US1957546A - Indicating plug fuse - Google Patents

Description

May '3, 1934. F. c, LA MAR 1,957,546

INDICATING PLUG FUSE Filed Feb. 19, 1932 I Patented May 8, j

UNITED STATES PATENT OFF-ICE.

INDICATING PLUG FUSE Frank G. La Mar, New York, N. Y.

Application February 19, 1932, Serial No. 594,024

Claims. (Cl. 200-121 Thisinvention relates to electrical devices, parproduce a combined fuse and fuse integrity inticularly to thermal fuses for use in connection dicator which will be substantially the same exwith electrical circuits, and more especially to temel dimensions as B- t derd D 18 what is known as a plug fuse, combined with Other objects and advantages will pp 88 5 means for indicating the integrity of the fusible the description of the particular physical em- 60 element. bodiments selected to illustrate the invention It is quite universally known that it is necesprogresses, and the novel features will be parsary to protect electrical circuits by means of deticularly pointed out in the appended claims. vices, such as thermal fuses, which melt or be- In describing the invention in detail and the come disintegrated or destroyed when an exces- Particular Physical embOdiments s c ed to 11- 65 sive flow of current passes through the circuit of lustrate the invention, reference will be had to which the fuse forms a part. An especially well the accompanying drawing and the several views known form of thermal fuse is that known as thereon, in which like characters of reference plug fuses". Ordinary plug fuses consist, gendesignate like parts throughout the several views, erally, of an insulating body having two terand in which: 70

minals on the outside thereof so constructed and Figure l is a top plan view of a device embodyarranged as to be readily brought in contact with ins appli an s inv n ion of a combined fuse and the terminals of an electrical circuit, by way of fuse integrity indicator; Fig. 2 is an elevational what is known usually as a fuse block. These v w e de e as s own by Fig. 1; Fig. 3 is fuses are so universally used, and are made by a top plan view of applicant's device, as shown 76 so many different manufacturers, and must all .by 1. t wi h the p le indicating 9 be usable in practically any of the well known tion removed; Fi 4 is a p P w 0 h forms of fuseblock, that they have become, in separabl indicating p r of pp nt's intruth, standard, so that they may well be revention with the top cover removed; Fig. 5 is an ferred to as, standard, fuse plugs. At any rate enlarged elevational cross-sectional view of the 80 they are substantially standard as regards their device a h wn by Fi 2; Fi 6 is n enlar ed v} I general external dimensions, elevational cross-sectional view of the device as various forms of plugfuses have been made, Shown by taken on a p a at a ri h angle especially for the purpose of enabling one to t th pla up n whi h Fi 5 is ta n; 7 is rapidly discern whether or not the fusible or an vet al View, P y in 566151011, 0f mpdithermal element is intact. It is quite the univerfied 0 0f pp b ned fuse and fuse sal impression that success has not been attained integrity indicator; Fig. 8 is an elevational crossin regard to the feature of indicating the insectional view of another modified form embodytegrity of the fusible element. ing applicant's invention of a-combined fuse and 35 A principal object of applicant's invention is fuse integrity indicator; Fig. 9 is a fragmentary to provide a device, which may well be called a elevational view illustrating the parts of a porcombined fuse and fuse integrity indicating detion of the device, as shownby Fig. 8. as viewed vice. In providing such a device, applicant has from either side thereof as shownin Fig. 8; 10 had in mind that it preferably should be in exis an elevational cross-sectional view of another 40 ternal dimensions substantially the size of the modified form of device embodying applicants standard plug fuse, so that it may be used with invention; Fig. 11 is an elevational cross-sectional a facility equal to that of a plug fuse in those view of the device as shown by Fig. .10, but taken situations where a plug fuse is now used. upon a plane at a right angle to the plane upon A further object which applicant has in mind which the view, Fig. 10, is taken.

45 in producing his combined fuse and fuse integrity The parts corresponding to the parts of the indicator is that the cost must be reduced to a ordinary standard plug fuse are well illustrated point where, if possible, it approximates the by Figs. 2 and 5. Just as in the device illustrated present cost of ordinary plug fuses. To this in Figs. 2 and 5, the ordinary plug fuse includes end, applicant has, as a further object of his 'abody of insulating material, generally hollow, 1;

invention, the production of a device in two parts, a, threaded metallic shell or terminal 2 attached separable one from the other, one part performto the body; a metallic button or terminal 3; a ing the functions now performed by the ordinary metallic conductor 4 and a metallic conductor 5, plugfuse, and the otherpart performing the inone in electrical contact with the terminal 3, and dicating functions desired by applicant. the other in electrical contact with the threaded 55 A further object of applicant's invention is to shell terminal 2, both of which at some portion mal element 8 connecting the members 4 and 5 at the points 6 and 7 respectively. All of the parts hereinbefore described, arranged substantially as shown, are common and ordinarily found in the ordinary standard plug fuse. The ordinary standard plug fuse includes an enlarged portion 9 forming the manually manipulative portion of the plug fuse, by which it is grasped when it is screwed into a fuse block for insertion in an electrical circuit.

Applicants device contains not only all of the parts as hereinbefore described, but in addition has the metallic contact members 10 andll positioned at the open upper end of the plug and connected electrically respectively with the conducting members 4 and 5. Applicant's device contains a shield 12, preferably of insulating material, such as isinglass or mica, held removably in place by the spring ring 13 positioned in a groove of the body. The ordinary standard plug also includes a shield corresponding to applicant's shield 12, although it is generally placed in a diflerent position, but functions substantially as applicants shields function, that is, it prevents molten metal or extremely hot vapor from being projected without the hollow. of the body 1 when the fusible or thermal element 8 is destroyed by an excessive flow of current.

A device embodying all of the parts hereinbefore described. would constitute an efficient and practicable plug fuse and could be so used, but in order to ez'hibit applicants invention, there must be a-fuse integrity indicating means in addition.

The fuse integrity indicating means of appplicant may be of various kinds, but applicant prefers an electric lamp 14, and preferably a dis tinctive indication lamp, such for instance, as a neon filled lamp, or the glow type, operated by an electrical discharge within the lamp, so that when lighted it will give an arrestive indication even in the presense of white or yellow light as commonly used for illumination. The electric lamp, whatever its form, will generally and preferably have two terminals as 15 and 16. These terminals will be electrically and mechanically connectedto metallic prongs as 17 and 18 through a resistor 35 of suitable value and form, such, for instance, as the well known grid leak type. The prongs 17 and 18 will be so formed that they are adapted to cooperate with the metallic contact members 10 and 11, that is, the prongs 17 and 18 will make mechanical and electrical contact with metallic contacts 10 and 11 so that thereby the lamp 14 is in a shunt circuit to the thermal element 8.

Applicant prefers to mount the lamp 14 and the metallic prongs, as 17 and 18, in a hollow disc like structure 19. This structure is made of insulating material and has a substantially fiat surface 20 with apertures, as 21, therein so that the light from lamp 14 may shine therethrough.

" The bottom 22 of the disc 19 is formed of a portion of insulating material cemented or otherwise properly attached to the annulus 19 of the disc and supports, mechanically, in separated position, the metallic prongs, as 17 and 18. The hollow disc 19 is preferably made of such dimension, vertically, as shown in Fig. 5, that it adds a minimum to the total length of the plug, at

any rate it does not add an amount sufiicient to ordinarily prevent the combined device from being used in those positions where an ordinary standard plug fuse now may be used.

As some strain may be put upon disc 19 in turning the plug into its socket, applicant has provided that the disc 19 shall fit into an oval depression 23 of the hollow body 1. The wall of this oval depression supports the disc 19 so that if strain is placed thereon, the prongs l7 and 18 will not be obliged to stand the strain.

In Fig. 7 applicant has shown a modification, in that the separable indicating portion 24 is made in the form of a tube within which is positioned the lamp 14, and to the metallic ends 25 and 26 to which are connected the terminals 15 and 16 of the lamp. The metallic end pieces 25 and 26 are attached to metallic prongs 17 and 18, just as are shown in Fig. 5, and these prongs function exactly as do the prongs of Fig. 6. In order to prevent strain upon the prongs l7 and 18, in the form as shown by Fig. 7, applicant places the tube 24in a slight recess of the both! 28, corresponding approximately in function to the recess 23 of body 1 of Fig. 1.

In Fig. 8, applicant has shown a further modified form of the device embodying his invention. In this form the disc 19 is let into the tube of the body portion 29 corresponding to the body portion 1 of Fig. 2 to such an extent that the top of the disc 19 is flush with the top of the body 29. Applicant illustrates nail spaces 30 and 31 for the insertion of the nail of the finger for the purpose of removing the disc 19.

In Figs. 10 and 11, applicant has illustrated a further modified form of the invention. In this form the body portion is formed in two parts, a lower part 31 and an upper part 32, the combined length being that of the standard plug fuse,-

the separation being made along the line 33.

In the form as shown by Figs. 10 and 11, the portion 32 corresponding with the disc 19 of Fig. 5 has a cover portion 20 which is held in place by a spring ring 34, thereby enabling one to more readily get to the lamp 14.

From the hereinbefore given description, it will be seen that applicant has provided a combined fuse and fuse integrity indicator formed of two separable parts, one of which corresponds with and is capable of performing all of the functions of the ordinary standard plug fuse, the other of which combined with the first mentioned part serves to indicate the integrity of the thermal element proper, in that when the thermal element proper is destroyed the indicating means will show such facts by the lighting of a lamp.

It is further apparent that all forms of applicants combined device are such that each has an over-all lengtlnot too great to successfully allow the use in those positions in which the ordinary standard fuse is now used, if one bears in mind, that in practically all cases, some slight allowance is made between the end of an ordinary standard plug fuse block and the cover ordinarily used to protect it.

It is further seen that some of applicants forms,

originally and previously used may be combined with the new thermal element portion.

Although I have particularly described several particular physical embodiments of my invention and explained the operation, construction and principle thereof, nevertheless, I desire to have it understood that the forms selected are merely illustrative, but do not exhaust the possible physical embodiments of the idea of means underlying my invention.

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

1. In a plug fuse, in combination: an insulating hollow body; two terminals on the outside of the body for cooperation with terminals of an electrical circuit to be protected; two combined conducting and mechanical connecting members,

each connected electrically to one of the terminals, at least, partially exposed within the body; a thermal element connecting said two conducting members; said conducting members forming contact terminals for cooperation with the contact terminals of a separable thermal element integrity indicator; 8. thermal element integrity indicator and mechanical connecting means for attaching the integrity indicator to the hollow body cooperating with the said two combined conducting and mechanical connecting members.-

2. A combined thermal fuse and fuse integrity indicator consisting of a plug portion and a separable indicating portion; the plug portion comprising an insulating body provided with two terminals for cooperation with terminals of an electrical circuit to be protected, 8. thermal portion connecting the first mentioned terminals, and two combined metallic electrical and mechanically attaching contacts, one connected to each of the first mentioned terminals; the separable indicating portion including an indicating electric lamp provided with two terminals and two combined metallic electrical and mechanically attaching members, one connected to each of the lamp terminals, for attaching the indicating portion to the plug portion mechanically and electrically connecting the metallic contacts of the plug portion to the metallic members of the indicating portion and a housing for the lamp formed substantially as a hollow disc with observation slits therein.

3. A combined'thennal fuse and fuse integrity indicator consisting of a plug portion and a sepa rable indicating portion; the plug portion comprising an insulating body provided with two terminals for cooperation with terminals of an electrical circuit to be protected; a thermal portwo metallic contacts, one connected to each of the first mentioned terminals; the separable indicating portion including a distinctive indication indicating electric lamp provided with two terminals and two metallic members, one connected to each of the lamp terminals, for attaching the indicating portion to the plug portion and electrically connecting the metallic contacts of the plug portion to the metallic members of the indicating portion and substantially a hollow disc formed with observation slits for housing the lamp.

4. A combined fuse and fuse integrity indicator formed of two separable parts; one part having substantially the form and shape of the lower one half terminal end of a standard plug fuse and supporting and containing terminals and a thermal element connecting the terminals and in addition two metallic contacts adjacent the open end; and theother portion corresponding to the upper or manually grasping and manipulating half, separable from the other half, and supporting and containing an indicating lamp having metallic members connected to the terminals thereof for contact with the metallic contacts carried by the other half whereby the whole may be used and positioned for use in the same manner as an ordinary plug fuse but when the thermal element of the fuse becomes destroyed the lamp will light and when renewal of the thermal element is accomplished the original separable indicating lamp portion is used therewith.

5. A fuse integrity indicator formed substantially as a hollow disc with apertures open ng in one flat surface; an indicating lamp provided with terminals within the hollow of the disc; and two separated metallic prongs projecting from the substantially fiat surface of the disc opposite the surface in which the apertures are formed, one of the metallic prongs being connected to one terminal of the lamp, and the other prong being connected to the other terminal of the lamp, said prongs adapted to contact and make electrical connection with the ends of a fusible element of an electrical circuit thereby placing the lamp in shunt to said fusible element whereby upon the destruction of the fusible element the lamp will be lighted to indicate the disruption of the fusible element.

FRANK C. LA MAB;

tion connecting the first mentioned terminals, and

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