Abstract: A transducer stack (10) includes rings (16) of piezo-electric ceramic alternating with metal electrodes (18) along a threaded central shaft (32) extending from a titanium back plate (20). A spacer or threaded element (14) threaded on to the shaft (32) holds the ceramic rings (16) and electrodes (18) in compression against the back plate (20). The transducer stack (10) is mountable eccentrically to a horn (12) of an ultrasonically-vibratable tool, away from an axis of an elongate waveguide (56) extending from the horn (12). The transducer stack (10) may vibrate in a flexural mode perpendicular to the waveguide (56), generating torsional mode ultrasonic vibrations in the horn (12) and waveguide (56), or in a flexural mode parallel to the waveguide (56), generating longitudinal mode ultrasonic vibrations in the horn (12) and waveguide (56).

Abstract: Apparatus (5,50) for generating torsional-mode ultrasonic vibrations comprises a stack of axially-polarized piezo-electric ceramic rings (10) having a torsional converter (1,51,53) mounted coaxially to either one face of the stack or to two opposite faces thereof. Each torsional converter (1,51,53) has a cross-sectional inhomogeneity comprising a plurality of helically-extending grooves (2,55) extending substantially from end to end of the converter. The grooves (2,55) each have a length, measured axially along the converter (1,51,53), of approximately half the wavelength of ultrasonic vibrations therein. When the stack is energized, the stack and the converter (1) or converters (51,53) resonate together in a purely torsional-mode vibration. The apparatus (5,50) is compact and axisymmetric, and is straightforward to incorporate into a simple tool handpiece. The ultrasonic vibrations may be transmitted along a conventional elongate waveguide (3) of a tool to a distal operative tip (35).

Abstract: An ultrasonic surgical tool has an elongate waveguide operatively connected or connectable to a source of ultrasonic vibrations. An operative element at a distal end of the waveguide has a diameter less than that of the waveguide. A connecting portion of intermediate diameter may connect the operative element and the waveguide. A proximal end of the operative element forms a first step junction, located at a nodal plane of ultrasonic vibrations in the waveguide and operative element, producing a velocity amplitude gain across the step junction. A second zero-gain step junction between the connecting portion and the waveguide is located at an anti-nodal plane. The operative element may include a curved distal cutting and welding element having a pair of elongate welding grooves defining a cutting edge. Alternatively, the operative element may include a welding element having a flat or slightly ridged operative face.

Abstract: A transducer stack (10) includes rings (16) of piezo-electric ceramic alternating with metal electrodes (18) along a threaded central shaft (32) extending from a titanium back plate (20). A spacer or threaded element (14) threaded on to the shaft (32) holds the ceramic rings (16) and electrodes (18) in compression against the back plate (20). The transducer stack (10) is mountable eccentrically to a horn (12) of an ultrasonically-vibratable tool, away from an axis of an elongate waveguide (56) extending from the horn (12). The transducer stack (10) may vibrate in a flexural mode perpendicular to the waveguide (56), generating torsional mode ultrasonic vibrations in the horn (12) and waveguide (56), or in a flexural mode parallel to the waveguide (56), generating longitudinal mode ultrasonic vibrations in the horn (12) and waveguide (56).

Abstract: Apparatus (5,50) for generating torsional-mode ultrasonic vibrations comprises a stack of axially-polarised piezo-electric ceramic rings (10) having a torsional converter (1,51,53) mounted coaxially to either one face of the stack or to two opposite faces thereof. Each torsional converter (1,51,53) has a cross-sectional inhomogeneity comprising a plurality of helically-extending grooves (2,55) extending substantially from end to end of the converter. The grooves (2,55) each have a length, measured axially along the converter (1,51,53), of approximately half the wavelength of ultrasonic vibrations therein. When the stack is energised, the stack and the converter (1) or converters (51,53) resonate together in a purely torsional-mode vibration. The apparatus (5,50) is compact and axisymmetric, and is straightforward to incorporate into a simple tool handpiece. The ultrasonic vibrations may be transmitted along a conventional elongate waveguide (3) of a tool to a distal operative tip (35).

Abstract: A transducer stack (10) includes rings (16) of piezo-electric ceramic alternating with metal electrodes (18) along a threaded central shaft (32) extending from a titanium back plate (20). A spacer or threaded element (14) threaded on to the shaft (32) holds the ceramic rings (16) and electrodes (18) in compression against the back plate (20). The transducer stack (10) is mountable eccentrically to a horn (12) of an ultrasonically-vibratable tool, away from an axis of an elongate waveguide (56) extending from the horn (12). The transducer stack (10) may vibrate in a flexural mode perpendicular to the waveguide (56), generating torsional mode ultrasonic vibrations in the horn (12) and waveguide (56), or in a flexural mode parallel to the waveguide (56), generating longitudinal mode ultrasonic vibrations in the horn (12) and waveguide (56).

Abstract: An ultrasonic surgical tool has an elongate waveguide (102) operatively connected or connectable to a source of ultrasonic vibrations. An operative element (100, 130, 140) at a distal end of the waveguide (102) has a diameter less than that of the waveguide (102). A connecting portion of intermediate diameter may connect the operative element (100, 130, 140) and the waveguide (102). A proximal end of the operative element (100, 130, 140) forms a first step junction (126, 134), located at a nodal plane of ultrasonic vibrations in the waveguide (102) and operative element, producing a velocity amplitude gain across the step junction. A second zero-gain step junction between the connecting portion and the waveguide (102) is located at an anti-nodal plane. The operative element (100, 130) may comprise a curved distal cutting and welding element (114) having a pair of elongate welding grooves defining a cutting ridge.