Patent Description:
End-of-stroke stopping mechanisms, also referred to as stop modules, dissipate excess rotational kinetic energy of a rotational drive system to stop rotation when a travel limit in a given direction of travel is reached. In some applications, the excess rotational kinetic energy may be significant, and it must be dissipated very quickly. For example, a GRA in an actuation system for displacing an aircraft flight control surface may be driven by a hydraulic motor at very high revolutions per minute, and rotation must be safely stopped within a very short time span. Conventional end-of-stroke stopping mechanisms known to applicant use frictionally contacting brake plates or a torsionally compliant shaft system to dissipate excess rotational kinetic energy of the rotational drive system. These conventional stopping mechanisms are typically heavy and large in size, characteristics that are disadvantageous for aircraft applications. Some conventional stop modules are located downstream in the actuator gear train so that the stroke range is manageable, and as a result, the upstream gears are between the stop module and the motor (flywheel), and therefore have to carry the stopping torque. <CIT> shows an ephaser cushion stop with a related actuator according to the preamble of claim <NUM>. <CIT> shows a geared rotary actuator with internal stop mechanism. <CIT> shows an electric drive camshaft phaser with torque rate limit at travel stops.

According to the present invention, the above mentioned problems are solved by an actuator according to claim <NUM> and a method according to claim <NUM>.

Preferred embodiments of present invention are laid down in the dependent claims.

An actuator with a stop module disclosed herein is useful for emergency over-travel rotary stop applications where jamming of the actuator at the end stop must be prevented. The disclosed stop module employs a timing gear system to articulate a stopping pawl, and a low inertia, deformable stopping disk or other deformable element that can safely dissipate excess rotational kinetic energy of the rotating shaft system. A unique feature is that the stop module does not rely on friction to stop and dissipate the excess kinetic energy, but instead relies on predictable deformation of a metallic element (the deformable disk) which may be provided in a stopping cartridge of the stop module. Because the deformable stopping element is consumed in a high-speed stop, the stop module may be a single-use mechanism. Use of a deformable element to dissipate excess energy allows the disclosed stop module to be designed lighter and smaller than conventional end-of-stroke stopping mechanisms mentioned above.

The nature and mode of operation of the present invention will now be more fully described in the following detailed description taken with the accompanying drawing figures, in which:.

<FIG> shows a motor <NUM> connected to a GRA <NUM>. Motor <NUM> may be any type of motor, for example a hydraulic motor, an electric motor, or a pneumatic motor. Motor <NUM> is operable to rotatably drive an input shaft <NUM> transmitting a rotational input to GRA <NUM>. Input shaft <NUM> may be supported for rotation about its axis by a pair of rotary bearings <NUM>. GRA <NUM> is configured to include a stop module <NUM> described in detail below.

An end portion of input shaft <NUM> may have external gear teeth to act as a sun gear <NUM> of a first planetary gear stage of GRA <NUM>. Sun gear <NUM> meshes with a first set of planet gears <NUM>, which in turn are meshed with internal gear teeth in housing <NUM> such that housing <NUM> acts as a ring gear for the first planetary gear stage. A first stage carrier <NUM> is coupled to planet gears <NUM> and is driven to rotate about the axis of input shaft <NUM> upon rotation of the input shaft. An end portion of first stage carrier <NUM> may have external gear teeth to act as a sun gear <NUM> of a second planetary gear stage of GRA <NUM>. The second planetary gear stage further includes a second set of planet gears <NUM> meshed with sun gear <NUM> and with internal gear teeth in housing <NUM> forming another ring gear. A second stage carrier <NUM> is coupled to planet gears <NUM> and is driven to rotate about the axis of input shaft <NUM> upon rotation of the input shaft and first stage carrier <NUM>. Second stage carrier <NUM> may include an output spline <NUM> for connection to a load (not shown). An end cover <NUM> may be fastened to housing <NUM>.

Referring also now to <FIG>, stop module <NUM> of the present invention uses a timing gear system based on first stage carrier <NUM> to trigger deformation of a deformable disk <NUM> to dissipate excess kinetic energy. Deformable disk <NUM> may be contained within a stopping cartridge assembly formed by a first part <NUM> and a second part <NUM>. Cartridge assembly parts <NUM> and <NUM> may be threaded together and locked together by a pin (not shown). Deformable disk <NUM> is shown squeezed between hard (i.e. rigid) deforming elements, for example, balls <NUM> and <NUM> that are constrained in the stopping cartridge assembly. Balls <NUM> and <NUM> may normally be seated within internal pockets (not labelled but visible in <FIG>) in second part <NUM> and first part <NUM>, respectively. Ball <NUM> may normally occupy a recess <NUM> (see <FIG>) in deformable disk <NUM>. In the depicted embodiment, the deforming elements are shaped as spherical balls, however the deforming elements may be rigid bodies having a non-spherical shape.

Deformable disk <NUM> may be splined onto input shaft <NUM> so as to rotate with the input shaft. The cartridge assembly parts <NUM> and <NUM> are free to rotate relative to input shaft <NUM> about the axis of input shaft <NUM>, but will normally rotate with input shaft <NUM> and deformable disk <NUM> due to the constraint of deformable disk <NUM> within the stopping cartridge assembly. Thrust bearings <NUM> may be arranged to hold deformable disk <NUM> splined on part <NUM> to prevent axial movement of the splines and cartridge assembly parts <NUM> and <NUM> between bearings <NUM>. First part <NUM> of the stopping cartridge assembly may include an external protrusion <NUM> defining a pair of radial faces 35A and 35B (see <FIG>).

Attention is also directed now to the remaining <FIG> in addition to <FIG> and <FIG>. The timing gear system mentioned above may be enclosed by an internal housing comprising parts <NUM> and <NUM>. Internal housing <NUM>, <NUM> may mount on one of the input shaft reaction bearings <NUM>, and may be externally splined to an internal splined surface of housing <NUM>. First stage carrier <NUM> may include a hub portion <NUM> having external gear teeth meshing with planet gears <NUM> rotatably mounted on a support plate <NUM>. Planet gears <NUM> may be bifurcated to mesh on one side with internal ring gear teeth provided in internal housing part <NUM>, and on the other side with a timing ring gear <NUM> which carries a tang ring <NUM>. Rotation of first stage carrier <NUM> caused by rotation of input shaft <NUM> is transmitted to planet gears <NUM>, thereby causing rotation of timing ring gear <NUM> and tang ring <NUM> about the axis of input shaft <NUM>. Tang ring <NUM> may include one or more of angularly spaced tangs <NUM>, and each tang <NUM> may have a corresponding set screw <NUM>. While the drawings show tang ring <NUM> as a toothed plate which fits tightly into ring gear <NUM>, tang ring <NUM> may be provided as a plate welded to ring gear <NUM> and then ground flush with the ring gear.

A hardened spacer <NUM> abutting with a radial step in housing <NUM>, and a hardened washer <NUM> engaging the spacer <NUM>, may be arranged between first stage carrier <NUM> and internal housing part <NUM>. A hardened washer <NUM> may be provided between internal housing part <NUM> and ring gear <NUM> such that ring gear <NUM> is allowed to rotate.

A stopping pawl <NUM> may be arranged outside internal housing <NUM>, <NUM> and may be pivotable about an axis of a pivot pin <NUM> for engaging one of the radially extending faces 35A or 35B of protrusion <NUM> depending upon the pivot direction. Pivot pin <NUM> may be seated within aligned openings <NUM> though pawl <NUM> and through a ring-shaped keeper <NUM> fixed within housing <NUM>. Under normal operation (i.e. not at an emergency limit stop condition), stopping pawl <NUM> remains in a centered pivot position about the axis of pivot pin <NUM> and does not impede rotation of the stopping cartridge assembly. Pawl <NUM> may be biased to occupy the centered pivot position by a pair of spring-loaded ball detents (not shown) engageable with recesses <NUM> in pawl <NUM> to center pawl <NUM> when the pawl is not pivoted to a tipped position at an end of stroke, as described below. Pawl <NUM> is shown as having an extension arranged to extend through a passage <NUM> in internal housing part <NUM> and terminating at an actuation end <NUM>. Shims (not labelled) may be arranged between end cover <NUM> and keeper <NUM> to axially constrain keeper <NUM> and internal housing <NUM>, <NUM> within external housing <NUM>.

The timing gear system is designed so that timing ring gear <NUM> and tang ring <NUM> rotate slowly through less than one complete revolution during the actuator stroke. The timing gear system and angular spacing of tangs <NUM> may be configured such that a set screw <NUM> on one of the tangs <NUM> engages actuation end <NUM> of pawl <NUM> at the end of stroke or over-travel position of the actuator to pivot pawl <NUM> about the axis of pivot pin <NUM>. When pawl <NUM> is pivoted, as illustrated in <FIG>, it engages one of the radial faces 35A or 35B of protrusion <NUM>, thereby preventing first part <NUM> and second part <NUM> of the stopping cartridge assembly from rotating with input shaft <NUM> and deformable disk <NUM>. The system may be bidirectional, wherein the set screw <NUM> on a different tang <NUM> engages the actuation end <NUM> of pawl <NUM> when input shaft <NUM> rotates in an opposite direction, thereby pivoting pawl <NUM> in an opposite direction to engage the other radial face 35B or 35A of protrusion <NUM>. As will be understood by those skilled in the art, the configuration of the timing gear system is subject to design options. By way of non-limiting examples, a Geneva mechanism or similar timing mechanism may be used in place of the illustrated timing gear system and is considered to be within the scope of this invention.

When pivoting of pawl <NUM> prevents first part <NUM> and second part <NUM> of the stopping cartridge assembly from rotating with input shaft <NUM> and deformable disk <NUM>, balls <NUM> and <NUM> cause deformation of deformable disk <NUM>. The balls remain in the internal pockets in first part <NUM> and second part <NUM>, and permanently deform disk <NUM> to dissipate kinetic energy as the disk <NUM> continues to rotate relative to balls <NUM>, <NUM> until rotation of disk <NUM> and input shaft <NUM> is stopped. The torque generated by the deforming balls <NUM>, <NUM> reacts a side load through the two radial bearings <NUM>.

As will be appreciated, pawl <NUM> is only pivoted from its centered position when the mechanical stroke of the actuator is exceeded, and once the motor has stopped and is reversed to back up into the normal stroke range of the actuator, the pawl <NUM> pivots back to its centered position with no drag at all, i.e. the system is non-jamming.

In a modified embodiment, two or more stopping pawls <NUM> and corresponding protrusions <NUM> may be provided and arranged so as to eliminate the momentary side load generated by the stopping pawl on bearings <NUM>. For the example, a pair of pawls <NUM> and a pair of protrusions <NUM> may be arranged <NUM> degrees apart about the rotational axis of input shaft <NUM>, thereby cancelling any side load due to stopping torque.

While one set of deforming elements <NUM>, <NUM> is shown for permanently deforming disk <NUM>, another set of deforming elements may be arranged and configured to dissipate more rotational kinetic energy from the system by straightening out the deformed regions of disk <NUM> (e.g. bumps or ridges formed by the first set of deforming elements <NUM>, <NUM>) as the disk continues to rotate while coming to a stop. For example, one or more secondary deforming elements may be angularly spaced from the first set of deforming elements <NUM>, <NUM> about the rotational axis of input shaft <NUM> to act on and flatten the previously deformed regions as deformable disk <NUM> continues to rotate while coming to a stop.

In the depicted embodiment, the deformable element is shown as a disk <NUM>. However, the shape of the deformable element may be other than a disk shape. For example, and without limiting the invention, the deformable element may have a cylindrical shape. The deformable element may be formed as a separate element as described above, or it may be integrally formed with one of the constituent parts <NUM> or <NUM> of the cartridge assembly.

Claim 1:
An actuator (<NUM>) for transmitting rotary motion from an input element (<NUM>) to an output element (<NUM>), the actuator having an end-of-stroke limit, wherein the actuator comprises:
a deformable element (<NUM>) and a deforming element (<NUM>, <NUM>);
a stopping element (<NUM>) movable between a non-stopping position and a stopping position, wherein the deforming element (<NUM>, <NUM>) rotates with the deformable element (<NUM>) when the stopping element (<NUM>) is in the non-stopping position, and wherein relative motion occurs between the deformable element (<NUM>) and the deforming element (<NUM>, <NUM>) when the stopping element is in the stopping position; and
a timing gear (<NUM>) responsive to rotation of the input element (<NUM>) or the output element (<NUM>);
wherein the deforming element (<NUM>, <NUM>) causes deformation of the deformable element (<NUM>) when relative motion occurs between the deformable element (<NUM>) and the deforming element (<NUM>, <NUM>);
characterized in that:
the deformable element (<NUM>) is connected to the input element (<NUM>) such that the deformable element (<NUM>) rotates in response to rotation of the input element (<NUM>); and
the timing gear (<NUM>) is configured to move the stopping element (<NUM>) to the stopping position when the end-of-stroke limit is reached;
whereby kinetic energy in the actuator (<NUM>) is dissipated through the deformation of the deformable element (<NUM>) when the end-of-stroke limit is reached.