IMAGE FORMING APPARATUS

Abstract

A detecting device for detecting the presence or absence of a sheet contained in a sheet containing portion includes a rotatable arm portion brought into contact with the sheet contained in the sheet containing portion, a stopper portion rotatable in association with the arm portion for determining the position of the arm portion when there is no sheet in the sheet containing portion and whose rotation is regulated when there is no sheet in the sheet containing portion. And when the sheet in a conveying path is to be pulled out, the arm portion is retreated from a position determined by the stopper portion due to the pressure of the sheet being pulled out.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating a construction of a laser beam printer, which is an example of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a view illustrating a construction of a sheet presence or absence sensor portion provided at the above laser beam printer.

FIG. 3 is a side view illustrating the construction of the above sheet presence or absence sensor portion.

FIG. 4 is a view illustrating a state of the above sheet presence or absence sensor portion before a jammed sheet is pulled out.

FIG. 5 is a view illustrating a state of the above sheet presence or absence sensor portion when the jammed sheet is pulled out.

FIGS. 6A, 6B and 6C are views illustrating the construction of the sheet presence or absence sensor portion provided at an image forming apparatus according to a second embodiment of the present invention.

FIG. 7 is a view illustrating a construction of a conventional laser beam printer.

FIG. 8 is a view illustrating a state at jam clearance in the above laser beam printer.

Claims

1. An image forming apparatus comprising: an image forming portion; a conveying path for conveying a sheet to the image forming portion; a sheet containing portion configured to contain the sheet; and a detecting device configured to detect a state of the sheet contained in the sheet containing portion, the detecting device including:an arm portion, which is rotatable and brought into contact with the sheet contained in the sheet containing portion;a sensor configured to output a signal according to a position of the arm portion; anda stopper portion rotatable in association with the rotation of the arm portion and determining the position of the arm portion while not in contact with the sheet contained in the sheet containing portion;wherein the arm portion can be retreated from the position determined by the stopper portion to an outside position of a rotating range for an operation of detecting the sheet of the arm portion.

2. An image forming apparatus according to claim 1, further comprising an elastic member configured to elastically connect the arm portion and the stopper portion, wherein the arm portion can be retreated against an elastic force of the elastic member.

3. An image forming apparatus according to claim 1, wherein in a state in which the arm portion is in contact with the sheet contained in the sheet containing portion, the stopper portion is rotated along with the arm portion, while in a state in which the arm portion is out of contact with the sheet contained in the sheet containing portion, the stopper portion is brought into contact with a regulating portion so as to determine a position of the arm portion.

4. An image forming apparatus according to claim 3, wherein the regulating portion is provided at the sensor.

5. An image forming apparatus according to claim 1, wherein the conveying path is a re-conveying path for reversing the sheet so that an image is formed on a second face opposite to a first face of the sheet on which an image is formed by the image forming portion and for conveying the sheet to the image forming portion again, and in the re-conveying path, a lower conveying guide arranged above the sheet containing portion and constituting the re-conveying path is openable and closable with respect to a sheet containing portion side so that the sheet can be removed from the re-conveying path by pulling out the sheet containing portion from an image forming apparatus body and opening the lower-conveying guide.

6. An image forming apparatus according to claim 1, wherein a relation between a contact width D with the sheet and a fundamental thickness d of the arm portion is D>d.

7. An image forming apparatus according to claim 1, wherein both ends of the arm portion in a width direction orthogonal to a sheet pullout direction are curved.