Container with heat-sealed composite plastic and metal screw closure

1. A container assembly comprising:

a container having an open top end, the top end defining a rim, the rim defining an upper sealing surface formed of a heat-sealable material, the top end further defining an external screw thread extending helically along an outer surface of the top end at a location spaced below the rim;

a closure comprising a screw cap formed of plastic ring assembled with a separately formed disk inserted in the cap, the cap defining an internal screw thread extending helically along an inner surface of the cap and engageable with the external screw thread on the top end of the container for attaching the closure to the container when the closure is rotated in a first direction, the cap further comprising an inwardly projecting lip,

the disk being constructed of a laminated metal having an upper metal layer and a lower heat-sealable layer affixed to an underside of the metal layer and further comprising a raised peripheral bead and a curl located radially outward from the raised peripheral bead, wherein the raised peripheral bead of the disk is located between the inwardly projecting lip and an outer surface of the cap; and

a heat seal between the heat-sealable layer of the disk and the heat-sealable material of the upper sealing surface of the rim, the heat seal affixing the disk to the rim such that the disk seals closed the open top end of the container without depending on a continuous compressive force of the disk by the cap,

wherein the cap further consists of a single projection extending inwardly from the cap, wherein the projection does not extend fully circumferentially within the cap, and wherein the projection is structured and arranged such that as the cap is unscrewed, the projection exerts an upward force on a localized region of the disk's circumference and such that the localized region progresses around the circumference in the second direction as the closure is unscrewed, causing the heat seal to be broken between the disk and the upper sealing surface of the rim at the localized region to allow the disk to be detached from the rim.

2. The container assembly of claim 1 , the projection being located such that, with the closure rotated fully in the first direction to attach the closure to the container, the projection is below the rim but above the external screw thread, and wherein the projection extends below and inwardly past an outer periphery of the disk to keep the disk captive within the cap.

3. The container assembly of claim 1 , wherein the cap comprises a ring that is open at bottom and top ends thereof, the top end of the ring defining an overhang portion that lies above a top surface of the disk around the circumference thereof.

4. A container assembly comprising:

a container having an open top end, the top end defining a rim, the rim defining an upper sealing surface formed of a heat-sealable material, the top end further defining an external screw thread extending helically along an outer surface of the top end at a location spaced below the rim;

a closure comprising a screw cap formed of plastic ring assembled with a separately formed disk inserted in the cap, the cap defining an internal screw thread extending helically along an inner surface of the cap and engageable with the external screw thread on the top end of the container for attaching the closure to the container when the closure is rotated in a first direction, the cap further comprising an inwardly projecting lip,

the disk being constructed of a laminated metal having an upper metal layer and a lower heat-sealable layer affixed to an underside of the metal layer and further comprising a raised peripheral bead and a curl located radially outward from the raised peripheral bead, wherein the raised peripheral bead of the disk is located between the inwardly projecting lip and an outer surface of the cap; and

a heat seal between the heat-sealable layer of the disk and the heat-sealable material of the upper sealing surface of the rim, the heat seal affixing the disk to the rim such that the disk seals closed the open top end of the container without depending on a continuous compressive force of the disk by the cap,

wherein the cap further consists of a single projection extending inwardly from the cap, wherein the projection is sized such that it comprises less than the full circumference of the cap, and wherein the projection is structured and arranged such that as the cap is unscrewed, the projection engages the curl on the disk and exerts upward force on a localized region of the disk's circumference such that the localized region progresses around the circumference in the second direction as the closure is unscrewed, causing the heat seal to be broken between the disk and the upper sealing surface of the rim at the localized region to allow the disk to be detached from the rim.

5. The container assembly of claim 4 , the projection being located such that, with the closure rotated fully in the first direction to attach the closure to the container, the projection is below the rim but above the external screw thread, and wherein the projection extends below and inwardly past an outer periphery of the disk to keep the disk captive within the cap.

6. The container assembly of claim 4 , wherein the cap comprises a ring that is open at bottom and top ends thereof, the top end of the ring defining an overhang portion that lies above a top surface of the disk around the circumference thereof.