US2205067A - Electric arc - Google Patents

Description

June 18, 1940. N. PIIERRON ET AL ELECTRIC ARC Filed Oct. 30, 1957 2 Sheets-Sheet 1 l N Vi N E S N l Rarren .FIer re W j HIHIH lxllllll June 1940- N. PIERRON ET AL 5, 7

ELECTRIC ARC Neal Rerrb Pmrre Avbrg INVENToZ Patented June 18, 1940 UNITED STATES PATENT OFFICE France, assignors to Pathe Cinema, Anclens Etablissements Pathe Freres, Paris, France, a

company of France Application October 30, 1937, Serial No. 111,888 In France July 19, 1937 6 Claims.

It is known that the brilliancy of the crater of the positive carbon of a "high intensity elec-- tric arc is a function of the current density in the carbon (number of amperes per unit of sec- 5 tion). This function is not linear-4n fact, the brilliancy increases at a much higher rate than the current density, and when this variation is graphically represented, the result will be a curve, termed brilliancy-density characteristic, the slope of which increases very rapidly.

On the other hand, the rate of consumption of a given carbon depends exclusively upon the energy W consumed in the arc. This rate of consumption also increases much more rapidly than 15 W, and in this case as before, the graphic representation of the phenomenon leads to a curve,

termed consumption-energy characteristic. the

slope of which also increases very rapidly.

It will follow from the preceding considera- 20 tions that in order to obtain in an are a very great brilliancy of the crater, which is the ob ject to be attained, it is desirable to use for the positive carbon as great a value of current as possible (this being however compatible with the stability of the arc and the optical arrangement of the lantern), but this will cause a very rapid consumption of the carbon. as the energy taken up by the arc increases with the current density.

The points which represent an operation with good efficiency are thus located, on the characteristic curves of the arc, in regions in which the slope is very rapid, but at these points, the least variation of the energy taken up by the arc is at once manifested by a marked variation in the rate of consumption.

One object of the present invention is to provide a method for regulating the electrodes producing an electric arc adapted for lighting, heating, or the like. in which each of the two electrode carriers is actuated independently from one another by a common electric motor operating at a constant speed. by the use of two separate transmission devices the ratios of which can be adjusted.

Experience as well as theory (as will be further disclosed) show that for constant and determined feeding speeds of the electrodes, the consumption of these electrodes will afford automatically-for a given current-a constant spacing and'hence a constant useful efiect, whether this effect is an intensity'of light or a quantity of generated heat. I

In order ,to increase this useful effect, which thus will correspond to a new value of the current, it is simply necessary to increase the speed (Cl. PIG-51) at which the two electrodes are fed. When the current increases, the consumption will also increase, and after a short time, the arc will be again stabilized at the spacing which corresponds to the new value of the current desired.

The invention further consists of an arc apparatus, (lamp, heating apparatus) for carrying out the aforesaid method of regulation.

The said apparatus comprises an electric motor operating at a constant speed,-a cam or like member which is rotated by the said motor through the medium of a speed-reducing mechanism, two free-wheel mechanisms the driving elements of which are given an alternating movement, in one direction by the said cam, and in the other direction by elastic reaction devices, whilst the two driven elements are each connected to one of the respective electrodes by a suitable transmission, and two stops which are adapted to be adjusted independently from one another and are each combined with the driving element of one of the two free-wheel mechanisms, in such a manner as to regulate the amplitude of its oscillations by adjusting the extent of the return movement.

Further features of the said invention will be set forth in the following description.

In the accompanying drawings, which are given solely by way of example: i

Fig. l is a diagram relating to the method.

Fig. 2 is a diagrammatic longitudinal section of an arc lamp.

Fig. 3 is an enlarged cross-section on the line 3-3 of Fig. 2.

Fig. 4 is a diagrammatic view of an electrooptical device for the automatic regulation of the position of the negative electrode.

In Fig. 1 is shown a positive electrode I consisting of a carbon in which a crater l is formed. and a coaxial negative electrode 2 which has a smaller diameter and ends in a tip 2 According to the invention, the electrodes I and 2 are given contrary displacements, in the directions of the arrows f and f and the speeds V and V of the said electrodes are such that they will compensate for the linear consumption U and U corresponding to the electrical conditions for a given distance e between the end planes AA and BB of the two electrodes.

In these conditions, if the two electrodes ar moved apart, this will cause a reduction in the consumption of energy W, but this will greatly reduce the linear consumption or rates of consumption U and U of the electrodes. On the contrary, if the electrodes are brought nearer together, W will increase, and the rate of consumption will increase.

It is now supposed that the feeding movement of the electrode 2 exactly compensates for its consumption so that the said electrode will be stationary in space. Electrode I is fed at the speed V and its consumption takes place at a speed U corresponding to a distance 6.

If the end of the positive carbon I is brought in the plane A. A, W will increase. The rate of consumption of the carbon will increase more rapidly than W, and will reach a value V. As the speed V is at this time less than U. the crater of the carbon I will tend to recede until the distance e again becomes equal to e, thus affording a consumption W corresponding to a consumption U equal to V The conditions are quite the same when the end of electrode I is brought in the plane A". A". and it is thus evident that the arc will always stabilize when U =V and this. for a given current. will afford a given distance 6 and a consumption W to which corresponds a well-defined useful effect.

It will be thus observed that a self-regulation of the distance between the carbons takes place, provided that the speed of translation V is constant if it is not desired to introduce other factors which. being independent of the characteristic of consumption. would cause trouble and would entirely transform the principle of selfregulation.

It should be noted that it is advantageous to operate in the part of the consumption-energy characteristic having a great slope, so that to slight variations of current (i. e. to slight variations of the distance e) will correspond great variations in the speed of consumption of the electrodes. In this manner, the sensitiveness of the adjustment is greatly increased, as the rapid variations of the speed of consumption will afford a very rapid return to the normal distance 6, after a disturbance. for instance due to the nature of one of the electrodes, has caused a variation of said distance.

In the preceding considerations; it has been supposed that the end of the negative carbon 2 has remained in the plane BB, and that the rate of consumption W of the negative carbon was exactly equal to the rate of the feed V Now. the characteristic curve of the consumption of the negative carbon in function of the power W has not the same form as the characteristic curve of the consumption of the positive carbon. The slope of the curve of the consumption of the negative carbon in function of W increases but little with the increase of W contrarily to the slope of the curve of the consumption of the positive carbon. In consequence, admitting that the rate of consumption W of the negative carbon 2 is less than the rate of feed V of this carbon, the negative carbon will move towards the positive carbon. When the distance between the carbons decreases, W will increase. But the positive carbon, the rate of consumption of which is considerable, will be consumed more rapidly, and its crater moves back, so that the gap of the arc remains constant. Thus there is observed a movement of the two carbons in one direction or the other according as the rate of consumption U of the negative carbon is larger or smaller than its feeding rate V.

In the arc lamps used for the projection of motion picture films, as the crater I of the positive carbon I should be located at the focus of an optical system, it is evident that a movement of the carbons will cause a reduction of the optic l efliciency of the apparatus. Fortunately, experience shows that the very slow consumption of the negative carbon 2 permits a relatively exact regulation of its feeding speed.

By way of example, an arc can be made to operate with the adjustment according to the invention for 30 or 40 minutes, without being obliged to make any manual correction. Inasmuch as in a motion picture plant, an arc must operate for 20 to 25 minutes at the maximum without stopping, it may be considered that the are which is regulated by supposing the negative electrode stationary, does not require any manual correction.

Figs. 2 and 3 show by way of example an arc lamp according to the invention.

The said lamp comprises in the known manner, in the interior of a casing 3, a mirror 4 adapted to reflect, through an opening 5, a strong beam of light issuing from the are which is formed between the crater I oi! a positive carbon I and the point 2 of a negative carbon 2. The crater of the positive carbon I must be maintained at the focus of the mirror I, in spite of the consumption of this carbon, and the negative carbon 2 must be maintained at a given distance e from the positive carbon I, which distance e depends, as above stated, upon the current I and the desired power W, and also upon the nature and the crosssections of the electrodes I and 2.

The positive carbon I, which rests at the front part upon a supporting fork 5, is clamped, at the rear, by means of a screw 6 operated by a lever I, in a carbon clamp 8 mounted on a bracket 9 which is pivoted about an axle I Ii on a support I I. Support II to which is connected a wire I2 for the supply 01 current, is secured, with interposition of a plate and insulating tubes, to a carriage I! which, at the outside of the casing 3, forms a nut upon a'driving screw it The carriage I3 can be uncoupled from the said screw by known means, not shown.

Said screw I 4 may be operated by hand from the outside of the casing 3 by means of a shaft I 5 and bevel gearing I8, in view of regulating the carbon I by hand.

To provide for the automatic feed in the direction of the arrow 1 at the speed V corresponding to a rate of consumption U the screw I4 extends as far as a case I! (Figs. 2 and 3) which is secured to the rear side of the casing 3 and contains the driving mechanism.

The said mechanism comprises an electric motor I8 operating at constant speed, and actuating, for example through a torque-limiting device IS, the driving shaft of a speed-reducing device 20. On the driven shaft 2| of the said speed-reducing device is mounted an eccentric cam 22, which acts at each revolution to drive back, in succession, two rollers 23 and 24.

Roller 23 is mounted on a push-rod 25 which is slidable in a tubular member 26 carried by the case II. The said push-rod acts upon an arm 28 which is integral with a sleeve 29 which is concentric with the end of screw I4 actuating the carriage I! of positive carbon I. Sleeve 29, which is urged in the direction of the arrow 1 (Fig. 3) by a spring III, is connected, as to rotation, to the screw I4 by av free-wheel mechanism of any known type comprising balls and inclines or the like, so that the sleeve 29 will actuate the screw I4 in the proper direction to move the positive carbon I towards the negative carbon 2 when the said sleeve rotates in the contrary direction to the a row by the action of the push-piece 25. The return or the said sleeve under the two carbons I, 2.

action of the spring 30 has no effect upon the screw i4.

011 the same side as the push-piece 28, is mounted an adjustable stop 32' formed by the end of a screw 33 which is provided with an operating head and can be screwed more or less into the wall of the case II. The said stop limits the return stroke of the sleeve 28 and the arm 28 under the action of the spring 30. As the extent of the working stroke is fixed and is determined by the maximum forward movement of the pushpiece 25 under the action of the cam 22, it will be noted that the amplitude of the successive oscillations of the said sleeve and hence, of the successive rotations of the screw I 4 in the same direction, will depend upon the position of the stop 32. By adjusting this stop, it is an easy matter to regulate the forward speed V of the positive carbon I, the speed of the motor l8 remaining constant. and such that it is capable. taking account of the speed-reducing device 28 and the cam 22. to impart to the carbon I the greatest speed that can be required.

The other roller 24, which is acted upon by the cam at each rotation, is mounted on the end of an arm 35 which is urged by a spring 36 and is integral with a sleeve 31 which actuates a worm 39 by means of a free-wheel 38 when it oscillates in the direction of the arrow 1. Worm 33 meshes with a worm-wheel 40. Said worm-wheel is loosely mounted upon a transverse shaft 43 but is adapted. to drive said shaft in rotation through a disc 41 which is urged in frictionalengagement with one of the end faces of the worm-wheel 40 by a spring 42 which also provides for rotation of shaft 43 with disc 4!.

A screw-stop 44 the position of which is adcessive rotations, all of which are in the same direction, which are imparted to the worm-wheel 40 and hence to the shaft 43, owing to the friction coupling 4|, 42. The said shaft 43 can also be actuated by hand, by means of a knob 46. In

this case, the worm 39 is held stationary, and the worm-wheel 40 will rotate about the shaft 43, owing to the friction-coupling 4|, 42. To the shaft 43 is keyed a pinion 41 consisting of insulating material. 46 movable in guides 49 mounted upon a supporting member 50, which is secured to the case i! by screws 5| provided with washers and insulating bushings, being thus insulatedagainst bodycontact. The rack 48 is connected by an axle IN to the lower jaw 52 of the negative carbon holder. The other jaw 53 is pivoted to the jaw 52 by a pivot-axle 54, and the negative carbon is clamped between the two jaws by a screw 56.

The negative current is supplied to the electrode 2 by a conductor 66.

It is observed that the feed of the negative carbon 2 in the direction of the arrow f can be obtained from the shaft 43, either by hand by means of the knob 46, or automatically. from the motor I8, by means of the cam 22, the arm 35, the free-wheel 38, the worm 38 and the wormwheel 48, the feeding speed V being regulated by the stop-screw 44.

' The negative carbon 2 rests upon a supporting fork 51 which is adjustable both laterally and vertically by screws 58.

The apparatus is completed, in the known manner, by means for indicating the positions of the The said pinion engages a rack Such means, not shown, consist of two. indicating marks which are located at the outside of the casing 3 and upon which an optical device projects through an opening 68 in the said casing the image of the incandescent ends I and 2' of the two carbons.

The operation is as follows. The operator is aware that he is to work with a given current I, taking due account of the nature and the quality of the carbons in use. The current being supplied, with the electrodes l-2 in any position, the operator handles the hand control knobs in order to bring the ends i -2 of these electrodes adjacent the two respective indicating marks, then by acting upon the stops 32 and 44 he re ulates the automatic feeding speeds V and W of the electrodes in such way that these speeds will correspond to the rate of consumption U and W for the given operating conditions (current I, distance e of the electrodes, power consumed W). When the adjustment has been made and corrected if necessary, the distance e between the electrodes |2 is automatically maintained constant as above described, and since the consumption of the negative carbon 2 may be considered as practically constant for a relatively long operating period, the two carbons l and 2, the distance e of which is now constant, remain practically fixed in space, and the crater I of the positive carbon I remains at the focus of the mirror.

However, in the case in which an arc providsd with the aforesaid regulating devices is required to operate in an inaccessible place and for a very long time, it may be provided with means forautomatically fixing in space the point 2 of the negative carbon 2.

Such means may comprise.,as shown in Fig. 4, a lens; 59 which receives the light from the incandescent point 2 of the negative carbon 2.

justable screen 60 which is slotted at 60, and

in the rear of which is located a photo-electric cell 6|.

This cell controls a relay 6| adapted to open and close the circuit of an electromagnet 62 which acts upon a pawl 63 engaging a toothlng 64 rovided on the sleeve 31 which is secured to the lever 35.

The regulation consists in giving to the feeding speed V of the negative carbon 2, a value which exceeds the rate of consumption U In 'these conditions, when the image of the negative point 2 is no longer opposite the slot 60 in the screen 60, the photo-electric cellfil actuates the relay Bl which closes the circuit of the electromagnet 62, and thus the soft iron pawl 63 is attracted by the electromagnet and it will engage the toothlng of the sleeve 31 when this latter is at the end of its working stroke. The sleeve 31 is thus held stationary, and under the action of its spring 36 it can only oscillate, at the maximum, through an angle corresponding to the distance between two teeth of the toothlng 64. 'As the amplitude of oscillation of the lever 35 has thus diminished, the rate of feed of the negative carbon has also diminished. Owing to the consumption of the carbon 2, the point 2 will move rearwardly, and its image will again coincide with the slot BM of the screen 60 and will thus act again upon the cell 6|. The relay lil then opens the circuit of the electromagnet 62, and the pawl 63 drops down, thus releasing the sleeve 31 and the amplitude of the oscillations of lever 35 will again take their maxi- ,The image of this point is projected upon an ad- 7 mum value corresponding to the initial adjustment.

Thus the mechanism will act the more frequently as the rate of feed of the negative carbon 2 is greater in proportion to the rate of consumption of the carbon.

As a principle, the distance e of the carbons 1-2 being constant, it will be understood that if the position of the negative carbon 2 is fixed in space, the position of the positive carbon l is also fixed.

Obviously, the said invention is not limited to the embodiments herein described and represented, which are given solely by way of example.

Having now described our invention what we claim as new and desire to secure by Letters Patent is:

1. In an electric arc apparatus, the combina tion with the two electrode-holders of a motor rotating at a constant speed during constant time units, and for each electrode-holder an independent speed reducing gears actuated by said motor and feeding means adapted to displace said electrode-holder towards the other electrode-holder, and transmission means between said motor and each feeding means, the transmission ratio of each transmission means being independently adjustable, whereby each electrode-holder is given a regular and constant displacement during each time unit.

2. In an electric arc apparatus, the combination with the two electrode-holders of a motor rotating at a constant speed during constant time units, and transmission means comprising independently for each electrode-holder a pivoted member adapted to oscillate between two adjustable extreme positions and actuated by said motor, a rotatable shaft and a one way clutch between said pivoted member and said shaft adapted to rotate said shaft in one direction, and feeding means between each electrode-holder and the corresponding shaft actuated by said shaft to displace said electrode-holder towards the other electrode-holder, whereby each electrode-holder is given a regular and constant displacement during each time unit.

3. In an electric arc apparatus, the combination with the two electrode holders, of a motor rotating at a constant speed, a cam rotated by said motor, and between said cam and each of said electrode holders transmission means comprising a free wheel mechanism including a driving member and a driven member, spring means,

said driving member effecting a working stroke under the action of said cam and against the action of said spring means and a return stroke under the action of said spring means, said driven member rotating with said driving member during said working stroke and being released from said driving member during said return stroke, stop means limiting the return stroke of said driving member whereby the amplitude of the working stroke is also limited, and means provided between said driven member and the corresponding electrode-holder to feed the electrode when said driven member rotates.

4. In an electric arc apparatus, the combination with the two electrode holders, of a motor rotating at a constant speed, a cam rotated by said motor, and between said cam and each of said electrode holders transmission means comprising a free wheel mechanism including a driving member and a driven member, spring means, said driving member efiecting a working stroke under the action of said cam and against the action of said spring means and a return stroke under the action of said spring means, said driven member rotating with said driving member during said working stroke and being released from said driving member during said return stroke, adjustable stop means limiting the return stroke of said driving member whereby the amplitude of the working stroke is also limited, and means provided between said driven member and the corresponding electrode-holder to feed the electrode when said driven member rotates.

5. In an electric arc apparatus, the combination with the two electrode holders, of a motor rctating at a constant speed, a cam rotated by said motor, and between said cam and each of said electrode holders transmission means comprising a free wheel mechanism including a driving member and a driven member, spring means, said driving member effecting a working stroke under the action of said cam and against the action of said spring means and a return stroke under the action of said spring means, said driven member rotating with said driving member during said working stroke and being released from said driving member during said return stroke, adjustable stop means limiting the return stroke of said driving member whereby the amplitude of the working stroke is also limited, and means provided between said driven member and the corresponding electrode-holder to feed the electrode when said driven member rotates, a photo-electric cell positioned to receive a flux of light from the incandescent end of the negative electrode, a relay supplied with current by said photo-electric cell, a screen intercepting said flux of light when the position in space of said incandescent end changes, electromagnetic means controlled by said relay so that the supply circuit of said electromagnetic means is closed when said flux of light is intercepted as a result from a too rapid feeding movement of said incandescent end, locking means holding against rotation the driving member of the free-wheel mechanism controlling the negative electrode when said electromagnetic means are supplied with current, whereby, when the one of said stop means corresponding to said negative electrode is adjusted for a feeding speed which exceeds the rate of consumption of the negative electrode, said incandescent end is maintained in a fixed position in space.

6. A combination as claimed in'claim 5, in which said locking means comprise a pawl attracted by said electromagnetic means and a toothing provided on the driving member controlling the negative electrode, said pawl engaging said toothing when attracted by said electromagnetic means and to hold said last mentioned driving member against rotation.

NOEL PIERRON. PIERRE AUBRY.

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