US2043024A - Fuse - Google Patents

Description

m m m M w T m 9 w 2 r E. A. WILLIAMS FUSE Filed May 5, 1934 Inventor: Edwin AWHHams,

His A torneg 5 Patented June 2, 1936 x UNITED STATES PATENT OFFICE FUSE Edwin A. Williams, Springfield, Pa., assignor to General Electric Company, a corporation of New York Application May 5, 1934, Serial No. 724,041 Claims. (Cl. 200-117) My invention relates to fuses and more parterminal. To assist in the rapid separation of ticularly to fuses of the expulsion type. Expulthe severed ends of fusible element l5 upon the sion fuses have been employed for general use in operation of the fuse, a Compression spring 21 is protecting high voltage circuits and machinery provided and located between the lower end of 5 e connected in such high voltage circuits. The tube Ill and contact Ill. The tension produced operation of expulsion fuses has proven quite through the intermediary Of Spring 21 is e satisfactory for heavy overloads but some difllsarily greater than the fusible link I5 is able to culty has been experienced in the operation of withstand especially when the fuse is designed these fuses with overloads which are slightly in for operation on a circuit at a'relatively low ourexcess of the overloads for which the fuse is derent value. Thus to relieve fusible link I5 of this ll) signed to operate. In such cases an overload tension, strain member ISis provided and secured though relatively light may do considerable damto contact 24 at one end and terminal 19 at the age by failure of the fuseto operate at all or on other end. Strain member It may consist of a failure of the fuse to operate in a sufliciently wire of a nickel chromium alloy, stainless steel,

0 short time to prevent damage to machinery conor similar materiaL which will withstand the relal5 nected in the circuit. v tively high tension even when of small cross sec- The object of my invention is to provide a fuse tion. It has been the previous practice to proof the expulsion type which will operate certainly vide a strain member for the fusible element and quickly on relatively light overloads. which is electrically connected to the terminals of Q0 What I consider to be novel and my invention the fusible element. Such a strain member which will be better understood by reference to the folis placed in parallel with the fusible element, due

lowing specification and appended claims when to its high specific resistance, carries a relatively considered in connection with the accompanying 10W P of the Current which passes through drawing in which Fig. 1 is a sectional view of an the fuse link. Upon the blowing of the fusible expulsion fuse embodying my improvements and e t a l f t clJIrent Whih is passing Fig. 2 is a detailed view of a part of the fuse. t u h th fus l nk mu t then pas thr u h t Referring to the drawing, l0 indicates a tube strain member. It has been found that the smallof insulating material which forms the housest strain wire which can be used to transmit the ing for an expulsion fuse. Ferrules II and I2 are necessary tension and also withstand the usual secured to each end of tube I0 and are made of operating conditions of vibration, rough handling, 30 metal and adapted to contact with terminals conetc., will carry 25 amperes for five minutes before nected in an electric circuit. In order to comit operates. Obviously fuses for operation on ourple'te the connection of the circuit through the rents below 20 amperes cannot make use of the fuse, a fuse element I3 which consists of a flexconventional strain member without a great reible conductor I4, fusible link l5, and strain wire duction in its section and a corresponding reduc- 35 I6, is located within tube I0. Flexible conductor tion in mechanical strength. To reduce both II is connected at one end to a copper shoe 11 the current required to operate the fuse and the which has a conical end which fits within the time of operation without reduction in mechaniconical opening in contact l8. Conductor l4 tercal strength, strain member I6 is provided and minates at its opposite end in a swaged terminal placed. in parallel physically to fuse link 15 but 40 I9. Fusible link i5 consists of a wire 20 which is is electrically insulated from one terminal of fuse made of one of the well known fusible elements link l5. Strain member I6 is directly connected which is readily fusible upon an increase in temby a grommet 28 to contact 24 by means of bolt perature due to the passage of electric current 25. The other end of strain member i6 is molded therethrough and which has a relatively low speas an insert in a plate or member 29 of insulating 45 ciflc resistance. Wire 20 is connected at one end material, as better indicated in Fig. 2. The end to a metal terminal 2| which is connected to terof strain member I6 is formed into a loop 30 with minal Is by means of a bolt 22. The other end the free end of the strain member I6 being wound of wire 20 is connected to a terminal 23 which is tightly about the adjacent portion of the wire.

connected to a contact 24 by means of a bolt 25. The loop 30 is then placed in a mold and insulat- 50 A tube 26 of insulating material completely suring material molded about it in the form of a rounds wire 20 between terminals 2| and 23. flat plate with an opening 3|. Opening 3! in Contact 24 rests upon the top of tube l0 and is plate 29 is provided to permit the passage of bolt in engagement with ferrule l I to complete con- 22 therethrough to secure the lower end of strain nection between fuse link l3 and the top contact member ii to terminal l9. Thus, strain member 55 I8 is electrically connected to one end of fusible link I! and is insulated from the other end of the fusible link. By this arrangement, the strain member is not connected in parallel electrically to the fusible link as is the usual practice and is not in the electrical circuit of the fuse element at all as long as the fusible link I 5 remains intact. Upon the blowing of the fusible link the continuity oi the circuit broken and an arc terminal I! to an is drawn which strikes from adjacent portion of strain member I. As is well known, an arc seeks the shortest path and so would not strike from terminal I! to the other terminal 23 of the fusible link I I but as stated above would strike to an ad- Jacent portion of the strain member IS. The current then flows through a portion of the strain member IS. The combination of the current through the strain member l6 and the arc striking the strain member will burn the wire through and thus release the tension produced by compression spring 21 to immediately separate the blown ends of the fusible link l5 and positively clear the circuit. It has been found that while the strain member It may not be melted by the e of 25 amperes through the strain member in less than five minutes, an arc of 1 amperes will burn through the strain member IS in .05 second. Thus, by my improved strain member ii the fuse .will operate at a relatively low overload and the blown ends of the fusible link begin to separate within .05 seconds after the melting of the fusible element. At the same time, a mechanically strong fuse which does not require careful handling is provided.

The upper end of the fuse tube I0 is closed by means of a cap 32 which is soldered within the top of ferrule I I to form a waterproof joint. The lower end of tube It is closed by a frangible disc 33 held in the end of ferrule l 2 which is turned in at spaced points 34 to loosely hold the disc 33 in position. Upon operation of the fuse, disc 33 is forced out of the lower end of the tube by the expansion of spring 21. The passage is then open for the fuse element It to be expelled from the lower end of tube Ill. The connection between copper shoe l1 and contact I 8 is collapsed upon movement of the fuse element i3 and so does not interfere with .the exodus of the fuse element from the tube III. Frangible disc 33 by closing the lower end of tube ill prevents moisture and dust from entering the tube l0 and also serves as a target to indicate the operation of the fuse.

From the foregoing it may be seen that by means of my improved fuse the current required to operate the fuse and the time of operation on relatively low overloads is greatly reduced without any reduction of mechanical strength of the fuse element. This reduction in time of operation of the fuse greatly reduces the damage which might be done to the machinery interconnected in the circuit protected by the fuse. In addition, my improved fuse insures a completed operation of the fuse on relatively low overloads to thus greatly reduce the upon failure of operation of the fuse.

through the fuse element is damage which might occur What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a fuse having a fuse element under tension, a fusible wire conductor, a metallic strain wire, means for electrically and mechanically connecting said wires together at one end and for maintaining the wires in spaced apart relationship at their connected ends, and means for mechanically connecting the other ends of said wires together in non-conducting relationship including a member of insulating material rigidly attached to one of said wires and secured to said other end of the other of said wires.

2. In a fuse having a fuse element under tension, a. fusible wire conductor and means for relieving the wire conductor of tension comprising a metallic strain wire, means for mechanically and electrically connecting one end of the strain wire to one end of said wire conductor with the connected ends of the wires in spaced apart relationship, a block of insulation material molded securely onto the other end of said strain wire, and means for securing said block of insulating material to the other end of said fusible wire conductor with said other ends of the wires in spaced apart relationship.

3. In a fuse device, the combination with a fuse tube having a pair of spaced apart terminals for supporting a fuse element extending longitudinally through the tube and having means for tensioning said fuse element, of a fusible wire conductor connected between said terminals, a metallic strain wire, means for securing one end of said strain wire to one of said terminals in electrical conducting and spaced apart relationship with the adJacent end of said wire conductor, a member of insulating material secured to the other of said terminals, and means for fastening the other end of said strain wire to said insulating member with the strain wire extending through said tube in spaced apart relationship with respect to said wire conductor, whereby the strain wire carries no current while the fusible wire conductor is intact but is severed by an are upon the blowing of the wire conductor.

4. In a fuse having a fuse element under tension, a fusible link, insulating material surrounding said fusible link, and a strain member for the electrically connected to one terminal of the fusible link and insulated from the other terminal of the fusible link whereby the strain member does not carry any of the current passing through the fuse element while the fusible link is intact but is severed by an are upon the blowing of the fusible link.

5. In a fuse having a fuse element under tension, a fusible link, terminals for each end of said fusible link, insulating material surrounding said fusible link between said terminals, and a strain member for the fusible link electrically connected to one of said terminals and insulated from the other of said terminals whereby the strain member does not carry any of the current passing through the fuse element while the fusible link is intact but is severed by an are upon the blowing 01' the fusible link.

EDWIN A. WILLIAMS.

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