IMAGE FORMING APPARATUS

Abstract

A sheet surface detecting mechanism, which detects the upper surface of sheets stacked on a tray, including: a sensor disposed in a position spaced apart from a conveying portion; a pivotal sensor flag turning the sensor ON/OFF; and a sheet surface detecting member being disposed in parallel with the sheets stacked on the tray, moving in a vertical direction while causing the sensor flag to pivot in contact with the upper surface of the sheets, and turning the sensor ON/OFF via the sensor flag.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating a schematic construction of a printer, being one example of an image forming apparatus provided with a sheet feeding device according to an embodiment of the present invention.

FIG. 2 is a view illustrating construction of the above-mentioned sheet feeding device.

FIG. 3 is a first view for illustrating sheet feeding operation of the above-mentioned sheet feeding device.

FIG. 4 is a second view for illustrating sheet feeding operation of the above-mentioned sheet feeding device.

FIG. 5 is a third view for illustrating sheet feeding operation of the above-mentioned sheet feeding device.

FIG. 6 is a view for illustrating construction of a sheet surface detecting mechanism provided in the above-mentioned sheet feeding device.

FIG. 7 is a view for illustrating construction of a sheet surface detecting sensor flag provided in the above-mentioned sheet surface detecting mechanism.

FIG. 8 is a first view for illustrating sheet surface control operation of the above-mentioned sheet feeding device.

FIG. 9 is a second view for illustrating sheet surface control operation of the above-mentioned sheet feeding device.

FIG. 10 is a third view for illustrating sheet surface control operation of the above-mentioned sheet feeding device.

FIGS. 11A and 11B are views of the above-mentioned sheet surface detecting mechanism taken from diagonally below a sucking and conveying belt.

FIG. 12 is a view illustrating the state in which a sensor flag mechanism provided in the above-mentioned sheet surface detecting mechanism is housed in a suction duct.

FIG. 13 is a block diagram for making control of the above-mentioned sheet feeding device.

FIG. 14 is a view for illustrating operations of a conventional sheet feeding device.

FIG. 15 is a view for illustrating a sheet surface detecting mechanism of the conventional sheet feeding device.

FIG. 16 is a view illustrating the state in which air is blown to curled sheets in the conventional sheet feeding device.

Claims

1. An image forming apparatus, which forms an image on a sheet fed from a sheet feeding device in an image forming portion, the sheet feeding device comprising:a tray which supports sheets;an air blowing portion which blows air to an end portion of the sheets supported by the tray;a conveying portion which sucks and conveys the sheet blown up with air blown by the air blowing portion; anda sheet surface detecting mechanism, which detects an upper surface of the sheet blown up,the sheet surface detecting mechanism including:a sensor portion disposed at a position spaced apart from the conveying portion to an upstream side in a sheet conveying direction;a sensor flag which turns the sensor portion ON and OFF; anda sheet surface detecting member connected to the sensor flag, extending from a side on which the sensor portion is disposed to under the conveying portion and toward a downstream side in the sheet conveying direction, and being contactable with the sheet blown up.

2. An image forming apparatus according to claim 1, wherein the conveying portion including: a plurality of sucking and conveying belts disposed in a direction perpendicular to the sheet conveying direction; a suction duct disposed inside the plurality of sucking and conveying belts; and a suction fan generating a negative pressure in the suction duct, and wherein the sheet surface detecting member, with an upstream side thereof in the sheet conveying direction being connected to the sensor flag, and a downstream side thereof being connected to a support member of which one end side is pivotally disposed in the suction duct, and of which the other end side protrudes from between the plurality of sucking and conveying belts, forms a link movable in parallel in a vertical direction.

3. An image forming apparatus according to claim 2, wherein the suction duct is provided with an opening through which the support member rotatable in the vertical direction is protruded, and wherein when a sheet is sucked to the sucking and conveying belt, the sheet surface detecting member is retracted into a side of the suction duct by a sucked sheet to close the opening.

4. An image forming apparatus according to claim 1, wherein the sensor portion is provided with a first and a second sensors, the sensor flag is provided with a first and a second detecting portions to be detected by the first and second sensors, and wherein when air is blown to sheets by the air blowing portion, the sheet surface detecting member is moved by an uppermost sheet blown up so that each sensor is selectively turned ON/OFF by an associated detecting portion of the sensor flag, and the tray is lifted or lowered based on ON/OFF of each sensor to keep the uppermost sheet blown up in a position in which the sheet can be sucked and conveyed by the conveying portion.