GB2211471A

GB2211471A - Hot-melt type ink jet recording apparatus

Info

Publication number: GB2211471A
Application number: GB8825120A
Authority: GB
Inventors: Takemi Yamamoto; Jun Sakai; Mamoru Imaizumi
Original assignee: Brother Industries Ltd
Current assignee: Brother Industries Ltd
Priority date: 1987-10-27
Filing date: 1988-10-27
Publication date: 1989-07-05
Anticipated expiration: 2008-10-27
Also published as: GB8825120D0; GB2211471B

Abstract

In an ink jet printer of the kind which employs a hot melt ink, provision is made for heating the substrate printed upon. The hot melt ink is thus able to permeate the fibres of the substrate before solidifying, thereby rendering the printing more durable.

Description

HOT-MELT TYPE INK JET RECORDING APPARATUS The present invention relates to a hot-melt type ink jet recording apparatus.

A number of ink jet recording methods and apparatuses have been proposed in which ink particles produced in accordance with an electric signal are ejected against a recording medium to thereby perform recording. Of these, attention has particularly been drawn to an ink jet recording apparatus using a thermally-fusable ink which is solid under room temperature and is brought to a liquid phase when heated. Such ink is generally referred to as 11hot- melt type ink" as disclosed in Japanese Patent Application Kokai No. 61-98546.

According to the ink jet printer disclosed in this publication, there are provided a platen for supporting a printing paper; a printing paper feeding mechanism; an ink supply mechanism storing therein a solid ink and having a heater for melting the ink; and an ink injection head for injecting the ink supplied from the ink supply mechanism and printing an image on the printing sheet. With this arrangement, clear image without any ink smearing and burring is obtainable on the printing sheet.

While such a recording apparatus is advantageous in that recording can be performed irrespective of the kinds of recording mediums, it is disadvantageous in that ink formed on the recording medium is liable to be peeled off when an external force, e.g. scratching, bending, is exerted on the recording medium. That is, upon ink deposition onto the sheet, the ink is immediately cooled and solidified before the liquidized ink is sufficiently permeated into the fibers of the sheet. Instead, the injected ink may protrude from the sheet surface in the solidified state, and therefore, the solid imaging zone may be peeled off from the sheet upon application of mechanical force, such as, upon contact with mechanical components.

Japanese Patent Application Kokai No. 62130863 discloses a heating body mounted on a platen of an ink jet printer so as to heat a printing sheet. In the printer of this type, liquid aqueous ink at room temperature is used for the printing. The heating body is adapted to immediately dry the aqueous ink after printing so as to avoid ink smearing and burring.

The present invention has been made in view of the foregoing drawback accompanying the known ink jet e recording apparatuses. It is therefore an object of this invention to provide an ink jet recording apparatus using a thermally-fusable ink, which can produce such a hard copy that ink will not be peeled off from the recording medium even when an external force is exerted on the recording medium, or is less likely so to peel.

To achieve this and other objects, there is provided, according to one aspect of the invention, an ink jet recording apparatus for recording an image on a recording medium in accordance with input data, comprising: a recording head for ejecting ink against the recording medium to form the image thereon with the ink and a heating means for thermally fixing the image on the recording medium.

In operation, when a recording medium on which an image is recorded by the recording head passes along the heating means, the ink on the recording medium is fused by the heat generated by the heating means, so that the ink deeply permeates into the recording medium so as not to be easily peeled off.

According to another aspect of the present invention, there is provided a hot-melt type ink jet printer for printing an image on a printing sheet comprising: a platen for supporting the printing sheet and for defining a printing position; a printing sheet feeding mechanism for feeding the printing sheet; an ink supply mechanism for storing a solid ink therein, the solid ink having a solid phase at room temperature, and the ink supply mechanism having a solid ink heater for heating the solid ink to obtain a liquidized ink; an ink ejection head connected to the ink supply mechanism and confronting the platen for ejecting the liquidized ink onto the printing sheet; a printing sheet heating unit for heating the printing sheet, the heating unit being positioned at one of immediately upstream of the printing position, the printing position, and downstream of the printing position.

If the printing sheet heating unit is positioned immediately upstream of the printing position or at the printing position, the printing sheet is heated at the timing of ink injection. Therefore, the ink deposited onto the sheet does not immediately solidifv, but is properly permeated into the sheet. Further, if the printing sheet heating unit is positioned downstream of the printing position, the liquidized ink deposited onto the printing sheet is immediately cooled and solidified. However, the ink carrying sheet is then heated by the heating unit, so that the solidified ink is again melted and properly permeated into the sheet. Therefore, no substantial solid ink protrusions are formed on the printing sheet, and as a result, printed ink images do not peel off from the printing sheet even under mechanical force.

The invention will be further described by way of nonlimitative examples with reference to the accompanying drawings, in which: FIG. 1 is a schematic diagram showing an ink jet recording apparatus according to this invention; FIG. 2 is a partial cross-sectional view illustrating an ink deposition on the surface of a recording medium before heat application by a heating means of the invention; FIG. 3 is a partial cross-sectional view illustrating an ink deposition on the surface of the recording medium after heat application by the heating means of the invention.

FIG. 4 is a schematic side view showing an essential portion of a hot melt type ink jet printer according to another embodiment of this invention; FIG. 5 is a front view partially cross-sectioned showing an ink injection head used in the printer of this invention; FIG. 6 is a cross-sectional view showing an ink supply mechanism used in the printer according to this invention; FIG. 7 is a block diagram showing a control device for controlling the printer according to this invention; and, FIG. 8 is a schematic side view showing an essential portion of a hot melt type ink jet printer according to a still another embodiment of this invention; FIG. 1 schematically illustrates an ink jet recording apparatus according to the embodiment of this invention. A rolled recording medium 1 is drawn out from a recording medium supply unit 2 and is conveyed by means of feed rollers 3, 4 and 5.A cutter 6 is disposed between the rollers 4 and 5, and a heat-generating wire 7 is disposed downstream of the rollers 5 with respect to a recording medium conveying direction.

A recording system is provided in the apparatus, which includes a recording head 8, a driver 9 for driving the recording head 8, and a controller 10 for controlling the driver 9 in accordance with recording data received from an external unit (not shown).

-In operation, the recording medium 1 drawn from the supply unit 2 is brought by means of the rollers 3 to a position confronting the recording head 8, whereat recording data is externally supplied to the controller 10 and the recording head 8 is driven by the driver 9. The recording head 8 includes a heater (not shown) which fuses a thermallyfusable ink to a liquid phase when the apparatus is in operation. When the recording medium 8 is driven by the driver 9, ink particles 11 formed in accordance with the recording data are ejected against a given location on the recording medium 1 to thereby form an image on the recording medium 1. Then, the image-bearing recording medium 1 is fed by the feed rollers 4 and is cut at a desired widthwise line by the cutter 6. The separated recording medium is conveyed beneath the heater 7 by the feed rollers 5 for heating and fixing.

The ink 13 that has deposited on the recording medium 1 is cooled immediately after recording by the recording head 8 and is quickly solidified. The ink 13 only stays on the surface of the recording medium 1 as shown in FIG. 2.

After heating by the heater 7, the ink 13 deeply permeates into gaps 15 between fibers 14 constituting the recording medium 1, as shown in FIG. 3, so that the ink is hard to be peeled off from the surface of the recording medium 1 even if an external force were exerted thereon. After thermal fixing by means of the heater 5, the recording medium 1 is discharged out of the apparatus through the recording medium discharging port 12, thus completing the recording operation.

A second embodiment of this invention is shown in FIGS. 4 thru 7. The above-described first embodiment concerns principle of the present invention. In the second and third embodiments a heater used is adapted to heat a printing sheet.

As best shown in FIG. 4, a shaft 112 of a platen 110 is rotatably supported to a frame (not shown), and is driven by a platen drive motor 114 (see FIG. 7). Below the platen 110, two feed rollers 116 and 118 are rotatably provided.

These rollers are directed in parallel with the platen 110 and are in rotational surface contact therewith for feeding a printing sheet 120 in corporation with the platen 110.

Above the platen 110, a sheet pulling roller 122 and a pinch roller 123 are provided for pulling up the printed sheet 120. The sheet pulling roller 122 is direven by a sheet pulling roller drive motor 124 (see FIG. 7), so that the sheet already printed is discharged out of the printer in cooporation with the pinch roller 123. According to the embodiment, the above described platen 110, the sheet feed rollers 116,115, the platen drive. motor 114, the sheet pulling roller 122, the pinch roller 123 and the roller drive motor 124 serve as a printing sheet feeding mechanism.

An ink injection head 128 and the ink supply mechanism 130 are disposed in confrontation with the platen 110. The ink injection head 128 and the ink supply mechanism 130 are mounted on a carriage 132. The carriage 132 is connected to a carriage drive motor 133 (FIG. 7) so that the carriage 132 is moved in a direction paralled with the axial direction of the platen 110. Accordingly, the ink injection head 128 is moved along the printing sheet 120.

As best shown in FIG. 5, the ink injection head 128 has a main body 134 in which a plurality of injection nozzles 135 are formed in a single array in vertical direction. Each of the injection nozzles 135 is connected to each of ink chambers 136 which chambers 136 are in fluid communication with an ink reservoir 137. At each lateral one side of each of the ink chambers 136, a rectangular vibration plate (not shown) is provided. This vibration plate is electrically deformable so as to produce a liquid pressure change within the ink chambers 136, to thereby eject ink from the injection nozzles 135 toward the printing sheet. Printing is made by the lateral displacement of the ink injection head 128 and the travel of the printing sheet 120.

The ink supply mechanism 130 is shown in FIG. 6 in which a cup-shaped cylindrical ink ' case 139 is provided.

Within the ink case 139, a solid cylindrical ink 140 is disposed slidable in an axial direction of the case 139.

The ink 140 has a solid phase at a room temperature.

Further, a coil spring 142 is disposed between a bottom of the case 139 and a tail end of the solid cylindrical ink 140 so as to urge the latter toward an open end of the case 139.

At the open end of the case 139, an ink heater 144 is provided. The ink heater 144 includes a heating plate 146 formed with a conduit 150 and a resistance heating element 148 for heating the heating plate 146. A part of a leading end of the solid ink 140 is in surface contact with the heating plate 146, and is melted to become a liquid phase.

The liquidized ink is passed through the conduit 150 and is accummulated in an ink tank 152. A resistance heater plate 154 is attached to the ink tank 152 so as to prevent the liquized ink from its solidification. The liquidized ink in the tank 152 is then introduced into the ink reservoir 137 of the ink injection head 128.

Further, an ink amount sensor 162 is connected to the ink tank 152 for measuring the amount of liquidized ink therein. The sensor 162 is connected to an ink heater control circuit 164. When the measured ink amount in the tank 152 becomes less than a predetermined level, the ink heater 144 is operated for a predetermined period, so that the heating plate 146 is heated for melting the solid ink 140. The ink heater 144 does not always operated for continuously melting the solid ink 140, but is temporarily operated so as to melt the solid ink by a small amount.

Therefore, excessive heating to the solid ink is avoidable for accummulating a given amount of liquidized ink in the tank 152. Further, at the ink case 139, a solid ink sensor 166 is provided for the detection of amount of solid ink.

The sensor 166 is a photo-electric sensor which includes a light emitting portion 168 and a light receiving portion 170. When an axial length of the solid ink 138 becomes small, the light receiving portion 170 receives light from the light emitting portion 168. As a result, the solid ink sensor 166 generates output signal indicative of small length of the solid ink. Further, a solid ink sensor control circuit 172 sends a signal to the ink heater controlling circuit 164 so as to terminate operation of the ink heater 144.

As shown in FIG. 4, a printing sheet heating unit 176 is provided at a position between the platen 110 and the sheet pulling roller 122 or the pinch roller 123. That is, the printing sheet heating unit 176 is disposed at a position downstream of the printing position with respect to travelling direction of the printing sheet 120. This heating unit 176 includes a hollow retainer 178 and a heater 180 disposed in the retainer 178. The retainer 178 is formed with a recessed portion 182 which extends in the travelling direction of the printing sheet 120. The open end of the recessed portion 182 confronts the platen 110. The bottom wall of the recessed portion 182 serves as a heating surface 184.The recessed portion 182 guides travel of the printing sheet 120 and the heating surface 184 is slightly spaced away from the printing surface 186 of the printing sheet 120. Upon heat generation of the heater 180, air confined within the retainer 178 is heated, so that the temperature of the heating surface 184 is elevated. As a result, the printing surface 186 of the pringing sheet 120 is heated when the sheet 120 passes through the recessed portion 182.

A heater control circuit 188 is connected to the heater 180 so as to control electrical current supply thereto. A temperature sensor 189 is provided in the retainer 178. The heater control circuit 188 controls electrical current to be supplied to the heater 180 in response to the detection signal from the temperature sensor 189, so that the temperature at the heating surface 184 is maintained unchanged. It should be noted that the heating temperature is less than a melting point of the solid ink 140. That is, according to this embodiment, the solid ink 140 has a melting point of 600C, and therefore, the heating surface 184 has a temperature about 2 to 30C lower than the melting point.

The ink jet printer according to this invention is controlled by the control device 190 shown in FIG. 7. The control device 190 is a microcomputer which primarily includes CPU 192, ROM 194, RAM 196, and a bus 198 for connecting these elements. The bus 198 is connected to an input interface 200 which in turn is connected to a host computer 202 adapted to supply a printing data. Futher, the bus 198 is connected to an output interface 204 which is connected to the platen drive motor 114, the roller drive motor 124, the ink injection head 128 and the carriage drive motor 133 through the platen drive circuit 206, the roller drive circuit 208, the head drive circuit 210, and the carriage drive circuit 212, respectively. Further, the output interface 204 is connected to the ink heater control circuit 164, the solid ink sensor control circuit 172, and heater control circuit 188.

With the structure, thus organized, upon manupulation of a print start switch (not shown), the heater 180 is heated, and the ink heater control circuit 164 and the solid ink sensor control circuit 172 initiate operations. At the same time, driven are the platen 110, the sheet pulling roller 122, the ink injection head 128 and the carriage 132, so that printing is performed in accordance with the printing data supplied from the host computer 202. After the ink ejected from the ink injection head 128 is deposited onto the printing surface 186 of the printing sheet 120, the ink is immediately cooled and solidified. However, the printing sheet 120 is heated by the heater 180, so that the ink is melted and properly permeated into the sheet 120.

Accordingly, there is no substantial printing mass on the printing surface 186, but the ink is stabilizingly fixed on the sheet. In this case, the temperature of the heating surface 184 is about 2 to 30C lower than the melting point of the solidified ink 140. Therefore, avoidable is complete melting and subsequent flowing of the ink for degradation of the printing quality. Instead, the ink is appropriately melted and permeated into the printing sheet 120. Incidentally, sufficient distance is provided between the rollers 122,123 and the heating surface 184, so that the ink melted at the heating surface 184 is completely dryed when it passes through these rollers 122, 123. Accordingly, there is no ink adhesion to these rollers.

According to this embodiment, since the heater 180 is adapted to heat the printing sheet 120 at its printing surface 186. Therefore, even if thickness of the printing sheets are changed, the sheet is properly subjected to heating at a perper temperature for allowing the deposited and solidified ink to be permeated into the sheet.

Otherwise, the heat is not easily transmitted toward the deposited and solidified ink, and large heat amount is required, and most disadvantagenously, optimum heating temperature must be provided in accordance with the thickness of the printing sheet, to thus render the temperature control difficult. According to this invention, the heater does not heat the back surface of the printing sheet, and therefore, the above-described drawbacks can be obviated. Further, the temperature of the printing surface 186 is required to be high enough for permeating the solidified ink into the sheet, and it is unnecessary to heat the back surface of the sheet for the ink permeation. By so doing, required heat amount can be reduced, and heating temperature can be maintained at a constant level regardless of the thickness of the printing sheet.Furthermore, large free space is provided at the position downstream of the printing position, and therefore, the sheet heating unit 176 can be easily installed at the space.

A still another embodiment according to this invention is shown in FIG. 8. In the foregoing embodiment, the sheet heating unit 176 is disposed at downstream side of the print position. However, in the third embodiment, the heating unit is positioned at the printing position. That is, a heat generating element 316 such as a halogen lamp is disposed within a platen 314, so that the printing sheet is heated at its back surface. Further, in a modification, a plate like platen is used, and the heater in the platen is adapted to only heat a printing portion and a portion adjacent thereto of the printing sheet.

In the second and third embodiments, the printing sheet heating unit is positioned downstream of the printing position and adjacent thereto, or is positioned at the printing position. However, the heating unit can also be installed at the position immediately upstream of the printing position or downstream thereof and spaced away therefrom. Such modification may be made dependent on optimum printing quality and mechanical arrangement of the printer.

Although the present invention has been described with reference to specific embodiments, the present invention is in no way restricted to the above embodiment, but a variety of changes and modifications may be made without departing from the scope and spirit of the invention. For example, the heat-generating wire used in the first embodiment serving as a heating means may be replaced by a halogen lamp, ceramic heater, carbon heater, high-frequency induction heating mechanism or electromagnetic wave heating mechanism.

Further, the heating means may not be of a heat radiation structure but may be of the type in which the recording medium is heated through a direct contact with a heating body.

In a modification to the first embodiment, the heating means may be located along the conveying path either between the feed rollers 5 and the cutter 6, or between the feed rollers 4 and the cutter 6, or between the feed rollers 4 and the recording head 11.

The rolled recording medium may be replaced by a cut sheet type. Further, the heating means may be such that it applies pressure to the recording medium simultaneous with heat application.

As should be understood from the above description, according to this invention, since the ink deposited on the recording medium is fixed by the heating means after recording is done by the recording head, the ink would not be peeled off from the recording medium even when an external force is exerted thereon, whereby reliability of the recording is improved.

Claims

1. An ink jet recording apparatus for recording an image on a recording medium in accordance with input data, comprising: a recording head for ejecting ink against the recording medium to form the image thereon with the ink and a heating means for thermally fixing the image on the recording medium.

2. An ink jet recording apparatus according to claim 1, wherein a thermally-fusible ink is thermally fused to a liquid phase to provide the ink

3. An ink jet recording apparatus according to claim 1 or 2, wherein said heating means is disposed to be in spacedapart relation with the recording medium on which the image is formed.

4. An ink jet recording apparatus according to claim 1 or 2, wherein said heating means is disposed to be in direct contact with the recording medium on which the image is formed.

5. An ink jet recording apparatus according to claim 1 , 2, 3 or 4wherein said heating means comprises a heatgenerating wire.

6. An ink jet recording apparatus according to claim 1, 2, 3 or 4 wherein said heating means comprises a halogen lamp.

7. An ink jet recording apparatus according to claim 1, 2, 3 or 4 wherein said heating means comprises a ceramic heater.

8. An ink jet recording apparatus according to claim 1, 2, 3 or 4 wherein said heating means comprises a carbon heater.

9. An ink jet recording apparatus according to claim 1, 2, 3 or 4 wherein said heating means comprises a highfrequency induction heating mechanism.

10. An ink jet recording apparatus according to claim 1, 2, 3 or 4 wherein said heating means comprises an electromagnetic wave heating mechanism.

11. An ink jet recording apparatus according to any preceding claim further comprising a conveying means for conveying the recording medium in a predetermined direction and wherein said heating means is disposed downstream of said recording head with respect to the predetermined direction.

12. An ink jet recording apparatus according to claim 11, further comprising a pressure means for exerting pressure on the image bearing recording medium which has been heated by said heating means.

13. A hot-melt type ink jet printer for printing an image on a printing sheet comprising: a platen for supporting said printing sheet and for defining a printing position; a printing sheet feeding mechanism for feeding said printing sheet; an ink supply mechanism for storing a solid ink therein, said solid ink having a solid phase at room temperature, and said ink supply mechanism having a solid ink heater for heating said solid ink to obtain a liquidized ink; an ink injection head connected to said ink supply mechanism and confronting said platen for injecting said liquidized ink onto said printing sheet; a printing sheet heating unit for heating said printing sheet, said heating unit being positioned at one of immediately upstream of said printing position, said printing position, and downstream of said printing position.

14. An ink jet printer according to claim 13, wherein said printing sheet heating unit is positioned at immediate downstream of said printing position, and heats a printing surface of said printing sheet.

15. An ink jet printer according to claim 13 wherein said printing sheet heating unit is positioned at said printing position, and heats said printing sheet at its back surface.

16. An ink jet printer according to claim 13 or 14, further comprising: a control device for controlling the temperature of said heater unit; a heater control circuit connected to said control device; and a temperature sensor connected to said heater control circuit for detecting temperature of said heater unit, said heater control circuit controlling an electrical current to be supplied to said heater unit in response to said detection signal, so that a temperature of said heater unit is slightly lower than a melting point of said solid ink.

17. An ink jet printer. substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.