JPH0372465B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Background of the Invention] The present invention relates to an ink ejection device, and the ink used in the ejection device is of a phase change type, and the ink is, for example, a thermosoluble ink.

Phase change or thermofusible inks of this type used in ink jetting devices have solid properties at room temperature. When heated, the ink melts to a jettable consistency.

It has been found that improper heating degrades the performance of the ink and ink jetting performance. In order to avoid functional deterioration due to such long-term heating, the reservoir is cooled while it is on standby and only the head is heated, thereby limiting the amount of ink heated.
It also makes it possible to minimize functional deterioration of the ink due to its unfavorable working properties.

The extremely high localized temperatures in the ink ejector subject the localized ink to unfavorable conditions, which are, of course,
It has also been found that localized ink causes functional deterioration that also affects work.

Furthermore, temperature gradients within the ink ejection device,
i.e. a change in temperature from one location to another,
adversely affects the ink jetting operation. In addition to degrading workability, the temperature effects mentioned above also adversely affect reliability.

[Summary of the invention]

It is an object of the present invention to minimize the effects of heating on operability and reliability in phase change ink ejection devices.

Another object of the present invention is to provide increased reliability in a phase change ink ejection device.

A more particular object of the present invention is to minimize temperature gradients in such ink ejection devices that include localized heating locations.

Still another object of the present invention is to provide a phase change type ink ejecting device that can be kept cool in a standby state and rapidly raised to a desired working temperature.

Yet another object of the present invention is to provide a phase change type ink ejection device that is constructed of materials that do not react adversely with the ink contained within the device.

Yet another object of the present invention is to minimize the weight associated with the ink ejector, thereby achieving rapid movement of the ink jet relative to the surface being scanned.

In accordance with these objects of the invention, an ink ejection device for ejecting droplets of ink includes at least one ink ejection opening including one chamber, one orifice and one inlet. .
A heater means is coupled to the ink jet for heating the ink so that it undergoes a phase transformation from a solid state to a liquid state.

In the present invention, the ink jet has at least 0.03 g
The inclusion of a material having a thermal conductivity of at least 0.2 cal/seccm ² (°C/cm) provides a heat transfer effect that achieves the aforementioned objective.
Thermal conductivity is gcal/seccm ² (°C/cm). According to the present invention, a number of high thermal conductivity materials can be used, including stainless steel, although aluminum is preferred.

Further in accordance with the objects of the invention, the device also includes a reservoir coupled with heater means. Like the ink jets, this reservoir also preferably has a thermal conductivity of at least 0.03 gcal/seccm ² (°C/cm).
It is made of a material with a temperature of 0.2 gcal/seccm ² (°C/cm) or more.

〔Example〕

With reference to FIG.
Drawing head 1 containing two ink jets 12
0 and one reservoir 14. The ink ejection device is adapted to eject droplets of hot melt or phase change ink. In accordance with the present invention, substantially all of the drawing head 10 and reservoir in contact with the molten ink are comprised of highly thermally conductive materials, thereby minimizing thermal gradients and avoiding ink degradation.
Ink ejection devices are increasingly achieving high performance and reliability.

As shown in FIG. 1, a block 16 of solid ink is juxtaposed to the opening of a trough 18. If the pellet 16 falls into the trough 18,
Pellet 16 begins to melt in response to heat generated by heater 20 located below sloped surface 22 at the bottom of reservoir 14.

As shown in FIG. 1, the ink jet orifice 12 includes a chamber 24 having an orifice 26 for ejecting droplets of ink, and a reservoir 14.
and an inlet 28 extending to the lowermost tip 30 adjacent the sloped bottom 22 of the holder.

The head 10 has a thermally resistive barrier 34 made of an insulating material.
It has its own heater 32 located between the head member 36 and the head member 36. By providing the heater 32 independent from the heater 20, the head 10
can be maintained at a different temperature than the reservoir 14. This allows the reservoir 14 and the ink within the reservoir to be kept cool on standby, thereby avoiding heating and deterioration of large amounts of ink, but at the same time the drawing head 1
It is also possible to maintain the ink in liquid form within 0 to avoid underfilling the ink.

With respect to preventing underfilling, the inlet 28 passes through a highly thermally conductive head member 36 so that heat is directed to the end 38 to maintain a puddle 40 of ink in liquid form near the end 38. However, the remaining ink in the reservoir 14 can be cooled to a particularly solid state while the device is on standby. As shown in FIG. 1, a puddle 40 of liquid ink is maintained in a solid mass 42 of ink extending to a level 44.

As shown in FIG. 1, a transducer 46 is juxtaposed to the end of chamber 24. The transducer with electrode rods is energized by a signal provided via a printed circuit board 48 located above member 36. Converter 46 and printed circuit board 4
8 are therefore housed within head members 50 and 52.

As also shown in FIG. 1, the head includes a chamber plate 54 forming a chamber 24 communicating with a leg 56 located at the end of the transducer 46. As the transducer changes state in response to applied signals, the position of legs 56 changes to expand or compress the volume within chamber 24. The inlet 28 feeds into a manifold 58 provided in a plate 60 that is coupled to a confined flash port for the spout 12 . In fact, the manifold 58 is the injection port 1 shown in FIG.
2, a plurality of limited inlet ports are provided in the same array of ink jet orifices.

As shown in FIG. 1, the reservoir 14 also includes a filter 6 located below a port 64 which is adapted to be opened and closed by a needle valve 66.
Contains 2. Needle valve 66 is used to close port 64 during the filling operation.

As also shown in FIG. 1, an insulating barrier 34 providing a high thermal resistance to the conduction path is also provided on the portion 70 of the reservoir 14 using an o-ring 72 characterized by suitable insulating properties. sealed against. Preferably, the lowermost portion 30 within the reservoir 14
A downwardly extending member 36 is slightly spaced from portion 70 of reservoir 14 . This spacing provides an adequate thermal barrier and high thermal resistance path to uniquely achieve heating of the ink within the head compared to the heat within the reservoir 14.

Finally, FIG. 1 shows redundant level sensing elements 74 and 76, which may be FR level sensors or other electrical sensor means. A regulating device 78 is also provided within reservoir 14 .

As mentioned above, the head 10 is connected to the reservoir 1.
Similarly to No. 4, it is preferable to have a thermal conductivity exceeding 0.3 gcal/seccm ² (°C/cm). Preferably,
The thermal conductivity between the head 10 and the reservoir 14 is 0.2g
Cal/seccm ² (°C/cm) or more. In this regard, it is preferred to use aluminum, although other materials with similar conductivity can be used, such as stainless steel as well as metal-plastic composites.

Various materials suitable for use are shown in the table below: Material Thermal conductivity gcal/seccm ² (°C/cm) Copper 0.92 Aluminum - 99% 0.50 Aluminum 7075 0.289 Aluminum 6061 0.409 Aluminum 356 0.36-0.40 Aluminum A13 0.29 Aluminum 380 0.23−0.26 Brass 0.25−0.31 400 Series Stainless Steel (420) 0.0595 300 Series Stainless Steel (316) 0.0389 High thermal conductivity to minimize temperature gradients and hot spots where aluminum is the preferred material Benefits associated with this have been achieved as well as rapid heating to the desired working temperature.

Furthermore, due to its relatively low specific gravity, aluminum provides a relatively lightweight imaging head 10 and reservoir 14, reducing their inertia, thereby reducing the scanning surface (image reproduction surface). allows for rapid movement of the spout. Furthermore, aluminum does not react chemically with ink.

Of course, it is clear that the entire imaging head 10 and the entire reservoir 14 are not meant to be made of high heat transfer material. For example, the thermal resistance barrier 34 is 0.005 gcal/seccm ² (°C/
cm) or less. Thermal barrier is also achieved without the benefit of insulation by minimizing metal contact between head 10 and reservoir 14. However, substantially all of the head 10 and reservoir 14 in direct or indirect contact with the ink are comprised of highly thermally conductive materials, with the notable exception of filter 62.
Indirect contact is accomplished where the material, such as copper, is coated to minimize any reaction with the ink. It is also possible to use more than one high thermal conductivity material in the ink ejector. For example, part of the head 10 can be made from aluminum and part or all of the reservoir 14 can be made from stainless steel.

Although preferred embodiments of the invention have been shown and described encompassing various materials, other embodiments within the spirit of the invention and the scope of the claims will occur to those skilled in the art.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an ink ejecting device embodying the present invention. 10...Drawing head, 12...Ink jet port,
14...Reservoir, 16...Ink block, 18
...Trough, 20, 32...Heater, 24...
Chamber, 26... Orifice, 28... Inlet, 34... Thermal barrier, 36... Head member,
42... solid state mass of ink, 46... converter,
48...Printed circuit board, 50, 52...Head member, 54...Chamber plate, 56...
... Legs, 58 ... Manifold, 62 ... Filter, 66 ... Needle valve, 74, 76 ... Level sensor, 78 ... Adjustment device.

Claims (1)

Claims: 1. A reservoir for replenishing phase change ink; a drawing head comprising at least one ink jet orifice including a chamber, an orifice, and an inlet coupling the ink jet chamber to the reservoir; a first heater means for heating the ink in the jet orifice so that the ink undergoes a phase transformation from solid to liquid without loss of quality; second heater means for heating the ink in the reservoir to undergo conversion; the first heater means adapted to be independently controlled with respect to the second heater means; and a thermally resistant barrier means between the drawing head and the reservoir to thereby enable the drawing head to be maintained at a different temperature than the reservoir; /seccm ² (℃/cm)
A thermofusible ink ejection device for ejecting droplets of phase change ink, comprising a material having a thermal conductivity of . 2 Materials are at least 0.2 gcal/seccm ² (℃/cm)
2. The device of claim 1, having a thermal conductivity of . 3. The device of claim 1, wherein the material comprises stainless steel. 4. The device of claim 1, wherein the material comprises aluminum. 5. The reservoir also has at least 0.03 gcal/seccm ²
2. The device of claim 1, comprising a material having a thermal conductivity of (° C./cm). 6 Materials with at least 0.2 gcal/seccm ² (℃/cm)
6. The device of claim 5, having a thermal conductivity of . 7. The device of claim 5, wherein the material comprises stainless steel. 8. The device of claim 5, wherein the material comprises aluminum. 9 Substantially all of the ink jet and reservoir materials in contact with the ink are at least 0.03 gcal/seccm ²
6. The device of claim 5, having a thermal conductivity of (°C/cm).