Longitudinal perforating device for paper printing and/or processing machines

Abstract

 A device (4) for the intermittent, longitudinal perforation of a continuous web of paper (1) which moves across a longitudinal perforation group (2) comprising a countersupport roller (3). The group also comprises a circular tool (5) with a sharp, toothed edge which is mounted in a rotatable manner on a support (7) and is suited to roll on the roller (3), producing a longitudinal perforation (6) on the paper (1). The support (7) is able to simultaneously carry out a translation movement along the bar and a rotation movement with respect to the bar's axis. The rotation movement greatly facilitates the rapid approach of the tool (5) with respect to the paper (1) and roller (3), in a direction tangential to them, upon the action of actuators (12, 13, 23, 24). It is thus possible to intermittently perforate the paper without wear on the tool since it rotates at a surface speed equal to that of the countersupport roller (3) and the paper (1).

Description

[0001] The present invention relates to the field of paper and more precisely to a longitudinal perforating device for paper processing and/or printing machines.

[0002] In machines for processing and/or printing paper it is often necessary to carry out longitudinal perforations on the web of paper, which make it possible to tear the paper along the obtained perforated line at a later time.

[0003] This can be necessary for example for separating the side strips that have holes along them for the paper advance from the central portion, or for dividing sheets of paper into smaller sheets, for example in order to detach a payment notice from a bill.

[0004] In most cases, the line of perforation is continuous. The cutting tool, which is a sharp, toothed wheel, engages in a rolling manner, pressing on a countersupport roller on which the paper advances. The movement of approach of the tool towards the roller and at the end against it must be regulated with care since any kind of impact that could damage the sharpness of the tool must be avoided.

[0005] It is, however, frequently necessary to have a discontinuous perforation. This, for example, may be necessary when, in printing a bill, one sheet from which a label must be formed, delimited by two transversal perforations and by at least one longitudinal perforation, is followed by a sheet which must not have longitudinal perforations, for example a financial statement.

[0006] In the above-mentioned case, the problem of the alternate longitudinal perforation is currently resolved with a tool having a circular edge which is cam shaped, regular for only a portion of the circumference, the other portion being slightly squashed or even being entirely missing so that it does not make contact with the paper.

[0007] The use of such a cam shaped tool has, however, two inconveniences.

• it is not possible to perforate the paper in a non alternating discontinuous way;
• it is not possible to vary the length of the perforated tract or non perforated tract without having to change the tool.

[0008] These inconveniences are particularly felt when the machine is of a flexible type or, in other words, when it can process and/or print in rapid succession, upon computerized command, a series of different documents, some of which require continuous perforations and others of which require alternating or discontinuous perforations in an irregular manner.

[0009] To overcome these inconveniences, in some machines, an effort has been made to make the approach of the tool rapid so as to permit its nearing or distancing from the countersupport roller at a frequency controlled by computer. Notwithstanding the high precision of the movement of approach on guides orthogonal to the roller, and although the tool is extremely light and mounted on idle supports with minimum friction, it is impossible for the tool to make contact with the roller without impact with the countersupport roller, with the consequence of a rapid wearing of the cutting edge and, therefore, the necessity of changing the tool very frequently. This brings about discontinuity in the efficiency of the cutting as well as high maintenance costs, due mostly to having to stop the machine frequently for the substitution of the tool.

[0010] In addition, when the paper is advanced at a high speed, it is not possible for the tool to contact the paper without tearing it locally, resulting in an evident disadvantage in terms of quality. In the case, moreover, in which the frequency of nearing and distancing movements is very high, similar, for example, to the frequency of alternating perforation obtained with the tool having a cam shaped profile mentioned above, the cutting edge would become worn out so rapidly that it would make this solution entirely inconvenient.

[0011] The object of the present invention is to provide a longitudinal perforating device for paper processing and/or printing machines which is extremely simple to construct and which makes it possible to perforate the paper in an intermittent discontinuous way also making it possible to vary the length of the perforated tract or of the non perforated tract without having to change the tool and without subjecting it to rapid wearing.

[0012] These and other objects are accomplished by the device according to the invention whose novel feature is that it comprises a circular tool for perforation mounted on a motorized support which gives the tool a tip speed substantially equal to that of the paper and the countersupport roller and that simultaneously provides a movement of alternating approach of variable frequency.

[0013] Preferably, the support of the tool determines an approach movement according to a curved trajectory, the tool nearing the countersupport roller and the paper in a tangential direction.

[0014] According to one preferred solution, the support of the tool is mounted in a rotatable manner on a transversal grooved bar which rotates around its own axis and to which a gear wheel for transmitting motion to the tool is keyed, the support being able to contemporaneously rotate around the grooved bar and translate along it, so that it is also possible to position the line of perforation in a direction transversal to the paper.

[0015] Further characteristics and/or advantages of the device according to the invention will become apparent in the following description of one of its possible embodiments, given as an example and not limitative, with reference to the attached drawings in which:

• figures 1 and 2 are simplified perspective views of a couple of longitudinal perforation devices according to the invention applied to a machine for paper processing and/or printing;
• figure 3 is a scrap longitudinal sectional view of a longitudinal perforation device according to the invention;
• figure 4 is a scrap transversal sectional view of a couple of longitudinal perforation devices according to the invention.

[0016] With reference to figures 1 and 2, a continuous web of paper indicated with 1 crosses a longitudinal perforation group 2 comprising a countersupport roller 3 and a couple of perforation devices 4 according to the invention.

[0017] The perforation devices each comprise a circular tool 5 with a sharp, toothed edge suited to roll on roller 3 producing a longitudinal perforation 6 on paper 1. Each tool 5 is mounted in a rotatable manner on a support 7 and is set in rotation by a grooved transmission bar 8 on which a gear wheel 10 is keyed which is, in turn, connected to a gear 11 integral with tool 5. Support 7 is connected in an idle rotatable manner to bar 8 by means of a bearing 9, so that it can simultaneously carry out a translation movement along it and a rotation movement with respect to its axis, respectively according to arrows A and B of figure 4.

[0018] The translation movement allows for the placement of tool 5 in a transversal direction so as to vary the distance of perforation 6 with respect to the edges of paper 1. The rotation movement, on the other hand, makes it possible to rapidly approach tool 5 to paper 1 and roller 3 with extreme ease.

[0019] As can best be seen in figures 3 and 4, the angular position of support 7 with respect to grooved bar 8 is controlled automatically by a small piston 12 which acts on a lever 7a protruding from support 7. The piston 12 is part of a double-acting pneumatic actuator 13 supplied by a conduit 13a and integral with a carriage 14 which can slide transversally, in a way that can be blocked by means of a handle 15, on a couple of guides 16 so as to allow for the transversal placement of tool 5 with respect to paper 1.

[0020] The guides 16 (figs. 1 and 2) extend transversally between the support walls 17 to which also roller 3, bar 8 and paper dragging rollers 18 are keyed. Dragging rollers 18 are set in rotation by belt drive means 20 and a belt 21. In addition to actuator 13, carriage 14 (figs. 3 and 4) is connected to support 7 by means of a bearing 22 which allows for its dragging in a transversal direction when carriage 14 slides along guides 16. Furthermore, a pusher 23 is provided for as part of an actuator 24 which acts against a lever 7b protruding from support 7. Pusher 23 functions to counterbalance the action which piston 12 has on support 7 thus dampening the approaching movement of tool 5 at the time of contact with roller 3.

[0021] In the above-mentioned figures, a paper feed 25 mounted on a guide 26 and set in rotation by a grooved bar 27 is also shown.

[0022] As can be seen in figure 3, the approaching movement of tool 5 occurs according to a curved trajectory C in a substantially tangential direction with respect to roller 3, reducing the probability of impact between the sharp edge of tool 5 and roller 3 itself to a minimum, and thus considerably increasing the duration of the sharp edge. These probabilities of impact are further reduced by the presence of pusher 23 which also ensures a constancy and punctuality of the sinking of the tool in the paper. The fact that actuator 13 is of a pneumatic type further facilitates the dampening action on the part of pusher 23 and reduces the damaging effect of a possible contact of tool 5 with roller 3.

[0023] It should be noted that the movement of approach of tool 5 to roller 3 is illustrated in figure 3 in an exaggerated manner with respect to the real values which are on the order of a few tenths of a millimetre. Actuators 13 and 24, in fact, have extremely limited strokes which are, in substance, comparable to small jerks in the two opposite directions which allow for the nearing and distancing of tool 5 with respect to the paper on roller 3.

[0024] The increase of the duration of the sharp edge is, however, mostly due to the fact that tool 5 of the device according to the invention is motorized by bar 8 and its surface speed is constantly equal to that of the paper and the countersupport roller 3, depending on the choice of the diameters of gears 21. With respect to the known technology, therefore, no tangential forces are discharged on the sharp teeth of tool 5 since, at the time of contact, the tool is rotating at a surface speed different from that of paper 5 and roller 3, with the consequent local tearing of the former and inertial impact against the latter. The surface speeds of tool 5 and roller 3, on the contrary, make it possible for the cutting edge of the former to join the paper when it makes contact to cut onto it. The sudden and short movement of approach of tool 5, on the order of a few tenths of a millimetre, makes it so that its cutting edge sinks instantaneously in the paper at the desired moment, substantially without touching roller 3 and thus without losing its sharpness even following intermittent use over a prolonged time.

[0025] The characteristics described above allow machines incorporating the device according to the invention to carry out a discontinuous perforation on the paper they advance even when the advance speed is fast (i.e. several meters a second). The movement of piston 12, in fact, can be controlled directly by a computer which knows the position of each sheet and -can calculate the exact moment in which tool 5 must lower itself toward and raise itself from the paper.

[0026] One very advantageous use for the device according to the invention can be made in the case of the printing of bills that have to be addressed to a large number of customers and which incorporate a postal notice for payment which, as known, often extends to a length greater than the width of standard A4 size sheets of paper. According to the known technology, the paper used had to be of a width sufficient to contain the transversally placed notice and had to be separated by transversal perforations. According to the invention, on the other hand, it is possible to perforate the notice in the longitudinal direction and only in the sheet that has to contain it, whereas the subsequent sheet or each of the subsequent sheets making up the same bill comprising the notice are not perforated longitudinally. Thanks, therefore, to the longitudinal placement of the notice, standard A4 width paper can be used.

Claims

1. Longitudinal perforation device for paper processing and/or printing machines, comprising a countersupport roller (3) on which said paper (1) advances, a circular perforating tool (5) acting on said countersupport roller (3), a motorized support (7) on which said tool (5) is mounted, said motorized support (7) giving to said tool a tip speed substantially equal to that of said paper (1) and said countersupport roller (3), said motorized support (7) giving also to said tool (5) an alternative approaching movement to said paper (1) of variable frequency.

2. Longitudinal perforating device according to claim 1, wherein said support (7) determines an approaching movement of the tool (5) with respect to said roller according to a curved trajectory (C) substantially tangential to said countersupport roller (3) and said paper (1).

3. Longitudinal perforating device according to claims 1 and 2, wherein a transversal grooved bar (8) rotating about its own axis is provided on which said support (7) is mounted in a rotatable manner, a gear wheel (10) being comprised coaxially mounted on said grooved bar (8) and transmitting the motion of the bar (8) to the tool (5), the support (7) being able to contemporaneously rotate around the bar (8) and translate along it.

4. Longitudinal perforation device according to claims 2 and 3, wherein there are comprised transversal guides (16), a carriage (14) on which said support (7) is mounted and sliding on said transversal guides (16), said carriage (14) allowing for the transversal positioning of said support (7) along said transversal guides (16).

5. Longitudinal perforation device according to claim 4, wherein a piston (12) is mounted on said carriage imparting said alternative approaching motion by acting against said support (7).

6. Longitudinal perforation device according to claim 5, wherein a pusher (23) is provided to act against said support (7) and thus counterbalance said piston (12) when said tool (5) comes close to said roller (3).

7. Longitudinal perforation device according to claim 6, wherein a central control unit and pneumatic actuators (24, 13) operated by said control unit are provided, operating said pusher (23) and said piston (12) depending on the paper advance.

Drawing