SHEET TRANSFER UNIT IN AN INTERFOLDING MACHINE

AND METHOD OF USE THEREOF

Technical Field

[1] The present invention relates to a device for the transfer of bundle of sheets interposed between a pair of folding rollers and an unloading plan in a machine for the transformation of paper, in particular a machine for the production of interfolded.

[2] The invention also relates to a method for the separation of bundle of sheets of appropriate size from a growing stack of sheets in an interfolding machine.

Background Art

[3] As known, there are numerous paper made articles, especially of the disposable type, such as paper towels, handkerchiefs, toilet paper or similar, which are sold in sheets packaged in such a way that a single pack is constituted by a plurality of individual sheets suitably folded and stacked one on the other in an interfolded mode.

[4] To obtain this type of products they are used machines called interfolding

machines in which there are a plurality of rollers arranged in two distinct sequences each of which receives a strip of paper material, usually tissue, from which the sheets are obtained. The tape is first cut into sheets of suitable length and then conveyed toward a pair of counter-rotating folding rollers, each constituting the last roller of the above said rollers sequences. In correspondence with the folding rollers, the paper material sheets are folded and suitably overlapped in such a way that on a sheet coming from the first rollers sequence is partially overlapped a subsequent sheet coming from the second rollers sequence.

[5] At the exit from the folding rollers, the stacked and partially overlapped sheets are separated into default size bundles and then transferred to an unload unit.

[6] Between the folding rollers and the unload unit it is therefore present a transfer unit that has the function of separating a stack of sheets that has reached the default size by the following incoming sheets and of temporarily supporting it and / or compacting it to allow an effective subdivision into bundles of sheets. The separation, compaction, sustenance of the stack of sheets are obtained by pluralities of separation members which, disposed to the side of the stack of sheets, are inserted with the appropriate timing into the stack of sheets itself.

[7] A conventional transfer unit of this type is described for example in US4770402 in which, as soon as a stack of sheets on a storage surface reaches a certain height, a first plurality of separation members is introduced into the stack of sheets from one side, while a second plurality of separation members is introduced into the stack of sheets on the other side. In this way the stack of sheets of a given height is contained between the storage surface and the first plurality of separation members, while the second plurality of separation members supports the new growing stack of sheets until the return of the storage surface. The separation members are connected to the storage surface and perform a rotation movement with respect to this.

[8] Another conventional transfer unit is described in EP 1640305, more versatile than the previous one, as quickly adaptable to operate with interfolded products of different configuration, for example, Z, V, and W, and also in presence of sheets not previously separated but also with pre-cut tape with discontinuous cutting line. This transfer unit includes first separation members and second separation members located on opposite sides of the stack of sheets and compaction means and supporting means for the stack of sheets similarly located on opposite sides of the stack of sheets. Each of the above said members of separation, compaction and support are slidably mounted both horizontally and vertically on guides and are independently operable one from the other. Transfer unit such as that one outlined above that have separation members which are introduced below the folding rollers with pure translatory movement are suitable to be used in machines in which the folding rollers, usually of the type operating by vacuum creation, are assisted in the folding operation by further mechanical folding members, so that the separation members may be introduced at a certain distance from the output point of the sheets from the folding rollers. Otherwise, machines that include the use of a mechanically operated folding rollers, for example of the wedge and clamp type, do not require the presence of auxiliary folding members, and yet it is appropriate that the separation members are as close as possible to the output point of the sheets issued by the folding unit, and it is therefore necessary that the separating members are also equipped with a rotatory movement.

[9] Other conventional transfer unit are described in US 4721295, US 6322315, WO

2011045647 and all of them include the separation members arranged on the sides of the growing stack of sheets and that are introduced with the appropriate timing in the latter by a horizontal translation movement or by a rotation.

[10] A common problem for transfer units in the interfolding machines, that the transfer units above described can not efficiently overcome, consists in the necessity to work at high speeds imposed by the paper treatment lines, without having to resort to too heavy, complex and expensive structures. In fact, the side introduction movement of the separation members must be run at very high speed compared to the other descent and ascent movements.

[11] The problems with the conventional transfer units are mainly due to the inertias played during the movement of the separation members that make it particularly difficult to move these latter from their position on the side of the stack of sheets to the working position in which they are introduced into the stack of sheets, in the time lapse of a few hundredths of a second dictated by the normal working speeds of today's interfolding machines. Even designing separation members with a very light structure and using very powerful actuators, it is yet difficult to ensure the required speeds of movement, and are also to be considered the structural and costs problems that these design needs involve.

[12] In fact, with the conventional transfer unit above described, as soon as a stack of sheets is completed, the most commonly adopted solution is to reduce the speed of the machine, that is to say the paper feeding speed, so as to enable the separation members to be properly introduced between two consecutive sheets.

Summary of the invention

[13] The object of the present invention is to propose a transfer unit in an interfolding machine so as to overcome the above noted problems in the prior art.

[14] More specifically, an object of the present invention is to propose a transfer unit in an interfolding machine which allows high working speeds without the need to provide high power actuators.

[15] Another object of the present invention is to propose a transfer unit in an interfolding machine with a simple and economic structure.

[16] Another object of the invention is to propose a transfer unit particularly suitable to be used in interfolding machines comprising folding rollers mechanically actuated, in particular with the clamp and wedge folding unit.

[17] The above mentioned objects are achieved by a transfer unit in an interfolding machine provided with means suitable to provide stacked sheets arranged in an in- terfolded configuration and with an unload unit suitable to receive bundles of stacked sheets, with the above said transfer unit suitable to separate the interfolded stacked sheets into bundles of appropriate size and to transfer the separated bundles to the unload unit of said machine, wherein the transfer unit comprises at least a first separation unit provided with a first plurality of separation members suitable to cause the separation of the formed stack in a lower portion which constitutes a bundle of sheets of appropriate size and in a top portion which constitutes a growing stack of sheets, and with a support and handling assembly of the above said first plurality of separation members thanks to which the above said separation takes place as a result of a side introduction movement of the above said first plurality of separation members in the growing stack of sheets, characterized in that said support and handling assemblies comprise constraint members suitable to allow the movement of said first plurality of separation members according to a work path of their own comprising said side introduction movement, at least one electric motor suitable to determine the advancement of said first plurality of separation members along said work path and at least a pneumatic actuator suitable to push said first plurality of separation members during said side introduction movement.

[18] The transfer unit of the invention above outlined allows, with a simple and low- cost structure, to not have to reduce the speed of the machine at the moment when the separation members have to perform the side introduction movement to separate the formed stack of sheets in two portions, top and lower. With the adopted solution, this is possible whatever it is the trajectory of the side introduction movement of the separation members thanks to the fact that, only in the path portion of the separation members that constitutes the side introduction movement, the electric actuators that determine the sequence of the path are assisted by pneumatic actuators which, getting pressurized with the appropriate timing, significantly reduce the inertia due to the weight of the separation members and of the related supporting structures which opposes to the acceleration of the electric actuator at the time of the cue, so as to say at the start of the side introduction movement.

[19] The above mentioned objects are achieved also by a method for the separation of a formed bundle of sheets from a growing stack of sheets in an interfolding machine provided with means suitable to provide stacked sheets arranged in an interfolded configuration, with an unload unit suitable to receive bundle of stacked sheets and with a transfer unit suitable to separate in bundles of appropriate size the interfolded stacked sheets and to transfer the separated bundles to the unload unit of said machine, wherein said transfer unit comprises at least a first separation unit provided with a first plurality of separation members suitable to cause the separation of the formed stack of sheets in a lower portion which constitutes a bundle of sheets of appropriate size and in an top portion which constitutes a growing stack of sheets, and with a support and handling assembly of the above said first plurality of separation members thanks to which the above said separation takes place as a result of a side introduction movement of the above said first plurality of separation members in the growing stack of sheets, in which said support and handling assembly comprises constraint members suitable to allow the movement of said first plurality of separation members according to a work path of their own comprising said side introduction movement, a downward support movement in which said first plurality of separation members move vertically downwards at a speed synchronized with the speed of delivery of the stack of sheets by the means, a retraction movement in which the first plurality of separation members come out with a horizontal movement by vertical grid members of said means for standing alongside of said stack of sheets, and a return and preparation movement in which the first plurality of separation members are returned to the standby position to carry out said side introduction movement, and wherein said support and handling assembly is provided with electric motors and pneumatic actuators provided for moving said first plurality of separation members according to relative directions identified by said constraint members, said method being characterized in that said pneumatic actuators are activated only for the execution of said side introduction movement.

[20] Further characteristics and specific embodiments of a transfer unit according to the invention are described in the dependent claims.

Description Of Drawings

[21] These and other advantages associated with the transfer unit of the invention will become more easily understood through the illustration of a preferred embodiment, non-limiting, as described below with the aid of the enclosed drawings, in which:

• Figures 1 to 4 schematically show an embodiment of a transfer unit according to the invention, a unit suitable to provide bundled sheets arranged in an in- terfolded configuration and an unload unit suitable to receive stack of bundled sheets in an interfolding machine, in various operative sequences of the invention's transfer unit;

• Figure 5 shows a work path of separation members in a transfer unit

according to the invention.

Detailed description of preferred embodiments

[22] In figures from 1 to 4 it is schematically shown a portion of an interfolding

machine that comprises a unit suitable to provide stacked sheets arranged in an in- terfolded configuration, 10, an unload unit, 20, and a transfer unit, 100.

[23] The unit suitable to provide stacked sheets arranged in an interfolded configuration

10 comprises a pair of counter-rotating folding rollers, 11, 12, which receive the paper sheets from two separate sheets supply units, not shown, and are provided with members, not shown, suitable to selectively retain the sheets and to create transverse folding lines in the sheets themselves. The unit 10 also comprises a pair of vertical grid members, 13, which receive and guide the formation of the bundle of sheets in interfolded configuration output from the folding rollers 11 and 12, suitably folded possibly with the aid of folding arms, not shown, that may be present below the folding rollers 11 e 12 themselves.

[24] The formed stack, 30, is guided by the pair of vertical grid members 13 until the unload unit 20 which comprises a belt conveyor, 21.

[25] Between the output from the pair of folding rollers 11, 12 and the unload unit 20, the growing stack of sheets is separated into bundles of appropriate size, supported, compacted and transferred to the unload unit 20 by the transfer unit 100.

[26] The transfer unit 100 comprises a first separation unit, 110, and a second

separation unit, 170. The first separation unit 110 is provided with a first plurality of separation members, 120, suitable to cause the separation of the bundle of sheets formed in a lower portion which constitutes a formed bundle of sheets, 31, of appropriate dimensions and in an top portion that constitutes a growing stack of sheets, 32. The second separation unit, 170, is provided with a second plurality of separation members, 180, suitable to pick up a growing stack of sheets from said first plurality of separation members 120 and to support it up to deposit a stack of sheets formed on said unload unit 20.

[27] According to the working mode above defined, as some of its stages of progress are shown in figures from 1 to 4, the first plurality of separation members 120 performs a work path, 60, schematically shown in fig.5. More precisely, fig. 5 shows the trajectory followed by the fingers tip, 121, of the first plurality of separation members 120, which is sufficiently illustrative of the work path 60. The work path 60 comprises: a side introduction movement, 61, whose initial position is shown in fig. 1 and the final position is shown in fig. 2, in which the first plurality of separation members 120 that are located at the side of the vertical grid members 13 are introduced at high speed and with a proper trajectory below the pair of folding rollers 11, 12, so as to insert themselves in the growing stack of sheets and separate the growing stack of sheets in a lower portion which constitutes a bundle of sheets 31 and an top portion that constitutes the growing stack of sheets 32; a downward support movement, 62, which begins in fig. 2 and ends in fig. 4, in which the first plurality of separation members 120 move vertically downwards at a speed synchronized with the speed of delivery of the formed stack 30 by the unit 10; a retraction movement, 63, in which the first plurality of separation members 120 come out with horizontal movement from the vertical grid members 13 ceasing to support the growing stack of sheets 32 and standing alongside of the same; a return and preparation movement, 64, in which the first plurality of separation members 120 are returned to the standby position of fig. 1 first by a vertical translation movement and then by a subsequent rotational movement. The downward support movement 62 is performed as already specified with a speed synchronized with the speed of delivery of the stack of sheets 30, that is, at very low speed, the retraction movement 63 and the return and preparation movement 64 are performed at a higher speed with respect to the previous but still does not require special speed performance, while the side introduction movement 61 has to start from a substantially zero speed and be completed in a time equal to a few hundredths of a second and therefore it needs particularly high speeds and accelerations. A support and handling assembly, 130, of the first plurality of separation members 120 below described is capable of moving the first plurality of separation members 120 according to the work path 60 and with the requirements of speed and acceleration above described.

[28] The support and handling assembly 130 comprises a first translation assembly,

140, rotation means, 150, and a second translation assembly, 160. The first translation assembly 140 comprises a first linear rail, 141, along which vertically translets a relative carriage, 142. The first linear rail 141 is advantageously a belt linear rail in which the carriage 142 is translated along the tracks of the guide by a first electric motor, 143, arranged at an end of the rail 141. The carriage 142 is also supported by at least a first pneumatic actuator, 144, advantageously a double-acting pneumatic cylinder, with its axis parallel to the axis of the first linear rail 141, as to say with vertical axis.

[29] The second translation assembly 160 is connected to the carriage 142 by the

rotating members 150 which comprise hinge constraining means with horizontal axis, 151, an electric motor, 152, suitable to determine the swinging movement of the second translation assembly 160 around the axis of the hinge means 151, and at least a pneumatic actuator of rotation movement, 153, advantageously a pneumatic double- acting cylinder, hingedly constrained with one of its own end to the carriage 142 and with the other of its own end to the second translation assembly 160, so that the rotation axis of the pneumatic actuator 153 is spaced from the axis of the hinge means 151 in a way to create a moment which tends to cause the rotation of the second translation assembly 160 with respect to the axis of the horizontale hinge means 151. The electric motor 152, in the depicted embodiment, is a gearmotor whose output axis is coaxial with the axis of the hinge means 151, however, for a specific sector expert, it will be easy to provide motion transmission members of a different type, for example also by means of linkages or other kinematic motions, however, in a way to cause a relationship of phase between the rotation of the electric motor 152 and that one of the second translation members 160 with respect to the axis of the hinge means 151.

[30] The second translation assembly 160 includes a guide rail, 161, which is rigidly coupled to the hinge means 151 and to the pneumatic cylinder 153 of rotation movement. Along the guide rail 161 can slide a support frame, 162, to which are integral the first plurality of separation members 120. The movement of the support frame 162 along the guide rail 161 is determined by an electric motor, 163, through appropriate motion transmission members, not shown, and at least by a second pneumatic actuator, 164, constituted by a double-effect pneumatic cylinder, which is constrained at one of its own end to the guide rail 161, and at the other of its own ends to the support frame 162 so as to have its axis parallel to the guide rail 161.

[31] The support and handling assembly 130 realizes a support system of the first

plurality of separation members 120 with three degrees of freedom, two degrees of freedom of translation and one of rotation, which allow the first plurality of separation members 120 to perform the work path 60 according to the proper orientation. In particular, the downward support movement 62, the retraction movement 63 and the return and preparation movement 64 are determined only by the selective actuation of the electric motors 143, 152, 163. The side introduction movement 61 provides a trajectory of the first plurality of separation members 120 which involves the movement according to all three degrees of freedom above defined. The side introduction movement 61 takes place with a start from a substantially standby position in a few hundredths of a second time thanks to a substantially simultaneous activation of the three electric motors 143, 152, 163 and of the three pneumatic actuators 144, 153, 164. In fact, the actuation of the pneumatic cylinders allows to considerably reduce the inertia experienced by the electric motors 143, 152, 163 and then to use electric motors with starting torque also relatively low and to obtain the acceleration and speed performance required by the side introduction movement 61.

[32] The second separation unit 170, comprising the second plurality of separation

members 180, provides a second support and handling assembly, 190, of conventional type. The second support and handling assembly 190 has two degrees of freedom of translation, one of vertical translation and one of horizontal translation. The vertical translation is obtained by a belt linear guide, 191, vertically disposed, whose carriage, 192, is vertically moved by a relative electric motor, 193. Integral with the carriage 192 it is a horizontal guide rail, 194, on which is horizontally movable a support frame, 195, which integrally carries the second plurality of separation members 180. The movement of the support frame 195 is determined by a relative electric motor, 196.

[33] Obviously, the shown and described embodiment is only an example and variations and modifications may be envisaged without departing from the inventive concept of the present invention. In fact, the above said embodiment is particularly suitable when the side introduction movement 61 is relatively complex since it involves a movement of roto-translation of the first plurality of separation members 120.

[34] Alternatively, in the case, for example, that the side introduction movement 61 results in a pure horizontal translation, it might be envisaged only the presence of the second pneumatic actuator 164 and the corresponding electric motor 163, while a vertical translational movement, however usually required in other phases of the work path 60, might be performed only by the electric motor 143. Similarly, in the case that the side introduction movement 61 is constituted by a pure rotation movement around a horizontal axis, it could be envisaged only the pneumatic actuator of rotation movement 153 to assist the work of the corresponding electric motor 152.

[35] In a further different embodiment, also in the case that the first plurality of

separation members 120 have to follow a side introduction movement 61 of roto- translation, one or two of the pneumatic actuators 144, 153, 164 may be omitted. For example, according to a particularly advantageous embodiment as simple and economical, it is omitted the second pneumatic actuator 164. In fact, if the support frame 162 and the first plurality of separation members 120 constitute a sufficiently light structure and then with a limited inertia, the second translation movement, with mainly horizontal component, can also be effectively performed by a single electric motor with relatively contained size and starting torque, thus making superfluous the presence of the pneumatic actuator 164.

[36] A further embodiment may provide, for example, that the second plurality of

separation members 180 is associated with a support and handling assembly 130 similar to that one of the first plurality of separation members 120.

[37] Certainly, in addition to the above explained, many other variants can be brought to the transfer unit of the invention, by replacing the individual components with other functionally equivalent, remaining within the context of the implementation of the inventive idea above described and within the field of protection defined by the following claims.