.-l7,1946. 2,412,605 G. F. DRAKE SPEED ADJUSTING MECHANISM Filed Feb. 5, 1943 3 Sheets-Sheet l Eiyl, INVENTOR ' George Forrest Drake I %.M ATTORNEYS Dec. 17, 1946. G, F, DRAKE 2,412,605 SPEED ADJUSTING MECHANISM Filed Feb. 3, 1945 3 Sheets-Sheet 2 INVENTOR George Forrest .Dra/(e BY - - I ATTORNEYS Dec. w, 194% G. F?. DRAKE 2,412,605 SPEED ADJUSTING MECHANISM Filed Feb. 3, 1943 3 Sheets-Sheet 5 "/04 \N G m 740 INVENTOR George Forrest Dre/(e BYE-44., Kym/21a?: ATTORNEYS Patented Dec. 17, 1946 2,412,605 ' UNITED STATES PATENT OFFICE. 2,412,605 _ SPEED ADJUSTING MECHANISM George Forrest Drake, Rockford, Ill., assignor to Woodward Governor Company, Rockford, 111., a corporation of Illinois Application February 3, 1943, Serial No. 474,549 . 11 Claims. (CI. 60-97) 2 This invention relates generally to mechanisms for adjusting the speed setting of a governor or other regulating device from a remote point of control, and in certain of its aspects relates to improvements in a synchronizing mechanism of the general character disclosed in my copending l2 rotatable with the propeller and operating on the follower l3 of a cam ill which, through bevel gear connections, turns the propeller blades on their longitudinal axes. The governor includes a rotary head l5 piv application Serial No. 525,913, ?led March 10, 1944, to which this application is subordinate, otally supporting fiyballs l6 having arms I?! bear ing upwardly against the head l8 of a valve rod l9 which is urged downwardly by an adjustable said application Serial No. 525,913 being a con speeder spring 28. The head I5 is on the upper tinuation-in-part of application Serial No. 10 end of a sleeve 2i journaled inthe governor casing and driven from its lower end through a 426,362, ?led January 10, 1942, the latter now gear connection with the engine crankshaft 23. ' The valve rod [9 has spaced lands 24 and 25 One object is to combine a speed adjusting thereon coacting with ports in the sleeve 2| and mechanism'for a plurality of prime movers with a novel means for effecting automatic synchro 15 shiftable upwardly? by the ilyballs in response to a speed increase above the prevailing speed nization of the prime movers. setting to admit pressure fluid from a supply, A further object is to incorporate in such a line 28 to a conduit 29 leading to the rod end combined adjusting and synchronizing control a of the servo motor cylinder. The servo piston novel means for rendering the synchronizing con trol operative and inoperative automatically as 20 moves to increase the propeller pitch until the valve is again closed as shown in Fig. 2. In re an incident to starting and stopping of the man ually operable adjusting mechanism. sponse to a speed decrease, the valve rod is low ered permitting the flow of fluid out of the servo Other objects and advantages of the invention through the conduit 29 past the land 25 to the will become apparent from the following detailed description taken in connection with the accom 25 sump. The propeller pitch is thus decreased panying drawings, in which until the speed reduction has been corrected for. Oil under the proper pressure is supplied to the . Figure 1 is a schematic view and wiring dia line-28 by a, booster pump 30 driven from the gram of the improved speed adjusting control. rotating sleeve 2i and supplied with oil by the Fig. 2 is a schematic view of the speed adjuster 30 engine lubricating pump 3i. for one power unit. ' From the foregoing, it will be apparent that the Fig. 3 is a vertical sectional view of the speed abandoned. governor operates automatically through the pitch-changing mechanism to maintain the speed selecting mechanism. Fig. 4 is a section taken along the line 4-4 of Fig. 3. ' of the engine constant and at a value determined - Figs. 5 and 6 are similar views showing differ 35 by the load imposed on the flyballs by the speeder ent positions. ?The invention has been shownv in the drawings spring 20. This load may be adjusted by turn ing a pinion 32 meshing with rack teeth on a plug 33 which is mounted in the governor for move and will be described herein as applied to the ment axially of the spring. speed control of a plurality of internal combus tion engines M and S. It is to be understood, 40 In accordance with the present invention, the pinion shaft 34 of the governor of the engine M however, that I do not intend to limit the inven is ?adapted to be turned by an electric motor 35 tion by such disclosure nor to the particular mounted on the governor casing and acting illustrated constructions of the various switch, I through reduction gearing 36. This motor is on governor, motor units and electrical transmitters, I but aim to cover all modi?cations, alternative 45 the receiving end of an electrical transmitting system controllable from a transmitter located at constructions, and uses falling within the scope a, point of manual control remote from the en of the invention as expressed in the appended gine. Herein, the motor is of the step type hav claims. ing a permanently magnetized rotor 31 adapted The speeds of the engines M and S may be controlled by individual governors ll arranged 50 to occupy any one of twelve well-de?ned angu lar positions according to the combination of to actuate the engine throttles or, as shown, to effect the speed regulation byadjusting the pitch of propellers l0 driven by the engines. This may be accomplished by applying hydraulic pressure controlled by the governor II to a servo motor 65 direct current potentials applied to three sets of distributed windings 38 on its stator 39. When the windings are deenergized, the rotor will come to an abrupt stop. 3 Operation of the step motor in one direction or the other is effected by turning the shaft 458 of - of the commutator switch 58 and the step motor 52, beenbrought into synchronism with the mas the transmitter which is a commutator switch it! ter M. having angularly spaced segments 62, �, and @113 To enable the di?erential motor 58 to be dis abled at certain times as during the adjustment engaged as shown in Fig. 2 by contacts 55, 56, �, and 88. These are arranged in pairs respectively connected to the di?erent polar terminals ofha _ ~of the engine speeds under manual control, the ' switches 66 and 67 are connected to the arma -battery d8 through conductors 58' and 5t. T e ture of a magnetic relay 68 interposed in a cir segments are connected directly to the windings cuit extending from one power lead 58 through of the step motor 35'through suitable brushes 10 one or more normally closed manually operable and conductors 563. The construction of the step switches 69, a conductor '58, the relay'coil 58, motor is such that as the switch shaft ?38 turns one or more normally open switches it ?connected in one direction, the windings of the ?step motor in parallel, and a conductor ?l3 connected to will be energized in successive combinations caus the other power lead 5|. When the relay coil ing the rotor 67 to follow the movements of the 15 is energized by closure of one of the switches switch shaft. Reverse operation of the motor ?ll, the switches 66 and 67 will be closed and the takes place when the commutator switch is differential motor 68 will be rendered operative. turned in the opposite direction. , Such operation of the relay also results in clo The governor of the engine S is similarly sure of a- switch ?12 which completes a holding adapted for adjustment of its speeder spring by 20 circuit through the relay coil and the switches a step motor 52 of the same construction as the 69. Thus energization of the relay 68 is main motor 35. This motor is, in accordance with one tained until one of the switches 68 is opened aspect of the present invention, adapted to be ' whereupon the switches 66 and 67 are opened energized alternatively either under the control and the diiferential motor is disabled. a, of the commutator switch M or of a commutator To adjust the speed settings of the governors switch 53 of the same construction also located ll under manual control from a remote point, at the remote point of control and having its parts the shaft 48 of the transmitter or commutator indicated by corresponding primed reference switch iii is connected to the shaft of a rever numbers. The motor 52 may be connected to the segments of the switch 58 through conductors 55 30 sible motor l3? preferably of the type having a permanent magnet stator ?M and a wound rotor including switches 56 or it may be energized from 75. The direction of operation of such a motor the commutator switch 85 through conductors may be reversed by reversing the current ?ow 57 and 57', the latter having switches 58 inter through the rotor winding. Herein, this winding posed therein. The movable contacts of the is energized selectively or deenergized by a mag switches 56?and 59 are connected to the armature 35 of a magnetic relay 58 in a manner such that the switches 56 are closed and the switches 58 are open when the relay coil is deenergized, the con netic reversing switch ?I6 operated differentially - by the energization of coils 11 and '88. As shown, _ the switch comprises a frame 19 pivoted inter mediate its ends at 88 and adapted to be actu dition being reversed when the coil is energized. The battery leads 50 and 5| are extended to the 40 ated from opposite ends by the armatures of stationary contacts of the switch 53. . In accordance with one aspect of the present invention, one of the engines, in this instance M, is selected as the master, and the speed of the the magnets 71 and T8. * Projecting from the frame are spring arms 8! which cooperate with stationaryv contacts to form switches 82 and 83 which are both closed when other or slave engine S is matched accurately by 45 both of the coils T! and 18 are deenergized. Arms 84 on the frame cooperate with stationary con operation of the commutator switch 53 in direc tacts to'form switches 85 and 86 which are both' tions and amounts such as to correct for any open when the coils 11 and 18 are deenergized. departure of the slaveengine speed from that of the master. The speed matching is effected by a differential three phase motor or so-called dif ferential Selsyn 68 comprising a thred'phase two pole stator and a three phase two pole rotor hav - ing windings 6i and 6|?, the rotor being fast on The stationary contacts of the switches 82 and 50? 85 are connected by a conductor 81 to one ter-. minal of the rotor winding while the contacts of 4 the switches 83 and 86 are connected to the other terminal by a conductor 88. A conductor the commutator switch shaft 48'. These wind 89 extendsfroni the arms 84 to one battery lead ings are energized respectively by small perma 55 58 while a conductor 90 connects the other arms nent magnet generators 62 and 63 respectively 8| to the other battery lead 5|. mounted on the engines Mv and S and driven The coils ?I1 and 18 are connected together at one end and their insulated terminals are thereby. Generators of the type suitable for this joined by conductors 9| and 82 to contacts 93 purpose are disclosed in Patent No. 2,071,536. The generator 63 is connected to the rotor wind 60 and 84 of two control switches 95 and 96 (Fig. 4) . ing 6|? by conductors 65 including switches 66 having a common intermediate contact 91 con while vswitches 61 are included in conductors 68 nected by a conductor 98 to the battery lead 50. leading from the generator 62 to the stator wind It will be apparent that when the coil 11 is .en ing 6|. ' ergized, the frame 18 will .be pushed downwardly With both windings energized and the engines 65 and tilted counterclockwise about the center 80 M and S running at the same speed, the fre-' opening the switch 82 and closing the switch 85 quencies of the two currentlsources will be iden so that current ?ows through the motor? 13? from tical so that the rotor shaft 48' will not turn. the lead 58, conductor 89, switch 85, conductor When thespeeds of the master ?and slave en 81, rotor 15, conductor 88, and switch 83 to the gines are di?erent, the frequencies of the cur 70 lead 5!. Current ?ows in the reverse direction rents supplied by the respective generators will through the switches 82 and 86 when the coil di?er proportionately, and the di?erential rotor 18 is energized tilting the frame 79 clockwise. shaft will turn in ?a direction? determined by When both coils TI and 18 become deenergized, which frequency is higher. Such operation will the switches 82 and 83 both close thereby short continue until the slave engine has, by operation 75 circuiting the rotor 15 to produce abrupt stop 2,412,605 5 ' 6 ping of the commutator'switch 4| and therefore gine speed any desired number of revolutions sim of the step motors controlled thereby. ply by changing the position of the lever the same I In. accordance with the present invention, the motor is started in one direction or the other by movement of a manually operable member I00 to a position corresponding to a newly selected speed setting where the member is retained, fric tionally in this instance, and operation of the motor continues until the governors II have reached the selected speed setting whereupon the motor will be stopped automatically. While the manually operable. member may take various forms, it is shown herein lever fast on a shaft IOI and projecting from one which houses the motors number of revolutions as read on the scale I00. _With the switches 95 and 96 thus arranged, the motor ?I3? will be idle when the cam notch II?! is positioned opposite the roller II3 as shown in Fig. 1, both switches?then being open. Now, if the lever I00 is turned clockwise as shown in Fig. 5 to select a new speed setting, the arm I01 and the contact 9?! thereon will engage the contact 94 and carry the latter and the arm I09 along with the lever, the roller II3 riding up the in cline II5 after the contact engagement occurs. as comprising a hand which is journaled in The relay coil ?I8 and the relay 58 are thus en- ' wall of a casing I02 15 ergized to start the motor and also connect the 00 and ?I3?, the com step motor 52 tothe commutator switch 4|. The mutator switches AI and 53, and the-relays 58, motor runs the switch shaft 40 in a direction to 68, and ?I6.v This lever may be mounted in any convenient location within the reach of the op erator or pilot. Rotatable with the shaft IOI is a disk I03 which is urged by a, compression spring I03? against a stationary'plate I04 to create the fric tion necessary to hold the lever I00 in?any-se lected position while permitting the lever to be swung manually in either direction. A pointer I05 on the lever coacts with a scale 606 to in dicate the speed setting'in revolutions per minute change the speed settings of both governors II to correspond to the newly selected speed and at 20 the same time .to turn the cam H4 in a direction to follow up the movement of the arm I0?_I and advance the notch II'I toward the roller II3. In .this operation, the selected position of the lever I00 and the contact 94 are maintained by the friction created between the disk I03 and the plate I04, and the incline II5 acts on the bell crank H2 to prevent opening of the switch 99 until the cam H0 has been turned sufficiently or other units Mounted on an arm I01 project to present the notch iI?I opposite the roller II3. ing upwardly from the disk I03 are the common 30 As the latter becomes centered in the notch as contacts 9?! which are disposed between spaced lugs I08 carrying the contacts 93 and 94 and pro� jecting rearwardly from an upwardly projecting . arm I09. The latter is on a loose bushing IIO shown in Fig. 6 with the lever in its new position, the arm I09 is moved by the spring II 9 to cause the contact 94 to disengage the lever contact 91 thereby opening the switch 9E5v and stopping the on the shaft WI and carries the pivot III of a 35 motor ?I3?. , bell crank II2. A roller II3 on one arm of the bell crank constitutes the follower of a heart shaped cam II4 having gradual rises H5 and H6 on opposite sides of a notch II?!. A spring II9 acting between the bell crank and the arm I09 holds the roller in contact with the cam sur Thus, the extent of motor operation is determined by the selected position of the lever I00 and this without the necessity of the pilot holding the lever to retain the selection. The same operation? takes place when a reverse speed setting is selected by moving the lever I00 in the opposite direction. In that case, the switch 95 is closed and the relay coil 11 is ener gized along with the relay 58 so that the motor are disposed out of engagement with the con 13' and the step motors 35 and 52 run reversely tacts 93 and 94 as shown in Figs, 4 and 6. ' When 45 changing the speed settings of the governors cor the roller is engaging either incline, the contacts respondingly until the incline I It has moved past 93 and 94 are shifted relative to the arm I01? and the roller I I3 and the latter has become centered one or the other is pressed against one contact in the notch II?I. At this time, the switch 95 91. The cam H4 is fast on a sleeve H9? which opens, stopping the motor ?I3? and simultaneously carries a gear I I9 driven through reduction gears disconnecting the step motor 52 from the com I20 to I21 from a pinion I20 on the shaft I40 of mutator switch GI while connecting it to the the motor ?I3?. The direction of this drive is al commutator switch 53. By actuating the relay ways such as to move the notch II?! of the cam switches 56 and 59 automatically as above de back toward the follower roller~I I3. scribed in response to energization of the motor It will be observed that the two arms I01 and ?I3? for operation in either direction, the adjust M9 are swingable about a common axis and are ing step motors for both the master and ?slave gov adapted for the limited degree of relative move emors will be adjusted simultaneously and all of ment required to actuate the switches. The cam the associated engines will be brought rapidly to H4 and its follower provide a connection between the speed selected by positioning of the single the arm I09 and the cam shaft which is adapted lever I00. Thus, the lever, the step motors 35 and to yield in either direction after closure of one 52, .the commutator switch 4 I, the motor ?I3?, and switch and permit both arms to move in unison the control for the latter may be utilized as a face. The arrangement is such that when the roller is disposed in the notch, the contacts 91 to the selected switch position. Thereafter, the I cam operates to determine the extent of separa remotely controlled mechanism for adjusting the ' speeds of all of the engines during take-off and tion of the motors and therefore the amount of 65 landing, or to change the engine speeds to be adjustment of the speed regulator or governor. maintained during automatic synchronizing. This action is obtained by correlating the gear Such synchronizing may be effected in the trains and other parts so that the range oi mo present instance simply by the addition of the tion of the hand lever corresponds to the range of commutator switch 53, the differential motor 60 speed adjustment of the governor. That is to say, 70 and the generators 62 and 63. These become a given change in the lever position will,- under effective when the switches 66 and 61 are closed the control of the switches and the transmitting thereby completing the connections from the system, produce a proportional change in the movement of the governor adjusting plug. In this way, the pilot may increase or decrease the en generators to the differential motor 60 whereupon the slave step motor 52 will be operated auto matically to adjust the slave governor and match 2,412,605 ~ 3 - v _ 8 , , the speed of the slave engine against that of the member, and means ?operable to shift the con master. mutator switch during operation of said driving . trol ofsaid slave step motor to said master com a The synchronizing mechanism is disabled au tomatically while the engine speeds are being adjusted manually. This is accomplished by dis connection .of the step motor 52 from the com mutator switch 4| automatically as an incident to energization of the manually controlled ad means in either direction and to said second com mutator switch when said driving means is idle. - 3. A control for matching the speeds of slave and master power units having, individual speed regulators, said control comprising, in combina tion, slave and master step motors each arranged justing motor 16?. < The automatic control is re ? stored-automatically when the selected master 10 to actuate one of, said regulators, a master com engine speed adjustment has been completed and this, without further attention by the pilot. To disable the automatic synchronizing mech anism manually, it is only necessary to open one of the switches 69 and thereby interrupt the hold ing circuit for the relay 68. The resulting de _mutator switch operable to control the master step motor, a second. commutator switch, means automatically responsive to di?erences in the speeds of said master and slave units to actuate 15 said second commutatorswitch in a direction to correct for such di?erences, motor driven means for driving said master commutator switch, ?means operable selectively under manual control energization of the latter disconnects the Selsyn SE from the generators 62 and 63 until one of to operate said driving means, and means oper the switches ?H is again closed to reenergize the relay 68 and reestablish automatic synchronizing. 20 able automatically to snift the control of- said slave step moton to said master commutator? switch during operation of said driving means and to said second commutator switch when said It will be observed that the number of slave engines S to-be synchronized with the master ' M may be increased as desired simply by multi plying the number of step motors, commutator ?switches, differential motors, generators, relays 53 and 68, these being connected in the control circuits in the same ways as the corresponding units shown. I claim as my invention: driving means is idle. 25 e. A control for matching the speeds of slave and master power units having individual speed regulators, said control comprising, in combina tion, slave and master step motors each arranged I to actuate one of said regulators, a master com 1. A control for matching the speeds of slave 30 mutator switch operable to control the master step motor, a second commutator switch, means and master power units each having an adjustautomatically responsive to differences in the able speed regulator, said icontrol comprising, in speeds of said master and ?slave units to actuate combination, slave and master step motors each said second commutator switch in a direction to arranged to actuate one of said regulators, a mas- ' correct for such di?erences, motor driving means ter commutator switch operable to control the for said master commutator switch, means op master step motor and connectable selectively erable selectively under, manual control to cause to the slave step motor, a second commutator operation of said driving means, and means op switch connectable selectively to said slave step erable automatically'to cause energization of said motor, a differential motor'for driving said sec ond commutator switch and operable selectively 40 slave step motor from said master commutator switch alone during operation of said driving in accordance with the differences in the speeds means. of said master and slave units, a reversible rotary electric motor driving means for said master com mutator switch, a? manually operable member adapted to' remain in a manually selected posi tion, switching means operable in response to a ' _ 5. A control for matching the speeds of slave , and master power units each having an individual 45 speed regulator, said control comprising, in com bination, remotely controlled means for adjust ing the master speed regulator, means automat change in the position? of said member to start ically responsive to differences in the speeds of said driving means and then continue the oper said master and slave units to adjust the slave? ation thereof until said master speed regulator has been adjusted to a setting corresponding to 50 speed regulator and correct for such di?erences, and means operable automatically during adjust that selected by said member, and means oper ment of said master speed regulator to-disable able to effect energization of said slave step motor said last mentioned means and cause adjust--v from said master commutator switch during op ment of the slave speed regulator in unison with eration of said driving means in either direction and from said second commutator switch when 55 the master regulator. 6. A control for matching the speeds of slave said driving means is idle. and master power units having individual speed 2; Av control for matching the speeds of slave regulators, said control comprising, in combina and master power units each having an adjust tion, slave and master motors each arranged to able speed regulator, said control comprising, in combination, slave and master step motors each 60 actuate one of said regulators, synchronizing means automatically responsive to di?erences in arranged to actuate one of said regulators, a mas the speeds of said master and slave? units to ac ter commutator switch operable to control the tuate the slave motor in a directionto correct for master step motor, a second commutatorswitch, such differences, motor driving means for con a differential motor operable to drive said second commutator switch in accordance with di??er 65 trolling the operation of said master adjusting . motor in opposite directions, means operable se ences in the speeds of said master and slave lectively under manual control to operate said units, reversible electric motor driving means for driving means, and means operable automatically said master commutator switch, a manually op during operation of said driving means to cause erable member movable independently of said regulators, switching means operable in response 70 operation of the slave motor in a corresponding direction independently of said synchronizing to a change in the position of said member to start means. said driving means in a corresponding direction '7. A control for matching the speeds of slave and then continue the operation thereof until and master power units having individual speed ' said master speed regulator has been adjusted regulators, said control comprising, in combina to a setting corresponding to that selected by said 2,412,005 10 tion, slave and master receiving motors arranged means and cause operation of said receiving m0 to actuate the respective regulators,v a master tors by said transmitter in a direction to move _ electrical transmitter operable to energize the said regulators to settings corresponding to said master receiving motor and cause rotation of speeds, follow-up means actuated by said driv ing means for continuing the operation thereof the latter in unison with the transmitter, a sec until the regulator setting selected by said mem ond transmitter, means automatically responsive ber has been attained, mechanism automatically to di?erences in the speeds 0! said master and responsive to a difference in the speeds of said slave units to actuate said second transmitter in master and slave power units to energize said a direction to correct for such differences, motor driving means for operating said master trans 10 slave speed regulator in a direction to correct for such difference, and means operable automati mitter and cause operation of said master motor cally to maintain said mechanism disabled dur selectively in one direction or the other, ?means ing operation of said driving means and then to operable selectively under manual control to cause render said mechanism again operative. operation of said driving means, and means op 10. A control iorlmatching the speeds of slave erable automatically to cause energization of said 15 and master power units each having an adjust slave receiving motor from said master trans mitter alone during operation of said driving able speed regulator, - said control comprising slave and master receiving electric actuators ar ranged to actuate the respective regulators, an 8. A control for matching the speeds of slave and master power units each having an adjust 20 electrical transmitter operable to energize said receiving actuators and cause rotation of the lat able speed regulator, said control comprising ter to adjust said master and slave regulators in slave and master receiving electric actuators ar means. . ranged to actuate the'respective regulators, an ' unison, electric motor driving means, means in cluding a manually operable member shiftable receiving actuators and cause operation of the 26 selectively to different positions corresponding to speeds of said power units and operable. when latter to adjust said master and slave regulators electrical transmitter operable to energize said ' in unison, an electric motor, switching means controlling the operation thereof, means includ ing a manually operable member shiftable selec moved to a new position. to energize said driv ing means and cause operation of said receiving motors by said transmitter in a direction to move? tively to di?erent positions corresponding to speeds 30 said regulators to settings corresponding to said speeds, mechanism automatically responsive to a of said power units and operable, when moved to a new position, to actuate said switching means diii?erence in the speeds-of said master and slave power units to energize said slave speed regula and energize said motor for operation of said re tor in a. direction to correct -for such difference ceiving motors by said transmitter in a direction to move said regulators to settings corresponding 35 and maintain ?said units svnchronized. and elec tric switching means actuated automatically as to said speeds, follow up means actuated by said motor and actuating said switching means to an incident to movement of said member to select continue the operation thereof until the regula a new speed setting to disable said mechanism until such speed setting of said regulators is at tor setting selected by said member has been attained, mechanism automatically responsive to 410 tained and then. to render said mechanism ?again operative. a difference in the speeds of said master and slave ii. A control for matching the speeds of slave power units to energize said slave smed regulator and master power units each having an adjusts in a direction to correctior such difference, a relay energized and deenergized under the con� able speed regulator. said control comprising trol of said switching means during operation 45 slave and master receiving electric actuators ar= ranged to actuate the respective regulators, an thereof by said member and said follow up means, and means actuated by said relay to disable said electrical transmitter operable to energize said mechanism until a new speed setting of said reg receiving actuators and cause rotation of the lat ulators selected by said member has been at ter to adjust said master and slave regulators in tained and then to render said mechanism again 50 unison, means manually operable to cause actua operative. tion of said transmitter and said receiving mo 9. A control for matching the speeds of slave tors in a direction to move said regulators to a and master power units each having an adjust selected speed setting, mechanism automatically able speed regulator, said control comprising responsive to a difference in the speeds of said slave and master receiving electric actuators ar 55 master and slave power units to energize said ranged to actuate the respective regulators, an slave speed regulator in a direction to correct?ior electrical transmitter operable to energize said such di?erence and maintain said units synchro receiving actuators and cause operation of the nized, and means actuated automatically as an latter to adjust said master and slave regulators incident to actuation of said manually operable in unison, electric motor driving means, means 60 means to select a new speed setting to disable including a manually operable member shiitable said mechanism until such speed setting oi? said selectively to different positions corresponding to regulators is attained and then to render said speeds of said power units and operable, when mechanism again operative. _ moved to a new position, to energize said driving K ' GEORGE FORREST DRAKE.