The invention relates to a method for narrowing a paper roll, defined in the introductory section of patent claim 1. Furthermore, the invention relates to an apparatus defined in the introductory section of claim 4.

The general principle in printing plants is to try and order paper as near as possible to the exact amount that is needed in a particular print job. For a given print job, there is generally needed paper of a certain width. Irrespective of calculations for consumption, from a given printing batch there may remain paper rolls that have to be stored, because they cannot be used immediately for another print job that requires paper of a different width, maybe narrower. Consequently waste and costs are created because paper must be stored, sometimes for long periods of time before it can be used, in case it can be used at all.

In the prior art there is known, from the German publication DE - 1,611,767 an apparatus where a wide paper roll is divided into at least two paper webs, so that the web to be cut is discharged in web form directly into a printing machine or other further treatment. The drawback in this apparatus is that for the web to be removed, there must be arranged a separate device for treating the web, for instance for conducting the web into a printing machine or rolling back to a roll. The apparatus described in the said publication is mainly meant for dividing a wide paper roll into fairly wide parts.

In the prior art technique, a paper roll is narrowed to a desired width at the same time as the paper web is fed from the roll into the printing machine. In that case the web part cut off the paper roll must be conducted to a separate shredder device, which cuts the web part into shreds immediately after the cutting. In printing plants, such a shredder device must be arranged in connection with each printing machine, which means a remarkable increase particularly in investment costs, but also rurining costs, and requires extra space in connection with the equipment for treating the paper roll.

The object of the present invention is to eliminate the above mentioned drawbacks. A particular object of the invention is to introduce a method and apparatus that enable an easy and measurewise accurate removal of an essentially narrow, disc-like paper roll part from off the end of the paper roll in order to narrow the roll.

Another object of the invention is to introduce a novel method and apparatus whereby extra paper rolls left over for example from a given print job and stored in printing plants can be put into use more rapidly than before and with minor costs.

Yet another object of the invention is to introduce a method and apparatus which ensure that in a printing plant storage, there can be kept a certain amount of paper without defining a given print job in advance, which paper is then put to use when needed and narrowed into a width suitable for the print job at hand.

A particular object of the invention is to introduce a method and apparatus whereby the disc-like waste piece removed from the paper roll is quickly and accurately cut off and easily treated further.

The method of the invention is characterized by the novel features enlisted in the appended patent claim 1. The apparatus of the invention is characterized by the novel features enlisted in the patent claim 4.

In the method according to the invention for narrowing a paper roll into a given width, in which method from the end of the paper roll there is removed a disc-like part by cutting, and in which method the paper roll is rotated around its axis during the cutting, the cutting is carried out by means of a cutting blade comprising a disc- like round blade, provided with a wedge-like blade edge on the circumference thereof, the said cutting blade being rotatably geared to a blade support; the cutting blade is pressed at right angles against the side of the paper roll, towards the central axis of the roll, so that during the narrowing operation, the first blade side of the wedge-like blade edge is supported, on the side of the main part of the paper roll, against the end surface of the paper roll to be cut, and the second blade side is used for shifting the disc-like part away from the main part of the paper roll as the cutting operation proceeds.

The apparatus of the invention for narrowing a paper roll into a given width comprises a rotating device for rotating the paper roll and a narrowing cutter provided with a cutting blade for shortening the paper roll by removing a disc-like part from the end thereof by cutting. According to the invention, the cutting blade of the narrowing cutter is a disc-like round blade with a wedge-like blade edge on the circumference thereof; the said narrowing cutter also comprises a blade support whereto the cutting blade is geared to be freely rotatable, and a first shifting device

whereby the cutting blade is pressed at right angles against the side of the paper roll towards the central axis thereof, so that during the narrowing operation, the wedge- like blade edge of the cutting blade is arranged to be supported on the side of the main part of the paper roll, to the end surface of the paper roll to be cut, and the second blade side is arranged to shift the disc-like waste piece away from the main part of the paper roll.

Other preferred embodiments of the method and apparatus are apparent from the dependent patent claims and from the description of the method and apparatus of the invention given below with reference to illustrative examples.

It is an advantage of the invention that the it enables and easy and measurewise accurate removal of the essentially narrow part from the end of the paper roll in order to narrow the said roll so that the part removed therefrom, i.e. the waste piece, does not create problems. Advantageously the waste piece can be formed into a disc to be treated as a whole, so that there is not necessarily needed any special equipment for the treatment thereof. On the other hand, the waste piece can also be treated easily in a suitable shredder device or the like.

Another advantage of the invention is that by means thereof, paper rolls left over from a given print job and stored for example in a printing plant can be put back to use more rapidly than before and with low costs. Yet another advantage of the invention is that in the storage of a printing plant, there can be kept a certain amount of paper without defining a given print job in advance; when needed, the paper can be taken and narrowed into a suitable measure required by the job at hand. If the paper consumption happens to be higher than was planned and prepared for, more paper can be taken from storage and cut into suitable measure by means of the method and apparatus of the invention.

The invention is described in more detail below, with reference to the appended drawings, wherein figure 1 is a schematic side-view illustration of an apparatus for narrowing a paper roll, i.e. a paper roll narrowing apparatus; figure 2 is a side-view illustration of the cutting blade of the narrowing apparatus; figure 3 is an enlarged side-view illustration of the cutting blade of the narrowing apparatus; and

figure 4 is a schematic illustration of the cutting blade of the narrowing apparatus, seen from the end of the paper roll in the direction of the axis thereof, along the section E-E of figure 2.

In figure 1, the paper roll narrowing device 1 comprises a frame 2 provided with a support 3 and a rotating device 4, and the paper roll 1 is supported at its collar 5 rotatably in between the support 3 and the rotating device 4. The frame 2 includes a crossbar 6, which is arranged to pass in the direction of the support 3 and the fastening members of the rotating device 4, and at the same time in the direction of the lengthwise axis A-A of the paper roll 1, above all these. The narrowing cutter 7 proper for shortening the paper roll 1 is attached to the crossbar 6. The frame 2 and the crossbar 6 are advantageously adjustable so that the support 3 and the rotating device 4 are adjustable at a desired distance from each other, depending on the length L of the paper roll 1 to be shortened, i.e. narrowed.

The narrowing cutter 7 comprises a cutting blade 8, a blade support 9 and a shifting device 10 for the cutting blade. In shape the cutting blade 8 is a disc-like round blade with a wedge-like blade edge 8a (figures 2 and 3) on the circumference thereof. The diameter d of the cutting blade 8 is advantageously of the order 100 - 250 mm. The cutting blade 8 is attached and geared, at the axis 8b passing through the center of the blade, in a freely rotatable fashion to the blade support 9. The blade edge 8a and the blade plane B-B passing therethrough is arranged at a slight angle α with respect to the cutting plane C-C, so that the blade edge 8a and simultaneously the cutting blade 8 are inclined towards the blade support 9, on the opposite side with respect to the cutting blade edge point F. The angle α is of the order 1 - 5 degrees, preferably 1.5 - 3.0 degrees, and most preferably about 2 degrees. The most preferable size, i.e. about 2 degrees, of the angle α is defined experimentally by cutting various paper rolls. The first blade side 8c of the blade edge 8a is at a corresponding angle α with respect to the blade plane B-B, the same as the blade edge 8a with respect to the cutting plane C-C, but in the opposite direction. Now the first side 8c of the blade edge 8 is essentially parallel to the cutting plane C-C. On the plane of the radius of the round blade, i.e. on the cross- sectional plane, the first side 8c of the blade edge 8 is now relatively narrow in width e, i.e. of the order 5 - 20 mm, advantageously 7 - 12 mm. The second blade side 8d of the blade edge 8 is at a distinctly larger angle β with respect to the blade plane B-B than the first blade side 8c thereof. The angle β is for instance within the range 10 - 35 degrees, advantageously 20 - 30 degrees. The second blade side 8d of the blade edge 8 is straight on the cross-sectional plane, but it may also be convex

or generally curved, as is illustrated in figure 3. On the cross-sectional plane, the second blade side 8d of the blade edge 8 is also in width g clearly larger than the first blade edge 8c.

The blade support 9 of the narrowing cutter 7 is advantageously a straight rod, which is for example a flat square in cross-section. The narrowing cutter 7 also comprises a first shifting device, i.e. the shifting device of the cutting blade, which advantageously is a hydraulic cylinder 10. The blade support 9 is attached to the piston rod 11 of the cutting blade shifting device, in this case the hydraulic cylinder 10. The blade support 9 and the piston rod 11 are advantageously parallel.

The narrowing cutter 7 is arranged movably on the crossbar 6 belonging to the frame 2 of the apparatus by means of a rider 13. The cutting blade shifting device, such as a hydraulic cylinder 10, is adjusted at its cylinder frame 12 in a rider 13 or a similar device which is movable along the crossbar 6. In that case, the rider 13 includes the said second shifting device for moving the narrowing cutter 7 along the crossbar 6 in the direction of the axis A-A of the paper roll under treatment.

The narrowing device of the paper roll 1 also includes a control unit 23 (figure 1), advantageously a microprocessor-based control unit, whereby the position and operation of the narrowing cutter 7 proper are adjusted. The device also includes position defining means for defining the position of the narrowing cutter 7. On the basis of the messages received from the control unit 23 and from the position defining means, the position of the narrowing cutter 7 and particularly the position of the cutting blade 8 thereof are adjusted in relation to the paper roll 1 to be cut. By using the position defining means, there is defined the place of the rider 13 or the like in the lengthwise direction of the crossbar 6 (on the axis A-A), and the vertical position of the disc-shaped cutting blade, particularly that of the cutting blade edge 8a, on the axis D-D.

The apparatus for narrowing a paper roll is operated, under the control of the control unit 23, as follows. Into the control unit 23, there is fed information of the paper roll 1 to be cut (i.e. length L, diameter H) and the desired length L ₁ of the paper roll. The position of the narrowing cutter 7 (of the rider 13 and the cutting blade 8) in relation to the paper roll 1 is defined, whereafter the narrowing cutter 7 is shifted, by means of another shifting device, i.e. the rider 13, along the crossbar 6 to the cutting point in the direction of the axis A-A of the paper roll. The cutting of the paper roll 1 for removing the paper roll disc la is started. By means of the

hydraulic cylinder 10, and particularly by means of the piston rod 11 and blade support 9 thereof, the disc-like cutting blade 8 is pressed in the direction of the lengthwise axis D-D of the cylinder against the cylindrical surface of the paper roll 1, and essentially towards its central axis A-A; now the blade edge 8a of the cutting blade 8 meets the cylindrical surface of the paper roll in the direction of the axis A- A thereof, at an accurately predetermined point, so that a desired length L] is obtained for the resulting paper roll. The paper roll 1 is rotated, with the rotating device 4, at a suitable rotating speed, for instance 200 - 300 rpm. The freely geared cutting blade 8 rotates around its axis as attached to the blade support 9 and rotated by the paper roll 1. The blade edge 8a of the cutting blade 8 is advantageously pressed first slowly through the outermost paper layers of the paper roll 1, so that the cutting starts exactly at the predetermined point. Thereafter, in the cutting operation proper, the cutting blade 8 is pressed by means of the first shifting device, such as the hydraulic cylinder 10, preferably with an even force, into the paper roll 1 rotating in the direction of the axis D-D; at the same time, owing to the inclined position of the disc-like cutting blade 8, and particularly to the slight angle α of the blade edge 8a, the first blade side 8c of the blade edge 8a is pressed against the cutting surface lb of the paper roll 1 on the side of the main part of the paper roll, and is supported against it. Now the major part of the force directed to the cutting blade 8 in the direction of the axis D-D is focused in cutting the paper roll 1 on the cutting plane C-C, at right angles to the paper roll 1, and a small part of the force is focused in pressing the cutting blade 8 into the cutting surface lb of the paper roll via the first side 8c of the blade edge 8a. Thus the cutting blade 8 is throughout the cutting operation supported against the paper roll 1, and the cutting surface lb remains controUably as a measurewise accurate perpendicular surface against the axis A-A of the paper roll.

The second side 8d of the blade edge 8a of the disc-like cutting blade 8 is at a steeper angle with respect to the blade plane B-B of the blade edge 8a than the first blade side 8c, and this side also is fairly wide. In the direction of the radius of the cutting blade, the second blade side 8d is a planar surface or advantageously a concave surface, as is illustrated in figure 3. This curved shape of the second side 8d of the blade edge 8a is particularly advantageous when the paper roll disc la cut off the end of the paper roll 1 is relatively narrow. By means of the second side 8d of the blade edge 8a, the paper roll disc la is effectively pushed away from the paper roll and from the cutting surface lb. The paper roll disc la may remain unbroken in the cutting stage, whereafter it is removed. On the other hand, in the cutting stage the paper roll disc la can be treated by suitable auxiliary means so that if it happens

to break, it does not cause problems in the cutting process nor destroy the cutting surface.

By means of the control unit 23, the rotating speed of the paper roll 1 and/or the feeding speed of the cutting blade 8 can be adjusted and controlled so that the area of the paper surface to be cut per time unit is a predetermined optimal standard. By means of the control unit 23, rotating speed of the paper roll 1 can be automatically increased according to the distance of the cutting blade 8 in relation to the central and rotating axis A-A of the paper roll 1. The position defining means of the cutting blade 8 can be utilized in identifying the position of the cutting blade at any given moment. By means of the control unit 23, the feeding of the cutting blade 8 can be sped up according to the distance of the blade edge 8a of the cutting blade in relation to the axis A-A of the paper roll 1. After starting the cutting at a given optimum speed, the feeding of the cutting blade 8 is sped up, and simultaneously the rotating speed of the roll is increased. The rotating speed has a certain maximum value, which depends on the size of the roll. The circumferential speed of the roll must not rise higher than the critical maximum value.

The invention is not restricted to the above described preferred embodiments only, but many modifications are possible within the scope of the intentional idea defined in the appended patent claims. Thus the rotating device can be of the conventional type, whereto the paper roll is installed for instance by pin coupling or axis coupling. The paper roll can be rotated at the hub, or alternatively at the roll surface, for example by means of a drive gear. Moreover, even if the paper roll in the examples above was arranged in a horizontal position, it may in some applications be arranged in a vertical position. Let us also point out that although the invention is particularly advantageous to be used in printing plants for narrowing paper rolls, it is obvious that the invention can be used and applied in all possible circumstances where a large paper roll must be narrowed easily and with low costs. The apparatus can also be used for cutting any rolled, web-like fairly thin material, such as cardboard, plastic, etc.