Background Art In motor vehicle applications, particularly off the road vehicles, a fan situated behind a radiator draws a large quantity of air through the radiator, as the vehicle speed is relatively low. Low noise level is also a requirement. Therefore quieter compact fans are needed to reduce cooling system size and still meet the sound and cooling requirements of off road motor vehicles.

U. S. Patent 4,358,245 describes a low noise, axial flow fan particularly suited for use in a turbulent airflow such as the flow existing in an automobile radiator. The fan has a shroud secured to the outer end of the fan blades. The blades are forwardly skewed and have an increasing blade angle as the blade extends outwardly. The shroud forms a converging nozzle. Each blade has an airfoil cross- section and the entire fan is formed as a single injection molded plastic integral structure.

Disclosure of the Invention Among the objects of the invention may be noted the provision of a quiet, compact and efficient radiator cooling fan.

In general, a radiator-cooling fan for an internal combustion engine, when made in accordance with this invention comprises a hub portion and a shroud portion having an inlet end and an outlet end.

The hub portion has radially outwardly extending portion adjacent the inlet end and then a portion which progresses axially and radially outwardly to the outlet end. The shroud portion has a radially inwardly extending portion adjacent the inlet end then a portion which progresses radially inwardly and axially connected to a portion which progresses radially outwardly and axially to the outlet end. A plurality of forward sweep, airfoil shaped blades extend from the hub to the shroud to form a mixed flow fan with improved blade loading and aeroacoustic performance.

Brief Description of the Drawings The invention as set forth in the claims will become more apparent by reading the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts throughout the drawings and in which: Figure 1 is a partial sectional view of a compact, quiet fan made in accordance with this invention; Figure 2 is a front elevational view of the fan; Figure 3 is partial view of a blade for the fan showing the forward sweep of the blade relative to a radial, axial plane;

Figure 4 shows a typical cross section of the blades; Figure 5 is a table giving the coordinates of the hub and shroud surfaces relative to a central axis shown in Figure 1; and Figure 6 is a table giving the coordinates of the outer surface of the cross section of the blade shown in Figure 4.

Best Mode for Carrying out the Invention Referring now to the drawings in detail and in particular to Figure 1, there is shown a portion of a compact, quiet mixed flow fan 1 comprising a hub portion 3, a shroud portion 5 and a plurality of airfoil shaped blades 7.

The hub portion 3 starting at an inlet end and ending at an outlet end comprises a radially outwardly extending portion 9 having a central bore 11 and a plurality of bolt holes 13 disposed in a circular array out board of the bore 11. A curved portion 15 provides a smooth transition between the radially outwardly extending portion 9 and an axially and radially outward extending frustoconical portion 17 having an inner surface, which if extended to its apex would form an included angle generally about 90 degrees. Thus forming a hub portion 3 that progresses axially and radially outwardly from its inlet end to its outlet end.

The shroud portion 5 starting at its inlet end and ending at its outlet end comprises a radially inwardly extending portion 19. A trumpet shaped portion 21 extending radially and axially inward to form a smooth transition between the radially inwardly extending portion 19 and an axially and radially

outward extending frustoconical portion 23. The frustoconical portion having an inner surface, which if extended to its apex would form an included angle generally about 50 degrees. The hub portion 3 and shroud portion 5 cooperating to form a converging annular opening which directs the flow from the fan generally axially and radially outward at an angle substantially less than 90 degrees with respect to the axis of rotation the fan 1.

The lines CC and 00 are references for lying out the surfaces on the hub and shroud portions 3 and 5 utilizing the table in Figure 5. The hub and shroud surfaces, which contact the blades 7 are indicated as X1 and the hub and shroud surfaces, which do not contact the blades 7 are indicated as X2. R1 and R2 are the radii in millimeters from the centerline CC to the coordinates X1 and X2, respectively. In the table in Figure 5 negative coordinates XI and X2 are in millimeters to the left of line 00 which represents a plane perpendicular to the centerline CC and positive coordinates X1 and X2 are in millimeters to the right of line or plane 00. The table in Figure 5 is utilized to provide the coordinates (X1, R1) and (X2, R2), which define a plurality of circles that are connected to form the smooth continuous surfaces of revolution which form the hub and shroud portions 3 and 5 of the fan 1.

As shown in Figure 2, the plurality of blades 7 are disposed in a circular array and have a leading edge 25 that is swept forward adjacent the shroud. The blades 7 are formed integral with the hub 3 and shroud 5.

Figure 3 shows the forward sweep of the leading edge 25 is generally in the range of about 10

degrees and generally extends down from the shroud 5 about 20% of the height of the blade 7. The inner 80% of the leading edge 25 may sweep slight backward with respect to a radial line.

Figure 4 shows a typical airfoil cross section of the blades 7. The lines XX and YY are axes for laying out the airfoil surfaces utilizing the table in Figure 6. P indicates the pressure surface, which is concave and S indicates the Suction surface, which is convex. Positive X numbers are coordinates of the airfoil surface in millimeters to the right of the line YY and negative X numbers are coordinates in millimeters to the left of the line YY. Positive Y numbers are coordinates in millimeters above Line XX.

The pitch of the blades 7 is generally the same from the hub 3 to the shroud 5 and is generally about 60 degrees with respect to the axis of rotation of the fan.

The shape of the hub 3 and shroud 5 cooperates with the airfoil shaped, forward swept blades 7 to maintain uniform blade loading and superior aerodynamic performance with no separation of the air flow over the entire blade span while reducing ingestion noise to produce a quiet compact efficient radiator fan 1.

While the preferred embodiments described herein set forth the best mode to practice this invention presently contemplated by the inventors, numerous modifications and adaptations of this invention will be apparent to others of ordinary skill in the art. Therefore, the embodiments are to be considered as illustrative and exemplary and it is understood that the claims are intended to cover such

modifications and adaptations as they are considered to be within the spirit and scope of this invention.

Industrial Applicability The quiet compact mixed flow fan with forward swept blades, herein before described, advantageously produces a specific noise level generally about 30 decibels providing a quiet fan, which is both a cost and space effective solution to cooling system performance of off the road vehicles. Manufacturing the fan as an aluminum casting provides a cost effective fan that is durable and has good damping characteristics.