US2023502A

US2023502A - Tension device

Info

Publication number: US2023502A
Application number: US719140A
Authority: US
Inventors: Harry Y Armstrong
Original assignee: Individual
Current assignee: Individual
Priority date: 1934-04-05
Filing date: 1934-04-05
Publication date: 1935-12-10
Anticipated expiration: 1952-12-10

Description

w, .1935 H. Y. ARMSTRONG Q zflfiggw TENSION DEVICE 7 Filed April 5, 1934 ATTORNEYS.

Patented Dec. 10, 1935 UNITED STATES PATENT OFFICE 7 Claims.

This invention relates to a device for maintaining a uniform tension upon a rotatable shaft, or to yieldably resist the rotation of a shaft.

An object of the invention is a device which will '5 at all times yieldably resist the rotation of a rotatable member with a uniform resistance.

Another object of the invention is a device which tends to effect retrograde rotation to the rotatable member, to prevent over-running of 10 the rotatable member, particularly a rotatable member having an intermittent feeding movement.

Another object of the invention is a device of the class referred to which is of maximum sim- 15 plicity, and of minimum cost to manufacture.

Another object of the invention is a device, of the class referred to, which can be readily and easily removed, or disconnected, from the shaft and replaced thereon without necessitating any 20 adjustments, or the services of a skilled operator, and which is impossible to get out of order.

The invention consists in the novel features and in the combinations and constructions hereinafter set forth and claimed.

25 In describing this invention, reference is had to the accompanying drawing in which like characters designate corresponding parts in all the views.

Figure 1 is a side elevation of the device se- 30 cured to a rotatable shaft which carries, and from which is unwound, a roll of web material.

Figure 2 is an end elevation of the structure shown in Figure 1.

Figure 3 is a partial plan view of the tension 35 device.

Figures 4, 5, 6 and '7 are end elevations of the tension device showing successive stages of the operation of the device during rotation of the shaft.

40 The invention consists generally in a shaft, suitable bearings for rotatably supporting the shaft, a cylindrical body, or worm, provided with a helical thread, or groove, on its periphery, a cord secured to the body and arranged to thread into 45 said groove, and a weight suspending from the free end of the cord, the shaft and the cylindrical body constituting one form of rotatable member.

in designates a shaft which is rotatably mount- 50 ed in suitable bearings ll. As here shown, the bearings are secured to the frame work [2.

I3 designates a roll of paper, or sheet material, in the form of a web, which is temporarily secured to the shaft I in any suitable manner,

55 and rotatable therewith.

The frame I2 may consist of a part of any machine performing operations upon the web I4 as it is unrolled from the roll l3, as for example,

a bread wrapping machine, or a stamping machine for fabricating articles from the web [4. 5 Obviously, the web It may be metallic, or fibrous, and may be in the form of a band or wire. Usually, where a web is unrolled from a roll, as referred to, the web is moved, or indexed, along by suitable mechanism whereby the operations on the web may be successively carried on. Where the roll is permitted to freely rotate upon the shaft, or the shaft permitted to freely rotate in its bearings, an appreciable amount of slack in the web is effected during its movement through the machine. This results from the inertia, orcoasting effect of the roll which often is considerable, particularly when the roll is of large diameter and results in an appreciable amount of slack in the web, which is undesirable and often affects the indexing, or proper progression, of the web through the machine.

Various forms of friction devices are commonly employed to maintain a tension on the shaft, or the roll of material. However, the tension of said devices varies greatly due to wear of the friction elements, atmospheric conditions, changes in temperature, and the like. Very often, the web is exceedingly thin, and dimculties are incurred as the result of the changes in the resistance of the friction devices.

The frame 12, or its equivalent, is usually provided with automatic means to prevent retrograde movement of the web it after it has been indexed, or moved, from one station to the next of the forming machine. As here shown, this means comprises a cam or eccentric 55 provided with a weighted portion or handle l6 which tends to rotate the eccentric I 5 in a clockwise direction,

and clamp the web l4 between theeccentric and 40 the top of the frame I2. Any retrograde movement of the web It obviously tends to tighten the eccentric or the cam 55, tighter. Any suitable means, in place of the eccentric it, may be used to prevent retrograde movement of the web 14.

The tension device proper consists of a cylindrical body I! which is formed on its periphery, or provided, with a helical groove, 01 thread I8. The member I! is secured to the shaft It in any suitable manner, but preferably so that it may .be readily removed from the shaft l0 and replaced thereon. As here shown, the body I! is provided with a bore to slidably receive the end of the shaft Ill, and is secured thereto, and rotatable therewith, by means of the key IS. The

body I1 is arranged on the end of the shaft so that the end of the shaft terminates in, or within, the plane of the end of the body, and the helical thread, or groove I8 is so formed that it tends to thread outwardly toward the end of the body,

upon rotation of the shaft ID in the desired direction to effect unrolling of the Web I4.

20 designates a cord, or similar flexible element, such as a chain, rope, cable, band, or the 10 like. One end of the cord 20 is secured to the body I! as at 2|, andthe cord is:threaded into the groove I8. A weight 22 is suspended from the free end of the cord.

Referring to Figure 2 of the drawing, it will be observed that the unwinding of the web I4 will effect rotation of the shaft II! ina clockwise .di-. rection. Accordingly, if the thread of the body II, which is secured to the rightend of the shaft Figure 1, is right handed, the cord will, upon 20 unwinding of the web I 4 from roll I3, thread onto the body I], .and the weight v22 .willmove upwardly .and outwardly. When the cord 20 reaches -.the .endof the thread or groove I8, the freeportion of the cord 26 will drop off from the body II. This action is illustrated in Figures 4 to 7 inclusive.

.In Figure .4, .the .cord has been wound in the groovexupon the body I1, and has approached the end 101' the groove, or thread indicated at 23.

39' Further rotation of the body II, in a clockwise direction, .Figure 5, will bring the end of the threadat the top side of the body, as indicated in Figure 5. In this position, .due to the fact that the groove or thread I8 now has only one side,

the cord 25 will feed off, or drop out, of the grooveover the end of the body and the shaft.

Figure 6 represents rotation of the shaft and body through an arc of 45 ,over that shown in Figure 5. It will be observed that in this position, the cord 20 is dropping out of thergroove I8 and overthe end of the body.

Figure 7 designates the same relative position of the shaft and body, as shown in Figure 6, but withthe .cord dropped-out of the threadfor approximately one-half the circumference of the body. It will be understood that when the end 23 .of the thread I8 reachesits uppermost position, as in Figure 5, and the cord has noouter wall to retain it, it drops 01f immediately. In

other words, the operation indicated in Figures 5, 6 and 7, is consummated instantaneously.

It Will be observed, Figure 7, that the cord has again assumed a position tangential to the rear side of the body, and is now eifective to establish 1 resistance to the rotation of the shaft in a clockwise direction. Upon rotation of the shaft and the body, the operations shown in Figures 4 to 7 inclusive, again take place. In other words, the cord 20 never becomes wound up upon the body 0 I1, and during the winding up of the cord the tension is uniform in that it is effected by the weight 22.

It will be observed that the weight 22 tends to rotate the shaft II] and the roll I3 in a retrograde, or counter-clockwise, direction, Figures 2 to 7. Accordingly, in addition to establishing a tension, or yieldable resistance, to the rotation of the roll I3 in a clockwise direction, the device will, in the event of the formation of any slack 0 in the web between the roll I3 and the lock I5, immediately rotate the roll in reverse direction, and remove the slack. This feature of my device is .of .appreciable importance. In friction devices heretofore used, a tension is maintained upon'the web I4. However, asa webis indexed, or moved along, through the forming machine, a certain amount of slack in the web is created during each indexing movement, and in as much as the friction device holds the roll I3 from rotation in both directions, this slack is gradually built up and eventually creates an undesirable situation, permitting the web to become entangled in the operating machine, or pile up upon the floor. With my device, any slack created by the unwinding of the web It is immediately taken up. 10 In'instances where the additional resistance, caused by the cord dropping ofi over the end of .the body, is objectionable, the cord 20 may be provided with a helical tension spring 25, or the equivalent, to lessen, or dampen, the shock caused 15 by the weight falling a distance equal to substantially'the diameter of the body II. It will be observed that as the cord passes out of the groove I8 and drops over the end of the body, a rotary motion will be imparted to the weight which may, 29 in someinstances, increase the wear on the cord 20. ..To avoidthis situation, the cord 20 may also be providedwith a swivel device 26 which also assists in preventing a swinging movement to the weight. 25 In order to maintain a retrograde force on the shaft and prevent over-running when the coil is being displaced, and hence, theshaft momentarily released of the braking force of the weight whenthe cord .and weight are passing from the 30 position shown in Figure 6 to that shown inFigure '7, the shaft Ill may be provided with a similardevice at its opposite end, as shown in Figure 1. In this instance, the body I I of one device would be secured to the shaft Ill insuch'manner that the end 23 of the groove or thread I8 would assume a relationship whereby the end of the groove I8 on the other body would be offsetsubstantially With this structure, one-of the cords 20 would always be winding up when the 40,

other cord dropped over the end of the other body.

The resistance required under different conditions and for different webs can be readily varied by adding to, or subtracting from, the 45 weights 22. This may be accomplished by forming the main portion of the weight 22 with a stem 28 connecting the ends of the weight, and additional weights may be inserted between :the

ends, the additional weightsbeing provided with 50,

a slot to'receive the stem 28.

It will be observed that by my device, ,Imot only maintain substantially uniformtension upon theroll I3, but I also maintain a uniformretrograde force. Also, on account of its extremesim- 55,

plicity,. there is nothing in my device to become out of order, and the device may bereadily removed and replaced on the ends of the shaft Ill. The operation of the device is fully automatic, as rotation of the roll I3 and shaft I0 eventually 0 wind up the cord 20, and as the bodies I are secured to theshaft in a predetermined position by the key I9,'the device may be removed and replaced on the .shaft'b-y any unskilled labor.

'What I claim is:

1. .The combination of a rotatable shaft,.a cylindricalbody secured to one'end' thereof "and rotatable therewith, said body being formed on its periphery with -a helical groove, a cord having one endsecured to the body and arranged to :be 7.0.

wound on the body in the groove upon rotation of the shaft inone-direction and to threadout of the groove and off of the body over the end thereof, a'xweight suspended from the free end of the cord, and means to prevent rotation of 75 the weight about its vertical axis when the cord threads off the end of the body.

2. The combination of a rotatable shaft, a cylindrical body secured to each end of the shaft with the ends of the shaft terminating within the planes of the outer sides of the bodies, the bodies being provided with a helical groove threading outwardly toward the outside of the bodies upon rotation of the shaft in one direction, a cord secured to each of said bodies and being arranged to wind upon the bodies upon rotation of the shaft, and a weight suspended from the free end of each cord.

3. The combination of a rotatable member, a cord winding on the member and having means for applying tension in opposition to the rotation of the member, the member having means for periodically displacing off the end of said member the last coil of the cord contiguous of the portion connected to the tensioning means and initially tangent to said member, whereby the tensioning means is free to react and return said portion of the cord to its original tangential relation to the rotating member and apply a momentary braking impulse to the member.

4. The combination of a rotatable member, a cord winding on the member and having means for applying tension in opposition to the rotation of the member, the member having means for periodically displacing off the end of said member the last coil of the cord contiguous of the portion connected to the tensioning means and initially tangential to said member, whereby the tensioning means is free to react and return said portion of the cord to its original tangential relation to the rotating member and apply a momentary braking impulse to the member, said displacing means comprising a helical groove in the rotating member-in which the last coil lies, the groove breaking through the end face of the rotating member at a location where the cord is initially tangent to the member, whereby the portion of the cord continuous of the last coil shifts crosswise of the end face of the rotatable member as said member rotates and said location shifts about the axis of said member.

5. The combination of a rotatable member, a cord winding on the member and having means for applying tension in opposition to the rotation of the member, the member having means for periodically displacing off the end of said mem- 5 ber the last coil of the cord contiguous of the portion connected to the tensioning means and extending tangential to said member, whereby the tensioning means is free to react and return said portion of the cord to its original tangential relation to the rotating member and apply a momentary braking impulse to the member, and means tending to rotate said 'member in a retrograde direction when the cord is returning to its original tangential relation to the rotatable member.

6. The combination of a rotatable member, cords winding on the member, and each having means for applying tension in opposition to the rotation of the member, the rotatable member having helical grooves in each of which the last coil of each cord lies, each groove breaking through an end face of the rotating member at a location where the cord therein is initially tangent to the member, whereby the portion of the cord contiguous of the last coil shifts crosswise of the end face of the rotatable member as said member rotates and said location shifts about the axis of the rotatable member, the location where the grooves open through the end face of the rotatable members being so arranged that either of said cords is in position to apply retrograde movement to the rotatable member, when the other is displaced from the rotatable member.

'7. The combination of a rotatable member, of means for continuously and yieldingly resisting rotation of said member including a cord winding on the member and traveling toward the end of the member and having means for applying 40 tension in opposition to the rotation of the member, the member having means for periodically displacing off the end of the member the last coil of the cord and subsequently, rewinding the displaced portion of the cord.

HARRY Y. ARMSTRONG.