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1. WO2002025748 - PIEZOELECTRIC CYLINDER COUPLER FOR VARIABLY COUPLING TWO BODIES AND JOINT INCORPORATING THE COUPLER

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[ EN ]

CLAIMS
1. A controlled collapse joint for selectively controlling the relative motion of two bodies, the joint comprising:
an outer member concentrically mounted on an inner member for relative motion about or along an axis;
the outer member having an inner wall;
the inner member comprising a piezoelectric cylinder having inner and outer walls, the piezoelectric cylinder being radially deformable in response to a voltage difference between the inner and outer walls of the cylinder;
the outer member mounted on the piezoelectric cylinder with the inner wall of the outer member and the outer wall of the piezoelectric cylinder engaging each other in an initial interference fit to frictionally couple the inner and outer members and resist relative motion of the two members;
means for mounting the outer member to a first body;
means for mounting the inner member to a second body;
a voltage source having terminals for generating a voltage difference across the terminals;
first and second electrical connections for applying the voltage difference generated by the voltage source between the inner and outer walls of the piezoelectric cylinder to radially deform the piezoelectric cylinder and thereby vary the interference fit from the initial interference fit to an operating interference fit;
the first electrical connection electrically connecting one terminal of the voltage source to the outer wall of the piezoelectric cylinder and the second electrical connection connecting the other terminal of the voltage source to the inner wall of the piezoelectric cylinder; and
a control system operatively connected to the voltage source for selectively setting the voltage difference applied to the piezoelectric cylinder.
2. The controlled collapse joint of claim 1 wherein the voltage difference has a polarity that causes the piezoelectric cylinder to deform radially outwardly.

3. The controlled collapse joint of claim 2 wherein the operating interference fit is greater than the initial interference fit.
4. The controlled collapse joint of claim 1 wherein the outer member is formed from a material that conducts electricity and the outer member forms a portion of the first electrical connection.
5. The controlled collapse joint of claim 4 wherein the interference fit between the outer member and the outer wall of the piezoelectric cylinder electrically connects the inner wall of the outer member with the outer wall of the piezoelectric cylinder.
6. The controlled collapse joint of claim 1 wherein the second electrical connection includes a conductive film adhering to the inner wall of the piezoelectric cylinder.
7. A piezoelectric coupler for coupling two bodies, the coupler comprising:
a first member having a surface;
a second member concentric with the first member, the second member comprising a piezoelectric component having inner and outer walls, one of the walls cooperatively engaging the surface of the first member to enable relative motion of the two members on such surface and forming a first interference fit with such surface to frictionally couple the two members;
means for attaching the first member to a first body and means for attaching the second member to a second body;
first and second electrical connections for applying a voltage difference between the inner and outer walls of the piezoelectric member, the first electrical connection including a first electrode electrically connected to the one wall of the piezoelectric member and the second electrical connection including a second electrode electrically connected to the other wall of the piezoelectric member;
whereby when a voltage difference is applied across the two electrodes, the one wall of the piezoelectric member is urged towards or away from the surface of the first member and forms a second interference fit with the surface of the first member, the second interference fit being different than the first interference fit to vary the coupling of the two members.
8. The piezoelectric coupler of claim 7 wherein the surface of the first member surrounds and engages the outer wall of the piezoelectric component.
9. The piezoelectric coupler of claim 8 wherein the first member is a conductor of electricity and forms a portion of the first electrical connection.
10. The piezoelectric coupler of claim 8 wherein the second electrical connection includes a conductive member on the inner wall of the piezoelectric component .
11. The piezoelectric coupler of claim 7 wherein the first member is formed from an electrically conductive material and forms a portion of the first electrical connection.
12. The piezoelectric coupler of claim 11 wherein the first electrode is attached to the first member.
13. The piezoelectric coupler of claim 7 wherein the second electrical connection includes a conductive member on the other wall of the piezoelectric component.
14. The piezoelectric coupler of claim 13 wherein the conductive member is a thin film.
15. The piezoelectric coupler of claim 13 wherein the second electrode is attached to the conductive member.
16. The piezoelectric coupler of claim 7 wherein the interference fit between the one wall of the piezoelectric cylinder and the surface of the first member increases in response to an increase in the voltage difference across the first and second electrodes.
17. The piezoelectric coupler of claim 7 wherein the piezoelectric component is a piezoelectric cylinder.
18. The piezoelectric coupler of claim 17 wherein the piezoelectric cylinder is surrounded by the surface of the first member .
19. The piezoelectric coupler of claim 7 including a voltage source having terminals for generating a voltage difference across the terminals, each electrode electrically connected to a different terminal, and a control system operatively connected to the voltage source for selectively setting the voltage difference applied to the piezoelectric component .