US1252412A - Protective device for electric circuits. - Google Patents

Description

L. E. DICKINSON." PROTECTIVE DEVICE FOR ELECTRIC CIRCUITS. APPLICATION TILED NOV- 6.1916.

1,252,412. Patented Jan. 1918.

TUNITEWD STATES PATENT OFFICE.

LEWIS E. DICKINSON, OF BOONTON, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, 011' NEW YORK, N. Y., A CORPORATION OF NEW YORK.

PROTECTIVE DEVICE FOR ELECTRIC CIRCUITS.

Patented Jan. 8, 1918. 4 Application filed November 6, 1916. Serial No, 129,767.

1,252,412 Specification of Letters Patent.

To all whom it may concern:

Be it known that I, Lnwrs EDMUND DICK- INsoN, a citizen of the United States, residing at Boonton, in the county of Morris generated by the current flowing tl'irough the heating element is concentrated at a given point and very efliciently utilized in melting the fusible material, the softel'iing and State of New Jersey, have invented of whichallows the device to function and certain new and useful Improvements in protect the apparatus. This is accomplished Protective Devices for Electric Circuits, by making the metal parts which are joined of which, the following is a full, clear, conby the fusible metal small in mass, and heatcise, and exact description. insulating these parts from the surround- This invention relates to protective deing metal parts of the protective device and vices for electric circuits, and more particits mountings. ularly to heat coils for the protection of The several features of this invention telephone apparatus against abnormal curmay be more readily understood by referrents, which, although not of suflicient value ence to the accompanying drawing in which to operate the fuses, would, if allowed to there is shown a cross-sectional view of a flow, result in injury to the apparatus. preferred type of heat coil, wherein. 1 repn the type of heat coils commonly used, resents a pin of wood or other suitable heat it is the general practice to employ a metal insulating material having a recessed porpin as a switching member, this pin being tion in which a strip of metal foil 2 is fastened to a metal sleeve by means of low wrapped and priclcpunched to hold it in fusing solder, which is. softened through place. Surrounding this portion of the pin the medium of heat generated by abnormal is a thin metal tube or sleeve 3, preferably currents which flow through the heating of copper, one end of which is flared out or element. In still other types, parts of the flanged, as shown at 4, and a washer 5 of heat coils are soldered directly to the mountfiber or other non-heat-conducting material ing springs. However, in all of these types is placed over this tube and against the the parts joined by, the low fusing solder fiared-out portion. A second washer 6 of are of relatively generoussize, thereby refiber or other non heateonducting mate quiring that a considerable amount of heat rial is, placed against the flared-out end of be generated before these parts are raised the tube, and a metal band 7 is spun .over

to the temperature at which the solder be comes plastic. Not only is considerable heat taken up by these parts, due to their mass, but no provision is made for the heat insulation of these parts from the surrounding metal parts of the device itself or the mounting springs which act as additional conducting and radiating surfaces. It therefore becomes necessary to generate an amount of heat far in excess of that utilized for melting the solder, which in turn necessitates a' heating element of high resistance. The object of this invention is to provide a heat coil which will not'only be certain and reliable in its operation, but which will also be very efficient in o 'ieralion, thereby making it possible to decrease the resistance of the heating element. Since this heating element is placed directly in the line circuit, it highly important that its resistance be kept as low as possible, especially in the case of heat coils to be used on long and expensive toll lines.

To attain these objects thisinvcntion consists of improvements whereby the heat the washers to make them a unitary strucover the pin 1, and a drop of low melting solder 9 is inserted in the perforation 10 of the tube, which, when solidified, holds the pin and tube rigidly together. IA winding 11, preferably of a material having a high positive temperature coeflicient, is placed over the tube 3, one end being'first connected tothe metal band 7. The assembled pin and tube are then placed within the shell 12. which is of bakelite or other insulating material, and into one end of which is crimped a metal cap 13. The end of the pin extends into the hollow hub 14 of the metal cap 13, and is rigidly fastened by means of a crimping or staking operation. The assembly of the heat .coil is then completed by drawing the unfastencd end of the winding through a slot in the shell and soldering it to the cap 13.

As the method of inserting coils of the i of August 17, 1897, it is thought to be unnecessary to illustrate the method in the present case.

In service the heat coil is under spring pressure, and in case the solder is softened;

by abnormal currents in winding 11, relative movement is permitted between the pin 1 and the sleeve 3, allowing said pin to project farther through the sleeve, and in so doing, to ground the line in the well-known manner as illustrated by the patent herein before referred to. While the device shown is a preferred type, there are many modifications which might be made without in any way departing from the spirit of the invention. For example, under certain conditions, it might be preferable to employ a metal pin instead of one ofwood or other similar material. Such a construction would be slightly less efficient than that shown, since it would increase the massof-metal in the. device to be heated, but the construction nevertheless, would be such as to prevent any considerable amount of heat being con-. ducted away to the mounting springs. Again, where a pin of insulating material is used, instead of Wrapping a piece of metal foil in the recessed portion of the pin, it

might be found preferable to. resort to the use of a metal ring molded on the pin.

What is claimed is: 1. In a protective device for telephone cuits, a sleeve of heat-conducti1ig material,

a circuit controlling element extending through said sleeve, heat-softena'ble material for mechanically oining saidsleeve and said CIIOUItOOIItI'OIllIlg element, a heatgenerating element, terminals for said heatgeneratmg element, and means for normally insulating said sleeve from said terminals.

2. Irra protective device fortelephone cir- .cults, a sleeve of. heat-conductin material,

a cireuit-controlling element 0 non-conducting material extending through said sleeve, heat-softenable material for mechanically joining said sleeve and said circuit-controlling element, a heat-generating element, terminals Qfor said heatgenerating element, and means fornormally insulating said sleeve from said terminals.

3. In a protective device for telephone circuits, a sleeve of heat-conducting material,

a circilit-controllingelement of non-conduct ing material extending through said'sleeve and provided with a metallic section for attachment to said sleeve, and heat-softenable material for mechanically joining said sleeve and said circuit-controlling element.

4. In a protective device for telephone tachment to said sleeve, heat-softenable mamgsaid s eeve from said terminals.

for attachment to said sleeve, heat-softe'nable material for mechanicall joining said sleeve and said circuit-control ing element, a heat-generating element, terminals for said heat-generatin element, and means for insulating said 5 eeve from said terminals. v

5. In a protective device for telephone cirouits, a sleeve of heat-conducting material. a circuit-controlling element of non-conducting-material extending through said sleeve and provided with a metallic section for atterial for mechanically joining said sleeve and said circuitcontrolling element, aheatgenerating element composed of material having a high positive temperature coefficient, terminals for said heat-generating' ee element, and means for insulating said sleeve from said terminals.

6. In a protective device for telephone circuits, a shell of non-conducting material, a metal cap attached to one end of said shell, said cap being provided with a hollow hub into which extends a circuit-controlling element, a sleeve of heat-conducting material surrounding a portion of said circuit-controlling' element, heat softenable material for mechanically joining said sleeve and said circuit controlling element, a heat gen erating element, terminals for said heat generatin element, and means for insulat- 7. In a rotective device for telephone circuits, a sell of non-conducting material,

a metal cap attached to one end of' said shell, said cap being provided with a hollow." Hub, and a circuit-controlling element ex tending into said hub.

8. In a protective device for telephone circuits, a shell of non-conducting material, a metal cap attached to one end of said shell, said cap being provided with a hollow hub, and a circuit-controllin element of non-conducting material exten ing into saidihub;

9. In a protective device for telephone circuits, a sleeve of heat-conducting material having an outward extendin member 0 one end, a terminal band earrie by said sl eve, I and insulating means between said band nd said sleeve.

In witness whereof I hereunto subscri e my name this4th day of November A. 1916..

s LEWIS E. DICKINSON.

Images