Abstract:
A unitarily molded seal membrane (310) includes an integral microphone support (304) which includes a diaphragm (306). A cavity wall (406) is located about said diaphragm (306) on one side of the seal membrane (310). The cavity wall (406) defines a cavity area (410) for receiving a microphone (504). The cavity wall aligns the diaphragm (306) in front of the microphone (504), thereby allowing for environmental sealing of the microphone (504).

Description:
TECHNICAL FIELD 
     This invention relates generally to seal membranes and more particularly to a seal membrane with integral microphone support. 
     BACKGROUND 
     In portable radio applications it is typically necessary to provide some form of water intrusion sealing for the internal microphone cartridge which is found within the radio housing. One prior art technique for sealing the microphone is shown in FIG. 1. This prior art technique uses a rubber boot 102 for retaining the microphone cartridge 104 to the radio housing 108. A separate water resistant layer of felt, GORETEX™, polyurethane membrane, or other water resistant material 106 is disposed between the rubber boot 102 and radio housing 108 and blocks microphone port 110, in order to protect the microphone cartridge 104 from water intrusion. Both the rubber boot 102 and water resistant layer 106 are attached to radio housing 108 using adhesives or other well known attachment techniques. A set of wires 112 interconnect the microphone cartridge to the radio electronics. 
     In FIG. 2, a second prior art technique for environmentally protecting the microphone cartridge 206 is shown. In this prior art technique, a rubber boot 208 which is pressure fitted to radio housing holds the microphone cartridge 206 in place. This method also requires that a felt or GORETEX™ layer 204 be attached to radio housing 202 between the microphone port and the microphone cartridge 206. Here again, a set of wires 210 interconnect the microphone cartridge to the rest of the radio electronics. 
     The prior art techniques for sealing an internal microphone as discussed above require a large number of parts and require a great amount of labor which increases the cost of producing a product having an internal microphone, such as a portable two-way radio. A need thus exists in the art for a seal which can provide environmental sealing to the internal microphone cartridge in a cost effective manner. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a first prior art drawing of a microphone sealing structure. 
     FIG. 2 shows a second prior art drawing of a microphone sealing structure. 
     FIG. 3 shows a front view of a keypad in accordance with the present invention. 
     FIG. 4 shows the back view of the keypad of FIG. 3. 
     FIG. 5 shows a partial cross-sectional view of a microphone assembly in accordance with the present invention. 
     FIG. 6 shows an electronic device using the integrated seal member of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings and in particular to FIG. 3, a unitarily molded seal or seal membrane 300 in accordance with the present invention is shown. In FIG. 3, the preferred embodiment of a unitary elastomeric keypad having an integral microphone support is shown. Seal 310 includes a set of individual keys 302 which are integrally molded as part of the main body of seal 310. Seal 310 is preferably formed from an elastomeric material such as silicone, polyurethane, rubber, or other similar materials. Integrally formed into seal 310 is a microphone section 304 which includes tapered side walls 308 which form cone shaped area for directing sound waves towards the integral microphone diaphragm 306. Diaphragm 306 is formed as thin as possible in order to provide environmental protection to the microphone cartridge which is mounted in back of microphone section 304 while at the same time minimizing the distortion effect on the incoming sound waves. In the preferred embodiment, the diaphragm area 306 is approximately 0.1016 millimeter (0.004 inch) thick, although the thickness of the diaphragm 306 will depend on the specific application being designed for. For example, in designs where some distortion of the incoming sound waves is permissible, a thicker diaphragm can be used, while in applications where good sound reproduction is a requirement, a thinner wall (such as in the preferred embodiment) would be best. The thinness of the wall will also depend on the material used, the ability of the manufacturing process used in controlling the wall thickness, size of overall seal being designed, etc. Given the small diameter of diaphragm 306, very little distortion is generated by the diaphragm 306 since it tends to flap very little when sound waves push against it. 
     In FIG. 4, the back side of the unitarily molded seal member 300 is shown. Each of the individual key members 302 include a conductive carbon area 402 which is disposed on the back side of each individual key 302. When a key 302 is depressed, the conductive area 402 activates a circuit in the electronic device the seal member is a part of. The back side of the microphone section includes a cavity area 410 defined by a microphone cavity wall or support wall 406 which accepts the microphone cartridge 504 (shown in FIG. 5). A set of support members 404 provide support for the microphone support wall 406 since the sides of the support wall 406 are separated from the main body of the seal member 310 by slots 408. The set of support members 404 are an integrally molded portion of unitarily molded seal member 300 and are located between the main body of the seal member 300 and support wall 406. Slots 408 allow for the microphone support wall to expand outward when a microphone cartridge is pressure fit into cavity area 410. The separated support wall 406 also provides isolation to the microphone cartridge from movement of the seal member 310 caused by activation of keys 302, etc. 
     Referring now to FIG. 5, a partial cross-sectional view of the microphone section of the present invention sandwiched between a radio housing 506 and an internal printed circuit board 502 is shown. The housing member 506 such as a radio housing includes an aperture or microphone port 508 for allowing sound waves to travel through the port. The seal 310 is shown carrying a microphone cartridge 504. Microphone cartridge 504 is preferably pressure fit into the cavity found in seal 310. The thin silicone diaphragm 306 is positioned in front of the microphone cartridge 504 and provides minimum distortion to sound waves entering the microphone cartridge while providing for environmental sealing of the microphone 504. The tapered side walls 308 form a cone shape which help to concentrate incoming sound waves towards diaphragm 306. A perimeter seal ledge 510 which is part of seal 310 is located about the cone shape area helps provide a good pressure fit against the housing member. When seal 310 is pressure fit against housing member 506, seal ledge 510 compresses and provides for a good environmental and acoustical seal around aperture 508. This helps prevent any moisture or dust from entering the electronics found inside of the housing. 
     In FIG. 6, an electronic device such as a remote microphone/keypad device 600 is shown. The remote keypad/microphone 600 is typically connected to a communication device such as a two-way radio via a cable assembly which is not shown. The remote keypad/microphone 600 allows for remote operation of the two-way radio as is typically required in a vehicular environment. The keypad/microphone device 600 includes the unitarily molded seal in this case an elastomeric keypad having an integral microphone support as shown in FIGS. 3 and 4. The elastomeric keypad seals the internal electronics from environmental intrusion such as water and dust, and also provides a seal for the microphone cartridge which is located inside of the remote microphone keypad housing. 
     In summary, the present invention provides for a unitarily molded seal membrane such as an elastomeric keypad 300 which includes an integral microphone support section. The invention also provides for a simple and cost effective way of environmentally and acoustically sealing and supporting a microphone cartridge 504. The integral microphone support includes a resilient cavity wall 406 which allows for pressure fitting of the microphone cartridge 504 within a cavity area 410. This provides for ease of assembly and overall cost reduction of the finished assembly. The microphone support section also preferably includes tapered walls 308 (forming a cone shaped front portion) in front of diaphragm 306 which help direct incoming sound waves towards microphone cartridge 504. Although the preferred embodiment has been shown as a elastomeric keypad, a unitarily molded seal having an integral microphone support section alone could be designed for those application where a keypad section is not required.