US2924314A - Intermittent drive apparatus - Google Patents

Description

Feb. 9, 1960 F. H. SHEPARD, JR

INTERMITTENT DRIVE APPARATUS 2 Sheets-Sheet 1 Filed July 17, 1956 FIG.|

INVENTOR FRANCIS HvSHEPARD JR. BY %ms%d ATTORN Feb. 9, 1960 Filed July 17, 1956 F. H. SHEPARD, JR

' INTERMITTENT DRIVE APPARATUS 2 Sheets-Sheet 2 24 56 3 Z 84- 89 m J QZ L J J E E L INVENTOR. FRANCIS H. SHEPARD, JR. BY

, ziW/mz/ AT TO curately the amount of movement given the output shaft fed into the electric-control circuitinfordentofswitch off the clutch electromagnetand switch on the brake to ,stop theoutput drive shaft'of'the unit at the proper time to place, for exampleflhe next line of paper in a typewriter in proper position'forftyping.= An advantage of this line-finder wheel is that no actual contact is made between wheel and pickup coil and hence .dirtandithelikecannot interfere with its operation. Another advantagel'is'that the wheel is self-powered, i.e. it does not require a separate power supply to provide energy for the .contr'olpulses generated in the pickup coil. This wheel is; therefore'inexpensive to make and inexpensive to maintain. ,Since the clutch-brake unit is so fast acting and sincethe linefinder wheel is able to generate control. pulses of rela tively large amplitude occurring precisely. whena mag netic piece on; the wheelmoves past -a pickup coil, the

v belt f52 leading toa sheave 53. This last is carried by a frotatable load. shaft54 tobe driven by unit 10.: For a resolution obtained with this arrangementis excellent.

The material being advanced by the output. drive shaft .of

the clutch-brake unit can therefore be advanced line by line quickly and with the samehigh accuraeymany millionsoftimes. 1 A better understanding of the invention togflier with'a fuller appreciation of its many advantages will best be gained from the following descriptiongiven inconnection with the accompanying drawings in which: 1 Figure 1 is a side view partly in section ofthecl'utchbrake unit embodying'fea'tures of the invention; 7 w

Figure 2 is a face view of one of the electromagnets of the unit;

Figure 3 is a face view of the spiderqwheel which is fixed to the outputadrive shaft of the unit'and which carries the individualplates of the clutch element; 1 5.

Figure 4 is a partial section view alonglline ofthe spider wheel shown in'Figure 3;

Figure 5' is a side view of a removable of the unit of Figure; 1;

Figure 6 is a diagram of the control embodying.

features of the invention;

in connection with the circuit of Figure 6; and r Figure .8. is a perspective view of a. line-finderjwheel embodying features of the invention; Referring now to Figure 1, there is shown here a brakeclutch unit 10 which includes a clutch electromagnet 12 arida brake electromagnet 14. Clutch 12 is rotatably mounted near its left end on a collar bearing16 which is carried by the fixed support 18. The right end of clutch '12;is rotatably supported on the bearing .17. mounted between clutch and the shaft. 42 to .be describedwlater.

' Near the left end of thesclutchis a groove 20which is engaged by a belt 22 which in turn runs to adrivelmot'or .(not shown) and by which the clutch is.adapted ito be continuously rotated. Clutch 12 has recessedl below its right face an annular space intowhich a coil 24 is placed.

when properly energized with current led in fromthc.

' anem a y I necessary. By'rnaking these rings 30 and 32 of hardened and polished steel their resistance to wear can be made very high. Since they contribute only a small amount of encircling them setsof cooling fins 38 which carry away any excess heat generated-by the action of, clutching and braking. r

To the right of clutch 12 and closely spaced therefrom is the thin spider wheel 40s This wheel is rotatably mounted by means of the drive shaft 42 to which it is fixed and whichin turn is supported at its two ends by the bearings 44. These last are held by fixed supports :46 and ,47. Shaft42 runs through opening 34 in clutch 12 andthrough a similarppening 48 in brake 14 and is. .thus-freeIto rotate relative to these two members. Shaft 42 .near its left end carries a sheave 50which engages a given rate of advance of shaft .54, shaft 42 is run atthe lowest rate consistent with the, .required resolution in starting and stoppingshaft54, and within the torque liinit Q on shaft 42 permitted by the clutch and brake .unit. ,By

running shaft,42'-at this minimum rate, the inertia of the system is effectively reduced as previously mentioned. Spiderwheel 40, which is also shown in Figure ;3, carries looselyfitted within corresponding cut-through portions in itself several segment shaped plates 55, four, for example, whichare made of magnetic material. These plates will .be drawn against rings 30 and 32 and held with great force across air gap 36 when coil 24 of clutch 12 isenergized., When so held, spider unison with clutch 12.

To the rightof. wheel40 is positioned brake 14 which is stationary and.which is very similar in structure to. clutch 12. Brake 14 includes a coil 56 energized through leads not shown, and annular face rings 58 and 60 sub- 'stantially the same aslrings 30 and 32 and separated by the air gap 62. When clutch 12 is de-energized and brake -14 energized, the plates carried by wheel 40 lock .the

Q 7 45 1. Figures7 (a), (b), and (c illustrate various waveforms wheelto the brake andkeep the wheel from rotating.

The thickness of the; plates 55 relative to that of wheel 40 can be just slightly larger ,than the thickness of the Wheel as is indicated in Figure 4. Plates 55 canbe made between plates55 and the faces of the brake or clutchunit and assuresquick release of these plates; Brake 14 is removably clamped to the stationary member 47 by the screws 64 and the insert or spacer 66. By simply loosening these screws and slipping out the insertr(seen'- also in Figure 5) "the brake can be moved tothe right exposing spiderwheel 40. Then plates 55 in the wheel can easily and quickly bereplacedl The lateral distance between rings; 30, 32 and rings 58; is normally held fixed ata value slightly greater. than the thickness of spider wheel 40 or of plates 55. D'Ihusthere stationarybrushes .26 through theslip rings '28 carried a 1 on the clutch, this coil will induce in the clutch a strong magnetic field. By making the body of the clutch of magnetic material, such as soft iron, the clutch will actas a very powerful electromagnet when energized: -;Thepole faces for this magnet consist of the concentric annular flat rings 30 and 32 fastened in the same: plane, at the right end of the body of the clutch and concentric with the opening 34 which runs along the longitudinalsaxis=thereof. This opening 34 .is largerthan shaft 142. Polefaces :30, 32, also shown in- FigureZ, are of magneticmaterial and can be xremovably fastened/to the clutch body by screws,for examplain order .to facilitate replacementif isnopossibilitythatwheel 40 can become locked to clutch 12andto brake 14 at the same time.

element an integral annulus or a disk, for example, by making wheel 40v a solid disk of magnetic material and brake face almost instantaneously and without chatteror screeching. Any small vibratory motion which may develop in a plate 55 is quickly damped out .byfriction betweenit' and spider wheel 40. a If on the other handfinstead of usingrthese loose plates 5 5, wheel 40 were solid wheel 40 is forcedto turnin By dividing the laterally movingclutch element of 10 into the segmentalplates SS instead of makingthis assume 2 and were used asthemoving clutchielenientnantattempt to clamp it, .while rotating, .against :the brake, for e :ample, would result in a gyrltoryactionrof wheel 40 and it would take an :appreciable interval beforethe twheel :couldbe brought to rest againstthe brake. Thiszgyratony gyrating fifty-cent piece against :a hat .':table :size and light weight, the inertia of the moving parts,

which are connected tooutput drive shaft42'is further held to a minimum. The inertiaofclutch '12 insteadaof hindering the operation of unit 10 in'facthelps to'bring shaft 42 up to full speed almost instantaneously.

The large inductance of coil 24and of:coil 56=would I normally prevent currents from rapidly changing in them.

This would be a serious limitation *whereQas here, the energizingcurrents for these coils must-be .broughtupito strength almost instantaneously to' providethe required fastclutch or brake action for unit 10. However, according to another aspect of the invention, the efiect of the large inductances of coils 24 and 56 is minimized.

The control circuit for applying currents to coils 24 t and 56 is shown diagrammatically in Figure 6. Coil '24 is connected to be supplied with current from the high voltage direct current supply line 'B+ through the inductor 70 connected in common with it and coil 56. Current'through coil 24 is controlled by tube 72 and flows or not depending on whether this tube is conducting or not. Similarly current from the lead B+ via inductor 70=through coil 56 is controlled by the tube 74. Tubes 72 and 74 are biased so that one is fully conducting and the other is cut-off, this condition 'beingreversible at 'will. The biases applied to these tubes are supplied by a bista'ble flip-flop arrangement including the tubes 76 and 78, one or "the other of which is always conducting. This flip-'flop arrangement is well known tothe art and does not require detailed description of its operation. A positive pulse applied to the grid of the buffer amplifier tube 80 causes tube 78 to become conducting and tube 76 to cut ofi. Thereafter these'tubes will remain in this condition until a positive pulse is applied to the. grid of the bufier amplifier tube 82 whereupontube 76 becomes conducting and tube 78 cuts off.

When tube 78 becomes conducting, its plate will pull the grid of tube 74 sufliciently negative to "cut that latter tube ofi. At the same time, tube 76 cuts off allowing the grid of tube 72 to go sufficiently positive to make tube 72 conducting. Thus the current which had been flowing through coil 56 via inductor 70 is switched tocoil 24. At :this instant this happens, though'there is no current flowing into coil 24, current rapidly builds up to-full'value because of the current flowing through inductor 7 which can not change quickly and which has no return path except through coil 24. To avoid a destructive voltage surge, a path for the current Whichis flowing in coil 56 'when tube 74 cuts off is provided by the small capacitor 84 and the capacitor 85 and resistor 86 connectedin shunt-across the coil, a similar capacitor 88, and capacitor 89 and resistor 90 being connected across coil 24.

Figures 7(a), and 7(c) respectively show the qualitative etfect of inductor 70 on the buildup of current through clutch coil 24 and alternatively, through brake coil 56. Without inductor 70, current through these coils would change relatively slowly to and from a maximum value I along the dotted lines C in Figure 7(a) and 7(0). With inductor 70 in circuit, however, the current through coil 24 or 56 rises much more rapidly as indicated by the dotted lines D which very closely approach the perfect 7 square waves shown by the solid lines. The voltage surges across inductor 70 which adds to the supply voltage to cause the coil currents to follow lines D instead of lines C are indicated in Figure "7( b). These surges go :tfromwkB to voltage V: imashorttinstantnndathen droptto -+.B again -at the respectivetirnes noted. ,Themaximum anluemf "Yfis jlimited by;a small :capacitor 92 il18h11l1t across-inductor 70. p

,Theramount of .rotation ,impartedto the rotatable shaft 54 in unit for each cycle of operationiis controlled b the itime :ditference duet-ween :a positive starting pulse rappliedg-totube80in Figure 6 and the first positive stopzipingz'pulsejthereafterapplied to.tube-82. A particularly .ft'filCifiIlt and advantageous means of. obtaining stopping gplllses timed-ingaccordance'withthe rotation of shaft-5.4 includes the line-finder wheel shown in,Figure 8 and which' al'so embodies-features of theinventiou.

Referring to Figure 18., line-finder wheel '94. includes the disk 95 :which .is nonmagnetic and which is'adapted rto [be rotatably mounted, for :example, directly on the shaft-25.4. ,Disk95 carriesrecessed around :its periphery :the magnetic tp'ieces 96, which :can Ebe permanent .magnets, :these pieces ibeing evenly :spaced and *being positioned ttransyjerse' wto :the rim JOf-fthfi diSk. Twopickup tween, are placed 'oppositezthe ,arimvof :disk ,-95 so that when a apiece =96 :moves tpastwone of sithe ;coils, it will :in- :duce:a-yoltage;in :the-coil winding. These coils, :todetect-anonrmagnetized but ma-gnetic-;material,.:can be suitinbly :energized .by a zsma'll permanent magnet, .for 5.671- :ampl'e,-with;a steadysstatetflux. 'l'jodetect-pieces 96"when they are :permanent magnets, 'no ;such auxiliary ,fiuxais u'jequired. The :pulse :of voltage obtained from either ,coil97 or :98, after suitable shaping and clipping in ciricuits-well kndwn to'sthezart, :can then be applied in'positivesense ;to'ithe :grid of tube :82 to .switch unit 10fror n clutch to :brake ;condition.

As seen in Figure '.8, coil 98 is spaced :relative zto coil 97 and disk so that when a piece 96 passesltheilegs :ofcoil. 9.7.,:the legs of :the =-c oil198.are halfway between :two-other-magneticpieces 96. .Thus disk 95.need rotate tonlyzhalf the {distance between pieces '96 for one of .them

itoinduce a-voltage in :one-ofthe coils97, 98.

The above description is intended in illustration :and rnot-zinilimitation of the invention; Various changes in gtheiarrangement described-may occur to those :skilled iHtthe art :and these ,can. be .made withontadeparting Efrem gthespirit.or scopetofithednvention essetforth; I;cl im:' s ;In .an intermittent :drive apparatus, :a body ihaviing ,twozconcentric arms :of magnetic :material rterminatingtin faces :at least .one of which are locatedlevel with each other :and taretseparated by a circular magnetic flux gap, iaxthinsspider heel -,co-axial :with said ;arms and rotatably positioned in azpa-rallel .plane closely :adjacent said faces, a plurality .of delutch plates loosely arecessed in :said wheel, :said lates being of magnetic material and sbeingmovable relative to said wheel substantially only toward and away from said flat faces whereby whenta magnetic field is developed across said flux gap said plates will be tightly held thereacross and .said wheel will be held :from rotating relative to .said arms, and means to generate .a magnetic field across said gap a plurality of times for each revolution of said spider wheel.

2. The combination of elements as in claim 1 in which said concentric arms are shaped around an annular opening in said body and in further combination with a multi-turn coil positioned in said opening and adapted 1 tWhiCh ,faces :is annular :andgboth-rof which said spider wheel carries a plurality of magnetic members positioned in generally symmetrically arranged magnets.

able "magnetic elements adapted to be moved toward or away from said face therebyto hold ornothold said wheel with respect thereto, and a load shaft adapted to be started and stopped a number of times per revolution and connected in at least one-to-one drive relation with said wheela T i 5; The combination of elements as in claim 4 in which said wheel is non-magnetic and has cutthr'ough it'a pluralityof openings inwhich saidmagnetic elements are loosely carried and in which said wheel is rotatably carried ,on a shaft extending through an opening along the common axis of said electromagnet.

6. In a clutch-brake unit wherein a load shaftis to be suddenly started and suddenly stopped a number of times per revolution, a brake electromagnet, a clutch electromagnet spaced therefrom, a spider wheel carried on a drive'shaft and rotatably positioned 'betweenf said electromagnets, said wheel loosely carrying at least one magnetic member movablys only perpendicular relative to the wheel toward and away from said electromagnet s, the thickness of said wheel being small and being only slightly less than the separations betweenflsaid electroinductance.coiluassociated wi'ththe clutch electromagnet -and.1a second large-inductance coil associated with the ltbrake elec'tromagnet,. :a'jsource ofdirectvoltage, a large inductor connected in series with'saidsource, and an electric switchifor suddenly connecting said firstrcoiLin series "with said fsourceand said inductor and alternativelyfor suddenlyconnecting said second coil in place ofsaidfirst coil. a

- 11: In an apparatusofthe character described, a rotata a --bly mounted load shaft adapted to advance the paper in a itypewrit'erline by line Lajpluralityof times for each revolution of said load shaft, a rotatably mounted drive shaft magnets, a load shaft for advancing the-paperinwa=typewriter line by line, said load shaft being connected to said drive shaft in the lowest drive ratio permitted-by the required resolution of starting and-stopping, and

means to energize said electromagnets to-stop*and "start said load shaft a plurality of times per revolution; 7. The combination of elements as in claim:

cutout portions in said wheel, and in which said electromagnets each have a circular, or annular magneticflux gap acrosswhich said magnetic membersare adapted to be held.

r 8. An intermittent drive apparatus comprising a brake telectromagnet and a clutch electromagnet eachhavin'g =relatively.large inductance, and energizing means to supply said electromagnets alternatively with current V for operating said electric sw tch to start and to stop-said.

source at aratelgreater than energy can be supplied: by

saidsource alone, whereby current is built up to full value in said :electromagnet'in a very short time after :it is connected tosaid source. 1 I r r l 9. The combination of elements as in claim 8 wherein said energy storage means includes a large inductor connected in series with said source and adapted to be connected alternatively in series with each of said electro- 10. A control Um r circuitfor suddenly switching" current i y from a brake ele'ctromagnet toa .clutch electromagnet to .suddenlystop or suddenly start adrive shaft controlled. by

said electromagnets, said circuit including a first largeiductive coilin: each of said electromagnets,

'connected'in at least lone to one driverelation with said load shaft, a thin, non-magnetic spider wheel carried by :.;said drive shaft a clutch electromagnet'rotatably; mounted around saiddrive shaft and rotatablerelative thereto, a

lfixed brakeelectromagnet mounted aroundsaid drive shaft and ,rot'atablyclearin'g it, the faces of said electromagnets being spaced closely on; opposite sides of said spiderwheel and generally parallel thereto, each of said electromag- Tnets having an annular air gap opposite said spider wheel, a .plurality of laterally movable magnetic elements loose- ;ly, carriedinopenings through said wheel and adapted to be clamped in turn to one. then the other of said electromagnetsracrossits respective air gap, a respective confor energizingsaid coils one after the other in turn including a source of direct current, an inductor connected [in series with said source and each ofsaid coils, and an Pelectric switch for connecting one then the other of said coils withsaid inductor across said source; p t p N12. The combination of elements as inclaim ,11 infurther combination with means including a line finder wheel loadshaft a plurality of times per revolution.

13. The combination of elements as inclaim llwherein said clutch electromagnet isrotatably mounted on a fixed frame and said brake electromagnet is fastened to said frame by screws and by a spacer, said spacer being .removable by loosening said screws and when removed permitting said brake electromagnetto-be movedlaterallyaway from said spider wheel whereby said magnetic elemerits can quickly and easily be replaced. l

References. Cited in the file pateritffl and means

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