Apparatus For Making Filter Means

What is this patent about?

'429 is related to the field of manufacturing cigarette filters, specifically addressing the need for high-efficiency filters that don't compromise on pressure drop, taste, or cost. Prior art filters, particularly those made of cellulose acetate, often required increased density or length to improve filtration, leading to unacceptable pressure drops for smokers. The invention aims to overcome these limitations by providing a filter with a high surface area for filtration without a corresponding increase in pressure drop.

The underlying idea behind '429 is to create a tubular filter element with a high surface area by forming a hollow rod of filtering material and then crimping it at specific intervals. This design maximizes the contact area between the smoke and the filter material while maintaining a low pressure drop. The hollow structure and crimping create elongated cavities that increase the available surface area for filtration.

The claims of '429 focus on an apparatus for continuously producing the filter elements. The apparatus includes an air nozzle with a mandrel to form a tubular tow of filtering material, steam and air curing stations to set the shape, a crimping device to create the desired cavity structure, and an overwrapping station to enclose the filter element in a plug wrap. The claims cover the specific arrangement and interaction of these components to achieve high-speed, continuous production.

In practice, the apparatus works by feeding a tow of filtering material through the air nozzle, where it's formed into a hollow tube around the mandrel. Steam and air curing stations then stabilize the shape of the tube. The key step is the crimping station, which uses heated crimping wheels to create the characteristic crimped structure with alternating compressed and uncompressed sections. This crimped rod is then overwrapped and cut into individual filter elements.

The differentiation from prior approaches lies in the combination of the tubular structure, the specific crimping pattern, and the continuous manufacturing process. Unlike simple plug filters, this design maximizes surface area without increasing density. The continuous process, with synchronized curing and crimping, allows for high-speed production without the need for handling individual baffles or other extraneous elements. The option to add additional materials, like activated carbon, further enhances the filter's performance.