U.S. patent application number 16/692613 was filed with the patent office on 2020-06-18 for method of cooking a food item.
The applicant listed for this patent is Easygrill Pty Ltd. Invention is credited to David AYRE, Toby HARTLEY, George KOTSIOPOULOS, Callum MACLEOD, John PETSCHEL.
Application Number | 20200187709 16/692613 |
Document ID | / |
Family ID | 54697718 |
Filed Date | 2020-06-18 |
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United States Patent
Application |
20200187709 |
Kind Code |
A1 |
AYRE; David ; et
al. |
June 18, 2020 |
Method of Cooking a Food Item
Abstract
A cooking apparatus has a user interface for selecting a cooking
preference, a measurement sensor for measuring a distance between a
pair of plates when a food item lies between the pair of plates, a
weight sensor for measuring weight of the food item, and a control
system for receiving at least one signal from the measurement and
weight sensors to determine a cooking profile for cooking the food
item to the cooking preference and to calculate a total amount of
energy required to cook the food item according to the cooking
profile and an amount of energy to be transferred per unit time to
the food item, and to control power supply to the heating element
based on the calculated amount of energy transferred per unit time
to the food item.
Inventors: |
AYRE; David; (Toorak,
AU) ; MACLEOD; Callum; (Ferntree Gully, AU) ;
KOTSIOPOULOS; George; (Ferntree Gully, AU) ; HARTLEY;
Toby; (Ferntree Gully, AU) ; PETSCHEL; John;
(Ferntree Gully, AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Easygrill Pty Ltd |
Abbotsford |
|
AU |
|
|
Family ID: |
54697718 |
Appl. No.: |
16/692613 |
Filed: |
November 22, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15314349 |
Nov 28, 2016 |
10517426 |
|
|
PCT/AU2015/000325 |
May 29, 2015 |
|
|
|
16692613 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A47J 33/00 20130101;
A47J 37/0611 20130101; A47J 2037/0617 20130101 |
International
Class: |
A47J 37/06 20060101
A47J037/06; A47J 33/00 20060101 A47J033/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 30, 2014 |
AU |
2014902073 |
Claims
1. A method of cooking a food item using an apparatus comprising a
pair of plates in between which a food item is to be cooked and at
least one of the plates having a heating element for cooking a food
item including the steps of: selecting a cooking preference;
measuring a distance between the pair of plates when the food item
lies there between to determine a thickness of the food item;
measuring a weight of the food item; determining a cooking profile
for cooking the food item according to the cooking preference based
on at least one of the thickness of the food item and the weight of
the food item; calculating a total amount of energy required to
cook the food item according to the cooking profile based on the
weight of the food item; calculating an amount of energy
transferred per unit time to the food item based on the thickness
of the food item; and controlling power supply to the heating
element based on the amount of energy transferred per unit time to
the food item to cook the food item.
2. The method for cooking a food item according to claim 1
including comparing the amount of energy transferred to the food
item to the total amount of energy required to cook the food item
during the cooking process.
Description
[0001] This application is a Divisional Application of co-pending
U.S. application Ser. No. 15/314,349 filed on Nov. 28, 2016, which
is a U.S. nationalization under 35 U.S.C. .sctn. 371 of
International Application No. PCT/AU2015/000325, filed May 29,
2015, which claims priority to Australian Application No.
2014902073, filed May 30, 2014; the entire contents of each are
incorporated herein by reference.
[0002] The present invention relates to an apparatus for cooking
food, and in particular for cooking food between a pair of
plates.
BACKGROUND
[0003] Food presses, such as sandwich presses or hamburger presses,
use a pair of plates, whereby the sandwich, for example, is placed
between a pair of heated plates to warm the bread and its filling.
However, sandwich presses rely on a user to insert the sandwich and
monitor the time spent warming the sandwich before removing it. As
often happens, the user can become distracted and forget to remove
the cooked sandwich, which then burns. It is known to provide
timing devices on sandwich presses to alert the user that the food
item is cooked but these are not always accurate to properly cook
the food item, and require setting by the user.
[0004] On the other hand, food presses can also inconsistently cook
food items, leading to undercooking. Taking for example sandwiches,
thick sandwiches in particular are prone to undercooking, where the
heat from the plates to the center of the sandwich takes a longer
time to transfer than anticipated. To address this problem, the
sandwich has to be squashed between the plates to improve heat
transfer from the plates to the sandwich. This is undesirable as it
inevitably crushes the sandwich, spilling its filling, and can
generally affect the palatability of the sandwich.
[0005] Furthermore, inconsistent cooking may also cause food
poisoning particularly if the sandwich is not freshly prepared and
insufficient heat has been applied to kill any bacteria.
[0006] It is desirable to provide a cooking apparatus that can
accurately and consistently heat or cook a variety of food
items.
SUMMARY
[0007] In accordance with the invention, there is provided a
cooking apparatus comprising a pair of plates in between which a
food item is to be cooked, at least one of the plates having a
heating element for cooking the food item, the cooking apparatus
having a user interface for selecting a cooking preference, a
measurement sensor for measuring a distance between the pair of
plates when the food item lies between the pair of plates, a weight
sensor for measuring weight of the food item, and a control system
for receiving at least one signal from the measurement and weight
sensors to determine a cooking profile for cooking the food item to
the cooking preference and to calculate a total amount of energy
required to cook the food item according to the cooking profile and
an amount of energy to be transferred per unit time to the food
item, and to control power supply to the heating element based on
the calculated amount of energy transferred per unit time to the
food item.
[0008] The cooking apparatus calculates and applies an amount and
rate of energy input to cook the food item according to the cooking
profile, which is a temperature cooking profile, based on the
thickness and/or weight of the food item. The cooking profile
specifies how the total amount of energy required to cook the food
item is transferred to the food item during cooking.
[0009] Suitably, whilst cooking, the control system monitors and
continuously adjusts the temperature to achieve the desired cooking
outcome.
[0010] The cooking preference may be based on one or more variables
including type of food item and the user's preferred cooking
outcome for the food item. For example, a user can use the user
interface to identify the type of food item, for example, a piece
of steak or chicken, and the desired cooking outcome, for example,
rare or well done.
[0011] The type of food item for which the control system may be
programmed to include in a cooking preference includes, but is not
limited to, fish, red meat, poultry, pork, vegetables and bread, or
combinations thereof such as a sandwich. The preferred cooking
outcome includes but is not limited to `well done`, `medium`,
`rare` and `warm`, or a standard selection for food items including
sandwiches such as `done`.
[0012] Based on the cooking preference, the cooking profile used to
cook the food item is determined by the control system. The cooking
profile in turn determines the cooking temperature or range of
cooking temperatures to cook the food item to the cooking
preference.
[0013] Suitably, the control system compares the amount of energy
transferred to the food item to the total amount of energy required
to cook the food item during the cooking process.
[0014] The comparison between the rate of energy transferred to the
food item and the total amount of required energy to cook the food
item may be carried out continuously or at discrete intervals. For
example, the comparison may be conducted at 2, 5, 10, 15, 20 or 30
second intervals, or any time in between. Alternatively, the
comparison may be conducted a set number of times before the
projected completion time, for example, once or twice in the
cooking process. Still alternatively, the comparison may be
continuous throughout the cooking process.
[0015] Preferably, the rate of energy transferred to the food item
is calculated per second of time.
[0016] In an embodiment, the control system predicts when the food
item is cooked by monitoring the amount of energy transferred to
the food item. The food item is predicted as cooked when the amount
of energy transferred to the food item substantially equals the
total amount of energy required to cook the food item.
[0017] In an embodiment, the cooking apparatus stops transferring
energy into the food item once the energy transferred to the food
item is substantially equal to the total amount of energy required
to cook the food item. In this respect, the control system stops
supplying power to the heating element once the energy transferred
to the food item equals the amount of energy required to cook the
food item.
[0018] In an embodiment, the control system reduces the power
supply to the heating element to maintain the plates at a
predetermined temperature after cooking completes.
[0019] Generally, the controller uses a closed loop transfer
function (also known as a feed forward system) to regulate the
cooking temperature to ensure that the food item is cooked
according to the selected cooking preference. In this respect, the
controller identifies a specific cooking outcome for a selected
food item and regulates the cooking temperature to achieve the
outcome.
[0020] In contrast, most conventional cooking apparatuses use a
feedback system whereby temperature is set and the apparatus simply
attempts to maintain that desired setting, for example, a sandwich
press. The user then decides when the food item is cooked to their
satisfaction. There is no closed loop system generating a specified
cooking outcome for a selected food item.
[0021] The control system preferably calculates the total energy
required to cook the food item according to the cooking profile
based on the weight of the food item. More preferably, the control
system calculates the energy required to cook the food item
according to the cooking profile based on the weight of the food
item and temperature difference between the selected cooking
temperature to achieve the preferred cooking outcome and the
initial food item temperature.
[0022] The control system preferably calculates the total energy
required to cook the food item according to the cooking profile
based on the weight of the food item, the specific heat capacity of
the food item, the required cooking temperature to achieve the
preferred cooking outcome and the initial food item
temperature.
[0023] The total energy required to cook the food item according to
the cooking profile may be calculated using the following equation,
wherein Q is the total energy required to cook the food item
according to the cooking profile, C.sub.p is the specific heat
capacity of the food item, M is the weight of the food item,
T.sub.2 is the required (target) temperature to achieve the
selected cooking preference and T.sub.1 is the initial food item
temperature:
Q=Mc.sub.p(T.sub.2-T.sub.1)
[0024] T.sub.2 is preferably measured in the core of the food
item.
[0025] The cooking temperature is the temperature required to
achieve the target temperature of the food item. The cooking
temperature may not be the same as the target temperature. For
example, the cooking temperature may be initially set higher than
the target temperature in order to sear the food item, the cooking
temperature may subsequently be lowered to ensure that the food
item does not overcook after searing.
[0026] The control system preferably calculates the amount of
energy transferred to the food item per unit time during the
cooking process based on the thickness and/or weight of the food
item. The control system can also calculate the amount of energy
transferred into the food item during the cooking process based on
the change in temperature of each of the plates. For example, the
amount of energy may be calculated based on the surface area of the
food item in contact with the pair of plates and the change in
temperature of each of the plates of the cooking apparatus.
[0027] The energy (q) transferred to the food item per unit time
may be calculated using the following equation:
q=.DELTA.T.sub.1R.sub.th+.DELTA.T.sub.2R.sub.th, where
.DELTA.T.sub.1/2=T.sub.plate1/2-T.sub.food item temp
[0028] .DELTA.T.sub.1 is the temperature difference between a first
plate (T.sub.plate 1) and the food item temperature (T.sub.food
item temp) per unit time and .DELTA.T.sub.2 is the temperature
difference between a second plate (T.sub.plate 2) and the food item
temperature (T.sub.food item temp) per unit time.
[0029] Suitably, the first plate is a top plate of the cooking
apparatus and the second plate is a bottom plate of the cooking
apparatus.
[0030] In an embodiment, the thermal resistance of the food item
may be calculated based on the surface area of the food item in
contact with the pair of plates, the thickness of the food item and
the thermal conductivity of the food item.
[0031] The thermal resistance (Rh) of the food item may be
calculated using the following equation, wherein A is the
calculated surface area, (x) is the measured thickness and (k) is
the thermal conductivity of the food item:
R th = k A x ##EQU00001##
[0032] In an embodiment, the surface area (A) of the food item in
contact with the plates is calculated based on the thickness,
weight and density of the food item.
[0033] The surface area (A) of the food item in contact with the
plates may be calculated using the following equation, wherein (x)
is the measured thickness, (M) is the weight and (.rho.) is the
density of the food item:
A = M x .rho. ##EQU00002##
[0034] In another embodiment, the surface area of the food item in
contact with the plates is estimated using sensors. Preferably, the
sensors are temperature sensors. Other sensors such as pressure
sensors may be used.
[0035] A temperature gradient exists between the surface and the
core of the food item. The surface temperature of the food item
will be close to the surface temperature of the plate in contact
with the food item and the temperature of the rest of the food item
will be a function of the distance from the plate, the heat
capacity of the food item and the temperature differential between
the plate and the food item.
[0036] The calculated net food item temperature is cumulative,
adding the incremental temperature gain to the previous temperature
value.
[0037] On this basis, the amount of energy transferred into the
food item during the cooking process may be calculated and measured
against the total amount of energy required to cook the food item
accordingly to the cooking profile. The cooking process completes
when the amount of energy transferred to the food item equals the
total amount of energy required to cook the food item.
[0038] The cooking profile may maintain the food item at a
predetermined temperature after cooking. This may prevent the
cooked food item from getting cold before it is consumed. This may
avoid the need for a resting period after the food is cooked to
allow the cooked food item to reach its target temperature.
[0039] Suitably, the predetermined temperature is the target
temperature. This may allow the cooked food item to be maintained
at the target temperature for a prolonged period of time without
overcooking. In this embodiment, the plates are preferably made
from a high thermal conductivity material to allow the temperature
of the plates to reach the predetermined temperature quickly from
the cooking temperature. In contrast, a low thermal conductive
material increases the risk of the food item overcooking due to an
excessive amount of energy being transferred to the food item when
the plates cool to the selected temperature.
[0040] Suitably, the thermal conductivity of the plates ranges from
30-400 Wm.sup.-1K.sup.-1. Preferably, the thermal conductivity of
the plates ranges from 200-400 Wm.sup.-1K.sup.-1. More preferably,
the thermal conductivity of the plates ranges from 200-300
Wm.sup.-1K.sup.-1.
[0041] The cooking temperature and/or the cooking duration may be
adjusted when the option to maintain the cooked food item at a
predetermined temperature is selected.
[0042] The plates are relatively movable with respect to each other
to lie against the food item therebetween. The plates are
preferably parallel and may be oriented at any angle from a
horizontal to a vertical position. Suitably, the pair of plates are
horizontally arranged to define top and bottom plates in between
which a food item is to be cooked. Both plates suitably include
heating elements, although the apparatus may function with only one
element in one plate. Each plate may include two elements to
provide temperature zoning. This allows separate food items to be
cooked using different cooking profiles at a time.
[0043] In an embodiment, either or both plates may be made of
aluminum. Suitably, either or both the plates further include a
matrix of embedded copper and an outer coating of stainless
steel.
[0044] In an embodiment, either or both plates may have high
thermal inertia to maintain sufficient heat to cook the food
item.
[0045] Each plate may include a thermocouple for measuring the
local temperature and feedback to the control system. The initial
temperature of the food item may be measured by the thermocouple.
The thermocouple may also allow the cooking apparatus to determine
the location of the food item by measuring the temperature drop
when a food item is placed on the plate. The temperature drop
detected by the thermocouple may be used to estimate the surface
area of the food item.
[0046] Suitably, each plate includes four thermocouples to improve
the accuracy of the temperature measurement.
[0047] The pair of plates may be automated to be movable relative
to one another and to maintain contact with the food item during
the cooking process based on feedback from a plate pressure
sensor.
[0048] One or both plates may include a plate pressure sensor to
measure pressure of a plate against a food item during cooking and
to transmit a corresponding signal to the control system to
maintain a predetermined pressure of the plate on the food item
during cooking.
[0049] One of the plates may be automated to disconnect from the
food item after completion of the cooking time.
[0050] The power output of each heating element may range from
50-5,000 W. Suitably, the power output of each heating element
ranges from 1000-1,200 W.
[0051] The user interface may include an LED screen for displaying
the options available for selecting a cooking profile.
[0052] The measurement sensor (also known as a plate separation
sensor) may take many forms for measuring the distance between,
i.e. the separation of, the plates.
[0053] The measurement sensor may be a position/angle/displacement
sensor located at a pivot through which the plates are linked and
rotated to separate. The pivot may be a pivot of a lever
arrangement where specifically the handle is levered to the cooking
apparatus to open and close one plate relative to the other. In
this embodiment, the measurement sensor measures the angle at which
the handle is pivoted when a food item is placed between the pair
of plates. The angle measurement is processed by the control system
to calculate the distance between the pair of plates.
[0054] The measurement sensor may be located at any position on one
or both plates to measure the distance between the pair of plates.
For example, the measurement sensor may be located on an edge of a
plate and transmits a signal to the other plate or another sensor
on the other plate to determine the positions of the pair of plates
relative to each other. Suitably, at least two measurement sensors
are mounted on the front and rear of the cooking apparatus.
[0055] The measurement sensor may be an acoustic or an optical
sensor. For example, an ultrasonic sensor could be used for
measuring distance between the pair of plates. The ultrasonic
sensor transmits a signal from one plate that is reflected off the
other plate and the time taken for the signal to reflect back is
used to measure the distance between the plates.
[0056] The measurement sensor may be an optical/light sensor that
uses a light beam to measure the distance between the pair of
plates. For example, the sensor could be an infra-red sensor or an
optical position sensor. Preferably, the sensor includes a
plurality of light beams that can be sequentially disrupted or
blocked to measure the distance between the pair of plates.
[0057] The measurement sensor may have an accuracy ranging from
1-55 mm. Suitably, the accuracy ranges from 1-3 mm.
[0058] The measurement sensor may be located on one plate and
comprises a sliding pin mounted on one end to a printed circuit
board located within the plate and on the other end to a guide
mounted to a handle of the cooking apparatus. The sliding pin may
be located on a side of the plate and is mechanically connected to
the handle via a slot on the guide to be movable with the relative
separation of the plates. Movement of the handle, which in turn
moves the sliding pin, transmits a signal from the measurement
sensor to the control system which calculates the distance between
the pair of plates.
[0059] The measurement sensor may measure the distance between the
pair of plates directly or indirectly. For example, an indirect
measurement method involves measuring the angle at which a levered
handle of the cooking apparatus is pivoted when a food item lies
between the pair of plates, and the distance between the plates is
calculated using the measured angle. An example of a direct
measurement method involves using an ultrasonic sensor to measure
the distance between the pair of plates by transmitting a signal
from one plate to the other.
[0060] The weight sensor may be in the form of a load cell.
Suitably, the load cell is positioned within or underneath the
plate.
[0061] The weight sensor may have an accuracy ranging from
0.05-15%.
[0062] The user interface may be a control panel on the cooking
apparatus, a smart phone app, a remote control or the like. The
user interface may include an LCD or LED display.
[0063] The control system may be a micro-processor PCB. The PCB may
be mounted on a heat sink. A USB interface may be used for
programming updates and a RJ45 network connection may be used for
communicating with the user interface. In an embodiment, the USB is
used for logging data and a multi-pin connection ribbon is used to
interface with a CPU for programming updates.
[0064] The control system may be programmed with predetermined
settings of specific heat capacity, thermal resistance and thermal
conductivity values, and alternatively or additionally, based on
data received from the user interface.
[0065] The control panel includes an override for manually
controlling the cooking profile regardless of the distance between
the pair of plates or the weight of the food item. For example, the
cooking temperature may be manually entered using the user
interface into the control panel.
[0066] The override may also allow a user to cook a food item
regardless of whether both plates are in contact with the food
item. For example, when the top plate is lifted from the food item
during cooking, the control system allows the cooking process to
continue on the basis that energy is only transferred via the lower
plate. When the top plate re-contacts the food item, the control
system re-adjusts to continue the cooking process on the basis that
energy is transferred via both plates. The cooking apparatus may
include a rack that is actuated to lift the food item off a bottom
plate after completion of the cooking time. Actuation of the plates
and/or the rack after completion of the cooking time is automated
by the control system.
[0067] The control system may switch off the heating element after
completion of the cooking process. Alternatively or additionally,
the control system may transmit an audio and/or visual indication
to alert a user of completion of the cooking process.
[0068] The cooking apparatus may include zoned cooking areas,
whereby each zone comprises a heating element that is localized to
function independently to heat the corresponding zone at an
independent cooking profile to the other zones.
[0069] In accordance with the invention, there is also provided a
control system for a cooking apparatus, the cooking apparatus
comprising a pair of plates, at least one of the plates having a
heating element for cooking a food item, a measurement sensor for
measuring a distance between the pair of plates when the food item
lies between the pair of plates, and a weight sensor for measuring
a weight of the food item, wherein the control system is configured
to: [0070] receive data from a user interface to select a cooking
preference; [0071] receive a signal from the measuring sensor to
calculate the distance between the pair of plates; [0072] receive a
signal from the weight sensor to determine the weight of the food
item; [0073] determine a cooking profile to cook the food item
according to the cooking preference, where the cooking profile is
determined based on at least one signal from the measuring sensor
and the weight sensor; [0074] calculate a total amount of energy
required to cook the food item according to the cooking profile
based on the signal from the weight sensor; [0075] calculate an
amount of energy per unit time to be transferred to the food item
per unit time based on the signal from the measuring sensor; [0076]
switch on the heating element; and [0077] control the heating
element based on the cooking profile.
[0078] The control system may control the heating element to vary
the amount of energy transferred to the food item per unit time.
This, in turn, may be used to control the cooking time.
[0079] The control system may compare the amount of energy required
to cook the food item according to the cooking profile and the
amount of energy transferred to the food item per unit time to
determine the percentage completion of the cooking process.
[0080] The control system may compare the amount of energy
transferred to the food item to the total amount of energy required
to cook the food item at discrete intervals.
[0081] The control system may perform the following steps for
controlling the heating element: [0082] determine a time that has
lapsed since the heating element is switched on; [0083] determine a
temperature of the heating element based on the cooking profile
from the time since the heating element is switched on; [0084]
measure a temperature of the heating element; and [0085] control
the heating element to either increase or decrease in temperature
based on the cooking profile and the current temperature of the
heating element to thereby either increase or decrease the
temperature of the heating element.
[0086] The control system may determine a cooking temperature based
on the cooking profile.
[0087] The control system may calculate the total amount of energy
required to cook the food item according to the cooking profile
based on the weight of the food item.
[0088] The control system may predict when the food item is cooked
by monitoring the amount of energy transferred to the food item.
The food item is predicted as cooked when the amount of energy
transferred to the food item substantially equals the total amount
of energy required to cook the food item.
[0089] The control system may compare the amount of energy
transferred to the food item to the total amount of energy required
to cook the food item during the cooking process.
[0090] The control system may stop the power supply to the heating
element once the energy transferred to the food item is equals the
amount of energy required to cook the food item.
[0091] The control system may reduce the power supply to the
heating element to maintain the plates at a predetermined
temperature after cooking completes.
[0092] The control system may use a closed loop transfer function
to regulate cooking temperature to ensure that the food item is
cooked according to the selected cooking preference.
[0093] The control system may calculate the total amount of energy
required to cook the food item according to the cooking profile
based on the weight of the food item and a temperature difference
between cooking temperature and initial food item temperature.
[0094] The control system may calculate the total amount of energy
required to cook the food item according to the cooking profile
using the following equation, wherein Q is the total amount of
energy required to cook the food item according to the cooking
profile, C.sub.p is the specific heat capacity of the food item, M
is the weight of the food item, T.sub.2 is the required (target)
temperature to achieve the cooking preference and T.sub.1 is the
initial food item temperature:
Q=Mc.sub.p(T.sub.2-T.sub.1)
[0095] The control system may calculate the amount of energy
transferred to the food item per unit time (e.g. per second) based
on the thickness and weight of the food item.
[0096] Suitably, the control system calculates the amount of energy
transferred to the food item per unit time (q) using the following
equation, wherein .DELTA.T.sub.1 is the temperature difference
between a first plate (T.sub.plate 1) and the food item temperature
(T.sub.food item temp) per unit time and .DELTA.T.sub.2 is the
temperature difference between a second plate (T.sub.plate 2) and
the food item temperature (T.sub.food item temp) per unit time and
R.sub.th is the thermal resistance of the food item:
q=.DELTA.T.sub.1R.sub.th+.DELTA.T.sub.2R.sub.th, wherein
.DELTA.T=T.sub.plate 1/2-T.sub.food item temp
[0097] and, wherein the thermal resistance of the food item is
calculated based on the surface area of the food item in contact
with the pair of plates, the thickness of the food item and the
thermal conductivity of the food item.
[0098] The control system may automate the pair of plates to
maintain contact with the food item during cooking based on
feedback from a plate pressure sensor.
[0099] The control system may actuate a rack on the cooking
apparatus to lift the food item off a plate after completion of
cooking.
[0100] In accordance with the invention, there is also provided a
method of cooking a food item using an apparatus comprising a pair
of plates in between which a food item is to be cooked and at least
one of the plates having a heating element for cooking a food item
including the steps of: selecting a cooking preference; measuring a
distance between the pair of plates when the food item lies
therebetween to determine thickness of the food item; measuring a
weight of the food item; determining a cooking profile for cooking
the food item according to the cooking preference based on at least
one of the thickness of the food item and the weight of the food
item; calculating a total amount of energy required to cook the
food item according to the cooking profile based on the weight of
the food item; calculating an amount of energy transferred per unit
time to the food item based on the thickness of the food item; and
controlling power supply to the heating element based on the amount
of energy transferred per unit time to the food item to cook the
food item.
[0101] The method may include determining a cooking temperature
based on the cooking profile.
[0102] The method may include calculating the total amount of
energy required to cook the food item according to the cooking
profile based on the weight of the food item.
[0103] The method may include comparing the total amount of energy
required to cook the food item according to the determined cooking
profile and the amount energy transferred to the food item per unit
time to determine the percentage completion of cooking.
[0104] The method may include comparing the amount of energy
transferred to the food item to the total amount of energy required
to cook the food item at discrete intervals.
[0105] The method may include predicting when the food item is
cooked by monitoring the amount of energy transferred to the food
item. The food item is predicted as cooked when the amount of
energy transferred to the food item substantially equals the total
amount of energy required to cook the food item.
[0106] The method may include comparing the amount of energy
transferred to the food item to the total amount of energy required
to cook the food item during the cooking process.
[0107] The method may include stopping the power supply to the
heating element once the energy transferred to the food item is
equals the amount of energy required to cook the food item.
[0108] The method may include reducing the power supply to the
heating element to maintain the plates at a predetermined
temperature after cooking completes.
[0109] The method may include using a closed loop transfer function
to regulate cooking temperature to ensure that the food item is
cooked according to the selected cooking preference.
[0110] The method may include calculating the total amount of
energy required to cook the food item according to the cooking
profile based on the weight of the food item and a temperature
difference between cooking temperature and initial food item
temperature.
[0111] The method may include calculating the total amount of
energy required to cook the food item according to the cooking
profile using the following equation, wherein Q is the total amount
of energy required to cook the food item according to the cooking
profile, C.sub.p is the specific heat capacity of the food item, M
is the weight of the food item, T.sub.2 is the required (target)
temperature to achieve the cooking preference and T.sub.1 is the
initial food item temperature:
Q=Mc.sub.p(T.sub.2-T.sub.1)
[0112] The method may include calculating the amount of energy
transferred to the food item per unit time (e.g. per second) based
on the thickness and weight of the food item.
[0113] Suitably, calculating the amount of energy transferred to
the food item per unit time (q) uses the following equation,
wherein .DELTA.T.sub.1 is the temperature difference between a
first plate (T.sub.plate 1) and the food item temperature
(T.sub.food item temp) per unit time and .DELTA.T.sub.2 is the
temperature difference between a second plate (T.sub.plate 2) and
the food item temperature (T.sub.food item temp) per unit time and
R.sub.th is the thermal resistance of the food item:
q=.DELTA.T.sub.1R.sub.th+.DELTA.T.sub.2R.sub.th, wherein
.DELTA.T=T.sub.plate 1/2-T.sub.food item temp
[0114] and, wherein the thermal resistance of the food item is
calculated based on the surface area of the food item in contact
with the pair of plates, the thickness of the food item and the
thermal conductivity of the food item.
[0115] The method may include automating the pair of plates to
maintain contact with the food item during cooking based on
feedback from a plate pressure sensor.
[0116] The method may include lifting the food item off a plate
after completion of cooking.
BRIEF DESCRIPTION OF THE DRAWINGS
[0117] Embodiments of the present invention are hereinafter
described by way of example only, with reference to the
accompanying drawings, wherein:
[0118] FIG. 1 is a flow chart illustrating the sequence of messages
displayed on the user interface during the cooking process
according to one form of the invention.
[0119] FIG. 2 is a flow chart illustrating the steps taken by the
control system during the cooking process according to one form of
the invention.
[0120] FIG. 3 is a flow chart illustrating the steps taken by the
control system to detect errors in the system according to one form
of the invention.
[0121] FIG. 4 is a perspective view of one embodiment of a cooking
apparatus in accordance with the present invention and having an
ultrasonic sensor according to one form of the invention.
[0122] FIG. 5 is an enlarged view of an ultrasonic sensor on the
cooking apparatus in FIG. 4 according to one form of the
invention.
[0123] FIG. 6 is an enlarged view of a pivot of a lever arrangement
of a cooking apparatus including an angle sensor according to one
form of the invention.
[0124] FIG. 7 is a perspective view of a cooking apparatus
including a light beam sensor according to one form of the
invention.
[0125] FIG. 8 is a perspective view of a cooking apparatus
including a slider sensor according to one form of the
invention.
[0126] FIG. 9 is a perspective view of a cooking apparatus
including a four-bar linkage handle according to one form of the
invention.
[0127] FIG. 10 is a perspective view of a cooking apparatus with a
rack for lifting the food item from the bottom plate after cooking
according to one form of the invention.
[0128] FIG. 11 is a perspective view of a cooking apparatus with
zoned cooking areas according to one form of the invention.
[0129] FIG. 12 is a block diagram schematically illustrating
components of the cooking apparatus according to one form of the
invention.
[0130] FIG. 13 is a flow chart illustrating the function of the
control system of the cooking apparatus according to one form of
the invention.
[0131] FIG. 14 is a flow chart according to one form of the
invention.
[0132] FIG. 15 illustrates the temperature profile of the core meat
temperature against the theoretical thermodynamic curve of Example
1.
[0133] FIG. 16 illustrates the temperature profile of the surface
meat temperature against the theoretical thermodynamic curve of
Example 2.
[0134] FIG. 17 illustrates the temperature profile of the core meat
temperature against the theoretical thermodynamic curve of Example
3.
DESCRIPTION
[0135] Several embodiments of the cooking apparatus in accordance
with the invention are illustrated. All embodiments generally
relate to a cooking apparatus comprising a pair of plates in
between which a food item is cooked. At least one of the plates has
a heating element for cooking the food item. The cooking apparatus
further includes a user interface for selecting a cooking
preference.
[0136] In one embodiment, the selected cooking preference
determines the available cooking temperature profiles (hereinafter
referred to as "cooking profile") to cook the food item according
to the user preference.
[0137] A measurement sensor and a weight sensor on the cooking
apparatus measures a distance between the pair of plates when a
food item is placed between the plates and the weight of the food
item, respectively, and each of these sensors sends a signal to a
control system (also referred to as a controller) in the apparatus.
The control system calculates the total amount of energy required
to cook the food item according to the cooking preference and the
amount of energy to be transferred to the food item per unit time
using either one or both of these signals.
[0138] A cooking profile is also determined by the control system,
or may be pre-selected by a user, which specifies the cooking
temperature or range of cooking temperatures for cooking the food
item according to the cooking preference using the calculated total
amount of energy. The control system then controls the heating
element to cook the food item to a desired result.
[0139] A flowchart illustrating the sequence of messages displayed
on the user interface during the cooking process according to one
embodiment of the invention is shown in FIG. 1. Once the user
commences the cooking process by pressing the Start button on the
user interface, the control system heats the plates in a
"Preheating" step to a cooking temperature determined by the
cooking profile. During the preheating step, the control system
determines the power required for the subsequent "Waiting" step
while preheating step is being carried out.
[0140] Once the preheating step is completed, the control system
applies the power determined for the "Waiting" step to maintain the
heated plates at the cooking temperature. The power required for
the subsequent "Cooking" step is determined during the "Waiting"
step. Once a food item is placed on the plate, the "Cooking" step
commences to cook the food item according to the cooking profile by
ensuring the plates are maintained at the cooking temperature.
[0141] The control system also performs a series of checks to
identify errors in the system and minimize undesirable operating
conditions (see FIG. 3).
[0142] In order to cook a food item, the control system calculates
the total energy (Q) required to cook the food item according to
the cooking profile and calculates the energy that has to be
transferred per unit time (q) to the food item in order to cook the
food item according to the cooking profile. The amount of energy
transferred per unit time to the food item is measured against the
total amount of energy required to cook the food item according to
the cooking profile. The cooking process completes when the amount
of energy transferred into the food item equals the total amount of
energy required to cook the food item. Namely, this occurs
when:
Q=qt,
[0143] where t is the cooking time.
[0144] The amount of energy transferred per unit time to the food
item may be regularly monitored and compared against Q. The cooking
process stops when the calculated total amount of energy is
transferred to the food item.
[0145] Alternatively, the time (t) taken to transfer the total
amount of energy (Q) to cook the food item is calculated from the
amount of energy transferred per unit time, and the cooking process
stops when t is reached.
[0146] The control system calculates the total energy (Q) required
to cook the food item according to the cooking profile based on the
measured weight (M) of the food item, the specific heat capacity
(c.sub.p) of the food item, the required temperature (T.sub.2) to
achieve the preferred cooking outcome and the initial food item
temperature (T.sub.1) using the following equation:
Q=Mc.sub.p(T.sub.2-T.sub.1)
[0147] he specific heat capacity of the food item is estimated from
literature, for example, from The Engineering ToolBox
(www.engineeringtoolbox.com). It may also be derived empirically or
may be a combination of literature and empirical values.
[0148] The required temperature may be obtained from literature,
for example, Green, Aliza, Field Guide to Meat, 2005, and/or
empirically, by visual inspection of the food item.
[0149] The control system calculates the energy transferred per
second to the food item (q) using the following equation where
.DELTA.T.sub.top is the temperature difference between the top
plate and the food item temperature per unit time, .DELTA.T.sub.btm
is the temperature difference between the bottom plate and the food
item temperature per unit time and R.sub.th is the thermal
resistance of the food item:
q=.DELTA.T.sub.1R.sub.th+.DELTA.T.sub.2R.sub.th, wherein
.DELTA.T=T.sub.plate 1/2-T.sub.food item temp
[0150] The food item temperature is cumulative, adding the
incremental temperature gain to the previous temperature value.
[0151] The thermal resistance of the food item is calculated using
the following equation:
R th = k A x ##EQU00003##
[0152] wherein A is the surface area of the food item in contact
with the plates, x is the measured thickness and the k is the
thermal conductivity of the food item.
[0153] The surface area (A) of the food item is calculated using
the measured thickness (x) and weight (M) of the food item, and the
density (.rho.) of the food item using the following equation:
A = M x .rho. ##EQU00004##
[0154] The density of the food item is estimated from literature.
It may also be derived empirically or may be a combination of
literature and empirical values.
[0155] One form of the cooking apparatus 10 is illustrated in FIGS.
4 and 5.
[0156] The cooking apparatus 10 comprises a horizontally arranged
top plate 12A and a bottom plate 12B in between which a food item
is cooked, wherein each plate has a heating element (not shown) for
cooking the food item.
[0157] In another embodiment, the pair of plates may be oriented at
any angle from a horizontal to a vertical position.
[0158] The angle of the pair of plates may allow fluids such as oil
or rendering to flow from a food item to reduce fluids from soaking
the food item. The angle of the pair of plates, for example, when
positioned in a substantially vertical position may allow the food
item to be released from the cooking apparatus when the cooking has
completed onto a tray or rack positioned below the cooking
apparatus.
[0159] The top plate 12A is linked to the bottom plate 12B by a
handle 18, whereby the handle 18 is levered to the cooking
apparatus 10 to open and close plate 12A and plate 12B (FIG. 6).
Handle 18 is substantially `U` shaped in that it has a gripping bar
18A that extends across a front of the apparatus 10, which is where
a user takes hold of the handle, and side arms 18B that extend from
each side of the gripping bar down the side of the apparatus to
each return at the rear of the apparatus and connect to a rear
hinge 13 fixed to the rear of the bottom plate 12B. Rear hinges 13
provide the pivot point that allows handle 18 to lever up and down
in order to open and close the top plate 12A of the cooking
apparatus. Each side of the top plate 12A is pivoted to the handle
18 through a pivot pin 22 that is mounted on each of the handle's
side arms at a point (approximately midway) between the gripping
bar and the rear hinge. The top plate 12A is rotatable about pivot
pins 22 so that the top plate 12A `floats` on pins 22 as the
cooking apparatus is opened by levering the handle 18 upward. This
floating effect is useful to accommodate uneven-shaped food items
and to maximize contact of the top plate 12A on the food item.
[0160] The cooking apparatus 10 includes a weight sensor 13, and a
measurement sensor 14 for measuring a distance between the pair of
plates. The measurement sensor 14 may take many forms for measuring
the distance between, i.e. the separation of, the plates. For
example, the measurement sensor may be a position, angle or
displacement sensor using, for instance, an electro-mechanical
device (such as a strain gauge) or a transformer or transducer
(such as a piezo-electric transducer). It is understood that the
examples of sensors provided are illustrative only and that any
suitable type of sensor may be incorporated into the cooking
apparatus 10.
[0161] The cooking apparatus 10 also includes a user interface 820
in the form of a control panel 16 for transmitting data on cooking
variables from the user (i.e. the cooking preference) to the
control system 870. The user variables are used to determine the
cooking profile.
[0162] The user interface includes a display device 830 which
provides a visual indication of the user selection and a user input
device 840 for the user to enter data on the cooking variables.
[0163] The control system 870 receives signals from the measurement
sensor 14, the weight sensor 13 and the control panel 16 to
calculate the total amount of energy required to cook the food item
and to calculate the amount of energy being transferred to the food
item during the cooking process, which in turn, is used to control
the heating elements on the pair of plates, namely to ensure the
temperature on the plates is maintained at the cooking
temperature.
[0164] The cooking apparatus described herein automates and
controls cooking based on the total amount of energy required to
cook the food item and the amount of energy per unit time
transferred to the food item. This allows the food item to be
cooked consistently to the preferred cooking outcome regardless of
the thickness or weight of the food item.
[0165] In contrast, a conventional comparable cooking apparatus
would rely on manual inspection and adjustment of a food item by a
user to control the cooking process. This is time consuming and
often inconvenient for a user who has to watch and move the food
item on the cooking apparatus as needed.
[0166] The cooking apparatus 10 takes into account the type of food
item cooked. Different types of food such as red meat, fish and
chicken cook at different rates at the same temperature. As such,
there is a low likelihood of overcooking or undercooking a food
item with the described cooking apparatus.
[0167] The cooking apparatus 10 allows a user to automate the
cooking process without requiring the user to tend to the food item
during the cooking process to produce consistently cooked food
items. It achieves this by selecting a cooking preference (i.e.
selecting the type of food item and preferred cooking outcome)
which determines the cooking profiles available to cook the food
item to the desired cooking outcome.
[0168] Based on the weight and thickness of the food item, a
cooking profile is determined which in turn determines the cooking
temperature or range of cooking temperatures to cook the food item.
The control system 870 calculates the total energy required to cook
the food item to the preferred cooking outcome and the amount of
energy to be transferred to the food item per unit time. The
calculated amount of energy is transferred to the food item to cook
the item to the desired cooking outcome.
[0169] The weight sensor 13 is a load cell embedded within bottom
plate 12B. The measurement sensor 14 measures the distance between
the pair of plates. The measurement sensor 14, in the embodiment of
FIGS. 4 and 5, is an ultrasonic sensor mounted on the bottom plate
12B. The ultrasonic sensor may be mounted anywhere along the edge
of bottom plate 12B and is associated with a projection 20 on top
plate 12A that reflects a signal from the ultrasonic sensor. The
ultrasonic sensor operates similar to known ultrasonic sensors in
that the distance between the pair of plates is determined by the
time taken for a signal to return to the sensor 14 after reflecting
off the projection 20 on the top plate 12A.
[0170] The projection 20 may be located on the handle 18 instead of
top plate 12A, as handle 18 is associated with movement of the top
plate. Accordingly, the position of the projection 20 on the handle
18, when the top plate 12A contacts a food item placed on bottom
plate 12B, is used by the ultrasonic sensor to calculate the
distance between the pair of plates.
[0171] In another embodiment of the cooking apparatus (illustrated
in FIG. 6), the measurement sensor 14 is an angle sensor located at
the pivot point at rear hinge 13 through which the top and bottom
plates are pivoted. As the handle 18 is levered to receive a food
item such as a steak between the pair of plates, the sensor 14
measures the angle of the pivot at the rear hinge compared to a
reference point, such as fully closed position with no food item
between the plates. From the angle of pivot the distance between
the pair of plates can be calculated by determining a corresponding
change in angle through which the handle is pivoted.
[0172] In the embodiment illustrated in FIG. 7, the measurement
sensor 14 is an optical position sensor that includes a curtain of
light beams mounted along the edge of the bottom plate 12B. The
curtain of light beams are associated with a blocking cover 21 and
the sensor measures the distance between the pair of plates based
on the number of beams disrupted or blocked by a blocking cover
21.
[0173] The blocking cover 21 is mounted on the top plate 12A and is
positioned to disrupt or block the curtain of discrete light beams
as the distance between the pair of plates decreases. For example,
in an inoperative position whereby the top plate 12A is at a
maximum distance from the bottom plate 12B, the light beams are
completely exposed. As the top plate 12A is lowered towards the
bottom plate 12B, the blocking cover 21 gradually covers a number
of light beams, such that all the light beams are completely
blocked when the top plate 12A contacts the bottom plate 12B. The
sensor 14 measures the distance between the pair of plates based on
the number of light beams covered by the blocking cover 21 (FIG.
7).
[0174] The blocking cover 21 may alternatively be located on a side
arm of the handle 18 rather than of the top plate 12A. In that
embodiment, the number of light beams covered by the blocking cover
21 on handle 18 when the top plate 12A contacts a food item placed
on bottom plate 12B is used controller to calculate the distance
between the pair of plates.
[0175] In the embodiment of the cooking apparatus illustrated in
FIG. 8, the measurement sensor 14 comprises a sliding pin 14A that
is mounted to a printed circuit board located within the bottom
plate 12B at one end and movably connected to a guide 23 that is
mounted to handle 18 at the other end. The guide 23 has a slot to
receive sliding pin 14A such that as the top plate 12A moves
towards the bottom plate 12B, the sliding pin 14A moves
proportionally with the distance between the pair of plates along a
track 14B to transmit a signal to the control system to measure the
distance between the pair of plates (FIG. 8). The distance moved by
the sliding pin 14A along the track provides an indication of the
separation between the top and bottom plates.
[0176] The cooking apparatus may include more than one measurement
sensor. For example, a pair of measurement sensors may be located
on diametrically opposed corners of one plate. This arrangement
allows the control system to determine an average separation
between the pair of plates based on an average reading of the
distances between each measurement sensor. This can be used to
determine the thickness of unevenly-shaped food items.
[0177] FIG. 14 is a flow chart according to an embodiment of the
invention.
[0178] In operation, a user uses the control panel 16 to select the
cooking preference by selecting settings such as the type of food
item to be cooked and preferred cooking outcome for the food item.
For example, a user can cook a piece of steak to "medium" by
pressing the appropriate buttons on control panel 16 (Step (A) in
FIG. 14). The user's selection will be transmitted to the control
system.
[0179] The food item is placed onto the bottom plate 12B and the
handle 18 is moved to contact the top plate 12A with the steak.
[0180] The top plate 12A is connected to the handle 18 about the
pivot pin 22 to form a self-centering top plate whereby the top
plate 12A self-pivots on the contour of the food item (FIG. 4). In
this embodiment, the pair of plates may not be parallel to each
other during the cooking process. This embodiment is suitable for
uneven shaped food items such as a whole chicken or fish, whereby
the pivotable nature of the top plate 12A allows maximum contact of
the top plate 12A with the food item.
[0181] In another embodiment of the cooking apparatus, the top
plate 12A is connected to the handle 18 by a four-bar linkage (FIG.
9). As in previous embodiments, the handle side arms are linked to
the bottom plate 12B through rear hinge 13, but the top plate 12A
is further linked to the bottom plate 12B by a pair of short arms
19 which connect the pair of plates in a diagonal fashion and which
short arms 19 are parallel to the handle side arms. As illustrated
in FIG. 9, short arm 19 is connected toward the rear of the bottom
plate 12B at one end and connected to the front of the top plate
12A at the other end to form a link between the pair of plates.
[0182] This arrangement maintains the top plate 12A parallel to the
bottom plate 12B regardless of the contours of the food item. This
embodiment is suitable for flat-shaped food items such as a piece
of steak or a fish fillet which do not require the top plate 12A to
pivot to maintain maximum contact with the food item.
[0183] Once the top plate 12A contacts the food item by levering
the handle 18 about the rear hinge 13, the control system uses the
weight signal from the weight sensor 13 and/or the measurement
signal from the measurement sensor 14 to calculate the total amount
of energy required to cook the food item and to determine a cooking
profile (Step (B) of FIG. 14).Alternatively, the cooking profile
may be selected by a user.
[0184] The determined cooking profile specifies how the food item
is to be cooked using the calculated total amount of energy by
determining the temperature or a range of temperatures at which the
food item is to be cooked (Tc in Step (C) of FIG. 14). For example,
the food item may be subjected to (i) a high searing temperature
for a short period of time (Cooking profile (1) in Step (B) of FIG.
14), (ii) a lower searing temperature for a longer period of time
followed by a constant low temperature "warming" heat (Cooking
profile (2) in Step (B) of FIG. 14) or (iii) a low cooking
temperature for an extended period of time (Cooking profile (3) in
Step (B) of FIG. 14). Each of these cooking profiles transfers the
same amount of energy to the food item at the end of the cooking
process. In an alternative embodiment, Steps (B) and (C) can occur
at the same time.
[0185] The plates 12A and 12B are then preheated to the determined
temperature. The cooking process completes when the amount of
energy transferred into the food item equals the total amount of
energy required to cook the food item.
[0186] Throughout the cooking process the control system 870
regularly compares the amount energy transferred to the food item
per unit time against the total amount of energy required to cook
the food item (according to the determined cooking profile) to
determine when the cooking process is completed, and to
additionally determine the percentage of completion of the cooking
process, which is displayed on the display device 830.
[0187] The control system performs various functions including:
[0188] (a) determining a cooking profile for cooking the food item
according to the cooking preference based on the user's selection
and at least one of the thickness and weight of the food item; (b)
switching on the heating element;
[0189] (c) determining a time that has lapsed since the heating
element is switched on;
[0190] (d) determining a cooking temperature of the heating element
based on the cooking profile from the time since the heating
element is switched on;
[0191] (e) measuring a temperature of the heating element; and
[0192] (f) controlling the heating element to either increase or
decrease an input current based on the cooking temperature and the
current temperature of the heating element to thereby either
increase or decrease the temperature of the heating element;
[0193] (g) calculating the total amount of energy required to cook
the food item according to the cooking profile based on the weight
of the food item;
[0194] (h) calculating the amount of energy transferred to the food
item per second based on the weight of the food item and the
distance between the pair of plates (i.e. the thickness of the food
item); and
[0195] (i) controlling the heating element to stop transfer of
energy into the food item once the energy transferred to the food
item equals the total energy required to cook the food item.
[0196] FIG. 13 demonstrates some of the above functions of the
control system and the functional relationships between the control
system and the user interface, sensors and plates.
[0197] FIG. 12 illustrates the physical relationship of the
components of the cooking apparatus.
[0198] The temperature sensor 810 provides real time information on
the plate temperature to indicate to a user when to load the food
item into the apparatus.
[0199] As discussed above, a temperature sensor 810 could be
embedded into one or both of top plate 12A and bottom plate 12B to
determine the starting temperature of the food item. A signal
transmitted from the temperature sensor 810 to the control system
could be used to adjust the cooking temperature and/or cooking time
if, for example, a food item is placed in between the plates before
a pre-heat temperature is reached.
[0200] The present cooking apparatus has the ability to control the
cooking process by taking into account the thickness and weight of
the food item. This means that the cooking apparatus can apply a
shorter cooking time to the food item to achieve a desired cooking
outcome, without the risk of overcooking or undercooking the food
item.
[0201] The cooking apparatus may include other optional features to
enhance usability or improve cooking outcomes. For example, the
control panel 16 may include a memory for saving parameters such as
specific heat capacity values and thermal conductivity values.
These parameters can be entered by a user.
[0202] As illustrated in FIG. 10, the cooking apparatus 10 may also
include a rack 24 which is actuated to lift the food item away from
the pair of plates after completion of the cooking process. The
rack 24 is mounted to the bottom plate 12B by an upwardly biased
spring-loaded hinge 26. During the cooking process, the food item
is placed on the rack and the top plate 12A is lowered to contact
the food item using the handle 18. As the top plate contacts the
food item, the rack 24 is pushed onto and contacts the bottom plate
12B. Accordingly, during the cooking process, the food item is in
direct contact with the rack 24 which is in turn heated by the
bottom plate 12B.
[0203] Once cooking is finished, the handle is either manually or
automatically moved to lift the top plate away from the food item.
Without the pressure of the top plate against the food item, the
spring-loaded hinge 26 lifts rack 24 off the bottom plate 12B to
allow the food item to rest in a warm position but away from direct
heat.
[0204] In another embodiment of the cooking apparatus, the bottom
plate 12B includes an embedded plate pressure sensor 800 to
transmit a signal to the control system in response to any changes
in pressure on the plate.
[0205] The pair of plates may be controlled to move in response to
a change in thickness or height of the food item. For example, loss
of moisture from a piece of steak during cooking will result in
shrinkage and consequently, thickness of the piece of steak. As a
result, the steak could lose contact with the top plate 12A, which
will affect the cooking process.
[0206] Furthermore, the pair of plates may be automated by the
control system based on the signal from the plate pressure sensor
800 to allow the pair of plates to move in response to any changes
in thickness of the food item to maintain contact between the
plates and the food item without exerting excessive pressure.
[0207] For example, a response from the control system to a change
in pressure resulting from shrinkage of the steak would be to lower
the top plate 12A and restore contact with the steak, but without
applying too much pressure.
[0208] Additionally, the plate pressure sensor 800 can also detect
whether excessive pressure has been exerted on the steak. In
response, the control system would raise the top plate 12A from the
steak.
[0209] Continuous monitoring and movement of the pair of plates
with any changes in thickness of the steak ensures contact between
the steak and the pair of plates is maintained during the cooking
process and ensures that the piece of steak is consistently cooked.
Accordingly, the cooking apparatus is able to adjust cooking
parameters and cooking functions in real time during the cooking
process in response to feedback from various distance, pressure and
temperature sensors.
[0210] As discussed above, the control system may automate the top
plate 12A to raise the top plate from the steak. Removing the plate
12A from contact with the food item reduces the likelihood of the
food item overcooking. For example, in FIGS. 4 to 9 and 11, the top
plate 12A may lift off the food item to allow the food item to rest
on the bottom plate.
[0211] In combination with the rack 24 positioned on the bottom
plate 12B as described above, upon completion of the cooking time
the top plate may be moved away from the food item and at the same
time, the rack raises the food item off the bottom plate. FIG. 10
illustrates this embodiment where the top plate 12A lifts off the
food item which in turn causes the rack 24 to be raised off the
bottom plate 12B to allow the food item to rest.
[0212] After the cooking process has concluded, the control system
could be programmed to transmit an audio and/or visual signal to
indicate completion of cooking to a user.
[0213] The cooking apparatus may furthermore include zoned cooking
areas, whereby one heating element is positioned adjacent another
heating element, whereby the heating elements are located on side
by side twin pairs of plates to provide localized heating to one
area of the cooking apparatus. FIG. 11 illustrates this
embodiment.
[0214] Specifically, FIG. 11 shows heating elements positioned to
create zones 26A and 26B on the bottom plate 12B which are heatable
to different temperatures. Corresponding heating elements are
provided in two independently movable top plates 12A each overlying
a zone 26A or 26B. Zones 26A and 26B comprise separate heating
elements that are localized to function independently to heat the
corresponding zone based on different cooking profiles that are
controlled by separate control panels 16. This allows multiple food
items to be cooked simultaneously based on different predetermined
settings and/or cooking outcomes that can be programmed via
separate control panels 16.
[0215] The cooking apparatus may include a cover such as a shell
that covers the pair of plates 12A and 12B during the cooking
process so that the splattering of fluids such as oil during the
cooking process is reduced. The cover also allows the food item to
rest in an enclosed space to minimize heat loss.
[0216] In another embodiment, the cooked food item is maintained at
the target temperature after completion of the cooking process to
avoid the need for a resting step (see Example 3). Advantageously,
this prevents the cooked food item from getting cold before it is
consumed.
EXAMPLE 1
[0217] Type: Beef steak
[0218] Weight: 198 g
[0219] Thickness: 13 mm
[0220] Target temperature (T.sub.2): 63.degree. C. (Medium)
[0221] Initial temperature (T.sub.1): 17.degree. C.
[0222] Cooking temperature: 190.degree. C.
[0223] Thermal conductivity of beef: 0.780 W/mK
[0224] Cooking time: 55 seconds
[0225] The thermal conductivity of beef was determined empirically
and takes into consideration the thermal conductivity of beef and
the plate.
[0226] The plates were pre-heated to 190.degree. C. based on the
user selection of "beef steak" and "medium", rising at a rate of
around 25.degree. C. per minute. The core temperature of the steak
was measured by inserted a temperature probe into the center of the
steak.
[0227] The steak was cooked on the plates maintained at 190.degree.
C. for 55 seconds (from about 4:20 to about 5:15 in FIG. 15) and
rested for 80 seconds to achieve the desired cooking outcome (from
about 5:15 to 6:35 in FIG. 15). The cooking time was based on the
time taken to transfer the calculated total amount of energy
required to cook the food item to the food item.
[0228] The temperature profile of the core meat temperature against
the theoretical thermodynamic curve is illustrated in FIG. 15,
which indicates that the actual core temperature of the steak
follows the target temperature of 63.degree. C. based on the
required energy calculations. A visual inspection of the cooked
steak also confirms that the steak was cooked to medium.
EXAMPLE 2
[0229] Type: Beef steak
[0230] Weight: 183 g
[0231] Thickness: 15 mm
[0232] Target temperature (T.sub.2): 62.degree. C. (Medium)
[0233] Initial temperature (T.sub.1): 13.degree. C.
[0234] Cooking temperature: 190.degree. C.
[0235] Thermal conductivity of beef: 0.780 W/mK
[0236] Cooking time: 65 seconds.
[0237] The experimental set up is similar to Example 1. The
temperature profile of the surface meat temperature against the
theoretical thermodynamic curve is illustrated in FIG. 16, which
indicates that the actual surface temperature of the steak follows
the theoretical thermodynamic curve.
[0238] The steak was cooked on the plates maintained at 190.degree.
C. for 65 seconds (from about 3:37 to about 4:42 in FIG. 15) and
rested for 69 seconds to achieve the desired cooking outcome (from
about 4:42 to 5:51 in FIG. 15).
EXAMPLE 3
[0239] Type: Beef steak
[0240] Weight: 194 g
[0241] Thickness: 20 mm
[0242] Target temperature (T.sub.2): 90.degree. C. (Well done)
[0243] Initial temperature (T.sub.1): 5.degree. C.
[0244] Cooking temperature: 200.degree. C.
[0245] Thermal conductivity of beef: 0.780 W/mK
[0246] Cooking time: 90 seconds.
[0247] The thermal conductivity of beef was determined empirically
and takes into consideration the thermal conductivity of beef and
the plate.
[0248] The plates were pre-heated to 200.degree. C. based on the
user selection of "beef steak" and "well done". The core
temperature of the steak was measured by inserted a temperature
probe into the center of the steak.
[0249] The steak was cooked on the plates maintained at 200.degree.
C. for 90 seconds (from about 0:00 to about 01:30 in FIG. 17).
Thereafter, the plate temperature is reduced to allow the steak to
maintain the target temperature of 90.degree. C. without being
removed from the plate to rest (from about 20:00 to 40:00).
[0250] The temperature profile of the core meat temperature against
the theoretical thermodynamic curve is illustrated in FIG. 17,
which indicates that the actual core temperature of the steak is
maintained at the target temperature of 90.degree. C.
[0251] It will be understood to persons skilled in the art of the
invention that many modifications may be made without departing
from the spirit and scope of the invention.
* * * * *