Abstract:
A feeding device for a packaging machine used to feed individual goods to a packaging station of the machine includes at least one continuously rotating conveyor which comprises at least one driver element used to drive the individual goods, which are to be guided, along a conveyor path. The inventive feeder device is embodied in such a manner that, for each conveyor, only one individual driver element can be placed in a driving position of the individual goods which are to be guided at any one time. The device reduces the feeding path of a packaging machine and also increases the position precision of the individual goods.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a 35 USC 371 application of PCT/EP 2006/060255 filed on Feb. 24, 2006. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to an improved feeding device of a packaging machine and to an improved method for feeding bulk products into a packaging station of a packaging machine. 
   2. Description of the Prior Art 
   Feeding devices of the type with which this invention are concerned are known for instance from U.S. Pat. Nos. 3,417,544, 6,122,898, and 5,689,942. These publications disclose horizontal bag-making machines in which bulk products are individually delivered to a folding station, where they are encased with packaging film and the film is shaped into individual tubular bags; they are supplied with sealing seams, and the individual bags are cut apart from one another. So that the individual bulk products will arrive in a predefined spacing in the folding station, they are engaged beforehand by a revolving driver element chain, and each bulk product is transported by its own driver element and transferred to the folding station. Typically, a leading span is located upstream, in the conveying direction, of this driver span, and in the leading span the products are given a predetermined spacing and are thus transferred incrementally to the feeding conveyor. 
   These feeding devices have indeed proven themselves in practice. However, it is disadvantageous that the delivery span, that is, the leading span and the length of the feeding device, requires a relatively large amount of space. 
   SUMMARY AND ADVANTAGES OF THE INVENTION 
   It is an object of the invention to shorten the delivery span of a packaging machine, in particular a horizontal bag-making machine. 
   In the attainment of this object, feeding device of the invention for a packaging machine for feeding bulk products into a packaging station of this machine has at least one endlessly revolving conveyor with at least one driver element for driving the bulk products to be fed along a conveyor path. The feeding device is embodied such that per conveyor, only a single one of this at least one driver element can be put simultaneously into a position that drives a bulk product that is to be fed. 
   The feeding device is especially, but not exclusively, suitable for use in a horizontal bag-making machine. 
   Since only a single bulk product at a time, rather than a plurality of bulk products, is transported simultaneously per conveyor, the delivery span can be shortened. The shortening can be improved still further if an accelerating conveyor is used in the leading span. Since the bulk products are subsequently conveyed individually to the accelerating conveyor and at mutually independent speeds to the packaging station, they can have a relatively slight spacing from one another on the accelerating conveyor. 
   A further advantage is that an indexing belt in the leading span is unnecessary. 
   If the speed of the driver element is adapted to the position at the time of the bulk product, then incorrect positions can be corrected, and the bulk product can be transferred positionally precisely to the packaging station. That is, bulk products located too close to the next bulk product ahead of them in the in the column of bulk products finished along the leading span can be slowed down by means of the driver element, and the spacing from the neighbor ahead can thus be increased. Bulk products that trail behind, or in other words are spaced too far apart from the next bulk product ahead, can be speeded up by means of the driver element and the spacing can be reduced. In both cases, preferably virtually all the bulk products are pushed by means of their driver elements, until they have reached their desired position. 
   Preferably, at the latest shortly before the transfer of the bulk product to the transporting means of the packaging station, the driver element is brought to the conveying speed that this transporting means is also at. The transporting means, in a horizontal bag-making machine, is typically the packaging material or the packaging film itself, so that the speed of the driver element is adapted to the conveying speed of the tube. 
   For driving the driver elements or their conveyors, servo motors are preferably used. 
   A her advantage of the device of the invention is that for the same feeding capacity, the bulk products can be transferred to the packaging station at a relatively slight conveying speed. Because of the more-precise positioning of the bulk products in the tube, a somewhat shorter length of film drawn off can be allowed. This means that the tube speed can be reduced somewhat as well. 
   It is also advantageous that the same feeding device can be used for different sizes of bulk products. The spacing between the individual driver elements is no longer important. As a result, upon a change of the type of bulk product, the pitch of the driver elements on the conveyor no longer has to be changed, so that changing driver elements becomes unnecessary. 
   Thanks to the device of the invention, it is possible to shorten the delivery span, depending on the system, by from 500 to 800 mm, for instance. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     One exemplary embodiment of the invention will be described in further detail herein with reference to the drawings, in which: 
       FIG. 1  is a side view of a feeding device of the invention and a part of a packaging station, in a first conveying position; 
       FIG. 2 , the device and the packaging station of  FIG. 1  in a second conveying position; 
       FIG. 3 , the device and the packaging station of  FIG. 1  in a third conveying position; and 
       FIG. 4 , a perspective view of the device of  FIG. 1 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   In the example shown in the drawings, the packaging machine is a horizontal bag-making machine; that is, the bulk products are fed individually to a packaging material S, in particular a packaging film, which is folded around the individual bulk products P, provided with sealing seams, and cut apart into individual bags. Horizontal bag-making machines of this kind are well known in the prior art and will therefore not be described in further detail here. 
   The bulk products P are brought by a conveyor  1 . Preferably, his is an accelerating conveyor  1 , which brings the bulk products P. The spacings between the individual bulk products are relatively short. This accelerating conveyor  1  may be formed by at least one endlessly revolving conveyor, a conveyor chain, or some other suitable conveying means. Its conveying direction is represented in the drawings by an arrow. The lower end, in terms of the conveying direction, of the accelerating conveyor  1  is formed by a deflection roller  10 . 
   Adjoining this accelerating conveyor  1  is the packaging station  2  with its transporting means; this station extends the delivery span in a straight line. The transporting means  3  in this preferred example is formed by the bottom of the tube S, on the bottom of which the bulk products P rest. 
   The feeding conveyor  4  of the invention is disposed below the conveyor path, in the transition region from the accelerating conveyor  1  to the packaging station  2 , that is formed by the delivery span and the conveying span of the packaging station. It may also be disposed laterally of the conveyor path or above it. 
   This feeding conveyor  4  is disposed on a load-bearing frame  44 . It has at least one and in this case two endlessly revolving conveyor chains  40 ,  40 ′. Instead of the conveyor chains  40 ,  40 ′, still other conveying means may be employed. The conveyor chains  40 ,  40 ′ are driven via drive wheels  41  and preferably via servo motors, and a central controller triggers these motors. 
   At least one driver element  42 ,  43  is disposed on each of these conveyor chains  40 ,  40 ′ and is movable by means of them. In the preferred exemplar embodiment shown here, a plurality of driver elements  42 ,  43  per conveyor chain  40 ,  40 ′ are secured, spaced apart from one another, to the chains  40 ,  40 ′. The driver elements  42  of the first chain conveyor  40  are shown shaded, while the driver elements  43  of the second chain conveyor  40 ′ are represented only by their outlines. The use of two or more conveyors  40 ,  40 ′ has the advantage that a plurality of bulk products P can be transported simultaneously by means of driver elements, and thus the throughput can be increased, without sacrificing flexibility in terms of transporting the individual bulk products P or having to increase the conveying speed in the packaging station  2 . 
   Each driver element  42 ,  43  has a driver carriage  423 , which is secured nondisplaceably and positionally fixedly on one or more chain links of the conveyor chain  40 . One end of a first swivel plate  421  and one end of a second swivel plate  422  are each pivotably secured to this driver carriage  423 . The other ends of the swivel plates  421 ,  422  are joined by a driver element arm  420 . This driver element arm  420  is essentially L-shaped; the two ends of the swivel plates  421 ,  422  are pivotably secured, spaced apart from one another, to its long leg  424 , while its short leg  425  points away from the conveyor chain  40 . Preferably, the short leg  425  protrudes approximately perpendicularly from the conveyor chain  40 . Because of the parallel fastening of the swivel plates  421 ,  422 , an at least approximately rectilinear raising and lowering of the driver element arm  420 , and in particular of the short leg  425 , is possible. 
   The feeding conveyor  4  furthermore includes at least one slide track  45 , which extends parallel to the at least one conveyor chain  40 ,  40 ′. The slide track  45  extends parallel to the particular span of the feeding conveyor  4  that is oriented toward the packaging station  2 . In this example, this is the upper run of the feeding conveyor  4 . 
   If two or more conveyor chains  40 ,  40 ′ are present then preferably each conveyor chain  40 ,  40 ′ has its own slide track  45 . This slide track  45  has a lowered span portion  450  and a raised span portion  451 , which merge with one another via a ramp  452 . The slide track  45  and in particular the ramp  452  can be clearly seen in  FIG. 4 . 
   Either every driver element arm  420 , every first swivel plate  421 , or every second swivel plate  422  has a protruding engagement means, such as a bump, which rests on the slide track or, if it is embodied as a groove, engages it. As a result, on traversing the upper run of the feeding conveyor  4 , each driver element arm  420  rises from a lowered state along the lowered span portion  450  of the slide track  45  to a raised state along the raised span portion  451 . At the end of the curved path  45 , or in other words shortly between the transition from the upper run to the lower run, the curved path  45  descends again. The driver element which extends along this final span  453  thus dips out of the conveyor path again and vanishes from the region of the packaging station  2 . The feeding device is designed in such a way, or in other words the spacings between the driver elements  42 ,  43  of the same chain conveyor  40  relative to the slide track  45  are selected such, that only a single driver element  42 ,  43  at a time is located on the raised span portion  451  and is thus in the raised state. This too is clearly seen in  FIG. 4 . 
   This raising and lowering of the driver element arm  420 ,  430  is now utilized for transporting the individual bulk products in the desired manner. This will be described below in conjunction with  FIGS. 1 through 3 . 
   In  FIG. 1 , the frontmost driver element  43 , in terms of the conveying direction, of the second chain conveyor  40  is located in the raised span portion  451  of the slide track  45 , and is thus in driving engagement with a bulk product P. The following driver elements  43  on this chain conveyor  40 ′ are located in the lowered span portion  450  and thus do not protrude into the conveyor path. The bulk products P disposed above them continue to be transported solely by the accelerating conveyor  1 . The frontmost driver element  42 , in terms of the conveying direction, of the first chain conveyor  40  is located precisely on the ramp  452  of the slide track  45 , so that the driver element arm  420  is now raised into the conveyor path. 
   The position of this first, frontmost driver element  42  and its speed are independent of the position of the above-described second, frontmost driver element  43  and are dependent only on the position of the bulk product P to be driven, or in other words delivered to the packaging station. If the bulk product P is located too far forward, then the conveyor chain  40 ′ and thus the first driver element  42  are driven more slowly in order to increase the spacing between this bulk product P and the hulk product P ahead of it. If the bulk product P is located too far to the rear, then the first driver element  42 , as soon as it contacts this bulk product, is speeded up in order to push it forward and to reduce the spacing from the bulk product P ahead of it. 
   These positions of the bulk products P are preferably detected on or in front of the accelerating conveyor  1  by means of at least one sensor and reported to the central controller. This controller then controls the speeds of the at least one chain conveyor  40 ,  40 ′. If there are more than one chain conveyor  40 ,  40 ′, then they are preferably triggered independently of one another. 
   In a preferred embodiment, between the sensor and the feeding conveyor  4  there is at least one ejector means, such as an arm that can be pivoted into the delivery span and that removes individual bulk products P from the delivery span. The criteria for ejection may be for instance if the position of bulk product P is located outside a predetermined position range, or if a bulk product that has not yet been packaged has damage. 
   Preferably all the driver elements  42 ,  43  in the region of the final span  453  have the same speed as the transporting means  3  of the packaging station  2 , or in other words the tube formed here from the packaging material S. This enables a transfer, with as little force as possible, of the bulk products P to this transporting means  3 . 
   In  FIG. 2 , it can now be seen what then happens with the first and second frontmost driver elements  42 ,  43 . The second driver element  43 , which is still in the lead, is still in driving engagement with its bulk product P. However, in the meantime, the first driver element  42 , following the second one, has reached the raised span portion  451  and is transporting its bulk product P. The other driver elements of these two conveyor chains  40 ,  40 ′ are located, as before, below the conveyor path and are not in any kind of driving engagement with bulk products P. 
   In the conveying position shown in  FIG. 3  and defined at a later time, the leading, second driver element  43  has now reached the final span  453  and is lowered. As can be seen, its bulk product P is now transported solely by the packaging material S. For this purpose, the next second driver element  43  on this conveyor chain  40 ′ is located on the ramp  452  and is raised and is about to take on the task of transporting its bulk product P. 
   In the example described here, the individual speeds of the driver elements  42 ,  43  are determined by the conveying speed of the individual chain conveyors  40 ,  40 ′. These are preferably driven by servo motors. The chain conveyors  40 ,  40 ′ are controlled here independently of one another via a controller as a function of sensor signals, which contain the position of the individual bulk products P. To attain precise positioning of the bulk products P on the packaging material S, all the bulk products P are preferably pushed by driver elements  42 ,  43 , and the speed at which the pushing is done depends on the position, detected earlier, of the bulk product P. In this example, the raising and lowering of the individual driver element arms  420 ,  430  is attained by mechanical means, in the form of slide tracks  45 . 
   The different speeds of the driver elements  42 ,  43  and their raising and lowering may, however, also be attained by other means. In particular, all the driver elements may be raised or lowered. For example, it is also possible for each driver element  42 ,  43  to be driven by its own motor, with the motor causing the raising and lowering and/or pushing forward of the driver element  42 ,  43 . 
   The device and the method of the invention thus make it possible to shorten the delivery span of a packaging machine while at the same time increasing the positional precision of the individual bulk products. 
   The foregoing relates to a preferred exemplary embodiment of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.