Tamper-evident child resistant closure device

A tamper-evident child resistant screw-on closure for use on a container having a threaded portion threadedly engageable with said screw-on closure, comprising:

• an inner cap comprising a top and a cylindrical skirt depending from said top. the inner surface of said skirt being threaded for said threaded engagement with said container when said inner cap is rotated in one direction and is disengageable therefrom when said inner cap is rotated in the opposite direction;
• an outer cap comprising a top and a cylindrical skirt coaxial with and surrounding the skirt of said inner cap, said inner and outer caps being in close confronting relation and being coaxially movable relative to one another;
• the inner surface of said skirt of said outer cap having a first set of knurling extending away from the top thereof in an angular direction extending axially and in said one direction and the outer surface of said skirt of said inner cap having a second set of knurling complementary to said first set of knurling so that when said outer cap is turned in said one direction said first and second sets of knurling will meet to cam said outer cap relative to said inner cap axially toward said inner cap to rotate said inner cap in said one direction to threadedly engage said inner cap on said container and when said outer cap is rotated in said opposite direction said first and second sets of knurling will cam said outer cap axially away from said inner cap to prevent the rotation of said inner cap in said opposite direction to open said container, the camming of said outer cap axially away from said inner cap being preventable by the manual exertion of an axial force on said outer cap toward said inner cap to enable said outer cap to impart rotation to said inner cap in said opposite direction when such axial force is applied;
• cooperating engageable means on said inner and outer caps for holding said inner and outer caps in a position axially away from one another whereby to prevent the meshing of said first and second sets of knurling to impart rotation to said inner cap by rotation of said outer cap through said meshed knurling, at least one of said cooperating engageable means being movable out of engagement with the other of said cooperating engageable means to permit the axial movement of said outer cap toward said inner cap, whereby to mesh said first and second sets of knurling, the movement of said one cooperating engageable means out of engagement with the other being readily visually detectable whereby to make tampering with said container visually evident;
• and
• one-way drive means for imparting rotation to the inner cap when the outer cap is rotated in the closing direction but not for imparting rotation to the inner cap in the opening direction when said outer cap is turned in said opening direction.