US2666908A - Lightning arrester - Google Patents

Description

c. w. KLOSTERMANN 2,666,908

LIGHTNING ARRESTER Jan, 19, 1954 2 Sheets-Sheet 1 Filed May 12, 195Q Jan. 19, 1954 c. w. KLOSTERMANN LIGHTNING ARRESTER Filed May 12, 1950 2 Sheets-Sheet 2 a? 23 24 AL I ii' 27 7 7 kiiiulllw,

Patented Jan. 19, 1954 UNITED STATES PATENT OFFICE LIGHTNING ARRESTER Curt W. Klostermann, Chicago, Ill., assignor to American Phenolic Corporation, Chicago, 111., a corporation of Illinois Application May 12, 1950, Serial No. 161,647

3 Claims. 1

The present invention relates to lightning arresters, and will be described in connection with a preferred embodiment of the invention, specifically designed for use in connection with frequency modulation radio receivers, television sets, or any similar equipment employing a leadin such as a 300 ohm, twin-lead transmission line.

The lightning arrester art is very old, and in the many years which have passed since the telephone and radio arts brought about a need for this equipment, there have been many and various forms of arresters devised. These have been utilized with varying degrees of success, but so far as known to the applicant the arresters of the prior art have been, for the most part at least, of quite complex nature mechanically as Well as electrically, with the result that they have ordinarily been very bulky, and in most instances quite expensive. Notwithstanding the above, it is believed undeniable that most of the arresters disclosed in prior art teachings have been quite inadequate from an electrical standpoint.

The reasons for this are many. For one thing, in prior types of arresters, the values of the resistors, spark gaps or other electrical means employed have not remained constant at their intended values. On the contrary, they have varied considerably with changes in humidity, temperature, barometric pressure, and with corrosion arising from long exposure, so that (even if they are fairly efficient when new) they soon lose their efficiency as a result of continued weatherns.

It is, therefore, a primary aim of the present invention to provide a lightning arrester of novel and improved electrical design, so arranged that it may be manufactured as an unusually small and compact unit physically, but nevertheless possessed with electrical properties superior to those ordinarily incorporated into an arrester adapted for use in connection with the ordinary home radio receiving set. This object is accomplished, according to the present teaching, by a unit wherein the principal operating parts of the arrester circuit, that is, the antenna conductors, ground conductor and the spark gaps associated therewith, are all completely embedded in a solid block of dielectric material in such a manner that the parts are held in precisely spaced relationship, even under the most severe cases of impact or physical strain on the unit. As a matterof fact, with an arrester according to the present teachings, it has been found impossible to cause significant variations in the spacing of the spark 2 gaps employed by any physical violence falling short of complete destruction of the unit.

This aim is accomplished in the present invention by the unique structure and method of manufacture here disclosed. In the present invention, the three essential conducting parts of the unit are first formed as a single unitary metal stamping. This stamping is then placed in a mold and a solid block of insulating material molded around it, with the insulating material and metal in surface contact throughout, so that even microscopic relative motion or shifting between the two metal parts and the body is impossible. The spark gaps are then formed. by cutting saw slots through the metal insert at appropriate places. When this is done, the metallic inserts of the unit become electrically separate, but are none the less positively held in their predetermined physical positions with respect to each other. It follows that the spark gaps, which are formed by the precision saws with which the units are severed, will necessarily be the precise width found to give the best results. The entire unit is then sealed by application of a plastic sealing compound. The result is an arrester in which the values of the spark gaps, resistors, etc., which are employed, will show no tendency to vary, even as a result of long use, or because of exposure to repeated temperature changes, humidity or adverse weather.

The preferred embodiment of the invention is illustrated in the drawings hereof, wherein:

Figure 1 is a perspective view of a present commercial embodiment of the present teaching;

Figure 2 is a perspective view of the metallic insert, or conductor employed in this form of the arrester;

Figure 3 is a plan view of the arrester, showing the manner in which it is attached to the lead in line of a radio or television set;

Figure 4 is a schematic circuit diagram of the arrester as applied to a typical radio receiver;

Figure 5 is a bottom plan view of the arrester;

Figure 6' is a detail sectional view taken substantially on the plane of the line 66 of Figure 5;

Figure 7 is a detail sectional view taken substantially on the plane of the line l! of Figure 5;

Figure 8 is a detail perspective view of a transmission line contact clip as here employed; and

Figure 9- is a detail sectional view which may be considered as taken on the plane of the line 9--9 of Figure 7.

As illustrated, the arrester includes a unitary,

rectangular body portion It, which is molded as a single integral piece of dielectric plastic ma terial. The molding may include a pair of holes H for mounting screws and, as shown, is provlded with a transverse channel l2 across which the lead-in wires of the installation may be extended. A typical installation is illustrated in Figure 3, wherein the lead-in comprises a flat, twin-lead transmission line 13 having individual conductors Hi and l spaced apart from each other and embedded in the insulation along the opposite edges of the line.

The electrical circuit employed by the arrester is best illustrated in Figure l, wherein it will .be seen that the individual conductors i4 and t5 of the transmission line it are each grounded through a spark gap and a resistor in parallel. That is, the conductor M is grounded through the spark gap i6 and the resistor l1, while the conductor i5 is grounded through the spark gap t8 and resistor it. To this end, the circuit includes a terminal clip 2i to establish electrical conduct with the conductor i4, and a similar ter minal 22 for the conductor 5. The arrester has a ground terminal 23 common to all the resistors and spark gaps as shown.

The circuit just described is, or" course, fairly conventional in. the lightning arrester art, but its efiiciency depends on the accurate maintenance of the spacing of the spark gaps, the maintenance of proper values in the resistors, the maintenance of adequate insulation throughout, as well as the establishment or" low resistance contacts at all unions, so that unwanted resistances are not imposed into the circuit. This is ideally accomplished according to the present teachings, by forming the internal conducting parts of the device as a single integral stamping of several branches, which is first embedded in the insulating material by having material molded around it, and is then separated into its three components by sawing shallow slots into the insulating block to sever the metal at the points desired.

The metal insert is shown in Figure 2, wherein it will be seen that the stamping includes a pair of upwardly extending antenna terminals 2| and 22 adapted to project upwardly through the top of the insulating body and be bent over into the positions shown in Figure l. The unit also includes a ground terminal 23 which is common to both of the antenna terminals 2i and 22, and is arranged to extend outwardly from the side of the unit as shown. The ground terminal 23 carries a threaded contact screw as outside of the insulated body to facilitate connection with the grounded wire. The terminal 23 is formed integrally with one branch 25 of the insert, which extends inwardly through the molded insulation of the body I 0, however, to a point where it joins the branches 25 and 21.. These extend outwardly from the branch 25 and have oppositely disposed, laterally extending offset portions 28 and 29 extending to the terminals 2| and 22, respectively. The offset portions 28 and 29 have upwardly crimped ribs 3| and 32, so that when the upper end portions of the terminals 2| and 22 are bent over as shown in Figure l, the slots 33 and 34 in these terminals will overlie the center of the upwardly crimped portions 3| and 32. Thus, the parts are so positioned that holes for the terminal clamping screws 35 and 36 may be drilled downwardly through the insulating material and threaded through the angularly shaped sections of metal 3| and 32. Thus, While the screws are threaded into the insulation, they 4 nevertheless are provided with a metallic reinforcement as a safeguard against stripping of the threads of the insulating material.

The central branch 25 of the insert (Figure 2) forms the common ground conductor of the unit and. is accordingly provided with a T-shaped extension M, the opposite ends or" which carry downwardly extending resistor terminals 42 and 43. These are spaced away from their coacting terminals 44 and 45, which are integral downwardly extending tabs on the branch sections 26 and 2.1 of the stamping. When the stamping is molded in the body portion, it is so held that the terminals .2 i, 22' and 23 extend from the body at the top and side thereof, while the terminals 42, 43', .M and 45 extend into a cavity 47 on the back side of the unit (Figure 5). The terminals 42, 43, 44 and 45 are each provided with a diagonal slot 416., so that the resistors I? and Ill may be inserted as shown and retained in position by closing the slots against the terminal wires 4-8 in the manner shown in Figure 9.

It will be apparent that when the stamping shown in Figure 2 is thus molded into position, all of its parts are firmly bonded into the dielectric material, so that they are entirely surrounded by the insulating material and held in absolutely fixedposition with respect to it. Thus, when the .molding has been completed, the spark gaps l6 and I8 may conveniently be formed by sawing narrow slots 5! and 52 through the branches 2G and 21 on each side of the common branch 25. Thus, the portions 26 and 21 are electrically separated from the common ground 23 by an air gap the width of these slots.

It has been previously stated that it is of considerable importance to prevent short circuiting of these gaps and to maintain them at the preferred dimension (about .008 or .010 of an inch). To this end, it is contemplated that, after assembly, the cavity 41 will be filled with a plastic insulating compound. In applying this compound it is important, however, that it does not flow between the poles of spark gaps, and to prevent this, a small piece of pressure sensitive insulating tape 54 is positioned in the bottom of the cavity 41, as shown in Figure '7. The cavity is then filled with insulating compound, and the unit is in condition for operation.

To attach the arrester to the lead-in line, it has been found convenient to provide toothed clips 56 as shown in Figure 8, so shaped that they may be inserted under the end portions of the terminals 2i and 22, so that when these terminals are tightened down by the screws 36 and 35, the teeth 51 of the clips will cut through the insulating material surrounding the individual conductors of the transmission line and establish an intimate electrical connection between these conductors and the corresponding terminals of the arrester.

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

1. In an electrical apparatus, in combination, a terminal body consisting of a solid unitary block of dielectric plastic material, with a relatively wide shallow channel extending across one exterior surface of the block and adapted to receive a length of twin-lead radio frequency transmission line, together with a pair of metallic terminal inserts disposed on opposite sides of the channel from; each other and of substantially identical shape but oppositely oriented with re 511 171 0 each other; each of said inserts including an upright portion imbedded in the block at a point spaced from the channel therein, with a lower branch extending inwardly toward and under said channel; each of said terminal inserts also including an exposed metallic contact strip above the surface of the block and extending inwardly from the upright portion of the insert to a point overlapping one edge of said channel; and a clamping screw positioned between said channel and the upright portion of said insert; said clamping screw engaging said exposed metallic contact strip and extending through an aperture in the dielectric and screw threaded into the lower branch of the insert, whereby the contact strips of the inserts may be clamped against the opposite edges of a. transmission line disposed in the channel of the dielectric block.

2. In an electrical apparatus, in combination, a solid unitary body of dielectric plastic material and an electrical conductor afiixed thereon; said conductor including an upright metallic strip embedded in the dielectric plastic material and extending through an external surface thereof, with a lower branch of said metallic strip integral with the upright portion thereof and extending laterally from said upright portion at a point substantially spaced from said exterior surface of the dielectric body; said insert also having a terminal portion integral with the upright portion thereof and outside of the dielectric plastic body, said terminal portion comprising an exposed metallic strip extending laterally from the upright portion of the conductor on the same side thereof as the lower branch, and doubled back across the exterior surface of the dielectric body in clamping relationship therewith; with a clamping screw parallel with the upright metal strip and spaced apart therefrom; said clamping screw passing through an aperture in said terminal portion and extending into an aperture in the dielectric body thereunder; said screw being threaded into the lower branch of said conductor whereby the exposed terminal portion of the conductor may be forced toward the exterior surface of the dielectric body to clamp an electrical conductor therebetween; with teeth carried by said terminal strip having sharp edges disposed toward the surface of the dielectric body to pierce the insulation of the conductor.

3. In an electrical apparatus, in combination, a solid unitary body of dielectric plastic material and an electrical conductor affixed thereon; said conductor including an upright metallic strip embedded in the dielectric plastic material and extending through an external surface thereof, with a lower branch of said metallic strip integral with the upright portion thereof and extending laterally from said upright portion at a point substantially spaced from said exterior surface of the dielectric body; said insert also having a terminal portion integral with the upright portion thereof and outside of the dielectric plastic body, said terminal portion comprising an exposed metallic strip extending laterally from the upright portion of the conductor on the same side thereof as the lower branch, and doubled back across the exterior surface of the dielectric body in clamping relationship therewith, with a clamping screw parallel ,with the upright metal strip and spaced apart therefrom; said clamping screw passing through an aperture in said terminal portion and extending into an aperture in the dielectric body thereunder; said screw being threaded into the lower branch of said conductor whereby the exposed terminal portion of the conductor may be forced toward the exterior surface of the dielectric body to clamp an electrical conductor therebetween.

CURT W. KLOSTERMANN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 857,849 Titus June 25, 1907 1,171,166 Brach Feb. 8, 1916 1,311,916 Reid Aug. 5, 1919 1,794,831 Caruso Mar. 3, 1931 1,873,450 McFarlin Aug. 23, 1932 1,885,477 Potter Nov. 1, 1932 2,196,147 Dunn Apr. 2, 1940 2,261,986 Frank Nov. 11, 1941 2,440,748 Johnson May 4, 1948 FOREIGN PATENTS Number Country Date 384,669 Germany Nov. 5, 1923

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