Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
372 words
A key actuated membrane switch comprising a key operated switch actuating member mounted on a displacement sensing means in the form of a sealed package, said package consisting of first and second insulative membranes respectively positioned on either side of a further membrane comprising an apertured spacing member, the switch actuating member being mounted on the first of said membranes and said first and second membranes each bearing a respective one of an opposed pair of coaxially disposed contacts associated with the switch actuating member, each contact consisting of a conductive film deposited on the internal surface of the respective membrane and comprising part of a normally open circuit which is closed when the said first membrane is flexed into a space normally between the membranes provided by a corresponding one of the apertures in the spacing member so as to contact the said second membrane, the said conductive films thereby touching and said switch actuating member applying pressure on said first membrane along the actuating axis of said contacts through the intermedium of an electrically isolated spring formed as a flat strip having a bend at an intermediate position along its length so as to define a lever having first and second elongate portions which are distinguished by the discontinuity of direction at the said bend, said spring having a free end and a supported end, said bend being aligned with the actuating axis of the contacts, said first elongate portion extending from said supported end of the spring to the bend along a plane which is substantially parallel to the plane of the said first membrane, and said second elongate portion extending from the bend to the free end of the spring generally in the same direction as said first portion and in a plane disposed at an angle intermediate the plane of said first membrane and the plane perpendicular to said first membrane, the free end of the spring being arranged so as to be displaced by the switch actuating member when the latter is actuated, and the bend in the spring forming a knee which is pressed by said actuation against the adjacent said first membrane so as to displace it into contact with the said second membrane.
Claim 2
Dependent Claim
372 words
A key actuated membrane switch comprising a key operated switch actuating member mounted on a displacement sensing means in the form of a sealed package, said package consisting of first and second insulative membranes respectively positioned on either side of a further membrane comprising an apertured spacing member, the switch actuating member being mounted on the first of said membranes and said first and second membranes each bearing a respective one of an opposed pair of coaxially disposed contacts associated with the switch actuating member, each contact consisting of a conductive film deposited on the internal surface of the respective membrane and comprising part of a normally open circuit which is closed when the said first membrane is flexed into a space normally between the membranes provided by a corresponding one of the apertures in the spacing member so as to contact the said second membrane, the said conductive films thereby touching and said switch actuating member applying pressure on said first membrane along the actuating axis of said contacts through the intermedium of an electrically isolated spring formed as a flat strip having a bend at an intermediate position along its length so as to define a lever having first and second elongate portions which are distinguished by the discontinuity of direction at the said bend, said spring having a free end and a supported end, said bend being aligned with the actuating axis of the contacts, said first elongate portion extending from said supported end of the spring to the bend along a plane which is substantially parallel to the plane of the said first membrane, and said second elongate portion extending from the bend to the free end of the spring generally in the same direction as said first portion and in a plane disposed at an angle intermediate the plane of said first membrane and the plane perpendicular to said first membrane, the free end of the spring being arranged so as to be displaced by the switch actuating member when the latter is actuated, and the bend in the spring forming a knee which is pressed by said actuation against the adjacent said first membrane so as to displace it into contact with the said second membrane.
Claim 3
Dependent Claim
82 words
A key actuated membrane switch according to Claim 1 wherein the spring forms part of a channel-section member which is mounted by means of its interconnected web on the said first membrane, said spring being defined by means of a U-shaped slot in the said interconnecting web and said second portion thereof being struck out of the plane of the web along a line intersecting the arms of the U-shaped slot at a position intermediate of the two ends of the spring.
Claim 4
Dependent Claim
38 words
A key actuated membrane switch according to Claim 2 in which the switch actuating member is supported on the channel-section member by means of lugs which enter into corresponding apertures in the flange members of the channel-section member.
Claim 5
Dependent Claim
49 words
A membrane keyboard having a plurality of switches, each according to Claim 2 or Claim 3 wherein a plurality of springs are formed in the interconnecting web of the channel-section member along and coaxially with a longitudinal axis thereof, each spring being associated with a respective switch actuating member.
Claim 6
Dependent Claim
87 words
A key actuated membrane switch according to Claim 1 wherein the switch actuating member comprises a plunger and a housing in which the plunger slides, the said housing having a substantially planar base which incorporates an asymmetric foot, the said spring being attached to the outer end of the foot at its supported end and the said base being held fast by means of an adhesive on the said first membrane or on an apertured membrane which is intermediate said switch actuating member and said first membrane.
Claim 7
Dependent Claim
88 words
A key actuated membrane switch according to Claim 5 wherein the outer end of the foot incorporates a vertical slot which extends from its underside and said spring has a dog leg portion arranged substantially at right angles to the said first part of the cantilevered portion at its supported end which is entered into this slot, the walls of the latter serving to retain the spring in the housing by virtue of an interference fit by the said dog leg portion between the walls of the slot.
Claim 8
Dependent Claim
41 words
A key actuated membrane switch according to Claim 6 wherein said slot is provided with ribs on its internal walls, whereby the said dog leg portion of the spring is bowed on its insertion into the slot about a vertical axis.
Claim 9
Dependent Claim
17 words
A membrane keyboard having a plurality of switches each according to any of Claims 5 to 7.
Claim 10
Dependent Claim
118 words
A membrane keyboard according to any preceding claim, wherein said first- - - - - - -- -- - - - - -- - - - - - - - - - - - - - - - - - -and second membranes are separated by an adhesively coated apertured spacing sheet of prescribed thickness whereby the normal separation of the contacts of said pairs of contacts is assured, there being an array of apertures in said spacing sheet each of which respectively coincides with the pairs of contacts appertaining to a respective switch actuating member, said first and second membranes being bonded to said spacing sheet by the adhesive coating so as to provide said sealed package.
Claim 11
Dependent Claim
26 words
A membrane keyboard according to Claim 9 wherein said spacing sheet has a plurality of slots which respectively link the apertures of respective rows of apertures.
Claim 12
Dependent Claim
36 words
A membrane keyboard according to Claim 10 wherein the said slots communicate with pneumatic terminals whereby air may be admitted to or exhausted from the spaces defined by said rows of apertures in the spacing sheet.
Claim 13
Dependent Claim
37 words
A key actuated membrane switch according to Claim 1 or any claim appendant thereto wherein the said spring is dimensioned so as to provide a mechanical advantage of approximately 4:1 during the initial operation of the switch.
Claim 14
Dependent Claim
38 words
A membrane keyboard according to any of Claims 9 to 11 wherein the spring of each switch actuating member is dimensioned so as to provide a mechanical advantage of approximately 4:1 during the initial operation of the switch.