Method and device for feeding wrapping material and a tear strip to a wrapping machine

Abstract: A method and device for feeding wrapping material and a tear strip to a user machine, whereby a strip of wrapping material (2) and a tear strip (3) are fed continuously along respective paths (6, 12) to a joining station (23) where they are joined integral with each other to form a wrapping strip (25) complete with a tear strip; a compensating store (32) for compensating the wrapping strip (25) being located between the joining station (23) and a cutting station (34) at which the wrapping strip (25) is cut into a succession of portions (36).

Description: The invention relates to a method of feeding wrapping material and a tear strip to a user machine. The present invention is particularly advantageous on machines for overwrapping packets or cartons of cigarettes, to which application the following description refers purely by way of example. On known normally intermittent overwrapping machines the wrapping material is generally fed continuously through a compensating store, which compensates for any cyclic difference in the supply and utilization speed of the wrapping material by varying the length of the path along which it is fed, and by imparting to the wrapping material a substantially constant tension. Downstream from the compensating store, the wrapping material is joined to a tear strip to form a wrapping strip, which is fed to a cutting station where it is cut into portions, each forming an overwrapping for a packet or carton of cigarettes. On overwrapping machines of the above type, the wrapping material of each portion, when cut off, has been found to pucker along the edges of the portion adhering to the tear strip, thus making it practically unusable. Furthermore a device in accordance with the preamble of claim 6 is known from EP-A-248225. It is an object of the present invention to provide a method of feeding wrapping material and a tear strip to a user machine, designed to overcome the aforementioned drawback. According to the present invention, there is provided a method of feeding wrapping material and a tear strip to a user machine, the method comprising the steps of pushing, as opposed to drawing, the wrapping material and the tear strip along respective first path portions to a joining station so as to keep the wrapping material and tear strip substantially tensionless upstream of the joining station; joining the tear strip to the wrapping material at the joining station so as to form a wrapping strip complete with a tear strip; and feeding said wrapping strip from said joining station to said user machine along a second path portion by imparting a given tension to the wrapping strip. The invention also relates to a device for feeding wrapping material and a tear strip to a user machine. According to the present invention, there is provided a device for feeding wrapping material and a tear strip to a user machine, the device comprising a joining station for joining together said wrapping material and a tear strip to form a wrapping strip; first and second supply means for respectively feeding the wrapping material and the tear strip along respective first path portions to the joining station; traction means for feeding said wrapping strip along a second path portion extending from said joining station; and counteracting means, located along said second path portion and upstream from said traction means, for imparting a given tension to said wrapping strip; characterized in that said first and second supply means are pushing means for respectively pushing, as opposed to drawing, the wrapping material and the tear strip along the respective first path portions and towards the joining station, so as to keep the wrapping material and tear strip substantially tensionless upstream of the joining station. The invention will be described with reference to the accompanying drawing, which shows a partially sectioned, schematic side view, with parts removed for clarity, of a preferred, non-limiting embodiment. Number 1 in the accompanying drawing indicates a device for continuously feeding a strip of wrapping material 2 and a tear strip 3 to an overwrapping machine 4. Device 1 comprises a first line 5 for feeding material 2 to machine 4 along a path 6, material 2 being unwound off a reel 7 having a core 8 mounted on a shaft 9 rotated anticlockwise (in the drawing) about its axis by a motor 10; and a second line 11 for feeding tear strip 3 along a path 12 and off a reel 13 presenting a core 14 mounted on a shaft 15 rotated clockwise (in the drawing) about its axis by a motor 16. A control unit 17 provides for feedback controlling motors 10 and 16 to maintain the same surface speeds of reels 7 and 13, the diameters of which are constantly controlled by respective known position transducers 18 and 19 on the basis of measurements made by respective known feeler elements 20 and 21. Path 12 of tear strip 3 converges with path 6 on a conveyor plate 22 at a joining station 23 where a pressure pad 24, moved to and from an operating position contacting plate 22 by a known actuating device (not shown), joins tear strip 3 integral with material 2 on plate 22 to form a wrapping strip 25 complete with a tear strip. More specifically, downstream from station 23, path 6 presents a portion 6a in common with path 12, whereas, upstream from station 23, path 6 extends about a guide roller 26, and path 12 about a series of diverting rollers 27, one of which is a compensating roller connected to an actuator 28 for moving the compensating roller transversely and so varying the length of path 12 for the reasons explained later on. Device 1 also comprises a traction assembly 29, in turn comprising a powered unwinding roller 30 and a pressure roller 31 rotating in opposite directions and which provide for feeding strip 25 along path portion 6a through a compensating store 32 and about a diverting roller 33 to a cutting station 34 where it is cut in known manner into a succession of portions 36 by a known cutting unit 35 comprising a movable blade and a fixed counterblade. As shown in the accompanying drawing, station 23 is located at the input end of portion 6a, assembly 29 is located immediately upstream from station 34 and substantially at the output end of portion 6a, and compensating store 32 is located along portion 6a and upstream from assembly 29 and roller 33. Store 32 provides for compensating any cyclic difference in the supply and utilization speeds imparted to strip 25 by motors 10, 16 and traction assembly 29 respectively, and for imparting to strip 25 a given, substantially constant tension. For which purpose, store 32 comprises a cup-shaped container 37 defining an inner chamber 38, one end of which communicates externally via an opening 39, and the opposite end of which is closed by a bottom wall 40 fitted through with a conduit 41. Conduit 41 communicates with a known suction source 42 for generating a vacuum inside chamber 38 and drawing in a portion of strip 25 to form, inside chamber 38 and through opening 39, a loop 43, the length of which varies with time and is controlled by two optical sensors 44, 45 fitted to the lateral wall 46 of container 37 and which provide, in known manner, for controlling motors 10 and 16 so that the length of loop 43 is maintained within a given range. The substantially constant vacuum inside chamber 38 also provides for imparting a substantially constant given tension to the portion of strip 25 extending along portion 6a, and more specifically, to the portion of strip 25 extending between chamber 38 and assembly 29. Consequently, material 2 and tear strip 3 are fed to joining station 23 at speeds maintained substantially equal by control unit 17; actuator 28 and the compensating roller provide for varying the length of path 12 to compensate for any minor differences in the above two speeds, with substantially no tension being applied to tear strip 3; and material 2 and tear strip 3 are pushed (as opposed to drawn) by motors 10 and 16 to station 23. Since, upstream from station 23, material 2 and tear strip 3 present substantially no tension and no difference in speed, strip 25 downstream from station 23 presents no difference in tension between material 2 and tear strip 3, both of which are subjected to the same tension by store 32. The situation at station 23 is again repeated in each portion 36, in which the tension imparted to strip 25 by store 32 is obviously eliminated. In other words, portions 36 also present no difference in tension between material 2 and tear strip 3, thus eliminating any possibility of material 2 puckering in the region contacting tear strip 3.

Claims: A method of feeding wrapping material (2) and a tear strip (3) to a user machine (4), the method comprising the steps of pushing, as opposed to drawing, the wrapping material (2) and the tear strip (3) along respective first path portions (6, 12) to a joining station (23) so as to keep the wrapping material (2) and tear strip (3) substantially tensionless upstream of the joining station (23); joining the tear strip (3) to the wrapping material (2) at the joining station (23) so as to form a wrapping strip (25) complete with a tear strip; and feeding said wrapping strip (25) from said joining station (23) to said user machine (4) along a second path portion (6a) by imparting a given tension to the wrapping strip (25). A method as claimed in Claim 1, characterized in that said pushing the wrapping material (2) and the tear strip (3) along said respective first path portions (6, 12) to the joining station (23) is obtained by feeding the wrapping material (2) and tear strip (3) from respective reels (7, 13) mounted on respective motor driven shafts (9, 15). A method as claimed in Claim 2, characterized in that said motor driven shafts (9, 15) are activated so as to confer substantially identical peripheral speeds to said reels (7, 13). A method as claimed in any one of the preceding Claims, characterized in that said second path portion (6a) extends upstream from a cutting station (34) where said wrapping strip (25) is cut into portions (36). A method as claimed in any one of the preceding Claims, characterized in that said tension is applied by drawing said wrapping strip (25) by suction into a compensating vacuum chamber (38). A device for feeding wrapping material (2) and a tear strip (3) to a user machine (4), the device comprising a joining station (23) for joining together said wrapping material (2) and a tear strip (3) to form a wrapping strip (25); first and second supply means (10, 16) for respectively feeding the wrapping material (2) and the tear strip (3) along respective first path portions (6, 12) to the joining station (23); traction means (29) for feeding said wrapping strip (25) along a second path portion (6a) extending from said joining station (23); and counteracting means (32), located along said second path portion (6a) and upstream from said traction means (29), for imparting a given tension to said wrapping strip (25); characterized in that said first and second supply means (10, 16) are pushing means for respectively pushing, as opposed to drawing, the wrapping material (2) and the tear strip (3) along the respective first path portions (6, 12) and towards the joining station (2), so as to keep the wrapping material (2) and tear strip (3) substantially tensionless upstream of the joining station (23). A device as claimed in Claim 6, characterized in that said first and second supply means (10, 16) respectively comprise first and second motor driven shafts (9, 15), which are adapted to support respective reels (7, 13) of the wrapping material (2) and the tear strip (3) respectively. A device as claimed in Claim 7, characterized in that control means (17) are provided to activate said motor driven shafts (9, 15) so as to confer substantially identical peripheral speeds to said reels (7, 13). A device as claimed in any one of the foregoing Claims from 6 to 8, characterized in that said counteracting means (32) comprise a compensating store (32). A device as claimed in Claim 9, characterized in that said compensating store (32) defines a vacuum chamber (38) for forming a loop (43) of variable length along said wrapping strip (25). A device as claimed in one of the foregoing Claims from 6 to 10, characterized in that said joining station (23) comprises a plate (22) and pressure means (24) movable to and from a position wherein they contact and exert pressure on said plate (22) to press said wrapping material (2) and said tear strip (3) against said plate (22) and form said wrapping strip (25).

Inventors: BORIANI SILVANO, GAMBERINI ANTONIO, BORIANI, SILVANO, GAMBERINI, ANTONIO
Applicants: GD SPA, G.D SOCIETA' PER AZIONI
Application year: 1995
Main classification: B65B61
IPC codes: B31B1, B65B11, B65B61