Abstract:
A method for treating flexible bags, comprising transporting, opening, filling and closing the bags in subsequent treatment stations in which the bags are transported in holding devices on several tracks from one treatment station to the next. In one embodiment of the present invention, the bags are transported in a continuous motion; during treatment, the respective treatment station is moved from its initial position synchronously with the motion of the bags; and after treatment, the respective treatment station is returned to its initial position.

Description:
[0001]    The present application is the national phase of International Patent Application No. PCT/DE2006/000672, filed Apr. 18, 2006, which claims priority to German Patent Application Nos. 102005018441.3 filed Apr. 20, 2005 and 102005018699.8 filed Apr. 21, 2005, which are herein incorporated by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a method for treating flexible bags, especially for transporting, opening, filling and closing the bags in subsequent treatment stations by transporting the bags in holding devices on multiple lines from one treatment station to the next. Furthermore, the invention relates to a system for treating flexible bags which are particularly suitable for the implementation of the method. 
       BACKGROUND OF THE INVENTION 
       [0003]    Methods and systems for treating flexible bags are well-known. The applicant, for example, has for years distributed an structure whereby bags are suspended on holding devices which are fitted onto a rotating device and led past different treatment stations which comprise opening means, filling means for solid or liquid material and, finally, closing means. In US 2004/0011008 A1, a transfer device feeds bags to a clocked rotating device by way of a storage unit. 
         [0004]    EP 1 164 081 A1 discloses a transfer structure which moves single, clocked, successively arriving bags by means of a suction holding device to a filling and packaging structure. 
         [0005]    EP 1 043 233 A1 discloses a filling and packaging system comprising bags which are held in holding devices and led past treatment stations on a circulating transportation device. The bags are supplied by a supply structure that moves synchronously with the transportation structure. 
         [0006]    EP 0 908 386 B1 discloses a method and device for treating flexible bags comprising web film bags that undergo various treatments at various operating speeds. Several bags simultaneously and synchronously pass the treatment station while suspended in a row moving perpendicular to the direction of movement. In this manner, the bags are treated simultaneously and synchronously in a row in a stationary treatment station. The bags are suspended in the holding devices on a receiving element comprising at least two holding devices per bag whereby the first holding device and the corresponding second holding device are movable relative to each other. 
         [0007]    The device disclosed in DE 103 22 556 A1 for treating containers is particularly suitable for filling and closing bottles, pots or cans. In other words, containers with stable shapes which are led past various treatment stations by a conveyer unit that is also continuously operated. The containers are correspondingly continuously transported to gripper elements which are not described in any further detail and which place the containers in receiving elements in the conveying structure. 
         [0008]    WO 99/44892 discloses a method for producing containers which are suitable for automatic filling from a web of flexible material. To this end, successions of horizontally oriented bags are reoriented to successions of vertically oriented bags which are still arranged in a row. Each device for opening, filling and sealing is fitted on an endless loop chain that extends in a horizontal direction. Each treatment station performs a synchronized horizontal motion with the containers that are to be treated and that are arranged on an endless loop chain that extends in a vertical direction. This system operates on one line which in addition to the one transport line comprises structures for shaping, filling and sealing the containers. 
         [0009]    U.S. Pat. No. 4,330,288 relates to a packaging machine that comprises a mechanism for transferring and opening bags. Bags are successively cut and then each bag is gripped. The bags are then led to a continuous endless chain in the respective filling and cutting sections. To allow the bags to be turned after cutting in such a way that they can enter the machine, the system can be adjusted to have a constant center distance that is smaller than had the bags been successively transported edge to edge. In this way the machine operation route is shorter. 
         [0010]    US 2003/0233812 A1 discloses a method for filling flexible bags which subsequently are treated in several parallel lines. The conveying structure is continuous. The carrier chain for the filling section or, as the case may be, the sealing section, must be aligned with the conveying structure for the bags and must be moved at the same speed. 
         [0011]    EP 1 249 400 A2 relates to a continuous conveying type bag filling machine comprising an empty bag supplying device whereby said device receives empty bags on a vertical plane and picks up these empty bags with the opening facing up and moves them to corresponding gripper pairs in the continuous conveying type bag filling machine. The gripper pairs are continuously moved at a constant speed and, with uniform spacing between them, they grip both edges of the bag with gripper sections to move the suspended bag on a vertical plane. Downward-facing bag holding members which open and close at a specified rate and when closed hold the upper parts of the bag, perform a back and forth motion along an arc-shaped path on a horizontal plane, said motion being caused by a back and forth mechanism that also causes the bags that are held by the holding members to be set substantially parallel to a direction of movement of said gripper pairs at all times. The speed of the back and forth motion of the bag holding members in the direction of movement of the gripper pairs is set to be substantially equal to a moving speed of said gripper pairs at least within the bag transfer region. The arc-shaped path comprises an intermediate point at the beginning of the forward motion. 
       SUMMARY OF THE INVENTION 
       [0012]    It is the object of the present invention to provide a method and a system for treating flexible bags which facilitates rapid and effective treatment of the bags. 
         [0013]    Aspects of the present invention that include a method and system that achieve this object are recited in the claims herein. Preferred embodiments are recited in the dependent claims. Aspects of a device for producing flexible bags which are particularly suitable for the implementation of a system for treating flexible bags are also recited in the claims herein. 
         [0014]    According to the invention, a method for treating flexible bags that involves transport of the bag holding devices on multiple lines from one treatment station to the next and transporting the bags in a continuous motion, comprises using a continuously moving transfer structure that picks up the bags from a transfer position on several lines and delivers them on several lines to a bag transport system that passes treatment stations. The treatment of the bags is particularly quick since several bags are being picked up and delivered simultaneously. The method is effective because it comprises only a single transfer structure, which requires only a single driving assembly. Preferably, the bags are both produced and transported to the transfer position in a clocked manner. 
         [0015]    The bags could be transported while suspended whereby they are held in mechanical holding devices laterally or longitudinally to the transport direction. The bags could also be transported in standing position in nests which, for example, simplifies handling in connection with a storage and provisioning unit which is described in further detail below. The bags, usually those with a round standing surface, would then be conveyed in the suspended nests instead of being gripped individually by the mechanical holding devices. 
         [0016]    The advantage of the suspended transportation method is that the volume of the bag is of no relevance to the operation process. In a preferred embodiment of the invention, the bags in at least one line differ with respect to type, size, type of filling and other such parameters from bags in the other lines. This means that not only different bags can run through the same system but different products can also be filled into the bags. The number of lines on which the bags are transported through the system determines the maximum number of different bags and products that can be used. 
         [0017]    Preferably, the production of bags occurs, firstly, as at least one film web is formed to a roll. Then, the roll or rolls are sealed and cut in a clocked manner to produce bags that are open at one end. The bags are then gripped and, in a clocked manner, transported to a transfer position where they are released and simultaneously picked up to achieve continuous motion. The bags are preferably suspended while being transported and the relative suspended position cannot be changed between the pick up and the transfer steps. 
         [0018]    The system according to the invention for treating flexible bags comprises at least one treatment station in which the bags are opened, filled or closed and a bag transportation system that moves the bags past treatment stations as well as a continuously operating transfer structure which picks up bags from a transfer position and delivers them to the bag transportation system. The system is effective because only a single transfer structure is associated with only a single driving device and the system operates faster since said single transfer structure picks up several bags simultaneously and in a parallel manner. 
         [0019]    Preferably, the system comprises mechanical holding devices for the bags and a driving structure for the mechanical holding devices whereby said driving structure continuously moves the mechanical holding devices through the system. An additional driving structure, which may comprise several driving assemblies, is provided for the treatment stations, which move the treatment station during treatment synchronously with the motion of the bag to be treated and which bring the treatment station back to its respective initial position after treatment. For this purpose, it is preferable if this additional driving structure comprises one or several independently working driving assemblies for every treatment station. 
         [0020]    Preferably, the bags are transported in holding devices on multiple lines from one treatment station to the next, whereby, unlike in prior art, the bags then are transported in a continuous motion which practically prevents mass velocity of the content of the bags. During treatment, the respective treatment station is moved from its initial position synchronously with the motion of the bags and, after treatment, the respective treatment station is returned to its initial position to commence treatment of the newly arrived bags. 
         [0021]    Preferably, the speed of the treatment station during the return is greater than or equal to the speed during the treatment period. 
         [0022]    The bags could be transported while suspended whereby they are held in mechanical holding devices laterally or longitudinally to the transport direction. The bags could also be transported in standing position in nests which, for example, simplifies handling in connection with a storage and provisioning unit which is described in further detail below. The bags, usually those with a round standing surface, would then be conveyed in the suspended nests instead of being gripped individually by the mechanical holding devices. 
         [0023]    The advantage of the suspended transportation method is that the volume of the bag is of no relevance to the operation process. In a preferred embodiment of the invention the bags in a least one line are different with respect to type, size, type of filling and other such parameters than bags in the other lines. This means that not only different bags can run through the same system but different products can also be filled into the bags. The number of lines on which the bags are transported through the system determines the maximum number of different bags and products that can be used. 
         [0024]    Preferably, the production of bags occurs, firstly, as at least one film web is formed to a roll. The roll or rolls are then sealed and cut in a clocked manner to produce bags that are open at one end. The bags are then gripped and, in a clocked manner, transported to a transfer position where they are released and simultaneously picked up to achieve continuous motion. The bags are preferably suspended while being transported and the relative suspended position cannot be changed between the pick up and the transfer steps. 
         [0025]    The system according to the invention for treating flexible bags comprises at least one treatment station which opens, fills or closes the bags, with mechanical holding devices for the bags and with a driving structure for the mechanical holding devices whereby said driving structure continuously moves the mechanical holding devices through the system. An additional driving structure is provided for the treatment station which moves the treatment station during treatment synchronously with the motion of the bag to be treated and which brings the treatment station back to its respective initial position after treatment. For this purpose, it is preferable if this additional driving structure comprises one or several independently working driving assemblies for every treatment station, whereby the interaction of all driving assemblies is facilitated by a superordinate control structure. In this manner it is, for example, possible to carry out not only the required back and forth motion in a treatment station but also an up and down motion if necessary. 
         [0026]    It is preferable if the system according to the invention comprises several transport elements whereby several mechanical holding devices are integrated into a transport element and the corresponding holding devices each define a transport element on a treatment line. Such a link of transport elements forms a closed gripper chain without the need for additional linking elements allowing several flexible bags to be transported in a row on multiple lines. The number of holding devices in a transport element varies and determines the number of lines used in the system. 
         [0027]    A control structure for the mechanical holding devices centrally controls the opening or closing motion of the bag, preferably using a relative motion laterally or longitudinally to the direction of movement of the transport elements. 
         [0028]    It is particularly preferable that the mechanical holding devices can, at least partly, be either manually or automatically adjusted to fit one or several different bag widths by way of a relative motion lateral to the transport direction. 
         [0029]    In preparation for treatment in the system according to the invention a device is provided for producing flexible bags from a web of film which comprises a structure that changes the shape of the web of film into a roll and a sealing and a cutting structure which cuts bags that are open at one end from the roll. In this manner, the bags are intermittently or continuously produced on a line, or, in other words, on a single line. The bags can also be cut from one endless string of bags on multiple lines. When the film is cut, individual bags are formed which are arranged in a row and, in accordance with the invention, are then transported to a transfer structure which in accordance with the objectives of the system for treating flexible bags, arranges the bags on multiple lines and delivers them to the system. 
         [0030]    The device for producing flexible bags operates in a clocked manner while the transfer structure operates continuously. In accordance with the present invention, the transfer structure connects the clocked bag separator with the continuously working treatment station for the flexible bags. In this connection, the transfer structure is designed in such as manner that the relative motion of transferring transport elements to transport elements that pick up over a predetermined transfer path equals zero and the relative suspended position of the bags will not change. Preferably, the bags are held stretched out in the transfer structure by holding strips to match the line spacing that will later be needed. The transport system also comprises a gripper system for bags which is fitted with gripper strips that, like the arriving bags, are led to the transfer position in a continuous motion. The simultaneous opening and closing motion of the gripper system holding strips or gripper strips in the conveying structure and in the transfer structure facilitates precise transfer. Finally, transportation of the bags resumes in a continuous motion. 
         [0031]    According to the present invention it is often practical to store and sort bags and then allow later introduction to the system on multiple lines by means of a transfer structure. Therefore, it is particularly preferable if at least one storage unit is filled spatially and temporally independently from the rest of the bag treatment process. Finally and as needed, the bags are automatically assigned a storage unit which sorts the bags according to minimum filling capacity. The advantage of this approach is that the process of the subsequent system can run continuously without interruption and does not require additional personnel. 
         [0032]    Preferably the system comprises structures for the relative movement of the holding devices which are controlled by the continuous transport motion of the bags, eliminating the need for employment of an additional motor. 
         [0033]    The transport system and the transfer structure are both characterized by the fact that they are not fitted with driving structures but have devices for the relative motion of the holding devices which hold the bags and which are controlled by the continuous transport motion of the bags. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]      FIG. 1  is a perspective view of a system for treating flexible bags that is operated in accordance with the method of the present invention. 
           [0035]      FIG. 2  is a view that illustrates details of the transport system. 
           [0036]      FIG. 3  is a detailed view of  FIG. 2 . 
           [0037]      FIG. 4  is an enlarged frontal view of the system in  FIG. 1 . 
           [0038]      FIG. 5  is a representation of the device that grips the flexible bags and that also can facilitate a central format conversion. 
           [0039]      FIG. 6  is a perspective view of the entire structure comprising devices for producing bags and the system in  FIG. 1 . 
           [0040]      FIG. 7  is a perspective view of the transfer structure which connects the device for producing the bags with the transport system in  FIG. 3 . 
           [0041]      FIG. 8  depicts a storage unit with structures for storing and separating bags which are kept ready for the system in accordance with the invention. 
           [0042]      FIG. 9  depicts the device in  FIG. 5  placed in front of the device in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0043]      FIG. 1  shows a perspective view of a system for treating flexible bags according to an embodiment of the present invention which comprises a treatment station  10  which in successive steps takes over the bags, opens them and if necessary performs an inspection to verify if an open bag is duly suspended on every holding device  14 , a filling station  20  and a closing station  30 . As is easier to see in  FIG. 2 , bags run on several lines in the treatment station  10 , and in this case the bags are held by a transport element  12  and run in eight lines into the treatment station  10 . In this connection, a transport element  12  comprises opposite facing holding devices  14  which can be adjusted to fit various bag widths by means of a relative motion laterally to the transport direction A whereby the adjustment occurs centrally. The relative motion can be controlled either manually or automatically. The suspended bags are held by the holding devices  14  and, as can be seen in  FIG. 1 , are continuously led through the system  100 , not in a clocked manner as in prior art, and are treated there. The corresponding treatment stations  10 ,  20 ,  30  are continuously moved with the bags on the respective transport element during the treatment and return to their initial position subsequent to treatment. Corresponding driving assemblies, such as  105 ,  110 ,  115 ,  120 , which facilitate the back and forth motion of the treatment stations and, if necessary, the up and down motion of an entire station or parts thereof, are fitted to the frame portal, for example  130 ,  140  which also carry all other components of the treatment station, for example  10 , as shown here. The described arrangement prevents the stand-still of the transport elements  12  or the bags suspended in it so that when liquid is being filled into the bags the danger of spillage is extensively eliminated. In the closing station  30 , the filled bags are sealed either thermally or using ultra sound or sealed using other sealing processes. Subsequently, the bags may optionally be cooled to achieve better impermeability of the sealing seam. 
         [0044]      FIG. 2  shows details of the transport system which leads the bags through the various treatment stations  10 ,  20 ,  30  ( FIG. 1 ). Gripper strips  330  on which the holding devices  14  are fitted are moved through the system by way of driven tracks  310 ,  312 . The relative motion of the holding devices  14  which are shown clearer in  FIG. 3  with suspended bags  300  in them occurs during the continuous transport without the use of a separate driving structure by way of a superimposed motion that is derived from the transport motion. The same applies to the opening and closing motion of the holding devices  14  on the treatment station  10  and the closing station  30 . Mechanical structures  320 ,  322 ,  324 ,  326  are provided in pairs on each side of the transport system and they allow the holding devices  14  on the gripper strips  330  to perform the relative motion necessary for the respective treatments. 
         [0045]      FIG. 4  shows an enlarged view of the view in  FIG. 1  in which the transfer position of the treatment station  10  is easier to see. Every holding device  14  comprises holding elements (bag gripper pairs) which are movable relative to each other and which can be operated perpendicular to the transport direction A by means of a driving structure  200 . The transport elements  12  which are attached to a carrier  16  move the held bags to the transfer grippers  18  from where they are moved to additional treatment steps, firstly for the opening of the bag. 
         [0046]    In  FIG. 5  it is more evident how the relative motion of the holding devices  14   a ,  14   b  in the direction of the arrow B, in other words, perpendicular to the transport direction A, is suitable for the adjustment by means of a central format adjustment unit  30  to fit different bag sizes. 
         [0047]    Depending on the spacing between the opposite placed elements  14   a  and  14   b , bags of different widths can be processed. A bag nest  22  which is depicted in an almost phantom-like manner is an alternative to the holding device  14  or the holding elements  14   a  and  14   b . The relative motion of the holding devices  14   a ,  14   b  also causes the bags to open or close, a motion that is controlled by the transport motion as was discussed in connection with  FIGS. 2 and 3 . 
         [0048]      FIG. 6  shows a perspective view in which the system  100  for treatment of flexible bags from  FIG. 1  is centrally placed. On both sides of the system  100 , mirror-symmetrically to area C are devices that keep the bags ready for treatment in the system. Firstly, the film material in the form of a strip is readied and prepared to a roll in stations  40  or  40 ′ and then led to a sealing machine  50  or  50 ′. Behind the sealing machine is a cooling station  60  or  60 ′. The material in the form of a strip is then led to a printer  70  or  70 ′ for coding and finally pre-embossing in presses  80  or  80 ′ before it is cut into individual bags in a cutting station  90  or  90 ′, said bags being arranged in a row. The sorted bags are introduced to the system by means of a transfer structure on multiple lines in accordance with the objectives of the system  100  or the transport elements  12 . In the embodiment shown in  FIG. 6 , two devices for bag production are symmetrically arranged so that they each operate on one half of the line. 
         [0049]      FIG. 7  shows the transfer structure which connects the bag sorting unit with the bag transport system which is shown in  FIG. 2 . In a practical embodiment, the transfer structure is arranged on the device described in connection with  FIG. 2  in such a way that the transfer grippers  710 , which are more clearly depicted in position  720 , collect the bags from the correct place in the bag sorting location. In this connection, the transfer gripper  720  comprises latch rails  722  which press on the bags to immobilize them. Should the simple method of using latch rails  722  not suffice, suction pressure can be used to achieve a vacuum connection  714 ,  724  which will further aid in holding the bags. Bags are assumed by a transfer gripper system on multiple lines at the transfer position of the bag sorting step and are in this way held by the transfer grippers  710 ,  710 . In this way, the bags are held stretched out to match the spacing between the lines of the transport system. The transfer is analogous to the process described in connection with  FIGS. 2 and 3  during the continuous transport motion of the transfer gripper system. 
         [0050]    The opening and closing motion of the transfer gripper thus occurs without the aid of a separate drive, but rather is achieved using the superimposed closing and opening motion of the transport motion. In this manner, precise pick-up and transfer is possible. Subsequent to pick-up, the bags are moved in a continuous motion to the transport system in  FIG. 2 . During this step, the relative suspended position of the bags between pick-up and transfer does not change. These simultaneous opening and closing motion of the gripper system is also important to facilitate precise transfer. In addition, the transfer gripper systems are led in circumferential parallel-guiding mechanisms. 
         [0051]    It is also possible to initially produce the bags and temporarily store them in a storage unit  500  as is shown in  FIG. 8 . The storage unit  500  is designed to correspond to the number of lines used in the system, in this case eight lines, and preferably it can easily be disconnected from the provisioning element  510  and be replaced by another storage unit. In the provisioning element  510 , protected by a hood  512 , bags which are destined for the sorting step  520  are stored. Said step is fitted with a sensor for the minimum filling capacity of bags so that it, for example, can be determined that there is sufficient material left for a certain amount of operating time but that after this time no transfer can occur. The provisioning element  510  ensures that there is enough bag material for the sorting step  520 . When the provisioning element  510  is empty a storage unit  500  delivers more bags. In this manner, the bags can automatically be forwarded to the transfer structure without the need for additional personnel. 
         [0052]    Finally, in  FIG. 9  the device shown in  FIG. 8  is placed in front of the system shown in  FIG. 1  so that the sorted bags can be transferred to the system in  FIG. 1 . 
         [0053]    The characteristics of the invention revealed in the above specifications, in the drawings, as well as in the patent claims, could be significant for the realization of the invention individually as well as in any combination.