Information
-
Patent Grant
-
6225604
-
Patent Number
6,225,604
-
Date Filed
Tuesday, August 29, 200024 years ago
-
Date Issued
Tuesday, May 1, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Walberg; Teresa
- Fastovsky; Leonid
Agents
-
CPC
-
US Classifications
Field of Search
US
- 219 400
- 219 681
- 126 21 A
- 425 430
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International Classifications
-
Abstract
A blower assembly for a cooking appliance having an oven cavity adapted to operate in at least cleaning and convection cooking modes includes a blower element mounted for rotation though a shaft member supported by at least one bearing unit. The shaft member is constituted by a tubular section which is secured to the blower element and a solid shaft section which extends within the tubular section. The solid shaft section is formed from a material having a higher thermal conductivity than the tubular section and concentrically arranged relative to the bearing unit. With this arrangement, the shaft section acts as a heat sink for directing heat, to which the blower element is subjected, away from both the tubular section and the bearing unit. The shaft section preferably terminates within the tubular section at a distance spaced from the blower element such that a thermal air gap is defined within the tubular section.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to the art of cooking appliances and, more particularly, to a drive and support structure for a blower used in a self-cleaning convection oven.
2. Discussion of the Prior Art
Tremendous advancements have been made in the art of cooking appliances in the relatively recent past. For instance, it was not many years ago that conduction and/or radiant heat sources were almost exclusively relied upon in connection with household ranges and wall ovens. However, more recent trends are to further take advantage of convection as an additional heating system. That is, a flow of air can be circulated through an oven cavity, while being subjected to one or more heat sources, with the heated air being distributed into the oven cavity to develop substantially uniform cooking of a food product.
As with more conventional oven cooking arrangements, it is desirable to provide a self-cleaning function for the oven cavity regardless of the particular type of heating source(s) used with the convection oven. However, with such an arrangement, the air handling system can be subjected to extreme temperatures. Various components of the air handling system, such as a bearing arrangement utilized to rotatably support a blower element of the system, can be adversely affected when subjected to such high temperatures.
Based on the above, there exists a need in the art for a blower assembly used in a cooking appliance, including an oven cavity adapted to operate in at least cleaning and convection cooking modes, wherein sensitive components of the blower assembly are isolated from extreme temperatures during operation of the cooking appliance. In addition, there is a need for a blower assembly for a convection cooking appliance which is easy to assemble, reliable and cost effective, while being designed to establish a temperature gradient between its various components which assures that more temperature sensitive components are protected.
SUMMARY OF THE INVENTION
The present invention is directed to the drive and support structure for a high speed blower assembly used in a self-cleaning, convection oven. In such an environment, a blower element of the assembly can be subjected to extreme temperatures, including those reaching and exceeding 900° F. (approx. 480° C.). In accordance with the invention, the blower element is secured to the first end of a tubular section of a drive shaft which, in turn, is rotatably supported by one or more bearing units. In the most preferred form of the invention, an opposing end of the tube has secured thereto a sheeve used for rotating the blower element and drive shaft through a motor and pulley arrangement.
In accordance with the invention, it is desired to reduce the conduction of heat from the blower element, through the tube and into at least the bearings. For this purpose, the tube has fitted therein a rod which is formed of a material having a relatively high thermal conductivity as compared to the tube. In the most preferred embodiment of the invention, the tube is formed of stainless steel and an aluminum rod is pressed-fit into the tube. Most preferably, the rod extends from the second end portion of the tube, concentrically past the bearings, but terminates short of the blower element such that a thermal air break zone is defined, within the tube, between the aluminum rod and the blower element.
With this arrangement, given the relatively low coefficient of thermal conductivity of the tube, as well as its reduced cross section, the temperature gradient between the blower element and the tube is increased. The aluminum rod acts as a heat sink which functions to further reduce the temperature to which the bearings are subjected. Therefore, due to the gradient created and the function of the heat sink, the operational temperatures experienced by the shaft bearings are substantially reduced.
Additional objects, features and advantages of the present invention will become more readily apparent from the following detailed description of a preferred embodiment thereof when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several view.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a schematic side view of a convection oven incorporating a blower assembly constructed in accordance with the present invention; and
FIG. 2
is an enlarged, schematic and partial sectional side view of the blower assembly incorporated in the convection oven of FIG.
1
.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
With initial reference to
FIG. 1
, a cooking appliance
1
is schematically shown in the form of a wall oven. Appliance
1
includes an oven cavity
5
generally defined by a bottom wall
8
, a top wall
9
, a rear wall
10
and a pair of side walls, one of which is indicated at
11
. Oven cavity
5
also has associated therewith an access opening
13
for food items to be placed into or withdrawn from cavity
5
. About access opening
13
is provided a frontal plate
16
. In a manner known in the art, frontal plate
16
is adapted to be mounted against a substantially vertical wall such as in the kitchen of a residential home, and would have a door (not shown) pivotally attached thereto for selectively sealing off access opening
13
.
Extending generally along bottom, top and rear walls
8
-
10
of cavity
5
is an air channel assembly
26
defined by ducting that leads into and out of cavity
5
. More specifically, air channel assembly
26
includes a lower air return section
29
, an upper air delivery section
30
and a rear air transfer section
31
. Lower air return section
29
is open into cavity
5
through a substantially central return air outlet
33
formed in bottom
8
. In the most preferred form of the invention, return air outlet
33
is constituted by a generally circular insert provided with various spaced holes (not shown). In a similar manner, upper air delivery section
30
includes a discharge or delivery inlet
35
formed in top wall
9
. Although not shown in detail, inlet
35
is also preferably constituted by a generally circular-shaped insert which is attached to the remainder of upper air delivery section
30
and which is provided with a plurality of holes. As will become more fully evident below, the particular construction of cooking appliance
1
can significantly vary in accordance with the present invention. More specifically, it is only important in accordance with the present invention that cooking appliance
1
include an air channel assembly, such as that discussed above with reference to assembly
26
, as well as a blower assembly, such as that generally indicated at
40
, for use in generating a circulating flow of air through oven cavity
5
. Although not considered a part of the present invention, a preferred construction for oven cavity
5
and air channel assembly
26
can be found in U.S. patent application entitled “OVEN CAVITY CONSTRUCTION” filed on even date herewith which is hereby incorporated by reference.
In the preferred embodiment shown, cooking appliance
1
constitutes an electric appliance and, more specifically, a combination convection, microwave and radiant cooking device. As shown in this Figure, cooking appliance
1
is provided with an annular filter basket
46
, having a multitude of circumferentially spaced holes
47
, which is positioned within lower air return section
29
and through which the air flowing from cavity
5
through return air outlet
33
is directed. Arranged below filter basket
46
is a microwave generator unit
48
incorporating a magnetron (not specifically shown). Encircling at least a portion of filter basket
46
is a first electric heating unit
52
. Heating unit
52
is shown as constituted by a sheathed electric resistance heating element having upper and lower interconnected legs
53
and
54
. First electric heating unit
52
is preferably provided to heat return air flowing from oven cavity
5
, through outlet
33
and filter basket
56
prior to the air reaching a catalyst indicated at
57
. In a manner known in the art, catalyst
57
functions to eliminate smoke and the like from the air stream. As shown, catalyst
57
extends partially within a rotatable blower element
60
which forms part of blower assembly
40
. Although blower element
60
can take various forms while performing the desired air flow generating function, blower element
60
preferably constitutes a centrifugal unit arranged at the conjure of lower air return section
29
and rear air transfer section
31
. In general, blower element
60
is secured to a rotatable shaft member
62
. Shaft member
62
also has attached thereto, for non-relative rotation, a sheeve
66
which is adapted to receive a belt (not shown) for use in rotating blower element
60
through shaft member
62
in combination with an electric motor (also not shown). As illustrated, sheeve
66
is preferably arranged within a housing extension
68
which projects from rear air transfer section
31
.
Preferably mounted in upper air delivery section
30
adjacent rear transfer section
31
is a second electric heating element arrangement
70
that is preferably constituted by a bank of heating coils. Although not pertinent to the present invention, second heating unit
70
can be defined by a single electric coil that runs back and forth across upper air delivery section
30
or multiple, separately controllable coil elements. In any event, second heating unit
70
functions to further heat the air flowing through channel assembly
26
prior to the air reaching discharge inlet
35
. Also shown in this Figure is a third electric heating unit
72
which, in a manner similar to first electric heating unit
52
, is preferably constituted by a sheathed, resistance-type heating element. Third electric heating unit
72
preferably extends adjacent top wall
9
and constitutes an additional heat source for cavity
5
of cooking appliance
1
. The particular manner in which first, second and third electric heating units
52
,
70
and
72
are utilized during operation of cooking appliance
1
for both cooking and cleaning modes of operation are not considered to constitute part of the present invention. Instead, these details can be found in U.S. patent applications entitled “HEATING SYSTEM FOR A COOKING APPLIANCE” and “SELF-CLEANING SYSTEM FOR A COOKING APPLIANCE”, both of which are filed on even date herewith and incorporated by reference. In general, each of blower assembly
40
, microwave generator
48
and first, second and third electric heating units
52
,
70
and
72
are linked to an appliance control (not shown) and regulated based on established operator settings, as well as signals received from a temperature sensor
75
.
The present invention is particularly directed to the structure of blower assembly
40
. Therefore, as indicated above, cooking appliance
1
can take various forms without departing from the invention and the particular construction described above should only be considered exemplary and not restrictive. It is only important that blower assembly
40
is utilized in connection with a cooking appliance that can operate in a cleaning mode wherein rather high temperatures, generally in the order of 900° F. (approx. 480° C.) are generated within oven cavity
5
for pyrolytic cleaning purposes such that blower element
60
is subjected to an air stream having a temperature of this general magnitude. Given that such temperatures can have detrimental effects on the useful life of various components of such an air handling system, blower assembly
40
is configured in manner which effectively protects vulnerable components thereof from these high temperatures as will be detailed more fully below.
FIG. 2
illustrates the preferred construction of blower assembly
40
in accordance with the present invention. Therefore, this Figure shows a rear panel portion
78
of blower element
60
to which is attached a shaft member
62
. More specifically, shaft member
62
includes a first, tubular section
80
having a first end portion
82
and a second end portion
83
. As shown, first end portion
82
is secured to blower element
60
, such as through a crimping operation with one of the resulting crimps being generally indicated at
84
. Shaft member
62
also includes a second, solid shaft or rod section
86
having a first end
88
and a second end
89
. As shown, second section
86
of shaft member
62
is positioned within tubular section
80
, with second end
89
being arranged generally concentric with second end portion
83
and with first end
88
terminating short of first end portion
82
such that a thermal air break zone or gap
94
is defined within tubular section
80
, between first end
88
and rear panel portion
78
of blower element
60
.
In the most preferred form of the invention, first, tubular section
80
is formed from stainless steel, while second, solid section
86
is formed from aluminum. Regardless of the particular materials utilized, second section
86
is configured to have a higher thermal conductivity than tubular section
80
for the reasons which will become more fully evident below.
In the embodiment shown, blower element
60
is rotatably mounted through shaft member
62
and a bearing assembly
100
defined by a dual bearing including a first bearing unit
102
and a second bearing unit
103
. As shown, shaft section
86
preferably extends within tubular section
80
concentric with bearing assembly
100
and beyond bearing assembly
100
towards blower element
60
. Sheeve
66
is shown to include an outer radial portion
108
, which is provided with spaced, upstanding annular lips
110
and
111
between which is defined a belt receiving zone
112
. The actual configuration of belt receiving zone
112
can vary in accordance with the present invention to be splined, V-shaped, smooth or the like as is widely known in the art. Sheeve
66
, which is also preferably casted of aluminum, further includes an inner radial portion
114
shrink-fit onto tubular section
80
. As should be readily evident, sheeve
66
is adapted to be rotated through the use of a pulley and motor arrangement (not shown) for use in rotating shaft member
62
about a central, axially extending axis defined by shaft member
62
, with shaft member
62
being supported for rotation by bearing assembly
100
in order to drive blower element
60
. In such a drive arrangement, it should be recognized that sheeve
66
could be drivingly connected to shaft member
62
in various ways, including a spline connection. In addition, shaft member
62
could be directly driven by a motor, through a gearing system, a chain drive arrangement or the like. In addition, sheeve
66
could be formed of various other materials without departing from the invention. Sheeve
66
could also be formed of nylon, preferably with a powdered metal core which is press-fit onto tubular section
80
. In any event, various material and drive arrangements are possible in accordance with the invention.
Although the particular components and construction of blower assembly
40
can vary in accordance with the present invention, it is important to note that blower element
60
can be subjected to rather high temperatures, particularly when cooking appliance
1
is utilized in a self-cleaning mode. For instance, in such a mode of operation, oven cavity
5
can reach temperatures in the order of 930°-950° F. (approx. 500°-510° C.), with the air flowing in air channel assembly
26
being subjected to this temperature which, in turn, develops an ambient temperature in the order of approximately 900° F. (approx. 480° C.) at blower element
60
. The invention is particularly concerned with isolating bearing assembly
100
, as well as other components of blower assembly
40
, from these extreme temperatures. In accordance with a first aspect of the invention, the use of tubular section
80
provides a reduced cross section at the connection with blower element
60
versus if a solid drive shaft were utilized. Therefore, the area in which conduction heat transfer can occur is substantially reduced. Second, solid shaft section
86
, by virtue of its high thermal conductivity, tends to function as a heat sink to further direct heat away from tubular section
80
. Furthermore, the inclusion of the thermal air gap
94
also operates as an insulator. With this arrangement, it has been found that the temperature of tubular section
80
at bearing assembly
100
will typically only reach in the order of 220°-250° F. (approx. 100°-120° C.) versus the 900° F. (approx. 480° C.) experienced by blower element
60
. Therefore, bearing assembly
100
is subjected to these much lower temperatures which can be readily handled without degrading the operation or useful life of the bearing assembly
100
. Based on tests conducted in comparing the blower assembly
40
with an arrangement wherein a single solid shaft is utilized for driving the blower element, the temperatures at which bearing assembly
100
is subjected in accordance with the present invention is significantly lower, generally in the order of 70°-100° F. (approx. 20°-40° C.).
Based on the above, it should be readily apparent that the particular construction of blower assembly
40
can enhance its overall useful life, while still representing a relatively simply constructed and cost effective system. However, although described with respect to a preferred embodiment of the invention, it should be readily understood that various changes and/or modifications can be made to the invention with departing from the spirit thereof. Instead, the invention is only intended to be limited by the scope of the following claims.
Claims
- 1. In a cooking appliance including an oven cavity adapted to operate in at least cleaning and convection cooking modes, a blower assembly comprising:at least one bearing unit; a tube supported by the at least one bearing unit for rotation about an axis; and a blower element for developing a flow of air for the oven cavity upon rotation of the blower element, said blower element being drivingly connected to the tube, with the at least one bearing unit rotatably supporting the blower element through the tube.
- 2. The blower assembly according to claim 1, further comprising: a heat sink for directing heat, to which the blower element is subjected, away from the at least one bearing unit.
- 3. The blower assembly according to claim 2, wherein said heat sink is constituted by a shaft concentrically arranged within said tube.
- 4. The blower assembly according to claim 3, wherein said tube has an associated length, with the shaft being shorter than said length.
- 5. The blower assembly according to claim 4, wherein at least a portion of the shaft is concentric with the at least one bearing unit.
- 6. The blower assembly according to claim 4, further comprising: a thermal air gap, defined within the tube, between the blower element and the shaft.
- 7. The blower assembly according to claim 3, wherein the shaft is formed from aluminum.
- 8. The blower assembly according to claim 7, wherein the tube is formed from stainless steel.
- 9. The blower assembly according to claim 2, further comprising: a mechanism for driving the tube for rotation about said axis.
- 10. The blower assembly according to claim 9, wherein said driving mechanism includes a sheeve non-rotatably secured to the tube.
- 11. The blower assembly according to claim 10, wherein said sheeve is shrink-fit onto the tube.
- 12. The blower assembly according to claim 10, wherein the sheeve is formed from aluminum.
- 13. The blower assembly according to claim 10, wherein the tube is rotatably supported solely through the at least one bearing unit which is positioned entirely between the blower element and the sheeve.
- 14. In a cooking appliance including an oven cavity adapted to operate in at least cleaning and convection cooking modes, a blower assembly comprising:a rotatable blower element arranged in fluid communication with the oven cavity for developing a flow of air for the oven cavity upon rotation of the blower element; and a shaft member for rotatably supporting the blower element, said shaft member being formed from first and second concentrically arranged shaft sections, with the second shaft section being formed of a material having a higher thermal conductivity than the first shaft section.
- 15. The blower assembly according to claim 14, wherein the second shaft section is formed from aluminum.
- 16. The blower assembly according to claim 14, wherein the first shaft section is constituted by a tube within which the second shaft section extends, said tube having an associated length and the second shaft section being shorter than said length.
- 17. The blower assembly according to claim 16, further comprising: a thermal air gap, defined within the tube, between the blower element and the shaft section.
- 18. The blower assembly according to claim 17, further comprising: at least one bearing unit rotatably supporting the shaft member for rotation about an axis.
- 19. The blower assembly according to claim 18, wherein the second shaft section is concentric with the at least one bearing unit.
- 20. The blower assembly according to claim 18, further comprising: a sheeve fixed to the first shaft section for use in rotatably driving the blower element, said sheeve being arranged further from the blower element than the at least one bearing unit.
US Referenced Citations (16)
Foreign Referenced Citations (2)
Number |
Date |
Country |
4-87547 |
Mar 1992 |
JP |
8-196058 |
Jul 1996 |
JP |