Ink tank and ink jet recording apparatus having the ink tank

Abstract: A waste ink tank (1) for containing waste ink in an ink jet recording apparatus comprising an opening (22) provided in the waste ink tank (1), for introducing the waste ink into the ink tank (1), an ink absorbing member (16) disposed in the waste ink tank (1), and a volume expanding member (34) arranged in contact with a predetermined position of the ink absorbing member (16), the volume expanding member (34) expanding due to absorption of ink and having a coef­ ficient of volumetric expansion higher than that of the ink absorbing member (16).

Description: This invention relates to a waste ink tank for containing waste ink, and an ink jet recording apparatus having such a waste ink tank. More particularly, it relates to a waste ink tank or an ink jet recording apparatus having a mechanism for detecting the amount of ink in the waste ink tank. In conventional ink jet recording apparatus the ink discharging openings of the recording heads tend to become clogged or jammed due to the increase in viscosity of ink which occurs if there are relatively long intervals between printing operations of the recording heads and/or when dust adheres to the ink discharging openings of the recording heads. Various "restoring" mechanisms have been proposed for removing accumulations of viscous ink, dust and such like. In one arrangement a cap which covers the discharge openings in the recording head when it is in its idle position is provided, which protects the discharge openings. In this arrangement the restoring mechanism removes viscous ink from the discharge openings through the cap by applying pressure to the ink, for example by suction. The ink removed from the discharge openings (including the viscous ink) is stored in a waste ink tank. Fig. 1 shows a perspective view of such a conventional ink jet recording apparatus. In the illustrated apparatus the waste ink tank 1 is mounted with ink cartridges 2, which contain colored ink such as cyan, magenta, yellow and black ink respectively, in a carriage 3. A recording head 5 and a printed circuit board 6 are also mounted on the carriage 3. The carriage 3 can be moved along to slide shafts 8 by a driving force transmitted to the carriage 3 via a driving belt 9. Movement of the carriage 3 enables the recording head 5 to print images on a recording medium such as a sheet of paper (not shown), as the recording medium is fed onto a platen 7, by discharging ink onto the surface of the recording medium. During the recording operation, the carriage 3 moves to a position where it faces a cap 11 at appropriate times, which may be predetermined. The cap 11 forms part of a discharge restoring apparatus 10. In this position the cap 11 covers the discharge openings of the recording head 5 and a waste ink pipe 12, which forms part of the discharge restoring apparatus 10, is connected to the waste ink tank 1 for discharging ink thereto. The ink is sucked from the recording head 5 by the action of a pump (referred to below) provided in the discharge restoring apparatus 10, the waste ink being transmitted to the waste ink tank 1 via the waste ink pipe 12. Fig. 2 shows a sectional view of the discharge restoring system. The four recording heads 5 corresponding to cyan, magenta, yellow and black ink respectively, are capped or covered by the four corresponding caps 11. A suction pump 101 sucks the waste ink from the four recording heads 5, the waste ink then being transmitted to the waste ink tank via the pipe 12. Unless the waste ink tank is removed and replaced by a new, empty tank when it is filled to a predetermined level, continued supply of waste ink to the tank when full will result in the ink overflowing, thereby marking the recording medium and/or contaminating the electrical systems such as printed circuit boards and the like of the recording apparatus - which is likely to result in damage. For this reason, various techniques for detecting when the ink level in a waste ink tank reaches a predetermined amount have been proposed. One simple proposal has been to construct the waste ink tank from a transparent material. This allows the amount of waste ink tank collected to be visually inspected, so that overflow of ink can be prevented by replacing the full ink tank with a new, empty one at appropriate times. Although this proposal is simple in construction, it is disadvantageous because the operator must always monitor the amount of ink in the ink tank, which is inconvenient. Another proposal works by weighing the whole waste ink tank and the ink contained therein using a balance ("seesaw" type of scales) on one pan of which the waste ink tank is mounted. When the amount of ink in the tank exceeds a predetermined level, the beam on which the pan holding the ink tank is mounted pivots about its axis, thereby lowering the ink tank, which is detected electrically or physically. In the proposal described in the preceding paragraph the weighing and detection system required takes up a large amount of space, which results in the ink jet recording apparatus being inconveniently large. Further, the sensors for detecting movement of the ink tank are expensive. A third proposal uses an ink absorbing material which increases its volume by absorbing ink contained in the waste ink tank. Thus, the absorbing material expands in the tank as ink is supplied thereto. When the absorbing material reaches a predetermind size, this is detected electrically or optically. JP-A-60 189 455 describes such an arrangement, wherein expansion of an ink absorbing member causes an electrical contact mounted on the internal surface of the waste ink tank to bend and contact another electrical contact, thereby completing a circuit. This type of arrangement is disadvantageous because the ink absorbing material is relatively expensive and, because the ink absorbing material does not necessarily expand uniformly, incorrect detection of ink level can occur. According to one aspect of the invention there is provided a waste ink tank for containing waste ink in an ink jet recording apparatus, comprising: an opening provided in said waste ink tank, for introducing said waste ink into said waste ink tank; an ink absorbing member disposed in said waste ink tank for containing collected ink; and detecting means for detecting a change in accordance with an amount of ink contained in said ink tank; characterised in that the ink tank further comprises a dimensionally changeable member at a defined position on or in said ink absorbing member, said dimensionally changeable member undergoing a change in its dimensions on contact with the ink; and in that said detecting means is provided in association with said dimensionally changeable member for detecting displacement caused by a change in dimensions of said dimensionally changeable member. According to another aspect of the invention there is provided an ink jet recording apparatus capable of mounting thereon at least one recording head having a discharge opening for discharging ink, said apparatus comprising: a supply system for supplying the ink to said recording head; and a waste ink tank as described in the preceding paragraph for containing waste ink from said recording head and/or said supply system. The invention may allow the quantity of ink in the waste ink tank to be detected relatively reliably without adding unduly to the size of an ink jet recording apparatus in which it is used and also without requiring constant visual monitoring of the level of ink in the waste ink tank by the operator. For a better understanding of the invention an embodiment of it will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of an example of a conventional ink jet recording apparatus; Fig. 2 is a sectional view showing the details of Fig. 1; Fig. 3 is a schematic side sectional view of an ink jet recording apparatus according to a preferred embodiment of the present invention; Fig. 4 is a schematic perspective view showing details of a waste ink tank and a detecting mechanism for detecting an amount of ink associated with the ink tank shown in Fig. 3; Fig. 5 is a schematic perspective view showing detail of a waste ink tank shown in Fig. 3; Figs. 6A-6C are schematic conceptual views showing a photo-interrupter; Fig. 7 is a schematic perspective view of a detecting mechanism for detecting an amount of ink according to another embodiment of the present invention; Fig. 8 is a schematic exploded perspective view showing an ink tank according to another embodiment of the present invention; Figs. 9A and 9B are schematic exploded perspective view showing an ink tank according to the other embodiment of the present invention; and Figs. 10A, 10B, 10C and 10D are schematic perspective views showing the state of penetration of ink in the waste ink tank shown in Figs. 9A and 9B. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be explained in connection with the accompanying drawings. It should be noted that the present invention is not limited to embodiments described hereinbelow, but can be embodied as any forms which fall within the scope of the claims. Further, the present invention is preferably adapted to an ink tank, particularly a waste ink tank for storing waste or exhaust ink. First of all, the present invention will be explained with reference to a first embodiment thereof. Fig. 3 shows a side sectional view of an ink jet recording apparatus according to the first embodiment of the present invention. The ink jet recording apparatus shown in Fig. 3 has a similar construction to that shown in Fig. 1, and thus, the similar constructural elements will be designated by the same reference numerals, and the detailed explanation thereof is omitted. The ink jet recording apparatus shown in Fig. 3 mainly differs from that shown in Fig. 1 (conventional apparatus) in the construction of the waste ink tank 1. The waste ink tank shown in Fig. 3 (present invention) is not mounted on the carriage 3, but is positioned on the bottom of the ink jet recording apparatus so that the load on the driving means for driving the carriage 3 can be reduced. Fig. 4 shows a schematic perspective view of the details of the detecting mechanism for detecting an amount of ink associated with the waste ink tank shown in Fig. 3. In Fig. 3 or Fig. 4, a sensor attaching plate 46 (for holding a sensor) is fixed to a body of the ink jet recording apparatus and has means (not shown) for removably mounting the waste ink tank 1 thereon. The sensor attaching plate 46 includes a hole 41 communicating with an intake opening 22 of the waste ink tank 1, a shaft supporting member 42 for rotatably supporting a hinge pin 39 around which a sensor arm 31 and a photo-arm 32 are rotated, an opening 43 through which the sensor arm 31 can be rocked, and an opening 44 through which the photo-arm 32 can be rocked. Further, a photo-interrupter 33 attached to the sensor attaching plate 46 can engage with the photo-arm 32. A signal from the photo-interrupter 33 is sent to a predetermined circuit (for example, a control circuit) in the printed circuit board 6A provided on the body of the apparatus through a lead wire 21. Fig. 5 shows a schematic perspective view of the details of the waste ink tank 1 shown in Fig. 3 or Fig. 4. The waste ink tank 1 has the afore-mentioned ink intake opening 22 and a detecting window 27 formed therein, and further includes a ratch pawl 26 by which the ink tank is mounted on the sensor attaching plate 46. Further, on an inner surface of the waste ink tank 1, a pair of positioning walls 1B are provided around the detecting window 27, for regulating position and height of a volume expanding member 34 which will be explained. A flexible bag 15 positioned in the waste ink tank 1 encloses an ink absorbing member 16 and the above-mentioned volume expanding member 34 attached to a predetermined position of an upper portion of the ink absorbing member 16. Further, a hole complementary to the ink intake opening 22 is formed in the bag 15. The volume expanding member 34 may be comprised of powdered resin having high water-absorbing capacity enveloped by a semipermeable membrane such as a Japanese paper and have ability of expanding its volume by a few times to few hundred times, for example. The volume expanding member 34 is attached, by means of a duplicated adhesive tape and the like, to the upper surface of the ink absorbing member 16 in the flexible bag 15 at a position corresponding to the position of the detecting window 27. With this arrangement, when the waste ink is continued to be introduced into the waste ink tank to exceed the preferable ink-absorbing capacity of the ink absorbing member 16, the waste ink is spreaded or smudged onto the upper surface of the ink absorbing member 16 and then is absorbed to the volume expanding member 34. Consequently, the volume expanding member 34 swells or expands due to absorption of the waste ink to finally lift the sensor arm 31. Next, the ink detecting operation in the waste ink tank by using the above ink detecting mechanism will be explained with reference to Figs. 6A-6C. When the waste ink tank 1 is not mounted on the ink jet recording apparatus, as shown in Fig. 6A, the sensor arm 31 is lowered, and accordingly, the photo-arm 32 is also lowered to offset or disengage from the photo-interrupter 33. In this condition, the photo-interrupter does not generate a signal (OFF-signal). When the waste ink tank 1 is mounted on the apparatus, the sensor arm 31 is rocked upwardly to a horizontal position by abutting against the flexible bag through the detecting window 27. Consequently, as shown in Fig. 6B, the photo-arm 32 is also brought to a horizontal position to engage with the photo-interrupter 33, thus energizing the latter to produce a signal (ON-signal). Next, when the waste ink tank 1 is filled with the waste ink, as mentioned above, the volume expanding member 34 expands upwardly to further lift the sensor arm 31 through the flexible bag 15. Consequently, as shown in Fig. 6C, the photo-arm 32 is also further rotated upwardly to disengage from the photo-interrupter 33, thus disenergizing the latter. In this case, the photo-interrupter does not generate a signal (OFF-signal). Indications on the basis of such ON-signal and OFF-signal are displayed on a control panel and the like. As apparent from the above explanation, the OFF-signal from the photo-interrupter 33 indicates the fact that the waste ink tank 1 is not mounted on the ink jet recording apparatus or that the waste ink tank 1 has been filled with the waste ink. In any case, an operator must mount or dismount the waste ink tank 1 with respect to the apparatus. As an example of another detecting mechanism for detecting an amount of ink, a detecting mechanism having two microswitches in place of the photo-interrupter will be explained with reference to Fig. 7. When the waste ink tank 1 is not mounted on the ink jet recording apparatus, a microswitch 52A is in an OFF condition; whereas, a microswitch 52B is depressed by the weight of the sensor arm 31 and a rockable arm 51 to maintain an ON condition. When the waste ink tank 1 is mounted on the apparatus, the microswitch 52 will be in the ON condition due to rotation of an arm 53. When both of the microswitches 52A and 52B are in the ON condition, the waste tank permits the introduction of the waste ink therein. In this case, the ink jet recording apparatus can be used as a printer. When the volume expanding member 34 expands due to absorption of the waste ink to rotate the sensor arm 31 upwardly, the microswitch 52B is released from the rockable arm 51 (which is rotated upwardly together with the sensor arm 31) and will be in the OFF condition. The microswitches 52A and 52B are electrically connected so that, when either or both of the microswitches are in the OFF condition, the discharge restoring operation is stopped and the abnormality of the waste ink tank (missing of the tank or presence of the completely filled tank) is displayed on the control panel to indicate the fact that the operator must mount on the apparatus or replace the filled ink tank by a new empty one. Next, a waste ink tank according to a second embodiment of the present invention will now be explained with reference to Fig. 8. In this embodiment shown in Fig. 8, a fixing plate 40 forms a part of the waste ink tank 1 and is in the form of a flat plate. The fixing plate 40 has a detecting window 27 and a waste ink intake opening 22 formed therein. A bag-shaped sheet material is adhered or fixed a circumference or a portion of the fixing plate 40 to constitute a flexible bag 15. Accordingly, the waste ink tank 1 is constituted by the fixing plate 40 and the flexible bag 15 covering the detecting window 27. In the waste ink tank, an ink absorbing member 16 having a volume substantially corresponding to that of the ink tank and a volume expanding member 34 attached to an upper surface of the ink absorbing member 16 in a confronting relation to the detecting window 27 are disposed. The fixing plate 40 further includes two fixing hooks 41. A waste ink tray 45 are removably attached to the waste ink tank 1. The tray 45 has a handle portion 25 used in the mounting or dismounting operation of the ink tank with respect to the ink jet recording apparatus, and a attachment portion 44 having hook receiving holes 42. When the waste ink tank 1 is attached to the waste ink tray 45 by engaging the hooks 41 with the corresponding hook holes 42, since the attachment portion 44 of the tray are slightly inclined upwardly as shown, the fixing plate 40 attached to the attachment portion 44 of the tray urges the flexible bag 15 downwardly by a resilient force caused by the attachment portion 44, thereby determining the position and level of the volume expanding member 34 in the tank through the flexible bag 15. The waste ink tank 1 and the waste ink tray 45 are removed from the ink jet recording apparatus, and thereafter, only the ink tank may be replaced; accordingly, during the mounting or dismounting operation of the ink tank, the contamination of the elements of the apparatus due to the waste ink is prevented effectively. Of course, although not shown, a detecting mechanism for detecting an amount of ink (such as the sensor arm) is provided in the ink tank of Fig. 8. Further, in the two embodiments mentioned above, since the ink detecting mechanism also acts as means for detecting the presence of the waste ink tank in the ink jet recording apparatus, the construction of the apparatus itself can be simplified. In addition, the operator can easily check the condition of the waste ink tank by means of the detecting mechanism, which facilitates the manipulation of the apparatus. Incidentally, it should be noted that the detecting mechanism is not limited to the optical photo-interrupter, but may be constituted by the mechanical means wherein the microswitches are controlled by the movement of the sensor arm, as described above. Lastly, a waste ink tank according to a third embodiment of the present invention will be explained with reference to Figs. 9A and 9B. As shown in Fig. 9A, a waste ink tank 100 is constituted by a flexible transparent sheet 115 enclosing an ink absorbing member 116 therein. The sheet 115 has a hole forming an ink intake opening 122, and a corresponding through hole 140 is formed in the ink absorbing member 116. By providing such through hole 140, penetration of ink (described later) can be generated to effectively collect the waste ink. In this embodiment, preferably, the ink absorbing member has high ink holding capacity and does not swell or expand so much; for example, in the embodiment, a laminated sheet "HATOSHEET" (registered trademark) sold by Honshu Seishi K.K. in Japan was used as the ink absorbing member which has a width a of 60 - 100 mm, a length b of 100 - 150 mm and a thickness of 8 - 15 mm. A volume expanding member 134 is arranged between the ink absorbing member 116 and the sheet 115, opposed to the ink intake opening 122 with respect to a center X of the waste ink tank. The volume expanding member 134 has its center designated by 0'. The volume expanding member 134 is preferably made of water-absorbing polymer, and in particular, is made of material which can swell until the weight thereof (when absorbes the ink) increases up to a value more than the original weight by 8 - 600 times. In this embodiment, a material "SUMIKAGEL" (registered trademark) sold by Sumitomo Kagaku Kogyo K.K. in Japan was used as the volume expanding member. The waste ink tank is inserted into a tray 145 shown in Fig. 9B from a direction indicated by an arrow and is mounted together with the tray onto the ink jet recording apparatus as mentioned above. Figs. 10A - 10D show the state of the penetration of ink into the waste ink tank progressing or growing with time. As shown in Fig. 10A, the waste ink dropped to the bottom of the ink tank through the ink intake opening 122 spreads along the lowermost layer of the ink absorbing member 116 and also penetrates into the ink absorbing member around the intake opening 122. Thereafter, the penetration of the ink grows or progresses gradually as shown from Fig. 10B to Fig. 10D. As mentioned above, in order to use the ink absorbing member 116 effectively, it is desirable to absorb the ink by the volume expanding member 134 after the ink has been absorbed by the ink absorbing member 116 substantially up to its maximum ink-absorbing capacity. To this end, a distance between the center 0 of the intake opening 122 and the center 0' of the volume expanding member 134, i.e., a distance d (Fig. 9A) is so selected to be larger than b/2 and the centers 0, 0' are opposed to each other with respect to the center X of the waste ink tank. Further, the volume expanding member 134 is arranged so that the peripheral edge of the volume expanding member is not contacted with edges m of the sheet 115 enclosing the ink absorbing member (for example, g > 0, refer to Fig. 9A). Particularly, in this embodiment, when the elements of the ink tank are arranged according to a range e/b ≦ 1/6 and (g+f)/b ≧ 1/7 , a desirable result was obtained. In this case, the detecting mechanism is activated when the ink absorbing member absorbs the amount of ink of 50% - 90% (volume ratio) of the maximum ink absorbing capacity thereof, because, in the above range, the leakage of the ink is prevented since the ink absorbing member is effectively used to maintain the ink holding capacity thereof in that range. The above value (50% - 90%) can be selected by appropriately determining the above dimensions (a, b, c, ...). As mentioned above, the ink absorbing member has high ink-absorbing capacity, and, preferably has extremely low coefficient of volumetric expansion; whereas, the volume expanding member preferably swells by a few times to a few hundred times, as described above. In this way, a water-absorbing polymer such as urethane foam and the like can be as the above-mentioned volume expanding member. As apparent from the foregoing explanation, it is possible to detect a predetermined amount of ink in the waste ink tank by detecting the change in volume of the volume expanding member. Consequently, the embodiment described provides an ink jet recording apparatus which is relatively cheap and can absorb the ink effectively and has a detecting mechanism for properly detecting the amount of ink.

Claims: A waste ink tank for containing waste ink in an ink jet recording apparatus, comprising; an opening (22) provided in said waste ink tank (1), for introducing said waste ink into said waste ink tank; an ink absorbing member (16) disposed in said waste ink tank for containing collected ink; and detecting means (31,32,33,39,41) for detecting a change in accordance with an amount of ink contained in said ink tank; characterised in that the ink tank further comprises a dimensionally changeable member (34) at a defined position on or in said ink absorbing member (16), said dimensionally changeable member (34) undergoing a change in its dimensions on contact with the ink; and in that said detecting means is provided in association with said dimensionally changeable member for detecting displacement caused by a change in dimensions of said dimensionally changeable member. An ink jet recording apparatus capable of mounting thereon at least one recording head (5) having a discharge opening for discharging ink, said apparatus comprising: a supply system (2) for supplying the ink to said recording head; and a waste ink tank as claimed in claim 1 for containing waste ink from said recording head and/or said supply system. A tank according to claim 1 or an apparatus according to claim 2, wherein said detecting means includes a photo-sensor (33) for detecting said displacement optically. A tank according to claim 1 or an apparatus according to claim 2, wherein said detecting means includes a switch (53B) for detecting said displacement mechanically. A tank or apparatus according to any preceding claim, wherein said tank is constituted by a flexible film (15), and said dimensionally changeable member (34) is arranged between said ink absorbing member (16) and said film (15). A tank or apparatus according to any preceding claim, wherein said opening (22) and said dimensionally changeable member (34) are arranged one on each side of a cross-section of the ink absorbing member (16) passing through a centre thereof. A tank or apparatus according to any preceding claim, wherein said ink absorbing member (16) comprises a laminated sheet. A tank or apparatus according to any preceding claim, wherein said dimensionally changeable member (34) includes a material which can have a weight more than that of an original weight thereof by at least eight times due to absorption of the ink. A tank or apparatus according to any preceding claim, wherein said dimensionally changeable member (34) includes a liquid-absorbing polymer. A tank or apparatus according to any one of claims 1 to 8, wherein said dimensionally changeable member (34) comprises powdered resin having a high liquid-absorbing capacity enveloped by a semipermeable membrane. A tank or apparatus according to any preceding claim, wherein said ink absorbing member (16) has a low coefficient of volumetric expansion relative to said dimensionally changeable member (34). A tank or apparatus according to any preceding claim, wherein said dimensionally changeable member (34) comprises urethane. A tank or apparatus according to any preceding claim, wherein said opening (22) and said dimensionally changeable member (34) are both substantially symmetrically disposed on a longitudinal central axis of said ink absorbing member (16). A tank or apparatus according to any preceding claim, wherein said ink absorbing member (16) has a substantially rectangular form having a length of b , and said dimensionally changeable member (34) is arranged to meet a relation d > 1/2 . b, when a component of distance between a centre of said opening (22) and a centre of said dimensionally changeable member (34) which is parallel to said length is d . A tank or apparatus according to any preceding claim, wherein said ink absorbing member (16) is arranged away from ends of said ink tank. A tank or apparatus according to any preceding claim, wherein, when a distance between the centre of said dimensionally changeable member and the nearest end of the ink tank is y (= g+f) in a direction of the length of the ink absorbing member, said waste ink tank is constituted to meet a relation 7 y ≦ b, where b is said length. A tank or apparatus according to any preceding claim, wherein, when a distance between the centre of said opening (22) and the nearest end of the ink tank is e in a direction of the length of the ink absorbing member, said waste ink tank is constituted to meet a relation 6 e ≦ b, where b is said length. A tank or apparatus according to any preceding claim, wherein said detecting means is activated when said ink absorbing member absorbs more ink than 50%, by volume, of a maximum ink-absorbing capacity thereof. An ink jet recording apparatus according to any one of claims 2 to 18, wherein said waste ink tank can be mounted at the bottom of the ink jet recording apparatus. An ink jet recording apparatus according to any one of claims 2 to 19, wherein said waste ink is ink exhausted from a discharge restoring means (10) provided in the ink jet recording apparatus. An ink jet recording apparatus according to any one of claims 2 to 20, wherein said discharge restoring means is deactivated when a signal indicates the fact that the ink has reached predetermined amount. A tank or apparatus according to any preceding claim, wherein said dimensionally changeable member (34) increases in volume on contact with the ink. A tank or apparatus according to any preceding claim, wherein said dimensionally changeable member (34) has a coefficient of volumetric expansion higher than that of said ink absorbing member (16). A tank or apparatus according to any preceding claim, characterised in that the dimensionally changeable member (34) is arranged to change in volume to signify that the tank is close to being full. A tank or apparatus according to any preceding claim, wherein the dimensionally changeable member (34) is a volume expanding member which expands its volume by absorbing ink. Apparatus according to any one of claims 2 to 25, including the at least one recording head (5).

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