US3704820A

US3704820A - Web tension control device

Info

Publication number: US3704820A
Application number: US139602A
Authority: US
Inventors: Harold M Frederick; Dewey M Sims Jr
Original assignee: Burroughs Corp
Current assignee: Unisys Corp
Priority date: 1971-05-03
Filing date: 1971-05-03
Publication date: 1972-12-05
Anticipated expiration: 1989-12-05

Abstract

A web feeding device is provided having a receptacle for peripherally supporting a web supply roll, a web feeder for moving a web past a print station or the like upon demand and a web tension control device mounted therebetween for supplying web from the former to the latter. The web tension control device has a pressure roller pivotable to press a passing web effectively against a continuously rotatable friction roller in response to an increase in web tension as detected by a lever contacting the web and operatively coupled to the pressure roller.

Description

United States Patent Frederick et al.

1451 Dec. 5, 1972 154] WEB TENSION CONTROL DEVICE [72] lnventors: Harold M. Frederick, Birmingham; Dewey M. Sims, Jr., Westland, both of Mich.

[73] Assignee: Burroughs Corporation, Detroit,

Mich.

[22] Filed: May3, 1971 [211 Appl. No.: 139,602

[52] US. Cl. ..226/34, 226/44, 242/68.7 [51] Int. Cl. ..B65h 25/04 [58] Field of Search .....226/25, 34, 35, 44; 242/68.7,

[5 6] References Cited UNITED STATES PATENTS 1,586,719 6/1926 Swab ..226/34 2,990,989 7/1961 Carlson ..226/35 Primary Examiner-Richard A. Schacher Attorney-Kenneth L. Miller and Edwin W. Uren [5 7 ABSTRACT A web feeding device is provided having a receptacle for peripherally supporting a web supply roll, a web feeder for moving a web past a print station or the like upon demand and a web tension control device mounted therebetween for supplying web from the former to the latter. The web tension control device has a pressure roller pivotable to press a passing web effectively against a continuously rotatable friction roller in response to an increase in web tension as detected by a lever contacting the web and operatively coupled to the pressure roller.

9 Claims, 2 Drawing Figures PATENT-ED "EC 5 I97? 3 704,820 sum 1 OF 2 mvszv'rons HAROLD M. FREDERICK BY DEWEY M. SIMS JR.

PATENTEU 5 I97? 3.704.820

sum a nr 2 WEB TENSION CONTROL DEVICE BACKGROUND OF THE INVENTION The invention relates generally to web feeding devices and more particularly to web tension controlling devices used in conjunction therewith.

Prior art discloses devices for controlling web tension by damping web drag variations. A first type of device uses resiliently biased levers responsive to slack loops in the web to damp variations in web tension and thereby provide more uniform feed. Similar devices use resiliently biased idler rollers or combinations of resiliently biased levers and idler rollers to obtain uniform feed. Devices of this type provide no relief from web drag for the web feeders other than by tending to stabilize the values of the drag. Indeed, by virtue of their own intrinsic friction, they add to the total amount of web drag which must be overcome by the web feeders.

A second type of device uses gravitationally or resiliently biased, class-one levers to provide a more uniform feed. These exert braking forces on axially supported web supply reels upon decreases in web tension and release the reels to rotate freely upon increases in web tension. Devices of this type also provide no relief from web drag for the web feeders, except as noted previously, and also add to the total amount of web drag which must be overcome by the web feeders. In addition, these devices require some type of axial support for web supply rolls; and this results in more costly manufacturing and maintenance and inconvenience in replacing the supply rolls.

A third type of device disclosed by prior art uses a resiliently biased, class-two lever responsive to a slack loop in the web to actuate a switch controlling an auxiliary web driver. When web slack is reduced to a certain amount by the action of the web feeder, the auxiliary web driver is actuated until the web is overdriven with respect to the feeder by a predetermined amount, whereupon the auxiliary driver is disengaged until the web slack loop has again been depleted by the feeder. Devices of this type require additional components for controlling the auxiliary web drivers, thus inflating the manufacturing and maintenance costs and increasing the probability of operational malfunctions.

A fourth type of device uses a resiliently biased, class-two lever pivotable by a diminishing web loop by virtue of the stiffness of the web to thereby force the web against a rotating friction roller. Such devices find suitable application in cinematographic equipment wherein the web being fed is typically motion picture film having a relatively high degree of stiffness. The same principle would not be readily applicable to feeding more pliant, flexible webs. In addition, the normal force holding the web against the friction roller is that derived from the web tension and applied by the lever against the force of its own resilient bias. Since the driving force exerted on the web by the friction roller is equal to the product of this normal force and of the coefficient of friction, which is always less than unity, existing between the roller and the web, the driving force is thus limited.

SUMMARY OF THE INVENTION The invention resides in the provision of an actuatable web driver responsive to web tension for driving a web in the direction of a web feeder, thereby relieving the latter of a substantial portion of the drag inherent in a web feeding device.

Accordingly, it is an object of the present invention to provide a web tension control device which will relieve a feeder of a substantial amount of web drag, particularly that component arising from the inertial force of the heavy web supply roll.

It is another object of the invention to provide a web feeding device which will receive and peripherally support a web supply roll, no axial support being required, thus providing for a relatively simple supply roll changing procedure.

It is yet another object of the invention to provide a web tension control device requiring a minimum of components, the control device being effectively selfactuated by web tension variations.

It is still another object of the invention to provide a web feeding device which will direct a newly inserted web to the web feeder without manual threading.

Another object of the invention is to provide a web feeding device for use in a printing apparatus wherein the shape of the platen used may be either flat or curved.

Still another object of the invention is to provide a web feeding device which will readily accept webs of varying stiffness, thickness and numbers of layers.

Yet another object of the invention is to provide a web feeding device which will allow manual actuation of the web tension control mechanism.

An important aspect of the invention is the use of a pair of magnets for magnetically biasing the web tension control device in either one of two positions.

Another important aspect of the invention is the use of a resilient material to form a lever actuating the web tension control device, thus permitting the lever to flex in response to variations in web tension, thereby accumulating energy in proportion to lever displacement for rapidly transferring the web tension control device from one to the other of its two magnetically biased positions in response to a sufficient change in web ten- SIOII.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects, aspects and advantages of the invention will be more clearly understood from the following description when read in conjunction with the accompanying drawings, in which:

FIG. 1 is a partially fragmented, perspective view of a web feeding device embodying features of the invention; and

FIG. 2 is a side view of the device of FIG. 1, shown with one side plate removed therefrom.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION The web feeding device shown in FIGS. 1 and 2 has a support structure or frame, generally indicated at 10, a web supply roll receptacle, generally indicated at 12, a web feeder, generally indicated at 14, an actuatable web driver, generally indicated at 16, and web driver control, generally indicated at 18. The receptacle is mounted on the frame, spaced apart from the feeder; and the driver and driver control are mounted effectively therebetween.

The frame has a horizontally disposed base plate 20 and a pair of upright side plates 22-22, one of which is not shown in FIG. 2, each extending upwardly from an opposing edge of the base plate. Extending between the side plates is a V-shaped plate 24, it being supported by and at the same time serving to reinforce the side plates. The shape of the plate 24 enables it to function as a web supply roll receptacle 12, its sloping, interior surface providing peripheral support for a roll 26. The edge of the receptacle plate extending toward what will hereinafter be referred to as the forward end of the web feeding device is downwardly arcuated to form a smooth lip 28 over which a passing web 30 may be freely guided.

The web feeder 14 is represented in this embodiment by a rotatable feed roller 32 journaled in and extending perpendicularly between the side plates 22-22 near the forward end of the web feeding device and a pressure roller 34 effectively overlying the feed roller. It should be understood, however, that any suitable type of web feeder could be used without departing from the scope of the invention. As previously stated, one of the objects of this invention is to provided a web feeding device in which may be used either a flat or a curved platen. An elongated platen 36 having a flat surface is shown for the sake of illustration. Like the web feeder it underlies, it extends perpendicularly between the side plates, its impression surface being coplanar with the path the web follows as it is drawn toward the feeder.

A V-shaped guide plate 38 is supported between the side plates, forward of the receptacle plate 24. Like the latter, it also serves to reinforce the side plates. The rearward edge of the guide plate is spaced apart from the receptacle 12, leaving an elongated opening therebetween; and the plane of the guide surface extending therefrom is tangent to the outer surface of the downwardly arcuated edge of the receptacle plate. The shape of the guide plate enables it to function as a guide to direct a web driven from the receptacle toward the platen 36 and web feeder 14. The forward edge of the guide plate is curved downwardly to form a smooth lip past which a web may be freely drawn.

The actuatable web driver 16 has a continuously rotatable friction roller 40 journaled in and extending perpendicularly between the side plate such that it is disposed in the elongated opening between the forward edge of the receptacle plate 24 and the rearward edge of the guide plate 38 and is slightly, peripherally recessed from the adjacent plane of the guide plate. The web driver control 18 is pivotally supported by and is slidable along a shaft 42 extending between the side plates parallel to and spaced apart from the friction roller. A web driver pressure roller 44 is rotatably mounted on the control such that it is rockable effectively toward or way from the friction roller as the control is pivoted about its axis. The control has a lever 46 extending therefrom and along the downwardly sloping portion of the guide plate 38, the free end falling just short of the upwardly sloping portion thereof. The lever is formed of a resilient material, which will permit flexing thereof; and its free end is curved upwardly to form a smooth, arcuate surface around which a web may be freely drawn. The inner portion of the curved lever end houses a weight 48 which is normally sufficient to pivot the control 18 such that the pressure roller 44 attached thereto will be swung away from the friction roller 40.

A pair of elongated limit plates 50-50 extends perpendicularly between the side plates and overlies the web driver control 18. An arm 52 extends upwardly from the control and passes between and somewhat beyond the two limit plates. The opposing surfaces of the two limit plates are coplanar with those of the arm as it swings from one respective plate to the other when the control is pivoted. One of a pair of elongated magnets 54-54 is disposed on each of the limit plates to effectively bias the arm thereagainst, the arm being formed of a magnetically attractable material.

OPERATION OF THE INVENTION The web feeding device may be loaded by placing a web supply roll 26 into the receptacle 12 as shown in FIGS. 1 and 2. The roll requires no axial support but simply rests peripherally on the V-shaped receptacle plate 24. The leading edge of the web 30 is then inserted into the web driver 16 between the friction roller 40 and the pressure roller 44 thereof. The leading edge needs no special preparation, such as being cut squarely, but can merely be that edge formed when a previous length of web was manually separated. Also, the web thickness may vary; or the web may be formed of several individual layers. After the web has been inserted between the rollers, the arm 52, which has until this time been positioned as indicated by the broken lines in FIG. 2 under the influence of gravity acting on the lever 46 and the mass 48, is manually moved to its rearwardmost position as indicated by the solid lines in the same figure. As the arm is moved rearwardly, the web driver control 18 pivots in a counterclockwise direction, as viewed, around the shaft 42, rocking the pressure roller 44 against the friction roller 40 and pinching the inserted web therebetween. Since the friction roller is continuously rotating in a clockwise direction as viewed, the web will be drivern forwardly thereby. As the web is driven forwardly, it will follow the contour of the guide plate 38, passing under the extended lever 46 and moving upwardly to emerge just below the platen 36. Once a suitable length of web has been driven through, the leading edge may then be fed into the web feeder 14 between the feed roller 32 and the pressure roller 34. In the feeder embodiment shown for the sake of illustration, this would be done manually; but, in a slightly more sophisticated embodiment, the web could be automatically guided through the feeder, for example, by simply extending and suitably forming the guide plate 38. Also, in a more sophisticated embodiment, the arm 52 could be operatively connected to a convenient operating lever on or near the front of the device.

After the device has been loaded as previously described, the lever 46, arm 52 and pressure roller 44 will be positioned as indicated by the broken lines in FIG. 2. As the feeder 14, upon demand, advances the web 30 past the platen 36, the slack loop in the web formed above the guide plate 38 will be reduced. As the web becomes more taut, the free end of the lever will be raised, flexing the body of the lever since the arm is held forward by one of the magnets 54. When the counterclockwise force exerted on the driver control 18 due to increasing web tension acting on the lever exceeds the clockwise force exerted on the driver control due to the magnetic attraction acting on the arm, the arm will pivot rearwardly. The arm will continue to be driven rapidly in this direction, until it abuts the rearwardmost limit plate 50, under the influence of the restoring force of the flexed lever 46 and terminally under the influence of the magnet 54 mounted on the limit plate toward which it is moving, the arm subsequently being held thereagainst by this magnet.

As the driver control 18 is pivoted in a counterclockwise direction, the pressure roller 44 is swung toward the recessed periphery of the friction roller 40, pressing the web thereagainst. The ratio of the lengths of the lever 46 and of the arm 52 with respect to the distance between the rotational axis of the pressure roller and the pivotal axis of the driver control is large enough to provide a suitable mechanical advantage such that the normal force pressing the web against the friction roller is adequate for driving the web therewith.

As the web 30 is driven by the friction roller 40, a slack loop is again formed in the web above the guide plate 38. The lever 46, once supported by the web in the raised position indicated by the solid lines in H0. 2, will swing downward under the influence of gravity acting on the lever and on the weight 48 attached to its free end, flexing the body of the lever in this direction since the arm 52 is held rearward by one of the magnets 54. When the clockwise force exerted on the driver control 18 due to decreasing web tension acting on the lever exceeds the counterclockwise force exerted on the driver control due to the magnetic attraction acting on the arm, the arm will pivot forwardly. The arm will continue to be driven rapidly in this direction, until it abuts the forwardmost limit plate, under the influence of the restoring force of the flexed lever and terminally under the influence of the magnet mounted on the limit plate toward which it is moving, the arm subsequently being held thereagainst by this magnet. As the driver control 18 is pivoted in a clockwise direction, the pressure roller 44 is swung away from the recessed periphery of the friction roller 40, releasing the web being held thereagainst. At this time, the lever, arm and pressure roller will again be positioned as indicated by the broken lines in FIG. 2. The components of the web feeding device will remain in this position until such time as a demand upon the web feeder reduces the web slack loop sufficiently to transfer the arm to the rearwardmost limit plate, initiating another cycle of operation as previously described.

While the web feeding device has been shown and described in considerable detail, it should be understood that many changes and variations may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

l. A web tension control device comprising:

a support structure;

an actuatable web driver having a continuously rotatable friction roller mounted on said support structure and a pressure roller pivotable against said friction roller for pressing a passing web effectively thereagainst;

a web drive control pivotally mounted on said support structure and supporting said pressure roller,

s 'd control havin a lever extendin therefrom to e ectively contac a web being ed thereby to pivot said pressure roller toward or away from said friction roller in response to a respective increase or decrease in web tension; and

a pair of limit plates mounted on said support structure parallel to but spaced apart from said friction roller and also having an arm extending from said web driver control between said plates, whereby the angular displacement of said control is limited.

2. A web tension control device as defined by claim 1 wherein said arm operatively extends past said limit plates, whereby provision is made for manual actuation of said web driver.

3. A web tension control device as defined by claim 2 and additionally having a pair of magnets, each disposed on a respective one of said limit plates for magnetically biasing said web driver in either one of two positions, said arm being formed of a magnetically attractable material.

4. A web tension control device as defined by claim 3 wherein said lever is formed of a resilient material, whereby it will be permitted to flex in response to variations in web tension.

5. A web tension control device as defined by claim 4 and additionally having a weight secured to the extended end of said lever, whereby force is provided for transferring said web driver from one to the other of its two magnetically biased positions in response to a sufficient decrease in web tension.

6. A web feeding device comprising:

a support structure;

V-shaped plate mounted on said support structure to form a receptacle for receiving and peripherally supporting a web supply roll;

a web feeder mounted on said support structure spaced apart from said receptacle;

an actuatable web driver disposed effectively between said receptacle and said web feeder and having a continuously rotatable friction roller mounted on said support structure and a pressure roller pivotable against said friction roller to press a passing web effectively thereagainst; and

a web driver control pivotally mounted on said support structure and supporting said pressure roller, said control having a lever extending therefrom to effectively contact a web being fed thereby to pivot said pressure roller toward or away from said friction roller in response to a respective increase or decrease in web tension.

7. A web feeding device as defined by claim 6 and additionally having a web guide mounted on said support structure and forming a pathway from said actuatable web driver to said web feeder, whereby a web manually inserted into said driver will be directed to said feeder.

8. A web feeding device as defined by claim 7 wherein said friction roller is peripherally recessed in said web guide.

9. A web feeding device as defined by claim 8 wherein said web driver control is slidable along its pivotal axis, whereby webs of different dimensions may be effectively accommodated.

Claims

1. A web tension control device comprising: a support structure; an actuatable web driver having a continuously rotatable friction roller mounted on said support structure and a pressure roller pivotable against said friction roller for pressing a passing web effectively thereagainst; a web drive control pivotally mounted on said support structure and supporting said pressure roller, said control having a lever extending therefrom to effectively contact a web being fed thereby to pivot said pressure roller toward or away from said friction roller in response to a respective increase or decrease in web tension; and a pair of limit plates mounted on said support structure parallel to but spaced apart from said friction roller and also having an arm extending from said web driver control between said plates, whereby the angular displacement of said control is limited.

6. A web feeding device comprising: a support structure; V-shaped plate mounted on said support structure to form a receptacle for receiving and peripherally supporting a web supply roll; a web feeder mounted on said support structure spaced apart from said receptacle; an actuatable web driver disposed effectively between said receptacle and said web feeder and having a continuously rotatable friction roller mounted on said support structure and a pressure roller pivotable against said friction roller to press a passing web effectively thereagainst; and a web driver control pivotally mounted on said support structure and supporting said pressure roller, said control having a lever extending therefrom to effectively contact a web being fed thereby to pivot said pressure roller toward or away from said friction roller in response to a respective increase or decrease in web tension.