Articulable column
AssigneeJohn Madocks
InventorsJohn E. Madocks, Thomas M. Young
Life of this patent
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Abstract
Presented is a method and apparatus for incrementally varying the frictional forces along an articulable column having succesive joints formed of alternate ball and socket members. Friction is varied by varying the contact angle between said ball and socket members along the length of the column and by supplying a compressive force to said joints via a tensioned means throughout the column. The effect of varying the frictional forces along the column is to vary the stiffness of individual column joints creating a structural member which can be tailored to the load requirements of a specific application.
Claims8
The method of varying by incrementally different amounts the frictional engagement forces simultaneously applied along an articulable column having successive joints formed by alternate ball and socket members arranged along an elongated central axis, comprising the steps of:
- (a) applying a compressive force at said ball and socket joints where said compressive force is applied in the direction of said elongated central axis of the column;
- (b) varying by different incremental amounts the ball/socket contact angle defined by a plane perpendicular to the column axis and including the center of the ball and a line including said contact point of said ball and socket and said ball center, whereby incorporation of different contact angles at selected ball and socket joints varies said frictional forces at each joint responding to the formula:
- F=(T*u)/SIN (A)
- where F=the frictional force at said joint, T=the applied compressive force, u=the coefficient of friction of the materials in contact, and A=the contact angle.
An articulable column having an elongated central axis, comprising:
- (a) a series of ball and socket members arranged along said central axis to form articulable ball and socket joints frictionally engaged over the length of the column, said ball member having a center common to the frictional surface thereof and an aperture therethrough coincident with said column axis;
- and
- (b) means generatively associated with said ball and socket members retaining said ball and socket members in frictional engagement;
- (c) said socket members comprising a cradle having surfaces contiguously receiving said ball members at a contact angle defined by a plane perpendicular to the column axis and including said ball center and a line including the contact point of said socket member on said ball member and including said center;
- (d) said contact angle of a first ball and socket joint comprising a first predetermined value;
- (e) said contact angle of a second ball and socket joint comprising a second predetermined value larger than or smaller than said contact angle of said first ball and socket joint;
- (f) whereby the first and second predetermined values of contact angles for the first and second ball and socket joints provide incrementally varying frictional forces in said series of ball and socket joints over the length of the column.
Dependencies are inferred from the claim text.