A Paper Seal for the Aluminium Coffee Capsule A Grooved Gasket That Replaces Silicone

This application covers an aluminium coffee capsule whose rim carries a layered paper gasket with a groove or concave rib pressed into it, instead of the silicone seal that the specification says was the only thing that ever worked. It was filed by two individuals, Leslie Gort-Barten and Alex Gort-Barten, who are also the named inventors. It is a divisional of Australian application 2020269937, the national phase of PCT/EP2020/062787.

The Problem

The specification starts from the Nespresso style of capsule machine, where a sealed aluminium capsule is clamped in a capsule cage and pierced by blades so that water at high pressure can run through it. Aluminium is a good barrier to oxygen and water, so the coffee keeps. It is also soft. The document says it deforms easily during filling and packing, and that it is hard and expensive to make a reliable seal on the rim. The only seal it describes as known to work is a silicone elastomer (EP1654966), which needs an extremely high capital investment that the document says is beyond most companies.

The alternatives are listed one by one. Raised ribs pushed out of the rim itself shrink the flat area where the foil lid is sealed, which the document says gives unacceptably high foil seal failure rates, so the capsule degasses and the coffee goes stale. Paper gaskets have also failed, for three reasons. They delaminate when the brew chamber depressurises as the handle is lifted. They delaminate a second way when printed ink forms a waterproof barrier that stops pressure escaping from inside the gasket. And they burst, because the paper lacks the wet strength to survive extraction pressure. Delaminated scraps then build up in the machine and make later capsules leak and give short shots.

What This Invention Does

Claim 1 is a capsule for a coffee machine that has a capsule cage holding the capsule in its extraction position. The capsule is made of a ductile metal and has a generally frusto-conical form, with an upper surface, a lower surface and an annular flange at the lower end. An annular seal sits on that flange. The seal comprises a cellulose material such as paper that deforms in use, it has first and second layers, and it is provided with an annular groove or concave rib.

The groove is the claimed hook. Dependent claim 2 says the groove can receive the capsule cage of the machine, and claim 3 adds a matching groove on the capsule flange. The description of Figure 5a shows the paper seal and the flange both shaped to nest together, and Figure 5b shows a convex rib version where the cage engages a protrusion to form the seal.

The abstract and the description lean on a different feature, a first layer of long, well bound cellulose fibres made by the chemical pulping process. In the claims that appears only in dependent claim 6, which names chemical (sulphate) pulp or CTMP (chemi-thermomechanical pulp). So the independent claim is about the layered, deformable, grooved seal, and the pulp choice is a narrower fallback. Several other features discussed in the description are not claimed here at all, including the fluted capsule wall and the raised annular surface that guides the piercing blades.

The specification gives working numbers for the seal material. Thickness is 200 to 595 microns, grammage 150 to 550 gsm, tear resistance 3000 to 5000 mN, internal bond strength at or above 90 J per square metre, and moisture content 7.0 to 8.5 per cent. Edge wicking, measured with hot water at 95 degrees C for 10 minutes, should be 5 mm or less. Claims 14 and 15 pick up the wicking, tear and bond figures.

Key Features

• A grooved, deformable paper gasket. The annular seal on the flange carries a groove or concave rib that can receive the machine’s capsule cage, so the paper deforms into the cage rather than tearing.
• Two or more layers. The seal is layered. One described version is a hybrid laminate of an elastic layer (foam, plastic or silicone) under a non elastic paper layer that deforms plastically on top.
• Pulp chosen for wet strength. Dependent claim 6 specifies chemical sulphate pulp or CTMP. The spec says the long, well bound fibres give high strength, water resistance and good edge wick holdout.
• Adhesive or no adhesive. The seal can be fixed with a starch based biodegradable adhesive with a melt range around 140 degrees C, high enough to survive the roughly 100 degrees seen in extraction. Alternatively, claims 9 and 10 apply it with heat and pressure alone, so the gasket swages out and tightens around the inner diameter.
• Printing that cannot delaminate or stick. The seal can be non coated board, or coated on one side only, with ink on the uncoated side so it soaks into the board. A dot or hatch pattern can break the print layer into small pieces so pressure escapes, and the seal can be laminated over the print so ink never touches the brew chamber.
• Thin aluminium. The description puts the capsule metal at 0.075 to 0.125 mm thick.

Who Is Behind It

The applicants are two named individuals. The specification does not say who they are or what company they work for, and it names no commercial product. From public records rather than from this document, Leslie Gort-Barten is described as managing director of Dualit, the British kitchen appliance maker founded by his father Max, and his son Alex is described there as a company director who trained in product design. The same Wikipedia article records that Dualit launched Nespresso compatible capsules in 2012 and that Nestle sued over them in 2013, with the court finding for Dualit. Dualit sells coffee pods and appliances through its own website. Treat the link between these individuals and that company as an inference from public sources, because the application itself does not make it.

On priority, the specification states that the parent is a national phase of PCT/EP2020/062787 filed 7 May 2020, which claims priority to GB application 1906430.2 filed 7 May 2019. That puts the priority country in the United Kingdom. The title page lists the Adelaide firm Madderns Pty Ltd as agent.

Why It Matters

Capsule coffee is dominated by a few brands, and each brand’s machine is built around its own capsule. Third party capsules have to work in machines they were not designed for, and in the aluminium format that means matching the rim, the cage and the blades closely while keeping the cost of the seal down. If silicone really is the only proven rim seal, a paper based alternative that grips the cage through a groove could be cheaper to run and, as the specification puts it, more easily recycled than silicone.

The document is candid about how hard the paper route is. Its list of earlier paper gasket failures is long, and most of the dependent claims are answers to one failure each: wet strength, edge wicking, ink blocking pressure release, ink sticking to the brew chamber. What the specification does not give is test data on failure rates, leak rates or shelf life of finished capsules. The numbers it gives are material properties of the seal board, not results from brewing trials.

Related Concepts

• Single-serve coffee container – the capsule and pod category this application belongs to.
• Espresso machine – the high pressure brewing equipment whose 15 to 19 bar cycle the seal has to survive.
• Gasket – the sealing component type, here made from paper board instead of silicone.
• Kraft process – the sulphate pulping route that gives the strong chemical pulp named in claim 6.
• Aluminium recycling – the end of life route that motivates a seal which is easier to separate than silicone.

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AU 2026202256 was published in the Australian Official Journal of Patents on 9 April 2026 and is open for public inspection. Patent applications represent inventions that are sought to be protected and do not necessarily reflect commercially available products.