US2683788A - Time lag fuse link - Google Patents

Description

July 13, 1954 F, 3- VN HOORN 2,683,788

TIME LAG FUSE LINK i Filed Jan. 19, 1953 Fred Gyn Hg` His Att@ y.

' 6 as shown in Fig. 1. l. scribed is a known one and is to be taken as typi- Y cal of any suitable cartridge-type fuse.

Patented July 13, 1954 TIME LAG FUSE LINK .Fred G. von Hoorn, Trumbull, Conn., assigner to General Electric Company, a, corporation `of New York Application January 19, 1953Serial No. 331,813

lllClaims. 1

This application is a continuation-in-part of my application, SerialNo. 203,706, filed December 30, 1950, now abandoned.

The invention relates to time lag fuse links such as are used in fuses of the cartridge type and has for its objectv to provide an improved time lag fuse linkwhich is simple in structure,

kreliable in operation, has good operating char- According to my invention, the improved fuse l link comprises two spaced-apart fuse members between the inner ends of which is. a V-shaped spring, the legs of which are provided with supporting arms upon which-rests a heat-absorbing mass or disk. The legs of the spring are ,A

tensioned to bring the ends of the arms into engagement with the adjacent endsv of the fuse members. The arm. ends and the heat absorbing mass are connected to the ends of the fuse members by fusible solder, the arrangement being such that Whenthe solder melts ,the legs of the V-shaped spring contract and the circuit through the spring` and the heat absorbing mass is opened.

, In the drawing, Fig. l Ais a sectional View .of` a cartridge type fuse-` in which is a fuse link embodying my invention;

Fig. 2 is a plan view of the fuse link;

Fig. 3is a sectional view showing the fuse link blown; and

rFig. 4 is a sectional View of a modication.

Referring tothe drawingthe casing of a vcartridge type fuse formed from a suitable liber insulating material has metal end caps 2.y and 3.

In the casing is a fuse link carrier comprising a strip l of insulating material which forms a supporting space for the terminal knife blades 5 attached to the spacer ends by screws 6. rEhe fuse link is attached to the carrier by the screws The structure so far de- My invention has to do with the structure of the fuse link.

The fuse link comprises ktwo end fuse link members 'I and 3 each of which at its outer end; is provided With suitable'means for attaching itto a fuse link carrier. Ingthe presentrinstance link member I` is vprovi-ded with a furcateend 9 and link memberv 8 is provided `with a hooked end I0 for attaching thexlink under. the headsgof screws G, this being a known fuse link attaching means. The fuse links themselves are suitably made of copper or Zinc as is well known in the art.

The inner endsof fuse link members I and 8 are positioned in spaced relation to each other and attached to such ends by suitable low melting point solder is a V-shaped spring member comprising legs I I and I2, the outer ends of which are bent outwardly to provide supporting arms I3 and I4. The spring is preferably made of a Phosphor bronze or beryllium copper which has a relatively low electrical conductivity and a high 'Vfor lthis purpose may be employed, the solders `ducting portion of the fuse.

suitably having a melting point in theY range of 200 to 300 FahrenheitY so that fuse operation at y.destructively high temperature is avoided. When the V-shaped spring member is in its unstressed condition as shown in Fig.` 3, the ends of supporting arms I3 and I4 are spaced apart a distance less than a distance. between the adjacent inner ends of link members I and 8, so that when attached to the link .members as shown in Fig. l

the spring member is stressed and is held stressed by the fusible solder.

Supported on rarms I3 and I4 is a metal disk or block I6 which forms a heat storage or heat absorbing mass and also serves as a current con- Disk I6 is of a diameter less than the distance between the inner vends ofy link members l and 8 and is attached to arms I3 and I4 by the same 10W melting point solder I5 which attaches arms I3 and YI4 to link members 'I and 8, it being positioned midway of the space between. linkmembers 'I and 8. The

exact shape of the mass is otherwise not significant, and themass may be any materialhaving a conveniently high specific heat andelectrlcal conductivity such as copper or brass.

-Tlie link members 'I and 8 are provided with y notches I' which serve to form regions I8 of limited crossfsectonal area, the function of which is to provide heat generating sections.

With the above-described arrangement, the

,spring member is normally` heldrunder tension or stressed by the 10W melting point solder I5 which attaches it to link members 'Irand 8 and it supports the heat storage mass or disk IB which likewise is held by solder I5. The heat storage mass absorbs heat caused by flow of current through the heat generating regions I8 of the fuse link but with normal now or with flow above normal rating for a short period of time, the heat is dissipated rapidly enough so that the mass or disk i6 does not reach a ternperature high enough to fuse solder I5. However, with sustained iiow above normal rated flow, the mass or disk I will reach a temperature high enough to elect the melting of the solder whereupon the legs I I and I2 of the spring member are drawn together and it and the disk I6 fall away from the link members 'I and 8, leaving a gap between them as illustrated in Fig. 3. While at current values less than the fuse rating some of the current will flow through the spring, annealing of the spring thereby may be readily avoided as by control of the relative resistances of the spring and mass.

In case of a short circuit, the fuse members l' and 8 themselves blow at the regions I8 as is well understood in connection with the operation of fuse links of the time lag type.

A feature of my invention as described in relation to Figs. l, 2 and 3, is that of providing the stressed V-shaped spring with supporting arms positioned between and connected to the link members by fusible solder, the heat storage mass or disk being supported on the arms of the spring members and attached to them by low melting point solder and having a diameter less than the distance between the inner ends of the two link members so that when the fuse functions due to the melting of the solder both the spring and the heat storage mass will fall away from the link members and without the possibility of bridging the space between them thus causing faulty fuse operation. At the same time, the fuse link is simple in structure, comprising a minimum number of simple parts and is capable of being manufactured at low cost.

Referring now to Fig. 4, another modification of my inventionv is illustrated in which the spring is made integral with one of the fuse links. Accordingly, one of the fuse links Iii has a conventional flat mounting end 2Q and an extended inner portion which is shaped to define a V-shaped spring 2l with an end support portion 22 which is substantially in the same plane as the unbent portion 2e of the link. In addition to the V-shaped bend, the spring portion 2I is also bent in the region 23 between the beginning of the V and the flat fuse link portion 2B so that when the spring is unstressed, it tends to pull the end portion 22 down and out of the plane of the remainder of the fuse link as indicated in dotted outline. It is desirable for reasons of sii iplicity and economy of manufacture to make the entire link I9 of a spring material such as Phosphor bronze or beryllium copper. Of course, if desired, the V-Shaped spring portion 2| may be separately fabricated and attached to the remainder 2G of the fuse link as by welding.

The other fuse link 2d corresponds to the fuse links 'i and il of the embodiment described in Figs. l, 2 and 3 except that the inner end of the fuse link 2li is preferably struck up to provide a iiange 25. A mass portion 2s bridges most of the gap between the fuse links It and 24, this mass portion suitably taking the form of a thick strip of a metal such as copper or brass having a relatively high specific heat as well as a suitably high electrical conductivity. One end of the mass strip 2% is welded or otherwise secured to the flat fuse link portion 2d for good thermal and electrical contact, no low melting point solder being necessarily employed since separation of the mass and fuse link at this point is not necessary for operation of the fuse.

In assembly of the fuse, the `J-shaped spring portion 2| is stressed so as to both open the V and force the end portion 22 up into engagement with the end flange 25 of the fuse link 2li. In this position, the unsecured end of the mass strip 26 bears against a spring portion 22 but falls short of being coextensive with it. The space between the end of the mass strip and the opposing fuse link flange 25 is filled with a body of low melting point solder 2l, the solder bonding the mass strip to one part of the spring end portion 22 and the fuse link flange 25 to the end surface of the spring end portion 22 as well as providing a conductive path directly from the mass strip to the fuse link 2d. The fuse links I9 and 24 are suitably notched or otherwise congured so as to include heat generating portions corresponding to the restricted cross section area portions I8 indicated in Fig. 2.

In operation, when an overload current such as imposed by a high motor starting current is sustained for an undesirably long period of time, the current through the fuse assembly causes the heat generating portions of the fuse link to heat the assembly and melt the body oi solder 2I holding the V spring in tension. As a result, upon fusion of the solder, the spring contracts and the solder between the end of the mass strip and fuse link flange 25 drops out to open the circuit. In addition, since the spring also moves laterally or transversely, the spring end thereby helps to draw out the melted solder and the air gap is increased. In case of short circuit the fuse links themselves blow as previously mentioned. While in this structure the air gap produced by operation due to sustained overloads is not as large as that produced by the double breaking action of the embodiment previously described, the fuse structure itself is simpler and more economical to manufacture.

While the present invention has been described by reference to a particular embodiment thereof, it will be understood that numerous modifications may be made by those skilled in the art without actually departing from the invention. I, therefore, aim in the appended claims to cover all such equivalent variations as come within the true spirit and scope of the foregoing disclosure.

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

l. A fuse link comprising two members arranged in axial alignment with the inner ends spaced apart, at least one of said link members being provided with a region of relatively small cross-sectional area to cause generationof heat by passage of current therethrough, a spring member shorter than the distance between the inner ends of said link members, said spring member being stressed in axial tension so that it is connected between the said link members, and a heat absorbing mass connected to the ends of said spring member, the connection between at least one end of the heat absorbing mass and an end of the spring and the same end of the spring and the adjacent link comprising fusible Solder means whereby said spring mem- Y ber contracts when said solder melts and opens the fuse circuit.

2.-.A fuse link comprising two members arranged in axial alignment with the inner ends spaced apart, at least one of said link members being provided with a region of relatively small cross-sectional area to cause generation of heat by passage of current therethrough, an electrically conductive V-shaped spring member shorter than the distance between the inner ends of said link members and having axially aligned end supporting arms, said spring member being stressed in axial tension with the end supporting arms thereof connected between the inner endsof said link members, and a heat absorbing mass connected to the end arms of seid spring member yin thermal contact therewith, the connection between at least one end oi the heat absorbing mass and an end arm of the spring member and the same end arm and the adjacent link member comprising fusible solder means whereby said spring member contracts when said solder melts and opens the fuse circuit.

3. A fuse link comprising two members arranged in axial alignment with the inner ends spaced apart, at least one of said link members being provided with a region of relatively small cross-sectional area to cause generation of heat by passagel of current therethrough, a spring member shorter than the distance between the inner ends. of said link members, said spring member being stressed in axial tension with the ends thereof positioned between the inner ends of said link members, and a heat absorbing mass connected adjacent the ends oi said spring member and spaced from the inner end of at least one of said link members, said at least one of said link member inner ends being connected to said mass and an end of said spring with fusible solder whereby said spring member contracts when said solder melts and opens the fuse circuit.

4. A fuse link comprising two members arranged in axial alignment with the inner ends spaced apart, at least one of said link members being provided with a region of relatively small cross-sectional area to cause generation of heat by passage of current therethrough, an electrically conductive V-shaped spring member shorter than the distance between the inner ends of said link members and having axially aligned end supporting arms, said spring member being stressed in axial tension with the end supporting arms thereof positioned between the inner ends of said link members, and an electrically conductive heat absorbing mass connected adjacent the end arms of said spring member in thermal contact therewith and spaced from the inner end of at least one of said link members, said at least one link member inner end being connected to said mass and a spring member end arm by fusible solder whereby said spring member contracts when said solder melts and opens the fuse circuit.

5. A fuse link comprising two members arranged in axial alignment with the inner ends spaced apart, at least one of said link members being provided with a region of relatively small cross-sectional area to cause generation of heat by passage oi current therethrough, a spring member shorter than the distance between the inner ends of said link members, said spring member being stressed in axial tension with the ends thereof positioned between the inner ends of said link members, and a heat absorbing mass being supported on the ends of said spring member, said spring member ends and said mass being connected to said link member ends by fusible solder whereby said spring member and said mass will fall away from the inner ends of said link members when said solder melts.

6. A fuse link comprising two members arranged in axial alignment with the inner ends spaced apart, at least one of said link members being provided with a region of relatively small cross-sectional area to cause generation of heat by passage of current therethrough, a spring member shorter than the distance between the inner ends of said link members and a heat absorbing mass having an axially extending dimension less than the distance between the inner ends of said link members, said spring member being stressed in axial tension with the ends thereof 'positioned between the inner ends of said link members, said heat absorbing mass being supported on the ends of said spring member, and said spring member ends and said mass being connected to said link member ends by fusible solder whereby said sp ing member and said mass will fall away from the inner ends of said link members when said solder melts.

'7. A fuse link comprising two fuse link members arranged in axial alignment with their inner ends spaced apart and their outer ends shaped for connection with Contact members of a cartridge fuse, said link members being provided with regions of relatively small cross-sectional area to provide heat generating sections, a tension spring having axially aligned supporting end portions, the ends thereof being spaced apart a distance less than the distance between the inner ends of said link members, anda heat absorbing mass having an axial dimension less than the distance between the inner ends of said link members, said spring end portions being positioned between the inner ends of the link members with the spring member stressed in tension, said heat absorbing mass being supported on said spring end portions, and said spring end portions and said mass being connected to said link member ends b5 fusible solder whereby said spring member and said mass will fall away from the inner ends of said link members when said solder melts.

8. A fuse link comprising two fuse link members arranged in axial alignment with their inner ends spaced apart and their outer ends shaped for connection with Contact members of a cartridge fuse, said link members being provided with regions of limited cross-sectional area to provide heat generating sections, a V-shaped spring member, the ends of the legs of which are bent outwardly to form supporting arms having supporting surfaces, the ends of the arms when the spring member is unstressed being spaced apart a distance less than the distance between the inner ends of said link members and a heat absorbing mass of a width less than the distance between the inner ends of said link members, said arms being positioned between the inner ends of said link members with the legs of the spring member stressed to bring the ends of the arms into engagement with the inner ends of said link members, said heat absorbing means being supported on said arms, and said arm ends and mass being connected to said link member ends by fusible solder whereby when said solder melts, said spring member and said mass will fall away from the inner ends of said link members.

9. A fuse link comprising two fuse link members arr nged in axial alignment, at least one of said link members being provided with regions of limited cross-sectional area to provide heat generating section, one of said link members having an inner end comprising a spring for producing axial tension, the end of the spring when unstressed being spaced from the inner end of the other link member, and an axially extending heat absorbing mass having one end secured to said one link member and having the other end spaced from the inner end of said other link member, said spring end engaging the inner end of said other link member with the spring stressed in axial tension, and said spring end and said other end o said mass being connected to said inner end of Said other link member by fusible solder whereby said spring member contracts to open the fuse circuit when said solder melts.

10. A fuse link comprising two fuse link members arranged in axial alignment with their inner ends spaced apart and their outer ends shaped for connection with contact members of a cartridge fuse, said link members being provided with regions of limited cross-sectional area to provide heat generating sections, one of said link members having an inner end extension comprising a V-shaped spring member With an axially extending end portion, the end portion being axially spaced from the inner end of the other link member when the spring is unstressed, and an axially extending heat absorbing mass having one end secured to said one link member and having the other end spaced from the inner end of said other link member, said spring end engaging the inner end of said other link member with the legs of the spring member stressed in axial tension, and said spring end and said other end of said mass being connected to said inner end of said other link member by fusible solder whereby said spring member contracts to open the fuse circuit when said solder melts.

11. A fuse link comprising two fuse link members arranged in axial alignment with their inner ends spaced apart and their outer ends shaped for connection with contact members of a cartridge fuse, said link members being provided with regions of limited cross-sectional area to provide heat generating sections, one of said link members having an inner end extension comprising a V-shaped spring member with an axially extending end portion, the end portion being both axially spaced and laterally deflected from the inner end of the other link member when the spring is unstressed, and an axially extending heat absorbing mass having one end secured to said one link member and having the other end spaced from the inner end of said other link member, said spring end engaging the inner end of said other link member with the legs of the spring member stressed in axial tension, and said spring end and said other end of said mass being connected to said inner end of said other link member by fusible solder whereby said spring member contracts to open the fuse circuit when said solder melts.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,081,675 Muldoon May 25, 1937 2,530,228 Cihlar et al Nov. 14, 1950 2,556,018 Von Hoorn June 5, 1951

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