Blow molded plastic bottle and antitamper cap

A molded plastic cap, for use with a blow molded plastic bottle having an externally screw threaded neck at its mouth, said neck having an upper inwardly directed circumferential lip,

• said plastic cap adapted to be screwed onto said neck to cover said mouth and having an upper wall, a cylindrical side wall with an internal thread corresponding to said external thread, and a downwardly directed circular plug for engaging said lip when said cap is screwed onto said neck and to form an anti-leak seal by pressing against said lip,
• said cap having antitamper means, including a permanently deformable element, for cooperating with means on said bottle, said antitamper means permitting said cap to be rotated in one direction to screw said cap onto said neck to bring said plug into sealing relation to said lip and then preventing rotation in an unscrewing direction unless said element is visibly deformed,
• said threads being double-start threads comprising
• a pair of external threads of identical pitch having effective portions substantially symmetrically disposed around the periphery of said neck and
• a pair of internal threads of identical pitch having effective portions substantially symmetrically disposed around the internal periphery of said cap,
• said cap having an axial height of about 1/2 inch and an axial thread height of about 0.2 inch, a size to fit a neck about 11/2 inches in diameter and a weight of about 2 to 3 grams.

A blow molded plastic milk bottle having a neck, said neck having external threads and an upper inwardly directed circumferential lip adapted to be engaged by a downwardly directed circular plug of an internally threaded plastic cap for said bottle so as to form an anti-leak seal by pressure between said plug and said lip, said bottle having antitamper means for cooperating with antitamper means on said cap, said antitamper means on said cap including a permanently deformable element, said cooperating antitamper means of said bottle permitting said cap to be rotated in one direction to screw said cap onto said neck to bring said plug into sealing relation to said lip and then preventing rotation in an unscrewing direction unless said element is visibly deformed,

• said threads being double-start threads comprising
• a pair of external threads of identical pitch having effective portions substantially symmetrically disposed around the periphery of said neck and
• a pair of internal threads of identical pitch having effective portions substantially symmetrically disposed around the internal periphery of said cap,
• said external threads being bends in the wall of said neck and said neck thus having corresponding internal grooves,
• the diameter of said neck being about 1 to 2 inches, the wall thicknesses of said neck and said lip being about 0.02 to 0.03 inch,
• said neck having a cylindrical portion having an axial height less than 0.8 inch and having a screw thread occupying an axial height less than 0.4 inch.