US614995A

US614995A - Underground conduit for electrical conductors

Info

Publication number: US614995A
Authority: US
Publication date: 1898-11-29
Anticipated expiration: 1915-11-29

Description

Patented Nov. 29, |898.

C. H. SEWALL. UNDERGROUND CONDUIT FOR ELECTRICAL GONDUCTDRS.

(Application led Mar. 2, 189B.)

(No Model.)

me uonms mins coyuorouwmwnsn UNITED STATES ATENT rricn.

CHARLES II. SEVVALL, OF CHICAGO, ILLINOIS.

UNDERGROUND CONDUIT i-V'OR ELECTRICAL CONDUCTORS;

SPECIFICATION forming part of Letters Patent No. 614,995, dated November 29, 189e.

Application iiled March 2, 1898. Serial No. 672,246. (No model.)

To all whom z5 may concern.-

Be it known that I, CHARLES H. SEWALL, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Underground Conduits for Electrical Conductors, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to underground conduits for electrical conductors, my object being to provide an effective form of conduit that may be economically constructed, while possessing all of the desirable qualities as to mechanical construction and electrical installation.

My invention has more particular reference to those classes of underground conduits wherein the conduit-ducts are formed or embedded in a body or mass of hydraulic concrete or similar material. When hydraulic concrete or mortar is employed, it is desirable to maintain the concrete moist, as thereby a stronger and firmer mechanical structure results. The moisture in the concrete may be secured from the atmosphere as the air is drawn through the conduit from one manhole to another, as is usually the practice, the water of condensation from the air thus serving to maintain the mass of concrete uniformly moist. The presence of the moisture in the concrete also results in desirable electrical properties, such as the prevention of condenser action. The moisture serves, for instance, to bond together the lead sheaths of the cables in the conduits, thus reducing the insulation resistance between the sheaths of the cables and materially reducing the tendency of inducing currents from one cable to another. This is especially advantageous in telephone construction, where the presence of even small induced currents results in defective operation of the telephone system. There maybe instances, however, wherein the presence of moisture in the concrete will be found objectionable--as, for instance,when the conduit is in proximity to an electric railway, Where leakage takes place from the rails through the earth. In such cases it may happen that the extraneous currents thus passing through the earth will penetrate the mass of concrete due to the moisture therein and traverse the sheaths of the cables in the conduits, thus resulting in electrolytic corrosion at points where the extraneous currents pass from the metallic sheaths to an electrolyte-a in the present instance lthe moisture in the concrete. To obviate any such difficulty, I surround the mass of hydraulic concrete or similar material by a layer or sheath of insulating material, such as asphalt or bituminous concrete, to eifectively insulate the hydraulic concrete and the moisture therein from the earth. Should induced currents be found present in the sheaths of the cables, they may be readily carried off by bonding the sheaths of the cables together at the manholes and connecting the same to ground at a point beyond the ield of any extraneous currents.

In accordance With the present invention I surround the foundation and inclosure of hydraulic concrete or other conduit-carrying material by means of a layer of insulating material, such as asphalt or bituminous concrete, whereby the hydraulic concrete is insulated from the surrounding earth, and, while retaining the desirable water of condensation, is removed from contact with the earth, whereby the Water of condensation is prevented from forming a path for extraneous currents through the body of concrete. I may form the insulating sheath or layer in any desired manner, as by pouring asphalt or bituminous concrete or the like material around the hydraulic concrete and permitting the same to cool to form a continuous and jointless sheath, or by previously forming slabs or planks of bituminous concrete or the like material, which are laid in the trench with the joints sealed by plastic material, after which the conduit is built up, the upper wall of the hydraulic concrete being in a similar manner covered by the slabs or planks and all the joints being effectively sealed. In this manner the hydraulic concrete is thoroughly insulated from the earth. The moisture drawn in through the conduits from the external air will be found sufficient to compensate for any evaporation of the water of condensation of the hydraulic concrete, and will thus maintain the hydraulic concrete in the desirable moist condition, which thus in IOO n`o manner impairs the electrical properties of the conduits.

I preferably construct the conduits in accordance with the plan shown in an application filed by me May S, 1805, Serial No.

lSlS, wherein inverted channels are employed which may be made of any desired material and which for mechanical reasons are usually made in short lengths or sections adapted to be placed end to end to form a prolonged cond uit, thus giving rise to the necessity of providing` some convenient and effective bridge adapted to be placed over the joints, thereby effectively connecting the adjoining sections together when the inclosing body of concrete is placed in position. In said application I have described an archshaped bridge which may be made of woven wire or other open frame of metal or other material, as reeds, or cloth shellacked to impart rigidity thereto, the frame being adapted to be placed over the joint upon the exterior of the sections, so that the bridge is molded into the surrounding body of concrete, and thus holds the sections securely in position. I have experienced difficulty in preventing the plastic concrete from passing through the cracks between the adjoining ends of the sections, and in order to prevent this I have provided upon the bridge, upon either the exterior or the interior face, a medial band orstrip of cloth, paper, or other material adapted to cover the joint or crack, and thus prevent the plastic concrete from passing therethrough.

My invention further contemplates an improved form of inverted channel adapted to be placed upon the continuous floor of indeiinite width and length, the inverted channel comprising a block having a plurality of channels or grooves on the under face to form conduit-ducts when placed upon the floor, the blocks being molded into the inclosing body of concrete.

I have illustrated my invention in the accompanying drawings, in Which- Figure lis a transverse sectional View illustrating the conduit of my invention. Fig. 2 is a view illustrating two sections of the inverted channels placed in position with the bridge covering the joint. Fig. 3 is a View of the bridge. Fig. l is a sectional view of the preferred form of the inverted channel. Fig. 5 is a view of an inverted channel or block having a plurality of conduit grooves or channels.

Like letters refer to like parts in the several figures.

I have illustrated my invention in connection with the structure which I have adopted in practice, wherein the inverted channels are molded in sections a a with an intermediate layer of woven wire l) or otheropen metallic frame to afford strength to the structure, the plastic material of which the section is formed being preferably of hydraulic concrete. The present invention, however,

as to the insulating-sheath is equally applicable to conduits of other forms. In the formation of the conduit a trench is dug, upon the bottom of which are placed a series of planks or slabs c c, of bituminous concrete, the sides of the trench being likewise lined With similar slabs or planks c c. Upon the bottom slabs is placed a body or foundation CZ, of hydraulic concrete, a floor being formed upon the surface thereof, preferably by sprinkling fine sand and cement thereover and smoothing and polishing the same to make a smooth floor which Will facilitate the drawing of the cables through the conduits. Upon the continuous door thus formed, which may be of an indefinite Width and length and which preferably extends across the trench, are placed a number of inverted channels a a, and a second body of hydraulic concrete d/ is placed upon the inverted channels to inclose and surround the same, the concrete during the drying and setting thereof forming itself integral with the foundation of concrete along those portions of the floor exterior to the conduits, whereby the conduits are surrounded and inclosed by an integral and continuous body of concrete. IVhere a second tier of conduits is to be formed a iioor is formed upon the surface of this second body of concrete d', upon which are placed a second series of sections a a, which in turn are inclosed within a third body of concrete d2, which forms the foundation of a third tier of inverted channels inclosed by a body of concrete d3, and so on for the desired number of tiers. Upon the top of the body of concrete as thus formed slabs c c of bituminous concrete are placed and the trench is then iilledA The joints between the slabs c c are sealed by means of plastic asphalt or bituminous concrete, thus inclosing the body of hydraulic concrete in a continuous and unbroken sheath of insulating materiahwhich prevents the passage of Water or moisture and which also prevents the passage of earth-currents.

As the inverted channels ct a are placed in position end to end, Fig. 2, a bridge cis placed in position over each of the joints, the bridge carrying a strip e of cloth, paper, or the like to cover the joint and prevent the passage of concrete therethrough. This strip may be placed upon either face of the bridge; but I preferably place the strip e upon the exterior of the bridgefvvhile upon the interior is placed a narrow strip e2, which is pasted or glued to the exterior strip at intervals, whereby the exterior strip is held securely in position. The bridge, as before stated, may be made of metal or may be formed of reeds or from cloth, in any case a medial band or strip being provided adapted to iit over and seal the joint against the entrance of the plastic inclosing material.

In Fig. 5 I have illustrated a form of inverted channel or block in Which a plurality of conduit channels or grooves are provided. The blocks are made in sections and placed end to end to form a plurality of prolonged IOO IIO

conduits. The blocks or channels are placed upon the continuous door of indefinite Width and length formed on the surface of the foundation, as above described, and are then surrounded and inclosed by a body of concrete, which may form the foundation for a second inverted channel when desired. The inverted channels may thus be provided with a plurality of conduit-grooves, as shown in Fig. 5, or may be provided With a single groove, as shown in Fig. l. In each case the inverted channel is placed upon the iioor and then covered With the plastic material, which forms integral with the foundation to form an inclosing body of integrally-formed material. Bridges may be placed over the joints, as before described, the bridges being shaped to fit the particular contour of the blocks. In this figure the inclosing sheath cis shown as continuous and jointless.

Having described my invention, What I claim as new, and desire to secure by Letters Patent, is

l. The combination with a body of material having a conduit or conduits inclosed therein, of an inclosing layer or sheath of insulating material completely surrounding said body of material on the top, bottom and sides and effectively insulating the same from the earth to prevent the access of extraneous currents to the inclosed body of material, substantially as described.

2. The combination With a body of hydraulic concrete, or similar material, having a conduit or conduits inclosed therein, of an inclosing layer or sheath of bituminous concrete, or similar insulating and impervious material, completely surrounding said body of hydraulic concrete on the top, bottom and sides to prevent the passage of extraneous currents to the sheathing of the cables in the conduits, substantially as described.

3. The combination with a foundation of hydraulic concrete, or similar material, having a floor formed on the surface thereof, of a series of inverted channels thereon placed end to end, a body of hydraulic concrete, or similar material, inclosing and surrounding said inverted channels and formed integral with said foundation, and a layer or sheath of bituminous concrete or similar material inclosing and surrounding said mass of hydraulic concrete and insulating the same from the earth, substantially as described.

4. The combination with a foundation having formed upon the surface thereof a continuous floor of indefinite Width and length, of an inverted channel or block resting thereon and having a plurality of conduit-grooves therein, substantially as described.

5. The combination with a foundation of plastic material adapted to harden and set and having formed upon the surface thereof a continuous floor of indefinite width and length, of an inverted channel or block resting thereon and having a plurality of conduit-grooves therein, and a body of plastic material inclosing and surrounding said in- Verted channel or block and formed integral with said foundation, substantially as described.

6. The combination with a series of conduit-sections adapted to be placed together end to end, of a bridge formed of an open frame adapted to be placed over the joint, and a medial strip or band to prevent the passage through the joint of the material surrounding the sections, substantially as described.

7. The combination with a series of conduit-sections adapted to be placed together end to end, of a bridge formed of an open frame adapted to be placed over the joint, and a pair of strips or bands of cloth or the like, one upon the exterior and the other upon the interior face of the bridge said strips being secured together through the apertures in said bridge, substantially as described.

In witness whereof I have hereunto subscribed my name in the presence of tWo Witnesses.

CHARLES H. SEWALL.