US2009089A - Indicating plug fuse - Google Patents

Description

July 23, 1935. F. c. LA MAR INDICATING PLUG FUSE Filed Jan. 11, 1934 INVENTOR i ATTORNEY equal to that of a plug fuse in those situations.

Patented July 23, 1935 UNITED STATES PATENT OFFICE mmcarmo PLUG'FUSE Frank 0. La Mar, New York, is. r. Application January 11,1934, Serial No. 706,171 6 Claims. (Cl. 200-121) well known form of thermal fuse is that known as a "plug fuse", Ordinary plug fuses consist, generally, of an insulating body having twoterminals on the outside thereof, so constructed and arranged as to be readily broughtin contact with the terminals of an electrical circuit, by way of what is known usually as afuse block. These fuses are \miversally used: are made by many different. manufacturers; and must all be usable in practically any of the well known forms of fuse blocks; so that they have become, in truth, standard, and may well be referred to as, standard fuse plugs. At any rate they are substantially standard as regards their general external dimensions.

Various forms of plug fuses have been made, especiallyfor the purpose of enabling one to quickly discern whether or not the fusible or thermal element 'is intact. It is quite the universal impression that success has not been fully attained in regard to the feature of indicating the integrity of the fusible element.

A principal object of applicant's invention is to provide a device, which may well be called a combined fuse and fuse integrity indicating device. In providing'such a device, applicant has had in mind that it preferably should be in external dimensions substantially'the size of the standard plug fuse, so that it may be used with a facility where a plug fuse is now used.

A further object which applicant has in mind in producing his combined fuse and fuse integrity indicator is that the cost must be reduced to a point where, if possible, it approximates the present cost of ordinary plug fuses. To this end, applicant has, as a further object of his invention, the production of a device in two parts, separable one' from the other, one part supporting and protecting the thermal element, which part is removable, and the other part performing the indicating functions desired by applicant,

"and combinable with the first part to make a complete indicating fuse part.

A further object of applicant's invention is to produce a combined fuse and fuse integrity indicator which will have substantially the same ex- 5 ternal dimensions as a standard plug fuse.

Other objects and advantages will appear as the description of the particular physical embodiments selected to illustrate the invention progresses, and the novel features will be par- 16 ticularly pointed out in the appended claims.

In describing the invention in detail and the particular physical embodiments selected to illus- 4 trate the invention, reference will be had to the accompanying drawing and the several views 15 thereon, in which like characters of reference designate like parts throughout the several views, and in which:

Figure 1 is a cross-sectional view of a plug fuse embodying applicant's invention; Fig. 2 is a 20 top plan view of the device as shown by Fig. i; Fig. 3 is a cross-sectional view of the device as shown by Fig. 1 on the plane indicated by the line III-III viewed in the direction of the arrows at the ends of the line; Fig. 4 is a cross-sectional view of the device as shown by Fig. l on the plane indicated by the line IV--IV of Fig. I, viewed in the direction of the arrows at the ends of the line; Fig. 5 is an elevational view of the indicator portion of applicant's combined fuse and fuse integrity indicator, with some parts broken away to more clearly show the construction.

Figure 1, broadly considered, shows a combined plug fuse and fuse integrity indicator having as essential parts the usual end contact terminal I; the screw threaded shell terminal 2; and a thermal fusible element 3 connecting terminal I and screw thread shell 2. These parts are comparable with and constitute the principal parts of the usual and ordinary fusible plug. In addition to the plug portion there is an indicator portion which broadly includes a gaseous discharge lamp 4, preferablyof the neon filled type, having one terminal 5 connected to the contact terminal I and the other terminal connected, through a high ohmic resistance 6, to an electrical conducting rod 1 electrically connecting to screw shell 2. A construction such as has been described serves all of the functions of the ordinary plug fuse and in addition operates to indicate the integrity of the fusible element 3 because when that element is intact the lamp 4 is not illuminated, but when the thermal element 3 is destroyed then the lamp 4 is illuminated indicating the destruction of the fusible element 3.

andl2' which cooperate with the disc 8 to retain it in place.

In order to separate the lamp 4 from the interior of the fuse plug within which the fusible element 3 is positioned, applicant provides an interior cylindrical tube 13 which has an internal diameter corresponding with the diameter of the upper opening H of the body8 and has anexternal diameter such that it just fits within the bore l5 which is slightly larger than-the opening H of the body 8.. p I

Applicant provides a closure for IS thereover which fits {tightly against the wall of the cylindrical tube ,andis preferably provided with a depending'bulge I! for a purpose .to be" hereinafter'described,

Applicant provides an indicating carrier" designated as awhole by C. This carrieris pref erablyformed in two parts 18 'arid'lS divided designated 22. The arms 2| and 22 rest one within the other so that. the top surface of 2l,is one continuous unbrokenline. and the bottom surface of the two is one continuous unbroken line. J

members together, applicant prefers to use a me-.

tallic-band- 23 at the upper portion, which although, perhaps not absolutely necessary, is desirable, and a metallic cap 24 at the lower portion.

This metallic cap 24 fits tightly around the interfitted hollow semi-cylindrical members and is provided with anorifice 25 for'the passage therethrough of one lead 5 of the lamp 4.

Thelead 26 of the lamp 4 is preferablycarried up and alongside of the lamp 4 and then connected to one terminal of the resistance 8. This resistance 6 is of the grid leak type and where appllcants device is to be used on 110 volt circuits is of the order of about 50,000 ohms resistance. The other terminal of the resistance} is connected by the conductor 21 to the metallicrod 1.

Metallic rod 1 is positioned, preferably, by

. moulding in the arm 22 ofthe hollow semi-cylinder member is and is positioned to pass down through a bore 215 formed in the body 8 so that its lower preferably scarfed or'pointed end 28 may contact with the metallic screw threaded shell 2. The assembly of the device is accomplished by first soldering one end of the fusible member 3 in the terminal I and at the same time soldering the bulge H of the metallic cap Hi of the cylindrical tube l3 to the same terminal. The disc 9 carrying with it the associated parts is then put in place, as shown by Fig. v1, with one end of the fusible link 3 passing through an orifice 28 and positioned to contact withscrew threaded shell..

2, and the upper end of the cylindrical tube I3 I the lower end. .of the cylinder tube 13 by placing a metallic cap ti'on. along the, plane indicatedi byfl ine 2i) and each being for. a. greater portion of its length'substan tially the half of a hollow cylinder so thatvappli-j cant calls the. members hollow l,.s'eml-.cylindrical.' Each of the mernbers-ld and lllhas outstanding arms at its upper. portion that attached to [8'1 being designated 2| and that attached tojdbeing seating in the bore I5, whereupon the screw thread shell 2 is screwed onto the body 0 and holds all parts in proper position.

In order to assemble the indicator carrier C the lamp 4 has one terminal thereof, 5, passed through the orifice 25 in the cap 24 and a drop of solder applied, then the other terminal is connected to a resistance 6 which in turn is connected to rod 1, after which the two portions of the carrier are placed together as shown in Fig. 1 with the band 23 slipped up over them and the cap 24 placed over; their lower'ends, the resistance 6 resting in "a cavity formed therefor.

The carrier C is positioned by inserting it in the orifice it while the rod 1 is inserted in the bore 21' after which it is forced home, as shown by Fig. 1, with the small drop of solder 30 resting in the bulge ll of the metallic cap it and the rod plug formed exactly asis the bodyt with its associat'edpar'ts Although I have particularly'descrlbed'one particularjphysicalembod'iment ofj'rny lnventiouand explained the operation, construction and princi- 'ple thereof,nevertheless, I desire to have'itunderstood that the form ,selectedismerely illustrative,

but does notexhaust the possible P ysical embodimer ts of theideaof means underlying jmy invenn attain new a nd a'essas m ters BatentfoftheUnited States, is; j ln a s'eiha ine in omb n on an Outer "cylindrical screwjthreaded metallicshell fcbntact; a metallic contact positioned axially 'of the shell;

a1 t mal elemen rmet 'e h 'tbnta'cts: a lam a s't 'o te'rm na sim w p ortin and rnt sm inemgrfand. s ns we a w h fitsilongitddirfifl axis axially pfthe metallic shell, fsaidmean's removable ,bodily'and including means I A for]forming eleetrical connections to the con- .In order to hold the hollow semi-cylindrical .tac't's, said last fmentioned means including a rod carried by the lampsupporting means position to make contactwith'the screw threaded "metalli shell. I

metallic contact closing one end'of the hollow body; a cylindrical'tube within the hollow body, .one end of thetube fitting within a bore of the hollow body of greater diameter than the 'end opening of the hollow body, the other end of the cylindrical tube being provided with a metallic cap embracing a portion of the outer surface of the cylindrical tube and being soldered together with one end of a. fusible element to the centraliy disposed contact of the disc, the other end of the fusible element being carried through an orifice in the body and positioned against the outside periphery of the-body; and a screw threaded shell adapted to cooperate with the screw threads of the body and provided with means for holding the discin place.- i a 3. As a plug portion of a combined fusible plug and indicator,. thecombination of a hollow substantially cylindrical body provided with an internal wall supporting and defining, from the remainder of thespace within the hollow body, a space'communicating with one openend of thehollow body; a fusible link positioned within the said remaining space; means for closing the other open 75 end of the cylindrical body, a substantially central metallic terminal carried by the said means for closing; a metallic shell surrounding a portion of the outside of the hollow body; and a fusible link connecting the shell and the metallic terminal.

4. As an indicator lamp carrier of a combined fuse and fuse integrity indicator, in combination: two substantially semi-cylindrical members; means for holding said members together to substantially form a tube closed at one end; each of said members bearing an arm interfitting with an arm of the other member; a metallic rod attached to one of said arms and depending therefrom so positioned that when the combined semicylindrical portions are positioned centrally of a plug fuse the depending arm will be positioned to pass through a bore of the plugfuse and contact the ordinary screw shell on the outer periphery thereof; and an indicator lamp having a resistance in series therewith connected between the said rod and the metallic holding means closing one end of the assembled semi-cylindrical mem-- bers.

5. An indicating plug fuse of substantially standard contour and over-all dimensions, having in combination; a hollow body of insulating material; an outer cylindrical threaded metallic shell contact; an exterior metallic contact positioned axially of the body, and having a contact portion extending within said body; a thermal element connecting the contacts; a fuse integrity indicating lamp including an evacuated shell having two terminals; and means supporting and enclosing the lamp and provided with contacts for engagement with portions of said plug contacts when said lamp and its supporting means are assembled with said plug; said lamp contacts including means positioned to make contact with the interior of the screw threaded metallic contact.

6. An indicating plug fuse of substantially standard contour and over-all dimensions, having in combination; a hollow body of insulating material; an outer cylindrical threaded metallic shell contact; an exterior metallic contact positioned axially of the body, and having a contact portion extending within said body; a thermal element connecting the contacts; and having its most readily fusible portion confined within said hollow body; a. fuse-integrity-indicating lamp having two terminals; and means supporting and enclosing the lamp and provided with contacts for engagement with portions of said plug contacts when said lamp and its supporting means are assembled with said plug; said lamp contacts including a rod positioned to make contact with the interior of the screw threaded metallic contact, said lamp-support, lamp and lamp contacts being removable bodily from said plug, by a right line movement of said lamp support.

FRANK C. LA MAR.

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