US2946913A - Carbon arrangements for highintensity electric arcs - Google Patents

Description

July 26, 1960 J. A. PERRIN 2, 4

CARBON ARRANGEMENTS FOR HIGH-INTENSITY ELECTRIC ARCS Filed May 17, 1956 In venlar Fig.4 F gg- Fig-7 Y Mire.

United States Patent CARBON ARRANGEMENTS FOR HIGH- INTENSITY ELECTRIC ARCS Jean Adrien Peri-in, Pagny-sur-Moselle, France, assignor to Societe le Carbonate-Lorraine, Paris, France Filed May 17, 1956, Ser. No. 585,421

4 Claims. (Cl. 313-231 The present invention relates to a device which can be applied to the cathodes of very high intensity electric arcs which exceed 500 amperes for instance, so that these arcs may be stabilised and that advantage can be taken of their high light output.

The form of the arc plasma between carbon or graphite electrodes changes in accordance with the electrical intensity. In the range of the small intensities, say from a few amperes to 80 amperes, the part situated near the cathode contracts. At about 80 amperes, there appears a small vein emanating from the cathode spot. When 1 the intensity is increased, this vein becomes more precisely outlined, grows taut and is surrounded with coaxial gaseous sheaths, and the cathode part of the discharge, from approximately one hundred amperes onwards, looks like a sheaf which has several zones and does not seem to be influenced by the current intensity. This special form of the discharges, in particular with an intensity of approximately 200 amperes, is sometimes referred to as a contracted column and is well-known and has been described by a number of authors. However, when certain higher intensities are reached, which depend on the nature of the cathode and the functioning conditions, the cathode column changes abruptly; its aspect becomes blurred and homogeneous, its volume increases, the central vein and the sheaths which surround it disappear, the arc becomes very noisy, whilst its operation is disturbed in an annoying manner: the vapours emitted by the anode are dispersed, and the current partly encroaches on the periphery of the crater whose depth decreases. Brilliancy diminishes to a large extent. Ger- 1 man authors have established that the temperature of the cathode spot then reaches that of carbon sublimation at atmospheric pressure.

The present invention has for its object substantially to remove these drawbacks through a suitable cooling of 1 the cathode. This is obtained by utilizing a special cathode current input which has the following characteristics: (1) A hollow current input head placed very near to (approximately 2 cm. from) the extremity of the cathode. (2) An internal cooling of the current input head by means of a circulation fluid. The internal cooling fluid is preferably a liquid (water for instance), but it can also be a gas (air for instance). V

(3) The blowing of a gas in order to press back positive vapours and to decrease their radiation on the cathode; the gas for pressing back can be atmospheric air.

The form of the hollow current input head for the cathode carbon avoids the striking of a parasitic are between the cathode head and the cathode. This head is made of metal, preferably a very good electricity and heat conductor, such as silver or copper. The inside ofv the head is hollowed out, and has two apertures through which the cooling fluid flows in and out respectively.

The gas blowing tube is provided with an aperture whose main dimensions are unequal. The gas jet which comes out of it thus forms a sheet which is preferably given a large dimension which is approximately equal to the diameter of the flow of anode vapours which is to be pressedback, i

pointing in opposite directions.

2,946,913 Patented Jul 26, 1 960 "ice tube are united into one single part, it is preferable to tilt the gaseous sheet, andthus the outlet aperture or apertures of the tube, towards the cathode axis, which enables the current input head to have suitably reduced. dimensions. It is prefer-red that the gas inlet jet be situated above the zone where the cathode and anode flames meet.

The invention will be better understood with reference to the accompanying figures. Taking an arc of from 600 to 650 amperes as a non-limiting example, the various forms indicated hereunder have been established.

Figure 1 represents a mounting comprising: a positive carbon 1 of 24 mm. diameter and normally taking an intensity of 450 amperes, inclined by degrees to the positive carbon axis.

A negative carbon 2 whose diameter is 18 mm., basically having an outer layer graphited in the mass, provided with a wick whose diameter is 2.5 mm., and whose composition, which is moreover variable within certain limits, remains independent from the characterising features of the invention. According to this device the current input head and the blowing tube are independent from each other.

Figure 2 shows the shape of the outlet aperture of the blowing tube.

Figure 3 represents a modification according to which the current input head and the blowing tube are assembled to form one single part.

Figures 4, 5, 6 and 7 show schematically some modifications of the device of Figure 3.

With reference to Figures 1 and 2 the and signs indicate the anode and the cathode respectively. The cathode is supported by the metallic head 3, internally hollowed out in channels or in a chamber (not shown) intended for the circulation of the cooling fluid.

In order to simplify the drawing, these various parts have not been shown. The cathode 2 can slide with an easy fit.

' The'blowing tube is represented by 4; it is made for instance of a. cylindrical tube whose inlet aperture is shown at 5; the outlet zone is flattened in such a manner that the blown gas comes out as an approximately plane sheet and that the terminal aperture has the shape shown in plan in Figure 2. The elongation 'of this aperture is thus perpendicular to the plane of Figure 1. The anode flames 7 and the cathode flames 6 meet and mix in the zone situated between the axis of the cathode and the median plane of the blowing tube, a plane whose trace 8, 9 can be seen on the top right hand side of Figure 1.

In Figure 3 the anode and the cathode are disposed as in Figure l. The current input head 13 which is constructed in the same way as the corresponding head 3 of Figure 1, forms a single body with the blowing tube 14. i At the bottom the circulation of the cooling fluid has been shown schematically by means of two parallel arrows A channel 14 situated at the upper part, receives the blowing gas from the bottom, said gas flowing through the internal passage in the direction of the arrow 15 and coming out atthe' upper. part. Whereas the gas inlet at the side'of arrow I; 15. single, .the outlet 16.is arranged so as to produce the almost plane sheet of the outflow gas. To that effect, this outlet aperture has been made according to one of the devices shown schematically in Figures 4, 5, 6, 7, by way'of example. These figures showthe single part .13, 1450f Figure 3 as it looks when it is examined: facing the tip of the cathode.

In'Figure 4, the cathode slides in the central aperture 22.: It. has been represented as a circle,but any section whatsoever can be made in order to fit exactly thestraight section of the cathode, the latter beingforinstance elliptical, rectangular or square. The cathode head 23 is pierced atthe upper part of the aperture 24 of .the blowing gas. In'this embodiment, the gaseous sheet flowing out is no longer almost plane but. is slightly curved inwardly which does not impair its efiicie'ncy.

Figure 5 differs from the preceding drawings only in the rectilinear shape of the blowing aperture. 34; the cathode-bearing channel 32 and the cathode head 33 are again'seen on it.

According to Figures 6 and 7, instead of usinga single and continuous sheet of blowing gas, the latter is made to flow out through a number of diflerent'apertures 46,

In the latter figures the arrangement has the advantage,

thanks to internal lay-out of the ducts extending from the inlet aperture to each of the outlet apertures, that the outlet speeds at the various apertures may be made unequal and that each of the jets may be directed at will, these being all parallel to the cathode axis, or being more or less tilted towards this axis,'thus enabling a more eflicient blowing at the place where it is most needed, generally through the axial aperture 46. The number and the dimensions of these apertures can moreover vary. If they are present in odd numbers, the median aperture is generally speaking, placed on top of the device; if they are in even numbers, the median part remains full and the apertures are symmetrically in relation tothe vertical plane passing through the cathode axis.

As far as the directions taken by the gaseous flow in coming out of the apertures 46 is concerned, it is preferred that they be substantially parallel. It is not, however, a necessary condition. It is for instance, possible to tilt somewhat the axes of the ducts 46 in order to give some slight convergence to the various individual flows and to facilitate or improve the desired cooling.

Figures 4, 5, 6, 7 can relate to a special method of cooling the cathode head wherein the fluid projected on the anode flame also helps to cool down this head. The heads 23, 33, 43, 53 are provided with their respective channels 22, 32, 42, 52, as previously. The apertures 24, 34, 46, 54 and 57 allow the escape, towards the anode, of the fluid injected in the head which is cooled at the same time as the Walls of the channels 22, 32, 42, 52.

The use of a single part consisting of a cooled cathodebearer and blowing tube can be effected either by making the various ducts and necessary cavities in one piece from a metallic mass, or by constructing separately the two devices which are finally assembled, for instance, by welding them together.

Example By way of a non-limiting example which can serve as an indication, the feeding of an arc of from 600 to 650 amperes will be described. The anode has a thick wick and its diameter is 24 mm.; the cathode has a small wick, with a graphite outer-layer, its diameter measuring 18 mm. the wick being about 2.5 mm. The angle of the two axes of these carbons is 135. The cathode support is, ofthe. type of Figure 1 being .cooled bymeans of water circulation; the distance 18 between the cathode tip and the front face of its support is on the average 17 mm. The distance between the axis of the tube 4 and that of the cathode is 50 mm. The blowing gas is atmospheric air. Under these conditions the arcs functioning is maintained regular and without any disturbance at all current intensities, up to- 650 amperes approximately. However, it suffices to stop the blowing for the cathode flame to become blurred as from 475 amperes onwards approximately which proves the efficiency of the device.

The use of thevarious modifications described has led to the same findings; the stability of the arc has always persisted during the blowing, up to current intensities which are very much higher than those which are possible when the blowing is stopped.

In the. foregoing description it will be clear that a carbon arrangement is provided wherein blowing means is carried by and asymmetrically located with respect to the negative carbon.

It should be also stressed that the cooling of the cathode tip is obtained according to the invention by acting at one and the same time through heat exchanges between the cathode-bearer and the cathode, through calorific convection produced by blowing, and through decrease of the radiation coming from the anode flame, each time under the effect of the blowing. Each of these means is favorable but only their association has made it possible to reach a stable functioning up to the current intensities indicated.

I claim:

1. A carbon. arrangement for high-intensity electric arcs comprising a positive carbon, a negative carbon, said carbons being. non-coaxially arranged but with their axes meeting at the positive carbon, and a blowing tube located adjacent said negative carbon and running parallel to said negative carbon for part of its length, said blowing tube being bent away from said negative carbon and having an outlet for blowing gas in front of and above said positive carbon.

2. A carbon arrangement for high-intensity electric arcs comprising a positive carbon, a negative carbon, said carbons being non-coaxially arranged but with their axes meeting at the positive carbon, and a blowing tube located adjacent said negative carbon and running parallel to said negative carbon for part of its length, said blowing tube being bent away from said negative carbon and being formed with a flat outlet aperture for blowing gas in front of and above said positive carbon.

3. A carbon arrangement for high-intensity electric arcs comprising a positive carbon, a negative carbon, said carbons being non-coaxially arranged but with their axes meeting at the positive carbon, a blowing tube located adjacent said negative carbon and running parallel to said negative carbon for part of its length, said blowing tube being bent away from said negative carbon and being formed with a curvilinear outlet aperture for blowing gas in front of and above said positive carbon.

4. A carbon arrangement for high-intensity electric arcs comprising a positive carbon, a negative carbon, said carbons being non-coaxially arranged but with their axes. meeting at the positive carbon, a blowing tube arrangement located adjacent said negative carbon and running parallel to said negative carbon for part of its length, said blowing tube being bent away from said negative carbonand being formed with a plurality of outlet apertures for blowing gas in front of and above said positive carbon.

References Cited in the file of this patent UNITED STATES PATENTS 1,995,144 Crocker Mar. 19, 1935 2,063,249 Hansell Dec. 8, 1936 2,105,463 Cordes Jan. 18, 1938 2,540,256 Gretener Feb. 6, 1951 2,788,459 Gretener Apr. 9, 1957

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