Cut and seal unit for sheet material

Abstract: A cut and seal unit (1) for sheet material (4), the unit being defined by two rollers (6, 7) located on either side of the path (P) of the sheet material (4), mounted for rotation about respective fixed parallel axes (8, 9), and presenting respective cut and seal heads (10, 11) cooperating cyclically with each other at a portion (12) of the path (P) extending between the two rollers (6, 7); the heads (10, 11) presenting respective cutting operating members (18, 21) and respective sealing operating members (19, 22); and at least one of the operating members (18, 19; 21, 22) of each head (10; 11) being movable in relation to the relative axis (8; 9) and to and from the other axis (9; 8) by a respective adjusting device (32; 51).

Description: The present invention relates to a cut and seal unit for sheet material. The present invention may be used to advantage in the food packing industry, to which the following description refers purely by way of example. In the food packing industry, so-called "form fill and seal" machines are used whereby an orderly succession of equally spaced products is fed along a given path, and inside a tubular wrapping, between two opposed rollers of a cut and seal unit. The two rollers have respective cutting and sealing tools cooperating cyclically with each other with the tubular wrapping in between; and the unit provides for sealing the opposite walls of the tubular wrapping at a seal portion between each pair of adjacent products, and for simultaneously cutting the tubular wrapping at each seal portion to form a succession of sealed wrappings, each containing a respective product. The two cut and seal rollers normally extend crosswise to the path of the tubular wrapping, are fitted to respective shafts rotating respectively about a fixed axis and a transversely movable axis, and are maintained substantially tangent to each other by a spring assembly acting transversely on the movable-axis shaft. The above known cut and seal unit has several drawbacks, mainly due to the difficulty in adjusting the spring assembly to keep the rollers perfectly parallel, which is an essential condition for ensuring an even seal, completely cutting the tubular wrapping, and at the same time compensating for wear of the cutting and sealing tools. The aforementioned drawback is partially overcome by the cut and seal unit for sheet material disclosed in DE-A-1921817, where two rollers are provided located on either side of a path of the sheet material, mounted for rotation about respective fixed parallel axes, and having respective cut and seal heads cooperating cyclically with each other at a portion of the path extending between the two rollers. Each cut and seal head comprises respective cutting operating members and respective sealing operating members, and the cutting operating members of one head are movable in a radial direction in relation to the relative axis and to and from the other axis. The above known cut and seal unit allows keeping the rollers perfectly parallel, but involves a relatively poor quality of sealing, due to the absence of any adjusting device for compensating the wear of the sealing tools. It is an object of the present invention to provide a cut and seal unit designed to overcome the aforementioned drawback. According to the present invention, there is provided a cut and seal unit for sheet material, the unit comprising a first and second roller on either side of a path of the sheet material and rotating respectively about a first and second axis fixed and parallel to each other; and at least a first and second cut and seal head fitted respectively to the first and second roller and cooperating cyclically with each other at a portion of said path extending between the rollers; said first and second head comprising operating means in turn comprising respective first and second cutting operating means, and respective first and second sealing operating means; characterized in that at least one of said cutting operating means and at least one of said sealing operating means are movable operating means movable in a radial direction in relation to the relevant axis and to and from the other axis; a first and second adjusting device being associated respectively with the cutting operating means and the sealing operating means; and each of said adjusting devices comprising lock means for locking one of the relevant operating means in relation to the relevant said axis and in such a position as to be tangent to said path; the other of the relevant said operating means being a said movable operating means. The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a front view of the cut and seal unit according to the present invention; Figure 2 shows a section along line II-II in Figure 1; Figure 3 shows a section along line III-III in Figure 2; Figure 4 shows a section along line IV-IV in Figure 2. Number 1 in Figure 1 indicates a cut and seal unit for packing products 2 inside respective so-called "pillow pack" wrappings 3 formed by cutting into portions a tubular wrapping 4 fed axially in direction 5 along a path P extending through unit 1. Unit 1 comprises two rollers 6 and 7 mounted for rotation about respective fixed axes 8 and 9 located crosswise to direction 5 and on either side of path P. Rollers 6 and 7 present respective operating heads 10 and 11 equally spaced about respective axes 8 and 9, and are connected to a known actuating device (not shown) by which they are rotated in opposite directions and in time with each other, so that each head 10 travels along a portion 12 of path P in direction 5 simultaneously with a corresponding head 11. As shown in Figures 3 and 4, rollers 6 and 7 comprise respective tubular bodies 13 and 14 coaxial with respective axes 8 and 9 and from which respective longitudinal forks 15 and 16 extend radially outwards. Each fork 15 comprises two arms 17 parallel to each other and to axis 8, and forms the inner supporting structure of a respective head 10, which comprises a cutting member 18 housed between and sliding in relation to arms 17 in a radial direction in relation to axis 8, and a substantially cup-shaped sealing member 19 located with its concavity facing axis 8, and fitted to relative fork 15 so as to slide in relation to arms 17 and in a radial direction in relation to axis 8. Each fork 16 comprises two arms 20 parallel to each other and to axis 9, and forms the inner supporting structure of a respective head 11, which comprises a cutting member 21 housed between and sliding in relation to arms 20 in a radial direction in relation to axis 9, and a substantially cup-shaped sealing member 22 located with its concavity facing axis 9, and fitted to relative fork 16 so as to slide in relation to arms 20 and in a radial direction in relation to axis 9. At the ends facing radially outwards in relation to respective axes 8 and 9, sealing members 19 and 22 are closed by respective walls 23 and 24 defined externally by respective cylindrical, longitudinally grooved surfaces 25 and 26, which are coaxial with respective axes 8 and 9, and present respective longitudinal openings 27 and 28 engaged in sliding manner by respective cutting members 18 and 21. Each pair of corresponding cutting members 18 and 21 define a cutting assembly 29, and respectively comprise a blade, hereinafter indicated 18, with an end cutting edge 30 parallel to axis 8, and an anvil, hereinafter indicated 21, presenting a flat end surface 31 parallel to axis 9 and which is positioned tangent to edge 30 of blade 18 at portion 12 to transversely cut wrapping 4. To ensure cutting members 18 and 21 of each cutting assembly 29 are always positioned tangent to each other at portion 12 of path P, each assembly 29 presents an adjusting device 32 comprising an actuating device 33 connected to a first of members 18 and 21 to move it radially in relation to relative tubular body 13, 14 and lock it in a given radial position, and an elastic thrust device 34 interposed between a second of members 18 and 21 and relative tubular body 13, 14, to push the second cutting member towards the first. In the example shown, actuating device 33 is connected to anvil 21 and comprises two pins 35, each of which is fitted for rotation through two holes 36 formed through arms 20 of relative fork 16 and coaxial with each other and with an axis 37 crosswise to axis 9. Each pin 35 presents a cylindrical intermediate portion 38 eccentric in relation to axis 37 and which engages a slot 39 formed through anvil 21 and presenting a width, measured crosswise to axis 9, equal to the diameter of intermediate portion 38, and a length, measured parallel to axis 9, equal to at least the diameter plus twice the eccentricity of intermediate portion 38. A threaded end portion of pin 35 projects outwards of relative fork 16, and engages a nut 40 for axially locking pin 35 to fork 16. By rotating pins 35 about respective axes 37, actuating device 33 as described above provides for maintaining surface 31 of anvil 21 perfectly parallel to axis 9 and in such a position as to travel, as tubular body 14 is rotated about axis 9, along a path tangent to path P at portion 12. In the example shown, elastic device 34 is defined by a tube 41 presenting a longitudinal cut 42 and fitted by radial pins 43 to the bottom of relative fork 15, parallel to axis 8, between relative arms 17, and in contact with the lateral surface 44 of blade 18 at the opposite end to cutting edge 30. Blade 18 presents a transverse through hole 45 engaged in radially slack manner by the central portion of a cylindrical pin 46, the opposite end portions of which engage two holes 47 coaxial with each other and with an axis 48 crosswise to axis 8 and formed through arms 17 of relative fork 15, and two sliding pads 49 interposed between arms 17 and blade 18. The radial slack between the surface of hole 45 and the surface of pin 46 defines the maximum radial travel of blade 18 in relation to tubular body 13 and between an extracted and a withdrawn position in which the distance between cutting edge 30 and axis 8 is respectively greater and smaller than the distance between portion 12 and axis 8. Consequently, if, by means of actuating device 33, the distance between surface 31 of anvil 21 and axis 8 is maintained equal to the distance between axis 8 and portion 12, the cutting edge 30 of blade 18 is brought into contact with the corresponding surface 31 at a given pressure, depending on the transverse elasticity of tube 41, when blade 18 skims portion 12 together with anvil 21. Each pair of corresponding sealing members 19 and 22 define a respective sealing assembly 50 in which surfaces 25 and 26 are positioned tangent to each other at portion 12 to seal tubular wrapping 4 along the transverse cut made through wrapping 4 by respective cutting assembly 29. To ensure sealing members 19 and 22 of each sealing assembly 50 are positioned tangent to each other at portion 12 of path P, each assembly 50 presents an adjusting device 51 comprising a lock device 52 connected to a first of members 19 and 22 to lock it radially in relation to relative tubular body 13, 14, and an elastic thrust device 53 interposed between a second of members 19 and 22 and relative tubular body 13, 14 to push the second sealing member towards the first. In the example shown, lock device 52 is connected to member 19 and comprises three screws 54, each of which engages in rotary manner a hole 55 formed through a lateral wall of member 19, and a threaded through hole 56 formed through arm 17 of relative fork 15. The free end of each screw 54 contacts the outer surface of tube 41, and exerts variable radial pressure on tube 41 to adjust the elastic response of elastic thrust device 34 as required. Screws 54 are so located as to lock member 19 in such a position that the cylindrical surface coaxial with axis 8 and comprising surface 25 is tangent to path P at portion 12. In the example shown, elastic device 53 is defined by two strips 57 of elastomeric material interposed between the free edges of respective lateral walls 58 of member 22 and the outer surface of tubular body 14. The radial travel of member 22 towards the corresponding member 19 and produced by elastic device 53 is regulated by three pins 59, each of which presents an axis 60 crosswise to axis 9, and is locked axially in relation to relative member 22 by a nut 61. Each pin 59 presents an intermediate portion 62 engaging in radially slack manner two slots 63 formed through arms 20, and a hole 64 formed through anvil 21. The radial slack between each pin 59 and the inner surface of hole 64 permits radial displacement of anvil 21 in relation to relative fork 16, and the radial slack between each pin 59 and the inner surface of relative slot 63 defines the maximum radial travel of member 22 in relation to tubular body 14. Operation of unit 1 as described above is self-explanatory. One point to note, however, is that the thrust members defined by tube 41 and strips 57 of elastomeric material extend over the full length of blade 18 and sealing member 22 respectively, and provide for moving blade 18 and member 22 outwards in relation to respective axes 8 and 9 in such a manner that the contact pressures on anvil 21 on the one hand and member 19 on the other are evenly distributed along unit 1 in a direction parallel to axes 8 and 9.

Claims: A cut and seal unit for sheet material (4), the unit comprising a first and second roller (6, 7) on either side of a path (P) of the sheet material (4) and rotating respectively about a first and second axis (8, 9) fixed and parallel to each other; and at least a first (10) and second (11) cut and seal head fitted respectively to the first (6) and second (7) roller and cooperating cyclically with each other at a portion (12) of said path (P) extending between the rollers (6, 7); said first and second head (10, 11) comprising operating means (18, 19, 20, 21) in turn comprising respective first (18) and second (21) cutting operating means, and respective first (19) and second (22) sealing operating means; characterized in that at least one of said cutting operating means (18; 21) and at least one of said sealing operating means (19; 22) are movable operating means (18; 22) movable in a radial direction in relation to the relevant axis (8; 9) and to and from the other axis (9; 8); a first (32) and second (51) adjusting device being associated respectively with the cutting operating means (18, 21) and the sealing operating means (19, 22); and each of said adjusting devices (32, 51) comprising lock means (33, 52) for locking one (19; 21) of the relevant operating means (18, 19; 21, 22) in relation to the relevant said axis (8; 9) and in such a position as to be tangent to said path (P); the other (18; 22) of the relevant said operating means (18, 19; 21, 22) being a said movable operating means (18; 22). A cut and seal unit as claimed in Claim 1, characterized in that one (18) of said movable operating means (18; 22) is fitted to the first roller (6), and one (22) to the second roller (7). A cut and seal unit as claimed in Claim 1 o 2, characterized in that each of said adjusting devices (32, 51) comprises thrust means (34; 53) for moving the relative said movable operating means (18; 22) away from the relative said axis (8; 9). A cut and seal unit as claimed in Claim 3, characterized in that said thrust means (34, 53) are elastic thrust means. A cut and seal unit as claimed in Claim 3 or 4, characterized in that said cutting operating means (18, 21) comprise an anvil (21) and a blade (18) fitted respectively to the second (7) and the first (6) roller; the blade (18) constituting said movable cutting operating means (18). A cut and seal unit as claimed in Claim 5, characterized in that the lock means (33) of said first adjusting device (32) comprise a pin (35) fitted in rotary manner to said second roller (7) and crosswise to the second axis (9); said pin (35) comprising an eccentric cylindrical portion (38) engaging in rotary manner a slot (39) formed through said anvil (21). A cut and seal unit as claimed in Claim 5 or 6, characterized in that said thrust means (34) of the first adjusting device (32) comprise a tube (41) presenting a longitudinal cut (42) and supporting said blade (18); the tube (41) being parallel to said first axis (8) and extending substantially the full length of the blade (18) measured parallel to the first axis (8). A cut and seal unit as claimed in Claim 7, characterized in that it also comprises means (54) for adjusting the transverse elasticity of said longitudinally cut tube (41). A cut and seal unit as claimed in any one of the foregoing Claims from 5 to 8, characterized in that said sealing operating means (19, 22) comprise a first (19) and second (22) sealing member respectively defined externally by a first (25) and second (26) cylindrical surface respectively coaxial with the first (8) and second (9) axis; said second sealing member (22) constituting said movable sealing operating means. A cut and seal unit as claimed in Claim 9, characterized in that said thrust means (53) of the second adjusting device (51) comprise at least one strip (57) of elastomeric material supporting the second sealing member (22); said strip (57) being parallel to said second axis (9) and extending substantially the full length of the second sealing member (22) measured parallel to the second axis (9).

Inventors: GREPIONI LORIS, SPATAFORA MARIO, GREPIONI, LORIS, SPATAFORA, MARIO
Applicants: AZIONARIA COSTRUZIONI ACMA SPA, AZIONARIA COSTRUZIONI MACCHINE AUTOMATICHE-A.C.M.A.-S.P.A.
Application year: 1996
Main classification: B65B51
IPC codes: B65B51