US2016647A - Device for treating paper stock - Google Patents

Description

oct. s, 1935A. WIB MCMARTIN l 2,016,647

DEVICE FOR TREATING PAPER STOCK Filed ,Oct 14, 1955 Patented Oct. 8, 1935 PATENT OFFICE DEVICE FOR TREATING PAPER STOCK william B. MoMmin, Hoosiok Fans, N. Y., ossignor to The Noble & Wood Machine Company, Eo'osick Falls, N. Y., a corporation of New York l Application October 14, 1933, Serial No. 693,583

claims. (ci. 259-97) l My invention relates to paper making and more particularly to a'device for treating paper stockl by agitation, and this application is a continuation m part of my application Serial No. 567,901 5 liled October 9, 1931.

It is quite usual to provide stock chests with paddle-like agitators which rotate at very low speed and serve merely to eiect a slow stirring of the stock. Where only a single paddle is employed, the stirring or stock movement is conned more or less to a rather limited zone about the paddle, and where several paddles are distributed throughout the stock the power' oozisumed in operating them is very great. It is desirable in all cases to keep the stock moving. Moreover, where the chest is used as a drop chest, it is quite essential that the beater loads be thoroughly and quickly, blended otherwise stock`of variable character finds its way to 2 the machine with resulting variations in the finished sheet. With the present available equipment it is very dimcult to mix and thoroughly blend colored stocks so that mottled and olfshade papers are avoided.

It has been proposed to use rotating worms or screws for agitating and blending the stock, but these merely advance or propel the material forward with little or no intermixing,` and prolonged circulation is required to attain even'a fair degree of blending. With a worm or screw there is no lateral outthrow of stock, even at substantial speed, and the action is simply a pushing or conveying movement whi produces circulation with substantially no 1 termixing. This is apparentto anyone familiar with the operation of screw conveyors many of which opcrate in open troughs. V

Screw propellers having separate blades, on the o other hand, il rotated at substantial speed, not only push the stock forward but throw' it out laterally or radially to such an extent that unless the radial stock movement is limited or restrained by some surrounding means the propeller, particularly with concentrated stocks, may merely tend to cut an opening for itself and produce very little if any forward pushing or circulating stock movement. On the other hand, this lateral outthrow produces the violent agitation and in- 5o termixing of the material which is so essential in attaining a rapid, eiiicient and positive blending. A screw propeller of relatively large diama y eter as compared with the diameter of the chest vis not necessary, in fact it is not desirable be- 65 cause of the power required to operate it and because a comparatively large propeller interferes with the rapid circulation of the stock.. l The principal object of my invention, therefore, is to provide a stock agitator which will quickly and positively produce a complete blend- 5 ing and intermixing of the stock in the chest with a minimum power expenditure. Another object is to provide a device of the character described which will operate eciently with stock of much higher consistency than is possible with 10 present agitators, I accomplish this object by so combining a screw or worm with a screw propeller having separate blades that the worm, which requires a relatively small amount of power to operate it and may extend through a major 15 portion of the chest, maintains a constant and lpositive ow of stock 'towards a screw propeller of moderate size which, in turn, produces not only a violent agitation and intermixing of the `material, but in which the tendency to radial outthrow of stock is so restrained and directed that the propeller itself impels the stock forwardly and assists in maintaining a rapid eirculation in the chest, all with a. minimum power expenditure.

' My invention, therefore, includes the novel elements and the combinations and arrangements thereof described below and illustrated in the accompanying drawing in which- Fig. 1 is a vertical section of my invention in 30 its preferred forni in which the propeller is surrounded -by a frusto-conical ring flared downwardly and outwardly;

Fig. 2 is a fragmentary sectional view similar to Fig. 1. illustrating a modified form of ring surrounding the propeller;

Fig. 3 is a fragmentary sectional view illustrating a further modied form of ring surrounding the propeller; and

Fig. 4 is a vertical, fragmentary section illus- 40 'trating my invention applied to a horizontal type il is secured a screw propeller I4 comprising a plurality of blades surrounded by a tubular member or ring i5 which, in the embodiment of my invention illustrated in Fig. 1, is frusto-conical and iiared downwardly and outwardly throughout its major portion, the upper edge I5I of the ring being turned downwardly and inwardly; the better to direct the stock from the region ofy the chest above the ring into the propeller. The;` ring I5 is mounted on brackets I6 suitably se' cured to the bottom of the tank, the lower portion of the tubular member thus being spaced from the tank bottom to permit the material, which is forced downwardly and outwardlyvby the propeller, to flow underneath the lower edge of the ring from which the material is directed' upwardly by the curved bottom IUI of the tank;

Secured to the shaft II above the propeller is a screw or worm I8 the pitch of which is in the same direction as that of the -propeller and which is thus rotated at the same speed as the propeller and which serves primarily to push the stock downwardly toward the propeller. The diameter of the worm preferably gradually decreases from the upper end thereof to the lower end as indicated in the drawing. In the embodiment illustrated, the shaft is driven by an electric motor I9 through a gear reducing device 20 which may be of any approved construction,

` the reduction being such that the shaft will preferably be driven at a speed from 100 to 250 R. P. M. The indvidual blades of the propeller extend through a comparatively small arc only circumferentially of the shaft whereas the screw conveyor having a continuous helical surface extends through a comparatively large arc and, in the embodiment illustrated, extends approximately twice around the shaft.

'The operation of the device illustrated in Fig. 1, is as follows:

The screw propeller I4 subjects the u'ent paper stock or stuff to a violent agitation, and tends to throw the material outwardly. The material ows through the space between the ring I5 and the bottom of the chest, the .outward flaring of the ring deecting the material outthrown from the propeller towards the outer wall of the chest, and the circulating movement of the material being further facilitated by curving the bottom of the chest outwardly and upwardly from beneath the propeller. The zone of violent agitation is thus more or less limited to the immediate vicinity of the propeller. At the same time the screwor worm I8 feeds the material from the upper and intermediate portions of the tank to the propeller.

In Fig. 2 I have illustrated a slightly modified form of my invention in which the tubular member I5a is cylindrical throughout its upper portion, the outwardly fiared portion b thereof which permits outthrow of the material being confined to the lower portion of the ring.

In Fig. 3, I have illustrated the tubular member I5c as cylindrical throughout.

It will be understood that the size of the propeller will be designed in accordance with the shape and size of the chest. For example, a larger propeller will be used with a comparatively shallow chest of large diameter than with a deep chest of comparatively small diameter. I find that the average diameter of the screw conveyor may be somewhat less than one-half that of the propeller, although it will, of course, be understood that my invention is not limited to the foregoing proportion.

In the embodiment of my invention illustrated in Fig. 4 the chest Illa is horizontal and the propeller Illa is secured to a shaft IIa horizontally mounted in the bottom of the tank Ia, the bottom of which slopes as at |03 and the screw 01' worm I8a tapers towards the propeller. 'Ihe propeller and the adjacent portion of the worm are located above the higher portion of the bottom of the chest while the portion of the worm of larger diameter is located above the lower por- 5 tion of the tank, so that the lowermost points of the successive turns of the screw are located vin a line substantially parallel to the bottom of the tank. While I have chosen a stock chest for the purpose of illustrating a receptacle suitable for my,- agitator, it will be understood that it may be used with any tank or other receptacle in which it is desirable to agitate, mix or circulate fluent material.

The maximum tank consistency now found practicable in devices of this character is about 31/2%. When the consistency exceeds this percentage substantially, the propeller, which is rotated at a relatively low speed, simply cuts through the material in the zones and produces very little if any circulation. I have found, in practice, that the device embodying my invention is capable of satisfactorily handling paper stock having a consistency as high as 6%, and hence a tank equipped with my invention is ca- 2 pable of treating the same amount of stock as a tank of twice the size and equipped with agitating devices heretofore used.

It will, of course, be understood that the speed of rotation of the shaft on which the propeller and worm are mounted will be varied to t the size of the tank, the shape thereof, and other factors. 0n small tanks, the shaft may adl vantageously be operated at a speed of 250 revolutions per minute, while on larger tanks, a speed of only 100 revolutions per minute may be required. Again, with a comparatively shallow tank' of large diameter, a larger propeller may be used than in a .deep tank of comparatively small diameter. A ratio of propeller diameter to tank 40 diameter, when the tank is vertical, of 1 to 3 will usually be found satisfactory. I have built a device in which the diameter of the screw or worm is less than one-half of that of the propeller, al though, of course, it will be understood that I am not limited to these proportions. The diameter of the screw or worm, however, is, in any event, preferably less than that of the propeller.

In the operation of the device, large chunks of material may be thrown into the receptacle and will be sucked down by the worm to a position within the inuence of the propeller. In the absence of the worm, the large chunks of material float on the top of the stock and cannot be broken u I have found in practice that a screw propeller provided with a plurality of blades in combination with a screw or worm which feeds the material to thepropeller, causes the material to be subjected at one point to a violent intermixing agitation. At the same time the propeller forces the material downwardly and outwardly towards the outer walls of the chest thereby assisting in creating a rapid circulation of the material which is promoted by the provision of a tubular member surrounding the agitator.

In my application Serial No. 567,901 the type of ring about the propeller is that shown in Fig. 3 of the drawing. I find that by outwardly flaring the bottom of the ring, as shown m Fig. 2, a.

marked increase in the eiciency of the device is noted and a still greater increase is obtained than by forming the ring as shown in Fig. 1.

I have found that a plurality of spaced screw propellers Or a plurality of spaced worms will not produce agitator which is anywhere near as eflicient the combination herein disclosed. The propellers alone consume an excessive amount of-power and tend either to throw most y of the stock outwardly or, where thef consistency is high, merely to turn in the stock. In either case, circulation which is essential to bringing the stock'repeatedly into the zone of cutting action of the propeller blades, is impeded or entirely lacking, and the effect of one propeller is largely neutralized by the other. Y

Worms alone, on the other hand, merely drive th'e stock forward. There is no substantial lateral out throw and no cuttingand rapid intermixing action such as is eiiected by the separate blades of a screw propeller. Circulation is not only slow but the stock tends to travel in striae withvlittle -if any turbulence which is obviously quite essential to rapid and complete blending.

By combining a worm and screw propeller, and' so positioning and proportioning these two elements relative `to each other and to the confining walls of the chest or other receptacle within which they are located that the worm will feed the stock downwardly through the central portion of the chest to the propeller and the out throw of the propeller will be so directed as to drive the stock outwardly and upwardly around the stock which is -moving downwardly under the action ofthe worm, not only a very rapid circulation is attained 'with a minimum power consumption, but every bit ofstock is repeatedly brought into the zone of action of the propeller blades to be cut, blended and intermixed thereby.

While I have described my invention in its I.

preferred embodiment, it is to be understood that the words which I have used are words of description and not of limitation. Hen'ce, changes within the purview of the appended claims may be made without departing from the true scope and spirit of my invention in its broader aspects.-

What I claim is: v i

1. A device of the character prising a chest, a vertical shaft rotatably mounted therein, means for rotating said shaft, a screw propeller having a plurality of blades mounted on the lower portion of s aid shaft, a tapered worm pitched in the same direction as the propeller mounted on the upper portion of said shaft and having its largest diameter at the top -and extending from a point near the normal level of material in said chest to a point near said propeller, and a stationary ring slightly spaced from and extending about the periphery of said propeller eral flow is permittedafter the material passes described comtain a uent material, of a screw propeller having 5 separate blades and mounted to rotate aboutv a vertical axis within said receptacle near the bottom thereof, and a downwardly and outwardly' flared stationary ring sul rounding said propeller and having a length substantially coextensive with the axial length of said propeller; whereby unlimited lateral outthrow of material from said propeller is restrained but substantially free latthe propeller.

-3. In combination a receptacle for paper stock in fluent condition, said receptacle having a sloping bottom, a horizontally extending shaft provided'with a propeller located above the higher portion of. the bottom and a screw conveyor tapering towards said propeller and having the portion of greater diameter located above the lower portion of the bottom of the tana.

.4. In a device of the character described, a

`chest, a vertical shaft rotatably mounted therein,

a worm on the upper end of said shaft pitched to advance the material downwardly, a screw propeller on said shaft below said worm and pitched' to advance the material in the same direction as said worm, said propeller comprising a plurality of blades each of -which extends through a comparatively small arcy only, and a tubular element surrounding said propeller and spaced from the bottom of said chest to restrain the lateral outthrowof material from said propeller and direct the flow thereof downwardly, the diameter of said propeller being greater than that of s aid worm.

5. In a device, a chest, a shaft rotatably mounted therein, arcontinuous worm mounted on one -portion of said shaft and pitched to advance the material in said chest towards one of the walls thereof, a screw propeller mounted 'on another portion of said shaft intermediate said worm and one-of said walls andpitched in the same direction as said worm, each of said blades extending through a comparatively small arc only circumferentially of said shaft, said worm gradu- .ally decreasing in diameter towards said propeller, whereby said worm will convey material to said propeller where it the cutting and slicing action of said blades and will be subjected to

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