Replaceable ink mist filter

Abstract: A vacuum system is usable with an ink jet printer, the printer having an access door (40). The vacuum system comprises an ink reservoir (44), wherein a vacuum is supplied to the ink reservoir (44). A user replaceable mist filter (22) is situated within the access door (40) of the printer for capturing ink mist from the ink reservoir (44). The location of the mist filter (22) makes the mist filter (22) easily accessible, removable and replaceable.

Description: Technical Field The present invention relates to continuous ink jet printers and, more particularly, to an easily replaceable apparatus for the collection of ink mist generated in an ink reservoir. Background Art Ink jet printing systems are known in which a print head defines one or more rows of orifices which receive an electrically conductive recording fluid from a pressurized fluid supply manifold and eject the fluid in rows of parallel streams. Printers using such print heads accomplish graphic reproduction by selectively charging and deflecting the drops in each of the streams and depositing at least some of the drops on a print receiving medium, while others of the drops strike a drop catcher device. Printers of this type have a front door to allow the user access to certain components, such as ink bottles and the like. In an ink supply system for an ink jet printer of the type shown in U.S. Patent No. 4,399,446, clogging of the vacuum system downstream of the ink reservoir was observed during testing of the system. The clogging material appeared to be ink which entered the vacuum system, proceeded through the system to a restriction, dried in the restriction, and caused clogging. This problem was exacerbated by a high degree of ink splatter in the ink reservoir in the area of the vacuum port, which is where much of the ink entering the vacuum port was believed to originate. Several attempts were made to solve this problem. One method for solving this problem was to install a baffle to prevent splattered ink from entering the vacuum port. However, clogging of the vacuum system still occurred, in spite of the effectiveness of the baffle in splatter control. Another attempt to solve the clogging problem was to separate the suck dry vacuum and the system vacuum to isolate the two systems. Although no ink appeared to enter the system vacuum when this method was employed, clogging of the system vacuum still occurred. Upon further investigation, dried ink mist was unexpectedly discovered in a T-fitting connecting the ink reservoir to the system vacuum, and in a check valve in the system vacuum. The pattern of the build up in the check valve indicated that the clogging was caused by a gradual accumulation of ink mist which was dried by the continual flow of air through the system. An object of the invention is to provide an ink jet printer comprising a customer replaceable ink mist filter, which allows the customer operator to remove and replace the ink mist filter at the required intervals. According to the present invention, there is provided an ink jet printer including a vacuum system, the printer comprising: an ink reservoir; a means for supplying vacuum to the ink reservoir; and a user removable and replaceable ink mist filter for collecting ink mist generated in the ink reservoir under vacuum, the user removable and replaceable ink mist filter being located inside an access door of the printer. The location of the mist filter makes the mist filter easily accessible, removable and replaceable. An embodiment of the invention will now be described with reference to the accompanying drawings. Brief Description of the Drawings Fig. 1 is a block diagram of a prior art vacuum system; Fig. 2 is an exploded view of a mist filter housing of Fig. 1, incorporating the user replaceable feature of the present invention; Fig. 3A is a block diagram illustrating the initially considered location of the mist filter; and Fig. 3B is a block diagram illustrating the location of the mist filter in this embodiment of the present invention. Detailed Description of the Preferred Embodiment The present invention protects vacuum system components from ink mist generated in the air from an ink reservoir, by employing a user replaceable mist filter. Referring to the drawings, in Fig. 1 a prior art vacuum system 10 is illustrated. The vacuum system 10 includes an ink reservoir 12 which stores ink for recirculation in an ink supply system for a typical ink jet printer of the type shown in commonly assigned U.S. Patent No. 4,399,446, issued August 16, 1983, to McCann et al. The ink reservoir 12 is under vacuum to provide a means for returning ink from the ink supply system to the ink reservoir 12. In the top of the ink reservoir 12 is a port 14 to which a vacuum source, such as vacuum pump 16, is attached. The vacuum in the ink reservoir 12 is provided by vacuum pump 16, which may be any commercially available vacuum pump such as a WISA model no. 113.079.100.0. The port 14 is situated well above the surface of the ink stored in the ink reservoir 12. A float switch 18 controls the fluid level in the ink reservoir 12. Referring now to Fig. 2 and continuing with Fig. 1, a mist filter housing 20 containing the user replaceable mist filter 22 shown in Fig. 2, is connected between the vacuum pump 16 and the ink reservoir 12 to protect the vacuum pump 16 from ink mist and moisture. The mist filter 22 eliminates clogging of the vacuum system downstream of the ink reservoir caused by dried ink mist in the system 10. An exploded view of the housing 20 is shown in Fig. 2 to illustrate the user replaceable mist filter 22. A first inlet port 24 of the housing 20 connects directly to the top of the ink reservoir 12 of Fig. 2, by any suitable means, such as a tube. A second inlet port 26 of the housing 20 is connected to a servo controlled vacuum bleed 28, shown in Fig. 1, which regulates the vacuum in the ink reservoir 12. Under certain environmental conditions, condensation of water vapour in the air from the reservoir 12 can occur on interior side and bottom walls of the filter housing 20. This moisture can possibly collect to the point that it is passed on to the vacuum pump 16 through the mist filter 22. To eliminate this potential problem, the vacuum bleed 28 of fresh air is included in the system 10 to reduce the humidity in the filter housing 20. Inclusion of the vacuum bleed 28 in the system 10 also provides the advantage of allowing greater latitude in the onset of condensation. The housing 20 of Fig. 2 is comprised of a body 30 which is mounted inside the system. A mist filter receptor means within the machine securably and slidably receives the user replaceable mist filter 22. A release means, such as button 32, is mounted at the front of the ink jet printing system for release of the filter 22. The mist filter 22 is inserted into a filter fitting or elbow 34, which is easily accessible inside an access door of the ink jet printer, making the filter 22 easily replaceable by the user. When it is desired to remove and/or replace the filter 22, the operator simply opens the access door of the printer, engages the release button 32 to release the filter 22 from the elbow 34, and slides the filter out. A tube 36 interconnects the mist filter with the fluid system of the ink jet printer. The mist filter 22 is preferably a non-hollow, cylindrically shaped filter. The mist filter 22 material is preferably a melamine foam, or equivalent material, having minuscule lattice work openings on the order of 140 microns each. As the air-mist mixture from the reservoir 12 flows through the filter 22, the resulting ink mist collects on the lattice work openings of the filter 22. Eventually, of course, the mist filter becomes restricted by the collection of ink mist, and requires replacement. In accordance with the present invention, replacement of the mist filter 22 can now be accomplished by the user, merely requiring opening of the access door of the printer to access the filter 22, and sliding the filter out of the elbow fitting. Referring now to Fig. 3A, there is shown a block diagram illustrating an initially considered location of the mist filter 22. Fig. 3B is a block diagram illustrating the location of the mist filter in this embodiment of the present invention. The location of the ink mist filter 22 initially proposed requires removal of a cover 38 to access, and thus to replace, the ink mist filter. However, UL reliability requirements prevent the customer operator of the system from opening the cover, thereby preventing access to the ink mist filter except by service personnel. In this embodiment, the ink mist location of the ink mist filter is such that the filter is user replaceable. The mist filter 22, as shown in Fig. 3B, is situated within access door 40 of printer 42 for capturing ink mist from ink reservoir 44. This location of the mist filter 22 makes the mist filter easily accessible, removable and replaceable. Locating the filter 22 inside the door 40 of the ink jet printing system allows the user access to the filter. Industrial Applicability and Advantages The present invention is useful in the field of ink jet printing, and has the advantage of providing a user replaceable system for protecting components from ink mist generation from an ink reservoir. The present invention provides the further advantage of allowing more reliable operation of the ink supply system for an ink jet printer. Finally, the present invention provides the advantage of allowing the user easy access to the mist filter, for removal and replacement of the filter.

Claims: An ink jet printer including a vacuum system, the printer comprising: an ink reservoir (12); a means (16) for supplying vacuum to the ink reservoir (12); and a user removable and replaceable ink mist filter (22) for collecting ink mist generated in the ink reservoir (12) under vaccum, the user removable and replaceable ink mist filter (22) being located inside an access door (40) of the printer. A vacuum system as claimed in claim 1 characterised by a mist filter receptor means (30) for securably receiving the user removable and replaceable mist filter (22). A vacuum system as claimed in claim 2 characterised in that the mist filter receptor means (30) slidably receives the user removable and replaceable mist filter (22). A vacuum system as claimed in claim 3 characterised by a release mechanism (32) for releasing the user removable and replaceable mist filter (22) from the mist filter receptor means (30).

Inventors: BARTLEY RUSELL L, BARTLEY, RUSELL L.
Applicants: SCITEX DIGITAL PRINTING INC, SCITEX DIGITAL PRINTING, INC.
Application year: 1996
Main classification: B41J2
IPC codes: B41J2