MXPA98007283A - Ink supply systems for ink jet printheads - Google Patents

Abstract

An ink supply system for an ink jet printhead (10) having orifices (14) includes an air pump (52) and an ink reservoir (38) connected through a valve (34) and a luer connection (33) to an ink supply container (28). The reservoir has a desired ink level sensor (44), a low ink condition sensor, and a control unit (50) controlling the pump responsive to the low ink condition sensor to produce a vacuum in the reservoir, thereby drawing ink from the container. A restricted passage (56) connects the reservoir to atmosphere through a filter (54). A purge reservoir (42) is connected to a supply line (24) leading from the ink reservoir to the printhead. Another air pump (64) applies air pressure to the purge reservoir. A solenoid valve (40) in the line between the purge reservoir and the ink reservoir is closed for ink refill and purging.

Description

"INK SUPPLY SYSTEMS FOR INK JET PRINT HEADS" DESCRIPTION TECHNICAL FIELD This invention relates to ink supply systems for ink jet printheads.

ANTECEDENTS OF THE TECHNIQUE In many ink jet print heads it is important to maintain a negative pressure in the orifices from which the ink is ejected in order to avoid ink bleeding from the orifices when the print head is not operating. In addition, it is occasionally necessary to purge the print head by ejecting the ink under pressure through the print head. It is also necessary in many cases to refill the reservoir from which the ink is supplied to the print head from a distant ink supply periodically, in order to maintain a desired level of ink in the ink reservoir, and to provide a supply of distant ink that connects quickly and easily with the print head, in an economical way. Certain prior art arrangements such as those described in the Robinson Patent Number 4,187,511, the Matsumoto Patent Number 4,536,777, the Eremity Patent and others Number 4,602,662 and the Mizusawa Patent and other Number Number 4,677,448 provide a distant ink supply from where the ink is attracted to a reservoir for an ink jet head by a vacuum arrangement, but these arrangements are complicated and expensive. In other prior art arrangements, such as described for example in the Okamura Patent and other Nos. 5,485,187, the level of ink in the reservoir from which the ink is supplied to a print head is maintained at a desired separation by below the holes in the print head, in order to produce a desired negative pressure in the holes in the ink jet head and a positive pressure can be applied for the purge, but the ink level in a distant ink supply it must be the same as the ink level in the tank. The prior art furthermore does not disclose a simple and inexpensive dual-tank ink supply system for an ink jet print head wherein the ink in the reservoir can be maintained at a desired level, while allowing convenient replenishment of the reservoir from a distant ink supply that can be placed at any level and which also provides means for purging the print head in a convenient manner, and provides a simple and convenient arrangement for connecting and remove a distant ink supply.

EXHIBITION OF THE INVENTION Accordingly, an object of the present invention is to provide a dual reservoir ink supply system for ink jet print heads that overcomes the disadvantages of the prior art. Another object of the invention is to provide a dual-tank vacuum ink supply system for an ink jet print head wherein the ink in an ink reservoir that delivers the ink to the print head is normally maintained at a desired level while providing means for purging the print head when necessary and for replenishing the ink reservoir in a convenient and economical manner. These and other objects of the invention are achieved by providing an ink supply system that it includes an ink reservoir capable of being connected with a distant ink supply and an air pump connected to the ink reservoir whereby a vacuum can be applied to draw the ink from the distant ink supply through a valve, towards the ink tank. The ink reservoir includes an ink sensor for detecting the presence of the ink at a desired level in the reservoir, and the ink supply system also provides a purge reservoir where the ink is normally kept at the same level as the reservoir from ink, and where pressure can be applied to purge the print head when another valve connecting the purge tank and the ink tank is closed. Preferably, an air pump is provided to apply vacuum to the ink tank for replenishment from the remote ink supply and another air pump is provided to apply pressure to the ink in the purge tank when purging is required. The valves that control the communication between the tanks of preference are solenoid valves. To allow for convenient replacement of the distant ink supply, a friction fit connection must be used.

BRIEF DESCRIPTION OF THE DRAWINGS Additional objects and advantages of the invention will become apparent from a reading of the following description along with the accompanying drawings, in which: Figure 1 is a schematic diagram illustrating a representative embodiment of an ink supply system for an ink jet print head positioned in accordance with the invention; and Figure 2 is a perspective and detailed view illustrating a representative embodiment of a remote ink supply unit.

BEST MODE FOR CARRYING OUT THE INVENTION In the typical embodiment of the invention illustrated in Figure 1, an inkjet print head 10 has an orifice plate 12 formed with holes 14 from which the ink droplets are selectively ejected in response to the impulses. pressure applied to the ink, in a corresponding ink pressure chamber 16 which is schematically illustrated in the drawing. A filter 18 interposed between the pressure chamber 16 and the holes 14 is designed to trap the solid particles that are large enough to block the holes 14 but to allow the smaller solid particles pass through the orifice, as described for example, in Moynithan's copending application Serial No. 08 / 231,102, filed on April 22, 1994, the disclosure of which is incorporated herein by reference. - Each pressure chamber 16 receives the ink from an internal print head collector 20 which in turn is supplied with the ink through a filter 22 connected to the ink receiving line 24. To provide the ink for the ink jet print head 10, a remote ink supply unit 28 having an air vent 30 and an ink filter 32 is connected through a connector 33 with a valve 34. of normally closed solenoid leading to an ink supply line 36. If desired, the solenoid valve 34 can be replaced by a check valve oriented to prevent ink from flowing from the line 36 to the ink supply unit 28. The internal filter 32 in the ink supply unit 28 is provided to protect the print head in the event of any contamination that is introduced into the ink which may cause the print head to fail and also to filter any solid material introduced into the ink. ink supply unit during manufacture and assembly. This avoids the need to clean the supply container and to fill the supply unit in a clean environment. The connector 33 forms an airtight friction fit between the tapered narrow-fit male and female parts, thereby providing a convenient and economical structure by which the ink supply unit 28 can be easily connected and disconnected from the system. A representative embodiment of the remote ink supply unit 28 according to the invention is illustrated in Figure 2. In that embodiment, the ink supply unit consists of a plastic cup 80 and a cover 82 of plastic sealed to the cup. by ultrasonic welding around the flange 84 of the vessel. The cover 82 has an opening 86 in which a filler plug 88 is similarly welded after the unit has been filled with ink. In addition, a tube 92 extends towards the bottom of the vessel from a housing 94 of the connector formed in the cover and an air vent 90 is provided in the housing 94. The filter 32 is inserted in the connector housing _, and a plastic female connector 96 and then sealed in the connector housing, for example, by welding ultrasonic to complete the assembly of the ink supply unit 28. For installation in an inkjet system, a female connector 98 at the end of the ink supply line 36 that opens into the print head is frictionally adjusted on the female connector 96 in the manner shown in Figure 1. Preferably, the male connector 98 It is made of stainless steel. The ink supply line 36 is connected to a vacuum tank 38 and is also connected via a normally open solenoid valve 40 to a purge tank 42 and to the ink receiving line 24 of the print head. Within the vacuum reservoir 38, an ink level sensor 44 is provided to control the level of the ink in the reservoir. In order to replenish the supply of ink in the vacuum reservoir 38, a control unit 50 responds to the detection of a low ink level in the reservoir, as represented by a signal supplied on a line 45 from the detector 44, sending signals through a line 70 to open the solenoid valve 34, through a line 51 to operate the air pump 52 that pumps the air out of the reservoir 38 and through a line 48 to close the solenoid valve 40 . This creates a vacuum in the vacuum reservoir that attracts the ink from the unit 28 of supply of distant ink through the valve 34 open towards the vacuum tank. When a predetermined period of time has elapsed sufficient to refill but not to excessively fill the vacuum tank, the air pump 52 is turned off and the valves 34 and 40 are returned to their normal state. The remaining vacuum in the reservoir attracts air from the atmosphere through a filter 54 and a passage 56 restrained back towards the reservoir so that the ink in the reservoir is maintained at atmospheric pressure. Restricted passage 56, which may, for example, be an orifice with a diameter of approximately .254 millimeters or may be a section of reduced diameter conduit, deviates from air pump 52 and provides a sufficiently high air flow rate. low to prevent short circuit of the air pump 52 during operation, but high enough to cause the ink in the tank 38 to be maintained at atmospheric pressure during the use of the print head. The air pump 52 for example, can be a simple and economical diaphragm pump of the type used to supply the air to the aquarium which produces a negative air pressure suitable for drawing the ink from the ink supply unit 28 through the filter 32, when the ink supply is placed upwards at a distance of about 30.48 centimeters or more below the reservoir 38. If the ink has not reached the level of the sensor 44 after one or two cycles of pump operation, indicating that the unit 28 of the remote ink supply is empty, the control unit 50 activates a signal 72 to warn the operator to replace the remote ink supply unit. In order to control the pressure and the ink and in the hole 14 at a desired negative level to prevent it from flowing out of the hole, the ink sensor 44 in the empty tank is placed at a level 58 which is "below the level". 60 of the orifice 14 by a distance 62 which for example can be from about 2.54 to 10.16 centimeters to produce a corresponding negative pressure of about 2.54 to 10.16 centimeters, of the water calibrator in the orifice 14. The purge tank 42 is connected to a air pump 64 which is similar to air pump 52 but is oriented in the opposite direction in order to apply air pressure in the purge tank during operation A restricted passage 66 which may be an orifice of approximately .254 millimeter diameter of a section of small diameter conduit deflects the air pump and flows into a filter 68 through which the purge tank is connected to the atmosphere to prevent contamination by air attracted to the tank. As in the case of the restricted passage 56, the passage 66 is small enough to prevent shorting of the air pump 64, but large enough to allow the ink in the purge tank 42 to be maintained at atmospheric pressure during the operation of the system. Consequently, as long as the solenoid valve 40 remains open and is not functioning in any of the air pumps 52 and 64, the level of the ink in the purge tank 42 will be the same as that in the vacuum reservoir 38 after any ink flow between the tank touches. It is necessary to purge the ink from the print head 10 to clear the holes 14 and the related ink passages in the print head, the normally open solenoid valve 40 is closed by a signal on a line 70 from the control unit 50 and operation of the air pump 64 is initiated by a signal on a line 72 in order to apply pressure to the ink in the purge tank 42, causing the pressure of the ink in the print head to be increased and from this force the ink out of the holes in the hole plate and the adjacent passages inside the print head to clear those passages from air bubbles or trash. Since the air pumps 52 and 64 can be simple and economical diaphragm pumps, the ink supply system of the invention eliminates the complexity and expense in piston-type pumps that require a piston that moves in airtight relationship to the piston. fluid up to a cylinder such as have been used in conventional ink supply systems to transfer the ink from a distant ink supply to an ink reservoir. As mentioned above, the negative air pressure generated by these air pumps is high enough to cause the ink to be attractively attracted from an ink supply that is essentially below the level of the ink tank and through any Necessary ink filter so that the distant ink supply can be placed anywhere in the appliance. In addition, adhesion and separation of the ink supply unit 28 can be achieved in a quick and economical manner by using the connection. Although the invention has been described herein with reference to a specific embodiment, many modifications and variations will readily occur to those skilled in the art. By Consequently, all these variations and modifications are included within the proposed scope of the invention.

Claims (20)

R E I V I N D I C A C I O N E S:

1. An ink supply arrangement for an ink jet print head comprising: an ink reservoir connected to an ink jet print head for supplying ink thereto; an ink supply container connected to the ink reservoir through a supply valve positioned to prevent the ink from passing from the ink reservoir to the ink supply container; and an air pump connected to the ink reservoir to generate a vacuum therein in order to attract the ink from the ink supply container to the ink reservoir.

An ink supply arrangement according to claim 1, including: a passage of restricted air by deflecting the air pump and opening to the atmosphere in order to keep the ink in the reservoir at atmospheric pressure when it is not running the air pump.

3. An ink supply arrangement according to claim 2, and including: a filter through which the restricted passage communicates with the atmosphere.

4. An ink supply arrangement according to claim 1, wherein the supply valve is a solenoid valve.

5. An ink supply arrangement according to claim 1, wherein the supply valve is a check valve. -

6. An ink supply arrangement according to claim 1, including: a filter in the ink supply container to prevent the solid contaminants in the ink therein from passing to the ink tank when the ink is attracted to the reservoir from the ink supply container.

7. An ink supply arrangement according to claim 1, including: an ink supply line connecting the ink reservoir to an ink jet print head; a purge tank connected to the ink supply line; and a valve normally open in the ink supply line between the purge tank and the ink tank which is placed to close during the purge operation and when a vacuum is generated in the ink tank.

8. An ink supply arrangement according to claim 7, including: an additional air pump positioned to supply air under pressure to the purge tank to raise the pressure of the ink in the supply line and a jet print head of ink connected therewith so as to cause the ink in the print head to be ejected through the ink jet holes therein.

9. An ink supply arrangement according to claim 8, including: a restricted passage connecting the purge tank to the atmosphere and diverting the additional air pump.

10. An ink supply arrangement according to claim 9, including: a filter between the purge reservoir and the atmosphere through which the purge reservoir communicates with the atmosphere.

11. An ink supply arrangement according to claim 1, including: an ink level sensor in the ink reservoir; and a control unit for controlling the operation of the air pump in accordance with the signals received from the ink level sensor.

12. An ink supply arrangement according to claim 10: wherein the control unit controls the operation of the air pump to cause the ink to be attracted to the ink reservoir for a predetermined period of time after the sensor of ink level transmits a signal to the control unit.

An ink supply arrangement according to claim 12: wherein the level of the ink in the ink tank detected by the ink level sensor is positioned at a position below the level of a hole in the ink head. ink jet printing to provide a desired liquid or negative pressure loading in the hole in the ink jet head.

An ink supply arrangement according to claim 1, including: an ink supply line connecting the ink supply container with the supply valve; a connector in the ink transmission line to facilitate adhesion and separation of the ink supply container.

15. An ink supply arrangement for an ink jet printhead comprising: an ink container; an air vent in the ink container; an ink outlet from the ink container through which the ink can be removed; and a connection arrangement for connecting the ink outlet from the ink container to the ink entry line for an ink jet printhead.

16. An ink supply arrangement according to claim 15, including: an ink filter in the ink outlet from the ink container.

17. An ink supply arrangement according to claim 15, wherein the ink package comprises: a plastic cup; and a plastic cover; the plastic cup and plastic cover are welded together around the periphery of the plastic cup.

18. An ink supply arrangement according to claim 15, wherein: the ink outlet from the ink package includes a female connector and the ink entry line contains a male connector.

19. An ink supply arrangement according to claim 18, wherein: the ink outlet from the ink container and the female connector are made of plastic material and are joined together.

20. An ink supply arrangement according to claim 18, wherein the male connector is made of stainless steel.