JPS6329564Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ink drop ejecting device for an inkjet printer that records patterns such as characters and figures using ink droplets.

Inkjet printers are non-impact type printers and have excellent features such as low noise generation, the ability to use plain paper as a recording medium, and the ability to easily print in color. Currently, there are charge control types, electric field control types, ink mist types, and on-demand types that are in practical use, but they do not require collection of unnecessary ink, are extremely easy to colorize, and are capable of producing ink droplets. On-demand inkjet printers have been widely used because they have the advantage of being able to express shading by changing the particle size of the inkjet printer. In general, this type of on-demand inkjet printer, and in particular its ink droplet ejecting device, is equipped with an ink ejecting head having an ink reservoir equipped with an orifice and a diaphragm in a part of the peripheral wall, and an electric signal is applied to the diaphragm. This is a so-called non-airflow type in which the ink is vibrated and the ink in the ink reservoir is ejected from the orifice toward the recording paper, or a ventilation chamber with a blowhole facing the orifice is formed in front of the ink reservoir. However, there is a so-called air flow type in which pressurized air is ejected through a blowhole toward the recording paper, and ink droplets ejected from the orifice are sprayed onto the recording paper by an air flow from the blowhole.
However, in any of these structures, the orifice opens into the air, so when the ink ejecting head is not in use, the ink moisture in the ink reservoir evaporates through the orifice, and the ink components dry and stick to the periphery of the orifice, causing the orifice to evaporate. In addition to the possibility of blockage, when the volume of ink decreases due to evaporation of ink water, air is sucked into the ink reservoir, causing poor propagation of pressure waves from the diaphragm to the ink, resulting in malfunctioning ink droplet ejection. There were some shortcomings.

As a means to eliminate such drawbacks, for example, in the case of an airflow type ink droplet ejecting device, when the ink ejecting head is not in use, the blow chamber of the ventilation chamber is closed and ink is introduced from the tank into the ventilation chamber, By filling the ventilation chamber with ink, the orifice of the ink reservoir is kept immersed in the ink, preventing ink moisture from evaporating through the orifice, and preventing clogging of the orifice or air being sucked into the ink reservoir. A structure designed to solve this problem has been proposed by the present applicant (Japanese Patent Application No. 16180/1983).

However, in such a configuration, the gap between the wall of the ink reservoir where the orifice opens and the wall of the ventilation chamber where the blowhole opens is usually very narrow in order to increase the flow velocity of the air flow. When introducing ink into the ventilation chamber, if foreign matter such as ink components is stuck to the wall around the orifice,
Wetting by ink becomes poor and air bubbles tend to remain near the periphery of the orifice, and even if ink is introduced into the ventilation chamber, the area around the orifice becomes dry and the ink moisture evaporates, resulting in clogging of the orifice and ink pooling. There was a problem in that problems such as air being sucked into the interior could not be resolved.

The present invention has been developed in view of the above circumstances, and its purpose is to provide a configuration in which the ink ejection head and the tank containing the liquid to be supplied to and discharged from the ventilation chamber are movable relative to each other in the vertical direction. Ink droplets are ejected from the ink reservoir through the orifice into the ventilation chamber in response to the upward movement of the tank relative to the ink ejection head, promoting ink wetting around the orifice and ensuring that no air bubbles remain around the orifice. An object of the present invention is to provide an ink droplet ejecting device capable of preventing the above problems.

Hereinafter, the present invention will be specifically explained based on drawings showing embodiments thereof. FIG. 1 is a schematic sectional view showing the ink droplet ejecting device according to the present invention (hereinafter referred to as the device according to the invention) when it is in use, and FIG. 2 is a schematic sectional view showing the state when the device is not in use. In the figure, 1 is an ink ejecting head, 53 is a sub-tank, 2 is a rotating drum, and 3 is a recording sheet. The ink ejecting head 1 is constructed by providing a pressure chamber 12, an ink reservoir 13, and a ventilation chamber 14 in a head main body 11.The pressure chamber 12 is located in the center of the head main body 11 and has a diameter increasing from the rear side to the front side. has been reduced to have a horn shape as a whole, and a diaphragm 12a made of a piezoelectric element or the like is provided on the rear side, and a microhole 12b for pressure equalization is bored at a position offset from the center on the front side. Each of the ink reservoirs 13 is provided with a diaphragm plate 12c, and the ink reservoir 13 is formed concentrically with the pressure chamber 12 over the outer periphery and front of the pressure chamber 12, and the front side is closed by a front plate 13b having an orifice 13a in the center. The ventilation chamber 14 is formed concentrically with the pressure chamber 12 over the outer periphery and front of the ink reservoir 13, and the front side is closed by a cover plate 14b having a blowhole 14a at a position facing the orifice 13a.

The inside of the pressure chamber 12 is filled with ink without intervening air bubbles, and the ink reservoir 13 is connected to an ink cartridge (not shown) through a communication hole 13c and an ink tube 13d communicating with the lower part thereof, and the inside is filled with ink. The ventilation chamber 1 is filled with ink fed from the cartridge.
4 is connected to an air pump (not shown) through a communication hole 14c and an air tube 16 leading to the upper part thereof, and air supplied from the air pump is supplied to the blowhole 14.
It is designed to be ejected in front of it through a.

In the present device, one end of each flexible tube 51, 52 is connected to the upper and lower part of the ventilation chamber 14 in the ink ejecting head 1, respectively, and the other end of each tube 51, 52 is connected to the sub tank 5.
A closed circuit including a sub-tank 53 is formed between the upper and lower parts of the ventilation chamber 14. The sub-tank 53 is attached to an elevating frame 54 driven by an electromagnetic actuator (not shown), and the elevating frame 54 allows
When using the ink ejection head 1, the sub tank 53
such that the level of the ink contained therein is located below at least the orifice 13a;
Further, when the ink ejecting head 1 is not in use, it is moved up and down so that the level of ink in the sub tank 53 is at least higher than the position of the orifice 13a.

Reference numeral 61 denotes a pad made of sponge or the like, and a holder 63 rotates around the shaft 62 at a position off the left end of the rotating drum 2, that is, at a position corresponding to the home position of the ink ejecting head 1.
When the ink ejecting head 1 is returned to the home position, it is rotated by an operating mechanism (not shown) from the position shown by the imaginary line to the position shown by the solid line, and is brought into contact with the front surface of the ink ejecting head 1. touched,
The blowhole 14a opening in the cover plate 14b is closed.

Reference numeral 62 denotes a control unit for the diaphragm 12a, which emits an electric signal to cause the diaphragm 12a to eject ink for recording, returns the ink ejection head 1 to its home position, and moves the holder 63 to the shaft 62. The pad 61 is brought into contact with the front surface of the ink ejecting head 1 and the blowhole 14a is closed by the pad 61. Furthermore, the sub tank 53 is moved upwardly relative to the ink ejecting head 1 by the elevating frame 54. In response to this, a signal is continuously applied to the diaphragm 12a from the control section 62 for a predetermined period of time, so that ink droplets are ejected from the orifice 13a toward the ventilation chamber 14. That is, when the ink ejecting head 1 finishes printing and returns to the home position, and the elevating frame 54 is operated to raise the sub-tank 53, the ink in the sub-tank 53 flows into the lower part of the ventilation chamber 14 through the tube 52. However, by vibrating the diaphragm 12a in response to the upward movement of the sub-tank 53 and ejecting ink droplets from the orifice 13a, the ejected ink is absorbed by the blowhole 14a being sealed by the pad 61. The ink then flows down inside the ventilation chamber 14 along the front surface of the front plate 13b or the rear surface of the cover plate 14b, and merges with the ink flowing from below the ventilation chamber 14. This allows the periphery of the orifice 13a to be immersed in the ink smoothly without leaving any air bubbles, even if the ink components dry and stick to the periphery of the orifice 13a and inhibit wetting by the ink. This prevents air bubbles from entering the ink reservoir 13 due to evaporation. The ink droplet ejection time should be determined by the orifice 13a, which should be performed when the ink ejection head 1 returns to the home position.
Even if the ink from the sub-tank 53 does not flow into the ventilation chamber 14 for some reason when ink droplets are ejected from the sub-tank 53, the inside of the ventilation chamber 14 can be filled with the ink ejected from the orifice 13a. It is sufficient if it is of a certain extent.

Therefore, the volume of the ventilation chamber 14 is V, the orifice 1 is
If the ink droplet ejected from the orifice 13a is regarded as a sphere, and its radius is r, and the number of ink droplets ejected from the orifice 13a per unit time (second) is n, then the volume of the ink droplet ejected from the orifice 13a is Since it only needs to be larger than the volume V of the chamber 14, the following formula (1) holds true, assuming that the ink droplet ejection time from the orifice 13a is T.

V<4/3πr ³・n・T...(1) When formula (1) is rearranged with respect to T, it becomes the following formula (2).

T>3/4·V/πr ³ ·n (2) It has been confirmed that it is practically sufficient to set the ink droplet ejection time to more than 2 seconds.

As described above, in the present device, since the ink ejecting head and the liquid tank connected to its cavity are moved relative to each other in the upward and downward directions, the gas in the ventilation chamber is smoothly discharged and No air bubbles remain, and in addition, when introducing the liquid from the tank into the ventilation chamber, ink droplets are ejected from the orifice and the ink is sent into the ventilation chamber, ensuring the formation of air bubbles around the orifice. Not only can this be prevented, but even if the introduction of liquid from the tank fails, the periphery of the orifice can be reliably immersed in the ink, greatly improving the ability to prevent bubble formation.
The present invention has excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of the ink ejecting head in the present apparatus when it is in use, and FIG. 2 is a schematic sectional view of the ink ejecting head when it is not in use. 1... Ink ejection head, 2... Rotating drum,
3... Recording paper, 12... Pressure chamber, 13... Ink reservoir, 14... Ventilation chamber, 51, 52... Flexible tube, 53... Sub tank, 54...
Elevating frame.

Claims (1)

[Scope of utility model registration request] It has an ink reservoir with an orifice provided in a part of the peripheral wall, and a ventilation chamber that communicates with the ink reservoir via the orifice and has an opening in the peripheral wall facing the orifice, and the ink in the ink reservoir is drained from the orifice and the opening. In an ink drop ejecting device comprising an ink ejecting head configured to eject ink droplets through a
A tank that communicates with the ventilation chamber and contains liquid to be supplied to and discharged from the tank, and when the ink ejection head is not in use, the liquid in the tank is supplied to the ventilation chamber, and when the ink ejection head is in use, the liquid in the ventilation chamber is supplied to the tank. means for moving the tank up and down relative to the ink ejection head to discharge the ink into the tank; a lid for closing the opening of the ventilation chamber when the ink ejection head is not in use; An ink drop ejecting device comprising: a control unit that issues a signal to eject ink droplets from an ink reservoir into a ventilation chamber for a predetermined period of time.