US2251826A - Making metal-sheathed cables - Google Patents

Description

Aug. 5, 1941. L, E, FOGG 2,251,826

MAKING METAL-SHEATHED CABLES Filed Dec. 18, 1959 3 Sheets-Sheet l Aug. 5, 1941. L. E. FOGG MAKING METAL-SHEATHED CABLES 3 Sheets-Sheet 2 Filed Dec. 18, 1959 Aug. 5, 1941. L, E, FOGG 2,251,826

MAKING METAL-SHEATHED CABLES Filed Dec. 18, 1939 3 Sheets-Sheet 3 Patented Aug. 5, 1941 AUNITED STATES PATENT OFFICE MAKING METAL-SHEATHED CABLES Leigh E. Fogg. East Providence, R. I., assignor to Kennecott Wire and Cable Company, Phillipsdale, R. I., a corporation Application December 18, 1939, Serial No. 309,736

3 Claims.

This invention relates to improvements in processes of making metal-sheathed cables, and more particularly to processes of making metalsheathed paper or the like insulated electrical cables.

One object of this invention is to provide an improved process of making a metal-sheathed cable whereby the cable-core 'can be more elllciently treated to remove moisture and prevent the reabsorption of the same by the cable-core.

Another object of this invention is to provide an improved process of making a metal-sheathed cable by enclosing a cable-core in loosely-fitting relation with a cable-sheath and extracting they moisture and the gas from the cable-core and saturating the latter with insulating material, and reducing the diameter of the cable-sheath to bring it into close fitting engagenent with the cable-core. (if

With the above and other objects in view, as will appear to tiiose skilled in the artfrom the present disclosure, this invention includes all features in the 'said disclosure which are novel over the prior at.

In the accompanying drawings forming part of the present disclosure, in which certain ways of carrying out the invention are shown for illustrative purposes:

Fig. 1 is a side elevation of one form of apparatus for performing the first-stage reduction of the cable-sheath;

Fig. 2 is a transverse sectional view on line 2--2 of Fig. 1;

Fig. 3 is a transverse sectional view on line 3-3 of Fig. 1;

Fig. 4 is a longitudinal sectional view on line 4 4 of Fig. 1;

Fig. 5 is a schematic side elevation of one form of apparatus for performing the second-stage or final reduction of the cable-sheath;

Fig. 6 is a .transverse sectional View on line 6 6 of Fig. 1;

Fig. '7 is a transverse sectional view on line 1-1 o1' Fig. 1;

Fig. 8 isa transverse sectional view Online 8-8 of Fig. 5; and ji Fig. 9 is a view similar to Fig. 5 of another form of apparatus for performing the secondstage or final reduction of the cable-sheath.

In the description and claims, the various parts and steps are identified by specific names for convenience, but .they are intended to be as generic in their application as the prior art will permit.

Fig. 6 shows cable I 0 including a cable-core Il loosely assembled in a metal cable-sheath I2,

and with the space between the 'core and sheath illledwith insulating oil orlmaterial or compound i3 which also impregnates the paper or the like insulation covering, forming part of the cable-core. A suitable loose-fitting relation between the core and sheath,'depen'ding on .the diameter and length of the cable, is obtained by having the external diameter of the core from about 115 to about 1A." smaller than the internal diameter of the sheath. Prior to 'introducing the insulating material I3 into the space between the core and sheath in the construction illustrated in Fig. 6, the core within` the looselyfitting sheath is suitably treated to remove moisture and gas, after 'which the insulating material or compound i3 is introduced into the space between the core andsheath, and the sheath is later reduced inl diameterv so that the core and sheath are in close relationship.

But inasmuch as the insulating material which it is desirable to use is of relatively-high viscosity at ordinary room temperatures, I have foundthat instead of attempting to completely reduce the cable-sheath from the diameter shown in Fig. 6 tothat shown in Fig. 8 in a single operation, that marked advantages result from dividing this reducing operation into at least two stages, in the first of which stages the sheath is reduced to near its final size. as illustrated in Fig. 7, and subsequently the sheath is reduced the final small amount to bring it into final close-fitting relation with the core, as

`illustrated in Fig. 8. During the iirst or major reduction of the sheath, I have found that it is highly desirable to have theinsulating compound (and the sheath and core) at an elevated temperature such, for example, as at from to C., while the second or final stage of the reduction is carried out with the sheath and its 'contents at a normal room temperature of about 25 C. For typical widely-used insulating compounds, the viscosity at 25 C. is from 1600 to 3700 centipoises, whereas at 100 C. it is from 17 to 27 centipoises.

Thus, by making the rst-stage reduction of the sheath while the insulating material is heated and consequently of relatively-low viscosity, permits it to flow longitudinally of the cable between the core and sheath as the reduction in size of the sheath takes place. On the other hand, if the insulating material were not in a heated condition, its viscosity would be so high that the closing in or reducing operation on the sheath would produce so high a pressure in the insulatingcompound along the portion oi the sheath adjacent to the place of reduction in diameter. that dangerous bursting stresses would be developed which would tend to :burst or unduly bulge the sheath. After the rst-stage reduction operation has been completed at an elevated temperature, the entire cable, including the insulating compound, is permitted to cool to ordinary temperatures. This, however, causes a greater shrinkage of the insulating compound than of the other parts of the cable, with the consequence that voids or spaces occur between the core and sheath along the length of the cable. To eliminate these void spaces in the insulating compound, the second-stage or iinal reduction oi' the sheath is brought about. But inasmuch as this ilnal-stage reduction is made while the insulating compound is at ordinary room temperature and, therefore, at relativelyhigh viscosity, in order to avoid bringing about undue bulging or bursting pressures in the insulating compound within the cable, considerable care is needed not to apply too great reduction in diameter of the cable-sheath. Control of this operation can be accomplished by automatic means, as will be later more fully set forth.

Figs. 1 to 4 show views of an apparatus for bringing about the first-stage or main reduction oi the sheath of the cable. Rotatably mounted on the frame or base I4 is a lower roll I5 having side-ilanges I6 between which fits an upper roll Il having a semicylindrlcal groove I8 which with the straight side-faces I8 form relatively-sharp outer edges 20, and with the semicylindrical groove 2i of the lower roll i5 forms a cylindrical area (Fig. 3). The upper roll Il is rotatably mounted on a slide 22 which can be adjustably pressed downward by a screw 23 carrying a handwheel 24. A second pair of grooved rolls 25 and 26 are arranged at right angles to the ilrst pair of rolls I5, Il, the roll 25 being rotatably mounted on the frame or base i4, and the roll 25 being rotatably mounted on a slide 2l which can be Y adjustably forced toward the roll 26 by means of a screw 28 carrying a hand-wheel 29.

Fig. 2 illustrates the manner in which the sheath is distorted from the round form shown in Fig. 6 to elliptical form as it starts in between the rolls i and il, while Fig. 3 illustrates the completion of the first-stage reduction operation after it has passed through the pair of rolls I5 and I'l. The second pair of rolls 25 and 26 mainly removes any iins that may be formed by the edges as a result of passage through the pair of rolls I5 and I 1. The cable is then permitted to cool down -to ordinary temperature with the result that the insulating compound I3 in the cable shrinks more than the cable-sheath, thereby causing voids or spaces to occur between the core and sheath along the length of the cable. In order to eliminate these voids or spaces, the cable is then passed through suitable mechanism such, for example, as that illustrated in Fig. 5, in order to further reduce the diameter of the sheath and eliminate the voids or spaces. But inasmuch as the insulating compound in the sheath has now become very viscous, great care is necessary in further reducing the cable so as not to cause too great a longitudinal ilow of the insulating compound with consequentexcess of bulging or bursting stresses being imposed upon the sheath. In order to accomplish this result, it is desirable to ilnally reduce the cable-sheath by means oi an apparatus in which the reduction of the sheath is controlled more or less automatically to avoid undue bursting stresses on the sheath.

Referring to the apparatus illustrated in Fig. 5, the cooled-oir cable, illustrated in Fig. '7 in cross section, is drawn between the pair of rolls Il and li and wound onto a drum l! by means of an electric motor I3. A guide-roll 34 is used to position the cable in -a substantially-horizontal position as it enters Ithe rolls II-IL The roll 34 is rotatably mounted in ilxed poistion on a base na, while the roll Il is rotatably mounted on a slide 35 vertically slidable in a frame ll and having secured to the slide, a screw-threaded rod Il threadedly engaged by a worm-wheel Il driven by a worm l! driven from a reversible electric motor 4I through a friction-clutch 4| and a reducing-gear unit 42.

A follower-rod 43 carries a roller 44 at its lower end which is pressed into contact with the cable I0 by a spring 45 and is pivoted at its upper end to a switch-lever or arm 4I which latter is pivoted to the frame 36. The switchlever 46 has secured at one end thereof, an electric contact 41 adapted to engage contacts 48, 49, 5l and 5i under certain conditions. The contacts 4l to 5i are merely schematically illustrated, and in actual fact may consist of any suitable type of switches such, for example, as mercury switches which are actuated by tilting.

Assume now that the rolls 30, 3| in Fig. 5 are adjusted to close-in the cable from the condition shown in Fig. 7 to its ilnal closed-in stage shown in Fig. 8, and assume the main switch 52 to be closed, as illustrated. This will supply electric power to the reeling-motor 33, which thus draws the cable III to the left in the direction of the arrow 53. Prior to formation of a bulge 54 in the cable-sheath. the switch-lever 46 will close electric contacts to cause the roll 3| to travel down closer to roll 30, as will be later more fully described, or, the switch-lever 46 could be temporarily held in neutral or opencircuit position, but in either case, presently the insulating oil or compound within the cable starts to be crowded to the right within the sheath of the cable with suillcient force to expand the cable sufilciently to produce a slight bulge 54 which is sufficiently large to raise the roller 44 and follower-rod 43 to cause the switch-lever 46 to occupy the midway or open-circuit position, so that all electrical contacts operated by it are in open condition. Now assume that an additional accumulation of insulating compound enlarges the bulge 54 still more and thus pushes the follower-rod 43 up against the action of the spring 45 and swings the switch-end of the switch-lever 46 downward to close the contacts 41 and 4I, with the result that the magnetic switch-closer or contactor 5l closes the doublepole switch 5l against the action of the spring 51, to thus start the motor 4I at slow speed to actuate the mechanism to raise the roll Il to relieve the pressure somewhat upon the cable I I. If this results in sumcient release, sumcient excess insulating compound will be permitted to move forward with the cable to cause the bulge 54 on the cable to become smaller in size as the cable is wound on the drum l2, with the result that the roller 44 descends, thus permitting the spring 45 to swing the switch-lever 45 and break the circuit formed by the switch-contacts 41 and 4I, thus stopping the motor 4l. Preferably, the roll 3| will be moved very slowly so that perhaps ten feet or more of cable will move between the rolls 30, 3| while an adjustment of rc-li 3! of only a few thousandths of an inch is made.

But if instead of the foregoing described raising of the roll 3| being suilicient to relieve the stress, it should happen that the accumulation of insulating oil or material in the cable causes even a larger bulge notwithstanding the action of the motor 40 to relieve this condition by raising the roll 3|, then the switch-arm 46 is swung still further, to close the contacts 41 and 49, while maintaining the contacts 41 and 46 closed, thereby acting on the magnetic switch-closer or contactor 56 to close the single-pole switch 69 against the action of the spring 66 and thus short circuit the resistance coil. 6|, with the result that the motor 40 increases in speed and, therefore, works faster to raise the roll 3| faster to overcome the tendency to increase the size of the bulge 54 in the cable-sheath. If this action has now been successful in causing the bulge on the cable-sheath to become smaller, then the roller 44 is forced downward by the spring 45 to thus swing the switch-arm 46 to successively break the two sets of switch-contacts 41, 49 and 41, 46 with the result that the circuit to the motor 46 is broken and it cornes to a stop.

If, however, there is insuflicient bulge produced in the cable-sheath, then roller 44 descends so far as tocause the switch-arm 46 to swing and engage the switch-contacts 41 and 50 with the result that the magnetic switch-closer or contactor 62 actuates the double-pole switch 63 against the action of the spring 64 to closed position, thus supplying power to the armature of the motor 40 in the opposite direction and thus causing the motor 40 to rotate in the reverse direction, with the result that the upper roll 3| is forced downwardly toward the roll 30. If the bulge 54 continues to decrease in size, then the switch-arm 46 will swing further to close the switch-contacts 41 and 5|, while maintaining the contacts 41, 50 closed, to thus actuate the switch-closer 56 to close the single-pole switch 59 against the action of spring 60 to thus short circuit the resistance coil 6| and, in consequence, speed up the action of the motor 40 to thus force the roll 3| downward even faster. When nally a proper slight degree of bulge occurs in the cable-sheath, then the switch-contacts 41, and 41, 56 again open, and the switch-arm 46 remains in open-circuit position ready to act in either direction to accomplish the adjustment of the roll 3| in one direction or the other as heretofore described.

In the form of the invention illustrated in Fig. 9 which is a modification of the form of the invention illustrated in Fig. 5, such of the parts as bear the same reference characters in Fig. 9 as they do in Fig. 5, are essentially the same as the corresponding parts in Fig. 5. Referring to Fig. 9 when the follower or feeler roll 44 is raised by pressure from the bulge 54 of the cable I6 to cause the follower rod 43 to swing the switch-lever or arm 65 upward to close the electric contacts 66 and 61, the switch-closer 55 closes the double-switch 56 against the action of the spring 51 to cause the reversible electric motor 66 to start in operation at the same time that the brake-release coil 69 releases the spring-held brake 10, which normally holds the shaft of the motor 66 stopped, thus, through the train of drive elements 4|, 42, 39 and 38, raising the screwthreaded rod 31 and the slide 35 upward, which slide carries along with it the electric-contacts 61 and 1| which are mounted on an insulation support 12 mounted on the slide, thus breaking the circuit between the contacts 66 and 61 with the result that the double-pole switch 66 is opened by the spring 51 thus breaking the circuit to the motor 66 and the brake-release coil 66 in consequence of which the motor 66 stops and the brake 10 is applied, thus quickly stoppingvthe shaft of the motor. If the bulge 54 continues to enlarge and thus again brings the contact 66 in engagement with contact 61, the preceding series of operations is repeated and the motor 66 is again brought to a stop as previously described.

If now the bulge 54 sufficiently decreases in size to cause the switch-lever 65 to swing downwardly and engage the contacts 1| and 13, then the switch-closer 62 closes the double-pole switch 63 against the action of the spring 64 and thus actuates the motor 66 in the reverse direction at the same time that the brake-release coil 66 is actuated, to thus cause the screw-rod 31 and the slide 35 to move downward until the circuit is broken between the contacts 1| and 13, whereupon the motor is stopped as previously described. But if the bulge 54 continues to grow smaller, then the contacts 1| and 13 are again engaged and the motor is started up again until the contacts 1|V and 13 are again separated to thus again cause the motor 68 to stop. If desired, or necessary, adjustable limit means such as a screw 14 might be mounted, as for example on the frame 36, to prevent the roll 3| from moving down too close to the roll 30.

In the form of the invention illustrated in Fig. 9, as will be seen from the description Just given, while an above-normal size of bulge exists, the motor 66 will continue to operate to separate the rolls 30, 3| only while the bulge continues to enlarge. And similarly, while an under-normal size bulge exists, the motor will continue to operate to close the rolls closer together only while the bulge continues to become smaller.

The invention may be carried out in other spe cifc ways than those herein set forth without departing from the spirit and essential characteristics of the invention,and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

I claim: v

l. The process of making a metal-sheathed cable comprising: assembling a cable-core having solid insulation thereon in a loosely-fitting metal cable-sheath, the maximum diameter of said cable-core being considerably less than the corresponding internal diameter of said cablesheath; extracting moisture from the cable-core while it is in loosely-fitting relation with the cable-sheath; filling the remaining space in said cable-sheath with iiowable insulating compound which is of relatively high viscosity at ordinary temperatures and of relatively low viscosity when suitably heated; reducing the diameter of said cable-sheath to nearly final size while said insulating compound is heated to a temperature at which it is of relatively-low viscosity, the internal shape of such reduced sheath being substantially the same as the shape oi' said cablecore; and further reducing the diameter of the cable-sheath to final size after said insulating compound has cooled to a condition of relatively high viscosity.

2. 'I'he process of making a. metal-sheathed cable comprising: assembling a cable-core in a loosely-fitting metal cable-sheath; filling. the remaining space in said cable-sheath with iiowable insulating material which is of relativelyhigh viscosity at ordinary temperatures and of relatively-low viscosity when suitably heated; reducing the diameter ot said cable-sheath to nearly final size while said insulating material is heated to a temperature at which it is of relatively-low viscosity; and further reducing the diameter oi' the cable-sheath to iinal size after said insulating material has cooled to a condition of relatively-high viscosity by reducing means which is adjusted to vary the final diameters of dliferent sections of the cablesheath in accordance with the tendency of said insulating material to enlarge the cable-sheath during the final reducing operation.

3. 'I'he process of making a metal-sheathed cable comprising: assembling a cable-core in a 20 loosely-fitting metal cable-sheath; nlling the remaining space in said cable-sheath with ilowable insulating material which is of relativelyhigh viscosity at ordinary temperatures and ot relatively-low viscosity when suitably heated: reducing the diameter o! said cable-sheath to nearly final size while said insulating material is heated to a temperature at which it is of reiatively-low viscosity; and further reducing the diameter oi the cable-sheath to iinal size after said insulating material has cooled to a condition of relatively-high viscosity by a pair of reducing rolls which are automatically adjusted relatively to one another to vary the iinal diameters of different sections of the cable-sheath in accordance with the tendency of said insulating material to enlarge the cable-sheath during the inal reducing operation.

LEIGH E. FOGG.

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