US2440748A

US2440748A - Lightning arrestor for television transmission lines, etc.

Info

Publication number: US2440748A
Application number: US745205A
Authority: US
Inventors: Ernest O Johnson
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1947-05-01
Filing date: 1947-05-01
Publication date: 1948-05-04
Anticipated expiration: 1965-05-04

Description

May 4, 1948.

S ETC I E. O. JOHNSON LIGHTNING ARRESTOR FOR TELEVISION TRANSMISSION LINE I Fileql lay 1.1947

. Zhmcmor iklvisr 0 .b/m so/v attorney Patented May 4, 1948 LIGHTNING ARRESTOR FOR TELEVISION TRANSMISSION LINES, ETC.

Ernest 0. Johnson,

Haddoniield, N. J minor to Radio Corporation of America, a corporation oi Delaware Application May 1, 1947, Serial No. 745,205

Claims. I '1 This invention relates to improvements in electrical connectors for tapping a plural wire signaltransmission line and will be described as embodied in a lightning arrestor unit for a television receiver installation. a

As is well known, dipole and other antennas employed in television receiver installations may acquire very high static charges from the ambient atmosphere. even in the absence of lightning. Hence, safety requirements dictate the provision of a tap at a convenient point in the transmission line between the antenna and the receiver, for rounding such charges. The usual lightning arrestor tap comprises an elongated porcelain cylinder containing a resistor and a row of binding posts to which the wires of the transmission line are separately connected. The principal objection to such taps resides not alone in the mechanical difliculties incident to mounting the porcelain cylinder and in cutting, spreading and connecting the wires to the binding posts, but also in the fact that these several operations give rise to a bump (i. e., an abrupt change in impedance) or other electrical discontinuity in the line.

Accordingly, the principal object of the present invention is to provide a lightning arrest-or which, when connected to a television or similar (high frequency) transmission line, introduces substantially no electrical discontinuity in the line and one which, in its attachment dispenses with the cable-slitting, splicing and soldering operations required in the installation of comparable prior art units.

Another and important object of the invention is to provide a. lightnin arrestor which shall meet all of the standards of safety required of such devices and one nevertheless characterized by its low price and its low cost of installation.

Another and related object of the present iu-- vention is to provide a lightning arrestor unit which, by reason of the simplicity and economy of its parts, lends itself readily to mass produotion methods.

In the drawing:

Fig. l is an exploded view of a lightning arrestor unit constructed in accordance with the principle of the invention;

Fig. 2 is atop plan view and Fig. 3 is a sectional view, taken on the line IH-ZIE of Fig. 2 showing the device of Fig. 1 assembled and installed upon a convenient support for use in grounding a conventional two wire transmission line.

In the drawing wherein like reference char acters designate the same parts in all figures, I designates generally the body and 2 the cap of a plug-like fixture which is adapted to be attached by means of a dependent metal strap 3 and a bolt 4 to a water pipe 5 or other convenient ground." In one practical embodiment of the invention both the body I and the cap 2 of the fixture were injection-molded of a thermo-setting synthetic resin (in this case'Bakelite) and were of the illustrated substantially cylindrical shape; the dimensions of the cylinder being approximately 2 long. 1 in diameter.

As shown more clearly in Fig. 1, the upper or cap-end of the body I is provided with external threads 6 and this threaded portion is divided by a transverse slot 1 of a width sufilcient to accommodate a tape-like electrical transmission line 8 containing two parallel wires 9 and (see Fig. 2). This slot 1 communicates with a. central cavity H which has a preferably concave bottom surface 12 and a rectangular opening it in said surface for accommodating the metal attaching strap 3. The strap 3 is not molded into the insulating body i but is simply seated therein by folding the strap and passing the adjacent ends thereof through the opening it (from the interior of the cavity) and spreading an intermediate section to (Figs. 1 and 3) of the strap over the concave bottom it of the cavity The spread or collapsed strap section M on the concave inner bottom surface of the cavity provides a seat for a spring which, in the instant case, shown in form of a U-shape or trough shape member 56- which may simply be dropped into the cavity with its rounded bottom resting upon the spreacL.

out portion to or the strap. The upwardly es:- tending arms of the spring it are preferably bent outwardly, as indicated at Ma, Fig. 3, to form a pedestal for a ol'wc-like insert 55 constituted of a resistive material. such as carbon. This insert is designed to provide a leakage path, from each of the conductors 9 ill, to ground, of approximately assoc ohms.

The cavity it has two oppositely located shoulders it moulded therein, at a level slightly below that of the base or bottom. oi the transverse slot i and these shoulders serve as a support for a rectangular insert ll constituted of insulating material. This insert El is provided with a number. (in-this case, four) of spaced-apart metal pins l 8, lilo, etc., which extend upwardly through said insulating material and terminate at a level slightly above that of the base of the slot 1 in the path of the tape-like transmission line 8. The points of these pins it are designed to pierce assume the insulating tape 9 within which the transmismission wires 9 and iii are enclosed and are mounted on the insert it in register with the said wires so that they each form a conductive connection between the wires and the resistive insert i5, when the tape is pressed down onthe pins.

The force required to cause the pins it to penetrate the tape 3 and to bring them into conductive engagement with the separate wires e and it is applied by screwing the cap 2 down on the body i of the unit. To this end, the cap is provided with internal threads 63, which engage the complementary external threads 3, and with a centrally -located protuberance 29 whose leadin end bears against the tape 3 when the tape is within the slot 71 and the cap is screwed down on the body of the unit.

It will be observed upon inspection of Fig. 3

that the biasing force applied to the underside 1 of the resistive insert i5 by the spring it causes the said insert to bear against the heads (or lower terminals) of the pins i8 and thus ensures excellent electrical continuity between the transmission wires 9 and it, the pins i, the resistor IS, the spring i4 and the grounding strap 3.'

Prior to use, i. e. when the transmission line 8 is not in the slot 1, the forceoi the spring It may lift the insert i'l upon which the pins it are mounted, upwardly against the central protuberance on. the cap. Accordingly, the leading end of this protuberance 2B is provided with a circular recess 26a (Fig. 3) within which the points of the pins are accommodated so that they will not be bent out of shape by contact with said surface.

The lower surface of the receptacle I is preferably concave in outline as indicated at 2! so that the unit may be mounted directly on the water pipe 5 or other fixture to which the grounding strap is affixed. The said metal strap 3 is provided with a number of spaced-apart mounting holes 22 so that it may be aflixed by its bolt d, to a pipe of substantially any standard size.

Since the tap of the present invention dispenses with the necessity of slitting the transmission line 3 and spreading its wires 9 and 3, its installation can introduce little or no change in impedance or "electrical bump in the high frequency transmission system. It will likewise be apparent that the simple, inexpensive and trouble-free construction of the said tap permits it to be installed and used with entire safety in any conventional home-television installation.

What is claimed is:

1. A tap for grounding an insulated transmission line, said tap comprising an insulating receptacle having an aperture therein through which said transmission line is adapted to pass and containing a cavity which communicates with said aperture, a plurality of pins mounted in said cavity with the points of said pins projecting into said aperture in register with said transmission line whereby said points are adapted to penetrate the insulation on said line, a resistive element in said cavity adjacent to said pins, conductive means for biasing said resistive element into engagement with said pins, and a conductor connected to said biasing means within said cavity and extending to the exterior 01, said receptacle.

2. The invention as set forth in claim 1 and wherein said conductor comprises a metal strap both ends of which extend to the exterior of said receptacle.

3. A tap for grounding a plural wire transmission line comprising an insulating body having an opening therein through which said transmission line is adapted to extend, a plurality of pins individual to respective ones of said wires pro- Jecting into said opening in a direction normal to the direction of extension ofsaid transmission line, means for pressing said wires into intimate contact with said pins, a resistive element within said insulating body in contact with said pins, and a conductor electrically connected to said resistive element and extending to the exterior of said insulating body for grounding said wires through said pins and resistive element.

4. A tap for grounding a tape-like parallel wire transmission line, said tap comprising an insulating structure having a channel in a surface thereof within which said tape is adapted to be laid and containing a cavity beneath said channel, a plurality of pins projecting from said cavity into said channel with the points of said pins positioned to engage separate ones of said parallel wires when said tape is pressed down thereon, an insert constituted of resistive material in said cavity adjacent to the inner ends of said plus, a spring in said cavity for biasing said resistive insert into engagement with said pins and a conductive connection including said spring extending to the exterior of said cavity for grounding said parallel wires through said resistive insert.

5. A tap for grounding a plural wire transmission line comprising, an insulating body con-' taining a cavity and having a transverse slot ad- Jacent to one end of said cavity for receiving said transmission line and an axially extending aperture in its opposite end through which a grounding strap extends, a spring within said cavity in contact with said strap, a disc of resistive material on said spring, an insulating support mounted within said cavity, a plurality of pins extendin through said support into engagement with said resistive material and with the points of said pins in register with the plural wires in said transmission line, and an adjustable cap on said insulating body for exerting a clamping force on said tape against the biasing force of said spring whereby said plural wires are brought into electrical engagement with said grounding strap through said pins, said resistive element and said spring.

ERNEST 0. JOHNSON.

REFERENUES CE'EIED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,219,497 Smith Mar. 20, 1917 1,423,742 Silverman July 25, 1922 1,5523% Everett Sept. 8, 1925 1,627,631 Chizlett May 10, 1927 2,012,342 Everett Aug. 27, 1935 2,419,683 Henschke Apr. 29, 19%?