US3250488A - Braking and tension roll - Google Patents

Description

May 10, 1966 G. .1. PRAGER BRAKING AND TENSION ROLL Filed Oct. 5, 1965 IN VEN TOR. p/Wef United States Patent O 3,250,488 BRAKING AND TENSION ROLL George J. Prager, Rosemont, Pa., assignor to Beloit Eastern Corporation, Downingtown, Pa., a corporation of Delaware A Filed Oct. 3, 1963, Ser. No. 313,684 2 Claims. (Cl. 242-754) The present invention relates to a web tension control means and particularly to an improved method and mechanism for maintaining a constant tension in a traveling web from an unwinding paper roll.

In an unwinding mechanism a web is continually drawn off of a supply roll for an operation on the web such as a-slitting, coating or surface treating operation and it is essential that the tension in the traveling web be maintained constant and be controlled across the full Width of the web. The unwinding machines are continuous with a fresh roll being placed in the machine as the unwinding roll is expiring and a dying splice being made to splice the lead end of the web from the fresh roll to the traveling surface of the web of the expiring roll. The requirements for constant tension across the Width of the web continue all during the unwinding operation including during the time of making the splice.

Web tension control has been conventionally done by applying a braking torque to the unwinding roll. However, the unwinding roll is continually changing in diameter so that in order to maintain a constant tension in the web the braking torque must be constantly changed. In other words, as the diameter of the unwinding roll decreases the torque must be increased, and the speed of rotation of the unwinding roll in revolutions per minute continually changes while maintaining constant web surface speed. Attempts to overcome the difliculties have included brakes operating on variable size drums, the use of dance rolls, and other devices all of which require a mechanism over and above simple braking devices and which cannot obtain constant tension in a simple manner.

It is accordingly an object of the present invention to provide a web unwinding mechanism capable of delivering a traveling web at uniform web tension across the Web at uniform speed without requiring complex mechamsm.

A further object of the invention is to provide an unwind mechanism utilizing a method and apparatus for controlling the tension of the web by providing a tensioning force directly to the surface of the traveling web, utilizing the advantage of the constant speed of travel of the web and applying a constant braking force theret0.

A more broad object of the invention is to provide a tension control device for maintaining a constant tension across the width of a traveling web for utilization in 'various types of devices embodying a traveling web moving at constant web speed. It will be understood that while the principles of the invention may he utilized and are applicable in various environments for the purposes above described, the principles are particularly well suited to use in an unwinding mechanism and have a special coaction therewith in the combinations set forth so that the disclosure and description of the invention will be presented principally in connection with an unwinding machine.

The invention contemplates providing a mechanism for controlling the tension of a web being paid otf an unwinding roll having an unwinding roll support stand with a pull roll receiving the web traveling from the unwinding roll and drawing it forwardly, having a roll brake on the unwinding roll on the support stand for preventing overrunning ofthe unwinding roll and maintaining a slight control in the web, and additionally having a web brake with a tension control web roll wrapped by the web and with a constant running torque brake connected to the web roll for maintaining a predetermined tension in the web.

Other objects, advantages, and features will become more apparent with the teachings of the principles of the invention in connection with the disclosure of the preferred embodiments thereof in the specification, claims and drawings, in which:

FIGURE 1 is a side elevational view shown largely in schematic form of an unwinding mechanism constructed and operating in accordance with the principles of the present invention; and

FIGURE 2 is a fragmentary schematic side elevational view of a web brake of modified form.

On the drawings:

As illustrated in FIGURE 1, an unwinding web W travels at a constant speed from a roll on an unwinding stand l0. The tension of the web W is maintained constant across the web by a web brake roll 11 in frictional engagement with the web. The web travels through a treatment zone 12 which may be a web slitter, coater, surface finisher or other treatment mechanism such as is known to the art of paper making and converting, and passes through rolls 13 and 14 of a pull stack and over rolls 1S onto a Wind up roll 16. The wind up roll is driven by a suitable mechanism to wind up the paper Web which is moved forwardly at constant speed by pull rolls such as that of the pull stack rolls 13 and 14.

The Web is maintained in frictional contact with the web brake roll 11 by a wrapping roll 17 positioned to preferably wrap the web around the major arc of the brake roll 11. A pre-selected constant torque is applied to the web brake roll 11 by a brake 18. The brake 1S may be' of various desirable types capable of applying a constant torque, such as an eddy current brake with a regenerative motor, or other types Aof brakes such as an air brake, an hydraulic brake, or electric brake may be employed. In other words, the brake applies a constant force to the brake roll 11 so that a constant braking force is applied to the web W which is wrapped over the brake roll 11.

The roll 11 has a web engaging surface of a high friction material such as rubber. I have discovered that polyurethane provides unforeseen results on the surface of the braking roll, and has an unusual frictional effect on a traveling paper web. Therefore, the preferred form of braking roll will have a polyurethane surface. In some environments Where a very low tensile strength web is to rbe handled web braking rolls of other surfaces may be employed such as a polished steel surface which will permit slippage of the web without web breakage if conditions change suddenly. Also, the amount of surface area of the web braking roll 11 wrapped by the traveling web W may be changed in accordance with the tensioning force to be applied to the Web with the angle of wrap being diminished in cases Where the Ltension on the web approaches the ultimate tear stress of the web so that slippage can occur in case of sudden change of conditions. Under normal operating circumstances With a strong web, utilizing a polyurethane covered -roll no slippage will occur and positive web tension control is obtained completely across the web at constant we'b speed Without having to contend with the variables caused by diminishing roll diameters such as must be encountered if tensioning is obtained by applying forces to the Iunwinding roll. Attempts to control tension in unwinding webs have included, in addition to applying a braking force directly to the unWinding roll, applying tapes or bands to the surface of the roll, and the methods are limited to uncoated stocks and low tension factors in order to prevent s-cufling and glazing of the sheet.

The present arrangement contemplates using :a roll brake in order to prevent overrunnning of the parent roll as it unwinds and in order to stop the rotation of the core of the expired roll after the splice has been made. As shown on the drawing, an expiring roll 19 is supported on a turret 21 on a stand 25. Connected to the support for the roll 19 is a brake and drive 20. During unwinding a slight brake force is applied merely to provide a control tension to the web between the unwinding roll and the web braking roll 11. For example, a light tension of l to 3 pounds is applied to the web approaching the web ybraking roll 11. rDhe tension in the web between the braking roll and the pull rolls 13 and 14 can be controlled by the variable brake 18 and, for example, a constant tension of pounds may be applied to the web.

The turret 21 is arranged with a guide roll 23 on an arm 22 for guiding the web to the splicing and cutting device 28. Carried at the other side of the turret 21 is a fresh roll 26 also provided with .a brake and drive 27. As the Poll 19 begins to expire, the fresh roll 26 is driven in rotation until its surface speed is the same as the speed of the traveling web W, and at that time the lead end of the second web on the second or fresh roll 26 is spliced to the surface of the web W.

For forming the splice, a splice roll 32 is forced against the web W carrying it against the surface of the fresh roll 26 and the splice is made usually by splice tapes having pressure sensitive adhesive located on the lead end of the web on the fresh roll 26.` The first web is then cut by a cutter 34. The :splice roll and cutter carried on a pivotal arm 30 are pivotedvat 31, and the arm is pivoted by an air piston and cylinder 33. The cutter 34 is operated lby an air piston and cylinder 35.

If a fresh roll 26 is to be unwound in the direction opposite that shown by the arrow on the roll 26, the turret 21 will be swung in the direction opposite that shown by the arrowed line appearing on the turret 21.

More particularly, prior to loading the fresh roll 26 into the turret, the roll 19 will be in the position now occupied by roll 26 in FIGURE 1. The fresh roll 26 is then loaded into the turret and the turret is swung in either rotational direction depending upon the direction in which roll 26 i-s to be unwound, bringing the roll 26 in the position in which it is shown in FIGURE l. If it is swung in the direction indicated by the arrowed line on the turret 21, the elements will take the posit-ion shown in FIGURE 1, and if the turret is swung in the opposite direction the web W will 4be guided by the roll 24 and the splicing mechani-sm 29 will be employed. This mechanism i-s substantially the same as the splice mechanism 28 and includes a splice roll 36 carried on an arm .40 which is pivoted on its pivotal support 31 by an air piston and cylinder 37. Also carried on the arm 40 is a cutting knife mechanism l33 operated by an air piston and a cylinder 39.

In operation the web W will be paid off of the unwinding roll, braked slightly by the brake mechanism 20. The web moves forwardly at a constant speed drawn by the pull rolls 13 and 14 and fa constant tension is maintained across the web by the web braking roll 11. A predetermined constant braking torque is applied to the roll 11 by the :brake 18 and the tension in the web will remain constant in its travel through the web treatment zone 12. When the roll 19 expires a splice is made to splice the lead end of the web from the roll 26 to the web W, .and the fresh web will then travel over the braking roll 11 and throughout the :splicing operation and with the transition in webs, constant tension will be maintained without requiring a critical control of the braking fonce applied by the roll brakes and 27 and the splice will take place without :any adverse affect to the uniform tension in the web as it passes through the treatment zone 12.

FIGURE 2 illustrates another form of engagement between the braking roll and the web wherein a web brak-ing roll 41 frictionally engages a web W which is held against the roll by a pinch roll 42 forming a nip Nwith the braking roll 41. The :overall frictional force between the web W and braking roll 41 can be varied by varying the nip pressure by suitable mechanisms shown schematically by the arrowed line 43. This arrangement may also be employed where the web is handled which ha-s a tension limit close to the applied operating tension.

Thus, it will be seen that I have provided a traveling web tension control mechanism which meets the objectives, advantages and features above set forth, and which is well suited to all phases of the paper industrys unwinding loperations including paper making, processing, finishing and printing. The mechanism controls tension across the full width of the sheet at a point where the sheet speed is constant instead of contending with speed changes due to decreasing diameters. This also necessitates a smaller `range off control requirements and permits providing braking mechanism which can operate at optimum efficiency and also permits using a braking mechanism of less complex nature and less expensive construction. The unique frictional coaction between la traveling fpaper web and the polyurethane roll reduces slippage to substantially zero and highly critically finished paper webs may be `handled without any adverse effect to the surface qualities. The braking force is applied to the web after it leaves the unwinding roll and constant tension is maintained eliminating problems heretofore encountered in the rolls being unwound and in the wind up roll.

The drawings and specification present a detailed disclosure of the preferred embodiments of the invention, and it is to be understood that the invention is not limited to the specific forms disclosed, but covers all modifications, changes and alternative constructions and methods falling within the scope of the principles taught by the invention.

I claim as my invention:

1. An unwind mechanism for continually delivering a traveling web comprising,

a first unwind roll support for a roll having a first web unwound therefrom,

a second unwind roll support for a fresh roll having a second web to be spliced to the first while it is traveling,

a pull roll receiving the first web,

a tension control web braking roll frictionally engaging the surface of said first roll between said supports and said pull roll,

a brake means having a constant running torque oonnected to said web braking roll for maintaining a predetermined tension in the web,

means for driving said second roll for bringing the surface speed to the speed of said first web,

la roll brake for said first roll preventing overrun and stopping the roll after splicing the second web to the first,

and a splice means for splicing the second web to the first while it is traveling and .cutting the first web so that said web breaking roll will uniformly continue to apply constant braking force sequentially to both said first and second webs without change in tension to the pull roll.

2. An unwind mechanism for continually delivering a traveling web comprising,

an unwind stand having a turret thereon mounted on a horizontal taxis on the stand with a first support for an unwinding roll having a first web being paid olf the first roll and having a second support for a second fresh unwinding roll having a second web to be spliced to the surface of the first web,

said turret being rotatable through positions for loading with a fresh roll and removing an empty core from an expired roll,

a rst cutting and splice means positioned above the second roll in a splice position for splicing the second web to the rst web,

a ysecond cutting and splice means positioned below the second roll in said splicing position for splicing the second web to the rst web when said second roll is -rotating in an opposite direction,

a Wind up roll,

guide rolls guiding the Web to said Wind up roll with lsaid guide rolls and Wind up roll drawing the web forwardly,

means defining a web treatment zone between the un- Winding roll and the Wind up roll,

a tension control web b-raking roll having a surface of polyurethane positioned between said treatment zone and the unwinding roll,

a` Web Wrapping roll positioned to wrap the Web around a major farc of said web braking roll,

a constant torque brake connected to said web braking roll for applying a constant tension to the traveling web ata constant speed of travel,

and roll brakes connected to 4said irst and second rolls for preventing overrun of the rolls and stopping the rolls after they have become unwound,

said constant torque brake being lcontrollably variable for varying the tension in the web and obtaining a predetermined constant tension during Web travel.

References Cited by the Examiner UNITED STATES PATENTS 1,263,419 4/1918 James 242-752 2,177,489 10/ 1939 Jamieson 242-45 2,485,75 7 10/ 1949 Michel d 242-75 .4 2,707,083 4/ 1955 Kohler 242-75 .2 2,728,973 1/ 1956 Kummel 28-1 A 2,995,768 8/ 1961 Tomberg 242-7544 3,08 5,762 4/ 1963 Subklew 242-58 FOREIGN PATENTS 745,224 2/ 1956 Great Britain.

STANLEY N. GILREATH, Primary Examiner.

MERVIN STEIN, Examiner.

D`l E. WATKINS, Assistant Examiner.

Claims (1)

1. AN UNWIND MECHANISM FOR CONTINUALLY DELIVERING A TRAVELING WEB COMPRISING, A FIRST UNWIND ROLL SUPPORT FOR A ROLL HAVING A FIRST WEB UNWOUND THEREFROM, A SECOND UNWIND ROLL SUPPORT FOR A FRESH ROLL HAVING A SECOND WEB TO BE SPLICED TO THE FIRST WHILE IT IS TRAVELING, A PULL ROLL RECEIVING THE FIRST WEB, A TENSION CONTROL WEB BRAKING ROLL FRICTIONALLY ENGAGING THE SURFACE OF SAID FIRST ROLL BETWEEN SAID SUPPORTS AND SAID PULL ROLL, A BRAKE MEANS HAVING A CONSTANT RUNNING TORQUE CONNECTED TO SAID WEB BRAKING ROLL FOR MAINTAINING A PREDETERMINED TENSION IN THE WEB, MEANS FOR DRIVING SAID SECOND ROLL FOR BRINGING THE SURFACE SPEED TO THE SPEED OF SAID FIRST WEB, A ROLL BRAKE FOR SAID FIRST ROLL PREVENTING OVERRUN AND STOPPING THE ROLL AFTER SPLICING THE SECOND WEB TO THE FIRST, AND A SLICE MEANS FOR SLICING THE SECOND WEB TO FIRST WHILE IT IS TRAVELING AND CUTTING THE FIRST WEB SO THAT SAID WEB BREAKING ROLL WILL UNIFORMLY CONTINUE TO APPLY CONSTANT BRAKING FORCE SEQUENTIALLY TO BOTH SAID FIRST AND SECOND WEBS WITHOUT CHANGE IN TENSION TO THE PULL ROLL.

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