Image forming apparatus that varies size of transmission aperture for light from light emitter of sheet sensor, by rotating each of two actuators each having slit

Abstract

A sheet feeding device includes a sheet table, a sheet sensor, a first actuator including a contact portion and a first screen, and a second actuator including an effector and a second screen. The first actuator rotates in a second direction when the contact portion is lifted by a sheet, and rotates in a first direction when the contact portion falls into a hole. The second actuator rotates in the second direction such that the second slit overlaps with the first slit, when the effector is subjected to pressure of the sheet. The first slit is formed so as to differ a size of an aperture, depending on whether the contact portion is in contact with the sheet, or in the hole. The second slit is formed so as to reduce the size of the aperture compared with when the effector is free from the pressure.

What is claimed is;: 
     
         1 . An image forming apparatus comprising:
 an image forming device that forms an image on a sheet;   a sheet feeding device that supplies the sheet to the image forming device; and   a control device including a processor, and configured to act as a controller that controls an operation of the sheet feeding device, when the processor executes a control program,   wherein the sheet feeding device includes:   a sheet table supported on an upstream side in a sheet feeding direction so as to pivot in an up-down direction, and having a groove or a hole;   a sheet sensor including a light emitter, and a photodetector opposed thereto;   a first actuator including a first rotary shaft configured to rotate; an contact portion extending from the first rotary shaft toward the sheet table, and configured to be abutted against the sheet on the sheet table located at a predetermined standby position, by being biased in a predetermined first rotation direction about the first rotary shaft; and a first screen extending from the first rotary shaft to a space between the light emitter and the photodetector, and including a first slit; and   a second actuator including a second rotary shaft coaxial with the first rotary shaft, and configured to rotate independent from the first rotary shaft; an effector extending from the second rotary shaft toward a sheet feeding path, and configured to contact the sheet feeding path by being biased in the first rotation direction; and a second screen extending from the second rotary shaft to a space between the light emitter and the photodetector, and including a second slit,   the controller locates the sheet table at a predetermined sheet feeding position, by causing the sheet table to pivot upward from the standby position, when causing the sheet feeding device to feed the sheet,   the first actuator rotates in a second rotation direction, opposite to the first rotation direction about the first rotary shaft, when the contact portion is lifted up by the sheet on the sheet table because of the sheet table being located at the sheet feeding position, and rotates in the first rotation direction, when the contact portion falls into the groove or the hole because of the sheet on the sheet table having run out,   the second actuator is located such that the second screen keeps from blocking light emitted from the light emitter, when the sheet is not proceeding along the sheet feeding path, and located such that the second slit overlaps with the first slit, by rotating in the second rotation direction about the second rotary shaft, when the effector is subjected to pressure of the sheet proceeding along the sheet feeding path,   the first slit is formed such that a size of a transmission aperture for the light emitted from the light emitter varies, depending on whether the contact portion is in contact with the sheet on the sheet table, or in the groove or the hole, and   the second slit is formed so as to reduce, by overlapping with the first slit, the size of the transmission aperture, compared with a case where the effector is not subjected to the pressure.   
     
     
         2 . The image forming apparatus according to  claim 1 ,
 wherein the first slit and the second slit are formed in an arcuate shape having a radial center coinciding with an axial center of the first rotary shaft, and   a detection line of the sheet sensor extends in a radial direction of the first rotary shaft.   
     
     
         3 . The image forming apparatus according to  claim 1 ,
 wherein the first slit is formed in a shape that makes the size of the transmission aperture different, between when the sheet table is located at the standby position, and when the sheet table is located at the sheet feeding position.   
     
     
         4 . The image forming apparatus according to  claim 3 ,
 wherein the first slit and the second slit are formed in a shape that makes the size of the transmission aperture different, between when the effector is subjected to the pressure, and when the sheet table is located at the standby position.   
     
     
         5 . The image forming apparatus according to  claim 1 ,
 wherein the control device further acts as a decider that decides a status of the sheet, on a basis of a difference in light reception amount of the photodetector.   
     
     
         6 . The image forming apparatus according to  claim 2 ,
 wherein the first slit is formed in the first screen, so as not to overlap with the detection line, when the contact portion is caught in the groove or the hole.