US2440122A - Arc lamp - Google Patents

Description

April 20, 1948. R. E. SHEAHAN ARC LAMP Filed Sept. 25, 1946 Inventor:

Robert E. Sheahan b mmyw His Ac.oT-T1eg- Patented Apr. 20, 1948 ARC LAlVIP Robert E. Sheahan, Bridgeport, Conn, assignor to General Electric Company, a corporation of New York Application September 25, 1946, Serial No. 699,287

2 Claims. 1

My invention relates to are lamps, and more particularly to electrode feed control systems for such lamps.

The invention has for its principal object the provision of a new and improved apparatus for continuously feeding and simultaneously rotating an arcing electrode.

A further object of the invention is to provide, in conjunction with such apparatus, an electrode feeding and rotating mechanism which shall be of simple, light, and inexpensive construction without sacrifice of durability and dependability in operation.

In the operation of arc lamps, such as searchlights and the like, it has heretofore been common to continuously rotate but only intermittently advance the positive electrode. Purely intermittent advancement of the positive electrode may be disadvantageous in that it causes considerable fluctuation of the arc. Alternatively, it has been suggested that the positive electrode may be continuously rotated and continuously advanced at a predetermined constant speed. Such an arrangemnt, however is difficult to adjust, and if not adjusted for precisely the proper rate of feed the crater will not remain in the desired position.

According to my invention the positive electrode of an arc lamp is continuously rotated and continuously advanced at one of two selectable speeds. The low speed of advancement is slightly less than and the high speed slightly greater than the normal burning rate of the electrode. In this way, the advantages of continuous forward feed and rotation are obtained, but means are also provided to ensure that the crater remains in the desired position in the event that the burning rate varies slightly.

For a more complete understanding of my in vention and a further appreciation of its objects and advantages, reference should now be had to the following detailed specification, taken in conjunction with the accompanying drawing, the single figure of which is a schematic circuit diagram of an electrode feed control system for are lamps embodying my invention, the electrode feed mechanism being shown in cross section.

Referring now to the drawing, I have shown an arc Searchlight comprising a positive electrode and a negative electrode 2 arranged to be connected through a contact 3 of a line contactor 4 to the corresponding terminals of a suitable source high voltage electric current supply, such as a 60-volt direct current generator 5. The line contactor 4 is provided with an actuating wind- 2 ing 6 arranged to be energized through cut-out switch 1 from a low voltage source of control power, such as a 24-volt line 8.

The negative electrode 2 is supported by a pair of driving rollers Hi, i5 and a pair of spring pressed electric conducting guide brushes It, ll. Current is supplied to the electrode 2 through the brushes l6, IT, as shown. The roller i5 is serrated and driven by a reversible negative drive motor l8, thereby to advance or retract the electrode 2. The drive motor i8 is provided with a normally engaged magnetic brake i9 and a pair of oppositely wound series field windings 26, 2|. The magnetic brake i9 is arranged to be disengaged upon energization of the motor 8 by a brake coil 22 connected in series circuit relation in the motor circuit. The series field windings 20 and 2| are arranged to be alternatively connected to the source or control power 3 through the switch 1 and a current regulator 23. The regulator 23 comprises a current responsive actuating winding 26, a pair of normally closed contacts 25 and a pair of normally opened contacts 26. The winding 2 is connected in series circuit relation in the arc circuit of the electrodes and 2. The contacts 25 and 26 are controlled by bridging contact 27. The motor 18, when energized through the series field winding 2!, is arranged to drive the electrode 2 in a forward direction toward the electrode i. The motor field winding 26, when energized, causes the motor I3 to operate in the opposite direction, thereby to retract the electrode 2. The field winding 25) is energized through the contacts 25 only when the current through the arc, and thus through the regulator winding 24, exceeds a predetermined maximum value.

The positive electrode i is arranged for continuous rotation and forward feed alternatively at one or the other of two selectable speeds. For this purpose the electrode is mounted in a rotatable head 28 which is journaled in a fixed support 29. The head 28 comprises a hollow sleeve 30 within which the electrode is slidable loosely. The sleeve 3%) carries at one end a gear bracket 3i. In the gear bracket 3| the electrode is supported between a guide roller 32 and a serrated or toothed driving roller 33. The electrode is further guided and also supplied with current by a pair of spring-pressed electric conducting sliders 34 and 35. Upon the shaft of the driving roller 33 there is mounted a driving pinion 36. The pinion 35 meshes with a worm gear 31 journaled at 33 in the rotatable head bracket 3|. The shaft of the worm gear 37 carrles at its opposite end a planetary spur gear 39 which meshes with a sun gear 48 journaled in the frame 29 and rotatable with respect to the electrode head 28. Specifically the sun gear 40 is attached to a hollow sleeve 4| which is journaled in the frame 29. On the sleeve 4| adjacent to the sun gear 40 there is mounted a spur gear 42. The hollow sleeve 39 forming part of the rotatable head 23 is rotatably journaled within the sleeve 4|. At the end of the sleeve 30 remote from the gear bracket 3| there is mounted a spur gear 43 fixed to the sleeve 30 by a setscrew 44. The spur gear 43 is of slightly greater diameter than the spur gear 42'. Finally the gears 42 and 43 are simultaneously and continuously driven by a pair of pinions 45 and 46. The pinions 45 and 46 are journal'ed in the frame 28 and connected, as by a shaft 41 (indicated schematically), to a driving motor 48. The pinion 46 is slightly smaller than the pinion 45, so that the spur gear 42 is driven at a greater speed than the gear 43. It will of course be appreciated that, if desired, the gear 42 may be driven slightly slower than the gear 43, it being only necessary that the gears 42 and 43 be driven at unequal speed. It may be noted however that if the speed relationship is reversed from that shown it is also necessary to reverse the dlrection of rotation of the motor 4% so that the electrode I will advance.

It will be observed that, in the operation of the positive electrode driving mechanism, the spur gear 133, driven by the motor 48 and attached to the electrode head 28, rotates the electrode head about its "own axis, thereby continuously to rotate the electrode I. If now the spur gear 42' were not driven, but were allowed to rotate idly upon the sleeve 36, it would be carried around by the supporting head '28 and the gears 3"! and 39 at the same speed as the head, so that the gears 3'! and 39 would not Totate upon their own axis and therefore would not drive the electrode 1 longitudinally. However, the spur gear 4'2 is positively driven by the pinion 45 at a speed slightly greater than the speed of the head 28 itself. Thus the planetary gear to is caused to roll slowly around the sun gear to, thereby to rotate the worm gear 31 on its own axis and continuously to drive the positive electrode I forward as 'it rotates.

As will be more fully explained hereinafter, the crater at the end of the positive electrode 1 is maintained in a predetermined desired .position by providing two selectable driving speeds for the positive head mechanism, in conjunction with a control system responsive to crater position. During normal arcing operation the positive driving motor .8 is connected to the low voltage source of control power '8 through the cut-out switch 1. The motor 48 is provided with a shunt field winding '48. For control of the speed of the motor 48 there is connected in series with the motor armature a variable resistor -59 which arranged to be shunted by a thermally responsive switch 51. The switch 51 is closed when cold and opens its contacts when hot to insert the resistor to in the motor circuit.

The thermally responsive switch '51, and thus the speed of the motor 4-3, is controlled in accordance with the position of the crater in the end or the positive electrode I. Tlns'control may conveniently be effected by any well known optical system such as that described in U. Patent 1,590,543 issued on June 29, I926, to Martin L. Patterson. Briefly such a system comprises an optical arrangement for reflecting the image of the positive crater directly upon the thermal responsive switch member 5| when the crater is in the desired position. In this position of the crater the switch 5! is held open and the motor 48 operates at its low speed. If however the crater burns back farther than desired the image of the crater moves on of the thermal responsive switch member 5!. The switch 5| closes its contacts and the speed of the motor 43 is increased, thereby to drive the electrode I forward at. a greater speed.

With the foregoing description of the various elements of my feed control system, the operation of the system as a whole will now be readily understood from the following brief description.

Let it be assumed that the electrodes are separated as illustrated, and that the cut-out switch I is closed. With the cut-out switch I closed, energizing circuits are completed for the driving motors i8 and t8, the circuit for the negative drive motor 58 passing through the bridging contact 2? of the regulating relay 23. In parallei circuit relation with the motors there is also completed an energizatlon circuit for the actuating Winding 5 of the line contactor 4. Accordingly, therefore, as soon as the switch "I is closed the drivin motors l3 and '48 are placed in operation and the line contactor 4 is picked up to apply arcing voltage to the electrodes.

Since no are yet exists, the regulator contacts 25 are closed and the negative driving motor drives the electrode 2 forward into engagement with the electrode The positive electrode l is simultaneously being driven forward at its maximum speed because the thermal responsive switch member 5i is cold and the resistor 50 shunted. As soon as the electrodes come into contact an arc is struck. The high current through this short are picks up the regulating relay '23, thereby to close the contacts 26 and to withdraw the electrode 2 by reverse operation of the motor is. With arcing taking place, the crater at the end of the positive electrode l is maintained in a predetermined desired position by operation of t e thermal responsive member 55 and the motor :33, and the negative electrode is advanced or retracted as required in order to maintain the arc current substantially constant.

While I have described only a preferred embodiment of my invention by way of illustration, modifications will occur to those skilled in "the art, and I therefore wish to have it understood that I intend in the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an arc lamp including a pair of arcing electrodes, electrode feed control means for continuously rotating and advancing at least one of said electrodes comprising, a rotatable electrode holder, a concentric sun gear rotatable with respect to said holder, a planetary gear journaled in said holder meshing engagement with said sun gear, and means for continuously and positively driving said holder and said sun gear at unequal speeds.

2. In an arc lamp including a pair of arcing electrodes, electrode feed control means for con tinuously rotating and advancing at least one of said electrodes comprising, a rotatable electrode holder, a concentric sun gear rotatable with respect 'to said holder. a planetary gear .journaled in said holder in meshing engagement with said sun gear, means actuated by rotation of said planetary gear about its own axis for advancing said electrode, and means for continuously and positively driving said holder and said sun gear at unequal speeds.

ROBERT E. SHEAHAN.

REFERENCES CITED file of this patent:

Number UNITED STATES PATENTS Name Date Thompson June 8, 1926 Mole Oct. 12, 1926 Pennow Dec. 13, 1938

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