US2410127A - Machine for impregnating electric insulation - Google Patents

Description

Oct. 29, 1946. A w b so ETAL I 2,410,127

' MACHINE FOR IMPREGNAT INGELECTRiC INSULATION Filed Sept. 16, 1945 DRUM H54 r50 T0 250 .3 0 0 "F v INVENTORS' ATTORNEYS r 3% of moisture.

Patented Oct. 29, 1946 I UNI TE l;

MACHINE FGR IMPREGNATING ELECTRIC INSULATION John W. Olson, Hastings-on-Hudson, N. Y., and Charles W. Bechle, Sycamore, Ill., assignors to Anaconda Wire and Cable Company, New York, N. Y., a corporation of Delaware "Application September 16, 1943, SerialNo. soacsz I 4 Claims.

This invention relatesto insulated electricconductors, and has. for its object the provision "of certain improvements in saturating or impregnating the fibrousinsulation of such conductors with a bituminous orasphaltic saturant.

Certain types of electric conductorsjand cables are insulated with fibrous material, such as paper, cotton and the like, impregnated with a waterproofing bituminous or asphaltic saturant. At normal room temperatures, the saturant is usually a solid or very viscous material, and it is hence the usual practice to heat the saturant to a temperature at which it is a mobile liquid, .usuallyabout 350-375 F. When the fibrous insulation is immersed in this hot molten saturant, excessive moisture in the fibrous material is .promptly volatilized, frequently with explosive Violence. Under normal atmospheric conditions, the fibrous insulation usually contains 45% of moisture, and when such fibrous insulation is immersed in the hot saturant a substantial proportion, if not all, of this moisture is volatilized with attendant objectionable ebullition and foaming of the bath of hot saturant. The fibrous insulation is frequently a hard, tough, dense material such as kraft paper, and even when substantially dry such material is difiicultly and often incompletely impregnated with the saturant. In other cases the fibrous insulation'is a comparatively soft porous paper, such as toweling stock, crumpled and twisted about the conductor and characterized by a multiplicity of minute interstitial spaces which are difiicultly filled with the saturant solely by capillary action.

Bulk-drying of the fibrous insulation prior to impregnation has heretofore been commercially practiced. In accordance with the customary practice, the conductor covered with the fibrous insulation is wound on reels and dried for about 16 hours in a dry kiln at a temperature of about 200-250" F. The covered wire is usually tightly wound on the reel to a radial thickness of about one foot. The inner turns onthe reel are seldom satisfactorily dried, and frequently contain-up to discomfort in entering the dry kiln, theworkmen usually take out two or more reels at a time, and

often appreciable moisture isre-absorbed by, the

fibrous material while the reel is exposed to the atmosphere awaiting to be run through the saturant. i

Vacuum oven drying has also been proposed for-drying the fibrous insulation prior to impregnation with the hot saturant, but this has proved little,- if any, better than simplekiln drying. In

Moreover, due to the physical Y the-United States patent of Johnson and Olson objectives.

In the course of an exhaustive investigatiomwe have found that the fibrous insulation is very completely-and satisfactorily impregnated with the saturantfwhen the insulation is first dried to a substantially negligible moisture content, then immediately subjected to a high vacuum,

and run directly into the saturantwhile in its dried and evacuated conditio'n,fthe drying and vacuum treatment "being separate operations. Based on this discovery, the invention contem plates the improvement in impregnating fibrous insulation surrounding an electric conductor with a s'aturant comprising drying and-evacuating the fibrous insulation in separate but succeeding operations, and then immersing the dried and eV'ac-' uated insulation in :the saturant in its dried and evacuated condition. In a preferred embodiment of the ,inventionin which the covered conductor is drawn through a bath of the saturant in a substantially continuous manner, the invention involves wrapping a plurality of convolutions of the covered conductor over the heated cylindrical surface" of a'rota'table drum, and drawing the covered conductor directly from the drum through an-elongated vacuum chamber communicating directly with the'bath of sa'turant. The invention further contemplates a novel combination of "apparatus *for carrying out the foregoing improvements in impregnating fibrous insulation with a saturant.

3 end of the vacuum chamber, in the apparatus of Fig. 1, communicating with the saturant.

The drawing illustrates the impregnation of a layer of fibrous insulation 5 surrounding and covering an electric conductor fi either stranded or solid, with a hot molten saturant i. The covered conductor is drawn (in the direction of the arrows) from an unwinding reel or the like (not shown) through the bath of saturant onto a winding-up reel or the like (not shown) in a substantially continuous manner. Within the bath of saturant, several convolutions of the covered conductor are drawn over the surface of a rotatably mounted drum 8. The drum 8 may, if desired, be appropriately driven by any suitable source of power, or it may rotate freely and all the power required to draw the covered wire through the apparatus may be applied to the aforementioned winding-up reel. The rate of travel of the conductor and the number of convolutions wound around the drum 3 are correlated to provide a sufiiciently long immersion period to completely and satisfactorily impregnate the fibrous insulation. With a hot molten saturant of bituminous or asphaltic nature maintained at a temperature of about 350-375 lit, immersion times of from 6 to 20 minutes are common. It is to be understood, however, that the invention is not limited to saturants of this nature, but is applicable to any kind of saturant for the fibrous insulation of electric conductors and cables. The saturant I is contained in a tank 5. A wiper l secured to one side of the tank removes excess saturant from the covered conductor as it is drawn from the tank.

In accordance with the embodiment of the invention illustrated in the drawing, several convolutions of the covered conductor are drawn over the heated cylindrical peripheral surface ll of a rotatable drum I2. The drum .is mounted to rotate freely about its horizontal axis, and is rotated by the drawing of the covered conductor thereover. The rate of travel of the conductor, the number of convolutions wound around the drum l2 and the temperature orthe cylindrical surface H of the drum are correlated to heat the fibrous insulation until its moisture content is substantially negligible. It will be understood that the drum l2 (and likewise the drum 8) is provided witha pusher device of conventional construction for properly aligning the first and last convolutions of covered conductor on the drum with the supply reel (not shown) and the evacuating device, respectively.

The drum [2 is shOWn in the drawing as heated byan interior steam chamber I3 adjacent the cylindrical peripheral surface H. Steam is supplied to the chamber l3 through a radial pipe I4 connected to an axial steam supply pipe l5. The cylindrical surface of the drum is advantageously heated to a temperature of 250-30050. Any other suitable means of heating the cylindrical surface of the drum l2 may be provided, as for example, electric heating, gas flames, etc.

The vacuating device comprises an elongated vacuum chamber it connected by a pipe I! to an air pump or other suitable means (not shown) for maintaining as high a vacuum as possible in the chamber, say approximating" 30 inches of mercury. In practice, the vacuum chamber it may be from 3 to 5 feet in length, or even longer if necessary. It is preferably cylindrical with a sectional diameter several times the diameter of the largest covered conductor to be passed there- 4 through. A removable steel die [8 is mounted at the entrance or forward end of the vacuum chamber, and is secured in osition by a threaded nut 9. The traveling covered conductor fits tightly in the die 18 and effectively seals this end of the vacuum chamber.

The exit or rear end of the vacuum chamber has an inner shoulder 20 and a prolong 2! to which is coupled an extension 22 extending below the surface of the bath of saturant. The diameter of the prolong and extension may be somewhat less than the diameter of the vacuum chambenbut still suflicient to freely accommodate the largest covered conductor to be passed therethrough. The extension is coupled and secured to the prolong by a threaded nut 23.

A removable steel die 24 abuts against the shoulder 20 and is firmly held in position by the traveling covered conductor which fits loosely in. this die. A water jacket, or chamber 25 surrounds the die 24, and serves to artificially cool the die. Any other suitable means for artificially cooling the die 24 and the exit end of the vacuum chamber may be provided. An opening or manhole 26 and a cover 21 therefor are provided in the vacuum chamber near the exit end for permitting access to the chamber when changing the die 24. The evacuating device is sup? ported by a bracket 28 secured to the side of the tank 9 and a post 29 near the forward end of the device. The dies [8 and 24 may be of diiferent sizes 'to' accommodate different sizes of covered conductor. As previously stated, the GOV? ered conductor makes a tight fit in the die l8 and a loose fit in the die 24.

In 'practicingthe invention the covered conductor is drawn over the heated drum l2 until the moisture content of the fibrous insulation is reduced to substantially zero. With the cylin drical peripheral surface of the drum heatedto a temperature of 250-300" the covered conductor should remain in contact with the heated surfaceior from 3 to 8 minutes,-'depending upon the size of the covered conductor, in order to reduce the moisture content of the fibrous insulation to substantially zero. From the drum l2, the dried insulated conductor passes directly and immediately, and before any moisture can be reabsorbed by the fibrous insulation, through the sealing die l8 into the vacuum chamber It. In its travel through the vacuum chamber, air and othergases are almost completely removed from the interstitial spaces of the'fibrous insulation. The evacuated. covered conductor is drawn through the exit die 24 or the 'vacuurn, chamber and'immediately contacts the. saturant which is drawn up the extension 22 into the p1'olong'2i as a resultof the vacuum and the comparatively loose fit between the covered conductor and the diev 24. However, thesaturant will not pass beyond the die 24 into the vacuum chamben be cause of vthe cooling effect of the water jacket 25. The artificialf cooling at the exitj' endof the vacuum chamber chills the. saturant in the ad jacent part of the prolong, 2! to a very viscous and almost solid condition, and this chilled'satu-i rant cooperates with the die 24 and thetrave'ling covered conductorto .efiectively, sealithe exi't'end of the vacuum chamber. Atthe same time, the travel of the covered conductor through the die 24 keeps. the die clear, and carries back into-the hot saturant in the prolongj orextensionjany accumulation .of chilled saturant that might otherwise tend togclog the die; .The exit end of the vacuum tube is thus sealed'bythe die 24, and

the traveling covered conductor in conjunction with the chilled saturant surrounding the covered conductor as it enters the prolong 2|.

The invention provides a simple 'and effective method of and apparatus for saturating or impregnating the fibrous insulation of electric conductors and cables. The entire operation of drying, evacuating and impregnating is carried out in a substantially continuous and rapid manner. As contrasted with bulk-drying, the over-all time interval of operation is reduced by many hours, no large quantity of covered conductor is tied-up in process, and no reabsorption of moisture, after drying, can take place. The separation of the drying and evacuating treatment enables each to be carried out under optimum conditions. Evacuation following drying is particularly ad,- vantageous, since the vacuum is called on to remove only air or other occluded gases from the interstitial spaces of the already substantially dry insulation. This is of special advantage in impregnating crumpled and twisted paper insulation which inherently is honey-combed with minute interstitial spaces which, even when the insulation is bulk-dried in accordance with previous practice, cannot be completely filled with saturant by capillary action, the only force or means available to draw the saturant into the interstitial spaces. When the dry, fibrous insulation is evacuated in accordance with the invention, the saturant is forced under atmospheric pressure into the evacuated interstitial spaces, thereby promptly and completely filling these spaces with saturant. When the conductor has a layer of rubber or the like interposed between it and the fibrous insulation, the invention insures complete impregnation of the fibrous insulation without impairing the underlying layer of rubber.

We claim:

1. The combination with means for holding a saturant bath for impregnating fibrous insulation surrounding an electric conductor as the covered conductor is drawn through the bath of staturant in a substantially continuous manner, of means for heating the fibrous insulation in the course of its travel towards the bath of saturant until its moisture content is substantially negligible, and a vacuum chamber through which the dried covered conductor passes in its travel from said heating means to the bath of saturant.

2. The combination of claim 1, in which the heating means is the heated cylindrical peripheral surface of a rotatable drum over which the covered conductor is drawn.

3. The combination of claim 1, in which the heating means is a rotatable drum having an interior steam chamber adjacent its cylindrical peripheral surface for heating that surface to a temperature sufficiently high to remove substantially all of the moisture from the fibrous insulation as a plurality of convolutions of the covered conductor are drawn over the drum.

4. The combination with means for holding a hot saturant bath for impregnating fibrous insulation surrounding an electric conductor, of a rotatable drum whose cylindrical peripheral surface is adapted to be heated to a temperature sufliciently high to remove substantially all of the moisture from the fibrous insulation as a plurality of convolutions of the covered conductor wrapped around the drum are drawn over the drum, and an elongated vacuum chamber having a sealing die at each end through which the dried covered wire is adapted to be drawn directly from said drum, the exciting end of the vacuum chamber being in direct communication with the hot saturant bath and the die at that end of the chamber being artificially cooled to prevent seepage of the saturant into the vacuum chamber.

JOHN W. OLSON. CHARLES W. BECHLE.

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