Strapping machine for strapping a load with one strap

Description

[0001] The invention relates to a strapping machine for strapping a strapping item with a strapping band, which is preferably a weldable plastic band, with the features specified in the preamble of patent claim 1.

[0002] In the context of the invention, the term "strapping material" is understood to encompass various, usually similar, goods that are combined into an easily manageable bundle using one or more strapping bands. A typical example of a strapping material is a stack of folding box blanks. Since the individual folding box blanks are difficult to handle and transport without strapping, they are bundled into a bundle using a strapping band.

[0003] A strapping machine comprises a machine table that supports the strapped material during strapping, and at least one strapping device. Such strapping machines are known, for example, from WO 2012 / 152626 A2, CH 704 537 A2, or DE 198 21 918 A1. DE 198 21 918 A1 discloses a modular handling unit that can be configured as a removal module, buffer module, corner transfer module, or strapping unit. Depending on the desired function, the handling unit is equipped with drives, light barriers, etc.

[0004] State-of-the-art strapping machines are highly reliable and highly efficient. They are usually located at the back end of a longer process chain. If everything in this process chain runs smoothly, only flawless strapped items will be processed into a bundle using one or more strapping bands.

[0005] If, for example, a bundle of 50 folding box blanks contains only one defective folding box blank, the entire bundle must be removed from the production process, the bundle opened, and the defective folding box blank replaced with a flawless one. The stack of folding box blanks can then be fed back into the strapping machine and bundled into a bundle.

[0006] To ensure that only bundles containing flawless folding box blanks reach the customer, it is necessary to subject each bundle to 100% quality control in real time after strapping, so that only bundles containing flawless products are processed further in the process chain and any bundle containing a faulty folding box blank or other faulty product is rejected and sent for separate post-processing.

[0007] Typically, quality control of bundles is performed downstream of the strapping machine. If a bundle is detected there that contains one or more defective folding box blanks or other defective strapping material ("defective bundle"), it is removed from the production process at a downstream reject station and sent for further processing.

[0008] In total, three stations arranged one behind the other are required for strapping, quality control, and rejecting. Transport equipment such as conveyor belts is necessary to move the bundles through these stations. This configuration requires a lot of space, is expensive, and prone to failure due to the interlinking.

[0009] DE 10 2017 102 854 B3 describes a bundling device with a permanently installed camera beneath a table or a camera mounted on a press beam that captures the side edges of the bundled material. A similar configuration is also known from DE 10 2008 031 236 A1.

[0010] DE 20 2009 017 138 U1 and DE 10 2014 103 336 A1 describe devices for longitudinal strapping with an optical device that captures the contour of the strapped material from above. JP 200255512 A also shows a strapping device with a fixed camera.

[0011] The invention is based on the object of improving the functionality of a strapping machine and of making the overall space requirement of a process chain, which includes, among other things, the steps of strapping a strapping item into a bundle, quality control and ejecting defective bundles, more economical, space-saving and reliable.

[0012] This object is achieved according to the invention in a generic strapping machine for strapping a strapping item with a strapping band having the characterizing features of claim 1.

[0013] Because, according to the invention, a camera in the strapping machine is directed at least temporarily at the strapped goods, errors in the strapped goods can be detected and a bundle identified as faulty, which contains a faulty product / a faulty folding box blank, can be removed from the process chain directly in the strapping machine.

[0014] Because the strapping machine is located relatively far at the end of the process chain, the camera installed in the strapping machine according to the invention can detect all visually detectable defects in the products or folding box blanks. Once a defect is detected, the bundle containing the defective product / folding box blank can be removed from the process chain. It is irrelevant where in the upstream process chain the defect occurred. This makes the quality control according to the invention very effective, and the defect detection rate is high. Conversely, this means that almost no bundles containing defective products or defective folding box blanks reach the end of the process chain and subsequently reach the customer undetected.

[0015] According to the invention, the camera can be moved in a direction orthogonal to a plane spanned by the machine table. The movement device, for example in the form of a ball screw guide, makes it possible to "traverse" the front, back, and / or one side of the bundle with the camera and take images of the corresponding side of the bundle. Through appropriate image analysis, defective bundles can be detected and rejected.

[0016] The camera can be moved along a Z-axis (i.e., orthogonal to the XY plane spanned by the machine table). This makes it possible to move the camera out of the direction of movement or conveying direction (X-axis) of the bundle as soon as the bundle is to be conveyed out of the strapping machine.

[0017] The camera's mobility also makes it easy to adapt the strapping machine according to the invention to product stacks of different sizes. Further flexibility is achieved if the camera can be moved along a second axis (Y-axis), which preferably extends orthogonally to the first axis of movement. Then, for example, the entire front or back of a bundle can be captured by the camera, even if it can only take images of part of the bundle. It is also possible to specifically move to individual spots on the front, back, or sides of the bundle. This allows the camera to specifically move to and capture the points on the bundle where defects are expected. The rest of the bundle's surfaces then do not need to be captured by the camera.

[0018] If the strapping material is a stack of multiple folding box blanks, the gaps of the folding box blanks are arranged one above the other in the bundle. This means that the gaps of the folding box blanks are arranged along a vertical line (Z-axis). According to the invention, the camera is positioned so that it moves along the Z-axis, scanning all the gaps of the product stack, taking images of the gaps. Through suitable image analysis, gaps that are too wide or too narrow can be detected. Whenever a gap is detected that lies outside the specified tolerance ranges, the folding box blank is defective, and the defective bundle is rejected. The term "camera" is defined very broadly in the context of the invention. All image recording devices known from the prior art can be used as cameras.CCD sensors, matrix cameras, line scan cameras, or laser triangulation sensors are preferred. It is important that the camera can visually capture the characteristics of the bundle, especially parts or the entire surface of the bundle. The images obtained are evaluated using an algorithm that can determine whether the products in the stack are faulty or not. This evaluation can be performed in a control unit of the strapping machine or a separate processor. If a faulty bundle is detected, a signal is issued that causes this bundle to be ejected.

[0019] The strapping machine according to the invention comprises a console arranged above the machine table, at least one pressing beam movably mounted on the console, and at least one manipulator movably mounted on the console for deflecting the strapping band. A movement axis of the manipulator runs orthogonally to a plane spanned by the machine table. The manipulator is thus part of the strapping machine. The movement directions of the manipulator and the camera are parallel (in the direction of the Z-axis). Therefore, it is particularly advantageous if the camera or the device for optically capturing the product stack is attached directly or indirectly to the manipulator. The camera can then capture images of the product stack / bundle simultaneously and in parallel with the actual function of the manipulator.As soon as the product stack has been bundled with strapping, it is immediately clear whether the bundle contains a defective product or not. Dual use of the manipulator saves costs and installation space.

[0020] In a particularly preferred design, the machine table and the console are connected to one another by one or more supports, wherein the distances between the supports in a conveying direction (X-axis) of the strapping material are greater than the length of the strapping material.

[0021] It has proven advantageous to have a feed device for transporting the strapping material to the machine table upstream of the machine table, and / or to have a removal device for transporting the strapping material away from the machine table in the conveying direction downstream of the machine table. This ensures that the strapping material can be conveyed into the machine according to the invention and, after strapping, can also be removed from the strapping machine again.

[0022] Configurations are also conceivable in which, for example, the device located directly upstream of the strapping machine in the process chain takes over the transport of the strapped material into the strapping machine. In this case, a separate feed device or one associated with the strapping machine can be eliminated.

[0023] The same applies to a device that is located behind the strapping machine in the process chain.

[0024] If this device can transport the bundle away from the strapping machine, a separate device assigned to the strapping machine for transporting it away from the strapping machine is not required.

[0025] In a further advantageous embodiment of the invention, an ejection station is integrated in the strapping machine, which can transport a defective bundle out of the strapping machine in an ejection direction that deviates from the normal transport direction (X-axis) (e.g. in the direction of the Y-axis).

[0026] This means that whenever a product stack containing a defective product is detected, this product stack is immediately removed from the process chain by being moved sideways out of the strapping machine. For practical reasons, the removal direction (Y-axis) is perpendicular (orthogonal) to the conveying direction (X-axis).

[0027] It has also proven advantageous if the machine table and the console are connected by one or more supports, and the distance between the supports in the conveying direction (X-axis) of the strapping material is greater than the length of the strapping material. This makes it possible to eject a defective strapping material from the side of the strapping machine between the supports, allowing the ejection of a defective bundle without requiring additional space.

[0028] The ejection device can be designed in a simple and highly effective version as a pusher that is pneumatically, electromechanically, or hydraulically driven. As soon as a faulty product stack is detected, the pusher is activated and pushes the product stack sideways out of the strapping machine between the supports that connect the machine table and the console.

[0029] Alternatively, it is also possible to integrate the discharge device into the machine table. It is particularly advantageous if the surface of the machine table is realized with a ball grid conveyor belt. Such a ball grid conveyor belt is marketed by Ammeraal Beltec Holding BV in the Netherlands under the name "uniQNB Ball." It has the feature that the conveying direction of this ball grid conveyor belt can be controlled by the machine control system. If a product stack is classified as "good," the ball grid conveyor belt conveys the product stack out of the strapping machine in the conveying direction (X-axis). If a product stack is classified as "bad," the ball grid conveyor belt changes the conveying direction by 90° and discharges the product stack identified as defective laterally out of the strapping machine in the Y-axis direction.The strapping machine according to the invention can be a longitudinal strapping machine.

[0030] The camera according to the invention can use any suitable technology known from the prior art.

[0031] For example, these devices can be a matrix camera, a line scan camera, or a laser distance sensor. If, in a preferred embodiment, the camera is a laser distance sensor, then this laser distance sensor can operate according to the principle of triangulation or the time-of-flight principle. Both modes of operation are suitable for detecting the shape, contour, and position of grooves, as well as for detecting the width of gaps.

[0032] The inventive strapping machine integrates 100% quality control of the bundles and the rejection of defective bundles. These functionalities can be implemented without requiring additional space compared to the installation space required by a conventional strapping machine. This is a significant advantage, especially when installing process chains (i.e., multiple devices arranged one behind the other) in existing buildings and where space is limited.

[0033] In addition, the costs of the strapping machine according to the invention with the integrated functionalities are significantly lower than if these three functionalities were implemented in three separate devices.

[0034] Further advantages and advantageous embodiments of the invention can be found in the following drawings, their description and the patent claims. drawing

[0035] They show: Figure 1 shows an isometric view of a strapping machine according to the invention; Figure 2 shows a front view of a strapping machine according to the invention; Figure 3 shows a side view of a strapping machine according to the invention; and Figure 4 shows a detail of a top view of the strapping machine according to the invention. Description of the embodiment

[0036] In the Figure 1 An isometric view of an embodiment of a strapping machine according to the invention is shown. The three spatial directions are represented in the form of a Cartesian coordinate system with the axes X, Y, and Z. The direction of the X-axis corresponds to the conveying direction of the strapped material through the strapping machine.

[0037] In the Figure 1The strapping material 3 enters the machine from the rear and exits the machine at the front end if the strapping material is free of defects. If a defect in the strapping material is detected in the strapping machine according to the invention, the product stack with the defective product is ejected from the strapping machine laterally, i.e., in the direction of the positive Y-axis.

[0038] The strapping machine comprises a machine frame 1 on which a machine table for receiving the strapping material 3 is arranged. In the illustrated embodiment, the machine table comprises two conveyor belts 10 that run parallel to each other and are capable of conveying the strapping material 3 in the conveying direction through the strapping machine.

[0039] Of course, instead of the conveyor belts 10, other embodiments of machine tables, in particular ball grid conveyor belts, roller belts or other means can be realized.

[0040] The strapping machine comprises several supports 4, of which in the Figure 1 only three are visible. Two supports 4 each support a bracket 5. A press beam 6 is arranged on each bracket 5. The press beam 6 serves to compress the strapping material 3, in this case a stack of folding box blanks, before the strapping devices integrated into the brackets 5 place a strapping band around the strapping material 3, which is then welded in a welding device 7 to form a closed band.

[0041] The press beams 6 are connected to the brackets 5 via linear drives 9. The linear drives 9 can be designed as ball screws or pneumatic cylinders. In any case, it is necessary that a sufficiently large force can be exerted on the strapping material using the linear drives 9. For example, if the strapping material consists of folding box blanks stacked on top of each other, these will be compressed by the press beams before being bundled into a bundle with the strapping band.

[0042] With the strapping machine according to the invention, it is possible to eject a bundle identified as defective laterally, i.e., in the direction of the positive Y-axis. For this reason, the distance between the supports 4 in the direction of the X-axis is greater than the length of the strapped material. This design is very space-saving and allows the integration of the functions of an ejection station into the strapping machine without requiring additional space.

[0043] The ejection can be carried out, for example, by Figure 1On the left side of the machine table or the conveyor belts 10, there is a pusher (not shown), which is pneumatically, electromechanically, or hydraulically operated when a defective bundle needs to be ejected laterally. Normally, i.e., when the strapping material 3 is free of defects, the pusher remains deactivated, and the conveyor belts 10 transport the strapping material 3 through the strapping machine 1 in the X-axis direction.

[0044] The functioning of a strapping machine, in this case a longitudinal strapping machine, is well known to the person skilled in the art, so that a detailed description of it is omitted.

[0045] In connection with the invention, it is important that a camera 11 or another optical sensor is arranged on a linear guide 13. The linear guide 13 can be designed as a ball screw drive or as a pneumatically actuated linear guide. The requirements for the linear guide 13 in terms of precision and speed are relatively low. It is important that, with the aid of the linear guide 13, the camera 11 can be moved in the direction of the Z-axis in front of the front of the strapping material 3 from top to bottom or from bottom to top, so that either the entire front of the strapping material 3 or only a selected area of ​​the strapping material 3 is captured by the camera 11. The same applies if the back or the sides of the strapping material 3 are to be captured by the camera.

[0046] In order to ensure sufficient brightness and consistent lighting conditions, one or two optional light sources (without reference symbols in the Figure 1 ). The light sources are aligned so that they provide sufficient illumination in the image section captured by camera 11.

[0047] In the Figure 4 The light sources 15, the camera 11, and the linear guide 13 are shown enlarged and more clearly. The optical sensor 11 and the light sources 15 are attached to the linear guide 13 with a support, so that the light sources 15 and the camera 11 always assume the same relative positions to each other.

[0048] In the Figure 2A front view of the strapping machine according to the invention is shown. In this view, the camera 11 with the light sources 15 is clearly visible. It can also be seen that the camera 11 is located at the lower end of the movable part of the linear guide 13. If the camera 11 is moved upwards far enough in the direction of the Z-axis, the camera 11 and the light sources 15 no longer hinder the removal of the bundle from the strapping machine according to the invention.

[0049] In the Figure 2In the position shown, the camera 11 and the light source 15 are in the way of the removal of the strapping material 3. It is therefore important that the camera 9 and the light sources 15 can be moved upwards. This first direction of movement (parallel to the Z-axis) is indicated by a double arrow 17. In addition, the linear guide 13 is movably mounted on a second linear guide 21. The direction of movement of the second linear guide 21 is indicated by a double arrow 19. This means that by controlling the first linear guide 13 and the second linear guide 21, the camera 11 can visually capture every point on the front or back of the strapping material 3 or a bundle.

[0050] In the Figure 2 The strapping material 3 is a stack of folding box blanks that have a gap. This gap is in the Figure 2indicated by a small square black area. These columns are arranged in a row extending along the Z-axis when several folding box blanks are stacked on top of each other. The center axis of this row is indicated as a dot-dash line 23 in the Figure 2 For reasons of clarity, the small black areas in the extension of the dot-dash line 23, which represent the column, are not provided with reference symbols.

[0051] It is now possible to insert the first linear guide 13, starting from the Figure 2 shown position to the right until the camera 11 is positioned in front of the columns in the folding box blanks and then to move the camera 11 from bottom to top or from top to bottom along the columns and to capture images of the column.

[0052] By appropriately evaluating the images captured by camera 11, the width of the gap can be determined and any defective gaps (too large or too small) can be identified. Whenever a defective folding carton blank is detected in a bundle of folding carton blanks, the bundle is ejected to the side and replaced outside the regular folding carton blank process chain.

[0053] Of course, if other errors occur (too many folding box blanks in a bundle, too few folding box blanks in a bundle, main dimensions of the bundle outside the tolerance, ...), the defective bundle can also be rejected.

[0054] In the Figure 3A side view through two supports 4 of the strapping material 3 as well as the first linear guide 13 and the camera 11 is shown. The second linear guide 21 is concealed by the press beam 6 in this view. Typically, the second linear guide 21 is screwed or otherwise connected at its ends to one of the two press beams 6.

[0055] The Figure 4 shows a section of a top view of the arrangement according to the invention. In this illustration, the first linear guide 13 with the camera 11 arranged thereon and the light sources 15 are clearly visible. The light cones of the light sources 15 are indicated by lines 24. The image section of the camera 11 is indicated by lines 25. In the upper part of the Figure 4The strapping material, namely folding box blanks, is shown in a section. The folding box blanks have a glue point 27 and a (lead) gap 29. The gap 29 is formed by the two edges of the folding box blank, which was glued in the area of ​​the glue point 27. Therefore, if the glue point 27 is faulty, the gap 29 is either too wide or too narrow. In many cases, both are intolerable, so that the folding box blank must be rejected. The width of the gap 29 is indicated by the black rectangular areas in the extension of the dot-dash line 23 in the Figure 2 shown.

Claims

1. Strapping machine for strapping a product (3) to be strapped using a weldable plastics band, the strapping machine comprising a machine table for receiving the product (3) to be strapped during strapping and at least one strapping device, the strapping machine comprising at least one camera (11), and the camera (11) being directed at the product (3) to be strapped at least temporarily, characterized in that the camera (11) is arranged on a linear guide (13), and in that the at least one camera (11) can be moved orthogonally (Z-axis) to a plane spanned by the machine table.

2. Strapping machine according to claim 1, characterized in that the linear guide (13) is movably mounted on a second linear guide 21, and in that the camera (11) can additionally be moved in a second direction (Y-axis).

3. Strapping machine according to either of the preceding claims, characterized in that the at least one camera (11) is a matrix camera, a line-scan camera, or a laser distance sensor.

4. Strapping machine according to any of the preceding claims, characterized in that it has a discharge device which can transport a faulty bundle out of the strapping machine in a discharge direction (Y-axis) which is different from the normal transport direction (X-axis).

5. Strapping machine according to claim 4, characterized in that the discharge device is designed as a slider.

6. Strapping machine according to claim 4, characterized in that the discharge device is integrated into the machine table.