US2346523A - Process for impregnating cables - Google Patents

Description

April 1944- R. s. VINCENT 2,346,523

PROCESS FOR IMPREGNATING CABLES Filed Jan. 28, 1939 2 Sheets-Sheet l Inventor WJW Why/9% A itorneyi April 11, 1944. R. s. VINCENT 3 5 PROCESS FOR IMPREGNA'IING CABLES Filed Jan. 28, 1939 2 Sheets-Sheet 2 ,EJQ g5 /46 b2 E58 Inventor Y1 78 'MAXM 1 F i 75 1 19.0. 75 27% I 6%;

Attorney Patented Apr. 11, 1944 .I'NITED STATES PATENT opt-ms PROCESS FOR IMPREGNATING CABLES Russell Swale Vincent, London, England, assignor to Callenders Cable and Construction Company Limited, London, England, a British oom- Application January 28, 1939, Serial No. 253,454

- In Great Britain February 2, 1938 3 Claims.

It is the object of the present invention to provide an improved process whereby cable. may

be continuously treated for removal of gas and moisture or for impregnation or for the two purposes in successive operations. Further objects are to provide an improved inlet gland, to provide improved combinations of inlet and outlet sealing devices and to provide improvements in heating the cable. 'I'he invention specially contemplates the combination of a dry inlet gland with an outlet seal consisting of a barometric leg. The scope of the invention is defined in the appended claims.

In a preferred form of the invention the cable ispassed into a zone of moderately reduced pressure in which it is partly dried, degassed and heated and then passed into a zone of higher vacuum where it is further degassed and dried. It may then be passed into a zone where impregnation is accomplished under vacuum, then into a zone where impregnation is accomplished under atmospheric or superatmospheric pressure, and

finally into a one where it is cooled, preferably by One manner of practising the invention will be described in greater detail with reference to the accompanying drawings, in which:

P18. 1 is a diagrammatic elevation of a suitable plant,

Fig. 2 is a side sectional elevation of a suitable form of gland for use, in the apparatus shown in Fig. 1, and

Fig. 3 is a diagrammatic sectional elevation of a form of electrical induction heater suitable for heating or preheating cables having metallic passage in contact with cold impregnating liquid.

Heating may be employed in the impregnating zones. Such heating may be accomplished by passing the cable through a casing which is externally heated, e. g. by means of steam.

It is also advantageous in addition to preheat the cable, i. e. to raise its temperature prior to its entry into a region of low pressure where degassing is carried out.

During its passage from one zone to another of different pressure, the cable passes through a pressure seal. This may consist in some cases of a barometric leg fllled with liquid which may be surrounded by a heating means and may serve as a zone of treatment. Alternatively, it may consist of a dry gland.

The heating of the cable prior to its impregnation is necessary to remove gas and moisture from it or from its covering, e. g. a paper wrapcores.

In Fig. 1 of the drawings, I is a sealed inlet box,

2 is an inlet tube for cable, 2 is a gland on tube 2, 4 is a preheater (such as that shown in greater detail in Fig. 3) on tube 2, 5 is a pulley in box I, 8 is an up-run tube, 1 is a jacket for tube 6, 8 is a seal box connected to tube 6; 9 is a pulley therein, It is a connection from box 8 to a vacuum pump (not shown), II is a down-run tubev connected to seal box 8, I2 is a jacket for tube l I, I2 is a gland at lower end of tube H, 14 is a seal box connected to tube ll, 44 is a pulley therein, is is an up-run tube connected to seal box l4, I6 is a jacket for tube l5, I1 is a seal box connected to tube l5, I! is a pulley therein, is is a connection from box ll to a vacuum pump (not shown), 22 is a dowu-run-tube connected to box l'l, 2| is a jacket therefor, 22 is an open liquid tank connected to tube 20, 23 is a pulley therein, 24 is another up-run tube, 25 is a jacket therefor, 26 is a collecting funnel surrounding the top of tube 24, 21 is a. pipe connecting funnel 26 with tank 22, 22 is a gland on the bottom end of tube 24, 29 is a gland on the top end of tube 24, 20 is an inlet pipe to tube 24 for degassed impregnating fluid delivered by pump 3|, 22 is an unenclosed pulley,

22 is a final down-run cooling tube. 34 is a jacket therefor, 25 is a collecting funnel on top of tube l2, 22 is an exit trough, 31 is a pulley therein, 28 is a pump, as is a pipe connecting trough 26 with pump 22 and 40 is a pipe connecting pump 38 with funnel 25. Inlets and outlets 4! are provided for heating and cooling fluids on jackets 6, II, I5, 24, 24 and 22. 42 is a pump for conveying liquid from tank 22 through a degassifler (not shown) to a sealed storage vessel (not shown) for degassed impregnated medium, such as a mixture of 25% of rosin and 75% of heavy oil such as valve 011. The glands 2, i2, 28 and 29 may be of the type shown in greater detail in Fig. 2.

In Fig. 2, Si is a flange, drilled at 52, for securing tube 53 against an apertured face. Tube is is also flanged at 84 forming with distance 55 pieces 55 and back plate I1, the gland body. It

to enable the hole in the disc 67 to be enlarged uniformly. Each strainer may be associated with 7 several wires, e. g. four.

In Fig, 3, b8 is the insulation and as is the conductor of a cable passing through a sleeve $39, which is of electrically insulating and heat-resisting material. This sleeve supports the coppen solenoid it, which is formed of rectangular section tube through which cooling water is passed from inlet ii to outlet i2. it are .connections to a source of high frequency current (not shown). In the operation of the apparatus shown in Fig. 1 a partial vacuum is produced in tubes 6 and it by the pump (not shown) connected to pipe it and a high vacuum is produced in tubes it and it by the pump (not shown) connected to pipe i9. This causes liquid in tank 22 to rise in tube 2 and form a barometric seal column.

A paper-wrapped cable indicated diagrammatiestates tion under pressure, for an impregnation at atmospheric pressure or for cooling, if desired.

In the form of the invention described above,

the preheating is eflected by causing the cable cally by the line marked 63 is fed to the right hand side of the apparatus. It passes through gland 3, preheater t, under pulley b and up tube 6, over pulley 9 and down tube ii. In tubes 6 and it it is partially. dried and degassed by the moderate vacuum. Then it passes through gland 63, under pulley st, up tube It, over pulley it and down tube 20. In tube it it is further degassed and dried under high vacuum and in tube 20 it is impregnated while still under vacuum. From tube 20 is passes under pulley 23, through gland 28, up tube 26, where it is impregnated under superatmospheric pressure, through gland 28, over pulley 32, down tube 33 where it is cooled by passage through cold impregnating liquid, under pulley ti and out of trough 36 at the left hand side of the apparatus. The pulleys serve to guide the cable through the tubes but some or all of them may be driven to assist the passage of the cable through the apparatus.

The height necessary for tube 20 depends upon the density of the impregnating liquid. In general, a height of about 40 feet is required to enable an adequate degree of vacuum to be employed. Theup-run and down-run tubes have their internal diameter only slightly laiger than the maximum external diameter of the cables to be treated in the apparatus. In this way good heating efliciency is assured and it is possible to maintain an adequate head of cool liquid in tube 83 without circulating an undue amount. If it should happen that the cable treated has a much smaller diameter than tube as, it may be desirable to provide a gland at the lower end of this tube.

The pressure maintained in tube 2% may be 40 lbs. per square inch. At this pressure the amount of liquid leaking through glands 28 and 29 is not great. That leaking through gland 28 collects directly in tank 22; that leaking through gland 29 collects in funnel 26 and runs thence through pipe 21 into tank 22. y

In the drawing six tubes are shown. Further tubes may be provided for .the preliminary degassing, for the degassing and drying, for the impregnation under vacuum, for the impregnato pgss through the field of a solenoid, to which high frequency current is ted, so that the heating is accomplished by the eddy currents induced in the conductor of the cable after the manner of an induction furnace. The method of heating may also be used in the degassing and/or drying and/or impregnation. Other methods of heating and/or preheating may be used oi which the following are examples:

(1) The cable may be heated by causing the metallic core to act as a conductor for an electric current, which may conveniently be induced in it by surrounding a portion of the cable with a coil through which intermittent or alternating current is ed, one or both ends of the cable being earthed.

f (2) The capacitative effect of the cable may be taken advantage of by causing the metallic core to form one plate of a condenser of which the other plate is earthed, and inducing a current in the core by placing it in the field of a coil through which high frequency current is passed.

(3) The cable may be passed closely adjacent to a surface which is caused to radiate heat at a wave-length which the paper or other coating will trat,

t) The cable may be passed through a gaseous medium which will transmit the heat from a adjacent heated surface by convection.

(5) The cable may be brought into direct contact witha preheated gaseous medium, e. g. hot air.

(6) The drum or the like from which the cable is unwound before passage through the impregnating machine may be surrounded by a casing which is heated in any convenient manner or through which a hot gaseous medium is passed, to heat the whole mass of the cable.

Methods (4), (5) and (-6) are particularly suitable for preheating the cable, while the other methods are suitable not only for preheating the cable, but for heating it during its passage through the apparatus shown in Fig. 1. Those methods which depend upon any form of electrical induction will, however, require a careful choice of suitable materials for the casing through which the cable is passed during its treatment.

In place of the gland shown in Fig. 3, other forms of glands may be used.

One such other form of gland may be constituted by a ring of resilient material such as rubber of a suitable size to press upon the cable which is passed therethrough. Such ring may have metal insertions to give greater rigidity and if desired may also have an outer reinforcement of thin metal strip or wire arranged, for example, in the formof a spiral. Such ring is arranged to abut against a rigid face on the side remote from that to which the cable is fed.

Another form of gland which may be used in practising the present invention is constituted by a sleeve of resilient material suchas rubber, ar-

ranged in the form of a double cone which fits snugly upon the cable at its point of minimum cross section. This may be pressed upon the cable during the passage of the cable therethrough by the prevailing pressure of the surrounding atmosphere, or may be mounted in a closed casing whereby any desired fluid pressure may be applied to the exterior.

Another form of gland which may be employed in practising the present invention consists of a hollow sleeve loosely packed with small solid spheres made of material which is inert to atmospheric influences or to the influence of any materials with which it may come into contact. Thus, small glass balls may be used. The sleeve is arranged to provide just suflicient clearance to permit the cable to pass therethrough, and the free movement of the spherical objects allows them to pack themselves closely around the cable. The spheres are preferably as small as possible, but must be sufliciently large not to permit their escape or jamming between the apertures in the sleeve and the cable.

Another form of gland which may be employed in practising the invention is constituted by an assembly of pairs of plates having concave cutout portions adapted to press a little upon opposite sides of the cable. Such an assembly of plates may be constituted by two pairs of plates arranged to press together at right angles to one another, presenting an aperture after the manner of an iris diaphragm. The edges of the plates which contact with the cable may be suitably rounded to eliminate friction, and to obviate damage to the cable. More than two pairs of plates may constitute the assembly, if desired, and the elements of each pair may be pressed together by spring means or by gravity.

A further form of gland which may be employed in the present invention is constructed after the manner of a labyrinth such as is employed in conjunction with steam turbines. One form of such a labyrinth could, for example, consist of an elongated sleeve of metal which has been partially collapsed by known means, so as to produce a bellows form of such internal diameter that the cable will just pass through with a small clearance. A succession of annular spaces is thereby provided along the sleeve which assists in preventing the passage of air or gas from the zone of high pressure on one side to the zone of low pressure on the other side.

The dry glands above described are suitable for use not only on the inlet or outlet of a cable treating machine, but for use at the boundaries of zones of different pressure. By arranging for the cable to pass through successive zones of diminishing or increasing pressure, no undue load is placed on any gland since it is required merely to prevent undue leakage between zones which may not differ very considerably in pressure.

The invention is of particular value for the treatment of electric cables, but is not limited thereto since it can be used, for example, for the treatment of cords or ropes.

It will be apparent, however, that not all the forms of heating described can be employed for treating materials which have not got metallic cores.

I declare that what I claim is:

1. A method of treating insulated cable in continuous lengths which comprises continuously passing the cable between surfaces engaging the cable by dry friction in vacuum-sealing relationship into an evacuated space and out of said space through a liquid seal of impregnating composition, and subjecting the cable to preliminary heating before its entry into said evacuated space.

2. A method of treating insulated cable in continuous lengths which comprises continuously passing the cable between surfaces engaging the cable by dry friction in vacuum-sealing relationship into an evacuated space and out of said space through a liquid seal of impregnating composition, and electrically heating the cable before its entryv into said evacuated space.

3. A method of treating insulated cable in continuous lengths which comprises continuously passing the cable between surfaces engaging the cable by dry friction in vacuum-sealing relationship into an evacuated space and out of said space through a liquid seal of impregnating composition, impregnating the cable in vacuo, and continuously impregnating the cable with a liquid composition under pressure after said impregnation in vacuo.

RUSSELL SWALE VINCENT.

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