U.S. patent application number 11/203291 was filed with the patent office on 2005-12-08 for deep fryer.
Invention is credited to Chung Lau, Joseph Wing, Lai, Wallace.
Application Number | 20050269309 11/203291 |
Document ID | / |
Family ID | 34912352 |
Filed Date | 2005-12-08 |
United States Patent
Application |
20050269309 |
Kind Code |
A1 |
Chung Lau, Joseph Wing ; et
al. |
December 8, 2005 |
Deep fryer
Abstract
A deep fryer has an outer housing (4) closed by a lid (14) and
an immersed type heating element (28) extending into an oil
containing receptacle (22), the housing having an upper rim at
which the lid (14) is supported, with the underside of the lid (14)
having an upwardly domed shape and the rim formed with a channel
(44) arranged beneath the periphery of the underside of lid (14) to
receive droplets of moisture condensing on the underside of the lid
during use, a sensor (31) being provided which includes a thermal
use and temperature sensing element (56) disposed in a single
tubular housing.
Inventors: |
Chung Lau, Joseph Wing;
(Pokfulam, HK) ; Lai, Wallace; (Kowloon,
HK) |
Correspondence
Address: |
Edward G. Greive
Renner, Kenner, Greive, Bobak, Taylor & Weber
Fourth Floor
First National Tower
Akron
OH
44308-1456
US
|
Family ID: |
34912352 |
Appl. No.: |
11/203291 |
Filed: |
August 15, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11203291 |
Aug 15, 2005 |
|
|
|
10794814 |
Mar 8, 2004 |
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Current U.S.
Class: |
219/441 |
Current CPC
Class: |
A47J 37/1261 20130101;
A47J 36/38 20130101; A47J 37/129 20130101; A47J 37/1266
20130101 |
Class at
Publication: |
219/441 |
International
Class: |
H05B 001/02; A47J
037/12 |
Claims
1. A sensor for use in an electrical cooking appliance of the type
having an immersed heating element, comprising a temperature
sensing element and a thermal fuse disposed within a single outer
heat conductive tubular housing.
2. A sensor according to claim 1 wherein the tubular housing is
closed at its end by a plug of thermally conductive material.
3. A sensor according to claim 2 wherein the temperature sensing
element is disposed within or adjacent said plug.
4. A sensor according to claim 3 wherein the plug is formed with an
internal cavity with the sensing element located therein.
5. A sensor according to claim 1 wherein the temperature sensing
element is a thermistor.
6. A deep fryer having an immersion type heating element for
immersion into a receptacle for containing a cooking medium,
wherein a sensor according to claim 1 is supported adjacent to the
heating element.
7. A deep fryer according to claim 6 comprising a control unit to
which the sensor and heating element are connected and including a
solenoid-activated relay switch connected to the heating element,
the thermal fuse being connected to the solenoid side of said relay
switch.
8. A deep fryer according to claim 7 wherein the control unit has a
pair of relay switches, the thermal fuse being connected to the
solenoid side of both relay switches.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional application of U.S. patent
application Ser. No. 10/794,814 filed Mar. 8, 2004.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a fryer for culinary use of
the type having a deep receptacle for containing a cooking medium
such as oil into which the food is immersed, such fryers being
commonly referred to as "deep fryers" or "deep fat fryers".
[0003] Deep fryers have been used for frying of food in commercial
establishments for very many years. It is only more recently that
deep fryers of a smaller dimension have become popular for use in
the home. Such deep fryers generally have an outer housing which
may be plastic or metal which supports an inner oil containing
receptacle formed of metal or other heat resilient material such as
ceramic or tempered glass. A heating element is arranged either
immediately below the receptacle in a so-called "non-immersion"
type, or extends into the receptacle either through an opening in
the receptacle wall or is shaped to extend over the top of the wall
down towards the bottom of the receptacle in an "immersion" type.
In the latter type the oil is heated directly, which has the
advantages that the thermal performance is generally better than
the non-immersion type with pre-heat time is reduced, response time
to regain proper cooking temperature on immersion of food reduced,
and the power rating can generally be smaller for equal cooking
effect.
[0004] For fryers to be used in the home, it is highly desirable to
provide the fryer with a lid, both for safety reasons preventing
accidental access to or the spitting out of hot oil, and to contain
or at least partly contain the vapours produced during cooking to
limit their spread through the home. A problem however with
providing a lid is that this traps moisture which has been released
from the food being cooked, the moisture tending to condense on the
lid and dripping back into the receptacle of hot oil where it
adversely affects the cooking process. The present invention seeks
to overcome this problem.
SUMMARY OF THE INVENTION
[0005] In a first aspect the invention provides a deep fryer
comprising an outer housing closed by a lid, the housing having an
upper rim at which the lid is supported, wherein the underside of
the lid has an upwardly domed shape and the rim is formed with a
channel arranged beneath the periphery of the underside of lid to
receive droplets of moisture condensing on the underside of the lid
during use.
[0006] This arrangement ensures that the condensing moisture is
largely prevented from dripping into the hot oil, thereby greatly
reducing undesirable and potentially hazardous spitting of oil, and
reducing the deleterious effect on quality of cooking.
[0007] A wide variety of domed shapes can be used for the underside
of the lid from a relatively shallow dome to a steeper dome.
Preferably, the shape is smoothly curving, being free of any
discontinuities in shape which might encourage the collection of
droplets of moisture.
[0008] In the preferred embodiment the upper rim of the housing is
formed with a lip disposed inwardly of said channel on which, in
use, a receptacle for a cooking medium is seated. The rim is formed
at its uppermost and outermost region with a ledge on which the lid
sits. The channel may extend around substantially the entire upper
rim, and gently slopes around the rim, with one or more drainage
openings formed in the rim, and the rim sloping towards the or each
drainage opening. A moisture containing receptacle is arranged on
the housing beneath the or each drainage opening.
[0009] Such deep fryers are also generally provided with some means
of monitoring the oil temperature, either simply to give an
indication of temperature to the user, or being connected to a
control unit which controls the heating by the heating element.
Conventionally, such fryers use a temperature sensor and safety
limitor which consists of an oil filled sensor bulb located
adjacent the heating element connected to a detection circuit in
the control unit by means of a fine capillary tube. The expansion
or contraction of oil in the sensor bulb and capillary is detected
in the electronic circuit in the control unit, serving to cut the
electrical supply to the heating element in an overheat condition,
and otherwise providing a temperature indication. Such capillary
type sensors have several drawbacks. The fine capillary tube is
fragile, and it can be difficult to see if it becomes broken. In
the event that it does break, this causes a complete failure of the
control. The mineral oil used in the sensor is also not safe for
human consumption.
[0010] In a further aspect the present invention is directed to
providing an improved type of sensor.
[0011] According to a further aspect the invention provides a
sensor for use in an electrical cooking appliance of the type
having an immersed heating element, comprising a temperature
sensing element and a thermal fuse disposed within a single outer
heat conductive tubular housing.
[0012] Such a structure is significantly more robust than the
conventional capillary-type arrangement, is far easier to install
and is easier for the user to clean.
[0013] The tubular housing is preferably closed at its end by a
plug of thermally conductive material, with the temperature sensing
element is disposed within or adjacent said plug. The plug is
formed with an internal cavity with the sensing element located
therein.
[0014] Preferably, the temperature sensing element is a thermistor.
Use of such an element within the described sensor structure is
able to produce a sensor of considerably more accurate nature than
the conventional capillary arrangement, and which has a greater
sensitivity to temperature variations.
[0015] The invention also resides in a deep fryer having an
immersion type heating element for immersion into a receptacle for
containing a cooking medium, wherein a sensor as defined above is
supported adjacent the heating element. The deep fryer may also
have a control unit to which the sensor and heating element are
connected and including a solenoid-activated relay switch connected
to the heating element, the thermal fuse being connected to the
solenoid side of said relay switch. It may also be arranged that
the control unit has a pair of relay switches, the thermal fuse
being connected to the solenoid side of both relay switches, this
arrangement providing a degree of redundancy in case of failure of
either relay switch.
[0016] In a still further aspect the invention resides in a deep
fryer having an inner cooking receptacle which sits within an outer
housing, and a heating unit comprising a heating element and a
control unit, the heating unit being supported on the housing, a
portion of the heating unit resting on an upper peripheral rim of
the receptacle, and whereby the heating unit is supported in a
lower position in the absence of the receptacle, the control unit
including cut-out switch means arranged to disable the control unit
in the lower position.
[0017] The housing may be provided with a support for the heating
unit which support has an opening which is aligned with an
actuating portion of the cut-out switch in the lower position.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] An embodiment of the present invention is now described, by
way of example only, with reference to the following drawings in
which:
[0019] FIG. 1 is an external view of a deep fryer in accordance
with a first aspect of the invention;
[0020] FIG. 2 shows the front of the deep fryer of FIG. 1;
[0021] FIG. 3 is a cross-sectional view taken along the line A-A in
FIG. 2;
[0022] FIG. 4 is a disassembled view of the deep fryer;
[0023] FIG. 5 shows a receptacle with immersed heating element and
control sensor according the prior art;
[0024] FIG. 6 shows a receptacle with immersed heating element and
control sensor according to a further aspect of the invention;
[0025] FIG. 7 is a part-schematic circuit diagram of the electrical
components of the fryer;
[0026] FIG. 8 is a longitudinal part-sectional view through the
control sensor; and
[0027] FIG. 9 is a part cut-away view of an outer housing, with
enlarged insets showing water-directing channels in section;
[0028] FIG. 10 is a rear view of the housing;
[0029] FIG. 11 shows the heating unit correctly fitted into a
coating receptacle; and
[0030] FIG. 12 shows the heating unit erroneously fitted directly
into the receptacle, to illustrate a safety cut-out switch.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0031] Turning to the drawings, a deep fryer according to an
embodiment of the invention is illustrated in FIG. 1 being
generally indicated by numeral 2. As best seen in FIGS. 1 and 4 the
deep fryer 2 comprises an outer housing 4 having four sidewalls 5,
6, 7, 8 respectively and a base 10. The housing may be formed of a
variety of different materials most preferably of a plastics
material or metal for ease of construction. The housing has an
upper rim 12. A lid 14 closes the housing, sitting on the rim 12.
The lid 14 is formed with a vent region 18 to allow the limited
egress of steam and other cooking vapours. A handle 20 is provided
to facilitate opening and closing of the lid. Further
constructional details of the lid will be described below.
[0032] A receptacle 22 is provided which in use receives the
cooking oil, this being in the form of a simple bowl of similar
shape to the housing 4. An upper outwardly turned rim 24 simply
rests on a portion of the upper housing rim 12 and can be lifted
off and removed for cleaning purposes. The receptacle 22 may be
formed of a metal such as stainless steel, or other heat resistant
materials such as a ceramic material or a tempered glass, as is
well-known in the art. If tempered glass is used the housing 4 may
also be formed of a translucent or transparent plastics so that it
is then possible to observe the cooking of the food. In this case
it is also desirable from a safety point of view if the receptacle
22 includes a visual indication to the user that the receptacle
should not be placed directly on gas flame or electric element of a
stove top, by way of a prominent warning notice. Although the
tempered glass can be highly heat resistant, depending on the exact
specifications such a glass receptacle may not be suited to use on
a stove top.
[0033] A heating unit 26 is provided comprising a conventional
resistance type heating element 28 connected to a control unit 30,
shaped so that the control unit 30 is in use installed on the
exterior of the housing 4 with the heating element 28 extending
over the rim 24 of the receptacle 22 down into and along the bottom
of the receptacle 22. As is conventional, the heating element 28
may have a serpentine-like portion at the lower region to maximise
the area providing the heating effect at the bottom of the
receptacle 22. Also disposed on the heating element 28 is a sensor
element 31, further details of which are discussed below. The
control unit 30 with heating element 28 and sensor 31 can be
detached from the housing to allow removal of the receptacle for
cleaning purposes.
[0034] A food-holding basket 32 is provided, which in use sits just
over the heating element 28. This is preferably of mesh-like
construction. A handle 34 is joined to the basket through long and
relatively thin members 35 which serve minimise heat transfer
between the oil and the handle 34. As can be seen in FIG. 3, the
underside and rear of the basket 32 is formed with a wire member 36
on which the main part of basket 32 rests on the heating element
28, and so that the food remains spaced from the heating
element.
[0035] Returning to the details of the lid 14, this has at least an
underside of a downwardly concave upwardly domed form, ideally
having a relatively shallow and smooth profile free of any
discontinuities or protuberances. As best seen in FIG. 9 the upper
rim 12 of the housing is specifically constructed so as to define
an upper ledge 38 which supports the outermost periphery of the lid
14. A vertical wall 40 extends down from this upper ledge to an
inwardly directed portion 41 and a short upwardly directed flange
42 defining a channel 44 therebetween. The upper rim 24 of the
receptacle 22 rests on the flange 42.
[0036] During cooking, moisture in the food turns to steam, some of
which escapes through the vent holes 18, a major part of which will
inevitably condense as droplets on the underside of the lid. The
smoothly domed surface results in controlled run-off of the
droplets to the periphery of the lid where the droplets will drip
off the lid into the channel 44 or run down the wall 40 into
channel 44. It is also arranged that the channel 44 is inclined
around the rim 12 to have its lowest point on the rear of the
housing, opposite to the control unit 30. The highest point may be
adjacent the control unit 30 (ie at the left hand side of FIG. 3 or
right-hand side of FIG. 9) in which case two identical ramps are
provided around opposite sides of the rim, or might alternatively
be immediately adjacent the lowermost part with a step
therebetween, so that there is a single path for water flow around
the rim. At the lowest point of the channel 44 a drip catcher 46 in
the form of a removable enclosure is provided. This has an opening
adjacent a ramp portion 49 which fits beneath an opening in the
channel 44. This arrangement ensures that a major part of the
moisture condensing on the lid is prevented from dripping back into
the hot cooking oil, but is instead collected from where it can be
disposed of after use of the deep fryer.
[0037] Further details of the sensor and control of the deep fryer
are now discussed. A conventional sensor is illustrated in FIG. 5,
which as discussed below has one or more oil-filled bulbs 100 one
of which constitutes an overheat sensor connected to a control
circuit via capillaries 102. The control circuit has components
which respond to the oil level within the capillary and output a
signal dependent thereon, and hence dependent on temperature.
[0038] In contrast, the present invention utilises a quite
different arrangement. As shown in FIG. 8 the sensor 31
incorporates several sensing components into a single sensor
housing. More specifically a tube-like housing 52 is provided
extending from the control unit 30 between opposite ends of the
heating element 28 down into the receptacle 22 and lying between
adjacent bends of a portion of the element 28. Within the housing
52 are disposed a thermal fuse 54 and an electronic temperature
sensing element 56. The thermal fuse 54 can be of a variety of
types, the basic condition being that an element is provided which
becomes non-conducting when a predetermined temperature indicative
of an overheat condition is reached. For example, the element may
be a fuse of the type sold under the brand name SEFUSE of
NEC/SCHOTT, SF Type, containing a pellet which melts at a
predetermined temperature breaking an internal electrical contact.
The temperature sensing element 56 can likewise take a variety of
forms such as a thermistor, the requirement being that a change in
temperature produces a change in resistance. An example of a
particularly appropriate component is the thermistor of Sentech
Model DT104-3977-3P.
[0039] The thermal fuse 54 is arranged within an electrically
insulating sleeve 55 which is open to allow heat exchange with the
rest of the sensor. Lead wires 57 are connected to opposite ends of
the thermal fuse, the lead wire extending from the open end of the
sleeve 55 having an outer thermally insulating sleeve 58.
[0040] The temperature sensing element 56 is arranged near the
detecting end of the sensor, being enclosed in an internal cavity
within a plug 60 of thermally conductive material which closes the
end of the tube 52. It will be seen that the plug 60 is provided
with a pair of deep grooves 62 which receive sealing o-rings 64.
Towards the outer end, additional grooves 66 are formed which are
filled with a synthetic sealing compound at 68. The temperature
sensing element 56 is joined to lead wires 70 through a pair of
connectors 72 and insulation sleeves 74, all embedded in the cavity
within the plug 60 in a volume of sealing compound which fills the
plug cavity.
[0041] FIG. 7 shows the control circuit, the major part of which is
arranged within the control unit 30. The deep fryer is intended to
powered by a conventional mains ac supply typically 240V or 110V.
The supply is led across the heating element 28 through a pair of
solenoid controlled relays 80, 82 which are controlled by the
thermal fuse 54. A conventional voltage regulator 84 provides low
voltage outputs utilised in the thermal fuse 54 and relay control
circuits. If the thermal fuse 54 cuts out in response to an
overheat condition the solenoids of both relays 80 and 82 remain
open so that no current flows through the heating element. The use
of a pair of relays provides redundancy in case of failure of one
relay, or total failure of a controlling microcontroller 83. It
will be appreciated that whilst the circuit shows solenoid relays,
a wide variety of alternative electronic components can be readily
substituted, as the skilled person will well understand, for
example TRIAC type switches could be employed.
[0042] The microcontroller 83 is programmed to effect the various
control functions, receiving an input directly from the temperature
sensing element 56 and driving an LED or LCD display 84 which shows
actual detected temperature as well as displaying other information
about the deep fryer, for example time and programming information.
A keypad 86 allows the user to input various information such as
desired cooking times and temperatures and other operational
functions. A low voltage dc battery 88 may be provided as an
optional or back-up battery for the microcontroller 83. As will be
appreciated, the microcontroller 83 can be programmed to output a
signal to open one or both relays on a predetermined temperature
being sensed, thereby switching off the heating element. With
appropriate programming, the microcontroller can employ techniques
such as "fuzzy logic" to anticipate a desired heating control to
effect a desired temperature or cooking profile.
[0043] FIGS. 10, 11 and 12 show an additional safety feature. In
the case of a deep fryer having both a housing 4 and receptacle 22
of transparent or translucent material, there is a tiny risk that
users might become momentarily confused between the two, and try to
cook in the housing 4 installing the heating unit 26 directly into
the housing 4. Such a situation is illustrated in FIG. 12. As can
be seen in FIG. 10, the rear of the housing 4 is provided with a
support plate 106 onto which the heating unit 26 is fitted, with
locating ribs on the control unit (not shown) fitting into the
vertical slots 108, 110. The control unit 30 is provided with a
cut-out switch 112 having a spring actuating pin 114 protruding
therefrom towards the plate 106 adjacent the slot 108. Assuming the
deep fryer is correctly assembled, with the receptacle 22 fitted,
an upper portion of the heating element 28 sits on the upper rim of
the receptacle 22. In this position the pin 114 of the cut-out
switch 112 faces a lug 116 on the plate 106, which prevents its
outward travel. This represents an on position, with the control
unit 30 activated. In the event that the receptacle 22 is missing,
the heating unit 26 can slide to a lower position, with the upper
portion of the heating element instead resting on an upper rim 42
of the housing. In this position the actuating pin 114 springs
outwardly into an opening 118 below the lug 116, separating an
internal contact pair (not shown) within the control unit and
thereby deactivating this, preventing the fryer from being switched
on.
* * * * *