US1101629A - Arc-control mechanism for projectors. - Google Patents

Description

J. L. HALL.

ARG CONTROL MECHANISM FOR PROJEGTORS.

APXDLTGAMON FILED MA R.20 1908.

1,101,629, Patented June 30,1914.

4 SHEETS-SHEET 1.

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J. L. HALL.

ARC CONTROL MEGHANIBM FOR IROJEGTORS.

APPLICATION FILED MAR. 20, 1908. l

' Patented June 30, 1914.

4 SHEETS-SHEET 2.

John LHal by Wimesses:

J. L. HALL.

ARG CONTROL MEGHANISM FOR PROJECTORS.

APPLICATION FILED MAR.20,1908. Y

Patented June 30, 1914 4 SHEETSASHBET 3.

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J. L. HALL.

ARC CoNTRoL MBCHANISM'POR PROJEGTORS.

APPLICATION FILED MARZO, 1908. Patented June 30, 1914.

4 SHEETS`SHEET 4.

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L/o/m L, /f/d j anism for Projectors, of which the :followi `UNrrnn STATES PATENT ornren JOHN' L. HALL, OFXSCHAENEOTADY,`NEW YORK', ASSIGNOR T0 GENERAL ELECTRIC COMPANY, CORPORATION OF NEW YORK.

Anc-emmen MECHANISM ron Pnomorons.

Specification of Letters Patent. Application filed March 20, 1908. Serial No. 422,253.

Patented June 30, 1914.

To all wlw/ml it may concern.'

zen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented'certain new and useful Improvements in Arc-Control Meching is a. specification.

My invention relates to yarc controlling mechanism, and more particularly 'to the mechanism by whichthe length and position of the arc is controlled in searchlights,

projectors and similar devices in which an arc is used as a source of light. l

The arc control mechanism for projectors heretofore used has usually been provided with an automatic feeding device which can advance the electrodes toward each other after the arc is established or struck by means of a series magnet, and thereby diminish the gap between them to compensate for the consumption of the carbone while burning, but which is unable to feed the electrodes through varying small amounts and thereby I increase the gap between them to compensate for arc changes.

. In large projectors and similar devices, espel cially wherelarge carbon electrodes are used the arc current and volts vary depending on the crater formation and carbon texture and cause a sudden decrease as well as increase of the arc drop, making it desirable Vvto automatically increase as well as decrease the arc length `to'maintain constant condition and even illumination.

` The object of my invention is to provide a control mechanism for the arc which will automatically, accurately and rapidly either increase ordiminish the gap between the electrodes and thereby maintain a constant arc condition; which in searchlights will, by feeding both carbons or electrodes, maintain the arc in approximately the same position during their consumption, and which j is in generalan improvement in the construction and operation of arc control mechanism, particularly Yfor searchlights and proj ectors.

rapid and exact, and b ro rl ro ortioning the feed of the iwb) cs iboiisrto Ldorrespond tothe relative sizes of the two carbons the arc will be maintained in approximately thefocus of the lens or mirror. The adjustment of the gap between the `electrodes to maintain'the arc length constant is preferabl controlled by some automatic regulating evice which responds to variations in potential between the electrodes. Such a .regulating device may assume many different forms, but in the preferred arrangement some suitable motor or driving mechamsm 1s arranged to move one or both electrodes either to increase or diminish the gap between the electrodes, and is controlled by a relay orA pilot device which determines both lthe direction and extent of movement required to kee the arc length constant. The relay is ma e very sensitive and is connected so that in one position it causes the e in the form of an electromagnet, is made responsive to potential between the electrodes by being connected in parallel with them, and controls the driving mechanism in any suitable way, preferably by means of a locking mechanism which instantly and positively stops and holds the driving mechanism and instantly releases it so that the driving mechanism starts without delay and is instantly stopped without overrunning.

The relay is preferably, though not necessarily, provided with a series coil connected in series with the arc and wound to oppose the shunt coil, which is connected in parallel with the arc. By using a sensitive relay to control a powerful motor or driving mechanism directly connected across the line a very quick, powerful and accurate adjustment of the length of the gap between the .electrodes is secured, even though the adjustment requires a large and heavy electrode to be quickly moved in either direction.

vMy invention will best be understood in connection with the accompanying drawings, which show one of the many forms in which it may be embodied and in which` Figure 1 is a diagrammatic view show- 11o ing the relation of the regulating and feed- I ing mechanisms to the electrodes; Fig. 2 iS. a side view of a projector embodying my invention with the electrode supports shown in dotted lines; Fig. 3 is a plan view of the framework for guiding the electrode sup` ports, said framework containing electrodeactuating mechanism of a form built and in use; Fig. 4 is a vertical longitudinal section of the construction shown in Fig. 3, with the actuating mechanism shown in elevation; andFig. 5 is an end view of the construction shown in Fig. 3, with the ratchets and pawls for actuating the feed screws shown in elevation.

In the specific. form shown in the drawings for purposes of illustration, the arc is drawn between electrodes 1 and 2, mounted on and carried by suitable supports or holders 3 and 4, which are both moved by `any suitable actuating mechanism responsive to voltage across the arc to increase or diminish the gap between the electrodes and thereby maintain the arc length constant. The supports or holders may be made movable inany desired manner, preferably by mounting them on carriages 5 and 6, which slide on guides in a I framework and are moved toward and away from each other by any suitable feeding mechanism which forms part of the actuating mechanism for the electrodes. In the particular construction shown in the drawing, the carriage 5 is provided at each end with grooved wheels' 5a which run upon guide rails 5b. The electrode support 3 is` rigidly secured to the carriage 5, but is insulated from it by insulation 5, while current is delivered to the electrode support 3 and the electrode 1 through a flexible U- shaped connection 3, formed of a plurality of thin strips of copper each with one end secured to the support 3, while the other end is secured to a flat bar 3b connected to one lead of the circuit which supplies current to the projector. The other carriage 6 is provided with grooved wheels 6a which run upon suitably shaped guide rails 6b and the electrode support 4 is mechanically secured to'the carriage but insulated from it by means of insulation 6C. Current is supplied to the electrode support 4 through a flexible connection 4 'made of flexible strips ofcopper each connected at one end to the electrode support 4 and at the other end to the `bar 4b, which in turn is connected to the vertical bar 4c to which current is supplied from y the other lead of the supply circuit through connections hereinafter described. The form of feeding mechanism shown in the drawings consists of a feed screw 7 engaging a nut 5d on the carriage 5 and a feed screw 8 engaging a nut Gd on the carriage (i, the two feed screws being geared together through Gearing 9 and 10 so proportioned that the lectrodes are fed toward each other at such a rate that the arc remains in practically the same position,,notwithstanding the fact that one electrode is consumed more rapidly and is considerably larger than the other.

The actuating mechanism for increasing and diminishing the gap between the electrodes also comprises in addition to the carriages and feed screws above described some kind of a motor or actuating device for rotating the feed screws in one direction or the other to cause the two electrodes to approach or to recede from each other. Any motor or driving mechanism by means of which the feed screws may be rotated in either direction fis suitable for this purpose, but the preferred form of actuating mechanism or motor is that shown in the drawings, in which a ratchet wheel 11 mounted on the feed screw 8 is engaged by a pawl 12 and isyrotated in one direction when the pawl is actuated, and is also engaged by another pawl 13 by which it may be rotated in the other direction. The pawls 12 and 13 are actuated by suitable connections 14 and 15, shown diagrammatically in Fig. 1 as bell crank levers, and which in the specific form shown in the other figures lare projections or lugs on pivoted armatures 16 and 17 moved by means of an actuating magnet 18 connected directly across the supply circuit and thereby subjected to the full difference of potential on the supply circuit. The circuit of the magnet 18 is'broken at two gaps comprising rigid contacts 19 and 20 arranged, as shown in Fig. 1, so that the closure of either gap completes the circuit through the electromagnet, while the armatures 16 and 17 extend beyond theirvpivots and carry yielding contacts 21 and 22, which engage the contacts 19 and 2O when the armatures are drawn away from the magnet by a spring 23, and thereby complete the circuit and energize the magnet 18. The contacts for controlling the circuit of the electromagnet 18 ymay be made in various ways but are preferably constructed as shown 1n the drawing, in which the yieldin contacts 21 and 22 are in the form of U-s apcd spring blades secured to the armatures in a position to engage the rigidcontacts 19 and 20. As y yielding contact will be drawn away from the stationary contact as the armature is attracted into engagement with the electromagnet 18. As shown in Fig. 1, each armature completes the circuit of the electromagnet and energizes it when the armature is drawn away from the magnet by the spring,

While the' movement of the arma-ture into the armature drops back to its original position. Eitherof the armatures 1-6 or 17 will',

- if unrestrained", vibrate rapidly and strongly aslong'astlie electromagnet 18 is connected to the circuit. y

The mechanism above described constitutes the motor part of an actuatingmechanis'm for the electrodes, in which the vibration 'of the armature 16 will actuate the ratchet wheel 11 andthe feed screws 7 and 8 and cause the electrodes 1S and 2 to approach each' other and the gap between them, while the vibration of the other armature will drive the ratchet wheel 11 in the reverse direction and causethe electrodes to move apart and increase the gap between them. Since both electrodes are movable and the armatures 16 'and- 17 .vibrate with strong impulses and at high speed when they are unrestrained, the adjustment of the electrodes with relation to each other isl accomplished very quickly and the length of the arc remains substantially constant;

In' order to secure the best results the actuating mechanism for controlling the gap between'the electrodes should"D automatically respond to' variations in the potential between the electrodes to maintain the length ofthe arc and the differente of potential betweenthe electrodes constant. In the projectors heretofore used, a shunt coil, connected in parallel with the arc was arranged toA feed the electrodes toward each other as the gapbetween the electrodes became too great, but had the disadvantage of not providing any means for increasing the gap between the electrodes in case the arc became too short,A and also the disadvantage that a very sensitive coil did not have suliicient power to operate the electrodes satisfactorily; while a coil powerful enough to move the electrodes quickly was not suliciently sensitive to variations in voltage. Where large electrodes are used the variation in the arc characteristics may make a very considerable difference in the difference of-potential between the electrodes, and if the arc is to be maintained at constant length, the gap between the electrodes must be either increased or decreased very quickly by some comparatively powerful actuating mechanism, which moves one or both of the electrodes. In my invention this result is attained by making the motor or driving mechanism for moving one or both of the electrodes as powerful, as may be necessary, and the entire actuating mechanism for controlling the gap between the electrodes is made responsive to variations of the potential between the electrodes by the use of arelay, or similar selective device, which is responsive to said variations and controls the Amotor or driving mechanism in any suitable manner, preferably mechanically through some locking device or mechanism which will instantly release the driving mechanism' and permit it to run and will instantly and positively stop and Vhold it in any desired position, thereby avoiding the use of electrical contacts which may become oxidized.' Since the work the relay 's called upon to dois very light it may be ade as sensitive as desired and may be made in many dilierent" forms and connected in varousl ways so long as it is responsive to the variations in arc length. The preferred arrangement, as shown in the drawings, is one in which, between the regulating resistance 24 and the electrode l, a relay magnet comprising a shunt coil 25 is connected across the circuit in parallel with the electrodes 1 and 2'. Itis preferable but not necessary to connect in series with thearc, a series coil 26 differentially wound as regards the shunt coil 25, and mounted upon a core 27 common to both coils so thatthe magnetization ,-0 of the core 27 of the relay or pilot -magnet a depends on boththe shunt current due to the difference of potential between the electrodes 1' and 2, and also with the currentflowing between the electrdes and depends 9 on the algebraic sum of the two excitations ca-used by said currents. In the specific arrangement shown in the drawings, the series coil 26 is connected in series with the electrode support 4 by means of connec- 100 tion bar 26- which joins one end ofthe series coil to the bar 4c and by means of a curved connection bar` 26", which joins the other end of the series coil to a flat bar or lead 26, which in turnisl connected -to a 105 binding post by 'means of which one of the leads of the supply circuit may be secured to the projector. In theoperation of the device the current l'ows from one lead of the supply circuit to the Hat bar 3b, thence 110 through the flexible U-shaped connector 3a to the electrode support 3 and electrode l, I y thence through the arc` to the electrode 2, through the electro-de support 4 and the flexible connector la to connector bars 4" 115 and 4, thence through the conductor 26a, series coil 26, U-shaped connection 2Gb, and

the connecting bar 26c to the other lead of the supply circuit.

The relay or pilot magnet may control the motor or driving mechanism for one or both electrodes by means of any suitable locking or controlling mechanism; buta form of control particularly adapted to the control of the. driving mechanism illustrated in the drawings comprises an armature28 responsive to the relay or pilot magnet, and connected to a pivoted latch or detent 29, which normally, under the influence of lgravity, or of a spring, tends to engage the armature 16 130 andlhold it -against the magnet 18 in the inoperative position shown in Fig. 1. At the other end of the relay -magnet a correspondingv armature 30 is connected to a pivoted latch 3l, controlled by a spring 32 normally tending to move the armature 30 away from the relay magnet and to move the latch 31 into the position lshown in Fig. 1, where the armature 17 is freetovibrate under the in.- fluence of the spring 23land of the magnet 18.

fmovement; but if the potential between the.

The various parts are so proportioned that when the current through the relay magnet is normal, both ldetents 29 and 31 restrain the two armatures 16 and 17 Aagainst electrodes varies and consequently. the eurrent increases above, or decreases below its -normal value, `the relay and its armatures respond to the variations of potential, and one or the other of the detents ismoved v and releases its armature, which thereupon begins to vibrate and the necessary adjustment in the gap between the electrodes 1 and 2 is made very quickly and accurately.A The driving mechanism always tends or is biased to operate the adjusting mechanism as' long as there vis a difference of potential f on the supplyleads of the projector and consequently the driving mechanism begins to act the instant the detent is lifted and the mechanism lis free.

Owing to the comparaf tively" lightweight of the moving parts as comparedA with the force vexerted by theb electronviagnet 18 there is practically no inertiafor time lag in starting the mechanism and on the other hand it is stopped instantly and inthe exact' position desired when one or the other of the detents 29 or 31' drops into locking position and holds the corre- `a-sponding armature immovable. As aresult of this construction, the tendency ofthe driving mechanism to overrun and move theelectrode support beyond the desired position is overcome and theA adjustment of the,

electrodes is made much more accurately j and quickly than'where a motor or similar device having considerable inertia is used as the driving mechanism.

The operation of the device is -as follows: If it be assumed that with the parts in the position shown in Fig. 1 the electrodes 1 and 2 are too close together, then the resist ance between them is below the normal, and as a result the amount' of current flowing through the shunt coil 25 'is considerably The slight increase in".

that`the relay magnet is unable to hol the 17 into the position shown in Fig. 1, thereby causing the bridging contact 22 to close the' circuit of the magnet 18 through the gap formed between two stationary contacts` 20. As soon as this occurs the magnet 18 issubjccted to the full potential of the supply circuit across the line, and the armature 17 begins to vibrate rapidly, making and breaking the circuit of the ma et 18, and at the same 4time vibrating the ellcrank lever 15 and the pawl 13, and causing a rotation in one direction of the feed screws 8 and 7. The rotation of the feed screws moves the electrode holders 3 and 4 and causes a separation of the electrodes and a corresponding increase in the gap between them. As a result of the increase in the gap the resistance of the arc and the,

difference of potential between the electrodes increase, causing more and more current to flow through the shunt coil 25. The mechamsm. continues to operate and to increase .the gap between the electrodes until 'the current through the shunt coil 25 reaches such a value that the relay magnet is enabled to draw the armature'. 30 down against the spring 32, and .thereby bring the detent 31 into the positionto-engage and hold the armature l17 against themagnet 18 and restrain it from further movement, As vthe are continuesl to burn the carbons waste away, and eventually the length of the arc vand the diference of potential between'the electrodes become greater than normal. When this occurs a current greater than normal is flowing through the shunt coil 25,

energizing the relay magnet to a,y point where it is enabled to piek u the armature 28 and thereby lift the etent 29 out of engagement with the armature 16. When this occurs the spring 23 -draws the` armature 1G away from the magnet`18, and simultaneously closes the circuit of the mag# net through the gap formed between stationary contacts 19, whereupon the armaturex 16 begins to-vibrate and moves and. actuates through the bell crank 14 and pawl 12, and thereby drives the feed screw 8 and the feed screw 7 in the reverse direction.

The movement of the feed screws in the reverse-direction shifts thesupports 3. and 4,

and lcauses the electrodes land 2- to preach each otherA and correspondingly iminish the gap Abetween them. The vibration of the armature 16 continues until the arc length and the differenceof potential between the electrodes 1 and 2 becomes normal, Awhereupon the current through the lshunt coil 25 diminishes to such a oint armature 28 and the detent 29 out of the locking position, so that the armature and detent drop and lock the armature 16 in the inoperative position shown in Fig. 1. These operations are repeated as the length of the i are fluctuates on each side of the normal, and since the relay or pilot magnet is sensitive, and the motor or driving mechanism is powerful, the required adjustment of the gap between the electrodes is made very quickly, and the length of the arc remains substantially constant during the operation of the device.

My invention may be vembodied in many other forms than that shown and described, and I, therefore, do not wish to be' restricted to the precise form disclosed, but intend to'cover by the appended claims all changes and modifications within the spirit or 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 control mechanism, the combination with electrodes movable in two directions to vary the arc lbetween them, of electrically controlled step-by-step mechanisms comprising two pawls and a common ratchet for Inoving said electrodes one pawl for moving them in one direction and the other for moving them in the other direction, and electrically controlled means for locking lsaid mechanisms against movement in either or both directions.

2. InA an arc control mechanism, the combination with a movable support for an electrode, of an actuatingelectromagnet having two pivoted armatures, 'each arranged to make'and break the circuit of said electromagnet, feed mechanism for said support actuated by one armature to increase and by /the other armature to decrease the gap between the electrodes, and means responsive to variations of potential between the electrodes for locking either or both of said armatures against movement.

3. In an arc control mechanism, the combination with a movable support for 'an elec- 'cuit when in operation, a locking device for positively holding said member stationary in circuit opening position and electroresponsive means connected to said locking device to control said movable member.

4. In an arc control mechanism, the combination with movable supports for a pair of electrodes, of electro-responsive actuating mechanism permanently connected to the supply leads and comprising a pair of movable members either of which is adapted to close the circuit of said mechanism and to periodically open the same when-in operation, locking devices cooperating with said members to positively hold the same stationary in circuit-opening position, and electroresponsive means for selectively releasing said locking devices.

5. In an arc control mechanism, the combination with movable supports for a pair of electrodes, of electro-responsive actuating -mechanism permanently connected to the supply leads and comprising a pair of movable members either of which is adapted to close the circuit of said mechanism and to periodically open the same when in operation, and means for locking said movable members and for selectivelyv releasing the same comprising an electro-magnet and two cop'erating armatures for operating the respective locks.

In witness whereof, I have hereunto set my hand this 19th day of March, 1908.

. JOHN L. HALL.

Witnesses:

HELEN ORFORD, BENJAMIN B.. HULL.

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