Dual contact system for folding in a concertina-fashion

p0001The invention relates to a device for enveloping preferably palletized piece goods with a tubular or hood-shaped stretch film according to the preamble of claim 1 and a corresponding method according to the preamble of claim 14.

p0002Devices for wrapping piece goods are, as regards their basic components, usually carried out as the device described by the European patent application 0344815 A1. They generally consist of a machine frame on which a lifting frame (in an approximately vertical direction) is moved up and down. The lifting frame usually carries the folding frame which is opposite to the lifting frame in the transverse direction (ie, in an approximately horizontal direction) are in turn moved to stretch the stretch film to the reefing of the stretch film on the folding frame in the transverse direction to be able ie elastically stretched, ie the so-called Horizontal Stretch be able to generate. Is a common horizontal and transverse stretch from 10% to well over 50%, based on the unstretched dimensions of the stretch film in the transverse direction. The folding frame can be configured very differently. The options here range from a very simple, finger-like design to the intended for a stronger stretching Reffbügeln which often have a T-like shape by a substantially vertical shaft for receiving the reefed stretch films and carried thereby, consist essentially horizontally extending, running with a specific radius of curvature portion which forms the respective corner of the stretched film on the Reffbügeln held round. To aufzureffen a tubular or hood-shaped stretch film, the folding frame are regularly introduced into the inner, lower end of the tubular or hood-shaped stretch film. Agent Refforganen is then the section of stretch film that is later to cover the side surfaces of the product to be packaged cargo, reefed to the folding frame.

p0003As Refforgan that part of the device is in the local context, understood to be brought to the reefing of stretch film in contact with it and forces applied by means of its drive appropriately to the stretch film, so this by overcoming the frictional forces occurring at the Reffbügeln in concertina like folds is reefed on the folding frame. Typically, each folding frame is assigned a Refforgan in the form of a motor-driven folding roller. The Refforgan can be moved up to the folding frame in question as a rule, that the folding roller as an abutment presses using the folding frame on the stretch film and so taking advantage of the friction forces which stretch film draws on the folding frame, so it can reefing. The aufgereffte stretch film is then deposited in said accordion-like folds on the Reffbügeln from.

p0004The finished aufgereffte section of stretch film is then transversely stretched by appropriate methods of folding frame, so usually stretched in substantially horizontal direction. They must avoid any wrinkles and in particular said accordion-like folds are strongly pressed against each other. Thereby two or more layers of stretch film come at various points strongly pressed against each other - seen in the horizontal direction - to lie on one another, so wrinkles develop, which can be described as "Überlappfalten".

p0005The coefficient of friction "film to film" is generally less than the friction coefficient "film against folding frame". The first scanned border peel off the stretch film of the Reffbügeln (during the stretch film pull-down operation) in motion and therefore have to Reffbügeln sliding along Überlappfalten ideally tends applicable to pull apart in the course of sliding along the folding frame that the overlap is canceled before the Überlappfalte reaches the upper edge of the respective folding frame. However, it often happens that individual Überlappfalten not pull apart fast enough, but not smoothed jump off the folding frame. In this case there is a lashing pulling the Überlappfalte whose individual film layers are no longer pressed against each other by friction when the fold is subtracted from the folding frame. This often leads to thin drawing the stretch film and thus to tear.

p0006Furthermore, it may in modern Reffbügeln then already come to a tearing of the film when a Überlappfalte is only reaching the region of the discharge-sided upper edge of the respective folding frame and pulled apart only there. Because modern folding frame are designed so that the maximum load of the stretch film wrapping occurs in the discharge-sided top of the folding frame.

p0007In practice, various solutions have already been disclosed to cope.

p0008So is already known, the folding frame, seen in vertical direction, long enough to carry out and which removes the reefing on the folding frame bewerkstelligenden Refforgane with their driven reefing rollers are each approximately in the center of the folding frame, and far enough from the withdrawal side top of the folding frame, attack to make, is stored so that below the reefing rollers reefed the stretch film accordion-shaped and rests above the reefing rollers, due to the tensile forces, the stretch film hood over a not small track smoothly on the extended portion of the folding frame. Such larger dimensions of the folding frame is undesirable. It leads to additional construction costs, in particular to a larger total amount of investments and increased mainly the path that must be traveled in the vertical direction of the Reffbügeln or they holding lifting frame at each packaging operation. In order for the operating speed of the device is impaired, which is of particular importance.

p0009Furthermore, devices are known which achieve the desired result in the end in that the reefing the bewerkstelligenden on the folding frame reefing rollers are moved towards the end of Reffvorganges translationally to withdrawal side top of the folding frame in practice. Such movement has the result that the stretch film is regionally smoothed on the respective folding frame or smoothed, so as to form the subsequent transverse stretching only at some distance from the discharge end of the folding frame Überlappfalten. Such additional movement of the reefing rollers at the end of Aufreffvorgangs represents an additional step in the preparation of stretch film for coating, the in high-performance systems leads straight to an unacceptable loss of time. In addition, an additional translational movement of the reefing rollers caused a corresponding apparatus expenditure, ie costs, and also represents an additional source of potential interference. Otherwise it is not ensured under all circumstances that such smoothing succeed.

p0010Furthermore, already was in the prior art, for example, in corresponding to the preambles of claims 1 and 14 DE 40 37 105 C1, proposed to provide on the long sides of Reffrahmens pairs of rollers or roller pairs, which, once the Reffrahmen in the record- Streif position of the stretch hood , serve as clamping roller pairs for stretch wrapping of stretch hood in its longitudinal direction, wherein the reefing fingers all roles with the same peripheral speed and in the same direction to work acting during Reffvorganges the stretch film. When removing or donning the stretch film cover over the product to be packed, the rollers are then driven against their Reffrichtung, wherein upon removing the rollers are driven at different circumferential speeds to ensure a smooth Trouble-free removal of the stretch film.

p0011The invention is therefore to create or vehicle quickly and with simple means capable of a the side surfaces enveloping section of stretch film so aufzureffen on the folding frame, so that the danger of the object of providing an apparatus and a method of the generic type that arrive after stretching when the film is Überlappfalten up in critical areas of the folding frame, is substantially reduced and the film in these areas will not thin pulled or damaged.

p0012The related to the device part of the object is achieved by a device with the features of claim 1, wherein each Refforgan having reefing with which it at least temporarily can thus act simultaneously in two spaced in Reffrichtung zones on the stretch film, that between the section of stretch film two zones located is arranged without overlap on the Reffbügeln concerned. In this case, each Refforgan at least a first folding roller and a relative to the Aufreffrichtung subsequently arranged second draw roller, whereby the folding roller during the folding operation of the apparatus at its kicking with the stretch film in contact periphery, a lower circumferential speed than the draw roller, so that between the folding roller and the tension pulley located section of stretch film drawn, preferably stretched and disposed without overlapping on the Reffbügeln concerned. Possibly reaching into the area between the zones wrinkles are pulled smoothly both during reefing and peel off in this area.

p0013In this way ensures that the stretch film at the beginning of the soundtrack drawing process in a certain, not to short range (the is hereinafter referred to as "smoothening") prior to the withdrawal side top of the folding frame smooth, so is the Reffbügeln without Überlappfalten. All Überlappfalten that may be deducted in the course of covering the stretch film on the load to be wrapped by the film supply concertina-shaped reefed held initially and then slide the folding frame in question along, do so in a defined, greater distance from the critical region near the discharge-sided top the respective folding frame, wherein Überlappfalten regularly should not penetrate into the critical range. It is thus ensured that each Überlappfalte that do not already dissolved instantly when pulled out of the concertina-shaped aufgerefften stretch film stock, only a certain distance has to slide on the respective folding frame along before they can reach the critical area of ​​the respective folding frame. During this sliding over a longer distance, the majority of all Überlappfalten dissolves before the critical range is reached. The risk of interference by thin pulling or tearing of the stretch film, which is particularly problematic given from the stretch film before stretch film hoods were formed is substantially reduced.

p0014Preferably, said two zones are so far apart that dissolve the Überlappfalten reliable. Ie that Überlappfalten between zones are present. Only in a few cases and may reach the critical area. This effect is advantageously achieved both during reefing the film to the folding frame as well as during removal of the film from the same.

p0015As already mentioned, the Refforgane are so equipped that each Refforgan comprising two drivable, based on the Aufreffrichtung successively arranged reefing formed of rollers, namely a first folding roller and a second, arranged behind the pull roll whose spacing from one another is advantageously adjustable.

p0016The device is designed so that the folding roller, so that role to the film at the beginning of Aufreffvorgangs first meets, at their passing with the stretch film in contact circumference with slower peripheral speed than the second, so subsequent tension pulley so that the between the section of stretch film rolls located is pulled during Aufreffens or smoothed or pulled without folds. Such a Drag (without significant expansion of the film) causes any guessed when reefing the hood in the area between the two rollers folds are pulled apart reliably.

p0017Preferably, the device is designed so that the stretch film during operation of the device at least one point on an imaginary direct joining line between the said zones come into contact neither with nor with the Reffbügeln Refforganen. In this way it is possible particularly effective, smooth draw guessed when reefing and pulling into the area between the two rollers folds. Because eventually arrived in this area wrinkles can be pulled apart easily with such a configuration, since the friction of the individual layers of film is released in the folds once the relevant fold on the direct connecting line between the said zones with either the Reffbügeln still with Refforganen in contact comes. Any force that acts perpendicular to the fold and could hold the fold friction is canceled.

p0018Here, a design of the device of the type is especially preferable when operating the apparatus, the stretch film pressed into one of the two rolls against an elastic resilient region of the respective folding frame. In this way a particularly effective interaction between the two rollers is ensured in their effect and in any case avoid overloading the film in the area between the two rollers. Because in the region of the roll, which presses against the resilient region can (if necessary) slip between the film and the role occur. Preferably, the spring force of the resilient portion is adjustable so that it can be matched exactly when slippage occurs.

p0019It is cheap, at least one of the two rollers, preferably the pulley to raise the profile so that it is not continuous at a rolling in the stretch film to the stretch film into contact. This favors the pulling apart of the reefing in the area between the rollers more advisable wrinkles. The same applies to an elastic cross Great Profile.

p0020Designed to the device so that the two rollers of each Refforgans be driven during operation of the device by a single motor, then results in a particularly low construction cost. It is also advantageous for one of the two roles, particularly the pulley, to be provided with a freewheel, which allows free rotation in the drawing direction, in order to ensure the unimpeded withdrawal of the film from the Reffbügeln. However, it is also conceivable that for the rollers separate drive motors are provided, which enable individual control by accelerated or delayed rotation of the rollers in order to achieve a braking effect z. B..

p0021Even more, the device can be simplified when the reefing only the pulley positive, ie motor, drives and the folding roller negatively drives the operation of the device, ie brakes. Even then arises between these two rollers a tension that pulls apart guessed when reefing in the area between the two rollers folds reliable.

p0022Furthermore, it is conceivable, each provide a separate, independently operated motor drive and / or independently operable Zustellorgane for the roles. The preference is nevertheless to give the illustrated hereinafter by the figures for the concrete embodiment, structurally very simple and extremely reliable solution, which under certain conditions even suitable for retrofitting of existing plants, as the piston rod of the advancing device instead of the previous single folding roller with its motor only the role tandem must be placed, which is also driven through the chain or belt transmission only of a single Reffmotor and therefore makes no fundamental changes in the control of the machine required.

p0023Of particular importance is the invention for packaging machines of gattungsgemä-KISSING kind, not only with a strong horizontal stretch, but also with an additional, not inconsiderable Vertical Stretch in the amount of about 10% to 50%, especially more than 50%, based the ungestretchten vertically state work. Because with processing of stretch films, which are subject to such, highly biaxial stress state, it is particularly true of crack induction prevent by slide on Überlappfalten.

p0024The procedural part of the object is achieved by the method according to claim 14, wherein is acting on the stretch film during Aufreffens by Refforgane respectively by means of two spaced apart reefing at least temporarily simultaneously in two spaced in Aufreffrichtung zones on the stretch film, that after termination of Aufreffens between the two zones located section of stretch film is arranged without overlap on the folding frame in question. When pulling reaching wrinkles are possibly in the area between the zones also smoothed out, so that they can not enter the critical region of the upper edge of the folding frame.

p0025In the following, an embodiment of the invention with reference to drawings will be explained in more detail. Show it:<dl id="dl0001"><dt>Fig. 1</dt><dd>the essential detail of the apparatus according to the invention, namely a folding frame and its associated Refforgan,</dd><dt>FIG. 2</dt><dd>a side view of the essential section of the apparatus of the invention during the Aufreffens the film to the folding frame prior to transverse stretching, and</dd><dt>Fig. 3</dt><dd>a side view of the essential section of the inventive device before removing the foil from the quergestretchten Reffbügeln.</dd></dl>

p0026The inventive apparatus, which is not shown as a whole here, consists essentially of the initially mentioned in connection with the discussion of the prior art, known basic components that can be designed or modified in many ways. Numerous other known components that are necessary to successfully complete a packaging operation of stationary type in question here, come - depending on the individual case - added.

p0027FIG. 1 shows a generally four - but occasionally more, about six or eight - Reffbügeln 1, and an associated therewith Refforgan 2. The folding frame 1 is designed for mounting on a drive determines the way it along an arrow S in the horizontal direction - and can reciprocate. The Refforgan 2 consists of a feeding device 4, here in the preferred form of an advantageously pneumatically driven feed cylinder, 5b consisting of a folding roller 5a and a draw roller reefing boom system, one the two rollers driving Reffmotors 3 and a caring for the required translation chain or belt transmission 6. the feeding device 4 is accordingly controlled and ensures may be that the folding roller 5a and the pulley 5b driven up to its working position and retracted in due course from its working position, respectively by moving left or right along an arrow V. feeding device 4 is usually mounted with its base 7 on the same drive unit, which is also the folding frame 1 along the arrow S reciprocated. In this way it is ensured by simple means that the Refforgan 2 is for the purpose of Querstretchens of stretch film driven back in a apart of the folding frame with the folding frame. 1

p0028As can be seen with reference to FIG. 2, the folding frame 1 at its discharge-sided upper edge of a critical area K. In this critical area K should reach when pulling off the stretch film from a reefed held stretch film reservoir 8 only a few, preferably virtually no Überlappfalten. This is because in the critical area K of the strap section greatly changes. As shown in FIG. 1, for example, the folding frame in the region of the constriction 9 tapers locally, while the film then even aufdehnt even more below the area of ​​the upper bracket part 10. So the film glides along this section K, so changes its load in rapid succession. Due to this Überlappfalten should not reach in this area, since they otherwise under the influence of this rapid load change, the risk of film thin drawing or possible - increase, rip. The critical region K is the conventional practice used in the plants in the area of ​​the upper edge of the folding frame. Alternatively, however, the use of up down nearly smooth top Reffbügeln without significant changes in cross section is conceivable, it is then only to prevent in this way designed Reffbügeln that Überlappfalten "jump" from the Reffbügeln.

p0029At the beginning of each Aufreffvorganges the Refforgane along the arrow V are retracted, so that a noticeable gap between the respective folding frame 1 and the rollers 5a and 5b is made. The folding frame 1 and the other (not shown) folding frame be a short piece inserted far into the most open through additional aids Stretch film tube, preferably about so far that the lower edge of the stretch film tube an held on folding frame 1, idler wheel 11 just covered. Due to the relatively short paths required the folding frame is therefore to position fairly quickly in the stretch film hose.

p0030Then the Refforgane be delivered, so that the stretch film between the free roller 11 and the folding roller 5a is held by friction. Then, the Reffmotor started 3, whereafter the stretch film is pulled through the frictional contact with the folding roller 5a of the folding frame 1, downwards. Shortly thereafter, the lower end of the stretch film tube is detected by the downstream drawing roller 5b friction. To the stretch film thus now acts via a first contact zone (zone Z1), the folding roller 5a and a second contact zone (zone Z2), the draw roller 5b. Since the connecting chain or belt transmission 6 is designed in this embodiment so the two rollers to one another, the downstream tension pulley rotates 5b faster than the folding roller 5a, the film is located between the two rollers 5a and 5b, in the region between the contact zones (Z1 and Z2) pulled taut and, depending on difference of the rotational speeds of the two rollers 5a and 5b even stretched temporarily by a certain amount.

p0031As shown by Fig. 1 and 2, the lower tension pulley 5b advantageously not supported in its operative position directly on a substantially rigid portion of the folding frame 10 from, but rather acts together with a bracket 12, as seen in the horizontal direction by a screw 14 is fixed and spring loaded on a held by a screw compression spring 13 in the horizontal direction so far that a pressure of the strap 12 is realized on the pulley. Instead of such, preferably floating mounting the bracket 12 can be mounted resiliently-mounted. It limited the bracket 12, the force that can muster the pulley 5b on the film. This means that the frictional forces are limited, it can raise the pulley 5b on the film. Before there is an overload of the film during reefing between the slower-running folding roller 5a and the faster current draw roller 5b, therefore slip between the film and the draw roller will occur 5b. Advantageously, the spring force with which the bracket 12 is held adjustable, which is not shown here.

p0032Especially when reefing of formed of stretch film stretch film hoods hoses it is inevitable that occasionally happen foil folds the folding roller 5a during Aufreffens and enter the area between the two rollers 5a and 5b. There they are, effectively pulled apart due to the fact that there is a train is applied to the film by the faster moving downstream tension pulley 5b and 12 lose those wrinkles in the area between the free roller 11 and the bracket contact with the folding frame.

p0033A useful contribution to the elimination of wrinkles and to improve the smoothing makes 5b the profile of the pulley. This profile consists of individual, resilient in the circumferential direction lugs 17 between which each wide spacings are (profile gaps). In this way an in rapid sequences rising and falling tensile load is applied to the present between the two rollers 5a and 5b slide that optimizes the result.

p0034Due to this design of the Refforgans with at least two, along the vertical axis of the folding frame 1, so in Aufreffrichtung successively arranged rollers 5a and 5b is ensured at the conclusion of reefing that between the critical area K and the range shown in FIG. 2 ZH, in which the film supply is 8 reefed concertina-like manner, a not only insignificantly far extending portion G is where the stretch film is kept practically smooth. Mark the limits of the range G in Aufreff- and withdrawal direction the zones Z1 and Z2, that is, the areas where the folding roller 5a, the film against the idler wheel 11, and the pulley 5b the film against the bracket 12 press and so with the film come in frictional contact.

p0035The concrete needed in a particular case vertical extent of the region G, the expert can easily identify each. It depends in addition to the device and the example provided by the to use films parameters (friction coefficient between folding frame and film, between the film and foil coating speed of stretch film about loads, concrete geometry of the folding frame, amount of horizontal and possibly vertical stretchs etc .) of the desired reliability, ie the degree of protection from, with the expert wants to prevent Überlappfalten in the critical area K reach. As a rule, there is an optimum compromise between the required compactness of the folding frame on the one hand and a sufficiently reliable avoiding Überlappfalten in the critical area K on the other hand. Preferably, the area G between the critical area K and the area ZH, in which the film supply is 8 reefed concertina-like. To adjust the range G and the area ZH, can the bracket 12 in its vertical position, ie be kept in a vertical direction, set the folding frame 1, while in addition / or alternatively, the distance between the rollers 5a, 5b may be adjustable.

p0036The result described above can be achieved under certain circumstances also by the fact that the pulley 5b is supported, for example, pivotable and is delivered shortly before completion of Reffvorganges separately that it cooperates with the folding roller 5a. The preferred solution is however so designed as shown in the preferred embodiment illustrative figures. For such a design of the construction cost is kept low and also reduces the risk of error, which is about characterized results that may occur under unfavorable circumstances an undesirable film jam or the like by subsequently delivering the traction roller 5b.

p0037The rollers 5a and 5b have also seen in Aufreffrichtung not absolute lie exactly with each other. A certain, the function of not substantially interfering lateral offset between the two rollers 5a and 5b is permitted.

p0038As further shown with reference to FIG. 3, which contained after reefing on the Reffbügeln, loosely deposited film is first stretched in consequence of a carried to the required width depending on the product to be packaged apart driving the folding frame and Refforgane in a substantially horizontal direction. The resulting from the moving apart traction the Zodiac stretched now in a substantially horizontal direction film has the effect that the superposed in the region ZH of loosely deposited during Aufreffvorganges stretch film supply 8 Überlappfalten 18 Creating considerable tension in the region ZH closely to the folding frame.

p0039During by vertical movement of the entire device during the pull-down operation of the stretch film about the load to be wrapped caused peeling operation of the Reffbügeln is. 1 shown advantageous embodiment of the device to ensure due to the described and shown in Fig, that the stretch film to the beginning of the stall operation in the smoothening before the withdrawal side top of the folding frame 1 smoothly, without Überlappfalten is on Reffbügeln. All Überlappfalten that may be deducted in the course of covering the stretch film on the load to be wrapped by the concertina-shaped reefed held, under considerable tension film supply 8 and then first slide the respective folding frame 1 along, do so in the defined, greater Distance from the critical area K near the discharge-sided top of the respective folding frame 1, wherein Überlappfalten penetrate advantageously usually not in the critical region. It is thus ensured that each Überlappfalte that do not already dissolved instantly when pulled out of the concertina-shaped aufgerefften Stretch film supply 8, only a certain distance has to slide on the respective folding frame along before they can reach the critical area K of the respective folding frame. 1 During this sliding over this distance between the zones Z1 and Z2, the majority of all Überlappfalten in area G dissolves before the critical area K is achieved. The risk of interference by thin pulling or tearing of the stretch film, which is particularly problematic given from the stretch film before stretch film hoods were formed, is thereby substantially reduced.

p0040While pulling the unit to the pulley 5b is supported in its operating position further on the seen in the horizontal direction floating bow 12 from in order to continue to maintain the smoothing effect in the region G between the zones Z1 and Z2 during pulling upright. Here, the lower tension pulley 5b advantageously to a bracket 12 is supported in its operating position, which is seen in the horizontal direction is fixed by the screw 14 and spring-loaded on a held by a screw 13 spring in the horizontal direction so far that a pressure of the strap 12 is realized on the pulley. As already stated, the bracket instead of such, preferably floating bearing may be mounted resiliently pivotable.

p0041In order to avoid in particular a sheet jam in G between the zones Z1 and Z2 during the peeling of the film due to the diverging peripheral speeds of the two rollers 5a and 5b, it is advantageous for the storage or the drive of the draw roller 5b in such shape that these during Aufreffvorgangs over the Reffmotor 3 in Aufreffrichtung is accordingly driven to the difference of the peripheral speeds of the two rollers 5a and 5b to ensure and thus to achieve the desired smoothing in the area G, the storage, or the drive of the 5b pulling roll but additionally with a freewheel is fitted, which allows the rotating with the traction roller 5b with the film in the withdrawal direction during pulling. During the removal process, therefore, the folding roller 5a and pulley 5b almost the same circumferential speed. A particularly low-friction, elaborately designed freewheel is not necessary here, since the frictional forces of the traction roller 5b and the freewheel are rather desirable because while through this a certain, albeit slight braking action is applied to the film, which in turn the desired smoothing effect now has pulling the result. Alternatively, it would also be possible to brake the free-running tension pulley accordingly or to drive at an equipped with two drives means those of the pulley with a lower speed, so that also the desired effect occurs.