Drop generator

A drop generator that includes a pressure chamber and an outlet channel that includes a circular outlet channel section and a non-circular outlet channel section.

BACKGROUND OF THE DISCLOSURE

The subject disclosure is generally directed to drop generators that can be useful for applications such as ink jet printing.

Drop on demand ink jet technology for producing printed media has been employed in commercial products such as printers, plotters, and facsimile machines. Generally, an ink jet image is formed by selective placement on a receiver surface of ink drops emitted by a plurality of drop generators implemented in a printhead or a printhead assembly. For example, the printhead assembly and the receiver surface are caused to move relative to each other, and drop generators are controlled to emit drops at appropriate times, for example by an appropriate controller. The receiver surface can be a transfer surface or a print medium such as paper. In the case of a transfer surface, the image printed thereon is subsequently transferred to an output print medium such as paper.

A known ink jet drop generator structure employs an electromechanical transducer to displace ink from an ink chamber into a drop forming outlet passage, and it can be difficult to control drop velocity and/or drop mass.

DETAILED DESCRIPTION OF THE DISCLOSURE

FIG. 1is schematic block diagram of an embodiment of a drop-on-demand printing apparatus that includes a controller10and a printhead assembly20that can include a plurality of drop emitting drop generators. The controller10selectively energizes the drop generators by providing a respective drive signal to each drop generator. Each of the drop generators can employ a piezoelectric transducer. As other examples, each of the drop generators can employ a shear-mode transducer, an annular constrictive transducer, an electrostrictive transducer, an electromagnetic transducer, or a magnetorestrictive transducer. The printhead assembly20can be formed of a stack of laminated sheets or plates, such as of stainless steel.

FIGS. 2 and 3are a schematic plan view and a schematic elevational view of an embodiment of a drop generator30that can be employed in the printhead assembly20of the printing apparatus shown inFIG. 1. The drop generator30includes an inlet channel31that receives ink33from a manifold, reservoir or other ink containing structure. The ink33flows into a pressure or pump chamber35that is bounded on one side, for example, by a flexible diaphragm37. An electromechanical transducer39is attached to the flexible diaphragm37and can overlie the pressure chamber35, for example. The electromechanical transducer39can be a piezoelectric transducer that includes a piezo element41disposed for example between electrodes43that receive drop firing and non-firing signals from the controller10. Actuation of the electromechanical transducer39causes ink to flow from the pressure chamber35to a drop forming outlet channel45, from which an ink drop49is emitted toward a receiver medium48that can be a transfer surface, for example. The outlet channel45can include a nozzle or orifice47at an end thereof.

The ink33can be melted or phase changed solid ink, and the electromechanical transducer39can be a piezoelectric transducer that is operated in a bending mode, for example.

The outlet channel45generally includes a plurality of sections or segments of differently shaped cross-sections. For example, the outlet channel45can include a first circular outlet channel section451having a circular cross-section, a first non-circular outlet channel section452having a non-circular cross-section, a second circular outlet channel section453having a circular cross-section, and a second non-circular outlet channel section454having a non-circular cross-section. By way of illustrative example, the first circular outlet channel section451is connected to the ink pressure chamber35, the first non-circular outlet channel section452is connected to the first circular outlet channel section451, the second circular outlet channel section453is connected to the first non-circular outlet channel section452, and the second non-circular outlet channel section454is connected to the second circular outlet channel section453. As another example, the outlet channel45can include a non-circular outlet channel section connected to the ink chamber35, a circular outlet channel section connected to the non-circular outlet channel section and a non-circular outlet channel section connected to the circular outlet channel section.

The first circular outlet channel section451can have substantially co-axial circular sub-sections451A,451B,451C of different cross-sectional areas, for example. Similarly, the second circular outlet channel section453can have substantially co-axial circular sub-sections453A,453B,453C of different cross-sectional areas.

The first non-circular outlet channel section452can have an oval cross-section, while the second non-circular outlet channel section454can have an egg-shaped cross-section. The nozzle or aperture can be located at a smaller end of the egg-shaped cross section, for example at a center of the radius of the end of the cross-section having the smaller radius.

The first circular outlet channel section451, the first non-circular outlet channel section452, and the second circular outlet channel section453can be centered on an outlet channel axis CA. For the example of a second non-circular outlet channel section454having an egg shaped cross-section, the center of the radius of the larger end of the egg-shaped cross-section can be located on the outlet channel axis CA and the nozzle or aperture would offset from the outlet channel axis CA.

The first circular outlet channel section451can have a length L1that is less than about 20/1000 inches, for example in the range of about 11/1000 inches to about 13/1000 inches. The first circular outlet channel section451can have an average diameter in the range of about 10/1000 inches to about 20/1000 inches, for example. The first circular outlet channel section451can also have an average diameter in the range of about 11/1000 inches to about 13/1000 inches. Average diameter refers to the average of the diameters of the sub-sections of the first circular outlet channel section451.

The second circular outlet channel section453can have a length L3that is less than about 40/1000 inches, for example in the range of about 24/1000 inches to about 26/1000 inches. The second circular outlet channel section453can have an average diameter in the range of about 8/1000 inches to about 15/1000 inches. As another example, the second circular outlet channel section453can have an average diameter in the range of about 12/1000 inches to about 14/1000 inches. Average diameter refers to the average of the diameters of the sub-sections of the second circular outlet channel section453.

The first non-circular channel section452can have a length L2that is less than about 40/1000 inches, for example in the range of about 27/1000 inches to about 29/1000 inches. The first non-circular outlet channel section can have an effective diameter in the range of about 10/1000 inches to about 20/1000 inches, for example. As another example, the first non-circular outlet channel section452can have an effective diameter in the range of about 15/1000 inches to about 17/1000 inches. Effective diameter refers to a diameter of a circle having the same area as the cross-sectional area of the first non-circular outlet channel section452.

The second non-circular outlet channel section454can have a length L4in the range of about 4/1000 inches to about 10/1000 inches. As another example, the second non-circular outlet channel section454can have a length L4in the range of about 7/1000 inches to about 9/1000 inches. The second non-circular outlet channel section454can have an effective diameter in the range of about 8/1000 inches to about 16/1000 inches. By way of further example, the second non-circular outlet channel section454can have an effective diameter in the range of about 13/1000 inches to about 16/1000 inches. Effective diameter refers to a diameter of a circle having the same area as the cross-sectional area of the second non-circular outlet channel section454.

The outlet channel45can have an overall length in the range of about 59/1000 inches to about 79/1000 inches. As another example, the outlet channel45can have an overall length in the range of about 69/1000 inches to about 77/1000 inches.

The nozzle or aperture47can have a length of about 1.5/1000 inches, and a diameter of about 41.5 micrometers.

The ink chamber35can be generally parallelogram shaped or generally rectangular, for example. The corners of the ink chamber35can be rounded. By way of illustrative example, the ink chamber35can have a height or thickness H in the range of about 3/1000 inches to about 5/1000 inches, a width W in the range of about 29/1000 inches to about 37/1000 inches, and a length L in the range of about 38/1000 inches to about 47/1000 inches. By way of further example, the ink chamber35can have a height or thickness H in the range of about 4/1000 inches, a width W in the range of about 33/1000 inches to about 35/1000 inches, a length L in the range of about 42/1000 inches to about 44/1000 inches. The width W and the length L refer to those dimensions of a parallelogram or rectangle that define the area of a parallelogram or rectangle.

The inlet31and the outlet channel45can be connected to the ink chamber35at opposing corner regions of a generally trapezoidal or generally rectangular ink chamber35, for example. By way of illustrative example, the inlet31can have a length in the range of about 49/1000 inches to about 62/1000 inches, a width in the range of about 6/1000 inches to about 10/1000 inches, and a height in the range of about 2/1000 inches to about 5/1000 inches.

By way of illustrative example, the drop generator can operate at a drop emitting frequency in the range of about 23 KHz to about 30 KHz. The drop generator can emit drops having a drop mass in the range of about 20 nanograms to about 30 nanograms, for example. As another example, the drop generator can emit drops having a mass in the range of about 23 nanograms to about 27 nanograms.