Fan shroud structure

Claim 2

A fan shroud structure for use with a rotary, axial flow fan having a plurality of circumferentially spaced, radially extending impeller blades, said blades having an effective axial width (AW) measured axially along the rotational axis of the fan between a first plane and a second plane, said planes being axially spaced and parallel with respect to each other and disposed substantially normal to the rotational axis of the fan, said first and second planes extending radially, respectively through points on the leading edges of the blades at the radial tip portions thereof and through points on the trailing edges of the blades at the radial tip portions thereof, the combination including said fan, comprising, a generally cylindrical axially extending throat section encircling the fan; an annular generally radially extending flat portion, said flat portion being radially spaced outwardly and axially from one axial end of said throat section; an annular intermediate section extending between said one axial end of said throat section and said radial flat portion, said throat section, intermediate section, and said radial flat portion being effective to produce a low pressure region between the air stream flowing over the surface thereof and such surface when the fan is in operation; and an annular supplementary low pressure vortex creating means formed in said throat section, intermediate section and radial flat portion of the fan shroud structure whereby an additional low pressure region is generated between the air stream flowing over the surface of the fan shroud structure and such fan shroud structure surface when the fan is in operation.

Claim 3

A fan shroud structure as set forth in claim 1, wherein said throat section, flat portion, and intermediate section have an overall axial length measured along the rotational axis of the fan substantially equal to AW plus or minus 25 percent of AW.

Claim 4

A fan shroud structure as set forth in claim 1, wherein said fan is axially positioned with respect to said intermediate section so that said second plane is substantialy coincident with the radial plane containing the end of said intermediate section opposite the end thereof operatively connected to said one axial end of said throat section.

Claim 5

A fan shroud structure as set forth in claim 1, wherein said fan is axially positioned with respect to said throat section so that said first plane is substantially coincident with the radial plane containing one axial end of said throat section.

Claim 6

A fan shroud structure as set forth in claim 1, wherein said fan is axially positioned with respect to said throat section, intermediate section, and flat portion so that said first plane is axially spaced from and on either axial side of said radial plane containing said one axial end of said throat secton a distance of 0 to 12 percent of AW and said second plane is axially spaced from and on either axial side of said radial plane containing said end of said intermediate section opposite the end thereof operatively connected to said throat section a distance of 0 to 12 percent of AW.

Claim 7

A fan shroud structure as set forth in claim 5, wherein said supplementary low pressure vortex creating means is disposed adjacent the intersection of said throat section and said intermediate section.

Claim 8

A fan shroud structure as set forth in claim 5, wherein said supplementary low pressure vortex creating means is disposed adjacent the intersection of said intermediate section and said radial flat portion.

Claim 9

A fan shroud structure as set forth in claim 5, wherein said supplementary low pressure vortex creating means is disposed intermediate the axial ends of said intermediate section.

Claim 10

A fan shroud structure for use with a rotary, axial flow fan having a plurality of circumferentially spaced, radially extending impeller blades, said blades having an effective axial width (AW) measured axially along the rotational axis of the fan between a first plane and a second plane, said planes being axially spaced and parallel with respect to each other and disposed substantially normal to the rotational axis of the fan, said first and second planes extending radially, respectively, through points on the leading edges of the blades of the radial tip portions thereof and through points on the trailing edges of the blades at the radial tip portions thereof, comprising, a generally cylindrical axially extending throat section encircling the fan; an annular, generally radially extending flat portion, said flat portion being radially spaced outwardly and axially from one axial end of said throat section; an annular, radially and axially curved, intermediate section extending between said one end of said throat section and said radial flat portion, said throat section, intermediate section, and said radial flat portion being effective to produce a low pressure region between the air stream flowing over the surface thereof and such surface when the fan is in operation, and the following relationships exist: RF = AW/3 plus or minus 12 percent of AW, CF = AW/3 plus or minus 12 percent of AW, and R = 2AW/3 plus or minus 12 percent of AW where RF is the radial length of the radial flat portion, CF is the axial length of the cylindrical throat section, and R is the radius of curvature of the intermediate section; and an annular supplementary low pressure vortex creating means formed in said throat and intermediate section, and radial flat portion of the fan shroud structure such that an additional low pressure region is generated between the air stream flowing over the surface of the fan shroud structure and such fan shroud structure surface when the fan is in operation.

Claim 11

A fan shroud structure for use with a rotary, axial flow fan having a plurality of circumferentially spaced, radially extending impeller blades, said blades having an effective axial width (AW) measured axially along the rotational axis of the fan between a first plane and a second plane, said planes being axially spaced and parallel with respect to each other and disposed substantially normal to the rotational axis of the fan, said first and second planes extending radially, respectively, through points on the leading edges of the blades of the radial tip portions thereof and through points on the trailing edges of the blades at the radial tip portions thereof, comprising, a generally cylindrical axially extending throat section encircling the fan; an annular, generally radially extending flat portion, said flat portion being radially spaced outwardly and axially from one axial end of said throat section; an annular, radially and axially curved, intermediate section extending between said one end of said throat section and said radial flat portion, said throat section, intermediate section, and said radial flat portion being effective to produce a low pressure region between the air stream flowing over the surface thereof and such surface when the fan is in operation, and the following relationships exist: RF = AW/3 plus or minus 12 percent of AW, CF = AW/3 plus or minus 12 percent of AW, and R = 2AW/3 plus or minus 12 percent of AW where RF is the radial length of the radial flat portion, CF is the axial length of the cylindrical throat section, and R is the radius of curvature of the intermediate section; and an annular supplementary low pressure vortex creating means formed in said throat and intermediate section, and radial flat portion of the fan shroud structure such that an additional low pressure region is generated between the air stream flowing over the surface of the fan shroud structure and such fan shroud structure surface when the fan is in operation.

Claim 12

A fan shroud structure as set forth in claim 9, wherein said supplementary low pressure vortex creating means is disposed adjacent the intersections of said throat section and said intermediate section.

Claim 13

A fan shroud structure as set forth in claim 9, wherein said supplementary low pressure vortex creating means is disposed adjacent the intersection of said intermediate section and said radial flat portion.

Claim 14

A fan shroud structure as set forth in claim 9, wherein said supplementary low pressure vortex creating means is disposed intermediate the axial ends of said intermediate section.

Claim 15

A fan shroud structure for use with a rotary, axial flow fan having a plurality of circumferentially spaced, radially extending impeller blades, said blades having an effective axial width (AW) measured axially along the rotational axis of the fan between a first plane and a second plane, said planes being axially spaced and parallel with respect to each other and disposed substantially normal to the rotational axis of the fan, said first and second planes extending radially, respective, through points on the leading edges of the blades at the radial tip portions thereof and through points on the trailing edges of the blades at the radial tip portions thereof, comprising, a generally cylindrical, axially extending throat section encircling the fan, said first plane being substantially coincident with the radial plane containing one axial end of said throat section; an annular, generally radially extending flat portion, said flat portion being radially spaced outwardly and axially from the other axial end of said throat section; an annular intermediate section extending between said other axial end of said throat section and said radial flat portion, said throat section, intermediate section, and said radial flat portion being effective to produce a low pressure region between the air stream flowing over the surface thereof and such surface when the fan is in operation, said intermediate section being radially and axially curved, and the following relationships exist: RF = AW/3 plus or minus 12 percent of AW, CF = AW/3 plus or minus 12 percent of AW, and R = 2AW/3 plus or minus 12 percent of AW where RF is the radial length of the radial flat portion, CF is the axial length of the cylindrical throat section, and R is the radius of curvature of the intermediate section, and said first plane may be axially spaced from and on either axial side of radial plane containing said one axial end of said throat section a distance of 12 percent of AW and said second plane may be axially spaced from and on either axial side of a radial plane containing said end of said intermediate section opposite the end thereof operatively connected to said throat section a distance of 12 percent of AW; and an annular supplementary low pressure vortex creating means formed in said throat and intermediate sections, and radial flat portion of the fan shroud structure whereby an additional low pressure region is generated between the air stream flowing over the surface of the fan shroud structure and such fan shroud structure surface when the fan is in operation.

Claim 16

A fan shroud structure for use with a rotary, axial flow fan having a plurality of circumferentially spaced, radially extending impeller blades, said blades having an effective axial width (AW) measured axially along the rotational axis of the fan between a first plane and a second plane, said planes being axially spaced and parallel with respect to each other and disposed substantially normal to the rotational axis of the fan, said first and second planes extending radially, respective, through points on the leading edges of the blades at the radial tip portions thereof and through points on the trailing edges of the blades at the radial tip portions thereof, comprising, a generally cylindrical, axially extending throat section encircling the fan, said first plane being substantially coincident with the radial plane containing one axial end of said throat section; an annular, generally radially extending flat portion, said flat portion being radially spaced outwardly and axially from the other axial end of said throat section; an annular intermediate section extending between said other axial end of said throat section and said radial flat portion, said throat section, intermediate section, and said radial flat portion being effective to produce a low pressure region between the air stream flowing over the surface thereof and such surface when the fan is in operation, said intermediate section being radially and axially curved, and the following relationships exist: RF = AW/3 plus or minus 12 percent of AW, CF = AW/3 plus or minus 12 percent of AW, and R = 2AW/3 plus or minus 12 percent of AW where RF is the radial length of the radial flat portion, CF is the axial length of the cylindrical throat section, and R is the radius of curvature of the intermediate section, and said first plane may be axially spaced from and on either axial side of radial plane containing said one axial end of said throat section a distance of 12 percent of AW and said second plane may be axially spaced from and on either axial side of a radial plane containing said end of said intermediate section opposite the end thereof operatively connected to said throat section a distance of 12 percent of AW; and an annular supplementary low pressure vortex creating means formed in said throat and intermediate sections, and radial flat portion of the fan shroud structure whereby an additional low pressure region is generated between the air stream flowing over the surface of the fan shroud structure and such fan shroud structure surface when the fan is in operation.

Claim 17

A fan shroud structure as set forth in claim 13, wherein said supplementary low pressure vortex creating means is disposed adjacent the intersection of said throat section and said intermediate section and includes an annular, radially extending step operatively connected to and extending radially outwardly from one axial end of said throat section, said step being operatively connected to one end of said intermediate section.

Claim 18

A fan shroud structure as set forth in claim 13, wherein said supplementary low pressure vortex creating means is disposed adjacent the intersection of said intermediate section and said radial flat portion and includes an annular, axially extending step operatively connected to and extending axially toward said throat section from the radially outermost end of said intermediate section, said step being operatively connected to the radially innermost end of said radial flat portion.

Claim 19

A fan shroud structure as set forth in claim 13, wherein said supplementary low pressure vortex creating means is disposed intermediate the axially spaced ends of said intermediate section and includes an annular, concave groove formed in the surface of said intermediate section over which the air stream flows when the fan is in operation.