Trigger dispensing head with reduced piston chamber

A trigger dispensing head applicable to a bottle of a trigger dispensing device for dispensing a product, comprising:

• a frame, suitable for supporting components of the trigger dispensing head, comprising a main opening in communication with an internal compartment of the bottle;
• a cylinder chamber annularly delimited by a cylinder wall having an inner chamber surface, and by a bottom wall at the bottom;
• a manually-operable piston for translating between an initial rest position and a final end-of-stroke position;
• a pressure chamber in which said manually-operable piston operates;
• a suction duct suitable for putting the internal compartment of the bottle in communication with the pressure chamber;
• a dispensing duct suitable for putting the pressure chamber in communication with an external environment;
• valve means for adjusting a flow of the product from the suction duct to the pressure chamber during a suction step and from the pressure chamber to the dispensing duct during a dispensing step;
• and
• a sleeve having a sleeve axis, housed in the cylinder chamber, comprising:
• a bottom sleeve wall transverse to the sleeve axis;
• an annular inner sleeve wall extending from said bottom sleeve wall and annularly delimiting the pressure chamber;
• and
• an annular outer sleeve wall extending from the bottom sleeve wall, positioned radially externally spaced from the annular inner sleeve wall and placed in contact with the inner chamber surface;
• wherein the sleeve further comprises an annular vent wall that extends radially between the annular inner sleeve wall and the annular outer sleeve wall, internally delimiting a secondary vent passage passing radially in the annular inner sleeve wall and in the annular outer sleeve wall.