Abstract:
The present invention refers to a packaging machine ( 1 ) comprising at least one workstation ( 2, 3, 4 ) and a device ( 11 ) for generating compressed air. The invention is characterized in that the device ( 11 ) for generating compressed air is connected to a lifting gear ( 21 ) of the workstation ( 2, 3, 4 ), wherein the device ( 11 ) is drivable by the movement of the lifting gear ( 21 ) of the workstation ( 2, 3, 4 ). The invention also refers to a method for operating a corresponding packaging machine ( 1 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to German Application No. 102010019636.3 filed May 6, 2010, the disclosure of which is incorporated in its entirety by reference. 
     TECHNICAL FIELD 
     The present invention refers to a packaging machine and to a method for operating a packaging machine. 
     BACKGROUND 
     Packaging machines are normally available in production halls in which a central compressed-air supply is available to feed all kinds of production machines with compressed air. Specifically in deep-draw packaging machines compressed air is needed for deep-drawing and/or forming cavities into the lower foil web. Likewise, for the sealing operation compressed air is needed for generating the contact pressure of the upper film web onto the lower film web, which contact pressure is required for the sealing process. 
     In small food processing companies or butcher shops there are no central compressed-air supplies. However, deep-draw packaging machines should also be used in this sector. In such companies it would be of advantage if the deep-draw packaging machine only needed an electrical connection, and further media connections for media such as compressed air, vacuum and cooling water are not required. 
     SUMMARY 
     It is the object of the present invention to provide a packaging machine and a method for operating such a packaging machine in which the above-described requirements are satisfied. 
     In packaging machines, particularly deep-draw packaging machines, the drives of the film feed of the lower film and lifting systems of the workstation e.g. for molding, sealing and cutting are often motor-driven. For instance, a motor on the molding station for closing the chamber moves the lower part of the mold tool upwards by means of a lifting gear. 
     Subsequently, cavities are deep-drawn and formed, respectively, by means of compressed air and/or vacuum into a film web heated by a heating plate. With a subsequent downward movement of the lower part of the mold tool the chamber is opened again and the film web with the molded cavities is transported further by the film feed. 
     The upward and downward movement of the lower part of the mold tool is carried out by a lifting gear which converts the movement of the motor drive into a lifting movement. According to the inventive packaging machine this machine has a device for generating compressed air so as to be able to dispense with supplied compressed air from the outside. This device for generating compressed air is driven by the movement of the lifting gear of the workstation. 
     Advantageously, the movement of the lifting gear is vertical. Due to the weight above all of the lower part of the mold tool, there will be maximum efficiency when the downward direction of movement is exploited in the lifting gear. 
     One or both directions of movement can here be used for driving the device for generating compressed air. However, it may be necessary that both directions of movement are used for driving the device if the demand for generated compressed air is correspondingly high or an increased pressure is needed. 
     Since the different processes such as heating the film web, molding, evacuating, gas-treating, sealing, cutting, feeding the film web, inserting products, lifting gear movements of the workstations, etc. are defined in the production process, it is advantageous according to the invention when the compressed air generated by the device is temporarily stored in a compressed-air store so as to make it available in the subsequent processes since these processes do not necessarily take place at the same time. 
     In the packaging machine according to the invention the device for generating the compressed air is e.g. connected via mechanical and/or hydraulic means to the lifting system of one or more workstations. 
     Advantageously, the device comprises a piston pump which exploits the movements of the lifting gear for compressing air. This compressed air is supplied to the compressed-air store and is stored and/or compressed there. 
     Advantageously, the workstation is configured as a molding station of a deep-draw packaging machine that drives the device for generating compressed air because on the molding station itself the compressed-air consumption is maximal and there are thus the least losses on account of short line lengths. 
     The device expediently comprises valves which are connected to a controller. The valves are controlled according to the movement of the lifting gear, the state of the compressed-air store and the process of the workstation. 
     In the method according to the invention for operating the packaging machine comprising a workstation and a device for generating compressed air, the device is driven by means of mechanical and/or hydraulic connection by the movement of the lifting gear of the workstation. 
     Subsequently, the generated compressed air is received in a compressed-air store for temporary storing. As a consequence, the compressed air is available for the processes at the required time. 
     Compressed air is advantageously generated in one or two successive work cycles of the workstation and this generated compressed air is at least partially used in the same work cycles. A work cycle e.g. of a molding station consists of the following repeating steps:
         0. closing the molding station by moving the lower part of the mold tool upwards;   1. heating the film web by means of a heating plate in the upper part of the mold tool;   2. molding a cavity by supplying compressed air from the compressed-air store into the upper part of the mold tool and/or by applying a vacuum in the lower part of the mold tool;   3. venting the chamber and opening the molding station by moving the lower part of the mold tool downwards;   4. transporting the film web with the formed cavities out of the molding station by way of the film feed.       

     To achieve an efficiency factor that is as high as possible and to keep the energy costs low, the compressed air is generated in the method according to the invention in steps 3 and/or 0 and is used in the subsequent work cycle in step 2 for forming cavities into a film web in the molding station. 
     The generated compressed air is fed by means of valves, which are connected to a controller, to the compressed-air store and/or the workstation. 
     In further variants it is conceivable that a plurality of compressed-air stores are present or that further workstations such as sealing station or cutting stations jointly generate compressed air by way of their lifting gear movements by means of piston pumps or by devices of similar action and supply it to one or more compressed-air stores. Likewise, the compressed air in the compressed-air store(s) can be supplied to a plurality of workstations for corresponding process sequences. 
     In the following an advantageous embodiment of the invention is explained in more detail based on a drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side view of a packaging machine according to the invention in the form of a deep-draw packaging machine; 
         FIG. 2  is a schematic view of a device for generating compresses air; and 
         FIG. 3  is a schematic side view of a device with valves. 
     
    
    
     DETAILED DESCRIPTION 
     In the figures identical components are designated with the same reference numerals throughout. 
       FIG. 1  shows a schematic view of a packaging machine  1  according to the invention in the form of a deep-draw packaging machine. This deep-draw packing machine  1  has a molding station  2 , a sealing station  3 , a transverse cutting device  4  and a longitudinal cutting device  5  which are arranged in this order in working direction R on a machine frame  6 . At the input end on the machine frame  6  there is a feed roll  7  from which a film  8  is pulled off. In the region of the sealing station  3  a material store  9  is provided from which a lid film  10  is pulled off. At the output end on the packaging machine a removal device  13  in the form of a conveyor belt is provided with which finished, singled-out packages can be taken away. Furthermore, the packaging machine  1  has a feed device, which is not shown and which grips the film  8  to transport it further in the working direction R during each main operating cycle. The feed device can, for example, be realized using transport chains arranged on both sides. 
     In the illustrated embodiment the molding station  2  is formed as a deep-drawing station with which cavities  14  can be formed in the film  8  by deep drawing. Here, the molding station  2  can be formed such that several cavities can be formed adjacent to one another in the direction perpendicular to the working direction R. A device  11  for generating the compressed air needed for deep drawing is shown in the region after the molding station  2  and under an insertion section  15  in the machine interior. In the working direction R behind the molding station  2  the insertion section  15  is provided in which the cavities  14  formed in the film  8  are filled with the product  16 . 
     The sealing station  3  has a closable chamber  17  in which the atmosphere in the cavities  14  can be replaced, for example by gas flushing with a replacement gas or with a gas mixture before sealing. 
     The transverse cutting device  4  is formed as a punch which parts the film  8  and the lid film  10  in a direction transverse to the working direction R between adjacent cavities  14 . Here, the transverse cutting device  4  operates such that the film  8  is not parted over the complete width, but rather is not parted at least in a marginal region. This facilitates controlled further transport by the feed device. 
     In the illustrated embodiment the longitudinal cutting device  5  is formed as a cutter arrangement with which the film  6  and the lid film  10  are parted between adjacent cavities  14  and on the side edge of the film  8  so that singled-out packages are available behind the longitudinal cutting device  5 . 
     The packaging machine  1  also has a controller  18 . It has the task of controlling and monitoring the processes running in the packaging machine  1 . A display device  19  with operating elements  20  is used for visualizing or influencing the process sequences in the packaging machine  1  for, respectively by, an operator. 
     The general principle of operation of the packaging machine  1  is briefly described in the following. 
     The film  8  is pulled off the feed roll  7  and transported through the feed device into the molding station  2 . In the molding station  2  cavities  14  are formed in the film  8  by deep drawing. The cavities  14  are transported further together with the surrounding region of the film  8  in a main operating cycle to the insertion section  15  in which they are filled with the product  16 . 
     Then the filled cavities  14  are transported into the sealing station  3  by the feed device in the main operating cycle together with the surrounding region of the film  8 . The lid film  10  is transported further with the feeding movement of the film  8  after a process of sealing onto the film  8 . Here the lid film  10  is pulled from the material store  9 . By sealing the lid film  10  onto the cavities  14  closed packages are created which are transported singled-out in the following cutters  4  and  5  and transported out of the packaging machine by means of the removal device  13 . 
       FIG. 2  illustrates the device  11  for generating compressed air with a lifting gear  21  for the molding station  2 . The lifting gear  21  moves a lower part of the mold tool  22  to the upper part of the mold tool  23 , thereby forming a closed chamber. After the molding process the lifting gear  21  moves the lower part of the mold tool  22  downwards, thereby opening the chamber. 
     With the help of push rods  24 , which are connected to the lifting gear  21  and two piston pumps  25 , the air below the pistons  26  of the piston pumps  25  is compressed upon a downward lifting movement of the lifting gear  21 . During the upward lifting movement the air above the pistons  26  can also be compressed. 
       FIG. 3  shows valves  27 ,  28  and  29 , as well as a compressed air store  30 . Upon a downward movement of the lifting gear  21  the valves  28  and  29  are closed and the valve  27  is opened for feeding the air to the compressed air store  30  and to compress the air. The piston pump  25  above the piston  26  is here fed by a device (not shown) with ambient air. 
     Upon an upward movement of the lifting gear  21  the valves  27  and  29  are closed and the valve  28  is opened to feed the air to the compressed air store  30  and to compress it. The piston pump  25  below the piston  26  is here fed by a device (not shown) with ambient air. 
     After the lifting movements the valves  27  and  28  are closed and the compressed air is fed from the pressure store  30 , after the valve  29  has been opened, via line  31  to the upper part of the mold tool  23  so as to form and deep-draw, respectively, the cavities  14  into the film web  8 . 
     A sequence is also conceivable in which several lifting movements are carried out without consumption of the compressed air for a process, but for increasing the pressure in the compressed-air store  30 .