Compact centrifugal fan

• US 5,570,996 A
• Filed: 06/27/1994
• Issued: 11/05/1996
• Est. Priority Date: 06/27/1994
• Status: Expired due to Term

• Current Assignee: Trane International Inc. (Trane Technologies plc)
• Original Assignee: American Standard Companies Incorporated (Ideal Standard International Topco SCA)
• Inventors: Smiley, William A. III
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): LARSON, JAMES
• Application Number:
  US08/266,905
• Time in Patent Office: 862 Days
• Field of Search: 415/53.2, 415/206, 415/204, 415/208.1, 415/211.1
• US Class Current: 415/53.2
• CPC Class Codes: F04D 29/4226 Fan casings
• CPC Class Codes: F04D 29/441 especially adapted for elastic fluid pumps
• CPC Class Codes: F05D 2250/52 Outlet

Abstract

A centrifugal fan includes a housing that defines an air inlet leading to an air chamber defined within the fan impeller and an air exit port coupled to an air passageway. The housing includes a shroud that defines a two zone air passageway in the housing. The first zone, commencing adjacent to the base of the exhaust port, is a conformal portion that is conformal to the exterior diameter of the centrifugal fan and spaced slightly apart therefrom. The second zone of the shroud is a scroll portion wherein the angle of expansion is capable of expanding between 10° and 15°. An air restrictor plate is supported inside the air chamber of the centrifugal fan. At the greatest width of the air restrictor plate, the air restrictor plate subtends an arc that is substantially coextensive with the arc subtended by the first conformal zone of the shroud. The restrictor prevents the flow of inlet air through the centrifugal fan in the region of the conformal shroud.

Claims

1. An improved centrifugal fan having an impeller and a housing, the impeller having an inner diameter and a substantially greater outer diameter and being designed to accelerate air drawn from a central chamber defined within the inner diameter of the impeller to an air passageway defined in the housing substantially surrounding the outer diameter of the impeller, the air passageway terminating in an air exhaust port, the air exhaust port having an inner base that is generally tangential to the outer diameter of the impeller, the housing substantially enclosing the impeller and defining the air exhaust port and an air inlet fluidly coupled to the central chamber defined within the inner diameter of the impeller, the improvement comprising:

a shroud forming a portion of the housing defining the air passageway, the shroud having a first conformal zone being of substantially fixed radius and a second scroll zone being of expanding radius; and

a restrictor plate operably coupled to the housing and disposed proximate a portion of the inner diameter of the impeller for restricting the flow of air from the central chamber to the impeller;

wherein the first conformal zone of the shroud has a leading edge and a trailing edge, the leading edge being disposed proximate the base of the air exhaust port;

wherein the restrictor plate has a shape defined by a steeply rising leading edge to an intermediate portion substantially overlapping the entire width of the impeller and a gradually tapering trailing edge; and

wherein the restrictor plate is disposed within the central chamber defined within the inner diameter of the impeller such that the intermediate portion subtends an arc that is substantially coextensive with an arc subtended by the first conformal zone of the shroud.

2. A centrifugal fan as claimed in claim 1 wherein the first conformal zone of the shroud subtends an arc of substantially a fourth of a revolution around the impeller.

3. A centrifugal fan as claimed in claim 1 wherein the second scroll zone of the shroud extends through an arc that is substantially more than one quarter and less than three quarters of a revolution around the impeller.

4. A centrifugal fan as claimed in claim 1 wherein the radius of the second scroll zone of the shroud expands at a rate of between five and twelve degrees.

5. A centrifugal fan as claimed in claim 1 wherein the first conformal zone of the shroud has a radius that is greater than the radius of the outside diameter of the impeller such that the first conformal zone of the shroud is spaced apart from the impeller and defines an air passageway therebetween having a substantially constant radial dimension.

6. A centrifugal fan as claimed in claim 1 wherein the second scroll zone of the shroud has a leading edge and a trailing edge, the leading edge of the second scroll zone of the shroud being operably coupled to the trailing edge of the first conformal zone of the shroud and the trailing edge of the second scroll zone of the shroud defining an outer portion of the air exhaust port.

7. A centrifugal fan as claimed in claim 1 wherein the leading edge of the restrictor plate is radially disposed proximate the leading edge of the first conformal zone of the shroud and the gradually tapering trailing edge of the restrictor plate commences the taper from full width radially proximate the trailing edge of the first conformal zone of the shroud.

8. An improved housing for a centrifugal fan, the fan having an impeller defining a central chamber therein from which air is drawn by the impeller, the improvement comprising:

a shroud disposed peripheral to the impeller for defining an air passageway and having a first conformal zone and a second scroll zone; and

a restrictor plate disposed within the central chamber and arranged to restrict the flow of air to the impeller;

wherein the restrictor plate has a shape defined by a steeply rising leading ee to an intermediate portion substantially overlapping the entire width of the impeller and a gradually tapering trailing edge;

wherein the restrictor plate is disposed within the central chamber defined within the impeller such that the intermediate portion subtends a first arc that is substantially coextensive with a second arc that is subtended by the first conformal zone of the shroud.

9. A housing as claimed in claim 8 wherein the first conformal zone of the shroud extends substantially a fourth of a revolution around the impeller.

10. A housing as claimed in claim 8 wherein the second scroll zone of the shroud extends through an arc that is substantially more than one quarter and less than three quarters of a revolution around the impeller.

11. A housing as claimed in claim 8 wherein the second scroll zone of the shroud has an expanding radius that expands at a rate of between five and twelve degrees.

12. A housing as claimed in claim 8 wherein the first conformal zone of the shroud has a radius of fixed dimension throughout an arc subtended by the first conformal zone that is greater than the radius of the impeller such that the first conformal zone of the shroud is spaced apart from the impeller and defines an air passageway therebetween having a substantially constant radial dimension.

13. An improved centrifugal fan having an impeller rotatably carried within a housing about an axis, the housing having at least one air inlet and an air discharge port, the fan being designed to be disposed within a relatively confined enclosure, said enclosure restricting the flow of air into the air inlet and defining a reduced space for accommodating the disposition of the fan, the improvement comprising:

a conformal zone of the fan housing having a constant radius relative to the axis of the impeller;

a device restricting the flow of air from the air inlet to the impeller, the device including a leading edge, a trailing edge and an intermediate portion between the leading and trailing edges, the intermediate portion subtending a first arc substantially coextensive with a second arc subtended by the conformal zone and;

a scroll shaped air passageway conveying fan discharge air to the air discharge port, the passageway forming a portion of the fan housing, wherein;

the device restricting the flow of air from the air inlet to the impeller and the scroll shaped air passageway are cooperatively disposed relative to each other and to the impeller such that inlet air is admitted to the impeller and discharge air is conveyed from the impeller through a limited portion of a revolution of the impeller and the device is uniformly curved with a radius that is less than a radius of an inside diameter of the impeller.

14. An improved fan as claimed in claim 13 wherein the scroll shaped air passageway extends through an arc that is substantially more than one quarter and less than three quarters of a revolution around the impeller.

15. An improved fan as claimed in claim 14 wherein the scroll shaped air passageway has an expanding radius that expands at a rate of between five and twelve degrees.

16. An improved centrifugal fan having an impeller and a housing, the impeller having an inner diameter and a substantially greater outer diameter and being designed to accelerate air drawn from a central chamber defined within the inner diameter of the impeller to an air passageway defined in the housing substantially surrounding the outer diameter of the impeller, the air passageway terminating in an air exhaust port, the air exhaust port having an inner base that is generally tangential to the outer diameter of the impeller, the housing substantially enclosing the impeller and defining the air exhaust port and an air inlet fluidly coupled to the central chamber defined within the inner diameter of the impeller, the improvement comprising:

a shroud forming a portion of the housing defining the air passageway and having a first zone a varying radius from a first ray to a second ray and a second zone being of radius expanding at a rate different from the varying radius;

a restriction plate operably coupled to the housing and disposed proximate a portion of the inner diameter of the impeller for restricting the flow of air from the central chamber to the impeller;

wherein the restrictor plate is disposed within the central chamber defined within the inner diameter of the impeller such that the restrictor plate has an intermediate portion which subtends a first arc that is substantially coextensive with an arc subtended by the first zone of the shroud.

17. A restrictor plate comprising:

a surface having a constant radius relative to an axis, the surface including first, second and third edges where the third edge lies in a plane substantially perpendicular to the axis;

said surface being substantially perpendicular to the third edge and each of the first and second edges being located proximate opposite ends of the third edge; and

the first and second edges being separated by a first distance which decreases as a second distance from the third edge increases;

wherein the first edge has a rate of change which decreases the first distance at a linear rate, and wherein the second edge has a rate of change which decreases the first distance at a non-linear rate.