JP7578223B2 - Metallic object detector - Google Patents

Description

The present invention relates to a metallic foreign matter detection device that detects metallic foreign matter that has been mixed into an object to be inspected. In particular, the present invention relates to a metallic foreign matter detection device that detects metallic foreign matter that has been mixed into an object to be inspected that has been filled into a packaging bag made of non-magnetic metals such as aluminum or aluminum-deposited film, or non-metallic materials such as plastic resin film.

Metal foreign body detection devices are used in a variety of fields. A typical example is the detection of metal foreign bodies that have become mixed into products during the manufacturing process. Specifically, in the manufacturing process of foods, pharmaceuticals, etc., parts of various containers such as conveyors, cleaners, mixers, cutters, kneaders, steamers, blades, sieves, etc. used in the manufacturing process of foods, pharmaceuticals, etc. can become worn, fatigued, etc., and metal pieces caused by swelling, breakage, peeling, scraping, chipping, etc. can become mixed into foods and other products as foreign bodies.

It is important to detect these foreign bodies and remove them from products. Electromagnetic wave type sensor coils and the like are used as a means of detecting magnetic metallic foreign bodies that have become mixed into the products being inspected. The metallic foreign bodies are often austenitic stainless steel, which is used to make the various containers, blades, sieves, etc. mentioned above. When austenitic stainless steel is plastically deformed, it undergoes martensitic transformation, changing into a crystal structure with weak magnetism.

For this reason, a magnet booster is placed near the sensor coil and its strong magnetic lines magnetize metallic foreign objects, making it possible to detect metallic foreign objects with high sensitivity. When an object to be inspected passes through the magnet booster, the magnetism generated by the magnet booster orients the magnetic properties of the metallic foreign objects in a certain direction, magnetizing them. The applicants of the present invention have proposed a metallic foreign object detection device using this principle as the invention described in Patent Documents 1 and 2.

The devices described in Patent Documents 1 and 2 detect metallic foreign bodies in objects such as food, and have succeeded in detecting minute magnetic bodies that are metallic foreign bodies using the proposed sensor coil. Specifically, Patent Document 1 discloses a metallic foreign body detection method and metallic foreign body detection device for detecting metallic foreign bodies that have been mixed into objects. This invention not only detects metallic foreign bodies such as stainless steel that have been mixed into objects, but can also detect metallic foreign bodies that have been mixed into objects such as food, medicine, and industrial materials that are wrapped in conductive packaging materials.

The metallic foreign body detector described in Patent Document 1 generates a minute magnetic field using a detection unit having a single coil consisting of a conductor wound around a core, detects the magnetic field from metallic foreign bodies that responds to the minute magnetic field as a detection voltage or detection current of the coil, and outputs a detection signal. This minute magnetic field is a voltage applied to the coil at a frequency of several hundred Hz to several tens of kHz, or direct current, and the current supplied is minute, and utilizes the nonlinear portion of the magnetization (B-H) characteristics of the core that constitutes the coil, where the magnetic flux density (B) and magnetic field (H) are minute values near 0.

When a metallic foreign object passes near the coil, the formation of the magnetic lines of force that link with the coil is disrupted, causing changes in the amplitude, phase, and frequency of the signal voltage, thereby detecting the metallic foreign object. This device has excellent sensitivity and can detect metallic foreign objects of 1 mm or less. It is also possible to detect long and thin metallic objects such as needles inside aluminum packaging, and antioxidants made of metal powder.

The metal detector disclosed in Patent Document 3 consists of a transport path for transporting objects to be detected, a sensor coil that is provided midway along the transport path and has a coil wound around a core for generating a magnetic field by passing an electric current through it, and a magnet that is placed in contact with the core. More specifically, an unequal static magnetic field is formed by the static magnetic field of the magnet and the alternating current of the sensor coil. When an object to be detected crosses this unequal magnetic field, the metallic foreign object is temporarily magnetized, and at the same time, the magnetic field generated by the magnetized object disrupts the magnetic field that interlinks with the sensor coil.

The sensor coil sends out a detection signal that detects this disturbance in the magnetic field. Patent Document 4 discloses a metal foreign body detection device that detects metal foreign bodies in flowing packaging bags just before they reach an accumulator that temporarily stores the packaging bags. The metal foreign body detection device passes the packaging bags through a long, hollow tubular guide and detects metal foreign bodies using sensor coils arranged on both sides of the tubular guide.

In addition, a small metal foreign body detection device has been disclosed that uses a sensor consisting of a sensor coil to detect metal foreign bodies contained in the packaged object (Patent Document 5), and is made up of a roller conveyor with an adjustable inclination angle of the conveying surface.

International Publication No. WO2003/027659 JP 2005-188985 A JP 2004-85439 A Utility model registration No. 3177557 JP 2018-063229 A

However, most of these conventional metal detectors and metal foreign body detection devices are devices for inspecting products transported on a belt conveyor, or inspect products by manually passing them near a sensor coil. The metal foreign body detection device described in Patent Document 5 is a small metal foreign body detection device that can be used on a tabletop, detecting products by dropping them by gravity without a belt conveyor, so that it can be used in food processing sites that handle a wide variety of rods on a small scale.

This desktop metal foreign matter detector is a small type whose conveying surface is entirely made up of rollers, which generates vibrations and causes variations in the signals detected by the sensor. In addition, because the object being inspected accelerates as it slides along the rollers, there is a problem that the speed at which the object passes through the sensor coil is not constant, leaving room for improvement.

The present invention has been made under the above-mentioned technical background, and achieves the following objects.
An object of the present invention is to provide a small metallic foreign matter detector capable of detecting metallic foreign matter contained in small-scale, diverse samples of medicines, cosmetics, foodstuffs and other items to be inspected.

Another object of the present invention is to provide a compact metallic foreign matter detector in which the speed at which an object passes through the sensor is constant.
It is still another object of the present invention to provide a small metallic foreign matter detector equipped with a conveying surface that does not generate vibrations when an object to be inspected passes by a sensor.

In order to achieve the above object, the present invention employs the following means.
The metal foreign matter detection device of the present invention 1 is
a conveying means for conveying the object to be inspected on an inclined surface serving as a conveying path by utilizing the gravity of the mass of the object to be inspected itself;
a magnetizing means for magnetizing or enhancing magnetization of the magnetic body that is a metallic foreign body in the object to be inspected, the magnetizing means being provided in the middle of the transport path;
a sensor means provided in the middle of the transport path and disposed below the magnetizing means, the sensor means detecting the magnetic body in the passing test object and outputting a detection signal;
a signal processing unit that receives the detection signal, processes the detection signal, determines whether the magnetic body is present, and outputs an output signal that indicates the result of the determination,
The conveying means is
a first transport path located at an upper portion of the inclined surface, along which the object to be inspected slides while being accelerated;
a second transport path that is located below the first transport path and forms the inclined surface that is continuous with the first transport path ,
the first transport path and the second transport path are detachably replaceable with transport paths having different friction coefficients in order to change the speed at which the test object slides down the inclined surface ;
The first transport path is characterized by comprising an angle fine adjustment means for finely adjusting the inclination angle of the inclined surface.

The metallic foreign matter detection device of the present invention 2 is the same as in the invention 1, and is characterized in that it comprises a detector that is disposed adjacent to the sensor means between the sensor means and the magnetization means, detects both the timing when the object starts to pass and the timing when it finishes passing, and transmits the results to the signal processing unit.

The metallic foreign matter detecting device of the third aspect of the present invention is the device of the first or second aspect of the present invention, characterized in that the first transport path is a roller conveyor.

The detection principle of the above-mentioned detection unit is to generate a minute magnetic field by applying a voltage or supplying a current to at least one sensor coil, and detect the magnetic field from a metallic foreign object of the magnetic body in the test object that responds to the minute magnetic field as a detection voltage or detection current of the sensor coil, and output a detection signal. This detection signal is analyzed to identify the metallic foreign object. Since the detection voltage or detection current of the sensor coil is a minute value and is easily affected by external magnetic fields or magnetic field disturbances, the detection unit, including the sensor coil, is magnetically shielded from external magnetic fields or magnetic field disturbances.

A micromagnetic field is one in which the voltage applied to or current supplied to a sensor coil is very small, and among the magnetization (B-H) characteristics of the core that constitutes the sensor coil, the magnetic flux density (B) and magnetic field (H) that represent the magnetization characteristics utilize a nonlinear portion that is a very small value near 0, the current or voltage has a frequency of several hundred Hz to several tens of kHz or is direct current, and when a metallic foreign object passes near the sensor coil, a voltage or current is induced to flow in the sensor coil. This can also be said to change the frequency of the sensor coil.
The minute magnetic field of the sensor coil is a known technique as shown in Patent Document 1, etc., and a detailed description thereof will be omitted.

The applicant of the present invention has filed a patent application for a "Method and Apparatus for Detecting Metallic Foreign Objects" (Patent Document 1). The entirety or part of the contents of this invention are also included in the present invention. The method for detecting metallic foreign objects of this invention comprises a conveying step of conveying an object to be detected on a conveying path in order to detect metallic foreign objects that have been mixed into the object during the manufacturing process within a package, and a metallic foreign object detection step of generating a magnetic field using a detection unit provided on the conveying path and having a coil configured with a conductor wound around a core, to detect metallic foreign objects that have been mixed into the object to be detected. In this method, a minute magnetic field is generated by applying a voltage or supplying a current to one of the coils, and the detected magnetic field from the metallic foreign object that responds to the minute magnetic field is detected as a detection voltage or detection current of the coil. It comprises a detection signal output process for outputting a signal, and a signal analysis process for analyzing the detection signal to identify the metallic foreign object, and the minute magnetic field is characterized in that the voltage applied to the coil or the current supplied to the coil is minute, and that the magnetic flux density (B) and magnetic field (H) representing the magnetization characteristics are minute values near 0 in the magnetization (B-H) characteristics of the core constituting the coil, and the current or voltage has a frequency of several hundred Hz to several tens of kHz, and the frequency changes when the metallic foreign object passes near the coil.

In the metallic foreign body detection device of the present invention, the current supplied to the sensor coil or the voltage applied thereto is not limited to the above-mentioned frequency, but can supply a direct current to an alternating current of several hundred Hz. Even if no current or voltage is actively supplied to the sensor coil, a bias voltage from an amplifier is applied to detect magnetic metallic foreign bodies. When an object to be inspected passes near the sensor coil, the magnetic field generated by the magnetic material inside the object to be inspected switches the sensor coil off and changes its state, which is detected by the sensor coil and the signal processing that follows.

The metallic foreign matter detector of the present invention can detect magnetic bodies in non-metallic objects with high sensitivity. Furthermore, it can detect magnetic bodies in objects such as packaging bags and containers that are wrapped in conductive materials such as aluminum and aluminum alloys.

The present invention provides the following advantages.
The metallic foreign matter detector of the present invention adjusts the inclination angle of the slide and provides conveying surfaces with different friction coefficients, thereby making it possible to keep the speed at which the test object passes the sensor constant.
Furthermore, the metallic foreign matter detector of the present invention improves detection sensitivity by making the conveyance surface in the vicinity of the sensor a conveyance surface that does not generate vibrations.

Furthermore, in the metallic foreign matter detector of the present invention, the inclination angle of the slide can be adjusted by the adjustment means, so that the inclination angle of the slide can be adjusted to match the friction coefficient of the surface on which the inspection object is conveyed.
Furthermore, the use of a small roller conveyor enabled miniaturization, making it possible to use the device on a table.

FIG. 1 is an external view showing the appearance of a metallic foreign matter detector 1 according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing an outline of the front of the metallic foreign matter detector 1 according to the embodiment of the present invention, and is a front view of FIG. FIG. 3 is a schematic diagram showing an outline of the plan view of the metallic foreign matter detector 1 according to the embodiment of the present invention, and is a plan view of FIG. 4A and 4B are diagrams showing an example of the configuration of a sensor coil of the sensor 3, in which FIG. 4A is a front view of the sensor coil, FIG. 4B is a plan view of FIG. 4A, and FIG. 4C is a cross-sectional view taken along line A-A of FIG. 4A. FIG. 5 is a cross-sectional view showing an outline of the roller conveyor 23 of the metallic foreign matter detector 1 according to the embodiment of the present invention. FIG. 6 is a conceptual diagram for analyzing the movement of the inspection object 2 when it moves on the sliding surface 20 in the metallic foreign matter detection device 1 according to the first embodiment of the present invention. FIG. 7 is a side view illustrating an overview of a metallic foreign matter detection device 1 equipped with an angle fine adjustment means in a metallic foreign matter detection device 1 according to a second embodiment of the present invention. FIG. 8 is a view taken along the line A in FIG. 7 of a metallic foreign matter detector 1 having an angle fine adjustment means in a metallic foreign matter detector 1 according to a second embodiment of the present invention.

[Embodiment]
Fig. 1 is an external view illustrating the appearance of a metallic foreign matter detection device 1 according to an embodiment of the present invention. Fig. 2 is a conceptual diagram illustrating an outline of the front side of the metallic foreign matter detection device 1 of Fig. 1, and Fig. 3 is a conceptual diagram illustrating an outline of the plan view of the metallic foreign matter detection device 1 of Fig. 1. The metallic foreign matter detection device 1 is for detecting or finding metallic objects (magnetic foreign objects) in an object 2 to be inspected and notifying the presence thereof.

The metal foreign body detection device 1 is intended to detect or detect and notify of metal foreign bodies that have been mixed into an object to be inspected 2, which is an object to be inspected that has been filled or contained in a packaging bag or the like. The object to be inspected is not particularly limited, but examples include solid, liquid, or gel foods, and medicines filled in a packaging bag. The packaging bag is made of a known material such as aluminum foil, a synthetic resin film, paper, etc., or a laminated material that combines these materials.

[Configuration of Metal Foreign Matter Detection Device 1]
The metallic foreign matter detection device 1 generally comprises a box-shaped main body 6, a slide 5 connected to one end of the main body 6 by a connecting member 15 which serves as a hinge, and a sensor 3 and a magnetization unit 4 fixed to the slide 5. The slide 5 is capable of swinging freely around the connecting member 15. As the sensor 3 and other components are arranged on the slide 5, when the object to be inspected 2 is dropped on the slide 5 by gravity within a set speed range, a magnetic body in the object to be inspected 2 can be detected.

The metallic foreign matter detection device 1 generally comprises a sensor 3 for detecting magnetic material in the object 2 to be inspected, a magnetization unit 4 for magnetizing the magnetic material in the object 2 to be inspected, a slide 5 for guiding and transporting the object 2 to be inspected, a main body 6, an angle adjustment member (fixing member) 7 for adjusting the inclination angle of the slide 5, a detector 8 for detecting the passage of the object 2 to be inspected, etc. The main body 6 comprises a box-shaped housing 11, a power switch 12 installed in the housing 11, a display unit 13, an operation switch 14, a signal processing unit 16 (see FIG. 2) housed within the housing 11, etc.

The signal processing unit 16 is an electronic circuit or computer that processes the signal detected by the sensor 3, determines the presence or absence of a metallic foreign object, and outputs the determination result. The housing 11 is a box-shaped case for housing the power switch 12, display unit 13, operation switch 14, signal processing unit 16, etc. The housing 11 has a compact structure so that it can be used on a table. The detector 8 is a sensor for detecting whether an object has passed in front of it, and in this example, an optical sensor is used.

The detector 8's main function is to detect the timing when the object to be inspected 2 enters the sensor 3, so it is basically installed in front of the sensor 3. In this example, it is installed adjacent to the sensor 3, between the sensor 3 and the magnetization means 4. This allows it to accurately detect the timing when the object to be inspected 2 is transported and passes the sensor 3, and transmits this to the signal processing unit 16. The detector 8 detects both the timing when the object to be inspected 2 starts to pass in front of it, and the timing when it finishes passing in front of it, and transmits this to the signal processing unit 16.

The signal indicating the passage of the object to be inspected 2 detected by the detector 8 can also be called a passage signal of the object to be inspected 2. The metallic foreign matter detection device 1 is basically connected to a power outlet via a power cable (not shown) and power is supplied to it. The power switch 12 is a switch for connecting and disconnecting the power cable in order to supply power to the metallic foreign matter detection device 1. When the power switch 12 is connected, power is supplied to the sensor 5, display unit 13, signal processing unit 16, etc., and they operate.

The display unit 13 is a display for displaying the overall operating status of the metal foreign matter detection device 1, and is made up of, for example, a liquid crystal display. The operation switch 14 is for setting the detection sensitivity of the sensor 5. The slide 5 is made up of a housing 21 and a slide surface 20 installed on the upper surface of the housing 21. The slide surface 20 is made up of a small roller conveyor 23 with multiple rollers 25 (see Figure 5) arranged in parallel, and a slide surface 22 consisting of a flat surface.

In this example, about half of the sliding surface 20, in other words up to the sensor 5, is a roller conveyor 23. A cross-sectional view of the roller conveyor 23 is shown in Figure 5, and will be described in detail later. A number of roller conveyors 23 are arranged in the flow direction of the objects 2 to be inspected, and are fixed by guides 23a so that they do not move left or right. The swingable housing 21 is for fixing the sliding surface 20, the sensor 3, the magnetization section 4, and the detector 8, and in this example, is a hexahedral box. The housing 21 is installed on the top surface of the main body 6, and one end of the housing 21 (the right side in Figure 1) can be installed up or down by using the angle adjustment member 7.

The other end of the housing 21 (left side in FIG. 1) is connected to the main body 6 by a connecting member 15. The sensor 3 and magnetization unit 4 are fixed to the side of the housing 21 by a support plate 34. The support plate 34 has elongated holes 32 and holes 42 for adjusting the height of the upper sensor 3 and magnetization unit 4. The upper sensor 3 and magnetization unit 4 are fixed to the support plate 34 at a predetermined height in the holes 32 and 42 by a fixing means such as a bolt. In this embodiment, the magnetization unit 4 and sensor 3 are installed at a predetermined distance above the sliding surface 20.

The magnetized part 4 is located on the top of the sliding surface 20 (slide 5), and the sensor 3 is located on the bottom of the sliding surface 20 (slide 5). In other words, the magnetized part 4 is located on the top side of the sensor 3 on the sliding surface 20, and the sensor 3 is located on the bottom side of the magnetized part 4 on the sliding surface 20. The test object 2 passes between the magnetized part 4 and the sliding surface 20, and between the sensor 3 and the sliding surface 20. The test object 2 passes through the magnetized part 4 and the sensor 3 while sliding from one side of the sliding surface 20 to the other. Although not shown, guides may be provided on both sides of the sliding surface 20 to prevent the test object 2 from sliding off. Such guides are fixed to the housing 21 of the slide 5 or the side of the sliding surface 20.

As shown in FIG. 2, the sensor 3 is composed of a sensor coil 31 installed on the top of the sliding surface 20, and a housing 33 that houses the sensor coils 31 installed on the top and bottom sides of the sliding surface 20. The housing 33 is fixed to a support plate 34 whose both ends are fixed to the slide 5. The upper and lower sensor coils 31 have the same structure and detect changes in the magnetic field around them. The magnetic field generated by magnetic metals such as metal objects and foreign metal objects in the test object 2 changes the magnetic field around them. In other words, the sensor coil 31 detects changes in disturbances in the magnetic field around it, and outputs a detection signal of voltage or current according to the change in the magnetic field.

In this embodiment, the housing 11 of the main body 6, the housing 21 of the slide 5, the housing 33 of the sensor 3, the housing 43 of the booster 4, the support plate 34, etc. are made of stainless steel from the viewpoint of rust prevention, etc. On the slide 5, the magnetization section 4, the detector 8, and the sensor 3 are arranged in this order along the transport direction of the test object 2. The test object 2 is a solid, a liquid such as soup stock, a paste, etc., which is individually packaged and sealed in aluminum packaging or the like, and is transported while sliding on the roller conveyor 23 of the slide surface 20 and the slide surface 22.

The object to be inspected 2 slides from top to bottom on the sliding surface 20, passing in that order the magnetization unit 4, the detector 8, and the sensor 3. The detection signal detected and output by the sensor 3 is sent to the signal processing unit 16 for signal processing. The signal processing unit 16 analyzes the detection signal received from the sensor 3 and determines whether or not there is a magnetic body in the object to be inspected 2. The signal processing unit 16 notifies the result of this determination (electrical signal, warning sound, display, etc.). If the object to be inspected 2 contains a magnetic body, in other words if a defective product (metallic foreign body) is detected, the signal processing unit 16 issues an alarm signal by a specified alarm means.

For example, this output signal is sent from the signal processing unit 16 to the display 13 for display, and lights up or flashes when a missing item (metallic foreign object) is detected. Alternatively, the output signal is sent from the signal processing unit 16 to a sound generating means, and an alarm signal such as a buzzer is generated when a missing item (metallic foreign object) is detected. A speaker or the like for sounding the buzzer is not shown in the figure, but is installed inside the housing 11, etc.

The signal processing unit 16 does not need to be built into the housing 11 as in this example, but may be installed in any location as long as it is in an environment where it can receive and process the detection signal from the housing 11 via wired or wireless communication. Any known communication standard can be used as the communication method for this wired and wireless communication, and detailed description thereof will be omitted as it is not the purpose of the present invention.

[Sensor coil]
2 and 4, the sensor 3 of the metallic foreign matter detection device 1 is composed of two sensor coils 31 of the same structure. The sensor coils 31 are arranged above and below with the sliding surface 20 in between. The object to be inspected 2 passes through the space between the two sensor coils 31 arranged opposite each other. The upper and lower sensor coils 31 are arranged opposite each other at the upper limit with the sliding surface 20 in between. The sensor coils 31 are arranged perpendicular to the transport direction of the object to be inspected 2 and parallel to the sliding surface 20.

Figure 4 illustrates the structure of the sensor coil 31. Figure 4(a) is a front view of the sensor coil 31, Figure 4(b) is a plan view of the sensor coil 31 in Figure 4(a), and Figure 4(c) is a cross-sectional view taken along line A-A in Figure 4(a). The upper and lower sensor coils 31 have an elongated shape as shown in Figure 4(a) and are basically identical. In this example, the sensor coil 31 has a elongated rod shape with a rectangular cross section.

The sensor coil 31 is made of an elongated iron core 35 made of conductive material with an E-shaped cross section, and a coil 36 wound around the groove. The iron core 35 is made by laminating plates such as silicon steel and amorphous steel. A ferrite core, permanent magnet, etc. may also be used for the iron core 35. When an AC power source is applied to the sensor coil 31, an alternating magnetic field is generated from the sensor coil 31 in the surrounding area.

When a magnetic body passes through this alternating magnetic field, the magnetic field is disturbed by the magnetic field of the magnetic body, affecting the sensor coil 31 and causing the current flowing through the sensor coil 31 to change. The sensor coil 31 of the present invention can detect metallic foreign bodies of 1 mm or more, but is also used primarily to detect minute metal objects of 1 mm or less. The side view of Figure 2 shows an example of the arrangement of the sensor 3.

The two sensor coils 31 of the sensor 3 are arranged with the coils 36 of the E-shaped iron core 35 facing each other. This configuration is used in order to detect the upper and lower parts of the object 2 with good sensitivity. Furthermore, by providing two sensor coils 31, the object 2 to be inspected is detected as it moves through the hollow space between them, and magnetic bodies are detected with good sensitivity. Metal foreign bodies in the object 2 to be inspected can be detected with just one of the sensor coils.

The sensor coil 31 detects metal objects by utilizing the nonlinear portion of the magnetization (B-H) characteristics of the coil 36, where the magnetic flux density (B) and magnetic field (H) that represent the magnetization characteristics are minute values near 0. The technical ideas regarding this magnetization characteristic and how it is utilized are described in detail in Patent Document 1, so only the gist of the description will be given here. All or part of the invention described in Patent Document 1 has substantially the same structure and circuitry as the present invention, and these constitute the present invention.

However, the voltage, current, and frequency applied to the sensor coil 31 may all or partly have values different from those in Patent Document 1 in the embodiment of the present invention. The sensor coil 31 can detect metallic foreign matter on a magnetic body even if no current or voltage is specifically supplied to it. For example, the bias voltage of the amplifier is applied to the sensor coil 31. This causes the input bias current of the amplifier to flow through the coil of the sensor coil 31.

When the magnetic flux that crosses the sensor coil 31 changes in response to changes in the surrounding magnetic field, the current and/or voltage flowing through the sensor coil 31 changes, resulting in an output signal. When an AC power source of several kHz is applied to the sensor coil 31, an alternating magnetic field is generated in the sensor coil 31. When a tiny piece of stainless steel approaches the sensor coil 31, the static magnetic field magnetizes the tiny piece of stainless steel, generating a magnetic pole.

For example, when austenitic stainless steel (such as SUS304) undergoes plastic deformation such as breaking, crushing, bending, or chipping, martensite-induced transformation occurs, and the weakly magnetic parts are magnetized by the static magnetic field, generating magnetic poles. This change in magnetic poles affects the alternating magnetic field, which is detected by a detection circuit including the sensor coil 31. In particular, the closer the test object 2 is to the sensor coil 31, the greater this effect becomes, so the sensor coil 31 can reliably detect tiny metallic foreign bodies in the test object 2.

Magnetic materials that may be mixed in as foreign matter in the object to be inspected 2 include ferromagnetic materials such as iron, nickel, and cobalt, alloys of these materials, martensitic stainless steel, and the like. When a pair of sensor coils 31 are arranged on two sides of a bridge circuit, when a constant AC voltage is applied, the current flowing through the bridge circuit made up of the sensor coils 31 does not change, and the output current of the bridge circuit is constant. When a magnetic material passes near the sensor coils 31, the form of the alternating magnetic field is disturbed, and the output current of the bridge circuit changes. This output current is processed in the downstream signal processing unit 16 and detected as a foreign matter in the object to be inspected 2.

[Magnet Booster]
2, the magnetization unit 4 is made up of two magnet boosters 41 installed above and below the sliding surface 20, and two housings 43 housing the two magnet boosters 41. Both sides of the two housings 43 are fixed to a support plate 34 fixed to the slide 5. The magnet boosters 41 are for magnetizing or strengthening the magnetization of the magnetic material in the object 2 to be inspected, and are made up of permanent magnets.

The installation position of the magnetization unit 4 consisting of the magnet booster 41 is not limited to this position. The magnet booster 41 can be composed of one permanent magnet or two or more permanent magnets, but in this example, it is composed of multiple permanent magnets. The magnet booster 41 is placed perpendicular to the transport direction of the inspection object 2. In other words, two elongated magnet boosters 41 are placed in the cross-sectional direction of the inspection object 2.

The magnet booster 41 is arranged so that its longitudinal axis is perpendicular to the transport direction of the object 2 to be inspected. The magnet booster 41 is arranged parallel to the sliding surface 20. The two magnet boosters 41 are composed of multiple magnet elements. The magnet elements of the upper and lower magnet boosters 41 are arranged above and below facing each other, with the same magnetic poles facing each other, in other words, the same magnetic poles facing the object 2 to be inspected.

When arranged in this manner, metallic foreign matter in the test object 2 is magnetized by the repulsive force of the same magnetic poles of the magnet elements arranged opposite each other above and below. In this example, the magnet booster 41 is composed of multiple magnet elements made of neodymium magnets. By using strong magnets such as neodymium magnets in this manner, the range in which the magnetic field of the permanent magnet affects the magnetic material can be greatly expanded, improving the detection sensitivity of the sensor 3.

[Slide 5]
The upper surface of the slide 5 is the slide surface 20. A part (upper stage) of the slide surface 20 is a small roller conveyor 23 (see FIG. 5), so that a power source such as a motor is not required. When the test object 2 is placed on the upper end of the slide surface 20, the test object 2 is subjected to a downward force due to gravity acting on its own weight, and is transported while sliding on the slide surface 20 by itself. The roller conveyor 23 may be composed of a single roller conveyor as a whole, or may be composed of a plurality of small roller conveyors lined up. In the example shown in FIG. 1 and FIG. 3, the roller conveyor 23 is composed of six rows (in the falling direction) of small roller conveyors lined up.

Figure 5 shows an example of a cross-sectional view of a roller conveyor 23. As shown in Figure 5, the roller conveyor 23 is composed of a frame 24 that supports the entire conveyor, rollers 25 mounted on the frame 24, etc. The frame 24 may have a connecting plate (not shown) for connecting and fixing adjacent frames 24. When the sliding surface 20 is composed of multiple roller conveyors 23, the frames 24 are connected and fixed to each other by a connecting plate, a screw mechanism, etc.

The roller 25 is supported at a specific, minute distance from the bottom of the frame 24 and rotates freely. The roller 25 has a long, thin rod shape with a circular cross section and has a through hole along its longitudinal axis. As shown in Figure 5, the shaft 26 is inserted into this through hole 25a. Both ends of the shaft 26 are inserted into holes in the frame 24. The roller 25 rotates freely around the shaft 26.

The slide 5 has a connecting member 15 whose one end (the left side in FIG. 1) is connected to the main body 6. The connecting member 15 has a plate-like member fixed to the top surface of the housing 11, and is detachably fixed to the slide 5 with a knob bolt 15a or the like. The other end (the right side in FIG. 1) of the slide 5 is adjustable so that it can be moved a predetermined distance up from the main body 6 by the angle adjustment member 7. This allows the inclination angle (θ angle shown in FIG. 2) of the slide 5 (slide surface 20) to be adjusted.

In this example, as shown in Figs. 1 and 2, the angle adjustment member 7 is composed of an elongated plate-shaped stay 7a, a plate-shaped stay holder 7b with a stepped elongated hole 7c, and the like. One end (upper part) of the stay 7a is fixed to the side of the housing 21 of the slide 5 with a bolt and nut mechanism 37. The other end (lower part) of the stay 7a is fixed to the stay holder 7b with a bolt and nut mechanism 38. One end (lower part) of the stay holder 7b is fixed to the upper surface of the main body 6 with a fixing means such as a bolt. The stay holder 7b has a stepped elongated hole (slit) 7c from the slide 5 side to the main body 6 side, and the shaft part of the knob bolt of the bolt and nut mechanism 38 enters this hole 7c so that it can be sliced up and down.

The hole 7c is provided with multiple recesses for step adjustment to adjust the inclination angle in stages. In this example, the hole 7c is provided with three recesses for step adjustment, recesses 7d, 7e, and 7f. The shaft of the knob bolt of the bolt-nut mechanism 38 slides through the hole 7c and is positioned at one of the recesses 7d, 7e, or 7f. The bolt-nut mechanism 38 is tightened at each of these positions to fix the stay 7a and the stay holder 7b.

In other words, the worker holds one end of the slide 5 (the right end of the slide 5 in Figs. 1 and 2) and lifts it, fastening the shaft of the knob bolt of the bolt-nut mechanism 38 in the recesses 7d, 7e, and 7f at the specified angle, and then turns and tightens the head of the knob bolt. The bolt-nut mechanism 38 is a fixing mechanism for adjusting the angle of the slide 5, and any fixing mechanism that achieves a similar function can be used. Figs. 1 and 2 show an example of the installation position when the slide 5 is installed on the main body 6 so as to have an inclination angle θ (see Fig. 2).

In this example, the inclination angle θ can be adjusted in multiple stages by adjusting the positions of the recesses 7d, 7e, and 7f of the hole 7d. In this example, the positions of the recesses 7d, 7e, and 7f correspond to inclination angles of 25 degrees, 20 degrees, and 15 degrees. The inclination angle is proportional to the conveying speed of the object 2 to be inspected, and the larger the inclination angle, the faster the conveying speed. Switching the inclination angle can also be considered as switching the conveying speed. The slip coefficient, or in other words the friction coefficient, differs depending on the object 2 to be inspected and the material of its packaging, etc., and the conveying speed differs.

Therefore, the inclination angle is adjusted to obtain an appropriate transport speed for the object 2 to be inspected. The inclination angle (transport speed) of the slide 5 can be freely adjusted. The rollers 25 of the slide surface 20 are made of a non-magnetic material such as synthetic resin or stainless steel plate. The metallic foreign matter detection device 1 of the present invention is small enough to be used on a table. In this example, although not limited to this, the metallic foreign matter detection device 1 has a length (machine length) of 666 mm, a width of 280 mm, and a height of 476 mm (inclination angle 25°).

The distance from the housing 33 that houses the sensor coil 31 to the sliding surface 20 is 76 mm. This distance is the height (size) of the object 2 to be inspected at which the object 2 can pass through the sensor 3. Therefore, the sensor 3 has an effective detection width of 216 mm and a standard passing height (maximum distance between the upper sensor coil 31 and the sliding surface 20) of 76 mm. By making the metal foreign matter detection device 1 into these dimensions, it becomes a small device that can be placed on a general-purpose desk or other stand.

The falling speed varies depending on the surface properties of the slide 5 and the type and properties (mass, material, liquid/solid state, etc.) of the test object 2. The packaging of the test object 2 is made of various materials such as metals such as aluminum, paper, vinyl, plastic, and other synthetic materials, and in some cases the surface is treated with paint, etc. For this reason, even with the same inclination angle and slide 20, the falling speed varies depending on the surface material of the test object 2 and its contents, etc.

The material of the rollers 25 of the roller conveyor 23 and the sliding surface 22 can be any material such as metal, wood, synthetic resin, etc., and is selected appropriately depending on the type of the object 2 to be inspected. For example, the rollers 25 of the roller conveyor 23 are made of a resin such as polyacetal, and the frame 24 is made of a resin such as polystyrene. The sliding surface 22 is made of a flat plate made of, for example, polyethylene.

The falling speed basically depends on the coefficient of friction where the sliding surface 20 and the object to be inspected 2 come into contact. In other words, it depends on the material and surface layer of both. The sliding surface 20 determines the falling speed, which is determined by rolling friction in the case of a roller and sliding friction in the case of a corrugated sheet. In the metal foreign matter detection device 1, it is desirable for the object to be inspected 2 to fall at as uniform a speed as possible, and for this reason the inclination angle of the slide 5 is freely adjustable. The sliding surface 20 can also be freely replaced to suit the properties of the object to be inspected 2.

As described above, the slide 5 has been described using the roller conveyor 23 as an example, but the roller conveyor 23 can be replaced to match the detection of the object to be inspected 2. The slide 5 is detachably fixed to the main body 6 by the connecting member 15, so the entire slide 5 can be replaced by removing this connecting member 15. Rather than replacing the entire slide 5 that is prepared in advance for each object to be inspected, it is better to divide the slide 5 into two parts, an upper part and a lower part, and select only one of the slide surfaces, or the optimum surface such as a roller. In this way, the sliding surface 20 of the slide 5 can be replaced and adjusted to suit the type and properties of the object to be inspected 2.

The rollers 25 are often made of materials such as synthetic resin and metal, and the coefficient of friction varies depending on the surface treatment of the synthetic resin or metal. This difference in friction coefficient makes it possible to adjust the falling speed of the test object 2. In the above example, the sliding surface 20 is a small roller conveyor 23, but it can be replaced with a roller conveyor 23 having rollers 25 of different sizes. In addition, the sliding surface 20 can be replaced with a roller conveyor 23 having rollers 25 with different coefficients of friction.

Furthermore, the sliding surface 20 can be made of a flat or corrugated plate. The roller 25 can be replaced with a sliding surface made of a corrugated plate, and the flat or corrugated plate can be fixed to the frame 24. Alternatively, the entire frame 24 and roller conveyor 23 can be replaced with a flat or corrugated plate. In this way, the sliding surface 20 is removable and can be made to suit the type and properties of the object to be inspected.

[Inclination angle of slide 5]
Fig. 6 shows a conceptual diagram for analyzing the movement of the inspection object 2 when it moves on the conveying surface 20 in the metal foreign matter detection device 1 of this embodiment. With reference to this conceptual diagram, an analysis of the adjustment of the inclination angle θ of the sliding surface 20 when the inspection object 2 slides on the slide 5 (roller slide) will be shown. Fig. 6 shows the top surface 6a of the main body 6 arranged horizontally, the sliding surface 20 installed on this top surface 6a at an inclination angle θ, the sliding surface 22 that constitutes the sliding surface 20, and the roller conveyor 23. Below, the analysis will be performed by taking the x-axis along the sliding surface 20 and the y-axis perpendicular to the x-axis (sliding surface 20).

The sliding speeds of the object to be inspected 2 at positions _x1 , _x2 , and _x3 are _V1 , _V2 , and _V3 . Therefore, the position where the object to be inspected 2 is placed on the roller conveyor 23 is _V1 = 0, the speed at which it enters the sliding surface 22 is _V2 , and the speed at which it passes the sensor 3 is _V3 . The position where the object to be inspected 2 is placed on the roller conveyor 23 of the sliding surface 20 is _x1 , the upper end position of the sliding surface 22 is _x2 , and the position of the object to be inspected 2 after it has passed the sensor 3 is _x3 . In addition, the distance that the object to be inspected 2 slides on the roller conveyor 23 is _S1 , and the distance that it slides on the sliding surface 22 is _S2 .

[Sliding of the inspection object 2 on the roller conveyor 23]
When the test object 2 slides along the x-axis of the inclined surface, the following equation holds in the inclined surface direction (x-axis direction).
mα=mg・sinθ−F...(1)
Here, m is the mass of the test object, α is the acceleration in the x-axis direction, θ is the inclination angle of the conveying surface of the test object, g is the acceleration of gravity, μ is the static friction coefficient of the test object, and F is the back force.
Moreover, in the direction perpendicular to the inclined surface (y-axis direction), the following equation holds:
m・β=N−mg・cosθ...(2)
Here, β is the acceleration in the y-axis direction, and N is the normal force to the test object.

When the detected object 2 is not slipping and is in a stationary state, the acceleration α=β=0, and the following relationship is obtained from the above (1) and (2).
F=mg・sinθ...(1')
N=mg・cosθ...(2')
Conditions for the detected object 2 to start rolling (moving):
F>μN
∴ mg・sinθ＞μ・mg・cosθ
Therefore, the test object 2 starts to roll from the rest position (x ₁ ) under the following conditions.
tanθ＞μ ⇒ θ＞tan ^-1 μ

[Sliding speed of the test object 2]
The work _Wm done by gravity when the test object 2 with mass m slides over a moving distance _S1 in the x-axis direction is given by:
W _m = directional component of gravity x distance traveled S ₁
W _m = mg・sinθ・S ₁ ... (3)

According to the law of conservation of energy, the following formula is established, provided that the height from which the test object 2 is dropped is h ₁ (=S ₁ ·sin θ) and the kinetic friction of the sliding surface 23 is μ ₁ .
1/2 mV ₂ ² - 1/2 mV ₁ ² = (work done by gravity W _m ) + (work done by friction W)
= mg・h ₁ − μ ₁ mg・cosθ・S ₁ ... (4)
∴1/2mV ₂ ² -1/2mV ₁ ² -mg・h ₁ = -μ ₁ mg・cosθ・S ₁ ... (5)

The velocity _V2 of the test object 2 at the end of the sliding surface 23 is given by:
Since h ₁ = S ₁ · sin α, from equation (4), 1/2 mV ₂ ² - 1/2 mV ₁ ² = mg · S ₁ · sin θ - μ ₁ mg · cos θ · S ₁
1/2V ₂ ² -1/2V ₁ ² = g・S ₁・sinθ−μ ₁ g・cosθ・S ₁
V ₂ ² - _{V 1} ² = 2g・S ₁ (sin θ - μ ₁ cos θ)
V ₂ = SQRT(V ₁ ² +2g・S ₁ (sinθ−μ ₁ cosθ)) ...(6)
Here, SQRT( ) is the square root.

Since the test object 2 is placed on the sliding surface 20 (slide 5) by human movement or the like during the test, V ₁ =0, and the sliding speed V ₂ is given as follows.
V ₂ = SQRT (2g・S ₁ (sin θ - μ ₁ cos θ)) ... (7)

[Sliding speed of the test object 2 on the slide 5]
As described above, the object 2 to be inspected is accelerated to a sliding speed _V2 in the section of distance _S1 on the roller conveyor 23 of the sliding surface 20, and falls to the entrance of the sliding surface 22, which is a sensing area where there are no rollers. Metallic foreign matter is detected in the object 2 to be inspected by the sensor 3 (sensor coil 31 arranged above and below the sliding surface 20), but due to the characteristics of the sensor 3 (sensor coil 31), it is preferable to drop the object 2 at a predetermined constant speed.

The relationship between the speed _V2 when entering the area of the slideway 22 from the area of the roller conveyor 23, the moving distance _S2 on the slideway 22, and the speed _V3 when the dynamic friction coefficient of the slideway 22 is _μ2 is given by the above equation (6) as follows.
V ₃ = SQRT(V ₂ ² +2g・S ₂ (sinθ−μ ₂ cosθ)) ... (8)
That is, it is better to set the approach speed _V2 from the area of the roller conveyor 23 to an optimum speed that matches the characteristics of the sensor 3, and to let it fall at a constant speed ( _V2 ) without accelerating. Overall, there is no waste in the measurement time.

Therefore, in order to make the constant speed _V3 and the intrusion speed _V2 of the inspection object 2 equal to _V3 = _V2 ,
sinθ-μ ₂ cosθ=0
Therefore, the following formula is obtained.
μ ₂ = sinθ/cosθ=tanθ...(9)
That is, from this formula (9), it is preferable to adjust the dynamic friction coefficient _μ2 of the sliding surface 22 and the inclination angle θ of the conveyor table of the inspection object 2 to match tan θ. In this manner, the inclination angle θ of the sliding surface 20 is determined.

[First adjustment: inclination angle θ of slide 5]
As described above, in the section sensed by the sensor 3, the object 2 needs to be moved at a constant speed due to the characteristics of the sensor 3 in order to prevent erroneous detection. In the section where the magnetic metal foreign body in the object 2 is magnetized, the object does not need to be moved at a constant speed because there is no effect on magnetization. On the other hand, depending on the type, material, condition of the sliding surface, etc. of the object 2, the object may not slide smoothly on the sliding surface 20.

That is, contrary to theory, the sliding speed of the test object 2 varies depending on the mass, and bags with water inside are difficult to slide. This leads to a delay in the test time. Therefore, first, the inclination angle θ of the sliding surface 20 is determined (first adjustment) by adjusting the inclination angle according to the type, material, and condition of the sliding surface of the test object 2, taking into account the friction coefficient (μ ₂ ) of the sliding surface 20 from the above formula (9), so that the constant speed (V ₃ ) of the allowable error is obtained (first adjustment).

[Roller slide angle adjustment function]
The inspection object 2 slides and accelerates (α) on the sliding surface of the roller conveyor 23 with low friction (μ ₁ ) inclined at the inclination angle θ set in the above-mentioned first adjustment procedure to an approach speed (V ₂ ). If this approach speed (V ₂ ) is within the error of the constant speed (V ₃ ) set in the above (1), the adjustment of the sliding surface is now complete.

However, if the penetration speed ( _V2 ) is too fast or slow at the angle θ determined in the above step (1), the type of roller conveyor 23 (rollers 25) is replaced, or the angle of only the roller conveyor 23 is adjusted (fine adjustment mechanism).As described above in detail, the present invention is a slide surface 20 (slide surface or slide platform of the inspected object 2) that can be detected at a speed that shortens the inspection time and increases the detection accuracy.

The metal foreign matter detection device 1 of the present invention uses, as an example of a roller conveyor 23, one with a nominal width of 100 mm and a length of 329.4 mm. In addition, multiple roller conveyors 23 with different friction coefficients are prepared as spares and are replaced to match the product. The sliding surface 22 can also be replaced with a roller conveyor. In other words, if the sliding surface 22 is made of rollers, vibrations will be generated by the sliding of the inspected object 2, accelerating the conveying speed, but this is used when it is within an acceptable range.

The roller conveyor 23 has an angle fine adjustment function that adjusts the roller surface, particularly the upper part, up and down using a screw mechanism or the like. The angle fine adjustment function is used particularly when it is essential that the sliding speed of the inspected object 2 be constant (within the tolerance) in the section passing the sensor 3. Since the friction coefficient changes when the inspected object 2 changes slightly depending on the material, weight, etc. of the packaging of the inspected object 2, the angle fine adjustment function is used to adjust the speed to be constant.

[Example of configuration of signal processing unit 16]
The signal processing unit 16 is composed of an amplifier/filter circuit, a waveform processing unit, a digital computer processing unit, a signal output unit, etc. The sensor coil 31 of the sensor 3 is connected to the amplifier/filter circuit. The signal output from the sensor coil 31 is amplified by the amplifier/filter circuit and output to the waveform processing unit. The waveform processing unit shapes the waveform of the input signal, converts it into a digital signal, adjusts the receiving sensitivity, and outputs it to the digital computer processing unit.

At this time, the signal converted into a digital signal is subjected to threshold processing and the receiving sensitivity is adjusted. The digital computer processing unit receives the digital signal from the waveform processing unit, processes the signal, and determines whether or not a magnetic body is contained in the object to be inspected 2. If the digital computer processing unit determines that a magnetic body has been detected, it outputs an output signal to the signal output unit. The sensor coil 31 is directly connected to the electronic circuit of the amplification/filter circuit. A bias voltage is applied to the sensor coil 31 by a DC bias circuit to operate the amplifier of the amplification/filter circuit.

This excites the sensor coil 31, and the magnetic flux of the static magnetic field from the magnet booster 41 constantly interlinks with the sensor coil 31. Fluctuations in the bias voltage applied to the sensor coil 31, disturbances in the external magnetic field, etc., cause weak DC fluctuating currents to constantly flow through the coil. In other words, AC currents at the commercial power frequency, AC currents at multiples of that frequency, and AC currents at frequencies superimposed with the external environmental magnetic field flow, albeit very small.

When the object 2 to be inspected is transported near the sensor coil 31 in this excited state, the magnetic metal foreign matter contained in the object 2 is magnetized by the magnet booster 41 into a magnetic dipole (a pair of small magnets with a north and south pole). The sensor coil 31 then outputs a minute foreign matter signal due to this magnetic metal foreign matter. More specifically, a weak induced voltage as explained by Lenz's law is generated in the sensor coil. The foreign matter signal is amplified by an amplifier/filter circuit (gain amplifier) and output to the waveform processing section and digital computer processing section.

The amplifier/filter circuit amplifies the output of the sensor coil 31 by several tens to several hundreds of dB, and in some cases by more than a thousand dB. In this example, the output is amplified by about 120 dB. The digital computer processing unit is a signal processing unit consisting of an electronic computer equipped with a bus, memory, central processing unit (CPU), input interface, output interface, etc. The memory, CPU, input interface, and output interface are connected to each other by a bus 70, and transmit and receive data via this bus.

The digital computer processing unit executes a program stored in memory using the CPU, and judges whether there is a metallic foreign object in the inspection object 2. The digital computer processing unit can also be realized by a circuit means consisting of an analog circuit or a digital circuit having the same function, but a detailed description of this will be omitted here. The digital computer processing unit can have input devices such as a mouse, keyboard, touch panel, etc., which are not shown.

These input devices are connected to the input interface and are operated by an administrator of the metallic foreign matter detection device 1 to use them to initialize and configure the metallic foreign matter detection device 1. The calculation program is stored in memory. The calculation program is stored in the ROM of the memory, an auxiliary storage device, etc. The digital computer processing unit determines whether or not there is a magnetic material (metallic foreign matter) in the detected object 2.

The detection signal of sensor 3 is received from the digital computer processing unit and waveform processing unit, and the detection signal is subjected to waveform analysis and compared with standard data (comparison waveform) to determine whether or not the detection signal is a detection signal that indicates a metal structure. Metal structures contained in the object to be inspected 2 are uniform in size and material, and therefore the waveform of the detection signal is basically the same pattern for each type of metal structure. The standard data that serves as the basis for the foreign object signal waveform is compared with the detection signal output by sensor 3, and a metallic foreign object is identified based on the degree to which the standard data and the detection signal are similar.

Second Embodiment
A second embodiment of the present invention will be described with reference to the drawings. The metallic foreign matter detection device 1 of the second embodiment of the present invention has the same basic structure and function as the metallic foreign matter detection device 1 of the first embodiment described above, and differences will be described here. The metallic foreign matter detection device 1 of the second embodiment of the present invention is provided with an angle fine adjustment means, which will be described with reference to Figures 7 and 8.

Figure 7 shows an overview of the metallic foreign matter detection device 1 equipped with the fine angle adjustment means, but the sensor 4, magnetization unit 4, and detector 8 are not shown. Figure 8 is a side view of the metallic foreign matter detection device 1, viewed from the direction of arrow A shown in Figure 7. The fine angle adjustment means comprises an angle adjustment guide 50, a fixing bolt 51, etc. One angle adjustment guide 50 is provided on each side of the roller conveyor 23. The angle adjustment guide 50 is a guide that is wedge-shaped in the longitudinal direction and has an L-shaped cross section. The angle adjustment guides 50 are installed on both sides of the roller conveyor 23 and are fixed to the housing 21 of the slide 5.

Specifically, the angle adjustment guide 50 is installed on the guides 23a (see FIG. 1) on both sides of the roller conveyor 23 or on the outside of the frame 24 (see FIG. 5) of the roller conveyor 23, with the L-shaped portion in contact with both sides and the bottom of the roller conveyor 23. The fixing bolt 51 is installed in a hole provided so as to penetrate the angle adjustment guide 50 from top to bottom. The fixing bolt 51 passes through the angle adjustment guide 50 and is screwed into a bolt receiver provided in the housing 21 of the slide 5 itself, or a bolt receiver 52 installed inside or outside the housing 21 of the slide 5, and is fixed.

A swing shaft is provided at the contact point between the slide surface 22 and the roller conveyor 23 for the angle fine adjustment mechanism. This makes it possible to maintain a predetermined distance between the contact point between the slide surface 22 and the roller conveyor 23 regardless of the inclination angle of the roller conveyor 23. It also makes it easy to lift the top of the roller conveyor 23 and install the angle adjustment guide 50.

Fixing bolts 51 can be provided as necessary to fix the angle adjustment guide 50. In this example, two are provided at the top and two at the middle of the angle adjustment guide 50. As shown in FIG. 8, there is a space between the two angle adjustment guides 50, between the roller conveyor 23 and the housing 21, but the two angle adjustment guides 50 can be continuous and form a single plate-like angle adjustment guide 50.

The inclination angle of the roller conveyor 23 is adjusted by changing the angle (thickness) of the angle adjustment guide 50. In addition, multiple types of angle adjustment guides 50 with different angles are prepared in advance and can be replaced as necessary depending on the type of object 2 to be inspected, allowing fine adjustment of the angle.

As mentioned above, the angle adjustment guide 50 is wedge-shaped, but in addition to this mechanism, the angle fine mechanism can also use a screw mechanism in which a bolt is screwed into the frame 24 of the roller conveyor 23, etc., and the tip of the bolt comes into contact with the housing 21 to move the roller conveyor up and down.

The present invention can be used to detect metallic foreign bodies in the fields of manufacturing and service of pharmaceuticals, cosmetics, and food products, where products are filled into packaging such as packaging bags, and in the service field where such products are sold.

LIST OF SYMBOLS 1...Metal foreign matter detection device 2...Inspected object 3...Sensor 4...Magnetized portion 5...Slide 6...Main body 7...Angle adjustment member 7a...Stay (of angle adjustment member 7) 7b...Stay holder (of angle adjustment member 7) 7d, 7e, 7f...Recess (of stay holder 7b) 8...Detector 11...Housing (of main body 6) 12...Power switch 13...Display 14...Operation switch 15...Connecting member 16...Signal processing unit 20...Slide surface 21...Housing (of slide 5) 22...Slide surface 23...Roller conveyor 24...Frame 25...Roller 26...Axis 31...Sensor coil 32...Hole (for fixing sensor 3)
33: Housing (of sensor 3) 34: Support plate 35: Iron core 36: Coil 37, 38: Bolt and nut mechanism 41: Magnet booster 42: Hole (for fixing magnetized portion 4)
43: Housing (of magnetization unit 4) 50: Angle adjustment guide 51: Fixing bolt 52: Oscillation shaft

Claims (3)

a conveying means for conveying the object to be inspected on an inclined surface serving as a conveying path by utilizing the gravity of the mass of the object to be inspected itself;
a magnetizing means for magnetizing or enhancing magnetization of the magnetic body that is a metallic foreign body in the object to be inspected and provided in the middle of the transport path;
a sensor means provided in the middle of the transport path and disposed below the magnetizing means, the sensor means detecting the magnetic body in the passing test object and outputting a detection signal;
a signal processing unit that receives the detection signal, processes the detection signal, determines whether the magnetic body is present, and outputs an output signal that indicates the result of the determination,
The conveying means is
a first transport path located at an upper portion of the inclined surface, along which the object to be inspected slides while being accelerated;
a second transport path that is located below the first transport path and forms the inclined surface that is continuous with the first transport path ,
the first transport path and the second transport path are detachably replaceable with transport paths having different friction coefficients in order to change the speed at which the test object slides down the inclined surface ;
a first conveying path including an angle fine adjustment means for finely adjusting an inclination angle of the inclined surface, 2. The metallic foreign matter detection device according to claim 1 ,
a detector for detecting a timing at which the object passes through said sensor means, said detector being installed adjacent to said sensor means between said sensor means and said magnetizing means, said detector detecting both the timing at which the object starts to pass and the timing at which it finishes passing and transmitting the detected timings to said signal processing unit. 3. The metallic foreign matter detection device according to claim 1,
The metallic foreign matter detecting device according to claim 1, wherein the first transport path is a roller conveyor.

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