Manually-operated precompression type spray head

A spray head for use with a receptacle containing a liquid which is maintained under pressure by a propellant gas, thereby enabling a product to be packaged so that it is protected from coming into contact with the air, said spray head being of the type comprising a manually-operated precompression pump which includes a pump chamber comprising first and second cylinders capable of engaging telescopically, said chamber being closed by relative displacement of said cylinders, said first cylinder being integral with a pump outlet valve and being provided at one of its ends with a circular sealing lip capable of engaging against and of sliding along the wall of said second cylinder, which second cylinder is in communication with the inside of said receptacle, said wall being provided with a relief constituted by grooves or notches formed on that end of said second cylinder which is furthest from said receptacle, said notches having a length of not less than 1.5 mm, so that when said sealing lip lies over said relief, said relief causes sealing to be broken, opening a passage suitable for passing said propellant gas at a rate of flow which is sufficient for filling said receptacle.