The invention is related to a device for the strapping with a strapping tape of an essentially cube-shaped (cuboid) object, for example, of a stack of printed products or suchlike.
Known from prior art are various devices, which serve for the strapping of stacks of printed products by means of strapping, in particular of a strapping tape. In the case of these devices, a stack of printed products to be strapped is brought to a strapping device by a feeding device, where one or several strapping tapes are laid around the stack. After the strapping, the strapped stack is conducted away from the work zone. Utilised as strapping tapes are mostly plastic tapes, e.g., made of polyethyleneterephthalate or polypropylene.
Strapping means are primarily laid around a stack, resp., around a cube-shaped (cuboid) device in two directions: In the direction of conveyance (longitudinal strapping), in which the stack brought into the work zone, and transverse to it (transverse strapping). While the strapping in transverse direction can be coped with by the devices known from prior art, a strapping in longitudinal direction with the same devices is in most cases associated with certain problems, because as a result of the principle involved parts of the machine are arranged in a manner, which makes them liable to interfere with the process.
From DE 41 00 276 a device is known, which comprises a curved, longitudinally slotted channel, which is arranged at an angle above and adjacent to a stack of printed products to be strapped. A strapping tape is introduced into the channel, in order to thereupon be laterally pulled out of it. Until the tape finally has been laid around a stack to be strapped, it first has to slide over an inclined surface and then has to overcome at an angle a free stretch in the air. This arrangement encompasses certain uncertainties, because as a result of the inclined trajectory it is only poorly possible to determine, where the tape will come to lie.
From DE 42 30 730 a further device is known, which comprises a static and a movable tape guide channel. This channel is arranged at an oblique angle to a feeding device. In order to be in a position to rationally strap a stack of printed products, it is necessary to align it at a corresponding angle relative to the channel.
From EP 0 725 005 a device is known, in the case of which a strapping tape is conveyed across a free stretch of air by means of air pressure. This device has the disadvantage, that a secure conveyance of the strapping tape across the free stretch of air is only able to be guaranteed with difficulty. Apart from this, as a result of the principle it is only possible to form the tape into a loop after a stack to be strapped has reached a work zone.
It is the objective of the invention presented here to demonstrate a strapping device, which avoids the disadvantages known from prior art. The device is to make it possible to rapidly strap objects in longitudinal—and/or in transverse direction in a simple manner.
The objective is achieved with the invention defined in the claims.
The invention divulged here is in preference suitable for the strapping of printed products and other objects. These can have differing dimensions and positions. The invention is in particular distinguished by a rapid processing and a high flexibility, because the loop can be prepared independent of the position of the stack to be strapped. Because of only a small number of fast moving parts, an optimised cycle is achieved. The invention is suitable in particular for a strapping both in longitudinal as well as in transverse direction.
The invention is based on the fact, that a means of strapping, in particular a strapping tape, which is to be laid around a stack of printed products, is prepared by means of a suitable loop forming device in a waiting position, independent of and free of (uninfluenced by 90°) the momentary position of the stack to be strapped, i.e., is formed into a loop. This prepared loop thereupon, as soon as the stack to be strapped has reached a strapping position, by means of a loop movement device by turning (e.g., folding over by) and/or by lateral displacement is brought into a stacking position from the waiting position, in which it encircles the stack at a certain distance in preference centrally. Subsequently the loop, starting out from the stacking position, is laid around the stack, tightened and locked so as to form a strapping.
The invention can be designed in such a manner, e.g., that the loop forming device is a groove embedded in a horizontal work surface, which serves as guide track, resp., guide means for the strapping device. Into this groove the means of strapping is introduced, resp., inserted in longitudinal direction and formed into a loop (loop in waiting position). In doing so, the groove is designed in such a manner, that the loop does not protrude from the groove and so does not have an obstructive effect. As soon as the stack to be strapped has reached a strapping position, the loop present in the groove in the waiting position is raised away from the work surface into an upright position by means of the loop forming device (e.g., by rotation around a point) in such a manner, that the loop comes to lie above and lateral to the stack to be strapped. The loop is now in the stacking position.
The loop movement device, for example, comprises one or several straight or curved arms arranged as fixed or movable, along which grippers are located, which can be displaced under control. The grippers are designed in such a manner, that they are in a position to bring the means of strapping (strapping tape) from the waiting position into the stacking position. For example, the grippers, depending on the field of application, can have an open or closed, single- or multi-part construction. In preference they are of lightweight construction, so that they can be displaced rapidly.
Particularly suitable as drive for the loop movement means, resp., for the grippers, are recirculating traction elements, air pressure (compressed air), hydraulic systems, solenoid or piezo-electric drives. The one or more loop movement means advantageously are designed in such a manner, that the movement of the grippers along the arms and the position of the arms, resp., their relative course, is adjustable. As a result of this, objects of the most differing size (height, width, length and shape) are able to be processed. Because of the flexible design, it is possible to influence the loop even while it is brought from the waiting position to the stacking position, in that, for example, the arms are moved relative to one another. This has the effect of specifically enlarging the loop or of making it smaller. The stack can assume differing strapping positions.
In the stacking position, the loop is bigger than the circumference of the stack to be strapped, in such a manner, that it encircles the latter at a certain distance. Starting out from the stacking position, the loop is separated from the loop movement device, resp., from the one or more grippers and drawn together in such a manner, that the strapping means tightly girdles the stack to be strapped. Subsequently the means of strapping is tied down and closed to form a strapping.
FIG. 1 schematically and in a strongly simplified way illustrates a strapping device 1 in accordance with the invention. This, i.a., comprises a work surface 2, a groove 3 embedded in the work surface and two loop movement devices 4. The groove 3 embedded in the work surface 2 runs essentially along the edges of a rectangle and serves as means of guidance (guide channel) for guiding a strapping means, resp., the strapping tape 5. The groove 3 is designed in such a manner, that the strapping tape 5 can be introduced into it, in that it is pushed into it in the direction of the arrow P either actively or passively from a supply magazine, for example, from a supply roll, which is located underneath the work surface 2. If so required, additional tape feeding means (not depicted in more detail), for example, in the form of tape feed rolls (not depicted in more detail) are present, which assist in the introduction of the strapping tape 5 into the groove 3. The depth of the groove 3 is selected in such a manner, that a strapping tape 5 introduced into it does not protrude from the groove 3. Additional elastic elements (not illustrated in more detail), such as lamella or bristles, close off the groove 3 against the work surface 2 in such a manner, that the strapping tape 5 is secured against inadvertently coming out of the groove 3 and that the danger of contamination with dirt of the groove 3 is reduced. The groove 3 can also be closed-off during the introduction of the strapping tape 5 by means of a rigid element (not illustrated in more detail).