Patent Publication Number: US-2012031737-A1

Title: Device for conveying objects in packaging machines

Description:
RELATED APPLICATIONS 
     The present patent document claims the benefit of priority to European Patent Application No. EP 10172001.9, filed Aug. 5, 2010, and entitled “DEVICE FOR CONVEYING OBJECTS IN PACKAGING MACHINES,” the entire contents of each of which are incorporated herein by reference. 
     FIELD AND BACKGROUND 
     The invention relates to a device for conveying objects in packaging machines. 
     These types of devices are used in particular in the pharmaceutical industry to transport folding boxes, into which stacks of blister packs are to be inserted. Such devices for conveying objects in packaging machines usually consist of two endless transport units, usually in the form of roller chains, which move the objects forward. The first transport unit, like the second unit, is equipped with driver elements in the form of upward-projecting fingers, for example, which serve to support the objects. Driver elements which function as pushing elements are assigned to the first transport unit, whereas the driver elements of the second transport unit function as counterholding elements. The distance between the pushing driver elements and the counterholding driver elements, which is defined by the relative position of the two transport devices, thus determines the size of the support surface available for the objects. 
     When the format is to be changed to accommodate packages of a different size, it is therefore necessary for the pushing driver elements to be shifted relative to the counterholding driver elements. This is accomplished by shifting the positions of the two transport units with respect to each other. The distances must be observed with millimeter accuracy. 
     In modern devices for conveying objects in packaging machines, the two endless transport units are driven by two shafts; the first shaft is connected to a drive motor and is also connected to the second shaft by way of a belt drive, for example. When the format is to be changed, manual operations are usually required. 
     It is known from DE 101 23 220 A1 that a self-locking adjusting device can be provided, which is connected to a first shaft and which can be actuated manually via an opening. To make the adjustment, an adapter is rotated relative to the first shaft, and this rotational movement is transmitted by a toothed belt and a toothed disk to the second shaft, the angular position of which with respect to the first shaft is thus changed. After the adjustment process, it is necessary to conduct reference and control runs. 
     In DE 10 2006 007 986 A1, it is proposed that the two shafts be connected by a clutch, which is not specified in detail, so that the drive, under normal operating conditions, moves the two transport units parallel to each other, whereas, under format adjustment conditions, it moves them relative to each other. No details of a concrete realization, however, are presented. Every automatic change or format requires in principle a large number of individual parts and a considerable amount of control engineering. 
     BRIEF SUMMARY 
     It is an object of the present invention to provide a device for conveying objects in packaging machines, in which the changeover to a new format can be accomplished with modest mechanical effort, with considerable speed, and with precise adjustment. 
     According to an aspect of the invention, the device for conveying objects in packaging machines comprises: 
     a first endless transport unit, which moves first driver elements; 
     a second endless transport unit, which moves second driver elements; 
     a drive shaft, which is driven by a motor and which drives the first endless transport unit; 
     an auxiliary shaft, which drives the second endless transport unit; and 
     a belt-type or chain-type connecting element for transmitting the drive power from the drive shaft to the auxiliary shaft. 
     The connecting element between the drive shaft and the auxiliary shaft is guided over a plurality of stationary auxiliary rollers and over at least two adjusting rollers, which can be shifted simultaneously in the direction perpendicular to their axes of rotation. The connecting element is guided in such a way that a shift of the adjusting rollers brings about a movement of the connecting element on the auxiliary shaft and thus a change in the angular position of the auxiliary shaft. 
     With this design, the complicated process of changing formats can be accomplished easily and quickly, if necessary even while the device is operating, wherein highly precise adjustments are possible. 
     In a preferred embodiment, the adjusting rollers can be shifted in the same direction. As a result, the mechanism for format change occupies only a small amount of space. 
     It is also advantageous for the adjusting rollers to be of equal size and to be shiftable over the same distance. In this way, the simplest possible mechanical design is created, which makes the adjustment process especially easy. 
     Both the auxiliary rollers and the adjusting rollers can be arranged in axially symmetric fashion with respect to an axis of symmetry, as a result of which it becomes even easier to calculate the distance by which they must be shifted. Ideally, the axis of symmetry passes through the axes of rotation of the drive shaft and of the auxiliary shaft. 
     When the adjusting rollers are shifted, optimal transmission of the power to the auxiliary shaft can be achieved by ensuring that the section of the connecting element which is entering the adjusting roller is parallel to the section of the connecting element which is leaving the adjusting roller. 
     In a preferred embodiment, the connecting element is a toothed belt, toothed belt pulleys are mounted on the drive shaft and on the auxiliary shaft, and the adjusting rollers are toothed belt pulleys. 
     Alternatively, the connecting element can be a roller chain, sprockets are mounted on the drive shaft and on the auxiliary shaft, and the adjusting rollers are sprockets. 
     So that the adjusting mechanism can be guided reliably, the adjusting rollers can be shifted by means of a linear guide unit. 
     The linear guide unit can comprise a format adjusting plate, which is permanently connected to the adjusting rollers and which is guided in at least one straight guide rail. 
     The auxiliary shaft can be shifted precisely and thus rotated with millimeter accuracy by the use of an adjusting motor with an integrated absolute encoder to shift the adjusting rollers. Then there is also no need for any reference runs or control measurements when changing formats. 
     In one embodiment, the adjusting motor drives a spindle of the linear guide unit. 
     So that both transport units can be driven in the area where they reverse direction, the auxiliary shaft is preferably connected by means of a belt drive to an engagement unit rotatably supported on the drive shaft; this engagement unit engages with the second endless transport unit and thus drives it. As a result, the drive mechanisms for both transport units are supported on the drive shaft and are thus directly adjacent to each other. 
     In a preferred embodiment, the engagement unit can comprise a toothed belt pulley supported rotatably on the drive shaft, this pulley being connected to the belt drive and permanently connected to a sprocket, which is also mounted rotatably on the drive shaft. The sprocket in turn engages in the second endless transport unit and thus drives it. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Additional features and advantages of the present invention can be derived from the following description, which refers to the drawings: 
         FIG. 1  is a schematic perspective view of essential elements of a device for conveying objects in packaging machines according to the invention; 
         FIG. 2  is a schematic perspective view of the drive section of the device for conveying objects in packaging machines; 
         FIG. 3  shows a cross section through the drive section of the device for conveying objects in packaging machines; 
         FIG. 4  is a schematic perspective view of the drive section of the device for conveying objects in packaging machines with an adjusting motor for the adjusting rollers; 
         FIG. 5  is a schematic perspective view of the drive section of  FIG. 4  with a linear guide unit for shifting the adjusting rollers; 
         FIG. 6  is a perspective top view of the partial area shown in  FIG. 5 ; 
         FIG. 7  is a schematic perspective view of the rear of the drive section shown in  FIG. 6 ; and 
         FIG. 8  is a perspective cross-sectional diagram of the drive section of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     The invention is described in detail below with reference to the exemplary embodiment illustrated in  FIGS. 1-8 . 
     So that objects  2 , especially folding boxes, can be transported during the packaging process, receiver cells adapted to the size of the objects  2  must be formed. Because the width of the receiver cells may have to be changed depending on the format of the objects  2  to be transported, it should be possible to adjust the size of the receiver cell slightly. 
     According to the present exemplary embodiment, each receiver cell is formed by first driver elements  4  and second driver elements  6  (see especially  FIGS. 1 and 2 ). In the exemplary embodiment shown here, the first driver elements  4  are designed as pushing driver elements, whereas the second driver elements  6  are designed as counterholding elements. The opposite configuration is also conceivable. The driver elements  4 ,  6  can be designed as fingers as shown here, but they could also take the form of a continuous plate. 
     The first driver elements  4  are attached to a first endless transport unit  8 , whereas the second driver elements  6  are attached to a second endless transport unit  10 , the driver elements projecting from the transport units in each case. The first transport unit  8  and the second transport unit  10  can be designed preferably as roller chains, which, during the operation of the device, are in a fixed relationship to each other. To change the format, this fixed relationship must be suspended, and the transport units  8 ,  10  must be shifted with respect to each other. As a result, the distance between the first driver elements  4  and the second driver elements  6  is changed, and thus the size of the receiver cell is changed. 
     As can be seen especially in  FIGS. 2 and 3 , a drive shaft  12 , which is preferably designed as a spline shaft, drives an engagement unit  14  mounted on it, such as a sprocket, which engages with the first transport unit  8  and drives it. This is preferably done at the reversal point of the endless transport unit  8 . The drive shaft  12  itself is driven by a motor (not shown). 
     From the drive shaft  12 , a belt-type or chain-type connecting element  16  leads to an auxiliary shaft  18 . As a result, the drive power is transmitted from the drive shaft  12  to the auxiliary shaft  18 , which, under normal operating conditions, therefore runs synchronously with the drive shaft  12 . The connecting element  16  is designed either as a roller chain or, as shown in the figures, as a toothed belt, and, in a corresponding manner, sprockets or toothed belt pulleys  20 ,  22 , which engage with the connecting element  16 , are mounted on the drive shaft  12  and the auxiliary shaft  18 . 
     The auxiliary shaft  18  drives the second transport unit  10 . This can be done, for example, by way of a sprocket (not shown) mounted on the auxiliary shaft  18 , but preferably the engagement unit  23 , which is driven by the auxiliary shaft  18  and engages with the second transport unit  10 , is mounted rotatably on the drive shaft  12 . This offers the advantage that the points where power is transmitted to the first transport unit  8  and to the second transport unit  10  can be located next to each other and thus in the area where the transport units  8 ,  10  reverse direction. 
     In a preferred embodiment, therefore, an additional belt drive  24  extends from the auxiliary shaft  18  to the engagement unit  23 , which is supported on the drive shaft  12  and which, in a preferred embodiment, comprises a toothed belt pulley  26  mounted rotatably on the drive shaft  12 , this toothed belt pulley being connected to the belt drive  24  and permanently connected to a sprocket  28 , which is also supported rotatably on the drive shaft  12 , and which in turn engages in the second endless transport unit  10  and thus drives it. 
     As can be seen most clearly from  FIGS. 2 and 4 , the connecting element  16  in the example shown here extends between the drive shaft  12  and the auxiliary shaft  18  by way of two adjusting rollers  30  and four auxiliary rollers  32 . When the connecting element  16  is designed as a toothed belt, the adjusting rollers  30  will be designed as toothed belt pulleys, whereas the auxiliary rollers  32  can be designed as smooth rollers. When the connecting element  16  is designed as a roller chain, both the adjusting rollers  30  and the auxiliary rollers  32  will be designed as sprockets. 
     In the exemplary embodiment shown here, one of the two adjusting rollers  30  is arranged above the other, and both can be shifted in the vertical direction. In addition, the two adjusting rollers  30  are of the same size and are shifted over the same distance. Both the auxiliary rollers  32  and the adjusting rollers  30  are axially symmetric to an axis of symmetry, which preferably passes through the axes of rotation of the drive shaft  12  and the auxiliary shaft  18 . The connecting element  16  extends as an endless element from the drive shaft  12 , around one of the auxiliary rollers  32  (90° turn), around the upper adjusting roller  30  (180° turn), and then around another auxiliary roller  32  (approximately 120° turn). From this point it returns to the drive shaft  12  by first passing around the auxiliary shaft  18  and then by tracing a symmetrical path over two additional auxiliary rollers  32  and the lower adjusting roller  30 . Whereas the adjusting rollers  30  are supported so that they can be shifted in a direction perpendicular to their axes of rotation, the auxiliary rollers  32  are preferably supported in a stationary manner, so that, although they can rotate, no translation is possible. 
     With a design such as this, it is guaranteed that the section of the connecting element  16  which is entering one of the adjusting rollers  30  always stays parallel to the section of the connecting element  16  which is leaving the adjusting roller  30  on the other side (180° turn). As a result, straight, length-compensating sections of the connecting element  16  are created, which, when the two adjusting rollers  30  are shifted in the same direction, become shorter or longer to the same degree. When now the two adjusting rollers  30  are shifted up or down, the adjusting rollers  30  change the angular position of the auxiliary shaft  18  as a result of the change in the position of the connecting element  16 . Because the drive power is exerted on the second transport unit  10  by the auxiliary shaft  18 , this transport unit also shifts relative to the first transport unit  8 . In the example shown here, this is accomplished via the rotation of the toothed belt pulley  26  mounted in freely rotatable fashion on the drive shaft  12  and the rotation of the sprocket  28  permanently connected to it. 
     So that the format adjustment can be carried out in fully automated and highly precise fashion, the adjusting rollers  30  can preferably be moved with the help of a linear guide unit  34 , which is shown in  FIG. 5 . In the example shown here, the linear guide unit  34  comprises a format adjusting plate  35 , to which the adjusting rollers  30  are attached by screws, for example. The format adjusting plate  35  can be shifted along one or more straight guide rails  37  by means of an adjusting motor  36 , for example. The adjusting motor  36  should comprise an integrated absolute encoder. A servomotor can also be used. The adjusting motor  36  can drive a spindle  38 , for example, which engages in a thread on the format adjusting plate  35 . At the same time, the stationary auxiliary rollers  32  can be mounted on a base plate  40  (see  FIG. 4 ) of the device. 
     In addition to the embodiment shown here, many other embodiments which fall within the scope of the invention are also possible. For example, more than two adjusting rollers  30  as well as any desired number of auxiliary rollers  32  can be provided. The individual adjusting rollers  30  can be of different sizes, and their position and arrangement can also be varied. The arrangement does not necessarily have to be symmetric or one-above-the other. Shifting the adjusting rollers  30  in the vertical direction is not mandatory either; a horizontal shift of the adjusting rollers  30  is also conceivable, provided that the connecting element  16  is guided suitably. The path along which the adjusting rollers  30  move can also be different in cases where the adjusting rollers  30  are of different sizes or when an odd number of adjusting rollers  30  is provided. The important point in all cases is that the overall distance traveled by the connecting element  16 , which is defined by the length of the connecting element  16 , remains constant and that, because of the way in which the connecting element  16  is guided, a shift of the adjusting rollers  30  causes the connecting element  16  to move on the auxiliary shaft  18 , which in turn produces a change in the angular position of the auxiliary shaft  18 . 
     To ensure a uniform driving action, multiples of some of the elements of the drive section described above are preferably provided and arranged with mirror symmetry with respect to the longitudinal axis of the device. As can be seen especially in  FIG. 2 , this pertains to the first transport unit  8  with the first driver elements  4 , to the second transport unit  10  with the second driver elements  6 , to the engagement units  14  and  23 , and to the belt drive  24 . 
     Alternatively to the use of the adjusting motor  36  to adjust the adjusting rollers  30 , the adjusting rollers  30  could also be adjusted manually, or the spindle  38 , which would be equipped with a digital readout, could be rotated by hand.