Abstract:
The invention is in the field of devices enabling the sticking of splicing tapes to the ends of strips put into rolls, to prevent their later unwinding. The present invention relates to a device ( 1 ) for applying splicing tapes ( 22 ) on a strip ( 30 ) made of flexible material. The device ( 1 ) is equipped with a passive device ( 50 ) enabling the elimination of the electrostatic forces that disturb the operation of the device. The device ( 1 ) according to the invention is mainly used on photographic film or paper slitters.

Description:
FIELD OF THE INVENTION 
   The present invention is in the field of devices that enable the sticking of splicing tapes onto other strips usually made of flexible material. These devices must operate correctly, and especially not cause sticking faults due to electrostatic phenomena. More specifically, the invention is in the field of automatic devices for sticking splicing tape onto the strands of the ends of strips forming rolls or reels of photographic films or papers; with the sticking process intended to prevent the strips from unwinding, just after they have been cut on a slitter. 
   BACKGROUND OF THE INVENTION 
   The use of slitters is universally known in the photographic industry. Slitters enable the simultaneous cutting into several strips with preset widths of a wider strip or axis of film or paper previously coated with a photosensitive emulsion layer. The wider strip to be cut has a programmed length itself. The cut strips obtained from the wider strip are wound around a central core. Each of the rolls thus obtained ends with a free strand. The free strand is intended to take a pre-glued splicing tape of flexible material, to fix this free strand of the strip end onto its roll, in order to prevent the roll from unwinding during later manipulations or operations in the process, in particular during the operation of packaging the rolls and transport of the rolls. The splicing tape is applied to the roll using an automatic sticking device, attached to an annexed part of the slitter. This sticking device automatically places and sticks the splicing tapes onto the free strands of the respective rolls. Before the sticking operation of the splicing tapes to the roll, they are previously unstuck or separated from a support strip. The unsticking generates electrostatic forces that cause quality faults, because the separated splicing tape is deviated from its planned path towards the free strand of the strip end to be stuck. Therefore, it does not stick the free strand onto its roll. In addition the deviated splicing tape is often found, for example, inside the sticking device and disturbs its operation It is an object of the present invention to eliminate the effect of electrostatic forces in sticking devices used on slitters. 
   The principle enabling electrostatic forces to be eliminated is well known to those skilled in the art. It includes using ionization of the air. To eliminate electrostatic forces, passive induction means, comprising points linked to ground for example are used, as described in Patent EP 708,580. 
   SUMMARY OF THE INVENTION 
   The present invention relates to a splicing tape sticking or application device equipped with a passive means that enables the elimination of the electrostatic forces that disturb the operation of the device as far as stopping the operation. Stopping the operation of the sticking device causes the slitter to stop; these stops generate significant productivity losses that the device according to the invention eliminates. 
   The present invention relates to a device for applying precut splicing tapes initially attached successively to a first strip serving as support made of flexible material, onto a second strip made of flexible material of the roll end, by successively separating the splicing tapes of the first strip. The device comprises a frame in which are arranged the means for unwinding, winding, guiding, and mechanical tension check of the first strip, and a pressure part that enables the splicing tape separated from the first strip to be applied to the second strip of the roll end when the roll is approached by the pressure part. The device is characterized in that it further comprises a passive means of electrostatic discharge acting by the electrical field effect and attached to one of the device&#39;s guiding means. The passive means has its end placed in the sticking zone just before the intersection of the paths of the separated slicing tape and the second strip to be stuck, as close as possible to the path of the separated slicing tape without touching the tape, and without touching the second strip to be stuck, so as to generate the electrostatic discharge of the zone and prevent attraction of the separated tape by the pressure means. 
   Other advantages and characteristics of the present invention will appear in the following description and more particularly in a preferred embodiment of the invention illustrated in the following figures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  represents a diagram of the device according to the invention; 
       FIG. 2  represents a splicing tape and its support used in the device according to the invention; 
       FIG. 3  represents cross-section  3 — 3  of  FIG. 2 ; 
       FIG. 4  represents the operation of a device which does not comprise the means according to the invention; and 
       FIG. 5  represents the operation of the device according to the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The following detailed description refers to a preferred embodiment of the invention; this with reference to the drawings of the above figures, wherein the same reference numbers identify the same parts for each of the various figures. 
     FIG. 1  represents a diagram of the device  1  according to the invention. It is attached, for example, on a slitter for photographic film or paper using a slide  2  and a locking means  3 . The slide  2  is, for example, dovetail shape and the locking means  3  is a device comprising a shaft and cam lever. The device  1  enables the application and sticking of splicing tapes  22  onto the free strand  30  of a roll  32  of strips of photographic film or paper having a preset width, so that the free strand  30  is fixed onto the roll  32  (FIGS.  4  and  5 ). The application of the splicing tapes  22  by the device  1  onto the roll  32  prevents the roll  32  from unwinding during later operations or handling. It is contemplated to attach to the slitter several devices  1  for applying splicing tapes according to the invention, i.e. one device per cut strip on the machine, which enables the simultaneous sticking of the free strands  30  of each of the corresponding rolls  32 . The device  1  comprises a frame  4  in which are arranged various means that enable the storage and running of a strip  20 . The means of the device  1  are respectively an unwinder means or device  5  of the strip  20 , a guide or guiding means  6 ,  7 ,  8 ,  9 ,  10 ,  11 ,  12 ,  18 , a mechanical tension checker or mechanical tension check means  15  of the strip  20 , a winder or winding means or device  17  of the strip  20  and an applicator or means  19  that enables application and pressing of the splicing tape  22  separated from the strip  20  onto the free strand  30 . According to a preferred embodiment of the invention, the unwinding  5  and winding  17  means are rotating metal cylinders. The means  15  enables checking of the tension of the strip  20  during its unwinding from the cylinder  5 . The means  15  is, for example, a preset mechanical device attached to the shaft of the cylinder  5 ; this device brakes the cylinder  5  during unwinding, so as to maintain an appropriate tension opposed to the unwinding of the strip  20 . During operation of the device  1 , this tension stays less than the winding tension of the cylinder  17 . Guiding means  6 ,  7 ,  8 ,  9 ,  10 , are rotating cylinders made of plastic, for example PVC; the means  18  and  19  are for example rotating metal cylinders not coated or coated with polyurethane or neoprene. The guiding means  11  and  12  are flat guiding parts attached to the frame  4 ; these guiding means  11  and  12  comprise adjacent plane surfaces  11 P and  12 P that enable holding of the strip  20  and separation of the splicing tape  22  from the strip  20  at  11 D. According to a preferred embodiment, the flat guide  11  and the flat guide  12  are metal, in order to provide good electrical conduction. While in another embodiment, the flat guide  12  can be for example metalized Teflon. 
   The device  1  enables a roll  23  of strip  20  to be automatically unwound.  FIG. 2  represents the strip  20  whose essential part is a support strip  21  coated with a fine layer of solid saturated hydrocarbons  26 . On the support  21  splicing tapes  22  precut into pre-glued adhesive foils are placed one following the other. The layer of hydrocarbons  26  enables the tapes  22  to stick to the support strip  21 . The splicing tape  22  comprises at least one pre-glued zone  24  and one zone without glue  25 , as shown in  FIGS. 2 and 3 . The pre-glued zone  24  is on the side opposite the support  21 . The strip  20  is for example a roll of wax paper  21  on which are arranged at regular intervals thin precut splicing tapes  22  made of plastic. The device  1  according to the invention unwinds from the roll  23 , the strip  20  comprising the support strip  21  which is usually paper and on which are set the splicing tapes  22 . As shown in  FIGS. 4 and 5 , the strip  20  comes to the outlet of the device  1  in the flat guides  11  and  12  zone following the path D 1 . When part of the strip  20  supporting the splicing tapes  22  comes to the break line  11 D forming the end of the flat extended guide  11 , the strip  22  is folded back to follow the path D 2 . At  11 D, by the break generated by the shape of the flat guide  11 , the splicing tape  22  is unstuck from its support  21  and by inertia follows the path D 3 , to go between the pressure cylinder  19  and the free strand  30  of the roll  32 . The roll  32  has been placed close to the pressure cylinder  19  by a not shown means attached to the slitter. In the  11 D zone, the unsticking of the splicing tape  22  from its support  21  generates significant electrostatic forces. 
   According to the splicing tapes  22  used, and in particular according to their surface area, the surface density of the corresponding charge is variable. For example, for splicing tapes with a surface area of 11 square centimeters (1.8 cm by 6.3 cm) intended to stick the free strand  30  of a roll of photographic paper  32 , the surface density of the average charge is approximately 1.4 nanocoulomb per square centimeter. The electrostatic forces generated by the unsticking of the splicing tape  22  from its support  21  and the friction of the support  21  of the strip  20  on the flat guide  11  have the effect of attracting the splicing tape  22  to the rotating pressure cylinder  19  as shown in FIG.  4 . Despite the glued zone  24  provided to stick the slicing tape  22  onto the roll  32  and the force exerted by the pressure cylinder  19 , the resulting electrostatic force is large enough for the splicing tape not to stick to the roll  32 , and stay attracted by the cylinder  19 . The consequence of this phenomenon is on the one hand not sticking to the free strand  30  on the roll  32  and on the other hand accumulating the splicing tapes  22  on the cylinder  19 . The secondary consequences are unwanted separations of the stuck tapes, for example, one with another and which are found everywhere in bunches in the device  1  or around it, or even accumulate and contaminate the roll  32 . The electrostatic charge created when unsticking the splicing tape  22  generates a matching charge on the pressure cylinder  19 . The charge on the cylinder  19 , by the metal nature of the cylinder  19  and because the radius of curvature of the cylinder  19  is less than the radius of curvature of the roll  32 , is greater than the charge of the same sign created on the roll  32 . In addition, as the charge on the splicing tape  22  that is not electrically very conductive is of the opposite sign to that of the pressure cylinder  19 , the tape  22  is attracted by the cylinder  19  which exerts an attraction force greater than that of the roll  32 . The charge on the splicing tape  22  that is not electrically very conductive persists in time, i.e. the relaxation time enabling the tape  22  to fully discharge the electricity is about several tens of seconds after the unsticking. Whereas the application process of a splicing tape  22  using the device  1  only lasts a few seconds; thus the embodiment corresponding to  FIG. 4  systematically generates the problems mentioned above. 
   The device according to the invention includes using a simple and robust means  50  in the device  1  to eliminate the interfering electrostatic forces generated by the unsticking of the splicing tape  22  at  11 D. The means  50 , used in the invention, is a “passive” means of electrostatic discharge in the sense that it does not include or use an energy source. The means  50  acts by electrical field effect and by its low radius of curvature; it enables charges matching those generated on the splicing tape  22  to concentrate at its end  51  placed in the sticking zone  52 . The electrical field has sufficiently high intensity to reach a value greater than or equal to the ionization potential of the ambient air in the sticking zone  52 . The air zone thus ionized is made electrically conductive. The sticking zone  52  is thus practically discharged and the resulting charge on the splicing tape  22  is no longer enough for the tape  22  to be attracted by the pressure cylinder  19 . 
   According to a preferred embodiment of this invention, this means  50  is a very thin metal foil, attached to the concave top part  12 C of the guide  12  with fixing means enabling the foil  50  of the guide  12  to not be electrically insulated. The thickness of the foil is between 0.05 mm and 0.10 mm. In a preferred embodiment of the invention the thickness of the foil is 0.06 mm. The guide  12  in combination with the extended flat guide  11  ensures the guiding of the strip  21  carrying the splicing tapes  22 . For this purpose the guides  11  and  12  comprise adjacent plane surfaces  11 P and  12 P. The emerging length  51  of the foil  50  in relation to the guide  12  is situated in the ionized air zone  52 , just before the line of intersection Li of the paths of the splicing tape  22  and the strip  30  of the roll  32 . The emerging length  51  is adjusted to not make contact with the roll  32 , while being situated as close as possible to the path D 1 , D 3  of the splicing tape  22 . Thus positioned, the foil  50  enables electrostatic discharge of the tape  22  separated or unstuck from its support  21 , which prevents the separated tape  22  from being attracted by the rotating cylinder  19 . In a preferred embodiment, the foil  50  is supported by the metal guide  12 , to ensure electrical continuity of the assembly to ground through the frame  4  of the device  1 . In the zone to be discharged the uniformity of electrostatic discharge using the foil  50  is better than using for example a point. 
   While the invention has been described in detail and with reference to a preferred embodiment it will be apparent that all changes and modifications of this preferred embodiment leading to other embodiments within the spirit and scope of the claims should be considered as equivalent and integrated in the present application.