Deployable fan with linear actuator

A linear actuator for use with a fan with deployable fan blades to deploy the fan blades when in use and stow the fan blades when not in use. The linear actuator utilizes a drive element having a driver that moves linearly along a shaft of the linear actuator. Linear movement of the driver causes radial movement of arms connected to the linear actuator and the fan blades. Radial movement of the arms causes rotational movement of gears attached to the ends of the fan blades to cause the fan blades to rotate into the deployed or stowed configuration.

BACKGROUND

The basic powered blade deployment of a ceiling fan is covered by U.S. Pat. No. 7,857,591 B2, which is incorporated in its entirety here by this reference. The individual fan blades are mounted to a rotating platform that is powered by a main fan motor. Development of the technology for commercial use has depended upon a good solution for transmitting controllable power to this rotating platform, for precisely actuating the fan blades.

Initial designs used one or more electric motors on the rotating platform to actuate the blades. This relied on a rotating electrical interface, or slip ring. This approach is lacking because slip rings tend to be expensive and wear out too quickly for the expected life of a ceiling fan. There is also a problem with coordinating the deployment of the blades, and with corrosion of the slip ring contacts during typical long periods when the fan is not used.

A first approach to an alternative power source for the blades is described in our second patent—U.S. Pat. No. 8,864,463 B2, which is incorporated in its entirety here by this reference. This approach uses the main fan motor mounted to a planetary gear set. When the planetary gears are locked, the fan rotates as a unit. When the planetary gears are unlocked, the rotating platform can be locked and the main motor planet carrier drives the blade deployment and retraction in a coordinated fashion. This approach has proven to work, but is difficult to implement into a commercial product. The required clutches are noisy, prone to wear, and difficult to control accurately. Coordinating the main motor speed in all conditions in order to ensure smooth blade action has been a challenge with this design. In short, this approach has not given the quality experience customers would expect from a high-end ceiling fan.

SUMMARY OF THE INVENTION

After the main motor/planetary gear drive experience, extensive research resulted in a blade actuation solution that accomplishes the following objectives: low cost, durable, low energy consumption (Energy Star rating is desirable in the industry), plenty of power to actuate blades of various sizes, good coordination and control of blades, low or minimal adjustments over the life of the product, easy to operate as part of a normal ceiling fan remote control, excellent sound quality in line with a high-end product, no rotating electrical interface, compact size to allow for a variety of housing designs.

The new fan actuator and structure described here meets all of these requirements by coupling radial deployment of fan blades using a linear actuator while the fan blades or rotating. The fan blades can further be pitched up during deployment. When the fan is turned off and the fan blades return to their stowed configuration, the fan blades automatically pitch down until flat as the fan blades retract radially back into a housing.

DETAILED DESCRIPTION OF THE INVENTION

The detailed description set forth below in connection with the appended drawings is intended as a description of presently-preferred embodiments of the invention and is not intended to represent the only forms in which the present invention may be constructed or utilized. The description sets forth the functions and the sequence of steps for constructing and operating the invention in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and sequences may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention.

The invention of the present application is a system and method of automatically deploying and stowing one or more fan blades120by moving a carriage104in a first linear direction along a linear actuator102mounted to a fan motor122, wherein the carriage104is operatively connected to the fan blade to rotate with the fan blade120. Moving the carriage104in the first linear direction converts the linear movement of the carriage104in the first linear direction into movement of the fan blade120in a first radial direction away from the linear actuator, and moving the carriage104in a second linear direction along the linear actuator104, opposite the first linear direction converts the movement of the carriage in the second linear direction into movement of the fan blade in a second radial direction towards the linear actuator. In some embodiments, movement of the fan blade in the first radial direction pitches the fan blade up; and movement of the fan blade in the second radial direction pitches the fan blade down. In some embodiments, movement of the carriage in the first linear direction causes housing sections138a,138bof a housing138to separate and reveal the fan blade120; and movement of the carriage104in the second linear direction causes the housing sections138a,138bto mate together to hide the fan blade120inside the housing.

As shown inFIG. 1, the fan100of the present invention comprises a fan platform108defining a central axis A, and a linear actuator102operatively connected to the fan platform108and aligned substantially with the central axis A of the fan platform108. The fan platform108comprises at least one fan blade120having a proximal end142and a distal end143. The actuator102moves a carriage104in both directions along the central axis A. The carriage104is operatively connected to the fan blade120, preferably at the proximal end142, and configured so that movement of the carriage104along the central axis A in one direction causes the fan blade120to deploy and movement of the carriage104along the central axis A in a second direction, opposite the first direction, causes the fan blade120to move towards a stowed configuration in which the fan blade120is at least partially hidden within a housing138. By use of an anti-friction bearing106, it is possible to rigidly mount the actuator102in place while allowing the movable carriage104to rotate with a fan platform108about the actuator102. This configuration allows the fan blades120to deploy simultaneously as the fan blades rotate.

As shown inFIG. 2, the linear actuator102comprises a drive element110. In the preferred embodiment, the drive element110comprises a motor112, such as a stepper motor, servo motor, dc motor, and the like, and a shaft114operatively connected to the motor112, such that the motor causes rotation of the shaft114. Preferably, the shaft114is a threaded shaft defining a longitudinal axis L. A driver116, such as a lead screw nut, is mounted on the shaft114, such that the shaft114can move the driver116. For example, rotation of the driver116about the shaft114in a first direction may cause the driver116to move in a first linear direction along the shaft114, and rotation of the driver116about the shaft114in a second direction, opposite the first direction, causes the driver116to move in a second linear direction along the shaft114opposite the first linear direction. The driver116is connected to the carriage104so that movement of the driver116is transferred to movement of the carriage104. Therefore, actuation of the motor112causes rotation of the shaft114in the first direction. If the driver116is prevented from rotating with the shaft114, the driver116moves in the first linear direction. Because the driver116is attached to the carriage104, the carriage104also moves in the first linear direction. Actuation of the motor112in the opposite direction causes the shaft114to rotate in the second direction. If the driver116is prevented from rotating with the shaft114, the driver116moves in the second linear direction. Because the driver116is attached to the carriage104, the carriage104also moves in the second linear direction.

These units are easily controlled, provide substantial force at various speeds, and have pleasing sound quality. In the preferred embodiment, less than 10 watts of electrical power is required to completely deploy and retract fan blades120, including a fan blade with a 58 inch diameter. Most importantly, the drive element is inexpensive, readily available, and has a service life over 1 million actuation cycles. This life is essentially infinite in a fan deployment application.

With the actuator102rigidly mounted on the central axis A of the fan100and driving a rotatable carriage104up and down along the central axis A of the fan100, it is necessary to transmit that carriage motion into movement of fan blades120. In the preferred embodiment, this is accomplished by operatively connecting the carriage104to the fan platform108to convert the vertical motion of the carriage104into a radial motion of the fan blades120towards and away from the central axis A of the fan100. For example, the carriage is operatively connected to the fan platform to convert movement of the carriage in a first linear direction into movement of the fan blade in a first radial direction away from the central axis, and to convert movement of the carriage in a second linear direction, opposite the first linear direction, into movement of the fan blade in a second radial direction towards the central axis.

With reference toFIGS. 3-5, the fan platform108comprises a fan motor122, a fan plate124that is driven by the fan motor122, a rotary drive plate126mounted on the fan plate124and configured to rotate along a face of the fan plate124, and a deployment system128operatively connected to the fan blades120. The fan motor122is operatively connected to the fan plate124to cause the fan plate124to rotate about the central axis A. The fan plate124is operatively connected to the fan blades120. Therefore, rotation of the fan plate124causes rotation of the fan blades120. The rotary drive plate126being mounted on the fan plate124also rotates with the fan plate124and fan blades120; however, the rotary drive plate126is also independently movable relative to the fan plate124. Thus, the rotary drive plate126can rotate independently of the fan plate124about the central axis. This independent rotational movement of the rotary drive plate126, along with the deployment system, accounts for the deployment and stowing of the fan blades120.

The deployment system128comprises an arm130and a sliding block132. The arm130comprises a first end134and a second end136opposite the first end134. The first end134of the arm130is connected to the carriage104and the second end136of the arm is connected to the sliding block132. The number of arms130and sliding block132are determined by the number of fan blades120. Each fan blade120would have associated with it, one arm130and one sliding block132. Therefore, for a two-blade fan as shown in the figures, there would be two arms130a,130band two sliding blocks132a,132b. For ease of description, deployment of a single fan blade120will be described. Based on the description, a person of ordinary skill in the art will know how to implement the concepts with multiple fan blades120.

As shown inFIGS. 3-5, the arm130is operatively connected to the fan plate124and the rotary drive plate126via the sliding block132. The sliding block132rotates with the fan plate124. Note that the attachment of the arm130to the sliding block132causes the arm130to rotate synchronously with the fan plate124. The anti-friction bearing106provided in the carriage104allows this rotation to occur while the actuator102stays still. Linear movement of the carriage104along the linear actuator102causes the sliding block132to move radially towards or away from the central axis A.

The arrangement of the components as shown inFIGS. 1-5allows a fixed actuator102to create usable motion on the rotating fan plate124, independent of fan speed, while avoiding a rotating electrical interface.

As shown inFIGS. 5-7, to achieve deployment and storage of the fan blade120, in the preferred embodiment, each blade120rotates about its own blade pivot axis B near a proximal end142of the fan blade120, near the location where the fan blade120is connected to the fan plate124. Thus, it is necessary to translate the radial sliding motion of the sliding block132into a rotational motion at the fan blade pivot axis B.

In the preferred embodiment, each fan blade120can rotate approximately 180 degrees, through a plane perpendicular to the central axis A, from a fully stowed position in the fan housing138to a fully deployed position with the fan blade120extended away from the housing138. A gear arrangement is employed for this purpose. The rotary drive plate126is mounted on the fan plate124in a manner that permits the rotary drive plate126to pivot about the central axis A, relative to the rotating fan plate124. A sector gear140is mounted to the rotary drive plate126at its periphery. At a proximal end142of the fan blade120is a driving spur gear144. The driving spur gear144is attached to the proximal end142of the fan blade such that rotation of the driving spur gear144causes rotation of the fan blade120about the blade's pivot axis B. Therefore, as the driving spur gear144rolls along the sector gear140in a first direction, the fan blade120rotates about its blade pivot axis B in a first rotational direction causing the blade120to deploy. As the driving spur gear144rolls along the sector gear140in a second direction, opposite the first direction, the fan blade120rotates about its blade pivot axis B in a second rotational direction, opposite the first rotational direction, causing the fan blade120to move towards a stowed configuration.

The method used in the preferred embodiment to translate the sliding block132motion into motion of the rotary drive plate126(relative to the main rotating fan plate124) is very important. Special drive slots are provided in the rotary drive plate126and the fan plate124that engages the sliding block132via a drive roller146.

Referring toFIGS. 6 and 7, the fan plate124is provided with a fan plate drive slot148and the rotary drive plate126is provided with a rotary plate drive slot150. The fan plate drive slot148has a linear or box-like configuration creating a straight path, whereas the rotary drive plate drive slot150has an offset configuration relative to the fan plate drive slot148. Therefore, the rotary drive plate126is mounted on top of the fan plate124in such a manner that only a portion of the rotary plate drive slot150overlaps with a portion of the fan plate drive slot148. As such, the drive roller146can be inserted through the fan plate drive slot148and the rotary plate drive slot150. Therefore, properly configured, the sliding block132resides in the fan plate drive slot148to move linearly within the fan plate drive slot148in a direction radially towards or away from the central axis A, and the drive roller146resides in the rotary plate drive slot150to move along the rotary plate drive slot150.

With reference toFIGS. 6 and 7, because the remaining portions of the rotary plate drive slot150is offset from portions of the fan plate drive slot148, and because the rotary drive plate126is rotatably mounted on the fan plate124, linear movement of the sliding block132along the fan plate drive slot148causes linear movement of the drive roller146. The rotary drive plate126, in order to keep a portion of the rotary plate drive slot150aligned with the fan plate drive slot148, rotates either clockwise or counterclockwise relative to the fan plate124. Because the sector gear140is attached to the perimeter edge of the rotary drive plate126, the sector gear140moves with the rotary drive plate126. Movement of the sector gear140causes rotation of the spur gear144which in turn causes the fan blade120to rotate about the blade pivot axis B causing the fan blade to deploy or become stowed depending on the direction of movement.

For example,FIG. 7shows the sliding block132moved to the innermost position (radially inward) on the fan plate124. The drive roller146engages the rotary plate drive slot150to turn the rotary drive plate126in the blade retract direction.

The shape of the rotary plate drive slot150in the rotary drive plate126is very important for smooth blade deployment. It is desirable for the blades120to start deploying slowly, then pick up to a steady speed until near the end of the motion. Critically, at the end of blade deployment the speed should drop to zero so that the mechanism has infinite mechanical advantage in the blade open position. This serves to “lock out” the blades in the fixed open position.

It is important to have the blades120accurately positioned in the full open position while the fan is running, or balance will be compromised. Giving the mechanism infinite mechanical advantage in the deployed position also reduces the actuator arm forces to near zero. This prevents unbalanced side loading of the actuator carriage104and allows tolerances/slack to be easily taken up.

Another important function of the large rotary drive plate126is that it can coordinate the deployment of two (or more) blades120. Without a means of coordination, the arms can push the slide blocks132in an unbalanced manner, creating jerky uneven motion of the deploying fan blades.FIG. 8shows how the rotary drive plate126spans both sides of the fan to connect and coordinate the motion of the two blades. Note that three or more blades may be actuated with a similar construction.

Referring back to the rotary plate drive slot150ofFIGS. 5-8, a preferred blade motion profile is shown inFIG. 9. The shape of the rotary plate drive slot150is derived from the length of the actuator102, the kinematics of the arms130, the location of the sliding blocks132, and the distance of the blade pivot axis B from the center axis A of the fan. A preferred rotary plate drive slot150profile will give a blade displacement curve similar to that ofFIG. 9.

The same preferred drive slot shape will give a blade speed curve vs. actuator position shown inFIG. 10. Note that the speed settles down near zero as the blade120reaches its full deployed position. This gives maximum (near infinite) mechanical advantage to the mechanism in order to lock out the blades120while minimizing compression loads on the arms130.

The new blade deployment mechanism described above fulfills the “wish list” for a high-end deployable blade ceiling fan. The mechanism is powerful, quiet, and smooth. In the preferred embodiment it uses less than 10 watts of electrical energy to move the blades and has shown greater than 25 years life expectancy in normal service. The structure is compact, allowing for aggressive housing designs and it lends itself to low-cost manufacturing methods. Many of the parts will be made from molded reinforced plastics, for example.

The blades120are stowed inside the housing138in a “flat” configuration, for minimum use of space. In other words, the plane of each blade surface121is substantially perpendicular to the fan center axis A when in the stowed position. In order for the blades120to move air when the fan is turning, the blades must be “pitched up” to a predetermined angle relative to the fan center axis A, when in the deployed position. It is important that the blade pitch angle be accurate and repeatable over the life of the fan, or aerodynamic imbalances will occur while the fan is running. It is also important that the blade pitch mechanism be strong and robust, to resist damage from blade impacts or abuse.

In order for a ceiling fan to blow air towards the user effectively, the fan blades should be angled relative to the central axis A. In other words, the fan blade120should have a pitch. The fan blade120comprises a leading edge152and a trailing edge154. The leading edge152leads the fan blade120during the rotation and the trailing edge154follows the rotation. It is understood that the rotation of the fan blades120can be reversed and so the leading edge152can become the trailing edge154and vice versa. However, for purposes of this discussion, only one direction of rotation will be discussed with the leading edge152designating the edge of the fan blade120that leads the rotation. With this understanding, when the fan100is deployed, the fan blade120should have a pitch such that the leading edge152is elevated above the trailing edge154. When the fan100is in the stowed configuration, the leading edge152and the trailing edge154are substantially within the same plane.

FIGS. 11 and 12show the basic blade pitch mechanism160. A sliding blade tilt plate162engages a blade tilt cam164. The blade tilt cam164is attached to a blade tilt shaft166that allows the blade120to rotate, or “pitch” on pitch axis P substantially perpendicular to the central axis A and blade pivot axis B. In this example, the blade tilt shaft166is attached to the proximal end142of the fan blade120at the trailing edge154. The sliding blade tilt plate162is driven against the blade tilt cam164as the blade120is deployed, effectively increasing the pitch angle, or angle of attack, of the blade120.

In many embodiments, the fan blade120is not mounted at its center of mass on the blade tilt shaft166. Thus some force may be required to push the blade tilt plate162and pitch the fan blade to the “up” position where it can move air. In the preferred embodiment, a spring168is provided to assist the blade tilt plate162movement.FIG. 13shows how such a spring168is employed to reduce the force necessary to pitch the fan blade120up.

In the preferred embodiment, the blade tilt plate162is actuated in the pitch “up” direction as the blade120is rotated out to the deployed position. Likewise the blade tilt plate162is actuated in the pitch “down” direction (against the spring168) as the blade120is rotated into the stowed position inside the housing138. Thus the blade120will be flat as it enters the housing138and will require minimal space.

It is desirable to pitch the blade120up slowly as it moves out of the housing138. This is pleasing to the user and it also spreads the work of moving the blade120up over a larger motion of the linear actuator102. For instance, if the blade120was to suddenly pitch up only at the very end of deployment travel, it would require higher force. In addition, experience has shown that spreading the pitch up movement over the whole blade deployment motion is also more accurate and repeatable as it reduces large movements over short distances. It is important to have accurate, repeatable blade pitch angle to ensure balance while the fan is running.

The preferred embodiment utilizes an eccentric cam170arrangement on a blade mount plate172that interacts with the blade tilt plate162to cause the fan blade120to pitch up and down. The blade tilt plate162has two opposing drive faces163a,163b. The drive faces163a,163bare curved toward each other and spaced apart sufficiently to allow the eccentric cam170to reside in the space between the drive faces163a,163b. In between the drive faces163a,163bis a hole165through which the blade tilt cam164can protrude.

The blade mount plate172may be rigidly fixed to the fan plate124. The blade tilt plate162is mounted to the blade mount plate172such that the eccentric cam170engages the drive faces163a,163bof the blade tilt plate162as the blade tilt plate162rotates about the eccentric cam117. The eccentric cam170causes the blade tilt plate162to slide linearly, for example, perpendicular to the pitch axis P.

Therefore, as the fan blade120moves from a stowed configuration to a deployed configuration, the blade tilt plate162rotates about the fan blade pivot axis B, while the blade mount plate172remains fixed relative to the fan plate124. This causes the drive face163bto engage the eccentric cam170and the eccentricity of the cam170forces the blade tilt plate162to move in a linear direction. Linear movement of the blade tilt plate162causes the blade tilt plate162to push against blade tilt cam164causing the blade tilt cam164to rotate about the pivot axis P. Rotation of the blade tilt cam164causes the blade tilt shaft166to rotate about the pivot axis P, which in turn causes the fan blade120to rotate and causes the leading edge152to move upwardly higher than the trailing edge154(pitched up). A spring168is positioned against the blade tilt plate162to facilitate this upward movement. In moving back to the stowed configuration, the blade tilt plate162rotates about the blade pivot axis B in the opposite direction causing a second drive face163ato engage the eccentric cam170. This causes the blade tilt plate162to move in the opposite linear direction causing the blade tilt cam164to rotate about the pitch axis P in the opposite direction, causing the blade tilt shaft to rotate about the pitch axis P in the opposite direction, which in turn causes the leading edge152of the fan blade120to lower into the same general plane as the trailing edge154(pitch down). This provides a smooth pitch movement of the blade120over its entire 180 degree deployment.FIGS. 14-15show the eccentric cam170arrangement on the blade mount plate172, which fixes the blade to the main rotating fan plate via the blade tilt shaft166. InFIGS. 14-15, the blade120has rotated to its full deployed position and the eccentric cam170drives blade tilt plate162via drive face163bto the deployed position. The blade assembly is thus moved to its fully pitched up position (with the help of the spring168), via blade tilt cam164and blade tilt shaft166. In this example, the spring168biases against the blade tilt plate162to slide the blade tile plate162linearly in a direction that causes the fan blade120to pitch upwardly. Therefore, as the fan blade120is deployed, the spring168assists in pitching the blade upwardly.

InFIGS. 16-17, the blade120has rotated back to its stowed and pitched flat position. In the preferred embodiment, the weight of the blade120works with the eccentric cam170and drive face163aof blade tilt plate162(against the spring168) to bring the blade pitch to a “zero” or flat position for storage inside the housing138. This is accomplished slowly by the eccentric cam170over the full 180 degrees of blade rotation back into the housing138.

In the preferred embodiment of the fan invention described herein, the blades120are provided with an adjustment for the fully deployed position. This adjustment is necessary to account for manufacturing tolerances. InFIG. 18, the position of sector gear140can be varied relative to rotary drive plate126via slots141aand141b. Varying the position of sector gear140causes an adjustment to spur gear144, with resultant adjustment to the angular position of blade assembly120. Set screw127, mounted to rotary drive plate126, provides this adjustment within the limits defined by slots141aand141b. In the preferred embodiment, each blade assembly120has its own set screw127for independent adjustment of the fully deployed position. In practice it is most important to secure proper adjustment of each blade assembly120in the fully deployed position. This ensures proper balance and function for the fan to move air. It is also desirable to ensure that each blade assembly120is fully retracted into housing138when in the stowed position. A fixed adjustment, such as provided by set screw127for the deployed position, is generally not practical for the stowed position of each blade120. In order to best handle manufacturing tolerances and service wear, one or more resilient elements are provided for this purpose.FIG. 19is a section view showing resilient elements129installed to automatically adjust the stowed position of a blade assembly120.

As inFIG. 18, sector gear140is allowed to move relative to rotary drive plate126via slots141aand141b. Set screw127provides a fixed stop adjustment for the deployed direction of motion for blade assembly120. When retracting the blade assembly120to the stowed position, sector gear140is urged to move away from set screw127. One or more resilient elements, such as springs129, are provided to limit this motion and provide tension for blade assembly120in the stowed position via gear144. Each blade assembly120is provided with independent resilient elements129, which enable automatic adjustment of the stowed position inside housing138. Generally resilient elements129will have sufficient compression travel to take up wear over the life of the fan.

Linear actuator102is also generally configured with extra travel to allow compression of resilient elements129. Note that elements are shown as springs inFIG. 19, but they may be made of other compressible materials such as rubber, etc. Other means of providing adjustment, such as extension springs, are also easily employed.

In the general configuration of the preferred embodiment of fan100, housing138has independent upper and lower sections, with blade assemblies120mounted in between. InFIG. 20, upper housing138ais mounted to the upper end of stator shaft123of main fan motor122. Lower housing138bis mounted to the distal end103of actuator assembly102. Actuator assembly102is mounted to the lower end of stator shaft123via mounting plate182, so it does not rotate with main fan motor122. A plurality of screws186are provided to fix the proximal end of actuator assembly102to mounting plate182. In the general configuration, spacers184separate the proximal end of actuator assembly102from mounting plate182. Thus the clearance between lower housing138band the stowed blade assemblies120may be adjusted. Spacers184may also be constructed of a resilient material, such as urethane rubber, to isolate noise while actuator102is operating.

In a more advanced configuration of fan100, screws186may be configured with additional length relative to the length of spacers184. This extra length allows the body of actuator102to move along main fan axis A, towards and away from mounting plate182. Blade assemblies120and upper housing138aare fixed so they cannot translate along main fan axis A. Since lower housing138bis mounted to the distal end of actuator assembly102, lower housing138bmay also translate along main fan axis A. This creates several design advantages for fan housing138. For instance, lower housing138bcan be brought up close to blades120when blades120are stowed, but can move away for more clearance when blades120are deployed and running. In another configuration, lower housing138bcan be raised to completely cover the outside edges of blades120when they are in the stowed position. This would allow blades120to be totally concealed when not in use. The difference between the installed length of screws186and spacers184will determine the distance that lower housing138bmoves during operation.

The movable mounting of actuator102allows for automatic timing of the movements of blades120and lower housing138b, without the need for additional actuators or controls. Referring toFIG. 20, with blades120in the fully deployed position, actuator102moves carriage104downward along axis A to begin retracting blades120. During retraction, reaction force of deployment system128along axis A urges the body of actuator assembly102to move upwards toward mounting plate182. Lower housing138b, attached to actuator assembly102, can be designed with sufficient weight to overcome this reaction force. Thus housing138bwill stay in the down position until blades120are in the fully stowed position. With deployment system128no longer able to move, carriage104will keep traversing downward along axis A and the body of actuator102(with lower housing138battached) will now be forced to move upward along axis A toward stowed blades120. Therefore, in some embodiments, the fan blades120can be stowed within the housing138as shown inFIG. 21, or the fan blades can be completely hidden from as shown inFIG. 22. The limit of travel for actuator body102and lower housing138bis defined by the length of spacers184. Note that the timing effect of lower housing138bcan be enhanced by inserting one or more biasing elements, such as springs, between the proximal end of actuator assembly102and mounting plate182. This would have the same effect as adding weight to lower housing138b.

The automatic timing of the movement of lower housing138bis similar during blade deployment. With blades120in the stowed position, actuator102and lower housing138bis held against gravity in a proximal position relative to blades120. As deployment of blades120starts, carriage104moves upward and relaxes the holding force. This allows gravity to translate actuator body102and lower housing138bdownward away from the stowed blades120. Eventually actuator body102and lower housing138bwill reach a lower limit of travel defined by the length of screws186. At this point carriage104continues its movement and deployment system128is forced to start deploying blades120. Lower housing138bat this point is well clear of the moving blades.

In the preferred embodiment of fan100, a digital control system is provided to coordinate the movement of deployment system128with rotation of main fan motor122. When fan100is not in use, it is generally desirable to have blades120in a stowed position inside housing138. When a user commands fan100to turn on and operate, it is desirable to first deploy blades120and then start turning main fan motor122. The digital control system inhibits the operation of main fan motor122until it has sensed that blades120are in a suitable deployed position. Likewise, when the user commands fan100to turn off, it is desirable to immediately cut power from main fan motor122, and wait until fan100has slowed down to a suitable low speed before retracting the blades. The digital control system employs a tachometer sensor to inhibit retraction of the blades until fan100has slowed to desired speed, or even stopped turning.

The digital control system may also monitor the forces encountered during blade deployment and retraction, to detect one or more blades120striking an object or deployment system128binding. Likewise, retraction of blades120into housing138may create a pinching hazard for hands and fingers. The digital control system can be configured to monitor forces in deployment system128to detect pinching and immediately reverse the blade retraction.

In the preferred embodiment, actuator102is a stepper-type motor. The distance moved by such a stepper actuator may be monitored to adjust for wear in service and ensure full movement of deployment system128in both deployment and retraction.

In some embodiments, the basic steps for the control system to start fan100from an OFF configuration are: inhibit rotation of main fan motor122, start actuator102in the DEPLOY direction, monitor distance traveled (steps) until blades120have deployed sufficiently, monitor force in deployment system128to detect blade strike or bind, start main fan motor122once blades120have deployed sufficiently, stop actuator102once blades120have fully deployed.

In some embodiments, the basic steps for the control system to stop fan100from an ON/RUNNING configuration are: immediately cut power to main fan motor122, monitor rotational speed of main fan motor122via a tachometer sensor, inhibit actuator102until main fan motor122speed has dropped to a suitable level, start actuator102in the RETRACT direction once main fan motor122speed is suitably low, monitor distance traveled (steps) until blades120have reached the fully stowed position, monitor force in deployment system128to detect blade pinch or bind, stop actuator102once blades120have fully retracted.