Patent Publication Number: US-6209819-B1

Title: Device and method for automatic changing of film rolls

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     This application claims the priority of German patent application 198 09 516.3, filed Mar. 5, 1998, the disclosure of which is expressly incorporated by reference herein. 
     The present invention relates to a method and apparatus for automatically changing rolls of self adhesive protective film. 
     In the mass production of motor vehicles, the vehicles must be prepared for shipment so that they do not suffer any damage, especially so that paint is not adversely affected by shipment and weathering influences. If shipment by rail or ship is required for transport to the customer, it has been conventional heretofore to coat vehicles with a protective layer of wax which must be removed before delivery to the customer. Removing the protective wax without leaving any residue was not only a labor-intensive task but also imposed burdens on both people and the environment because of the solvents used. Therefore, a change has recently been made to protecting bodies during shipment by using self-adhesive films. 
     Such films are usually pulled manually from a film roll and applied to the parts to be protected. It is also known to mount film rolls in a holder and to pull the film off under machine control. Replacement of such film rolls has proven to be very labor-intensive. For example, the remaining film supply must be constantly monitored so that the film roll can be replaced when its end is reached. The used film roll must then be removed and replaced by a new film roll. Since the new film roll is usually not stored in the immediate vicinity of a film application device, this results either in prolonged production interruptions or a need for an operator constantly to monitor the film roll as it unrolls so that preparation for replacement can begin shortly before the end of the film roll. 
     Hence, one object of the invention is to provide a method and apparatus for automatically changing film rolls, in which the replacement of film rolls is less awkward by comparison with the prior art, so that production interruptions can be avoided. Another object of the invention is to eliminate the need for extra personnel to monitor the production process with regard to the changing of film rolls. 
     Still another object of the invention is to provide a method and apparatus by which, all of the film roll changers can be loaded at any desired point in time in order thus to ensure that the film length is sufficient for an entire shift for example. 
     These and other objects and advantages are achieved by the method and apparatus according to the invention, in which simple automatic changing of film rolls is possible without production interruptions, by moving a replacement roll (second film roll), which is stored in a standby position in the device, into a working position, in which film can be pulled from a film roll (first film roll). By a suitable choice of film roll sizes it is possible to perform an adjustment to a film length that is required for example during a shift. 
     Since it was conventionally possible to provide a replacement roll only immediately when a film roll ran out or reached the end or to load it into the changing device, the device according to the invention represents a considerable simplification. An operator can, within certain time limits, load the device according to the invention with another film roll at any time without adversely affecting the production process in any way. The loading process can be performed during a shift or between two shifts for example or during the unsticking process. Furthermore, the film roll can be changed in a very simple fashion essentially by means of a single traveling movement of a replacement roll, since a used film roll can be removed from the working position by moving the replacement roll and then bringing the replacement roll into the working position. 
     According to one preferred embodiment of the invention, the device has an ejection device with means for holding or moving the second film roll, by means of which the first film roll can be removed from the working position during the movement of the second film roll. This makes it possible to change a film roll in an especially simple and mechanically reliable fashion. 
     Advantageously, the device according to the invention has a lifting device for essentially vertical movement of a pallet on which the second film roll can be placed, especially on rotatable support rollers. By means of such a lifting device, the second film roll can be brought into the working position in a simple fashion. Furthermore, the rotatable support rollers facilitate pulling off the end of the film for sticking it to a locking tube, described below. 
     Advantageously, the device has a pivotable ejection loop that is connected with the pallet for removing the first film roll from the working position as the second film roll moves vertically. Such an ejection loop can remove a film roll to be replaced from its holder in simple fashion during the upward lifting movement of the pallet, and the loop can be guided past a new film roll held in the working position during a subsequent downward movement because of its ability to pivot. 
     According to one preferred embodiment, the pallet can be positioned on a carriage which can be introduced into a frame of the device in such fashion that the second film roll located on the pallet can be brought into the standby position. A carriage of this type makes it possible in simple fashion to introduce a new film roll into the device at any point in time during the operation of the device, such as during the pulling of the film from the first film roll, without adversely affecting operation in any way whatever. The carriage can have a plurality of rollers that can be made rotatable depending on the space conditions. As a result, movement of the carriage between a film roll storage area and the device for changing film rolls can be accomplished in simple fashion. 
     Advantageously, at least two centering pins are provided to secure the pallet in position on the carriage. With such centering pins, the pallet can be suitably positioned on the carriage that can be introduced into the device. 
     According to one preferred embodiment, the device has a compensating roller that is drivable and/or brakable and can be brought into an operating connection with the first film roll. By means of such a compensating roller, when the film is pulled off the film roll, its pulling edge can be secured in simple fashion, with the pulling off of the film being supported if necessary by a corresponding rotary movement of the compensating roller. Furthermore, the roll can advantageously also be drivable in the opposite direction so that film that has been pulled off can be rewound by means of the compensating roller. The ability to brake the film roll ensures a defined pulling off of the film. 
     Advantageously, the device also has a measuring means that can be brought into an operating connection with the first film roll, especially a measuring wheel for measuring the film pulled off the film roll, and with signal generating means cooperating with the measuring means to output a signal to a control device on the means for triggering the lifting or movement of the second film roll. As a result, in simple fashion, it is possible to determine the length of the film pulled off the film roll that is in the working position. When the end of the film is reached, it is then possible to replace the old film roll by a new film roll. The measuring wheel can generate a signal suitable for this purpose and send it to control means or transmit it directly to the lifting device. 
     According to one preferred embodiment, a locking tube is mounted on the lifting device or the pallet, to which tube the beginning of the film pulled off the second roll can be secured. As a result, the end of the film that has been pulled off the second film roll can be secured in simple fashion so that after the second film roll moves into the working position, further pulling off of the film is simplified. 
     Advantageously, the device according to the invention has a suction strip by means of which the film end of the second film roll secured to the fixing tube, when the working position is reached, can be secured further in preparation for pulling off the film as provided. 
     Advantageously, a cutting device is provided for cutting the film between the locking tube and the suction strip. As a result, the end of the film on the second film roll can be separated in simple fashion from the locking tube so that the tube, together with the pallet or the lifting device, can be lowered again. 
     According to one preferred embodiment of the method according to the invention, when the signal indicating the end of the film on the first film roll is generated, before or during the lifting or movement of the second film roll, the film that has already been pulled off the first film roll and not yet cut is rewound on the film roll. As a result, the first film roll can be removed subsequently from the working position in a very simple fashion. 
     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective front view of the device according to the invention; 
     FIG. 2 is a perspective, essentially lateral view of the device according to the invention; 
     FIG. 3 is a perspective rear view of the device according to the invention; 
     FIG. 4 is a perspective view of a lifting device used according to the invention; 
     FIG. 5 is a drive unit used according to the invention for actuating the lifting device; 
     FIG. 6 is a film roll lock used in the device according to the invention, in a perspective view; 
     FIG. 7 is a perspective view of the unrolling unit used in the device according to the invention; 
     FIG. 8 is a cutting device used in the device according to the invention, in a perspective view; 
     FIG. 9 is a perspective view of a carriage used in the device according to the invention; 
     FIG. 10 is a perspective view of a carriage guide used in the device according to the invention, and 
     FIG. 11 is a perspective view of a pallet used in the device according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     The device according to the invention has a frame  1  with a left frame part  2  and a right frame part  3  connected to one another by cross struts  4  and  5  (FIGS. 1 to  3 ) which are aligned with the width of the film rolls to be processed and/or used. A lifting device  6  is provided on each of the two frame parts  2  and  3  (see also FIG.  4 ). Each lifting device has an endless belt  7  guided around two reversing rollers  8  and  9 . The lower reversing rollers  9  of the lifting devices  6  are secured to the ends of a driven shaft  11  of drive unit  10 , and can be driven by the drive unit  10  (FIG.  5 ). Shaft  11  is driven by means of an endless belt  12  by an electric motor  13  (FIG.  5 ). To prevent an undesired lowering of the lifting devices  6 , for example in the event of a power failure, it is possible to design the drive unit with a locking disk. 
     A pallet  14  holding a film roll  15  can be raised and lowered by means of lifting devices  6 . As a result it is possible to move the film roll  15  between a standby position S and a working position W provided in the upper part of the frame, in which the film is pulled off the film roll for use as provided. To secure the pallet  14  on lifting devices  6 , the devices are equipped with locking and/or centering pins  6   a  or support plates  6   b . (FIG.  1 ). 
     To introduce the pallet  14  supporting the film roll  15  into the frame  1 , the pallet can be placed initially on a carriage  16  (FIG. 9) that can be pushed into the lower part of frame  1  as shown in FIG.  1 . Carriage  16  travels on four rollers  17 , which can be made rotatable depending on the space available. The reception and/or holding of pallet  14  on carriage  16  is accomplished by means of least two centering pins  18  by which tolerances can be compensated in simple fashion. For exact introduction or positioning of carriage  16  in the lower part of frame  1 , a carriage guide  19  is provided that is fastened to the floor beneath frame  1  (FIGS.  1  and  10 ). The positioning is accomplished by means of curved rollers  17   a  provided on the carriage, which can be introduced into a tapering guide channel  19   a  of the carriage guide  19 . By positioning the carriage  16  in the carriage guide  19 , the pallet can be brought into a removal position or the film roll  15  can be brought into the standby position S from which lifting device  6  raises the pallet. Carriage  16  is locked in carriage guide  19  by clamps  20  for example (FIG.  10 ). 
     Pallet  14  that can be placed on carriage  16  is shown in detail in FIG. 11, and consists of frame  21  on which a receiving mount  22  for the film roll  15  is mounted. The film roll is then placed on two rotating rollers  23  of receiving mount  22  that can be introduced into matching receptacles  22   a . As a result, for example, the end of the film can be pulled off in simple fashion in preparation. To lock the end of the film and to make it accessible, after being pulled off film roll  15  the film end can be secured or glued to a locking tube  24  provided on pallet  14 , said tube preferably having a rectangular cross section. A possible variable outside diameter of film roll  15  (in practice between 250 and 350 mm) can be accommodated by different insertion heights of rotary rollers  23 . This is accomplished in simple fashion by choosing appropriate recesses  22   a . As a result, film rolls  15  from different manufacturers can be used for example. Pallet  14  also has an ejection loop  25  by means of which a film roll  26  that is in the working position of the device, after use, can be ejected into a cardboard core receptacle  27  as explained below. Ejection loop  25  can be pivoted upward around an axis  28 , as shown in the diagram in FIG. 11 for example. 
     The means for locking film roll  26  in the working position W of the device are shown in detail in FIG.  6 . The film roll is locked in working position W, on both sides by means of a conical receptacle  29  on each side. Conical receptacles  29  can be moved separately by cylinders  30 ; that is, they can be moved away from film roll  26  or toward it. Film roll  26  can be aligned in working position W for example by one of the two cylinders  30  that serves as the determining cylinder. As a result of differences in pressure on the left and right, the determining cylinder  30  is fully extended so that film roll  26  can be aligned in the desired fashion. 
     At this point, especially with reference to FIGS. 1-3, the operation of the device shown for transporting and/or lifting film rolls  15  from the standby position into the working position in which they are held by conical receptacles  29  will be described. In the operating state shown in FIGS. 2 and 3, the first film roll  26  is in the working position W, secured by the conical receptacles or clamping mandrels  29 , and a second film roll  15  is then in its standby position S on pallet  14 , which still rests on carriage  16 . A roll core  26   a , which was removed at an earlier point in time from working position W lies in a cardboard core holder  27 . By means of their locking pins  6   a  and support plates  6   b , the respective lifting devices  6 , upon actuation of drive unit  10 , engage matching recesses and engagement surfaces in the underside of frame  21  of pallet  14 . (See FIG. 1.) 
     By means of lifting devices  6 , pallet  14  is then lifted from the carriage and moved upward. Ejection loop  25  initially comes in contact with the film roll  26  that is in the working position or with its core. Shortly before the ejection loop  25  comes in contact with the film roll  26 , the conical receptacles or clamping mandrels  29  that held film roll  26  during the film unrolling process are opened. When pallet  14  travels further upward, the film roll  26  is contacted by ejection loop  25  and falls backward into the cardboard core receptacle  27  as indicated in the drawing of the roll core  26   a . Further lifting of the pallet  14  brings the film roll  15  mounted on the pallet  14  into the working position and it can be secured there by means of the conical receptacles  29 . By means of a single lifting movement it is therefore possible to remove the used film roll  26  and replace it by a new film roll  15 . As explained below, it is also possible at the same time to cut the end of the film from the locking tube  24 . Then the pallet  14  can be lowered again in the same way, with the ejection loop  25 , by pivoting around axis  28 , being capable of being carried past the new film roll  15  that is now in the working position. 
     The unrolling unit  40  shown in FIG. 7 will now be described in detail, which permits a defined pulling of the film off the film roll  26  in the working position. The unrolling unit  40  is located in the upper part of frame  1  in the vicinity of cross strut  5 . It has measuring means with a measuring wheel  41  and an electronic counter. The measuring means are in an operating connection with the film roll that is in the working position and they determine the length of the film that has been pulled off, and when the film has been pulled out correspondingly far, 800 meters for example, they trigger the automatic film roll change described. For example, a signal that can be generated by the measuring means can be transmitted to a control device  41   a  of the device. Unrolling unit  40  also has a compensating roller  42 . This roller can be driven by a motor, for example a pneumatic motor or electric motor. When the film is pulled off the film roll  26  that is in the working position, the motor is used as a brake for compensating roller  42 . The braking torque can be chosen to be fixed or variable. It should be pointed out that as an alternative, shoe brakes, disc brakes, or eddy current brakes can be used. By an appropriate adjustment of the compensating roller  42 , the pull-off point or the pull-off edge of film that is on film roll  26  can be varied in suitable fashion. The pressure of the compensating roller on the film roll can be adjusted. 
     When the automatic film roll change essentially already described is triggered, the film roll removal from film roll  26  is halted first. Then the remaining film is rewound onto film roll  26 . This rewind is performed by compensating roller  42  which is driven accordingly for the purpose. Then the components of unrolling unit  40  are brought out of the engagement area of lifting device  6 . After the replacement process described above is completed and the new film roll has been positioned in working position W, components  41 ,  42  of unrolling unit  40  are again brought into an operating connection with the new film roll. The unrolling unit can be equipped with a device to discharge any static that collects on the film. For this purpose, a combination of a fixed upper strip and a pivotable lower strip is possible. 
     As already described, during the lifting of the new film roll  15  into working position W, its end is secured to a locking tube  24 . When a new roll  15  reaches the working position, the film stretched between film roll  15  and the locking tube abuts a suction and cutting device  50  located in the upper frame part (FIG.  8 ). This device for example has a comb-like suction strip  51  to which the stretched film on film roll  15  can be secured. It is also possible to hold the film in cyclic fashion by clamps on the suction strip  51  in order to prevent a film loss for example if the suction strip should not function. Then the film is separated from the film roll by a knife  52 . The new film roll  15  is then secured in the working position and prepared for pulling film off the film roll. The knife  52  is guided for example by a piston-less cylinder, permitting a long knife life and an easy and simple knife replacement. During the cutoff process it is possible to hold the film by cutting clamps in addition. 
     According to the invention, a device is therefore provided for fully automatic film change. The old roll is ejected and the new roll inserted by a single (motorized) lifting movement. The device need be loaded with a new film roll only once during a shift, for example at the beginning of the shift. The device can be loaded at any time, independently of production. Since loading is performed by a carriage, the storage location can be selected freely. When the film rolls are replaced, there is only a very short interruption of the production process, if any. A cycle is extended only slightly if at all by the replacement of the film roll, since replacement can take place for example during a perforation time, a time when the film is applied to a motor vehicle, or during the remainder of the time spent handling film that has been pulled off. The modular design allows the device according to the invention to be adapted in simple fashion for different film widths. It is merely necessary to modify the transverse connecting parts to match the width of the film. 
     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.