Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2000-01-19
2001-03-13
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C141S114000, C141S351000
Reexamination Certificate
active
06199975
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to print heads for ink jet printers. The invention relates more particularly to an ink jet printer having an ink jet print head which can be displaced in the direction of a line of print between side walls of a printer frame, and having an ink filling device for filling the ink jet print head.
Ink jet print heads have a limited ink supply, which is generally sufficient for printing about 1-4 million printed characters. In the case of ink jet printers which must be available day and night, on weekends and even during holiday periods, such as those in fax machines, for example, and in uses with a high permanent loading, such as in cash register printers, the ink supply stored in the ink jet print head is not sufficient.
It has therefore already been proposed, in Japanese Patent Document JP-A-90 29 991, to refill an ink jet print head while it is installed in an ink jet printer. For this purpose, the ink jet print head is equipped with level detectors, which detect its minimum and maximum permissible ink level. If the level falls below the minimum, the ink jet print head is transported with its feed opening underneath an ink refilling device where, with the aid of an electromagnet, a nozzle connected to an ink reservoir which is placed higher up is lowered into the feed opening and is lifted off the latter after the maximum level has been reached.
This arrangement ensures that the ink jet print head is always ready to print. On the other hand, the amount of ink transferred into the ink jet print head is determined by electrically controlled means and depends only on a level detector. If the voltage supply fails during a filling operation, or if the level detector fails, the ink flow from the ink reservoir cannot be interrupted.
U.S. Pat. No. 4,178,595 discloses an ink jet printer in which the ink jet print head is arranged such that it can be displaced in the direction of a line of print between side walls of the printer frame. The feed opening is arranged on one side wall of the ink jet print head, and a discharge opening of an ink filling device is arranged on one side wall of the printer frame, aligned coaxially with the feed opening. In this case, the feed opening can be connected to the discharge opening in a liquid-tight manner by displacement of the ink jet print head in the direction of a line of print toward the discharge opening.
The discharge opening of the ink filling device is fitted to a variable-volume cylinder which, when its volume is increased, removes ink from an ink reservoir and, when its volume is reduced, discharges ink through the discharge opening. The cylinder is dimensioned such that it picks up and discharges only a small amount of ink in each case. When its volume is reduced, a connecting line between the cylinder and the ink reservoir is closed, so that no ink can flow from the ink reservoir into the cylinder or back from the cylinder into the ink reservoir. The reduction in volume of the cylinder is carried out by a piston which can be displaced with the aid of an electromagnet, the increase in volume is carried out by a spring which pushes the piston back. The amount of ink to be transferred into the ink jet print head is determined by the period during which current is applied to the electromagnet.
The known ink filling device additionally needs an electromagnet and additional outlay on control for the electromagnetic. In addition, the electromagnet has to be of powerful design, since it has to produce the flow pressure for the ink, and has to overcome the friction of the piston in the cylinder and the restoring force of the spring.
SUMMARY OF THE INVENTION
One object of the present invention is to provide an ink jet printer having an ink filling device for an ink jet print head and an ink jet print head that can be filled therewith. Another object of the present invention is to provide such an ink jet printer and print head wherein only a specific amount of ink is transferred into the ink jet print head without requiring additional outlay for the drive system.
In meeting these and other objects, features and advantages of the present invention, an ink jet printer is provided having a print head which can be displaced in the direction of a line of print between sidewalls of a printer frame. The printer has an ink filling device by which the print head can be filled while it is installed in the ink jet printer. The filling device has an ink reservoir and a discharge opening. The print head has an ink chamber with a feed opening for receiving ink. The discharge opening is fitted to a variable-volume hollow body which, when its volume it increased, removes ink from the ink reservoir and, when its volume is reduced, discharges ink through the discharge opening. The feed opening is arranged on one sidewall of the print head and the discharge opening is arranged on one sidewall of the printer frame and is aligned coaxially with the feed opening. The feed opening can be connected to the discharge opening in a liquid-tight manner by displacement of the ink jet print head in the direction of a line of print toward the discharge opening. The hollow body is arranged on the inside of the sidewall of the printer frame. The reduction in volume is performed by a further displacement of the print head toward the sidewall beyond the point where the feed opening of the print head is connected to the discharge opening. An increase in volume is carried out by a displacement of the print head in the opposite direction with the existing connection between the feed opening and the discharge opening.
The invention is based on the idea that the drive motor, which is needed in any case to displace the ink jet print head between the side walls of the ink jet printer along the line of print, can be used to influence the volume of the hollow body, if the hollow body is arranged on the side wall of the printer frame. The same drive motor is used for docking the ink jet print head with the discharge opening. The reduction in volume is then carried out by further displacement of the ink jet print head toward the side wall, beyond the point at which the feed opening of the ink jet print head is connected to the discharge opening. An increase in volume is carried out by displacing the ink jet print head in the opposite direction. Therefore, the drive motor needed to displace the print head along the line of print, preferably a stepping motor, can also be used to influence the volume of the hollow body, with the effect of triple use. This means that no additional drive elements are necessary.
The arrangement according to the invention has the advantage that only a well-metered volume of ink can pass to the ink jet print head. With regards to the flow of ink, the arrangement has an inherently safe operating state during every operating state of the ink jet printer. Only when the hollow body is being acted on with the effect of reducing its volume is the discharge opening opened. When the volume is constant or when the volume of the hollow body is being increased, the discharge opening is securely closed, so that no ink can flow out.
In an advantageous development of the invention, the amount of ink discharged from the ink filling device to the ink jet print head is determined by the magnitude of the adjustment or the further displacement. As a result, even ink jet print heads which have been partly emptied can be filled with the necessary amount of ink, and the use of ink jet print heads having different holding capacities is possible without changing the arrangement. The hollow body is then only partially emptied. As its volume is increased, its filling is also then only carried out in accordance with the amount of ink removed.
According to a further development of the invention, the time and/or the amount of ink of an ink fill can be controlled on the basis of a prescribable number of printed dots or printed characters that are printed. This is because the ink jet print head was inserted into the ink jet printer and, aft
Baitz Gunter
Burchart Joachim
Le N.
Nguyen Judy
Schiff & Hardin & Waite
Siemens Nixdorf Informationssysteme Aktiengesellschaft
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