Патент USA US2122475код для вставки
July 5, 1938. N. M; KNIGHT 2,122,475 PULP SCREENING IACHINE Filed Jan. 3, 1956 4 Sheets-Sheet 1 35 F191.' 32 34 33 50 as s 93 ,2s 27 94 I6 42 44 4 6 lnvenTov Neìson MKnìghT www2.7M July 5, 1938. N. M. KNIGHT , 2,122,475 PULP SCREENING IACHINE 'Filed Jan. s. 1936 4 sheets-sheet 2 Invènïor. Nelson M_Knighï byßa/«JMÈM July s, 193s. ‘ N. M. KNIGHT ì - 2,122,415 I_’ULP SCREENING incarna ' Filed Jan. 3, 1936 , 4 Sheets-Sheet 5 Figlëlf ' 56 ‘25? f A sa \\\x\\\ sa v'3070. 23° 30 // . Y E i i E ~ v ì v _. ' E î 66’ . «23 v 65167 2s ' 566 3| = / ` 3S " ss 2S“ lnvenïor. M. Kn ig hT / AJuly 5, 1938. , l ' N. M.v KNIGHT " ' PUL? SCREENING “CHINE Filed Jan. 3, 1936 Fig@ I È 2,122,475 gä y 4 Sheets-Sheet 4 -6,2 $8 26.2 /2 ff, ì 4 lnvenTov ____ _4 43 5 Nelson MKnìghT bymMkZ-¿MM Patented July 5, 193i' 2,122,475 UNITED' STATES PATENT OFFICE 2,122,475 PULP >SGREENI'I‘ÍG MACHINE Nelson M. Knight, Weymouth Heights, Mass. A Application January 3, 1936. Serial No.'57,378 17 Claims. (Cl. 92-34) This invention relates to pulp screening ma chinesand particularly to machines of the type illustrated in my Patent No. 2,003,150, dated May 28, 1935. ` The pulp screening machine shown in said patent comprises a casing having an inlet for unscreened pulp and an outlet for the screened pulp,»a screen within the casing through which the pulp passes as it flows from the inlet to the 10 outlet, said screen having a plurality of baille plates rigid therewith, and pulp-pulsating plates situated between the baille plates and movable toward and from the latter, the movement of cleaning runners are provided on the inlet side of the screen which are given a rotative move ment about the screen for the purpose of assist ing in keeping the screen clean. Another feature of my invention relates to an 5 - -improved construction of the screen-cleaning ele vment. , Another feature of the invention relates to an improvement in the means for giving the simple harmonic movement to the pulsating plates by which the amplitude of vibrating movement of the plates may be readily changed from the ex terlor of the machine. l the pulsating plates relative to the baille plates l Other features of the invention relate to vari 15 serving to force the pulp back and forth through ous improvements in pulp screening machines the screen as it flows from the inlet toward the which will be more fully hereinafter set forth and will then be pointed out in the appended claims. outlet. InA the device of said patent the pulp-pulsating ' In the drawings: plates are given their vibrating movement by an Fig. 1 is a vertical sectional View through a eccentric, as a result of which they have a simple pulp screening machine embodying my invention. _ Fig. 2 is a section on the line 2-2, Fig. l. harmonic movement, the movement of said pul sating plates relative to the baille plates being Fig. 3 is> a view showing one section or unit of relatively slow'at the beginning and ending of the screen-cleaning element construction. each stroke and relatively rapid at the mid portion Fig. 4 is a View of the driving mechanism for the pulsating plates and the runners with parts of the'stroke. This _uneven relative movement between the . brokenout to better show the construction. pulsating plates and the baille plates produces an Fig. 5 is a section on the line 5_5, Fig. 4. Fig. 6 is a side view of the pulp screening ma-. uneven pulsation of the pulp through the screen, and as the pulsating plates are vibrated relatively chine with one of the plates of the casing re 30 rapidly, such uneven motion subjects both sets moved to give access to the screen-cleaning ele of plates to considerable strain. ~It is one of the objects of the present inven tion to provide a novel construction by which a more even relative movement Vwill be produced 35 between the pulsating plates and the baille plates notwithstanding the fact that the pulsating plates have the simple harmonic motion result ing from being actuated by an eccentric or crank. This end is accomplished by providing screen 40 supporting means _which permits the screen to yield slightly in the direction of the movement of the pulsating plates so that as the speed of movement of the pulsating plates increases from the beginning of each stroke to the center there 45 of the pressure to which the baille plates are sub jected will cause a yielding movement of the screen in the same direction as that of the pulsating plates, although of less extent, with the result that the relative movement between the two sets 50 of plates will be a much more even and uniform movement than where the baille plates are ñxed or stationary ’as in the device illustrated in said patent. ` ' In said patent the pulp screen is shown as a cylindrical screen and a plurality of screen ment. ' ' Fig. 7 is an enlarged fragmentary sectional view showing the operation of the resilient sup port forthe screen. l Figs. 8 and 9 are diagrammatic views illus trating the manner in which the eccentric for op erating the pulp-pulsating plates can be _adjusted to vary the amplitude of movement. Fig. 10 is a fragmentary perspective view show ing a detail of the sectional shaft 29. 40 Fig. 11 is a fragmentary view showing the two sections of the shaft 29 connected together. In the drawings I indicates generally the cas ing of the machine which is shown as a ver tical cylindrical casing having an upper head 45 2 provided with an inlet 3 for the unscreened` pulp and also provided with the lower head 4 having a discharge 5 for the screened pulp. This casing is supported on suitable legs or supports i‘and the upper head 2 has attached thereto a bearing member 1 having the inlet passage 8 through which the unscreened pulp is delivered to the inlet 3. The casing I may be made in any appropriate way and as herein shown it comprises a plu- 55 2 2,122,475 rality of curved plates 9 which are connected to ber 1. The motor shaft 34 has a belt pulley 35 vertically-extending post members I Il, there be ing four of these post members and consequent thereon which is belted to a pulley 36 on ly four plates 9. 'I‘he posts are shown as hav 'il ing a channel-iron shape and the plates 9 have ilanges II at their vertical edges which mate and are clamped to the flanges of the channel iron posts I0 by means of clamping bolts I2. With this construction the interior surface of the cas ing I is formed partly by the plates 9 and partly by the inner faces of the posts I8. The screen which is situated Within the cas the shaft 29 through the medium of a driving belt 31. The upper head I4 of the screen has a bearing 38 through which the spindle 22 ex tends. The spindle 22 is keyed to the bearing sleeve 26 through the medium of a key 94. The ends of the key are provided with- fingers 93 which engage the bearing and thus retain the key in place. The key-94 permits vertical re ciprocation of the spindle 22 but prevents rota tive movement thereof. ing is indicated at I3 and it is shown as having As stated above the motion given to the pulsat a cylindrical screening wall which is connected at ing plates I8 by the eccentric 28 is a simple its upper end to an upper non-perforated screen head I4 and at its lower end to a lower screen harmonic motion in which the movement of the head I5 that is provided with an outlet opening each stroke is relatively slow while the eccen tric is leaving or approaching the dead center and is relatively rapid while the eccentric is mid way between the two dead centers. If the baf 20 fle plates Vare stationary this uneven movement I6 registering with the discharge opening 5. the discharge opening I6 thus communicating with the interior of the cylindrical screen. The un pulsating plates at the beginning and ending of screened pulp thus flows into the casing and through the screen I3, thence through the out of the pulsating plates causes an uneven pulsa- y let I6. tion of the pulp through the screen plate and The screen I3 has a plurality of baille plates I'I rigid therewith and preferably extend ing at right angles to the screen wall and situ ated between these baiile plates are pulp-pulsat ing plates I8 mounted for movement toward and from the baille plates. This relative movement causes of the the pulsating pulp to plates be pulsated I8 and or forced baille plates back and forth’through the screen as it flows frein the in let to the outlet inthe manner described in my above-mentioned patent'. In the construction herein shown the baille plates I‘I are annular it plates situated on the inside or delivery side of the screening wall I3 and are rigidly connected at their periphery to said screening wall. These plates -are held spaced from -each other by means of spacing elements I9 and the spacing elements furthermore subjects the baille plates to a con siderable strain at the time that the pulsating 25 plates have their highest speed of movement. In order to produce a more even relative move ment between the pulsating plates and the baille >plates and thereby to relieve the plates from this undue strain and also to cause a more even pul 30 sating movement of the pulp through the screen,/ I propose to so mount the screen that it can yield or give in the dire-ation in which the pulsating plates are moving as the pressure against said badle plates increases due to the increasing speed 35 of movement of the pulsating plates at their mid-stroke. Various ways of thus mounting the screen to provide for this yielding movement may be employed without departing from the inven One simple expedient is herein shown which is especially adapted for a screen pulp in 40 are retained in position by means of tie rods Ition. 2U which extend through the spacing elements and tie the upper and lower heads I4 and I5 which the scre‘en has a vertical arrangement. Y together. The spacing elements I9 extend through apertures 2l formed in the pulsating This means comprises yielding supports on which the screen rests and which are capable of yielding te' allow a slight downward movement ef the 45 screen during the downward movement of the pulsating plates and which provide for a corre plates I8. The pulsating plates are rigidly se cured to an axially-situated spindle 22 as in the above-mentioned patent. This spindle has two sets of radially-extending arms 23, each set of arms carrying one of the pulsating plates I8. The other pulsating plates are rigidly con nected to these two pulsating plates by means of tie rods 24 which extend through all of the 60 sponding upward movement' of the screen during the upward movement oi the pulsating plates, the movement of the screen in each direction, however, being less than that of the pulsating plates so that the required relativev movement pulsating plates and which tie together the top ` will be produced rbetween the pulsating plates and and bottom plates, and spacing elements 25 baille plates. In the construction herein shown through which the tie rods pass and which hold the screen is supported on a plurality of spherical the pulsating plates properly spaced. These spac , supporting elements 39 in the forniv of rubber balls ers 25 extend through openings formed in the which rest in seats 48 mounted onfthe lower cas- f baille plates I1 as described in the above-men ing head 4. The lower head I5‘of the screen is tioned patent. provided with seat members 4I having on their The lower end of the spindle 22 is mounted for axial reciprocation in a bearing 26 carried by the lower head I5, said bearing being supported in a hub s2 of a spider member integral with the head I5 and having radial arms 2'I, the space 65 between the arms forming the outlet passage I6. This spindle 22 is connected at its upper end to an eccentric 28 on a drive shaft 29 that is mounted in suitable bearings carried by the bear ing member 1. 'I’he eccentric 28 has the ‘usual eccentric strap 38 which is connected to the spin die 22 through the arms or links 3l. The shaft 29 may be driven in any suitable way and as herein shown power for .driving the shaft is furnished from a suitable motor 32 car ried on a bracket 33 secured to the bearing mem under faces spherical recesses to receive the balls 60 39. These seat members 4I _are shown as re tained in position by the tie rods 28, said tie rods being screw-threaded at their _upper ends into the upper screen head I4 and extending through the lower screen head I5 and being screw-threaded into the >seats 4I. The head I5 lis provided with a'tubular neck portion 42 which ñts within an opening formed in the lower casing head 4, said neck being capable of axial movement through 70 the opening. 43 indicates a bearing of Babbitt metal or other similar material to provide a tight slip joint and 44 indicates a ring of rubber or other yielding material which surrounds the neck 42 and is confined between the lower head 4 of the 75 3 2,122,475 casing and a shoulder 45 formed on the lower head I5 of the screen. 80 indicates a spring encircling the spindle 22 , situated between the hub 82 of the spider 21 and the hub 8l of the lower set of arms ‘23. This spring will preferably be under some compression when the pulsating plates are at the highest point in their travel and during each downward move ment of the spindle 22 said spring will be com 10 pressed somewhat. ` 'I’he upper head I4 of the screen carries a cushion member 4G of rubber which is shown as faced with a metal plate 41, the latter having bearing against the hub portion' of a rotating 15 runner-carrying member 48 by which lthe rotary runner above-referred to and presently to be described is supported. With this construction assuming that the ec ward movement of the pulp-pulsating plates the screen will have a slight downward movement and such downward movement ofthe screen‘wlll occur largely while the pulp-pulsating plates I8 are moving Amost rapidly at the middle portion of their stroke. As the operating eccentric 28 passes its low center and thepulp-pulsating plates begin to move upwardly, the pressure of the spring 80 will gradually be relaxed and the resiliency of the 10 rubber supports >39 will cause the screen and baille plates to move upwardly again during the upward movement of the pulp-pulsating plates. 'I'he spring 80, together -with the cushion member 46, serves to cushion the upward movement of 15 the screen. With this construction, therefore, the screen itself has an up-and-down movement along with centric 29 is on its upper dead center then the\ the up-and-down movement _of the pulp-pulsat 20 runner plates and baffle plates will have the rela tive position shown in full lines in Fig. "I, the pulsating plates being relatively close to the baffle plates above themy and at a maximum distance from the baille plates below them. ~As the pul 25 sating plates are moved downward by the eccen tric 28 the speed of downward movement in creases progressively from zero at the starting point to a maximum speed at the mid-stroke and then decreases progressively from the mid-stroke 30 to the lower end of the stroke. As the pulsating plates move downwardly the pulp between each pulsating plate and the baille plate below it is subjected to pressure tending to force the pulp outwardly through the screen and at the same 35 time a suction will be produced between each pul sating plate and the baille plate above it tending to draw the pulp inwardly through the screen. As each pulsating plate moves upwardly the pulp be Ltween it and the baffle plate immediately above 40 will be subjected to pressure, tending to lforce the pulp outwardly through the screen while a suc tion will be produced beneath each pulsating plate tending to draw the pulp inwardly through the screen, this being the same operation as that described in my above-mentioned Patent No. ing plates, although the amplitude of the move 20 ment of the screen and baille plates is less than that of the pulsating plates. This construction provides a relatively even relative movement be tween the pulp-pulsating plates and baille plates notwithstanding the simple harmonic movement of the pulp-pulsating plates. The screen-cleaning element which rotates about the exterior of the screen for keeping the latter clean is indicated generally at 49, and as stated above it is carried by a rotating disk or support 48. This support 48 is secured to the lower end of a sleeve 50 which extends through and has bearing in the bearing member 1 and is provided at its upper end with a worm` gear 5I which meshes with and is driven by a worm 52 on a shaft 53 that is mounted in suitable bear ings 54. This shaft 53 has a sprocket wheel 98 thereon which is connected by a sprocket chain 55 to a sprocket wheel 56 on the shaft 29, this construction being similar to that shown in my 40 above-mentioned patent. . The screen-cleaning element 49 is formed with a plurality of spirally-arranged runners 51, and it is divided vertically at 9I into separate units, any one of which is of a size to be removed 45 through the space provided when any one of the plates 9 is removed. Each section or unit of the With the construction herein‘illustrated dur ing the downward movement of the pulsating screen-cleaning element is made up of a plurality plates the downward pressure produced on the of runner sections 51 having an inclined or spiral arrangement shown in Figs. 3 and 8, the runner 50 50 baille plates through the medium of the pulp to gether with the pressure applied to the lower sections of any unit being _tied together by means head I5 of the screen through the spring 88 will - of tie rods 58. Each runner sectionA is formed with two bosses 59 through which the tie rods 58 cause the yielding supports 39 to yield downward ly, thus permitting the downward movement of extend and these bosses 59 are of sufiicient length the screen as a unit, as shown in Fig. 7, wherein so that they hold the runners properly spaced the full lines show the relative position of the from each other. The upper end of each tie rod pulsating plates and the baffle plates when the 58 is screw-threaded into the lower end of a nut pulsating plates are at the upper end of their 60 and the lower end of each tie rod screws into stroke, and the dotted line positions represent another nut 6I. The nuts 60 at the upper end of co4 the tie rods are detachably secured to the plate co, the position of the pulsating plates during their or disk 48 by’means of clamping screws 82. 83 downward movement and the corresponding po sition which the screen and the baille plates have indicates a ringwhich is clamped to the under due to the downward pressure thereon and the side of the lower nuts >IiI by means of clamping screws 84. , fact that the screen is yieldingly supported. The separate sections or units of the screen 65 As the pulp-pulsating plates I8 move down wardly from the full line position toward the cleaning element preferably have a circumfer » 2,003,150, dotted line position they subject the pulp be ential dimension `slightly less than that of any tween them and the baille plates below them to plate 9, and as herein shown the screen-cleaning pressure which istransmitted to the baffle plates. element is made up of live of such units. If it is necessary or desirable to remove any 70 This pressure not only causes the pulp to be _ unit of the screen-cleaning element this can be forced outwardly through the screen but cooper ates with the downward pressure against the easily done by removing one of the plates 9 and screen through the spring 8D to cause the resilient then backing off the screws 62 and 64 for said or yielding balls 39 to yield downwardly, as- shown unit until the screws are free from the nuts SII and 6I. When this has been done the unit can 75 in dotted lines, Fig. 7. Hence, during the down 4 2,122,475 be removed as a single structure because the runner sections 5l remain clamped together by the tie rods 58 and the nuts 60, 6|. This con struction facilitates the assernbly of the device as Well as any necessary repa1rs. The machine herein shown also provides means plitude of movement of the pulsating plates. When the desired adjustment has been effected the clamping bolt 69- is tightened thereby clamp ing- the sleeve 65 to the shaft 29 in its adjusted position.. The fact that the clamping bolt 69 is accessible from the end of the shaft facilitates by which the amplitude of vibrating movement -greatly'the operation of making the desired ad of the pulsating plates I8 can be Varied, this justment in the eccentric. being accomplished by varying the eccentricity of I claim. ' 10 the operating eccentric 28. The eccentric 28 is a double eccentric having the two eccentric por tions and two eccentric straps 30, as shown in Fig. 4, 4each eccentric strap being connected through a link 3| to the spindle 22. These ec 15 centrics 28 are formed on a sleeve 65 which is mounted for rotation on an eccentric portion 66 of the shaft 29 and is adapted to be clamped to 1. A pulp screen comprising a casing having 10 .an intake for unscreened pulp and an outlet for screened pulp, a vertical screen situated between -the inlet and outlet and through which the pulp flows, said screen having baille plates extending therefrom, pulp-pulsating plates situated between the baille plates, means to move the pulsating plates toward and from the baille plates, thereby said shaft in different angular positions.- The- causing the pulp to be forced back and forthv shaft 29 is a divided shaft and comprises the sec-`“ through the screen as it flows from the inlet to 'the outlet, and a support for the screen yieldable 20 and the section 29h to which the sprocket wheel `in the direction of movement of the pulsating 56 is secured, the division between the sections plates.' being wtihin the eccentric sleeve 65 so that the 2. A pulp screen comprising a casing having an eccentric portion 66 of the shaft is formed partly intake for unscreened pulp and an outlet for 25 on the section 29a and partly on the section 29h. screened pulp, a screen situated between the in 20 tion 29a to which the driving pulley- 36 is secured The’two sections 29a, 29h are coupled together to rotate as a unit through the medium of a coupling member 6l which is received in slots 98 formed in the adjacent ends of the two shaft 30 sections. Means are provided which are accessible from the end of the shaft for clamping the eccentric sleeve 65 to the shaft or unclamplng said sleeve from the shaft whenever it is desirable to adjust 35 it to change the amplitude of vibration of the pul sating plates. This eccentric sleeve 65 is confined between two flanges 68 formed on the two shaft sections 29a, 29h and the shaft section 29D has a clamping bolt 69 extending axially thereof which 40 extends through the coupling member 61 and screws-into the end of the shaft section 29lb as 'shown at 10. The shaft sections are spaced slightly from each other at the adjacent ends and the coupling member 61 is of a size to permit a 45 slight movement of the shaft sections toward each other. When the clamping bolt 69 is tightened the two shaft sections are drawn toward each other thereby clamping the eccentric sleeve 65 firmly between the flanges 68. W'hen the two ec centrics 28 and 66 are adjusted so that the eccen tricity of each is on the same side of the axial line of the shaft, as shown in Figs. 5 and 8, then the amplitude of movement of the pulsating plates will be that given by` the two eccentrics combined. On the other hand, if the two ec centrics 28 and 66 are adjusted so that they op pose each other then the amplitude of movement of the pulsating plates will be that resulting from the difference between the throws of the two ec centrics, and if the two eccentrics have the same throw then by adjusting them so that they op pose each other the rotation of the shaft 29 will produce no vertical movement in the spindle 22. Whenever it is ‘desired to make an adjustment in 65 the amplitude of movement of the pulsating plates the clamping bolt 69 is lbacked off suiil ciently to relieve the clamping pressure on the eccentric sleeve 65 and the operator then turns the shaft 29 through the medium of the wheel 16. The friction of the eccentric straps 30 on the eccentrics 28 will hold the latter from turning with tho shaft 29 after the eccentric sleeve 65 has been unclamped so that by turning the shaft 29 the two eccentrics can be adjusted into any 75 desirable relative position to give the desired am let and outlet and through which the pulp flows, said screen having baille plates extending there from, pulp-pulsating plates situated between the baille plates, means to move the pulsating plates' toward and from the baille plates, thereby caus ing the pulp to be forced back and forth through the screen as it flows from the inlet to the outlet, and resilient support for the screen yieldable in the direction> of movement of plates. the pulsating : 3. A pulp screen comprising a casing having an intake for unscreened pulp and a screened pulp outlet, a screen situated between the inlet and outlet, said screen having baille plates ex tending therefrom on the delivery side thereof, 40 pulp-pulsating plates situated between the baf ile plates, means to move the pulsating plates to ward and from the baille plates, thereby caus ing `the pulp to be forced back and forth through the screen as it flows from the inlet to the outlet, 45 said screen being movable in the direction of movement of ‘the pulsating plates, and resilient means to resist such movement of the-screen. 4. A pulp screenv comprising a casing having a pulp inlet and a screened-pulp outlet, a screen situated between the inlet and outlet, baille plates rigid with the screen, pulp-pulsating plates sit uated between the baille plates,`means to move the pulsating plates toward and from the baille plates, thereby causing the pulp to be forced back and 55 forth through the screen as it flows from the inlet to the outlet, and means for supporting the screen which permits it to have a limited move ment in the direction of- movement of the pul sating plates. 5. A pulp screen comprising a casing having a pulp inlet and a screened-pulp outlet, a screen situated between the inlet and outlet, baille plates rigid with the screen and extending therefrom, pulp~pulsat-ing plates situated between the baille 65 plates, means to move the pulp-pulsating plates toward and from the baille plates, thereby caus ing’the pulp to be forced back and forth through the screen as it ñows from the inlet to the outlet, and a support for the screen yieldable in the di 70 rection ofthe movement of the pulsating plates. 6. A pulp screen comprising a casing having a pulp intake and a screened-pulp outlet _a cylin drical screen within the casing, baille plates rigid with the screen and situated on the delivery side 75 ES` 2,122,475 thereof, pulp-pulsating plates situated between cleaning velement being divided in a, plurality of the baille plates, means to vibrate the pulsating ' places along lines -substantially parallel to the plates toward and from the baille plates, and tie rods of the cylindrical screen thereby to form yielding means supporting the screen and per separate screen sections, there being atleast one mitting limited movement thereof in the direc of said tie rods in each section, a rotary support tion of vibration of the‘pulp-pulsating plates. ing member coaxial with the screen at one end '7. A pulp screen comprising a.A casing having a thereof, means to rotate said member, and means pulp inlet and a screened-pulp outlet, a contin for independently attaching each section of'the uous-walled screen within the casing through screen-cleaning element to said supporting mem which the pulp ñows inwardly, baille plates rigid ber. ly secured to the screen on the inside thereof, 13. A pulp screen comprising a casing having pulp-pulsating plates between the baille plates, an inlet and an outlet, a cylindrical screen means to vibrate the pulp-pulsating plates to ward and from the baille plates, and yielding screen-supporting means permitting yielding through which the pulp flows inwardly, a rotary screen-cleaning element encircling the screen, movement of the screen in the direction of move ment of the pulp-pulsating plates. said element comprising a plurality of runners spiralling about the screen, each runner having a plurality of apertured bosses, tie rods extend 8. A pulp screen comprising a casing having a ing through said bosses and rigidly connecting pulp inlet and a screened-pulp outlet, a screen the runners, nuts screw-threaded to the ends of 20 within the casinghaving a vertical screening -each tie rod and by which the runners are 20 wall, baffle plates rigidly secured to the screen on the delivery side thereof, pulp-pulsating plates situated between the baflle plates, means to vibrate the pulp-pulsating plates in a/vertlcal 25 direction, and a vertically-yielding support for the screen. 9. A pulp screen comprising a casing having an intake for unscreened pulp and an outlet `for screened pulp, la screen situated between the in 30 let and outlet and through which the pulp flows, said screen having baille plates extending there from, pulp-pulsating plates situated between the baille plates, means to move the pulp-pulsating plates toward and from the baille plates, thereby causing the pulp to be forced back and forth through the screen as it flows from the inlet to the outlet, a yielding support for the screen and a spring interposed between said screen and the pulp-pulsating plates and resisting relative move 40 ment in one direction between said plates and screen. clamped together, a rotary supporting member coaxial with the screen, and bolts carried by said supporting member and screw-threaded into the nutsat one end of the screen-cleaning element thereby securing said element to said supporting 25 member. . 14. A pulp screen comprising a casing having an inlet and an outlet, a cylindrical screen through which the pulp flows inwardly, a rotary screen-cleaning element encircling the screen, 30 said element comprising a plurality of runners spiralling about the screen, the runners having apertured bosses by which they are spaced from each runner, tie rods extending through said bosses, clamping nuts screw-threaded to the ends of the tie rods, said screen-cleaning element be ing divided longitudinally of the screen in a plu rality of places, a rotary supporting member co axial with the screen, and bolts carried by said member and having screw-threaded engagement 40 with the clamping nuts at one end of the screen 10. A pulp screen comprising a casing having cleaning element, whereby each section of the a pulp inlet and a screened-pulp outlet, a screen screen-cleaning element can be removed from the within the casing having a vertical screening supporting element independently. 45 wall, baille' plates rigidly secured to the screen on the delivery side thereof, pulp-pulsating plates 15. A pulp screen comprising acasing having 45 an inlet and an outlet, a cylindrical ‘ screen situated between the baille plates, means to vi brate the pulp-pulsating plates in a vertical di through which the pulp'flows inwardly, a rotary screen-cleaning element encircling the screen, rection, a vertically-yielding support vfor the ' said element comprising a plurality of parallel 50 screen, and a spring interposed between the screen and the pulp-pulsating plates and resist ing downward movement of said plates relative to the screen. 11. A pulp screen comprising a casing having 55 an inlet and an outlet, a cylindrical screen through which the pulp flows inwardly, a rotary screen-cleaning element encircling the screen, runners spiralling about the screen, each runner being divided into a plurality of separate sec tions with the ends of the sections of any runner lined up with the ends of the corresponding- sec tions of the other runners along lines extending substantially parallel to the axis of the screen 55 cleaning element, means for rigidly connecting together the corresponding runner sections of all said element comprising a plurality of runners spiralling about the screen, each runner having a plurality of spacing bosses which are in line with and engage corresponding bosses on the adjacent runners, said connected corresponding runner sections forming separable sections of the screen- . runners, tie rods extending through the alined bosses and clamping the runners together, a ro means for separately and detachably securing each section of the screen-cleaning element to tary supporting member coaxial with the screen Asaid rotary supporting member. 65 at one end thereof, and means to secure said runner element to said supporting member. 12. A pulp screen comprising a casing having an inlet and an outlet, a cylindrical screen be tween the inlet and outlet and through which 70 the pulp ñows inwardly, a rotary screen-cleaning element encircling the screen, said element com prising a plurality of runners spiralling about the screen, tie 'rods extending parallel to the axis of the screen-cleaning element and rigidly 75 connecting the runners together, said screen cleaning element, a rotary supporting member 60 coaxial with the screen at one end thereof, and 16. A pulp screen comprising a casing having 65 a pulp intake and a screened-pulp‘outlet, a cy lindrical screen within the casing, baille plates ` rigid >with the screen and situated on the delivery ` side thereof, pulp-pulsating plates situated be tween the baille plates, means to vibrate the pul 70 sating plates toward and from the baille plates, and yielding means supporting the screen and permitting limited movement thereof in the. di rection of vibration of the pulp-pulsating plates but of less amplitude than that of said plates. 75 v6 l 2,122,475 17. A pulp screen comprising a casing having an inlet and an outlet, a. cylindrical screen within said casing through which the pulp flows inward ly, a rotary;V screen-cleaning element encircling the?rscreen, said element comprising a plurality of parallel runners spiralling Vabout the screen, each runner being divided into a plurality of separate sections with the ends of the sections of any run ner lined up with the ends ¿of the corresponding 10, sections of the other runners along lines extend ing substantially parallel to the axis of the screen cleaning element, means for rigidly connecting together the corresponding runner sections of all the runners, each set of connected-together run ner sectidns forming a separable section of the screen-cleaning element, a rotary supporting member coaxial with the screen atrone endfthere of, an annular member at the other end ?of the screen, and means for separately and detachably securing each separable ¿section of the screen cleaning elementi to both the rotary supporting member and saldgannularfmembera 10 NELSON M. KNIGHT.