Flexible joint arrangement incorporating flexure members
Improved 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. In other embodiments, 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. An expandable device, comprising:
a first base member and a second base member;
a plurality of flexure assemblies disposed between the first base member and the second base member, wherein each flexure assembly comprises:
a first structural member connected to the first base member with a first flexure member;
an intermediate block connected to the first structural member with a second flexure member; and
a second structural member connected to the intermediate block with a third flexure member and to the second base member with a fourth flexure member, wherein each structural member is rotatable with respect to the first base member and the second base member via the corresponding flexure members to move the first base member relative to the second base member such that the first base member and the second base member are movable between a compressed configuration and an expanded configuration relative to each other,
wherein a wrapping surface is defined, in each of the first base member adjacent the first flexure, member, the intermediate block adjacent the second flexure member, the intermediate block adjacent the third flexure member and the second base member adjacent the fourth flexure member, and
wherein each wrapping surface provides a guide for rotation of the corresponding flexure member that, defines a traveling, instantaneous axis of rotation about which the flexure member rotates that moves along a path defined by an interface of the wrapping surface and the corresponding flexure member as, the flexure member rotates,
wherein each point along each flexure member has a radius of curvature that changes only in discrete quantum steps without reversing from either a positive radius of curvature or a negative radius of curvature to the other of a positive radius of curvature and a negative radius of curvature as the first base member and the second base member are moved from the compressed configuration to the expanded configuration, and
wherein the plurality of flexure assemblies, first base member and second base member comprise a unitary one-piece monolithic body.
2. The expandable device of claim 1 , wherein one or more of the wrapping surfaces has a concave cross-sectional shape.
3. The expandable device of claim 1 , wherein one or more of the wrapping surfaces has a convex cross-sectional shape.
4. The expandable device of claim 1 , wherein one or more of the wrapping surfaces has a flat cross-sectional shape.
5. The expandable device of claim 1 , wherein each flexure rotates elastically.
6. The expandable device of claim 1 , wherein each wrapping surface provides a guide for rotation of the corresponding flexure member by interfacing with the flexure member as the flexure member rotates such that a portion of the flexure member contacting the wrapping surface conforms to a shape of the wrapping surface.
7. The expandable device of claim 1 , further comprising a drive mechanism extending through the intermediate block, the drive mechanism rotatable to cause the first base member and the second base member to move between the compressed configuration to the expanded configuration.
8. The expandable device of claim 7 , wherein the intermediate block translates along the drive mechanism as the drive mechanism is rotated.
9. The expandable device of claim 7 , wherein the drive mechanism is a screw.
10. An expandable device, comprising:
a first base member and a second base member;
a plurality of flexure assemblies disposed between the first base member and the second base member, wherein each flexure assembly comprises:
a first structural member connected to the first base member with a first flexure member;
an intermediate block connected to the first structural member with a second flexure member; and
a second structural member connected to the intermediate block with a third flexure member and to the second base member with a fourth flexure member, wherein each structural member is rotatable with respect to the first base member and the second base member via the corresponding flexure members to move the first base member relative to the second base member such that the first base member and the second base member are axially expandable between a compressed configuration and an expanded configuration relative to each other,
wherein each flexure member defines a traveling instantaneous axis of rotation about which the corresponding flexure members rotate as the first base member and the second base member are moved relative to each other such that the axes of rotation of each flexure member travel at different heights within a plane define transverse to the axes without overlapping as the first base member and the second base member are axially expanded and contracted relative to each other, and
wherein the plurality of flexure assemblies, first base member and second base member comprise a unitary one-piece monolithic body.
11. The expandable device of claim 10 , wherein a wrapping surface is defined in each of the first base member adjacent the first flexure member, the intermediate block adjacent the second flexure member, the intermediate block adjacent the third flexure member and in the second base member adjacent the fourth flexure member, wherein each wrapping surface provides a guide for rotation of the corresponding flexure member and defines a radius of curvature of at least a portion of the corresponding flexure member as the first base member and the second base member are axially expanded and contracted relative to each other.
12. The expandable device of claim 7 , wherein each wrapping surface provides a guide for rotation of the corresponding flexure member by interfacing with the flexure member as the flexure member rotates such that a portion of the flexure member contacting the wrapping surface conforms to a shape of the wrapping surface.
13. The expandable device of claim 11 , wherein one or more of the wrapping surfaces has a concave cross-sectional shape.
14. The expandable device of claim 11 , wherein one or more of the wrapping surfaces has a convex cross-sectional shape.
15. The expandable device of claim 11 , wherein one or more of the wrapping surfaces has a flat cross-sectional shape.
16. The expandable device of claim 11 , further comprising a drive mechanism extending through the intermediate block, the drive mechanism rotatable to cause the first base member and the second base member to axially move between the compressed configuration to the expanded configuration.
17. The expandable device of claim 16 , wherein the intermediate block translates along the drive mechanism as the drive mechanism is rotated.
18. The expandable device of claim 16 , wherein the drive mechanism is a screw.
19. The expandable device of claim 10 , wherein each flexure member rotates elastically.