US2677078A

US2677078A - Electrical apparatus

Info

Publication number: US2677078A
Application number: US776904A
Authority: US
Inventors: Lewis I Knudson
Original assignee: Bendix Aviation Corp
Current assignee: Bendix Aviation Corp
Priority date: 1947-09-30
Filing date: 1947-09-30
Publication date: 1954-04-27
Anticipated expiration: 1971-04-27

Description

April 27, 1954 KNuDsoN ELECTRICAL APPARATUS Filed Sept. 30, 1947 INVENTOR.

(2411, a. Baum/z,

ATTORNEY Patented Apr. 27, 19,54

ELECTRICAL APPARATUS Lewis I. Knudson, Sidney, N. Y., assignor to Bendix Aviation Corporation, New York, N. Y., a corporation of Delaware Application September 30, 1947, Serial No. 776,904

3y Claims. (Cl. 317-206) This invention relates to .electrical apparatus and more particularly to an induction device adapted for use by Way of example in apparatus for investigating the operation of the ignition systern of an internal combustion engine or the like.

One of the objects of the present invention is to provide a novel apparatus for magnetically, i. e., inductively picking up electrical energy from an electrical conductor which means are so constructed as to substantially eliminate the effects of capacity components.

f Another object of the invention is to provide novel apparatus of a simpliiied nature which may be readily associated with an electrical conductor and adapted to respond to changes in the flow of energy through the conductor.

A further'object is to provide a novelly constructed radio shielded unit for picking up energy by induction -from a single electrical conductor and which may be readily associated with a radio shielded conductor.

Still another object is to provide a novel transformer device which may be readily and quickly inserted in the input lead for an internal electric spark plug or other electrical conductor for generating signals in a circuit which is wholly free of direct electrical connection to said conductor, said signals being in response to voltage variations in said conductor.

The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read in conjunction with the accompanying drawing. It is to be expressly understood, ho-wever, that the drawings are for the purpose of illustration only and are not intended as a dennition of the limits of the invention, reference for this latter purpose being had primarily to the appended claims.

In the drawings wherein like reference characters refer to like parts throughout the several views,

Fig. 1 is a side elevational view partly in section and with parts broken away showing one form of device embodying the invention.

Fig. 2 is a detail elevational view with parts broken away and partly in section showing the coil and core structure of the device shown in Fig. 1` as viewed from the right in said figure; and

f l'igy3 is a section taken substantially on lin 3 3 of Fig. 2.

Thesingle embodiment of the invention illustrated in the drawings, by way of example, is designed for use in conjunction with a radio shielded ignition system of an internal combustion engine but it'A is to be' understood that the invention is not limited to use in such environnient.; The-device as shown comprises Va metallic casing 5 which serves as a shield for intercepting electrical and magnetic emanations which would interfere with radio reception and may be fabricated in any suitable manner, and said casing is preferably provided with oppositely disposed outlets or openings 6 and l for the the passage of an electric conductor 8 which is preferably insulated as shown. In order that conductor 8 may be conveniently and quickly inserted in a spark plug circuit, for example, of an ignition system, outlet E is adapted for connec tion with a. short length of flexible metallic tubing 9 through which cable 8 may extend and terminate in a plug connector (not shown) of the type commonly used for making connection to a shielded spark plug.v Outlet 'l is adapted to threadedly receive a barrel or socket (not shown) of the type found on shielded spark plugs in common use and adapted to receive the terminal of l a spark plug lead for connection with the other end of cable 8.

A novelly constructed induction coil unit is mounted within casing 5 in operative relation to cable 8 in such a manner that the coil thereof will be energized in response to variations in the flow of current in the cable and so that the current picked up by the coil will be-substantially free of capacity components. The illustrated coil unit comprises a two-part laminated core ill-l0, the two U-shaped parts of which are secured together in any suitable manner such as by: means of a metallic strap I l and a clamp l2 which joins the ends of the strap to form a continuous ring shaped metal core of metallic i'lux conducting material. The conductor 8 passesthrough the central opening in core I0 so that the latter will serve as a path for the lines of magnetic ilux created around the conductor by the flow of current there-y through Core i0, I0 ma-y be fabricated by first wrapping a continuous metal strip around a mandrel having the desired size and thereafter cutting the same into two parts to permit mounting of the coil to be next described. It will be understood. of course, that the core may be fabricated in other known ways and, if desired, thev laminations Imay-.extend at right angles to those illustrated and consister" flat rectangu* lar stampings, split for mountingin a pre-wound coil. f i -1 A coil i4 has a winding l5-which surrounds a section of one of the U-shaped parts of core l0, the same being tightly wound on an insulating sleeve i6 and between two insulating end guides I'l-Il. Said sleeve and guides may be cemented to the core structure or otherwise suitably secured in place thereon. In a suitable embodiment for use in the spark plug circuit of a large aircraft engine, coil winding I5 was constituted by about 1400 turns of No. 38 or No. 40 copper 3 wire. As shown, the ends of winding I5 are connected by means of leads I8 and I9 to a pair of terminals of a plug andsocket connector, only the plug part of which is illustrated as being secured in an opening in the wall of casing 5. 1f desired, the low potential end of the coil winding may be connected to ground through casing 5. Core i0 is also yconnected to ground by a lead 2! which is soldered or otherwise suitably secured to the casing at 22.

1n order to substantially eliminate the capacity components in the currents induced in coil I4, a discontinuous metallic sleeve 23,v preferably a steel sleeve, surrounds the winding I5. Said sleeve is split at 24 and is connected to ground by a lead 25 which may be an extension of lead 2l. A protective covering of tape may also be wound around the coil and sleeve structure to reinforce the saine structurally. Shielding sleeve 23 is eiective to pick up the electro-static capacity radiations emanating from conductor 3. and carries the same to ground so that the current induced in winding l5 is substantially free of any capacity components.

The coil unit and cable may be properly positioned and resiliently supported in casing 5 by a yieldable insulating compound ,29. The latter is preferably injected into casing 5 under pressure through a small opening while the casing is substantially evacuated so that the entire space i within the same will be filled with the compound. The latter may be injected in liquid form and permitted to. set te solid form either with or without the application of heat. There. are a number of known compounds suitable for this purpose, such as for example, polymerized Cashew-nut shell oil. The openings 5 and l may be closed with suitable covers (not shown) during the lling step and said covers may support a greased rod of suitable size in the place oi cable 8, sothat when removed a suitable passage will be providedl for ther cable.

Inl operation, whenever there is a change in the amount of current flowing through conductor 8, therel will be a corresponding variation in the magnetic fluxv lines surrounding the conductor and hence passing through coil M. If the variationY sufficiently rapid and of appreci able magnitude, a vflow of current will be induced in winding i5y when the sameis cutI by the magnetic flux lines. When conductor 8 forms a part of a spark plug: lead, for example, the circuit including coil I4.v is shocked in toiexcitation whenever there is av ilow'bf energytlirough the conductor causingqihe, spark plug to nre. The signal thus. picked 'upf coil M may: be. usefully employed apparatus' for investigating the oplv eration of the Sentire, ignition vsystem of the engine.

The electrostatic. shield may, if desired, take ar difierent form from the sleeve. 23 around the coil.. Forv example, the, shield maybe in the form ofl a metal tube. 21l as illustrated by' dotted lines in Fig. 11. The enlarged `end orsaid tube` is soldered or otherwise suitably secured to the nipple 28 of opening.` 6 and extendsy through the central openingr of core l0 to: a position relatively close to the` nipple 29 around opening l. The free end of tubel 2li will, of course, be additionally supported and insulated from the, casing by the filling compound 29. The shield may also consist of two telescoping tubes, each secured to one of the. nipples 28J or 29 in the same manner thatI tube 2,1 is secured.A At the telescoping ends,y the tubes may"l have a sufficient diierence in diameters to permit the compound 26 to insulate them from one another.

There is thus provided a novel and eflicient energy pick-up device which may be suitably designed for ready and quick installation in an electric lead for detecting variations in the flow of current through the lead. Novel means are also provided in the inductive pick-up unit comprehended for eliminating capacity components from the induced energy. The unit is of relatively simple and compact construction and yet sturdy and reliable.

Although only one embodiment of the invention has been illustrated and described in the accompanying drawings and the foregoing specification, it is to be expressly understood that the invention is not. so limited.' It is not necessary, for example, to. provide a complete shielding casing in all installations. Various other changes: may be made particularly in the design and` ar` rangement of the parts illustrated withouty departing from the. spirit and scope of the invention as it will now be understood by those skilled, in the art. For a definition of the limits, of the invention, reference is had primarily to. the appended claims.

What is claimed is:

1. Apparatus of the class described comprising a metallic casing having cable outlets in opposite sides thereof, an electrical conductor supported in the casing and extending between said outlets, a laminated core of magnetic ilux conducting metal completely surrounding a section of said conductor in said casing, a coil closely surrounding only a portion of said core and insulated therefrom, a double-ended longitudinally-split metallic sleeve substantiallysurrou-ndn ing the periphery of said coil, means electrically connecting said core and sleeve to the casing, an electrical outlet in the wall of said casing having f at least one contact electrically connected to the high potential end of said coil, and yieldable electrical insulation completely filling the remaining space in said casing and supporting said -f coil and core therein.

2. An induction coil unit as defined in claim 1 wherein said core. comprises` two cooperating U-shaped parts.

3. An induction coil` unit as defined in claim 1 wherein said core. comprises two cooperating U-shaped parts, said parts being secured together by means including a metallic strap.

Beiercps Cited in the le of this patent UNITED STATES PATENTS Number Namey Date 783,533 Moody Feb. 28, 1905 1,629,132 Thordarson May 17, 1927 1,702,159 Grunow Feb. l2,` 1929 1,709,826 Austin Apr. 23, 19.29 1,830,541 Harris Nov. 3, 1931 2,081,979 Bentley June 1 1937 2,136,609 Butterfield et al. Nov. 15,l 1938 2,170,048V punning et al. Aug. 22, 19,39 2,183,355 Mauerer Dec. 12, 1939` 2,187,950 15111152.11 et, al, Jan. 23, 1940 2,214,915 Wehrlin Sept. 17, 1940 2,249,057 Stahl July 15, 1941 2,327,774 Dickinson Aug. 24, 1943 2,408,211 Hodnette Sept. 24,` 194.6 2,476,121 Smith, Jr. July 12,1949

FOREIGN PATENTS Number Country DateL 96,764 Austria Nov. 14, 1,938