US3694312A

US3694312A - Disintegrating and deflocculating device in inlet boxes or papermaking machines

Info

Publication number: US3694312A
Application number: US146841A
Authority: US
Inventors: Helge Natanael Skoldkvist
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-04-25
Filing date: 1971-05-25
Publication date: 1972-09-26
Anticipated expiration: 1989-09-26
Also published as: JPS5018084B1; DE1920912A1; CS150254B2; FR2006918A1

Abstract

Apparatus for disintegrating coagulated fibrous material comprising a chamber, a stirring means therein including a first and second group of parallel spaced stirring bars, a first rotatable shaft, means for mounting the first group of stirring bars for rotation in parallel relation to each other and in parallel relation about the axis of said first shaft, means for mounting the second group of stirring bars for rotation in parallel relation to each other and in parallel relation about the axis of said second shaft, and means for rotating said shafts in opposite directions.

Description

p 5, 1972 H. N. sKbLDKws'r 3,594,312w

DISINTEGRATING AND DEFLOCCULATING DEVICE IN INLET BOXES OF PAPERMAKING MACHINES Original Filed April 1'7, 1969 4 Sheets-Sheet 1 p 26, 1972 H. N. SKGLDKVIST 4,

DISINTEGRATING AND DEFLOCCULATING DEVICE IN INLET BOXES OF PAPERMAKING MACHINES Original Filed April 17, 1969 4 ShGOtS-ShBGt 2 P 1972 H. N. SKOLDKVIST 3,594,312

DISINTEGRATING AND DEFLOCCULATING DEVICE IN INLET BOXES or PAPERMAKING MACHINES Original Filed April 17, 1969 4 Sheets-Sheet 3 P- 25, 7 H. N; SKOLDKVIST 3,594,312

DISINTEGRATING AND DEFLOCCULATING DEVICE IN INLET BOXES OF PAPERMAKING MACHINES Original Filed-April 17, 1969 4 Sheets-Sheet 4.

United States Patent ()1 3,694,312 Patented Sept. 26, 1972 Rice 3,694,312 DISINTEGRATING AND DEFLOCCULATING DE- VICE IN INLET BOXES OR PAPERMAKING MACHINES Helge Natanael Skiildkvist, deceased, late of Rundviksverken, Sweden, by Amy Maria Skiildkvist, Storgatan 28A, Umea, Sweden, Hans Marten Skiildkvist, 910 02, Rundviksverken, Sweden, and Birgitta Helena Paget, Regngation 4, Uppsala, Sweden, sole heirs Continuation of application Ser. No. 817,300, Apr. 17, 1969. This application May 25, 1971, Ser. No. 146,841 Claims priority, application Sweden, Apr. 25, 1968, 5,577/68 Int. Cl. D21f J/06 US. Cl. 162-342 7 Claims ABSTRACT OF THE DISCLOSURE Apparatus for disintegrating coagulated fibrous material comprising a chamber, a stirring means therein including a first and second group of parallel spaced stirring bars, a first rotatable shaft, means for mounting the first group of stirring bars for rotation in parallel relation to each other and in parallel relation about the axis of said first shaft, a second rotatable shaft coaxial with said first shaft, means for mounting the second group of stirring bars for rotation in parallel relation to each other and in parallel relation about the axis of said second shaft, and means for rotating said shafts in opposite directions.

This application is a continuation of U.S. patent application Ser. No. 817,300, filed Apr. 17, 1969, now abandoned.

In the making of paper, cardboard and fiberboards one of the most diflicult problems is the one of preventing flocculation While the suspension of fibers passes through the inlet box or of disintegrating, effectively, flocks already formed. Another difficulty is the one of balancing the differences in speed across the machine and of spreading the suspension of fibers on the wire into a flow of a uniform thickness.

In an inlet box of a conventional construction the tendency of the fibers to clog and flocculate is due substantially to the nature of the flow while the suspension is passing through the inlet box and to the consistency of the suspension. In order to prevent flocculation, the flow must be turbulent and the turbulence must exceed a given critical value. It is essential that the pattern of flow in the inlet box should be such that flocculation is prevented or flocks, already formed, are disintegrated. This can be done by designing the inlet box in such a manner that during the entire time of flow there is always a suflicient degree of turbulent flow. The usual way, however, is to subject the suspension to occasional strong turbulent shearing stresses, which are strong enough to cause disintegration of the flocks of fibers, and inbetween to allow the flow to proceed more quietly with less or no turbulence. -It is essential, however, that the period during which the flow proceeds more quietly should not be so long as to allow the fibers to clog to form disturbing flocks. The final formation of the Web on the wire is decisively determined by the way in which the turbulent forces are generated and by the possibility of subsequently transforming the suspension into a uniform flow moving at a constant speed of discharge across the entire width of the machine.

A common way of obtaining the aforementioned turbulence within the suspension is by using, in the inlet box, stirring members in the form of single-rotating hollow rolls, barbed rolls or rolls provided with longitudinally extending tubes. Another known method is the one of generating the turbulence by injecting a liquid at a high speed angularly to the main direction of flow. The aforementioned constructions, however, involve the disadvantage of not always making it possible to introduce shear stresses of a size sufficient to bring about an effective disintegration of the flocks formed without simultaneously disturbing the profile of speed across the Web. Moreover, the flow of the suspension of fibers through the inlet box has not been such, either, that a flow of a uniform thickness could be obtained. The present invention relates to means for improving the method of disintegrating flocks formed and for keeping the suspension of fibers under so strong hydrodynamic shearing stresses that practically no flocculation of fibers can occur during the flow of the fibers from the inlet to the outlet of the box. At the same time said disintegrating means operates in such a manner that there cannot occur any disturbing variations in speed across the direction of the machine, including resulting non-uniform distribution of the substance.

For achieving the aforesaid object, the inlet box according to the invention is characterized by at least one stirring means comprising at least two groups of axial bars located between the side walls of the box and adapted to rotate about a common shaft counter each other, each along its own path of rotation. According to the invention it is possible to determine the surfaces of the paths of the stirring means in such a manner that by choosing, in a suitable way, the number of revolutions of each group of bars the stirring work can be adjusted to a suitable level. By choosing a suitable number of bars, by choosing their speeds and the radii of their paths, the suspension of fibers flowing through the double-rotation stirrer will not leave the stirrer with any disturbing unidirectional outflow, as is the case in ordinary single-rotation stirrers. Usually, several stirring devices are applied in the inlet box. The suspension of fibers, subsequent to having passed through the last stirring device, will flow onto the wire without any flocculation taking place, forming a layer of uniform thickness, and without any disturbing variations in speed occuring. By arranging the pairs of stirrers, having opposite directions of rotation in each pair, close to each other in the inlet box, the suspension of fibers all the time will flow from one stirring device to the other, the time for flocculation between the individual stirring devices hereby becoming so short that flocculation does not occur. If, however, on some occasion a more or less unidirectional outflow from one or all of the stirring devices should be desired, this can most easily be done with or without adjusting the effect of disintegration by changing the number of revolutions of the individual stirrers of the stirring devices in question, or also by allowing rotation of only one of the stirrers, all depending on the desired degree of the unidirectional outflow.

In order to prevent re-flocculation during the formation of the wet sheet, and particularly in the case of thick fiber webs and, for example, when the forming is carried out in accordance with the disclosure of the co-pending United States patent application No. 724,665, filed Mar. 26, 1968 in the name of Helge Natanael SkiSldkvist, now deceased, it is possible to do so by connecting to and before the inlet box according to the present invention, a means for the generation of impulses, said means comprising a rotating drum having a certain number of longitudinally extending apertures, which at intervals and under pressure discharge the suspension of fibers through an adjustable opening into the inlet box proper and the stirring devices of the latter.

The frequency and the amplitude are controlled by the number of revolutions of the drum and by the pressure in the zone of the drum as well as by the adjusted opening to the stirrer zone.

The pulsations or shocks thus obtained will spread through the inlet box and to the gap between the bottom and top wires, and thereby prevent re-flocculation of the fibers prior to when the solid wet sheet begins to form.

Particularly in the making of thick fiber webs, it is advantageous, according to the invention, to subject the suspension of fibers during its passage through the inlet box to hydrodynamic forces of such a strength that existent flocks of fibers become distintegrated and remain disintegrated all the way to the outlet of the inlet box, and to impart to the suspension of fibers such vibrations or such pulsations that they spread to the forming zone.

These and other details and advantages, characterizing the invention, will be evident from an embodiment of the inlet box provided with stirring devices according to the invention shown by way of example in the accompanying drawings.

FIG. 1 is a schematic longitudinal section through a paper forming machine with an inlet box provided with means according to the invention, FIG. 2 is an enlarged partial view of the inlet box, in which are provided disintegrating and stirring devices according to the invention and impulse producing means in the form of a rotating drum having valve openings, PI-G. 3 is a sideview of the disintegrating devices according to FIG. 2, and FIG. 4 shows, diagrammatically, the driving of the disintegrating devices and of the impulse-producing drum.

The inlet box 1 merges into a tapering forming section 2, through which the upper wire 3 and the lower wire 4 extend.

The fiber suspension is pumped in at the bottom of the inlet box and passes through a number of valve openings 5 in a rotating drum 6, which is mounted in an ante-chamber 1a and which admits, intermittently, the suspension of fibers to a passage 7. At the outlet end of said passage the fiow is controlled by means of a slide valve 811 in order to provide for an adjustable opening 8. Thus, the inlet of the inlet box proper is formed by the openings 5, the passage 7 and the adjustable opening 8, the periodically occurring opening and closing of said inlet causing the suspension of fibers to flow through the inlet box in a pulsating and possibly also vibrating manner.

In the inlet box there are provided three disintegrating or stirring

devices

9, 10, 11 in accordance with the invention. For reasons of simplicity only the lowermost stirring device 9 will be described.

As will appear from FIGS. 2 and 3, the stirring device comprises two groups of axial bars. One of the groups comprises three

outer bars

12, 13, 14 which are at their ends supported by

radial spokes

15, 16 secured to two

hubs

17, 18. The hub 17 is secured to one end of a driven shaft 19, which extends through the side wall 20 of the inlet box and which is mounted in a bearing 21. The hub 18 forms a bearing around a second driven shaft 22, said shaft extending through the other side wall 23 of the box and all the way to the hub 17, in which the end of the shaft is mounted.

The other group of bars comprises four

inner bars

24, 25, 26, 27 which, in relation to the path of rotation 28 of the outer bars, are situated on an inner path of rotation 29 and supported by a number of radial spokes 30 secured to the shaft 22.

Each of said two shafts is provided with a sprocket wheel 31, 32. The driving of the sprocket wheel 31 and its associated sprocket wheels is effected by a chain 33 and a motor 34. The drum 6 is driven by a motor 35. On the other side of the inlet box there is provided corresponding means for driving the sprocket wheel 32 and the associated sprocket wheels of the other devices and 11. The sprocket wheels 31, 32 are driven in such a manner that the outer bars will rotate in a direction opposite to that of the inner bars, as indicated by arrows along the

paths

28 and 29 in FIG. 2.

Within the scope of invention the number of bars in each group may be varied according to desire. Furthermore it is possible to provide a plurality of groups of bars, having different paths of rotation but being supported by one and the same shaft, whereby a number of groups of bars is obtained, said groups rotating in a direction opposite to that of a number of groups of bars supported by the other shaft.

As shown in FIG. 2, it is suitable to have three equal- 1y spaced bars along the outer path of rotation and four equally spaced bars along the inner path of rotation.

What is claimed is:

1. Apparatus for preventing flocculation of a fibrous suspension and for disintegrating coagulated fibrous material comprising a chamber, with sidewalls, through which the suspension is passed, a stirring means therein including a first group and a second group of parallel spaced stirring bars extending substantially transversely across said chamber, a first rotatable shaft, means for rigidly mounting said first group of stirring bars for rotation in parallel relation to each other and in parallel relation about the axis of said first shaft, the bars of said first group being equally spaced from the axis of said first shaft, a second rotatable shaft coaxial with said first shaft, means for rigidly mounting said second group of stirring bars for rotation in parallel relation to each other and in parallel relation about the axis of said second shaft, the bars of said second group equally spaced from the axis of said second shaft at a greater distance from the axis of rotation than the bars of said first group, and means for rotating said shafts in opposite directions.

2. Apparatus as claimed in claim 1 wherein the number. of bars in the first group exceeds the number of bars in the second group.

3. Apparatus as claimed in claim 1 wherein the bars of each group are spaced equally from each other along their paths of rotation.

4. Apparatus as claimed in claim 1 wherein said first rotatable shaft extends substantially transversely across said chamber, wherein said means for rigidly mounting said second group of stirring bars comprises hub members disposed within said chamber and adjacent the side walls thereof and rotatably mounted on said first shaft, and wherein one of said hub members is rigidly mounted for rotation by said second shaft, means for rigidly mounting said second group of stirring bars on said hub members.

5. A device as claimed in claim 1 and further comprising means for intermittently introducing the fibrous suspension into said chamber to provide a pulsating flow of the fibrous suspension through said chamber.

6. A device as claimed in claim 5 wherein the means for intermittent introduction of fibrous suspension includes valve means for alternately opening and closing communication with said chamber.

7. A device as claimed in claim 1 wherein said chamber is provided with at least two stirring means sub-' stantially parallel to each other and spaced from each other substantially in the direction of flow of the fibrous suspension through said chamber.

References Cited UNITED STATES PATENTS 2,876,082 3/1959 Morrison 259- X 2,440,727 5/1948 Rosmait 162-342 2,764,917 10/1956 Niks 162342 X FOREIGN PATENTS 616,209 6/1935 Germany 162-342 S. LEON BASHORE, Primary *Examiner A. L. CORBIN, Assistant Examiner US. Cl. X.R.

l622l6, 261, 343; 259l05