US2613297A - Lag fuse - Google Patents

Description

Oct. 7, 1952 G. F. LAING LAG FUSE Filed Oct. 25, 1950 mm Q QN mm mm m 4 mfl M E Q Q m wy QM WMMM @NQN MN Patented Oct. 7, 1952 LAG FUSE,

Gordon F. Laing, Delavan, Wis., 'assignor to Economy Fuse and Manufacturing 00., Chicago, 111., a corporation of Illinois Application October 23, 1950, Serial No. 191,627

The present invention relates to improvements in lag fuses.

More particularly, the present invention relates to the type of electric fuse which will open an electric circuit promptly upon a high surge of current, such, for example, as accompanies a short circuit,.:but will delay the opening of the electric circuit for predetermined periods upon moderate overloads such as those frequently encountered in motor. starting operations.

Though a preferred embodiment of the present invention has been illustrated in a non-renewable fuse of the ferruletype, it will be understood as the description proceed-s that th ..invention is equally applicable to other types of fuse.

An object of the present invention is to provide a lag fuse which is dependable in protecting an electric circuit under conditions approximating short circuit, but will delay for predeterminable longperiods the opening of the circuit upon moderate overloads.

A further object is to provide a lagfuse of the type just referred to which is relatively simple to manufacture and dependable in service,

A further object is to provide a lag fuse of a relatively high heat capacity whereby moderate overloads may be carried for prolonged periods of time with assurance that the circuit will be openedwhen a predetermined product of overload and time factors has been reached.

A further object is to provide a lag fuse Well adapted tomeet the needs of ordinary service.

Other'objects will appear as the description proceeds.

Referring to the drawings- Figure l is a longitudinal sectional view illustrating a preferred embodiment of the present invention, the parts being shown in current passing relationship with one another; and

Figure 2 is a view similar to Figure l, but showing the parts located in positions they will assume when the fuse has operated to break the circuit after the lapse of a predetermined period of overload.

The numeral l indicates a tube which according to usual practice may be composed of fiber or the like. Located at the two ends of the tube It are the ferrules II and l2, which are cup-shaped members closely receiving the ends of the tube It. Said ferrules l l and I2 are slotted in their bottom portions to receive extremities of fuse links to be referred to presently. Said extremities of said fuse links are soldered or otherwise electrlcally connected to said ferrules I l and l2.

5 Claims. (Cl. zoo-12s) Located within the tube It is a fuse assembly indicated as a whole by the numeral I3; Said fuse assembly I3 is composed essentially of the slugheat reservoir 14, the tubular heat reservoir l5, the plunger reservoir [6, portions of low melt ing point eutectic solder Zita and 2% connecting said reservoirs l4 and i5 and said reservoirs l6 and i5, respectively, the spring l1 and the fuse links H 8 and it, which fuselinks comprise heating members for said reservoirs and said portions of solder. The fuse links it and 19 are electrically and mechanically united to the slug heat reserwith restricted portions It and 2|, respectively,

or a plurality of such restricted portions, according to usual practice.

=Located upon and fitting the fuse links [8 and 19, respectively, are fiber washers 22 and 23, which fiber w'asherstogether with the two ferrules H. and I2 provide chambers 24 and 25, respectively, at the two ends of the fuse for receiving quenching powder. Between the two washers 22 and 23 is the chamber 25 receiving the slug heat reservoir 14, the plunger'reservoir IS, the tubular reservoir l5, together with the spring l1, and the two portions 26a and 26b of low melting point eutectic solder for holding said reservoirs in series relationship against the tension of said spring.

The plunger reservoir I6 has the head portion 21 and the shank portion 28, which shank portion fits loosely within a corresponding hole in the tubular reservoir l5. The fit between the shank portion 28 and the tubular reservoir l5 should not be so close that compressed air will retard the movement of said shank 28 into said tubular reservoir IS.

The plunger reservoir 5 is urged toward the right as the parts are viewed in the drawing by the spring l1, the left hand convolutions of which are threaded onto a corresponding groove in the head portion 21 of said plunger reservoir I8. The

outer diameter of the tubular reservoir I5 is of a size to receive the coil spring I1. Said tubular reservoir [5 at its right hand end is provided with an end portion 29 of reduced diameter, providing a shoulder for receiving the right hand end convolution 30 of the spring I1. In other words, the

' [6 into the tubular reservoir 15 and away from the slug heat reservoir M.

The mode of operation of the above described embodiment of the invention will1be clear with-- out detailed-explanation. When the-fuse is lo-- cated in an electric circuit, said fuse will protect such circuit against conditions approximating short circuit for the reason that the fuse links lit and I9 will fuse in the manner well understood under such short circuit conditions;

Under overload conditions the. fuse.- links; is and [9 will warm up, acting as heaters com municating heat to the members. l4, |5,-an cl-- [6,. which, being heat reservoirs, will store up such heat to a predetermined extent, depending. jointly upon the degree of. overload and the prolongation: of; the. period: Qfioverload. The; melting: point of; the: utectic older; uniting; the,

the tubular reservoir" 1 5; may be accurately; pre.

determined; and:v when sufficient-heat has. been.

storediinzthe members; It; lfifandlfirtomelt, this.

eutectic-rsolder,. the. spring; I]: will; move, the:

plunger; reservoir I51 to. the. right; effectually; opening. the: circuit between .the. slug heatreservoir: I14; andjthe, plunger;- reservoir l5;- thereby.

titions. in said casing; dividing; it-;into:. end: and

central: compartments, fuse. links. in: said: end. compartments each extending between the ad.- jacent casing terminal and th proximate partitioninto the central compartment; the terminus of. each. link in. the central compartment. being: inispaced relation. to'; the: opposite .lil'lk'l terminustherein; a. relatively massive-.metallic conductor of large thermal .capacityr bridging. and. connect--- ing; the. link terminals .in the: central cnmpantsment, said; massive conductor: being: formed" in: three. parts: one partof which; is connected in.

permanent mechanical i and electrical union. with: theterminus ofrone fuse link;- an; opposite: part:

which. is; simiiarlynonnectedto the opposite-fuse 4 link terminus in spaced relation to said one part, and a connecting part in telescoping engagement with said one part and joined to it and to said opposite part by low meltingpoint solder: and a spring extending under tension between the telescoped parts when the three parts are soldered together so as to bias the connecting part awamfromsaid oppositepert 2i Th fuse-construction specified in claim 1, in which said spring is a helical spring within the bore of which said telescoping parts are accommodated, one convolution of said spring being sufficiently reduced in diameter to engage an axial; bearing; on; one. of said telescoping parts.

* the other ofsaidtelescoping parts having screwthreads complementary to the convolutions of said. spring whichare screwed into engagement with the latter when telescoped relative to the other part.

3. The fuse construction specified in claim 1, the-end; chambers oiisaid casinsabeingfllledrwith quenching powder in which said fuse are;

embedded;

of each; other into. and out of; abutting; relation to. thethird part; and a helical: spring tending to withdraw said sliding. parts from abutment: withsaidathirdapart;andlow-melting=point:solder" holding saidithree partsxinr abutting relation;

5; The lag. fuse assembly specified in claim- 4, in. which: said-s helical spring. has convolutions at one. of itsends in. screw-threaded engagement with. one of sai'dglsii'ding parts, and a constricted convolution at; its. opposite end: bearing upon a portion of reduced diameter on theother slid ing part; said; parts being: coaxial with said spring,

and withreach other.

GORDON F.

REFERENCES L GIZDEDi The foliowing references are of record in the file of this patent-i.

UNITED STA ES'P T N Number N amev Date- 2,044 22c: Rawlin'si i Juno-16; rm: 23211311 I aylor June 1531 943

Images