US2695348A - Indicating current limiter with particle-filled body - Google Patents

Description

Nov. 23, 1954 IJF. MATTHYSSE EIAL 2,695,348

INDICATING CURRENT LIMITER WITH PARTICLE-FILLED BODY Filed April 15, 1953 United States Patent Ofiiice 2,695,348 Patented Nov. 23, 1954 INDICATING CURRENT LIMITER WITH PARTICLE-FILLED BODY Irving F. Matthysse, Norwalk, Conn., and Leonard Greer, Bogota, N. J., assignors to Burndy Engineering Co., Inc., a corporation of New York Application April 15, 1953, Serial No. 349,070 4 Claims. (Cl. 200-121) Our invention rel-ates to current limiters and more particularly to a current interrupting device having visible indication of its condition.

Objects of our invention are to provide a lightweight airtight, accurate limiter for aircraft adapted to withstand increased generator capacities and voltages used in present day aircraft without danger of explosion occurring during the interruption, and which will give a positive and easily visible indication of its condition.

These and other objects we accomplsh and obtain our new results as will be apparent from the device described in the following specification, particularly pointed out in the claims, and illustrated in the accompanying drawings, in which- Fig. l is a plan view, partly in section, of an embodiment of our indicating current limiter;

Fig. 2 is a side elevation thereof;

Fig. 3 is a cross-sectional view taken in the plane 3-3 of Fig. 2;

Fig. 4 is an end view of our device.

Fig. 5 is a perspective view of the indicator.

Our device comprises a glass tubular enclosure mounted to a pair of knobs 12 provided with finger shields 14, a pair of contact blades 16 and 18, a fusible element 20, and are suppressing means 22.

The glass enclosure which may be made of Pyrex, is capable of withstanding differential temperature conditions and shock without breakage. The knobs are made of insulating material, such as a phenolic resin having shield portions overhanging the blades, so as to prevent contact therewith during installation or removal. The knobs are recessed as at 24 and 26 forming sockets to receive the ends of the glass. The fusible element is usually made of silver wire brazed to the copper blades which support the element substantially centrally of the glass tube.

tion of the limiter from being ascertained. In order to permit such inspection, we provide an indicator link 28,

and the glass envelope. A cross-shaped link with centrally extending portions 30 aids in positioning and supporting the link on the inner surface of the glass envelope.

The silver fusible element being more conductive will carry most of the current. When interrupted centrally within the sand filling, the current will be bypassed to the Nichrome Wire which normally carries a small fraction of the main load. When the Nichrome link on the inner surface is interrupted, it will be readily apparent to the observer.

All the joints are fully sealed with cement 32 to prevent leakage, which permits the limiters to be used by aircraft at various heights with uniform limiter ratings.

For a readily discernible inspection of the condition of the fuse, a brght color changing paint is used which will discolor noticeably when the fuse is blown. An example of such indicating paint is identifiable on the open market as Pyromark, a trade product of the Tempil Corporation of New Jersey.

We have thus described our invention, but we desire it understood that it is not confined to the particular forms or uses shown and described, merely illustrative, ried out in other ways without departing from the spirit of our invention, and, therefore, we claim broadly the right to employ all equivalent instrumentalities coming within the scope of the appended claims, and by means of which objects of our invention are attained and new results accomplished, as it is obvious that the particular embodiments herein shown and described are only some of the many that can be employed to attain these objects and accomplish these results.

We claim:

1. A current limiter having a fusible element, a transparent envelope body therefor, and contacts extending therefrom, said envelope containing an inert substance enclosing the fusible element for absorbing the molten fuse particles when the circuit is interrupted, said fusible element having a parallel circuit of high resistance metal contained Within the envelope body and extending toward the inner surface of the envelope body and barrier means for preventing the inert substance from enter- References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 737,280 Sachs Aug. 25, 1903 1,443,136 La Mar Jan. 23, 1923 1,868,464 La Mar July 19, 1932 2,490,950 Dryer Dec. 13, 1949

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