Image forming apparatus with cartridge supporting member and preventing member for preventing movement of cartridge supporting member

An image forming apparatus for forming an image on a recording material, said image forming apparatus comprising:

• a cartridge supporting member including a plurality of mounting portions in which a plurality of cartridges is detachably mountable, each of said plurality of cartridges including a developer accommodating portion for accommodating developer for developing an electrostatic latent image formed on a photosensitive member, said cartridge supporting member being movable between an inside position inside a main assembly of said image forming apparatus and an outside position outside the main assembly;
• a preventing member provided movably in the main assembly, wherein said preventing member is movable, when said cartridge supporting member is moved from the outside position to the inside position, between (i) a first position in which said preventing member prevents movement of said cartridge supporting member from the outside position to the inside position by contacting said cartridge supporting member and (ii) a second position, retracted from the first position, in which said preventing member permits the movement of said cartridge supporting member;
• and
• a plurality of releasing means provided movably in said cartridge supporting member, wherein said plurality of releasing means is movable between (i) a releasing position in which one of said releasing means positions said preventing member at the second position, with said one of said releasing means in contact with said preventing member, only when an associated cartridge is mounted in an associated mounting portion and (ii) a non-releasing position in which said one of said releasing means positions said preventing member at the first position, with said one of said releasing means not in contact with said preventing member, when the associated cartridge is not mounted in said associated mounting portion.