JPH0760993A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To prevent, under any condition, a solvent in an ink from increasing of vaporizing in the air and to maintain lowering a running cost by providing a residual energy absorbing means that reduces a load at a time when the lift difference between a gutter and a pump is generated by placing the gutter upper than the lowest position. CONSTITUTION:When an ink jet recorder is provided, a speed controller 3 controls to lower the speed until a residual energy of a pump 7 becomes the lowest, that is, right before ink drops are not collected from a gutter 1 by confirming that the ink drops are collected from the gutter 1. As a result, even when the disposing height of the gutter 1 is higher than the lowest position so that the lift difference between the gutter and pump is generated, or e.g. the gutter 1 is disposed on the highest position, a flowing speed in a ink collection passage is maintained at a constant level same as when the gutter is disposed on the lowest position and an amount of an air flowing into from the gutter is suppressed rather than before, thereby obtaining the ink jet recorder wherein an amount of vaporization of a solvent component and setting the running cost at a low price.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, and more particularly to an ink collecting mechanism for an industrial ink jet recording apparatus.

[0002]

BACKGROUND OF THE INVENTION Industrial ink jet recording devices are used to print at various locations on a wide variety of products, such as the bottom of a can or the side of a bottle.

In the ink jet recording apparatus, the distance between the ejection nozzle and the printing object is limited to several millimeters, and the gutter is installed adjacent to the printing object together with the ejection nozzle.

[0004]

By the way, in the above-mentioned industrial ink jet recording apparatus, the pumping capacity is set in accordance with the installation height of the gutter according to the maximum load installed at the lowest position. If the height of the gutter is different from that of the pump when the height of the gutter is higher than the lowest level, for example, at the minimum load when the height of the gutter is set to the highest level, the ink recovery capacity becomes excessive and the ink recovery path becomes excessive. Increase the flow velocity in. The fluid in the ink recovery path is the ink and air recovered from the gutter, but the amount of ink recovered from the gutter is determined by the print content, so if the gutter is installed above the lowest position as described above. The amount of air sucked from the gutter increases, and the amount of the solvent contained in the ink volatilized into the air increases, which in turn increases the running cost of the inkjet recording apparatus.

However, heretofore, the increase in running cost due to the above-mentioned phenomenon has not been recognized.

An object of the present invention is to install a gutter in an ink jet recording apparatus in which the installation height of the gutter is variable for both ejection nozzles and the pumping capacity is set according to the maximum load installed at the lowest position of the gutter. The increase in the amount of ink solvent volatilized into the air due to the difference in height can be suppressed, and even if the gutter installation height is at the highest level, the amount of solvent component volatilized can be maintained and the running cost is low under all conditions. Another object of the present invention is to provide an improved ink jet recording apparatus of this kind.

[0007]

The object is to provide a gutter for capturing ink particles not used for printing, a means for conveying the ink particles from the gutter, and a means for holding the ink particles conveyed from the gutter. In addition, the height of the gutter is set higher than the lowest in an ink jet recording device in which the height of the gutter is variable along with the ejection nozzles and the pump capacity is set according to the maximum load installed in the lowest height. It is achieved by providing a means for absorbing surplus energy by reducing the load when a head difference is created between the gutter and the pump.

[0008]

According to the above construction, the installation height of the gutter is set to be higher than the lowest position, and excess energy is not generated due to load reduction when a head difference occurs between the gutter and the pump. It is possible to prevent an increase in the flow velocity of the ink, suppress an increase in the amount of air sucked from the gutter, and suppress an increase in volatilization of the solvent contained in the ink into the air under all conditions.

[0009]

EXAMPLE FIG. 1 shows an example of the present invention. The gutter 1 captures ink particles not used for printing. Gutter 1
The ink particles captured by
The material is conveyed in 4, 6 and 8 and collected in a container 9. The ink collected in the container 9 may be discarded, but normally the ink comes out of the ejection nozzle and is captured by the gutter 1, and the ink and the air come into contact with each other before being collected in the container 9, so that the ink surface changes into the air. Since the solvent component volatilizes, the volatilized solvent component is replenished to adjust the ink to an appropriate concentration, and the ink is used again for printing. In order to replenish the solvent, a method in which cheese or the like is connected before the pump 7 and the solvent is sucked by the pump 7 is often used. The filter 5 is installed in order to remove foreign substances mixed in the air sucked from the gutter 1 and the ink particles, and is generally installed in front of the pump 7 in order to prevent a malfunction of the pump 7 due to the foreign substances. Speed controller 3
Is installed to adjust the load of the recovery system from the gutter 1 to the container 9 by opening and closing.

The capacity of the pump 7 installed between the recovery passages 6 and 8 is the lift ΔH, the pressure difference between the gutter 1 and the pump 7 is Δp,
Assuming that the difference between the squares of the speeds of the gutter 1 and pump 7 is Δ (υ ² ), the specific gravity of the fluid flowing in the recovery passage is γ, the gravitational acceleration is g, and the energy loss in the recovery passage is Δh, Can be expressed as

[0011]

[Equation 1]

Since the distance between the ejection nozzle and the printing object is limited to several millimeters in the ink jet recording apparatus, the gutter 1 is installed adjacent to the printing object together with the ejection nozzle. However, since the pump 7 and the container 9 are installed in the main body, the pressure difference Δp between the gutter 1 and the pump 7 changes depending on the equipment using the inkjet recording device. Also, the energy loss Δh in the recovery path can be said to be a constant possessed by the inkjet recording apparatus unless the speed controller 3 is taken into consideration. Therefore, the pump 7 may have a surplus capacity with respect to the capacity required for collecting the ink particles depending on the condition of the equipment. This surplus energy becomes velocity energy and velocity increase of the fluid flowing in the recovery passage according to the equation (1). Since the installation range of the gutter 1 is limited by the length of the recovery path, the capacity of the pump 7 is set to the capacity that satisfies the range, that is, the capacity that can recover even when the gutter 1 is installed at the lowest level. . Or depending on the capacity of pump 7, gutter 1
The installation range is limited.

Considering the case where the velocity of the fluid flowing in the recovery passage increases as described above, the amount of ink particles to be recovered from the gutter 1 is determined by the printing conditions such as thinning and speed printing conditions and the printing amount according to the printing content. It can be seen that the amount of air taken in along with the ink particles changes. The ink particles volatilize the solvent component into the air from the surface thereof, but the amount thereof is determined by the saturated concentration determined by the temperature and the amount of air, so that the increase of the air amount increases the amount of the solvent component evaporated.
That is, the running cost is increased. In an industrial inkjet recording device, it was confirmed by experiments that when the length between the gutter 1 and the pump 7 is set to about 5 m, the volatilization amount of the solvent component at the same temperature becomes about twice as high as the lowest. It was

The loss energy Δh of the recovery passage of the equation (2) is a resistance due to friction of the inner wall of the recovery passage, curvature of the recovery passage, change of inner diameter of the recovery passage, and merging branch, and is usually constant by the ink jet recording apparatus.

However, in order to suppress the increase in the volatilization amount of the solvent component due to the installation height of the gutter 1, the loss energy Δh is changed from the equation 1 to absorb the excess energy of the pump 7,
Since it is effective to prevent the excess energy from being converted into an increase in the velocity of the fluid, the speed controller 3 which is an adjustable throttle having a variable loss coefficient ζ is set in this embodiment. As a result, when the ink jet recording apparatus is installed in the equipment, the surplus energy of the pump 7 is minimized while the speed controller 3 confirms that the ink particles are collected from the gutter 1, that is, the ink particles are collected from the gutter 1. Narrow down until just before it disappears. Alternatively, the flow controller is used to adjust the speed controller 3 in advance so that the ink flow rate becomes a predetermined appropriate value.

As described above, even when the installation height of the gutter 1 is set higher than the lowest position and there is a head difference between the gutter and the pump, for example, when the installation height of the gutter is installed at the highest position. Also, as in the case of installing it at the lowest position, keep the flow velocity in the ink collection path uniform, reduce the amount of air sucked from the gutter as compared to the past, and use an inkjet recording device with a small amount of solvent component volatilization. Therefore, the running cost can be set at a low cost.

In the embodiment of FIG. 2, in order to change the loss energy Δh, instead of the speed controller 3 which is an adjustable throttle having a variable loss coefficient ζ, a diaphragm 10 having a constant loss coefficient ζ is used. Is. That is, the diaphragm 10 having a predetermined appropriate loss coefficient ζ is prepared and attached in advance for each facility in which the inkjet recording apparatus is incorporated. Actually, several kinds of diaphragms 10 having different loss coefficients ζ are prepared and selected from them. To do.

The loss coefficient ζ of the throttle 10 is determined by the frictional resistance in the fluid due to the change of the inner diameter of the recovery passage as shown in FIG. 3, but as shown in FIG. Equation 3 holds for the boundary layer of.

[0019]

[Equation 2]

In equation 3, ρ is the density of the fluid, k is a constant, V is the flow velocity, δ is the thickness of the boundary layer, μ is the coefficient of friction of the wall surface, f '(0) is the velocity distribution function, and L is the pipe wall. Is the length of.

As a result, since the loss coefficient ζ of the diaphragm 10 can be changed with the length, the diaphragm 10 is designed by changing the inner diameter and the length. However, since clogging of the ink occurs in the diaphragm 10, the inner diameter of the diaphragm 10 is about 1 mm at the minimum. Also,
When the length of the diaphragm 10 is about 10 mm, the loss coefficient ζ becomes stable,
There is little change beyond that. Therefore, the loss coefficient ζ may be insufficient with one diaphragm 10, and in this case, the diaphragm 10
Are used in combination.

In the above description, the case where the loss coefficient ζ of the throttle 10 is adjusted has been described, but instead of this, a method of changing the capacity of the pump 7 may be considered.

In the ink jet recording apparatus, a gear pump or a diaphragm pump is generally used as the ink recovery pump 7. Therefore, the gear pump is provided with a controller for the number of revolutions, and the diaphragm pump is provided with a frequency control, so-called inverter, and its adjustment is performed at a speed. Controller 3
Similarly, while confirming that the ink particles are recovered from the gutter 1 when the ink jet recording apparatus is installed in the equipment, the excess energy of the pump 7 is adjusted to be the minimum. Alternatively, a flow rate system is used to adjust the flow rate in advance to a predetermined value.

[0024]

According to the present invention, in the ink jet recording apparatus in which the installation height of the gutter is variable together with the jet nozzle, and the pumping capacity is set in accordance with the maximum load installed at the lowest installation position of the gutter. Even when the installation height of the ink is set higher than the lowest position and a head difference occurs between the gutter and the pump, that is, the volatilization increase of the solvent contained in the ink into the air is suppressed under all conditions, and The running cost of this type of inkjet recording device can be maintained at a lower cost than before.

[Brief description of drawings]

FIG. 1 is a system diagram of an ink particle recovery system showing an embodiment of the present invention.

FIG. 2 is a system diagram of an ink particle recovery system showing another embodiment of the present invention.

FIG. 3 is a diagram illustrating a loss coefficient of a diaphragm shown by reference numeral 10 in FIG.

FIG. 4 is an explanatory view of a boundary layer with a fluid due to an upstream end wall surface of the throttle shown by reference numeral 10 in FIG.

[Explanation of symbols]

1 ... Gutter, 2, 4, 6, 8 ... Ink particle recovery path, 3 ...
Speed controller, 5 ... Filter, 7 ... Pump, 9
… Container, 10… Squeeze.

Claims (4)

[Claims] 1. A gutter for catching ink particles not used for printing, a means for conveying the ink particles from the gutter, and a means for holding the ink particles conveyed from the gutter, and the installation of the gutter together with the ejection nozzle. In an inkjet recording device that has a variable height and the pump capacity is set according to the maximum load installed at the bottom of the gutter, install the height of the gutter above the bottom and set the gap between the gutter and the pump. An inkjet recording apparatus comprising means for absorbing surplus energy due to load reduction when a head difference occurs. 2. An ink jet recording apparatus according to claim 1, wherein a valve having a variable loss coefficient is provided in the ink recovery path as means for changing the installation height of the gutter to absorb surplus energy due to load reduction. 3. The valve according to claim 1, wherein the loss factor is constant and the valve is replaced and used as a means for absorbing surplus energy due to load reduction by changing the height of the gutter. An inkjet recording device equipped with multiple diaphragms. 4. An ink jet recording apparatus according to claim 1, wherein a pump capable of varying the discharge amount is installed in the middle of the ink recovery path as a means for absorbing the excess energy due to the load reduction by changing the installation height of the gutter.