Patent ID: 8168099

Claim:
An injection molding process of the plastic material for making laboratory test tubes comprising steps of: prearranging at least one mold comprising a forming chamber which extends along a central axis and is defined by a female element and a male element, said female element comprising a head portion, in which an inlet mouth has been made for said male element, and a bottom portion formed by a number of first and second counter-shaped radial wedges, which alternate and couple one with the other at radial interface zones, at least each second wedge being susceptible to move elastically in radial direction with respect two adjacent first wedges from a rest position, in which it abuts with interference onto both adjacent first wedges at said interface zones, to an operative position, in which it is pushed outwards distancing itself from the two adjacent first wedges such to create a gap in correspondence of each interface zone, which defines a slit putting in fluidic communication said forming chamber with the outside; inserting said male element inside said female element along said central axis; injecting said melted plastic material under pressure into said forming chamber through a number of injection side points made on said female element between said bottom portion and said head portion, progressively filling said forming chamber with said plastic material to obtain said test tube; while simultaneously moving said first wedges from the rest position to the operative position under pressure of melted plastic material and evacuating air contained in said forming chamber progressively from said mold under the pressure of said plastic material through the slits created at the interface zones between said first and second wedges, said slits being adapted to permit the exit of air contained in the forming chamber under said pressure and having dimensions sufficient to permit the passage of the air and at the same time block emission of said melted plastic material from said mold; extracting said male element from said female element; and removing said test tube from said mold.