The present invention relates to methods and apparatus for applying a coating to a rim or finish of a container.
In an effort to create an air seal around the rim, or finish, of a container such as a glass bottle, and/or to provide a means of detecting whether the contents have been tampered with, it has been conventional to attach a foil seal to the bottle rim after the product has been inserted into the bottle. The foil may comprise a piece of aluminum foil which carries a plastic heat seal substance. The foil is placed on the bottle rim with the heat seal substance facing the rim. Upon the application of heat, the heat seal substance melts and thereafter cures and bonds to the rim.
A problem experienced in connection with such a practice involves a tendency for the foil to become detached from the bottle when subjected to highly humid atmospheric conditions, e.g., during storage of the bottle.
One known solution to that problem involves the application of a conventional hydrophobic substance to the rim prior to placement of the foil thereagainst. Accordingly, the rim becomes hydrophobic and the bond between the foil and the rim will remain intact even in a highly humid environment.
The assignee of the present application has heretofore commercially utilized a number of different machines for applying substances to bottle rims. For example, in one machine, each bottle is individually gripped by a yoke and rotated beneath a stationary applicator, so that a liquid substance is wiped from the applicator onto the rim. However, such a procedure is relatively time-consuming and not well suited to mass production.
In another machine, an applicator was lowered into contact with the rim of an advancing bottle and displaced in the same direction and at the same speed as the bottle. The applicator was reciprocated up and down to daub a substance onto the rim. In a different embodiment of the same type of machine, the applicator was rotated 90.degree. while held in contact with the rim in order to transfer the substance onto the rim by a wiping action. Following the application of the substance, the applicator was raised off the rim and returned to a start position to make contact with another bottle. Such an apparatus requires a relatively complicated mechanism for manipulating the applicator and is not able to treat bottles at as high a rate as would be desired for mass production.
In another machine, advancing bottles were passed beneath a roller applicator which rotated about a horizontal axis extending perpendicular to the direction of bottle travel. As a bottle rim contacted the applicator, a substance was transferred from the applicator to the rim.
Notwithstanding the technical advancements provided by the above-described apparatuses, room for improvement remains, especially from the standpoint of applying a coating to the bottle rims in a manner suited to mass production. Furthermore, the coating should be uniform and the substance should not run or drip downwardly along the side surface of the bottle.