Piezoelectrically driven ultrasonic transducer

An ultrasonic transducer comprising:

• a first cylindrical member including a mechanical vibration amplifying part formed in symmetry around the axis thereof and having a gradually increased cross-sectional area toward a base portion thereof, said base portion being formed with an axially thinnest walled portion and at flat surface perpendicular to the axis thereof, and an annular rigid part integrally formed with said mechanical vibration amplifying part coaxially therewith, said annular rigid part being extended from said thinnest walled portion axially and radially outwardly to have sufficient rigidity and weight, and said annular rigid part being provided, in the proximity of said thinnest walled portion, with an annular groove which axially extends from the surface of said annular rigid part to a depth which at least corresponds to the axial thickness of said thinnest walled portion of said mechanical vibration amplifying part;
• a second cylindrical member comprising a backing block of a cylindrical body, the base portion of which is formed with a flange and a flat surface perpendicular to the axis thereof;
• an ultrasonic transducer portion interposed between said flat surfaces of said first and second cylindrical members and including a pair of piezoelectric elements having flat surfaces perpendicular to the axis of said first and second cylindrical members, and an electrode plate interposed between said pair of piezoelectric elements;
• and
• fastening means for pressingly abutting said flat surfaces of said piezoelectric elements against said flat surfaces of said first and second cylindrical members and integrally clamping said annular rigid part and said flange of said second cylindrical member to each other in a manner to circumvent said annular groove and said ultrasonic transducer portion, wherein
• said first cylindrical member is one member comprising said mechanical vibration amplifying part of a stepped type horn,
• said base portion is formed in a disc like shape of small volume, and
• said annular rigid part which connects to said annular thinnest walled portion of said base portion, and which has an annular axial groove having a predetermined depth provided adjacent to said annular thinnest walled portion to reduce the area of said flat surface of said first cylindrical member contacting said piezoelectric element has four axial threaded holes at positions superposing on said annular groove;
• said second cylindrical member comprises a hat-shaped solid member having a petal type flange of larger diameter than that of said flange of said first cylindrical member, said petal type flange having four holes at the projecting part thereof;
• said ultrasonic transducer portion comprises said piezoelectric elements having a disc-like shape, said electrode plate having a thin disc-like shape and two circular sheets inserted between said piezoelectric elements and flat surfaces of said first and second cylindrical members, said piezoelectric elements and electrode plate are connected to an ultrasonic oscillator, and the diameters of said piezoelectric elements, electrode plate and two circular sheets are smaller than that of said flat surface of said first cylindrical member;
• and
• said fastening means comprises four bolts respectively inserted into four holes of said petal type flange of said second cylindrical member and said four threaded holes of said annular rigid part of said first cylindrical member;
• and further including supporting means comprising an annular member having a stepped portion to be engaged with the outer periphery of said annular rigid part and having four axial holes, an annular supporting member having four threaded axial holes and four bolts respectively inserted into said four axial holes of said annular member and said four threaded axial holes of said annular supporting member, thereby supporting the ultrasonic transducer by sandwiching said annular rigid part between said annular member and annular supporting member,
• whereby cracking of piezoelectric elements is prevented to ensure stabilized operations without transitional variations in electric impedance and resonance frequency and to allow continuous vibrating operations of large amplitude over a long period of time.

An ultrasonic transducer comprising:

• a first cylindrical member including a mechanical vibration amplifying part formed in symmetry around the axis thereof and having a gradually increased cross-sectional area toward a base portion thereof, said base portion being formed with an axially thinnest walled annular portion and a flat surface perpendicular to the axis thereof, and an annular rigid part integrally formed with said mechanical vibration amplifying part coaxially therewith, said annular rigid part being extended from said thinnest walled portion axially and radially outwardly to have sufficient rigidity and weight, and said annular rigid part being provided, in the proximity of said thinnest walled portion, with an annular groove which axially extends from the surface of said annular rigid part to a depth which at least corresponds to the axial thickness of said thinnest walled portion of said mechanical vibration amplifying part;
• a second cylindrical member comprising a backing block of a cylindrical body, the base portion of which is formed with a flange and a flat surface perpendicular to the axis thereof;
• an ultrasonic transducer portion interposed between said flat surfaces of said first and second cylindrical members and including a pair of piezoelectric elements having flat surfaces perpendicular to the axis of said first and second cylindrical members, and an electrode plate interposed between said pair of piezoelectric elements;
• and
• fastening means for pressingly abutting said flat surfaces of said piezoelectric elements against said flat surfaces of said first and second cylindrical members and integrally clamping said annular rigid part and said flange of said second cylindrical member to each other in a manner to circumvent said annular goove and said ultrasonic transducer portion, wherein
• said first cylindrical member is one member comprising said mechanical vibration amplifying part of a stepped type horn having a threaded tip portion,
• said base portion is formed in a disc-like shape of small volume, and
• said annular rigid part which connected to said annular thinnest walled portion of said base portion, and which has an annular axial groove having predetermined depth provided adjacent to said annular thinnest walled portion to reduce the area of said flat surface of said first cylindrical member contacting said piezoelectric element has four axial threaded holes at positions superposing on said annular groove;
• said second cylindrical member comprises a hat-shaped solid member having a petal type flange of larger diameter than that of said flange of said first cylindrical member, and having a small threaded projection coaxially formed therefrom, and an annular member having the same outer diameter as that of said hat-shaped solid member and having a threaded inner wall for engaging with said threaded projection, said petal type flange having four holes at the projecting parts thereof;
• said ultrasonic transducer portion comprises said piezoelectric elements having a disc-like shape, said electrode plate having a thin disc-like shape and two circular sheets inserted between said piezoelectric elements and flat surfaces of said first and second cylindrical members, said piezoelectric elements and electrode plate are connected to an ultrasonic oscillator, and the diameters of said piezoelectric elements, electrode plate and two circular sheets are smaller than that of said first cylindrical member;
• and
• said fastening means comprises four bolts respectively inserted into four holes of said petal type flange of said second cylindrical member and said four threaded holes of said annular rigid part of said first cylindrical member;
• further comprising supporting means comprising an annular member having a stepped portion to be engaged with the outer periphery of said annular rigid part and having four axial holes, an annular supporting member having four threaded axial holes and four bolts respectively inserted into said four axial holes of said annular member and said four threaded axial holes of said annular supporting member, thereby supporting the ultrasonic transducer by sandwiching said annular rigid part between said annular member and annular supporting member, and
• further including an ultrasonic machining tool comprising a disc shape member having an annular leg portion which has a threaded inner wall to engage with said threaded tip portion of said mechanical vibration amplifying part,
• whereby cracking of piezoelectric elements is prevented to ensure stabilized operations without transitional variations in electric impedance and resonance frequency and to allow continuous vibrating operations of large amplitude over a long period of time.

An ultrasonic transducer comprising:

• a first cylindrical member including a mechanical vibration amplifying part formed in symmetry around the axis thereof and having a generally increased cross-sectional area toward a base portion thereof, said base portion being formed with an axially thinnest walled portion and a flat surface perpendicular to the axis thereof, and an annular rigid part integrally formed with said mechanical vibration amplifying part coaxially therewith, said annular rigid part being extended from said thinnest walled portion axially and radially outwardly to have sufficient rigidity and weight, and said annular rigid part being provided, in the proximity of said thinnest walled portion, with an annular groove which axially extends from the surface of said annular rigid part to a depth which at least corresponds to the axial thickness of said thinnest walled portion of said mechanical vibration amplifying part;
• a second cylindrical member comprising a backing block of a cylindrical body, the base portion of which is formed with a flange and a flat surface perpendicular to the axis thereof;
• an ultrasonic transducer portion interposed between said flat surfaces of said first and second cylindrical members and including a pair of piezoelectric elements having flat surfaces perpendicular to the axis of said first and second cylindrical members, and an electrode plate interposed between said pair of piezoelectric elements;
• and
• fastening means for pressingly abutting said flat surfaces of said piezoelectric elements against said flat surfaces of said first and second cylindrical members and integrally clamping said annular rigid part and said flange of said second cylindrical member to each other in a manner to circumvent said annular groove and said ultrasonic transducer portion, wherein
• said first cylindrical member comprises
• an annular member having a threaded inner wall and forming a base part of a stepped type horn, said base portion being formed in a disc like shape of small volume, and said annular rigid part being connected to said annular thinnest walled portion of said base portion, said annular rigid part having an annular axial groove with predetermined depth provided adjacent to said annular thinnest walled portion to reduce the area of said flat surface of said first cylindrical member contacting said piezoelectric element and having four axial threaded holes at positions superposing on said annular groove;
• a tip cylindrical member having a threaded inner wall and forming a tip part of said stepped type horn;
• and
• a bolt having a threaded outer wall for engaging with said threaded inner walls of said annular member and tip cylindrical member in the whole of length to integrally fasten said annular member and said tip cylindrical member;
• said second cylindrical member comprises:
• a first hollow cylindrical member having a threaded inner wall and a petal type flange of a larger diameter than that of said flange of said first cylindrical member, said petal type flange having four holes at the projecting parts thereof;
• a second hollow cylindrical member for adjusting the resonance vibration having a threaded inner wall;
• and
• a bolt having a threaded outer wall for engaging with said threaded inner walls of said first and second hollow cylindrical members to integrally fasten the members, said ultrasonic transducer portion comprises said piezoelectric elements having a disc-like shape, said electrode plate having a thin disc-like shape and two circular sheets inserted between said piezoelectric elements and flat surfaces of said first and second cylindrical members, said piezoelectric elements and electrode plate are connected to an ultrasonic oscillator, and the diameters of said piezoelectric elements, electrode plate and two circular sheets are smaller than that of said flat surface of said first cylindrical member;
• and
• said fastening means comprises four bolts respectively inserted into four holes of said petal type flange of said second cylindrical member, four holes of an annular spacer and said four threaded holes of said annular rigid part of said first cylindrical member;
• and further including supporting means comprising an annular member having a stepped portion to be engaged with the outer periphery of said annular rigid part and having four holes, an annular supporting member having four threaded axial holes, and four bolts respectively inserted into said four axial holes of said annular member and into said four threaded axial holes of said annular supporting member, thereby supporting the ultrasonic transducer by sandwiching said annular rigid part between said annular member and annular supporting member
• whereby cracking of piezoelectric elements is prevented to ensure stabilized operations without transitional variations in electric impedance and resonance frequency and to allow continuous vibrating operations of large amplitude over a long period of time.