# US 8,541,707 B2 · Keypad with long key travel and improved touch feeling > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,541,707 B2 - Document ID: US8541707B2 - Status: Granted - Kind: B2 - Application number: 13/126,425 - Filed: 2009-09-23 - Published: 2011-09-08 - Granted: 2013-09-24 - Earliest claimed: 2008-10-28 - Assignees: Thales - Applicants: Jean-Louis Bigand - Inventors: Jean-Louis Bigand - Web page: https://patentgrep.com/patent/US8541707B2 ## CPC - H01H 13/702: with contacts carried by or formed from layers in a multilayer structure, e.g. membrane switches - H01H 13/84: characterised by ergonomic functions, e.g. for miniature keyboards; characterised by operational sensory functions, e.g. sound feedback (legends H01H13/83) - H01H 13/85: characterised by tactile feedback features - H01H 2215/002: Longer travel - H01H 2215/004: Collapsible dome or bubble - H01H 2221/044: Elastic part on actuator or casing - H01H: ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES (contact cables H01B7/10; electrolytic self-interrupters H01G9/18; emergency protective circuit arrangements H02H; switching by electronic means without contact-making H03K17/00) ## Abstract A keypad includes at least one push-button switch and a key to operate the switch along a translational axis. The geometric dispersions of the keypad are accounted for, to the lengthening of the travel of the key and to the enhancement of the tactile sensation when the key is pressed to operate the switch. The keypad includes a plunger, interposed between the key and the switch, of which a stiffness along the translational axis increases continuously with an increase in the compression of the plunger. A slight stiffness at the beginning of compression allows a long travel of the key, while a greater stiffness at the end of compression gives a good tactile sensation with an assured contact even when there are off-center pressures on the key. ## Claims ### Claim 1 A keypad comprising: a push-button switch; a key for operating the push-button switch along a translational axis; and a plunger interposed between the key and the push-button switch, wherein a stiffness of the plunger along the translational axis increases with a travel of the key along the translational axis before the push-button switch is actuated, the plunger being in contact with the switch, wherein the plunger comprises a recess, a portion of the plunger comprising the recess defining an upper portion of the plunger which has a first stiffness, and a remaining portion of the plunger defining a lower portion of the plunger which has a second stiffness, the second stiffness being greater than the first stiffness, wherein the lower portion of the plunger is interposed between the upper portion of the plunger and the push-button switch, wherein at the beginning of the travel of the key toward the push-button switch, the plunger is essentially deformed at the upper portion of the plunger, the upper portion of the plunger being fitted onto a lug of the key, the lug being distant from a bottom of the recess along the translational axis at the beginning of the travel of the key toward the push-button switch, the bottom of the recess separating the upper portion of the plunger and the lower portion of the plunger, the recess being opened toward the key and closed toward the push-button switch by the bottom of the recess, and wherein beyond a point of travel for which the lug comes into contact with the bottom of the recess, the plunger is essentially deformed at the lower portion of the plunger, the stiffness of the plunger therefore increasing continuously in line with the first stiffness and then the second stiffness before the switch is actuated. ### Claim 2 (depends on 1) The keypad of claim 1, wherein the first stiffness and second stiffness are substantially constant. ### Claim 3 (depends on 2) The keypad of claim 2, further comprising: means for ensuring a progressive transition between the first stiffness and the second stiffness during the travel of the key. ### Claim 4 (depends on 1) The keypad of claim 1, wherein the plunger is made of a single piece of uniform material. ### Claim 5 (depends on 1) The keypad of claim 1, wherein the plunger is made of an elastomeric material. ### Claim 6 (depends on 1) The keypad of claim 1, wherein the plunger is cylindrical. ### Claim 7 (depends on 1) The keypad of claim 1, wherein the recess is cylindrical. ### Claim 8 (depends on 1) The keypad of claim 1, wherein the lug has a shape to match a shape of an upper portion of the recess, the lug being inserted into said upper portion of the recess. ### Claim 9 (depends on 1) The keypad of claim 1, wherein the lug or the bottom of the recess has a shape ensuring a progressive increase of a contact surface between the key and the bottom of the recess, the lug or the bottom of the recess forming the means for ensuring a progressive transition between the first stiffness and the second stiffness during the travel of the key. ### Claim 10 (depends on 1) The keypad of claim 1, further comprising: a front face secured to the push-button switch and comprising an opening traversed by the key; and means for limiting a travel of the key on the side opposite to the push-button switch, the plunger being prestressed between the key and the push-button switch. ### Claim 11 (depends on 10) The keypad of claim 10, wherein the means for limiting the travel of the key comprises: a shoulder on the key, and a counterbore made on the front face. ### Claim 12 (depends on 1) The keypad of claim 1, wherein a hardness of the material of the plunger is between 60 and 80 Shore A. ### Claim 13 (depends on 1) The keypad of claim 1, wherein the plunger is in contact with the switch during an entire travel of the key along the translational axis. ### Claim 14 (depends on 1) The keypad of claim 1, wherein the lower portion of the plunger is solid. ### Claim 15 (depends on 1) The keypad of claim 1, wherein the upper portion of the plunger includes a tubular portion delimiting the recess. ### Claim 16 (depends on 1) The keypad of claim 1, wherein the bottom of the recess is flat. ### Claim 17 (depends on 1) The keypad of claim 1, wherein the bottom of the recess has a convex shape. ### Claim 18 (depends on 1) The keypad of claim 1, wherein the lug has a convex shape that comes into contact with the bottom of the recess at a point of travel of the key for which the lug comes into contact with the bottom of the recess. ### Claim 19 (depends on 1) The keypad of claim 1, wherein the plunger is compressed during travel of the key before the lug comes into contact with the bottom of the recess and after the lug comes into contact with the bottom of the recess.