DE2319235C3 - Scanning device with a rotatably mounted optical scanning element - Google Patents

Description

The present invention relates to a scanning device according to the preamble of claim 1. In particular, the invention relates to a scanning device for xerographic copiers. They are xerogranhis-he Copiers are known in which the original is scanned by means of a pivotable mirror and a strip-shaped one over the master copy moving area onto a drum rotating at a corresponding speed, which is a photoconductive electrostatically evenly charged surface 'is mapped. In DT-OS 23 02 986 Such a copier is described in which the mirror effecting the scanning has a disengageable Coupling is swiveled by a motor only as far as it is with regard to the respective Length of the master copy is required. The mirror is returned to its rest position by means of a: spring that takes effect when the clutch is disengaged

In order to ensure reproducible operation of such a scanning device, one must Provide a mechanical stop that precisely defines the rest position of the scanning mirror.

The return of the mirror to its rest position should! in practice as quickly as possible to get high To achieve copy speeds. However, if the mirror aul during the return movement by the return spring a high angular velocity is then accelerated abruptly by the mechanical stop is stopped, disturbing shocks and vibrations occur, and the adjustment of the; Mirror and dei associated parts of the scanning system will be affected does. If, on the other hand, the return flow is carried out with a viscous liquid or the like. If the shock absorber is slowed down, the return duration increases considerably, which is an undesirable reduction in de Copy speed.

The present invention is based on the task of creating a scanning device with de a short return period can be achieved, ohm that one thereby shocks or vibrations in chew must take.

This object is achieved according to the invention by a scanning device of the type mentioned with de: characterizing features of the claim

^CT e! East:

In the scanning device according to the invention, the optical scanning element rotates during the largest Part of the return period with high Winkelgeschwin speed, so that there are very short return times and it is braked in a controlled manner before reaching the stop derai, so that no disruptive impacts un

3 4

• "pn occur and also the adjustment does not run out of an opening in the

Vibrations ^ underside of the outlet 23 on the photoconductor layer 13

^be f ^'n the following, an embodiment of the drum. While the developer mix is on the

• λ "with reference to the drawing closer to the photoconductor layer flows, toner particles are from the

Invention under β __ carrier granules to the charged areas of the

explains _{χ graphic} copier, in which the photoconductor layer is drawn and stick there, so

' ^g i nrichtune according to the invention use that the latent electrostatic image in a corresponding

Scanning inside ts ^ _{visible md or pattern of} pigmented or

find Ka, _Schernatic representation of an execution-colored toner particle is converted. The development

'Form of the scanning device according to the invention, 10 winding mixture (minus the latent electrostatic _build-up

cancellation. _{External representation} of parts of the image on the photoconductor layer 13 of the drum η

Alignment according to FIG. 2 and adhering toner particles) after it runs over the

^A c 4 DUaramme to explain the operation of the photoconductor layer 13 has flowed into the sump of the

, !! ^ «device according to FIG. 2 and 3. developer container 21 back.

^de xerographi- shown schematically, ₅ comes Upon further rotation of the drum 11 as in Fig 1 nt

? Knee device 10 has several treatment station patterns of toner particles that are electronically attached to the

_sche Ko jergeraj ι rotatable drum charged areas of the latent electrostatic

The drum 11 is attached to an image on the photoconductor layer 13, to one

Attached to shaft 12 and is during the passing sheet of paper 26, which is with one of the

fieren "Sin drive motor (not shown) ₂₀ peripheral speed of the drum gtach, cn

, E S rotates. The outer surface of the drum speed is transported.ert so that essentially

f, ΐ, mk a photoconductor layer 13 of a chen no relative movement between the sheet of paper ^{LSL to} _nar t _s photoconductor material beispiels- 26 and the adjacent Umfangste.l the drum U

takes place. ..,

14 with 25 The sheet of paper 26 becomes a transmission

^ ÄÄSÄoderOntfn.1 14 with ₂₅ Äerblatt 26 becomes a transition

The page to be copied is directed downwards onto a portion of the drum 11 by a J; ansportm ~ hams of the head. c, _D ; _{Form of a porous} conveyor belt 35 transport

fooSe B M ΓΪ dl "through" einf suitable animals on which the paper sheet 26 through, the = suction

r CeHe (not shown) through the transparent plate of a vacuum source (not shown) ^fes \? ^e ^ ΐÄS with ^{the inner} t ^S JT ^F ° ^ld 7 ^band

sii

13 on ^ - ^b _n ^ _K 7 _pi ^d - _{es image of the} original. 4 on the

^ tJAiTng ^ ti dt BJdinformation ^ «f ^ fA _{untcr dcm} Hciz., rh, r

containing light beam. durd, der, Bebe ^ tungsspal 9 D _dS Pap «rWat, 26 ^^ ^,

does the photole.terschicht 13 of the Tiomme 11 run below _4? , Suction from a vacuum source

a corona discharge device where it is held in place with the interior

listed elektrosttt.sch uniform Ladungsd.chte ^ f ^^ f ^^ / ^ _{29 umschiosS} enes region in

^lad B ^e _e ⁿ in the ^ir running past under the exposure slit 19 ^ uyehL _Tonenmislel, from

the photoconductor layer 13 is corresponding to the ₅ o "^ J ^U be trag g ^^ ^ ^ ^

Brightness distribution of the to ^ P ' ⁶ ^ = ". ⁰ " ⁸ ^ ", 26 remains on the drum surface

selectively discharged, so that on at least one part of the ^ P ^e ^ ^al _To ner _t cilchen back. Around

_{Photoconductor layer 13 to} remove a latent electrostatic B. d certain _T ^ particles, the photo

arises (whereby the size of the latent Elektro Tau ^es ™ 'is subsequently under another

_S che image containing portion of the Photoleltersch h of ₅₅ leuerschic _{corotron 30 htndur} CHGC

the size of the ongma s to be copied 14 depend ^ Koronac g Pho.oleiterschicht remained,

As the drum 11 continues to rotate, the latent lunrt aie _{d ß dje runs} electrostatically,

Lctostatic image on the photoconductor sheet c 13 in Res ^ adung n ^ uImIimc. ^. ^ _{Toncrlei | ch ni}

As the drum 11 continues to rotate, the la _{d ß dje runs} electrostatically,

electrostatic image on the photoconductor layer 13 in res ^ adung n ^ uImIimc. ^. ^ _{Toncrlei | ch ni}

a developer container 21 in the lower, Je or J ⁿ ^ _h ^ _terschicht reduced or beseii.g] ^ rd

f d label holder 21 is located s.ch a 60 ^ no ilh d through

a developer container 21 _terschicht reduced or the unteJ J ^ _h ^ beseii.g] ^ w, approx.

"Sump" of the developer container 21 is s.ch a 60 ^ no toner particles are through a

KftrniL developer mixture 22 of resin-coated _ _; The ^r « ^tllc ^ _{e (> nt! Irhpn dust-tight} housing

Steel beads and electroscopic toner powder un'rergebrachie ^ reddening brush 31 mechanically from

The developer mixture is removed from a ^ erband ^un _r p ^g _holole iterschicht 13 of the drum 11 un

24 with scoops 25 running from ^ Jf _e ^ brushed toner particles are through cn

Developer container after an outlet 23an or ,. _6s ⁰ ^ S sucked off. Before leaving di

near the top of the developer container ^ ™ f _e ^ _{rd d} f _e filtered air laden ^{with g} _Toncr

^ge S ^rt Further rotation of the drum 11 flows and frees the toner particles.

After the remaining toner particles have been removed from the photoconductor layer 13 by means of the rotating brush 31 have been removed, the photoconductor layer 13 is irradiated with a light source 34 to a substantially ensure complete discharge of the photoconductor layer. Thereafter, the photoconductor layer 13 is through the Corona discharge device 20 in preparation for the next copying process again evenly charged.

As Fig. 2 shows in detail, the mirror 16, which is mounted on a rotatable shaft 36, normally held in an initial or rest position shown in solid lines. The mirror 16 is by a spring 37 which presses it against a mechanical stop 38, normally in an extended position shown starting or rest position held. A limit switch 39 is mechanical with the mirror 16 coupled, which generates a signal on a line 40 when the mirror 16 is in the rest position.

The mirror 16 can be driven by a drive motor 41 which runs at a predetermined angular speed is running in the scanning direction (arrows 43 and 44). The drive motor 41 is connected to the shaft 36 via a clutch 42 is coupled which is engaged, when the original 14 is to be scanned, and after scanning the entire length of the original 14 is disengaged. The dashed lines 45 show the position of the scanning "beam" in the rest position located mirror 16, while the dashed lines 46 the position of the scanning beam at the end of the Scan trace, d. H. in the maximum forward position of the mirror 16, indicated by the dashed line of the mirror. Since the scanning beam (the scanning beam) has a finite width n (typically on the order of an inch). the original 14 must be equal to the width by an amount of the Abiasisirahis to be scanned over so it is ensured that the photoconductor layer of the drum 11 from all parts of the to be copied Originals 14 is evenly exposed.

The angular velocity of shaft 36 must satisfy the following equation:

2R

where ω _{Λ is} the angular speed at which the shaft 36 is rotated when the original 14 is scanned with the mirror 16, t / the angular speed of the shaft 12 carrying the drum 11, R the scanning radius and / ■ the distance from the axis of rotation of the shaft 12 of the photoconductor layer 13 of the drum 11 are.

When the mirror 16 from the drive motor 41 via the Coupling 42 is rotated in the scanning direction at an angular velocity ω ,, according to equation (1) is, the linear speed with which the original 14 is scanned is equal to the linear speed, with which the photoconductor layer 13 of the drum 11 runs past the exposure pack 19, so that this is ensured is that the electrostatic image formed on the photoconductor of the drum 11 is accurate corresponds to the original 14.

After the clutch 42 has been engaged so long that the abiastcndc mirror 16 has moved from the position shown in solid lines to the position shown in dashed lines. ie when the scanning beam has the position indicated by dashed lines 46 at the end of Jes Originals 14 envk'ht. the clutch 42 is disengaged by a control signal and the mirror 16 is retracted into the rest position by a return spring 37. A feedback signal generated by limit switch 39 on line 40 prevents clutch 42 from engaging before mirror 16 has returned to the rest position, thus preventing premature start of a new duty cycle for the next copy.
Normally the return spring 37 would be the

ίο mirror 16 at such a high angular velocity accelerate that when it hits the mechanical stop 38 of the mirror 16 and the associated Components would be exposed to significant impacts and vibrations.

To cope with shock and vibration without excessive speed reduction, with Which of the mirrors 16 returns from the maximum forward position to the rest position are to be avoided Reverse motor 47 and a reverse clutch 48 are provided.

The reverse motor 47 rotates a second shaft 49 connected to the reverse clutch 48 at a constant angular velocity ω _Γ . The return clutch 48 is a one-way or one-way clutch which couples the shaft 36 carrying the mirror 16 to the shaft 49 whenever the angular velocity of the shaft 36 in the return direction (ie in the direction opposite to the arrows 43 and 44) is greater than the angular velocity of the shaft 49 rotating in a direction corresponding to the return direction. Since the shaft 49 is rotated at a constant angular speed by the return motor, the angular speed of the rotation of the shaft 36 is limited to a value corresponding to the angular speed of the rotation of the shaft 49 by the aforementioned arrangement.

The angular speed of the shaft 49 does not necessarily have to be equal to the desired maximum Angular velocity of the shaft 36 in the return direction, as by a suitable transmission mechanism between the shaft 36 and the coupling 48 or between this and the shaft 49 any desired ratio between the angular velocities of shafts 36 and 49 can be made.

Like F i g. 2 shows, the drive motor 41 also rotates the drum 11 at the same time, so that the synchronism between the rotations of shafts 36 and 12 it is maintained. This drive system is in detail

described in DT-OS 23 02 986.

Separate motors 41 and 47 do not necessarily have to be provided, but one can if desired, use only a single motor and the desired angular speeds for the shafts connected to the clutches 42 and 48 by means of a suitable transmission mechanism produce. A suitable control system for actuating the drive clutch 42 is shown in FIG the DT-OS 23 06 261 described.

(.0 In the return arrangement described above, the return spring 37 accelerates the mirror 16 and the shaft 36 until the angular velocity of the shaft 36 equals the value of the angular velocity of the shaft 49 reached, whereupon the overrunning clutch 48 engages: the

The angular velocity of shaft 3fi then becomes one of the angular velocity of shaft 49 corresponding value is held until the one-way clutch 48 disengages when the angular speed of the shaft

36 by a mechanism not shown in FIG is decreased.

The arrangement of the essential mechanical components of the scanning system is shown in detail in FIG. 3 shown:

A first sector member 50 is fastened on the shaft 36. The return spring 37 is at one end a fixed holder 51 and attached to the other end at a point of the sector member 50, which is of the Shaft 36, on which the mirror 16 is also attached, is removed.

At a distance from the shaft 36 is another one, to her arranged parallel shaft 52 on which a second sector member 53 is attached.

A flexible drawstring 54 connects a point on the periphery of the first sector link 50 to one corresponding point on the periphery of the second sector member 53 and is through at these points Screws 55 and 56 attached.

Preferably, the sector members 50 and 53 are made of a relatively rigid material such as iron, Steel or aluminum, while the drawstring 54 is a steel or beryl copper band.

The waves 36 and 52, the sector members 50 and 53. das Drawstring 54 and the return spring 37 form a modified parallelogram linkage, so that when the Shaft 42 in either the scanning direction (indicated by arrows 57) or the return direction (indicated by the arrows 58) is rotated, the shaft 36 and the mirror 16 are synchronized with the shaft 52 rotate.

Preferably, the sector members 50 and 53 have a relatively low moment of inertia with respect to of shafts 36 and 52.

A further shaft 59, on which a disk 60 is fastened, is arranged parallel to the shafts 36 and 52 is. A pivot pin 61 is attached to the disk 60 at a distance from the shaft 59. One / further trunnion 62 is attached to the second sector glicd 53 at a distance from the shaft 52. The trunnions 61 and 62 are coupled together by a link 63 which is eccentric about the center of the pivot pin is articulated on the second sector member 53 as well as on the disk 60. that the disc 60 is in the direction of the Arrow 64 rotates when the second sector glicd 53 rotates in the return direction (arrows 58).

The link 63 made of a relatively rigid material such as iron or steel is adjustable to a desired length by means of a tensioning sleeve mechanism 65.

On the second sector member 53 is one of its Surface protruding stop pin 66 fixed at a location remote from shaft 52. The second ': Sector member 53 lies in a plane offset from the plane of the disk 60, so that the stop lift 66 strikes against the circumference of the disk 60 when the shaft 52 is rotated in the return direction (arrows 58), whereby a Further rotation of the shafts 36 and 52 is prevented and the ruiieiygc of the mirror 16 is fixed.

The stop pin 66 is attached to the sector glicd 53 by means of a screw 67 which has an eccentric Bore in the stop pin 66 penetrated. As a result, the rest position of the mirror 16 can be set precisely.

The drive motor 41 rotates the shaft 68 at the constant angular speed ei, - corresponding to the desired scanning speed of the mirror 16

The return motor 47 rotates the shaft 49 with the Angular velocity ei., Which is the maximum permissible

Angular velocity of rotation of shaft 36 and mirror 16 in the return direction (arrows 58) is equivalent to.

The clutch 42 couples the shafts 52 and 68, while the one-way clutch 48 selectively couples the shafts 59 and 49 clutch. Preferably, the clutch 42 is a quick-on, magnetically-actuated disc clutch, which engages essentially slip-free. The overrunning clutch 48 is preferably with a clutch only negligible backlash, for example a Torrington needle clutch. She is with waves 59 and 49 connected so that they only engage when the angular velocity of shaft 59 is in the direction of the Arrow 64 strives to exceed the angular speed of the shaft 49. Under this condition prevents engagement of the overrunning clutch 48 that the angular velocity of the shaft 59 the angular velocity Girder shaft exceeds 49.

The scanning mechanism is shown in Figure 3 with the mirror 16 in the maximum forward or pivot position. The clutch 42 is disengaged when the maximum pivot position is reached and the return spring 37 then rotates the selector member 50, the shaft 36, the sector member 53, the shaft 52, the disc 60 (via the connecting member 63) and the shaft 59 in FIG Return direction (arrows 58 and 64). The angular speeds of the shafts 36, 52 and 59 increase under the action of the return spring 37 until the angular speed of the shaft 59 reaches a value equal to ω _Γ , the angular speed at which the shaft 49 is rotated by the return motor 47. At this moment the overrunning clutch 48 is engaged so that the angular speeds of the shafts 36, 52 and 59 are limited to a predetermined value.

When the disk 60 is rotated in the direction of the arrow 64 the pivot pin 61 and link 63 move downward, and the angular velocity the shaft 52 takes due to the eccentric action of the connecting member 63 in connection with the Washer 60. The angular velocity at which the stop pin 66 extends the circumference of the disk 60 reached is independent of the scanning angle. The dimensioning and the spacing of the shafts 52 and 59th of the Scktorgliedes 53, the disc 60 and the connecting member 63 are chosen so that the angular velocity of shaft 52 has a relatively low value (but not zero). when the stop pin 66 of the Reached the edge of the disc 60 and thereby the rest position the shaft 36 and the mirror 16 defines. The stop pin 66 attacks the edge of the disc 60, whom the lower part of the connecting member 63 reaches the position 69 shown by the dashed line, the conn Extension member 63 can then no longer move downward, so that the angular velocity de Disc 60 and the shaft 59 decreased and the overrunning clutch 48 disengaged. Both the disk 60 al The stop pin 66 also have surfaces made of hardened steel in order to keep wear to a minimum.

When the next abiast cycle rjiirrh indentation dt Drive clutch 42 is initiated, the drive motor 41 rotates the shaft 52 in the direction of the PlciU 57. so that the connecting member 63 moves oht. Home turning shafts 36, 52 and 59 three thus the disk 60 back and forth, so that the mirror 16 then runs through the desired scanning angle back to its initial rest position returns. The disk 60 rotates in the manner h

709 643/2

and so that the pivot pin 61 revolves within an angular sector A by the while 59. The size and the position of the angular sector A should preferably be dimensioned such that a straight line running between the pivot pins 61 and 62 never passes through the center point of the shaft 59. If this were to be allowed, the connecting member 63 could block and thereby the mechanism according to FIG. 3 become inoperable.

The in F i g. The diagrams shown in FIG. 4 illustrate the operation of the mechanism according to FIG. 2 and 3 and give the change in angular position and speed of shaft 36 during a single scan cycle again.

As FIG. ₄ shows, the shaft 36 and the scanning mirror 16 rotate during the scanning of the original 14 at a constant angular velocity ω 4. When the maximum pivot position is reached at time T \ , the drive coupling 42 is disengaged and the return spring 37 rotates the shaft 36 and the mirror 16 back into their starting or rest position. Like F i g. 4 (b) shows, the return spring 37 causes the angular velocity of the shaft 36 and mirror 16 in the scan or advance direction to decrease very rapidly to zero up to time 71 and then to increase very rapidly in the return direction until it reaches the value M _r reached, whereupon the overrunning clutch 48 engages and thereby limits the angular speed of the shaft 36 in the return direction to w _r. When the disk 60 is rotated in the direction of the arrow 64 (FIG. 3), the angular velocity of the shafts 36 and 52 decreases due to the eccentric action of the connecting member 63, so that it is almost zero (but not entirely zero) when the stop pin 66 hits the edge of the disk 60 reached.

By limiting the maximum angular velocity of the return of the shaft 36 in the rest position and by reducing the angular velocity of the shaft 36 when approaching the rest position, mil the mechanism according to FIG. 2 and 3 show the shock and vibra experienced by the operator of the scanning mechanism This greatly reduces the scanning accuracy and the reliability of the copier: raise. This advantageous effect is achieved with minimal loss of time per scanning cycle.

For this purpose 4 sheets of drawings

Claims (10)

Patent claims: 1. Scanning device with an optical scanning element which is rotatably supported by a shaft, which by a scanning drive from a rest position defined by a stop to one predetermined angle in the scanning direction and by an initially accelerating the shaft on return Return drive can be rotated back into the rest position, characterized in that the return drive (37, 47, 48, 50, 51 to 57, 59 to 63) a coupling arrangement (48), which the shaft (j'6) with a return with a predetermined, constant angular velocity rotating component (49) couples when the Winkelgeschwindigkeii the shaft strives to exceed a predetermined limit value, as well as a gear (53, 60, 63), that controls the angular speed of the shaft as it approaches the rest position reduces the fact that the stop (66) at a relatively low angular speed of the shaft (36) is achieved, contains. 2. Scanning device according to claim 1, characterized in that the shaft (36) has a second Coupling (42) is coupled to a scanning drive motor (41). 3. Scanning device according to claim 2, characterized in that the second coupling (42) with a locking device (39) is provided, which only allows the engagement of the second clutch, when the shaft (36) is in its rest position. 4. Scanning device according to claim 1, 2 or 3, characterized in that the shaft (36) with an arrangement that pulls them into the rest position and via an overrunning clutch (48) with a second shaft (49) is coupled, which is driven by a reverse motor (47) with a predetermined angular speed is driven and the shafts (36, 49) connects to each other only when the Angular speed of the first shaft (36) by the angular speed of the second shaft (49) strives to exceed a certain limit value. 5. Scanning device according to claim 4, characterized in that the second shaft (49) through the One-way clutch (48) is coupled to a third shaft (59) carrying a disk (60) and that the disc via an eccentrically articulated connecting member (63) with a component (53) is connected, which is coupled to the first shaft (36) and rotates with this. 6. Scanning device according to claim 5, characterized in that a on the first shaft (36) second component (50) is attached to which one to rotate the first shaft in the return direction aspiring spring (37) is attached, and that the second component via a flexible band (54) with the on a fourth shaft (52) fastened first component (53) is connected. 7. Scanning device according to claim 5 and 6, characterized in that the first and the second component (53,50) are sector-shaped. 8. Scanning device according to claim 5 or 6, characterized in that the first component (53) a projecting stop pin (66) carries, which at a certain angular position of the second Component strikes against the circumference of the disc (60) and thereby the rest position of the first shaft (36) definitely. 9 scanning device according to claim 8, characterized in that the stop pin (66) is eccentric is stored and adjustable. 10 scanning device according to one of claims 5 6 7 8 and 9, characterized in that the Reverse motor (47) via the overrunning clutch (48) with the third shaft (59) carrying the disc (60) s-k "'3pe! t and that the forward drive motor (41) is coupled via'die second coupling (42) to the fourth shaft carrying the first component (53).