US2218274A - Circuit interrupter - Google Patents

Description

Oct. l5, 1940. M, B fWOOD 2,218,274

I CIRCUIT INTERRUPTER Filed Oct. 2, 1937 f To i@ l im Patented Oct. 15, 1940 UNITED 'STATES PATENT OFFICE 2,218,214 cnwurr INTERBUPTER Morris B. Wood, Newburyport, Mass., assignor to The Chase-Shawmut Company, Newburyport, Mass., a corporation of Massachusetts Application October 2, 1937, Serial No. 167,005

28Clalms.

This invention relates to circuit interrupters of the type containing a fusible mass which upon fusing releases a conductor so that it is free to move in a circuit opening direction, the fusible mass receiving heat from aheating element traversed by the current traversing the device.

The invention in particular relates t0 a nontamperable plug fuse type of interrupter andespecially one having a long center contact. lo One of the objects of the present invention is the provision of such a type of interrupter having a center contact that contains a well for the fusible material, as is generally disclosed in United ,States Letters Patent No` 2,168,815, l granted August 8, 1939, on an application filed in my name, and wherein the center contact member is composed of resistance material and is so constructed and arranged as to become sufficiently highly heated by the current traversing it to melt the fusible mass and effect the interruption of the circuit.

For currents of relatively small value where it is somewhat diiiicult to provide a center contact member having sufiicient resistance and mechanical strength within the available dimensions of the contact member I prefer to make the contact member hollow and to locate within the contact member a resistance element which heats a fusible mass located within the plug body to effect circuit interruption. Such a construction constitutes a further objectv of the invention.

Another object of the inventionl is the provision of an interrupting device having a center contact and means providing a receptacle for a fusible mass at the upper end of the contact with an electric heating element within the contact and transmitting heat to the fusible mass within the receptacle.

A furtherA object of. the invention is the pro- -vision of an interrupter Acomprising a hollow contact member containing a heating element that is connected at its lower end with the contact member atv or adjacent the contact face thereof, the upper end of the heating element 5 passing into an insulating cup containing a fusible mass, the cup also constituting a bushing which insulates the upper end of the resistance element from engagement with the upper end of the contact member. Another obiect of the invention is the provision of a circuit interrupter comprising an electric resistance element .connected at one end to a terminal of the interrupter and having at its upper end a sizeable metallic mass comprised at 5g least in part of a readily iusible metal ywhich (ci. zoo-123) normally holds a movable circuit interrupting element in electrical connection with the upper rend of the heating element, combined with means for eiecting separation of the circuit interrupting member and heating element upon the fusing 5 of the readily fusible metal mass. A*

A further object of the invention is the provision of a circuit interrupter having a fu/sible metal mass and a movable circuit interrupting element, which can be a. fusible link, normally 10 a member having tamper-preventing meansandfzo for instance, comprising an annular cylinder` concentric with the center contact and provided with teeth or other serrations at its bottom end, combined with improved means for connecting the taglia-preventing member and body non-rotat- 25 a An additional object of the invention is generally to improve the construction and operation of circuit interrupting devices.

Fig. 1 is a plan view oi the top of a circuit 30 interrupter embodying the present invention.

Fig. 2 is a sectional elevation through the'interrupter.

Fig. 3 is a plan view of the top of the interrupter with the cover removed. 35 Fig2. 4 is a section taken along line 4-4 of Fig.

Fig. 5 is a sectional detail of the interrupter taken along line 5-5 of Fig. 2.

Fig. 6 is a view similar to Fig. 2 but illustrating o the circuit open condition of the device.

Fig. I is a detail similar to Fig. 2 but illustrating a modied form of holder for the fusible mass.

Fig. 8 is a view similar to Fig. 7 but illustrating 5 a further modification.. Y

Figs. 9 and l0 are views similar to Fig. 2 but illustrating modincations wherein straight and helical Aheater elements, respectively, are associated with fusible masses retained by the body 50 of the interrupting device.

Fig. 11 ls a view similar to Fig. 2 but illustratingv a construction wherein the centerv contact member constitutes both the receptacle for the fusible mass and the heating element therefor.

but illustrating a further modiiled form 10 cuit interrupting chamber I6 which is closed at the bottom by an integral bottom wall i8 and is open at the top. The top is closed by a transparent disc 20 preferably of mica and a metal cover or cap 22, the side wall 24 of which is inturned over the bottom edge of the enlarged head 26 of the plug body. The ca'p 22 is provided with an opening or' window 28 therein which overlies the open top of the chamber I6. The side wall of the plug body is provided with outstanding screw threads 30 on which an exteriorly and interiorly screw-threaded metal terminal shell 32 is received. The bottom of the plug is provided with a recess 34 and an axially projectingannular rib 36 which surrounds the recess, the terminal shell 32 having an inwardly turned ilange 38 which is seated upon the end of the rib 36.

rl'he bottom wall I8 has a recess 40 therein formed with a flat bottom face 42 and a hexagonal peripheralwall 44, see especially Fig. 4,' in which is located a tamper preventing member 46 composed preferably of a molded articial resin and having an end wall 48 which is seated on the bottom face 42 of the recess and has a hexagonal periphery 50 which engages the hexagonal periphery 44 of the recess to prevent rotation of the tamper preventing member in the recess. 'Said tamper preventing member has an axially projecting cylindrical rib 5| which is co-axial with and radially spaced inwardly from the plug o body and projects therebelow, the end face of the rib 5i being provided with angularly spaced series of alternate ribs 52 and recesses 54 or otherwise serrated to catch upon conductingmaterial such as tinfoil, small wires and the like placed 45 in the recess of the socket which receives the interrupter to disrupt the conducting material and to dislodge it from bridging relation with the terminals of the socket so as to prevent the bridging of the socket terminals by the conducting 5@ material.

A center contact member in the form of a relatively long tube 56, as shown in Fig. 2, is passed through aligned apertures in the tamper-preventing member 46 and in the bottom wall i6 55 of the plug body i4 and has its upper or inner j/'enting member. The flanges S5 and 60 iix the 70 rent rating of the device.

center contact to the plug body and maintain the tampenpreventing member thereagainst.

nheater element comprising an electrical'resis-tance element 62 is located within the tubular contact member coaxially therewith and has its lower end terminated approximately flush with the lower end of the contact member and secured electrically thereto by solder 64 or other means. The wire 2 is oi a diameter suited for the cur- It will be relatively small for low currents and larger for higher currents and the composition of the wire may be 'varied to iit the physical dimensions and the electrical resistance thereof to the desired operating characteristics of the device.

In Fig. 2 the upper end of the rod passes through a cup 66 of insulating material, such as fibre. The cup preferably has a neck 66 which projectsrinto the upper end of the contact tube and may be frictionally retained therein, thereby to prevent accidental contact of the upper endy mitted lengthwise thereof into the solder withl which it is in intimate contact. The amount of solder is intended to be sulciently great so that the melting thereof is delayed for a considerable period of time following the initiation of a moderate overload current which traverses the heating element. The amount of the mass of solder is adjusted to secure the intended time delay of operation.

A flexible conductor 12 has the lower end thereof embedded in the fusible mass 10 and thereby normally retained' therein in electrical connection with the upper end ofthe heater element. Said conductor extends upwardly in the chamber I6 and has a part approximately parallel. with the window 20 and thence passes downwardly in a channel 14 of the plug body where the end thereof is electrically connected by a mass of relatively high melting point solder 16 with the terminal shell 32.

Spring means are provided to separate the conductor 12 and the heating element 62 upon the fusing of the fusible mass 10. Said spring means comprises a U-shaped cantilever spring generally indicated by the numeral 16 having a pair of generally parallel legs 80 disposed on opposite sides of the conductor 12 and an integral connecting portion 62 which is extended under the conductor and cross-wise thereof and bears upwardly thereagainst. The ends 64 of the legs 80 are located in vertical recesses of the plug body. The conductor maintains the spring 1B normally in a depressed and tensioned position. When the metal mass fuses or the conductor is ruptured the spring is released and moves upwardly into a position against the mica disc 20 as is illustrated in Fig. 6, thereby insuring a rapid separation of the conductor and the heating element or a rapid separation of the ruptured ends of the conductor.

The conductor 12 for some purposes may comprise a fuse link and may have a weakened or most readily fusible portion, provided, for instance, by a perforation B6, see Fig. 5, located in that part of the link between the spring and the fusible metal mass. The link is `so constructed that it will fuse or blow in the vicinity of the perforation only when traversed by currents of relatively high value approaching short-circuit value and will blow practically instantly when traversed by such currents. The arrangement of the heater element and the fusible mass, however, is such that the fusible mass will ultimately fuse and effect the ultimate release of the link and the interruption of the circuit when traversed by small overload currents. The combined arrangement thus provides for a relatively long delay of interruption on moderate overloads and an instant interruption on short-circuit.

There are some conditions of operation where the f use link or conductor 12 is traversed by a current which causes the link 'I2 to heat conv siderably, although not sufficiently to melt it.

This heat is sometimes suiiicient to anneal or remove the springiness of the portion 02 of the spring that underlies and is in contact with the link. 'I'he heat, however, does not get into the legs 80 of the spring and these legs retain their springiness so that the spring can function at all times.

In the modification illustrated in Fig. 7 the solder cup 66a is supported entirely upon the end of the heating element 62 and is not in engagement with the contact tube 58. In this instance the cup 66a is made of thin metal and is of sufficient capacity to contain enough mass of solder to provide for at least the major part of the required time delay characteristics of the device. The heater wire 62 passes loosely through an insulating bushing 08a, which can be of glass, for instance, located in the inner end of the contact member to hold the heater wire 62 from contact with the contact member. With a heater wire stiff enough to be surely self-supporting under conditions of the device. the bushing 68a can be omitted, as is illustrated in Fig. 8.

In the modification illustrated in Fig. 8 the time delay is obtained largely by means of a metal plate 80 which is secured to the upper end of the heating element 62 by a relatively small mass 90 of low melting point solder which also serves to connect the conductor or fuse link '12 with the heating element. Said plate 00 is of sufllcient mass and has such thermal characteristics as to delay the melting of the low melting point solder 90 for the required period of time.

In the modifications illustrated in Figs. 9 and 10 the cup 66 of Fig. 2, or 68a of Fig. 7, is replaced by a cup-shaped depression or well 02 formed in the inner face of the bottom wall l0 of the plug body. 'I'he upper flange 58 of the contact tube 50 is located in the bottom of the cup 92. An insulating bottom plate 94 overlies the flange and the passage in the contact tube and is in snug engagement with the cylindrical side wall of the cupso that the low melting point solder thereabove cannot come in contact with the tube. The heating element 62 is extended through the middle of the plate 04 into the cup and a low melting point solder mass 96 is located therein in electrical and thermal engagement with the upper end of the heating element and also with the lower end of the conductor 12.

In Fig. 9 the heating element is shown as a straight resistance wire. In Fig'. 10 the heating element 02a is illustrated as a small diameter -wire wound in helical form so that a considerable length of wire can be contained within the contact tube. With the arrangement shown in Fig. l0 the device can be made to operate upon relatively small currents, as an ampere or less, although this construction can be used for larger currents by increasing the diameter of the wire and by using wire of lower resistance.

The construction illustrated in Fig. 11 can be best used where relatively large currents. say upwards of 10 amperes, are to be controlled. In this construction the center contact 56a .is solid and of itself forms the cup for the lower melting point alloy and is made of resistance material so that it is adapted to become heated and melt the alloy to secure the operation of the device. The contact is provided with a well 0l in its upper end` in which the low melting temperature alloy |00 is located. The contact below the cup thereof. g A solder cup is formed in the upper endof thecontact by an insulating plug |08 or other suitable means located in the tube below the top thereof to form the bottom wall of the cup which receives the fusible alloy H0. In this instance the tubular contact is made of resistance material having a sidewall oi' suitable thickness to provide the desired resistance, the heat generated in the contact being transmitted into the alloy.

In the modification illustrated in Fig. 13, which in some respects is preferred over the structure of Fig. 2, for instance, as being cheaper, the center contact ||2 is in general like the contact 06h of Fig. 12 except that it is made of metal of good conductivity. A heater element IIB, herein illustrated as a straight wire, is soldered to the inner face of the integral end `wall ||0 of the contact and carries a low melting alloy mass |20 at its upper end, which alloy is preferably of conical form and cast onto the end of the wire and onto the end of the fuse link |22 in a suitably shaped mold. A tube |24 of insulating material, such as formed of a flat sheet curled into tubular iorm is located within the center contact to insulate it from engagement with the heater element and also to support the fusible mass, the upper end of the tube upstanding beyond the upper end of the Contact sufiiciently to hold the mass from electrical engagement with the contact.

I claim:

1. An electric circuit interrupter comprising an insulating casing, a fusible mass within said casing, a conductor within said casing normally retained in a circuit closed position by said mass, said conductor and fusible mass being arranged for relative movement to separate said conductor and said mass upon the fusing of said mass, and a heating device for said mass carried by said casing and located mainly outside thereof and having a part in heat transferring relation with said mass.

2. An electric: circuit nterrupter comprising an insulating casing, a fusible mass within said casing, a conductor within said casing normally retained in a circuit closed position by said mass and arranged `for movement free from said mass into a circuit open position upon the fusing of said mass, a heating device for said mass carried by said casing and located mainly outside'thereof and having a part in heat transferring relation with said mass, and having means externally of the casing providing a contact face.

3. A circuit intermpter comprising a casing; a terminal structure supported by said casing comprising means providing a well for a readily fusible mass. 'means for heating said mass, and a contact face; and a conductor within said casing normally retained by the solidified mass in a circuit closed position, said conductor being movable to an open circuit position upon the fusing of said mass.

4. An electric circuit interrupter comprising an insulating casing, a terminal structure on said casing having an exterior part provided with a contact face, another exterior part constituting a heat generating element and a part accessible from the interior of said casing constituting a holder for a readily fusible mass, a readily fusible mass in said holder, and a conductor normally retained in circuit closing position by the solidia conducid in circuit closed position by said sclidied mass and movable therefrom into a circuit open position upon the fusing of said mass.

6. An electric circuit interrupter comprising a casing having an end wall, a center contact in said end wall and having its major portion extended outwardly thereof, said center contact having a well accessible from the interior of the casing, a fusible mass in said Well, said center contact having a least a part composed of resistance material adapted to heat and fuse said fusible mass, and a conductor within said casing normally restrained in a circuit closed position by the solidified fusible mass and arranged to move into a circuit open position upon the fusing of said mass.

7. An electric circuit interrupter comprising a casing, a center contact of resistance material carried by and having its major portion extending beyond said casing, and means responsive to the heating of said contact by the current traversing it to effect interruption of the circuit through the interrupter.

8. An electric circuit interrupter comprising a casing, separable circuit interrupting elements within the casing, a center contact structure carried by and having its major portion extending beyond the casing having at least a part composed of resistance material adapted to become heated by the current traversing it to effect separation of said separable elements and the interruption of the current.

9. An electric circuit interrupter comprising a casing, a center contact carried by said casing having a Well accessible to the interior of the casing and having a relatively long stem exteriorly of the casing composed of resistance material and terminated in a contact face, a fusible mass in said well, and a circuit interrupting element normally retained releasably in circuit closed position by the solidified fusible mass, the electrical resistance of said contact being such as to vcause the heating and fusing of said mass when said contact is traversed by an overload current.

10. An electrical circuit interrupter comprising a casing, a center contact member carried by said casing and projecting therebeyond and having at one end a well exposed to the interior of the casing, a contact face at the other and outer end, and an intermediate portion located mainly Outside of said casing and having substantial electric resistance, a fusible mass in said well, and a circuit interrupting member normally retained releasably in circuit closed position by said mass.

11. An electric circuit interrupter comprising a casing, a center contact structure carried by said casing and projecting outwardly therebeyond and comprising a member of resistance material located mainly outside of said casing and 5 having a well at its upper end open to the interior of the casing and a contact face at its lower end, a fusible mass in said well, and a circuit interrupting element within said casing normally retained releasably in circuit closed posi- 11 tion by the solidified fusible mass.

12. An electric circuit interrupter comprising a casing, a tubular center contact carried by and extended outwardly of said casing, meansV providing a well within said casing, a fusible mass ll in said well, a heating element for said fusible mass located within said contact member and connected electrically to the outer end thereof and having a substantial part of its heating length disposed in the outwardly extended part 21 of said tubular contact, and a circuit interrupting element associated with the said fusible mass.

13. In an electric circuit interrupter, the combination of a casing, a tubular contact member carried by said casing and extended outwardly 2.* therebeyond, a heating element within said contact member having a substantial part of its heat generating length in that part of said contact member that is outwardly of the casing and having its outer end connected electrically to the 3| outer end of said tubular contact member and having a readily fusible mass on its other and inner end, and a circuit interrupting element associated with said fusible mass.

14. An electric circuit interrupter comprising 81 a casing having a long tubular center contact carried by and projected beyond said casing, a straight resistance element within said tubular contact and spaced from the inner face of the wall thereof and having its outer end only con- 41 nected to the outer end of said contact, a fusible mass on the inner end of said straight resistance element, and a circuit interrupting element associated with said fusible mass.

15. An electric circuit interrupter comprising 4g a casing, a tubular center contact fixed at one end to said casing and projected therebeyond, a cup of insulating material located in the inner end of said tubular contact, a straight resistance element extended at one end into said cup and 5( within said contact and spaced from the inner face of the wall of said tubular contact and fixed at its other end to the outer end of said contact,

a fusible mass in said cup, and a circuit interrupting element associated with said fusiblel 55 end extended through said neck into said cup and 55 having its outer end fixed to the outer end of said tubular center contact, a fusible mass in said cup, and a circuit interrupting element associated with said fusible mass.

17. An `electric circuit interrupter comprising a 70 chambered casing having a bottom wall, means providing a well in the bottom part of the chamber, a tubular center contact having its upper end in the bottom of said weil and projected outwardly beyond said casing, a fusible mass in said well insulated from said tubular center contact, an electric heating element within and spaced from the inner face of the wall of said contact and having its inner end in electrical and thermal connection with said fusible mass and its outer end connected electrically to the outer end of said center contact, and a circuit interrupting element associated with said fusible mass.

18. An electric circuit interrupter comprising a chambered casing having an end wall, means providing a well in the bottom part of the chamber, a fusible mass in said. well, an electric heating element disposed mainly exteriorly of said casing in electrical and thermal connection with said fusible mass, a hollow contact member on said casing under said well under and insulated from said fusible mass, said contact member enclosing said heating element and said heating element be ing insulated from said contact except at one end which is connected electrically therewith, and a circuit interrupting element associated with said fusible mass. f

19. An electric circuitinterrupter comprising a ,casing supporting an internally disposed fusible mass and a mainly externally disposed heat generating element and a circuit interrupting element which is associated with said fusible mass and which is arranged to be separated therefrom upon fusing of the mass.

20. An electric circuit interrupter of the Aplug fuse typelcomprising a cylindrical casing having a said center contact,-a circuit interrupting element` associated with said fusible mass and terminal shell.

2f In an electric circuit interrupting device, a current carrying terminal composed of resistance material and constructed and arranged to become heated by the current traversing it, and fusible circuit interrupting means fusible in response to the heating of said terminal to effect the interruption of the current.

22. In an electric circuit interrupting device, a fusible mass, a heating element for fusing said mass, a flexible current carrying conductor normally anchored to the solidified fusible mass, said conductor adapted to become heated by the current traversing it, and a cantilever spring for moving said conductor away from said heating element having a part which underlies and traverses and bears against said conductor and a resilient part which is remote from the heat of said conductor and exerts pressure on said trav,- erse part.

23. In an electric circuit interrupting device, an enclosing casing having terminals, a fusible mass within said casing connected to one terminal, a conductor normally anchored by the solidified mass and connected to the other terminal and adapted to become heated by the current traversing it, and a cantilever spring arm having one end anchored to said casing andextended generally parallel with said conductor and having an angularly related part extended transversely of and underlying and exerting pressure on said conductor in a direction to move it away from the fused mass.

24. In an electric circuit interrupter, an 'encosing casing having terminals, a fusible mass connected to one terminal, a conductor having one end anchored by the solidified mass and the other end connected to the other terminal, and a U- shaped spring member for moving said conductor away from the fused mass, said spring having the ends'of its resilient arms anchored to said casing and its intermediate portion traversing and underlying and bearing against said conductor.

25. An electric circuit interrupter comprising a cylindrical ceramic casing having external screwthreads and an integral bottom wall, an exteriorly screw-threaded terminal shell screw-threaded on the screw-threads of said casing, said bottom wall having a non-circular'recess in its outer face, a molded tamper-preventing member having a non-circular peripheral portion conformed to the non-circular shape of said recess and located therein and held against independent turning thereby, a 4center contact passed through said bottom Wall and said tamper preventing member and clamping said wall and said member together, and. a circuit interrupting element in said casing connecting said center contact and terminal shell.

26. An electric circuit interrupter comprising a casing having a chamber, a hollow center contact carried by said casing and opening into said chamber, a heater element having a heat generating part in said contact member having a readily fusible mass on its upper end within said chamber, a terminal on said chamber, a conductor connected between said fusible mass and terminal, and an insulating support for said fusible mass carried by said contact member. y

27. An electric circuit interrupter comprising a casing having a chamber, a hollow center contact carried by said casing and opening into said chamber, a heater element'having a heat generating part in said contact member having a readily fusible mass on its upper end within said chamber, a terminal on said chamber, a conductor connected between said fusible mass and terminal, and an insulating support for said fusible mass carried by said contact member comprising an insulating tube 'in said contact member and upstanding above the inner end into said chamber and disposed in engagement with said fusible mass.

28. An electric circuit interrupter comprising a casing having a chamber, a hollow center contact carried by said casing and opening into said chamber, a heater element in said contact member having a readily fusible mass on its upper end within said chamber, a terminal on said chamber, a conductor connected between said fusiblemass and terminal, and an insulating support for said fusible masscarried by said contact member comprising an insulating tube in said contact member and upstanding above the inner end into said chamber and disposed in engagement with said fusible mass, said fusible mass being of inverted conical shape seated on and partially within said tube.

MORRIS B. WOOD.

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