Food or edible material: processes – compositions – and products – Packaged or wrapped product – Having specific electrical or wave energy feature
Patent
1994-07-01
1995-08-22
Yeung, George
Food or edible material: processes, compositions, and products
Packaged or wrapped product
Having specific electrical or wave energy feature
215253, 215274, 215321, 219734, 426113, 426234, 426243, 426401, 426405, 426407, B65B 5500, B65B 4100, B65B 8500, H05B 600
Patent
active
054438535
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
Jars and similar containers which are packed with a food product under vacuum (having less than atmospheric pressure in the head space above the food product) are more difficult to open than those which are not packed under vacuum. Atmospheric pressure above the closure exceeds the pressure in the head space beneath the closure, so that a net pressure differential force acts downwardly on the closure to hold it on the container. Since this pressure force is proportional to the area of the mouth of the container, it increases as the square of the radius of the container increases. Moreover, this pressure force rapidly increases as the size of the mouth of the container increases. Because the pressure force acts in conjunction with the frictional force of the closure threads, lugs, snaps, or other securing means to hold the closure on the container, it is much more difficult to remove a closure on a vacuum packed product. If the closure is unitary with an integral top panel screw thread, the mechanical friction between it and the container threads and the vacuum force must be overcome simultaneously. This occurs with these types of closures as they are rotated off the containers.
So-called composite closures, in which a separate insert disk or lid is rotatable within a threaded skirt or shell, facilitate opening vacuum packed containers because the shell can be rotated on the container to overcome the starting or mechanical friction without at the same time rotating the disk on the top or breaking the vacuum. Once the starting or mechanical friction is overcome, the threads gradually lift the disk and break the vacuum.
However, the problem is more difficult with closures of the so-called "press-on, pry-off" type, which are not removed by rotation. Such closures have a protrusion inside the shell which snaps beneath a snap rib on the container finish to secure the closure. Since no threads or lugs provide a mechanical advantage to lift the insert disk, the closure must be removed by prying it upwardly, as with a thumb positioned on its lower edge or an outwardly projecting tab, so as to force the shell protrusion over the snap rib. Both the pressure differential force and the tension of the snap must also be simultaneously overcome by the upward lifting force. Indeed, the required lifting force is so great that press-on, pry-off closures are impractical for some vacuum packed product containers, especially if the container's mouth diameters are greater than about 72 mm., unless an outwardly extending thumb tab is provided to give the needed leverage.
The force required to press open a press-on, pry-off closure is greater still if a tamper evidencing band is present. Such bands are designed to break or tear away before the closure can be opened or the contents interfered with, and are widely used to provide a visible indication if the closure has been partially or fully opened. Breaking the band adds another resistance which must be overcome, and thus further increases the pry-open force required.
In addition to the above-mentioned problems associated with removing closures from vacuum-packed containers, there is the ever increasing problem of a "dirty finish" on the container outer necks and snap ribs resulting from faster container filling and capping speeds. In other words, as the container filling and capping speeds increase, the more likely it is that the contents, such as food products, with which the containers are to be filled, will spill or splash onto the outer necks and snap ribs of the containers.
This "dirty finish" is also a common occurrence with those containers that are subject to retorting, i.e., following container filling and capping, food or vacuum-packed containers are cooked to temperatures on the order of about 250.degree. F. to sterilize the food contents filled therein. During the retorting process, if there is less than, for example, a 6% head space left in the containers due to overfill or if there is too much pressure within or too little pressure outside of the food or
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Anchor Hocking Packaging Co.
Yeung George
LandOfFree
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