US3006136A

US3006136A - Method and apparatus for controlling the tension in tapes

Info

Publication number: US3006136A
Application number: US13125A
Authority: US
Inventors: Grieve George Thomas Wilson; Watson Harold William Ritchie
Original assignee: BICC PLC
Current assignee: Balfour Beatty PLC
Priority date: 1959-03-12
Filing date: 1960-03-07
Publication date: 1961-10-31
Anticipated expiration: 1978-10-31

Description

Oct. 31, 1 G. T. w. GRIEVE ET AL 3,006,136

METHOD AND APPARATUS FOR CONTROLLING THE TENSION IN TAPES Filed March 7, 1960 s Sheets-Sheet 1 B Mummy;

Oct. 31, 1961 G. T. w. GRIEVE ET AL 3,006,135

METHOD AND APPARATUS FOR CONTROLLING THE TENSION IN TAPES Filed March 7, 1960 3 Sheets-Sheet 2 W W Attorney Oct. 31, 1 G. T. w. GRIEVE ET AL 3,006,136

METHOD AND APPARATUS FOR CONTROLLING THE TENSION IN TAPES Filed March '7, 1960 3 Sheets-Sheet 3 v A) y )bg'plfl/ Mata WAUomey;

Unite States This invention relates to a method of and apparatus for controlling the tension in tapes, especially in tapes being drawn off from a roll or pad and lapped helically upon a core, for instance an electric cable conductor, or wound spirally on a core as in the manufacture of wound capacitors.

When drawing off tape from a roll or pad (each hereinafter for convenience referred to as a pad) it is desirable to use a pad of which the initial diameter is as as great as practicable. For example it is common practice for the paper cable maker to use pads of 16" diameter and in some cases pads of 25" diameter have been used. To prevent overrunm'ng of such pads it is essential to apply a braking load which in the case of the 25" diameter pads may impose upon the paper being drawn off a tension of about 1 /2 lbs. As more and more tape is drawn off from the pad the braking load necessary to prevent overrunning naturally diminishes though not proportionally to the reduction in pad diameter. At the same time the tension in the paper per unit of retarding torque imposed on the coil increases. Numerous devices have been suggested for effecting a gradual reduction in the braking load as the pad diameter is reduced, with the object of ensuring that the tension in the tape as it runs on to the core on which it is to be lapped or wound remains substantially constant. Other devices purporting to ensure reasonably constant tension in the tape irrespective of pad diameter involve imparting an additional retarding force to the tape after it has left the pad and for the gradual reduction of this additional tensile loading of the tape to correspond with the additional tensile load due to the gradual reduction of pad diameter. In practice it is found that with both forms, errors occur and that the percentage error increases as the theoretical lapping or winding tension diminishes. Accordingly, existing systems of tape tension control, though reasonably satisfactory :for tapes of the kind most generally used by cable makers, e.g. for pape tapes having a width of 1 inch or more and a thickness of about four mils, are not satisfactory for narrower and thinner tapes.

Moreover, in the case of impregnated paper insulated cables, it is desirable that all the tapes used to build up the dielectric wall shall be applied with the same tensile stressfor example some particular value of tensile stress within the range 500 to 1,000 lbs. per square inch. While it is possible to maintain an approximation to such a stress when lapping thick and wide papers it becomes difiicult to do so when lapping thin tapes of narrow width unless pads of small diameter are used-which is uneconomical as it reduces the load factor of the machine. This will be appreciated if one considers for instance a paper tape of .62 inch width and 3 mils thickness. To lap such a tape at a definite stress of within the range of say, 500 to 1,000 lbs/sq. in. involves running the tape on to the conductor under a tension within the range 14 to 29 ozs. But to prevent overrunning of a pad of 25 inch diameter may require a braking torque which imposes initially a tension of 24 ozs. in the paper. As the pad reduces in diameter the tension in the paper neces sary to overcome this braking torque (if the braking atent i"- torque be not reduced in proportion) increasesin which event it becomes impossible to maintain the stress in the lapped paper at the desired figure.

The present invention provides an improved method of and apparatus for controlling the tension in tape as it is being lapped or wrapped or otherwise wound on a core which reduces to a substantial extent the difiiculties inherent in existing devices and permits of the use of large pads of thin tape of narrow width.

In accordance with our invention the tension in the tape as it runs on to the core on which it is to be lapped or wrapped or otherwise wound is maintained at a value approximating the desired value by applying a retarding force to the tape in excess of the winding tension and applying an advancing force to the tape between the point or points of application of the retarding force and the Winding point and adjusting the value of the one applied force relative to the other to give the approximate residual winding tension required.

The retarding force may be due principally to the retarding torque exerted on the coil due to brake action and bearing friction or to a combination of such torque and to the frictional retarding effect of a brake or brakes acting directly on the linearly traveling tape. Reduction of the tension in the tape to the required residual value and its maintenance at such value within reasonably close limits as winding proceeds may be achieved either by maintaining the retarding force constant within reasonably close limits as by gradually reducing the brake action on the coil as it reduces in diameter, or by allowing the retarding force to vary as by omitting to reduce the braking action on the coil as it reduces in diameter and varying the value of the advancing force applied to the tape, or by a combination of both methods. We prefer to maintain the value of the retarding force as constant as practicable and to maintain the residual tension in the tape at the required value by initially adjusting the value of the advancing force applied to the tape. This preferred method of operation has the important advantage that any errors in the value of the retarding force that may occur as winding proceeds are automatically reduced and appear in the residual winding tension merely as a fraction of the corresponding errors in the retarding force, this fraction corresponding to the ratio between the residual tension and the initial tension in the tape.

The invention also includes apparatus for carrying out the aforesaid method of controlling the winding tension which comprises means for applying an advancing force of variable value to the tape as it travels to the core on which it is to be wound, comprising a driving member, for example a capstan or a belt, acting upon a surface of the tape and means for imparting to the surface of the driving member in engagement with a surface of the tape a speed of travel in excess of that of the tape so that there is slip between the tape and its driving member. Where the driving member is a capstan its peripheral speed of travel is in excess of that of the tape and where the driving member is a belt its lineal speed of travel is in excess of that of the tape. We have found it better from the point of View of obtaining a more accurate control of the residual tension for the speed of the driving surface to exceed that of the driven tape very considerably-the speed of the driver being preferably at least three to four times as fast as that of thetape. As a driving member We prefer to employ a driven capstan. The capstan is preferably of ceramic material but at least its driving surface may be of a metal which is inherently corrosion proof, for example the capstan may be of stainless steel, or it may be plated on its peripheral surface with a metal which is inherently corrosion proof for example nickel or rhodium.

3 We prefer to use a motor-driven capstan rather than one driven by a drive taken from the winding head itself.

Control of the value of the advancing force applied to the tape by such a capstan is obtained by varying the arc of contact between the capstan and the tape. This may be done by means of guide rollers on the approach and departure sides of the capstan, these guide rollers and/ or the capstan being movable, the one relative to the other. In a preferred arrangement there is a guide roller on the approach side of the capstan and a second guide roller on the departure side. Tape approaches under the approach guide roller and passes partly round the capstan and round a skewed roller having its axis at an angle of 4550 to the axis of the capstan and back round the capstan and ofif under the departure guide roller. The diameter of the skewed roller is such as to ensure that the second Wrap of tape round the capstan is displaced from the first to an extent to leave a safe gap between their neighbouring edges. For example the diameter of the skewed roller may be /2 the capstan diameter, giving a lateral displacement of the second wrap to the first wrap equal to the capstan diameter. With this preferred arrangement by providing for movement of the capstan and its skewed roller relative to the approach and departure rollers in a direction perpendicular to a plane tangential to the approach and departure guide rollers, the aggregate arc of contact between the tape and the capstan may be varied from about 60 to 320. Alternatively, the approach and departure guide rollers may be swung to a limited extent about the capstan.

An example of a preferred form of apparatus for controlling tension in tape in accordance with the invention will now be described with reference to the accompanying drawings, wherein:

FIGURE 1 is a plan view, partly broken away, of an arm of a cable paper lapping machine carrying means for applying a braking torque to the paper tape and means for applying an advancing force to the tape,

FIGURE 2 is a side elevation, partly in section, of the means shown in FIGURE 1 for applying the braking torque, but drawn to a large-r scale,

FIGURE 3 is an enlarged plan View of the means shown in FIGURE 1 for applying the advancing force to the tape and,

FIGURE 4 is a sectional view of the apparatus of FIGURE 3 taken along the line IVIV thereof.

FIGURE 1 shows the invention applied to a cable paper lapping machine of the kind in which paper pads 1 are carried bodily around a longitudinally advancing cable core 2. The spindle 3 for the pad 1 is mounted on an arm 4 of the machine and tape 5 as it is taken from the pad passes under a roller 6 forming part of the gear for controlling the braking torque applied to the pad, then through apparatus for applying an advancing force to the tape and finally on to the cable core 2.

The gear for controlling the braking torque applied to the pad is shown in FIGURES 1 and 2.. The axle 7 of the roller 6 under which the tape passes is supported on the outer end of an arm 8 formed on a spindle 9 rotatably mounted on the arm 4 of the machine. The spindle 9 has formed on it a second arm 10 and to the outer end of this is attached, by a hinge 1 1, a wedge member 12 having two inclined faces. Two cranked levers 13 are pivotally mounted on a support 14 fixed to the arm 4 of the machine and on one end of each lever 13 is rotatably mounted a roller 15. Bridging the two levers 13 between the support 14 and the rollers is a compression spring 16 adjustable by a screw 17. The ends of the levers 13 remote from the rollers are each. provided with a disc 18 having pads 19 of oiled felt on their opposed fiat faces. A metal brake disc 20 is fastened to one end of the pad spindle 3 and the felt pads 19 are arranged one on each side of the metal brake disc 20 and in registration with one another.

The retarding force applied to the tape 5 by the pad braking means is arranged to be in excess of the lapping tension and is maintained constant within reasonably close limits as the pad reduces in diameter by suitably reducing the brake action on the pad. The latter is effected as follows: When the tape 5 is applied from a full pad the spring 16 acting through the levers 13 is arranged to press the felt pads 19 into contact with the metal brake disc 20 to provide the required braking torque, the rollers 15 being out of contact with the inclined faces of the wedge 12. As the diameter of the pad reduces, any slight increase in the tension of the tape is transmitted to the roller 6 and produces a slight rotation of the spindle 9. This causes the arm 10 to move in a direction to drive the wedge member 12 in between the rollers 15 so that the inclined faces of the wedge 12 make contact with the rollers 15 and urge the rollers 15 apart slightly, thereby producing a slight pivotal movement of the levers 13 in opposition to the spring 16 and slightly relieving the pressure of the oiled felt pads 19 on the brake disc 20 and reducing the braking load. By careful initial adjustment of this gear the retarding force applied to the tape by the brake as the pad reduces in diameter may be kept reasonably constant.

After leaving the roller 6 the tape 5 is guided over a roller 21 to the apparatus for applying an advancing force to the tape. This is shown in FIGURES 3 and 4. It comprises a base-plate 22 fixed to the arm 4 of the machine and supporting the casing 23 of an electric motor whose spindle 24 carries a capstan 25 of ceramic material. Also fixed to the base-plate 22 is a bracket 26 carrying at a distance from the capstan 25 a freely rotatable roller 27, the axis of which is set at an angle of about 45 to the axis of the capstan. There is a guide roller 23 on the approach side of the capstan 25 and a guide roller 29 on the departure side. These rollers are freely rotatably mounted on a U-sh-aped plate 30 having a threaded bore through which passes a lead screw 31 rotatably held by a bracket 32 fixed to the base-plate 22. The lead screw is provided with a handle 33 at its end remote from the screw-thread. A clamping screw 34 and nut 35 are provided to clamp the U shaped plate 30 in any desired position on the threaded portion of the lead screw. To move the U-shaped plate 36 from one position to another along the lead screw the clamping nut 35 is loosened and the handle 33 of the lead screw is turned until the U-shaped plate 30 is in the new position, when the clamping nut 35 is tightened. Two bars 36 parallel one with the other guide the U- shaped plate 30'.

The tape 5, after passing over the roller 21, passes under the approach guide roller 28 and passes partly round the capstan 25 and the skewed roller 27, back partly round the capstan and ofi under the departure roller 29. From there it is led over a roller 37 and then under a roller 38 set at an angle such that the tape is applied tangentially to the core 2 (see also FIGURE 1).

The U-shaped plate 30 and

rollers

28 and 29 are shown in FIGURE 3 in full lines in the position of maximum wrap of the tape on the capstan 25, in which the aggregate arc of contact between the tape and the capstan is about 320. In the position shown in chain dotted lines in FIGURE 3 the aggregate arc of contact between the tape and the capstan is the minimum value, about 60. It will be appreciated that any are of contact between the tape and the capstan within the range 60 to 320 may be obtained by adjustment of the position of the U-shaped plate 30 on the threaded part of the lead screw 31. Then by using a motor which drives the capstan at a peripheral speed in excess of that of the tape,'for example at a speed at least three times as fast as the tape and by suitable adjustment of the aggregate arc of contact, an advancing force may be applied to the tape which reduces the initial tension in the tape to the required residual value for lapping on the core. For

r. as

example the aggregate arc of contact may be adjusted so that the tension in the tape is reduced from a value of say 4 lbs. plus or minus say 4 ozs. on the input side of the capstan to a value of say 4 ozs. plus or minus 4 oz. on the output side of the capstan.

What we claim as our invention is:

1. A method of controlling the tension in tape as it runs on to a core on which it is to be wound, which comprises applying a retarding force to the tape in excess of the winding tension, applying an advancing force to the tape between the point or points of application of the retarding force and the winding point, and adjusting the value of the one applied force relative to the other to give the approximate residual winding tension required.

2. Apparatus for controlling the tension in tape as it runs on to a core on which it is to be wound, comprising means for applying a retarding force to the tape, a driving member for acting upon a surface of the tape between the point or points of application of the retarding force and the winding point, and means for imparting to the surface of the driving member in engagernent with a surface of the tape a speed of travel in excess of that of the tape.

3. Apparatus for controlling the tension in tape as it runs on to a core on which it is to be Wound, comprising means for applying a retarding force to the tape, a capstan for acting upon a surface of the tape between the point or points of application of the retarding force and the winding point, and means for driving the capstan at a peripheral speed of travel in excess of that of the tape.

4. Apparatus as claimed in claim 3, in which the capstan is of ceramic material.

5. Apparatus as claimed in claim 3, in which at least the driving surface of the capstan is of metal which is inherently corrosion proof.

6. Apparatus as claimed in claim 3 comprising a driving motor solely for the capstan.

7. Apparatus as claimed in claim 2 in which the means for imparting to the surface of the driving member in engagement with the tape a speed of travel in excess of that of the tape is adapted to drive said surface of the driving member at a speed at least three times as fast as the speed of the surface of the tape.

8. Apparatus for controlling the tension in tape as it runs on to a core on which it is to be wound, comprising means for applying a retarding force to the tape, a capstan for acting upon a surface of the tape between the point or points of application of the retarding force and the winding point, a pair of guide rollers, one on the approach side of the capstan and one on the departure side, means for adjusting the guide rollers relative to the capstan to vary the aggregate arc of contact between the tape and the capstan, and means for driving the capstan at a peripheral speed of travel in excess of the tape speed so that there is slip between the tape and the capstan.

9. Apparatus for controlling the tension in tape as it runs on to a core on which it is to be wound, comprising means for applying a retarding force to the tape, a capstan for acting upon a surface of the tape between the point or points of application of the retarding force and the winding point, a guide roller on the approach side of the capstan and a second guide roller on the departure side, and a skewed roll having its axis at an angle of 45 50 to the axis of the capstan, whereby the tape approaches under the approach guide roller and passes partly round the capstan and around the skewed roller, back partly around the capstan and otf under the departure guide roller.

10. Apparatus as claimed in claim 9 in which the diameter of the skewed roller is /2 the capstan diameter.

11. Apparatus as claimed in claim 9 in which means are provided for effecting relative movement between the capstan and its skewed roller on the one hand and the approach and departure guide rollers on the other hand in a direction perpendicular to a plane tangential to the approach and departure guide rollers.

12. In a cable lapping machine of the kind in which pads of tape are carried on arms bodily around a longitudinally advancing cable core, apparatus as claimed in claim 8 carried on an arm carrying a pad, the capstan being fixed relative to said arm and the approach and departure guide rollers being mounted on a slide adjustable with respect -to said arm to permit the wrap on the capstan to be adjusted to a value which will result in the initial tension in the tape being reduced to the required residual value.

References Cited in the file of this patent UNITED STATES PATENTS 2,253,740 Van Hook Aug. 26, 1941 2,462,043 Neidel Feb. 15, 1949 2,623,345 Grieve Dec. 30, 1952