Abstract:
The disclosure relates to a working station for a packaging machine for quickly cutting a top film and to a method for operating such a working station.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims foreign priority benefits under 35 U.S.C. §119(a)-(d) to German patent application number DE 10 2010 055 967.9, filed Dec. 23, 2010 which is incorporated by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The disclosure relates to a working station as well as to a method for operating such a working station for cutting a width of film. 
       BACKGROUND 
       [0003]    Known from DE 10 2008 032 306 A1 is a tray sealing machine with a working station that comprises a sealing tool for sealing trays with a top film and a cutting tool for cutting the top film. An electric motor drive is provided for moving the sealing tool and the cutting tool. The cutting tool can be moved relative to the sealing tool and to a chamber upper part or to the tray that is to be sealed. 
         [0004]    The speed of the movement of the cutting tool with respect to the top film that is to be cut is low, because the electric motor drive has a spindle that is designed for producing high forces. The cutting of flexible films that have, for example, a thickness of less than 50 μm or that have been heated for skinning does not lead to a visually appealing film edge, in spite of the use of serrated blade edges. 
       SUMMARY 
       [0005]    The object of the present disclosure is therefore to provide a working station for a packaging machine whereby this working station has improved and yet economical cutting. 
         [0006]    The working station is especially suitable for a small table tray sealer in which the tray is to be inserted into a drawer. 
         [0007]    The working station for a packaging machine according to the disclosure for sealing trays comprises a sealing tool upper part, a sealing tool lower part, a sealing frame, a cutting tool and a blade for cutting a width of film, wherein the blade is provided on the cutting tool and the blade is adapted to an edge of the tray. At least one energy storage device is provided between the cutting tool and the sealing frame in order to have potential energy accumulated after a relative movement of the sealing frame with respect to the cutting tool. The movement of the sealing frame and the subsequent cutting movement of the cutting tool are consequently made possible by only one drive, consequently simplifying the design of the working station. The energy storage device is preferably a spring, preferably a compression spring. This allows an economical and space-saving design. Alternatively, correspondingly acting elements in which a medium is expandable or compressible can be used. 
         [0008]    In a preferred form, at least one holding means is provided in order to hold temporarily the cutting tool on a part of the working station that is stationary with respect to the cutting tool and the sealing frame, preferably on the sealing tool upper part. The increase in the spring force of the spring element is consequently brought about and the detachment of the cutting tool from the holding element is controlled. 
         [0009]    The holding means is preferably a permanent magnet or an electromagnet, preferably a pot magnet, because the pot magnet has a low magnetic stray field. 
         [0010]    The detachment of the cutting tool from the holding means is preferably provided by means of switching off the electromagnet by means of a controller or by means of exceeding the retention force of the holding means by the sealing frame and the energy storage device, preferably a compression spring. The detachment of the cutting tool from the holding means is likewise conceivable by means of a limit stop or a stroke limitation that is provided between the sealing frame and the cutting tool in order to limit the relative movement. 
         [0011]    Preferably at least one cushioning element is provided in order to cushion the impact of the cutting tool on the sealing frame. This protects the affected components that impact against one another at the end of the cutting movement. 
         [0012]    In the case of a method according to the disclosure for operating a working station for a packaging machine for sealing trays and for cutting a top film, a sealing frame executes a relative movement with respect to a cutting tool and consequently loads at least one energy storage device (or energy accumulation device). 
         [0013]    A spring is preferably tensioned during this process. As a result, only one drive is needed that moves the sealing frame, because the cutting movement of the cutting tool is executed via the energy storage device or the spring quickly and independently of the movement of the sealing frame, above all much faster than the drive of the sealing frame would allow. 
         [0014]    Preferably a holding means holds the cutting tool on a part of the working station that is stationary with respect to the cutting tool and the sealing frame, preferably on the sealing tool upper part, and the cutting tool is let loose and quickly moves in the direction of the top film. This fast movement results in an improved cutting result. 
         [0015]    Preferably a blade mounted on the cutting tool cuts the top film on an edge of the tray in order to obtain the smallest possible overlap of the cut top film with respect to the tray edge. 
         [0016]    Preferably the cutting tool is cushioned by means of at least one cushioning element at the end of the cutting movement in order to brake the cutting tool harmlessly and in order to avoid a negative influence on the sealing. 
         [0017]    In the following, an advantageous embodiment of the thermoforming machine according to the disclosure and of the method according to the disclosure is described in more detail with reference to the below drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a schematic view of a packaging machine according to the present disclosure; 
           [0019]      FIG. 2  is a schematic sectional view of a working station according to the present disclosure in the initial position; 
           [0020]      FIG. 3  is a schematic sectional view with a tensioned compression spring; 
           [0021]      FIG. 4  is a schematic sectional view after a cutting process; 
           [0022]      FIG. 5  is a schematic sectional view with the cutting tool on the holding element; 
           [0023]      FIG. 6  is a schematic sectional view with raised sealing tool upper part; and 
           [0024]      FIG. 7  is a schematic sectional view with extracted drawer. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    Components that correspond to one another are consistently given the same reference numbers in the figures. 
         [0026]    In the following, an embodiment of the disclosure is described with reference to  FIG. 1  to  FIG. 7 , taking as an example a single-use tray sealing machine or a table tray sealer. 
         [0027]      FIG. 1  shows the table tray sealer  1  as a packaging machine with a working station  2 , a top film guide  3  for a top film  4  and a display and control device  5  that controls the operation of the table tray sealer  1 . The table tray sealer  1  has a drawer  6  that simultaneously serves as a sealing tool lower part  6  and a chamber lower part  6 . A tray  7  filled with product  8  (see  FIG. 2 ) is placed into the drawer  6  or into the sealing tool lower part  6  and manually slid into the working station  2 . 
         [0028]      FIG. 2  shows a schematic sectional view of a working station  2  according to the disclosure in an initial position. After the sealing tool lower part  6  is slid in, the top film  4  is clamped together between the sealing tool lower part  6  and a sealing tool upper part  9  by means of a seal  10  running around the circumference in such a way that a chamber that can be evacuated results. 
         [0029]    An electromagnet  11  that holds a cutting tool  12  is mounted on the sealing tool upper part  9 . The cutting tool  12  can be moved relative to the sealing tool upper part  9  over guides  13 . A blade  14  is mounted on the cutting tool  12 , wherein the contour of this blade essentially corresponds to the edge  15  of the tray  7 . A sealing frame  16  can be moved relative to the sealing tool upper part  9  over guides  13 . A compression spring  17  is provided between the cutting tool  12  and the sealing frame  16  in such a way that the compression spring  17  tenses against a bolt  18  during a sealing movement of the sealing frame  16  in the direction of the clamped top film  4  and the tray  7 , whereby this bolt is in turn connected to the cutting tool  12 . 
         [0030]    In  FIG. 3 , the sealing frame  16  has been moved down via a drive that is not shown, and the sealing frame clamps the top film  4  and the tray  7  against the sealing tool lower part  6  via a sealing gasket  19 . This tensions the compression spring  17 . The retention force of the electromagnet  11  is thereby greater than the force of the tensioned spring  17 . 
         [0031]      FIG. 4  shows the cutting tool  12  after the holding magnet  11  has released the cutting tool  12  by means of the controller  5  and the tensioned compression spring  17  has moved the cutting tool  12  downwards at a very high speed by means of the bolt  18 . The cutting tool  12  is preferably provided with a low weight in order to have a low inertia in order to achieve a high acceleration. A high speed of the blade  14  leads to very good cutting results and a visually appealing edge of the cut top film  4  on the tray  7 . 
         [0032]    At least one cushioning element  20  causes the cutting tool  12  not to impact, without braking, against the sealing frame  16  after the cutting of the top film  4 . For example, the cushioning element  20  is made of silicone and mounted circularly on the sealing frame  16  or on the cutting tool  12 . In a variant that is not shown, the electromagnet  11  can be replaced by a permanent magnet. The force for detaching the cutting tool  12  from the sealing tool upper part  9  can be applied both by tensioning the spring  17  on the block and a still further movement of the sealing frame  12  downwards, and also by achieving the detachment force by tensioning the spring  17  shortly before or at the moment of the clamping of the top film  4  between the sealing frame  12  and the sealing tool lower part  6 . In an advantageous manner, the impact, at least for a short time, increases the force of the sealing frame  16  on the top film  4  and the tray  7  without thereby negatively influencing the sealing. 
         [0033]      FIG. 5  shows the position of the cutting tool  12  after the cutting tool  12  has been raised upwards against the electromagnet  11  by a movement of the sealing frame  16  and the electromagnet  11  has been activated via the controller  5 , in order to hold the cutting tool  12  on the sealing tool upper part  9 . The sealing frame  16  thereby raises the cutting tool  12  via the bolt  18 . 
         [0034]    The sealing frame  16  and the sealing tool upper part  9  then move further upwards, as shown in  FIG. 6 , in order to release the drawer  6  for extraction. 
         [0035]      FIG. 7  shows how the drawer  6  is extracted from the working station  2  in order to remove the package  21  and in order to make it possible to insert the next tray  7  that is to be sealed. 
         [0036]    The electromagnet  11  or a permanent magnet can act directly on the cutting tool  12  or on a ferromagnetic material mounted thereon. A variant provides that the holding element  11  is mounted on the cutting tool  12  and acts on the sealing tool upper part  9 . 
         [0037]    Alternatively, the holding element can be a mechanical grid that is opened by means of the controller  5  and that independently locks into place in order to hold the cutting tool  12  on the sealing tool upper part  9 . 
         [0038]    In a further variant, it is conceivable that the top film  4  is cut by the blade  14  before the top film  4  is clamped against the tray  7  by the sealing frame  16  for sealing. This variant makes it possible for the top film  4  to be cut within the edge  15  of the tray  7  so that the package  21  can be further improved visually. 
         [0039]    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.