Apparatus for exciting an array of ink jet nozzles and method of forming

An apparatus for simultaneously exciting a plurality of pressurized ink streams to produce substantially uniform droplets in each stream including:

• a plurality of ink jet nozzles;
• means to mount said ink jet nozzles in a linear array so that their axes are substantially parallel to each other;
• means cooperating with said mounting means to form an ink supply cavity for said ink jet nozzles;
• an arcuate sector of a cylinder of a piezoelectric material having its mean radius, its wall thickness, and its arcuate angle selected so that said arcuate sector vibrates only in a selected symmetrical mode at a selected resonant frequency when a voltage at the selected resonant frequency is applied, said arcuate being disposed adjacent said cavity to periodically produce pressure waves in the ink within said cavity when said arcuate sector vibrates at the selected resonant frequency in the selected symmetrical mode with the amplitude of each pressure wave being substantially uniform at the entrance to each of said ink jet nozzles to simultaneously excite the ink stream in each of said ink jet nozzles periodically to produce the ink droplets from each of the streams with the ink droplets of each of the streams being of substantially uniform size and each of the streams having substantially the same break-off point;
• said mounting means including a substantially planar wall, the side of said wall of said mounting means in communication with said cavity having inclined surfaces on opposite sides of a line connecting the axes of said ink jet nozzles to direct each of the periodic pressure waves toward said ink jet nozzles;
• said arcuate sector having a length greater than the length of the linear array of said ink jet nozzles;
• means to apply a voltage of a selected magnitude at the selected resonant frequency to said arcuate sector to cause vibrations only in the selected symmetrical mode of said arcuate sector at the selected resonant frequency, the selected magnitude of the voltage being strong enough to produce satellite free droplets;
• said arcuate sector being disposed relative to the linear array of said ink jet nozzles so that the amplitude of each of the periodic pressure waves applied to the ink streams in said ink jet nozzles by said arcuate sector vibrating at the selected resonant frequency is substantially uniform at the entrance to each of said ink jet nozzles;
• and said arcuate sector constituting a boundary wall of said ink cavity with said boundary wall contacted by ink in said ink cavity and said arcuate sector being disposed opposite the entrance to each of said ink jet nozzles.

An apparatus for simultaneously exciting a plurality of pressurized ink streams to produce substantially uniform droplets in each stream including:

• a plurality of ink jet nozzles;
• means to mount said ink jet nozzles in a linear array so that their axes are substantially parallel to each other;
• means cooperating with said mounting means to form an ink supply cavity for said ink jet nozzles;
• an arcuate sector of a cylinder of a piezoelectric material having its mean radius, its wall thickness, and its arcuate angle selected so that said arcuate sector vibrates only in a selected symmetrical mode at a selected resonant frequency when a voltage at the selected resonant frequency is applied, said arcuate sector being disposed adjacent said cavity to periodically produce pressure waves in the ink within said cavity when said arcuate sector vibrates at the selected resonant frequency in the selected symmetrical mode with the amplitude of each pressure wave being substantially uniform at the entrance to each of said ink jet nozzles to simultaneously excite the ink stream in each of said ink jet nozzles periodically to produce the ink droplets from each of the streams with the ink droplets of each of the streams being of substantially uniform size and each of the streams having substantially the same break-off point;
• said mounting means including a substantially planar wall, the side of said wall of said mounting means in communication with said cavity having inclined surfaces on opposite sides of a line connecting the axes of said ink jet nozzles to direct each of the periodic pressure waves toward said ink jet nozzles;
• said arcuate sector having a length greater than the length of the linear array of said ink jet nozzles;
• means to apply a voltage of a selected magnitude at the selected resonant frequency to said arcuate sector to cause vibrations only in the selected symmetrical mode of said element at the selected resonant frequency, the selected magnitude of the voltage being strong enough to produce satellite free droplets;
• and said arcuate sector being disposed relative to the linear array of said ink jet nozzles so that the amplitude of each of the periodic pressure waves applied to the ink streams in said ink jet nozzles by said arcuate sector vibrating at the selected resonant frequency is substantially uniform at the entrance to each of said ink jet nozzles.

An apparatus for simultaneously exciting a plurality of pressurized ink streams to produce substantially uniform droplets in each stream including:

• a plurality of ink jet nozzles;
• means to mount said ink jet nozzles in a linear array;
• means cooperating with said mounting means to form an ink supply cavity for said ink jet nozzles;
• and an element of piezoelectric material having a geometry that causes said element to vibrate only in a selected symmetrical mode at a selected resonant frequency when a voltage at the selected resonant frequency is applied, said element being disposed adjacent said cavity to periodically produce pressure waves in the ink within said cavity when said element vibrates at the selected resonant frequency in the selected symmetrical mode with the amplitude of each pressure wave being substantially uniform at the entrance to each of said ink jet nozzles to simultaneously excite the ink stream in each of said ink jet nozzles periodically to produce the ink droplets from each of the streams with the ink droplets of each of the streams being of substantially uniform size and each of the streams having substantially the same break-off point.

An apparatus for simultaneously exciting a plurality of pressurized ink streams to produce substantially uniform droplets in each stream including:

• a plurality of ink jet nozzles;
• means to mount said ink jet nozzles in a linear array;
• means cooperating with said mounting means to form an ink supply cavity for said ink jet nozzles;
• an arcuate sector of a cylinder of a piezoelectric material having its mean radius, its wall thickness, and its arcuate angle selected so that said arcuate sector vibrates only in a selected symmetrical mode at a selected resonant frequency when a voltage at the selected resonant frequency is applied, said arcuate sector being disposed adjacent said cavity to periodically produce pressure waves in the ink within said cavity when said arcuate sector vibrates at the selected resonant frequency in the selected symmetrical mode with the amplitude of each pressure wave being substantially uniform at the entrance to each of said ink jet nozzles to simultaneously excite the ink stream in each of said ink jet nozzles periodically to produce the ink droplets from each of the streams with the ink droplets of each of the streams being of substantially uniform size and each of the streams having substantially the same break-off point;
• and said arcuate sector constituting a boundary wall of said ink cavity with said boundary wall contacted by ink in said ink cavity, said arcuate sector being disposed opposite the entrance to each of said ink jet nozzles, said arcuate sector being disposed relative to the linear array of said ink jet nozzles so that the amplitude of each of the periodic pressure waves applied to the ink streams in said ink jet nozzles by said arcuate sector vibrating at the selected resonant frequency is substantially uniform at the entrance to each of said ink jet nozzles.

An apparatus for simultaneously exciting a plurality of pressurized ink streams to produce substantially uniform droplets in each stream including:

• a plurality of ink jet nozzles;
• means to mount said ink jet nozzles in a linear array;
• means cooperating with said mounting means to form an ink supply cavity for said ink jet nozzles;
• and an arcuate sector of a cylinder of a piezoelectric material having its mean radius, its wall thickness, and its arcuate angle selected so that said arcuate sector vibrates only in a selected symmetrical mode at a selected resonant frequency when a voltage at the selected resonant frequency is applied, said arcuate sector being disposed adjacent said cavity to periodically produce pressure waves in the ink within said cavity when said arcuate sector vibrates at the selected resonant frequency in the selected symmetrical mode with the amplitude of each pressure wave being substantially uniform at the entrance to each of said ink jet nozzles to simultaneously excite the ink stream in each of said ink jet nozzles periodically to produce the ink droplets from each of the streams with the ink droplets of each of the streams being of substantially uniform size and each of the streams having substantially the same break-off point.

A method of forming an apparatus for simultaneously exciting a plurality of pressurized ink streams to produce substantially uniform droplets in each stream including:

• disposing a plurality of ink jet nozzles in a linear array and in communication with an ink supply cavity;
• selecting the mean radius, the wall thickness, and the arcuate angle of an arcuate sector of a cylinder of piezoelectric material so that the arcuate sector vibrates only in a selected symmetrical mode at a selected resonant frequency, when a voltage is applied at the selected resonant frequency to the arcuate sector, to produce periodic pressure waves in the ink cavity with the amplitude of each pressure wave being substantially uniform at the entrance to each of the ink jet nozzles to form the ink droplets of each of the streams of substantially uniform size with each of the streams having substantially the same break-off point;
• disposing the arcuate sector adjacent the ink cavity so that it produces the periodic pressure waves in the ink cavity when the voltage at the selected resonant frequency is applied to the arcuate sector to cause vibration of the arcuate sector only in the selected symmetrical mode at the selected resonant frequency;
• and disposing the arcuate sector as a boundary wall of the ink cavity for contact with ink in the ink cavity and opposite the entrances to the ink jet nozzles.