Bottles and jars – Closures – Receptacle interior communicable with exterior with closure...
Patent
1982-09-30
1984-08-21
Norton, Donald F.
Bottles and jars
Closures
Receptacle interior communicable with exterior with closure...
53488, B65D 5116
Patent
active
044665482
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to screw closures for containers having externally screw-threaded necks and in particular to screw closures of the type in which the thread is rolled in situ by inwardly deforming the skirt of a cup-shaped metal blank between adjacent turns of the screw thread on the container neck. The invention is also concerned with apparatus for applying the closure blanks to such containers.
A screw-capped bottle containing a carbonated beverage is susceptible to release a large quantity of carbon dioxide from solution as a result of shaking. As discussed in British Patent Specification No. 2,029,808, this may involve somewhat violent release of the cap when fully unscrewed. In that Specification it was proposed that one or more transverse notches be formed in the container thread and/or in the closure cap thread to allow the pressurised gas to blow off after release of the seal between the cap gasket and the container and before complete removal of the cap from the container. In other words at least part of the gas pressure is released across the threads, via the notches, whilst the closure cap thread is still engaged with the container thread. This release of pressure reduces or avoids the danger of the closure cap flying off on becoming fully unscrewed from the container.
In the prior proposal the notches both in the container thread and in the cap thread were preformed. We have now realised that the principle of the prior proposal can be adapted to rolled-on closures, in which the notches cannot be preformed.
According to one aspect of the invention there is provided a combination of a container and closure of the type in which the thread is formed by inwardly deforming the skirt of a cup-shaped metal blank wherein the inwardly-directed closure thread is interrupted at at least one position along its length to provide at least one notch for release of pressurised gas during unscrewing the cap.
In the container-closure combination of the present invention the neck of the bottle or other container is preferably provided with at least one vertical groove, forming a notch through each turn of the container thread to form a gas escape passage, which becomes particularly effective when it is brought into register with like notches in the cap thread.
It is preferred to provide more than one such vertical groove in the container thread and/or to provide notches in the cap thread at angular intervals of substantially less than 360.degree.. In the normal course of applying closure blanks to containers by the roll-on method the containers are presented in random orientation to the capping machinery and it is impracticable to relate a notch or notches in the cap thread formed by rotating thread rollers with the start or starts of the container thread. By adopting this preferred arrangement registration of a container thread groove with a cap thread notch is ensured before the cap has been turned 360.degree..
In conventional rolled-on closures, the closure thread is normally formed by pressing at least one free-turning roller against the closure skirt, the rollers being narrow and deforming the metal, generally aluminium, into the valleys between the neck threads and being arranged to follow such threads. As the roller is rolled around the closure, it follows the neck thread down and runs out at the bottom of the neck thread, leaving the closure firmly engaged with the neck thread.
Conventional metal closure blanks are somewhat oversize in relation to the container thread and the skirt becomes somewhat reduced in diameter over the apices of the container thread as a result of the action of the thread rollers. Where an interruption is provided in the rolled closure thread, there tends to be greater clearance between the closure and the adjoining container thread apices at such position, to provide an improved gas leakage path. In consequence notches in the container thread are not essential for the improved container/closure combination, in which notch-forming interruptions are provided in the thre
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patent: 1160596 (1915-11-01), Hammer
patent: 1579942 (1926-04-01), Jensvold
patent: 1783314 (1930-12-01), Scofield
patent: 3039247 (1962-06-01), Thomas et al.
patent: 3648874 (1972-03-01), Moller
patent: 3775944 (1973-12-01), Roberts
Bryan Roland T.
Metal Closures Limited
Norton Donald F.
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