JP2567223B2 - Ink viscosity adjusting device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus capable of automatically adjusting the viscosity of ink with high accuracy.

Conventional technology For example, in gravure printing, gravure ink that is extremely easy to dry and has high fluidity is transferred to the plate surface on the plate cylinder,
It is characterized in that excess ink is scraped off by a doctor blade and the ink is left only in the recesses on the plate surface for printing. The gravure ink used in this gravure printing is generally a mixture of a pigment dissolved in a resin dissolved in a volatile solvent such as toluene or xylene, and is stored in a predetermined amount in an ink pan provided in the printing mechanism section. The ink is transferred directly to the plate surface of the plate cylinder that is freely rotatable inside.

[Problems to be Solved by the Invention] The gravure ink transferred to the plate surface of the plate cylinder is transferred to the paper at the contact portion with the impression cylinder, whereby printing on the printing paper is achieved. The ink transferred onto the paper dries in an extremely short time to prevent the ink from being retransferred to another paper or a feed roll. The quick-drying property of this ink largely depends on the presence of the above-mentioned volatile solvent, but on the other hand, the presence of such a volatile solvent causes volatilization of the solvent during the printing operation, which causes There is a difficulty in increasing the ink viscosity over time. When the increase in the ink viscosity reaches a certain limit value or more, good printing cannot be performed and the print quality deteriorates.

Therefore, in order to deal with this kind of situation, the ink is collected in the Zahn cup in the ink pan and the viscosity is checked, and the appropriate amount of solvent is replenished by the operator's experience and intuition to recover the proper viscosity. It is generally practiced. However, since this requires a skilled experience of workers and relies on human beings for everything, it cannot be overlooked that they are not familiar with the operation of modern mass printing.

As a device that automatically adjusts the ink viscosity, the ink in the ink pan is circulated between it and a separate ink tank, and the ink viscosity is constantly checked by a rotary viscometer inserted in this ink tank. A mechanism has been proposed in which the solvent is automatically replenished when the limit value for proper printing is reached. This is excellent in that the ink viscosity can be automatically adjusted, but the mechanism becomes complicated and the device main body becomes expensive, and since the ink viscosity in the ink pan is not directly measured, strict viscosity adjustment is required. There are drawbacks such as inability.

OBJECT OF THE INVENTION The present invention has been proposed in view of the above-mentioned drawbacks inherent in the prior art described above, and has been proposed to suitably solve the above-mentioned drawbacks. It is an object of the present invention to provide a novel device capable of strict adjustment of viscosity by directly checking the viscosity of the ink inside.

Means for Solving the Problems In order to achieve the intended purpose to overcome the above problems, the ink viscosity adjusting device according to the present invention is a diaphragm pump for pulsatingly circulating the ink in the ink pan, and the ink A solvent tank for storing a volatile solvent to be replenished, a solenoid valve that is introduced from the solvent tank and is interposed in a supply pipe opening to the ink pan, and the pulsation number of the diaphragm pump is set so that the ink in the ink pan is A preset circuit capable of presetting an integer value as an upper limit value of an initial state that retains a good viscosity and a lower limit value that is a limit state immediately before the viscosity increases with time and affects print quality, respectively. A sensor that detects the pulsation of the diaphragm pump and sends a pulse signal, and when the viscosity of the ink increases to the limit value of the practical ink range, The number of pulses of the signal obtained from the sensor,
It is characterized by comprising a subtraction circuit that outputs an opening command to the solenoid valve at the time when the pulsation number as the lower limit value of the diaphragm pump preset in the preset circuit is lowered.

Examples Next, the ink viscosity adjusting device according to the present invention will be described below with reference to preferred examples. The present invention is based on the fact that the inventor empirically noticed the fact that the gravure ink in the ink pan was circulated and supplied using a pulsating pump, for example, a diaphragm pump to operate the gravure ink. Therefore, first, this point will be described, and then the specific configuration will be described.

The diaphragm pump given as an example receives the supply of air pressure to reciprocally drive the diaphragm inside the pump casing, and thereby the fluid (here, gravure ink)
The pulsation of the diaphragm is grasped as a kind of pulsating motion. In this pump, when the viscosity of the fluid to be pumped increases, the resistance correspondingly increases, and the pulsation interval of the diaphragm gradually increases. This means that the pulsation number of the pump decreases as the viscosity of the fluid to be pumped increases, and the pulsation number of the pump increases as the viscosity decreases.

FIG. 3 is a graph showing the relationship between the ink viscosity and the pulsation number of the pump. In this case, the practical range of the viscosity of the gravure ink is, for example, in the range of viscosity 14 to 22, but during this period, the graph draws a gentle curve and can be regarded as a straight line. Then, the inventor found that an expression approximate to the following expression holds in this area.

If pump pulsation number x ink viscosity = 648, that is, 648 = K (constant), pump pulsation number = K
/ Ink viscosity, so pump pulsation is inversely proportional to ink viscosity. Therefore, from the initial state where the ink in the ink pan maintains a good viscosity to the limit state immediately before the viscosity increases and the print quality is affected, the pulsation rate of the diaphragm pump is It becomes almost constant. Then, this pulsation number was empirically measured in advance, and it was found that when the pulsation number passed after the start of ink circulation, it was determined that the ink viscosity became unsuitable for printing and the volatile solvent was replenished. This is the basic point of the present invention.

In the figure, reference numeral 10 indicates an ink pan, and a predetermined amount of gravure ink 12 is stored in the ink pan 10. A plate cylinder 14 is exposed in the ink pan 10, and the lower half thereof is immersed in the ink. Then, by feeding the printing paper between the plate cylinder 14 and the impression cylinder 15, required printing is performed.

The gravure ink 12 in the ink pan 10 is a suction pipe 18 connected to the suction side of a diaphragm pump 16 arranged in proximity.
After being sucked through, the ink is returned to the ink pan 10 from the return pipe 20 connected to the discharge side of the pump, and constantly circulates in the ink pan 10 during the printing operation. Further, on the side of the ink pan 10, a solvent tank 22 for storing a volatile solvent used for the gravure ink 12 is arranged,
Supply pipe 26 derived from this tank 22 via a solenoid valve 24
Has an opening with its end facing the ink pan 10.

The diaphragm pump 16 is of a reciprocating type that uses compressed air as a driving source, and is preferably used for transferring the gravure ink, the organic solvent and other chemical liquids. Compressed air is supplied to a diaphragm pump 16 from a compressor (not shown) through an air conduit 28, an auxiliary device 30 such as an air pressure filter interposed in the middle thereof, and a needle valve 32, and after driving the built-in diaphragm, the pump It is emitted to the outside from the silencer 34 provided in 16. In this embodiment,
As shown in FIG. 2, a steel ball 36 is housed in the muffler 34,
The behavior of the steel ball 36 that floats up and falls in the muffling chamber 34a due to exhaust pressure during pump pulsation is constantly monitored by a non-contact sensor 38 such as a photoelectric element or a magnetic switch. Therefore, the signal obtained from this sensor 38 is responsive to the pulsatile pressure change as the pump 16 is pneumatically driven to pulsate the built-in diaphragm. The signal from the sensor 38 in response to the pump pulsation is input to the control circuit described later.

The control circuit 40 includes a preset circuit 40a and a subtraction circuit 40b.
It has. That is, the preset circuit 40a, the pulsation number in the diaphragm pump 16, the upper limit of the initial state in which the ink 12 in the ink pan 10 retains a good viscosity and the viscosity increases over time to affect print quality. As a lower limit value which is a limit state immediately before exertion, it can be preset by an integer value. Further, the subtraction circuit 40b is provided for the sensor when the viscosity of the ink 12 in the ink pan 10 increases to the limit value of the ink practical area.
The number of pulses of the signal obtained from 38 is the preset circuit
An opening command is output to the solenoid valve 24 at the time when the pulsation number as the lower limit value of the diaphragm pump 16 preset to 40a is reduced. Then, when the solenoid valve 24 is opened, the volatile solvent is replenished from the supply pipe 26 to the gravure ink in the ink pan 10. The opening time of the solenoid valve 24 is set to the most suitable time according to the composition and other properties of the gravure ink.

Further, in FIG. 1, the needle valve 32 provided in the air conduit 28 is provided with a mechanical valve 42 in parallel therewith, and the mechanical valve 42 is always closed. The mechanical valve 42 is opened when transferring the gravure ink 12 in the ink pan 10 to another tank, such as changing the color,
It is used to fast feed ink by bypassing air pressure to the needle valve 32 and operating the diaphragm pump 16 at high speed.

Operation of Embodiment Next, the operation of the ink viscosity adjusting device according to this embodiment having the above-described configuration will be described. In the structure shown in FIG. 1, a predetermined amount of gravure ink 12 is stored in the ink pan 10, and the lower half of the plate cylinder 14 is dipped in the ink. The diaphragm pump 16 pulsates the built-in diaphragm by the air pressure supplied through the air conduit 28 and the needle valve 32, so that the gravure ink 12 is sucked into the suction pipe.
The pressure air after being circulated fluidly through the path of 18 → pump 16 → return pipe 20 → ink pan 10 and driven by the diaphragm is diffused outside from the silencer 34.

The muffler 34a of the muffler 34 accommodates a steel ball 36 that repeatedly rises and falls due to exhaust pressure when the pump pulsates, and the behavior of the steel ball 36 is constantly monitored by the non-contact sensor 38. That is, the sensor 38 is a steel ball in the vicinity of its detection surface.
As 36 moves, a pulse signal in response to the pulsation of the diaphragm is emitted, and this is input to the control circuit 40.
In this case, the preset circuit 40a in the control circuit 40
Is the pulsation rate of the diaphragm pump 16 as described above.
The upper limit value in the initial state where the gravure ink 12 retains a good viscosity and the lower limit value that is the limit state immediately before the viscosity increases with time and affects the print quality are preset as integer values. There is. The pulsation number is experimentally determined according to the components and properties of the gravure ink used.

The pulse signal from the sensor 38 input to the control circuit 40 is compared in the subtraction circuit 40b. Then, when the number of pulses of the pulse signal when the ink viscosity increases to the limit value of the ink practical region, at the time when the pulse number becomes the lower limit value of the diaphragm pump 16 preset in the preset circuit 40a, the control circuit 40 Outputs an electric command to open the solenoid valve 24 of the solvent tank 22.
As a result, the volatile solvent in the tank is replenished to the gravure ink 12 via the supply pipe 26, and the viscosity of the ink is restored to an appropriate value. This operation is repeated thereafter.

Effects of the Invention As described above, the ink viscosity adjusting device according to the present embodiment can be manufactured at a low cost with a simple structure. Moreover, since the ink viscosity in the ink pan is directly checked, there is an advantage that the viscosity can be strictly adjusted.

[Brief description of drawings]

The drawings show a preferred embodiment of the ink viscosity adjusting device according to the present invention. FIG. 1 is an explanatory view showing a schematic configuration of the ink viscosity adjusting device according to the embodiment, and FIG. FIG. 3 is a longitudinal sectional view showing an example of a pulsation detecting sensor incorporated in a silencer of a diaphragm pump used, and FIG. 3 is a graph showing a relationship between ink viscosity and pulsation number of the pump. 10 …… Ink pan, 12 …… Gravure ink 14 …… Plate cylinder 16 …… Pulsating pump (diaphragm pump) 18 …… Suction pipe, 20 …… Return pipe 22 …… Solvent tank, 24 …… Solenoid valve 26 …… Supply Pipe, 28 ... Air conduit 30 ... Auxiliary equipment, 32 ... Needle valve 34 ... Silencer, 34a ... Silence chamber 36 ... Steel ball, 38 ... Non-contact sensor 40 ... Control circuit, 40a ... Preset circuit 40b …… Subtraction circuit 42 …… Mechanical valve

Claims (1)

(57) [Claims] 1. A diaphragm pump (16) for pulsatingly circulating the ink (12) in an ink pan (10), and a solvent tank (22) for storing a volatile solvent to be replenished in the ink (12). , A solenoid valve (24) which is introduced from the solvent tank (22) and is provided in a supply pipe (26) which opens to the ink pan (10)
The pulsation number of the diaphragm pump (16) is set to the upper limit of the initial state in which the ink (12) in the ink pan (10) retains a good viscosity and the viscosity increases with time to improve print quality. As a lower limit value, which is the limit state immediately before the influence, a preset circuit (40
a), a sensor (38) for detecting a pulsation of the diaphragm pump (16) and transmitting a pulse signal, and the sensor (38) when the viscosity of the ink (12) increases to a limit value of an ink practical area. 38) Opened to the solenoid valve (24) at the time when the number of pulses of the signal obtained from the same dropped to the pulsation number as the lower limit value of the diaphragm pump (16) preset in the preset circuit (40a). An ink viscosity adjusting device comprising a subtraction circuit (40b) for outputting a command.