Patent Publication Number: US-6667451-B1

Title: Push button assembly

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a new and improved push button assembly and to a manner in which heat is transferred from the push button assembly. 
     Push button switch assemblies have previously utilized incandescent light sources to illuminate displays. Push button switch assemblies having such a construction are disclosed in U.S. Pat. Nos. 3,315,535 and 4,496,813. However, push button switch assemblies having incandescent light sources may require maintenance to replace failed or burnt out light sources. 
     It has been suggested that solid state light sources may be utilized to illuminate a display in a push button switch assembly. Known push button switch assemblies having solid state light sources to illuminate displays are disclosed in U.S. Pat. Nos. 5,659,297 and 6,153,841. When circuit components which emit heat are disposed adjacent to the solid state light sources, there is a possibility that the light sources may tend to overheat. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a new and improved push button assembly which is used to move switch contacts between an actuated condition and an unactuated condition. The push button assembly includes a plurality of solid state light sources which are energizable to emit light. A display is illuminated by light from the solid state light sources when the solid state light sources are energized. 
     A metal heat sink is disposed adjacent to electrical circuit components which emit heat. To conduct heat away from the heat sink, the metal heat sink may be disposed in engagement with a metal housing. The heat sink may be formed by a single member or by a plurality of members. The member or members forming the heat sink may advantageously have projections which extend through side walls of a base. The projections are engagable by the metal housing to facilitate the conduction of heat between the heat sink and the housing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other features of the invention will become more apparent upon a consideration of the following description taken in connection with the accompanying drawings wherein: 
     FIG. 1 is a schematic illustration of a switch assembly which is connected with a control panel; 
     FIG. 2 is an enlarged upper pictorial view of a push button assembly which is constructed in accordance with the present invention and which may be used in the switch assembly of FIG. 1 to move switch contacts between actuated and unactuated conditions; 
     FIG. 3 is a lower pictorial view of the push button of FIG. 2; 
     FIG. 4 is an exploded upper pictorial view of the push button assembly of FIGS. 2 and 3; 
     FIG. 5 is an exploded lower pictorial view of the push button assembly of FIGS. 2 and 3; 
     FIG. 6 is an enlarged upper pictorial view of a heat sink and a base of the push button assembly of FIGS. 2 and 3 prior to installation of the heat sink in the base; 
     FIG. 7 is an upper pictorial view of the base of the push button assembly with the heat sink installed, the base of the push button assembly being offset by approximately 90 degrees from the orientation illustrated in FIG. 6; 
     FIG. 8 is an upper pictorial view illustrating a printed circuit and electrical circuit components prior to installation of the printed circuit and electrical circuit components in the base of the push button assembly of FIGS. 2 and 3; 
     FIG. 9 is an exploded upper pictorial view, generally similar to FIG. 4, of a second embodiment of the push button assembly; 
     FIG. 10 is an upper pictorial view illustrating a heat sink utilized in the push button assembly of FIG. 9; and 
     FIG. 11 is a lower pictorial view illustrating the relationship of the heat sink of FIG. 10 to a printed circuit and electrical circuit components. 
    
    
     DESCRIPTION OF A SPECIFIC PREFERRED EMBODIMENTS OF THE INVENTION 
     Push Button Assembly 
     The manner in which a push button switch assembly  20  is installed in a control panel  22  of a vehicle, such as an aircraft, is illustrated schematically in FIG.  1 . The known push button switch assembly  20  includes a push button assembly  34 . The push button assembly  34  includes a display  36  which is illuminated by incandescent light sources (not shown) in response to actuation of the push button switch assembly and/or an occurrence at a remote location. The occurrence at a remote location may be either the operation of a device or the failure of a device to operate. 
     The push button assembly  20  has a known construction which includes a housing  24 . The housing  24  encloses a switch assembly  26 . The switch assembly  26  includes a stationary contact  28  and a movable contact  30 . Although the push button switch assembly  20  is disposed in an aircraft, it is contemplated that the push button switch assembly may be utilized in other types of vehicles, such as land or water based vehicles. Alternatively, the push button switch assembly may be associated with a control panel for equipment in a factory. 
     The push button switch assembly  20  has a construction similar to the construction disclosed in U.S. Pat. Nos. 3,315,535 and/or 5,296,826. The disclosures in the aforementioned U.S. Pat. Nos. 3,315,535 and 5,296,826 are hereby incorporated herein in their entirety by this reference thereto. The push button switch assembly  20  is a series  584 , Four Pole Lighted Push Button Switch which is commercially available from Eaton Corporation, Aerospace Controls Division, Costa Mesa, Calif. 
     It is contemplated that it may be desired to improve the push button switch assembly  20  by replacing the push button assembly  34  with an improved push button assembly  40  (FIGS.  2 - 5 ). The improved push button assembly  40  includes solid state light sources  42  (FIG. 4) which are disposed on a light source board  44 . The solid state light sources  42  and light source board  44  are connected with a flexible printed circuit  46 . A plurality of electrical circuit components  48  are connected with the printed circuit  46 . 
     The solid state light sources  42 , light source board  44 , printed circuit  46 , and electrical circuit components  48  are all received in a recess  50  (FIGS. 4,  6  and  7 ) in a base  52 . The recess  50  has a general rectangular configuration and is formed by side walls  54 ,  56 ,  58  and  60  which extend upward from a bottom wall  62 . The base  52  is molded of a suitable electrically insulating polymeric material. Metal terminals  68  (FIGS. 3-7) extend through the base  52  into the recess  50  (FIG.  7 ). 
     The solid state light sources  42  (FIG. 4) are energizable to illuminate a display  72 . When the display  72  is illuminated, it is clearly visible to an individual adjacent to the push button assembly  40 . The specific construction of the display  72  will depend upon the environment in which the push button assembly  40  is to be used. However, it is contemplated that the display  72  may have a construction similar to the construction disclosed in U.S. Pat. Nos. 5,295,050; 5,544,019; 5,659,297; 5,820,246; 5,913,617; and/or 5,951,150. It should be understood that the display  72  may have any desired construction and may include indicia which becomes visible when the solid state light sources  42  are energized to illuminate the display. 
     A divider  76  is provided to direct light from groups of the solid state light sources  42  onto specific areas of the display  72 . In addition to directing the light from the light sources  42  towards predetermined areas on the display  72 , the divider  76  functions as a reflector to maximize the intensity of the light which is directed onto a particular portion of the display  72 . A gasket  80  (FIG. 5) is provided between the divider  76  and the display  72  to block leakage of light from the push button assembly  40 . 
     A metal housing  84  is provided to enclose the display  72 . The metal housing  84  has flat metal side walls  85 ,  86 ,  87 , and  88  (FIG.  4 ). The side walls  54 - 60  on the base  52  are partially enclosed by the metal side walls  85 - 88  of the housing  84 . Thus, the side walls  54 - 60  on the base  52  are telescopically enclosed by the side walls  85 - 88  on the housing  84 . 
     A pair of identical retainers  90  are integrally formed as one piece with the side walls  56  and  60 . Although only the retainer  90  connected with the side wall  56  is illustrated in FIGS. 4-7, it should be understood that a similar retainer is integrally formed as one piece with the side wall  60 . The retainers  90  snap into rectangular openings  92  (FIGS. 4 and 5) formed in the housing  84 . 
     A cylindrical actuator or plunger  96  extends downward (as viewed in FIGS. 2-7) from a center of the base  52 . The actuator  96  has a recess  98  (FIG. 7) which is engaged by a resilient retainer rod or wire to hold the actuator in the housing  24  (FIG. 1) in a known manner. A pin  102  (FIG. 7) extends from the actuator  96  and transmits force from the actuator in the same manner as is disclosed in U.S. Pat. No. 5,296,826. 
     When the improved push button assembly  40  is to be substituted for the known push button assembly  34  in the push button switch assembly  20  of FIG. 1, the push button assembly  34  is pulled straight upward (as viewed in FIG. 1) from the housing  34 . As this occurs, a resiliently deflectable wire or rod which engages a recess, corresponding to the recess  98  of FIG. 7, in an actuator (not shown) is deflected. As this occurs, the known push button assembly  34  (FIG. 1) is pulled from the switch assembly  20  without disconnecting the switch assembly from the panel  22  in which the housing is mounted. 
     The improved push button assembly  40  is then moved downward (as viewed in FIGS. 2 and 3) into the housing  40 . The push button assembly  40  has the same outside dimensions as the push button assembly  34 . In addition, the recess  98  (FIGS. 5 and 7) in the actuator  96  on the push button assembly  40  cooperates with the resilient pin or wire in the housing  24  in the same manner as does the push button assembly  34 . Therefore, the push button assembly  40  can be moved into the housing  24  without disconnecting the housing  24  and/or switch assembly  26  from the control panel  22 . This facilitates replacement of the known push button assembly  34  with the improved push button assembly  40 . 
     Heat Sink 
     The electrical circuit components  48  (FIGS. 4,  5  and  8 ) in the improved push button assembly  40  emit heat when they are energized by electrical energy. The heat which is emitted by the electrical circuit components  48  may tend to result in overheating of the solid state light sources  42  (FIG. 4) in a manner which would be detrimental to their operation. 
     In accordance with one of the features of the push button assembly  40 , a heat sink  110  (FIG. 6) is provided in the push button assembly  40 . The heat sink  110  includes first and second identical metal sections  112  and  114 . The first and second sections  112  and  114  are disposed on opposite sides of the recess  50  in the base  52 . 
     The first section  112  of the heat sink  110  is mounted in engagement with the side wall  60  (FIG. 7) of the base  52 . The second section  114  (FIG. 6) of the heat sink  110  is mounted into engagement with the side wall  56  of the base  52 . The first and second sections  112  and  114  of the heat sink  110  are positioned in a parallel relationship with each other by engagement with the parallel side walls  56  and  60  of the base  52 . 
     The first section  112  of the heat sink  110  is integrally formed from a single piece of sheet metal. The first section  112  of the heat sink  110  includes a pair of flat rectangular metal panels  116  and  118 . The panels  116  and  118  are interconnected by a connector  120 . A slot  122  is disposed between the panels  116  and  118  and receives an inner wall  126  disposed in the recess  50  in the base  52  (FIGS.  6  and  7 ). The inner wall  126  extends between and is perpendicular to the side walls  56  and  60  of the base  52 . 
     The first section  112  of the heat sink  110  (FIG. 6) includes a pair of projections  132  and  134  which extend from the panels  116  and  118 . The metal projections  132  and  134  extend through a pair of slots  140  and  142  in the side wall  60  (FIG.  7 ). The projections  132  and  134  (FIG. 6) have a generally hook shaped configuration and extend through the slots  140  and  142  and in a downward direction along an outer surface of the side wall. 
     The second section  114  of the heat sink  110  has the same construction as the first section  112 . The second section  114  of the heat sink  110  is integrally formed from a single piece of sheet metal. The second section  114  of the heat sink  110  includes flat metal panels  150  and  152  (FIG. 6) which correspond to the panels  116  and  118  on the first section  112  of the heat sink  110 . The panels  150  and  152  are interconnected by a connector section  154 . A slot  156  receives a portion of the inner wall  126 . 
     A pair of projections  160  and  162  extend from the panels  150  and  152 . The metal projections extend through slots  166  and  168  in the side wall  56  (FIG.  6 ). The projections  160  and  162  have a generally hook shaped configuration and extend downward (as viewed in FIG. 7) along the outer surface of the side wall  56 . The projections  132  and  134  from the first section  112  of the heat sink  110  extend downward along the outer surface of the side wall  60  in the same manner as the projections  160  and  162  from the second section  114  of the heat sink  110  extend downward along the outer surface of the side wall  56  (FIG.  7 ). 
     The first and second sections  112  and  114  of the metal heat sink  110  are positioned relative to the recess  50  and the base  52  by engagement of the slots  122  and  156  with the inner wall  126  (FIG. 7) of the base. The first section  112  of the heat sink  110  is also positioned relative to the recess  50  and base  52  by engagement of the projections  132  and  134  with the slots  140  and  142  in the side wall  60  of the base. Similarly, the second section  114  of the heat sink  110  is positioned relative to the recess  50  by engagement of the projections  160  and  162  with the slots  166  and  168  in the side wall  56  of the base (FIG.  7 ). 
     The heat sink  110  includes two separate sections or pieces  112  and  114  which are disposed on opposite sides of the recess  50 . However, the heat sink  110  could be formed by a lesser or greater number of pieces if desired. For example, the heat sink  110  could be formed as a single piece of metal having sections along opposite sides of the recess  50  interconnected by a section extending along the bottom of the recess. Alternatively, the heat sink  110  may be formed by four separate metal sections, each of the sections being disposed along one of the side walls  54 ,  56 ,  58 , and  60  of the base  52 . 
     Printed Circuit 
     The printed circuit  46  (FIG. 8) is flexible. The printed circuit  46  includes a flat main section  180 . A plurality of secondary sections  182 ,  184 ,  186  and  188  extend downward from and are perpendicular to the main section  180 . The printed circuit  46  contains conductors which are enclosed in a suitable electrically insulating polymeric material in a well known manner. Although the printed circuit  46  is flexible, it has sufficient rigidity to maintain the configuration illustrated in FIG. 8 once the printed circuit has been bent to this configuration. 
     The metal conductors in the printed circuit  46  extend across the main section  180  and into the secondary sections  182 - 188 . At least some of the metal conductors in the printed circuit  46  are connected with metal terminal rings  192  (FIG.  8 ). The terminal rings  192  telescopically receive and are connected with metal terminals  68  (FIGS. 3,  5  and  7 ). There are four metal terminal rings  192  which engage metal terminals  68  disposed at the four corners of the base  52  (FIG.  5 ). 
     In addition to the four corner terminals  68 , there are two additional terminals. These terminals extend through openings  194  (FIG. 8) in the printed circuit  46  without making electrical contact with conductors in the printed circuit. Thus, the terminals  68  which extend through the openings  194  are free of electrically conductive connections with conductors in the printed circuit  46 . The terminals  68  which extend through the openings  194  in the printed circuit  46  are electrically connected with the solid state light sources  42  by the rigid printed circuit board forming the light source board  44  (FIGS.  4  and  5 ). There are two additional openings  196  (FIG. 8) through which terminals associated with a push button assembly having a construction which differs from the construction of the push button assembly  40 , may extend. 
     Electrical circuit components  48  are mounted on the secondary sections  182 - 188  of the printed circuit  46 . In addition, electrical circuit components  48  are mounted on the main section  180  of the printed circuit  46 . The location and construction of the electrical circuit components  48  may vary depending upon the environment in which the push button assembly  40  is used. 
     In the specific embodiment of the push button assembly illustrated in FIGS. 1-8, the electrical circuit components  48  include power resistors  202 . The power resistors  202  are mounted on outwardly facing side surfaces of the secondary sections  182 - 188  of the printed circuit  46 . The outwardly facing side surfaces on the secondary sections  182 - 188  of the printed circuit  46  are formed as a continuation of a flat upper side surface  206  on the main section  180  of the printed circuit  46 . The upper side surface  206  on the printed circuit  46  extends perpendicular to the secondary sections  182 - 188  of the printed circuit. 
     In addition to the power resistors, the electrical circuit components  48  include a plurality of zener diodes  210  which are mounted on a flat lower side surface  212  of the main section  180  of the printed circuit  46 . Although only two zener diodes  210  are clearly visible in FIG. 8, it should be understood that there are four zener diodes disposed beneath the main section  180  of the printed section  46 . The zener diodes are positioned beneath the main section  180  of the printed circuit  46  and between the secondary sections  182 - 18  of the printed circuit. 
     Although the illustrated electrical circuit components  48  include power resistors  202  and zener diodes  210 , other known electrical circuit components may be utilized. These known electrical circuit components may be used in place of the power resistors  202  and zener diodes  210  or may be used in addition to the power resistors and zener diodes. It is contemplated that the electrical circuit components may be arranged on the printed circuit  46  in a manner which is different than the manner illustrated in FIG.  8 . 
     A plurality of rigid metal conductors  216  are disposed in a central portion of the printed circuit  46  (FIG.  8 ). The conductors  216  extend perpendicular to the upper side surface  206  of the main section  180  of the printed circuit  46  and are connected with the light source board  44  (FIGS. 4 and  5 ). A spacer  218 , formed of an electrically insulating material, extends around the conductors  216 . The spacer  218  maintains a desired space between the light source board  44  (FIGS. 4 and 5) and the printed circuit  46 . 
     The printed circuit  46 , with the electrical circuit components  48  mounted thereon, is positioned in the recess  50  (FIG. 7) in the base  52 . When the printed circuit  46  is positioned in the recess  50  in the base  52 , the power resistors  202  are positioned in flat abutting engagement with the panels  116  and  118  on the first section  112  of the heat sink  110  and in flat abutting engagement with the panels  150  and  152  on the second section  114  of the heat sink  110  (FIG.  6 ). 
     The base  52  includes an inner wall  222  (FIG. 7) which extends parallel to and is spaced from the side wall  60  of the base. The inner wall  222  intersects and extends perpendicular to the inner wall  126  in the base. The inner wall  222  engages the secondary sections  182  and  188  (FIG. 8) of the printed circuit  46  to position the power resistors  202  mounted on these secondary sections in flat abutting engagement with the panels  116  and  118  on the first section  112  of the heat sink  110 . In addition, the inner wall  222  engages the zener diodes  210  which are adjacent to the secondary sections  182  and  188  of the printed circuit to position these zener diodes in the recess  50 . 
     Although only the inner wall  222  is illustrated in FIG. 7, it should be understood that there is a corresponding inner wall adjacent to the side wall  56  of the base  52 . The inner wall adjacent to the side wall  56  of the base extends parallel to the inner wall  222  and to the side wall  56 . The inner wall which extends adjacent to the side wall  56  of the base engages the secondary sections  184  and  186  of the printed circuit  46  to position the power resistors  222  mounted thereon in flat abutting engagement with the panels  150  and  152  of the second section  114  of the heat sink  110 . 
     In addition to the inner walls  126  and  222 , the base  52  include a ledge  224  (FIGS. 6 and 7) which extends around the inside of the recess  50 . The ledge  224  engages the light source board  44  (FIGS. 4 and 5) to support the light source board above the bottom wall  62  of the base  52 . The light source board  44  is supported in a parallel spaced apart relationship with the main section  180  (FIG. 8) of the printed circuit  46  by the ledge  224 . 
     The flat abutting engagement of the power resistors  202  with the panels  116 ,  118 ,  150  and  152  on the sections  112  and  114  of the heat sink  110  promotes heat transfer from the power resistors to the heat sink. Heat is transferred from the zener diodes  210  to the power resistors  202  through metal conductors (not shown) in the printed circuit  46 . These metal conductors perform the dual function of conducting electrical energy between the zener diodes  210  and the power resistors  202  and of conducting heat from the zener diodes to the power resistors  202 . This heat from the zener diodes  210  is transferred from the power resistors  202  to the heat sink  210 . 
     Housing 
     In accordance with one of the features of the present invention, heat is conducted from the heat sink  110  to the metal housing  84  (FIGS.  2 - 5 ). The side wall  85  (FIG. 4) on the metal housing  84  engages the projections  132  and  134  (FIG. 6) on the first section  112  of the heat sink  110 . Similarly, the side wall  87  (FIG. 4) on the metal housing  84  engages the projections  160  and  162  (FIG. 6) on the second section  114  of the heat sink  110 . 
     Engagement of the metal heat sink projections  132 ,  134 ,  160  and  162  (FIG. 6) with the metal housing  84  (FIG. 4) results in heat being transmitted from the heat sink to the metal housing. The housing  84  is exposed to the environment around the push button switch assembly  20 . Therefore, heat is transferred from the housing  84  to the environment and the housing is relatively cool. Of course, the metal housing  84  is substantially larger than the metal heat sink  110  and can absorb a greater amount of heat. 
     The heat sink projections  132 ,  134 ,  160  and  162  (FIG. 6) have downwardly (as viewed in FIG. 6) extending flanges  232 . The flanges  232  extend generally parallel to the panels  116 ,  118 ,  150  and  152  on the sections  112  and  114  of the heat sink  110 . However, the flanges  232  flare slightly outward away from the panels  116 ,  118 ,  150  and  152  on the sections  112  and  114  of the heat sink  110 . This results in the flanges  232  being resiliently deflected inward toward the side walls  56  and  60  (FIGS. 6 and 7) of the base  52  by the housing side walls  85  and  87  as the housing  84  is telescopically moved downward (as viewed in FIG. 5) around the side walls  54 ,  56 ,  58 , and  60  on the base  52 . 
     The resilient deflection of the flanges  232  results in the flanges being firmly pressed against inner side surfaces on of the housing side walls  85  and  87 . The pressure applied by the flanges  232  against the inner side surfaces of the housing side walls  85  and  87  ensures that there is solid engagement between the sections  112  and  114  of the heat sink  110  and the metal housing  84 . This enables heat to be readily conducted from the sections  112  and  114  of the heat sink  110  to the metal housing  84 . If desired, the sections  112  and  114  of the heat sink  110  may be sized so that there is an interference fit between the inner side surfaces of the housing side walls  85  and  87  and the flanges  232  on the projections  132 ,  134 ,  160 , and  162 . If this is done, the flanges  232  may extend perfectly parallel to the panels  116 ,  118 ,  150  and  152  of the sections  112  and  114  of the heat sink  110 . This is because the interference fit would result in solid engagement of the metal flanges  232  with the metal housing  84 . 
     In the embodiment of the push button  40  illustrated in FIGS. 1-8, the sections  112  and  114  of the heat sink are initially separate from the base  52 . However, it is contemplated that the base  52  may be molded around the projections  132 ,  134 ,  160  and  162  (FIG. 6) from the sections  112  and  114  of the heat sink. If this is done, the outer side surfaces on the flanges  232  would be exposed for engagement with the metal housing  84 . Similarly, the inner side surfaces of the panels  116 ,  118 ,  150  and  152  would be exposed for engagement with the power resistors  202 . Molding the base  52  around the projections  132 ,  134 ,  160  and  162  would allow the flanges  232  to be extended in any desired direction to increase the extent of engagement of the flanges  232  with the metal housing  84 . 
     During operation of an apparatus with which the push button switch assembly  20  is associated, such as an aircraft or other vehicle, the power resistors  202  emit heat. This heat is conducted directly to the panels  116 ,  118 ,  150  and  152  (FIG. 6) on the sections  112  and  114  of the heat sink  110 . In addition, the zener diodes  210  (FIG. 8) emit heat. 
     Heat from the zener diodes  210  is conducted through the metal conductors disposed in the printed circuit  46  to the power resistors  202 . The heat from the zener diodes is transmitted from the power resistors  202  to the panels  116 ,  118 ,  150  and  152  of the sections  112  and  114  of the heat sink  110  along with the heat emitted by the power resistors themselves. Thus, heat from both the zener diodes  210  and the power resistors  202  is transmitted to the heat sink  110 . 
     The heat is transmitted from the projections  132 ,  134 ,  160  and  162  on the sections  112  and  114  of the heat sink  110  to the metal housing  84 . The metal housing  84  has a relatively large, exterior surface exposed to the environment around the push button assembly  20  to enable heat transmitted to the housing to be dissipated. In addition, the housing  84  may absorb heat without becoming excessively hot. 
     It is contemplated that it may be desired to increase the area of contact of the heat sink  110  with the metal housing  84 . This may be done by providing the heat sink  110  with additional sections, similar to the sections  112  and  114 . These additional heat sink sections may be positioned in engagement with the zener diodes  210  and extend through openings, in the side walls  54  and  58  of the base  52 . These additional openings in the side walls  54  and  58  would correspond to the openings  140 ,  142 ,  166 , and  168  in the side walls  60  and  56  of the base  52 . 
     It is also contemplated that the area of engagement between the heat sink  110  and the housing  84  may be increased by providing a metal band around the outside of the base  52 . The metal band may extend completely around the base  52  and may be engaged by the projections  132 ,  134 ,  160  and  162  on the sections  112  and  114  of the heat sink  110 . Alternatively, projections may extend inward from the metal band around the outside of the base into engagement with the sections  112  and  114  of the heat sink  110 . 
     If desired, the metal band which extends around the outside of the base  52  may be connected with a metal band on the inside of the base by a plurality of metal pins which extend through the side walls  54 - 60  of the base  52 . Rather than being connected between metal bands on the inside and/or outside of the base  52 , the metal pins may have head end portions which engage the heat sink  110  and the housing  84 . 
     Light Sources 
     The solid state light sources  42  are mounted on a light source board  44 . The light source board  44  is a rigid printed circuit board which is connected with the conductors  216  (FIG.  8 ). If desired, electrical circuit components  236  (FIG. 5) may be mounted on the lower side of the light board  44 . 
     A heat sink may be positioned adjacent to the electrical circuit components  236 . If a heat sink is positioned adjacent to the electrical circuit components  236 , it may have the same general construction as the heat sink  110  of FIG.  6 . The heat sink associated with the electrical circuit components  236  may extend through openings in the side walls  56  and  60  of the base in the same manner as does the heat sink  110 . Since the light source board  44  is disposed above the printed circuit  46 , the heat sink for the electrical circuit components  236  disposed beneath the light source board  44  would be disposed above the heat sink  110 . Alternatively, the heat sink associated with the electrical circuit components  236  may extend through openings in the side walls  54  and  58 . 
     Rather than providing a separate heat sink for the electrical circuit components  236 , it is contemplated that the panels  116 ,  118 ,  150 , and  152  on the sections  112  and  114  of the heat sink  110  may be extended upward to a location adjacent to the electrical circuit components  236 . If this is done, additional projections, corresponding to the projections  132 ,  134 ,  160  and  162  may be provided in association with a portion of the heat sink adjacent to the electrical circuit components  236 . It should be understood that the electrical circuit components  236  may be omitted from some embodiments of the push button assembly  40 . 
     The solid state light sources  42  are light emitting diodes (LED). However, other known solid state sources of light may be utilized if desired. The light sources  42  are arranged in groups on the light source board  44 . The divider  76  separates the groups of light sources from each other and directs the light from any one group of light sources  42  toward an associated portion of the display  72 . Therefore, only a portion of the display  72  may be illuminated. This would result in indicia on the illuminated portion of the display  72  being visible to personnel adjacent to the push button switch assembly  20 . Indicia on portions of the display  72  which are not illuminated would not be visible. 
     Second Embodiment 
     In the embodiment of the push button assembly illustrated in FIGS. 2-8, the heat sink  110  is formed by two separate sections  112  and  114 . In the embodiment of the invention illustrated in FIGS. 9-11, the heat sink is formed as one piece. Since the embodiment of the invention illustrated in FIGS. 9-11 is generally similar to the embodiment of the invention illustrated in FIGS. 1-8, similar numerals will be utilized to designate similar components, the suffix letter “a” being associated with the numerals of FIGS. 9-11 to avoid confusion. 
     A push button assembly  40   a  (FIG. 9) includes a base  52   a  which is formed of a suitable electrically insulating polymeric material. A rigid printed circuit  46   a  is received in a generally rectangular recess  50   a  formed a base  52   a . Metal terminals  68   a  extend through a bottom wall  62   a  of the base  52   a  into the recess  50   a  and engage the printed circuit  46   a . Electrical circuit components  48   a  (FIGS. 9-11) are disposed on the printed circuit  46   a.    
     Electrical circuit components  48   a  include power resistors  202   a  which are disposed on the upper (as viewed in FIGS. 10 and 11) side of the rigid printed circuit  46   a . In addition, the electrical circuit components  48   a  include zener diodes  210   a  (FIG. 11) which are disposed on the lower side of the printed circuit  46   a.    
     The printed circuit  46   a  includes a plurality of terminal rings  192   a  which telescopically receive terminal  68   a  and are electrically connected with conductors in the printed circuit  46   a . In addition, openings  194   a  extend through the printed circuit  46   a  and are not connected with conductors contained in the printed circuit. The printed circuit  46   a  is a rigid board which is not flexible. 
     The electrical circuit components  48   a  emit heat. This heat is transmitted to a heat sink  110   a  (FIG.  10 ). The heat sink  110   a  is formed of a single piece of sheet metal. The metal heat sink  110   a  is electrically insulated from the power resistors  202   a  by a layer  250  of electrically insulating and thermally conductive foam. 
     The metal heat sink  110   a  includes a flat main panel  256 . A pair of end panels  258  and  260  extend perpendicular to the main panel  256  and parallel to each other. Projections  262  and  264  extend from the end panel  258 . Similarly, projections  266  and  268  extend from the end panel  260 . The projections  262 - 268  extend through openings, similar to the openings  272 , in side walls  56   a  and  60   a  in the base  52   a  (FIG.  9 ). The main panel  256 , end panels  258  and  260 , and the projections  262 - 268  are integrally formed as one piece of metal. 
     The projections  262 - 268  have flanges  232   a  (FIGS.  10  and  11 ). The flanges  232   a  extend along the outside of the side walls  60   a  and  62   a  of the base  52   a . The projections  262 - 268  are engagable by a metal housing  84   a  (FIG.  9 ). The metal projections  262 - 268  engage inner side surfaces of metal side walls  85   a  and  87   a  of the housing  84   a.    
     Heat emitted by electrical circuit components  48   a  is conducted from the main panel  256  of the heat sink  110   a  to the projections  262 - 268 . The flanges  232   a  on the projections  262 - 268  are engaged by the metal housing  84   a . The heat is transmitted from the metal housing  84   a  to the environment around the push button assembly  40   a.    
     Conductors  216   a  extend from the printed circuit  46   a  through the layer  250  of electrically insulating and thermally conductive foam and through the heat sink  110   a  to a light source board  44   a . A spacer  218   a  (FIG. 10) is provided to separate the rigid light source board  44   a  (FIG. 9) from the heat sink  110   a . The spacer  218   a  is formed of an electrically insulating material. 
     Solid state light sources  42   a  (FIG. 9) are disposed on the light source board  44   a . The solid state light sources  42   a  are light emitting diodes (LED). However, it is contemplated that other types of solid state light sources may be utilized if desired. 
     A divider  76   a  is provided between the light source printed circuit board  44   a  and a display  72   a . A gasket  80   a  prevents light from leaking between the divider  76   a  and the display  72   a . The metal housing  84   a  encloses the display  72   a  and telescopically receives the upper end portion of the base  52   a.    
     The zener diodes  210   a  (FIG. 11) are disposed beneath the rigid board forming the printed circuit  46   a . It may be desired to provide a separate heat sink adjacent to the lower side of the printed circuit  46 . The heat sink provided adjacent to the lower side of the printed circuit may be constructed in two separate sections, similar to the sections  112  and  114  of the heat sink  110  (FIG.  6 ). Although it may be preferred to provide the sections of the heat sink adjacent to the lower side of the printed circuit with projections which extend through side walls of the base  52   a  (FIG.  9 ), these projections may be omitted if desired. Alternatively, the sections of the heat sink adjacent to the lower side of the printed circuit  46   a  may be connected with the heat sink  110   a.    
     CONCLUSION 
     In view of the foregoing description, it is apparent that the present invention provides a new and improved push button assembly  40  which is used to move switch contacts  30  between an actuated condition and an unactuated condition. The push button assembly  40  includes a plurality of solid state light sources  42  which are energizable to emit light. A display  72  is illuminated by light from the solid state light sources  42  when the solid state light sources are energized. 
     A metal heat sink  110  is disposed adjacent to electrical circuit components  48  which emit heat. To conduct heat away from the heat sink  110 , the metal heat sink may be disposed in engagement with a metal housing  84 . The heat sink  110  may be formed by a single member or by a plurality of members. The members  112  and  114  forming the heat sink  110  may advantageously have projections  132 ,  134 ,  160  and  162  which extend through side walls  56  and  60  of a base  52 . The projections  132 ,  134 ,  160  and  162  are engagable by the metal housing  48  to facilitate the conduction of heat between the heat sink  110  and the housing.