WO2010139336A1

WO2010139336A1 - Ink trap

Info

Publication number: WO2010139336A1
Application number: PCT/DK2010/050124
Authority: WO
Inventors: Michael JØRGENSEN
Original assignee: Enilorak Aps
Priority date: 2009-06-03
Filing date: 2010-06-03
Publication date: 2010-12-09

Abstract

Ink trap, for collecting used ink from a capping station (2) for a printing head (1), wherein the ink trap comprises a waste ink reservoir (10) connected to the capping station (2), which waste ink reservoir is substantially airtight, and which reservoir is connected to an air inlet (13) via a first valve (12) and an air outlet (14), where a pump (5) is arranged in the air outlet (14) for evacuating air from the waste ink reservoir (10), where an ink outlet (23), comprising a second valve (21) and a pump (22), is arranged adjacent a lower section of the waste ink reservoir.

Description

Ink trap

Field of the Invention

The present invention relates to an ink trap as well as a printing device including an ink trap.

Background of the Invention

In the art printers are used for transferring an image to a printable surface as for example a foil, paper or the like. Before the printer initiates printing it will usually purge itself, i.e. clean the printing head by issuing a certain quantity of ink through the printing head in order to remove any dust, dried-up ink or other foreign material from the printing head as such in order to make the printing head ready for action.

This procedure is performed in a capping station which will absorb or in any other way accumulate the discharged ink together with any foreign matter. The capping station is traditionally connected to an ink waste tank by means of a pump. The pump may be a traditional pump such that a tube section will connect the capping station with the pump, and the pump with the waste tank, or as is often the case the pump may be a peristaltic pump, wherein the tube is left unbroken through the pump between the capping station and the waste tank.

As the amount of ink issued during the purge of the printer head is very limited, only a very limited ink flow will be present in the flexible hose. Especially for inks comprising solvents the limited flow will cause the volatile parts of the ink, i.e. the solvents to evaporate and in many instances the remaining ink portions to crystallize. Ink crystals are relatively hard and sharp and as such damages the relatively soft hoses causing leakage in the hoses. It is therefore necessary to replace the hose, clean the pump and destroy the accumulated ink at regular intervals. Object of the Invention

The present invention aims at avoiding these drawbacks by providing a system wherein the limited amount of ink is kept liquid at all times and evaporation is avoided and furthermore where the accumulated waste ink under certain circumstances may be reused.

Description of the Invention

The present invention solves this problem by providing an ink trap for collecting used ink from a printing head through a capping station in, wherein the ink trap comprises a waste ink reservoir connected to the capping station, which waste ink reservoir is substantially airtight, and which reservoir is connected to an air inlet via a first valve and an air outlet, where a pump is arranged in the air outlet for evacuating air from the waste ink reservoir, where an ink outlet, comprising a second valve and a pump, is arranged adjacent a lower section of the waste ink reservoir in fluid connection with a waste ink container.

In this manner the purged ink from the printer head when positioned in the capping station is sucked into the ink reservoir by means of the air pump. Consequently no liquid ink will be present in the hose connection the capping station with the ink reservoir such that the above-mentioned crystallization of the ink in the flexible hose is avoided altogether. By furthermore keeping the reservoir substantially evacuated, i.e. in popular terms at a vacuum, the ink in the reservoir will not dry out and will therefore remain liquid.

As the ink in the ink reservoir needs to be transferred to the waste ink container the first valve opens allowing air into the reservoir and at the same time the second valve and the pump is activated such that the waste ink in the reservoir is pumped from the reservoir into a waste ink container. The air inlet and the ink outlet opening valves and pumps are coordinated such that the under-pressure inside the reservoir is substantially maintained during the operation.

In a further advantageous embodiment of the invention a float switch is arranged in the waste ink reservoir, where the first and second valves are solenoid valves, and where said float switch generates an input to a control circuit, which control circuit generates output to the appropriate pump and/or solenoid valve, in order to evacuate the collected ink from the waste ink reservoir when a certain predetermined amount of ink has accumulated in the waste ink reservoir.

The provision of the float switch makes it possible to activate the evacuation procedure once a certain minimum quantity of ink has been accumulated inside the reservoir such that the first and second valves and the connected pumps are only activated for short periods of time, i.e. when the reservoir needs to be emptied into the waste tank.

Typically, the ink reservoir will accumulate a volume of between 30 ml and 50 ml before the float switch activates the solenoid valves allowing the waste ink to be transferred to the waste ink container. By using solenoid valves, electric pumps etc. it is possible to hook the entire ink trap up to the existing electrical system already provided in the printer and as such no major installation needs to be carried out in order to install the ink trap in existing printers.

In a further advantageous embodiment the tubes connecting the capping station, the different valves, the different pumps and reservoir are latex or latex based tubes.

With the types of pumps usually installed in printers of this type the latex or latex based tubes ensures that the ink can be pumped. As the problems with crystallization as already mentioned above are avoided with the present system, the problems relating the crystals causing leaks in the relatively soft latex tubes are avoided such that a relatively long life expectancy may be provided with the present construction.

A further advantage of using latex or latex based tubes is the fact that they are very flexible such that the tubes may be accommodated inside the printer without interfering with the existing construction. Other types of tubes such as silicone, polyethylene, PVC and the like may also be used with the present invention, especially since the tubes, for the most part only will contain air, as the ink is sucked rapidly to the waste ink tank and/or container. The invention is also directed at a printer of the type having a printing head using a capping station, where said printing head is parked in a capping station, wherein an ink trap as described above is arranged in fluid connection with the capping station.

As already hinted above, the ink trap according to the present invention maybe installed during manufacture of the printer such that it becomes an integrated part of the overall printer construction or it may be retrofitted to already existing printers in that the ink trap as such does not require much space or any special constructions which are not either already provided by existing printers or which may easily be modified for use with existing printers, for example power supply, tube outlets etc. The appropriate tube connections may be installed using standard tube connectors etc.

The control circuit controlling the opening and closing of the solenoid valves and the activation of the various pumps may be a separate unit provided with the ink trap such that it specifically operates in response to for example the float switch or may be connected to the printer as such, such that the solenoid valves and the pumps are activated after a certain number of purges has taken place by the printing head in the capping station.

In a still further advantageous embodiment the printer has a dedicated ink trap provided for each separate colour and/or printing head. In this manner it becomes possible to collect the different colours in different waste ink reservoirs such that the pure ink may be re-used which depending on the type of printer and print-job concerned may provide further savings.

Description of the Drawing

The invention will now be further explained with reference to the accompanying drawings wherein

Fig. 1 illustrates a prior art system Fig. 2 schematically illustrates the invention In figure 1 is illustrated an existing system where a printing head is parked in a capping station 2. The capping station 2 is by means of a flexible hose 3 in fluid communication with a waste ink container 4. In order to facilitate the transport of the waste ink from the capping station 2 to the waste ink container 4 through the tube 3 a pump 5 is pro- vided. In this manner waste ink issued by the printing head during for example the purging of the printing head prior to printing is transported through the tube 3 into the waste ink container 4. As the ink amounts issued during purging are very limited and often contain solvents, the ink amounts in the tube 3 are very limited which means that an amount of ink will be present in the tube 3 between each time the printing head 1 purges into the capping station 2.

This ink will contain solvents which will evaporate and at the same time the ink residue will crystallize creating relatively large hard and sharp crystals which when forced to enter the pump 5 will shear and thereby create leaks in the hose 3. When a leak is cre- ated liquid ink will have a tendency to seep out through the hose polluting the immediate environment and at the same time the tube needs to be replaced and the entire pump and possibly also the interior of the printer in this area need to be cleaned thoroughly.

In order to avoid these disadvantages an ink trap as illustrated in figure 2 is the subject of the present invention. The same elements are provided with the same reference numbers as were used with reference to figure 1.

The printing head 1 is again parked in the capping station 2 which by means of a tube 6 is in fluid communication with an ink reservoir 10. The ink reservoir 10 is furthermore by means of a further tube 11 connected to a first solenoid valve 12 which regulates the air inlet 13 to the waste ink reservoir 10.

The pump 5 is reused as an evacuation pump where the tube 14 is used for evacuating air from the ink reservoir 10.

When the printer head 1 is in its position in the capping station 2, surplus ink may be sucked into the waste ink reservoir 10 by activating the pump 5 and at the same time allowing air through the first valve 12 such that a constant under-pressure is maintained inside the waste ink reservoir 10. In this manner there will be an under-pressure in the tube 6 such that the waste ink is drawn from the capping station 2 into the waste ink reservoir 10.

In this embodiment of the invention a float switch 20 is provided inside the waste ink reservoir 10. As the ink accumulates in the waste ink reservoir, the float of the float switch 20 will rise and at a pre-determined level a control circuit (not illustrated) will activate a second solenoid valve 21 and an electrical pump 22 whereby the accumu- lated ink in the waste ink reservoir by the tubes 23, 24, 25 is transferred to the waste ink container 4.

When the second valve 21 and the pump 22 are activated, the first valve 12 allows the air inlet 13 to open such that the under-pressure inside the waste ink reservoir is less- ened facilitating the transfer of the waste ink from the waste ink reservoir 10 to the waste ink tank 4 by means of the solenoid valve 21 and the electrical pump 22. In this manner the system according to the invention operates in two modes. A first mode, in which mode ink from the printing head 1 is collected in the capping station 2 and transferred to the waste ink reservoir, while the pump 5 creates an under-pressure thereby sucking the purged ink into the waste ink reservoir. This process will go on until a certain amount of waste ink has accumulated in the waste ink reservoir whereby the float switch 20 has reached a pre-determined level at which level the control circuit will activate the second mode - the emptying cycle. In this mode the air inlet is opened, the second valve 21 and the pump 22 is activated in order to pump the amount of ink from the waste ink reservoir 10 to the waste ink tank 4. Once the waste ink is collected in the waste ink tank 4 it may, depending on the purity of the ink, either be reused or be discarded.

During the entire process the tubes 6, 11, 14, 23, 24, 25 are empty except for the very limited periods when ink is being pumped in the tube 6, 23, 24 and 25. Therefore, no crystallization will occur in the tubes and a much longer life expectancy of the system may be achieved. Above the invention has been described with reference to a specific example, but the scope of protection shall only be limited by the appended claims.

Claims

1. Ink trap, for collecting used ink from a printing head through capping station in, characterised in that the ink trap comprises a waste ink reservoir connected to the cap- ping station, which waste ink reservoir is substantially airtight, and which reservoir is connected to an air inlet via a first valve and an air outlet, where a pump is arranged in the air outlet for evacuating air from the waste ink reservoir, where an ink outlet, comprising a second valve and a pump, is arranged adjacent a lower section of the waste ink reservoir which is in fluid connection with a waste ink tank.

2. Ink trap according to claim 1, characterised in that a float switch is arranged in the waste ink reservoir, and that further the first and second valves are solenoid valves, where said float switch generates an input to a control circuit, which control circuit generates output to the appropriate pump and/or solenoid valve, in order to evacuate the collected ink from the waste ink reservoir when a certain predetermined amount of ink has accumulated in the waste ink reservoir.

3. Ink trap according to claim 1, characterised in that tubes connecting the capping station, the different valves, the different pumps and reservoir are silicone, polyethyl- ene, latex or latex based tubes.

4. Printer of the type having a printing head using a capping station, where said printing head is parked in a capping station, characterised in that an ink trap according to any of claims 1 to 3 is arranged in fluid connection with the capping station.

5. Printer according to claim 4, characterised in that a dedicated ink trap is provided for each separate colour and/or printing head.