Holder for the cradle of a coating bar or for a coating blade

Abstract: The invention concerns a holder for the cradle of a coating bar or for a coating blade in a coating unit, which is fitted to spread and to smooth a size film or a corresponding layer of coating agent onto the face of a moving base to be coated, such as a roll (1) of a size press or the web passed over a back-up roll, by means of a coating bar (13) or a coating blade loaded against said moving base (1). The cradle (14) of the coating bar or the coating blade, respectively, is mounted in a holder arranged in an application beam (11) transverse to the machine direction. Into the frame (15) of the holder, a journalling duct (18) transverse to the machine direction has been formed, into which duct an oblong member (19) has been fitted rotatably, which member comprises a cam-like projection (20) of eccentric section. Said member can be rotated, for the purpose of fixing the cradle (14) of the coating bar or the coating blade in its place, so that the cam-like projection (20) rests against the rear face (14a) of the cradle of the coating bar or of the coating blade and secures said cradle (14) or coating blade against the support (12) provided on the application beam (11).

Description: The invention concerns a holder for the cradle of a coating bar or for a coating blade in a coating unit, which is fitted to spread and to smooth a size film or a corresponding layer of coating agent onto the face of a moving base to be coated, such as a roll of a size press or the web passed over a back-up roll, by means of a coating bar or a coating blade loaded against said moving base, the cradle of the coating bar or the coating blade, respectively, being mounted in a holder arranged in an application beam transverse to the machine direction. In surface-coating, in particular in surface-sizing, of paper and board, a technique is commonly employed in which a film of a coating agent is spread onto the faces of rolls that form a nip by means of coating devices, whereupon the films of coating agent are fitted to adhere to the faces of the paper or board to be coated as it runs through the nip formed by the pair of rolls. In a coating device, the coating agent is, as a rule, introduced under pressure into the application zone, which is defined by the roll face, by a coating member, such as a coating blade, bar, or equivalent loaded against the roll face, by a dam blade, and by lateral seals. On the other hand, for example in pigmenting of paper, a technique is used in which the pigment coating is applied by means of coating devices directly onto the face of the web. In such a case, the web is passed over a back-up roll, and the coating member, such as a coating bar or a coating blade, is loaded against the web running over the back-up roll so that the coating member applies the desired layer of coating agent onto the web face. The coating agent is introduced onto the web in some suitable way before the coating member. In prior art, see for example GB-A-2 040 738, the cradle of the coating bar or the coating blade, respectively, was mounted by means of a holder that was displaceable pneumatically, i.e. by means of a loading hose loaded by means of compressed air. Such a mounting involved certain drawbacks, of which, for example, failures of hoses should be mentioned. If the loading hose of the holder is broken, it must, of course, be replaced, for which reason it has often been necessary to stop the machine completely. Variations in temperature have also created problems in prior-art solutions. In size presses and also in other coating devices, the problems related to variations in temperature are manifested with emphasis in connection with replacements of rolls. When new rolls or rolls with new coatings are mounted, they are cold. During the operation of the machine, the temperature of the rolls and also of the other constructions, in the case of bar coating, especially the temperature of the cradle of the coating bar, is changed, whereby the cradle is subjected to an extensive thermal expansion. The prior-art mode of fixing, however, prevents thermal expansion of the cradle, which has resulted in considerable problems of the profile of the coating-agent film. The problems of the prior-art solutions further include the complicated fixtures with a number of locks and guides, as well as the fact that the prior-art holders are readily jammed especially when running with pastes. The object of the present invention is to provide a solution by whose means the drawbacks related to the prior-art devices are avoided and by whose means a considerable improvement is obtained over the prior art. In view of achieving this, the invention is mainly characterized in that, into the frame of the holder, a journalling duct transverse to the machine direction has been formed, into which duct an oblong member has been fitted rotatably, which member comprises a cam-like projection of eccentric section and which member can be rotated, for the purpose of fixing the cradle of the coating bar or the coating blade in its place, so that the cam-like projection rests against the rear face of the cradle of the coating bar or of the coating blade and secures said cradle or coating blade against the support provided on the application beam. By means of the invention, a number of advantages are obtained as compared with the prior art, of which advantages, for example, the following should be stated. As the holder solution in accordance with the invention is fully mechanical with respect to its operation, it is highly reliable in operation. Thus, when a solution in accordance with the invention is used, no standstills similar to those experienced in prior art are to be expected. The costs of the construction in accordance with the present invention are substantially lower than those of prior-art solutions. The invention permits the desired fastening tightness of the coating-bar cradle or of the coating blade, even so that the degree of tightening is adjustable. In such a case, possible thermal expansions do not cause any problems in the construction. Owing to the circulation of water provided in the holder of the present invention, seizing or jamming does not cause a problem similar to those occurring in prior art either. The other advantages and characteristic features of the invention come out from the following detailed description of the invention. In the following, the invention will be described in more detail with reference to the figures in the accompanying drawing. Figure 1 is a fully schematic side view of a size press or of a corresponding coating device in which the solution of the invention is applied. Figure 2 is an enlarged detail of the illustration of Fig. 1, wherein, in an embodiment of bar coater, the construction and the operation of a holder in accordance with the invention are illustrated in more detail. Figure 3 is an illustration corresponding to Fig. 2 of an application of a holder in accordance with the invention to a blade coater. Thus, Fig. 1 is a schematic illustration of a size press or of a corresponding coating device, which comprises press rolls 1 and 2, so that the first roll 1 and the second roll 2 form a nip N with one another, through which nip the paper or board web W is passed. In the solution as shown in Fig. 1, the web W is guided into the nip N over a guide roll 3. In the size press, a first size film is metered onto the face of the first roll by means of a coating unit 10 and, in a corresponding way, onto the face of the second roll 2, a second size film is metered by means of a coating unit 10a. In the roll nip N, the size films are transferred from the faces of the rolls 1 and 2 onto the paper or board web W that runs through the nip. The application beam 11 in the coating unit 10 is mounted on the frame 4 of the size press pivotally by means of an articulation shaft 7 transverse to the machine direction. For this purpose, a bracket 8 has been fitted on the frame 4 of the size press for mounting of the application beam 11. The application beam 11 is further supported on the frame 4 of the size press by means of a loading cylinder 5, which is linked with the application beam 11 by means of an articulated joint 6. By means of said loading cylinder 5, the application beam 11 can be pivoted in relation to the articulation shaft 7. The construction described above is quite conventional and is in common use to-day, and the solution of the invention can be applied to said construction. Unlike the solution illustrated in Fig. 1, the invention can also be applied to a coater in which the web W is passed over a back-up roll and the coating agent is metered directly onto the face of the web. Such an embodiment is not shown in the figures in the drawing, but it is readily understood from the following description referring to Figs. 2 and 3 that the invention is also applicable to such a solution. Thus, Fig. 2 is a more detailed illustration of an application of the invention to a bar coater. In Fig. 2, the reference numeral 1 denotes the moving base to be coated, which may be, for example, the face of a roll in a size press as shown in Fig. 1, or a web that runs along a back-up roll. In the embodiment of Fig. 2, the coating member consists of a coating bar 13, which is mounted revolvingly in the cradle 14 of the coating bar. In the way known in prior art, the material of the cradle 14 is, for example, polyurethane or equivalent. The coating bar 13 is loaded against the moving base 1 to be coated by means of a loading hose 16 acting upon the rear face of the cradle 14, and by means of this loading, in the way known in prior art, the thickness of the layer of coating agent applied onto the base 1 to be coated is affected. According to the embodiment shown in this figure, the loading hose 16 is mounted in a profiled rib 17, which can be deflected in the desired way by means of adjusting spindles (not shown) so as to profile the layer of coating agent applied onto the base 1 to be coated. The cradle 14 of the bar 13 is mounted in a holder provided in the application beam 11, which will be described in more detail below. To the application beam 11, the frame 15 of the holder is attached, which is provided with a journalling duct 18 transverse to the machine direction and open towards the cradle 14 of the bar. In said journalling duct 18, a pipe 19 transverse to the machine direction has been arranged rotatably, to the outer face of which pipe 19 a rod 20, cam or equivalent parallel to the pipe 19 has been fixed by welding. Further, the pipe 19 is, at least at one end, provided with a turning device, such as a lever 21 shown in the figure, by whose means the pipe 19 can be rotated in the journalling duct 18. After the cradle 14 of the bar has been mounted into its place in the holder in the way shown in Fig. 2, the front face of the cradle 14 rests against the support 12 provided in the application beam 11. In the simplified illustration in Fig. 2, the support 12 is shown as an integral part of the application beam, but it is preferable that said support 12 can be fixed to the application beam 11 detachably. When the cradle 14 is in its place, the pipe 19 has been turned by means of the turning device 21 into the position shown in the figure, in which the rod 20 is pressed against the rear face 14a of the cradle and secures the cradle 14 in its place between the support 12 and the rod 20. When the cradle 14 is to be removed from the holder, the pipe 19 is rotated by means of the turning device 21 so that the rod 20 is shifted into the position 20a illustrated by the dashed line. When necessary, water is passed into the pipe 19, which water is discharged out of the pipe 19 through holes 22 drilled into the wall of the pipe. The water that enters through these holes 22 into the journalling duct 18 lubricates the pipe 19 and prevents its jamming in the journalling duct 18. The adjustment of the degree of tightening of the fastening of the cradle 14, which can be achieved by means of the holder, can be accomplished, e.g., by means of the adjusting screws 23 shown in Fig. 2. A number of said adjusting screws 23 are provided in the transverse direction of the machine, and by tightening of said screws, the pipe 19 can be shifted closer to the cradle 14 and, in a corresponding way, when the screws are untightened, the pipe 19 is shifted apart from the cradle 14. In Fig. 3, an embodiment of the invention is shown in which the holder in accordance with the invention is fitted in connection with a blade coater. Similarly to Fig. 2, in Fig. 3, the moving base to be coated is also denoted with the reference numeral 1. The coating blade 114 is mounted in a holder fitted in the application beam 111, and the coating blade 114 is loaded against the base 1 to be coated by means of a loading hose 116. In a way corresponding to Fig. 2, the loading hose 116 is mounted in a profiled rib 117, which can be deflected in the desired way by means of adjusting spindles (not shown), i.e. by pulling and pushing, whereby the coating blade 114 can be profiled. The holder of the coating blade 114 consists of a holder frame 115 attached to the application beam 111, into which frame 115 a journalling duct 118 transverse to the machine direction and open towards the coating blade 114 has been formed. Into said journalling duct 118, a pipe 119 has been fitted rotatably, which pipe is provided with a rod 120 or equivalent, which is parallel to the longitudinal direction of the pipe and which has been fixed to the outer face of the pipe by welding. Further, the holder includes a support 112, which has been fixed to the application beam 111 permanently or detachably and against which the coating blade 114 is supported when it is mounted in its place. According to the illustration of Fig. 3, the coating blade 114 is secured in its position against the support 112 by rotating the pipe 119 so that the rod 120 or equivalent is supported against the rear face 114a of the coating blade. In order to make sure that the coating blade 114 remains in its position, a groove 124 that is transverse to the machine direction and open towards the coating blade 114 has been formed into the support 112, and in a corresponding way, a projection 125 is provided on the coating blade 114, which projection is transverse to the machine direction, is continuous or fragmentary, and which projection penetrates into the groove 124 provided in the support 112. Further, the pipe 119 is provided with a turning device fitted at least at one end of the pipe, such as a lever 121 as shown in Fig. 3, by means of which lever the pipe 119 can be rotated in the journalling duct 118. When the coating blade 114 is mounted in its place, the pipe 119 has been pivoted by means of the lever 121 into the position shown in Fig. 3 so that the rod 120 secures the coating blade 114 against the support 112. When the coating blade 114 is to be removed from the holder, the pipe 119 is rotated by means of the turning device 121 so that the rod 120 is shifted to the position 120a illustrated by the dashed line in Fig. 3. When necessary, water is passed into the pipe 119, which water is arranged to be discharged out of the pipe 119 through the holes 122 drilled into the wall of the pipe into the journalling duct 118. Said circulation of water is supposed to prevent seizing and jamming of the pipe 119. It is also illustrated in the embodiment of Fig. 3 that, in the holder in accordance with the invention, it is possible to arrange the degree of tightening of the coating blade 114 adjustable, e.g., by means of a system of adjusting screws 123 corresponding to that shown in Fig. 2. In connection with Figs. 2 and 3, it was described that the securing of the cradle 14 of the bar and of the coating blade 114, respectively, is arranged by means of a rotatable pipe 19,119 fitted in the journalling duct 18,118 and by means of a rod 20,120 fixed to said pipe. This arrangement can, of course, be replaced, e.g., by means of a solution in which the pipe in itself has been shaped eccentric so that it comprises a cam which is supported against the rear face 14a, 114a of the cradle or of the coating blade when the pipe is rotated. Further, a rotatable pipe can be substituted for by any eccentric, oblong, rotatable member fitted in the journalling duct 18,118 provided that the rotation of said member permits securing of the bar cradle 14 or of the coating blade 114 in its position. In such an oblong member, it is also possible to arrange circulation of water, e.g., by means of various bores.

Claims: Holder for the cradle of a coating bar or for a coating blade in a coating unit, which is fitted to spread and to smooth a size film or a corresponding layer of coating agent onto the face of a moving base to be coated, such as a roll (1) of a size press or the web passed over a back-up roll, by means of a coating bar (13) or a coating blade (114) loaded against said moving base (1), the cradle (14) of the coating bar or the coating blade (114), respectively, being mounted in a holder arranged in an application beam (11,111) transverse to the machine direction, characterized in that, into the frame (15,115) of the holder, a journalling duct (18,118) transverse to the machine direction has been formed, into which duct an oblong member (19,119) has been fitted rotatably, which member comprises a cam-like projection (20,120) of eccentric section and which member can be rotated, for the purpose of fixing the cradle (14) of the coating bar or the coating blade (114) in its place, so that the cam-like projection (20,120) rests against the rear face (14a, 114a) of the cradle of the coating bar or of the coating blade and secures said cradle (14) or coating blade (114) against the support (12,112) provided on the application beam (11, 111). Holder as claimed in claim 1, characterized in that the oblong member (19,119) fitted in the journalling duct (18,118) is provided with a bore or with an equivalent cavity that extends across its length. Holder as claimed in claim 1 or 2, characterized in that the oblong member (19,119) that is fitted in the journalling duct (18,118) is provided with a number of transverse bores (22,122), which extend into said longitudinal bore or into said equivalent cavity, circulation of water being passed into said longitudinal bore or into said equivalent cavity so that the water is discharged out of the transverse bores (22,122) into the journalling duct (18,118) for lubrication. Holder as claimed in any of the preceding claims, characterized in that the oblong member (19,119) fitted in the journalling duct (18,118) can be shifted in the journalling duct (18,118) towards the bar cradle (14) or coating blade (114) and apart from said cradle or blade by means of adjusting screws (23,123) or equivalent so as to adjust the fixing tightness of the coating-bar cradle (14) or of the coating blade (114). Holder as claimed in any of the preceding claims, characterized in that the oblong member (19,119) fitted in the journalling duct (18, 118) is provided with a turning device (21,121) that is fitted at least at one of its ends. Holder as claimed in any of the preceding ciaims, characterized in that the oblong member fitted in the journalling duct (18,118) comprises a pipe (19,119), which is provided with an eccentric cam (20,120) or equivalent. Holder as claimed in claim 6, characterized in that the cam (20, 120) or equivalent has been fixed to the outer face of the pipe (19,119) by welding or in a corresponding way permanently. Holder as claimed in claim 6 or 7, characterized in that the cam (20,120) or equivalent is a rod that has been welded onto the outer face of the pipe (19,119). Holder as claimed in claim 6, characterized in that the whole of the pipe (19,119) has been shaped as eccentric so that it is provided with a cam.

Inventors: ORAVA TAUNO, SALO MARKKU, ORAVA, TAUNO, SALO, MARKKU
Applicants: VALMET CORP, VALMET CORPORATION
Application year: 1993
Main classification: D21H23
IPC codes: D21H23, B05C11