Vandal-resistant telephone keypad switch

A shielded push-button switch assembly comprising:

• a pressure-actuated switch matrix containing a base plate and multi-layer electrically-conductive, pressure-activated switch points formed on said base plate;
• said switch points being arrayed in regular rows and columns;
• a continuous flexible membrane having a lip formed at the periphery thereof and having formed thereon at each of the switch points, a relatively thick protruding button-like portion whereby the lip of the membrane seals the layers of the switch while allowing switch points to be depressed via said protruding portions;
• a rigid shield plate formed with an array of throughgoing apertures aligned with and generally identical to the locations of the relatively thick protruding button-like portions of said membrane and a lip portion;
• the projecting portions of the membrane projecting forward through the apertures of the shield plate past the front face thereof and the lip portion of the plate coacting with the lip of said membrane;
• means for securing the shield plate, the membrane, and the switch with the apertures of the shield plate aligned with the projecting portions of the membrane and the switch points of the switch;
• and
• respective rigid caps fitted over the thickened portions, projecting forward through the shield plate apertures, said relatively thick portions being mounted on said membrane via frusto-conical surfaces formed on said membrane whereby the force exerted by said frusto-conical surface urges said relatively thick portions away from said swich points.

A pressure-actuated switch comprising:

• a first thin, flat base layer having electrically-conductive paths formed formed thereon, said paths including points for electrical contact;
• an intermediate layer having a plurality of apertures therein, said apertures overlying said points of electrical contact;
• a third layer having electrically-conductive paths including a switch points formed thereon, said switch points overlying said apertures in said intermediate layer and said switch points in said base layer, said third layer further including a ribbon cable portion thereof formed integrally therewith, said ribbon cable portion including electrically-conductive paths formed thereon;
• an electrical connector coupled to said ribbon cable and joining with said electrically-conductive paths thereon;
• said switch generating an electrical signal on contact of the switch points in said base layer and said third layer;
• and
• membrane means for sealing said base layer, said intermediate layer and said top layer, said membrane including means to urge said switch points into contact, said urging means including:
• a plurality of thickened portions overlying respective ones of said switch points;
• said thickened portions being spaced from said switch points and from the surface of said membrane via frustro-conical supports;
• each of said frusto-conical supports creating a frusto-conical volume beneath said support;
• and, a plurality of air release channels connected between said supports so as to reduce the pressure of air beneath said supports;
• a rigid shield connected to said switch and enclosing said membrane sealing means apertures on said intermediate layer;
• the thickened portion projecting forward through the apertures of the shield plate past the front face thereof;
• push-button means consisting of a plurality of caps interfitting over said thickened portions;
• the force required to depress said thickened portions being controlled by said frusto-conical supports whereby an initial higher force and subsequent lesser force is required.

A switch assembly comprising:

• a pressure-actuated switch including a rigid base plate having a front face;
• a first flexible layer adhesively secured to said rigid base plate formed with an array of electrically-conductive paths thereon;
• an intermediate layer formed on said last-mentioned layer having a plurality of apertures formed therethrough overlying portions of said electrically-conductive paths;
• a flexible top layer formed on said intermediate layer having electrically-conductive paths thereon, portions of said paths overlying said apertures in said intermediate layer;
• a continuous flexible membrane overlying said top layer including a lip portion overlying and sealing said switch, and formed at each of said last-named oerlying portions with a relatively thick projecting portion in front of the respective top layer overlying portion whereby the membrane seals the rigid base and said flexible layers while allowing said electrically-conductive paths in said top layer and said first flexible layer to contact each other;
• said relatively thick portions being formed on said flexible membrane via a frusto-conical support for each member, the frusto-conical support urging said overlying thick portions away from said pressure-actuated switch;
• a rigid shiled plate formed with an array of through-going apertures aligned with those of said intermediate layer, a rear face confronting said membrane, and a side portion overfitting said lip portion, the thick projecting portions of said membrane projecting forward through the apertures of the shield plate past the front face thereof;
• means for securing the shield plate in front of the membrane with the apertures aligned;
• and respective rigid caps fitted over the thickened portions, projecting forward through the shield-plate apertures.

A shielded push-button switch assembly comprising:

• a continuous flexible membrane having a plurality of relatively thick protruding button-like portions formed thereon, said thick portions supported on said membrane via frusto-conical support portions coupling said thick portions to said membrane;
• a rigid shield plate formed with an array of throughgoing apertures aligned with said relatively thick portions, said portions of the membrane projecting forward through the apertures of the shield plate past the front face thereof;
• respective rigid caps fitted over the projecting portions of said membrane;
• a pressure-actuated switch having contact points located beneath said frusto-conical support portions;
• said switch being supported and sealed by said membrane;
• said pressure-actuated switch including a solid support layer;
• a base layer of flexible material formed on said support layer, said base layer having electrically-conductive portions formed thereon;
• an intermediate spacing layer formed on said base layer, said spacing layer having apertures therein overlying a portion of said electrically-conductive portions of said base layer, said apertures being aligned with the thickened portions of said membrane;
• a top layer of flexible material hacing electrically-conductive portions thereon, said electrically-conductive portions overlying said intermediate layer and said apertures;
• and
• said membrane and said shield plate enclosing and sealing said switch.

A switch assembly comprising,

• a pressure actuated actuated switch including a solid support layer;
• a base layer of flexible material formed on said support layer, said base layer having electrically-conductive portions formed thereon;
• an intermediate spacing layer formed on said base layer, said spacing layer having apertures therein overlying a portion of said electrically-conductive portions of said base layer, said apertures being aligned with the thickened portions of ssaid membrane;
• a top layer of flexible material having electrically-conductive portions thereon, said electrically-conductive portions overlying said intermediate layer and said apertures;
• a continuous flexible membrane overlying said switch and formed ast each of the apertures with a relatively thick projecting portion in front of the respective apertures whereby the membrane seals the layers while allowing same to be depressed via the thick portions;
• and
• means urging the overlying portions forward from the front face;
• a shield assembly comprising:
• a rigid shield plate formed with an array of through-going apertures aligned with and generally identical to those of said intermediate layer and having a rear face confronting the front face of said membrane, the thick projecting portions of the membrane projecting forward through the apertures of the shield plate past the front face thereof;
• means for securing the shield plate in front of the membrane with the apertures aligned;
• and
• respective rigid caps fitted over the thickened portions, projecting forward through the shield-plate apertures, and each having an outwardly projecting flange extending generally parallel to and lying between the plates and of greater size than the respective shield-plate aperture, the means urging the respective flanges forward against the rear face of the shield plate.