US1176544A - Protective device. - Google Patents

Description

G. F. GRAY.

PROTECTIVE DEVICE.

APPLICATION FILED MAR. 1o. |913.

Patented Mar. 21, 1916.

Fig. l.

Inventor: Geo e F' rag S CDY-neg.

Witnesses;

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lUNTTED STATES PATENT OFFICE.

GEORGE -F. GRAY, OF SCHENECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

PROTECTIVE DEVICE.

Speciication of Letters Patent.

Patented Mar. 21, 1916.

Application tiled March 10, 1913. Serial No. 753,179.

T o all whom it may concern:

Be it known that I, GEORGE F. GRAY, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Protective Devices, of which the following is a specification.

My invention relates to protective devices, and more particularly to that type of device for use in the protection of low voltage'circuits.

The protection of low voltage apparatus from damage by lightning is an important problem to engineers engaged in telephone, railway signal and similar' lines of work. Various kinds of protective devices have been installed on low voltage lines but with apparently little success. Most of the devices used have the disadvantage of grounding or short circuiting which in railway signal work is especially dangerous because, as is often the case, the grounding of such a circuit causes a false signal to be given. These devices furthermore are subject to such a great maintenance expense that their use is to a great extent restricted.

The object of my invention is to provide a protective device for use upon all low voltage circuits such as telephone, telegraph, railway signal. fire alarm, and similar circuits, which will be of economical and durable construction, with low maintenance cost and capable of discharging lightning strokes without damage to itself and also free from any possibility of short circuiting. To this end I provide a protective device of unit construction consisting of -a hollow metallic tube especially adapted to maintain a vacuum or inert atmosphere. The metallic tube itself forms one electrode for a spark gap, the other electrode being a metallic disk mounted within the tube. With this construction a protective unit is provided, with a spark gap in a vacuum or in an inert atmosphere. The protective unit is so arranged that it can be easily inserted in a spring socket member mounted upon an insulating base thereby operatively connecting the protective unit into the line to be protected. Y

The novel features which I believe to be characteristic of my invention will be defined in thegclaims appended hereto. The

features of construction and mode of operation will be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 is a front elevation, partly in section, of a protective device embodying the novel features of my invention; Figs. 2, 3 and 4 are sectional views of various forms of the protective unit shown in Fig. 1; Fig. 5 is a diagrammatic view of connections shown in Fig. 1; and Fig. 6 is a diagrammatic view of another electric circuit in which my protective unit is used.

Referring to the drawings, I provide a protective unit A, consisting of a hollow drawn metal electrode 1. This electrode may be made in several shapes and of any non-corrosive metal but in the preferred construction the electrode consists of a hollow tube made of brass. Extending through and projecting outside the tubular electrode `1 is an electric conductor in the form of a metallic rod 2. This conductor' or rod 2 is suitably supported within the tubular electrode 1 and insulated therefrom as will be hereinafter more fully described. Within the tubular electrode 1 is a coperating metallic electrode 3 which may be of a variety of shapesV but preferably in the form of a plate or disk. This plate or disk electrode 3 is securely mounted concentrically within the tubular electrode 1, and upon one end of the conductor or rod 2, being in conductive relation therewith. The plate or disk electrode 3 is preferably of a non-arcing metal such as a bronze or a brass` and may have either a plain or a knurled edge. A metallic sleeve 4 preferably made of a non-arcing metal is securely mounted upon the inner surface of the tubular electrode 1. The sleeve 4 and the disk electrode 3 are separated from each other by a concentric spark gap 5. As the metallic sleeve 4 is in conductive relation with the-tubular electrode 1, it forms a non-arcing facing for the electrode 1. The protective unit A therefore consists essentially of two non-arcing electrodes separated by a spark gap. The tubular electrode is arranged to be evacuated or to contain an inert atmosphere so that the spark gap 5 will always be in an inert atmosphere which will cause it t0 break down under a f lower potential than an air gap. By the use of the term inert atmosphere in this trode 1 and in so passing,

specification and in the claims appended hereto, I wish to broadly include either an inert gas or a vacuum.

My object in using non-arcing electrodes is to adapt the protective unit A kto more fully protect a low voltage circuit from abnormal conditions, Isuch as lightning discharges, current rushes due to crossing with power circuits, etc. Non-arcing electrodes separated by a spark gap in an inert atmosphere reduces the excessive arcing and offers a preventive to the following of the line or dynamic ycurrent after a discharge takes: place.

The conductor or rod 2 is rigidly supported and well insulated from the tubular electrode 1 by a specific arrangement of insulating materials as will be hereinafter described. As shown in Fig. 2 the conductoror rod 2 is insulated and rigidly held by a bushing 6.. which may be made of any durable insulating material such as porcelain, glass, etc. In the construction shown the bushing 6,l1 is made of glass and is cast upon the conductor 2 and inclosed in a metallic casing 7. f

It was found in practice, in the type of construction shown in Fig. 2, that a discharge may under some conditions, pass from the conductor 2 to the tubular elecchp off portions of the bushing 6a. To resist thistendency the type of construction as shown `in Fig. 3 was adopted. In Fig. 3 the bushing 6 is of an insulating non-chipping material, such as porcelain. By non-chipping, I mean not liable to be continually chipped offor pitted by spark discharges. In the construction shown in Fig. 3, I further provide a metallic collar 8. which is mounted upon the conductor 2 directly below and in conductive relation with the disk electrode 3. This collar 8 fits into a hollow circular projection9 of the insulating bushing 6b and is separated therefrom by a small space as shown in the figure- The small space between the collar 8 and the inside of the hollow projection 9 prevents any short circuiting of the collar 8 and the tubular electrode 1. When the spark gap 5 breaks down continuously, metal is vaporized which subsequently deposits upon the surface of the bushing 6b impairing its dielectric strength and offering a conductive path from the tubular electrode 1 over the surface of the bushing. This conductive path is, however. interrupted by the small space shown, which is too narrow for the metallic vapor to penetrate and hence no'dep osition of metallic vapor takes place. This small space, therefore affords ample protection from short circuiting caused by the depositionmf metallic vapor. The disk electrode -3 is brought into close proximity with thc'top of the circular projection 9 which greatly reduces the tendency of 'arcing bei insulating bushing 6 is of the same shape and of the same material as the'bushing 6b of' Fig. 3 but the collar 8 is longer than .in Fig. 3 `and the outer surface of thecircular projection 9 has a metal facing or sleeve 10 preferably of vnon-arcing material. This metallic facing 10 extends above the top of the hollow projection 9 in such a way as to break up any arc which may form between the conductor 2 and the tubular electrode 1 thus easily extinguishing it.

In Figs. `2, 3 and 4, below and adjacent to the insulating bushings 6, 6,.,and 6b isa layer of insulating material 11 of high melting point. This material may be of a variety of well-known materials but what I prefer to use is a mixture of resin and coal tar pitch which has a melting point about 125o C. Adjacent t9 insulating material 11 is a layer of another insulating material 12, which is of plastic nature, of low solidifying point and of low`melting point. This material may likewise be of a variety of materials but I prefer to use a vegetable pitch which has a melting point about 60 C. A pressed, board washer 13 saturated With linseed oil is placed next to the insulating material 12 and adjoining the Washer is another layer of insulating material 11. The board washer 13 is .placed between the insulating material 12 and the last layer of insulating material 11 to prevent any mixing of the two insulating materials. The insulating materials are added in a fluid state, and'unless the board washer is used, when the last layer of insulating material 11 is added, owing to its higher melting point, it mixes with the insulating material 12 which is undesirable. To suitably finish and close the tubular electrode, an insulating plug 14 is placed adjoining the last layer of insulating material 11. This plug may be of any durable insulating material preferably porcelain, and is securely held in place by spinning in the usual manner.

The closingof the tubular electrode 1, in the manner shown, is a novel feature of the applieants invention. The materials used and their specific arrangement secures a maximum eiiciency for the device. The bushings 6 and 6b are especially constructed and made of anon-chipping` material which is at the same time a material which can be accurately molded and is usually strong and able to withstand the sudden changes of temperature incident to arcing. The bush-` ings 6 and 6 are not depended upon to preserve the inert atmosphere in the tubular electrode 1, but such atmosphere is preserved by the especially developedinsulating materials 11 and 12 and the specific arrangement of them. Having the plastic insulating material 12 so located in the tubular electrode is of material advantage. This material is of sulicient adhesiveness to adhere securely both to conductor 2 and the sides of the tubular electrode 1 and is only slightly affected by temperature change. Any expansion or contraction of the tubular electrode 1 due to normal temperature changes has a tendency to cause the insulating material 11 to crack or draw away from the side of the tubular electrode. In such a case the insulating material 12 is of suflicient plasticity to fill up any cracks or fissures which may occur and thus keep theinert atmosphere always intact.

When the insulating plug 14 is secured in place, the tubular electrode is ready to be evacuated or an inert atmosphere introduced. One end of the tubular electrode 1 contains a depression 15 in which there is a small perforation 16 through which the tube is evacuated or the inert atmosphere introduced in any manner desired. The depression 15 is partially filled with a fusible material 17 through which a small hole is bored to the perforation 16. When the tubular electrode 1 contains the proper amount of inert atmosphere, the fusible material 17 is rendered sufficiently fluid to close the small hole bored in it. thereby closing the perforation 16 and sealing and finishing the tubular electrode 1. The fusible material 17 may be a. solder or any other low melting point alloy.

If a continued discharge takes place between the disk electrode 3 and thetubular electrode 1, the tubular electrode becomes heated and the fusible material 17 becomes sufficiently softened to flow through the perforation 16. In such a case there would be danger of the fusible material coming in contact with the disk electrode 3 in such a way as to bridge the spark gap 5 and short circuit the tubular electrode 1 and the disk electrode 3. To prevent this action from taking place, a metallic diaphragm 18. is securely mounted Within the tubular electrode 1 beneath the depression 15. To effectively eyacute the tubular electrode it is necessary that the metallic diaphragm 18 be perforated. These perforations or apertures 19 are shown at the end of the protubcrances 20. The diaphragm 18 is made with protuberances 20 containing apertures 19 in such a way as to form a cup shaped receptacle 21 into which any fusible material 17 will flow. This receptacle 21 is of sufficient size and the apertures 19 so situated that no fusible material 17 can pass through the diaphragm 18, and tbe unit A is thus protected from any possibility of short circuiting.

Having thus described in detail the construction of the protective unit A, I will now describe the means by which this unit is applied to the circuits to be protected. The unit A consists essentially of the tubular electrode 1 which forms the outer casing of the protective unit and a disk electrode 3 mounted therein and separated therefrom by a spark gap in an inert atmosphere. This unit is adapted to be removably positioned in a spring socket member 22, shown in Fig. 1, which is mounted upon an insulating base 23 preferably of porcelain. In Fig. 1 there is shown two protective units A and A mounted in spring socket members 22 and 22a, respectively. The spring socket members 22 and 22a are both connected to the same metallic plate 24 which in turn is connected to a groundingr terminal or binding post 25. Thus both tubular electrodes 1 and 1a are connected to the terminal The coperating disk electrodes 3 and 3a which terminate in conductors or rods 2 and 2a respectively, pass through insulated openings in the base 23 which are situated at the center of the base of the spring socket members 22 and 22a respectively. These conductors 2 and 2.i make contact with spring blades 26 and 26a respectively in which turn are connected to line connecting terminals or binding posts 27 and 27a respectively.

One of the novel features of my invention is the adaptability of the protective unit A to the circuit to be protected. This unit is constructed so as to be easily inserted into the spring socket members 22 or 22a Without interrupting working conditions upon the line. Should a unit be damaged in any way, it can be easily and quickly replaced without shutting down the line. In its construction, the unit is so arranged that the tubular electrode 1 and the conductor 2 which is conductiyely related to the disk electrode 3, are connected simultaneously into the circuit. By simultaneously, I mean that both electrodes are connected in the circuit by one motion, which is the insertion of the unit in the spring socket member 22.

Fig. 1 shows the connections for the protectiye unit when used in low voltage circuits especially telephone circuits, and Fig. 5 shows diagrammatically the connections shown in Fig. 1. Une side of the line is connected to line connecting terminal 27 and through spring blade 26, to conductor 2 of the protective unit A. Discharge is then made through spark gap 5 to tubular electrode 1 through spring socket member 22, metallic plate 24 to terminal 25 and thence to ground. The other side of the line is connected to line connecting terminal 27a through spring plate 26a to conductor 2a of the protective unit A. Discharge from this line is-through spark gap 5a to tubular electrode 1a and thence through spring socket member 22a, metallic plate 24 to grounding terminal 25 and thence to ground.

the circuit to be protected, without departhvoltage circuits or on .circuits where there ingHfrom the scope of my invention.

he adaptabihty of my protective device for the protection of other low voltage c1rcuits such as telegraph, railway signal and fire alarm circuits will be apparent to those skilled in the art without especially showing ,or describing the connections for the same.

In low voltage circuits the spark gap 5 is sufficient to prevent its breaking down under the nor al volta e of the line. The device Jcan also e used or the protection of higher is a possibility of crossing with high potential circuits, by providing fuses in the line or by using several of the protective units in series. As is shown diagrammatically in Fig. 6, choke coils or inductance can also be used in conjunction with the protective unit for the protection of circuits where unusual conditions of. service, especially in certain railway signal circuits, demand it.

T here are certain advantages inherent 'in ,V my protective device of the structure shown,

which can be enumerated as follows: First, the protective device is economical and of durable and simple construction. Secondly, the device is adapted for use upon all low voltage circuits irrespective of their funcl tion. Thirdly, the device protects the circuit from all abnormal conditions which may arise such as lightning discharge, current rushes due to crossing with power circuits. etc., and with no possibility of short circuiting, and lastly, the'protective device is of unit construction, so that the unit can be easily and quicklyconnected' in the line or in case of damage can be easily replaced by another unit, in all cases Without dis-- turbing the working conditions of the line.

My invention may be embodied in many other forms than that shown and described and I therefore do not desire to be restricted to the precise construction shown, but intend to cover by the appended claims all changes and modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Let-ters Patent of the United States, is

1. A protective device comprising, a hollow metallic electrode containing an inert atmosphere, one end of said electrode havf.

ing a depressionJ containing a perforation, fuslble materlal 1n sald depresslon and coverlng said erforation, a coperating metallic electro e mounted within said hollow fusible material in said depression and covering said perforation, a perforated metallic diaphragm mounted `within said electrode beneath said depression, a coper ating metallic electrode mounted within said hollow electrode and separated therefrom by a spark gap, an electric conductor connected to said coperating electrode and extending outside said hollow electrode, and

meansfor rigidly supporting and insulating said conductor from said hollow electrode. e

3. A protective device comprising, a hollow metallic electrode containing an inert atmosphere, one end of said hollow electrode having a depression containing a perforation, fusible material in said depression and covering said perforation, a perforated metallic diaphragm mounted within said 'hollow electrode directly beneath said depression, a'cc'perating metallic electrode mounted within said hollow electrode and normally'- separated therefrom by a spark gap, an electric conductor connected to said coperating electrode extending outside said hollow electrode and insulated therefrom,

i and means for preserving said inert atmosphere in said hollow electrode.

/4. A protective device comprising, a hollow metallic electrode containing an inert atmosphere. a coperating metallic electrode mounted within said hollow electrode and separated therefrom bv a spark gap, an electric conductor connected to said coperating` 'electrode and extending` outside said hollow electrode, an insulating bushing mounted within said hollow electrode and rigidly supporting said conductor, the top surface of said bushing sloping upward from said hollow electrode and from said conductor, and means adjacent said bushing for hermetically sealing said hollow electrode.

5. A protective device comprising, a hollow metallic electrode containing an inert atmosphere, one `end of said electrode having a depression containing a perforation,

fusible material in said depression and coverlng sald perforatlon, a metalllc cooperating electrode mounted within said hollow o electrode, means for preventing said fusible low metallic electrode containlng an inert atmosphere, one end of said electrode having a` depression containing a perforation, fusible material in said depression and covering said perforation, a metallic disk electrode mounted within said hollow electrode and separated therefrom by a spark gap, means for preventing said fusible material when fluid from short circuiting said disk electrode and said hollow electrode, an electric conductor connected to said disk electrode' and extending outside said hollow electrode, and means for insulating said conductor from said hollow electrode and fo-r preserving said inert atmosphere in said hollow electrode.

7. A protective device comprising, a hollow metallic electrode containing an inert atmosphere, one end of said electrode having a depression containing a perforation, fusible material in said depression and covering said perforation, a disk electrode mounted within said hollow electrode and separated therefrom by a spark gap, a perforated metallic diaphragm mounted within said hollow electrode beneath said depression, an electric conductor connected to said disk electrode and projecting outside said hollow electrode, and means for insulating said conductor from said hollow electrode and for preserving said inert atmosphere in said hollow electrode.

8. A protective device comprising, a hollow metallic electrode containing an inert atmosphere, a non-arcing metallic electrode mounted within said hollow electrode, a nonarcing metallic sleeve mounted within said hollow electrode\ concentric with Said nonarcing electrode and normally separated from said non-arcing electrode by a spark gap, an electric conductor connected to said non-arcing electrode and extending outside said hollow electrode, and an insulating bushing mounted within said hollow electrode and rigidly supporting said conductor the'top surface of said bushing sloping upwar'd from said hollow electrode and from said conductor.

9. A protective device comprising, a hollow noncorrosive metallic electrode containing an inert atmosphere, a coperating metallic electrode mounted within said hollow electrode and separated therefrom by a spark gap, an electric conductor connected to said cooperating electrode and extending outside said hollow electrode, an insulating bushing mounted Within said hollow electrode and supporting said conductor, alternate layers of high melting point and low melting point insulating material surrounding said conductor beneath and adjacent to said bushing, the top and bottom of said alternate layers being of said high melting point material, and an. insulating plug adjacent to said alternate layers of insulating material, -said plug closing the end of said hollow member.

10. A protective device comprising, a tubular metallic electrode containing an inert atmosphere, a knurled metal electrode mounted within said tubular electrode, a non-arcing metallic sleeve mounted within said tubular.electrode and normally separated from said knurled electrode by a spark gap, an electric conductor connected to said knurled electrode projecting outside said tubular electrode and insulated therefrom, and means for preserving said inert atmosphere in said hollow electrode.

11. A protective device comprising, a tubular metallic electrode containing an inert atmosphere, one end of said electrode having a depression containing a perforation, fusible material in said depression covering said perforation, a metallic perforated diaphragm mounted within said tubular electrode beneath said depression, a metallic disk electrode mounted Within said tubular electrode, a non-arcing metallic sleeve mounted within said tubular electrode concentric with said disk electrode and normally separated from said disk electrode by a spark gap, an electric conductor connected to said disk electrode extending outside said tubular electrode and insulated therefrom, and means for rigidly supporting said conductor and for preserving said inert atmosphere in said tubular electrode.

12. A protective device comprising, a tubular metallic electrode containing an inert atmosphere, one end of said electrode having a depression containing a small perforation, fusible material in said depression covering said perforation, a metallic diaphragm mounted within said tubular electrode beneath said depression, a plurality of protuberances upon said diaphragm each containing a small perforation, a metallic disk electrode mounted within said tubular electrode and separated therefrom by a spark gap, an electric conductor connected to said disk electrode and projecting outside said tubular electrode, and means for insulating said conductor from said tubular electrode and for preserving said inert atmosphere in said tubular electrode. y

13. A protective device comprising, a hollow metallic electrode containing an inert atmosphere, a metallic disk electrode mounted within said hollow electrode and separated therefrom by a spark gap, an electric conductor connected to said disk electrode and extending outside said hollow electrode, an insulating non-chipping bushing mounted within said hollow electrode, alternate layers of high melting point and low melting point insulating material surrounding said conductor beneath and adjacent to said bushing, a washer4 between the last layer of said high melting point and `said low melting point insulating materials,

and an insulating plug adjacent to said alternate layers of insulating material and closing the end of said hollow electrode.

14. A protective device comprising, two electrodes normally separated by a spark gap in an inert atmosphere, one of said electrodes being a hollow member inclosin said inert atmosphere, lthe other of sai electrodes being a disk member mounted .within said hollow member, a ground terminal for said hollow member, a line connecting terminal for said disk member, and means whereby said electrodes may be simultaneously connected to their respective terminals.

15. In a protective device, the combination with a protective unit comprising a hollow electrode, a disk electrode mounted within said hollow electrode and separated v therefrom by a spark gap, and aconductor connected to said disk electrode and extend- )and said conductor to said spring blade simultaneously. l

16. In a protectivedevice, the combination with a protective unit comprising a hollow electrode, a co erating electrode mounted within said ho low electrode and separated therefrom by a spark gap, and a conductor connected to said coperating electrode and extending outside said hollow electrode, of two terminals, a spring blade connected to one of said terminals, anda spring socket member connected to the other of said terminals, said protective unit being removably positioned 'in said socket member to connect said hollow electrode to said socket member and said conductor to said spring blade simultaneously.

In witness whereof, I have hereunto set my hand this 8th day of March, 1913.

GEORGE F. GRAY. Witnesses:

BENJAMIN B. HULL, HELEN ORFORD.

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