Patent #'s 10525627 and 10220559
Foam in place gasketing is a versatile process, but requires very expensive equipment. Just the foaming equipment is typically $50,000 and when all of the various required components are in place the pumping equipment can spiral to $100,000 pretty easily. While there are PU foam systems that are less expensive, so far we have found them to be maintenance intensive. Ideally, we would like to have the features of foamed gaskets without the upfront, steep hardware costs or maintenance headaches.
Hollow gaskets can fulfill many of the roles assigned to foamed gaskets. These gaskets can be produced using simple materials such as silicones and the pumping equipment is almost an order of magnitude less costly.
Because these are extruded gaskets, many unique profiles can be applied and we are no longer constrained to simple circular sections with the typical height:width ratios of 1:2 or at best 1:1. Instead, we have produced ratios not only of 1:1 but also up to 1.5:1. The profiles can be other than the classical circular section such as triangular, rectangular, "M' shaped, or whatever best serves the sealing need.
These gaskets will have one or more hollow segments and the segments can be filled with air, nitrogen, or even conductive polymers.
These gaskets can even form sealed channels that can transport air or other fluids in a specific pattern, thus forming heat exchangers or allowing seals that can be pressurized AFTER the mating surfaces have been engaged.
Hollow gaskets have several advantages over traditional foamed gaskets:
1) Tall profiles can readily be formed. Current testing has produced 0.5" tall (12.5mm tall) seals.
2) Because of the extrusion process, the height of the gasket can be held to a very high tolerance.
3) Can be easily compressed more than 60% of overall height with light compressive force
4) When compared to the traditional 1:2 (H:W) profile of a foamed seal with 50% foaming, hollow seals use 47.5% less material.
5) When compared to the traditional 1:2 (H:W) profile of a solid material seal, hollow seals can use 74% less material.
In one particular sample case the overall seal height was 0.48" (12.98mm) and the weight of material per inch was 1.56g.
One issue to keep in mind is that these seals are extruded horizontally onto a surface. As a result, ideal applications are not endless! We can only approximate endless by running the start and stop parallel to one another as seen in the 13mm tall sample photo below. On the other hand, this method allows precise gasket extrusion with many possible profiles.