JP6994285B1 - Inkjet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet printer capable of avoiding a situation in which a solid ink is deposited on the surface of an electrode or the like constituting a print head and the constituent members or the constituent members and a cover are short-circuited to cause a printer failure. In an inkjet printer of the present invention, an air outlet is formed around a slit through which ink droplets pass in a cap of a head cover, and air is blown from the outlet toward an object to be printed. Since the air outlet is formed independently of the slit and the air ejection direction is substantially parallel to the flight direction of the ink droplets, the ink droplets that pass through the slit and fly toward the printed object are air. Almost never hits. On the other hand, the ink particles that bounce off the printed matter are pushed back by the air blown out from the air outlet, and the amount of ink particles that enter the head cover through the slit is suppressed. [Selection diagram] Fig. 2

Description

The present invention relates to a continuous inkjet printer, and more particularly to the prevention of stains on the print head due to ink bounced off the printing surface.

In a continuous inkjet printer, ink is ejected from a nozzle by a pump, the ink droplets are charged by a charging electrode at a position where the ejected ink is separated into ink droplets, and the trajectory of the ink droplets is bent by a deflection electrode to be covered. Ink dots are formed by colliding with a predetermined position of a printed matter.

In the continuous type inkjet printer, since the constituent members of the print head are contaminated by the ink due to the property of ejecting ink to perform printing, countermeasures are taken according to the cause of the stain.

The first cause of stains is the ink mist generated by the ejected ink, and in order to reduce the stains caused by the ink mist, the print head is covered with a head cover and the inside of the cover is kept at a positive pressure (Patent Document). See 1).

Specifically, by holding the inside of the head cover at a positive pressure by a pressurizing means, the ink mist floating around the head constituent member is discharged to the outside through a slit for passing ink droplets. As a result, the ink mist is suppressed from adhering to the constituent members, and as an incidental effect, foreign matter such as dust is prevented from entering from the outside, and the inside of the cover is prevented from dew condensation.

The second cause of the stain is the minute ink particles generated by the bounce when the ink droplet collides with the printed matter.

The ink droplets flying from the print head have kinetic energy, and when the ink droplets collide with the object to be printed, they are destroyed by the kinetic energy, and the split ink particles bounce off and scatter around the print surface. Then, some of the scattered fine ink particles enter the inside of the cover through the slit at the tip of the head cover.

The ink particles that have entered the head cover through the slits adhere to the surface of the deflection electrode or the like constituting the print head, and are deposited as solid matter. On the other hand, the continuous type inkjet printer uses conductive ink, and the main body of the head cover is made of metal. Therefore, if the ink deposit is left unattended, not only the surface of the electrode or the like becomes dirty, but also the deposited ink and the metal component of the head including the cover are short-circuited, which causes a failure.

In particular, since a high-voltage DC voltage is applied to the deflection electrode to deflect ink droplets, leaving it unattended may lead to a serious accident.

Japanese Unexamined Patent Publication No. 2018-83369 Japanese Unexamined Patent Publication No. 2014-100876

As a method of preventing ink particles from entering through the slit, it is conceivable to increase the positive pressure in the cover to increase the flow rate of the air blown out from the slit. It is not possible to easily increase the pressure because it leads to a decrease in the pressure.

As another method for preventing the intrusion of ink particles from the slit, it has been proposed to blow air in a direction intersecting the flight direction of the ink droplets (see Patent Document 2).

However, in the method described in Patent Document 2, when the air to be blown is strong, the flight direction of the ink droplets is bent and the print quality is deteriorated, as in the method of increasing the pressure in the cover. Therefore, there is a limit to the strength of the air, and it is not possible to sufficiently suppress the intrusion of ink particles from the slit.

Further, the sprayed ink particles adhere to the surface of the conveyor that conveys the object to be printed and become dirty, which causes a new problem that the conveyor must be cleaned every time printing is performed.

The present invention has been made in view of such conventional problems, and is an inkjet printer capable of minimizing stains on print head components and conveyors without affecting print quality. The purpose is to provide.

In order to achieve the above object, the inkjet printer according to the present invention
A gun that applies vibration at regular intervals to the ejected ink to generate continuous ink droplets,
A charging electrode that charges the ink droplet by applying a stepped wave voltage synchronized with the cycle of the ink droplet,
A deflection electrode that deflects the charged ink droplets vertically or horizontally according to the degree of charging and causes the ink droplets to land on the printed surface of the printed matter.
The print head is provided with a cylindrical head cover in which the gun, a charging electrode, and a deflection electrode are housed in a cavity and a slit through which the charged ink droplets pass is formed.
An inkjet printer in which ink droplets ejected from the print head are landed on the object to be printed moving in the horizontal or vertical direction, and characters are formed by a plurality of rows of print dots.
The head cover is composed of a tubular cover body having a sealed rear end and a cap attached so as to cover the front part of the cover body.
The cap is formed with the slit and an outlet so as to surround at least a part of the slit.
It is characterized in that air is blown from the air outlet toward the printed object.

Here, it is preferable that the cap is formed with a port for connecting an air supply tube and an air flow path for connecting the port and the air outlet.

Further, it is preferable that the cover body is made of metal.

Further, it is preferable that the outlet is formed so as to surround the end of the slit closer to the outer peripheral portion of the cap.

Further, it is preferable that air is supplied from an external compressor to the hollow portion of the head cover, and the hollow portion is held at a positive pressure while the print head is being driven.

In the inkjet printer according to the present invention, an air outlet is provided so as to surround at least a part of the slit of the head cover, and air is blown from the outlet toward the printed matter, and fine particles rebound from the printed matter. Minimizes ink particles from entering the cover through the slits.

Further, since the air outlet is formed independently of the slit and the air ejection direction is substantially parallel to the flight direction of the ink droplets, the print quality is not affected.

Further, the fine ink particles whose scattering is stopped by the air are dispersed in the air, and the amount of ink adhering to the surface of the transport conveyor is significantly reduced, so that the number of times the conveyor is washed can be reduced.

It is a perspective view which shows the appearance of the print head which concerns on Embodiment 1 of this invention. It is a partial cross-sectional front view which shows the schematic structure of the continuous type inkjet printer which concerns on Embodiment 1 of this invention including the print head of FIG. It is a figure explaining the operation when printing on the object to be printed using the inkjet printer of FIG. It is a top view of the head cover in which a slit through which ink droplets pass is formed. It is a front view (a) and a sectional view (b) (c) of the cap. It is a photograph which shows the state which the head cover was removed from the print head, (a) is a photograph of a conventional print head, and (b) is photograph of the print head which concerns on Embodiment 1. It is a top view of the cap which concerns on Embodiment 2 of this invention. It is a front view (a) and a sectional view (b) (c) (d) of the cap.

Hereinafter, the inkjet printer according to the embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a perspective view showing the appearance of the print head 10 to which a function of preventing stains due to ink splashed on the print surface is added, and FIG. 2 is a continuous method according to the present embodiment including the print head 10. It is a partial cross-sectional front view which shows the schematic structure of the inkjet printer (hereinafter, simply abbreviated as "printer") 1. Further, FIG. 3 is a diagram illustrating an operation when printing on a printed object using the printer 1 of FIG. 2.

The constituent members of the printer 10 according to the present embodiment are members related to supplying ink to the print head 10 to perform printing (hereinafter, these are referred to as "ink supply system") and pressurizing the print head 10. It is roughly classified into members related to supplying air for preventing stains (hereinafter, these are referred to as "air supply system"). First, the components of the ink supply system will be described.

<Ink supply system>
As shown in FIG. 2, the printer 10 includes a print head 10, an ink tank 20, and pumps 30a and 30b. Of these, the print head 10 is composed of a gun 12, a charging electrode 13, a detection electrode 14, a deflection electrode 15, a gutter 16, and pipes 17a and 17b, and these members are housed in a cylindrical head cover 11.

Members such as the gun 12 constituting the print head 10 are actually arranged in close contact with the cavity 110 of the head cover 11, but in FIG. 2, in order to explain the configuration and function of each member in an easy-to-understand manner. , Shows a schematic layout.

The gun 12 ejects the ink droplet ID toward the side surface of the printed object, for example, the cosmetic box 4 (see FIG. 3) in which the product is packed, and the gun body 121, the ultrasonic oscillator 122, and the nozzle 123. It is configured. The ink discharged from the ink tank 20 by the pump 30a and supplied to the gun body 121 through the pipe 17a is ejected from the hole of the nozzle 123 in a state where vibration is applied by the ultrasonic vibrator 122.

The ink column IP ejected from the hole of the nozzle 123 is separated into an ink droplet ID by the vibration applied by the ultrasonic vibrator 122, further charged by the charging electrode 13, and then the ink required for printing by the deflection electrode 15. Only the drop ID is deflected according to the amount of charge charged, passes through the slit 114 formed in the front portion of the head cover 11, and lands on the printed surface of the printed matter.

FIG. 3 shows a dressing box (printed object) 40 moving at a constant speed on a belt conveyor (not shown) in the direction indicated by the arrow. In FIG. 3, the head cover 11 of the print heads 10, which is not related to the printing operation, is omitted in consideration of readability.

The surface of the cosmetic box 40 is coated with a film made of polyethylene or polypropylene, and after food or the like is packed in the box, the serial number, expiration date, etc. are printed on the film to form the final product. Become.

As shown in FIG. 3, when the dressing box 40 is moving in a direction orthogonal to the flight direction of the ink drop ID, it lands on the side surface of the dressing box 4 by changing the deflection amount of the ink drop ID. When the position of the ink droplet ID changes and the ink droplet ID is repeatedly deflected in synchronization with the movement of the dressing box 4, a character (“A” in the figure) is printed on the printed surface.

On the other hand, the uncharged ink droplet ID and the charged ink droplet ID that is not used for printing are not deflected and jump into the ink recovery gutter 16 as they are and are collected in the ink tank 20. The ink recovered by the gutter 16 is transferred to the ink tank 20 through the pipe 17b by the pump 30b and reused.

The operation of the printer 10 is controlled by a controller (not shown). The controller is composed of a CPU, a memory (ROM, RAM, etc.), a timer, and a display. The ultrasonic vibrator 122 of the gun 12, the pulse power supply 131 of the charging electrode 13, the detection electrode 14, the DC power supply 151 of the deflection electrode 15, and the DC power supply 151. It controls the operation of the pumps 30a and 30b.

Specifically, the controller drives the pump 30a to apply pressure to the ink contained in the ink tank 2 and supply the ink to the gun body 121. Further, the controller controls the timing of the pulse voltage applied from the pulse power supply 131 to the charging electrode 13 based on the signal detected by the detection electrode 14, and adjusts the number and timing of the ink droplet IDs charged by the timing. Further, the controller adjusts the deflection amount of the ink droplet ID deflected by the deflection electrode 15 by controlling the voltage of the DC power supply 151.

<Air supply system>
Next, the air supply system of the printer 10 will be described with reference to the above-mentioned FIGS. 1 and 2 and the new FIGS. 4 and 5. 4A and 4B are plan views of a cap 112 of the head cover 11 in which a slit 114 through which ink droplets pass is formed, FIG. 5A is a front view of the cap 112, and FIG. 5B is FIG. A cross-sectional view cut along the line AA, FIG. 5C is a cross-sectional view cut along the line BB.

In the present invention, two functions are realized by using air compressed by a compressor. Specifically, the function that keeps the inside of the head cover at a positive pressure, which is installed as a standard function in continuous printers, and the function that blows air to the ink particles that bounce off the printing surface, the ink particles pass through the slit and the head cover. It has a function to prevent it from invading inside.

Although not shown, the air supplied from the compressor through the tube is first drained with a drain catch to remove excess water, and then with a mist separator to remove oil mist.

After that, the air is branched into two, the air AR1 that has passed through one tube is supplied to the cavity 110 of the head cover 11, and the air AR2 that has branched into the other tube is supplied to the air outlet 115 provided in the cap 112. Will be supplied.

The functions of the two air AR1 and AR2 will be described together with the configuration of the head cover 11. As shown in FIG. 2, the head cover 11 is composed of a cylindrical cover main body 111 and a cap 112 detachably attached to the front portion of the cover main body 111.

The cover body 111 is made of metal in order to enhance resistance to external noise, while the cap 112 is made of resin in consideration of ease of molding.
First, the function of the first air AR1 will be described. A regulator (not shown) is attached in the middle of one of the above-mentioned tubes in order to reduce the pressure of the air compressed by the compressor to an appropriate value, and the air AR1 whose pressure is adjusted by the regulator is the head cover 11. Is supplied to.

As shown in FIG. 2, the lid 19 that seals the rear end portion of the cover main body 111 of the head cover 11 is formed with a hole through which the tube 18 is passed, and the tip of the tube 18 is opened to the hollow portion 110 of the head cover 11. Has been done. The cavity 110 is sealed except for the vertically elongated slit 114, which is an opening into which the ink droplet ID is ejected, and most of the air AR1 (indicated by the white arrow) supplied through the tube 18 is the head cover 11. Stay inside to increase air pressure.

In a continuous printer, a part of the ink ejected from the nozzle 123 drifts to the surrounding atmosphere as ink mist and adheres to the surface of the constituent members, which causes stains and malfunctions. Therefore, the inside of the head cover 11 is periodically used. It is necessary to clean the parts. In addition, dust enters the ink circulation system through the gutter and clogs the pipes and the like, causing a malfunction.

Therefore, by accommodating the main member of the print head 10 in the head cover 11 and keeping the inside of the head cover 11 at a positive pressure, the ink mist is discharged to the outside, and dust from the outside is collected in the head cover 11. It prevents it from entering. By these treatments, the cycle of cleaning the constituent members can be prolonged, and clogging of pipes and the like due to dust can be avoided.

Next, the function of the second air AR2 supplied to the cap 112 of the head cover 11 through the other tube will be described. A thick portion 113 is formed on the upper portion of the bottomed cylindrical cap 112, and the thick portion 113 has a slit 114 for ejecting ink droplets and an outlet 115 for blowing air AR2 toward the printed matter. It is formed.

As shown in FIG. 5A, the outlet 115 of the second air AR2 is formed so as to surround the slit 114. Inside the thick portion 113, as shown in FIGS. 5 (b) and 5 (c), a port 116 for connecting an air tube (not shown) supplied from the compressor, a port 116, and an outlet 115 are provided. A flow path 117 is formed to connect with and.

As shown in FIG. 5B, the flow path 117 extending from the port 116 is formed so as to surround the outlet 115 because of the strength of the air AR2 blown out from the outlet 115. This is to make it uniform so as not to affect the flight of ink droplets passing through the slit 114.

As shown in FIG. 4, a pair of locking pieces 118 are formed at opposite positions of the rear end of the cylindrical portion of the cap 112, while the front portions of the cover main body 111 face each other as shown in FIG. A pair of locking holes 119 are formed at the positions.

When attaching the cap 112 to the cover body 111, the locking piece 118 of the cap 112 is inserted into the front portion of the cover body 111, and then the locking piece 118 is engaged with the locking hole 119 to engage the cover body 111. And the cap 112 are integrated.

As shown by the solid arrow in FIG. 2, in the present embodiment, the air outlet 115 is formed around the slit 114 through which the ink droplets pass in the cap 112 of the head cover 11, and the air outlet 115 is formed from the outlet 115. Air AR2 is blown toward the printed matter.

Since the outlet 115 of the air AR2 is formed independently of the slit 114 and the direction of the air AR2 is substantially parallel to the flight direction of the ink droplet ID, the air AR2 passes through the slit and flies toward the printed matter. Almost no air hits the ink drop ID. Therefore, the flight path of the ink droplet ID is not bent by the air AR2, and the print quality is not deteriorated.

On the other hand, the ink particles bounced off the printed matter are pushed back by the air AR2 blown out from the outlet 115, so that the amount of ink particles entering the head cover 11 through the slit 114 is suppressed.

As a result, the components of the print head 10 can be kept to a minimum from being contaminated with ink. Further, it is possible to avoid a situation in which solid ink is deposited on the surface of the electrode or the like, and the deposited ink is short-circuited with the metal component of the head including the cover, resulting in a printer failure.

Further, as a secondary effect of the air AR2, by blowing air on the ink that has landed on the printed surface, it is possible to promote the drying of the ink and prevent the ink from fading and transfer.

If the pressure of the air AR2 blown out from the outlet 115 is too strong, it affects the flight of ink droplets passing through the slit 114 and deteriorates the print quality. On the contrary, when the pressure of the air AR2 is weak, the amount of ink particles penetrating into the head cover 11 increases. Therefore, it is necessary to set the pressure of the air AR2 within a range that does not affect the flight of ink droplets and suppresses the intrusion of ink particles throughout the experiment.

FIG. 6 is a photograph showing a state in which the head cover is removed from the print head after repeated printing using a continuous printer, and the upper and lower deflection electrodes 15 of the print head 10 are photographed from the front. Is.

In FIG. 6, (a) is a photograph of a conventional print head having no air outlet, and (b) is a photograph of a print head according to the present invention having an air outlet.

In the experiment, as a conventional print head, a cap having a slit with a center distance of 9 mm and a width of 2.6 mm was used. Further, as the print head according to the present invention, a cap in which the circumference of the above-mentioned slit is surrounded by an outlet having a width of 1 mm is used. Then, air AR1 is supplied to the conventional print head, and AR1 and AR2 are supplied to the print head according to the present invention so that the wind is slightly blown out from the slit and the flight of ink droplets is affected from the outlet. The air pressure was adjusted so that no wind would blow out.

As shown in FIG. 6A, in the conventional print head having no air outlet, ink adheres to the tip of the upper deflection electrode and solid matter is deposited, for example, as surrounded by a white circle. As described above, if the solid matter is left unattended, the tip of the solid matter comes into contact with other components or the cover body, which may cause a failure or an accident.

On the other hand, as shown in FIG. 6B, in the print head 10 according to the present invention in which the air outlet 115 is provided on the cap 112, almost no solid matter is deposited on the surface of the upper deflection electrode 15. Therefore, it is possible to prevent failures and accidents due to the accumulation of solid ink.

(Embodiment 2)
7 and 8 show other examples of head cover caps. 7 is a plan view of the cap 112A, FIG. 8A is a front view of the cap 112A, FIG. 8B is a sectional view taken along the line CC of FIG. 7, and FIG. 8C is a sectional view thereof. , FIG. 8 (d) is a cross-sectional view cut along the same ED line, and is a cross-sectional view taken along the same EE line.

In the figure, members having the same function as the cap 112 of the first embodiment are designated by the same reference numerals. Further, in order to distinguish it from the cap 112 of the first embodiment, the alphabet "A" is added to each code.

As shown in FIG. 5 described above, in the cap 112 according to the first embodiment, the flow path 117 is formed so as to surround the outlet 115 so that uniform air is blown out from the air outlet 115, and the flow path 117 is formed between them. In addition, the flow paths connecting the air outlet 115 and the flow path 117 are formed at equal intervals.

Generally, the cap 112 is manufactured by injection molding, but if the flow path 117 connecting the port 116 and the outlet 115 is complicated, the manufacturing cost of the mold becomes high.

On the other hand, in the cap 112A according to the present embodiment, as shown in FIG. 8, a semicircular outlet 115A is formed in the upper part of the slit 114A, and the outlet 115A and the port 116A are formed into a rectangular parallelepiped flow. It is connected by road 117A. Since the shape of the flow path 117A is simplified, the manufacturing cost of the mold can be suppressed as compared with the cap 112 of the first embodiment.

The air outlet 115A according to the present embodiment has a bias in the air blown to the printed surface as compared with the air outlet 115 according to the first embodiment. However, as a result of the experiment, it was found that if the air flow path 116A formed so that the air blown out from the outlet 115A slightly toward the center of the cylinder, the effect of preventing the adhesion of ink is almost the same.

Therefore, depending on the specifications required for the print head 10, the operation is performed without forming the outlet 115 having a shape surrounding the slit 114 and the flow path 117 having a complicated shape as shown in the first embodiment. As shown in the second embodiment, the arcuate outlet 115A and the simple flow path 117A may be adopted.

In each of the above-described embodiments, a cylindrical head cover is used as the head cover of the print head, and the main member is housed in the hollow portion of the head cover, but the shape of the head cover is not limited to the cylindrical shape. A head cover having a quadrangular or hexagonal cross section may be used according to the shape and arrangement of the constituent members.

Further, in each of the above-described embodiments, the case of printing on the printed matter moving in the horizontal direction has been described, but the moving direction of the printed matter is not limited to this, and for example, the printed matter moves in the vertical direction. Even in this case, it is possible to introduce a function of preventing the print head from being contaminated by the ink bounced off the printed surface. In that case, the ink droplets will be deflected in the horizontal direction.

AR1, AR2 Air 1 Inkjet printer 10 Print head 11 Head cover 12 Gun 13 Charging electrode 14 Detection electrode 15 Deflection electrode 16 Gutter 17a, 17b Pipe 20 Ink tank 30a, 30b Pump 40 Printed object 110 Cavity 111 Cover body 112 Cap 113, 113A Thick part 114, 114A Slit 115, 115A Outlet 116, 116A Port 117, 117A Flow path

Claims (5)

A gun that applies vibration at regular intervals to the ejected ink to generate continuous ink droplets,
A charging electrode that charges the ink droplet by applying a stepped wave voltage synchronized with the cycle of the ink droplet,
A deflection electrode that deflects the charged ink droplets vertically or horizontally according to the degree of charging and causes the ink droplets to land on the printed surface of the printed matter.
The print head is provided with a cylindrical head cover in which the gun, a charging electrode, and a deflection electrode are housed in a cavity and a slit through which the charged ink droplets pass is formed.
An inkjet printer in which ink droplets ejected from the print head are landed on the object to be printed moving in the horizontal or vertical direction, and characters are formed by a plurality of rows of print dots.
The head cover is composed of a tubular cover body having a sealed rear end and a cap attached so as to cover the front part of the cover body.
The cap is formed with the slit and an outlet so as to surround at least a part of the slit.
An inkjet printer characterized in that air is blown from the outlet toward the object to be printed. The inkjet printer according to claim 1, wherein the cap is formed with a port for connecting an air supply tube and an air flow path for connecting the port and the outlet. The inkjet printer according to claim 1 or 2, wherein the cover body is made of metal. The inkjet printer according to any one of claims 1 to 3, wherein the outlet is formed so as to surround the end of the slit closer to the outer peripheral portion of the cap. The inkjet printer according to any one of claims 1 to 4, wherein air is supplied to the hollow portion of the head cover from an external compressor, and the hollow portion is held at a positive pressure while the print head is being driven.

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