US2639400A - Carbon arc lamp operation and arc intensity control - Google Patents

Description

y 9, 1953 J. J. MAscucH ET AL CARBON ARC LAMP OPERATION AND ARC INTENSITY CONTROL Filed March 25, 1950 3 Sheets-Sheet 1 J C mm y 3 k H mi M W 3; R. 1K4 3 H 2 iw M 1m% 6 Km mm hm Om mm 19, 1953 J. J. MASCUCH ETAL 2,639,400

CARBON ARC LAMP OPERATION AND ARC INTENSITY CONTROL Filed March 25, 1950 3 Sheets-Sheet 2 INVENTOR5 JOSEPH J. MA 501/04 JnMss K flaaQ/w/ y 1953 J. J. MASCUCH ETAL ,400

CARBON ARC LAMP OPERATION AND ARC INTENSITY CONTROL Filed March 25, 1950 3 Sheets-Sheet 3 INVENTORS. J05PH J lfQSCl/CH JAMES K EZDEEK/A/ Patented May 19, 1953 CARBON ARC LAMP OPERATION AND ARC INTENSITY CONTROL Joseph J. Mascuch, Maplewood, and James K. Elderkin, Montclair, N. J.

Application March 25, 1950, Serial No. 151,834

' 2 Claims. 1

This invention relates to carbon arc lamps, and particularly to the control of, and degree of effective illumination obtained from such a lamp. In the operation of arc lamps, notably arc lamps employed in motion picture film projection work. there is much variation in the effectiveness of the are under diiferent conditions encountered as the carbon electrodes burn away, and also as between the performance of different individual carbon elements. Moreover, even under the most advantageous conditions, a large part of the illumination supplied by the arc is dissipated before it is directed to the location where it can be most effective as an illuminating instrumentality for the article to be exhibited as, for example, a moving strip of film bearing images to be projected onto a viewing screen.

One major cause of dissipation of illuminating power is lack of complete magnetic control of the arc. As electric energy flows across the gap between negative and positive electrodes, a magnetic field is set up, and the arc burns in a dense ball of flame and gas, concentrated about the electrodes.

As the burning proceeds, the two electrodes become incandescent. The negative electrode tends to round off. The positive electrode produces a flat, slightly concave face, normal to the electrode axis. It is the image of this concave face, heated to white heat, which being placed at the theoretical focal point of an elliptical condensing mirror, produces the white projected light desirable in projection lamps. This burning of the arc, however, without complete external magnetic control, envelopes the positive electrode face in a shroud of partially burned, colored gases, which dissipate the white desirable light emitted from the positive face of crater. As stated above. these gases being highly ionized are subject to magnetic influences.

The present invention has for one of its objects, the correction of the above described dissipating and enshrouding of the .inherent magnetic field by novel methods and means. Specifically, the novel method of correction herein disclosed involves the step of introducing a corrective secondary magnetic field of such a magnitude and disposition, in relation to the original magnetic field created by the arc itself, as to create an overpowering magnetic stress that is effective to accelerate the unburned gaseous matter upwards and away from the image crater, in a predefined narrow path, leaving the image crater substantially free of enshrouding, light dissipating gases, thereby making it possible for the maximum,

2 candescent strength of the image crater to be utilized in projection.

The novel means employed to practice this novel method of control, is herein illustrated as taking the form of an electro-magnet mounted at a distance from the aligned carbon electrodes but having a projecting polar element, or corepiece, of suificient length to reach almost to the point of arc formation, so that said core can be effective, upon passage of energizing current through the winding surrounding the core, to create the over-powering secondary magnetic stress above described, and thereby direct the gases or flame tail into the desired shape and direction.

Another object of the invention is to provide a novel system of control of the feeding of the positive and negative electrodes toward each other; the novelty including the use of motordriven reduction gear assemblies individual to each of two feed screws actuating the respective carbon carriers; and independently adjustable electronic timer circuits for controlling motor energizationselectively and intermittently, to obtain at each feed screw a rate of advance, per minute of operation, that is exactly correct for the burning characteristics of the carbon rod driven therebyit being well known that positive and negative carbon rods usually have differing characteristics. Other objects and novel features are pointed out in the following description.

In the accompanying drawing, Fig. 1 shows the invention applied to a pair of aligned carbon electrodes; l

Fig. la shows an exploded view of one of the clutch assemblies; Figure lb shows the details of the solenoid.

Figs. 2 and 2A illustrate the tendency of the electrode crater to become enshrouded by lightdissipating gases, in the absence of complete magnetic control.

Figs. 3 and 3A show. the appearance of the flame, after its position and shape have been corrected by the use of the present invention.

Fig. 4 shows schematically the electrical connections for control of one of the actuating motors; the said connections being duplicated for the other motor.

Fig. 5 is a schematic wiring diagram.

Referring first to Fig. l, the apparatus there illustrated includes a pair of carbon electrodes, 10, H in alignment, one with the other, and adapted to be fed toward each other by the rotation of two feed screws, each of which is inthreadedlit ngageuwitn corresponding threadscut internally of said hubs, are feed screws I6, 23,

whose ends are rotatably supported in bearings ll,

24 on the base plate 21. The motors rotate the feed screws at greatly redu'd siiee'ii,- in rla tion to motor speed. by reason of the interposed"- reduction gear trains i8 and- =25 coupled to gears 28. 28 of the feed screw clutch'assemblies; This consists of the clutch body 23, leather facing washers 30, backing washer est-springwasner" 36, and nut 31, which can be tightened or loosened to give the proper slipping value to enable the carriages 9 and 22 to bemoved back or forward to"coire'ctly"set' the initial -arc" gap? ac complished by means of manually turning the Tlie"rotation"of the"tw'o res-a screws serves to keep-"the two carbon? electrodes moving toward eaen' other at the desired respective rates, as

regulated by'itliefrespectivniotor'control circuits mmybne or whie'h iulmstrateu 4), the orsjetfve'beinfg tc'i' move each electrode ro'rwa'rfd at aconstanfrate c'rr'espbnumge'xacuy to "the rate at"wli'ich its tip is being burned away, and thusmaintaina constant width of arc" gap"b;- tweenthetwoelectrodetipsi The'novelnieansfor obtaining greater intensity of illumination from the crater image is shown inrigz lb' 'as including a solenoids! navinga magnetic core 37L ex't'en'din g horizontally "therefrom, and"then"turning 'up'w'ardto form a ver'-' ticallydisposed fextension" 3a terminating V in a magnetic h'ea'd 3 l"disp"osed iznmediately'adja'cent the'arc.'gap';" the core '32 being'shift'able'both longitl'idiiially'and'rotationally of its axis A to "secure the" desired positioning. for most effective" arc brilliazrcewsjee-rfig'st 3" and 3A5 and" then locked" insuclfoptlmumiaositioni As previously-noted; the magnetic neld set up luminescent electrode crater; But "the introdu' c'- tionbf'a correcting magnetic field;'as' bysending' current through the windings of solenoid 3i has the effect of "pointlng'' the surrounding" gases (or 't'ail name" as they are"called) into'a'th in vertical cone-like shape (Fig. 3) thus minimizing the'shroudin'g' effect and thereby resultingiin'a clear brilliant white light emanating fr'o'm" the positive crater. By reason of the maximurn'li'ght" eilic'iencyithus attained; the"- lamp isdecidedly 4 more effective as an illuminating means for picture projection or analogous purposes.

As indicated in Fig. 4 for the control of motor I2, each motor is energized by a circuit having therein a switch-=9 oscillating between make" and break" positions, as a relay 6 is alternately energized and de-energized; the relay 6 being part of a timer circuit having a single thyratron unit-i whose'grids 3, 4 functionin collaboration with resistors R1'' R5, condensers (31 0 and resistor R4. to send spaced energy impulses across the tube terminals 2, S and thus intermittently energize the relay 6. Supply lines 8 serve as the energy source, both for motor (2, and relay 6.

The resistors R4 and Rs are manually adjustable to set the desired frequency rate for the relay 6 and thus control the feeding of electrode l or i 0 as the case may be. Fig. 5 is a schematic wiring diagram showing an automatic cut off device 30 for automatically interrupting the screw drives when there is no arc current flowing. With the timers i and 2 operating, energy impulsesam sent through the respective feed meters l 3, l2 through'relay 30 (see 4' also)? ar'ifbac'ii timers completing the circuit. may '30, how ever, will only close when current passesth'rgiigh its coil, that is, only afterth a'rcis struckf Ireog thefeed motors are automatically stop pd'whe'il ever the arc is stopped.

What'we claim'isf ll In a carbon arc lamp' operating system? a pair of aligned carriages movable toward "each other, a positive carbonclecti'od carriedby one of said carriages, a negativecarboiielectrod ried by the other of said carriages, nian siricl d-' ing a pair of motors and a"pairof gear'and clutch assemblies for driving sa'id carriages"; salid'dri'virig' means also including a pair of feed 'sfwsQeach" having motion translating engagement with" its respective carriage, and means "including -el'ctrcnic circuits operating indep'endently'of voltage conditions across said-electrodes'for controlling; current flow to each of said motors," to; central selectively the feedingrate of 'each carb'ofi'el'- trode. I

2. An operating system as defined in claiin 1,' including automatic drive intrrupting xnaiisresponsive to are extinctiom' I EPH J.- JAlMES Kl References Cited in'the meet this atent UNITED: STATES PA'I'E'N'rs' 3

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