Arrangement in a variable-crown roll provided with loading shoes

[0002] The invention concerns an arrangement for prevention of foaming of fluid in a variable-crown roll provided with loading shoes.

[0003] Variable-crown rolls comprise a stationary axle inside the roll, on which axle the roll mantle is fitted to revolve. The roll mantle is supported in the press direction on the axle of the roll by means of loading shoes acting upon the inner face of the roll mantle, which shoes are pressed against the inner face of the roll mantle by means of the pressure of a fluid.

[0004] In paper machines, rolls which form a dewatering press nip are used commonly. It is important that the distribution of the linear load, i.e. the profile, in the axial direction of the rolls can be made invariable and that the profile can be regulated in the desired way, for example, in view of controlling the cross-direction moisture profile and/or thickness profile of the web. Also in supercalenders, the aim is to be able to regulate the calendering nip in the axial direction of the calender rolls so that the cross-direction thickness profile of the web becomes as desired. For this purpose, from the prior art, a number of different variable-crown or adjustable-crown rolls are known, at which attempts are made to act upon the distribution of the linear load in the nip.

[0005] In the rolls mentioned above, it has been noticed that foaming of the fluid is a drawback. The rolls comprise a central stationary axle, in which the loading shoes have been fitted, and the loading shoes project from the axle so that their loading members reach contact with the inner face of the roll mantle. When fluid is sprayed onto the inner face of the roll mantle for the purpose of cooling, or when fluid enters onto the inner face of the roll mantle through lubrication of the loading shoes, the fluid strikes against said loading shoe constructions, in which connection the fluid is atomized and is then readily mixed with air. Great changes in the direction of the fluid cause so-called whipping, which further affects the fluid detrimentally and foams it, in which case the fluid must already be replaced after a short period of use. The operation of the hydraulic components of the system is disturbed and their service life becomes shorter.

[0006] In the present application, a novel arrangement is suggested for elimination of the drawback mentioned above. In an embodiment of the application, it is suggested that a separate fluid guide is employed, which is fitted to be attached to the displaceable loading shoe by means of an arm. By means of a spring, the guide is pressed into contact with the inner face of the roll mantle. The guide comprises a gently curved face, by whose means the fluid is guided to fall back into a fluid collecting trough before it meets the side face of the loading shoe. Since the guide is attached to the displaceable loading shoe, the guide always follows the shape of the roll mantle and is, thus, in contact with the inner face of the roll mantle in a controlled way irrespective of any deformations of the roll mantle.

[0007] In a second preferred embodiment of the invention, a guide is used which comprises a separate loading member, for example a piston operating with fluid pressure, at whose end the guide is fitted. In such a case, the fluid pressure is fitted to be effective at the other side of the piston, and by means of the fluid pressure the guide is kept in contact with the inner face of the roll mantle.

[0008] In a third embodiment of the invention, the guide is provided with a through opening, in which connection, by means of a curved face of the guide, the fluid is guided from the inner face of the roll into the through opening and further to fall down into the fluid collecting trough. Also in this embodiment, a separate actuator acts upon the guide, which actuator can be a hydraulic piston actuator, or it can also be a spring actuator, by whose means the guide is kept in contact with the inner face of the roll mantle in connection with any deformations of the roll mantle. Through the through opening in the guide, the doctored fluid can flow through the guide and fall into the fluid collecting trough by the effect of gravity. The embodiment is in particular suitable for press constructions in which the loading shoes are in a lower position.

[0009] The invention is characterized in what is stated in the patent claims.

[0010] 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.

[0011] FIG. 1 shows a prior-art solution, in which the fluid is guided to flow towards the side by means of an inclined face structure of the shoes.

[0012] FIG. 2 shows a solution in accordance with the present invention, in which striking of the fluid applied to the inner face of the roll mantle against the inner face of the loading shoe is prevented so that the stationary central axle of the roll is provided with a separate fluid guide which extends substantially over the entire length of the roll.

[0013] FIG. 3A is a side view of the construction shown in FIG. 2.

[0014] FIG. 3B is an axonometric illustration in part of the construction shown in FIGS. 2 and 3A.

[0015] FIG. 3C is an axonometric illustration in part of an embodiment of the construction of a guide.

[0016] FIG. 4 shows an embodiment of the invention in which the guide is connected with the displaceable loading shoe by means of an arm and a spring.

[0017] FIG. 5A shows an embodiment of the invention in which the press nip is placed at the bottom in the roll and in which the guide is fitted, by means of a spring member and a shaft, in connection with the stationary axle so that, by means of the spring member, the guide is pressed into contact with the inner face of the roll mantle, which guide comprises, in this embodiment of the invention, a flow opening passing through the guide so as to pass the fluid into the fluid collecting trough placed underneath.

[0018] FIG. 5B shows a second mode of suspension of the guide shown in FIG. 5A.

[0019] FIG. 5C shows the fastening of the guide shown in FIG. 4 by means of a leaf spring to the piston.

[0020] FIG. 1 shows a prior-art solution for prevention of foaming of fluid. In an earlier solution of the applicant, the side faces of the loading shoes 20 have been made inclined so that the fluid can flow towards the sides and further through the gaps between the loading shoes. In the solution, the roll 10 comprises a stationary axle 12, from which the loading shoes 20 project. The roll mantle 11 is fitted to revolve on support of bearing means 14.

[0021] FIG. 2 shows a solution in accordance with the invention, in which, before the loading shoes 20, a fluid guide 13 has been fitted in connection with the inner face of the roll mantle 11, which guide 13 extends over the entire length of the roll and by means of which guide the fluid is guided to fall directly into the fluid collecting trough. The guide 13 does not have to be made of one piece, but it may consist of a number of parts or pieces.

[0022] FIG. 3A is a side view of the solution shown in FIG. 2. The guide 13 comprises loading means 15, by which the guide 13 is supported on the central axle 12 and by whose means the guide 13 is further pressed against the inner face of the roll mantle. The loading means 15 comprise a piston part 16 and a fluid space 17 placed in the stationary axle, into which fluid space the pressurized fluid is introduced, in which connection the fluid acts upon the piston 16. Then, by means of the fluid pressure, the guide 13 is pressed against the inner face of the roll mantle. As is shown in the figure, the cross-sectional shape of the guide 13 is a construction that includes a curved guide face 13a, by means of which guide face, in the way shown in the figure, the fluid is made to flow smoothly away from the connection with the roll mantle and fitted to fall into the fluid collecting trough 19. In the figures, the guiding of the fluid by means of the guide 13 is denoted with the arrows L₁. The sense of rotation of the roll mantle is denoted with the arrow S₁.

[0023] FIG. 3B is an axonometric view of the construction shown in FIG. 3A. The guide is connected with a number of loading members 15 over its length, which members are piston devices in the embodiment shown in the figure. The guide may also be composed of separate parts or pieces, so that at least two pistons or springs act upon each piece.

[0024] FIG. 3C illustrates an embodiment of the guide 13. As is shown in the figure, the face 13′ of the guide that is placed against the roll mantle may be provided with grooves U₁,U₂. . . or with other ducts, by whose means the flow of a certain amount of fluid further is permitted, for example, for purposes of cooling. The face 13′ may also be roughened in such a way that a small amount of fluid can flow through the guide.

[0025] FIG. 4 shows a second embodiment of the invention, in which the guide 13 is connected with the displaceable shoe portion 20aof the loading shoe 20 by means of a spindle 21 and a spring 22. In such a case, the guide 13 always follows the movement of the loading shoe 20aand is, thus, in contact with the inner face of the roll mantle while complying with all deformations of the roll mantle produced by the loading shoe/shoes. By means of the spring 22, the guide 13 is pressed into contact with the inner face of the roll mantle. The spring is compressed between the stationary axle 12 and the guide 13. The spiral spring 22 is fitted around the spindle 21. The spindle 21 is fitted with a glide fitting in the hole n in the side face of the loading shoe 20, so that it can be displaced in a way similar to a slide.

[0026] FIG. 5A shows an embodiment of the invention in which the loading shoes are placed in the lower position. In the embodiment of the invention, the guide 13 includes a central flow opening 23, which permits falling of the fluid, after separation of the fluid, through the guide into the collecting trough 19 placed underneath. In this embodiment, the guide is pressed with spring force by means of the spring 24 against the inner face of the roll mantle, while the guide 13 is attached to the stationary axle 12 by means of the spindle 25 and while the spring 24 is fitted around the spindle 25 between the stationary axle 12 and the guide 13. The spindle 25 is fitted in the hole (n) in the axle 12 by means of a glide fitting, in which connection the spindle 25 receives its control and can be displaced into different positions in compliance with any deformations of the roll mantle.

[0027] FIG. 5B shows a second mode of suspension of the guide 13 shown in FIG. 5A. The guide 13 is suspended on the axle 12 so that the guide 13 is connected with a spindle 21, which is guided in through openings e₁and e₂in the suspension brackets p₁and p₂. The spindle 21 is connected with a flange plate d, and the spring 22 is fitted as compressed between the bracket p₂and the flange plate d around the spindle 21. Thus, the spring 22 presses the flange d, which, being fixed to the spindle 21, further presses the spindle 21 and the connected guide 13 towards the inner mantle 11′ of the roll 11.

[0028] FIG. 5C shows a second mode of suspension of the guide 13 as shown in FIG. 4 on the piston 20. In the embodiment of FIG. 5C, the guide 13 has been suspended by means of a leaf spring 220. The leaf spring 220 is a resilient, flexible construction element, which is fixed both to the piston 20 and to the guide 13, and by its means the guide 13 is pressed against the inner face 11′ of the roll mantle. A similar mode of suspension can also be applied to the guide 13 shown in FIGS. 5A and 5B.