Compact self-centering compliant joint
A self-centering compliant joint for connecting an actuator and an effector, provides five degrees of freedom, minimizes the effects of side loads, transfers compressive loads into tensile loads on internal components, and self-centers.
1. A compliant joint for transferring force from an actuator to an effector, the compliant joint comprising:
a lower spider housing comprising a lower spider housing base with an upper surface and a lower surface, a plurality of lower fingers extending from the upper surface of the lower spider housing base, and the lower surface of the lower spider housing base having a centered lower spherical concavity;
an upper spider housing comprising an upper spider housing base with an upper surface and a lower surface, a plurality of upper fingers extending from the lower surface of the upper spider housing base, and the upper surface of the upper spider housing base having a centered upper spherical concavity;
a central rod with a lower end and an upper end, extending through a bore through the lower spider housing base and the upper spider housing base;
a lower spherical bearing attached to the lower end of the central rod, and an upper spherical bearing attached to the upper end of the central rod; and
a lower cap having a plurality of bores therethrough for securing the lower cap to the upper fingers with a plurality of bolts, and an upper cap having a plurality of bores therethrough for securing the upper cap to the lower fingers with a plurality of bolts;
wherein upon assembly the lower fingers and upper fingers interlock, the lower spherical bearing is situate in the lower spherical concavity, and the upper spherical bearing is situate in the upper spherical concavity.
2. The compliant joint of claim 1 , wherein the compliant joint, the caps, the spider housings, and the rod are cylindrical.
3. The compliant joint of claim 1 , wherein the lower fingers and the upper fingers are threaded to receive the plurality of bolts passing through the upper spider housing and the lower spider housing, respectively.
4. The compliant joint of claim 1 , wherein, when placed under a compressive load, the compliant joint accommodates a side load by the lower spherical bearing and upper spherical bearing moving within the upper concavity and lower concavity, respectively.
5. The compliant joint of claim 4 , wherein the compliant joint transfers the compressive load to a tensile load on the rod, whereby the rod self-centers.
6. The compliant joint of claim 1 , wherein a gap is provided between the lower and upper fingers and their opposed spider housing bases.
7. The compliant joint of claim 6 , wherein the lower and upper interlocking fingers have longitudinal gaps therebetween.
8. The compliant joint of claim 1 , wherein the caps and spider housings are constructed from a material selected from the group consisting of metals, alloys, resins, polymers, composites, and carbon fiber.
9. The compliant joint of claim 1 , wherein the caps and spider housings are constructed from super duplex stainless steel.
10. The compliant joint of claim 9 , wherein the rod is constructed from a material selected from the group consisting of stainless steel, titanium, and monel K-500.
11. The compliant joint of claim 1 , wherein the spherical bearings are constructed from a material selected from the group consisting of metals, alloys, resins, polymers, composites, and carbon fiber.
12. The compliant joint of claim 11 , wherein the spherical bearings are constructed from a polymer material.
13. The compliant joint of claim 1 , wherein the spherical bearings are retained on the rod, each with a nut and a washer.
14. The compliant joint of claim 13 , wherein the rod has a flange at one end to retain one of the spherical bearings.
15. The compliant joint of claim 1 , wherein the nut is constructed from monel K-500.
16. The compliant joint of claim 15 , wherein the rod is constructed from monel K-500, and the spherical bearings are constructed from a polymer material.