Arrangement in a variable-crown roll provided with loading shoes

An arrangement of equipment in connection with a variable crown roll provided with loading shoes to prevent foaming of fluid. The arrangement includes a separate guide and a face that guides the fluid in order to guide the fluid smoothly away from the inner face of the roll mantle of the roll and into a collecting trough.

FIELD OF THE INVENTION
 The invention concerns an arrangement for prevention of foaming of fluid in
 a variable-crown roll provided with loading shoes.
 BACKGROUND OF THE INVENTION
 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.
 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.
 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.
 OBJECTS AND SUMMARY OF THE INVENTION
 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.
 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.
 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.
 The invention is 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 drawings, the invention being, yet, not supposed to be
 confined to said embodiments alone.

DETAILED DESCRIPTION OF THE INVENTION
 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.
 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.
 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 L.sub.1. The sense of rotation of
 the roll mantle is denoted with the arrow S.sub.1.
 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.
 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 U.sub.1,U.sub.2 . . . 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.
 FIG. 4 shows a second embodiment of the invention, in which the guide 13 is
 connected with the displaceable shoe portion 20a of 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 20a and 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.
 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.
 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 e.sub.1 and e.sub.2
 in the suspension brackets p.sub.1 and p.sub.2. The spindle 21 is
 connected with a flange plate d, and the spring 22 is fitted as compressed
 between the bracket p.sub.2 and 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.
 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.