Rotory die cutter unit with rapid die connection

Abstract: There is described a rotary die cutter unit with rapid die connection comprising: a die (1) equipped with connecting bars (5); and a die-holding cylinder (3), equipped with: longitudinal grooves (7) with openings receiving the bars (5) when connecting the die (1) to the die-holding cylinder (3); connecting teeth (9), housed in the openings of the grooves (7), that circumferentially move on the cylinder (3), and assume an unconnection position in which they completely disappear from the groove (7), and a connection position in which they protrude into the groove (7); and control sticks (11) corresponding to the grooves (7), having small irregular teeth (15) with one (19) of the two sides whose height is progressively decreasing in the form of a chute. The control sticks (11), when longitudinally moving, operate on roller bearings (25) in such a way as to gradually move the connecting teeth (9) between their two extreme connection and unconnection positions.

Description: The present invention refers to a rotary die cutter unit with rapid die connection, for cardboard shapes for boxes, that is part of a shape-production line, that prints, feeds and cuts the shapes themselves through such rotary die cutter unit, before cleaning, stacking and placing them on pallets to ship them. Various types of rotary die cutter units are known in the art, comprising a rotary die-holding cylinder, on which a wooden die with inserted blades is mounted to cut and shape the cardboard, according to the type of box to be produced. The major problem for all devices built so far has been prearranging an effective connection between die-holding cylinder and die, that guarantees an easy and quick replacement, contact efficiency between the two parts for shape die-cutting accuracy, operating life under optimum accuracy conditions. In addition to the old type of connection with common screws, that surely is not the optimum solution due to its cumbersome and long operations, above all if frequent die changes occur, the most recent technical solutions are those disclosed in European Patent n. ⊘ 384 161 in the name of Martin and in Italian Patent Application n. TO92A⊘⊘⊘177 assigned to the same Assignee of the present invention. The solution described in European Patent n. ⊘ 384 161 shows connecting half-circumferences on the die that come into engagement with grooves on the cylinder and are kept engaged by longitudinal bars pushed against them: however, in addition to sliding problems for the bars in dusty environments, this solution has a problem dealing with connection accuracy, that is not uniform if, due to any reason, the bar is not able to couple all half-circumferences on the die: since the bar has a single working stroke, connection misalignments, that are frequent in harsh environments like the cardboard cutting ones, are transmitted on the whole bar impairing contact accuracy between die and cylinder. On the other hand, the solution described in Italian Patent Application n. TO92A⊘⊘⊘177, though solving the previously mentioned problems, is difficult to realize, due both to costs and to the great number of connecting devices used. US 2236230 relates to a mechanism for holding and applying peripheral tension to printing plates upon a printing press cylinder. The mechanism disclosed in US 2236230 comprises a longitudinally sliding bar provided with wedge-like projections and a rotating bar, the first bar being for holding a hook like bar formed on the inner face of the plate at one end or head thereof, and the second bar being for applying peripheral tension to a corresponding hook like bar formed on the inner face of the plate at the other end or tail thereof. Purpose of the present invention, therefore, is solving the above-mentioned problems, providing a rotary die cutter unit that guarantees a high connection accuracy between die and cylinder, imparting a circumferential type of connection force generated by a simple longitudinal movement of a control stick; the solution is further of a simple construction and shows high reliability under difficult environmental conditions (dust, moisture, etc.). The above and other purposes and advantages of the invention, as will appear from the following description, are obtained with a rotary die cutter unit with rapid die connection comprising at least a semicircular die and a die-holding cylinder, wherein said die is equipped with a plurality of longitudinal connecting bars with a C-shaped section, said longitudinal bars being secured to said die through securing means in connection positions; said die-holding cylinder is equipped with: a plurality of longitudinal grooves in a position corresponding to said longitudinal connecting bars, said grooves being equipped with a plurality of openings along a length thereof, said grooves being adapted to receive said connecting bars during a connection step of said die to said die-holding cylinder; a plurality of connecting teeth, each one housed in one of said plurality of openings in said grooves, said connecting teeth being able to circumferentially move with respect to said die-holding cylinder, and being able to assume an unconnection position in which they are completely retracted into said openings and disappear from said groove, and a connection position in which they protrude into said groove; a plurality of longitudinal control sticks inserted in said cylinder, each one next to each of said longitudinal grooves, said control sticks having a side with an irregular toothed shape equipped with a plurality of small teeth, each one of said small teeth having an upper plane part with a side with a sharp edge and another side whose height is progressively decreasing in the form of a chute, said control sticks when longitudinally moving being adapted to cooperate, through said small irregular teeth thereof, with a plurality of roller bearings connected to said connecting teeth in such a way as to gradually move said connecting teeth between said two extreme connection and unconnection positions. The present invention will be better described by some preferred embodiments thereof, provided as a non limiting example, with reference to the accompanying drawings, in which: Figure 1 is a front view of an embodiment of the die cutter unit according to the present invention pointing out, on the right side, the connection condition between die and cylinder and, on the left side, the unconnection condition with hooks in a retracted position; Figure 2 is a reduced side view of the die-holding cylinder according to the present invention; Figure 3 is a reduced side view of the stick controlling hook movement; Figure 4 is a front view, partially in section, of the die-holding cylinder where constructive and operating features of securing hooks are pointed out; and Figure 5 is an enlarged side view, partially in section, of an embodiment of the securing hook. With reference to the Figures, a rotary die cutter unit with rapid die connection, for cardboard shapes for boxes, substantially comprises at least one (and usually two) wooden semicircular die 1 and a die-holding cylinder 3, that are shown in the connection and unconnection positions thereof respectively on the right and left sides in Fig. 1. As appears evident when examining Fig. 1, the die 1 must be equipped with a plurality of longitudinal connecting bars 5, with a very bent, C-shaped section: these longitudinal bars 5 are secured to the die 1 through common securing means, for example screws, in the provided connection positions, that, in the preferred embodiment described here, are four, mutually equidistant on every half-circumference of the die 1. To realize the connection step shown on the right side in Fig. 1, it will be necessary to prearrange connecting means cooperating with the bars 5 and that can be moved between an engagement position and a disengagement position, for example a "disappearing" one, before connecting a new die and to allow also unconnecting the already coupled die. To realize such connecting means, the die-holding cylinder 3, first of all, is equipped with a plurality of longitudinal grooves 7 in a position respectively corresponding to that of the longitudinal connecting bars 5. The grooves 7 are equipped with a plurality of openings obtained at regular intervals along the length thereof and receive, inside them, the connecting bars 5 during the connection step of the die 1 to the die-holding cylinder 3. The cylinder 3 is further equipped with a plurality of connecting teeth 9, each one housed in one of the openings in the longitudinal grooves 7. These connecting teeth 9 are able, as will be described below, to circumferentially move with respect to the die-holding cylinder 3, and assume an unconnection position in which they are completely retracted into the openings and disappear from the groove 7 (as shown on the left side in Fig. 1), and a connection position in which they protrude into the groove 7 to engage the longitudinal bars 5 on the die 1 (as shown on the right side in Fig. 1). The connecting teeth 9 operate in the respective openings through a constructive solution secured to the cylinder 3 through screws 1⊘ (Fig. 4). In order to be able to perform displacement of the connecting teeth 9, a plurality of longitudinal control sticks 11 have been provided, each one placed, inside the cylinder 3, next to each of the longitudinal grooves 7 and sliding into the recesses 12 in the cylinder 3. These control sticks 11 have a side 13 with an irregular toothed shape: each one of the small teeth 15 thereof shows an upper plane part 17 with a side 18 with a sharp edge and another side 19 whose thickness is progressively decreasing in order to form a sort of chute. Every control stick 11 is terminated on one end by a small rod 21 that protrudes on one side of the die-holding cylinder 3; the opposite end 22 is engaged with a return spring 23 to bring back the stick 11 to its rest position, next to which the connecting teeth 9 protrude from the grooves 7 and perform the connection. The small irregular teeth 15 of the control sticks 11 push, by acting on their side 19, corresponding roller bearings 25 that are secured, through adequate pins 27, to each one of the connecting teeth 9. Pushing, operating along a circumferential direction, of the stick 11 on the bearings 25 generates a circumferential movement of the connecting teeth 9 opposing the force of the springs 29 connected to one end of the connecting teeth 9 themselves: the circumferential movement is such that the connecting teeth 9 completely disappear in the grooves 7 being retracted in the adequate openings that are housing them. Purpose of the springs 29 is bringing back the teeth to an engagement position when connecting the die 1. The connection/unconnection step of the die 1 from the rotary die cutter unit according to the present invention, will now be described. When it is necessary to carry out the replacement of a die 1 on the die-holding cylinder 3, to uncouple the previous die 1 a pair of pistons 31 and 33 are actuated that push, through respective small blocks 35 and 37 and along the direction shown by arrow A in Fig. 2, suitable plates 39 and 41 connected to the small rods 21 of the control sticks 11. Pushing of the pistons 31 and 33 makes the control sticks 11 move along the longitudinal direction with respect to the die-holding cylinder 3 for a length that is exactly equal to the length of the side 19 "in the form of a chute", opposing the return force of the spring 23. The side 19 beats against the roller bearing 25 and pushes backwards, along the circumferential direction, all connecting teeth 9, making them disappear from the grooves 7. After having removed the old die 1 and having placed the new one in position, the action of pistons 31 and 33 is stopped and therefore the force of the return springs 23 of the control sticks 11 and the force of the springs 29 acting on the various connecting teeth 9 make both sticks 11, and teeth 9 go back to the initial position, that corresponds for the teeth 9 to the complete protrusion in the grooves 7 and therefore to the connection engagement with the bars 5 on the die 1.

Claims: Rotary die cutter unit with rapid die connection comprising at least a semicircular die (1) and a die-holding cylinder (3), wherein said die (1) is equipped with a plurality of longitudinal connecting bars (5) with a C-shaped section, said longitudinal bars (5) being secured to said die (1) through securing means in connection positions; said die-holding cylinder (3) is equipped with: a plurality of longitudinal grooves (7) in a position corresponding to said longitudinal connecting bars (5), said grooves (7) being equipped with a plurality of openings along a length thereof, said grooves (7) being adapted to receive said connecting bars (5) during a connection step of said die (1) to said die-holding cylinder (3); a plurality of connecting teeth (9), each one housed in one of said plurality of openings in said grooves (7), said connecting teeth (9) being able to circumferentially move with respect to said die-holding cylinder (3), and being able to assume an unconnection position in which they are completely retracted into said openings and disappear from said groove (7), and a connection position in which they protrude into said groove (7); a plurality of longitudinal control sticks (11) inserted in said cylinder (3), each one next to each of said longitudinal grooves (7), said control sticks (11) having a side (13) with an irregular toothed shape equipped with a plurality of small teeth (15), each one of said small teeth (15) having an upper plane part (17) with a side (18) with a sharp edge and another side (19) whose height is progressively decreasing in the form of a chute, said control sticks (11) when longitudinally moving being adapted to cooperate, through said small irregular teeth (15) thereof, with a plurality of roller bearings (25) connected to said connecting teeth (9) in such a way as to gradually move said connecting teeth (9) between said two extreme connection and unconnection positions.

Inventors: BRAZZO ROBERTO, BRAZZO, ROBERTO
Applicants: TEXO SRL, TEXO S.R.L.
Application year: 1995
Main classification: B26D7
IPC codes: B26D7