US2418547A

US2418547A - Method and apparatus for defibering paper stock

Info

Publication number: US2418547A
Application number: US479450A
Authority: US
Inventors: Cowles Edwin
Original assignee: COWLES CO
Current assignee: COWLES CO
Priority date: 1943-03-17
Filing date: 1943-03-17
Publication date: 1947-04-08
Anticipated expiration: 1964-04-08

Description

April 8, 1947. 5 COWLES' 7 2,418,547

IEIHOD AND APPARATUS FOR DEFIBERING PAPER STOCK Filed larch 17, 1943 2 Sheets-Sheet 1 INVENTOR T 7 4 x ii/$.54

ATTORNEYS.

April 8, 1947. CQWLES 2,418,547

- METHOD AND APPARATUS FOR DEFIBERING PAPER STOCK Filed lax-ch17, 1943 2 Sheets-Sheet 2 50 sw/nw Z7 Z4 25 40 405 MOTO/P c'o/vr4cr/A/6 26 EL 1 E WATT ME TL")? I MAI/v M0 702 ATTORNEYS Patented Apr. 8 1947 METHOD AND APPARATUS FOR DEFIBERING' PAPER STOCK Edwin Cowles, Cayuga, N. Y., assignor to The Cowles Company, Princeton, N. J., a corporation of New Jersey Application March 17, 1943, Serial No. 479,450

8 Claims. 1

This invention relates to methods and apparatus for treating paper stock, and pertains more particularly to defibering and otherwise preparing paper stock for use on paper making machines.

The apparatus is intended for continuous operation, that is, an operation in which dry fibrous material and water are added continuously to the apparatus and in which treated material suspended in water is continuously removed from the apparatus. It is an object of the invention to provide modifications of or improvements on the apparatus disclosed in my prior Patent No. 2,265,936 dated December 9, 1941.

It is a further object of the invention to provide an apparatus adapted to handle waste paper stock which usually contains considerable quantities of trash of various kinds, and to provide for at least a preliminary or partial separation of such trash from the useful material.

Other objects and advantages of .the invention will appear hereinafter.

A preferred embodiment of the invention selected for purposes of illustration is shown in the accompanying drawings, in which Figure 1 is a top plan view of the apparatus.

Figure 2 is an enlarged top plan view of the impeller.

Figure 3 is a section on the line 33 of Figure 2 showing one of the vanes in elevation.

Figure 4 is an elevation showing the screen for withdrawal of defibered material.

Figure 5 is a vertical section through the apparatus, and

Figure 6 is a circuit diagram.

Referring to the drawings, the apparatus comprises a tank I, preferably cylindrical in shape, the said tank having a bottom surface 2 which slopes toward a centrally located outlet opening 3, the slope being sufficient to cause heavy trash, such as pieces of metal, glass, stone, sand and the like to tend to roll or slide downward toward the opening 3, preferably centrally located. Such movement of heavy objects, and particularly smaller pieces thereof such as sand, paper clips, etc., i's-assisted b the circulation of the stock in the tank under the influence of the impeller 4 as hereinafter described. The circulation beneath the impeller is, generally speaking. a rotary circulation around the axis of the impeller, together with a circulation in the vertical plane as indicated by the arrows, Figure 5, such circulation being induced by skin friction of the bottom surfaces of the impeller, or if desired by small vanes on the under side of the impeller, and a mild circulating effect is exerted tending to move heavy objects toward the center where they may drop into the opening 3. Such opening is connected by a passage 5 to the bottom of a trash ,well 6. from which such heavy objects may be removed in any suitable manner. For example, the trash well may be inclined, as shown, and accumulations of trash may be removed therefrom by apparatus such as disclosed in my prior Patent No. 2,317,978 dated May 4, 1943.

The impeller 4 is overdriven, i. e. suspended and driven from above, being mounted on a shaft '1, extending through a bearing box 8, and having a pulley 9 mounted on its upper end adapted to be driven b V-belt connection to an electric motor. A non-rigid suspension for the impeller is preferred, in order to permit slight displacement of the impeller on impact with large pieces of material, and to allow the impeller to find its natural center of rotation. This may be accomplished by the provision of rubber rings l l, H surrounding the bearing box and engaging the plate [2 which may be supported on a floor 13, as shown, or in any other suitable manner. The rubber rings are held between upper and lower plates I4, l4 secured to the bearing box 8.

As protection to the shaft 1, and to prevent elongated pieces of trash such as rope, cloth, wire and the like from winding around the shaft, a cylindrical shield I5 is employed. Such shield may be suspended from the floor l3. coaxially with the shaft 1, as shown, and extends downwardly into close proximity with the impeller. As

' said shield is stationary and of a diameter substantially larger than that of the shaft, there is little or no tendency for such trash to wind around the shield.

The impeller 4, which, as shown, is in the form of, a solid circular disk, is provided with a multiplicity of vanes I! located adjacent the periphery of the disk and adapted to impel stock outwardly in the form of an annular disk extending substantially at right angles to the axis of rotation of the impeller. The said vanes may, if desired, be constructed and arranged in accordance with the disclosure of my prior Patent No. 2,351,492, dated June 13, 1944, but for purposes of the present invention need not necessarily be limited in height to the 1 to 30 ratio of height to impeller diameter as therein set forth. In certain stock preparation systems to which the present apparatus is adapted for use as a primary defiberingunit adapted to replace the usual breaker beater, it is not always required that complete defiberization take place in the primary defibering unit. In such systems a partial alias" defiberization, sometimes known in the industry as slushing down," is all that is required, and in such cases the l to 30 ratio of vane height to impeller diameter need not be resorted to. The nature of the disintegrating and deflberins action remains the same, however, being due to the differential of velocity between the disk of stock discharged at relatively high velocity by the impeller and the surrounding body of stock moving at low velocity. Furthermore, in cases where complete deilberization is not required, it is possible to reduce the velocity of rotation of the impeller, and thereby affect savings in consumption of power, so long as the velocity is sumcient to produce circulation in the tank adequate to produce a hollow core vortex as hereinafter described.

The maintenance at all times during the operation of the apparatus of a vortex having a hollow core extending downward from thesurface of the stock to the impeller as shown in the drawings is of the highest importance to the satisfactory and eiilcient operation of the apparatus. Suzh a vortex is maintained by establishing a proper balance between the velocity of rotation of the impeller and the number and height of the vanes. For efilcient operation, the vanes should be relatively closely spaced, as shown, and for any given number of vanes, the higher the vanes, the less the velocity required to produce a hollow core vortex. Once the vane height is established, therefore, taking into consideration the type of deilbering required, the velocity required to produce a hollow core vortex may be easily determined.

When such a vortex is maintained above the impeller, the circulation of the stock in a vertical plane through the axis of rotation is, as indicated by arrows, Figure 5, outward from the vanes, then upward, then inward and then downward toward the surface of the impeller. At the same time, of course, there is circulation in the horizontal plane around the axis of the impeller. As a result, any piece of undefibered material floating on the surface of the stock in the tank moves in a generally spiral path toward the hollow core of the vortex where it is drawn downward toward the impeller and quickly subjected to disintegrating action. In continuous operations where relatively large pieces of dry fibrous material are being added continuously, the normal tendency of such material is to float on the surface. The maintenance of a hollow core vortex not only quickly submerges such material, but brings it quickly into the zone of effective disintegrating action.

Furthermore, when such a vortex is maintained, all of the material in the tank above the plane of the impeller is maintained in constant circulation and is repeatedly subjected to disintegrating action. There are no dead spots" where circulation is sluggish or inactive, and disintegration and defibering take place rapidly and uniformly.

Finally, when such vortex is maintained, it is possible to continuously extract trash such as rope, cloth, wire and the like by the method described in my prior Patent No. 2,340,511, filed February 1, 1944. The self-forming rope l8 of such trash is shown in Figures 1 and 5, together with a reel I9 for withdrawing the same.

The maintenance of a proper vortex during the operation of the apparatus is closely connected with the maintenance of uniform consistency of the stock being treated. That is, if a certain impeller is rotated at a certain predetermined velocity to maintain a hollow core vortex having substantially the conformation shown in the drawings when working with stock of a given consistency, say 2%, for example, a change in consistency will result in changing the conformation of the hollow core. It the consistency decreases the hollow core will open up, i. e. increase in diameter. while if the mnsistency increases, the hollow core will close in, i. e. decrease in diameter. 11' the increase in consistency is sufficient, the hollow core may even disappear entirely.

I have discovered that the conformation of the hollow core responds quite sensitively to even small variations in consistency of the stock in the tank, and I have devised means for utilizing this phenomenon to maintain a substantially uniform consistency of the stock in the tank.

As previously explained, the apparatus is intended for continuous operation, water and dry fibrous material being added continuously, and treated material suspended in water being continuously removed. Water may be added continuously in any suitable manner, as through the pipe 20. or through the trash well 6 and passage 5, or both. it having been found advantageous to introduce some water through the trash well to induce an upward current in the passage 5 to prevent loss of useful fibrous material The dry fibrous material may be added by any suitable motor driven conveying apparatus such as the ordinary belt conveyor 2| mounted above the tank in such manner as to discharge material into the tank.

Treated material suspended in water may be removed from the tank through any suitable screening device, but I prefer to use a rotary or spinning screen 23 such as disclosed in my prior Patent No. 2,057,478, but eliminating the discharge nozzle as shown in said patent. as such nozzle is unnecessary when the screen is used only for withdrawal purposes. Preferably such screen is located in the side wall of the tank, as shown, being located at a height such as to maintain the stock in the tank at the desired level. In this connection, it may be noted that the said screen should be so located as to maintain the operating or overflow level of the stock at a distance above the upper surface of the impeller not exceeding the diameter of the impeller and not less than half the radius of the impeller.

In the operation of the apparatus, if the consistency tends to decrease, the vortex tends to open up, and the power required to rotate the impeller at a constant speed tends to decrease, due both to the decrease in consistency and to the decrease in skin friction caused by the opening up of the vortex. This effect is greatly increased if and when the vortex opens up sufliciently to uncover the inner ends of the vanes. for in this event, there is a great change in the power required to rotate the impeller at a constant speed. Conversely, and for similar reasons, if the consistency tends to increase, the vortex tends to close in, and the power required to rotate the impeller at a constant speed tends to increase. Such changes in the power required may be indicated by a variety of instruments. For example, if an electric motor is used to drive the impeller, a watt meter inserted in the power line will indicate such fluctuations in the power required to rotate the impeller, and if said watt meter be a contacting watt meter, it may be used directly to control the factors which atveyor 2 I.

fect consistency, i. e. rate of feeding of dry fibrous material to the tank or the rate of feeding water to the tank. However, since the rate of feeding water to the tank controls the rate of overflow through the screen 23, and hence controls the rate of production of the apparatus. I prefer to control consistency by varying the rate of feeding dry fibrous material, for it is usually desirable to maintain a substantially uniform rate of production, and variations in the rate of feeding dry material have little or no effect thereon.

Referring to Figure 5, I have shown a circuit diagram showing one manner'in which such control may be effected. In said diagram, three phase power circuits are shown, as such circuits are best adapted to this use. As shown, a contacting watt meter 24, is inserted in the power lines 25 leading to the motor 26 which drives the impeller 4. The said contacting watt meter is connected by lines 21 to an electrically operated switch 28 inserted in the power lines 29 leading to the motor 30 which drives the con- The feeding capacity of the conveyor 2| when the motor 30 is operated at full speed should be in excess of that required to maintain the desired consistency of stock in the tank. In the operation of the apparatus, therefore, the contacting watt meter 24 is adjusted to open the switch 28 whenever the consistency of the stock, and hencethe load on the motor 26, reaches a predetermined maximum. This stops the. motor 30 and the conveyor 2|, with the result that the continued inflow of water and the continued withdrawal of treated material begins to reduce the consistency of the stock. When the consistency, and hence the load on the motor 26, reaches a predetermined minimum, the switch 28 is again closed to start th motor 30 to resume feeding by the conveyor.

One of the advantages of this method of control is that the utilization of the conformation of the vortex to effect control of consistency automatically results in the maintenance of a full vortex at all times, thus maintaining conditions most favorable to the eflicient operation of the apparatus.

It will be understood that the invention may be variously modified and embodied within the scope of the subioined claims.

I claim as my invention:

1. In an apparatus for defibering paper stock, in combination, a tank, an impeller mounted for rotation in said tank, said impeller comprising a disk having a multiplicity of vanes thereon adapted to discharge stock outwardly therefrom, said impeller being carried on a shaft suspended from above and rotating in a plane spaced from the bottom of the tank, the bottom surface of the impeller also being adapted to discharge stock outwardly therefrom, said tank having a discharge opening below said impeller but within the contour thereof, and said tank having a sloping bottom converging toward said opening, said impeller being spaced above said sloping bottom at a distance such that the stock discharged from the bottom of the impeller impinges against the side of the tank above said sloping bottom and returns along said sloping bottom thereby assisting heavy trash toward said discharge opening.

2. In an apparatus for deflbering paper stock, in combination, a tank, an impeller mounted for rotation in said tank, said impeller comprising a disk having a multiplicity of vanes thereon adapted to discharge stock outwardly therefrom, said impeller being carried on a shaft suspended from above and rotating in a plane spaced from the bottom of the tank, the bottom surface of the impeller also being adapted to discharge stock outwardly therefrom, said tank having a discharge opening below said impeller but within the contour thereof, said tank having a sloping bottom converging toward said openin said impeller being spaced above said sloping bottom at a distance such that the stock discharged from the bottom of the impeller impinges against the side of the tank above said sloping bottom and returns along said sloping bottom thereby assisting heavy trash toward said discharge opening and said tank having a screened opening in its side wall through which defibered material is removed, said screened opening being arranged above the impeller to maintain the overflow level of the stock at a distance above the upper surface of the impeller not less than one-half the radius of the impeller.

3. In an apparatus for deflbering paper stock, in combination, a tank, an impeller mounted for rotation in said tank. said impeller comprising a disk having a multiplicity of vanes thereon adapted to discharge stock outwardly therefrom, said impeller bein carried on a shaft suspended from above and rotating in a-plane spaced from the bottom of the tank, and a cylindrical shield surrounding said shaft and extending from a point above thelevel of the contents of the tank to a point close to the upper surface of said impeller. a

4. In an apparatus for deflbering paper stock, in combination, a tank, an impeller mounted for rotation in said tank, said impeller comprising a disk having a multiplicity of vanes thereon p d to discharge stock outwardly therefrom, said impeller being carried on a shaft suspended from above and rotating in a plane spaced from the bottom of the tank, and said tank having a screened opening in its side wall through which defibered material is removed, said screened opening being arranged above the impeller to maintain the overflow level of the stock at a distance above the uppersurface of the impeller not less than one-half the radius of the impeller.

5. In an apparatus for the continuous defibering of paper stock. in combination, a tank, an impeller mounted for rotation in said tank, said impeller carrying vanes discharging stock outwardly and maintaining a hollow core vortex in said tank, means for feeding water to said tank, a conveyor for feeding dry fibrous material to said tank, means for withdrawing defibered material from said tank, an electric motor for driving said impeller at a constant speed, a contacting watt meter connected to said motor, and means controlled by the variations in power required to rotate said impeller as indicated by said watt meter as said vortex tends to alter its predetermined contour by receding from or approaching toward said vanes to stop said conveyor when the power load on said impeller motor reaches a predetermined maximum and to start said conveyor when the power load on said impeller m'otor reaches a predetermined minimum.

6.-In a process for the continuous defibering of paper stock in which dry fibrous material and water are added continuously to a treating tank and defibered material suspended in water is continuously'removed from said tank while maintaining a constant level or stock in said tank. and in which the contents or the tank are continuousLv circulated to maintain a hollow core vortex therein, the method of controlling the consistency of the contents of the tank which consists in varying the rate at which the materials which affect the consistency of the stock in said tank are added to said tank in accordance with the increase or decrease in power required to maintain a predetermined contour of said vortex at the maintained stock level.

'7. In a process for the continuous deflbering of paper stock in which dry fibrous material and water are added continuously to a treating tank and defibered material suspended in water is continuously removed from said tank while maintaining a constant level 01' stock in said tank, and in which the contents of the tank are continuously circulated to maintain a hollow core vortex therein, the method of controlling the consistency of the contents of the tank which consists in interrupting the feeding or dry fibrous material when the power required to circulate the contents ofthe tank to maintain a predetermined contour of said vortex at the maintained stock level reaches a predetermined maximum and resuming the feeding of dry fibrous material when the power required to circulate the contents of the tank to maintain a, predetermined contour of said vortex at the maintained stock level reaches a predetermined minimum.

8. In an apparatus for the continuous delibering of paper stock, in combination, a tank. an impeller mounted for rotation in said tank, said impeller carrying vanes discharging stock out- 8 wardly and maintaining a hollow core vortex in said tank, means for feeding water to said tank, a conveyor for feeding dry fibrous material to said tank, means for withdrawing deflbered material from said tank, means to rotate said impeller at a constant speed, and means controlled by the variations in power required to rotate said impeller as said vortex tends to alter its predetermined contour by receding from or approaching toward said vanes to control the rate at which the materials which aflect the consistency oi the stock in said tank are added to said tank to maintain u'nii'orm consistency of the stock in said tank.

EDWIN cowLns.

REFERENCES CITED flhe following reierences are 01' record in the file of this patent:

UNITED STATES PATENTS