Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2002-03-29
2004-03-16
Lam, Thanh (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S089000
Reexamination Certificate
active
06707202
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention pertains to a bearing supporting a rotating shaft of an electrical device, for example an electric motor, and a sleeve that is mounted on the shaft in engagement with the bearing. Together the bearing and sleeve function to simplify the construction of the electrical device by eliminating one of a pair of retaining rings from the shaft that was previously necessary to hold the shaft and bearing in relative positions, and by eliminating a second retaining ring from the shaft that was used as a locator to positively locate a machined surface on the housing of the electrical device relative to the second ring and to positively locate a rotating component on the end of the shaft.
(2) Description of Related Art
In home appliances that employ water pumps driven by electric motors, for example dishwashers or clothes washers, the housing of the water pump is often mounted against the housing or end shield of the motor to reduce the amount of the interior area of the appliance that is occupied by the water pump and motor. In addition, mounting the pump housing against a portion of the motor housing positively locates the pump relative to the motor and positively locates the motor shaft in the pump housing interior. Proper positioning of the pump housing relative to the motor and the motor shaft is necessary to insure that the pump impeller mounted on the motor shaft inside the pump housing is properly positioned relative to the pump housing interior surfaces to prevent the pump impeller from contacting with the pump housing interior surfaces on operation of the pump and possibly seizing up the pump.
In order to insure that a pump housing and a pump impeller contained in the pump housing are both properly positioned relative to each other when the pump housing and pump impeller are assembled to the motor, the motor shaft is often used as a reference point in positioning a machined surface on the electric motor housing against which the pump housing seats. The motor shaft is also used as a reference point for the impeller of the pump, to properly position the impeller in the interior of the pump housing. Thus, the motor shaft is used as a reference point to properly position both the pump housing relative to the motor housing and to properly position the impeller relative to the pump housing interior for proper operation of the water pump.
One example of a prior art electric motor
12
is shown in FIG.
1
. The particular construction of the electric motor
12
is typical of most electric motors and therefore the construction is shown schematically and only one end of the electric motor, the end from which the motor shaft
14
extends, is shown in FIG.
1
. The motor is shown positioned with the motor shaft
14
oriented vertically. The motor could also be positioned with the shaft
14
oriented horizontally. The motor in
FIG. 1
is an open-frame construction type of motor having a pair of end shields
18
, only one of which is shown in
FIG. 1
, secured to opposite axial ends of the motor. The end shield
18
shown in
FIG. 1
has a shaft opening
22
at its center. The two end shields are secured to axially opposite ends of the motor stator core
24
covering over the stator winding end turns
26
. The rotor
28
of the motor is mounted on the motor shaft
14
and is positioned in the interior bore of the stator core
24
. The shaft
14
is supported at its axially opposite ends by a pair of bearings mounted in the end shields.
FIG. 1
shows only one of the bearings
32
mounted in the shaft opening
22
of the motor end shield.
The motor
12
is shown in
FIG. 1
positioned with its shaft
14
oriented vertically where the shaft rotates a rotary component of a home appliance, for example an impeller of a pump in a dishwasher or clothes washer. In order to use the motor shaft
14
as a point of reference for locating machined surfaces on the housing of the motor
12
and for locating the pump housing and pump impeller relative to the shaft, it is necessary that the shaft
14
not move axially (i.e. in a direction along the shaft center axis
34
) relative to the motor. In the prior art solution to prevent axial movement of the shaft
14
, a pair of annular grooves
36
,
38
are machined in the shaft. The grooves
36
,
38
are positioned on the shaft an axial distance from each other that corresponds to the axial width of the bearing
32
. With the shaft grooves
36
,
38
positioned on opposite sides of the bearing
32
, retainer rings, for example C-type retainer rings or E-type retainer rings
42
,
44
are pressed into the two shaft grooves
36
,
38
on opposite sides of the bearing
32
to secure the shaft in its axial position relative to the bearing. This in turn secures the shaft
14
in its axial position relative to the motor
12
. This enables use of the shaft
14
as a reference point for locating a machined seating surface on the housing of the motor
12
when the motor is used with a pump, and for locating a rotating component of the pump, for example the impeller, relative to the shaft and the pump housing.
To locate the pump housing and pump impeller relative to the shaft
14
, a third annular groove
46
is formed in the shaft and an additional retainer ring
48
is inserted into the groove. The additional retainer ring
48
is used as a point of reference to positively locate the pump impeller
52
relative to the shaft, relative to the end shield
18
of the motor
12
, and relative to the pump housing. With the impeller
52
positively located relative to the shaft
14
and the motor
12
, and the proper position of the impeller relative to the pump housing being known, the additional retainer ring
48
is used as a point of reference for positively locating a machined surface
54
on the end shield
18
of the motor
12
to serve as a seating surface with the pump housing
56
(represented by dashed lines in FIG.
1
). Thus, the additional retainer ring
48
serves the dual purpose of positively locating the pump impeller
52
on the shaft
14
and positively locating the machined surface
54
on the motor end shield
18
that is then used to properly locate the pump housing
56
relative to the motor shaft
14
.
However, problems were encountered in the above-described apparatus and method of locating the pump impeller
52
and locating the machined surface
54
relative to the motor end shield
18
. In assembling the impeller
52
on the end of the motor shaft
14
, the impeller would often be rotated on the shaft as it was pressed downward over the top end of the shaft as shown in FIG.
1
. Rotating the impeller
52
as it was pressed downwardly onto the shaft
14
would at times cause the third retainer ring
48
to become dislodged from its shaft groove
46
. This would result in the impeller
52
being improperly positioned on the shaft
14
. The improperly positioned impeller would contact the interior of the pump housing when rotated by the motor which would detract from the proper operation of the pump. In addition, in using the third retainer ring
48
as a locator for machining the seating surface on the motor end shield, the motor would typically be mounted on a mandril with an indexing part of the mandril engaging against the third retainer ring. The engagement of the mandril indexing part with the third retainer ring would positively locate the plane of the machined seating surface to be formed on the motor end shield. The machined surface would be cut or ground into the cast metal of the end shield relative to the position of the third retainer ring
48
on the motor shaft. The third retainer ring
48
becoming dislodged from its shaft groove
46
would result in the seating surface machined on the motor housing being improperly positioned. As a result, the pump housing would be assembled in a misaligned position on the motor end shield
18
, presenting the potential for the impeller
52
contacting with the pump housing interior and seizing up.
SUMMARY OF THE INVENTION
Fadler Richard J.
Fischer Carl R.
Torbit Michael C.
Trost George D.
Emerson Electric Co.
Lam Thanh
Thompson & Coburn LLP
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