US646691A - Circuit-protective device. - Google Patents

Description

Patented Apr.' a, |900.

No; 646,69l.

- w. D, GHARKY. l

CIRCUIT PROTECTIVE DEV''CE.

Q V I (Appliation filed June 1B, 1898.)

ullnllllllllx (No Model) WITNESSS= INVENTOR UNITED STATES PATENT OEEICE.

VILLIAM D. GIIARKY, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO THE SUN ELECTRIC MANUFACTURING COMPANY, OF NEV JERSEY.

CIRCU lT-PROTECTIVE DEVICE.

SPECIFICATION forming part of Letters Patent No. 646,691, dated April 3, 1900.

Application filed June 16, 1898. Serial No. 683,633. (No model.)

To ftZZ 2071/0711 it may concern:

Be it known that I, WILLIAM D. GHARKY, a citizen of the United States,residing in the city andcounty of Philadelphia, State of Pennsylvania, have invented a certain Circuit-Protective Device, of which the following is a specification.

My invention relates to devices which are used to protect electric circuits from abnormal 'conditions produced by atmospheric or accidental causes. v

The device is especially intended for use with telephonie circuits, although it will be apparent that it is not necessarily thus limited in its scope.

For the operation of a telephone system currents of comparatively-low potential and volume are employed and the apparatusA used is correspondingly designed. It sometimes happens, however, that the lines become accid'entally crossed with Wires carrying currents of greater magnitude or static charges due to atmospheric disturbance are present on the lines. The delicacy and consequent liability to injury of the telephonie apparatus requires protection which will not only insure its safety against any disturbance of whatever character, but which will be absolutely reliable undcr all circumstances, and will consequently satisfy the rigid requirements now made by the iireunderwriters. There are three forms of discharge to be provided against in such adevice-first, the static or lightning discharge; second, current due to a direct cross with a high-potential circuit; third, a sneak current or one which is of such small magnitude not to blow the lightest sort of fuse, but which when continued for a sufficient length of time will gradually heat the winding of a magnet-spool to the charringpoint, finally setting fire to the apparatus. The sneak current is the mcstdifiicult to provide against. In designing my protector I have combined the three forms in one piece of apparatus. For the high-potential currents which would find no difficulty in passing through apparatus of medium or low resistance, thereby injuring the same, I provide a fuse, for the static discharges I provide a spark-gap, and for thesneak currents I provide a device which depends for its op* eration upon what is known as the Peltier effect. rihe operative parts are inclosed within a casing having movable portions which are adapted to be displaced by the sudden expansion of the interior atmosphere, due to the blowing of the fuse by an excessive current. I utilize this displacement to actuate an alarm. The arrangement is such that the same displacement, with the consequent alarm, is caused by the operation of the sneakcurrent detector or, in fact, by any breaking of the circuit within the tube.

My invention is illustrated in the accompanying drawings, which show the preferred embodiment thereof; but it Will be obvious from the above statement that many other forms might be employed without departing from the scope and purview of the invention.

Referring to the drawings,wherein the same letters refer to the same parts throughout, Figure 1 is a longitudinal sectional view of my protector. Fig. 2 is a side view of the same mounted upon a base, showing a modified forni of tension-spring.

In the drawings, A is a tube of porcelain or earthenware inclosed within another tube B of brass. Fitted to one end of the porcelain tube, which is provided with a shoulder to rest upon the end of the brass tube, is a brass plug C. This plug is drilled axially to receive the end of a fine brass wire H, the drilled hole being countersunk in order that the outside end of the wire may be soldered to the plug and the solder faced off flush. D is a second and shorter porcelain or earthenware tube, also provided with a shoulder d and slipped loosely into the other end of the brass tube B. Upon the outside of the said tube B, I secure an abutment which is shown as a ring or flange K. This furnishes a stop for a spiral spring J, the other extremity of which bears against the shoulder d of the tube D, the spring being compressed when the tube D is in place. Fitted within the tube D is a plug E of an alloy to be herein` after described. This plug is provided with a head e, which rests upon the outside of the tube D.

The tubes B, A, and D are of such relative. lengths that a space is left within the tube B between the adjacent ends of the two porce- IOO lain tubes where the brass is internally exposed. I have indicated this exposed portion of the tube by 5c. lVithin this portion I provide a small cylindrical plug F of the same alloy as plug E. To one end of this plug F is connected the fine brass wire H, while the other end is joined to the plug E by a link or wire G of a material thermo-electrically positive to the alloyof which the plug E and the cylinder F are composed.

\Vith the construction thus far described the operation is as follows, the circuit of the apparatus to be protected being understood to lead into the plug O, through the wire H, the cylinder F, the wire link G, and the plug E: If an excessive current due to a cross between the protected circuit and some wire carrying a high-potential current should enter through this circuit, the wire II will immediately fuse, an are will be momentarily formed and the expansion of the contained air will blow out one or both of the plugs O and D. This expansion is sufficiently violent to shatter the porcelain tube if it were not reinforced by the inclosing brass tube, and the length of this porcelain tube Within the brass tube, which is sufficient almost entirely to close the fuse-wire H, effeetually prevents the arc from traveling back along the inside of the brass tube to cause a general fusion. If, on the other hand, a sneak current should enter on the circuit, a separation of the same will take place between the parts F and E. These two parts themselves are formed of an alloy composed of two parts of antimony and one part of zinc. The connecting-link G is of bismuth. Obviously these materials may be relatively interchanged without affecting the result. These parts are secured together by solder and their separation by the passage of a sneak current depends upon the principle known as the Peltier etfect-that is, when two metals possessing relatively positive and negative thermo-electric values are united in series by solder a current from an external source in passing through the junction from positive to negative metal will cool it. lVhen, however, the current flows in the reverse orderthat is, from negative to positivethe junction is heated. This heating is much greater than that traceable tothe ordinary Joule effect. Moreover, the heat is concentrateddirectly at the point of union of the two metals. Itis obvious that a sneak current passing in either direction upon the circuit will produce the effect desired, for the reason that I have an electropositive metal inserted between two portions of electronegative metal, or vice versa. Thus one junetion is always certain to be heated until the solder melts and permits a separation under the action of the spring J.

Electrostatic charges are enabled to pass off to ground by means of the tube B, which is grounded. The cylinder or plug F is centered within the exposed portion of this tube, as shown, and the air space or clearance becasser tween it and the tube is so proportioned as to constitute a proper gap. It is obvious that other shapes than that shown maybe given to the plug or cylinder F, and points or edges may be formed thereon, if desired.

Referring to Fig. 2, my protector is shown mounted upon a base, with the spring J omitted. In order to obtain a constant opposite tension upon the plugs O and D, l malto the supports S S', upon which the tube is mounted, of spring' metal, with a strong tendency to move in opposite directions. One or both ol.` these springs S S' should be connected to the ground. The operation of the device in this form is obviously the same as that described in connection with Fig. l.

In order that any operation of the protector which results in opening the circuit shall call the attention of the subscriber or the operator, as the case may be, I provide a localalarm circuit controlled by the movable parts O and D. In Fig. l the alarm is a closed-eircuit alarm, in which a portion of the alarmcircuit consists of a lead wire L, attached at one end to the insulating-plug D in any suit able manner and at the other end to the tube B, insulation being interposed at one or both of these connections. Obviously when the plug blows or is forced ont of the tube the lead wire will be broken, and the signal be ing thus placed upon an open circuit will op crate. In Fig. 2 I have shown an open-eircuit alarm, the wires from which are lcd. to contacts carried upon the base and one actu ating-spring S of the protector, respectively. Obviously as long as the circuit is 'intact these are held separated, but the destruction of the integrity of the connecting means bctween the plugs O and D will permit these contacts to close and sound the local alarm. In mounting the protector, as shown in Fig. 2, Iconduct my protected circuit through the tube either by means ot' binding-posts upon the plugs O and E or light contact-springs or terminal straps attached thereto in any suitable manner.

The structure I have described and the ein ployment of the Peltier effect for this purpose permits an adjustment for any given set of conditions very much more delicate and accurate than any which has heretofore, to my knowledge, been obtained. It :is obvious that inasmuch as the increase in heating el? feet duc to a rise in current in the circuit is in very much greater ratio than a similar in crease in accordance with the Joule principle ordinarily employed a very satisfactory ad justment of the point at which the parts F, G, and E will separate is possible, and this by simply changing the sectional area of the wire link` G at the junctions. So far as I know I am the first person to employthe Peltier effect in apparatus of this character, and I therefore claim the same, broadly, as my invention. Its use enables me to dispense with the heat-coils that are new the only satisli'ac tory agents for the detection of and protec- ICC IIC

tion against sneak currents and to make a complete, simple, and self-contained piece of apparatus that in spite of its simplicit y is susceptible of accurate adjustment.

The wire H is includ ed to give length to the entire fuse, as the bismuth or other material employed for the thermo-electric couple has insuflicient tenacity to be drawn out in a wire terials that are thermo-electrically positiveand negative with relation to each other, substantially as described.

3. In an electric-circuit protector, a casing, and a fuse therein, a portion of the length of the fuse consisting of a thermo-electric couple, substantially as described.

4. In a circuit-protector, an inclosing casing, a fuse contained therein, portions of said fuse being composed of thermo-electrically positive and negative materials connected to form a couple, a part or parts adapted to be displaced, but normally retained in place by the fuse, and an alarm actuated by the said displacement, substantially as described.

5. In an electric-circuit protector, atubular metallic casing, a fuse axially housed therein, and a non-combustible insulating tubular shield surrounding a portion of the length of the fuse between the fuse and easing, substantially as described.

6. In an electric-circuit protector, a metallic casing connected to ground, a continuous fuse housed therein, part of said fuse composed of a thermo-electric couple, and a sparkgap between a portion of the fuse and the casing, substantially as described.

7 In an electric-circuit protector, a metallic tube connected to ground, a fuse therein consisting in part of thermo-electric elements joined to form a couple, non-combustible insulating material between portions of the tube and fuse, and a spark-gap between the relatively-exposed portions thereof, substantially as described.

In testimony whereof I have hereunto set my hand, this 3d day of June, A. D. 1898, in the presence of two Witnesses.

WM. D. GI-IARKY.

Witnesses:

MORTIMER A. JONES, CHARLES F. TREGO.

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