U.S. patent application number 10/700308 was filed with the patent office on 2005-05-05 for injection molded centrifugal air impeller.
Invention is credited to O'Connor, John F. JR..
Application Number | 20050095133 10/700308 |
Document ID | / |
Family ID | 34551190 |
Filed Date | 2005-05-05 |
United States Patent
Application |
20050095133 |
Kind Code |
A1 |
O'Connor, John F. JR. |
May 5, 2005 |
Injection molded centrifugal air impeller
Abstract
A centrifugal air impeller designed for injection molding has a
mold parting line extending intermediate the sides of the blades
thus permitting optimum configurations of the inner and outer blade
edges and enhanced impeller performance. The impeller inlet ring
has an inner diameter less than that of the outer edges of the
blades and an outer diameter greater than the outer diameter of the
blades. The backplate has a diameter greater than that of the inner
diameter of the blades.
Inventors: |
O'Connor, John F. JR.; (New
Hartford, CT) |
Correspondence
Address: |
Russel H. Marvin
Torrington Research Company
89 Commercial Boulevard
Torrington
CT
06790
US
|
Family ID: |
34551190 |
Appl. No.: |
10/700308 |
Filed: |
October 31, 2003 |
Current U.S.
Class: |
416/187 |
Current CPC
Class: |
F04D 29/023 20130101;
F05D 2300/43 20130101; B29L 2031/08 20130101; B29C 33/005 20130101;
B29C 45/00 20130101; F04D 29/283 20130101; F05D 2230/53
20130101 |
Class at
Publication: |
416/187 |
International
Class: |
B63H 001/16 |
Claims
1. A plastic injection molded centrifugal impeller comprising a
circumaxially spaced series of air moving blades each having inner
and outer edges and longitudinally extending inner and outer
portions on opposite sides of an intermediate longitudinal line, an
end ring at the inlet end of the impeller formed integrally with
and interconnecting the blades, said ring having an inner diameter
greater than that of the blade inner edges and an outer diameter
greater than that of the blade outer edges, and a back plate formed
integrally with and interconnecting the blades at an end thereof
opposite the inlet ring, the diameter of the back plate being at
least equal to that of the inner edges of the blades, and the
foregoing characteristics of the impeller accommodating the molding
of the blade inner portions in the core of the plastic injection
mold and the molding of the blade outer portions in the cavity of
the mold.
2. A plastic injection molded centrifugal impeller as set forth in
claim 1 wherein the inner diameter of the inlet ring is
approximately 1 to 7 percent less than the diameter of the outer
edges of the blades.
3. A plastic injection molded centrifugal impeller as set forth in
claim 1 wherein the outer diameter of the inlet ring is
approximately 1 to 7 percent greater than that of the outer edges
of the blades.
4. A plastic injection molded centrifugal impeller as set forth in
claim 1 wherein the diameter of the back plate is larger than that
of the inner edges of the blades, and wherein the blades have
notches at their inner edges adjacent the back plate to receive the
same
5. A plastic injection molded centrifugal impeller as set forth in
claim 1 wherein the blades are notched to receive an inner edge
portion of the end ring.
6. A plastic injection molded centrifugal impeller as set forth in
claim 1 wherein the end ring extends axially a short distance
beyond the ends of the blades.
7. A plastic injection molded centrifugal impeller as set forth in
claim 1 wherein the blades have rounded inner edges.
8. A plastic injection molded centrifugal impeller as set forth in
claim 1 wherein the impeller blades are forwardly curved.
9. A plastic injection molded centrifugal impeller as set forth in
claim 1 wherein the outer portions of the blades are thinner than
the inner portions thereof.
10. A plastic injection molded centrifugal impeller as set forth in
claim 2 wherein the inner diameter of the inlet ring is
approximately 2 to 5 percent less than the diameter of the outer
edges of the blades.
11. A plastic injection molded centrifugal impeller as set forth in
claim 3 wherein the outer diameter of the inlet ring is
approximately 2 to 5 percent greater than that of the outer edges
of the blades.
Description
[0001] (This application claims the benefit of provisional
application Serial Number [not received to date] filed on Aug. 29,
2003.)
BACKGROUND OF INVENTION
[0002] Injection molded centrifugal air impellers with forwardly
curved blades have an air flow pattern which is three dimensional.
In the plane of rotation, there is a circulation that flows
outwardly through the blades for approximately three hundred
degrees (300.degree.) of rotation. After passing the eye of
circulation the flow reverses direction and passes back through the
blades. Air flows into the blower inlet substantially along the
section where the main circulation is outward. Although some air
may flow out of the inlet along the section where the main
circulation is inward, there is a net through flow of air out the
blower discharge. The center of the main circulation is located
near the inner edge of the impeller blades at the point where the
flow reverses from outward to inward. Since the main circulation is
larger than the impeller it is possible to have air velocities
higher than blade tip speed and develop pressure coefficients
greater than one. The ability of this type of impeller to achieve
high performance in a small space is dependent on the regenerative
effects of the main circulation as some of the flow is pumped
through the impeller twice.
[0003] With the foregoing flow pattern in mind, optimum blade
configurations must be provided. Since the flow direction reverses
the blades do not have leading and trailing edges in the normal
sense. High efficiency can only be achieved with optimum blade
configurations particularly at the blade edges.
[0004] Prior art impeller designs have required mold parting lines
between cavity and core along the outer edges of the blades. Shut
off angles for long mold life, have resulted in irregularities
along the blade outer edges and other conditions causing low
efficiency and noise generation. A reduced shut off angle can
result in shortened mold life and flash along the blade edge.
[0005] A general object of the present invention is to provide an
improved impeller design well suited to plastic injection molding
resulting in an optimum blade configuration.
SUMMARY OF THE INVENTION
[0006] In fulfillment of the foregoing object and in accordance
with the present invention, the improved impeller accommodates a
shut off or parting line intermediate the inner and outer edges of
the blades. With the reversing flow pattern in mind, both inner and
outer edges of the blades are provided with smooth uniform
contours.
[0007] More particularly, the impeller design accommodates forming
of an inner edge portion of each blade in the core of the mold and
forming of an outer edge portion of each blade in the cavity of the
mold. This allows for a proper shut off angle, which reduces the
likelihood of flash at the parting line and minimizes mold
wear.
[0008] As will be seen, the impeller back plate is designed so that
the blades extend radially beyond the outer edge of the back plate.
The inlet ring on the other hand extends radially beyond the outer
edges of the blades but its inner edge resides inwardly of the
blade outer edges. This ring configuration provides the required
structural integrity and yet allows for a mold shut off which
extends mold life and at the same time results in an aerodynamic
advantage. Leakage flow around the blade ends at the inlet is
inhibited and this enhances impeller performance High velocity
leakage flow around the blade ends is known to disturb the inlet
flow pattern and thus reduce efficiency.
DRAWINGS
[0009] FIG. 1 is perspective view partially broken away of a prior
art impeller,
[0010] FIG. 2 is another perspective view of the FIG. 1 impeller,
the opposite half being broken away with respect to FIG. 1,
[0011] FIG. 3 is a perspective view, partially broken away, of the
improved impeller of the present invention,
[0012] FIG. 4 is a schematic view along the axis of the impeller of
FIG. 3.
DESCRIPTION OF PREFERRED EMBODIMENT
[0013] Referring initially to FIGS. 1 and 2, a prior art impeller
indicated generally at 10 has a back plate 12, a plurality of
circumaxially arranged air moving blades 14,14 integral with the
back plate 12, and an end ring 16 integral with the blades at an
end thereof opposite the back plate. The outer diameter of the back
plate coincides with that of the blades and the inner diameter of
the end ring coincides with the outer diameter of the blades. Thus,
it will be apparent that the cavity of the mold forms only the
inlet ring and the core of the mold forms the back plate and
blades. It will also be apparent that the shut off and parting line
must reside along the outer edges of the blades the aforementioned
attendant disadvantages being encountered.
[0014] The improved impeller shown in FIG. 3 at 20 has a plurality
of blades 22,22, a back plate 24, and an end ring 26. Each blade 22
has inner and outer edges 28 and 30 and adjacent inner and outer
elongated portions 32 and 34 which extend longitudinally and which
are partially defined by a mold parting line 36. The mold parting
line 36 is displaced angularly from the blade centerline for ease
in separating the mold parts. As will be observed, the parting line
intersects the outer diameter of the back plate 24 at one end and
the inner diameter of the end ring 26 at the other end. It is
important that the end ring have an inner diameter, 36 FIG. 4,
greater than that of the blade inner edges, 37 in FIG. 4, and an
outer diameter, 38 in FIG. 4, greater than that of the blade outer
edges, 39 in FIG. 4. The back plate 24 should have a diameter at
least equal to that of the inner edges 28,28 of the blades and as
shown and preferred has a diameter somewhat greater than that of
the blade inner edges. Reverting to FIG. 3, it will be observed
that the inner edges of the blades are notched to receive the outer
edge portion of the back plate. This provides a generous passage
for the free flow of molten plastic to the blades during the
molding operation.
[0015] The impeller design as described results in a molding
process wherein the inner portions of the blades, from the parting
line radially inwardly, are formed in the core of the mold and the
outer portions of the blades, from the parting line radially
outwardly, are formed in the cavity of the mold. The back plate is
also formed in the core and the end ring in the cavity.
[0016] The precise location of the parting line on the blades may
vary but it is preferred that the inner diameter of the end ring be
approximately 2 to 5 percent less than that of the outer edges
30,30 of the blades. Similarly, it is preferred that the outer
diameter of the inlet ring be 2 to 5 percent greater than that of
the outer edges 30,30 of the blades.
[0017] As mentioned above, the improved impeller design, and
particularly the location of the parting line at an intermediate
portion of the blades, results in optimum design of the leading and
trailing edges of the blades and in enhanced impeller performance.
While the foregoing discussion has been directed to forwardly
curved blades, impellers with other blade configurations will also
benefit substantially from the design features of the improved
impeller.
* * * * *