GB2207661A - Sheet feeding - Google Patents

Abstract

Sheets S e.g. in selective printing apparatus, are fed from feeding tray (14) to a discharge sheet tray (19) by a sheet feeding roller (15) for feeding sheets S from the sheet feeding tray (14) one by one and a sheet discharge roller (22) for introducing the sheets one by one in the discharge sheet tray (19). An electric motor (26) rotatable in both senses, transmits rotation of the motor (26) via one-way clutch (30, Fig. 1) to the sheet feeding roller (15) in one sense only, and via another one-way clutch (31) to the sheet discharge roller (22) in the opposite sense only. <IMAGE>

Description

AUTOMATIC SHEET FEEDING APPARATUS This invention relates to an automatic sheet feeding apparatus.

Automatic sheet feeding apparatus automatically supplies a sheet to be printed to an output device for a printer or a copying machine.

Previously proposed apparatus, includes a sheet feeding tray and a discharge sheet tray. Sheets contained in the sheet feeding tray are sequentially supplied to a printer unit of an output device, where they are printed and the printed sheets are stacked in the discharge sheet tray has been heretofore known. In this apparatus, a sheet feeding roller for feeding sheets in the sheet feeding tray and a sheet discharge roller for introducing printed sheets into the discharge sheet tray must be provided.

The sheet feeding roller and the sheet discharge roller are driven by an electric motor provided in the output device for rotating a rubber roller for conveying the sheet.

However, the drive of the sheet feeding roller and the sheet discharge roller by the motor for rotating the conveying roller in the output device by means of the sheet feeding roller and the sheet discharge roller must mesh with gears secured respectively to the ends of the rubber roller, the sheet feeding roller and the sheet discharge roller.

The sheet feeding apparatus body is consequently relatively large in particular when the automatic sheet feeding apparatus is exclusively used for sheets of small size. Furthermore, when the rubber roller, the sheet feeding roller and the sheet discharge roller are driven by the motor in the output device in this manner, there is a further drawback. When the sheet feeding roller and the sheet dischage roller are driven after the rubber roller is stopped, or when the rubber roller is, on the contrary, driven after the sheet feeding roller and the sheet discharge roller are stopped, a complicated mechanism is required to switch the power transmission therebetween.Moreover, when the final sheet is introduced by the sheet discharge roller into the discharge sheet tray of the automatic sheet feeding apparatus so as to drive and stop the sheet feeding roller and the sheet discharge roller synchronously, there arises a problem that the sheet feeding roller is also driven so that an unnecessary sheet must be supplied to the output device.

An object of this invention is to provide an improved automatic sheet feeding apparatus.

According to the present invention there is provided an automatic sheet feeding apparatus having a sheet feeding tray, an exhausted or discharged sheet tray, a sheet feeding roller for feeding sheets in the sheet feeding tray one by one and a sheet exhausting or discharge roller for introducing the sheets one by one in the the exhausted or discharge sheet tray, comprising an electric motor rotatable in both normal and reversible directions, a one-way clutch for transmitting only unindirectional rotation of the motor to the sheet feeding roller, and another one-way clutch for transmitting the rotation of the other direction of the motor to the sheet exhausting roller.

In the apparatus to be described only one of the sheet feeding roller and the sheet discharge roller is selectively rotated in the rotating direction of the motor Thus, when the sheet in the sheet feeding tray is to be supplied to the printer unit of the output device, the sheet feeding roller is rotatably driven, and when the printed sheet in the printer unit is to be introduced into the discharge sheet tray, the motor is rotated reversely to the previous rotation to rotatably drive the sheet discharge roller.

Automatic sheet feed appartus embodying the present invention will now be described, by way of example with reference to the accompanying diagrammatic drawings in which: Fig. 1 is a fragmentary side elevation of an automatic sheet feeding apparatus embodying the the present invention.

Fig. 2 is a perspective view of a printer incorporating the automatic sheet feeding apparatus; and Fig. 3 is a longitudinal section through the printer of Fig. 2.

The printer 1 shown in Figure 2 has a platen 5. A carriage 4 is disposed movahly along the longitudial direction of the platen 5. A printing head 5 facing the platen 5 is placed on the carriage 4. To bring the printing head 5 into contact with the platen 5 the carriage 4 is inclined. This causes the head 5 to impress a sheet S disposed in a printing unit 6 between the platen 5 and the printing head 5. A rubber conveying roller 7 of large-diameter for supplying the sheet S to the printing unit 6 is arranged adjacent the platen 9 in the printer 1. The conveying roller 7 is rotatably driven by an electric motor (not shown) disposed in a printer body 8.Two guide rollers 9 and 9 engage the conveying roller 7 to convey the sheet S interposed between the conveying roller 7 and the guide rollers 9. Further, a guide plate 10 for introducing the sheet S between the conveying roller 7 and the guide rollers 9 projects obliquely from the ends of the guide rollers 9. The sheet S when printed by the printing head 5 in the printing unit 6 is guided to directly above the printing unit 6.

An oblique plate 12 located in the sheet feeding apparatus body 11 of the automatic sheet feeding apparatus 2 is detachably placed on the printer body 8 of the printer 1, a.nd a horizantally extending support shaft 12 is arranged on the upper end of the oblique plate 12. A sheet feeding tray 4 disposed on the oblique plate 12 is pivotally secured to the shaft 17.

A sheet feeding roller 15 is rotatably supported at a position spaced from the lower end of the sheet feeding tray 14 and from the sheet feeding apparatus body 1. The sheet feeding roller 15 is so disposed that when the automatic sheet feeding apparatus 2 is placed in the printer 1 the plane containing the guide plate 10 in the printer body 8 is tangential to the roller 15. The sheet feeding roller 15 Is rotated in a counterclockwise sense to supply sheets S in the sheet feeding tray 14 between the conveying roller 7 of the printer 1 and the guide rollers 9. A coiled spring 15 for applying a counterclockwise rotating trend to the sheet feeding tray 14 in Fig. 3 lies between the oblique plate 12 and the sheet feeding tray 14, and the lower end of the sheet feeding tray 14 is urged in contact with the sheet feeding roller 16 by means of the coiled spring 16.A base for supporting the lower ends of the sheets S contained in the sheet feeding tray 14 is located in the sheet feeding apparatus body 11 near the sheet feeding tray 14, and a supporting surface 18 of a direction substantially perpendicular to the sheet feeding tray 14 is formed on the base 17.

A discharge sheet tray 19 for receiving printed sheets S is located in the sheet feeding apparatus body 11 adjacent to the sheet feeding roller 15. The discharge sheet tray 19 is of substantially L-shaped section and formed by an oblique back plate 20 and a similarly oblique bottom plate 21. A sheet discharge roller 22 for introducing the sheet S into the discharge sheet tray 19 is rotatably supported by the sheet feeding apparatus body 11 and extends obliquely under the discharge sheet tray 19. The sheet discharge roller 22 rotates the printed sheets S which project upwardly from the printing unit 6 of the printer 1 in a counterclockwise sense to introduce the sheets S into the discharge sheet tray 19. The outer peripheral surface 23 of the roller 22 is uneven to obtain a frictional force. Further, a circular-arclike guide plate 24 for introducing the sheet S into the discharge sheet tray 19 is disposed on the outer periphery of the sheet discharge roller 22. A stacker 25 is mounted on the upper end of the sheet tray 19.

The sheet feeding roller 15 and the sheet discharge roller 22 are selectively driven rotatably by means of a stepping motor 26 provided in the automatic sheet feeding apparatus 2 as schematically shown in Fig.1. More specifically, a pinion 27 rigid with the rotational shaft (not shown) of the stepping motor 26 makes with gear 28A provided at the end of a gear train 28 for driving the sheet feeding roller 15 and a gear 29A provided at the end of a gear train 29 for driving the sheet discharge roller 22. The sheet feeding roller 15 and the sheet discharge roller 22 are coupled through spring clutches 30 and 31 as one example of one-way clutches with the gears 28D and 29C provided at the ends of the gear trains 28 and 29, respectively. The spring clutches 30 and 31 are so provided as to transmit the unidirectional rotations of the gear trains 28 and 29.Since the sheet feeding roller 15 and the sheet discharge roller 22 are all rotated counterclockwise in Fig. 1 to convey the sheet S, the spring clutches 30 and 31 transmit only the counterclockwise rotations of the gear trains 28 and 29 provided at the ends of the spring clutches 30 and 31 to the sheet feeding roller 15 and the sheet exhausting roller 22. When the gear trains 28 and 29 rotate in a clockwise sense, the sheet feeding roller 15 and the sheet exhausting roller 22 do not rotate. Since the sheet feeding roller 15 and the sheet discharge roller 22 are so provided as to be selectively rotated, when the stepping motor 26 is, for example, rotated in counterclockwise sense, only the sheet feeding roller 15 rotates, while when the stepping motor 26 is rotated in clockwise sense, only the sheet exhausting roller 22 rotates.Thus, four gears 28A to 28D are formed on the gear train 28, while 3 gears 29A to 290 different in number from the gear train 28 are provided on the gear train 29 to selectively rotate the sheet feeding roller 15 or the sheet discharge roller 22 in the same sense by the reverse rotation of the stepping motor 26.

A pair of arms 32 and 32 are obliquely suspended adjacent to the right hand and left hand lower ends of the sheet feeding apparatus body 1 in such a manner that the fork ends 33, of the arms 32 engaged the supporting shaft 34 of the printer body 8 to support the automatic sheet feeding apparatus 2 in the printer 1.

In operation in order to print by placing the automatic sheet feeding apparatus 2 in the printer 1, a plurality of sheets S of predetermined size are first stacked in the sheet feeding tray 14 of the automatic sheet feeding aparatus 2. When the print button (not shown) of the printer 1 is then pressed, the stepping motor 26 of the automatic sheet feeding apparatus 2 is rotated in a counterclockwise sense as viewed in Fig. 1 to rotate the gears 28A to 28D, 29A to 29C of both the gear trains 28 and 29.

The gear 28D of the gear train 28 is rotated in a counterclockwise sense, and the gear 29C of the gear train 29 is rotated in a clockwise sense. Since the spring clutches 30 and 31 transmit only counterclockwise rotations of the gears 28D and 290 to the sheet feeding roller 15 and the sheet discharge roller 22, the rotation of the gear 28D is transmitted to the sheet feeding roller 15, but the rotation of the gear 29C is not transmitted to the sheet discharge roller 22.Thus, the sheet feeding roller 15 is rotated counterclockwise in Fig. 3, the sheet S urged into contact with the sheet feeding roller 15 is fed out of the sheet feeding tray 14 by the operation of the coiled spring 16, and introduced into the printer body 8 along the guide plate 10 of the printer 1 to be suplied to between the conveying roller 7 and the guide rollers 9. When the end of the sheet S arrives at the conveying roller 7 and the guide rollers 9, the stepping motor 26 is stopped, and the conveying roller 7 is rotably driven by the motor, not shown, to convey the sheet S until the sheet S reaches the printing unit 6. At this time, the sheet feeding roller 15 is driven by the frictional force with the sheet S. When the sheet S is stopped at the predetermined position, the carriage 4 is moved to seially print the sheet S using the printing head S.When the conveying roller 7 is again rotatably driven to feed the sheet S for one line, the carriage 4 is returned to the original position while the sheet being fed is again fed to serially print the sheet S using the printing head 5.

Thus, while the printing of the printing head 5 and the conveying of the sheet sby the conveying roller 7 are alternatively executed, the end of the sheet S is gradually projected over the printing unit 6 of the printer 1 to be conveyed toward the discharge sheet tray 19 along the guide plate 24 of the automatic sheet feeding apparatus 2. When the printer is finished and the rear end of the sheet S is removed from between the conveying roller 7 and the guide rollers 9, the motor for driving the conveying roller 7 is stopped. The stepping motor 26 of the automatic sheet feeding apparatus 2 is then rotated in a clockwise sense as viewed in Fig. 1 this time to rotate the gear 28D of the gear train 28 in a clockwise sense and to rotate the gear 29 of the gear train 29 counterclockwise sense.Then, both the spring clutches 30 and 31 transmit only the counterclockwise rotations of the gears 28D and 29 to the sheet feeding roller 15 and the sheet discharge roller 22. Thus, the rotation of the gear 29C is transmitted to the sheet discharge roller 22, but the rotation of the gear 28D is not transmitted to the sheet feeding roller 15. Therefore, the clockwise rotation of the stepping motor 26 is not transmitted to the sheet feeding roller 15, but transmitted only to the sheet feeding roller 22.

Thus, the sheet feeding roller 22 is rotated in a counterclockwise sense in Fig. 3 to introduce the printed sheet S into the discharge sheet tray 19.

According to the embodiment described above, the sheet feeding roller 15 and the sheet discharge roller 22 can be selectively rotated by rotating the stepping motor 26 provided in the automatic sheet feeding apparatus 2 in either direction. Therefore, the automatic sheet feeding apparatus body 11 can be reduced in size to increase the degrees of freedom when designing. Since the stepping motor 26 is further independently provided, its control can be simply executed. Further, since the sheet feeding roller 15 and the sheet discharge roller 22 are selectively rotated in either sense, unused sheets S are not introduced into the printer body 8.

With the sheet feed apparatus described another electic motor is provided. Therefore, it is not necessary to provide a power transmission mechanism for transmitting the drive to the printer and a switching mechanism for switching therebetween.

Using a second motor control is simplier and we can reduce the size the sheet feeding apparatus body to increase the degrees of freedom when designing.

Further, since the sheet feeding roller and the sheet discharge roller can be selectively driven an unnecessary sheet need not be supplied into the output device.

Claims (5)

1. Automatic sheet feeding apparatus having a sheet feeding tray, a discharge sheet tray, a sheet feeding roller for feeding sheets in the sheet feeding tray one by one and a sheet discharge roller for introducing the sheets one by one in the discharge sheet tray, the apparatus comprising an electric motor rotatable in both forward and reverse senses, a one-way clutch for transmitting rotation of the motor to the sheet feeding roller in only one sense, and another one-way clutch for transmitting the rotation of the motor to the sheet discharge roller in the opposite sense.

2. Automatic sheet feeding apparatus according to Claim 1, wherein said motor is a stepping motor.

3. Automatic sheet feeding apparatus according to Claim 1, or to Claim 2 wherein the or each said one-way clutch is a spring clutch.

4. Automatic sheet feed apparatus substantially as hereinbefore with reference to the accompanying drawings.

5. A printer incorporating apparatus according to any preceeding claim.