U.S. patent application number 13/047884 was filed with the patent office on 2011-07-07 for griddle plate having a vacuum bonded cook surface.
This patent application is currently assigned to ALL-CLAD METALCRAFTERS LLC. Invention is credited to William A. Groll.
Application Number | 20110162535 13/047884 |
Document ID | / |
Family ID | 36459765 |
Filed Date | 2011-07-07 |
United States Patent
Application |
20110162535 |
Kind Code |
A1 |
Groll; William A. |
July 7, 2011 |
Griddle Plate Having a Vacuum Bonded Cook Surface
Abstract
A composite griddle plate comprising a first sheet of metal
defining a cook surface and a core plate of a metal having a
relatively high coefficient of heat conductivity wherein the first
sheet remains in intimate contact with an upper surface of the core
plate with the aid of a vacuum.
Inventors: |
Groll; William A.;
(McMurray, PA) |
Assignee: |
ALL-CLAD METALCRAFTERS LLC
Canonsburg
PA
|
Family ID: |
36459765 |
Appl. No.: |
13/047884 |
Filed: |
March 15, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11245478 |
Oct 6, 2005 |
7926418 |
|
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13047884 |
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60616801 |
Oct 7, 2004 |
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Current U.S.
Class: |
99/422 |
Current CPC
Class: |
B23K 2103/14 20180801;
A47J 37/067 20130101; B23K 26/28 20130101; B23K 26/206 20130101;
B23K 2103/50 20180801; B23K 26/32 20130101; B23K 9/0026 20130101;
B23K 2103/05 20180801; B23K 2103/16 20180801 |
Class at
Publication: |
99/422 |
International
Class: |
A47J 37/10 20060101
A47J037/10 |
Claims
1. A composite griddle plate for cooking food and adapted to be
heated by an external source acting on a lower surface thereof,
comprising at least a first sheet of metal defining a cook surface
and a core plate of a metal having a relatively high coefficient of
heat conductivity wherein the said first sheet remains in intimate
contact with an upper surface of the core plate with the aid of a
vacuum, and wherein the griddle plate is sealed around a perimeter
thereof to maintain the vacuum, and wherein the first sheet of
metal is thinner than the core plate to prevent thermal warpage
during use.
2. The griddle plate of claim 1 wherein the core plate is made from
a metal selected from the group consisting of aluminum and
copper.
3. The griddle plate of claim 1 wherein the first sheet is one of
stainless steel or titanium.
4. The griddle plate of claim 1 wherein the composite griddle plate
is sealed around a perimeter thereof.
5. The griddle plate of claim 1 wherein the griddle plate is under
a permanent vacuum.
6. The griddle plate of claim 1 wherein the griddle plate is under
a continuous vacuum selectively applied by a vacuum pump during
use.
7. The griddle plate of claim 1 wherein the seal is provided by
welding.
8. A composite griddle plate for cooking comprising a high heat
conductivity core plate selected from aluminum or copper, upper and
lower sheets of metal facing said core plate, said upper sheet
selected from one of stainless steel or titanium, said griddle
plate having a perimeter sealed by welding and defining an interior
that is under a permanent vacuum whereby said upper and lower
sheets remain in intimate contact with the high heat conductivity
core plate by virtue of said vacuum and wherein said upper and
lower sheets of metal are thinner than the core plate to prevent
thermal warpage during use.
9. The griddle plate of claim 8 wherein the upper and lower sheets
are stainless steel.
10. The griddle plate of claim 8 wherein the upper sheet is
titanium and the lower sheet is stainless steel.
11. The griddle plate of claim 8 wherein the lower sheet is a
ferromagnetic material to permit heating of the griddle plate by
induction.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/245,478 filed Oct. 6, 2005, which claims
the benefit of U.S. Provisional Application No. 60/616,801 filed
Oct. 7, 2004, both of which are incorporated by reference herein in
their entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to commercial
cooking griddles and, more particularly, to a composite cooking
griddle having a thin cook surface layer, preferably of stainless
steel, that intimately contacts a thicker heat conductive core
layer of copper or aluminum by means of a vacuum.
[0004] 2. Description of Related Art
[0005] In commercial cooking griddles there is a long-felt need to
provide a cook surface with a fast thermal recovery time when
cooking, for example, frozen hamburger patties. In conventional
steel plate griddles, areas of the cook surface occupied by the
frozen patties experience a decrease in temperature which requires
a prolonged recovery time to reach a desired temperature for proper
cooking of the meat. This is caused by the fact that steel does not
possess a relatively high coefficient of thermal conductivity. When
the hamburger patties are flipped to cook the other side, the
patties are usually placed in areas previously occupied by a frozen
side and oftentimes are exposed to less than ideal cooler
temperatures for proper cooking. Thus, in conventional fast
food-type commercial griddles, the throughput time is extended. If
the cooking time is not increased, there is a real danger that the
meat is not thoroughly cooked, resulting in a health hazard due to
the possible presence of E. coli bacteria.
[0006] An ongoing effort to improve thermal recovery of commercial
cooking griddles is evidenced by my U.S. Pat. No. 6,109,504 which
utilizes a thick, thermally conductive core layer of copper
explosion bonded and rolled with a cook surface of stainless steel.
This has proved to be very workable from a commercial cooking
standpoint since the copper core offers a much faster heat recovery
than does the typical commercial griddle plate made from carbon
steel. Unfortunately, the explosion bonded and hot rolled griddle
plate of my aforementioned patent is relatively costly to
manufacture.
[0007] The present invention solves the problems heretofore
encountered in the prior art by providing a composite griddle plate
having a core of high conductivity metal which transfers heat to an
outer cook surface layer of a different metal, much like a roll
bonded composite, but at a much lower cost.
SUMMARY OF THE INVENTION
[0008] Briefly stated, the present invention is directed to a
composite griddle plate comprising a core consisting of a metal
having a high coefficient of thermal conductivity such as copper or
aluminum. The core plate is faced at least with an upper sheet of a
metal such as stainless steel or titanium which defines the cook
surface of the griddle plate. The interface between the core plate
and upper sheet is under the reduced pressure of a vacuum so as to
cause intimate contact between the core and cook surface which
increases the thermal conductivity to the cook surface and, thus,
reduces the thermal recovery time of the griddle.
[0009] Various additional presently preferred embodiments of the
invention are disclosed herein. For example, the griddle plate of
one such embodiment comprises a high heat conductivity core of
copper or aluminum having upper and lower sheets of stainless steel
in intimate contact with the core. The entire perimeter of the
griddle plate is sealed as by welding and the interior is under a
permanently sealed vacuum. Another such presently preferred
embodiment utilizes an upper sheet of stainless steel or other
metal having a non-stick coating applied thereto. The upper sheet
is removably secured to the heat conductive core plate under vacuum
utilizing a high temperature gasket or adhesive sealant to maintain
the vacuum. The upper sheet may be mechanically secured by bolts or
the construction may be placed under a constant vacuum using a
vacuum pump. When the non-stick surface ages and/or otherwise loses
its non-stick properties, such as with a PTFE-type non-stick
coating, the upper sheet can be easily replaced with a freshly
non-stick coated upper sheet and the vacuum reestablished.
[0010] These, as well as other attributes of my invention, will
become more readily apparent when reference is made to the
accompanying drawings taken with the detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a cross-sectional, exploded view of the
construction of one presently preferred embodiment of the griddle
plate of the present invention;
[0012] FIG. 2 is a cross-sectional side view of the griddle plate
of the invention, similar to FIG. 1, taken along section line II-II
of FIG. 3;
[0013] FIG. 3 is a plan view of the griddle plate with the top
sheet removed as viewed along line III-III of FIG. 2;
[0014] FIG. 4 is a cross-sectional side elevation view of a further
embodiment of the griddle plate of the invention;
[0015] FIG. 5 is a plan view of the griddle plate of FIG. 4;
[0016] FIGS. 6A and 6B depict a further presently preferred
embodiment of the present invention;
[0017] FIGS. 7A to 7C depict yet another presently preferred
embodiment of my invention;
[0018] FIG. 8 is a cross-sectional side view of a vacuum evacuating
and sealing tool for use in making the griddle plate of the
invention, the tool forming another aspect of the invention;
[0019] FIG. 9 is a cross-sectional longitudinal side view of a
further embodiment of the griddle plate construction of the present
invention;
[0020] FIG. 10 is a fragmented plan view of the upper sheet of
stainless steel forming the cook surface of the griddle plate of
FIG. 9 prior to fabrication;
[0021] FIG. 11 is a fragmented plan view of the vacuum fitting
employed in the embodiment of FIG. 9;
[0022] FIG. 12 is a cross-sectional side view of the griddle plate
and fitting of FIG. 11; and
[0023] FIG. 13 is a cross-sectional view of a fixture for drawing a
vacuum along with a fragmented partial side view of the griddle
plate of FIG. 9.
DETAILED DESCRIPTION OF THE INVENTION
[0024] One presently preferred embodiment of the present invention
is depicted in FIGS. 1-3 showing the composite griddle plate 2
comprising a core plate 4 having an upper sheet or cook surface 6
and a lower sheet 8. The core plate 4 is a metal having a high
coefficient of thermal conductivity such as copper or aluminum. Of
the two materials, copper is preferred from the standpoint of
thermal conductivity, while aluminum is attractive from a weight
standpoint in that aluminum is much lighter than copper in an
equivalent thickness while having only a slightly lower coefficient
of thermal conductivity. The sheets 6 and 8 in a preferred
embodiment are both selected from stainless steel such as Type 304
stainless. However, they need not be of the same type. For example,
the upper sheet may be of 304 stainless while the bottom sheet 8
can be a ferromagnetic material such as a carbon steel or a 400
grade ferritic stainless steel for induction cooking purposes.
Bottom sheet 8 could also be a nickel/iron material having a Curie
temperature within a selected range for griddle cooking. One such
material is, for example, 30-50 nickel/balance iron, which has a
Curie temperature under induction cooking conditions of from about
400.degree.-450.degree. F. The upper sheet 6 can also be made from
titanium which offers a very hard scratch-resistant cook surface
which is relatively lightweight and is inert to food products.
[0025] The composite griddle plate 2, as shown in the exploded view
of FIG. 1, is formed as a welded pack having bars 10 along the ends
and bars 12 along the sides forming a border around the perimeter
of the griddle plate 2. The upper and lower sheets 6 and 8,
respectively, are welded to the bars 10 and 12 to form an airtight
seal around the perimeter of the griddle plate 2. Preferably, a
small space 14 is maintained between the bars 10 and 12 and the
peripheral edges of the core plate 4 to permit improved evacuation
of the interior space 14 between the bars 10, 12 and the core plate
4. A vacuum pump 20 communicates with the interior space 14 by way
of a conduit 22. The vacuum pump 20 withdraws the atmosphere from
the interior of the griddle plate after the assembly has been
welded. The pump 20 preferably pulls a vacuum while the composite
griddle plate 2 is heated to about 400.degree. F. to drive off the
volatiles and expand the atmosphere within the interior. The vacuum
is pumped down preferably to at least 29 inches of mercury. At that
point the area of the conduit 22 indicated at 24 along the
perimeter of the griddle shown in FIG. 3 is closed off and sealed
to maintain the vacuum condition within the welded pack.
[0026] In this regard, the bar stock 10 and 12 may also be formed
preferably of 304 stainless steel. The surfaces of the outer facing
sheets 6 and 8 can be polished and have small grooves formed
therein to enable the evacuation of the interface between the
sheets 6 and 8 and the core plate 4. In the evacuated condition of
the vacuum, the sheets 6 and 8 tightly engage the core plate 4 to
ensure that no voids are present at the interface so as to increase
the thermal conductivity through the cross section of the griddle
plate construction. After the griddle plate 2 of FIGS. 1-3 has been
constructed in this manner, various elements such as brackets or a
grease trap can be welded to the griddle plate without destroying
the vacuum condition within the interior. The weld is preferably a
tungsten inert gas or a TIG weld, or it may be an automated laser
weld. The thinner the sheets 6 and 8, the more the composite acts
like the core, and no thermal warpage is present as the griddle
plate is heated due to the differences in thermal expansion
properties between the core 4 and the sheets 6 and 8.
[0027] A further variation of the griddle plate shown in FIGS. 1-3
can be better appreciated with reference to FIG. 3 wherein two
spaced-apart core plates 4 and 4' are utilized having a space 16
therebetween. In such a construction, the griddle can be divided
into two independent heating zones maintained at two different
temperatures by virtue of the insulating air gap provide by space
16 between the adjacent core plates 4 and 4'. In this manner, of
course, a multitude of different heating zones can be achieved
merely by utilizing separate core plates separated by spaces. For
example, four separate heating zones could be achieved in the
griddle plate 2 by utilizing four separate core plates 4, each
placed in one of the four quadrants of the griddle plate and
separated by spaces 16 providing heat insulating air gaps
therebetween.
[0028] A further presently preferred embodiment of my invention is
depicted in FIGS. 4 and 5 and identified generally as griddle plate
30. Griddle plate 30 comprises an upper sheet 32 having a gasket or
bead of high temperature adhesive sealant 33 applied around its
perimeter in contact with the high heat conductive plate 38. A
presently preferred high temperature, adhesive sealant 33 is a
copper silicone "CU-371" sealant manufactured by INTEK Adhesives
Ltd., U.K. The upper sheet 32 preferably is a drawn shape having an
upwardly formed edge 34 with a non-stick cook surface 36 of
Teflon.RTM., for example, applied thereto. A vacuum pump 35
communicates with the space 39 between the sheet 32 and plate 38 by
way of a conduit 37 to maintain a constant vacuum in the space 39
to ensure intimate contact between the sheet 32 and the high heat
conductive plate 38 of copper or aluminum. The sheet 32 is
preferably stainless steel. It is contemplated that the griddle
plate 30 would be sold as a unit with the vacuum pump 35 integral
therewith. The pump 35 would be activated when the griddle is in
use so as to maintain an intimate contact between the cook surface
sheet 32 and the high heat conductive plate 38. In the event the
non-stick surface 36 becomes worn, the entire plate 32 can be
replaced merely by shutting off the vacuum pump 35 and removing the
sheet 32 from the plate 38. A new upper sheet 32 with a fresh
non-stick surface 36 applied thereto may then be reapplied over the
high heat conductive plate 38 and the vacuum reestablished by
activation of the vacuum pump 35. A fresh gasket or bead of
adhesive sealant 33 would also be applied as previously described
in order to establish a vacuum-tight seal between the new upper
sheet 32 and the existing plate 38.
[0029] A still further embodiment of the present invention is
depicted in FIGS. 6A and 6B designated by reference numeral 40. The
griddle plate 40 comprises a deep-drawn lower sheet 42 preferably
of stainless steel and an upper sheet 44, also preferably a
stainless steel. The upper sheet 44 defines the cook surface. An
inner core 43 of copper or aluminum is, likewise, provided. The
lower sheet 42 carries an upturned peripheral flange 45 which
conveniently supports the top sheet 44. A weld bead 46, as more
clearly seen in FIG. 6B, establishes an airtight seal within the
interior of the griddle plate. A vacuum pump 48 communicates with a
conduit 49 for establishment of a vacuum within the interior. Once
again, a vacuum, preferably greater than 29 inches of mercury
within the interior, is preferred to establish intimate contact
between the sheets 42, 44 and core plate 43. When a vacuum of the
desired magnitude has been established, the conduit 49 is sealed
off and the griddle plate 40 is ready for use.
[0030] A still further embodiment of the present invention with a
replaceable cook surface is depicted in FIGS. 7A-7B by reference
numeral 50 and 50'. The griddle plate 50 shown in the left-hand
portion of drawing FIGS. 7A and 7B comprises an upper sheet 52 and
a lower sheet 54 of stainless steel carrying, respectively, flanges
52' and 54'. The upper and lower sheets 52 and 54 closely engage a
core plate 53 of copper or aluminum, for example. A peripheral seal
is mechanically established by way of a plurality of bolts 55 and
nuts 56 which threadably engage the threaded bolt shaft 57, FIG.
7B. A gasket or adhesive sealant (not shown) may also be applied
within the interface between the flanges 52' and 54' to ensure that
a vacuum condition is established as previously described.
[0031] A further embodiment of the griddle plate 50' is shown on
the right-hand portion of FIG. 7A wherein the lower sheet 54'' is
joined at weld bead 51 around the perimeter of the griddle plate to
peripheral bars 10'. The top sheet 52'' is bolted to the bar 10' by
way of a plurality of bolt-like fasteners 59 threadably secured
within threaded bores 58 formed in the bar 10'. Likewise, an
airtight gasket or high temperature sealant may be applied (not
shown) between the upper plate 52'' and the peripheral bars 10'.
While not shown specifically in FIG. 7A, of course, it would be
understood that an external vacuum would be applied to the interior
of the griddle plate to establish a vacuum of at least 29 inches of
mercury and then sealed off prior to use as previously described
with the embodiments discussed above.
[0032] A novel vacuum fixture generally designated 60, useful in
pulling a vacuum on the griddle plates and for sealing the griddle
plates of the present invention, is depicted in FIG. 8. The vacuum
fixture 60 comprises a cup-like member 61 having a sealing edge 62
for engagement with the sidewall 68 of the griddle plate which, in
most instances, would be the previously-described bar stock 10 or
12. The sealing edge 62 of the fixture 60 carries an O-ring 63 and
has an opening 64 with O-ring seals 65 in place thereon for
receiving a movable tapered pin 66. The pin 66 has a tapered end 67
for insertion into a hole 69 in the sidewall of the griddle plate.
A vacuum pump 70 communicates with a conduit 71 which, in turn,
communicates with the interior 60' of the cup 61 and the interior
of the griddle plate via the hole 69. When the prescribed vacuum,
for example, at least 29 inches of mercury has been reached, the
tapered pin 66 is driven in the direction of the arrows shown in
FIG. 8 to force the pin 66 into the hole 69. The tapered end 67 of
the pin 66 then becomes tightly wedged in the hole 69 and seals off
the hole as it is driven therein. The pin 66 which protrudes away
from sidewall 68 may then we machined away flush with the exterior
of the griddle plate and a precautionary weld bead or solder may be
applied to further seal the assembly. The fixture 60 may then be
removed and used to reseal additional griddle plates.
[0033] A still further embodiment of the griddle plate of the
present invention is depicted in FIGS. 9-13. The griddle plate of
this embodiment, designated generally by the numeral 2', dispenses
with the bars 10 and 12 as described in the previous embodiments.
In the embodiment of the griddle plate 2', an upper cook surface 71
is made from a relatively thinner gauge stainless steel than the
lower sheet 72, as perhaps best seen in FIG. 9. In this
construction of griddle plate 2', the upper and lower sheets 71 and
72 are blanked in a configuration as shown in FIG. 10 and then
fabricated by welding the blanks into box-like shapes which are
later joined.
[0034] As shown in FIG. 10, the upper sheet 71 is generally of a
rectangular shape assuming the overall dimension of the finished
griddle plate 2'. The corners 73 are cut out when the sheet is
blanked and then the fold line portions shown by dotted line 74 are
folded at a 90.degree. angle so that the sheet assumes a shallow
box-like structure, as shown in FIG. 9. As stated, after the sheets
are bent along the fold lines 74, the then-joined edges at
previously cut-out corners 73 are welded to form an airtight
junction or seal therealong. The bottom sheet 72 is formed in
similar fashion and then the interior surfaces are thoroughly
cleaned. An aluminum or copper core plate 75 of high thermal
conductivity is placed in the interior of the lower box-like shape
formed by the lower sheet 72, as shown in FIG. 9. The top sheet 71
is then fitted on the top of the upstanding side walls of lower
sheet 72 and welded in place therealong, as shown by weld beads 76
in FIG. 9, along the entire perimeter thereof to establish an
airtight seal. The fold lines for lower sheet 72 are designated by
numeral 74' in FIG. 9.
[0035] A vacuum is established within the interior of the
fabricated griddle plate 2' of FIGS. 9-13 by way of a vacuum
fixture 80 shown in detail in FIG. 13. In order to establish a
vacuum, a round fitting 77 having a threaded central bore 78 formed
therethrough is welded at weld bead 76 to the upper sheet 71 around
a hole 71' formed through the surface of the upper sheet 71, see
FIG. 12. The fitting 77 is positioned within a bore 81 formed
within the core plate 75. The bore 81 communicates with a space 79
between the perimeter of the core plate 75 and the vertical edges
72' of the lower sheet 72 by way of lateral holes 82 which radially
extend from the bore 81 outwardly to the space 79, FIG. 12. The
round fitting 77 is attached to the inside surface of the upper
sheet 71 via a weld bead 76' prior to the fabrication and welding
between the upper and lower sheets at weld beads 76. Otherwise,
access could not be gained to the interior of the griddle plate
2'.
[0036] In order to establish a vacuum within the griddle plate 2'
so as to obtain intimate contact between the upper cook surface 71
and the core plate 75 and lower sheet 72, a vacuum fixture 80
depicted in detail in FIG. 13 is employed. The fixture 80 includes
a body 83 which carries a C-frame clamp structure 84 having a
threaded bolt 85 to permit a tight contact between the fixture 80
and the griddle plate 2' when the vacuum is established. In order
to effect a seal between the fixture 80 and the griddle plate 2'
surface 71, an O-ring seal 86 is positioned at the bottom face of
the fixture 80 to engage the upper sheet 71.
[0037] Fixture 80 further includes a vertically movable seal rod 86
having a threaded distal end 87 which is sized to threadably engage
the threaded bore 78 of the round fitting 77. The seal rod 86
vertically moves within a bore 88 formed within the alignment cap
member 89 which, itself, is threadably fitted at the top of the
vacuum fixture 80, as shown in FIG. 13. The bore 88 is accurately
machined such that when the seal rod 86 is fitted therein, the end
87 of the rod will accurately engage the threaded bore 78 and
threadably engage therewith. A plurality of O-ring seals 90 is
positioned within the interior of the fixture 80 to provide a
slidable vacuum-tight seal therein. The fixture 80 also has a
threaded bore 91 formed therethrough communicating with the
interior 93 of the fixture 80 to permit attachment of a vacuum hose
fitting 92 therewithin so that a vacuum can be drawn within the
interior 93 of the fixture 80. The interior 93 also communicates
with the threaded bore 78 of the round fitting 77 which, in turn,
communicates with the bore 81 of the core plate 75 as well as the
lateral holes 82 and the space 79. Hence, when the vacuum is drawn
by way of a suitable vacuum pump with fitting 92, a vacuum
condition exists within the space 79 via the communicating holes
82, 81, 78, 93 and 91. When a suitable vacuum has been established
within the interior of the griddle plate 2', the upper sheet 71 and
lower sheet 72 will closely engage the core plate 75. After this
degree of vacuum has been established, the seal rod 86 is
vertically slid downwardly through the alignment cap 89 such that
the distal end 87 threadably engages the threaded bore 78 of the
round fitting 77. The upper end 86' of the rod 86 may then be
gripped by a suitable pliers or like tool, and rotated to permit
the threads 87 to further engage with the threaded bore 78. Once
sufficient threaded engagement has been established between the rod
86 and the fitting 77, the vacuum pump may be de-energized, and the
C-clamp structure 84 may be unfastened by loosening the screw 85.
The seal 90 at O-ring 86 is then broken and the clamping structure
of fixture 80 is removed from the griddle plate 2' by lifting
vertically upwardly leaving the seal rod 86 in place within the
threaded bore 78. At this point, the upwardly protruding portion of
rod 86 is cut along the surface of the upper sheet 71 and a TIG
weld, for example, may be applied around the area of the rod 86 to
ensure permanent sealing. The upper sheet 71 may then be
appropriately finished and smoothed to provide a cosmetically
pleasing appearance. The cook surface of upper sheet 71 may be
further buffed to a mirror finish, if desired. After finishing,
there is little or no evidence that a hole had been previously
formed within the surface 71 where the fixture 80 had previously
been employed. The griddle plate 2' is then ready to be placed into
service.
[0038] The above-described griddle plate 2' offers excellent
service and provides an advantage in that the upper surface 71
forming the cook surface may be much thinner than the lower surface
72. This provides quicker thermal response in the cook surface and
also allows for welding of fittings to the heavier gauge lower
sheet 72 for brackets, holders, grease traps, et cetera, which may
be desirable in commercial griddle constructions.
[0039] By way of example, the upper sheet 71 may be constructed of
a 300 series stainless steel while the bottom sheet 72 may be
constructed of a like material or a 400 series ferritic stainless
steel or other ferromagnetic material to provide the possibility of
induction heating. The upper sheet 71 may be of a thinner gauge, as
alluded to above, of, for example, 0.015 inch thick, while the
lower sheet 72 may be of a heavier gauge, for example, 0.030 inch
thick. This box-like construction of griddle plate 2' is also
attractive for commercial food installations because the inner core
75 of aluminum or copper is fully enclosed. The round fitting 77 is
also preferably made of stainless steel. The lower surface 72 is
preferably of a finish which is dull or blackened to absorb heat
more readily, particularly for radiant transfer purposes. The space
79 is as close as possible between the stainless steel of lower
sheet 72 and the core 75 when the griddle plate 2' is in a hot
state. Once again, the welding at bead 76 is preferably of a
tungsten inert gas (TIG) or MIG or laser weld. The overlap between
the upper sheet 71 and lower sheet 72 at the corners where weld
bead 76 is applied is preferably about one-eighth inch of overlap.
The core plate 75 is preferably about one-half inch in thickness,
and a typical griddle plate 2' may be on the order in plan view of
about 2 feet by 3 feet, for example.
[0040] In constructing the upper and lower sheets 71 and 72, the
blanks shown in FIG. 10 are folded with the bottom sheet 72 welded
at its inside corners while the top sheet 71 is welded at the
outside of the corners. In this manner, a snug fit is obtained
between the upper and lower corners, as shown in FIG. 9.
[0041] Still further, a film such as a graphite layer (not shown)
may be applied between the core plate 75 and the cook surface
formed by upper sheet 71 to accommodate any foreign particles that
may remain between the core plate and the cook surface which would
otherwise cause air gaps or bumps in the finished griddle plate.
While it is difficult to weldably join a 400 series stainless steel
to a 300 series steel, this could be accomplished by a continuous
spot welding operation.
[0042] While specific embodiments of the invention have been
described in detail, it will be appreciated by those skilled in the
art that various modifications and alternatives to those details
could be developed in light of the overall teachings of the
disclosure. The presently preferred embodiments described herein
are meant to be illustrative only and not limiting as to the scope
of the invention which is to be given the full breadth of the
appended claims and any and all equivalents thereof.
* * * * *