Ultrasonic sheet feeder, low-profile ultrasonic motor, and method of driving the same

A low-profile ultrasonic motor comprising:

• a pair of resonators, each having an upper arm portion and a lower arm portion in opposing relation to each other, and each having a bottom portion formed by connecting one end of the upper arm portion to one end of the lower arm portion, and each of said pair of resonators having a U-shaped longitudinal section;
• a convex shell having a protruding middle portion and being connected to the other end of the upper arm portion of each of said pair of resonators;
• a support portion connected to the other end of the lower arm portion of each of said pair of resonators;
• piezoelectric ceramic elements respectively mounted on the upper arm portion of each of said pair of resonators;
• and
• a roller urged into opposing relation with the middle portion of said convex shell.

A low-profile ultrasonic motor comprising:

• a pair of resonators, each having two arm portions in opposing side-by-side spaced relation to each other, and each having a bottom portion formed by connecting one end of one of the arm portions to a corresponding one end of the other arm portion, and each of said pair of resonators having a U-shaped cross section;
• a convex shell having a protruding middle portion and being connected to the other end of the arm portions of said pair of resonators;
• piezoelectric ceramic elements having different polarization directions on each of said pair of resonators and being respectively mounted on the arm portions of said pair of resonators;
• and
• a roller urged into opposing relation with the middle portion of said convex shell.

A method of driving a low-profile ultrasonic motor, said low-profile ultrasonic motor including a pair of resonators each having two arm portions in opposing upper and lower relation to each other and said pair of resonators each having a bottom portion formed by connecting one end of one of the arm portions to a corresponding one end of the other arm portion and each of said pair of resonators having a U-shaped longitudinal section, a convex shell having a protruding middle portion, said convex shell being connected to the other end of one of said two arm portions of one of said pair of resonators and being connected to the other end of a corresponding one of said two arm portions of the other of said pair of resonators, piezoelectric ceramic elements respectively mounted on one of the arm portions of each of said pair of resonators, and a roller urged into opposing relation with said middle portion of said convex shell, comprising the steps of:

• applying a driving power source to said piezoelectric ceramic elements;
• driving said piezoelectric ceramic elements at a resonance frequency at which said convex shell is translated;
• setting a phase difference of about 90.degree. between vibration displacements output from said piezoelectric ceramic elements to produce elliptical movement of said middle portion of said convex shell;
• and
• rotating said roller in a resonance mode as said piezoelectric ceramic elements are driven at said resonance frequency.

A method of driving a low-profile ultrasonic motor, said low-profile ultrasonic motor including a pair of resonators each having an upper arm portion and a lower arm portion in opposing relation to each other and each of said pair of resonators having a bottom portion formed by connecting one end of the upper arm portion to one end of the lower arm portion and each of said pair of resonators having a U-shaped longitudinal section, a convex shell having a protruding middle portion and said convex shell being connected to the other end of the upper arm portion of each of said pair of resonators, a support portion connected to the other end of the lower arm portion of each of said pair of resonators, piezoelectric ceramic elements respectively mounted on the upper arm portion of each of said pair of resonators, and a roller urged into opposing relation with said middle portion of said convex shell, comprising the steps of:

• applying a driving power source to said piezoelectric ceramic elements;
• driving said piezoelectric ceramic elements at a resonance frequency at which said convex shell is translated;
• setting a phase difference of about 90.degree. between vibration displacements output from said piezoelectric ceramic elements to produce elliptical movement of said middle portion of said convex shell;
• and
• rotating said roller in a resonance mode as said piezoelectric ceramic elements are driven at said resonance frequency.

A method of driving a low-profile ultrasonic motor, said low-profile ultrasonic motor including a pair of resonators each having two arm portions in opposing side-by-side spaced relation to each other and said pair of resonators each having a bottom portion formed by connecting one end of one of the arm portions to a corresponding one end of the other arm portion and each of said pair of resonators having a U-shaped cross section, a convex shell having a protruding a middle portion, said convex shell being connected to the other end of the upper arm portion of each of said pair of resonators, piezoelectric ceramic elements having different polarization directions on each of said pair of resonators and said piezoelectric ceramic elements being respectively mounted on the arm portions of said pair of resonators, and a roller urged into opposing relation with said middle portion of said convex shell, comprising the steps of:

• applying a driving power source to said piezoelectric ceramic elements;
• driving said piezoelectric ceramic elements at a resonance frequency at which said convex shell is translated;
• setting a phase difference of about 90.degree. between vibration displacements output from said piezoelectric ceramic elements on one of said pair of resonators with respect to the piezoelectric ceramic elements on the other of said pair of resonators to produce elliptical movement of said middle portion of said convex shell;
• and
• rotating said roller in a resonance mode as said piezoelectric ceramic elements are driven at said resonance frequency.

A method of driving a low-profile ultrasonic motor, said low-profile ultrasonic motor including a pair of resonators each having two arm portions in opposing side-by-side spaced relation to each other and said pair of resonators each having a bottom portion formed by connecting one end of one of the arm portions to a corresponding one end of the other arm portion and each of said pair of resonators having a U-shaped cross section, a convex shell having a protruding a middle portion, said convex shell being connected to the other end of the upper arm portion of each of said pair of resonators, piezoelectric ceramic elements having different polarization directions on each of said pair of resonators and said piezoelectric ceramic elements being respectively mounted on the arm portions of said pair of resonators, and a roller urged into opposing relation with said middle portion of said convex shell, comprising the steps of:

• applying a driving power source to said piezoelectric ceramic elements;
• driving said piezoelectric ceramic elements at a resonance frequency at which said convex shell is translated;
• setting a phase difference of at least one of about 90.degree. and about 270.degree. between vibration displacements output from said piezoelectric ceramic elements on one of said pair of resonators with respect to the piezoelectric ceramic elements on the other of said pair of resonators to produce elliptical movement of said middle portion of said convex shell;
• and
• rotating said roller in a resonance mode as said piezoelectric ceramic elements are driven at said resonance frequency.