Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-06-23
2001-06-26
Sells, James (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S580100, C156S580200
Reexamination Certificate
active
06251203
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to apparatus and methods for assembling components of thermoplastic food containers. In particular, the present invention is an apparatus and method for ultrasonically welding together a base portion and a body portion of a container. The apparatus and method employs a self leveling ultrasonic welding horn that accommodates inaccuracies in and misalignment of the base and body portions of the container.
BACKGROUND OF THE INVENTION
One area where the use of plastic containers has become widespread is in the food packaging industry. Accordingly, it is common for these plastic food containers to serve as the end display package in which the product is presented for sale to the customer. Typical of these containers are those used for dairy products such as cottage cheese, sour cream, yogurt or the like where an integral body of the container is provided having a sidewall that tapers down to an integral transverse bottom wall with the top opening being closed by a plug fit lid. Normally, the lid has a depending peripheral skirt which locks onto the upper rim of the tapered wall of the container body. Many of these food product plastic containers have their parts formed by a thermoforming process. In thermoforming, a thin plastic sheet is formed into the desired shape by heating and forcing the sheet against a mold to produce a container part having a uniform, very thin, cross-sectional thickness and flexible walls.
In addition to the food product container having the downwardly tapering sidewall and the plug fit lid, there is currently available thermoformed containers that have a reverse tapered sidewall with a larger diameter bottom. This type of thermoformed plastic food container is typically used to package yogurt, e.g., flavored yogurt. Generally, this reversed taper sidewall type container has three main components. These three components are a body portion better known as a sleeve member, a base portion better known as a bottom closure member and a removable lid member. The sleeve member is the part of the food container that forms the reversed taper sidewall of the container itself. This sleeve member is thermoformed so that it is open at both its smaller diameter top and at its larger diameter bottom. The separate bottom closure member is also formed by thermoforming and is attached to the sidewalls of the sleeve member by a spinwelding process to close off the open, larger diameter bottom of the sleeve member. The bottom closure member includes a base panel and depending skirt wall which is the portion of the bottom closure member that is spinwelded to an interior surface of the sidewall of the sleeve member to permanently attach the pieces together. Once permanently attached, the sleeve member and bottom closure member defines the food container and as such can be filled with the flavored yogurt. Unlike the previously described plug fit top closure lids which are designed to be opened, the bottom closure member for this particular yogurt container does not have a locking skirt which locks onto a rim of the sidewall and which can be opened to gain access to the food therein. Instead, after being filled with yogurt, the open, smaller diameter top of the sleeve member is closed by the removable lid member. This removable lid member typically is a flexible foil seal that is secured about the open, smaller diameter top of the sleeve member of the container by an adhesive. To gain access to the yogurt, the flexible foil seal is peeled open from over the smaller diameter opening at the top of the container sidewall.
This thermoformed and spinwelded yogurt container as described above suffers from numerous shortcomings. Foremost is that this spinwelding technique requires specialized handling and filling equipment that results in a relatively slow production of containers for filling. For example, to spinweld the bottom closure member to the reversed tapered sidewall of the sleeve member, both of these components need to be thermoformed with integral gripping lugs. These integral gripping lugs must project relatively far radially inward relative to the sleeve member sidewall and the bottom closure member skirt wall so that they can be grasped by the spinwelding equipment for rotating the two parts relative to each other to create a frictional heating for welding the parts together. The bottom closure has these lugs formed near a lower edge of its skirt wall, while the sleeve member sidewall lugs are formed near the smaller diameter open top of the sleeve member. In order to grasp these lugs, the container component handling equipment, the spinwelding equipment and the container filling equipment must operate at a relatively slow rate of speed to insure that the components of the container and the completed container itself are properly assembled and filled. Moreover, because of the complexity of machines required to accommodate the spinwelding lugs and inaccuracies in the container components due to the thermoforming process, the bottom closure and sleeve members are susceptible to relative misalignment which results in the assembling of containers that are at best misshapen and not aesthetically pleasing from a consumers point of view and at worst not fluid tight.
Since the sleeve and bottom closure members of the above-described yogurt container are thermoformed parts having a constant wall thickness, these radially inward projecting lugs form corresponding indentations on the exterior wall surfaces of the resulting container. Because of the aforementioned display function of the exterior surface of the yogurt container, maximizing the amount of surface area available for printing information, such as product characteristics, e.g. ingredients, nutritional content, or other required information about the product, is an important consideration, especially where the containers are relatively small, such as for example with the preferred 6 oz. (170 g) yogurt containers. As such, the lugs at the top of the sidewall of the sleeve member restrict the height of the printing that can be received on the container sidewall. In addition, because of the lugs, there are unsightly indentations on the container sidewall that are readily visible to the purchaser. Moreover, because of the radial extent to which the lugs project into the container interior, they can unduly interfere with removing the food product therefrom, e.g. spooning yogurt out from the container.
Therefore, there exists a substantial need for an improved apparatus and method for assembling plastic food containers, defined by a sleeve member and a bottom closure member, that eliminates the need for, and the attendant drawbacks to, the radially inward projecting lugs. The apparatus and method of assembly should be capable of assembling the bottom closure member to the sleeve member to form a food product container that is aesthetically pleasing, is fluid tight and better maximizes the print receiving surface area thereon. In particular, the apparatus and method should be capable of accommodating inaccuracies and misalignment of the container components. Finally, the apparatus and method of assembly needs to assemble the containers relatively quickly so as to be cost efficient especially when compared to the process of spinwelding of the container components.
SUMMARY OF THE INVENTION
One aspect of the present invention provides a manufacturing apparatus for assembling containers. Each of the containers has a body portion with an annular rim configured to be secured to an annular rim of a base portion of the container. The manufacturing apparatus includes a container supporting assembly, at least one tool member, a drive assembly, an oscillator assembly and a suspension assembly. The container supporting assembly supports the body and base portions of at least one container with the annular rim of the base portion engaging the annular rim of the body portion. The drive assembly is connected to the at least one tool member for moving the tool member along a first axis betwee
Konle Hans
Reishus Terry
Vala Warren
Zopf Thomas
General Mills Inc.
O'Toole John A.
Rendos Thomas A.
Sells James
Taylor Douglas J.
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