US 821873 A
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PATBNTBDMAYQQ, 190e. 0. o. HOFFMANN. ELECTRIC FUSE, APPLICATION FILED APB. 25, 1904.
'UWE/WOR ma c NITED sTATEs FATENT OFFICE. f
CORPORATION OF NEW YORK.
OTTO c. HOFFMANN. OF BUFFALO, NEW YoEnAssrcNoF 'ro-THE FUsE WIRE a MANUFAOTUEING COMPANY, OF BUFFALO, NEW YORK,
Patented May 29, 1906.
Application led April 2.5, 1904- Serial No. 204,707. 'I v To all whom it may concern:
Beit known that I, O'r'ro C. HOFFMANN, a citizen of the UnitedStates, residing at Buffalo, inthe county of Eriev and State of New York, have invented new and useful Improvements in Electric Fuses, of which the followin is a specification. i
y invention'relates to fusesfor electrical circuits; and it relates more particularly to that portion of the fuse which is employed as an indicator and also to the form and design of the fuse thus employed, together with its location and surroundings, all of which coperate to bring about a esirable function in connection with the articleas a'whole.
It also consists in a new article of manufacture in which there' is associated with the main fuse an auxiliary fuse havin peculiarities and structure herein speciie and particularly pointed out in the claims forming a part hereof, the same beirg illustrated in the drawings, in which- A Figure 'l is a longitudinal section of the fuse. Fig. Z is an alternate form of the fuse;
Fig. 3, one view of the indicator; Figs. 4 andA 5, details of the indicating-fuse.
Like letters indicate similarparts ,throughout.
Referring now\ to the drawings, We lobserve that terminals T T (shown in Fig. 1 in the form of blocks and in Fi 2 in the form of metallic'caps) are suitab y supported uponan insulating material A andmay be protect- ,ed by a coverin preferably of insulating material, or shie d a. These terminals are electrically connected by a plurality of fusible conductors which traverse two paths in connecting the terminals, one or more passing practically in a straight line, as seen at B, Whereas another, and preferably one of less conductivity, C, passes to theexterior ofthe shield or case a, for a short distance of its vfor the? further length. At the point where the conductor C passes to the exterior of the case, the case is preferably de ressed at this point, as indicated at I), fr the etter protection of the fuse and purpose of better providing a backgroun for the fuse, which may be colored to contrast not only with the case a itself, but with the color of the fuse C. It will be further observed that this fuse C may consist of a small cylindrical wire, as shown in Fig. 4, which has'been flattened out or otherwise deformed at a predetermined point, (indicated by e,) and this deformation f is carried to such an extent as to actually reduce the sectional area at this point. It has been found in practice that even this reduction of sectional area' must be carried suffi-A ciently far so that the extra radiating-surface provided in increase of surface will be overcome and the fuse will blow or rupture along this particular section of the wire e.
As a matter of fact this conductor C will perform all its functions vif it is simply the merest hair-like conductor, and it is four d preferable to make it of very slight conductivity, inasmuch as such conductor will at once eliminate all necessary recalibration of the .standard fuses B; but the difficulty arises that it cannot be seen orreadily detected', and therefore is almost useless as an indicator. Such conductors have heretofore been employed, but rendered practical only when em loyed in connection 'with some combustib e or ex losive substance which it is desired to avoi especially in any device designed to 'protect a ainst fire loss, as is the case with the inc osed fuse. To avoid the use of these combustibles or explosives, I have discovered that an extremely-small conductor, not much Alarger than a hair, may be employed and the wire rendered visible by the mere act of Hattening it out to a degreewhich will insureits rupture and fusing at this particular point, as illustrated at e in the figures. To render its action more certain and to be 'able to detect the indicator more readily, it is found expledient to place it within the depression,
as been explained,'providing the surface of the depression with a color which may be of firep roof material and a backing which will discolor upon the normal rupture or blowing of the fuse, and to still further increase this protective factor, as well as the discoloration due to blowing, it is found that a varnish of a suitable material will still further increase the discoloration. It will render the parts more observable through the magnifying effect and trans arent qualities of the varnish, this lat ter e ect being one similar to the magnifying of the mercury column Within a thermometer.
Among such Varnishes may be lnentioned the cellulosic lac uers and tie gums, such as transparent ellac. .'.llhe Varnish also acts as acernent to tightly hold the indicating- 9CIA i oo
fuse in position. In Figs. 1 and 2 it will be Y observed that the main conductor or conductors B is shorter than the entirelength between the terminals T and that avsupplenientary conductor B/ Bis employed t'o com-. plete the circuit. While it is true that this conductor is of larger area than B, it will be seen at the same time it is of larger crosssec tion, and therefore a better conductor, where .as the enlarged area e'of the conductor C is one which produces a small cross-section and is therefore of less conductivity.
Having thus described the invention, its loperation will be apparent from the previous statement.
The function of the indicator-conductor C is to give the indication, which in this instance is visual, that the main conductor or conductors B have been destroyed or opencircuitcd. The visual indication in the present instance consists not only of the rupture and destruction of the part e of the conductor O, but supplementary to this act and brought into existence thereby is a very considerable discoloration of the backing and surrounding surface l), the combined action being such as to bring about a condition instantly observable at a distance and one found in practice to be extremely satisfactory.
' It is not intended that this invention should. be limited to the exact details illus-r` trated and described, as equivalent and other devices may be used to 'fulfil the functions.
It is further understood, While the details may be employed 'in substantially the relation indicated, that some of the parts may be omitted and the remaining ones employed either alone or with natural and operative substitution for those omitted, and the invention extends to such use.
1. A fuse for electric circuits consisting of an integral cylindrical conductor flattened to a thin sheet-lile section and thus presenting the greatest area at its fusing-point.
an integral conductor presenting the greatest area and a thinner section ata predetermined y oint along its length which is to become yits using-point. f I
3. A fuse for electric circuits consisting of an integral cylindrical conductor presenting the greatest area and the smallest cross-section at a predetermined point along its length which is to become its fusing-point- 4. In an inclosed fuse, a casing, an indicator for the fuse consisting of a fine difficultly-visible wire attened and reatly extended as Vto area so as to be visib e at a pre-` determined point in' its length, and a depression extending partially through the wall of the casing in which the indicator lies, for the purpose set forth.
5. In an inclosed fuse an indicator consist-l ing of a fusible conductor of small size passing from themterior to the exterior ofthe n- `closure flattened so as to be visible at a point outside the inclosure, and a backing for the fuse depressed below the general surface of i the surrounding material against which the attened part lies, the walls of the depression of different color than the surroundings.
` 6.. In an inclosed fuse .an indicator. consisting of a fusible conductor of small size flattened so as to be visible at a predetermined oint in its length, a backing for the fuse, 'the use lying upon the` backing and a varnish for coverin the fuse.
7. In an lnclosed fuse an indicator consisting of a fusible conductor of small size, a discolorable backing, the fusel lying. upon the backing and a discolorable varnish covering the fuse. l
In testimony whereof I have hereunto set my hand in presence of two subscribing witnesses.
' OTTO C. HOFFMANN. 'fi/Vitnesses: ,v
A. N. MACNABB, LEWIS SHIPMAN.'