Process cartridge unit

A unit to be used in an image forming apparatus, the unit comprising:

• a developer storage portion configured to store a developer;
• a frame member;
• a seal forming portion provided on the frame member;
• a seal member configured to prevent leakage of the developer to an exterior of the unit and to be formed on the seal forming portion through injection molding with a molten resin;
• an injection path provided in the frame member and through which the molten resin flows when the seal member is formed through injection molding;
• an injection port provided at one end side of the injection path in an injection direction in which the molten resin flows through the injection path, and through which the molten resin is injected into the frame member;
• and
• a discharge port which is provided at another end side of the injection path in the injection direction and is configured to discharge the molten resin having passed through the injection path to the seal forming portion,
• wherein the injection path penetrates linearly through the frame member and, in a direction perpendicular to the injection direction, the injection path includes a portion of which a sectional area is narrower than a sectional area of the injection port.