Sundstrand Corporation

Gary D Gillingham

Jeffrey D Metcalf

David J Lang

Teddy L Jones

Gary L Miles

Steven C Paul

John R Chapman

Jonathan E Beimborn

Craig G Milius

Eric Stoutenborough

The problem of providing a flight control panel actuation system, including asymmetry brakes, which will fit into aircraft wings having narrow supercritical air foil shapes, and yet provide a degree of safety with regard to preventing asymmetry which is as good or better than that provided by prior actuation systems is solved by an actuation system which positions an asymmetry brake inboard of an outermost flight control panel actuator within the aircraft wing. The asymmetry brake utilizes a jaw type clutch coupled to an electrical solenoid through a ball spline mechanism to provide significantly greater braking capacity in a given volume than other types of braking devices. The outermost control panel actuator includes an integral no-back to hold that actuator against further movement, should a driveline connection between the asymmetry brake and the actuator be severed. Where the actuation system includes multiple actuators, only one of the actuators is equipped with end of travel stops, therefore allowing the remaining actuators in the system to be physically smaller because they are not required to react loads incident with limiting end of travel. By making the other actuators in the system physically smaller, they are more readily fitted into supercritical wings.

Flap/slat actuation system for an aircraft

A compact ball screw type actuator having both load limiting capability above a pre-determined value and position holding capability at all load values above, below and at the pre-determined value is provided through use of a resettable force limiting assembly acting directly on an element of the ball screw, in conjunction with a friction drag device operating directly upon an input shaft operatively coupled through a crossed-helical gear train to the ball screw. The force limiter utilizes axial force on the ball screw above the pre-determined value for engaging clutch teeth to limit the force applied by the ball screw, or to provide the position holding function and for preventing backdriving of the actuator. For force levels at or below the pre-determined value, the input drag device provides the position holding function.

Compact actuator including resettable force limiting and anti-backdrive

Volume, weight and complexity difficulties in the fabrication of torque limiters are avoided in a construction including a housing (10), a shaft (20) journalled in the housing (10) and adapted to be connected to a source (22) of rotary power, and a rotary output (28) journalled in the housing (10). A ball ramp coupling (44) is disposed within the housing (10) and includes an axially movable drive element (46) coupled to the shaft (20), a driven element (42) coupled to the output (28), a spring (52) biasing the elements (42,46) towards each other, facing ramps (61,62) in the elements (42,46) at the interface of the elements and balls (64) in the ramps. A first set of teeth (72) is carried by the drive element (46) while a second set of teeth (82) is carried by the housing (10) and aligned with the first set of teeth (72). When resistance to rotation of the output ( 28) is encountered relative movement between the elements (42,46) will occur which in turn will cause the ball (64) to move the drive element (46) axially relative to the driven element (42) causing the teeth (72,82) to engage to halt further torque transmission between the input shaft (20) and the output (28).

Resettable pilot operated torque limiter

Overheating of hydraulic fluid in a hydraulic motor system subject to aiding loads can be avoided without paying a weight or volume penalty by providing a return port (64) adapted to be connected to the system return (22) in fluid communication with a cavity (46) within an hydraulic motor housing (32) that houses the swash plate (34). A pressure relief valve (62) is connected to the supply port (38) of the hydraulic motor (30) as well as to the return port (64) and is operative to open when the pressure at the supply port (38) increases as a result of an aiding load so as to allow recirculation of hydraulic fluid through the motor (30). By placing the swash plate cavity (46) in the recirculation line, increased heat sink capacity is added to the system without increasing weight or volume.

Swash plate type pump with flow path through cavity containing swash

In order to lock a drive system from operation during maintenance procedures, while providing a positive mechanical engagement regardless of index position, a locking mechanism includes a sector gear associated with a rotatably mounted shaft. The rotatably mounted shaft and the sector gear have a common axis of rotation which extends generally tangentially of a system gear associated with a mechanical transmission of the drive system. With the system gear being mounted for rotation in a plane and having a plurality of equally spaced teeth completely about the periphery thereof, the sector gear also includes a plurality of equally spaced teeth, but disposed about only a portion of the periphery thereof. The rotatably mounted shaft is disposed in spaced relation to the teeth of the system gear and the sector gear is mounted for rotation into and out of the plane of the system gear. Moreover, the locking mechanism includes a lost motion mechanism accommodating limited relative rotation between the rotatably mounted shaft and the sector gear and also includes a cam accommodating limited axial movement of the sector gear relative to the rotatably mounted shaft, whereby the teeth of the sector gear are automatically aligned during rotation for meshing enagagement with the teeth of the system gear.

Mechanical transmission locking mechanism

A bi-directional snub valve provides two parallel fluid paths therethrough and means for restricting the fluid flow through each of the parallel paths to one preferred direction. A movable piston is provided with two land portions which selectively are movable into blocking association with two openings in a fluid chamber. Blockage of either of the two openings in the fluid chamber and the corresponding fluid flow path does not effect the ability of the alternate path to conduct a fluid therethrough. The bi-directional snub valve therefore is able to slow the flow of fluid therethrough as a movable object approaches its end-of-travel position. However, because of the nature of the two parallel flow paths, the movable object can be moved away from its end-of-travel position at full speed. A cam arrangement is used to move the piston of the snub valve in response to movement of the movable object.

Bi-directional snub valve

In order to avoid a large torque spike in a system in the event of a system failure, a shaft relative speed limiting system includes a lost motion device and a brake. The lost motion device is operatively associated with a pair of shafts normally driven at selected speeds such that one of the shafts drives the other of the shafts in the event of a system failure. The brake is operatively associated with the pair of shafts normally driven at selected speeds through first and second portions of a relative speed limiting device and limits the relative speed between the shafts in the event of a system failure. Additionally, the first portion of the relative speed limiting device is normally driven by one of the shafts at the selected speed thereof and the second portion of the relative speed limiting device is normally driven by the other of the shafts at the slected speed thereof in the shaft relative speed limiting system.

Shaft relative speed limiting system

Rotational overtravel stops are often crucial components of actuators used in environments where not only cost but also power requirements, reliability, weight, size and simplicity are important. A bi-directional overtravel stop for a rotatable actuator shaft is disclosed which includes first and second brake plates secured for rotation with the shaft in opposite directions by a pair of oppositely disposed one-way clutches. A non-rotatable brake member is mounted for axial movement relative to the shaft and means are provided for biasing the brake member to frictionally engage one or the other of the brake plates when the shaft has reached the selected limit of its rotation in one direction or the other. The actuating structure of the overtravel stop includes a sleeve over the shaft and secured to the brake member, and a tubular threaded member over the sleeve, said threaded member and sleeve being secured against relative rotation and allowing telescoping relative to one another. Stops are provided so that, at either end of the telescoping motion, the sleeve is appropriately biased to move the brake member toward engagement with the appropriate brake plate. The threaded member is driven axially by a nut which is itself driven by the shaft. The one-way clutches are springs wound spirally around the shaft with one end of each spring being fixed to its associated brake plate.

Bi-directional overtravel stop

An overtravel stop for a rotating shaft has a pair of gears associated with the shaft to rotate therewith. Each gear engages an associated limiting gear and the two engaged gear pairs have different gear ratios. One of the limiting gears is threaded over a shaft which is secured for rotation with the other limiting gear, such that the different gear ratios causes the one limiting gear to translate over the shaft. At selected travel limits, the one limiting gear is caused to lock relative to the other, thereby causing one of the gears associated with the shaft to shift therearound. A cam structure is provided which axially shifts a stop member associated with the shaft into engagement with a fixed stop when the one gear shifts about the shaft. Two different cam structures are shown including a pin and slot connection between the stop member and the shaft, and an ear and cam recess connection between the stop member and one of the shaft gears.

A linear no-back device for transmitting bi-directional linear motion from an input shaft to an output shaft while preventing motion of the output shaft independently of the input shaft and enabling movement of the input shaft when the output shaft is jammed. The linear no-back device has a fixed member having a bore with a pair of spring discs loosely mounted on the output shaft and having flexible ears at the periphery thereof in engagement with a wall of the bore. A pair of spaced-apart stop rings on the output shaft limit separating movement of the spring discs axially of the output shaft and a preloaded compression coil spring urges the spring discs away from each other. Actuating members associated with the input shaft are effective upon movement of the input shaft in either linear direction to effectively disengage the spring discs from the wall of the bore and transmit motion of the input shaft to the output shaft through a motion-transmitting connection including the preloaded compression coil spring. Further compression of the preloaded compression coil spring enables movement of the input shaft relative to the output shaft when the latter is jammed.

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Cherry Valley, IL, United States of America

Gary D Gillingham