JPH01321228A - Sheet feeder - Google Patents

Abstract

PURPOSE:To feed a sheet piece by piece so accurately even to such one as large in a friction factor by installing a sheet separation means provided with an air blasting means, and discharging gas to a front edge of the sheet. CONSTITUTION:When a suction head 31 comes to a stop at an optimum position (e), a separate fan 40 starts its operation in accordance with a preprogrammed procedure, and almost simultaneously a suction fan 35 also starts its suction. With this constitution, air discharged out of a blast duct 41 flows in a lower part of the suction head 31 from a notch installed in one side of a cassette 10, and it comes to a state of being somewhat floated and is blown to each front edge of transfer sheets S, separating them into piece, while the suction fan 35 starting its operation attracts the transfer sheet S situated on a topmost part by suction, making it attract the underside of a suction plate 30. Next, the separate fan stops its operation, and simultaneously link levers 28, 28 restart their operation, making the suction head 31 go up archedly toward the front of a conveying direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sheet feeding device suitable for application to image forming apparatuses and the like.

[Prior Art] A transfer sheet feeding device applied to a copying machine, especially a transfer sheet feeding device using a cassette, is generally attached to a spring as seen in Japanese Patent Application Laid-Open No. 55-40155. A mechanism is employed in which the transfer sheet is constantly pressed from below against the paper feed roller by a biased pressing member.

This type of device has the advantage that it has a simple mechanism and does not cause many inconveniences such as multi-sheet feeding as long as it transports plain paper. A transfer sheet, in other words, a transfer sheet that is pressed against a photosensitive film coated with dispersed microcapsules to transfer the dye precursor (liquid) inside the capsules and visualize the latent image formed on the photosensitive film. Since the surface of the sheet is coated with a color developer and a brightening agent, the coating agent on the sheet side and the oily component on the paper feed roller side react with each other due to pressure contact with the paper feed roller. This may contaminate the surface of the paper feed roller, the large friction coefficient of the coating layer may easily cause multiple sheets to be fed in humid conditions, or the friction between sheets during paper feeding may cause friction on the lower transfer sheet. This causes inconveniences such as scratches and the like, which adversely affect the image.

[Problems to be Solved by the Invention] The present invention has been made in view of these inconveniences, and its purpose is to prevent any other adverse effects on sheets with particularly large surface friction coefficients. It is an object of the present invention to provide a highly reliable device that can reliably feed one sheet at a time without causing damage.

[Means for Solving the Problems] That is, the present invention provides a sheet feeding device for achieving the above object, which includes a sheet conveying means disposed above the front edge of the stacked sheets, and an arrangement of the sheet conveying means. A sheet suction/holding means that moves back and forth between the installation position and the rear upper surface of the front edge of the sheet and includes a suction means therein, and a blower means that is disposed opposite to the front edge of the stacked sheets. In the sheet feeding device, the suction and holding means is stationary at an appropriate position between a position where the suction and holding means contacts the sheet and an upper limit position of the suction and holding means. At the same time as the suction is started, the sheet separating means including the blowing means discharges gas to the leading edge of the sheet.

[Example] Therefore, Fig. 6 for explaining the embodiment shown below shows an example of a photosensitive transfer type image forming apparatus to which the apparatus of the present invention is applied. Reference numeral 2 is a film cassette loaded into the main body 1 of the apparatus, and the photosensitive film f stored therein is
Microcapsules that contain cyan, magenta, and yellow dye precursors (liquids) and that harden when exposed to red, green, and blue wavelength light energy are dispersed and coated. Reference numeral 3 denotes an exposure stand disposed on the conveyance path of the photosensitive film f, which is exposed to light reflected from the original d on the original platen 5 irradiated by the lamp 4 and incident thereon via the SELFOC lens array 6. The structure is such that a perfect image is formed on the photosensitive film section that is transported at the same speed as d.

Reference numeral 7 denotes a pressure developing device disposed on the downstream side of the exposure table 3 in the film conveyance direction, in which the photosensitive film f that has undergone the exposure process and the transfer sheet in the cassette 10 that has been conveyed by the conveyance roller 8 and the nip roller 9 are stored. A pair of pressure developing rollers 13 and 14 are disposed in pressure contact with S, and the pressing force of a strong coil spring 16 is applied via a Biyadal-type intermediate roller 15 (FIG. 7) with a large diameter at the center in the longitudinal direction. By applying pressure to one of the above-described pressure developing rows 213 and 14, the photosensitive film f and the transfer sheet S are strongly pressed, destroying the microcapsules on the photosensitive film portion that have not been cured during the exposure process, and transferring the ink inside. At the same time as the ink is transferred to the transfer sheet), the ink is reacted with a color developer applied to the transfer sheet) to develop color.

Also, on the discharge side of this pressure developing device 7, there is a Gaitoro・-2
18 and a guide plate 19 are disposed, and the photosensitive film f that has undergone the developing process is guided by the guide roller 18 and stored in the above-mentioned film cassette 2, while the transfer sheet S that has undergone the developing process is guided by the guide plate 19. After that, it enters the heating fixing device 20, where the coloring reaction is promoted and the image is subjected to gloss treatment using a brightening agent applied to the transfer sheet S.

By the way, FIG. 1 shows a transfer sheet feeding device which is a characteristic part of the present invention applied to the above-described image forming apparatus, and this feeding device 22 is roughly divided into a cassette 10
It is comprised of a sheet feeding unit 23 that feeds the inner transfer sheet S between the transport row 28 and the nip roller 90, and a sheet separation unit 39 that separates the uppermost transfer sheet S to be fed from other sheets.

The sheet feeding unit 23 described above is further slidably supported by a downward U-shaped unit frame 24 that reciprocates between a position above the leading end of the cassette 10 and a position below the rear end of the cassette 10 at the loading position. and a suction head 31. That is, the fixing plate 25 provided directly above the cassette 10 has the cassette 10
A platen (platen) 27.27 is fixed at the tip of the platen, and a pair of parallel link rods 28, 28 on the left and right sides, which are moved up and down rearward in the transport direction by a drive mechanism (not shown), are swingably supported here. . The unit frame 24 described above is
These parallel rods 28, 28 are supported horizontally with pins at their free ends, so this unit frame 24 is
While maintaining a horizontal posture according to the up-and-down movements of the parallel rods 28, 28, the cassette 11 moves downward toward the transfer sheet S while drawing an arcuate trajectory from above the tip toward the rear thereof. A guide shaft 29 that is horizontal in the conveying direction is fixed to the unit frame 24, and a suction head 31, which will be described later, is slidably attached to the unit frame 24 while being always urged backward in the conveying direction by a spring 30. There is.

On the other hand, the suction head 31, which is slidably attached to the guide shaft 29 on the unit frame 24 through the front and rear sliding holes 52, 52 provided at the upper end, is attached to the bottom surface of the unit as shown in FIG. It is composed of a suction plate 34 provided with a shallow suction recess 33 and a cylindrical body 36 communicating with the suction recess 36 and incorporating a small suction fan 35 inside.
At the rear end of 6, the suction head 31 is attached to the unit frame 24.
At the same time, a protrusion 37 is integrally provided which comes into contact with the vertical perpendicular plate 26 provided on the fixed plate 25 in the process of descending in an arcuate trajectory backward in the conveyance direction.

On the other hand, the above-mentioned separation unit 59 is constituted by a ventilation duct 41 equipped with a small separate fan 40 therein, and its outlet 42 is formed in a notch provided from one end side of the nip roller 9 to the front end a-side of the cassette 10. 11 (FIG. 2), air is blown onto the front edge side of the transfer sheets S stacked inside to separate them from each other.

In this embodiment, a cassette 10 is used which has four parts 12 at the tip of the bottom plate, so that when the transfer sheet S is loaded, the tip part is shifted at this part and separated. Reference numeral 44 in the figure indicates an entry sensor that detects the leading edge of the transfer sheet S.

Next, the feeding operation of the transfer sheet S by the above-described device will be explained.

In the standby state shown in FIG. 1, the pair of parallel link rods 28, 28 are erected, and the unit frame 24, which is pivotally supported at the free ends thereof, is in the uppermost position, and the suction head 31 held therein is moved to the cassette 10. When a sheet feed command signal is outputted in a standby state where the sheet S is positioned above the leading end of the sheet S, a drive mechanism (not shown) starts operating and rotates the link rods 28, 28 backward in the conveyance direction of the sheet S. For this reason, the suction head 3 is supported by the unit frame 24 via the guide shaft 29.
1 starts descending backward in the sheet conveyance direction while maintaining a horizontal position while drawing an arc whose radius is the length of the link rod 2B,
During the descending process, it collides with the percussion plate 26 arranged at the rear,
Move to the left in the figure on the guide shaft 30 against the spring 50,
While moving horizontally relative to the unit frame 24, it further descends along the perpendicular plate 26 and contacts the sheet S at a right angle at a position slightly rearward from the leading edge of the transfer sheet S. (Fig. 4 (α)
)).

When the suction head 31 contacts the transfer sheet S, the sheet detection microswitch 45 generates an electric signal indicating that the suction head 31 has descended to the position of the transfer sheet S,
The suction head 31 moves the suction fan 35 from above the paper surface of the transfer sheet S. Separate fan 40. It rises to the optimum position e determined by the shape of the cassette 10 and stops once (
Figure 4(b)).

In this embodiment, the optimum position e is 3rn! on the top surface of the transfer sheet S! The optimum position is within a range of about 10 mm from n.

As mentioned above, the range of the optimum position e is based on the suction capacity of the suction fan 35, the air blowing capacity of the separate fan 40, and the cassette 1.
It has been experimentally revealed that the value of the optimum position C is determined by the shape of the transfer sheet S. It will be about. When the suction head 31 is out of the range of this optimum position e, if the value is small, the occurrence rate of multiple sheet feeding increases, and if the value is too large, the occurrence rate of paper feeding failures called bottom feeding increases. An increase was actually confirmed (Fig. 8).

FIG. 8 is a correlation diagram showing the relative distance between the suction head 31 and the transfer sheet S and the incidence of paper feeding failure.
Using a suction fan of 35 types, transfer sheet) S each 100
This is an experiment on 0 sheets and a diagram of it.

In FIG. 8, the line graph shown by a solid line shows the case where the rated suction fan 35 in this embodiment is used, and the line graph shown by the broken line shows the case where the suction fan 35 having twice the suction capacity of the above-mentioned rated 7 am is used. The case is shown below.

In this embodiment, from FIG. 8, the optimum f'Ae of the upper surface of the transfer sheet S and the suction head 31 is determined to be 6rrtm.

When the suction fan 31 stops at the optimum position e, the separate fan 40 starts operating according to a preprogrammed procedure as shown in FIG. 5, and the suction fan 35 also starts suction at the same time.

Thereby, the air discharged from the ventilation duct 41 is transferred from the notch 11 provided on one side of the cassette 10 to the suction hect 3.
1 flows downward, becomes slightly raised, and blows against the leading edge of the transfer sheet (S), separating them.
The suction unit 35 that has started to operate sucks the transfer sheet S located at the top and attracts it to the lower surface of the suction plate 30 (FIG. 4(C)).

When this suction is performed, a slight load acts on the suction 7 unmotor, and the pressure inside the suction head 31 also changes slightly, so these changes confirm that the transfer sheet S is suctioned. Then, the separate fan 40 stops operating, and at the same time, the link rods 28, 2B start operating again, causing the suction head 31 to move upward in an arc toward the front in the transport direction. When the suction head 31 is pulled up to the uppermost position in this way, the leading end of the transfer sheet S protruding from the front end of the head 31 is moved to the conveying roller 8 disposed here.
Then, the suction fan 35 is stopped and the two openings 28 and 9 are connected at the same time, and the transfer sheet S is sandwiched between them, and the transfer sheet is synchronized with the photosensitive film f. 4(d)).

The above-mentioned embodiment is configured as a device that transports sheets with a relatively large coefficient of friction, such as those used in photosensitive transfer type image forming devices. The present invention can also be applied to a printing device that handles paper with a large coefficient and a conveyance device that handles plain paper, thereby making it possible to prevent double feeding accidents of sheets in humid conditions.

[Effects of the Invention] As described above, according to the present invention, the sheet suction and holding means is reciprocated between the position above the leading edge of the stacked sheets and the rear upper surface of the leading edge of the sheet. In this case, the front end portion of the sheet can be left in contact with the rear upper surface of the sheet so that the sheet can be delivered to the sheet conveying means, and can be held by suction.
The suction-held sheet can be pulled up forward in the transport direction and delivered to the sheet 1 feeding means. Moreover, since the blowing means is provided opposite to the leading edge of the laminated sheets, and the gas is blown onto the leading edge of the sheets, the laminated sheets work together with the suction holding means, which is controlled and stopped at an optimal position. The sheets can be reliably separated without disturbing the sheets, and accidents such as multiple feeding can be prevented.

[Brief explanation of the drawing]

Figure 1 is a side view of a device showing an embodiment of the present invention, Figure 2 is a top view of the main parts, and Figures 3 (cL) and (b) are a front view and bottom view of the suction head incorporated in the same device. 4(a) to (d) are explanatory diagrams showing the sheet feeding operation, FIG. 5 is a diagram showing its timing, and FIG. 6 is an example of a photosensitive transfer type image forming apparatus equipped with the above device. FIG. 7 is a side view showing the intermediate roller, and FIG. 8 is a correlation diagram showing the relationship between the relative distance between the suction section and the transfer paper and the incidence of paper feeding failure. 2...Film cassette 7...
. . . Pressure developer 8 . . . Conveyance roller 9 . . . Nip roller 10 . . . Cassette 20 . ... Feeding device 23 ... Feeding unit 24 ... Unit frame 26 ... Perforating plate 28 ... Link rod 31 ... ...Suction head 35...Suction fan 59...Separate unit 40...Separate fan 45...Sheet detection micro switch d...
...Original e...Optimum position f...Photosensitive film S...Transfer sheet or more Applicant: Seiko Epson Co., Ltd. Company agent Patent attorney Kizobe Suzuki (and 1 other person) Figure 2 4''o (d) Figure 4

Claims (1)

[Claims] A sheet conveying means disposed above the front edge of the stacked sheets, and a sheet suction holding device that moves back and forth between the position of the sheet conveying means and the rear upper surface of the front edge of the sheet and has a suction means inside. and a sheet separating means including a blowing means disposed opposite to the leading edge of the stacked sheets, wherein the suction holding means separates the sheets of the suction holding means. At the same time, the sheet separation means including the air blowing means discharges gas to the leading edge of the sheet. A sheet feeding device characterized by operating as follows.