Abstract:
A sheet feeding apparatus includes a sheet supporting device for supporting sheets, a supply device for feeding the sheets supported by the sheet supporting device in a sheet feeding direction, a separating claw device for separating, one-by-one, the sheets fed by the supply device by regulating at least one front corner of the sheets relative to the sheet feeding direction. A switching device selectively switches positions of the separating claw device between a first position where the separating claw device is separated from the sheet supporting device and a second position where the separating claw device is adjacent to the sheet supporting device. A separation device separates, one-by-one, the sheets fed by the supply device in a condition that the separating claw device is in the second position.

Description:
This application is a continuation of application Ser. No. 07/916,676, filed Jul. 22, 1992, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sheet feeding apparatus for separating and feeding out stacked recording media (sheets) one by one to a recording portion or other portions. 
     2. Description of the Related Art 
     Nowadays, pursuant to the remarkable progress of information processing equipment, various recording systems such as printers, electronic typewriters and the like have been used in various offices. In such recording systems, plain paper sheets and/or thicker sheets such as post cards, envelopes and the like are used as recording media, and the recording media can be manually inserted and/or can be automatically supplied to a recording portion by an automatic sheet feeding apparatus. To this end, the recording system is provided with a manual sheet insertion opening and a sheet supply opening for the automatic sheet feeding apparatus to cope with various recording media. Further, since the above-mentioned automatic sheet feeding apparatus are generally of a separating claw type which can be made inexpensive, the kind of recording media which can be stably separated is limited to the plain paper sheet alone. Thus, in order to supply or feed the thicker sheets such as post cards, envelopes and the like, an exclusive automatic sheet feeding apparatus of other separation type, for example, of a friction separation type must be used. 
     However, in the conventional cases, when the plain paper sheets and the thicker sheets such as post cards are to be used each in its proper way as the recording media, the corresponding automatic sheet feeding apparatuses must be exchanged with respect to the recording system each time, thus worsening the operability and requiring an additional installation space for the dismounted automatic sheet feeding apparatus. 
     Further, even when the automatic sheet feeding apparatus for the plain paper sheets is incorporated into the recording system and only the automatic sheet feeding apparatus for the thicker sheets is detachably mountable within the recording system, since the recording system itself becomes large-sized, the installation space for the recording system will be increased. Furthermore, since at least two automatic sheet feeding apparatuses are required the overall recording facilities will be expensive. In addition, since not only the sheet supply opening for the automatic sheet feeding apparatus but also the manual sheet insertion opening are required, the overall recording system becomes large-sized and expensive. 
     SUMMARY OF THE INVENTION 
     The present invention aims to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide an automatic sheet feeding apparatus which can feed or supply not only plain paper sheets but also thicker sheets such as post cards, envelopes and the like without using plural automatic sheet feeding apparatuses, and to permit the manual sheet insertion with such a automatic sheet feeding apparatus. 
     In order to achieve the above object, the prevent invention provides a sheet feeding apparatus comprising a sheet supporting means for supporting sheets, a supply means for feeding out the sheets supported by the sheet supporting means, a separating claw means for separating the sheets fed out by the supply means one by one by regulating front corners (in a sheet feeding direction) of the sheets supported by the sheet supporting means, a switching means for selectively switching positions between a first position where the separating claw means is separated from the sheet supporting means and a second or retard position where the separating claw means is retarded toward the sheet supporting means. A separation means separates the sheets one by one when the sheets supported by the sheet supporting means are fed out by the supply means in a condition that the separating claw means is in the retard position. 
     With this arrangement, when the separating claw means is positioned in the first position where it is separated from the sheet supporting means, the sheets can be supplied from the sheet supporting means and the sheets can be separated by the separating claw means. On the other hand, when the separating claw means is positioned in the retard position, the sheets can be fed over the separating claw means and can be separated one by one by the separation means without the resistance of the separating claw means. 
     In this way, the plain paper sheets can be separated and supplied by the separating claw means, and the sheet having the greater ridigity such as thicker sheets which cannot be separated by the separating claw means can be separated and supplied by the separation means. Accordingly, it is possible to separate and feed the plural kinds of sheets only with a single sheet feeding apparatus. 
     Incidentally, the separation means preferably includes abutment plates so that the sheets are separated one by one by riding the sheet over the abutment plates against which leading ends of the sheets are abutted by the supply means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a sheet feeding apparatus according to a preferred embodiment of the present invention; 
     FIG. 2 is an elevational sectional view of the apparatus of FIG. 1; 
     FIG. 3 is an elevational sectional view of the apparatus of FIG. 1, showing a condition that plain paper sheets are supplied; 
     FIG. 4 is an elevational sectional view of the apparatus of FIG. 1, showing a condition that separating claws are separated from a pressure plate; 
     FIG. 5 is an elevational sectional view of the apparatus of FIG. 1, showing a condition that the separating claws are positioned near the pressure plate; 
     FIG. 6 is an elevational sectional view of the apparatus of FIG. 1, showing a condition that a manual sheet insertion is effected in the case where the plain paper sheets are stacked; 
     FIG. 7 is a partial perspective view of a sheet feeding apparatus according to another embodiment of the present invention; 
     FIG. 8 is an elevational sectional view of the apparatus of FIG. 7, showing a condition that plain paper sheets are supplied; 
     FIG. 9 is an elevational sectional view of the apparatus of FIG. 7, showing a condition that separating claws are separated from a pressure plate; 
     FIG. 10 is an elevational sectional view of the apparatus of FIG. 2, showing a condition that the separating claws are positioned near the pressure plate; 
     FIG. 11 is an elevational sectional view of the apparatus of FIG. 7, showing a condition that a manual sheet insertion is effected in the case where the plain paper sheets are stacked; and 
     FIG. 12 is a schematic elevational view of an image forming system incorporating the sheet feeding apparatus according to the present invention therein. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be explained with reference to the accompanying drawings. 
     FIG. 1 is a perspective view of a sheet feeding apparatus according to a first embodiment of the present invention, and FIG. 2 is an elevational sectional view of a main portion of the apparatus of FIG. 1. 
     In FIGS. 1 and 2, a frame 1 serves to support a sheet feeding mechanism, and sheet supply rollers 4a, 4b are mounted on a sheet supply shaft 8 in such a manner that they can slide along the sheet supply shaft and a rotational force is supplied to these rollers via the sheet supply shaft. The sheet supply rollers 4a, 4b are provided with grooves 4a-1, 4b-1, respectively, by which U-shaped recessed portions 3a-1, 3b-1 of sheet regulating guides 3a, 3b (described later) are engaged, so that, when the sheet regulating guides 3a, 3b are slid, the supply rollers 4a, 4b are also slid along the shaft through the engagement between the grooves and the recessed portions. A drive gear 71 secured to one end of the sheet supply shaft 8 serves to transmit a driving force from a motor (not shown) to the sheet supply shaft 8. 
     A pressure plate 2 for urging stacked recording media (referred to as &#34;sheets&#34; hereinafter) against the sheet supply rollers 4a, 4b is pivotally mounted on the frame via pins 2a and is normally biased toward the sheet supply rollers 4a, 4b via a pressure spring 11. The sheet regulating guides 3a, 3b for regulating lateral edges of the sheets are mounted on the pressure plate 2 for sliding movement in a widthwise direction of the sheet, and are provided with cam receiving portions 3a-2, 3b-2, respectively, against which release cams 5a, 5b  (described later) can be abutted when the cams are rotated. When the release cams 5a, 5b are abutted against the cam receiving portions 3a-2, 3b-2, the pressure plate 2 is pushed down to separate from the sheet supply rollers 4a, 4b, together with the sheet regulating guides 3a, 3b. 
     Separating claws 6a, 6b are provided at their front corners (in a sheet feeding direction) with claw portions 6a-2, 6b-2 by which the sheets are held down. The separating claws 6a, 6b are pivotally mounted via pivot pins 6a-1, 6b-1 and are normally abutted against the pressure plate 2 by their own weights. In this embodiment, while the separating claws were abutted against the pressure plate by their own weights, in such a case where the sheet feeding apparatus is installed in an inclined posture, the separating claws may positively be biased toward the pressure plate 2 by means of a spring and the like. Further, on the other ends of the separating claws 6a, 6b remote from the claw portions 6a-2, 6b-2, there are provided push-down portions 6a-3, 6b-3 against which claw opening cams 5a-1, 5b-1 formed on the release cams 5a, 5b can be abutted. When the push-down portions 6a-3, 6b-3 are pushed down by the rotation of the release cams 5a, 5b, the separating claw 6a, 6b are rotated around the pivot pins 6a-1, 6b-1, thereby separating the claw portions 6a-2, 6b-2 (opposite to the push-down portions 6a-3, 6b-3) from the pressure plate 2 to reach a claw opening condition. 
     Incidentally, since the sheet regulating guides 3a, 3b are provided with recessed portions 3a-3, 3b-3 for receiving the claw portions 6a-2, 6b-2; so that the claw portions 6a-2, 6b-2 of the separating claws 6a, 6b do not protrude from sheet passing surfaces of the sheet regulating guides 3a, 3b in a condition that the separating claws 6a, 6b are abutted against, or adjacent to, the pressure plate 2, even when the sheets are set on the pressure plate, the corners of the sheets are not caught by the claw portions 6a-2, 6b-2 of the separating claws 6a, 6b. 
     Similar to the sheet supply rollers 4a, 4b, the release cams 5a, 5b are slidably mounted on a cam shaft 9 in such a manner that a rotational force is transmitted to the release cams via the cam shaft. Thus, by rotating a release lever 10, the rotational force is transmitted to the release cams 5a, 5b via the cam shaft 9. Further, since the release cams 5a, 5b are received in the recessed portions or cam receiving portions 3a-2, 3b-2 of the sheet regulating guides 3a, 3b, the cams are shifted on the cam shaft 9 in synchronously with the sliding movement of the sheet regulating guides 3a, 3b. 
     Ramp plates 7a, 7b serve to separate and supply thicker sheets such as post cards, envelopes and the like. In the condition that the claw portions 6a-2, 6b-2 of the separating claws 6a, 6b are abutted against the pressure plate 2, when the thicker sheets such as post cards, envelopes and the like stacked on the pressure plate are fed out by the sheet supply rollers 4a, 4b, leading ends of the fed thicker sheets are abutted against inclined surfaces 7a-1, 7b-1 of the ramp plates 7a, 7b, with the result that only an uppermost thicker sheet contacted with the sheet supply rollers 4a, 4b is fed out due to the resistance of the resiliency of the sheet. The ramp plates 7a, 7b are provided with arms 7a-2, 7b-2 by which the grooves 4a-1, 4b-1 of the sheet supply rollers 4a, 4b are engaged, so that the ramp plates can be shifted synchronously with the sliding movement of the sheet regulating guides 3a, 3b, similar to the sheet supply rollers 4 a, 4b. 
     Next, the operation of the sheet feeding apparatus having the above-mentioned arrangement will be explained with reference to FIGS. 3 to 6, in connection with the cases where the plain paper sheets and thicker sheets are used. 
     Normally, in a condition that the plain paper sheets are supplied, as shown in FIG. 3, since the release lever 10 is positioned in a sheet feeding position, the release cams 5a, 5b driven by the release lever 10 are not abutted against the cam receiving portions 3a-2, 3b-2 of the sheet regulating guides 3a, 3b and the push-down portion 6a-3, 6b-3 of the separating claws 6a, 6b. Thus, the sheets S are urged against the sheet supply rollers 4a, 4b by the pressure plate 2 and the front corners of the sheets S are held down by the claw portions. 6a-2, 6b-2 of the separating claws 6a, 6b. As a result, when the sheet supply rollers 4a, 4b are rotated in a direction shown by the arrow the sheet can be fed or supplied one by one. 
     Now, an operation for setting the sheets S on the pressure plate 2 will be explained. As shown in FIG. 4, first of all, the release lever 10 is rotated so that the release cams 5a, 5b are rotated in a direction shown by the arrow. When the release cams 5a, 5b are so rotated, the pressure plate 2 is pushed down and the claw portions 6a-2, 6b-2 of the separating claws 6a, 6b are separated from the pressure plate 2 by the claw opening cams 5a-1, 5b-1 on the release cams 5a, 5b to be lifted toward the sheet supply rollers 4a, 4b, thereby establishing the release position. Now, the sheets are set on the pressure plate 2. Then, when the sheet regulating guides 3a, 3b are slid so that a distance between the guides is equal to a width of the sheet, the sheet supply rollers 4a, 4b, separating claws 6a, 6b, release cams 5a,  5b and ramp plates 7a, 7b are also slid synchronously with the sliding movement of the sheet regulating guides because of the engagement between these elements and the guides. In this way, it is possible to accommodate sheets having various widths. When the release cams 5a, 5b are returned to the aforementioned release position by rotating the release lever 10, the front corners of the sheets are held down by the separating claws 6a, 6b and the sheets are urged against the sheet supply rollers 4a, 4b (FIG. 3), thus permitting the feeding of the plain paper sheets. 
     On the other hand, in setting the recording sheets S on the pressure plate 2, when the release lever 10 is rotated so that the release cams 5a, 5b are rotated in a direction shown by the arrow in FIG. 5 opposite to the direction shown in FIG. 4, the claw opening cams 5a-1, 5b-1 of the release cams 5a, 5b are not abutted against the push-down portions 6a-3, 6b-3 of the separating claws 6a, 6b, but push down only the pressure plate 2. In this case, the claw portions 6a-2, 6b-2 of the separating claws 6a, 6b are abutted against the pressure plate 2 by their own weights (separating claw retard condition). In this condition, when the thicker sheets such as post cards, envelopes and the like are set on the pressure plate 2, since the claw portions 6a-2, 6b-2 of the separating claw 6a, 6b are retarded in the recessed portions 3a-3, 3b-3 of the sheet regulating guides 3a, 3b, the sheet can be set on the pressure plate regardless of the existence of the claw portions 6a-2, 6b-2 of the separating claws 6a, 6b. Thereafter, even when the release cams 5a, 5b are returned to the sheet feeding position, the corners of the sheets are not held down by the separating claws 5a, 5b. Thus, when the sheet supply rollers 4a, 4b are rotated, since the sheets are not separated by the separating claws 6a, 6b, but separated by the ramp plates 7a, 7b, it is possible to supply the thicker sheet such as post card, envelope and the like having the greater resiliency. 
     FIG. 6 shows a condition that the sheet is manually supplied or inserted into the sheet feeding apparatus. When the release cams 5a, 5b are rotated in a direction shown by the arrow in FIG. 6 to establish the separating claw retard position in a condition that the sheets S are stacked on the pressure plate 2, the pressure plate 2 is lowered to separate from the sheet supply rollers 4a, 4b while the corners of the sheets S being held down by the claw portions 6a-2, 6b-2 of the separating claws 6a, 6b. Accordingly, in this condition, when another sheet S1 is set on the pressure plate, the set sheet S1 is rested on the claw portions 6a-2, 6b-2 of the separating claws 6a, 6b. Thus, when the release cams 5a, 5b are returned to the sheet feeding position and the sheet supply rollers 4a, 4b are rotated, only the sheet S1 is supplied or fed (manual sheet supply). 
     FIG. 7 is a perspective view of a sheet feeding apparatus according to a second embodiment of the present invention, wherein a one-sided separating claw is used. 
     In FIG. 7, the reference numeral 101 denotes a sheet supply roller for feeding out sheets; and 102 denotes a pressure plate for urging the sheets S stacked on this plate against the sheet supply roller 101. The pressure plate 102 is pivotally mounted via pivot pins 102b and is biased toward the sheet supply roller by a pressure spring (not shown). The pressure plate 102 is provided with a projection 102a against which a release cam 104 (described later) can be abutted when the cam is rotated. The projection 102a can be engaged by either cam surface 104b or 104c of the release cam 104 so that the pressure plate can be lowered to separate from the sheet supply roller 101 by the release cam 104. A separating claw 103 is provided at its front corner (in a sheet feeding direction) with a claw portion 103b by which the front corner of the stacked sheets S is held down. 
     The separating claw 103 is pivotally mounted via a pivot pin 103d and is normally abutted against the pressure plate 102 by its own weight. As in the aforementioned embodiment, also in this embodiment, the separating claw 103 may positively be biased toward the pressure plate 102 by means of a spring and the like. The pressure plate is provided with a recessed portion 102c so that the claw portion 103b of the separating claw 103 such that the claw portion 103b does not protrude from a sheet passing surface of the pressure plate 102 in a condition that claw portion 103b of the separating claw 103 is abutted against the pressure plate 102. Thus, in the condition that the separating claw 103 is abutted against, or adjacent to, the pressure plate 102, even when the sheets are set on the pressure plate, the corner of the stacked sheets is not caught by the claw portion 103b of the separating claw 103. Further, on the other end of the separating claw 103 removed from the claw portion 103b, there is provided a push-down portion 103a against which only the cam surface 104b of the release cam 104 can be abutted. When the push-down portion 103a is pushed down by the release cam 104, the separating claw 103 is rotated around the pivot pin 103d, thereby separating the claw portion 103b (opposite to the push-down portion 103a) of the separating claw 103 from the pressure plate 102 to establish a claw opening condition. 
     The release cam 104 includes the cam surface or cam portion 104b for rotating the pressure plate 102 and the separating claw 103 simultaneously, and the cam surface or cam portion 104c for rotating the pressure plate 102 alone. The release cam 104 is rotatable around the cam shaft 104a and is provided with a cam gear 104d which is meshed with a lever gear 105a of a release lever 105. The release lever 105 is rotatably mounted via a pivot shaft 105b. 
     Next, the operation of the sheet feeding apparatus having the above-mentioned arrangement will be explained with reference to FIGS. 8 to 11, in connection with cases where the plain paper sheets and thicker sheets such as post cards, envelopes and the like are used. 
     Normally, in a condition that the plain paper sheets are supplied, as shown in FIG. 8, since the release lever 105 is positioned in a sheet feeding position, both the cam portions 104b and 104c of the release cam 103 driven by the release lever 105 are not abutted against the projection 102a of the pressure plate 102 and the push-down portion 103a of the separating claw 103. Thus, the sheets S are urged against the sheet supply roller 101 by the pressure plate 102 and the front corner of the stacked sheets S is held down by the claw portion 103b of the separating claw 103. As a result, when the sheet supply roller 101 is rotated in a direction shown by the arrow, the sheet S can be fed or supplied one by one. 
     Now, in setting the sheets S on the pressure plate 102, as shown in FIG. 9, when the release lever 105 is rotated in a direction shown by the arrow a, the release cam gear 104d meshed with the lever gear 105a is rotated, with the result that the pressure plate 102 is pushed down to separate the sheet supply roller 101 and the claw portion 103b of the separating claw 103 is lifted toward the sheet supply roller 101 due to the fact that the opposite push-down portion 103a is pushed down, thereby establishing the release position for the separating claw 103. Now, the sheets S are set on the pressure plate 102. Then, when the release lever 105 is returned to the sheet feeding position, the front corner of the stacked sheets S is held down by the separating claw 103, thus permitting the feeding of the plain paper sheets. 
     On the other hand, when the release lever 105 is rotated in a direction b as shown in FIG. 10, although the release cam 104 is rotated, since only the cam portion 104c is abutted against the projection of the pressure plate 102, the claw portion 103b of the separating claw 103 is lowered toward the pressure plate 102 by its own weight (retard condition). In this condition, when the thicker sheets such as post cards, envelopes and the like are set on the pressure plate 102, since the thicker sheets are rested on the retarded claw portion 103b of the separating claw 103, even when the release lever 105 is returned to the sheet feeding position, the corner of the sheets is not held down by the separating claw 103. Thus, when the sheet supply roller 101 is rotated, since the claw separation is changed to the direction separation, it is possible to supply the thicker sheets. 
     FIG. 11 shows a condition that the sheets are manually inserted one by one. When the release lever 105 is rotated in a direction shown by the arrow b, the pressure plate 102 is lowered while the sheets S being held down by the claw portion 103b of the separating claw 103. Accordingly, in this condition, when another sheet S1 is set on the pressure plate, the set sheet S1 is rested on the claw portion 103b of the separating claw 103. Thus, when the release lever 105 is returned to the sheet feeding position and the sheet supply roller 101 is rotated, only the sheet S1 is supplied or fed, thus permitting the manual sheet supply. Therefore, since a manual sheet insertion opening is not required, and the manual sheet supply can be effected by using the same sheet supply opening as that for the automatic sheet feeding apparatus, it is possible to make the apparatus small-sized and inexpensive. 
     In the above-mentioned embodiments, while the release cam or cams were driven by the release lever, in place of the release lever, a release knob may be integrally formed with the cam to rotate the cam or cams directly. Alternatively, the separating claw 103 may be shifted between the release position and the retard position with respect to the pressure plate 102 by the direct rotation of the release lever 105. Although not described in the explanation of the ramp plates, when the one-sided separating claw is used, the ramp plate can be fixed with respect to the widthwise direction of the sheet, or the ramp plate may be integrally formed with the frame. Furthermore, in the embodiment wherein the one-sided separating claw is used, when a sheet reference is provided only in association with the one-sided separating claw, the same reference mechanism at the other side is not required, thus making the apparatus simpler, reducing the number of parts and making the apparatus inexpensive. 
     FIG. 12 is a constructural view showing an image forming system 50 incorporating therein the sheet feeding apparatus A of one embodiment of the present invention. 
     An image forming means of this image forming system is of an ink jet type wherein ink is selectively discharged from discharge openings by the growth of bubble(s) generated by the film boiling of ink caused by electrical/thermal converter(s), thereby forming an image. 
     In FIG. 12, a recording head 51 is mounted on a carriage (not shown) reciprocally shiftable in horizontal directions (perpendicular to a plane of the sheet). The sheet supplied from the sheet feeding apparatus A is fed to a platen 53 by a pair of feed rollers 52, and the image is gradually formed on the sheet by the recording head 51. The sheet on which the image was formed is ejected onto an ejection tray 55 by a pair of ejector rollers 54. In this way, it is possible to form the image on the sheet such as plain paper sheet, post card, envelope and the like supplied from the sheet feeding apparatus A. 
     Incidentally, the image forming means is not limited to the ink jet type, but may be of other suitable types. 
     As mentioned above, since the separating claw means can be switched, in synchronously with the releasing operation of the pressure plate, between the retard position where the separating claw means is retarded toward the pressure plate and the position where the separating claw means is separated from the pressure plate, it is possible not only to supply both the plain paper sheet and the thicker sheet such as post card, envelope and the like, but also to manually supply a sheet in the retard position, with the single sheet feeding mechanism. 
     Incidentally, while an example that the thicker sheets are separated by the ramp plate(s) was explained in the above-mentioned embodiments, the present invention is not limited to this example, but other separation mechanisms (for example, comprising a separation pad having a greater coefficient of friction and a drive roller urged against the separation pad) may be used. 
     Further, while the release lever 10, 105 was rotated manually, the release lever may be automatically rotated by a reversible motor and the like.