It is known to use plastic containers in the food preparation and restaurant industry to package prepared foods. The typical food container of the prior art consists of a clear or solid colored base and a clear lid. In order to maintain the quality of food contents and prevent tampering with the contents of a sealed container, it is desirable that the food container, once initially sealed, not be capable of being initially opened without visible indication of the container having been opened. To achieve this feature, container manufacturers have designed containers having integral tamper evident features. Typically, these containers consist of a lid that is hingedly attached to a base. The lid seals to the base by superposing the rim of the lid upon the rim of the base. These types of plastic containers are sold as one-piece containers and are often referred to as “clamshell” containers or packages.
Some manufacturers of tamper evident clamshell containers have incorporated tamper evident features as part of the structure that forms or includes the hinge. In these containers, the container is designed to require a severance near the hinge in order to unseal (initially open) the container. This construct make the hinge a single use hinge. One example of a container with a tamper evident hinge structure is shown in U.S. Pat. No. 9,580,219 (Cimmerer, et al).
One deficit of the prior art tamper evident container lies in the fact that they are not adapted to hold warm foods or cut produce that create internal vapor or gas (collectively referred to herein as “vapor” pressure). In fact, if the container is not vented properly, the buildup of pressure in a sealed container can overcome the force of the container's rim engagement and cause the container to pop open, thereby defeating its tamper evident quality. On the other hand, one cannot simply utilize the common venting techniques used with standard containers on a tamper evident container. In this respect, in the food packaging industry it is known to provide apertures or slits in the top surface of a plastic container for purposes of venting the container. However, adding such vents to a tamper evident container provides access ports into the container that defeat the purpose of the tamper evident structures of the container. Holes and slits in the container top surface also permit the leakage or spillage of food contents should the container turn over. They also allow the ingress of bacteria into the container.
It is also known in the food packaging industry to provide venting structures in the engaging rims of the container so as to allow for venting through the rims of the container. An example of a container with such structures is disclosed in U.S. Pat. No. 8,875,927 (Pohlman, et al). The venting mechanism of the container of Pohlman is built into the rim-engaging surfaces of the lid and base rims and utilizes internal vapor pressure to cause at least one of the rims to move slightly relative to the other to create a venting path through the rims when the container is under pressure. The known through-the-rim venting solutions, however, do not work with prior art tamper evident containers because the lid rims and base rims of such containers are designed to strongly and immovably engage when the container is sealed. Hence, the rims, once engaged, do not allow for a secondary venting movement vis-à-vis each other once the container is sealed. This is because these rigid rim engagement designs prevent opening of the containers via any technique other than through deployment of the opening mechanism built into the container. Providing for through-the-rim venting around the periphery of the container could therefore focally weaken the frictional engagement of the lid and base rims and thereby circumvent the need to use the provided-for opening mechanism. Also, providing vent channels in the accessible rims could provide possible leverage or insertion points at which to insert a slender tool or object through the rims of the container,
There is thus a need in the art for a tamper evident plastic food container that allows for the elimination of excess vapor pressure yet allows the container to retain its tamper evident functionality.