US3767022A — Return spring key stem boot

Claim 1

Independent Claim 233 words

A spring-like stem boot adapted to surround a reciprocable stem coupled to a key element for providing a restoring force urging said key element toward a rest position, said stem boot comprising a hollow, resilient member including: a cylindrical base portion adapted to be secured to a mounting means, a top portion having a central bore adapted to be coupled to said stem, the outer diameter of said top portion being smaller than the inner diameter of said cylindrical base portion, a frusto-conical intermediate portion forming a first integral junction at the largest diameter portion thereof with a first end of said cylindrical base portioN and forming a second integral junction at the smallest diameter portion thereof with said top portion, the thickness of said frusto-conical portion increasing along the length thereof from said first junction to said second junction, said recited characteristics of said cylindrical base and frusto-conical portions of said stem boot providing a nonlinear restoring force exhibiting increasing resistance with increased displacement of said key element up to a maximum and thereafter exhibiting decreasing resistance to increased displacement of said key element, said recited structure of said stem boot enabling said stem boot to function as a toggle having two stable states, one of which is said rest position, and stop means associated with said stem boot for preventing displacement of said key element past the equilibrium of said toggle.

Claim 2

Dependent Claim 233 words

A spring-like stem boot adapted to surround a reciprocable stem coupled to a key element for providing a restoring force urging said key element toward a rest position, said stem boot comprising a hollow, resilient member including: a cylindrical base portion adapted to be secured to a mounting means, a top portion having a central bore adapted to be coupled to said stem, the outer diameter of said top portion being smaller than the inner diameter of said cylindrical base portion, a frusto-conical intermediate portion forming a first integral junction at the largest diameter portion thereof with a first end of said cylindrical base portioN and forming a second integral junction at the smallest diameter portion thereof with said top portion, the thickness of said frusto-conical portion increasing along the length thereof from said first junction to said second junction, said recited characteristics of said cylindrical base and frusto-conical portions of said stem boot providing a nonlinear restoring force exhibiting increasing resistance with increased displacement of said key element up to a maximum and thereafter exhibiting decreasing resistance to increased displacement of said key element, said recited structure of said stem boot enabling said stem boot to function as a toggle having two stable states, one of which is said rest position, and stop means associated with said stem boot for preventing displacement of said key element past the equilibrium of said toggle.

Claim 3

Dependent Claim 38 words

The stem boot of claim 1 wherein said frustoconical portion and the axis of said cylindrical portion are formed at an angle enabling the formation of hoop stresses at said first junction when said key element is actuated.

Claim 4

Dependent Claim 17 words

The stem boot of claim 2 wherein said angle is in the range from 30* to 35*.

Claim 5

Dependent Claim 44 words

The stem boot of claim 1 wherein the angle between the outer surface of said frusto-conical portion and the axis of said cylindrical portion is substantially 30* and the angle between the inner surface of said frusto-conical portion and said axis is substantially 35*.

Claim 6

Dependent Claim 33 words

The stem boot of claim 1 wherein said stop means comprises an upturned annular flange arranged circumferentially of said cylindrical base portion and adapted to abut the advancing edge of said key element.

Claim 7

Dependent Claim 218 words

A return spring for biasing a pushbutton supporting plunger away from a guide base relative to which the plunger is movable along a line substantially normal to the base, the spring comprising a tubular element fabricated of a resilient elastomeric material, the element being arranged for disposition coaxially of the plunger between the base and the pushbutton and normally configured to define first and second opposite coaxially aligned terminal cylindrical portions and a central frustroconical portion integrally connected circumferentially of its opposite ends with the adjacent ends of the first and second cylindrical portions respectively, the first cylindrical portion having an inner diameter sized to mate with the plunger adjacent the pushbutton end thereof, the inner diameter of the second cylindrical portion being greater than the outer diameter of the first cylindrical portion, the second cylindrical portion being arranged for support by the base circumferentially of the plunger and having sufficient length that the end thereof connected to said frusto-conical portion is deformable radially outwardly to enable said frusto-conical portion to deform into a planar state between said first and second cylindrical portions in response to a compressive load applied axially of the tubular element by depression of said plunger, said frusto-conical portion deforming past said planar state with a snap action in response to additional compressive loads.

Claim 8

Dependent Claim 218 words

A return spring for biasing a pushbutton supporting plunger away from a guide base relative to which the plunger is movable along a line substantially normal to the base, the spring comprising a tubular element fabricated of a resilient elastomeric material, the element being arranged for disposition coaxially of the plunger between the base and the pushbutton and normally configured to define first and second opposite coaxially aligned terminal cylindrical portions and a central frustroconical portion integrally connected circumferentially of its opposite ends with the adjacent ends of the first and second cylindrical portions respectively, the first cylindrical portion having an inner diameter sized to mate with the plunger adjacent the pushbutton end thereof, the inner diameter of the second cylindrical portion being greater than the outer diameter of the first cylindrical portion, the second cylindrical portion being arranged for support by the base circumferentially of the plunger and having sufficient length that the end thereof connected to said frusto-conical portion is deformable radially outwardly to enable said frusto-conical portion to deform into a planar state between said first and second cylindrical portions in response to a compressive load applied axially of the tubular element by depression of said plunger, said frusto-conical portion deforming past said planar state with a snap action in response to additional compressive loads.

Claim 9

Dependent Claim 39 words

Apparatus according to claim 6 in which the wall of the frusto-conical portion of the element decreases in thickness from the end thereof connected to the first cylindrical portion to the end thereof connected to the second cylindrical portion.

Claim 10

Dependent Claim 35 words

Apparatus according to claim 6 wherein the end of the second cylindrical portion opposite from the frusto-conical portion is joined to a flat sheet of the resilient material peripherally of an aperture in the sheet.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1976-10-22	1977-04-23	1977-10-23	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1980-10-22	1981-04-23	1981-10-23	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1984-10-22	1985-04-23	1985-10-23	$7700.00	Window Closed / Lapsed

Return spring key stem boot

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