Shredding machine for strapping bands

Abstract

A shredding machine (1) for shredding straps (2), in particular strapping straps, comprising: - a feed opening (3) for feeding a strap (2) to be shredded, - a cutting unit (4) for cutting the strap (2), and - a conveying unit (5) arranged between the feed opening (3) and the cutting unit (4), driven by a drive motor, for conveying the strap (2) from the feed opening (3) to the cutting unit (4), characterized in that the conveying unit (5) has a conveying roller (6) driven by the drive motor, which has a drive toothing (7) on only part of its roller circumference for the indexed conveying of a fed strap (2), and that the cutting unit (4) only cuts the strap (2) when the strap (2) is not carried by the conveying roller (6).

Description

The invention relates to a shredding machine for shredding straps, in particular strapping straps, comprising a feed opening for feeding a strap to be shredded, a cutting unit for cutting the strap and a conveying unit arranged between the feed opening and the cutting unit, driven by a motor, for conveying the strap from the feed opening to the cutting unit. Such shredding machines for shredding strapping bands are well known. Strapping bands, available in a wide variety of widths, thicknesses, and materials, are widely used in the packaging industry. Products or packages strapped with them are securely held together for transport. Due to their light weight, flexibility, and high tensile strength, as well as their ease of use and low cost, strapping bands are used in large quantities for packaging and securing goods. They are made from various materials, including plastics, steel, paper, and textiles. The most common materials are plastic straps, particularly those made of PP or PET, and steel straps. Strapping bands are typically supplied on rolls, unwound during the packaging process, wrapped around the goods, tensioned, and then joined together to securely strap the goods. The strapping is then cut to separate it from the rest of the wound band. The ends can be joined by welding the strapping or using plastic or steel clips. Depending on the application, manual, semi-automatic, or fully automated processes are used to process the strapping bands. The recipient of the package typically cuts the strapping band using a manual or motorized cutting device when unpacking. After use, the strapping band remains as packaging material, which then needs to be disposed of or, better yet, recycled. Storing and disposing of this strapping band is often difficult, time-consuming, and usually unsatisfactory in terms of the end result. This is mainly because the strap sections generally have a high elasticity and are therefore difficult to wind up permanently or otherwise easily compact. If the strapping bands are cut into small particles or sections, the required storage volume is significantly reduced. It is advantageous and desirable to transfer strapping bands into a defined recycling process after use. This is easily possible with steel strapping, while with plastic strapping, this process can be optimized, especially if new strapping bands can be manufactured from used sections. This type of micro-recycling cycle enables optimal material utilization with minimal effort and little waste material that cannot be reused. However, this requires that the two most commonly used plastic materials, PP and PET, can be separated easily and cleanly so they can be used as raw materials for new strapping bands. This is achieved most simply and effectively using the float / sink method. For this, the strapping bands need to be shredded into particles of a defined size.These particles are placed in a water bath and then separate due to their different material densities. PP particles collect on the surface of the water bath, and PET particles at the bottom. The aim of this invention is to optimally fulfill both requirements, namely effective and simple compaction of the used strapping bands at the point of origin while simultaneously optimally preparing the material for subsequent material recycling. Existing solutions on the market that attempt to meet these two requirements have several drawbacks for the user. These devices are generally relatively large, heavy, loud, and expensive. Furthermore, ease of use and maintenance often fall short of the desired level. To offer a user-friendly solution, it must be as compact, quiet, cost-effective, and user-friendly as possible. This is especially true if the devices are to be installed wherever strapping is generated. Even in small and medium-sized companies, this can often be the case in multiple locations. A concept that addresses this situation allows the user to shred and compact the strapping directly at the point of generation. This eliminates both the otherwise necessary, cumbersome intermediate storage of the used strapping and its transport to a central shredding unit.The behavior of the strapping bands to be shredded also argues against intermediate storage; if they are stored in bags, for example, they occupy a very large volume due to their resilience. Furthermore, the bands tend to become entangled immediately, which makes subsequent separation at the central shredding unit extremely difficult. Therefore, there are many arguments in favor of establishing decentralized solutions. However, since a decentralized solution requires several machines for the various collection points, it is often only economical for the user if the required machines are significantly smaller, more efficient, and less expensive than machines designed primarily for large quantities and centralized processing. Known technical solutions for cutting strapping into particles of defined length generally employ a feed unit followed by a cutting unit. The strapping is fed in by the operator, drawn into the machine, and cut into particles of predetermined length. The strap feed runs continuously as long as a strap is being fed into the running machine. The cutting unit typically consists of a blade attached to the feed unit, positioned so that the strapping is guided over it and the blade's cutting edge is approximately perpendicular to the strapping's longitudinal edge. A counter blade, mounted on a driven rotor, acts as a counter blade. The rotor's axis of rotation is parallel to and positioned at a certain distance from the stationary cutting edge.The rotating knife is attached to the rotor in such a way that the stationary and rotating knife edges are only minimally separated as the rotor passes the stationary knife during its rotation. When the belt is transported over the stationary knife by the feed unit, it is cut by the rotating knife at its cutting edge. If multiple counter-knives are installed on the rotor, this cutting process can occur several times during a single rotor revolution. This relatively simple principle has several drawbacks. One disadvantage is that the stationary and rotating blades must be very precisely aligned, which becomes particularly apparent when changing blades, especially when they become dull. If the distance between the blade edges is too great, the strapping, particularly thinner straps, will not be cut but will instead tend to be kinked by the rotating blade against the stationary blade. This leads to an immediate blockage of the machine, as the strap feeder continues to feed the strapping. If the distance is too small, there is a risk of the rotating blade colliding with the stationary blade. This is especially critical because the rotor is often massively constructed to act as a flywheel, and therefore, due to its high moment of inertia, a collision can cause significant damage to the machine or even pose a danger to the customer.There is another disadvantage to the aforementioned setup, where the strapping band is continuously fed. This is the moment when the cutting process takes place, i.e., when the blade edges cross. During this time, the fed strapping band cannot move freely. This results in a brief bunching of the band, or, especially with very stiff strapping bands, the drive elements of the feed mechanism may slip briefly on the strapping band. Both cases can lead to undesirable effects, such as the band not being cut cleanly or the drive elements, which are engaged with the strapping band, becoming clogged with strapping debris and thus no longer transporting it reliably. Known devices with the previously described design are generally relatively large and heavy due to the necessary flywheel mass of the knife rotor and often require a relatively large drive motor so that the rotor can be set in motion even when there are still strips of tape in the system and the rotor cannot be brought up to the target speed without a load. The object of the present invention is to overcome the described disadvantages. In particular, it is intended to ensure that the strapping band, or more generally any band, is not transported further during the cutting process, that the device design is compact and implemented without large inertia, and that the blade change can be made simple and safe for the operator. This task is solved in the aforementioned shredding machine by the fact that the conveying unit has a conveying roller driven by the motor, which only has a drive toothing on part of its roller circumference for the timed transport of a supplied belt, and that the cutting unit only cuts the belt when the belt is not being transported by the conveying roller. According to the invention, the conveyor roller, with its partially circumferential drive teeth, ensures a timed belt feed for a defined belt particle length and drives the motion-coupled cutting unit in a correspondingly timed manner, so that the strapping belt is only cut when it is not being fed by the conveyor roller. The conveyor roller has, for example, a (partial) drive tooth in the central region of its outer circumferential surface, which draws in the belts and transports them onward in a timed manner. This ensures that, with the rotating conveyor roller, the strapping belt is only transported when the drive tooth is engaged. In areas without drive teeth, the strapping belt remains stationary while the conveyor roller is rotating. Preferably, the cutting unit is oscillatingly driven or motion-coupled by the conveyor roller or by a shaft located in the drive train of the conveyor roller. The conveyor roller or the shaft located in the drive train of the conveyor roller can, for example, have at least one (eccentric) cam or at least one eccentrically mounted lever arm that moves the cutting unit in an oscillating motion to cut the supplied strapping band in a timed manner. To optimize the acceptance and transport behavior of the conveyor roller, at least one non-driven counter roller or counter roller is installed so that the strapping band is received between the conveyor roller and the counter roller. To account for the fact that strapping bands come in various widths and thicknesses, made from a wide range of materials, the center-to-center distance, and thus the gap between the feed roller and the counter roller, is preferably adjustable. For example, at least one of the two rollers, particularly the counter roller, can be spring-loaded in contact with the other roller. By applying spring tension to the counter roller bearings, the counter roller is pressed against the feed roller, and the gap between the rollers is limited to the extent required by the thickness of the strapping band fed between them. This allows the necessary contact force for transporting the strapping bands, which presses the strapping band against the feed roller, to be easily applied by means of the spring tension on the counter roller. To ensure the strapping is transported safely, the described contact force of the strapping against the conveyor roller and the profile of the drive teeth are crucial. The conveyor roller should mesh as well as possible with the strapping to guarantee secure transport; however, this can also cause the strapping to wrap around the conveyor roller. To prevent this, preferably both the conveyor roller area and the counter roller area are designed such that the area in contact with the strapping has circumferential (ring) grooves that divide this area into several segments. This creates disc-shaped areas with and without corresponding teeth on the conveyor roller, and possibly even without any teeth on the counter roller.The grooves contain wiper elements, which, however, are overridden by disc-shaped elements in the area where the feed roller and counter roller meet, so that the profile of the feed shaft's toothing comes into contact with the straps. The wiper elements extend beyond the outer diameter of the rollers along the axis of the fed strapping band. This allows the strapping band to be fed to the feed and counter rollers via these wiper elements and then cleanly discharged from them. The wiper elements thus ensure that the strapping band cannot wrap around the feed roller or counter roller, as the band is guided continuously between the wiper elements and the rollers only protrude between the wipers. The cutting unit preferably comprises a knife slide guided linearly displaceable at right angles to the feed direction of the strip. This knife slide is oscillated by at least one cam or at least one eccentrically mounted lever arm and carries a knife to cut the strip in a timed manner against a stationary counter-knife. In the first case, rollers attached to the knife slide can roll on the outer contour of the cam(s). The knife slide itself can only move along a straight guide arranged perpendicular to the fed strip. The knife slide and its rollers are pressed against the outer contour of the cams by means of spring tension. When the feed roller and, with it, the cams rotate, the rollers follow the circumferential surface of the cam elements, thereby setting the knife slide into a translational motion.In the second case, the lever arm(s) are articulated to the knife carriage and also set the knife carriage in a translational motion. During one revolution of the conveyor roller, the knife carriage moves from a first starting position to a second position, at which point the carriage's direction reverses and it returns to the starting position. This results in an up-and-down movement of the carriage relative to the fed strapping band. During this up-and-down movement, the knife slides along a stationary counter-knife. The cutting edges of the two knives face each other, such that during the knife movement there are sections of movement in which a gap forms between the cutting edges, and sections in which the cutting edges slide past each other, leaving no gap between them.The knives are arranged so that the strapping to be cut is transported through the gap between them. As the knife edges slide past each other, they cut the strapping. The section of the feed roller with the drive teeth is positioned so that the strapping is transported further during the section of movement where a gap forms between the two knives, allowing the strapping to be transported without collision. During the subsequent movement, and thus with further rotation of the feed roller, the two knife edges eventually overlap and cut the strapping. The strapping should not be transported further during this phase, which is why the feed roller has corresponding sections without drive teeth.The length of the cut strip section is determined by the diameter of the conveyor roller and the angle segment, which has teeth on the conveyor roller. With a larger roller diameter and a larger toothed angle segment, a longer strip section is conveyed and cut per revolution, while with a smaller diameter and a smaller angle segment, a shorter strip section is conveyed and cut per cut. The cam's outer contour determines, firstly, the maximum deflection of the knife carriage and thus of the knife edges relative to each other. Secondly, the cam's slope also influences the timing of the knife movement. The slope of the contour thus determines in which ranges of the conveyor roller's rotation the knife is accelerated or decelerated more or less strongly. The distance between the conveyor roller's center axis and the center axes of the rollers on the carriage changes continuously during a single revolution of the conveyor roller, as these rollers follow the cam's contour. This distance is equivalent to the length of the lever arm between the center axes of the two elements. The lever arm length and the slope at each point on the cam's outer contour therefore correlate directly with the maximum force that the drive can transmit to the knife via the conveyor roller.The force and movement sequence can thus be directly influenced by the cam-shaped element, so that, for example, more force is available during the cutting process with a slower knife speed, or less force is available for returning the knife to its starting position with a faster knife movement. The blade slides particularly smoothly along the stationary counter-blade throughout the entire oscillation movement of the carriage. This design allows for easy blade changes, as the two blades do not need to be adjusted relative to each other. Since the strapping bands to be shredded can sometimes have significant kinks or fraying, etc., malfunctions in the strapping band feed cannot be completely avoided. With conventional solutions, this usually means that parts of the device have to be disassembled to resolve the malfunction. This results in increased workload for the user, the need to have the necessary tools on hand, and in the worst case, even a hazard, especially if the device was not disconnected from the power supply beforehand. To circumvent or avoid the aforementioned disadvantages and hazards, the feed area of ​​the solution according to the invention can preferably be opened without tools by, for example, a counter-roller unit comprising the counter-roller being pivotably mounted on the machine housing between a closed position and an open position in which the feed roller is accessible. In the closed position, the counter-roller unit is locked to the machine housing, for example, by means of a bracket. Preferably, the pivot axis of the counter-roller unit is located behind the feed roller in the feed direction, particularly behind the cutting unit. This moves the counter-roller unit, including the associated scraper elements, away from the opposite feed roller and its associated scraper elements. The feed area for the strapping bands is thus completely cleared. Strap remnants, etc.This allows them to be easily and conveniently removed, thus simplifying the resolution of any malfunctions. This swivel mechanism is electronically monitored, for example by an electrical switch, and the device's drive is stopped immediately as soon as the swivel mechanism is unlocked by the user. With this functionality, the user can easily, without tools, and safely resolve any malfunctions in the feed area. For example, a counter-roller unit comprising at least one counter-roller can be pivotally mounted on the machine housing between a closed position and an open position in which the feed roller is accessible. The counter-roller unit can be locked to the machine housing in the closed position by means of a bracket. For safety reasons, an electrical switch should be installed between the counter-roller unit and the machine housing, which cuts off the power supply to the shredder when the counter-roller unit is opened. As in the belt feed area, it cannot be guaranteed that particles will never accumulate in the discharge area, through which the cut strapping sections leave the machine. This can lead to blockages and malfunctions. In such a case, the operator should be able to resolve the problem quickly, easily, and, above all, safely. Under no circumstances should the operator be able to reach the cutting unit, consisting of the blade and counter-blade, while the machine is running and injure themselves by getting caught between the moving blades. Common solutions on the market often ensure this in the discharge area by securely bolting the machine to the necessary collection container system. The operator can then only detach the machine from the container to access the discharge using tools.Once the device is disconnected from the container, the operator can clear any blockage in the discharge area and reassemble the unit. Since disconnecting the device from the container system requires tools, it is generally not mandatory to also disconnect the device electrically. This means the device remains functional even when disconnected, which can pose a hazard to the operator. As an alternative to permanently connecting the device head to the container system, some models use mechanical barriers at the discharge area to prevent direct access to the cutting unit. These barriers also typically require tools to remove and are not electrically secured. Neither option is convenient for the operator. Firstly, they need to have the necessary tools readily available, and secondly, dust removal requires a considerable amount of time due to the additional time needed for disassembly and subsequent reassembly. Unfortunately, this can lead to the operator failing to reconnect the collection system or mechanical barrier correctly after dust removal, for example, by not fully or completely re-tightening the necessary screws. To circumvent the aforementioned disadvantages, the outlet area in the invention can be unlocked and then opened without tools. When the outlet area is unlocked, the device stops automatically and can only restart once the area is closed and locked. With the outlet area open, it is fully accessible, making it easy, tool-free, and safe to clear a conveyor belt jam. With the outlet area open, the blade system is also accessible, allowing for easy and safe replacement of worn blades. As described, the blade system requires no complex adjustment process, further simplifying replacement. For the user, it is advantageous that the blade is reversible, meaning it can be easily flipped for another use. For example, the cutting unit can be pivotally mounted on the machine housing between a closed position and an open position in which the cutting unit is accessible. In the closed position, the cutting unit can be locked to the machine housing by means of a bracket. For safety reasons, an electrical switch should be installed between the cutting unit and the machine housing, which cuts off the power supply to the shredder when the cutting unit is opened. The invention is illustrated in the drawings and explained in more detail with reference to an exemplary embodiment. The drawings show (each without drive motor, electrical control unit, and housing parts): Fig. 1a, Fig. 1b the shredding machine according to the invention in the closed state (Fig. 1a) and in the open state (Fig. 1b); Fig. 2a, Fig. 2b a conveyor roller with cams shown in Fig. 1b and a knife slide driven by the cams in a perspective view from above (Fig. 2a) and in a perspective view from below (Fig. 2b); Fig. 3 an outlet area of ​​the shredding machine shown in Fig. 2b. The shredding machine 1 shown in Fig. 1a, Fig. 1b is used for shredding strapping bands 2 and comprises a feed opening 3 for feeding a strapping band 2 to be shredded, a cutting unit 4 for cutting the strapping band 2 and a conveying unit 5 arranged between feed opening 3 and cutting unit 4, driven by a drive motor, for conveying the strapping band 2 from the feed opening 3 to the cutting unit 4. As shown in Fig. 2a, the conveying unit 5 has a conveying roller 6 driven by the drive motor, which has a drive toothing 7 on only part of its circumference for the indexed conveying of the supplied strapping band 2. A non-driven counter roller 8 is associated with the conveying roller 6, so that the strapping band 2 is received between the two rollers 6 and 8. The counter roller 8 can be spring-loaded in contact with the conveying roller 6 to accommodate strapping bands 2 with different thicknesses between them. The conveying roller 6 and the counter roller 8 each have circumferential annular grooves 9 into which wiper elements 10 engage. The feed roller 5 has a cam 11 on each side of the drive toothing 7, which moves the cutting unit 4 in an oscillating motion to cut the supplied strapping band 2 in a timed manner. For this purpose, the cutting unit 4 has a knife slide 12, which is guided in a slide guide 13 perpendicular to the feed direction 14 of the strapping band 2 and is linearly displaceable (double arrow 15) and is moved back and forth in an oscillating motion by the cams 11. The cams 11 interact with two rollers 16 of the knife slide 12, the knife slide 12 being held in contact with the cams 11 by two springs 17. As shown in Fig. 2b, the knife carriage 12 carries a knife 18 to cut the strapping band 2 at a timed interval against a stationary counter knife 19, here in the form of a knife opening 20 for the fed strapping band 2. The knife 18 slides along the counter knife 19 during the entire oscillation movement of the knife carriage 12. The feed roller 6, with its only partial drive teeth 7, ensures a timed band feed for a defined band particle length and drives the motion-coupled knife carriage 12 at a correspondingly timed interval via the cams 11, so that the strapping band 2 is only cut when it is not being fed by the feed roller 6. The (partial) drive teeth 7 draw in the strapping band 2 and transport it onward at a timed interval. This ensures that when the conveyor roller 6 is rotating, the strapping band 2 is only transported further when the drive toothing 7 is engaged with it.In areas without drive teeth, the strapping band 2 remains stationary while the conveyor roller 6 is running and is cut into band sections 21 of equal length by the knife 18. A counter-roller unit 22, comprising the counter-roller 8, is pivotably mounted on the machine housing 23 between a closed position (Fig. 1a) and an open position (Fig. 1b), in which the conveyor roller 6 is accessible. In the closed position, the counter-roller unit 22 is locked to the machine housing 23 by means of a handle 24. An electrical switch (not shown) can be arranged between the counter-roller unit 22 and the machine housing 23, which switches off the power supply to the shredding machine 1 when the counter-roller unit 22 is opened. The cutting unit 4 can also be pivotally mounted on the machine housing 23 between a closed position and an open position shown in Fig. 3, in which the cutting unit 4 is accessible. In the closed position, the cutting unit 4 is locked to the machine housing 23 by means of a handle 25. An electrical switch (not shown) can be arranged between the cutting unit 4 and the machine housing 23, which switches off the power supply to the shredding machine 1 when the cutting unit 4 is opened.

Claims

A shredding machine (1) for shredding straps (2), in particular strapping straps, comprising: - a feed opening (3) for feeding a strap (2) to be shredded, - a cutting unit (4) for cutting the strap (2), and - a conveying unit (5) arranged between the feed opening (3) and the cutting unit (4), driven by a drive motor, for conveying the strap (2) from the feed opening (3) to the cutting unit (4), characterized in that the conveying unit (5) has a conveying roller (6) driven by the drive motor, which has a drive toothing (7) on only part of its roller circumference for the indexed conveying of a fed strap (2), and that the cutting unit (4) only cuts the strap (2) when the strap (2) is not carried by the conveying roller (6). Shredding machine (1) according to claim 1, characterized in that the cutting unit (4) is driven in an oscillating manner by the conveyor roller (6) or by a shaft present in the drive train of the conveyor roller (6). Shredding machine (1) according to claim 2, characterized in that the conveyor roller (6) or the shaft present in the drive train of the conveyor roller (6) has at least one cam (11) or at least one eccentrically articulated lever arm which actuates the cutting unit (4) for the timed cutting of the supplied belt (2). Shredding machine (1) according to one of the preceding claims, characterized in that the feed roller (6) is assigned at least one non-driven counter roller (8) so that the belt (2) is received between the feed roller (6) and the counter roller (8). Shredding machine (1) according to claim 4, characterized in that the center distance between the conveyor roller (6) and the counter roller (8) is variable. Comminution machine (1) according to claim 4 or 5, characterized in that at least one of the two rollers (6, 8), in particular the counter roller (8), is spring-loaded in contact with the other roller. Shredding machine (1) according to one of the preceding claims, characterized in that the conveying roller (6) and / or the counter roller (8) have circumferential annular grooves (9) into which scraper elements (10) engage. Shredding machine (1) according to one of the preceding claims, characterized in that the cutting unit (4) has a knife slide (12) which is guided linearly displaceable at right angles to the feed direction (14) of the belt (2), which is moved oscillatingly by the at least one cam (11) or the at least one eccentrically articulated lever arm and which carries a knife (18) to cut the belt (2) in a timed manner against a stationary counter knife (19). Crushing machine (1) according to claim 8, characterized in that the knife (18) slides along the counter knife (19) during the entire oscillation movement of the knife carriage (12). Crushing machine (1) according to claim 8 or 9, characterized in that the counter knife (19) has a knife opening (20) through which the belt (2) is conveyed. Crushing machine (1) according to one of the preceding claims, characterized in that a counter roller unit (22) having at least one counter roller (8) is pivotably mounted on the machine housing (23) between a closed position and an open position in which the conveyor roller (6) is accessible. Crushing machine (1) according to claim 11, characterized in that the counter roller unit (22) is locked in the closed position by means of a bracket (24) on the machine housing (23). Crushing machine (1) according to claim 11 or 12, characterized in that an electrical switch is arranged between the counter roller unit (22) and the machine housing (23), which switches off the power supply to the crushing machine (1) when the counter roller unit (22) is opened. Shredding machine (1) according to one of the preceding claims, characterized in that the cutting unit (4) is pivotably mounted on the machine housing (23) between a closed position and an open position in which the cutting unit (4) is accessible. Shredding machine (1) according to claim 14, characterized in that the cutting unit (4) is locked in the closed position by means of a bracket (25) on the machine housing (23). Shredding machine (1) according to claim 14 or 15, characterized in that an electrical switch is arranged between the cutting unit (4) and the machine housing (23), which switches off the power supply to the shredding machine (1) when the cutting unit (4) is opened.

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