Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-11-01
2001-02-13
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C370S902000, C370S902000, C029S596000
Reexamination Certificate
active
06188156
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention pertains to a rabbet joint between two component parts and a method of forming a rabbet joint. More particularly, the present invention pertains to an apparatus and method for eliminating the radius commonly formed between the faces of an annular rabbet.
(2) Description of the Related Art
When joining components of an assembly, a rabbet is often useful on at least one of the components to provide a plurality of engagement surfaces between mating components of the assembly. In addition to providing structural support, rabbets also facilitate proper alignment of the components with respect to each other.
Typically, a rabbet takes the form of a right-angle groove or channel made into the edge of a component part that is adapted to receive and engage the corner of a mating component. As an example, rabbets are used to facilitate the assembly of components in dynamoelectric devices. Dynamoelectric devices are commonly comprised of, a rotor and shaft assembly, a stator encircling the rotor and shaft assembly, a cylindrical shell housing secured to and encircling the stator, and a pair of end shields secured to the ends of the housing. Because the end shields typically support bearings mounted on the rotor and shaft assembly and thereby position the rotor and shaft assembly relative to the stator, proper alignment of the end shields with respect to the housing can be critical to the operation of the dynamoelectric device. It is therefore common to provide a rabbet around the edge of the end shield to ensure that proper alignment with the housing is made.
A prior art end shield is shown in FIG.
1
. The end shield
10
has a hole
12
that allows a shaft of a dynamoelectric device to pass therethrough. An annular boss
14
extends around the hole
12
and is adapted to support a bearing mounted on the shaft. The end shield
10
also has a cylindrical rim
16
protruding from the perimeter of its main body and has a rabbet
18
formed thereon. Although end shields similar to the end shield
10
shown are common in the industry, many variations exist. For example, in
FIG. 1
the end shield
10
is shown having a solid web
19
extending from the boss
14
to the rim
16
. However, it is also common to have a plurality of spokes extending radially from the boss
14
to the rim
16
with ventilation openings therebetween in place of the solid web
19
. Similarly, it is not necessary for an end shield to have a hole
12
for passage of the shaft therethrough, nor that the rim
16
extend axially from the main body. It is an improvement to the prior art annular rabbet
18
that is a focus of this invention.
The particular prior art rabbet
18
is formed on the rim
16
of the end shield
10
. The rabbet
18
is comprised of a cylindrical surface
20
and an adjacent, perpendicular annular surface
22
. The two surfaces form a right-angle shoulder around the rim
16
adapted to engage an end of a cylindrical shell housing of the dynamoelectric device. The diameter of the cylindrical surface
20
is approximately equal to that of a cylindrical interior surface of the housing nearest the housing end. Thus when the end shield
10
is assembled onto the housing, the cylindrical surface
20
engages the interior surface, thereby radially positioning and supporting the end shield
10
relative to the housing. Similarly, the annular surface
22
is designed to axially position the end shield
10
relative to the housing by engaging an annular end surface of the housing that is perpendicular to the interior surface of the housing. Once in proper alignment, the components may be further secured to each other by fasteners, adhesives, interlocking tabs or catches, or by other means for securing together components of an assembly as known to those skilled in the art.
As shown in the detailed cross-section of the prior art rabbet
18
in
FIG. 2
, a radius
24
is often inadvertently formed between the annular surface
22
and the cylindrical surface
20
. This radius
24
can be the result of cutting tool wear when a machining process is used to form the rabbet
18
on the end shield
10
. Additionally, the radius
24
may be the result of wear of the dies or molds used to cast or mold the end shields
10
. When precise alignment of the components within an assembly is required, any radius
24
formed between the annular surface
22
and the cylindrical surface
20
is undesirable in that, the radius
24
may prevent the annular surface
22
from engaging its mating component resulting in improper axial alignment of the components and the undesirable appearance of a gap between the end shield
10
and the shell housing.
Prior art solutions to this problem include reworking the end shield
10
by machining the rabbet
18
using sharp cutting tools to reduce the radius
24
. The extra machining process required by this solution greatly adds to the expense of production. Since the preferred method of fabrication is to mold or cast the end shields
10
, another solution has been to periodically rework or replace the molds or dies. This solution unnecessarily burdens the production process when the molds and dies are otherwise adequate. Yet another solution is to provide a chamfer or radius on the housing between the interior surface and the annular end surface of the housing that is larger than that of the radius
24
, thus providing relief in the housing for the radius
24
when the components are properly aligned. Like the other solutions, modifying the housing increases the cost of production and it is therefore desirable to find alternative solutions to the problem that can eliminate the radius
24
without adding a process step or otherwise increasing the cost of production.
The present invention overcomes the problems associated with prior art rabbet joints by utilizing a plurality of separated coplanar surfaces in place of the prior art annular surface
22
and by positioning a plurality of cylindrical surface segments perpendicular to and between the coplanar surfaces. The aggregate of the cylindrical surface segments replaces the cylindrical surface
20
of the prior art rabbet
18
. In accordance with this invention, no common edge is formed between the coplanar surfaces and adjacent cylindrical surface segments and, therefore, no radius
24
can be formed regardless of die, mold, or tool wear during the manufacturing process. This invention allows a component, such as an end shield, to be molded or cast with an annular rabbet type fitting and to align perfectly when assembled to a sharp edged mating component, regardless of minor die or mold wear.
SUMMARY OF THE INVENTION
The annular rabbet of the present invention replaces the prior art annular rabbet on an end shield. In accordance with the present invention, an end shield is formed with a plurality of cylindrical surface segments that are spaced circumferentially about a common axis by recesses in the end shield. Perpendicular and adjacent to the cylindrical surfaces are a plurality of spaced, coplanar surfaces with recesses therebetween. The coplanar surfaces are positioned circumferentially about the common axis between the cylindrical surface segments. The cylindrical surface segments and the coplanar surfaces are adapted to engage with an end of the cylindrical shell housing. The configuration of the cylindrical surface segments and the coplanar surfaces eliminates the mutual edge or corner formed between the cylindrical surface and the annular surface on prior art end shield rabbets. By eliminating such an edge on the present invention, an undesirable radius cannot be formed thereon.
In another aspect of the invention, a method of forming a rabbet joint between two component parts of an assembly comprises the steps of forming a plurality of cylindrical surface segments on a first component with the cylindrical surface segments being separated circumferentially about a common axis by recesses formed into the first component, forming a plurality of coplanar surfa
Emerson Electric Co.
Howell & Haferkamp LC
Lam Thanh
Ramirez Nestor
LandOfFree
Cast rabbet joint for proper alignment of assembled components does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cast rabbet joint for proper alignment of assembled components, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cast rabbet joint for proper alignment of assembled components will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2589851