US3255979A

US3255979A - Web tension control

Info

Publication number: US3255979A
Application number: US299738A
Authority: US
Inventors: Ernest H Treff
Original assignee: FL Smithe Machine Co Inc
Current assignee: FL Smithe Machine Co Inc
Priority date: 1963-08-05
Filing date: 1963-08-05
Publication date: 1966-06-14
Anticipated expiration: 1983-06-14

Description

June 14, 1966 E. H. TREFF WEB TENSION CONTROL 6 Sheets-Sheet 1 Filed Aug. 5, 1963 INVENTOR. 679N557 TQEFF ATTORNEYS June 14, 1966 E. H. TREFF 3,255,979

WEB TENSION CONTROL Filed Aug. 5, 1963 6 Sheets-Sheet B I a a gi Z02 INVENTOR [RA/E5 7 TEE/=7:

ATTORNEYS June 14, 1966 TREFF 3,255,979

WEB TENSION CONTROL Filed Aug. 5, 1963 6 Sheets-Sheet 3 INVENTOR. f/P/VES 7- 72 5;;

ATTORNE Y June 14, 1966 T F 3,255,979

WEB TENSION CONTROL Filed Aug. 5, 1965 6 Sheets-Sheet 4 INVENTOR. 5 AFR/V557" 77FF ATTORNE Y June 14, 1966 TREFF 3,255,979

WEB TENSION CONTROL Filed Aug. 5, 1965 6 Sheets-$heet 5 w 64 a I 74 6'9 I i Z ll 5 I a 50 7% 66 I 72 w/ I I l V INVENTOR. EPA 5 r 7%577 ATTORNEYS June M4, M66

E. H. TREFF 3,255,979

WEB TENSION CONTROL Filed Aug. 5, 1963 6 Sheets-Sheet 6 INVENTOR. Em/5 7 7k ATTORNEYS United States Patent 3,255,979 WEB TENSION CONTROL Ernest H. Treff, Port Washington, N.Y., assignor to F. L.

Smithe Machine 00., Inc, New York, N.Y., a corporation of New York Filed Aug. 5, 1963, Ser. No. 299,738 13 Qlairns. (Cl. 24275.44)

This invention relates to web feeding mechanisms and in particular to improvements in mechanisms for controlling the tension of the web during the acceleration and deceleration thereof, associated with the starting and stopping of the machine employing the web.

The present invention is particularly applicable to Web feeding apparatus which supplies material to a webfeed envelope making machine. The size of the envelopes made by such a machine dictates that the width of the web material be small, as compared with material utilized in other web feeding apparatus such as newspaper printing presses for instance. It can be appreciated that breakage in such web material is more likely to occur due to its relatively small size. However, the improvements comprising this invention are not restricted to web feeding apparatus which supply envelope forming machines, but may be utilized in any web feeding apparatus.

When web feeding apparatus of the type towards which this invention is directed is stopped, a break is applied to the roll of web material to stop the roll because it otherwise would continue to rotate due to its inertia. However, if the brake decelerates the web supply roll at a rate faster than the rate of deceleration of theassociated envelope forming machine, the tension of web therebetween will obviously increase. If the tension becomes too great, the web will, of course, break. However, if the application of the brake does not suffice to 'decelerate the web supply roll as fast as the machine, ex- I cessive slack will develop and render the machine inoperable. This invention is directed towards novel means for sensing an increase in web tension and for controlling the brake in response thereto to prevent such breakage, by maintaining a predetermined average web tension during the stopping of the machine, which is substantially independent of web roll inertia. Furthermore, in Web feeding apparatus of the type herein described a second cause of web breakage may occur when the machine is started and the web in the machine is abruptly accelerated. Thus, if there were any slack in the web material the abrupt movement of the web when the machine is activated would tend to snap the material due to the resistance produced by the inertia of the heavy roll of material. Again, the present invention is directed towards obviating breakage of this type by instantly and smoothly applying a web roll accelerating torque, in the form of web tension, that is proportional to the difference in instantaneous speeds between the machine and web roll. The invention includes pressure sensitive apparatus which reacts to changes in the tension of the web material. In addition there is provided a dancer roll mechanism connected to the pressure sensitive apparatus, which engages the web material in such a manner as to move with changes in the tension of the web. Upon stopping the machine the dancer roll mechanism communcates the changes to the pressure sensitive apparatus and when the rate of change exceeds a predetermined amount the apparatus is activated, which in turn energizes a switching means that releases the brake thereby relieving the web of its accumulated tension. The dancer roll continuously acts to take up slack in the web during all phases of the operation, i.e., acceleration, deceleration, steady running state and while the web is stopped.

3,255,979 Patented June 14, 1966 It is, therefore, an object of the present invention to provide relatively uncomplicated yet efficient apparatus for relieving tension in the web material of web feeding apparatus.

Another object of this invention is to provide improved tension relieving apparatus utilized in the web feeding sections of envelope forming machines.

Still another object of the present invention is to provide apparatus for releasing the web rol'l brake upon sensing a predetermined rate of change of tension in the web material.

A further object of this invention is to provide apparatus for taking up any slack in the web material after the apparatus has been shut off.

For other objects and a better understanding of this invention reference may be had to the following detailed description taken in connection with the accompanying drawings, in which: I

FIG. 1 is a diagrammatic view of the web feeding apparatus of this invention.

FIG. 2 is a side view of the web feeding apparatus of this invention.

FIG. 3 'is a top plan view of the web feeding apparatus of this invention.

FIG. 4 is a section taken along the line 44 of FIG 3.

FIG. 5 is a section taken along line 5-5 of FIG. 3.

FIG. 6 is a section taken along line 6-6 of FIG. 3.

FIG. 7 is a section taken along line 77 of FIG. 6.

FIG. 8 is a section taken along line 88 of FIGS. 6 and 7.

FIG. 9 is a schematic representation of the electrical system which is embodied in the present invention.

FIG. 10 is a further embodiment of this invention wherein a friction clutch assembly is employed in lieu of the pressure actuated switch in FIG. 6.

Turning now to the drawings, there is shown in FIG. 1 web feeding apparatus indicated in general by the numenal 10.

As can be seen by reference to FIG. 1, web material 12 is unrolled from a roll of web material 14 and deployed through a series of guides to a further section of the machine, not shown. As the web material is unwound from roll 14 it passes over roller 16 and under floating idler 18 and from there upwardly and around fixed roller 20. Web material 12 then descends to and around

rollers

22 and 24 and upwardly between machine drive roller 26 and upper opposed roller of a parent machine such as an envelope forming machine, the remainder of which is not shown. The web material is pulled forward by utilizing parent machine motor 27, shown schematically in FIG. 9, through shaft 23 and bevel gears 21. A spring unit 29 serves to keep a predetermined amount of pressure applied to roller 25, thereby providing a smoothing and gripping action to the web material 12.

A pair of damping arms 28 are connected together at one end by rod 30. Damping rollers 32-, mounted upon rod 30, in cooperation with friction block 33 (FIG. 2)

also secured to rod serve to apply pressure to roll 14 thereby tending to slow the rotation of the roll. The surface of friction block 33 may be provided with a suitable friction material such as felt or rubber (not shown) to supply the desired drag on the web roll. To the other end of damping arm 28 there is secured a rod 34 which is engaged by slotted arm 36. To slotted arm 36 is adjustably secured a link chain 38 which engages and is secured to sprocket wheel 40. The angle through which arms 28 will pass may be varied by adjusting chain 38 along slotted arm 36. A shaft 42 is turned by the movement of the sprocket 40 and is in turn connected to hub 44, which is connected to counterweight 46. It can be understood, therefore, that the counterweight 46 through sprocket 40, chain 38 and damping arms 28 to block 33 and rollers 32 applies suflicient force to supply a damping effect upon the rotary motion of roll 14. As the roll grows smaller and the arms 28 move toward a horizontal position, counterweight 46 drops from the 90 position (relative to chain 38) shown in FIG. 1 to an angle less than 90. Thus less pressure is applied to rollers 32 and friction block 33 as roll 14 grows smaller.

However, the damping tension produced by friction block 33 and rollers 32 adds to the friction tension developed by the rotating

members

60, 54, 56, 52, 48 driven by the unwinding web roll shaft. As the unwinding roll 14 becomes smaller the angular speed of rotation of the roll increases. The increased speed of the rotating members produces an increase in the friction energy of these machine elements. In addition, the effectiveness of this friction torque in restraining rotation of the web roll shaft increases as the web roll diameter decreases. For instance, the web tension produced (by the friction torque on the web roll shaft doubles as the roll decreases to one half its original size.

In view of the foregoing considerations, the present invent-ion includes a novel means for decreasing the force applied to rollers 32 and block 33 as the rpm. of the roll 14 increases with a decrease in its diameter. This is accomplished, as explained hereinabove, through the cooperation of friction block 33, counterweight 46 and their associated elements which apply progressively less pressure to roll 14 as the roll grows smaller. In other words, the variable frictional restraining means operating upon the web roll periphery compensates for variations in the web shaft restraint means so that a uniform web tension is maintained irrespective of web roll diameter r..p.m.

Another function of damping arms 28 relates to their function in providing constant alignment of the edge of roll 14 relative to

rollers

25 and 26. The angular wobble of the roll, due to a lack of squareness of the side surface of the roll with its axis of rotation, would ordinarily move the web out of alignment with

rolls

25 and 26. Arms 28 serve to obviate such misalignment by forcibly restraining the edge of roll 14 .to thereby cause the web roll shaft 15 to oscillate axially in the support bearing 17.

A braking apparatus 48 which is actuated when motor 27 is de-energized is connected through

sprocket wheels

52 and 54 and link chain 56 to shaft 58. Shaft 58 in turn is connected to the shaft upon which the roll 14 rotates, through

gears

60 and 62. It can be seen by reference to FIGS. 1 and '2 that the rotary motion of roll 14 is transferred through the gears and link chain to the braking apparatus 48, the application of which tends to counteract the rotary motion of the roll to thereby slow it, and finally stop it. Idler 63 provides for the regulation of the tension of the chain 56 by the adjustment of bar 65 to which idler 63 is connected. Braking apparatus 48 is activated and deactivated by apparatus to be explained more fully hereinbelow.

FIG. 9 serves to illustrate the pertinent sections of the electrical circuits involved in this invention. The activation of motor 27 causes an electrical current to be transmitted through solenoid 65 which holds switch 57 open. Contact arm 122 of switch assembly 68 is shown in its normally closed position. Winding 59 is adapted to operate ibrake 48 when switch 57 is closed and contact arm 122 is closed thereby completing the circuit to source 61. Thus when motor 27 is turned off and contact arm 122 is closed brake 48 will be activated. Foot switch 595 allows the operator to release the ibrake even though motor 27 is deactivated and contact arm 122 is in its closed position.

Turning now to one of the features of the present invention, there is shown in FIG. 1 a dash pot 64 which is affixed to shaft 66. Support arms 67, FIG. 4, are connected at one of their ends to shaft 66 and at the other to support bars 69. Dash pot 64 is connected to a normally closed switch assembly 68 which, when open, deactivates brake 48. Dash pot 64 is connected by one end to dancer roll arm assembly 70. Dancer roll arm assembly 70 is comprised of a pair of opposed arms 72 connected at three points by pivot rod 74 and

rods

76 and 78. Rotatably mounted to rod 78 are opposed arms 80 which are in turn rotatably secured at their other ends to idler shaft 82. A bearing 84 is afiixed to each end of idler shaft 82 thereby providing for the freely sliding movement of the shaft along runners 86. Depending downwardly from arms 72 are tension springs 88 which are connected to frame 90 of the web feeding apparatus, through slotted bars 91 which provide for the adjustment of the tension of said springs.

Thus a constant tension of predetermined degree may be applied to the dancer roll arm apparatus. There is a continuous downward pressure applied to floating idler 18 because springs 88 tend to move arms 72, and consequently arms 80, which connect to arms 72 through rod 78, downwardly. Floating idler 18 connected to arms 80 through shaft 82, therefore, applies a constant pressure on web 12, as best understood by reference to FIG. 1, to thereby take up any slack which may be present in the web.

As can be seen from FIG. 2, safety springs 92 are secured at one end to support posts 94 and at the other end to opposed arms 72. This safety spring acts to prevent the dancer roll arm assembly 70 from dropping down past a certain predetermined point. The safety springs also act to provide continuously varying tension on web 12, as the position of idler 18 varies, by partially or wholly supporting the weight of the entire movable dancer roll mechanism. Thus, the tension can be zero when the idler is at the bottom of its travel in runners 86 and smoothly increase in tension to a maximum at the top of the idlers travel.

Turning now to a more specific explanation of the dash pot 64, there is shown in FIGS. 6 to 8 detailed views of said dash pot. A piston rod 96 is secured at its upper end to shaft 66 and its lower end to piston 102. A cylinder 100 rotatably secured by its lower end 101 to rod 76, is adapted to accept piston 102 in a tight but slideable relationship thereto. A cap 103 is secured to the top of cyhnder 100 by bolts 105 and includes vent 107. The piston, therefore, remains stationary while the cylinder 100 is free to move along the piston when the dancer roll arm assembly is moved up or down. The position of the piston and cylinder in relation to the direction of gravitational force disclosed in this embodiment obviates the need for seals to completely contain the oil. However, it should be understood that other suitable arrangements of the piston and cylinder assembly may be employed.

Piston 102 includes variable restriction orifices 104 which provide a relatively slow leakage therethrough of the fluid from the portion of the cylinder beneath piston 102 through the piston to the portion of the cylinder above the piston when there is pressure exerted on the fluid beneath the piston. Adjusting screws 106 provide for the regulation of the amount of fluid that may pass through the orifices for any given amount of time. The screws, as shown in FIG. 7 are in their maximum open position and allow a maximum amount of fluid to pass through the orifices 104. In addition to the variable restriction orifices 104 there are also shown one-way orifices 108. Secured to the bottom of the piston 102 by screws 110 are flappers 112. Flappers 112 in their closed position seal off one-way orifices 108. However, when cylinder 100 moves downwardly the pressure of the fluid which normally holds the flappers closed is reduced thereby allowing the flappers to fall away from the orifices and permitting the rapid passage therethrough of fluid from the portion of the cylinder above the piston to the portion of the cylinder beneath the piston.

The switch assembly 68, as can best be seen from FIG. 6, is connected to the dash pot through a hollow threaded S extension 113. A passage 114 provides for fluid connection between the lower section of the dash pot and piston 116 of the switch assembly. A coil spring 118 tends to resist the inward movement of piston 116. Piston rod 120, aflixed to one end of piston 116 extends through the switch assembly to contact arm 122. Leads 124 are connected to provide the necessary circuit when the contact arm is closed, to actuate the brake when the driver motor is turned off. Thus with the application of sufficient tension to the web, opposed arms 80 tend to rise, which in turn tend to move the cylindrical shell 100 upwardly thereby applying pressure to the fluid in the portion of the cylinder beneath the piston. This pressure serves to close flappers 112, leaving only the small restriction orifices 104 open to the passage of the fluid through piston 102.

It can be understood from the foregoing that a slow increase in the web tension will not activate the switching apparatus since orifices 108 allow the passage of a small amount of fluid therethrough, thereby cancelling the effect of small amounts of pressure on the fluid. However, when the tension on-the web increases rapidly the pressure applied to the fluid dash pot 64 is too great to be accommodated by the fluid flow through orifices 108. When this occurs the pressure generated in the fluid in the portion beneath piston 102 is transmitted down through passage 114 and is applied to piston 116. Piston 116 is moved against coil spring 118 which tends to oppose the inward movement of the piston. Piston rod 120 in turn is moved so that the contact arm 122 is opened to the position shown in dotted lines in FIG. 6, breaking the circuit and shutting off the brake.

At one end of support bar 69 there is shown alatch 130 supported by means of arm 128. Latch 130 is utilized when, in the process of changing the roll of web material it is necessary to hold arms 28 and damping rollers 32 away from the area of the roll. Thus, the rod 30 may be lifted upwardly and fitted into notch 132, giving support to the damping assembly, thereby allowing the operator to more easily eflect a change of the web rolls.

From the foregoing it can be understood that the apparatus of the present invention provides a means for preventing breakage of the web material during both the acceleration and the deceleration of the web. When motor 27 is oif and contact arm 122 is in the closed position, brake 48 will be applied thereby slowing the rotation-a1 movement of the roll of web material 14. However, simultaneously, web material 12 is being pulled forward, even though the motor is turned off, due to the momentum of the driving apparatus. Tension is therefore applied to the web material causing the opposed arms 80 to be moved upwardly. When this occurs the cylinder 100 is also moved upwardly, pressure is applied to the fluid which is transmitted back to the passage 114, and piston 116 and piston rod 120 cooperate to move the contact arm 122 away from the contacts. The electrical circuit which actuates the brake is broken and the brake is released thereby relieving the tension on the web and the roll of web material is now free to rotate once again. After the tension has been relieved by the releasing of the brake, the tension applied by springs 88 tends to pull opposed arms 80 downwardly which in turn pull the cylinder 100 downwardly thereby relieving the pressure on the fluid in the portion of the cylinder beneath piston 102. Piston 116 is restored to its original position by the action of coil spring 118, and the contact arm 122 is again returned to its closed position thereby closing the electrical circuit and actuating the brake. This process is repeated until the entire apparatus has been completely halted.

The tension produced by springs 88 which tends to pull the arms 80 downwardly, thereby relieving the tension of the web in cooperation with the action of the braking apparatus which tends to tighten or apply tension to the web, serves to keep a proper amount of tension on the 6 web after the motor 27 has been deactivated. This tension will thereby obviate the presence of any slack in the web material after the entire apparatus has been complete-1y halted. The presence of slack in the web when the apparatus is started would ordinarily cause the web to snap.

Since web roll 14 is driven by web tension only, an equilibrium of forces is established when the apparatus is running steadily and the springs exert a force exactly equal (if corrected for mechanical advantage in arms 72) to the total friction eifect in all rotating members between roller and brake 48, a running tension in the web is thus established. When the parent machine is started the tension in the web exceeds this running tension by an amount required to accelerate the web roll. The additional tension results from the additional force required to overcome the inertia of the web roll. The web roll, therefore, is not set into motion until the machine drive rolls and 26 have pulled enough paper out of the dancer roll loop, moving the dancer roll and stretching the springs to a higher force level, to provide the additional tension needed to accelerate the roll. The resulting time lag then requires that the web roll be accelerated faster than the parent machine thereby producing even higher web tensions than what would have been needed to accelerate the roll at the same rate as the machine. As can be seen from the foregoing, a simple spring loaded tensioning device, not employing applicants novel invention in cooperation with a dancer roll assembly, on a Web being rotated under the influence of the tension only, produces a self destructive unstable dynamic reaction when being accelerated.

A purpose of the damping piston, therefore, is to practically eliminate the time delay by producing a reaction force on the Web, which in turn produces the additional web tension needed for acceleration of the roll, that is essentially proportional to the diflerence in instantaneous speed of the parent machine (drive rolls 25 and 26) and the web roll. The time delay disadvantages of the prior art wherein simple spring loaded tensioning devices are utilized can be explained alternately; since it requires an increment of time to establish a higher tension in the web by the reaction of the springs to the motion of the dancer roll, a condition exists where the parent machine has already accelerated to a finite instantaneous speed at the instant the web has accumulated sufiicient tension to start the roll. Thus, under the constant urging of the parent machine, which for all intents and purposes is trying to run away from the web roll by accelerating, the web roll tension increases to a point where it exceeds the strength of the paper.

The longer the time delay between the initial start of the machine and the start of the web roll, the greater the difierence in speed and the harder the machine yanks on the web to set the web roll in motion. Thus, the damping system of the present invention reduces to an acceptable minimum the time delay between the start of the parent machine and that web tension which will begin to accelerate the web roll. Adjusting screws 106 vary the amount of time delay.

It follows from the foregoing discussion that reducing the time delay reduces the maximum tension developed upon acceleration of the machine. The porting in the piston is primarily designed to allow the dancer roll to drop quickly and easily and to produce the required additional tensioning force when being moved upward. This in no way effects web tension when the machine is running at a steady speed. In stopping the parent machine the generated pressure resulting from the difference in instantaneous speed between the parent machine and the web roll is used to sense this error and to activate means for releasing the brake. The braking eflort, in order for this system to operate properly, must always produce a greater deceleration in the roll than that deceleration experienced by the parent machine.

Turning now to FIG. 10, there is shown a further embodiment of this invention wherein pressure switch 68 may be replaced by the apparatus as shown. The apparatus depicted in FIG. serves to operate the brake by the motion of the dancer arm, as contrasted with switch 68 which actuates the brake as a function of rate of change of web tension.

Opposed arms 80 are secured to shaft 134 which in turn is connected to a conventional friction clutch 136. To friction clutch 136 there is attached clutch arm 138 whose movement is restricted by limit bars 140. A normally closed microswitch 142 supplies the same results as switch assembly 68 relative to the braking and closing of the brake circuit. Springs 144 are connected by one end to arms 80 and by the other to a fixed member not shown. As tension is applied to web 12 the pressure on floating idler 18 tends to move arms 80 upwardly thereby pivoting said arms such that shaft 134 is rotated, which in turn moves clutch arm 138 in a direction to provide contact between key 146 of the microswitch and adjustable member 148. When key 146 is pushed upwardly by member 148 the normally closed microswitch will open thereby breaking the circuit which holds the brake in its operating position, releasing said brake as in the previous embodiment. When the brake is released, spring 144 which applies pressure that tends to pivot arm 80 in a counterclockwise movement, comes into play and moves arm 80 in a counterclockwise movement. Thus clutch arm 138- is returned to its original position and the microswitch 142 is once again returned to its normally closed position, thereby activating the brake. Friction clutch 136 provides for the clockwise movement of arms 80 even after clutch arm 138 has moved to its furthest position in either direction, without applying an excess of pressure on limit bars 141).

Thus, function of the web tension control system can be divided into three (3) modes of operation: (1) acceleration of the web roll, (2) steady state of running of the web roll, and (3) deceleration or stopping of the web roll.

The damping piston permits rapid acceleration of the web with limited web stress. The damping system does no appreciable work during steady state of running, at which time the web tension is maintained primarily by the tension springs 88 and the weight of the dancer roll linkage. The damping system pressure is also utilized to provide the tension sensing function for operating the brake cut-out switch during deceleration of the machine and web roll. The damping system is used as a damper only during acceleration of the machine and is used as a web tension sensing means during deceleration of the machine. The first is an active function working directly on the web and the latter is a passive function which causes an active member to be controlled.

The purpose of the spring loaded dancer roll is to maintain a controlled predetermined tension on the web while the machine is running at a steady speed. This required function produces a dynamic transient condition which exists upon starting the machine and usually results in breaking the web, necessitating apparatus as described hereinabove.

The present invention, therefore, provides apparatus for web feeding mechanisms which alleviates an excessive rate of change of increase in the tension on the web when the feeding mechanism has been turned oif and the web roll braking apparatus has been turned on. In addition, the present invention provides that there will always be sufficient tension applied to the web material such that there will never be any slack in the web material prior to the starting of the drive motor. Further, tension on the web material 12 will remain at a degree which is predetermined by the various adjustments of the apparatus described. This tension will provide that any sudden acceleration of the machine whether the roll of web material be full or partially full, will not cause the web material to break.

I have described what I believe to be the best embodiments of my invention. I do not wish, however, to be confined to the embodiments shown, but what I desire to cover by Letters Patent is set forth in the following claims.

I claim:

.1. Web feeding apparatus adapted to support a roll of web material for rotation, comprising driving means, driven means operatively connected to said driving means for unwinding the roll of web material by pulling the web through the apparatus, braking means for opposing the rotation of the roll of web material when said driving means for said driven means is deactivated, means comprising a dancer rol-l assembly including dancer roll means for providing tension in the web irrespective of the position of said dancer roll means, tfluid dash pot means operatively connected to said dancer roll assembly, and means responsive to the fluid pressure in said dash pot means for releasing said brakes means when the tension of the web increases above a predetermined limit.

2. A web feeding mechanism comprising a roll of web material, means for unwinding the roll of web material by pulling the web, a braking mechanism adapted to restrain the movement of the roll of web material, a dancer roll arm assembly including a dancer roll for providing tension in the web material irrespective of dancer roll position, means operatively connected to said dancer roll arm assembly for sensing the tension in the web, said sensing means comprising a fluid dash pot having one end thereof connected to said dancer roll arm assembly, and a pressure switch connected to the dash pot, said switch being adapted to deactivate said braking mechanism upon the application of a predetermined pressure on said dash pot by the web tension through said dancer roll arm assembly.

-3. In combination, a roll of web material, means for pulling the web from said roll to unwind said web from said roll, means for removing the slack in said web between said roll and said pulling means and for applying a tension to said web extending therebetween, means for braking the unwinding of said roll when said pulling means is deactivated and means, cooperative with said means for removing the slack from said web, for sensing a predetermined increase in the web tension to thereby deactivate said braking means and restore the web tension to within predetermined limits, said slack removing means including a dancer roll arm assembly comprising dancer roll means, and a spring connected to said assembly for applying tension to the web irrespective of the position of said dancer roll means, said sensing means including a iiuid dash pot and switch means for responding to changes in the pressure of the fluid within the dash pot.

*4. Means for establishing a constant tension in a web of sheet material as it is unwound at a. uniform linear velocity from a roll, comprising, a shaft rotatably supporting said roll, means connected to said shaft for applying an angular restraining force thereto in increasing amounts in proportion to increases in angular velocity of said shaft as the diameter of the roll decreases, and means cooperative with the periphery of said rollfor applying a decreasing roll unwinding restraining force in inverse proportion to increases in said shaft angular restraining force so that a constant tension is maintained in said web irrespective of roll diameter and angular velocity.

5. Means according to claim 4 wherein said last mentioned means includes flange portions for engaging the side edges of said roll to prevent axial wobble thereof as said roll unwinds.

6. Means according to claim 4 wherein said last mentioned means includes a pivoted counterweight, means positioning said counterweight horizontally of its pivot when said roll is at its maximum diameter, and means for allowing said counterweight to rotate to a position below its pivot as said roll decreases in diameter.

7. Web feeding apparatus adapted to support a roll of web material for rotation comprising driven means for unwinding the roll of Web material by pulling the web through the apparatus, braking means for opposing the rotation of the roll of web material, means including pressure switch means for applying said brake when the drive for the unwinding means is deactivated, and fluid dash pot means responsive to the increase in tension of the web at above a predetermined rate and operative with said pressure switch means to release the braking means.

8. A web feeding mechanism comprising means adapted to support rotata-bly a roll of web material, means for unwinding the roll of web material by pulling the Web, a braking mechanism adapted to restrain the rotation of the roll, a dancer roll assembly including a plurality of rolls for guiding the web and a dancer roll movable with respect thereto in response to changes in tension in said web, a dash pot operatively connected to said dancer roll to restrain motion of said dancer roll in response to increase in tension in the Web, and pressure sensing means responsive to the pressure within the dash pot operative to release the braking mechanism when the pressure reaches a predetermined value. 1

9. A web feeding mechanism in accordance with claim 8 in which the dash pot permits unrestrained motion of the dancer roll in response to decrease in tension in the web.

10. Web feeding apparatus adapted to support a roll of web material for rotation, said apparatus comprising driving means, driven means operatively connected to said driving means for unwinding the roll of web material by pulling the web through the apparatus, braking means for opposing the rotation of the roll of web material when the drive for said unwinding means is deactivated, means comprising dancer roll means :for providing tension in the web, and means operatively connected to said dancer roll means for releasing said brake means when a predetermined increase in the tension of the web is reached, said brake releasing means comprising a. fluid dash pot and switch means connected to the dash pot for deactivating said brake means when a predetermined rate of change of web tension is exceeded.

11. In combination, means adapted to support a roll of web material for rotation, means for unwinding the roll by pulling the web, a dancer roll assembly comprising a plurality of rolls for guiding the web and a dancer roll engaging the web movable in response to change in web tension, motion restraining means restraining movement of the dancer roll in response to increase in web tension to a value below a predetermined velocity, whereby to increase the web tension during acceleration of the unwinding means, said restraining means comprising a fluid dash pot operatively connected to the dancer roll for operation by movement thereof, means for braking the unwinding of said roll, and switch means for responding to changes in the pressure of the fluid within the dash pot during the deceleration of the pulling means for releasing the braking means.

12. In combination a roll of web material, means for pulling the web from said roll to unwind said web from said roll, means for removing the slack in said web between said roll and said pulling means and for applying a tension to said web extending therebetween, means for braking the unwinding of said roll when said pulling means is deactivated and means, cooperative with said means for removing the slack from said web, for sensing a predetermined increase in the web tension to thereby deactivate said braking means and restore the web tension to within predetermined limits, said sensing means including a fluid dash pot and switch means for responding to changes in the pressure of the fluid within the dash pct.

13. In a web feeding mechanism having means adapted to support a roll of web material, drive means adapted to rotate the roll :by pulling on the web, a brake for opposing rotation of the roll, a dancer roll for engaging the web and establishing a predetermined tension in the web irrespective of dancer rol-l position, rate-responsive means operatively connected .to the dancer roll responsive to an increase in tension at above a predetermined rate, and control means actuated by said rate-responsive means connected to the brake for releasing the brake in response to such increase, said rate-responsive means including a dash pot and said control means including a switch responsive to the pressure of the fluid within the dash pot.

References Cited by the Examiner UNITED STATES PATENTS 1,122,878 12/1914 Dowler 242--75.45 1,242,927 10/1917 Du Brul 242-l56.1 1,671,685 5/1928 Scott 242--75.43 1,832,906 1 1/1931 Johnstone 242-75.43 1,868,310 7/1932 Cline 242-7543 2,099,313 11/1937 Potdevin 242-75.41 2,502,688 4/1950 Wieking 24275.4 X 2,525,600 10/ 1950 Horn-hostel 242-7543 2,675,191 4/1954 McGraw 24275.43 2,824,705 2/1958 Bowman 242-75.4 2,825,016 2/1958 Bailey 242-75.51 X 2,834,556 5/1958 Kraft 242-75.51 X 2,965,326 12/1960 Rockstrom 242-7545 X 3,036,787 5/1962 Triquet 242-754 3,081,957 3/1963 Van De Bilt c 242-156.2 X

FOREIGN PATENTS 331,746 7/ 1930 Great Britain.

ME RV-IN STEIN, Primary Examiner. STANLEY N. GILREATH, Examiner. W, S. BEIRDEN, Assistant Examiner.

Claims

1. WEB FEEDING APPARATUS ADAPTED TO SUPPORT A ROLL OF WEB MATERIAL FOR ROTATION, COMPRISING DRIVING MEANS, DRIVEN MEANS OPERATIVELY CONNECTED TO SAID DRIVING MEANS FOR UNWINDING THE ROLL OF WEB MATERIAL BY PULLING THE WEB THROUGH THE APPARATUS, BRAKING MEANS FOR OPPOSING THE ROTATION OF THE ROLL OF WEB MATERIAL WHEN SAID DRIVING MEANS FOR SAID DRIVEN MEANS IS DEACTIVATED, MEANS COMPRISING A DANCER ROLL ASSEMBLY INCLUDING DANCER ROLL MEANS FOR PROVIDING TENSION IN THE WEB IRRESPECTIVE OF THE POSITION OF SAID DANCER ROLL MEANS, FLUID DASH POT MEANS OPERATIVELY CONNECTED TO SAID DANCER ROLL ASSEMBLY, AND MEANS RESPONSIVE TO THE FLUID PRESSURE IN SAID DASH POT MEANS FOR RELEASING SAID BRAKES MEANS WHEN THE TENSION OF THE WEB INCREASES ABOVE A PREDETERMINED LIMIT.