JP2001287341A - Ink amount sensing sensor and ink leakage preventing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable sensing of two types of ink amounts having different objects of sensing the ink amount in an ink reservoir for automatically supplying the ink amount to maintain the ink amount in a predetermined range in the reservoir, and sensing an abnormal increase in the ink amount in the reservoir by one ink amount sensing sensor. SOLUTION: The ink amount sensing sensor 27 for sensing the amount of the ink by sensing an electrostatic capacity of the ink stored in the ink reservoir 15 comprises a needle 27a inserted into the ink in the reservoir 15 to sense an increasing or decreasing state of the ink in a predetermined range, and an abnormal increase sensing unit 27b to be contacted with the ink when the ink in the reservoir 15 is abnormally increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink amount sensor for detecting the amount of ink accumulated in an ink reservoir of a printing apparatus, and to prevent leakage of ink from the ink reservoir using the ink amount sensor. The present invention relates to a device for preventing ink leakage.

[0002]

2. Description of the Related Art As an example of a conventional printing apparatus, the structure of a stencil printing apparatus will be described with reference to FIGS. FIG. 5 is a longitudinal sectional front view showing the internal structure of the stencil printing machine, FIG. 6 is a front view showing the structure of the ink amount detection sensor and the arrangement of the ink amount detection sensor in the ink reservoir, and FIG. is there. The stencil printing apparatus includes an image reading unit 1,
It comprises a plate making section 2, a printing section 3, a plate discharging section 4, a sheet feeding section 5, a sheet discharging section 6, and the like.

The image reading section 1 is for optically reading an image of a document located on a contact glass.

The plate making section 2 is read by an image reading section 1 by holding a master base paper 7 wound in a roll shape, a platen roller 9 for pulling out the master base paper 7, and heating and perforating the master base paper 7 by melting and perforating. It comprises a thermal head 10 for forming a perforated image corresponding to the image of the document, a cutter 11 for cutting the master base paper 7 on which the perforated image is formed to a predetermined length, and the like. A master (not shown) is created by cutting the master base paper 7 on which the perforated image is formed into a predetermined length by the cutter 11.

The printing unit 3 is rotated around an axis and is wound around the outer peripheral surface thereof. A porous cylindrical cylinder 12 on which a master is wound, and a press roller movable to a position which comes into contact with and separates from the outer peripheral surface of the plate cylinder 12. 13, an ink supply mechanism 14 provided inside the plate cylinder 12, an ink reservoir 15 formed in the plate cylinder 12 and storing the ink supplied by the ink supply mechanism 14, and the like. In the printing unit 3, the printing paper 16 fed from the paper feeding unit 5 is sandwiched between the plate cylinder 12 around which the master is wound and the press roller 13, and at this time,
Printing is performed by the ink supplied by the ink supply mechanism oozing from the perforated portion of the master and transferred to the printing paper 16.

[0006] The plate discharging section 4 is a place where the used master that has become unnecessary after the printing of a predetermined number of sheets is peeled off from the outer peripheral surface of the plate cylinder 12 and the peeled master is stored. Peeling mechanism 1 for peeling from the outer peripheral surface of
7 and a storage box 18 for storing the master peeled off from the plate cylinder 12.

The paper supply section 5 is where the printing paper 16 to be fed to the printing section 3 is set, and the paper discharge section 6 is where the printing paper 16 after printing is discharged.

The ink supply mechanism 14 includes an ink container 19,
Ink pump 2 for sucking ink in ink container 19
0, a pump drive motor 2 for driving the ink pump 20
1. It is constituted by an ink supply branch pipe 22 for guiding the ink sucked by the ink pump 20 to the ink reservoir 15 and the like.

The ink reservoir 15 is a wedge-shaped space formed by being sandwiched between an ink roller 23 and a doctor roller 24 arranged inside the plate cylinder 12 with an axis parallel to the axis of the plate cylinder 12. When the ink roller 23 and the doctor roller 24 rotate in the direction of the arrow shown in FIG. 6 together with the rotation of the plate cylinder 12 during printing or the like, the ink is rotated and flows into the ink in the ink reservoir 15 with the rotation. The force acts, and the ink in the ink reservoir 15 rotates and flows in the direction of the arrow around the rotational flow center "A".

Further, the ink in the ink reservoir 15 is
While performing this rotational flow, the ink reservoir 1
5 in the longitudinal direction, and the lateral movement makes the ink amount substantially uniform over the entire area of the ink reservoir 15 in the longitudinal direction.

In such a stencil printing apparatus, when the amount of ink in the ink reservoir 15 reaches the lower limit, the ink pump 20 is driven to automatically supply ink into the ink reservoir 15 and When the amount of ink in the ink reservoir 15 reaches the upper limit, the operation of the ink pump 20 is stopped, and an automatic ink replenishment method is employed in which the amount of ink in the ink reservoir 15 is maintained within a predetermined range. In order to perform this automatic ink replenishment, the ink reservoir 15 has an electrostatic capacity that detects the amount of ink accumulated in the ink reservoir 15 by detecting the capacitance of the ink accumulated in the ink reservoir 15. Ink amount detection sensor 25 of capacity detection type
Is arranged. This ink amount detection sensor 25 includes:
A pair of needle portions 25a and 25b to be inserted into the ink in the ink reservoir 15 are formed, and a lead wire 26 for connecting to a control unit (not shown) is provided. A pump drive motor 21 is connected to the control unit. The control unit receives a detection value (capacitance detection output value) of the capacitance of the ink accumulated in the ink reservoir 15 from the ink amount detection sensor 25. Then, a control signal is output to the pump drive motor 21 according to the capacitance detection output value, and the ink pump 20 is turned on / off via the pump drive motor 21. When the ink pump 20 is turned on and off in this manner, the supply of the ink into the ink reservoir 15 is automatically performed.

The capacitance detection output value output from the ink amount detection sensor 25 depends on the printing conditions such as changes in the environment in which the stencil printing apparatus is installed, changes in the ink itself, and variations in the type of ink. May be greatly reduced. For example, when the surrounding environment becomes extremely low in humidity, when the ink in the ink reservoir 15 is rotated for a long time without being consumed, or when the ink in the ink reservoir 15 is left for a long time. Under non-normal printing conditions, such as evaporation of water in the ink, the dielectric constant of the ink is reduced, and even though a sufficient amount of ink is present in the ink reservoir 15, the static electricity from the ink amount detection sensor 25 is detected. The capacity detection output value decreases. In such a case, the replenishment of the ink into the ink reservoir 15 is continued even though a sufficient amount of ink is present in the ink reservoir 15, and the ink reservoir 15
The ink inside increases abnormally, and the supplied ink leaks out of the ink reservoir 15. The ink leaking out of the ink reservoir 15 stains the stencil printing machine itself, stains the printing paper 16 fed to the printing unit 3, and stains the periphery of the place where the stencil printing machine is installed. .

An invention for preventing such leakage of ink from the ink reservoir is disclosed in Japanese Patent Application Laid-Open No. 60-1473.
The invention described in Japanese Patent Publication No. 82 is known. According to the invention described in Japanese Patent Application Laid-Open No. Sho 60-147382, an optical sensor for detecting an abnormal increase in the amount of ink in an ink reservoir is used for automatically replenishing ink. It is provided separately from the ink amount detection sensor of the capacitance detection type.

[0014]

Problems to be Solved by the Invention JP-A-60-1473
According to the invention described in JP-A-82-82, an optical sensor is required separately from an electrostatic capacity detection type ink amount detection sensor for automatically replenishing ink, and a detection circuit corresponding to each sensor is required. Is required separately. For this reason, two types of sensors and two types of detection circuits are required, which increases the cost.

Further, since the sensor has two types of sensors, a large installation space for installing the sensors is required.
Further, the number of parts for installing the sensor and the number of assembly steps for installing the sensor are increased.

In addition, the optical sensor is complicated since it has to be cleaned each time ink adheres to the ink when the amount of ink is abnormally increased. Furthermore, scattered ink may adhere even if ink does not occur due to an abnormal increase in the amount of ink.If the scattered ink adheres to the optical sensor, the amount of ink in the ink reservoir may be an appropriate amount. Nevertheless, it may be erroneously detected that the ink amount is abnormally increased.

According to the present invention, the amount of ink in the ink fountain for detecting the amount of ink in the ink fountain for automatically replenishing the ink so as to maintain the amount of ink in the ink fountain within a predetermined range, and the amount of ink in the ink fountain is abnormally increased 2 with different purpose with detection of
An object of the present invention is to provide an ink amount detection sensor capable of detecting various kinds of ink amounts.

An object of the present invention is to provide an ink leakage preventing device for preventing the ink in the ink reservoir from abnormally increasing to a predetermined amount or more and leaking ink from the ink reservoir.

[0019]

According to the first aspect of the present invention,
In a capacitance detection type ink amount detection sensor for detecting an amount of ink accumulated in an ink reservoir formed in a plate cylinder driven to rotate about an axis, a needle portion inserted into the ink in the ink reservoir. And an abnormal increase detecting section that comes into contact with the ink when the ink in the ink reservoir increases abnormally.

Therefore, when the amount of ink in the ink reservoir increases or decreases within a predetermined range, the needle portion (part of the ink amount detection sensor) inserted into the ink in the ink reservoir along with the increase or decrease of the ink. ) And the ink changes, and the ink amount detection sensor detects the capacitance of the ink in accordance with the change, and detects the ink amount based on the capacitance detection output value. In addition, when the ink in the ink reservoir increases abnormally, the abnormally increased ink contacts the abnormal increase detecting section and the contact area between the ink and the ink amount detecting sensor increases. The capacitance detection output value also increases, and an abnormal increase in ink is detected. For this reason, one ink amount detection sensor detects the amount of ink in the ink fountain for automatically replenishing the ink so as to maintain the amount of ink in the ink fountain within a predetermined range, and the amount of ink in the ink fountain is It is possible to detect two types of ink amounts having different purposes, that is, detecting the abnormal increase.

According to a second aspect of the present invention, in the ink amount detecting sensor according to the first aspect of the present invention, the needle portion and the abnormal increase detecting portion are integrally formed.

Therefore, the structure of the ink amount detection sensor can be simplified and downsized, and the ink amount detection sensor can be installed in a small installation space. The number of components and the number of assembling processes required for installing the detection sensor are reduced.

According to a third aspect of the present invention, in the ink amount detecting sensor according to the first or second aspect, the abnormal increase detecting section is configured to reduce a contact area with the ink when the ink in the ink reservoir increases abnormally. It is formed in a shape that increases rapidly.

Therefore, when the ink in the ink reservoir increases abnormally, the contact area where the ink comes into contact with the abnormal increase detecting portion sharply increases, so that the capacitance detection output value from the ink amount detecting sensor sharply increases. As a result, the abnormal increase in ink can be reliably detected.

The invention described in claim 4 is the first to third aspects of the present invention.
In the ink amount detection sensor according to any one of the above, in a portion of the abnormal increase detection unit facing the ink in the ink reservoir, a rotational flow direction of the ink that rotates and flows in the ink reservoir when the plate cylinder rotates. Has an inclined surface portion inclined in the forward direction.

Therefore, after the abnormally increased ink comes into contact with the abnormal increase detecting section, when the ink is consumed and gradually decreases, and the contact between the ink and the abnormal increase detecting section is eliminated, the ink is moved to the inclined surface section. The ink is cut off from the abnormal increase detection part because it slides down along the way, and it is prevented that the ink is abnormally increased even if the abnormal increase state of the ink is eliminated. You.

[0027] The invention according to claim 5 is the invention according to claims 1 to 4.
In the ink amount detection sensor according to any one of the above, the needle portion and the abnormal increase detection portion are spaced apart from each other by a predetermined dimension along an axial direction of a rotational flow center of the ink rotationally flowing in the ink reservoir portion. Have been.

Therefore, when the abnormally increased ink in the ink reservoir contacts the abnormal increase detector and the needle, the abnormal increase detector and the needle respectively rotate and flow in the ink reservoir 15. Even if it becomes resistance, part 2
By the synergistic action of the two resistances, it is possible to prevent the rotational flow of the ink in the ink reservoir 15 from being largely obstructed. For this reason, even when the ink is abnormally increased in the ink reservoir, the rotational flow of the ink is smoothly performed, and the lateral movement of the ink accompanying the rotational flow is smoothly performed.

According to a sixth aspect of the present invention, there is provided the ink leakage preventing device according to any one of the first to fifth aspects, wherein the ink leakage preventing device is disposed in an ink reservoir formed in a plate cylinder that is driven to rotate about an axis. An ink pump for replenishing the ink reservoir with ink; and a control unit for turning on and off the ink pump according to a detection result from the ink amount sensor.

Therefore, when the amount of ink in the ink reservoir increases abnormally, the abnormally increased ink comes into contact with the abnormal increase detecting portion of the ink amount detecting sensor to detect the abnormal increase. In response, the control unit turns off the ink pump, stops further ink supply into the ink reservoir, and prevents leakage of ink from the ink reservoir.

[0031]

FIG. 1 shows a first embodiment of the present invention.
A description will be given based on FIG. The same parts as those described in FIGS. 6 to 8 are denoted by the same reference numerals, and description thereof will be omitted. The basic structure of the stencil printing apparatus according to the present embodiment is the same as that described with reference to FIG. 6, and the difference is the structure of the ink amount detection sensor 27.

FIG. 1 is a front view showing the structure of the ink amount detection sensor 27 and the arrangement of the ink amount detection sensor 27 in the ink reservoir 15. Ink amount detection sensor 2
Reference numeral 7 denotes a sensor for detecting the capacitance of the ink in the ink reservoir 15, which is formed of a thin metal plate such as stainless steel, and the needle portion 27a and the abnormal increase detection portion 27b are integrally formed. It is screwed to a bracket 28 made of resin. One end of a lead wire 26 is connected to the upper end of the ink amount detection sensor 27, and the other end of the lead wire 26 is connected to a control unit (not shown). A pump drive motor 21 is connected to the control unit, and the control unit receives a detection value (capacitance detection output value) of the capacitance of the ink in the ink reservoir 15 detected by the ink amount detection sensor 27. Then, a control signal is output to the pump drive motor 21 according to the capacitance detection output value, and the ink pump 20 is turned on / off via the pump drive motor 21. By turning on and off the ink pump 20 in this manner, automatic supply of ink into the ink reservoir 15 and prevention of abnormal increase in ink in the ink reservoir 15 are performed.

The needle portion 27a is formed so as to be inserted into the ink in the ink reservoir 15 when the ink amount detection sensor 27 is screwed to the bracket 28, and the ink amount in the ink reservoir 15 is predetermined. It functions to detect the capacitance of the ink when it is increasing or decreasing within the range.

The abnormal increase detecting section 27b is formed so that when the ink in the ink reservoir 15 increases abnormally when the ink amount detecting sensor 27 is screwed to the bracket 28, the abnormal amount increases. It functions to detect the capacitance of the applied ink. The abnormal increase detecting section 27b is formed in a shape such that when the ink in the ink reservoir section 15 abnormally increases, the contact area with the ink sharply increases. A portion of the abnormal increase detecting portion 27b facing the ink in the ink reservoir 15 has an inclined surface portion 27c inclined forward in the rotational flow direction of the ink rotating and flowing in the ink reservoir 15.
Are formed.

FIG. 2 is a graph showing the relationship between the amount of ink in the ink reservoir 15 and the capacitance detection output value from the ink amount detection sensor 27. "A" of capacitance detection output value
Is a threshold at which the pump drive motor 21 is turned off under the control of the control unit and the supply of ink by the ink pump 20 is stopped.

The solid line in the graph of FIG. 2 indicates that, under normal printing conditions, for example, in an environment of normal temperature and normal humidity, and that the ink in the ink reservoir 15 is rotated for a long time without being consumed. And the amount of ink in the ink reservoir 15 under the printing conditions where the ink in the ink reservoir 15 is not left for a long time and the capacitance from the ink amount detection sensor 27 corresponding to the amount of ink. The relationship with the detection output value is shown. “A” indicates the ink in the ink reservoir 15 and the needle 2
The amount of ink when contact with 7a starts, "b" is when the amount of ink in the ink reservoir 15 gradually increases and the capacitance detection output value from the ink amount detection sensor 27 reaches the threshold value "A". Is the amount of ink when the ink in the ink reservoir 15 is abnormally increased and the contact with the abnormal increase detecting unit 27b is started. The ink comes into contact with the needle portion 27a, and the capacitance detection output value increases as the contact area between the ink and the needle portion 27a (part of the ink amount detection sensor 27) increases as the ink amount increases. When the ink comes into contact with the abnormal increase detection section 27b, the contact area between the ink and the ink amount detection sensor 27 increases rapidly,
The capacitance detection output value also increases rapidly.

Under the normal printing conditions, the ink reservoir 1
When the ink is automatically supplied to the ink reservoir 5, the amount of ink in the ink reservoir 15 becomes "b" and the capacitance detection output value from the ink amount sensor 27 reaches the threshold "A", the pump is driven. The motor 21 is turned off (that is, the ink pump 2
0 is turned off), and the supply of ink into the ink reservoir 15 is stopped. When it is detected based on the output of the capacitance detection output value from the ink amount detection sensor 27 that the ink in the ink reservoir 15 has been consumed and the ink has been reduced to a predetermined amount, the pump drive motor 21 is turned on. (Ie, the ink pump 20 is turned on), and the ink reservoir 1
Replenishment of ink into 5 is started.

The dashed line in the graph of FIG. 2 indicates the case where the ambient environment becomes extremely low in humidity under the unusual printing conditions, for example,
When the ink in the ink reservoir 15 is rotated and flowed for a long time without being consumed, or when the ink in the ink reservoir 15 is left for a long time, the dielectric constant of the ink is reduced due to evaporation of water in the ink. The ink level sensor 27
4 shows the relationship between the amount of ink in the ink reservoir 15 and the capacitance detection output value from the ink amount detection sensor 27 in accordance with the amount of ink under the printing condition in which the capacitance detection output value has decreased. . “D” indicates that the ink in the ink reservoir 15 is abnormally increased and comes into contact with the abnormal increase detecting section 27b, so that the capacitance detection output value sharply increases, and the capacitance detection output value becomes the threshold “A”. Is the amount of ink when it reaches.

Under the unusual printing condition, when the ink is automatically supplied to the ink reservoir 15, even if the amount of ink in the ink reservoir 15 becomes "b", the ink amount sensor 27 Since the capacitance detection output value does not reach the threshold value “A”, replenishment of ink is continued. When the ink amount becomes “d” and the capacitance detection output value from the ink amount detection sensor 27 reaches the threshold “A”, the pump drive motor 21 is turned off (that is, the ink pump 20 is turned off). And the supply of ink is stopped.

In such a configuration, the ink reservoir 1
During printing under normal printing conditions in which the ink amount in 5 and the capacitance detection output value from the ink amount detection sensor 27 have the relationship shown by the solid line in FIG. 2, the contact between the needle portion 27a and the ink occurs. The capacitance detection output value output from the ink amount detection sensor 27 changes in accordance with the change in the area, and the ink pump 20 is controlled to be turned on and off in accordance with the change. Replenishment is performed.

On the other hand, at the time of printing under unusual printing conditions in which the amount of ink in the ink reservoir 15 and the output value of the capacitance detection from the ink amount detection sensor 27 have the relationship shown by the broken line in FIG. When the ink replenished in the ink reservoir 15 comes into contact with the abnormal increase detection unit 27b and the contact area between the ink and the ink amount detection sensor 27 increases rapidly, the capacitance detection output value sharply increases, Ink reservoir 15
It is detected that the ink inside has abnormally increased. And
When the ink pump 20 is turned off in response to this detection result, the supply of ink is stopped, and further supply of ink to the ink reservoir 15 and leakage of ink from the ink reservoir 15 are prevented.

Here, the abnormal increase detecting section 27b is formed in such a shape that the contact area with the ink increases suddenly when the ink in the ink storing section 15 abnormally increases. When the amount of ink abnormally increases, the contact area between the ink and the abnormal increase detecting section 27b rapidly increases, and the capacitance detection output value from the ink amount detecting sensor 27 rapidly increases, resulting in an abnormal increase in ink. Can be reliably detected.

The portion of the abnormal increase detecting section 27b facing the ink in the ink reservoir 15 is provided with the ink reservoir 15 when the plate cylinder rotates (ie, when the ink roller 23 and the doctor roller 24 rotate). Inclined surface portion 27 inclined in the forward direction along the rotational flow direction of the ink rotating and flowing in the inside
Since c is formed, after the abnormally increased ink comes into contact with the abnormal increase detection unit 27, when the ink is consumed and gradually decreases, the contact between the ink and the abnormal increase detection unit 27 is eliminated. The ink slides down along the inclined surface portion 27c, and the ink from the abnormal increase detecting portion 27 is more easily cut. For this reason, it is possible to prevent erroneous detection that the ink is abnormally increased even though the abnormally increased state of the ink is eliminated.

Next, a second embodiment of the present invention will be described with reference to FIG.
A description will be given based on FIG. 1 and 2 are denoted by the same reference numerals, and description thereof will be omitted. FIG. 3 is a front view showing a structure of the ink amount detection sensor 29 and an arrangement state of the ink amount detection sensor 29 in the ink reservoir 15, and FIG. 4 is a side view thereof.

The ink amount detecting sensor 29 is a sensor for detecting the electrostatic capacity of the ink in the ink reservoir 15, is formed of a thin metal plate such as stainless steel, and has a needle portion 29a and an abnormal increase detecting portion 29b. It is screwed to a bracket 28 made of a non-conductive synthetic resin.

The needle portion 29a is formed so as to be inserted into the ink in the ink reservoir 15 when the ink amount detection sensor 29 is screwed to the bracket 28, and the amount of ink in the ink reservoir 15 is predetermined. It functions to detect the capacitance of the ink when it is increasing or decreasing within the range.

The abnormal increase detecting section 29b is formed so that when the ink in the ink reservoir 15 increases abnormally when the ink amount detecting sensor 29 is screwed to the bracket 28, the abnormal amount increases. It functions to detect the capacitance of the applied ink. The abnormal increase detecting section 29b is formed in such a shape that when the ink in the ink reservoir section 15 abnormally increases, the contact area with the ink sharply increases. A portion of the abnormal increase detecting portion 29b facing the ink in the ink reservoir 15 has an inclined surface portion 29c inclined forward in the rotational flow direction of the ink rotating and flowing in the ink reservoir 15.
Are formed.

The needle part 29a and the abnormal increase detecting part 29b
The ink rotating and flowing in the ink reservoir 15 is arranged at a predetermined distance “L” along the axial direction of the rotational flow center of the ink. The predetermined dimension “L” is specifically equal to or greater than 20 mm. When the ink that has abnormally increased in the ink reservoir 15 comes into contact with the needles 29 a and the abnormal increase detector 29 b at the same time, these needles 29 a Even if the abnormal increase detecting section 29b becomes a resistance of the ink flowing and rotating in the ink reservoir 15, respectively, the synergistic action of the two resistances prevents the rotational flow of the ink in the ink reservoir 15 from being largely obstructed. It is a dimension that can be done.

In such a configuration, the ink reservoir 1
When the ink abnormally increased in 5 contacts the needle portion 29a and the abnormal increase detection portion 29b, the needle portion 29a and the abnormal increase detection portion 29b respectively reduce the resistance of the ink that rotates and flows in the ink reservoir 15. Even if this happens, the synergistic action of these resistances prevents the rotational flow of the ink in the ink reservoir 15 from being greatly impeded. For this reason, the rotational flow of the abnormally increased ink is smoothly performed, and the lateral movement of the ink accompanying the rotational flow is smoothly performed.

Next, a third embodiment of the present invention will be described with reference to FIG.
It will be described based on. The ink amount detection sensor 30 of the present embodiment has the same basic structure as the ink amount detection sensor 29 described in the second embodiment, is formed of a thin metal plate such as stainless steel, and has a pair of needle portions 30a. An abnormal increase detection unit 30b. Each needle part 30a and abnormal increase detection part 30
b is a predetermined size “L” along the axial direction of the rotational flow center of the ink that rotates and flows in the ink reservoir 15.
They are spaced apart. An inclined surface portion 30c that is inclined in the forward direction along the rotational flow direction of the ink that rotates and flows in the ink reservoir portion 15 is formed in a portion of the abnormal increase detection portion 30b that faces the ink in the ink reservoir portion 15. .

In such a configuration, in the present embodiment, since the needle portions 30a are provided in a pair, the detection accuracy of the electrostatic capacitance of the ink at the time of the automatic supply of the ink is improved.

When the ink abnormally increased in the ink reservoir 15 comes into contact with the needle 30a and the abnormality detector 30b, the needle 30a and the abnormality detector 30b are connected to each other in the ink reservoir 15. Even if the resistance of the ink flowing and flowing becomes large, it is possible to prevent the rotational flow of the ink in the ink reservoir 15 from being largely obstructed by the synergistic action of these resistances. For this reason, the rotational flow of the abnormally increased ink is smoothly performed, and the lateral movement of the ink accompanying the rotational flow is smoothly performed.

[0053]

According to the ink amount detection sensor according to the first aspect of the present invention, the needle portion inserted into the ink in the ink reservoir and the abnormal increase of the ink in the ink reservoir when the ink in the ink reservoir abnormally increases. With the detection section, the needle section can be used to detect the amount of ink in the ink reservoir for automatically refilling the ink to maintain the amount of ink in the ink reservoir within a predetermined range. Detection of an abnormal increase in the amount of ink in the unit can be performed using the abnormal increase detection unit, and two types of ink amounts for different purposes can be detected by one ink amount detection sensor.

According to the second aspect of the present invention, in the ink amount detecting sensor according to the first aspect of the present invention, since the needle portion and the abnormal increase detecting portion are integrally formed, the structure of the ink amount detecting sensor is provided. Can be simplified and downsized, and the ink amount detection sensor can be installed in a small installation space.
The number of parts and the number of assembling steps required for installing the ink amount detection sensor can be reduced.

According to the third aspect of the present invention, in the ink amount detection sensor according to the first or second aspect, the abnormal increase detecting section increases the contact area with the ink when the ink in the ink reservoir increases abnormally. When the ink in the ink reservoir increases abnormally, the contact area where the ink comes in contact with the abnormal increase detector increases rapidly, and the capacitance detection from the ink amount sensor is performed. Since the output value rapidly increases, it is possible to reliably detect the abnormal increase in the ink.

According to the fourth aspect of the present invention, in the ink amount detecting sensor according to any one of the first to third aspects, the portion of the abnormal increase detecting section facing the ink in the ink reservoir is provided with a plate cylinder. It has an inclined surface that is inclined forward in the direction of the rotational flow of the ink that rotates and flows in the ink reservoir during rotation. After the abnormally increased ink contacts the abnormal increase detector, the ink is consumed and gradually decreases. By doing so, when the contact between the ink and the abnormal increase detection section is eliminated, the ink will slide down along the inclined surface, so the ink from the abnormal increase detection section will be better cut off, It is possible to prevent erroneous detection that the amount of ink is abnormally increased despite being eliminated.

According to the fifth aspect of the present invention, in the ink amount detecting sensor according to any one of the first to fourth aspects, the needle portion and the abnormal increase detecting portion are configured to rotate the ink that rotates and flows in the ink reservoir portion. Since the ink is arranged at a predetermined distance along the axial direction of the flow center, when the ink that has abnormally increased in the ink reservoir contacts the abnormal increase detecting portion and the needle portion, these abnormal increase detecting portion and the needle Even if each part becomes a resistance of the ink rotating and flowing in the ink reservoir part, the synergistic action of the two resistances can prevent the rotational flow of the ink in the ink reservoir part from being greatly obstructed, and the ink in the ink reservoir part can be prevented. Even in the case of an abnormal increase, the rotational flow of the ink can be smoothly performed, and the lateral movement of the ink accompanying the rotational flow can be smoothly performed.

According to the ink leakage preventing device of the present invention, the ink leakage preventing device is disposed in an ink reservoir formed in a plate cylinder which is driven to rotate about an axis. Ink sensor that supplies ink to the ink reservoir, and a controller that controls the on / off of the ink pump according to the detection result from the ink reservoir. When the ink amount sensor detects that the ink has increased abnormally, the control unit turns off the ink pump in response to the detection result and stops refilling the ink into the ink reservoir. Further replenishment of the ink is stopped, and leakage of the ink from the ink reservoir can be prevented.

[Brief description of the drawings]

FIG. 1 is a front view showing a structure of an ink amount detection sensor according to a first embodiment of the present invention and an arrangement state of the ink amount detection sensor in an ink reservoir.

FIG. 2 is a graph showing the relationship between the amount of ink in an ink reservoir and the capacitance detection output value from an ink amount detection sensor.

FIG. 3 is a front view showing a structure of an ink amount detection sensor and an arrangement state of the ink amount detection sensor in an ink reservoir in a second embodiment of the present invention.

FIG. 4 is a side view thereof.

FIG. 5 is a side view showing a structure of an ink amount detection sensor and an arrangement state of the ink amount detection sensor in an ink reservoir in a third embodiment of the present invention.

FIG. 6 is a vertical sectional front view showing a schematic structure of a conventional stencil printing apparatus.

FIG. 7 is a front view showing a structure of a conventional ink amount detection sensor and an arrangement state of the ink amount detection sensor in an ink reservoir.

FIG. 8 is a side view thereof.

[Explanation of symbols]

 12 Plate cylinder 15 Ink reservoir 20 Ink pump 27, 29, 30 Ink amount detection sensor 27a, 29a, 30a Needle 27b, 29b, 30b Abnormal increase detector 27c, 29c, 30c Inclined surface

Continuing on the front page (72) Inventor Keisuke Asada 3 Shinmei-do, Nakamei Ichimoji, Shibata-cho, Shibata-gun, Miyagi Prefecture, 1 Tohoku Ricoh Co., Ltd. (72) Kengo Tsubaki Kengo Tsubaki, Shimada, Shimada-cho, Shibata-cho, Miyagi Prefecture 3 No. 1 Tohoku Ricoh Co., Ltd. (72) Yoshio Kanamori Inventor Yoshimitsu Kanamori, Shibata-cho, Shibata-cho, Miyagi Prefecture 3 Nakamei Ichimoji Shinmei-do No. 1 F-term in Tohoku Ricoh Co., Ltd. 2C250 DB08 DB14 DB21 EA25 EB17 EB50

Claims (6)

[Claims] 1. An ink amount detection sensor of a capacitance detection type for detecting an amount of ink accumulated in an ink reservoir formed in a plate cylinder driven to rotate about an axis, wherein the ink in the ink reservoir is provided. An ink amount detection sensor, comprising: a needle portion inserted into the ink reservoir; and an abnormal increase detection portion that comes into contact with the ink when the ink in the ink reservoir increases abnormally. 2. An ink amount detection sensor according to claim 1, wherein said needle portion and said abnormal increase detection portion are formed integrally. 3. The abnormal increase detecting section is formed in such a shape that when an ink in the ink reservoir increases abnormally, a contact area with the ink sharply increases. 2. The ink amount detection sensor according to 2. 4. A portion of the abnormal increase detecting section facing the ink in the ink reservoir is inclined in a forward direction along a rotational flow direction of the ink rotationally flowing in the ink reservoir when the plate cylinder rotates. 4. An ink amount detection sensor according to claim 1, wherein the sensor has an inclined surface portion. 5. A method according to claim 1, wherein said needle portion and said abnormal increase detecting portion are spaced apart from each other by a predetermined dimension along an axial direction of a rotational flow center of the ink rotationally flowing in said ink reservoir portion. The ink amount detection sensor according to any one of claims 1 to 4, wherein: 6. An ink reservoir formed in a plate cylinder that is driven to rotate about an axis.
An ink amount detection sensor according to any one of the above, an ink pump for replenishing ink to the ink reservoir, and a control unit for controlling on / off of the ink pump according to a detection result from the ink amount detection sensor, An ink leakage prevention device comprising: