Abstract: At least one example embodiment provides an electron emitter apparatus having a first ring of field-effect emitter needles, the field-effect emitter needles of the first ring forming a first emitter surface on an inner side of the first ring; and a second ring of field-effect emitter needles, the field-effect emitter needles of the second ring forming a second emitter surface on an inner side of the second ring, wherein the first ring and the second ring are arranged in such that the first emitter surface and the second emitter surface form a substantially contiguous three-dimensional overall emitter surface, the substantially contiguous three-dimensional overall emitter surface defining a hollow channel along a longitudinal axis of the electron emitter apparatus.

Abstract: An air-supply device for supplying breathing air into a breathing-air region. An inflow opening connected to an outflow region via an interior. An outflow region connected to the outflow region via the interior. The outflow region formed on a flexible, air-permeable material. For flexible use of the air-supply device and to avoid significant adverse effect to a user, provision is made for the air-supply device to have a sheet-like, flexible portion, which has a first flat side and a second flat side, located opposite the first. The outflow region arranged on the first flat side. The interior formed between the first flat side and the second flat side. In the interior, at least the outflow region has arranged on it at least one spacer, which prevents the outflow region from butting against the second flat side.

Abstract: An air-supply device (1) for supplying breathing air into a breathing-air region (2) has at least one inflow opening (4, 6) for supplying breathing air, and also has an interior (10) and at least one outflow region (11), via which breathing air flows out into the breathing-air region (2). The inflow opening (4, 6) is connected to the outflow region (11) via the interior (10). The outflow region (11) is connected to the outflow region (11) via the interior (10). The outflow region (11) is formed on a flexible, air-permeable material (12). In order to provide for flexible use of the air-supply device (1) and to avoid any significant adverse effect to a user, provision is made for the air-supply device (1) to have a sheet-like, flexible portion (16), which has a first flat side (7) and a second flat side (8), located opposite the first. The outflow region (11) is arranged on the first flat side (7). The interior (10) is formed between the first flat side (7) and the second flat side (8).

Abstract: The invention relates to a supply device (1, 51, 81, 101) for supplying breathable air to a breathable air region (2, 52, 82) which is at least partially open to the surroundings. Said supply device comprises means for generating a flow of air (3, 53, 83) for supplying breathable air to the breathable air region (2, 52, 82). Said supply device (1, 51, 81, 101) also comprises means for generating at least one shielding air flow (4, 5, 54, 84) which shields the breathable air flow (2, 52, 82) at least partially with respect to the surroundings.