Automatic document conveying device

Abstract: The present invention relates to an automatic document conveying device suitable for use in an image forming apparatus. The conveying device comprises a main portion (14) mounted for movement between a closed position to cover a transparent plate (8) and an open position which exposes the transparent plate (8). A conveyor belt mechanism comprises a driven roller (76) and a follower roller (78) as well as a plurality of pressing rollers (80, 82, 84, 86) disposed therebetween. The pressing rollers are adapted for vertical movement and are downwardly urged to press the lower portion of an endless belt (88) onto the transparent plate (8). At least one (84, 86) of the pressing rollers has a diameter greater than the diameter of the driven roller (76) and the follower roller (78) in order to prevent the upper portion of the endless belt (88) from slackening in the downward direction.

Description: The present invention relates to an automatic document conveying device adapted to an image processor such as an electrostatic copying machine or an image reader. It is widely accepted practice to provide image processing machines such as electrostatic copying machines and image readers with an automatic document conveying device in order to automatically handle the documents in the image copying operation or in the image reading operation. Prior literature disclosing automatic document conveying devices can be represented by Japanese Patent Laid-Open Publication Nos. 91747/1978 and 118551/1985, and Japanese Utility Model Laid-Open Publication No. 49348/1986. The image processing machine such as the electrostatic copying machine or the image reader has a housing, and on the upper surface of the housing is disposed a transparent plate on which will be placed a document that is to be processed. The automatic document conveying device is usually equipped with a document introduction portion, a main portion and a document delivery portion. The document introduction portion includes an introduction portion frame member disposed on the upstream side of the transparent plate and a document table that extends toward the upstream side from the introduction portion frame member. In the introduction portion frame member is formed a document introduction passage that extends from the document table toward the transparent plate. A plurality of pieces of documents placed on the document table are sent onto the document introduction passage piece by piece by the operation of document sending means, and are carried onto the transparent plate through the document introduction passage by the operation of document introduction means. The main portion of the automatic document conveying device includes a movable main portion frame member that is mounted to pivot between a closed position to cover the transparent plate and an open position to bring the transparent plate exposed to view, and document conveying means which conveys the document along the transparent plate when the movable main portion frame member is at the closed position. The document conveying means is usually constituted by a conveyer belt mechanism mounted on the movable main portion frame member. The document delivery portion includes a delivery portion frame member disposed on the downstream side of the transparent plate. In the delivery portion frame member is formed a document delivery passage. Further, a document re-introduction passage is often formed therein branched from the document delivery passage and extending toward the downstream end of the transparent plate. The document on the transparent plate is sent onto the document delivery passage, delivered through the document delivery passage by the operation of the document delivery means, and is discharged onto a document receiving tray, or is introduced into the document re-introduction passage from the document delivery passage and is re-introduced onto the transparent plate. The document receiving tray is disposed on the main portion or on the delivery portion. The conventional automatic document conveying devices have the following problems. The movable main portion frame member in the main portion of the automatic document conveying device is constituted by a support base member and a cover member, and the document conveying means is constituted by the conveyer belt mechanism mounted on the support base member. The conveyer belt mechanism is constituted by a driven roller and a follower roller disposed in a document delivery direction maintaining a distance, an endless belt wound around the driven roller and the follower roller, and a plurality of pressing rollers that are disposed between the driven roller and the follower roller and that press the lower running portion of the endless belt onto the transparent plate. The support base member of the movable main portion frame member extends between the lower running portion and the upper running portion of the endless belt. In such a conventional automatic document conveying device, there arises no problem when the endless conveyer belt mechanism is driven in a predetermined direction, i.e. in a direction in which the upper running portion of the endless belt is stretched. When the conveyer belt mechanism is driven in the reverse direction, i.e. in a direction in which the upper running portion of the endless belt is slackened, the upper running portion of the endless belt that is slackened comes in contact with the support base member that is extending under the endless belt and produces large noise and is further damaged within short period of time due to the friction. The object of the present invention is to provide an improved automatic document conveying device in which the upper running portion of an endless belt is sufficiently reliably prevented from coming into contact with a stationary member such as the support base member that extends under the endless belt even when the conveyer belt mechanism is rotatably driven in a direction in which the upper running portion of the endless belt is slackened in the conveyer belt mechanism that constitutes the document conveying means in the main portion of the automatic document conveying device. According to the present invention, an automatic conveying device is provided as defined in claim 1. At least one pressing roller among a plurality of pressing rollers disposed between the driven roller and the follower roller in the conveyer belt mechanism, has a diameter which is greater than the diameters of the driven roller and the follower roller by more than a predetermined amount. Fig. 1 is a perspective view which illustrates an automatic document conveying device constituted according to the present invention and mounted on an electrostatic copying machine under the condition where a central main portion thereof is at the closed position; Fig. 2 is a perspective view which illustrates the automatic document conveying device of Fig. 1 under the condition where the central main portion thereof is at the open position; Fig. 3 is a section view illustrating the automatic document conveying device of Fig. 1 under the condition where the central main portion thereof is at the closed position; Fig. 4 is a perspective view illustrating the support base member of central main portion in the automatic document conveying device of Fig. 1 and document conveying means (conveyer belt mechanism) mounted thereon; Fig. 5 is a perspective view illustrating, in a disassembled manner, the support base member of the central main portion in the automatic document conveying device of Fig. 1 and document conveying means (conveyer belt mechanism) mounted thereon; Fig. 6 is a plan view illustrating the support base member of the central main portion in the automatic document conveying device of Fig. 1 and document conveying means (conveyer belt mechanism) mounted thereon. The automatic document conveying device constituted according to embodiments of the present invention and mounted on an electrostatic copying machine will now be described in detail with reference to the accompanying drawings. Overall Constitution Figs. 1, 2 and 3 illustrate an electrostatic copying machine 2 and an automatic document conveying device generally designated at 4 that is mounted on the electrostatic copying machine 2. The electrostatic copying machine 2 which per se may be of a known form is equipped with a nearly parallelopiped housing 6. A transparent plate (Figs. 2 and 3) made of a glass which may be of a rectangular shape is disposed at a central portion on the upper surface of the housing 6. A document placing-position restricting member 10 is disposed at one end edge of the transparent plate 8 (left end edge in Fig. 3). The document placing-position restricting member 10 extends in a direction perpendicular to the surface of the paper in Fig. 3 along one end edge of the transparent plate 8. Though not diagramed, in the housing 6 of the electrostatic copying machine 2 are disposed various constitutional elements including a rotary drum that has an electrostatic photosensitive member on the surface thereof. As is well known, the document to be copied is placed on the transparent plate 8 with its surface to be copied being faced downwards and its one end edge being contacted to an inside edge of the document placing-pos-ition restricting member 10 (left end edge in Fig. 3). A latent electrostatic image is formed on the rotary drum by the step of forming latent electrostatic image in which the lower surface of the document placed on the transparent plate 8 is optically scanned and is projected onto the rotary drum, and the latent electrostatic image is developed to a toner image which is then transferred onto a copying sheet which may be a common paper. The thus transferred toner image is fixed onto the copying sheet. Thus, an image-copied sheet is obtained. The diagramed automatic document conveying device 4 constituted according to the present invention is made up of a document introduction portion 12, a central main portion 14, and a document delivery and reintroduction portion 16. The elements of the document sending means 42 (document sending roller 46 and document separation roller pair 48), document introduction means 44 (upper roller 60 and lower roller 62) and placed document detector 66 do not constitute any novel features of the present invention and may be those of the forms known by people having ordinary skill, e.g. may be those of the forms disposed in the specification and drawings of Japanese Laid-Open Patent Publication No. 100939/1990 filed by the present applicant entitled "Automatic Document Conveying Device and Image Processing Machine Equipped Therewith)". Therefore, the specification of this application does not describe their constitutions in detail. The central main portion 14 in the automatic document conveying device 4 is equipped with a movable main portion frame member 70. The main portion frame member 70 is mounted on the upper surface of the housing 6 of the electrostatic copying machine 2 via a pair of hinge mechanisms 72 (Fig. 2) disposed at the rear side of the transparent plate 8, and can be manually opened or closed between a closed position shown in Figs. 1 and 3 and an open position shown in Fig. 2. When the main portion frame member 70 is brought to the closed position, the transparent plate 8 is covered with the main portion frame member 70. On the other hand, when the main portion frame member 70 is brought to the open position, the transparent plate 8 is exposed to the view. A portion of the main portion frame member 70 that covers the transparent plate 8 at the closed position assumes the box-like shape with its lower surface open. As clearly shown in Fig. 3, document conveying means 74 that conveys the document onto the transparent plate 8 is disposed in the box-like portion of the main portion frame member 70. The document conveying means 74 is constituted by a conveyer belt mechanism that includes a driven roller 76, a follower roller 78, pushing rollers 80, 82, 84 and 86 disposed maintaining a distance in a direction in which the document is conveyed (right-and-left direction in Fig. 3), and an endless belt 88 wound around these rollers. The frame member 70 is equipped with a main portion drive source 89 (Fig. 3) which may be a reversible electric motor. The main portion drive source 89 selectively drives the document conveying means 74 either in the normally conveying direction indicated by arrow 90 or in the reversely conveying direction indicated by arrow 92. The upper surface of the box-like portion of the main portion frame member 70 constitutes a first document receiving tray 94 that receives the document discharged through the document delivery and re-introduction portion 16. The document delivery and re-introduction portion 16 does not specifically constitute the present invention and may be those of the forms disclosed in detail in the specification and drawings of U.S. Patent Application Serial No. 07/550853 filed on July 10, 1990 (US-A-5 064 188) or European Patent Application No. 90113174.8 filed on July 10, 1990 (EP-A-0 407 984) corresponding to Japanese Patent Application No. 175523/1989 (filed July 10, 1989 entitled "Automatic Document Conveying Device") filed by the present applicant. Therefore, they are not described in detail in the specification of the present application. The automatic document conveying device 4 conveys the document in any one of a simple mode, a reversing mode or a double reversing mode. Details of the document conveying system in the simple mode, reversing mode and double reversing mode have been described in the specification and drawings of U.S. Patent Application Serial No. 07/557703 filed on July 25, 1990 (US-A-5 027 162) or European Patent Application No. 90114376.8 filed on July 26, 1990 (EP-A-0 410 454) corresponding to Japanese Patent Application No. 192544/1989 (filed July 27, 1989, entitled "Automatic Document Conveying Device") filed by the present applicant. Therefore, its detailed description is not repeated in this specification. In the diagramed automatic document conveying device 4, the central main portion 14 that includes the movable main portion frame member 70 and the document conveying means (conveyer belt mechanism) 74 mounted thereon, is constituted quite separately from the document introduction portion 12 and the document delivery and re-introduction portion 16. No mutual action of driving force or no mutual action of pressing force exists between the main portion 14 and the document introduction portion 12 or between the main portion 14 and the document delivery and re-introduction portion 16. The introduction portion drive source 69, main portion drive source 89 and delivery portion drive source 165 are arranged in the document introduction portion 12, main portion 14 and document delivery portion 16, respectively, and there does not quite exist any drive coupling relationship between the main portion 14 and the document introduction portion 12 or between the main portion 14 and the document delivery portion 16. Furthermore, the pair of rollers that press each other and that work in cooperation together are not so disposed that one of them exists on the main portion 14 and the other one exists on the document introduction portion 12 or the document delivery and re-introduction portion 16. Therefore, no mutually pressing relationship exists at all between the main portion 14 and the document introduction portion 12 or between the main portion 14 and the document delivery and re-introduction portion 16. Thus, even when open and close operation of the movable main portion frame member 70 is carried out repetitively, the movable main portion frame member 70 of the main portion 14 and the document conveying means (conveyer belt mechanism) 74 are not adversely affected by the driving force or the pressing force and are stably placed at the required position with respect to the transparent plate 8 maintaining sufficiently high precision. Central Main Portion Next, detailed description will be given in respect to the central main portion 14. As described already with reference to Figs. 1 to 3, the central main portion 14 includes the movable main portion frame member 70 and the document conveyer means (conveyer belt mechanism) 74 mounted on the main portion frame member 70. The main portion frame member 70 is mounted on the upper surface of the housing 6 of the electrostatic copying machine 2 by a pair of hinge mechanisms 72 disposed maintaining a distance in the conveying direction so as to pivot between the closed position shown in Figs. 1 and 3 and the open position shown in Fig. 2. As described with reference to Figs. 4 and 5, the movable main portion frame member 70 mounted on the upper surface of the housing 6 via the pair of hinge mechanisms 72 includes a support base member 216 and a cover member 218 (Figs. 1 to 3) mounted on the support base member 216. The support base member 216 has a pair of coupling members 220 and a pair of support plates 222 secured to the coupling members 220, respectively. If described with reference to Figs. 4 to 6, a shaft member 348 is rotatably fitted via bearing sleeves 344 and 346 between one end (upper end portion of Fig. 6) of the driven-side support member 296 of the front-side support means 292 and one end (upper end portion in Fig. 6) of the driven-side support member 300 of the rear-side support means 294, and a driven roller 76 that continuously extends in the direction of width (right-and-left direction in Fig. 6) is secured to the shaft member 348. Furthermore, a shaft member 354 is rotatably fitted via bearing sleeves 350 and 352 between one end (lower end portion in Fig. 6) of the follower-side support member 298 of the front-side support member 292 and one end (lower end portion in Fig. 6) of the follower-side support member 302 of the rear-side support means 294, and a plurality of follower rollers 78 are fastened to the shaft member 354 maintaining a suitable distance in the axial direction thereof. As clearly shown in Fig. 3, an endless belt 88 is wound round the driven roller 76 and the follower roller 78. In the diagramed embodiment constituted according to the present invention, the driven-side support member 296 and the follower-side support member 298 constituting the front-side support means 292 have a size in the up-and-down direction which is smaller than the diameters of the driven roller 76 and of the follower roller 78, and the upper running portion and the lower running portion of the endless belt 88 wound round the driven roller 76 and the follower roller 78 are positioned over and under the driven-side support member 296 and the follower-side support member 298, respectively. In view of the above fact, a belt locking member 355 (Figs. 5 and 6) is mounted on one end (upper end portion in Fig. 6) of the driven-side support member 296 of the front-side support means 292. The belt locking member 355 that may be made of a suitable synthetic resin has an inside shape that corresponds to the outer at one end of the driven-side support member 296, and is detachably and resiliently engaged with one end of the driven-side support member 296. On the inside of the belt locking member 355 is formed a locking flange 357 that is positioned opposed to one side edge of the endless belt 88 and that prevents the endless belt 88 from moving forward. Further, on the outside of the belt locking member 355 is formed a grip piece 359 that can be gripped by hand at the time when the belt locking member 355 is to be mounted on, or removed from, the driven-side support member 296. If further described with reference the Figs. 3 to 6, the aforementioned pressing rollers 80, 82, 84 and 86 are mounted between the front-side support means 292 and the rear-side support means 294. As shown in Fig. 5, shaft mounting members 356 are secured by set-screws 358 to the upper surface at the front end and rear end of the pair of support members 222 in the support base member 216. The shaft mounting members 356 have a box-like portion with its inside in the direction of width being open. A shaft member 360 having pressing rollers 80 fastened thereto maintaining a distance in the axial direction and a shaft member 362 having pressing rollers 82 fastened thereto maintaining a distance in the axial direction, are rotatably inserted at their both ends in the bearing members 364 which are accommodated in the box-like portions of the shaft mounting members 356 and can move up and down. The bearing member 364 has an engaging protrusion 366 that protrudes upwardly, and a compression spring 368 that constitutes resiliently urging means is fitted to the engaging protrusion. The compression spring 368 is interposed between the bearing member 364 and the upper wall of the box-like portion of the shaft mounting member 356, and resiliently urges the shaft members 360 and 362 downwardly, i.e. urges the pressing rollers 80 and 82 downwardly. Openings 370 and 372 are formed in the band plate portion 238 of the pair of support plates 222 to correspond to the pressing rollers 80 and 82 which are, therefore, allowed to downwardly protrude through these openings 370 and 372. As clearly shown in Fig. 3, the pressing rollers 80 and 82 act on the lower running portion of the endless belt 88 to press it onto the transparent plate 8 of the electrostatic copying machine 2. Between the pair of support plates 222, a rearwardly protruded support piece 374 is formed on the driven-side support member 296 of the front-side support means 292, and a forwardly protruded support piece 376 is formed on the driven-side support member 302 of the rear-side support means 294 to correspond thereto. A pair of shaft mounting members 378 are secured by set-screws 379 to each of these support 374 and 376 maintaining a distance in the conveying direction. The shaft mounting members 378 may be constructed in the same manner as the aforementioned shaft mounting members 356, and have a box-like portion with its inside in the direction of width (right-and-left direction in Fig. 6) being open. The shaft member 380 having pressing rollers 84 fixed thereto maintaining a distance in the axial direction and the shaft member 382 having pressing rollers 86 fixed thereto maintaining a distance in the axial direction, are rotatably inserted at their both ends in the bearing members 384 which are accommodated in the box-like portions of the shaft mounting members 378 and can move up and down. The shaft member 380 and pressing rollers 84 fixed thereto as well as the shaft member 382 and pressing rollers 86 fixed thereto, are downwardly urged by their own weight and act on the lower running portion of the endless belt 88 to press it onto the transparent plate 8 of the electrostatic copying machine 2. As will be clearly understood with reference to Fig. 3, the pressing rollers 84 and 86 positioned at the central portion of the conveyer belt mechanism in the conveying direction have a diameter larger by more than a predetermined amount than the diameter of the driven roller 76 and the follower roller 78, and are sufficiently greater than the size in the up-and-down direction of the support plates 222 disposed on both sides of the pressing rollers 84 and 86. In the diagramed embodiment, the uppermost portions of the pressing rollers 84 and 86 pressed onto the transparent plate 8 via the endless belt 88 are substantially equal to, or are slightly higher than, the uppermost portions of the driven roller 76 and the follower roller 78. When the endless belt 88 is driven in a direction indicated by arrow 90 in Fig. 3, the driven roller 76 is rotated in a direction to take up the upper running portion of the endless belt 88. Therefore, the upper running portion of the endless belt 88 is maintained under the stretched condition. When the endless belt 88 is driven in a direction indicated by arrow 92 in Fig. 3, however, the driven roller 76 is rotated in a direction to forward the endless belt 88. Therefore, the upper running portion of the endless belt 88 is slackened and its central portion deflects downwardly to some extent. In the diagramed embodiment, however, the pressing rollers 84 and 86 positioned at the central portion in the conveying direction have a diameter larger by more than a predetermined amount than the diameter of the driven roller 76 and the follower roller 78, and are sufficiently larger than the size in the up-and-down direction of the support plates 222 that are arranged on both sides of the pressing rollers 84 and 86, as mentioned above. Even when the central portion of the upper running portion of the endless belt 88 is downwardly slackened to a considerable degree in the conveying direction, the endless belt 88 is reliably prevented from coming in contact with the stationary support plates 222 and so is effectively prevented from wearing. If described with reference to Fig. 6, a support bracket 386 is secured to the rear surface of the driven-side support member 300 of the rear-side support means 294. The main portion drive source 89 which may be a reversible electric motor is mounted on the support bracket 386. A toothed pulley 388 is fastened to the output shaft of the main portion drive source 89. A shaft member 390 is rotatably fitted between the driven-side support member 300 and the support bracket 386, and toothed pulleys 392 and 394 are fixed to the shaft member 390. The rear end portion of the shaft member 348 to which the driven roller 76 is fastened protrudes rearwardly penetrating through the driven-side support member 300, and has a toothed pulley 396 fixed thereto. A toothed endless belt 398 is wound round the toothed pulley 388 and the toothed pulley 392, and a toothed endless belt 400 is wound round the toothed pulley 394 and the toothed pulley 396. Thus, the driven roller 76 of the conveyer belt mechanism is coupled to the main portion drive source 89, and the conveyer belt mechanism is driven by the main portion drive means 89.

Claims: An automatic document conveying device to be applied to an image processor that has a transparent plate (8) disposed on the upper surface of a housing (6) so that a document to be processed is placed thereon, comprising: a main portion (14) including a movable main portion frame member (70) that is mounted to move between a closed position to cover said transparent plate (8) and an open position to expose said transparent plate (8) into view, and a document conveying means (74) mounted on said main portion frame member (70) to convey the document along said transparent plate (8) when said main portion frame member (70) is located at said closed position; wherein said main portion frame member (70) is constituted by a support base member (216) and a cover member (218), said document conveying means (74) is constituted by a conveyer belt mechanism mounted on said support base member (216), and said cover member (218) covers said conveyer belt mechanism; wherein said conveyer belt mechanism includes a driven roller (76) and a follower roller (78) disposed maintaining a distance in the document conveying direction, a plurality of pressing rollers (80, 82, 84, 86) disposed between said driven roller (76) and said follower roller (78) maintaining a distance in the document conveying direction, and an endless belt (88) wound round said driven roller (76), said follower roller (78) and said plurality of pressing rollers (80, 82, 84, 86), wherein said plurality of pressing rollers are so mounted as to move over a predetermined range in the up-and-down direction and are downwardly urged in order to press the lower running portion of said endless belt (88) onto said transparent plate (8) when said main portion frame member (70) is located at said closed position; and said support base member (216) of said main portion frame member (70) extends between the upper running portion and the lower running portion of said endless belt (88), and at least one (84, 86) of said plurality of pressing rollers (80, 82, 84, 86) has a diameter greater by more than a predetermined amount than the diameter of said driven roller (76) and said follower roller (78), in order to prevent the upper running portion of said endless belt (88) from downwardly slackening to come in contact with said support base member (216). The automatic document conveying device according to claim 1, wherein a pressing roller (84, 86) disposed in a central region between said driven roller (76) and said follower roller (78) has a diameter greater by more than a predetermined amount than the diameter of said driven roller (76) and said follower roller (78). The automatic document conveying device according to claim 1 or 2, wherein said conveyer belt mechanism includes a front-side support means (292) and a rear-side support means (294) which are mounted on said support base member (216) of said main portion frame member (70) maintaining a distance in the direction of width, and said driven roller, said follower roller and said pressing rollers (80, 82, 84, 86) are mounted between said front-side support means (292) and said rear-side support means (294).

Inventors: IRIE YOICHIRO, KIDA YASUHIKO, NAGAO TSUYOSHI, TAKEDA YOSHIYUKI, IRIE, YOICHIRO, KIDA, YASUHIKO, NAGAO, TSUYOSHI, TAKEDA, YOSHIYUKI, NAGAO, TSUYOSHI, TAIHOMIDORIBASHI CT
Applicants: MITA INDUSTRIAL CO LTD, MITA INDUSTRIAL CO., LTD.
Application year: 1990
Main classification: G03G15
IPC codes: G03G15