The invention concerns an equipment for replacing a doctor blade, a doctor blade, and a method in the use of a band-like doctor blade.

For example, from the patent publications FI 54,076 and US 4, 691, 406, the use of a band-like doctor blade material is known for servicing of roll faces. Thus, it is known to transfer a used doctor blade onto a winder for the used blade, and the unused doctor blade is fed from its own reel. The prior-art equipments are mainly hydraulic, and in their case oscillation of a doctor blade has also been permitted.

In the prior art devices, however, it is a particular drawback that the contact between the doctor blade and the roll is not fully adequate, because at the edges of the holder the doctor blade is bent in an uncontrolled way, and in such a case the wear of the doctor blade is also uncontrolled, which has the further consequence that the oper- ation of the doctor blade in the prior-art solutions is not sufficiently reliable.

In the present patent application, it is suggested that such an equipment for replacing a doctor blade is used in which the doctor blade is passed from a reel of doctor blades, preferably from a storage box for doctor blades. Thus, at one end of the roll, the equipment comprises a blade feed device, and at the opposite end of the roll a blade pulling device. Both of said devices are operated when a blade is fed from a reel of doctor blades into connection with the roll. The doctor blade is passed into a blade opening of a blade holder for a conventional doctor blade, which holder is provided on a frame beam, and the blade is locked in its position in the blade opening by means of loading hoses which operate as a blade positioning device and, at the same time, as locking means.

In accordance with the present invention, it is an essential feature of the equipment for replacing a doctor blade and of the doctor blade and of the method in the use of the doctor blade in accordance with the present invention that the doctor blade is provided with edge notches at one longitudinal edge of the doctor blade. During operation of the doctor, said notches are placed at both ends of the area of use proper of the doctor blade. The notches permit controlled and uniform bending of the doctor blade during operation. In such a case, the blade is worn uniformly.

When it is desirable to change the area of operation of said doctor blade, doctor blade is fed from the reel of doctor blades so that the edge notch at the outlet side of the doctor blade is placed at the end of the area of operation on the doctor blade holder, and the new edge notch is transferred in such a way into connection with the blade that it is placed at the inlet end of the doctor blade holder, as viewed in the feed direction Li-Thus, the doctor blade is fed periodically always over the length of one distance El between notches.

From the blade pulling device the used doctor blade is fed further to the winding device for used blade.

The blade solution in accordance with the invention mentioned above makes it possible to provide an equipment of an entirely novel type for replacing a doctor blade. In accordance with the invention, a band-like doctor blade can be fed directly out of a storage package for doctor blades from a reel, and said feed is carried out periodically always over the length of one distance E1 between notches. Thus, a blade in accordance with the invention is provided with notches at the side or edge, which notches permit satisfactory operation of the blade in accordance with the invention. In accordance with the invention, it is possible to use existing frame beams and doctor blade holders of a doctor equipment. In such a case, the blade is fed through the blade opening on the holder, at which time the blade loading members have been released. As the loading means, it is possible to use ordinary pneumatic hoses or equivalent. Also, other loading means can be used in order to lock the doctor blade in its holder.

The equipment for replacing a doctor blade, the doctor blade, and the method in the use of a band-like doctor blade in accordance with the invention are characterized in what is stated in the patent claims.

The invention will be described in the following with reference to some preferred embodiments of the invention illustrated in the figures in the accompanying draw- ings, the invention being, yet, not supposed to be confined to said embodiments alone.

Figure 1A is a schematic illustration of an equipment in accordance with the inven- tion as viewed in the machine direction.

Figure 1B is a side view of a doctor blade.

Figure 1C shows the equipment of Fig. 1B as viewed in the direction of the arrow kl in Fig. 1B.

Figure 2A shows a doctor blade in accordance with the invention.

Figure 2B is a sectional view of a doctor blade taken along the line 1-1 in Fig. 2A.

Figure 3A is an axonometric view illustrating the feed of a doctor blade in accord- ance with the invention while making use of a photocell.

Figure 3B is a side view of a feed device 12.

Figure 3C shows an embodiment in which the position of the edge notch is read from the location of the edge notch by means of a photocell device 50au, 50a2.

Figure 3D shows a second embodiment of the invention, in which the feed device comprises a gearwheel, a toothed wheel, or equivalent.

Figure 3E shows an embodiment of a doctor blade related to the embodiment shown in Fig. 3D, in which embodiment the doctor blade is provided with perforations M1, M2... for engagement with the teeth.

Figure 4 is a schematic illustration of a solution of equipment in accordance with the invention.

Fig. 1A shows an equipment 10 in accordance with the invention for replacing a doctor blade. The doctor blade 11 is placed on a reel 100 in a storage box P, from which it is taken as a band to a feed device 12 and passed through the feed device 12 and through a blade opening provided in the blade holder 14 provided on the doctor blade frame 13 further to a pulling device 16 and through it to a winding device 17 for used doctor blade.

In the figure, the direction of feed of the doctor blade 11 from the blade feed device 12 through the blade holder 14 to the pulling device 16 is denoted with the arrow Li-Thus, the doctor blade is fed from the tending side H of the machine to the driving side K of the machine along with the face T'of the roll T. Between the frame of the doctor and the blade holder, there are means J1, J2, favourably loading hoses, by whose means the blade holder 14 provided on the frame can be pivoted so that the doctor blade 11 fitted in the blade holder reaches contact with the roll T face T'. In this connection, the blade 11 is also kept locked in its blade holder 14.

The frame 13 of the doctor blade, i. e. the doctor frame, can be oscillated by means of a cylinder device 15 (arrow S1). By means of the loading hoses J1, J2, which are loaded by a pressure of a medium, the blade can be pressed so that the loading hose presses the doctor blade 11 into contact with the faces of the holder 14 and keeps the blade locked in the holder.

Fig. 1B is a side view of the blade holder, and Fig. 1C shows the equipment as viewed in the direction of the arrow kl in Fig. 1B. The holder 14 of the doctor blade 11 is fitted on the doctor frame 13, which has been mounted by means of

bearing means G1, G2. In an oscillating movement, the whole doctor frame 13 is displaced along a linear path (arrow Sl). The equipment 10 in accordance with the invention for replacing a doctor blade 11 can be used in connection with existing doctor frames 13 and their blade holders 14. The doctor frames 13 can be provided with oscillating devices 15, in which case, in a solution of equipment in accordance with the invention, the doctor blade frame 13 and, thus, the doctor blade 11 can be oscillated in the lateral direction of the roll T, in which connection, for example, a movement of oscillation of 100 mm is permitted so that the blade feed device and the blade pulling device are coupled free. A controlled bending of the blade 11 is permitted by notches 18ai, 18a2... at the edge, and in this way a movement of oscillation is also permitted.

Fig. 2A illustrates a blade 11 in accordance with the invention. The blade 11 is provided with notches 18au, 18a2... at the edge, and the distance between said notches, i. e. the gap E1 between the notches, is equal to the length of the roll T. In such a case, the notches 18ai, 18a2... at the edge can be fitted outside the two lateral edges of the blade holder. The notches at the edge permit bending of the blade 11 and, thus, uniform wear.

The notches 18al and 18a2 at the edge are preferably of rectangular section, and their depth, i. e. height, = dl, and their width = d2, and the gap E1 between the notches is preferably equal to the length of the roll T, i. e. preferably the length over which the doctor blade must be in contact with the roll face T'in view of its servicing.

The gap E1 between the notches is preferably in a range 1000 mm... 15,000 mm The depth dl of each notch 18al, 18a2... at the edge is preferably in a range 5 mm... 100 mm, and the width d2 of each notch 18al, 18a2... at the edge is preferably in a range 5 mm.. 1200 mm, and optimally in a range 100 mm 1000 mm.

Fig. 2B shows the doctor blade 11 as a sectional view taken along the line 1-1 in Fig. 2A. In the embodiment shown in the figure, the doctor blade 11 is a web-like, oblong material to be unwound from a reel, which material comprises a blade edge lla which is placed against the roll face and fitted at an oblique angle against the roll face. Further, on the top face of the doctor blade 11, there are pins 60al, 60a2..., by whose means it is prevented that the doctor blade should fall away from the gap in the blade holder when the doctor blade is not loaded and when the blade is in a position in which it can fall away from the blade space of the blade holder by the effect of gravity.

Fig. 3A shows an embodiment of the invention in which the equipment is controlled by means of a system of photocells. Further, for the feed of the doctor blade 11, a feed device 12 and a pulling device 16 are used, which comprise friction wheels 12al, 12a2; 16al, 16a2. Thus, the feed device and the pulling device form a friction equipment, in the way shown in Fig. 3A, for feeding the doctor blade 11 in the feed direction Ll. In the way shown in Fig. 3A, when the edge notch 18al at the blade 11 reaches the location of the photocell device 50, the feed is stopped. The photocell device 50 comprises a source of light 50a, and a detector 5°a2 that receives light. In such a case, the notches 18al and 18a2 at the, edge are placed at the ends H and K of the blade holder 14 of the doctor blade 11. The blade is always fed as a length equal to the gap El between the edge notches 18al and 18a2, i. e. as a length over which the doctor blade 11 is in contact with the roll T face T'. The friction wheels 12al and 16al are rotated by electric motors. The backup wheels 12a2 and 16a2 can be freely revolving.

Fig. 3B illustrates the construction of the feed device 12. The feed device 12 comprises feed wheels 12au, 12a2, preferably friction wheels, of which preferably the friction wheel 12al is provided with drive. The drive is taken favourably from an electric motor. The oblong doctor blade band 11 is passed through the nip between the wheels 12au, 12a2 and is fed forwards by means of the wheel 12au. The feed direction is indicated by the arrow L1. The gap E1 between notches, i. e. the distance

between adjacent notches 18al, 18a2... at the edge, is in a range 1000 mm 15,000 mm, depending on the length of the roll.

Fig. 3C is a separate illustration showing the determination of the position of the doctor blade 11 by means of a photocell device 50. The photocell device comprises arrangements of equipment fitted above and below the blade 11, i. e. a transmitter of a signal, preferably a source of light 50a, which emits light, and a detector 50a2 which detects light, in the present case preferably a photocell. When the notch 18al at the edge of the blade 11 has reached the location of the photocell device, said situation is detected by means of the detector 50a2, and the feed of the blade 11 is stopped. Then, the detector 5°a2 receives a signal, preferably a beam of light, from the signal transmitter 50al, preferably a source of light. The information from the detector 5°a2 is transferred to the central unit 200, as is illustrated in Fig. 4.

Fig. 3D shows a second embodiment, in which the doctor blade is provided with holes M1, M2, M3..., which are placed at regular distances from one another and which operate as grasping holes for the blade 11 feed device 12 and for the blade pulling device 16, which devices comprise teeth on the drive wheels 12au, 16al, the teeth cl, c2... in the toothings entering into said holes M1, M2... and operating as blade 11 feeders. A solution of said sort also permits reliable calculation of the blade length that has been fed, because the blade 11 feed device 12 can comprise a detector device on the drive wheel 12au, by means of which detector device the distance of blade that has been fed can be calculated from the number of revolutions of the drive wheel of the feed device 12.

Fig. 3E is a separate illustration showing an embodiment of the invention which is related to Fig. 3D, i. e. to the toothed-wheel drive. In the embodiment shown in Fig.

3E, the lateral area of the band 11 is provided with notches M1, M2 which are grasped by the teeth on the toothed wheel 12al so as to feed the doctor blade 11 in the feed direction.

Fig. 4 is a schematic illustration of a solution of equipment in accordance with the invention. The central unit 200 comprises data transfer buses el, e2... passing to the blade feed device 12 and to the blade pulling device 16 and to the winder 17 of used blade 11.

The notch gap El between the edge notches 18al, 18a2 can be favourably pro- grammed in advance in the central unit 200, in which case the central unit 200 is provided with a counter, by whose means it sums the blade length that has been fed and compares it with the blade length provided on the reel and notifies the operating personnel, by means of a display monitor or otherwise, of the necessity of replacing a new reel of doctor blades or of the total blade length still present on the reel.