ROTARY CUTTING HEAD, PARTICULARLY FOR TOBACCO CUTTING MACHINES

Abstract: The device comprises: a fixed support structure (A, B); a shaft (1) supported by the structure (A, B) so as to be rotatable about an axis lying at an angle to the direction of advance of the block of tobacco (24); at least one movable element (15) rotatable by the shaft (1) and carrying at least one cutting blade (20) adapted to intersect and penetrate a block of tobacco (24) leaving the supply device (21, 25, 26), the blade (20) being movable axially relative to the shaft (1); drive means (4) for rotating the shaft (1), and control means (12, 13, 18) for effecting an axial translational movement of the blade (20) of the at least one movable element (15) in synchronism with the rotation of the shaft (1) during the cutting of the block of tobacco (24).

Description: Rotary cutting head, particularly for tobacco cntτing machines The present invention relates to a rotary cutting head, particularly for tobacco cutting machines. It is known that, in order to make high quality cigarettes, it is necessary for the tobacco to be cut cleanly into strips of uniform width in an optimum manner, with a minimum percentage of tobacco powder. The object of the present invention is to provide a rotary cutting head'which is particularly suitable for tobacco cutting machines and enables a block o£ tobacco leaving a supply device to be cut in an optimum manner, so that the tobacco is effectively cut and not broken into bits, and has very uniform dimensions .and a minimum percentage of powder. This object is achieved according to the invention by means of a cutting head according to the appended Claim 1. —I Further characteristics and advantages of the cutting head according to the invention will become apparent from the detailed description which follows with re_-3'reE_-__e to the appended drawings, provided purely by way of non-limiting example, in which: Figure 1 is a partially-sectioned, cut-away front view of part of a tobacco cutting machine incorporating a cutting head according to the present invention, - 2 - Figure 2 is a simplified side elevational view of the raas ine shown in Figure 1, with the associated device for supplying a block of tobacco by extrusion, Figure 3 is a simplified view of the machine shown in Figure 1 from above, Figure 4 is a front view of a cam included - in the machine of Figure 1, Figure 5 is a simplified, partially-sectioned front view similar to the view.of Figure 1, Figure 6 is a front view of a tappet-holder disc forming part of the machine according to the invention, * Figures 7 and 8 are two cross-sectional views, on an enlarged scale, of a movable blade-holder device forming part of the cutting head according to the invention, in first and second conditions of use respectively, Figure 9 shows a detail on the arrow IX Figure 8, and" Figure 10 is a sectional view taken on the line X-X of Figure 9. Figure 1 shows a tobacco cutting machine comprising a fixed support structure including two vertical pillars A and B located side by side. A cutting head according to the present invention, generally indicated H, is rαtatably mounted between the- pillars. e head includes a shaft 1 rotatably supported at its ends by - 3 - the pillars A and B by means of rolling bearings 2, and held axially by a double thrust bearing 3. One end of the shaft 1 passes through the pillar B and a pulley 4 is keyed onto it. A hub 7 „disposed around the shaft 1 is clamped axially by means of a sealed keying device 6 of known type and is rendered rigid with the shaft by means of keys 8. A hub 10 is mounted on the shaft between the end of the hub 7 facing the pillar B and the pillar, an d has a circumferential disc appendage 11. The hub 10 is slidable axially along the shaft 1 but is rendered torsionally rigid with the latter by means of keys 9. The end of the shaft 1 which passes through the 'pillar B is hollow so as to allow the pneumatic supply of a plurality of pusher cylinders 12 arranged parallel to the shaft 1 and each having its respective body fixed to a radial appendage of the hub 7. A rotary pneumatic distributor of known type is mounted on the hollow end of the shaft 1. In the embodiment shown by way of example in the drawings, the cutting head has six cutting blades 20 each carried by a respective movable elements 15. For simplicity, Figure 2 illustrates only one movable element 15, although all the other blades are indicated. Each movable element includes a shaped blade-holder body 15 which, as seen particularly from Figures 2, 7 and 8, is provided on one side with a pair of parallel guides 14 having respective V-shaped guide profiles which engage, in the corresponding V-shaped grooves in a plurality of pairs of opposing rollers 16 (Figures 1 and 2) carried by a corresponding longitudinal flange 7a lying almost tangential to the hub 7 (Figure 2). The movable elements 15 are thus rigid for rotation with the shaft 1 and the hub 7 but can move axially relative to them. As soon particularly from Figures 1, 3 and 5, each movable element 15 carries, at its end facing the pillar A, a roller 17 which engages the drive profile of a bell-shapod cam member 18 fixed to the top of the column and having a central hub-shaped portion in which the shaft 1 is supported for rotation. Each cylinder 12 is associated with a correponding movable element 15 and- as shown partieularly in the lower part of Figure 1. tne rod of each αf these cylinders is connected to one end of t e associated movable element. When the cutting head H is rotated by means of a belt coupled with the pulley 4 , the pressure supplied to the cylinders 12 makes them urge the movable elements 15 into the position in which the respective feeler roller 17 engages the shaped drive profile of the cam 18. For each revolution effected by the head H, the movable blade-holder elements 1^ execute a reciprocating axial translational movement. The cam 18 is particularly shaped so that, under the action of the pneumatic cylinders 12, each movable blade-holder element 15 effects a sharp axial movement (from right to left for an observer of Figures 1 and 3) when the blade carried thereby passes in front of the aperture or outlet opening 21 of an extrusion supply device C{Figure 2)and intersects and penetrates the block of tobacco 24. By way of example, Figure 2 illustrates a known type of supply device for extruding a wad of tobacco, including a lower fixed track 25 and an upper movable track 26. Each blade 20 of the cutting head thus penetrates the mass or block of tobacco with a true and proper slicing action, achieving an optimum clean cut through the tobacco with a minimum percentage of powder. As stated above, the axial translational movement of the movable elements 15 is controlled by the drive profile of the cam 1>8 and is determined by the force of the pneumatic cylinders 12, each of which acts on a respective movable element. These cylinders, con¬ veniently °f t ~ single-acting type, are kept constantly under pressure from a pressure supply by * means of the rotary pneumatic distributor 13 and through the hollow shaft 1. The blades 20 may be sharpened periodically, for example, by means of a rotary grinding wheel 22 operated by a motor 22a carried by an axially movable support structure 23. «■ The cutting device according to the invention is not provided with any heating system for cleaning the cutting blades 20. In effect, in the device according to the invention, a certain quantity of heat is developed as a result of the action of the pneumatic cylinders 12 and it , also has an automatic self-cleaning effect on the blades as a result of their axial translational movement. Of particular importance in a rotary cutting device for tobacco is the micrometric regulation of the position of the cutting blades for recovery of wear. In the device of the invention, the wear of the cutting edge of the blade is considerably reduced compared with prior art guillotine cutting devices. However, it is in any case necessary periodically to effect a micrometric advance of the blades to recover the wear due to cutting and to enable the sharpening device 22 to dress the cutting edge. With reference to Figures 5, 7 and 8, there is mounted in each movable element 15 a ' rack rod 27 which extends longitudinally along the entire element and is movable axially relative thereto under the action of a spring 29 (Figure 5). ' This spring, which reacts against an annular end shoulder of the rack 27, keeps the fatter projecting permanently from the element 15 (towards the right for an observer of Figure 5). The projecting end of each rack 27 faces and is aligned with a respective tappet 31 carried by the disc portion 11 of the hub 10. As stated above, the disc 11 is slidable axially along the shaft 1 and, in the embodiment illustrated, carries six tappets 31 arranged parallel to the axis of the shaft 1, at positions axially adjustable by screws 32. As shown in Figures 5, 7 and 8, two internally-threaded bushes 36 are provided adjacent the rack 27 in each movable element 15 and have their axes arranged perpendicular to the, length of the rack 27. and trie blade 20. These bushes are coupled by free wheel devices 35 to sprockets 28 which mesh with the rack 27. The threaded portions 37a of rods 37 are engaged in the - 7 - internal threadings of the bushes 36 and extend through a ~ .e_?-ber 38 to which the cutting blade 20 is fixed by means of screws 39. The heads of the --" ■ -'-"- 39 extend into slots in the upper covering member of the movable eleme-.- 15. These' slots are arranged, as shown in Figure 3, to allow the cutting blade 20 to move in the direction of the axes of the rods 37. The free wheel devices 35, which are of known type, enable the threaded bushes 36 to rotate solely in the sense corresponding to unscrewing of these bushes from the threaded parts of -he rods 37, and hence enable the cutting blades 20. to move towards the right for an observer of Figures 7 and 8. The position of the disc 11 relative to the shaft. 1 can be controlled bv means of a lever 33 pivoted at 33a (Figure 1} and having one end articulated to the rod of a pneumatic cylinder 34 controlled by a programmed electronic unit 50 through solenoid valves 51. 3y means of the cylinder 34 and the lever 33, the disc 11 can be moved between a withdrawn or rest position, illustrated R in Figure 1, in which the tappets 31 do not interfere with the racks 27 of the movable elements* and a plurality of advanced positions, such as that indicated in Figure 1, in which the tappets 31 can make the racks 27 re-enter the movable elements 15 when these are urged towards the. pulley 4 by the cam 18. When the rack 27 of a movable element 15 is made to re-enter (Figure 5), it- : causes a rotation of _ the sprockets 28 and, by means of the free wheel devices 35, a corresponding rotation of the threaded bushes 3-6 and unscrewing of the bolts 37 from these bushes. The associated cutting blade 20 is then advanced. The amount of advancement of the cutting blade 20 depends on the amount of axial movement of the rack 27 caused by the tappet-holder disc 10. Figure 7 shows a movable element with a new cutting blade 20, while Figure 8 shows a movable element in which the blade 20 has a smaller width as a result of considerable wear and is held in an advanced position by the wear take-up device described above. When a rack 27 is made to re-enter its respective movable element by the tappets of the disc 11, the threaded bushes 36 act on the threaded portions 37a of the bolts 37 in the manner of nuts. These bolts move axially, their rotation being prevented by screws 40 (Figures 9 and 10) which are screwed into the blade-holder member 38 and the heads of which extend into lateral recesses formed in the end heads of the bolts 37. When it is necessary to return the blade-holder members 38 to the withdrawn position illustrated in-. Figure 7, it suffices to loosen the clamping screws 40 to free the heads of the bolts 37, and then to rotate the latter in the sense in which they screw into the threaded bushes 36. in order to replace the cutting blades 20, it suffices to remove the screws 39. Naturally, the principle of the invention remaining the same, the forms of embodiment and details of realisation - 9 - may be varied widely with respect to that described and illustrated purely by way of non-limiting example, without thereby departing from the scope of the present invention.

Claims: - 10 - CLAIMS 1. Cutting device, particularly for cutting a block of tobacco (24) leaving a supply device (21, 25, 26), characterised in that it comprises: a fixed support structure (A,B); 5 a shaft (1) supported by the structure (A,B) so as to ** be rotatable about an axis lying at an angle to the direction of advance of the block of tobacco (24) * , at least one movable element (15) rotatable by the shaft (1) and carrying at least one cutting blade (20) 0 adapted to intersect and penetrate a block of tobacco (24) % leaving the supply device (21,25,26), the blade (20) being movable axially relative to the shaft (1) ; drive means (4) for rotating the shaft (1) , and control means (12 * 13, 18) for effecting an axial 5 translational movement of the blade (20) of the at least one movable element (15) in synchronism with the rotation of the shaft (1) during the cutting of the block of tobacco (24). 2. Device according to Claim 1, characterised in ~ 0 that control means include a stationary cam member (18) having a shaped drive profile, and in that the at least one blade (20) is operatively associated with a feeler member (17) cooperating with the cam profile (18) and thrust means (12) arranged to urge the feeler 25 (17) against the drive profile of the cam member (18). - 11 - 3. Device according to Claim 2, characterised in that the thrust means include a pneumatic cylinder (12). 4. Device according to Claim 1, characterised in that it includes a plurality of movable elements (15) which are equiangularly-spaced about the shaft (1) and each of which carries at least one cutting blade (20). 5. Device according to any one of the preceding claims, characterised in that it includes regulating means (10,11,26-40,50,51) for causing a controlled advance of the cutting blade (20) of each movable element (15) in a direction perpendicular to the cutting edge of the blade (20) to compensate for wear of the blade.

Inventors: BRAGAGLIA GIORGIO, BRAGAGLIA, GIORGIO
Applicants: COMAS SRL, COMAS S.R.L.
Application year: 1987
Main classification: A24B7
IPC codes: A24B7, A24C5, B26D1, B26D7