This invention relates to an ultrasonic resonant vibrator, particularly to an ultrasonic resonant vibrator including an improved magnetostrictive transducer for use in a surgical handpiece.
Apparatus incorporating an ultrasonic resonant vibrator is known in the art for surgical use, particularly for surgical handpieces comprising tools for fragmenting tissue. In such apparatus the required ultrasonic vibrations may be produced by magnetostrictive means transmitted through a connecting member to an appropriate tool.
A representative example of such an apparatus is disclosed in U.S. Pat. No. 4,223,676, the disclosure of which is incorporated herein by reference. In the apparatus disclosed in U.S. Pat. No. 4,223,676 the magnetostrictive transducer is a magnetostrictive stack composed of a sandwich of nickel alloy strips such as is taught in U.S. Pat. No. RE 25,033. The said stack comprises a plurality of elongated strips of magnetostrictive material, i.e. nickel alloy, forming a laminated structure. The laminations are necessary to reduce adverse effects, e.g. energy loss from eddy currents.
In a later improved design the laminated stack was made with a shallow curved profile for added rigidity.
In order to function properly, a laminated transducer preferably:
1. should be mechanically stiff: PA1 2. have minimum acoustic losses; and PA1 3. should be relatively easy to handle away from its operating environment.
The prior art transducer described above has proved to be effective and highly serviceable in its use in surgical procedures. However, despite its good performance record it still has certain disadvantages. For example, the flat laminated structure tends to overheat if the flow of coolant is reduced for any reason and such overheating may result in serious damage to the apparatus. Also the flat construction gives substantial mechanical stiffness in only one plane. This lack of overall rigidity may result in mechanical damage due to mishandling and, if the laminations become separated or bent, the entire apparatus may be rendered useless.
The above disadvantages may be overcome if the transducer is made in the form of a substantially rigid column comprising elongated strips arranged in the form of radially extending fins as described and claimed in application Ser. No. 287,748, filed concurrently herewith and the disclosure of which is incorporated herein by reference.
The improved magnetostrictive transducer of Ser. No. 287,748 comprises a plurality of elongated strips of magnetostrictive material, each strip having a proximal end, a distal end and a substantially V-shaped cross section wherein each arm of the V is formed by the longitudinal length of the strip, each strip being attached to an adjacent strip at both the proximal end and the distal end to form an integral substantially rigid column having a central axis with fins extending radially relative to said axis.
It has now been found that a still further improved ultrasonic resonant vibrator incorporating a finned magnetostrictive, transducer as disclosed in Ser. No. 287,748 is provided if said transducer is made to have a central tunnel of sufficiently large diameter to accommodate at least part of a resonant member, especially the connecting portion which transmits the ultrasonic vibrations to the operating member, e.g. a surgical tool or a conduit for fluid movement It further has been found that it is immaterial for the efficient operation of the final device whether said connecting portion is attached externally, end-to-end, to the transducer, or attached internally, as hereinafter described, in a configuration which is herein termed a "folded resonator".