Device for weighing conveyed products in reverse operation

Abstract

Weighing device for automatic, in particular dynamic, weighing of products conveyed at, in particular, high speed, with several physical belt scales (S1, S2, S3, S1', S2', S3') arranged one behind the other in the conveying direction (x, x'), with a switching device for changing the direction of conveying (x, x'), characterized in that the weighing device is designed such that it is operable for weighing in the forward direction (x) and also for weighing in the reverse direction (x'), a) wherein a first reference reference is provided to define the beginning of a first process path in the forward direction and, in addition, a second reference reference is provided to define the beginning of a second process path in the reverse direction, whereby the distance between both reference references is defined or b) one of the two reference references and the distance to the other reference reference is provided to define the other reference reference.

Description

[0001] The invention relates to a device for dynamic, automatic weighing of products conveyed at high speed in a conveying direction.

[0002] Such processes are used, for example, in the logistics sector, especially in heavy-duty applications, where products must be conveyed at high speed and weighed in motion. Weighing takes place automatically, i.e., without operator intervention, and with high accuracy.

[0003] In contrast to static weighing, this saves a lot of time and money.

[0004] The present invention is therefore based on the object of creating a method and a device for carrying out such a method, which also enable dynamic automatic weighing of products conveyed at high speed with high accuracy in the reverse direction.

[0005] This object is achieved according to the invention with a device having the features of claim 1.

[0006] According to the invention, dynamic, automatic (i.e., performed without operator) weighing of products conveyed at high speed is carried out by means of several physical belt scales arranged one behind the other in the conveying direction. The high speed can, for example, be in a range of greater than or equal to 1 m / s, in particular greater than or equal to 1.5 m / s, or even greater than or equal to 3 m / s. The conveying direction can be switched between a forward direction (forward operation) and a reverse direction (reverse operation) to enable weighing in both directions.

[0007] In a product flow with products of different lengths and distances (mixed flow), the throughput can be increased or optimized by using several belt scales arranged one behind the other, preferably with different lengths (by assigning one of the belt scales to be used ideally for determining the weight of a product).

[0008] The products to be conveyed are preferably heavy-duty products, for example logistics products such as crates, boxes, cartons, etc., which typically weigh several kilograms, for example greater than 3 kg or 10 kg, preferably greater than or equal to 15 kg or 30 kg and up to 120 kg.

[0009] In order to reduce influences on measurement results caused by a static-dynamic offset, i.e. offset between dynamic measurement result and static reweighing, a respective first correction factor for weighing in the forward direction is known or has been determined for each physical belt scale.

[0010] In addition to geometric properties of the belt body (unevenness on the belt body, in particular unevenness / curvatures of the upper surface of the belt body, i.e., the platform for guiding / supporting / resting the underside of the upper run of a conveying device running above it, such as a revolving belt, belt, chains, etc.), the causes of static-dynamic misalignment include aerodynamic effects (lift effects) on the product to be weighed, which is moving at high speed. Therefore, when correcting static-dynamic misalignment, not only the geometry, in particular the unevenness of the belt body or platform, the position of the measuring window, etc., but also the speed, the mass of the product, as well as its geometry and the resulting aerodynamic effects, must be taken into account.

[0011] In order to take into account all or at least some of the aforementioned influences for a static-dynamic offset, a model can be developed (derived from the influences), for example with the help of neural networks or artificial intelligence (Kl), and with this a correction factor for a (physical but also logical) scale can be determined.

[0012] To reduce interference with measurement results, including when weighing in reverse, the invention uses a second correction factor for reverse operation. In the simplest case, the first correction factor is used for this, so that the second correction factor corresponds in value to the first. For this purpose, a second correction factor can be used to correct the weight of a product, at the latest when determining it. The value of the first correction factor can be called up as the second correction factor. Alternatively, a separate second correction factor, which has been set equal to the first correction factor, can be used as the second correction factor.When using a storage device (local, on the local network or in the cloud), the correction factor can be stored at a single memory address, or two corresponding correction factors can be stored at two different memory addresses.

[0013] Since the aforementioned influences that influence a correction factor, particularly the unevenness of a belt body, are usually not symmetrical to the belt center in the conveying direction, the second correction factor can also differ from the first correction factor. This is due to an off-center curvature of the belt body surface that occurs during operation, for example, a parabolic shape, particularly in the longitudinal direction / conveying direction, which distorts the measurement result, particularly making the product appear lighter.

[0014] The second correction factor can be derived from the first correction factor, for example by taking into account the height and position of the curvature and their different influences on the measurement results depending on the conveying direction.

[0015] Alternatively, the second correction factor can be derived from the measurement data underlying the first correction factor in the forward direction, or it can be determined without deriving it from the first correction factor using a proprietary model (e.g., using mathematical modeling methods, neural networks, or AI) for weighing in the reverse direction, or it can be derived from measurement data determined in the reverse direction. The proprietary model can preferably be derived from a model already created for determining the first correction factor.

[0016] By deriving a second correction factor, the determination of which incorporates the first correction factor in the manner described above, the effort required to determine the second correction factors (for weighing in the reverse direction) can be advantageously reduced or even eliminated entirely. In the latter case, no acceleration section is required in the reverse direction, which significantly shortens the required overall length of the weighing device and reduces the number of acceleration belts. Time-consuming programming (of a belt scale) to determine a second correction factor in reverse operation (using a large number of runs with test specimens, as required for the conventional determination of a first correction factor for physical belt scales) is eliminated or can be avoided.

[0017] In an advantageous embodiment of the invention, at least two physical belt scales arranged consecutively in the conveying direction are connected to form a logical scale, wherein the weighing results or the weighing signals of the individual belt scales are summed, preferably synchronously, to form a total weight or total weight signal. This advantageously allows even products that are longer than the length of a physical belt scale to be weighed by resting them on the logical scale for a time window sufficiently long for dynamic measurement.

[0018] In a preferred embodiment of the invention, in order to determine a first correction factor for weighing in the forward direction for the logical scale, the logical scale is taught using appropriate test specimens or the correction factor is derived via a model (for example, using mathematical modeling methods, neural networks, or AI, taking into account existing influences (parameters for a static-dynamic offset) such as belt body geometry, in particular camber, conveyor speed, etc.). For derivation via a model, it is also conceivable to derive the correction factor of the logical scale from the correction factors of the connected physical belt scales, as explained above for physical belt scales.

[0019] In a further embodiment of the invention, a respective second correction factor is used for weighing in the reverse direction for each logical scale, which - analogous to the second correction factor explained above for weighing in the reverse direction for each physical belt scale - corresponds to the respective first correction factor or was derived from the first correction factor or was derived from the measurement data in the forward direction on which the first correction factor is based or was determined by means of a model for weighing in the reverse direction or was derived from measurement data determined in the reverse direction.

[0020] In a particularly preferred embodiment of the invention, the weighing device comprises at least three – preferably of different lengths – physical belt scales, which can be connected to form several different logical scales. With three physical belt scales, this results in three logical scales (first and second; second and third; first, second, and third scales) in addition to the physical scales in forward operation, and also three logical scales (third and second; second and first; third, second, and first scales) in reverse operation.

[0021] In this case, the physical belt scales and the logical scales for reverse weighing can be regrouped according to the opposite direction to facilitate assignment. For this purpose, the scales are not physically modified, but rather renamed with an internal numbering system.

[0022] In addition, the determined correction factors can be automatically assigned depending on the respective physical or logical scale and the respective direction. This automatic assignment of the correction factors takes place according to the specified or detected conveying direction from a storage device, for example, directly to a scale's load cell or during signal processing and weight determination in a control and / or evaluation device.

[0023] In an embodiment according to the invention, a weighing device comprises, in addition to a plurality of physical belt scales, a switching device for changing the direction of conveyance, as well as a storage device (internal or external, for example cloud) with a first set of first correction factors for weighing in the forward direction and a second set of second correction factors for weighing in the reverse direction for each physical belt scale or for each physical belt scale and for each logical scale.

[0024] In addition, the weighing device according to the invention is designed in such a way that when determining the weight depending on the conveying direction, the respective set is retrieved from the storage device and used.

[0025] In a further embodiment of the invention, the belt scales have deflection shafts on the input side and output side, both of which have a crown, in particular double crown (two radial beads spaced apart from each other in the axial direction), in order to prevent the belt from running away sideways in both conveying directions.

[0026] In an advantageous embodiment of the invention or as an independent invention, the weighing device is designed such that it can be operated and is used for weighing in the forward direction and also for weighing in the reverse direction. A first reference is provided to define the start of a first process section in the forward direction. In addition, a second reference is provided to define the start of a second process section in the reverse direction. By defining the two reference references, their distance is defined. Preferably, the position of the second reference reference or the distance between the two reference references is already defined when parameterizing the forward operation. This enables automatic calculation (without manual input) of the parameters for the reverse operation.

[0027] Alternatively, one of the two reference references and the distance to the other reference reference can be provided to define the other reference reference.

[0028] A process line within the meaning of the invention represents a data model of the weighing device. This model simulates the individual physical components of the weighing device (such as weighing belts, infeed and outfeed conveyors, sorting devices, light barriers, barcode readers, cameras, labeling systems), as well as the products conveyed on the weighing device, their movements, and product positions for data input and output, while correctly taking into account the sequence of the process flow. The process line serves, among other things, for temporal and / or spatial product tracking.

[0029] This means that a control system knows at what point in time the individual components are in certain functional states (e.g. “belt occupied”, “belt free”), or at which location (position) the products are currently located.

[0030] According to the invention, the weighing device for the forward and reverse directions can have a common process section or different process sections, in particular of different lengths.

[0031] A reference reference, as defined by the invention, is a local position. This serves as a reference point (zero point) for determining the local positions of the aforementioned physical components or parts thereof (e.g., the leading and trailing edges of the weighing belts), as well as the conveyed products.

[0032] For example, the leading edge or flank of the infeed belt can be used as the first reference point in forward operation. However, it is also conceivable to use the light barrier as the first reference point in forward operation. Similarly, the leading edge or flank of the infeed belt in reverse operation, or the light barrier in reverse operation, can be used as the first reference point.

[0033] In a further embodiment, the weighing device is designed such that, for weighing in the reverse direction, parameters (position and / or time values) of the second process line are automatically calculated from parameters of the first process line. This is done in particular with the aid of the two reference points, preferably by the control of the weighing device (e.g., control and evaluation device).

[0034] The calculation can be performed before the conveying direction is switched, or during the switching or by the switching itself (e.g. by an external, in particular binary switching signal or direction signal).

[0035] In a preferred embodiment, the weighing device has a first light barrier at the inlet of the first belt scale and a second light barrier at the outlet of the last belt scale, viewed in the conveying direction, wherein only one of the two light barriers is used for a weighing process depending on the conveying direction.

[0036] By means of the method according to the invention and the device for implementing such a method, measurement errors or deviations due to static-dynamic offsets can advantageously be significantly reduced or even eliminated. Furthermore, the effort required to determine the second correction factors (for weighing in the reverse direction) can be reduced or completely eliminated. In the latter case, no acceleration section is required in the reverse direction, which significantly shortens the required overall length of the weighing device and reduces the number of acceleration belts.

[0037] Further advantageous embodiments of the invention emerge from the dependent claims.

[0038] The invention is explained in more detail below using an embodiment shown in the drawing.

[0039] The drawing shows: Fig. 1 is a schematic plan view of a weighing device according to the invention with three physical belt scales in forward operation; Fig. 2 a schematic plan view of the weighing device according to Fig. 1 in reverse operation and Fig. 3 Schematic representation in side view of a non-linear product movement on a single physical belt scale.

[0040] The Fig. Figure 1 shows a weighing device 1 in forward operation, i.e., with a conveying direction in the forward direction x. The weighing device 1 comprises, viewed in the conveying direction, a first belt scale S1, a second belt scale S2, and a third belt scale S3, each of which may have a different length (viewed in the conveying direction).

[0041] On the input and output sides, a feed area 9 and an outlet area 11 are provided, which are designed, for example, as belt conveyors.

[0042] If a product to be weighed (not shown in the drawing) is conveyed through the feed area 9 via the belt scales S1, S2, and S3 (S3 being the longest scale in the example) to the discharge area 11, the product is (temporarily) located on the belt scales S1, S2, and S3. As long as the product length is within the usable length of one of the scales S1, S2, and S3 for weighing, the product is weighed on a single scale within a short time window (in the ms range) without resting on the adjacent scales S1, S2, and S3.

[0043] In order to also enable the weighing of products with a greater length (seen in the conveying direction) (than the longest physical belt scale), the individual physical belt scales S1, S2 and S3 can be connected to form logical scales S4, S5 and S6. In this case, the logical scale S4 comprises the belt scales S1 and S2, the logical scale S5 comprises the belt scales S2 and S3 and the logical scale S6 comprises the belt scales S1, S2 and S3. As long as the length of the product to be weighed at least does not exceed the usable length of the entire network of scales, i.e. in the illustrated embodiment with only three physical scales, the logical scale S6, the weight of this product can also be determined within a corresponding time window.

[0044] In order to determine and track positions, in particular the leading edge of products (or their length) at a known speed in the conveying direction x, x' (process line with object tracking), a light barrier L (weighing in forward direction), L' (weighing in reverse direction) can be provided on the input side.

[0045] In order to have sufficient time to assign one of the belt scales ideally to be used for determining the weight of a product, the light barrier L, L' can be moved forward to the feed area 9, 9'.

[0046] As in Fig. 1, the front edge of the infeed belt 9 and the position of the light barrier L can coincide in forward operation and be used as the first reference.

[0047] As in Fig. 2, the front edge of the infeed belt 9' and the position of the light barrier L' can coincide in reverse operation and be used as a second reference.

[0048] Using a control and / or evaluation device not shown in the drawing, the start and end of data processing of measurement signals (measurement window) can be set, assuming the conveyor speed and length of the weighing device, as well as the lengths of the individual scales, are known. The start of the measurement window is set at the earliest when the trailing edge of the product is reached at the input of the first scale.

[0049] The final weight value determined and to be output should be available as early as possible (at the latest when the front edge of the product reaches the output position A, A') in order to be transmitted, for example, to a subsequent data processing unit (e.g. label printing unit / labeler) (in order to enable a short design of the weighing device).

[0050] An output position A, A' in the run-out area can be used to determine the end of data processing of measurement signals of a measurement, whereby reaching the run-out area can also be determined via the time required for the distance w, w'.

[0051] Fig. Figure 2 shows the aforementioned weighing device 1 in reverse operation, i.e., with a conveying direction in the reverse direction x'. In contrast to forward operation, viewed in the conveying direction x', the weighing device 1 now has the belt scale S1' (the longest scale in the example) as the first belt scale, the belt scale S2' as the second belt scale, and the belt scale S3' as the third belt scale.

[0052] A feed area 9' and an outlet area 11' are now provided on the input and output sides.

[0053] In the Fig. In the reverse operation shown in Figure 2, the individual physical belt scales S1', S2', and S3' are now connected to form logical scales S4', S5', and S6'. Logical scale S4' includes belt scales S1' and S2', logical scale S5' includes belt scales S2' and S3', and logical scale S6' includes belt scales S1', S2', and S3'.

[0054] As can be seen, apart from the conveying direction x, x', the physical scales S1 and S3', the scales S2 and S2', and the scales S3 and S1' correspond to each other. Likewise, the logical scales S4 and S5', the logical scales S5 and S4', and the logical scales S6 and S6' correspond to each other.

[0055] Therefore, if the conveying direction of the weighing device 1 is changed from forward operation to reverse operation by means of a switching device not shown in the drawing, the physical scales and the logical scales must be regrouped or renamed accordingly for reassignment.

[0056] As from Fig. As can be seen in Figure 3, the belt guidance in the upper run does not necessarily correspond to the ideal of a linear guidance, but runs along a curve (curvature), for example a parabola, with a maximum height δ relative to the horizontal.

[0057] The difference Δm in the weight or the determined mass of a product is represented by a function of the mass m of the product, the conveying speed and the curve, in particular the height δ. Δm=f(m,v,δ)

[0058] A high speed v is of considerable importance in dynamic weighing. Accordingly, the static-dynamic offset is influenced not only by buoyancy effects but also by the flatness of the belt body and the resulting movement curve of a product, especially parabola (see Fig. 3) significantly influenced.

[0059] In order to obtain a correct measurement result despite the static-dynamic offset, a correction factor K vi for each physical scale S1, S2 and S3 - i.e. correction factor K v1 for scale S1, correction factor K v2 for scale S2 and correction factor K v3for scale S3 - which is or was determined, for example, by teaching in a larger number of runs with test weights or test packages.

[0060] For example, the same test package is weighed 30 times, then another package with a different load is weighed 30 times at different speeds. The number of runs thus corresponds to, for example, 120 individual measurements (4 different loads, 30 times each), which is then multiplied by the number of speeds.

[0061] Alternatively, such a correction factor K vi can also be derived from a model, for example using neural networks or using AI, which takes into account the various aforementioned influences of the weighing device and, if applicable, the dimensions of the product (buoyancy).

[0062] For the logical scales S4, S5 and S6, a respective correction factor K can also be determined in the above-mentioned manner. vlogi It is also conceivable to use the correction factors of the physical scales S1 to S3 - i.e. correction factor K vl1 for scale S1, correction factor K v2 for scale S2 and correction factor K v3 for scale S3 - to be used or at least consulted.

[0063] Since in practice the geometry of the belt body of a belt scale, in particular the curvature on the surface, etc., is not necessarily symmetrical to the center of the belt body in the conveying direction, the aforementioned curve is not identical in the forward and reverse directions.

[0064] For this reason, especially at high speeds, even initial correction factors K vi and K vlogi which were determined for forward operation cannot simply be used for reverse operation.

[0065] A second correction factor K ri can be calculated from the first correction factor K vi be derived, for example by taking into account the belt body, in particular its curvature and its position and height and their different influences on the measurement results depending on the conveying direction.

[0066] Alternatively, the second correction factor K ri from the first correction factor K vi underlying measurement data in the forward direction or are determined without deriving from the first correction factor using a separate model (for example using mathematical modeling methods, neural networks or AI) for weighing in the backward direction or are derived from measurement data determined in the backward direction.

[0067] By using a second correction factor K riAdvantageously, a time-consuming teaching-in of a physical belt scale in reverse operation by means of a large number of runs with test specimens can be avoided and an acceleration section in the reverse direction can be dispensed with.

[0068] Throughout the entire description, a correction factor is understood to be a quantity to which a fixed absolute value is assigned, taking into account the influences mentioned above (which flow into a static-dynamic offset), in particular the belt geometry, the conveyor speed, etc., in order to obtain a correspondingly corrected weight value of a product as a measurement result.

[0069] Of course, it is possible according to the invention for several scales to have the same or a common correction factor, so that several respective correction factors correspond to one another in terms of value. However, unless the belt scales are completely identical (with identical design), the respective correction factors of different scales preferably differ from one another.

[0070] For the purposes of the invention, dynamic weighing is understood to mean weighing during a movement, preferably during a uniform movement. In a broader sense, dynamic weighing also includes weighing during an accelerated or decelerated movement, or even during a briefly stopped movement, insofar as static-dynamic effects (e.g., sloshing of the product) occur and can influence the weighing accuracy.

[0071] Accordingly, the first and second correction factors K vlogi and K rlogi for a logical scale can be determined, derived or taught.

[0072] Of course, the invention is not limited to the embodiment, namely to a combination of three scales, so that a different number (2, 4, 5 or more) of physical scales can also be used. List of reference symbols 1.1' weighing device S1 first belt scale seen in forward direction S2 second belt scale seen in forward direction S3 third belt scale seen in forward direction 9 Feed area in forward direction 11 Run-off area in forward direction S4 logical scale from belt scales S1 and S2 S5 logical scale from belt scales S2 and S3 S6 logical scale consisting of belt scales S1, S2 and S3 S1' first belt scale seen in reverse direction S2' second belt scale seen in reverse direction S3' third belt scale seen in reverse direction S4' logical scale from belt scales S1' and S2' S5' logical scale from belt scales S2' and S3' S6' logical scale consisting of belt scales S1', S2' and S3' 9' feeding area in reverse direction 11' run-off area in reverse direction x Conveying direction forward (forward operation or forward weighing operation) x' Conveying direction backward (reverse operation or reverse weighing operation) K vi first correction factor of a physical belt scale i in forward operation K ri second correction factor of a physical belt scale i in reverse operation K vlogi first correction factor of a logical belt scale i in forward operation K rlogi second correction factor of a logical belt scale i in reverse operation i1,2,3 m mass of the product v Speed ​​of conveying δ maximum height of the curvature l Length of the tape L Light barrier at the entrance seen in forward direction L' light barrier at the entrance seen in reverse direction A, A' output position w Length of the path between light barrier L and output position A w' Length of the path between light barrier L' and output position A'

Claims

[1] Weighing device for automatic, in particular dynamic, weighing of products conveyed at, in particular, high speed, with several physical belt scales (S1, S2, S3, S1', S2', S3') arranged one behind the other in the conveying direction (x, x'), with a switching device for changing the direction of conveyance (x, x'), characterized by , that the weighing device is designed such that it is operable for weighing in the forward direction (x) and also for weighing in the reverse direction (x'), a) wherein a first reference reference is provided to define the beginning of a first process path in the forward direction and, in addition, a second reference reference is provided to define the beginning of a second process path in the reverse direction, whereby the distance between both reference references is defined or b) one of the two reference references and the distance to the other reference reference is provided to define the other reference reference. [2] Device according to claim 1, characterized by that the first and second process sections have the same length and opposite conveying directions (x, x'). [3] Device according to claim 1 or 2, characterized by that the weighing device is designed such that the physical belt scales (S1, S2, S3, S1', S2', S3') for weighing in the reverse direction (x') are automatically regrouped according to the opposite direction upon switching. [4] Device according to one of the preceding claims, characterized by that the weighing device is designed such that for weighing in the reverse direction (x') parameters of the second process section are automatically calculated from parameters of the first process section. [5] Device according to claim 4, characterized bythat the weighing device is designed in such a way that when the conveying direction is switched, the parameters of the second process section are calculated and their use begins. [6] Device according to one of the preceding claims, characterized by that the weighing device is designed such that at least two physical belt scales (S1, S2, S3, S1', S2', S3') following one another in the conveying direction are connected to form a logical scale (S4, S5, S6, S4', S5', S6'). [7] Device according to one of the preceding claims, characterized by that the belt scales (S1, S2, S3, S1', S2', S3') have deflection shafts on the input and output sides, both of which have a crown to prevent a belt or belt from running away sideways in both conveying directions (x, x'). [8] Device according to one of the preceding claims, characterized bythat the weighing device has a first light barrier (L, L') at the inlet of the first belt scale (S1, S1') and a second light barrier (L', L') at the outlet of the last belt scale (S3, S3'), seen in the conveying direction (x, x'), whereby only one of the two light barriers is used depending on the conveying direction (x, x').

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