US2396492A - Automatic tension device - Google Patents

Description

March 12; 1946.

H. F. CHILDERS AUTOMATIC TENSION DEVICE 2 Sheets-Sheet 1 Filed March 23, 1944 March 1946. H. F. CHILDERS AUTOMATIC TENSION DEVICE Filed March 25, 1944 2 S-heets-Shegc 2 INVENTOR HARRYF. CHILDERS ATTORNEY Patented Mar. 12, 1946 2,396,492 AUTOMATIC. TENSION. DEVICE Harry F. Childers, Merriam, Kane, assignor to Colgate-Palmolive-Peet Company, Jersey City, N. 3., a corporation of Delaware Application March 23, 1944, Serial No. 527,694

Claims.

This invention relates to wrapping machines and more particularly to a machine for controlling the tension applied to a web of wrapping material during unwinding from a storage reel.

. Most wrapping machines, regardless of structural detail, include a wrapping material storage reel, means for unwinding the Wrapping material from that reel, means for cutting the wrapping material into sheets of adequate size to accomodate the particular article to be wrapped and meansfor folding and sealing the cut sheets about the article.

In generaL'a Wrapping material for use in connection with small articles such as bars of soap is prepared in the form of. a continuous band of substantial'widthL This band is printed with whatever indicia the wrapped articles are to bear and at the same time is perforated marginally of the printed areas. Thereafter the wide band is wound about a hollow cop or tube and the.

resulting cylindrical body is radially slit, into a plurality of narrow wound bodies, the webs of which are each stored on a cop or tube for unwinding during use.

For the wrapping operation, the cop is mounted over a rotatable support and th roll of wrapping material is unwound therefrom by frictional.

draw-off rollers which grip successive portions of the web between their circumferential faces. After leaving the draw-off rollers, the perforated margins of the web are engaged by a sprocket device and cutter, the registry of the sprockets with the perforations serving to insure the cutting of the web at properly timed intervals consistent with the printed indicia which each wrapped article is ultimately to bear.

The success of the foregoing arrangement has very largely depended upon the positiveness of the drive of the draw-off rollers which operate by friction. If the draw-off were to be effected by the sprocket devices themselves, there would be too much tendency to tear the web perforations due to the web tension between the roll of material and the sprockets. To avoid this tension, frictional draw-off rollers are provided, these rollers serving, in theory, to feed the web to the sprocket devices under substantially no tension so as to prevent tearing of the marginal perforations of the web by the sprockets. ,The arrangement just described, although theoretically satisfactory, is not in practice wholly desirable for serious diiiiculty has been encountered in preventing slippage between the draw-off rollers and the wound roll of wrapping material, such slippage resulting in increases in tension between the draw-off rollers and thesprocket devices of such a magnitude as to cause rupture of the margins of the web resulting in the operation of the cutting mechanism out of synchronism with the printed indicia on the web. As a consequence of this, the articles may be incompletely wrapped or the printed material may be wrongly located on said articles. 4

Upon analysis of the foregoing problem it was found that, because the reel is initially of great diameter and the force exerted by the draweoff,

rollers is a constant, there is a high starting torque tending. to rotatev the reel. During the unwinding operation this torque is progressively reduced as a function of the reduction in diameter of the web-on the reel. Thus the drawofi rollers tend to rotate the reel too rapidly during the initial stage of unwinding, causing excessive slack between the reel and said rollers while, during the latter stages of unwindipg, the torque is so low that the rollers may slip relative to the web in attempting to rotate the reel.

Once the foregoing problem was recognized.

efforts were mad to control tension. Among these were suggestions that a brake be applied to the reel in opposition to the high starting torque. During unwinding the operator could.

gradually release this brake so that there would be virtually no opposition to the low tnrqugttalue existing near the end of the unwinding operation. This arrangement is satisfactory subject to constant attention by th operator. Such constant attention is, however, dificult to maintain and, even if maintained, not economically feasible. Other braking arrangements in which the braking efiect could be automatically reduced during unwinding were unsatisfactory either because of the complexity of the machinery involved or because of reliance on unsound principles of engineering.

With the foregoing in mind it is an object of this invention to overcome the dimculties encountered in the prior art in connection with the maintenance of tension between a storage reel and the draw-oil rollers associated therewith by providing resilient braking means normally acting on the reel to retard rotation thereof and means for progressively reducing the loading of said resilient means at a rate and of a magnitude correlated with the rate and magnitude of diameter reduction whereby the arrangement is susceptible to use without adjustment with webs of varying thickness unwound at various speeds.

It is contemplated according to this invention that the foregoing objects be accomplished concomitantly with continuous operation inwhich nexed drawings, wherein:

Figure 1 is a vertical sectional view of a pair of package supports, the brake engaging and releasing elements being shownin front elevation;

Figure 2 is a view in section taken along the line 2-2 of Figure 1:

assess:

tion may be effective on the roll of wrapping material, the latter is indirectly connected to sleeve I2. To this end flange I1 of sleeve I2 is bolted Figure 3 is a view in section taken along the line 3-2 of Figure'l; and a Figure 4 is a perspective view of the apparatus of Figure 1 showing a reel of wra ping material in operative position and indicating in broken lines the movementvof portions of the brokenleasing elements during an unwinding operation. 1

The apparatus illustra ed in the foregoing figures of the drawings constitute-but a part ofa wrapping machine of a type in which a printed wrapper in the form of a continuous band is withdrawn from a reel and cut at re ular intervals for wrappin about a bar of soap or other art cle. The continuous strip or band. 2 is withdrawn from the stora e reel by two draw-off rolls. not shown. operating in per pheral contact on either side of the band or strip; A pull of constant force, such as is exerted by the un-: winding rolls on the band. produces a torque equal to the product of that .force times the effective radius of the reel from which; the band to a flange 25 of reel support 22. Reel support 26 comprises, in addition to flange 25, an integral semi-cylindrical portion 21 extending for about 180 around stud I2 and terminating in an annular portion 22 having an interior central bore of a diameter greater than the external diameter of stud I2. Interposed between annular end portion 22 and stud I2 is a sleeve 29 having thereon a shoulder 20; The portion of this sleeve which is of lesser'external diameter is of a size to receive thereover, in bearing engagement, annular portion 22 of reel holder 26. Between annular portion 22 and shoulder 20 there is interposed an annular lubricating washer II. A similar washer 22 is disposed at the other end of annular portion 22.' Surrounding sleeve 29, at a point between washer 22 and the end of said sleeve, is an annular bearing element 22. This element is attached to sleeve 29. Sleeve 29 iskeyed to stud' I2 by a slot and pin arrangement, a pin projecting radially from stud l2 and engaging is being unwound. When the reel is full this radius is large resulting in a high torque but as the band is unwound the eflective radius de-,

creases with a resulting decrease in torque which may cause slippage between the draw-oi! rollers and the band. Since such slipping may result in disruption of the synchronism between the cutter and the printed material9 on the continuous band, it is proposed according to this invention to apply a resilient braking force on the reel during the initial stages of. unwinding and to progressively decrease this force responsive to reductions in the effective diameter of the reel which results in reduced torque during the end winding period.

In order to understand how the braking forceis applied and reduced it will be necessary first a to consider the supports for holding the wrapper containing reels,

The rolls of wrapping material each wound on a cop or tube are supported on spindle assemblies Ill and II which in turn are supported from a plate I2 which acts as a supporting element not only for said assemblies but as well for the braking apparatus to be hereinafter more fully described. Inasmuch as assemblies in and II areidentical in structure and function, only one of them will be described indetail;

In connection with assembly II it should be noted that a stud I3, threaded at its ends, is anchored in bearing I4 by a nut I2 to plate I2,

the free end of the stud extending outwardly from the plate a distance somewhat in excess of in an axially extending slot 22 through sleeve 29 at its left hand end as viewed in Figure 2. Because slot 25 is of greater length than the diameter of pin- 22, sleeve 29 is susceptible to axial movement on stud 1 I2. This movement is controlled by an adjusting nut 22 threadedly engaging. the end of the stud and connected to the sleeve 22 by an adjusting nut. retainer 21 which looks the nut to the sleeve so that the latter between the interior walls of the tube and theexterior surface of reel holder 22,spring 22 exerting sufficient force to lock cop C and reel holder 22 for rotation as a unit. As the roll is placed in position the cylindrical interior of cop C compresses spring 22 from its reposed position and is then axially moved until one vertical wall of the roll abuts against paper stop disc 22. I! then, the marginal perforations of the web do not correctly register with the sprockets of the cutter, adjusting nut 22 is'turned to change the axial position of the marginal perforations. This adjustment 'is of small magnitude .seldom amounting to anielghth of an inch. However, because brake sleeve i2 and flanged sleeve I2 are splined together, relative axial movement of these two elements is possible without disrupting the position of the brake sleeve I2 which is held by brake shoes 22 and at I2.

Reel holder H which has Just been described 2i lying within the groove is similar in all respects to reel holder IO and corresponding parts have been designated by like numerals followed by the sumx "11. It is intended that while one of the reels on eitherholder ill or H isbeing unwound the other reel may be changed for the purpose of replacing an empty one by a full one. The braking arrangement operates on either reel regardless of which is being unwound at any particular time. Since the braking force exerted by brake shoes 20' and H is to be reduced proportionately to the reduction in diameter of that reel as it is unwound, a follower wheel 50 is provided to contact the periphery of the wound band of wrapping mate'- rial on the reel. Since follower 50 contacts the top tangent point of the reel it will maintain Contact therewith y r y-throughout the un- Winding operation. g

, Follower wheel Ellis pivoted between the shank of a yoke constituting one end 0! a lever 52. The other end of lever 52 is keyed at 53 .to a

55'. This stud is threaded at one end for passage through plate l2. The stud is therefore held in position extending outwardly from the plate by a nut 56. The sleeve 54. is held'against axial displacement on stud 55 by an annular washer 51 held in position by a. bolt 58. The end ofv sleeve remote from washer 51' is provided with a flange 59 which is attached to cam 60. Cam 60 is a thick disc-like.p1ate having a rear wall 'adand 81. The ends of theselinks are attached at 88 and 89 respectively to toggles 80 and-8i re-x spectively. The toggle arms of toggle 9! are pivotally connected at 92 and 93 to the ends of brake shoes 2i! and 23, said shoes beingncrmally urged apart by internal spring as. Corresponding parts function in a corresponding manner in connection with reel supporting assembly iii, It can now be seen that spring 19 acting on lever 3i tends to shorten the distance between pivot points 82 and 93 thus drawing together brake sh'oes 20 and 2i against the action of spring 94. This causes the brake shoes to press against the brake'drum at 19, so tending to retardrotationof the reel support to which the reel is locked by actions! leaf spring 38. However, as follower wheel 50 moves inwardly toward the axis of reel supporting assembly 3, due to the unwinding of material from the reel, cam 60 will be turned in a clockwise disleeve 54 which is rotatably supported on a stud rection as viewed in Figure 1 causing cam face 62 to gradually lower cam follower 8! which in turn will lower rod 68 and cross-head it thus disposing the-upper edges 01' adjusting nuts 18 and 11 in a'lower horizontal plane. This increases the distance between said nuts and levers 80'and.8| so that the springs 18 and-i9 are less jacent and parallel to plate I2. The front face is recessed todefine cam surfaces 6! and 62 and an intermediate neutral zone therebetween, while a-hub 63 functions as a. central reinforcement. In front of. but spaced from hub 63, is a sleeve 64 which is also keyed to sleeve 54. Between hub 63 and sleeve 64 the shanks of a yoke SS-are passed, the distance between said shanks corre-' spondingto the external diameter of sleeve 64. Just below the point of origin of the shanks'of yoke 65, a pin 66 is passed therethrough having on one end'thereof a roller 61 mounted for free rotation. Said rolleris in a position to'follow the contour of cam surface 62 as indicated in Figure 3. A rod 88 is connected to the lower end of yokeSB, said rod being guidedfor vertical movement in a bearing-69 connected by bolts 10 to plate ii. The lower end of rod 68 is attached to a cross-head H through the opposite ends of which spring guides 12 and 13 are passed. These the, upper ends are provided withnuts illand I5. At the lower ends they are provided with knurled adjusting nuts l6 and 11 while, between said adjusting nuts and the cross-head H, coil springs 18 and 19 are disposed surrounding the spring guides.

Brake operating levers 80 and s: are pivoted respectively to plate l2 at 82 and 83. One end or the lever Si is provided with a hole so that it may fit over spring guide 73 with the defining- 'edges of the hole resting on the top of coil spring 19. "There is a similar arrangement in the caseof lever arm 80, spring guide I2 and spring 18.

V spring guides are threaded at both ends and at I the reel supported by assembly Ii,

compressed and therefore exert less thrust against the respective levers permitting springs 94 and 94a to spread pivot pointssz and 93 of toggle 9i and 32a and 93a of toggle 86 to a slight extent thereby somewha'treieasing the brakes.

It 'is to be understood that earn surfaces 5! and 62 are of substantially straight line development,

i. e.. the movement of follower Bl varies substan tially in direct proportion'tc angular'displacement of the cam throughout its active arc of I movement. Since thisis true it is evident that the release of the brakes will vary substantially in direct proportion'to the reduction in diameter of the web of wrapping material onthe reel. The rateot brake release will be varied automatically with'the rate of unwinding, regardless of the speed of operation of the draw-oil. rollers or the:

thickness of material 8.

In Figure 1 there is a diagrammatic indication oi! a. partially exhausted roll on reel supp rtin assembly ill; While this roll is icing unwound a full reel may be placed on the equivalent assembly ll'.- Then when thereel an assembly In is exhausted'it is on y necessary for the operator to swing lever 52 180* in a counterclockwise direction as viewed in Figure 1 so as to place follower wheel 50 in contact with the band of material on This action turns cam 6!! 180 and brings cam face 82 into co-action with follower 61 rather than cam face It can now be seenthat the end of lever 8| remote from spring guide 53 and on the opposite side of pivot pointBZi is urged in a counterclock-- wise direction as viewed in Figure 1. The same situation obtains in connection with lever 80 except the corresponding portion thereof is urged in a clockwise direction as viewed in Figure 1. At the ends of levers 8i! and Bi remote respectively p from spring guides 12 and 1:; connecting links 84 and 85 are pivotally attached respectively at 85 5!. Once this is done the operation is repeated as before, see Figure 4. The follower wheel 50 will cause lever 52 to turn in a counterclockwise direction as the reel is exhausted and thus follower 61 wili'gradually lower cross-bandit to release the compression of springs 18' and 19.

While it is true that springs '58 and'lfl are un loaded simultaneously according to the require=' ments 0! but one reel the braking eifectonthe other reel is immaterial due to the fact that it is not supplying material to the that time.

'What is claimed is:

i. .In' a web tension control apparatus including a pair of supports mounted for rotation about a spaced fixed axes, each'adapted to receive thereover a roll of web material for rotation therewith, braking means normally acting on each suppers to retard rotation thereof, means connected in v draw-oi rollers at both braking means for simultaneously reducing the braking eifect thereof, and roll diameter sensing means for operating the means for reducing apparatus may be continuously operated by plac-f ing a full roll on one of the supports while a roll on the other is being unwound and after completion of that unwinding, shifting the sensing means to operate with the full roll.

2. In a web tension control apparatus including a pair of rotatabl e supports mounted for rotation about spaced fixed axes, each adapted to receive thereover a roll of web material for rotation therewith, a brake drum fixed to each support, brake shoes acting on each drum, separate spring means each for urging the brake shoes acting on one of the drums to braking position,

' means for independently preloading each spring means, and means responsive to reduction in the diameter of a roll on one of said supports for simultaneously equally reducing the loading on both of said spring means at a rate and magnitude correlated with the rate and magnitude of the roll diameter reduction, said roll diameter reduction responsive means being movable to act with a roll on either support, whereby the machine may be continuously operated by placing a full roll on one of the supports while a roll on the other is being unwound and after completion of that unwinding, shifting the roll diameter reduction responsive means to operate with the full roll.

3. In a web tension control apparatus including a pair of rotatable supports each adapted to receive thereover for rotation therewith a roll of web material; a brake drum fixed to eachsupport, brake shoes acting on each drum, independent spring means for urging the brake shoes acting on each drum to braking position, cam means having. two cam surfaces developing in the same way from a reference point, means pivotally mounting said cam means intermediate said supports, a lever connected to said mounting means, a follower on said lever in position to contact a roll of web material on either of said supports by rocking of the lever from one to the other, and a cam follower for simultaneously reducing the thrust of both the said independent spring means in response to angular displacement of said cam means. i

4. In a web tension control apparatus, a pair of rotatable roll holders each adapted to mount a roll of web material, a brake for each roll holder, a movable cam, a shiftable roll diameter sensing member for actuating said cam adapted to be selectively associated with a roll on either of said roll holders, and a follower for said cam operatively connected to said brakes.

5. In aweb tension control apparatus, a pair of rotatable roll holders each adapted to mount a roll of web material, a brake for each roll holder, a cam rotatable about an axis, a lever rigid with said cam and movable about said axis in response to changing diameter of an associated roll, said lever being shiftable for operative association with a roll on. either of said roll holders, and a follower forsaid cam connected operatively to said brakes.

6. In a web tension control apparatus, a, pair of spaced rotatable roll holders mounted for rotation about spaced fixed axes and each adapted for mounting a roll of web material, a brake for each roll holder, and brake control means comprising a movable member adapted to change its position in response to changes in diameter of an operatively associated roll, said member being shiftably mounted to be selectively placed in operative association with a roll on either of said roll holders.

7. In a web tension control apparatus, a pair of spaced rotatable roll holders mounted for rotation about spaced fixed axes and each adapted for mounting a roll'of web material, a brake for each roll holder, 9. pivoted sensing member adapted to be selectively swung into operative association with a roll on either of said roll holders and responsive to changes in diameter of said associated roll, and brake control means actuated'by said sensing member.

8. In a web tension control apparatus wherein a' single roll diameter sensing member is adapted to be selectively associated'with a roll of web material on either of two rotatable roll holders, said sensing member comprising a pivoted lever, a rotatable cam actuated by said lever, a single cam follower operatively connected to brakes for both of said roll holders, and spaced control surfaces on said cam one of which is adapted to co-act with said follower when said lever is moved into association with one or the other of said roll holders.

9. In the web tension control apparatus defined in claim 8, said cam and lever being rigid and rotatable about a common axis.

10. In a web tension control apparatus, a pair of rotatable roll holders mounted for rotation about fixed spaced axes each adapted to mount a roll of .web material, a brake for each roll holder, and shiftable r011 diameter sensing means adapted to be selectively associated with a roll on either of said roll holders operatively connected to said brakes.

' HARRY F. CHILDERS.

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