Mechanism for opening/closing a toner falling aperture

A mechanism for opening/closing a toner falling aperture, applied to an image forming apparatus comprising:

• a developing unit main body removably set in a housing cavity in a main body of said image forming apparatus;
• a toner cartridge main body slidably connected to a top surface of said developing unit main body and removably set in said housing cavity;
• and upper and lower toner falling apertures respectively formed in a bottom of said toner cartridge main body and in the top surface of said developing unit main body, said apertures being adapted to communicate with each other,
• said mechanism comprising:
• an upper shutter member slidably disposed under said bottom of said toner cartridge main body for opening/closing said upper toner falling aperture;
• first biasing means for normally biasing said upper shutter member to close said upper toner falling aperture;
• a lower shutter member slidably disposed on said top surface of said developing unit main body for opening/closing said lower toner falling aperture;
• second biasing means for normally biasing said lower shutter member to close said lower toner falling aperture;
• first engaging means disposed at said lower shutter member and adapted to be engaged with an engaging portion of said main body of said image forming apparatus such that said lower shutter member opens said lower toner falling aperture when said developing unit main body is inserted into said housing cavity;
• and
• second engaging means respectively disposed at said upper shutter member and said lower shutter member for engaging said upper and lower shutter members with each other.