GB2238419A

GB2238419A - Display device

Info

Publication number: GB2238419A
Application number: GB9024572A
Authority: GB
Inventors: Tomoyuki Nishikawa; Masahiro Kita; Takaaki Yano; Tatsuya Yoshida; Ryoji Honda; Kiyoshi Negishi; Shoji Kamasako; Tsutomu Sato
Original assignee: Asahi Kogaku Kogyo Co Ltd
Current assignee: Pentax Corp
Priority date: 1989-11-10
Filing date: 1990-11-12
Publication date: 1991-05-29
Also published as: GB9024572D0; DE4035706A1

Abstract

A display device such as a liquid crystal display is constructed such that a display panel mounted on a base plate 70 is sandwiched between the main body and the base plate. An opening 76 is formed on the main body, the peripheral edge of the opening being formed to be a stepped portion 76a so that the display panel is fitted therein. The base plate mounting the display panel is fixedly secured to the main body with screws 71, 77. <IMAGE>

Description

1 :; 2;:: E3,, A- LE:3 DISPLAYING DEVICE Baekground of the Invention

TI-ic, present invention relates t-o a di-1;P1(1Yh19 device suell as a Uquid crystal display pallel fOr displaying tlie operational stattis or an ripparatljs ont.o the body of' the apparatus.

Fig. 7 11"lustrates a display patiel support structure heretorore in use.

A general liquid crystal. display panel. is built hy mounting two sheets or glass plates 72, 73 on a substrate 70 vla conductive rubber 71 and sandwiching a layer of 11(juld crystal 74 between the glass plates 72, 73. Moreover, the edges of the glass plates are enclosed with a frame 75, which is secured to the substrate 70. The substrate 70 is secured with screws 77, 77 onto the body via bushes 78, 78 so that the display panel can be viewed through an opening 76.

The conventional display panel support structure described above substantially needs a (1 number of parts, thus posing a problem In that the process of assemblJng the parts Lends to become complicated.

Tri view of the foregoing problems, It. is therefere an object or the present Invention to provide a display panel support structure such that the requIred number or compornent. part.s is small and hence the process or assembling the part,; Is made;impl.ific(l.

For the above object, according to tlic invention, there Is provide(] a cll.ql)liyl.ng dev.1ce comprising:

display panel; main body having an opening, the per.lpheral edge of said opening being formed to be a stepped portion so that said display panel is fitted thereto; and a supporting means for supporting said display panel, said supporting means being secured to said main 2()body with said display panel being fixedly sandwiched between said supporting means and said stepped portion.

With the aforementioned arrangement. no ad ditional means Is required for securing the display panel to the support plate as the display panel. Is fixedly held 25between the main body and a plate as a supportin means.

1 An example of the present invention will now be described with reference to the accompanying drawings, in which:- Fig. 1 is a schematic sectlonal view of a printer 5 including a displaying device embodying the present invention; Fig. 2 Is a top view of the paper conveying pol-tion, or a print,Cr or Fig. 1; Fig. 3!c; a perspective vi.ew or a scraper in a 10 1.oner box; Figs. 4 and 5 are qich, views or the waste toner sensor; 6, s-liows i dlse ror use In gencrating PI.S ptil ses; Fig. 7 illustrates cl supporting construction or a conventional Liquid crystal dIsplay panel.; Fig. 8 shows a supporting construction of a Ll-quId crystal display panel of the printer of F1g. 1; F!g. 9 is a block diagram 111iisLi-atJr)g a control 20 system in the printer of Fig.

FIgs. 1.0 and 11 are graphs Illustrating temperature control of the heat roller for the printer or Fig. 1; Fig. 12 is a graph ilAustrating power supply control of the printer of Fig. 1.

Figs. 1. through 12 show a printer having a displaying device embodying the present Invention.

A printer 100 shown In Fig. 1 Is a laser beam printer employing an clectrophotographic image., transfer system. The printer 100 comprises In sequence a trarisrer unit 10 including a photoconductive ditim 11-, a tractor unit 20 having an endless belt 21 for feeding jo recording sheet, and a fixing unit.30 hilVing cl palr (;f' rollerg 31, 32 for licating and pressing in unrixed toner linage in order to fix it on the recording sheet.

cirry!T]!' printing data from a host computer or the Ilke Is emitted from a laser scanning unit (I.SU) 13, the charged surrace or the I)Ijol.ocoii(Itict.lve drum 11 _is cxpoq(,(] to 1,11e, li.glit, and a latent Image is formed on the cIrcumferential. surface of the photoconductive drum 11. Toner is stuck to the circumferential surface of the photoconductive drum.1.1 to devel-op a toner Image by a developing unit 1.4. Then the toner image is transferred onto the recording sheet at a transfer charger IF), and the Image thus transferred Is fIxed by a fixing unit 30. The printer 100 employs the electrophotograhic Image transfer system, and so it is designed to be a page printer 1 1( 1 1 whIch starts printing after the printing data for one page is acciiinijl,. ,lted. The laser scanning unit 1.3 Is secured to.in tipper cover UC. The tipper covet, UG Is rotatably disposed on the main body of the printer 100 5 so that It can be rocked around a pivot axis P.

This printer 100 uses a continuous form recording sheet FP, which Is known as fan-fold sheet. The fanfold Is a foldable continuous sheet having feed holes at both side ends, and perforated tear Mnes along which the recording sheet. FP is cut, off casily. Projections are provided on the endless belt 21 whIch are to be fitted to the feed holes of the continuous form recording sheet. FP. The contAnuous form recording sheet FP is fed from a feed port 1 to a discharge port 2. It should be noted that the printer 100 Is designed to print pages between perforations In order to prevent printed data from parting apart when the recor(li.ng sheet FP is torn off at the perforated tear -lines. In case or a printer using a cut-sheet, the distance between transferring posItIon and fixing position is not so important because printing data for one page Is printed onto one sheet of recording paper. On the other hand, In a printer using a continuous sheet, if the whole portion of the sheet carrying unfixed toner image is caused to pass through the fixing k 6 position and fixed, paper may be wasted to the extent of the distance between transfer and fixing positions. Consequently, it is necessary to determine the portion of the sheet carrying a torier image tol)e fixed. In other words, It is necessary to determine the portion carrying an unfixed torier image to remain in the printer between the transfer an(] fixing positions.

When the printing quality Is taken Into consideratlon, the interruption and resumption of transfer and, fixing should preferably be made at tile perforations where data is riot printed. For this reason, the distance between the transfer position and fixing position Is preferably arranged equal. to the length olf one p,-,ige so thdt the perforations are located at the transfer and fixing positions when printing is stopped.

As arranged above, the portion carrying an unfixed toner Image for one page remains between the transferring and fixing positions in a standby state when the printing is terminated. When another page is printed, the unfixed toner image is fixed and the remained page is discharged. In this way, waste of paper due to the fixing of every transferred image 25 becomes avoidable.

k 7 The distance bet.ween the,ill(] Fixing positions of this printer 100 is set to 11. inclies (27.94 cm) long for the continuous recording sheet which page length is 11 inches (27.94 cm) long.

The transfer urill..10 comprises a chav-ger 12 For chargIng a I)Iiot.oreeel)l.or oil Che cit-ciinirereritial- sur-Cace or Che pholoconductive drum 11 wit,Ii (-1e(.t.rl(.1t.y, the laser scanning tinll. 1,3 For exposing liglit, to tile 1)110t,o(.011(111(.tive 11, Ule.

10(,'(,vclo,,)liig will, 14 for torier to 1.he finage f'ormed on the. photoconductive drum 11, the transfer charger 15) f'oi- cluirging the shecl FP with to cause the toner image to be transferred to 1.1w recording sheet F11, a cleartIng unit -1.6 for 15removing the resJdtiil. torier on the drum, and a (31scharging LED 17 for totally exposing the photoconductive drum 11 to 1Aght so as to remove the charge thereon.

The 1)Iiol.oc.oii(ltic.tlve drum 11 should be exclianged 20 after being u sed for printing a certain number of pagesp sInce It w111. deLerlorate In Its propertles and fail to ensure cl.ear prIntIng. For example, a IlmIt or use Is set at approxImately 20,000 pages. The number of printed pages are el.ectrIcally counted and recorded 1n 25a counter by a control system whIch Is descrIbed Jaler.

i i 8 rhis couricer Is reset. when -ill tjl)i)ei- cover uc is slitit.

after a flew druill 11 Is instal lod.

All outwardly projectIon (nol. shown) h; provIded oil a new photoconductive druirr 11. As 1. 1) c Sprojectlon presses down a reset switch, not, shown, oil the body SIde, the COTILI-01 Syst-cill call det.ect that. the flew pholoconductIve druill 11 IS 1)1,1(C(I Ill 1)0Sit.1011.

1)1-0je(.t1OTI r(,1,1-11cls whell 1-11c 01)(,1-11t ioll [.S and ar) Indication of the flew The collfrol losystei,.) resets the coulitclwhell the 111)1)CI. cover 11C Is Slilit art-ler 1.11o resel, swItch Is 011-lied oil.

The laser scanning un-II I.S. which is in tile 11P1)el- cover UC, contlfluously ON/01.1--- modulaled beanis from a lascr fitot shown) 15by means or a polygon m.frror 1-3a. The 1,1qet- bealns are converged by means of a fO leris (not, shown), reflected by a beam bender 13b so Lliat scanning lines are form(,(] on the photoconductive drum 11, then all eLc(, ti-ost.,il.l(, latent linage oil a (lot basIs Is formed as the druin 20rotates.

The developing urdt 14 comprises a toner cense 14a In which toner Is accumulated, a developIng rol.ler 141) for stlclclng the toner onto the eircutrirereritlal surface of the photoconductIve (]rum 11 provIded at the lower end of the case 14a. and a plezoelectric sensor as a 1 " 9 toner low sensor 14c for detecting the presence or absence oil' the toner in the case 1-4a.

In normal text printing, the prInting of letters are started from the left-hand side of paper so that Sfrequency of use of toner normally tends to become high In a portion correspondIng to the lert-hand side or the paper. For this reason. the toner low sensor 14c Is provided in the portlon corresponding to the lerl-hand side of the paper where the toner consumption ls large.

lleretorore, two dry development. inethods have been generally known. One or them Is a so-called monocoii,,7,)oti(,,,it development method, and the other is a two-component development method.

In the twocomponent development method, carrIer 151s mixed with toner, and stIrred at relatively high speed by a scraper or the ll.ke in order to charge the toner.

On the other hand, In the monocomponent development. method, toner Is fed to a developing roller 20or the Ilke without using carrIer for charging the toner. ThIs monocomponent development method is disclosed in the U.S.P. No.3,909,258. However, there is a problem in this monocomponent development method. That Is, the toner tends to form a block In a toner 25 box. In order to overcome the above problem. an 1 1 1 improved monocomponent development method, in which relatively little amount of carrier is mixed with the toner, is disclosed in the U.S.P. No. 4,640,880. Wi th mixture of a little amount of carrier-with the toner, lubrication between the toner grains is Improved, which prevent the toner from forming blocks. I"t should be note(] that the mixture of' the carrier does riot affect chtirge,ability of the torier. In tlils improved monocomporient development inothod, the main function of Uie scraper is to feed tlic toner to the developing roller or the like. Accordingly, the scraper rotates relatively slowly 1n the toner box. In the priner of the ernbodii,,ient, above-sald improved monocomponent development method Is employed.

A scraper 19 Is provide(] in Llie toner case 14a. Tlie scrapcr 19 slowly rotz.ites to stipply the inner toner to the develop.1jig roll-er 14b. The scraper 1.9 is, as shown In Fig. 3, composed of a rotziry sliart J-9a to be driven by a main motor, and rour pleces or blades 3.91), 19c, 1.9d, 19c fitted sucli t.liat the angle between the surfaces of' the blades 19b and 19c is (90 degrees, tfiat of the blades 19b and 19d is 180 degrees, and tlll(-, of the blades 19b an(] 19e is 270 degrees. In Ulls specification, this angle will be ca-Hed a motinting

25angle, i.e., the mounting;ingles, w1th respect to Hie i 11 blade 19b, or the blakles 19c, 19d, and 19e are S)0 degrees, 180 degi-ces, all(] 270 degrecs, The blades 19b through 19e are driven lo ill tile direction of the arrow shown in Fig. 3.

Since the rout- biades are arranged to have different, 111o1111L.111g aligles,1.1, becollies possIble that, the load applied when the Coner Is rorced out, Is as one as (.1tat. or I.ii(! convent.lotial seraper having all the blades scl to linve the same mounlingr angles.

Con t, ly, tile load applied to the 11101or deel-cases and fluctuates less with the scraper of this embodiment, llitis siipl)res.,-,irig iioi,.;(, generation.

By sequentially making the mouijtlng angles of the blades of the scraper -1,9 d.ifferent as stated above, a certain amount of toner Can be gradually moved to a portion corresponding to the r.iglit,-liaii(l stde or the paper as the scraper 1.9 slowly rotates.

When toner consumption Ill the portion correspond.ing to the right-hand side of the paper increases as it Is used for a graphic output, for instance, toner low is left undetected by the toner low sensor 14c. In such a case, as the conventional scrapers do not have a function to move the toner in the manner stated above, carrier may be transferred onto the circumferential. surface of the photoconductive A 1 12 drum 11.

With the scraper in this embodiment, the occurrence or the carrier being transferred on the photoconductive drum 1-1 Is made avoidabLe even when the toner consumption Is large on the side where the toner low sensor 14c is not provided.

The transfer charger 15 Is secured to an arm 15a. which car) be rotated by a cam mechanism around a pivot ha f t 1-, 1 Moreover, a pair of guide rollers 18a, 181) iare integrally secured to the arm 15a, the gilide rollers 18a and 18b being laterallY positioned so that the continuous form recording sheet FP is nipped therebetweeri.

When. pr i n Ii rig Is s Lar ted, j 1. 1 s needed to 1 (11 y rotate the photoconductive drum 1,1 without feeding the recording sheet until the exposed portion of the photoconductive drum 11 Is located at the traTisrer position. In this case. the arm 15a Is moved down to lower the guide rollers 18a, 1.81), and accordingly. the recording sheet FP is retracted from the circumferential surface of the photoconductive drum 11. The life of the photoreceptor material is thus prevented from being shortened because of wearing. ln addition, the paper is also prevented from being soiled by residual toner on the photoconductive drum 11.

k 13 An opening is formed in the transfer charger 15. The opening of the transfer charger 15 Is arranged so that Its rearward half in the feeding direction or the recording sheet FP is covered with a Mylar film 151), and the discharging area, which is uncovered. of the transfer charger 15 Is arrange(] at the upstream side in the rotaLlorial direction of the photoconductive drum 11. with respect to the contact portlon between the photoconductive drum 11 and the recording sheet FP.

Conventionally, the whole opening of a transfer charger has been left opened for charging. With such cl setting, however, trarisrer efficiency tends to cons.1 deral) Ly vary as amblent hurnid 1 t. y changes. By narrowing the discharge area, corona discharge errIciency can be increased to prevent toner from being reversely charged under the influence of the corona discharge. Moreover, the perlod of tIme In which the recording sheet FP contacts the photoconductive drum ll- under pressure after toner image Is transferred thereto can be set longer than that of conventional printers. As a result, transfer efficiency in the whole humidIty range can be by far Improved. Experlinerits show that the transfer efficiency Is Improved to a great extent especially when humidity is low. It is also possible to arrange k 14 the transfer charger 15 itself in upstream side In the shect feed direction in order to prolong tI)c period of' time for applying pressure after transfer.

The toner sticking to the photoconductive drum 11 is not totally removed therefrom after the termination of the transferring process. As the residual toner is unnecessary for next printing, it is removed by a cleaning unit I.G. Tlie waste toner tlius removed Is stored In a waste toner box 60 detachably fitted to the 10side of' tlie photoconductive drum 11 as shown In Fig. 2.

Wien a certain amount of waste toner is accumulated In the waste toner box 60, it overflows into the printer unless It Is discarded. The waste toner may soll the inside If printing is started 15without the waste toner box 60.

In conventional. printers, sensors have been used to respectively detect the presence or absence of such a waste toner box 60 and the full condition of the waste toner box 60. The problem is that the p1tirality 20of sensors thus required tends to render the control system complicated, .

In the printer or the present embodiment, only one sensor is used to detect both conditions.

Fig. 4 Illustrates the detecting mechanism. The waste toner box 60 is movably inserted along a guide of the body, the waste toner box 60 being verllcally movable. An actualnr 62 Is rotatably pivoted about a fulcrum 61 on the body such that a contact portion 62a 5 is located at a position where the bottom side of the waste toner box 60 Is located. A fin-sli,.riped portlon 62b is provided at the other end of the actuator 62, and a light-shading wall 62c is formed on the arcuate peripheral edge of the fari-shaped portion. The liglit,- w,,,il.l 62c Is capable of' crossing the space between a light receiving element and a light emitting clement or a r)lioto-l.ntet-rxipt.ci- 63.

If the waste toner box is not attached, the actuator 62 is caused to revolve clockwise by its own weight as 15shown by a continuous.11.ne in F1g. 4 so that. it.s contact portion 62a, ascends an(] the light-shadIng wall 69c is located under the photo- interrupter 63. In this state, the photointerrupter 63 produces a signal. indicating that no rays of light are shaded and the 20control. system decides that an error relating to the waste toner box 60 has occurred.

When the waste toner box 60 is attached, the contact portion 62a Is forced down by the weight of the box and the actuator is revolved counterclockwise up to a substantially horizontal state as shown by a broken 1 1 16 line or Fig. 4. The -1-jgtit-sli,,,iding wall 62c is set In a position where lt screens the photo-interrupter 63. 1.11 this state, the photointerrupter produces a signal indicating that the rays of light are. shaded arid the control system decides that no error relating to the waste toner box 60 has occurred.

When the waste toner box 60 Is filled with the wasl.p- toner, the contact portion of the actuator is caused to descend further due to the weight of accumulated toner as shown in Fig. 5 and the lighlshading wall 62c moves up to the left-hand -side (as shown) of the photo-interrupter 63. 1n this state, the control system decides again that an error relating lo the waste toner box 60 has occurred.

In this way, one sensor can be used to detect that the waste toner box 60 is not installed and that the waste toner box 60 is filled with the waste toner. Although this sensor is so arranged as to monitor the Presence or absence o amount of waste toner f the waster toner box and the from the balance In weight between the actuator 62 and the waste toner box 60, it is possible to employ a spring or the 131ke to hold the balance as well as the dead load of the actuator 62.

The tractor unit 20 Is arranged so that, as shown in Fig. 2, the two endless belts 21, 21 stretched between a driving shaft 23 and a driven shaft 22 are 1 17 driven by n main motor 40 via a field clutcli (not shown, hereinafter called the F clutch) and a gear train (not shown) provided in a box 41.

The gear train extending from the main motor 40 up 5to the driving shaft 23 in the tractor unit 20 is arranged so that the continuous recording sheet FP is fcd at the velocity or 50 mm/sec. if the tractor unit 20 is independent.1y feeding the r(-cordin(ii slinot F'P. Moreover, the gear train contains a unId1rectional LOclutcli which races with a predetermined resistance in compliance with a tension whon flie paper is drawn at a rate higher than 50 inm/sec,(preventing motor overdriving).

The driven sliaft 22 is connected with dise 25 vin a chain 24. The d1sc 25 is rotatable In response 15to the rotation of the driven shaft 22. As shown in Fig. 6, the disc 25 is provided w1th slits 25a whicli are apart from each other by a predetermined space. 'The disc 25 is provided between the liglit emitLing member and tlie liqlit receiving inember of Lhe plioto- interrupter 26, and a pulse corresponding to Lite moved amount of recording sheet-FP is obtainable. I'lie pliotointerrupter 26 is hereinafter called the PFS (Paper Feed Sensor) with its output as a PFS pulse.

The PFS pulse is outputted such that when the recording 25 sheet is fed by 1/2 inch (1-27 cm), one pulse is 1 k is outputted. Further, the signal corresponding to the slAt portion 25a and the Signal corresponding to the portion other than the slit 25a correspond to the perforated lines of the continuous r6cording sheet FP 5 and the non-perforated portion, respectively.

The positional relation between the disc 25 for use In generating the PFS pulse and a base piate on which the photo-Interrupter 26 Is mounted may not be the same in individual printers because of' assembly errors. If the slits 25a formed in the disk 25 are rectangular along the radius, the pulse widtli thus outputted may vary depending on where the photointerrupter 26 has detected the slits 25a in the radial direction of the disc 25, and depending on when the relative position between the disc 25 and the photointerrupter 26 radially shifts.

As this prInter is arranged so that the paper feed error is judged from the detection of the PFS pulse, the variation of the pulse width may result In 20misjudgment on the error.

For this reason, the slit 25a formed in the disc 25 is fan-shaped so that its width gradually increases toward the circumference. In other words, the slit 25a is defined by a pair of radli of the disc 25. With this fan shape, the ratio between the slit portion 25a and the portion other than the slit 25a remains constant so that the width of the pulse thus outputted . 0 19 can be unified Irrespective of the position where the photo- interrupter has detected the slIt in the radial. direction of the dIsc 25, thus preventing the misjudgment on the error. In addItiori, the assembly precision required is eased and hence assembly workability Is Improved.

Sensors for detecting paper errors w11.1 be stjt)seqtlon,l.ly CescrIbed.

In a conventional laser printer using exit sheets, two sensors are provided al.ong a sliceL feed path to detect the jamming of recordIng sheet.. Paper errors are detected when the sheet does not pass the downstream side sensor a predetermined ti-ine after it passed the up-stream side sensor. SInce there are no breaks in the contInuous recording sheet, the aforementioned method of detection cannot be utilized in a printer using a continuous recording sheet.

In this printer 100, there are provided four kinds of sensors for detecting the presence or absence of the paper along the sheet feed path. The sheet empty and paper jamming conditions are detected by detecting the changing of a sheet feed speed and the lifting up of the sheet.

The first sensor is an empty sensor 50 provIded 25 between the feed port 1 and the transfer unit 10. This 1 k pr1riter 100 does riot prJnt, on the pot-tlon adjacent to the perforated lines which are use(] as a break between 1) a g, e s. nie, perforated lines are located right under the photoconductive drum 1-1 or the transfer unit 10 and 5at the position of the fixing rol,lers 31, 32 when printing is stopped in. this printer 100. 'File sheet empty condItLon can be detected from the output of the empty sensor 50 when the last page or the recording sheet FP is located In the printer. Moreover-, It Is deteellable by counting the PFS pulse,,; that what poi-tioris of the recoi-ding sheet position(,(] cit. the transfer un! L 10, at the fixing unit 30, and further at sensor. Cori sequen tl y, the counting of the PFS pulse and the output of the empty -sensor 50 (--an be 15used to detect the recording sheet FP being torn off at a nonperforated portions.

The second sensors comprise skew sensors 51, 51 provided between the fixing unit 30 and the tractor unit 20. The skew sensors 51, 51 are used for 20dctectIng the skew and cutting-off of the continuous recording sheet FP. The sensors 51, 51 are capable of detecting the sheet when at least one side thereof lifts up.

The third one is a top sensor 52 provided in the 25central part between the skew sensors 51, 51. The top I- # 21 sensor 52 is used for detecting the leading end or the paper when the printing Is started. After the predetermined numbers of the pulses have been counted after the leading end of the recordIng sheet FP passed 5 the top sensor 52. the leadlng end thereof reaches the fixIng unit 30, whereas the followIng perforations. are positi.oned at tile transfer unit 1.0.

The 'fourth one Is a jam sensor 53 provide(] Ill the upper cover 1M substantially oppos.ite to the top sensor 52 with the sliect feed path therebetween. 'I'lle Jam (sensor 53 Is used for detectIng the sheet when the sheet is jammed in the fixing unit. 30, in(] the central. part of the recordIng sheet swells out to contact the jair, sensor 53.

is The fixing unit 30 comprises a heat roller 31 provIded in the upper portlon of Fig. 1, and a press roller 32. The continuous recording sheet FP is nipped between the rollers 31, 32, and is pressed against the heat roller 31 by the press roller 32 wIth a predetermIned pressure. In the heat roller 31, a heating halogen lamp, and a thermistor for temperature detection are provided.

The heat roller 31 is driven by the main motor 40 to rotate vIa the F clutch and the gear train and arranged so that, when tile continuous recording sheet 1 ' k 22 F.P j s he. l cl be tween th c ro M ers.31. 32. It As fed at th c speed of 75 min/sec.. As a result. the continuous recording shect F11 is - actually driven in the fIxing unit 30, whereas the tractor unit 20 rit,,,, ilrily functions 5 to prevent skewing of the continuous recording sheet FP.

If the continuous recording sheet 1711 is kept being pressed against the lient roller.31 whIle printing is in standby state, the paper may be scorched with the licat 3-Oof the heat roller 31. In ordel. to avold the Scorchl;1g or the sheet, in this printer 1.00, the 1)r,ess roller 32 facing the heat roller 3.1. Is made vertically movable so that the conti-nuous sheet roller 31 while printing is- in standby state.

In the meantime, the rockIng of the press roller 32 and that or the transfer charger 15 are implemented by the same drive means.

In Mquid crystal display unit 170 of this embodiment. there is provided a stepped portion in the 20peripheral edge of the opening 76 of the body as shown in Fig. 8. The glass plates 72, 73 between which the liquid crystal. layer 74 is inserted are directly mated with the stepped portion 76a and the combination is secured with screws 77, 77 onto the body via bushes 78, 78. With this arrangement, the frame can be omitted, Is retracted rrom the heat L 1 1 23 so that the number of parts becomes reducible.

With this arrangement, the liquid crystal display unit 170 is held beLween the substrate 70 and the body so that the display unit is fixed therebetween without 5 using a frame.

If the display panel is simply abutted against the peripheral edge of the opening, the display panel may be moved in the lateral direction. In order to prevent the display panel from laterally shaking, with the 10prescrit invcntlon, the display pariel 170 Is mated with Ihe stopped portion 76a or the body.

Fig. 9 shows -,.i control circult of the printer.

This (.11-Cult Comprise's a colltrol.Ler 81 for developl-rig the. printing data received from a host 15computer into a maj) on a dot basis and outputting the map, and a driver 82 comprLsIng two CPU's: one or which is an A-IC 8:3 for mainly controlling printing; and the other is a B-IC 84 for mainly making error detection. The. controller 81 Is provided with abuffer which is 20crapable of developing printing data corresponding to three pages of the recording sheet. New data is successively written to the buffer from time to time as the data is transferred to the drIver.

The controller 81 and the driver 82 are connected 25via a video interface (vIdeo I/F) for transferring k 24 prinLing data arid a command 1.1ne for transmitting various data.

The A-JC 83 is connected with a high voltage circult to which bizises for the charg6r 1.2 art(] the like In the transfer untt 10 are connected, and further, a drive system Including the main motor 40, the F clutch 41, the halogen Jamp In the heat rol.l.er 31 are connected to the A-IC 83 as those to be controlled.

A thermistor 85 for dotecting the temperature oP the heat roller 31, a cover sensor 86 for detect],ng the opening and closing of the tipper cover UC, and the Pl-,'S sensor (or photo- interrupter) 26 are connected to the A-IC 83 as the sensors for supplying data to the A-IC 83.

The heat roller 31. Is so controlled as to have high temperature.(; as fixing temperatures only during printing, and low temperatures as standby temperatures when the printer is in standby state to save power and to prevent the printer temperature from rising.

Power is supplied to the halogen lamp provJded In t1le heat roller 31. as a heat source from the power supply 87 for supplying 100 volts a.c.. The power supply is turned ON/OFF by a signal from the A-IC 83. The A-IC 83 receives an analog output from the thermistor provided adjacent to the heat roller 31. and 25 executes A/D conversion so as to execute temperature cl c k, k control The temperature control is effected with an allowance or approximately 5 degrees. As a restilt, the actual temperature of the hent roller 31 fluctuates 5within upper and lower limits as shown In Fig. 10. Accordingly, there occurs the difference In time required to lower the temperature to a certain value depending upon the actual temperattire, of the heat. roller 31. Jf the actual tempernt.ure or the heat 10roller 31 is at the upper 11mit, of' the NxLng temperature, the time required t.o lower tlie temperat.llre to the certain temperature Is relativeLy long, whi.le, if the actual- temperature is at the lower lirrilt or thefixing temperature, the time Is relatively short.. In 15other aspect, the temperature of the heat roller.11 after a predetermined time has past differs depending upon the temperature of the heat roller 3.1 when the temperature began to be lowered. It Is obvlous that it will be required more warm-up time to raise the 20temperature of the heat roller 3-1 to operab1c (fixing) temperature from lower temperature than higher temperature.

Fig. 11 shows the dIfference between two cases that when the temperature of the beat roller 31 is 251owered to a predetermined temperature set between the k 26 fixing and the standby temperatures. A point A shows a point where the temperature downs to.1 predetermined temperature wbich is lowered from the lower limit of the fixing temperature, and a point B'shows a point 5where the temperature downs to a predetermined temperature which Is raised to the upper limit, then Iowered from the upper- limit. In this example, there are approximately 30 seconds between two points A and B. 1 In thc printer of' this embodiment, when the teinpcratiii-c Is -lower-ed from t-he fixing temperattire to the standby temper-attire, the temperature is raised tip to the upper -limit of the flxlng temperature before being lowered. In this waY, the temperature is prevented 15from being lowered from the re.lativel.y low temperature within the fixing temperature so that the warm-up t1me required to ralse the temperature up to the fixing temperature again can be shortened.

The B-l.C 84 is connected with a semiconductor 203aser of the laser scanning unit 13 and an EEPROM 88 for storing pi- inter 11re data.

As to means for Inputting data to the B-IC 84, the empty sensor 50, the skew sensor 51, the top sensor 52 and the Jam sensor 53 care connected to the B-IC 84 25which are concerned with the paper feeding. In 27 addition, the 13-IC 84 is coiilleete(l with the w,,,1 c ste toner sensor for warning the 1)re,,;ellce Or absence of t.lie wIst(' toner box 60 and the amount of accumulate(] waste toner, and the toner low sensor 14C for warning the shortage 5of toner, which are provided in the transfer unit 10 as those concerned with toner.

As to the toner low sensor In a conventional laser printer, it As common practice to set the sensor to output low level- sIgna] when no toncy. is detected.

10With this arrangement, however, the problem Is that when the sensor Is disconnected, the low level signal indicating the toner low condition cannot be detected. _In other word, the dlsconnectlon of the sensor an(] the Loner-stiff.!(.-!,c,nt. condition cannot be distinguished in 15the conventional. printer.

In this embodiment. the toner low sensor 14c outputs a high level signal when toner low is detected, while the B-IC 84 receives the signal In a pull-up state with use of a resistance 89 for receiving the 20.sjgllaj in the pull-up state.

HIGH is thereby Inputted to the B-IC 84 when toner low is detected by the sensor 14c, when disconnection occurs In the sensor system and when the developing unit 14 Installed with the toner low sensor 14c is not 25attached to the printer 1-00. In other words, a number 28 of symptoms can simultaneously be detected with one sensor 14c.

The toner low sensor 14c comprises the piezoelectric element incorporated In. the hotLom surface of the toner case 1.4a and it outputs a LOW level signal on sensing the pressure applied by thetoner accommodated In the toner ease 14a; and a HIGH level sIgnal without such pressure.

When the toner is sufficiently stored in [lie Loner 10case 1.4a, the toner Is always placed on the piezoele(.trlc element as the toner low sensor 14c, despite the operation of the scraper 19, and the LOW level signal. is always outputted. On the otlier band, whe.i the amount of toner is low, the HIGH level si.gn,,-il.

151s outputted irrespective of the operation of the scraper 19.

If the toner case 14a is substantially half filled with toner, the toner is alternately placed on and swept out of the toner low sensor 14c as the scraper 19 rotates. thus causing alternative output of the LOW and HIGH signals. Monitoring the duty ratio of the output of the toner low sensor 1.4c, the B-IC 84 judges the amount of the toner to be low when the HIGH sIgnal- exceeds 80 percent.

As the toner is not supplied on the developing k 29 roller 1.4b by the scraper -1-9 immediately after power is supplied, the output of the toner low sensor in first three seconds for two rotations of the scraper is Ignored.. After the elapse of thre'e seconds, the 5toner low sensor 14c starts monitoring. Misjudgment on the toner low can thereby be prevented before the operat-Ion of the scraper 19 when power is supplted.

The A-fC 93 and the B-TC, 84 controls the printer -100 with exchanging data vin a p.lurallty of signal 101ines. From the 13-IC 84 to the A-1C 83, transmitted i th I are si 4-gnals,;uch -is a sigrial indicating that e BC 84 is in a standby state, a STOP signal for immediately stopping the operation of each unit of the printer 100 when an emergency error occurs even if the printing Is 15being executed, and a PAUSE signal for stopping the operation of each unit after the predetermined operations when a less urgent error occurs.

On the other hand, error signals Indicating errors in the drive system are transmitted from the A-IC 83 to 20the 13-fC, 84.

The B-IC 84 analyzes the error detected by itself and the errors transmitted from the A-IC 83 thereto, then determines their degrees of emergency In accordance wIth predetermined standards. The B-IC 84 25selects the STOP or PAUSE signal depending on the degree of emergency, and then transmits the signal to the AIC 83. The less urgent errors are the errors of a toner overflow, a toner low and a paper empty, while the other errors are. treated as emergency errors.

one Inindred volt.s a.c. is applied to the prinLer, the system beIng (lrlvcii it 5) volts d.(... the driving system such as the motor being driven at 24 volts d.c.. When a main switch 90 of the printer 100 is turned off, Lhe volLage gradually drops from 24 volts d.c. to uItJinaLeJy 0 volt as shown by a brokei) 11ne 1n F 1 g..12-.

The 5 volts (I.C. power Supply for Ule Cont.l.ol system Is so desIgned that more than 90 pereent. or the rated voltage (i.e. 4.5 volts d.c) is held at least 20 msec. for storing data after the maln power supply Is turned off. At Is because If the voltage becomes less than 90 percent of the raled voltage, the controlsystem may fail to control the driving system.

As to 24 volts d.c. power supply for the driving 20system, the voltage tends to fluctuate while It drops because of the operation of a protection circuit on the power supply side, besides, the control system does not operate, as the 5 volts d.c has been cut off at that point of time, which may cause the vibration of the 25motor and hence malfulictiolls.

1 b 31 In this printer 1.00, the Volt,'rige applIed to the driving system is instantaneously dropped from 24 volts d.c. to 0 volt on turnIng off the 100 volts a.c. main power supply 87 in order to prevent the aforementioned 5 malfunctions. A relay is provided between the power supply and the driving system as a switch for the function stated above. The relay operates to cut off 24 volts d.e. eJtlier when a power good signal (PGS) representing the ON/OFF of the mal.n power 87 supply is 10cut off or when the upper covet, Is opened.

By instantaneously droppIng the voltage from 24 volts d.c. to 0 volt as above, the driving system Is stopped while the control system functions with substantially 5 volts d.c. being applied. Moreover, the fluctuation of the voltage is prevented while it is dropping. consequently, the motor is prevented from vibrating and hence malfunctioning.

Laser printers are generally provided with a data recovery function for reprinting a blank page due to 20jamming or the like.

The printer 100 of this embodiment Is designed to determine the number of pages to be reprinted (page data) In the driver according to the respective errors: the paper jamming error, the paper empty error detected 251n a portion other than perforations or when the upper 32 cover UC is opened during printing. Based on the number of pages, the controller 81 request the host computer to transmit printing data to be reprinted.

The driver detects the page be-ingi, printed at Spresent according to the PFS pulse.

There are four kInds of page recovery daLa to be transmitted; namely, data "0" requiring no recovery. "I" requiring only one whole page which Is beIng transferred to be reprinted, "2" requirIng the 10being transferred and the page precedingly transferred to be reprInted, and "X' requIrhig tile page beIng and two to be When trouble occurs during the first page printing, the page data 11111 is transmitted and the controller 81. requests -c being Ill-inLed 1.1le host ror dal.n oil 1.11c pall and 0-1111s11111's 1,1)e dat-'n Lo Ule agaill aCIP1.

(]('VC]ol)illK It. oil 1.1le 1)tlrf(-1-.

When trouble occurs during the second page printing, the third page or thereafter, the respective data is set at 11211 2Cor "X' and (.he cotitrol ler 81 request-s the llosf. (.oltil)tjtet for data oil Lhe page to be Whel) tile operll[lg or 1.11c tillper cover UC is delect-ed during the third page printing, the page data is set at 11111 It may otherwise be arranged that the page data on 25reprintIng Is not determined by the page that has 1 M 1 -f 33 undergone trouble as stated above but by the number of pages to be traced back, depending on the place where jamming has occurred.

Although a reference has been made.to the use of continuous sheet whose page length is 11 inches (27.94 em) long in the embodiment shown, the continuous sheet whose page length is 12 inches (30.48 em) long may also be used by changing a counter for counting PFS pulse-, therefor.

If 12-inch (30.48 eTn) page length sheet is used in this printer 100, some additional arrangements may also be considered such that the last page carrying an unfixed toner image Is discharged when the prJnting Is termi.nated, that the page remalned In the prInter 100 Is fed when prIntIng is restarted, or that a perforated line is located at the fixing unit with the portion one inch from the next perforation being located at the transfer unit 14.

As set forth above, the display panel support structure embodying the present invention is SImplj ri C(1 W1 th the ef f ect of decreasing the number of parts and therefore assembling the parts is facilitated.

34

Claims

1 A displaying device comprising:

a display panel; a main body having an opening, the peripheral edge of sald opening beIng formed to be a st-.epped port.lon so that- sald display pannI is fit-tod t.lir,,r('to; arld 71 suppotling means for,;,1j(l (1j!-,,,1,ly panel, said support i.,iq means heincl to;, i( ril c,-1 -1,ill body witli said display Faiifl I)Einq fixedly 1) c twe c ri sai (1 su p p or t in g ill c cin S aTI d Sil 1 (1 S I-CP I) C (1 POrt i 0 n

2. 'I'lle (1l.ql)llylrig device according to (,'1,iim 1, wherein said supporting inearis comprises a base and conductive rubber placed between said display panel can(] sald base p- lat,e.

3. The displaying device according to claim 1 or 2, wherein said supporting means comprises buslies and screws, sald base PlaLe being secured to sald ma1n body with said screws vl.,,,i said bushes.

4. The displaying device according to any preceding claim, wherein said display panel comprises a liquid crystal display panel.

5. A displaying device substantially as herein described with reference to Figs. 1 to 6 and 8 to 12.

Published 1991 atTbe Patent Office. State House. 66/71 High Holborn. LondonWCIR47P. Further copies may be obtained from Sales Branch. Unit 6, Nine Mile Point. Cwmfelinfacb. Cross Keys. NewporL NPI 7HZ. Printed by Multiplex techniques lid. St Mary Cray. Kent.

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