Rotary die cutter

Abstract: Herein disclosed is a rotary die cutter which comprises: a rotatable anvil cylinder; and a knife cylinder (2) made rotatable in a face-to-face relation to and in synchronism with the anvil cylinder and having knives (4) fixed on the outer circumference thereof for subjecting a sheet running at the central portions of the two cylinders to a predetermined cutting treatment by clamping the same together with the anvil cylinder. A thin film (6) having a tape adhered thereto is attached removably to the outer circumference of the anvil cylinder in registration with the corresponding edges of the knife cylinder (2).

Description: The present invention relates to a rotary die cutter with the features of the preamble of claim 1 to be installed in a corrugated board boxing machine. Description of the Prior Art Before entering into a detailed description of the present invention, cursory review will be made on the existing general types of the rotary die cutter with reference to Figs. 8 and 9. This rotary cutter is a machine for punching or ruling a corrugated board 1, which has been printed at a preceding step by a printer, into a predetermined form corresponding the specifications of a box to be manufactured. This machine is constructed, as shown in Fig. 1, of a pair of election frames 13a and 13b which are erected at the two widthwise ends of the boxing machine and connected through an upper stay 11 and a lower stay 12. In the frames 13a and 13b, there are borne an anvil cylinder 5 and a knife cylinder 2 which is juxtaposed in a lower position to the former cylinder 5. These two cylinders 5 and 2 are caused to rotate in a face-to-face relation to and in synchronism with each other through both gears 14 and 15 at their shaft ends and not-shown gear drive means. A pair of feed rolls 16a and 16b are disposed upstream of those cylinders 5 and 2, and cutting knives 4 or creaser knives are attached to the outer circumference of the aforementioned knife cylinder 2 through an edge anchor bed 3. In the structure thus far described, the corrugated board 1 is sequentially delivered from the printing unit of the preceding step by the actions of the feed rolls 16a and 16b so that it can be subjected to a predetermined treatment such as the punching or ruling treatment by the clamped rotations of the anvil cylinder 5 and the knives 4 or the creaser knives fixed on the knife cylinder 2. Next, the cutting function will be described in the following. Generally speaking, the basic structure of the rotary cutter for cutting the corrugated board 1 into a predetermined shape are classified into the two types, as shown in Figs. 8 and 9. The structure of Fig. 8 is called the "soft cut" type, in which the knife cylinder 2 having the cutting knives 4 fixed on its outer circumference through the edge anchor bed 3 is combined with the anvil cylinder 5 having its outer circumference covered with a shock absorber 17 of urethane rubber or the like. The cutting knives 5 are caused to pierce the corrugated board 1 and to have their edges bite into the shock absorber 17 of the anvil cylinder 5 thereby to cut the corrugated board 1. According to this type, the cutting knives 4 can be prevented from wear and can have their edge bites set roughly to some extent by the shock absorber 17. Thus, this type is advantageous in that it can adjust the parallelism and shaft distance between the anvil cylinder 5 and the knife cylinder 2. Since, however, the knives 4 are caused to bite into the shock absorber 17, there arises a disadvantage that the punching lengths of the corrugated board 1 are dispersed to degrade due to the difference in the bite (usually of 1.0 to 2.5 mm). Next, the structure of Fig. 9 is called the "hard cut" type, in which the knife cylinder 2 having the cutting knives 4 fixed on its outer circumference through the edge anchor bed 3 is combined with the anvil cylinder 5 having no coverage of the shock absorber 17, i.e., having an iron surface. Thus, the corrugated board 1 is cut by bringing the cutting knives 4 into contact with the outer circumference of the anvil cylinder 5 or by pushing them under a proper pressure. This type is advantageous in that the punching precision is improved because the cutting knife edges and the anvil cylinder surface have their circumferential rotation speeds equalized. Since, however, the surface hardness of the anvil cylinder 5 is set at a higher level than that of the edges of the cutting knives 4, the edges may wear to lose their shapeness or may be broken if the knives 4 are adjusted to be forced onto the anvil cylinder 5. Another difficulty of failure to cut the corrugated board 1 takes place if the edges of the knives 4 have a low contact pressure. For these reasons, it is seriously difficult to adjust the parallelism and gap (or engagement) between the edges of the cutting knives 4 and the surface of the anvil cylinder 5. The rotary die cutters of the prior art, as exemplified in Figs. 8 and 9, have the above-specified advantages and disadvantages individually. Incidentally, the following counter-measures have been taken at present for eliminating the disadvantages of the hard cut type. As shown in Figs. 6 and 7, there is adopted a method for punching the corrugated board by manually adhering a tape (having a thickness of about 0.01 to 0.02 mm) directly to the outer circumference of the anvil cylinder 5 in a manner to correspond to the layout of the knives 4 of the edge anchor bed 3 thereby to cause the edges of the knives 4 to bite into the tape 10. Thus, the punching precision of the board is maintained at an improved level, and the adjustment of the engagement of the cutting knife edges is facilitated. However, the counter-measures of the prior art have to be adhered each time of an order change to the anvil cylinder 5 juxtaposed in conformity with the arrangement of the knives 4 of the edge anchor bed 3. Moreover, these works are not only dangerous under a restricted narrow circumstance but also troublesome in preparations so that they are major causes for reduced operating efficiency, i.e., the productivity. As has been described hereinbefore, most of the rotary die cutters adopt the hard cut type, in which the cutting knives fixed on the knife cylinder are brought into direct engagement with the outer circumference of the juxtaposed anvil cylinder of iron, with a view to improving the dimensional accuracy in the punching treatment. Since, however, this system requires a high technology for adjusting the engagement of the edges, there is adopted the simplified method of applying the thin tape to the outer circumference of the anvil. According to this method, the tape is adhered directly to the outer circumference of the anvil cylinder in a manner to correspond to the layout of the cutting knives fixed to the pairing knife cylinder. These works are accomplished inefficiently within the narrow space and take a long time for the adhesions so that they are major causes for blocking the improvement in the productivity. Another prior art die cutter with the features of the preamble of claim 1 is known from FR-A-332 952. This cutter comprises cylinders for cutting of cardboard sheets in longitudinal and transversal directions, respectively, and a cylinder serving as an anvil cylinder for the latter two cylinders. On the outer circumference of the anvil cylinder is removably attached an elastic rubber sheet and a steel sheet on top of the rubber sheet, the compression of the rubber sheet allowing for an adjustment of the contact pressure between the knives and the steel sheet. SUMMARY OF THE INVENTION It is an object of the present invention to provide a rotary die cutter which is free from the disadvantages specified above. In order to achieve this object, according to the present invention there is provided a rotary die cutter according to claim 1. In the present invention, the tape can be adhered, for a subsequent order and outside of the machine, to the thin film to be wound on the outer circumference of the anvil cylinder. In case of an order change, therefore, it is sufficient to replace the film of the old order with the prepared new film. Moreover, the aforementioned preparations are worked outside of the machine so that they can be accomplished in parallel with the productions of the prevailing order. As a result, the safety of the works can be warranted, and the intermission of the machine for the order change can be remarkably shortened. Thus, it is possible to improve the productivity and to prevent the wear of the cutting knives thereby to elongate their lifetimes. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a front elevation showing a rotary die cutter according to the present invention; Fig. 2 is a side elevation of the same; Fig. 3 is a detailed side elevation showing a P portion of Fig. 2; Fig. 4 is a detailed side elevation showing an S portion of Fig. 2; Fig. 5 is an explanatory view showing the adhered state of a tape to a thin film in accordance with the present invention; Fig. 6 is a perspective view showing the state in which the tape is adhered to the anvil cylinder of the prior art; Fig. 7 is a side elevation of the same; and Figs. 8 and 9 are explanatory views respectively showing the cut states of the corrugated boards by the rotary die cutters of the prior art. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in the following in connection with a rotary die cutter according to one embodiment thereof, as shown in Figs. 1 to 5. The rotary die cutter of Figs. 1 to 5 is installed in a corrugated board boxing machine and has basic functions similar to those described in connection with the prior art in that it punches the corrugated board 1, which has been printed at a preceding step by the printer, into a predetermined shape and rules it, as necessary for being bent. The rotary die cutter of the present invention contemplates to improve the function of the anvil cylinder 5 which is to come into engagement with the cutting knives 4 fixed on the knife cylinder 2 through the edge anchor bed 3. On the outer circumference of the anvil cylinder 5 of the rotary die cutter, as shown in Figs. 1 and 2, there is provided fixing means 7 for fixing a thin film 6 in an axial direction, as exemplified in Fig. 4. The thin film 6 is equipped, as better seen from Fig. 5, with a fixing projection 8 at its one side end and a hook 9 at its other side end. The aforementioned fixing means 7 is formed with a recess 7' and a groove 7'', which are to be engaged by the fixing projection 8 and hook 9 of the thin film 6, respectively. Thus, the thin film 6 can be easily attached to and detached from the anvil cylinder 5 by bringing the fixing projection 8 and the hook 9 into and out of engagement with the recess 7' and the groove 7'', respectively. To the thin film 6, there is adhered the tape 10 in a manner to correspond to the layout of the knives 4 which are fixed in the edge anchor bed 3. Thus, the tape 10 can be replaced together and in combination with the edge anchor bed 3 when the production order is to change. The works of adhering the tape 10 to the thin film 6 can be outside of the machine during the run (or production) of the prevailing order in accordance with the specifications of the product board of a subsequent order. The replacement of the film 6 may be effected merely by substituting the film of the preceding order so that the drop in the operating efficiency of the rotary die cutter can be reduced. Moreover, the engagement between the thin film 6 wound onto the anvil cylinder 5 and the knives 4 fixed on the outer circumference of the knife cylinder 2 through the edge anchor bed 3 is adjusted such that the edges of the knives 4 slightly bite into the tape 10, as shown in Fig. 3. Thus, the present invention can facilitate the adjustment of the gap between the edges of the knives 4 and the outer circumference of the anvil cylinder 5 to some extent, although the adjustment has been difficult in the hard cut system shown in Fig. 9. In addition, the present invention can eliminate the drop in the punching precision, which has been a disadvantage of the soft cut system shown in Fig. 8. In short, the present invention can not only establish the functional effect of the adhesion of the tape 10 to the outer circumference of the anvil cylinder 5 but also remarkably shorten the time period for the resetting works for an order change, so as to eliminate the disadvantages of the rotary die cutter of the prior art shown in Figs. 8 and 9. On the other hand, the fixing means for fixing the film 6 on the anvil cylinder 5 may be exemplified in various manners by the means for mounting the plate on the bed of a printer. Since the present invention is constructed, as has been described in detail hereinbefore, the thin film having the tape adhered thereto can be prepared in advance for the knife layout of the edge anchor bed so that the thin film of the old order on the anvil cylinder may be replaced for an order change with that new one. Since, moreover, the thin film having the tape adhered thereto is applied to the outer circumference of the anvil cylinder, the adjustment of the gap between the anvil cylinder and the knives engaging with the cylinder can be rather roughly set. In addition, the bits of the knife edges into the tape are small so that the drop in the punching precision can be reduced while elongating the lifetimes of the cutting knives. Thus, according to the present invention, it is possible to shorten the setting change for an order change and to produce corrugated boards of high quality.

Claims: A rotary die cutter comprising: a rotatable anvil cylinder (5); a cutting cylinder (2) having knives (4) fixed on the outer circumference thereof and being rotatably mounted parallel to said anvil cylinder (5) and driven in synchronism with said anvil cylinder (5) for cutting a sheet (1) fed in between central portions of said cylinders (2, 5); and a thin film (6) removably attached on the outer circumference of said anvil cylinder (5); characterized in that a tape (10) is adhered to those portions of the surface of said thin film (6) which, in use, register with said knives (4) of said cutting cylinder (2), said cutting cylinder (2) and said anvil cylinder (5) being aligned in such a manner that said knives (4), in use, slightly bite into the tape (10). A rotary die cutter according to claim 1, characterized in that there are provided fixing means (7) mounted in the axial direction on the outer circumference of said anvil cylinder (5); and engagement means (8, 9) formed on the both side edges of said thin film (6) for removably engaging with said fixing means (7) to removably fix said thin film (6) on the outer circumference of said anvil cylinder (5).

Inventors: BABA YASUYUKI C O MIHARA MACHI, MORINAGA HIROSHI C O MIHARA MA, OKAMOTO ARIFUMI C O MIHARA MAC, BABA, YASUYUKI, C/O MIHARA MACHINERY WORKS, MORINAGA, HIROSHI, C/O MIHARA MACHINERY WORKS, OKAMOTO, ARIFUMI, C/O MIHARA MACHINERY WORKS
Applicants: MITSUBISHI HEAVY IND LTD, MITSUBISHI JUKOGYO KABUSHIKI KAISHA
Application year: 1991
Main classification: B26D7
IPC codes: B26D7, B31B1, B26F1