JPS6248584B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to ink jet printing devices, and more particularly to an improved method and apparatus for maintaining a supply of ink to a printing device.

In cyclic ink jet printing systems, fluid ink, typically pressurized to 2 to 5 atmospheres absolute, is supplied to the ink jet nozzles. Of the ink droplets directed to the printing surface, those that are not used for printing are captured and removed. This unused ink is returned to the ink supply and circulated through the apparatus. Traditionally, this ink circulation was accomplished by using a pump to supply pressurized ink to the nozzles and draw the ink from a vented container. The reversion ink is placed in this vented container. Problems associated with this method are the poor mechanical reliability of the pumps and valves and the difficulty in achieving chemical compatibility of the different inks used. It should be noted that the pump produces periodic pressure fluctuations, or pulses, which must be minimized by regulating the fluid pressure. It is necessary to maintain a steady stream of droplets with a constant velocity to avoid deterioration of print quality. For this purpose, the pressure of the ink supplied to the injection nozzle must not fluctuate. The use of pumps therefore has a detrimental effect on printing.

Another widely used fluid pressurization and circulation method is to force fluid ink from a pressure vessel using a constant volume of compressed gas at a regulated pressure and supply it to a nozzle. The returned unused ink is temporarily stored in another container. When the reservoir supplying ink to the nozzle is empty (or nearly empty), the ink captured from the stream of ink droplets is automatically removed from the return ink reservoir with the pressure reservoir vented to atmosphere. manually and manually into this pressure vessel. Although the problems associated with the pump system can be overcome when using this method, the continuous operating time of the system is limited by the capacity of the ink pressure container and the number of nozzles to be supplied with ink.

The object of the invention is to provide an ink jet printing device with an ink supply device capable of continuously operating a pump device adapted to supply compressed gas at a constant pressure.

Another object of the present invention is to provide an ink jet printing device having a new and improved ink supply device.

The above objects of the invention are achieved by providing an apparatus adapted to pressurize an ink tank to supply ink to an ink jet printing head. Unused ink droplets in the ink stream are captured and returned to a suitable container, which container is returned at a predetermined time, i.e., when the amount of ink in the ink tank or return ink container reaches a predetermined value. It is designed to hold this ink until When this condition is reached, the trapped ink is pressurized back into the ink tank. When the ink is of a type requiring the addition of additives, equipment is provided for adding this additive to the acquired ink. A device may also be provided for adding new ink to the ink tank as required. This fresh ink is added under pressure to an ink tank or to a refill ink container from which it is transferred to said ink tank. The ink tank can therefore continuously supply ink at a constant pressure to the nozzle head.

Next, embodiments of the present invention will be described with reference to the accompanying drawings.

An ink supply tank 10 contains a supply of ink which is delivered by supply hoses 12 to the various printing heads 14 where the ink is to be used. A two-way valve 16 is connected to each print head to shut off ink from the ink tank during testing or when a problem occurs. This valve 16 is not part of the present invention.

Each printing head directs a stream of ink droplets onto a printing surface (not shown). The stream of ink droplets not used for printing is directed to a catcher 18. The ink in the ink tank 10 enters the printing head through a tube 12 from where it is jetted by a volume of compressed gas. The gas is typically supplied from a source 20
The air is supplied by a pump (which can be a pump). The pressurized gas is supplied to a pressure regulator 22 whose output is delivered to the ink tank 10 by a line 24.

The ink captured by the trap 18 and other print head traps is transferred to the tube 26, buffer container 28,
It is returned to the captured ink container 36 through a pipe 30 and a three-way valve 34. The three-way valve has three ports N, A, and S. The top of the captured ink container is connected by a tube 38 to another three-way valve 40. This valve has three ports: NN, AA, and SS. This three-way valve connects port AA to the atmosphere through port NN, or to subatmospheric pressure (vacuum) if required for ink transfer, or by tube 42 through port SS. It operates so as to be connected to another pressure regulator 44.

The ink supply container 50 containing fresh ink is connected to the valve 5
2 to the ink tank 10. When this valve is actuated, ink can pass through the valve. The new ink container 50 has a valve 4
6. Can be pressurized by connecting to a pressure gas source through tube 42 and pressure regulator 44.

In order to reuse the captured ink, a tank 54 for holding additives is used when using a type of ink in which the evaporation of the volatile ink base must be compensated for. If desired, the additive can be mixed with the inflow captured ink by means of a three-way valve 56.

Valves 34, 40, 46, 56, 52 can be controlled by a level sensor 60 as required;
A time control or other necessary control for replenishing the ink in the ink tank can be provided. The level sensor mentioned above can be cited as an example. The sensor sends a control signal to the valves 34, 40 when the ink in the ink tank drops below a predetermined level. Valve 34 is set to allow captured ink to flow into container 36 when ink tank 10 is not being supplied with ink. Valve 3 in response to the level sensor signal
4 connects mouth A to mouth S. A three-way valve 40, which normally connects the top of the vessel 36 to the atmosphere or a vacuum source through AA, NN as appropriate, also controls a pressure regulator 44 in response to a level sensor signal.
Ink container 3 captured by SS, AA and tube 38
Connect to the top of 6. The trapped ink thus flows out of the container 36 and into the ink tank 10 through the tube 62. A check valve 61 in the pipe 62 is provided to prevent backflow of ink.

Note that the "first control signal" described in the claims of the present specification refers to a control signal that operates the first valve device so that the ink captured in the buffer container 28 flows into the captured ink container 36. and "second control signal" means a control signal that operates the first valve device to cause ink to flow into the ink tank 10.

Furthermore, the “third claim” described in the above claims
``control signal'' indicates that the ink is in a new ink container 50.
"Fourth control signal" means a control signal that operates the second valve device to prevent ink from flowing from the fresh ink container 50 to the ink tank 10; means a control signal that actuates the second valve arrangement to permit.

Fresh ink can be dispensed at any time by activating the two-way valve 46 and causing gas from the pressure gas source to flow through the pressure regulator 44 and the two-way valve 46 into the fresh ink container 50. It can be made to flow into the ink tank 10. However, it is desirable to add fresh ink when the amount of ink in tank 10 reaches a predetermined value that is different from the value at which the captured ink is added to the contents of the container. At this time, the level sensor 60 generates a signal that activates the valves 52 and 46, so that the level of ink in the ink tank 10 reaches a predetermined value, and the two-way valves 46 and 52 cause the flow of new ink into the ink tank 10. This tank is supplied with fresh ink until the tank is shut off.
Level sensing devices that generate electrical signals in response to variations in ink level are well known and will not be described in detail.

Buffer container 28 collects captured ink or returned ink as captured ink container 36 is supplying ink to ink tank 10. The reason is that the mouth N of the valve 34 is closed at this point. If a vacuum is required to place the trapped ink into the trapped ink container, the valve is connected to the atmosphere through line 29, or to a suitable vacuum source.

Pressure regulator 44 generates a slightly higher pressure than pressure regulator 22 to allow ink to flow from containers 36, 50 into ink tank 10. When it is desired to drain ink from these containers, the ink tank 10 is pressurized by the pressure regulator 22. The pressure within the ink tank 10 is always controlled by a pressure regulator 22.

According to the invention, the ink supply to the printing head is maintained at a constant pressure and there is no need to interrupt operation to replenish the ink in the tank 10. According to the present invention, the ink capacity is not limited. The tank 10 and fresh ink container 50 can be large or small depending on the type of printing to be done.

Another method for adding new ink to the system is to connect a fresh ink container 51, vented (to the atmosphere), to the ink return tube 30 through a three-way valve 56. This valve 56 allows additional or new ink to flow in as required. This device can be operated slowly, but in this case valves 46, 5
2 is no longer necessary, and the new ink container 50 no longer needs to be a pressure container. In such an arrangement, fresh ink flows into a scavenged ink reservoir. When ink flows from the scavenged ink container into the ink tank 10, this tank will contain fresh ink or scavenged ink or a mixture of both. Of course both devices can be used simultaneously. Which one to use depends on the working conditions.

As described above, the present invention provides a novel and useful ink supply device for ink jet printing devices.

[Brief explanation of the drawing]

The accompanying drawings are schematic illustrations of the device according to the invention. In the figure, 10 is an ink tank, 12 is a hose, 14 is a printing head, 16 is a two-way valve, 18 is a trap, 20 is a pressure gas supply source, 22 is a pressure regulator, 24 and 26 are tubes, and 28 is a buffer container. , 30 is a pipe, 34 is a three-way valve, 36 is a captured ink container, 38
is a pipe, 40 is a three-way valve, 42 is a pipe, 44 is a pressure regulator, 46 is a valve, 50 and 51 are new ink containers, 52 is a valve, 54 is a tank, 56 is a three-way valve, 6
0 is a level sensor, 61 is a check valve, and 62 is a pipe.

Claims (1)

[Scope of Claims] 1. Ink is supplied from an ink tank to a nozzle, by which it is projected as a stream of droplets towards a printing surface, and a portion of the droplets in the stream print on the printing surface. In an ink jet printing device of the type which is deflected in order to produce a gas flow and which is adapted to capture residual ink droplets in said stream, said printing device supplies a pressurized gas. a first pressure regulator for delivering gas at a first pressure from the gas supply device to the ink tank, thereby causing ink to flow from the ink tank to the nozzle; a scavenging ink container; a first valve arrangement coupled to the captured ink reservoir, the first valve arrangement having a first operating condition for directing captured ink to the captured ink reservoir; a second operating state which prevents further supply to the captured ink container and directs ink from the captured ink container into the ink tank; a second pressure regulator that increases the pressure of the gas coming out of the pressurized gas supply device and supplies the pressurized gas at a second pressure higher than the first pressure; and the first valve device. a device for communicating the captured ink reservoir through the second pressure regulator with the device for supplying pressurized gas when the device is in its second operating state; actuating a first valve arrangement from its first actuated state to its second actuated state; and in response to a second control signal, said first valve arrangement from its second actuated state to its first actuated state. a container of fresh ink; a first operating condition for allowing ink to flow from said container of fresh ink to said ink tank; The second block prevents new ink from flowing into the tank.
a second valve arrangement having an actuated state; and when the second valve arrangement is in the first actuation state, communicating the fresh ink container with the second pressure regulator to lower the first pressure. Also high 2nd
apparatus for supplying pressurized gas to said container of fresh ink; and responsive to a third control signal, actuating said second valve apparatus from its first operating condition to its second operating condition. , and the second control signal in response to the fourth control signal.
an apparatus for actuating a valve device from its second operating state to its first operating state. 2. The ink jet printing device according to claim 1, wherein the second valve device is in its first operating state and the first valve device is in its first operating state. An ink jet printing apparatus, sometimes comprising a device for coupling said second valve arrangement to said first valve arrangement to allow both captured ink and fresh ink to flow into said captured ink reservoir. 3. The ink jet printing apparatus according to claim 1, wherein the second valve device includes a device for directly connecting the second valve device between the new ink container and the ink tank. Printing device. 4. The ink jet printing apparatus according to claim 1, wherein the captured ink container is pressurized via the second pressure regulator when the first valve device is in its second operating state. a first operating state in which a device in communication with a device for supplying a gas is configured to couple an output of the second pressure regulator to the captured ink reservoir; and a flow of gas from the second pressure regulator to the captured ink reservoir. and a third valve arrangement having a second actuation state for blocking the captured ink reservoir and connecting the captured ink container to a source of gas at a pressure lower than the first pressure, and in response to the first control signal, actuating a first valve arrangement from its first actuated state to its second actuated state; and in response to a second control signal, said first valve arrangement from its second actuated state to its first actuated state. a device for causing said third valve device to simultaneously move said third valve device from its first actuated state when said first valve device is actuated from its second actuated state to its first actuated state; and at the same time when said first valve arrangement is actuated from its first operating state to its second operating state; An ink jet printing device comprising a device for actuating from two operating states to a first operating state thereof. 5. An ink jet printing device according to claim 1, wherein the first valve device communicates with the captured ink container and retains the captured ink when the first valve device is in its first operating state. An ink injection device with a buffer container.