Synthetic resin container closure
A container closure formed from a synthetic resin as a single unit has a circular top panel wall and a cylindrical skirt wall extending downwardly from the peripheral edge of the top panel wall. An outer cylindrical sealing protrusion, an inner cylindrical sealing protrusion, and annular sealing ridge, all having a predetermined shape and a predetermined size, are formed on the inner surface of the top panel wall. In one embodiment, the thickness of the center portion of the top panel wall is reduced to a predetermined range and a plurality of ribs having a predetermined thickness are formed on the inner surface of the center portion of the top panel wall.
1. A synthetic resin container closure for closing a container having a mouth-neck portion with an internal diameter D 4 , said container closure comprising:
a circular top panel wall;
a cylindrical skirt wall extending downwardly from the peripheral edge of the top panel wall and formed from a synthetic resin as a single unit with the top panel wall;
an outer cylindrical sealing protrusion extending downwardly from the inner surface of the top panel wall;
an inner cylindrical sealing protrusion extending downwardly from the inner surface of the top panel wall and having a maximum external diameter D 3 ; and
an annular sealing ridge located between the outer cylindrical sealing protrusion and the inner cylindrical sealing protrusion and projecting downwardly from the inner surface of the top panel wall, wherein:
0.25 mm≦(D 3 −D 4 )≦1.50 mm, so that when the container closure is mounted on the mouth-neck portion of the container, the inner peripheral surface of the outer cylindrical sealing protrusion is in close contact with the outer peripheral surface of the mouth-neck portion, the outer peripheral surface of the inner cylindrical sealing protrusion is in close contact with the inner peripheral surface of the mouth-neck portion, and the annular sealing ridge is in close contact with the top surface of the mouth-neck portion;
the inner peripheral surface of the outer cylindrical sealing protrusion extends downwardly with an outward inclination at an angle θ 6 with respect to the center axis of the container closure and then extends downwardly and radially outwardly in an arc form;
the outer peripheral surface of the inner cylindrical sealing protrusion extends downwardly with an outward inclination at an angle θ 1 with respect to the center axis of the container closure and then extends downwardly with an inward inclination at an angle θ 2 with respect to the center axis;
the inclination angle θ 1 is 5° to 25° and the inclination angle θ 2 is 5° to 30°;
the inner peripheral surface of the inner cylindrical sealing protrusion extends downwardly with an outward inclination at an angle θ 3 with respect to the center axis, and then extends substantially parallel with the center axis;
the inclination angle θ 3 of the inner peripheral surface of the inner cylindrical scaling protrusion is larger than the inclination angle θ 1 of the outer peripheral surface of the inner cylindrical sealing protrusion at a position above the position having the maximum external diameter D 3 ; and
the thickness of the inner cylindrical sealing protrusion gradually decreases as the inner cylindrical sealing protrusion extends downwardly from the inner surface of the top panel wall.
2. The container closure of claim 1 , wherein the outer peripheral surface of the outer cylindrical sealing protrusion extends substantially parallel with the center axis.
3. The container closure of claim 1 , wherein the outer peripheral surface of the inner cylindrical sealing protrusion has the maximum external diameter D 3 at a position spaced from the inner surface of the top panel wall by a length L 1 of 2.50 mm to 3.50 mm.
4. The container closure of claim 1 , wherein 10°≦θ 6 ≦25°.
5. The container closure of claim 1 , wherein the inner surface of the top panel wall is devoid of ribs.