Abstract:
A hand held mobile terminal includes at least one torque cell for facilitating a torsionally stiff housing structure. The torque cell includes a plurality of first locking members located around a perimeter of a first housing and a plurality of second locking members located around a perimeter of a second housing. The first and second locking members are slidably engageable with each other so as to create a plurality of interlocking joints around the perimeter of the torque cell. Accordingly, the torque cell structure provides several advantages over the conventional mobile terminal housing, such as: better torsional rigidity, simplified assembly, improved volumetric efficiency, reduced need for shock absorbing materials, lighter overall weight, decoupling of impact loads, and mitigation of stress concentrations.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Application Ser. No. 60/470,008, filed on May 13, 2003, and entitled TORQUE CELL. 

   TECHNICAL FIELD 
   The present invention generally relates to portable electronic devices. In particular, the present invention relates to systems and methods for a rugged housing design for a mobile terminal. 
   BACKGROUND OF THE INVENTION 
   Hand held mobile terminals have become widely accepted as personal and business organizational tools. Many users carry hand held mobile terminals on a daily basis. Accordingly, it is desired that housings for mobile terminals meet a number of criteria. A housing for a hand held mobile terminal should be aesthetically appealing. Moreover, the housing should be rugged to protect inner electronics from damage in the event of a drop. As mobile terminals become more and more powerful, a need for strength in the housing is at odds with a need to minimize volume occupied by the housing, and thus unavailable for packaging the electronics. Further, any mechanism used to hold the housing together should minimize any volume occupied and provide a secure latching system to prevent the disengagement of the housing parts. 
   Hand held mobile terminals are generally assembled by enclosing internal electrical components, such as a Central Processing Unit (CPU) board, display, keyboard, and internal wiring, within a housing made of plastic or another structural material. The enclosure is normally formed in two parts having an upper housing and a lower housing. The electronic components are mounted to one or both sides of the housing with or without subframes. The display and sometimes the battery are also located within the enclosure. The display and the battery represent large masses that can impart undesirable impact loads to the CPU board during a drop event. 
     FIG. 11  depicts a conventional housing  1100  for a hand held mobile terminal. The housing  1100  comprises two halves  1110  and  1120 . The two halves  1110  and  1120  are fastened together to contain electronics (not shown). Bosses  1130  are included in the housing  1100  such that fasteners  1140  can penetrate both sides of the housing  1100 . The fasteners, or screws,  1140  are inserted through bosses  1130  on one half of the housing  1100  through to the other half of the housing to provide the closing force needed to hold the assembly together. These features use volume that would otherwise be utilized for electrical components. Thus, the existence of bosses  1130  reduces volumetric efficiency of the housing  1100 . 
   Additionally, the assembly of the components into the housing  1100  requires several manufacturing processes. Before the housing  1100  is fastened together, the CPU board, the display and other components must be assembled to a subframe, to the housing, or to some other subassembly. Such assembly steps are generally time consuming and expensive in manufacturing. 
   Further, the conventional housing assembly has poor torsional rigidity due to discontinuity of the housing surfaces at the mating band. Accordingly, stresses from deflections and impact loads during a drop are concentrated at the bosses  1130 . Housing failure is often attributed to boss failure caused by deflection and impact load stresses. 
   SUMMARY OF THE INVENTION 
   The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later. 
   The present invention provides systems and methods for a rugged hand held mobile terminal design. The mobile terminal includes at least one torque cell for facilitating a torsionally stiff housing structure. The mobile terminal design includes a base housing having a portion of a torque cell and a rear cover having a mating portion of the torque cell. The torque cell includes a plurality of first locking members located around a perimeter of the base housing torque cell portion and a plurality of second locking members located around a perimeter of the rear cover torque cell portion. The first and second locking members are slidably engageable with each other so as to create a plurality of interlocking joints around the perimeter of the torque cell. Accordingly, the need for bosses and/or fastening hardware is mitigated. Alternatively, a handle portion having a plurality of second locking members can be coupled to the base housing to create a gun-shaped mobile terminal. The mobile terminal structure can also include a second torque cell for coupling a modular keypad to the terminal. The torque cell structure of the present invention provides several advantages over the conventional mobile terminal housing, such as: better torsional rigidity, simplified assembly, improved volumetric efficiency, lighter overall weight, mitigation of stress concentrations and a uniform compression of a sealing gasket for waterproof mobile terminals. 
   To the accomplishment of the foregoing and related ends, the invention then, comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative aspects of the invention. These aspects are indicative, however, of but a few of the various ways in which the principles of the invention may be employed and the present invention is intended to include all such aspects and their equivalents. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a cross section of a mobile terminal with a torque cell structure according to one aspect of the present invention. 
       FIG. 2  illustrates a perspective view of a hand held mobile terminal design having a torque cell in accordance with an aspect of the present invention. 
       FIG. 3  illustrates an example of a module keypad in accordance with an aspect of the present invention. 
       FIG. 4  illustrates an example of a module keypad in accordance with an aspect of the present invention. 
       FIG. 5  illustrates an example of a module keypad in accordance with an aspect of the present invention. 
       FIG. 6  illustrates an example of a module keypad in accordance with an aspect of the present invention. 
       FIG. 7  illustrates a perspective side view of the hand held mobile terminal of  FIG. 2  in accordance with an aspect of the present invention. 
       FIG. 8  illustrates a perspective view of another hand held mobile terminal design having a torque cell in accordance with an aspect of the present invention. 
       FIG. 9  illustrates a methodology for fabricating a hand held mobile terminal housing in accordance with an aspect of the present invention. 
       FIG. 10  illustrates a methodology for assembling a hand held mobile terminal in accordance with an aspect of the present invention. 
       FIG. 11  illustrates a conventional hand held mobile terminal housing. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention relates to systems and methods for a rugged hand held mobile terminal design. The present invention will now be described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. It is to be appreciated that the various drawings are not drawn to scale from one figure to another nor inside a given figure, and in particular that the size of the components are arbitrarily drawn for facilitating the reading of the drawings. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It may be evident, however, that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block form in order to facilitate describing the present invention. 
   Referring initially to  FIG. 1 , an example of a torque cell structure  100  for a mobile terminal housing is depicted. This figure represents a cross section through the mobile terminal. The mobile terminal housing comprises an upper housing  110  and a lower housing  120 , which are coupled via an interlocking joint  130  located around a perimeter portion of the mobile terminal. The interlocking joint  130  includes first and second locking members from the upper housing and the lower housing, respectively. For example, the lower housing can include a substantially L-shaped member  140  and the upper housing can include a receiving member  150  configured to slidably receive and interlock with the L-shaped member  140 . However, it is to be appreciated that any other suitable locking members can be employed and is contemplated as falling within the scope of the present invention. As will be discussed in greater detail below, the interlocking joints  130  are located about the perimeter so as to create a distributed load path such that there are no concentrated loads on the housing. Accordingly, clamping on a perimeter seal of the housing is substantially uniform. Moreover, the mobile terminal housing employing the torque cell structure  100  is structurally stiffer in torsion and bending as compared to the conventional housing, which employs bosses and/or fastening hardware. 
   In  FIG. 2 , an example of a hand held mobile terminal housing design  200  is illustrated. The hand held mobile terminal  200  can be a palm top (“palm-sized”) portable computer system, a cellular telephone, global positioning system (GPS), bar code scanner, or the like. The hand held mobile terminal  200  comprises a generally bar-shaped elongate housing having two generally opposed long broad upper faces, two generally opposed long, shallow side faces, a rear end, and a front end. The housing can be fabricated from metal, plastic, or any other suitable structural material. At least one torque cell is provided within the housing. For example, a first torque cell  210  can be located at a top rear portion of the housing to house a display (not shown) for the mobile terminal  200 . The display can display information relating to a mode of operation of the mobile terminal  200 , or display check information relating to an item being read by an optical scanner (not shown) located in the mobile terminal  200 . The display can be a touch screen and may employ capacitive, resistive touch, infrared, surface acoustic wave, or grounded acoustic wave technology. Further, the display can be a liquid crystal device, cathode ray tube (CRT), field emission device (FED, also called flat panel CRT) or any other display device suitable for creating graphic images and alphanumeric characters recognizable to the user. 
   The first torque cell  210  includes a plurality of interlocking joints located around a perimeter of the first torque cell  210 . The first torque cell  210  comprises two housing portions: a base housing  220  and a rear cover (not shown). The base housing  220  includes a plurality of first locking members  230  located along a perimeter of two opposing sides of the first torque cell  210 . The rear cover portion includes a plurality of corresponding second locking members, which are adapted to slidably engage with the first locking members  230  located on the base housing  220 , as will be described in further detail below. The interlocking joint between the base housing  220  and the rear cover facilitates a torsionally stiff structure such that the mobile terminal  200  can be twisted and/or dropped without failure. For example, the mobile terminal  200  can be dropped repeatedly from a distance of approximately six feet without failure. Moreover, the interlocking joints are substantially evenly distributed about a perimeter portion of the torque cell  210  to create a distributed load along the perimeter of the housing. Thus, external loads are carried by the housing without discontinuities or stress concentrations. Accordingly, the structure of the mobile terminal  200  is more rigid than the conventional mobile terminal housing design, as described with respect to  FIG. 10 . 
   Moreover, a first gasket (not shown) can be provided about a perimeter of the display opening and/or the display itself and a second gasket (not shown) can be provided about a perimeter of the torque cell  210 . The first and second gaskets are operable to mitigate contamination, which might otherwise enter the mobile terminal assembly from outside and thereby affect performance of the mobile terminal  200 . By providing a plurality of interlocking components about a perimeter of the torque cell  210 , clamping on the gasket is substantially uniform around the torque cell  210 . The gaskets can be of rubber, foam, or any other elastomer, operable to sufficiently seal the assembly of the mobile terminal  200 . 
   A second torque cell  240  can be located at a front bottom portion of the mobile terminal  200 . The second torque cell  240  can be employed to couple a modular keypad to the mobile terminal. The modular keypad facilitates manufacturing and service, marketing flexibility, expansion and accessory, and customer reconfiguration. Examples of modular keypads which can be employed with the mobile terminal are illustrated with respect to  FIGS. 3-6 . The selected keypad can be employed to enter identification information concerning the user into the mobile terminal. Additionally, the keypad can be utilized to enter information concerning modes of operation of the mobile terminal or to carry out cancellation or manipulation operations on information provided by the terminal. 
   Turning now to  FIG. 7 , the second torque cell  240  for the mobile terminal of  FIG. 2  is better illustrated. The second torque cell  240  comprises the base housing  220  and a modular keypad  250 . When the modular keypad  250  is coupled to the base housing  220 , L-shaped members, or latches,  260  on the keypad are aligned with corresponding latch receiving members  270  on the base housing  220 . The modular keypad  250  can be slidably moved into engagement with the base housing  220  to create a plurality of interlocking joints around a perimeter portion of the second torque cell  240 . The interlocking joints can be substantially evenly distributed about the perimeter of the second torque cell  240  so as to create a distributed load around the perimeter. Accordingly, the possibility of disengagement of the mobile terminal housing during impact is substantially reduced as the interlocking joints between the modular keypad  250  and the base housing  220  facilitates a torsionally stiff structure. The modular keypad  250  can be disassembled from the mobile terminal  200  by slidably disengaging the keypad latches  260  and the mating housing latches  270 . 
   The mobile terminal  200  also includes an open end  280  in the base housing  220  for receiving a battery to power the terminal  200 . It is to be appreciated that although the open end  280  is illustrated as being located at a bottom portion of the housing, the open end  280  can also be located at any other suitable portion of the terminal  200 . An acoustic modem can also be provided for uploading and/or downloading information to and from the terminal  200 . Additionally, the mobile terminal  200  can include a communication interface for information transfer. For example, the communication interface can be a serial communication port and/or any other suitable communication standard and/or protocol, e.g., parallel, SCSI, Firewire (IEEE 1394), Ethernet, etc. Additionally, a radio transmitter can be provided for transmitting information to a remote receiver and/or a radio receiver can be provided for receiving information from a remote transmitter. 
   Turning now to  FIG. 8 , another example of a hand held mobile terminal design is depicted. The mobile terminal can be an optical reader  800  in the shape of a gun having a handle portion  805  and a base portion  810 . The handle and base portions  805  and  810  can be fabricated from metal, plastic, or any other suitable structural material. The mobile terminal  800  includes at least one torque cell, which improves mechanical efficiency and reduces assembly time for the mobile terminal  800 . Bosses and/or fastening hardware as required by conventional housings are unnecessary in the mobile terminal  800  of the present invention as the torque cell(s) includes a plurality of interlocks. Thus, external loads are carried by the torque cell(s) without discontinuities or stress concentrations. Accordingly, the structure of the mobile terminal  800  is more rigid than the conventional design. 
   A first torque cell  815  can be formed between the handle portion  805  and the base portion  810 . The handle portion  805  includes a plurality of first locking members located along two opposing sides of a perimeter of the torque cell  815 . Likewise, the base portion  810  includes a plurality of second locking members located along two opposing sides of a perimeter of the torque cell  815 . The first and second locking members are slidably engageable with each other so as to create a torsionally stiff coupling between the base portion  810  and the handle portion  805 . The mobile terminal  800  also includes a second torque cell  820  for coupling a modular keypad (not shown) to the base portion  810 . The modular keypad can be coupled to the base portion  810  in a manner similar to that described with respect to  FIG. 7  herein. Accordingly, such description will be omitted for the sake of brevity. 
   A reading window  825  through which a light beam passes is generally located at an end face of the base portion  810 , and the reader  800  is aimed at indicia to be read by a user holding the handle portion  805 . A trigger  830  can be situated in a region of a junction between the handle portion  805  and the base portion  810  for operation by the user to actuate the optical reader  800 . The trigger  830  can be of any known arrangement. For example, the trigger  830  can be spring-loaded and have contacts which form a circuit with contacts within the housing when the trigger  830  is depressed to actuate the reader  800 . Power can be conserved with such an arrangement as the reader  800  will be activated when the trigger  830  is depressed; thereby allowing the reader  800  to remain idle when no indicia are to be read. 
   In view of the foregoing structural and functional features described above, methodologies in accordance with various aspects of the present invention will be better appreciated with reference to  FIGS. 9-10 . While, for purposes of simplicity of explanation, the methodologies of  FIGS. 9-10  are shown and described as executing serially, it is to be understood and appreciated that the present invention is not limited by the illustrated order, as some aspects could, in accordance with the present invention, occur in different orders and/or concurrently with other aspects from that shown and described herein. Moreover, not all illustrated features may be required to implement a methodology in accordance with an aspect the present invention. 
   Turning now to  FIG. 9 , a methodology  900  for fabricating a hand held mobile terminal is illustrated. The methodology begins at  910  where a base housing is fabricated from any suitable structural material, such as plastic and/or metal. The base housing includes first and second torque cell portions located therein. At  920 , a rear cover is fabricated with a third torque cell portion which corresponds with the first torque cell portion. The torque cells include a plurality of interlocking structures to facilitate a torsionally stiff coupling between the base housing and the rear cover. The interlocking structures are configured such that the base housing and the rear cover are slidably engageable with each other. Alternatively, a handle portion can be formed at  920  and coupled to the base housing via a plurality of interlocks. At  930 , a modular keypad having a fourth torque cell portion is formed. The fourth torque cell portion has a plurality of interlocking structures which correspond to mating interlocking structures located in the second torque cell portion. Accordingly, the modular keypad can slidably engage the base housing to create a torsionally stiff structure. 
     FIG. 10  depicts a methodology for assembling a housing for a hand held mobile terminal is depicted. The methodology begins at  1010  where a base housing is provided. The base housing can be of any suitable material, such as plastic and/or metal. The base housing includes first and second torque cell portions. At  1020 , a display is coupled to the base housing. Then, at  1030 , a rear cover or handle portion having a third torque cell portion is provided over the display. Interlocking structures in the third torque cell portion are slidably engaged with interlocking structures in the first cell portion to couple the rear cover to the base housing. At  1040 , a modular keypad is coupled to the base housing. The modular keypad includes a fourth torque cell portion which comprises interlocking structures that slidably engage with interlocking structures located in the second torque cell portion to couple the modular keypad to the base housing. 
   It is to be appreciated that the rugged hand held mobile terminal design of the subject invention, as described herein, has wide applicability. The design can be employed for example in numerous types of commercial and industrial electronic devices (e.g., computers, personal digital assistants, cameras, electronic games . . . ). Moreover, the methodologies of the subject invention can be employed in connection with processes associated with fabricating rugged housings related to such devices. It is also to be appreciated that the scope of the present invention is intended to include any portable electronic device. 
   What has been described above includes exemplary implementations of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims.