Sheet storage device and image forming apparatus including same

A sheet storage device comprising:

• a lift plate on which a sheet is placed;
• a push-up member
• which is turnably supported below the lift plate,
• to which power of a motor is transmitted and
• which is turned in a lift-up direction to push up the lift plate;
• a first gear which is rotated in one direction by the power of the motor;
• a second gear which meshes with the first gear;
• a transmission mechanism which includes at least a third gear that meshes with the second gear to transmit the power of the motor to the push-up member;
• and
• a turning restriction member which restricts turning of the push-up member in a direction opposite to the lift-up direction,
• wherein the first gear includes a cylindrical support portion with a center axis of the first gear being a cylindrical axis,
• the turning restriction member includes
• an annular portion to which the support portion is fitted and which is slidable on an outer circumferential surface of the support portion in the direction of the rotation and
• a protrusion portion which protrudes outward in a radial direction from the annular portion to be able to engage with the second gear and
• the protrusion portion
• has a shape such that the protrusion portion cannot pass through a gap between the second gear and the annular portion in a direction orthogonal to an axial direction and
• is located, relative to the gap, on a downstream side in a direction of rotation of the second gear caused by the power of the motor.