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Auge v5, ` L.. MAY ¿ATH TÜMATIC ALTITUDE CONTROL ÉDE'î/’IIGE File È, _-- K. ¿N ,w w ES INVEN’mR. 9055,??- L . MA'VÉÍ??? Patented Aug. 6, 1946 2,405,228 UNITED STATES PATENT OFFICE 2,405,228 y _ AUTOMATIC `ALTITUDE CONTROL DEVICE Robert L. Mayrath, Dodge City, Kans. Application December 26, 1944, Serial No.'569,8'69 14 Claims. 1 (c1. 172-282) ' (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 o. G. 757) 2 The invention described herein may be manu relative each other responsive to changes in al factured and used by or for the Government for titude of an associated aircraft and wherein an governmental purposes, without the payment to electrical contact engagement occurs between an me of any royalty thereon. element displaced in response to barometric pres This invention relates to altitude control de Ol sure and one or the other of a pair of contact vices for aircraft, and more particularly, to al portions of another element, depending upon titude control devices for automatically actuat Y whether the aircraft is rising or falling. Contact ing aerodynamic control elements of radio con engagement of the elements is provided periodi trolled aircraft, responsive to changes in altitude, cally by mechanical pressure eans so that the for the purpose of maintaining flight at a prede- ' termined level. > Present methods of automatic altitude control in radio controlled aircraft contain a number of drawbacks, one of which is that the systems in use are complicated and expensive, which makes the cost factor considerable where such systems are installed in aircraft used for target purposes. Another drawback is found in some systems in that extreme angles of climb'and dive are met. Such eXtreme angles sometimes cause an aircraft , to stall in a down draft greater than the maxi mum climb rate of the aircraft, or cause the air craft to dive to a destructive speed'in a violent up draft. Various angle limiting systems have been proposed, one of which is to limit the actua- ‘ tion of the aerodynamic controls of the plane by limiting the extent of rotation of a trim mo tor adapted to actuate such elements under au tomatic control responsive to altitude changes. first-named element may be constructed of light flexible material and easily displaced by the baro metric pressure responsive mechanism. The con tact engagement with one or the other of the contact portions serves to energize an electric motor’in one direction or the other, respectively, which actuates aerodynamic control elements of the aircraft, in a well understood manner, and simultaneously displaces the contact portion car rying element in the direction of displacement of the barometric pressure responsive element to restore the initial conditions corresponding to a setting for predetermined level flight. Means arev incorporated in the device whereby the dis placement of the barometric pressure responsive element is limited to avoid eXtreme angles of climb or dive. Additional means are provided for ac tuating the device independently of the automatic control mechanism in order to provide a prede termined flight level by radio control, and by Such methods of limitation, however, are not de 30 virtue of a lost motion linkage provided in the sirable in radio controlled aircraft, since the trim automatic control system, it is possible to provide motor must be capable of obtaining effects of independent control by radio for climbing or div stalling the aircraft to make landings and must ing the aircraft at extreme angles under guidance also be capable of effecting diving at steep angles to perform various missions. In order to achieve these effects, other systems introduce further of an operator when so desired. Other objects and features of my invention will be made apparent by the detailed description which now follows with reference to the appended complications in the use of trim motors with dou ble limits, or two trim motors, one for automatic drawing, in which: altitude control and the other for radio control. Fig. 1 is a perspective showing the arrange It is an important object of the present inven 40 ments of the elements thereof; and tion to provide a simple device for maintaining Fig. 2 discloses a modification of one of thev a predetermined level flight of an aircraft and elements. wherein automatic altitude control means are With reference to Fig. 1, the device comprises incorporated comprising elements adapted to lim a contact arm generally indicated as I supported it the extent of automatic control insofar as the rate of dive or climb are concerned. It is a further object of the invention to pro vide an automatic control device having features whereby control from the ground by means of radio may be effected independently of the opera tion of the automatic altitude control system. In accordance with the above objects, I provide barometric pressure responsive means comprising a lost motion linkage in combination with cer tain electrical elements disposed for displacement " by and keyed to a shaft 3 and disposed for pivotal movement relative a contact or pick-oil plate generally indicated as 5, plate 5 being keyed to a supporting shaft 6. Arm I is pivotally actuated by contraction or expansion of a diaphragm 1 of the type used in conventional altimeters, being responsive to barometric pressure. VDiaphragm 1 is coupled to arm I through a bidirectional lost motion mechanism comprising a slot and pin arrangement I0 and a lever and pin arrange ment I3; comprising, respectively, a slotted mem 2,405,228 - 3 even though diaphragm '| may be expanding or contracting at the time, since the lost motion pro vided between pin lob and the slot in member lßa will permit diaphragm 'l to expand without forcing angular displacementv of arm l clockwise, and the lost motion provided between lever |_3a and pin |31) will permit diaphragm 1 to contract without forcing angular displacement of arm | counterclockwise. The bidirectional lost motion structure is an important feature of the device for the above reason, and for other reasons which will be understood from the description of the manner in which the device operates hereinafter set forth. If it is desired, any suitable length adjusting means 6| may be provided on rod 41 _to provide Variation of the time of engagement lever i3d by virtue of the tendency to uncurl of a spring 39 secured between a post 3| integral with gear i6 and a shafti33. Shaft 33 is coupled at one end by a pinion 35 to gear sector |3c and is rotatably secured at kits other end, in any suit able‘manner, to a web of gear i6. The mechani cal system thus far disclosed is completed by a gear S8 keyed to shaft 33 and engaging a pinion 25 39 keyed to shaft 3, whereby reversible pivotal moti-on of contact arm i 4is providedA responsive to functioning of diaphragm l. 'Means for actuat ing arm l independently of diaphragm 'l is pro* 4 tion of tongue la against plate 5, no angular dis placement of the tongue la is intended to occur ber | @a secured to the movable end of diaphragm l., a pin lilo, and a lever lûc, and, a lever |311, pin |319 and gear sector iäc. A gear IB, through which axial shaft 3 passes rotatively, serves to carry diaphragm 'l and the lost motion system by virtue of an integral beam |'| securing the rela tively stationary end of diaphragm .'l, and the shaft 2l rotatably supported in any suitable man ner in a web of gear it, and having keyed thereto the levers |90 and i3d and rotatably supporting gear sector lâc, it being noted that gear sector 3c is thereby provided with vpivotal freedom rela- v tive shaft 2|. Pin lill? is biased toward engage ment with the upper end of the slot in Amember' ma by virtue of a spring 25 secured in tension between beam il and a lever 2e keyed to shaft 2|. Pin |319 is biased toward engagement with ' between tongue la and pick-off plate 5. An elec trical ground connection, as indicated on the drawing, is provided for yoke 54 and contacts 5a and 5b are electrically connected through relays 64a and b, respectively, and thence through'bat tery 66 to ground so that a series connection is established at such times as tongue la engages contact 5a or 5b, thereby energizing the corre spondingly lettered relay to close a circuit ener gizing a motor lil. Motor 1.0 is a reversible type and will be understood to include a reduction gear system having an output shaft 'ma connected in videdin the form of an electric motor »llt having 30 such a manner that the direction of rotation is a lpinion 4| engaging gear I6, motor 4|! being dependent on whether relay 64a or 64b has been energizable by a radio contr-ol system, in a well known manner, as indicated on the drawing. ,Attention is now invited rto the pick-off sys energized .subsequent to Contact of tongue |a with contact 5a or 5b. A linkage system, generally in dicated by l2, couples the shaft of motor ‘lll to tem ycomprising arm | and pick-off plate 5, as 35 shaft ë, and a linkage system, generally indicated heretofore' described. ,The arm | comprises a by 14, couples the shaft of motor l!! to the con metallic flexible strip or tongue la secured by an trols of anassociated aircraft, e. g., the throttle insulating joint vib to a supporting member |c lever, pitch control mechanism, or gyro base line. keyed to the shaft 3. The pick~oif plate 5 com Motor 'Illl is independently controllable by a radio prises 'a disc of hardrubber, or the like, having control system indicated on the drawing, which, a peripheral ridge supporting ñush with the sur of course, may be the sameradio control system face thereof a pair of metallic contact segments indicated in conjunction with the motor 40.. A or. portionsfäa and 5b. An insulating portion radio controlled switch is provided at 1| in the l¿c of widthv greater than that of tongue la is circuit of battery 66 for cutting out the auto provided separating contacts 5a and 5b and is matic' control system at such times as motor 'lû arranged flush with the surfaces thereof. Tongue is independently operated, the switch at 'Il being |a is arranged in spaced relation to the contact cut in by radio control when resuming automatic portions of plate 5 by a small fraction of an inch, operation. land is brought into periodic engagement there In operation, assuming the device is installed with by a continuously rotating motor |85 which on a grounded aircraft and motor 45 is rotating, v'causes reciprocation of a rod 41 lby virtue of a tongue la is so positioned relative pick-off plate camfmechanism 48, in a well-known manner, 5 that periodic engagement with insulating sur thereby oscillating a bar 5d, pivoted at 5|, through face 5c is established. This'is regarded as normal force'transmitted thereagainst by a spring 52, periodic engagement, motor 'i’û being deenergized rod ll'tbeing slidable in a bore provided in bar 55 since the surface 5c is a nonoperative point in 5G.' Oscillation of ‘bar 5S eiî'ects bending or de sofar as energization of relays 64a and 64b are flection of tonguev |a against plate 5 by Virtue concerned. At such time, tongue la is midway of an abutting yoke member 54 having stops 5M between stops 54a and 54o and pin Iûb is in abut and 5th thereon to limit pivotal motion of tongue la. ln' 'practice it 'has been found feasible to 60 ment with thev top of the slot in member Illa, while lever |3a is in abutment with pin |3b. The space stops â'íia >and b apart a distance corre device'may then be set for predetermined flight sponding' to an altitude~ vchange of 100 feet. Yoke level by energization of motor 4E, through the 54 is secured throughl an insulating member 51 radio control system or by direct control, whereby to bar 56.1 A periodic engagement between tongue la and pick-off plate 5 of 2,00 times per minute 65 gear I6 is rotated counterclockwise by pinion 4| , the entire mechanism '|-39 rotating bodily with has been lfound >suitable for practical operation. gear |95, including shaft 3 and arm l. After Rod 4T is provided with an end abutment 59 and gear IG is rotated approximately 30° tongue la 'spring' 52 is sufficiently strong to hold bar 50 abuts stop 54a. Continued rotation of gear I6 against abutment 5e until tongue Ia has been pressed firmly against pick-,off plate 5 at some 70 then serves to wind up spring 30 secured to shaft The stroke 33 due to a counterclockwise rotation of gear 38 of'bar 5i) is such that periodically yoke 54 will caused‘by reaction against the now stationary pinion 39, and simultaneously gear sector |30 is rotated clockwise due to engagement with pinion 75 35, which rotates with gear 3a. lThe dashed ar point on the surfaces 5a, 5b or 5c. clear tongue iatoallow freedom for pivotal move ment thereof responsive to functioning of dia phragm l'. During the momentary clamping ac 5 2,405,228 6 „rows on the drawing indicate the relative rota point on the contact 5b, the extent of arcuate tion of the gear train as just described. Rotation travel of arm l depending upon the altitude of gear sector I 3c displaces pin |3b away from deviation encountered. Relay 64b is thus ener lever l 3a, thus providing a lost motion gap there gized and motor 10 responds accordingly, oper between. The extent of the lost motion gap de Ul ating the aircraft control elements to effect div termines the height at which the aircraft will ing of the aircraft. Simultaneously, plate 5 is level off in night, and is determined in any suit rotated clockwise to followup arm l, which in able manner, such as by timing the duration of turn, is now being affected by contraction of .energization of motor 40, in relation to a known diaphragm 1 through the mechanism '1_39 re maximum extent of gap corresponding to the 10 sponsive to the present diving of the aircraft flight ceiling of the particular aircraft. Simul so that the rotational direction is reversed, ire., taneously with the foregoing functioning of the arm l starts moving towards surface 5c while mechanism 1-39, periodic engagement between surface 5c is still moving clockwise to follow up tongue la and contact 5a is occurring, whereby the original displacement of arm l, since tongue motor ‘I0 is correspondingly periodically energized la is still in periodic engagement with surface 5b. by operation of relay 64a, shaft 10a rotating in The rate of restoration of normal periodic en a counterclockwise direction, thereby setting the gagement between tongue la and surface 5c is control elements of the aircraft for climb, by ac thus increased, the relative angular velocities of tuation of linkage 1.4, and simultaneously linkage arm I and plate 5 being dependent on the sensi 12 rotates pick-off plate 5 to restore the condi 20 tivity of system 1_39, speed of motor 1D and tion of normal periodic engagement, i. e., plate rate of dive, in general. Ultimately, normal 5 follows arm l counterclockwise at a rate deter mined by the R. P. M. of the reduction gear out put shaft of motor 10. Ultimately the insulated surface 5c arrives in position to be periodically engaged by tongue l a which is in its limit posi tion in abutmentagainst stop 54a, thereby break ing the circuit to relay 64a and deenergizing mo tor 10. Motor 40, however, runs pursuant to op erator control and may be stopped either before or after the insulating surface 5c has rotated into register with arm l, the point of stopping of mo tor 40 being dependent only on the selected flight level. It will be appreciated that the rate of climb is determined by the arc of travel of arm l prior to abutting the stop 54a, since motor 'lû which sets the controls is energized only for the length of time required to effect the followup rotation periodic engagement is restored as a result of the action just described, and if at the time of restoration lever I3a just abuts pin I3b, the air craft is operating at the predetermined flight level. If, however, due to conditions of design and/or the existing air currents the aircraft has dived below the predetermined level in the action just described, then diaphragm 'I contracts and causes counterclockwise rotation vof arm l, whereby periodic engagement with surface 5a is resumed at some point corresponding to a materially lessened travel arc of arm I, as com pared with the prior engagement therewith, and once more the aircraft climbs. The hunting action thus continues, each reversal having a materially lessened arc of. arm l until equilibrium is obtained, i. e., lever l3nt just abuts pin I3b but transmits no torque to gear sector l3c and arm of plate 5. The followup arc is, of course, iden 40 I is positioned substantially midway between tical substantially with the travel arc of arm I, stops 54a and 54h, the tongue la periodically and accordingly limited as a design matter by engaging surface 5c, which is the initial `condi the arcuate spacing of stop 54a (or 54h in the tion of all these elements prior to predetermina reverse direction) from the center of yoke 54. tion of the flight level. It Will be further appreciated that the width of If, for any reason, the aircraft should lose alti insulating surface 54e relative the width of tude from the predetermined level; diaphragm 1 tongue la determines the extent to which the arm travel arc and the plate followup arc are identical, such relative width being likewise a matter of design which may be varied to suit desired operation, such width likewise determin ing the extent of altitude variation operation ally encountered prior to initiation of corrective response. The flight level having been predetermined, , will contract, thereby actuating the lever |3a counterclockwise, and thus permitting spring 30 to uncurl, the ensuing rotation of shaft 33 driv ing gear 38 clockwise whence pinion 39, shaft 3 and arm l are rotated counterclockwise. Tongue la is accordingly brought into periodic engage ment with the surface 5a, the arc of travel of tongue la being proportional to the rate at which the aircraft is losing altitude as compared with the mechanical inertia of the system |---39, and relay 64a is energized whence motor 'l0 actuates the control elements in the direction of climb. Likewise, if for any reason the aircraft should assuming the aircraft now takes off, it rises by virtue of the setting of the control elements for climb, as just described. The aircraft continues to rise until diaphragm 1 expands sufficiently to permit rotation of lever Hic, lever 26 and shaft 60 gain altitude, diaphragm 1 will expand, permit 2| (in a clockwise direction) by virtue of the ting clockwise rotation of lever i3d under the biasing action of spring 25, to a degree sufficient influence of spring 25, whence the gear train to close the gap between lever 13a and pin i317. I3c-39 causes clockwise rotation of arm I, At this time the aircraft has arrived at the whereby engagement of tongue la with surface predetermined fiight level but is continuing to 5b produces diving actuation of the aircraft con rise since the aircraft control velements are still trol surfaces. In either case, the followup oper set for climb, whereupon diaphragm l expands ation of plate 5 is responsive to angular displace further, thus permitting lever 13a to drive gear ment o-f arm l and in the same direction. It will sector I3c clockwise due to the biasing influence be appreciated that stops 54a and 54h limit the of spring 25, this motion being transmitted 70 rotary displacement of arm l and therefore limit through pinion 35, shaft 33, gear 38, pinion 39, the angle of climb or dive of the aircraft to avoid shaft 3 to arm l, causing clockwise rotation unreasonable values which might cause stalling thereof away from stop 54a. The rotation of arm or destructive diving speeds. l .serves to remove the point of periodic engage With the aircraft in level flight at some pre ment from the insulating surface 5c to some 75 determined altitude, it is possible to change the 2,405,228 7 altitude to some other predetermined level by remote radio control of motor 4E), the action of the device for predetermining a higher level being the same as that described for preñight predetermination. This follows from the fact that the relative positions of lever 13a, pin l3b, arm- I, plate 5 and yoke 54 are restored after the aircraft has found the originally predeter 8 energization of the aircraft control motor, i. e., motor 10, (Fig. 1) would not be energized as much during the complete followup of the pick off plate shown in Fig. 2 were this plate substi tuted for the plate 5 of Fig. 1. This follows from consideration of the coaction between tongue la and either of the sloping surfaces 18 andI 19. Where coaction of tongue la is provided with a surface uniformly receding from engagement due mined level, as noted above. In order to predetermine a level lower than 10 to a followup rotation, as is the case of a plate formed as shown in Fig. 2, the duration of each that at which the aircraft is flying, motor 4U is controlled by radio to rotate counterclockwise, whence the system l-SS rotates bodily clockwise until tongue la abuts stop 54h, thus locking pinion 39 against clockwise rotation. Further rotation of motor 40 serves to rotate gear IE, gear 38, shaft 33, and pinion 35 clockwise, causing gear sector |30, pin |3b, lever i3d, shaft 2l and lever Ißc to rotate counterclockwise, whence pin lilb engagement will progressively diminish from the beginning to the end of a followup rotation since progressively more time is used in nonengaging deflection during each deflection cycle of tongue la. Accordingly, motor 10 receives energy im pulses of progressively diminishing duration and the aircraft control elements are operated corre spondingly. Such a feature is useful in high speed rides downwardly in the slot in member lila. „ aircraft where response to the aircraft control elements may be disproportionately large as com Tongue la having been brought into periodic en pared with the rate of operation of the automatic gagement with surface 5b, the electrical control altitude control mechanism. By providing a system becomes operative to dive the aircraft. pick-off plate shaped as in Fig. 2, the response of vThe duration of dive depends on the extent of the aircraft will be made to progressively de 25 `lost motion provided between pin lob and the crease, thereby attaining the advantage of a rela upper end of the coacting slot, which in turn is tibely large and prompt initial response com dependentl on the duration of energization of bined with a gradual tapering off in rate of re motor 40, the controllable factor. The dive is sponse so as to make the overall altitude change 'continued until diaphragm 'l has contracted sufli ciently to translate member loa downwardly so 30 proportional to the extent of altitude deviation affecting the automatic mechanism rather than that pin Iûb abuts the upper end of the slot. to the speed of the aircraft. Functioning of pick-off plate 5 to followup arm l Having thus described my invention, I claim: has been occurring from the time of energization l. In a device as set forth in claim l2, wherein after some hunting, due to the aircraft diving 35 said altitude response means comprises a gear axially aligned with said contact arm, a pressure beyond the newly predetermined level. Accord of motor 1U, equilibrium condition being restored ingly, with the aircraft in flight, any number of flight levels may be successively predetermined responsive diaphragm carried by said gear, a pin ion coaxial with said gear and secured for rota tion with said contact arm, a driver for said as desired, by radio control of motor lll), due re pinion mounted for rotation on said gear, and gard being had for the direction of rotation there 40 linkage means connecting said diaphragm with of, depending on whether a flight level is desired said driver whereby pulsating of said diaphragm higher or lower than the existing flight level. responsive to altitude deviations of said asso In the event that it is desired to stall the air ciated aircraft is operative to rotate said contact craft or to produce a fast or deep dive, motor 'l0 arm in a direction depending on the direction of is remotely controlled by radio to operate the air pulsation of said diaphragm, and means opera craft control elements independently of the sys tem I---64b, power from battery 56 being obtained tively connected to said gear and operable inde pendently of said diaphragm to rotate said gear for the purpose of displacing said contact arm by viding a multiple switch at il, which automati 50 torque acting on said pinion, and transmitted cally disconnects battery 6@ from the system through said gear, said linkage system and said I-Gdb and connects it to motor ‘l0 in a control driver, to predetermine flight level of said asso lably reversible manner. The details of the radio ciated aircraft. system and switching arrangement form no part 2. _In a device as set forth in claim l2 wherein of the present invention and are accordingly in said means for causing periodic engagement of 55 dicated only generally on the drawing. By in said arm with said contact member comprises an dependent operation of motor l0 the aircraft oscillating member disposed for periodic abut may be brought into extreme stall or dive angles ment against said arm in such a manner as to at the will of the operator, and altitude change cause ñexure thereof against said Contact mem in either direction, although causing a contrac ber, said oscillating member carrying stop means tion or expansion of diaphragm T, does not thereon whereby displacement of said contact actuate the system i-54b to the point of damage >arm responsive to altitude changes of said asso since arm l comes to rest against either stop 54a ciated aircraft is limited in response thereto. or 54h and contraction or expansion of diaphragm 3. In a device as set forth in claim 12, wherein 1 thereafter serves, respectively, to rotate lever said altitude response means comprises dia i3d away from pin I3b or translate member lila phragm means responsive to barometric pressure, relative pin lûb in an upward direction, as» seen bidirectional lost motion linkage means connect from the drawing, whereby pin l?b rides harm ing said diaphragm means to said contact arm lessly in the slot in member ita. whereby reversible angular displacement thereof In Fig~ 2 is disclosed a modification of the pick corresponding to expansion or contraction of said off plate 5 of Fig. l, wherein the contact portions diaphragm means is realized, said means for caus 18 and 19 differ from contacts 5a and 5b of plate ing periodic engagement comprising an oscillat 5 in that they are sloped, being gradiently spaced ing member adapted to abut said contact arm in from the plane of insulating material 80 toward such a manner as to cause flexure thereof against the intermediate insulating portion 82. The slop said contact member, said oscillating member 75 ing construction provides a decreased time of therefor in any suitable manner, such as by pro 2,405,228 9 10 comprising stop means adapted to limit angular point at an existing flight level, means including displacement of said contact arm in either di a barometric pressure responsive element for dis placing said arm relative said plate to effect en gagement of said arm with one of said operative rection, whereby lost motion in said lost motion linkage means is operative to prevent bending strain'cn said contact arm when said contact arm has traveledto one or the other limits of its an points dependent on a gain or loss of altitude of an associated aircraft, means operative in re sponse to engagement of said arm with said op gular displacement. 4. In a device as set forth in claim 12, compris ing means for rotatably mounting said contact member, electrical relay means connected to said ‘Y’ contact portions and operative to energize an elec tric motor in one direction of rotation or the other dependent on periodic engagement of said Contact arm with one or the other of said contact portions, means actuated upon energization of 7 erative point to actuate controls vof said aircraft for effecting a compensating altitude change, means operative in response to actuation of said last-named means to elîect displacement of said plate to restore said normal engagement, means connecting saidrarm and said barometric pressure responsive element comprising a bidirectional lost motion linkage means, and means for effecting said motor for operating ascent or descent con trols of said associated aircraft dependent on the direction of rotation of said motor, and means op eratively connected to said contact member and reversible displacement of said arm for engage ment with one or the other of ’said operative points independently of altitude changes, for pre deterinining a llight level higher or lower than the existing flight level, means for causing a de actuated by said motor for simultaneously ro tating said contact member in the same direction as the direction of displacement of said contact gree of lost motion in said bidirectional lost mo tion linkage means, alternatively, 'depending on the direction of independent displacement of said 5. An automatic altitude control device, com arm subsequent to displacement thereof in either prising a contact arm and a contact plate, said 225 direction to a limited extent, whereby said baro arm being engageable with said plate, said plate metric pressure responsive element is mechani having a nonoperative point for engagement with cally unaifected by said independent ’displace said arm and an operative point for engagement ment of said arm, said altitude responserelement therewith, said arm being adapted normally for being operative to take up >said lost motion pro arm. ' engagement with said non operative point, means including a barometric pressure responsive ele ment for displacing said arm relative said plate to effect engagement of said arm with said op erative point in response to an altitude change of an associated aircraft, means operative in re sponse to engagement of said arm with said op n. level.` 33 erative point to actuate controls of said aircraft for eifecting an altitude change, and means op erative in response to actuation of said last named means to effect displacement of said plate to restore said normal engagement. 6. In a device as set forth in claim 5, including store said normal engagement. '7. In a device as set forth in claim 5, including means connecting said arm and said barometric pressure responsive el-ement comprising a lost mo point independently of altitude changes, for pre » > operative point therebetween, means whereby other, relative displacement between said ele ments being effective to shift the point of en gagement to an operative point therebetween, means responsive to engagement at said operative point effective to actuate control means of said aircraft, and means responsive to actuation of said control means to provide an opposite rel ative displacement between said elements where by engagement at said inoperative point is 50 restored. 10. In a device as set forth in claim 9, wherein said means whereby said elements are displace able relative each other includes an altitude tion linkage, and means for effecting displacement of said arm for engagement with said operative ' said elements are displaceable relative each a second operative point on said plate, said non ing correspondingly reversíbly displaceable to re ’ Y9. An’ aircraft control device comprising, in combination, a pair of contact elements, means for causing engagement of said elements, en gagement thereof normally occurring at a non operative point being disposed intermediate said operative points, said means for displacing said arm in response to altitude change being opera tive to effect said displacement reversibly corre sponding to gain or loss of altitude, said plate be portionally as said aircraft approaches said pre determined level, the degree of lost motion being proportional to the altitude difference between'the predetermined flight level and the existing flight responsive element and lost motion linkage 55 means connecting said altitude responsive ele determining a flight level deviating from the ex isting level of said aircraft, means for causing a degree of lost motion in said lost motion linkage subsequent to independent displacement of said arm to a limited extent, whereby said barometric 60 pressure element is mechanically unaffected by ment to one of said contact elements for dis placement thereof responsive to altitude changes, stop means for limiting displacement of said con tact element, whereby, when said contact element is at the limit of displacement thus provided, further altitude change is operative to effect lost motion compensation in said lost motion link said independent displacement of said arm, said age means to relieve additional displacing force altitude response element being operative to take up said lost motion proportionally as said aircraft 65 on said contact element and whereby the extent of actuation of said aircraft control means is approaches said predetermined level, the degree of correspondingly limited. lost motion being proportional to the altitude 11. In a device as set forth in claim l2, difference between the predetermined flight level wherein said plate comprises a pair of contact and the existing flight level. members having surfaces which slope in relation 8. An automatic altitude control device, com to the plane of displacement thereof, whereby prising a contact arm and a contact plate, said 70 periodic engagement with said arm occurs with arm being engageable with said plate, said plate progressively varying duration of contact as said having a nonoperative point intermediate a pair plate is displaced relative said arm. of operative points, said arm being adapted nor 12. In an automatic altitude control device, a mally for engagement with said nonoperative 75 contact arm, a contact member having a pair of 2,405,228 12 trol motor to said first electric switch element for moving said elognated contacts in coincidence with movement of said controls, a second electric switch element comprising a single contact for conveying current to one or the other of said elongated contacts, normally situated in said in sulating space and out of contact with said elongated insulating contacts but movable along elongated contact portions separated by an in sulated portion, said contact arm being normally positioned to engage said insulated portion only, altitude sensitive means responsive to changes in altitude of an associate aircraft whereby said arm is displaceable away from said insulated portion and along one or the other of said elongated contact portions, means for periodically causing engagement of said contact arm with said elongated contacts in either direction, inde“ said contact member, normally against the in 10 pendently of the movement of said iirst electric switch element, means to selectively set said sulated portion but displacement of said arm second electric switch element in one or the other along said elongated contact portions in response direction along one or the other of said elongated to altitude changes being operative to change the insulated contacts, whereby said control motor point of periodic engagement of said arm with said contact member to one of the contact por tions thereof, means responsive to contact be 15 operates said controls for climb or dive and co incidentally moves said insulating space to a tween said arm and one of said contact portions position in alignment with said single contact, an altitude sensitive means, and linkage connect to vary the controls of said associate aircraft ing said altitude sensitive means to said second to provide ascent or descent depending on the specific contact portion engaged, and means re 20 electric switch element operative by movement of said altitude sensitive means upon change in sponsive to periodic engagement of said arm with altitude of said associated aircraft to return said said specific contact portion to displace said con single contact to the starting position, whereby tact member in the direction of the displacement said control motor returns to the neutral posi to restore said normal periodic engagement. tion for maintaining the selected altitude. 25 13. In a device for bringing an associated air 14. The device defined in claim 13 in which ' craft to a preselected altitude and maintaining the first electric switch element is a rotatable it at said altitude, a co-ntrol motor operable from dielectric disc, the elongated insulated contacts a neutral position in one or the other directions to set the controls of the associate aircraft for being arcuate metal pieces carried in said disc, connected to each motor terminal and arranged pieces. climb or div-e, a first electric switch element 30 and the second electric switch element is an in dependently rotatable conductive contact arm carrying two elongated insulated contacts with adapted for contact with said arcuate metal an insulating space therebetween, one electrically to convey current to revolve said motor in one or the other direction, linkage connecting said con 35 ROBERT L. MAYRATH.