Abstract A key arm mechanism for keys of a typewriter or data entry device in which a uniform spring rate is achieved by varying the cross-sectional area of the key arms as a direct relation to the distance of the key support posts from a cantilever point. The entire key arm mechanism is formed of a unitary molded material. In one embodiment, the cross-sectional area of each key arm is uniform from the cantilever point to its associated key support post. In another embodiment, the cross-sectional area of each key arm decreases linearly from the cantilever point to its associated key support post. Uniform initial preload tension can be applied to the key arms by a slotted member which engages the ends of the key arms remote from the cantilever points. Non-uniform preload tension can be achieved by varying the height of some slots of the slotted member or by varying the height of the key arms at the ends thereof remote from the cantilever points. Adjustment of the preload tension can be achieved by an eccentric positioned adjacent the cantilever points.
Inventors
👤 Wendell C. Johnson
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-11-04 22:14
CPC Classifications
B; B41; B41J; B41J5/00; B41J5/08; B41J5/26
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
169 words
A unitary key arm mechanism for a key actuated device comprising a support section, a plurality of key arms emanating from said support section, each of said key arms having a key support post projecting therefrom such that each key arm supports a support post, the distance of some of said support posts from said support section being greater than the distance of other of said support posts from said support section and less than the distance of still other of said support posts from said support section, the cross-sectional areas of said key arms supporting said some of said support posts being both greater than the cross-sectional areas of said key arms supporting said other of said support posts and smaller than the cross-sectional area of said key arms supporting said still other of said support posts, said cross-sectional areas being measured for all key arms at a fixed distance from said support section and between said support section and the support post closest to said support section.
Claim 2
Dependent Claim
169 words
A unitary key arm mechanism for a key actuated device comprising a support section, a plurality of key arms emanating from said support section, each of said key arms having a key support post projecting therefrom such that each key arm supports a support post, the distance of some of said support posts from said support section being greater than the distance of other of said support posts from said support section and less than the distance of still other of said support posts from said support section, the cross-sectional areas of said key arms supporting said some of said support posts being both greater than the cross-sectional areas of said key arms supporting said other of said support posts and smaller than the cross-sectional area of said key arms supporting said still other of said support posts, said cross-sectional areas being measured for all key arms at a fixed distance from said support section and between said support section and the support post closest to said support section.
Claim 3
Dependent Claim
31 words
The key arm mechanism of claim 1 wherein said cross-sectional area of each of said key arms is constant throughout its length between said support section and its related support post.
Claim 4
Dependent Claim
31 words
The key arm mechanism of claim 1 wherein the cross-sectional areas of at least some of said key arms decreases at a linear rate from their value at said support section.