EP 0853515 B (CROWN CORK & SEAL TECHNOLOGY CORP.) is a blow forming apparatus in which a whole can body is held in a three part movable mould: base, centre and top part while compressed air is introduced to force the can body to conform to the interior profile of the moving mould parts. Whilst this is suitable for forming complex shapes, such shaping requires complex blow forming machinery and is not always be needed for holding a can when carrying out more simple rotational operations.
U.S. Pat. No. 5,694,822 (REYNOLDS METALS COMPANY) describes an apparatus for trimming cylindrical can bodies. The can bodies are successively mounted with vacuum onto a support mandrel so that the open end portion of the can body projects between an outside circular cutting knife and an inside trimming edge. The invention of this patent is said to be less complex than traditional trimmers in which the closed end of the can body is held by vacuum onto a base pad. The base pad of the traditional trimmer comprises a holder which has a flat face and a circular centralising feature. The holder has holes or channels through which negative air pressure or “suction” is applied. This generally allows the can body to be held concentrically and permits rotational operations to be performed accurately in a plane perpendicular to the longitudinal axis of the article.
Although considered by Reynolds to be over-complex, this method of holding can bodies or shallower cup-shaped articles is well suited to high-speed manufacturing equipment. In such equipment, containers are loaded onto and unloaded from holders at high speed. The application of suction is sometimes complemented by the application of small amounts of compressed air when releasing the container.
The base of a container such as a beverage can often has a bead or rim portion known as a stand (bead), which stiffens the container and allows it to rest on a flat surface without rocking. The container is thus be conveniently held rigidly by a holder using suction onto a flat surface and a seal is formed between the surface and the stand.
It is also known to provide a raised feature on the face of the holder, which fits within a recess in the base of the container and provides a circular centralising feature. If there is no suitable recess in the base of the container or cup-shaped article, the centralising feature comprises a raised feature, which fits outside the base of the article. However, machine motion often limits the ability to provide a holder of a larger diameter than the container, which constrains the design of the centralising feature.
Due to the variability in manufacturing processes, it is often necessary to allow a radial clearance between the container or cup-shaped article and the centralising feature. Without this clearance, the container can fail to seat properly on the flat face, and this may impair the seal or cause it to rock on the holder. Unfortunately, this clearance can lead to non-concentrical holding of the container or article and allows sideways/radial movement of the article.
If seal or grip is lost due to improper seating of the container or cup-shaped article, then manufacturing defects can occur. For example, a cutting operation may not cut through the full circumference due to rotation of the container/article on the holder. Sometimes, the cut becomes spiral if the article is lifted away from the holder. If grip is lost in a cap or can flanging or curling operation, an incomplete or uneven flange or curl results. Similarly, if grip is lost in a lining operation, a defective lining is created.
This invention seeks to provide a holder, which addresses these problems. In the following text, which relates to the present patent application, expressions such as “container” or “cup-shaped article” are used interchangeably and are intended to cover a wide variety of items, including lids, closures and metal can bodies. Use of either expression is not intended to be limiting or to exclude equivalents or standard alternatives in the packaging trade.