US2752458A - Circuit interrupters - Google Patents

Description

June 26, 1956 lllll l Fig. l. WITNESSES:

B. P. BAKER ETAL CIRCUIT INTERRUPTERS Filed July 26, 1952 INVENTORS Benjamin P. Baker and Wilhom A. Guskill.

ATTORN Fig.2.

nited States Patent CIRCUIT INTERRUPTERS Benjamin P. Baker and William A. Gaskill, Turtle Creek, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 26, 1952, Serial No. 301,112

18 Claims. (Cl. 200-149) This invention relates generally to circuit interrupters, and, more particularly, to arc-extinguishing structures therefor.

A general object of our invention is to provide an improved circuit interrupter, which will more effectively interrupt the current passing therethrough than has heretofore been obtained.

A particular object is to make possible the use of a selfgenerated gas-blast interrupter in devices such as loadbreak disconnecting switches where the circuit must be interrupted many times without renewing the arc-extinguishing structure, as has been done in the past with fuses which are one-shot devices. The invention is also usable in fuses, particularly those of the renewable type in which the same arc-extinguishing structure is used a number of times.

A more specific object is to provide an improved and more effective are passage for a circuit interrupter, which will be highly effective in interrupting currents over a wide current range and which will maintain its interrupting ability, particularly with respect to low currents, after a considerable number of interrupting operations,

Still a further object is to provide an improved and more effective arc-extinguishing structure, which restricts the are drawn therethrough and produces desired turbulence to effect more rapid arc extinction.

A further object is to provide a substantially tubular arcextinguishing structure comprising a plurality of tubular gas-evolving blocks disposed in end-to-end relationship and being interspersed with one or more washer-shaped insulating members having a high resistance to arc erosion so as to increase the interrupting life of the device. Preferably, the washers have a smaller diameter than the diameter of the gas-evolving tubular members.

Further objects and advantages will readily become apparent upon reading the following specification, taken in conjunction with the drawing in which:

Figure l is a side elevational view, partially in vertical section, of a circuit interrupting device, in this instance a fuse, embodying the features of the invention;

Fig. 2 is a side elevational view, partially in vertical section, of a circuit interrupter embodying the principles of our invention, the contact structure being shown in the closed-circuit position; and

Fig. 3 is a sectional view taken along the line III-III of Fig. 2 looking in the direction of the arrows.

Referring to the drawing, and more particularly to Fig. 1 thereof, the reference numeral 1 generally designates a fuse structure embodying an insulating cylindrical casing 2 having the ends 3 and 4 thereof threaded. The threaded ends 3 and 4 of the casing 2 secure into place ferrules 5, 6 to which conducting terminal structures 7, 8 are respectively secured.

Disposed interiorly of the casing 2, at the lower end thereof, is a thin conducting metallic cylinder 9 having an out-turned flange portion 10 at the lower end thereof. The flange portion 10 is secured fixedly into place by the abutment of the terminal structure 8 with the lower ferrule 6.

Secured to the interior wall of the cylinder 9, at the upper end thereof, as by screws 9a, is a pair of flexible connectors l1, which have their other ends secured, as by spotwelding, to a conducting plate 12 having a centrally threaded aperture 13 provided therethrough. Threadedly secured within the central aperature 13 of the plate 12 is a movable fuse rod 14 having secured to its upper end a fuse link The fuse link 15 is adapted to fuse upon toe passage of overload currents through the fuse structure l.

A compression spring 16 seats upon the plate 12 and has its upper end seated against a radially inwardly-extending flange portion 17 of the conducting cylinder 9. Consequently, the fuse rod 14 is biased downwardly by the compression spring 16 in an opening direction, and is maintained in its closed position, as shown in Fig. 1, by the fuse link 15.

The upper end of the fuse link 15 is preferably secured by a screw 18 to a conducting spider portion 19 of the upper terminal structure 7.

Disposed interiorly within the tubular casing 2 of the fuse structure 1 is a plurality of gas-evolving insulating cylindrical members or apertured blocks 20. The gasevolving members may be formed of any suitable material which gives off arc-extinguishing gases when subjected to the heat of the arc, such as boric acid, fibre, polyethylene, etc.

Boric acid (H3303) decomposes under the action of an are forming mainly water vapor (steam) which is noninflammable and condensible, and boric oxide (B203). Fiber will decompose into carbon monoxide, hydrogen, water vapor and a little carbon. Polyethylene decomposes into hydrogen, carbon monoxide, carbon dioxide, water vapor and some carbon. Boric acid is considered the best of the three mentioned gas-evolving substances since it gives off a non-inflammable and condensible gas.

As shown, the gas-evolving cylindrical members 20 are interspersed by insulating washers or apertured blocks 21, having a smaller internal diameter than the gas-evolving members 2%. Preferably, the insulating washers 21 are formed of an arc-resisting material which will have high arc-erosion characteristics. Materials which are resistant to arc erosion are well known to those skilled in the art. Examples of such materials are polytetrafiuoroethylene, zircon, and such like materials.

The operation of the fuse structure 1 is as follows: Upon the passage of an excessive amount of current through the device, the fuse link 15 will fuse, thereby permitting the compression spring 16 to force the released fuse rod rd downwardly to draw an are along the arc passage 23, provided by the gas-evolving cylindrical members 20 and the washer-shaped arc-resistant insulating members 21. The heat of the established arc will evolve considerable quantities of arc-extinguishing gas from the adjacent gas-evolving cylinders 20. However, this evolved gas must necessarily pass through the series of restricted holes, or orifices 25, of small diameter provided by the insulating washers 21. The net result is that the evolved gas is caused thereby to come into intimate contact with the established arc, and there results thereby highly effective arc-extinguishing action. The evolved gas may pass either downwardly into the region 24, or upwardly into a condensing chamber of conventional style, not shown, but which is disposed interiorly of the upper ter-- minal structure 7 of the device.

It will be noticed that the device 1 is completely selfcontained, that is, it generates its own arc-extinguishing gas at the desired time, namely during circuit interruption. The function of the orifice discs 21 is twofold. First, the apertured discs 21 of highly arc-resistant material for mechanical guides for the movable fuse rod 14 and protect the gas-evolving cylinders 20, which have very little strength, from mechanical erosion. Secondly, the orifices 25, provided by the insulating washers 21, form restrictions in the interrupting chamber 23, which controls the gas pressure and provides constrictions through which the arc is drawn. These constrictions produce regions of very high gas velocity in close proximity to the arc stream, which in turn results in intense turbulence and enhanced interrupting ability, especially at the low values of current, Consequently, the device is very suitable for interrupting currents over a wide current range, and has a longer life since the areresistant discs 21 maintain their orifices of small diameter even though the gas evolving material 29 is consumed to the extent that the passages in the blocks are enlarged.

The fuse device 1 is particularly effective during low current interruption, and has highly increased life as a result of using the alternate sections of dissimilar material. One section, namely, the arc-resistant apertured discs 21 has as its function the ability to resist mechanical shock and wear and to restrict the arc passage to produce regions of high velocity and turbulent gases, and to withstand considerable voltage. The other section, namely, the gas-evolving cylinders 20 of larger internal diameter has as its function the ability to produce an intense blast of gas or vapor when exposed to heat, and also to withstand considerable voltage.

Figs. 2 and 3 illustrate a second embodiment of our invention, which utilizes the same arc-passage construction 23 but is adaptable for repeated operation by incorporating a cooperable pair of stationary and movable contacts 28, 29. The movable rod-shaped contact 29 has its lower end secured to a plate 30, to which a flexible connector 31 is secured. The other end of the flexible a connector 31 is secured, as at 32, to a lower terminal ferrule 33. An accelerating compression spring a biases the plate 30 and hence the rod 29 in an opening direction.

Means are provided to latch the plate 30 into position, and thereby maintain the contacts 28, 29 in closedcircuit position. In this instance, such a latching means 34 includes a pivotaliy-mounted latch 35, having a nose 36 which latches under the plate 30. The latch has an integrally formed armature tripping portion 38, which is moved upwardly, as viewed in Fig. 2, upon the energization of a tripping solenoid 39. As shown, the solenoid 39 is fixedly secured to one side of the lower terminal ferrule 33.

From the foregoing description, it will be clearly apparent how the circuit interrupter of Figs. 2 and 3 operates. To open the circuit, the tripping solenoid 39 is energized. This will attract the armature 38 to thereby release the latch 35 from the plate 30. The released plate 30, under the opening biasing action of the spring 30a, will rapidly move the rod-shaped movable contact 29 downwardly away from the finger type stationary contacts 28, to draw an arc therebetween within the elon gated arc passage 23. The are passage 23 has the same construction as described heretofore in connection with Fig. 1, and the established arc is extinguished in the same manner, with the exception that evolved gases are only permitted to pass upwardly into the condensing chamber disposed interiorly within the upper terminal structure 7a. The are is rapidly extinguished by the volumes of evolved gases, which pass through the constricted orifices 25 provided by the spaced arc-resistant washerlike members 21.

It is to be clearly understood that although we have disclosed two embodiments of our invention as applied to relatively simple structures, the broad features of our invention may be easily applied, by those skilled in the art, to other interrupting structures, such as load-break disconnecting switches and circuit breakers. It is to be observed that the interrupter is highly effective over a wide current range and is completely self-contained. Al

though devices of the prior art in certain instances are effective in interrupting relatively high overload currents, little attention has been directed to the interruption of low currents, such as line-charging, transformer-magnetizing and normal-load currents, generally falling in the low-current range. As mentioned, our devices are particularly suitable for interrupting such low currents. Moreover, our devices have a very low rate of erosion by virtue of the use of the arc-resistant insulating discs 21, which gives it a long life and serves an important guiding function.

Although we have shown and described two specific structures of simplified form, it is to be clearly understood that the same were merely for the purpose of illustration and that the principles of our invention may be readily applied, with modification, by those skilled in the art, to other devices without departing from the spirit and scope of the invention.

We claim as our invention:

1. A circuit interrupting device including means defining an elongated arc passage having an opening at one end, means for establishing an are within the arc passage, a plurality of gas-evolving insulating apertured blocks disposed along the arc passage whereby a blast of gas flows longitudinally along the arc passage and out said opening, and a plurality of relatively nonerodible arc-resistant insulating apertured blocks interspersed between the aforesaid gas-evolving blocks and having apertures no larger than the apertures in the gas-evolving blocks.

2. A circuit interrupting device including means defining an elongated arc passage, means for establishing an are within the arc passage, said first-mentioned means having a plurality of gas-evolving insulating portions disposedalong the arc passage, and a plurality of insulating less erodible arc-resistant portions interspersed between the aforesaid gas-evolving portions and spaced no farther away from the arc than the gas-evolving insulating portions.

3. A circuit interrupting device including means defining an elongated arc passage having an opening adjacent one end thereof, means for establishing an arc within the arc passage, a plurality of gas-evolving interspersed between the aforesaid gas-evolving blocks, and

the internal diameter of the arc-resistant insulating blocks being less than the internal diameter of the insulating gas-evolving blocks.

4. A circuit interrupting device including tubular means defining an elongated arc passage, means for establishing an arc within the arc passage, a plurality of gas-evolving cylindrical insulating blocks disposed along the arc passage, and a plurality of arc-resistant non-gasevolving cylindrical insulating blocks interspersed between the aforesaid gas-evolving cylindrical blocks having an internal diameter no larger than the internal diameter of the gas-evolving cylindrical insulating blocks.

5. A circuit interrupting device including tubular means defining an elongated arc passage having an opening at one end thereof, means for establishing an arc within the arc passage, a plurality of gas-evolving cylindrical insulating blocks disposed along the arc passage whereby a blast of gas flows axially along the arc passage and out said opening, a plurality of cylindrical blocks of insulating material which is less erodible than the material of thesaid gas-evolving blocks interspersed between the aforesaid gas-evolving blocks, and the internal diameter of the relatively less-erodible blocks being less than the internal diameter of the gas-evolving blocks.

6. A circuit interrupting device including tubular means defining an elongated arc passage, means for esaverages tablishing an are within the are passage, a plurality of thick gas-evolving cylindrical insulating blocks disposed along the arc passage, and a plurality of relatively thin insulating non-erodible arc-resistant washers interspersed between the aforesaid gas-evolving cylindrical insulating blocks having an internal diameter no larger than the internal diameter of the gas-evolving cylindrical insulating blocks.

7. A circuit interrupting device including tubular means defining an elongated arc passage, means for establishing an are within the arc passage, a plurality of gasevolving cylindrical insulating blocks disposed along the arc passage, a plurality of relatively thin insulating areresistant non-gas-evolving washers interspersed between the aforesaid gas-evolving cylindrical insulating blocks, and the internal diameter of the relatively thin washers being less than the internal diameter of the gas-evolving cylindrical blocks.

8. A circuit interrupting device including means defining an elongated arc passage having an opening adjacent one end thereof, means for establishing an are within the arc passage, a plurality of gas-evolving apertured blocks of boric acid disposed along the are passage so that a blast of gas flows axially along the arc passage and out through said opening, and a plurality of apertured blocks of an insulating material less erodible than the boric acid blocks interspersed between the aforesaid gas-evolving blocks of boric acid and having apertures no larger than the apertures in the blocks of boric acid.

9. A circuit interrupting device including means defining an elongated arc passage, means for establishing an are within the arc passage, a plurality of gas-evolving members disposed along the arc passage which give off a non-inflammable gas, and a plurality of relatively nonerodible members of insulating material interspersed between the aforesaid members and spaced no farther away from the arc than the gas-evolving members.

10. A circuit interrupting device including means defining an elongated arc passage having an opening adjacent one end thereof, means for establishing an are within the arc passage, a plurality of gas-evolving members disposed along the arc passage which give ofi a condensible gas so that a blast of gas flows axially along the arc passage and out through said opening, and a plurality of relatively non-erodible members of insulating material interspersed between the aforesaid members and spaced no farther away from the arc than the gas-evolving members.

11. A circuit interrupting device including means defining an elongated arc passage, means for establishing an are within the arc passage, a plurality of gas-evolving members disposed along the arc passage of appreciable axial length which give off a non-inflammable gas, and a plurality of relatively arc-resistant non-gas-evolving thin members of insulating material interspersed between the aforesaid members and spaced no farther away from the arc than the gas-evolving members.

12. A circuit interrupting device including means defining an elongated arc passage, means for establishing an are within the arc passage, a plurality of gas-evolving members disposed along the arc passage of appreciable axial length which give off a condensible gas, and a plurality of relatively non-erodible thin members of insulating material interspersed between the aforesaid members and spaced no farther away from the arc than the gasevolving members.

l3. A circuit interrupting device including means defining an elongated are passage, means for establishing an are within the arc passage, a plurality of gas-evolving members disposed along the arc passage which give off water vapor, and a plurality of relatively non-erodible members of insulating material interspersed between the aforesaid members and spaced no farther away from the arc than the gas-evolving members.

14. A circuit interrupting device including means defining an elongated arc passage, means for establishing an arc tin are pa. 3, plurality gas-evolving members disposed along the arc passage of appreciable axial length which give off water vapor, and a plurality of less-erodible thin members of insulating material interspersed between the aforesaid members and spaced no farther away from the arc than the gas-evolving members.

15. A circuit interrupting device including means defining an elongated arc passage, means for establishing an are within the are passage, a plurality of boric acid members disposed along the arc passage, and a plurality of relatively non-erodible members of insulating material interspersed between the aforesaid members and spaced no farther away from the arc than the boric acid members.

16. A circuit interrupting device including means defining an elongated arc passage, means for establishing an are within the arc passage, a plurality of boric acid members disposed along the arc passage, and a plurality of relatively non-erodible thin members of insulating material interspersed between the aforesaid members and spaced no farther away from the arc than the boric acid members.

17. A circuit interrupting device including means defining an elongated arc passage having an opening adjacent one end thereof, means for establishing an are within the arc passage, said first-mentioned means having a plurality of gas-evolving insulating portions disposed along the are passage whereby a blast of gas flows longitudinally along the arc passage and out said opening, and a plurality of insulating less erodible arc-resistant portions interspersed between the aforesaid gasevolving portions and spaced no farther away from the arc than the gas-evolving insulating portions.

18. A circuit interrupting device including means defining an elongated arc passage, means for establishing an are within the arc passage, said first-mentioned means having a plurality of gas-evolving insulating portions disposed along the arc passage, and a plurality of insulating less erodible arc-resistant portions interspersed between the aforesaid gas-evolving portions and spaced a lesser distance away from the arc than the gas-evolving insulating portions.

References Cited in the file of this patent UNITED STATES PATENTS 2,077,282 Strom et a1. Apr. 13, 1937 2,082,028 Rawlins June 1, 1937 2,337,504 Strom Dec. 21, 1943 2,452,477 Leeds Oct. 26, 1948 2,611,846 Applegate Sept. 23, 1952

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