Abstract:
A guide member for accommodating a removable module is formed from a thermally conductive material having at least one thermally conductive element to provide a new primary heat dissipation path to manage thermal energy generated by operation of the module. The guide member may also be used to guide the module into proper connection with a module connector which electrically connects the circuit on the module with other circuitry. A plurality of thermally conductive elements, such as spring fingers, ribs and fins, provide additional thermal heat dissipation paths and enhance the rigidity of the guide members.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of thermal energy management, and more particularly to a method and apparatus for dissipating thermal energy produced by removable modules, such as modules used in cable television systems. 
     BACKGROUND OF THE INVENTION 
     There are currently various devices on the market using removable modules that can be inserted into an insertion port for electrical connection with another device. These removable modules may contain a programmable circuit containing, for example, proprietary algorithms for providing information or controlling access to another device. The programmable circuit can include, for example, a Static Random Access Memory (SRAM) or the like to form a confidential or secured portion of the removable module memory in which the proprietary algorithm is stored. 
     Cable television systems in particular may use removable modules to allow subscribers controlled access to dozens or even hundreds of channels of television programming. The current trend is for cable television systems to provide additional services such as premium channels, pay-per-view programming, video-on-demand programming and even internet access. In advanced cable television systems, each subscriber is typically provided with a set-top terminal. The set-top terminal is a box of electronic equipment that is used to connect the subscriber&#39;s television, or other electronic equipment, to the cable television system. The set-top terminal processes the signal received from the cable television system to provide the services of the cable system to subscribers. 
     As the premium services of the cable television system expand, security techniques for those premium services become crucial to ensure that only subscribers who have paid for the premium services have access to them. For example, premium channels, such as some movie channels, are scrambled before transmission to prevent unauthorized reception and viewing of those channels. Subscribers who pay additional fees to receive the premium channel or channels are provided with the means to descramble and view the premium channel or channels. 
     There are many techniques for controlling the remote descrambling of scrambled television signals. Typically, a system subscriber who has paid to receive the scrambled premium channel or channels is provided with a descrambler unit that is connected between the source of the television signal source (e.g., a cable feed or a satellite receiver) and the subscriber&#39;s television set. While this descrambler unit may be a self-contained unit, descrambling circuitry is frequently and preferably incorporated into the subscriber&#39;s set-top terminal. 
     Unfortunately, proprietary algorithms used by descrambling circuitry can frequently, with enough effort, be “broken” or duplicated by an unauthorized party. Thereafter, unauthorized means of descrambling the cable system&#39;s premium channels might be made available to subscribers. To avoid this, the operator of the cable system may need to periodically change the proprietary algorithm used to scramble and descramble premium channels. 
     If the subscriber&#39;s descrambling circuitry is incorporated in a set-top terminal, the old descrambling circuitry must be removed and new descrambling circuitry inserted. To facilitate this process, the descrambling circuitry can be included in the removable modules to plug into a removable module port of the set-top box. The removable modules in this context are also known as point-of-deployment (POD) modules. When the descrambling circuitry is to be changed or upgraded, the old removable module can be pulled from the set-top box, and a module with the new circuitry is inserted in the port. Other elements or programming of the set-top terminal that need to be updated periodically can also be provided in the removable module. 
     In this application, the removable module is meant to be removed when the cable television company providing the services decides to update or change the proprietary decrypting algorithm or when the cable subscriber changes cable service providers and thus changes decrypting algorithms. Such a change may occur infrequently, in the case when the cable subscriber does switch cable service providers, or regularly as a security precaution, when improved security or other features become available for inclusion in the set-top boxes, or after the decrypting algorithm has been broken by an unauthorized user. Additionally, the inadvertent removal of the removable module typically renders the set-top box non-functional. 
     Moreover, as noted above, the current trend is for the amount and diversity of services provided by cable television companies to expand to include, for example, the transmission of computer data, a greater quantity of television programming and, eventually, telephone calls. To accommodate the existing and new services, set-top terminals will eventually require many more ports than presently exist. This will reduce the space available for including a separate port for a removable module. 
     Placing the removable module underneath and, perhaps, inside the casing of the set-top terminal, however, contributes to other problems in the design of the set-top box. Specifically, the electronic circuitry of the removable module inherently generates heat or thermal energy during operation. This thermal energy must be dissipated efficiently to prevent accumulation and overheating that may damage or be detrimental to the module or the device in which the module is inserted. Although prior art devices using PCMCIA cards attempt to dissipate heat away from the card by conducting heat through the card contacts to a main board in the device, this method risks damage to the main board if the amount of heat generated by the card overcomes the main board&#39;s ability to dissipate it. Further, removable modules are being developed that generate more heat than PCMCIA cards, making efficient dissipation of heat even more important. Note that control and dissipation of thermal energy is also important if the removable module is used in applications other than cable television set-top boxes. 
     Therefore, there is a need in the art for an improved method and apparatus for managing the thermal energy generated by the operation of a removable module when it is inserted into a removable module port. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to meet the above-described needs and others. Specifically, it is an object of the present invention to provide an improved method and apparatus for managing the thermal energy generated by the operation of a removable module in a set-top box of a cable television system or any other device requiring insertion of a removable module into a removable module port. 
     Additional objects, advantages and novel features of the invention will be set forth in the description which follows or may be learned by those skilled in the art through reading these materials or practicing the invention. The objects and advantages of the invention may be achieved through the means recited in the attached claims. 
     The invention is directed to a guide member, preferably a guide member for receiving a removable module that electrically connects to circuitry when the removable module is inserted into the guide member. In one embodiment, the guide member forms or is otherwise disposed in a removable module port and includes a first surface that is in physical contact with the removable module when the removable module is inserted into the guide member and at least one thermally conductive element on the first surface that provides a physical heat dissipation path from the exterior of the removable module to the exterior of the guide member and into the ambient air. The guide member is made of a thermally conductive material to ensure an efficient transfer of thermal energy away from the removable module. 
     The guide member may align and guide the removable module into proper connection with a module connector in the removable module port. This facilitates the insertion and connection of the module to the set-top box. 
     The present invention also comprises the method of implementing the apparatus described above. Specifically, the present invention includes a method of managing thermal energy dissipation in a set-top box for use in a cable television system, where the set-top box has a removable module port formed at least in part by the guide member for receiving a removable module therein. The method is performed by conducting thermal energy away from the removable module to ambient air through at least one surface of the guide member that is in physical contact with the removable module when the removable module is placed in the guide member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings illustrate the present invention and are a part of the specification. Together with the following description, the drawings demonstrate and explain the principles of the present invention. 
     FIGS. 1 a  and  1   b  are a perspective view and a representative diagram, respectively, of a thermal energy management system incorporating one embodiment of the inventive structure. 
     FIGS. 2 a  and  2   b  are top and side views, respectively of the inventive structure shown in FIG. 1 a.    
     FIGS. 3 a  and  3   b  are top and side views, respectively, of a spring finger used in one embodiment of the inventive structure; and 
     FIG. 4 side view of a fin used in an embodiment of the inventive structure. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 a  is a perspective view of a removable module  100  that is inserted into one embodiment of the inventive guide member  102 , while FIG. 1 b  is a simplified representative diagram of the removable module  100  in the guide member  102  that shows the manner in which thermal energy travels through the guide member  102  into the ambient air within and outside a device  103 . As can be see in FIG. 1 a , the guide member  102  has at least one surface  104  that is adjacent to, and in physical contact with, the exterior of the removable module  100  when the removable module is inserted into the guide member  102 . Consequently, when the module  100  is inserted in a removable module port  105  formed by the guide member  102 , the surface  104  of the guide member  102  contacts the module  100  and thereby aligns the module  100  with, for example, another electronic component via a module connector (not shown) to facilitate correct connection. 
     Typically, the connection between the module  100  and the module connector includes a series of pins (not shown) that mate with pin receptacles on the other component. By aligning the module  100  with the module connector, the guide member  102  helps prevent any damage or bending to the pins of the connection potentially caused when a user forces the module  100  against the module connector without properly aligning the pins and pin receptacles of the connection. 
     Additionally, the guide member  102  provides an additional thermal energy transfer path  108  through which thermal energy is conducted away from the module  100 . In such a case, the guide member  102  is preferably made of a thermally conductive material, e.g., a metal or alloy. The surfaces  104  of the guide member  102  are preferably in the form of relatively flat plate-like structures to provide a large surface area for contacting the module  100 , thereby providing a larger surface through which thermal energy dissipation can occur. 
     More particularly, when at least one surface of the guide member  102  is in physical contact with the module  100  when the module is inserted in the port  102 , the thermal energy from the module  100  will be conducted from the exterior surface of the module  100  through the guide member surface  104  into the ambient air, thereby preventing the module  100  from overheating. 
     Preferably, the guide member surface  104  physically contacts a majority of the top and bottom side surfaces of the module  100 . Increasing the area of physical contact between the module  100  and the guide member  102  increases the size and effectiveness of the thermal energy conduction path  108  away from the module  100 . Additional thermally conductive surfaces may also be provided on the sides of the module  100  to provide additional physical contact. 
     FIG. 1 b  illustrates one example of thermal energy management in the inventive system. As shown in FIG. 1 b , the guide member  102  is disposed in a hollow device  103 , such as a set-top box chassis. The port  105  for the removable module  100  includes a module connector  110  that links the module  100  electrically to circuitry such as, for example, a printed wire assembly  111 . The link provided by the module connector  110  provides power to the module  100  and allows the use of any programming, algorithm or processing capability resident in the module  100 . 
     As can be seen in FIG. 1 b , there are several paths through which the thermal energy generated by the module  100  can be dissipated to maintain the module  100  and the device  103  within an acceptable operating temperature range. For example, heat is conducted through a conduction path  112   a  from the module  100  through the module connector  110 . This heat is, in turn conducted through a conduction path  112   b  to the circuitry  111  of the device  103 , released by convection  113  into the ambient air within the device  103 . Heat within the device  103  is released by convection  115  from the exterior of the chassis or through an exchange path  116 . The exchange path may include a vent, with or without a fan, in the device  103 . 
     Alternatively, thermal energy is released by convection  117  from the exterior surface of the module  100  into the ambient air within the device  103 . As described above, heat within the device  103  is then released by convection  115  from the exterior of the chassis  103  or through the exchange path  116 . Additionally, the guide member  102  provides an additional thermal energy transfer path  118  through which thermal energy is conducted away from the module  100 . 
     Consequently, as the guide member  102  is in physical contact with the module  100  when the module is inserted in the port  105 , thermal energy from the module  100  will be conducted via a conduction path  118  from the exterior surface of the module  100  through the guide member  102  and into the device  103 . The thermal energy escaping from the module  100  into the device  103  via the conduction path  118  is then dissipated from the device  103  by convection  115  from the exterior surface of the device  103 . The device may also release heat by convection into the ambient air within the chassis  103  which can be released through the exchange  116 . 
     The guide member  102  in this embodiment also has a plurality of spring fingers  110  that are preferably punched or formed out of the guide member  102 . The spring fingers  110  help provide more reliable physical and thermal contact between the module  100  and the guide member  102 . Each spring finger  110  may create an opening  112  when it is formed and preferably extends downward from a guide member surface  104 . The spring fingers  110  shown in FIG. 1 can be formed into any desired shape, such as a “C”, “V”, or “M” shape, as long as they protrude from the guide member surface  104 . Of course, the opening  112  will not be created if the spring fingers  110  are formed in a manner that leaves the guide member surface  104  unbroken. The guide member  102  may also include a series of fins  114 . The spring fingers  110  and fins  114  provide structural rigidity to the guide member  102  and also increase the surface area through which heat can dissipate. Of course, the spring fingers  110  and the fins  114  do not both need to be incorporated into the same structure and instead can be used alone in the guide member  102 . 
     As can be seen in FIG. 1, each spring finger  110  and fin  114  provides an additional thermal conduction path through which thermal energy from the module  100  can be released into the ambient air. Further, because the spring finger  110  is in direct physical contact with the module  100  when the module  100  is inserted into the guide member  102 , the thermal conduction path  108  formed by the spring finger  110  efficiently moves heat away from the module  100 . The thermal energy escaping from the module  100  into the ambient air via the thermal energy conduction paths  108  is then dissipated from the guide member  102  by convection from the exterior surface of the guide member  102 . 
     In this way, the present invention provides new primary thermal energy dissipation paths for the module  100 , through both the guide member surfaces  104  and through the spring fingers  110  and fins  114  on the guide member  102 . This allows the module  100  to more easily maintain an acceptable operating temperature. Additionally, the thermal energy conduction paths  108  through the guide member, spring fingers  110  and fins  114  conduct heat efficiently away from the module into the ambient air, bypassing the circuitry of the device, such as a set-top box, in which the guide member  102  is installed. This allows the circuitry of the device to maintain an acceptable operating temperature more easily. 
     FIGS. 2 a  and  2   b  are top and side views, respectively, of a guide member  102  having the spring fingers  110  and fins  114  described above. In FIGS. 2 a  and  2   b , the spring fingers  110  have a “C” shaped profile, but any shape can be used as long as the spring fingers  110  extend into the guide member  102  to allow direct physical and thermal contact with the module when it is inserted. In addition to the plurality of heat dissipating spring fingers  110 , the series of fins  114  are positioned adjacent to spring fingers  110  in this embodiment. As can be seen in FIG. 2 b , the fins  114  protrude above the surface  104  of the guide member  102 , while the spring fingers  110  extend into the port area  105  in which the module  100  is to be inserted. 
     FIGS. 3 a  and  3   b  offer a further view of the spring finger  110  in a preferred embodiment of the present invention. As can be seen in the figures, if the spring finger  110  is formed by punching down the fingers  110  from the guide member surface  104 , the formation process leaves an opening  112  having roughly the same outline (in this case, a C-shape) as the spring finger  110 . A first planar portion  300  of the spring finger  110  extends away from the guide member surface  104  and terminates at distance d 1 , and a second planar portion  302  extends parallel to the guide member surface  104  at the distance d 1 . The second planar portion  302  is preferably deflectable when a module  100  is inserted so that there is good physical and thermal contact between the module  100  and second planar portion  302  the spring finger  110 . Further, the spring finger  110  is preferably integrally formed into the guide member  102  from a single piece of material, such as stainless steel. 
     FIG. 4 shows a side view of the fin  114  which is integrally formed in the guide member  102  in this embodiment. Each fin  114  preferably has, but is not limited to, a width d 3  and a height d 4 . The fins  114  generally are adjacent to and in parallel with a plurality of columns of spring fingers  110 , an example of which can be seen in FIGS. 1 and 2. 
     The use of the guide member  102  of the present invention to conduct heat away from the module can be enhanced by modifying the design of the module itself  100 . For example, the module  100  should be designed to achieve a uniform temperature distribution across its surface, which is preferably metallic, for efficient conduction of thermal energy into the guide member  100 . Additionally, the removable module  100  typically comprises various components, for example integrated circuits and a battery, that have different power dissipations. A conforming thermally conductive material can be placed inside the housing of the removable module between these various components and the housing to help generate a substantially uniform heat distribution on the exterior surface of the module housing. Moreover, the components of the module  100  that generate the most heat should be placed nearest the end of the module  100  that connects to the module connector. Components of the module  100  that generate little heat, such as a battery, should be placed at the other end of the module  100 . This arrangement can provide a shorter thermal path for heat from the module components that produce the most heat into the guide member  102 . 
     With respect to the guide member  102  structure itself, as noted above, the spring fingers  110  and fins  114  are preferably all integrally formed in the guide member  102 . The material used for the guide member  102  should be thermally conductive and flexible enough so that the spring fingers  110  will deflect when a module  100  is inserted into the guide member  102  to provide good physical and thermal contact. 
     As described above, the present invention is a guide member for receiving a removable module in which generated thermal energy can be more effectively managed and dissipated than in prior art devices. The present invention therefore allows better control of thermal energy generated by removable modules, improving module performance. 
     The preceding description has been presented only to illustrate and describe the invention. It is not intended to be exhaustive or to limit the invention to any precise form disclosed. Many modifications and variations are possible in light of the above teaching. 
     The preferred embodiment was chosen and described in order to best explain the principles of the invention and its practical application. The preceding description is intended to enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims.