A
cartridge mountable and dismountable by moving in the direction crossing with an axial direction of the
drive shaft of a main
assembly of the apparatus, includes a rotatable member rotatable by receiving a rotational force from the apparatus; a
coupling engageable with the rotational force applying portion to receive a force for rotating said rotatable member, said
coupling including a
coupling member rotatable about an axis, a first rotational force receiving portion, provided at one end portion of said coupling member, for receiving the rotational force from the driving shaft, a rotational force transmission member engaged with the other end portion of said coupling member and having opposite ends projected out in a crossing wherein said coupling member is pivotable between a transmitting angular position for transmitting the rotational force from the driving shaft to said rotatable member and a mounting-and-dismounting angular position which is inclined relative to the axis of said rotatable member; a
flange mounted to said rotatable member and rotatable about an axis, said
flange including an opening accommodating said transmission member with a gap, a regulating portion, provided in said opening, for regulating movement of said transmission member in the crossing direction when said coupling takes the transmitting angular position, a second rotational force receiving portion for being abutted by said transmission member to receive the rotational force from said coupling, an opposing portion opposing to said second receiving portion, wherein in a state that said coupling is in the transmitting angular position and that one end of said transmission member contacts to said regulating portion to be confined in movement, when said coupling inclines relative to said
flange such that a side in which a
projection distance of said rotational force transmission member is relatively smaller moves away from said first receiving portion, an engagement depth between said side of said transmission member and said second receiving portion and an engagement depth between said side of said transmission member and said opposing portion are larger than zero.