In many industries it is necessary or desirable to sequentially expose individual articles to specialized controlled environments. For example, in the food packaging industry several methods and devices exist for sequentially exposing containers of food products to a vacuum or to an inert atmosphere, and for sealing the container to retain the applied vacuum or atmosphere and thereby preserve freshness of the food products.
One technique for supplying a controlled environment utilizes individual "bell jar" enclosures which surround the container. Such a device is disclosed, for example, by U.S. Pat. No. 2,292,887 issued to McBean. Although such devices may be adapted for continuous operation, the apparatus necessary for moving the container and/or the "bell jar" relative to one another adds considerable complexity and cost to the device.
Other devices are known which cooperate directly with the opening of the container to apply, for example, a vacuum substantially to the interior of the container only. U.S. Pat. No. 2,457,690 issued to Kronquest discloses an example of such a vacuum-head apparatus. Such devices, however, are complex, and are not readily adaptable to use with containers having differing configurations and sizes.
It is further known to utilize a multi-chambered rotary drum, in which individual chambers may accept a container to be subjected to the controlled environment or vacuum. As the drum rotates, the chambers transporting the containers move past and engage and outer enclosure which seals the opening of the chamber, and a vacuum is applied. The container is then sealed, normal atmosphere is returned to the chamber, and the drum rotates past the enclosure so that the sealed container may be removed. U.S. Pat. Nos. 1,751,643 issued to Malmquist, 2,521,746 issued to Preis, and 1,774,529 issued to Sharp illustrate various configurations of such known devices.
Unfortunately, previous rotary drum devices have suffered from several shortcomings which limit their usefulness. For example, tolerances between the surface of the rotary drum and the outer enclosure must be very close in order to prevent excess leakage between the outer atmosphere and the enclosed inner chamber and controlled environment. The interface between the moving drum and the stationary enclosure is subject to wear and introduces considerable friction which must be overcome to rotate the drum. These problems are increased when a vacuum is applied to the chambers of the drum, for the pressure of the atmosphere on the outside of the stationary enclosure increases the frictional contact with the rotary drum. Such pressure may also distort the enclosure and interfere with a good vacuum seal.
Various configurations of rotary drums and enclosures have been utilized in attempts to minimize these difficulties, including specialized gaskets, sliding seals, and bearings described in the prior art. However, such attempts have been largely unsuccessful, and have added to expense and complexity which reduces reliability.
Further, prior systems have not been readily adaptable to accommodate numerous configurations and sizes of containers. As a result, it has been difficult or impossible to utilize a single device in conjunction with differing sizes or shapes of containers without extended down-time for reconfiguration of the system.
Accordingly, it is an object of the present invention to provide a rotary drum sealing device and method which provide a secure closure of desired individual chambers during rotation of the drum without significantly interfering with such rotation. A related object is to provide such a method and apparatus which do not introduce significant friction between the sealing enclosure and the rotating drum.
A further object is to provide a rotating drum vacuum sealing apparatus and method which eliminate the need for sliding seals.
An important object of the present invention is to provide a rotary drum vacuum sealing apparatus and method for use in a continuous sealing operation, which is mechanically simple, having few components, and which is therefore economical and highly reliable.
Another object is to provide such a sealing apparatus which is readily adaptable for use with varying sizes and configurations of jars and other containers. A related object is to provide such a device including means for closing the container which is adaptable to differing heights of containers. A further related object is to provide such a system adapted for receiving containers of differing diameters.
These and other objects shall be apparent in light of the present specification.