The present invention relates to an axial flow fan that is advantageous in terms of noise like a backward sweep fan while having excellent performance like a backward sweep fan, the axial flow fan including: a hub serving as the center of rotation; a plurality of blades disposed radially outside the hub, each having a blade root connected to an outer circumferential surface of the hub; and a fan band disposed outside the plurality of blades while a blade tip of each of the blades is connected thereto, wherein each of the blades includes: an inner blade positioned inside in a radial direction and bent in an opposite direction to a rotation direction of the axial flow fan; and an outer blade positioned outside in the radial direction and bent in the same direction as the rotation direction of the axial flow fan.

Today the low noise blades and especially the super low noise blades for large diameter axial fans which are employed in the big cooling machines and cooling plants are so costly and are requiring so many extra costs on the other related equipment, that the noise pollution abatement can increase the whole cooling apparatus cost by up to a 35%. This invention, provides a new technology to make low noise fans able to transform any common blade into a low noise or very low noise at very low cost, preserving the same high efficiency and tip speed, as opposite to all the other low noise blades at actual status of art. As the fans for the big cooling apparatus are generally their main noise source, this invention will offer the opportunity to dramatically reduce the noise pollution produced by big cooling machines and cooling plants.

An air-sending device includes a propeller fan to rotate about a rotational axis, and a ducted bell mouth surrounding an outboard area of the propeller fan. The propeller fan includes a plurality of blades. Each of the blades includes, in its outboard portion, a reflexed part bent upstream of an airflow that is generated in the direction of the rotational axis by rotation of the propeller fan. In the propeller fan, within an area that is closer to the trailing edge than is the near mid-chord area, the propeller fan is inclined downstream of the airflow from the inboard edge to the reflexed part. In at least a portion of an area where the cylindrical part of the bell mouth and the outboard edge of each blade face each, the reflexed part has a reflex angle of greater than or equal to 90 degrees.

An axial-flow fan includes: a hub; and blades disposed on an outer peripheral surface of the hub and spaced apart from each other in a circumferential direction. The hub includes: an outer wall having a tubular shape; an inner wall having a tubular shape and being disposed radially inward of the outer wall; a boss to which a shaft is mounted and that is disposed radially inward of the inner wall; a first sidewall connecting an end portion of the outer wall that is closer to a first side in a rotation axis direction of the hub with an end portion of the inner wall that is closer to the first side in the rotation axis direction; and a second sidewall connecting the end portion of the inner wall with an end portion of the boss that is closer to the first side in the rotation axis direction.

A propeller fan includes a hub, and a plurality of wings provided at an outer circumference of the hub. Each of the wings includes a protrusion tapered and positioned on a rotation direction rear side in a radially outer portion of the wing, the protrusion includes a top positioned at a rearmost end in the rotation direction, an outer circumferential rear edge positioned radially outside the top, and an inner circumferential rear edge positioned radially inside the top, the outer circumferential rear edge includes a first serration having a first serration shape, and the inner circumferential rear edge includes a second serration having a second serration shape.

A propeller fan includes a hub, and a plurality of wings provided at an outer circumference of the hub. Each of the wings includes a protrusion tapered and positioned on a rotation direction rear side in a radially outer portion of the wing, the protrusion includes a top positioned at a rearmost end in the rotation direction, an outer circumferential rear edge positioned radially outside the top, and an inner circumferential rear edge positioned radially inside the top, the outer circumferential rear edge includes a first serration having a first serration shape, and the inner circumferential rear edge includes a second serration having a second serration shape.

A fan blade device includes a plurality of main fan blades and extension fan blades. Each main fan blade includes a main fan blade body arranged obliquely, a plurality of first protrusions, and at least one engaging groove. Each extension fan blade includes an extension fan blade body arranged obliquely and having a top surface that is contiguously flush with a top surface of the main fan blade body of a respective main fan blade, a plurality of second protrusions respectively abutting against the first protrusions of the respective main fan blade, and at least one engaging piece engaging the at least one engaging groove of the respective main fan blade.

A diagonal fan having an electric motor and a diagonal impeller which can be driven about an axis of rotation (RA) by means of the electric motor. The diagonal impeller determines an air inlet and an air outlet and has a hub and impeller vanes which are distributed in the circumferential direction, extend radially outwards from the hub and are surrounded radially externally by a slinger ring. A flow angle αD formed by the slinger ring relative to the axis of rotation (RA) increases from the air inlet to the air outlet, and a flow angle αN formed by the hub relative to the axis of rotation (RA) decreases from the air inlet to the air outlet.

A propeller fan includes a shaft portion disposed on a rotation axis, and a blade disposed on an outer peripheral side of the shaft portion and including a leading edge and a trailing edge. The blade includes a negative pressure surface in which a plurality of recesses are formed, and the plurality of recesses include a first recess and a second recess disposed on the trailing edge side than the first recess in a circumferential direction about the rotation axis as a center. The first recess has a depth larger than a depth of the second recess.

A propeller fan includes a shaft portion disposed on a rotation axis, and a blade disposed on an outer peripheral side of the shaft portion and including a leading edge and a trailing edge. The blade includes a negative pressure surface in which a plurality of recesses are formed, and the plurality of recesses include a first recess and a second recess disposed on the trailing edge side than the first recess in a circumferential direction about the rotation axis as a center. The first recess has a depth larger than a depth of the second recess.