CONVEYOR SCALE WITH METAL DETECTOR

Description

[0001] The present invention relates to a conveyor belt scale for transporting piece goods, comprising an infeed belt, a weighing belt, and a discharge belt. The weighing belt is supported on a load cell that detects the weight of piece goods transported along the weighing belt. The conveyor belt scale includes a metal detector comprising at least one transmitter coil and at least one receiver coil.

[0002] Metal detectors are used in the food industry to detect metallic contamination in food. Metallic contamination occurs, for example, when a component in a meat processing machine breaks off and falls into the food. For example, small screws can come loose during operation, or small fragments, such as a knife, can break off. These fragments are often only a few millimeters in size, for example, 2 mm to 4 mm. Food products with such contamination must be identified and sorted out at the end of the production process. For example, conveyor belt scales or price labelers are often equipped with a metal detector for weight checks and, if necessary, for labeling packaging, such as trays containing food.These metal detectors work with X-ray technology or with a tunnel formed by a circular coil, allowing the food to be transported vertically through the coil by the conveyor belt. This is usually only possible with a complex setup.

[0003] Such a metal detector is shown in EP2865614B1. A conveyor belt scale comprises a feed belt that passes through a metal detector configured as a tunnel.

[0004] The RU2583346C2 shows a metal detector for detecting a metallic object embedded in another object. For example, a water, electrical, or gas pipe can be detected in a wall.

[0005] DE102020113024A1 shows a metal detector designed as a tunnel through which a conveyor belt passes.

[0006] The object of the invention is to provide a conveyor belt scale for piece goods, in particular for foodstuffs, which are packaged in trays, which comprises a metal detector which is integrated in a simple manner.

[0007] This object is achieved according to the invention with a conveyor belt scale according to claim 1.

[0008] According to the invention, a conveyor belt scale for transporting piece goods, comprising an infeed belt, a weighing belt, and a discharge belt, is proposed. The weighing belt is supported on a load cell that detects the weight of piece goods transported via the weighing belt. The conveyor belt scale comprises a metal detector that has at least one transmitter coil and at least one receiver coil. The at least one transmitter coil and the at least one receiver coil are each designed as a planar coil. A person skilled in the art understands a planar coil to be, in particular, a coil with only one turn, i.e. a circular or rectangular conductor structure that is not closed, but whose two ends are guided together except for a small distance. The planar coils are each located in a plane that runs parallel to the upper run of the conveyor belt and thus parallel to the conveying direction.Planar coils have the advantage that they can be manufactured relatively easily, reliably, inexpensively and with low tolerances.

[0009] In one embodiment, at least one planar coil is embodied as a conductor structure on a printed circuit board. In one embodiment, all planar coils are embodied as conductor structures on at least one printed circuit board. On a printed circuit board, the planar structures can be easily manufactured using a known process, and virtually any conductor structure can be formed in one plane. The planar coil is formed in a metallization plane of the printed circuit board.

[0010] In one embodiment, the conveyor belt scale comprises a conveyor belt. The conveyor belt comprises a belt body around which a conveyor belt is guided via deflection rollers mounted at the beginning and end. At least one coil of the metal detector is integrated into the belt body between the upper and lower runs of the conveyor belt.

[0011] In one embodiment, all coils of the metal detector are integrated into the belt body between the upper and lower runs of the conveyor belt. This has the advantage that the item on the upper run of the conveyor belt slides over the coils of the metal detector, eliminating the need for additional structures in the conveyor belt's conveying area.

[0012] In one embodiment, a receiver coil is electrically assigned to a transmitter coil. The receiver coil assigned to the transmitter coil is arranged on the same circuit board and essentially in the same geometric region of the circuit board, but on a different metallization level. In this context, electrically assigned is to be understood as meaning that the receiver coil detects a magnetic reaction caused by the transmitter coil in a metal object. On a circuit board with multiple metallization levels, the transmitter coil and receiver coil are arranged one above the other, so to speak. This should also include the transmitter coil and receiver coil being slightly offset from one another, for example, but essentially still overlapping. Furthermore, this should also be understood as meaning that the transmitter coil and receiver coil are arranged rotated relative to one another.

[0013] In one embodiment, half of the metal detector coils are integrated into the belt body between the upper and lower runs of the conveyor belt. Half of the metal detector coils are positioned above the upper run and at a distance from the upper run of the conveyor belt. Above the upper run means that there is enough free space between the upper run of the conveyor belt and the coils for the item to pass under the metal detector coils, but the coils are positioned close enough to the conveyor belt for the coils' magnetic field to interact with the item.

[0014] In one embodiment, the coils arranged within the belt body and the coils arranged above the upper run of the conveyor belt are arranged at substantially the same height in the transport direction. This means that, viewed in the transport direction, the coils lie one above the other. If multiple coils are present, at least some of them are arranged next to each other perpendicular to the transport direction.

[0015] In one embodiment, a first number of two or more coils, in particular four coils, are arranged in the belt body between the upper and lower runs of the conveyor belt. The same number of coils is arranged above the upper run of the belt body. Each coil in the belt body between the upper and lower runs of the conveyor belt is electrically assigned a coil above the upper run of the belt body.

[0016] In one embodiment, transmitter coils and / or receiver coils consist of extended electrical conductor structures. These are arranged, in particular, in a circular or rectangular shape. They are arranged, in particular, on a circuit board.

[0017] In one embodiment, the conductor structures are formed essentially as a rectangular function, in particular as a regular rectangular function. The rectangular function runs along a circular path or a rectangular path.

[0018] In one embodiment, the metal detector comprises a signal generator that generates an alternating current signal. The alternating current signal is fed to the at least one transmitter coil. The alternating current signal fed to the at least one transmitter coil generates a magnetic field. The magnetic field induces eddy currents in a metallic object to be detected in a piece of goods on the conveyor belt. The piece of goods is an object to be inspected, for example a food product. The metallic object is, for example, a contaminant in the food product that could pose a danger to a consumer and should therefore be detected. The metal detector comprises a signal evaluation device. The signal evaluation device detects a magnetic field generated by the eddy currents in the metallic object in the piece of goods, which is received by the receiver coil.

[0019] In one embodiment, the signal generator generates a pulsed AC signal. That is, the signal generator generates an AC signal that is periodically switched on and off.

[0020] In one embodiment, the signal evaluation device does not perform any signal evaluation at the time at which the pulsed alternating current signal from the signal generator is greater than zero. This means that no signal evaluation is performed when the transmitter coil generates a magnetic field. This magnetic field from the transmitter coil would interfere with the signal evaluation device's signal evaluation. Those skilled in the art will understand that the signal from the signal generator is greater than zero when the signal from the signal generator is switched on and equal to zero when the signal from the signal generator is switched off. Since, due to practical implementation, infinitely steep edges are not possible with a pulsed signal, those skilled in the art will understand that zero is to be understood as a threshold value in the range of a very low signal strength.

[0021] In one embodiment, the transmitter coils and the receiver coils are electrically shielded from each other.

[0022] In one embodiment, the conveyor belt scale comprises a light barrier or a distance sensor for detecting a package within the detection range of the metal detector. The conveyor belt scale comprises a control device that activates the metal detector when the light barrier or the distance sensor detects a piece of goods conveyed on the conveyor belt scale within the range of the metal detector.

[0023] Some embodiments of the invention are shown by way of example in the drawings and described below. They show, in schematic representations: Fig. 1Conveyor belt scale with metal detector according to the prior art, Fig. 2Conveyor belt with integrated metal detector according to a first embodiment, Fig. 3aConductor structure of a coil according to a first embodiment, Fig. 3bConductor structure of a coil according to a second embodiment, Fig. 4Conveyor belt with integrated metal detector according to a second embodiment, Fig. 5Conductor structure of a coil according to a third embodiment.

[0024] Fig. 1 shows a conveyor belt scale 10 consisting of an infeed belt 12, a weighing belt 14 supported on a load cell, and a discharge belt 16. Following the discharge belt 16 is a metal detector 18 comprising a conveyor belt 20 that receives piece goods from the discharge belt and transports them downstream. The metal detector 18 comprises a housing 24 in which a coil arrangement (not shown) is located. The housing 24 has a through-opening 26 for piece goods and for the conveyor belt 20.

[0025] The piece goods are transported on the conveyor belt 20 along the conveying direction through the through-opening 26 of the housing 24. The coil arrangement consists of coils arranged one behind the other in the conveying direction, namely a first receiver coil, followed by a transmitter coil, and then a second receiver coil. All coils are arranged parallel to one another and consist of circular windings mounted within the housing 24. The coils are formed in a plane perpendicular to the conveying direction. Each coil wraps around the through-opening 26. The coils comprise a plurality of windings of a metallic wire. The metal detector comprises a control device 22, in which the signal generation for the transmitter coil and the signal processing of signals from the receiver coils take place.Following the metal detector 18, a printer station is mounted, which in turn comprises a conveyor belt 32 and includes a top labeler 28 for labeling piece goods from above and a bottom labeler 30 for labeling piece goods from below.

[0026] Fig. 2 shows a conveyor belt 40 with an integrated metal detector according to a first embodiment of the invention. The conveyor belt consists of a belt body consisting of a frame 46. At both longitudinal ends of the frame 46, i.e., at the beginning and end of the frame 46, deflection rollers 42, 44 are mounted, around which a conveyor belt 48 is guided. Fig. 2 the conveyor belt 48 is interrupted to illustrate the area 50 within the frame 46. In reality, however, the conveyor belt 48 is closed and can therefore be guided in endless rotation around the deflection rollers 42, 44, one of which is driven. Piece goods are transported on the conveyor belt 48 in the transport direction. In the area 50 within the frame 46, a circuit board 52 is attached transversely to the transport direction of the conveyor belt 40, which in this case comprises two coils 54, 56. The number of coils 54, 56 depends on their size and the width of the conveyor belt 48. There are so many coils 54, 56, in particular arranged on a straight line transversely to the transport direction, that the electromagnetic fields of the coils 54, 56 completely illuminate the area across the entire width of the conveyor belt 48, so that the piece goods transported on the conveyor belt 48 are completely illuminated. The coils 54, 56 are electrically connected to the control device 22.The transmission signal of each coil 54, 56 is generated in the control device 22. The reception signals of each coil 54, 56 are evaluated in the control device 22. The control device 22 comprises a signal generator that generates an alternating current signal, which is fed to the at least one transmitter coil 54, 56. The alternating current signal fed to the at least one transmitter coil 54, 56 generates a magnetic field, which induces eddy currents in a metallic object to be detected in a piece of goods on the conveyor belt 48. The control device 22 comprises a signal evaluation device, which detects and evaluates a magnetic field generated by the eddy currents in the metallic object in the piece of goods, which is received by the receiver coil 54, 56. A plate (not shown), in particular a metal plate, is mounted on the frame 46, on which the conveyor belt 48 slides and by which the conveyor belt 48 is supported.If this plate is made of a material that does not interfere with the electromagnetic field of the coils, the plate can also be mounted continuously above the circuit board 52. If the plate is made of a material that interferes with the electromagnetic field of the coils, in particular metal, the plate must be interrupted in the area of ​​the coils. The metal detector integrated into the conveyor belt 40 comprises only one circuit board 52 below the upper run of the conveyor belt 48 in the area 50 within the frame 46. On this circuit board 52, the transmitter coils and receiver coils are embodied as conductor structures, as shown in FIG. Fig. 3a und Fig. 3b shown in a first and a second embodiment.

[0027] Fig. 3a shows a conductor structure of a coil 54, 56, which serves as both a transmitter coil 62 and a receiver coil 60. Two similar conductor structures are arranged electrically insulated from each other, having the same or a similar contour. These conductor structures are electrically insulated from each other by being arranged on a circuit board 52 with multiple metallization levels on different metallization levels. Fig. 3a The conductor structure 60, drawn with the solid line, shows the uppermost metallization level. This is the receiver coil 60. The conductor structure 62, drawn with the dashed line, shows a conductor structure on an underlying metallization level. This is the transmitter coil 62. In principle, the transmitter coil and receiver coil can also be interchanged. However, it has been shown that the signal caused by small pieces of metal in the piece goods is very small and difficult to detect. For this reason, it is advantageous to attach the receiver coil 60 to the uppermost metallization level of the circuit board 52 in order to increase sensitivity. The receiver coil 60 is connected to the control device 22 via an electrical connection 66. The transmitter coil 62 is connected to the control device 22 via an electrical connection 64. The conductor structures 60, 62 of the transmitter coil 62 and receiver coil 60 follow a periodic, i.e.regular rectangular function. This rectangular function is arranged on a circular path. The conductor structures 60, 62 are thus star-shaped, with the tips being flat. The transmitter coil 62 and the receiver coil 60 are arranged directly above one another, i.e., geometrically overlapping, or slightly twisted and / or shifted relative to one another. In one embodiment, the sizes of the transmitter coil 62 and the receiver coil 60 could differ slightly.

[0028] Fig. 3b shows a conductor structure of a coil 68, which serves both as a transmitter coil 76 and as a receiver coil 74. The arrangement on a circuit board 52 on different metallization levels basically corresponds to the embodiment of Fig. 3a The conductor structures of the transmitter coil 76 and the receiver coil 74 are also designed as periodic rectangular functions. However, unlike Fig. 3a along a rectangle. Thus, a transmitter coil 76 and a receiver coil 74 can occupy a large portion of the printed circuit board 52 beneath the conveyor belt 48, thus generating an electromagnetic field across the entire width of the conveyor belt 48. The transmitter coil 76 is connected to the control device 22 via an electrical connection 72. The receiver coil 74 is connected to the control device 22 via an electrical connection 70.

[0029] Fig. 4 shows a conveyor belt with an integrated metal detector according to a second embodiment of the invention. The conveyor belt comprises a first circuit board 90 within the frame of the belt body of the conveyor belt. The metal detector also comprises a second circuit board 92 above the upper run of the conveyor belt 48. The item conveyed on the conveyor belt 48 is conveyed through the area between the first circuit board 90 and the second track 92, while the conveyor belt 48 is guided around input-side and output-side deflection rollers 42, 44. A control device 94 is electrically connected to the circuit boards 90, 92. Fig. 5 shows a circuit board 90, 92 of the metal detector of the second embodiment. Again, the coils 80, 84 are designed as a regular, ie periodic rectangular function, which is as in Fig. 5 shown runs along a circular path. Alternatively, the conductor structure of the coils 80, 84 can also run along a rectangle or oval. The coils 80, 84 are connected to the control device 94 via the terminals 82, 86 and are electrically controlled. The conductor structures on the first circuit board 90 and the associated conductor structures on the second circuit board 92 (transmitter coils and receiver coils) are arranged geometrically one above the other in the conveying direction so that they interact. One coil 80, 84 on the first circuit board 90 and one coil 80, 84 on the second circuit board 92 serve as the associated transmitter coil and receiver coil. In one embodiment, all transmitter coils can be arranged on the first circuit board 90 and all receiver coils on the second circuit board 92. In one embodiment, all transmitter coils can be arranged on the second circuit board 92 and all receiver coils on the first circuit board 90.Transmitter coils and receiver coils can also be arranged alternately on the first circuit board 90, and the associated receiver coils and transmitter coils are then arranged alternately on the second circuit board 92.

[0030] One in Fig. 5 The printed circuit board shown with conductor structures in only one metallization level can also be used in the first embodiment according to Fig. 2 as circuit board 52. The conductor structures 80, 84 serve as transmitter coils and receiver coils. The transmission signal is generated via the signal generator of the control device 22 and applied in pulsed form to the coils 80, 84, or the signal generator generates a pulsed alternating current signal. After the transmission signal has been applied to the coils 80, 84, the signal is switched off, and the signal received by the coils is evaluated. Thus, both coils 80, 84 serve, offset in time, as transmitter coils and receiver coils. In this exemplary embodiment, decoupling between the transmission signal and the reception signal does not occur via electrical decoupling of the coils, but rather via the time offset.

[0031] The conveyor belts with integrated metal detector according to the embodiments according to Fig. 2 or Fig. 4can be arranged at the location of the feed belt 12, the discharge belt 16 or the separate metal detector belt 20 and replace the respective belt.

[0032] The functions of various elements shown in the drawings, including the functional blocks, may be implemented by dedicated hardware or by generic hardware capable of executing software in conjunction with the corresponding software. If the functions are provided by a processor, they may be provided by a single dedicated processor, a single shared processor, or multiple generic processors that may in turn be shared. The functions may be provided, without limitation, by a digital signal processor (DSP), network processor, application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), read-only memory (ROM) with stored software, random access memory (RAM), and non-volatile memory.

Claims

1. Conveyor belt scale for transporting piece goods, having an infeed belt (12), a weighing belt (14) and a discharge belt (16), wherein the weighing belt (14) is supported on a weighing cell which detects the weight of piece goods transported via the weighing belt (14), wherein the conveyor belt scale comprises a metal detector which comprises at least one transmitter coil (54, 56) and at least one receiver coil (54, 56), and wherein the conveyor belt scale comprises a conveyor belt which comprises a belt body (46) about which a conveyor belt (48) is guided in a revolving manner by way of deflection rollers (42, 44) assembled at the beginning and at the end, characterized in that the at least one transmitter coil (54, 56) and the at least one receiver coil (54, 56) are in each case embodied as a planar coil (60, 62, 74, 76, 80, 84) and in each case located in a plane which extends parallel to the upper lead of the conveyor belt and thus parallel to the conveying direction, and in that at least one coil of the metal detector is integrated in the belt body between the upper lead and the lower lead of the conveyor belt (48).

2. Conveyor belt scale for transporting piece goods according to Claim 1, characterized in that at least one planar coil, in particular all planar coils (60, 62, 74, 76, 80, 84), is / are designed as conductor structures on at least one printed circuit board (52, 90, 92).

3. Conveyor belt scale for transporting piece goods according to Claim 1 or 2, characterized in that all coils of the metal detector are integrated in the belt body between the upper lead and the lower lead of the conveyor belt (48).

4. Conveyor belt scale for transporting piece goods according to Claim 3, characterized in that a receiver coil is in each case electrically assigned to a transmitter coil, and the receiver coil assigned to the transmitter coil is arranged on the same printed circuit board and substantially in the same geometric region of the printed circuit board (52), but on a different metallization plane.

5. Conveyor belt scale for transporting piece goods according to Claim 1 or 2, characterized in that half of the coils of the metal detector are integrated in the belt body between the upper lead and the lower lead of the conveyor belt (48), and half of the coils of the metal detector are arranged above the upper lead and at a spacing from the upper lead of the conveyor belt (48).

6. Conveyor belt scale for transporting piece goods according to Claim 5, characterized in that the coils which are arranged within the belt body (46) and the coils which are arranged above the upper lead of the conveyor belt (48) are arranged at substantially the same level in the transport direction.

7. Conveyor belt scale for transporting piece goods according to Claim 6, characterized in that a first number of two or more coils, in particular four coils, are arranged in the belt body between the upper lead and the lower lead of the conveyor belt (48), and a second number of coils, corresponding to the first number, are arranged above the upper lead of the belt body, each coil in the belt body between the upper lead and the lower lead of the conveyor belt (48) being electrically assigned a coil above the upper lead of the belt body.

8. Conveyor belt scale for transporting piece goods according to one of Claims 1 to 7, characterized in that transmitter coils and / or receiver coils consist of extended electrical conductor structures which are arranged in particular in a circular or rectangular shape, in particular on a printed circuit board (52, 90, 92).

9. Conveyor belt scale for transporting piece goods according to Claim 8, characterized in that the conductor structures are substantially formed as a rectangular function, in particular a regular rectangular function and the rectangular function extends along a circular track or a rectangular track.

10. Conveyor belt scale for transporting piece goods according to one of Claims 1 to 9, characterized in that the metal detector comprises a signal generator which generates an alternating current signal that is supplied to the at least one transmitter coil, wherein the alternating current signal supplied to the at least one transmitter coil generates a magnetic field that induces eddy currents in a metallic object to be detected in a piece goods item on the conveyor belt, and in that the metal detector comprises a signal evaluation device that detects a magnetic field which is generated by the eddy currents in the metallic object in the piece goods item and is received by the receiver coil.

11. Conveyor belt scale for transporting piece goods according to Claim 10, characterized in that the signal generator generates a pulsed alternating current signal.

12. Conveyor belt scale for transporting piece goods according to Claim 11, characterized in that the signal evaluation device, at the point in time at which the pulsed alternating current signal of the signal generator is greater than zero, does not carry out a signal evaluation.

13. Conveyor belt scale for transporting piece goods according to one of Claims 1 to 12, characterized in that the transmitter coils and the receiver coils are electrically shielded in relation to one another.

14. Conveyor belt scale for transporting piece goods according to one of Claims 1 to 13, characterized in that the conveyor belt scale comprises a light barrier or a distance sensor for detecting a packaging in the detection range of the metal detector, and in that the conveyor belt scale comprises a control device which puts the metal detector in an active state when the light barrier or the distance sensor detects a piece goods item conveyed on the conveyor belt scale in the range of the metal detector.