US2073565A

US2073565A - Electric circuit breaker

Info

Publication number: US2073565A
Application number: US57940A
Authority: US
Inventors: Strauss Frida
Original assignee: Individual
Current assignee: Individual
Priority date: 1935-07-03
Filing date: 1936-01-07
Publication date: 1937-03-09
Anticipated expiration: 1954-03-09
Also published as: DE690566C; FR798333A; NL53195C

Description

S. RUPPEL Marv-h 3, i937a ELECTRC CIRCUIT BREAKER Filed Jan. 7, 1956 3 Sheets-Sheet l llamwn March 9, 1937. s. RUPPEL 2,073,565

ELECTRIC CIRCUIT BREAKER Filed Jan. 7, 195e s sheets-sheet `2 March 9, 1937. s. RuPPl-:L

ELECTRIC CIRCUIT BRLAKER Filed Jan. "l", 1956 3 Sheets-Sheet 5 Fig, i2

Patented Mar. 9, 1937 PATENT OFFICE ELECTRIC CIRCUIT BREAKER Sigwart Ruppel, Berlin,

Germany; Frida Strauss,

ne Ruppel, heir of Sigwart Ruppel, deceased Application January 7, 1936, Serial No. 57,940 In Germany July 2, 1935 24 Claims.

In interrupting a high-voltage electric circuit the separation of the circuit-breaker contacts is usually effected inside a substantially closed chamber which is sometimes known as the arcchamber. The walls of this chamber are often made of an insulating material which has to be either protected from the action of the arc or of an arc-resistant nature. Materials have been used for this purpose which give off gas or vall) pour or both under the action of the heat of the arc or decompose at the surface into gas or vapour and are protected from further attack by a layer of the gas or vapour thus produced. This gas or vapour may be made use of for exl5 tinguishing the arc. However, the materials which have hitherto been employed for this purpose have various disadvantages which limit their sphere of application or necessitate the ernployment of special expedients for overcoming 20 them. If an inorganic material having a metal base, such for example as boric acid, is employed, a solid residue, boric oxide for example, remains after the evolution of the vapour or gas and this residue is no longer able to give 01T gas and in 25 some cases becomes conductive. If an organic material is employed there is often the danger of combustibility. Moreover, not only is gas evolved but free carbon is usually formed also. This carbon forms on the surface of the insulating :i0 member and considerably impairs the surface insulation. Moreover the carbon is present as soot in the gas which is evolved, and separates out and is liable to be deposited at some point in the path of the gas where it also impairs the 35 surface insulation.

The chief object of the invention is to avoid thc disadvantages associated with the materials which have been proposed hitherto for the purpose in question, it is applicable not only to a 40 switch chamber but to any insulating part which may be exposed to the action of the arc. This object is achieved by making the insulating member, at least at the point Where it is exposed to the arc, of an artificial resin which contains 45 nitrogen as a chemical constituent. The material is preferably one in which the nitrogen is combined with hydrogen in the molecule and more particularly one of the so-called carbamide resins or amino-plasts in the production of ""0 which are employed either urea. CO(NH2). or thio-urea, CS NH2)2, and formaldehyde. Such materials are already on the market for example under the trade names Pol1opas and Resopal.

00 The chemical compounds which are produced in the making of these materials, for example methylol and their polymerization products, have a structure which makes them particularly suitable for use in accordance with the present invention. The union of the hydrogen with the nitrogen to form amino groups results on the one hand in the advantage that these materials are practically incombustible while on the other hand, the low carbon-content with direct union with oxygen results practically in freedom from soot. Experiments show that with these materials the formation of free carbon is so small as to be negligible. Moreover they retain unchanged the character of their surface and their surface insulation even after being exposed to the arc. The gases which result from the action of the arc are substantially hydrogen, nitrogen and carbon-dioxide. These gases are particularly suitable for extinguishing the arc. Further advantageous properties of these materials are their resistance to atmospheric effects, particularly to moisture, and their capacity for being shaped and easily Worked.

The amino-plasts may be given properties which render them suitable for various different applications by the addition of iillers or other materials. Thus, it is possible to increase the evolution of gas by the use of suitable fillers. Of particular advantage are fillers which themselves evolve hydrogen, nitrogen and carbondioxide. Ammonium compounds, for example ammonium carbonate, ammonium acetate, ammonium alum, as well as hydrazine compounds are particularly suitable for evolving nitrogen and hydrogen. Furthermore urea may be added and affords carbon-dioxide, nitrogen and hydrogen. Ammonium carbonate as well as other carbonates afford carbonio acid. Such additional materials may be dissolved in the artificial resin or incorporated in it in the colloidal state or even in the form of small grains or theI like. If too great an evolution of gas is not desired, stable metal oxides (of the earth and alkaline earth metals, for example) may serve as fillers. Material of a fibrous nature, such as organic fibres, for example cellulose, or even threads of asbestos or the like, may serve for increasing elasticity and mechanical strength.

The amino-plasts may be produced by moulding or pressing with subsequent heating, as Well as by casting. Moreover subsequent working in the cold is also possible. of suitable constructional expedients the artificial resin may be substantially relieved from mechanical stresses. Thus, particularly in the case By the employment i `of solid parts which are introduced into the path of the arc, the member of artificial resin may contain a core or a skeleton of stronger or more rigid material: for example, pins of artificial resin may be provided with metal cores.

Such artificial resin materials may be used, for example, for the construction of the hollow members of electric circuit-breakers in the interior of which the arc burns and which consist of particularly strong insulating material, for example of hard paper, hard fabric, fibre, ceramic material or the like. These members merely need to be covered wholly or partly with a layer of artificial resin which is sufficiently strong and thick to protect it from the action of the arc. There then results the further advantage that the covering of the member with artificial resin protects it from being aiiected by the moisture in the air so that it may even consist of hygroscopic material. Insulating members constructed in this way may be employed in open-air installations Without any further protection. The connection between the insulating member proper and the surface protective layer can be made particularly intimate if the two are united to one another before the artificial resin is hardened. For example, inserts could be provided in the casting or other mould so that the artificial resin is connected with the insulating member without a joint. It is of particular advantage if, when an insulating supporting member is employed, the latter consists of fibrous material which is held together by the hard paper on a carbamide resin base. In this way there is produced a homogeneous body particularly if hardening of the resin in the basic material and of the resin forming the surface protective layer is eiiected at the same time. The satisfactory electrical, chemical and mechanical properties of the nitrogen-'containing artificial resins make it possible to employ them for numerous apparatus in the high-tension electrical art. Thus, for' example, condenser bushings may be made with or without the employment of papel, as well as insulators and especially supports in conductors insulated by pressure gas. Moreover coils for transformers, converters or the like may also be insulated by means of this resin and be hardened in the finished condition. Several insulating materials could be employed for the formation of the arc chamber. In this way the formation of gas may be iniiuenced to a great extent both qualitatively and quantitatively. For example, in the case of a tubular arc-chamber, several insulating materials in the form of perforated plates or of hollow cylinders could be arranged coaxially` one above the other.

In the case of a switch in which the arc is drawn into this arc-chamber on operation of the switch, the arc may, for example, be caused to burn at the beginning of its formation at a part of the wall which consists of material having a particularly strong gasevolving capacity, or various gases may be generated one after the other to give a reaction which takes place suddenly and thus a particularly strong extinguishing eiiect.

A further possibility resides in the arrangement of various insulating materials as strips in the axial direction so that they have substantially the shape of'slender segments of a hollow cylinder. Thus, one material may serve as a support and other materials be inserted in grooves in the iirst. As the arc often burns, as

a result of electromagnetic action, on one side of .the arc-chamber which is therefore particularly attacked by it, it is sufiicient in such cases to dispose a strip of the material which is to be mainly attacked ln this direction.

A particularly strong construction of switch tube which might also be applied informing the insulating pin is obtained by employing a winding process such as has hitherto been proposed in the production of tubes of hard paper. The layer-forming material, for example paper, cotton, or linen fabric, wool fabric or silk is saturated with the artificial resin and wound into the form of a tube or rod. At the point which is exposed to the arc an amino-plast is employed as the articial resin. The layer of amino-plast must be suiiiciently thick and containy enough amino-plast to be able to give off enougi extinguishing gas even after being in operation a considerable time. At the point protected from the arc any artificial resin may beemployed which gives suiiicient strength or a particularly convenient production. Not only amino-plasts but even pheno-plasts and other resins may be employed. In this way are obtained members of particularly great radial and axial strength. Such members may be secured with respect to axial tensile stresses by Vmoulding them with transverse grooves or the like before hardening and at the same time providing them with a pressed-round metal member.

The invention may be employed with advantage in all circuit-breakers in which extinction of the arc is effected between walls of insulating material. It is of particular advantage in the case of switches according to my copending patent application Ser. No. 36,859 of 19th August 1935. However, the extinguishing chambers of oil or other liquid switches such as water switches may be lined with amino-plast or consist of amino-plast. Above all, these artificial resins may be employed with advantage in switches, fuses and quenching spark gaps, particularly for leading oii excess voltage, as well as rectiiiers, in which the arc is subjected to a blast of pressure gas. Arrangements which are particularly advantageous result if the switch gases are employed for extinguishing the arc or assist in this. In such circuit-breakers it is necessary as a rule for an arc to burn between the walls of gas or vapour-evolving insulating material which closely surround it. In the case of fuses (so-called exhaust or blow-cut fuses) this may easily be brought about by appropriately close dimensioning of the path of the fusing conductor. The fuse is preferably given the form of a tube of strong insulating material such as hard paper, porcelain,

or the like, the inner wall of which `is lined with a coating of amino-plast.

Various examples of electric circuit-breakersh or diiierent types constructed in accordance with Vthe invention are illustrated in the accompanying" Figs. 6 to 8 are sectional views- Figs. l0k to tubular movable contact. 5 is a switch tube which, as well as the insulating iilling pin 'I, consists of nitrogen-containing artificial resin, preferably amino-plast. The arc formed on separation of the contact is drawn into the narrow annular space between the tube 5 and the filling pin I and there produces, from the walls of these parts, the gas which is necessary for the extinction of the arc. The gas is partly stored up in the contact chamber 8 until the contact 2 leaves the tube 5 at the top and it then ows out suddenly so that the interruption of current is brought about. The following dimensions have proved to be satisfactory: length of the extinguishing tube about 150 mm., clear diameter 21 mm., diameter of the filling pin 'I about 15 mm., diameter of the movable contact 2 16-20 mm. Currents from -4 kA, can be interrupted with such a switch at 10 kV. The contact chamber 8 should not be too large if amino-plasts are employed, that is to say it should not have a clear volume of more than 100 cubic centimetres, for otherwise, in the case of small currents, the pressure is too small for extinguishing the arc. The filling pin 1 may be provided with a metallic core 9 or an insert of strengthening insulating material. The switch tube is strengthened by means of a metal insert I0.

In Fig. 2 another example of construction is illustrated, in which the artificial resin insert II is surrounded by a tube I2 of mechanically strong insulating material. Instead of this, however, the tube of artiiicial resin could have paper, plaited material or ribbon wound on to it and in some cases this winding could be covered with the artiiicial resin, an example of which construction has been depicted in Fig. 5 of the drawings.

Fig. 3 illustrates a switch of large capacity. The filling pin 1, contrary to the arrangement of Fig. 1, is connected with the switch member 2 and moves together with it. As the switch pin almost iills up the tube in the closed condition of the switch, this switch is able to carry a higher current with the same cross-section of tube.

. Dimensions which have been found to be advantageous are a tube length of about 130 mm. for l0 kV., a clear diameter of the tube of 23 mm., switch pin of 22 mm. diameter, and a lling pin of 2l mm. diameter. If the switch is to be used to separate under load, the iilling pin may b'e allowed to remain in the switch tube in the open condition of the switch, in contradistinction to what is the case with a switch employing organic materials such as have been hitherto proposed for'the walls of the switch chamber, and without it being absolutely necessary to connect in series an air gap in order to maintain the insulating ability of the switch, as the amino-plasts have, and retain, a high surface resistance.

Fig. 4 illustrates the application cf the nitrogen-containing artiiicial resin `to pressure-gas switches and, in fact, to a construction in which the switch pin 2 is moved through a nozzle I6 of insulating/material in the opposite direction to the direction of flow of the pressure-gas. As the arc reaches the walls of this nozzle I6, it is essential for the working of the switch, particularly with regard to security from back-ignition, that the surface-insulation of the nozzle should be retained. This is attained according to the invention by making the parts of the insulating nozzle with which the arc comes into Contact of nitrogen-containing artificial resin. Mechanical strength can be obtained by means of an insulating member II which may be separated or connected with the nozzle. In this way the capacity of the switch for continuous working is maintained. Furthermore it is preferable to protect all the insulating pressure-gas conduits with a coating of such an artificial resin because in this way there is avoided the formation of leakage paths due to the precipitation of moisture on the walls and the destruction of the surface insulation which results from it.

Even in the case of pressure-gas switches it is possible to make use of the evolution of gas from the nitrogen-containing artificial resin for the extinction of the arc. This gas facilitates particularly the extinction of arcs due to heavy currents. For this purpose it is merely necessary to adopt expediente which make possible a temporary accumulation of the gas which is produced or an eiiective blasting of the arc. This may be attained, for example, by giving the switch member 2 an extension which forms a lling, similar to the extension 'I in the arrangementof Fig. 3, so that the arc has to burn while constricted in the nozzle and a particularly intense evolution of gas results. It is further possible to prevent the iiow of gas out of the blast chamber I8, by means of valves, dampers or the like, until the switch member has moved over a certain path. It may also be expedient to reverse the direction of the blast, the contact I then being situated in an extinguishing chamber similar to that of Fig. 3 to which. pressure gas is supplied and when it moves releasing the extinguishing blast.

Fig. 5 shows a spark gap with a movable electrode. In the case of spark gaps for excess-voltage protection the length of the arc, which is determined by the flash-over voltage of the device for leading away the excess voltage, is under some circumstances too small for extinguishing the nominal-voltage arc. One electrode 2 may then be arranged to be movable, as illustrated in Fig. 5, and to be moved, upwards in the example, by the gas which is generated on the production of the arc, against the force of the spring 3 to extinguish the arc. The blasting operation takes place only after the release of the opening ll, as soon as the length of the arc has become sufliciently great. In order to prevent burning-away, the electrodes may advantageously consist of diiiicultly-fusible materials, e. g. tungsten alloys. 5 is the gasevolving wall of amino-plast articial resin; 6 is the supporting member which is produced in this case by winding sheet material upon itself as is common in the construction of tubes, which may be united with the part 5; I3 is the flash-over gap, the field of which is determined by screens I4 and I5 in order to reduce the delay in ashingover.

The parts of amino-plast, which in themselves have too small a mechanical strength, instead of being strengthened by means of supports, can have their strength increased by mixing suitable iillers with the artificial material. This expedient aiords particular advantages if those materials of animal origin are employed as iillers which gasify in the heat of the arc in a similar way to resins Without leaving behind substantial residues. Such materials are, for example, hair, wool, silk threads, leather, skin, horn etc. These materials must for the present purpose be pure and not, as is often the case with commercial products, contain inorganic salts for the purpose of loading or the like. These lillers, particularly if of fibrous material, may be embedded in the urea-resin directly at the surface of the insulating member. Laminated materials such as the Cil well-known hard paper and hard fabric are particularly satisfactory in which a thin material in the form of a layer which gasifles as completely as possible e. g. paper of animal fibres (e. g.

wool or silk) or thin woollen or silk fabric are impregnated with urea-resins and moulded as tubes, plates or shaped members. 'Ihe hair or other animal material is previously prepared and disintegrated so that it binds firmly with the resin, and in some cases absorbs it, so thatvthe resin penetrates even into the interior of the hair or the like.

In a similar way animal skins, which have been so disintegrated that substantially only the tissue (bres) remains may be employed as a filler or supporting tissue for the resin.

' It will be seen from Figs. 1 to 5 that the members of amino-plast are mainly necessary, for the present application, in the form of tubes or pins. The method ofproducing these artificial materials involves the carrying out of a hardening operation at a definite temperature. As the best quality of the material is obtained with plates of a limited thickness, tubes the thickness of which exceeds a certain value cannot be produced having the desired high quality. A further feature of the invention therefore consists in assembling the tubular bodies of amino-plast from separate parts of dimensions in which the aminoplast can be satisfactorily produced.

It will be seen, for example, from Figs. 6 and '7 how such urea-resin tubes may be assembled from perfor-ated plates 2l which are stamped or cut out from sheets of the material. The perforated plates 2l are for this purpose inserted in a supporting tube 22 which is usually of an` insulating character and which consists of mechamcally strong material.. e. g. hard paper, hard fabric, hard rubber, the material known as Micalex, or ceramic material. The plates may be secured against displacement therein by means of noses or by being given a special shape, e. g. a hexagonal form. They may also be secured with respect to one another by means of grooves, projections or the like, which also give satisfactory packing. They may also be held together among themselves and with the supporting tube by means of screw-threads. The screw-thread connection according to Fig. 7 results in a gas-tight tube. The plates, besides being held as a result of their shape may be closely connected with one another and with the tube by means of cement or glue. It is also possible to wind material in the form of a layer or fabric, e. g. paper, linen, asbestos yarn, wool or hair, round the ready built-up tube of amino-plast and then effect hardening. rFhe interior of the tube maybe provided with a fairly thick layer of amino-plast after it has been built up. Insulating pins of amino-plasts may be wound or built up in a similar manner. In that case, instead of a surrounding supporting tube, a supporting rod would be passed through it. In some forms of switch this rod would preferably consist of metal, the

insulating material surrounding it like a cup.

i sheets.

In this case a oneor multi-part tube'of articial resin may be drawn over the rod, into which tube on one side a stopper of artificial resin is pressed, cemented or shrunk.

The perforated plates need not be made from They may be moulded or cast in special moulds, the particular advantage of the optimum quality of the material with a uniformly proceeding hardening operation being obtained, if

the thickness satisfactory for the plates is retained.

The individual perforated plates may contain, for strengthening purposes, inserts of materials such for example as fibrous materials such as asbestos, cotton or linen fabric, paper, and further hair, wool or silk, possibly in the form of string. When inorganic fibres are employed such as asbestos, and fibres having a cellulose base, it is not Vdesirable for these materials to come into contact with the arc especially if the upper layer of the artificial resin has been burned away after a number of switching operations. At the points with which the arc comes into contact, therefore, the coating of aminoplast is given an appropriate thickness in addition to that which is necessary for constructional reasons.

Fig. 8 shows afurtherpossibilityin the construction of insulating tubes in which several strips 23 and 2li, which may be made from sheet material, are assembled in the axial direction of the tube and are pressed together radially by means of a supporting tube 22. 25 is the clear space of the tube. As the result of the employment of a rectangular cross-section, the construction is particularly simple. The flat strips 23 and 2t are made slightly Wedge-shaped and pressed into the supporting tube by making use of the wedging action.

Fig. 9 shows a form of construction for a fuse having four wires 26 connected in parallel which are arranged between two plates of amino-plast. 27 are holes for the screws which hold the plates together, possibly by means of rigid outer pressure-plates.

Fig. 10 illustrates the switching position of a filling switch having an annular chamber, in the `construction of which the properties of aminoplast have been borne in mind. A tulip-shaped contact 3| is situated in a gas chamber 35 which is closed by means of a switch-tube 33. The movable contact 32 is made of tubular form. Theswitch-tube is constricted by a stationary filling member S. The switch-tube and the filling pin preferably consist of amino-plast. After the contacts have separated, the arc is produced between the tubular contact 32 and the burning-ring 36. In the case of vlarge currents,

extinction is effected relatively quickly as the result of the great delivery of energy, possibly before the tubular contact has passed through half the length of the tube 33. The tube 33, as Well as the pin 3d, are therefore arranged at the lower part especially for the extinction of arcs due to large currents. In order to reduce the formation of gas and burning-away the switch tube 33 is widened at its lower portion and the pin 3Q reduced at the part 40. In'many cases it is suilicient if the appropriate expedient is adopted only for the tube 33 or only for the pin 36. Arcs due to small currents are not extinguished at the same point as those due to heavy currents. 'I'heir extinction is effected only on the further movement of the tubular contact to the small-current point between the part 38 of the pin and the part 39 of the tube. Here an intensive extinguishing action is obtained, because the gap between the

parts

38 and 39 is made as narrow as possible. A further improvement of the extinguishing action may be brought about by employing, for the

parts

38 and 40 or 39 and lil of the wall, materials of different mechanical properties and different gasifying-capacity. It is particularly desirable to make the parts 39 and 4l of the wall of the switch-tube of material which either evolves gas only to a small extent or not at all and which moreover does not burn away, while the

parts

38 and 40 of the filling pin consist of gas-evolving material which is consumed, namely amino-plasts. In this connection it is desirable to select for 38 a strongly gas-evolving material, that is amino-plast containing only a small quantity of filler, while for 40 a mechanically strong material vvith a relatively low evolution of gas, that is amino-plast with a higher content of filler, is advantageous. This construction takes into account the requirements for extinguishing an arc which differ materially according as to whether the arc to be extinguished is due to a large or a small current. 'I'he requirements for extinguishing an arc due to a large current are:--

1. Great mechanical strength.

2. Great thermal strength, particularly in view of the large differences of temperature in the vicinity of the are.

3. Moderate wear due to gasifying and so on.

4. Moderate development of gas so that an unnecessarily high pressure is not produced.

On the other hand the requirements for the extinction of arcs due to small currents are:-

1. Large formation of gas, in order even in the case of small currents to create a pressure which is suicient for eiective blasting.

2. High surface-insulation, as the point where small currents are interrupted serves as a rule for throttling the recurring voltage. Arcing-l back as a result of leakage currents 1s prevented if the surface-insulation is high.

Therefore, as was explained above, the parts of amino-plast are graded in such a manner as regards their content of ller that at the points which are subjected to the greatest thermal stresses (point of extinguishing arcs due to heavy current) a. higher mechanical strength on the one hand and a lower capability for gasifying on the other hand is provided, than at the other parts of the path of the arc (point of extinguishing arcs due to small currents).

An intermediate region may be provided between the regions of heavy-current and smallcurrent which may have properties lying between those of the two regions so that it represents to a certain extent a transition. The properties may also change gradually along the transition region, e. g. the extent of the constriction of the arc.

It is of advantage, in addition to grading of the parts of amino-plast to moisten their surfaces with -a suitable liquid.

At `the large-current point the employment of a layer of liquid on the wall of the arc-chamber protects the wall from the heat of the arc. Burning-away is in this way reduced to a minimum.

The additional increase in pressure which is effected by vapourizing of the liquid is desired at the small-current point. The duration of the arc is reduced. Wear remains small even after many successive switching operations.

The arrangement of Fig. 1l differs from that of Fig. 10 essentially in the fact that the filling pin which consists of the parts 38 and 48 is connected with the movable contact 32 as in Fig. 3. Fig. ll shows. the switch in a condition which corresponds to about the moment of extinction of the large-current arc. The arc burns in the annular space between 4D and 4l, which is relatively wide. 'I'he wall 4l evolves little or no gas. In tne case of smaller currents the arc still burns when the thickened part 38 passes into the amino-plast tube 39. Extinction is then effected mainly in the annular space between 38 and 59. The part 39 of the wall is made strongly gas-evolving. It should be arranged so as to be as easily exchangeable as possible. Extinction is further effectively assisted by the arc-chamber between the parts 38 and 4l for the part 38 of the pin is likewise strongly gas-evolving and the space between 38 and 4I is sufficiently narrow.

Fig. 12 shows details of the construction of the filling

38, 40 according to Figs. 10 and 1l. A pin 42 of a mechanically strong insulating material, for example hard paper or hard fabric, serves as a supporting member. Over this rod are slid two tubular pieces 48 and 38 of amino-plast or other gas-evolving material. Different materials may be employed or even the same material, an excessive formation of gas at thev large-current point 4B by reducing the diameter of the switch pin with respect to the small-current point 38 being then avoided. The

tubes

38 and 40 may also be sub-divided transversely into several parts in order to limit cracking in the axial direction. Bindings of metal or strong material which does not evolve gas may also be let into the surface of the tubes 38 and 48 and ensure the cohesion of the parts even in the possible event of cracking. The

tubes

38 and 40 are fixed to the insulating rod 42 by a nut 43.

The employment of parts of amino-plast is of particular advantage also in liquid switches and indeed in such switches employing insulating switching liquid, e. g. oil switches, as well as in switches employing water or some other conducting liquid. In the case of oil switches the nitrogen, which is freed by the action of the arc on the amino-plast, contributes to the improvement and conserving of the oil. A further advantage resides in the fact that the parts or ammo-plast can be brought nearer to the arc without the surface being impaired by cracking or the burning of conductive paths by the arc. In the case of water switches the insulating capacity of the extinguishing medium is considerably increased and moreover its freezing point depressed by the nitrogen, the ionization temperature of which is particularly high. In order to obtain these effects, it is expedient to make the constructional parts of the arc-extinguishing device of the liquid switch, particularly the extinguishing chamber, the switch tube, the filling pin and so on, either of amino-plast or to cover their surfaces with this material. An increased eiect in this direction is obtained if, according to a further modification of the invention, a material having a high nitrogen content is dissolved or emulsified in the switch liquid. Of the metal-free salts, ammonium and hydrozine compounds, e. g. ammonium carbonate or ammonium nitrate are of particular importance. These salts may in themselves be explosive, but as they are only employed according to the invention in an aqueous or other solution, any danger of explosion is avoided. The hlgn speed of decomposition of these materials is even desirable if an intensive and sudden evolution of gas is ensured.

When organic substances are employed, it is desirable to make use of a material which contains as little carbon as possible as otherwise there is the danger of soot being formed. Materials such, for example, as carbo-hydrates (sugar etc.), alcohols (glycerine etc.) are therefore not suitable for assisting in the extinction. On the other hand organic materials having a high nitrogen content, e. g. acetamide, acetylene diamine,

formamide, methyl nitrate, and above all urea and its derivatives, such as thio-urea, methylthio-urca, etc. are particularly suitable. These orga-nic materials are as a rule preferable to salts as they only increase the conductivity of water a little if at all. It is further of advantage to employ materials which are themselves fluid as in this way crystallizing or separating out of the additional material is made impossible. Apart from increasing the extinguishing capacity, these materials may be employed to depress the freezing point of the switching liquid in the Well known manner. In choosing the material it is important to see that neither the material itself nor its products of decomposition attack. the insulation or the contact material.

In the case of oil switches it is advantageous if the additional material decomposes at a substantially lower temperature than the oil. A gas bubble is then produced around the arc which originates from the gasied material and protects the oil from contact with the arc. The oil then serves essentially as an insulator while the extinguishing blast is furnished by a gasifying material e. g. the amino-plast or the uid material which is added or both.

Fig. 13 illustrates such a liquid switch. The fixed contact I is situated in a container 53 of extinguishing chamber form, the single opening 56 of which is constructed as an insulating nozzle. Through this opening and almost closing it is introduced the switch pin 2. The chamber 53 contains the conducting or non-conducting switch liquid 55 which washes the point of con- In order to concentrate the action of the arc on the liquid, the arc is drawn into an insulating tube 56. In this tube there is situated during the switching operation a certain small quantity of liquid which is forced in through the channels 51. This liquid is gasied or vaporized when the switch is opened and increases the gas pressure in the chamber 58. The gas or gas-vapour mixture which is stored in the chamber 58 and is under pressure, blows through the nozzle 54 and thus extinguishes the arc. The switch tube 56 consists of amino-plast. Consequently gas is also produced from the wall of the tube by the heat of the arc so that extinction is assisted. It is also of advantage to line the wall of the extinguishing chamber 53 with amino-plast. It is possible to make the switch tube porous so that separate openings l may be dispensed with. The arc then vaporizes the liquid which is situated in the pores. The gas and vapour thus produced protect the surface of the switch tube. A particular advantage of the employment of a porous or moistened switch tube resides in the dosing of the gas and Vapour which is produced during the switching operation so that an unlimited increase of pressure is not possible.

Fig. 14 illustrates a similar liquid switch in which in addition to liquid extinction anA extinguishing tube 59 is employed. The movable contact 2 is, as in the arrangements of Figs. 1

and 10, made in the form of a tube and moves in an annular arc chamber which is formed by the tube 59 and an insulating lling pin 60. The arc is iirst drawn between the contacts I and 2 into the extinguishing liquid 55. `The gas and vapour thus produced increase the gas pressure in the chamber 58. Then the arc is drawn into the annular arc chamber between 59 and 60. The walls of this chamber consist of gas-evolving materials, namely amino-plast. The switch tube as well as the lling pin may be made porous and be saturated with the liquid so that vaporizing of the liquid takes place in this chamber also. In this arrangement therefore the arc is extinguished on the one hand as a result of its constriction in the annular extinguishing chamber, and on the other hand as a result of an intense blasting through this chamber from the chamber 58.

I claim:-

1. An electric circuit-breaker including an insulating member which is exposed to the arc or spark produced when the circuit is broken and which gives off gas or vapour as a result of the action of said arc or spark, wherein said member consists wholly or partly of articial resin containing nitrogen as a chemical constituent.

2. An electric circuit-breaker including an insulating member which is exposed to the arc or. spark produced when the circuit is broken and which gives oi gas or vapour as a result of the action of said arc or spark, wherein said member Consists wholly or partly of articial resin containing nitrogen as a chemical constituent, and means for conning said gas or vapour for extinguishing said arc or spark.

3. An electric circuit-breaker including an insulating member which is exposed to the Iarc or spark produced when the circuit is broken and which gives oi gas or vapour as a result of the action of said arc or spark, said member consisting wholly or partly of amino-plast.

4. An electric circuit-breaker according to claim 3, wherein said amino-plast contains a filler.

5. An electric circuit-breaker according to claim 3, wherein said amino-plast contains a filler which itself gives oi gas or vapour under the action of the arc.

6. An electric circuit-breaker according to claim 3) wherein said ller is of brous material.

7. An electric circuit-breaker according to claim 3, where in said ller is of brous material.

8. An electric circuit-breaker including an insulating member which is exposed to the arc or spark produced when the circuit is broken and which gives olf gas or vapour as a result of the action of said arc or spark, said member comprising a winding of material impregnated with amino-plast.

9. An electric ycircuit-breaker including an insulating member which is exposed to the arc or spark produced when the circuit is broken and which gives off gas or vapour as a result of the action of said arc or spark, said member comprising a support of insulating material and a layer of amino-plast thereon.

10. An electric circuit-breaker including an insulating member which is exposed to the arc or spark produced when the circuit is broken and which gives olf gas or vapour as a result of the action of said arc or spark, said member comprising a support of insulating material and a subsequently-hardened layer of amino-plast applied thereon.

11. An electric circuit-breaker including an insulating member which is exposed to the arc or spark produced when the circuit is broken and which gives of gas or vapour as a result of the action of said arc or spark, said member comprising a support of insulating material containing articial resin and a layer of amino-plast thereon.

12. An electric circuit-breaker including a member of insulating material, and means for introducing said member into the path of the arc or spark produced when the circuit is broken,

wherein said member has a surface of aminoplast.

13. An electric circuit-breaker including a tubular member within which the arc or spark is produced when the circuit is broken, at least the inner wall of said tubular member consisting at least partly of amino-plast.

14. An electric circuit-breaker including a tubular member within which the arc or spark is produced when the circuit is broken, said tubular member beingcomposed of a plurality of elements of amino-plast.

15. An electric circuit-breaker according to claim 14, wherein said tubular member consists of a series of superposed perforated plates.

16. An electric circuit-breaker according to claim 14, wherein said tubular member consists of a series of superposed perforated plates, said plates having interengaging securing projections and grooves.

17. An electric circuit-breaker according to claim 14, wherein said tubular member consists of a series of superposed perforated plates secured together by an adhesive of which the basic material is similar to that of said plates.

18. A liquid circuit-breaker including an insulating member which is exposed to the arc or 'spark produced when the circuit is broken and which gives oi gas or vapour as a result of the action of said arc or spark, wherein said member consists Wholly or partly of artificial resin containing nitrogen as a chemical constituent, and wherein a material having a high nitrogen content is present in the switch liquid.

19. An electric circuit-breaker including an insulating member which is exposed to the arc or spark produced when the circuit is broken and which gives off gas or vapour as a result of the action of said arc or spark, said member consisting Patent No. 2,075, ses

wholly or partly of amino-plast which contains a filler the content of which is graduated along the path of the arc or spark so that at the point where the thermal stress is greatest the content of filler is higher and the capability for evolving gas lower than at other points in the path.

20. An electric circuit breaker according to claim 19 wherein said insulating member defines an arc chamber, a restricting member composed of amino-plast received in said arc chamber, said restricting member being of reduced cross-section at the point of greatest thermal stress.

21. An electric circuit breaker according to claim 19 wherein said insulating member defines an arc chamber, a restricting member composed of amino-plast received in said arc chamber, the walls dened by said insulating member and said restricting member being disposed at a greater distance from one another at the point of greatest thermal stress.

22. An electric circuit-breaker according to claim 1, wherein means is provided for moistening the surface of said member to reduce its consumption.

23. An electric circuit interrupter having an arc extinguishing device comprising a tubular chamber open at one end and a pair of separable contacts therein, the inner walls of said chamber comprising a nitrogen evolving synthetic resinous material which serves as a source of gas when subjected to an arc produced between the contacts.

24. A housing defining an arc chamber for electrical apparatus, said housing containing a nitrogen evolving L synthetic resinous composition which is insoluble in water and which serves as a source of gas when subjected to an arc.

SIGWART RUPPEL.

CERTIFICATE OF CORRECTION.

March 9, 1957.

SIGWART RUPPEL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Page 6,

Second column, line 59,- claim 6, after the claim reference numeral "3" strike out the parenthesis; line 4l, claim 7, for the words "where in" read wherein; and for "fibrous" read animal; and that the said Letters Patent should be read with these corrections therein that the same may conform to the' record of the case in the Patent Office.

Signed and sealed this 11th day of May, A. D. 1957'.

(Seal) Henry Van Arsdale Acting Commissioner of Patents.