| 摘要 |
An acoustic catheter (10) has a shaft (18) driven by a rotary motor (60). The shaft drives a rotary-to-axial motion converter (30) near the distal end (14) of the catheter. The converter (30) includes a rotary driver (42) with a wavy or sinusoidal bearing surface (36) facing a similarly wavy face (38) of a follower element (44). As the rotary driver (42) rotates, the follower (44) moves axially with a reciprocating motion. High rotational speeds are required to achieve high acoustic frequencies. The high speeds and high acceleration rate of the follower result in frictional forces which cause undesired heating. The heating effects are reduced by a magnetic bearing arrangement associated with the mating bearing surfaces of the rotary driver and follower, which tends to keep them slightly separated, and thereby reduce friction. Other embodiments use magnets to restore the follower to its proximal position following each excursion, and use magnetic thrust bearings for the rotary driver.
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