United States Patent (19) 11) Patent Number: 4,661,822 Hirota et al. 45 Date of Patent: Apr. 28, 1987 54 INKJET PRINTER 56) References Cited U.S. PATENT DOCUMENTS 75) Inventors: Tetsuro Hirota, Zama; Shigeyuki 4,535,339 8/1985 Horine et al. ......................... 346/75 Araki, Komae; Shizuo Yokoyama, 4,555,711 11/1985 Sato ....................................... 346/75 Atsugi: Haruyoshi Masui, Yokohama; Toshitaka Hirata, Primary Examiner-E. A. Goldberg Tokyo, all of Japan Assistant Examiner-Gerald E. Preston Attorney, Agent, or Firm-Mason, Fenwick & Lawrence 73) Assignee: Ricoh Company, Ltd., Tokyo, Japan 57 ABSTRACT An inkjet printer includes a pump which pressurizes an ink to be supplied to a nozzle, which projects an inkjet. 21 Appl. No.: 838,337 When the ink pressure which is supplied to the nozzle exceeds a given value or when the deflection of the ink 22 Filed: Mar. 10, 1986 jet is improper, pressure oscillations are applied to the nozzle by alternately and repeatedly driving and ceas ing to drive the pump in order to remove a plugging of 30 Foreign Application Priority Data the nozzle. If the repeated operation does not result in a Mar. 11, 1985 JP Japan .................................. 60-47808 reduced ink pressure, the nozzle is connected to a low pressure ink vessel, causing the pressure prevailing 51) Int. Cl. ............................................. G01D 15/18 within the nozzle to be reduced. 52 U.S. C. .................................. 346/75; 346/140 R 58) Field of Search .............................. 346/75, 140 R 9 Claims, 18 Drawing Figures U.S. Patent Apr. 28, 1987 Sheet 1 of 16 4,661,822 Fig.1a --- tneras al---108 --" 23 T-103 : CPU (ELFMD E 8O8 5A 3155/O CES9 104 U.S. Patent Apr. 28, 1987 Sheet 2 of 16 4,661,822 90 data 91 --ester opesating data transfer controller 92 <> /F RES : 95 T< a. | 2. -- -- - 94, CP CC /o st 8255 l/F host unit initi- : alize g - 96 CP- ROM 98 HTC 101 109. Eas- C Vo RAM 99 109. 8741 sync U.S. Patent Apr. 28, 1987 Sheet 3 of 16 4,661,822 T?EogTBWTBITËdTSWTldTVNAV } U.S. Patent Apr. 28, 1987 Sheet 4 of 16 4,661,822 U.S. Patent Apr. 28, 1987 Sheet 5 of 16 4,661,822 U.S. Patent Apr. 28, 1987 Sheet 6 of 16 4,661,822 U.S. Patent Apr. 28, 1987 Sheet 7 of 16 4,661,822 Fig.8a. (power on initialization busy output to host Cate at Cre position yo 5 ink pressure high 6 pump 71,74. On wo error M energize valve 76 YS li yaS 6 <sper)-lebail open ? 2 15 (A) deflection 13 establishment e 60 sec, passed ? y2S phase retrieval 14 (D) U.S. Patent Apr. 28, 1987 Sheet 8 of 16 4,661,822 Fig.8b 7 intermittently energize buzzer three times and clear busy Output 8 load T-80sec. in timer O8. WAL Off 3 print camand 2)/2 print 25 line feed IF Y2 e-out FF YAO ut ink exhausted ? yeS cover Or paper bail open P KT-80 sec. passed ?) YES 3 3 load T-80sec, in timer O8 GD) 34 35 GB) YSS A?o discard projection U.S. Patent Apr. 28, 1987 Sheet 9 of 16 4,661,822 FiC81g.öC 36 busy output to host 37 clear timer 108 38 39 deenergize valve 76 40 pumps 74,71 off vibrator 80 off energize buzzer once 41 wAL flashing 42 43 Jé(RES on 2) V 44 initializingE. Y(fo command ? Ya 45 pumps 74,71 on 46 energize valve 76 47 vibrator 80 on 43 of 49 30sec. passed ? y U.S. Patent Apr. 28, 1987 Sheet 10 of 16 4,661,822 Fi C. 9 3. print O 50 signal from GF) host present ? Yas 5. 52 signal-comand ? yas 53 55 2S Store data in buffer line feed LF 2 memory 60 54 bufferpointer-lstaff if 56 buffer pointer-l. page-out FF ? 2 set up LF amount return 5 7 y2S/ buffer pointer operating command P - GE) U.S. Patent Apr. 28, 1987 Sheet 11 of 16 4,661,822 reset buffer pointer, start carriage, print, increment pointer, carriage return and reset pointer 67 increment no paper counter as paper feed occurs 74 busy output to host U.S. Patent Apr. 28, 1987 Sheet 12 of 16 4,661,822 Fig.9c print flag set 2 print flag set 2 Set up IF amount busy Output to host to load paper clear busy output U.S. Patent Apr. 28, 1987 Sheet 13 of 16 4,661,822 Fig 10a high pressure Oo busy signal Output to host O 102 103 104 yes 31 <gles O data recall eS 132 pumps 74,71 off NYSAS data recall 128 GE) all timers and 29 Counter S2's U.S. Patent Apr. 28, 1987 Sheet 14 of 16 4,661,822 100ms, intervald Over ? eS 22 4Sec. interva Over ? eS U.S. Patent Apr. 28, 1987 Sheet 15 of 16 4,661,822 Fig.11 phase retrieval - Onecontro cycle retrieval| etrieval. OK? yes O 45 48 O valve 76 deenergized vibrator 80 off yes U.S. Patent Apr. 28, 1987 Sheet 16 of 16 4,661,822 Fig.12 15 deflection establishment * C 49 controln cycle deflection s 15O eflection OK yes O 151 return yes 153 Start 5min, tinner 154 pumps 74,71 off Start 4Sec, timer 4.sec. interva. e Qver? yes 156 pumps 74,71 on Start Sectiner lSec. interval Over ? 159 IS yes 62 min, interva. OVer ? 164 ..0 - M yes valve ?e deemergized vibrator 8O off error 4,661,822 1. 2 From the foregoing, it will be seen that there has been INKJET PRINTER a relatively frequent occurrence in the prior art practice that a standby mode in which the projection of an ink FIELD OF THE INVENTION stream is interrupted is established due to the plugging The invention relates to an inkjet printer in which ink 5 or the possibility of plugging of the ink projecting head, under pressure is projected from a nozzle, and more in particular, when the printer is used infrequently or particularly, while not limited thereto, to the control of the printer is left out of use over an increased length of the supply of ink under pressure to a nozzle by means of time. Accordingly, there arises a problem that a print a pressure pump in an inkjet printer as disclosed in out at a desired time is disabled or a problem that the pending U.S. patent application Ser. No. 755,174 filed 10 maintenance required an increased amount of labor or July 15, 1985 in the name of Tetsuro Hirota and as manual intervention in checking or cleaning the head. signed to the assignee of the present application. SUMMARY OF THE INVENTION BACKGROUND OF THE INVENTION It is an object of the invention to increase the reliabil 15 ity of a printer by reducing the chance of a disabled In an inkjet printer, of charge controlled type, for print-out due to the imperfect projection of an ink example, in which ink under pressure is projected from stream from the nozzle of an ink projecting head or by a nozzle, ink is pumped by a pump from an ink vessel to reducing the frequency of checking or cleaning the be supplied to an ink projecting head. The ink project head. ing head is provided with a vibrator, which vibrates at 20 The degree to which the nozzle of an ink projecting a given frequency to impart pressure oscillations of a head becomes plugged depends on the environment in given period to the ink received within the head. The which the printer is placed or the length of time during ink is normally projected from the nozzle under a given which the printer has been left out of use. The imperfect pressure and with a given pressure oscillation, whereby projection of an ink stream may be caused by various the ink stream is separated into ink particles at a given 25 factors and occur in different manners. In one instance, distance from the nozzle. A charging electrode is dis the ink located within the nozzle may be completely posed forwardly of the nozzle, and when a charging solidified to cause a perfect plugging. Alternatively, voltage is applied between the charging electrode and dust such as powder of paper may be precipitated into a the ink contained within the head in synchronism with high viscosity ink located within the nozzle or a solidi the separation of the stream of an inkjet into ink parti 30 fied component of the ink may adhere to a portion of cles, the resulting ink particles will bear an electric the nozzle, thus causing the ink stream to be projected charge which depends on the magnitude of the charg in an improper direction or at an undesirable speed even ing voltage. The charged ink particles are deflected by though the ink stream itself can be projected. It is found an electric field established across a pair of deflection that in most cases, if an ink stream is maintained though electrodes for impingement upon a record paper. An 35 the flow rate may be reduced, such ink stream is effec inkjet printer of the type described is well known, and tive to flush away or urge dust or solidified ink compo is disclosed, for example, in U.S. Pat. No. 3,596,275 nent out of the intended path, re-establishing a proper issued to Richard G.