Abstract:
A dual, or single, case mobile computing and communication system with rapid mobility for usage in the field, consisting of a component mounting mechanism, a mobile computer and peripheral data switching micronetwork, an enclosed modular peripheral power system, and a plug-in modular component card system. The universal mounting mechanism holds multiple peripherals in such a way that they can be easily and quickly installed and removed from the case configuration. It locks the peripherals so they do not move during transportation. It is also low in profile so it does not obstruct the use of the items being held. The system offers rapid reaction mobility, by isolating and securing the many data and power cables necessary to connect up to 8 peripherals. The data part of this micronetwork includes data switching to connect the single computer&#39;s parallel and serial interface to these peripherals. The power system is modular and supports unique power outputs to multiple devices from either a single AC or DC input. The invention combines multiple modular component cards that snap together allowing ease of use and quick field exchange of panels for the system.

Description:
This Appln claims the benefit of US Provisional No. 60/041,590 filed Mar. 25, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a mobile modular computing and communication system, consisting of a computer and supporting peripherals integrated in one or more transportable cases or enclosures. The cases include fully integrated data and power systems to support mobile computing and communication applications. 
     2. Background Art 
     Portable computing systems and other systems-designed to deploy electronic, medical, data entry, and remote sensing technology in a mobile enclosure are readily available in many forms. Some have even included a power system to support the computer and/or peripherals in the case. However, several problems faced by integrators and end users when deploying and using mobile systems have remain unsolved. For example, the needs of some mobile users of mobile modular computing and communication system are not satisfied by a single portable computer, and in addition have a need to deploy several additional peripherals that need both power supply and data connections to the portable computer. Such devices may include scanners and digital cameras to collect imagery and other data, as well as cellular, satellite, and/or encryption technology to facilitate communications. Terrestrial infrastructure in some field-deployed situations is very limited. In some cases, a single AC or DC source is available, but in many other cases battery power must be used. Therefore, the system with the multiple peripherals must be made operational with either a battery or form a single AC or DC power source connection. 
     Many field users have no access to a technician or service facilities. Therefore, the integrated case system also needs to be modular, allowing easy and rapid removal and replacement of components in the field. 
     Mobile system users need to make their system field-operational as quickly and easily as possible. Connecting and disconnecting data and power cables each time the system is used may cause system failure, cable loss, and end user confusion as well as delay during setup. The problems can be severely exacerbated when setting up the system in low light conditions, or in conditions of high stress or time urgency. Mobile systems without an integrated case enclosure and locked-down cable structure present the user with a confusing array of tangled cables and connectors that are difficult to sort out in the field, and may delay setting up the system. Worse yet, many of these loose parts can be lost. At the same time, permanent fasteners are not appropriate, as the user may need to remove the peripheral for use outside the case system, or replace it with a repaired or an upgraded component. Therefore, a new connection technology is needed that gives both a stable support as well as quick and easy release when the mounted object needs removal. The integrated system needs a design and dimension facilitating comfortable ergonomic operation of the system on a desktop surface. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of this invention to provide a mobile computing and communication system that can be made field-operational quickly and easily with little or no cable routing and without need to rely on external power supplies if none are available. Another object of this invention is to provide a method of assembling a modular data processing and communication system that minimizes cost and provides for maximal flexibility in making repairs and installing upgraded components. Still another object of this invention is to provide a process of performing data processing and communication functions, such as digital imaging, scanning, printing, copying, secure and open voice and digital communications and data backup that obviates the need for a mass of external cables. 
     These and other objects of the invention are attained in a mobile modular computing and communication system having modular components enclosed within one or more cases, and connected by a stable mechanical connection to the main structure of a case, i.e. a modular physical connector system. The mechanical connection provides the capability of quickly and easily installing and later removing these components. This mechanical connection is a universal mount that can be applied to objects of differing shapes and sizes. In general terms, the a dual or single case containing components constituting a mobile computing and communication system. These include a computer and component mounting technology, a mobile computer and peripheral data switching micronetwork, an enclosed modular peripheral power system, and a plug-in modular component card system. 
     Once the devices are mechanically attached, two categories of connections are provided: a data connection and a power connection. These connections are part of a micronetwork. The micronetwork is a microcosm of the larger network used in the office environment to connect the desktop PC to peripherals and local area network resources, i.e. printers and modems. Several methods of data connection can be used: 1) Serial-9 pin or 25 pin, 2) Parallel 25 pin, 3) Universal Serial Bus (USB), 4) PC Card SCSI, 5) Firewire 1394, and 6) Direct modem or 7) Ethernet interface on the outside of the mobile computer. To facilitate connection between the single serial and parallel port on the laptop to multiple serial and parallel peripherals, data switching of these connections is provided. Although the USB interface does not require switching, a USB hub is integrated to allow the connection of multiple USB devices. Cable connections to either a Firewire 1394 port, a modem port or a direct network connection are provided as part of this micronetwork. These connections are done with cabling that is secured to the system, routed appropriately to support needed connections, reducing cabling congestion and preventing loss or damage to cables. 
     Power systems are provided to the computer and peripherals in the system. This power source is not standard and thus each device needs its own specific power source, i.e. 14 Volts @ 2.5 Amperes. 
     The mounting system enables continual updating and upgrading of the components in the system to the most recent technology. The enclosure system support modularity so these upgrades can be accomplished without replacing the entire system. Field replacement of components is possible to allow easy repair of the system. 
     The universal mounting mechanism holds multiple peripherals in position for immediate use when the cases are opened, and also in such a way that they can be easily and quickly installed and removed from the case configuration. The mechanism locks the peripherals so they do not move during transportation. The mechanism holding the system is also low in profile so it does not obstruct the use of the items being held or raise the elevation too high to make the system difficult to use when placed on a standard height work surface. The support mount has surfaces on two sides that prevent horizontal movement. The third surface is held in place by a small plate that can be unlocked and rotated out of the way when the peripheral needs removal. 
     This invention offers rapid reaction mobility, by providing a micronetwork that isolates, secures and simplifies the many data and power cables necessary to connect multiple peripherals. The data part of this micronetwork includes data switching to connect the single computer&#39;s parallel and serial interface to multiple peripherals. Furthermore, the integrated USB hub allows even more data connectivity and a simple USB bus structure within the system. The power part of the micronetwork directs power cables from the central power source to the peripherals. The power system included in our invention is modular and supports unique power outputs to multiple devices from either a single AC or DC power source. 
     The universal mounting mechanism and portions of the micronetwork are combined in an integrated fashion in multiple modular component cards which snap together allowing ease of use and quick field exchange of panels for the system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view from the rear of the two-case system, deployed and operational with lids removed and connecting cables attached. 
     FIG. 2 is a rear perspective view of the main case shown in FIG. 1, with lid removed, with a laptop computer and a printer mounted. 
     FIG. 3 is a rear perspective view of the peripheral case shown in FIG. 1, with lid removed, with a telephone and a scanner mounted. 
     FIG. 4 is a data distribution and switching wiring diagram. 
     FIG. 5 is a wiring diagram for the power supply. 
     FIG. 6 is a front perspective view of a mounting mechanism holding an electronic component, such as a laptop computer, peripheral or the like. 
     FIG. 7 is a perspective view like FIG. 6, showing the vertical support plates rotated to the open position. 
     FIG. 8 is a perspective view of another mounting mechanism, shown in assembled and closed position. 
     FIG. 9 is an exploded perspective view of the components of the mounting mechanism shown in FIG.  8 . 
     FIG. 10 is a perspective view of a data mount used to secure the laptop shown in FIG. 1, and make parallel and serial data connections to the system. 
     FIG. 11 is a perspective view of the flat ribbon cable data connector mounted on the support component of the datamount from FIG. 10, and a perspective view of the cover plate component of the data mount from FIG.  10 . 
     FIG. 12 is an exploded perspective view of the modular plug-in component cards that can optionally be used for quick replacement of system parts in the field. 
     FIG. 13 is an exploded perspective view of case  1 , illustrating structural details. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     This system invention is primarily a dual-case solution with an option for a single-case configuration. The computer and printer are fully functional in case  1 , while the other peripherals are accessible and usable in the case  2 . These become transportable when lids  32  and  34  are attached. The system capabilities include processing data, scanning and digital imagery input, secure and unclassified voice and data communications, Global Positioning input, printing, and copying. All of these functions can be accomplished independent of any terrestrial infrastructure. The system innovation includes several individual solutions described in more detail below. 
     A single power cable  3  connects the main case  1  to the peripheral case  2  and carries power to the peripherals in the peripheral case  2 . A parallel cable  52  and a serial cable  53  make the data connection between the two cases. The two-case solution is presented in FIGS. 1 through 3 below. Within each case, data and power are routed through an integrated micronetwork, as described below. 
     The system shown in FIG. 1 includes the main case  1  with a base  15 , peripheral case  2  with a base  27 , data connections  52  and  53 , and power cable  3 . The cases are set up for working condition. The details are given in the following figures. 
     FIGS. 2 and 3 support the description of the cases and their peripherals. FIGS. 4 and 5 represent data and power connections and supplement FIGS. 2 and 3. 
     As shown in FIG. 2, the laptop computer  14  and printer  13  are mounted on an aluminum support panel  15 . FIG.  13  and the description below details the structure and attachment mechanism for both case  1  and case  2 . This panel also holds the system electronics and cabling on the bottom side. Case  1  features a very low profile, even with all electronics and peripherals attached. This low profile allows the system to be placed on a table and used exactly as it stands with no modification to any items. Only a power switch  18  needs to be turned on and the system is ready for operation. If external AC power is used, an AC power cable connects to socket  16 . If external DC power is used the cable connects to socket  17 . The power switch  18  controls the external power connection from socket  16  and socket  17  to the internal power system. Another power-related port, a 16-pin power receptacle  9 , carries DC power to the peripherals in case  2  from case  1 , when a case-to power cable  3  is connected. This power is provided to the individual pins from the DC voltage converter within case  1 . The power connection runs to case  2  with the power connectors  21  for the camera  28 , the power connection  29  for a secure telephone  24  and the power cable connection inside the case  2  for the scanner  20  and the tape drive mechanism  23  below (not shown). This case-to-case power cable  3  mates with a similar port in case  2 , item  25  in FIG.  3 . The battery connected to the system can be disconnected by the switch  4 . 
     Serial data connections from the laptop computer in case  1  to the peripherals in case  2  are made via a serial case-to-case cable  53 , connecting the serial port  5  to the serial port  49  in case  2 . Once this serial cable is connected, the switch  19  activates either the camera  21  data cable  22  or the secure telephone serial connection cable  29 , all in case  2 . 
     The external parallel port  7  connects to the case-to-case parallel cable  52  and is activated by switching from the data connection to the parallel printer  13  to the external parallel port  7  via the parallel switch  6 . On case  2 , the connection is made to the parallel port  30  and to either the scanner  20  or the tape drive  23  (below the scanner, not shown) via the data switch  50 . 
     The holding mechanism for the computer consists of the upright supports  10  on the front (explained further in FIGS.  6  &amp;  7 ), the small low profile supports  11  on the back two corners of the laptop computer  14 , and the serial and parallel data port connections  8  (these are also covered in FIGS.  10  and  11 ). All of these items work together to properly support the laptop computer  14  with a quick release capability when the laptop does need removal. 
     The smaller low profile supports  11  used on the laptop computer  14  are also placed at all Four Comers of the printer  13 . Two upright brackets  12  have Velcro strapping that pulls across the top of the printer  13  to hold it in place between the supports  11 . Alternative lower profile printers that are not so high are simply held in place with supports  10  placed at each corner of the printer. The function of these supports is described in detail in FIGS. 6 &amp; 7. 
     FIG. 3 shows the base  27  of case  2 , which is the peripheral case that can be optionally attached to case  1  to operate the peripherals including a secure or non-secure telephone  24 , a digital camera  28 , a scanner  20 , and a tape backup drive  23  (below the scanner, not shown). On this rear view, the lid  34  has been removed. Once again the items are fully operable upon opening the case with the exception of the scanner  20 , which must be placed in its base  33  for operation. The necessary connections include a single 16-pin power connector  25  that connects to item  9  of Case  1 . A 9-pin serial cable  53  connects item  49  of case  2  to item  5  of case  1 . A 25-pin parallel connector cable  52  runs from item  30  of case  2  to item  7  of case  1 . Once these three cables are connected between the cases and power is applied to case  1 , the system is fully operational and data switches activate the various peripherals without any other cable changes. 
     FIG. 3 illustrates the secure telephone  24  connected to the serial data connector  31  and to the power cable  3  at port  25 , the scanner  20  sitting in its base  33 , the tape drive  23  (not shown) sitting underneath the scanner mounted to the main aluminum panel  27  and a small hole where the digital camera power cable  21  and digital camera data cable  22  exit the aluminum panel  27 . The data switches are also visible which provide the switching between the various peripherals in the system. The parallel data switch  50  controls parallel port connections from either the scanner  20  or the tape drive  23  in case  2  to the laptop computer  14  in case  1 . When the system is ready for sport the scanner  20  is placed on its side on the foam supports item  26 . A Velcro strap  51  is then wrapped around the scanner to hold it in place during transport. Another Velcro strap runs under the scanner base and holds the handset of the telephone  24  over the scanner base  33  during transport. 
     Mounting Mechanism Technology 
     The system components, except for the scanner  20 , are functional as soon as the case system is opened, without need to shift or move components. No further trays or mechanismsare needed or used to make a fully operational system. The modular physical connector facilitates this capability. This capability is further enhanced by the use of a low profile base that holds the components. The system is at the desktop operating level when it is opened, so it is immediately ready for use without further adjustment. 
     The computer and peripherals are easily installed and removed from the system because they are held in place with a releasable locking mounting mechanism. The mechanism is described below and illustrated in FIGS. 6 &amp; 7. The mounting mechanism consists of an upright cylindrical post  10 , shown in FIG. 2, with a one quarter section removed. The structure provides a corner for engaging the corner of the computer or other component (illustrated in FIGS. 6 and 7 generally as a component  35 ), so the shape of the post  10  is not limited to cylindrical. One post  10  is placed at two or more corners of the component  35  and the flat faces prevent horizontal movement in any direction. 
     The upward movement of the component  35  is prevented through the use of a metal cap in the form of a disc  36  that rotates on the post over the top of the component  35  and is hand-tightened via the small thumbscrew  37 . This mounting mechanism can be used for various components, electronic equipment, medical equipment, etc., when mounted on a plate  38 , which in this disclosure could be the panel  15  of the modular component plug-in boards  54 ,  55 , and  56  described below. Note the small round flat caps  36  are rotated over the top of the object, and thumb screws  37 , tightened down to hold both the caps and in turn the object being held in place from any vertical movement. The horizontal movement is prevented by the flat faces of the upright support mount  10  in the quarter cutout. As shown in FIG. 7, removal of the component  35  is accomplished by turning the thumbscrew  37  to loosen the disc  36 , and rotating the disc  36  away from the quarter cutout in the support. In this position, the component being mounted can be slipped up and out of the support. 
     As shown in FIGS. 8 and 9, another embodiment of the universal mounting mechanism is shown at  10 ′ using some of the principles of the mount  10  shown in FIGS. 6 and 7, but offers in addition a universal mount adjustable to support objects of various heights. This height adjustment is done the first time the object is mounted or simply when the mounting system is manufactured. Thereafter the mount acts as a quick release system for the object being secured. The universal mounting mechanism  10 ′ has a main mount  39  that slides vertically inside a support mount  40 . Threaded holes in the uprights of the support mount  40  hold set screws  43  which when tightened hold the main support  39  at the proper height. The base of the support mount  40  has two holes, and two screws serve here to attach the mount to the aluminum panel  15  of the case system or wherever an object is being mounted. The support has a cutout or opening that corresponds to the object that will fit into it, i.e. usually a 90 degree opening which fits the corner of a laptop or peripheral. The flat faces of this opening prevent horizontal movement of the object. We now have a horizontal support that can be height adjusted to fit the dimension of the object being mounted. Now the challenge is to cap the support to prevent vertical movement of the computer or other object. 
     The upward support mechanism needs to be unobtrusive, yet easily moved out away from the support opening to allow the mounted object to be slid out from the supports. In this embodiment a round opening is cut into the top of the main mount  39 . The cap is a flat piece of thin metal formed to allow a round thumbscrew to be inset into this round opening and tightened onto this thin metal to prevent movement of the cap. When loosened, the cap is rotated to the side freeing the top of the support to allow the removal of the mounted object. The inward curvature of the main mount  39  allows the thumbscrew  42  to be easily rotated by the thumb and forefinger to tighten the flat plate  41  to the mount  39 . FIG. 8 shows a breakaway representation of the mounting mechanism. 
     Many other embodiments are envisioned for this capping mechanism. These include a cap hinged at the back top surface of the support that allows the cap to snap down onto the support. The complete support mechanisms of either type have two threaded holes at the bottom. Screws are placed through the supporting panel and attach to these threaded holes. The cylindrical mounting mechanism  10  and the is designed to be used not only for the peripherals presented in this application but also as a universal mounting mechanism for numerous computer, medical, aviation, and field deployment applications. 
     Data Dock Port 
     FIG. 10 shows the data mounts  8  that sit on the back of the portable computer  14  in position to plug into the data parts. These provide a type of docking mechanism and prevent the laptop from sliding at the back in either a horizontal or vertical direction. 
     As represented in FIGS. 10 and 11, the data mounts  8  are actually constructed of two parts. The L-shaped bracket  45  has a cutout that allows a 25-pin parallel connector  44  or a 9-pin-serial connector  44  with a flat ribbon cable to be mounted via screws on the sides of the connector. The ribbon cable connects to either a switch or simply another data connector on the aluminum panel  15  holding everything. The L-bracket itself is attached via two holes  46  on the base of the L-bracket  45 . FIG. 11 shows a hood  47  that shields and protects the rest of the mounting mechanism. It fits snug over the L-bracket  45 , leaving no open space around the upright leg of the L-bracket  45 , and mounts to the panel  15  via holes  48 . The lower or horizontal leg of the L-bracket terminates short of the back of the hood  47  and the ribbon cable passes through an opening in the panel  15  between the end of the L-bracket lower leg and the back of the hood  47 . 
     This mount stays stationary and as the peripheral or computer is placed in the case it slides down between the cutout cylinders at the same time it is sliding into the data mounts. Once in place and secured by the discs on the cutout cylinders, the component is locked in place against vertical or horizontal movement. Furthermore this mechanism allows the data cables to be directed into the closed area of the case and out of the way of the user. 
     Mobile Micronetwork Technology 
     The data component of the micronetwork, illustrated in FIG. 4, provides connectivity to the peripherals from the portable computer  14  via the parallel port and an internal cable XX to a parallel switch  6  in the main case  1 . The switch  6  enables routing of the data to either the printer  13  or the external parallel port  7 . This external parallel port  7  can be connected to a corresponding parallel port  30  in the peripheral case  2  via a case-to-case parallel cable  52 . An internal cable routed under the base in the peripheral case  2  connects the parallel port  30  to another parallel switch  50  that can be manually switched by the user to choose connectivity to either the scanner  20  or to the tape drive  23 . The portable computer serial port connects to the external serial port  5  in the main case  1  and a case-to-case cable  53  connects the serial port  5  to a serial port  49  in the peripheral case  2 . The serial connectivity can switched by way of a serial switch  19  between the camera  28  and the secure telephone  24 . 
     The system may be provided with a universal serial bus (USB) connectivity option main case  1  and the peripheral case  2  have that is illustrated by the areas of the FIG. 4 with phantom lines. The laptop computer  14  has a USB port to which is connected an internal USB cable  69  routed under the base XX to the a USB port  68  on the main case  1 . A USB case-to-case cable  62  can be plugged into the USB port  68  and into a corresponding USB port  71  on the peripheral case  2 . The USB port  71  on the peripheral case  2  connects to a USB hub  72  via an internal USB cable  70  routed within the base of the peripheral case  2 . The USB hub then provides four USB active ports supporting up to 500 ma power and the data connection. Internal cables (not shown) are installed to the peripherals from USB hub  72 . 
     Modular Power Center 
     FIG. 5 illustrates the power distribution and conversion component of the micronetwork. The system is designed to take one of three single power sources, AC 100-240V, DC 12-24V, or 12V battery power and distribute this to each component in the system at the proper voltage level. The power system consists of the an AC to DC converter  64 , a modular power center assembly, plug in power cards  69 - 76  supplying the power requirement of each device, a system control panel, one or more batteries  77 , and the switches, cabling and connectors completing the system as a whole. The power center for this configuration is similarly innovative in its use of a single 12V-24V DC or 110-240V AC source for all peripherals in the system. The system can be set to automatically switch to battery operation when external power is interrupted. The system packaging is designed to be rugged and compact with good distribution of the heat generated during power conversion by use of potting materials having good heat conductivity and heat dissipation surfaces such as fins and the like. All power board modules are encased in epoxy-filled aluminum extrusions to assure that the heat is properly dissipated and the circuitry will withstand the rough environment encountered in portable use. 
     AC power is connected at the IEC port  16  and from there directly to item  64 , an AC to DC power converter. The DC output from this converter runs to the DC Power switch  18 . This switch in turn directs power from either the external DC power source or from the AD-DC converter to the modular power center assembly  65 . Individual power cards represented by items  69  through  75  connect to the power center assembly  65  and provide either single or dual DC power output depending on the requirements of the peripherals it supplies. The battery charge module  76  supplies power to the battery  77  when the system is in charging mode and when the battery cutoff switch  4  is in the battery connect position. The peripherals in case  2  are powered when the system is turned on and the case-to-case power cable  3  is connected. When connected, the peripherals scanner  20 , tape drive  23 , digital camera  28 , secure telephone  24  and an optional Universal Serial Bus (USB) hub  63  are powered. The USB hub will provide both power and data and thus if newer USB capable peripherals are placed in the peripheral case  2 , the USB connection will replace the need for both a separate power source from the power motherboard or data connection from the serial and parallel ports. However, the USB connection itself needs a power source and this will still be provided via a power card on the power motherboard. Another option is to simply add more peripheral connections. 
     Modular Component Board Design 
     The modular plug-in system, shown in FIG. 12, allows the user to replace components that need field replacement as well as the ability to add new capabilities to the system through the simple interchange of the modules. The panels are self-contained and each provides a specific function to the overall system. This system can be implemented in the base  15  of case  1 , allowing a snap-in/snap-out replacement of the mount and electronics associated with a particular peripheral. This is an optional configuration of that presented above. 
     As an example, the component board  54  for the computer  14  holds the physical mounts, and the power/data interface and components to support the computer  14  within the system. If the computer needs to be swapped for another with a different size, this complete modular component board is changed. Correspondingly, the printer component board  56  has the physical mounts, and power/data interfaces necessary to hold the printer in the system. In this example, the third board  55  could hold a cellular phone or GPS system, data and power switches, and port interfaces to connect other devices or a second case. 
     To make a functional integrated system, the three individual component boards  54 ,  55 , and  56  must have power and data connections to one another and to the base of the case. Two system design innovations are included to provide this connection. The preferred embodiment uses a vertical snap down connection for each component board to a power and data bus physically attached to the base of the case system. Data and power receptacles at the bottom of each component board plug in to a corresponding receptacle on the data/power bus. This in turn provides the circuitry and cabling to connect the data and power systems on the individual component cards. The component cards can optionally be connected via plugs on the side of the cards in a horizontal direction. Once all the cards are connected, the entire system can then be mounted into the base of the case. This is similar to connecting pieces of a puzzle and then placing the assembled article into its place. 
     The details of the physical structure of the main case  1 , as shown in FIG. 13 includes three parts: 1) the actual base  58  of the case  1  representing the lower half of the outer shell of the external case, 2) two aluminum rails  59  with mounting holes  61 , and 3) the aluminum panel  15  which supports the peripherals, the mounting mechanism, the electronics, and the cabling and switches for the data system. This panel is attached to the aluminum rails  59 , which in turn are attached to the base  58 . When completely assembled and loaded with peripherals, this is referred to as case  1  in FIGS. 1 and 2. 
     The panel support mechanism shown in FIG. 13 provides a robust, low profile construction. The metal rails  59  are ‘Z’-shaped in cross section and attach to the base and sides of the case bottom  58  by rivets. This provides a strong flat surface with threaded holes  61  to attach the aluminum panel  15 . This same support surface is used when attaching the modular components  54 ,  55 , and  56  to the case. The rails  59  provide a resilient mount for the panel  15 , and can yield slightly in the event of impacts and spread the impact shock somewhat, and they also strengthen the structural integrity of the case bottom  58 . 
     Obviously, numerous modifications and variations of this preferred embodiment will occur to those skilled in the art in light of this disclosure. Accordingly, it is expressly to be understood that these modifications and variations, and equivalents thereof, shall be considered to be within the spirit and scope of invention as defined in following claims.