JP2015197321A - metal detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal detector capable of inspecting an object to be inspected with high sensitivity regardless of whether a coil arrangement inside a detection head is a facing type or a coaxial type.SOLUTION: A surface on the frame side of a detection head 40 is provided with rotary shafts 71, 72, respectively. The frame is also provided with bearing members 73, 74 pivotally supporting the rotary shafts 71, 72, respectively. The rotary shafts 71, 72 and the bearing members 73, 74 are arranged on a rotation center line O along the width direction (Y direction) of a conveyance belt. A first fixing plate 75 is fixed on the upper part of the detection head 40, and this first fixing plate 75 is formed with an arcuate long hole 76. The side face of the frame is fixed with a second fixing plate 77, and this second fixing plate 77 is formed with a circular bolt insertion hole 78. The long hole 76 of the first fixing plate 75 and the bolt insertion hole 78 of the second fixing plate 78 are inserted with a bolt 79 of which top end is screwed with a wing nut 80.

Description

  The present invention relates to a metal detection device that detects the presence or absence of metal in an inspection object based on a magnetic field change that occurs when the inspection object passes through an inspection space in a detection head.

  In general, in an inspection line for food or the like, a metal detection device that inspects whether or not a metal foreign object is mixed in an inspection object such as food while the inspection object is being transported is used. This metal detection apparatus determines the presence or absence of metal contamination by detecting a magnetic field change that occurs when an object to be inspected passes through an inspection space formed in a detection head.

  Usually, the inspection space of the detection head is set with a margin in the vertical width so as to correspond to a plurality of types of inspection objects having different sizes. For this reason, when inspecting an inspection object having a relatively low height with respect to the height from the upper surface of the conveyor belt to the upper end of the inspection space, the distance between the inspection object and the metal detection coil in the detection head May become large and the detection sensitivity may decrease.

  On the other hand, conventionally, in a metal detection device using a detection head having an opposing coil arrangement, one of a transmission coil and a reception coil is provided on the upper side and lower side of the detection head as a metal detection coil in the detection head. Since the other and the other are arranged, changing the spacer between the upper part and lower part to a different height changes the passing position of the object to be inspected with respect to the metal detection coil in the detection head doing. In other words, the height of the inspection space can be changed by changing the spacer.

  Also, a metal detection device is known that includes a mechanism for changing the vertical position of the detection head so as to change the passing position of the inspection object with respect to the detection head (see, for example, Patent Document 1). The device described in Patent Document 1 includes a mechanism for changing the vertical position of the detection head by changing the height of the nut that supports the detection head from below with respect to the bolt.

JP 2004-271278 A

  However, the technique of changing the distance between the upper side and the lower side of the detection head by changing to a spacer having a different height is applicable only to a detection head having a coil arrangement facing the transmission head. There is a problem that it cannot be applied to a coaxial detection head in which the receiving coil is coaxially arranged.

  Further, in the technique described in Patent Document 1 in which the passage position of the inspection object is changed by changing the vertical position of the detection head, since the vertical width of the inspection space is constant, the passage position of the inspection object Since the other is separated from the upper side and the lower side of the detection head, there is a problem that a sufficient improvement in detection sensitivity cannot be desired.

  Therefore, the present invention has been made to solve the above-described conventional problems, and the object to be inspected can be detected with high sensitivity regardless of whether the coil arrangement in the detection head is a facing type or a coaxial type. It aims at providing the metal detection apparatus which can be test | inspected.

  The metal detection apparatus according to the present invention includes a conveyor (30) that conveys an object to be inspected (W) on a conveyance belt (35), and an inspection space (41) through which the conveyance belt is inserted. A detection head (40) for detecting a magnetic field change that occurs when the inspection object passes through the generated magnetic field, and metal is mixed into the inspection object based on the magnetic field change detected by the detection head. In the metal detection device (10) for determining whether or not it is, the support means (71, 72,) for rotatably supporting the detection head around a rotation center line (O) along the width direction of the transport belt. 73, 74).

  With this configuration, even if the detection head has a coaxial coil arrangement, by rotating the detection head around the rotation center line along the width direction of the conveyor belt, the apparent inspection space in the detection head can be obtained. The height can be reduced. For this reason, since the metal detection coil in the detection head can be brought close to the inspection object, the metal in the inspection object can be detected with high sensitivity. Therefore, it is possible to inspect the inspection object with high sensitivity regardless of whether the coil arrangement of the detection head is the facing type or the coaxial type. Further, by rotating the detection head, the magnetic field forms an angle with respect to the passing direction of the object to be inspected, so that the thin metal can be detected with high sensitivity.

  Further, the metal detection device according to the present invention is characterized in that it includes fixing means (75, 77, 79, 80) for fixing the detection head at an arbitrary rotational position.

  With this configuration, even when the weight balance around the rotation center line of the detection head is not balanced, the detection head can be fixed at an arbitrary rotation position.

  Further, in the metal detection device according to the present invention, the upper surface of the transport belt is inserted through the central portion in the vertical direction of the inspection space, and the rotation center line is disposed in the vertical direction of the inspection space and the central portion in the transport direction It is characterized by being.

  With this configuration, the detection head can be rotated while the distance between the upper side of the detection head and the upper surface of the conveyor belt and the distance between the lower side of the detection head and the upper surface of the conveyor belt are kept equal. Can do. For this reason, as the detection head rotates, the upper side portion and the lower side portion thereof can be brought close to the conveyance belt equally, so that the detection head is rotated to the maximum angle immediately before the detection head contacts the conveyance belt. be able to.

  Moreover, the metal detection apparatus according to the present invention includes at least one of an upper part (40a) above the inspection space of the detection head and a lower part (40b) below the inspection space of the detection head. Is provided with a rotation position restricting means (76) for restricting the rotation position of the detection head within the range of the rotation limit position immediately before contacting the conveyor belt.

  With this configuration, the detection head can be rotated to the rotation limit position immediately before at least one of the upper side portion and the lower side portion contacts the conveyance belt, thereby preventing contact between the detection head and the conveyance belt. Meanwhile, the rotation angle of the detection head can be increased.

  The present invention can provide a metal detection apparatus capable of inspecting an inspection object with high sensitivity regardless of whether the coil arrangement in the detection head is an opposing type or a coaxial type.

It is a front view which shows the structure of the metal detection apparatus which concerns on one Embodiment of this invention. It is a side view which shows the structure of the metal detection apparatus which concerns on one Embodiment of this invention. It is a top view which shows the structure of the metal detection apparatus which concerns on one Embodiment of this invention. It is a figure which shows the structure of the control circuit of the metal detection apparatus which concerns on one Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. First, the configuration will be described. As shown in FIGS. 1 to 3, the metal detection device 10 includes a gantry 21, frames 23 and 24, a conveyor 30, a detection head 40, and an operation panel 25.

  The gantry 21 constitutes a leg portion of the metal detection device 10, supports the conveyor 30, and supports the detection head 40 via the frames 23 and 24. A screw type adjuster 22 for height adjustment is provided at the bottom of the gantry 21.

  The conveyor 30 has a pair of side plates 31 and 32 that are formed in a U-shape that opens upward. The side plates 31 and 32 face each other with a conveyance belt 35 described below therebetween. 21 is fixed to the top.

  A driving roller 33 is rotatably supported between upper portions of the side plates 31 and 32 on one end side in the conveying direction (X direction). Further, a driven roller 34 is rotatably supported between the upper portions of the side plates 31 and 32 on the other end side in the conveying direction. Between the driving roller 33 and the driven roller 34, an endless conveying belt 35 for conveying the inspection object W is stretched. Here, the inspected object W is a container in which food such as chocolate is accommodated in a rectangular paper box.

  A lower plate 36 is fixed inside the conveying belt 35 between one side upper portion and the other end upper portion of the side plates 31 and 32 in the conveying direction, and the lower plate 36 is driven from the driving roller 33 side to the driven roller 34. The conveyor belt 35 is supported from below so that the upper conveyor belt 35 moving to the side forms a horizontal plane.

  The lower conveying belt 35 returning from the driven roller 34 side to the driving roller 33 side is configured to move along a path close to the lower surface of the lower plate 36. The conveyor belt 35 and the lower plate 36 are made of a synthetic resin material that has very little influence on the magnetic field.

  A motor (not shown) is integrally provided on one end side of the drive roller 33, and the drive roller 33 is rotationally driven by this motor.

  Vertical frames 23 and 24 are fixed to the top of the gantry 21. The frames 23 and 24 are respectively arranged on the front side and the back side of the apparatus so as to face each other with the detection head 40 and the conveyance belt 35 interposed therebetween.

  A detection head 40 formed in a vertically long rectangular frame shape is disposed between the frames 23 and 24. The frames 23 and 24 rotatably support the detection head 40 with the width direction (Y direction) of the conveyor belt 35 as a rotation center line. The support structure of the detection head 40 by the frames 23 and 24 will be described later.

  The detection head 40 is formed in a substantially square shape when viewed from the side, and has a rectangular parallelepiped inspection space 41 penetrating in the X direction. The inspection space 41 is inserted with a conveyor belt 35 and a lower plate 36 of the conveyor 30 so that the inspection object W is conveyed therein.

  A transmission coil 53 that generates a magnetic field in the inspection space 41 is wound around the detection head 40 so as to surround the inspection space 41. Around the transmission coil 53, a pair of reception coils 54 a and 54 b for detecting a change in the magnetic field generated in the inspection space 41 is wound around the transmission coil 53 so as to surround the inspection space 41.

  That is, the detection head 40 has a configuration of a coaxial arrangement in which the transmission coil 53 and the reception coils 54a and 54b are coaxially arranged. In addition, as arrangement | positioning of the transmission coil 53 and the reception coils 54a and 54b, there exist opposing type arrangement | positioning other than coaxial type arrangement | positioning. In the opposed arrangement, the transmission coil 53 is arranged on one side across the conveyance path of the conveyor 30, and the two reception coils 54a and 54b are arranged to face the transmission coil 53 on the other side. The detection head 40 is not limited to the coaxial arrangement, and may be configured as an opposed arrangement.

  A magnetic shield material that does not transmit magnetic flux is provided on the outer periphery of the detection head 40. For this reason, most of the magnetic flux generated by the transmission coil 53 passes through the inside of the detection head 40 and the inside of the inspection space 41. In addition, the magnetic flux generated by the transmission coil 53 intersects the two reception coils 54a and 54b in substantially equal amounts.

  A light projecting / receiving device 48 is provided on the entrance side surface of the detection head 40, and the light projecting / receiving device 48 optically detects the entry of the inspection object W into the inspection space 41. . Specifically, the light emitter / receiver 48 includes a light projector and a light receiver. When the light emitted from the light projector is blocked by an object to be inspected and the light receiver cannot receive the light, the light emitter / receiver 48 is installed in the position where the light emitter / receiver 48 is installed. It detects the passage of the inspection object and outputs a passage signal.

  A substantially rectangular operation panel 25 is fixed to the front side of the frame 23. On the front surface of the operation panel 25, an operation unit 14 operated by a user and a display unit 15 for displaying various information are provided. From the operation unit 14, for example, information such as instructions for various operations, a set value of the conveyance speed of the conveyor 30, a threshold value for metal detection, and the like are input by the user. The display unit 15 displays, for example, magnetic field changes due to the passage of the inspection object W, inspection results of the inspection object W, and the like as necessary.

  Further, inside the operation panel 25, control for performing various processes including driving of the motor of the conveyor 30, driving of the transmitting coil 53 in the detection head 40, and processing of signals from the receiving coils 54a and 54b. A circuit 50 is provided. Hereinafter, the configuration of the control circuit 50 will be described.

  As shown in FIG. 4, the control circuit 50 includes an AC generator 51 that generates a transmission signal having a predetermined frequency, and an amplifier 52 that amplifies the transmission signal generated by the AC generator 51. The transmission coil 53 described above generates an alternating magnetic field corresponding to the frequency of the transmission signal amplified by the amplifier 52. Further, the control circuit 50 includes a tuning circuit 55 that outputs a reception signal that is a difference between induced voltages of the reception coils 54a and 54b.

  In addition, the metal detection device 10 includes an amplifier 56 that amplifies the reception signal output from the tuning circuit 55 and a phase control unit that adjusts the phase of the transmission signal generated by the AC generator 51 for synchronous detection to generate an AC signal. 57.

  The control circuit 50 also includes a phase shifter 58 that shifts the phase of the AC signal generated by the phase control unit 57 by 90 °, and a reception that is amplified by the amplifier 56 based on the AC signal phase-adjusted by the phase control unit 57. And a synchronous detector 59 that removes a high-frequency component corresponding to the transmission signal from the signal by synchronous detection.

  In addition, the control circuit 50 includes a synchronous detector 60 that removes a high-frequency component corresponding to a transmission signal by synchronous detection from the reception signal amplified by the amplifier 56 based on the AC signal phase-shifted by the phase shifter 58, and synchronous detection. A band-pass filter (hereinafter referred to as “BPF”) 62 that removes unnecessary frequency components from the signal detected by the detector 60, and an amplifier 64 that amplifies the signal output by the BPF 62.

  The control circuit 50 also includes a BPF 61 that removes unnecessary frequency components from the signal detected by the synchronous detector 59 and an amplifier 63 that amplifies the signal output by the BPF 61.

  The control circuit 50 also includes an A / D converter 65 that converts the signals amplified by the amplifiers 63 and 64 from analog signals to digital signals, and a signal that is converted to a digital signal by the A / D converter 65. A computer 66 for detecting the presence or absence of metal in the inspection object W and a storage device 67 for storing various information used by the computer 66.

  The computer 66 controls various operations of the metal detection apparatus 10. A ROM (Read Only Memory) (not shown) in which a program is recorded and a CPU (Central Processing) (not shown) that operates based on the program recorded in the ROM. Unit) and a RAM (Random Access Memory) (not shown) which is a work area of the CPU.

  An operation unit 14 is connected to the computer 66, and information from the operation unit 14 that is input and operated by a user is input. Information input from the operation unit 14 and information such as a magnetic field change detected by the detection head 40 are stored in the storage device 67.

  A display unit 15 is connected to the computer 66, and various information output from the computer 66 is displayed on the display unit 15. A projector / receiver 48 is connected to the computer 66. The computer 66 detects or calculates the timing at which the inspection object W enters the inspection space 41 of the detection head 40 by receiving a passing signal of the inspection object W from the projector / receiver 48.

  Next, a support structure for the detection head 40 will be described. In the present embodiment, rotating shafts 71 and 72 are provided on the surfaces of the detection head 40 on the frames 23 and 24 side, respectively. The frames 23 and 24 are provided with bearing members 73 and 74 that pivotally support the rotation shafts 71 and 72, respectively. The rotation shafts 71 and 72 and the bearing members 73 and 74 are disposed on a rotation center line O along the width direction (Y direction) of the conveyor belt.

  Specifically, with the detection head 40 standing upright before rotation, the upper surface of the transport belt 35 is inserted through the center of the inspection space 41 in the vertical direction (Z direction), and the rotation center line O is The inspection space 41 is arranged at the center in the vertical direction (Z direction) and the transport direction (X direction).

  A first fixing plate 75 is fixed to the upper portion of the detection head 40, and an arc-shaped long hole 76 is formed in the first fixing plate 75. A second fixing plate 77 is fixed to the side surface of the frame 23, and a circular bolt insertion hole 78 is formed in the second fixing plate 77. Bolts 79 are inserted through the elongated holes 76 of the first fixing plate 75 and the bolt insertion holes 78 of the second fixing plate 77 from the device rear side toward the device front side.

  A wing nut 80 is screwed to the tip of the bolt 79 inserted through the bolt insertion hole 78. As a result, the first fixing plate 75 and the second fixing plate 77 are jointed by the bolt 79 and the wing nut 80 by gripping and tightening the wing nut 80 with the detection head 40 rotated to an arbitrary rotation position. Since it is fastened and easily fixed, the rotation position of the detection head 40 is fixed. The first fixing plate 75, the second fixing plate 77, the bolt 79, and the wing nut 80 constitute fixing means for fixing the detection head 40 at an arbitrary rotational position.

  The second fixing plate 77 is marked with an indicating needle, and the first fixing plate 75 has a rotation angle θ at a predetermined rotation position of the detection head 40 and an apparent height of the inspection space 41. H2 is marked.

  Here, the apparent height H2 of the inspection space 41 is the inspection object W from the upper surface of the conveyance belt 35 to the upper end of the projection shape in the projection shape obtained by projecting the inspection space 41 in the conveyance direction (X direction). Is the height of the passable area. In other words, when the rotation angle θ of the detection head 40 exceeds 0 °, the distance from the upper surface of the upper conveyor belt 35 to the exit side opening of the inspection space 41 becomes the apparent height H2 of the inspection space 41. . Similarly, an apparent height H2 exists below the upper conveyor belt 35 between the entrance-side opening of the inspection space 41. Since the apparent height H2 when the detection head 40 rotates is smaller than the actual height H1 before the detection head 40 rotates, by rotating the detection head 40, the detection head 40 40 is close to the inspection object W. By recording this apparent height H2 on the first fixed plate 75, it is possible to set the rotational angle θ and the apparent height H2 of the detection head at a predetermined rotational position without actually measuring it. It becomes.

  The elongated holes 76 of the first fixing plate 75 are such that the rotation position (rotation angle) of the detection head 40 is above the inspection space 41 of the detection head 40 and below the inspection space 41 of the detection head 40. At least one of the lower side portion 40b and the lower side portion 40b is regulated within the range of the rotation limit position immediately before contacting the upper surface of the conveyor belt 35. In addition, since the rotation center line O is disposed on the upper surface of the conveyance belt 35, in practice, when the detection head 40 is rotated, the corner of the outlet side opening portion of the upper portion 40a of the detection head 40 is conveyed upward. Before coming into contact with the upper surface of the belt 35, the corner of the inlet side opening of the lower portion 40b of the detection head 40 comes into contact with the lower surface of the lower (return side) transport belt 35. For this reason, the rotation limit position is a position immediately before the corner of the inlet side opening of the lower side portion 40 b comes into contact with the lower surface of the conveyor belt 35. Thus, the long hole 76 constitutes a rotation position restricting means for restricting the rotation position of the detection head 40 to be within a predetermined range. In other words, in the present embodiment, the detection head 40 can be largely rotated to the limit rotation position where it does not contact the conveyance belt 35. Note that the position of the rotation center line O is not limited to the upper surface of the upper conveyor belt 35. The rotation center line O may be disposed between the upper conveyor belt 35 and the lower conveyor belt 35. In this case, the rotation angle of the detection head 40 can be maximized. The rotation center line O may be disposed on the lower surface of the lower conveyor belt 35 for design reasons or the like.

  In this embodiment, the detection head 40 is manually rotated from the vertical position. However, the detection head 40 may be rotated using a driving member such as a motor. In that case, an arc-shaped rack gear may be formed on the outer periphery of the first fixed plate 75, and a pinion gear meshing with the rack gear may be provided on the second fixed plate 77 or the frame 23, and the pinion gear may be rotated by a motor. The motor control circuit may be integrated into the control circuit 50 or may be provided independently.

  As described above, in the metal detection device 10 according to the present embodiment, the detection head 40 is moved with respect to the frames 23 and 24 by the rotation shafts 71 and 72 and the bearing members 73 and 74 in the width direction (Y ) Around the rotation center line O along the direction).

  With this configuration, even if the detection head 40 has a coaxial coil arrangement, the detection head 40 is rotated around the rotation center line O along the width direction (Y direction) of the conveyor belt 35 to thereby detect the detection head. The apparent height H2 of the 40 examination spaces 41 can be reduced. For this reason, since the detection head 40 can be brought close to the inspection object W, the metal in the inspection object W can be detected with high sensitivity.

  Therefore, the inspection object W can be inspected with high sensitivity regardless of whether the coil arrangement in the detection head 40 is the facing type or the coaxial type.

  Further, by rotating the detection head 40, the magnetic field forms an angle with respect to the passing direction of the inspection object W, so that a thin metal can be detected with high sensitivity.

  Further, the metal detection device 10 according to the present embodiment includes a first fixing plate 75, a second fixing plate 77, a bolt 79, and a wing nut 80 as fixing means for fixing the detection head 40 at an arbitrary rotation position. ing.

  With this configuration, even when the weight balance around the rotation center line O of the detection head 40 is not balanced, the detection head 40 can be fixed at an arbitrary rotation position.

  Further, in the metal detection device 10 according to the present embodiment, the upper surface of the transport belt 35 is inserted through the central portion of the inspection space 41 in the vertical direction (Z direction), and the rotation center line O is the vertical direction of the inspection space 41 ( (Z direction) and the center part of a conveyance direction (X direction).

  With this configuration, the distance between the upper portion 40a of the detection head 40 and the upper surface of the conveyor belt 35 is detected while the interval between the lower portion 40b of the detection head 40 and the upper surface of the conveyor belt 35 is kept equal. The head 40 can be rotated. For this reason, as the detection head 40 rotates, the upper side portion 40a and the lower side portion 40b can be brought close to the upper surface of the conveyance belt 35 equally, so the maximum immediately before the detection head 40 contacts the conveyance belt 35. The detection head 40 can be rotated to an angle.

  In addition, the metal detection device 10 according to the present embodiment detects within the range of the rotation limit position immediately before at least one of the upper side portion 40a and the lower side portion 40b of the detection head 40 contacts the transport belt 35. A long hole 76 for restricting the rotational position of the head 40 is provided.

  With this configuration, the detection head 40 can be rotated to the rotation limit position immediately before at least one of the upper side portion 40a and the lower side portion 40b contacts the conveyance belt 35. Therefore, the detection head 40 and the conveyance belt 35 can be rotated. The rotation angle of the detection head 40 can be increased while preventing contact with the head.

  As described above, the metal detection device according to the present invention has an effect that the inspection object can be inspected with high sensitivity regardless of whether the coil arrangement in the detection head is the facing type or the coaxial type. In addition, the present invention is useful as a metal detection device that detects the presence or absence of a metal in the inspection object based on a magnetic field change that occurs when the inspection object passes through the inspection space in the detection head.

DESCRIPTION OF SYMBOLS 10 Metal detection apparatus 23 Frame 30 Conveyor 35 Conveyance belt 40 Detection head 40a Upper part 40b Lower part 41 Inspection space 71, 72 Rotating shaft (support means)
73, 74 Bearing member (supporting means)
75 First fixing plate (fixing means)
76 Long hole (turning position restricting means)
77 Second fixing plate (fixing means)
78 Bolt insertion hole 79 Bolt (fixing means)
80 Wing nut (fixing means)
O Rotation center line W Inspected object

Claims (4)

A conveyor (30) for conveying the object to be inspected (W) on the conveyor belt (35);
An inspection space (41) through which the conveyor belt is inserted, and a detection head (40) for detecting a magnetic field change that occurs when the inspection object passes through a magnetic field generated in the inspection space;
In the metal detection device (10) for determining whether or not metal is mixed in the inspection object based on the magnetic field change detected by the detection head,
A metal detection device comprising support means (71, 72, 73, 74) for rotatably supporting the detection head around a rotation center line (O) along the width direction of the conveyor belt. .   The metal detection apparatus according to claim 1, further comprising fixing means (75, 77, 79, 80) for fixing the detection head at an arbitrary rotation position. The upper surface of the conveyor belt is inserted through the center in the vertical direction of the inspection space,
The metal detection apparatus according to claim 1, wherein the rotation center line is arranged in a vertical direction of the inspection space and a central portion in a transport direction.   Rotation immediately before at least one of the upper side (40a) above the inspection space of the detection head and the lower side (40b) below the inspection space of the detection head contacts the conveyor belt. The metal detection device according to any one of claims 1 to 3, further comprising a rotation position restricting means (76) for restricting a rotation position of the detection head within a range of a limit position.

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