Severing machine for cutting logs or paper rolls into small rolls of lesser axial length, and related method

Abstract

 The severing machine comprises an electronic control (30), a feed system (5, 3) for feeding logs (L) to be cut and a cutting member (15). The feed system and the cutting member are controlled by the electronic control so as to subdivide each log into a plurality of small rolls (R). The electronic control is associated with a vision system (33), which detects at least one optically identifiable element on the log (L) so as to phase the cut relative to said optically identifiable element.

Description

Technical Field

[0001] The present invention relates to improvements to the machines for cutting paper rolls or logs, especially made of so called tissue paper, such as toilet paper, kitchen towels or the like, to subdivide the logs or rolls into individual small rolls destined for packaging and distribution.

[0002] The present invention also relates to a method for cutting rolls or logs into small individual rolls of lesser axial length destined for packaging and consumption.

State of the Art

[0003] In particular in the field of tissue paper converting, but also in other web product processing fields, the need is present for producing rolls or small rolls of given axial length destined for consumption and obtained by cutting or subdividing a roll or log with greater axial length. Typically in the field of tissue paper converting for producing rolls of toilet paper, kitchen towels or the like, logs are manufactured by winding a preset quantity of tissue paper, with or without the use of a winding spindle or core. The obtained logs or rolls have an axial length approximately equal to a multiple of the axial length of the small rolls destined for the final consumption, as well as head and tail portions, which must be discarded as trimmings.

[0004] Numerous machines are known to cut these logs into individual rolls or small rolls of adequate dimension, which provide also for the discard of the head and tail trimmings. An example of a machine of this type is described in US-A-5799555.

[0005] These machines include a feed system for feeding the rolls or logs to be cut, typically constituted by a chain or by a plurality of chains carrying pushers, and a cutting member which cuts the head and tail trimmings and subdivides the remaining part of each log into individual small rolls. The feed movement of the logs by means of the feed system and the movement of the cutting member are synchronized so as to obtain the correct operation of the machine and therefore the disposal of the head and tail trimming and the subdivision of the intermediate portion of the log into small rolls of adequate length.

[0006] Recently, rolls or logs of tissue paper have been produced, decorated through band printing or embossing, i.e. obtained through winding of a web material, on which adjacent longitudinal areas are printed and/or embossed also with patterns or colors different from one another, so as to obtain on a same log or roll portions with decorative patterns different in design or color. In some cases these bands are mutually separated through white areas so as to avoid contamination of the color for printing one band with the color for printing the adjacent band. These rolls or logs must be cut in such a way so as to reject the head and tail trimmings and to subdivide the log into individual small rolls by means of cuts substantially orthogonal to the axis of the log according to cutting planes which intersect the log at the separation areas between the bands, in particular cuts at correspondence of the white bands that divide one colored area from the other when these bands are provided for.

[0007] Cutting these logs in a synchronized manner, i.e. in a manner phased with the printing patterns, can present some difficulties, in particular due to the fact that the paper or other web material which is wound on individual logs can shift transversely relative to the paper feeding direction, so as to obtain sequentially not perfectly identical logs. Consequently, the cut which is phased on a given log can be out-phased relative to the printing patterns obtained in the subsequent log or logs, when a shifting or other alteration phenomena occurs in the feeding of the paper in the rewinding machine which forms the logs.

Objects and summary of the invention

[0008] According to one aspect, the object of the present invention is to provide a machine and a method that entirely or at least partially overcomes at least one of the drawbacks of the traditional machines and methods.

[0009] The object of an embodiment of the present invention is to provide a machine which allows a correct phasing of the cut of the logs relative to the patterns, printing motifs, embossing motifs or the like, obtained in consecutive bands on the same roll.

[0010] Substantially, according to one embodiment, the present invention provides a severing machine for cutting logs of wound web material, comprising an electronic control, a feed system for feeding the logs to be cut and a cutting member, wherein the feed system and the cutting member are controlled by said electronic control in order to subdivide each log into a plurality of small rolls; characteristically, the electronic control is associated with a vision system, which detects at least one optically identifiable element on said log in order to phase the cut with respect to said optically identifiable element.

[0011] In some advantageous embodiments of the present invention, the optically identifiable element is defined by a print on the web material, although it would be possible to provide vision systems for viewing embossing motifs or other optically detectable characteristics on the roll or log.

[0012] In some embodiments of the present invention, the electronic control controls the feed system and the cutting member in such a manner that the log is subdivided into small rolls in correspondence of annular bands, which subdivide consecutive portions of the log that must correspond to individual consecutive small rolls which can be obtained from the cut of said log.

[0013] For example, the electronic control may be performed to phase the cut of the log depending upon the position of a separating band, which separates a first log portion of which must form a first small roll from a second log portion which must form a second small roll.

[0014] In some embodiments of the present invention, the electronic control is performed to phase the first cut of each log with a head trimming of the log, said head trimming being detected by means of said vision system.

[0015] In some preferred embodiments of the present invention, the electronic control is designed in such a manner as gradually to correct any displacement between the cut and said at least one optically identifiable element on said log, said gradual correction being set in such a manner that the small rolls obtained from the cut of said log have axial lengths variable within a preset maximum tolerance.

[0016] The vision system can be positioned far from the area in which the wounded logs are cut, but preferably it is arranged near the cutting plane in which said cutting member moves.

[0017] According to a further aspect, the present invention provides a method for subdividing a log of wound web material into single small rolls by means of a cutting member controlled in a synchronized manner with the feed of the log, wherein it is provided for maintaining or adjusting the phase between the position of the roll or log to be cut and the cutting member through the reading of at least one optically identifiable element on the surface of said log.

[0018] Further advantageous characteristics and embodiments of the method and of the machine according to the present invention are indicated in the appended dependent claims and shall be described in greater detail with reference to a non limiting embodiment of the invention.

Brief description of the drawings

[0019] The invention will be better understood by means of the description below and the attached drawing, which shows a non-restrictive practical embodiment of the invention. More in particular, in the drawing:

figure 1 shows a schematic side view of a severing machine to which the present invention can be applied;

figure 2 shows a diagram in axonometric view of a roll or log which must be subdivided into individual small rolls at correspondence of white bands which separate areas or bands decorated with motifs preferably different from each other on the same roll;

figure 3 shows an axonometric view of an individual small roll obtained by cutting the log of figure 2; and

figures 4A, 4B show schematic side views of two rolls obtained sequentially by a rewinding machine wherein the web material has been displaced between the winding of a roll and of the subsequent one.

Detailed description of embodiments of the invention

[0020] Figure 1 shows, in a very schematic manner, a severing machine, indicated as a whole with number 1, in which the present invention is incorporated. It should be understood that the configuration shown in figure 1 is just one of the possible configurations of a severing machine for paper logs or rolls, in particular of tissue paper, to which the present invention can be advantageously applied. The structure, the operation features, the mechanical elements and members of the severing machine can vary also in a substantial manner relative with those illustrated only by way of example in the attached drawing, provided that it is possible to incorporate in this severing machine the system subject of the present invention, which allows the correct phasing of the feed system for feeding the logs relative to the cut.

[0021] Severing machines of this type are known to those skilled in the art for example from US-A-5799555 and from other documents, as well as from numerous existing embodiments of machines of this category. Therefore, in the present description only the elements of the severing machine necessary to the understanding of the present invention will be schematically described.

[0022] The severing machine, indicated as a whole with number 1, comprises a feed system for feeding logs or rolls L to be cut towards a cutting head 11. The feed system can comprise for example a series of pushers 3 constrained to a chain 5 driven around wheels 7 and 9 supported by a bearing structure 10. As it is known per se, the severing machine 1 can be provided with more feed channels for feeding more logs or rolls R in parallel, in each channel being advantageously provided a chain 5 with respective pushers 3, which can also be independent of each other, for example actuated by independent motors for each channel, although this is not strictly necessary.

[0023] The head 11 includes a rotating unit 13 which carries a cutting blade or other cutting member 15. In the illustrated example, A-A indicates the axis of rotation of the rotating unit 13, and B-B indicates the axis of rotation, for example parallel to the axis A-A, of the cutting member 15 represented in this case by a rotary disc blade. These axes can be parallel to each other and to the direction of feed of the logs or rolls L, although this is not necessary, other configurations with skew axes being known. In some embodiments, the rotating unit 13 can be provided with a backwards and forwards alternate movement, so as to follow the feeding movement of the log during the cut.

[0024] Other arrangements of the cutting system are also possible; the system for example can also comprise a band blade, two disc blades instead of one, or any other configuration known per se.

[0025] In general, independently of the configuration of the head 11, the cutting member 15 moves in a cyclical manner so as to co-act with the roll or log L and to subdivide it into individual small rolls R with axial length equal to the final dimension of the product destined for use. Depending upon the longitudinal dimension of the initial roll or log L, from each log small rolls R can be obtained even in high number, due to the fact that modern rewinding machines can produce logs or rolls L with a length even of about 5 m.

[0026] In general, along the feed channel for feeding the log or roll L a cutting area is provided, in which the cutting member 15 acts and preferably in this area elements are provided for transversally retaining the log being cut. In the example shown in figure 1, numbers 21 and 22 indicate two retaining elements of this type, spaced from one another so as to leave between them an area in which the cutting member formed by the disc blade 15 penetrates and moves.

[0027] In some embodiments of the present invention, the rotation of the rotating unit 13 is controlled by a motor 23, whilst the rotation of the cutting member 15 is controlled by a second motor 25. The feed system 3, 5 for feeding the rolls or logs L can include and independent motor 27. A central unit, schematically indicated with the number 30, can be provided in order to control in a synchronous manner the feed system 3, 5 through the motor 27, and the cutting member 15 through the motor 23.

[0028] Characteristically, according to the present invention, in an adequate position along the forward trajectory of the rolls L a vision system 33 is arranged. In some embodiments of the present invention, the vision system 33 can include a camera and preferably one camera for each feed channel for feeding the rolls L. The camera or other vision system 33 can be arranged also upstream of the severing machine 1, in an adequate position between the severing machine and the station of the paper processing line upwards of the severing machine or in any other suitable position.

[0029] Preferably, as shown in figure 1, the vision system 33 is positioned in the cutting area, for example in such a manner so as to see the log L when it moves forward in the cavity between the transverse retaining elements 21 and 22 which transversally support the log being cut.

[0030] The function of the vision system 33 will be described in particular with the aid of figure 2. In this figure a log L is schematically illustrated, which must be subdivided into five small rolls indicated with R1, R2, R3, R4 and R5. More in particular, the log L has a head trimming RFT and a tail trimming RFC, both of which must be eliminated through cutting by means of the cutting member 15. In fact, these head and tail trimmings have frayed and defective areas of the web material with which the roll L is formed. These frayed areas are due to irregularities in the longitudinal edge of the web material, to displacements of the web during the production phases and in particular during rewinding, or to other factors.

[0031] In the illustrated example the small rolls R1, R2, R3, R4 and R5 are separated by bands F1, F2, F3, F4. It should be understood that the number of small rolls R1 - R5 is only an example, and that actually a log or roll L can have a much higher length, this resulting in the production of a much higher number of small rolls R.

[0032] The individual small rolls R1, R2, R3, R4 and R5 correspond to longitudinal areas of the wound web material provided with printing and/or embossing patterns which can be equal to each other or different from each other, and preferably are distinguished for example in the color from a small roll to the other. The bands F1 - F4 separate a pattern from the other, thus avoiding contamination between inks of different colors used for adjacent bands of the roll or log L. Cutting of the log L into the small rolls R1 - R5 must occur therefore in phase with the bands F1 - F4 and it must furthermore eliminate the head RFT and tail RFC trimmings. All this must occur in such a manner that the cuts are phased as much as possible with the areas or bands F1 - F4, so that on each small roll R1 - R5 longitudinal border areas are formed for example devoid of color and as much as possible equal to each other on the two ends of the small roll, as shown in particular in figure 3, in which one of the rolls R1 - R5 is represented by way of example and is indicated with R, provided with end bands FA - FB.

[0033] The correct positioning of the cutting plane relative to the trimmings RFT, RFC and to the bands F1 - F4 is obtained due to the effect and with the aid of the vision system 33, interfaced with the programmable control unit 30 which, in turn, controls the motors 27 and 23 described above or other systems for moving forwards and handling the cutting group.

[0034] The vision system, for example a camera 33, allows to observe the log L which arrives in the cutting area defined between the transverse retaining elements 21, 22. The camera detects the image of the log L and in particular it is able to see the head trimming RFT and the point where the printing pattern of the first small roll R1, which must be obtained from cutting the log L, begins. The actuation of the cutting member 15 can be controlled or adjusted by means of the central control unit 30 based upon this observation. One can assume for example that the machine 1 is phased on a log L correctly produced, whose head trimming RFT has a preset dimension. If this dimension changes due for example to the effect of a displacement of the web material during winding, the phase between the movement of the cutting member 15 and the feed system 3, 5 must be modified so as to avoid that the cuts generated by the cutting member 15 result outphased relative to the position of the bands F1 - F4 and/or of the head and tail trimmings RFT and RFC.

[0035] This adjustment can occur for example by modifying in one single step (i.e. with only one adjusting intervention between one cut of the log L and the subsequent cut) the movement of the feed system 3, 5 relative to the movement of the cutting member 15. Figures 4A, 4B show an example of what can occur in the case of paper displacement with consequent production of a log whose head trimming RFT has a dimension different from that for which the machine has been synchronized.

[0036] Figure 4 shows the situation for which the machine has been originally synchronized. A roll L1 is shown with a head trimming RFT and a series of areas from which the small rolls R1, R2, R3, R4 ... must be obtained, separated by bands F1, F2, F3 ... T1, T2, T3 ... indicate the planes along which the cuts must be performed by the cutting member 15 to obtain the correct subdivision of the log or roll L1 into the individual small rolls R1, R2, R3 ..., so that each small roll has an adequate border or end white band as shown in figure 3.

[0037] Figure 4B shows a log L2 which has a head trimming RFT1 of greater longitudinal dimension, i.e. in the axial direction of the log L2, relative to that for which the machine has been phased, i.e. synchronized. In this case, without an adequate adjustment, the cut T1 and the cut T2 will form a small roll R1 whose axial length is correct but which will present a white band wider than the due one on one side, and will be devoid of white band on the other side. Also the subsequent small roll R2 will be provided with a wider white band on one side and will be devoid of band on the other side.

[0038] In other words, each small roll R1, R2, R3 ... will present a pattern outphased relative to the front faces of the small roll.

[0039] To solve this situation, the vision system 33 is used, which is suitable to detect the line 1 which separates the head trimming RFT1 from the decorated area of the first small roll R1, and, based upon the signal obtained, by processing the image detected by the camera 33 or other vision system, it is possible, with the central unit 30, to put in phase the feed system 3, 5 relative to the cutting member 15 and to the movement thereof.

[0040] The adjustment may occur, as schematically indicated in figure 4B, by making, between the first cut T1 and the second cut T2, the small roll L2 to move forward by an entity X greater than the normal length of a small roll R, length which is indicated with LR in figure 4B. In this way, by returning the movement forward of the subsequent small rolls to the normal length LR, the cuts, subsequent to the cut T1, performed first by the machine, will be arranged in positions T2C and T3C instead of T2 and T3 (figure 4B). Consequently, the first small roll R1 defined between the cuts T1 and T2C will have a length X greater than the preset length, and it may be eventually discarded as it could cause difficulties during the packaging phase. Furthermore, it will be characterized by a white band on one end greater than the due band because of the changed dimension of the head trimming RFT1. Vice versa, the subsequent small rolls R2, R3, ..., will be correctly cut at the length LR, and will have end white bands FA, FB positioned in a correct manner relative to the central pattern.

[0041] This operating mode, i.e. this cutting method with adjustment of the phase between cutting planes and position of the decorative band of the individual small rolls has the advantage that, in case of error, this is immediately adjusted, and therefore only one small roll R1 is discarded in the illustrated example, and then generating subsequent small rolls correctly cut with the pattern correctly centered between the two white lateral bands FA, FB.

[0042] However, this method can have some drawbacks as regards the management of the cut-offs. In fact, in this case it is necessary that a control system provides for the discarding of the first small roll R1, which can have an excessive axial length to be manipulated in the subsequent packaging stations, as its defect in axial length (X-LR) will be greater than the allowance compatible with the correct operation of the packaging machines.

[0043] According to a different method for cutting and adjusting the phase between cutting planes and decorative patterns on the log or roll L, the adjustment may be gradual. In this case, when an error occurs, and is detected by means of the vision system 33, in the positioning between the first cutting plane T1 and the first line I of the decorative pattern of the small roll R1, instead of using the control unit 30 for total adjustment of the error by making the log or roll L to increase or decrease by the necessary entity the advancement of the log before the subsequent cut on the plane T2C, the adjustment will be made in a stepped manner, by subdividing the error in an adequate number of steps, so that each subsequent small roll will be generated with an error equal to a fraction of the error detected as a whole, so that it can be packaged as its difference in length relative to the standard length LR is compatible with the tolerances allowable in the packaging machines, and at the same time the outphase between the cutting planes and the decorative pattern of the individual small rolls will be compatible with the aesthetical characteristics of the individual small rolls produced.

[0044] In this second operating mode, the subsequent small rolls will be therefore produced slightly outphased, i.e. with the decorative pattern not centered relative to the front faces, and therefore side bands FA, FB not perfectly equal for a certain number of small rolls, but (except in exceptional cases) all the small rolls can be used in the downstream packaging machines, as the adjustment made is within tolerance limits on the axial length LR of the individual small rolls, compatible with the needs for dimensional accuracy and regularity required by the downstream packaging machines.

[0045] In both the cases, with the vision system represented by the camera 33 or other suitable system, it is possible to adjust in an automatic and sufficiently fast manner any error in positioning of the decoration areas of the individual small rolls R1 - Rn, and it is therefore possible to reduce defects in the small rolls produced and destined for packaging.

[0046] It is understood that the drawing only shows an example provided by way of a practical arrangement of the present invention, which can vary in forms and arrangements without however departing from the scope of the concept underlying the invention. Any reference numbers in the appended claims are provided for the sole purpose of facilitating reading of the claims in the light of the description and the drawing, and do not in any manner limit the scope of protection represented by the claims.

Claims

1. A severing machine for cutting logs of wound web material, comprising an electronic control, a feed system for feeding the logs to be cut and a cutting member, said feed system and said cutting member being controlled by said electronic control in order to subdivide each log into a plurality of small rolls, characterized in that said electronic control is associated with a vision system, which detects at least one optically identifiable element on said log in order to phase the cut with respect to said optically identifiable element.

2. A severing machine as claimed in claim 1, characterized in that said optically identifiable element is defined by a print on said web material.

3. A severing machine as claimed in claim 1 or 2, characterized in that said electronic control controls the feed system and the cutting member so that the log is subdivided into small rolls in correspondence of annular bands, which divide consecutive portions of the log that must correspond to single consecutive small rolls which can be obtained from the cut of said log.

4. A severing machine as claimed in one or more of the previous claims, characterized in that said electronic control is designed so as to phase the cut of the log in accordance to the position of a separation band for separating a first log portion, which must form a first small roll, from a second log portion, which must form a second small roll.

5. A severing machine as claimed in one or more of claims 1 to 3, characterized in that said electronic control is designed so as to phase the first cut of each log with a head trimming of the log, said head trimming being identified through said vision system.

6. A severing machine as claimed in one or more of the previous claims, characterized in that said electronic control is designed in such a manner as gradually to adjust any displacement between the cut and said at least one optically identifiable element on said log, said gradual adjustment being set so that the small rolls obtained from the cut of said log have axial lengths variable within a preset maximum tolerance.

7. A severing machine as claimed in one or more of the previous claims, characterized in that said vision system is arranged in proximity to a cutting plane, in which said cutting member moves.

8. A severing machine as claimed in claim 7, characterized in that it comprises retaining elements for transversely retaining the log in correspondence of a cutting area, and in which said vision system comprises a vision member arranged near said retaining elements.

9. A severing machine as claimed in one or more of the previous claims, characterized in that said vision system comprises a camera associated with a microprocessor on which an image processing program runs.

10. A method for dividing a log of wound web material into single small rolls through a cutting member controlled in a synchronized manner with the feed of the log, characterized by maintaining or adjusting the phase between the position of the log and the cutting member through the reading of at least one optically identifiable element on the surface of said log.

11. A method as claimed in claim 10, characterized by phasing the first cut of the log with a head trimming, defining through optical reading the longitudinal dimension of said trimming.

12. A method as claimed in claim 10, characterized by performing a first cut for the elimination of the head trimming of the log and by phasing the subsequent cuts with said at least one optically identifiable element on the surface of said log.

13. A method as claimed in claim 10, 11 or 12, characterized by adjusting the phase between the position of the log and the cutting member in a gradual manner, maintaining the dimension of each small roll obtained from the cut of the log within a preset tolerance range.

Drawing