Sheet processing apparatus and image forming system

Abstract

A stacking portion stacks a sheet processed by the processing portion. A lifting/lowering portion lifts and lowers the stacking portion. A displacement portion is provided on the stacking portion and displaced according to a presence or absence of the sheet on the stacking portion. An output portion is provided in the processing unit outputs an electric signal according to the displacement of the displacement portion. A reception portion is provided in the processing unit and receives the electric signal output from the output portion. The wiring portion is provided in the processing unit and connects the output portion and the reception portion. The determination portion determines the presence or absence of the sheet on the stacking portion according to the electric signal received by the reception portion.

What is claimed is: 
     
         1 . An image forming system comprising:
 an image forming unit including an image forming portion configured to form an image on a sheet;   a processing unit including a processing portion configured to perform predetermined processing on the sheet on which the image is formed by the image forming portion, and a sending portion configured to send the sheet processed by the processing portion;   a stacking portion configured to stack the sheet sent by the sending portion;   a lifting/lowering portion provided in the processing unit and configured to lower the stacking portion such that a height of an uppermost sheet among the sheets sent by the sending portion and stacked on the stacking portion falls within a predetermined range and to lift the stacking portion in a case where the sheets stacked on the stacking portion are removed;   a displacement portion provided on the stacking portion and configured to be displaced according to a presence or absence of the sheet on the stacking portion;   an output portion provided in the processing unit and configured to output an electric signal according to the displacement of the displacement portion;   a reception portion provided in the processing unit and configured to receive the electric signal output from the output portion;   a wiring portion provided in the processing unit and configured to connect the output portion and the reception portion; and   a determination portion configured to determine the presence or absence of the sheet on the stacking portion according to the electric signal received by the reception portion.   
     
     
         2 . The image forming system according to  claim 1 , wherein the output portion is configured to output the electric signal according to the displacement of the displacement portion in a state in which the stacking portion is at a predetermined position. 
     
     
         3 . The image forming system according to  claim 2 , further comprising:
 a light emitting portion provided in the processing unit; and   a light receiving portion configured to receive light emitted from the light emitting portion and provided in the processing unit,   wherein the output portion is configured to output the electric signal according to a light receiving state of the light receiving portion,   the light emitting portion is disposed on one side of a stacking surface, on which the sheet is stacked, of the stacking portion in a width direction of the sheet intersecting a sheet sending direction of the sending portion,   the light receiving portion is disposed on the other side of the stacking surface in the width direction, and   the displacement portion is configured to block the light emitted from the light emitting portion such that the light emitted from the light emitting portion is not received by the light receiving portion in a case where there is no sheet on the stacking portion and the stacking portion is at the predetermined position or, in a case where there is the sheet on the stacking portion and the stacking portion is at the predetermined position.   
     
     
         4 . The image forming system according to  claim 2 ,
 wherein the output portion is configured to output the electric signal according to a position of the stacking portion or a position of the sheet stacked on the stacking portion in a case where the stacking portion is positioned below the predetermined position, and   the determination portion is configured to determine a position of a stacking surface of the stacking portion on which the sheet is stacked or a position of an upper surface of an uppermost sheet among a plurality of sheets stacked on the stacking surface according to the electric signal output from the output portion.   
     
     
         5 . The image forming system according to  claim 4 , further comprising
 a height detection portion configured to detect a height position of the stacking portion in a lifting/lowering direction,   wherein the determination portion is configured to determine that there is the sheet on the stacking portion regardless of the electric signal of the output portion in a case where a height position of the stacking portion is a lowered position lower than a predetermined height position when the stacking portion is lifted and the output portion transitions from a first state to a second state, the first state being a state in which the output portion outputs the electric signal in a case where there is no stacking portion or there is no sheet stacked on the stacking portion, the second state being a state in which the output portion outputs the electric signal in a case where there is the stacking portion or there is the sheet stacked on the stacking portion.   
     
     
         6 . The image forming system according to  claim 5 , wherein in a case where the lifting/lowering portion lifts the stacking portion and a position of the stacking portion when the output portion transitions from the first state to the second state is a lifted position equal to or higher than the predetermined height position, the lifting/lowering portion is configured to move the stacking portion to the predetermined position and the determination portion is configured to determine the presence or absence of the sheet on the stacking portion according to the electric signal of the output portion in a state in which the stacking portion is at the predetermined position. 
     
     
         7 . The image forming system according to  claim 1 , further comprising:
 a light emitting portion provided in the processing unit; and   a light receiving portion configured to receive light emitted from the light emitting portion and provided in the processing unit,   wherein the output portion is configured to output the electric signal according to a light receiving state of the light receiving portion, and   the displacement portion is configured to reflect the light emitted from the light emitting portion and cause the light receiving portion to receive the light in any one of a case where there is no sheet on the stacking portion and a case where there is the sheet on the stacking portion.   
     
     
         8 . The image forming system according to  claim 1 ,
 wherein the displacement portion is a first displacement portion,   the image forming system further comprises a second displacement portion provided in the processing unit and configured to be displaced according to displacement of the first displacement portion by coming into contact with the first displacement portion in a state in which the stacking portion is at a predetermined position and in any one of a case where there is no sheet on the stacking portion and a case where there is the sheet on the stacking portion, and   the output portion is configured to output the electric signal according to the displacement of the second displacement portion.   
     
     
         9 . The image forming system according to  claim 1 , further comprising:
 an interlocking portion provided on the stacking portion so as to protrude from one end portion of the stacking portion in a width direction of the sheet intersecting a sheet sending direction of the sending portion and configured to interlock with the displacement of the displacement portion;   a light emitting portion provided in the processing unit; and   a light receiving portion configured to receive light emitted from the light emitting portion and provided in the processing unit,   wherein the output portion is configured to output the electric signal according to a light receiving state of the light receiving portion,   the light emitting portion and the light receiving portion are disposed at positions deviated from a lifting/lowering range of the stacking portion in a substantially vertical direction and disposed so as to sandwich the interlocking portion, and   the interlocking portion is configured to block light such that the light emitted from the light emitting portion is not received by the light receiving portion in any one of a case where there is no sheet on the stacking portion and a case where there is the sheet on the stacking portion.   
     
     
         10 . The image forming system according to  claim 1 , further comprising
 a conveyance portion disposed above the stacking portion and configured to move to a conveyance position where the conveyance portion comes into contact with the sheet on the stacking portion and conveys the sheet upstream in a sheet sending direction of the sending portion, and a retraction position where the conveyance portion retracts upward from the conveyance position,   wherein the conveyance portion is positioned at the conveyance position in a case where the determination portion determines the presence or absence of the sheet on the stacking portion according to the electric signal output from the output portion.   
     
     
         11 . A sheet processing apparatus comprising:
 a processing unit including a processing portion configured to perform predetermined processing on a sheet and a sending portion configured to send the sheet processed by the processing portion;   a stacking portion configured to stack the sheet sent by the sending portion;   a lifting/lowering portion provided in the processing unit and configured to lower the stacking portion such that a height of an uppermost sheet among the sheets sent by the sending portion and stacked on the stacking portion falls within a predetermined range and to lift the stacking portion in a case where the sheets stacked on the stacking portion are removed;   a displacement portion provided on the stacking portion and configured to be displaced according to a presence or absence of the sheet on the stacking portion;   an output portion provided in the processing unit and configured to output an electric signal according to the displacement of the displacement portion;   a determination portion provided in the processing unit and configured to determine the presence or absence of the sheet on the stacking portion according to the electric signal output from the output portion; and   a wiring portion provided in the processing unit and configured to connect the output portion and the determination portion.   
     
     
         12 . An image forming system comprising:
 an image forming unit including an image forming portion configured to form an image on a sheet; and   the sheet processing apparatus according to claim  11 ,   wherein the sheet processing apparatus is configured to perform the predetermined processing on the sheet on which the image is formed by the image forming portion.   
     
     
         13 . A sheet processing apparatus comprising:
 a processing unit including a processing portion configured to perform predetermined processing on a sheet received from an image forming unit including an image forming portion configured to form an image on the sheet, and a sending portion configured to send the sheet processed by the processing portion;   a stacking portion configured to stack the sheet sent by the sending portion;   a lifting/lowering portion provided in the processing unit and configured to lower the stacking portion such that a height of an uppermost sheet among the sheets sent by the sending portion and stacked on the stacking portion falls within a predetermined range and to lift the stacking portion in a case where the sheets stacked on the stacking portion are removed;   a displacement portion provided on the stacking portion and configured to be displaced according to a presence or absence of the sheet on the stacking portion;   an output portion provided in the processing unit and configured to output an electric signal according to the displacement of the displacement portion;   a reception portion provided in the processing unit and configured to receive the electric signal output from the output portion;   a wiring portion provided in the processing unit and configured to connect the output portion and the reception portion; and   a transmission portion provided in the processing unit and configured to transmit the electric signal received by the reception portion to the image forming unit including a determination portion configured to determine the presence or absence of the sheet on the stacking portion.   
     
     
         14 . An image forming system comprising:
 an image forming unit including an image forming portion configured to form an image on a sheet; and   the sheet processing apparatus according to claim  13 ,   wherein the sheet processing apparatus is configured to perform the predetermined processing on the sheet on which the image is formed by the image forming portion,   the reception portion is a first reception portion,   the image forming unit includes a second reception portion configured to receive an electric signal output from the output portion transmitted from the transmission portion, and   the determination portion is configured to determine a presence or absence of a sheet on the stacking portion according to the electric signal received by the second reception portion.