US2609998A

US2609998A - Tension control system

Info

Publication number: US2609998A
Application number: US625504A
Authority: US
Inventors: Arthur W Sear
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1945-10-30
Filing date: 1945-10-30
Publication date: 1952-09-09
Anticipated expiration: 1969-09-09

Description

Sept. 9, 1952 A w, SEAR TENSION CONTROL SYSTEM Filed 001;. 30, 1945 s Sheets-Sheet 1 Invehborr Arthur W. Sear, 135% 3% H is Atbcrne g.

P 9, 1952 A. w. SEAR 2,609,998

TENSION CONTROL SYSTEM Filed 001;. 30, 1945 5 Sheets-Sheet 2 Fig.2.

Inventor: Arthur W Sear,

His Attorne s.

Patented Sept. 9, 1952 TENSION CONTROL SYSTEM Arthur W. Sear, Stratford, Conn assignor to General Electric Company, a corporation of New York Application October 30, 1945, Serial No. 625,504

17 Claims. 1

My invention relates generally to tension control systems for traveling strip material such as wire, tape, and the like. More particularly, the invention relates to wire driving and reeling mechanisms for magnetic wire recording apparatus and the like, and has for its object the provision of an improved system and apparatus for maintaining substantially constant wire speed and tension.

The recording medium commonly used in magnetic wire recording apparatus is a slender wire of suitable magnetizable material approximately 4 mils in diameter. This fragile wire is generally drawn through the recording unit at speeds up to approximately 6 feet per second. It will therefore be evident that, in order to prevent breakage. of the wire, it is necessary accurately to control its tension. In some recording units now in use the take-up spool is driven at approxi mately a uniform speed so that, as the wire builds up on the take-up spool, the linear speed of the wire through the recording head increases. This slow variation in speed does not ordinarily affect the fidelity of reproduction, since the wire is usually run through the apparatus in the same direction in reproducing operation as in recording operation. If, however, the wire is cut; so that a portion of the wire upon which a recording was made at one limit of winding of the take-up spool is played back with the take-up spool near its opposite limit of winding, the difference between recording and reproducing speeds will have an undesirable effect upon the reproduction.

A more pronounced disadvantage of the takeup reel drive is that, as the wire builds up, its surface becomes somewhat uneven. The uneven surface causes irregular motion of the wire which results in sudden speed changes or Wow" in reproduction. It will therefore be evident that, for fidelity of reproduction, it is desirable to run the wire at a predetermined fixed linear speed at all times. Moreover to prevent breakage of the wire, and to prevent wire slippage where a capstan drive is used, it is desirable that the tension be maintained substantially constant.

Accordingly, it is a general object of my invention to provide an improved tension control system for strip material winding and reeling apparatus.

Still another object of my invention is the provision of constant tension driving means for a reversible strip winding apparatus or the like.

It is a further object of my invention to provide constant linear speed driving means for strip material winding and reeling apparatus.

It is a more particular object of the invention to provide an improved wire driving apparatus It is a still further object of my invention to minimize wow in magnetic recording and reproducing apparatus and the like.

It is a specific object of my invention to provide a readily reversible constant speed and constant tension wire driving apparatus for magnetic wire recording equipment and the like.

In accordance with a preferred embodiment of my invention, a constant speed driving pulley or capstanintermediate the supply and takeup reels is arranged to drive the wire at a substantially constant linear speed'independent of the reel speeds. The reels themselves are both driven in the direction of travel of the wire through separate variable transmission elements from a common friction driving disk. The reel speeds are controlled to maintain the wire tension substantially constant by providing between the capstan and each reel a dancer pulley arranged to control the driving ratio of the transmission element associated with the adjacent reel. Each variable transmission comprises a friction spool connected to transmit power from a driving disk to a driven disk. The spool is mounted upon a linkage permitting axial movement of the spool to control the speed ratio between the disks; and the linkage is so arranged that a damping function is introduced into the motion of the spool, thereby to minimize hunting of the apparatus.

My invention itself, along with further objects and advantages thereof, will be fully appreciated by referring now to the following detailed specification taken in conjunction with the accompanying drawings, in which Fig. 1 is an exploded perspective view of a magnetic recording apparatus embodying my invention; Fig. 2 is a plan View of the front panel of the apparatus shown at Fig. 1; Fig. 3 is a schematic line diagram showing the transmission linkage of Fig. 1 in elevation; Fig. 4 is a vector diagram of velocity illustrating the theory of operation of a single friction transmission element; Fig. 5 is a schematic diagram of a single transmission element embodying my invention in another form; and Fig. 6 is a front elevation of still another transmission linkage embodying my invention.

At Fig. 2 I have indicated schematically the layout of the front panel of a magnetic recording apparatus embodying my invention. As indicated in this figure, a traveling magnetic recording medium, such as a wire I, is passed between a pair of spaced reels 2 and 3 through a magnetic recording head 4 and an erasing head 5. In passing between the reels, the. wire 5 passes over a driven capstan 6 intermediate the reels, a pair of dancer pulleys l and 8 on opposite sides of the capstan, and a pair of level winding idler pulleys 9 and I0 intermediate the danc 3 er pulleys 1 and 8 and the reels 2 and 3, respectively. 'I'havealsoshown mounted upon the panel a controlswitch H and a reversing lever l2.

Referring now to Fig. 1, I have shown therein a perspective view of the apparatus with the panel removed. Driving power is obtained from a reversible electric motor Id controlled by the line switch H and a reversing switch Hi. The switch l4 connected by a suitable linkage IE to a reversing shaft l2a connected to the reversing lever 12. A friction roller Iii-mounted upon the shaft of the motor [3 drives a disk I! mounted upon a shaft IS. The disk I1 is preferably of appreciable mass, sothat by its flywheel effect it aids in stabilizing the wire speed. The wire driving capstan '6- is-mounted .upon the opposite end of the shaft l8.

Themotorlsalso drivesboth reels'ii and t in the direction-in which thewire is traveling and at suchspeeds that. the wire tension forces adjacent each. reel .are maintained substantially constantand equal. For this purpose, the shaft 18 is providedwithapulley 19 connected through a belt 20 to drive a pulley 2| mounted upon a shaft 22paralle1 to the shaft I8. The shaft 22 carries a friction drivingdisk23. The disk 23 is connected by separatelyvariable friction transmission mechanisms 24 and-25 to drive a pair of driven friction disks 26 and2'l, respectively. The

.disks 26 and 21-. are disposed; in the same plane asthe disk 23 and :are. mounted upon shafts 28 and.29. respectively. The shafts.28 and 29 are parallel to the shaft I8 and carryat their opposite ends the reels-2 and 3,- respectively.

The transmission'elementsl i and 25 are of similar construction and each comprises a pair of parallel jackshafts30, 3| .mounted in quills 32 and 33, respectively,and'carrying at opposite ends friction rollersengaging the disk 23 and one of the disks .26 01x21. Referring specifically to the transmission element 25,-the jackshaft 36 carries at opposite ends a pair of

friction rollers

34 and 35, while the jackshaft 3! carries a similar pair of'friction rollers 36 and 3'9. The rollers 34- and 35 onthe shaft '30 are in lateral alignmentwith the rol1ers'36 and 31, respectively, on the shaft-3|. The rollers 34 and 36 engage the driving disk-23 and the rollers 35 and-3T engage the drivendisk 21. The quills -32 and 33 are connected together by a plate 3B fixedly connected to the quill 33 and having a pin and slot connection with the quill 32. The quills 32 and-33 are positioned on opposite sides of the disks 23 and 21 and are biased toward each other to bring the rollers-into engagement with opposite sides of the disks. Biasing of the quills is accomplished by means of a tension spring39 connected between the quills.

The transmission mechanism .25 is mounted upon a pair of links 40 and 4|, the upper ends of which are pivotally connected to opposite ends of the quill 32. Similarly, the transmission mechanism .24 is mountedupon a pair of

links

42 and 43. Thelower ends of the

links

49 and 42, which will be referred to hereinafter as control links. are pivotally connected to rocker arms 44 and 45, respectively. The rocker arms 44, 45 are mounted upon fixed pivot pins 45 and 41', respectively. The lower ends of the links All and 43, which will be referred to hereinafter as damping links, are connected to pins 48 and 49, respectively, which are slidably mounted in arcuate slots and 5|, respectively, in a fixed panel 52. The pins 48 and 49 are connected together by a shift 4 bar 53, and the pin 48 is provided with an ex tension: 54 engaging a slotone endgof a rocker arm 55. The rockeraarmi55 is mounted upon a fixed pivot 56 with its other end in pin and slot engagement with a crank 51 carried by the reversing shaft 12a. The reversing shaft l2a is provided also with a positioning cam 58 engageable with .a's-pring pressed detent 59, thereby selectively to'maintain the reversing shaft in either its forward or its rewind position. The pins 48 and. 49 are thus in one end of the slots iii and 59 for forward operation and in the opposite ends for reverse operation. In both positions the damping links are normally angularly disposed with respect to the perpendicular fromthe common. diameter of the associated'driVingJand driven disks.

The driving ratio of the transmissionelements 2d and 25 is varied .by movement. of thecontrol links 42 and 48, respectively, in responsetomovement of the dancer pulleys 1 andii; respectively. For this purpose, 1 the dancer, pulleys T1 tandlif are mounted respectively upon armsB 'andi'fil -extending laterally from apair of rotatable shafts 62 and 63, respectively. The .shaftsBZ and 63 are mounted insuitable bearings .(not shown)fand are biased by helical springs I'Bianidi'fif, -respectively, to maintain.tension.onithe wireil. Specifically. the shaft 62. is biased in aicounter'clockwise direction andthe 'shaftL63 isTbiase'dfin'a clockwise direction, as viewedat "Fig. :1. The pulley. arms iiilan'dfSl may, if desired, be made of relatively stiff-spring material to absorb's hock and thereby add tothestability-Oftheitransmission mechanism. The "shafts"62"and"63"are each providedatone end with collarsB6andf61, respectively, towhich the biasin vspringsfiM'and are connected. A. pair of?1inksf68..an'd.69are eccentrically pivoted to "the collars 'f66 "andt'l, respectively, at one end and have theirothererids pivotally connected to the rockerilevers 45and 44, respectively, .at the ends,oppositethecontrol links 42 and 46, respectively.

The idler pulleys 9. and I0. arerotatably mounted upon axially movable-and non-rotatable shafts ill and H, respectively, disposedparallel tothe shaft [8. The shafts?!) and H are continuously reciprocated by a level winding mechanism 12 driven from the shaft22 by. a wormi'l3 mounted thereon. The worm "l3 meshes with :aworm wheel 14 mounted upon .a counterfshaftTEthe other end of whichcarr-iesa spurlgear 1B. The spur gear'lt meshes. with a spurgearWl mounted upon a counter .shaft lfiithe other. end of'which carries a bevel gear 7-9. The bevelggearflfi 00- operates with .abevel geariflil, mountedtupona shaft 81 perpendicular. to the shaft'l'S. an'dcarrying at its opposite end a,pairiof.eccentricycam disks 82 and83. "Theldisks82, andifiil peripherally engage a pair .of.level winding leversf84-and 85, 1-espectively,,which are mounted .upon'fixed'pivots 86 and 87!, respectively. 'The'movableerfds of" the levers 84 and'B5 engage axial'slotsinttheishafts if! and H, respectively, andthe'leversarebiased into engagement with theperipheryof theidisks 52 and 133, respectively, by helical compression springs 88 and tfi engaging ,collarsiml and! l "on the shafts T0 and ll, respectively. "It will be evident that. as the lovers 84' and"'85*ar e" oscillated by the cam disks their respective shaftsarecontinuously reciprocated toeffect level windingpf the wire I uponthe reels'Z an'cl3. 7

It has been found thatjbecause of friction losses in the'dancer pulleys land B'and'iIrthe recording and erasing heads 4 and 5, respectively,

ciated withthe take-up reel.

the tension on opposite sides of the capstan 6 may be maintained equal only if the spring tension on the forward dancer pulley is somewhat greater than that on the trailing dancer. By the forward dancer pulley is meant that dancer asso- For this purpose, the biasing force exerted by the spring 64 upon the dancer pulley l is adjusted to be greater than that exerted by the spring 65 upon the dancer pulley 8, and an additional spring 92 controlled by the reversing shaft l2a is arranged to add to the effect of the spring 65 in forward operation when the reel 3 is serving as a take-up reel and to exert little or no efiect upon the spring 65 when the reel 2 is serving as a take-up reel in rewind operation. For this purpose, the spring 92 is connected at one end to the lower end of the link 69 and at the other end to an arm 63 mounted upon the reversing shaft [2a. The arm 93 is so disposed that, when the reversing shaft is in its forward position, tension is applied to the spring 92, while when the reversing shaft is in its rewind position the spring 92 is substantially untensioned. By this arrangement, it is possible to maintain the tension on opposite sides of the capstan pulley 6 substantially equal, so that there is no tendency for the wire to slip upon the capstan.

With the foregoing understanding of the construction and arrangement of a wire recording apparatus embodying my invention, the mode of operation of the apparatus will be fully understood from the following description.

Let it first be assumed that the reversing lever I2 is positioned for forward operation, as shown at Fig. 1, so that the wire I is supplied from the reel 2 to the reel 3, passing through first the erasing head 5 and then the recording head 4. In this operation, the friction disk I! is driven by the motor l3 in a counterclockwise direction, as indicated upon the drawing. Also, the damping

links

41 and 43 are disposed with their lower ends in the right-hand ends of the slots 50 and 5|, respectively. In this position, the pins 48 and 49 are displaced to the right of a perpendicular to the common diameter of the driving and driven disks. The control links 40 and 42, in the normal mid-position of the apparatus shown, are substantially vertical or perpendicular to the common diameter.

In the counterclockwise or forward direction of rotation of the disk H, the belt and pulley 2| rotate the disk 23 in a counterclockwise direction. The capstan pulley 6, being connected directly to the shaft l8, also rotates counterclockwise and in the same direction as the disk 23. The variable transmission 24 connecting the disk 23 to the disk 26 effects clockwise rotation of the disk 26 and the connected reel 2. Similarly, the variable transmission connecting the disk 23 to the disk 21 effects clockwise rotation of the disk 21 and connected reel 3. Both reels are thus positively connected to be driven in the direction of wire travel. In the forward direction of operation, the reel 2 serves as a supply reel and the reel 3 functions as a take-up reel. As the Wire travels from one reel to the other, the level winding mecha nism 12 continuously reciprocates the shafts 1i) and H and the connected idler pulleys 9 and [0, respectively, thereby smoothly to wind the wire upon the take-up reel.

It is, of course, desirable to maintain the wire tension equal on both sides of the capstan 6, so that there is no tendency for the wire to slip on the capstan. If the wire has the same desired tension on both sides of the capstan, and if the reels contain about equal. lengths of wire Wound thereon, the dancer pulleys 1 and 8 will be maintained in such positions that the jackshafts 39 and 3! of the variable transmission mechanisms 24 and 25 lie along the common diameters of their associated driving and driven disks. The

disks

26 and 2! are then driven at the same speed as that of the driving disk 23. It is this position of the mechanism which has been illustrated at Fig. l and to which the term normal position in the claims refers. It will be recalled also that, in order that the wire tension upon opposite sides of the capstan 6 may be maintained equal, the biasing force on the dancer pulley 8 is greater than that on the dancer 1 in forward operation and less than that on the dancer 1 in reverse operation. As shown on the drawing, the spring 92 connected to the reversing lever shaft is posttioned to aid the helical spring 65 in biasing the dancer pulley 8 for clockwise rotation.

It will of course be understood that the symmetrical positions of the variable transmission mechanisms 24 and 25 illustrated on the drawing cannot be maintained except for a short interval during the operation when the diameter of the wire upon both reels 2 and 3 is approximately the same. In operation, the capstan 6 drives the wire I at a predetermined constant linear speed, while the transmission mechanisms 24 and control the speeds of the reels 2 and 3, respectively, to maintain the wire tension constant adj acent the reels as the amount of wire on the reels changes. Thus as the wire winds up on the takeup reel its speed is gradually reduced, whilethe speed of the supply reel is gradually increased.

Let it be assumed, for example, that the diameter of the coil of wire upon the reel 2 is such that wire is supplied too rapidly from the reel 2 and the tension at the dancer pulley I becomes less than a predetermined desired value. In such a case, the dancer pulley 1 moves a small distance in a counterclockwise direction under the action of its biasing spring 64, and the consequent rotation of the crank hub 86 moves the link 68 downwardly. Thus through the rocker arm 45 the control link 42 of the variable transmission 24 is moved upward and the quill 32 of this transmission element is rotated about its point of pivotal connection with the damping link 43. Since the jackshaft 36 is now no longer diametrically disposed with

respect todisks

23 and 26, it has imparted thereto an axial component of movement. With the friction roller 35 above the hori zontal diameter of the disk 26, this axial movement is toward the right as shown in the drawings, or away from the disk 26 and toward the disk 23. As the jackshaft 31'; moves axially, the damping link 53 rotates in a clockwise direction about its lower end thereby to raise the friction roller 34 of the transmission 24 and to restore the quill 32 to a horizontal position. Eventually, a new position of equilibrium is reached in which the jackshaft 36 lies parallel to and above the common diameter of the

disks

23 and 26 with the friction roller 35 spaced from the center of the disk 26 by a distance greater than that between the friction roller 34 and the center of the disk 23. It is therefore evident that the speed of the disk 2%; will be less than that of the disk 23, and that the speed of the reel 2 is thus reduced, thereby to preventfurther decrease in the tension of the wire I as it leaves the reel-and to maintain the tension substantially constant within differential limits. I

disk '23.

saeoegees Similarly, few-111 be evident that, if thezreel-fZ is revolving too slowly, :so that the tension at :the dancer pulley I -increases,lthe dancer .pulley is moved ina' clockwise directiona'the link68 raised,

and the control l-ink ilis lowered. lWith the friction roller- 35 below the horizontal centerlinerof the disk 26, axial movement of the iackshaftfw and below the common diameter of the disks-and the distance between the1O116f-35 alld the-center of the disk 26' less than that 'betWeen-the'roller "stand the center of the -disk 23. Thusfthe disk 25 is driven at "a speed greater than thatf the disk 23, so that wire is supplied from 'the reel 2 at a greater rate, thereby to maintain the'desired tension within differential limits.

The variable transmission mechanism-25 functions inan entirely similar manner to control the speed of the'take-upreel 3-in'such away that the tension of the wire between -the "capstan 6 and the reel'3 is maintaine'd'at the desired value.

In general, therefore,- it 'will' be evident that, at

the beginningof a winding operation, when substantially all thewire is on the supply reel 2" and very little wire upon'the-reel 3,*the "reel 2 -is driven more slowly than thedriving disk 23 and the reel 3 -driven -more-rapidly than the driving --As the roll of wire is reduce'dupon the reel 2, the speed of" the "reel gradually increases, and as thewire -builds'np upon the reel 3, the speed 'of the reel=3=graduallydecreases. Throughout the-operation; the linear speed" of the wire I' is maintained constantby the 'vviredriving capstan-'6.

Attention is directed to the'factthat the damping links 4| and 43 are difierentlydisposed in the two transmission mechanisms- 2 land 2 and that their relative disposition is reversed' uponreversal of the'wi're movement. This-disposition is required by the directions of axialmovement required' of the *jackshafts '30 and --3 I in the two transmission mechanisms. general,- it is to be noted that the damping links 4|"and 43 are so inclined thataxial' movement-of the associated jackshaft in response to movement of the associated control link is in such-a direction that the damping link tends to restore the quill 32to a horizontal position as a resultof' theaxial'movement. For such restoring action the damping links must always be disposed at such an angle to the connected jackshaft thatywhen the jackshaft is tilted toward theperpendicular to the damping link, axial movement of the shaft-wilL take place in the direction away from the damping link. Specifically, in the embodimentof the invention shown and 'with the direction of rotation of the parts assumed for forward operation,

it will be noted that the links 42' andll3" are spaced apart farther at their lower endsthanat their upper ends,while the links" 40 and 4| are spaced closer at theirlower-"ends than-at=their upper ends. The spacingof the upper ends'of course is 'fixed by pivotakconnec-tion to the quill 32.

These relations will be clarified byreference to Fig. 3, in-which'I have shown a line diagram of the linkage shownat Fig. 1. At Fig.:-3,"I have shown by dotted lines tilted positions of the jackshafts 30 illustrating the aboverelationforfor-= 8 kwardwire movement. Itwillibe evidentithatthe I same I relation. exists for: reverse wire: movement only if the damping links .areishifte'd tdthe' opposite. endsof the slots in the. plates53.

:In :order further. to: explain.theitheoreticalre- .lationsi affecting the operationof myapparatus, :I haveshowni at Fig.4 a line "diagrammfza simplisfie'd friction transmission similar-tethe-transmiszsionsi24 and 'Z 5 described above, but 'in whichithe damping functioniis omitted. .'In the arrange- ;ment'shown at.Fig. 4 the jack'shaft3ll iszpivotally mounted at a fixed: point I00. and istaxiallymovable with'respectito its pivot point. .Thefshaftis shown in a tilted position. .l'Ih-e drivingidisk 23 an'dthe driven disk Zlare shown with theirdi- T'IGCtlOI'iS :ofcrotation :as previously assumed. The disks: 23. and52l are in contact with the 1 rollers l34and 35, respectively. Theivelocity of the disk :23: at its point of contact with the: roller 34: is 1 illustrated bythe vector V 23; and: the velocity of 5 therdisktfl at its point of contact with theroller o35iis2i11115t18id by the: vector V2.7. "-The disk 23 therefore tends to impart to the'roller'34 a tan- .gential velocity VnT: and an axial velocity Vse i. while thedisk 2ltends to impart-to the roller 35 :a tangential velocity Van-and an axial velocity VssA. -It will thus be evident that, since the jackshaft 39 is axially movable, the shaft and itsconnectedrrollers will move axially in the direction :indicated toward the-center'of the disk-23 and away from the center of the disk-"11. Thus'in the course of'one revolution,xlthe'pointof contact of the roller 34 with the "disk- 23 -w-i1l -f0lloiz/ a spiral :path -I M indicated by dotted lineat Fig. 4. It may bedemonstrated mathematically that the 1 theoretical axial: velocities V34A a11d V35A are not the-same, so that there-willinecessarily be some eslight slippage. 7

From Fig. I 4, it' will be evident. that if desired thejackshaft 30 may be'slidabiy mountedin a .-short'qui1l centrally pivoted-ate fixed-point, rather than being carried on the control and damping-links described with reference to Figs. .1 and 3. At'jFig. 5, I have shown a fragmentary .linediagram ofa portionof the apparatus includingone suchquill IE2 centrally pivoted atafixed pointzand provided with an-extending=arm I02a. Those portions of the apparatus shown at Fig; 5 corresponding to like elements shown'in the other figures have been assigned the same reference numerals. The mechanism 'of Fig. 5 is'inverted with respect to Fig. 1 and-the wire is oppositely wound:on the're'els. This relation should-be =.rborne"inr mind in noting thecorrespondence of elements between the two-figures. 'lt will' be noted at-Fig. 5 that the quill-102' is shorter than the jackshaft'dfl and thatthejjackshaft 30; is axially movable within the "quill. The dancer pul ley" I of Fig: 5*is mountedupon a; bell crank I 03 which -ispivotally mounted at afixed. point I04 and connected tothe. jackshaft'arm 192a by -a'link I05. The dancer pulley is biased by means ofa spring Hit in a direction to:.apply.tension to the .wire I. The jackshaft 30 is shown tilte'd atan angle a with: respect. to the common diagonal "thIOUghthediSksZS' and 26 and displaced a;dis .tancem from its mid-position inthe quill l 02. I It .will be understood .thatthe .',tilting of .the jackshaft atv the angle a. results from liftingofithe 'dancer pulley? throughadistance y; from its position when the jackshaft is horizontahand that the axial movement ,of the 'jackshaft =through the distance a: arises" from its tiltingas explained'with respect to Fig. 4.

It'may-"be 'demonstrated by the equations of motion that, for the mechanism shown at Fig. 5, the axial velocity or the jackshaft 30 is a function of the distance 1 only, and that, because of the speed changes in the disks effected by the axial movement, simple harmonic axial oscillation of the jackshaft will result. In order to effect damping of such oscillations, it is necessary to introduce into the axial velocity of the jackshaft a function of the displacement at. This is accomplishedby the damping links M and 43 previously described. As will now be evident, these damping links have the effect of reducing the angle a and thereby reducing the axial velocity of the jackshaft as the displacement :1; increases and without affecting the displacement g. It will be evident that other suitable damping mechanisms may be utilized to accomplish this purpose within the scope of my invention.

At Fig. 6, I have shown a further embodiment of my invention having a control and damping linkage similar to that of Fig. l and including additionally mechanisms for braking the reel when the wire is slack, such as in th event of Wire breakage or when the wire is changed. Those elements of Fig. 6 corresponding to like elements of Fig. 1 have been assigned the same reference numerals. In noting the correspondence of parts in the two figures, itshould be observed that the pulley orientation of Fig. 6 is reversedvvith respect to Fig. 1 and the wire is oppositely wound on the reel. At Fig. 6, the dancer pulleys I and 8 are mounted upon pivoted arms 60 and BI and biased by springs 64 and 65, respectively, as at Fig. l and links 68 and 69 connect the arms 60 and El with the leaves 55 and M3, respectively. At Fig. 6, however, I provide also apair of brake shoes Ill! and I Elli pivotally mounted upon fixed pivots Hi9 and Ill) and arranged toengage the driven disks 2! and 26, respectively. If desired, of course, the brake shoes may engage the reels directly or may engage separate brake drums on the reel shaft. The brake shoes are actuated by links HI and H2 connecting the shoes to extensions on the dancer pulley levers BI and 69, respectively. Thus if the wire breaks or becomes slack for any reason, the brakes will come into action. Preferably, the brakes have a differential action, so that more brakingis obtained upon any reel when it is turning in a direction to unwind the wire. Thus, the supply or trailing reel is braked the most so that the wire is kept taut. The brakes will ordinarily come into action only when the wire is changed and if the initial position of the rollers is 'incorrect for the diameters of the new reels. Thebrake on the delivery reel will then check the rotation of the reel during the first two or three turns until equilibrium is established.

While I have described only certain preferred embodiments. of my invention by way of illustration, many modifications will occur to those skilled in the art and therefore, it is intended that the invention should not be limited except as defined by the following claims.

What I claim a new and desire to secure by Letters Patent of the United States is:

1. In a tension control system for a traveling strip of material, a pair of spaced reels, constant speed driving means engaging said strip in-- termediate said reels, a driving disk, a driven. disk connected to each said reel and positioned in the plane f said driving disk, a pair of axially movable jackshafts each carrying at one end a friction roller engaging said driving disk and ally movable jackshaftseach carrying at one end a friction roller engaging said driving disk and at the other end a friction roller engaging one of said driven disks, separate means responsive to the tension of said strip between each said reel and said strip driving means for tilting the associated jackshaft with respect to the common diameter of its driving and driven disks thereby to effect axial movement of said jackshaft, and separate means responsive to axial movement of said jackshafts for restoring the associate-d jackshaft to a position substantially parallel to said common diameter.

3. In a tension control system for a traveling strip of material, a pair of spaced reels, constant speed driving means engaging said strip intermediate said reels, a driving disk, a driven disk connected to each said reel and positioned in the plane of said driving disk, a pair of axially movable friction spools each engaging said driving disk and one of said driven disks and being normally disposed with their axes substantially parallel to the common diameter of the associated driving and driven disks, separate means responsive to the tension of said strip between each said reel and said strip driving means for tilting the associated friction spool with respect to said common diameter thereby to effect axial movement of said spools and change the driving ratio of said disks, and separate means responsive to axial movement of said spools for controlling the angle of tilt of the associated spool to prevent hunting thereof.

4-. In a tension contro1 system for a traveling strip of material, a pair of spaced reels, means engaging said strip intermediate said reels for driving said strip at a predetermined linear speed, a driving disk, a driven disk connected to each said reel and positioned in the plane of said driving disk, a pair of jackshafts each carrying at one end a roller engaging said driving disk and at the other end a roller engaging one of said driven disks, a pair of parallel pivoted links each supporting oneend f one of said jackshafts in a normal position substantially parallel to the common diameter of the associated driving and driven disks, and separate means controlled by the tension of said strip between each said reel and said strip driving means for tilting the associated jackshaft about said supporting link thereby to effect axialmovement f the shaft, said supporting links being normally angularly disposed with respectto said common diameters thereby to effect restoring movement of said jackshafts toward said normal position in. response to axial movement thereof.

5. In a tension control system for a traveling strip of material, a pair of spaced reels, constant speed driving means engaging said material intermediate said reels, a driving disk,a driven disk connected to each said reel and positioned in the plane of said driving disk, a pair of jackshafts each carrying at one end a friction roller enagingsaid driving. disk. and at the .opposite end a friction roller engagingone-of said driven disks, a pairof 'quills inwhich said jackshaft's aremounted, a pair of pivoted links .supporting each said quill in' a normal position. parallel'to the common diameter of the associatedldriving and driven disks, and meansincludingone link of "each said pair of links and responsiveto. the tension. of said strip between. each. said. reel and said strip drivingmeans fortilting the associated quill. with respect to said. common diameter thereby to efiect axial movement of the associated jackshaft; the other link of each saidIpair of links. being disposed to .restore the connected quilljto parallel relation with said .commonldiameter "response to said -axial movement.

6;A- constantfltension' control system for a travelingstrip' of "material comprisingv a. reel, a driven"disk.'connected to said reel, a driving disk' in: theplane' ofsaidfdr'iven disk a .jacksh'aft carryin'gat' one end'a .friction rollerengaging. said driven disk' 'and'iatth other end a friction. roller engaging 'saiddrivingdisk, --means normally supporting. said jackshaftin substantially parallel' relation 'withthe 'common .diameterof said disks, and means responsive tohthetensionlof saidstrip for tilting. said 'jacksha-ft'witl'i -respect to' said' commondiam'eter thereby. to effect axial movement of I said'jacksh'aft and to change. the.

driving ratio between said 'dis'ks.

'IJA constant: tension. control system. for a traveling" strip of material comprising. ,aireel, a driven disk connected to.said reel,ia driving disk.

in the'plane of Lsaididriven disk, a..friction spool,-

means. normally supporting; said I spool in. substantially parallel relation with. the. common. di.-- ameter'offsaid. disks with opposite. endslof .said spool engagingsaid driving. .andld-riven disks .re=-

spectively means responsive to. thehtension. of said strip for tilting saidJspool liwith .respect to said common' diameter thereby to. effctaxial movement "of"said."sp ool and Ito. changethe-driving; ratio betweensaidfdis'ks, and. dampingv means comprising means responsive-to said 'axial movement'for restoring saidspool to itsunormal pare allel. relation with" resp'ectlto.saidcommon diameter:

8'; A" constant" tension control systmior a. travelingstrip of .material 'compris'ing a reel, a driven disk connected 'to saidreel; a-dliving disk. in the-plane -of' said" driven. disk, ,a. friction spool having opposite ends engaging said driving and driven "disks respectively, means including a pivoted link normally having an angular-- relation.

with"1'espect"to1the common diametenof-said.

disk' for supporting said? spool Lin a-normal .position" With'iits axis substantially... parallelLto .said common diameter; means responsive.ton theztem sion'of'said strip?for'tilting'theaxis of said. spook v about said link thereby to efie'ct axial movementof said'spool, said: link restoring .theparallel re..-.

latiombetween'lthe axis 1 of "said? spool and said;

common diameter" in response. to. said. axial movement:

9: A constant .ten'sion' system ion a. traveling strip of material comprising azreel; aldrivendisk connected;to-saidreel, a driving disk inthe :planev is mounted; a' air of "links pivotally connected. to opposite 'ends'o said' quill and pivotally mounted to supportsaidquill in a normallposition. par

allel' to-"the com on diameter. of said disks said T linksebeing angularly disposed with respect to each other. and .one of said-links .being normally substantially,perpendicular to said common diameter, and means including said perpendicular link'. and responsive to-. the tension of-said strip forztilting saidiquill about thenother of said links thereby. lto..eifect.axial-movement of said jackshaft'... I

10. .A .constanttension. control system for a traveling, strip of materialcomprising a reel,- a driven .diskiconnectedc-to said reel, a. driving disk inatheeplane of said v driven disk, a jackshaft carrying =at. oneeend a. friction. roller engaging saidldriven disk and-.-at the' other end a friction roller:engagingsaiddfiving -disk,.a quill in which saidjackshaftis mounted. a. pair of supporting links ivotallytconnectedto opposite ends of said quill and pivotallymounted .to support said quill in.a..normal position substantially parallel to the common. diameter .otsaid .d-isks, said links being angularly disposedwith respect to each other and one. ofsaidlinks being-normally substantially perpendicular.to..said..common diameter, means including said perpendicularlink and responsive to theatensionaofsaid. strip for tilting said jackshaft'abouttheother ofsaid links thereby to eifect .axial..movement of said jackshaft and to change. thevdriving: ratio between said disks, means for. reversing the. direction of rotation of saiddriving disk, andmeansassociated with said reversing means for-reversing the angular relation of.said.links saidaangularly disposed links being-arranged .in either directionof rotation of said disksto restorertheparallel relation between saidjackshaft .and: said. common. diameter in responseito axial .movement'of said jackshaft.

11.1A.constant.tension control system for a traveling strip{.of-..materialcomprising a reel, a driven .diskkconnectedto saidreel, a driving disk in. theplane .of said driven. disk, means associated with said.driving,.disk.,andengaging said strip for driving said strip at apredetermined linear speed, a jack'shaft carryingat 'one end a friction roller engaging,..saidldriventdisk and at the other end a frictionroller:engagingsaiddriving disk, mean normally(supporting. said .jackshaft in substantially .parallel relationwith. the common diameter of .Tsaidcdis'ks,Landlmeans responsive to the tension of Jsaid.strip. .for tilting; said jackshaft with respect .to saidcommondiameterthereby to effect axialf'movement 'of fsaid'jackshaft and to change thedr'iving ratio .between. said disks.

12'. In. atension .control .system fora traveling strip'oflImateriaLfa. pair. of spaced reels, means intermediate. saidree1s..for. driving said strip at a. predetermined. lineanspeed, means for driving both said reels inthedirection. of travel of said strip;,sep,arate meansresponsive to the tension of said strip between each said reel and said strip driving means .ior controlling the speed of the associated reel, .andfmeansactuated by said tension responsivemeansiorbraking-said reels upon apredetrminedldecrease in the tensionof said strip.

13'. In a tensioncontrol-system for a traveling strip,.of.lmaterial, ,a. pair of..spaced .reels, means intermediate said-.reels. for driving said strip at a predetermined linear speed, means for driving both'said. reelsin thedirection of travel of said strip, .separate..means responsive to the tension ofsaidstriploetween each said reel and said strip driving-meansfor.control1ing the speed of the associated reel, difierential braking means associatediwith each said reel andarranged to apply to each reel aibraking force greater in the direc- 13 tion of unwinding of said strip than in the direction of Winding, and means responsive to a predetermined decrease in the tension or said strip for actuating said braking means.

14. A reeling apparatus comprising a pair of spaced reel carrying an elongated strip of material, a driving capstan engaging said strip intermediate said reels, operating means slidably engaging said strip adjacent said capstan, a pair of dancer pulleys engaging said strip and positioned to include said capstan and said operating means therebetween, means for applying to said dancer pulleys fixed biasing forces of unequal value, means for reversing said capstan, and

means controlled by said reversing means for superposing an additional bia upon the dancer pulley having the smallest fixed bias.

15. A reeling apparatus comprising a pair of spaced reels carrying an elongated strip of Ina-- terial, a driving capstan engaging said strip intermediate said reels, operating means slidably engaging said strip adjacent said capstan, a pair of dancer pulleys engaging said strip and positioned to include said capstan and said operating means therebetween, spring means for applying to said dancer pulleys fixed biasing forces of unequal value, means for reversing said capstan, and additional spring means controlled by said reversing means for increasing the bias of the dancer pulley having the smallest fixed bias to a value greater than the larger fixed bias by approximately the diiference between said fixed biasing forces.

16. A reeling apparatus comprising a pair of spaced reels carrying an elongated strip of material, a driving capstan engaging said strip intermediate said reels, means for driving either of said reels as a take-up reel, operating means slidably engaging said strip adjacent said capstan, a pair of dancer pulleys engaging said strip and positioned to include said capstan and said operating means therebetween, spring means for applying to said dancer pulleys fixed biasing forces of unequal value, means for reversing said capstan, and additional spring means controlled by said reversing means for increasing the bias of the dancer pulley having the smallest fixed bias by approximately twice the difference between said fixed biasing forces, said reversing ing an elongated magnetic record medium, a

driving capstan engaging said record medium intermediate said reels, means for driving either of said reels as a take-up reel, a magnetic operating head frictionally engaging said record medium adjacent said capstan, a pair of dancer pulleys engaging said record medium and positioned to include said capstan and said operating head therebetween, spring means for applying to said dancer pulleys fixed biasing forces of unequal value, additional spring means having a disabled position and a position for superposing upon the smaller of said biasing forces an additional bias equal approximately to twice the diiference between said fixed biasing forces, means for reversing said capstan, and means controlled by said reversing means for positioning said additional spring means always to maintain the larger net bias upon the dancer pulley adjacent the takeup reel.

ARTHUR W. SEAR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date 839,261 Braud et a1 Dec. 25, 1906 1,406,665 Ljungstrom Feb. 14, 1922 1,520,546 Murray Dec. 23, 1924 1,700,981 Hayes Feb. 5, 1929 1,865,410 Byles June 28, 1932 2,012,208 Wildy Aug. 20, 1935 2,304,913 Herzig Dec. 15, 1942 2,328,322 Berthold Aug. 31, 1943 2,338,605 Tuttle et a1 Jan. 4, 1944 2,462,558 Scheuermann et a1. Feb. 22, 1949 FOREIGN PATENTS Number Country Date 568,627 France Dec. 24, 1923 587,628 France Jan. 20, 1925