A GUMMING DEVICE

Abstract: The invention relates to a gumming device wherein a gumming roller (5) and a dosing roller (7) with horizontal, counter-rotating axes (11, 16) are elastically pressed against each other and have respective, essentially cylindrical surfaces (9, 13) in contact with each other in a zone (22) of tangency along a common generator to form a space (23); an adhesive substance (2) is fed to the space (23) through a distributor element (27) that has an end portion (28) located between the rollers (5, 7) at and over the space (23) and laterally defined by cylindrical surfaces (35, 36), these surfaces being coaxial with the rollers (5, 7) and, together with the surfaces (9, 13) of the rollers (5, 7) define two feed channels (37, 38); the distributor element (27) has two opposite downflow walls (29, 30) connected to the channels (37, 38), the adhesive (2) flowing down the walls (29, 30) through the channels (37, 38) to the zone (22) of tangency between the two rollers (5, 7) according to a laminar flow (31, 32).

Description: Description A gumming device Technical Field The present invention relates to a gumming device. The invention can be used to good advantage to apply an adhesive substance to lengths of paper tape in machines for the tobacco industry to which the description below refers but without thereby restricting the scope of the invention. In particular, the invention relates to a gumming roller device used in a cigarette filter tip attaching machine to apply a layer of adhesive substance to a continuous paper tape that is subsequently cut into individual lengths or strips to be used to attach the filter tips to cigarettes. Background Art A gumming device used to apply a layer of adhesive to a continuous paper tape from which the connecting strips of filter paper for a cigarette filter tip attaching machine are cut is disclosed by United Kingdom patent No .2 , 067 , 436 , this gumming device comprising a pair of horizontal, counter-rotating rollers, placed side by side and elastically pressed against each other along a zone of reciprocal tangency. One of the two rollers is a dosing roller and the other a gumming roller whose surface, being essentially cylindrical, is tangent to the continuous tape. The facing portions of the two cylindrical surfaces, just above the zone of tangency between the dosing roller and the gumming roller, define a space above which there is located a nozzle connected to the outfeed end of a pipe from a tank containing an adhesive substance. The adhesive accumulates inside the said space, which extends along the entire contact generator between the two rollers, so as to constantly supply the gumming roller. While the gumming roller rotates in a defined direction, its outer cylindrical surface transfers a layer of adhesive to the continuous paper tape, the thickness of the layer being adjusted by the pressure between the two rollers. Practice has shown that a gumming device of the type described cannot cope with the high operating speeds reached by the latest generation, of cigarette makers, causing the two rollers to turn at very high speeds, because it is unable to correctly transfer a layer of adhesive onto the surface of the of the continuous paper tape to be gummed. This is because the mass of adhesive substance inside the said space is subjected to a high-speed wave-like motion by the cylindrical surfaces of the two rollers, giving rise to strong turbulence with high pressure gradients within the mass of adhesive. This turbulence traps air inside the adhesive creating bubbles and causing the adhesive to splash when the air bubbles burst. Moreover, when the air bubbles come into contact with the cylindrical surface of the gumming roller, they prevent the adhesive from being properly distributed on the surface and creating breaks and uneven patches in the layer of adhesive transferred by the gumming roller. As a result, parts of the surface of the continuous paper tape to be gummed have no adhesive on them at all. Disclosure of the Invention The aim of the present invention is to provide a gumming device that overcomes the above mentioned disadvantages. Accordingly, the present invention provides a gumming device comprising a first and a second roller, with horizontal, parallel axes, in contact with each other at a zone of tangency along a common generator, defining a space between the respective cylindrical surfaces just above the zone of tangency; and means for feeding an adhesive substance into the space, the device being characterized in that the adhesive feed means comprise means designed to distribute the adhesive located and shaped in such a way, in relation to the rollers, as to partially occupy the space. The invention will now be described with reference to the accompanying drawings which illustrate two preferred embodiments of the invention and in which: Figure 1 is a front view, partly m cross section and with some parts cut away m order to better illustrate others of a preferred embodiment of the gumming device made according to the present invention; - Figure 2 is a front view, partly m cross section and with some parts cut away in order to better illustrate others of another preferred embodiment of the gumming device illustrated m Fig. 1. With reference to Fig 1, the numeral 4 indicates a cigarette filter tip attaching machine illustrated only partially and the numeral 1 indicates as a whole a gumming device used to apply an adhesive substance 2 to a continuous paper tape 3 which moves forward m a feed direction D and which is cut into individual lengths (not illustrated) used to attach filter tips (not illustrated) to cigarettes (not illustrated) . The device 1 comprises a first, gumming roller 5 designed to apply a layer of adhesive substance 2 to the tape 3 at a gumming station 6, a second, dosing roller 7 designed to operate m conjunction with the gumming roller 5 to dose the quantity of adhesive 2 to be applied to the tape 3 and a unit 8 for the continuous feeding of the adhesive 2 to the two rollers 5 and 7. The gumming roller 5 has a cylindrical lateral surface 9, which is tangent to the tape 3 at a gumming station 6, and is keyed to a shaft 10 with a horizontal axis 11 The shaft 10 is driven by a motor (not illustrated) ana rotates the roller 5 about the axis 11, m a counterclockwise direction m Fig. 1, relative to a fixed fork 12 which supports the shaft 10 itself. The dosing roller 7 has an essentially cylindrical outer surface, with recessed areas or pockets 14, and is keyed to a central shaft 15 whose axis 16 is essentially horizontal and parallel to the axis 11 with which the axis 16 makes an essentially horizontal plane. As shown m F g. 1, the shaft 15, which is driven by the shaft 10 through transmission means that are not illustrated, rotates the roller 7 about the axis 16 at a peripheral speed equal to that of the roller 5 and is supported by a fork 17 m such a way that it can rotate. The side of the fork 17 opposite that which supports the shaft 15 is hinged to a fixed frame 18 in such a way that it can swing in relation to the frame 18 itself about an axis 19 parallel to the axes 11 and 16, under the action of an actuator 20. The actuator 20 and the fork 17 together form a pushing device designed to move the dosing roller 7 closer to the gumming roller 5 so that their respective outer surfaces 9 and 13 come into contact with each other at a zone 22 of tangency along a common generator, parallel to the axes 11 and 16, thus defining a space 23 between the zone 22 of tangency and the parts of the surfaces 9 and 13 upstream of the zone 22 of tangency in relation to the sense of rotation of the rollers 5 and 7. As shown in Fig. 1, the feed unit 8 comprises a tank S containing the adhesive 2 and having an outfeed pipe 24 which communicates with an essentially funnel-shaped receptacle 25 in which the adhesive 2 collects and having an outlet 26 at which there is located a distributor element 27 whose longitudinal dimension, measured in a direction parallel to the axes 11 and 16 of the rollers 5 and 7, is substantially the same as the longitudinal dimension of the rollers 5 and 7. As illustrated in Fig. 1, the distributor element 27 has a head 27a, which joins the aforesaid outlet 26 of the receptacle 25 in such a way as to leave two lateral gaps or slits 33 and 34 for the outflow of the adhesive 2, an end portion 28, located and shaped in such a way as to partially occupy the aforementioned space 23, and two opposing lateral walls 29 and 30 that connect the head 27a to the end portion 28. The two lateral walls 29 and 30 form in the distributor 27 two adhesive 2 downflow surfaces 29 and 30 which hydrodynamically and uninterruptedly connect the two lateral outflow gaps 33 and 34 to the aforementioned end portion 28, which, in the embodiment illustrated in Fig. 1, is essentially cusp-.shaped with a rounded vertex V located in the proximity of, and facing, the aforesaid zone 22 of tangency between the rollers 5 and 7. A s shown in Fig. 1, the end portion 28 is laterally defined by two essentially cylindrical lateral surfaces 35 and 36, which are essentially coaxial with the rollers 5 and 7 and which meet at RECTIFIED SHEET (RULE 91) the vertex V. The surfaces 35 and 36, together with the surfaces 9 and 13 of the rollers 5 and 7, form two arched channels 37 and 38, which connect with the downflow surfaces 29 and 30 and form two channels that feed the adhesive 2 to the zone 22 of tangency between the two rollers 5 and 7. Again with reference to the sense of rotation of the rollers 5 and 7, as shown in Fig. 1, the gumming device 1 comprises, in the area below the zone 22 of tangency between the two rollers 5 and 7 , a recycling vessel 40 which communicates with a pipe 41 through which the adhesive 2 that collects in the vessel 40 is pumped back into the tank S by a pump 42. During operation, before the tape 3 starts being gummed, the device 21 is activated so as to elastically press the rollers 5 and 7 against each other, with their surfaces 9 and 13 in contact at the aforesaid zone 22 of tangency along a common generator. After this, the adhesive 2 feed unit 8 is activated and the adhesive starts flowing out through the pipe 24 and collects in the receptacle 25. In particular, the adhesive 2 is fed at a rate such as to keep the level in the receptacle 25 constant. Thus, the adhesive 2 flows with constant motion towards the outlet 26 and through the outflow slits 33 and 34 to reach the distributor element 27 on whose downflow surfaces 29 and 30 there are formed essentially laminar flows 31 and 32 of adhesive 2, respectively. The flows 31 and 32 move by gravity until they arrive at the channels 37 and 38, along which the flows 31 and 32 run essentially tangent to the respective surfaces 9 and 13 of the rollers 5 and 7 and reach a zone of confluence 39 between the surfaces 9 and 13, limited, at the top, by the vertex V of the element 27 and, at the bottom, by the zone 22 of tangency between the rollers 5 and 7. The adhesive is free to flow out of the zone of confluence 39, which is open at both the longitudinal ends, and drops into the vessel 40. As the laminar flows 31 and 32 pass through the channels 37 and 38, the adhesive 2 adheres to the surfaces 9 and 13 of the rollers 5 and 7 and, following the rotation of the rollers 5 and RECTIFIED SHEET (RULE 91) ISA/EP 7, is drawn towards the zone of tangency 22 and out of the space 23. As it continues to rotate, the gumming roller 5 transfers the adhesive 2 picked up in this way to the station 6 where a layer of the adhesive 2 is applied to the tape 3. The thickness of the adhesive 2 that adheres to the roller 5 depends on the pressure with which the dosing roller 7 is pressed against the gumming roller 5 and, in particular, only the quantity of the adhesive 2 that flows inside the pockets 14 of the roller 7 is allowed to flow out of the space 23. It should be noticed that, during the operation of the device 1, the particles or droplets G of adhesive 2 which inevitably drop off the roller 5 just downstream of the station 6, in relation to the feeding of the tape 3 in the direction D, and which are the parts of the adhesive 2 which have not adhered to the tape 3, are intercepted by the wall 29 on which the flow 31 runs, thus preventing the droplets G from being splashed onto parts of the filter tip attaching machine 4. In the embodiment illustrated in Fig. 2, the downflow section of the element 27 is only the wall 29 while its portion 35 is coupled with the surface 9 of the gumming roller 5 to form the channel 37, and it is along the latter that, during operation, the adhesive 2 adheres to the surface 9 of the gumming roller 5. From the above description, it appears that the distributor means 25, 27, and, in particular, the presence of the portion 28 within the space 23, make it possible to prevent turbulence in the adhesive which, as stated above, in the devices known to prior art, prevent the adhesive from being applied correctly to the tape 3.

Claims: Claims 1. A gumming device comprising a first and a second roller (5, 7), with horizontal, parallel axes (11, 16), in contact with each other at a zone (22) of tangency along a common generator, defining a space (23) between the respective cylindrical surfaces (9, 13) just above the zone (22) of tangency; and means (8) for feeding an adhesive substance (2) into the space (23), the device (1) being characterized in that the adhesive feed means (8) comprise means (25, 27) designed to distribute the adhesive (2) located and shaped in such a way, in relation to the rollers (5, 7) , as to partially occupy the space (23) . 2. A gumming device comprising a first and a second roller (5, 7) , with horizontal, parallel axes (11, 16) , in contact with each other at a zone (22) of tangency along a common generator, defining a space (23) between the respective cylindrical surfaces (9, 13) just above the zone (22) of tangency; and means (8) for feeding an adhesive substance (2) into the space (23), the device (1) being characterized in that the adhesive feed means (8) comprise means (25, 27) designed to distribute the adhesive (2) and having an end portion (28) located between the rollers (5, 7) at the space (23) over the zone (22) of tangency. 3. The device according to claim 2 characterized in that the end portion (28) is laterally defined by at least one essentially cylindrical surface (35, 36) that is essentially coaxial with one of the two rollers (5, 7) and, together with the surface (9, 13) of the roller (5, 7) , defines a channel (37; 38) that feeds the adhesive (2) to the zone (22) of tangency between the two rollers (5, 7) . 4. The device according to claim 2 characterized in that the end portion (28) is laterally defined by essentially cylindrical surfaces (35, 36) that are essentially coaxial with the rollers (5, 7) and, together with the surfaces (9, 13) of the rollers (5, 7) , define two channels (37, 38) that feed the adhesive (2) to the zone (22) of tangency between the two rollers (5, 7) . 5. The device according to claim 3 or 4 characterized in that the means (25, 27) for distributing the adhesive (2) are defined, above the end portion (28), by downflow walls (29, 30) connected at the bottom to the channels (37, 38) and designed to convey an essentially laminar, continuous flow of adhesive (2) from a tank (S) to the channels (37, 38) themselves. 6. The device according to any of the foregoing claims from 1 to 5 characterized in that the distributor means (25, 27) comprise an essentially funnel-shaped receptacle (25) in which the adhesive (2) collects and connected to an element (27) that distributes the adhesive (2) itself; a tapered end portion (28) of the distributor element (27) being located in the space (23) and being in cross section essentially in the shape of a cusp with a rounded vertex (V) facing the zone (22) of tangency between the two rollers (5,7); the distributor element (27) having first and second downflow walls (29, 30) opposite each other; the first wall (29) having, at the end portion (28) , a portion (35) that is essentially adjacent to the surface (9) of the first roller (5) and the second wall (30) having a portion (36) that is essentially adjacent to the surface (13) of the second roller (7) ; the adhesive (2) flowing down at least one of the first and second walls (29, 30) according to a laminar flow (31, 32) . 7. The device according to claim (6) characterized in that the portions (35, 36) are parts of cylindrical surfaces which meet at the vertex (V) and are coupled, respectively, with the surface (9) of the first roller (5) and with the surface (13) of the second roller (7) in such a way as to form with the surfaces (9, 13) themselves a first curved channel (37) and a second curved channel (38), at least one of the first and second channels (37, 38) being crossed by an essentially laminar flow (31, 32) of adhesive (2) . 8. The device according to any of the foregoing claims from 1 to 7 characterized in that the first roller (5) is a gumming roller (5) positioned tangent to a continuous tape of paper (3) feeding in a direction (D) so as to apply the adhesive (2) to the tape (3) at a gumming station (6); the second roller (7) being a dosing roller (7) to dose the quantity of adhesive (2) on the gumming roller (5) . 9. The device according to one of the foregoing claims from 6 to 8 characterized in that the first wall (29) of the distributor element (27) is designed to intercept droplets (G) of adhesive (2) that drop off the gumming roller (5) just downstream of the gumming station (6) in the feed direction (D) of the tape (3) . 10. A cigarette making machine characterized in that it comprises a gumming device as described in claims 1 to 9.

Inventors: DRAGHETTI FIORENZO, GHERARDI GIAN LUIGI, DRAGHETTI, FIORENZO, GHERARDI, GIAN, LUIGI
Applicants: DRAGHETTI FIORENZO, GD SPA, GHERARDI GIAN LUIGI, DRAGHETTI, FIORENZO, G.D S.P.A., GHERARDI, GIAN, LUIGI
Application year: 1998
Main classification: B05C1
IPC codes: B05C1