The invention relates to a temperature-controlled drawer
apparatus that can be mounted in cabinetry and can be maintained at a preselected
temperature for warming and cooking food items.
Many residential kitchens are provided with a warming drawer
that is heated, typically by electrical or gas heating elements, to a desired temperature
for various purposes, such as warming plates to receive cooked food, or warming
or maintaining previously cooked foods at a desired temperature without further
cooking. Such warming drawers serve many of the purposes of a cooking oven, but
are of a simpler design, less expensive, smaller, and operate at a lower temperature,
thereby enabling the principal kitchen oven to be used for cooking other foods while
selected food items are warmed or maintained in a warmed condition.
Warming drawers are frequently mounted in wooden cabinetry.
Current safety standards limit the temperature of the cabinet as heated by the warming
drawer. Consequently, the warming drawer must typically be enclosed within a larger,
insulated cavity. This impacts the overall and working dimensions of the drawer,
and increases the cost of the warming drawer. The safety standards can also limit
the temperature to which the warming drawer can be heated, thereby limiting its
A warming drawer for mounting within a cabinet having a
recess in which the warming drawer is received. In one embodiment, the warming drawer
comprises a housing defining a chamber with an open face and having opposing side
walls that define at least a portion of the chamber, a drawer moveably mounted to
the housing for movement into and out of the chamber through the open face, and
at least one spacer extending from each of the side walls to space the side walls
from the cabinet when the warming drawer is mounted within the recess of the cabinet
to form dead air spaces between the side walls and the cabinet.
In another embodiment, the warming drawer is moveably mounted
to the housing for movement into and out of the chamber through the open face between
a closed position and an opened position. A seal is provided on one of the housing
and the drawer, and forms a seal between the housing and drawer when the drawer
is in the closed position. An active closer urges the drawer into the closed position.
In yet another embodiment, the warming drawer comprises
a bottom wall and a peripheral wall extending upwardly from the bottom wall. A heating
element is located in the housing such that the heating element is beneath the drawer
when the drawer is in the closed position, and the heating element is configured
such that a portion of the heating element is nominally located beneath the peripheral
The invention will be further described by way of example
with reference to the accompanying drawings, in which:-
Figure 1 is a perspective view of an embodiment of the
invention comprising a warming drawer installed in a cabinet, with the cabinet illustrated
in phantom for clarity and the warming drawer in a closed position.
Figure 2 is a perspective view of the warming drawer and
cabinet illustrated in Figure 1 with the warming drawer in an open position.
Figure 3 is an exploded view of the warming drawer illustrated
in Figure 1.
Figure 4 is a rear perspective view of the warming drawer
and cabinet illustrated in Figure 1 showing a pair of spacers for spacing the warming
drawer from the cabinet.
Figure 5 is a perspective view of the warming drawer illustrated
in Figure 1 with selected elements shown in phantom and showing an active closer
for urging the warming drawer into a closed position
Figure 6 is a sectional view taken along view line 6-6
of Figure 1 with elements shown in phantom and illustrating the relative positions
of a heating element and warming drawer walls.
Figure 7 is a sectional view taken along view line 7-7
of Figure 4 illustrating the spacing of the warming drawer from the cabinet.
Figure 8 is an enlarged elevational view of a control switch
and power switch assembly illustrated in Figure 2.
Prior to describing an embodiment of the invention, a brief
overview of the benefits of the invention should prove useful to a full understanding
of the invention. The invention advantageously combines the slow cooking functionality
of a traditional slow cooker, a/k/a crock pot, with a warming drawer. Traditional
slow cookers are operated at a temperature range of 220 to 250°F, which is
higher than the temperatures achievable with a traditional warming drawer (about
210°F). Warming drawers typically cannot be operated at the slow cooking temperatures
and still meet current safety standards, such as those promoted by Underwrites Laboratory.
These safety standards require that the temperature of the cabinet surrounding the
warming drawer not exceed a predetermined threshold temperature. Slow cookers do
not have this concern as they are not mounted in a cabinet and their heat can be
dissipated into the air, whereas, for a warming drawer, the heat is transferred
to the surrounding cabinet structure. The invention results in a warming drawer
structure that permits the warming drawer to be operated at slow cooking temperatures
and times while cost effectively meeting the relevant safety standards for a warming
drawer. As such, the warming drawer described herein can provide both warming drawer
functionality and slow cooking functionality. The addition of the slow cooking functionality
is expanded on by the warming drawer in that the warmer drawer can accommodate larger
size containers than a slow cooker and can accommodate irregularly shaped containers,
unlike the traditional slow cooker that is limited to a specifically designed container.
The warming drawer according to the invention also has
the ability to accurately maintain relatively low temperatures (around 100°F),
which is suitable for bread proofing. Not all warming drawers can accurately maintain
a low enough proofing temperature over the desired time. If the temperature is too
high, the bread begins to bake instead of rise. Thus, the warming drawer of the
invention is able to operate at temperatures suitable for proofing, warming, and
slow cooking. Prior art warming drawers are not capable of providing such a temperature
range because of an inability to meet the requisite safety standards and/or an inability
to accurately maintain the lower temperatures.
Referring now to the Figures, and in particular to Figures
1 and 2, an embodiment of the invention comprising a warming drawer 10 is illustrated
mounted in a cabinet 12, such as conventional kitchen cabinetry, in a recess 14
configured to receive the warming drawer 10 therein. Figure 1 illustrates the drawer
22 in a closed position relative to the housing 20 and Figure 2 illustrates the
drawer 22 in an open position. It is contemplated that the warming drawer 10 can
be mounted in cabinet structures other than kitchen cabinets. For example, cabinet
12 can be a masonry cabinet formed in an outside barbeque area. The invention is
not limited to the cabinet structure.
As illustrated in Figures 2 and 3, the warming drawer 10
comprises a housing 20 enclosing a drawer 22 and a heating element 24, with the
heating element 24 being controlled by a control module 26. The housing 20 comprises
a housing shell 30 having a planar top wall 32 and a planar bottom wall 34 in parallel
opposed disposition, interconnected along parallel edges by a back wall 36 extending
orthogonally thereto. A pair of parallel opposed planar side walls 38, 40 extend
between the top wall 32, the bottom wall 34, and the back wall 36. A front wall
42 extends in parallel opposed disposition to the back wall 36 between the top wall
32, the bottom wall 34, and the side walls 38, 40. The front wall 42 has an opening
44 therethrough to define an open face 46. The walls 32-42 define a drawer chamber
48, access to which is provided by the opening 44. A peripheral lip 54 extends around
the periphery of the opening 44 for attachment of a resilient, heat-resistant seal
50 thereto. The open face 46 adjacent the peripheral lip 54 defines a peripheral
flange 98, which transitions laterally away from a side edge of the opening 44 to
define a control module flange 52 associated with the control module 26.
Referring to Figures 3 and 4 the side walls 38, 40 each
comprise a planar side panel 56 having a spacer strip 58 extending longitudinally
along an upper edge thereof in parallel opposed disposition to a spacer strip 60
extending longitudinally along a lower edge thereof. The spacer strips 58, 60 extend
orthogonally away from the side panel 56 to terminate in contact flanges 62, 64,
respectively, extending orthogonally toward each other to define a somewhat C-shaped
cross-section. Alternatively, separate spacers not integrated into the side panel
56 can be used between the side panel 56 and the cabinetry. Such spacers must be
mounted between the side walls 38, 40 or side panels 56 and the cabinetry when the
warming drawer 10 is installed, and may be supplied in different sizes corresponding
the required spacing between the side walls 38, 40 and the cabinetry. However, the
spacer strips 58, 60 integrated with the panel 56 are preferable as they eliminate
the potential for using an incorrect spacer, and ensure the proper spacing to meet
the applicable safety standards.
The spacers form an air gap 130 that spaces the side walls
38, 40 from the surrounding cabinet structure. The spacers are the only contact
points between the side walls 38, 40, which minimizes the conduction of heat directly
from the side walls 38, 40 to the cabinet 12 because the side walls 38, 40 do not
contact the cabinet 12. With the side walls 38, 40 spaced from the cabinet 12, convection
is the primary mode of heat transfer from the housing 20 to the cabinet 12, which
is less efficient at transferring heat than conduction. The cabinet 12 also has
more time to dissipate heat into the surrounding environment, which keeps the cabinet
temperature within applicable safety limits. The spacers 58, 60 are selected such
that the air 130 is sized to permit the warming drawer to meet the current safety
standards, without the need to wrap the housing in insulation, even when the drawer
is operated at the higher slow cooking temperatures of around 250°F.
A pair of drawer guides 66, 68 is attached to the side
walls 38, 40, respectively, opposite the spacer strips 58, 60.
Referring again to Figure 3, the drawer 22 comprises a
generally well known box-like structure having a front wall 70, a back wall 72,
a pair of sidewalls 74, 76, and a bottom wall 78 forming a generally rectilinear
configuration. The walls 70-76 define a peripheral wall 96. A pair of drawer slides
80, 82 is attached to the side walls 74, 76, respectively, for cooperative registry
with the drawer guides 60, 68 to enable the drawer 22 to be readily moved between
an open position and a closed position within the housing 20. The drawer 22 defines
a heating chamber 28 in which cooking dishes and the like can be received for heating.
One or more support members 84 can be movably supported
between the side walls 74, 76 for supporting a container 86 having dimensions smaller
than the dimensions of the heating chamber 28.
Referring also to Figure 5, the drawer 22 is finished along
the front wall 70 by an inner face panel 88 joined to an outer face panel 90. The
inner face panel 88 is a generally planar member having a peripheral flange adapted
for contact with the seal 50 around the opening 44. The outer face panel 90 can
be provided with a handle to facilitate the opening and closing of the drawer 22.
Incorporated into and between the inner face panel 88 and the outer face panel 90
is an active closer assembly illustrated in the form of a plurality of closer magnets
94. A pair of closer magnets 94 is attached to the inner face panel 88 along an
upper edge thereof, and a single closer magnet 94 is attached to the inner face
panel 88 along a central portion of a lower edge thereof. The closer magnets 94
are configured for magnetic engagement with a plurality of closer magnets 92 incorporated
into the housing 20. A pair of closer magnets 92 is attached to the interior of
the front wall 42 along an upper edge thereof in opposed disposition with the pair
of upper closer magnets 94, and a single closer magnet 92 is attached to the interior
of the front wall 42 along a central portion of a lower edge thereof in opposed
disposition with the single closer magnet 94. The closer magnets 92, 94 will be
in magnetic registry when the drawer 22 is fully received in the drawer chamber
48. A greater or lesser number of magnets, or a different configuration of magnets,
can be employed based upon such factors as the closure force desired.
The closer magnets 92, 94 can be configured to deliver
approximately 5 to 10 pounds of closing force to the drawer 22, sufficient to maintain
the drawer 22 tightly closed against the open face 46 of the front wall 42. The
tight closure of the drawer 22 causes a complete contact of the seal between the
drawer 22 and the housing 20, which results in an improved retention of heat in
the drawer, and further contributes to the control of temperatures in the drawer.
That is, with a complete seal, there is minimal or no heated air escaping from the
heating chamber and being replaced by ambient or cooler air. Thus, the control system
need not activate the heating element 24 as often to maintain the temperature at
the set temperature. The force is great enough that the drawer will self-close when
it gets within a few inches of the housing. The force is also sufficient to compress
the seal between the drawer and the housing along the entire periphery of the seal,
which enhances the sealing between the drawer and the housing. The force is small
enough that it does not hinder a user from opening and closing the drawer.
Referring now to Figure 6, the heating element 24 is made
from a well known resistance heating element material, such as a Calrod element.
The heating element is formed into a planar heater loop 100, and positioned along
a lower portion of the drawer chamber 48 parallel to the bottom wall 34. The heater
loop 100 is configured to follow generally the periphery of the drawer 22. Thus,
each leg of the heater loop 100 extends parallel to and generally beneath the walls
70-76 of the drawer 22. This results in a more even heat distribution within the
heating chamber 28 by heating the peripheral wall 96 which then radiates heat into
the heating chamber 28, thereby contributing to the reduction of temperature gradients
within the drawer 22. This configuration also reduces the heating of the bottom
wall 78, particularly in the center, which minimizes the occurrence of a hot spot
in the center of the heating chamber 28. The heater loop 100 terminates in a pair
of heater terminals 102, 104 which are electrically connected to the control module
26 in a generally well-known manner. The heater terminals 102, 104 extend through
the side wall 38 into the control module 26.
A portion of the heater terminals 102, 104 comprises a
non-resistive portion 106, 108, thereby minimizing the heating of the non-resistive
portions 106, 108 at their penetration through the side wall 38. A temperature sensor
110 extends from the control module 26 through the side wall 38 into the drawer
chamber 48 intermediate the heater terminals 102, 104. The positioning of the temperature
sensor 110 between the non-resistive portion 106, 108 minimizes direct radiation
from the heating element 24 to the temperature sensor 110, which could cause an
artificially high temperature reading, thus providing a more accurate reading of
the temperature in the heating chamber. The length of the non-resistive portion
can vary depending on the type of heating element and the type of temperature sensor.
However, the non-resistive portion need only extend as far as necessary to permit
the temperature sensor to be unaffected.
It was found that the location of the temperature sensor
toward the bottom of the drawer chamber gave more accurate temperature readings
than at the top of the chamber as in prior art warming drawers. However, this placed
the temperature sensor closer to the heating element, which increased heating element's
impact on the temperature sensor. By making the portions of the heating element
adjacent the temperature sensor non-resistive, it was possible to locate the heating
element in the best position for accuracy while minimizing the influence of the
cycling of the heating element on temperature sensor. The temperature sensor 110
configuration described above provides much greater accuracy than prior warming
Referring now to Figure 7, and again to Figure 3, the control
module 26 comprises a power switch 112 and a temperature control switch 114 operatively
connected to a circuit board 116. The temperature control switch 114 is a rotary-type
switch enabling the selection of temperatures between 100°F and 250°F.
The circuit board 116 is configured for operable control of the heating element
24 and the temperature sensor 110. As illustrated in Figure 8, the control module
26 has a face plate 120 with an embossed or printed temperature scale 122. The face
plate 120 can be attached to the control module flange 52, or the temperature scale
122 can be printed or embossed directly onto the control module flange 52. The temperature
control switch 114 comprises a control knob 124 operably disposed with respect to
the temperature scale 122 for selecting an operating mode and temperature for the
heating chamber 28. These modes and approximate temperatures include:
The temperature control switch 114 can comprise multiple stops over the food warming
range to provide a plurality of selectable temperatures between 140°F and 210°F
in order to enable a more precise warming temperature for foods of different types
- Bread proofing/raising -- 100°F
- Food warming, low -- 140°F
- Food warming, medium -- 175°F
- Food warming, high -- 210°F
- Slow cooking, low -- 220°F for 8 hours
- Slow cooking, high -- 250°F for 4 hours.
The warming drawer as disclosed herein is able to maintain
a very even temperature distribution without the aid of a convection fan. Most prior
art warming drawers having even temperature distribution rely on a convection fan
to circulate the air within the cooking chamber to achieve the even temperature
distribution. The ability to eliminate the convection fan while still maintaining
even heat distribution for cooking performance provides the warming drawer with
a substantial cost advantage.
The following Table 1 illustrates the control of temperature
achieved with the warming drawer 10 during a controlled laboratory test. The nominal
temperature is a selected temperature to which the interior of the drawer was heated.
Nine temperature sensors were installed in the drawer at the center (i.e. mid-height)
left rear, center center rear, center right rear, center left center, center center
center, center right center, center left front, center center front, and center
right front of the drawer. The target temperature variation among the sensors is
±10°F. As the tabular data illustrates, the maximum variation in temperature
was not greater than ±10°F between any 2 sensors.
TABLE 1: TEMPERATURE DISTRIBUTION IN WARMING DRAWER
Nominal Temperature, °F
Range of Temperatures Within Drawer, °F
Maximum Variation in Temperature, &Dgr;°F
Variation from Mean Temperature, °F
The following Table 2 illustrates the effectiveness of
the drawer configuration in maintaining the temperature of the adjoining cabinetry
below Underwriters Laboratories criteria during a controlled laboratory test. The
Drawer Center temperature represents a selected temperature to which the interior
of the drawer was heated.
The Side Rail data in the next three columns represents
the temperature of the side walls 38, 40 corresponding to the indicated Drawer Center
temperature. The Cabinet data in the final three columns represent temperature data
corresponding to the indicated Drawer Center temperature for the walls of a wood
cabinet enclosing the drawer 10 in a conventional installation such as might be
found in a household kitchen. The UL criteria relates to the temperature rise above
ambient temperature, and limits the rise to no more than 117°F, or 65°C.
TABLE 2: TEMPERATURE RISE IN ADJOINING CABINET WALLS, °F
Drawer Left Side Rail-Bottom
Drawer Left Side Rail-Top
Drawer Right Side Rail
Cabinet Left Side
Cabinet Right Side
As the data indicates, the temperature rise in the cabinet
walls is well below the UL-standard of no more than a 117°F rise above ambient
temperature. For example, during the test, at a Drawer Center temperature of 265.9°F,
the Ambient Temperature was 93.7°F and the Left Side Cabinet temperature was
138.3°F. Thus, the rise in temperature was 138.3°F - 93.7°F = 44.6°F,
which is well below the 117°F UL specification.
The warming drawer described herein provides a range of
heating modes, such as bread proofing, low, medium and high food warming, low temperature
slow cooking, and high temperature slow cooking. The heating element configuration
relative to the peripheral wall of the drawer provides a more even, more easily
controlled temperature in the drawer, without hot spots. The positioning of the
temperature sensor between non-heat generating heater terminal portions provides
greater accuracy in temperature sensing, thereby contributing to enhanced temperature
control in the drawer. An active magnetic closer assembly ensures that the drawer
is closed and remains closed during warming and cooking operations. The integrated
spacers ensure that the side walls of the warming drawer are sufficiently spaced
from adjoining cabinetry, and minimize the heat that is conducted from the warming
drawer to the cabinetry.
The integrated spacers have been described and illustrated
for the side walls of the drawer. However, in an alternate embodiment, an integrated
spacer can also be used to space the back wall of the drawer from an adjoining cabinet
wall, or to space any other drawer surface that may otherwise conduct heat to an
adjoining cabinetry surface.
While the invention has been specifically described in
connection with certain specific embodiments thereof, it is to be understood that
this is by way of illustration and variation and modification are possible within
the scope of the invention as defined in the appended claims.
control module flange
inner face panel
outer face panel
temperature control switch