US764372A - Thermal cut-out. - Google Patents

Description

No. 764,372. PATENTED JULY 5, 1904 R. H. READ. THERMAL GUT-OUT.

APPLICATION FILED OUT. 23, 1902.

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N0. 764,372. PATENTED JULY 5, 1904. v R. H. READ.

THERMAL GUT-OUT.

v APPLICATION FILED 0OT.23, 1902.

N0 MODEL.

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lph/ENTo Rb HR d. MW bqflwbail NO. 764,372. Patented July 5 190 1.

UNITED STATES PATENT OFFICE.

ROBERT H. READ, OF SCHENECTADY, NEWV YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

'THERMAL CUT-OUT.

SPECIFICATION forming part of Letters Patent No. 764,372, dated July 5, 1904;. Application filed October 23, 1902. Serial No. 128,464. (No model.)

To all whom it y 00711087"! The object may be carried out in a variety 5 Be it known that I, ROBERT H. READ, acitiof ways, several of which will be described by zen of the United States, residing at Schenecway of example. tady, in the county of Schenectady, State of The increasing heat of the granular envelop New York, have invented certain new and around the fuse due to its current-carrying causeful Improvements in Thermal Cut-Outs, pacity after partial fusion may be employed to 55 of which the following is a specification. melt a fusible joint of large current-carrying This invention relates to thermal cut-outs capacity, which under normal overloads will for electric circuits. the object being to rennot be affected, and a spring or other device der the opening of the circuit more certain, employed to effect the break when such weak particularly when the cut-out is operated unjoint is loosened, or the heated gases deliv- 6O der extremely heavy loads or short circuits. ered by the fuse maybe directed by means of It is the common practice in modern systems a vent across such a joint or a latch or detent of distribution to employathermal cut-out or of any form which normally restrains the 5 fuse in which provision is made against the opening of the secondary break.

scattering of the heated metal or the flaming I prefer to mount a cartridge embodying 5 of the are, particularly in cases where the pomy improvements upon a spring-controlled tential is five hundred volts or upward. Soarm adapted to be locked into position where called -cartridge-fuses have been employed it closes the circuit by means of a detent for this purpose, consisting of a fuse strip or such as referred to, so that when the fuse wire inclosed within a non-conducting shell blows if the are holds over and the granular 7 and immediately surrounded by a porous or material is made a carrier of current the degranular non-conducting material which abtent will be released and the cartridge bodily sorbs heat and chills the vapors developed shifted away from the terminals, so as to pro- 2 5 when the fuse blows. One of the most .efduce a secondary break which will safely open feetive materials for this spacer is coarsethe circuit. 75 grained sand or small pebbles of flint. I Vith In the case of a high-tension fuse I prefer such a fuse the operation on ordinary o'verto employ on such a spring-actuated arm a load is so quiet that it is difficult to detect plurality of cartridges connected in series,

when the fuse blows, a soft hiss or spit being each adapted to care for a fractional part of the only indication that the fuse has blown. the entire voltage of the circuit, one or more VV'th heavy currents, however, the sand imdetents being provided of the character almediately inclosing the fuse when the latter luded to, which are released when necessity blows is heated to such a degree that it bearises to efi'ect with certainty the rupture of 3 5 comes an electric conductor of considerable rethe circuit.

sistance, but carries the current, and as the My invention therefore comprises a ther- 5 heat rises, due to such transmission, the sand mal cut-out having means determined by the is fused and forms a good conductive connecheat generated by operation of the cut-out for tion between the fuse-terminals. This action effecting a secondary break in the circuit at a 4 if the device is allowed to remain in circuit point exterior to the fusible element itself.

would soon prove disastrous. In a more specific sense it comprises a car- 9 It is the object of my invention to guard tridge fuse containing granular material against such a contingency, in doing which I around the fuse and means for effecting a secprovide for an auxiliary break in the circuit ondary break after the fuse has blown. It 45 determined by the blowing of the fuse, said comprises other features the novelty of which auxiliary or secondary break being at a point will be hereinafter described, and definitely in the circuit where the action of the fuse indicated in the claims appended to this speciitself or its envelop cannot continue the mainfication. tenance of current. In the accompanying drawings, which illustrate the invention, Figure 1 is a side elevation, partly in section, of athermal cut-out of the cartridge type embodying'my improve-- ments. Fig. 2 is a similar View of another form of my invention. Fig. 3 is a similar view of a third form, showing also the mode of mounting the cartridge in a spring-controlled holder. Fig. 4 is an end view of a gravity-controlled secondary break. Fig. 5 is a front elevation of a high-potential device embodying my improvements. Fig. 6 is an end view of the same. Fig. 7 is a detail of a detent controlling the secondary break, and Fig. 8 shows another way of effecting the secondary break.

Referring to the drawings, 1 represents an insulating-shell, 2 2 metallic caps firmly secured on the ends of the same, and 3 a strip of fuse wire or ribbon connecting the caps.

4: represents an insulating granular material, such as coarse sand or line gravel. The cartridge-fuse as commonly constructed is set in a pair of terminal clips, which embrace or bear against the metallic endcaps 2 2. The blowing of the fuse heats up the sand and causes a partial fusion of the same, making of it a conductor across which the current leaks in constantly-augmenting volume until a dangerous heat is developed and an opportunity afforded for an are which may endanger an installation. The current which holds over after the fuse blows and which is due to the conversion of the sand into an electrolytic conductor is very weak by reason of the high resistance of the fuse-circuit. In the various types of device shown in the drawings this weak current is interrupted by a secondary break. In the form shown in Fig. 1 this break is effected by means of a vent 4 in the shell, around which is fastened a strip of fusible or combustible material 5, se-

. cured to the tines of a fork or yoke 6, which engages a latch and holds the device which carries the fuse in a position of strain. The cartridge is carried in a holder-as shown in Fig. 3, for example comprising a pivoted arm 7 controlled by a stout spring 8. When the holder is put under tension, it is locked with the spring in a tense condition by any suitable device. In the form shown in Fig. l the perforated end of the yoke 6 engages a latch 9. (See Fig. 6.) The gases developed by the blowing of the fuse traverse the gravel and are robbed of much of their heat, a stream of hot vapor or gas pouring from the vent 4E and charring the combustible material of which the strip 5 is composed or fusing the fusible metal, as the case may be.

sion of the spring then frees the cartridge from the yoke 6, withdrawing it from the terminal clips in which it is supported. In the form shown in Fig. 2 the end caps are provided with a reentrant plug 10 of some little heat-storing capacity, and on the outside is attached by a solder having any desired fusing-point a ter- The ten- .6 is a fusible strip 5, fastened by set-screws or minal 11, one of which is fastened at each end. I

of the cartridge. With this type when the fuse blows the vapors are absorbed by the sand, and on ordinary overload the arc is instantly extinguished by the dissipation of the heat through the sand. If, however, a shortcircuit or extremely heavy overload occurs, such as would be sufficient to fuse down part of the sand before the circuit is opened, then the accumulating heat will be conveyed by the metallic plugs 10 to the solder by which the terminals 11 are secured to the caps, thereby melting the same and permitting the springholder to discharge the cartridge from its terminals which remain secured in the clip 12.

(See Fig. 3.) Thus the secondary break opens the circuit, rendering it impossible for the arc to hold. Inasmuch as the current carried by i the sand at an early stage of its fusion is small by reason of its high resistance, this secondary break may be easily opened. The springholder may be given any desired range of movement, so that arcs of considerable potential may be easily ruptured. After the cartridge is started the break is so quick that the.

rupture of the circuit is not attended with any considerable are.

In the form shown in Fig. 3 vents 13 13 may be placed in the end caps adjacent to the soldered joint, and the discharge of the hot gases will convey heat to the joint and free the shell.

Another form is shown in Fig. 4, in which gravity may be relied upon to effect the secondary break. The terminals are connected to the end terminals by means of solder, and the fuse is supported in a vertical position, as indicated. It will be evident that if the are holds over and raises the heat of the contents of the cartridge to a sufficient point the joint will be broken and the shell will fall away from the terminals, leaving the latter secured in the clips, thus effectually opening the circuit.

Where it is desired to open a circuit of very high potential, I employ a plurality of such fuses connected in series, as indicated in Figs. 5 and 6. With such an organization each fuse cares for a part of the potential drop across the switch, and in cases of very heavy overload a plurality of arcs will form simultaneously in the several cartridges. Over one or more of them will be placed a release device for withdrawing the detent from the switcharm, freeing it to the control of its spring and permitting the secondary break to be established.

The particular form shown in Figs. 5 and in any other suitable way to the yoke 6, in

which is formed a notch or recess 14 for a de- .dotted lines in Fig. 5, by which the several,

fuses will be in series relation when the circuit is closed. The. entire switch is thus a unit, and when the frame is pressed into the terminal clips 15 15 the circuit is closed, the detent on bracket 9 hooking over the projection on the yoke 6.

In lieu of the particular type of detent shown any other form might be employed. For instance, as seen in Fig. 8, thelatch itself might be extended, so as to overlap the vent 4, the pressure of the issuing gases pushing it away from the recess in which it is held. In all cases it will be seen that I effect a secondary break in the circuit later than the main break, which is a direct or indirect resultof the heat generated if the fuse should fail to open the circuit.

What I claim as new, and desire to secure by Letters Patent of the UnitedStates, is

1. A thermal cut-out provided with a secondary break-point in the circuit exterior to its fusible element, and means determined by the failure of the fusible element to open the circuit when operating for effecting an opening of the circuit at said break.

2. A thermal cut-out provided with a secondary break-point in the circuit exterior to the fusible element and in series therewith, and means for opening the circuit at said breakpoint on extreme overloads, said means being dependent on the failure of the fuse to open the circuit. V

3. A the'rmal cut-out provided with a secondary break-point in the circuit auxiliary-to its fusible element, and means for opening said break dependent for action on failure of the fuse to extinguish the arc.

4. A thermal cut-out provided with a secondary break auxiliary to the fuse and in series With the same, and means determined by the failure of the fuse to open the circuit for opening said auxiliary break.

5. A thermal cut-out having two breaks in series relation, one at the fusible element and the other independent thereof, the latter operated by the heat of the fuse when said fuse fails to open the circuit.

6. Athermal cut-out having two breaks in series relation, one at the fuse and the other exterior thereto, a movable terminal connected to the auxiliary break, and means for operating said terminal to open the circuit when the fuse fails to open the same.

7 A thermal cut-out comprising a springoperated holder, a fuse carried thereby, each controlling a break-point of the circuit, and means for releasing the holder to open the circuit when the fuse fails to open the same.

8. A thermal cut out comprising a cartridge-fuse, and means for automatically removing the cartridge and thereby breaking the circuit if the fuse fails.

9. A thermal cut out comprising a car tridge-fuse, a spring-holder for the same, and

means for releasing the holder and breaking the circuit by its motion when the fuse blows.

10. A thermal cut-out comprising a fusible element, a granular non-conductor inclosing the same, and a secondary break in the circuit operated by action of the fuse.

11. A thermal cut-out comprising a cartridge-fuse having the fusible element surrounded by a porous non-conducting material, a spring for establishing a secondary break in the circuit, and a retaining device for the spring adapted to be released by the blowing of the fuse.

12. A thermal cut-out comprising a cartridge-fuse having the fusible element surrounded by a porous non-conducting material, a spring for establishing a secondary break in the circuit, and a fusible retaining device for the spring adapted to be melted by the blowing of the fuse.

13. A thermal cut-out comprising a cartridge-fuse having the fusible element surrounded by a granular non-conductor, means for establishing a secondary break in the circuit,and a fusible retaining device for restraining said means and in heat-conductive relation to the cartridge.

14. A thermal cut-out comprising a cartridge-fuse having the fusible element surrounded by a granular non-conductor, means for establishing a secondary break in the circuit, a fusible restraining device for said means, and a vent for the fuse-gases adjacent to said restraining device.

15. A thermal cut-out comprising a car tridge-fusehaving the fusible element surrounded by sand, means for establishing a secondary break in the circuit, a fusible restraining device for said means, and means depending on the operation of the fusible element for melting the restraining device.

16. A thermal cut-out comprising a springactuated holder, a plurality of fuses connected in series relation carried thereby, and means for releasing the holder and effecting a secondary break in the circuit when the fuse operates.

, 17. A thermal cut-out com prising a springactuated switch, a plurality of fuses connected in series relation carried thereby, means for restraining the switch, and means for releasing the same when a fuse blows.

18. A thermal cut-out comprising a springretracted switch, a plurality of fuses connected in series relation carried thereby, a latch restraining the switch when set, and means for releasing the latch when a fuse blows.

In witness whereof I have hereunto set my hand this 22d day of October, 1902.

ROBERT H. READ.

\Vitnesses:

BENJAMIN B. HULL, HELEN Onronn.

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