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(11) | EP 1 698 451 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Embossing assembly |
| (57) An embossing assembly (2) for embossing packing material has two embossing rollers
(6, 7), each rotating about a respective axis of rotation (9, 10) to emboss a strip
(5) of packing material which, in use, is fed along an embossing plane (A), substantially
tangent to the two rollers (6, 7), and through an embossing passage (13) defined between
the two rollers (6, 7); the axes of rotation (9, 10) being skewed with respect to
each other and substantially parallel to the embossing plane (A).
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[0001] The present invention relates to an embossing assembly for embossing packing material, to a packing machine featuring the embossing assembly, and to packing material obtained using the embossing assembly.
[0002] The present invention may be used to advantage in the packing of cigarettes, to which the following description refers purely by way of example.
[0003] More specifically, the present invention relates to a packing material embossing assembly comprising a first and a second embossing roller rotating in opposite directions about a first and a second axis of rotation respectively. The first and second embossing roller are arranged to define an embossing passage, through which the packing material is fed, in use, and embossed, and at which the first and second roller are substantially tangent to an embossing plane substantially parallel to the first and second axis of rotation.
[0004] Though fairly efficient, known embossing assemblies of the type described above produce embossed packing material which is relatively rigid and has a tendency to curl spontaneously.
[0005] Both spontaneous curling and the rigidity of the embossed packing material make it relatively difficult to handle (e.g. convey, cut, and fold about the product).
[0006] Moreover, the embossing rollers (particularly relatively long embossing rollers) of embossing assemblies of the above type at times fail to satisfactorily emboss a central portion of the packing material.
[0007] It is an object of the present invention to provide an embossing assembly, a packing machine, and packing material, designed to at least partly eliminate the aforementioned drawbacks, and which, at the same time, are cheap and easy to implement.
[0008] According to the present invention, there are provided an embossing assembly, a packing machine, and packing material, as claimed in the accompanying independent Claim or in any one of the Claims depending directly or indirectly on said independent Claim.
[0009] A number of non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which:
Figure 1 shows a schematic front view, with parts removed for clarity, of a portion of a packing machine comprising an embossing assembly in accordance with the present invention;
Figure 2 shows a schematic, partly sectioned side view of a detail in Figure 1;
Figure 3 shows a schematic underside view, with parts removed for clarity, of a detail in Figure 2;
Figure 4 shows a schematic detail of the Figure 1 embossing assembly;
Figure 5 shows an alternative embodiment of the Figure 4 detail;
Figure 6 shows a view in perspective of a detail in Figure 2.
[0010] Number 1 in Figure 1 indicates as a whole a portion of a packing machine. Portion 1 comprises an embossing assembly 2, in turn comprising an embossing unit 3, a traction unit 4, and a known cutting unit (not shown). In actual use, a strip 5 of packing material is fed to the cutting unit (not shown) along a path P and via an embossing station, where embossing unit 3 embosses strip 5, and a traction station, where traction unit 4 elastically deforms or stretches strip 5.
[0011] Embossing unit 3 comprises two embossing rollers 6 and 7 fitted to a frame 8 to rotate about respective axes of rotation 9 and 10, and having respective substantially cylindrical outer surfaces having respective numbers of teeth 11 and 12 (Figures 4 to 6) which mesh at an embossing passage (Figures 1 and 2) defined between rollers 6 and 7. The outer surfaces of rollers 6 and 7 are substantially parallel to axes 9 and 10 respectively.
[0012] In actual use, strip 5 of packing material is fed through embossing passage 13 and embossed by rollers 6 and 7, which are substantially tangent to an embossing plane A at embossing passage 13.
[0013] For the sake of clarity, in Figure 2, the distance between the outer surfaces of rollers 6 and 7 and the thickness of strip 5 are shown proportionally larger than in actual fact. More specifically, as stated, teeth 11 and 12 mesh, so that plane A is to be considered tangent to the outer surfaces (ideally considered smooth) of rollers 6 and 7 with rollers 6 and 7 contacting each other.
[0014] Roller 6 is a drive roller fitted to a respective shaft 14, which is coaxial with axis 9, is fitted to frame 8 with the interposition of bearings 15, and is connected angularly to an output shaft (not shown) of a motor 16 (shown schematically), fixed to frame 8, to receive a given drive torque from motor 16.
[0015] Roller 7 is mounted for rotation, with the interposition of internal bearings (not shown), on a shaft 17 coaxial with axis 10 and supported in angularly fixed manner by a supporting unit 18, and is rotated by roller 6 by virtue of friction between the sides of teeth 11 and 12.
[0016] The cross sections of rollers 6 and 7, crosswise to respective axes 9 and 10, are of substantially the same diameter. In alternative embodiments not shown, said cross sections differ in diameter.
[0017] With particular reference to Figure 6, teeth 11 are arranged on the outer surface of roller 6 in rows D substantially parallel to axis 9, and in substantially circular rings C having respective centres along axis 9. Teeth 12 are arranged on the outer surface of roller 7 in rows D' (Figures 4 and 5) substantially similar to rows D, and in rings C' (not shown) substantially similar to rings C.
[0018] In preferred embodiments, the number of teeth 11 in a specific ring C is a prime number with respect to the number of teeth 12 in a specific ring C'; and teeth 11 in specific ring C mesh at least partly with teeth 12 in specific ring C', so as to achieve substantially even wear of all the teeth 11 and 12 in specific rings C and C' respectively.
[0019] In Figure 6, teeth 11, which are truncated-pyramid-shaped with a square base, are shown proportionally larger than in actual fact and deformed for reasons of clarity.
[0020] In alternative embodiments not shown, the shapes of teeth 11 and 12 may differ from the one described above, and may, for example, be selected, independently of each other, from the group consisting of: conical, truncated-cone, pyramidal, truncated-pyramid.
[0021] With particular reference to Figure 3, it should be pointed out that rollers 6 and 7 are mounted with axes 9 and 10 skewed with respect to each other, so that, as shown in Figures 4 and 5, the position of teeth 11 with respect to relative teeth 12 at embossing passage 13 varies along the length of rollers 6 and 7. In Figures 4 and 5, teeth 11 are indicated "X" and teeth 12 "0". More specifically, in the Figure 4 embodiment, a tooth 12a at one end of roller 7 is substantially located between four teeth 11, whereas a tooth 12b at a central portion of roller 7 is only located between two teeth 11. In the Figure 5 embodiment, a tooth 12a at the end of roller 7 is substantially only located between two teeth 11, whereas a tooth 12b at the central portion of roller 7 is located between four teeth 11.
[0022] It should be pointed out that Figures 4 and 5 show a schematic representation of the relative position of teeth 11 and 12 along the whole length of rollers 6 and 7 at embossing passage 13. In actual fact, teeth 11 and 12 are obviously much greater in number, are much smaller, and are arranged contiguously (as shown in Figure 6); the distance between the centres of two contiguous teeth 11 or 12 may be selected from the group consisting of: 0.25, 0.3, or 0.4 millimetres, and is typically about 0.4 millimetres; and the length of a toothed outer surface of an embossing roller ranges between 140 and 150 millimetres, and is typically 148 millimetres, though a length of 300 millimetres or over is also possible.
[0023] The non-homogeneous relative arrangement of teeth 11 and 12 provides for reducing the tendency of the strip to curl spontaneously. This is presumably achieved by the fibres of the packing material of strip 5 not undergoing preferential fractures. In other words, embossing is not completely homogeneous.
[0024] Another important point to note is that the skew position of axes 9 and 10 also enables satisfactory embossing at the central portions of rollers 6 and 7, which deform during use (in particular, relatively long rollers 6 and 7 are subject to bending, so that each forms a concavity facing the other roller).
[0025] Another point to note is that strip 5 embossed by embossing unit 3 is relatively slack at the edges, and can therefore be curved laterally and guided relatively easily along path P downstream from embossing unit 3.
[0026] In connection with the above, tests have shown particularly good results to be obtained with axes 9 and 10 skewed with respect to each other by an angle of 0.05° to 0.40°, preferably of 0.10° to 0.30°, more preferably of 0.15° to 0.25°, and even more preferably of 0.20° (in Figure 3, the skew of axes 9 and 10 is exaggerated for the sake of clarity).
[0027] Supporting unit 18 allows roller 7 to oscillate about an instantaneous axis of rotation 19 movable substantially parallel to axis 10. Axis 19 is perpendicular to a plane B (in Figure 2, plane B is shown substantially parallel to the sheet plane) containing axis 10 and which in turn is substantially perpendicular to plane A.
[0028] Supporting unit 18 is interposed between roller 7 and a push assembly 20, which in turn is interposed between supporting unit 18 and frame 8, and transmits to roller 7 a compression force F through axis 19 at all times and directed onto roller 6 in a direction substantially perpendicular to axis 9 to grip strip 5 between rollers 6 and 7.
[0029] Axes 9 and 10 are substantially parallel to plane A, i.e. are substantially parallel to plane A at least in an original balanced embossing condition.
[0030] In the embodiment shown (Figure 2) , supporting unit 18 comprises a U-shaped fork 21 defined by a cross member 22 located on the opposite side of roller 7 to roller 6, and by two arms 23 substantially perpendicular to cross member 22 and at opposite ends of roller 7.
[0031] Supporting unit 18 is an articulated "rocking" unit, wherein the opposite ends of shaft 17 are fixed to the free ends of arms 23, and a surface 24 of cross member 22
- which may be flat, as in the embodiment shown, or, as in a variation not shown, a curved surface with its convexity facing outwards - rocks on a surface 25 of a base 26, which, together with fork 21, defines supporting unit 18 and is fitted to frame 8 with the interposition of push assembly 20 to move, on frame 8, in the direction of compression force F. In the example shown, surface 25 is curved with its convexity facing cross member 22, but, in a variation (not shown) in which surface 24 is curved, may be flat or even curved with its concavity facing cross member 22. In a variation not shown, surface 24 may be a curved surface with its concavity facing base 26, and surface 25 may be a curved surface with its convexity facing cross member 22.
[0032] In actual use, surfaces 24 and 25 roll, without sliding, one on the other, and the point of contact between cross member 22 and surface 25 defines an instantaneous centre of rotation lying on axis 19 and movable along surfaces 24 and 25 as a function of the angular position of roller 7 about axis 19.
[0033] In an embodiment not shown, as opposed to being an articulated "rocking" unit, supporting unit 18 is defined by an articulated quadrilateral.
[0034] More specifically, supporting unit 18 is substantially the same, and operates in the same way, as the supporting unit described in Italian Patent Application IT 2004B0000519, to which full reference is made herein for reasons of clarity.
[0035] It is important to note that the structure of supporting unit 18 as defined above provides for compensating any disturbance, such as transverse shift of strip 5, which causes a shift in the point of application of a reaction force R (by strip 5) to force F.
[0036] It should be pointed out that supporting unit 18 is particularly advantageous in combination with the skew axis 9 and 10 arrangement of rollers 6 and 7. In which case, the ability of at least one of rollers 6 and 7 (or, in further embodiments, of both rollers 6 and 7) to oscillate provides for more effectively meshing teeth 11 and 12, especially at the ends of rollers 6 and 7.
[0037] Traction unit 4 (Figure 1) comprises a traction roller 27 rotating about an axis of rotation 28 and having a number of peripheral suction nozzles 29 connected to a known suction source (not shown).
[0038] In actual use, strip 5, travelling along path P downstream from embossing unit 3, winds substantially 180° about roller 27 by virtue of a guide roller 30 downstream from roller 27. A motor 31 (shown schematically in Figure 1) rotates roller 27 at a tangential speed greater than that at which rollers 6 and 7 are rotated, so that, between embossing unit 3 and traction unit 4, strip 5 is subjected to traction which deforms it permanently in controlled manner to reduce undesired, embossing-induced deformation.
[0040] It should be pointed out that Figure 1 shows only one possible embodiment of traction unit 4, which in fact may be modified in various respects, even applying the teachings of Italian Patent Application IT 2005B0000114, to which full reference is made herein for reasons of clarity.
[0041] Tests have shown that using traction unit 4 in combination with embossing unit 3 as described above greatly reduces the tendency of strip 5 to curl.
[0042] Embossing assembly 2 also comprises a sensor 32 connected to a central control unit 33 and for detecting reference marks on strip 5; and central control unit 33 adjusts the rotation speed of rollers 6 and 7 and roller 27 as a function of the readings of sensor 32 and of the operating stage of the cutting unit (not shown).
1. An embossing assembly for embossing packing material, comprising a first and a second
embossing roller (6, 7) rotating in opposite directions about a first and a second
axis of rotation (9, 10) respectively; the first and second embossing roller (6, 7)
being arranged to define an embossing passage (13) through which, in use, the packing
material is fed and embossed; the first and second embossing roller (6, 7) being substantially
tangent, at the embossing passage (13), to en embossing plane (A) substantially parallel
to the first and second axis of rotation (9, 10); and the embossing assembly (2) being
characterized in that the first and second axis of rotation (9, 10) are skewed with respect to each other.
2. An embossing assembly as claimed in Claim 1, wherein the first and second embossing
roller (6, 7) respectively comprise a first and a second substantially cylindrical
outer surface, each substantially parallel to the relative axis of rotation (9, 10);
the first and second outer surface each have a respective number of teeth (11, 12);
and the teeth (12) on the second outer surface meshing with the teeth (11) on the
first outer surface, so that at least one tooth (12) on the second outer surface is
located between two teeth (11) on the first outer surface.
3. An embossing assembly as claimed in Claim 2, wherein the teeth (12) on the second
outer surface mesh with the teeth (11) on the first outer surface, so that at least
one tooth (12) on the second outer surface is located between four teeth (11) on the
first outer surface.
4. An embossing assembly as claimed in Claim 3, wherein the teeth (11) on the first outer
surface are arranged to define at least one first substantially circular ring (C)
whose centre lies on the first axis of rotation (9); the teeth (12) on the second
outer surface are arranged to define at least one second substantially circular ring
(C') whose centre lies on the second axis of rotation (10); the teeth (11, 12) in
the first and second ring (C, C') meshing at least partly; and the first ring (C)
having a number of teeth (11) differing from the number of teeth (12) in the second
ring (C').
5. An embossing assembly as claimed in Claim 4, wherein the first ring (C) has a prime
number of teeth (11) with respect to the number of teeth (12) in the second ring (C').
6. An embossing assembly as claimed in any one of the foregoing Claims from 1 to 5, wherein
the first and second embossing roller (6, 7) have cross sections, crosswise to the
first and second axis of rotation (9, 10) respectively, of substantially the same
diameter.
7. An embossing assembly as claimed in any one of the foregoing Claims from 1 to 5, wherein
the first and second embossing roller (6, 7) have cross sections, crosswise to the
first and second axis of rotation (9, 10) respectively, of different diameters.
8. An embossing assembly as claimed in any one of the foregoing Claims from 1 to 7, and
comprising permanent deformation or stretching means (4) located along a path (P)
of a strip (5) of packing material downstream from said first and second embossing
roller (6, 7).
9. An embossing assembly as claimed in Claim 8, wherein said permanent deformation or
stretching means (4) comprise at least one traction roller (27) rotating about a third
axis of rotation (28).
10. An embossing assembly as claimed in Claim 9, wherein the traction roller (27) is a
suction traction roller.
11. An embossing assembly as claimed in Claim 9 or 10, and comprising first actuating
means (16) for rotating the first and second embossing roller (6, 7) so that the first
and second embossing roller (6, 7) rotate at a first tangential speed; and second
actuating means (31) for rotating the traction roller (27) at a second tangential
speed.
12. An embossing assembly as claimed in Claim 11, wherein the second tangential speed
is greater than the first tangential speed, so that the strip (5) of packing material
is subjected to pull along a portion of the path (P) between the embossing rollers
(6, 7) and the traction roller (27).
13. An embossing assembly as claimed in Claim 12, wherein the second tangential speed
approximates in excess the first tangential speed.
14. An embossing assembly as claimed in Claim 13, and comprising at least one sensor (32)
for detecting reference marks on the strip (5) of packing material; and a central
control unit (33) connected to the first and second actuating means (16, 31) to adjust
the first and second tangential speed as a function of the readings of the sensor
(32).
15. An embossing assembly as claimed in any one of Claims 8 to 14, and comprising a cutting
unit located downstream from the first and second embossing roller (6, 7) and for
cutting the strip (5) of packing material into portions.
16. An embossing assembly as claimed in any one of the foregoing Claims from 1 to 15,
and comprising a push assembly (20) for pushing the first and second embossing roller
(6, 7) against each other and gripping the packing material, in use, with a compression
force (F); at least one of the first and second axes of rotation (9, 10) oscillating
about an instantaneous axis of rotation (19), which is parallel to the embossing plane
(A) and movable parallel to the oscillating axis of rotation (10) in response to movement,
parallel to the oscillating axis of rotation (10), of a point of application of a
reaction force (R) to the compression force (F).
17. An embossing assembly as claimed in Claim 16, wherein the instantaneous axis of rotation
(19) is substantially perpendicular to a further plane (B) perpendicular to the embossing
plane (A) and containing the oscillating axis of rotation (10).
18. An embossing assembly as claimed in Claim 16 or 17, wherein that of the two embossing
rollers (6, 7) rotating about the oscillating axis of rotation (10) is an oscillating
embossing roller (7); the embossing assembly (2) comprising a supporting unit (18)
located between the oscillating embossing roller (7) and the push assembly (20) to
support the oscillating embossing roller (7).
19. An embossing assembly as claimed in Claim 18, wherein the supporting unit (18) is
an articulated unit.
20. An embossing assembly as claimed in Claim 19, wherein the supporting unit (18) comprises
a "rocking" unit.
21. An embossing assembly as claimed in Claim 20, wherein the supporting unit (18) comprises
a base (26) having a first surface (25); a fork (21) comprising two arms (23), and
a cross member (22) having a second surface (24); and a shaft (17) coaxial with said
oscillating axis of rotation (10); at least one of said first and second surfaces
(24, 25) being a curved surface contacting the other of said first and second surfaces
(24, 25) at at least one point through which said instantaneous axis of rotation (19)
extends.
22. An embossing assembly as claimed in Claim 21, wherein said push assembly (20) is connected
to said base (26).
23. A packing machine comprising an embossing assembly (2) as claimed in any one of Claims
1 to 22.
24. Packing material obtained using an embossing assembly (2) as claimed in any one of
Claims 1 to 22.