Centrifugal air blower

Abstract

A centrifugal blower includes a main scroll portion and a scroll opening through which air is discharged. A transitional portion conducts air discharged through the scroll opening away from the blower. The transitional portion includes an internal passageway that provides for the smooth passage of air essentially without causing any abrupt changes in the direction of the flow of the air through the passageway. An impeller assembly can be mounted within the main scroll portion for rotation so as to circulate the air in a spiral path within the main scroll portion and force the air through the scroll opening and the passageway in the transitional portion. The impeller assembly can have a platen that has a perimeter and a plurality of impeller blades mounted at the platen for rotation with the platen. Each impeller blade can have a distal end that extends beyond the perimeter of the platen.

1 . A centrifugal blower comprising:
 a main scroll portion having an internal surface and a scroll opening through which air can be discharged to the exterior of the centrifugal blower from within the main scroll portion, the internal surface of the main scroll portion having a progressively increasing radius beginning at an air discharge cut-off site at the internal surface of the main scroll portion that is located substantially adjacent a first side of the scroll opening and proceeding along the internal surface of the main scroll portion to a side of the scroll opening that is substantially opposite the first side of the scroll opening, whereby the air can be circulated in a spiral path along the internal surface of the main scroll portion;   a transitional portion for conducting away from the centrifugal blower air discharged from within the main scroll portion through the scroll opening, the transitional portion including (a) an entry opening through which the air discharged from within the main scroll portion enters the transitional portion, the entry opening being essentially the same size as the scroll opening, and the main scroll portion and the transitional portion being joined to one another at the scroll opening and the entry opening, respectively, (b) an exit opening that is smaller than the entry opening in the transitional portion, and (c) a body portion joining the entry opening of the transitional portion and the exit opening of the transitional portion and providing an internal passageway for the air to exit from the main scroll portion, the internal passageway of the body portion being constructed so as to provide for the smooth passage of air from the scroll opening in the main scroll portion past the air discharge cut-off site to the exit opening in the transitional portion essentially without causing any abrupt changes in the direction of the flow of the air through the passageway and at the air discharge cut-off site such as would result in the generation of unwanted noise; and   an impeller assembly mounted within the main scroll portion for rotation so as to circulate the air in a spiral path along the internal surface of the main scroll portion and force the air through the scroll opening and the passageway in the body portion of the transitional portion, the impeller assembly having an axis of rotation that, in relation to the internal surface of the main scroll portion, is nearest the air discharge cut-off site at the internal surface of the main scroll portion, the impeller assembly comprising (a) a platen having a perimeter, the platen being mounted for rotation about the axis of rotation, and (b) a plurality of impeller blades mounted at the platen generally radially to the axis of rotation of the platen for rotation with the platen, each impeller blade having a distal end that extends beyond the perimeter of the platen a distance such that the distal ends of the impeller blades pass the air discharge cut-off site at the internal surface of the main scroll portion by an interval that is sufficiently small to maintain at substantially a minimum the recirculation of the air within the main scroll portion as the impeller blades pass the air discharge cut-off site.   
   
   
       2 . A centrifugal blower comprising:
 a main scroll portion having an internal surface and a scroll opening through which air can be discharged to the exterior of the centrifugal blower from within the main scroll portion, the internal surface of the main scroll portion having a progressively increasing radius beginning at an air discharge cut-off site at the internal surface of the main scroll portion that is located substantially adjacent a first side of the scroll opening and proceeding along the internal surface of the main scroll portion to a side of the scroll opening that is substantially opposite the first side of the scroll opening, whereby the air can be circulated in a spiral path along the internal surface of the main scroll portion; and   a transitional portion for conducting away from the centrifugal blower air discharged from within the main scroll portion through the scroll opening, the transitional portion including (a) an entry opening through which the air discharged from within the main scroll portion enters the transitional portion, the entry opening being essentially the same size as the scroll opening, and the main scroll portion and the transitional portion being joined to one another at the scroll opening and the entry opening, respectively, (b) an exit opening that is smaller than the entry opening in the transitional portion, and (c) a body portion joining the entry opening of the transitional portion and the exit opening of the transitional portion and providing an internal passageway for the air to exit from the main scroll portion, the internal passageway of the body portion being constructed so as to provide for the smooth passage of air from the scroll opening in the main scroll portion past the air discharge cut-off site to the exit opening in the transitional portion essentially without causing any abrupt changes in the direction of the flow of the air through the passageway and at the air discharge cut-off site such as would result in the generation of unwanted noise.   
   
   
       3 . A centrifugal blower comprising:
 a main scroll portion having an internal surface and a scroll opening through which air can be discharged to the exterior of the centrifugal blower from within the main scroll portion, the internal surface of the main scroll portion having a progressively increasing radius beginning at an air discharge cut-off site at the internal surface of the main scroll portion that is located substantially adjacent a first side of the scroll opening and proceeding along the internal surface of the main scroll portion to a side of the scroll opening that is substantially opposite the first side of the scroll opening, whereby the ait can be circulated in a spiral path along the internal surface of the main scroll portion; and   an impeller assembly mounted within the main scroll portion for rotation so as to circulate the air in a spiral path along the internal surface of the main scroll portion and force the air through the scroll opening, the impeller assembly having an axis of rotation that, in relation to the internal surface of the main scroll portion, is nearest the air discharge cut-off site at the internal surface of the main scroll portion, the impeller assembly comprising (a) a platen having a perimeter, the platen being mounted for rotation about the axis of rotation, and (b) a plurality of impeller blades mounted to the platen generally radially to the axis of rotation of the platen for rotation with the platen, each impeller blade having a distal end that extends beyond the perimeter of the platen a distance such that the distal ends of the impeller blades pass the air discharge cut-off site at the internal surface of the main scroll portion by an interval that is sufficiently small to maintain at substantially a minimum the recirculation of the air within the main scroll portion as the impeller blades pass the air discharge cut-off site.   
   
   
       4 . The centrifugal blower of  claim 1  wherein the exit opening of the transitional portion is substantially cylindrical in cross-section and a tubular extension having a through opening the diameter of which is substantially equal to the cross-sectional diameter of the exit opening is connected to the exit opening such that the exit opening and the through opening in the tubular extension are arranged in line with one another. 
   
   
       5 . The centrifugal blower of  claim 1  wherein the interval by which the impeller blades pass the air discharge cut-off site at the internal surface of the main scroll portion is no more than approximately 2.5 millimeters. 
   
   
       6 . The centrifugal blower of  claim 3  wherein the interval by which the impeller blades pass the air discharge cut-off site at the internal surface of the main scroll portion is no more than approximately 2.5 millimeters. 
   
   
       7 . The centrifugal blower of  claim 4  wherein the interval by which the impeller blades pass the air discharge cut-off site at the internal surface of the main scroll portion is no more than approximately 2.5 millimeters. 
   
   
       8 . The centrifugal blower of  claim 2  wherein the exit opening of the transitional portion is substantially cylindrical in cross-section and a tubular extension having a through opening the diameter of which is substantially equal to the cross-sectional diameter of the exit opening is connected to the exit opening such that the exit opening and the through opening in the tubular extension are arranged in line with one another.