GB2144296A

GB2144296A - Image forming apparatus

Info

Publication number: GB2144296A
Application number: GB08415947A
Authority: GB
Inventors: Toshio Yoshimoto; Hisaji Masaki
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1983-06-22
Filing date: 1984-06-22
Publication date: 1985-02-27
Also published as: GB8415947D0; DE3422942A1; GB2144296B

Abstract

An image forming apparatus comprises first (22) and second (25) image forming units for forming images or a record medium (P1 or P2), and control means for controlling the first or second image forming unit in accordance with a selected record mode; (M1 - both sides of P1 medium, first side in 22, second side in 25; M2 - first side only of P1 in 22; M3 - first side only of P2 in 25). When the second (25) or first (22) image forming unit is in a predetermined state (e.g. non-operative), the control means inhibits the image forming operation in a first record mode (M1) and permits the image forming operation in second record modes (M2 or M3 respectively). <IMAGE>

Description

SPECIFICATION Image Forming Apparatus Background of the Invention Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a laser beam printer or a facsimile, and more particuiarly to an image forming apparatus having a plurality of image forming units.

Description of the Prior Art In the past, a double-side copying machine shown in Fig. 1 which can record images on both sides of a record sheet has been known. In such a machine, the images are recorded on the front and back sides of the record sheet P by a single image forming unit 3 including a semiconductor laser 1 and a photoconductive drum 2. More specifically, the image is recorded by the image forming unit 3 on the front side of the record sheet P fed to the image forming unit 3 from a sheet feed unit (sheet feed cassette) 4 through a feed path 5, and the record sheet P is then reversed through feed paths 7 and 8 of a record sheet reversing unit 6.Then, the record sheet P is again fed to the image forming unit 3 through the feed path 5 so that the image is recorded on the back side by the image forming unit 3, and the record sheet P is ejected to a sheet stacker (ejection tray) 10 through a feed path 9.

Such a prior art machine is usually constructed to operate in a single-side copy mode by the selection by feed path switching means. However, if any fault occurs in the image forming unit, not only the double-side recording but also the singleside recording are disabled. As a result, the copying function is totally lost. Thus, a utilization efficiency and a run rate of the machine are lowered.

An image forming apparatus having a plurality of image forming units has been proposed.

However, in such an image forming apparatus, it is not possible to control the apparatus as simply as to control image forming apparatus having one image control unit, and hence the construction of the apparatus is very complex.

Summary of the Invention The present invention aims generally to provide an improved image forming apparatus.

In one aspect the present invention aims to provide an image forming apparatus having a high utilization efficiency and a high run rate.

In another aspect the present invention aims to provide an image forming apparatus with simplified control of the feeding of a record sheet.

In a further aspect the present invention aims to provide an image forming apparatus having a plurality of image forming units and having a high practicability.

In yet another aspect the present invention aims to provide an image forming apparatus which can select feed paths of record sheets.

The other objects of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings.

Brief Description of the Drawings Fig. 1 shows an internal structure of one example of a prior art apparatus, Fig. 2 shows an internal structure of one embodiment of an image forming apparatus of the present invention, Fig. 3 is a block diagram of an electric circuit of the image forming apparatus of the present invention, Fig. 4-lisa flow chart for a control operation when a failure occurred in the image forming apparatus of Fig. 2 and Fig. 3, Fig. 4-2 shows another control flow chart, Fig. 5 shows a second embodiment of the present invention, Fig. 6 shows a control circuit of the image forming apparatus of Fig. 5, Fig. 7 is a control flow chart for the image forming apparatus of Fig. 5 and Fig. 6, and Fig. 8 shows a third embodiment.

Detailed Description of the Preferred Embodiments Fig. 2 shows an embodiment of the image forming apparatus of the present invention.

Numeral 21 denotes an outer case which accommodates elements to be described later, numeral 22 denotes a first image forming unit for forming an image on a front side of a record medium such as a record sheet P1 fed from a first sheet feed unit 23, numeral 24 denotes a sheet arranging unit which selectively reverses the record sheet P 1 fed from the first image forming unit 22 or ejects the record sheet P 1 depending on a record mode to be described later, numeral 25 denotes a second image forming unit for selectively forming on a front side of a record medium such as a record sheet P2 fed from a second sheet feed unit 26 or on a back side of the record sheet P 1 fed from the first image forming unit 22 through the sheet arranging unit 24 depending on the record mode, and numeral 27 denotes a sheet stacker for stacking the record sheet P 1 or P2 on which the images have been formed.

The first image forming unit 22 is a conventional electro-photographic printer which includes an image forming device 223 including a scanner 220 having a semiconductor laser and a rotating polygon mirror, a mirror 221 and a photoconductive drum 222; feed paths 224 and 226 along which the record sheet P 1 is fed and an ejection roller 225 for ejecting the record sheet P 1. Numeral 230 denotes a sheet feed roller of the first sheet feed unit 23.

The sheet arranging unit 24 includes a feed-in path 240 coupled to the feed path 226 of the first image forming unit 22, a first ejection path 241 for ejecting the record sheet P 1 to the second image forming unit 25, a second ejection path 242 coupled to the feed-in path 240 for ejecting the record sheet P1 to the first ejection path 241 or the sheet stacker 27, and a sheet selector (not shown) located at 243. The sheet selector has a ratchet and is located at the junction 243 of the feed-in path 240, the first ejection path 241 and the second ejection path 242. It switches the feed path in synchronism with the feed direction X or Y of the second ejection path 242 to feed the record sheet P 1 fed through the feed-in path 240 to the second ejection path 242 or feed the record sheet P 1 from the second ejection path 242 to the first ejection path 241.The second ejection path 242 feeds the record sheet P 1 in the X and Y directions, or only in the X direction, depending on the record mode by reversible drive means (not shown).

The second image forming unit 25 is essentially identical in construction to the first image forming unit 22 and it includes an image forming device 253 including a scanner 250 having a semiconductor laser and a rotating polygon mirror, a mirror 251 and a photoconductive drum 252; feed paths 254, 256 and 257 and an ejection roller 255. The feed path 257 is connected to the ejection port of the first ejection path 241 of the sheet arranging unit 24 and feeds the record sheet P 1 fed from the first ejection path 241 to the image forming device 253. The feed path 256 is connected to the sheet stacker 27 and ejects the recorded record sheet P 1 or P2 to the sheet stacker 27. Numeral 260 denotes a sheet feed roller of the second sheet feed unit 26.It is driven only in the single-side record mode to feed the record sheet P2 in the second sheet feed unit 26 into the image forming device 253 through the feed path 254.

Fig. 3 shows a configuration of an electrical circuit of the image forming apparatus of Fig. 2.

CPU denotes a microprocessor which functions as a central processing unit. It has a ROM which contains processing sequences of the image forming apparatus, carried out arithmetic and logical operations necessary for the image forming process, and controls the units 22-26 and 300-302 such as the image forming units connected to a bus BUS through a system bus.

Numeral 300 denotes an operation unit (a console panel) having various control buttons such as a copy button and a mode selection button (not shown) for selecting a first or second single-side record mode or a double-side record mode. The record mode information specified by keying the mode selection button is supplied to the microprocessor CPU through the bus BUS.

Numeral 301 denotes a detector for detecting an error in the apparatus. The error signal produced by the detector 301 is compared with the record mode selection information supplied from the operation unit 300 by the microprocessor CPU which controls the units 22-26 and 302 in accordance with the compare result. Numeral 302 denotes a warning unit which issues a warning to an operator by lighting a lamp when the double-side recording is inhibited, and also indicates an effective record mode.

Operations of the image forming apparatus of Figs. and 3 in the respective record modes are now explained. The record mode can be selected by keying the mode selection button on the console panel 300. The record modes include double-side record mode M1.0 first single-side record mode M2, and (ss) second single-side record mode M3. The record operations in those record modes are explained below. The control of the record operations in those record modes is attained by the microprocessor CPU.

(!)Double-sided record mode M1 In this record mode, the first and second image forming units 22 and 25 are used and the images are recorded on the front and back sides of the record sheet P 1. If the double-side record mode is selected by the mode selection button when the double-selection record mode M1 is permitted and the copy button is depressed, the sheet feed roller 230 is driven to feed the record sheet P1 from the first sheet feed unit 23 to the first image forming unit 22 through the feed-path 224, and the image is recorded on the front (first) side of the record sheet P 1. The image is recorded by a conventional electrophotographic process.A latent image is formed on the photoconductive drum 222 in accordance with a laser beam from the semiconductor laser 220, the latent image is developed, transferred to the record sheet P 1 and fixed.

The record sheet P1 having the image recorded on the front side is fed by the rotating ejection roller 225 to the feed-in path 240 of the sheet arranging unit 24 through the feed path 226, passes through the sheet switching unit and fed to a predetermined position in the X direction by the second ejection path 242 which moves in the X direction. When detection means (e.g. a microswitch), not shown, detects that a trailing edge of the record sheet P 1 has passed the predetermined position, the sheet switching unit is switched to the first ejection path 241 and the second ejection path 242 is reversed to the Y direction. As a result, the record sheet P 1 is fed in the Y direction on the second ejection path 242 and fed to the image forming device 253 of the second image forming unit 25 through the first ejection path 241 and the feed path 257.

In this manner, the record sheet P1 reversed by the sheet arranging unit 24 is fed to the image forming device 253 which records the image on the back side (second side) of the record sheet P 1 in the same manner as the first image recording on the front side. The record sheet P 1 having the images recorded on the both sides is ejected to the sheet stacker 27 by the rotating ejection roller 255 and stacked therein.

Q2 First single-side record mode M2 In this record mode M2, the first image forming unit 22 is used and the image is recorded only on the front side of the record sheet P 1. When the record mode M2 is permitted and designated and the copy button is depressed, the sheet feed roller 230 is rotated so that the record sheet P1 in the first sheet feed unit 23 is fed to the image forming device 223 of the first image forming unit 22 and the single-side image recording is effected. The record sheet P 1 having the image recorded on one side is fed into the sheet arranging unit 24. In this record mode M2, the sheet switch unit is always switched to the second ejection path 242 and the second ejection path 242 is always driven only in the X direction.As a result, the record sheet P1 having the image recorded on one side and fed into the sheet arranging unit 24 is fed along the second ejection path 242 in the X direction and ejected to the sheet stacker 27 and stacked therein.

(X) Second single-side record mode M3 In this record mode M3, the second image forming unit 25 is used and the image is recorded only on the front surface of the record sheet P2.

The sheet arranging unit 24 is not used but in a rest state. When the record mode M3 is permitted and designated and the copy button is depressed, the sheet feed roller 260 is rotated so that the record sheet P2 in the second sheet feed unit 26 is fed into the image forming unit 253 of the second image forming unit 25 and the image is recorded only on one side of the record sheet P2.

The recorded sheet P2 is ejected to the sheet stacker 27 by the ejection roller 255 and stacked therein.

A control operation when a failure occurred in the image forming apparatus of Figs. 2 and 3 is now explained with reference to a flow chart of Fig. 4-1.

When the record mode is designated by the operation unit 300 after the power-on, the occurrence of the failure in the first image forming unit 22 is checked by a signal from the detector 301 in a step S1, and if the decision is NO, the program proceeds to a step S2 where the occurrence of the failure in the second image forming unit 25 is checked by the signal from the detector 301. If the decision is NO, the image forming units 22 and 25 are normal and the program proceeds to a step S3 where the apparatus is set to the ready state and the normal image processing in the record mode M1, M2 or M3 designated by the operation unit 300 is permitted.

On the other hand, if the failure occurred in the first image forming unit 22 or the second image forming unit 25, the decision in the step S1 or the step S2 is YES indicating the occurrence of the failure. Thus, the program proceeds to a step S4 where a warning for inhibiting the double-side record mode M1 is generated by the warning unit 302. Then, the program proceeds to a step S5 where the record mode designated by the operation unit 300 is checked to determine whether it is the double-side mode M1 or not, and if the decision is YES, the program proceeds to a step S6 where the apparatus is set to a non-ready state.

If the record mode designated by the operation unit 300 is the first single-side record mode M2 or the second single-side record mode M3, the decision in the step S5 is NO and the program proceeds to the step S3 where only the normal image forming unit 22 or 25 is set to the ready state. For example, when the first single-side record mode M2 is designated by the operation unit 300 and the failure occurred in the first image forming unit 22, it is indicated by the warning unit 302 and the normal second singleside record mode M3 is designated by the operation unit 300 so that the apparatus starts the copy operation in the second single-side record mode M3. The same is true when the failure occurred only in the second image forming unit 25.Accordingly, even if the double-side record mode is inhibited, the copy operation is permitted in the normal single-side record mode.

Fig. 4-2 shows another control flow chart for the present apparatus. In a step 41, it is checked if an error flag of the first image forming unit 22 was set. The error flag is set by the detector 301 of Fig. 3. It is set when any one of the elements necessary for forming a normal image such as an illumination or an intensity of a laser beam, a rotating speed of a polygon mirror and a temperature of a fixing unit is abnormal.

Accordingly, the error flag is reset only when all of the above elements are normal. If the error flag is not set in the step 41 , the program proceeds to a step 42 where an error flag of the second image forming unit 25 is checked. The error flag of the second image forming unit 25 is also set and reset in the same manner as the error flag of the first image forming unit 22. If the error flag is not set in both the steps 41 and 42, it is determined that the first and second image forming units 22 and 25 are normal and a ready signal is issued to a host (step 47) and the print operation in the designated record mode is effected (step 48). The ready signal indicates that the apparatus is ready to receive the image data and ready to print. If the error flag is set in the step 41 or 42, the record mode is checked in a step 43.If the double-side record mode M1 is designated, the program proceeds to a step 49 where a signal for inhibiting the double-side record mode M1 is issued to the warning unit 302 and it is checked if the record mode has been changed to the single-side record mode. If an operator changes the record mode to the single-side record mode by the operation unit 300, the image forming unit whose error flag is not set is selected (step 50). Then, the program proceeds to steps 47 and 48 and a similar operation to that described above is carried out.

If the single-side record mode is designated in the step 43, the program proceeds to a step 44 where it is checked if the error flag of the image forming unit to be used is set or not. For example, if the error flag of the first image forming unit 22 is set, the program proceeds to a step 45 where it is checked if the single-side record mode was changed from M2 to M3 by the operator. If it was, the program proceeds to a step 46 where the second image forming unit 25 is selected. If the single-side record mode was not changed, the program proceeds to a step 51 where a non-ready signal indicating that the apparatus is not ready to receive the image data is issued to the host and the apparatus is stopped (step 52).

While only the error in the image forming units is checked in the present embodiment, the record mode may be switched in response to a failure in the sheet arranging unit 24.

In the present embodiment, even if the doubleside record mode is inhibited, the recording function is not totally lost. When one of the first image formung unit 22 and the second image forming unit 25 is abnormal, the permitted singleside record mode M2 or M3 is informed to the operator by the warning unit 302, or it is informed to the external unit. The operator or the external unit that received the information may instruct to the present apparatus to continue the operation in the single-side record mode. Accordingly, the run rate of the present apparatus is improved.When the present invention is applied to the copying machine such as a laser beam printer which outputs coded information to a magnetic tape, a problem that no coded information is outputted when a failure occurs and the content of the information cannot be identified can be resolved, and a utilization efficiency of the apparatus is improved.

While the image forming units 22 and 25 in the present embodiment are electro-photographic systems such as laser beam printers, they may be other recording means such as thermal transfer printers or ink jet printers.

A second embodiment of the present invention is now explained. Fig. 5 shows a schematic view of a copying machine in accordance with the second embodiment of the present invention.

Numerals 31 and 32 denote sheet boxes. Sheets stacked in the sheet boxes 31 and 32 are fed out one by one by sheet feed rollers 33 and 34, respectively. D1 and D2 denote drums for forming images. Arranged around the drums D1 and D2 are chargers, developing units and other devices (not shown) necessary for forming the images.

Electrostatic latent images on the drums D1 and D2 are visualized by the developing units (not shown) and the visualized images are transferred to record sheets by transfer chargers 43 and 44, and permanent images are formed by fixing units 41 and 42. Numeral 37 denotes a deflector which selects a path of the record sheet supplied from the fixing unit 41 from path a to a path c or d. It is driven by a solenoid, not shown. Numeral 38 denotes a reversible reverse feed roller, numerals 39 and 40 denote ejection trays for the recorded sheets, and numerals 45 and 46 denote a light emitter and a photodetector of a sensor for detecting the presence or absence of the record sheet.

The deflector 37 is normally oriented by the solenoid to feed the record sheet on the path a to the ejection tray 39 through the paths c and e, and the roller 38 is rotated clockwise CW.

Numerals 47 and 48 denote scanners for scanning laser beams. The laser beams are reflected by mirrors 49 and 50 to the drums D1 and D2, respectively, so that the electrostatic latent images are formed on the drums D1 and D2.

The feed path includes the paths a, b, c, d and e. The record sheet fed from the sheet box 31 can pass through one of the following three feed paths.

i) aecee ii) aod iii) arced On the other hand, the record sheet fed from the sheet box 32 can pass through only the path bod.

In i) above, the deflector 37 and the roller 38 are not actuated, in ii) above, only the solenoid of the deflector 37 is actuated, and in iii) above, the double-side print mode is selected, and when a trailing edge of the record sheet fed from the path a to the path c (the roller 38 is rotating clockwise CW) is detected by the photodetector 46 of the sensor, the roller 38 is rotated counterclockwise CCW. In this case, the roller 38 which is rotating counterclockwise CCW is rotated again clockwise CW when the trailing edge of the record sheet fed from the path c to the path d is detected by the sensor. In the present apparatus, when the roller 38 is rotated counterclockwise, the record sheet is fed from the path c to the path d independently from the operation of the deflector 37.

Fig. 6 shows a control circuit for carrying out the above control. All controls are effected by a CPU 51 and the control circuit includes a readonly memory ROM 52 for a control program and a random access memory RAM 53 which serves as a control work area.

A data DA transmitted from a document reader of the present apparatus or external communication means is stored in a buffer 54 page by page of the original documents. The data includes a designation data to designate a drum to be used and a print data. The CPU determines the drum D1 or D2 on which the print data is to be written, based on the designation data, controls a selector 55 in accordance with the designation data, so that the print data is supplied to a drum D1 page buffer 56 or a drum D2 page buffer 57. Then, the print data is supplied to a laser device 58 or a laser device 59 by an instruction from the CPU 21.

Fig. 7 shows a control flow chart for the control circuit of Fig. 6. When the data DA is stored in the buffer 54, the designation data for designating the drum to be used is read from the data DA (step 31). If it designates the drum D2, the sheet feed roller 34 is driven to feed out the sheet from the sheet box 32 (step 33). As a result, the sheet is fed through the paths b and d and an image is printed thereon by the drum D2. If the designation data designates the drum Dl, the sheet feed roller 33 is driven (step 32). As a result, the sheet is fed through the path a and an image is printed thereon by the drum D1.

If an overprinting on the same sheet is desired or the sheet is to be fed to the ejection tray 40 (step 34), the solenoid of the deflector 37 is actuated so that the record sheet is fed to the feed path d. When the passage of the record sheet through the deflector 37 is detected by a detector (not shown), the solenoid of the deflector 37 is deactuated (steps 41,42 and 43). In other cases (that is, when the double-side printing or the feeding to the ejection tray 39 is desired), the solenoid of the deflector 37 is kept deactuated. If the double-side printing is not designated, the rotating direction of the roller 38 is not changed.

On the other hand, when the double-side printing is designated, the rotation of the roller 38 is stopped when the trailing edge of the record sheet is detected by the photo-detector 46 of the sensor of Fig. 6 (steps 36 and 37) and the roller 38 starts to rotate counterclockwise CCW at a timing synchronized with the image on the drum D2 (step 38). When the photodetector 46 again detects the trailing edge of the record sheet after the record sheet started to be fed backward, the roller 38 again rotates clockwise CW.

During the steps 35-40 of the flow of Fig. 7, the drive of the sheet feed roller 34 is inhibited, and during the steps 41-43, the drive of the sheet feed roller 34 is also inhibited.

In the feed paths shown in Fig. 5, the sheet boxes 31 and 32 may be common and the feed paths a and b may be common.

The control of the rotating direction of the reversible roller 38 need not be synchronized with the photo-detector 46 of the sensor but may be synchronized with a drum clock which is generated in synchronism with the rotation of the drum D1 or D2.

Fig. 8 shows feed paths in other embodiment of the present invention.

In Fig. 8, the like elements to those shown in Fig. 5 are designated by the like numerals and the explanation thereof is omitted. When some or all of a distance 1, from the leading edge of the record sheet in the sheet box 31 to the transfer station of the drum Do, a distance 12 from the leading edge of the record sheet in the sheet box 32 to the transfer station of the drum D2 and a distance 13 from the position of the sheet presence/absence sensors 45 and 46 to the transfer station of the drum D2 are equal, the control can be more simplified. For example, when 1" 12 and 13 are equal, the sheet feed timings in the forward sheet feeding and the backward sheet feeding may be equal and the sheet feed control can be simplified.

The following special print modes may be possible. In Fig. 5, the same data is written on the drums D1 and D2 and the sheet fed from the sheet box 31 is printed by the drum D1 and fed to the sheet ejection tray 39 while the sheet fed from the sheet box 32 is printed by the drum D2 and fed to the sheet ejection tray 40 so that two sets of files are prepared. Alternatively, the sheet ejection trays 39 and 40 may be common and odd-numbered pages of the original documents are printed by the drum D1 and the evennumbered pages are printed by the drum D2, alternately.

While the control of the present invention is effected for each page of the original documents, the modes may be set at the preparation time of the printer or at the switching time of the file consisting of a plurality of pages of data.

While the image forming units of the present embodiment are laser beam printers, they may be other recording means such as ink jet printers.

The present invention is not limited to the illustrated embodiments but various modifications may be made within a scope of the appended

Claims

claims. CLAIMS

1. An image forming apparatus comprising: first and second image forming units for forming images on a record medium; and control means for controlling said first or second image forming means in accordance with a record mode; said control means inhibiting the image forming operation in a first record mode and permitting the image forming operation in a second record mode when one of said first and second image forming units is in a predetermined state.

2. An image forming apparatus according to Claim 1 wherein said control means renders said first and second image forming units to form images on both sides of the record medium in a double-side record mode, and inhibits the image forming.operation in the double-side record mode when one of said first and second image forming units is in an abnormal state.

3. An image forming apparatus according to Claim 1 wherein said control means permits the single-side image forming operation by an available image forming unit when one of said first and second image forming units is in an abnormal state.

4. An image forming apparatus according to Claim 2 wherein said control means permits the single-side image forming operation by an available image forming unit when one of said first and second image forming units is in an abnormal state.

5. An image forming apparatus according to Claim 1 further comprising warning means for warning the inhibition of the image forming operation in the predetermined record mode.

6. An image forming apparatus according to Claim 1 further comprising a console unit for selecting the record mode.

7. An image forming apparatus comprising: first and second image forming units for forming images on a record medium; a plurality of feed paths associated with said first and second image forming units; memory means for storing information relating to said feed paths; and control means for selecting said feed path in accordance with the information stored in said memory means and controlling said first and second image forming units.

8. An image forming apparatus according to Claim 7 wherein said memory means stores information relating to the image forming unit to be used and an image data.

9. An image forming apparatus according to Claim 7 wherein said control means selects the feed path in accordance with a record mode.

1 0. An image recording apparatus comprising: image forming means having first and second image forming devices for image formation on a recording medium: control means for operating said image forming means selectively in any of a plurality of possible modes, said plurality of modes including at least a mode in which both of said image forming devices operate and a mode in which only one image forming device operates, said control means being operable to allow image formation in one mode despite the detection of a condition indicating image formation in another mode cannot or should not take place.

11. An image recording apparatus which includes a plurality of image recording devices and which normally is selectively operable in a plurality of modes of image recording, wherein the arrangement is such that image recording is still permitted in one mode even when a condition exists precluding image recording in another mode.

12. An image recording apparatus comprising: image forming means having first and second image forming devices for image formation on a recording medium; control means operable to control the movement of recording medium through the apparatus, said control means being operable in each of first and second single-side recording modes to cause recording medium to travel through a respective one of said first and second image forming devices for image recording on one side thereof, and in a double-side recording mode to cause recording medium to travel successively through said first and second image forming devices for image recording on first one then the other side thereof.

13. Apparatus for image recording on a recording medium which apparatus normally is selectively operable in a plurality of modes of image recording, said modes involving different paths of movement of the recording medium, the arrangement being such that image recording is still permitted in one mode even when a condition exists precluding image recording in another mode.

14. An image forming apparatus substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.

1 5. An image forming apparatus substantially as hereinbefore described with reference to Figures 2 to 4 of the accompanying drawings.

16. An image forming apparatus substantially as hereinbefore described with reference to Figure 5 of the accompanying drawings.

1 7. An image forming apparatus substantially as hereinbefore described with reference to Figure 5 to 7 of the accompanying drawings.

18. An image forming apparatus substantially as hereinbefore described with reference to Figure 8 of the accompanying drawings.