Fluid reaction surfaces (i.e. – impellers) – Perimetric blading extending axially between annular members
Reexamination Certificate
1999-05-21
2001-01-30
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Perimetric blading extending axially between annular members
C416S20400A
Reexamination Certificate
active
06179566
ABSTRACT:
TECHNICAL FIELD
The present invention includes to a blower wheel assembly and methods of manufacturing the same. In particular, the invention includes a blower wheel assembly with a steel hub having protrusions to securely attach the hub to a backplate of the blower wheel assembly.
BACKGROUND OF THE INVENTION
FIG. 1
shows a prior art centrifugal blower wheel assembly
10
which includes a backplate
12
, a hub
14
, and a plurality of blades
16
. The hub
14
and the blades
16
are attached to the backplate
12
, which is typically a separate part. The blades
16
are secured to a ring
17
; alternatively, the blades may be formed as a single piece, known as a bladestrip. The assembly
10
is used by attaching it to a rotational mechanism (not shown) via the hub
14
by means of a shaft (not shown). Rotation of the shaft causes rotation of the hub
14
, backplate
12
and blades
16
, thereby providing air flow. The connection between the backplate
12
and the hub
14
therefore is required to transmit the rotational torque of the shaft.
The maximum torque the hub
14
can withstand before coming loose with respect to the backplate
12
is termed the holding torque. The holding torque is a function of the way in which the hub is attached to the backplate. In addition, the holding torque can decrease over time as use changes the strength of that attachment. If the holding torque is exceeded, the hub becomes loose and will spin independently of the backplate
12
, resulting in a catastrophic failure of the blower wheel assembly.
FIGS. 2A-2C
illustrate details of a prior art hub and backplate configuration. The hub
14
has a concentric rim or lip
18
protruding from a front surface
19
of the hub
14
. The lip
18
is designed to be placed in a hole
20
of the backplate
12
as illustrated in FIG.
2
C. The hub
14
has a back surface
22
through which a hole
24
extends in order to receive a shaft (not shown) or other member for rotation. A threaded set screw hole
26
is provided along a radius of the hub. A set screw (not shown) can be threaded in the hole
26
to allow for the assembly
10
to be fixed with respect to the shaft within the hole
24
.
The hub
14
is attached to the backplate
12
by forcing back (via stamping, for example) the rim or lip
18
while the rim or lip
18
extends through the hole
20
of the backplate
12
, thereby crimping the rim or lip
18
against the backplate
12
and holding the hub
14
thereto. In some circumstances, however, the holding torque for this type of arrangement is either insufficient or inconsistent, and therefore undesirable.
The backplate
12
, the hub
14
, and the blades
16
are all typically made of steel, which provides for high strength, low cost, and ease of manufacture.
An objective of the invention is to provide a blower wheel assembly with a hub that is more strongly attached to the backplate, that can be used over a wide range of temperatures, and that is inexpensive to manufacture.
SUMMARY OF THE INVENTION
The invention includes a blower wheel assembly and method characterized by a steel hub with protruding lugs that mate with a corresponding array of holes in a backplate of the assembly. The lugs are riveted or otherwise deformed to upset the lug material, thereby permanently and securely attaching the hub to the backplate. The lugs may be formed on the hub by a machining process. The holes in the backplate may have stress relief portions to avoid stress concentrations in corners of the holes.
According to one aspect of the invention, a blower wheel assembly includes a backplate with an array of hub mounting holes therein; a plurality of blades attached to the backplate; and a steel hub attached to the backplate, the steel hub having one or more lugs corresponding to the array of holes, the lugs being formed by a machining process.
According to another aspect of the invention, a method of manufacturing a blower wheel assembly includes forming a steel hub having one or more machined lugs; and attaching the steel hub to a backplate which has an array of hub mounting holes corresponding to the one or more lugs, wherein the attaching includes inserting the lugs in the hub mounting holes and deforming the lugs to lock the hub in place.
According to yet another aspect of the invention, a blower wheel assembly includes a backplate with an array of hub mounting holes therein, each hub mounting hole having a stress relief portion; a plurality of blades attached to the backplate; and a hub attached to the backplate, the hub having one or more lugs corresponding to the array of holes.
To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.
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Andulics Joseph H.
Nagy Gregory R.
Amin, Eschweiler & Turocy, LLP
Beckett Air Incorporated
Look Edward K.
Rodriguez Hermes
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