JPS63242556A - Ink jet head - Google Patents

Abstract

PURPOSE:To cover both an ink reservoir and an opening with a common cover and to simplify the handling, by providing a bubble-removing branch path vertically connecting from the middle of an ink supply path to an opening formed to be flush with the front end face of the ink reservoir. CONSTITUTION:A bubble invading into an ink supply path 15 from an external ink supply mechanism, e.g. an ink bottle, through a joint 15c invades into a large-diameter branch path 15d connecting from the middle of a horizontal part 15b to an opening 17 formed to be flush with the front end surface of an ink reservoir 12 before reaching to a small-diameter vertical part 15a. After moving upwards due to the buoyancy inside, the bubble is discharged outside a head out of the opening 17 of the top part. Since the opening of the top end of the bubble-removing branch path is so formed as to be flush with the surface for the front end face of the ink reservoir, both the ink reservoir and the opening can be covered with a common cover, for example, in the storage of this ink jet head with an ink loaded, and the handling is also simplified. In addition, since the opening at the top end of the bubble-removing branch path is set laterally in use, dusts hardly invade into the branch path.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to an inkjet head installed in an inkjet printer.

2. Description of the Related Art Inkjet printers, which perform printing by ejecting ink droplets and flying them to the surface of recording paper, have various advantages such as less noise than the currently mainstream dot impact printers. There are two types of inkjet heads installed in such inkjet printers: continuous jet type and drop-on-demand type.
The latter type is considered to be promising in terms of the small size and simplicity of the device.

There are various types of drop-on-demand type inkjet heads, but a type having an ink reservoir in front of an orifice as shown in FIG. 2 has been developed as a high-performance head.

This inkjet head includes an orifice 21, an ink reservoir 22 having a rear end face including the orifice 21 and a front end face in contact with the atmosphere, and a pressure chamber 2 filled with ink and pressurized by an electromechanical conversion element 26.
4, a pressure propagation path 23 that extends from the pressure chamber 24 forward and is connected to the ink reservoir 22 via the orifice 21, and approaches the ink reservoir 22 from below and is connected to the ink reservoir 22 at its peripheral portion. The ink supply path 25 is also provided.

In this inkjet head, by forming an ink reservoir 22 in front of the orifice 21, it is possible to control the direction and speed of ink droplet jetting that occurs when excess ink adheres to the vicinity of the orifice of an inkjet head that does not have this. The structure is designed to effectively prevent fluctuations and stabilize the injection characteristics.

Problems to be Solved by the Invention In the conventional inkjet head described above, an ink reservoir is formed in front of an orifice, and ink is supplied from an ink supply path into a pressure chamber via this ink reservoir and the orifice. This stabilizes the direction and speed of droplet jetting.

In the structure shown in FIG. 2, in order to secure space for forming the pressure chamber and the electrical/mechanical transducer, the vertical portion 25a of the ink supply path 25 is moved from the horizontal portion 25b formed near the bottom of the head to the portion near the top. The ink reservoir 22 is approached from below over a long distance. The inner diameter of the vertical portion 25H of this ink supply path is set to a value smaller than 5 necessary to pull up ink by capillary force.

Therefore, if air bubbles enter the ink supply path 25 through the joint 25C with an external mechanism (not shown) for some reason, the air bubbles will pass through the horizontal portion 25b and
As illustrated in FIG. 2, there is a problem in that the ink accumulates in the middle of the vertical portion 25a and obstructs the subsequent ink supply.

Means for Solving the Problems The inkjet head of the present invention has a branch path for air bubble removal that connects in the vertical direction from a midway point of the ink supply path to an opening formed on the same plane as the front end surface of the ink reservoir. It is configured to include.

In the inkjet head of the present invention, air bubbles that have entered the ink supply path are discharged to the outside of the head through a branch path that exits from the middle of the ink supply path to the top of the ink reservoir. This prevents the ink from penetrating into the vertical portion of the ink, thereby preventing ink supply from being obstructed.

In addition, since the opening at the tip of the air bubble removal channel is formed on the same plane as the front end surface of the ink reservoir, when storing this inkjet head with ink filled, the ink reservoir The apertures can be covered together with a common lid, which reduces manufacturing costs and eases handling.

Hereinafter, further details of the present invention will be explained in detail together with examples.

Embodiment FIG. 1 is a sectional view showing the structure of an inkjet head according to an embodiment of the present invention.

This inkjet head includes an orifice 11 and an ink reservoir 12 having a rear end face including the orifice 11 and a front end face in contact with the atmosphere. Furthermore, this inkjet head has a pressure chamber 14 that is filled with ink and pressurized by an electromechanical transducer 16.
, a pressure propagation path 13 extending from the pressure chamber 14 forward thereof, and an ink supply path 15 connected to the ink reservoir 12 in a peripheral portion thereof.

Because it is necessary to secure a space for forming the pressure chamber 14 and pasting the electrical/mechanical transducer 16, the ink supply path 15 connects the joint 15C with an external mechanism (not shown) and the horizontal portion 15b connected to the head. A small diameter vertical portion 25 is formed at the bottom and rises from the horizontal portion 15b of the bottom.
a is brought close to the upper ink reservoir 12 and communicated with the surrounding area. Horizontal portion 15b of this ink supply path 15
A branch path 15d for removing air bubbles is formed which connects in the vertical direction from a midway point to an opening 17 formed on the same plane as the front end surface of the ink reservoir 12.

Such a change in the cross-sectional shape along the ejection direction can be easily realized by configuring the inkjet head as a laminated structure formed by stacking thin plates.

This inkjet head is installed so that the pressure propagation path 13 is horizontal during normal use. Therefore,
In this normal usage state, the vertical portion 15a of the ink supply path 15 extends vertically, as its name suggests.

A pulsed electrical signal is intermittently applied to an electrical/mechanical conversion element 16 made up of a piezo element or the like attached to the rear outer wall surface forming the pressure chamber 14, and a pressure wave is generated within the pressure chamber 14. Occur. This pressure wave is propagated through the pressure propagation path 13 to the orifice 11, from where it breaks through the front ink reservoir 12 and ejects an ink droplet. Immediately after this ink droplet is ejected, the negative pressure generated in the pressure chamber 14 causes the pressure propagation path 13 to flow from the ink reservoir 12 through the orifice 11.
Ink is sucked into the printer. The ink in the ink reservoir 12, which tends to be insufficient due to this suction, is supplied from the ink supply path 25 in the peripheral portion.

Air bubbles entering the ink supply path 15 from an external ink supply mechanism (not shown) such as an ink bottle through the joint 15c immediately move to the ceiling portion of the horizontal portion 15b due to their buoyancy. This bubble slowly moves along the wall surface of the ceiling in the direction of the vertical portion 15a as the ink flows as the ink is supplied.
Before reaching the ink tank, the ink enters the large diameter branch passage 15d that communicates with the opening 17 formed on the same plane as the front end face of the ink reservoir 12 from the middle of the horizontal part 15b, and rises inside the branch passage 15d by buoyancy. It is discharged from the opening 17 to the outside of the head.

Effects of the Invention As explained in detail above, the inkjet printer of the present invention
Since the head is configured to include a branch path for removing air bubbles that vertically connects a point in the middle of the ink supply path to an opening formed on the same plane as the front end surface of the ink reservoir, air bubbles are removed from the ink supply path. Even if the ink enters the ink, it is easily discharged to the outside of the head through the branch path, and an adverse effect on the ink supply is effectively prevented.

In addition, since the opening at the tip of the air bubble removal branch is formed on the same surface as the front end surface of the ink reservoir, when this inkjet head is stored with the ink reservoir filled, For example, the ink reservoir and opening can be covered together with a common lid, which reduces manufacturing costs and eases handling.

Another advantage is that the opening at the tip of the air bubble removal branch is oriented sideways rather than upward during normal use of the inkjet head, making it difficult for dust to enter the branch. .

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of an inkjet head according to an embodiment of the present invention, and FIG. 2 is a sectional view showing the structure of a conventional inkjet head. 11... Orifice, 12... Ink reservoir, 13.
... Pressure propagation path, 14 ... Pressure chamber, 15 ... Ink supply path, 15a ... Vertical portion, 15b ... Horizontal portion, 15c ... Joint with external mechanism, 15d ... Branch road,
16... Electrical/mechanical conversion element, 17... Opening. Patent applicant: NEC Home Electronics Co., Ltd.

Claims (1)

[Scope of Claims] A pressure chamber filled with ink and pressurized by an electrical/mechanical conversion element, a pressure propagation path extending from the pressure chamber forward thereof, and a rear end connected to the pressure propagation path. an ink reservoir having an end surface and a front end surface in contact with the atmosphere; an ink supply path that approaches the ink reservoir from below and is connected to the ink reservoir at its peripheral portion; and a front end of the ink reservoir from a midway point of the ink supply path. An inkjet head characterized by having a branch path for air bubble removal vertically connecting an opening formed on the same surface as the surface.