Apparatus and method for generating a repetitive pattern on a web of sheet material

Abstract

An apparatus (10) adapted to generate a repetitive pattern along longitudinal portions of the surface of a web (R) of sheet material, comprising a modification device (12) of the surface of the web (R), periodically interacting with the surface of the web (R) to generate said pattern, feeding and guiding means (14) of the web (R) along a path including a section wherein the modification device (12) is arranged, comprising at least one unwinding reel (15a) of the web (R) and a pulling device (16), wherein said feeding and guiding means (14) generate a continuous forward motion of the web (R) with a substantially constant pulling speed; a slowing down and / or accelerating device (18) of the web (R), periodically causing localized slowing down and / or acceleration of the forward motion of the web (R) in the section of the path wherein the modification device (12) is arranged, while keeping the pulling speed of the web (R) unchanged, and actuator means (20) for the synchronized actuation of the slowing down and / or accelerating device (18) and the modification device (12), in accordance with said predetermined frequencies, such that the slowing down and / or accelerating device (18) of the web (R) generates the periodic stop or absence of relative motion, in the longitudinal direction of the web (R), between the web (R) and the modification device (12), in synchrony with the interaction of the modification device (12) with the web (R), generating said repetitive pattern.

Description

[0001] Apparatus and method for generating a repetitive pattern on a web of sheet material

[0002] Technical field

[0003] The present invention generally relates to the field of processing sheet materials; in particular, the invention relates to an apparatus and a method for generating a repetitive pattern on a web of sheet material.

[0004] Summary of the invention

[0005] The present invention concerns an apparatus for continuously generating, on the surface of a web of sheet material, a predetermined repetitive pattern extending along longitudinal portions of the web.

[0006] The apparatus object of the present invention is specifically implemented for use as a component of a machine or plant for continuous packaging, which performs the packaging of items in at least one respective wrapping sheet that wraps each item and is achieved inline from a continuous web of sheet material.

[0007] In particular, the invention concerns an apparatus comprising feeding and guiding means for a web along a path including a section wherein a modification device is arranged, and comprising at least one unwinding reel of the web arranged upstream of the modification device and a pulling device arranged downstream of the modification device, wherein the feeding and guiding means generate a substantially constant continuous pulling travel motion of the web.

[0008] The term "modification device" refers to any device that interacts with the surface of the web to modify its shape or surface characteristics by generating a repetitive and periodic pattern.

[0009] The invention applies in particular to modification devices which, for generating the repetitive pattern in a precise manner, require the stopping of the web or the absence of relative motion in the longitudinal direction of the web between the web and the modification device.

[0010] To perform operations that require the absence of relative motion between a continuously travelling substrate and a substrate modification device, a solution is known that provides for apparatuses wherein the modification device, interacting with the substrate, moves itself so as to follow the latter. However, depending on the type of the modification device, its tracking movement of the substrate, particularly with a back-and-forth motion, may require apparatuses which are bulky and are complex to implement, due to, for example, the high inertia of the support structure of the modification device, especially when a high interaction frequency is required between it and the web, such as for example around 400 interactions / minute or more.

[0011] An object of the present invention is to overcome the aforementioned problems, in particular by providing a simple-to-build and compact apparatus that allows the modification device to interact with a continuously travelling web without relative motion, without necessarily having to move the modification device and without varying the average travel speed of the web, which can thus be kept substantially constant.

[0012] To achieve this result, an apparatus according to the invention comprises a slowing down and accelerating device for the web, adapted to cause localized deceleration of the travel motion of such web in the section of the path wherein the modification device is located, up to the absence of relative motion between the web and the modification device (or, preferably, until the travel motion of the web stops). Actuator means are also provided for the synchronized actuation of the slowing down and accelerating device and the modification device, so that the former generates the periodic stopping or the periodic absence of relative motion between the web and the modification device, in synchrony with the interaction of the latter with the web, thus generating the repetitive pattern.

[0013] An apparatus and a method configured according to the invention can allow to achieve an interaction frequency between the modification device and the web equal to or greater than 400 interactions per minute (more preferably, equal to or greater than 700 interactions per minute). This clearly allows maximizing production volumes while reducing the complexity of the machine (since the movement of the modification device, which is the most delicate and complex part of the apparatus, may substantially require even only one degree of freedom).

[0014] The above and other objects and advantages are achieved, according to an aspect of the invention, by an apparatus and method having the features defined in the appended claims.

[0015] Brief description of the drawings

[0016] The functional and structural features of some preferred embodiments of an apparatus and method according to the invention will now be described. Reference is made to the accompanying drawings, wherein:

[0017] - Figures l(a)-(b) are schematic representations of two different methods for impressing a pattern on a web of sheet material by removing portions of the same, to create a plurality of interconnected and subsequently separated disks, according to two embodiments of the invention;

[0018] - Figure 2 is a schematic perspective view of an apparatus for generating a repetitive pattern on a web of sheet material, according to an embodiment of the invention;

[0019] - Figures 3 and 4 are two schematic front views of a portion of the apparatus shown in Figure 2, wherein in particular the web modification station is shown comprising a slowing down and accelerating device and a modification device, in two operating configurations, according to an embodiment of the invention;

[0020] - Figure 5 is a schematic perspective view of the modification station wherein a mechanism for the transmission of the motion to the slowing down and modification devices, according to an embodiment of the invention is shown;

[0021] - Figure 6 is a detailed view of Figure 5; and

[0022] - Figure 7 is a schematic front view of the apparatus in Figure 5.

[0023] Detailed Description

[0024] Before explaining in detail a plurality of embodiments of the invention, it should be clarified that the invention is not limited in its application to the construction details and component configuration described in the following disclosure or illustrated in the drawings. The invention can take other embodiments and be implemented in practice in various ways. It should also be understood that the phraseology and terminology have descriptive purposes and should not be construed as limiting.

[0025] Referring by way of example to Figure 1, an apparatus 10 adapted to generate a predetermined repetitive pattern on a surface of a web R of sheet material, extending along longitudinal portions of said web R, comprises a modification device 12 of the surface of the web R, periodically interacting with the surface of the web R, according to a predetermined interaction frequency, to generate said pattern in absence of relative motion, in the longitudinal direction of the web R, between the web R and the modification device 12.

[0026] Feeding and guiding means 14 of the web R are also provided along a path including a section wherein the modification device 12 is located, comprising at least one unwinding reel 15a of the web R arranged upstream of the modification device 12 and a pulling device 16 preferably arranged downstream of the modification device 12, wherein said feeding and guiding means 14 generate a continuous travel motion of the web R with a substantially constant pulling speed.

[0027] The apparatus 10 comprises a device 18 for slowing down and accelerating the web R, adapted to cause in a periodical manner, at a predetermined frequency equal to or a multiple or sub-multiple of the interaction frequency with the web R of the modification device 12, the localized slowing down of the travel motion of the web R, in the section of the path wherein the modification device 12 is arranged, up to the absence of relative motion, in the travel direction of the web R, between the web R and the modification device 12, or preferably until the forward motion of the web R stops, at the modification device 12, while keeping the pulling speed of the web R generated by said feeding and guiding means unchanged.

[0028] Preferably, the interaction frequency between the modification device 12 and the web R is equal to or greater than 400 interactions per minute (more preferably, equal to or greater than 700 interactions per minute). Actuator means 20 are provided for the synchronized actuation of the slowing down and accelerating device 18 and the modification device 12, in accordance with said predetermined frequencies, so that the slowing down and accelerating device 18 of the web R generates the periodic stop or the periodic absence of relative motion, in the longitudinal direction of the web R, between the web R and the modification device 12, in synchrony with the interaction of the modification device 12 with the web R, which generates said repetitive pattern.

[0029] Preferably, the pulling device 16 is arranged downstream of the modification station and is adapted to generate a traction force of the web R such as to drive the web R at a constant speed. Thus, even though the web is subjected to localized accelerations or slowing down along its path, the average speed of the web is kept substantially constant, ensuring that the modified web can be continuously fed into subsequent operations, such us in particular to a packaging apparatus.

[0030] Between the reel 15a and the slowing down and accelerating device 18, a pneumatic loop system 19 (known per se) may also be present, adapted to keep a predetermined tension value of the web by applying pneumatic vacuum, which produces a more or less pronounced elongation and / or tensioning of the web section upstream of the slowing down and accelerating device 18. A system of this type is known, for example, from EP 670278 Al.

[0031] To avoid actuation interruptions caused by web depletion, the feeding means of the web preferably include a first unwinding reel 15a and a second unwinding reel 15b (one reel being the actuator reel and the other being a backup reel) and a splicing system 17 that connects the web of the backup reel to the web of the reel currently being fed, when the control system of the apparatus signals the imminent depletion of the web. A splicing system of this type is known, for example, from EP 1388513 Al.

[0032] Both reels 15a and 15b are preferably motorized and adapted to unwind from time to time the web being processed, preferably at the same speed generated by the pulling device. Number 44 denotes a sensor device, such as, for example, a photocell that detects the splice between the two webs.

[0033] According to a preferred embodiment, the modification device 12 is configured to perform shearing of the web R of sheet material, so as to obtain a continuous pre-sheared web R according to said predetermined repetitive pattern.

[0034] Preferably, the apparatus 10 comprises a support structure 11, which is fixed with respect to the web R (when the latter is driven by the pulling device 16), and which includes a modification station of the web R. The modification device 12 is supported by the support structure 11 and, in one embodiment, comprises a movable member with reciprocating motion between a position of interaction with the surface of the web R at the modification station and a non-operative position. The actuator means 20 are configured to drive the reciprocating motion of the movable member of the modification device 12 and to actuate the slowing down and accelerating device 18, so that the modification device 12 is in the interaction configuration with the surface of the web R in synchrony with the travel stop of the web R (or the absence of relative motion, in the longitudinal direction of the web R, between the web R and the modification device 12 at the modification station). When the modification device 12 is a device configured to perform shearing of the web R, the movable member may be a punch (of a type known per se), and the interaction position of this movable member with the web R is the position where the punch cuts the surface of the web R.

[0035] According to a preferred embodiment, the movable member moves with a reciprocating motion along a direction perpendicular to the surface of the web R (in the illustrated example, a vertical direction).

[0036] In the illustrated example, the modification device 12 comprises a punch 13, adapted to engrave the web R, potentially until removing a portion thereof. For example, the punch 13 may be configured to modify the profile of the lateral edges of the web R, initially straight and parallel to one another, by removing a pair of triangular portions P from the web (or similar) arranged symmetrically with respect to the web longitudinal direction (as illustrated, for example, in Figures l(a)-(b)), thereby cutting out a sequence of circular or polygonal shapes adapted to form, once separated from the others, individual discs (D) of sheet material, which could be used, for example, for application as sheet wrap portions for packaging cosmetic, food, etc.

[0037] According to a preferred embodiment, the slowing down and accelerating device 18 comprises a trolley 22, actuated by the actuator means 20 and translatable with reciprocating linear motion with respect to the support structure 11 between a first and a second position, wherein said trolley 22 includes auxiliary transport means 24 for the web R, integral with the trolley 22. These auxiliary means 24 are adapted to engage the web R in a loop configuration and are arranged upstream and downstream of the modification station, so that the translation of the trolley 22 from one said position to the other causes the slowing down of the travel motion of the web R in its section that crosses the modification station, preferably up to its stop.

[0038] Conveniently, the auxiliary transport means 24 may comprise a first and a second cylinder 25a, 25b, fixed in rotation and integral with the trolley 22, respectively upstream and downstream of the modification station.

[0039] Preferably, such first and second cylinders 25a, 25b have a diffusely perforated surface, in fluid connection with a pneumatic source, to generate a fluid film suitable for supporting the web R in the loop configuration.

[0040] A preferred embodiment is characterized by the fact that said feeding and guiding means 14 comprise a first and a second deviating roller 26a, 26b, rotatably supported by the support structure 11, respectively upstream of the first cylinder 25a and downstream of the second cylinder 25b. The first and second deviating rollers 26a, 26b are thus rotatable around fixed rotation axes with respect to the rotation axes of the respective first and second cylinders 25a, 25b, which are instead movable integrally with the trolley 22.

[0041] Conveniently, the auxiliary transport means 24 may be configured such that the web R, coming from the reel 15, first winds around the first deviating roller 26a, then passes around the first cylinder 25a, from which it proceeds to the second cylinder 25b (crossing the modification station, wherein the modification device 12 interacts with the web), then from said second cylinder 25b winds around the second deviating roller 26b, to finally reach the pulling device 16.

[0042] In the section of the path between first 25a and second 25b cylinders, the web R preferably runs on a plate 40. If the modification device is a shearing device that removes portions of the web, the plate 40 may have apertures 42 communicating with a suction box 46 to remove the scrap portions of the web.

[0043] A possible mode for operating the invention is schematically illustrated in Figures 3 and 4, which respectively show a first configuration of the modification assembly, wherein the modification device 12 avoid interacting with the web R (in the illustrated example, the movable member of the modification device 12 is in a vertically raised position with respect to the web) and the trolley 22 is in a fully translated position in the travel direction of the web, and in a second configuration of the modification assembly, wherein the modification device 12 interacts with the web R (in the illustrated example, the movable member of the modification device 12 is in a vertically lowered position with respect to the web) and the trolley 22 is in a retracted position with respect to the travel direction of the web. The retraction of the trolley 22 with respect to the travel direction of the web causes localized slowing down of the web R (which continues to be pulled at a constant speed by the pulling device 16), until reaching a condition of localized absence of relative motion of the web with respect to the modification device 12, which in this condition interacts with the web R.

[0044] The movement of the modification device 12 and the slowing down device 18 can be implemented using any suitable actuator means, such as for example pistons (for the vertical translation of the modification device 12), rack-and-pinion devices (for the horizontal translation of the trolley 22), electric, hydraulic, pneumatic linear actuators, etc.

[0045] Preferably, the actuator means 20 may comprise a single driving shaft 28 which, through a mechanical transmission system, synchronously drives the modification device 12 (e.g., imparting reciprocating motion to the movable member of such modification device 12) and the slowing down and accelerating device 18. Conveniently, the driving shaft 28 may be rotatably supported by the support structure 11.

[0046] As shown as example in Figures 5 and 6, the actuator means 20 may conveniently comprise a connecting rod 30 having one end connected to the driving shaft 28 eccentrically with respect to the axis of said driving shaft 28, and the opposite end connected to the modification device 12 (conveniently, to the movable member of said modification device 12), such that the rotary motion of the driving shaft 28 is converted into a reciprocating motion of the modification device 12 (conveniently, of its movable member).

[0047] Preferably, the actuator means 20 comprise a cam 32, integral in rotation with the driving shaft 28, and a V-shaped rocker arm, whose free ends are engaged by the cam 32. The rocker arm 34 is oscillatable about an axis passing through an intermediate point between the free ends and parallel to the axis of the driving shaft 28, and is mechanically connected to a transmission adapted to convert the oscillation of said rocker arm 34 into a reciprocating motion of said slowing down and accelerating device 18.

[0048] The rocker arm 34 may also be oscillable integrally with a pin 36, which in turn rotates integrally with a bracket 38 extending perpendicularly with respect to the pin 36, such bracket 38 having one end connected to the slowing down and accelerating device 18, so that the oscillation of the cam 32 puts into rotation the pin 36 and the bracket 38, resulting in the reciprocating translation of the slowing down and accelerating device 18.

[0049] In an apparatus configured as exemplificatively illustrated in Figures 5 and 6, the rotation of the driving shaft 28 imparts, via the eccentric connection to the connecting rod 30, a vertical reciprocating motion to the modification device 12 (conveniently, to the movable member of the modification device 12). Simultaneously, the cam 32 (taken into rotation by the driving shaft 28) engages the free ends of the V-shaped rocker arm 34, which, following the eccentric profile of the cam 32, will oscillate integrally with the pin 36 (conveniently, the oscillation axis of the rocker arm 34 may coincide with the axis of that pin 36). In turn, the pin 36 will cause the bracket 38 to oscillate, which will impart a horizontal reciprocating translation to the trolley 22. Throughout the present description and in the claims, terms and expressions indicating positions and orientations, such as "longitudinal", "transversal", "vertical", or "horizontal", refer to the travel direction of the web R.

[0050] Several aspects and embodiments of an apparatus and method for generating a repetitive pattern on a web of sheet material according to the invention have been described. It is understood that each embodiment can be combined with any other embodiment. Additionally, the invention is not limited to the described embodiments but may be modified within the scope defined by the appended claims.

[0051] Thus, although the invention has been described with particular reference to a modification device represented by a shearing device, which constitutes a preferred embodiment, it is understood that the invention is not limited to this device, as the constructive principle can be applied to other modification devices.

[0052] For example, the modification device may be an embossing device for the web or a printing device. Similarly, although the repetitive pattern has been described in a preferred embodiment wherein a shearing device modifies the profile of the longitudinal edges of a web, it is understood that such a repetitive pattern may involve any portion of the surface of the web, such as for example a transverse portion or an internal portion of the web.

Claims

CLAIMS1. An apparatus (10) adapted to generate, on a surface of a web (R) of sheet material, a predetermined repetitive pattern extending along longitudinal portions of said web (R), the apparatus (10) comprising:- a modification device (12) of the surface of the web (R), periodically interacting with the surface of the web (R), according to a predetermined interaction frequency, for generating said pattern in the absence of relative motion, in the longitudinal direction of the web (R), between the web (R) and the modification device (12),- feeding and guiding means (14) of the web (R) along a path including a section wherein said modification device (12) is arranged, comprising at least one reel (15a) for unwinding the web (R) arranged upstream of the modification device (12) and a pulling device (16) preferably arranged downstream of said modification device (12), wherein said feeding and guiding means (14) generate a continuous forward motion of the web (R) with a substantially constant pulling speed of the web (R),- a device for slowing down and / or accelerating (18) the web (R), adapted to cause periodically, according to a predetermined frequency which is equal to or a multiple or submultiple of the interaction frequency of the modification device (12) with the web (R), the localized deceleration and / or acceleration of the travel motion of the web (R), in the section of the path where the modification device (12) is arranged, up to the absence of relative motion, in the feed direction of the web (R), between the web (R) and the modification device (12), or preferably until the travel motion of the web (R) stops, at the modification device (12), keeping unchanged the pulling speed of the web (R) generated by said feeding and guiding means, and- actuator means (20) for the synchronized actuation of the slowing down and / or accelerating device (18) and of the modification device (12), in accordance with said predetermined frequencies, so that the slowing down and / or accelerating device (18) of the web (R) generates the periodic stop or the periodic absence of relative motion, in the longitudinal direction of the web (R), between the web (R) and the modification device (12), in synchrony with the interaction of the modification device (12) with the web (R), generating said repetitive pattern.

2. The apparatus according to claim 1, comprising a support structure (11) which includes a modification station of the web (R), wherein the modification device (12) is supported by the support structure (11) and comprises a member movable with a reciprocating motion between a first position, wherein said movable member interacts with the surface of the web (R) at the modification station, and a second position not interacting with the web (R), and wherein the actuator means (20) are configured for the actuation of the reciprocating motion of the movable member of the modification device (12) and for the actuation of the slowing down and / or accelerating device (18), in such a way that the movable member of the modification device (12) is in the first interaction position with the surface of the web (R) in synchrony with the stop of the travel motion of the web (R) or the absence of relative motion, in the longitudinal direction of the web (R), between the web (R) and the modification device (12) at the modification station.

3. The apparatus according to claim 2, characterized in that said slowing down and / or accelerating device (18) comprises a trolley (22), operated by the actuator means (20) and translatable with reciprocating linear motion with respect to the support structure (11) between a first and a second position, wherein said trolley (22) comprises auxiliary means (24) for transporting the web (R), integral with the trolley (22), suitable for engaging the web (R) in a loop configuration, arranged upstream and downstream of the modification station, in such a way that the translation of the trolley (22) from said one position to the other of causes the deceleration (and / or acceleration) of the travel motion of the web (R), in the section thereof that crosses the modification station, preferably up to its stop.

4. The apparatus according to claim 3, characterized in that said auxiliary transport means (24) comprise a first and a second cylinder (25a, 25b), fixed in rotation to and integral with the trolley (22), upstream and downstream of the modification station, respectively.

5. The apparatus according to claim 4, characterized in that said first and second cylinders (25a, 25b) have a diffused surface perforation, in fluid connection with a pneumatic source, to generate a fluid film suitable to support the web (R) in the loop configuration.

6. The apparatus according to one of claims 4 or 5, characterized in that said feedingand guiding means (14) comprise a first and a second deviating roller (26a, 26b), rotatably supported by the support structure (11), upstream of said first cylinder (25a) and downstream of said second cylinder (25b), respectively.

7. The apparatus according to any one of claims 2 to 6, characterized in that said actuator means (20) comprise a single driving shaft (28) which, by means of a mechanical transmission system, synchronously drives the reciprocating motion of the movable member of the modification device (12) and the slowing down and / or accelerating device (18).

8. The apparatus according to claim 7, characterized in that said actuator means (20) comprise a connecting rod (30) having one end connected to the driving shaft (28) in an eccentric manner with respect to the axis of said driving shaft (28), and the opposite end connected to the movable member of the modification device (12), said connecting rod (30) being configured to convert the rotary motion of the driving shaft (28) into a reciprocating motion of said movable member of the modification device (12).

9. The apparatus according to claim 7 or 8, characterized in that said actuator means (20) comprise a cam (32), integral in rotation with the driving shaft (28), and a V-shaped rocker arm, the free ends of which are engaged by said cam (32), said rocker arm (34) being oscillatable around an axis passing through an intermediate point between said free ends and parallel to the axis of the driving shaft (28), said rocker arm (34) being mechanically connected to a transmission adapted to convert the oscillation of said rocker arm (34) into a reciprocating motion of said slowing and / or acceleration device (18).

10. The apparatus according to claim 9, characterized in that the rocker arm (34) can be oscillated integrally with a pin (36) which in turn rotates integrally with a bracket (38) extending perpendicularly to said pin (36), said bracket (38) having one end connected to the slowing down and / or accelerating device (18), so that the oscillation of said cam (32) rotates the pin (36) and the bracket (38), causing the reciprocating translation of the slowing down and / or accelerating device (18).

11. The apparatus according to any one of the preceding claims, wherein the pullingdevice (16) is arranged downstream of the modification station and adapted to generate a traction of the web (R) such as to drive the web (R) at a constant speed.

12. The apparatus according to any one of the preceding claims, wherein the modification device (12) comprises a shearing device configured to carry out a shearing of the web (R) of sheet material, in such a way as to obtain a continuous web (R) pre-sheared according to said predetermined repetitive pattern.

13. The apparatus according to claim 12, wherein the modification device (12) comprises a stamp (13), adapted to engrave the web (R).

14. A process for generating on a surface of a web (R) of sheet material a predetermined repetitive pattern extending along longitudinal portions of said web (R), with the use of a modification device (12) of the surface of the web (R) periodically interacting with the surface of the web (R), according to a predetermined interaction frequency, so as to generate said pattern in the absence of relative motion, in the longitudinal direction of the web, between the web (R) and the modification device (12), including the operations of:- continuously feeding the web (R) along a path including a section wherein said modification device (12) is positioned with a travel motion having a pulling speed, downstream of said modification device (12), substantially constant,- periodically causing, according to a predetermined frequency, which is equal to or a multiple or submultiple of the frequency of interaction with the web (R) by the modification device (12), the localized deceleration and / or acceleration of the travel motion of the web, in the section of the path wherein the modification device is arranged, up to the absence of relative motion in the travel direction of the web, between the web (R) and the modification device (12), or preferably up to stop the travel motion of the web (R), at the modification device (12), keeping the aforementioned pulling speed unchanged, and- periodically operating the modification device (12), in accordance with said predetermined frequency, in such a way that the modification device (12) interacts with the surface of the web (R) to generate said repetitive pattern, in synchrony with the stopping of the web travel motion or with the absence of relative motion in the direction of travel of theweb, between the web (R) and the modification device (12), at the modification device (12).

15. The process according to claim 14, characterized in that it is carried out with an apparatus according to any one of claims 1 to 13.

16. The process according to claim 14 or 15, wherein the periodic actuation of the modification device (12) is carried out in such a way as to produce an incision or shearing of the web (R) to achieve said pattern.

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