Sheet feeding apparatus and image forming apparatus

Abstract

A sheet feeding apparatus includes a stacking portion on which a sheet is stacked, a drive source configured to generate a driving force, a pick-up member rotatable with the driving force and configured to rotate in contact with the stacked sheet to feed the sheet, a feed member configured to feed the sheet fed by the pick-up member, an elevating unit configured to raise and lower the stacking portion with the driving force to bring the sheet and the pick-up member into contact with each other, and a control unit configured to control the elevating unit, when a trailing edge of a first sheet fed to the pick-up member is upstream of the feed member and downstream of the pick-up member, to bring a second sheet stacked on the stacking portion and to be fed subsequently to the first sheet and the pick-up member into contact with each other.

What is claimed is: 
     
         1 . A sheet feeding apparatus comprising:
 a stacking portion on which a sheet is stacked;   a drive source configured to generate a driving force;   a pick-up member provided to be rotatable with the driving force of the drive source and configured to rotate in contact with the sheet stacked on the stacking portion to feed the sheet;   a feed member configured to feed the sheet fed by the pick-up member;   an elevating unit configured to raise and lower the stacking portion or the pick-up member with the driving force from the drive source to bring the sheet stacked on the stacking portion and the pick-up member into contact with each other; and   a control unit configured to control the elevating unit,   wherein at least in a state where a predetermined number or more of sheets are stacked on the stacking portion, the control unit controls the elevating unit, at a timing of when a trailing edge in a feeding direction of a first sheet fed to the pick-up member is upstream of the feed member and downstream of the pick-up member, to bring a second sheet stacked on the stacking portion and to be fed subsequently to the first sheet and the pick-up member into contact with each other.   
     
     
         2 . The sheet feeding apparatus according to  claim 1 , further comprising a clutch mechanism configured to transmit the driving force from the drive source to the pick-up member so that the pick-up member rotates after the sheet stacked on the stacking portion and the pick-up member come into contact with each other. 
     
     
         3 . The sheet feeding apparatus according to  claim 2 , wherein the clutch mechanism rotates the pick-up member after a trailing edge of the second sheet passes through the feed member. 
     
     
         4 . The sheet feeding apparatus according to  claim 2 , wherein the clutch mechanism includes:
 a clutch input portion configured to rotate when the driving force of the drive source is input thereto:   a clutch output portion configured to transmit the driving force from the drive source to the pick-up member by engaging with the clutch input portion; and   a movement mechanism configured to move the clutch input portion between a disengagement position where the clutch input portion disengages from the clutch output portion and an engagement position where the clutch input portion engages with the clutch output portion.   
     
     
         5 . The sheet feeding apparatus according to  claim 1 , further comprising a shaft provided to be rotatable,
 wherein the pick-up member feeds the sheet when the shaft rotates,   wherein the elevating unit raises and lowers the stacking portion or the pick-up member when the shaft rotates, and   wherein the clutch input portion rotates when the shaft rotates.   
     
     
         6 . The sheet feeding apparatus according to  claim 5 , wherein the elevating unit includes an elevating cam configured to raise and lower the stacking portion when the shaft rotates, and
 wherein the clutch input portion moves between the disengagement position and the engagement position while the shaft rotates once.   
     
     
         7 . The sheet feeding apparatus according to  claim 4 , wherein the movement mechanism includes:
 a cam provided on the clutch input portion;   an elastic member configured to urge the clutch input portion toward the clutch output portion; and   a clutch restriction member configured to lock the clutch input portion at the disengagement position by coming into contact with the cam urged by the elastic member,   wherein, when the drive source is driven to rotate the clutch input portion, a locked state between the cam and the clutch restriction member is released so that the clutch input portion moves from the disengagement position to the engagement position, and   wherein, when the clutch input portion further rotates, the cam and the clutch restriction member are locked again so that the clutch input portion moves to the disengagement position.   
     
     
         8 . The sheet feeding apparatus according to  claim 1 , wherein the elevating unit separates the sheet stacked on the stacking portion and the pick-up member from each other after the sheet stacked on the stacking portion is fed to the pick-up member. 
     
     
         9 . The sheet feeding apparatus according to  claim 1 , further comprising a separation member provided at a position opposing the feed member and configured to separate sheets with a frictional force. 
     
     
         10 . The sheet feeding apparatus according to  claim 1 , further comprising a detection unit provided downstream of the feed member and configured to detect the sheet,
 wherein the control unit controls the elevating unit based on a result of detection by the detection unit.   
     
     
         11 . The sheet feeding apparatus according to  claim 1 , further comprising a size acquisition unit configured to acquire information about a length in a conveyance direction of the sheet to be fed,
 wherein the control unit controls the elevating unit based on a result of detection by the detection unit.   
     
     
         12 . A sheet feeding apparatus comprising:
 a stacking portion on which a sheet is stacked;   a pick-up member configured to come into contact with the sheet stacked on the stacking portion to feed the sheet;   a feed member configured to feed the sheet fed by the pick-up member;   a drive source configured to generate a driving force;   an elevating unit configured to raise and lower the stacking portion or the pick-up member with the driving force from the drive source to bring the sheet stacked on the stacking portion and the pick-up member into contact with each other; and   a control unit configured to control the elevating unit,   wherein the control unit controls the elevating unit, at a timing of when a trailing edge in a feeding direction of a first sheet fed to the pick-up member is upstream of the feed member and downstream of the pick-up member, to bring a second sheet stacked on the stacking portion and to be fed subsequently to the first sheet and the pick-up member into contact each other.   
     
     
         13 . A sheet feeding apparatus comprising:
 a stacking portion on which a sheet is stacked;   a pick-up member configured to come into contact with the sheet stacked on the stacking portion to feed the sheet;   a feed member configured to feed the sheet fed by the pick-up member;   a drive source configured to generate a driving force;   an elevating unit configured to raise and lower the stacking portion or the pick-up member with the driving force from the drive source to bring the sheet stacked on the stacking portion and the pick-up member into contact with each other; and   a control unit configured to control the elevating unit,   wherein the elevating unit is configured, after a leading edge in a feeding direction of a first sheet fed by the pick-up member reaches the feed member, to separate the sheet stacked on the stacking portion and the pick-up member from each other, and   wherein the control unit controls the elevating unit, at a timing of when a trailing edge in the feeding direction of the first sheet fed by the pick-up member is upstream of the feed member and downstream of the pick-up member, to bring a second sheet stacked on the stacking portion and to be fed subsequently to the first sheet and the pick-up member into contact each other.   
     
     
         14 . The sheet feeding apparatus according to  claim 13 , further comprising a clutch mechanism configured to transmit the driving force from the drive source to the pick-up member,
 wherein the clutch mechanism includes:   a clutch input portion configured to rotate when the driving force of the drive source is input thereto;   a clutch output portion configured to transmit the driving force from the drive source to the pick-up member by engaging with the clutch input portion, and   a movement mechanism configured to move the clutch input portion between a disengagement position where the clutch input portion disengages from the clutch output portion and an engagement position where the clutch input portion engages with the clutch output portion.