Arrows in the drawings indicate up, down, front, and back directions for the sake of convenience.

<FIG> is a diagram illustrating an example of the configuration of the sheet processing apparatus according to the embodiment of the present invention. A sheet processing apparatus <NUM> is a banknote depositing and dispensing machine. The sheet processing apparatus <NUM> comprises an upper case <NUM> and a lower case <NUM>.

The upper case <NUM> comprises, in an upper part, an inlet section <NUM> in which banknotes to be fed into are disposed and an outlet section <NUM> in which banknotes to be fed out are disposed. The upper case <NUM> also comprises, inside thereof, a transport section <NUM> that transports banknotes, an identification section <NUM> that identifies banknotes, a control section <NUM> that controls other components of the sheet processing apparatus <NUM>, and a temporary storage section <NUM> that temporarily stores banknotes. A second outlet section <NUM> may be provided adjacent to the outlet section <NUM>. The configuration of the second outlet section <NUM> may be the same as that of the outlet section <NUM> or may be different from that of the outlet section <NUM>.

In the inlet section <NUM>, a feeding section (e.g., refer to <FIG>) that feeds banknotes to the transport section <NUM> one by one at certain time intervals is provided. In the outlet section <NUM>, a stacking section (not illustrated) that stacks transported banknotes on one another is provided.

The transport section <NUM> is a transport apparatus that transports banknotes at a certain transport speed. The transport section <NUM> comprises a belt mechanism and a roller mechanism for transporting banknotes. The transport section <NUM> comprises a loop transport path 15a that transports banknotes in a looped manner, and a first branch path 15b, a second branch path 15c, a third branch path 15d, fourth branch paths 15e, and a fifth branch path 15f that diverge from the loop transport path 15a. The first to fifth branch paths 15b to 15f may be regarded as part of the loop transport path 15a.

The first to fifth branch paths 15b to 15f connect the loop transport path 15a to the inlet section <NUM>, the outlet section <NUM>, the temporary storage section <NUM>, a first storage <NUM> and a second storage <NUM>, which will be described later, and a detachable storage section <NUM>, which will be described later, respectively. Diverters (not illustrated) for distributing banknotes are provided at connections between the first to fifth branch paths 15b to 15f and the loop transport path 15a. When the second outlet section <NUM> is provided, another branch path that connects the loop transport path 15a to the second outlet section <NUM> may also be provided.

The identification section <NUM> is an identification apparatus that reads information on banknotes and that identifies the banknotes. The identification section <NUM> comprises a sensor such as an image sensor, an optical sensor, or a magnetic sensor and identifies banknote information regarding banknotes transported by the transport section <NUM>, such as authenticity, denomination, fitness, and serial numbers.

A serial number is a unique number given to each banknote and is, for example, a <NUM>-digit character string comprising alphabets and numbers. The identification section <NUM> identifies <NUM> characters of each serial number.

The temporary storage section <NUM> is a storage apparatus that temporarily stores banknotes. The temporary storage section <NUM> can take in and store banknotes one by one and feed out the stored banknotes one by one.

The temporary storage section <NUM> is, for example, a storage section of a winding type, in which banknotes are wound around a rotating body. Alternatively, the temporary storage section <NUM> may be a storage section of a stacking type, in which banknotes are stacked on one another.

The control section <NUM> is a control apparatus comprising a processing section such as a CPU and a storage section such as a memory. The control section <NUM> controls, through the transport section <NUM>, the components of the sheet processing apparatus <NUM> and the detachable storage section <NUM> such that banknotes are transported between the inlet section <NUM>, the outlet section <NUM>, the temporary storage section <NUM>, the first storage <NUM> and the second storage <NUM>, which will be described later, and the detachable storage section <NUM>, which will be described later.

The lower case <NUM> comprises the first storage <NUM> and the second storage <NUM>, which is provided under the first storage <NUM>.

The first storage <NUM> is, for example, a safe. A lockable storage door <NUM> is provided on a front surface of the first storage <NUM>.

In the first storage <NUM>, a first storage section <NUM>, a second storage section <NUM>, a third storage section <NUM>, which is provided over the second storage section <NUM>, a fourth storage section <NUM>, a fifth storage section <NUM>, and a sixth storage section <NUM> are provided in this order from the front to the back. One of the fourth branch paths 15e that extends from the loop transport path 15a toward the second storage <NUM> is disposed between the first storage section <NUM> and the second and third storage section <NUM> and <NUM>.

The fourth branch paths 15e that diverge from the loop transport path 15a are connected to the first storage section <NUM> and the third to sixth storage sections <NUM> to <NUM>. A sixth branch path <NUM>, which diverges from the fourth branch paths 15e extending from the loop transport path 15a toward the second storage <NUM>, is connected to the second storage section <NUM>.

The first to sixth storage sections <NUM> to <NUM> are storage sections of the stacking type, in which banknotes are stacked on one another. Alternatively, the first to sixth storage sections <NUM> to <NUM> may be storage sections of the winding type, in which banknotes are wound around a rotating body. Banknotes sorted in accordance with results of identification performed by the identification section <NUM> are stored in the first to sixth storage sections <NUM> to <NUM>.

A sensor (not illustrated) that detects passing banknotes is provided at an entrance of each of the first to sixth storage sections <NUM> to <NUM>. The sensor is an optical sensor comprising a light emission section that emits light such as infrared light and a light reception section that receives light emitted from the light emission section. Any type of sensor may be used insofar as the sensor can detect storage of banknotes in a corresponding storage section.

The second storage <NUM> is, for example, a safe. The second storage <NUM> comprises a collection section <NUM> inside thereof. The collection section <NUM> comprises a storage area inside thereof, and the storage area stores banknotes collected from among ones taken in from the inlet section <NUM> and ones stored in the first storage <NUM>. The collection section <NUM> is connected to one of the fourth branch paths 15e that diverge from the loop transport path 15a.

After banknotes to be collected are stored in the collection section <NUM>, a collector collects the banknotes from the collection section <NUM>. Alternatively, after banknotes to be collected are stored in the collection section <NUM>, a collector removes the collection section <NUM> from the sheet processing apparatus <NUM> together with the banknotes.

The lower case <NUM> comprises a mounting section <NUM> for mounting the detachable storage section <NUM> on a front outer surface of the first storage <NUM>. The outer front surface of the first storage <NUM> refers to an outer front surface of the first storage <NUM> that can be accessed without unlocking the storage door <NUM>, that is, more specifically, an outer front surface of the lower case <NUM> or a front surface of the storage door <NUM>.

The mounting section <NUM> comprises a fixing medium for fixing the detachable storage section <NUM> mounted on the mounting section <NUM>. The fixing medium may comprise a locking apparatus.

The mounting section <NUM> comprises a terminal (not illustrated) for supplying control signals from the control section <NUM> to the detachable storage section <NUM>. The detachable storage section <NUM> comprises a terminal (not illustrated) connected to the terminal of the mounting section <NUM>.

When the detachable storage section <NUM> is mounted on the mounting section <NUM>, the terminal of the detachable storage section <NUM> is directly or indirectly connected to the terminal of the mounting section <NUM>. When the detachable storage section <NUM> is mounted on the mounting section <NUM>, a storage area inside the detachable storage section <NUM> is connected to the fifth branch path 15f.

The detachable storage section <NUM> is a storage section of the stacking type, in which banknotes are stacked on one another. Alternatively, the detachable storage section <NUM> may be a storage section of the winding type, in which banknotes are wound around a rotating body.

The detachable storage section <NUM> comprises a driving mechanism (not illustrated), such as a motor, for taking in banknotes and discharging banknotes. Alternatively, when the detachable storage section <NUM> does not comprise the driving mechanism, the sheet processing apparatus <NUM> comprises the driving mechanism and transfers driving force to the detachable storage section <NUM> mounted on the mounting section <NUM>.

<FIG> is a diagram illustrating an example of the configuration of a feeding section <NUM> provided for the inlet section <NUM>. In <FIG>, the same components as in <FIG> are given the same reference numerals. As illustrated in <FIG>, the feeding section <NUM> comprises a stage <NUM>, kicker rollers <NUM>, feed rollers <NUM>, gate rollers <NUM>, transport rollers <NUM>, a board <NUM>, and banknote guides <NUM>.

The stage <NUM> is arranged in such a way as to connect to an entrance of the first branch path 15b. The stage <NUM> is a flat, plate-like member, for example, on which banknotes P1 are stacked on one another. A bottom one of the banknotes P1 stacked on the stage <NUM> comes into contact with a surface of the stage <NUM>. The banknotes P1 stacked on the stage <NUM> are fed into the first branch path 15b one by one from the bottom to the top, for example, in accordance with a deposit operation performed by a user.

The kicker rollers <NUM> are provided under the stage <NUM> and the board <NUM> such that part of the circumference thereof protrudes from the stage <NUM> and the board <NUM>. The stage <NUM> and the board <NUM> are provided with openings for allowing the part of the circumference of the kicker rollers <NUM> to protrude.

The kicker rollers <NUM> rotate clockwise in <FIG>. The kicker rollers <NUM> kick a bottom one of the banknotes P1 stacked on the stage <NUM> toward the first branch path 15b.

The feed rollers <NUM> are provided near the entrance of the first branch path 15b (at a slightly deeper position in the first branch path 15b than the entrance). The feed rollers <NUM> are provided under the first branch path 15b and the board <NUM> such that part of the circumference thereof protrudes from the first branch path 15b and the board <NUM>. The first branch path 15b and the board <NUM> are provided with openings for allowing the part of the circumference of the feed rollers <NUM> to protrude.

The feed rollers <NUM> rotate clockwise in <FIG>. The feed rollers <NUM> feed a bottom banknote kicked by the kicker rollers <NUM> into the first branch path 15b.

The gate rollers <NUM> face the feed rollers <NUM> from above the feed rollers <NUM>. The circumference of the gate rollers <NUM> is in contact with the circumference of the feed rollers <NUM>. The gate rollers <NUM> comprise a one-way clutch (not illustrated), for example, and can rotate clockwise in <FIG>. As a result, banknotes passing through gaps between the feed rollers <NUM> and the gate rollers <NUM> are fed into the first branch path 15b one by one.

The transport rollers <NUM> are provided in the first branch path 15b. The transport rollers <NUM> feed banknotes fed from the feed rollers <NUM> into the loop transport path 15a.

The board <NUM> is provided under the stage <NUM> and the entrance of the first branch path 15b. The board <NUM> is provided with coils that detect foreign objects such as pieces of metal. The board <NUM> is provided in contact with or immediately below the stage <NUM> in order to efficiently detect, with the coils, a foreign object on the stage <NUM> or near the entrance of the first branch path 15b. A surface of the board <NUM> is parallel to the surface of the stage <NUM>.

<FIG> is a diagram illustrating an example of arrangement of the rollers at a time when the feeding section <NUM> is viewed from above. In <FIG>, the same rollers as in <FIG> are given the same reference numerals. As illustrated in <FIG>, the feeding section <NUM> comprises three kicker rollers <NUM> and six feed rollers <NUM>. The number of kicker rollers <NUM> is not limited to three, and the number of feed rollers <NUM> is not limited to six.

<FIG> is a diagram illustrating an example of the configuration of the board <NUM>. As illustrated in <FIG>, the board <NUM> comprises coils <NUM> to <NUM> and openings 54a to 54c and 55a to 55f.

The board <NUM> is, for example, a multilayer board. The coils <NUM> to <NUM> are formed on a surface of the multilayer board or within a certain layer. The coils <NUM> to <NUM> illustrated in <FIG> are hatched for the purpose of distinction.

<FIG> is a diagram illustrating an example of the configuration of the coil <NUM>. As illustrated in <FIG>, the coil <NUM> is rectangular and spirally wound on a plane.

A current or a voltage is supplied to terminals 51a and 51b of the coil <NUM> illustrated in <FIG> in accordance with control performed by the control section <NUM>. The coil <NUM> generates a magnetic field from the current or the voltage supplied in accordance with the control performed by the control section <NUM>.

The coils <NUM> and <NUM> have the same shape as the coil <NUM> and are spirally wound on a plane. The number of turns is the same between the coils <NUM>, <NUM>, and <NUM>. The number of turns of the coil <NUM> is four in <FIG>, but is not limited to this.

<FIG> is referred to again. As described above, the coils <NUM> to <NUM> generate magnetic fields in accordance with the control (supply of a current or a voltage) performed by the control section <NUM>. The coils <NUM> to <NUM> are wound spirally on planes in the board <NUM> in a rectangular manner. A magnetic field at the center of the coil <NUM> is generated in such a way as to penetrate through the board <NUM> vertically. Magnetic fields at the centers of the coils <NUM> and <NUM> are also generated in such a way as to penetrate through the board <NUM> vertically.

As illustrated in <FIG>, the board <NUM> is provided in contact with or immediately below the stage <NUM>. The surface of the board <NUM> is parallel to the surface of the stage <NUM>. As a result, surfaces of the coils <NUM> to <NUM> formed in the board <NUM> are parallel to the surface of the stage <NUM>, on which the banknotes P1 are stacked. Alternatively, the surfaces of the coils <NUM> to <NUM> formed in the board <NUM> are parallel to surfaces of the banknotes P1 stacked on the stage <NUM>. The magnetic fields of the coils <NUM> to <NUM>, therefore, are generated above the stage <NUM> near the entrance of the first branch path 15b, that is, in a space where the banknotes P1 are stacked (a space inside the inlet section <NUM> in which the banknotes P1 are taken). In other words, the magnetic fields of the coils <NUM> to <NUM> are generated in a space above the stage <NUM> near the first branch path 15b that a foreign object might enter.

The coils <NUM> to <NUM> are arranged such that adjacent coils partially overlap with each other. The coils <NUM> to <NUM> are arranged side by side in a direction parallel to the surfaces of the banknotes P1 stacked on the feeding section <NUM> or the surface of the stage <NUM> on which the banknotes P1 are stacked and perpendicular to a feeding direction of the banknotes P1 (from "front" to "back" in <FIG>). The adjacent coils <NUM> and <NUM>, for example, partially overlap with each other in an area A1. The adjacent coils <NUM> and <NUM> partially overlap with each other in an area A2.

The coils <NUM> to <NUM> are provided for the board <NUM> in correspondence with the arrangement of the kicker rollers <NUM>. For example, the coil <NUM> corresponds to the left kicker rollers <NUM> illustrated in <FIG>. The coil <NUM> corresponds to the central kicker rollers <NUM> illustrated in <FIG>. The coil <NUM> corresponds to the right kicker rollers <NUM> illustrated in <FIG>.

When viewed in a direction perpendicular to the stage <NUM>, that is, in a direction perpendicular to the surfaces of the coils <NUM> to <NUM>, the surfaces of the coils <NUM> to <NUM> may overlap the corresponding kicker rollers <NUM>. Alternatively, the coils <NUM> to <NUM> may be provided in such a way as to surround the corresponding kicker rollers <NUM>. Alternatively, the coils <NUM> to <NUM> may be provided for the board <NUM> such that the corresponding kicker rollers <NUM> are located at the centers of the coils <NUM> to <NUM>. Two adjacent ones of the coils <NUM> to <NUM> may corresponding to the same feed roller <NUM>. For example, the coils <NUM> and <NUM> correspond to the second leftmost feed roller <NUM> illustrated in <FIG>. The coils <NUM> and <NUM> correspond to the second rightmost feed roller <NUM> illustrated in <FIG>. When viewed in the direction perpendicular to the stage <NUM>, that is, in the direction perpendicular to the surfaces of the coils <NUM> to <NUM>, two adjacent coils may overlap one of the feed rollers <NUM>. Alternatively, two adjacent coils may be provided in such a way as to surround one of the feed rollers <NUM>.

The openings 54a to 54c allow part of the circumference of the three kicker rollers <NUM> illustrated in <FIG> to protrude. The openings 55a to 55f allow part of the circumference of the six feed rollers <NUM> illustrated in <FIG> to protrude. Since the board <NUM> comprises openings 54a to 54c and 55a to 55f, the board <NUM> can be provided in contact with or immediately below the stage <NUM>.

The number of coils <NUM> to <NUM> provided for the board <NUM> is not limited to three. The number of coils may be two, or four or more.

<FIG> is a diagram illustrating the feeding section <NUM> illustrated in <FIG> viewed from a direction indicated by an arrow A11. <FIG> illustrates the stage <NUM> and the kicker rollers <NUM> illustrated in <FIG>. <FIG> also illustrates the coils <NUM> to <NUM> illustrated in <FIG>.

As illustrated in <FIG>, the surfaces of the coils <NUM> to <NUM> are parallel to the surface of the stage <NUM>. In addition, the coils <NUM> to <NUM> are arranged (substantially) equidistantly from the space in which the banknotes P1 are stored. The space is defined by the feeding section <NUM>, and the banknotes P1 that have been taken in are stacked in the space. In addition, the coils <NUM> to <NUM> are arranged substantially equidistantly from the surface of the stage <NUM> on which the banknotes P1 are stacked. For example, a distance between the coil <NUM> and the bottom one of the banknotes P1 is the same as a distance between the coil <NUM> and the bottom one of the banknotes P1. The distance between the coil <NUM> and the bottom one of the banknotes P1 is the same as a distance between the coil <NUM> and the bottom one of the banknotes P1.

Although the coils <NUM> to <NUM> illustrated in <FIG> are drawn thickly for the purpose of distinction, the actual coils <NUM> to <NUM> formed on the surface of the board <NUM> or in a layer in the board <NUM> are extremely thin. For example, the coils <NUM> to <NUM> may be formed as wiring patterns on the board <NUM>. In this case, the board <NUM>, on which the coils <NUM> to <NUM> are formed, is parallel to the surface of the stage <NUM>, on which the banknotes P1 are stacked. Alternatively, the board <NUM>, on which the coils <NUM> to <NUM> are formed, is parallel to the banknotes P1 stacked on the stage <NUM>.

<FIG> is a diagram illustrating an example of the configuration of a foreign object detection control system. <FIG> illustrates the control section <NUM> illustrated in <FIG> and the board <NUM> illustrated in <FIG>. The shape of the board <NUM> illustrated in <FIG> is partly different from that of the board <NUM> illustrated in <FIG>. As illustrated in <FIG>, the foreign object detection control system comprises the control section <NUM>, a detection control section <NUM>, and the board <NUM>.

The control section <NUM> comprises a CPU <NUM>, a field-programmable gate array (FPGA) <NUM>, and a memory <NUM>. The CPU <NUM> controls the entirety of the sheet processing apparatus <NUM>. The CPU <NUM> determines whether there is a foreign object in the feeding section <NUM> (entry of a foreign object) on the basis of signals (data) output from the detection control section <NUM>.

The FPGA <NUM> controls communication of data between the CPU <NUM> and the detection control section <NUM>. The FPGA <NUM> may perform part of the control supposed to be performed by the CPU <NUM> on the board <NUM>. For example, the FPGA <NUM> may turn on and off a switching circuit <NUM> instead of the CPU <NUM>. The memory <NUM> stores a program for the CPU <NUM> to operate. The memory <NUM> also stores data used by the CPU <NUM> to perform processing and control the other components.

The detection control section <NUM> comprises a detection control integrated circuit (IC) <NUM> and the switching circuit <NUM>. The detection control IC <NUM> comprises driving conversion sections 71a to 71c. The driving conversion sections 71a to 71c output, to the switching circuit <NUM>, currents or voltages for energizing the coils <NUM> to <NUM>, respectively, in accordance with control (instruction) performed by the CPU <NUM>.

The currents or the voltages for energizing the coils <NUM> to <NUM> are alternating currents or voltages. For example, the currents or the voltages for energizing the coils <NUM> to <NUM> are sine-wave currents or voltages. Amplitudes and frequencies of the currents or the voltages for energizing the coils <NUM> to <NUM> are (substantially) the same. As described with reference to <FIG>, the number of turns is the same between the coils <NUM> to <NUM>, and magnitudes of the magnetic fields generated by the coils <NUM> to <NUM> are the same.

The driving conversion sections 71a to 71c monitor the currents flowing to the terminals (e.g., the terminals 51a and 51b illustrated in <FIG>) of the coils <NUM> to <NUM> or the voltages between the terminals of the coils <NUM> to <NUM>, respectively. The driving conversion sections 71a to 71c output amplitudes (or absolute values of amplitudes) of the currents or the voltages monitored thereby to the CPU <NUM> through the FPGA <NUM>. For example, the driving conversion sections 71a to 71c convert analog values of the currents or the voltages monitored thereby into digital values and output the digital values to the CPU <NUM> through the FPGA <NUM>. The currents or the voltages for energizing the coils <NUM> to <NUM> will also be referred to as "energizing signals" hereinafter. The currents flowing to the terminals of the coils <NUM> to <NUM> or the voltages between the terminals of the coils <NUM> to <NUM> will also be referred to as "reception signals" hereinafter.

The switching circuit <NUM> comprises switches 72a to 72c. The switches 72a to 72c turn on and off connections between the driving conversion sections 71a to 71c and the coils <NUM> to <NUM>, respectively, in accordance with control performed by the CPU <NUM> through the FPGA <NUM>. When the switches 72a to 72c turn on, for example, the driving conversion sections 71a to 71c and the coils <NUM> to <NUM> are connected to each other. When the switches 72a to 72c turn off, the connections between the driving conversion sections 71a to 71c and the coils <NUM> to <NUM> are disconnected from each other.

The energizing signals output from the driving conversion sections 71a to 71c are input to the coils <NUM> to <NUM>, respectively. The coils <NUM> to <NUM> generate magnetic fields from the input energizing signals. If there is a foreign object, such as a piece of metal, near the coils <NUM> to <NUM> and the magnetic fields of the coils <NUM> to <NUM> are affected, amplitudes of reception signals change from those when there is no foreign object near the coils <NUM> to <NUM>.

As described above, the driving conversion sections 71a to 71c monitor reception signals of the coils <NUM> to <NUM> and output amplitudes of the reception signals to the CPU <NUM> through the FPGA <NUM>. The CPU <NUM> detects entry of a foreign object into the feeding section <NUM> on the basis of the amplitudes of the reception signals. The reception signals can be regarded as foreign object detection signals output from the coils <NUM> to <NUM>.

<FIG> is a timing chart illustrating an example of the operation of the foreign object detection control system illustrated in <FIG>. T1 in <FIG> indicates timings at which the banknotes P1 stacked on the stage <NUM> are fed into the first branch path 15b one by one. Time taken for a banknote to be fed into the first branch path 15b is denoted by t1 as indicated in <FIG>. In other words, one of the banknotes P1 stacked on the stage <NUM> is fed into the first branch path 15b in each period t1.

ON for the switches 72a to 72c in <FIG> denotes timings at which the switches 72a to 72c turn on. The switches 72a to 72c are turned off during periods other than ones indicated by ON in <FIG>.

D1 to D3 for the coils <NUM> to <NUM> in <FIG> denote timings at which energizing signals are input to the coils <NUM> to <NUM> and the driving conversion sections 71a to 71c output amplitudes of reception signals to the CPU <NUM>, respectively.

After the sheet processing apparatus <NUM> is turned on, for example, the CPU <NUM> controls the driving conversion sections 71a to 71c and outputs energizing signals from the driving conversion sections 71a to 71c. As a result, the energizing signals are input to the switches 72a to 72c.

After causing the driving conversion sections 71a to 71c to output the energizing signals, the CPU <NUM> turns on and off the switches 72a to 72c one by one within the period t1. As indicated by an arrow A31a in <FIG>, for example, the CPU <NUM> keeps the switch 72a turned on for a certain period of time and then turns off the switch 72a. As indicated by an arrow A31b, after turning off the switch 72a, the CPU <NUM> keeps the switch 72b turned on for a certain period of time and then turns off the switch 72b. As indicated by an arrow A31c, after turning off the switch 72b, the CPU <NUM> keeps the switch 72c turned on for a certain period of time and then turns off the switch 72c. As a result, the energizing signals are sequentially input to the coils <NUM> to <NUM> within the period t1. The coils <NUM> to <NUM> in turn sequentially generate magnetic fields within the period t1. As described above, the process for sequentially turning on and off the switches 72a to 72c may be performed by the FPGA <NUM>, instead.

The driving conversion sections 71a to 71c monitor reception signals of the coils <NUM> to <NUM> while the switches 72a to 72c remain turned on, respectively, and then output amplitudes of the reception signals to the CPU <NUM> through the FPGA <NUM>. For example, the driving conversion section 71a monitors a reception signal of the coil <NUM> and outputs an amplitude of the reception signal to the CPU <NUM> through the FPGA <NUM> in a period D1 indicated by an arrow A32a in <FIG>. The driving conversion section 71b monitors a reception signal of the coil <NUM> and outputs an amplitude of the reception signal to the CPU <NUM> through the FPGA <NUM> in a period D2 indicated by an arrow A32b in <FIG>. The driving conversion section 71c monitors a reception signal of the coil <NUM> and outputs an amplitude of the reception signal to the CPU <NUM> through the FPGA <NUM> in a period D3 indicated by an arrow A32c in <FIG>.

Upon receiving the amplitudes of the reception signals from the driving conversion sections 71a to 71c, the CPU <NUM> determines whether a foreign object has entered the feeding section <NUM> on the basis of the received amplitudes of the reception signals. For example, when the CPU <NUM> has obtained the amplitudes of the reception signals of the coils <NUM> to <NUM> in the periods D1 to D3 indicated by the arrows A31a to A31c in <FIG>, the CPU <NUM> determines, in a period t1 indicated by an arrow A33, whether a foreign object has entered the feeding section <NUM> on the basis of the amplitudes of the reception signals received in the periods D1 to D3 indicated by the arrows A31a to A31c in <FIG>. That is, after receiving amplitudes of reception signals of all the coils <NUM> to <NUM>, the CPU <NUM> determines, in a period t1 in which a next banknote is to be fed, whether a foreign object has entered the feeding section <NUM>.

Now, a relationship between a position of a foreign object and the amount of change in amplitudes of reception signals of the coils <NUM> to <NUM> will be described with reference to <FIG>. The amount of change in an amplitude of a reception signal caused by a foreign object, such as a piece of metal, right above a wire (lead wire) of one of the coils <NUM> to <NUM> is smaller than the amount of change in an amplitude of a reception signal caused by a foreign object within an area surrounded by the wire of one of the coils <NUM> to <NUM>.

For example, a broken line A21 in <FIG> indicates a position right above the wire of the coil <NUM>. If there is a foreign object, such as a piece of metal, on the line A21, the amount of change in an amplitude of a reception signal of the coil <NUM> is usually small.

The coils <NUM> and <NUM>, however, partly overlap with each other as described above. A foreign object on the line A21, therefore, is located not only right above the wire of the coil <NUM> but also within an area surrounded by the wire of the coil <NUM>. The amount of change in an amplitude of a reception signal caused by a foreign object on the line A21 is large in the coil <NUM>.

For example, a broken line A22 in <FIG> indicates a position right above the wire of the coil <NUM>. If there is a foreign object, such as a piece of metal, on the line A22, the amount of change in an amplitude of a reception signal of the coil <NUM> is usually small.

The coils <NUM> and <NUM>, however, partly overlap with each other as described above. A foreign object on the line A22, therefore, is located not only right above the wire of the coil <NUM> but also within an area surrounded by the wire of the coil <NUM>. The amount of change in an amplitude of a reception signal caused by a foreign object on the line A22 is large in the coil <NUM>.

Similarly, a broken line A23 in <FIG> indicates a position right above the wire of the coil <NUM>. The amount of change in an amplitude of a reception signal caused by a foreign object on the line A23 is large in the coil <NUM>. A broken line A24 in <FIG> indicates a position right above the wire of the coil <NUM>. The amount of change in an amplitude of a reception signal caused by a foreign object on the line A24 is large in the coil <NUM>.

The coils <NUM> to <NUM> are thus provided for the board <NUM> such that adjacent ones of the coils <NUM> to <NUM> partly overlap with each other. The CPU <NUM> controls the switches 72a to 72c in such a way as to sequentially energize the coils <NUM> to <NUM>. As a result, even if there is a foreign object right above the wire of one of the coils <NUM> to <NUM>, another of the coils <NUM> to <NUM> outputs a reception signal whose amplitude has been significantly changed.

An example of operations performed by the CPU <NUM> in the determination as to a foreign object will be described. For example, the operations performed by the CPU <NUM> comprise an operation for obtaining reference values and an operation for making a determination as to a foreign object using the obtained reference values.

The CPU <NUM> obtains amplitudes (reference values) of reception signals of the coils <NUM> to <NUM> at a time when there are no banknotes or foreign objects (clean state) in the feeding section <NUM>. For example, the CPU <NUM> obtains, with the feeding section <NUM> in the clear state, the reference values for the coils <NUM> to <NUM> after the sheet processing apparatus <NUM> is turned on.

After the sheet processing apparatus <NUM> is turned on, for example, the CPU <NUM> outputs energizing signals to the coils <NUM> to <NUM> as indicated by D1 to D3 in <FIG>. The CPU <NUM> receives, through the FPGA <NUM>, amplitudes (reference values) of reception signals output from the driving conversion sections 71a to 71c and stores the reference values in the memory <NUM>.

<FIG> is a diagram illustrating an example of the reference values. In <FIG>, r1, r2, and r3 denote the reference values for the coils <NUM>, <NUM>, and <NUM>, respectively. That is, r1 to r3 in <FIG> denote amplitudes of reception signals of the coils <NUM> to <NUM> at a time when there are no banknotes or foreign objects in the feeding section <NUM>. The reference values r1 to r3 are stored in the memory <NUM>.

In order to facilitate understanding of the present invention, it is assumed that the reference values (the amplitudes of the reception signals) output from the coils <NUM> to <NUM> comprise signal components that depend on a surrounding environment and signal components that do not depend on the surrounding environment. C1 to C3 in <FIG>, for example, denote signal components of the coils <NUM> to <NUM>, respectively, that do not depend on the surrounding environment. Nr in <FIG> denotes signal components that depend on the surrounding environment of the coils <NUM> to <NUM>. Nr varies depending on the surrounding environment of the coils <NUM> to <NUM>.

Here, the coils <NUM> to <NUM> are configured such that the signal components of the coils <NUM> to <NUM> that depend on the surrounding environment become substantially the same. The signal components that depend on the surrounding environment become substantially the same by, for example, using the same material, the same shape, and the number of turns for the coils <NUM> to <NUM>.

Alternatively, the coils <NUM> to <NUM> may be coils whose signal components that depend on the surrounding environment are substantially the same with at least one of the material, the shape, and the number of turns different between the coils <NUM> to <NUM>. The surrounding environment is, for example, surrounding temperature of the coils <NUM> to <NUM>. The coils <NUM> to <NUM> may be coils at least whose signal components that depend on temperature are substantially the same, instead. A case where temperature, which is an example of the surrounding environment, affects the coils <NUM> to <NUM> will be described hereinafter.

The CPU <NUM> determines whether a foreign object has entered the feeding section <NUM> in, for example, a deposit process using obtained reference values.

There are three operations performed by the CPU <NUM> to make the determination. The operations performed by the CPU <NUM> comprise, for example, a first operation for obtaining amplitudes of reception signals of the coils <NUM> to <NUM>, a second operation for subtracting reference values obtained in advance from the amplitudes of the reception signals obtained in the first operation, and a third operation for determining whether a foreign object has entered the feeding section <NUM> on the basis of results of the subtraction performed in the second operation.

As indicated by D1 to D3 in <FIG>, for example, the CPU <NUM> outputs energizing signals to the coils <NUM> to <NUM> once in each period t1. In other words, the coils <NUM> to <NUM> are sequentially energized once while a banknote P1 is being fed. The CPU <NUM> then receives (obtains) amplitudes of reception signals of the coils <NUM> to <NUM> at the timings indicated by D1 to D3 in <FIG>.

<FIG> is a diagram illustrating an example of the amplitudes of the reception signals obtained by the CPU <NUM>. It is assumed in <FIG> that a foreign object has entered an area A25 indicated by a dash-dot line in <FIG>.

In <FIG>, d1 to d3 denote the amplitudes of the reception signals of the coils <NUM> to <NUM>, respectively.

In <FIG>, C1 to C3 denote signal components of the coils <NUM> to <NUM>, respectively, that do not depend on temperature. C1 to C3 in <FIG> are the same as those in <FIG>.

In <FIG>, Nd denotes signal components of the coils <NUM> to <NUM> that depend on temperature. A surrounding temperature when the CPU <NUM> has obtained the amplitudes d1 to d3 of the reception signals is different from a surrounding temperature when the CPU <NUM> has obtained the reference values r1 to r3 illustrated in <FIG> are different from each other, and therefore Nd ≠ Nr.

In <FIG>, E1 to E3 denote signal components of the coils <NUM> to <NUM>, respectively, affected by the foreign object. As indicated by the area A25 illustrated in <FIG>, the foreign object is distant from the coil <NUM>, and therefore E1 = <NUM>. The foreign object overlaps the coils <NUM> and <NUM> and is also located inside the wire of the coil <NUM>, and therefore E2 < E3. It is assumed in <FIG>, too, that the signal components of the coils <NUM> to <NUM> comprise signal components that do not depend on temperature, signal components that depend on temperature, and signal components affected by the foreign object.

Upon obtaining the amplitudes of the reception signals of the coils <NUM> to <NUM>, the CPU <NUM> subtracts the reference values for the coils <NUM> to <NUM> from the obtained amplitudes of the corresponding reception signals of the coils <NUM> to <NUM>.

For example, the CPU <NUM> subtracts the reference values for the coils <NUM> to <NUM> from the amplitudes of the reception signals of the coils <NUM> to <NUM>, respectively.

In the case of the reference values illustrated in <FIG> and the amplitudes of the reception signals illustrated in <FIG>, results (differential values) Δ1 to Δ3 of the subtraction of the reference values for the coils <NUM> to <NUM> from the corresponding amplitudes of the reception signals are as represented by the following equations <NUM> to <NUM>. <MAT> <MAT> <MAT>.

Upon obtaining the results (hereinafter also referred to as "first differential values") of the subtraction of the reference values for the coils <NUM> to <NUM> from the amplitudes of the corresponding reception signals, the CPU <NUM> calculates absolute values of results (hereinafter also referred to as "second differential values") of subtraction of the obtained first differential values from each other. The CPU <NUM> then determines, on the basis of the calculated absolute values of the second differential values, whether a foreign object has entered the feeding section <NUM>. If at least one of the absolute values of the second differential values exceeds a certain threshold, for example, the CPU <NUM> determines that a foreign object has entered the feeding section <NUM>.

In the case of the results (first differential values) represented by equations <NUM> to <NUM>, the absolute values of the differential values (second differential values) between the first differential values are as represented by the following equations <NUM> to <NUM>. <MAT> <MAT> <MAT>.

If at least one of the absolute values of the second differential values represented by equations <NUM> to <NUM> exceeds a certain threshold, the CPU <NUM> determines that a foreign object has entered the feeding section <NUM>.

<FIG> is a diagram illustrating an example of the determination made by the CPU <NUM> as to whether a foreign object has entered the feeding section <NUM>. <FIG> illustrates the absolute values of the second differential values represented by equations <NUM> to <NUM>. If at least one of the absolute values of the second differential values exceeds the certain threshold, the CPU <NUM> determines that a foreign object has entered the feeding section <NUM>. In the example illustrated in <FIG>, Δ31 exceeds the threshold. The CPU <NUM> determines that a foreign object has entered the feeding section <NUM>.

In equations <NUM> to <NUM>, the signal components (Nr and Nd) that depend on temperature are canceled. The CPU <NUM> can therefore accurately determine whether a foreign object has entered the feeding section <NUM> regardless of an effect of a change in the surrounding temperature of the coils <NUM> to <NUM>.

If a foreign object is smaller than the area of the coil <NUM>, an effect of the foreign object upon at least one of the coils <NUM> to <NUM> becomes (substantially) zero. At least one of Δ12, Δ23, and Δ31, therefore, becomes equal to a change in the amplitude of the reception signal caused by the foreign object.

<FIG> is a flowchart illustrating an example of a process performed by the CPU <NUM> to obtain amplitudes of reception signals. The CPU <NUM> performs the process illustrated in the flowchart of <FIG>, for example, each time one of the banknotes P1 stacked on the stage <NUM> is fed into the first branch path 15b (in each period t1). It is assumed in the following description that the CPU <NUM> has obtained the reference values and stored the reference values in the memory <NUM>. It is also assumed that the CPU <NUM> controls the driving conversion sections 71a to 71c in such a way as to output energizing signals to the switches 72a to 72c, respectively.

The CPU <NUM> turns on the switch 72a (step S1). As a result, the energizing signal output from the driving conversion section 71a is input to the coil <NUM>. The driving conversion section 71a outputs an amplitude of a reception signal of the coil <NUM> to the CPU <NUM> through the FPGA <NUM>.

The CPU <NUM> receives the amplitude of the reception signal of the coil <NUM> from the driving conversion section 71a through the FPGA <NUM> (step S2). The CPU <NUM> stores the received amplitude of the reception signal of the coil <NUM> in, for example, the memory <NUM>.

The CPU <NUM> turns off the switch 72a and turns on the switch 72b (step S3). As a result, the energizing signal output from the driving conversion section 71b is input to the coil <NUM>. The driving conversion section 71b outputs an amplitude of a reception signal of the coil <NUM> to the CPU <NUM> through the FPGA <NUM>.

The CPU <NUM> receives the amplitude of the reception signal of the coil <NUM> from the driving conversion section 71b through the FPGA <NUM> (step S4). The CPU <NUM> stores the received amplitude of the reception signal of the coil <NUM> in, for example, the memory <NUM>.

The CPU <NUM> turns off the switch 72b and turns on the switch 72c (step S5). As a result, the energizing signal output from the driving conversion section 71c is input to the coil <NUM>. The driving conversion section 71c outputs an amplitude of a reception signal of the coil <NUM> to the CPU <NUM> through the FPGA <NUM>.

The CPU <NUM> receives the amplitude of the reception signal of the coil <NUM> from the driving conversion section 71c through the FPGA <NUM> (step S6). The CPU <NUM> stores the received amplitude of the reception signal of the coil <NUM> in, for example, the memory <NUM>.

The CPU <NUM> turns off the switch 72c (step S7), and ends the process illustrated in the flowchart.

After receiving the amplitudes of the reception signals of all the coils <NUM> to <NUM> in the period t1 (after storing the amplitudes of the reception signals in the memory <NUM>), the CPU <NUM> determines, in the next period t1 on the basis of the amplitudes of the reception signals stored in the memory <NUM>, whether a foreign object has entered the feeding section <NUM>.

<FIG> is a flowchart illustrating an example of a process performed by the CPU <NUM> to determine whether a foreign object has entered the feeding section <NUM>. The CPU <NUM> performs the process illustrated in the flowchart of <FIG>, for example, each time one of the banknotes P1 stacked on the stage <NUM> is fed into the first branch path 15b (in each period t1).

The CPU <NUM> obtains first differential values by subtracting reference values stored in the memory <NUM> from amplitudes of reception signals stored in the memory <NUM> (step S11). For example, the CPU <NUM> subtracts the reference values for the coils <NUM> to <NUM> stored in the memory <NUM> from the amplitudes of the reception signals of the coils <NUM> to <NUM>, respectively, stored in the memory <NUM> (differential values Δ1 to Δ3 of the coils <NUM> to <NUM> are obtained as a result of the subtraction).

The CPU <NUM> calculates second differential values (absolute values) by subtracting the first differential values from each other (step S12). For example, the CPU <NUM> obtains an absolute value Δ12 of a result of subtraction of the differential value Δ2 of the coil <NUM> from the differential value Δ1 of the coil <NUM>. The CPU <NUM> obtains an absolute value Δ23 of a result of subtraction of the differential value Δ3 of the coil <NUM> from the differential value Δ2 of the coil <NUM>. The CPU <NUM> obtains an absolute value Δ31 of a result of subtraction of the differential value Δ1 of the coil <NUM> from the differential value Δ3 of the coil <NUM>.

The CPU <NUM> determines whether at least one of the second differential values exceeds a threshold (step S13). For example, the CPU <NUM> determines whether at least one of Δ12, Δ23, and Δ31 exceeds the threshold. If determining that none of Δ12, Δ23, and Δ31 exceeds the threshold (NO in S13), the CPU <NUM> ends the process illustrated in the flowchart. If determining that at least one of Δ12, Δ23, and Δ31 exceeds the threshold (YES in S13), on the other hand, the CPU <NUM> stops rotation of the kicker rollers <NUM> (step S14). As a result, the foreign object is prevented from entering the first branch path 15b.

Before starting a deposit process, for example, the CPU <NUM> may perform the processes illustrated in the flowcharts of <FIG> and <FIG> at least once. That is, before the banknotes P1 taken in the inlet section <NUM> are fed into the first branch path 15b, the CPU <NUM> may perform the processes illustrated in the flowcharts of <FIG> and <FIG> at least once. As a result, the foreign object is prevented from entering the first branch path 15b.

In addition, the CPU <NUM> may keep performing the processes illustrated in the processes of <FIG> and <FIG> even while the banknotes P1 are being fed into the first branch path 15b. In this case, even if a foreign object enters the feeding section <NUM> while the banknotes P1 are being fed into the first branch path 15b, the foreign object is prevented from entering the first branch path 15b.

As described above, the sheet processing apparatus <NUM> comprises the coils <NUM> to <NUM> that are provided in the feeding section <NUM>, which feeds banknotes that have been taken in into a transport path, and that generate magnetic fields and the CPU <NUM> that determines whether a foreign object has entered the feeding section <NUM> on the basis of differential values between amplitudes of reception signals output from the coils <NUM> to <NUM>. The coils <NUM> to <NUM> are foreign object detection coils that output different signals depending on whether there is a foreign object nearby. As a result, the sheet processing apparatus <NUM> improves the accuracy of detecting entry of a foreign object while suppressing an increase in the number of parts. For example, the sheet processing apparatus <NUM> can accurately determine whether a foreign object has entered the feeding section <NUM> regardless of an effect of a change in surrounding temperature without a temperature sensor, a reference coil, or the like.

The sheet processing apparatus <NUM> is just an example of an apparatus on which the present invention is implemented. The present invention can also be widely implemented on sheet processing apparatuses comprising the feeding section <NUM> that feeds banknotes that have been taken in into a transport path. A feeding section on which the present invention is implemented is not limited to the above-described feeding section <NUM>, and any feeding section comprising a function of feeding banknotes into a transport path one by one may be used.

Although the CPU <NUM> obtains reference values after the sheet processing apparatus <NUM> is turned on in the above description, the CPU <NUM> may obtain reference values at another timing, instead. For example, the CPU <NUM> may obtain reference values at a timing specified by a user. The reference values may be values stored in the memory <NUM> in advance, instead.

Although the driving conversion sections 71a to 71c output amplitudes of reception signals of the coils <NUM> to <NUM> to the CPU <NUM> through the FPGA <NUM> in the above description, the driving conversion sections 71a to 71c may output frequencies of reception signals of the coils <NUM> to <NUM> to the CPU <NUM> through the FPGA <NUM>, instead.

In this case, the CPU <NUM> stores frequencies of reception signals of the coils <NUM> to <NUM> in the memory <NUM> as reference values. The CPU <NUM> subtracts the reference values for frequencies of the coils <NUM> to <NUM> from the frequencies of the reception signals of the coils <NUM> to <NUM> output from the driving conversion sections 71a to 71c (calculates first differential values). The CPU <NUM> then calculates differential values (second differential values) between the first differential values and determines whether a foreign object has entered the feeding section <NUM> on the basis of the calculated second differential values.

Alternatively, the driving conversion sections 71a to 71c may output amplitudes and frequencies of reception signals of the coils <NUM> to <NUM> to the CPU <NUM> through the FPGA <NUM>.

In this case, the CPU <NUM> stores amplitudes and frequencies of reception signals of the coils <NUM> to <NUM> in the memory <NUM> as reference values. The CPU <NUM> subtracts the reference values for amplitudes of the coils <NUM> to <NUM> from the amplitudes of the reception signals of the coils <NUM> to <NUM> output from the driving conversion sections 71a to 71c (calculates first amplitude differential values). The CPU <NUM> also subtracts the reference values for frequencies of the coils <NUM> to <NUM> from the frequencies of the reception signals of the coils <NUM> to <NUM> output from the driving conversion sections 71a to 71c (calculates first frequency differential values).

The CPU <NUM> then calculates differential values (second amplitude differential values) between the first amplitude differential values. The CPU <NUM> also calculates differential values (second frequency differential values) between the first frequency differential values. If at least one of the second amplitude differential values exceeds a threshold and at least one of the second frequency differential values exceeds a threshold, the CPU <NUM> determines that a foreign object has entered the feeding section <NUM>.

Although the board <NUM> is provided under the stage <NUM> in the above description, a position at which the board <NUM> is provided is not limited to this. For example, the board <NUM> may be provided on a back surface (a position indicated by a broken line A41 in <FIG>) of the banknote guides <NUM> illustrated in <FIG>, instead.

In addition, although banknotes are set flat in the sheet processing apparatus <NUM> in the above description, the present invention can also be implemented on sheet processing apparatuses in which banknotes are set upright.

<FIG> is a diagram illustrating an example of the configuration of a sheet processing apparatus <NUM> in which banknotes are set upright. As illustrated in <FIG>, the sheet processing apparatus <NUM> comprises kicker rollers <NUM>, feed rollers <NUM>, gate rollers <NUM>, a transport path <NUM>, a stage <NUM>, a fixed guide <NUM>, and a movable guide <NUM>. <FIG> illustrates banknotes P101 set upright. Pushing members (not illustrated), such as springs, of the movable guide <NUM> push the upright banknotes P101 toward the fixed guide <NUM>.

The board <NUM> (not illustrated) may be provided under the stage <NUM> (a position A101 indicated by a broken line in <FIG>). Alternatively, the board <NUM> may be provided on a back side (a position A102 indicated by a broken line in <FIG>) of the fixed guide <NUM>. Alternatively, the board <NUM> may be provided on a back side (a position A103 indicated by a broken line in <FIG>) of the movable guide <NUM>. The sheet processing apparatus <NUM> also comprises the control section <NUM> illustrated in <FIG> and the detection control section <NUM> (not illustrated).

The foreign object detection control system can thus be used for the sheet processing apparatus <NUM> in which banknotes are set upright.

The configuration of the foreign object detection control system is not limited to the example illustrated in <FIG>. The FPGA <NUM>, the detection control IC <NUM>, and the switching circuit <NUM> may be achieved by a single chip. Alternatively, the CPU <NUM> may comprise the functions of the FPGA <NUM>, the detection control IC <NUM>, and the switching circuit <NUM>. The detection control section <NUM> may be mounted on the board <NUM>, instead.

The driving conversion sections 71a to 71c may output energizing signals such that adjacent ones of the coils <NUM> to <NUM> generate opposite magnetic fields. For example, the driving conversion sections 71a to 71c may output energizing signals such that the coil <NUM> generates a magnetic field directed to a nearer side of the page of <FIG>, the coil <NUM> generates a magnetic field directed to a deeper side of the page of <FIG>, and the coil <NUM> generates a magnetic field directed to the nearer side of the page of <FIG>.

As a result, when the coils <NUM> to <NUM> are sequentially energized, the coils <NUM> to <NUM> are hardly affected by magnetic fields of coils that have been previously energized. In addition, when winding directions of adjacent ones of the coils <NUM> to <NUM> are different from each other, the coils <NUM> to <NUM> generate opposite magnetic fields even if energizing signals of the same phase are input to the adjacent ones of the coils <NUM> to <NUM>.

The operation for calculating the first differential values may be omitted, and the second differential values may be results of subtraction of amplitudes of reception signals of the coils <NUM> to <NUM> from each other, instead. In this case, absolute values of the second differential values are as represented by the following equations <NUM> to <NUM>. <MAT> <MAT> <MAT>.

Here, C1 to C3 are signal components of the coils <NUM> to <NUM> that do not depend on temperature and are unique to the coils <NUM> to <NUM>, respectively. When C1 to C3 have been measured in advance, C1 - C2, C2 - C3, and C3 - C1 can be identified.

In the process for determining whether a foreign object has entered the feeding section <NUM> illustrated in <FIG>, the threshold for the differential value between the coils <NUM> and <NUM> is a value that takes into consideration C1 - C2, the threshold for the differential value between the coils <NUM> and <NUM> is a value that takes into consideration C2 - C3, and the threshold for the differential value between the coils <NUM> and <NUM> is a value that takes into consideration C3 - C1. The control section <NUM> can then determine whether a foreign object has entered the feeding section <NUM> by comparing the thresholds (the thresholds that take into consideration C1 - C2, C2 - C3, and C3 - C1) and the absolute values represented by equations <NUM> to <NUM>, respectively. Whether a foreign object has entered a feeding section can thus be determined on the basis of differential values between signals output from a plurality of coils.

The sheet processing apparatus on which the present invention is implemented comprises a plurality of coils that are provided in a feeding section which feeds a sheet that has been taken in into a transport path and that generate magnetic fields and a control section that determines, on a basis of differential values between signals output from the plurality of coils, whether a foreign object has entered the feeding section. The control section causes the plurality of coils to sequentially generate the magnetic fields one by one and detects the signals output from the plurality of coils while the coils are generating the magnetic fields.

Although the coils <NUM> to <NUM> are energized once in the period t1, in which the feeding section <NUM> feeds out one of the banknotes P1 in the above embodiment, the present invention is not limited to this mode. The coils <NUM> to <NUM> may be energized a plurality of times while the feeding section <NUM> is feeding out one of the banknotes P1.

For example, while the feeding section <NUM> is feeding out one of the banknotes P1, the control section <NUM> performs, a plurality of times, a process for sequentially energizing the coils <NUM> to <NUM> and detecting signals output from the coils <NUM> to <NUM> while the coils <NUM> to <NUM> are generating magnetic fields. According to the invention, while the feeding section <NUM> is feeding out one of the banknotes P1, the control section <NUM> performs a process for sequentially energizing the coils <NUM> to <NUM> a plurality of times and detecting, the plurality of times, signals output from the coils <NUM> to <NUM> while the coils <NUM> to <NUM> are generating magnetic fields.

Claim 1:
A sheet processing apparatus, comprising:
a plurality of coils (<NUM> to <NUM>) that are provided in a feeding section (<NUM>) which is configured to feed a sheet that has been taken in into a transport path and that are configured to generate magnetic fields;
a control section (<NUM>) that is configured to determine, on a basis of differential values between signals output from the plurality of coils, whether a foreign object has entered the feeding section; and
a plurality of kicker rollers (<NUM>) that are configured to kick the sheet toward a gate section, wherein
the plurality of coils are foreign object detection coils that output different signals depending on whether there is the foreign object nearby, characterised in that
the plurality of coils are arranged in correspondence with arrangement of the plurality of kicker rollers, and are arranged to surround the plurality of kicker rollers such that a portion of each of the kicker rollers penetrate an opening formed by the plurality of coils.