Abstract:
The invention relates to a method for operating a chamber packaging machine, wherein the position of a sealing bar is during the evacuation of a diaphragm checked using a sensor.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application claims priority to German Application Number 102012017827.1 filed Sep. 10, 2012, to Jürgen Steidele entitled “Method for operating a chamber packaging machine,” currently pending, the entire disclosure of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention relates to a method for operating a chamber packaging machine or a conveyor belt packaging machine. 
     BACKGROUND OF THE INVENTION 
     The applicant&#39;s conveyor belt packaging machines are known from practice in which a sealing device comprises a sealing bar and a diaphragm. To seal a bag, the diaphragm is subjected to pressure to press the sealing bar against a counter-pressure bar in order to heat-seal the bag neck clamped between the sealing bar and the counter-pressure bar. During the evacuation of the bag, the sealing bar is moved to an evacuation position in which the gap between the sealing bar and a counter-pressure bar is at a maximum. This is accomplished by evacuating the diaphragm, and by a device pressing the sealing bar against the diaphragm with springs. The diaphragm is connected to a vacuum pump, which is also connected to the vacuum chamber for evacuating the bag, via a supply line that is partially provided also outside of the vacuum chamber. If the supply line is leaking in a section between the vacuum chamber and the vacuum pump, then this leakage can cause the sealing bar not to reach its evacuation position and the gap between the sealing bar and the counter-pressure bar, and thereby the opening of the bag neck is reduced such that evacuation or minimizing the oxygen content is not sufficient to meet the specified minimum shelf life, especially for foods to be packaged, such as meat, so that returns and complaints can occur. Such leakage of the diaphragm or in the supply line can also lead to the intended sealing pressure not being reached, and thereby the quality of the sealing seam being reduced, without this being easily apparent to the user during a visual check. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to increase process reliability of a chamber packaging machine or a conveyor belt packaging machine. 
     A method according to one embodiment of the present invention for operating a chamber machine or conveyor belt machine comprising a control unit, a sealing bar, a diaphragm and a sensor, comprises the steps of:
         forming a vacuum chamber by closing a cover,   evacuating the vacuum chamber,   evacuating the diaphragm and checking with the sensor whether the sealing bar is in its predetermined evacuation position,   applying compressed air to the diaphragm after evacuation to generate sealing pressure between the sealing bar and a counter-pressure bar in order to seal the product in a bag in an airtight manner.       

     This method offers the advantage that any defects or leaks in the diaphragm, the supply lines inside and outside of the vacuum chamber or a compressed air source are detected by the control unit and are communicated to the user by an error message via a display. Also, broken springs can be detected that press the sealing bar against the diaphragm, or any blockade of the sealing bar. 
     The sealing pressure may be checked with a pressure measurement unit in a supply line to the diaphragm. The pressure measuring unit can be connected to the control unit to automatically perform this check. 
     In one embodiment, the control unit transmits information to the operator via a display when checking the position of the sealing bar using the sensor during evacuation of the diaphragm or checking the sealing pressure during the sealing procedure is negative, i.e., a value outside a predetermined range is obtained. It can thereby be prevented that a defective seal, barely recognizable by the operator, leaves the production and, where the product is food, such as meat, the shelf life is not ensured which results in complaints. 
     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 perspective view of a chamber machine in accordance with one embodiment of the present invention; 
         FIG. 2  is a side sectional view of a chamber machine in an open position in accordance with one embodiment of the present invention; 
         FIG. 3  is a side sectional view of the chamber machine of  FIG. 1  during evacuation; and 
         FIG. 4  is a side sectional view of the chamber machine of  FIG. 1  during sealing. 
     
    
    
     Identical components are throughout the figures designated with the same reference numerals. 
     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 chamber machine  1  according to one embodiment of the present invention with a cover  2  comprising a sealing bar  3 , and a housing  4  comprising a counter-pressure bar  5  and a display  6 . 
     In a side sectional view of the chamber machine  1 ,  FIG. 2  shows the set-up of the sealing bar  3  in the cover  2 . The sealing bar  3  may comprise a blade bar  7  for severing a bag neck  19  (see  FIG. 4 ) of a bag  17 . With springs—not shown—the sealing bar  3  can be connected to a support  8  to be supported at the cover  2 . A diaphragm  9  can be provided between the sealing bar  3  and the support  8 , which can move the sealing bar  3  relative to the cover  2 . A sensor  10 , specifically, a position sensor, such as a non-contact inductive or capacitive proximity switch or a light barrier, can examine whether the sealing bar  3  reaches an evacuation position (see  FIG. 3 ). The sensor  10  can be connected to a control unit  11 . The diaphragm  9  can be, via a supply line  12 , connected to a vacuum pump  13  and optionally to a compressed air source  14  and is switchable using a 3-way valve  15  between the vacuum pump  13  and the compressed air source  14 . The sealing bar  3  can be held in the evacuation position, which is checked by the sensor  10 , both by springs as well as by the vacuum pump  13 . 
       FIG. 3  shows the chamber machine  1  in the evacuation mode. In this mode, the vacuum chamber  16 , in which the bag  17  with a product  18  is located, is evacuated by the vacuum pump  13  to reduce the oxygen content as much as possible in the bag  17 , preferably if the product  18  is a food product. It is important that the gap S between the sealing bar  3  and the counter-pressure bar  5  has a defined minimum width, because otherwise the result can deteriorate despite the final vacuum being set and reached. For example, a leak in section B of the supply line  12  of the diaphragm  9  would cause the vacuum generated in the vacuum chamber  16  to draw the ambient pressure into the diaphragm  9 , and the diaphragm  9  to thereby expand, and the sealing rail  3  to move downwardly and the gap S to be uncontrollably reduced. This error can be recognized by the control unit  11  via the sensor  10 , as soon as the sealing bar  3  moves from the evacuation position downwardly. The control unit  11  can display via the display  6  a respective error message to an operator. 
       FIG. 4  shows the chamber machine  1  when sealing the bag  17  after the adjusted final vacuum in the vacuum chamber  16  has been reached. For this purpose, the control unit  11  can switch the supply line  12  of the diaphragm  9  from the vacuum pump  13  to the compressed air source  14  using the valve  15 , so that the compressed air fills the diaphragm  9  and presses the sealing bar  3  downwardly against the counter-pressure bar  5 . The bag neck  19  clamped between the sealing bar  3  and the counter-pressure bar  5  is sealed in that the sealing bar  3  itself is heated or in that a heating wire is provided on the underside of the sealing bar  3 . During the downwardly motion of the sealing bar  3 , the blade bar  7  may separate the bag neck  19  from the bag  17 . In order to be able to maintain the quality of the seal, the pressure at which the diaphragm  9  is acted upon can be monitored by the control unit  11  using a pressure measuring unit  20  arranged at the supply line  12 . During this check, any defect or any leakage in either the diaphragm  9 , or the supply line  12 , or the compressed air source  14  may be detected. 
     When the sealing operation has been terminated after a predetermined time, the control unit  11  can switch back the valve  15 , so that the supply line  12  is again connected to the vacuum pump  13  and the sealing bar  3  moves upwardly away from the counter-pressure bar  5  as to release the bag  17 . The vacuum chamber  16  is then vented and the cover  2  can be opened to remove the bag  17  with the product  18 . 
     This type of chamber machine  1  may also include a conveyor belt machine that conveys the bag  17  on a conveyor belt into the vacuum chamber  16  and out of the vacuum chamber  16 , where the cover  2  opens and closes automatically. 
     It is conceivable to have the diaphragm  9  communicating with the ambient pressure during the sealing operation instead of to the compressed source if, for example, at a final vacuum of 20 mbar, a sealing pressure of approx. 1 bar is sufficient in order to close a bag  17  in an airtight manner. 
     An embodiment is possible in which the counter-pressure bar  5  is provided at the cover  2  and the sealing bar  3  with the diaphragm  9  in the vacuum chamber  16 , or another sealing bar is provided in place of the counter-pressure bar  5 . 
     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.