Sheet stacking apparatus, sheet conveying apparatus, and image forming apparatus

A sheet stacking apparatus comprising:

• a stacking plate on which a sheet material is stacked;
• an elevating member that elevates the stacking plate;
• a first rotating member that transmits, when rotating in a first direction, a force for elevating the stacking plate to the stacking plate;
• a second rotating member that meshes with the first rotating member and rotates in conjunction with rotation of the first rotating member;
• a support member that supports the second rotating member such that the second rotating member can move;
• and
• a locking member by which the second rotating member is enabled to be locked so as to stop rotation of the second rotating member, wherein
• the second rotating member is movable to a first support position and to a second support position on the support member,
• when the first rotating member rotates in the first direction, the second rotating member rotates at the first support position in conjunction with rotation of the first rotating member to permit the rotation of the first rotating member,
• when the first rotating member rotates in a second direction opposite to the first direction, the second rotating member moves to the second support position under a force received from the first rotating member in an area where the second rotating member meshes with the first rotating member, and at the second support position, the second rotating member is locked on the locking member, and the locked second rotating member prevents the first rotating member from rotating in the second direction, and
• the second rotating member moves to the first support position and to the second support position by moving relative to the support member in a direction of an axis of rotation.