US2970197A - Shock-resistant circuit interrupter - Google Patents

Description

Jan., 31, 1961 R. E. FRINK SHOCK-RESISTANT CIRCUIT INTERRUPTER Filed NOV. 6, 1951l 5 Sheets-Sheet l ATTORNEY 5 Sheets-Sheet 2 R. E. FRlNK SHOCK-RESISTANT CIRCUIT INTERRUPTER Cement- Impregnu'red Gloss Mcl'f Jan. 31, 1961 Filed Nov. 6, 1957 Jan. 3i, 1961 R. E. FRINK 2,970,197

SHOCK-RESISTANT CIRCUIT INTERRUPTER Filed Nov. 6, 1957 3 Sheets-Sheet 3 SHCK-RESISTANT CIRCUIT INTERRUPTER Russell E. Frink, Forest Hills, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania 'Filed Nov. i6, 1957, Ser. No. 694,881

4 Claims. (Cl. 2004147) This invention relates to shock-resistant circuit interrupters in general and, more particularly, to arc-extinguishing structures for circuit interrupters, which are particularly adapted to resist breakage during shock conditions.

A general object of the present invention is to provide an improved circuit interrupter, which is so constructed as to resist damage during shock conditions, such as may be encountered when apparatus, including such circuit interrupters, is installed `aboard fighting service craft.

A more speciiic object of the present invention is to provide an improved shock-resistant circuit interrupter having an arc-chute assembly, so constructed as to resist breakage of the several parts thereof during shock conditions.

A further object of the present -invention is to provide an improved extinguishing structure for a circuit interrupter, which is rendered shock resistant by utilizing cement over considerable supporting areas of the arcchute structure.

Yet a further object of .the invention is to provide an improved shock-resistant, air-break circuit interrupter of the magnetic blowout type, in which the unitary arcchute plate assembly is covered over wide areas thereof by cement. This cement is therefore disposed between said unitary arc-chute plate structure and the insulating side supporting plates of the arc-chute assembly.

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

Figure l is Ia fragmentary, side elevational view, partially in vertical section, of a magnetic blowout type of air-break, shock-resistant circuit interrupter employing the principles of the present invention, the contact structure thereof being illustrated in the closed-circuit portion;

Fig. 2 is a fragmentary, vertical sectional view through the arc-chute structure of Fig. 1, taken along the line lI-II of Fig. l, with the contact structure omitted for purposes of clarity;

Fig. 3 is a fragmentary, plan View, in section, taken substantially along the line lII--III of Fig. 2, looking in the direction of the arrows;

Fig. 4 is a fragmentary, plan View, in cross-section, taken through a modified type of arc-chute structure; and

Fig. 5 is a view similar to Fig. 4 but illustrating still a further modiiication of the invention.

Referring to the drawings, and more particularly to Fig` 1 thereof, the reference numeral 1 generally designates a shock-resistant circuit interrupter including contact structure, generally designated by the reference numeral 2, and a magnetic blowout type of arc-chute structure, generally designated by the reference numeral 3. As well-known by those skilled in the art, the circuit interrupter 1 functions to establish an arc across the separated contact structure 2, which established arc is moved upwardly by the natural looping effect of the arc itself, coupled with the magnetic blowout field, to become extinguished within the arc-chute structure 3.

Patented Jian., 31, 1961 tee t More specifically, the contact structure 2 includes a relatively stationary main contact 4 spaced from another main contact 5, which contacts 4 and 5 are bridged in the closed-circuit portion, as shown in Fig. 1, by a conducting bridging member 6, the latter being carried by a rotatable contact arm 7. The rotatable Contact arm 7 rotates about a stationary axis, not shown, which is in electrical Contact with the lower main contact 5, as well understood by those skilled in the art. At the upper extremity of the rotatable contact arm 7 is a movable arcing contact 3, coperable with a relatively stationary arcing contact 9, the latter being affixed to the upper main contact 4. As shown, the upper main contact 4 is secured t0 the outer end of a terminal stud 10, which extends through an insulating bushing 11. The insulating bushing 11 is supported upon a suitable supported framework, not shown.

The arc-chute structure 3 includes a magnetic blowout device, generally designated by the reference numeral 12, which includes a magnetizing coil 13, encircling a core 14, the latter making abutting contact with a pair of laterally extending magentic pole plates 15. As shown, the core 141 and the pole plates 15 are preferably of laminated construction to minimize magnetic losses due to the circulation of eddy currents.

The core 14 and the magnetic pole plates 15 generally straddle an arc-chute, generally designated by the reference numeral 16, which includes a pair of insulating side support plates 17 preferably formed from glass melamine. Disposed between the insulating support plates 17, at the opposite ends thereof, as illustrated in Fig. 3, is a pair of insulating channel members 1S, the latter being secured by bolts 19 and nuts 20 to the side support plates 17.

With reference to Fig. 3, it will be observed that disposed between the side support plates 17 and immediately adjacent to the chanel strip 18 is a support plate 21, which carries an inner arc horn 22, as shown in Figs. l and 3 of the drawings. The arcing horn 22 is spaced away from the insulating support plate 21 by screws 23 and tubular spacers 2.4. Additional insulating strips 25 space a unitary plate stack 26 away from the support plate 21.

The unitary plate stack 26, which is formed from a plurality of spaced slotted insulating plates 27, has spacing strips 28 constituting elongated strip-like insulating spacing means, formed of sections of asbestos rope, functioning to maintain the slotted plates 27 a xed distance apart.

As shown in Fig. 2 of the drawings, each insulating plate 27 has a tapered elongated slot 29 therein, the upper closed end 3i) being positioned olf center from the center line 31 of the plate.

During the assembly operations, the ceramic plates 27 are staggered, so that the upper end 3i) of the slot 29 rst extends to one Side of the center line 31, and then to the other side of the center line 31, so that a zig-zag tarc passage 32 extends throughout the plate stack 26. The plates 27 are spaced apart, as shown in Fig` 3, to provide a plurality of spaced Venting passages 33 therebetween. The vent passages 33 result from the use of sections of the asbestos rope 2S, which are positioned at the outer side edges of the plates 27, as shown. In practice, the several plates 2'7 and the asbestos rope sections 28 are cemented together, in a preliminary process, so that a unitary, cemented, plate stack 26 results. This unitary plate stack 26 may be bodily handled, as a stack unit, during subsequent assembly steps.

As shown in Fig. 2, a pair of arc shields 3S are bolted by bolts 36 and nuts 37 to the side insulating support plates 17 at a location, more clearly shown in Fig. 2

of the drawings. The spaced arc shields 35 are tapered inwardly, as shown in Fig. 2, leading gradually into the-V zig-zag arc passage 32.

The opening operation of the circuit interrupter 1 will now briey be described. During the opening operation, the rotatable contact arm '7 is rotated in a clockwise direction about its stationary pivot axis, not shown, by suitable mechanism, which forms no part of the present invention. The conducting bridging bar 6 iirst separates from the stationary, spaced main contacts 4, 5, thereby compelling the current to pass through a pair of secondary contacts 3S, 39 and the arcing contacts 8, 9. The secondary contacts 38, 39 then separate, forcing the current -to pass between the arcing contacts 8, 9. Subsequently, the arcing contacts 8, 9 separate, and :an arc 4t) is established between the relatively stationary contact 9 and the movable arcing contact 8, which is shown in its partly open position at the location 41 in Fig. 1.

Because of the natural looping tendency of the arc 40, it will bow upwardly to the position 42, so that a portion thereof will contact inner arc horn 22. This portion of the arc is indicated by the dotted line 42a. Since the magnetic blowout coil 13 is electrically connected by a connector 43 to the stationary contact 9, and by a jawshaped contact 44 to the arc horn 22, it will be obvious that the blowout coil 13 is in electrical parallel across the arc portion 42a, which extends between the lower end of arc horn 22 and stationary arcing contact 9.

The impedance offered by the blowout coil 13 to the flow of current is less than that offered by the arc portion 42a; consequently, the arc portion 42a will become extinguished, and the entire current, passing through the interrupter 1, will flow through the blowout coil 13. This current tiow through coil 13 will generate magnetic flux across the arcing space 32 between the side magnetic pole plates 15, and will, as a result, force the arc 45, now extending between the arcing horns 22, 46 upwardly into the plate stack 26. The end of the arc 42, terminating at movable arcing Contact 8 has, during this time, of course, transferred to the front arc horn 46, the latter being electrically connected by a exible connector 4-7 to the rotatable contact arm 7.

The intense magnetic eld, now existing between the magnetic pole plates 15, will move the arc 45 upwardly Iwithin slots 29 of the plates 27, causing it to be elongated and cooled because of the zig-zag configuration of the arcing passage 32. Extinction of the arc 45 occurs at the closed ends 30 of the slots 29 in a manner described in U.S. Patent 2,442,199, issued May 25, 1948, to Robert C. Dickinson and Russell E. Frink, and assigned to the assignee of the instant application.

The type or arc-chute structure 3, heretofore described, contains as the active elements thereof parts, such as the plates 27, which must be able to withstand extreme heat shock, in addition to being subjected momentarily to extremely high arc temperatures. The plates 27 mustnot become conducting at these high arc temperatures, and preferably must give off virtually no gas. The best material that has been found for this purpose is a red, Zircon porcelain. To obtain the desired properties, the porosity is maintained at such a value that the plates 27 are relatively fragile with respect to mechanical shock. rl`his can be tolerated for most applications, but occasionally an `application is encountered, which requires more resistance to breakage. Such an application would be the use of electrical apparatus incorporating circuit breakers 1, as set out in Fig. 1, when used aboard combat ships.

The present invention is particularly concerned with a method of construction, which provides a more rigid ininterrupter, better adapted to applications, where high mechanical shock may be encountered. The arc-chute stack 26 operates in the manner heretofore described, and is mounted between the magnetic pole plates 15 and asside insulating plates 17 and the two end channels 18. There.-is-thus provideda rectangular enclosure 48 for accommodating the plate stack 26. As mentioned, the plate stack 26 comprises the spaced plates 27 and the asbestos rope spacers 28 cemented together, and baked, so as to form an integral unit.

The increased shock resistance is provided by sheets of glass mat 49, and pads 50 (Fig. 2), which are impregnated with `a suitable cement on assembly, and the entire unit is baked to polymerize the cement. The result is that the entire arc-'chute 3 is a rigid assembly, with no freedom for movement between any of the components. Also, the ceramic plates 27 are uniformly supported over a very wide area, so that there are no stress concentrations.

To more fully bring out features of the invention, a description of the assembly steps will now be described. On assembly, the side insulating plate 17, which is preferably 'mad'e from a melamine-glass laminate, is laid on its side. lts upper surface, which has preferably been roughened, as by sanding, is coated with a cement, which may, for example, be a urea-formaldehyde resin dissolved in a solvent and a suitable filler, auch as calcium carbonate. A layer of 'glass fiber mat 49 is then placed over the cement covered surface, and another coating of cement is applied to the mat 49, so that it is thoroughly saturated. The ceramic stack 26 and the arc shields 35, end vents 21, 25 and end channels 18 are then placed against the mat 49. Another coat of cement is applied to the top of the ceramic pants, another glass mat 49, another side insulating plate 17, and the entire assembly is bolted together, land baked, to polymerize the cement.

Further shock resistance may be provided by cementing another mat 51 between the outsides of side plates 17 and the magnetic pole plates 15, as illustrated in the modiiied type ofconstruction illustrated in Fig. 4 of the drawings.

Test work was performed on a section of a stack 26, which was cemented to a side plate 17 of glass melamine in the above manner. The edge of the plate 17 was clamped in a vice, and the opposite edge of the plate 17 was struck with a hammer blow of sufficient force to severely damage the edge of the plate 1'7. Under this shock, the section stack 26 remained firmly cemented to the plate 17, and was not damaged in any way.

Fig. 5 shows a still further modified type of construction, in which the glass mats 49, 51 are eliminated, and in their place a heavy-bodied cement is utilized. The heavy-bodied cement is disposed between the side plate 17 and the plate stack 26 and is designated by the reference numeral 52. The heavy-bodied cement disposed between the magnetic pole plates 15 and the insulating side plates 17 is designated by the reference numeral 53. The following is an example of a heavy-bodied cement, which has been found to be very suitable for such use. An epoxy resin is mixed with a suitable amine type catalyst, and a ller of silicon gel and titanium dioxide is ernployed. This heavy-bodied cement will cure within a short time, so it must be speedily used.

From the foregoing description of the invention, it will be apparent that there is provided an improved shockresistant circuit interrupter i1, of the type employing generally fragile plates 27, which has been rendered shock resistant by employing cement, or a glass mat 49 impregnated with cement, extending over a wide area between the side plates 17 and the side of the unitary plate stack 26. Y

The pads 50, shown in Fig. 2, may be formed from asbestos rope sections, impregnated with the cement, as was the case with the glass mats 49, 51. The asbestos rope pads 50 have, in addition, another function of preventing the cement 52 Vfrom seeping along the space S4 (Fig. 2) into the arcing passage 32.

sembled within an insulating enclosure 48, comprising the The glass mats 49, 51 may be employed where it is not desired to usea heavy-bodied cement, or thev glass mats 49, 51 may be eliminated, where the use of a heavybodied cement is desired. In either case, the use of the cement causes an adhering support of a wide side area of the plate stack 26 to the supporting side plates 17, thereby providing a construction in which each ceramic plate 27 is firmly supported at its outer side edges to the immediately adjacent side insulating support plates 17.

The use of the foregoing features has resulted in e11- abling magnetic, air-break circuit interrupters of the foregoing type, utilizing rather fragile plates 27, passing shock tests in a very satisfactory manner. Thus such shockresistant interrupters are very suitable for use aboard combat ships, with no danger of breakage of the plate stacks 26.

Although there has been shown and described specific structures, it is to be clearly understood that the same were merely for the purpose of illustration, and that changes and modications may readily be made therein, without departing from the spirit and scope of the invention. l

I claim as my invention:

l. A circuit interrupter including means for establishing an arc, means for extinguishing said arc including a plate stack, said plate stack including a stack of spaced slotted insulating arcing plates and elongated strip-like insulating spacing means extending along opposite sides of the slotted insulating arcing plates, said elongated strip-like insulating spacing means being disposed between the slotted arcing plates to space the slotted arcing plates a proper distance apart from each other, a pair of spaced side insulating support plates disposed on opposite sides of the plate stack, a sheet-like glass mat disposed between each side support plate and the side edges of the slotted arcing plates, the glass mats also contacting the elongated strip-like insulating spacing means extending along opposite sides of the plate stack, and a cement impregnating said sheet-like glass mats to cause adherence between the spaced side support plates and the individual slotted arcing plates.

2. A circuit interrupter including means for establishing an arc, an arc chute for effecting the extinction of said arc including a stack of spaced insulating plate portions, elongated strip-like insulating spacing means extending along at least one side of said arc chute at the outer side edges of the plate portions and between the plate portions to space the latter apart, said arc chute also including an insulating side support plate separate from said elongated strip-like insulating spacing means, an extensive layer of cement extending over an appreciable area of the inner surface of the side support plate facing said stack of plate portions, and said extensive layer of cement contacting not only said side edges of the insulating plate portions but also the outer side edges of the elongated strip-like insulating spacing means for adherence between the side support plate and the plate portions resulting thereby in a shock-resistant arc-chute construction.

3. A circuit interrupter including means for establishing an arc, an arc chute for effecting the extinction of said arc including a stack of spaced generally rectangularly-shaped ceramic plates, a plurality of pairs of spacing strips extending along the outer side edges of the plates and between the plates to space the stack of plates apart, the plurality of pairs of spacing strips being cemented to the plates for adherence, a pair of spaced opposed insulating side support plates separate froni said spacing strips, an extensive layer of cement extending over an appreciable area of the inner surface of each of the two opposed side support plates between said support plates and the interposed stack of rectangularly-shaped ceramic plates, and said extensive layer of cement contacting not only the outer side edges of the interposed stack of ceramic plates but also the outer side edges of the pairs of cemented insulating spacing strips whereby a shock-resistant arc chute results.

4. A circuit interrupter including means for establishing an arc, an arc chute for effecting the extinction of said arc including a stack of spaced generally rectangularly-shaped ceramic plates, a plurality of pairs of spacing strips extending along the outer side edges of the plates and between the plates to space thestack of plates apart, the plurality of pairs of spacing strips being cemented to the plates for adherence, a pair of spaced opposed insulating side support plates, a plate-like glass mat disposed between the inner surface of each of the two opposed side support plates between said support plates and the interposed stack of rectangularly-shaped ceramic plates, and a cement impregnating each of said plate-like glass mats to cause adherence between the side support plates and the ceramic plates whereby a shock-resistant arc chute results.

References Cited in the tile of this patent UNITED STATES PATENTS 2,337,949 Walle Dec. 28, 1943 2,708,698 Ainsworth May 17, 1955 2,734,842 Frink et al. Feb. 14, 1956 2,864,919 Stringfellow Dec. 16, 1958 2,905,792 Caswell Sept. 22, 1959

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