CN114571859A

CN114571859A - Ink-jet printer

Info

Publication number: CN114571859A
Application number: CN202210241374.7A
Authority: CN
Inventors: 堀口竜助
Original assignee: Kishu Giken Kogyo Co Ltd
Current assignee: Kishu Giken Kogyo Co Ltd
Priority date: 2021-10-04
Filing date: 2022-03-11
Publication date: 2022-06-03
Anticipated expiration: 2042-03-11
Also published as: CN114571859B; JP6994285B1; JP2023054396A

Abstract

The invention provides an ink jet printer, which can avoid the following situations: solid matter of ink is deposited on the surface of an electrode or the like constituting the print head, and the components or the cap are short-circuited to cause a failure of the printer. In the inkjet printer according to the present invention, an air outlet is formed around a slit through which ink droplets pass in a cover of a head cap, and air is ejected from the air outlet toward a print target. Since the air outlet is formed independently of the slit and the air outlet direction is substantially parallel to the flight direction of the ink droplets, the air hardly collides with the ink droplets that fly toward the print target through the slit. On the other hand, the ink particles that bounce off the print object are pushed back by the air blown out from the air outlet, and the amount of the ink particles that enter the head cap through the slit can be suppressed.

Description

Ink-jet printer

Technical Field

The present invention relates to a continuous ink jet printer, and more particularly, to a continuous ink jet printer that prevents contamination of a print head due to ink bouncing on a print surface.

Background

In a continuous ink jet printer, ink is discharged from a nozzle by a pump, the ink droplets are charged by a charging electrode at a position where the discharged ink is separated into ink droplets, and the trajectories of the ink droplets are bent by a deflection electrode and collide with a predetermined position of a print object to form ink dots.

In the continuous ink jet printer, since the components of the print head are contaminated with ink depending on the nature of printing by ejecting ink, a countermeasure is taken depending on the cause of contamination.

The 1 st cause of the contamination is generation of ink mist due to the ejected ink, and in order to reduce the contamination caused by the ink mist, the head is covered with a head cap while the inside of the cap is kept at a positive pressure (see patent document 1).

Specifically, the inside of the head cap is maintained at a positive pressure by the pressurizing unit, thereby causing the ink mist floating around the head constituent member to be discharged to the outside through the slits for passage of the ink droplets. This can prevent the ink mist from adhering to the component, and as an additional effect, can prevent foreign matter such as dust from entering from the outside, and can prevent condensation inside the cover.

The 2 nd cause of the contamination is minute ink particles generated by bounce when the ink droplets collide with the print object.

The ink droplets flying from the print head have kinetic energy, and when the ink droplets collide with the print object, the ink droplets are destroyed by the kinetic energy, and the broken ink particles are rebounded and scattered around the print surface. Part of the scattered fine ink particles intrude into the mask through the slit at the tip of the head cap.

The ink particles that have penetrated into the head cap from the slit adhere to the surface of the deflection electrode or the like constituting the print head, and are accumulated as a solid material. On the other hand, in the continuous ink jet printer, conductive ink is used, and the main body of the head cap is made of metal. Therefore, if the ink is left to be deposited, not only the surface of the electrode or the like is contaminated, but also the deposited ink may short-circuit with the metal component of the print head including the cap, causing a failure.

In particular, since a high-voltage dc voltage for deflecting ink droplets is applied to the deflection electrodes, there is a possibility that a serious accident may occur if ink is left to accumulate.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2018-83369

Patent document 2: japanese patent laid-open No. 2014-100876

Disclosure of Invention

As a method of preventing the intrusion of the ink particles from the slit, a method of increasing the positive pressure in the cover to increase the flow rate of the air blown out from the slit is considered, but if the flight direction of the ink droplets is changed by the air, the printing quality is degraded, and therefore, the pressure cannot be increased easily.

As another method for preventing the intrusion of ink particles from the slit, a method of ejecting air in a direction intersecting the flight direction of ink droplets has been proposed (see patent document 2).

However, in the method described in patent document 2, as in the method of increasing the pressure in the cap, if the ejected air is strong, the flight direction of the ink droplets is bent, and the print quality is degraded. Therefore, the strength of the air is limited, and the penetration of the ink particles from the slit cannot be sufficiently suppressed.

Further, since the ejected ink particles adhere to the surface of a conveyor that conveys a print target and cause contamination, a new problem arises in that the conveyor must be cleaned every time printing is performed.

In view of the above-described conventional problems, an object of the present invention is to provide an ink jet printer that can minimize contamination of components of a print head and a transport conveyor without affecting print quality.

In order to achieve the above object, an ink jet printer according to the present invention includes a print head including:

a spray gun for applying constant-period vibration to the ejected ink to generate continuous ink drops;

a charging electrode that applies a voltage of a step wave shape synchronized with a period of the ink droplet to charge the ink droplet;

a deflection electrode for deflecting the charged ink droplets in a vertical direction or a horizontal direction according to a degree of charging, thereby landing the ink droplets on a printing surface of a print object; and

a tubular head cover which accommodates the ejection gun, the charging electrode, and the deflection electrode in a hollow portion and has a slit formed therein through which the charged ink droplets pass,

forming characters by printing dots in a plurality of rows by landing ink droplets ejected from the print head on the object to be printed moving in a horizontal direction or a vertical direction,

it is characterized in that the preparation method is characterized in that,

the hood is configured to include: a cylindrical cover main body with a closed rear end; and a cover mounted in a manner of covering the front part of the cover main body,

the cover is formed with: the slit; and an air outlet which surrounds at least a part of the slit,

air is ejected from the air outlet toward the print target.

Here, it is preferable that the cover is formed with: a port to which a pipe for air supply is connected; and an air flow path connecting the port and the air outlet.

In addition, preferably, the cover main body is made of metal.

Further, preferably, the air outlet is formed such that: at least an end portion of the slit near the outer peripheral portion of the cover is surrounded.

Further, it is preferable that air is supplied from an external compressor to the hollow portion of the head cap, and the hollow portion is maintained at a positive pressure during driving of the print head.

In the inkjet printer according to the present invention, the air outlet is provided so as to surround at least a part of the slit of the head cap, and air is ejected from the air outlet toward the print target, so that the fine ink particles that bounce off the print target can be prevented from penetrating into the inside of the cap through the slit to the minimum.

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

Further, the fine ink particles prevented from flying by the air are dispersed in the air, and the amount of ink adhering to the surface of the conveyor for conveyance is greatly reduced, so that the number of times of cleaning the conveyor can be reduced.

Drawings

Fig. 1 is a perspective view showing an external appearance of a print head according to embodiment 1 of the present invention.

Fig. 2 is a partially cut-away front view showing a schematic configuration of a continuous inkjet printer according to embodiment 1 of the present invention including the print head of fig. 1.

Fig. 3 is a diagram for explaining an operation when printing a print target object by using the inkjet printer of fig. 2.

Fig. 4 is a plan view of the cap in the headcap formed with slits through which ink droplets pass.

Fig. 5(a) is a front view of the lid, and fig. 5(b) and 5(c) are sectional views of the lid.

Fig. 6 is a photograph showing a state where the headcap is removed from the print head, fig. 6(a) is a photograph taken of a conventional print head, and fig. 6(b) is a photograph taken of the print head according to embodiment 1.

Fig. 7 is a plan view of the cover according to embodiment 2 of the present invention.

Fig. 8(a) is a front view of the lid according to embodiment 2, and fig. 8(b), 8(c), and 8(d) are cross-sectional views of the lid according to embodiment 2.

Description of the reference numerals

AR1, AR2 … air; 1 … ink jet printer; 10 … print head; 11 … a head cover; 12 … spray gun; 13 … charged electrode; 14 … monitoring the electrodes; 15 … deflection electrodes; 16 … recovery tank; 17a, 17b … tubes; 20 … ink cartridges; 30a, 30b … pump; 40 … printed matter; 110 … hollow portion; 111 … a mask body; 112 … cover; 113. 113a … thick-walled portion; 114. 114a … slit; 115. 115a … outlet; 116. 116a … port; 117. 117a … flow path.

Detailed Description

An inkjet printer according to an embodiment of the present invention will be described below with reference to the drawings.

(embodiment mode 1)

Fig. 1 is a perspective view showing an external appearance of a print head 10 to which a function of preventing contamination by ink bouncing on a printing surface is added, and fig. 2 is a partially cut front view showing a schematic configuration of a continuous inkjet printer (hereinafter, simply referred to as "printer") 1 according to the present embodiment including the print head 10. Fig. 3 is a diagram for explaining an operation when printing a print target object by the printer 1 of fig. 2.

The components of the printer 10 according to the present embodiment are roughly classified into: components related to printing by supplying ink to the print head 10 (hereinafter, these are referred to as "ink supply systems"); and components related to supplying air for pressurization and contamination prevention to the print head 10 (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 cartridge 20, and pumps 30a and 30 b. The print head 10 includes an ejection gun 12, a charging electrode 13, a monitor electrode 14, a deflection electrode 15, a recovery tank 16, and

tubes

17a and 17b, and these components are housed in a cylindrical head cap 11.

Although the components such as the ejection gun 12 constituting the print head 10 are actually disposed in close contact with the hollow portion 110 of the head cap 11, fig. 2 schematically illustrates the arrangement of the components for easy understanding and explanation of the structure and function of the components.

The spray gun 12 is configured to spray ink droplets ID toward a side surface of a print target, for example, a cosmetic case 4 (see fig. 3) in which a commodity is packed, and includes a spray gun body 121, an ultrasonic vibrator 122, and a nozzle 123. The ink sent from the ink cartridge 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 of being vibrated by the ultrasonic vibrator 122.

The ink column IP ejected from the orifice of the nozzle 123 is separated into ink droplets ID by the vibration applied by the ultrasonic vibrator 122, charged by the charging electrode 13, deflected by the deflection electrode 15 in accordance with the amount of charge of only the ink droplets ID necessary for printing, passed through the slit 114 formed in the front portion of the headcap 11, and landed on the printing surface of the object to be printed.

Shown in fig. 3 are: a cosmetic box (printed matter) 40 moving at a constant speed in a direction indicated by an arrow on a belt conveyor (not shown). In fig. 3, the head cap 11 of the print head 10, which is not involved in the printing operation, is omitted in consideration of easy visibility.

The cosmetic case 40 is formed in the form of a final product by coating the surface with a film made of polyethylene or polypropylene, filling food or the like in the case, and then printing a product number, a service life, or the like on the film.

As shown in fig. 3, when the cosmetic case 40 moves in the direction orthogonal to the flight direction of the ink droplet ID, the position of the ink droplet ID landed on the side surface of the cosmetic case 4 changes by changing the amount of deflection of the ink droplet ID, and when the ink droplet ID is repeatedly deflected in synchronization with the movement of the cosmetic case 4, a character (in the drawing, "a") is printed on the printing surface.

On the other hand, the uncharged ink droplets ID and the ink droplets ID that are not used for printing even if charged are not deflected, but fly into the recovery tank 16 for ink recovery as they are, and are recovered in the ink cartridge 20. The ink recovered in the recovery tank 16 is transferred from the pipe 17b to the ink cartridge 20 by the pump 30b and reused.

The operation of the printer 10 is controlled by a controller, not shown. The controller includes a CPU, a memory (ROM, RAM, etc.), a timer, and a display, and controls the operations of the ultrasonic vibrator 122 of the spray gun 12, the pulse power supply 131 of the charging electrode 13, the monitor electrode 14, the dc power supply 151 of the deflection electrode 15, and the

pumps

30a and 30 b.

Specifically, the controller drives the pump 30a to apply pressure to the ink contained in the ink cartridge 2 and supply the ink to the gun body 121. Further, the controller adjusts the number and timing of the charged ink droplets ID by controlling the timing of the pulse voltage applied from the pulse power supply 131 to the charging electrode 13 based on the signal monitored by the monitor electrode 14. Further, the controller adjusts the amount of deflection of the ink droplets ID deflected by the deflection electrodes 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 fig. 1 and 2 and new fig. 4 and 5 described above. Fig. 4 is a plan view of the cap 112 in the headcap 11 in which the slits 114 through which ink droplets pass are formed, fig. 5(a) is a front view of the cap 112, fig. 5(B) is a cross-sectional view taken along the line a-a of fig. 4, and fig. 5(c) is a cross-sectional view taken along the line B-B of fig. 4.

In the present invention, air (gas) compressed by a compressor is used to realize 2 functions. Specifically, the following are realized: a function of holding the inside of the head cover at a positive pressure, which is mounted on the continuous printer as a standard function; and a function of preventing the ink particles from intruding into the headcap through the slit by ejecting air to the ink particles rebounded on the printing surface.

Although not shown, the air supplied from the compressor through the pipe is first freed of excess moisture by the drain collector, and further freed of oil mist by the oil mist separator.

Then, the air split is formed into 2 pieces, and the air AR1 passed through one of the tubes is supplied to the hollow portion 110 of the hood 11, and the air AR2 split into the other tube is supplied to the air outlet 115 provided in the cover 112.

The functions of the 2-stream air AR1 and AR2 will be described together with the structure of the hood 11. As shown in fig. 2, the head cover 11 is configured to include: a cylindrical cover main body 111; and a cover 112 detachably attached to the front portion of the cover main body 111.

The cover main body 111 is made of metal to enhance resistance to external noise, and the cover 112 is made of resin in consideration of formability.

First, the function of the 1 st air AR1 will be described. A regulator (not shown) is attached to a middle portion of one of the pipes described above so that the pressure of the air compressed by the compressor is reduced to an appropriate value, and the air AR1 whose pressure is adjusted by the regulator is supplied to the hood 11.

As shown in fig. 2, a hole through which the tube 18 passes is formed in the cover 19 that closes the rear end portion of the cover main body 111 of the head cover 11, and the front end of the tube 18 opens into the hollow portion 110 of the head cover 11. The hollow portion 110 is sealed except for the slit 114 having a longitudinal shape, which is an opening portion for ejecting the ink droplet ID, and most of the air AR1 (indicated by the blank arrow) supplied through the tube 18 is retained in the head cap 11 to increase the air pressure.

In the continuous printer, since a part of the ink ejected from the nozzle 123 is scattered in the ambient atmosphere as ink mist and adheres to the surface of the component, which causes contamination and failure, it is necessary to periodically clean the components in the head cap 11. In addition, dust enters the ink circulation system through the recovery tank, and the tube or the like is clogged and causes a failure.

Accordingly, the main components of the print head 10 are housed in the head cap 11 and the interior of the head cap 11 is maintained at a positive pressure, thereby facilitating the discharge of ink mist to the outside and preventing dust from the outside from entering the interior of the head cap 11. By the above-described treatment, the cycle of cleaning the component parts can be extended, and clogging of the pipe or the like due to dust can be avoided.

Next, the function of the 2 nd air AR2 supplied to the cover 112 of the hood 11 through the other pipe will be described. A thick portion 113 is formed on the upper portion of the bottomed cylindrical cap 112, and the thick portion 113 is formed with: a slit 114 for ejecting ink droplets; and an air outlet 115 for ejecting air AR2 to the print object.

As shown in fig. 5(a), the outlet 115 of the 2 nd air AR2 is formed so as to surround the slit 114. As shown in fig. 5(b) and 5(c), the thick portion 113 has formed therein: a port 116 to which a pipe (not shown) for air supplied from the compressor is connected; and a flow path 117 connecting port 116 and outlet 115.

As shown in fig. 5(b), the reason why the flow path 117 extending from the port 116 is formed so as to surround the outlet port 115 is that: the intensity of the air AR2 blown out from the air outlet 115 is made uniform, and the flight of the ink droplets passing through the slit 114 is not affected.

As shown in fig. 4, a pair of locking pieces 118 are formed at positions facing the rear end of the cylindrical portion of the cover 112, while a pair of locking holes 119 are formed at positions facing the front portion of the cover main body 111, as shown in fig. 1.

When the cover 112 is attached to the cover main body 111, the cover main body 111 and the cover 112 are integrated by inserting the locking piece 118 of the cover 112 into the front portion of the main body 111 and then engaging the locking piece 118 with the locking hole 119.

As shown by solid arrows in fig. 2, in the present embodiment, an air outlet 115 is formed around a slit 114 in the cover 112 of the headcap 11 through which ink droplets pass, and air AR2 is ejected from the air outlet 115 toward the print target.

The air outlet 115 of the air AR2 is formed independently of the slit 114, and the blowing direction of the air AR2 is substantially parallel to the flight direction of the ink droplets ID, so that the air hardly collides with the ink droplets ID flying through the slit toward the print object. Therefore, the flight path of the ink droplet ID is not bent by the air AR2 and thus the print quality is not degraded.

On the other hand, since the ink particles that bounce off the print object are pushed back by the air AR2 blown out from the air outlet 115, the amount of ink particles that enter the head cap 11 through the slits 114 can be suppressed.

As a result, the degree of contamination of the components of the print head 10 with ink can be minimized. Further, the following situation can be avoided: solid matter of ink is deposited on the surface of the electrode or the like, and the deposited ink is short-circuited to a metal component of the print head including the cap, thereby causing a malfunction of the printer.

Further, as a secondary effect of the air AR2, by ejecting air to the ink landing on the print surface to promote drying of the ink, it is possible to prevent occurrence of fading and transfer of the ink.

If the pressure of the air AR2 blown out from the air outlet 115 is too high, the flight of the ink droplets passing through the slit 114 is affected, and the print quality is degraded. On the other hand, if the pressure of the air AR2 is weak, the amount of ink particles intruding into the head cap 11 increases. Therefore, the pressure of the air AR2 needs to be set in a range that can suppress the intrusion of ink particles without affecting the flight of ink droplets by experiment.

Fig. 6 is a photograph showing a state in which the headcap is removed from the print head after printing is repeatedly performed using the continuous printer, and is a photograph taken from the front of the upper and lower deflection electrodes 15 in the print head 10.

Fig. 6(a) is a picture of a conventional print head having no air outlet, and fig. 6(b) is a picture of a print head according to the present invention having an air outlet.

In the experiment, a cap formed with a slit having a center distance of 9mm and a width of 2.6mm was used as a conventional print head. Further, as the print head according to the present invention, a cover is used in which the periphery of the slit is surrounded by a blowing port having a width of 1 mm. Then, the air AR1 is supplied to the conventional print head, and AR1 and AR2 are supplied to the print head according to the present invention, and the pressure of the air is adjusted so that the air is slightly blown out from the slit and the air of a degree not affecting the flight of the ink droplets is blown out from the blow-out port.

As shown in fig. 6(a), in the conventional print head having no air outlet, ink adheres to the tip of the upper deflection electrode and causes solid matter to accumulate, as surrounded by a white circle, for example. When the solid matter is left to accumulate as described above, the tip of the solid matter comes into contact with other components and the cover body, which causes a failure or an accident.

In contrast, as shown in fig. 6(b), in the print head 10 according to the present invention in which the air blowing port 115 is provided in the cover 112, the solid matter hardly accumulates on the surface of the upper deflection electrode 15. Therefore, it is possible to prevent troubles and accidents caused by the accumulation of the solid ink material.

(embodiment mode 2)

Fig. 7 and 8 show still another example of the cover of the head cover. Fig. 7 is a plan view of the cover 112A, fig. 8(a) is a front view of the cover 112A, fig. 8(b) is a cross-sectional view taken along the line C-C in fig. 7, fig. 8(C) is a cross-sectional view taken along the line D-D in fig. 7, and fig. 8(D) is a cross-sectional view taken along the line E-E in fig. 7.

In the drawings, members having the same functions as those of the cover 112 of embodiment 1 are denoted by the same reference numerals. Note that, in order to distinguish from the cover 112 of embodiment 1, a letter "a" is assigned to each reference numeral.

As shown in fig. 5 described above, cover 112 according to embodiment 1 has flow path 117 formed to surround air outlet 115, and has flow paths connecting air outlet 115 and flow path 117 formed at equal intervals so that air can be uniformly blown out from air outlet 115.

In general, the cover 112 is manufactured by injection molding, but when the flow path 117 connecting the port 116 and the outlet 115 is complicated, the manufacturing cost of the mold increases.

In contrast, in the cover 112A according to the present embodiment, as shown in fig. 8, a semicircular air outlet 115A is formed in the upper portion of the slit 114A, and the air outlet 115A and the port 116A are connected by a rectangular parallelepiped flow path 117A. Since the shape of the flow channel 117A is simplified, the manufacturing cost of the mold can be suppressed as compared with the cover 112 of embodiment 1.

Air outlet 115A according to the present embodiment is deviated from air outlet 115 according to embodiment 1 in the air ejected toward the print surface. However, from the experimental results, it is known that: if the flow path 116A is formed so that the air blown out from the air outlet 115A is directed slightly toward the center of the cylinder, the effect of preventing the adhesion of ink hardly changes.

Therefore, according to the specifications required for the print head 10, the arc-shaped air outlet 115A and the simple-shaped flow path 117A shown in embodiment 2 can be used without forming the air outlet 115 and the complex-shaped flow path 117 surrounding the slit 114 as shown in embodiment 1.

In the above embodiments, the cylindrical head cap is used as the head cap of the print head, and the main member is housed in the hollow portion of the head cap. The head cover having a quadrangular or hexagonal cross section can be used in accordance with the shape and arrangement of the constituent members.

In addition, in each of the above embodiments, the case where the print target moving in the horizontal direction is printed has been described, but the moving direction of the print target is not limited to this, and for example, even in the case where the print target moves in the vertical direction, the following can be introduced: the function of preventing contamination of the print head caused by ink bouncing on the printing surface. In this case, the ink droplets are deflected in the horizontal direction.

Claims

1. An ink jet printer includes a print head, and the print head includes:

it is characterized in that the preparation method is characterized in that,

the cover is formed with: the slit; and a blow-out port surrounding at least a part of the slit,

air is ejected from the air outlet toward the print target.

2. The inkjet printer of claim 1,

the cover is provided with: a port to which a pipe for air supply is connected; and an air flow path connecting the port and the air outlet.

3. The inkjet printer according to claim 1 or 2,

the cover body is made of metal.

4. The inkjet printer according to claim 1 or 2,

the air outlet is formed as follows: at least an end portion of the slit near the outer peripheral portion of the cover is surrounded.

5. The inkjet printer of claim 1,

air is supplied from an external compressor to the hollow portion of the head cap, and the hollow portion is maintained at a positive pressure during driving of the print head.

6. The inkjet printer of claim 2,

7. The inkjet printer of claim 4,