March 8, 194-9. 1', E, LARKlN ‘2,464,047 ‘ DEIC‘ING CONTROL SYSTEM Filed Sept. 24, 1947

‘ TA’J‘W/J Inventc?": Thom as T3..L&1T~Kin, by ‘ma/w." His Attorney. Patented Mar. 8, "1949 2,464,047v

UNITED STATES, PATENT OFFICE 2,464,047 CARBURETOR DEICING CONTROL SYSTEM Thomas E. Larkin, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application September 24, 1947, Serial No. 775,916 8 Claims. (Cl. 123-122) 1 2 This invention relates generally to aircraft in Pressurized air is supplied to the fuel induction ternal combustion engines and more particularly system by means of a turbosupercharger com to apparatus ‘for preventing the formation of prising a compressor 4 driven by a gas turbine 5 in the carburetor and other parts of the engine which is also of well known construction. Air fuel‘ induction system. enters the compressor 4 through a conduit 6 It is well known that during certain ?ight con where it is compressed and discharged through a ditions ice may quickly form in the carburetor of conduit 1 which is connected to the intake mani an resulting in reduction or com fold 2 through an 8, a conduit 9, and plete loss of engine power. Because of this dan a carburetor I U. The carburetor I0 is shown ger, a number of systems have been designed for 10 schematically as comprising the usual automatically increasing the temperature of the valve ll located downstream from a venturi l'2. intake air supplied to the carburetor upon the Fuel is injected into the engine under the control occurrence of conditions tending to produce ice. of a system of known construction In order to sense ice-forming conditions, tem (not shown) controlled in accordance with the perature responsive device-s have been used to pressure drop through the venturi l2 and other control the temperature of the carburetor air but control elements not shown, the fuel injection these systems have not been generally satisfactory pipe being indicated at 13. The injection may be because they do not respond quickly enough to direct to head of engine. prevent ice formation, nor do they provide an ac The gas turbine 5 is driven by the pressure of curate measure of ice-forming conditions. the exhaust gases in the 3 to An object of the present invention is to provide which it is connected. The turbine has a nozzle a carburetor de-icing control system which senses box l4 having ports (not shown) through which ice-forming conditions very rapidly and accu exhaust gases escape and impinge upon a bucket rately, thereby giving more complete protection wheel l5 causing rotation of the wheel and the against loss of engine power due to formation of 25 direct connected compressor. The speed of the ice in the carburetor or other parts of the fuel turbine and compressor is controlled by the usual induction system. wastegate [6 located in a by-pass conduit H, the Another object of the invention is to provide a position of the wastegate determining the ex detector for detecting ice-forming conditions in haust back pressure applied to the turbine. a moving air stream which is simple, reliable, and V The wastegate I6 is connected to be rotatably quick acting. positioned by means of a reversible motor it! A further object is to provide a carburetor de which is connected to the wastegate through a icing control system which operates in a stable worm gear l9 and a meshing pinion 20. The manner and does not cause wide ?uctuation of motor l8 may form a part of an intake manifold carburetor intake air temperatures. pressure regulator system (not shown) respon Further objects and advantages of my inven sive to engine intake manifold pressure or some tion will become apparent as the following de other control pressure which acts to position the scription proceeds and the features of novelty wastegate I6 and thereby control the speed of the which characterize the invention will be pointed gas turbine and compressor so as to maintain out in particularity in the claims annexed to and 40 some desired pressure condition. The automatic forming a part of this speci?cation. control system may, for example, be of the type In the drawing, shown in Patent 2,376,143 Edwards et al. Fig. 1 is a somewhat schematic representation During certain conditions of ?ight, as when of a supercharged aircraft internal combustion passing through clouds or storm areas, ice may engine having a carburetor ‘dc-icing control sys 45 tend to form in the carburetor i‘lJ resulting in a tem constructed in accordance with the present clogging of the venturi l2 and a resulting mis invention. functioning of the fuel injection system causing Fig. 2 shows constructional details of the de a loss or failure of engine power. In order to tector forming a part of the present invention. prevent this, it is customary to provide some Fig. 3 is a side view of the detector shown in 50 means for heating the induction air so as to pre Fig. 2. - vent the formation of ice or to melt the ice if Referring to the drawing, I have shown a radial it has already started to form. One convenient aircraft internal combustion engine I of well way to increase the temperature of the carburetor known construction, the engine having a fuel intake air in a supercharged system is to recir intake manifold 2 and an exhaust manifold 3. culate a part of the compressor discharge air 2,464,047 3 4 through the compressor so as to increase the com between the contact arm 31 and the conduit 23 pression heating effect. For this purpose there is acts to bias the detector in a counterclockwise provided a by-pass conduit 2| interconnecting the direction to the vertical position shown in which discharge conduit 1 and the intake conduit 6, the the frame 26 engages a ?xed stop 40a. In this amount of recirculation being controlled by. a position the contact arm 31 engages the station valve 22 located in the by-pass conduit. No claim ary contact 39 as shown. is here made for this method of heating carbure As best shown in Fig. 1 of the drawing, the tor air since this forms the subject matter of ?exible lead 32 of the screen 3%] is connected to Patent 2,356,370 Allen. one side, for example, the negative side, of a In the arrangement of the Allen patent, supra, 10 direct current power supply indicated at 4|. the recirculating valve is controlled in accord This power supply may, for example, be the 24 ance with the output of a sensing element re volt D.-C. supply customarily available on air sponsive to carburetor temperature. Under some craft. The common lead 35 is connected to the conditions of ?ight, the system of the Allen patent positive side of the power supply, indicated by may not operate fast enough or accurately the lead 42, through a control switch 43. Thus enough to increase the carburetor intake temper it will be clear that whenever the control switch ature before a substantial amount of ice has been 43 is closed, a circuit is completed for energizing formed in the carburetor. the heater wires forming the screen 39, causing In accordance with the present invention, I local heating of the screen. This heating of provide a new and improved control system for the screen 36 prevents formation of ice thereon operating the recirculation valve 22 which ‘oper whenever the system is in operation. The lower ates more quickly and accurately and in a more screen 3| is normally unheated so that ice may stable manner than previously known arrange form thereon during certain atmospheric con; ments. ditions. When this'happens, an unbalance in Referring now to the details of my improved the drag forces applied to the screens 36 and l3| system, it will be noted that there is provided occurs, this unbalance being su?icient to over a by-pass conduit 23 associated with conduit 9, power the biasing force of the light tension spring through which a sample portion of the carburetor 40 and cause a clockwise rotation of the detector intake air is diverted by means of a scoop 23a whereupon contact arm 3,‘! .disengages contact ,39 extending into the conduit 9. Located within 30 and engages contact 38. ' " the conduit 23 is an ice detector unit indicated In order to provide means for operating the generally at 24. The detector unit comprises recirculation valve 22 in accordance with the a rotatable shaft 25 which extends through position of the detector unit 2-4, there is provided diametrically opposite holes in the conduit 23 in a reversible motor 44 which drives a valve shaft which the shaft is journaled. Mounted on the 35 45 connected to valve 212 through a worm gear shaft 25 within the conduit 23 is a circular frame 46 mounted on the motor shaft “meshing with a member 26 across which extend two central bars pinion 41 carried on the valve shaft. The motor 21 and 28 forming with the outer edges of the 44, which may be a split series type of well frame 26 two semi-circular openings 29a and 29b. known construction, has forward and reverse The openings 29a and 2% are covered by screens 40 ?eld connections 48 and .49 and an armature 3!) and 3| formed by interweaving insulated connection 50. The ‘armature connection 50 is electrical heating wires. A ?exible lead 32 is connected to the positive power supply 1ine..4,_2 connected to one end of the wire forming screen through a potentiometer 5| and the control 30 and a ?exible lead 33 is connected to one end switch 43. The potentiometer 5| has a slider of the wire forming screen 3|. The other ends 4.5 52 mounted on the extension of the valve shat-t of the wires forming screens 35! and 3| have a 45 and it is arranged in such a vw-ay that as the common junction 34 connected to a ?exible lead motor moves the valve 22 toward the open posi .35. The leads 32, 33 and 35 are threaded through tion, the potentiometer acts to increase the re a hollow extension ‘35 of the shaft 25 as shown. sistance in the motor armature circuit. The frame 26 is made nearly as large as the 50 It will be assumed that when ‘the ‘motor con. internal diameter of the conduit 23 so that when nection 48 is connected to the power supply the frame is in the vertical position shown, the line 4|, the motor runs in ,a direction to close screens 30 and 3| cover most of the internal valve 22, and when the connection 439 is COB? cross-sectional area of the conduit 23 through nected to the power supply line 4|, the motor which the sample portion of the carburetor in runs in a direction to open the valve. The motor take air passes. It will be noted that the screens terminal 48 is arranged to be connected to the 30 and 3| are offset relative to the rotational supply line 4| through a circuit which ‘may be axis of the shaft 25, and due to the drag forces traced as follows: Connection 48, a wire 153, ,a of the air passing through the screens, there normally closed limit switch 54, a wire 55, nor-1 are torques produced associated with screens 30 60 mally open switch contacts 56, a wire 51, contact and 3| which tend to. rotate the shaft 25 in 39, contact arm 31;, ?exible lead 58 to power opposite directions. Preferably the screens 39 supply line 4|. The connection .49 of ‘the motor and 3| are of equal area and are located equi 44 is arranged to be connected to the power distant from the rotational axis of the shaft 25 supply lead 4| through a circuit which may be so that these torques tend to counteract and traced as follows: Connection 49, a wire 59, a balance each other in the absence of a factor normally closed interlock switch 5-0,, a wire 16.1,, tending to increase the air drag resistance of a normally closed limit switch 62, a wire $3, one of the screens such as may be caused by the contact 33, contact arm 3?, and ?exible lead 58 formation of ice thereon as will subsequently t0 the power supply vline 4|. be more fully described. _ The normally open switch contacts 56 are ar Rigidly connected to the rotatable shaft 25 of ranged to be closed by a bridging member t4; the detector is an electrically conducting contact which is fastened to and positioned by a thermal arm 3?, the outer end of which is adapted selec bellows 65. The thermal bellows ,65, which may tively to engage relatively ?xed spaced contacts be a well known liquid ?lled type,’ has connected; 38 and 39. A light tension spring :40 extending 75 thereto a temegratilre bulb 56 which extends into 125465504"? 5 . 6 the conduit 8 so as to be affected by the temper normal position more quickly than would other“ ature of the intake air supplied to the carburetor wise be the case. In order to accomplish this, I H). The arrangement is such that when the provide a circuit arrangement which causes the carburetor intake air reaches a predetermined lower screen 3| to become electrically heated value, such as, for example, 50 degrees F., the whenever the detector 24 is rotated to the clock bellows 65 expands moving the bridging arm 64 wise, heat-increase position. When the detector downwardly and closing the contacts 56. is rotated to the clockwise position, an energizing The limit switches 54 and B2 are connected circuit to heat the lower screen 3| is completed in the close valve and open valve circuits of the which may be traced as follows: Power supply motor 44 and function to prevent overtravel of 10 line 42, switch 43, lead 35, the wires forming the valve 22. The switch 62 is opened by an oper screen 3|, lead 33, an adjustable rheostat 69, wire ating member 61 carried on valve shaft 45 when 53, switch contact 38, contact arm 31, lead 58, to the valve reaches the open position and the the power supply line 4|. Because of the fact switch 54 is opened by the member 61 when the that the screen 3| becomes heated after the de valve reaches the closed position. 15 tector moves to the clockwise heat-increase posi The switch 6|] acts as an additional interlock tion, the ice previously formed thereon melts off in the valve opening motor circuit for preventing more quickly than would otherwise be the case, operation of the valve 22 in the opening direction permitting the tension spring 40 to restore the when the wastegate IE is moved to the fully closed detector to the counterclockwise heat-decrease position by the motor l8. For this purpose there 20 position. In this manner the arrival of heat to is provided a cam 68 mounted on the drive shaft the carburetor is anticipated and any tendency for the wastegate Hi, the cam 68 acting to open to overshoot is thereby reduced. switch 5| when the wastegate approaches the If the ?rst cycle of operation of the detector 24 closed position. The purpose of this additional does not result in su?icient opening of the recircu interlock switch 60 will become apparent as the 25 lation valve 22 and increase in intake air tempera description proceeds. ture to stop formation of ice, the cycle will be The operation of my improved carburetor de repeated, resulting in a further opening of the icing control system will now be described. valve 22. The amount which the valve 22 is To place the system in operation, the switch opened during each cycle of detector operation 43 is closed. Normally the detector unit 24 oc- - depends on the length of the detector cycle cupies the position shown in which the contact which may be controlled by adjusting the rheo arm 31 engages the stationary contact 39. It stat 69 which determines the amount of heating will be assumed that this has caused motor 44 in the lower screen 3|. to drive the valve 22 in the closing direction until When the detector 24 returns to the normal it reaches a closed position shown in which the heat-decrease position, the motor 44 may not im member 6? opens the limit switch 54 thereby de mediately drive the recirculating valve 22 back energizing the motor. towards the closed position due to the fact that It will now be assumed that ?ight conditions the switch contacts 56 may still be open. The are changed suddenly so that the carburetor in contacts 56 are not closed by the bridging mem~ take air ?owing through the conduit 9 becomes ber 64 until the carburetor intake temperature su?iciently cold to cause formation of ice. Since reaches a predetermined value which causes the a part of the carburetor intake air is diverted bellows 65 to expand and lower the bridging mem through the conduit 23, a formation of ice will ber 64 into engagement with the contacts 56. begin on the lower screen 3|. During this time The potentiometer 5| slows down the speed of no ice will form on the upper screen 30 because ‘I operation of the motor 44 as the valve 22 ap of the fact that the electric heating wires com proaches the open position by progressively in prising the screen 3|) are electrically heated. The serting resistance in the motor armature cir formation of ice on the lower screen 3| increases cuit. In this way the increments of valve open_ the resistance to the ?ow of air therethrough, ing motion are automatically decreased as the whereby a torque unbalance occurs which causes valve opens, thus further anticipating the arrival the frame 26 and the shaft 25 to rotate clockwise of heat at the carburetor and stabilizing the until the contact arm 31 moves away from con control system. tact 39 and engages contact 38. The engagement It may sometimes occur that the detector calls of the contact arm 31 and the stationary contact for an increase in carburetor heat at the same 38 completes the energizing circuit which causes time the intake manifold pressure regulator calls the motor 44 to drive the recirculation valve 22 for an increase in manifold pressure. This con in a direction to open the by-pass conduit 2|. dition may lead to an unstable hunting condi The opening of the by-pass conduit 2| permits a tion because of the fact that a closure of the portion of the compressor discharge air to be re wastegate l6 and a resulting increase in output circulated through the compressor thereby in 60 of compressor 4 is to a certain extent offset by creasing the temperature of the compressor dis an opening of the recirculation valve 22. As a charge air supplied to the carburetor intake con result, the wastegate l6 may close completely and duit 9. the valve 22 may open completely before counter If no additional control is provided, the in acting control effects can cause a reversal of valve crease in temperature of the carburetor intake 65 air will eventually melt the ice on the screen 3| action to take place. To reduce the magnitude and permit the tension spring 40 to return the of any hunting or overshooting under such con detector to the normal position in which a circuit ditions, the interlock switch 60 is provided which is established to close the recirculation valve 22. prevents the valve 22 from opening whenever the However, due to the fact that there is a time lag 70 wastegate l6 approaches the closed position. between the operation of the detector 24 and the This action insures that the intake manifold increase in carburetor temperature, the system pressure regulator has operated in a direction to may tend to hunt and become unstable. In order reopen the wastegate f6 before the recirculation to prevent such hunting, I provide an arrange valve 22 is permitted to open to increase ment which acts to restore the detector to the 76 buretor heat. 7 '8 ‘Under some conditions it may be desirable to digit during non-icing conditions, said biasing have the detector operate semewhat in advance means yielding to permit rotation of said detector: of reduction of air temperature to a point where away from said normal position when the flow ice forms elsewhere in the fuel induction system. tbreush said screen is impeded by formation of For this purpose a venturi Till is placed in the ice thereon. conduit 255 on the upstream side of the detector. 2,. Apparatus for preventing the formation of rIT-his venturi will cause a reduction in temperature ice in the carburetor of an internal combustion of the air impinging on the detector so that ice engine to which intake air is supplied compris will tend to form on the lower detector screen ing a conduit through which at least a portion advance of formation of ice elsewhere in the fuel 10 9:? Said. intake air is directed, an ice detector r9. induction system. This arrangement insures tatably mounted in said conduit comprising a that the control system will have adequate time pair of screens ‘mounted on opposite sides of the to increase the carburetor intake temperature rotation axis of said detector and disposed in the before a dangerous amount of ice forms. path of air flow through said conduit, and meansv The formation of ice in an engine fuel induc 15 for locally heating one of said screens to prevent tion system depends not only upon air intake the formation of ice thereon during icing condi temperature but also upon air , and tions causing the formation of ice on the other other factors. Therefore, my system, which of said screens whereby a torque is developed dure operates in response to actual formation of ice, ing icing conditions causing rotation of said dee is much more reliable and accurate than previous 20 hectoraway from a normal position. systems which respond only to air temperature 3. In a system for preventing the formation of since ice or may not form at ‘a given tem ice in the carburetor of an internal combustion perature, depending on humidity and other fac engine to which intake air is supplied by heating tors. Because of its accuracy and reliability my means controlled by a reversible motor for vary. system permits safe engine operation at carbure ing the temperature of said intake air the com tor intake temperatures relatively close to the bination comprising an ice detector ‘having a pair freezing point whereby detonation is avoided and of rotatably mounted screens mounted on oppo combustion efficiency is improved. Also, because site sides of the rotational axis thereof and dis- it operates in a stable manner, excessive ?uctua posed in the path of flow of said intake air, tion of carburetor intake air temperature is pre 30 switching means operable by said detector be Vented. tween heat-increase and heat-decrease positions It will be understood that my carburetor de for controlling said motor, said detector normallyv icing control system is not limited in application positioning said switching means in the heat-de to the illustrated system in which the carburetor crease position, and means for locally heating one intake air heating is provided by recirculating . of said screens to prevent formation of ice there varying amounts of air through a . on during icing conditions causing formation of As will be clear to those skilled in the art, other ice on the other of said screens whereby a torque air heating systems may be used, the only re is ‘developed during said icing conditions rotat quirement being that some means be provided ing said detector to position said switching means for adjusting the amount of heating which can inthe heat-increase position. be controlled by operation of the detector 24. .4. In a system for preventing the formation It will also be clear to those skilled in the of ice in the carburetor of an internal combus art that the detector 213 may be used to operate tion engine to which intake air is supplied andv an indicator either with or \without automatic heating means controlled by a reversible ‘motor carburetor heat control. While the detector is r are provided for varying the temperature of said especially useful in detecting ice-forming condi intake air the combination comprising an ice ti 11s in an engine fuel induction system, it may detector having a pair of rotatably mounted be used wherever indication or control of ice— screens mounted on opposite sides of the rota, forming conditions in a moving air stream is de tion-al axis thereof and disposed in the path of sired. For example, the detector may be mounted» ?ow of said intake air, switching means operable in the slip stream and used to indicate icing by said detector between heat-increase and heat cond he that would cause formation of ice on decrease positions for controlling said motor, said aircra. sings. In such a case, the detector may detector normally positioning said switching also control wing de-icer apparatus. means in the heat-decrease position, and means, Whiie I have shown and described particular for locally heating one of said screens to prevent embodiments of my invention, it will occur to formation of ice thereon during icing conditions those skilled in the art that various changes and causing formation of ice on the other of said modi?cations may be made without departing screens whereby a torque is developed during from my invention, and I therefore aim in the said icing conditions rotating said detector to po appended claims to cover all such changes and modi?cations as fall within the true spirit and sition said switching means in the heat increase scope of my invention. position, and means for locally heating said other What I claim as new and desire to secure by screen only when said switching means is in said Letters Patent of the United States is: heat-increase position to cause said detector to 1. Apparatus for preventing the formation of return to the normal heat-decrease position in, ice in the carburetor of an internal combustion advance of the arrival of su?icient heat from said, engine to which intake air is supplied comprising heating means to melt the ice on said other screen a conduit through which at least a portion of said thereby preventing substantial overshooting of intake air is directed, an ice detector rotatably the control system. mounted in said conduit and disposed in the path 5,. In a system for preventing the formation of of air ?ow therethrough, said detector comprise ice in the carburetor of an internal combustion ing a screen offset from the rotational axis of said engine to which intake air is supplied and heat detector, and means for biasing said detector to ing means controlled by a reversible motor are a normal position in which said screen extends provided for varying the temperature of said across the path of air ?owing through said con! 7.5 intake air the combination comprising an ice. (1% 2,404,047 10 tector having a pair of rotatably mounted screens being mounted relative to the rotational axis of mounted on opposite sides of the rotational axis said member so that the drag force of said air thereof and disposed in the path of flow of said stream ?owing through said screens produces intake air, switching means operable by said de torques tending to rotate said member in oppo tector between heat-increase and heat-decrease site directions, said torques being approximately positions for controlling said motor, said detector balanced when said screens are free of ice, and normally positioning said switching means in the means for heating one of said screens to prevent heat-decrease position, means for locally heating formation of ice thereon whereby upon formation one of said screens to prevent formation of ice of ice on the other of said screens the torque thereon during icing conditions causing forma 10 produced by said other screen predominates due tion of ice on the other of said screens whereby to the increased drag in said air stream causing a torque is developed during said icing condi rotation of said member thereby providing a tions rotating said detector to position said quick acting detection of icing conditions in said switching means in the heat-increase position, air stream. 1 and interlocking means actuated in accordance 8. A detector for detecting icing conditions in with the temperature of said intake air for pre a moving :air stream comprising a rotatable mem venting operation of said motor in the heat-de ber adapted to be positioned in said air stream, creasing direction until said intake temperature said member carrying a pair of screens olfset from reaches a predetermined temperature. the rotational axis of said member on opposite 6. A detector for detecting icing conditions in 20 sides thereof, one of said screens comprising in a moving air stream comprising a rotatable mem terwoven electric heating wires and means for ber carrying a screen adapted to be disposed in conducting electric current to said heating wires the path of said air stream, said screen being po to cause heating thereof. sitioned relative to rotational axis of said mem- ' THOMAS E. LARKIN. ber so that the drag force of said air stream flow ing through said screen tends to rotate said mem REFERENCES CITED ber away from a normal position, biasing means The following references are of record in the acting on said member to maintain it in said ?le of this patent: normal position when said screen is clear of ice, said biasing means yielding to permit rotation of 30 UNITED STATES PATENTS said member when said drag force increases due Number Name Date to increased resistance of said screen caused by 2,208,689 Sulzman ______July 23, 1940 formation of ice thereon. 2,338,574 Cunningham ______Jan. 4, 1944 7. A detector for detecting icing conditions in 2,356,370 Allen ______Aug. 22, 1944 a moving air stream comprising a rotatable mem 35 2,368,642 Crago ______Feb. 6, 1945 ber carrying a pair of screens adapted to be dis 2,382,365 Carssow ______Aug. 14, 1945 posed in the path of said air stream, said screens