Low profile lighted push button switch
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to lighted push button switches, and more particularly to a low profile, lighted push button switch assembly. 
     2. Description of the Prior Art 
     There is need for a low profile, i.e., thin, lighted push button switch, and there is a further need that the switch itself be sealed against the entrance of dust and other contaminates. It is further desirable that there be a light source associated with each push button of a group of push buttons, and that each light source be separately addressible, i.e., illuminated in response to actuation of the respective push button or some other push button, illuminated in response to the occurrence of some external event or condition, or illuminated at all times. 
     U.S. Pat. No. 3,766,350 discloses a low profile, lighted push button switch assembly wherein light emitting diodes are carried by the push button itself thus necessitating the use of flexible conductors for energizing the light emitting diodes. Other types of lighted push button switches have been proposed; however, to the best of the present applicant&#39;s knowledge and belief, such other lighted push button switches do not have a low profile configuration nor do they employ sealed contacts. Low profile lighted push button switch assemblies have been provided employing edge lighting of the push buttons; however, each push button does not have a separately addressable light source associated therewith. 
     SUMMARY OF THE INVENTION 
     In its broader aspects, the invention provides a low profile, lighted push button type switch assembly comprising a first insulative member having flat opposite surfaces with a recess formed in one surface. A switch including a resilient element is positioned in the recess, the element being actuatable between first and second positions in response to force exerted thereon. A relatively thin sheet of flexible insulating material engages the one surface of the first member covering the recess and switch element. A second insulative member is provided having flat opposite surfaces with one surface engaging the thin sheet, the sheet being sandwiched between the first and second insulative members. The second member has at least one opening therethrough communicating with the sheet and in alignment with a part of the recess in the first insulative member. Light source means are provided on the other surface of the second member for providing illumination in response to electrical energization. A push button member is provided having at least a first portion thereof formed of light-transmissive material, the first portion being disposed adjacent the other surface of the second member in light-receiving relation with the light source means. The push button member includes a second portion extending through the second member opening for movement therein, the second push button portion including means aligned with the recess in the first insulative member for engaging the sheet in response to depression of the push button member thereby to apply force on the switch element for actuating the same between said positions thereof. 
     It is accordingly an object of the invention to provide an improved, low profile, lighted push button switch. 
     Another object of the invention is to provide an improved, low profile, lighted switch wherein the switch element is sealed against contamination. 
     A further object of the invention is to provide an improved, lighted, push button switch wherein a light source is associated with the push button and is separately addressable without the use of flexible conductors. 
     The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side cross-sectional view illustrating the improved, lighted push button switch of the invention; 
     FIG. 2 is a bottom view of the push button of FIG. 1; 
     FIG. 3 is a bottom view of the switch actuating member of FIG. 1; 
     FIG. 4 is a fragmentary, exploded, perspective view illustrating the switch assembly of FIG. 1; and 
     FIG. 5 is a schematic illustration of one connection of the light source and switch element shown in FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIGS. 1 through 4 of the drawings, the improved, low profile, lighted push button switch assembly of the invention, generally indicated at 10, comprises a printed wiring board 12 having opposite flat surfaces. Conductors 18 and switch contacts 20 are printed or otherwise deposited in conventional fashion on surface 14 of board 12. 
     An insulative member 22, having opposite flat surfaces 24, 26 is positioned with its surface 26 engaging surface 14 of board 12. Insulative member 22 has opening 28 formed therein which exposes switch contacts 20 on surface 14 of board 12. Resilient switch element 30, which may be of the type shown and described in U.S. Pat. No. 3,796,843, is positioned in opening 28 cooperating with switch contacts 20 and is actuable between first and second positions in response to the application of force thereon. 
     It will readily be understood that board 12 and insulative member 22 may be formed as single member with opening 28 formed as a recess therein and with the conductors connected to the switch contacts 20 extending through the resulting unitary member. 
     Thin sheet 32 of insulating material is adhered to surface 24 of insulative member 22 covering opening 28 and switch element 30 therein thereby sealing switch element 30 against dust and other contaminates. 
     Insulative member 34 has opposite flat surfaces 36, 38 with surface 36 engaging sheet 32. Member 34 has opening 40 therein in alignment with opening 28 in member 22. Switch actuating member 42 is positioned in opening 40 and has a center projection 44 engaging sheet 32. 
     A second printed wiring board 46 has opposite flat surfaces 48, 50 with surface 50 engaging surface 38 of insulative member 34. Board 46 extends across opening 40 in member 34 and has a plurality of openings 52 communicating therewith. Light source 54, such as a light emitting diode (LED) or incandescent lamp, is mounted on surface 48 of board 46 and is adapted to be energized by conductors 56 printed or otherwise deposited on surface 48 of board 46. It will readily be seen that insulative member 34 and board 46 may be formed as a single member with opening 40 formed as a recess therein. 
     Insulative member 58 has flat opposite surfaces 60, 62 with surface 62 engaging surface 48 of board 46 and covering conductors 56 thereon. Member 60 has opening 64 therein having peripheral lip 66, opening 64 being aligned with openings 28 and 40. 
     Push button 68 formed of light transmissive material is positioned in opening 64 in member 58 and has peripheral flange 70 which cooperates with lip 66 to retain push button 68 in opening 64. Push button 68 has recess 72 formed therein into which light source 54 extends. Push button 68 has a plurality of post elements 74 respectively extending through openings 52 in board 46 and engaging actuating member 42. It will now be readily seen that manual depression of push button 68 results in downward movement of actuating member 42 so that projection 44 thereon engages sheet 32 and causes it, in turn, to apply force on switch element 30 to actuate the same from one to its other position. It will readily understood that when the depressive force is removed from push button 68, switch element 30 will resiliently return to its normal position thus urging actuating member 42 and push button 68 to their normal positions, as shown in FIG. 1. 
     Board 12, insulative member 22, insulative sheet 32, insulative member 24, board 46, and insulative member 58 are clamped in assembled relation by suitable threaded fastener 74. 
     Referring now to FIG. 5, it will be seen that conductors 56 associated with a particular light source 54 may be connected to conductors 18 for switch 30 of the same switch assembly 10 so that light source 54 is illuminated by battery 76 in response to closing of switch 30. It will also readily be seen that each light source 54 associated with a particular push button 68 is separately addressable by its conductors 56 and thus may be illuminated in response to actuation of a switch element 30 associated with a different push button assembly, or may be illuminated by external circuitry, such as computer circuitry to indicate to the operator which push button is to be actuated next in a series of complex instructions. As another alternative, all of the light sources 54 of a group of push buttons comprising a keyboard may be illuminated simultaneously. It will further be readily seen that each push button 68 may have two or even more light sources associated therewith. 
     It will now be seen that the lighted push button assembly of the invention permits a very low profile which is useful in applications where volume is at a premium such as in aircraft cockpits and citizen band radios; in a physical embodiment of the invention, the entire thickness of switch assembly 10 is only 0.4 inches. It will further be seen that the assembly is simple and relatively inexpensive to fabricate, and that the lighted push buttons can be closely grouped together; in the aforesaid physical embodiment of the invention, the push buttons are spaced on 0.5 inch centers. It will be understood that legends may be provided on the push buttons in any of several conventional ways such as etching, printing, etc. It will be further seen that the LEDs or lamps illuminating the push buttons are rigidly mounted on board 46 without the use of flexible conductors thus providing longer life. 
     While there have been described above the principles of this invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of the invention.