EP0722127A2

EP0722127A2 - Image forming apparatus

Info

Publication number: EP0722127A2
Application number: EP95309218A
Authority: EP
Inventors: Masahiko c/o Mita Ind. Co. Ltd. Nakao; Katsuhiro c/o Mita Ind. Co. Ltd. Yoshiuchi; Keizo c/o Mita Ind. Co. Ltd. Yamamoto
Original assignee: Mita Industrial Co Ltd
Current assignee: Kyocera Mita Industrial Co Ltd
Priority date: 1995-01-10
Filing date: 1995-12-19
Publication date: 1996-07-17
Also published as: JPH08190230A; EP0722127A3

Abstract

A copying machine using a roll sheet as a transfer sheet is provided which is capable of displaying the length of a remaining portion of the roll sheet. The copying machine includes pulse outputting devices 201, 204, 205 adapted to rotate with the rotation of feed reels 51, 52, 53 around which roll sheets 4A, 4B, 4C are respectively wound. When the roll sheet 4A, 4B, 4C is paid out, the feed reel 51, 52, 53 is rotated and, thereby, pulses are output from the pulse outputting device 201, 204, 205. A CPU 210 measures a pulse cycle L₁, L₂, L₃, which is compared with a reference cycle L₀. When the comparison result indicates that the measured cycle L₁, L₂, L₃ is not greater than the reference cycle L₀, the remaining sheet display 211 displays a notice that the length of a remaining portion of the roll sheet 4A, 4B, 4C has been reduced to a predetermined level. Therefore, a user can easily know the length of the remaining portion of the roll sheet, and the replacement of the roll sheet and stock management can be facilitated.

Description

The present invention relates to an image forming apparatus capable of forming an image on a large-size transfer sheet.
Electrophotographic copying machines are widely used which are adapted to scan a document original under light irradiation, form an electrostatic latent image on a photoreceptor by light rays reflected on the document original, develop the electrostatic latent image into a toner image, and thermally fix the toner image on a transfer sheet. Some of these copying machines are capable of copying a large-size document original such as of JIS A0 size.
The copying machines for copying a large-size document original have a reading mechanism capable of reading a large-size document original and a transporting mechanism capable of transporting a transfer sheet of a large size corresponding to the size of the document original.
In most cases, a roll sheet is used as the transfer sheet, which is paid out of a roll body into which an elongated transfer sheet is rolled. This is because it is inconvenient to handle large-size cut-sheets such as of A0 size and such large-size cut-sheets require a large storage space.
A conventional image forming apparatus adapted to use a roll sheet as a transfer sheet does not have a mechanism for detecting the length of a remaining portion of the roll sheet. A roll body is replaced with a new one, based on the fact that the roll sheet has completely run out. Therefore, the conventional apparatus not having such a mechanism is inconvenient. In particular, a large-size roll sheet having a large roll body requires a large storage space, and is liable to absorb moisture. This makes it difficult to always stock many roll bodies. Therefore, if an image forming apparatus capable of detecting the length of a remaining roll sheet is provided, a new roll body can be timely and conveniently supplied for replacement.
Not only a copying machine but also the other image forming apparatuses, for example a printing apparatus for printing an image on a large-size transfer sheets and the like, have a similer problem.
In view of the foregoing, it is an object of the present invention to provide an image forming apparatus using a roll sheet as a transfer sheet which is capable of outputting the length of a remaining portion of the roll sheet.

SUMMARY OF THE INVENTION

In accordance with one feature of the present invention, there is provided an image forming apparatus which uses a transfer sheet obtained by paying out an elongated roll sheet from a roll body and cutting the paid-out sheet into a predetermined length, the image forming apparatus comprising: pulse outputting means for outputting a pulse every time the roll body rotates by a predetermined unit angle; measuring means for measuring a cycle of pulses output from the pulse outputting means; and calculation means for calculating the length of a remaining portion of the sheet rolled into the roll body.
In accordance with another feature of the present invention, the pulse outputting means of the image forming apparatus includes a rotary disk having a multiplicity of marks radially and equidistantly provided along the periphery thereof and adapted to rotate with the rotation of the roll body, and a pulse generator disposed adjacent to the rotary disk for outputting pulses as the positions of the marks are changed with the rotation of the rotary disk.
In the image forming apparatus with the aforesaid features, the length of the remaining portion of the sheet rolled into the roll body can be generally correctly output and, therefore, a user can easily know the timing of replacing the roll body.
In accordance with another feature of the present invention, the calculation means for calculating the length of a remaining portion of the sheet includes storage means storing a predetermined reference cycle, and means for comparing the measured pulse cycle with the reference cycle and, when it is determined that the measured pulse cycle agrees with the reference cycle, outputting a notice that a remaining sheet number as indicating the length of the remaining portion of the sheet in the roll body has become a predetermined number.
In the image forming apparatus with the aforesaid feature, the length of the remaining portion of the sheet in the roll body is output as expressed as the remaining sheet number. Therefore, the user can easily know the number of the remaining transfer sheets.
Thus, the image forming apparatus of the present invention which uses a transfer sheet obtained by paying out an elongated sheet from a roll body allows a user to easily know the length of a remaining portion of the sheet in the roll body. Therefore, the replacement of the roll body can be made at an appropriate time, thereby facilitating the stock management of roll bodies.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic sectional view illustrating the internal construction of a copying machine in accordance with one embodiment of the present invention;
Fig. 2 is a perspective view illustrating the exterior construction of the copying machine in accordance with one embodiment of the present invention;
Fig. 3 is a perspective view illustrating the appearance of the copying machine which is performing a copying operation in accordance with one embodiment of the present invention;
Fig. 4 is a block diagram illustrating the electrical construction of a portion particularly related to the display of a remaining transfer sheet number in the copying machine in accordance with one embodiment of the present invention; and
Fig. 5 is a flow chart for illustrating a control operation for the display of the remaining transfer sheet number which is performed by a CPU shown in Fig. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will hereinafter be described, by way of example only, with reference to the attached drawings.
Fig. 1 is a schematic sectional view illustrating the internal construction of a copying machine in accordance with one embodiment of the present invention. Fig. 2 is a perspective view illustrating the external construction of the copying machine, and Fig. 3 is a perspective view illustrating the appearance of the copying machine which is performing a copying operation. The copying machine is adapted to obtain an image of a large-size document original such as of A0 size. In the copying machine, the document original is scanned under light irradiation by a stationary optical system while being transported, and an image is formed on the basis of the optical scanning.
Referring to Fig. 1, a machine body 1 has caster wheels 2 on the under side thereof for free movement. Referring to Figs. 1 to 3, a document-original transportation section 10 for transporting a document original 9 along a document-original transportation path 41 formed on the top face of the machine body 1 is provided on the machine body 1. A discharge port 54 for discharging a sheet having a toner image transferred thereon opens in a front face la of the machine body 1. The sheet discharged from the discharge port 54 is guided by a guide member 91, dropped through a guide opening 93 with the leading edge thereof oriented downward, and accommodated in a pocket 92 defined by a front cover 5 provided along the front face la of the machine body 1, as shown in Fig. 3. On an edge portion of the top face of the machine body 1 is provided an operation section 100 having switches, keys and the like for making various settings related to a copying operation.
Referring to Fig. 1, three roll sheets 4A, 4B and 4C which are located vertically in upper, middle and lower positions and each wound into a roll shape are accommodated within a portion between the vertically middle portion and the lower portion of the machine body 1. The roll sheets 4A, 4B and 4C are rolled around feed reels 51, 52 and 53, respectively. Examples of sheets to be used as these roll sheets 4A, 4B and 4C include normal paper, film and tracing paper. In the central portion of the machine body 1 is disposed a bypass transportation path D4 for feeding a cut-sheet preliminarily cut into a predetermined length such as of A0 size to A4 size through a manual sheet feeding section 30 provided on the front face la of the machine body 1.
The roll sheet 4A in the upper position is transported along a first transportation path D1 to a photoreceptor drum 20 through the feed reel 51, sheet feeding rollers 61, a first leading-edge detection switch 71 for detecting the leading edge of the transported roll sheet 4A, transportation rollers 62, a cutter mechanism 80, transportation rollers 63, a second leading-edge detection switch 72 for detecting the leading edge of the transported sheet 4A, 4B, 4C or 4D, and transportation rollers 33 in this order.
The roll sheet 4B in the middle position is transported along a second transportation path D2 to the photoreceptor drum 20 through the feed reel 52, sheet feeding rollers 64, a third leading-edge detection switch 73 for detecting the leading edge of the transported roll sheet 4B, the transportation rollers 62, the cutter mechanism 80, the transportation rollers 63, the second leading-edge detection switch 72, and the transportation rollers 33 in this order. The path downstream of the transportation rollers 62 is common to the first transportation path D1.
The roll sheet 4C in the lower position is transported along a third transportation path D3 to the photoreceptor drum 20 through the feed reel 53, sheet feeding rollers 65, a fourth leading-edge detection switch 74 for detecting the leading edge of the transported roll sheet 4C, the transportation rollers 62, the cutter mechanism 80, the transportation rollers 63, the second leading-edge detection switch 72, and the transportation rollers 33 in this order. The path downstream of the transportation rollers 62 is common to the first transportation path D1.
The bypass transportation path D4 is a path which leads the cut-sheet 4D introduced from the manual sheet feeding section 30 to the photoreceptor drum 20 through a fifth leading-edge detection switch 75 for detecting the leading edge of the transported cut-sheet, a separation roller 32 for separating cut-sheets one from another by an abut plate (not shown) abutted against the cut-sheets, a sixth leading-edge detection switch 76 for detecting the leading edge of the transported cut-sheet, resist rollers 39, the second leading-edge detection switch 72 and the transportation rollers 33 in this order. The path downstream of the second leading-edge detection switch 72 in the bypass transportation path D4 is common to the first transportation path D1.
The cutter mechanism 80 has an elongated stationary blade 81 provided in a casing 80A and extending in a direction perpendicular to a transportation direction of the roll sheet 4A, 4B or 4C, and a rotary blade 82 cooperating with the stationary blade 81 to cut the transported roll sheet 4A, 4B or 4C therebetween. The roll sheet 4A, 4B or 4C is transported upward through the cutter mechanism 80.
The document-original transportation section 10 is adapted to switch the transportation direction to either a regular direction R1 or a reverse direction R2 for the transportation of the document original 9. The image forming operation is performed when the document original is transported in the regular direction R1. When a plurality of copies are made from one document original, the document-original transportation section 10 alternates the regular transportation direction R1 and the reverse transportation direction R2 to transport the document original. The document-original transportation path 41 is provided upstream the document-original transportation section 10 with respect to the regular direction R1 on the top face of the machine body 1 and laterally projects from the top face of the machine body 1.
The document-original transportation section 10 has a first document-original edge detection switch 11, first transportation rollers 12, a second document-original edge detection switch 16, a second transportation roller 14 and third transportation rollers 15 arranged along the regular transportation direction R1 in this order.
The first transportation rollers 12 are driven in response to the detection of the leading edge (on the downstream side in the regular transportation direction R1) of the document original 9 when the first document-original edge detection switch 11 is switched on. The second transportation roller 14 facing opposite to a transparent plate 13 for exposing the document original 9 to slit light serves to press the document original 9 against the transparent plate 13. The third transportation rollers 15 serve to discharge the document original 9 after the light exposure.
The second document-original edge detection switch 16 is switched on when the document original 9 is transported therethrough in the regular transportation direction R1, thereby detecting the leading edge (with respect to the regular direction R1) of the document original 9. In response to the switch on of the second document-original edge detection switch 16, the transportation of the roll sheet 4A, 4B or 4C (hereinafter referred to simply as "roll sheet 4" when the term is used to explain the copying operation) is started, thereby coordinating the transportation of the roll sheet 4 with that of document original 9.
The first document-original edge detection switch 11 is switched off after the document original 9 is transported therethrough in the regular transportation direction R1, thereby detecting the tail edge (with respect to the regular direction R1) of the document original 9. The cutter mechanism 80 is driven at a preset time point a predetermined time period after the detection of the tail edge of the document original 9 to cut the roll sheet 4. In this embodiment, the length of the transportation path extending from the cutter mechanism 80 to an image transfer position 20b of a corona discharger 24 for image transfer is set longer than the length of the document-original transportation path extending from the first document-original edge detection switch 11 to a document-original light-exposure position 44 by a distance between the light exposure position 20a of the photoreceptor drum 20 and the image transfer position 20b, so that the tail edge of the sheet 4 cut at the preset time point can correspond to the tail edge of the document original 9 for image formation.
The second document-original edge detection switch 16 is switched off after the document original 9 is transported therethrough in the reverse transportation direction R2, thereby detecting the tail edge of the document original 9 transported in the reverse direction R2. In response to the switch off of the second document-original edge detection switch 16, the driving of the transportation rollers 12, 14 and 15 is stopped. At this time, the leading edge of the document original 9 is held between the transportation rollers 12 for the next copying operation. A reference numeral 8 denotes a reversion member for preventing the document original 9 from dropping to the rear side of the machine body 1 by reversing the transportation direction of the document original.
A stationary light source 17 for irradiating the document surface of the document original 9 is disposed in a predetermined relation with respect to the transparent plate 13. The light from the light source 17 is emitted onto the document surface through the transparent plate 13. The light reflected on the surface of the document original 9 is led to the surface of the photoreceptor drum 20 disposed in a generally central portion of the machine body 1 by means of a selfoc lens 18. Before being exposed to the light from the selfoc lens 18, the surface of the photoreceptor drum 20 is uniformly charged by a corona discharger 21 for electrostatic charging. After the light exposure, an electrostatic latent image corresponding to a document original image is formed on the surface of the photoreceptor drum 20. The electrostatic latent image is developed into a toner image by a developing unit 22. The toner image formed on the photoreceptor drum 20 is brought into the vicinity of the corona discharger 24 for image transfer, as the photoreceptor drum 20 is rotated in a direction indicated by the arrow 23.
On the other hand, the sheet 4 led to the photoreceptor drum 20 from the transportation path D1, D2 or D3 is led into the vicinity of the corona discharger 24 for image transfer with being brought into contact with the surface of the photoreceptor drum 20. Then, the toner image formed on the surface of the photoreceptor drum 20 is transferred onto the sheet 4 by way of corona discharge by the corona discharger 24 for image transfer. The sheet 4 having the toner image transferred thereon is removed from the surface of the photoreceptor drum 20 by way of corona discharge by a corona discharger 25 for sheet removal, and then led to a fixing unit 35 through the transportation path 34. In the fixing unit 35, toner is fixed onto the surface of the sheet 4 by heat-pressing the sheet 4 between a heat roller 37 and a press roller 38. The sheet 4 on which the toner is fixed is discharged out of the machine body 1 through a discharge detection switch 55 and discharge rollers 36, guided by the guide member 91, and accommodated in the pocket 92, as described above. After the toner image is transferred, the toner remaining on the surface of the photoreceptor drum 20 is removed by a cleaning unit 26 for the next electrostatic latent image formation.
Similarly, the cut-sheet 4D led to the photoreceptor drum 20 from the bypass sheet feeding path D4 is subjected to the toner image transfer and the toner fixation, and then discharged into the pocket 92.
Above the guide member 91 is disposed an auxiliary guide plate 94. The auxiliary guide plate 94 is pivotally supported by a stay 95 attached to the front face la of the machine body 1. The auxiliary guide plate 94 assumes either an attitude (indicated by a dashed line in Fig. 1) for guiding the discharged sheet 4 hanging down forwardly of the guide member 91 into the pocket 92 cooperatively with the guide member 91 or an attitude (indicated by a solid line in Fig. 1) for sheet accommodation in which the auxiliary guide plate 94 is supported by the stay 95. The attitude of the auxiliary guide plate 94 can be shifted by the pivotal movement thereof.
Image forming means is constituted by such members as the photoreceptor drum 20, the developing unit 22 and the corona discharger 24 for image transfer. In this embodiment, the copying machine further includes a main motor MM for driving the image forming means, a sheet feeding motor DM for driving the transportation rollers for feeding the sheet 4A, 4B, 4C and 4D, a fixation motor FM for driving the heat roller 37 and press roller 38 of the fixing unit 35, and a document-original feeding motor OM for driving the document original transportation section 10.
Referring to Fig. 1, a pulse outputting device 201 is provided in a predetermined relation with respect to the feed reel 51. The pulse outputting device 201 has a pulse plate 202 having a multiplicity of slits radially and equidistantly formed along the periphery thereof which is adapted to rotate with the rotation of the feed reel 51, and a light emitting/receiving element pair 203 disposed adjacent to the pulse plate 202. As the positions of the slits are changed with the rotation of the pulse plate 202, light emitted from the light emitting element to the light receiving element is alternately passed and blocked. Thus, pulses are obtained from the light receiving element as the pulse plate 202 rotates.
The feed reel 51 is coupled to the pulse plate 202, for example, via a plurality of gears (not shown) and, hence, the pulse plate 202 is rotated by the rotation of the feed reel 51.
Similarly, pulse outputting devices 204 and 205 are provided in predetermined relations with respect to the feed reels 52 and 53, respectively. The pulse outputting device 204 also has a pulse plate 206 adapted to rotate with the rotation of the feed reel 52, and a light emitting/receiving element pair 207. The pulse outputting device 205 also has a pulse plate 208 adapted to rotate with the rotation of the feed reel 53, and a light emitting/receiving element pair 209.
The feed reel 51 may be coupled to the pulse plate 202 via a plurality of gears or the like as described above or, alternatively, directly coupled to the pulse plate 202 in the same relation as that between the feed reel 52 and pulse plate 206 such that the pulse plate 206 is rotated directly by the rotation of the feed reel 52. The feed reel 51 may be coupled to the pulse plate 202 via a belt, a pulley and belt, or the like instead of the gears.
The pulse outputting devices 201, 204 and 205 are located in any suitable positions in the machine body 1 where these devices do not interfere with the operations of the other components. The pulse outputting devices 201, 204 and 205 may be connected to the feed reels via any suitable connection mechanism.
The pulse outputting devices 201, 204 and 205 may include, instead of the pulse plates formed with the slits, rotary disks having a multiplicity of magnetic strips radially and equidistantly provided along the periphery thereof, and employ proximity sensors instead of the light emitting/receiving element pairs.
Alternatively, the pulse outputting devices 201, 204 and 205 may include rotary disks having a multiplicity of marks having different electrical resistances radially and equidistantly provided along the periphery thereof and a contact element brought into contact with the rotary disk, whereby pulses are obtained from the contact element.
Fig. 4 is a block diagram illustrating the electrical construction adapted for the detection of the length of a remaining portion of the roll sheet in accordance with this embodiment.
Referring to Fig. 4, pulses generated by each of the pulse outputting devices 201, 204 and 205 are applied to a CPU 210. The CPU 210 has a memory 212 which preliminarily stores therein a reference cycle L₀. Though the CPU 210 controls the comprehensive operation of the copying machine of this embodiment, only an operation related to the calculation of the length of a remaining portion of the roll sheet will be herein described. Instead of the CPU 210 for controlling the comprehensive operation of the copying machine, a dedicated processing circuit may be provided for the calculation of the length of the remaining portion of the roll sheet.
The CPU 210 performs an arithmetic operation to calculate the length of a remaining portion of each of the roll sheets 4A, 4B and 4C. The calculation result is applied to a remaining sheet display 211. The remaining sheet display 211 has display portion for displaying the lengths of remaining portions or the remaining sheet numbers of the roll sheets 4A, 4B and 4C. The remaining sheet display 211 may have three display portions corresponding to the respective roll sheets, or have one display portion which is switched by a switch to selectively display the length of a remaining portion or the remaining sheet number of any one of the roll sheets. Alternatively, a display for displaying other display items concerning the operation of the copying machine, e.g., the number of copies to be made and the type of transfer sheets, may be adapted to also serve as the remaining sheet display 211 to display the length of a remaining portion or the remaining sheet number of a roll sheet when required.
Fig. 5 is a flow chart for illustrating the control operation for the display of the remaining transfer sheet number which is performed by the CPU 210 shown in Fig. 4.
Mainly referring to Fig. 5, the CPU 210 measures the pulse cycle applied from each of the pulse outputting devices 201, 204 and 205 in the control operation for the display of a remaining sheet number. The measurement of the applied pulse cycle is based on a machine clock incorporated in the CPU 210, for example. The measured pulse cycle is compared with a reference cycle L₀.
More specifically, the pulse cycle L₁ obtained from the pulse outputting device 201 is compared with the reference cycle L₀ (Step S1). If it is determined that the pulse cycle L₁ is not greater than the reference cycle L₀, the remaining sheet display 211 displays a notice that the remaining sheet number of the roll sheet 4A has become N₁ (Step S2).
If the pulse cycle L₁ is greater than the reference cycle L₀, then the pulse cycle L₂ obtained from the pulse outputting device 204 is compared with the reference cycle L₀ (Step S3). If it is determined that the pulse cycle L₂ is not greater than the reference cycle L₀, the remaining sheet display 211 displays a notice that the remaining sheet number of the roll sheet 4B has become N₂ (Step S4). Further, if the pulse cycle L₂ is greater than the reference cycle L₀, then the pulse cycle L₃ obtained from the pulse outputting device 205 is compared with the reference cycle L₀ (Step S5). If it is determined that the pulse cycle L₃ is not greater than the reference cycle L₀, the remaining sheet display 211 displays a notice that the remaining sheet number of the roll sheet 4C has become N₃ (Step S6).
In Steps S2, S4 and S6, the remaining sheet numbers are N1, N2 and N3 which are not equal to each other. This is because different kinds of sheets, for example, a normal paper sheet, film sheet and tracing paper sheet are employed as the roll sheets 4A, 4B and 4C, respectively. These sheets have different thicknesses and, therefore, it is assumed that the remaining sheet numbers of the roll sheets 4A, 4B and 4C are different depending on the sheet thickness.
Though the aforesaid control operation is adapted to display the remaining sheet numbers of the roll sheets 4A, 4B and 4C in Steps S2, S4 and S6, respectively, the lengths of remaining portions of the roll sheets 4A, 4B and 4C may otherwise be displayed.
The remaining sheet number to be displayed means how many transfer sheets of a predetermined size, e.g., A0 size, can be obtained from the remaining portion of a sheet roll for copying. The remaining sheet display may, of course, display the remaining sheet number as calculated on a basis of a different transfer sheet size.
Though a copying machine is taken as an example of the image forming apparatus in the foregoing description, the present invention is applicable to any other image forming apparatuses such as printing machine, which are adapted to form an image on a particularly large-size transfer sheet.

Claims

An image forming apparatus which uses a transfer sheet obtained by paying out an elongate roll sheet from a roll body (4A, 4B, 4C) and cutting the paid-out sheet into a predetermined length, characterized by comprising:
pulse outputting means (201, 204, 205) for outputting a pulse every time the roll body (4A, 4B, 4C) rotates by a predetermined unit angle;

measuring means (210) for measuring a cycle of pulses output from the pulse outputting means (201, 204, 205); and

calculation means (210) for calculating the length of a remaining portion of the sheet rolled into the roll body (4A, 4B, 4C).
An image forming apparatus as set forth in claim 1,
wherein the pulse outputting means (201, 204, 205) includes:

a rotary disk (202, 206, 208) having a multiplicity of marks radially and equidistantly provided along the periphery thereof and adapted to rotate with the rotation of the roll body (4a, 4b, 4c); and

a pulse generator (203, 207, 209) disposed adjacent to the rotary disk for outputting pulses as the positions of the marks are changed with the rotation of the rotary disk (202, 206, 208).
An image forming apparatus as claimed in claim 1 wherein the pulse outputting means includes a plate formed with apertures or slots and adapted to rotate with the rotation of the roll body; and a pulse generator adapted to output pulses as the positions of said apertures/slots change with rotation of the rotary disk.
An image forming apparatus as set forth in claim 1, 2 or 3
wherein the calculation means (210) for calculating the length of a remaining portion of the sheet includs:

storage means (212) storing a predetermined reference cycle; and

means (211, S2, S4, S6) for comparing the measured pulse cycle with the reference cycle and, when it is determined that the measured pulse cycle agrees with the reference cycle, outputting a notice that a remaining sheet number as indicating the length of the remaining portion of the sheet in the roll body (4A, 4B, 4C) has become a predetermined number.