Flexible joint arrangement incorporating flexure members
Flexible joint arrangements employ at least one flexure member that interfaces with wrapping surfaces defined on the bases to which the ends of the flexure member are connected. The flexure members are configured to define a traveling instantaneous axis of rotation that moves along a path defined by the interface of the flexure and the wrapping surfaces as the bases move relative to each other. The flexure members and the bases can be constructed of a monolithic material. The wrapping surfaces of the bases can be asymmetric in cross-sectional shape. The radius of curvature of the traveling instantaneous axis of rotation can be configured to change only in discrete quantum steps without reversals. The flexible joint arrangement can be configured as one or more three bar linkages in which the middle bar is rigid and the outer bars are flexure members in accordance with the various embodiments.
1. A flexible joint comprising:
a top base comprising a lower surface;
a bottom base comprising an upper surface; and
a plurality of flexure assemblies disposed between and unitarily formed with the top and bottom bases, each flexure assembly comprising:
an intermediate block comprising opposing upper and lower surfaces;
upper and lower structural members each disposed between the intermediate block and a respective one of the top and bottom bases, each structural member including opposing upper and lower surfaces and opposing side surfaces;
a flexure member disposed on each opposing upper and lower surface of each structural member, the flexure members connecting each structural member to a respective one of the upper and lower surfaces of the intermediate block and to a respective lower or upper surface of one of the top and bottom bases;
wherein the opposing upper and lower surfaces of the structural members, the upper and lower surfaces of the intermediate block, the lower surface of the top base, and the upper surface of the bottom base each comprise a wrapping surface adjacent a corresponding flexure member, and wherein the wrapping surfaces of the top base, bottom base, and intermediate block define an arcuate curve;
wherein each structural member is rotatable with respect to the top and bottom bases to move the top base relative to the bottom base, such that the top base and the bottom base are movable between a compressed configuration and an expanded configuration relative to each other,
the compressed configuration characterized by:
the top and bottom bases being moved toward each other such that the wrapping surfaces of each structural member are aligned with a side surface of a respective flexure member so that the flexure members conform to the shape of the wrapping surfaces of the structural member, and one of the opposing side surfaces of each structural member is shaped to correspondingly engage one of the respective upper or lower surfaces of the top and bottom bases; and
the expanded configuration characterized by:
the top and bottom bases being displaced from each other such that the arcuate wrapping surfaces of each of the top base, bottom base, and the opposing upper and lower surfaces of the intermediate block are engaged with an opposing side surface of a respective one of the flexure members so that the flexure members conform to the shape of the arcuate wrapping surfaces.
2. The flexible joint of claim 1 , wherein the arcuate wrapping surfaces of the top base and the bottom base provide a guide for rotation of the flexure members and define a radius of curvature of at least a portion of the flexure members as the top base and bottom base are moved relative to each other, wherein the wrapping surfaces provide a guide for rotation of the flexure members by interfacing with the flexure members as they rotate.
3. The flexible joint of claim 2 , wherein the arcuate wrapping surfaces have either a concave or convex cross-sectional shape.
4. The flexible joint of claim 1 , wherein the flexure members are selected from the group consisting of: a band flexure, a circular flexure, an elliptical flexure and a leaf flexure.
5. The flexible joint of claim 1 , wherein the arcuate wrapping surfaces of the top base and the bottom base each have a geometry that is different from a geometry of the other wrapping surface.
6. The flexible joint of claim 2 , wherein the interfacing of the arcuate wrapping surfaces with the flexure members results in translational movement of the structural members.