Abstract:
A chassis includes floating bus bars providing power and a sliding tray included in the chassis includes a power terminal and connecting fingers contacting the floating bus bars. As the sliding tray moves in a direction of motion, the connecting fingers remain in contact with the floating bus bars, providing power to components included on the sliding tray while it is repositioned. The floating bus bars are mounted inside the chassis in a direction parallel to the sliding direction of the sliding tray, and may be positioned within the chassis in a location that does not significantly impede airflow within the chassis.

Description:
BACKGROUND 
     This invention relates generally to connectors for providing power to sliding trays in a chassis. 
     Many servers and other computer systems contain components mounted on sliding trays, which allow a user to easily access and replace the components without having to open the chassis of the computer system. Conventionally, a flexible power cable is connected to the rear of the sliding tray to provide power to components on the tray. The flexibility of the power cable allows the cable to remain connected when the tray is slid out of the chassis. However, the power cable must be as long as the desired travel length of the tray. Thus, if access to the entire length of the sliding tray is desired, the power cable must be as long as the length of the tray. This causes the power cable to occupy a considerable amount of space when the tray is fully inside the chassis, and the occupied space impedes airflow within the chassis, limiting cooling of the components within the chassis. 
     SUMMARY 
     To improve airflow inside a chassis and to reduce the amount of occupied space inside the chassis, embodiments of the invention provide a floating bus bar and a bus bar connector for providing power to components on a sliding tray enclosed by the chassis. The bus bar connector includes a power terminal and two connecting fingers that engage with two floating bus bars, which are mounted inside the chassis in a direction parallel to the sliding direction of the sliding tray. The connecting fingers of a bus bar connector remain in contact with the bus bars as the sliding tray moves. The power terminal includes two conductors for connecting to a high supply voltage and a low supply voltage. Each conductor is coupled to one of the connecting fingers, and each connecting finger is positioned to contact with and press against one of the floating bus bars. The bus bars, connecting fingers, and power terminal are less obtrusive than a flexible power cable and other conventional solutions and can be mounted within the chassis without significantly impeding airflow within the chassis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a top-down view of a chassis containing a sliding tray having a sliding bus bar power connector, according to one embodiment. 
         FIG. 1B  is a top-down view of the chassis in  FIG. 1A  that illustrates the motion of the sliding tray, according to one embodiment. 
         FIGS. 2A and 2B  are perspective views of a sliding bus bar power connector and a pair of floating bus bars, according to one embodiment. 
         FIG. 3A  is top-down view of the connecting fingers of the sliding bus bar power connector, according to one embodiment. 
         FIGS. 3B and 3C  are side views of the connecting fingers of the sliding bus bar power connector, according to one embodiment. 
         FIG. 4  is a cross-sectional view of the floating bus bars, according to one embodiment. 
     
    
    
     The figures depict various embodiments of the present invention for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein. 
     DETAILED DESCRIPTION 
     A sliding bus bar connector provides power to a sliding tray within a chassis of a computing asset.  FIGS. 1A and 1B  illustrate an example chassis  100  including a sliding tray  110 , a sliding bus bar connector  120 , and bus bars  130 . Although only one sliding tray  110  is shown, the chassis  100  may also include additional sliding trays  110 .  FIGS. 1A and 1B  are illustrated with respect to a set of three axes that are used consistently throughout the figures in order to show how the views in the figures are oriented relative to each other. In addition to the x- and y-axes that are shown,  FIGS. 1A and 1B  also include a z-axis (not pictured) that is oriented upward in a direction perpendicular to the plane of the page. 
     A computing asset housed in the chassis  100  may be any device that contains electronic components. For example, the computing asset may be a server or a personal computer capable of running an operating system and executing software applications. Alternatively, the computing asset may be a limited-function device, such as a network-attached storage system with a memory controller and a plurality of hard disks or solid state drives. 
     The sliding tray  110  within the chassis  100  is used for retaining electronic components  112  of the computing asset. In the illustrated embodiment, some of the electronic components  112  are hard disk drives. The sliding tray  110  may also include additional or different components  112 , such as solid state drives, memory controllers, network controllers, processors, or other electronic devices. The sliding tray  110  is moveably mounted within the chassis  100  in a manner that allows the sliding tray  110  to slide between a first position, shown in  FIG. 1A , and a second position, shown in  FIG. 1B , along a sliding direction  114 . In the first position, the sliding tray  110  is within the chassis  100 . Being within the chassis  100  protects the components  112  from external hazards and allows the components  112  to be cooled by cooling systems that regulate the internal temperature of the chassis  100  (e.g., fans). In the second position, a portion of the sliding tray  110  is outside of the chassis  100 , allowing a user to easily access the components  112  on the tray  110 . 
     The sliding bus bar power connector  120  conductively couples the electronic components  112  in the sliding tray  110  to bus bars  130  mounted within the chassis  100 . The bus bars  130  are connected to a power supply unit  140 , which connects to an external power source. In one embodiment, the chassis  110  is mounted on a server rack and the power supply unit  140  is a connector that engages with a set of power bars mounted to the rear of the server rack. Alternatively, the power supply unit  140  includes a circuit that converts alternating current from a power outlet into direct current or another form more suitable for use by components in the sliding tray  110 . 
     Together, the sliding bus bar connector  120 , the bus bars  130 , and power supply unit  140  provide supply voltages powering the electronic components  112 . The sliding bus bar connector  120  is secured to the sliding tray  110  in a position that allows the sliding bus bar connector  120  to make contact with the bus bars  130  as the sliding tray  110  is moved between the first position and the second position along the sliding direction  114 . In one embodiment, the connector  120  is mounted at a corner of the sliding tray  110  distal to an opening of the chassis  100 . Thus, the components  112  remain connected to the supply voltages regardless of whether the sliding tray  110  is in the first position, in the second position, or being moved between the first and second positions. In addition, the bus bars  130  may be positioned within the chassis  110  so they do not significantly impede airflow within the chassis  110 . This allows for more efficient interior cooling than conventional methods of connecting a sliding tray to a power supply, such as a pair of flexible power cables. 
     Although the chassis  100  described in conjunction with  FIGS. 1A and 1B  may house any type of computing asset, the improvements provided by the chassis  100  are particularly beneficial when a large number of storage devices, such as hard disk drives or solid state drives, are housed by the chassis  100 . In these embodiments, the storage devices are retained in the sliding tray  110 , beneficially allowing a user to access the storage devices without removing a side panel of the chassis  100 . In addition, because the connector  120  and bus bars  130  may provide power to the components  112  on the sliding tray  110  regardless of the tray&#39;s position, a user may perform maintenance on one of the storage devices without powering down the other storage devices or components on the sliding tray  110 . For example, this configuration is beneficial when the storage devices are part of a redundant array of independent disks (RAID) and replacement of single storage device is needed without disrupting the operation of the computing asset. 
       FIG. 2A  is a perspective view of an embodiment of the sliding bus bar connector  120  and bus bars  130 . In the embodiment shown by  FIG. 2A , two bus bars  130 A,  130 B are mounted to a side of the sliding tray  110  (not shown in  FIGS. 2A and 2B ) so that a single sliding bus bar connector  120  engages both bus bars  130 A,  130 B. For purposes of illustration, in the embodiment shown by  FIGS. 2A and 2B , the power supply unit  140  maintains the first bus bar  130 A at a high supply voltage and maintains the second bus bar  130 B at a low supply voltage. In other embodiments, the voltages of the bus bars  130 A,  130 B may be reversed. 
     Each bus bar  130 A,  130 B includes a contacting strip  202 A,  202 B along a top surface and a supply terminal  204 A,  204 B at a rear surface. The contacting strip  202 A,  202 B physically contacts a connecting finger  206 A,  206 B of the connector  120  to conduct electricity from the power supply  140  to computing devices in the sliding tray  100  via the finger  206 A,  206 B. The supply terminal  204 A,  204 B conductively couples the bus bar  130 A,  130 B to the power supply unit  140  to provide power to maintain the bus bars  130 A,  130 B at the appropriate supply voltages. In one embodiment, each supply terminal  204 A,  204 B includes a hole for connecting a power cable to the bus bars  130 A,  130 B using a screw terminal or other suitable method. 
     Each connecting finger  206 A,  206 B of the sliding bus bar connector  120  contacts with and presses against a contacting strip  202 A,  202 B on the corresponding bus bar  130 A,  130 B. This forms an electrical connection between the connecting finger  206 A,  206 B and the bus bar  130 A,  130 B. Thus, the first connecting finger  206 A is at the high supply voltage of the bus bar  130 A and the second connecting finger  206 B is at the low supply voltage or the bus bar  130 B. 
     The sliding bus bar connector  120  also includes a printed circuit board (PCB)  208 , with a power terminal  210  mounted to the PCB  208 . The power terminal  210  includes conductors each for coupling to one of the supply voltages from the first bus bar  130 A and from the second bus bar  130 B to the electronic components  112  on the sliding tray  100 . For example, the first conductor of the power terminal  210  is coupled to the first connecting finger  206 A to provide a high supply voltage, and the second conductor is coupled to the second connecting finger  206 B to provide the low supply voltage. In one embodiment, the conductors of the power connector  210  are coupled to the corresponding connecting fingers  206 A,  206 B via conductive traces on the PCB  208 . In some embodiments, the connector  120  may include multiple power terminals  210 . For example, the embodiment illustrated in  FIGS. 2A and 2B  includes four power terminals  210  in a single housing mounted on the PCB  208 . 
     The connecting fingers  206 A,  206 B are secured to the PCB  208  with a plurality of fasteners  212  (e.g., screws). In some embodiments, the PCB  208  is mounted to a carrier bracket  214 , and the fasteners  212  also secure the connecting fingers  206 A,  206 B and PCB  208  to the carrier bracket  214 . The sliding bus bar connector  120  may also include additional fasteners  213  that directly secure the connecting fingers  206 A,  206 B to the carrier bracket  214 . To prevent unwanted conduction with the connecting fingers  206 A,  206 B and the PCB  208 , the carrier bracket  214  may be insulated (e.g., with a powder coat) or made of a non-conductive material. 
     In some embodiments, the non-contacting surfaces of the bus bars  130 A,  130 B and the connecting fingers  206 A,  206 B may be covered with a non-conductive material, such as a powder coat, to prevent unwanted electrical conduction. For example, every surface of the bus bars  130 A,  130 B apart from the contacting strips  202 A,  202 B and the supply terminals  204 A,  204 B may be powder coated. Similarly, every surface of the connecting fingers  206 A,  206 B apart from the area contacting the contacting strips  202 A,  202 B may be powder coated. 
       FIG. 2B  is a different perspective view of the sliding bus bar connector  120  and the sliding bus bars  130  shown in  FIG. 2A . Relative to  FIG. 2A , the view of  FIG. 2B  is rotated counterclockwise about the z-axis and zoomed out so that the entire length of the bus bars  130  is visible. As the sliding tray  110  is moved along the sliding direction  114 , the connecting fingers  206 A,  206 B remain in contact with the contacting strips  202 A,  202 B. Accordingly, the conductors in the power terminal  210  remain conductively coupled to the corresponding bus bars  130 A,  130 B. 
     In other embodiments, the bus bars may be configured differently than in the description presented with reference to  FIGS. 1A-2B . For example, a single bus bar is mounted on each side of the sliding tray  100 , which has two separate connectors each for engaging with one of the bus bars. In this configuration, each connector includes a single connecting finger. In another example, the chassis includes a single bus bar providing a supply voltage, and a different connection method (e.g., a flexible power cable) provides the second supply voltage to the sliding tray  110 . Other embodiments may include three or more bus bars to provide three or more voltages to the components  112  in the sliding tray  110  (e.g., a positive supply voltage, a negative supply voltage, and a ground or reference voltage). 
       FIG. 3A  is a top view of the two connecting fingers  206 A,  206 B. In the illustrated embodiment, each connecting finger  206 A,  206 B includes a series of four holes  302 A,  304 A,  306 A,  308 A,  302 B,  304 B,  306 B,  308 B for fastening the connecting finger  206 A,  206 B to the PCB  208  or to the carrier bracket  214 .  FIGS. 3B and 3C  are side views of the two connecting fingers  206 A,  206 B. As described above with reference to  FIG. 2A , fasteners  212 A,  212 B are inserted through the two holes  302 ,  304  of each connecting finger  206 A,  206 B to secure the connecting finger  206 A,  206 B to the PCB  208  and to the carrier bracket  214 . Another fastener  213 A is inserted through the fourth hole  308 A to secure the first connecting finger  206 A to the carrier bracket  214 . Meanwhile, a fastener  213 B is inserted through the third hole  306 B to secure the second connecting finger  206 B so that the third hole  306 B is at the same position along the x-axis as the fourth hole  308 A on the other connecting finger  206 A. Securing the connecting fingers  206 A,  206 B in this manner causes the second connecting finger  206 B to extend farther to the right than the first connecting finger  206 A, so the second connecting finger  206 B contacts the second bus bar  130 B. Further, rather than using different connecting fingers having different length, this configuration allows the two connecting fingers  206 A,  206 B to have the same mechanical dimensions, lowering manufacturing costs and reducing the overall complexity of the sliding bus bar connector  120 . 
     In some embodiments, the portion of the connecting finger  206 A,  206 B contacting the bus bar  130 A,  130 B has a downward curve. This prevents burrs on the edges of the connecting fingers  206 A,  206 B from damaging contacting strips  202 A,  202  of the bus bars  130 A,  130 B. 
       FIG. 4  is a cross-sectional view of one embodiment of the bus bars  130 A,  130 B. In the embodiment shown by  FIG. 4 , the cross section of two bus bars  130 A,  130 B has an L-shape allowing two bus bars  130 A,  130 B to be aligned and mechanically coupled to each other with one or more fasteners  402 . An upper portion of the first bus bar  130 A may have an upward curve  404  so that the conducting strips  202 A,  202 B of each of the bus bars  130 A,  130 B are positioned at the same height. Insulating sheets  406 ,  408  may be added in the space between the bus bars  130 A,  130 B to prevent short circuits. The insulating sheets  406 ,  408  may be omitted in embodiments where the non-contacting surfaces of the bus bars  130 A,  130 B are already covered with an insulating material, such as a powder coat. 
     SUMMARY 
     The foregoing description of the embodiments of the invention has been presented for the purpose of illustration; it is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above disclosure. 
     Finally, the language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of the embodiments of the invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.