GB2254069A - Feeding and cutting webs - Google Patents

Description

2254069 1.

1 A device for cutting strip material in machines for packaging commodities The present invention relates to a device by means of which to cut strip material, in machines for the packaging of commO'dities. Such a device finds application particularly in the manufacture of cigarettes, for dividing continuous silver foil strip material into discrete sheets or wrappers as used traditionally to envelo groups of cigarettes. Conventional cutter devices of the type in question consist most typically in a transverse knife and a longitudinal knife; in.one embodiment of such a device, disclosed in Italian Patent Application no 3538 A/90, the knives operate in conjunction with reaction means which serve also to support, retain and throughfeed the strip material. The longitudinal knife, in particular, interacts with the bottom of a circumferential track afforded by a cylindrical reaction roller, and since the longitudinal cut is not continuous but comprises a plurality of discrete cuts made in succession, it 1. 11 1 2 will be clear that contact between the longitudinal knife and the bottom of the circumferential track occurs repeatedly, though not without a solution of continuity. Given that the operating speed of the machines in question is especially high, it follows that the longitudinal knife is subjected to an unremitting succession of shocks, occasioning early wear and resulting in the need for its replacement, or at least for the edge to be sharpened. The frequency with which the knife strikes against the bottom of the circumferential track causes the components brought into mutual contact to 'beat', generating vibrations that are transmitted to other mechanically associated parts, and producing an irritating noise which, no less importantly, is a source of annoyance to the machine operator. The object of the present invention is to provide a cutter device affording a greater durability, and therefore greater dependability, than obtainable from devices currently in use. The stated object is realized, according to the present invention, in a device for cutting strip material in machines for packaging commodities, comprising means serving respectively to effect a 3 transverse cut and to effect a longitudinal cut in a continuously fed strip, of which at least the transverse cutting means interact with reaction means designed also to support, retain and advance the strip, characterized in that the longitudinal cutting means comprise a knife and a relative reaction element rotatable about -mutually parallel respective axes, of which the relative active profiles d-,scribe circular trajectories that are distanced axially one from the other in such a manner that the cutting edge of the knife does not enter into contact with the meeting edge of the reaction element. The invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which: -fig 1 is a schematic illustration of the device according to the present invention, viewed in cross section; -fig 2 is the schematic illustration of a detail of longitudinal cutting means forming part of a device as in fig 1, viewed from A; -fig 2a is the enlarged view of a detail of fig 2; -fig 3 illustrates an alternative embodiment of the longitudinal cutting means, viewed from B in fig 1.

4 A device according to the invention, denoted 1 in its entirety, for cutting a strip 4 of wrapping material, e.g. silver foil paper, comprises means 2 by which to effect a transverse cut in the strip and means 3 by which to effect a longitudinal cut in the strip. The means 2 which effect the transverse cut operate in conjunction with reaction means 5 structured in such a way as to support, retain and carry forward the strip 4 during the cutting cycle. The transverse cutting means 2 comprise a knife 6 rotatable about a horizontal axis and equipped with two longitudinal blades 6t and 6i. The blades 6t and 6i are diametrically opposed, one designed to effect a full transverse cut such as will sever a discrete length or sheet from the strip 4, and the other to produce a series of single aligned cuts or perforations serving to mark off an'area of the sheet which can then be detached easily from the remainder. The reaction means 5 operating in conjunction with the transverse cutting means 2 are embodied as a cylindrical roller 8, disposed with axis parallel to that of the knife 6 and equipped with a striking plate 9 that interacts with both blades 6t and 6i.

The cylindrical face of the reaction roller 8 affords a plurality of radial holes 11 that can be connected with a source of negative pressure (not illustrated). Preferably, the radial holes 11 will occupy a part of the roller 8 remote from the area of contact between the striking plate 9 and the blade 6i, for reasons about to be made clear. To advantage, the radial holes 11 will be caused by means not illustrated to connect with the source of negative pressure only through a distance extending from a position preceeding the transverse knife 6, in the direction of rotation of the roller 8, to a position substantially beyond the extreme bottom generator of the revolving cylindrical face, where the strip 4 is transferred from this roller 8 to a further cylindrical roller 17 positioned beneath. The roller 17 in question is disposed with its axis parallel to that of the roller 8 above and likewise affords a plurality of radial holes 171 connected periodically to a source of negative pressure. As discernible from fig 1, the continuous strip 4 of material approaches the reaction roller 8 along a substantially horizontal path (see arrow FA) from a location preceding the part of the cylindrical face rolling tangential to the transverse knife 6.

6 Conventionally, the strip 4 is directed toward the device (by means not illustrated) at a constant rate of feed slower than the peripheral velocity of the reaction roller 8, and the cylindrical face of the roller 8 is embodied absolutely smooth in such a manner that the strip can slide over the relative surface without suffering damage, notwithstanding the pulling force that is exerted by the roller 8 with suction generated through the holes 11. The longitudinal cutting means 3 comprise a knife 7 and a reaction element 20, both rotatable about axes parallel to the axis of the reaction roller 8. An essential feature of the longitudinal cutting means 3 (illustrated in detail by figs 2 and 2a) is that the relative knife 7 and reaction element 20 are set in motion in such a manner that the cutting edge 71 of the one and the meeting edge 21 of the other never enter into mutual contact. Naturally enough, the distance which separates the cutting edge 71 from the meeting edge 21 will be dependent on the thickness of the strip material 4, and such as to enable a faultless longitudinal cut. Observing figs 2 and 2a it will be seen, in the example illustrated, that the longitudinal knife 7 is associated with the roller denoted 17, and in 7 particular, that the roller 17 is embodied in two coaxial parts 26 and 27 separated by a distance piece 28; the distance piece 28 in turn affords a seating 29 in which to position a sector 30 that projects circumferentially both from the distance piece itself and from the coaxial parts 26 and 27 of the roller. The projecting part of the sector 30 (that is to say, of the knife 7) is contoured in such a way as to incorporate the cutting edge 71, as discernible from fig 2a. Coaxial alignment of the two rolling parts 26 and 27 is ensured by means of conventional embodiment, such as pins 31, the two parts 26 and 27 themselves being secured one to another likewise by conventional means (not shown in the - drawings). The reaction element 20 in this example is embodied as a cylindrical roller 22 disposed substantially tangential to the roller denoted 17 and affording a circumferential edge 21 with which the knife 7 is caused to interact. As shown in fig 2, the roller 22 is keyed onto a shaft 25 disposed parallel to the roller denoted 17 and carrying a further cylindrical roller 23. The periphery of this roller 23 is either faced with or fashioned from a resilient material, and rotates a permanently in contact with an area of the parallel roller 17 not occupied by the strip 4. Permanent contact thus being established between these two rollers 23 and 17, the roller 22 affording the meeting edge 21 is set in rotation about the axis of the shaft 25 in the opposite direction to that of the knife 7, as indicated by arrows denoted F17 and F22 in fig 1. Whilst fig 2 illustrates a roller 17 of practically constant diameter, discounting the knife 7, the part in contact with the resilient roller 23 might be of a diameter greater than that compassed by the knife 7, as shown by the phantom lines of fig 2 in which 171 and 231 denote the enlarged diameter of the one roller 17 and the correspondingly reduced diameter of the other 23, respectively. With this variation in embodiment, the peripheral velocity of the roller denoted 22, hence of its circumferential meeting edge 21, can be increased in relation to that of the cutting edge 71 thereby enhancing the quality of the longitudinal cut made in the strip. Such a facility is achieved wholly by virtue of the fact that the cutting edge 71 of the knife 7 and the meetji-icj edge 21 of the reaction element 20 are never brought into mutual contact.

9 Still in fig 2, it will be seen that the free end of the part denoted 27 can be encircled coaxially by a cylindrical collar 32 of diameter equal to or greater than that of the part 27 itself. In effect, the collar 32 coincides with the enlarged diameter portion 171 of the roller 17. In the embodiment shown schematically in fig 3, the reaction element 20 is provided by the roller 8 of the transverse cutting means 2; in this instance, the face of the roller 8 affords a circumferential seating 24 of which one side provides the meeting edge 21. The cutter device 1 is thus simplified, albeit in this embodiment the peripheral velocities of the two rollers 8 and 17 cannot be altered one in relation to the other, given that the strip 4 passes directly from the first to the second. In the example of fig 2, the position of the one roller 22 can be made adjustable in relation to the other roller 17, according to the thickness of the strip 4, though the clearance must remain constant during operation. Further advantages of the cutter device 1 according to the invention include the absence of wear and vibration achieved by virtue of the fact that there is no contact between the cutting edge 71 and the meeting edge 21 of the longitudinal cutting means. The advantage of simplicity in construction is evident in both embodiments of the cutter device 1 illustrated, i.e. as in fig 2 and in fig 3, insofar as there is no need for any synchronization between the cutting edge 71 and the meeting edge 21 which effect the longitudinal cut.

1 11 claims A device for cutting strip material in machines for packaging commodities, comprising means serving respectively to effect a transverse cut and to effect a longitudinal cut in a continuously fed strip, of which at least the transverse cutting means interact with reaction means designed also to support, retain and advance the strip, characterized in that the longitudinal cutting means comprise a knife and a relative reaction element rotatable about mutually parallel respective axes, of which the relative active profiles describe circular trajectories that are distanced axially one from the other in such a manner that the cutting edge of the knife does not enter into contact with the meeting edge of the reaction element.

2) A device as in claim 1, wherein the knife of the longitudinal cutting means is associated with a first cylindrical roller serving to retain and 12 advance the strip, and disposed with its cutting edge projecting from the roller in a direction normal to the generators of the rolling face, whilst the meeting edge of the reaction element is afforded by the circumferential edge of a second cylindrical roller positioned in close prox.imity to the trajectory described by the cutting edge of the knife and substantially tangential to the first roller.

A device as in claim 2, wherein the second roller is mechanically and coaxially associated with a Lurther cylindrical transmission roller faced with or fashioned in a resilient material, positioned permanently in contact with and thus caused to rotate about its own axis by the first roller.

4) A device as in claim 2, wherein the knife, required to effect a succession of discrete longitudinal cuts, consists in at least one sector to a circle associated coaxially with the first cylindrical roller.

A device as in claim 1, wherein the reaction mean.--interacting with the transverse cutting means 13 consist in a cylindrical roller affording at least one longitudinal striking plate a.nd incorporating the reaction element of the longitudinal cutting t ncides with the means, of which the meeting edge co edge of a circumferential seating afforded by the selfsame cylindrical roller.

6) A device for cutting strip material in machines for packaging commodities, substantially as described with reference to the figures of the accompanying drawings.