Abstract:
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.

Description:
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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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. 
     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. 
     FIG. 3A is a side view of the construction shown in FIG.  2 . 
     FIG. 3B is an axonometric illustration in part of the construction shown in FIGS. 2 and 3A. 
     FIG. 3C is an axonometric illustration in part of an embodiment of the construction of a guide. 
     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. 
     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. 
     FIG. 5B shows a second mode of suspension of the guide shown in FIG.  5 A. 
     FIG. 5C shows the fastening of the guide shown in FIG. 4 by means of a leaf spring to the piston. 
    
    
     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  13   a , 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 1 . The sense of rotation of the roll mantle is denoted with the arrow S 1 . 
     FIG. 3B is an axonometric view of the construction shown in FIG.  3 A. 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 1 ,U 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  20   a  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  20   a  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.  5 A. 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 1  and e 2  in the suspension brackets p 1  and p 2 . The spindle  21  is connected with a flange plate d, and the spring  22  is fitted as compressed between the bracket p 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.