Patent Description:
Fan systems, e.g., for circulating air for cooling computer systems and electronic systems housed within chassis or enclosures, are typically user-replaceable modules. Typical fan systems include fan blades that rotate at relatively high rotations per minute (rpm) in order to produce a desired level of airflow. The rotating fan blades typically continue to rotate at considerable speed for some period of time even after being electrically disconnected, electrically deactivated, physically disconnected, or physically removed from an enclosure. This is because the fan systems operate at high rpm's. The blades may continue to rotate for several seconds up to several minutes. The rotating fan blades present a safety hazard when a user or service technician places their hands and fingers inside a chassis or an enclosure housing a fan system, as the rotating fan blades may cause injury upon accidental contact with the hands or fingers. Such an injury may occur during removal of the fan system from the housing, for example. In order to avoid such a hazard, some fan systems include a formed wire guard or the like to prevent physical contact between the fan blades and a foreign object, e.g., a hand or finger.

<CIT> discloses a rotary flow inducing device having rotary flow inducing blades and a protection mechanism including a trigger to move the protection mechanism between an operational flow configuration and a protective no-flow configuration with respect to the rotary flow inducing blades. According to one example, a brake assembly comprises a lever arm which is coupled to a housing by a first pivot joint and coupled to an engaging arm by a second pivot joint. The brake assembly further comprises a spring mechanism which interacts with the lever arm to bias the lever arm inwardly towards the blades. A plurality of nodules are disposed about a circumferential section of a hub. Upon removal of the rotary flow inducing device from a flow passage, the spring mechanism rotates the lever arm about the first pivot j oint, thereby forcing the engaging arm to engage the nodules and stopping rotation of the hub.

<CIT> discloses a fan built into a plug-in unit for an electrical device such as a server computer. The fan has plurality of blades arranged on a hub. A pre-tensioned spring strip is arranged so that it may exert pressure onto the hub of the fan and quickly stop rotation of the fan. A locking mechanism is provided which directs the spring strip away from the hub of the fan when the plug-in unit is locked within the electrical device, and directs the spring strip onto the hub of the fan when the plug-in unit is unlocked.

<CIT> discloses a fan brake for decelerating a blower impeller. The fan brake comprises a pivotable arm coupled to a braking surface. The arm is adapted to apply the braking surface to the impeller under control of a cam or a solenoid.

<CIT> discloses a cooling fan module that comprises a module housing and a fan assembly. The fan assembly comprises a blade assembly coupled to a motor disposed within a fan housing that is disposed within the module housing. The fan housing comprises a tapered, or bell-shaped inlet that guides airflow toward the blade assembly. The blade assembly comprises radial blades and a hub that include features that improve an aerodynamic performance of the fan assembly. For example, the radial blades may have an aerodynamically optimized shape, and the hub may have a conical shape that helps smooth the flow of air into the blades.

The present invention is defined by the independent claims, taking due account of any element which is equivalent to an element specified in the claims. The dependent claims concern optional elements of some embodiments of the present invention.

In various embodiments, a fan system includes rotating fan blades and a braking mechanism that is operable to cause the rotating fan blades to stop rotating. The fan system includes, but is not limited to, a fan rotor, a fan motor, and a braking mechanism. The fan rotor includes a rotating blade assembly configured to rotate around an axis. The fan motor is configured to cause rotation of the rotating blade assembly around the axis. The braking mechanism is configured to apply friction to a flat circular region of the rotating blade assembly of the fan rotor when the braking mechanism is engaged. The friction is applied via a control arm having a braking portion that is configured to be disposed in a contact position against the flat circular region of the rotating blade assembly of the fan rotor when the braking mechanism is engaged. Application of friction to the flat circular region of the rotating blade assembly of the fan rotor stops rotation of the rotating blade assembly around the axis.

In some embodiments, the braking mechanism may be automatically activated when the fan system is removed from its operative position within a chassis or enclosure. The chassis or enclosure may be a standard component used for housing computer systems, electronics systems, or components thereof. The braking mechanism may be activated as a result of a user opening or removing a cover, door, or access panel for a chassis or enclosure that includes the fan system. The braking mechanism may be activated by a mechanical apparatus. The braking mechanism may be activated by electronic circuitry coupled with an actuator. The braking mechanism may be activated in response to activation of a switch, a button, or other physical input device operable by a user.

By applying friction to the flat circular region of the rotating blade assembly of the fan rotor, the braking mechanism may physically stop the rotation of the fan blades in a fan system in less than a second, or within a few seconds. Stopping the rotation of the fan blades by applying friction may stop the rotation of fan blades faster than fan systems which are configured to allow the fan blades to continue to rotate without any resistance after power to the fan rotor has been cut.

Fan systems with the braking mechanism, as described in various embodiments, may or may not include formed wire guards and the like. In at least one embodiment, the fan system with the braking mechanism does not include formed wire guards. The wire guards, which are designed to prevent injury caused by fingers coming into contact with rotating blades, may not be needed if the rotation of the blades is stopped prior to fingers being able to contact the blades. In at least one embodiment, the fan system with the braking mechanism does include formed wire guards. The formed wire guards may be used, for example, to hold the fan system, or protect the components of the fan system from being touched by fingers. The formed wire guards may also be used to prevent fingers from touching rotating blades when the blades are rotating without engagement of the braking mechanism. The formed wire guards may be removable components used temporarily during some tests.

A detailed example is described below for purposes of clarity. Components and/or operations described below should be understood as one specific example which may not be applicable to certain embodiments. Accordingly, components and/or operations described below should not be construed as limiting the scope of any of the claims.

<FIG> is a perspective view that illustrates a fan system <NUM>, in accordance with one or more embodiments. As illustrated in <FIG>, the fan system <NUM> includes a fan rotor <NUM>, a fan motor <NUM>, a fan housing <NUM>, a braking mechanism <NUM>, and a chassis interface <NUM>. In various embodiments, the chassis interface <NUM> may be disposed within a chassis or enclosure <NUM> that houses a computer system or electronics system. The chassis interface <NUM> may include power connections to provide electric power to the fan motor <NUM> when the fan housing <NUM> is fully inserted into the chassis interface <NUM>, and disconnect electric power from the fan motor <NUM> when the fan housing <NUM> is at least partially removed from the chassis interface <NUM>. The fan housing <NUM> may be disposed at an outside edge or wall of the chassis or enclosure <NUM> such that air may flow into the fan housing <NUM> from exterior to the chassis or enclosure <NUM> when the fan system <NUM> is operational. In one or more embodiments, the fan system <NUM> may include more or fewer components than the components illustrated in <FIG>.

The fan rotor <NUM> may be mounted on a shaft rotationally driven around an axis by the fan motor <NUM>. In some embodiments, the fan rotor <NUM> may be integrated with the shaft. In various embodiments, the fan rotor <NUM> may have a radius of between <NUM> and <NUM> inches, e.g., approximately <NUM> inches. The fan rotor <NUM> includes a rotating blade assembly <NUM>, which may have a plurality of blades <NUM> surrounding the axis of the shaft, around which the rotating blade assembly <NUM> rotates. The blades <NUM> of the rotating blade assembly <NUM> may be angled to cause air to flow along the airflow direction <NUM> through the rotating blade assembly <NUM>. Thus, the rotating blade assembly <NUM> may be operative to pull air from a region exterior to the fan housing <NUM> through the rotating blade assembly <NUM> when the fan motor <NUM> rotates the fan rotor <NUM> and rotating blade assembly <NUM> around the axis. In various embodiments, the fan rotor <NUM> may be formed as a single integrated part.

In various embodiments, the fan motor <NUM> may cause the fan rotor <NUM> to rotate under electric power. The fan motor <NUM> may cause the fan rotor <NUM> to rotate with a force of about <NUM> inch-pounds to <NUM> inch-pounds of torque. In various embodiments, the fan motor <NUM> may include a brushless electric motor.

The braking mechanism <NUM> is configured to apply friction to a flat circular region <NUM> of the rotating blade assembly <NUM> of the fan rotor <NUM> when the braking mechanism <NUM> is engaged. This application of friction is effective to stop rotation of the rotating blade assembly <NUM> around the axis of the shaft. The rotating blade assembly <NUM> includes the generally flat circular region <NUM> disposed at an approximate center of the rotating blade assembly <NUM>, e.g., close to and surrounding the axis while being disposed between the axis and the plurality of blades <NUM>. The generally flat circular region <NUM> is configured to rotate concurrently with the rotating blade assembly <NUM>.

The braking mechanism <NUM> includes a control arm <NUM>, a braking portion <NUM> disposed at one end of the control arm <NUM>, an actuating portion <NUM> on an opposite end of the control arm <NUM>, and a base portion <NUM> disposed between the braking portion <NUM> and the actuating portion <NUM>. The base portion <NUM> includes a pivot rod <NUM> disposed perpendicular to the control arm <NUM> between the braking portion <NUM> and the actuating portion <NUM>. The pivot rod <NUM> pivotably couples the braking mechanism <NUM> with the fan housing <NUM>. The pivot rod <NUM> may be coupled with pivot points <NUM>. In some embodiments, the pivot points <NUM> may include holes in the fan housing <NUM> through which the pivot rod <NUM> is inserted. The control arm <NUM> is configured to pivot about the base portion <NUM> between a contact position in which the braking portion <NUM> applies friction to the flat circular region <NUM> of the rotating blade assembly <NUM> of the fan rotor <NUM> to stop rotation of the fan rotor <NUM>, and a non-contact position in which the braking portion <NUM> is physically separated from the fan rotor <NUM> to permit the fan rotor <NUM> to freely rotate.

The base portion <NUM> includes a biasing element, e.g., a spring <NUM>, which may include a torsion spring, that biases the braking portion <NUM> of the control arm <NUM> toward the contact position. The spring <NUM> may engage the braking mechanism <NUM> when no external pressure is applied to the actuating portion <NUM>. In various embodiments, the spring <NUM> may apply a biasing force of about <NUM> to <NUM> inch-pounds of torque. An amount of torque applied by the spring <NUM> may depend upon a number of factors, for example, a speed with which the fan rotor <NUM> rotates, a mass of the fan rotor <NUM>, a radius of the fan rotor <NUM>, the friction applied to the fan rotor <NUM> during engagement of the braking mechanism <NUM>, and a length of the control arm <NUM> between the braking portion <NUM> and the base portion <NUM>. While the spring <NUM> is shown as an example of the biasing element, this should not be construed as limiting, as other forms of the biasing element may be used in other embodiments. For example, the biasing element may include a rubber band or elastic member in some embodiments. The spring <NUM> may be coupled with the fan housing <NUM> and the pivot rod <NUM>. In various embodiments, the biasing element may be integrated with the base portion <NUM>. In various embodiments, the base portion <NUM> may be integrated with the control arm <NUM>, the braking portion <NUM>, and the actuating portion <NUM>. In various embodiments, one or more of the components of the braking mechanism <NUM> may be formed of injection molded plastic, e.g., resin or polycarbonate, or may be formed of metal, e.g., metal casting or folded sheet metal. The material may be chosen according to its rigidity and resiliency to impact as well as its cost.

Characteristics of the spring <NUM> may be determined according to characteristics of the fan rotor <NUM>. For example, an amount of pressure necessary to stop the fan rotor <NUM> from turning within a desired period of time after engaging of the braking mechanism <NUM> may at least in part determine a desired strength of the spring <NUM>. In addition, a distance between the base portion <NUM> and the braking portion <NUM> along the control arm <NUM> and/or a distance between the base portion <NUM> and the actuating portion <NUM> along the control arm <NUM> may also at least in part determine a desired strength of the spring <NUM>. The spring <NUM> may be formed of a metal, a plastic material, or other material that provides biasing characteristics.

The control arm <NUM> may be aerodynamically shaped to present low air resistance to the airflow <NUM> flowing through the rotating blade assembly <NUM>. Key aerodynamic attributes of the control arm <NUM> may include an airfoil cross section of the control arm <NUM>. An angle of attack with respect to the airflow <NUM> may be determined according to a velocity of the airflow <NUM>. For example, in various embodiments, the angle of attack with respect to the airflow <NUM> may range between approximately <NUM> and <NUM> degrees, or between approximately <NUM> and <NUM> degrees. In an embodiment, the angle of attack may be approximately <NUM> degrees. In various embodiments, the shape of the control arm <NUM> may be tapered from a side closest to the fan rotor <NUM> and a side furthest from the fan rotor <NUM> along a path of the airflow <NUM>. The shape of the control arm <NUM> may be configured as an airfoil to improve aerodynamic performance. A width of the control arm may be as narrow as possible while meeting material strength and mechanical stability requirements to minimize its obstruction to the airflow <NUM>. In various embodiments, the control arm <NUM> may be less than about <NUM> or approximately <NUM> from the side facing the fan rotor <NUM> and the side facing away from the fan rotor <NUM>, and a span of the control arm <NUM> from the braking portion <NUM> to the actuating portion <NUM> may be between <NUM> and <NUM>, or approximately <NUM>. The aerodynamic attributes of the control arm <NUM> may result in better airflow and acoustic performance compared to a traditional fan guard.

The braking portion <NUM> may include an aerodynamically shaped portion having a wider portion that is configured to be disposed against the generally flat circular region <NUM> of the rotating blade assembly <NUM> when the braking mechanism <NUM> is engaged. In some embodiments, the aerodynamically shaped portion may be in a shape of a cone or a partial cone with a generally flattened narrow end. The aerodynamic shape of the braking portion <NUM> may be configured to reduce drag on the airflow <NUM> that flows through the rotating blade assembly <NUM>. Key aerodynamic attributes of the braking portion <NUM> may include a taper of the cone shape. A longer cone shape may result in better aerodynamic performance, but a length of the cone shape may be limited by a desired size of the fan system <NUM>. The aerodynamic attributes of the braking portion <NUM> may result in better airflow and acoustic performance compared to a traditional fan guard.

In some embodiments, the braking portion <NUM> may include a brake pad <NUM> disposed between the braking portion <NUM> and the generally flat circular region <NUM> of the rotating blade assembly <NUM> to apply friction to the generally flat circular region <NUM> when the braking mechanism <NUM> is engaged. The brake pad <NUM> may include a high friction material, e.g., an elastomer or a rubber, which may be glued or over-molded onto the braking portion <NUM>. By adjusting characteristics of the brake pad <NUM>, an amount of friction applied to the generally flat circular region <NUM> may be adjusted. In some embodiments, the braking portion <NUM> may apply friction directly to the generally flat circular region <NUM> when the braking mechanism <NUM> is engaged without including the brake pad <NUM>. In various embodiments, the brake pad <NUM> may apply a braking force of approximately <NUM> pound to <NUM> pounds. In some embodiments, any one or more of the braking mechanism <NUM>, brake pad <NUM>, and generally flat circular region <NUM> may include a texture to increase an amount of friction applied when the braking mechanism <NUM> is engaged. In some embodiments, the texture may include a series of bumps or peaks, e.g., having a height up to <NUM>. In some embodiments, the brake pad <NUM> may be disposed on the generally flat circular region <NUM> of the rotating blade assembly <NUM> instead of on the braking portion <NUM>, and the brake pad <NUM> may be configured to rotate concurrently with the rotating blade assembly <NUM> around the axis when the fan system <NUM> is in an operational mode.

The actuating portion <NUM> may engage with an actuator <NUM> affixed to or disposed on the chassis interface <NUM> to engage the braking mechanism <NUM> when the actuator <NUM> presses the actuating portion <NUM> toward the fan rotor <NUM> or a plane of the fan rotor <NUM> and disengage the braking mechanism <NUM> when the actuator <NUM> releases pressure from the actuating portion <NUM> and thereby allows the actuating portion <NUM> to be moved away from the fan rotor <NUM> or a plane of the fan rotor <NUM> by the bias of the spring <NUM>. In some embodiments, the braking mechanism <NUM> may be configured to disengage when an access panel, door, or cover of the chassis or enclosure <NUM> including the fan system <NUM> is closed, and engage when the access panel, door, or cover of the chassis or enclosure <NUM> including the fan system is at least partially opened.

In some embodiments, the actuator <NUM> may be fixedly attached to the chassis interface <NUM>, e.g., as part of an end stop that stops movement of the fan housing <NUM> when the fan housing <NUM> is inserted into the chassis interface <NUM>. The actuator <NUM> may include a fixed and non-movable element affixed to the chassis interface <NUM>. The actuator <NUM> may provide continuous actuation force against the actuating portion <NUM> to maintain disengagement of the braking mechanism <NUM> when the fan housing <NUM> is installed within the chassis interface <NUM>. In some embodiments, the braking mechanism <NUM> may be configured to disengage when the fan system <NUM> is installed within the chassis or enclosure <NUM> such that the fan rotor <NUM> may rotate freely, and engage when the fan system <NUM> is at least partially removed from the chassis or enclosure <NUM> to stop rotation of the fan rotor <NUM>. When the fan housing <NUM> is installed in operational position within the chassis interface <NUM>, the actuator <NUM> may press against the actuating portion <NUM> to disengage the braking mechanism <NUM> by causing the braking portion <NUM> to separate from the fan rotor <NUM> via a lever action of the control arm <NUM>. When the fan housing <NUM> is removed from the operational position within the chassis interface <NUM>, the actuator <NUM> may separate from the actuating portion <NUM> and permit the spring <NUM> to cause the pivot rod <NUM> to turn and the braking portion <NUM> to apply friction to the generally flat circular region <NUM> of the rotating blade assembly <NUM> and cause the fan rotor <NUM> to cease rotation. In this way, the fan system <NUM> may cease rotation of the fan rotor <NUM> promptly upon removal of the fan housing <NUM> from the chassis interface <NUM>, and the fan system <NUM> may permit rotation of the fan rotor <NUM> promptly upon installation or re-installation of the fan housing within the chassis interface <NUM>.

In some embodiments, which the braking mechanism <NUM> is engaged, motion of the control arm <NUM> may cause a rocker switch, contact switch, or the like to disconnect power from the fan motor <NUM>, and when the braking mechanism <NUM> is disengaged, motion of the control arm <NUM> may cause the rocker switch, contact switch, or the like to connect power to the fan motor <NUM>.

In some embodiments in which the spring <NUM> may not be present, the actuator <NUM> may actively control the motion of the actuating portion <NUM> toward or away from the fan rotor <NUM>, e.g., by a motor or solenoid under control of an electronic control system. In some embodiments, the actuator <NUM> may be biased in a position away from the actuating portion <NUM>, and when power is applied to a motor of the actuator <NUM>, the actuator <NUM> may push the actuating portion <NUM> toward the fan rotor <NUM>. For example, when a cover, door, or access panel of the chassis or enclosure <NUM> is opened, a sensor may trigger a control system to control the motor or solenoid of the actuator <NUM> to move away from the actuating portion <NUM> while power to the fan motor <NUM> is disconnected so that the braking mechanism <NUM> causes the fan rotor <NUM> to stop rotating. Then, when the cover, door, or access panel of the chassis or enclosure <NUM> is closed, the sensor may trigger a control system to power the motor or solenoid of the actuator <NUM> to move the actuator <NUM> toward the actuating portion <NUM> so that the braking mechanism <NUM> separates the braking portion <NUM> from the generally flat circular region <NUM> of the rotating blade assembly <NUM> while power to the fan motor <NUM> is restored. The sensor may include a contact switch.

<FIG> are a side views that illustrate the fan system <NUM> of <FIG> in an installed position in which the braking mechanism <NUM> is disengaged and a removed position in which the braking mechanism <NUM> is engaged, respectively, in accordance with one or more embodiments.

When the fan system <NUM> is installed in a chassis or enclosure <NUM> as illustrated in <FIG>, the braking portion <NUM> may be pivoted away from the fan rotor <NUM> by action of the actuator <NUM> pressing the actuating portion <NUM> of the braking mechanism <NUM> toward the fan rotor <NUM> or a plane of the fan rotor <NUM>. As a result, a gap <NUM> may be present between the braking portion <NUM> and the fan rotor <NUM>, thereby avoiding friction between the braking portion <NUM> and the rotating blade assembly <NUM>. Thus, the braking portion <NUM> may be configured to be disposed in a non-contact position with relation to the generally flat circular region <NUM> of the rotating blade assembly <NUM> and the fan rotor <NUM> when the braking mechanism <NUM> is disengaged.

When the fan system <NUM> is removed from the chassis interface <NUM> as illustrated in <FIG>, or even moved away from the actuator <NUM>, the braking portion <NUM> may be pivoted toward the fan rotor <NUM> by action of the spring <NUM>. As a result, the braking portion <NUM> may apply friction to the generally flat circular region <NUM> of the rotating blade assembly <NUM> and cause the fan rotor <NUM> to quickly cease rotation and come to a stop. The braking portion <NUM> may pivot by a rotation of the pivot rod <NUM> about the pivot points <NUM>.

While the illustrated design of the fan system <NUM> features a pivoting design for the braking mechanism <NUM>, this should not be construed as limiting, as other manifestations of the design may be implemented according to the teachings herein. For example, in various embodiments, the braking mechanism <NUM> may be mounted entirely within the fan motor <NUM>.

<FIG> is a block diagram that illustrates an example set of operations for engaging the braking mechanism <NUM> of the fan system <NUM> of <FIG>, in accordance with one or more embodiments. One or more operations illustrated in <FIG> may be modified, rearranged, or omitted all together. Accordingly, the particular sequence of operations illustrated in <FIG> should not be construed as limiting the scope of one or more embodiments.

In an operation <NUM>, a disengagement element may be separated from contact with an activation end of a control arm. The control arm may include the control arm <NUM>. The disengagement element may include the actuator <NUM> illustrated in <FIG>. The activation end of the control arm may include the actuating portion <NUM>.

In some embodiments, the disengagement element may be separated from contact with the activation end of the control arm when the fan system, which may include the fan housing <NUM>, is moved away from the actuator <NUM> and out of the chassis interface <NUM>. For example, the disengagement element may be separated from contact with the activation end of the control arm in response to the fan system <NUM> being at least partially removed from a chassis, e.g., the chassis or enclosure <NUM>.

In some embodiments, the disengagement element may be separated from contact with the activation end of the control arm when a motor of the actuator <NUM> is controlled to move the disengagement element away from the actuating portion <NUM>, for example, when a sensor detects that a cover, door, or access panel of a chassis or enclosure <NUM> is opened. For example, the disengagement element may be separated from contact with the activation end of the control arm in response to the chassis or enclosure <NUM> that contains the fan system <NUM> being at least partially opened.

In an operation <NUM>, in response to the separation of the disengagement element from contact with the activation end of the control arm in operation <NUM>, friction may be applied to at least one component of the fan rotor by a braking mechanism via an engagement end of the control arm. The fan rotor may be an embodiment of the fan rotor <NUM>. The braking mechanism may be an embodiment of the braking mechanism <NUM>. The control arm may be an embodiment of the control arm <NUM>. The engagement end of the control arm may be an embodiment of the braking portion <NUM>.

In an operation <NUM>, in response to the engagement end of the control arm applying friction to at least one component of the fan rotor in operation <NUM>, rotation of the fan rotor and/or rotating blade assembly of the fan rotor around an axis may be stopped. The rotating blade assembly may include the rotating blade assembly <NUM>. The speed with which the rotation may be stopped may be determined according to the level of friction applied by the engagement end of the control arm to the component of the fan rotor compared to the force applied to the fan rotor to cause it to rotate.

The braking mechanism <NUM> of the fan system <NUM> may be immediately actuated when the fan housing <NUM> is removed from the chassis or enclosure <NUM>, and the rotation of the fan rotor <NUM> may be quickly stopped upon actuation of the braking mechanism <NUM>. Because the rotation may be stopped quickly, there may be no safety hazard to a finger or hand during fan servicing, and therefore a traditional fan guard may be omitted from the fan system <NUM>. Elimination of a traditional fan guard may result in measurable and significant performance and acoustic improvements compared to traditional fan systems that include a traditional fan guard. These improvements may facilitate smaller fan systems of equivalent performance to traditional fan systems, higher performance fan systems of an equivalent physical size as traditional fan systems, lower power consumption compared to traditional fan systems, and reduced acoustic noise compared to traditional fan systems.

Embodiments are directed to a system with one or more devices that include a hardware processor and that are configured to perform any of the operations described herein and/or recited in any of the claims below.

In an embodiment, a non-transitory computer readable storage medium comprises instructions which, when executed by one or more hardware processors, causes performance of any of the operations described herein and/or recited in any of the claims.

Any combination of the features and functionalities described herein may be used in accordance with one or more embodiments. In the foregoing specification, embodiments have been described with reference to numerous specific details that may vary from implementation to implementation. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

According to one embodiment, the fan system <NUM> may be controlled by or used in conjunction with one or more special-purpose computing devices. The special-purpose computing devices may be hard-wired to perform the techniques disclosed herein, or may include digital electronic devices such as one or more application-specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or network processing units (NPUs) that are persistently programmed to perform the techniques, or may include one or more general purpose hardware processors programmed to perform the techniques pursuant to program instructions in firmware, memory, other storage, or a combination. Such special-purpose computing devices may also combine custom hard-wired logic, ASICs, FPGAs, or NPUs with custom programming to accomplish the techniques.

Common forms of storage media include, for example, a floppy disk, a flexible disk, hard disk, solid state drive, magnetic tape, or any other magnetic data storage medium, a CD-ROM, any other optical data storage medium, any physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, NVRAM, any other memory chip or cartridge, content-addressable memory (CAM), and ternary content-addressable memory (TCAM).

Claim 1:
A fan system (<NUM>) comprising:
a fan rotor (<NUM>) including a rotating blade assembly (<NUM>) configured to rotate around an axis, the rotating blade assembly (<NUM>) comprising a flat circular region (<NUM>) disposed at a center of the rotating blade assembly (<NUM>);
a fan motor (<NUM>) configured to cause rotation of the rotating blade assembly (<NUM>) around the axis; and
a braking mechanism (<NUM>) comprising a control arm (<NUM>), a braking portion (<NUM>) of the control arm (<NUM>) disposed at one end of the control arm (<NUM>), an actuating portion (<NUM>) disposed at an opposite end of the control arm (<NUM>), and a base portion disposed between the braking portion (<NUM>) and the actuating portion (<NUM>), wherein the base portion (<NUM>) includes a pivot rod (<NUM>) disposed perpendicular to the control arm (<NUM>), and wherein the pivot rod (<NUM>) is configured to pivotably couple the braking mechanism with a fan housing (<NUM>);
wherein the braking mechanism (<NUM>) is configured to apply friction to the flat circular region (<NUM>) of the rotating blade assembly (<NUM>) via the control arm (<NUM>) when the braking mechanism (<NUM>) is engaged, wherein application of friction to the flat circular region (<NUM>) of the rotating blade assembly (<NUM>) stops rotation of the rotating blade assembly (<NUM>) around the axis,
wherein the braking portion (<NUM>) of the control arm (<NUM>) is configured to be disposed in a contact position against the flat circular region (<NUM>) of the rotating blade assembly (<NUM>) when the braking mechanism (<NUM>) is engaged, and is configured to be disposed in a non-contact position in which the braking portion (<NUM>) is physically separated from the fan rotor (<NUM>) when the braking mechanism (<NUM>) is disengaged,
wherein the control arm (<NUM>) is configured to pivot between the contact position and the non-contact position, and
wherein the base portion (<NUM>) comprises a biasing element coupled with the pivot rod (<NUM>) and configured to bias the braking portion (<NUM>) of the control arm (<NUM>) toward the contact position.