Image forming apparatus and method for feeding sheet

Abstract

An image forming apparatus includes a driving source that rotates a first shaft around the first shaft; a feeding mechanism that includes a transmission mechanism that transmits rotation of the first shaft in a first direction to a second shaft and does not transmit rotation of the first shaft in a direction opposite the first direction to the second shaft; a roller that is fixed to the second shaft and feeds a sheet from a stack of sheets by rotating around the second shaft; and a releasing member that is fixed to the second shaft; and a holding mechanism that holds the feeding mechanism with the roller away from the stack, wherein when the transmission mechanism transmits the rotation of the first shaft to the second shaft, the releasing member releases the hold on the feeding mechanism by the holding mechanism.

What is claimed is: 
     
         1 . An image forming apparatus comprising:
 a driving source that rotates a first shaft around the first shaft;   a feeding mechanism that comprises:
 a transmission mechanism that transmits rotation of the first shaft in a first direction to a second shaft and does not transmit rotation of the first shaft in a direction opposite the first direction to the second shaft; 
 a roller that is fixed to the second shaft and feeds a sheet from a stack of sheets by rotating around the second shaft; and 
 a releasing member that is fixed to the second shaft; and 
   a holding mechanism that holds the feeding mechanism with the roller away from the stack, wherein   when the transmission mechanism transmits the rotation of the first shaft to the second shaft, the releasing member releases the hold on the feeding mechanism by the holding mechanism.   
     
     
         2 . The image forming apparatus according to  claim 1 , wherein the feeding mechanism comprises an arm that connects the first shaft and the second shaft. 
     
     
         3 . The image forming apparatus according to  claim 2 , wherein the arm turns the second shaft around the first shaft in a direction toward the stack when the first shaft rotates. 
     
     
         4 . The image forming apparatus according to  claim 2 , wherein the holding mechanism that holds the arm or the roller. 
     
     
         5 . The image forming apparatus according to  claim 2 , wherein the holding mechanism comprises a holding portion that holds the arm. 
     
     
         6 . The image forming apparatus according to  claim 5 , wherein
 the holding mechanism further comprises an elastic portion that presses the holding portion to the arm, and   the releasing member presses the holding portion in a direction away from the arm and releases to hold the arm by the holding portion.   
     
     
         7 . The image forming apparatus according to  claim 6 , wherein
 an engaging portion that engages with the holding portion is formed on a tip portion of the aim, and   the releasing member releases the engagement between the engaging portion and the holding portion.   
     
     
         8 . The image forming apparatus according to  claim 1 , wherein
 the transmission mechanism further comprises
 a plurality of gears that includes a first gear that rotates around the first shaft and a second gear that rotates around the second shaft, and 
 a clutch that is installed between at least one gear from among the plurality of gears and a rotational shaft of the at least one gear, and 
   the clutch switches transmission and non-transmission of rotation between the at least one gear and the rotational shaft based on a rotational direction of the at least one gear.   
     
     
         9 . The image forming apparatus according to  claim 8 , wherein
 the at least one gear is the second gear,   the clutch switches transmission and non-transmission of rotation from the second gear to the second shaft based on a rotational direction of the second gear, and   the releasing member is a cam formed integrally with the second gear.   
     
     
         10 . The image forming apparatus according to  claim 1 , wherein
 the transmission mechanism comprises a gear that rotates around the second shaft, and   the releasing member is a cam formed integrally with the gear.   
     
     
         11 . A method comprising:
 rotating, with a driving source, a first shaft around the first shaft;   transmitting, with a transmission mechanism, rotation of the first shaft only in a first direction to a second shaft;   feeding, with a roller, a sheet from a stack of sheets by rotating around the second shaft;   connecting, with an arm, the first shaft and the second shaft;   holding, with a holding portion, the arm or the roller with the roller away from the stack; and   when the transmitting transmits the rotation of the first shaft to the second shaft, releasing, with a releasing member, the hold on the arm or the roller by the holding portion.   
     
     
         12 . The method according to  claim 11 , wherein
 the holding comprises pressing, with an elastic portion, the holding portion to the arm, and   the releasing presses the holding portion in a direction away from the arm and releases to hold the arm by the holding portion.   
     
     
         13 . The method according to  claim 12 , wherein
 an engaging portion that engages with the holding portion is formed on a tip portion of the arm, and   the releasing releases the engagement between the engaging portion and the holding portion.   
     
     
         14 . The method according to  claim 12 , wherein
 the transmission mechanism further comprises
 a plurality of gears that includes a first gear that rotates around the first shaft and a second gear that rotates around the second shaft, and 
 a clutch that is installed between at least one gear from among the plurality of gears and the rotational shaft of the at least one gear, wherein 
   the transmitting comprises switching, with the clutch, transmission and non-transmission of rotation between the at least one gear and the rotational shaft based on a rotational direction of the at least one gear.