US2259058A - Mixing mill - Google Patents

Description

R. w. ALLEN Oct. 14, 1941` MIXING MILL l Filed Sept.l 29, 1959 4 Shee'bS--Sl'xeeiI 1 s Y E N R O T T A R'. w. ALLEN MIXING MIL'L Oct. 14, 1941.

Filed Sept. 29, 1939 4 Sheets-Shee'kl 2 ATTORNEYS R. W. ALLEN MIXING MILL Oct. 14, 1941.

4 Sheets-Sheet 3 Filed Sept. 29, 1939 llll INVEN-ro @7mo/VD W. LL EN E Il. lll

Oct. 14, 1941. I l R. w. ALLEN y 2,259,058

' MIXING MILL Y Filed Sept. 29, 1959 4 Sheets-Sheet 4 RIGHT END LEFT 54m/85 swI-rcH ATTORNEYS /05 f Patented Oct. 14, 1941 U NI TE D! This invention relates to mixing millsor'stli mixing or warming ofplastic; materia1::.suchras.- rubber composition-:and more ,especially it 're-1.r4 lates to' automaticallyV operating millswhereinia 1 blade moving relativelyiofbnef: theimill-frolls 5 eiects the strippingg'ofi a .sheet 4of.p1asti'c :magA terial therefrom andthefeedin'g oft'th'e-f strippedfa' material back into the biteofJthe rollsxwherebyV optimum mixing-.or Warmingof; the plastic lcomA positionvis eiected.

In apparatus of .the charactenmentioned; ase` heretofore provided', the blade: has been. moved f? into and out of engagementmith .the-'mill roil.v by-means of a fluid pressureioperated, cylinderf the latter being mountedrupon. a Vcarriages.that15 has a reciprocatory movementlongitudinally off the ymill roll, 1 a Vreversible electric: motornb'eingi; employed for moving :the carriage.; Reversing: switches Vat the ends of the:carriagestraverse:

and" Valve-operating;Y mechanisms .-usu'ally were positioned Yalong the course of 'the' i carriage for: operating the fluid' pressure Acylinder? carried thereby.

Videfan improvedrmixing: mill ibi the :character mentioned wherein; the 'use of .uid vpressure1oper^"Y -v ated cylinders is obviated;. tonnobviate the use of aplurality of valves such aszarernecessary;withf:

motor driven-means for efEe'cting.;th'e:-.raising andff lowering ofthe scraperbladeiofithemillito prof-L vide. means i for yieldingly applying: thescrap'ev blade to a mill roll; and to provide automatically* Figure 7 'isga VdiagrammaticLview. showingfthel course.ofithescraper;:b1a:deL

Figuresz; '9,';and loare idetail"elevations-eta pair Lof zswit'ches; and theirs operating.; means, as viewedfrom theline ofFigurei, 1in various;

phasesaof a cycleeof operation-of the^fapparatusand g' l Riguresfll; l2; 13, and V14'aredetail elevations,

of anotherl'fswitchfand lits operatinggzmeans; as f viewed 4:from the leftofrFigures 1; and 4; shown@v in :differentl phases of: a. cycle ,of pperation-ofz-the apparatusa;

Referring now to the drawings, especially Figuresl and.; 2` there0f',1ther e-is shown' fa Vfrubber'h working:millfjcomprising;endgf'framesfl 0, I U: in;- which are@y journaledc-[a vpair rof :-laterally ,disp osed horizontal' ro-11s 1I I; i I 2, that lare: geared :together f and :driven in: unisonzbygthe usual :drivingfmeans (notishowmr The rolls ;II,` I2-are adapted. to-` usuauy were provided for:l reversing;'1;hem0t;4;)r;V 20 'fornrrav sheet orsleeve I3 of plasticrcompositionj from a: rbank' LI 4 "offsuchf composition that is 'fed intoth'e -bite-between'said rolls, ,the-sheetIS be` I ing: shojwuh'ereiny asaform'edgon the front-roll'. lI 2-.

Asshown, the millfis :associatedi'with a=super The chief objects of the; invention arestocpro:` 2! posed;B8Jnbury='miXerfofwell'knownconstrucf tion V:wherein the l,various-constituent ingredients roff agbatch of-` rubber composition initiallygareras-,I

sembled and coo-mingled; the arrangement being; such thatthe batchfmaygbedischarged-from the uidl pressure Operated papparatus;gxtoi provide'ifibottom offtheBanbury3 'and-olirectly; receivedinl which :is designatedas-a -whole by' the;numeral I d0, comprises respective hollow endfhousings .I 5; I 5A that; are fsuperposed upony the respective end operated switch means for operating. theelectri'c-- Sgwframesil of the -mi11.- Of course,11;he fqgalnlmlryy allyrdriven mechanism of. the' apparatus 1in dei-1 terminate time sequence.v Otheri objects will Ibex-- manifest as the description'proceeds;hv

Of the yaccompanying drawings:

Figure 1 is a front elevation of. apparatus em'- 40 bodying the invention, .parts'bei-ng broken 'away' to reveal underlying mechanisms;` Figure 2 is a section, onta largerisca-le, on the line' 2-2 of Figure l, some parts beingshownfzirrf elevation; l v

Figure 3 is a sectionronfthelinei\3-3 rof Figl-L ure 2; I

Figure 4 is a sectional detail :ViewA On'th'elme' 4-#4 ofl Figures 1 and 6,parts b'eingshown in;`

elevation;

Figure 5 is a fragmentary sectional View on the. line 5--5 of Figure 6;

Figure 6 is Van end elevationmof the-.electric switchesV and their operating mechanism as viewed from the left ofjFiguresl and 4;-,

portion ,ofi the; milli rmay';be'omitted,if :desired:

Mounted uponA the confronting-2 walls,` Lof.: the. end housings `I 5,' I 5,.' .finteriorly .of the v'said :end L housingsrf'are bearinglplates- I8; lgtheiforme-r being inJ-the.end-housingw at the-left end-of, themill as---viewed in Figure l,A and-the-latter: beingJV in the end' housing -at the right end lof" the/mill.y

The r-wallA of' each housing Istructure'y I 5; backof- `the bearing plates I 8,1" I 9,;isV apertured to receive a pair 4of vertically'aligned-g annular, 'apertured sockets 20; 2IJl that.' are Vformecllonthe` rearv face.

of each'bearing-plate, the sockets-Ici one bearing plate -being` axially; aligned. with the sockets L off 1 50. the,.other. 4. Received .-in. :said f socketsf.. 2 0 yare the.

reducedvend Vportions offra 'pair of-.parallel;'horizontal guide barsor shafts 2 I, 2I,'saidguidebarsbeing-4 disposed in fthe same, verticalplane above f Threaded through the nut 40 is a feed screw 59, the same having threads thereon for about twothirds the distance from its upper end, the lower third of the screw being smooth, there being a flange 5| formed at the juncture of the threaded and the smooth portions, said smooth portion projecting through the open lower end 0f the carriage structure. The arrangement is such that rotation of the nut 40 will cause the feed screw 50 to move axially up or down according to the direction of rotation of the nut, the hollow extension 31 of the upper housing 36 receiving the through suitable apertures in confronting walls of the end housings I5, the left end of the feed screw being journaled in a bearing25, Figure 4, carried by the bearing plate IB. end of the screw 24 is journaled in a suitable bearing carried by the bearing plate I9, and has a terminal portion that projects beyond said bearing and is provided with a gear 26 thereon. The latter is in mesh with a pinion 21 mounted upon the shaft of a reversible motor 28, Which motor is supported upon a bracket 29 afxed to the bearing plate I9. The ratio of the pinion 21 to the gear 26 may be varied to obtain the desired mixing speed, or the motor 28 may be of variable speed. Access to the motor 28 is had through an aperture 30 in the outer wall of the housing I5, which aperture is provided with a cover plate 3|. The motor 28 is driven alternately in opposite directions, and control means for reversing the direction of rotation of the motor presently will be described.

The carriage 22 is a hollow structure comprising a rearwardly disposed bearing bracket portion 33 that engages the slide bars 2 I, and a transversely arcuate cover plate 34 on the front thereof. The structure is open at top and bottom, and mounted in its upper opening is a lower housing 35, and mounted upon the latter is an upper housing 36, the latter being formed with a tubular l axial extension 31 that extends upwardly and is closed at its-upper end. The lower housing 35 carries an axially disposed bearing 38 and the upper housing 36 carries an axially disposed bearing 39, said bearings rotatably supporting a nut 49 by engagement with opposite end portions thereof. Mounted upon the exterior of the nut The right hand- 4D is a gear 4I that is meshed with a pinion 42, Y

the latter being mounted upon the lower end of the shaft 43 of a motor 44. Said motor is supported upon the tubular extension 31 of upper housing 36, the shaft 43 extending through said housing. The motor 44 is reversible, and is supplied with electric current through a three-conductor cable 45 that extends from said motor to a trolley collector 46 that is supported upon the carriage 22, directly above the upper guide bar 2|. Said trolley collector is positioned within a trolley duct 41 that is mounted upon the bottom of the Banbury structure I4, said duct being open at the bottom to enable the collector 46 to move longitudinally thereof. The trolley collector and duct are of well-known construction, and are arranged to supply electric current to the three conductors of cable 45 at all positions of the carriage 22. Control means for reversing the direction of rotation ofthe motor 44 according to the position of the lcarriage in its traverse of the mill is included in the circuit of motor 44 and presently will be described. The said motor circuit also includes :a torque-limit relay (not shown) that serves to disconnect the electric current thereto when the drivingtorque exceeds a determinate maximum limit.

screw when it is moved upwardly. Formed in the bracket portion 33 of the carriage, along the parting plane thereof and its cover 34, are oppositely disposed, parallelslideways 52, 52, Figure 3, in which a slide 53 is mounted for sliding movement parallel to the screw 50. The slide 53 is mostly of transversely arcuate shape so as to extend about the screw 50 in spaced relation thereto, but intermediate the upper and lower ends of the slide there is formed a forwardly projecting ledge or shelf 54 through which the smooth lower end portion of the screw extends, there being a bushing 55 in said shelf about the screw to reduce friction as the slide and screw move relatively of each other. Mounted upon the smooth end portion of the screw 50 in abutting relation to the flange 5I is a collar 56, and mounted upon said screw between said collar and the ledge 54 of the slide 1s a compression spring 51, the latter being encased at its lower portion in a protective sleeve 58. Mounted upon the front of the slide 53 at the lower end thereof is a blade holder 59 that has limited adjustability in an up and down direction, the upper margin of said holder abutting a pair of set screws 6U, 69, Figure 1, that are threaded into the overhanging ledge 54, and which assist 1n retaining the holder in adjusted position against pressures to which it is subjected during use. A scraper blade 6| is secured to the front face of the holder '59, the lower margin of said blade constituting a cutting edge that extends below the bottom of said holder, in position for engagement with the mill roll I2. The blade holder '59 is formed with a central slot 62 extending downwardly from its upper margin, and the holder 53 is recessed behind said slot, as shown 1n Figure 1, to receive a slide block 63 that is mounted upon the lower end of screw 50, said block being slidable in said slot 62 and in said recess behind the same. The end of screw 5D is squared to receive said slide block, the arrangement being such that rotation of said screw is prevented, yet axial movement of the screw relatively of the slide is permitted. Thus downward movement of the screw 50 also moves the slide 53 downwardly until the blade 6| engages the mill roll l2, further downward move ment of the screw before stopping resulting in compression of the spring 51. The latter assures more even pressure of the blade against the mill roll notwithstanding unevenness of the surface of said roll. It also serves to increase the driving torque of the motor 44, which torque ultimately effects the automatic stopping of the motor.

As previously stated, the reversible motor 28, by driving the screw 24 alternately in opposite directions, impels the carriage 22 back and forth longitudinally of the mill rolls II, |2, and the reversible motor 44, by alternately driving the nut 40 in opposite directions, raises and lowers the screw 50 and with it the scraper blade 6|. These operations are effected in determinate time relation and impart to the scraper blade a compound movement that causes it to traverse a course that is diagrammatically illustrated in Figure 7. From this figure it will be apparent that as the movement, of the blade carries it toward the end of the roll, it is lifted from the roll for a brief interval, vand then lowered `into engagement with the roll before the end of the latteris reached. Upon reaching theend of the roll the direction ofv lateral travel of the blade is reversed andl it moves; toward the opposite end of the roll while still engaged therewith, and upon approaching the opposite end ofA the roll is again lifted oif the roll and again lowered into engagement therewith, in the same manner as previously described. When the blade 6| is moved toward the roll |2, near the end of the roll, itforces and cuts its way through the sheet of material I3 thereon.' IThen as its direction of lateralf movement is reversed and it moves toward the oppositeend `of the roll it forces its way through 'the sheet I3 and piles it up somewhat at its leading edge, as is best shown in Figure 1, and lays the stripped material in convolutions or folds that are disposed' obliquely of the roll. When the blade'subsequently rises, the fold ofstripp'ed material passes substantially lengthwise into the bite of rolls |I, I2 whereby intimate mixing and warmingof the ingredients thereof is effected. ,Y

The mechanism for controlling the driving of the motors 28, 44, and for reversing the direction of-vtheirr drivein determinate time relation is shown-in` detail'in Figures 4 to 14, to which attention now is directed. Mounted upon the bearing plate I8, at the left end of the apparatus is a closed gear case 6,5into which` the terminal portion of lthe feed `screw 24 extends, said terminal portion having'a gear worm 66 mounted thereon. The worm 66 is meshed with a worm gear 61 that is'mounted upon one end of a countershaft63, the latter being disposed transversely of the axis of worm 66, and journaled in the opposite lateral walls of the vgear case 65. Mounted yupon the shaft 68 near the middle thereof is a gear worm 69 that is meshed with a worm gear 10, the latter being mounted upon a cam shaft 1|. The said cam shaft is disposed parallel to the feed screw 24, and is journaled at onevend. in a bearing 12 in bearing plate I8, and is journaled in its medial region in a bearing-13 that is mounted in the wall of gear case 65, saidcam shaft extending through Athe latter and having a substantial portion of its structure projecting therefrom.

Keyed to the projecting end portion of the shaft 1I,V exteriorly of the gear case, is a hub structure 15 that is formed with a radially extending circumferential flange 16. Secured to the inner end face ofthe hub 15 by means of a pair `of clap screws 11, 11 is a cam plate 18, said screws vpassing through respective arcuate slots 19,A 19inthe camplate to enable the latter to be adjusted angularly, relatively of said hub. Mounted upon the front face of cam plate 18 is a cam 39, and mounted upon the rear face thereof is a cam 6|, both of said cams projecting beyond the periphery of the cam plate. `Said cams as shown are positioned upon centers that are substantially 90270 apart from each other,` but one of themis ladjustably mounted so that the said angle may be altered to a limited extent.

The gear case 651s formed integrally with a bracket 84 that is disposed above the cam shaft 1|, and whichcarries two electric switches that are'in 'the electrical circuit of the reversible 4motor 28 1 and Aserve'. to reverse the latter as said switches `are `operated inV alternation; Said switches are of any known or desired Vconstruction comprising` two make and two break contacts A(not shown) and are enclosed in suitable receptac1es-85, 86the switch in the former re` versing thermotor 28l when the carriage 22 isat the lright end of the screw 2 4 Vand the switch in receptacle 86 reversingI the motor when the car.-Y riage fis `at the voppositeend of the screw. The switch is provided with an operating plunger 81 that is engaged with an operating lever188 having acam 'roller B9 in its free end, said cam roller being disposedvin the orbit of the front cam In like manner the switch 86 is provided with an operating plunger 90 that is engagedwith anY operating lever 9| having a cam rollerv92 in its free end, which cam roller is disposed in the orbit of the rear cam 8|. The cam rollers 89, 92 are disposed substantially 26 apart with relation to the axis of camshaft 1|, and this dista-nceadded tothe 270 separation of cams 80, 8| makes an angle of 296 through which the cam shaft'is required to rotate during each halfcycle of operation, -that is, in moving from the position shown in Figure 9 to the position shown injFigure l0 vfor example, during which halfcycle the ucarriage 22-moves from one end of its traverse to the other. This `result is accom: plished bylthe worm gears 66, 61 and 69, 10 which provide a.2 50 to l reduction between the feed screw 24 andV thecountershaft 1|, the pitch of the threads Lof screw 24 being suchv as to impel the carriage 22 substantially throughout the l length of its threaded portion while the counter:

and lower scraperblade 6| at determinate regions of the-carriagers traverse, and to this end an annular cam plate 95 is mounted upon the hub 15 and `secured to the outer fa'ce of its flange 16 by cap screws 96 that extend through an. arcuate slotl 91 in said hub flange to provide angular adjustability of said cam plate. Projecting laterally from the outer face of cam plate 95 is a driving stud 98 that projects through an arcuate slot 99 formed in a disc cam |00, the latter being` journaled upon a bearing I0| on the terminal end of the countershaft 1|. The slot 99 is concentric with the axis of said countershaft and is in length. The stud 98 is received in one of a plurality of arcuately positioned holes 95a in the cam plate 95 (Figures 11-14). Diametrically opposite the middle of slot 99 the periphery of the cam |00 is formed with a recessed or depressed cam surface ||0. Below the cam shaft 1| on the gear case 65 an integral bracket |02 is formed', which Ybracket carries a receptacle or switch box |03 in which is contained an electric switch (not shown) that is in the electrical circuit of the reversible motor 44. The switch is provided with an operating plunger |04 that is engaged with anv operating lever |05 having a cam roller |06 journaled in its free end, said cam roller being disposed in vertical alignment with the cam shaft 1|, and urged upwardly against the periphery of cam |00; The` switch in. receptacle |03 is known` as the verticalmovement switch, and is soconstructed and arranged that when` the plunger |04 is `out or raised, as shown in the drawings, the motor lUllrotates in the directionthatelevates the scraper blade 6|, and when-the said plunger is in or is-depressed the motor rotates in the opposite directionV so as to-lower the scraper blade, rotation of the motor in either direction continung until the torquein the motor is sufficient to operate the torque-limit relay, whereupon rotation ceases. When theV cam is. so angularly positioned that the cam roller` |06 is on the depressed cam surface ||0 thereof, the plunger |04 is in elevated position andthe motor t4V is caused to rotate in the direction that raises the blade 6|. The length of the cam surface ||01is such that the plunger |04 remains in elevated position -while the cam |00 rotates through an angle of 43, the time interval during which said plunger is raised being suicient for the-motor 44 to raise the blade 6| to maximum height and to stop. The torque that effects the stopping of motor 44, as the scraper blade israised, is created by the compression of spring 5l after the collar 55 on screw 50 engages the lower end of lower housing 35.

As previously stated, the cam shaft v|| oscillates through an angle of-substantially 296, as does the hub 1.5 keyed thereto. Thus the stud 98 projecting from the flange of said hub and through slot 99 of cam |00 is adapted to oscillate the latter, but to a lesser degree, namely 156 (296 minus 140.)fthe cam surface IIO -being in the medial region of the 156 of cam surface that. engages the cam roller |06- during such oscillation. At the opposite ends of cam surface I I0 are respective cam surfacesfl I I, IAI2 of greater radial extent than depression IIO, said cam sur-l compressed, by the torque-limitv relay as prey viously explained.. rIhe camsurfaces ||Il, I|2 are ofV relatively short linearv extent, andcontiguous with them are respective shallow depres-V sions or relieved portions H3, 4 in the periphery of the cam |00. The-surfaces |I0to ||4 inclusive constituteabout 165 of the total periphery of .the cam, which, as previously stated,A oscillates through an. angle of 1569. When the cam is in such angular position that cam roller |0t is engaged with surfaces I I3 or -I thereof, the

switchv plunger |04 vis slightlyrraised from its fully depressed position, but not suciently to effect driving of the motor to elevate-the scraper blade. Thus there are shoulders'formed onthe cam at the juncture of surfaces II-I, |13'` and H2, |I4 which shoulders readilypassthecarn roller |06: when the cam isy positively driven by the stud 98; 1f, however, due to inaccurate fitting or other cause, there'is suicient -friction between the stud 98 and theV marginal "faces of slot 99 to cause the stud to drive -thecam before the stud has reached the end of vthes1ot,the resistance set up by engagement of the caniroller |08 with one of the shoulders aforesaid will be sufficient to overcome said friction and thereby to prevent further rotation of the cam until-the stud reaches the end of slot 99;'.

In the operationV of the apparatusfthe. millY rolls I I', I2 are set in Ymotion.in;the. .usuallmanner, and a bank of rubber.v composition I4 is fed.

into the `bite of said rolls to effect the forming of a sheet or sleeve I3 of the composition upon the roll |2.` Motor 28-'is then set in motionito operate the carriage 22, `the succeeding operations being-automatically-effected and the apparatus requiring no further attention. As the rubber composition becomes thoroughlymixed and warmed, portions of the sleeve I3 are cut therefrom for use in other rubber working apparatus, and as the bank of stock I4 becomes depleted,ladditional material is thrown into the bite of the rolls.

As the motor 28 rotates, the carriage 22 moves toward one end of the screw 24', .then reverses its direction and'moves toward the opposite end thereof, the blade 6| rising and descending at determinater pointsA along thetraverse of the carriage. YThe fcoursaof. the `blade `6| is =best shownin Figure 7, the arrows indicating the direction of its travel. When the cam plate 'IB is rotating in counterclockwise direction and is in the angular position shownI in Figure 8, the blade GI is at point A (Figure "7) of its course, bearing against roll I2 and moving toward the right. At thi'stirne cam |00 is 'in the position-shown in Figure 1l, the stud 98 already having moved this cam through 8,1the-c'amvroller |06 still being in depression I I4 of this cam. Continuing rotation of cam |00 in counterclockwise direction brings roller |08 onto cam surface I |70-when the scraper blade I is at point B, Figuref7,-of its traverse, with the result the switch plunger |04 rises and the switch r|03 is operatedto drive motor 44 in the direction that raises the scraper blade, rotation of the Vmotor stopping when the blade is fully elevated. The blade continues to move laterally while in elevated position, and while the cam roller is stillengaged with cam surface |I0, the position of the latter and said cam roller as shown in Figure l2 corresponding to point C of Figure '7. Continued rotation of cam |00 in counterclockwise direction from the position shown in Figure 12 carries cam surface ||0 beyond rollerA |06, therlatter then engaging cam surface II-I Vwhich effectsthedepressing of plunger |04 andthe reversing of the position of switch |03, with the result that motor 44 is set in motion in the direction that lowers scraper blade 6|-, After the `blade engages the mill roll I2, themotor 44! again ceases rotating, the blade being at the position shown at D, Figure '7, and the cam |00 being substantially at the position shown in Figure 13, with cam roller |06 4engaging cam surface II3. 'I'he carriage 22 continues to move to the right a short distance, until cam onlcam plate 'I8 engages and operates switch 85,V as shown in Figure 9, thus reversing the motor 28, the `position of the carriage 22 at this time being indicated at E, Figure 7. The movement of the carriage 22 toward the ends of its traverse may be cushionedby means of compression springs I I8, I 6 mounted upon the screw 24 at the opposite ends of its threaded portion, said springs also assisting the motor in initiating the reverse movement of the carriage.

Reversing of the motor 28 turns the screw 24 inthe direction that impels the carriage 22 toward the left, and also reverses the direction of rotation of cam shaft 1| so that the latter, and cam plate' 'I8 and the stud 98 then move in a clockwise direction. Stud88 moves in the slot 99, relatively of cam 00, for and engages saidcam just before the blade 6| reaches point F of its traverse, the position `of cam f |00 when the blade is at point F'being shown -in Figure 13,

The movementsof the blade '6| at the leftlendv of the machine are' the same as those previously described atv the right end of the machineand at points G, H, I, and 5J; Figure v'7, the-'blade follows a course identicaltolthe course followed at points B to E, inclusive. When the blade is'at point H, the cam is substantially at the position shown in Figure 14 and moving in the direction indicated by the arrow. When the blade reaches point J, cam 8| will have moved to the positionwhere it engages cam roller 92, as shown in Figure 10, to operate switch 8E and thus to reverse the motor 28 and thereby to move the carriage 22, in reverse direction, back to position A, the point of starting.

This completes a cycle of operation, which is continuous and automatic as long as motor 28 is in operation. The apparatus is superior in performance to similar apparatus of prior construction chiefly because its mechanisms are entirely electrically operated, thus obviating the use of iiuid pressure operated devices. The use of a torque-limit relay for stopping rotation of motor 44 obviates the use of other stop switches and braking means, and the single spring l is utilized to provide the torque for stopping the motor when rotating in either direction.

Note that the movement, or course of the blade 6| can readily be varied. This is done by removing the nut holding the cam |00 on the shaft 1| and then inserting another pin in another hole 95a in the cam plate 95 whereby the permitted relative movement of the cam plate 18 and the cam |00 is changed and the vertical movement of the blade 6| is varied relative to its horizontal position on the mill. Another manner in which the movement of the blade 6| can be changed is to substitute a different cam for the cam |00 with the new cam having a different length arcuate slot and/or different length cam surfaces formed thereon whereby the vertical movement of the blade 6| relative to its transverse position on the mill could be varied.

Modification may be resorted to without departing from the spirit of the invention, or the scope thereof as defined by the appended claims.

What is claimed is:

1. In a mill of the character described, the combination of a scraper blade engageable with one of the mill rolls, a reversible feed screw having operative connection with the said blade for impelling it edgewise back and forth along the mill roll, a cam shaft, means for oscillating the latter through the agency of the reverse rotation of the feed screw, a second feed screw having operative connection with the scraper blade for raising and lowering it relatively of the mill roll, a reversible electric motor driving said second feed screw, a reversing starting switch in the electric circuit of said motor, said circuit including a torque-limit relay for stopping the motor, and cam means on the cam shaft for operating said starting switch after the rst mentioned feed screw has made a determinate number of revolutions in either direction.

2. A combination as defined in claim 1 including means for increasing the torque on the motor as the blade reaches its fully raised or fully lowered positions.

3. In a mill of the character described comprising a scraper blade and means for moving it edgewise back and forth along a mill roll, the combination of a member connected to said blade and movable in an up and down direction for raising and lowering said blade relatively of the millroll, -a'motor `for moving said Vmember up and downf, 'and means forf increasing f the torque on the motor as said memberreach'es determinate upper and lower limits. f

491141 a mill of the characterdescribed com privsing a s'craper'blade and means for movingit edgewise back and forth along the mill roll, the combination of an upright feed screw connected at its lower end to said blade, a reversible electric motor, means connecting the motor with the feed screw whereby the motor is enabled to effect axial movement of the feed screw in either direction to raise and lower the screw and blade, and means for increasing the torque on the motor as the blade reaches determinate upper and lower limits.

5. In a mill of the character described comprising a scraper blade and means for moving it edgewise back and forth along the mill roll, the combination of an upright feed screw connected at its lower end to said blade, a reversible electric motor, means connecting the motor with the feed screw whereby the motor is enabled to effect axial movement of the feed screw in either direction to raise and lower the screw and blade, a compression spring moving axially with said screw, and means for effecting compression of said spring as the screw reaches determinate upper and lower limits of movement as a means for increasing the torque on the motor.

6. In a mill of the character described comprising a scraper blade and means for moving it edgewise back and forth along a mill roll, the combination of an up and down slide to the lower end of which the scraper blade is attached, an upright feed screw having its lower end connected to said slide and having limited axial movement relatively thereof, a compression spring mounted upon said feed screw between said slide and a collar aiiixed to said screw, a nut engaging the upper end of said screw, and a reversible motor having driving connection with said nut, rotation of the latter in either direction effecting axial movement of the screw.

7. In a mill of the character described, the combination of a scraper blade engageable with one of the mill rolls, a rotary feed screw having operative connection with said blade for impelling itback and forth along said mill roll, a rotary cam shaft, speed reducing means between said feed screw and said cam shaft for driving the latter, cam means on the cam shaft for reversing the direction of rotation of the feed screw after it has made a determinate number of revolutions, means for raising and lowering said scraper blade relatively of the mill roll, cam

. means on the cam shaft controlling the operation of the last mentioned means in determinate time relation to the reversing of the feed screw, and means for effecting relative movement of the two cam means on the cam shaft.

8. A combination as defined in claim '7 in which the means for effecting relative movement Y of the two cams consists of a lost motion driving connection between the cam shaft and one of the cams thereon.

9. In a mill of the character described, the combination of a scraper blade engageable with one of the mill rolls, a rotary feed screw having operative connection with said blade for impelling it back and forth along said mill roll, a rotary cam shaft, speed reducing means between said feed screw and said cam shaft for driving the latter, cam means on the cam shaft for reversing the direction of rotation of the feed screw after it scraperlbiede. operating'means being adjustable whereby the determinate time of operating the scraper' blade operating means with relation to the reversing of the feed screw can be varied, and means. forv effecting; relative movement of the two cantY means on the cam shaft.

' RAYMOND W. ALLEN.

Images