Note: Descriptions are shown in the official language in which they were submitted.
~18781 1
FABRICATED HOT PLATE, PARTICULARLY FOR
CORRUGATED PAPERBOARD MARING
Background of the Invention
The present invention relates to a hot plate
of fabricated steel construction adapted particularly for
the manufacture of corrugated paperboard and, more
particularly, to a hot plate apparatus for a double facer
where a liner web is attached to a single face corrugated
web.
In a typical prior art double facer, a liner
web is brought into contact with the glued flute tips of
a single face corrugated web and the resulting freshly
glued double face web is passed over the surfaces of a
number of serially arranged steam chests to cause the
starch-based glue to set. Double face web travel over
the steam chests may be provided by a wide driven
holddown belt in direct contact with the upper face of
the corrugated web with the top face of the belt held in
contact with the traveling web by a series of ballast
rollers or the like, all in a well known manner.
Beltless holddown and ballast systems have been developed
more recently in which the wide driven holddown belt is
eliminated, with the double face web pulled through the
system by other web drive devices, such as a downstream
vacuum belt.
Prior art steam chests, one example of which
is shown in U.S. Patent 3,175,300, are typically made of
heavy cast iron construction in the manner of a pressure
vessel in order to contain the high pressure steam which
is supplied to the steam chest. For example, the walls
of a cast iron steam chest are typically 1" or more thick
to safely contain superheated steam supplied, for
example, at 350F. (177C) and 160 psi (1103 kPa). A
steam chest has a flat upper web-supporting surface
having a length in a transverse direction sufficient to
support the full width of the traveling web and a width
in the direction of web movement of typically about 18"
to 24" (about 45 to 60 cm). Eighteen steam chests may be
~1 87~ 1 1
typically serially arranged in closely spaced relation in
a double facer.
The heavy cast iron construction of prior art
steam chests results in a number of well known
operational problems. The heavy walled construction of
these steam chests requires a long time to bring them up
to temperature on startup. Eventually, the steam chest
may be brought close to the temperature of the steam
being supplied to it. However, when operation is
commenced and the double face corrugated web is traveling
over the upper surfaces of the steam chests, heat is
drawn therefrom at a rapid rate and maximum surface
temperature may drop to levels as low as 280-290F (136-
143C). This lower effective operating temperature may
require the use of a substantially larger number of steam
chests in a given double facer than would be necessary if
more efficient heat transfer were attainable. Another
problem directly related to the inefficiency of heat
transfer through a heavy iron steam chest casting is the
transverse bowing of the upper surface of a conventional
steam chest during operation. As indicated, the
temperature of the flat upper wall of the steam chest is
reduced substantially relative to the bottom wall of the
steam chest resulting in a concave bowing of the upper
surface lengthwise of the steam chest (in the cross
machine direction with respect to the web traveling
thereover). As a result, the holddown belt and
transverse ballast rollers pushing the belt downwardly
against the upper surface of the web do not impose a
uniform load on the web. The result may be uneven curing
of the adhesive, zones of poor or no adhesion, and
crushing of the lateral edges of the web. Finally, the
heavy mass of cast iron steam chests results in high heat
retention and slow cool down, often requiring elaborate
systems to lift the web or lower the steam chests to
avoid excess heating of the web.
~1 87~1 1
U.S. Patent 5,183,525 includes a recognition
of certain of the foregoing operational problems in
systems utilizing heavy cast iron steam chests. In this
patent, the steam chest is replaced by a heavy steel
plate through which transverse horizontal bores are
drilled and interconnected at their opposite lateral ends
to form a serpentine steam passage through the plate.
The holes may be drilled in a manner forming a much
thinner web of material between the walls of the bores
and the upper surface of the plate to increase the
efficiency of heat transfer. The patent also teaches
that the problem of bowing or distortion of the upper
contacting face of the plate is minimized. However, the
construction of the heating plates in this patent is
still quite massive and heavy and the required drilling
or boring operations are elaborate and costly.
In U.S. Patent Application Serial No.
08/255,159, filed June 7, 1994, a hot plate for
supporting and heating the moving web of corrugated
paperboard in a double facer includes a web supporting
top plate made of a metal, such as copper, having a high
heat transfer efficiency (high thermal conductivity), a
series of spaced generally parallel tubes extending below
the plate transversely to the direction of web travel and
positioned in a planar array in operative heat conducting
contact with the underside of the top plate, and a pair
of steam supply manifolds each connecting the open ends
of the tubes along one lateral edge of the top plate.
The apparatus also includes a lower supporting frame
with anchoring means and vertical holddown means which
prevent vertical movement of the lateral edges of the top
plate, but allow horizontal lateral movement thereof as a
result of thermal expansion. This hot plate construction
has provided significant improvements over heavy cast
iron and fabricated steel construction, but still
exhibits problems of thermally induced plate distortion.
~ 878~ ~
There remains a need, therefore, for a
simple, efficient, and low cost hot plate system for a
double facer which effectively addresses the problems
typical of the prior art.
8ummary of the Invention
In accordance with the present invention, a
fabricated hot plate for use in supporting and heating a
web of material traveling over and in contact with the
plate and, more particularly, to such a hot plate for use
in a double facer for the manufacture of corrugated
paperboard, includes a series of elongate metal members,
preferably steel, which have angular cross sectional
shapes, each of which members is positioned with respect
to an adjacent member along abutting contact portions to
define an internal heating fluid channel and a flat
external surface portion, and including fluid-tight
molten metal or suitable adhesive connecting seams which
join the abutting contact portions to form a continuous
flat heating surface from said external surface portions
and a series of parallel heating fluid channels which
underlie the heating surface.
The elongate metal members from which the hot
plate is fabricated may comprise a wide variety of
angular cross sectional shapes which, in one embodiment,
includes upper and lower rectangular plates of
substantially the same shape, area and thickness, each of
which plates provides a flat heating surface, and a
plurality of separator bars disposed in parallel spaced
relation between said plates, each of which bars provides
a contact portion with each of the plates.
In another embodiment, the elongate metal
members include upper and lower rectangular plates,
similar to those of the preceding embodiment, but each of
which plates includes integral separator ribs which are
formed in spaced parallel relation on the side of the
plate opposite the heating surface, with each rib on one
8 ~
plate aligned with a rib on the other plate to provide a
contact portion.
In another embodiment, the elongate metal
members comprise T-section members, each of which
includes a face plate having parallel opposite face plate
edges, and an integral leg plate centered on and
extending perpendicularly to the face plate and having a
leg plate edge parallel to the face plate edges. Each of
the T-section members is positioned inverted with respect
to the adjacent T-section member, and face plate edges
from alternate adjacent members and the leg plate edge
from the inverted member intermediate said alternate
adjacent members provides the contact portions for one
connecting seam.
In yet a further embodiment, similar to the
immediately preceding embodiment, the elongate metal
members comprise C-section members each of which includes
upper and lower face plates with parallel face plate
edges and an integral leg plate extending perpendicularly
to and having upper and lower edges interconnecting the
face plates. The face plate edges of one C-section
member and the upper and lower edges of the leg plate of
the adjacent member provide the abutting contact portions
for the connecting seams.
Each of the foregoing embodiments of the
fabricated hot plate preferably includes a pair of
heating fluid distribution manifolds, each of which is
mounted to one lateral edge of the hot plate and connects
the open ends of the fluid channels along the edge to
which it is attached.
In a particularly preferred hot plate
assembly for supporting and heating a paper web, the
assembly includes upper and lower rectangular metal
plates of substantially the same shape, area and
thickness, each of which plates has a smooth outer
surface. A series of metal separator bars are disposed
in parallel spaced relation between and in contact with
2187B11
the plates to form therewith a series of heating fluid
channels which extend, in use, through the assembly in a
direction transverse to the direction of web travel.
Means are also provided for forming a permanent fluid-
tight connecting seam along the contact interfacesbetween each separator bar and the plates. The
connecting seams may be provided by welded or brazed
connections, or even by use of a high strength, heat
resistant epoxy-adhesive.
The hot plate assembly also preferably
includes a pair of heating fluid distribution manifolds,
each connecting the open ends of the heating fluid
channels along one lateral edge of the hot plate
assembly. A lower supporting frame includes a bottom
frame member which is adapted to underlie the hot plate
assembly in parallel vertically spaced relation thereto.
Anchoring means are provided for rigidly interconnecting
the hot plate assembly and the bottom frame member midway
between the manifolds, and additional vertical holddown
means interconnect the manifolds and the lateral edges of
the supporting frame to prevent vertical movement of the
lateral edges of the hot plate assembly and to allow
horizontal lateral movement thereof.
In another embodiment, utilizing the basic
hot plate constructions fabricated with one piece top and
bottom plates, the plates are curved to provide an outer
convex heating surface and a concave opposite surface
separated by a plurality of parallel spaced separator
bars, each of which provides a contact portion for a
connection with each of the plates, and adjacent pairs of
which define with the plates the heating fluid channels
through the plate.
In a further embodiment, the connections
between the metal members may be provided with a suitable
adhesive, such as a high strength, high temperature
resistant epoxy. High temperature and high strength
adhesive connections are particularly well suited for the
21~7811
embodiments of the hot plate utilizing rectangular
plates, but in one further embodiment, the elongate metal
members may comprise tubes. In particular, generally
square or rectangular section tubes may be joined
adhesively side-by-side and covered with a surface layer
of adhesive to provide the active outer web heating
surface.
Brief Description of the Drawings
FIG. 1 is a generally schematic side
elevation of a double facer utilizing the hot plate
assemblies of the present invention.
FIG. 2 is an end elevation, partly in
section, of the preferred embodiment of the hot plate
assembly of the subject invention.
FIG. 3 is an enlarged sectional view of the
hot plate taken on line 3-3 of FIG. 2.
FIG. 4 is an enlarged view taken on line 4-4
of FIG. 1.
FIG. 5 is a sectional view taken on line 5-5
of FIG. 4.
FIGS. 6-8 are sectional views, similar to
FIG. 3, showing three alternate embodiments of the
invention .
FIG. 9 is a sectional view of a modification
of the FIG. 3 embodiment.
FIG. 10 is a partial sectional view, similar
to FIG. 4, showing another embodiment of the invention.
FIG. 11 is a partial sectional view taken on
line 11-11 of FIG. 10.
Detailed Description of the Preferred Embodiments
Referring to FIG. 1, a double facer 10 of
generally conventional construction is shown
schematically and includes a series of hot plates 11
constructed in accordance with the subject invention.
Each of the hot plates 11 is identically fabricated and
performs the same heating function in the manufacture of
a double face corrugated web 12 as is provided by prior
2187811
- 8
art steam chests, described above. Thus, the hot plates
11 provide a flat, substantially continuous heated
surface over which the double face web, formed by joining
a single face corrugated web 13 and a liner web 14, is
conveyed by a holddown belt 15 which is pressed down
against the web 12 by a series of ballast rollers 16. As
also indicated briefly above, the holddown belt 15 and
ballast rollers 16 may be replaced by another type of
holddown apparatus and a separate web drive.
Referring also to FIGS. 2-5, each of the hot
plates 11 of the presently preferred embodiment of the
invention is fabricated from a pair of upper and lower
plates 17 and 18, respectively, which are spaced apart
and interconnected by a series of separator bars 20. The
separator bars are positioned in parallel spaced relation
between the upper and lower plates 17,18 to define a
series of channels 21 for conducting a heating fluid
through the hot plate assembly in a transverse or cross
machine direction with respect to the direction of travel
of the double face web 12 through the double facer 10.
It has been found that the hot plates 11 may
be fabricated using relatively thin steel plates 17 and
18, for example, about 1/8 inch (about 3 mm) in
thickness. The plates are preferably made of stainless
steel to resist corrosion. However, mild steel plates
may also be used, in which case the inside surfaces would
preferably be coated or plated for corrosion protection.
The spacer bars 20 are preferably rectangular in cross
section and, more particularly, square sections of about
1/4 inch (about 6 mm). The abutting contact surfaces 22
between each separator bar 20 and the opposing inside
faces of the plates 17 and 18 provide the interface for
connecting the assembly. By providing continuous
permanent connections along all contact surfaces 22, the
resultant fluid-tight seams provide a series of
independent channels 21 through which the heating fluid,
preferably steam, is applied to heat the plates. The
21818 1 1
thin, lightweight construction of the hot plate 11 not
only provides a lightweight assembly with a corresponding
saving in material costs, but provides a hot plate which
is much more thermally responsive, allowing it to be
heated and/or cooled rapidly. As a result, the heat may
be applied to the overrunning web 12 (or removed
therefrom) much more rapidly resulting in the ability to
control temperature of the web much more precisely.
The presently preferred method of fabricating
the hot plate assembly is by laser welding. A laser
welding tool is moved over one of the plates 17 or 18
directly above and along the length of the underlying
separator bar 20. The weld penetrates through the plate
and into the separator bar to form a continuous fluid-
tight welded seam 23. An inert gas shield is used withthe laser welding tool to prevent oxidation of the molten
base metal. Also, because the weld is formed from the
base metal itself without the addition of weld wire or
rod material, the outer surface of the plate 17 or 18 is
left relatively undisturbed after welding. As a result,
relatively little grinding or finishing is necessary to
provide the smooth outer surface 24 over which the web
travels.
Alternately, fabrication of the hot plate may
be done by brazing. For example, the contact surfaces-22
may be provided with a silver solder/flux composition,
the assembly clamped together, and heated in an oven to
brazing temperature.
As is typical of prior art steam chests, the
hot plates 11 of the present invention have a relatively
long dimension in the cross machine direction in order to
accommodate the maximum width of web to be processed, and
a substantially shorter dimension in the machine
direction or direction in which the web travels over a
parallel series of hot plates. Thus, the long cross
machine direction length of the plate may be as long as
96 inches (about 245 cm), while the narrower machine
21 8~
direction width of the plate will typically be in the
range of 18-24 inches (about 45-60 cm).
A manifold 25 is mounted to extend along each
of the opposite lateral edges of the hot plate 11 to
enclose the ends of the channels 21 and provide a common
header for supplying steam to all of the channel ends on
one plate edge and a common condensate collection header
for the channel openings on the opposite lateral edge of
the plate. Thus, the manifolds each have a length
approximately equal to the shorter machine direction
dimension of the hot plate. Each manifold 25 is
preferably formed from a pair of substantially identical
manifold portions 26 of generally L-shaped cross section
and, which when connected together and to the top plate
define a longitudinal through bore 27 of generally
rectangular cross section. The outer edges of the
manifold portions 26 are secured together with a series
of machine screws 28 with the joint between the abutting
faces of the manifold portions sealed with an appropriate
sealing material 30. The inside edges of the manifold
portions are interconnected through the lateral edge of
the hot plate 11 with a series of machine screws 31
positioned so that each screw extends through aligned
holes in the upper and lower plates 17,18 and the
intermediate separator bar 20, all as best seen in FIG.
4. The interfaces between the manifold portions and the
upper and lower plate surfaces are similarly sealed with
appropriate gaskets or sealing material 32 which extends
the full length of the manifold. The manifolds may be
welded to the plates in lieu of the bolted attachments.
The use of continuous welded seams would also obviate the
need for sealing gaskets. The manifold through bore 27
provides open communication with the open ends of all of
the channels 21 on one edge of the hot plate. A steam
supply or condensate drain opening 33 is provided
centrally in the lower face of each manifold 25.
Preferably and for reasons which will be discussed
2187811
hereinafter, a steam/condensate opening 33 is provided in
each of the upper and lower manifold portions 26, and
each opening is tapped to receive the threaded sleeve 34
of an adaptor union 35, or a threaded plug 36 if not
S being used. The lower end of the union 35 is interiorly
threaded to receive the threaded end of a steam supply
line 29. The similar opening 33 in the manifold on the
opposite edge of the hot plate would be connected to a
condensate return line 49. Steam supplied to the
manifold 25 is distributed along the through bore 27,
into and through each of the channels 21 to the
condensate collecting manifold on the opposite side of
the plate. The ends of the through bore 27 are sealed
with appropriate plugs 37.
The entire hot plate assembly, including the
upper and lower plates 17,18, separator bars 2 0 and
manifolds 25, is mounted on a lower supporting frame 38.
The supporting frame is constructed and connected to the
hot plate assembly in a manner permitting unrestricted
20 lateral thermal expansion of the hot plate, but
restricting vertical upward bowing of the lateral edges,
as described above with respect to the prior art. The
underside of the lower plate 18 is preferably insulated
from the lower supporting frame 3 8 by an insulating layer
25 39. The insulating layer 39 rests on a flat metal bottom
plate 40 which also defines the upper surface of the
supporting frame 38. The bottom plate 40 may, for
example, comprise a 1/4 inch (6 mm) rectangular steel
plate of approximately the same area as the underside of
30 the hot plate. The bottom plate 40, in turn, rests on a
box-like frame constructed from a pair of L-shaped side
angle members 41 interconnected by a pair of inverted L-
shaped cross members 42. The angle members 41 and cross
members 42 may be suitably connected with welds or any
35 other convenient connecting mechanism, and the bottom
plate 40 is similarly secured to the upper edges or faces
of the members 41 and 42.
2187~1
The fabricated hot plate 11 is fastened to
the bottom plate 40 of the lower supporting frame 38
midway between the manifolds with a pair of anchor
brackets 43 located at the forward and rearward edges of
the hot plate. Each anchor bracket 43 is secured at its
lower edge to the upper face of the bottom plate 40 with
a pair of machine screws 44. The top edge of the anchor
bracket is similarly secured to the lower plate 18 of the
hot plate assembly with a pair of machine screws 45 which
extend through the entire assembly, including the upper
plate 17, separator bar 20 and lower plate 18 for receipt
in threaded holes in the anchor bracket 43.
Although the uniform cross sectional
construction of the hot plate 11 of the present invention
minimizes the tendency for upward bowing of the outer
edges as a result of differential thermal expansion, as
is typical of prior art steam chests, it is nonetheless
preferable to provide a mechanism to inhibit the
possibility of any such bowing. Thus, both edges of the
hot plate are secured to the horizontal flange 46 of the
L-shaped side members 41 with a series of tie bolts 47
which are threaded into the lower surface of the manifold
25. As shown in FIG. 2, the horizontal flanges 46 are
provided with bolt holes 48 which are elongated in the
lateral cross machine direction to accommodate lateral
thermal elongation of the hot plate 11 while holding the
hot plate edges from bowing upwardly.
The symmetrical construction of the hot plate
11, using identical upper and lower plates 17 and 18,
allows the plate to be inverted after the original upper
plate has become worn in service. The various threaded
connections utilizing tie bolts 47 and machine screws 45
allow easy and rapid disassembly of the hot plate from
the lower supporting frame 38 to permit the plate to be
inverted to present a new upper plate surface.
Preferably, the manifolds 25 are left in place and the
threaded adaptor union 35 in the lower manifold portion
21 87~11
13
26 is exchanged for the threaded plug 36 in the
corresponding upper manifold portion 26. In this case,
threaded bores for the tie bolts 47 would also have to be
provided in the upper manifold portions for inverted
repositioning, as indicated. Alternately, the hot plate
11 could be inverted by disassembling the two piece
manifolds 25 from each lateral edge, removing the central
holddown machine screws 44, and inverting and reattaching
the plate to the manifolds and anchor brackets 43 as
previously described.
FIG. 6 shows a hot plate constructed in
accordance with an alternate embodiment of the invention.
In this construction, a pair of identical upper and lower
plates 51 and 52 having the same shape and area, as well
as a nominal thickness of about 1/8 inch (3 mm), as
previously described with respect to plates 17 and 18,
are formed with integral separator ribs 53 positioned in
spaced parallel relation on one side of the plate. The
separator ribs 53 may be formed by extrusion, machining,
casting, or any other convenient manner. The ribs
provide the same function as the separator bars 20
previously described, but have the advantage of having
only one abutting contact interface 54 to be connected by
welding, brazing, or a similar process. For example, the
welded interface 54 may be provided by a resistance
welding process in which high current-carrying electrode
wheels travel together on opposite sides of the plate
along the path of the separator ribs 53 while being
forced toward one another under a high clamping load.
Otherwise, the resulting hot plate 50 may be attached to
manifolds 25 and a supporting frame 38 in the same manner
previously described.
In FIGS. 7 and 8 there are shown two further
embodiments of a fabricated hot plate which also utilize
elongate metal component members of angular cross
sectional shape, but which are not of rectangular cross
section nor do they utilize one-piece upper and lower
. ~
Zl 8181 1
plate components. Nevertheless, when assembled as
hereinafter described, the resultant hot plates are
functionally the same as the two previously described
embodiments and may likewise utilize the same manifold
construction, connection and supporting frames previously
described. Also, the plates of the FIG. 7 and 8
embodiments are fully invertible in the same manner
already described.
In FIG. 7, the hot plate 55 is formed from a
series of elongate C-section members welded together to
define identical upper and lower plate surfaces 56 and 57
separated by a series of individual steam channels 58
running through the plate in the cross machine direction
transverse to the direction of web travel. Each C-
section member 56 comprises an upper face plate 61 and alower face plate 62 interconnected by an integral leg
plate 63. The members 56 are positioned with the free
edges 64 of the upper and lower plates 61 and 62 abutting
the respective upper and lower edges of the leg plate 63
to provide the abutting contact interfaces 65 for
appropriate connecting seams. The connections may be
provided, as previously described, by welding, brazing,
or any other suitable molten metal connecting process.
The use of conventional welding techniques may result in
weld material on both plate surfaces 57 and 58 which
would have to be ground flush prior to putting the hot
plate into service. The welded fabrication of the hot
plate 55 may require the addition of one end plate 66 to
close the C-section member 56 at one longitudinal plate
edge, as shown.
In FIG. 8, another embodiment of the
invention comprises a hot plate 67 which is fabricated
from a series of elongate T-section members 68 which are
positioned in serially adjacent alternately inverted
orientation and welded together. Specifically, each T-
section member 68 includes a face plate 70 having
parallel opposite face plate edges 71, and an integral
218781t
leg plate 72 which is centered on and extends
perpendicularly to the face plate and has a free leg
plate edge 73 parallel to the face plate edges 71. The
T-section members are each positioned to be inverted with
respect to the adjacent member 68 so that the face plate
edges 71 of alternate adjacent members and the leg plate
edge 73 from the inverted member intermediate said
alternate adjacent members provide the contact interface
74 for a welded or other connecting seam 75. As with the
FIG. 6 hot plate embodiment, surface build up of material
from the weld seams 75 may have to be ground away to
provide smooth web-engaging plate surfaces 76.
A modified hot plate 77, shown in FIG. 9,
utilizes the same basic components as the hot plate of
FIG. 3. The obvious difference, however, is that the hot
plate 77 includes a convex upper plate 78 and a concave
lower plate 80. These plates are spaced from one another
and interconnected by a series of spaced separator bars
81. The interfaces between the separator bars and the
plates may be connected by welding, brazing, or similar
methods as previously described.
The curved hot plate 77 does not have the
invertability provided by the previously described
embodiments, but provides many potential advantages when
used in a corrugator wet end as a replacement, for
example, for a web preheater. Prior art preheaters are
typically large diameter drums of heavy-walled
construction necessary to comply with pressure vessel
standards. The relatively thin walled construction of
the curved hot plate 77 and the small cross section steam
channels 82 make the construction exempt from pressure
vessel standards (as are all of the hot plate
constructions described herein).
Curved hot plate 77 is preferably fabricated
by using initially curved plates 78 and 80 and welding
the curved plates to the square cross section separator
16
bars 81 using, for example, the laser welding process
described with respect to the FIG. 3 embodiment.
In accordance with a further embodiment of
the invention, adapted particularly to the construction
shown in FIGS. 3-5, the material of the upper and lower
plates 17 and 18 and/or the separator bars 20 may be
selected from a metal other than steel which constitutes
the presently preferred material. Further, welded or
brazed seams may be replaced with suitable adhesives.
For example, the plates and/or separator bars
may be made of aluminum and, if the plates 17 and 18 are
so constructed, their outer surfaces may be provided with
a suitable hard surface cladding to reduce wear. There
are also available high strength, high temperature
resistant epoxy adhesives which may be utilized to join
the plates along the contact surfaces 22 with the
separator bars (or the contact interfaces 54 in the FIG.
6 embodiment). For example, a commercially available
epoxy adhesive is resistant to temperatures as high as
500F (260C) and has a tensile strength of 10,000 psi.
This epoxy also provides outstanding resistance to highly
corrosive liquids.
Another embodiment of the hot plate of the
subject invention which may be assembled utilizing a high
strength, high temperature resistant epoxy adhesive is
shown in FIGS. 10 and 11. The hot plate 83 is
constructed from a series of square section tubes 84
which are joined along adjacent side walls 85 with epoxy
adhesive joints 86. The epoxy material may be extended
beyond the joints 86 to provide continuous upper and/or
lower surface layers 87 which are suitably smoothed to
provide the active web contacting heat transfer surface.
Alternately, the adhesive joints 86 may be provided
individually between adjacent tubes 84 and the upper
and/or lower side walls 88 of the tubes finished to
provide the heat transfer surface (as generally shown and
described with respect to FIGS. 7 and 8). An epoxy
21 87~ 1
17
adhesive of the type generally described herein may also
include a suitable metal filler material to enhance heat
transfer. As shown in ~IG. 10, a two-piece manifold 89
(similar to that shown in FIG. 4) may enclose the ends of
the adhesively connected tubes 84 and be attached thereto
with the same epoxy adhesive.
