JPS59108641A - Sheet curl straightening device - Google Patents

Abstract

PURPOSE:To increase a sheet curl straightening effect ever so high, by making a linear speed for a driving roller in case of a sheet curl straightening roller speedier than a conveying speed for a sheet, while making full use of a squeeze by slippage between the sheet and the driving roller. CONSTITUTION:With a pressure mechanism employed, a driven roller 20a is forced by pressure toward a driving roller 20b, while nips are formed between these rollers. When a sheet P passes through these nips, linear speed for the driving roller 20b is set to be speedier than a conveying speed for the sheet P so that these produces slippage between the sheet P and the driving roller 20b, causing the sheet P to be squeezed in consequence, whereby a curl appearing on the sheet P is effectively straightened owing to a multiplier effect by the surface curvature and pressure force of the driving roller 20b plus this squeeze action.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a sheet conveyance mechanism in a copying machine, and more particularly to a sheet curl correction device.

PRIOR ART Conventionally, it is known that a sheet roller is passed between rollers formed in a nip (between a driving roller and a driven roller) to straighten the curls on the sheet. However, conventional curl straightening devices simply The sheet is simply passed through a nip under pressure, and in the case of flexible sheets or thick sheets, no great correction effect can be expected.

Curled sheets can cause transport problems in the copying machine's sheet transport path (for example, paper jams due to curled sheet ends) and image problems (for example, missing images at the sheet ends), so it is necessary to completely correct curls. There is.

1. The present invention was made based on the above circumstances,
It is an object of the present invention to correct the above-mentioned curl of a sheet, which has conventionally been considered difficult to correct, without adding a special new mechanism.

1 quart The structure of the present invention will be explained below based on examples.

FIG. 1 is a schematic overall configuration diagram of a copying machine equipped with a curl straightening device according to the present invention. In the figure, 1 is the manuscript table;
2 is an upper cover, 3 is a document holder, 4 is a fluorescent lamp, 5 is an exposure glass, 6 is a lens array, 7 is a photosensitive drum, 8 is a static elimination lamp, 9 is a charging charger, 10 is a toner tank,
11 is a magnetic sleeve, 12 is a transfer separation charger, 1
3 is a separation claw, 14 is a manual feed table, 15 is a manual feed insertion roller, 16 is a manual feed roller, 17 is a roll vapor, 18 is a roll paper feed roller, 19 is a cutter, 20
21 is a sheet curl correction roller, 21 is a Xe flash lamp for fixing, 22 is a separation conveyance tank, 23 is a separation conveyance belt, 24 is a copy receiver, 25 is a power supply unit, 26 is a cooling fan, 27 is a blower, 128 is a deodorizing filter,
29 is a fixing power supply unit, 30 is a roll diameter detection device,
40 is a sheet detector.

FIG. 2 is an enlarged longitudinal sectional side view of the vicinity of the sheet curl 'ATE roller 20 in FIG. 1.

The sheet curl correction roller 20 includes a driven roller 20a made of an elastic body and a drive roller 20b made of a rigid body such as metal or hard rubber. The driven roller 20a can be pressed against the drive roller 20b so as to slightly bite into it, and a nip for holding the sheet P between the rollers is formed. The surface of the drive roller 20b is roughened.

The sheet P is conveyed by the sheet curl correction roller 20 through the conveyance path 31 toward the transfer position of the photoreceptor drum 7, but the curl of the sheet P is removed when it passes through the nip portion of the sheet curl correction roller 20. It will be corrected.

FIG. 3 is a diagram showing the state of sheet curl correction, that is, a diagram similar to FIG. 2 showing a state in which the sheet P is passing through the sheet curl correction roller 20e.

When the leading edge (or trailing edge) of the sheet P passes the sheet detector 40, a timer 41, which will be described later, is triggered to generate a predetermined timing. At this time, the drive roller 20b is rotated by a drive mechanism (not shown), and the linear velocity (peripheral velocity of the surface) is the transport speed (process speed of the copying machine) of the rollers 15, 1.6, 1.
8), which is the conveyance speed of the photoreceptor drum 7, etc.). At a predetermined timing, a pressure mechanism, which will be described later, causes the driven t'-roller 20a to press against the drive roller 20b.
Pressure is applied in the direction of , and a nip is formed between both rollers.

When the sheet P passes through this nip, the curl of the sheet P is corrected and the sheet P is sent to the transfer section as described above.

The sheet curl is corrected by the curvature and pressing force of the surface of the drive roller 20b, as well as the slippage between the sheet P and the surface of the drive roller 20b. This is effectively done by "shigoki".

At this time, the conveyance force of the sheet curl correction roller 20 is set to be smaller than the conveyance force of the other pair of rollers 18 and 19 and the photosensitive drum 7, so that it does not affect the conveyance speed of the sheet P.

FIG. 4 is a block diagram of the control circuit of the curl straightening device.

A timer 41 is activated by the signal from the sheet detector 40,
Further, the timer signal is used to operate the υ one/yoft multivibrator 42, thereby driving the solenoid 90't-.

FIG. 5 is a simplified configuration diagram showing an embodiment of a mechanism for applying pressure to the drive roller 20b by the driven roller 20&.

In the figure, 50 is a pressure switching lever, 50a is a lever shaft, and 50b is a cam follower.

The driven roller 20a is pressed by one arm 50c of the pressure switching lever 50 and is pressed against the drive roller 20b.

60 is a pressure cam that determines the amount of pressure (interlocked with the clutch)
, 70 is a pressure switching clutch consisting of a spring clutch, 80 is a stop (-) of the pressure switching clutch 70,
It has claws 80a and 80b at the top and bottom. 90 is the aforementioned solenoid for pressure switching.

The operation will be explained next. When the solenoid 90 is pulled by the operation of the one-shot multivibrator 42 (turned ON), the lower pawl Bob of the stopper 80 of the pressure switching clutch 70 The clutch rotates as the clutch moves away from the groove. When the clutch rotates 1/2, the upper pawl 80a of the stopper 80
However, it gets caught in the groove of the sleeve and the clutch stops. At this time, the cam follower 50b of the pressure switching lever 50 is
In order to ride on the peak of the pressure cam 6o, the pressure switching lever 50 rotates to the left and pushes down the shaft of the driven roller 20&. As a result, the driven roller 20a is brought into pressure contact with the driving roller 20b, and a nip is formed between the two.

Effects As described above, in the present invention, the linear speed of the drive roller in the sheet curl correction roller is made faster than the conveyance speed of the sheet, so in addition to the conventional correction effect at the nip, the linear speed of the drive roller in the sheet curl correction roller is increased, and in addition to the conventional correction effect at the nip portion, the slippage between the sheet and the drive roller is improved. This corrective effect can be increased by ``shaking''. Furthermore, by providing this sheet curl correction roller at the pre-transfer position, it is possible to prevent sheet trouble at the photosensitive drum portion, which is the most difficult to remove.

[Brief explanation of the drawing]

Fig. 1 is a schematic side view showing the internal structure of a copying machine equipped with a curl correction device, Fig. 2 is an enlarged side view of the main parts, Fig. 3 is a similar view to Fig. FIG. 4 is a block diagram of the pressure contact control of the sheet curl correction roller, and FIG. 5 is a diagram of the pressure contact mechanism of the driven roller. 20a...Followed roller, 20b...
Drive roller, P... Sheet. 111 Figure 1 23￥ Button 2 Figure R311

Claims (1)

[Scope of Claims] α) A driving roller and a driven roller made of an elastic body opposed to the driving roller are provided in the conveyance path of the sheet, and the linear speed of the driving roller is set to be higher than the process speed of the copying machine. A sheet curl correction device characterized by: (2. A sheet curl correction device according to claim (1), characterized in that the driving roller and the driven roller are provided at a pre-transfer position.