Planar flexure members and actuators using them
A planar flexure member for resisting rotation about a central axis thereof includes, in various embodiments, a central portion comprising a plurality of attachment points; and at least one serpentine flexure arm extending from the central portion in a plane. The arm(s) terminate in an arcuate mounting rail that includes a series of attachment points. The rails are positioned in opposition to to each other to partially define and occupy a planar circular envelope radially displaced from but surrounding the central portion of the flexure member. A portion of the serpentine arms may extend to (or substantially to) the envelope between the mounting rails.
1. A planar flexure member for resisting rotation about a central axis thereof, the flexure member comprising:
a central portion comprising a plurality of attachment points; and
at least two serpentine flexure arms extending oppositely and symmetrically from the central portion in a plane, each of the arms terminating in an arcuate mounting rail, the mounting rails each comprising a plurality of attachment points and being positioned in opposition to to each other to partially define and occupy a planar circular envelope radially displaced from but surrounding the central portion, a portion of the serpentine arms extending substantially to the envelope between the mounting rails.
2. The flexure member of claim 1 , wherein the serpentine arms have a varying thickness with a thinnest portion thereof at the envelope.
3. The flexure member of claim 1 , wherein the arms and the central portion have a unitary height, the height being at least equal to a width of the arms at a narrowest portion thereof.
4. The flexure member of claim 3 , wherein a ratio of the height to the width is at least 2.
5. The flexure member of claim 1 , wherein the arms and the central portion have a non-unitary height.
6. The flexure member of claim 1 , wherein the flexure member is made of titanium.
7. The flexure member of claim 1 , wherein at least a portion of the arms has an I-beam cross-section.
8. The flexure member of claim 1 , wherein at least a portion of the arms has voids along a neutral bending axis thereof.
9. A rotary actuator comprising:
a motor configured for rotation about an actuation axis; and
a planar flexure member having a central output portion mechanically coupled to a load and at least two serpentine flexure arms extending oppositely and symmetrically from the central portion in a plane, each of the arms terminating in an arcuate mounting rail having a plurality of attachment points for mounting to the motor, the mounting rails being positioned in opposition to each other to partially define and occupy a planar circular envelope radially displaced from but surrounding the central portion, a portion of the serpentine arms extending substantially to the envelope between the mounting rails.
10. The actuator of claim 9 , wherein the serpentine arms have a varying thickness with a thinnest portion thereof at the envelope.
11. The actuator of claim 9 , wherein the arms and the central portion have a unitary height, the height being at least equal to a width of the arms at a narrowest portion thereof.
12. The actuator of claim 9 , wherein a ratio of the height to the width is at least 2.
13. The actuator of claim 9 , wherein the arms and the central portion have a non-unitary height.
14. The actuator of claim 9 , wherein the flexure member is made of titanium.
15. The actuator of claim 9 , wherein at least a portion of the arms has an I-beam cross-section.
16. The actuator of claim 9 , wherein at least a portion of the arms has voids along a neutral bending axis thereof.
17. The actuator of claim 9 , wherein the actuator has an actuation axis coaxial with an output axis.