US2328825A - Arc-extinguishing means - Google Patents

Description

4 Sheets-Sheet l f III- V/ a 0 RO .H. Q 3 OJ@ Q v ww l f Ww, #n Hm fw@ mw @www Y for@ @ha ,mwwm/dsw @JU @.OZMRMOW@ mm w www M@ fm FWN fm M Sept. 7, 1943. G. F. MCMAHON ARC EXTINGUISHING MEANS Filed Sept. 25 1941 4 Sheets-Sheet 2 Sept. 7, 1943. G. F. MCMAHON Filed Sept. 25 1941.

4 Sheets-Sheet 5 INVENTOR. 6260x396 FJCMCL/O/z www# Sept. 7, 1943. G. F. MCMAHON ARC EXTINGUISHING MEANS 4 Sheets-Sheet 4 Filed Sept. 25, 1941 Patented Sept. 7, i943 1 @FFQ George F.- ll/Ecltfaahcn,

Sept in iiicago, lli., assigner to Schweitzer as Conrad, inc., hicago, m., a corporation ai Beiaware 'bei' 25, Iiiii, Seriali No. dili My invention reliates, generally, to circuit iriterrupting apparatus, auch as circuit breakers, lightning arresters and fuses, and it has risicalar relation to new and improved arc extinguishing materials therefor.

in circuit interrupting apparatus it is customary to provide a structure for confining the arc that is drawn on operation or the device to interrupt the circuit. The surface of such a structure adjacent the arc is preferably formed oi' a material which will evolve an arc extinguishing medium under the heat of the arc so as to quickly destroy or put out the arc or create a condition such that it cannot be sustained. After the arc is extinguished the structure preferably has insulating characteristics such that there is no likelihood of an arc being reformed or restruck between the live parts of the circuit. it is customary to place circuit interrupters of this character out of doors where they are subject to the weather. Therefore, it becomes desirable to so construct the arc confining and extinguishing structure that it is relativelyWun-afiected by the weather.

It has been customary in the past to make thearc confining and extinguishing structure of different kinds of materials, each particularly adapted to perform certain functions. Thus, the material forming the surface adjacent the arc is adapted to evolve a relatively large quantity o! are extinguishing medium. Such material, as employed in the past, was relatively Weak from a mechanical standpoint and did not have weather resisting characteristics. Accordingly, it has been the practice to surround such a material with another material which was relatively strong and capable of resisting the pressures incident to circuit interruptions. In many instances, the pressure resisting material did not possess sumcient weather resisting properties and it was customary to surround it with material which did have good weather resisting characteristics.

An object of my invention is to provide an arc confining and extinguishing structure which may be formed of material of homogeneous character throughout and which combines in it all of the desired characteristics for such a. structure thereby not requiring that diii'erent kinds of material be employed to make up a composite arc extinguishing and confining structure as has been required in the past.

The following characteristics are desirable in an arc extinguishing and coniining structure:

i. should he capable ai being macliined, moulded, cast, or formed into the shape desired. Zit should be mechanically strong or strong enough to meet any treatment in handlm or assembly work. The surface should be hard to resist ordinary scratching and abuse while in service.

3. It should be insoluble in slater. Y

e. lt should be stable at ordinary operating temperatures and should not soften or change its shape at a temperature of l00 C.

5. lt should be non-inriammable.

6. It should be non-corrosive, either before or after operation or. arc extinction.

7. It should be non-poisonous or not dangerously poisonous.

8. It should be able to extinguish within reasonable clearances in circuit interrupting apparatus high or low alternating currents at high voltages.

9. Its insulating characteristics should be high.

l0. It should be strong enough to resist the pressure incident to circuit interruption.

1l. It should not track or produce a conducting path of carbon or crack or produce an excessive amount of soot upon operation under high voltage stresses.

l2. It should be relatively unaffected by prolonged exposure to bright sunlight, moisture and extremes of normal operating temperature.

Another object oi my invention is to provide circuit interrupting apparatus having an arc conilning and extinguishing structure formed of a homogeneous material and having essentially all of the foregoing characteristics.

Other objects of my invention will, in part, be obvious and in part appear hereinafter.

For a more complete understanding of the nature and scope of my invention reference can be hadto the following detailed description taken in connection with the accompanying drawings in which:

Figure 1 is a longitudinal sectional view which illustrates diagrammatically a circuit interrupter oi' the separable contact member type;

Figure 2 is a view, similar to that shown in Figure l, showing a lightning arrester construction;

Figure 3 is a longitudinal sectional view of a circuit interruptor of the fuse type;

Figures 4 and 5 are longitudinal sectional views of diiierent forms of replaceable or renewable fuse links 2 Figures 6 and 7 are longitudinal sectional views of different forms of replaceable fuse links or cartridges;

Figure 8 is a longitudinal sectional view of the upper end portion of a liquid type fuse in which the present invention is incorporated; and

Figure 9 is a longitudinal sectional view of one form of load-break device for use in conjunction with a disconnecting switch of the knife blade type.

Referring now particularly to Figure 1 of the drawings, it will be observed that the reference character I designates, generally, a circuit interrupter having a iixed or stationary contact member II and a movable contact member I2. In the circuit closed position the contact member I2 is in engagement with the stationary contact member II so as to complete a circuit therethrough. The circuit is opened by separating the contact members Il and I2. The circuit interrupter may be employed in an alternating current circuit the current carrying capacity of which normally is of the order of several hundred amperes at voltages ranging upwardly from 2300 volts. It will be understood that these iigures are in no wise to be considered as limiting the application of the present invention but are employed merely for illustrative purposes. The circuit interrupter I0 can be employed for circuits having less current carrying capacity and operating at lower voltages.

The primary function of the circuit interrupter I0 is to interrupt or extinguish the arc formed between the contact members II and I2 in an efficient manner. For this purpose an arc extinguishing and confining structure I3 is provided within which the arc between the contact members II and I2 is drawn in the bore Il thereof.

For the reasons indicated hereinbefore it is desirable that the arc confining and extinguishing structure be formed of a material which possesses various characteristics so that it is unnecessary to employ more than one material in making up the same.

I have found that melamine and other similar compounds derived from cyanamid, dicyanodi- A amid or guanidine from which synthetic resins or condensation products can be produced are satisfactory materials for this purpose. Melamine is a pure chemical and has been manufactured as such. It crystallizes from hot water as white monoclinic prisms. It has a-chemical forhood of 350 C. It does not seem to have any true melting point at atmospheric pressure. Melamine reacts with aqueous solutions of formaldehyde and other chemicals forming condensation products or vsynthetic resins varying in solubility depending upon how they are made or compounded during the reacting process. Variations in time, temperature and the use of catalysts are some of the controlling factors. The resultant condensation products are generally called melamine formaldehyde resins. Melamine is noninflammable as are the melamine formaldehyde resins. Their non-inflammability is due to the high nitrogen content. Some of the reacting resins can be placed in solution either with water, water and alcohol or hydrocarbons, the preferable solvent being a water-alcohol mixture. Some resins are more stable than others and stabilizing reagents may be employed. These solutions can be used to impregnate brous materials or they can be mixed with other brous materials or llers and dried without condensation and polymerization setting in and later used to form solid heat resistant insulating bodies under heat and pressure in suitable moulds or dies. Wood our can be used as a filler. Of particular value are powdered nllers containing magnesium, such as magnesium hydroxide. magnesium oxide, magnesium silicate and magnesium borate. Pure silica can be used. Compositions containing from 30% to 50% of melamine formaldehyde resin with these fillers can be used to advantage. The resins will condense and polymerize under heat and pressure evolving some formaldehyde and water vapor and thereafter are insoluble in water and a great many other solvents.

Melamine is a nitrogen containing cyclic organic compound. It is also known as 2,4,6-triamino-1,3,5 triazine, as cyanuric acid amide and as cyanuric triamide. Its chemical structure can be represend by a six membered ring compound with alte ate carbon and nitrogen atoms in the ring. This ring is indicated by the following conventional diagram.

It will be observed that no oxygen is present in this compound. Although melamine itself contains no oxygen, when it is combined with formaldehyde it is likely that some oxygen is present in the nal product containing one or more molecules of water of crystallization. Since melamine is oxygen free, it is reasonable to conclude that the polymerized or condensed resins thereof will be comparatively low in oxygen as during the process of moulding under heat and pressure some formaldehyde and water vapor is lost into the atmosphere. i

Melamine contains theoretically 66% nitrogen by weight.. It is because of this high nitrogen content. that resins of melamine are relatively non-inflammable. Also, because of the relatively high nitrogen content the melamine resin provides a satisfactory arc extinguishing material from which nitrogen, hydrogen and possibly small amounts of carbon containing gases are evolved due to the heat of the arc. Thiais hl mum of CSHSNS and it subumes in the neighbor- 5 m8 y effective in extinguishing the arc and preventing its restriking.

Melamine can be produced by many different processes but the most common or widely used methods make use of dicyanodiamide, cyanimide or guanidine as already mentioned.

In producing melamine other products of similar nature are derived, namely, melam, linclem, melon, ammelide and ammeline. All are cyclic organic compounds with nitrogen positioned in the ring structure and can be used to advantage in the production of resinous condensation products satisfactory for arc extinguishing purposes.

Resins can be produced from the melamines, preferably methylolamines by esteriiication. These products may be soluble in water. water and alcohol, hydrocarbons or are insoluble.

Melamine is weakly alkaline or basic in character and reacts therefore with many organic and inorganic compounds to produce stable compounds. With organic bases or acids complex resins are produced. One of the products produced through the reaction of melamine and formaldehyde .is hexamethylolmelamine, and contains one molecule of water of crystallization.

Melamine under certain conditions forms more complex nitrogen compounds one of which is tricyam'nelamine.

Melamine formaldehyderesins with modifying reagents, such as the carbohydrates, and polyhydric alcohols may be used although such additions have to be made with care in order not to produce electrically conducting materials.

Resinous .products may be used by reacting melamine with alkyl and aromatic aldehydes and ketones.

Unlike the urea formaldehyde resins, the melamine formaldehyde resins are more stable and water resistant. 'I'he urea formaldehyde condensations decompose at 350 F. whereas some of the melamine condensations are stable at 435 F. and in some cases 500 F., a valuable feature in electrical devices subject to abnormal temperature rise under service conditions.

The arc extinguishing and confining structure I3 can be formed in different ways such as moulding, casting or impregnation. For example, it can be formed of moulded melamine resin. This resin can be obtained from the American Cyanimid Company and is sold under the designation "M-l87 Melmac. Two grades of M-187 Melmac are available, one for compression moulding and the other for transfer moulding. The transfer grade contains a small amount of plasticizer while the other does not. These compositions comprise melamine formaldehyde resins and asbestos. They can be readily moulded under suitable heat and pressure to provide the desired shape of arc extinguishing and conflning structure I3. The moulding powders may or may not contain variable amounts of suitable plasticizer that facilitates formation of the desired shapes. The moulding process is preferably carrled. out at a temperature of about 310 F. with the pressure ranging from about 1200 to about 2400 pounds per square inch.

The structure I3 can be formed in tubular shape by moulding under heat and pressure a sheet of paper that has been impregnated with melamine formaldehyde resin. A resin sold by the American Cyanimid Company Aunder the designation S-77-V Melmac has been found to be particularly useful for this purpose. The paper is impregnated with this resin by applying one or two coats with a brush to one side. White alpha cellulose absorbent paper or white or colored paper can be used. After the paper is coated or impregnated with the melamine resin it is permitted. to dry for a few hours. Then it is wound on a mandrel under heat and pressure to the desired thickness of tubing. 'Ihe mandrel is preferably maintained at a temperature ranging from 150 to 180 F. After the tube is formed, it is cured at or above this temperature range. If it is desired to hasten Ithe curing of the tube, it can finally be carried out at a temperature of about 212 F. or somewhat vabove this tern` perature. Because of these relatively low ltemperatures, the paper is not affected adversely as would be the case if it were necessary to use substantially higher temperatures.

Coatings of melamine formaldehyde varnishes that are dried and baked are valuable arc resistant materials and are not easily affected by chemicals, especially those alkaline in reaction.

The structure I3 can also be formed of fiber glass impregnated with melamine resin. The fibrous material in sheet form is first covered or impregnated with the melamine formaldehyde resin solution and then after drying it is rolled into tubular forfm under heat and pressure to polymerize theresin and form a homogeneous construction.

In Figure 2 of the drawings there is illustrated at I0 a lightning arrester of the expulsion type. It is similar to the circuit interrupter I0, Figure 1, except that yit has a stationary lower terminal I5 which, as shown, is connected to ground, The terminal II is arranged to be connected to a high voltage line in accordance with conventional practice.

In Figure 3 of the drawings there is illustrated, generally, at I8 a circuit interrupter of the fuse type having an arc confining and extinguishing structure I1 in tubular form with terminals I8 and I9 at its ends. This construction provides the well known form of plain expulsion tube fuse device.

The terminals I8 and I9 are connected by a replaceable fuse link, illustrated generally at 20. The fuse link 20 comprises an upper terminal 2I having a threaded shank 22 on which is threaded a removable button head 23. It will be noted that the button head 23 abuts the upper end of the terminal I8 and that it is secured thereto by va `screw cap 24. Depending from the terminal v 2| are strain and fusible elements or wires 25 and 26. The strain wire 25 is preferably formed of nickel chromium alloy and the fuse wire 26 is preferably formed of silver. However, it will be understood that other metals can be employed for the strain and fusible wires 25 and 26. At their lower ends the strain and fusible wires 25 and 26 are fastened to a lower terminal 21 which is connected by means of a flexible conducting leady 28 to the lower fuse tube terminal I9. It is clamped thereto by a clamp 20 that is held in place by a screw 30.

The tube or arc extinguishing and confiningr structure I1 can be formed, as indicated, of moulded melamine resin or paper impregnated with melamine resin or fiber glass impregnated with melamine resin. The tube I1 can be formed from these materials in the same manner as described for the structure I3 of Figure 1.

It will be observed that the tube I1 is formed of a single homogeneous material. That is, it is not for-med of composite material having a liner of fiber, as in the prior art, and an outer covering of phenolic condensation product. It can be used out of doors where it is subjected to .the direct action of the weather since it is extremely weather resistant. The inner surface forming the bore 3| when subjected to the heat of the arc formed on fusing of the strain'and fusible Wires 25 and 26 between the terminals 2I and 21 evolves an arc extinguishing medium, i. e., nitrogen, which creates an expulsive effect to drive the terminal 21 out of the lower end of the tube I1 thereby extending the arc and at the same time substituting in the are space a relatively inert non-ionized medium which prevents the are from restrlking.

InFigure 4 of the drawings there is illustrated generally at 34 a replaceable fuse link of the type as shown in Ramsey Patent No. 2,144,707. The fuse link 34 comprises terminals 35 and 36 interconnected by strain and fusible elements 31 and 38. It will be understood that the terminal 35 is arranged to be connected to one circuit ter- 4minal while the terminal 36 is arranged to be confining and extinguishing structure or sleeve. shown generally at 49. The sleeve 48 comprises an outer sleeve 42 formed of moulded melamine resin or paper impregnated with melamine or fiber glass or other fibrous material impregnated with melamine resin. The inner sleeve or liner 43 is formed of material which is capable of evolving a relatively great quantity of water vapor. It can be formed of paper impregnated with magnesium borate or boric acid or it may be formed by arc extinguishing material with a binder of methyl cellulose as described in my copending application, Serial No. 369,162, filed December 9, 1940. The liner 43 is provided for evolving water vapor as an are extinguishing medium. In some instances it is desirable to employ this construction rather than to use the outer sleeve 42 alone without the liner 43. The particular construction used will depend upon the conditions that are to be met by the replaceable fuse link 34 in operation.

The composite sleeve 40 is arranged to be held in place on the terminal 35 by means of a pin 4|. If desired other means, such as knurling the terminal 35 can be employed for holding the composite sleeve 48 in place.

In Figure 5 of the drawings there is illustrated, generally, at 46 a replaceable spring link of the type shown in the copending application of Lindell, Serial No. 70,280, filed March 23, 1936. This fuse link comprises terminals 41 and 48 interconnected by a fusible element 49. The terminal 41 is arranged to be connected to one circuit terminal while the other terminal 48 is arranged to be connected by flexible conductor 58 to another circuit terminal. A coil tension spring 5| is provided for applying a predetermined tension to the fusible element 49. Surrounding the terminals 41 and 48 and the fusible element 49 is a sleeve 52 which provides an arc extinguishing and confining structure. The sleeve 52 is preferably formed of paper impregnated with melamine resin.

The fuse link constructions shown in lFigures 4 and 5 of the drawings are substantially unaffected by being immersed in Water for relatively long periods. On being removed from the water there is no warpage as is the case with other materials, such as ber for example.

In Figure 6 of the drawings there is shown, generally, at 55 a replaceable fuse link or fuse cartridge that is similar to the fuse link or cartridge shown in Triplett Patent No. 2,183,728. The replaceable cartridge 55 comprises a terminal 56 which is arranged to be connected to one line terminal. Connected to the terminal 56 is a replaceable fuse link, indicated generally at 51. The link 51 comprises a terminal 58 having a head portion 59 abutting shoulder 68 provided by the terminal 56. The terminal 58 is connected by a fusible element 6| to another terminal 62 which is connected by a flexible conductor 63 to another circuit terminal. A spring, indicated diagrammatically at 64, applies a tension to the fusible element 6| and serves to withdraw the terminal 62 through a bore 65 when the fusible element 6| is blown. 'Ihe bore 65 is formed in cylindrical blocks 66, 61 and 68 of moulded melamine resin composition. The blocks 65, 81 and 68 of melamine resin serve as a solid arc extinguishing material and an arc extinguishing medium comprising nitrogen, hydrogen and small amounts of carbon containing gases, i3 evolved therefrom due to the heat of the arc formed between the terminals 58 and 62 on blowing of the fusible element 6| which serves to assist in extinguishing this arc and expelling the terminal 58 and the attached head portion 59 from the terminal 58.

The blocks of molded melamine resin composition 66, 61 and 66 are positioned Within a cylinder 69 of insulating material, preferably fiber, which in turn is encased in a sleeve 18, preferably formed of phenolic condensation product. It will be understood that instead of forming the moulded melamine resin in the cylindrical blocks 66, 61 and 68 and providing the fiber sleeve 69 and the outer sleeve 18 of phenolic condensation product, all of this insulating material could be formed of one piece moulded melamine resin composition.

In Figure 7 of the drawings there is shown, generally, at 13 a replaceable or renewable fuse link or fuse cartridge of the type illustrated in Triplett Patent No. 2,226,838. The renewable link or cartridge 13 comprises a rod-like terminal 14 and an opposite terminal 15. The terminals 14 and 15 are interconnected by a strain element 16 and a fusible element 11. The rod-like terminal 14 is threaded as indicated at 18 for connection to one circuit terminal. The terminal 15 .is provided with a looped flexible conductor 19 for connection to the other circuit terminal.

'Ihe terminals 14 and 15 and the strain and fusible elements 16 and 11 are located in a bore 88 of an arc extinguishing and confining structure or sleeve 8| which is preferably formed of moulded or cast melamine resin composition. It will be observed that in the construction illustrated in Figure 7 and described hereinbefore, the arc extinguishing or confining structure 8| is formed of a single piece of material and is not formed by two or more insulating materials as is the case in the construction shown in Triplett Patent No. 2,226,838.

In Figure 8 of the drawings there is illustrated,

generally, at 84 a portion of a liquid fuse construction which is similar to that shown in Conrad Patent No. 2,091,430. The fuse construction 84 comprises a sleeve 85 of suitable insulating material, such as glass, which has at its upper end a terminal 86. A metallic spider 81, which is carried by the terminal 86, supports a terminal 88 from which depend strain and fusible elements 89 and 98. The strain and fusible elements 89 and 98 are connected to a terminal 8| that is arranged to be retracted into the housing or sleeve by a coil tension spring 92.

Surrounding the strain and fusible elements 8 9 and 88 is an arcing chamber or tube 93 that is held in place by a threaded ring 94 of suitable insulating material, such as a phenolic condensation product.

In order to inject a liquid arc extinguishing medium into the arcing chamber 93, the terminal 9|, which is retracted by the spring 92, is provided with radially extending pins 95 which support a liquid director 86. It will be understood that the liquid director 96 is moved downwardly into a liquid dielectric 91 when the strain and fusible elements 89 and 98 blow and that the liquid is forced by the liquid director 96 into the arcing chamber 93 where it assists in extinguishing the arc and deionizing the arc space. The fuse liquid 91 that is employed can be of the type disclosed in my Patent No. 2,077,429.

The arcing chamber 93 and the liquid director 96 are preferably formed of moulded or cast melamine resin. This material is not soluble in or does not react with any of the arc extinguishlng liquids now used in the fuse construction shown in Conrad Patent No. 2,091,430 and also described in my Patent No. 2,077,429.

In Figure 9 of the drawings there is illustrated, generally, at a portion of a load-break device which is employed in the switch construction disclosed in the copending application of Lindell and Van Ryan, Serial No. 349,898, filed August 2, 1940. The load-break device |00 is employed preferably in conjunction with a disconnecting switch of the knife blade type for opening the circuit after and closing it before the knife blade is moved to the switch open or closed position. It will be understood that the construction shown in Figure 9 is not limited to this particular use.

The switch construction |00 comprises a statlonary generally cylindrical terminal |0| and a movable generally cylindrical terminal |02 that is attached to a lever |03, only a portion of which i is shown. It will be understood that the lever |03 is connected to a suitable operating mechanism for moving the terminal or contact member |02 into and out oi engagement with the terminal or contact member |0|.

The contact member |02 is arranged to move in a bore |04 of a two part sleeve or liner |05 of moulded or cast melamine resin. Surrounding the liner |05 is a sleeve |06 of insulating material such as phenolic condensation product. An outer sleeve |01, formed of ceramic material such as porcelain, surrounds the liner |05 and sleeve |06,-

as shown. It will be apparent that the sleeve or vliner |05 can be replaced or renewed readily, if

necessary.

Attached by a pin |08 to the movable contact member |02 is a trailer rod |09 that is threaded into an insert ||0 around which is moulded a trailer or plug of melamine resin. 'I'he sleeve or liner |05 and the trailer or plug can be moulded or cast with suilicient accuracy so that no machining or other finishing thereof is required.

When the contact member 02 moves downwardly into the bore |08 and away from the stationary contact member |0l, an arc isY drawn therebetween, if the'circuit is opened under load conditions. This arc is quickly extinguished since it is confined between the bore |04 and the outer surface of the trailer or plug which moves into the bore |04 as the contact member |02 is moved downwardly.

The use oi' melamine resin for the sleeve |05 and plug is particularly advantageous in the construction of the load-break device |00. In this device reliance for quickly extinguishing arcs is placed to a considerable extent on the relatively close fit between the sleeve |05 and plug It is desirable that the dimensions of the sleeve |05 and plug remain substantially unchanged regardless of arcing over their surfaces. That is, the erosion due to the formation of arcs over these surfaces should be inappreciable. When melamine resin is employed for making the sleeve |05 and plug this end is substantially achieved.

Since it is obvious that there are many other I be evolved due to the heat of the arc for extinguishing the same, said means comprising a resixv derived from a cyclic organic compound with nitrogen positioned in the ring structure.

2. In electrical apparatus, a conductor from which anarc may be drawn, and arc extinguishing and confining means along the path of the are from which an arc extinguishing medium can be evolved due to the heat of the arc for extinguishing the same, said means comprising melamine.-

3. In electrical'apparatus, a conductor from which an arc may be drawn. and arc extinguishing and confining means along the path of the A arc from which an arc extinguishing medium can be evolved due to the heat of the arc for extinguishing the same, said means comprising melamine formaldehyde resin.

4. An electric circuit interrupter comprising, in combination, conductor means between which an arc is formed on interruption of the circuit, and arc extinguishing and confining means along the path of the arc from which an arc extinguishing medium can be evolved due to the heat of the arcfor extinguishing the same, said arc extinguishing and confining means comprising-a resin derived from a cyclic organic compound with nitrogen positioned in the ring structure.

5. An electric circuit interrupter comprising. in combination, conductor means between which an arc is formed on interruption of the circuit, and arc extinguishing and confining means along the path of the arc from which an arc extinguishing medium can be evolved due to the heat of the arc for extinguishing the same, said arc extinguishing and confining means comprising melamine resin.

6. A fuse device comprising, in combination. means adapted to fuse and form an arc on the occurrence of an overload in an electric circuit,

Vand an arc extinguishing and confining strucr comprising a resin derived from a cyclic organic compound containing nitrogen positioned in the ring structure.

7. A fuse device comprising, in combination. means adapted to fuse and form an arc on the occurrence of an overload in an electric circuit, and an arc extinguishing and confining structure along the path of the arc from which an arc extinguishing medium can be evolved due to the heat of the arc for extinguishing it, said structure comprising melamine formaldehyde resin.

8. A replaceable cartridge or fuse link comprising, in combination, a pair of spaced terminal members, fusible means interconnecting. said terminal members, and an insulating sleeve surrounding said fusible means comprising a resin derived from a cyclic organic compound containing nitrogen positioned in the ring structure.

9. A replaceable cartridge or fuse link comprising, in combination, a pair of spaced terminal members, fusible means interconnecting said terminal members, and an insulating sleeve surrounding said fusible means comprising melamine resin.

10, An arc confining and extinguishing structure comprising melamine resin.

11. An arc confining and extinguishing structure comprising melamine resin and an inorganic filler.

12. Anarc confining and extinguishing structure comprising melamine resin and a magnesium containing filler.

13. An arc confining and extinguishing structure comprising from 30 to 50% by weight of melamine formaldehyde resin and the balance comprising substantially magnesium borate.

14. An arc confining and extinguishing structure comprising a synthetic resin derivedirom the class consisting of cyanamid, dicyanodiamide and guanidine. l

' 15. An arc conning and extinguishing structure comprising a resin derived from a cyclic organic compound containing nitrogen in the ring structure and an alkalineearth element.

16. An arev confining and extinguishing structure comprising a resin derived from a cyclic organic compound containing nitrogen in the ring structure and a metallic hydrate.

17. A composite sleeve forming an varc confining and extinguishing structure comprising an outer layer containing melamine resin, and a liner therefor containing a material capable of evolving a relatively large quantity of arc extinguish- 1x18 medium when subjected to the heat of an electric arc.

18. A composite sleeve forming an arc conning the outer surface of said plug comprising melamine resin. 1

20. An electric circuit breaker comprising, in combination, separable contact members between which an arc is drawn on separation thereof, a sleeve into which the arc is drawn, and a plug disposed to' be moved into said sleeve for contining said arc betweenA its outer surface and the inner surface of said sleeve, the material forming the outer surface of said plug and the inner surface of said sleeve comprising melamine resin.

21. Method of making an arc confining and extinguishing structure which comprises impregnating ilber glass With melamine resin.

22. Method of making an arc confining and extinguishing structure which comprises, mouldingva mixture of melamine resin and inorganic illler to the desired shape and size under heat and pressure.

23. Method -of making an arc confining and extinguishing .structure which comprises, moulding a mixture of melamine resin and inorganic ller to the ,desired shape and size at a temperature. of about 310 F. and under pressure ranging from about 1200 to about 2400 pounds per square inch.

24. Method ofl making an arc conilning and extinguishing structure which comprises impreg- 19. An electric circuit breaker comprising. in l combination, separable contact members between which an arc is drawn on separation thereof, a`

nating a sheet of ilbrous material with melamine resin, and winding the impregnated sheet on a mandrel under sufficient heat and pressure to polymerizethe resin.

25. An arc confining and extinguishing structure comprising melamine resin and an organic illler.

26. An arc conilning and extinguishing structure comprising melamine resin and a filler of cellulose,

GEORGE F. MCMAHON.

DISCLAIMER 2,328,825-George'F.McMahon Chicago, Ill. Anc-EXTINGUISHINGMEANS. Patent dated Sept. 7, 1943. Disclamer led Sept. 19, 1946, by the assignee, Schweitzer cb Conrad, Inc. Hereby enters this disclaimer to claims 11, 22, and 23 of said patent.

[Oficial Gazette October 22, 1.946.]

DISCLAIMER. A 2,328,8251-George'F.MaMahom Chicago, 1 ]1. Anc-EXTINGUISHINGMEANS. Patent dated Sept. 7, 1943. Dsclalmer filed Sept. 19, 1946, by the assignee, Schweitzer t Conrad, Inc. y Hereby enters this' disclaimer to claims 11, 22, and 23 of said patent.

[Oficial Gazette October 22, 1946.] I

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