US2951784A - Paper making machine - Google Patents

Description

Sept. 6, 1960 T. R. MOORE PAPER MAKING MACHINE Filed June 25, 1957 Fl Ca.

IN V EN TOR.

BY THEODORE R. MOORE Q ATTORNEYS PAPER MAKING MA'CHINE Theodore R. Moore, West Monroe, La., assignorto Olin Mathieson Chemical Corporation, East Alton, 111., a corporation of Virginia Filed June 25, 1957, Ser. No. 667,793

12 flaims. (Cl. 162-212) This invention relates to a new and improved paper machine. More particularly, this invention concerns an apparatus for controlling the formation of pulp fibers on the wire of a paper machine.

It is an object of this invention to provide a means for controlling the fgrmation of the pulp fibers on the wire of a paper machine, so that the concentration of the pulp suspension is uniform across the wire. Still another object is to provide an apparatus of this type, for use in a cylinder type paper machine which includes the usual cylinder vat, wherein the cylinder vat opening may be maintained clean and unobstructed by accumulations of fibers. Still another object of this invention is to provide an apparatus of this type which assures that the suspension, when it is formed on the wire, is free of extraneous material.

Heretofore, considerable difficulty has been met in attempting to satisfy the foregoing objectives. This difficulty has been caused in part by the effects produced by stationary surfaces, particularly stationary surfaces such as the vat circle located in spaced parallelism with the cylinder mold. For example, flow of the stock suspension across the front of the inlet and on the wire of the mold, even at high rates of flow, is accompanied by the formation of a relatively stagnant film adjacent to the stationary surfaces. Accordingly, fibers accumulate ad'- jacent the stagnant surfaces and these collect until agglomerations are formed having suflicient size to break loose from the surfaces. When these agglomerations reach the sheet forming on the wire, they form dense spots, if composed of pulp, or dirt specks if composed of extraneous material, which ultimately appear as imperfections in the "sheet.

Cross flow of stock relative to the stagnant surfaces just in front of the mold surface sometimes results in the production of vortices which reduce the hydrostatic head at the surface, thereby creating disturbances because of reduced flow at localized areas. In some instances, these vortices draw air from the top of the vat pond down to the mold surface.

This invention is applicable to both the direct flow vat type of cylinder machine and the counterflow vat type of cylinder machine, both of which are well-known in the industry. Recently such machines of relatively high speed have been introduced and since the velocity of the stock entering the arcute vat passageway must approximate the peripheral speed of the molding wire, the deleterious effect of the stagnant surfaces has become more pronounced.

Thus, one of the objects of this invention is also to overcome the disadvantages created heretofore by the presence of a stagnant surface adjacent the mold cylinder. Still other objects and advantages of this invention will further become apparent hereinafter and in the drawings wherein:

Figure 1 is a semi-diagrammatic view in cross section of -a counterflow type of cylinder machine;

Figure 2 is a semi-diagrammatic cross sectional view of ice a direct flow type of cylinder machine in accordance with this invention; and

Figure 3 is a fragmentary, semi-diagrammatic view in cross section illustrating details of the valve structure forming still another feature of this invention.

The invention resides in the arrangement and specific structure of the parts especially to provide draw-ofi slots in the vat circle as set forth hereinafter. By arranging the slot size, number and spacing to suit the furnish, type of paper machine, machine speed, vat circle spacing and size and the product to be made, advantages are obtainable including some degree of recirculation desirable but not heretofore possible particularly in the counterflow circle machines without washing-01f of the. sheet as it is formed.

With reference to the specific form of the invention illustrated in Figure 1, the machine comprises a vat frame 1 within which there dips the rotating cylinder or mold 3 adapted to form a traveling web of paper 10 from the pulp stock supplied to the vat through the stock inlet pipe 2. The cylindrical mold 3 which is covered by a woven cylindrical wire screen of any desired mesh is supported on the frame so as to be immersed partially in the stock and to be rotatable therein. The stock is supplied from a source not shown by way of inlet pipe 2 to an apporach passageway 13 where the agitated stock is then led to the arcuate passageway 9 between the vat circle 6 and the forming surface of the mold 3. Arranged for coaction with the mold is an endless felt 5 which passes between the mold 3 and a couch roll 4 the pressure of which on the felt 5 causes the felt to pick up the formed sheet 10 from the wire screen. After Figure 1 the level in the vat circle is controllableby slots 7 exclusively of any overflow through weir 12 and pulp fibers are deposited without wash-off over a rather extended portion of the immersed part of the mold 3 which constitutes the forming surface. With respect to the mold the forming surface begins at 111, but with respect to the stream of stock the forming surface termin'ates at 11.

In accordance with this invention, means are provided for withdrawing a portion of the stock flowing over the forming surface. Perforations and preferably transversely extending slots 7 are provided in the vat circle 6 across the width and adjacent the cylinder mold 3. Withdrawing means, such as a pump or the like are provided in connection with the outlet pipe 8 for drawing off a portion of the stock continuously at any desired rate. The withdrawal rate may be controlled by the size and spacing of the slots 7 in the vat circle to suit the particular machine, the particular stock and the particular speed being employed. The ideal spacing would vary with the furnish, the product being made, the speed and the vat circle size. To some extent increased slot area will mean improved performance, but this eventually would be counterbalanced by the increased cost of additional stock recirculation. It is to be further understood that the rate of withdrawal may also be controlled by adjustable valves, not shown in Figure 1, relative to the various slots.

In the specific embodiment of Figure 2, rotating mold 23 is mounted on vat frame 21 so as to be immersed in the pool of stock fed from inlet pipe 22- to the vat 21 through the approach passage 33. Also mounted in the frame is the perforated vat circle 26A which with mold 23 defines an arcuate vat passage 29 through which the stock flows in the same direction in which the perforated forming surface of cylinder mould 23 turns. An adjustable overflow darn 32 is provided to control the level at which the spent stock is discharged from passage 29 to the main outlet pipe 28B.

Stationary circle 26A is provided with slots 27 which preferably extend uninterruptedly across the width of the web forming surface and through which part of the stream of pulp is withdrawn from the arcuate passage 29 through the draw-off chest 34 by'way of the auxiliary outlet or pulp draw-off pipe 28A. Control valves 2613, which are slide valves (Figure 2) acting like curtain shutters, preferably formed of thin sheet metal having sharp lower edges, extend over the inner surface of circle 26A for the purpose of controlling the circumferential opening of the slots 27 and, therefore, the rate of pulp withdrawal. These valves may be controllable in unison particularly when they take the form of a single curved shutter with circumferentially spaced transversely extending slots corresponding to slots 27, but preferably are controlled individually to take-care of any local condition particularly for this embodiment. For individual control, the shutters are a plurality of spaced metal straps 2613, each curved to fit the vat circle 26A, and extending :ubstantially parallel with its corresponding slot 27. Being of the slide type, the semi-diagrammatically shown valves or shutters 26B, whether they be formed in a single sheet or between a plurality of straps, may be rocked circumferentially by any suitable mechanism to draw them as a curtain to increase or reduce the size of the opening at the slots 27. It will be appreciated that part of the control may be obtained by varying the suction at pipe 28A by means of the recirculation pump or valves, for example, or hydrostatic head.

In the direct flow cylinder machine of Figure 2, drawoff slots 27 are shown to vary in spacing so as to compensate for the concentrated web formation in region 31 of the vat passage 29; and in the machine of Figure 1 the spacing and valving of the slots may also be varied. In either type of machine the valve means, particularly if of appreciable thickness may be located 'in the draw- E chambers 14 or 34 rather than in the vat passageways 9 or 29, respectively.

This advantageous arrangement (Figure 3) involves a vat circle 46A provided with slots 47 and also a slide or shutter valve structure 468 in draw-off chamber 54 instead of stock channel 49 adjacent cylinder mold 43. Slots 47 may extending across the width or" the machine uninterruptedly or as a transversely extending series of perforations. As before, slots 47 are circumferentially spaced along the vat circle 46A with either the uniform spacing shown in Figure 1 or any suitable non-uniform spacing with variation such as that shown in Figure 2. Valve structure 46B, as in the other embodiments, may be supported by any suitable conventional means such as arcuate guide grooves at the lateral edges, side supporting rolls in an arcuate array or by trunion bearings connected to the valve structure by a suitable linking arm or circular sector, none of which are shown. The valve structure may be moved by any suitable mechanism such as by the curved rack 60 on the valve structure and by the driving pinion 61.

As in the previous embodiment, the web 30 deposited on cylinder mould 23 is picked off by the wet wool felt 25 coacting with the couch roll 24.

It will be understood that the slots preferably run the full width of the vat. The number of slots, their circumferential width, and their spacing around the arc of the vet is adjusted for the particular machine and operation. As to the spacing of the vat circle from the cylinder mould, spacing somewhat larger than that now conventional may advantageously be employed.

With this invention, rapid stock circulation is obtained without undesired eddying and dead spots in the stream of stock. These are manifested as localized settling and stratification in the annular channels 9 and 29 and as uneven spots in the sheet or web 10 and 30 caused by clumps of pulp and/or impurities which build up and eventually break away to be deposited intermittently upon the forming web. In the specific embodiments described, the unformed pulp is maintained in uniformly dispersed condition across the arcuate forming channels, or at least there is no more variation in the dispersion than that which occurs gradually along the pulp stream as a result of web formation. It will also be appreciated that in the apparatus described herein accumulation of impurities such as pitch, iron, pipe-scale and the like in pockets is avoided because of the elimination of stagnant areas next to the stationary vat circle. Centrifugal sedimentation at higher mold speeds is minimized by draw-off through the slots, as is the effect of any settling out of heavy particles.

By this invention a cleaner and more uniform fibrous web may be formed at a given speed, or a web comparable to a web heretofore available may be formed at a much higher speed and better economy than heretofore possible. In any event, the resulting sheet is of good quality.

It will also be understood that this may be accon1- plished not only by the specific embodiments: now believed preferred and described hereinbelow for the purpose of illustrating rather than restricting this invention except as set forth in the appended claims, but also by various modifications and variations thereof which may occur to those skilled in the art without departing from the spirit and scope of the invention as set forth in the appended claims. a

In view of the foregoing description, what is claimed is:

1. Apparatus for web forming of pulp fibers on the moving cylindrical foraminous mold of a cylinder paper machine comprising means extending across the width and adjacent the forming surface of the mold and having a stationary surface spaced from said forming surface to provide a channel for flow of the pulp alongside said forming surface, means for supplying a stream of suspended pulp to one end of said channel, means for withdrawing the residual part of said stream at the opposite end from between said surfaces, and bypass means disposed at intervals along said channel intermediate said ends, and means for drawing off a part of the pulp supply adjacent substantially all of said stationary surface through said bypass means thereby maintaining substantially all of the unformed pulp between said surfaces in uniformly dispersed condition across said width.

2. The apparatus of claim 1 including means for regulating the rate at which said pulp is drawn off through said bypass means.

3. In a cylindrical mold paper making machine in cluding means for supplying pulp to said mold wherein a vat circle is provided to maintain said pulp supply in a channel along at least a part of the rotary mold the improvement comprising a plurality of discharge openings in the vat circle distributed at least in circumferentially spaced relationship along said channel adjacent the web forming surface of the rotating mold and means for withdrawing a part of the pulp supply adjacent the vat circle through said openings thereby maintaining substantially all of the unformed pulp free from transient clumps of pulp.

4. The apparatus of claim 3 wherein the openings are a series of draw-off perforations arrayed along the length and width of the channel adjacent substantially all of the web forming surface of the mold, said perforations being maintained at a size reiative to each other and a spacing from each other in a manner adapted to efiect substantially all of said web forming surface to form a web of substantially uniform quality.

5. The apparatus of claim 3 wherein the openings take the form of transversely extending slots and including valve means adjacent the vat circle for each slot on the side of the circle opposite the pulp supply for regulating the rate at which said pulp is drawn oif through said slots.

6. The apparatus of claim 3 wherein the openings take the form of transversely extending slots and including a thin slide valve adjacent the vat circle on the same side of the circle as the pulp supply for each slot for regulating the rate at which said pulp is drawn off through said slots.

7. Apparatus for web forming of pulp fibers on the cylindrical foraminous mold of a cylinder paper machine comprising a vat pool adjacent the forming surface of said mold and having a stationary arcuate surface spaced from said forming surface for supplying a slurry of pulp to said mold between said surfaces, a series of outlet slots in said stationary surfaces extending uninterruptedly across the width of said pool, and means for drawing 0135 a part of the pulp supply adjacent said stationary surface through said slots thereby maintaining substantially all of the unformed pulp between said surfaces in uniformly dispersed condition across said width.

8. Apparatus for web forming of pulp fibers on the rotating cylindrical foraminous mould of a cylinder paper machine comprising a vat pool adjacent the forming surface of said mould and having a stationary arcuate surface spaced from said forming surface for flowing a slurry of pulp to said mould between said surfaces in a direction opposite to the peripheral direction of rotation of said mould, a series of circumferentially spaced outlet slots in said stationary surface each extending uninterruptedly across the width of said pool, and means for drawing off a part of the pulp supply adjacent said stationary surface through said slots thereby maintaining substantially all of the unformed pulp between said surfaces in uniformly dispersed condition across said width.

9. The apparatus of claim 8 including valve means for individually regulating the rate at which said pulp is drawn through saidslots.

10. Apparatus for web forming of pulp fibers on the rotating cylindrical forminous mould of a cylinder paper machine comprising a vat pool adjacent the forming surface of said mould and having a stationary arcuate surface spaced from said forming surface for flowing a slurry of pulp to said mould between said surfaces in the same direction as the direction of rotation of said mould, a series of outlet slots in said stationary surface each extending uninterruptedly across the width of said pool, and means for drawing off through said slots a part of the pulp supply adjacent said stationary surface, said slots being more densely spaced circumferentially at the inlet portion of said pool and less densely spaced at the outlet portion of said pool, thereby maintaining substantially all of the unformed pulp between said surfaces in uniformly dispersed condition across said width.

11. The apparatus of claim 10 including valve means for each of said slots for individually regulating the rate at which said pulp is drawn off through said slots.

12. In the process of forming a web of paper on a moving foraminous mold from a pool of paper stock flowing between the moving web forming surface of said mold and a statinary pool forming surface spaced from said mold surface, the improvement comprising withdrawing a portion of said stock from said pool through outlet openings in said stationary surface at spaced intervals distributing said openings adjacent substantially all of said web forming mold surface, whereby substantially all of the pulp across said surfaces is maintained in substantially uniformly dispersed condition for rapidly forming a web of improved uniformity.

References Cited in the file of this patent UNITED STATES PATENT-S 2,001,208 Minskey et al May 14, 1935 2,402,063 Malkin June 11, 1946 2,473,270 Adams June 14, 1949 2,528,189 Temperley Oct. 31, 1950 2,609,732 Breyfogle Sept. 9, 1952 2,701,988 Mollis Feb. 15, 1955 FOREIGN PATENTS 50,877 Norway .May 18, 1932

Claims (1)

1. APPARATUS FOR WEB FORMING OF PULP FIBERS ON THE MOVING CYLINDRICAL FORAMINOUS MOLD OF A CYLINDER PAPER MACHINE COMPRISING MEANS EXTENDING ACROSS THE WIDTH AND ADJACENT THE FORMING SURFACE OF THE MOLD AND HAVING A STATIONARY SURFACE SPACED FROM SAID FORMING SURFACE TO PROVIDE A CHANNEL FOR FLOW OF THE PULP ALONGSIDE SAID FORMING SURFACE, MEANS FOR SUPPLYING A STREAM OF SUSPENDED PULP TO ONE END OF SAID CHANNEL, MEANS FOR WITHDRAWING THE RESIDUAL PART OF SAID STREAM AT THE OPPOSITE END FROM BETWEEN SAID SURFACES, AND BYPASS MEANS DISPOSED AT INTERVALS ALONG SAID CHANNEL INTERMEDIATE SAID ENDS, AND MEANS FOR DRAWING OFF A PART OF THE PULP SUPPLY ADJACENT SUBSTANTIALLY ALL OF SAID STATIONARY SURFACE THROUGH SAID BYPASS MEANS THEREBY MAINTAINING SUBSTANTIALLY ALL OF THE UNFORMED PULP BETWEEN SAID SURFACES IN UNIFORMLY DISPERSED CONDITION ACROSS SAID WIDTH.

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