WO1992011979A1

WO1992011979A1 - Cutter

Info

Publication number: WO1992011979A1
Application number: PCT/FI1991/000409
Authority: WO
Inventors: Matti +Di Paakki
Original assignee: Raute Oy; Paakki, Irma +Hf
Priority date: 1990-12-28
Filing date: 1991-12-23
Publication date: 1992-07-23
Also published as: FI86818C; FI906461A; FI906461A0; FI86818B

Abstract

The invention concerns a cutter for cutting a moving web at rightangles at selectable cutting intervals. The cutting action is executed by a rotatable blade pressed against the web. The rotational direction and speed of the blade are controlled for the cutting to be essentially the same as the advancing direction and speed of the web. According to the invention the blade construction consists of at least two independently controllable blades on the same shaft.

Description

Cutter

The object of the present invention is a cutter for the purpose of cutting a material web at rightangles to the direction of motion of the web. The cutter is especially intended to be used as a wood veneer cutter, for cutting veneer to set lengths, and for cutting off faulty por¬ tions.

Among cutters of this kind a cutter type is known, in which a mooving web is cut by means of a cutting blade extending across the web and mounted on a rotating shaft extending parallell with the web level. For a cutting action the blade is rotated in the mooving direction of the web into pressing contact with it so that the blade cuts trough the web, advantageously concurrently with an opposing drum or counter-blade mounted underneath the web and set in corresponding advancing moovment with it. In case the rotational speed of the cutting blade, as well as that of the opposing roller or counter-blade is ad¬ justed to be essentially equal to the speed of advance¬ ment of the web, the blade will not cause any obstruction to the advancement of the web at the moment of cutting.

Following the execution of the cutting action, the blade can be turned to its non-active position whereupon the web can move past it unobstructed. Whenever the need ari¬ ses again for the execution of the cutting action, the blade is turned on its supporting shaft to come into con¬ tact with the web.

Especially in the case of the plywood industry, there is a need (in addition to cutting the veneer to set lengths) to cut off narrow strips of veneer in order to get rid off faulty portions. These faults may be tens of mil¬ limetres in diameter and it is necessary to execute the cutting on either side of the faulty spot as close to it as possible in order to minimize the formation of waste.

Veneer cutters have been developed for the said purpose; one such device is described in the Finnish patent speci- fication no. 56326. The equipment therein described, an implementation of the so-called rotating-blade veneer cutter type, achieves the cutting action by means of a blade whose movements can be readily controlled due to the lightness of the structure. The web passing under- neath the blade is cut by the blade against a roll rotat¬ ing underneath the web. The cutting action of the blade is ensured by having a rotating roll mounted above the blade at such a distance from the opposing roller under¬ neath the web that the blade, when turned to its cutting position, becomes clamped between these rollers and the said clamping compression forces the blade to cut through the web of veneer. In accordance with the advantageous implementation of the equipment, the blade is provided with opposed cutting edges which means that the blade needs to be rotated only half a turn between consecutive cutting events.

Despite its speedy activation and small dimensions, even the half a turn of the blade takes so much time that a certain minimum interval applies between consecutive cut¬ ting operations. In the case of fast-running cutters, this interval is in the order of approximately 150 mm as against the diameter of faulty spots in the veneer which may be about 20 mm in diameter.

Known attempts have been made to solve the said problem by mounting two consecutively acting blades on the cut¬ ter, the said blades can be of the rotating type describ¬ ed above. In such a cutter, one blade is positioned to cut along one side of the faulty spot and the other blade is positioned to cut along the opposite side. The blades can be controlled independently of one another to execute cuts with of relative accuracy with regard to the desired spot whereupon hardly any wasteful cuts are executed. An example of a cutter operating on this principle is de¬ scribed is US patent specification no. 4 397 204. Despite its many advantages, the said cutter's basic problem is the motion of the veneer between the two cutting blades. In this stage the control of the veneer is especially difficult to accomplish reliably and it is possible that the veneer already cut by the first blade gets out of its route and causes problems.

Due to the the aforementioned problems connected to the use of the cutter in accordance with US patent specifi¬ cation no. 4 397 204, the invention in accordance with this application strives to achieve the advantages of the device known on the basis of the FI patent 56 326, an es¬ sential one of which is the passing of the veneer web through the cutting stage so that it is constantly under control, and to eliminate the disadvantages of the the last mentioned structure. As mentioned above the most important disadvantage involved in the structure of FI 56 326 is the delay in the blade action. In accordance with the basic idea of the invention, the solution to this problem is to mount two blades onto the blade shaft, and furnish them with control means capable to determine the rotational position of each of the two blades indepen¬ dently of each other. This independent adjustment does, of course, have its limits since in the simplest struc¬ ture (i.e. a structure embodying two blades) the angular position of a blade can be adjusted only to the point where it abuts to the other blade. With more blades, the adjustment scope becomes correspondingly more restricted.

In accordance with the central principle of the inven- tion, a blade structure embodying two independently con¬ trolled blades on the same shaft can be used to execute two cuts per cutting rotation of the blade set, whereby the interval between the cuts is adjustable. The said interval between two consecutive cuts can, in principle, be adjusted to be anything above zero.

The invention is described by means of the appended draw¬ ings, in which

Fig. 1 shows one embodiment of the invention

Fig. 2 shows an embodiment in accordance with fig. 1, but in another functional position

Fig. 3 shows another embodiment of the invention in one of its functional positions

Fig. 4 shows an embodiment in accordance with fig. 2, but in another functional position

Fig. 5 shows functional modes of the embodiments shown in figs. 2 and 3 at stages a-b and c-d, respectively.

In the construction according to fig. 1, representing one advantageous embodiment of the invention, attachments 4 have been fastened onto the blade shaft 3 that project outwardly at set intervals in a common plane in line with the shaft 3. A cutting blade 1 is fastened to the attach¬ ments, the said blade being of such a length as to extend across the web to be cut. The said illustration shows also a blade 1' , which is opposite to blade 1. This addi- tional blade 1' is fastened to another set of attachments that project outward from the shaft on the side opposite to attachments 4. The said blades 1 and 1' are, therefo¬ re, firmly fastened onto shaft 3 and follow its any move¬ ment.

The spaces left between the attachments 4 on the shaft 3 are taken up by sleeves 6, the said sleeves having a ro- tation clearance with respect to the shaft 3. Attachments 7 have been fastened onto the sleeves 6 which correspond to the attachments 4 fastened onto the shaft 3. The at¬ tachments projecting outward from the sleeves have been arranged into an outwardly projecting common plane in line with the shaft 3. The said attachments 7 constitute a fastenings for the second blade 2. In the embodiment shown, opposed attachments 7 ' have also been fastened onto the sleeves 6 which form a support for a further blade 2 ' . In the said structure, the blades 2 and 2 ' tie together the attachments 7 and 7 ' projecting outward from the various sleeves, resulting in a contiguous whole for¬ med of the sleeves 6, the attachments 7 and 7', and the blades 2 and 2 ' . The said whole can be connected with a drive mechanism of its own, whereupon its rotational po¬ sition with respect to the shaft 3 can be independently determined.

In the embodiment in accordance with figs. 1 and 2, the blades 1 and 2, as well as the blades 1 ' and 2' opposed to them, bear a sharpening chamfer 8 on the same side of the blade. In the event that the chamfers on adjacent blades 1 and 2, as well as on the blades 1' and 2' oppos¬ ed to them, are made on the opposed sides of the blades, it becomes possible to manufacture a blade structure in which adjacent blades can be placed against each another. When in the one-against-the-other position, the blades form a double blade that acts as one blade (fig. 3) . The blades can be distanced from one another in accordance with the invention in the manner shown in fig. 4.

The functioning of the cutter in accordance with the in¬ vention is illustrated in fig. 5.

In accordance with functional mode 5 a) , the blades while in their non-operating position can be mutually in a so¬ mewhat "open-scissors" position or (blade structure per- mitting) in a position where the sides of the blades are essentially against each another. When the need for cut¬ ting arises, a blade is rotated via the vertical cutting position assumed in fig. 1 to its new waiting position behind the cutting point, whereupon the opposed blade 1' is rotated along with it. In anticipation of the next cutting, the rotate command is given to blade 2, which then rotates in the same way via the cutting point to a new waiting position following on after blade 1 (with the blade pair 1,1' making room for it by rotating slightly onwards) . At this point the blade 1' is in turn to get the command to cut, etc.

In accordance with the above described functional mode, the blades can get their commands to cut at regular in¬ tervals, in which case the cutter cuts veneer sheets of even width. In the case of cutting away faulty spots in the veneer, however, the two consecutive blades, whose turn it is next to make cuts, can be given the cutting commands at quite brief intervals; i.e. they can be set in motion essentially simultaneously.

The simultaneous setting into motion for the purpose of cutting off a faulty spot is also possible in accordance with the functional mode depicted in fig. 5 b). In the said functional mode, the two consecutive blades 1,2 in¬ tended to make the cuts are given a certain mutual dis¬ tance separating them, this distance being determined on the basis of the data obtained concerning the faulty spot. Following this, the blades rotate through the cut¬ ting stage, retaining the said mutual distance. Having completed the cut, they assume their new, post-cutting position.

One of the invention's special functional modes is de¬ picted in stages c) and d) in fig. 5. This functional mode is an embodiment of the blade structure shown in figs. 3 and 4, in which the blades 1 and 2, and corres¬ pondingly the blades 1' and 2', have sharpening chamfers on opposite sides, and the blades 1 and 2 and 1' and 2' can be positioned to be side-to-side, whereupon the pairs of blades form two cutting units on opposite sides of the shaft 3. While in stage c) , the units are in their non- operating positions, from which position they can be ro¬ tated, supported by shaft 3, to position d) , in which position the pair of blades 1,2 executes a cutting action directed at the veneer web that passes along between the opposing roller 9 and the blades. From this position the blade set can be rotated to a position corresponding to stage c) , in which the blades 1 and 2 and 1' and 2' are, however, positioned on opposite sides when compared to stage c) . The said function c) - d) can, in principle, be used in executing regular cutting of the web to set lengths, although it is, of course, true that the bigger faulty spots can be cut off using the said function man¬ ner described in the aforementioned Finnish patent 56326.

In addition to this, the said blade structure can, of course, be also used in the manner described in stages a) and b) .

The cutter blade described in the above can be con¬ structed to be so sturdy that it is capable to execute the intended cutting operation without requiring special measures. From the point of view of keeping the mass to be moved at a low level, it is useful to have a sturdy opposite support (e.g. a roll, drum, or some other cor¬ responding structure) for the blade at the moment of cut¬ ting. The support has advantageously a peripheral speed equal to that part of the blade with which it is in con¬ tact.

Claims

Patent claims:

1. A cutter for the purpose of cutting a moving web at rightangles to the direction of movement and at select- able cutting intervals, in which cutter the cutting ac¬ tion is executed by a blade pressed against the web and essentially advancing at the speed of the moving web, the said blade being arranged to be supported rotatably by a shaft, characterized in that the said shaft supports at least two cutting blades (1,2), the angular position of of which being independently controlled in relation to any other blade.

2. A cutter as claimed in claim 1, characterized in that to each of the said blades (1,2) has been connected an essentially opposite blade (1',2') .

3. A cutter as claimed in claims 1 or 2, characterized in that each of the blades (1,1'; 2,2', fig. 1) has been sharpened on the same side with respect to the direction of rotation.

4. A cutter as claimed in claims 1 or 2, characterized in that each of the blades (1,1'; 2,2', fig. 1) has a sharpening chamfer on the side opposite to that of the blade adjacent to it.

5. A cutter as claimed patent claim 4, characterized in that the blade whose sharpening chamfer is inclined to- wards the direction of rotation (1, fig. 3) and the blade following it in the direction of rotation (2, fig. 3), as well as the blades opposite (l',2') to the said blades have been arranged so that they can be positioned side- to-side so that two blades form one cutting edge.

6. A cutter as claimed in any of the above claims 1-5, characterized in that one of the blades (2) and the op- tional opposed blade (2') have been mounted onto at¬ tachments (4) projecting outward from the shaft (3) , as well as the blade (1) adjacent to it and the optional opposite blade (1') have been mounted onto the said shaft (3) by means of attachments (7) projecting outward from sleeves (6) located in the spaces between the atachments (4) , whereby the shaft (3) and the sleeves (6) have been connected to a rotation mechanism of their own.

7. A cutter as claimed in any of claims 1-6, character¬ ized in that the rotation motion causing the cutting ac¬ tion of each of the blades has been arranged to take place with a, preferably adjustable, delay after the ac¬ tivation of the preceding blade.

8. A cutter as claimed in any of claims 1-6, character¬ ized in that each consecutive blade in the direction of rotation has been arranged to position itself in an angu¬ lar position different to that of the adjacent blade's angular position, the said position being advantageously adjustable prior to the rotation movement preceding each cutting action.

9. A cutter as claimed in any of claims 1-8, character- ized in that the blades are provided with a supporting structure with regard to the cutting line, the said structure being in a motion compatible with the motion of the blades at the cutting moment.