US2388667A - Electrical device - Google Patents

Description

Nov. 13, 1945. A, G. BUGLER ET AL. 2,388,6fi'7 ELECTRICAL DEVICES Filed Oct. 12, 1943 00 O O O OQOOOQQQODOOQO lNVEN 70/25 14. 6. BUGLEE fl EH50 7% BY! Q HTTO/P/VE'Y Patented Nov. 13, 1945 Arthur G.

ELECTRICAL DEVICE Bugler, Hinsdale, and Herbert P.

Heath, Riverside, 111., assignors to Western Electric Company, Incorporated, New York, N. Y., a corporation of Newv York Application October 12, 1943, Serial No. 505,942

7 Claims.

This invention relates to electrical devices and more particularly to electrical resistance coils.

The present invention is particularly useful where a high quality extremely compact small size resistance coil, having high resistance values, is necessary, such as, for example, for use in certain types of meter resistance coils.

An object of this invention is to produce a coil of compact small size in a simple, inexpensive and rapid manner and resulting in a simple rigid structure of high quality.

In accordance with the above object, the present invention, in one embodiment thereof, comprises a, small compact resistance coil without spoolheads, the coil being wound on a cellulose acetate tube having an internal diameter only slightly larger than its terminal leads, the exterior of the coil being covered with cellulose acetate, and the coil lead wires being connected to the terminal leads, covered with pyroxylin or coalescible acetate cement, and inserted with their connected ends doubled back into the hollow tube, after which a similar cement is used to seal the aperture and bond the terminal leads to the tube, as well as to the external cover.

Other objects and advantages of this invention will more fully appear from the following detailed description, taken in connection with the accompanying drawing, in which Fig. 1 is a perspective view of a resistance coil embodying the features of this invention and Fig. 2 is a longitudinal central section, partly in elevation and somewhat diagrammatic, on an enlarged scale, of the coil of Fig. 1. I

Referring to the drawing, particularly Fig. 2, Hi indicates a cellulose acetate non-conducting core tube for supporting a resistance winding ll of wire which may be wound in a usual wellknown manner thereon, the inner end of the winding being secured to the tube by a strip [2 of cellulose acetate fabric backed Scotch tape. The winding II in the present embodiment of the invention is an enameled nickel chromium wire. A suitable length of wire [3 is left free at its inner end outside its point of attachment to the tube for later splicing to a terminal lead 44 in a manner to be described hereinafter. During the winding of the particularly illustrated type of winding ll, one turn l5 of interleaving insulation, such as cellulose acetate sheet material, is inserted between each layer of the winding. The outer end of the winding II is led across the outside of the winding to the end of the coil opposite the lead wire [3 and over a strip ll of cellulose acetate fabric backed Scotch tape, a

suitable length of wire I8 being left free outside of its point of attachment to the winding for later splicing to a terminal lead [9. A small piece 2|] of similar tape is placed over the outer lead wire l8 on the end of the coil between the core tube aperture and the outside of the winding II and is pressed smooth against the end of the coil to insure a good bond. The tape 20 completely covers the lead wire l8 between the core tube aperture and the outside of the winding, and preferably extends over the periphery of the winding II for a short distance, the extreme end length of the lead wire l8 being left free and uncovered. Around the completed winding II is wrapped one turn of interleaving insulation, such as cellulose acetate sheet material 2|.

Spliced to the inner and outer lead wires 13 and I8, are the terminal leads l4 and I9, respectively, which are of an insulated and cellulose acetate coated and stranded type. The ends of the lead wires l3 and it are preferably wrapped a suitable number of turns around the bared or skinned ends or the terminal leads l4 and I9, respectively, or may be laid thereon in parallel arrangement, and then soldered thereto, the splices being indicated at 23. Thereafter, the splices 23 are each insulated with a piece 24 of cellulose acetate fabric backed Scotch tape and then each splice is dipped into pyroxylin or coalescible acetate cement, indicated at 25, and immediately pushed into the aperture of the core tube Ill to the positions shown in Fig. 2, the coil lead wires being doubled back into the core tube aperture. The cement 25 serves to seal the ends of the core tube aperture and coalesces and bonds the terminal leads to the wall of the aperture. Preferably, the insulation on the terminal leads I4 and i9 should extend a minimum of one-eighth inch inside the core tube aperture. It is to be understood that the length of the free ends of the lead wires l3 and H3 is such that the positioning of the terminal leads M and ill, as above described, will be permitted and also provides for suflicient slack in the lead wires l3 and I8, which is tucked into the core tube aperture. The core tube aperture has a diameter only slightly larger than that of the terminal leads [4 and i9, which, in the completed core, in addition to compactness, provides a very r id anchorage for the terminal leads.

After baking the coil at a suitable temperature and period of time in an oven and its removal therefrom and while the coil is still hot, it is brushed with or' dipped in an insulating varnish, such as Bakelite, care being taken to prevent the varnish from covering the terminal leads M and 9 for more than approximately one-quarter inch from the ends of the coil. Thereafter, the coil is again baked at,a suitable temperature and period of time and then it is covered with an inner cover comprising at least two turns of cellulose acetate sheet insulating material 26, the inner and outer ends thereof being secured with cellulose acetate cement. An outer cover 21 of cellulose acetate impregnated sheet muslin is then wrapped around the coil and both ends thereof are secured with a suitable cellulose acetate cement 28.

From the above description, it will be apparent that a compact small size headless electrical resistance coil is provided having high resistance values and of a simple and rigid high quality construction which may be assembled in an inexpensive and rapid manner and one wherein the terminal leads spliced to the lead wires are firmly anchored from pulling away from the coil and the entire coil sealed with a coalescible material.

Although the features of this invention have been described with reference to a particular type of electrical coil, such as an inductively wound resistance coil, it should be understood that modifications can be made and it is capable of other applications, including non-inductively wound resistance coils.

What is claimed is:

l. A coil comprising an inner tube of coalescible material, a plurality of convolutions of wire wound on said tube, a lead wire having a diameter slightly less than the bore of said tube, a splice connecting said lead wire to said winding, and a covering of coalescible material over said splice, said splice being inserted in the bore of said tube and coalesced thereto.

2. An electrical coil comprising an inner tube of coalescible material, a plurality of convolutions of insulated wire wound on said tube, an insulated lead wire having a coating of coalescible material and an external diameter slightly less than the bore of said tube, a splice connecting an uninsulated portion of said lead wire to an uninsulated portion of said winding, and a covering of coalescible material over said splice, said splice being inserted in the bore of said tube and coalesced thereto. I

3. An electrical coil comprising an inner tube of coalescible material, a plurality of convolutions of insulated wire wound on said tube, an insulated lead wire having a coating of coalescible material 4 and an external diameter slightly less than the bore of said tube, a splice connecting an uninsulated portion of said lead wire to an uninsulated end of a portion of said winding extending from an end of the coil, a covering of coalescible ma-. terial around said splice, a covering of coalescible cement over said covered splice, said splice'being inserted in the bore of said tube and coalesced thereto, and a covering of coalescible cement on I the end of the coil surrounding the coated lead wire to seal and further anchor the splice in the bore of the tube.

4. An electrical coil comprising an inner tube of coalescible material, a plurality of convolutions of insulated wire wound on said tube, an insulated lead wire having a coating of coalescible mat'erial and an external diameter slightly less than the bore of said tube, a splice connecting an uninsulated end of said lead wire to an uninsulated end portion of said winding extending outwardly from an end of the coil, a covering of coalescible cement over said splice, said splice being inserted in the bore of said tube and coalesced thereto, an end portion of the wire being doubled back into the bore of the tube and lying against the end of the coil, a cover of cellulose acetate material around the coil, and a covering of coalescible cement on the end of the coil for sealing and bonding the coated lead wire, the outer portion of the winding wire and said cover together and to the coil end.

5. An electrical coil comprising an inner tube of coalescible material, a plurality of convolutions of wire wound on said tube, a lead wire having a diameter slightly less than the bore of said tube, a splice connecting said lead wire to an outer convolution of said winding, the winding wire being extended across the periphery of the winding to an end of the coil, extending therefrom and spliced at its end to said lead wire, a covering of coalescible cement over said splice, said splice being inserted in the bore of said tube and coalesced thereto, and an end portion of the wire bein doubled back into the bore of the tube and lying against the end of the coil.

6. An electrical coil comprising an inner tube of coalescible material, a plurality of convolutions of wire wound on said tube, a lead wire having a diameter slightly less than the bore of said tube, a splice connecting said lead wire to an outer convolution of said winding, the winding wire beiig extended across the periphery of the winding to an end of the coil, extending therefrom and spliced at its end to said lead wire, coalescible material under said wire extending across the periphery of the coil, a covering of coalescible cement over said splice, said splice being inserted in the bore of said tube and coalesced hereto, an end portion of the wire being doubled back intothe bore of the tube and lying against the end of the coil, coalescible material over said latter portion of the wire extending from the bore of the tube to and along the periphery of the coil for a distance, and a covering of coalescible cement on the end of the coil for sealing and bonding the lead wire, coalescible material, and said latter portion of the wire to the coil end.

7. An electrical coil comprising an inner tube of coalescible material, a plurality of convolutions of insulated wire wound on said tube, insulated lead wires having a coating of coalescible material and an external diameter slightly less than the bore of said tube for connection to inner and outer ends of said winding, splices connecting uninsulated portions of said lead wires to uninsulated portions of said winding, coverings of coalescible material over said splices, said splices being inserted in opposite ends of the bore of said tube and coalesced thereto, end portions of said winding ends being doubled back into the bore of the tube and lying against the ends of the coil, and coverings of coalescible cement on the ends of the coil surrounding the coated lead wires to seal and further anchor the splices in the bore of the tube.

ARTHUR G. BUGLERL. HERBERT P. HEATH.

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