Metal detector

Abstract

To provide a metal detector for eliminating or at least moderating well-known defects.SOLUTION: In a metal detector (1) having at least one transmission coil (7) and at least one of reception coils (8, 13, 14), the transmission coil (7) and the reception coils (8, 13, 14) are disposed within a housing (6), the housing (6) is partially filled with a first filler (15), the transmission coil (7) and the reception coils (8, 13, 14) are connected with a measuring device, a product (11) is conveyed while passing through the metal detector (1), the housing (6) is partially filled with at least one kind of second filler (16), and a material composition and / or a chemical composition and / or a dimension and / or density of the second filler (16) differs from that of the first filler (15).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] A metal detector and method for manufacturing a metal detector, the metal detector having at least one transmitting coil and at least one receiving coil, the transmitting coil and receiving coil disposed within a housing, the housing being at least partially filled with at least one first filling material, the transmitting coil and receiving coil connected to a measurement device, and a product being conveyed past the metal detector. [Background technology]

[0002] Metal detectors of the kind considered here are used in particular for product control, for example in food production, to check individual products or more or less continuous product flows for metal contaminants, which may be metal pieces or particles, wires, screws or nuts, tools or other foreign objects.

[0003] In a metal detector, a magnetic field is generated which is disturbed by metal particles and this disturbance, the convergence or suppression of the magnetic field lines depending on the material of the contaminant, can be detected and evaluated.

[0004] In a typical application, the product is conveyed on a conveyor belt or similar conveying device past a metal detector, which includes three or more coils that surround the conveyor belt and the product being conveyed thereon.

[0005] A high-frequency alternating current is applied to one of the coils, which generates a magnetic field at the location of the product flow and therefore acts as a transmitting coil. The other two coils are used as receiving coils, i.e. a current is induced in them according to the generated magnetic field. In this case, the receiving coils are connected in series in opposite directions with respect to the winding direction, so that when the magnetic field is not disturbed, the resultant voltage is zero. If the magnetic field is disturbed, especially by a metallic foreign object, a different output voltage than zero results. For example, DE 19530987 discloses a corresponding metal detector.

[0006] Due to the use of metal detectors in industrial environments, the metal detectors are subject to mechanical shocks, which can change the mutual positions of the transmitting coil and / or the receiving coil or the position of the transmitting coil and / or the receiving coil relative to the housing. This can lead to the receiving coil detecting measurement signals that can result in being erroneously evaluated as metal signals. For example, corresponding mechanical shocks can be caused by conveyor belts. Furthermore, temperature fluctuations frequently occur in industrial environments, which have a negative effect on the mutual positions of the transmitting coil and / or the receiving coil or the position of the transmitting coil and / or the receiving coil relative to the housing.

[0007] In order to reduce the adverse effects, which may be vibrations, temperature variations or other mechanical shocks acting from the outside, the corresponding spaces between the housing and the transmitting and receiving coils are filled by a sealing system, which consists of cast resin, concrete, polymer concrete or quartz sand mixture. High strength of the sealing system as well as good adhesion with metal materials are important.

[0008] Such systems often have a high specific gravity and, depending on the strength to be achieved, require reinforcement of the housing for the filling process. In some, foamed epoxy resins are used, which fill most of the space to be filled with air and the other part with structural structure, thus fixing the former with a somewhat lighter weight. However, these systems have the drawback that the final network achieved of the epoxy resin system is non-uniform and weak, which has a negative effect on the strength of the system. Summary of the Invention [Problem to be solved by the invention]

[0009] SUMMARY OF THE DISCLOSURE It is therefore an object of the present invention to provide a metal detector which overcomes or at least mitigates the disadvantages known from the prior art. [Means for solving the problem]

[0010] This object is achieved in a metal detector as mentioned at the beginning, in that the housing is at least partially filled with at least one second filler material, the material composition and / or the dimensions and / or the density of the second filler material being different from the first filler material. In particular, the first filler material is a resin, in particular an epoxy resin, mixed with a hardener, whereby after hardening the resin becomes a thermosetting plastic. Additionally, the resin is mixed with aluminum powder, whereby the heat conductivity, impact resistance and pressure stability of the resin can be improved. Furthermore, a foaming agent can be mixed into the resin in order to introduce mechanical stresses and increase the volume of the hardened resin. This can affect both the weight and the strength of the filler material mixture.

[0011] In one alternative embodiment, the second filler is a hollow body, the second filler having, in particular, a spherical geometric shape. In particular, the second filler has a smooth surface, the average roughness value of the surface being between 0.2 μm and 25 μm, preferably between 0.6 μm and 3.2 μm, particularly preferably between 0.8 μm and 3.2 μm. This allows the first filler to flow unhindered along the surface of the second filler and to be evenly distributed inside the housing.

[0012] In one alternative embodiment, the diameter of the second filler is between 10 mm and 80 mm, preferably between 20 mm and 60 mm, particularly preferably between 30 mm and 50 mm. In particular, the second filler fills the interior space of the housing by at least 10%, at most 90%, preferably at most 85%, particularly preferably at least 75%. In particular, the second filler fills the interior space of the housing by at least 20%, preferably at least 35%, particularly preferably at least 50%. This can affect both the weight and the strength of the filler mixture.

[0013] In one alternative configuration, a second filler material consisting of at least two repeated layers is arranged in the interior space of the housing, the at least two layers being arranged one above the other and being interdigitated with each other, whereby the second filler material is surrounded by up to 12 other second filler materials. Between the two second filler materials arranged adjacent to each other and / or arranged one above the other, there is a gap or intermediate space, which at least partially extends around the circumference of the second filler material.

[0014] In one alternative configuration, the second filler is 0.01 g / cm 3 From 8g / cm 3 In particular, the second filler is made of a plastic, in particular a thermoplastic. Furthermore, the second filler has a density of 2H / m or less. of μ rIn this case, the second filler is dust-free in bulk. This means that when the second filler is introduced into the interior space of the housing, the second filler does not have any components that can remain suspended in the gas for any period of time. In other words, the bulk of the second filler does not have any components with a diameter smaller than 0.5 mm.

[0015] In one alternative configuration, the first filler at least partially, preferably completely, surrounds the second filler. This achieves a high strength of the filler mixture consisting of the first and second fillers. This also significantly reduces the weight of the metal detector without adversely affecting the detection accuracy of the metal detector. Advantageously, the second filler, which is formed in the shape of a hollow sphere, is filled with a gas, in particular with air. The hollow sphere has a spherical geometry, which has a predefined wall thickness, and the inside of the hollow sphere is hollow.

[0016] In one alternative configuration, the housing is conductive, thereby shielding the metal detector from electromagnetic interference.

[0017] In one alternative configuration, the housing has a search channel and the products are transported on a conveyor belt through the search channel of the metal detector. In particular, the housing is arranged perpendicular to the conveyor belt. Furthermore, at least one transmitter coil and / or at least one receiver coil are arranged transversely to the conveying direction of the conveyor belt. This ensures that all products pass both the at least one transmitter coil and the at least one receiver coil.

[0018] In one alternative configuration, at least one receiving coil and at least one transmitting coil are wound on a former. In particular, the first and second filling materials are arranged in an interior space of the housing, where the interior space is defined by the housing wall and the former. In particular, the former has at least two grooves for accommodating at least one transmitting coil and at least one receiving coil. The transmitting coil and the receiving coil are arranged in the grooves of the former and are thereby held in position. This further precludes the position of the transmitting coil or the receiving coil from changing relative to the receiving coil or the transmitting coil during manufacture or operation. Furthermore, the transmitting coil and the receiving coil are in particular formed from a winding, respectively.

[0019] In one alternative configuration, the metal detector has at least one second receiving coil, with at least one transmitting coil arranged between the two receiving coils. The two receiving coils are connected in series in opposite directions with respect to their winding directions. Furthermore, the at least one transmitting coil and the at least one receiving coil are arranged in mutually parallel planes. In particular, the transmitting coil and the receiving coil are arranged symmetrically in the housing. The transmitting coil generates a magnetic field that can be received by the two receiving coils and that induces a voltage in the two receiving coils. As long as there is no disturbance of the magnetic field, for example in the form of a metallic foreign object, the voltage appearing at the output terminals of the receiving coil is zero, since the receiving coils are connected in series in mutually opposite winding directions and are arranged symmetrically in the housing. If a metallic foreign object affects the magnetic field, the voltage appearing at the output terminals of the receiving coil is not zero.

[0020] During the manufacture of the metal detector, in which the metal detector consists of a housing, in which at least one transmitting coil and one receiving coil are wound on a former, the housing with the former and the transmitting coil and the receiving coil is prepared, in particular in a pre-assembled state. The second filling material is then introduced into the interior space of the housing, where the interior space is defined by the housing wall and the former. In a subsequent working step, the first filling material is introduced into the interior space of the housing, where the interior space is defined by the housing wall and the former. In particular, the first filling material is a plastic, and the material composition and / or its dimensions and / or its density of the second filling material differ from the first filling material. For this, the second filling material may have a diameter that is between 10 mm and 80 mm. Since the second filling material, in particular having a hollow spherical geometry, has a diameter, there is at least partially an intermediate space around two adjacent second filling materials, which intermediate space is at least partially filled, in particular completely filled, by the first filling material. When the interior space of the housing is completely filled, the first filler material completely surrounds the second filler material.

[0021] After the first filler is introduced into the interior space of the housing, the first filler hardens because a hardening agent has been added to the first filler, which hardening agent has already been mixed into the first filler before the first filler is introduced into the interior space of the housing. Since the first filler pushes out the air present in the interior space, the upper surface of the housing is provided with a degassing opening through which the air and the reaction gas of the first filler can escape. After the first filler hardens and all the air and the reaction gas escape from the interior space of the housing through the degassing opening, the degassing opening is closed. [Brief description of the drawings]

[0022] Further advantageous aspects will become apparent from the following description of preferred embodiments which refers to the accompanying drawings. [Figure 1] 1 shows a schematic diagram of a metal detector. [Diagram 2]2 shows a cross-sectional view of the metal detector along the conveying direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Fig. 1 shows a metal detector 1 with a conveyor belt 2, the upper transmission belt 3 of which runs through a search channel 4 of the metal detector 1 and the lower transmission belt 5 of which runs below the metal detector 1. The metal detector 1 has a housing 6 in which at least one transmitting coil 7 and at least one receiving coil 8 are arranged, the transmitting coil 7 and the receiving coil 8 each being arranged in one plane, the planes extending parallel to each other. The housing 6 is preferably made of metal, in particular special steel.

[0024] FIG. 2 shows a cross-sectional view of the metal detector 1 of FIG. 1. The transmitter coils 7 are arranged between the receiver coils 8. The metal detector 1 further comprises a former 9, which is provided with a groove 10, in particular with at least two grooves 10, preferably with at least three grooves 10. The transmitter coils 7 and the receiver coils 8 extend into the grooves 10. The grooves 10 have a triangular or polygonal cross section. However, the grooves 10 can also have a semicircular cross section. The products 11 are conveyed on the conveyor belt 2 in the conveying direction 12 through the search channel 4. The products 11 are thereby moved past the first receiver coil 13, the transmitter coil 7 and the second receiver coil 14, so that metallic foreign objects present in the products 11 can be reliably detected. For this purpose, the transmitter coil 7 generates a magnetic field at the location of the products 11 or the product flow. Currents are induced in the two receiver coils 8, 13, 14 depending on the generated magnetic field. In this case, the receiving coils 8, 13, 14 are connected in series in opposite directions with respect to the winding direction, so that any disturbance of the magnetic field by a metallic foreign object is detected by the receiving coils 8, 13, 14. If a metallic foreign object is detected in the product 11, the product 11 is immediately removed from the product flow. For this purpose, among other things, a corresponding device, in particular a pusher or a gate, for removing the product 11 or the products 11 can be provided behind the metal detector 1 in the conveying direction 12.

[0025] The housing 6 is disposed perpendicular to the conveyor belt 2, and the transmitter coil 7 and the two receiver coils 8 are disposed in a direction transverse to the conveying direction 12 of the conveyor belt 2. Furthermore, the transmitter coil 7 and the receiver coils 8, 13, 14 extend both above and below the conveyor belt 2.

[0026] A first filler material 15 and a second filler material 16 are arranged in the internal space of the metal detector 1. The first filler material 15 completely surrounds the second filler material 16. When filling the internal space of the housing 6, the second filler material 16 is first injected into the internal space of the housing 6. The first filler material 15 is then injected into the housing, during which the first filler material becomes at least temporarily fluid and flows through intermediate spaces 17 present between two adjacent second filler materials 16. In particular, the first filler material 15 has a viscosity of 1 mPa at 25° C. * s to 5,000 mPa * s. More preferably, the first filling material 15 hardens and becomes solid after a defined time, and is therefore no longer flowable, thereby fixing the positions of the second filling material 16 and the transmitting coil 7 and the receiving coils 8, 13, 14.

[0027] The second filler 16 is arranged next to and / or above one another, the second filler 16 being composed in particular of at least two repeated layers 18, 19 arranged above one another, in particular the first layer 18 and the second layer 19 being arranged so as to interdigitate with one another, whereby the second filler 16 is surrounded by up to twelve further second fillers 16.

[0028] The second filler material 16 is in particular a hollow body, in particular a hollow sphere, which is filled in particular with a gas, in particular with air. For this purpose, the second filler material 16 has a wall thickness of at least 0.1 mm. Furthermore, the diameter of the second filler material between the layers 18, 19 can be variable in order to achieve an optimal degree of filling of the interior space of the housing 6 with the second filler material 16.

[0029] The metal detector 1 does not have to be constructed in the shape of a parallelepiped, but can have a cylindrical shape, in particular a hollow cylindrical shape, and in the case of a hollow cylindrical shape, the metal detector 1 can also be attached to a pipeline. Even in the hollow cylindrical shape, it is possible to fill the inner space of the housing 6 with the first filling material 15 and the second filling material 16. [Explanation of symbols]

[0030] 1. Metal detector 2 Conveyor belt 3 Upper transmission belt 4. Discovery Channel 5 Lower transmission belt 6. Housing 7 Transmitting coil 8 Receiving coil 9 Reel Frame 10 grooves 11 Products 12 Conveying direction 13 First receiving coil 14 Second receiving coil 15 First filling material 16 Second Filling Material 17 Intermediate Space 18 First Layer 19 Second Layer

Claims

1. A metal detector (1) comprising at least one transmitting coil (7) and at least one receiving coil (8, 13, 14), A metal detector (1), comprising: a transmitting coil (7) and a receiving coil (8, 13, 14) disposed within a housing (6), the housing (6) being partially filled with a first filling material (15), the transmitting coil (7) and the receiving coil (8, 13, 14) being connected to a measuring device, and a product (11) being conveyed past the metal detector (1), said housing (6) being partially filled with at least one second filler material (16), the material composition and / or chemical composition and / or dimensions and / or density of said second filler material (16) being different from said first filler material (15); the second filling material (16) being hollow bodies filled with gas arranged in at least two repeated layers arranged one above the other in the interior space of the housing (6); A metal detector (1) characterized in that the first filling material (15) is a resin at least partially surrounding the second filling material (16).

2. The second filler (16) has a μ ｒ 2. A metal detector (1) according to claim 1, characterised in that it comprises:

3. 3. The metal detector (1) according to claim 1 or 2, characterized in that the second filling material (16) has a spherical geometric shape.

4. Metal detector (1) according to any one of claims 1 to 3, characterised in that the diameter of the second filling material (16) is between 10 mm and 80 mm.

5. The second filler (16) has a density of 0.01 g / cm ３ to 8 g / cm ３ 5. A metal detector (1) according to any one of claims 1 to 4, characterized in that it has a density between 0.01 and 0.

05.

6. 6. The metal detector (1) according to any one of claims 1 to 5, characterized in that the second filling material (16) fills the inner space of the housing (6) by at least 10% and up to 90%.

7. 7. Metal detector (1) according to any one of claims 1 to 6, characterized in that the second filler (16) is arranged in the form of a close-packed sphere packing.

8. Metal detector (1) according to any one of the preceding claims, characterized in that the transmitting coil (7) and the receiving coils (8, 13, 14) are arranged symmetrically within the housing (6).

9. 9. The metal detector (1) according to any one of claims 1 to 8, characterized in that the transmitting coil (7) and the receiving coil (8, 13, 14) are wound on a bobbin (9).

10. 10. The metal detector (1) according to claim 9, characterized in that the first filler (15) and the second filler (16) are provided in an internal space of the housing (6), the internal space being defined by a housing wall and the reel (9).

11. Metal detector (1) according to any one of the preceding claims, characterized in that the transmitting coil (7) and the receiving coils (8, 13, 14) are arranged in mutually parallel planes.

12. Metal detector (1) according to any one of the preceding claims, characterized in that the metal detector (1) comprises a search channel (4).

13. 13. Metal detector (1) according to claim 12, characterized in that a conveyor belt (2) is guided through the search channel (4).

14. A method for manufacturing a metal detector (1), comprising the steps of: The metal detector (1) consists of a housing (6), in whose interior space at least one transmitting coil (7) and one receiving coil (8, 13, 14) are wound on a former (9), the housing (6) is provided with the former (9) and the transmitting coil (7) and the receiving coil (8, 13, 14), subsequently a second filler material (16) is introduced into the interior space of the housing (6), the interior space being bounded by the housing wall and the former (9), and in a subsequent working step a first filler material (15) is introduced into the interior space of the housing (6), the second filler (16) is a hollow body filled with gas and arranged in at least two repeated layers arranged one above the other in the interior space of the housing (6), The first filler (15) is a resin and at least partially surrounds the second filler (16); 10. A method for manufacturing a metal detector (1), characterized in that the material composition and / or chemical composition and / or dimensions and / or density of the second filling material (16) are different from those of the first filling material (15).

15. 15. The method of claim 14, characterized in that the second filler (16) has a diameter between 10 mm and 80 mm.

16. 16. The method according to claim 14 or 15, characterized in that an intermediate space (17) exists at least partially around two adjacent second packing materials (16), said intermediate space (17) being at least partially filled by said first packing material (15).

17. 17. The method according to any one of claims 14 to 16, characterized in that the upper surface of the housing (6) is provided with degassing openings through which air and reaction gases of the first filling material (15) can escape.

18. 18. The method according to claim 17, characterized in that after hardening of the first filling material (15), the degassing openings are closed.

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