Switch assembly for food waste disposer

Details Switch assembly for food waste disposer Switch assembly for food waste disposer

2002-07-16

2003-08-26

Scott, J. R. (Department: 2832)

Electricity: circuit makers and breakers

Centrifugal

Liquid contact

C200S293000, C310S06800R, C310S06800R, C310S071000

Reexamination Certificate

active

06610942

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to food waste disposers and, more particularly to a switch assembly for use in a food waste disposer.
BACKGROUND OF THE INVENTION
Referring to
FIG. 1
, a portion of a conventional food waste disposer
10
is illustrated in a cross-sectional view. The conventional disposer
10
includes an upper food conveying section (not shown), a lower motor section
30
, and a central grinding section
20
disposed between the food conveying section and the motor section
30
. The food conveying section conveys food waste and water to the central grinding section
20
. The central grinding section
20
includes a grinding plate
22
containing grinding lugs
24
.
The motor section
30
includes an induction motor
40
, enclosed within a motor housing
32
having an upper end frame
34
and a lower end frame
36
. The motor
40
includes a stator
42
and a rotor
46
. The stator
42
includes windings
44
. The rotor
46
is disposed on a motor shaft
48
. The motor
40
imparts rotational movement to the motor shaft
48
, which turns the grinding plate
22
of the grinding section
20
.
The motor shaft
48
includes a mechanical or centrifugal actuator
50
disposed adjacent the lower end frame
36
. The centrifugal actuator
50
includes a body
52
attached to the motor shaft
48
. Two weights
54
are pivotably connected to the body
52
and are biased together by one or more springs
56
. The spring-loaded weights
54
move a movable plate
58
disposed about the motor shaft
48
, as will be explained in more detail later.
A switch assembly
60
is attached to the lower end frame
36
adjacent the motor shaft
48
and centrifugal actuator
50
. In particular, tabs
63
on the switch assembly
60
are press fit through apertures defined in the lower end frame
36
. The switch assembly
60
includes an internal switch having a lever arm or blade
66
in contact with the movable plate
58
of the centrifugal actuator
50
. When a certain rotational speed is reached by the motor
40
, the spring-loaded weights
54
of the centrifugal actuator
50
move apart due to centrifugal force. The separation of the weights
54
causes the movable plate
58
to lift. In contact with the movable plate
58
, the lever arm or blade
66
moves upward and an electrical connection is broken within the internal switch of the switch assembly
60
. Typically, the electrical connection is broken when the motor reaches approximately 1500 to 1600 r.p.m. for 60 Hz. Motors or 1300 to 1400 r.p.m. for 50 Hz. motors and may occur within about 0.3 seconds from start-up. As will be discussed in more detail below, the internal switch, lever arm or blade
66
, and centrifugal actuator
50
work in conjunction to control power to the windings
44
of the motor
40
.
The switch assembly
60
houses an overload switch
70
, which is typically a separately manufactured component. The overload switch
70
is used to cut power to the motor
40
under certain conditions. The overload switch
70
includes a reset button
72
disposed through an aperture
38
in the lower end frame
36
. The reset button
72
allows a user to reset the overload switch
70
from outside the disposer
10
.
Referring to
FIGS. 2A and 2B
, top views of two switch assemblies
60
a
and
60
b
according to the prior art are illustrated for use with the conventional disposer
10
. In
FIG. 2A
, the switch assembly
60
a
represents a start switch used in a food waste disposer produced by. In-Sink-Erator®, a division of Emerson Electric Co. In
FIG. 2B
, the switch assembly
60
b
represents a start switch produced by Whiterock Corporation of China.
The switch assembly
60
a
or
60
b
includes a body
62
that attaches to the lower end frame with retainers or tabs
63
. The body
62
includes a contact switch
64
a
or
64
b
and houses the overload switch
70
. The overload switch
70
may be, for example, a switch manufactured by Thermodisc Incorporated, a subsidiary of Emerson Electric Co., having a type 30M frame style. The overload switch
70
includes a terminal
81
and a connection point
85
.
In the switch assembly
60
a
of
FIG. 2A
, the contact switch
64
a
includes a plastic ever arm
66
a
pivotally connected to the body
62
and biased open by a spring (not shown). As described above in
FIG. 1
, the plastic lever arm
66
a
moves with the movable plate
58
of the centrifugal actuator
50
. A flexible, conductive blade
68
a
is connected to and movable with the lever arm
66
a
. The blade
68
a
is electrically connected to the terminals
82
and
84
. In contrast to the switch assembly
60
a
of
FIG. 2A
, the lever arm
66
b
and flexible blade
68
b
of the contact switch
60
b
in
FIG. 2B
are an integral conductive piece. Despite this difference, the contact switch
64
b
operates in a substantially similar fashion to the contact switch
64
a
of FIG.
2
A.
Referring to
FIG. 2C
, an electrical schematic of a switch assembly
60
according to the prior art such as assembly
60
a
or
60
b
, is illustrated. The switch assembly
60
is connected to leads L
1
-L
3
from the motor of the disposer. The motor has run windings
44
R and start windings
44
S. The switch assembly
60
is also connected to leads L
4
-L
5
from a power supply V.
The terminal
81
of the overload switch
70
connects in parallel to the windings
44
S and
44
R, and the connection point
85
connects to the power source V. Thus, the overload switch
70
can cut power to the windings
44
S and
44
R in case of a power overload. The terminal
82
is connected to the lead L
2
from the run windings
44
R. The terminal
83
is connected to the lead L
3
from the start windings
44
S. The terminal
84
is connected to the lead L
4
from the power source V.
The contact switch
64
of the switch assembly
60
is used to control activation of the start windings
44
S. At initial start-up of the motor
40
, the contact switch
64
is closed so that the start and run windings
44
S and
44
R are both engaged. The start windings
44
S are initially used in combination with the run windings
44
R to overcome inertial forces of the rotor, shaft, and grinding plate of the disposer, in addition to other forces. After a certain point and in response to movement of the movable plate
58
of the centrifugal actuator
50
, the contact switch
64
interrupts electrical connection between the power source V connected to terminal
84
and the start windings
44
S connected to terminal
83
, effectively shutting off the start windings
44
S.
Although the switch assemblies
60
a
and
60
b
of
FIGS. 2A and 2B
operate efficiently and effectively, manufacturers continually strive to improve the efficiency of, and hence reduce the cost of, the manufacture and assembly of such switches and of the disposers in which they are contained. Unfortunately, the prior art switch assemblies have some drawbacks, which prevent these goals from being reached.
For example, the switch assemblies
60
a
and
60
b
according to the prior art are relatively difficult to install in the disposer
10
. As noted above in
FIG. 1
, the switch assembly
60
a
or
60
b
includes tabs
63
that press fit into slots defined in the lower end frame
36
. The overload switch
70
includes a reset button
72
that extends from the bottom of the switch assembly
60
a
or
60
b
and is disposed through the hole
38
in the lower end frame
36
. During assembly, an operator manually positions the overload switch
70
within the housing
62
before attaching the assembly
60
a
or
60
b
to the lower end frame
36
. However, the switch assembly
60
a
or
60
b
does not positively retain the overload switch
70
. Consequently, the operator must hold the overload switch
70
in the assembly
60
a
or
60
b
while simultaneously pushing the tabs
63
into the slots defined in the lower end frame
36
and disposing the reset button
72
in the hole
38
. Thus, the attachment of the assembly
60
a
or
60
b
to the lower end frame
36
requires manual dexteri

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