US 3063228 A
Description (OCR text may contain errors)
N0 13 1962 M. sARRAclNo 3,063,228
APPARATUS FOR CONTROLLING THE TENSIONING OF THE TAPES IN ELECTRIC CABLE TAPING MACHINES Filed Aug. l, 1960 a Ziggy/v5 ys United States y Patent Otlfice 3,063,228 Patented Nov. 13, 1962 3,063,228 APPARATUS Fon coNTRoLLrNG THE TaNsIoN- The present invention relates to apparatus for controlling the tension of tapes in electric cable taping machines.
In the manufacture of electric cables, tapes made of paper or other suitable flexible material, herein referred to comprehensively as paper, `are widely used, the tapes being Wound on said cables by means of winding machines in which by the action of a suitable drawing device, the cable is made to move longitudinally lat constant speed while, at the same time, supply rolls of paper are caused to rotate about the axis of the -cable at a speed which is likewise constant. In this way, the tape is unwound from the rolls and wound helically on the cable.
Normally, a machine of this type comprises a considerable number of rolls of paper which, subdivided into groups, `are mounted on the common rotating support on which they are suitably spaced and oriented.
In the operation of taping electric cables, it is essential that the mechanical tension applied `to the tape which is being wound on the cable be maintained as constant as possible and equal to a predetermined value depending on the desired characteristics of the cable itself.
Normally, in such tapingmachines, in order to obtain the desired necessary tensioning of each tape in the portion between the supply roll and the cable, recourse is had to the action of -a mechanical brake concentric with the rotating `spindle on which the supply roll is secured. This brake is generally of the band or shoe type and its braking action is ensured by springs capable of being calibrated.
A brake of this type, however, would not, of itself, be sufficient to ensure a constant tensioning of the paper tape whilst being unwound from the roll and wound on the cable.
In fact, for an equal value of the tension of the springs ensuring the application of the brake 'and assuming the constancy of the coeicient of friction of the lining of said brake, the braking couple is constant, so that the tension in the tape is inversely proportional to the radius of the roll, the value of which decreases as the unwinding of the tape progresses. In other words, the tension of the tape increases during the unwinding of the roll.
In order to avoid these drawbacks, compensating devices'have been provided which act on the brake for the purpose of maintaining the tension in the tape automatically constant, within permissible limits, independently of the diameter of the roll and, possibly also of the coefficient of friction of said brake.
These are mechanic-al devices which cause, according to a given law, a variation of the tension of the 'springs acting on the brake in the sense of reducing said tension as the tension of the tape increases 4and Vice versa.
The devices of this type have also been provided with means whereby if, when the machine stops, yan excess of length is produced for any reason whatsoever in the portion of the tape payed off between the roll and the cable, the device recovers this excess within certain limits and maintains the tape under the required tension.
We have previously proposed mechanism of this character, by means of which, when the pull on the tape is lacking owing to the stopping of the machine, the tape is maintained equally under tension by rendering possible the recovery of any excess length of the tape which there may be in the portion located between the roll and the electric cable to be taped. Moreover, in the above mechanism, automatic stoppage is effected `in the event of the tape breaking or becoming completely slack.
However, the mechanical devices heretofore proposed, owing to the variability of the coefficient of friction 'and to the unavoidable imperfections of said mechanical devices, do not achieve that precision and constant value of the tension of the tape to be wound which is required in an increasing measure in the winding of electric cables.
The present invention has for its object a tape-tensioning apparatus for electric cable taping machines by means of which it is possible to obtain a more nearly const-ant tension of the tapes made of paper or other flexible material being wound on the cable by means which are simple yand permit exa-ct calibration of the apparatus, in respect of the tension of the winding tape, with the possibility of varying it also when the machine is in operation, according to the requirements of each type of cable.
The apparatus is extremely simple and reliable in operation. Moreover, it ensures automatic maintenance of the tension of the tape even in the event of stopping -of the machine and the recovery of any slack length produced, while it causes the automatic ystopping of the machine in the event of a tape breaking or la little before a supply roll is exhausted and must be replaced.
An essential feature of the apparatus forming the subject matter of the present invention resides in the fact that, contrary to other already known devices, a braking action is simultaneously exerted both on the tape being payed off from the supply roll and on the supply roll itself.
The invention consists in apparatus for controlling the tension of tapes in electric cable ytaping machines, cornprising braking means acting simultaneously upon thetape payed off from a supply roll and upon the said supply roll itself, the braking means comprising a braking roller secured to a shaft driven by an adjustable voltage motor and maintained adherent to the supply roll by spring pressure to follow the reductions in diameter thereof, the tape embracing lfor a suflicient are at rst the braking roller and then the supply roll, the braking action on the tape being due to the tractive effort exerted by the tape upon the braking roller and the braking action upon the supply roll being due to the iinal tension of the tape, said tension resulting maintained constant las the supply roll progressively decreases in diameter.
The braking action on the tape is generated'by the yfact that the braking roller, and consequently the rotor of the motor, is caused to rotate by the forward motion of the tape'v in the sense opposite to the normal sense of rotation of the motor, so that the latter is compelledto'work a's an electric brake. Moreover the electric motor lis mounted on a slide which, under the [action of springs, maintains the braking roller pressed against thesupply roll, compelling it to follow the diameter variations of the roll during its progressive exhaustion.
The electric motor, which functions as Ian electric brake may be, for example, a three-phase motor having a very highrotor resistance, so as to exhibit a torque characteristic, as a function of speed, which is very Hat, that -is to say that, within the range of speed variation when the motor is acting as a brake, the torque is independent of the speed. To control the electric braking action, the torque is controlled with great accuracy by varying the supply voltage, which results in a'corresponding variation of torque.
Single-phase or direct current motors may also be employed to obtain the aforesaid charactertistics.
The motor to be employed according to the invention operates in effect as asmall electric generator, the current vof which, in the example mentioned, is dissipated in the rotor. The apparatus is provided with -a suitable device for varying the supply voltage of the electric motor, by
means of which the braking action of the motor driven roller upon the paper tape is varied. This enables the braking action to be calibrated exactly to the required degree in order to obtain the necessary tensioning of the tape for any type of cable, which tensioning will be maintained strictly constant until the roll is exhausted.
By way of example, one practical embodiment of the invention will now be described in more detail with reference to the accompanying drawings, in which FIGURE l represents an elevation of the principal parts of a cable taping machine;
FIGURE 2 represents on a larger scale an elevation of one of the devices for feeding and controlling the tension of tape used in the machine of FIGURE l.
The majority of the references used in FIGURE 2 have, for the sake of clarity in the drawing, been omitted from the corresponding parts in FIGURE l.
In conventional practice -a taping machine for electric cables consists of several rotating cages G of t'ne type represented in elevation FIGURE l, driven from a comr'non transmission shaft A. Moreover, as schematically shown in FIGURE 1, a variable gearing, for instance of the belt or vchain type, is usually provided in the drive of each cage G which is supported by a base B. The cage rotates about its axis of rotation O O which is coincident with the axis of the cable K to be wrapped which is drawn axially forward along the taping machine, passing through the hollow shaft H of the cage G. On the cage G there are mounted a number of winding devices D, for instance, eight, each of which is situated in a plane passing through the axis of rotation O--O of the machine and is provided with a support for the paper roll, with the electric motor for actuating the braking roller which generates the desired tension in the tape to be wound on the cable and with all the necessary accessories, among which those more particularly pertaining to the invention will be described hereunder.
`FIGURE 2 represents a more detailed showing of one of the devices D. In said iigure the numberal y1 indicates the shaft supported by the frame 4 of each device of the rotating cage. The paper supply roll 2 is fastened to Said shaft -1 by means of the knob 3 which actuates any device for securing the roll 2 on the shaft 1.
The frame 4 carries two parallel longitudinal guides 5 directed normally to the line of action of the centrifugal force developed by the rotation of the frame 4 and on which are easily slidable both a transverse slide 6 carrying the shaft 7 for a tensioning roller 7 and a slide 8 carrying the adjustable-voltage motor 10 for driving a roller 11, the cylindrical surface of which (being made, for instance, of rub-ber) has a strong tractive etfect on the paper tape b passing thereover. The roller 11 is keyed on the shaft 9' of the motor 10 and is coplanar with the roll 2 and the roller 7.
The slide 6 is subjected to the action of a spring 12 enclosed in the frame 4, which spring is anchored at one end to said frame and is connected at the other end to a exible cord 13, made, for instance, of a synthetic linear superpolyamide, which passes over the transmission rollers 14 and is anchored to the slide 6.
The slide 8, on the other hand, is provided with hooks 15 for anchoring to one end of springs (not shown for simplicity) which are anchored at the other end to the hooks 16 xed to the frame 4.
In this way, the tensioning roller 7 tends to move laway from the roll 2, while the roller 11, fast with the rotor of the variable-voltage motor, tends to be constantly applied in the opposite direction, that is pressed against the roll 2 to followits diameter variations.
The paper tape is paid off from the roll 2 in the direction of the arrow F, so that the portion a thereof extends as far as the tensioning roller 7, from which a portion b of the tape passes over the roller 11 keyed on the shaft 9 of the motor 10 acting as an electric brake in the manner -described above. The motor 10 exerts its braking action inasmuch as, while it would tend to cause the roller 11 to rotate in the direction of the arrow F', the tape, on the other hand, passes over the braking roller 11 in the opposite direction F, exerting a drag on the roller against' its tendency to rotate in the opposite direction under the action of the motor 10.
The tape passes from the roller I11 on to the roll 2, which is in constant contact with the roller 11, and is wound thereon for a length c, to pass over the transmission rollers 17 and 18 mounted on the pivots 19 and 19', from which latter rollers the portion d of the tape is wound on the cable K which advances at a constant speed, passing through the hollow shaft H of the cage G carrying the rolls 2, which cage is also driven to rotate at a constant speed.
Owing to the effect of the spring 12 acting on the slide 6 carrying the tensioning roller 7, and of the springs acting, in the opposite direction, on the slide 8 carrying the motor 1t) and the roller 11 fast with the rotor of said motor, the tape is pressed against the roller 1v1 while it is being wound thereon and is subjected to the tangential braking action of said roller, which is caused by the action of the motor 10, as described above.
It will be seen from FIGURE 2 of the drawing that after passing over the braking roller 11 the tape follows round the circumference of `the supply roll 2 before passing over the transmission rollers 17 and 18. Since the slide 8 is drawn to the right by springs connecting the hooks 15 and 16 as already described above, the braking! roller 11 will exert the same constant braking action simultaneously on the supply roll 2 and on the length of paper tape which passes over said roller 11, and the tension on the tape winding up on the cable is maintained substantially constant as the roll 2 progressively decreases in diameter.
The braking action on the roll is thus entirely independent of the variation of the diameter of the roll 2 occurring as the unwinding of the tape from said roll progresses, for which reason, by maintaining constant the tangential force applied to the roller 11, which is dependent on the regulation of the voltage supplying the motor, the tension of the tape will be maintained strictly constant at the predetermined value for the whole of the time during which the tape is payed ofi from the roll to the cable.
As will have been seen, the apparatus maintains the tension of the tape constant automatically in the event of stoppage, for any reason whatsoever, of the machine, this being due to the effect of the winding action of the roller 11 subjected to the action of the motor 10, which ensures the recovery or taking up of any slack length produced.
In fact, when the normal switch for stopping the machine is actuated, some length of the tape still tends to unroll from the supply roll, due to the mechanical inertia and to the unavoidable clearances of the machine. The tape is no longer subjected to the predetermined winding tension, because the tractive effect exerted by the cable K on the portion d of the tape has ceased. In that case the motor 10, which tends to rotate counterclockwise, is no longer compelled to rotate clockwise, so that its action on the roller 11 overcomes that exerted by the tape. Therefore the motor 10, and consequently the roller 11, rotate counterclockwise and, as the roller 11 is pressed against the supply roll 2, the latter itself is rotated so as to take up any slack length of tape produced.
4In the event of breakage of the tape, the slide 6 and the roller 7 are no longer held in their working position by the tractive action of the two portions of tape a and b and, consequently, the spring 12 causes the slide 6 to move in the direction to separate the roller 7 from the roller 11. The slide 6 then strikes the nger 20 adapted to pivot about the pin 21, which finger, by means of the tie rod 22 and the rocking lever 23 adapted to oscillate about the iixed pivot 24, causes the operation of a switch 25 which effects the stopping of the machine.
A little before the unwinding of the roll 2 is completed, a projection 26 provided on the slide 8 strikes against the push rod 27, which causes actuation of the switch 28, which stops the machine.
For variation of the torque of the motor 10, whereby tension of the tape is controlled, a voltage regulator M of normal type is inserted in the motor supply circuit.
The taping machine is provided with an electric circuit comprising, inter alia, sliding electric contacts (slip rings and corresponding brushes) for carrying the supply current to the brake motor of each device D of the rotating cage and for transmitting the electric impulses which operate the stopping of the taping machine.
What I claim and desire to secure by Letters Patent of the United States is:
l. Apparatus for winding around an electric cable tape drawn from a supply roll, comprising in combination a mounting for said roll rotatable -about the cable and per.- mitting tape to be drawn from said roll on rotation of said mounting, a braking roller, means for pressing said braking roller into contact with said roll, means for leading said tape after it is drawn from said roll successively around said braking roller and around said roll, and an electric motor operatively associated with said braking roller and applying a torque thereto opposite in direction to the torque exerted on said braking roller by the said passage around it of the tape.
2. Apparatus as in claim l, including a tensioning roller around which the tape is passed after it is drawn from said supply roll and before its passage around said braking roller, movable mounting means for said tensioning roller, and means operative on said mounting means, for urging said tensioning roller away from said braking roller.
3. Apparatus as claimed in claim l, wherein the electric motor has a fiat torque/speed characteristic so that the torque is substantially independent of the speed wherein the motor torque opposes that applied by the travelling tape within the required range of speed variation.
4. Apparatus as claimed in claim 3, wherein the electric motor is a 3phase motor with a high rotor resistance.
5. Apparatus for winding around an electric cable tape drawn from a supply roll, comprising in combination a hollow shaft through which said cable is fed, at least one cage mounted for rotation about said shaft, a plurality of frames carried by said cage, mounted on each frame a supply roll for the tape, longitudinal guides directed normally to the direction of the centrifugal force-generated by rotation of the cage, on each guide two slides carrying respectively, a tape-tensioning roller spring-urged away from the supply roll to impart tension to the tape and a braking roller spring-urged toward and maintained pressed against, the supply roll, said braking roller having an electric motor applyin-g a torque opposite in direction to that exerted on said braking roller by the supply roll and yat least one freely rotatable transmission roller mounted on the cage in proximity to each frame.
6. Apparatus for winding around an electric cable tape drawn from a supply roll, comprising in combination a mounting for said roll rotatable about the cable and permitting tape to be drawn from said roll on rotation of said mounting, a braking roller, means for pressing said braking roller into contact with said roll, means for leading said tape after it is drawn from said roll successively around said braking roller and around said roll, an electric motor operatively associated with said braking roller and applying a torque thereto opposite in direction to the torque exerted on said braking roller by the said passage around it of the tape, a tensioning roller around which the tape is passed after it is drawn from said supply roll and before its passage around said braking roller, movable mounting means for said tensioning roller, means operative on said mounting means for urging said tensioning roller away from said braking roller, means for stopping rotation of a power-transmission shaft whereby the apparatus is driven upon breakage of the tape, and said means comprising a trip switch and mechanism, operable by said movable mounting means on breakage of the tape, for actuating said switch.
7. Apparatus according to claim 5 comprising a cut-out switch adapted to stop the machine upon the breaking of a tape, the said switch being actuated by a movable member operated by the motion of the slide which carries the tensioning roller.
8. Apparatus according to claim 5, comprising means for stopping the machine a little before the supply of tape from the supply roll is exhausted, said means comprising a striker member carried by the slide upon which is mounted the braking roller, said striker being adapted to operate a switch.
References Cited in the file of this patent UNITED STATES PATENTS 1,094,047 Ames Apr. 21, 1914 1,284,625 Emrick Nov. l2, 1918 1,968,251 France July 31, 1934 21,279,115 Ewaldson et al. Apr. 7, 1942