US1492794A - Method and apparatus for screening and refining paper stock - Google Patents

Description

May 6 1924. 1,492,794

A. J. HAUG METHOD AND APPARATUS FOR SCREENING AND REFINING PAPER STOCK Filed Nov. 21 1919 3 Sheets-Sheet '1 v J N N lnvenior: eflni'on J H mm May 6 1924.

A. J. HAUG METHOD AND APPARATUS FOR SCREENING AND REFINING PAPER STOCK Filed Nov. 21, 1919 5 Sheets-Sheet 2 fliaz'owa/ Z 1m Z1327 M May 6 1924.4 1,492,794

A. J. HAUG METHOD AND APPARATUS FOR SCREENING AND REFINING PAPER STOCK Filed Nov;. 21. 1919 3 Sheets-Sheet 5 mm P.

UNITED STAT ANTON J. HAUG, OF NASHUA, NEW HAMPSHIRE, ASSIGNOR TO IMPROVED, PAPER I MACHINERY COMPANY, OF NASHUA, NEW HAMPSHIRE, A CORPORATION OF MAINE.

METHOD AND APPARATUS FOR SCREENING AND.REFINING-PAPER STOCK.

Application filed November 21, 1919. Serial No. 339,563.

To all whom it may concern:

Be it known that I, ANroN J. Ham, a citizen of the United States, and a resident of Nashua, county of Hillsborough, State of New Hampshire, have invented an Improvement in Methods of and Apparatus for Screening and Refining Paper Stock, of which the following description, in connection with the accompanying drawings, is a specification, like characters on the drawings representing like parts. v

This invention relates to methods of and apparatus for screening and refining paper stock. One object is'to produce high grade pulp with maximum efiiciency and a minimum amount of waste, and under such conditions that there may be maintained a pro:

gressive advance of the stock from a source of supply through successive screening and refining operations, provision being made for the utilization in the ultimate product of such portions of the stock. as are rejected in the screening operations.

The invention will be best understood by reference to the following description when taken in connection with the accompanying illustration showing one specific. embodiment thereof, while its scope will be more particularly claims.

In the drawings:

Figure 1 shows more or less diagrammatically the application of a system to the refining of ground wood;

Fig. 2 is a similar view showing. the application of one form of the invention to the refiningof chemical pulp; and

Figs. 3, 4, 5, 6, 7 and 8 illustrate the course which the stock may be made to take in successive steps of refinement under. a variety of conditions.

Referring to the drawings, and firstto the illustrative embodiment thereof represented in Fig. 1, the system therein disclosed contemplates a continuing and preferably constant feed of stock from the pointed out in the appended source of supply, herein represented at 1. Such continuing and preferably uninterrupted supply of stock is subjected to a preiminary operation designed to separate the knots and other coarse, undersirable material from the stock supply. This opera-' tion should be carried out so as to prevent the passage of large pieces of bark or large I knots which would otherwise not only result in dirty stock, but tend to give trouble with the subsequent screening operations and the instrumentalities relied upon to perform them. This operation, for example, may be suitably carried out in a rotary knotter 94- s olelea,-

or other continuously acting knotter K of the construction illustrated in my prior Patents Nos. 1,183,297 and 1,183,298, dated May 16, 1916, in which the stock, after being received at the stock inlet represented in Fig. 1 at 2, is agitated, screened, washed and drained, the knots or coarse residue being discharged through the tailings outlet 3 and the screened residue through the discharge chamber 4.. The tailings from the knotter are delivered to the discharge pipe 5 and thence'through the waste pipe 6 to any suitable Wastereceptaole 7.

p The screened residue from the delivery chamber 4 of the knotter is withdrawn through the conduit 10 and is subjected to a screening action to subdivide the residueinto fine stock and coarse stock. If desired, the stock may be subjected before such screening action to the sedimentation of v a sand table 'or riflier, diagrammatically represented at S, although in the case of ground wood this step may be unnecessary. uch sedimentation will remove the larger pieces of sand from the digester lining, etc., which might be broken up in the subsequent screening operation and introduce impurities into the resultant stock. In order that the travel of the stock through the successive refining units as delivered by the continuous action of the knotter on the continuous supply of stock mayl be uninterrupted, there should preferably be no interruption of the progre'sion of the'stock at the sand table, such as is usually necess sitated when it is required to remove the accumulated sediment therefrom. Preferably, therefore, a continuously acting rifiier should be employed, such as is disclosed in my copending application Serial No. 339,564, filled Nov. 21, 1919 the riflier of which is characterized by the provision of a plurality of settling chambers for the sand table, with means for diverting stock without interruption of flow through'either one of the settling chambers at will, while the remaining chamber is being cleanedof its accumulations.

The subsequent screening operation is preferably carried on with a suitable centrifugal screen providing for thorough agitation and pressure of the stock against the screen. and thus insuring the removal of the slivers and the separation of the fiber bundles to the greatest extent. Such form of screen is also capable of receiving an uninterrupted supply of stock and discharging the screened stock and tailings continuously. The centrifugal screens disclosed in my prior Patents No. 1,147,239, July 20, 1915, and No. 1,172,239, February 15, 1916, are suitable for effecting the required screening operation, and a centrifugal screen of this type is indicated diagrammatically at C in Fig. 1.

The refined stock delivered by the knotter is discharged either through the sand table S or directly and independently thereof to the stock inlet 11 of the centrifugal screen C, the fine screen stock being delivered by the centrifugal screen to the screened stock outlet 12 and the taiiings to the tailings discharge pipe 18. The screened stock thus delivered from the passage 12 is thence carried through'a delivery conduit l t to any suitable delivery point, such as the receptacle 15, first passing, however, if desired, through a second sand table S for further sedimentation. The sand table S is preferably employed in order to remove sand, sawdust, etc., which is so fine as to be capable of being pressed through the screen piates in the cen trifugal screen, and which has not been removed in. the first sand table, because of the greater thickness of the pulp at that stage of the process and the presence of the fiber bundles which tend to hold the sand from settling. The stock delivered to the delivery receptacle 15constitutes the first grade of stock or that of the highest possible quality.

Referring now to the tailings or rejections from the centrifugal screen C, these are delivered uninterruptedly through the tailings conduit 13 to the inlet 16 of a tailings screener, indicated in the drawings and des ignated by T. Such tailings screener is preferably capable of screening the constant supply of tailings and slivers from the centrifugal'screener by a succession of screening actions in which the stock is agitated, lifted and dropped againstscreening plates, being T thinned and diluted between successive screenings, the refined or screened stock being delivered to the discharge pipe 17 and therejections of relatively coarse stock being delivered'through the tailings outlet 18.

' Such tailings screener, for example, may be similar to the tailings screener illustrated in my prior Patent No. 1,284,668, dated Nov. 12, 1918. I

The result of the screening operation on "the tailings is to separate from the coarser slivers the good, smaller fibres which have passed through the centrifugal screen with the slivers and discharge them as refined stock, leaving only the slivers which must be further reduced before they are suscep1 tible of further separation or screening.

The refined stock from the tailings screencr may be delivered to any suitable delivery receptacle indicated at 19 and withdrawn from the system as a second or relatively coarser grade of stock, being first preferably subjected, however, to sedimentation at the sand table S Or, if desired, the refined stock discharged from the tailings sc-reener through the pipe 17 may be returned to the system and to the stock supply thereof to be circulated therewith and subjected to one or more of the preceding refining actions, so that, subject to such further refinement, it becomes mingled with the high grade stock delivered to the delivery receptacle 15.

To this end suitable means are provided, such for example as the pump 20 which is connected to the pipe 17 by the conduit 21 and through a valve 22, or other suitable means is employed for diverting the discharge from the tailings screener T to the pump and by which it is forced back through the discharge pipe 23 through a system of conduits to the inlet 11 for the centrifugal screen or the inlet 2 for the knotter, as may be desired. The conduit 23 has connection through a two-way valve 24 with a conduit 25, and this in turn through the two-way valve 26 with a conduit 27, the latter serving to convey the refined stock from the tailings screener to the inlet 11 for the centrifugal screening. By means of the two-way valve 26, this dischar e, when desired, may be diverted to the conduit 28 and discharged into the inlet 2 for the knotter.

The rejections from the repeated screening operations in the tailings screener are now delivered to the inlet 29 for a continuously operating refiner indicated at R in the drawings, such refiner preferably operating to act upon the rejections from the tailings screener by a series of rolling or crushing actions, the number and pressure of which are predetermined, the stock being agitated and progressively advanced be tween each crushing action so that, as delivered from the discharge end 30 of the refiner, the product consists of rejections which are uniformly reduced in size and of suitable consistency. A type of such re finer is illustrated in my prior Patent No. 1,302,469, dated April 29, 1919, the evenness of supply, definiteness of the number and pressure of the crushing actions enabling the machine to turn substantially all the rejections from the tailing screener into good fibres, none of which is overground or, on the other hand, underground or too coarse, provided such rejections from the tailings screen-er are of a substantially uniform size. It will be observed that by screening the stock with the abnormally coarse particles first previously removed, as by the knotter K, and by again screening the tailings which come from the centrifugal screen C to thoroughly separate the residual fine stock from the relatively coarser slivers, the latterconstituting the rejections from the tailing screener Tare of substantially uniform coarseness, containing no oversize slivers and no fine pulp. In this way the refiner R which subjects the slivers to a. definite, predetermined reducing action, can be worked at its highest efliciency. Thus, if oversize slivers were to reach the refiner, these slivers would be either insufliciently reduced or the ordinary supply would be over-refined. If fine stock were allowed to enter the refiner R, it would be over-refined and pass through the wires of the deckers and wet machines which might be subsequently used in the process to remove the water from the stock. The removal of the over-sized slivers in ground wood, which consist chiefly of pieces of bark, and their elimination are of no substantial loss for, if refined, they would introduce dirt into the final product.

The degree of reduction or the fibre length of the refined pulp which is turned out by the refiner may be varied not only by increasing the length of the refiner or the number of refining devices to which the pulp is subjected, but may be varied by varying the consistency of the supply. A thin supply-that is, containing a large amount of watertends to produce a long fibre suitable, for example, for news pulp, while a heavy consistency with a lesser amount of water produces a short fibre suitable for fine papers and fillers.

The final action of the knotter, therefore, reduces the coarse rejections from the centrifugal screen and the tailings screener to slivers of a substantially uniform size, and the tailings screener thus delivers its rejections not only of a substantially uniform size but at a proper and constant consistency, thereby enabling the refiner to act under the greatest efliciency in reducing the stock, but avoiding an over reduction thereof. On the other hand, the successive screening operations at the centrifugal screen and tailings screener have removed the smaller fibres, thus avoiding the delivery to the refiner of those portions of the stock which might be overground if delivered thereto.

The coarser rejections from the screening operation being thus reduced may be utilized by subjection to'further screening and refining action, and if desired may be conveyed back to the stock which is progressing through the successive refining operations. Thus, for example,.the discharge passage 30 from the refiner is shown connected to the conduit 21 and the pump 20 by which the discharge from the refiner may be conveyed the screened stock and the rejections, in

delivering a highly refined grade of stock 1 at the delivery end of the system.

In Fig. 3, the constant supply of stock passes through the knotter K and the refined residue thence passes to the centrifugal screener C and the finely screened stock to the delivery point of the system. The tailings from the centrifugal screen pass through the tailings screener T, the screened stock from the latter being again returned to the centrifugal screen for further screening. The rejections from the tailings screen er pass to the refiner R and the refined product thereof is delivered back 'to the main supply and again enters the system at the knotter.

In Fig. 4 a similar course is given the stock and the rejections, excepting that the product from the refiner is returned to-the centrifugal screen C and again circulated therethrough, and the refined stock from the centrifugal screen is shown as through the sand table S.

In Fig. 5 there is illustrated an arrangement of the course which may be given the stock and the rejections through the pro visions of the system illustrated in Fig. 1, where two grades of stock are withdrawn, one high grade and one coarser. In Fig. 5 supply of stock passes through the knotter K. the centrifugal screen C and the sand table S to the delivery point for the good stock. The rejections from the centrifugal screen pass to the tailings screener T and the screenings therefrom over the sand table S to the delivery point-for the second grade of stock. The rejections from the tailings screen pass to the refiner R and then back again to the tailings screener again to circulate therethrougl It will be obvious that with the arrangement illustrated in Fig. 1. various other methods of utilizing the rejections from thesuccessive operations may be employed and the paths given various rejections may be varied to suit the particular object sought in each case. It will be obvious, however, that the full value of the stock is capable of being utilized and that the workof the various units is divided into distinct and simple operations, each unit being capable of perfecting its operations and each unit being so arranged that the maximum efficiency of the succeeding unit can be obtained without intermediate devices or processes, and that a continuous refining operation, dependent upon the action of the successive units, may be carried on without interrupting the conpassing tinuing advance of the stock through system.

Referring'to Fig. 2, I have there shown a modified arrangement of the system which is applicable more particularly to the refining of chemical stock such as sulphite. The main stock supply 40, as before, enters the inlet -ll of the knotter K, the screened residue thereof passing through the dis charge passage 42 and the knots being discharged from the discharge end 43 into the discharge conduit 44, where they may be diverted through the two-way valve 45 and the discharge pipe 46 to any waste receptacle 47. The screened stock from the knotter are then preferably carried through the sand table S to the centrifugal screen C the good stock from the latter passing through the discharge pipe 48 to the inlet 49 for the sand table S and being delivered -therefrom through the the delivery receptacle highest grade of stock. The tailings from the centrifugal screen C are discharged through the conduit 52 to the tailings screener T. The good stock from the latter are discharged through the pipe 53 to the sand table S and thence to the delivery receptacle 54which is adapted to receive the 9 second grade of stock. If desired, through means of the two-way valve 55, the conduit 56, the pump 57 and conduit 58, the discharge from the tailings screener may be carried to the inlet 49 for the sand table S and commingled with the good stock from the centrifugal screen and delivered to the delivery receptacle 51 for the first grade of stock.

The rejections from the tailings screener are delivered through the discharge end 59 thereof to the inlet 60 for the refiner R, and the product of the latter may pass to the discharge conduit 61 and thence to the delivery receptacle 62 and constitute either 66 a second or third grade of stock.

Or the reduced and refined product of the refiner by means of the two-way valve 63 and the conduit 64 may be carried back to the preceding tailings screener T',or, as here- 50 in illustrated, to a second tailings screener T the screened discharge of which is delivered through the conduit 65 to the delivery receptacle 66 providing a second or third grade of stock as the case may be.

5 The coarse rejections of the tailings screener T in this case are carried by means of the conduit 67 to a pump 68 or other suitable device, by means of which they are again returned to the system to circulate there- 0 through, this being done herein by means of the conduit 69, which discharges them into the inlet end 60 of the refiner R. The discharge from the tailings screener T therefore, is caused to circulate back through the 66 system until it is entirely reduced and delivery pipe 50 to 51 for the first or screened and utilized in the form of the screened, refined stock. By means of this system, therefore, two or three, grades of stock may be produced ;-one, high grade, white stock; the second, a medium stock; and the third, a brown or inferior grade. In the case of sulphite or other chemical stock, the pulp having been subjected to achemical action is more or less softened and, if desired, the coarser rejections from the knotter K may be diverted from the receptacle 47 and conducted to the inlet 60 of the refiner B through the conduit 70.

In Figs. 6, 7 and 8, I have indicated a variety of courses which may be given the stock in passing through the successive operations provided for in the system illustrated in Fig. 2. Thus, in Fig. 6, the main supply is delivered to the knotter K and the screened stock therefrom passes through centrifugal screener C, which latter discharges its refined stock to the delivery point for "the first grade of stock. The tailings from the centrifugal screener pass through the tailings screener T the screenings of 90 which is either turned back, mingled with the good stock from the centrifugal screener or delivered as a second grade of stock. The rejections from the tailings screener pass through the refiner R and are delivered as a second or third grade of stock.

In the arrangement shown in Fig. 7, the good stock from the tailings screener T are utilized as second grade stock, and the product of the refiner R is passed through a second tailings screener T the rejections of which are returned to the refiner 'R and the screened stock of which is utilized as a third grade of stock.

In Fig. 8 an arrangement similar to that shown in Fig. 7 is illustrated, the stock being subjected, however, to successive sedimentations, first, between the knotter and the centrifugal screener and again following the centrifugal screening and also following the screening action of the tailings screener.

While I have herein shown and described for purposes of illustration one specific form of the invention, it will be understood that the same is not limited to the specific construction or to the details herein shown or to the form or relative arrangement of parts, but that extensive deviations may be made therefrom without departing from the spirit thereof.

Claims.

1. The method of screening and refining paper stock which consists in maintaining a continuing supply of stock from a supply source to one or more delivery points and subjecting the same while being thus fed progressively to successive refining actions, the same comprising preliminarilyseparating the coarse, undesirable material from 1 -jections from said repeated screening actions to a uniformly refined product by subjecting the same to a redetermined rolling or crushing action, utilizing the product of the reducing action by returning the same to the stock supply for further screening action, and subjecting the refined stock in the course of its progress to sedimentation to remove foreign particles.

, 2. The method of screening and refining paper stock which consists in maintaining a constant, continuing feed of the stock from a supply to one or more delivery points and subjecting the same while being thus fed progressively to successive refining actions, the same comprising preliminarily separating the coarse, undesirable material from the constantly fed stock, subjecting the residue to a centrifugal screening action and thereby subdividing it into fine and coarse stock, conveying the fine stock to a stock delivery outlet, subdividing the coarse stock into rejections and relatively refined stock, conducting the relatively refined stock to a stock delivery outlet, reducing the rejections and utilizing the product of the reducing action by submittin it'to further screening.

3. The method 0 screening and refining paper stock which consists in maintaining a constant feed of the stock from a supply to one or more delivery points, preliminarily withdrawing the knots or coarser material, subdividing the residue by a centrifugal screening action into fine and coarse stock, progressively screening the continuouslv supplied stock, utilizing the good stock therefrom, subjecting the rejections from the last named screening action to a continuous and predetermined reducin action to reduce the said rejections into a e, uniform product,

and utilizing the product thereof by returning it to the system for further screening action. v a

4. The method of screening and refining paper stock which consists in maintaining a constant feed of the stock from a supply to one or more delivery points, preliminaril withdrawing the knots or coarser materia subdividing the residue by a centrifugal screening action into fine and coarse stock, progressively screening the continuously supplied stock, utilizing the good stock therefrom, subjecting the rejections from the last named screening action to a continuous and predetermined reducing action to reduce the said rejections into a fine uniform roduct, and utilizin the product thereo 5. The metho of screening or refining paper stock which consists in maintaining a stock suppl continuously withdrawing the coarse, un esirable material, subdividing the residue by screening action into fine stock and coarse stock, sub ecting the coarse stock to a second screening action to separate the remaining fine stock therefrom, thereby to insure uniformity of the coarse stock, reducing. by a single passage through the reducing agency the uniform coarse stock while maintainingit separate from the stock supply for the screening action into comparatively fine stock and utilizing said reduced fine stock.

6. The method of screening or refining paperstock which consists in maintaining a stock supply, continuously withdrawing the coarse, undesirable material, subdividing the residue by screenin action into fine stock and coarsestock, su jecting the coarse stock to repeated dilutions and screenings to insure separation of the fine stock from the coarse stock and the uniformity of the latter, reducing by a single passage through the reducing agency the uniform coarse stock while maintaining it separate from the stock supply for the screeningnetion into comparatively fine stock and utilizing said'refined stock.

In testimony whereof, I have signed my.-

name to this specification.

ANTON J. Hand.

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