Axial flow fan

Claim 2

An axially compact axial-flow fan comprising a fan wheel and a housing casing surrounding said fan wheel over at least substantially the entire axial length of said fan wheel, the fan wheel having a hub with a diameter which is at least half as large as the inner diameter of the housing casing, said housing casing having an inner axially extending cylindrical portion located in the axial central part and being broadened at least toward the exhaust side by way of corner pockets into a regular multicorner profile that circumscribes the diameter of the fan wheel, said hub of the fan wheel being provided on the inlet side with annular surface means that reduces the diameter on the inlet portion of said hub, said annular surface means extending at least over one-third of the entire axial length of said hub.

Claim 3

An axial-flow fan according to claim 1, wherein said annular surface means has a conical configuration toward the end face of said inlet side.

Claim 4

An axial-flow fan according to claim 2, wherein said conical configuration extends approximately over one-third of the entire axial length of said hub.

Claim 5

An axial-flow fan according to claim 2, wherein the angle of the annular surface with respect to the axial direction is about 20°.

Claim 6

An axial-flow fan according to claim 2, wherein said corner pockets are formed by inclined walls which extend from said central cylindrical portion.

Claim 7

An axial-flow fan according to claim 1, wherein said annular surface means has a cylindrical configuration toward the end face of said inlet side, the cylindrical surfaces being interrelated by stepwise reduced diameter toward said end face.

Claim 8

An axial-flow fan according to claim 6, wherein said cylindrical configuration extends approximately over one-half of the entire axial length of said hub and has a smaller diameter than said hub.

Claim 9

An axial-flow fan according to claim 1, wherein said regular multicorner profile is a square profile.

Claim 10

An axial-flow fan according to claim 1, wherein an odd number of fan blades are arranged in uniform distribution over the periphery of the hub.

Claim 11

An axial-flow fan according to claim 9, wherein the hub is part of a motor housing of an external rotor motor of the fan and wherein said fan wheel comprises fan blades formed of thin steel which are welded to the motor housing.

Claim 12

An axial-flow fan according to claim 9, wherein the hub is part of a motor housing of an external rotor motor of the fan and wherein said fan wheel comprises fan blades which extend over the entire axial length of the motor housing and contact with their inner edges the motor housing in the zone of the conical annular surface.

Claim 13

An axial-flow fan according to claim 11, said fan blades in their axial central part having an essential radial straight contour, perpendicular to the axis of rotation and the upstream part of said blade being inclined in its radial form in the direction of rotation, the down stream part of said blade being inclined in its radial form opposite the direction of rotation.

Claim 14

An axial-flow fan according to claim 12, said fan blades having a ratio of their average radial dimension to their axial over-all length of about 1 to 4.

Claim 15

An axial-flow fan according to claim 1, wherein said fan is a small-scale fan with the outside faces of said square profile each having a length between 60 to 100 mm.

Claim 16

An axial-flow fan according to claim 14, said length being on the order of 80 mm.

Claim 17

An axial-flow fan according to claim 1, wherein the hub is part of a motor housing of an external-rotor motor of the fan.

Claim 18

An axial-flow fan according to claim 1, wherein said corner pockets are formed by inclined walls which extend from said central cylindrical portion.

Claim 19

An axial-flow fan according to claim 1, wherein said corner pockets are formed by radially stepwise recessed portions which extend from said central cylindrical portion toward the exhaust side of the fan.

Claim 20

An axially compact axial-flow fan comprising a fan wheel and a housing casing surrounding said fan wheel over at least substantially the entire axial length of said fan wheel, said housing casing having an inner cylindrical passage of circular cross-section in the axial central portion and said cylindrical passage being broadened at least toward the exhaust side into a regular multicorner profile circumscribing the diameter of the fan wheel, said housing casing having at least one other portion directly connected to and rigid with said central portion providing a passage axially aligned and directly communicating with said cylindrical passage of said central portion, said passage of the other portion having an open end axially spaced from said cylindrical passage and having throughout its length and at said open end thereof a cross-sectional area greater than the cross-sectional area of said cylindrical passage and a transverse dimension greater than the diameter of said cylindrical passage, and an inner concentric part on the inlet side that is provided with annular surface means having a conical configuration toward the end face of said inlet side.

Claim 21

An axially compact axial-flow fan comprising a fan wheel and a housing casing surrounding said fan wheel over at least substantially the entire axial length of said fan wheel, said housing casing having an inner cylindrical passage of circular cross-section in the axial central portion and said cylindrical passage being broadened at least toward the exhaust side into a regular multicorner profile circumscribing the diameter of the fan wheel, said housing casing having at least one other portion directly connected to and rigid with said central portion providing a passage axially aligned and directly communicating with said cylindrical passage of said central portion, said passage of the other portion having an open end axially spaced from said cylindrical passage and having throughout its length and at said open end thereof a cross-sectional area greater than the cross-sectional area of said cylindrical passage and a transverse dimension greater than the diameter of said cylindrical passage, and an inner concentric part on the inlet side that is provided with annular surface means having a conical configuration toward the end face of said inlet side.

Claim 22

An axial-flow fan according to claim 19, wherein said hub of the fan wheel is provided on the inlet side with annular surface means that reduces the diameter on the inlet portion of said hub, said annular surface means extending at least over one-third of the entire axial length of said hub.

Claim 23

An axial-flow fan according to claim 19, wherein said fan wheel has a hub with a diameter which is at least half as large as the inner diamaeter of the housing casing.