Abstract:
The disclosure relates to a packaging machine with a sealing station for sealing trays with a top film, where said sealing station comprises a sealing tool upper part and a tray carrier for lifting at least one tray to said sealing tool upper part. Said packaging machine according to the disclosure is characterized in that a transport means defines a transport plane for the tray bottom to be transported and is provided within an opening for said tray in said tray carrier in order to transport said tray in the transport plane along said tray carrier. The disclosure also relates to a corresponding method for operating a packaging machine.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims foreign priority benefits under 35 U.S.C. §119(a)-(d) to European patent application number EP 11003534.2 filed Apr. 29, 2011, which is incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The disclosure relates to a packaging machine and to a method for operating a packaging machine with a transport device. 
     BACKGROUND 
     A tray sealer is known from DE 10 2008 030 510 A1, in which a gripper system grips trays which were positioned on a feeding belt by means of two horizontally movable grippers. The grippers transport the trays into a sealing station in which they are sealed with a top film. After the sealing procedure, the sealed trays are transported out of the sealing station by the two grippers and transferred onto a discharge belt. The grippers simultaneously transport both the unsealed trays into the sealing station as well as the sealed trays out of the sealing station. Such a gripper system requires a large amount of space for the gripper movements that occur outside and in particular at the side of the sealing station, as well as for driving and guiding means of the gripper system. Prerequisite for the use of gripper systems is, that the trays are respectively grouped and position at a distance from the grippers on a feeding belt, after being fed to the feeding belt of the sealing machine at an irregular or non-matching distance. Such a gripper system cannot be used for an at least three-lane tray sealer. 
     SUMMARY 
     An object of a packaging machine according to the disclosure is to provide a space-saving and universally employable option with respect to the number of lanes, for transporting trays into and out of a sealing station. 
     A packaging machine according to the disclosure, preferably a tray sealer, comprises a sealing station for sealing containers with a top film, where the sealing station comprises a sealing tool upper part and a tray carrier for lifting at least one container or tray to the sealing tool upper part. A transport plane is defined for the tray bottom to be transported, where a transport device is provided in the tray carrier within an opening for the tray and adapted to transport the tray in the transport plane along the tray carrier. In this, the trays can be supplied by a feeding belt at an arbitrary distance, as they are received by the transport device and positioned according to the opening in the tray carrier. 
     Preferably, the transport device is multi-row and/or multi-lane, in particular three-lane or multi-lane, to increase the number of trays in the sealing tool and thereby enhance the performance of the packaging machine. 
     In a particularly advantageous embodiment, there are openings provided in the transport device for the tray carrier. This allows for the tray carrier in a lowered position to be able to be lowered into the transport device or the transport device is arranged in the openings intended for the trays such that the upper edge of the tray carrier is arranged at the same level or at only a small distance, preferably 0.1 mm to 5 mm, below the transport plane of the transport device. 
     The transport device preferably comprises at least one transport belt for transporting the tray by placing the container bottom or tray bottom onto the transport belt. A transport belt is flexible in its use, since different tray dimensions and shapes of tray bottoms can be transported. Given such a transport belt, the transport plane for the tray bottom to be transported is defined by the top side of the upper run of the transport belt. Deflection rollers provided for the transport belt preferably comprise adjustment means, enabling conversion to other formats in combination with a corresponding tray carrier without changing the transport unit or a transport belt. 
     The transport device preferably comprises deflection rollers to direct the path of the transport belt such that lowering the tray carrier into the transport device is enabled, since in this case the transport belt is deflected such that a free space is provided for the tray carrier. To achieve a minimal deflection radius, so-called knife edges are also employable. 
     It is advantageous if a first group of deflection rollers or knife edges is provided, which determines the position of the transport belt in the transport plane and ensures that the transport belt is deflected from this transport plane downwards or from below into the transport plane, respectively. Spacings or steps are formed along the transport path by means of this deflection of the transport belt, into which the tray carrier can be lowered, so that it no longer protrudes upwardly above the transport plane and thus does not impair transportation of the trays on the transport device. A second group of deflection rollers, possibly having a larger diameter than the first group of deflection rollers, is preferably provided further below. The clearance between the upper end of a deflection roller of this second group of deflection rollers and the transport plane should at least correspond to the height of the tray carrier, preferably even be a bit larger so that the tray carrier in its lowered position still may well be above the deflection rollers but precisely does not protrude upwards beyond the transport plane. It is conceivable that the transport belt is guided around the rollers of this second group of deflection rollers in a U-shape. The diameter of this second group of deflection rollers thus determines the width of a spacing of the transport device, into which the tray carrier can be lowered. 
     The tray carrier preferably comprises a surface for receiving a tray edge, which during transportation of the tray is preferably at the same height or below the transport plane. In this, the tray can be slid on the surface of the tray carrier during transportation along the tray carrier when the tray bottom is not completely received by the transport device. This mainly occurs in the transition from a feeding belt to the transport system or between two adjacent openings of the tray carrier in the transport direction. 
     During the tray transfer from a feeding device to the transport device, the velocities of the transport belt of the transport device and a feeding unit, such as a feeding belt, of the feeding device are preferably synchronized, in order to thus also transfer information on the position of a tray, given in a control means of the feeding unit, to the transport device without any further sensor systems. 
     In an advantageous embodiment, the transport device has a plurality of successively arranged transport belts according to the number of trays to be sealed in a lane. This enables positioning of individual trays in the region of the openings in the tray carrier, independent of neighboring trays. 
     In a method according to the disclosure for positioning at least one tray in a sealing station of a packaging machine by means of a transport device, the tray is transferred e.g., by a feeding device onto the transport device and positioned such that a tray carrier can lift the tray from the transport device and move it to a sealing tool upper part for sealing the tray with a top film. A transport plane for the tray bottom to be transported is defined by the transport device, and the transport device transports the tray within an opening provided for the tray in the tray carrier in the transport plane along the tray carrier. This method can also be employed in a multi-row and/or multi-lane packaging machine and enables transfer of individual trays or even of a pre-grouped number of trays. 
     Preferably, the tray carrier, after sealing, places the trays onto the transport belt and the transport device transfers the trays to a discharge device. 
     Preferably the transport device, in a limited time period during the period of transferring the sealed trays to the discharge device, simultaneously receives the trays to be newly sealed from the feeding device in order to further increase performance of the packaging machine. 
     Preferably, the tray carrier lifts multiple trays being provided in the tray carrier in correspondence to the openings, which are consecutively and/or adjacently transported by the transport device, in order to lead them towards the seal tool upper part so that it can seal the group of trays with a top film. 
     In an advantageous embodiment, a sensor detects the position of a tray on the feeding device or on the transport device and a controller controls the transport device such that the tray is positioned congruently to the opening of the tray carrier and the tray carrier can thus receive the tray. 
     The method is particularly suitable for multi-row and multi-lane tray sealers (tray sealing machines), in which trays filled with products are transported towards the sealing station via multiple feeding belts arranged in parallel, and are accordingly positioned or arranged, respectively, by the transport device within the sealing station. The method, however, is not limited thereto and further embodiments are conceivable 
     In the following, an advantageous embodiment of the disclosure is further illustrated with reference to the below drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic view of a packaging machine according to the disclosure; 
         FIG. 2 a    shows a schematic side view of the transport device and the tray carrier in the transport position; 
         FIG. 2 b    shows a schematic side view of the transport device and the tray carrier in a lifted position; 
         FIG. 3  shows a schematic view of a sealing station with a feeding and discharge device having trays on the feeding device; 
         FIG. 4  shows a schematic view similar to  FIG. 3  with containers on the transport system; 
         FIG. 5  shows a schematic view similar to  FIG. 4  with a lifted tray carrier; 
         FIG. 6  shows a schematic view similar to  FIG. 3  with sealed trays placed on the transport system; 
         FIG. 7  shows a schematic view similar to  FIG. 6  with trays on the discharge device; and 
         FIG. 8  shows a schematic view of a three-row and three-lane embodiment. 
     
    
    
     Identical components are in the figures designated throughout with the same reference numerals. 
     DETAILED DESCRIPTION 
       FIG. 1  shows a packaging machine  1  according to the disclosure in the form of a tray sealing machine, also referred to as tray sealer, with a sealing station  2 , a feeding device  3  (including a movable feeding unit such as a movable feeding belt), and a discharge device  4  (including a movable discharge unit such as a movable discharge belt). A top film  5  is unrolled from a material storage  6 , guided below a sealing tool upper part  7  and wound onto a residual film winder  8 . A presently single-lane transport device  9  transports the trays  10  along a tray carrier  11 . In this, the trays  10  are transported in a transport direction R by the packaging machine  1 . 
       FIG. 2 a    shows the transport device  9  with a transport belt  12  and a plurality of deflection rollers  13   a ,  13   b  in the position in which the trays  10  are transported. A non-illustrated servo drive drives a shaft  14  via which the transport belt  12  is driven. The tray carrier  11  shown in its lowered position in  FIG. 2 a    comprises a frame  15  which is connected to a non-illustrated lifting device by means of guides  16 . The transport belt  12  is located in openings  20  (see  FIG. 3 ) of the tray carrier on the same level as the upper side of the tray carrier or extends slightly above the tray carrier  11  and with its upper side defines a transport plane E for the tray bottom  10   a . In this, the difference in height between the transport plane E and the tray carrier  11  is just large enough to ensure sufficient friction of the tray bottom  10   a  on the transport belt  12 . 
       FIG. 2 b    shows the tray carrier  11  in a lifted position, in which the trays  10  are received with their laterally projecting edge of the tray  17  by the tray carrier  11 . Spacings  18  for the stays  19  of the tray carrier  11  are clearly visible, wherein the spacings  18  are enabled by the deflection rollers  13   a ,  13   b  and the resulting course performed by the transport belt  12 . In this, the upper deflection rollers  13   b  are formed having a very small diameter in order to guide the transport belt  12  as closely as possible to the inner side of the opening  20  in the tray carrier  11 , in order to be able to bridge the distance S corresponding to the spacing between two adjacent openings  20  in the tray carrier  11  or between two adjacent sections of the transport belt  12 , respectively. 
     It is evident from  FIGS. 2 a  and 2 b   , that the lower deflection rollers  13   a  together with the shaft  14  arranged in the center determine the course of the lower run of the transport belt  12 . For determining the course of the upper run of the transport belt  12 , a first group of deflection rollers  13   b  or carrier rollers, respectively, is provided which is located directly below the transport or conveying path. A second group, in this case, of two upper deflection rollers  13   c , having a larger diameter than the carrier or deflection rollers  13   b  of the first group, is located at a greater distance downwardly from the transport plane E. The transport belt  12  is wrapped in a U-shape around these larger deflecting roll  13   c  of the second group. The deflection rollers of the first and the second group guide the upper run of the transport belt  12  such that two gaps or spacings  18  along the conveying path are created, into which the stays  19  of the tray carrier  11  can then be lowered. In the vertical direction, the distance between the upper side of the defection rollers  13   c  of the second group and the transport plane E is large enough for the tray carrier  11  in its lowered position not to extend upwards beyond the transport plane E, but preferably to be completely below the transport plane E. The deflection rollers  13   b  of the first group of upper deflection rollers have a diameter smaller than the deflection rollers  13   c  of the second group of upper deflection rollers  13   b , so that the spacings  18  are in the horizontal direction preferably not much wider than the stays  19  of the tray carrier  11 . 
       FIG. 3  shows three pre-grouped trays  10  on a feeding device  3  and a tray carrier  11  with three openings  20  for receiving a group of three trays  10 . A sensor  21  at the end of the feeding device  3  detects, for example, the front edge of the tray  10  that is located closest to the transport device  9 , and communicates this position to a controller C. The controller C is preferably also provided for controlling and actuating all of the drives existing in the packaging machine  1 . 
       FIG. 4  shows how the trays  10 , after being positioned by the transport device  9  along the tray carrier  11  in the transport direction R, are congruent with the openings  20  of the tray carrier  11 . 
       FIG. 5  shows the tray carrier  11  in a lifted position with respect to the sealing tool upper part  7  for sealing the trays  10  with a top film  5 , not shown in this figure. The sealing procedure can presently also be performed in a vacuum or modified atmosphere. 
       FIG. 6  shows the tray carrier  11  again in the lowered position like in  FIG. 4 . The three trays  10  are sealed with a part of the top film  5  and the tray bottom  10   a  is located on the transport belt  12  of the transport device  9 . 
       FIG. 7  shows the transfer of the sealed tray  10  to the discharge device  4 , which supplies the trays  10  to further production steps, such as examination by means of a metal detector, weighing or labeling. 
       FIG. 8  shows a three-row and three-lane version of the transport device  9  with three adjacent transport belts  12  arranged in parallel in the transport direction R. The tray carrier  11  respectively comprises nine openings  20 . 
     As a further variant, it is conceivable both for single-lane as well as multi-lane packaging machines, that for each opening  20  in the tray carrier  11 , a separate transport belt  12  is provided, which is driven either individually or in groups by means of a servo drive and is controlled by a machine control. 
     The transport device  9  is capable to also receive trays  10 , which are not pre-positioned on a feeding device  3 , from the feeding device and to position them congruently with the openings  20 . Each of the transport belts  12  may be synchronized with the feeding device  3  or any upstream or downstream transport belt  12  of the transport device  9 . 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.