Backward inclined fan impeller

A backward inclined fan impeller features a plurality of blades attached to a shroud ring and base for use in transporting corrosive materials. The impeller assembly is substantially corrosion resistant while maintaining adequate performance characteristics. Rotary power actuates the impeller assembly.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention concerns an impeller used in the field of fluid transfer 
using rotating machinery. The invention more particularly concerns an 
impeller specifically developed for use with corrosive fluids while 
maintaining standard performance characteristics. 
2. Discussion of the Background 
Traditional impellers employ blades to transfer the fluid from an inlet, or 
suction eye, through the interior of the impeller and then discharged 
through an outlet. The blades of the impeller can be oriented relative to 
the axis of rotation of the impeller in a radial direction, a forwardly 
inclined direction, or a backwardly inclined direction. The forwardly 
inclined blade design employs a blade which has an exit edge which is 
forward of the inlet edge of the blade relative to the direction of 
rotation of the impeller. For example, relative to a fixed rectangular 
coordinate system located at the axis of rotation of the impeller, but not 
fixed to the impeller, the exit edge of the blade crosses any one of the 
coordinate axes before the inlet edge of the blade crosses the 
corresponding coordinate axis when the impeller is rotated. Likewise, the 
backwardly inclined blade design employs a blade which has an inlet edge 
forward of the exit edge of the blade relative to the direction of 
rotation of the impeller. The backwardly inclined blade design is more 
efficient than either the radial or forwardly inclined blade designs. 
However, backwardly inclined blade designs have a major drawback over the 
other two types of blade orientation in that the blade stresses are much 
greater. The larger stresses have tended to require that the material of 
construction of the blades be restricted to steel due to its high 
strength, stiffness, and fatigue characteristics. As such, the steel 
blades allow for blade angles and contours which maintain good flow 
characteristics and performance characteristic. 
The steel blades are adequate for many uses and environments. However, when 
steel impellers are employed to transmit corrosive materials, the steel 
impellers corrode. The steel impellers employed to transmit the corrosive 
fluids work satisfactorily for a short period of time before the corrosive 
effect of the working fluid corrodes the steel impeller to the point of 
uselessness. To overcome the problem of corrosion to the material of the 
impeller, fiberglass reinforced plastic has been employed since fiberglass 
reinforced plastic has superior corrosion resistant properties as compared 
to steel. 
However, the large stresses mentioned earlier require that either the 
thickness of the blades be increased or the angle of inclination be 
compromised. Furthermore, increasing the thickness of the blades increases 
the mass moment of inertia of the impeller thus requiring increased 
operational power, limits the number of blades that can be placed on the 
impeller, and adversely affects blade aerodynamics. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide an impeller that transmits 
corrosive fluids while maintaining corrosion resistance and performance 
characteristics. 
In one form of the invention the backward inclined fan impeller takes the 
form of a plurality of backwardly inclined blades attached to a base. 
Attached to another side of the blades is a shroud ring. The shroud ring 
has an opening in its center forming a suction eye. Attached to the center 
of the base is a conical hub. The blades are made from corrosion resistant 
material. 
Thus, Applicant's invention is superior to the prior art. Applicant's 
invention provides for a backwardly inclined fan impeller which is able to 
operate in a corrosive environment while maintaining performance 
characteristics. Applicant's invention achieves this objective by 
employing a substantially corrosion resistant fiberglass reinforced 
plastic as the material of construction in combination with a conical hub, 
a shroud ring, a base, and blades so as to minimize stresses within the 
blades while maintaining efficient blade aerodynamics. The impeller is 
efficient because of the backward inclined orientation of the blades, the 
relatively thin blade width, and the use of the conical hub and shroud 
ring to alter the direction of the fluid flow. The blades of the impeller 
assembly are structurally sound since the blades are integrally connected 
to both the base and the shroud ring. The prior art fails to disclose the 
use of such structural features which provide the desired result. Such 
structural features distinguish Applicant's invention, structurally and 
functionally, over the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings, wherein like reference numerals designate 
identical or corresponding parts throughout the several views, and more 
particularly to FIG. 1 thereof, an impeller assembly 10 has been created 
which provides for the transmission of corrosive fluids while maintaining 
conventional performance characteristics. The embodiment of this invention 
is displayed in FIGS. 1 and 2. FIGS. 3-8 show details of various parts of 
the impeller assembly 10. 
FIG. 1 is a top view of the impeller assembly 10 where the blades 60 are 
shown in phantom line, the hub assembly 30 is also shown in phantom line, 
and the conical hub or portion 50 is also shown. FIG. 1 illustrates the 
placement of eight screws (not numbered) equally spaced around a mid 
portion of the conical hub 50 so as to secure the conical hub 50 to the 
base 40 (not shown), and the hub assembly 30 (not numbered). FIG. 1 
further illustrates use of backwardly inclined blades 60 which are located 
equidistant from each other along the base 40 (not shown) creating an 
annular array of impeller blades. The blades 60 are radially located 
between the outer periphery 52 of the conical hub 50 and the outer 
periphery of the base 40 (not shown). The impeller assembly 10 as shown in 
FIG. 1 rotates in operation in a clockwise direction. Outlets 70 are 
located between each adjacent set of blades 60. 
FIG. 2 is a partial cross-sectional side view of the impeller assembly 10 
taken along line 2--2 of FIG. 1. FIG. 2 clearly shows the conical shape of 
the conical hub 50. FIG. 2 further illustrates the location of the base 40 
on which the conical hub 50 is mounted. Likewise, the base 40 is mounted 
on the hub assembly 30. The shroud ring 20 connects to each of the blades 
60. Suction eye 22 of the shroud ring 20 introduces the corrosive fluid 
into the impeller to eventually be discharged through the outlets 70. The 
impeller assembly rotates about a rotational axis A. 
FIG. 3 shows a side view of a blade 60 which has an outlet edge 66, a 
straight connecting edge 64, a free edge 68, an inlet edge 69, and an 
inclined connecting edge 62. The free edge 68 and inclined connecting edge 
62 are located at one axial end of the blade 60. The straight connecting 
edge 64 is located at the other axial end of the blade 60. 
FIG. 4 shows a top view of a blade 60. The top view displays the relative 
thickness of a blade 60. 
FIG. 5 is a cross-sectional side view of the shroud ring 20. The suction 
eye 22 of the shroud ring 20 is clearly displayed. The corrosive material 
which enters through the suction eye 22 exits the shroud ring 20 through a 
flared end 24. 
FIG. 6 is a top view of the hub assembly 30. Specifically, the flange 32 of 
the hub assembly 30 is displayed showing the matching screw-hole pattern 
that matches the screw-hole pattern shown in FIG. 1. 
FIG. 7 is a side view of the hub assembly 30 which shows the flange 32 and 
the hub 34. The hub 34 is designed so as to receive rotary power from a 
power source (not shown). The hub assembly 30 is ideally made out of cold 
rolled steel plate. 
FIG. 8 is a cross-sectional side view of an assembly of a blade 60 to the 
base 40 and to the shroud ring 20. FIG. 8 illustrates how attachment 
material 80 composed of a mixture of fiberglass and plastic is applied to 
the blades 60, shroud ring 20, and the base 40. 
Components, other than the hub assembly 30, are ideally made from 
fiberglass reinforced plastic. 
The inclined connecting edge 62 of each blade 60 connects to an inner 
surface of the shroud ring 20 at its flared end 24, as shown in FIGS. 2 
and 8. Once the blades 60 and shroud ring 20 abut each other the 
attachment material 80 which consists of a mixture of fiberglass and 
plastic is applied to the surfaces of the blade 60 and shroud ring 20 so 
as to overlap the surfaces and blend them together. Also, as shown in 
FIGS. 2 and 8 are the connection of the blade 60 to the base 40. The 
straight connecting edge 64 of each blade 60 is brought into contact with 
a surface of the base 40. The outlet edge 66 of the blade 60 is placed 
perpendicularly adjacent to the outer periphery of the base 40 and the 
inlet edge 69 of the blade 60 is placed adjacent to the outer periphery of 
the conical hub 50. 
Again, the attachment material 80 composed of a mixture of fiberglass and 
plastic is applied so as to overlap the surfaces of the base 40 and blades 
60. Additionally, the attachment material 80 is blended into the corners 
created by the attachment of the blades 60 to the shroud ring 20 and to 
the base 40. 
In operation, a power source (not shown) transmits rotary power to the hub 
34 of the impeller assembly 10. The impeller assembly 10 rotates in a 
clockwise direction. The corrosive fluid then enters the impeller assembly 
10 through the suction eye 22 of the shroud ring 20 due to a pressure 
gradient. As the corrosive fluid passes through the suction eye 22 it 
flows towards the conical hub 50, where the flow of the corrosive fluid is 
altered in a direction substantially 90.degree. from the rotational axis 
of the impeller assembly 10. The corrosive fluid then flows in a radially 
outward direction through channels bounded by the base 40, the shroud ring 
20, and by adjacent sets of blades 60, so as to form outlets 70 through 
which the corrosive fluid is discharged. The corrosive fluid discharged 
from the impeller assembly 10 can be collected in a housing (not shown) so 
as to transport the corrosive fluid to some other location. 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described herein.