JPH0679869A - Image printing equipment - Google Patents

Abstract

PURPOSE:To position a diaphragm to a valve seat quickly and accurately. CONSTITUTION:A piezoelectric element 34 freely forwarded and retreated in the axial direction is engaged into a flange 20, to which a cap with an ink nozzle is installed, by insertion, and a valve seat is mounted at the opening end of the rear section of the ink nozzle. A compression coil spring pushing the piezoelectric element 34 against the valve seat side is set up, and a push scale 4 detecting pushing force by the compression coil spring is mounted. A sleeve 16 having a pressure medium 35 and fixing the piezoelectric element 34 to a holder 15 is installed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image printing apparatus for expressing a gradation of a pixel which is a minimum unit of an image by changing a recording area in the pixel or a printing density.

[0002]

2. Description of the Related Art An image for printing is composed of a set of pixels which is the minimum unit. Therefore, conventionally, an image printing apparatus for recording each of these pixels based on image information of each pixel has been developed. In this type of image printing apparatus, the printing area in the pixel is changed or the printing density of the pixel is changed. By doing so, gradation expression in each pixel is performed.

A conventional image printing apparatus of this type includes an actuator control device arranged near the original screen and a spray gun as a head electrically connected to the actuator control device via an electromagnetic valve. Is equipped with
The spray gun nozzle is directed toward the paper surface while moving the original image and paper synchronously, and the ink in the ink tank is drawn out by the siphon action generated by the pressure of the air whose flow rate is controlled by the solenoid valve. It is configured to be sprayed onto the paper surface from. At this time, the actuator control device outputs the image information for each pixel in the original image and controls the solenoid valve ON-OFF, so the ink is intermittently ejected from the nozzle of the spray gun and the image information of the original image is displayed on the surface to be printed. The image having the corresponding gradation is printed.

However, since the head in such a conventional image printing apparatus is a siphon type spray gun equipped with the above-mentioned solenoid valve, the weight of the entire apparatus including the valve element is heavy and not easy to handle. However, the valve structure has poor responsiveness, and the control of the ink amount through the air, which is a compressive fluid, further delays the response, resulting in poor reproducibility of image information. is there. Further, for the above reason, there is a problem that the adjustment and maintenance work when using this is complicated and requires a lot of labor and time.

Therefore, the present applicant has proposed and published a head of an image printing apparatus described in Japanese Patent Application No. 1-96355 as a solution to the above-mentioned problems, which will be described below. To do. This head is provided with a casing formed in a bottomed cylindrical shape and supported by a supporting member, and an air flow path is provided in the center of the nozzle head forming the bottom surface of the casing facing the printing surface. An air nozzle connected to an air source and an ink nozzle connected to an external pressurized ink tank via an ink flow path are concentrically arranged with the ink nozzle inside.

A valve seat is formed at the rear open end of the ink nozzle, and the central portion of the diaphragm whose outer peripheral portion is supported by the nozzle head is in close contact with the valve seat, and the central portion of the plane of the diaphragm. The working end of an actuator such as a piezoelectric element supported by a support member in the housing is integrally fixed to the.

With this configuration, when the air source is operated, the ink ejected from the ink nozzles is wrapped with the air ejected from the air nozzles provided outside the ink nozzles, and the ink is dispersed according to the adjusted dispersion distribution. Go straight.
At this time, the actuator control unit outputs the image information for each pixel in the original image to control the ON / OFF of the actuator, so the actuator advances and retracts the diaphragm to open and close the valve seat, and ink is intermittently ejected from the ink nozzle. Thus, an image having a gradation corresponding to the image information of the original image is printed on the surface to be printed.

[0008]

As described above, since the head of the above apparatus is not a spray gun, the weight is light and easy to handle, and the responsiveness and the reproducibility of image information are good. Such problems remain.

That is, when the ink supply pressure is changed to adjust the valve opening to zero or to adjust the ink density, the diaphragm is separated from the valve seat unless the position of the diaphragm with respect to the valve seat is adjusted to a predetermined position. In this case, the ink constantly flows out from the ink nozzles and printing does not work.
Also, if the diaphragm presses the valve seat strongly, even if the piezoelectric element is ON-OFF controlled and the diaphragm retracts,
There may be no gap between the diaphragm and the valve seat, and the ink may not flow out.

Therefore, in the above device, the positions of the piezoelectric element and the diaphragm are moved and adjusted by the screw mechanism until the ink does not flow out from the nozzle. In this case, the diaphragm strongly presses the valve seat as described above. The diaphragm is in the proper position with respect to the valve seat because the piezoelectric element is moved by the screw mechanism.
I don't know if it's pushed too far, so I have to adjust it many times while watching the print condition, and the amount of movement for adjustment is a few micron, so the adjustment is troublesome. There is a problem that it takes a long time.

The present invention has been made in view of the above points, and an object of the present invention is to provide an image printing apparatus capable of quickly and accurately adjusting the position of the diaphragm with respect to the valve seat.

[0012]

In order to achieve such an object, according to the present invention, a nozzle head having an ink nozzle and a housing in which the nozzle head is mounted are provided so as to be movable back and forth in the axial direction thereof. In an image printing apparatus including an actuator and a valve seat formed at the rear opening end of the ink nozzle, a pressing unit that presses the actuator toward the valve seat, and a pressing force detection that detects the pressing force by the pressing unit. Means and actuator fixing means for fixing the actuator to the housing are provided.

[0013]

When the printing operation is started, the pressurized air is sent from the air source of the head to the air chamber through the air flow path and ejected from the air nozzle. At the same time, the ink pressurized from the pressurized ink tank is discharged. It is guided to the valve seat through the ink flow path and the ink chamber, and is ejected from the ink nozzle through the gap between the valve seat and the diaphragm. The jetted ink goes straight with a dispersion distribution adjusted by being wrapped by the air flow formed by the air jetted from the air nozzle, and is printed as clear pixels on the printing surface of the paper.

At this time, ON-OFF according to the image information of the original image
Since the drive signal is input to the piezoelectric element 34, the piezoelectric element 34 is ON-OFF controlled, the diaphragm 25 advances and retreats, and the valve seat 29 opens and closes. As a result, the ink passes through the valve seat 29 only when the valve seat 29 is opened, so that an image having a gradation according to the image information of the original image is printed on the printing surface of the paper 1.

In the head which operates in this manner, the head of the head is placed at a position where the valve seat can be closed by pushing the actuator in the direction of closing the valve seat with a force slightly larger than the force generated by the ink supply pressure. The actuator can be adjusted in position.

[0016]

1 to 9 show an embodiment of an image printing apparatus according to the present invention. FIG. 1 is a vertical sectional view of a head, FIG. 2 is a front view of the head, and FIG. 3 is an enlarged vertical sectional view of a tip portion of the head. Figure, Figure 4
Is a front view of the entire image printing apparatus, FIG. 5 is a plan view of a head and its supporting portion, FIG. 6 is a front view of the same, FIG. 7 is a plan view of a push scale, and FIG. 8 is a plan view of a moving base for a head adjusting jig. 9 is a side view of the same. In the drawing, on the peripheral surface side of the drum 2 having the paper 1 wound around the peripheral surface, a plurality of sets, which are indicated by reference numeral 3, as a whole, four sets of image printing apparatuses, which is the number of printing colors in this embodiment, are provided on the drum 2 Base 4 parallel to the axial direction of
The base 4, which is fixed to the upper side and carries the image printing device 3, is configured to be driven by a driving device to advance and retreat in the axial direction of the drum 2 on a linear rail (not shown).

Each of the four sets of image printing devices 3 has a fixed base 5 supported on the base 4 and having a rectangular shape in plan view.
The fixed base 5 has a shaft hole extending in a direction (hereinafter, this direction is referred to as a front-back direction) orthogonal to its moving direction (hereinafter, this direction is referred to as a left-right direction). However, it is formed so as to be able to move back and forth in the front-rear direction and is pivotally supported.

At the protruding portion of the head support shaft 6 protruding from the fixed base 5 to the drum 2 side, a bracket 7 formed in an L shape in a front view is provided with a horizontal member 7a having a U-shaped cross section as the fixed base 5. The head 9 shown in detail in FIGS. 1 to 3 is supported by being split-tightened and fixed by the bracket 7.

The projecting ends of the pair of head support shafts 6 projecting rearward from the fixed base 5 are connected to the end faces of the head support shafts 6 by a connecting plate 10 fixed by bolts 52. A compression coil spring 11 for biasing the head 9 backward is interposed between the head support shaft 6 and the fixed base 5.

Further, an adjusting screw shaft 12 is provided on the rear end surface of the fixed base 5 so as to be located at the center of the fixed base 5 in the left-right direction, and the adjusting screw shaft 12 is connected to the connecting plate 10.
Through the shaft hole 10a and protrudes rearward from the connecting plate 10. Reference numeral 13 denotes an adjusting nut screwed to a rear end screw portion of the movement adjusting shaft 12 protruding rearward from the connecting plate 10, and having a boss portion fitted into the shaft hole 10a of the connecting plate 10 and a bolt 14
Is loosened by rotating the adjusting nut 13 after loosening the bolt 14, the compression coil spring 11
The head support shaft 6 moves while expanding and contracting, and the distance between the head 9 and the drum 2 is adjusted.

The head 9 is provided with a cylindrical holder 15 supported by a bracket 7, and a fixed bush consisting of a cylindrical sleeve 16 with a collar and a disk-shaped plate 17 at the rear open end thereof. 18 is fixed by a bolt 19. Further, a flange 20 formed in the shape of a stepped disc is fixed to a front opening end of the holder 15 by a plurality of setscrews 21.

At the center of the flange 20, a disc-shaped cap 23 having an air nozzle 22 chamfered like a dish on the holder 15 side is fitted, and at the step of the flange 20, A disk-shaped diaphragm 25 having a hemispherical tip 24 at the center is supported by the O-ring 25a and the end surface of the holder 15 at the outer peripheral portion and is interposed.

The central portion of the diaphragm 25 and the flange 20
An annular ink chamber 26 is formed between the ink chamber 26 and the center of the ink chamber, and the ink chamber 26 is connected to an external pressurized ink tank through an ink flow path 27 provided in the flange 20. In the air nozzle 22 at the center of the cap 23,
A nozzle portion 20a at the center of the flange 20 is engaged, and an ink nozzle 28 having one end open to the outside is bored at the center of the nozzle portion 20a.

At the rear opening end of the ink nozzle 28, a valve seat 29 that opens and closes due to deformation of the diaphragm 25.
Are formed. An annular air chamber 30 is formed around the base of the nozzle portion 20a.
0 is connected to an external air source via an air flow path 31 provided in the flange 20.

The holder 32 has a cylindrical shape.
Is a case slidably fitted in the inner hole 15a of the sleeve 16 and the inner hole of the sleeve 16, and a cap 33 is screwed to the threaded portion at the rear end of the case. A base of a piezoelectric element 34 as an actuator that is brought into contact with the hemispherical chip 24 is fixedly supported. The cylindrical pressure medium 3 is formed in the cylindrical portion of the sleeve 16.
5 is buried, by tightening the bolt 19,
The case 32 is slightly deformed in the axial direction, the pressure medium 35 is compressed and expands in the inner peripheral direction, and the case 32 becomes
It is configured to be fixed to the holder 15.

Further, the piezoelectric element 34 is connected to the control device by a lead wire 36, and a drive signal corresponding to the pixel information of the original image is input to the piezoelectric element 34, and the piezoelectric element 34 is turned on / off to control the diaphragm 25. It is configured to move back and forth in the front-back direction to open and close the valve seat 29.

Reference numeral 40 generally designates a head adjusting jig as a pressing means for pressing the piezoelectric element 34 through the case 32. The head adjusting jig moves in an L shape in a front view and a rectangular shape in a plan view. The moving base 41 is provided with a hook 42 protruding from the fixed base 5.
An elongated hole 41a that engages with is provided. A pair of left and right brackets 53, which are integrally formed with the moving base 41 and hang down from the bottom surface of the moving base 41, rotatably support a pin 54. The bolt 55 is screwed so as to move back and forth.

By doing so, the movable base 41 is fixed to the fixed base 5 while the elongated hole 41a and the hook 42 are engaged with each other.
Since the inclined surface of the hook 42 and the inclined surface of the long hole 41a are engaged with each other by placing the fixed base 5 on the upper side and pulling the fixed base 5 rearward, the fixing bolt 55 is rotated together with the pin 54 and the tip thereof is rotated. By tightening the fixing bolt 55 while facing the rear end surface of the base 4, the head adjusting jig 40
Since the whole is fixed to the fixed base 5, the attachment and detachment by the fixing and the fixing release are repeated for the four sets of image printing apparatuses 3 to perform the head adjustment described below.

An indicator 43 is provided on the upper surface of the moving base 41.
A case 45 of a push scale 44 provided with is supported so as to be able to move back and forth in the front-rear direction, and rods 48 of the bearings 46 and 47 provided on the front and rear end surfaces of the case 45 are the rear end surface of the case 32. The cap 33 is supported by the end face of the cap 33 so as to be adjustable in forward and backward directions.

A compression coil spring 50 for urging the rod 48 forward is interposed between the bearing 49 in the case 45 and the bearing 47. A bracket 56 is provided on the rear end portion of the moving base 41 so as to project upward, and the screw portion or the tip of the adjusting screw 51 is brought into contact with the rear end surface of the case 45 in a screw hole provided in the bracket 56. It is screwed in contact. By doing so, when the adjusting screw 51 is rotated, the case 4 is moved along with the rod 48 that moves forward and backward by the screw action.
5 moves forward and backward, the piezoelectric element 34 is pressed to adjust its position, and the load value of this pressing force is displayed on the display 43.

The operation of the image printing apparatus configured as above will be described. When the adjustment nut 13 is rotated before the printing operation, the moving plate 10 moves in the front-rear direction along with the head support shaft 6 by the screw action, and the head 9 supported by the head support shaft 6 via the bracket 7 is moved. By moving, the distance between the head 9 and the drum 2 is adjusted. Then, this adjustment is separately performed for each of the four color heads.

Next, the position of the piezoelectric element 34 for opening and closing the valve seat 29 is adjusted separately for each of the four color heads 9. For this purpose, the entire head adjusting jig 40 removed from the machine base is held behind the head 9 of the first color, and the long hole 41a provided in the moving base 41 is engaged with the hook 42 on the fixed base 5 side. After placing the head adjusting jig 40 on the fixed base 5 while moving the head adjusting jig 40 backward, the inclined surface of the long hole 41a and the inclined surface of the hook 42 are brought into contact with each other and are accurately positioned. At 55, the entire head adjusting jig 40 is fixed on the fixed base 5.

After mounting the head adjusting jig 40 in this manner, the bolt 1 for fixing the fixing bush 18 to the case 15
When 9 is loosened, the compression medium 35 elastically returns and the sleeve 1
The case 32 is released from the fixing of the case 32, and the case 32 and the piezoelectric element 34 integrated with the case 32 are movable. Then, when the adjusting screw 51 is rotated in the tightening direction, the push scale 44 of the head adjusting jig 40 moves against the elastic force of the compression coil spring 50, and the tip of the rod 48 causes the cap 33 of the head 9 to move. Push the rear end face.

When the case 32 integrated with the cap 33 moves together with the piezoelectric element 34, the load value of the push scale 44 changes, and the load value is calculated from the ink supply pressure while observing the display 43. When the turning operation of the adjusting screw 51 is stopped when the proper load value is reached and then the bolt 19 of the fixed bush 18 is tightened, the case 32 is slightly deformed in the axial direction, the pressure medium 35 is compressed, and the inner circumference is reduced. Enlarged in the direction, the case 32 is fixed to the sleeve 16 and the case 32.

By carrying out such adjustment of the load value for each of the four color heads 9 by attaching and detaching the head adjusting jig 40, the four color heads 9 are adjusted to proper states. The paper 1 is wound around the drum 2 to start the printing operation.

That is, the pressurized air from the air source of the head 9 is sent into the air chamber 30 through the air flow path 31 and ejected from the air nozzle 22. At the same time, the ink pressurized from the pressure ink tank is guided to the valve seat 29 through the ink flow path 27 and the ink chamber 26, passes through the gap between the valve seat 29 and the diaphragm 25, and is ejected from the ink nozzle 28. Gush out. The jetted ink travels straight with a dispersed distribution adjusted by being wrapped by the airflow formed by the air jetted from the air nozzle 22, and is printed as clear pixels on the printing surface of the paper 1.

At this time, according to the image information of the original picture,
Since the ON-OFF drive signal is input to the piezoelectric element 34, the piezoelectric element 34 is ON-OFF controlled, the diaphragm 25 advances and retreats, and the valve seat 29 opens and closes. As a result, the ink passes through the valve seat 29 only when the valve seat 29 is opened, so that an image having a gradation according to the image information of the original image is printed on the printing surface of the paper 1.

In the head 9 which operates in this way,
A position where the valve seat 29 can be closed by pushing the piezoelectric element 34 in the direction of closing the valve seat 29 with a force slightly larger than the force generated by the ink supply pressure,
It becomes possible to adjust the piezoelectric element 34 in the head 9 of each color.

In this embodiment, the piezoelectric element 34
Although the compression coil spring 50 is illustrated as the pressing means for pressing the valve seat 29 toward the valve seat 29 side, the present invention is not limited to this, and any device that can generate a load may be used. Further, in the present embodiment, the example in which the head adjusting jig 40 is detachably provided is shown, but it is not always necessary and a fixed type may be used. Further, the configuration of the head 9 is not limited to that of this embodiment, and any configuration may be used as long as the principle is the same. Further, the number and arrangement of the heads 9 are not limited to those in this embodiment.

Further, the display unit 43 may be one which is electrically detected and displayed, or may be one which is of the digital display type. Further, in the present embodiment, the example in which the sleeve 16 in which the pressure medium 35 is embedded is used as the fixing means of the actuator is shown, but the sleeve 16 may be fixed by a bolt or the like. However, the use of the sleeve 16 has an effect that the position of the case 32 does not shift.

[0041]

As is apparent from the above description, according to the present invention, a nozzle head having an ink nozzle, and an actuator provided in a housing in which the nozzle head is mounted so as to be movable back and forth in the axial direction thereof. An image printing apparatus including a valve seat formed at the rear opening end of the ink nozzle, a pressing unit that presses the actuator toward the valve seat, and a pressing force detection unit that detects the pressing force of the pressing unit,
By providing the actuator fixing means for fixing the actuator to the housing, it is not necessary to move the actuator with an accuracy of several microns as in the conventional case when adjusting the position of the actuator, and the load can be applied by a member with low dimensional accuracy such as a spring member. The workability is improved, the adjustment time is shortened, and the operation rate of the device is improved.

Further, even if the diaphragm, which is an intermediate member between the pressurizing means and the valve seat, the actuator, the case, etc. is deformed or compressed, the actuator is adjusted to an appropriate position only by holding the pressurizing load constant. Because you can
Workability is improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a head.

FIG. 2 is a front view of a head.

FIG. 3 is an enlarged vertical cross-sectional view of a head tip portion.

FIG. 4 is a front view of the entire image printing apparatus.

FIG. 5 is a plan view of the head and its supporting portion.

FIG. 6 is a front view of a head and a supporting portion thereof.

FIG. 7 is a plan view of a push scale.

FIG. 8 is a plan view of a moving base for a head adjusting jig.

FIG. 9 is a side view of a moving base for a head adjusting jig.

[Explanation of symbols]

 3 Image Printer 9 Head 15 Holder 18 Fixed Bushing 19 Bolt 23 Cap 25 Diaphragm 25a O-ring 26 Ink Chamber 27 Ink Channel 28 Ink Nozzle 29 Valve Seat 30 Air Chamber 31 Air Channel 32 Case 33 Cap 34 Piezoelectric Element 35 Pressure Medium 40 head adjusting jig 41 moving base 44 push scale 45 case 48 rod 50 compression coil spring 51 adjusting screw

Claims (1)

[Claims] 1. A nozzle head having an ink nozzle,
In an image printing apparatus including an actuator provided in a housing in which the nozzle head is mounted so as to be movable back and forth in the axial direction thereof, and a valve seat formed at a rear opening end of the ink nozzle, the actuator is provided with the valve. An image printing apparatus comprising: a pressing unit that presses the seat side; a pressing force detection unit that detects the pressing force of the pressing unit; and an actuator fixing unit that fixes the actuator to the housing.