US2259946A - Circuit interrupter - Google Patents

Description

Oct. 21, 1941. J. M. WALLACE CIRCUIT INTERRUPTER File'd Feb. 25, 1959 Bari-Aid H 1 9, 3 7' 5 3 a z x 4 w W z 1 .4 4 M 41M. III... IIIIH. ww m M a M x B I a w 4 f 1|- B a J INVENTOR James Mil aliens:

BY q 3 ZTTORNE;

Patented Oct. 21, 1941 CIRCUIT INTERRUPTER James M. Wallace, Braddock, Pa., asslgnor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 23, 1939, Serial No. 257,879

22 Claims.

This invention relates to improvements in circuit interrupters and, more particularly, to power fuse devices of the high-voltage high-current type. In recent years, high voltage power fuses of the expulsion type have been used more extensively in electrical circuits and to a certain extent have replaced the more costly circuit breaker structures in applications where overload protection is the prime objective. However, high ower fuses of the expulsion type have bee ated in their application to power circuits in which the normal load current does not exceed 400 amperes. The usual practice of using a fuse in a branch or feeder circuit protected by either another fuse or a circuit breaker makes it necessary to provide fuse structures having different operating characteristics so as to permit selective operation. A more extensive use of power fuses as protective devices in power circuits has been prevented by the lack of a high current fuse structure having a fast operating characteristic.

The main object of the invention is to provide 7 a power fuse structure of the high voltage type having a higher current carrying capacity than devices heretofore known in the art.

A further object of the invention resides in the provision of a power fuse of the foregoing type having a fast operating characteristic which is comparable in operating time to known fuse devices of materially lower current rating.

Another object of the invention resides in increasing the normal load capacity .of a high voltage power fuse without materially increasing the external dimensions of the fuse structure.

A more specific object of the invention is the provision of a high power fuse structure in which a conducting circuit through the arc passage is constituted by a movable conducting member connected at one end to an end terminal of the fuse holder by a short fusible member of relatively small cross section and at the other end to the other end terminal by separable contact means.

Additional objects and advantages will appear in the following description, when read in connection with the accompanying drawing, in which:

Figure 1 is a longitudinal sectional view of the fuse structure of my invention;

Fig. 2 is an enlarged elevation view partially in section of the refill unit of my fuse device; and

Fig. 3 is a cross sectional view of the refill unit taken along the line III-III of Fig. 2.

In general the fuse structure of my invention embodies a tubular fuse holder and a refill unit removably mounted therein of the general type shown and described in the patent to H. L. Rawlins, No. 1,978,634, issued October 9, 1934, and assigned to the assignee of this application.

Referring to the drawing, the fuse holder of my invention constitutes a pair of spaced terminal members 5 and I of conducting material secured to the ends of a pair of concentric tubes 9 and II of insulating material. The inner tube 9 is threaded at its'ends for engagement with corresponding internally threaded portions of the terminal members 5 and 1. The outer tubular member H is adapted to be seated in an annular recess i3 provided in the opposed end faces of the terminal members 5 and 1. Thus the internal tubular member 9 is placed in tension whereas the outer tubular member II is held in compression. The terminal member 1 is provided with a bore 15 for the reception of a refill unit ll shown more clearly in Fig. 2.

The refill unit I! comprises a metallic collar or ferrule l9 screw threaded on to the lower end of a tubular casing 2| of insulating material. The interior of the tubular casing 2| is preferably lined with a gas producing insulating material, in this instance a plurality of compressed tubular blocks 23 of boric acid. The blocks 23 are supported upon an annular ledge 25 of the ferrule [9 at the lower end of the refill unit and are held in compression by an annular closure member 21 of insulating material such as hard fibre screw threaded into the upper end of the tubular casing 2 I. The openings through the compressed blocks 23, the ledge 25 and the annular member 21 are disposed in alignment and form an arc passage, indicated at 29. Disposed within the arc passage 29 is a rod-like conducting member 3| of slightly less diameter than the diameter of the passage. The lower end of rod 2| is electrically connected to the ferrule I9 by a radially extending pin 33 of fusible material, such as copper orsilver or any other material having a high conductivity but a relatively low melting point. The lower end of rod II- is also joined to the ferrule l9 by a diametrically disposed strain pin 35, pref erably of steel or'other suitable material havin a high resistance and a high tensile strength. A sleeve 31 of insulating material disposed about the lower end of rod 3| serves as a spacer between the rod and the ferrule l9 and facilitates the assembly of the pins 33 and 35. The upper end of the rod 3| is provided with an enlarged contact portion 39 and a threaded portion 4| of reduced diameter, the purpose of which in each instance will appear more fully hereinafter.

'When the refill unit I1 is disposed within the bore ii, the upper shoulder 43 of the ferrule I9 is adapted to engage the lower surface of an inwardly extending flange 45 provided within the bore ii of the terminal member I. The ferrule i9 is firmly held in contacting engagement with the flange 45 by means of a tubular member 41 having threaded engagement with an appropriately threaded portion within the bore I5.

. the stop member 55.

The upper terminal member is provided with a bore 49 in which is disposed an operating spring 5|. The spring 5! is secured at .its upper end to the spring support member 53 and at its lower end to a similar support member 55. The spring support 55 is screw threaded to the threaded portion 4| of the rod 3! for joining the operating spring to the rod. The upper end of the spring support member 53 has a threaded portion 5i of reduced diameter which is adapted to extend through an annular guide and stop member 59 which is preferably screw threaded into the bore 59. A cap member 5i is screw threaded'on to the threaded portion 57, and maintains the spring support 53 in clamping engagement with Thus, the spring 5i exerts a biasing force upon the rod 3| for moving it through the arc passage 29 in response to fusion of the pins 33 and 35.

A sleeve 53 ofconducting material is threaded to the upper terminal 5 and extends downwardly into the tubular casing member 9 of insulating material. Supported from the lower end of the conducting sleeve 63 are a plurality of yieldingly mounted contact fingers 55 disposed in circumferentially spaced relation to form a tulip type contact structure adapted to cooperate with the enlarged contact portion 39 of the rod 3i. The

contact fingers 55 are biased into contacting engagement with the contact portion 39 by a coil spring t'l encircling the contact fingers.

From the foregoing description, it will now be apparent that an electrical circuit exists through the fuse device from the upper terminal member 5 through the conducting sleeve 63, the contact fingers 65, contact 59, rod 3!, fusible pin 35, ferrule l9, to the lower terminal member I. The spring support members 53 and 55 are also electrically connected in this instance by a plurality of flexible conductors 65 secured by screws to the respective members as shown. The flexible conductors 69, therefore, provide an additional conducting path between the movable rod 3! and the upper terminal member a.

The operation of my fuse device is as follows: When the movable rod 3i is in the position, as

shown in Fig. 1;; 'currentfrom the terminal mem--.

her 5 may flow to the terminal member l by the path previously defined. In the event of an overload, the short section of the fusible pin 33 between the rod 3i and the ferrule i9 fuses, thereby causing the current to flow from the rod 3!! through the strain pin 35 to the ferrule i5. Since the strain pin 35 is of high resistance material, such as steel, it immediately fuses and permits the operating spring 5i to move the rod 3! upwardly through thearc passage 29, thereby establishing an are between the ferrule 19 and the end of the rod. This are is quickly extinguished by expulsive action which is well known,

resulting from the action of the are upon the arc passage lining 23 of gas forming material. After moving a short distance in the upward direction, the contact portion 39 of the rod 3i moves out of engagement with the contact fingers 65, thereby transferring the entire arc current to the flexible conductors 69. The conductors 89 are so selected that they will carry the arc current on a severe overload during the arcing period, but do not have sufficient cross section to carry the normal operating load of the fusedevice.

The greater portion of the normal load current in this instance is carried by the separable contact structures 39 and 65. The provision of this separable contact structure permits the use of a operated successfully when the fuse pin 33 was constructed of silver having-an effective fusible section of 1 6 inch in diameter and a length of a inch. The strain pin 35 in this instance was also approximately 1* inch in diameter and formed of steel. A fuse device constructed in this manner operated in .0083 second while clearing a short circuit of 20,000 amperes at rated voltage, and is equally as fast in operation as fuse devices normally rated at 300 amperes for the same operating voltage.

It will be noted that the fusible section of the 'pin 33, being that section of pin 33 which spans the short distance between operating rod 3i and ferrule 59, is of materially less mass than that normally employed in fuse devices of thetype herein described. It is due to the relatively short length of this fusible section that it loses heat to the ferrule l 9 and the operating rod 3i so rapidly that during normal conditions of load, it never reaches the fusion temperature. However, on overloads, a large quantity of heat is generated so quickly that the small mass of the fusible sectlon is heated to the melting point before the heat can flow away to the adjacent elements. Because of the exceptionally small mass of fusible material, the operation of the fuse device is particularly rapid and considerably faster in operation than known fuse devices using a larger fusible section. The strain pin 35 of steel is of such high resistance that following the fusion of the fusible pin 33, the pin 35 fuses even more quickly. Therefore, it has little effect in delaying the operation of the fuse.

In general, after a fuse operation, removal of the refill unitll from the fuse holder is accomplished by removing the clamping member ll and the cap member M which permits the unit ii and the operating spring 5i with its support members 53 and 55 to drop through the bore l5 at the lower end' of the holder. The spring support 55 is removed from the conducting rod 3! and screwed onto the conducting rod of a new refill unit if. A suitable reloading tool may then be secured to the threaded-portion 57 and the new unit with the operating spring 5i attached is inserted in the holder through the bore Hi from the lower end thereof. The clamping member ll and the cap 6! are then replaced in the order named. For further details of construction of the refill unit and its associated operating mechanism as. well as the method of replacing such units, reference may be had to Rawlins Patent No. 1,976,634 referred to above.

Although I have shown and described a particular fuse device, it is to be understood that the same is for the purpose of illustration and that changes and modifications may be made by those skilled in the art without departing from the ispirit and scope of the appended claims.

I claim as my invention: v

1. In a circuit interrupter, a pair of spaced for interconnecting conducting means said terminal members, said including separable contacts and a fusible section arranged in series relation and means independent of the are formed for separating said contact means in response to fusion of said fusible section.

2. In a circuit interrupter, a pair of spaced conducting tenminal members, conducting means for interconnecting said terminal members, said conducting means including separable contact means and a fusible section arranged in series relation, means for separating said contact means in response to fusion of said fusible section, and flexible conducting means arranged in parallel relation with said separable contact means and of less current carrying capacity than said contact means for carrying the arc current upon separation of said contact means.

3. In a circuit interrupter, a pair of spaced conducting terminal members, conducting means for interconnecting said terminal members, said conducting means including a movable contact member, separable contact means connecting one of said terminal members with said contact member, a permanent connection in parallel with said separable contact means and of less current carrying capacity than said contact means, a fusible element connecting the other of said terminal members with said movable contact member, and means for moving said contact member upon fusion of said fusible element to elongate the arc caused by the fusion of said element and to separate said separable contact means to transfer the arc current to said permanent connection.

4. In a circuit interrupter, a tubular closure of insulating material, a conducting terminal member at each end of said closure, means defining an arc passage within said tubular closure, conducting means movable through said are passage to establish an arc therein, fusible means electrically connecting said conducting means with one'of said terminal members, separable contact means electrically connecting said conducting means with the other of said terminal members, a flexible conducting means connected in parallel with said separable contact means, and spring means responsive to the fusion of said fusible means for moving said conducting means through said arc passage to establish an arc therein and for separating said contact means to transfer the arc current to said flexible conducting means.

'5. In a fuse device, a stationary conducting member, a; movable conducting member having at least a portion thereof closely adjacent to but ing said movable conducting member away from said stationary conducting member, and fusible means spanning and electrically connecting said stationary and movable conducting members, the spanning portion of said fusible means having a cross section the greatest dimension of which is at least equal to the spanning length thereof.

6. In a fuse device, a stationary contact member having an aperture therethrough, a movable conducting member having a portion thereof extending into said aperture, said portion having a cross-section substantially equal in area to that of said aperture, a pin of fusible material electrically connecting the inner surface of said aperture with said portion of said movable conducting member, and means responsive to the fusion of said pin for moving said movable member away from said stationary member.

7. In a fuse device, a stationary contact member having a circular aperture therethrough, a

movable conducting rod one end of which extends into and substantially fills said aperture, a pin of low melting point fusible material extending radially from said contact member into said conducting rod for electrically connecting said contact member-and said conducting rod, spring means biasing said conducting rod away from said contact member, and a strain pin of greater tensile strength than said pin of fusible material extending from said contact member to said conducting rod for holding said rod against movement by said spring means while said pin of fusible material is in the unfused condition.

8. In a fuse device, a tubular closure of insulating material, a conducting terminal member at each end of said closure, a renewable refill unit normally positioned within said closure, said refill unit including means defining an arc passage, a conducting member movable through said are passage and fusible means normally connecting one end of said movable member with one of said conducting terminal members, separable contact means normally connecting the other end of said movable member with the other of said conducting terminal members, and means within said tubular closure for releasably engaging and actuating said movable conducting member through said are passage.

9. In a fuse device, a tubular closure of insulating material, a conducting terminal member at each end of said closure, means within said closure defining an arc passage, a conducting rod movable through said passage to establish an arc therein, fusible means normally connecting one end of said rod with one of said conducting terminal members, a plurality of contact fingers within said closure connected to the other of said conducting terminal members, means for normally biasing said contact fingers into engagement with the other end of said conducting rod, flexible conducting means of lower current carrying capacity than said contact fingers connecting said other terminal member and said conducting rod, and spring means operative upon fusion of said fusible means for moving said conducting rod through said are passage and for disengaging said contact fingers from said conducting rod to transfer the arc current to said flexible conducting means.

10. A refill unit for a fuse device comprising means defining an arc passage, a conducting terminal disposed at one end of said are passage, a movable conducting member in said passage, fusible means normally connecting said movable spaced from said stationary member, means biasmemberwith Said terminal and a Contact secured to and movable with said conductingmember to enable a separable circuit connection to be made with said conducting member.

11. A refill unit for a fuse device comprising means defining an arc passage, a conducting terminal disposed at one end of said are passage, a movable conducting member in said passage, fusible means normally connecting one end of said movable member with said terminal, the other end of said conducting member extending exteriorly of said are passage, and a contact carried by the exteriorly extending portion of said conducting member, said exteriorly extending portion having a mechanically engageable portion adjacent to said contact.

12. In a fuse device, a stationary contact member having an aperture therethrough, a movable conducting member having a portion thereof extending into said aperture, said portion having a. cross-section substantially equal in area to that of said aperture, said members respectively co prising substantial masses of electric and heat conducting material, a pin of fusible material electrically connecting the inner surface of said aperture with said portion of said movable conducting member, and means responsive to the fusion of said pin for moving said movable member away from said stationary member.

13. In a fuse device, a stationary conducting member, a movable conducting member having at least a portion thereof closely adjacent to said stationary member, fusible means electrically connecting said stationary and movable conducting member, and means biasing said movable conducting member for movement away from said stationary conducting member the largest cross sectional dimension of said fusible means being on the order of the distance between said members.

14. In a fuse device, a stationary conducting member, a movable conducting member having at least a portion thereof closely adjacent to said stationary member, fusible means electrically connecting said stationary and movable conducting members, strain means mechanically connecting said stationary and movable conducting members, and means biasing said movable conducting member for movement away from said stationary conducting member in a manner to. stress said fusible and strain means substantially entirely in shear,

15. In a fuse, separable terminals having portions normally maintained in closely spaced relation by a fusible connection, said connection having across sectional area such as to be fused substantially instantaneously by the heat developed by the passage of normal load currents therethrough when dissociated from said terminals, and at least one of said terminals comprising a sufficiently large mass of heat conducting material to conduct the heat developed in said fusible connection by normal load currents away from said fusible connection fast enough to prevent fusion thereof, but ineffective to conduct sufficient heat away from said fusible connection to prevent fusion thereof upon the passage there through of currents of a predetermined higher value.

16. In a fuse, separable terminals normally maintained against separation by a fusible connection, said connection having a cross-sectional area such as to be fused by the heat developed by the passage of currents therethrough of a value substantially below normal load currents when dissociated from said terminals, and at least one of said terminals comprising a sufiiciently large mass of heat conducting material positioned relative to said connection in a manner to conduct the heat developed in said fusible connection by normal. load currents away from said fusible connection fast enough to prevent fusion thereof, but ineffective'to conduct sufficient heat away from said fusible connection to prevent fusion thereof upon the passage therethrough of currents above said normal load currents.

17. In a circuit interrupter, a pair of spaced conducting'terminal members, conducting means for interconnecting said terminal members, said conducting means including separable contact means and a fusible section arranged in series relation, and resilient means for separating said contacts in response to fusion of said fusible section.

18. In a circuit interrupter, a tubular casing of insulating material, terminals at opposite ends of said casing, means of conducting material associated with one of said terminals and extending in one end of said casing, a movable rodlike contact, fusible means connecting said contact to the other of said terminals, separable conducting means one of which is movable with said rod-like contact for electrically connecting said rod-like contact and said means of conducting material, and means biasing said rod-like contact awayfrom said other terminal to draw out the are upon fusion of said fusible means and separate said separable conducting means.

19. In a circuit interrupter, a pair of spaced conducting terminal members, conducting means for interconnecting said terminal members, said conducting means including separable contacts associated, respectively, with one of said terminal members and a movable rod-like terminal, fusible means connecting said rod-like terminal with the other of said terminal members, and resilient means biasing said rod-like terminal for movement to elongate the are formed upon fusion of said fusible means and to separate said separable contacts.

20. In a circuit interrupter, a tubular casing of insulating material, terminals at opposite ends of said casing, tubular means of conducting-material associated with one of said terminals and extending in one end of said casing, a movable rod-like contact in said casing, fusible means connecting said contact to the other of said terminals, separable conducting means one of which is movable with said rod-like contact for electrically connecting said rod-like contact and said tubular means of conducting material, and means in said casing biasing said rod-like contact away from said other terminal to upon fusion of said fusible means and separate said separable conducting means.

21. In acircuit interrupter, a tubular casing of insulating material, terminals at opposite ends of said casing, means of conducting material associated with one of said terminals and extending in one end of said casing, a movable rod-like contact, fusible means connecting said contact to the other of said terminals, separable conducting means one of which is movable with said rodlike contact for electrically connecting said rodlike contact and said means of conducting material, and spring means connected between said one terminal and said rod-like contact for biasconducting means.

22. In a circuit interrupter, a tubular casing of insulating material, terminals at opposite ends means and separate means.

JAMES M. WALLACE.

draw out the arc' DISCLAIMER 2,259,946.James M. Wallace, Braddock, Pa. CIRCUIT INTERRUPTER. Patent dated October 21', 1941. Disclaimer filed March 5, 1943, by the assignee,

Westinghouse Electric c5: Manufacturing Company. Hereby enters this disclaimer to claims 1, 17 and 19 in said patent.

[Ofiicial Gazette March 30, 1943.]

DISCLAIMER 2,2 59,9 16.James 1M. Wallace, Braddock, Pa. CIRCUIT INTERRUPTER. Patent dated October 21, 1941. Disclaimer filed May 3, 1944, by the assignee, Westinghouse Electric Manufacturing Company.

Hereby enters this disclaimer to claims 2, 3, 4, 10, and 11 of said patent.

[Ofiicial Gazette May 80, 1.944.]

DISCLAIMER 2,259,946.James M. Wallace, Braddock, Pa. CIRCUIT INTERRUPTER. Patent dated October 21', 1941. Disclaimer filed March 5, 1943, by the assignee,

Westinghouse Electric da- Manufactum'ng Company. Hereby enters this disclaimer to claims 1, 17 and 19 in said patent.

[Oficial Gazette March 30, 1.943.]

DISCLAIMER 2,259,946.James M. Wallace, Braddock, Pa. CIRCUIT INTERRUPTER. Patent dated October 21, 1941. Disclaimer filed May 3, 1944, by the assignee, Westinghouse Electric d2 lllanufacturing Company. Hereby enters this disclaimer to claims 2, 3, 4, 10, and 11 of said patent [Official Gazette May 80, 1.944.]

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