Abstract:
The invention relates to band-like doctor blade assembly, a doctor blade and a method in the use of the doctor blade. The doctor blade assembly includes continuous and substantially infinite doctor blade that is placed in a reel, the doctor blade is then fed into a blade holder. The blade holder includes locking devices in its connection for locking the doctor blade in the blade holder. The continuous and substantially infinite doctor blade has a plurality of edge notches formed along an edge thereof and the doctor blade is fed over a length substantially equal to the distance between the edge notches, while the notches are placed, during the operation of the doctor blade, at both ends of the blade holder and permit bending of the continuous band-like doctor blade.

Description:
FIELD OF THE INVENTION 
     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. 
     BACKGROUND OF THE INVENTION 
     For example, from the patent publications FI 54,076 and U.S. Pat. No. 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 operation of the doctor blade in the prior-art solutions is not sufficiently reliable. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     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 L 1 . Thus, the doctor blade is fed periodically always over the length of one distance E 1  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 E 1  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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in the following with reference to some preferred embodiments of the invention illustrated in the figures in the accompanying drawings, the invention being, yet, not supposed to be confined to said embodiments alone. 
     FIG. 1A is a schematic illustration of an equipment in accordance with the invention as viewed in the machine direction. 
     FIG. 1B is a side view of a doctor blade. 
     FIG. 1C shows the equipment of FIG. 1B as viewed in the direction of the arrow k 1  in FIG.  1 B. 
     FIG. 2A shows a doctor blade in accordance with the invention. 
     FIG. 2B is a sectional view of a doctor blade taken along the line I—I in FIG.  2 A. 
     FIG. 3A is an axonometric view illustrating the feed of a doctor blade in accordance with the invention while making use of a photocell. 
     FIG. 3B is a side view of a feed device  12 . 
     FIG. 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  50   a   1 , 50   a   2 . 
     FIG. 3D shows a second embodiment of the invention, in which the feed device comprises a gearwheel, a toothed wheel, or equivalent. 
     FIG. 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 M 1 , M 2  . . . for engagement with the teeth. 
     FIG. 4 is a schematic illustration of a solution of equipment in accordance with the invention. 
    
    
     DETAILED DESCRIPTION OF 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 L 1 . 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 J 1 ,J 2 , 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 S 1 ). By means of the loading hoses J 1 ,J 2 , 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 k 1  in FIG.  1 B. The holder  14  of the doctor blade  11  is fitted on the doctor frame  13 , which has been mounted by means of bearing means G 1 ,G 2 . In an oscillating movement, the whole doctor frame  13  is displaced along a linear path (arrow S 1 ). 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  18   a   1 , 18   a   2  . . . formed along the edge of the blade  11  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  18   a   1 , 18   a   2 . . . at the edge, and the distance between said notches, i.e. the gap E 1  between the notches, is equal to the length of the roll T. In such a case, the notches  18   a   1 , 18   a   2 . . . 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  18   a   1 , and  18   a   2  at the edge are preferably of rectangular section, and their depth, i.e. height,=d 1 , and their width=d 2 , and the gap E 1  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 E 1  between the notches is preferably in a range 1000 mm . . . 15,000 mm. The depth d 1  of each notch  18   a   1 , 18   a   2 . . . at the edge is preferably in a range 5 mm . . . 100 mm, and the width d 2  of each notch  18   a   1 , 18   a   2 . . . 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 I—I in FIG.  2 A. 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  11   a  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  60   a   1 ,  60   a   2  . . . , 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  12   a   1 , 12   a   2 ; 16   a   1 , 16   a   2 . 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 L 1 . In the way shown in FIG. 3A, when the edge notch  18   a   1  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  50   a   1  and a detector  50   a   2  that receives light. In such a case, the notches  18   a   1  and  18   a   2  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 E 1  between the edge notches  18   a   1  and  18   a   2 , i.e. as a length over which the doctor blade  11  is in contact with the roll T face T′. The friction wheels  12   a   1  and  16   a   1  are rotated by electric motors. The backup wheels  12   a   2  and  16   a   2  can be freely revolving. 
     FIG. 3B illustrates the construction of the feed device  12 . The feed device  12  comprises feed wheels  12   a   1 , 12   a   2 , preferably friction wheels, of which preferably the friction wheel  12   a   1  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  12   a   1 , 12   a   2  and is fed forwards by means of the wheel  12   a   1 . The feed direction is indicated by the arrow L 1 . The gap E 1  between notches, i.e. the distance between adjacent notches  18   a   1 , 18   a   2 . . . 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  50   a   1  which emits light, and a detector  50   a   2  which detects light, in the present case preferably a photocell. When the notch  18   a   1  at the edge of the blade  11  has reached the location of the photocell device, said situation is detected by means of the detector  50   a   2 , and the feed of the blade  11  is stopped. Then, the detector  50   a   2  receives a signal, preferably a beam of light, from the signal transmitter  50   a   1 , preferably a source of light. The information from the detector  50   a   2  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 M 1 ,M 2 ,M 3  . . . , 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  12   a   1 , 16   a   1 , the teeth c 1 ,c 2  . . . in the toothings entering into said holes M 1 ,M 2 . . . 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  12   a   1 , 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 holes M 1 ,M 2  which are grasped by the teeth on the toothed wheel  12   a   1  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 e 1 ,e 2  . . . 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 E 1  between the edge notches  18   a   1 , 18   a   2  can be favourably programmed 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. 
     The invention is described above referring merely to the advantageous embodiment examples thereof, to the details of which the invention is not, however, intended to be exclusively restricted. A number of modifications and variations are conceivable within the scope of the inventive idea of the claims below. As such, the examples provided above are not meant to be exclusive and many other variations of the present invention would be obvious to those skilled in the art, and are contemplated to be within the scope of the appended claims.