US2415945A - Housing for lighting arresters - Google Patents

Description

Feb. 18, 1947. R G|L5QN HOUSING FOR LIQHTNING ARRESTERS Filed July 10, 1943 v IN VENT OR Robert/V. Gz'lmon 6L7 H16 ATTORNEY Patented Feb. 18, 1947 ICE HOUSING FOR LIGHTNING ARRESTERS Robert M. Gilson,'Pittsburgh,. 1%., assignorto The Union Switch & Signal Company, Swissvale, Pa., acorporation of Pennsylvania, v I

Aprlication'July 10, 1943,'Serial u 494,161

. 1 Claim. 1

My invention relates to lightning arresters and is directed more particularly to providing an arrester which is simple in its design and assembly and which has improved protective characteristics because of the combination of a substantially non-grounding air gap and a valve or resistance element which adequately limits the power-follow current and an excessive voltage drop between the gap terminals at comparatively high values of surge current is avoided.

There are available lightning arresters which have reasonably satisfactory non-grounding characteristics as well as an acceptably low impulse breakdown voltage, but which are readily destroyed by heavy surges and by power-follow current. Also, other arresters are available which are capable of satisfactorily limiting the power-follow current but which are unsafe due to the occasional loss of protection caused by grounding of the air gap. Such arresters have proved unsatisfactory for vital control circuits such, for example, as are present in the railway signaling field where safety and expeditious movement of trains require arresters of extreme reliability having both a non-grounding air gap and the ability to withstand surges and followup current without destruction.

One object of my invention is to provide a lightning arrester which combines in one unit a non-grounding air gap with a non-linear resistance element which prevents arc-over at the gap by the power-follow current. Another object of my invention is to provide a lightning arrester unit which can be readily inspected, removed, or replaced manually in the field without disturbing the mounting or connecting wires. A further object of my invention is to provide an arrester unit which is simple to manufacture and easy to take apart and assemble by hand without danger of breakdown or improper operation because no critical adjustment is required. Other objects, purposes, and features of my invention will be apparent from the description which folows.

I accomplish the foregoing objects by combining into a single easily removable structure a discharge gap element of the type having what is known as a preionizing air gap with a nonlinear resistance element or valve unit in series therewith; andby enclosing the elements in two concentric insulating cups, at least one of which is transparent, within which the elements are supported and are held together solely by spring pressure.

In the accompanying drawing, Fig. 1 is an 2 elevation showing one form of lightning arrester embodying my invention. Fig. 2 is an end view of the arrester unit of Fig. 1.

Similar reference characters designate similar parts in each of the views.

Referring to Fig. 1, the insulating base I having the raised portions 2 and. terminal posts 3 comprises a terminal block such; for example, as the standard terminal block adopted by the American Association of Railroads. The terminal posts of this block with their usual complement of washers and clamping nuts provide the electrical connections as well as the mechanical support for the removable lightning arrester unit designated, as a whole, by the reference character A. This unit is supported by the angle brackets 4 which are fastened together by the insulating strap 5 so that the whole lightning arrester assembly may be removed from the terminal block, if desired. The brackets 4 are slotted at the upper end to receive the pins l8 and to provide for manual removal of the arrester unit. Spring clips 6 engage the pins l8 and lock the arrester unit firmly in place.

The arrester unit itself includes the cupped saw-tooth disc 1 which cooperates with a disc or button 8 of high resistance and high heat resisting material such, for example, as Carborundum. The button 8 fits into a shallow metal cup 9, and the saw-tooth disc I is properly spaced from the button 8 and cup 9 by means of an insulating block I!) having the projecting lugs H and 12. These lugs fit into holes in the disc 1 and button 8 so as to align the parts which make up the discharge gap element. One suitable form of a preionizing air gap structure is that disclosed in Letters Patent of the United States No. 2,297,323, granted September 29, 1942, to F. X. Rees et a1. so that a detailed description of a discharge gap of this type is unnecessary. Electrical connection with the disc 1 is obtained through the metal plate I3 into which the metal pin I8 is fastened or is integral therewith. A transparent glass or plastic cup 14 encloses this portion of the assembly to keep foreign material gut of the air gap and provide for visual inspecion.

Cooperating with the air gap element is a valve element which in the form shown is a cylindrical block I 5 of suitable high resistance material such, for example, as Thyrite. Preferably, this block should have a resistance which varies logarithmically and is high at low voltages, but low at high voltage values. The block I5 is in contact at its one face with the metal cup 9 and at its other face with a metal washer I6. The two faces of the block I may be copper coated for improved contact. The Washer l6 has a raised or cupped portion l9 against which pressure is applied by the spring 6 through the supporting pin l8 and its disc 13 thereby providing good electrical contact. The block I5 is enclosed in a cup I! of insulating material such as Bakelite over which the transparent cup [4 is fitted to provide a complete housing for the arrester unit.

As will be apparent from the drawing, the arrester unit can be easily removed by hand from its supporting base and replaced by a new unit, or the old unit can be disassembled by hand without mechanical aid and any defective parts which -may have been injured by a lightning discharge can be repaired or replaced. Since the elements are held together wholly by spring pressure, the danger of breakage which might result from a too tight adjustment of other common clamping means during replacement is removed and more uniform conditions within the arrester are readily obtainable.

The advantages of the lightning arrester embodying my invention are that it combines a very reliable type of air gap and one which discharges at relatively low values of impulse voltage, with an integral valve element which protects the unit against destruction by arcing or by power-follow current, these elements cooperating within a compact unit which can be assembled or replaced wholly by hand.

Although I have herein shown and described only one form of lightning arrester embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claim without departing from the spirit and scope of my inventlon.

Having thus described my invention, what I claim is:

A housing and terminals including, in combination, two concentric insulating cups one fitting over the other to form a housing and one of said cups being transparent to permit visual inspection of the interior of the housing, each of said cups provided with an axial bore, two metal plates each having a metal pin secured thereto, said plates disposed one inside of one of said cups and having its pin extending through the bore of said one cup and the other plate disposed inside the other cup'and having its pin extending through the bore of said other cup, said plates forming two terminals within said housing and having connection outside the housing through said pins, two metal angle-shaped brackets secured to an insulation strip with their upright portions facing each other spaced to receive said cups between them, each of said upright bracket portions formed with a slot to receive said pins to support the cups, a spring clip secured to each bracket to engage the end of the pin supported by the respective bracket, and the leg portion of .each of said brackets formed to fit a terminal post mounted in said insulation strip.

ROBERT M. GILSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,935,810 McFarlin Nov. 21, 1933 2,018,672 Hill Oct. 29, 1935 2,297,323 Rees Sept. 29, 1942 2,242,838 Somes May 20, 1941 1,899,540 Towne Feb. 28, 1933 1,486,132 Egerton Mar. 11, 1924

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