Patent Publication Number: US-6700266-B2

Title: Multiple fault redundant motor

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to enhancing a motor&#39;s life span, and more particularly to a multiple fault redundant motor. 
     2. Description of the Related Art 
     As electronic devices, such as microprocessors, central processing units (CPUs), servers, and other similar types of electronic components become faster and are reduced in size, power consumed within the system per unit volume (power density) increases dramatically. Therefore, it is essential to dissipate the heat generated by electronic components within the system during its operation to keep the electronic components within their normal operating temperature ranges. If the electronic components operate outside of their operating temperature ranges, the life span of the electronic components will be reduced or fail immediately. 
     One effective technique for dissipating the heat from electronic components, such as a microprocessor, is to provide an internal fan, or fan assembly, to directly apply a relatively high-velocity air stream across the surface of the electronic components. By forcing high-velocity air across the surface of the internal component(s), the conductive heat transfer coefficient for the surface of the internal electronic components is increased, thus increasing the convection cooling. Another technique of dissipating the heat from an electronic component, such as a microprocessor CPU, is associating a heat sink with the microprocessor CPU to increase the heat-dissipating surface area of the CPU for more effective cooling. These heat sinks have multiple heat-dissipating fins or elements at an upper surface. A lower surface of the heat sink is coupled to the electronic component and attached with a retention clip. Since the heat sink is comprised of metal or metal alloys, the heat sink conducts heat away from the microprocessor CPU and allows convection cooling through the fins. 
     One method to achieve cooling on devices such as microprocessors is to add additional fans by placing fans in parallel and in series. A problem with this method of cooling is that if one fan fails, the remaining fan must force air through an inoperable fan. Upon forcing air through an inoperable fan, fan speed must be increased, which significantly increases noise and limits the types of fans that can be used. Single point failures often occur in motors, fans and mechanical devices. Many times, a bearing is the source of the single point failure. When a bearing fails in a fan, the motor or electronics subsequently fail. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one. 
     FIG. 1 illustrates an embodiment including a multiple redundant fan with in-line redundant motors. 
     FIG. 2 illustrates an embodiment including a multiple redundant fan with opposing redundant motors. 
     FIG. 3 illustrates an embodiment having redundant electronics. 
     FIG. 4 illustrates an embodiment of the invention having redundant electronics coupled to a single electrical attachment pad and a motor with bifilar windings. 
     FIG. 5 illustrates one embodiment having redundant electronics and redundant magnetic lobes. 
     FIG. 6 illustrates an embodiment having redundant electronics coupled to two electrical attachment pads. 
     FIG. 7 illustrates an embodiment having two independent motors coupled in series. 
     FIG. 8 illustrates a collapsed view of the embodiment illustrated in FIG.  7 . 
     FIG. 9 illustrates an embodiment having two separate counter rotating motors with shafts attached to a common hub. 
     FIG. 10 illustrates a collapsed view of the embodiment illustrated in FIG.  9 . 
     FIG. 11 illustrates an embodiment having a redundant bearing. 
     FIG. 12 illustrates an embodiment having a triple redundant bearing. 
     FIG. 13 illustrates an embodiment having a dual redundant bearing. 
     FIG. 14 illustrates an embodiment of a dual redundant bearing having roller bearings. 
     FIG. 15 illustrates an embodiment having redundant sets of bearings and a frangible link. 
     FIG. 16 illustrates an embodiment having a strain gauge to detect bearing failure. 
     FIG. 17A illustrates an embodiment having optical sensors to detect bearing failure. 
     FIG. 17B illustrates a bearing a having light hole. 
     FIG. 18A illustrates another embodiment used to detect bearing failure. 
     FIG. 18B illustrates a bearing having a reflective surface marker. 
     FIG. 19A illustrates yet another embodiment that detects bearing failure. 
     FIG. 19B illustrates a bearing having reflective markers coupled to one side of the bearing. 
     FIG. 20 illustrates an embodiment having a heat sink coupled to a multiple redundant fan. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention generally relates to a method and apparatus for fan redundancy. Referring to the figures, exemplary embodiments of the invention will now be described. The exemplary embodiments are provided to illustrate the invention and should not be construed as limiting the scope of the invention. 
     FIG. 1 illustrates an embodiment having a single fan with multiple redundant components. Fan  100  includes fan  110 , fan hub  120 , fan motors  130  and  135 , bearings  140  and housing  150 . In one embodiment, fan  110  contains three fan blades. One should note, however, that other embodiments can vary the number of fan blades without diverging from the scope of the invention. 
     FIG. 2 illustrates an embodiment having multiple redundant fan  200 . Multiple redundant fan  200  includes fan housings  220  and  225 , fan blades  210 , motors  230  and  235 , bearings  240  and fan hub  250 . In this embodiment, fan blades  210  include three fan blades. One should note, however, that fan blades  210  can include more or less fan blades without diverging from the scope of invention. 
     The embodiments illustrated in FIGS. 1 and 2 will now be discussed with reference to the various components. FIG. 3 illustrates an embodiment having motor and electronics  300 . In this embodiment, electronics A  320  and electronics B  330  are electrically independent sets of electronics that are structured in a parallel circuit. The windings of motor  310  are electrically connected to both sets of electronics A  320  and electronics B  330 . In one embodiment, motors  130  and  135  (illustrated in FIG. 1) can each be replaced by motor  310 . In another embodiment, motors  230  and  235  (illustrated in FIG. 2) can each be replaced by motor  310 . 
     As illustrated in FIG. 3, motor  310  includes one set of windings. Both electronics A  320  and electronics B  330  include speed control for motor  310 . Both electronics A  320  and electronics B  330  can use various means for controlling motor speed, such as pulse width modulation (PWM), voltage/resistance variation, or thermal speed control. Also, both electronics A  320  and electronics B  330  can use a tachometer or similar means for fan rotation feedback. 
     Electronics A  320  and electronics B  330  can both work together simultaneously to control motor  310 &#39;s rotational speed, or can each work independently. In the case where electronics A  320  and electronics B  330  run simultaneously, the control of motor  310  is “split” between electronics A  320  and electronics B  330 . In the case of failure of either electronics A  320  or electronics B  330 , the non-failed electronics will continue to control motor  310  to maintain fan speed. In the case where electronics A  320  and electronics B  330  do not control motor  310  simultaneously, upon a failure of either electronics A  320  or electronics B  330 , the non-failed electronics will take over and control motor  310 . This can be accomplished with a simple switch, feedback and control, voltage/current detection, etc. One should note that various fan speed feedback means can be implemented with signals sent to either electronics A  320  or electronics B  330  by means such as, tachometers, light sensors, etc. 
     By using redundant electronics (electronics A  320  and electronics B  330 ) to control motor  310 , motor  310  can continue to function in case of one of the electronics failing. In the case where motor  310  is used as a cooling fan for electronic components, the redundant electronics overcome the signal point failure of having a single electronics controller for motor  310 . Thus, cooling of electronic components can be maintained, and acoustical noise can be limited by having a single fan blade component coupled to a redundant fan motor system (e.g., fan  100 , illustrated in FIG. 1 or fan  200 , illustrated in FIG. 2) when coupled with an embodiment including electronics A  320  and electronics B  330 . 
     FIG. 4 illustrates an embodiment having motor and electronics  400 . In this embodiment, motor  410  includes bifilar windings (dual redundant windings) coupled to a single electrical pad  420 . One should note, however, that separate electrical pads can be coupled to motor  410  (as long as the separate electrical pads are electrically coupled similarly as to how pad  420  is coupled with the windings of motor  410 , electronics A  320  and electronics B  330 ). 
     In this embodiment, if either electronics A  320  or electronics B  330 , and either one of the bifilar windings fail, motor  410  continues with normal operation. Electronics A  320  and electronics B  330  are coupled in a parallel circuit structure. Also, the bifilar windings are structured in a parallel. The bifilar windings are electrically coupled to both sets of electronics, thus achieving dual fault capability. 
     FIG. 5 illustrates an embodiment having motor and electronics  500 . Motor and electronics  500  include electronics A  320 , electronics B  330 , first electrical pad  520 , second electrical pad  510 , and motor  530 . Motor  530  includes two sets of independent windings on different magnetic lobes. Therefore, motor  530  includes two independent sets of winding each having four magnetic lobes. One should note, that typical motors (e.g., DC fan motors) only include four magnetic lobes. Each set of four magnetic lobes is coupled to an independent set of electronics (electronics A  320  and electronics B  330 ). Between electrical pad  510  and electrical pad  520  there are two north and two south poles. Therefore, in this embodiment, motor  530  achieves redundancy via electronics and windings. If either set of electronics fail, and/or either set of windings fail, motor  530  can continue to run with normal operation. 
     FIG. 6 illustrates an embodiment having motor and electronics  600 . Motor and electronics  600  include motor  610 , first electrical pad  510 , second electrical pad  520 , electronics A  320  and electronics B  330 . Motor  610  includes four magnetic lobes with bifilar (dual redundant) windings. Each set of windings are coupled to a set of independent electronics (electronics A  320  and electronics B  330 ). In this embodiment, redundancy is achieved via electronics and/or windings. If either set of electronics or either set of windings fail, the motor will continue with normal operation. 
     FIG. 7 illustrates an embodiment having two independent motors coupled in series. Fan  700  includes fan blades  710 , fan hub  720 , fan housing  730 , dual in-line motors in series  740  and shaft  750 . In this embodiment, if one of the motors in series  740  fails, the non-failed motor can run fan  700  at full speed. Both in-line series motors  740  rotate in the same direction. 
     FIG. 8 illustrates a collapsed view of fan  700  illustrated in FIG. 7 (denoted  800  in FIG.  8 ). Fan  800  may have a thickness slightly greater than a fan having a single motor to accommodate the dual in-line series motors  740 . By having two motors in series, fan  800  reduces acoustical noise, and saves space over two separately housed fans. Either of the two motors in this embodiment can be operate simultaneously or independent. If either of the motors in this embodiment operates independently, feedback sensors can trigger control electronics to switch to the other motor in series with the failed motor. In one embodiment, in-line series motors  740  can run simultaneously wherein power may be split between the two in-line series motors to achieve necessary fan speed. One should note that other redundancies can be combined with this embodiment, such as redundant electronics, electrical pads, magnetic lobes, windings, etc. 
     FIG. 9 illustrates an embodiment having two separate motors that rotate in the opposite direction of each other and share a common shaft. Fan  900  includes a first housing  910 , a second housing  920 , fan blades  930 , fan hub  940 , first motor  950 , and second motor  960 . First motor  950  and second motor  960  can run simultaneously in the opposite rotation direction over the common shaft or can run independently. In case of a failure of either motor  950  or motor  960 , the non-failed motor will continue to rotate fan blades  930 . In one embodiment, motor  950  and motor  960  can each run simultaneously at a lower power that would necessitate rotating fan blades  930 . Upon failure in this case, the non-failed motor will have its power increased to compensate for the failed motor. By having two motors that run in the opposite rotation direction from one another, not only is space saved by not using two separate fans for redundancy, but acoustical noise is reduced by the single fan blade dual motor system. Also, when two separate fans are run in series, if one fan fails, the non-failed fan needs to push air through the failed fan. To do this, the non-failed fan would need to increase its fan speed. Thus, increasing acoustical noise. FIG. 10 illustrates a collapsed view of fan  900 . One should note that other redundancies can be combined with this embodiment, such as redundant electronics, electrical pads, magnetic lobes, windings, etc. 
     While the presented embodiments include redundant motors, electronics, windings and/or magnetic lobes, a device, such as a direct current (DC) fan, can still have a single point of failure that is a possibility. This single point of failure possibility is the bearing. To overcome the single point failure possibility, one embodiment includes redundant bearings. 
     FIG. 11 illustrates an embodiment having a redundant bearing  1100 . Redundant bearing  1100  includes outer sleeve  1110 , inner sleeve  1120 , inner bushing sleeve  1130  and bearing balls  1140 . In this embodiment, if the ball bearing portion fails (i.e.,  1110 ,  1120  and  1140 ) the sleeve bearing (i.e.,  1120  and  1130 ) will continue with normal operation. Therefore, redundancy in the bearing is achieved. One should note that bearing balls  1140  can be replaced with other types of bearings, such as roller bearings, without diverging in scope. 
     When redundant bearing  1100  is used in one of the presented embodiments having multiple redundancies, such as motors, electronics, windings and/or magnetic lobes, single point failures are overcome. One should note that this embodiment can be used in other devices besides DC fans, such as alternating current (AC) motors, wheels, and other devices requiring rotation over a shaft. This embodiment can be made of various metal, metal-alloys, synthetic materials, such as hardened plastic, etc. Moreover, this embodiment can be size adjusted, depending on the device incorporating the bearing and size required due to load. Also, further redundancies, i.e., bearing sets, can be added if necessary for the application. 
     By having a redundant bearing incorporated within embodiments having redundant motors, fan reliability and component life are increased by reducing single point failure possibilities. Also, devices that require fan cooling can achieve fan cooling redundancy with less of a fan footprint. Moreover, acoustical noise can be reduced in devices that would typically have redundant fan systems by using embodiments having multiple redundancies, thus, reducing fan count without sacrificing fan cooling redundancy. 
     FIG. 12 illustrates an embodiment having a triple redundant bearing. Triple redundant bearing  1200  includes outer sleeve  1210 , middle sleeve  1220 , inner sleeve  1230 , inner bushing sleeve  1240  and bearing balls  1250 . One should note that bearing balls  1250  can be replaced with other bearings means, such as roller bearings, without diverging in scope. As can be seen in FIG. 12, this embodiment has three sets of races and two sets of ball bearings. In this embodiment, if one set of ball bearings fail, the second set will continue with normal operation. Further, if both sets of ball bearings fail, triple redundant bearing  1200  then acts as a standard bushing adding additional life to the device using triple redundant bearing  1200 . Also, it should be noted that if any two of the redundancies fail, triple redundant bearing  1200  still continues to perform as a normal bearing. 
     Triple redundant bearing  1200  can be used in various rotating devices, such as motors, various mechanical devices, wheels, etc. This embodiment can be made of various metal, metal-alloys, synthetic materials, such as hardened plastic, etc. Moreover, this embodiment can be size adjusted, depending on the device incorporating the bearing and size required based on load. Also, further redundancies, i.e., bearing sets, can be added if necessary for the application. When triple redundant bearing  1200  is used in cooling fans, a typical single point failure of a typical bearing is overcome. Therefore, triple redundant bearing  1200  adds life to components needing cooling and to internal fan components, such as the electronics and windings of the fan motor. Thus, cooling redundancy can be achieved without necessitating separate redundant cooling fans. Therefore, it follows that acoustical noise is reduced by having triple redundant bearings incorporated into cooling fans by using a single fan with redundant bearings instead of using multiple separate fan devices for redundancy. 
     FIG. 13 illustrates an embodiment having a dual redundant bearing. Dual redundant bearing  1300  includes outer sleeve  1310 , middle sleeve  1320 , inner bushing sleeve  1330 , and bearing balls  1340 . One should note that other bearing means, such as roller bearings, can be used instead of bearing balls  1340  without diverging in scope. In this embodiment, there are three sets of sleeves and two sets of ball bearings. If one of the ball bearing sets fails (e.g., seizes due to loss of lubrication, change of ball shape, etc.) the second set will continue with normal operation. By using dual redundant bearing  1300 , a device incorporating bearing  1300  can extend its usefulness and/or life span. 
     Bearing  1300  can be used in various devices such as AC and DC motors, various mechanical devices, wheels, etc. This embodiment can be made of various metal, metal-alloys, synthetic materials, such as hardened plastic, etc. Moreover, this embodiment can be size adjusted, depending on the device incorporating the bearing and size required based on load. Also, further redundancies, i.e., bearing sets, can be added if necessary for the application. When this embodiment is incorporated in a device, such as a cooling fan, the bearing redundancy removes the necessity for having separate cooling fans that are required for redundancy protection. Also, acoustical noise level is reduced by eliminating separate redundant fan devices. By incorporating bearing  1300  into multiple redundant fans (e.g., previously discussed embodiments) single-point failures due to a single bearing failure is overcome. 
     As noted above, roller bearings can be used instead of ball bearings in the embodiments illustrated in FIGS. 11,  12  and  13 . For example, FIG. 14 illustrates the embodiment illustrated in FIG. 13 with the ball bearings replaced with roller bearings  1410 . Further, other known bearing means can be used in the place of balls or rollers without diverging from the scope of the embodiments of the invention. Also note that the embodiments illustrated in FIGS. 11,  12 ,  13  and  14  can be made with various metal, metal alloys, ceramics, synthetic materials, such as hardened plastic, etc. Moreover, these embodiments can be size adjusted, depending on the device incorporating the bearing and required size based on load. 
     FIG. 15 illustrates an embodiment having redundant sets of bearings and at least one frangible link. Frangible link  1510  (for example purposes, two frangible links are illustrated in  1500 ) is added to redundant bearing  1500  to achieve fail over operation rather than parallel redundancy. By using one or more frangible links, control is achieved as to which of the bearing redundancies to use first within a redundant bearing. In this embodiment, a failed bearing will transfer an impulse force to frangible link  1510  due to torque from a shaft, thus, breaking frangible link  1510  and resulting in the spin-up of a redundant bearing. One or more frangible links  1510  can be incorporated with the embodiments illustrated in FIGS. 11-14. 
     Frangible link  1510  can be attached to a redundant bearing by an adhesive, such as epoxy, using a heat source, such as a weld, etc. Frangible link  1510  can be made from a metal, a metal alloy, a ceramic material, synthetic material, such as a hardened plastic material, etc. Depending upon the use of a redundant bearing, such as redundant bearing  1500 , the tensile strength of frangible link  1510  is varied to effect efficient breaking of frangible link  1510  upon one of the redundant bearing sets failing (e.g., shaft torque due to seizing of a bearing because of loss of lubrication, etc.). 
     FIG. 16 illustrates an embodiment having at least one strain gauge to detect if a bearing has failed. Device  1600  illustrated in FIG. 16 includes main shaft  1610 , strain gauges  1620 , bearings  1640  and  1650 , and shaft  1630 . In this embodiment, at least a single strain gauge is used for each bearing coupled with main shaft  1610 . Bearings  1640  and  1650  are inserted into the main sleeve as illustrated in FIG.  16 . Bearings  1640  and  1650  are made in such a way as to not slip after placed within the main sleeve. 
     In one embodiment, bearing  1640  and  1650  have their outer surface knurled to provide a non-slippable contact between bearing  1640  and  1650 , and the main sleeve. If one of the bearings fail (i.e., seizes, loses lubrication, deforms, etc.) shaft  1630  will have increased friction against a bearing set. As this friction increases, an increase in torque would be transferred from the shaft to the main sleeve through the failed bearing. Strain gauges  1620  measure the increase in torque and detect if the shaft is rotating inside the bearing. Stain gauges  1620  can output an electrical signal based on the measured varied resistance caused by strain in the device. The signal output from strain gauges  1620  can be used to respond with an alert or event signal. For example, the output from strain gauges  1620  can be used to signal an alarm and shut down the device whose bearing has been sensed to have failed. 
     A process for detecting bearing failure for this embodiment is as follows. Determine a nominal value from strain gauges  1620  during normal operation. This can be simply collecting transmitted signals from strain gauges  1620  for a set period of time. Determine a tolerance level for an allowable difference between the normal operation of bearing  1640  and  1650  and a problem, such as additional friction caused from a failing bearing. With redundant bearings, a ratio of bearing sets to each other can be determined. Therefore, a difference if any, between an output of strain gauges  1620  for each bearing set ran can be determined based on the ratio. Transmit a signal from a strain gauges  1620  to a circuit or processor that will keep a running record of received signals for comparison. Upon exceeding the allowable difference between normal operation and a possible problem, transmit a warning signal to a user or circuit. Alternatively, transmit a shutdown signal to a circuit, processor, or device  1600 . 
     In one embodiment, bearing  1640  and  1650  are redundant bearings (i.e., bearings illustrated in FIGS.  11 - 15 ). In this embodiment, strain gauges  1620  can sense the change in torque as redundancies fail, e.g. when one of the redundant bearing sets fail. This embodiment also detects when all the redundancies in bearings  1640  and  1650  fail. In this embodiment, output signals from strain gauge  1620  can be used to trigger warnings and to apprise a user or other device that a bearing may soon fail. In response, the device using strain gauge detection can shut down the device before a component fails, such as over heated electronics, overheated motor windings, etc. 
     In one embodiment, device  1600  is used with a DC cooling fan (e.g., embodiments illustrated in FIGS. 1,  2 ,  7  and  9 ). In this embodiment, besides having multiple redundancies (i.e., redundant electronics, windings and/or magnetic lobes, motors and bearings). Device  1600  is incorporated to detect changes in torque along the shaft in order to warn of impending or complete bearing failure. In this embodiment, the output signals from strain gauges  1620  can be transmitted to a device, such as processor, server, circuit, etc., and a warning signal can be transmitted to a user (s). Alternatively, the output signals from strain gauges  1620  can be transmitted to a device such as processor, server, circuit, etc., and a shutdown procedures can be initiated. For example, if it is known that a bearing has or soon will fail (based on output signals from strain gauges  1620 ), a “soft” shut-down process can occur wherein a device or system can be brought down slowly without having components failing due to a “hard” shut down, or excessive heat buildup caused by a failing fan system. 
     FIG. 17A illustrates an embodiment using optical emitter/receiver (or optical emitter/sensor) devices to detect bearing failure. Device  1700  includes emitter/receiver  1730 , optical beams  1740  (transmitted/received by emitter/receiver  1730 ), hub  1710 , bearings  1720 , main sleeve  1755 , shaft  1750 , and printed circuit board (PCB)  1760 . Emitter/receiver  1730  can be receiver/sensors, such as photoelectric sensors, low powered lasers, photoelectric emitters, etc. Emitter/receivers  1730  are coupled between each inner sleeve of bearing  1720 . The purpose of Emitter/receiver  1730  is to detect a change in angular velocity of an inner sleeve of bearing  1720 . 
     FIG. 17B illustrates a redundant bearing having light hole  1770  in bearing sleeve  1780 . When an optical emitter (emitter/receiver  1730 ) emits an optical beam, as bearing  1720  rotates about shaft  1750  a portion of the beam transmits through light hole  1770  and is received on the opposite optical receiver  1740 . When one of the redundant bearing sets in bearing  1720  fails, a change in angular velocity can be detected by determining the difference in angular velocity based on receiver/sensors  1730  sensing a change in the sensed light beam. A processor or circuit compares the angular velocity for a set period (such as every two seconds, every ten seconds, etc.). If the angular velocity between periods changes, and the processor senses that fan speed has not changed (based on a set tolerance determined from redundancy ratios, etc.), a warning signal can be transmitted to users or other devices informing of bearing failure or possible bearing failure about to occur. Alternatively, a soft shut down signal can be issued by the processor or circuit for which the device connected with device  1700  and/or any other connected devices can be shut down without harm to any electronic components. 
     A process for detecting bearing failure for this embodiment is as follows. A light is emitted through light hole  1770  in a bearing  1720  coupled with shaft  1750 . The emitted light (light beams  1740 ) is received through light hole  1770  at emitter/receiver  1730 . Emitter/receiver  1730  transmits signals based on the received light. A circuit or processor determines if the bearing has a failure. The failure is detected by determining rotation rate of shaft  1750  and of bearing  1720 . The rotation rate of shaft  1750  is compared with the rotation rate of bearing  1720 . If there is no difference in rotation rate (i.e., the bearing is failed), or there is a slight difference (based on a normal known difference), a signal is transmitted from the circuit/processor to a user or other circuit/processor. Alternatively, a shutdown signal can be transmitted to shutdown a device before harm is done by improper cooling. 
     In the case where device  1700  is incorporated in one of the embodiments illustrated in FIGS. 1,  2 ,  7  and  9 , by using this embodiment, electronic components can be saved from overheating due to a failed bearing incorporated within a cooling fan. It should be noted that bearings  1720  can be used in non-redundant bearings where a light hole is placed on the outer or inner sleeve of a single bearing. In this case, as the bearing begins to fail, emitter/receiver  1730  can signal to a circuit or processor of the impending or complete bearing failure. 
     FIG. 18A illustrates device  1800  used to detect variations in angular velocity of inner sleeves on bearings. Device  1800  includes hub  1840 , bearings  1810 , shaft  1820 , sensor/emitter  1830 , PCB  1860  and main sleeve  1850 . In this embodiment, a light pipe is inserted into shaft  1820  to transmit an optical beam (illustrated as  1835 ) to bearings  1810 . In this embodiment, a small opening is made into shaft  1820  within the diameter of bearings  1810 . Through this opening, a light beam from sensor/emitter  1840  can be transmitted/received at sensor/emitter  1830 . 
     FIG. 18B illustrates bearings  1810  having reflective surface marker  1870  coupled with an inner sleeve of bearing  1810 . Reflective surface marker  1870  can be a reflective coating on a small portion of the inner sleeve, be formed as part of the inner sleeve, or other technique to coupled reflective surface marker  1870  to the inner surface of the inner sleeve (the surface that couples bearing  1810  to shaft  1820 ). Reflective surface marker  1870  can be any reflective marker, such as a black stripe, a colored stripe (paint or adhesively applied), different metal-alloy from the inner bearing sleeve that is compatible with the inner bearing sleeve, photo activated marker (paint or adhesively applied), etc. As bearing  1810  rotates about shaft  1820  sensor/emitter  1830  transmits an optical beam through the inserted light pipe, which reflects off reflective surface marker  1870  as bearing  1810  rotates. Upon bearing  1810  failing, angular velocity of the bearing will change as compared to the shaft. The angular velocity sensed from the light pipe to sensor/emitter  1830  is compared with a shaft tachometer (not shown). If there is a difference in angular velocity between the shaft and the reflective surface section sensed by sensor/emitter  1830 , a circuit or processor will transmit a signal indicating that the bearing  1810  is about to fail. Once it is known that bearing  1810  is about to fail, a warning signal can be sent to users or devices. Alternatively, a shutdown sequence can be initiated. One should note that bearing  1810  can be a non-redundant bearing or redundant bearing as illustrated in FIGS. 11-15. 
     A process for detecting bearing failure for this embodiment is as follows. A light (light beam  1835 ) is emitted by sensor/emitter device  1830  through a light pipe inserted through shaft  1820 . Reflected light is received after being reflected by reflective marker  1870  situated on bearing  1810 . Signals are transmitted from sensor/emitter device  1830  based on the received reflected light. It is then determined whether a bearing failure has occurred. The detection of bearing failure is as follows. Rotation rate of shaft  1820  and bearing  1810  is determined by a circuit or processor based on received signals from sensor/emitter device  1830 . The rotation rate of shaft  1820  is compared with the rotation rate of bearing  1810  by the circuit or processor. If there is any difference (based on a normal known difference), a signal is transmitted from the circuit/processor to a user, device or processor. Alternatively, a shutdown signal can be transmitted to shutdown a device before harm is done by improper cooling. 
     FIG. 19A illustrates an embodiment that detects variations in angular velocity between a shaft and a bearing. Device  1900  includes hub  1910 , bearings  1920 , shaft  1930 , main sleeve  1940 , PCB  1950  and sensor/emitters  1960 . Bearings  1920  can be non-redundant bearings or redundant bearings such as those illustrated in FIGS. 11-15. 
     FIG. 19B illustrates bearings  1920 . Bearings  1920  include a reflective surface marker  1970  used to reflect light emitted by sensors/emitter  1960  and received back at sensor/emitter  1960 . Reflective surface marker  1970  can be any reflective marker, such as a black stripe, a colored stripe (paint or adhesively applied), different metal-alloy from the inner bearing sleeve that is compatible with the inner bearing sleeve, photo activated marker (paint or adhesively applied), etc. Sensors/emitter s are placed such that beam  1965  is targeted at the reflective surface marker  1970 . Bearings  1920  have an outer surface to prevent bearing  1920  to slip once coupled with main sleeve  1940 . 
     During normal operation, the inner race rate per minute (RPM) matches shaft  1930 &#39;s RPM. If bearing  1920  fails or begins to fail, shaft  1930  will begin to rotate inside the inner bearing race. Sensor/emitter  1960  detects a change in RPM on the inner race. The difference in RPM between shaft  1930  and inner race  1975  of bearing  1920  is the measurement of how effectively the bearing is working. Once a difference in RPM between shaft  1930  and bearing  1920  is detected by sensor/emitter  1960  (coupled to a circuit or processor) a warning signal or shutdown signal can be transmitted in order to prevent possible harm. 
     It should be noted, that a tachometer or similar device is coupled to shaft  1930 , wherein the RPMs of shaft  1930  are accumulated and transmitted to a circuit or processor to determine a difference in RPM between the shaft and the inner race  1975 . In one embodiment, device  1900  is incorporated into a fan such as that illustrated in FIGS. 1,  2 ,  7  and  9 . In this embodiment, a fan tachometer is coupled with a fan speed controller. The fan speed controller and sensor/emitter  1960  coupled with a processor or circuit that checks for a difference in RPMs. A small tolerance can be used as a threshold value, or a difference greater than zero can be used for a set period, such as every 10 seconds, 20 seconds, etc. 
     A process for detecting bearing failure for this embodiment is as follows. A light is emitted by sensor/emitter device  1960  on reflective marker  1970  located on a sleeve of bearing  1920 . Reflected light is received after being reflected by reflective marker  1970  situated on the bearing sleeve. Signals are transmitted from sensor/emitter device  1960  based on the received reflected light. It is then determined whether a bearing failure has occurred. The detection of bearing failure is as follows. Rotation rate of shaft  1930  and bearing  1920  is determined by a circuit or processor based on received signals from sensor/emitter device  1960 . The rotation rate of shaft  1930  is compared with the rotation rate of bearing  1920  by the circuit or processor. The rotation rate of shaft  1930  is determined by a tachometer coupled with shaft  1930 . Output signals from the tachometer are transmitted to the circuit or processor. If there is no difference in rotation rate (i.e., the bearing is failed), or there is a slight difference (based on a normal known difference), a signal is transmitted from the circuit/processor to a user, device or processor. Alternatively, a shutdown signal can be transmitted to shutdown a device before harm is done by improper cooling. 
     FIG. 20 illustrates an embodiment having a heat sink coupled with a multiple redundant fan  2010 . Device  2000  includes multiple redundant fan  2010 , multiple redundant fan adapter  2020 , and heat sink  2030 . Multiple redundant fan  2010  can be a fan such as that illustrated in FIGS. 1,  2 ,  7  and  9 . In this embodiment, heat sink  2030  is also coupled with a processor (or multi-processor)  2040 . Multiple redundant fan  2010  can operate at low RPMs since it is used to bring in fresh air over/through heat sink  2030 . 
     In one embodiment, multiple redundant fan  2010  and heat sink  2030  is attached to a multi-processor  2040  that resides in a server system. In this embodiment, due to the redundancy of fan  2010 , less maintenance is required due to the redundancies. Further, acoustical noise is reduced since a reduced number of fans are needed to maintain cooling redundancy. Further, less space is required to house a server or system needing cooling redundancy. Moreover, electromagnetic interference (EMI) containment is increased by having reduced apertures for cooling in server chassis. 
     While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art.