Actuating device

An actuator is configured for transmitting a force or torque to a load. In one example configuration, the actuator includes an input device configured to apply an output force. A backstopping clutch is configured to transmit torque only in the input direction and to prevent back-driving of the input device. An overrunning clutch is configured to include a driven member moved in response to the transmitted torque in the input direction. The load may be moved in response to the driven member, or the load may be moved by a force applied directly to the load.

FIELD

This disclosure relates to actuating devices used for transmitting force to a load, and in one example application, to an actuating device configured for withdrawing a door into an aircraft against mechanical resistance.

BACKGROUND

Actuating devices configured to receive a mechanical input and provide a mechanical output are used in many applications. Accordingly, a number of such devices are known, each having structural characteristics appropriate to an intended application.

Unfortunately, while the number of known actuating devices is considerable, new applications with increasingly complex design requirements are not satisfied by existing actuating devices.

SUMMARY

An actuator is configured for transmitting a force to a load. In one example configuration, the actuator includes an input device configured to apply torque to an output member that in turn applies a force to a load. A backstopping clutch is configured to transmit the torque only when in one direction and to prevent back-driving of the input device in the opposite direction. An overrunning clutch is configured to include a driven member moved by a driving member in response to the transmitted torque in the input direction. The overdriving clutch allows the load to be moved by at least two alternative structural configurations and/or methods. In one alternative, the load may be moved in response to torque transmitted from the driven member. In a second alternative, the load may be moved by a force or torque applied directly to the load.

DETAILED DESCRIPTION

The present disclosure relates to several different actuator configurations. The actuators described herein are intended to illustrate general principles having wide applicability. In one example application, an actuator is adapted for transmitting a force used to move a load. Such an actuator may include a manually operated input device, and be configured to apply torque to a load, such as the resistance encountered when opening an aircraft door in flight. The manually operated input device may be in the form of a lever, a motor or other device. A backstopping clutch is configured to transmit torque in the driving direction, while preventing back-driving of the input device. Back-driving of the input device is a condition wherein the input device moves in response to conditions “downstream,” e.g. a movement of the load. In some configurations, the actuator may include gears, such as planetary gears, to provide mechanical advantage. An overrunning clutch is configured “in series” in the drive-train. In such a configuration, the clutch allows the input device to transmit torque in the driving direction, and alternatively allows direct actuation of the output (e.g. direct movement of the load) in the same direction. The clutch thereby allows a force applied directly to the load to move the load without having to overcome resistance created by the gears or other components. Accordingly, a two-clutch design prevents back-drive when sustained loads are encountered, and also allows the user to overdrive by direct movement of the load when resistance to moving the load is not present or is reduced. Due to the mechanical advantage provided in applications configured to include gears, in many applications a single worker may move a considerable load unassisted.

The example actuators described below are intended for general application. However, in an example application, an actuator based on some or all of the concepts introduced below, is adapted for opening an aircraft door. Such a door is typically opened outwardly and folded in the open position along the outside of the fuselage of the aircraft. However, in an in-flight emergency, the door must be opened inwardly, so that it is not pushed into the air stream. The example actuators may be configured to move the door inwardly, and are advantageously independent of existing aircraft electrical, hydraulic and pneumatic systems, and require minimal modification to the door. Additionally, the example actuators disclosed may be configured not to interfere with the normal operation of the aircraft door. The example actuator may be configured to engage the load (e.g. the door) automatically upon release of a manually operated handle, lever or other input device, allowing a user to immediately begin use. A geared design provides the mechanical advantage necessary for a single crew member to operate the actuator to retract the door from its seal against large dynamic pressure loads that may be present in flight. The example actuators may allow the user to act simultaneously and/or intermittently on the door in two modes. In a first mode, use of the geared actuator provides mechanical advantage when needed. In a second mode, the actuator allows the user to pull directly on the door when that is made possible by the absence of large resistance loads during all or part of the door-opening process. Following opening of the door, the actuator may be easily reset to allow conventional operation of the door. Accordingly, while the actuators described herein are intended for general purposes, each actuator could be configured for operation in a specific application, such as opening an aircraft door in an emergency. In such an example, the configuration may include an appropriate output link attached to the aircraft door.

FIG. 1illustrates one example configuration of an actuating device100. The actuating device100includes an input102configured to receive a torque having direction104. The torque may be applied manually by a lever arm, or alternatively by a motor, spring or other device.

The input torque is applied through a backstopping clutch106that allows rotation in the input direction104(seen in the example ofFIG. 1as counter-clockwise when looking from the input-to-output direction). However, the backstopping clutch prevents rotation in the opposite direction. The backstopping clutch is drawn symbolically as a driven member108(illustrated as a ball) which is allowed to move in the counter-clockwise direction, but is prevented from moving in the clockwise direction by a backstop110that is secured (i.e. grounded) in a fixed position. Again, the illustration is symbolic, and the reader should realize that the driven member108may make many revolutions in the allowed direction without interference from the backstop110, which illustrates only that the driven member cannot move in the non-allowed direction. Thus, operation of the backstopping clutch106allows torque to be transmitted in one direction, but prevents transmission in the other direction. Accordingly, the input source or device cannot be “back-driven” (i.e. input cannot be driven in reverse) by events downstream (i.e. closer to the output118) from the backstopping clutch106.

Output torque from the backstopping clutch106is input to the overrunning clutch112. The overrunning clutch112in the example ofFIG. 1transmits torque in counter-clockwise direction. In the symbolic drawing, a driving member114(illustrated as a ball) drives a driven member116(illustrated as a non-secured, i.e. non-grounded, backstop). Thus, movement of the driving member114in the counter-clockwise direction moves the driven member116in the counter-clockwise direction.

The overrunning clutch112allows the system to be overrun. In particular, if a force is applied to a load (not shown) driven by the output118, the driven member116will turn in the counter-clockwise direction independently of the driving member114. (A load is not shown inFIG. 1for clarity, but in the example ofFIG. 2, the load is seen as an output link216connected to a door222.) Accordingly, in the event of a force applied directly to the load, movement of the driven member116is not slowed, restrained or impeded by the driving member114. Stated somewhat differently, if a force is applied directly to the load, the driven member116will move without back-driving the drive member114. Thus, the output may be moved by operation of the driven member116or by a force applied directly to the output, or by a combination of the two.

FIG. 2illustrates a second example configuration of an actuating device200, wherein an output link216drives a load, such as a door222or other object. A handle202is configured to apply torque in an input direction104. The handle/lever202is illustrated inFIG. 2in a stroke-begin position. Movement of the handle/lever202from the stroke-begin position to the stroke-end position transmits rotary force through the ratchet device204. The ratchet device204allows return movement of the lever202from the stroke-end position to the stroke-begin position without driving downstream components. Accordingly, a user may apply input manually, by repeated strokes (e.g. a reciprocating input) of the input lever202.

In the example ofFIG. 2, output from the ratchet204is input to a torque limiter206. The torque limiter may be configured to transmit torque applied at less than a threshold value, and to reject and/or not transmit torque applied at greater than a threshold value. In one example, the torque limiter allows the input lever202to move from the stroke-begin position to the stroke-end position without resistance if torque greater than the threshold value is applied. In such an event, no torque in excess of the threshold value is applied by the input lever202. By limiting the torque, components may be efficiently sized and/or specified (such as by rating), and are thereby protected from forces too great for their construction. Additionally, the rate at which the load is moved may be limited by limiting torque.

The backstopping clutch106ofFIG. 2is similar to that seen inFIG. 1. The backstopping clutch106allows torque to be transmitted in one direction, and prevents rotation in the opposite direction. Accordingly, the input cannot be “back-driven” by events downstream from the backstopping clutch106.

Output208from the backstopping clutch106is input to gears210. In the example ofFIG. 2, the gears210are a two-stage planetary gear system. However, any alternative transmission system could be used, including sprocket/chain, belt/pulley systems or other gearing, as indicated by the particular application. However, planetary gears are compact and efficient, and provide the necessary torque needed for many applications. In most applications, the planetary gears will provide a substantial increase in torque and decrease in a rate of angular rotation.

The output212of the gears210is input to an overrunning clutch112having a driving member114and a driven member116. The operation of the overrunning clutch112is similar to the clutch ofFIG. 1, and allows a load to be moved in a direct manner—without use of the actuating device200and without the driving member114retarding the movement of the driven member116. Therefore, the overrunning clutch112allows direct movement of the load, and prevents direct movement of the load from applying torque to the gears210.

An output214of the overrunning clutch112is input to a drive transfer device, which can be used to regulate whether or not the drive output from the overrunning clutch is applied to an output, such as output link216. Thus, the actuator200can be coupled to, or decoupled from, the output or load by operation of the drive transfer device. In the example ofFIG. 2, the drive transfer device is a retractable drive spline218. In an extended position, the drive spline218is engaged to the load (e.g. output link216, which in turn is attached to a door or other load to be moved). In a retracted position, the drive spline218is disengaged from the load. In the example ofFIG. 2, the drive spline218is configured for movement from the retracted position to the extended position by relaxation of a spring220or similar device.

FIG. 3illustrates an example configuration of an actuating device300. A manually operated lever arm or handle302is configured for location either in a storage position or in an operable position. In the storage position, shown inFIG. 3, the handle302retains the bail320, which in turn retains the drive member322in a disengaged condition. In the operable position, the handle302provides mechanical advantage when applying torque. In the example ofFIG. 3, a pull-pin304secures a bracket306attached to the handle302to a bracket308attached to a main housing of the actuating device300. In operation, removal of the pin304allows the handle302to rotate about a pivot310between the storage and operable positions.

A torque limiter assembly312is configured to apply torque, received from the manually operated lever, having less than a threshold value. Torque over the threshold value is not transmitted. For example, if the torque exceeds the threshold, the torque limiter assembly may allow the lever arm302to move with no resistance (thereby allowing the lever arm to transmit no energy). A gearbox assembly314is configured to increase the torque applied by the lever arm, and to reduce the angular velocity (rpm) of the input. The gearbox assembly314may include planetary gears or other gearing as indicated by the design requirements of the particular application.

A door interface316adapts the actuating device300to opening an aircraft door or to movement of another load, depending on the application to which the actuator300is put. Accordingly, the interface316may be configured as required by the particular installation. In an installation similar to that ofFIG. 2, the door interface allows installation of the actuating unit300as required to position an output to withdraw the door against a load and into the aircraft cabin. In the application illustrated byFIG. 3, the output arm318(i.e. output of the actuator300) is configured to withdraw the door into the aircraft cabin. The output arm may act on a parallel linkage or other hardware attached to the door.

Movement of the lever arm302, from the storage position to the operable position, releases a bail320, results in deployment of a plunger322from a retracted position into an extended position. Moving the plunger between the retracted position and extended positions reconfigures the actuator300from disabled to enabled modes, respectively. In one example, movement of the plunger322results in movement of the retractable drive spline218shown inFIG. 2. Thus, with the plunger322in the extended position, the drive spline218is engaged to the load. With the plunger322in the retracted position, the drive spline218is disengaged from the load.

FIG. 4illustrates additional aspects of the actuator300. Removal of the locking pin304in the direction402allows movement of the lever arm302in the direction404from the storage position (as seen inFIG. 3) to an operable position (as seen inFIG. 4). Movement of the lever arm302releases the bail320for movement in the direction406. Movement of the bail320releases the plunger322to move in the direction408, thereby engaging the retractable drive spline218(FIG. 2) or other drive device. A spring220(seen inFIG. 2) may be used to produce the motion in direction408. After the actuator has moved from the disengaged position to the engaged position, the lever arm302may be manually moved between the stroke-begin position (on the left) and the stroke-end position (on the right) as indicated by arrow410. Note that the relative locations of the stroke-begin and stroke-end positions are arbitrary, and could be reversed if desired.

FIG. 5is a cross section view illustrating additional aspects of the actuator300ofFIG. 3. The ratchet assembly204allows torque to be applied in one direction, as the lever arm302is moved from the stroke-begin position to the stroke end position. The ratchet assembly204allows the lever arm302to be returned to the stroke-begin position without applying torque in the reverse direction. The torque limiting assembly206prevents application of excess torque to the gearing system. The backstopping clutch106allows transmission of input torque from the torque limiting assembly206via an input shaft, but prevents back-driving of the input, e.g. lever arm302or other input device. The two-stages210A and210B of the planetary gears210receive input torque from an input shaft502. The inclusion of gears, and what type of gears, depends greatly on the application. The gears illustrated are intended only as an example. The output of the two-stage gearing drives the load through an overrunning clutch112. The overrunning clutch112allows a load to which the actuator300is attached to be moved without operation of, and without being impeded by, the actuator300. The retractable drive spline218is extended by the spring220when the bale320moves in response to movement of the lever arm302. Operation of the actuator300moves the output link216(FIG. 2), which moves the load, such as an aircraft door.

FIGS. 6 and 7show isometric views of examples of an external driving spline600and an internal driven spline700, respectively. Each figure includes an enlarged view of a portion of the teeth of the spline, particularly showing features of the teeth that promote engagement of the splines. The driving and driven splines600,700are configured to engage and to disengage a drive-train (such as seen generally inFIGS. 1 and 2) from an output load (e.g. output link216ofFIG. 2). The engagement and disengagement is facilitated by relative movement of the external600and internal700spline shafts. In the disengaged condition, the driving (external) spline shaft600is retracted from the driven (internal) spline shaft700. In the disengaged condition, the teeth of the spline shafts600,700are not engaged. Upon release of the handle202/302(FIGS. 2 and 3) and bail320(FIG. 3) a spring220(FIGS. 2 and 5) propels the driving shaft600axially into the driven shaft700, thereby engaging the teeth of the splines600,700.

Depending on the relative rotation of the drive spline600and driven spline700, there may be some degree of rotational misalignment of external and internal spline teeth. Such misalignment may prevent engagement of the splines600,700. In such a misalignment condition, the input shaft600may be required to rotate as much as one circular pitch at the spline pitch radius to correct misalignment and allow engagement of splines600,700. The example splines600,700seen inFIGS. 6 and 7address the misalignment issue by providing that the shape of ends of the teeth of both splines allow rapid engagement of the two splines by axial force of the spring220with minimal rotary input motion.

Referring to the example ofFIG. 6, the teeth602of the external spline600include a rounded surface604and a tapered lead in surface606at an engagement end608of each tooth. (Note that the teeth602are oriented in an axial direction along the outer surface of the spline600. Accordingly, the engagement end608of the teeth602is the end that first makes contact with teeth702of the driven spline700.) The teeth602are also tapered axially from the engagement end608.

FIG. 7shows an example of a driven spline having teeth702that define a chamfered end surface704and a tapered lead-in surface706at their engagement end708. The internal spline teeth702are tapered to compliment the external spline teeth602.

In operation, the spring220(FIG. 5) propels the driving spline shaft600axially into the driven shaft700. If the drive spline600and the driven spline700are misaligned, the rounded end604of the external drive spline600and the chamfered end surface704of the internal driven spline700will make contact. Contact between the rounded end604and the chamfered end surface704prevent initial contact by sharp edges of the splines. Subsequently, the tapered lead-in surface606of the external driving spline600and the tapered lead-in surface706of the driven spline700make contact. Contact of the tapered lead-in surfaces606,706and an axial force provided by spring220or similar device results in a relative rotation of external and internal spline shafts600,700to allow engagement. Upon engagement, substantially the entire axial length of the teeth602of the drive spline600are in contact with substantially the entire axial length of the teeth702of the driven spline700. For example, as the external and internal spline shafts600,700shown inFIGS. 6 and 7are forced into engagement (such as by a spring502), the external shaft600will rotate counterclockwise as viewed from the input end.

The spline engagement features ofFIGS. 6 and 7will allow quick axial engagement of splines600,700with little or no actuator input motion (e.g. movement of the handle202/302ofFIGS. 2 and 3). Thus, in the example ofFIGS. 6 and 7, both the drive and driven splines include teeth having rounded and/or chamfered ends, and tapered lead-in surfaces606,706defined on an engagement end to produce relative rotation of the splines to facilitate engagement of teeth of the splines. Large gear ratios incorporated into an actuator may create a need for greater input motion to ensure engagement.

Although aspects of this disclosure include language specifically describing structural and/or methodological features of preferred embodiments, it is to be understood that the appended claims are not limited to the specific features or acts described. For example, some specific aspects (e.g. “counter-clockwise”) have been used in the disclosure. However, these aspects are meant to be illustrative of larger concepts, and could be replaced by other aspects/features if desired. Uses of the actuators disclosed are not limited to aircraft door movement or any other purpose. The invention may be employed in applications wherein a device may occasionally or intermittently encounter large loads, or where it is desirable to actuate a load directly, in concert with or instead of, by use of an actuator. Accordingly, the specific features and acts are disclosed only as instructional examples, and are representative of more general concepts.