Ink jet recording apparatus and discharge recovery device used with the same

Abstract: A discharge restoring device for a ink jet recording apparatus, comprising a cap member (11) for covering a plurality of discharge openings (4) for discharging ink, and a suction means (P) for sucking the ink and/or air from the plurality of discharge openings through the cap member, wherein a main communication port (12) communicating the suction means with the interior of the cap member is provided at an upper portion of the cap member. Further, an ink jet recording apparatus comprising a recording head having a plurality of discharge openings provided along an up-and-down direction for discharging ink, a cap member for covering the plurality of discharge openings, a suction means for sucking the ink and/or air from the plurality of discharge openings through the cap member, moving means for moving the cap member in a position where the cap member covers the plurality of discharge openings, and drive means for driving the suction means after the plurality of discharge openings are covered by the cap member by means of the shifting means, wherein a main communication port communicating the suction means with the interior of the cap member is provided at an upper portion of the cap member and the ink and/or air are sucked through the main communica­ tion port by the suction means.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an ink jet recording apparatus, and, more particularly, it relates to a discharge recovery or restoring device for an ink jet recording apparatus, which is provided with a cap capable of covering a recording liquid discharge surface to prevent the jamming of discharge openings of a recording head and to prepare initial charge or introduction of a recording liquid and of permitting suction of ink (recording liquid) and/or air. Related Background Art In a recording head used with an ink jet recording apparatus, flying drops of recording liquid are created by discharging the recording liquid from minute or small discharge ports or openings each having a diameter of the order of about 40 - 50 µm. However, with such a construction, there is a tendency for bubbles to accumulate in liquid passages into which the recording liquid is introduced, and dust to stick around the discharge openings and/or solidification of the recording liquid may cause non-discharge of the recording liquid (from the discharge openings) and deviation of the discharged liquid drops with respect to a recording medium. For these reasons, in the past, as shown in U.S. Patent No. 4,600,931 in order to eliminate the above drawbacks and to facilitate the initial introduction of the recording liquid to the liquid passages of the recording head, for example, when the recording head is used again after it is unused for a long time, a suction operation, called a restoring operation, been utilized by covering the recording liquid discharge face of the recording head by means of a cap member. Such a cap member was so constructed that the recording head brought into a home position was covered by the cap member and the recording liquid was sucked through the discharge openings arranged on the discharge face by means of an appropriate suction means communicating with the cap member. Fig. 1 shows an example of a cap member of the conventional discharge restoring device, such as shown in the U.K. Patent Laid-Open No. GB-2184066 A. This Figure shows a condition that a front plate 3 of a recording head 2 is covered by a cap member 1. The recording head 2 includes a plurality of discharge openings 4 arranged on the front plate 3 along an up-and-down direction, and a plurality of liquid passages 6 for communicating a common liquid chamber 5 with the corresponding discharge openings to direct the recording liquid in the liquid chamber 5 to the discharge openings 4. When the recording operation is started, the recording liquid is discharged from the discharge openings 4 by means of discharge energy generating means (not shown) such as piezo-electrical elements, electrical-thermal converters and the like. When the cap member 1 is mounted on the front plate 3 of the recording head 2 (as shown), a space 8 defined by the plate 3 and cover 1 is fluid-tight sealed with respect to the atmosphere by engaging an elastic seal 7 (such as a silicon rubber ring, butyl rubber ring and the like) arranged on a peripheral edge of the cap member 3 with the front plate 3. The cap member 1 has a communication port 9 at a lower portion of the space or cavity 8, which port 9 is communicated with an external suction pump 10. In this condition, air in the cavity 8 is sucked through the communication port 9 by the suction pump 10 to create pressure lower than atmospheric pressure in the cavity 8, thus introducing the recording liquid into the cavity 8 through the discharge openings 4 and then exhausting the recording liquid from the cavity to an appropriate exhaust liquid tank (not shown) by the action of the suction pump 10. By the way, in the conventional restoring device of this kind, the communication port 9 was positioned in the lower portion of the cavity 8 of the cover member 1 not to leave the recording liquid after the liquid was drawn through the communication port, thus preventing the liquid from dropping out of the cavity, and thus preventing the contamination of the apparatus, when the cover member 1 was separated from the front plate of the recording head 2. However, when a recent multi-nozzle recording head having a great number (for example, 128) of the liquid passages and discharge openings is used, for example during the initial introduction of the recording liquid into the liquid chamber 5, as shown by a hatching line in Fig. 1, the recording liquid is drawn or sucked through the discharge openings situated in the lower portion (i.e., not through all of the discharge openings) before the liquid chamber 5 is completely filled with the recording liquid, with the result that the restoring operation has been completed before the whole liquid chamber is filled with the recording liquid (i.e., before the discharge openings situated in the upper portion are filled with the recording liquid). Thus, in the conventional multi-nozzle recording head, there was a problem that, when the recording operation was initiated after such restoring operation, the recording liquid was not discharged from the discharge openings situated in the upper portion, whereby complete images as desired could not recorded on the recording medium. On the other hand, in a recording head of full-line type recording apparatus that the recording operation is performed by discharging the recording liquid from the discharge openings of the recording head stationary with respect to the recording medium, a great number (for example, about 1792) of the discharge openings are arranged substantially along a single line. In such a recording head of full-line type, since the array of the discharge openings extends substantially in a horizontal direction, the distance between two discharge openings situated on both ends of the array is relatively large, and accordingly, the length of the common chamber which must be communicated with all of the discharge openings is also relatively large in the horizontal direction. Thus, also in this case, if, by utilizing the suction effect through the cap member, the recording liquid is introduced into the recording head and the restoring operation is performed as in the above-mentioned case, there arises the same problem as described above. That is to say, if the communication port leading to the suction pump is provided at the left end of the cap member, the liquid passages situated at the right side of the recording head will not be filled with the recording liquid, whereas if the communication port is provided at the right end of the cap member, the liquid passages situated at the left side of the head will not be filled with the recording liquid. SUMMARY OF THE INVENTION According to the present invention a discharge recovery device for an ink jet recording apparatus, comprises: a cap member for covering a plurality of discharge openings for discharging ink; suction means for sucking the ink and/or air from said plurality of discharge openings through a cavity in said cap member and communicating with each of the discharge openings; a communication port for communicating said suction means with the interior of said cap member is characterised in that the communication port is provided at an upper portion of said cap member, the said upper portion being positioned above the uppermost discharge port of the plurality of discharge ports. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic sectional view showing an example of a conventional discharge restoring device for an ink jet recording head; Fig. 2 is a schematic sectional view showing a discharge restoring device for a recording head of an ink jet recording apparatus according to a first embodiment of the present invention; Fig. 3 is a schematic constructural view showing an ink jet recording apparatus according to a second embodiment of the present invention; and Fig. 4 is a perspective view of an ink jet recording apparatus according to an arrangement which is the subject of a divisional application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be fully and concretely explained in connection with the embodiments shown in Figures 2 and 3 of the drawings. First of all, a first embodiment shown in Fig. 2 will be explained. A cap member 11 is provided with a main suction port or communication port 12 communicating with an upper portion of a space or cavity 8 of the cap member, and a second suction port or communication port 13 communicating with a lower portion of the cavity 8. The communication ports 12 and 13 are communicated with a pump 14 through communication conduits or suction paths 12A and 13A, respectively, so that a recording liquid and/or air can be drawn or sucked from the cavity 8 through both of the communication ports 12 and 13. The diameter of the suction path 12A is larger than that of the suction path 13A. The suction paths i.e., communication conduits 12A and 13A are made of the same material; thus, due to the difference in diameter as stated above, channel resistance of the communication conduit 12A is smaller than that of the communication conduit 13A. Alternatively, the channel resistances of the communication conduits may be differentiated as above, for example, by changing the dimensions of the suction port and/or making walls of the conduits with different rough surfaces. With the construction mentioned above, when a recording head 2 is moved to a home position in order to perform initial introduction of the recording liquid into a common chamber 5 and liquid passages 6 of the head, the cap member 11 is shifted to cover a discharge face 3A of a front plate 3 of the recording head 2, then the air is sucked from the cavity 8 by the suction pump 14, thereby decreasing the pressure in the cavity 8, with the result that the recording liquid is introduced from the common liquid chamber 5 and liquid passages 6 and then introduced into the cavity 8 through discharge openings 4. In the illustrated first embodiment, during the suction operation, if the recording liquid is introduced in the manner shown in Fig. 1 to leave an air space or unfilled area in upper portions of the chamber 5 and cavity 8, since the air is continuously sucked through the main communication port 12 by the suction pump 14, the chamber 5, liquid passages 6 and cavity 8 are completely filled with the recording liquid as shown by a hatched portion in Fig. 2 for an extremely short time with less power, without leaving the air in the cavity as in the conventional device. Thereafter, by switching the pump to cooperate with the second communication conduit 13A, the recording liquid in the cavity 8 is completely drawn through the second lower communication port 13, thus emptying the cavity so that the cap member 11 can be separated from the recording head 2 without contamination of the recording apparatus. [Second Embodiment] Next, a second embodiment of the present invention will be explained with reference to Fig. 3. Fig. 3 shows an ink jet recording apparatus according to the second embodiment of the present invention. In this ink jet recording apparatus, recording head 121a, 121b, 121c and 121d can perform the recording operation while moving in a direction shown by an arrow AA, with respect to a recording medium P brought into a recording position by means of a platen roller 101 as a conveying means. The recording heads 121a, 121b, 121c and 121d can discharge cyan ink, magenta ink, yellow ink and black ink, respectively. The recording heads are mounted on a shiftable carriage 102 guided along a guide bar 103, so that the heads can be moved to perform a scanning operation. The carriage 102 is drive by a driving motor 104 through a belt 104A. Ink supply conduits 121 for supplying a predetermined inks to the corresponding recording heads are fixed to a conventional flexible cable 120 to move together with it and are connected to corresponding ink tanks (not shown). When the discharge restoring operation is performed, the recording heads 121a-121d positioned in the home position are covered by a cap member 110. The cap member includes cavities associated with the corresponding recording heads. The suction system of this embodiment is substantially the same as that of the first embodiment described above, except that a vent valve 112 is provided in the communication conduit at half way for communicating the corresponding cavity with the atmosphere. That is to say, in operation, first of all, the cap member 110 is shifted to cover the discharge openings of the recording heads by a shifting means 111. Thereafter, when a signal for initiating the restoring operation is inputted to a control unit 105, the control unit 105 switches the three-way valves 112 to connect pumps 113 to corresponding communication ports 114, then energizes the pump 113 to create the pressure difference between the cap member and the atmosphere, thus sucking the ink and/or air from the discharge openings of the recording heads 121a-121d through the communication ports 114, 115 provided on the cap member 110. After a predetermined period of time is elapsed, the control unit 105 switches the three-way valves 112 to vent the cavities of the cap member 110 to the atmosphere, thus sucking the inks filling the corresponding cavities through the lower communication ports 115 to empty the cavities and introduce the air into the cavities through the valves 112. In this way, according to this second embodiment, it is possible to maintain the discharge openings in a good condition and exhaust the inks in the cap member 110 positively. While the three-way valve 112 and the pump 113 were shown only in association with the recording head 121a, these elements 112, 113 may be provided for each of the recording heads (each of the colored inks) or may be provided in common for all of the colored inks. Further, each of the recording heads may include the ink tank therein and may be removably mounted on the carriage individually. Fig. 4 shows an ink jet recording apparatus of full-line type which does not fall within the claims of the present application but which is the subject of a divisional application. The recording apparatus includes a recording head 212 which can perform the recording operation when stationary with respect to a recording medium P, and a roller 201 for conveying the recording medium P. A cap 210 is so constructed as to move and cover discharge openings 212A of the recording head 212 in inoperative condition. The cap 210 includes communication ports 214 and 215 communicated with a suction pump 213 through corresponding communication conduits 214A and 215A, thus communicating the interior of the cap 210 with the suction pump 213. The communication port 215, is positioned in confronting relation to the leftmost (Fig. 4) discharge opening 212A, whereas the communication port 214 is positioned in confronting relation to the rightmost discharge opening 212A. In this way, since the cap is communicated with the suction generating source, at plural points, preferably, at both ends of the cap, it is possible to decrease the difference in suction forces for the respective discharge openings and to perform the effective restoring (suction) operation even in the recording head of full-line type. In the recording heads illustrated in the above-mentioned embodiments, it is preferable to adopt a method of producing images with a recording liquid that utilizes thermal energy for forming drops of the recording liquid. And, it is desirable to provide electrical-thermal converters in correspondence to the respective discharge openings to generate the thermal energy. Such recording head can preferably be used since it is easy to form multi-orifice construction. In the present invention the communication ports communicating with the interior of the cap member are provided at the upper portion of the cap member, "the upper portion" is defined to be above a position corresponding to the uppermost discharge opening (Fig. 2). As mentioned above, according to the illustrated embodiments of the invention, since the communication port communicating with the suction means is arranged in the upper portion of a sealed space defined by mounting the cap member against the discharge face of the recording head, during the restoring operation for the recording head, the air is sucked from the sealed cavity through the upper portion thereof, whereby the recording liquid can be introduced into the cavity through all of the discharge openings including the upper ones, thus completely filling the liquid chamber and all of the liquid passages with the recording liquid. Further, by providing a plurality of communication ports and associated communication conduits communicating with the sealed cavity of the cap member, it is possible to perform the more effective initial introduction of the recording liquid and to facilitate the ejection of the recording liquid from the cavity of the cap member.

Claims: A discharge recovery device for an ink jet recording apparatus, comprising: a cap member (11) for covering a plurality of discharge openings (4) for discharging ink; suction means (14) for sucking the ink and/or air from said plurality of discharge openings (4) through a cavity (8) in said cap member and communicating with each of the discharge openings (4); a communication port (12) for communicating said suction means (14) with the interior of said cap member (11) characterised in that the communication port (12) is provided at an upper portion of said cap member, the said upper portion being positioned above the uppermost discharge port of the plurality of discharge ports. A device according to claim 1, further including a second communication port (13) communicating said suction means (14) with the interior (8) of said cap member (11). A device according to claim 2, wherein said second communication port (13) is provided at a lower portion of said cap member (11). A device as claimed in claim 2, wherein the first port and/or communication channel has a resistance smaller than that of the second port and/or communication channel. A device according to claim 4, wherein said first communication conduit has a cross-sectional area larger than that of said second communication conduit. A discharge recovery device according to any preceding claim, wherein said suction means (113) comprises a pump. An ink jet recording apparatus comprising: a recording head (121) having a plurality of discharge openings provided along an upstanding direction for discharging ink; a discharge recovery device as claimed in any preceding claim; moving means (111) for moving said cap member (110) to a position where said cap member (110) covers said plurality of discharge openings; and drive means for driving said suction means so that said plurality of discharge openings are covered by said cap member by said moving means (111). An apparatus according to claim 7, wherein said recording head (121) includes an ink tank for containing the ink and is removably mounted on a carriage (102) for moving said recording head (121). An apparatus according to claim 7 or 8, wherein said recording head (121) is adapted to perform a recording operation by discharging the ink by utilizing thermal energy. An apparatus according to any of claims 7 to 9, wherein said recording head (121) includes electro-thermal converter elements.

Inventors: KYOSHIMA MASAYUKI, KYOSHIMA, MASAYUKI
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1988
Main classification: B41J2
IPC codes: B41J2