1. Field of the Invention
The invention relates in general to air filters and in particular to an air filter having two filter layers ultrasonically welded to a ribbon and a method and apparatus for the manufacture thereof.
2. Prior Art
Air filters are used to eliminate particles such as dirt, dust, smoke etc. from air that passes through the filter. Air filter bags are structures made from a filter media that capture particles and hold the particles in a confined space. Air filter bags facilitate disposal of the particles since the particles are captured within the bag body. A conventional air filter construction is shown in FIG. 1. As shown in FIG. 1, the air filter bag includes a first filter layer 2 and a second filter layer 4. The first filter layer and the second filter layer are joined by threads 6 which are sewn through the first filter layer 2 and the second filter layer 4. The sewing process creates holes in the filter layers and thus an adhesive 8 is applied over the areas that have been sewn. The filter layers may be joined, leaving an opening for the entrance of air, to form a filter bag as shown in FIG. 2. The threads 6 hold the air filter bag together as air passes though the filter layers 2 and 4.
Another conventional air filter construction is shown in FIG. 3. As shown in FIG. 3, the air filter is made up of a first filter layer 10 and a second filter layer 12. The first and second filter layers are joined by a series of tubes 14 made from a non-woven material. The tubes 14 are connected to the first and second filter layers using an adhesive.
The conventional filter constructions have several disadvantages. The sewn filter construction shown in FIG. 1 requires the addition of an adhesive to seal needle holes formed in the air filter layers. This increases the cost and complexity of manufacturing the filter. The filter construction shown in FIG. 3 requires forming tubes of non-woven material and connecting the tubes to the filter layers through an adhesive. Again, this increases the cost and complexity of manufacturing the filter.