Machine for preparing an infusion

A machine for preparing an infusion, comprising:

• an infusion chamber (14) that is designed to receive a product to be infused and that is delimited by a lower vat (3) and an upper tamping head (6) that moves relative to the lower vat (3);
• and
• a supply of pressurized hot water to the infusion chamber (14),
• wherein said tamping head (6) comprises an internal tube (26) that has an inlet (27) that communicates with the infusion chamber (14) and that makes possible passage of the infusion through the tamping head (6) in an upward direction toward a distribution outlet, and means (30) that are located in said internal tube (26) close to its inlet (27) and suitable for forming foam in the infusion during its passage through the tamping head (6) and for preventing the infusion from returning into said infusion chamber (14), and said means are formed by a deformable flexible part (30) that is pierced by at least one calibrated orifice (35) to form the foam and to keep the infusion from returning.