Abstract:
The present invention provides an uninterruptible power supply (UPS) having a chassis formed using mating panels of a sturdy, lightweight, substantially rigid material, such as ABS plastic, that are fixedly attached together to form a compact, user-friendly chassis using simple connection techniques that entail a minimum of tools and a minimal number of fastening mechanisms. In one general aspect, a UPS in accordance with the invention comprises an input to receive AC power from an AC power source, an output that provides AC power, a DC voltage source that provides DC power, the DC voltage source having an energy storage device, an inverter operatively coupled to the DC voltage source to receive DC power and to provide AC power, a transfer switch constructed and arranged to select one of the AC power source and the DC voltage source as an output power source for the uninterruptible power supply, and a chassis for housing at least the DC voltage source, inverter, and transfer switch. The chassis, in accordance with the invention, comprises a first panel having a substantially “L” shaped appearance, a second panel constructed and arranged to mate to the first panel, and a first fastener securing the first panel and the second panel into a substantially fixed configuration.

Description:
RELATED APPLICATIONS  
         [0001]    This application is related to a commonly assigned application having the title “Battery Wire Lead Management,” having an attorney docket number of 18133-065 and filed on Jan. 30, 2001, and the disclosure of this related application is hereby incorporated by reference  
         FIELD OF THE INVENTION  
         [0002]    Embodiments of the present invention are directed towards an enclosure or chassis of a device, particularly an electronic device such as an uninterruptible power supply (UPS), for receiving the components of the device. The components typically contained within such an enclosure include printed circuit boards (PCBs), transformers, batteries, switches, and the like. The enclosure is used to house and hold the device components in a fixed, mechanically stable location. More particularly, embodiments of the present invention are directed towards a lightweight, inexpensive enclosure having a simplified assembly process and, in particular, to apparatuses, systems, and methods for providing a UPS housed in an integrated, lightweight, low-cost, and easily assembled package.  
         BACKGROUND OF THE INVENTION  
         [0003]    An uninterruptible power supply (UPS) is a type of power supply used to power and protect an electrical load that is sensitive to fluctuations in or the absence of electrical power. The UPS can be connected between the load and a source of electrical power, such as a mains power source or other commercially provided electric power. The UPS uses commercially supplied AC power to charge a DC battery and provide the AC power to load. Upon outages of power, the load draws its AC power from the DC battery through the DC to AC inverter. This isolates the load from power surges or brownouts and also furnishes a source of power during brief outages.  
           [0004]    Commonly, a UPS comprises a rectifier, inverter, battery charger, DC battery, and other components, all housed within a single case or package. FIG. 1 shows a typical prior art UPS  1  used to provide regulated uninterrupted power. The UPS  1  includes an input filter/surge protector  2 , a transfer switch  3 , a controller  4 , a battery  5 , a battery charger  6 , an inverter  7 , and a DC-DC converter  8 . The UPS also includes an input  9  for coupling to an AC power source and an outlet  10  for coupling to a load.  
           [0005]    The UPS  1  operates as follows. The filter/surge protector  2  receives input AC power from the AC power source through the input  9 , filters the input AC power and provides filtered AC power to the transfer switch  3  and the battery charger  6 . The transfer switch  3  receives the AC power from the filter/surge protector  2  and also receives AC power from the inverter  7 . The controller  4  determines whether the AC power available from the filter/surge protector is within predetermined tolerances, and if so, controls the transfer switch to provide the AC power from the filter/surge protector to the outlet  10 . If the AC power from the rectifier is not within the predetermined tolerances, which may occur because of “brown out,” “high line,” or “black out” conditions, or due to power surges, then the controller  4  controls the transfer switch  3  to provide the AC power from the inverter  7 . The DC-DC converter  8  is an optional component that converts the output of the battery  5  to a voltage that is compatible with the inverter  7 . Depending on the particular inverter  7  and battery  5  used the inverter  7  may be operatively coupled to the battery  5  either directly or through a DC-DC converter  8 .  
           [0006]    As consumer electronic products such as computers, become more widespread, smaller, lightweight, and less expensive, there has been a corresponding increase in the need for smaller, lighter, lower-cost UPS systems. However, designers of electronic instruments such as UPS&#39;s typically have focused their energies on reducing the size and cost of the components contained within the device rather than redesigning the chassis or housing of the instrument. Thus, presently available UPS devices still take much time to assemble and require many connectors and fasteners that increase both weight and manufacturing cost. In addition, because parts such as batteries and transformers are heavy and awkward to install, it is difficult to design a simplified, lightweight UPS enclosure capable of securely containing such components.  
           [0007]    Known enclosures and chassis designs for a UPS commonly include a metal frame having several partitions or walls to which the components are mounted or attached. The frame itself can be fastened to an outer device housing. Manufacturing the prior art chassis for a UPS is a relatively complicated and time-consuming process. For example, making a metal chassis often requires stamping and bending metal sheets. The surfaces of the sheets may be treated, for example by galvanizing, before connecting the sheets to each other by an appropriate connection method, such as screwing, welding, riveting, adhesives, or a combination of these methods. Components are connected to the chassis by fastening elements like screws or rivets or other connection techniques. Sometimes components are connected to the sheets before the sheets are assembled together.  
           [0008]    It is also known to use hard plastic parts to form a chassis, but known plastic chassis designs nonetheless result in a complicated and time-consuming assembly process, because the fastening elements still must be attached to the chassis, for example by ultrasound welding, gluing, or pressing. Moreover, it is less common to use known plastic chassis designs for electronic devices such as UPS&#39;s, which typically include very heavy components such as transformers and batteries. These heavy components (and even the relatively lighter components, such as printed circuit boards (PCBs). often require additional holding members, such as brackets or angle plates, to hold the component securely at the preferred position within the chassis. The holding members add to the weight, cost, and complexity of the chassis.  
           [0009]    Thus, making a chassis for electronic instruments such as a UPS and assembling its components to it is costly and time-consuming, requiring the use of mounting tools, such as screw drivers, bending tools, riveting tools, welding tools, or adhesive dispensers. Metallic enclosures add an unnecessary amount of weight to the electronic instrument, but known plastic enclosures still require supporting members, if they are to be used with electronic instruments having particularly heavy components.  
         SUMMARY OF THE INVENTION  
         [0010]    It is one object of the present invention to alleviate the aforementioned difficulties in assembly and manufacture of electronic instruments such as UPS devices by providing a UPS formed using mating panels of a sturdy, lightweight, substantially rigid material, such as ABS plastic, where the panels are fixedly mounted together to form a compact, user-friendly chassis using simple connection techniques that entail a minimum of tools and a minimal number of external fasteners.  
           [0011]    In one general aspect, the invention provides an uninterruptible power supply for providing AC power to a load. The uninterruptible power supply comprises an input to receive AC power from an AC power source, an output that provides AC power. a DC voltage source that provides DC power, the DC voltage source having an energy storage device, an inverter operatively coupled to the DC voltage source to receive DC power and to provide AC power, a transfer switch constructed and arranged to select one of the AC power source and the DC voltage source as an output power source for the uninterruptible power supply, a chassis for housing at least the DC voltage source, inverter, and transfer switch. The chassis, in accordance with the invention, comprises a first panel having a substantially “L” shaped appearance, a second panel constructed and arranged to mate to the first panel; and a first fastener securing the first panel and the second panel into a substantially fixed configuration.  
           [0012]    The chassis can be formed from a material such as plastic, semi-rigid polycarbonate (PC), Acrylonitrile-Butadiene-Styrene (ABS), ABS/PC, flame-retardant PC, ABS and ABS/PC products, polyvinyl chloride (PVC), polystyrene, high impact polystyrene (HIPS), polybutylene Terephthalate (PET), PC/PET, polybutylene terephthalate (PBT), PC/PBT, polyetherimide (PEI), acetal copolymer (POM), engineering thermoplastics (ETP), polyamides, expanded polypropylene (EPP), polyurethane, polyethylene, and metal.  
           [0013]    The chassis, in one embodiment, also can comprise a third panel constructed and arranged to mate to the first panel and the second panel, wherein the first fastener is coupled to the third panel. The third panel can attach to the first panel using the first fastener and to the second panel using a second fastener.  
           [0014]    At least one of the first and second panels can further include an integrally formed latch and the third panel can further include an integrally formed hook constructed and arranged to pivotably engage the latch. The input to the UPS can further comprise a line cord assembly constructed and arranged to mate with a line cord opening integrally formed into the third panel. The line cord assembly can further comprise an integrally formed strain relief element operably engaging the line cord opening. In addition, the line cord assembly can further comprise an integrally formed detent constructed and arranged to catch the line cord opening to keep the line cord assembly attached to the rear panel.  
           [0015]    It is another object of the invention to provide a UPS chassis having integral preformed recesses capable of receiving and attaching electronic components therein, including heavy components such as transformers, using few, if any, fastening elements and simplified connection techniques, whereby the entire UPS can be assembled quickly and easily along a single axis of manufacture, using a minimum of tools.  
           [0016]    In another general aspect, the invention provides an uninterruptible power supply for providing AC power to a load. The uninterruptible power supply comprises an input to receive AC power from an AC power source, an output that provides AC power a DC voltage source that provides DC power, the DC voltage source having an energy storage device, an inverter operatively coupled to the DC voltage source to receive DC power and to provide AC power, a transfer switch constructed and arranged to select one of the AC power source and the DC voltage source as an output power source for the uninterruptible power supply, a chassis for housing at least the DC voltage source, inverter, and transfer switch. The chassis, in accordance with the invention, comprises a first panel having a substantially “L” shaped appearance, a second panel constructed and arranged to mate to the first panel, and a first fastener securing the first panel and the second panel into a substantially fixed configuration, wherein at least one of the first and second panels comprises at least one integrated fastening element constructed and arranged to attach one or more components of the UPS to the chassis.  
           [0017]    At least one of the first and second panels can further comprise an integrated fastener, such as a hook, constructed and arranged to attach a printed circuit board to the respective panel. At least one of the first panel and second panel can further includes at least one crush rib constructed and arranged to hold a component disposed adjacent to the crush rib, such as a transformer, in a substantially fixed position.  
           [0018]    The second panel can further comprise an integrally formed compartment, which compartment can be constructed and arranged to enclose one or more UPS components, such as the energy storage device. The chassis can include a movable access panel providing access to the compartment. The movable access panel could be completely removed to permit installation or removal of one or more components, such as batteries, contained within the compartment.  
           [0019]    It is another object of the invention to provide a method for constructing an uninterruptible power supply using a minimal number of tools and fasteners.  
           [0020]    The foregoing and other objects, aspects, features, and advantages of the present invention will become more apparent from the following detailed description of the invention when viewed in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    An understanding of the principles of the invention may be readily attained by reference to the following specification and the accompanying drawings in which:  
         [0022]    [0022]FIG. 1 is a block diagram of a typical uninterruptible power supply;  
         [0023]    [0023]FIGS. 2A and 2B are partially exploded front and rear perspective views, respectively, of a UPS chassis, in accordance with one embodiment of the invention;  
         [0024]    [0024]FIGS. 3A and 3B are partially exploded perspective views showing the assembly of the rear panel to the right and left panels, as viewed from the right and left sides, respectively, for the chassis of FIGS.  2 A- 2 B;  
         [0025]    [0025]FIG. 4A is a partially exploded perspective view showing the assembly of the right panel to the left panel, along with the battery compartment as viewed from the bottom, for the chassis of FIGS.  2 A- 2 B, and FIGS.  4 B- 4 C are perspective views showing the positioning and movement of a battery within the battery compartment of the chassis of FIGS.  2 A- 2 B;  
         [0026]    [0026]FIG. 5 is a perspective view of the rear side of the left panel of the chassis of FIGS.  2 A- 2 B, illustrating some of the components attached to the left panel;  
         [0027]    [0027]FIG. 6 is an enlarged view of the region labeled “A” in FIG. 5;  
         [0028]    [0028]FIG. 7 is another perspective view of the rear side of the left panel of FIG. 5, illustrating the transformer position;  
         [0029]    [0029]FIGS. 8A, 8B,  8 C, and  8 D are enlarged front perspective, side, rear perspective, and rear views, respectively of the lightpipe of FIG. 5;  
         [0030]    [0030]FIGS. 9A through 9C are a rear perspective views of the closing and opening of the battery door and of the battery door structure, respectively, for the chassis of FIGS.  2 A- 2 B;  
         [0031]    [0031]FIG. 10 is a right front perspective view of the right panel of the chassis of FIGS.  2 A- 2 B, as viewed from the top;  
         [0032]    [0032]FIG. 11 is a right front perspective view of the right panel of the chassis of FIGS.  2 A- 2 B, as viewed from the bottom;  
         [0033]    [0033]FIG. 12 is an enlarged perspective view of a portion of the right panel of the chassis of FIGS.  2 A- 2 B;  
         [0034]    [0034]FIG. 13 is a view of the rear side of the rear panel of the chassis of FIGS.  2 A- 2 B, showing some installed components;  
         [0035]    [0035]FIG. 14 is a view of the rear side of the rear panel of the chassis of FIGS.  2 A- 2 B, without installed components;  
         [0036]    [0036]FIG. 15 is a left perspective view of the rear panel of the chassis of FIGS.  2 A- 2 B, taken from the rear side, showing various components installed;  
         [0037]    [0037]FIG. 16 is a left side view of the line cord assembly; and  
         [0038]    [0038]FIGS. 17A through 17J are examples of an alternate rear panel designs.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0039]    [0039]FIG. 2A is a partially exploded front perspective view of a chassis  11 , in accordance with one embodiment of the invention. In this embodiment, the chassis  11  is used to contain a UPS device. The chassis  11  is in the general shape of a substantially rectangular box having top and bottom opposing sides, front and back opposing sides, and left and right opposing sides. The chassis  11  comprises a left panel  12 , a right panel  14 , a battery door  16  slideably engaged with the right panel  14 , and a rear panel  18 . The left panel  12  is a single integral piece that forms the left side and front side. The right panel  14  is a single integral piece that forms the right side, top side, and a portion of the bottom side. The battery door  16  is a single integral piece that forms the remaining portion of the bottom side, while the rear panel  18  forms the rear side.  
         [0040]    In other embodiments, the chassis  11  can have a shape other than that of a rectangular box, such as a square box, a trapezoidal box, a box having a hexagonal shape, a substantially cylindrical box, a substantially circular or semi-circular box, a substantially oval box, and the like. Those skilled in the art will recognize that a box having any of these shapes, in accordance with the invention, can be comprised of a minimal number of panels, formed in accordance with the principles and advantages recited herein.  
         [0041]    As will be described further herein, the chassis  11  is held together by constructing and arranging the left panel  12 , right panel  14 , battery door  16 , and rear panel  18  to mate together without fasteners, although in one embodiment the chassis  11  further includes a first screw (not visible in FIG. 2A) attaching the rear panel  18  to the right panel  12  and a second screw (not visible in FIG. 2A) attaching the rear panel  18  to the left panel  14 . Other types of fastening techniques, such as welds, rivets, adhesives, etc. are of course usable in place of the screws.  
         [0042]    The chassis  11  is made from any sturdy material capable of being formed into the integral component pieces (i.e., the left, right, and rear panels  12 ,  14 , and  18 , respectively, and the battery door  16 ) described herein. In a preferred embodiment, the chassis  11  is manufactured in a low-cost and rapid manner by molding the respective portions (namely, the left panel  12 , right panel  14 , battery door  16 , and rear panel  18 ) from a lightweight, low-cost material such as plastic.  
         [0043]    In different embodiments, the chassis  11  can be made from materials such as polycarbonate (PC), Acrylonitrile-Butadiene-Styrene (ABS), ABS/PC, flame-retardant PC, ABS and ABS/PC products, polyvinyl chloride (PVC), polystyrene, high impact polystyrene (HIPS), polybutylene Terephthalate (PET), PC/PET, polybutylene terephthalate (PBT), PC/PBT, polyetherimide (PEI), acetal copolymer (POM), or other similar plastic materials, in accordance with UPS regulatory and operational requirements.  
         [0044]    While the embodiments described herein are made from a synthetic, moldable material, so that all recesses for receiving the components can be manufactured by a single forming step, it should be understood that the UPS design in accordance with the principles of the invention could also be achieved by other manufacturing techniques capable of producing the respective parts of the chassis effectively, in a quick, simple, low-cost, or otherwise improved manner. For example, the chassis parts could be formed by milling, punching, filing, or cutting the respective parts of the chassis out of a solid material, such as a solid plastic material. It also should be understood that the chassis could be made using materials of biological or metallic origin that possess the desired mechanical qualities. Details of the above-described materials and the manufacturing methods are well known to those skilled in the plastics and materials arts and need not be disclosed herein in detail.  
         [0045]    It further should be understood that the different parts of the chassis (e.g., the left panel  12  right panel  14 , battery door  16 , and rear panel  18 ) can be made from different types of material than the other parts, so long as the parts are constructed to mate together securely.  
         [0046]    Referring again to FIG. 2A, it can be seen that the left panel  12  forms the front face and left side of the chassis  11 . Integrating the front face and the left side together reduces the overall parts count for the chassis  11 , eases the manufacture of the UPS, and improves the overall rigidity of the chassis  11  by eliminating a seam between its front side and the left side. The front panel portion of the left panel  12 , in one embodiment, includes a plurality of indicator openings  20  and a switch opening  22  usable with a pushbutton-type switch. The indicator openings  20  and switch opening  22 , in one embodiment, mate with a light pipe assembly (see FIGS. 8A through 8B), which is described further herein.  
         [0047]    At least one top tab  24  located on the top innermost side of the left panel  12  engages a slot (see FIG. 3B) integrally formed on the top side of the right panel  14 , to secure the left panel  12  to the right panel  14  along the top left side of the chassis  11 . In one embodiment, the left panel provides a plurality of separate top tabs  24  integrally formed on its top innermost side, which mate with one or more respective channels on the right panel. The use of separate top tabs  24  helps to more securely engage the left panel  12  with the right panel  14  during assembly of the chassis  11 , to prevent the respective panels (together with any components attached thereto) from sliding around. Using a tab  24  mated to a slot also helps to provide a smooth seam, without buckling, along this portion of the chassis  11 . Other integral techniques for mating the top of the left panel  12  to the right panel  14 , such as interlocking teeth, hooks, detents, and the like are, of course, usable in accordance with the invention. Also, as those skilled in the art will appreciate, the top tab  24  of the left panel  12  could instead be part of the right panel  14 , with the slot to which the top tab  24  mates being located on the top side of the left panel  12 .  
         [0048]    A PCB hook  26  is integrally formed into the front and left sides of the left panel  12  to hold in place a first PCB  28 . The geometry of the PCB hook  26  and number of PCB hooks required is defined by the nature (e.g., the thickness and size) of the first PCB  28  that the PCB hook  16  is designed to accept. In the embodiment of FIG. 2A, additional PCB hooks  26  (see FIG. 3) are used to securely attach the first PCB  28 .  
         [0049]    Although the illustrated left panel  12  has a substantially “L” shaped appearance, the left panel  12  could be formed in a shape other than an “L” shape. For example, the left panel  12  could be integral with the rear panel  18 , thus having a substantially “U” shaped appearance. With a left panel  12  having a “U” shaped configuration and integral rear panel  18 , the left panel  12  and right panel  14  could be joined using a single fastener (not shown). The left panel  12  furthermore could be integral with the rear panel  18  and also have a central panel (not shown), projecting in the same direction as the front side of the left panel  12 , having a substantially “E” shaped appearance, the central panel helping to form a compartment or tunnel in the chassis  11 . Other variations will occur to those skilled in the art.  
         [0050]    The right panel  14  includes a front lip  30  for attaching the top, right, and bottom front edges of the right panel  14  to the left panel  12 . The top front and right front portions of the front lip  30  fit into recesses formed integrally into the inside front of the left panel  12 ; this attachment is illustrated in greater detail herein. The bottom front portion of the front lip  30  mates with a channel (see FIG. 4) formed integrally into the bottom of the inside front of left panel  12  (see FIG. 4). A rear lip  32  is formed along the right rear side of the right panel  14  and fits into a recess formed integrally into the inside of the rear panel  18 .  
         [0051]    Integrally formed into the underside of the top of the right panel  14  is at least one rear latch (see FIGS. 2B, 3A, and  3 B) sized to engage a respective rear hook  36  formed along the back top side of the rear panel  18 . In one embodiment, the right panel  14  has a plurality of rear latches, each disposed to receive a respective rear hook  26 . In another embodiment (not shown), the right panel  14  includes at least one rear latch and the left panel  12  includes at least one rear latch, such that the rear hooks  36  can engage both the left panel  12  and the right panel  14 . A rear hook  36  permits the rear panel  18  to be attached to the right panel  14  and left panel  12  by engaging the rear hook  36  while pivoting the rear panel  18  downward into the latch and then pivoting the rear panel  18  shut over the rear lip  32  of the rear panel  18  and over a left rear portion (see FIG. 3B) of the left panel  12 . Thus, the rear panel  18  can capture the outside of the left panel  12  and the right panel  14  to keep them together.  
         [0052]    Ventilation openings  38  can be integrally formed into the right panel  14 , to provide cooling to one or more of the components contained within the chassis  11 . One skilled in the art will appreciate that the quantity and location of the ventilation openings  38  is determined by the type, quantity, and location of components contained within the chassis. The ventilation openings  38  could, of course, be formed in one or more of the other panels of the chassis, instead of or in addition to the ventilation openings  38  formed into the right panel. Generally, the ventilation openings  38  are located in a place on the chassis  11  capable of intaking ventilating air during use.  
         [0053]    It should be understood that although the embodiment of FIG. 2A shows the left panel  12  forming a right side and a front side, with the right panel  14  forming the top side, most of the bottom side, and the left side, it is of course possible to create the chassis  11  in a “mirror image” configuration, with the left panel  14  forming the left side and the front, the right panel  12  forming the right, top and part of the bottom side, etc.  
         [0054]    [0054]FIG. 2A also illustrates the battery door  16  as viewed from the underside. In the chassis of FIG. 2A, the battery door  16  is located at the bottom of the chassis  11 , to make the backup battery (not shown) easily accessible to the user. The battery door  16  mates with an opening formed into the right panel  14  via battery tabs  42  integrally formed with the battery door  16  and locks into place via a battery locking tab  40  integrally formed with the battery door  16 . When the battery door  16  is fully engaged and locked into the right panel  14 , it completes the bottom side of the chassis  11 . FIGS. 4A through 4C and FIGS. 9A through 9C provides greater detail about the design of the battery door  16  and the positioning of a battery.  
         [0055]    A related co-pending and commonly assigned application filed on Jan. 30, 2001 and having an attorney docket number of 18133-065 (the disclosure of which is hereby incorporated by reference) describes a type of battery wire connection mechanism usable with the battery compartment of the chassis  11  of the present invention. The disclosed battery wire connection mechanism, in combination with the chassis  11  and battery door  16 , permits easy user installation of battery(ies) and very simple replacement of the battery(ies) without using tools. This co-pending application also further illustrates the type and appearance of batteries usable in accordance with the present invention.  
         [0056]    [0056]FIG. 2B is a partially exploded rear perspective view of the chassis of FIG. 2A. Formed integrally into the right panel  14  are a pair of battery slots  46  that mate with the battery tabs  42  (FIG. 2A), along with a locking slot  48  that engages the locking tab  40  (FIG. 2A) of the battery door  16 . A pair of rear latches  34  is integrally formed into the underside of the top side of the right panel  14  to engage the rear hooks  36  (FIG. 2A). Visible on the bottom inside front side of the left panel  12  is a front channel  50  for receiving the bottom of the front lip  30  of the right panel  14 . A pair of rear feet  51  is integrally formed into the bottom of the rear panel  18 , to support the chassis  11  during use.  
         [0057]    The bottom rear sides of the left panel  12  and right panel  14  each includes a respective bore  52  integrally formed into the respective panel and adapted to receive a respective fastening element, such as a screw, inserted into a respective fastener opening  54  integrally formed in the rear panel  18 . In the disclosed embodiment, just two screws are required to hold together the left panel  12 , right panel  13 , and rear panel  18 , into a secure, substantially rigid chassis  11 . This manner of holding together the three panels adds structural integrity to the chassis  11  and simplifies assembly by requiring just two fastening elements. It should be understood, however, that the rear panel  18  could be attached to the left panel  12  and right panel  14  using other fastening techniques, such as snaps, welds, adhesives, and the like, such that no external fastening elements would be required at all.  
         [0058]    Referring again to FIG. 2B, the rear panel  18  has at least one integrated outlet receptacle  55  permitting a device to be protected by the UPS components (not shown) housed within the chassis  11  to be operably coupled to the UPS. In another embodiment, a plurality of integrated outlet receptacles  55  are provided whereby some of the integrated outlet receptacles  55  can be used for battery backup and some of the integrated outlet receptacles  55  can be used for surge protection.  
         [0059]    The rear panel  18  includes an optional integrated telephone/modem opening  56  sized to receive telephone/modem connectors (see FIG. 7), an optional integrated data opening  58  sized to receive a data port (not shown), an integrated surge protection opening  59  for receiving a surge protection indicator, an integrated circuit breaker opening  60  sized to receive a user-resettable circuit breaker, and an integrated line cord opening  62  for receiving a line cord assembly (see FIGS.  13 - 16 ). The outlet receptacle(s)  55  are, in one embodiment arranged in a so-called BLOCKSAFE configuration (BLOCKSAFE is a trademark of American Power Corporation of West Kingston, R.I.). The BLOCKSAFE configuration spaces outlet receptacles such that plugs attached to large charging devices, such as those used with mobile phones, can be connected to a given outlet receptacle  55  without blocking over the other available outlet receptacles  55 .  
         [0060]    Although not illustrated in FIG. 2B, the rear panel  18  also can have integrally molded accommodation for other features such as site wiring fault indicators, functional labeling, identification, signaling jacks, and the like. It should be understood that the illustrated openings, labels, and receptacles of the rear panel  18  are provided by way of example only. Those skilled in the art will recognize that other designs for the rear panel  18  can omit any or all or the recited openings and further can add additional integral features not described here, but well within the knowledge of those skilled in the art. Moreover, as described in connection with FIGS. 17A through 17J, the design of the rear panel  18  could be altered to vary the receptacle type depending on the particular type of receptacle used in a particular region of the world. Note that any of the different rear panel designs in FIGS. 17A through 17J are interchangeable with the rear panel  18  of FIG. 2B and can be coupled directly to the left panel  12  and right panel  14  without alteration to either the left panel  12  or the right panel  14 .  
         [0061]    [0061]FIGS. 3A and 3B are partially exploded perspective views showing the assembly of the rear panel  18  to the right panel  14  and left panel  12 , as viewed from the right and left sides, respectively, for the chassis  11  of FIG. 2A. FIGS. 3A and 3B illustrate more particularly the manner in which a rear hook  36  is aligned with and engaged to a rear latch  34 . In addition, FIG. 3B illustrates a top right slot  64  to which one or more of the top tabs  24  mate.  
         [0062]    [0062]FIG. 4A is a partially exploded perspective view showing the assembly of the right panel  14  to the left panel  12  as viewed from the bottom, for the chassis  11  of FIG. 2A. As shown in FIG. 4, at the front of the chassis  11 , the front lip  30  of the right panel  14  engages under a left panel lip  66  formed along the right edge of the front panel portion of the right panel  12 . A pair of front feet  67  is integrally formed into the bottom front of the left panel  12  to provide support to the chassis  11  during use. In addition, FIG. 4A illustrates more particularly the location of a rear latch  34  that engages the rear hook  36  (FIG. 2A).  
         [0063]    At the bottom front right side of the right panel  14 , a first junction tab  68  integrally formed into the right panel  14  mates to a first junction slot  78  (see FIG. 5) formed integrally into the bottom left edge of the left panel  12 . In one embodiment, there are a plurality of first junction tabs  68  arranged to provide spacing to permit the locking tab  40  (FIG. 2A) of the battery door  16  (FIG. 2A) to engage the locking slot  48 . In addition, the left panel  12  has a second junction tab  70  integrally formed along the rear of its bottom left edge. The second junction tab  70  mates with a second junction slot  64  (see FIG. 10) formed integrally into the bottom left edge of the right panel  14 .  
         [0064]    The first and second junction tabs  68 ,  70 , together with their respective junction slots, help to form a tight, stable seam between the bottom left edges of the left panel  12  and the right panel  14  and help to prevent movement and buckling of the panels during assembly of the unit and after assembly of the chassis  11  is complete. Providing some junction tabs on the left panel  12  and some junction tabs on the right panel  14  increases the rigidity of the seam between the left panel  12  and right panel  14 .  
         [0065]    The battery compartment  74  of the right panel  14  is integrally formed into the right panel  14 . The location of the battery compartment  74  is chosen so that it is sufficiently distant from signals and components that could be harmful to a user accessing the battery compartment  74 , such as high-voltage electronic components, components such as transformers that can have relatively high surface temperatures, etc. The size of the battery compartment  74  depends on the size of the battery  71  (see FIGS.  4 B- 4 C) to be installed. The walls of the battery compartment  74  include at least one rib  76  to enhance the strength of the walls and help to prevent movement of a battery  71  disposed within the battery compartment  74 .  
         [0066]    [0066]FIG. 4B is a perspective view showing the positioning of a battery  71  within the battery compartment  74  of the chassis  11 . The battery  71  is a representative example of the type, size, and style of a battery  71  usable with the UPS (and chassis) of the present invention. The highlighted portion  71 ′ of the battery  71  shows the part of the battery  71  that is engaged, such as by a user, to remove the battery  71  from the battery compartment  74  or to install the battery  71  into the battery compartment  74 . FIG. 4C is another perspective view showing the direction of movement of the battery  71  within the battery compartment  74 . FIG. 4C also illustrates a battery wire connection  71 ″ operably coupling the battery  71  to the other UPS electronic components (such as those shown in FIG. 1). The battery  71  and the details of its battery wire connections to the UPS are described more fully in the copending application entitled “Battery Wire Lead Management,” having an attorney docket number of 18133-065, filed Jan. 30, 2001, and referenced previously (the disclosure of which is hereby incorporated by reference).  
         [0067]    [0067]FIG. 5 is a perspective view of the rear side of the left panel  12  of the chassis  11  of FIG. 2A, illustrating some of the features of and components attached to the left panel  12 . In this view, the left panel  12  is lying on its left side and is being viewed from its top left rear corner. Formed along the bottom left edge of the left panel  12  is a first junction slot  78  that engages the first junction tab  68  (FIG. 4A). The first PCB  28  is held in place using one or more PCB hooks  26  integrally formed into the left panel  12 . The PCB hooks  26  have a tapered edge to permit the first PCB  28  to be aligned properly. In addition, a first PCB snap  27  also can be integrally formed into the left panel  12  and disposed opposite to the PCB hook  26 , to secure an opposite end of the first PCB  28 .  
         [0068]    The left panel  12  includes one or more left panel support members  80  integrally formed into the walls of the left panel  12 . Providing such left panel support members  80  provides strength and stiffness to the left panel and permits manufacture of the left panel  12  using thinner walls (and, thus, less chassis material). Using less material decreases the overall weight of the chassis  11  and decreases its cost.  
         [0069]    Integrally formed left transformer support members  82  form a left transformer enclosure  84  into which a flat surface of a UPS Transformer (see FIG. 7) is fitted. The left transformer enclosure  84  is sized to accommodate the weight and dimensions of a given UPS transformer, and cooperates with a substantially similar right transformer enclosure (see FIG. 10) on the right panel  14 , to hold the transformer of the UPS securely in place. Disposed along the left transformer support member  82  are one or more left transformer support ribs  83  to hold a transformer securely into place. In the illustrated embodiment, the left transformer support ribs  83  are provided along only one end of the left transformer enclosure  84  to enable the transformer to be installed more easily.  
         [0070]    In one embodiment, at least one of the left transformer support ribs  83  further includes a left crush rib  88 . The structure and design of a left crush rib  88  in accordance with the invention is further illustrated in FIG. 6, which provides an enlarged view of the region labeled “A” in FIG. 5. One function of the left crush rib  88  is to compensate for excess tolerance between the size of the transformer and the size of the left transformer enclosure  84 . Another function of the left crush rib  88  is to help to eliminate audible rattling of the transformer during use. This is accomplished by the crush rib  88  actually “crushing” or compressing during use, such that the amount of “crush” or compression is proportional to the amount of excess tolerance between the transformer and the transformer enclosure  84 . The left crush rib  88  can be implemented in many ways. For example, as shown in FIG. 5, it is integrally molded to the left panel  12 , as part of the left transformer support rib  83 . The left crush rib  88  also can be implemented using mechanisms other than crush ribs that compensate for tolerance gaps, such as integral plastic fingers, a loop of material, a spring, a spacer, a bumper, a foam pad, and the like.  
         [0071]    One or more left transformer vents  86  can be provided adjacent to the left transformer enclosure  84 , such that, during use, the left transformer vents provide a natural cross-flow of air to provide convection cooling.  
         [0072]    During manufacture of a molded left panel  12 , the dimensions of the left transformer enclosure  84  can be modified to accommodate a differently sized transformer (for example, different sizes and types of transformers might be required for the UPS to work properly in different regions of the world). For example, if the left panel  12  is created using injection molding, the transformer enclosure  84  can be modified simply by swapping a particular portion of the mold (not shown) used to make the left panel  12 . Those skilled in the art will recognize other techniques for changing the dimensions and features of the left transformer enclosure  84 .  
         [0073]    Another feature of the left panel  12  is the light pipe  90 . The light pipe  90  comprises a light pipe retainer structure that houses a switch button (not shown in FIG. 5) and that is operably coupled to a second PCB (see FIG. 2A) that holds light emitting diodes (LED&#39;s) and a switch. The light pipe  90  provides a mechanism for directing light from the LED&#39;s to the indicator openings  20  (FIG. 2A) on the front panel portion of the left panel  12 . The light pipe can be made of any type of material capable of transmitting light from an LED. In one embodiment, the lightpipe  90  is made of a clear polymer materials (e.g., polycarbonic, acrylic). It also is possible to construct a light pipe  90  using translucent polymer materials, glass, and the like. In one embodiment, the light-pipe is heat staked to the left panel  12 . However, the light pipe  90  can be attached to the left panel  12  by any technique known to those skilled in the art, such as welding, adhesives, integral clips formed into the left panel  12 , etc., that holds the light pipe  90  in proper alignment with the indicator openings  20 . FIGS. 8A through 8D illustrate the design and features of the light pipe  90  in greater detail.  
         [0074]    [0074]FIG. 7 is another perspective view of the rear side of the left panel  12  and battery door  16  of the chassis  11  of FIG. 2A, illustrating the construction of the left panel  12  in more detail along with some of the components attached and/or adjacent to the left panel  12 . As discussed previously, one or more PCB hooks  26  are integrally formed on the inside of the left panel  12  to hold a first PCB  28  in place. Typically, the first PCB  28  will include one or more electronic elements arranged on the board, but these elements have been omitted in the drawing for the sake of clarity.  
         [0075]    [0075]FIG. 7 also shows the second PCB  92  of the light pipe  90 , illustrating how a plurality of light pipe clips  94  help to hold the second PCB  92  in place. A transformer  96 , such as the type of transformer used in a typical UPS, is illustrated as partially enclosed within the left transformer enclosure  84 . In one embodiment, the core of the transformer  96  can be welded, such as by argon welding, to eliminate bolted style construction and allow for smoother installation and quieter operation.  
         [0076]    A screw  98 , which is but one type of fastening element usable with the invention, also is illustrated in the respective position it would be when installed into the bore  54  on the right panel  14  (a bore on the left panel  12  also is illustrated).  
         [0077]    Adjacent to the left panel  12 , and normally held in place by the rear panel  18  (not shown is a telephone surge PCB  100  coupled to telephone jacks  102 . The telephone surge PCB  100  can be part of the UPS and can snap into the rear panel  18 , as shown in FIG. 12  
         [0078]    [0078]FIGS. 8A, 8B,  8 C, and  8 D are enlarged front perspective, side, rear perspective, and rear views, respectively of the lightpipe  90  of FIG. 5. Referring to FIGS. 8A through 8D, at least one light transmitting member  104  is formed integral with the light pipe  90  and is provided to permit the light from an LED on the second PCB  92  (FIG. 7) to be transmitted to the front side of the left panel  12 , so that a user can view the indicator. The light transmitting member  104  can be angled as shown, to help transmit the light emitted by an LED on the second PCB  92  to the front panel portion of the left panel  12 . Light pipe clips  94  are integrally formed with the light pipe to hold the second PCB  92  in position. At least one attachment opening  106  is provided so that the light pipe  90  can be attached, such as by spot welding, to the left panel  12 .  
         [0079]    Each light transmitting member  104  is associated with at least one respective shade tab  108  integrally formed into the light pipe  90 . The shade tab  108  helps to ensure the light transmitting member  104  only transmits light associated with its respective LED on the second PCB  92  and helps prevent the light transmitting member  104  from transmitting light (and thus appearing to be illuminated) that actually is associated with the LED of a different indicator. The light pipe  90  also includes a key  110  mating to a respective opening or notch on the second PCB  92  (see also FIG. 7). The key  110  helps the light pipe  90  to mate properly with the second PCB  92 , so that each light transmitting member  104  will be properly aligned to its respective LED on the second PCB  92 .  
         [0080]    [0080]FIGS. 9A through 9C are a rear perspective views of the closing and opening of the battery door and of the battery door structure, respectively, for the chassis of FIGS.  2 A- 2 B. FIG. 9A illustrates the direction of movement for installing the battery  71  and then sliding the battery door  16  towards the left side of the chassis  11  (the left side is not visible in FIG. 9A) to close the battery door  16  over the battery compartment  74 . FIG. 9B is a perspective view of the chassis  11  illustrating the battery  71  in an installed position and showing the direction of movement in which the battery door  16  is moved to remove it and gain access to the installed battery  71  (or to otherwise gain access to the battery compartment  74 ).  
         [0081]    [0081]FIG. 9C shows an enlarged rear perspective view of the battery door of the chassis  11  of FIG. 2A. The battery door  16  is sized to support the weight and dimensions of a UPS battery  71  (FIGS.  9 A- 9 B) and is located on the chassis  11  to meet height and width restrictions imposed on the chassis  11  by the components contained therein. The battery door  16  includes a plurality of door ribs  112  integrally formed to the battery door  16  and sized to define one or more battery channels  114  that have widths smaller than the diameter of battery wires  71 ″ (see FIGS.  4 C and  9 A- 9 B). The sizing of the door ribs  112  helps to prevent the UPS battery wires  71 ″ from catching on or tangling with the battery door  16  when the battery door is moved. The battery door  16  also comprises a plurality of integrally formed battery ribs  116  providing strength and rigidity to the battery door  16 , and optionally can include a plurality of ramp ribs  118  disposed on the battery door  16  so as to align with a label (not shown) attached to the battery. The ramp ribs  118  help to prevent the battery door  16  from catching on or damaging the battery label.  
         [0082]    [0082]FIG. 10 is a right front perspective view of the right panel  14  of the chassis  11  of FIG. 2A, as viewed from the top. The right panel  14  provides a mounting structure for the UPS transformer that is substantially similar to that described in connection with the left panel  12 , including right panel support members  120  integrally formed into the walls of the right panel  14 , integrally formed right transformer support members  122  forming a right transformer enclosure  124  into which a flat surface of a UPS Transformer (see FIG. 7) is fitted, one or more right transformer support ribs  128 , at least one right crush rib  129 , and one or more right transformer vents  126 . These features are substantially the same as their “mirror image” features on the left panel  12  and their description and features are not repeated here.  
         [0083]    [0083]FIG. 11 is a right front perspective view of the right panel  14  of the chassis of FIG. 2A, as viewed from the bottom. This view shows a positive stop  130  integrally formed into the inside top rear surface of the right panel  14 . This positive stop  130  is provided to contact a PCB, such as the telephone surge PCB  100  (see FIG. 7), during assembly, to prevent the PCB from being pushed too far in. The positive stop  130  also can help to prevent vibration and/or movement of the telephone surge PCB  100  attached to the rear panel  18 . FIG. 12 is an expanded close up view of the telephone surge PCB  100  in contact with the positive stop  130 .  
         [0084]    [0084]FIG. 13 is a view of the rear side of the rear panel  18  of the chassis of FIG. 2A showing some components installed, and FIG. 14 is the same view without components installed. In FIG. 13, a plurality of bus bars  132  are installed and a line cord assembly  136  also is installed. Referring to FIGS. 13 and 14, the bus bars  132  are held in place by snapping the bus bars  132  into bus bar support members  136  that, in one embodiment, are formed integrally with the rear panel  18  as part of the integral receptacles  55  formed into the rear panel  18 . In one embodiment, the integral receptacles  55  are constructed and arranged so that the bus bars  132  can snap in and be retained without additional fasteners or retainers.  
         [0085]    In addition, in one embodiment, the bus bars  132  are laid out such that only two different types of discrete bus bar parts are required to form all six outlets, to reduce manufacturing cost and simplify assembly. Specifically, a bus bar  132  having ground connectors  135  is used in two positions (the outermost bus bar positions on the left and right sides, respectively, in FIG. 14), and the bus bars  132  having line neutral connectors  137  are arranged facing each other in the remaining four bus bar positions, as illustrated in FIG. 13. This embodiment could be used, for example, in the United States.  
         [0086]    The illustrated arrangement of the bus bars  132  to the rear panel  18  can, of course, be changed if the UPS is manufactured or used in a country or region having an alternate type of electrical receptacle and/or voltage (see FIGS. 17A through 17J). In those examples, the rear panel  18  could have receptacles  55  integrally formed into the rear panel, as shown in FIGS. 13 and 14, but which, together with the bus bars  132 , are constructed and arranged to mate to the types of plugs used.  
         [0087]    [0087]FIG. 15 is a left perspective view of the rear panel  18  of the chassis  11  of FIG. 2A, taken from the rear side, showing wires, bus bars  132 , and the line cord assembly  136  installed. FIG. 16 is a left side view of the line cord assembly  136 . Referring to both FIGS. 15 and 16, it can be seen that the line cord assembly  136  includes a strain relief portion  138  integrally molded as part of the line cord assembly  136 , to permit the line cord assembly to withstand pulling forces during assembly of the chassis  11  and during use. The strain relief portion  138  engages a portion of the line cord opening  62  integrally formed to the rear panel  18 , which portion mates with the contours of the strain relief portion  138 . In addition, the line cord assembly  136  includes a detent  140  designed to catch on the line cord opening  62  (FIG. 2), to enable the line cord assembly  136 , together with its strain relief portion  138 , to stay assembled to the rear panel  18  prior to the rear panel  18 &#39;s assembly to the left panel  12  and right panel  14 .  
         [0088]    As those skilled in the art will recognize, the chassis  11  of the present invention can be adapted to work with UPS&#39;s having components of varying sizes and weights. The chassis  11  and its associated UPS also can be adapted to work with differing line power systems around the world, simply by swapping internal components (if necessary) and changing the rear panel  18  (including its bus bars  132 , if necessary).  
         [0089]    [0089]FIGS. 17A through 17J are examples of such alternate rear panels usable with the present invention. FIGS. 17A and 17B are perspective and front views, respectively, of a rear panel  18  having receptacles  55  usable in locations such as the United States. FIGS. 17C and 17D are perspective and front views, respectively, of a rear panel  18 ′ having so-called “international” receptacles  55 ′. FIGS. 17E and 17F are perspective and front views, respectively, of a rear panel  18 ″ having receptacles  55 ″ usable in regions such as France. FIGS. 17G and 17H are perspective and front views, respectively, of a rear panel  18 ′″ having receptacles  55 ″, usable in regions such as Germany. FIGS. 17I and 17J are perspective and front views, respectively, of a rear panel  18 ″″ having receptacles  55 ″″ usable in regions such as China. Those skilled in the art will, of course, recognize that the various styles of rear panels illustrated in FIGS. 17A through 17J are merely representative of the different styles of rear panels that can be implemented to meet the particular voltage and receptacle needs of a particular region. Many other designs for the rear panel  18  are possible in accordance with the invention.  
         [0090]    It should be understood that the present invention is not limited to providing a chassis for a UPS but may also be used to provide a lightweight, inexpensive, sturdy chassis for virtually any type of electronic instrument.  
         [0091]    Having thus described at least one illustrative embodiment of the invention, various alterations, modifications and improvements will readily occur to those skilled in the art. Such alterations, modifications and improvements are intended to be within the scope and spirit of the invention. Accordingly, the foregoing description is by way of example only and is not intended as limiting.