US2453175A - Searchlight control system - Google Patents

Description

Nov. 9, 1948. D. A. YOUNGSON ETAL 2,453,175

SEARCHLIGHT CONTROL SYSTEM Filed Sept. 25, 1946 Inventors: bonaldAYouncgso RObeTtEMattheWs by www Their/ ttorney Patented Nov. 9, 1948 UNITED STATES PATENT YGFFICE SEARCHLIGHT CONTROL SYSTEM Application September 25, 1946, Serial No. 699,250

7 Claims.

"Our invention relates to light projectors of the arcing-electrode type, and more particularly to control systems for are searchlights and the like. The invention is especially applicable to searchlights wherein quick starting or are initiation is 'desired, as in searchlights used on aircraft or for aircraft observation.

In the operation of are light projectors it is customary to' advance the negative electrode until it makes contact with the positive electrode, andthereupon to withdraw the negative electrode to strike the arc. 'Time may be saved in this operation if the electrodes are brought into engagement immediately upon extinguishing the arc and allowed to remain in engage ment until the next are striking operation. Arc striking then is accomplished simply by withdrawing the negative electrode.

Accordingly it is a general object of our invention to provide new and novel control means for arc lightprojectors.

It is a further object of our invention to provide a low voltage quick starting electrode feed circuit for are light projectors which is entirely independent of the normal high voltage source ofarc current supply.

'It is a more particular object of our invention to provide new and novel mean for automatically-engaging the electrodes of an are light projector immediately upon deenergization of the energized during arcing operation from a low voltage source of electric current supply. In order to move the electrodes into engagement immediately upon extinguishment of the arc to prepare the'projector for quick starting operation, we provide switching means operable to connect the low voltagecurrent supply source to the electrode feed motor through an alternative circuit whenthearc currentsupply .is disconnected. During .such connection of the ,feed

motor, the low voltage source is'also connected 4 to the'electrodes in order to. detect engagement thereof and thereupon to disconnect the feed motor.

Forv a. more. complete .under'standing or our invention, reierenceshouldmow behad tothe fol lowing detailed specification along with theacline"!, through a cut-out switch 8, a-selector switch 9, and a pair of normally closed contacts ii) of a relay II. The switch! closes on a stationary contact l2 in its operating position and on a stationary contact l3 in its standby position.

The negative electrode 2 is supported by a pair of driving rollers 1 i5 and a pair of spring pressed electric conducting guide brushes l6, l1. Current is supplied to the electrode 2 through the brushes H5, H, as shown, and the roller 15 is serrated and driven by a negative drive motor 18, thereby to advance or retract the electrode 2. The drive motor 18 is provided with a normally engaged magnetic'brake l9 and a pair of oppositely wound series field windings 2i! and 2 l. The magnetic brake i8 is arranged to be disengaged upon energization of the motor I8 by a brake coil 22 connected in series circuit relation in the motor circuit. The series field'windings 20 and 2t are arranged to be alternatively connected to the source of control power 'I through the switches Band -9 and a current regulator 23. The regulator 23 comprises a current responsive actuating winding 24, a pair of normally closed contacts 25 and a pair of normally open contacts 26. The winding 24 is connected in series circuit relation in the arc circuit of the electrodes I and 2. "The contacts 25 and 25 are controlled by abridging contact" 21. The motor 18.. when energized through the series field winding 2i, is arranged to drivelthe electrodfe'2 in-a forward direction towardthe electrode l. The motor fieldwinding 20, when energized, causes the motor i8 t o operate in the opposite direction, thereby to retract the electrode 2. The field Winding 2i is energized through the regulator contacts 26 only when the current through thearc and thus through the regulator coil 2% exceeds a. predetermined maximum value.

Thepositive electrode l is arranged for con tinuous rotation and forward feed alternatively 3 at one or the other of two selectable speeds. For this purpose the electrode l is mounted in a 1'0- tatable head 28 which is journaled in a fixed sup port 29. The head 23 comprises a hollow sleeve 38 within which the electrode is slidable loosely. The sleeve 35 carries at one end a gear bracket 3i. Within the gear bracket 3! the electrode i is supported between a guide roller 32 and a serrated or toothed driving roller The electrode l is further guided and also supplied with current by a pair of spring pressed electric conducting sliders 34 and 35. The shaft of the driving roller 33 carries also a driving pinion 36. The pinion 35 meshes with a worm gear 31 journaled at 38 in the rotatable head bracket 3|. The shaft of the worm gear 31 carries 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 rotatable hollow sleeve 4| which is journaled in the frame 29. On the sleeve 4! adjacent the pinion 45 there is mounted a spur gear 42. The hollow sleeve 38 forming part of the rotatable head 28 is rotatably journaled within the sleeve 4!. At the end of the sleeve 313 remote from the gear bracket 3i there is mounted a spur gear 43 fixed to the sleeve 30 by a setscrew 44. The spur gear 43 is of slightly greater diamete 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 journalled in the frame 29 and connected, as by a shaft 41 (indicated schematically), to a driving motor 43. The pinion 46 is slightly smaller than the pinion 45, so that the spur gear 42 is driven faster than the gear 43. It will of course be understood 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 speeds. It ma be noted however, that if the speed relationship is reversed from that shown, it is also necessary to reverse the direction of rotation of the motor 48 so that the electrode I will advance.

It will be observed that in the operation of the positive electrode driving mechanism, the spur gea 43 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 36, 37 and 39 at the same speed as the head, so that the gears 31 and 39 would not rotate upon their own axis and therefore would not drive the electrode 1 longitudinally. In fact however the spur gear 42 is positively driven by the pinion 45 at a speed slightly greater than the speed of the head 28 itself. Thus, the planetary gear 39 is caused to roll slowly around the sungear 40, thereby to rotate the worm gear 37 ondits own axis and continuously to drive the .positive electrode i forward as it rotates. As will bfe explained more fully hereinafter, the crater'in the end of the positive electrode is maintained in a prede termined desired position providing two solectable driving speeds for the positive head mechanism in conjunction with a control system responsive to crater position, as described and claimed in copending application Serial Num ber 699,287, filed September 25, 1946, by Robert C. Sheahan, and having the same assignee as this application, which haspbecome U. S. Pat

ent 2,440,122, dated April 20, 1948..

During normal arcing operation, the positive driving motor 48 is connected to the low voltage source of control power 7 through the manually operable cut out switch 3 and the selector switch 9. The motor 48 is provided with a shut field winding 49. For control of the speed of the mo-- tor 48 there connected in series with the motor armature a variable resistor which is arranged to be shunted b a thermally responsive switch 5|. The switch 5| is closed when cold, and opens its contacts when hot to insert the resistor 5il in the motor armature circuit.

The thermally responsive switch 5|, and thus the speed of the motor 48, is controlled in accordance with the position of the crater in the end of the electrode 5. This control may conveniently be effected by any well known optical system, such as that described. in U. S. Patent 1,590,543, issued on June 29, 1926, to Martin L. Patterson, and entitled Feed control means for are lights. Briefly such a system comprises an optical arrangement for reflecting the image of the positive crater directly upon the thermal responsive member 5| when the crater is in the desired position. In this position of the crater, then, 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 oil of the thermal responsive member 5|, the member 5| closes its contact, and the speed of the motor 48 is increased, thereby to drive the electrode I forward at a greater speed.

As previously stated, means are provided for driving the electrodes l and 2 into contact immediately upon deenergization of the are between the electrodes, thereby to prepare for the next are striking operation. For this purpose, means are provided for connecting the electrode driving motors l8 and 4'8 to the low voltage source of control power ll through alternative circuits when the selector switch 9 is in its standby position on the contact l3. In this position of the selector switch a circuit is also completed for applying control potential from the source 7! to the electrodes and 2 so that, when the electrodes come into contact, a driving motor disabling circuit is completed.

Referring more particularly to the drawing, it will be observed that, when the selector switch 9 is in its stand-by position on the contact I3, a circuit is completed through the switches 8 and 9 from the control power source I to an actuating winding 52 of the relay l l. In parallel circuit relation with the winding 52 there is also a green indicating lamp 53 which is lighted in the stand-by position of the switch 9. It is desirable to provide also a red indicating lamp 54 which is lighted from the control power source 1 so long as the cutout switch 8 is closed. Thus, the lamp 54 onl is lighted during arcing operation, while the lamps 53 and 54 are lighted in the stand-by condition.

When the relay i l picks up, it first opens its contact iii, thereby'to deenergize the contactor actuatin winding 5 and to ensure dropout of the high voltage line contactor 4. Thus, disconnection of the high voltage generator 5 from the electrodes during stand-by or quick starting operation is assured. Upon energization, the relay H also closes three pairs of normally open contacts 55, 56, and 51. The contacts 55, when closed, complete an alternative energizing circuit for the driving motors it! and 48. This cir cuit may be followed from the control power source l through the cutout 8,-the selector romance 'sw-itch fi'in"itsL'stand-by position, a normally closed contact58 ofa relay58, .and the relay -contact' 55 to the" driving motors in parallel' circuit relation. The relay contacts 56 and 5?. when r closed prepare anrenergizing circuit for anzac- 'tuating/winding 8i) of therelay 59 through the electrodes I'. and.2. This circuit'mayrbe followed from the source of control power I. throughithe cutout switch 8; the selector switch 9 in its standby.-'.position,: the'relaycontacts 57, the electrode Lathe: electrode 2,1the relay contacts56, and. the actuating winding: 69: of the relay. 59.:back to the. control powersource I. .This latter-circuit, ofrcourse, isxnot-completed until the electrodes hand 2 come into'engagement.

With the foregoing description of" the various elements of our system and their individual mode of operation, the operation oftheisystem as auwhole will now be: readily'understood' from the following brief: description.

.To consider first normal arcing operation,,.let .it be. assumed that the electrodes are separated tas illustrated; and that the cutout switch 8 is closed and'the selector switch-9 placed in its operating position on the contact I2. With the -.switch8 closed thezred indicatin light 54. is energized. Through the sWitchrB and the con- ..tact I2 of'the switch il circuits are completed for thetdriving motors Hand 48 in the 'manner previously described, the circuit for" the negative drive motor I8 passing through the bridg- .ing contact 2! of-the. regulating relay- 23. In parallel circuit relation with :the motors, there is also completed anenergizing circuit for the actuating winding 6 of the'line contactor 4. This energizing circuit includes the normally closed contact Ill of the relay II. Accordingly, therefore, as soon as the switch 8 is closed and the "switch '9 placed in its operation position, the driving motors I8 and 48 are placed in operation and theline contactor 4 is picked up to apply arcing voltage to the..electrodes from the generator. 5.

..Since.no arc exists, the regulator contacts are closed and the negative driving motor drives the electrode 2 forward into engagement with the electrode I. The electrode I, of course, is simultaneously being driven forward at its maximum speed because the thermal responsive member 5I is cold. When the electrodes I and 2 come into contact, the resulting high current flow picks up the regulating relay 23, opening contacts 25 and closing contacts 26, thereby reversing operation of drive motor I8, which withdraws electrode 2 from contact causing an arc to be struck between I and 2. With arcing taking place, the crater at the end of the positive electrode I is maintained in a predetermined position by operation of the thermal responsive member 5| and the motor 48, and the negative electrode 2 is advanced or retracted as required in order to maintain the arc current substantially constant.

When it is desired to extinguish the arc, the selector switch 8 is moved from its operating position on the contact I2 to its stand-by posi tion on the contact I3. As soon as the contact I2 is disengaged, the normal operating circuit for the driving motors I8 and 48 is disabled and the actuating winding 6 of the high voltage line contactor 4 is deenergized. However, as soon as the selector switch 9 is placed upon the standby contact 53, an energizing circuit is completed for the actuating winding 52 of the relay II. When the relay II picks up, a new energizing circuitis completed for both electrode driving motors I8 and through'the' contact sacrum relay' 59 and the contact 55 of'the relay -II. JSi- :multaneously, controlpotential is applied tothe electrodes I and 2 through the actuating wind- 'ing'fifl' of the'r'elay'59 and the contacts 56 and 5! o? therelay II asheretoiore described. Accordingly, therefore, both electrodes are advanced until they come intoengagement. -As soon. as the electrodes I and 2 are engagedya circuit is completed through the electrodes for the actuatingwindinglfiil of the relay 58. "When the'relay 59 is pickedup, it opens itscontact-SB thereby told'eenergize'both driving motors I8 and =48. '.Thus, int-he stand-by position, the-"electrodes I. and 2 remain in engagement and the relays II andJSB'remain picked up, the relay 59 being energized from the low voltage control power. source through the electrodes I and 2 themselves. Both indicating lamps 53 and are lighted to indicate this condition.

It shouldrbe'n'oted that, if desired, thegreen lamp 53 may b'e-so connected that'it will'ubeli'ghtedsonly when the electrodes I and 2 actually-engage. If suchindication isdesired it is onlycnecessary-to connect the lamp 53 in serieswith the relay contacts 58, rather than as shown. I Itwill now he appreciated'that in: our new and improved system "resetting of the. electrodes for quick starting operation is s'carri-ed'z out entirely at low voltage so that the. system'is entirely safe and free from dange of reinitiating the are at undesired times. Disabling of the high voltage "circuit is ensured b the selector switchls, which, whenpla'ced in the reset position removes high voltage power from the electrodes.

While we have shown and described only -a preferred embodiment of our invention 'by Way of illustration, many;rnodifications "will OCCLll" to those skilled in the art and wetherefore wish to haveit understood that we intend in the appended claims to cover all suchmodifications as fall within the true spirit and scope of our. invention.

. -What we claimzasnew and'desire'tosecure by Letters-Patent of the United States. is:

1. In a light projector including a pair of arcing electrodes, means for connecting said electrodes to and disconnectin said electrodes from a source of high voltage electric current supply, electrode feed control means including an electric motor, means for connecting said motor to a source of low voltage electric current supply and simultaneously applying the potential of said low voltage source to said electrodes when said high voltage source is disconnected, said motor when so connected driving said electrodes toward engagement, and electrical means responsive to completion of a low voltage circuit by engagement of said electrodes for deenergizin said mo-,

tor.

2. Inv a light projector including a pair of arcing electrodes, electrode feed control means including an electric motor, means for simultaneously connecting said electrodes to a source of high voltage electric current supply and connecting said motor to a source of low voltage electric current supply, separate means operable when said high voltage source is disconnected for connecting said motor to said low voltage source, and relay means operable from said low voltage source upon engagement of said electrodes to disconnect said motor from said low voltage source.

3. In a light projector including a pair of arcing electrodes, electrode feed control means including an electric motor, switching means for simultaneously connecting said electrodes to a source of high voltage electric current supply and connecting said motor to a source of low voltage electric current supply, relay means operable by said switching means for connecting said motor to said low voltage source when said high voltage source is disconnected, and second relay means operative upon engagement of said electrodes when said first relay means is operated for disconnecting said motor from said low voltage source.

4. In a light projector includin a pair of arcing electrodes, electrode feed control means including an electric motor connected to drive one of said electrodes toward engagement with the other, first switching means for connecting said electrodes to a source of high voltage electric current supply and simultaneously connecting said motor to a source of low voltage electric current supply to energize said. motor, second switching means operable only when said first switching means is inoperative for connecting said motor to said low voltage source with said high voltage source disconnected and simultaneously applying said low source voltage between said electrodes,

and electro--responsive means operable from said low voltage source upon engagement of said electrodes to disable said second switching means thereby to deenergize said motor with said electrodes in engagement.

5. In a light projector including a pair of arcing electrodes, means for connecting said electrodes to a source of high voltage electric current supply, electrode feed control means including an electric motor connected to drive one of said electrodes toward engagement with the other,

means for connecting said motor to a source of low voltage electric current supply to energize said motor, and means responsive to engagement of said electrodes for rendering said low voltage connecting means inefiective, thereby to deenergize said motor with said electrodes in engagement.

6. In a light projector including a pair of arcing electrodes, means for connecting said electrodes to a source of high voltage electric current supply thereby to maintain an are between said electrodes, electrode feed control means including a reversible electric motor connected to drive one of said electrodes toward and away from the other, means for connecting said motor to a source of low voltage electric current supply to energize said motor, regulating means responsive to are current for controlling said motor to maintain said current substantially constant, said regulating means controlling said motor to drive said electrodes toward engagement when said high voltage source is disconnected and said are extinguished, and mean responsive to engagement of said electrodes for rendering said low voltage connecting means ineffective thereby to deenergize said motor with said electrodes in engagement.

7. In a light projector including a pair of arcing electrodes, means for connecting said electrodes to a source of high voltage electric current supply, electrode feed control means including an electric motor connected to drive one of said electrodes toward engagement with the other, first switching means for connecting said motor to a source of low voltage electric current supply when said are is operative, second switching means for connecting said motor to said low volt age supply source when said are is inoperative, and means responsive to engagement of said electrodes for disabling said second switching means, thereby to deenergize said motor with said electrodes in engagement DONALD A. YOUNGSON. ROBERT E. MATTHEWS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,701,372 Jefts Feb. 5, 1929 1,976,551 Frich Oct. 9, 1934

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