Multidose delivery pump

A delivery pump provided with a plug for the removable coupling to the neck of a container filled with a liquid to be delivered comprising:

• a hollow body defining a suction and compression chamber for said liquid having at least one suction duct for said liquid;
• a tight piston sliding in said hollow body to cause inflow and outflow to said liquid into and from said suction and compression chamber;
• at least a delivery duct for said liquid communicating with said suction and compression chamber;
• valve means arranged downstream said suction duct and upstream said delivery duct respectively, adapted to regulate inflow and outflow of said liquid into and from said suction and compression chamber;
• elastic means arranged between said tight piston and said hollow body;
• first constraint means belonging to said plug cooperating selectively with second constraint means belonging to said tight piston to define the stroke of said piston, said stroke being variable according to the mutual position of said first and second constraint means,
• wherein said plug holds a ring nut rotably coupled to said plug, said ring nut being provided with one or more said first constraint means to be coupled to said second constraint means.