US2664762A - Jet engine throttle control - Google Patents

Description

Jan. 5, 1954 w. B. MoRRls 2,664,762

JET ENGINE THROTTLE CONTROL Filed Allg. 5, 1951 2 Sheets-Sheet l Jlrl- 5, 1954 w. B. MORRIS I 2,664,762

JET ENGINE THROTTLE CONTROL Filed Aug. 3, 1951 2 Sheets-Sheet 2 Patented Jan. 5., 1954 tijd JET ENGINE THROTTLE CONTROL Willis B. Morris, Hawthorne, Calif., assigner to Northrop Aircraft, Inc., Hawthorne, Calif., a. corporation of California Application August 3, 1951, Serial No. 240,175

(Cl. i4-565) 2 Claims.

My invention relates to turbo-jet engine controls for airplanes, and more particularly to the pilots throttle controls where the turbo-jet engines are equipped with afterburners.

The term afterburner is used herein as meaning any means for admitting fuel to a jet engine to be burned in the jet gas after it has passed the turbine wheel of the engine. Such additional fuel is ignited by the heat of the jet gas, and adds substantial thrust to the iet. However, the fuel economy is relatively poor, and afterburning is usually resorted to only on takeoiis or to provide extra power in emergencies.

In the usual jet engine installation Where the engine is equipped with an afterburner, the throttle shaft of the engine controlling fuel admission thereto, has a minimum engine R. P. M. position, and a maximum R. P. M. position. It is required that fuel be admitted to the afterburner after the engine has reached a minimum of 90% R. P. M. It is usual for the throttle shaft to rotate beyond maximum R. P. M. position, to a position where fuel is also admitted to the afterburner.

A throttle arm is positioned for manual operation by the pilot of the airplane and is connected to rotate over a sector having positions corresponding to the minimum R. P. M., maximum R. P. M., and afterburner on, positions, with a detent type of retard at the maximum R. P. M. position, so that the pilot will feel the retard but can overcome the retard to move the throttle arm freely thereafter into afterburning position. lt has been found however, that such types of retards positioned at the maximum R. P. M. position are often overridden in the normal control of the jet engine R. P. M. by the pilot, and fuel accidentally admitted to the afterburner when not desired.

Por example, the throttle arm can be moved by the pilot to maximum R. P. M. position before the engine actually reaches even 90% of maximum R. P. M. and if, under these circumstances, such as might occur' when accelerating after a balked landing, fuel were to be admitted to the afterburner, the result might well be disastrous because the afterburner fuel would not burn properly.

lt is an object of the present invention to provide, in a jet engine throttle control system in an airplane, means for preventing accidental admission of fuel to an afterburner in said engine.

lt is another object of the present invention to provide, in a jet engine throttle system, a firm indication to the pilot of the airplane that 2 maximum R. P. M. position of the throttle has been reached.

It is still another object of the invention to provide means, in a jet engine throttle control, for imparting a forced time delay between maximum R. P. M. position and the position at which fuel is admitted to the afterburner. Such a time delay permits the engine to attain full R..P. M. before the fuel is admitted to the afterburner.

-Other objects will become apparent as the description of the invention progresses.

Briefly the present invention in one form comn prises a throttle arm operable by the pilot of an airplane to control a turbo-jet engine in the airplane between the minimum R. P. M. and the maximum R. P. M. of the engine, and movable beyond the maximum R. P. M. position to admit fuel to an afterburner in the engine. At the maximum R. P. M. position the throttle arm engages an inertia type governor, so that as the throttle arm is moved by the pilot toward the afterburning position, the force by which the throttle arm can be moved is increased over a remaining portion of the arc prior to reaching the position at which the afterburner fuel is turned on, and the pilot must, therefore, before the afterburner can be turned on, exert a steady and greatly increased force to cause the arm to pass through the sector position over which the governor is engaged. Short of structural failure, it is impossible for the pilot to rapidly push the throttle arm past maximum R. P. M. position, as the governor acts as a solid stop under these conditions until the arm speed is reduced to a speed permitted by the governor under the force applied. At any speed the inertia of the gov` ernor makes an unusually large force necessary for movement of the arm, as compared to the force required to move the throttle arm between minimum and maximum R. P. M. positions. Thus a time factor is introduced between the maximum R. P. M. position and the position Where fuel is admitted to the afterburner, this time delay being sufficient for the engine to reach a safe R. P. M. before the afterburner is turned on.

My invention will be more fully understood by reference to the drawings in which:

Figure l is a perspective View of a pilots throttle arm, along with a diagram showing con= nection to a turbo-jet engine driving an airplane.

Figures 2, 3 and 4 are side views of the governor shown in Figure l in various operational positions.

Referring first to Figure l, an airplane i (only 3 partially shown) is provided with a turbo-jet engine 2, the latter being mounted in the airplane l to provide an air inlet duct 3, and a tailpipe shroud t. Turno-jet engines, as at present used in airplanes, comprise a compressor portion 2a receiving air from inlet duct 3, a plurality of combustion chambers 2h in which fuel is burned in the air comingv from compressorsection 2c, and a turbine section 2c in which a turbine Wheel (not shown) is rotated by the heated compressed air.

the airplane as a jet through a tailpipe section 2d inside of the tailpipe shroud "ci to'provide-the' pro# pulsive thrust for the airplane.

As a substantial percentage or oxygen still remains in the turbine or the engine, it has become customary, particularly in military airplanes, to releas'eiuel into the jet for burningzthis residual oxygen.

rihis may 'ce done for example, by the useiofaring type afterhurner 5 disposed in the tailpipe seotionjust rearwardly ci the turbine wheel. Fuel releasedthrough fuel eed holes' inthe. afterburner ring ii immediately ignitediby thev hot jet gas and burns, thereby providing a substantial vadditional propulsive thrust for` the airplane.

However, as thefuel economy of such an'afterburner is very low, theraiteiourner' is only used when extraordinary thrust is required such 'as for taire-offs, on short eldsiror, inthecase of mili.- tary airplanesy for military power in' einergencies, particularly incombat.

As the aiterburner thrust is highestwii-en the jetengine is running at full R. P; lvl., it-.is customary for a throttle shaft i@ on the jetengine 2 to be made rotatable to control the fuel supply to. the combustion chambers 'ib from.: zero` to maximum, andv then to he further.v rotatable to admitfuel `to the aiterhurner A. pilots throttle. arm lo is. positioned in the airplane to be manually moved over anarc in an arm housing i5, the arm 'labeingconnectedto the throttle shaft it throughs. throttle arm pulley it, throttle cables il a throttle lever i3 attached to the throttle shaft lil on the engine 2,

Grdinarily, a substantial angle of.' rotation of the throttle arm ifiiszused to move the throttle from ori or Zero engine R. P. M. position A, to engineR. P. M. position B, at'which point a spring detent device is normally installed, to he felt overridden by Vthe vpilot incase vhe desires to more the throttle arm lll beyond the maximum R. P. M. position Iinto afterburnerl on position C. This latter position is. reached by moving the throttle arm lf?!- over a smaller angle X to the end of the control sector, at which point fuel is admitted to the afterburner.

[is a .spring detentsuch 'as just described offer only a momentary retard to the movement oi the throttle arm, the nature of a signal, it is readily possible ior the pilot to move the -arm iii past the detent into afterburning position before realizing what he has done, and it is Vpossible .for the aiterburner to be turned on before the engine has reached the 99% maximum R. P. M. required for proper aiterhurner operation. This is particularly apt to occur, and has occurred with damage to the engine, wheniull acceleration is desired from idling engine speed ior'exarnple.

To insure that proper engine speed is attained before the aiterhurner` can be turned on, the present invention utiliaesa governor which'prevents the arm lil from being moved rapidly Vover the angle X between maximum R. P; M.. position The hot gases, after passing through the turbine section Ec are exhaustedvrearwardly orV hot gases passingf, through. l the" 4 B and afterburner on position C, and which forces the pilot to greatly increase the force necessary to move the throttle arm I, thus providing a time delay during which time the engine speed can catch up to throttle arm position.

One form this governor can Itake is shown in all the figures. A go ernor lever 2G is mounted on a pin 2l supported by a housing bracket 22 to have an arm portion extending upwardly in the path of a governor block 2e slidably attached to the side of the throttle arm ill. Block 213 is foreedtowardfthe axis of rotation oi arm l by block spring 25 and the block is limited in travel byffhloclt pins 'attached to arm ill and operating inslotsZi in block 2li. rihe end of arm portion liisprovided with acamming surface 28a sloping tovvardposition C.

Governor lever d extends below pin 2l in the formfof'a gear segment Sil. In engaging at all times a pinion 3l, mounted on a pinion shaft 3?. extended from bracket 22, governor lever 26 is urged `rearwardly by spring wound around pin El'andhaving one end engaging a tooth in gear segment 3Q, the other end engaging a stop pin against which gear sector normally rests; asbest shown in igure 2.

A. star wheel :is is attached to pinion 3l to he rotated with it, and the points of star wheel llil are shaped to engage an ese-apement are fi! in a balanced wobble weight l2 free to rotate on a weight pin i3 also supported by bracket 22.

The operation'oi the device at diierent positionsis'shown in Figures 2, 3 and 4.

ln Fig re 2, arm block 2t is shown in its lower position contactingarm portion 23 of the governorv lever` 2li. rThis Contact is at iull R. P. M. position B. In order for the throttle arm l@ to. oe moved past this position, sufficient force must he used by the pilot to rotate governor lever' 2Q. which in turn rotates pinion 3l and attached star wheel fle. Star wheel di? cannot rotate without Wobbling wobble weight F22, which due to the inertia ofrepetitive direction change, prevents the pilot from moving the throttle it freely. between maximum RJ. P. M. position B the afterburner position C. The force must be continuously applied until a position is reached just prior to the aiterburncr on position C. At that point, Contact between arm block 2f? and arm523 of governor lever 2l? is lost, as shown in Figure 3, and the governor lever 2d is free to return to its original position under the urge or" spring 33, leaving the throttle arm iii iree to be moved slightly farther into afterburner on posil tion C.

When it is desired that the aiterburner be turned-oi and the throttle arm E4 returned to maximum R. P. M. position B, free movement of the arm ll is provided for, as arm block 2d on the return movement, hits the angular camming surface 23a on the end of the arm portion 23 of the lever Eil, andrises in slots 2l to pass over the arm portion 23. Arm block 2li then returns to its original position under the urge of clock spring 25.. The throttle arm lil is then hack in the engine R; P. M. range of the throttle arm ill.

It is to be noted that while the throttle arm ifi can be moved at various speeds through the range Where the force producing assembly is operating, that Ythe' force required to move the arm increases as the arm speed is increased, and that this force must be continuously applied over the entire range where the force producing assembly is in operation.

Under .normal circumstances, when the pilot wishes to move the arm i4 rapidly into the maximum R. P. M. position B, only a relatively light force is required. However, when Contact is made between the moving arm block 24 and the arm portion 23 of the governor lever, a solid stop effect is produced for that force. -Continued progress of the throttle arm I4 past the maximum R. P. M. position requires the continued application of a much higher force' by the pilot, a force that must be deliberately and consciously exerted and maintained over a substantial arc of the throttle arm between maximum R. P. M. sector position and afterburner, and a time delay is important to the movement of the throttle arm.

Thus the present invention makes it practically impossible for a pilot to accidentally move his throttle control arm into afterburning position, and prevents such motion until the engine has had time to accelerate to at least 90% full R. P. M.

While in order to comply with the statute, the invention has been described in language more or less specific asv to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise the preferred form of putting the invention into effect, and the invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

What is claimed is:

1. A pilots throttle assembly for controlling a jet engine propelling an airplane, when said jet engine is equipped with an afterburner which comprises a throttle shaft on said engine rotatable from minimum to maximum R. P. M. positions and beyond maximum R. P. M. position to admit fuel to said afterburner, a throttle arm shaft, a throttle arm mounted on said shaft and movable over a predetermined arc by the pilot of said airplane, means connecting said arm shaft to rotate said throttle shaft, said arm arc including a minimum R. P. M. position adjacent one end thereof, an afterburner fuel admission position adjacent the other end thereof, and a maximum R. P. M. position intermediate said minimum R. P. M. position and said afterburner fuel admission position, said arm being free to move between said maximum and minimum R. P. M. positions at the will of the pilot, a contact block slidably mounted on said arm, a spring urging said block to a lower position, a lever having one end thereof engageable with said contact block when said block is at said lower position and at said maximum R. P. M. position to move said lever as said throttle arm is progressed over a substantial distance toward said afterburner fuel admission position, governor means connected to be actuated by movement of said lever, said block disengaging from said lever as said afterburner fuel admission position is approached, means for returning said lever to its original position after block disengagement, and a camming surface on the end of said lever originally engaged by said block, over which said block rides when said throttle arm is returned to maximum R. P. M. position.

2. Apparatus in accordance with claim 1 wherein said governor means includes a gear sector on the other end of said lever, a gear pinion engaged with said sector, a star wheel connected to said pinion, a weight pivoted adjacent said star wheel, said weight having an escapement area positioned to be engaged by said star wheel.

WILLIS B. MORRIS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,358,769 Mardis Nov. 16, 1920 1,473,971 Petersen Nov. 13, 1923 1,998,362 Dodson Apr. 16, 1935 2,495,127 Oppel Jan. 17, 1950 FOREIGN PATENTS Number Country Date 475,164 Great Britain Nov. 12, 1937 626,297 Great Britain July 13, 1949

Images