Patent Abstract:
An airflow apparatus (e.g., a fan, a blower) is provided for impeding or facilitating airflow through a channel when the apparatus is inoperative. The apparatus comprises a set of blades or airfoils that, when operating, promote or force a flow of air through the channel. The apparatus includes a bias mechanism for biasing the blades of the apparatus toward failure positions blocking or opening the airflow when the apparatus is at rest or turned off. When the apparatus begins spinning, the bias mechanism is overcome and the blades take their normal operating positions. The bias mechanism may comprise a spring or elastic material that resists rotation, extension or other type of blade transition from the failure position to the operating position. Or, the bias mechanism may involve a blade design (e.g., edge weighting) that attempts to place a blade in its failure position.

Full Description:
BACKGROUND 
     This invention relates to the field of ventilation. More particularly, an airflow device, such as a fan, is provided with an automatic failure mode to place the device in a configuration to either impede or allow airflow. 
     Multiple fans or similar airflow-inducing devices (e.g., blowers) are often used together to increase the volume, rate or force of ventilation. For example, two or more small axial fans may be used in parallel or in series to generate airflow through a computer system or other piece of electronic equipment. In a parallel arrangement, the fans promote parallels flows of air through different apertures or openings in the equipment. In a series configuration, the fans are aligned in sequence from a single aperture. 
     When one fan in a multi-fan arrangement fails, its failure can significantly affect the operating efficiency of the other fan(s). In a parallel arrangement, when one fan fails, it may create a “short-circuit” that prevents air from flowing through much of the equipment. In a series configuration, the blades of the failed fan will impede the airflow generated by the remaining fan(s). 
     Attempts to alleviate the impact of a fan failure on a functioning fan have been ineffective or have caused other problems. For example, a baffle or flap may be added to a fan operating in a parallel configuration. The baffle is blown out of the way when the fan is operating, but is intended to block the fan if it fails. However, even if the baffle helps block the fan when it fails, while the fan is operating, some of the efficiency of the fan is wasted on keeping the baffle open. In addition, the baffle occupies space that may be put to better use. 
     In a series arrangement, a fan may be equipped with fewer blades so that it creates less impedance if it fails. However, the decreased number of blades affects the fan&#39;s efficiency when it is operating. 
     Therefore, there is a need for an airflow device (e.g., fan, blower) that can automatically fail into a mode or configuration that either blocks or opens an air channel through the fan, as desired. 
     SUMMARY 
     In one embodiment of the invention, an airflow apparatus (e.g., a fan, a blower) is provided for impeding or facilitating airflow through a channel when the apparatus fails or is inoperative. The apparatus comprises a set of blades or airfoils that, when operating, promote or force a flow of air through the channel. The apparatus also includes a bias mechanism for biasing the blades of the apparatus toward failure positions blocking or opening the channel when the apparatus is at rest or turned off. When the apparatus begins spinning, the bias mechanism is overcome and the blades take their normal operating positions. The apparatus may be employed by itself or as one of multiple apparatuses working together. 
     In different embodiments, the bias mechanism may comprise a spring or elastic material that resists rotation, extension or other type of blade transition from the failure position to the operating position or promotes rotation, contraction or other transition from the operating position to the failure position. In one implementation, the bias mechanism may involve a blade design (e.g., weighting) that attempts to place a blade in its failure position by the force of gravity. In these embodiments, and others, centrifugal force generated by the spinning blades places the blades into their normal operating positions. However, when that centrifugal force is terminated or sufficiently attenuated, the blades are returned to their failure positions. 
    
    
     DESCRIPTION OF THE FIGURES 
     FIGS. 1A-C are block diagrams depicting a fan in operating and failure positions, in accordance with an embodiment of the present invention. 
     FIGS. 2A-C comprise side views of the fan depicted in FIG. 1, demonstrating the orientation of the fans&#39; blades. 
     FIGS. 3A-B depict an apparatus configured for automatic failure of airfoils into an “open” position, with detail of a mechanism for promoting transition between an operating position and the failed position, in accordance with an embodiment of the present invention. 
     FIG. 4 is a block diagram of a blade assembly for biasing a fan blade toward a failure position, according to one embodiment of the invention. 
     FIGS. 5A-B provide detailed views of an illustrative blade assembly for automatically biasing a fan blade toward a failure position, according to one embodiment of the invention. 
     FIGS. 6A-B provide detailed views of one alternative blade assembly for automatically biasing a fan blade toward a failure position, according to one alternative embodiment of the invention. 
     FIGS. 7A-B provide detailed views of another alternative blade assembly for automatically biasing a fan blade toward a failure position, according to another alternative embodiment of the invention. 
    
    
     DETAILED DESCRIPTION 
     The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of particular applications of the invention and their requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art and the general principles defined herein may be applied to other embodiments and applications without departing from the scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. 
     In an embodiment of the invention, an apparatus is provided for generating or promoting flow of air (or other gas or liquid) when in an operating position, and either impeding or facilitating airflow in an automatic failure position. In different embodiments, the apparatus may comprise a fan, a blower or other device comprising airfoils (e.g., blades) that are configured to spin around a hub, spinner, axle or other component. When spinning, the airfoils impact the air at an angle to force the air to flow through a channel. The apparatus may be employed by itself or in combination with one or more additional apparatuses. 
     In one embodiment of the invention, when the apparatus fails or is turned off, the airfoils transition from their operating position to an open position in which they lie approximately parallel to the desired flow of air. Although the airfoils are not helping generate air flow, in this failure position the airfoils present little impedance to the flow of air through the channel. This embodiment may be particularly beneficial when one or more additional apparatuses are employed in series with the failed or inoperative one. 
     In another embodiment of the invention, when the apparatus fails or is turned off, the airfoils transition from their operating positions to a closed position in which they lie approximately perpendicular to the desired airflow. In this failure position, the airfoils present significant impedance to the flow of air through the channel. This embodiment may be beneficial when one or more additional apparatuses are employed in parallel with the failed or inoperative one. 
     FIGS. 1A-C provide views of an airflow apparatus (e.g., a fan) demonstrating a normal operating position and alternative failure positions, according to one or more embodiments of the invention. 
     In these embodiments, fan  102  comprises a plurality of airfoils (i.e., blades  104 ) coupled to hub  106 , which spins about an axle (not shown). Hub  106  may contain a motor for spinning the hub, or electronics or circuitry coupling the hub to a motor. Fan  102  also comprises supports  108  and casing  110 . Casing  110  defines a channel for the flow of air through the apparatus, while supports  108  provide rigidity and may comprise circuits or power for operating the fan. 
     FIG. 1A demonstrates fan  102  in an operating position, according to one embodiment of the invention. In this position, the surfaces of blades  104  are oriented at some angle, between 0 and 90 degrees, to the desired flow of air. In this position, when hub  106  rotates and spins the blades, air is forced through the channel defined by casing  110 . 
     FIG. 1B demonstrates fan  102  in an “open” failure position according to an embodiment of the invention. In this position, the surfaces of blades  104  are oriented substantially parallel to the desired air flow. Thus, when hub  106  is not spinning or is spinning very slowly, the blades present minimal impedance to any natural airflow through the channel or any airflow that may be due to the operation of other fans or devices. 
     FIG. 1C demonstrates fan  102  in a “closed” failure position according to one embodiment of the invention. In this position, the surfaces of blades  104  are oriented substantially perpendicular to the desired air flow. Thus, when hub  106  is not spinning or is spinning very slowly, the blades present significant impedance to any natural airflow through the channel or any airflow that may be due to the operation of other fans or devices. 
     FIGS. 2A-C provide side or cross-sectional views of fan  102  corresponding to FIGS. 1A-C. Thus, FIG. 2A demonstrates the normal operating position of airfoils  104  when they are operating. FIG. 2B demonstrates the open failure position of airfoils  104  from FIG.  1 B. FIG. 2C demonstrates the closed failure position of airfoils  104  from FIG.  1 C. 
     In one embodiment of the invention, a blade or other airfoil includes a shaft for coupling the blade to its hub or spinner. The hub may comprise bores or holes for receiving each shaft. A blade shaft may be coupled directly to the hub, or some coupling mechanism may be employed to couple them. 
     In this embodiment, blades transition between their operating and failure positions via rotation. In particular, each blade shaft may be configured to rotate within its hub bore. A bias mechanism biases a blade toward its failure position, but centrifugal force may be used to overcome the biasing force and rotate the blade toward its operating position when the hub spins or spins at a sufficient rate. Alternatively, the blades may be forced into their operating positions electrically or mechanically. 
     In an embodiment of the invention, bias mechanisms may comprise springs, elastic material, or other flexible components. For example, a bias mechanism may comprise a coil or torsion spring, or an elastic material anchored within the hub and connected to the shaft. The mechanism biases a blade toward its failure position when the centrifugal force of the spinning apparatus stops or is insufficient to overcome the strength of the bias. 
     In one alternative embodiment of the invention, a blade shaft may be shaped to allow extension from a hub, or retraction into the hub, as the shaft rotates. For example, a blade shaft may include one or more projections from the side of the shaft, which correspond to channels, grooves or slots in the hub bore into which the shaft is received. 
     As centrifugal or other force is applied to the blade, it extends outward from the hub, with the corresponding projection(s) and channel(s) interacting to rotate the shaft. The extension of a blade may be limited with stops or by the length of the channel(s). When the fan fails or is turned off, the blades automatically retract or rotate into their failure positions under the force of their bias mechanisms. 
     In another alternative embodiment, blades may be weighted to promote transition to or from a failure position. Thus, particularly in an orientation in which gravity may be taken advantage of, a blade may be weighted to promote its transition into the desired failure position (i.e., open or closed). Such weighting may be distributed across the surface of a blade or concentrated at one or more edges. Illustratively, the top edge of a blade may be weighted to help it fall into a “closed” position, or the bottom edge may be weighted to help rotate it into an “open” position. 
     FIGS. 3A-B depict a mechanism or means for automatically transitioning an airfoil into a failed position, according to one embodiment of the invention. In this embodiment, the blade&#39;s failure position is an “open” position, in which the blade is oriented substantially parallel to the desired airflow. 
     FIG. 3A depicts fan  302  in a normal operating position, which includes blades  304 , hub  306 , supports  308  and casing  310 . A bias mechanism is highlighted and detailed. The detailed view depicts a portion of blade  304 , a portion of a wall  320  of hub  306 , a hub bore or socket  322 , slot  324  in bore  322 , spring  334  and shaft projection  332 . Shaft projection  332  extends perpendicular to the shaft of blade  304 . The shaft is not visible in the detailed view. 
     In FIG. 3A, shaft projection  332  is positioned toward one end of slot  324 , which cuts an oblique angle across bore  322 . In this operating position, the surface of blade  304  is positioned at a suitable angle (e.g., between zero and ninety degrees) to the air channel through casing  310 . Spring  334 , which is coupled or attached to the shaft of blade  304 , is in a compacted or compressed position. Spring  344  may be compressed when hub  306  spins fast enough for the centrifugal force applied to blade  304  to overcome the tension of the spring. 
     FIG. 3B depicts fan  302  in its open failed position. In the detailed view, blade  304  has transitioned to its open position, thereby presenting an edge of the blade to airflow through the channel of casing  310  and causing minimal impedance to the airflow. In this position, shaft projection  332  is now located toward the opposite end of slot  324  in bore  322 . 
     FIG. 3B shows spring  334  in a relaxed or uncompressed state, in which it resists rotation of the shaft of blade  304 . In different embodiments of the invention, spring  334  may be compressed or tensioned when blade  304  is transitioned from its failure position to its operating position, but its equilibrium state substantially corresponds to the failure position of blade  304 , thereby biasing the blade toward that position. 
     Illustratively, the length of slot  324  may correspond to the degree of rotation needed to rotate blade  304  between its operating and failed positions. Thus, in FIGS. 3A-B, if blade  304  rotated approximately forty-five degrees, then slot  324  may extend approximately forty-five degrees about the circumference of bore  322 . 
     In one alternative embodiment of the invention, slot  324  may be aligned substantially perpendicular to the axis of bore  322 . In this alternative embodiment, blade  304  would not be extended from hub  306  when it rotates into its operating position from its failure position. Instead, as the hub spins faster, the force of air upon the open blade may overcome the bias of spring  334  and cause the blade to rotate into its operating position. When the hub slows sufficiently, the bias of spring  334  would cause the blade to rotate back into its failure position. 
     One of ordinary skill in the art would recognized from the preceding description how the embodiment of the invention depicted in FIGS. 3A-B could be modified for an apparatus in which the airfoils are to fail into a “closed” position. 
     FIGS. 4-7 demonstrate other means for biasing a blade or airfoil toward a failure position, according to alternative embodiments of the invention. 
     In FIG. 4, blade  410  is coupled to hub  404  via blade shaft  412  and bushing  418 . Elastic biasing member  420  biases the shaft toward rotating into the blade&#39;s failure position. Biasing member  420  is anchored by anchor  422  and is coupled to the blade via post  424 . Inertial weight  414  is coupled to blade shaft  412 . When blade  410  and hub  404  rotate about the hub axis (not shown) in the indicated direction, inertial weight  414  helps shaft  412  rotate into the blade&#39;s operating position. The direction of the views of FIGS. 5,  6  and  7  is shown in FIG.  4 . 
     In FIG. 5A, blade  410  is shown in its operating position; FIG. 5B depicts blade  410  in its failure (closed) position. In the embodiment of the invention depicted in FIGS. 5A-B, no elastic biasing means is necessary; inertial weight  414  helps rotate blade shaft  412  into the operating position when the blade moves fast enough, and promotes rotation of the shaft into the failure position when the blade slows. More particularly, inertial force helps keep blade shaft  412  in the operating position in FIG. 5A, while gravitational force helps rotate the shaft into the failure position in FIG.  5 B. Stops  516  limit the rotation of weight  414  and shaft  412 . 
     FIGS. 6A-B illustrate an embodiment of the invention in which inertial weight  414  is used with elastic biasing member  420 . In FIG. 6A, blade  410  is shown in its operating position; FIG. 6B depicts blade  410  in its failure (closed) position. As in the embodiment of FIG. 4, the elastic biasing member stretches between anchor  422  and post or hook  624 , and biases blade shaft  412  and blade  410  into the failure position. When the blade rotates fast enough about hub  404 , the inertial force of inertial weight  414  overcomes the elastic biasing member. Stops  616  limit the rotation of blade shaft  412  and inertial weight  414 . 
     FIGS. 7A-B demonstrate an embodiment in which elastic biasing member  420  is employed with a weighted blade instead of an inertial weight. In FIG. 7A, blade  410  is shown in its operating position; FIG. 7B depicts blade  410  in its failure (closed) position. The elastic biasing member and the weighted portion of blade  410  biases the blade into the failure position. When the blade rotates fast enough about the axis of hub  404 , the inertial force of the weighted blade overcomes the elastic biasing member. Stops  616  limit the rotation of blade shaft  412  and inertial weight  414 . 
     The foregoing embodiments of the invention have been presented for purposes of illustration and description only. They are not intended to be exhaustive or to limit the invention to the forms disclosed. Accordingly, the scope of the invention is defined by the appended claims, not the preceding disclosure.

Technology Classification (CPC): 5