Abstract:
The invention relates to a deep-drawing packaging machine and to a method of operating such a deep-drawing packaging machine, comprising a lifting device for a workstation, wherein a lower tool part connected to a stand and an upper tool part connected to a frame are coupled to each other and driven by a motor such that both tools may at least partially move together towards a film web.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application claims priority to European Application Number 13155942.9 filed Feb. 20, 2013, to Andreas Streitenberger, Elmar Ehrmann and Robert Maier entitled “Deep-Drawing Packaging Machine with Lifting Device,” currently pending, the entire disclosure of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention relates to a deep-drawing (viz. thermoforming) packaging machine and to a method of operating a deep-drawing packaging machine. 
     BACKGROUND OF THE INVENTION 
     DE 10 2010 019 634 A1 discloses a motor-driven lifting device for a cutting station of a deep-drawing packaging machine which moves a lower tool part or a cutting knife upwards towards a film web by means of a push rod driven by a motor. Here, an upper tool part or a counter knife is stationarily provided at the upper side of the film web. The production of packages containing products that project beyond the plane of the film web is not possible with this lifting device. 
     DE 197 34 513 A1 discloses a pneumatically driven lifting gear for a workstation of a deep-drawing packaging machine, wherein the upper tool part is coupled with the lower tool part via linkages in such a way that an upward motion of the lower tool part from the bottom to the film web is followed by a downward motion of the upper tool part from the top to the film web, the lifting motion of the lower tool part amounting to a multiple of the lifting motion of the upper tool part. 
     SUMMARY OF THE INVENTION 
     It is the object of one embodiment of the present invention to provide lifting gears in deep-drawing packaging machines with a top lift without using compressed air and complex linkages. 
     The deep-drawing packaging machine (viz. thermoforming packaging machine) according to one embodiment of the present invention comprises a lifting device for a workstation, the lifting device comprising a stand mounted to a machine frame and a lower tool part connected with a motor by means of a push rod. The packaging machine is characterized in that the lifting device can comprise a frame that is movable perpendicularly to a film web and relatively to the stand by means of a rotary element mounted on the axis of the motor and engaged with the frame. The lifting device may comprise an upper tool part connected to the frame, where the upper tool part and the lower tool part may at least temporarily be simultaneously moved towards the film web located between them. This has the advantage that a coupled movement of the lower tool part and the upper tool part towards the foil is permitted by means of only one motor. The lifting device may be designed such that the upper and lower tool parts perform different strokes. 
     The rotary element may be an eccentric, the eccentricity determining the stroke of the relative motion of the frame with respect to the stand and thus the stroke of the upper tool part. 
     The rotary element may be designed to cooperates with the frame in a guide to provide a restricted guide with only little clearance and the ability to absorb high forces. 
     In one embodiment, the rotary element is a lever with a guide pin, said guide pin cooperating with the frame in a guide which may be embodied as connecting link. The lever permits a large and adjustable eccentricity as the guide pin is able to assume different positions at the lever. 
     The connecting link can have a track guide for the guide pin, so that the upper tool part may temporarily not be moved during the movement of the lever relative to the film web, i.e., it may be kept stationary. The advantage resides in the fact that, for example, in a cutting station, the upper tool part may be designed as a counter knife and the lower tool part as a cutting knife, and a cutting knife which is not designed as a linear knife parallel to the film web presses the film web against the counter knife at first contact with the film web and during the further cutting operation. Since the counter knife does not perform any movement against the film web or away from the film web, no stress is exerted perpendicularly on the film web, and the formation of folds is prevented. 
     As an alternative, the guide comprises a track guide for the guide pin, so that the lower tool part may be temporarily not moved during the movement of the rotary element relative to the film web, i.e., it may be kept stationary. In case of a cutting station, this permits, for example, the use of a counter knife as the lower tool part and a cutting knife as the upper tool part. 
     The workstation may not only be a cutting station but also a sealing and/or forming station, each with an upper sealing or mould part and a lower sealing or mould part, respectively. 
     It may be suitable to provide a guiding facility between the stand and the frame. This permits to avoid tilting or a non-uniform movement of the frame along the guides in general. In other words, it is thus ensured that the tool part strikes the film web in an exactly defined orientation. For example, a mould or a cutting knife could remain oriented exactly parallel to the plane of the film web when the tool part strikes the film web. 
     The method according to one embodiment of the invention for the operation of a deep-drawing packaging machine with a lifting device for a workstation, wherein the lifting device comprises a stand mounted to a machine frame and a lower tool part connected to the motor by means of a push rod, is characterized in that the lifting device comprises a frame which is driven by the motor to perform a movement perpendicular to a film web and relative to the stand. The motor can move the lower tool part upwards to the film web, while an upper tool part, which is connected to the frame, is at least partially simultaneously moving downwards towards the film web. Thus, a coupled movement both of the upper tool part and the lower tool part towards the film web takes place with only one motor. 
     Particularly advantageously, the lower tool may be temporarily moved upwards to the film web by means of the motor as common drive, while the upper tool part temporarily stands still opposite to the film web, i.e., remains stationary. 
     The upper tool part may lie against the film web before the lower tool part reaches the film web, so that, for example in a cutting facility where the upper tool part may be designed as a counter knife, already at the first contact of the lower tool part, which is in this case designed as a cutting knife, with the film web, the counter knife functions as holding point and the formation of folds in the film web, and as a consequence an inaccurate cut, are thus excluded. 
     The workstation for which the method may be employed may be a forming station, a sealing station, and/or a cutting station. 
     It is also conceivable to equip in the deep-drawing packaging machine several, optionally different ones of these workstations with a lifting device in a manner according to the invention. 
     Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description. 
    
    
     
       DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       In the accompanying drawing, which forms a part of the specification and is to be read in conjunction therewith in which like reference numerals are used to indicate like or similar parts in the various views: 
         FIG. 1  is a schematic side view of a deep-drawing packaging machine in accordance with one embodiment of the present invention; 
         FIG. 2  is a side view in the production direction of a lifting device in accordance with a first embodiment of the present invention, the lifting device being used in connection with a transverse cutting unit and being shown in an opened position; 
         FIG. 3  is a side view of the lifting device of  FIG. 2  at the beginning of a cutting operation; 
         FIG. 4  is a side view of the lifting device of  FIG. 2  in a closed position; 
         FIG. 5  is a side perspective view of a lifting device in accordance with a second embodiment of the present invention, the lifting device being used in connection with a transverse cutting unit and being shown in an opened position; 
         FIG. 6  is a side view of the lifting device of  FIG. 5  in the production direction; 
         FIG. 7  is a side view of the lifting device of  FIG. 5  at the beginning of a cutting operation; 
         FIG. 8  is a side view of the lifting device of  FIG. 5  in a closed position; 
         FIG. 9  is a side view in the production direction of a lifting device in accordance with a third embodiment of the present invention, the lifting device being used in connection with a forming station and being shown in an opened position; and 
         FIG. 10  is a side view of the lifting device of  FIG. 9  in a closed position. 
     
    
    
     Similar components are always provided with the same reference numerals in the figures. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. For purposes of clarity in illustrating the characteristics of the present invention, proportional relationships of the elements have not necessarily been maintained in the drawing figures. 
     The following detailed description of the invention references specific embodiments in which the invention can be practiced. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments can be utilized and changes can be made without departing from the scope of the present invention. The present invention is defined by the appended claims and the description is, therefore, not to be taken in a limiting sense and shall not limit the scope of equivalents to which such claims are entitled. 
       FIG. 1  shows a deep-drawing packaging machine  1  according to one embodiment of the present invention in a schematic view. As illustrated, this deep-drawing packaging machine  1  comprises a forming station  2 , a sealing station  3 , a transverse cutting unit  4  and a longitudinal cutting unit  5  which are disposed at a machine frame  6  in this sequence in a production direction R. At the entry side, a feed roller  7  may be located at the machine frame  6 , from which roller a film web  8  is reeled off. In the region of the sealing station  3 , a material storage  9  can be provided from which a lid film  10  is reeled off. At the exit side, a discharge apparatus  13  in the form of a conveying belt may be provided at the deep-drawing packaging machine by means of which finished, separated packages are carried away. Furthermore, the deep-drawing packaging machine  1  can comprise a non-depicted feeder which grips the film web  8  and transports it further in the production direction R in each main cycle. The feeder may be designed, for example, by clamp chains  60  disposed on either side (see  FIG. 6 ). 
     In the shown embodiment, the forming station  2  is embodied as a deep-drawing station in which cavities  14  are formed into the film web  8  by deep-drawing. The forming station  2  may be designed such that several cavities are formed next to each other in the direction perpendicular to the production direction R. The forming station  2  can comprise a lifting device  30  to position a lower mould part to the top against an upper mould part in a working position for the forming process. In the production direction R downstream of the forming station  2 , an insertion section  15  may be provided in which the cavities  14  formed in the film web  8  are filled with products  16 . 
     The sealing station  3  can also have a lifting device  30  and a sealable chamber  17  in which the atmosphere in the cavities  14  may be replaced by a replacement gas or a gas mixture before sealing, for example by evacuation or gas flushing. 
     The transverse cutting unit  4  may also comprise a lifting device  30  and may be designed as a punching machine which cuts through the film web  8  and the lid film  10  between adjacent cavities  14  in a direction transverse to the production direction R. In the process, the transverse cutting unit  4  can operate such that the film web  8  is not cut through across its total width, but that it is at least not cut in an edge region. This permits a controlled further transport by the feeder. 
     In the shown embodiment, the longitudinal cutting unit  5  is embodied as a knife arrangement with several rotating revolving knives by which the film web  8  and the lid film  10  are cut through between adjacent cavities  14  and at the lateral edge of the film web  8 , so that separated packages are present downstream of the longitudinal cutting unit  5 . 
     The deep-drawing packaging machine  1  furthermore can comprise a control unit  18 . The latter has the task of controlling and monitoring the processes running in the deep-drawing packaging machine  1 . A display device  19  with operational controls  20  serves to visualize or influence the process operations in the packaging machine  1  for or by an operator. 
     The general operation of one embodiment of the packaging machine  1  will be briefly described below. 
     The film  8  is reeled off from the feed roller  7  and transported into the forming station  2  by the feed device. In the forming station  2 , cavities  14  are formed in the film web  8  by deep-drawing. In a main cycle, the cavities  14  are transported further, together with the surrounding area of the film web  8 , to the insertion section  15  where they are filled with products  16 . 
     Subsequently, in the main cycle, the filled cavities  14  are transported further, together with the surrounding area of the film  8 , to the sealing station  3  by the feed device. The lid film  10  is transported further with the feed motion of the film web  8  after a procedure of sealing it to the film  8 . In the process, the lid film  10  is reeled off from the material storage  9 . By sealing the lid film  10  onto the cavities  14 , closed packages are formed which are separated in the subsequent cutting operations  4  and  5  and transported out of the deep-drawing packaging machine  1  by means of the discharge means  13 . 
       FIG. 2  shows the lifting device  30  at the transverse cutting unit  4  in an opened position as a view in the production direction R. The lifting device  30  can comprise a stand  31  which is mounted to the machine frame  6  and is thus suspended at it. A frame  32  may be moved vertically relatively to the stand  31  by means of guides which are not shown in greater detail. A motor  33 , which may be a gear motor, can be mounted to the frame  32 , its axis  34  being oriented in the production direction R. A rotary element  35  in the form of a lever may be attached to the axis  34 , and a guide pin  36  provided at said rotary element  35  with a ball bearing  37  can be connected with a guide  38  embodied as connecting link in the stand  31  in such a manner that a rotation of the motor  33  results in a movement of the guide pin  36  in the guide  38  and thus in a relative movement of the frame  32  to the stand  31 . The guide  38  does not extend linearly but rather has a contour that causes a rotation of the rotary element  35  to temporarily not result in a relative movement of the frame  32  with respect to the machine frame  6  and thus the film web  8 , i.e., the frame  32  temporarily remains stationary relative to the stand  31  despite further rotation of the rotary element  35 . Further details in this respect will be given below. 
     The lid film  10  is here already sealed to the film web  8  and is thus lying against the film web  8 . Therefore, to simplify matters, reference is made below only to the film web  8 . 
     Below, the motion sequence of the lifting device  30  will be illustrated more in detail with reference to  FIGS. 3 and 4 .  FIG. 3  shows the lifting device  30  in a position in which a cutting knife  39 , which may generally also be referred to as lower tool part, and a counter knife  40 , which may generally also be referred to as upper tool part, are located at the film web  8 . The cutting knife  39  may be changeably mounted on a support  41  and the support  41  can be lifted by the rotary motion (see bent arrow) of the motor  33  via the rotary element  35  and a push rod  42  in the direction of the film web  8  (see arrow). In this rotary motion of the motor  33 , the counter knife  40  and/or the frame  32  move downwards (see arrow) relative to the stand  31  towards the film web  8 . 
     The contour of the guide  38  may have a course causing the counter knife  40  to rest against the film web  8  as of the position shown in  FIG. 3 , and causing the counter knife  40  to still rest against the film web  8  without moving relatively to it up to the position shown in  FIG. 4 , while the cutting knife  39  performs the further cutting operation. Concretely, the guide  38  may comprise a left first section and a right second section. The first section extends approximately horizontally. As long as the guide pin  36  of the rotary element  35  moves along said first section, this leads to a relative motion of the frame  32  relative to the stand  31 . At the situation shown in  FIG. 3 , the guide pin  36  has just reached the transition from the first section to the second section of the guide  38 . The course of the guide  38  in this second section corresponds to the radius of the guide pin  36  of the rotary element  35  about the axis  34 . Thus, the frame  32  may maintain its position with respect to the stand  31  despite a further rotation of the rotary element  35 , i.e., it may remain stationary relative to the stand  31 . The motor  33  will rotate further, and the cutting knife  39  is moved further over the film web  8  or into the film web  8 . The counter knife  40  can include a recess which is not shown in greater detail and allows the cutting knife  39  to dive into the counter knife  40  during the cutting operation. 
       FIG. 4  shows the closed or upper position of the lifting device  30 . Here, the cutting knife  39  has cut through the film web  8  transversely to the production direction R as far as predetermined by the contour of the cutting knife  39 . By the counter knife  40  lying flush against the film web  8  at the beginning and until the end of the cutting operation, no folds are formed and the film web  8  is not distorted, permitting an exact cut. Subsequently, the tools  39 ,  40  are moved apart again into their open initial positions according to  FIG. 2  by a rotary motion of the motor  33  in the opposite direction. During this movement of the tools  39 ,  40 , too, the film web  8  is pressed neither downwards nor upwards. 
     The height of the vertical lifting motion of the counter knife  40  is determined on the one hand by the distance A of the pin  36  to the axis  34  of the motor  33 , which corresponds to an eccentricity, and on the other hand by the course of the guide  38 . The height of the vertical lifting motion of the cutting knife  39  is determined on the one hand via the lever distances B and C of the rotary element  35  and the push rod  42 , and on the other hand by the opposite relative motion of the frame  32  with respect to the stand  31 . 
     In  FIGS. 5 to 8 , a first variant of the lifting device  30  for a transverse cutting unit  4  is shown. The primary difference to the embodiment as it is shown in  FIGS. 2 to 4  relates to the performance of the relative motion of the frame  32  to the stand  31 . The stand  31  is attached at either side of the machine frame  6 , which is not shown in greater detail, indirectly via retainers  45  and directly via retainers  46 . The frame  32  may be moved by means of a guide  47  vertically and with respect to the stand  31 . As shown, the frame  32  is connected to the upper tool part  40  designed as a counter knife via the guide rod  48 , and the upper tool part  40  is coupled to the frame  32  and its movement. The cutting knife  39  is disposed on the support  41 , and the support  41  may be guided on either side on two guide pillars  49  each and may be moved vertically. The movement of the support  41  may be transmitted from the motor  33  to the support  41  by means of the rotary element  35 , which is not visible here, and the push rod  42 . 
       FIG. 6  shows the lifting device  30  in an opened position in a view in the production direction R. In addition to the guide  47  of the frame  32 , the latter is guided via a guiding facility  50  with respect to the stand  31 . The guiding facility  50  shows two rails  51  disposed in parallel with respect to each other and at the frame  32  between which a pin  52  is guided, the pin being connected with the stand  31 . A bushing of a gliding material or a ball bearing may also be attached on the pin  52 . The film web  8  can be held by two clamp chains  60  disposed on either side which are represented only schematically and may be transported intermittently in the production direction R. 
       FIG. 7  shows the lifting device  30  in the position in which the counter knife  40  from above and the cutting knife  39  have approached the film web  8  such that the counter knife  40  is resting against the film web  8  and the cutting knife  39  starts to penetrate the film web  8  and begins with the cutting operation. The latter may be adapted with respect to the cutting knife  39  by adjustments of the rotary element  35 , which is hidden in this view, on the axis  34  of the motor  33 , which is hidden in this view, and with respect to the frame  32  and thus the counter knife  40  via the position and eccentricity E of an eccentric  62  as rotary element with respect to the axis  34 . Via a lever  61  and the eccentric  62 , the rotation of the axis  34  of the motor  33  may be converted into a relative motion of the frame  32  with respect to the stand  31 . The greater the eccentricity E, which is a radial distance of the axis  34  of the motor  33  to the receiving axis of the lever  61  at the eccentric  62 , is selected, the larger is the lifting motion (see the upper arrow and the lower short arrow) the counter knife  40  performs. 
       FIG. 8  shows the lifting device in its closed position at the end of the cutting operation where the cutting knife  39  has cut the film web  8  corresponding to the cutting line and has dived into the counter knife  40  in this process. In this configuration, the counter knife  40  has somewhat moved the film web  8  with respect to the position of  FIG. 7  to the bottom (see upper arrow) while exerting some pressure on the film web  8 . This lifting motion may be minimized by changing the position of the eccentric  62  on the axis  34  such that towards the end of the lifting motion of the cutting knife  39 , the counter knife  40  already performs a small downward movement against the film web  8  and back again to the top to then lie against the film web  8  without pressure at the end of the movement. Thus, the lifting motion that leads to a deflection of the film web  8  may be approximately halved, and the film web  8  is only minimally deflected. When this lifting device  30  is used as a lifting gear in a forming station  2  or in a sealing station  3 , such deflection is uncritical. 
       FIG. 9  shows a second variant of a lifting device  30 , here in the embodiment of a forming station  2 . The lower tool part  39  is designed as a lower mould part, and the upper tool part  40  is designed as an upper mould part. Like the lifting devices  30  of  FIGS. 2 to 8 , this lifting device  30  is also mounted to the machine frame  6 . As in the previous variants, the motor  31  can be mounted to the frame  32 , and a rotary element  35  in the form of an eccentric plate may be disposed on the axis  34 , the rotary element  35  being mounted in a guide  38 . A rotation of the rotary element  35  causes a relative motion of the frame  32  with respect to the stand  31 . The rotary motion of the axis  34  can cause a lifting motion of the lower tool part  39  via a lever  62  and a push rod  42  (see  FIG. 10 ), which act as toggle. 
     Starting from the embodiments represented here, the deep-drawing packaging machine according to the invention may be modified in many respects. It would be possible, for example, to attach the motor  33  not to the frame  32 , but to the stand  31 . 
     From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure. It will be understood that certain features and sub combinations are of utility and may be employed without reference to other features and sub combinations. This is contemplated by and is within the scope of the claims. Since many possible embodiments of the invention may be made without departing from the scope thereof, it is also to be understood that all matters herein set forth or shown in the accompanying drawings are to be interpreted as illustrative and not limiting. 
     The constructions and methods described above and illustrated in the drawings are presented by way of example only and are not intended to limit the concepts and principles of the present invention. Thus, there has been shown and described several embodiments of a novel invention. As is evident from the foregoing description, certain aspects of the present invention are not limited by the particular details of the examples illustrated herein, and it is therefore contemplated that other modifications and applications, or equivalents thereof, will occur to those skilled in the art. The terms “having” and “including” and similar terms as used in the foregoing specification are used in the sense of “optional” or “may include” and not as “required”. Many changes, modifications, variations and other uses and applications of the present construction will, however, become apparent to those skilled in the art after considering the specification and the accompanying drawings. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention which is limited only by the claims which follow.