Extended Length Cutoff Blower

Abstract

A blower assembly including a blower housing having a side wall with a first portion extending from the initial cutoff through an angle of at least 45° or more, the first portion having a radius which is substantially constant or which increases at a relatively small rate. The side wall additionally includes a second portion, extending from the end of the first portion to the outlet, which has an increasing radius which is increasing at a larger rate and has a rate of increase that is also increasing with housing angle. The shape of the side wall allows a reduction in the overall size of the blower housing for a given size of impeller.

1 . A blower assembly comprising:
 a motor having an output shaft that is rotatable in a rotation direction around a rotation axis, the rotation axis defining mutually perpendicular axial and radial directions relative to the blower assembly;   an impeller mounted on the output shaft for rotation with the output shaft, the impeller having a plurality of blades that are curved in the rotation direction; and,   a blower housing with an air inlet opening and an air outlet opening, the blower housing having an end wall with a shaft opening and a side wall that extends axially from the end wall parallel to the rotation axis and defines an interior of the blower housing, the motor being mounted on the end wall with the output shaft extending through the shaft opening to the impeller in the blower housing interior, the side wall having a first end that defines a cutoff adjacent the air outlet opening and a point on the side wall that is spaced in the rotation direction from the cutoff by an arc of more than 45°, the side wall being a radial distance from the rotation axis that increases at a first rate as the side wall extends from the cutoff to the point on the side wall and increases at a second rate as the side wall extends in the rotation direction from the point on the side wall toward the air outlet opening, the second rate being larger than the first rate, the first rate defining an expansion angle of the side wall of at most 3° and the second rate defining an increasing expansion angle of the side wall.   
   
   
       2 . The blower assembly of  claim 1 , further comprising:
 the point on the side wall being spaced in the rotation direction from the cutoff by an arc of at most 120°.   
   
   
       3 . The blower assembly of  claim 1 , further comprising:
 the first rate defining a constant expansion angle of the side wall.   
   
   
       4 . The blower assembly of  claim 3 , further comprising:
 the point on the side wall being spaced in the rotation direction from the cutoff by an arc of at most 120°.   
   
   
       5 . The blower assembly of  claim 4 , further comprising:
 the radial distance of the side wall from the axis of rotation increasing at the second rate as the side wall extends in the rotation direction from the point on the side wall through an arc of at least 180°.   
   
   
       6 . A blower assembly comprising:
 a motor having an output shaft that is rotatable in a rotation direction around a rotation axis, the rotation axis defining mutually perpendicular axial and radial directions relative to the blower assembly;   an impeller mounted on the output shaft for rotation with the output shaft, the impeller having a plurality of blades that are curved in the rotation direction; and,   a blower housing with an air inlet opening and an air outlet opening, the blower housing having an end wall with a shaft opening and a side wall that extends axially from the end wall parallel to the rotation axis and defines an interior of the blower housing, the end wall supporting the motor with the output shaft extending through the shaft opening to the impeller in the blower housing interior, the side wall having a scroll shaped length that extends in the rotation direction from a first end that defines a cutoff adjacent the air outlet opening, around the impeller to a second end on an opposite side of the air outlet opening from the first end, the side wall length having a first portion that extends in the rotation direction from the first end to a point on the side wall where the first portion of the side wall length subtends an angle of more than 45° at the rotation axis, the side wall length having a second portion that extends in the rotation direction from the point on the side wall to the second end, the side wall first portion having an expansion angle of at most 3° as the first portion extends in the rotation direction from the first end to the point on the side wall, and the side wall second portion having an increasing expansion angle as the second portion extends from the point on the side wall to the second end.   
   
   
       7 . The blower assembly of  claim 6 , further comprising:
 the first portion of the side wall length subtending an angle of at most 120° at the rotation axis.   
   
   
       8 . The blower assembly of  claim 7 , further comprising:
 the second portion of the side wall length subtending an angle of at least 180° at the rotation axis.   
   
   
       9 . The blower assembly of  claim 6 , further comprising:
 the first portion of the side wall length having a 0° expansion angle.   
   
   
       10 . A blower assembly comprising:
 a motor having an output shaft that is rotatable about an axis of rotation in a rotation direction, the axis of rotation defining mutually perpendicular axial and radial directions relative to the blower assembly;   an impeller mounted on the motor output shaft for rotation of the impeller in the rotation direction with the motor output shaft, the impeller having a plurality of fan blades that extend axially across the impeller and that curve in the rotation direction as the plurality of blades extend radially outwardly from the axis of rotation; and,   a blower housing having an interior containing the impeller and an outlet opening, the blower housing having an end wall with a shaft opening, the end wall supporting the motor with the output shaft extending through the shaft opening to the impeller in the blower housing interior, and the blower housing having a side wall that extends axially from the end wall parallel to the rotation axis and has a scroll shaped length that extends in the rotation direction from a first cutoff end of the side wall at one side of the blower housing outlet opening, around the impeller to a second end of the side wall on an opposite side of the blower housing outlet opening from the first end, the side wall having a first portion that extends from the first end in the rotation direction and subtends an angle of more than 45° at the axis of rotation, the side wall first portion being a radial distance from the axis of rotation that increases at a first rate as the first portion extends in the rotation direction from the side wall first end, the first rate defining a constant expansion angle of the first portion of at most 3°, and the side wall having a second portion that extends from the first portion in the rotation direction to the side wall second end, the side wall second portion being a radial distance from the axis of rotation that increases at a second rate as the side wall second portion extends in the rotation direction from the side wall first portion to the side wall second end, the second rate being larger than the first rate and defining an increasing expansion angle of the side wall second portion.   
   
   
       11 . The blower assembly of  claim 10 , further comprising:
 the first portion of the side wall length subtending an angle of at most 120° at the rotation axis.   
   
   
       12 . The blower assembly of  claim 11 , further comprising:
 the second portion of the side wall length subtending an angle of at least 180° at the rotation axis.   
   
   
       13 . The blower assembly of  claim 6 , further comprising:
 the first portion of the side wall length having no expansion angle.   
   
   
       14 . The blower assembly of  claim 10 , further comprising:
 the first portion of the side wall length having no expansion angle.   
   
   
       15 . The blower assembly of  claim 6 , further comprising:
 the first portion of the side wall length being spaced a constant radial distance from the rotation axis as the first portion of the side wall length extends in the rotation direction from the first end of the side wall length to the point on the side wall length.   
   
   
       16 . The blower assembly of  claim 10 , further comprising:
 the first portion of the side wall length being spaced a constant radial distance from the rotation axis as the first portion of the side wall length extends in the rotation direction from the first end of the side wall length to the point on the side wall length.   
   
   
       17 . The blower assembly of  claim 6 , further comprising:
 the second portion of the side wall length being spaced a radial distance from the rotation axis that increases at an increasing rate as the second portion of the side wall length extends in the rotation direction from the point on the side wall length to the second end of the side wall.