Abstract:
Apparatus for sealing thermoplastic sheet materials or for closing packs, such as bags, made of such sheet materials with the aid of heated sealing jaws ( 22 ) and mating jaws ( 25 ), which accommodate between them the sheet materials and/or folding or closing flaps which are to be connected, the (non-heated) mating jaw ( 25 ) having an elastically deformable abutment surface for the sheet materials which are to be sealed, such that any possible elevations produced by a multi-layered design of the folding or closing flaps are compensated for by the elasticity of the abutment surface of the mating jaw. The sealing jaw ( 22 ) and/or mating jaw ( 25 ) can be moved by a special, oil-free actuating mechanism which, during continuous driving, brings about a standstill phase of the sealing jaw or mating jaw, which can be moved back and forth.

Description:
FOREIGN APPLICATION PRIORITY DATA 
     The present application claims the benefit of foreign priority upon German patent application 100 00 052.5, filed Jan. 3, 2000 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an apparatus for producing and closing packs with multi-layered folding flaps by heat sealing with the aid of heated sealing jaws, in particular for closing (sheet-material) bags with closing flaps. The invention also relates to a mechanism for cyclically actuating sealing elements or similar tools. 
     2. Description of Related Art 
     The operation of sealing thermoplastic sheet materials poses difficulties if the surfaces which are to be sealed are of non-uniform thicknesses. This applies to folding flaps or closing flaps of packs or bags which on account of folds, in sub-regions, are of multi-layered construction. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the invention is to propose an apparatus which is intended for sealing folding flaps, closing flaps or the like and is suitable, in particular, for compensating for regions of the folding or closing flaps which are of different thicknesses such that a uniform sealing surface or sealing seam is provided despite these differences in thickness. 
     In order to achieve this object, the apparatus according to the invention is characterized by the following features: 
     a) the packs or bags can be conveyed cyclically through a sealing station with a plurality of successive units comprising a heated sealing jaw, on the one hand, and (non-heated) mating jaw, on the other hand, between which the folding or closing flaps are accommodated for sealing purposes, 
     b) from unit to unit, the sealing jaws and mating jaws are positioned on alternate sides of folding or closing flaps such that in the region of one unit the sealing jaws are positioned on one side, and in the region of the next unit the sealing jaws are positioned on the opposite side, of the folding or closing flaps. 
     Favourable sealing results are achieved, in particular, with multi-layered sheet materials or flaps by successive sealing on opposite sides of the sheet material. Particularly precise sealing regions are achieved if, according to the invention, at least the (non-heated) mating jaw has an elastic abutment surface, for example comprising a silicone strip. In this case, that region of the sheet material or of the folding or closing flap which is to be sealed is forced against the elastic region of the mating jaw by the sealing jaw. 
     A special feature of the invention is a mechanism for actuating the sealing jaw or other elements which can be moved cyclically or back and forth. The mechanism is characterized by the following features: 
     a) a drive element which is driven continuously in rotation is connected, via a coupling member, to the element or the sealing or mating jaw, 
     b) the coupling member is connected pivotably to the element, on the one hand, and to an intermediate element, on the other hand, 
     c) the intermediate element can be moved by the drive element such that the driven element has a standstill phase during a revolution of the drive element. 
     The special feature of this mechanism is that entire cam plates which are susceptible to malfunctioning and/or provided with special lubrication and are intended for controlling the movement of the sealing jaws or the like are avoided. The crank-like mechanism, which, on account of the special connection to an actuating arm, ensures a standstill phase as rotation proceeds continuously, is of straightforward construction and is not particularly susceptible to malfunctioning. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further details of the invention are explained more specifically hereinbelow with reference to exemplary embodiments, in which: 
     FIG. 1 shows a side view, partially in vertical section, of a sealing apparatus with special mechanism, 
     FIG. 2 shows the apparatus according to FIG. 1 with the relative positioning of elements changed, 
     FIG. 3 shows, on an enlarged scale, a sealing station as a detail of FIG. 1, and 
     FIG. 4 shows the sealing station according to FIG. 3 in a plan view in accordance with arrow IV. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The exemplary embodiment illustrated in the drawing relates to the production and closure of specific types of packs, namely of (tobacco) bags  10  made of heat-sealable sheet material. The bag  10  in this case is gusseted. In the region of a removal opening, the bag  10  is provided with an elongate closing flap. This is folded over against an (upwardly directed) front side  12  of the bag  10  and connected to the front side  12 , for example, by a tape or the like. 
     The closure flap  11  is connected to a (shorter) mating flap  13 . The closing flap  11  and mating flap  13  are connected to one another along a continuous, strip-like sealing seam by the transmission of heat and pressure. 
     The bag  10  or the sheet material thereof may be designed such that the walls, including the closing flap  11  and mating flap  13 , comprise in each case outer layers of thin sheet material and a paper blank positioned therebetween. However, it is also possible for the bag  10  to be formed from single-layered material. 
     In the region of the closing flap  11  and mating flap  13 , a gusset produces a multi-layered region on the border side. The gusset is folded inwards in the form of a V or M in this region. In this region, the closing flap  11  and mating flap  13  thus form at least four layers, and they form two layers outside this region. The sealing seam is intended to extend over the entire width of the opening, that is to say also in the region of the V-shaped or M-shaped fold. 
     In order to produce the sealing seam, the filled and correspondingly prepared bag  10  is conveyed into a sealing station  14 . For this purpose, the bags  10  are located on a top strand  15  of an endless pack conveyor  16 . The latter is subdivided into pockets by transversely directed partition walls  17 . The bags  10  are positioned on the top strand  15  and/or in the pockets such that the closing flap  11  and mating flap  13  are directed sideways and project beyond the pack conveyor  16 . A base surface  18  of the bag  10  is directed towards a stationary, angled side guide in the region of the sealing station  14 . 
     Provided in the sealing station  14  are sealing elements which produce the sealing seam in a number of successive sealing cycles, in the present exemplary embodiment in two sealing cycles. The sealing operation is executed by sealing units  20 ,  21 . Each sealing unit  20 ,  21  comprises a sealing jaw  22 ,  23  and a mating jaw  24 ,  25 . The sealing jaws  22 ,  23  are heated in each case. The mating jaws  24 ,  25  are not heated, and, if appropriate may be cooled. 
     The bags  10  are transported into the sealing station  14  by corresponding conveying cycles of the pack conveyor  16  such that in each case one bag  10  is located in the region of one sealing unit  20 ,  21  and the other during the standstill of the pack conveyor  16 . The closing flaps  11  of the bags  10 , which are located flat on the top strand  15 , are directed towards the free side and are located in an oblique upright plane. Correspondingly, the sealing jaws  22 ,  23 , on the one hand, and the mating jaws  24 ,  25 , on the other hand, are positioned in an oblique plane of approximately 30°. The closing flap  11  and mating flap  13  are accommodated in each case between a sealing jaw  22 ,  23 , on the one hand, and a mating jaw  24 ,  25 , on the other hand. 
     A special feature is that it is only those elements which are arranged on one side of the parts which are to be sealed which can be moved. In the sealing unit  20 , the sealing jaw  22  can be moved and the mating jaw  24  is position in a fixed manner. In the sealing unit  21 , the mating jaw  25  is arranged on the side of the sealing jaw  22  and can be moved, while the sealing jaw  23 , which is positioned alongside the mating jaw  24 , is arranged in a fixed manner. The respectively moveable elements can be moved back and forth in the oblique plane in accordance with double arrow  26 . 
     The sealing jaws  22 ,  23  have a planar, in particular metallic sealing surface  27  in accordance with the seal or sealing seam which is to be produced. The mating jaws  24 ,  25  are of special design. These have an elastic, compliant pressure-exerting or abutment surface for the sheet material. In the present exemplary embodiment, said abutment surface is formed by a strip  28  of elastic material, in particular silicone. Said strip  28  is positioned in the form of a U over an end surface of the mating jaw  24 ,  25  and anchored in the region of side surfaces by securing means  29 . This configuration of the mating jaw  24 ,  25  compensates for unevenesses in the region of the surfaces which are to be sealed, in particular on account of gussets. Any possible elevations are forced into the elastically deformable mating element by the (rigid) sealing surface  27  of the sealing jaw  22 ,  23 . 
     The moveable elements, namely sealing jaw  22 , on the one hand, and mating jaw  25 , on the other hand, can be moved individually or preferably jointly above the movement path of the bags  10 . For protection against undesired heat transmission, a stationary covering  30  is provided above the bags  10  at least in the region of the sealing jaw  22 . The sealing jaw  22 , and correspondingly the mating jaw  25 , is of contoured design in an end region, in adaptation to the form of the bags  10  and/or of the covering  30 . 
     The moveable elements, namely sealing jaw  22  and mating jaw  25 , can be moved by a special actuating mechanism  31 . The latter comprises a pivotable carrying element for the sealing jaw  22  and/or mating jaw  25 . This is an angled, single-armed actuating arm  32 . An upright leg  33  remote from the sealing jaw  22  and/or mating jaw  25  is connected pivotably, by a bearing  34 , to a carrying apparatus, namely to a (horizontal) carrying plate  35 . Another leg  36  serves as carrier for the sealing jaw  22  or mating jaw  25 . The leg  36  is connected to the leg  33  at an acute angle, namely such that it is oriented obliquely downwards. During a pivoting movement of the actuating arm  32  about the bearing  34 , the leg  36  is moved approximately in the plane marked by double arrow  26 . 
     The actuating arm  32  is connected to the actuating mechanism  31 , which is driven continuously in rotation or circulation, in particular by a central machine drive. The actuating mechanism  31  comprises a drive element which is driven continuously in rotation and is in the form of a crank mechanism  37 . A crank arm  38  is driven in rotation by a fixed shaft  39 . The shaft  39  is positioned in a stationary manner. A ring  40 , which is arranged on the shaft  39 , is connected to an annular rolling-contact bearing  41 . The latter, in turn, is mounted rotateably in a large-format bearing opening  42  of the crank arm  38 . During (continuous) rotation of the shaft  39 , a corresponding rotary movement is transmitted to the rolling-contact bearing  41  via the ring  40 . Said rolling-contact bearing is positioned in an offset or eccentric manner in relation to the shaft  39  with the result that a pendulum movement is transmitted to the crank arm  38 . 
     The crank arm  38  is connected, by a top end, which is remote from the shaft  39 , to a coupling mechanism  43  which transmits the uniform, continuous crank movement of the crank mechanism  37  to the sealing jaw  22  and/or mating jaw  25 , so as to produce, on the one hand, a back and forth movement of said element and, on the other hand, a temporary standstill of the same, namely during the sealing operation. For this purpose, the coupling mechanism  43  is connected to the actuating arm  32  by a link  44 , to be precise in the region of a bearing  45  formed at a corner point of the legs  33 ,  36 . 
     The other end of the link  44  is likewise connected to the coupling mechanism  43  via a pivot bearing  46 . 
     The coupling mechanism  43  has a (first) coupling member  47 . The latter can be pivoted about a fixed bearing  48  in accordance with the movement of the crank arm  48 . In the present case, the coupling member  47  can be rotated in the clockwise direction about the fixed bearing  48 . 
     The end of the crank arm  38  is connected to the coupling member  47  via a rotary bearing  49 , to be precise at a distance from the fixed bearing  48 . 
     A rotary bearing  51  connects the (first) coupling member  47  to a (second) coupling member  50 . Said rotary bearing  51  is arranged at a distance both from the fixed bearing  48  and from the rotary bearing  49 . The coupling member  50  is of more or less triangular design. First of all, the link  44  is connected to said coupling member  50  via the pivot bearing  46 . Furthermore, a bearing  52  provides a fixed point for the coupling mechanism  43 . This is a (further) fixed bearing  53 , to which the coupling mechanism  43  is connected via a further link  54 . Accordingly, the coupling member  50  is mounted in a freely moveable manner, namely in each case such that it can be rotated or pivoted about the bearings  46 ,  51 ,  52 . The link  54  can also be pivoted about the fixed bearing  53  in this case. 
     FIGS. 1 and 2 show two different positions of the actuating mechanism  31 . The interaction of the abovedescribed elements achieves the situation where, in the position according to FIG. 1, despite continued rotary movement of the shaft  39  and the crank mechanism  37 , the leg  36 , and thus the sealing jaw  22  or the mating jaw  25 , is at a temporary standstill, namely for the purpose of executing a sealing cycle. 
     A further special feature is that the entire actuating mechanism  31 , including actuating arm  32  with sealing jaws  22  and/or mating jaws  24 , can be moved out of the operating position, in particular for maintenance or repair purposes. For this purpose, the fixed bearing  53  is connected to a restoring mechanism, namely a (two-armed) actuating lever  55 . The latter can be pivoted about a pivot bearing  56 . By corresponding actuation of the actuating lever  55 , the fixed bearing  53  is drawn back, the actuating mechanism  31  being carried along in the process. Provided for this movement is a pressure-medium cylinder  57 , which acts on the free end of the actuating lever  55  by way of a piston rod. 
     The actuating mechanism  31  which has been described in terms of construction and functioning may also be used for the actuation and/or movement of other elements with a corresponding requirement profile. 
     Following the sealing station  14 , the unit comprising the closing flap  11  and mating flap  13 , said unit being formed by sealing, is folded over against the free front side  12  of the bag  10  and fixed by adhesive bonding or by tape. For this purpose, it is possible to see a segment-like folding element  58  which is illustrated in FIG. 3, in particular, and can be pivoted by a push rod  59  in order to fold over the closing flap  11 . 
     List of Designations 
       10  Bag 
       11  Closing flap 
       12  Front side 
       13  Mating flap 
       14  Sealing station 
       15  Top strand 
       16  Pack conveyor 
       17  Partition wall 
       18  Base surface 
       19  Side guide 
       20  Sealing unit 
       21  Sealing unit 
       22  Sealing jaw 
       23  Sealing jaw 
       24  Mating jaw 
       25  Mating jaw 
       26  Double arrow 
       27  Sealing surface 
       28  Strip 
       29  Securing means 
       30  Covering 
       31  Actuating mechanism 
       32  Actuating arm 
       33  Leg 
       34  Bearing 
       35  Carrying plate 
       36  Leg 
       37  Crank mechanism 
       38  Crank arm 
       39  Shaft 
       40  Ring 
       41  Rolling-contact bearing 
       42  Bearing opening 
       43  Coupling mechanism 
       44  Link 
       45  Bearing 
       46  Pivot bearing 
       47  Coupling member 
       48  Fixed bearing 
       49  Rotary bearing 
       50  Coupling member 
       51  Rotary bearing 
       52  Bearing 
       53  Fixed bearing 
       54  Link 
       55  Actuating lever 
       56  Pivot bearing 
       57  Pressure-medium cylinder 
       58  Folding element 
       59  Push rod