Aircraft autothrottle system

The throttle of an aircraft can be alternatively controlled either by a flight control computer or by the manual control of the pilot. A clutch is installed between the throttle control lever and a control input to the flight control computer which in the autothrottle mode of operation is engaged to enable control of the throttle by the flight control computer with the control lever being positioned in accordance with such control. When manual takeover of the throttle control is desired, a switch is actuated by the pilot which operates to disengage the clutch and thereby disconnects the control output of the computer from the lever so that only manual control is provided. A unique clutch mechanism is employed which utilizes a pair of locking wedges which operate in conjunction with a pair of rollers. The wedges and rollers are driven into engagement with each other by a solenoid, the opposing plates of the clutch being held in locking engagement through the intermediary provided by the wedges and rollers. Emergency "bump" disconnection of the clutch is effected by a pair of microswitches against which a cantilevered spring portion of the control lever abuts when the lever is "bumped", such switches operating to de-energize the solenoid and disengage the clutch.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to aircraft autothrottle systems and more 
particularly to a clutch mechanism for enabling the rapid connection and 
disconnection of the automatic throttle control to and from the throttle 
control lever. 
2. Description of the Related Art 
Throttle control levers or quadrants are generally provided in aircraft for 
use by the pilot in manually controlling the engine power as well as 
attitude control mechanisms such as the aircraft flaps. In more 
sophisticated aircraft, such throttle control is integrated with the 
flight control system and under normal flight conditions controlled 
thereby. It is essential, however, that in the event of a malfunction or 
other emergency situation that the pilot be able to instantly and 
positively take over control of the throttle. In such takeover situations, 
the pilot must be able to fully take over the control of the aircraft from 
the flight control system and when so desired instantly restore such 
automatic control. In implementing such instant switchover of operation, 
it is essential that the manual control lever be coupled to the flight 
control system when the system is in automatic operation so that such 
lever assumes and maintains the proper setting for any future manual 
takeover. 
Prior art autothrottle systems are described in U.S. Pat. No. 3,599,510 
issued Aug. 17, 1971 to Scott and U.S. Pat. No. 4,651,954 issued Mar. 24, 
1987 to Miller. Miller employs a D.C. stepping motor in controlling the 
throttle system which is coupled to the throttle actuator through a drum 
type friction clutch pack. In Scott, the clutch between the control lever 
and the automatic control system employs a clutch having friction shoes. 
Neither of these references suggests a clutch mechanism employing a 
combination of wedge and roller elements such as that of applicant's 
system which is of simple and reliable construction and which provides 
positive clutch engagement and disengagement in response to a switch 
actuated solenoid. 
SUMMARY OF THE INVENTION 
The present invention provides a system in which automatic operation of the 
throttle or manual operation thereof can alternatively be obtained in a 
simple and rapid manner by means of a unique clutch mechanism. This clutch 
mechanism is formed by a pair of wedge members which operate in 
conjunction with a pair of locking rollers to form a positive lock between 
two opposing plates which form the couplings for the units to be 
interconnected by the clutch. To interconnect the clutch plates, a 
solenoid is actuated, this solenoid having a toggle mechanism which drives 
the wedges against the rollers to effect a positive lock between the 
wedges, rollers and the two clutch plates, against which the wedges and 
rollers are respectively driven. When the solenoid is deactuated, the 
solenoid toggle is returned to its initial position by spring action, 
releasing the pressure on the wedges thereby releasing the wedges, rollers 
and plates from their interlocked relationship. 
The solenoid is manually actuated and deactuated by means of a switch on 
the control lever and in emergencies can be deactuated by sharp "bump" 
movement of the lever which causes the lever to itself actuate a 
microswitch which controls the solenoid. 
It is therefore an object of this invention to facilitate the switchover 
between manual and automatic control of an aircraft throttle. 
It is a further object of this invention to provide an improved clutch 
mechanism for use in the throttle control system of an aircraft. 
Other objects of the invention will become apparent from the following 
description in connection with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to FIG. 1, the system of the invention is illustrated in a 
functional block diagram. In initiating the manual mode of operation, the 
pilot(manual input control 10) momentarily actuates switch 15 which 
operates to deactuate solenoid 16 which in turn operates to release clutch 
17 to disengage throttle control lever 11 from drive gears 23. Drive gears 
23 receive the automatic flight control input from flight control computer 
30 through servo amplifier 32 and servo drive motor 22, and thus this 
automatic control input is disconnected with clutch 17 disengaged during 
the manual control mode of operation. 
During the manual mode of operation, the mechanical input to throttle 
control lever 11 provided by the pilot is fed directly to the control for 
the throttle with the output of the flight control computer being 
disconnected from the throttle control lever, as described above. 
When automatic throttle control is desired, the pilot momentarily actuates 
switch 15 which on such actuation operates to activate solenoid 16. In its 
activated condition, solenoid 16 operates to cause clutch 17 to engage 
thereby connecting the output of drive gears 23 to the throttle control 
lever. Drive gears 23 are driven in response to a throttle control signal 
from flight control computer 30. 
The throttle control signal is fed from flight control computer 30 to 
summing device 31. A signal representing the position of throttle control 
lever 11, as generated by position transducer 33, which includes gear 
train 18 and servo control 19 (See FIG. 3) is fed to summing device 31 for 
comparison with the throttle control signal from the computer. The output 
of summing device 31 which is an "error" signal representing the 
differential between the inputs fed thereto is fed to servo amplifier 32 
which provides a drive signal for servo drive motor 22. The mechanical 
output of motor 22 drives gears 23 which in turn are connected to the 
throttle control lever 11 through clutch 17. The position of the throttle 
control lever and the control of the throttle is thus effected in response 
to the throttle control signal generated in flight control computer 30. 
Referring now to FIG. 2, the operation of the system of the invention in 
its manual mode is illustrated. To obtain such manual operation the pilot 
must first momentarily actuate switch 15, which is a type of switch which 
closes and opens successively in response to successive actuations. 
Assuming the clutch had previously been engaged and the flight control 
computer in command, such an actuation of switch 15 will disengage clutch 
17 by virtue of the actuation of solenoid 16 to allow plate 37 to move 
independently of plate 36. Thus, the output of servo drive motor 22 will 
no longer have any effect in driving lever 11, and the lever will 
independently control the throttle in response to positioning by the 
pilot. 
Referring now to FIG. 3, the operation of the system in its automatic 
control mode is illustrated. To initiate automatic operation, the pilot 
momentarily actuates switch 15. When this occurs, clutch 17 is engaged by 
virtue of the actuation of solenoid 16 connecting plate 36 to plate 37. 
Thus, the output of servo drive motor 22, which as explained in connection 
with FIG. 1, is a function of the output of the flight control computer 
30, controls the position of lever 11 through drive gears 23. A signal in 
accordance with the throttle position is generated by position transducer 
33 which comprises gear train 18 connected to the throttle and servo 
control 19 which is driven by the gear train. Servo control 19 may 
comprise potentiometers. The operation of the position transducer is 
conjunction with the flight control computer has already been described in 
connection with FIG. 1. 
Referring now to FIGS. 4A and 4B, the operation of the device of the 
invention in response to a "bump" or sharp actuation of the control lever 
by pilot is illustrated. This type of operation would be used in an 
emergency situation where the pilot needs to rapidly take over the 
throttle from the flight control computer. Throttle control lever 11 has a 
portion thereof 11a which is a stiff cantilevered spring. Positioned 
adjacent to spring portion 11a are a pair of microswitches 40 and 41. 
Switch 40 when activated is normally open while switch 41 when unactuated 
is normally closed. With lever portion 11a in its neutral fully upright 
position, switch 41 is actuated so that it is in its "open" position while 
switch 40 is not actuated so that it is also "open". Switches 40 and 41 
are connected in parallel with each other and in parallel with the 
actuation switch 15 for solenoid 16 so that when either switch is 
"closed," the solenoid is actuated. With the lever in its neutral, fully 
upright position, switch 40 is not actuated ("open") and switch 41 is 
actuated ("open") providing no actuation of the solenoid. With a forward 
"bump" by the pilot, as shown in FIG. 4A, both switches will be 
unactuated, an actuation of the solenoid being provided through normally 
closed switch 41. With a rearward "bump" by the pilot, as shown in FIG. 
4B, both switches will be actuated, the solenoid being actuated by 
normally open switch 40. In an extreme emergency situation where the pilot 
is unable to disconnect the automatic control either by manually actuating 
switch 15 or by the "bump" operation just described, the clutch will still 
release in response to forces greater than the bump disconnect force which 
forces are within the normal capability of the pilot. 
Referring now to FIGS. 5, 5A, and 5B, the clutch mechanism of the preferred 
embodiment of the invention is illustrated. Solenoid 16 has an actuator 
arm 16a which is drawn downwardly when the solenoid is actuated. As can 
best be seen in FIG. 5A, arm 16a is supported for pivotal motion in 
bracket 16b which is attached to the top of the solenoid and is pivotally 
supported in U-shaped bracket 16c which is also attached to the top of the 
solenoid. Connected to arm 16a is a shaft 42 which in turn is connected to 
toggle mechanism 44. This toggle mechanism has a top arm 44a, there being 
a pair of tab members 44b pivotally connected to the bottom end of this 
arm. Pivotally supported on each of tab members 44b is an arm member 44c 
having a wedge shaped end portion 44d. A cylindrical roller 46 is mounted 
adjacent to each of the wedge shaped end portions, such rollers being 
urged in the direction of the wedges by springs, as to be explained in 
connection with FIGS. 6A-6D. 
When solenoid 16 is actuated, its arm drives the top portion 44a of the 
toggle downwardly which in turn causes arm members 44c to be forced 
outwardly away from each other so that their wedge shaped ends drive 
against rollers 46. This forcing action locks rollers 46 against clutch 
plate 36 and the surfaces of arms 44c against clutch plate 37. When the 
solenoid is deactuated, arm 11a is driven upwardly by virtue of the action 
of a spring(not shown) in the solenoid mechanism. The toggle is thereby 
lifted upwardly which draws arms 44c inwardly to release the force on the 
rollers and thus releases the clutch. 
Referring now to FIGS. 6A and 6B, the operation of the clutch mechanism of 
the invention is illustrated. FIG. 6A shows the clutch in the disengaged 
condition. As can be seen, the arms 44c of the toggle mechanism are not 
being forced outwardly and do not drive against the rollers 46. FIG. 6B 
shows the clutch in the engaged condition with arms 44c being outwardly 
and with the wedges shaped ends of such arms forcing against rollers 46. 
While the invention has been described and illustrated in detail, it is to 
be clearly understood that this is intended by way of illustration and 
example only and is not to be taken by way of limitation, the scope of the 
invention being limited only by the terms of the following claims: