SHEET FEED DEVICE

Abstract: A sheet feed device (5), for instance for a recording apparatus, for feeding sheets one-by-one from sheet receiving cassettes (1, 2) which are stacked one above another. Each cassette (1, 2) has a sheet sub-­ passge (34) penetrating the cassette from bottom to top. The sub-passages (34) are disposed such that they are positioned in alignment to form a common sheet feed passage penetrating the stack of the cassettes from bottom to top when all the cassettes are set in normal positions, and individual sheet feed passages (6) formed in the cassettes (1, 2) are joined to the common sheet feed passage. With the above configuration, sheet supplement operation to the cassettes (1, 2) and sheet jam clearing operations can be performed from the same side of the device, saving office space.

Description: The present invention relates to a sheet feed device for feeding a cut sheet, for example a cut paper sheet, for instance to an image transfer station or a printing station in a recording apparatus. It also relates to a sheet feed device wherein stacked cut recording sheets of different types, different in size or sheet quality, are held in corresponding cassettes and fed selectively one sheet at a time, for instance to an image transfer or a printing station. As typical example of apparatus with which a sheet feed device is used, a recording apparatus, in this case a laser electrophotographic recording apparatus will be described. In such recording apparatus, a photoconductive medium formed on the surface of a drum is charged to a substantially uniform potential to sensitize the surface thereof. The charged portion of the photoconductive surface is exposed to a light image of an original document to be reproduced. This results in formation of an electrostatic latent image on the photoconductive medium corresponding to the information areas contained within the original document. Thereafter, the latent image is developed by bringing a developer material into contact therewith. This forms a toner powder image on the photoconductive medium which is subsequently transferred to a recording sheet. Finally, the recording sheet is heated to permanently affix the toner powder image on the recording sheet. Generally, recording sheets used in recording apparatus are of a ribbon-like continuous sheet type of a single size, or of a cut sheet type having various sizes. The present invention is primarily concerned with the handling of recording sheets of cut sheet type. Such cut (non-continuous) recording sheets will be referred to simply as sheets hereafter. Sheets of one type (determined for example by size and/or quality) are held stacked in alignment in one cassette-like sheet holding means (hereinafter, referred to as a cassette). Usually, a plurality of cassettes are stacked one above another, forward drawably in supporting means such as shelves or rails fixed to a frame. Each cassette has a signal actuator for signifying the sheet type of sheets held therein. Fig. 1 and Fig. 2 are schematic diagrams illustrating the arrangement of prior art sheet feed devices. In the apparatus of Fig. 1, cassettes 101 and 102 are disposed so that they project out of an apparatus housing 103, thus taking up floor space in the office in which the apparatus is installed. A sheet delivered from cassette 101 is fed through a transfer passage 104, and a sheet delivered from cassette 102 through a feed passage 105. Sheets from both cassettes are fed to an image transfer station 109 one-by-one. In the transfer station a toner image formed on a photoconductive drum 106 is transferred onto a sheet by an image transfer member 107. Thereafter the sheet is fed through a passage 110 indicated by an arrowed line to an image fixer 108 for fixing the transferred image. The surface of the drum 106 is electrically discharged and cleaned by a discharger (not shown) after the image transfer. In the apparatus of Fig. 2, cassettes 111 and 112 are disposed stacked one above another at a lower portion of a housing 113 of a recording apparatus. A sheet delivered from cassette 111 is fed through a feed passage 114, and a sheet from cassette 112 through a feed passage 115. Through a drive roller pair 125 and a conveying passage 122, sheets from both cassettes are conveyed to an image transfer station 119. In the image transfer station a toner image formed on a photoconductive drum 116 is transferred onto a sheet by an image transfer member 117, and thereafter the sheet fed through conveying passage 122 indicated by an arrowed line to an image fixer 118 for fixing the transferred image. A manual feed passage 123 is disposed through the wall at a side F of the housing 113, facing the feed roller pair 125. The surface of the drum 116 is electrically discharged and cleaned by a discharger (not shown) after image transfer. A rectangular shape 120 indicated by a chain line in Fig. 2 represents a mechanism wherein the two feed passages 114 and 115 are joined to a common transfer passage 121 through which the sheets are delivered from the cassettes 111 and 112 to the conveying passage 122. Naturally, the structure 120 prohibits loading and unloading operation of the cassettes 111 and 112 from the side F of the housing 113, so these operations must be performed from the opposite side B of the housing. Thus, a sheet, if required, is fed manually through the manual feed passage 123 (namely from the side F). Further, in the event of sheet jamming in the cassettes 111 or 112, a jammed sheet or sheets must be removed by opening various portions of the housing 113. Sheet jamming tends to occur in the vicinity of a portion of the relevant cassette where a sheet is delivered from the cassette (namely at the side F). Operations to clear the sheet jam and resume recording operation are not easy and can be time consuming. Thus, in order to provide for manual sheet feed operation, and for jam clearing operations, floor space is required for an operator in front of the side F. Thus two spaces for operation, at both sides F and B of the housing 113, must be maintained in the office, reducing freedom of lay-out of the apparatus in the office and taking up floor space. The mechanism 120 has an adverse effect so far as office space-saving is concerned, which is an important consideration for the users of an office machine. The restrictions on placing of a sheet-feed device, for instance with its associated recording apparatus, within office space, due to the requirements of operational access or projecting cassettes, for example for operational access for loading and unloading sheets to or from the cassettes, is a disadvantage. Further, in prior art sheet feed means, the signal actuator used to signify the sheet type field in a cassette is of a fixed type. That is, it indicates only one sheet type peculiar to the cassette. As a result, a cassette specified to hold sheets of one type cannot be used as a cassette for receiving sheets of a different sheet type. EP-A-0 139 426 discloses a sheet feed means for a printer comprising also a plurality of paper trays or sheet holding means. According to the present invention there is provided sheet feed means, for recording apparatus for recording an image on a sheet, the sheet feed means comprising:- a plurality of sheet holding means, disposed one above another, each capable of holding a stack of sheets, and supporting means for supporting each of said plurality of sheet holding means in a predetermined normal position thereof, in a forwardly drawable state; each of said sheet holding means comprising:- an individual sheet feed passage, disposed forwardly of the sheet holding means, for passing therethrough a sheet fed from the stack of sheets in the sheet holding means, characterised in that each of said sheet holding means comprises:- a sheet feed sub-passage, disposed forwardly of the sheet holding means and penetrating through the sheet holding means, from bottom to top; the sheet feed sub-passages, when the members of said plurality of sheet holding means are set in their normal positions in the supporting means, being disposed so as to be serially aligned to constitute a common sheet feed passage which is operatively connected with each of the individual sheet feed passages, the common sheet feed passage allowing the passage therethrough of a sheet fed from any of the individual sheet feed passages. According to the present invention there is also provided sheet feed means for recording apparatus for recording an image on a sheet, the sheet feed means being capable of holding sheets of a plurality of sheet types and selectively feeding said sheets to sheet conveying means, and the sheet feed means comprising:- a housing having a pair of facing side walls; a plurality of pairs of rails disposed along the side walls of the housing, the pairs being arranged one pair above another, spaced one pair from another; a plurality of sheet holding means, each of which is supported, forwardly drawably, by a corresponding pair of rails, stacked one above another and spaced from each other with a small intervening space; and a sheet discharge outlet discharging a fed sheet, the outlet being disposed at an upper portion of the sheet feed means; characterised in that each of the sheet holding means comprises:- a guide path disposed forwardly thereof and passing through the sheet holding means from bottom to top, and a guide plate for guiding a sheet fed from the stack of sheets in the sheet holding means, guiding the sheet into the guide path; the guide paths in the respective sheet holding means being disposed such that in combination they form a common guide path passing through the stack of sheet holding means, from bottom to top of the stack, extending to the discharge outlet, when all the sheet holding means are set at predetermined positions. According to the present invention there is further provided recording apparatus for recording an image on a sheet, including sheet holding means for holding a plurality of sheets stacked in alignment in the sheet holding means, characterised in that the sheet holding means includes:- a sheet feed through-passage disposed towards one end of the sheet holding means, from which end the sheet holding means can be drawn out of the apparatus, and which through-passage penetrates the sheet holding means from bottom to top of the sheet holding means, the sheet feed through-passage having an inlet opening at the bottom and an outlet opening at the top of the sheet holding means. An embodiment of the present invention can provide a sheet feed device, for example for recording apparatus, which requires operational access from one side only for supplementing sheets in a cassette and for disposing of jammed sheets, if any. That is, an embodiment of the invention can provide a structure which enables cassettes to be drawn from the side of the structure where the sheet delivery outlet is disposed in the relevant cassette. An embodiment of the present invention may additionally provide for the use of a sheet cassette having sensor means which are selectively, e.g. manually, changeable, to indicate different sheet types in the cassette. This can enhance the freedom with which the cassette can be used. The actuator or sensor means may be such that it can be manually changed by an operator or automatically changed by a controller of the apparatus in accordance with requirements in individual cases. Reference is made, by way of example, to the accompanying drawings, in which:- Fig. 1 is a schematic diagram illustrating the configuration of a prior art sheet feed device; Fig. 2 is a schematic diagram illustrating the configuration of another prior art sheet feed device; Fig. 3 is a diagram illustrating in outline a sheet feed device according to an embodiment of the present invention; Fig. 4 is a cross-sectional side view of a recording apparatus employing an embodiment of the present invention; Fig. 5 is a perspective view of the structure of a cassette in Fig. 4; Fig. 6 is a schematic perspective view of a composite passage provided in the apparatus of Fig. 4, illustrating the spatial relationships of sub-passages and individual passages in the cassettes; Fig. 7 is a cross-sectional view of the apparatus of Fig. 4, illustrating one cassette set in a normal position, and another cassette drawn out of the apparatus, decomposing or disassembling the composite passage; Fig. 8 is a substantially schematic perspective view of a cassette illustrating mutual positional relationships between a signal actuator unit and a sensor; Fig. 9 is a schematic front view of a cassette illustrating relative positional relationship between a sensor and a signal actuator unit; Fig. 10(a) to 10(f) are diagrams illustrating positional relationships between sensor and signal actuator unit for various dispositions of the signal actuator unit; Fig. 11 is an enlarged perspective view of a signal actuator unit as shown in Fig. 5, illustrating the structure thereof; Fig. 12 is a schematic circuit diagram of a signal processor employed in an embodiment of the present invention; Fig. 13 is a table numerically representing the relationship between ON and OFF states of microswitches, analog signal voltages and digital signal voltages shown in Fig. 12; Fig. 14 is a schematic cross-sectional front view of a modified sensor means according to an embodiment of the present invention; Fig. 15(a) and Fig. 15(b) are schematic front views of the sensor means of Fig. 14; Fig. 16 is a schematic cross-sectional side view of a recording apparatus employing another embodiment of the present invention, having cassettes each accommodated in an individual cassette housing; and Fig. 17 is a schematic cross-sectional side view of a recording apparatus employing another embodiment of the present invention, including a sheet hopper at the bottom of the apparatus. Fig. 3 illustrates in outline recording apparatus with a sheet feed device 5 in accordance with an embodiment of the present invention. The sheet feed device 5 in this exemplary embodiment of the invention comprises two sheet cassettes 1 and 2 arranged one above another with a supporting means 4 for supporting the cassettes 1 and 2 so that they are forwardly drawable. The supporting means 4 is represented by broken lines and is disposed inside an apparatus housing 21. Sheet feed drive rollers 43 and 51 are secured to the supporting means 4. Each cassette 1 or 2 has a sheet feed sub-passage or through passage (hereinafter, simply referred to as a sub-passage) 34 which is disposed at a forward side thereof and penetrates through the cassette 1 or 2 from the bottom to top of the cassette, and a follower roller 37 disposed in the upper portion of the cassette 1 or 2. The cassettes 1 and 2 are adapted in the supporting means to be set at a predetermined position, which is hereinafter referred to as 'the normal position', such that all the sub-passages 34 of the cassettes 1 and 2 are positioned so as to compose a composite common sheet feed passage 3. Hereby, all the sub-passages are positioned in alignment. So, the composite common sheet feed passage is not of one body or unitary structure, but is composite and decomposable or disassemblable; namely parts forming the composite passage can be detached from one another. At the same time, the follower rollers 37 form respective sheet feed rollers pairs in combination with drive rollers 43 and 51. Each sub-passage 34 has an outlet 34a and an inlet 34b, and has a side opening, opened to face to the back of the cassette 1 or 2. Each cassette 1 or 2 has a guide plate (not shown) adjacent to the sub-passage 34. Along a curved surface of the guide plate, an individual sheet feed passage 6 (shown in Fig. 6) is formed, through which sheets stacked in a cassette 1 or 2 are advanced one sheet at a time. Thereafter, the sheet changes its feed direction upwardly, entering the composite common sheet passage 3, and being discharged out of the sheet feed device 5 from the outlet 34a of the upper cassette 1. In this example, the discharged sheet is conveyed through a conveying passage 44 shown by an arrowed line, with the aid of drive roller pairs 45, 46, 47 and 48. During passage through the conveying passage 44, an image developed on the surface of a photoconductive drum 24 is transferred to the sheet by an image transfer means 28, at the image transfer station 42, and fixed on the sheet by an image fixer 29. Then the recorded sheet is discharged from the apparatus. With the above-described configuration of sheet feed device, the cassettes 1 and 2 are drawably provided so that they can be drawn out of the housing 21 towards the front side F of the recording apparatus, since there is no single-body structure for guiding and feeding sheets delivered from each cassette as in the prior art apparatus of Fig. 2. Each of the above-described cassettes 1 and 2 of this exemplary embodiment of the invention has improved sensor pair means comprising a sensor (not shown) fixed to the housing 21 and an actuator (not shown) fixed to the cassette 1 or 2 to identify the type of cut sheets received in each cassette 1 or 2. The actuator is manually displaceable to change the sense signal indicating the sheet type received in the cassette. As a result, a cassette can receive sheets of different sheet types, enhancing the freedom with which the cassettes can be used. A signal processor for dealing with the above-described sense signal is also provided. Furthermore, a manual feed passage 44a is disposed on the wall of the housing 21 at the F side. The manual feed passage is positioned facing the feed roller pair 45. A sheet, if so required, is fed manually through the manual feed passage 44a. Fig. 4 is a cross-sectional side view of a recording apparatus employing a further exemplary embodiment of the present invention. To an extent, the apparatus has a conventional electrophotographic machine structure, comprising a photoconductive drum 24, a precharger 25, an optical system 26, an image developer 27, an image transfer device 28, an image fixer 29, a cleaner 30, and an apparatus housing 21 which encloses the above members thereinside. Descriptions of functions of the above-described members is omitted because their functions are the same of those of corresponding items in prior art apparatus. Sheet feed device 5 is the main concern of the present invention. The sheet feed device 5 is in this exemplary embodiment in a lower portion 21a of the apparatus housing 21. Two cassettes 1 and 2 are disposed inside the lower portion 21a, being stacked one above another, and supported by accommodating shelves 22 and 23 which are horizontally disposed inside the lower portion 21a of the apparatus housing 21 as shown in Fig. 4. In the frame of the apparatus housing 21, there are provided separating rollers 38 and 39, having segmental cross-sections, and feed rollers 43 and 51. The feed rollers 43 and 51 form feed rollers pairs respectively in combination with follower rollers 37 disposed in the cassette 1 and cassette 2, when the cassettes 1 and 2 are set in the normal position. Furthermore, similarly to the prior art recording apparatus of Fig. 2, a manual sheet feed passage 44a and the relevant sheet feed roller pair 45a are disposed on the F side of the housing 21. A sheet, if required, is fed through the passage 44a by hand of an operator. The structural of cassette 1 will be described in more detail referring to the cross-sectional view of Fig. 4 and the perspective view of Fig. 5. The cassette 1 has a frame box 10 which is adapted to the accommodating shelf 22 at the normal position of the cassette. The normal position is held steadily by enabling locking means including a lock finger 58 disposed on the upper portion of the cassette 1. Here, the front sie of the cassettes 1 and 2, that of the sheet feed means 5, and that of the recording apparatus, are defined as the side where the sheets are discharged from the cassettes 1 and 2. In the present invention, these front sides are coincident, and are designated by the reference letter F in the drawings. In the cassette 1, a receiving plate 32 is pivotally mounted around an axis portion 15 at the middle portion of the bottom of the box frame 10. Coil springs 31 energise (urge) the receiving plate 32 upwards. Restrict plates 11 and 13 having upstanding walls are movably mounted on the bottom floor of the frame box 10 through slidable fix members 12 and 14 respectively, being slidable in a lateral direction indicated by arrows Y. Another restrict plate 16 is mounted in a similar manner by the aid of a slidable fix member 17, being slidable in a longitudinal direction indicated by an arrow X. The front half portion of sheets stacked in alignment in the cassette 1 is placed on the receiving plate 32, and the horizontal (lateral) position of the stacked sheets is restricted by the restrict plates 11 and 13 contacting with one of the longitudinal side ends of the sheets, and the longitudinal position of the sheets is restricted by the restrict plate 16 contacting with the rear edge of the sheets. The position of the restrict plates 11, 13 and 16 is adjustably fixed in advance, depending on the size of sheets to be received, with the aid of respective slidable fix members 12, 14 and 17. A pair of separate hook members 33 are disposed adjacent to the leading front edge of the receiving plate 32 for hooking the leading front edge of the stacked sheets from the top side. Sheet jamming is an undesirable problem peculiar to a sheet feed device. One of the causes thereof is an excessive separating pressure exerted on the stacked sheets by rotation of a separating roller 38 or 39. This is caused by overloading of sheets, which excessively compresses the coil springs 32, disposed below the receiving plate 32, to a dead point, allowing no further compression thereof. To avoid such overloading, the height H of the restrict plates 11, and 13 and 16 is selected to limit the height of the stacked sheets to an appropriate height sufficient to eliminate sheet overloading. At the front side 10f of the box frame 10, sheet feed means is provided comprising:- a sub-passage 34 (a through-passage), a guide plate 35, a follower roller 37 and a platform 59 formed at the front of the frame box 10. The sub-passage 34 is defined by slanted passage side walls 36a and 36b penetrating through the cassette 1, having an outlet 34a on the top side and an inlet 34b on the bottom side. The passage side wall 36a extends from the bottom side to the top side of the cassette 1. The passage side wall 36b is shorter than the side wall 36a, facing the lower portion of the side wall 36a. As a result, the sub-passage 34 has an open-sided portion 34c (refer to Fig. 6) in the upper portion thereof where the side wall 36b does not exist. The open-sided portion 34c is located in line with a curved guide surface of the guide plate 35. The upper edge of the guide plate 35 is placed adjacent to the front edge of the receiving plate 32 and in parallel to the edge. The follower roller 37 is located just above the outlet 34a of the sub-passage 34, being rotatable around a horizontal shaft 37a which is supported by idle holes 60a opened in supporting plates 60 upstanding on the two sides of platform 59. The follower rollers 37 are resiliently pressed in a direction indicated by an arrow z by a spring plate 55. The lower end of the spring plate 55 is secured to a base portion 56 of the frame box 10 which is schematically shown in Fig. 4 by a small hatched square. The cassette 1 also has locking members consisting of vertically slidable lock fingers 58 disposed on the platform 59. Furthermore, a signal actuator unit 70 composed of a groove 72 and a slide cam 71 displaceable along the groove 72 is provided. The signal actuator will be described later. Fig. 6 is a schematic perspective view of a composite common passage 3 illustrating the spatial relationship of sub-passage 34 and the individual passages 6 of each cassette 1 or 2. When both cassettes 1 and 2 are received, as shown in Fig. 4, in the accommodating shelves 22 and 23 respectively, and set in the normal position, the composite common sheet passage 3 is composed of sub-passages 34 which are disposed in alignment in series. As easily seen, each of individual passages 6 joins with the composite common passage 3 at the relevant open-sided portion 34c of each sub-passage 34. A sheet is advanced by roller pairs composed of the rollers 37 and 43, or by rollers 37 and 51. Of course, the thus defined composite common passage 3 is easily decomposed or disassembled by drawing a cassette 1 or 2 off its accommodating shelves 22 or 23 towards the front side F. In the embodiment of Fig. 4, the sub-passage 34 of the lower cassette 2 is actually unnecessary, and may be omitted, because no sheet is transferred from a cassette disposed therebelow (in this exemplary embodiment). However, providing the same structure for both cassettes 1 and 2 gives users a favourable benefit in that the cassettes are exchangeable, and gives makers the advantage of reducing production costs of the recording apparatus. It will be clear that embodiments of the invention, using a configuration similar to that described above for two stacked cassettes, can provide sheet feed devices having three or more cassettes. Fig. 7 is a cross-sectional view of the apparatus of Fig. 4 illustrating cassette 2 already set in the normal position and cassette 1 pulled out. Subsequently, cassette 1 is pushed into the accommodating shelf 22, and locked in the normal position. As a result, the sub-passages 34 are aligned defining a composite common passage 3, and the follower rollers 37 are respectively pressed against the feed rollers 43 or 51 forming contact portions therebetween, ready for feeding a sheet from either of cassettes 1 and 2. The function of the sheet feed device 5 will be described briefly referring to Figs. 4, 5 and 6. Except so far as the constitution of the sheet feed passages is concerned, the function of the device is similar to that of a conventional sheet feed device. Pluralities of cut recording sheets, each of a sheet type having the same dimensions and the same sheet quality, are received in respective cassettes 1 and 2, being stacked in alignment with the aid of restrict plates 11, 13 and 16. The leading half portion of the stacked sheets in a cassette, for example cassette 1, are received by the receiving plate 32, being subjected to an upwardly directed pressure applied by the receiving plate 32 urged by the coil springs 31. The leading end of the uppermost sheet of the stacked sheets is hooked by the separate hook members 33. Sheets, which may be of different sheet type from those in cassette 1, are similarly received in cassette 2. Operations to feed sheets from cassette 1 will be described, with sheets in cassette 2 left unfed. When the separating roller 38 starts, selectively controlled by a printing controller (not shown), the uppermost sheet of the stacked sheets is separated from the stack in a well-known manner, escaping from hooking by the separate hook members 33, and being advanced forwardly along the individual passage 6 defined by the surface of the guide plate 35, entering the contact portion between the rollers 37 and 43 through the open-sided portion 34c, and being further forwardly transferred into the composite common sheet passage 3, finally being discharged from the outlet 34a of the uppermost cassette 1, and being sent into an introducing passage 44 in the main part of the apparatus. In the above case, the separating roller 39 is selectively disenabled under the control of the printing controller. Each of the separating rollers 38 and 39 has a positive disk clutch (not shown) comprising a driving member and a driven member. The driving members of both clutches are simultaneously driven by a commonly engaged drive belt (not shown) according to an appropriate time schedule for sheet feeding, and the driven members are fixed to a shaft 37a and another shaft (not shown) of the separating rollers 38 and 39 at each end of the shaft. The separating roller 38 or 39 is selectively rotated by selectively engaging the relevant clutch and selectively disengaging the other clutch. As described above, sheet jamming in a sheet-feed device, e.g. for a recording apparatus, tends to occur in the vicinity of a sheet discharge outlet of the relevant sheet feed device. In this embodiment of the present invention, the cassettes 1 and 2 can be drawn out from the side F of the apparatus housing 21. As seen from the drawings, the side F is adjacent to the discharge outlet 34a of the composite passage 3. As a result, sheet jamming disposal can be performed by drawing out the cassettes 1 and 2, with no need to open up the apparatus housing 21 (for example by opening access panels). In addition, as described above, a sheet can be fed manually by the operator through the manual feed passage 43a which is disposed on the F side of the housing 21. Thus, from the F side of the apparatus, the operator can load or unload sheets in the cassettes, can feed a sheet manually, and can also deal with a sheet jam, if such occurs. No further space is needed for operating the recording apparatus, such as a space at the B side of the apparatus, providing thus for space saving in the office environment. This is a distinct advantage as compared with the prior sheet feed devices of Figs. 1 and 1. As indicated above, embodiments of the present invention may employ signal actuator and sensor means, for designating and detecting sheet type in a cassette, which enable the same cassette to be used for different sheet types whilst appropriate sheet type designation and detection are provided. In the description of the exemplary embodiment of Fig. 4, a signal actuator unit 70 has been briefly described (Fig. 5). Signal actuator and sensor means which may be employed in embodiments of the invention will now be described in more detail. First, a signal actuator unit 70, as shown in Fig. 5 and a sensor 90 set in a pair therewith will be described with reference to Fig. 8. The actuator unit 70 is disposed in a forward portion on a side wall 10a of the frame box 10 of the cassette 1 for example. The sensor 90 is secured to a frame member 4 of the feed device 5. Fig. 8 is a substantially schematic perspective view of cassette 1 illustrating the mutual positional relationships between the signal actuator unit 70 and a sensor 90 only. The signal actuator unit 70 is disposed movably in both directions perpendicular to the major plane of the cassette 1, as indicated by arrows A and A′. The sensor 90 is composed of three microswitches 91a, 91b and 91c, being disposed side by side in the direction A-A′, and facing the signal actuator unit 70. Each microswitch has a single actuating button axially movable for switching the microswitch ON or OFF. The buttons are positioned on a line separated from each other with a fixed pitch p. The signal actuator unit 70 is composed of a slide cam 71 and a groove 72 (shown in Fig. 5). The slide cam 71 has projecting portions 75 and 76, and a depressed portion 77, being manually movable along the groove 72 with the pitch p. As a result, the position of the signal actuator unit 70 can be changed (stepped) by the pitch p or multiples of that pitch. In contrast, the position of the sensor 90 is fixed. The relative positions of the signal actuator unit 70 and the sensor 90, therefore, can be varied by the pitch of the arrangement of the microswitches 91a to 91c, or multiples of that pitch. Thus, the signal pattern output from the sensor 90 is changeable corresponding to the type of the sheets received in the relevant cassette 1, by displacing the slide cam 71 in the direction A-A′ by the pitch p or a multiple thereof. Fig. 9 is a schematic front view of cassette 1 illustrating one possible relative positional relationship between the sensor 90 and the signal actuator unit 70. When cassette 1 is set in the normal position, the sensor 90 and the signal actuator unit 70 are in the engaging position. A microswitch engaging with one of the projected portions 75 and 76 is made ON, and a microswitch engaging with the depressed portion 77 is made OFF. Figs. 10(a) to (f) are diagrams illustrating the different positional relationships between the sensor 90 and the signal actuator unit 70 for various positions of the signal actuator unit 70, which is manually displaced by an operator. The sensing means 7 is in this example capable of designating six different sheet types with respective different signal patterns, which correspond to six different three-bit digital signals. These digital signal patterns are transferred to a signal identify processor (not shown) employing three connecting wires per cassette, being identified thereby, and being sent to the printing controller to control relevant devices such as the separating rollers 38 and 39. With the above-described configuration of the signal actuator unit 70, the operator can set a signal pattern for the cassette 1, corresponding to the type of sheets received in the cassette 1, by hand. The number of different sheet types which can be designated is increased to six (as compared to one in the prior art), enhancing the freedom with which the cassette 1 can be used. Of course, this advantage is also available with respect to cassette 2 (or any further cassettes provided). Fig. 11 is a magnified perspective view of the signal actuator unit 70 shown in Fig. 5. The slide cam 71 and the slide wall 10a of the frame box 10 are made of plastics material. The groove 72 comprises a slit 73 opened in the side wall 10a in the direction A-A′ as shown in Fig. 8, and a stepped portion having a back side stepped wall 79 on which a plurality of depressed portions 77 are formed in parallel running in the direction A-A′ with pitch p. The slide cam 71 has a resilient plastic finger 74 extending in a direction perpendicular to the major surface of the side wall 10a through the slit 73. The finger 74 has a hook member 74a at the tip engaging with the surface of the side wall 10a. By means of the hook 74a, the slide cam 71 is resiliently and slidably pulled towards the side wall 10a. The slide cam 71 further has protruded portions 78 on the back side of the projected portions 75 and 76, the protruded portions 78 being designed to fittably engage with the depressed portions 79. With such a structure, the slide cam 71 is movable stepwise with pitch p by hand in the direction A-A′. In an embodiment of the present invention a system for processing digital signals provided by the sensor 90 in combination with the signal actuator unit 70 may be employed which is different from that described above. In the above-described example, three-bit digital signals are sent to the printing controller through three connecting wires (per cassette). In order to reduce the number of such connecting wires, a signal processor 80 may be employed having a wiring diagram as shown in Fig. 12. The microswitches 91a, 91b and 91c, respectively designated by SW1, SW2 and SW3 in Fig. 12, are connected in series to ground and to a voltage source V (+5V) through a series resistor R1. The signal processor 80 comprises a detector 85, an AD converter 86, and the printing controller 87. The detector 85 comprises a diode D1 connected to the microswitch 91a in parallel, two diodes D2, D3 connected in series with one another and connected to the microswitch 91b in parallel and four diodes D4, D5, D6, D7 connected in series with one another and connected to microswitch 91c in parallel. The voltage source V, the resistor R1, and the diodes D1 and D7 are connected in series in said order and grounded. These diodes D1 to D7 act as voltage dividing means. The node N between the resistor R1 and the diode D1 is connected to an output terminal T, represented by a small circle, through a resistor R2. The terminal is grounded through a resistor R3, and the signal voltage Vin at the terminal T is applied to the AD converter 86 through a single wiring line L1. The combination of ON and OFF states of microswitches SW1, SW2 and SW3 varies the voltage Vs at the node N stepwise. The voltage Vs is reduced to the Voltage Vin by the ratio R3/(R2+R3). The voltage Vin provides an analog signal which is converted into an eight-bit digital signal SiDT through the AD converter 86 in synchronization with clock signals and *ADCSL signals sent from the printing controller 87. Then, the digital signal SiDT is fed to the printing controller 87. Under the assumption that R2 = R3, and that the voltage drop in each of the diodes is 0.7V, then for different relationships between ON and OFF states of the microswitches SW1, SW2 and SW3, different analog signal voltages Vs and Vin and different digital signals SiDT, are provided as represented in Fig. 13. Different signal actuator and sensor means from those described above may be employed in embodiments of the present invention. Fig. 14 is a schematic cross-sectional front view of one possible modified sensor means 90a comprising a signal actuator unit 92 and a sensor 93 (an electrical resistance measuring instrument) having two parallel terminals 93a and 93b. The signal actuator unit 92 is a resistor 92a having a linearly varying resistance in the directions A and A′ indicated by two arrows in Fig. 14. The distribution of the resistance in linear and indicated simply by a triangle. The signal actuator unit 92 is displaceable in the direction A-A′ by hand. The location of the sensor 93 is fixed. Fig. 15(a) and Fig. 15(b) are schematic front views of the sensor means 90a. When the signal actuator unit 92 is lowered in the direction A′, as shown in Fig. 15(a), the detected resistance is low (1 Ohm for instance) and when elevated in the direction A, as shown in Fig. 15(b), the detected resistance is high (100 Ohm for instance). The signal of the detected resistance is analog, and can be processed in a manner similar to the processing of Vin in Fig. 12. It will be clear that either signal actuator and sensor means, employing other elements, such as an optical sensor and a displaceable black and white pattern, can be used in embodiments of the invention. In the above description, a sheet feed device, for instance for recording apparatus, having two cassettes or sheet holding means, in the lower portion of the apparatus housing, has been described. Of course, it will be clear to a man skilled in the art that embodiments of the present invention can provide a device having more cassettes, such as five cassettes. There may even be only one cassette. In order to increase the benefits to be gained from interchangeability of cassettes a different kind of housing structure from that described above may be employed in embodiments of the present invention. Fig. 16 is a schematic cross-sectional side view of recording apparatus employing an embodiment of the present invention with such a housing structure. The apparatus housing 221 itself holds and encloses only the elements of the apparatus other than those of the sheet feed device 205, namely housing 221 houses only the recording device 200 of the apparatus. Each cassette 201 or 202 is individually accommodated in a respective cassette housing, 222 or 223. The cassette housings 222 and 223 are designed with structure and configuration such that they can be stacked one above another (with two, three or more cassette housings in the stack), and to have a mechanical strength sufficient to hold the recording device 200 of the apparatus when stacked on top of the pile of the stacked cassette housings 222 and 223. The cassettes 201 and 202 have basically the same structure as that of cassettes 1 and 2 shown in Figs. 4 and 5. Each cassette has a sub-passage (a through passage) 234, and each cassette housing 222 or 223 has an upper hole 222a or 223a and a lower hole 222b or 223b corresponding to the outlet and inlet of the relevant sub-passage 234. With this configuration, sheets held in the cassettes are fed through a composite common sheet feed passage 203 composed of the sub-passages 234. Of course, the relevant feed rollers 243, and 251, and separate rollers 238, 239 are disposed in respect of each cassette housing 222 or 223 so as to be driven under control of control means (not shown) of the apparatus. Thus, the user of the recording apparatus can increase or decrease the number of cassettes depending on his requirements. Fig. 17 is a schematic view of a recording apparatus employing another embodiment of the present invention, which can employ the structure and means described above in relation to other embodiments. In operation of recording apparatus, there frequently occurs a situation in which a great number of recording sheets of one type are required whilst only small amounts of sheets of other types are occasionally required. Hereby, the former sheets are desirably held in holding means within high capacity, such as a sheet holding hopper 250, not in cassettes. As shown in Fig. 17, a sheet hopper 250 is disposed under the recording apparatus of Fig. 3. The sheet hopper has a conventional structure, comprising a horizontal hopper table 252, a screwed rotatable spindle 253, a driving motor 254, a feed roller pair 255, a separation roller 256, and a housing 251 which encloses and holds the above elements. A sheet pile 260 containing a large quantity of sheets of one type is stacked in alignment on the hopper table 252 which holds the pile 260 of the sheets and is vertically movable upwardly and downwardly by the rotation of the spindle driven by the motor 254. The motor 254 is under control of a sensor system (not shown) for sensing the position of the uppermost sheet of the sheet pile 260. The uppermost sheet of the sheet pile 260 is separated by the separation roller 256 and fed by the feed roller pair 255 toward a sheet discharge outlet 251a in a conventional manner. The separation roller 256 and the sheet feed roller pair 255 are under control of a printing controller (not shown). Hereby, the sheet discharge outlet 251a of the sheet hopper 250 must be disposed in alignment with the common sheet feed passage 3 such that the sheets stacked in the sheet pile 260 are fed into the common passage 3 one-by-one and further conveyed to an image transfer station 28 of the apparatus. An embodiment of the present invention provides a cut-sheet feed device, for instance for a recording apparatus, for feeding sheets one-by-one from cut-sheet receiving cassettes which are stacked one above another. Each cassette has a common sheet sub-passage penetrating the cassette from bottom to top. The sub-passages are disposed such that they are positioned in alignment to form a common sheet feed passage penetrating the stack of the cassettes from bottom to top when all the cassettes are set in normal positions, and individual sheet feed passages formed in the cassettes are joined to the common sheet feed passage. With the above configuration, sheet supplement operation to the cassettes and sheet clearing operation can be performed from the same side of the device, saving office space. The present invention provides sheet holding means, capable of holding a stack of sheets, having an individual sheet feed passage, for passing therethrough a sheet fed from the stack of sheets in the sheet holding means, and having a sheet feed sub-passage penetrating the sheet holding means from bottom to top thereof, such that when a plurality of such sheet holding means are disposed one above the other, the sub-passages of the different sheet holding means can be serially aligned to constitute a common sheet feed passage operatively connected with the individual sheet feed passages of the different sheet holding means, the common sheet feed passage allowing the passage therethrough of a sheet fed from any of the individual sheet feed passages. The sheet holding means may be provided with an individual housing therefor, so that a plurality of such sheet holding means can be stacked, housing on housing. Alternatively a common housing may be provided for the plurality of sheet holding means. The plurality of sheet holding means are drawable from the housing or housings in one direction, with the sub-passage towards the ends of the sheet holding means first drawn from the housing or housings.

Claims: Sheet feed means, for recording apparatus for recording an image on a sheet, the sheet feed means (5; 205) comprising:- a plurality of sheet holding means (1, 2; 201, 202), disposed one above another, each capable of holding a stack of sheets, and supporting means (4; 222, 223) for supporting each of said plurality of sheet holding means (1, 2; 201, 202) in a predetermined normal position thereof, in a forwardly drawable state; each of said sheet holding means (1, 2; 201, 202) comprising:- an individual sheet feed passage (6), disposed forwardly of the sheet holding means, for passing therethrough a sheet fed from the stack of sheets in the sheet holding means, characterised in that each of said sheet holding means (1, 2; 201, 202) comprises:- a sheet feed sub-passage (34; 234), disposed forwardly of the sheet holding means and penetrating through the sheet holding means, from bottom to top; the sheet feed sub-passages (34; 234), when the members of said plurality of sheet holding means (1, 2; 201, 202) are set in their normal positions in the supporting means (4; 222, 223), being disposed so as to be serially aligned to constitute a common sheet feed passage (3; 203) which is operatively connected with each of the individual sheet feed passages (6), the common sheet feed passage (3; 203) allowing the passage therethrough of a sheet fed from any of the individual sheet feed passages (6). Sheet feed means as claimed in claim 1, wherein each of said sheet holding means (1, 2; 201, 202) comprises:- a guide plate (35) defining said individual sheet feed passage (6), arranged for guiding sheets, fed one-by-one from the top of the stack of sheets held in the sheet holding means, to the common sheet feed passage (3; 203). Sheet feed means as claimed in claim 1 or 2, wherein each of the sheet holding means (1, 2; 201, 202) comprises:- a first passage side wall (36a) extending from bottom to top of the sheet holding means; a second passage side wall (36b), shorter than the first passage side wall (36a), disposed to face the lower portion of the first passage side wall approximately in parallel therewith, the first (36a) and second (36b) passage side walls defining the sheet feed sub-passage (34; 234) of the sheet holding means concerned, the sub-passage (34; 234) having an inlet (34b) at the bottom, an open-sided portion (34c) in the upper part thereof, through which the individual sheet feed passage of the sheet holding means (6) is joined to the sub-passage (34; 234), and an outlet (34a) at the top of the first passage side wall (36a). Sheet feed means as claimed in claim 3, further comprising:- frame means (21, 21a) to which the supporting means (4) is secured; and a plurality of pairs (37, 43; 37, 51) of feed rollers, provided in correspondence to respective sheet holding means (1, 2), each of the pairs comprising a drive roller (43, 51) and a follower roller (37), for sheet advancement, and being disposed above the said outlet (34a) of the sheet feed sub-passage (34) of the corresponding sheet holding means, each drive roller (43, 51) being disposed on the frame means (21, 21a) and each follower roller (37) being disposed in the corresponding sheet holding means, the drive roller (43, 51) and the follower roller (37) of a pair being disposed so that the two rollers are pressed together when the relevant sheet holding means is in its normal position, whereby a sheet held in a sheet holding means (1, 2) is fed to the roller pair (37, 43; 37, 51) corresponding to that sheet holding means through the sheet feed passage (6) of that sheet holding means, and is then advanced through the sheet feed sub-passage (34) of that sheet holding means by the roller pair towards the outlet opening (34a) of the sub-passage (34) of the uppermost sheet holding means. Sheet feed means as claimed in any preceding claim, wherein at least one of the said plurality of sheet holding means (1, 2; 201, 202) comprises means for indicating the type of sheets held in the holding means, the indicating means comprising:- a signal actuator unit (70) displaceably disposed on a wall (10a) of the sheet holding means (1, 2) concerned; and a sensor (90) secured to a wall of the supporting means (4; 222, 223), such that the sensor engages with the actuator unit, operable to output an indicating signal, whereby the indicating signal output is alterable, in correspondence to the sheet type of sheets held in the sheet holding means concerned, by displacing the signal actuator unit. Sheet feed means as claimed in claim 5, wherein the signal actuator unit (70) comprises:- a groove (72) formed in a side wall (10a) of the sheet holding means (1, 2) concerned; and a slide cam (71) slidable step-wise along the groove with a step pitch p, having a plurality of projecting portions (75, 76) and a plurality of non-projecting or indented portions (77), and wherein the sensor (90) comprises:- a plurality of microswitches (91a, 91b, 91c) disposed side by side, each of said microswitches having an actuating button movable in the axial direction thereof, the actuating buttons being positioned in alignment, with pitch p, and the microswitches being capable of outputting a variety of combinations of ON and OFF output signals of individual microswitches. Sheet feed means as claimed in claim 6, wherein the signal actuator unit (92) comprises a resistor (92a) disposed on a side wall (10a) of the sheet holding means (1, 2; 222, 223) concerned, displaceable in a given direction, the resistor (92a) having a linearly varying resistance in the given direction; and wherein the sensor (93) comprises an electrical resistance measuring instrument having two parallel measuring terminals (93a, 93b) which contact the resistor (92a), measuring the resistance between the two measuring terminals. Sheet feed means as claimed in claim 6, comprising signal processing circuitry (80) having:- signal generator means (85) for generating an analog signal based on the combination of ON and OFF output signals of individual microswitches (91a, 91b, 91c); an analog/digital converter means (86), arranged to receive the analog signal generated in the signal generator means, and to convert the analog signal to a digital signal (SiDT); and identification means (87) for identifying the digital signal. Sheet feed means for recording apparatus for recording an image on a sheet, the sheet feed means being capable of holding sheets of a plurality of sheet types and selectively feeding said sheets to sheet conveying means, and the sheet feed means comprising:- a housing (21, 21a; 222, 223) having a pair of facing side walls; a plurality of pairs of rails disposed along the side walls of the housing, the pairs being arranged one pair above another, spaced one pair from another; a plurality of sheet holding means (1, 2; 201, 202), each of which is supported, forwardly drawably, by a corresponding pair of rails, stacked one above another and spaced from each other with a small intervening space; and a sheet discharge outlet (34a) discharging a fed sheet, the outlet being disposed at an upper portion of the sheet feed means; characterised in that each of the sheet holding means (1, 2; 201, 202) comprises:- a guide path (34; 234) disposed forwardly thereof and passing through the sheet holding means from bottom to top, and a guide plate (35) for guiding a sheet fed from the stack of sheets in the sheet holding means (1, 2; 201, 202), guiding the sheet into the guide path; the guide paths (34; 234) in the respective sheet holding means (1, 2; 201, 202) being disposed such that in combination they form a common guide path (3; 203) passing through the stack of sheet holding means (1, 2; 201, 202), from bottom to top of the stack, extending to the discharge outlet (34a), when all the sheet holding means are set at predetermined positions. Recording apparatus for recording an image on a sheet, including sheet holding means (1, 2; 201, 202) for holding a plurality of sheets stacked in alignment in the sheet holding means, characterised in that the sheet holding means includes:- a sheet feed through-passage (34; 234) disposed towards one end of the sheet holding means, from which end the sheet holding means can be drawn out of the apparatus, and which through-passage penetrates the sheet holding means from bottom to top of the sheet holding means, the sheet feed through-passage having an inlet opening (34b) at the bottom and an outlet opening at the top (34a) of the sheet holding means. Recording apparatus as claimed in claim 10, wherein the sheet feed through-passage (34; 234) of the sheet holding means allows passage of a sheet fed from the bottom of the sheet holding means, through the inlet opening of the through-passage. Recording apparatus as claimed in claim 10 or 11, comprising:- a plurality of further sheet holding means (1, 2; 201, 202), each having the same structure and dimensions as the sheet holding means of claim 10 or 11; and supporting means (21, 21a; 222, 223) for supporting all of the sheet holding means, stacked one above another, with each of the sheet holding means at a predetermined normal position thereof, with the result that the through-passages (34; 234) are aligned with each other operatively forming a common passage (3; 203) penetrating the stack of sheet holding means (1, 2; 201, 202) from bottom to top. Recording apparatus as claimed in claim 10, 11 or 12, further comprising:- a sheet hopper (250) disposed beneath the or all of the sheet holding means (1, 2; 201, 202), said sheet hopper having a sheet discharge outlet (251a) at the top side thereof, whereby the said discharge outlet (251a) of the sheet hopper is disposed facing the inlet opening of the through-passage (34b), such that a sheet held in the sheet hopper (250) is allowed to pass through the through passage (3).

Inventors: OHYABU, KEIJI C/O FUJITSU LIMITED, SANO, HIDEAKI C/O FUJITSU LIMITED, WATARAI, SHINICHI C/O FUJITSU LIMITED
Applicants: FUJITSU LIMITED
Application year: 1988
Main classification: B65H1
IPC codes: B65H3, B41J13, B65H1