Thermal-insulating inner-boot for mountain boots and high thermal-insulation mountain boot

A thermal-insulating inner-boot (1) for mountain boots (100), the inner boot comprising:

• an upper (2) with a thermal-insulating structure, which is shaped so as to cover the user's foot and the lower part of the leg;
• and a plate-like insole (3) with a thermal-insulating structure, which is arranged to close a lower mouth of the upper (2) so as to cover the sole of the user's foot;
• wherein said upper (2) is shaped in a form of an overturned funnel and is longitudinally divided into a top tubular segment (2a) and a bottom tubular segment (2b) that seamlessly join to one another:
• the top tubular segment (2a) is shaped so as to contain the lower part of the user's leg;
• the bottom tubular segment (2b) is shaped so as to contain at least the lower part of the user's foot;
• the thermal-insulating inner-boot being characterised in that the upper (2) includes is a single-piece structure made of knitted fabric (5, 6, 7) that has a wall provided with at least one cavity-wall (8);
• and
• at least one sheet/piece of soft and flexible thermal-insulating material (9, 10) which is stably trapped within said cavity-wall (8) to form a thermal-insulating padding of the upper;
• wherein the bottom tubular segment (2b) of the upper (2) includes at least one first sector of said single-piece structure made of knitted fabric (5, 6, 7), which first sector has a double layer knitted structure so as to form the cavity-wall (8) accommodating said at least one sheet/piece of soft and flexible thermal-insulating material (9, 10);
• and
• wherein the top tubular segment (2a) of said upper (2) includes at least one second sector of said single-piece structure made of knitted fabric (5, 6, 7), which is contiguous to said first sector, has a single-layer knitted structure and seamlessly joins to said first sector having the double layer knitted structure.