Capsule Rigid Insert Prevents Liner Delamination During Piercing

The capsule wall is constructed as a composite structure with an outer cellulose pulp layer and an inner polymeric barrier liner film layer. The rigid holding insert is made of a third material (such as compressed cellulosic pulp, cardboard, or biodegradable polymer) that provides mechanical support. This multi-layer composite structure allows each material to contribute its specific properties: the pulp provides structural form, the liner film provides barrier properties, and the insert provides mechanical reinforcement at the piercing location.

A rigid holding insert is positioned at the bottom wall of the capsule where piercing occurs. This insert has a ring-shaped portion that locally reinforces the area where the water injection element pierces the capsule. The conical ring shape of the insert matches the bottom wall geometry, providing targeted reinforcement exactly where needed during the piercing operation, preventing delamination at the critical stress point.

The capsule combines cellulose pulp (renewable, biodegradable material) with a polymeric barrier liner and a rigid holding insert. This composite approach maintains the environmentally friendly cellulose pulp as the primary structural material while adding functional layers that provide barrier properties and mechanical reinforcement, allowing the pulp to retain its eco-friendly characteristics while achieving necessary mechanical strength.

The rigid holding insert is strategically positioned only at the bottom wall where piercing occurs, rather than making the entire capsule structure rigid. This localized reinforcement approach maintains the overall flexibility and eco-friendly nature of the cellulose pulp structure while providing the necessary mechanical strength at the critical piercing location to prevent delamination of the barrier liner.

The barrier liner film is made of a flexible polymeric material that can be easily thermoformed to conform to the cup-shaped cavity. This flexible polymer layer provides the necessary barrier properties while its flexibility allows it to be manufactured efficiently. The rigid holding insert compensates for any deformation during piercing, allowing the liner film to remain flexible and easy to manufacture while maintaining its barrier function.

The rigid holding insert acts as an intermediary element between the flexible barrier liner film and the piercing force. When the water injection element pierces the capsule, the rigid insert absorbs and distributes the mechanical stress, protecting the flexible liner film from direct deformation. This intermediary structure allows the liner film to maintain its flexibility for easy manufacturing while the insert provides the necessary resistance to piercing forces.