Image forming apparatus

Abstract: An image forming apparatus capable of storing the feeding station of the rotatable cassette in the memory means and rotating the rotatable cassette to the feeding station stored in the memory means when the rotatable cassette is out of both longitudinal feeding station and lateral feeding station. Further, the invention provides an image forming apparatus capable of selecting a desired cassette from a plurality of cassettes and instructing to rotate the rotatable cassette by depressing a minimum number of operation keys. The invention further provides an image forming apparatus wherein the rotatable cassette is taken out therefrom by setting the rotatable cassette in either of the longitudinal feeding station and the lateral feeding station, characterized in that the rotatable cassette is set in the feeding station specified as a rotatable cassette taking-out/insertion position each time an image formation is completed.

Description: The present invention relates to image forming apparatus such as copying machines and laser printers, and particularly to image forming apparatus having rotatable cassettes rotated between a longitudinal feeding position from which paper is fed in a longitudinal direction thereof and a lateral feeding position from which paper is fed in a lateral direction thereof. Image forming apparatus such as copying machines generally have a plurality of paper feed cassettes, i.e. a paper feed cassette for every size of copy paper to be used. When feeding paper using such a paper feed cassette, it is preferable to feed paper laterally oriented (hereinafter referred to as "lateral feeding") rather than paper longitudinally oriented (hereinafter referred to as "longitudinal feeding"), with respect to the feeding direction in order to facilitate high feeding speeds. In some conventional copying machines, large size papers such as B4 size paper and A3 size paper are fed laterally for the above reason. However, the lateral feeding of large size paper has a number of drawbacks because the size of the components disposed in a suitable copying machine such as the photoreceptor drum, delivery roller and delivery path for the paper are large, which results in high production costs. Therefore, a method is adopted in standard type copying machines so that large sized papers such as B4 sized and A3 sized papers are longitudinally fed while A4 sized paper and smaller sized paper are laterally fed. When using a copying machine having a variable magnification function for reducing and enlarging copying operations, paper feed cassettes of B5R size and A4R size are longitudinally fed into the copying machine when performing image reduction, and paper feed cassettes of B5 size and A4 size are laterally fed into the copying machine when normal copying is performed to facilitate high feeding speeds (the cassettes such as A4R and B5R are used for "longitudinal feeding" and the cassettes such as A4 and B5 are for "lateral feeding"). However, it is necessary when using various types of paper feed cassettes to enlarge the size of a copying machine or replace one cassette with another according to a desired copying function. As a result, the parts of the copying machine become large, increasing production costs in the former case, and the operation becomes more complicated and troublesome in the latter case. An image forming apparatus designed to solve the above problems is disclosed in Japanese Publication for Unexamined Patent Application Nos. 59245/1981 and 123859/1984, in which one cassette is used for both longitudinal feeding and lateral feeding by rotating the cassette. More specifically, a B5 size cassette is used as a B5R size cassette, and an A4 size cassette is used as an A4R size cassette. In the above apparatus, the rotatable cassettes are rotated in response to the actuation of a cassette rotation key for executing the rotation of a rotatable cassette. Since such rotatable cassettes are required to be mounted on a rotation mechanism, the cassette is generally housed in the main body of an image forming apparatus. In an image forming apparatus having rotatable cassettes, whenever an operator depresses the cassette rotation key the rotatable cassette is rotated, even if the cassette rotation key was pressed by mistake. Therefore, the rotatable cassette undergoes needless rotation and since noise is produced during rotation any quiet in the surroundings is broken and the service life of the rotation mechanism is reduced needlessly. Further, if the cassette rotation key is depressed during paper feeding from the rotatable cassette, paper jamming often occurs. When paper jamming occurs, the rotatable cassette is rotated to an initial feeding position and the copying operation is performed again to compensate for the deficient copies caused by the paper jamming. Thereafter, the cassette rotation key is depressed again in order to set the rotatable cassette to a desired feeding position. Thus, the rotatable cassette is forced to needlessly rotate as in the foregoing case, causing the generation of noise and a deterioration in the durability of the rotation mechanism. The above image forming apparatus is designed such that either one of the longitudinal feeding position or the lateral feeding position is set as a "preferential feeding position". When the power switch is turned on, or the rotatable cassette is inserted in the apparatus after refilling with paper, if the rotatable cassette is not in its preferential feeding position then the rotatable cassette is rotated such that it is positioned in its preferential feeding position. If paper runs out during paper feeding from the rotatable cassette, and the rotatable cassette gets out of a predetermined feeding position when the rotatable cassette is inserted into the image forming apparatus after being taken out therefrom for paper refilling the rotatable cassette is rotated to its preferential feeding position. If the originally set feeding position differs from the preferential feeding position, another operation for resetting the rotatable cassette in the originally set feeding position is necessary. This results in poor operating efficiency. The above image forming apparatus having (a) a plurality of rotatable cassettes, or (b) at least one rotatable cassette and one or more fixed cassettes is provided with a cassette selection key for selecting a cassette and cassette rotation keys for rotating a rotatable cassette. This increases the number of operation keys disposed on the operation panel and makes the key operation more troublesome. Furthermore, when the width of the opening from which the rotatable cassette is taken out from and inserted into the apparatus is limited, the rotatable cassette is required to be in a particular feeding position when being taken out from or inserted in the apparatus. Therefore, if the rotatable cassette is in a feeding position different from the position from which cassette insertion/taking out is only possible when copy paper runs out, the cassette needs to be reset. This makes refilling of the rotatable cassette with paper troublesome. The present invention aims to alleviate at least some of the aforementioned problems by providing an image forming apparatus having at least one paper feeding cassette, said cassette being rotatable between a first and second position to feed paper either in a longitudinal or lateral orientation respectively, characterised by the apparatus being arranged to delay a cassette movement signal for initiating movement of said cassette until generation of a cassette movement permission signal. This has the advantage that even if an error is made in operating cassette rotation instructing means such as a cassette rotation key, there is sufficient time for the error to be corrected thereby preventing the rotatable cassette from being needlessly rotated. In a preferred embodiment of the present invention, the cassette movement permission signal is generated by operating an image formation start instructing means. This has the advantage that the rotatable cassette is not rotated immediately after an instruction to rotate the rotatable cassette is issued but rotated only when an instruction to start image formation is issued by the image formation start instructing means. Thereby providing a time period in which an erroneous cassette rotation signal can be corrected. In another embodiment of the present invention, after operation of an image formation start instruction means the cassette movement permission signal is generated following completion of an image formation. The another embodiment has the advantage that, should the operator issue instructions to rotate the rotatable cassette during the image formation, the rotation is temporarily suspended and the rotation of the rotatable cassette is not started until the completion of the image formation is detected. Therefore, paper jamming caused by the rotation of the rotatable cassette in the course of image formation is avoided. This avoids having to rotate the rotatable cassette back to an initial feeding position in order to perform image formation again to compensate for the deficient copies caused by the paper jamming. In a further embodiment of the invention, after generation of a paper feeding start signal the cassette movement permission signal is generated following completing the paper feeding. An advantage of the further embodiment is that paper jamming which is caused by the rotation of the rotatable cassette during the paper feeding from the rotatable cassette is avoided, thereby avoiding the need for the rotatable cassette form rotating back to an initial feeding position in order to perform image formation again to compensate for the deficient copies caused by the paper jamming. This reduces the number of needless rotations of the rotatable cassette. In a yet another embodiment of the invention, there is provided an image forming apparatus having at least one paper feeding cassette, said cassette being selectively rotatable between a first and a second position to feed paper either in a longitudinal or lateral orientation respectively, characterised by the apparatus being arranged to detect deviation of the cassette from the most recently selected one of said positions and, in the absence of a cassette movement signal for initiating movement of the cassette from said most recently selected position to return the cassette to said most recently selected position. The above arrangement has the advantage that, even if the rotatable cassette gets out of both longitudinal and lateral feeding positions after supplying paper to the rotatable cassette, for example, and therefore normal paper feeding cannot be performed, the rotatable cassette is automatically rotated, without instructing operation by the operator, to a feeding station which is the most recently set. Thus, image formation can smoothly continue. In another aspect of the present invention there is provided an image forming apparatus having a plurality of paper feeding cassettes, at least one of said paper feeding cassettes being rotatable between a first and second position to feed paper in either a longitudinal or lateral orientation respectively; a cassette display means for displaying a selected paper feeding cassette; a paper display means for displaying paper size and orientation; and cassette changeover instructing means, characterised by control means responsive to repeated operation of the cassette changeover instructing means to advance through a sequence of paper selection modes, said modes each involving a given paper cassette and a paper size and orientation available using that cassette, and to control the operation of said cassette display means and paper display means so as to indicate the cassette, paper size and paper orientation involved in each currently selected paper selection mode, whereby a minimum number of cassette changeover instructing means is required for selection between the paper feeding cassettes and the different positions thereof. An advantage of this aspect of the invention is that since the same cassette changeover instructing means is used for selecting a cassette as well as instructing to rotate the rotatable cassette, the number of parts can be reduced. The rotatable cassette is rotated only when the image formation start display means is operated, that is, the rotatable cassette is not rotated until cassette selection or instruction to rotate the rotatable cassette is confirmed. Therefore, needless rotation of the rotatable cassette can be avoided. In a preferred embodiment of the another aspect of the present invention, when said cassette display means indicates the or a rotatable cassette, said control means determines the position of said rotatable cassette and, upon operation of image formation start instructing means, alters its position, if necessary, to conform with the paper orientation of the paper selection mode indicated by said paper display means. The above preferred embodiment has the advantage that the number of needless rotations of the rotatable cassettes can be reduced. In a further aspect of the present invention there is provided, an image forming apparatus having at least one paper cassette, said cassette being rotatable between a first and a second position to feed paper in either a longitudinal or lateral orientation respectively, the apparatus being adapted such that said cassette is insertable into and removable from said apparatus when said cassette is in a predetermined one of said positions, characterised by the apparatus being arranged to detect a position of said cassette on switching on said apparatus or on completion of an image formation and, if the detected position differs from said predetermined position, to move said cassette to said predetermined position. The further aspect of the present invention has the advantage that the rotatable cassette is set in a feeding station predetermined as a cassette taking-out/insertion position each time the power switch of the image forming apparatus is turned on and/or one image formation is completed. Thus, the rotatable cassette is always positioned in the predetermined feeding station from which the rotatable cassette can be taken out whenever the rotatable cassette is required to be taken out, for example, in order to supply paper thereto. Specific descriptions of the invention will now be given, with reference to the following drawings. Figs. 1 to 8 show one embodiment of the present invention. Fig. 1 is a flow chart showing the control operation of a microcomputer. Fig. 2 is a diagram showing the whole structure of a copying machine. Fig. 3 is a perspective view showing a part of the copying machine shown in Fig. 2 wherein a second rotatable cassette unit is drawn out. Fig. 4(a) is a partly diagrammatic sectional perspective illustration showing the structure of a first and the second rotatable cassette units shown in Fig. 2. Fig. 4(b) is an enlarged perspective view showing a nut shown in Fig. 4(a) and the periphery thereof. Fig. 5 is a perspective view showing the main part of a cassette mounting unit provided in a main body and a desk of the copying machine and a projecting member provided in each fixed cassette. Fig. 6(a) is a front view of an operation panel. Fig. 6(b) is a front view of a cassette operation unit of the operation panel. Fig. 7 is a block diagram showing the structure of a control unit. Fig. 8 is an explanatory diagram showing the rotating process of a rotatable cassette. Fig. 9 is a flow chart showing the control operation of a microcomputer of another embodiment of the present invention. Fig. 10 is a flow chart showing the control operation of a microcomputer of still another embodiment of the present invention. Fig. 11 is a flow chart showing the control operation of a microcomputer of yet another embodiment of the present invention. Fig. 12 is a flow chart showing the control operation of a microcomputer of another embodiment of the present invention. Figs. 13 and 14 show another embodiment of the present invention. Fig. 13 is a front view of a cassette operation unit of the operation panel. Fig. 14 is a flow chart of the control operation of a microcomputer. Figs. 15 to 17 show still another embodiment of the present invention. Fig. 15 is a main portion plan view of a copying machine. Fig. 16 is a main portion front view of the copying machine. Figs. 17 is a flow chart of a control operation. DESCRIPTION OF THE EMBODIMENTS The following description describes one embodiment of the present invention with reference to Figs. 1 to 8. A copying machine known as an image forming apparatus comprises, as shown in Fig. 2, a main body 1, a desk 38 on which the main body is placed, a sorter 19 positioned in the paper discharging side of the main body 1 and an automatic document feeder 3 (hereinafter referred to as ADF). As shown in Fig. 3, provided for the desk 38 are, in a descending scale, both side combining unit 21, a first rotatable cassette unit 26, a second rotatable cassette unit 27 and a third fixed cassette 25. The first rotatable cassette unit 26 comprises a rotatable cassette 32a disposed in an outer box 31a and the second rotatable cassette unit 27 comprises a rotatable cassette 32b disposed in an outer box 31b. The ADF 3 is installed on an original glass plate 2 of the main body 1 and capable of conveying a document (not shown) placed on the document placing tray 3a toward a predetermined position at the original glass plate 2 in accordance with the size of the document and a selected feeding direction (i.e. longitudinal feeding direction or lateral feeding direction), and discharging the document outward after the completion of the copying operation. When executing so-called duplex copying, the ADF 3 reverses a document one side of which has been copied and conveys it to a predetermined position at the original glass plate 2, and discharges the document outward after the duplex copying is completed. The document placing tray 3a comprises thereon conveying direction switches 5a and 5b for detecting the conveying direction of a document, and a guide 4 for guiding the document not so as to be shifted in a direction perpendicular to the conveying direction. The guide 4 includes a document size detection switch (not shown) for detecting the length of a document which is perpendicular to the conveying direction. The conveying direction switches 5a and 5b and the document size detection switch constitute a document size detection unit 54 (to be discussed later). Under the original glass plate 2 is disposed an optical system 6 having a basic function of guiding reflected light from the document into a photoreceptor drum 7, which is designed in order to perform variable magnification copying such as image reduction and image enlargement in addition to same size copying, the optical system 6 comprising a plurality of reflecting mirrors 6a and a lens 6b. Disposed around the photoreceptor drum 7 are a cleaner 8, a static eliminating charger 9, a main charger 10, a developing device 11 having toner for color copying, and a developing device 12 having toner for black-and-white copying. Disposed under the photoreceptor drum 7 are a transferring charger 13 and a separating charger 14. Disposed behind the separating charger 14 are a conveyor belt 17 and a fixing device 18. In same size copying, paper from the fixing device 18 is discharged to copy receiving trays 19a by way of the sorter 19. In duplex copying, paper guided from a paper returning path 20 to the both side combining unit 21 is guided to a paper feeding path 22 by way of a first feeding path 21a, an intermediate tray 21c and a delivery roller 21d within the both side combining unit 21. In complex copying paper guided from a paper returning path 20 to the both side combining unit 21 is guided to the paper feeding path 22 by way of a second feeding path 21b, the first feeding path 21a, the intermediate tray 21c and the delivery roller 21d within the both side combining unit 21. The end portion of the paper feeding path 22 reaches a paper stopping roller 15 in the neighbourhood of the photoreceptor drum 7. Paper is properly fed to the paper feeding path 22 from a plurality of paper feeding means. More concretely, there are provided, in the order to increasing distance to the paper stopping roller 15 disposed in the main body 1, a manual paper feeder 30, a first fixed cassette 29 capable of storing e.g. 500 sheets, a second fixed cassette 28 capable of storing e.g. 250 sheets, the both side combining unit 21, the first rotatable cassette unit 26, the second rotatable cassette unit 27 and a third fixed cassette capable of storing e.g. 250 sheets. The fixed cassettes 29, 28 and 25 and the rotatable cassette units 26 and 27 are all detachable from the copying machine. The first rotatable cassette unit 26 comprises, as shown in Fig 4(a), the outer box 31a and the rotatable cassette 32a disposed within the outer box 31a, for storing paper of a predetermined size. The rotatable cassette 32a has a rotating plate (not shown) for raising paper stored in the rotatable cassette 32a as the number of papers is decreased. The outer box 31a has, at the bottom wall, a cassette supporting plate 33 the center portion of which is apart from the bottom wall of the outer box 31a. A guiding hole 33a in the form of a long circle is disposed at the center portion of the cassette supporting plate 33 such that its longitudinal axis is parallel to a paper feeding direction. At the back face of the rotatable cassette 32a, there is provided a guiding shaft 34 positioned in the guiding hole 33a so as to project downward. The outer box 31a is provided with a threaded shaft 35 positioned parallel to the bottom wall of the outer box 31a, which extends in a direction perpendicular to the paper feeding direction. The threaded shaft 35 is rotatably supported by a bearing (not shown) and coupled with a cassette rotating motor 36 at one end thereof, so as to rotate normally and reversely. The threaded shaft 35 is connected to a nut 37 such that the nut 37 helically reciprocates along the threaded shaft 35 by the normal/reverse rotations of the threaded shaft 35. As shown in Fig. 4(b), the upper end of the nut 37 is pivotally connected to one corner of the rotatable cassette 32, and a light interrupting member 37a is formed at the lower part of the nut 37. A sensor HP₁ for detecting that the rotatable cassette 32a is rotated to the lateral feeding station and a sensor HP₂ for detecting that the rotatable cassette 32a is rotated to a longitudinal feeding station are respectively formed in the neighbourhood of both ends of the threaded shaft 35 on the bottom wall of the outer box 31a. The sensors HP₁ and HP₂ are photointerrupters each comprising a light emitting element and a light receiving element. When the rotatable cassette 32a moves to a predetermined feeding station, (i.e., either of the lateral and longitudinal feeding stations), either of the sensors HP₁ and HP₂ detects that light from the light emitting element to the light receiving element is interrupted by the light interrupting member 37a, thereby detecting the movement of the rotatable cassette 32a to the predetermined feeding station. The sensor HP₁ is "ON" when the rotatable cassette 32a moves to the lateral feeding station and the sensor HP₂ is "ON" when the rotatable cassette 32a moves to the longitudinal feeding station. The sensors HP₁ and HP₂ are not limited to a photointerrupter, but may be a magnetic sensor, contact type switch or other similar device. Since the first rotatable cassette unit 26 and the second rotatable cassette unit 27 are of twin structure, the foregoing description made to the former can be also applied to the latter, by replacing the outer box 31a and the rotatable cassette 32a with the outer box 31b and the rotatable cassette 32b. Therefore, the description of the second rotatable cassette unit 27 is omitted. As shown in Fig. 5, the first fixed cassette 29 and the second fixed cassette 28 disposed in the main body 1, and the third fixed cassette 25 disposed in the desk 38 are respectively provided with a projecting member 61. The projecting members 61 are positioned in accordance with the sizes of copy papers stored in the fixed cassettes 29, 28 and 25. At the cassette mounting units 62 in the main body 1 and the desk 38, there are provided a plurality of paper size switches 63 which are turned "ON" by the projecting members 61. For instance, there are four paper size switches 63 corresponding to A3, B4, A4 and B5 sizes respectively. The paper size switches 63 are connected to a microcomputer 51 (to be discussed later). With the above-described arrangement, the microcomputer 51 detects the sizes and feeding directions of papers stored in the fixed cassettes 29, 28 and 25. On the other hand, the sizes of papers stored in the rotatable cassettes 32a and 32b in the first and second rotatable cassette units 26 and 27 are inputted in the microcomputer 51 by the similar manner to the foregoing or other input means. The main body 1 comprises at the upper face thereof an operation panel 40 shown in Fig. 6(a). The operation panel 40 comprises a copy button 41 functioning as image formation start instructing means for instructing to start copying operation (image formation), ten keys 42 comprised of a plurality of numeral keys for setting the number of copies and the like, a copy number display 43, a cassette operation unit 44, a magnification display 45, magnification setting keys 46 and others. As shown in Fig. 6(b), the cassette operation unit 44 comprises a cassette changeover key 47 for cassette selection, a cassette rotation key 48 for instructing to rotate the rotatable cassette 32a in the first rotatable cassette unit 26 and a cassette rotation key 49 for instructing to rotate the rotatable cassette 32b in the second rotatable cassette unit 27 and others. The cassette operation unit 44 further comprises document size display lamps DSL₁ to DSL₆; paper size display lamps PSL₁ to PSL₆; and cassette display lamps CSL₁ to CSL₆ for indicating the manual paper feeder 30, the first fixed cassette 29, the second fixed cassette 28, the first rotatable cassette unit 26, the second rotatable cassette unit 27 and the third fixed cassette 25 by the numbers "1" to "6" in this order. The cassette display lamps CSL₁ to CSL₆ are selectively lighted in accordance with the selection of the rotatable cassette units 26 and 27, the fixed cassettes 25, 28 and 29, and the manual paper feeder 30 executed by operating the cassette changeover key 47. More concretely, when the first rotatable cassette unit 26 is selected by operating the cassette changeover key 47, the cassette display lamp CSL₄ is lighted. If A4 size paper is stored in the rotatable cassette 32a in the first rotatable cassette unit 26, and the rotatable cassette 32a is in the lateral feeding station, the paper size display lamp PSL₃ is lighted, thereby indicating that the selected paper is A4 and the feeding direction is lateral. Therefore, if the rotatable cassette 32a is rotated from the lateral feeding station to the longitudinal feeding station, the paper size display lamp PSL₄ is lighted, thereby indicating that the selected paper is A4 and the feeding direction is longitudinal. In the above case, if there is no paper stored in a selected cassette, the paper size display lamps PSL₁ to PSL₆ are not lighted. As shown in Fig. 7, the copying machine comprises the microcomputer 51 which functions as control means and memory means. The microcomputer 51 is connected to a motor driver circuit 52 for driving the cassette rotating motor 36 which functions as the cassette rotating means, the sensors HP₁, HP₂, the paper size switches 63, the document size detection unit 54, operation panel keys 55, operation panel display unit 56, a rotatable cassette paper feed solenoid 57 and a paper discharge detection switch 58 and others. Although being not shown in Fig. 7, the motor driver circuit 52 and the cassette rotating motor 36 are independently provided for both first and second rotatable cassette units 26 and 27. The motor driver circuit 52 comprises pull-up resistors R₁ and R₂, NOT circuits 59 and 60, transistors Tr₁ to Tr₄, resistors R₃ to R₈ and diodes D₁ to D₄ which function as surge absorbers, and is arranged to drive the cassette rotating motor 36 so as to rotate normally and reversely in accordance with the output of the microcomputer 51. The pull-up resistor R₁ is connected to voltage (+5V) at one end and an output terminal CW of the microcomputer 51 at the other end. The input of NOT circuit 59 and the base of the transistor Tr₄ are respectively connected to the output terminal CW of the microcomputer 51. The output of the NOT circuit 59 is connected to the base of the transistor Tr₁ via the resistor R₃. The base of the transistor Tr₁ is connected to one end of the resistor R₄ and the base of the transistor Tr₂ is connected to one end of the resistor R₅. The other ends of the resistors R₄ and R₅, the emitters of the transistors of Tr₁ and Tr₂, the cathodes of the diodes D₁ and D₂ are all connected to a terminal +24V, and voltage (+24V) is applied to the node of the above. The collector of the transistor Tr₁ and the anode of the diode D₁ are connected to one input terminal of the cassette rotating motor 36, and the collector of the transistor Tr₂ and the anode of the diode D₂ are connected to the other input terminal of the cassette rotating motor 36. The pull-up resistor R₂ is connected to voltage (+5V) at one end and an output terminal CCW of the microcomputer 51 at the other end. The input of the NOT circuit 60 and the base of the transistor Tr₃ are connected to the output terminal CCW of the microcomputer 51 and the output of the NOT circuit 60 is connected to the base of the transistor Tr₂ via the resistor R₆. The base of the transistor Tr₃ is connected to one end of the resistor R₇ and the base of the transistor Tr₄ is connected to one terminal of the resistor R₈. The other ends of the resistors R₇ and R₈, the emitters of the transistors Tr₃ and Tr₄, and the anodes of the diodes D₃ and D₄ are all connected to Ground. The collector of the transistor Tr₃ and the cathode of the diode D₃ are connected to one input terminal of the cassette rotating motor 36 and the collector of the transistor Tr₄ and the cathode of the diode D₄ are connected to the other input terminal of the cassette rotating motor 36. The motor driver circuit 52 is designed such that the rotatable cassette 32a in the first rotatable cassette unit 26 or the rotatable cassette 32b in the second rotatable cassette unit 27 are rotated to the lateral feeding station (e.g. A4 or B5 position) when the output terminal CCW of the microcomputer 51 is at a high level (with the output terminal CW being at a low level), and to the longitudinal feeding station (e.g. A4R or B5R position) when the output terminal CW is at a high level. The document size detection unit 54 supplys 4-bit data to input terminals OS₁ to OS₄ of the microcomputer 51. The operation panel keys 55 include the copy button 41, the ten keys 42, the magnification setting keys 46, the cassette changeover key 47, the cassette rotation keys 48 and 49, and others which are all provided on the operation panel 40 of the main body. The operation panel display unit 56 includes the copy number display 43, the magnification display 45, the document size display lamps DSL₁ to DSL₆, the paper size display lamps PSL₁ to PSL₆, the cassette display lamps CSL₁ to CSL₆ and others, which are all provided on the operation panel 40. The rotatable cassette paper feed solenoid 57 is for actuating paper feeding rollers 26a and 27a respectively disposed in the first and second rotatable cassette units 26 and 27 in order to feed paper. The paper discharge detection switch 58 (not shown in Fig. 2) is disposed at a paper discharging station led to the sorter 19 and used for detecting paper discharge from the main body 1. When one of the operation panel keys 55 is depressed, the microcomputer 51 starts its control operation according to the key depressed. For example, when the cassette rotation key 48 corresponding to the first rotatable cassette unit 26 is depressed, thereby entering a cassette rotation signal for instructing to rotate the rotatable cassette 32a in the first rotatable cassette unit 26 from the lateral feeding station to the longitudinal feeding station, the lever of the output terminal CW becomes high and the level of the output terminal CCW becomes low through the processes of the control operation shown in Fig. 1 (to be described later). On the other hand, if the cassette rotation signal for instructing to rotate the rotatable cassette 32a from the longitudinal feeding station to the lateral feeding station is entered, the level of the output terminal CCW becomes high and the level of the output terminal CW becomes low. When the rotatable cassette 32a is rotated to the longitudinal feeding station and the sensor HP₂ is turned ON (i.e. the light in the photointerrupter of the sensor HP₂ is interrupted), the level of the output terminal CW immediately becomes low, thereby halting the cassette rotating motor 36. Likewise, when the rotatable cassette 32a is rotated to the lateral feeding station and the sensor HP₁ is turned ON, the level of the output terminal CCW immediately becomes low, thereby halting the cassette rotating motor 36. The following description describes the rotation of the rotatable cassette 32a of the first rotatable cassette unit 26 and the rotatable cassette 32b of the second rotatable cassette unit 27 in the above arrangement. Suppose that A4 size paper is stored in the rotatable cassette 32a in the first rotatable cassette unit 26 and the rotatable cassette 32a is positioned in the lateral feeding station (i.e. A4 position). The sensor HP₁ is turned ON and the display for the first rotatable cassette unit 26 on the operation panel display unit 56 indicates A4. At this time, the nut 37 disposed at the threaded shaft 35 is located at the position P₁ as shown in Fig. 8. When the microcomputer 51 causes the output terminal CW to be high and the output terminal CCW to be low, the transistor Tr₁ and the transistor Tr₄ are turned ON and current flows through the (+24V) power source, the transistor Tr₁, the cassette rotating motor 36, the transistor Tr₄ and ground in this order, thereby normally rotating the cassette rotating motor 36 (rotating in the direction C in Fig. 4(a)). The threaded shaft 35 is accordingly rotated in the direction C. This rotation permits the nut 37 to move from the position P₁ to the position P₆ and the guiding shaft 34 of the rotatable cassette 32a is rotatively slided within the guiding hole 33a of the supporting plate 33 to move from the position Q₁ to the position Q₆ via the positions Q₂, Q₃, Q₄ and Q₅. Thereafter, the nut 37 reaches the sensor HP₂ to turn the sensor HP₂ ON, thereby halting the cassette rotating motor 36. At this stage, the rotatable cassette 32a is set in the predetermined longitudinal feeding station (A4R position). When the microcomputer 51 causes the output terminal CCW to be high and the output terminal CW to be low in the above state, the transistors Tr₂ and Tr₃ are turned ON, and current flows through the (+24V) power source, the transistor Tr₂, the cassette rotating motor 36, the transistor Tr₃ and ground in this order, thereby reversely rotating the cassette rotating motor 36. This rotation permits the rotatable cassette 32a to rotate from the longitudinal feeding station to the lateral feeding station with the guiding shaft 34 moving in the opposite process to the foregoing (i.e. from the position Q₆ to the position Q₁). When the sensor HP₁ is turned ON thereafter, the cassette rotating motor 36 is halted and the rotatable cassette 32a is set in the predetermined lateral feeding station. Referring now to the flow chart of Fig. 1, the control operation of the microcomputer 51 for the rotatable cassette 32a of the first rotatable cassette unit 32a and the rotatable cassette 32b of the first rotatable cassette unit 27 will be explained hereinbelow. In the following description, assume that the rotatable cassette 32a of the first rotatable cassette unit 26 is selected for paper feeding and the cassette rotation key 48 corresponding to the rotatable cassette 32a is depressed. After copying conditions are registered when copying operation is in a stand-by state (Step 1), the microcomputer 51 determines whether or not the copy button 41 is depressed (Step 2), and whether or not the cassette rotation key 48 is depressed (Step 3). Incidentally, the cassette rotation signal entered by depressing the cassette rotation key 48 prior to the actuation of the copy button 41 is stored by the memory means of the microcomputer 51. If it is determined in Step 2 and Step 3 that the copy button 41 is depressed and the cassette rotation key 48 is not depressed, the program immediately proceeds to Step 15, thereby performing a copying operation. On the other hand, if the copy button 41 and the cassette rotation kay 48 are both depressed, the microcomputer 51 then determines whether the sensor HP₁ is ON (Step 4). If the sensor HP₁ is ON, the output terminal CW becomes high (Step 5) and the output terminal CCW becomes low (Step 6). This causes the cassette rotating motor 36 to be normally rotated thereby rotating the rotatable cassette 32a to the longitudinal feeding station. Thereafter, the microcomputer 51 determines whether the sensor HP₂ has been turned ON (Step 7), and if the sensor HP₂ has been turned ON, the output terminal CW becomes low (Step 8). This causes the cassette rotating motor 36 to be halted and the rotatable cassette 32a is set in the longitudinal feeding station. Then, a copying operation is performed (Step 15). If it is determined in Step 4 that the sensor HP₁ is not ON, the microcomputer 51 then determines whether the sensor HP₂ is ON (Step 9). If the sensor HP₂ is ON, the microcomputer 51 causes the output terminal CW to be low (Step 10) and the output terminal CCW to be high (Step 11). This causes the rotatable cassette 32a to be rotated to the lateral feeding station. Thereafter, it is determined whether the sensor HP₁ is ON (Step 12), and if the sensor HP₁ is ON, the microcomputer 51 causes the output terminal CCW to be low (Step 13). In this stage, the rotatable cassette 32 is positioned in the lateral feeding station. Then, the program proceeds to Step 15 and a copying operation is performed. If it is determined in Step 9 that the sensor HP₂ is not ON, the occurrence of trouble is indicated (Step 14) since the rotatable cassette 32a is not set in either of the longitudinal feeding station or the lateral feeding station. In the above control operation, since the rotatable cassette 32a and 32b is rotated after turning on the copy button 41 under the condition that the rotatable cassette 32a in the first rotatable cassette unit 26 or the rotatable cassette 32b in the second rotatable cassette unit 27 is selected for paper feeding, the rotatable cassette 32a or 32b is not rotated each time the cassette rotation key 48 or 49 is erroneously operated by the operator. Since the rotatable cassette 32a or 32b is selected by finally depressing the cassette rotation key 48 or 49 prior to the turning on of the copy button 41 and is rotated after the copy button 41 is turned ON, the useless rotation of the rotatable cassette 32a or 32b can be prevented. In this embodiment, the arrangement is made such that a cassette rotation permission signal is entered in the microcomputer 51 by turning ON the copy button 41. In this embodiment, the number of cassettes can be arbitrarily changed on condition that the copying machine has at least one rotatable cassette in order to perform the foregoing control operation. Now reference is made to Figs. 7 and 9 for explaining another embodiment of the present invention. For simplifying the explanation, those members having functions substantially similar to those of the members in the foregoing embodiment are indicated by the same reference numerals and the description thereof is omitted. In the image forming apparatus of this embodiment, the microcomputer 51 shown in Fig. 7 functions as control means, memory means and a timer which is timing means, and performs the control operation shown in Fig. 9. The control operation of the microcomputer 51 having the above functions for the rotatable cassette 32a of the first rotatable cassette unit 26 and the rotatable cassette 32b of the second rotatable cassette unit 27 will be explained hereinafter with reference to the flow chart of Fig. 9. First of all, the rotatable cassette 32a of the first rotatable cassette unit 26 or the rotatable cassette 32b of the second rotatable cassette unit 27 is selected for paper feeding (Step 1) and the microcomputer 51 then determines which of the cassette rotation keys 48 and 49 that respectively correspond to the above cassettes is turned ON (Step 2). When either of the cassette rotation keys 48 and 49 is turned ON, either of the rotatable cassette 32a of the first rotatable cassette unit 26 and the rotatable cassette 32b of the second rotatable cassette unit 27 that corresponds to the cassette rotation key which has been turned ON is memorized as a selected paper feed cassette (Step 3). In other words, a cassette rotation signal corresponding to the selected paper feed cassette which is the rotatable cassette 32a or 32b is stored. Thereafter, timing carried out by a timer is commenced (Step 4) and it is determined which of the cassette rotation keys 48 and 49 has been turned ON (Step 5). When either of the above has been turned ON, the microcomputer 51 determines whether the rotatable cassette 32a or 32b that corresponds to the cassette rotation key which has been turned ON is equal to the rotatable cassette memorized in Step 3 (Step 6). If it is not the same, the program returns to Step 3 in order to memorize the rotatable cassette 32a or 32b and timing operation is again performed by the timer (Step 4). On the other hand, If it is determined in Step 6 that the rotatable cassette corresponding to the cassette rotation key which has been turned ON is equal to the memorized rotatable cassette or if neither the cassette rotation key 48 nor 49 is ON, upon completion of the timing by the timer (Step 7), the rotation of the memorized rotatable cassette 32a or 32b is commenced (Step 8). If interruption that causes the cassette rotatable key 48 or 49 to be turned ON is not executed thereafter (Step 9) and the sensor HP₁ or HP₂ is turned ON (Step 10), the rotation of the rotatable cassette 32a or 32b is halted (Step 11), the timer is reset (Step 12) and the program returns to Step 2. On the other hand, if such interruption is executed in Step 9, the rotatable cassette 32a or 32b is rotated to a predetermined initial feeding station and the program returns to Step 2. The operations in Steps 8, 10 and 11 in the above description are substantially equal to those in Steps 4 to 14 in Fig. 1. In the above control operation, after turning ON the cassette rotation key 48 or 49, timing by the timer is commenced and if the rotatable cassette which has been selected as a paper feed cassette is not changed until the completion of the timing, the rotation of the selected rotatable cassette is commenced. Therefore, even if the rotation of the rotatable cassette 32a or 32b is erroneously inputted by the operator, the useless rotation of the rotatable cassette 32a or 32b can be avoided by changing the rotatable cassette to be rotated so that only the rotatable cassette finally selected at the moment of the completion of the timing is rotated. In this embodiment, a cassette rotation permission signal is entered in the microcomputer 51 upon completion of the timing by the timer. The following description will discuss still another embodiment of the present invention with reference to Figs. 7 and 10. For convenience of explanation, those members having substantially similar functions to those of the members described in the first embodiment are indicated by the same reference numerals and the description thereof is omitted. The image forming apparatus of the present invention comprises the microcomputer 51 shown in Fig. 7. The paper discharge detection switch 58 connected to the microcomputer 51 functions as image formation completion detecting means. In the microcomputer 51, a copying operation is deemed to be completed when the discharge of a paper to the sorter 19 is detected by the paper discharge detection switch 58, that is, when the last paper passes by the paper discharge detection switch 58 in a continuous copying operation, and when the copy paper passes by the same in a single copying operation. The microcomputer 51 functions as control means, memory means and a timer, and performs the control operation shown in Fig. 10. Now reference is made to the flow chart of Fig. 10 for explaining the control operation of the microcomputer 51 in the above arrangement for the rotatable cassette 32a in the first rotatable cassette unit 26 and the rotatable cassette 32b in the second rotatable cassette. In the following description, assume that the rotatable cassette 32a in the first rotatable cassette unit 26 is selected for paper feeding and the cassette rotation key 48 corresponding to the rotatable cassette 32a is operated. First of all, copying conditions such as exposure, magnification, a paper size are set by the operator. The microcomputer 51 executes the corresponding process (Step 1) and then determines whether the copy button 41 is turned ON (Step 2). If the copy button 41 is turned ON, a copying operation is commenced (Step 3), and charging, paper feeding, exposing and development and other operations are performed. Thereafter, if the copying operation is completed (Step 4) and the cassette rotation key 48 is depressed (Step 5), the rotatable cassette 32a is rotated in a desired direction (Steps 6 to 16). The operations executed in Steps 6 to 16 are the same as the operations in Steps 4 to 14 in Fig. 1. A cassette rotation signal entered before the completion of the copying operation is stored in the memory means of the microcomputer 51. When the copying operation is not completed in Step 4 and the cassette rotation key 48 is not depressed in Step 5, the microcomputer 51 causes the outputs of the output terminals CCW and CW to be low (Step 17, Step 18), thereby prohibiting the rotation of the rotatable cassette 32a, and the program returns to Step 3. In the above control operation, since the rotation of the rotatable cassette 32a is prohibited after the start of the copying operation until the completion thereof, and since the rotatable cassette 32a is rotated after the completion of the copying operation if the cassette rotation key 48 is depressed and the rotation of the rotatable cassette 32a is required, a paper jamming resulted from the rotation of the rotatable cassette 32a during copying operation can be avoided. With such an arrangement, the useless rotation of the rotatable cassette 32a back to an initial feeding station, which is required for performing image formation to compensate for the deficient copy caused by the paper jamming, can be avoided. In this embodiment, a cassette rotation permission signal is entered in the microcomputer 51 by the paper discharge detection switch 58 at the time of detecting the completion of the copying operation. The following description describes still another embodiment of the present invention with reference to Figs. 2, 7, and 11. For convenience of explanation, those members having substantially similar functions to those of the members described in the first embodiment are indicated by the same reference numerals and the description thereof is omitted. The image forming apparatus of this embodiment comprises the microcomputer 51 shown in Fig. 7. The rotatable cassette paper feed solenoid 57 connected to the microcomputer 51, and the paper feeding rollers 26a and 27a respectively disposed in the first and second rotatable cassette units 26 and 27 shown in Fig. 2 compose paper feeding means. The rotatable cassette paper feed solenoid 57 is controlled by the microcomputer 51, so that when a paper feeding start signal is generated, the paper feeding rollers 26a and 27a are pressed against paper stored in the rotatable cassettes 32a and 32b, thereby performing paper feeding, and when a paper feeding completion signal is generated, the paper feeding rollers 26a and 27a are kept away from the paper stored in the rotatable cassettes 32a and 32b. The microcomputer 51 functions as control means and memory means, and performs the control operations shown in Fig. 11. The following description describes the control operation of the microcomputer 51 in the above arrangement for the rotatable cassette 32a of the first rotatable cassette unit 26 and the rotatable cassette 32b of the second rotatable cassette unit 27, with reference to the flow chart of Fig. 11. In the following description, assume that the rotatable cassette 32a of the first rotatable cassette unit 26 is selected for paper feeding and the cassette rotation key 48 corresponding to the rotatable cassette 32a is depressed. Firstly, the microcomputer 51 determines whether the rotatable cassette paper feed solenoid 57 is ON (Step 1) and whether the cassette rotation key 48 is ON (Step 2). If the rotatable cassette paper feed solenoid 57 is OFF and the cassette rotation key 48 is ON, the rotatable cassette 32 is rotated in a desired direction (Steps 3 to 13). The operations in Steps 3 to 13 are substantially equal to those in Steps 4 to 14 in Fig. 1. A cassette rotation signal entered before the rotatable cassette paper feed solenoid 57 is turned OFF is stored in the memory means of the microcomputer 51. If the rotatable cassette paper feed solenoid 57 is turned OFF in Step 1 and the cassette rotation key 48 is not ON in Step 2, the rotatable cassette 32a is not rotated. In the above control operation, since the rotation of the rotatable cassette 32a is prohibited while the rotatable cassette paper feed solenoid 57 is ON, i.e., during paper feeding from the rotatable cassette 32a, and the rotatable cassette 32a is rotated if the cassette rotation key 48 is ON upon completion of the paper feeding from the rotatable cassette 32a, a paper jamming caused by the rotation of the rotatable cassette 32a during paper feeding from the rotatable cassette 32a can be avoided. With such an arrangement, the useless rotation of the rotatable cassette 32a back to an initial feeding station, which is required for performing image formation to compensate for the deficient copy caused by the paper jamming, can be avoided. In this embodiment, a cassette rotation permission signal is entered in the microcomputer 51 upon turning OFF of the rotatable cassette paper feed solenoid 57. With reference to Figs. 7 to 12, yet another embodiment of the present invention will be explained hereinbelow. An image forming apparatus according to this embodiment is designed such that when the rotatable cassette 32a or 32b is out of both the longitudinal feeding station and the lateral feeding station, for example, after supplying paper thereto, the cassette can be reset in the initial feeding station without any special operation carried out by the operator. The copying machine of the embodiment has the same structure as that of the first embodiment described above. Reference is now made to the flow chart of Fig. 12 for explaining the control procedures. In the following description, assume that the cassette rotation key 48 corresponding to the first rotatable cassette unit 26 is depressed. Further, assume that A4 size paper is stored in the rotatable cassette 32a of the first rotatable cassette unit 26 and the rotatable cassette 32a is positioned in the longitudinal feeding station (i.e. A4R position). It is determined in Step 1 whether a cassette rotation signal has been generated by, for example, operating the cassette rotation key 48. If a cassette rotation signal has been generated, the microcomputer 51 stores the lateral feeding station (A4 position) in the memory means (Step 2) so as to rotate the rotatable cassette 32a from the longitudinal feeding station (A4R) position) to the lateral feeding station. Then, the rotatable cassette 32a is rotated to the lateral feeding station with the same process as those of the foregoing embodiments (Step 3) and a copying operation is performed thereafter. On the other hand, if a cassette rotation signal is not generated in Step 1, it is determined whether the sensor HP₂ is ON (Step 4). If the sensor HP₂ is ON, the rotatable cassette 32a is positioned in the longitudinal feeding station which is stored in the memory means of the microcomputer 51 and therefore a copying operation is immediately performed without executing the process in Step 5. On the other hand, If the sensor HP₂ is OFF in Step 4, the rotatable cassette 32a is not positioned in the longitudinal feeding station which has been selected, and therefore the microcomputer 51 actuates the cassette rotating motor 36 to rotate the rotatable cassette 32a to the longitudinal feeding station (A4R position) (Step 5), and then a copying operation is performed. With such control operation, even if the rotatable cassette 32a gets out of a predetermined feeding station due to some external force, it can be reset in the initial feeding station. Next, reference is made to Figs. 13 and 14 for explaining yet another embodiment of the present invention. The image forming apparatus of this embodiment has basically the same structure as that of the first embodiment, but they differ from each other in that the number of operation keys on the cassette operation unit 44 of the operation panel 40 is reduced in the latter apparatus. More specifically, in this embodiment, the structure of the cassette operation unit 44 is, as shown in Fig. 13, substantially the same as that of the first embodiment (see Fig. 6(b)), but provided with only a cassette changeover key 74 instead of the cassette changeover key 47 and the cassette rotation keys 48 and 49 in the first embodiment. As will be described later, cassette selection and instruction to rotate the rotatable cassettes 32a or 32b are performed by a single cassette changeover key 74 in this embodiment. Also, there is provided a paper size display lamp PSL₇′ for displaying a special size paper in addition to paper size display lamps PSL₁′ to PSL₆′ for displaying A3, A4, A4R, B4, B5 and B5R papers respectively. The document size display lamps are not shown in Fig. 13. Referring now to the flow chart of Fig. 14, the control operation of the microcomputer 51 for the cassette display lamps CSL₁ to CSL₆, the paper size display lamps PSL₁′ to PSL₇′, and the rotatable cassettes 32a and 32b is explained hereinbelow. In the following description, assume that the special size paper is stored in the manual paper feeder 30; A4 size paper is stored in the first fixed cassette 29 and the rotatable cassette 32a of the first rotatable cassette unit 26; B4 size paper is stored in the second fixed cassette 28 and the third fixed cassette 25; and B5 size paper is stored in the rotatable cassette 32b of the second rotatable cassette unit 27. The paper size display lamps PSL₂′ and PSL₃′ correspond to the rotatable cassette 32a, and the paper size display lamps PSL₅′ and PSL₆′ correspond to the rotatable cassettes 32b accordingly. When the cassette display lamp corresponding to the rotatable cassette 32a or 32b (i.e. CSL₄ or CSL₅) is turned ON, the paper size display lamp corresponding to the feeding station of the rotatable cassette 32a or 32b at the time is turned ON. For example, when the rotatable cassette 32a of the first rotatable cassette unit 26 is selected and the rotatable cassette 32a is positioned in the lateral feeding direction (A4 position), the paper size display lamp PSL₂ corresponding to A4 position is turned ON. In Fig. 14, the microcomputer 51 determines whether the cassette changeover key 47 is depressed (Step 1), and if so, the microcomputer 51 then determines whether or not the cassette which has been displayed by the cassette display lamp before the actuation of the cassette changeover key 47 is the rotatable cassette 32a or 32b (Step 2). If it is neither the rotatable cassette 32a nor 32b, the cassette display lamp and the paper size display lamp are changed so as to correspond to the next cassette, i.e., the cassette selection by depressing the cassette changeover key 47 in Step 1 (Step 3) and the program returns to the main routine. On the other hand, if it is determined in Step 2 that the cassette which has been displayed before the actuation of the changeover key 47 is the rotatable cassette 32a or 32b, the microcomputer 51 then determines whether a flag F provided in the memory means or other means of the microcomputer 51 is "1" (S4). The flag F is used for indicating whether the rotation of the rotatable cassette 32a or 32b is required at the stage immediately before the actuation of the cassette changeover key 47 is detected in Step 1 (i.e. whether the paper size indicated by the paper size display lamp does not correspond to the feeding station of the rotatable cassette 32a or 32b). If the above rotation is needed, the flag F is "1" and if not, the flag F is "0". In the case it is determined in Step 4 that the flag F is not "1" (i.e. the rotation has not been required before the actuation of the cassette changeover key 47), the actuation of the cassette changeover key 47 causes the necessity of rotating the rotatable cassette 32a or 32b. the rotation becomes necessary by operating the cassette changeover key 47. In this case, only the paper size lamp is changed over (Step 5), and after setting the flag F to "1" to indicate the condition wherein the rotation is required (Step 6), the program returns to the main routine. In Step 6, the rotation of the rotatable cassette 32a or 32b is not immediately executed but only the flag F is set to "1". If it is determined in Step 4 that the flag F is "1" (i.e. the rotation has been required before the actuation of the cassette changeover key 47), the cassette has been changed to the next by operating the cassette changeover key 47. Therefore, after the condition wherein the rotation is required is changed by setting the flag F to "0" (Step 7), the cassette is changed to the next cassette (Step 3) and the program returns to the main routine. The processes in Steps 1 to 6 will be explained by way of an example. Suppose that B4 size paper is stored in the second fixed cassette 28; A4 size paper is stored in the rotatable cassette 32a of the first rotatable cassette unit 26 which is set in the lateral feeding station (i.e. A4 position); and B5 size paper is stored in the rotatable cassette 32b of the second rotatable cassette unit 27 which is set in the longitudinal feeding station (i.e. B5R position). Further, assume that the second fixed cassette 28 is selected and the cassette display lamp CSL₃ is lighted. In the flow chart of Fig. 14, after the cassette changeover key 47 is depressed under the above condition, the program proceeds from Step 1 to Step 2 and it is determined whether or not the selected cassette is the rotatable cassette 32a or 32b. Since the second fixed cassette 28 is selected, the result is NO. The program proceeds to Step 3 and the next cassette i.e. the rotatable cassette 32a of the first rotatable cassette unit 26 is displayed. More concretely, the cassette display lamp CSL₃ is turned OFF and the cassette display lamp CSL₄ is turned ON, and successively, the paper size display lamp PSL₄ is turned OFF and the paper size display lamp PSL₂ is turned ON. Upon completion of the changeover of the above display switches, the program returns to the main routine. Thereafter, the cassette changeoever key 47 is again depressed and the program proceeds from Step 1 to Step 2 at which the determination is executed. The result is YES since the rotatable cassette 32a of the first rotatable cassette unit 26 is selected with the cassette display lamp CSL₄ being lighted. Then, it is determined in Step 4 whether the flag F is "1". The feeding station of the rotatable cassette 32a corresponds to the paper size display lamp PSL₂ at that time, and therefore the flag is "0" and the result of the determination is NO. The program then proceeds to Step 5. At that time, the cassette display lamp CSL₄ is continuously lighted. The paper size display lamp PSL₂ that displays A4 size is turned OFF, and the lamp PSL₃ that displays A4R size is turned ON. The flag F is set to "1" at Step 6 so as to indicate the condition wherein the rotation is required, and the program returns to the main routine. After the cassette changeover key 47 is again depressed, the program proceeds from Step 1 to Step 2. Since the rotatable cassette 32a of the first rotatable cassette unit 26 is selected, the program proceeds to Step 4 where it is determined whether the flag F is "1". The flag F is "1" at that time, and the program therefore proceeds to Step 7 where the flag F is set to "0". At Step 3, the cassette display lamp CSL₄ is turned OFF and the lamp CSL₅ is turned ON, and the paper size display lamp PSL₃ is turned OFF and the lamp PSL₆ is turned ON so as to indicate the next cassette, i.e., the rotatable cassette 32b of the second rotatable cassette unit 27. The following description describes the processes in Steps 8 to 11. If the cassette changeover key 47 is not depressed in Step 1 and the coppy button 41 is not depressed in Step 8, the program returns to the main routine. If the cassette changeover key 47 is not depressed in Step 1 and the copy button 41 is depressed in Step 8, the microcomputer 51 determines whether or not the selected cassette is the rotatable cassette 32a or 32b (Step 9). If the selected cassette is not the rotatable cassette 32a or 32b, the program returns to the main routine and a copying operation is performed. If it is determined in Step 9 that the rotatable cassette 32a or 32b is selected, the microcomputer 51 then determines whether the flag F is "1" (the condition wherein the rotation is required) (Step 10). If the flag F is not "1", the program returns to the main routine to perform a copying operation. On the other hand, if it is determined in Step 10 that the flag is "1", after rotating the rotatable cassette 32a or 32b to a predetermined feeding station (Step 11), the program returns to the main routine to perform a copying operation. As an example of the above control operation, the process is explained, wherein the first fixed cassette 29 storing A4 size paper is changed to the rotatable cassette 32b of the second rotatable cassette unit 27 so as to feed B5 size paper. When the first fixed cassette 29 is selected, the cassette display lamp CSL₂ and the paper size display lamp PSL₂ (indicating A4) are lighted. If the cassette changeover key 47 is depressed at this stage, the cassette display lamp CSL₂ is turned OFF and the lamp CSL₃ (indicating the second fixed cassette 28) is turned ON (i.e. the cassette display lamp is changed from CSL₂ to CSL₃). At the same time, the paper size display lamp PSL₂ is turned OFF and the lamp PSL₄ (indicating B4) is turned ON (i.e. the paper size display lamp is changed from PSL₂ to PSL₄). Thereafter, the cassette changeover key 47 is depressed, thereby changing the cassette display lamp from CSL₃ to CSL₄ (indicating the first rotatable cassette unit 26) and if the rotatable cassette 32a is positioned in the lateral feeding station, the paper size display lamp is changed from PSL₄ (indicating B4) to PSL₂ (indicating A4). When the cassette changeover key 47 is depressed thereafter, the cassette display lamp CSL₄ is not changed, while only the paper size display lamp is changed from PSL₂ (indicating A4) to PSL₃ (indicating A4R). At this stage, the feeding station is not changed by rotation. That is, the rotatable cassette 32a remains being positioned in the lateral feeding station (A4 position). This is the condition in which the rotation is required. When the cassette changeover key 47 is again depressed, the cassette display lamp is changed from CSL₄ to CSL₅ (indicating the second rotatable cassette unit 27). If the rotatable cassette 32b is positioned in the longitudinal feeding station, the paper size display lamp is changed from PSL₃ (indicating A4R) to PSL₆ (indicating B5R). When the cassette changeover key 47 is again depressed, the cassette display lamp CSL₅ is continuously lighted, while the paper size display lamp is changed from PSL₆ to PSL₅ (indicating B5). When the copy button 41 is depressed in the above state, it is considered that B5 size paper has been selected, and the rotatable cassette 32b of the second rotatable cassette unit 27 is rotated to the lateral feeding station (B5 position). After that, paper feeding is commenced and a copying operation is performed. In the above operation, the rotatable cassette 32a and 32b are designed to be positioned in the feeding station of high frequency in use when the copying machine is in a stand-by state, and the paper size display lamp corresponding to the feeding station in which the rotatable cassette 32a or 32b is positioned at that time is turned ON when the rotatable cassette 32a or 32b is selected, whereby paper of high frequency in use can be efficiently selected by fewer number of selecting operations. With reference to Figs. 15 to 17, still another embodiment of the present invention will be explained. As shown in Figs. 15 to 16, the image forming apparatus of this embodiment is designed such that the rotatable cassette 80 can be inserted and taken out in and from the main body 81 only when it is in either one of the feeding stations. For example, the rotatable cassette 80 can be inserted and taken out only when it is in the lateral feeding station. The rotatable cassette 80 is mounted on a cassette mounting table 82 which is supported at the center position thereof so as to be rotated by a cassette rotating motor 83 between the lateral feeding station A and the longitudinal feeding station B. One corner of the cassette mounting table 82 is provided with a projection 82a and in the main body 81, there are provided a sensor 84 for detecting that the rotatable cassette 80 is positioned in the lateral feeding station A and a sensor 85 for detecting that the rotatable cassette 80 is positioned in the longitudinal feeding station B, those sensors 84 and 85 respectively being composed of a photointerrupter or similar device used for photo-interruption together with the projection 82a. The main body 81 is also provided with an opening 86 from which the rotatable cassette 80 is taken out or inserted. The opening 86 is a little wider than the lateral length of the rotatable cassette 80 and narrower than the longitudinal length thereof. The rotatable cassette 80 can be, therefore, taken out or inserted only when it is positioned in the lateral feeding station A. In the above arrangement, when the copying machine serving as an image forming apparatus is switched ON or a copying operation is completed (the completion of an image formation), the rotatable cassette 80 is set in the lateral feeding station A which is set as a position from which a cassette is taken out and inserted from and in the main body 81. Since the rotatable cassette 80 is in the lateral feeding station A whenever the rotatable cassette 80 is taken out for supplying paper thereto, it can be readily taken out from the main body 81. There will be given an explanation on the processes of the control operation while making reference to the flow chart of Fig. 17. When the power switch of the copying machine is turned ON, it is determined based on the output signals of the sensors 84 and 85 whether the rotatable cassette 80 is positioned in the lateral feeding station A which is set as a cassette taking-out/insertion position (Step 1). If the rotatable cassette 80 is in the lateral feeding station A, warming-up is immediately started (Step 2). On the other hand, if the rotatable cassette 80 is positioned in the longitudinal feeding station B in Step 1, a cassette rotating motor 83 is actuated to rotate the cassette mounting table 82 through 90° to the lateral feeding station A (Step 3). After changing to the lateral feeding station A, warming-up in Step 2 is started. As described above, in the copying machine of this embodiment, the rotatable cassette 80 is always set in the cassette taking-out/insertion station when the warming-up is started after turning ON the power switch, and therefore the rotatable cassette 80 can be readily taken out from the opening 86. After the warming-up of the copying machine is completed, an automatic paper selection process is performed in accordance with the inputs of the document size detector (not shown), magnification setting key for setting copying magnification (not shown) and the like (Step 4). After selecting the feeding station of the rotatable cassette 82 by the automatic paper selection process, a copying operation is executed (Step 5). Upon completion of the copying operation in Step 5, it is determined again based on output signals from the sensors 84 and 85 whether the rotatable cassette 80 is positioned in the lateral feeding station (Step 6). If the rotatable cassette 80 is positioned in the lateral feeding station A, the process is completed. On the other hand, if the rotatable cassette 80 is in the longitudinal feeding station B in Step 6, the cassette rotating motor 83 is actuated to rotate the rotatable cassette 80 through 90° so as to be positioned in the lateral feeding station A (Step 7). Therefore, the process is completed. Since the rotatable cassette 80 returns to the cassette taking-out/insertion station each time a predetermined copying operation is completed, the rotatable cassette 80 can be readily taken out from the opening 86. In the foregoing embodiments, a copying machine is taken as an example of the image forming apparatus, but it should be understood that the present invention is applied to other image forming apparatus such as laser printers. As described above, the image forming apparatus of the present invention having rotatable cassettes rotated by cassette rotating means between a longitudinal feeding station from which paper is fed in a longitudinal direction thereof and a lateral feeding station from which paper is fed in a lateral direction thereof, is characterized by: (a) memory means for storing a cassette rotation signal for instructing to rotate the rotatable cassette; and (b) control means for permitting the memory means to store the cassette rotation signal when the cassette rotation signal is entered thereof and for controlling the cassette rotating means in accordance with the cassette rotation signal stored in the memory means, when a cassette rotation permission signal for permitting the rotation of the rotatable cassette is generated, so that the rotatable cassette is set in a predetermined feeding station. In the above arrangement, even if a cassette rotation signal is entered a plural number of times before the generation of the cassette rotation permission signals, the rotatable cassette is not rotated at each time. This prevents the useless rotation of the rotatable cassette caused by erroneous operation by the operator etc., reducing noise and ensuring extended service life of the rotation mechanism. Another image forming apparatus according to the present invention which comprises rotatable cassettes rotated by cassette rotating means between a longitudinal feeding station from which paper is fed in a longitudinal direction thereof and a lateral feeding station from which paper is fed in a lateral direction thereof, and is designed such that image formation starts when image formation start instructing means is operated, is characterized by: (a) memory means for storing a cassette rotation signal for instructing to rotate the rotatable cassette; (b) control means for permitting the memory means to store the cassette rotation signal entered therein and for controlling the cassette rotating means in accordance with the cassette rotation signal stored in the memory means when the image formation start instructing means is operated so that the rotatable cassette is set in a predetermined feeding station. In the above arrangement, even if a cassette rotation signal is entered a plural number of times before the actuation of an image formation start key which is the final operation for starting image formation, the rotatable cassette is not rotated at each time. This prevents the useless rotation of the rotatable cassette caused by erroneous operation by the operator etc., reduced noise and ensuring extended service life of the rotation mechanism. Another image forming apparatus according to the present invention which comprises rotatable cassettes rotated by cassette rotating means between a longitudinal feeding station from which paper is fed in a longitudinal direction thereof and a lateral feeding station from which paper is fed in a lateral direction thereof is characterized by: (a) memory means for storing a cassette rotation signal for instructing to rotate the rotatable cassette; (b) timing means for timing a predetermined period; (c) control means for permitting the memory means to store the cassette rotation signal and the timing means to start its timing operation when the cassette rotation signal is entered therein, and for controlling the cassette rotating means in accordance with the cassette rotation signal stored in the memory means when there is no change in the cassette rotation signal stored in the memory means until the completion of the timing operation by the timing means, so that the rotatable cassette is set in a predetermined feeding station. In the above arrangement, even if there is a change in the cassette rotation signal due to erroneous operation by the operator etc. before the completion of the timing operation by the timing means, the rotatable cassette is not rotated at each time. This prevents the useless rotation of the rotatable cassette, reducing noise and ensuring extended service life of the rotation mechanism. Still another image forming apparatus according to the present invention which comprises rotatable cassettes rotated by cassette rotating means between a longitudinal feeding station from which paper is fed in a longitudinal direction thereof and a lateral feeding station from which paper is fed in a lateral direction thereof, and is designed such that image formation is started by the operation of image formation start instructing means, is characterized by: (a) image formation completion detecting means for detecting the completion of image formation; (b) memory means for storing a cassette rotation signal for instructing to rotate the rotatable cassette; (c) control means for permitting the memory means to store the cassette rotation signal entered therein and for controlling the cassette rotating means in accordance with the cassette rotation signal stored in the memory means when the completion of image formation is detected by the image formation completion detecting means after the operation of the image formation start instructing means, so that the rotatable cassette is set in a predetermined feeding station. In the above arrangement, even if a cassette rotation signal is entered after the actuation of the image formation start instructing key until the detection of the completion of the image formation by the image formation completion detecting means, the rotatable cassette is not rotated, thereby preventing the occurrence of a paper jamming. The prevents the useless rotation of the rotatable cassette, reducing noise and ensuring extended service life of the rotation mechanism. Yet another image forming apparatus according to the present invention which comprises rotatable cassettes rotated by cassette rotating means between a longitudinal feeding station from which paper is fed in a longitudinal direction thereof and a lateral feeding station from which paper is fed in a lateral direction thereof, and is designed such that paper is fed from the rotatable cassette by paper feeding means, is characterized by: (a) memory means for storing a cassette rotation signal for instructing to rotate the rotatable cassette; (b) control means for permitting the memory means to store the cassette rotation signal entered therein and for controlling the cassette rotating means in accordance with the cassette rotation signal stored in the memory means when a paper feed completion signal for indicating the completion of the operation of the paper feeding means is generated after the generation of a paper feed start signal for indicating the start of the operation of the paper feeding means so that the rotatable cassette is set in a predetermined feeding station. In the above arrangement, even if a cassette rotation signal is entered after the generation of the paper feed start signal until the generation of the paper feed completion signal, the rotatable cassette is not rotated, thereby preventing the occurrence of a paper jamming. This prevents the useless rotation of the rotatable cassette, reducing noise and ensuring extended service life of the rotation mechanism. Yet another image forming apparatus according to the present invention which comprises rotatable cassettes rotated by cassette rotating means between a longitudinal feeding station from which paper is fed in a longitudinal direction thereof and a lateral feeding station from which paper is fed in a lateral direction thereof, is characterized by: (a) feeding station detecting means for detecting whether the rotatable cassette is positioned in the longitudinal feeding station or the lateral feeding station; (b) control means for controlling the cassette rotating means so as to rotate the rotatable cassette to a predetermined feeding station when a cassette rotation signal for instructing to rotate the rotatable cassette is generated, permitting memory means to store the feeding station in which the rotatable cassette has been set, and controlling the cassette rotating means to reset the rotatable cassette in the feeding station stored in the memory means if the feeding station detecting means detects that the rotatable cassette gets out of the feeding station stored in the memory means, when the cassette rotation signal is not generated. In the above arrangement, in case the rotatable cassette gets out of both longitudinal and lateral feeding station at the time of supplying paper to the rotatable cassette and hence normal paper feed can not be continued, image formation can be smoothly performed without the operator's instruction to rotate the rotatable cassette since the rotatable cassette is rotated to the most lately selected feeding station which is stored by the memory means. Yet another image forming apparatus according to the present invention which comprises (a) a plurality of cassettes including rotatable cassettes rotated by cassette rotating means between a longitudinal feeding station from which paper is fed in a longitudinal direction thereof and a lateral feeding station from which paper is fed in a lateral direction thereof; (b) image formation start instructing means for instructing to start image formation; (c) cassette display means for displaying a selected cassette; and (d) paper display means for displaying the size and feeding direction of paper stored in a selected cassette, and indicating the longitudinal feeding and lateral feeding as to paper stored in a selected rotatable cassette, is characterized by: (1) cassette changeover instructing means for instructing to change the cassette; (2) memory means for storing the feeding direction of the paper displayed by the paper display means; (3) feeding station detecting means for detecting whether the rotatable cassette is set in the longitudinal feeding station or the lateral feeding station; and (4) control means for successively switching the cassette display means and paper display means which correspond to each cassette when the cassette changeover instructing means is operated, permitting the memory means to store the feeding direction of the paper displayed by the paper display means which has been selected by the above changeover operation, and controlling the cassette rotating means such that the feeding station corresponding to the paper feeding direction stored in the memory means when the rotatable cassette is selected by the cassette changeover instructing means and the image formation start instructing means is operated, is made coincident with the feeding station in which the rotatable cassette is positioned detected by the feeding station detecting means, when those feeding stations are different from each other. In the above arrangement, the selection of a cassette and the instruction to rotate the rotatable cassette can be performed by the same cassette changeover instructing means, thereby reducing the number of parts in the image forming apparatus. Further, when the rotation of the rotatable cassette is required, the rotatable cassette is not rotated before the selection of a cassette or the instruction to rotate the rotatable cassette is determined, but performed only when the image formation start instructing means is operated. This prevents the useless rotation of the rotatable cassette. Still another image forming apparatus according to the present invention which comprises rotatable cassettes rotated by cassette rotating means between a longitudinal feeding station from which paper is fed in a longitudinal direction thereof and a lateral feeding station from which paper is fed in a lateral direction thereof, the rotatable cassette being designed to be inserted and taken out in and from the image forming apparatus, when it is positioned in a predetermined feeding station, is characterized by: (a) feeding station detecting means for detecting whether the rotatable cassette is positioned in the longitudinal feeding station or the lateral feeding station when the image forming apparatus is switched ON and/or an image formation is completed; (b) control means for controlling the cassette rotating means so as to rotate the rotatable cassette to a feeding station set as a rotatable cassette taking-out/insertion position, when the feeding station detected by the feeding station detecting means differs from the feeding station set as a rotatable cassette taking-out/insertion position. In the above arrangement, when an image formation is completed or the image forming apparatus is switched ON, the rotatable cassette is set in a feeding station determined as a rotatable cassette taking-out/insertion position, so that the rotatable cassette is always in a position from which it can be taken out whenever supplying paper to the rotatable cassette. The invention being thus described, it will be obvious that the same may be varied in many ways within the scope of the claims.

Claims: An image forming apparatus having at least one paper feeding cassette (32a), said cassette (32a) being rotatable between a first and second position to feed paper either in a longitudinal or lateral orientation respectively, characterised by the apparatus being arranged to delay a cassette movement signal for initiating movement of said cassette (32a) until generation of a cassette movement permission signal. An image forming apparatus as claimed in claim 1, wherein said cassette movement permission signal is generated by operating an image formation start instructing means (41). An image forming apparatus as claimed in claim 1, wherein after operation of an image formation start instructing means said cassette movement permission signal is generated following completion of an image formation. An image forming apparatus as claimed in claim 1, wherein after generation of a paper feeding start signal said cassette movement permission signal is generated following completing the paper feeding. An image forming apparatus as claimed in any preceding claim, wherein there is provided a memory means for storing said cassette movement signal and control means for permitting said cassette movement signal to be stored in said memory means and for initiating movement of said cassette (32a) by said stored cassette movement signal in response to said cassette movement permission signal. An image forming apparatus having at least one paper feeding cassette (32a), said cassette (32a) being selectively rotatable between a first and a second position to feed paper either in a longitudinal or lateral orientation respectively, characterised by the apparatus being arranged to detect deviation of the cassette (32a) from the most recently selected one of said positions and, in the absence of a cassette movement signal for initiating movement of the cassette (32a) from said most recently selected position to return the cassette (32a) to said most recently selected position. An image forming apparatus having a plurality of paper feeding cassettes (28, 29, 32a, 32b), at least one of said paper feeding cassettes (28, 29, 32a, 32b) being rotatable between a first and second position to feed paper in either a longitudinal or lateral orientation respectively; a cassette display means (CSL) for displaying a selected paper feeding cassette; a paper display means (PSL) for displaying paper size and orientation; and cassette changeover instructing means (74), characterised by control means responsive to repeated operation of the cassette changeover instructing means (74) to advance through a sequence of paper selection modes, said modes each involving a given paper cassette and a paper size and orientation available using that cassette, and to control the operation of said cassette display means (CSL) and paper display means (PSL) so as to indicate the cassette, paper size and paper orientation involved in each currently selected paper selection mode, whereby a minimum number of cassette changeover instructing means (74) is required for selection between the paper feeding cassettes and the different positions thereof. An image forming apparatus as claimed in claim 7, wherein when said cassette display means (CSL) indicates the or a rotatable cassette (32a, 32b), said control means determines the position of said rotatable cassette (32a, 32b) and, upon operation of image formation start instructing means, alters its position, if necessary, to conform with the paper orientation of the paper selection mode indicated by said paper display means (PSL). An image forming apparatus as claimed in claim 7 or 8, wherein said cassette display means (CSL) are cassette display lamps and said paper display means (PSL) are paper size lamps. An image forming apparatus as claimed in claim 8, wherein said image formation start instructing means comprises an image formation start key (41) and said control means comprises sensors (HP₁, HP₂) for determining the position of said rotatable cassette (32a, 32b). An image forming apparatus as claimed in any of claims 7 to 10 comprising a plurality of rotatable cassettes (32a, 32b) for respectively storing A4 size paper and B5 size paper, and a plurality of fixed cassettes (28, 29) for respectively storing B4 size paper and A3 size paper and a manual paper feeder (30). An image forming apparatus as claimed in claim 9 wherein the paper size display lamps respectively correspond to A3 size, B4 size, A4 size, A4R size, B5 size and B5R size. An image forming apparatus as claimed in any preceding claim, wherein said image forming apparatus is controllable by a microcomputer (51). An image forming apparatus as claimed in any preceding claim, wherein said cassettes (32a, 32b) are rotatably disposed within an outer box (31a, 31b), said outer box (31a, 31b) being adapted to be removable from or insertable into said image forming apparatus. An image forming apparatus having at least one paper cassette (80), said cassette (80) being rotatable between a first and a second position to feed paper in either a longitudinal or lateral orientation respectively, the apparatus being adapted such that said cassette (80) is insertable into and removable from said apparatus when said cassette (80) is in a predetermined one of said positions, characterised by the apparatus being arranged to detect a position of said cassette (80) on switching on said apparatus or on completion of an image formation and, if the detected position differs from said predetermined position, to move said cassette (80) to said predetermined position. An image forming apparatus as claimed in claim 15, having sensors (84, 85) for detecting said position. An image forming apparatus as claimed in claim 16, wherein said sensors (84, 85) comprise a sensor (84) for detecting that said cassette (80) is in a longitudinal position and a sensor (85) for detecting that said cassette (80) is in a lateral position. An image forming apparatus as claimed in claim 15 or claim 16, wherein said predetermined one of said positions of said cassette is said second position thereof. An image forming apparatus as claimed in any preceding claim, wherein said image forming apparatus is a copying machine or laser printer.

Inventors: ISHIKAWA KATSUTOSHI, KAJIWARA JUNICHI, MATSUO TOSHIHISA, MORI YOSHITERU, NARUKAWA ATSUSHI, NODA YOSHIYUKI, OKADA TADASHI, TANIGUCHI HIDEO, TOYODA MASASHI, YAMADA YOSHIKADO, ISHIKAWA, KATSUTOSHI, KAJIWARA, JUNICHI, MATSUO, TOSHIHISA, MORI, YOSHITERU, NARUKAWA, ATSUSHI, NODA, YOSHIYUKI, OKADA, TADASHI, TANIGUCHI, HIDEO, TOYODA, MASASHI, YAMADA, YOSHIKADO
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1989
Main classification: G03G15
IPC codes: G03G15