GB2389817A

GB2389817A - Ink cartridge containing a coil for ink flow control

Info

Publication number: GB2389817A
Application number: GB0304346A
Authority: GB
Inventors: Clive Drake
Original assignee: OPPORTUNITY EUROP LIMIMTED
Current assignee: OPPORTUNITY EUROP LIMIMTED
Priority date: 2002-06-21
Filing date: 2003-02-26
Publication date: 2003-12-24
Anticipated expiration: 2023-02-26
Also published as: GB0214370D0; GB2389817B; GB0304346D0

Abstract

An inkjet cartridge including a chamber (10), and means for controlling the flow of ink from the chamber in the form of a coil (a). The coil may be made of stainless steel. The coil (a) may be located in a trough formed in the bottom of the cartridge so that it is constantly immersed in ink. The ends of the coil may be sealed and the arrangement is such that the outside of the coil communicates with the ink chamber (10), while the centre of the coil communicates with a discharge outlet of the cartridge. The interaction of the viscosity of the ink in the chamber (10) and the surface drag within the gap between adjacent turns of the coil (a) acts to control the flow of the ink from the chamber.

Description

INKJET CARTRIDGES

Field of the Invention

This invention relates to inkjet cartridges, i.e. to ink cartridges for use in inkjet printers.

Background to the Invention

An inkjet printer includes a very precise micro-pump, i.e. there is a mechanism which, on the inlet side, produces a suction force which is then converted into the ejection of a liquid ink drop onto the medium beneath it.

If ink simply flooded out of the ink cartridge with no flood regulation, then the print head would simply be a valve which opened and closed to permit ink to flow, but this would not enable

the precise formation of an ink drop, which is what is required for digital printing.

The inkjet cartridges at present in use thus typically include a sponge the purpose of which is only to release the ink when the print head is actually creating a demand for it. This demand manifests itself as a suction force that is generated by the print head. If the ink is released too easily, the print head will flood and produce drops of varying sizes. If the ink is released too slowly, then ink starvation results. The print that is formed can thus have many drops missing, which are recognised as white lines. The optimum suction range is between about 4 and 50 mbar, depending on the properties of the printing liquid.

In currently available sponge-based inkjet cartridges, the sponge is compressed thereby producing a capillary force that regulates the flow of ink, i.e. the ink is released only when the print head suction is sufficiently great to overcome the capillary force of the sponge.

This arrangement has a number of disadvantages, as follows: a) as the cartridge is emptied during use, the ink has to travel further through the sponge, requiring an increased force to pull the ink into the print head, thus producing diminishing print quality during the final part of the life of the cartridge,

( 3 b) as the cartridge and the sponge will inevitably retain some of the impregnated ink, the actual yield of the cartridge falls a long way below the theoretical maximum, thus wasting ink, c) as the cartridge reaches the end of its print life, the print head will have to work harder to suck ink from the furthest extremities of the sponge, thus shortening the life of the print head, and d) the only inks which can be used are those which are not affected by the sponge and do not themselves affect the sponge.

It is an object of the present invention to provide an improved form of inkjet cartridge.

It is a more specific object of the present invention to provide an inkjet cartridge the design of which is such as to avoid the disadvantages of the sponge-based cartridges' as outlined above.

Summary of the Invention

According to the present invention there is provided an ink-

jet cartridge that includes a chamber for ink and means for controlling the flow of ink from the chamber in the form of a coil of sheet material.

The coil of sheet material is preferably of thin stainless steel sheet which is rolled into a coil in such manner that the tension in the coil ensures a substantially constant gap between adjacent turns of the coil.

The stainless steel sheet preferably has a length of the order of 30 mm. and is preferably so wound that the coil extends through at least two revolutions, and preferably less than three revolutions.

The coil preferably extends through two and a quarter revolutions.

The coil is preferably located in a trough formed in the bottom of the cartridge so that it is constantly immersed in ink.

The ends of the coil are preferably sealed and the arrangement is preferably such that the outside of the coil communicates with the inkcontaining chamber of the cartridge, while the centre of the coil communicates with the discharge outlet of the cartridge.

Communication between the centre of the coil and the discharge outlet is preferably via a feed column which provides a head of the order of 20 mm. to ensure a constant even feed of ink to the printer.

The arrangement will thus be such that the viscosity of the ink and the surface drag within the gap between adjacent turns of the coil provides the required resistance to maintain a constant head pressure within the cartridge.

Brief Descrintion of the Drawings

Figure 1 is a sectional view of the base of a first embodiment of inkjet cartridge, Figure 2 is a sectional view of the inkjet cartridge of Figure 1 at right angles to the section of Figure 1, Figure 3 is a perspective view of a spiral coil that sits in the base of the inkjet cartridge, Figure 4 is a sectional view, similar to Figure 1, of a second form of inkjet cartridge, Figure 5 is a sectional view similar to Figure 1, of a third form of inkjet cartridge, and Figure 6 is a sectional view of the cartridge of Figure 5 along the line 5 - 5 of Figure 5.

Description of the Preferred Embodiments

The inkjet cartridge shown in Figures 1 to 3 of the drawings is intended to be used in a standard inkjet printer having a print head mounted on a carriage that traverses a page to which ink is to be applied. The cartridge includes a chamber 10 within which the ink is contained and, at the base of the chamber 10, there is a trough 11 in which a stainless steel coil "a" is located. The stainless steel coil "a" comprises two and a quarter revolutions of micro-thin stainless steel sheet 30 mm. long wound into a spiral

coil in such manner that the tension in the coil ensures that there is a small, substantially constant gap between adjacent turns of the coil "a".

The interaction of the viscosity of the ink in the chamber 10 and the surface drag within the gap between adjacent turns of the coil "a" ensures that the required flow resistance is obtained to maintain the constant head pressure within the cartridge and the 2G (twice the force of gravity) impulse generated by the print head's carriage movement as it traverses the page during printing.

The stainless steel coil "a" thus acts as a flow control coil.

The flow control coil ita" is mounted at its ends between seals "b" and "c" and the flow control coil "a" is employed to induce the ink flow to the print head by vacuum-assisted gravity flow.

Positioning of the coil "a" in the trough 11 ensures that it is constantly immersed in ink and there is a 20 mm. head feed column "d" to ensure that there is a constant even feed of ink from the chamber 10 as and when the printer demands it.

The embodiment shown in Figure 4 functions in the same way as the embodiment described above. It includes a stainless steel flow control coil "a", as described above, which is contained in the base of the chamber 10 so that it is constantly immersed in the ink in the chamber 10. The coil "a" is sealed at its two ends and there is again a 20 mm. head feed column "d" to ensure that a constant even flow of ink from the chamber is maintained.

In the embodiment shown in Figures 5 and 6, there is again a stainless steel flow control coil "a", that is as described above, and the flow control coil "a" is sealed at its two ends by being mounted in adaptors 12 and 13 that are connected by a bridge piece 14 that serves to hold the adaptors 12 and 13 securely in position in the base of the chamber 10 of the cartridge. There is again a 20 mm. head feed column "d" to ensure that a constant even flow of ink from the chamber is maintained.

The provision of the stainless steel control coil "a'' reduces or avoids the various disadvantages of the known inkjet cartridges which contain sponges, as referred to in the introduction hereto.

Claims

( Claims:

1. An inkjet cartridge that includes a chamber for ink and means for controlling the flow of ink from the chamber in the form of a coil of sheet material.

2. An inkjet cartridge as claimed in Claim 1, in which the coil of sheet material is of thin stainless steel sheet. a

3. An inkjet cartridge as claimed in Claim 2, in which the stainless steel sheet is rolled into a coil in such manner that the tension in the coil ensures a substantially constant gap between adjacent turns of the coil.

4. An inkjet cartridge as claimed in Claim 2 or Claim 3, in which the stainless steel sheet has a length of the order of 30 mm.

5. An inkjet cartridge as claimed in Claim 4, in which the stainless steel sheet is so wound that the coil extends through at least two revolutions.

6. An inkjet cartridge as claimed in Claim 5, in which the stainless steel coil extends through less than three revolutions.

7. An inkjet cartridge as claimed in any one of the preceding claims, in which the coil extends through two and a quarter revolutions.

8. An inkjet cartridge as claimed in any one of the preceding claims, in which the coil is located in a trough formed in the bottom of the cartridge so that it is constantly immersed in ink.

9. An inkjet cartridge as claimed in any one of the preceding claims, in which the ends of the coil are sealed and the arrangement is such that the outside of the coil communicates with the ink-containing chamber of the cartridge, while the centre of the coil communicates with the discharge outlet of the cartridge.

10. An inkjet cartridge as claimed in Claim 9, in which I communication between the centre of the coil and the discharge outlet is via a feed column which provides a head of the order of 20 mm. to ensure a constant even feed of ink to the printer.

11. An inkjet cartridge constructed and arranged to function substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

Amendments to the claims have been filed as follows: 1. An inkjet cartridge that includes a chamber for ink and means for controlling the flow of ink from the chamber in the form of a coil of sheet material so arranged that the ink flows between adjacent turns of the coil.

2. An inkjet cartridge as claimed in Claim 1, in which the coil of sheet material is of stainless steel sheet.

4. An inkjet cartridge as claimed in Claim 2 or Claim 3, in which the stainless steel sheet has a length of about 30 mm.

5. An ink-jet cartridge as claimed in Claim 4, in which the stainless steel sheet is so wound that the coil extends through at least two revolutions.

10. An inkjet cartridge as claimed in Claim 9, in which communication between the centre of the coil and the discharge outlet is via a feed column which provides a head of about 20 mm.

to ensure a constant even feed of ink to the printer.