Abstract:
A device includes at least one bearing shield, at least one sonotrode which is rotatably mounted in the bearing shield, at least one anvil which interacts with the sonotrode to process the packing material, at least one other bearing shield to rotatably mount the anvil, whereupon a coupling mechanism is arranged to mechanically couple both bearing shields. The coupling mechanism is configured so that a relative motion between both bearing shields is made possible.

Description:
This application is a 35 U.S.C. §371 National Stage Application of PCT/EP2010/052484, filed Feb. 26, 2010, which claims the benefit of priority to Application Serial No. DE 10 2009 002 295.3, filed Apr. 9, 2009 in Germany, the disclosures of which are incorporated herein by reference in their entirety. 
     BACKGROUND 
     The feature of the disclosure are based on a device for processing a packing material by means of ultrasound according to the preamble of the independent claim. A generic device of said type is known for example from US 2004/0011452 A1. Said document describes an ultrasound-based transverse sealing device for bar packs, which transverse sealing device is composed of a rotating sonotrode and a rotating anvil. Said document however does not specify in any greater detail how the sonotrode and anvil are supposed to be mechanically arranged relative to one another. 
     The disclosure is based on the object of specifying a compact and robust device. Said object is achieved by means of the features set forth below. 
     SUMMARY 
     In contrast to this, the device according to the disclosure for processing a packing material by means of ultrasound has the advantage of permitting a single-piece, compact design of the ultrasound sealing station. In this way, it is made possible for conventional hot sealing devices to be replaced with the device according to the disclosure. Since at least one coupling means is provided between a bearing shield of the sonotrode and a bearing shield of the anvil, all the necessary setting parameters for the joining process of the material web can be precisely adjusted. Furthermore, the sealing force required for the ultrasound sealing can be easily imparted and set by means of the device thus formed. The coupling means may, with suitable design, serve to accommodate the forces during the sealing and cutting of the packing material in an overload situation. Specifically, the coupling means, in particular if designed as a bending beam, is capable of enlarging the sealing gap between the sonotrode and anvil if, in the event of a fault, a product or foreign body passes into the sealing point. 
     In an expedient refinement, it is provided that a bending beam is used as a coupling means. Said bending beam permits coupling which however allows a certain relative movement of the sonotrode and anvil. In contrast to a conventional bearing, the bending beam permits play-free, smooth-running coupling of the two bearing shields for anvil and sonotrode respectively. The lack of play of the coupling means has a positive effect for precise setting of the sealing gap. Furthermore, the bending beam does not become contaminated so easily, in contrast to a conventional bearing. Furthermore, the thermal expansion of the bending beam under normal ambient conditions is very small and thus barely influences the gap regulation. Furthermore, the bending beam is cheap to produce and exchange. 
     In an expedient refinement, it is provided that the bending beam should be attached between the sonotrode and anvil at a point spaced apart as far as possible from the sealing point. It is then possible, if necessary, to dispense with a readjustment of the roller positions of anvil and sonotrode during the setting of the sealing gap. In an expedient refinement, it is provided that the fastening elements for fastening the bending beam to the respective bearing shields are mounted on the respective outer ends of the bending beam. This reduces the probability of readjustments. 
     In an expedient refinement, it is provided that the bending beam may have a certain preload. Said preload increases the sealing force. 
     Further expedient refinements will emerge from the further dependent claims and from the description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of a device for processing a packing material by means of ultrasound are illustrated in the drawing and will be described in more detail below. 
       In the drawing: 
         FIG. 1  shows a perspective front view of the device for processing a packing material, 
         FIG. 2  shows the rear view of the device according to  FIG. 1 , 
         FIG. 3  shows a side view of a coupling means, 
         FIG. 4  shows a side view of a further alternative coupling means, 
         FIG. 5  shows a perspective illustration of a further exemplary embodiment of the device for processing a packing material, expanded to include an adjusting means, 
         FIG. 6  shows a side view of a first adjusting device, 
         FIG. 7  shows the side view of a second adjusting device, and 
         FIG. 8  shows the side view of a third adjusting device. 
     
    
    
     DETAILED DESCRIPTION 
     In the device according to  FIG. 1 , a sonotrode  10  is rotatably mounted on both sides by in each case one bearing shield  14 . The two bearing shields  14  for the sonotrode  10  are laterally connected to one another at the top side of the device  8  by an upper support means  22 , designed here by way of example as a support beam. A likewise rotatably mounted anvil  12  interacts with the sonotrode  10 . The anvil  12  is mounted in two bearing shields  16 . The bearing shield  14  of the sonotrode  10  is connected by a coupling means  20  to the bearing shield  16 , situated therebelow in each case, of the anvil  12 . The two bearing shields  16  of the anvil  12  are in turn laterally connected to one another by a lower support means  24 , which is formed by way of example as a support tube. Arranged in each case on the opposite side of the coupling means  20  in relation to the axes of rotation of the sonotrode  10  and anvil  12  are force means  18  by means of which the required sealing force can be applied to the sealing surface of the sonotrode  10  and anvil  12 . Setting means  30  are provided in each case above the force means  18 . In this way, the sealing force or sealing gap can be adjusted. 
     In the rear view, shown in  FIG. 2 , of the device  8  described in  FIG. 1 , it is clear that the bearing shield  14  of the sonotrode  10  is connected in each case to the bearing shield  16 , arranged therebelow, of the anvil  12  by the coupling means  20 , which is designed by way of example as a bending beam here. The coupling means  20  is connected at the top end to the end side of the bearing shield  14  by means of two fastening elements  21 , and is connected at the bottom end to the bearing shield  16  by means of two fastening elements  21 . Here, a gap is provided between the bottom edge of the bearing shield  14  of the sonotrode  10  and the top edge of the bearing shield  16  of the anvil  12 , which gap is bridged only by the coupling means  20 . Furthermore, a drive  28  is provided which, by means of a drive element  26 , drives both the sonotrode  10  and also the anvil  12  in opposite directions. 
     In the view of  FIG. 3 , the bearing receptacles for the rotating sonotrode  10  and the rotating anvil  12  are visible as round openings. The bearing shield  14  of the sonotrode  10  is connected to the bearing shield  16  of the anvil  12  at one side by the coupling means  20 , which is designed as a bending beam. On the opposite side, the force means  18  loads the bearing shields  14 ,  16  with a force toward one another via the coupling means  20 , which acts as a joint. In the direction of the coupling means  20 , the bearing shields  14 ,  16  each have recesses  23 . The desired bending capability of the bending beam  20  can thus be influenced by the bending length formed in this way. In the arrangement shown, the bending beam acts as a center of rotation, by means of which the spacing between the sonotrode  10  and anvil  12  can be varied. The design of the coupling means  20  as a bending beam offers a relatively rigid but nevertheless articulated connection between the two bearing shields  14 ,  16 . The use of a bending beam as a coupling means  20  also acts as an overload protection means in the event of a crash. The bending beam  20  thus permits a defined opening and bending of the sealing gap between the sonotrode  14  and anvil  16  even in the event, for example, of a product or foreign body becoming jammed between the sonotrode  10  and anvil  12 . Damage to the sonotrode  10  and anvil  12  is thereby prevented because the bending beam  20  permits an enlargement of the sealing gap. The bending beam is composed preferably of a metallic material. 
     The sealing gap between the sonotrode  10  and anvil  12  can be varied according to setting. The force means  18  has the effect of moving the upper and lower bearing shields  14 ,  16  toward one another about the center of rotation  56 , and thereby imparting a force to the sealing surfaces. For this purpose, a plunger  48  is connected at one side to the bearing shield  14  of the sonotrode  10  such that a movement of the plunger  48  also causes a movement of the bearing shield  14 . The plunger  48  is guided through an opening in the bearing shield  16  of the anvil  14 , so as to be movable relative to the bearing shield  16 , ends with a flange  51 . The flange  51  serves as a support surface for a spring  49  which, at the other side, is supported against the underside of the bearing shield  16  of the anvil  12 . The spring  49  is designed as a spiral spring and surrounds the plunger  48 . The force means  18  is preferably designed to be adjustable. For this purpose, it would for example be possible for the setting means  30  in the form of a screw to vary the preload of the spring  49  and thereby ultimately the sealing force. 
     In the exemplary embodiment of  FIG. 4 , as a coupling means  20 , a bush-pin connection is provided which permits a rotational movement of the two bearing shields  14 ,  16  relative to one another about a center of rotation  56 . It is however essential that the coupling means  20  permits a relative movement between the bearing shield  14  of the sonotrode  10  and the bearing shield  16  of the anvil  12  in such a way that the sonotrode  10  and anvil  16  can be moved relative to one another in order to realize the setting of a sealing gap depending on the packing material. The axis of rotation about the center of rotation  56  is parallel to the axis of rotation of the sonotrode  10  and anvil  12 . 
     The exemplary embodiment of  FIG. 5  differs from that of  FIGS. 1 and 2  substantially in that adjusting means  50  are additionally provided. The adjusting means  50  comprise a coupling  52  and a threaded bolt  54  for gap adjustment by adjusting the bearing shield  14  of the sonotrode  10  relative to the bearing shield  16  of the anvil  12 . Furthermore, in the exemplary embodiment of  FIG. 5 , the coupling means  20  is in a lateral arrangement. Here, a bolt is coupled to the bearing shield  14  of the sonotrode  10 , and a bush which engages correspondingly into the bolt is coupled to the bearing shield  16  of the anvil  12  at the center of rotation  56 . 
     The exemplary embodiments of  FIGS. 6 to 8  show different variants of the adjustment possibilities between the bearing shield  14  of the sonotrode  10  and the bearing shield  16  of the anvil  12 .  FIG. 6  corresponds to the variant illustrated in  FIG. 5 , where the adjusting means  50  presses via the coupling  52  and the threaded bolt  54  against the lower edge of the bearing shield  14  of the sonotrode  10  and thereby effects a relative movement about the center of rotation  56 . The adjusting means  50  is arranged at as great a distance from the center of rotation  56  as possible. As an adjusting device  50 , a servo motor is for example provided which, via the threaded bolt  54 , imparts a translatory movement to the bearing shield  14 . Here, the lower bearing shield  16  will function, in effect, as a base, and push the upper bearing shield  14  upward via the threaded bolt  54  as the latter is unscrewed. The force means  18  furthermore ensure that the upper bearing shield  14  always bears against the threaded bolt  54  and thus also moves downward as the threaded bolt  54  is screwed in. On account of the pressure acting continuously from above, the thread play does not have a noticeable adverse effect. The use of in each case one servo motor with threaded bolt  54  in the left-hand and right-hand bearing shields  14 ,  16  makes it possible for the sonotrode  10  and the anvil  12  to be automatically aligned parallel to one another. In the exemplary embodiment of  FIG. 6 , very small and also relatively large adjustment travels can be attained very accurately. 
     In the exemplary embodiment of  FIG. 7 , the spacing can be varied by means of an eccentric  58  which is rotatably mounted parallel to the axis of rotation of the sonotrode  10  and anvil  12 . The force means  18  again effects a preload between the two bearing shields  14 ,  16 . The rotational movement of a servo motor is converted by means of the eccentric disk  58  into a translatory movement. Whereas the eccentric disk  58  is fixedly mounted, the upper bearing shield  14  are raised and lowered by means of the eccentric disks  58 . 
     In the exemplary embodiment of  FIG. 8 , an actuator  60  is provided which engages relatively close to the center of rotation  56 . The actuator is for example a piezoelectric actuator  60  which converts electrical energy into a mechanical change in travel. Piezoelectric actuators  60  are advantageous because they can carry out movements in the sub-nanometer range. Furthermore, piezoelectric actuators  60  are maintenance-free and wear-free. In static operation, they require no power. Furthermore, high loads can be moved. 
     The device  8  for processing a packing material by means of ultrasound operates as follows. It comprises, as an essential element, the sonotrode  10  which, as an active welding tool, acts against the anvil  12 . The mains voltage is converted by an electric generator into a high-frequency electric voltage. A sound converter (converter) is connected to the generator and in turn converts the electrical energy into high-frequency mechanical vibrations. By means of an amplitude transformation piece (booster), the amplitudes are amplified or reduced and are transmitted from the converter to the sonotrode  10 . The anvil  12  is the passive workpiece. The workpiece to be welded, for example the packing material, is clamped between the anvil  12  and the sonotrode  10 , in order thereby to permit the transmission of energy between sonotrode  10  and the packing material. The anvil  12  absorbs the ultrasound vibrations of the sonotrode  10 . Both the sonotrode  10  and also the anvil  12  rotate in opposite directions and are designed, in effect, as sealing rolls. They have a plurality of sealing surfaces into which may also be integrated a cutting function for cutting the packing material. Depending on the type of packing material, a sealing gap must be set with high accuracy. A sealing gap denotes the spacing of the sealing surface of the sonotrode  10  from the sealing surface of the anvil  12 . Said sealing gap is adjusted to the desired size by adjusting means, illustrated by way of example in  FIGS. 5 to 8 , such as an adjusting drive  50 , eccentric  58  or actuator  60 . Said adjusting means act on at least one bearing shield  14  relative to the other bearing shield  16 . If the size of the sealing gap varies during ongoing operation, the adjusting means  50  can adjust said gap back to the desired setpoint size. The force means  18 , designed for example as a spring, on the end of the bearing shields  14 ,  16  serves to press the bearing shields  14 ,  16  together and impart the required sealing and/or cutting force. Furthermore, by means of the toothed belt drive, forces act on the sonotrode  10  which seek to raise the upper bearing shields  14 , which is prevented by the force means  18 . The force means  18  could also be of pneumatic or hydraulic design instead of a spring. The coupling means  20  serve to movably connect the bearing shield  14  of the sonotrode  10  to the bearing shield  16  of the anvil. In addition to the described variants, linear guides such as for example column guides could also be provided, which permit a relative linear movement of the bearing shields  14 ,  16  with respect to one another. 
     The bearing shields  14  form side cheeks which are connected to one another by the support means, specifically the support beam  22 . The support tube  24  could also serve for stabilization and as a holding facility in the packaging machine. The drive coupling of the upper and lower sealing rolls (sonotrode  10  and anvil  12 ) is realized by means of toothed belts. The rotational speed of the sealing rolls is dependent on the speed of the strip of the packing tube to be sealed and may for example be event-controlled. Said dynamics are attained by means of the drive  28 , for example a servo motor, which transmits the forces and torques by means of a drive element  26  designed as a toothed belt. The described device allows the parameters required for the joining process by means of ultrasound, such as for example the sealing gap, sealing force and sealing time, to be set very precisely and in a manner appropriate to the application. The setting of the sealing force can be realized via the force means  18 . The force means are designed for example as springs, such that it is possible for the sealing force to be set linearly with respect to the spring characteristic curve. The force means  18  act on the two bearing shields  14 ,  16 , such that the sealing force between the upper sealing roll, the sonotrode  10 , and the lower sealing roll, the anvil  12 , can be set. 
     The described device  8  is suitable in particular for the formation of a transverse sealing seam for tubular bags. Tubular bag machines of said type may be arranged horizontally or vertically depending on the product to be packed.