US2390547A - Torque amplifier - Google Patents

Description

Dec. 11, 1945. H. M. MccoY 2,390,547

TORQUE AMPLIFIER Filed July 8, 1944 I N V EN TOR. /70/4/190 M /76 by Patented Dec. 11, 1945 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 2 Claims.

The, invention described herein may be manufactured and used by or for the Government for governmentalV purposes, without the payment to me of any royalty thereon.

This invention relates to torque amplifiers, and among other objects, aims to provide an improved torque amplifier having proportionalizing (follow-up) means to minimize hunting. According to the preferred form of the invention, proportionalizing by rate as well as by time is made possible, to reduce hunting to the lowest practicable extent. However, the invention in its broadest aspect is independent of proportionalizing; it provides a simple, rugged, inexpensive remote positioning device for controlling whatever torque ampliflcation is necessary from a tele-signal. As the angular position of the power take-olf shaft is a direct function of the position of the master control, a position indicator associated with the master control may indicate the angles or positions of many things, for example, the angles of aircraft trim tabs. The invention could also be used to indicate the position of a gun turret, an antenna reel, a cowl nap, etc.

It is 01d, as in the Heath Patent N0. 1,292,315,

dated January 21, 1919, to synchronize two or more motors by means-of rapparatus comprising two or" more threaded hubs or nuts, each of which travels back and forth on a shaft (in a direction determined by the motor which is running at the slower speed) to close switches which cut out resistances in the circuit of the slower motor, thereby `to cause the latter to pick up speed until the speed of all the motors is the same. According to the Kessler Patent No. 2,023,139, dated Deceniber 3, 1935, a screw threaded shaft is adjusted by means of a crank to effect changes in the time intervals of reversing of electric current driving a motor operating a rotary furnace. Also limit switches of the traveling nut type for controlling electric motors are well known, as disclosed in Everett et al. No. 881,565, dated March 10, 1908, and Burrowes 838,681, dated December 18, 1906. Such prior art constructions, however, do not have the functions and advantages of my torque amplifier.

In the accompanyingy drawing forming a part of this specification, the single figure is a diagrammatic view of one form of apparatus embodying the invention.

Referring particularly to the drawing, a reversible electric servomotor 5 has a spring-loaded solenoid-released brake and clutch 6 simultaneously energized with the motor 5, to cause immediate stoppage of the motor 5 upon cutting oft 'to the use of the motor.

power, which reaches the servomotor elds through the leads l, 8, 9. Such brakes and clutches are conventional in electric servomotor art. They are used to minimize hunting. The motorshaft I0 drives a pinion I| which is illustrative of any power take-off that may be suitable Instead of a pinion, a torque arm, a pulley or some other driving element may be xed to the motorshaft. In the diagrammatic showing of the invention, motorshaft I0 is extended beyond the power take-01T and its extension I0a is supported by anti-friction bearings I2, |3. An elongated spur gear I4 is rigidly fixed upon the shaft extension |0a and hence is driven in either direction by the servomotor when energized; however, in actual practice, reduction gearing (not shown) may be interposed between the shaft which drives the elongated gear |4 and the motorshaft.

To govern the servomotor, a master control is provided which in the illustrative embodiment is a crank wheel l5 secured to one end of a flexible shaft (not shown) inclosed within a fiexible cable I6. The exible shaft is secured at its other end to the end of a shaft I1 rotatably supported by antifriction bearings I8, I9, and parallel to shaft extension |0a. Shaft may have a lead screw secured thereto or, as shown, has screw threads 20 cut thereon for a portion of its length which is nearly as long as the elongated gear I4. A spur gear 2| is internally threaded to engage with threads 20, and is in mesh with the elongated spur gear I4, so that when the latter is driven by the servomotor, spur gear 2| will travel in one direction or the other axially of shaft Il. It is thus seen that the angular position of the object driven from power take-off bears a constant relation (depending on gear reductions) to the angular position of control crank I5. Spur gear 2| cannot normally reach the end of the threaded portion 20, because the size and speed-power characteristics of servomotor 5 are selected for whatever object is driven from power take-off II to cause gear 2| to returnto the neutral position shown before gear 2| can run off the thread. However, when the elongated gear I4 is sta.- tionary, spur gear 2| will be locked against rotation, and any turning of shaft by means of the operator-controlled crank wheel I5 will move spur gear 2| longitudinally of shaft I1, to effect an adjustment which will now be described.

yoke 23 and vthe faces of gear 2|. Fixed to and extending outwardly from yoke 2| is an arm 23a having an annular yoke 24 at its opposite end, yoke 24, in the neutral position of the parts, surrounding a stop collar 25 secured to or integral with a splined shaft 26. Shaft 26 is continuously driven by a constant speed motor 21 through reduction gear train 2 8, which is illustrative-of any speed reduction drive. A speed governor 29 is provided to permit the operator to adjust the speed of motor 21. are splined on shaft 26 and each has a cam .32.33. respectively formed thereon, these cams' being mirror images of each other. A pair o f ."Softcoil springs 34, surround shaft 2 6 and `press against A pair of cam cylinders 30, 3l

the ends of cam cylinders 30, 3-| respectively 'to' resist sliding of the cam cylinders in eitherdirection from the illustrated neutral centralposition, wherein both cam cylinders abut -the fend faces of stop collar 25. Shaft 26 is supported in vimlGi-lriction bearings 36, `3l. By means of ,the construction so far described, the operator lby Atli'ri1i`nfgcrank wheel"l5"may shift either cam Vcylind V" allrlg the @continuously rotating Shaft `26 'against the .resistance of the .corresponding coil Spring". ''Also, vthe servomotor llay move either c 'arncyli'n'der as determined by thefdirection of rctationicf notorsnaft I'tl.l

"Calrs'32, y3'3 are 'designedto engage rollers `V38, A3.9 .Carried ionfthe ds `of bellcrank levers 40, Il respectively, l"springs'42,713 holding the rollers normally "contact with the perilheries of ythe cylinders. "Obviously thebell crank levers are cam followers.' llowever, when the` cam Cylindersare in 'the neutralpo'sition; which "is "illustrated, the

rollers 33, 3 9 ride over ,therspectivecam Cylind'e s WhO'uitCrtaCting the cams," due tothe fact th tithe cams terminate"shorter-the ends ofthe cylinders. In' therieutral'position the cam Vfcllowers are therefore 'Ilot jswu'ng ontheirv pivots '44, and no closing ojf' the servom'otor circuits cantake p'l e, Butmwhenoneof' the' cam cylinders has here' rshownta's battery 49, and anotherlead 50 extends from battery 49 Ito 'a pair A of conductors 5I 'leach :terminating 4in-amovable conductor `52 having-auk contact 53'at.the free end. 'Two'resistances`54,f55, which *areessentially rheostats, are connected by leads 56, 5l, respectively, with the movable contacts 45, 46.* These resistances are divided into s'egments'by vmeans of aplurality of conductors 58, each conductor 58 having a movable conductor 59 connected thereto, with'a contacti at the free fend ci aeach movable" conductor 59. 'An arm 62is" rigidly Vfixedtoarnuilar yoke 24 and therefore Amoves with'gear 2l. rAs 'the end of arinBZ engages either contact 53, .movable conductor'vSZ is bent yorro'cked until it engages contact .60 `of the` adjacent conductor/59. hThus a circuit iscornpletcd'vbut with, all the resistance 54 or 55, as the case may be) in series with the servomotor field.- vThe servomotor `thus starts slowly. Further y1li@vementy O f f arm 52 cuts out some of the ,-re'sistance, `and the servomotor speeds up. Re-

beer'iimevd outortheneutrar position; one ofthe may` bezomitted,A andtheiarm A62 "maymerely'vlose versal of the servomotor is effected by moving arm 62 in the opposite direction, with concomitant se` quential cutting out of the resistance as previously described. The described resistances are similar in principle to the Westinghouse Silverstat, and provide a compact series of contactors by which any series of resistances may be tapped in and out'of the servomot'or circuit, tozcontrol rotation of `the servomotorin either direction.'

Operation sistance .(54 or '5.5) in the eld circuit. Energization of the servomotor is only momentary, becauseof the shapeofcajznj32, or`33, which lifts the corresponding "-bell' crank Vlever tov close the circuit once duringeach revolution'of shaft '26. With further adjustment Aof "yoke" `23,`lf n=.ri`ce of veither camcylinder 3l), -3 l away r*fromthe neutral position, the Vcorresponding bell :crank lever `will effect a longer 'closing of lthe contactsl, 141er 46 48 as Athe case-maybe, andthe energizationcf "the servomotor will :take place fthreugh a 'longer `'Dro-- portion of Lthe peifiodof lone=rzvo'll'itlonof shaft '26, 'and in addition, the speed-of the fsfervomctor will Ibe increased because less :resistance will Lbe in the lield-circuit. fAny movement'of the ser-ve-A motor will oflcourselfbe freflected 'inflthefobject Whose position iscoritrolled by ltlie Servomowr through the `power"take-off. IHowever,*the yservomoter when *energized `rotates gear il 4, .which i-al. ways rotates gear-'21 engaging fthe screw-:threads 2l) of v'shaft 1H. '2llense with `Ishaft 1H stationary, gearl 2 I travels alongfsaidshaftfbackttowards the neutral lpositicmand" will V.usually come rto a ,stop exactly inthat.position` .Iflthereis ass'lightf-over.- travel, the servomotor `will. be 4.reversed and the parts will be broughtato neutral positionrbymovement in the opposite `direction; ihowever, with proper designiand adjustment. of theparts, .lovertravelandfhuntlngwillseldom'occur. Y The .described mechanismfshowslproportionalizing by `rate and time. iIf .lproportionalizing fzby rate only sfd'esireii, -`s'hat?26, the cam cylinders, the constantspcedzmotorand; the speed governor contacts to :close the vmotor circuit -in1rone direction or the other through-the resistencias A5km' 55. ilfitfis desired ltoproportonalize only-fthe tme,'lhe resistances 54,l :SSIand vtheir contacts may be omitted. The:described combination ofwpreportionalizing, .bothiinfrate andltime, will provide an yabsolute maximumgof. damping v(er 1 minimum of hunting); L, 1 a

...l i IIhe marlies@ 1f-the SeletivsV Speed @911ML @if motor Z1 andfsovernvr #Sis t0 prei/ide@ epdly adjustable meansffor changing the ffdmpng c1 laract,militiasY of the OllQW-.UP mechanism This isqdesirable to tuningthe follow-up characteristics as is necessary to prevent undesirable hunting'tomatch-the linertia,.chafacteristics 0f Whateverisdrverlfimm ethfpowsr beke-Offri l, In other words, 'alf I the f object driven from the` power take-off Il has a highpolar moment-.o inertia it will:l require adiiterent. follow-upspeed 0F motor .2 1 `than ifV Ithe .object ,had a relatively low polar moment of inertia.rl Ihat isfwitl'oin.the` limits of power'fuvrnishedhy the servolmotor. .The speed-power 4and acceleration `lcharacteristics ,oi

servomotor 5 are selected to drive the driven object (not shown) from power take-off Il so that by the time switches 46 0r 41 are fully closed and thus servomotor 5 is running at maximum rate, gear 2l cannot reach end of threaded portion 20 of shaft I1. It is thus seen that the servomotorrspeed is proportional whether in rate or time or both, to the rate at which control crank I5 is moved.

Obviously the invention may be embodied in many forms neither described nor shown.

What is claimed is:

l. A torque amplifier comprising, in combination, a reversible servomotor; circuits for said servomotor; a shaft driven by the servomotor; a power take-off driven by said shaft; an elongated gear driven by said shaft; a second gear meshing with the elongatedgear; a manually adjusted shaft for moving the second gear longitudinally of the manually adjusted shaft independently of any other mechanism; there being a screw thread connection between the second gear and the manually adjusted shaft, so that rotation of the second gear by the motor-driven elongated gear will effect adjustment of the second gear on its shaft; an arm moved by adjustment of the second gear; a yoke secured to said arm; a splined shaft; a pair of cam cylinders movable on said splined shaft; a pair of coil springs tending to hold the cam cylinders against the yoke on either side of the same, so that adjustment of the second gear may effect movement of one of the cam cylinders against the resistance of one of the coil springs; an electric motor driving the splined shaft and hence the cam cylinders at a reduced speed; operator-controlled means for varying the speed of said motor; cams on the cam cylinders; cam followers riding on the cam cylinders and adapted to be actuated by the cams; contacts engaged by said cam followers when so actuated to close said circuits governing the servomotor; the springs normally holding the cam cylinders in neutral position and the cam followers then riding on the cam cylinders without contact with the cams; a pair of resistances in the servomotor circuits; conductors dividing each resistance into segments; an arm secured to said yoke and adapted to engage said conductors sequentially to progressively cut out the resistance as the arm is moved farther from the neutral position; the servomotor speeding up in either direction as the resistance is cut out; the cams being so shaped that a greater proportion of the total time of one revolution of the splined shaft is expended in holding the servomotor circuit closed, the further the arm is adjusted from the neutral position.

2. A torque amplifier comprising, in combination, a reversible electric servomotor; a power take-off actuated by the servomotor; an elongated gear directly driven by the servomotor; a second gear meshing with the elongated gear; a screw-threaded shaft with which the second gear engages by means of screw threads; an operatorcontrolled mechanism for turning the screwthreaded shaft thereby to adjust the position of the second gear thereon; the second gear remaining in mesh with the elongated gear whatever its adjustment; a motor circuit including contacts for governing the direction of rotation of the servomotor; an arm moved by the second gear and hence adjustable by the operator, and adapted to close the motor circuit'through said contacts to effect rotation of the servomotor in one direction or the other; a pair of cams, one on either side of the arm; a shaft on which the cams are splined; a constant speed motor; mechanical, connections between the constant speed motor and the splined shaft so that the cams are constantly driven at a reduced rate of speed; cam followers respectively actuated by the cams and in turn closing the respective contacts to actuate the servomotor in one direction or the other; and springs acting to center the cams on the splined shaft, said cams being so constructed that when centered the cam followers are not actuated.

HOWARD M. MCCOY.

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