US2301201A - Method of and apparatus for classifying fibers - Google Patents

Description

Nv.1'o,1942. M. P. CHAPUN 2,301,201

METHOD OF AND APPARATUS FOR CLASSIFYING FIBERS Inve nim;

vNov. 10, 1942. M P, CHAPLlN. 2,301,201

METHOD 0F AND APPARATUS :FOR CLASSIFYING FIBERS Filed Feb. 2, 1937 q 2 Sheets-Sheet 2 Inventor,

WMF/wf Patented `Nov. 10, 1942 METHOD oF AND APPARATUS Fon oLAssIFYING riERs Merle P. Chaplin, South Portland, Maine, assignor to Chaplin Corporation, South Portland, Maine, a corporation of Maine application February 2, 1937, serial No. 123,684

' (ci. sie- 29) 22 Claims.

This invention relates to a method and apparatus for classifying or separating fiber particles according to size. It more particularly relates to the classifying or separating of ber particles which have appreciable length as compared to width or breadth and is particularly adapted to the screening of wood pulp fibers used for paper making.

Such fibers in their ideal condition are long, and relatively thin particles.7 For this reason, a screen opening must be provided which has considerably greater length than width in order that these long, thin fibres may pass through the screen openings and large fibers or groups oi bers which may be attached to each other, in which condition they are not suitable for use, can be separated from those thinner or individual iibers which are satisfactory.

The method hereinafter described is so arranged and its method of operation so determined that the ibers are brought into relation with the screen surface with their maximum length or dimension coinciding with the lengthwise direction of the slotted opening inthe classifying screen.

Thiskarrangement of fibers is obtained without the use`of mechanical agitators or rotating members for creating turbulence or circulation. All parts oftlre1`screening surface are submerged below the level ofthe liquid eliminating air in either the screened or unscreened material, .which air interferes with efficient classiiication and contributes to dificultles when the bers are felted on a paper machine.

A uniform pressure head on all parts of the screen surface is maintained making for maximum capacity and efliciency. This pressure head can be a'djsted as may be necessary or desirable 4for different materials and operating conditions. There are no moving or rubbing parts requiring lubrication which are in Contact with the pulp mixture. The absence of rubbing or friction parts and the mechanical agitators, stir- Cil rers or other circulating means results in vextremely low power operating requirements for screen operation.l

The anparatus is illustrated by 'the following drawings.

Fig. 1 is a vertical sectional elevation through the apparatus on line I-I of Fig. 2.

Fig. 2 is a plan view of the apparatus, a portion of which is shown in section through line 2 2 cf Fig. 1.

Fig. 3 is an end elevation on line 3-3 of Fig. 2 showing the method by which the lever arm is supported.

Fig. 4 is a sectional view through overflow box for rejected fibers.

Fig. 5 is a fragmentary view of a portion of the screening surface.

Fig. 6 is a diagrammatic view illustrating the method of operation by which the bers either pass through or are rejected by the screening surface. v

Fig. '7 is a diagrammatic view illustrating the segregation or separation of fibers of diierent size and weight.

Fig. 8 is a diagrammatic view illustrating the method by which the smaller fibers are disengaged or disentangled from amongst the larger bers and the means by which these disengaged fibers are brought into contact with the screen surface. y

The apparatus consists of a base I, on which is mounted the screening tank 2, the lever mounting bracket 3, and the eccentric shaft bearing 4. Screen tank 2 is generally cylindrical in shape and is supported from the base I supporting legs 5.

The fibers to be screened are mixed with water or othersimilar medium and enter the tank 2 through nozzle E, which nozzle is mounted tangentially on tank 2 near the bottom. On one side of the tank near the top is an overflow box l, which box has an adjustable Weir or gate 8 by means of which the height or level of the fibers and Water in the tank can be regulated.

Mounted on one side of the tank 2 and extending fora considerable portion of its height is a chamber Shaving connected thereto a plurality of spray nozzles I0. Water under pressure is supplied to chamber 9 through pipe II.

Mounted inside theV circular tank 2' is the screen proper. This consists of the screen itself I2 having elongated perforations I3 located therein as illustrated in Figure 5. This screen member I2 is supported on a bottom ange I4 which in turn is xed and secured to a tube or hollow member I5. The screen I2 isheld in place on member I4 by an upper member I6 and clamp nut I1.

With the tank 2 empty the screen itself can be readily removed for inspection by loosening and removing the clamp nut I1, lifting the upper member I6 from the screen and then lifting the entire screen I2 out of the tank. It can be reinstalled with equal facility after inspection.

The hollow member or tube I5 which supports the lower screen supporting member I4 is carried by a lever arm I8 being clamped therein by means of a split end I9 in said arm and clamp tively f link 2|.

' hollow tube I5.

, Wise about the fulcrum point 34.

bolts 20. The lever arm I8 is in turn carried by a swinging link 2| being pivotally connected thereto by means of a'lever bearing pin 22 which forms two pivot bearings 23a and 23h, these being-located above and below lever I8 respectively.

The opposite end of the link 2| is pivotally mounted to a bracket 3 by means of ,a bearing pin 24 which forms two bearings 25a and 25h located at the upper part and lower part respec- The bracket 3 is fixed to the base plate I by means of bolts 26.

The opposite end of the lever arm I8 is provided with a bearing 2l which bearing in turn is mounted on an eccentric 28. This eccentric 28 is fixed to a shaft 29 which shaft in turn is carried by a bearing 4 and bushing 38. This shaft is held in place vertically by means of an integral upper collar 3| on the shaft and an adjustable collar 32 on the lower end of the shaft. The shaft may be rotated or driven by any c-onvenient means such as a belt pulley 33.

When the shaft 29 is rotated in the direction of the arrow, the end of the lever I8 describes a small circle or moves in a circular path depending on the amount of eccentricity or throw of the eccentric 28. With the eccentric end of the lever I8 moving in a circular path, the center portion ofthe lever I8 at 34 is moved back and forth substantially cndwise,4 the point 34 swinging about the point 35 by means of the link 2| previouslydescribed.

The opposite end of the lever I8 to the eccen.

tric 28 is also moved in a circular path similar in magnitude to that imparted to the eccentric end of the lever lbut in the opposite direction as is indicated by the small arrow in the center of the The hollow tube I5 moved in a circular direction by the lever I8 of course carries with it the screen supporting and clamping member I4 and I6 and the screen I2 itself.

The link 2| not only permits a swinging motion about the point 35 enabling the lever arm I8 to movev endwise but also permits it to swing end- The link 2I has the further purpose ofv firmly supporting the lever I8, the hollow tube I5, the screen I2 and associated parts. While -rmly supporting lever and screen, the link 2| permits easy and ready movement of thescreen in a small circle as heretofore described under the urge and control ofA the eccentric 28 on the shaft 29.

As tank 2 contains a mixture of fibers and water or other liquid, it is necessary to provide a seal between the moving screen orl its bottom supporting member. I4 and the bottom of the tank 2. This isaccomplished by means of a rubber seal ring -36 secured to the bottom of member I4 by means of a clamp ring 31. The lower end of the rubber ring 36 is secured in a loose ring'38 which ring is clamped tightly to the inside of the tank 2 by means of clamp members 39. l

The purpose of this construction is to provide a flexible, durable and watertight'seal between themoving part I4 and the stationary part 2 and also to provide means by which `the hollow tube I5 together with the lrubber sealing ring 36 and associated parts can be removed from tank 2 for inspection. This is readily accomplished by loosening the clamp bolts 20-in the end of the lever I8 and removing clamp members i9. The entire tube and other parts including the rubber ring 36 and its clamp and sealing rings Located on one side of the tank near the topy is an overflow box 'I in which is located a Weir or gate 8. This weir or gate may be changed as to height which in turn will change the upper level 40 of the fibers and water in the tank 2. When the mixture in the tank 2 reaches the top of the gate 8 it can overflow passing off through pipe 4I.

It will be noted that the feed nozzle 6 is located practically at the bottom of the tank and when it is desired to empty the tank 2 for inspection or cleaning the pulp mixture therein can be drained back through the feed nozzle. If desired of course a drain valve can be provided in the bottom of tank 2.

In order to drain the inside of the screen itself, a valve 52 is provided inside the hollow tube I5. This valve consists of a sleeve which can be moved upward inside the tube normally resting on a seat 53. y

Just above seat 53 are located holes 54 through the screen supporting member I4 and through tube I5, these holes being located at the extreme bottom vof the inside of the screen chamber. Normally valve 52 resting on the seat 53 closes holes 54 and prevents escape of the water and fibers contained inside the' screen requiring them to normally overflow through holes, 44 near the.

top of tube I5. When it is desired to empty or drain the chamber inside the screen, the cap I'I at the upper end of tube I5 is removed and the valve 52 pulled upward by means of rod 55. The top of this rod when the valve is closed is located just below the inside top of cap I'I to insure that valve 52 is always closed when cap I'I is in place, and the screen about to be used.

In order to prevent any tendency of the screened material from effecting a syphoning action while flowing downward through tube I5 an air vent opening is provided in the top of cap I'I, consisting of a short pipe or tube 56 connecting to the interior of the cap and the top opening of the tube extending above the top of tank 2 to prevent unscreened bers from reaching the interior of the screen or tube I5.

Referring more particularly to Figs. 6, 7 and 8 I will now describe the method by which the apparatus previously illustrated and described operates.

Considering rst Figure '7. It has already been stated that the mixture of fibers and water which are to'be screened are introduced near the bottom of the tank through nozzle Ii. Thelocation of this nozzle is such that the flow of water and bers into the tank 2 imparts to them a natural rotary'motion around the walls of tank 2 vand around the screen I2 located within said walls. This rotary motion' of the fibers and water is a natural one, and is accomplished without the use of 'propellers, agitators or other, mechanical means which would disturb the flow of the mixture of the fibers and water about the screenv I2. This flow introduced through nozzle 6 naturally spirals or climbs upward as it passes -the ber size is satisfactory. been properly aligned with the slot it would have a natural segregation or separation of ber particles according to weight and in general according to size. This is indicated in Fig. '7 with the larger and heavier ber particles shown at 42 and` the smaller and lighter ber particles at 43. In Fig. 7 there is shown the outer wall of tank 2 and inside of this the screen I2 with its slotted or elongated openings I3.

It will be readily understood that the heavier and larger ber particles will gravitate outwardly and towards tank walls 2, leaving smaller and finer fiber particles nearer the screen surface. This action is not however, to be construed as effecting a complete separation or segregation of the ber particles according to size.

It has already been stated that' the fibers in the pulp mixture to be screened are in general long, thin, particles particularly those which are useful, these being indicated by the numeral 43. Mixed with these are larger and coarser particles indicated at 42, which are not suitable for use and which must be separated from the thinner bers.

It has already been described that in order to effect proper separation of the larger and smaller particles it is necessary to pass these through a relatively narrow opening as the important element in satisfactory screening is the measurement of particle width rather than length.

In order to effect such a separation and secure maximum screen capacity it is necessary .that the fiber particles be aligned or arranged parallel to the slot openings I3 in the screen I2 in order that their width may be determined and if less than the width of the slot I3 vthat they may pass through the screen and that if greater than the width of `slot I3 that they may be rejected by the screen and prevented from passing through.

On the other hand if a ber particle of satisfactory width approaches the screen crosswise or at an angle to slots I3 it cannot reasonably be expected to pass through the slot even though` If the fiber had passed through.

It is a welll known fact that logs floating down a stream or river will normally, if the flow of the stream or river is uniform, assume a path or direction lengthwise of the stream. This is due primarily to two causes.

First, the center of the stream is usually flowing slightly faster than other portions, hence if one end of the log extends over'near the shore where the water is moving slower than at the center of the stream, the motion of this end of the log is retarded tending to straighten the log out in the direction of stream llow.

Second, because the logs may actually touch or contact the bottom of 'the stream bed or its banks holding one end of the log back allowing the other end to go ahead, thus further effecting a straightening out or paralleling the .log length with the general direction of stream flow.

Such a condition is however only true where the stream flow is smooth and lacks undue turbulence. Where the stream flow is broken up by obstructions and is turbulent, flowing in eddies, circles and cross currents' the log no longer assumes or aligns its length with general direction of stream flow, but swings and turns as affected or influenced by the turbulence and cross currents-in the stream itself.

The bers under consideration are in elect small diameter particles of wood, and can be aligned with stream ow direction in exactly the same manner as the logs previously described and from whence these bers were made. However, to accomplish this, the stream flow must lack turbulence, agitation and disturbance and there must be effective means of retarding or slowing up one end of the fiber particularly as it approaches the screen I2 and more particularly the slot I3. In Fig, 6 there is illustrated diagrammatically the general operation and action of the bers as they move around the screen and inside tank 2.

It has previously been described that the introduction of the unscreened bers and water through nozzle B causes them to travel around the tank until they reach the top of gate 8 when they would overflow and pass from the tank. However, due to the fact that there are openings I3 in the screen I2 there is a tendency for the water of the mixture to flow through the screen openings.l3 and if possible to carry with it some of the fibers. These bers and water which pass through the screen openings I3 and into the space between the screen I2 and the tube I5 are allowed to overflow from this space through openings 44 in the tube I5 and after passing through said openings flow downward through the tube and out through the bottom at 45. These openings 44 are at a somewhat lower level than the upper part of the gate 8, this difference in level being indicated at 46 for that inside the screen and 40 for the level outside of the screen or in the tank 2.

This difference in level establishes a pressure head on the screen, this head being determined by the height of gate 8 which height is adjustable. This pressure head induces a flow of the water or the liquid with which the bers are admixed through the screen I2 thus drawing the fibers towards the screen as the mixture circulates or passes in a circularpath around said screen.

This ow through the screen naturally causes the bers 42 and 43 to be brought into close proximity therewith and if the fiber is not aligned with the screen as it approaches it and one end touches the surface of the screen I2 before the other the end that first touches Will be retarded and those bers will tend to straighten themselves 'out as illustrated in the right hand portion of Fig. 6. This condition obtains regardless of the motion of the screening surface and the function of which is described more in detail.

It has already been described how the screen I2 has imparted to it a circular motion, this being controlled and operated by the eccentric 28 op- `View as shown in Fig. 6 the outer tank wall is shown at 2, the screen in o ne posi-tion by full lines designated I2 andv in another position shown in dotted lines at I2a, this position being the one the screen would take after the eccentric 28 had made a half revolution from the screen position' indicated by the full lines. This circular motion is indicated diagrammatically by the circle 41. the arrow within that circle indicating the direction of motion,

This circular motion can for purposes of illustration be considered as consisting of four separate movements eacl'i being substantially in a straight line. These four motions are indicated by arrows placed about the circle 41, the arrows being designated 48, 49, 50 and 5I, I t will of course be understood that the screen motion will not be in absolutely a straight line as indicated by these arrows, but for all practical purposes it may be so considered,

It has already been described how circulation of the fibers about the screen I2 cause these bers to in general arrange themselves .parallel to the openings or slots I3 in the screen. It has also been described that due to the fact that the height or level of the pulp mixture outside of the screen is higher than that level on .the inside, a pressure head is established which induces a now through the screen openings I3 to the insidev of the screen.

As a ber particle approaches the screen hav-v ing naturally beenaligned parallel with the screen opening it must be tested or measured as to size .into proximity with the screen surface and are ready to be measured. At this time screen I2 can be considered as about to start moving in the direction of arrow 48. It will be observed that this motion is opposite to the general direction of circulation about the screen, and this motion of the screen in the direction of the arrow 48 further eiects or completes paralleling of the ber particles with the screen openings by contacting the trailing end of the ber.

When the motion 48 has beenocompleted the next motion'oi the screen is in direction 49 or for all practical purposes directly towards the previously aligned ber. The screen moving from the full line position indicated at I2 to the dotted line position at I2a., This motion of the screen in the direction of arrow 49' momentarily increases the pressure' head on this part of the screen and accentuates the ow through the screen opening. The iarge ber particle 42 and the smaller ber -particle 43 are thus urged against the screen. surface and against the slot opening I3 and 'tend`to pass through this opening. l The smaller particle can be assumed to be of such size that it will pass throughtthe slot I3 in which case, it will move-inside the screen and appear at some point such as 43a. The larger ber particle, however, can be assumed to be too vlarge to pass through the slot I3vunder which condition the screen by its motion in direction of i arrow 49 will push thislarger ber particle outward .to a position approximately 42a. Thus has screening or fiber-separation been accomplished tion of arrow 4.9,.the natural inward tendency now was increased due to the water and ber mass both inside and outside the screen resisting movement.. Similarly, when the screen is moved in direction of arrow 5I, the water and ber mass inside the screen I2l resists being moved in this direction resulting. in a brief reversal of ow through the screen slots.

This reversal dislodges any ber particle which may have partly entered slot I3 but which is slightly too large to pass entirely through. The ber, if left lodged in the slot, would interfere with other bers from passing through and thus decrease the screen capacity. The short but effective reversal of ow' through the screen slot f by the screen motion in directionlof arrow 5I dislodges such a ber, leaving the slot I3 available to measure additional bers.

It will be understood that the screen motion is relatively rapid and the motions asheretofore described and illustrated by the four arrows occur in rapid succession. portion of the screen surface is being utilized to complete the straightening out of the bers parallel to the screen slots, a larger portion of thev surface is being used to measure ber particle size when the screen moves in the direction of arrow 49 and a very small portion of the screen has its vow reversed in orderto dislodge any bers which may be partly wedged in any of the slots I3. It will thus be observed that all portions of the screen surface are performing some useful function, these functions in reality traveling about the screen .circumference with considerable rapidity.

In practice, it will be found that some of the smaller ber particles become entangled with the larger ones preventing effective and complete separation. As has already been described, a water pressure chamber 9 and a plurality of nozzles I0 are located in the tank wall 2 opposite the screen I2.

A'section through one of these nozzles is indicated in Fig. 8 with a somewhat diagrammatic representation of large and small ber particles "rection of the arrow. At the right hand portion by a measurement of ber width or its smallerv diameter with a minimum possibility that the ber, during movement, was lying 4at an angle or crosswise of the slot opening I3.

.' The screen motion heretofore described and indicated by the direction of the arrows 4&8 and 49 occurs during a half revolution of the eccentric 28. The remaining half revolution causes the screen first to move in the general direction of arrow 50 and nally in the general direction of arrow 5I or back to the starting point. The motion 50 is relatively unimportant but the inward motion in direction of arrow 5I. accomplishes a very useful purpose.

It will be understood that there is a mass of I of Fig. 8 there is indicated a mixture of large ber particles 42 which can be assumed to be entangled with each other requiring ,some additional means for separating them from each other.

As these bers circulate around the tank, lthey pass a plurality of nozzles IIJ through which is being forced, under pressure, water or lother liquid as indicated by the arrows and lines at the outlet of nozzle I0 in Fig. 8. These jets impinge on the circulating mass of bers and water as they pass around the tank breaking up any tendency for the bers to entangle with each other so that the smaller particles can gravitate towards the screen, the larger particles away from the screen or towards the tank wall 2. The result of the disentanglement is illustrated at the left hand portion of Fig. 8.

It is further to be noted that the jets are pointed in the general direction that the ber mixture is circulating about. the tank and *he ow through these nozzles aids in maintaini lg circulation of the mixture around the tank as it spirals upward from the inlet top of the tank and over the gate 8.

It will thus be seen that as the mixture of large and small bers `enter the tank 2 through This means that a .nozzle 6 to the action of the scre'en, these fibers areV either passed through the screen openings, or rebuffed therefrom and continue to circulate until they reach the-top of the gate 8 when they flow over this gate "and out through box l and pipe di, such bers` being rejected as unfit for the purpose intended.

During their travel around and around the screen they pass a plurality of washing jets 9,

above the perforations in thescreen, providing an outlet for the tank.

4. An apparatus for classifying fibers comprisinig an upright, substantially cylindrical screen-having elongatedgperfcrations therein, 'a

tank surrounding said sreen, a tangential inlet in said tank for the introduction of the mixture to be classified, means including said .inlet to induce a circulation of the incoming mixture within the walls of said tank and about said screen in substantial parallelism with the lengthwise dimension of the elongated perforations whereby the fibers of the mixture are brought into alignment with the elongated perforations,

which jets wash out any small acceptable fibers from their possible entanglement with the larger ones, bringing them to the screen surface where they can be tested for proper size, and either,

passed through the screen openings or rejected therefrom.

The satisfactory fibers are thus thoroughly separated from the unacceptable fibers, the acceptable ones flowing out through tube i5 at 35, andthe unacceptable ones flowing over the gate B and out through pipe M. l The incoming liquid is introduced in amounts sufficient to maintain the original consistency of the introduced mixture, thereby maintaining the proper ratioof liquid to fiber on the outside of the screen;` despiteA me fact that liquid is being discharged through the overflows at the top Aof the tank and in the hollow tube l5. "I

While the device heretofore described is particularly designed and adapted for the screening or separation according to their width or minimum dimension, this shall not be construed as limiting its use to the screening of particles having greater length and width.

In the screening of material where the measurement of particle width is unimportant or where particles may be round or of uniform general dimensions either slotted plates or screen plates with round or square holes may be utilized.

Having thus described my invention what I claim isl. An apparatus for classifying fibers comprising an upright, substantially cylindrical tank,

a slotted screen within said tank having closed bottom and top sections, the axis of said screen extending in the same general direction as the providing overflow holes in said tube above the screening area and a vent pipe in the top of said screen. l

2. An apparatus for classifying fibers comprising an upright, substantially cylindrical open top tank, a tangential inlet near the bottom and an overflow box near the top, a plurality of washing jets on one side and a non-rotating cylindrical screen disposed within said tank and means to move said screen bodily relative to said tank, through an orbital path.

3. An apparatus for classifying fibers comprising a tank, a screen within said tank, fixed means to introduce liquid and to establish 'circulation thereof in said tank, means to impart k the tank, and overflow means inside of the screen .axisrof the tank, a hollow tube supporting the bottom section, screen and top section, means v and means to move said screen to effect further fiber alignment with the elongated' perforations.

5. An apparatus for classifying fibers comprising a substantially cylindrical open top tank, a

'tangential inlet near the bottom, an overflow box near the top, a non-rotating, substantially cylindrical screen within said tank positioned with its axis extending in the same general direction as the. axis of the tank, a hollow supporting tube within said screen and a movable lever secured tolSaid tube, effective to move said screen and tube bodily relative to said tank.

6. in apparatus for classifying fibers, comprising a substantially cylindrical open top tank, a tangential inlet near the bottom, an open overflow box near the top, a non-rotating, substantially cylindrical screen within said tank posi- -tioned with its axis extending in the same general direction asthe axis of the tank, a'hollow supporting tube within said screen, a movable lever secured to said tube, effective to move said screen and tube bodily relative to said tank, and means tdsupport said lever for movement normal to the axis of the screen.

'7. An apparatus for classifying fibers, comprising a substantially cylindrical open top tank, a non-rotating, substantially cylindrical screen within said tank positioned with its axis extending in the same general direction as the axis of the tank, a hollow supporting tube within said screen, a lever secured to said tube, effective to move said screen and tube bodily relative to said tank, a link having one end pivoted to said lever midway of its extremities, and pivotal support means for the opposite end of said link.

8. An apparatus for classifying fibers, comprising a substantially cylindrical open top tank, a non-rotating, substantially cylindrical screen within said tank positioned with its axis extending in the same general direction as the axis of the tank, a hollow supporting tube within said screen, a movable lever secured to said tube, effective to move said screen and tube bodily relative to said tank, said lever being pivoted midway of its extremities, and means to impart a circular motion to said tube and screen thru said lever.

9. An apparatus for classifying fibers comprising a substantially cylindrical tank with an open top, a non-rotating screen within said tank positioned with its axis extending in the same general direction as the axis of the tank, said screen having closed ends, means to maintain a level "of stock above said screen in said tank; means to maintain a predetermined level of stock above screen openings inside of said screen and means to remove stock from inside of said screen when it has reached said predetermined level.

10. The method of classifying fibers which comprises introducing said fibers in a fluid mixture at the bottom of a vertically disposed prising an upright, f screen having elongated perforations therein, a

substantially cylindrical tank having therein a substantially cylindrical screen, imparting a circulatory rotary motion to said mixture within said tank and out-side of said screen, periodically washing said fibers as they circulate about said tank, imparting a circular but non-rotating motion to said screen, removing from the outside of the screen such vfibers as will not pass through and removing from the inside of said screen, such fibers as do pass through.

11. An apparatus for'classifying fibers., comprising a tank, a screen within said tank having elongated perforations therein, an inlet for the unscreened mixture to be classified near the bottom ofv said tank; means to impart a circular non-rotating motion to said screen whereby the fibers are alined to said screen openings and means, including the stock inlet and washing `jets spaced from said inlet, for insuring a circulatory movement of the unscreened stock about said screen.

12. An apparatus for classifying fibers comprising an upright, substantially cylindrical tank, a substantially cylindrical screen with closed top and bottom sections within said tank, the axis of said screen extending in the same general direction as the axis of the tank, a hollow tube supporting said screen with its closed top and 'bottom sections, means providing an overfiow opening from the interior of the screen to the interior of the tube, and means to move said screen and tube bodily relative to said tank with a non-rotary orbital movement.

13. An apparatus for classifying bers com`- prising an upright, substantially cylindrical tank, a slotted screen within said tank having closed bottom and top sections, the axis of said screen extending in the same general direction as the axis of the tank, a hollow tube supporting the bottom section, screen and top section, means providing overflow holes insaid tube above the screening area, a vent pipe in the top of saidscreen, and means to move said screen andi tube bodily relative to said tank with a non-rotary orbital movement.

14. An apparatus for classifying fibers comprising an upright, substantially cylindrical tank, a slotted screen within said tank having closed bottom and top sections, the axis of said screen extending in the same general direction as the axis of the tank,- a hollow tube supporting the bottom section, screen and top section, means providing overflow holes in said tube above the screening area, a-vent pipe in the top of said screen, means to introduce a liquid to be screened into said tank, and means including said supporting tube to mount said screen in complete submergence within the introduced liquid.

15. Anapparatus for classifying i'lbersv comprising a tank, a screen within said tank, fixed means to introduced liquid and to establish circulation thereof in said tank, means to impart a circular non-rotating motion to said screen, an overflow means outside of the screen'in said tank, eective to establish liquid level within the tank, and overflow means inside of the screen above the perforations in the screen, .providing an outlet for thetank, and means including said rst overflow means to completely submerge the screen within the tank.

16. An apparatus for classifying fibers comsubstantially cylindrical tank surrounding said screen,` a tangential inlet to be classified, means including said inlet to induce a circulation of thel incoming mixture within the walls of said tank and about said screen in substantial parallelism with the lengthwise dimension of the elongated perforations whereby the fibers of the mixture are brought into` alignment with the elongated perforations, l means to move said screen to effect further ber with its axis extending inthe same general direction as the axis ci the tank, a hollow supporting tube within said screen, a movable lever secured to said/tuba effective to move said screen and tube bodily relative to said tank, means to introduce a liquid to be screened into said tank, and means including said supporting tube to mount said screen in complete submergence Within the introduced liquid.

18. An apparatus forclassifying fibers, comprising a substantially cylindrical open t"op tank,

a tangential inlet near the bottom, an open overflow box near the top, a non-rotating, substantially cylindrical screen within said tank positioned with its laxis extending in the same general direction as the axis of the tank, a hollow supporting tube within said screen, a movable lever secured to said tube effective to move said screen and tube bodily relative to said tank, means to support said lever for horizontal movement, means to introduce a liquidfto be screened into said tank, and means including said supporting tube to mount said screen in complete submergence within the introduced liquid.

19. The method of screening and classifying bers which comprises confining the fibers in a liquid mixture between a wall of a tank and a screening surface in the tank, circulating the confined mixture about the screen toalign fiber particles relative to the screen openings, and to produce a centrifuging action effective to remove unacceptable fibers from the screen, moving the screen in a direction such that a segment thereof moves through a path opposed to the circulating movement of the mixture to create a head on the screen surface and to facilitate passage of accptable fibers therethrough, and thereafter moving the screen in the same direction as the circulating movement to effect a reversal of flow through the screen openings, and washing the bers thoroughly during the circulation of the confined mixture.

20. The method of screening and classifying fibers which comprises confining the fibers in a liquid mixture between a Wall of a tankand a screening surface in the tank, submerging the screening surface within said confined mixture to eliminate air, circulating the confined mixture about said screen to align fiber particles relative tvo the screen openings, and to produce a centri- .tuging action effective to remove unacceptable fibers from the screen, movingthe screen in a direction such that a segment thereof moves screen surfaceand to facilitate passage of acceptin said tank for the introduction of a mixture ablev fibers therethrough,thereaf ter moving the screen in the same Vdirection as the circulating movement to effect a reversal of flow through the screen openings, and washing the bers thoroughly during the circulation of the confined mixture.

21. An apparatus for screening and classifying fibers, comprising means to confine a liquid,v fiber mixture, between a wall of a tank and a screening means in the tank, said screening means Within said confining means, means to circulate a mixture confined in said confining means about said screen to align fiber particles relative to the screen openings land to produce a centrifuging action effective to remove unacceptable bers from the screen, means to move said screen rst, in a direction such that a segment thereof moves through a path opposed to the circulating movement of the mixture to create 4a head on the screen surface, and to facilitate passage of acceptable fibers therethrough, and thereafter in the direction of circulation to effect a reversal of flow through the screen openings, and means to wash the fibers thoroughly during the circulation of the confined mixture.

22. An apparatus for screening and classifying fibers, comprising means to confine a, liquid, fiber mixture, between a wall of a tank and a screening means in the tank, said screening means being positioned within said confining means comi pletely below the normal level of liquid mixture, whereby to eliminate air during a screening operation, means to circulate a mixture conned in said confining means about said screen to align fiber particles relative to the screen openings and to produce a centrifuging action effective to remove unacceptable flbers from the screen, means to move saidscreen first, in a direction such that a segment thereof moves through a path opposed to the circulating movement of the mixture to create a head on the screen surface and to facilitate passage of acceptable bers therethrough,

and thereafter in the direction of circulation to effect a reversal of flow through the screen openings, and means to wash the fibers thoroughly during the circulation of the c onned mixture.

MERLE P. CHAPLIN.

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