US 20020141879 A1
A cooling fan system has a fan assembly that is removably housed in a chassis. The fan assembly receives electrical power, and the fan blades rotate when housed inside the chassis. As the fan assembly is removed from an opening in the chassis, the power to the fan assembly is disconnected, but the fan blades may continue to rotate. A mechanical stopper, such as a row of bristles that extends into the opening in the chassis, interferes with the rotation of the fan blades as the fan assembly is removed from the chassis. The mechanical stopper stops rotation of the fan blades, thereby preventing harm to the user removing the fan assembly. After the fan assembly is completely removed from the chassis, a spring-loaded door closes the opening in the chassis further protecting the user from contacting adjacent spinning fan blades or hazardous energy sources within the chassis.
1. A hot-pluggable cooling fan system comprising:
a fan assembly having a plurality of fan blades; and
a chassis to removably house the fan assembly, comprising:
an opening through which the fan assembly can be inserted; and
a mechanical stopper to interfere with the motion of the fan blades as the fan assembly is removed from the chassis.
2. The hot-pluggable cooling fan system of
3. The hot-pluggable cooling fan system of
4. The hot-pluggable cooling fan system of
5. The hot-pluggable cooling fan system of
6. The hot-pluggable cooling fan system of
7. The door of
8. A hot-pluggable fan assembly for user insertion into and removal from a chassis, the fan assembly being electrically powered when inside the chassis and comprising a fan blade that is exposed to a user when outside the chassis, wherein, as the fan assembly is removed from the chassis, a mechanical stopper associated with the chassis stops any continued rotation of the fan blade.
9. The hot-pluggable cooling fan assembly of
10. The hot-pluggable cooling fan assembly of
11. The hot-pluggable cooling fan assembly of
12. The hot-pluggable cooling fan assembly of
13. A method for removing a fan assembly from a hot-pluggable cooling fan system that includes a fan assembly having a plurality of blades, and a chassis to removably house the fan assembly, the method comprising guiding the fan assembly out of the chassis through an opening in the chassis, thus causing a mechanical stopper associated with the chassis to interfere with the motion of the fan blades as the fan assembly is guided through the opening.
14. The method as defined by
15. The method as defined by
16. The method as defined by
17. The method as defined by
 This invention relates to heat dissipation from electronic components, and more particularly to a hot-pluggable cooling fan system.
 The electronic components and central processing units used in computer systems often generate heat, which could influence the system performance or result in damage to the components. Typically, one or more cooling fans are used to dissipate heat from the components and maintain a satisfactory operating temperature. Many computer systems that employ cooling fans for heat removal are vital to the user, so it is undesirable to eliminate power to the computer system for repair or replacement of a cooling fan. One solution to this problem is to use hot-pluggable parts. The hot-plugging technique, sometimes known as hot swapping, enables the repair or replacement of computer system parts without disturbing the operation of the system.
 Hot-pluggable cooling fans can be removed or inserted into a computer system without eliminating the power to the system, but the fan blades often remain spinning when the fan is removed from the system. In order to avoid any harm to a person removing the hot-pluggable cooling fan, the fan is usually surrounded by finger guards that prevent the person from touching the rotating fan blades. However, the finger guards add to the cost of the fan assembly, impede airflow under normal fan operating conditions, and add to the thickness of the fan assembly.
FIG. 1 is an exploded view of a hot-pluggable cooling fan system in accordance with the invention.
FIG. 2 is a perspective view of an embodiment of the invention having three of the hot-pluggable cooling fan systems of FIG. 1.
FIG. 3 is a perspective view of the embodiment shown in FIG. 2 from a different perspective, and with a section removed.
FIG. 4 is a perspective view of a further embodiment of the mechanical stopper in accordance with the invention.
 Like reference symbols in the various drawings indicate like elements.
 A hot-pluggable cooling fan system 5 in accordance with the invention is shown by exploded view in FIG. 1, and also by perspective views in FIGS. 2 and 3. FIGS. 2 and 3 show an embodiment of the invention having three hot-pluggable cooling fan systems 5 configured in a row. As best shown in FIG. 1, the hot-pluggable cooling fan system 5 includes a chassis assembly 10 and a fan assembly 15. Each fan assembly 15 is insertable into, and removable from, the chassis assembly 10. In FIGS. 2 and 3, the left-most fan assembly 15 is shown partially removed from its normal operating position inside its corresponding chassis assembly 10, while the other two fan assemblies 15 to the right are shown inside their corresponding chassis assemblies 10.
 The fan assembly 15, as best shown in FIG. 1, includes a square-shaped fan unit 20 having a number of fan blades 25. The fan assembly 15 also includes a handle piece 30 with two tongues 32 and 34 that fit around, and affix to, corresponding sides 36 and 38 of the fan unit 20. When the handle piece 30 is so affixed to the fan unit 20, a gap 41 (see FIG. 2) is formed between a top 40 of the handle piece 30 and a top 42 of the fan unit 20. The handle piece 30 has two holes 44 in its top 40 which allow a user to grasp the handle piece 30 and to easily insert and remove the fan assembly 15 into and from the chassis assembly 10. Notably, the fan assembly 15 does not have finger guards or similar structure to prevent the user's fingers from coming into contact with moving fan blades 25, because such protective structure is not needed for this invention.
 The chassis assembly 10 includes two sidewalls 50 and 52 and a hinged door piece 54 that extends between the two sidewalls 50 and 52. The chassis thus forms the chamber into which the fan assembly 15 is inserted. The chassis assembly 10 may be, for example, an integral part of a computer server assembly (not shown). Other structure from the computer server may also form part of the chassis structure, for example, some structure is needed to serve as a stop for the fan assembly 15 when the fan assembly 15 is placed in the chassis assembly 10. Also, when there are adjacent fan systems 5 as in the FIG. 2 and 3 embodiments, a sidewall, such as sidewall 35, may serve as a common sidewall for two chassis assemblies 10. The door 54 in FIG. 1 (and also in the leftmost fan system 5 in FIG. 2) is shown in an open position, thus making it possible for a user to insert, or to remove, the fan assembly 20 into, or from, the chassis assembly 10.
 The chassis assembly 10 also includes a pair of brushes 56 and 58. The brushes 56 and 58 are positioned on opposing sides of the chassis assembly 10 such that the bristles extend into the chamber formed by the chassis assembly 10. The bristles of brush 56 extend toward the bristles of brush 58, and in this particular embodiment, the bristles have similar thickness and flexibility to bristles on a paintbrush. The bristles of the brushes 56 and 58 are also positioned such that when the fan assembly 15 is removed from the chassis assembly 10, the brushes 56 and 58 will act as a mechanical stopper and come into contact with fan blades 25 (see the left-most fan system 5 in FIGS. 2 and 3), so that if the fan blades 25 are still rotating, that rotation will be stopped. When the fan assembly 15 is fully inserted into its chassis assembly 10, the bristles of the brushes 56 and 58 extend into gap 41 (see FIGS. 2 and 3), so that in this position the brushes 56 and 58 do not interfere with normal rotation of the fan blades 25. In FIG. 3 the brush 56 of the right-most fan system 5 was removed to show the location of the bristles of the brush 58 in the gap 41.
 The fan assembly 15 is a hot-pluggable, electrically powered device. When the fan assembly 15 is inserted into the chassis 10, it becomes plugged into electrical power in a conventional way, for example, by a conventional electrical connection (not shown) at a bottom 60 (FIG. 1) of the fan assembly 15. As such, when the fan assembly 15 is removed while the apparatus the fan is cooling (for example, a computer server) is still in operation, power will not be shut off to the fan assembly 15 until the fan assembly 15 first becomes unplugged.
 To remove a fan assembly 15 while the apparatus the fan is cooling is still in operation, and hence the fan blades 25 are rotating, a user opens the door 54 of the chassis assembly 10 and grasps the fan assembly 15 through holes 44. The user pulls the fan assembly 15 out of the chassis assembly 10. As this is being done, the bristles of brushes 56 and 58 come into contact with fan blades 25, which stops the fan blades 25 from rotating. The fan blades 25 are stopped from continued rotation before the spinning blades 25 are exposed in a way that presents a safety hazard. The door 54 may be spring-loaded. Once the fan assembly 15 is completely removed from the chassis assembly 10, the door 54 automatically closes and prevents the user from contacting the adjacent fan assembly 15 and hazardous energy sources.
 A safe, hot-pluggable fan system is thus possible without the need for finger guards as with the prior art. The invention thus may have one or more of the following advantages: a savings in cost, improved airflow, and reduced thickness of the fan assembly. A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, instead of brushes 56 and 58, two sets of flexible plastic fingers 66 and 68 (FIG. 4) may be used to interfere with the fan blades 25 as a fan assembly 15 is removed from the chassis assembly 10, or further yet, a single stopper, be it a brush (56 or 58) or a flexible finger, may be used. Another embodiment may use a mechanical stopper to contact only the hub of the fan unit instead of the fan blades 25. A further embodiment may use a brush (56 or 58) mounted on the door 54. Also, embodiments of the invention may include any number of fan systems 5, for example, an embodiment with three such systems 5 as shown in FIGS. 2 and 3. Accordingly, other embodiments are within the scope of the following claims.