INK CARTRIDGE FOR AN INK JET PRINTER

Abstract: An ink system (8) provides molten solid ink to an ink jet printer. The system has an ink reservoir (10), an ink sensor (11) for detecting the level of molten ink within the ink reservoir (10) and an ink cartridge (1) having a plurality of compartments (3) containing solid ink. A connection removably connects the solid ink cartridge (1) with the ink reservoir (10) and a heater (6) selectively heats each of the ink compartments. A control unit (20) controls the selective heating of each of the ink compartments (3) to melt the ink therein for supply through the connection to the ink reservoir (10) and issues an out-of-ink signal when all of the compartments (3) are empty.

Description: INK CARTRIDGE FOR AN INK JET PRINTER The present invention relates to ink jet printing apparatus and, more particularly, to an ink cartridge system for providing ink to such apparatus. A solid or hot melt ink of the type employed in ink jet printing is characteristically solid at room temperature. When the ink is heated, it melts and can be utilised for ink jet printing. Solid ink is generally provided to ink jet printing apparatus by means of a heated reservoir. A problem encountered in ink jet printers utilising reservoirs of solid ink is that the ink can be contaminated when it is added to the reservoir. Apparatus such as that disclosed in US-A-4823146 has been developed in order to reduce such contamination. That apparatus requires an inlet that allows the solid ink to be deposited from a sealed cartridge directly into the reservoir. Clearly, an open inlet such as that utilised in US-A-4823146 may still allow contamination of the ink in the reservoir. Also, during printing the reservoir is maintained at a temperature sufficient for the ink to remain molten. So, as all the ink supply is in the reservoir, it is all kept hot and degradation of the ink may occur over time. A large portion of the printing apparatus is also kept hot, and there is considerable power consumption. The present invention sets out to reduce ink contamination and to reduce the volume of ink maintained in a molten state and hence power consumption and ink degradation. According to the present invention there is provided an ink system for providing molten solid ink to an ink jet printer, the system comprising: an ink reservoir; an ink sensor for detecting the level of molten ink within the ink reservoir; an ink cartridge having a plurality of co-npartnents, each of the compartments containing solid ink; connection means for removably connecting the solid ink cartridge with the ink reservoir; heating means for selectively heating each of the ink compartments; and control means for controlling the selective heating of each of the ink compartments to melt the ink therein for supply through the connection means to the ink reservoir; and for issuing an out of ink signal when all of the compartments are empty. Preferably, the control means controls the selective application of heat by the steps of: receiving a demand for ink signal according ~ o the level of molten ink within the ink reservoir; determining which of the ink compartments have been heated and so are not full; commanding the heating means to heat a full ink compartment; and commanding the heating means to heat a further full ink compartment if the demand for ink signal is still received . The connection means may suitably comprise a barb which can connect to an ink passageway in the cartridge forming a sealed connection. It is desirable that the system also comprises a means of applying pressure to each of the ink compartments in order to facilitate the ejection of molten ink. This pressure may be applied by springs positioned contiguous to the solid ink compartments or by a pressurised gas surrounding collapsible ink compartments. The means of applying pressure to each of the ink compartments may be disposed in the ink cartridge or externally to it. The heating means may also be disposed in the ink cartridge or externally to it. The present invention includes a solid ink cartridge comprising : an outer casing; a plurality of solid ink pellets, each of the pellets being contained in a sealed ink compartment; and an ink passage connected to each of the ink compartments . Thus, it can be seen that the invention provides a clean and contamination free replaceable ink cartridge, and a system of supplying ink from this cartridge in an incremental and, therefore, energy efficient way. The invention will now be described in further detail with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of an example of the invention; Figure la is a schematic diagram of the cross-section of the ink cartridge shown in figure 1 ; Figure 2 is an isotropic view of an example of an ink cartridge ; Figure 3 is an isotropic view of another example of an ink cartridge; and Figure 4 is an exploded view of an example of a connection means in an ink cartridge. Referring to figures 1 and la, there is shown a solid ink cartridge 1 in a solid ink cartridge system 8. Ink pellets 2 are sealed inside ink compartments 3 adjacent to which springs 4 are disposed. The ink compartments 3 are connected to an ink passage 5. The cartridge has a housing 7 which ensures the correct alignment of the cartridge 1 in the system 8 necessary for proper location of a barb 9 in the ink passage 5 and correct positioning of the heater segments 6 contiguous to the ink compartments 3 and ink pellets 2. When the cartridge is in place and a control means 20 receives a demand for ink signal from a level sensor 11 the ink is supplied to an ink reservoir 10. The control means 20 commands a heater segment 6 to heat an ink compartment 3 containing an ink pellet 2 for a set length of time. The length of time is such that all the ink is melted and squeezed out of the compartment before the heater is turned off. If the demand for ink signal is still being received when the heater segment 6 is turned off then a further ink pellet 2 in another ink compartment 3 is melted. This continues until the demand for ink signal ceases, or there are no more ink pellets 2 left in the ink cartridge 1 at which time the control means 20 outputs an out of ink signal. There is also a sensor that detects if a cartridge is present and an out of ink signal is also outputted if no cartridge is detected. The molten ink is ejected from the ink compartments 3 under pressure exerted by the springs 4 which apply a force of around 20 N to the exterior of each of the ink compartments 3 via inflexible plates (not shown) which ensure an even pressure is applied. The molten ink is ejected into the ink passage 5 in which the barb 9 is located, allowing the ink to flow through the barb 9, along a heated hose 21, into the reservoir 10. From here the ink is supplied on demand through an ink outlet 13 to a printhead 12. It can be appreciated that the ink reservoir can be relatively small in comparison to a conventional reservoir within which an entire supply of ink must be contained. Referring to the example of an ink cartridge shown in figure 2, six ink pellets 14 are located inside ink compartments 15 in an ink cartridge 16. The ink compartments 15 are made from metal foil so that they collapse when pressure is applied in order to eject the ink. The casing 16 is shaped to connect with a corresponding receptacle in such a way that the barb 9 is correctly aligned with the ink passage 17. The ink compartments 15 may alternatively be made in the form of thin walled ointment tubes such as those found containing toothpaste, as illustrated in figure 3. In this arrangement a filler slug may be placed in each ink compartment 15 to reduce the amount of unused ink due to the shape of these compartments. Also to aid ejection of the ink as the ink is melted, a spring may slide along the outer surface of each tube towards the end of the tube at which the ink is ejected, squeezing the ink out by flattening the tube. In both of these examples a septum 18 is held in place over the ink passage 17 such that, when the barb 9 pierces the septum 18 and connects with the ink passage 17 ink flows from the cartridge through the barb 9. The septum 18 is held in place by a retainer 19, as shown in the exploded view of figure 4.

Claims: CLAIMS 1. An ink system for providing molten solid ink to an ink jet printer, the system comprising: an ink reservoir; an ink sensor for detecting the level of molten ink within the ink reservoir; an ink cartridge having a plurality of compartments, each of the compartments containing solid ink; connection means for removably connecting the solid ink cartridge with the ink reservoir; heating means for selectively heating each of the ink compartments; and control means for controlling the selective heating of each of the ink compartments to melt the ink therein for supply through the connection means to the ink reservoir; and for issuing an out of ink signal when all of the compartments are empty. 2. An ink system according to claim 1, wherein the control means controls the selective application of heat by the steps of: receiving a demand for ink signal according to the level of molten ink within the ink reservoir; determining which of the ink compartments have been heated and so are not full; commanding the heating means to heat a full ink compartment; and commanding the heating means to heat a further full ink compartment if the demand for ink signal is still received. 3. An ink system according to claims 1 or 2 , wherein the connection means comprises a barb forming a sealed connection with an ink passageway of the ink cartridge. 4. An ink system according to any of the preceding claims, further comprising means for applying pressure to each of the ink compartments. 5. An ink system according to claim 4, wherein the means for applying pressure to each of the ink compartments is disposed in the ink cartridge. 6. An ink system according to claim 4, wherein the means for applying pressure to each of the ink compartments is disposed externally to the ink cartridge. 7. An ink system according to any of claims 4 to 6 , wherein the means for applying pressure comprises one or more springs positioned contiguous with the ink compartments . 8. An ink system according to any of claims 4 to 6, wherein the means for applying pressure comprises a pressurised gas surrounding the ink compartments, and the ink compartments have collapsible walls. 9. An ink system according to any of claims 1 to 8 , wherein the heating means is disposed in the ink cartridge. 10. An ink system according to any of claims 1 to 9 , wherein the heating means is disposed externally to the ink cartridge . 11. A solid ink cartridge comprising: an outer casing; a plurality of solid ink pellets, each of the pellets being contained in a sealed ink compartment; and an ink passage connected to each of the ink compartments.

Inventors: OTT ROBERT JOSEPH, OTT, ROBERT, JOSEPH
Applicants: DOMINO PRINTING SCIENCES PLC, OTT ROBERT JOSEPH, OTT, ROBERT, JOSEPH
Application year: 1998
Main classification: B41J2
IPC codes: B41J2