Note: Descriptions are shown in the official language in which they were submitted.
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GRILL INCLUDING AUTOMATIC GAP CALIBRATION
BACKGROUND OF THE INVENTION
The present invention relates generally to a grill that automatically
calibrates a
gap between an upper grilling surface and a lower grilling surface.
Grills or griddles are used to cook various foods, such as hamburgers. In one
prior grill, the sides of the food are grilled separately. The food is placed
on a grilling
surface, grilling the side of the food that contacts the grilling surface.
After that side of
the food is cooked, the food is manually flipped to cook the opposite side.
After the food
is cooked, the food is manually removed from the grill for serving.
In another prior grill, both sides of the food are grilled simultaneously.
After
manually programming the type of food into a control unit, the food is placed
on a lower
grilling surface. An upper platen assembly having an upper grilling surface is
then
lowered onto the food, positioning the food in a gap between the upper and
lower grilling
surfaces to simultaneously grill both sides of the food. After a predetermined
amount of
time has passed, the upper platen assembly raises, and the food can be
manually removed
from the grill.
To ensure optimal performance, the upper grilling surface should be level to
ensure that the upper grilling surface uniformly contacts the food. If the
upper platen
assembly is not level, a service technician must travel to the site to
manually calibrate the
grill. This requires additional cost and labor.
Hence, there is a need in the art fora grill that automatically calibrates a
gap
between an upper grilling surface and a lower grilling surface and that
overcomes the
drawbacks of the prior art.
SUMMARY OF THE INVENTION
A grill includes an upper platen assembly pivotally attached to a lower platen
assembly. The lower platen assembly and the upper platen assembly each include
a
respective grilling surface. When the upper platen assembly is lifted by an
operator to a
raised position, the lower grilling surface is exposed. Food items are placed
on the lower
grilling surface by the operator for cooking. The upper platen assembly is
pivoted
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downwardly to a lowered position, positioning the food items in a gap between
the lower
grilling surface and the upper grilling surface.
The upper platen assembly includes three motors encased in a shell. A control
operates and controls the three motors. The motors each operate independently
to rotate
a shaft including a disc. The upper grilling surface suspends from cables. A
first end of
each cable is attached to the upper grilling surface, and an opposing second
end of each
cable is attached to one of the discs.
The grill is automatically calibrated to ensure that the upper grilling
surface is
level. An operator presses a button to initiate the auto-calibration sequence.
The upper
grilling surface is lowered to contact the lower grilling surface. One motor
is then
operated to rotate the shaft, raising a portion of the upper grilling surface.
A current
sensor detects the current in the motor. When the upper grilling surface is
slightly lifted
from the lower grilling surface, the current of the motor changes. When the
percent
change in the current increases over a threshold value, the position of the
upper grilling
surface and the motor setting are stored in the control. The calibration steps
are then
repeated.
The calibration steps are then performed by the other two motors individually
and
sequentially. After the calibrations steps are performed by all three motors,
the upper
grilling surface is level.
The grill also automatically recognizes a food item placed on the lower
grilling
surface. An operator presses a button to initiate a cooking cycle. The upper
grilling
surface lowers towards the lower grilling surface and onto the food items.
When the
upper grilling surface lifts from the food items on the lower grilling
surface, the current in
the motors changes. When the current sensor detects that the current changes,
the size of
the gap between the upper grilling surface and the lower grilling surface is
determined,
indicating the size of the food item. Based on the size of the food item, the
cooking
parameters of the grill are determined.
These and other features of the present invention will be best understood from
the
following specification and drawings.
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Brief Description of the Drawings
The various features and advantages of the invention will become apparent to
those skilled in the art from the following detailed description of the
currently preferred
embodiment. The drawings that accompany the detailed description can be
briefly
described as follows:
Figure 1 schematically illustrates a perspective view of a grill of the
present
invention in a lowered position;
Figure 2 schematically illustrates a perspective view of the grill in a raised
position;
Figure 3 schematically illustrates a perspective view of the grill in a closed
position with a shell removed;
Figure 4 schematically illustrates a top view of the grill with the shell
removed;
Figure 5 schematically illustrates a perspective view of a disc and a cable of
a
motor;
Figure 6 schematically illustrates a side view of the motor when rotating the
disc
in a first direction; and
Figure 7 schematically illustrates a side view of the motor when rotating the
disc
in a second opposite direction.
Detailed Description of the Preferred Embodiment
Figures 1 and 2 illustrate a grill 20 in a lowered position and a raised
position,
respectively. The grill 20 includes a lower platen assembly 22 and an upper
platen
assembly 24 pivotally attached to the lower platen assembly 22 by a hinge 28.
A
handle 26 on the upper platen assembly 24 can be grabbed by an operator to
pivot the
upper platen assembly 24 relative to the lower platen assembly 22 between the
lowered
position and the raised position. The lower platen assembly 22 and the upper
platen
assembly 24 each include a respective grilling surface 30 and 32. When the
upper
platen assembly 24 is lifted by an operator to the raised position, the lower
grilling
surface 30 is exposed.
Food items 34 are placed on the lower grilling surface 30 by the operator for
cooking. In one example, the food items 34 are hamburgers. The operator grabs
the
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handle 26 and pivots the upper platen assembly 24 downwardly to the lowered
position,
positioning the food item 34 in a gap 36 between the lower grilling surface 30
and the
upper grilling surface 32. An arm 42 contacts the lower grilling surface 30 to
provide a
mechanical stop that defines the gap 36 between the upper grilling surface 32
and the
lower grilling surface 30. The grilling surfaces 30 and 32 are heated by a
heater (not
shown) to cook the food items 34.
As shown in Figures 3 and 4, the upper platen assembly 24 includes a leveling
mechanism 38 that automatically levels the upper grilling surface 32 relative
to the lower
grilling surface 30. The leveling mechanism 38 includes three motors 46a, 46b
and 46c
encased in a shell 44 (shown in Figures 1 and 2). Each of the motors 46a, 46b
and 46c
operate independently to level a portion of the upper grilling surface 32. A
control 78
independently controls the three motors 46a, 46b and 46c. Although three
motors 46a,
46b and 46c are illustrated and described, it is to be understood that any
number of
motors 46a, 46b and 46c can be used. The motors 46a, 46b and 46c each operate
to
rotate a shaft 48a, 48b and 48c, respectively. Each shaft 48a, 48b and 48c
rotates a
respective disc 52a, 52b and 52c having a respective groove 54a, 54b and 54c.
The upper grilling surface 32 suspends from cables 58a, 58b and 58c. A first
end
60a, 60b and 60c of each cable 58a, 58b and 58c, respectively, is attached to
an upper
surface 88 of the upper grilling surface 32 by an attachment member 62a, 62b
and 62c,
respectively. As shown in Figure 5, an opposing second end 64a, 64b and 64c of
each
cable 58a, 58b and 58c is attached in the grooves 54a, 54b and 54c,
respectively, of the
disc 52a, 52b and 52c, respectively, such that a portion of each of the cables
58a, 58b and
58c is received in a groove 54a, 54b and 54c, respectively. Although cables
58a, 58b and
58c are illustrated and described, it is to be understood that metal drive
belts can be
employed.
Returning to Figure 4, the cable 58a is attached near a first corner 66 of the
upper
grilling surface 32 with the attachment member 62a, and the cable 58b is
attached near a
second corner 68 of the upper grilling surface 32 with the attachment member
62b. An
edge 70 is located between the first corner 66 and the second corner 68. The
third cable
58c is attached to the upper grilling surface 32 with the attachment member
62c at a
location between a third corner 72 and a fourth corner 74 of the upper
grilling surface 32.
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In one example, the attachment member 62c is substantially centrally located
between
the third corner 72 and the fourth corner 74. An edge 76 opposite to the edge
70 is
located between the third corner 72 and the fourth corner 74. Therefore, the
cables 58a,
58b and 58c are attached to the upper grilling surface 32 in a substantially
triangular
pattern. However, it is understood that any configuration of the cables 58a,
58b and 58c
is possible. Each of the motors 46a, 46c and 46c independently move and level
a portion
of the upper grilling surface 32 that is near the respective attachment
members 62a, 62b
and 62c.
As shown in Figure 6, as the motor 46a rotates the disc 52a in a first
direction A,
the cable 58a lengthens, lowering the upper grilling surface 32 toward the
lower grilling
surface 30. As shown in Figure 7, as the motor 46a rotates the disc 52a in an
opposing
second direction B, the cable 58a shortens and wraps around the disc 52a,
raising the
upper grilling surface 32 away from the lower grilling surface 30. Although
only the
motor 46a, the disc 52a and the cable 58a are illustrated and described, the
motors 46b
and 46c, the discs 52b and 52c and the cables 58b and 58c operate in a similar
manner.
The grill 20 is automatically calibrated to ensure that the gap 36 is
maintained at
the desired size between the lower grilling surface 30 and the upper grilling
surface 32.
By calibrated, it is meant that the upper grilling surface 32 is level
relative to the lower
grilling surface 30 to ensure proper cooking of the food items 34 in the grill
20. In one
example, the grill 20 is calibrated daily. If the upper grilling surface 32
becomes unlevel
during the day, the calibration steps performed the following day will correct
this.
However, if the operator notices that the upper grilling surface 32 has become
unlevel
during use of the grill 20, for example by observing the quality or appearance
of the food
items 34, the operator can press a button 84 to initiate the auto-calibration
sequence, as
described below.
When the grill 20 is first used on a given day, an operator presses the button
84 to
initiate the auto-calibration sequence that levels the upper grilling surface
32. The button
84 communicates with the control 78. The control 78 sends a signal for the
motors 46a,
46b and 46c to rotate the respective shafts 48a, 48b and 48c in the direction
A,
lengthening the respective cables 58a, 58b and 58c and lowering the upper
grilling
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surface 32 onto the lower grilling surface 30, providing a hard stop for the
upper grilling
surface 32 and providing slack in the cables 58a, 58b and 58c.
A current sensor 80 detects the current in the windings of each of the motors
46a,
46b and 46c. In one example, the current sensor 80 is a Hall-Effect sensor.
However, it
is to be understood that any type of sensor can be employed. When the upper
grilling
surface 32 raises and lifts from the lower grilling surface 30, the weight of
the upper
grilling surface 32 is transferred from the lower grilling surface 30 to the
cables 58a, 58b
and 58c. When the cables 58a, 58b and 58c begin to sustain the weight of the
upper
grilling surface 32, the tension in the cables 58a, 58b and 58c increases and
therefore the
current in the windings of the motor 46a, 46b and 46c changes.
After the upper grilling surface 32 is lowered onto the lower grilling surface
30,
one motor 46a is operated to rotate the shaft 48a in the direction B, wrapping
the cable
58a around the disc 52a to shorten and remove any slack in the cable 58a and
raise the
upper grilling surface 32. As the shaft 48a rotates and the upper grilling
surface 32 is
lifted, the current of the windings of the motor 46a is detected by the
current sensor 80.
As the upper grilling surface 32 is lifted, the current is detected at each
location of the
upper grilling surface 32. When the current sensor 80 detects a change in the
current in
the windings of the motor 46a, this indicates that the upper grilling surface
32 has lifted
from the lower grilling surface 30. When the percent change in the current
increases
over a threshold level, the settings of the motor 46a and the location of the
upper grilling
surface 32 are stored in the control 78.
The calibration steps are then repeated. The motor 46a rotates the shaft 48a
in the
direction A to lower the upper grilling surface 32 onto the lower grilling
surface 30. The
motor 46a is again operated to rotate the shaft 48a in the direction B,
wrapping the cable
58a around the disc 52a to shorten and remove any slack in the cable 58a. The
current of
the windings of the motor 46a is detected by the current sensor 80. When the
percent
change in the current increases over a threshold level, the settings of the
motor 46a and
the location of the upper grilling surface 32 are stored in the control 78 and
compared to
the settings of the motor 46a and the location of the upper grilling surface
32 previously
stored in the control 78. If the settings of the motor 46a and the location of
the upper
grilling surface 32 match within a given range, these values are stored and
indicate the
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calibration settings of the motor 46a. If the settings of the motor 46a and
the location of
the upper grilling surface 32 do not match, the calibration steps are repeated
until they do
match within a given range to settings determined in the previous set of
calibration steps.
By repeating the calibrating steps more than once, accurate calibration can be
ensured.
Although it is has been disclosed that the calibration settings of the motor
46a are
determined by detecting a percent change in the current over a threshold
level, it is to be
understood that the calibration settings of the motor 46a can be determined by
detecting a
specific current or an average current.
The calibration steps performed by the motor 46a are then repeated by the
motors
46b and 46c individually and sequentially. Although the motor 46a is described
as
performing the calibration steps first, it is to be understood that the motors
46a, 46b and
46c can perform the calibration steps in any order. Before each motor 46a, 46b
and 46c
performs the calibration steps, the upper grilling surface 32 is lowered onto
the lower
grilling surface 30. After all the motors 46a, 46b and 46c perform the
calibration steps,
the calibration settings of each of the motors 46a, 46b and 46c that result in
the leveling
of the upper grilling surface 32 are stored in the control 78. A calibration
point of the
upper grilling surface 32 is defined when each of the motors 46a, 46b operate
in the
calibration settings, resulting in the, upper grilling surface 32 being level.
Alternately,
the motors 46a, 46b and 46c are calibrated at the same time.
Additionally, the grill 20 automatically recognizes a food item 34 that is to
be
cooked in the grill 20. After the food item 34 is placed on the lower grilling
surface 30,
the operator grabs the handle 26 to lower the upper platen assembly 24 or
presses a
button 86 to initiate a cooking cycle. The button 86 communicates with the
control 78.
The control 78 actuates the motors 46a, 46b and 46c to lower the upper
grilling surface
32 towards the lower grilling surface 30. The upper grilling surface 32 lowers
to a pre-
determined location and compresses the food items 34 between the upper
grilling surface
32 and the lower grilling surface 30 to sear the food items 34.
The motors 46a, 46b and 46c are then operated to rotate the respective shafts
48a,
48b and 48c in the direction B, wrapping the respective cables 58a, 58b and
58c around
the respective discs 52a, 52b and 52c to shorten and remove the slack in the
cables 58a,
58b and 58c and raise the upper grilling surface 32. As the shafts 48a, 48b
and 48c
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rotate, the current of the windings of the motors 46a, 46b and 46c is detected
by the
current sensor 80.
When the current sensor 80 detects that the percent change in the current of
the
windings of the motors 46a, 46b and 46c increases over a threshold level, this
indicates
that the upper grilling surface 32 has lifted from the food items 34. The
control 78
determines the size of the gap 36 between the upper grilling surface 32 and
the lower
grilling surface 30 based on the settings of the motor 46a, 46b and 46c and
the
calibration point. The size of the gap 36 indicates the size of the food item
34. Based
on the size of the food item 34, the cooking parameters of the grill 20 are
determined.
The cooking parameters are programmed into the control 78. For example, based
on
the size of the gap 36, the cooking time, the cooking temperature and the size
of the
gap 36 during cooking of the food items 34 are determined. The control 78 sets
the
temperature of the heaters on the upper grilling surface 32 and the lower
grilling surface
30, the size of the gap 36 between the upper grilling surface 32 and the lower
grilling
surface 30, and the cooking time. After the cooking time has passed, the upper
platen
assembly 24 raises, allowing an operator to remove the food items 34 from the
lower
grilling surface 30.
Alternately, the size of the gap 36 is determined by detecting when the upper
grilling surface 32 contacts the food item 34 based on the detected current.
The foregoing description is only exemplary of the principles of the
invention.
Many modifications and variations are possible in light of the above
teachings. It is,
therefore, to be understood that within the scope of the appended claims, the
invention
may be practiced otherwise than using the example embodiments which have been
specifically described. For that reason the following claims should be studied
to
determine the true scope and content of this invention.
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