EP0768170A1

EP0768170A1 - Fabricated hot plate, particularly for corrugated paperboard making

Info

Publication number: EP0768170A1
Application number: EP96116435A
Authority: EP
Inventors: Carl R. Marschke; Larry M. Krznarich; Eugene C. Carlson; Robert L. Turnquist; Kenneth D. Danielson
Original assignee: Marquip Inc
Current assignee: Marquip Inc
Priority date: 1995-10-13
Filing date: 1996-10-14
Publication date: 1997-04-16
Also published as: JPH09309161A; KR970020411A; CA2187811A1

Abstract

A fabricated hot plate assembly, particularly suited for use in a corrugated paperboard double facer utilizes elongate angular steel components (17,18,20,84,51,52,78,80,81), which may be configured from a wide variety of shapes and assembled using molten metal connecting processes, such as welding and brazing, or high strength, temperature resistant adhesives. The connecting process results, in each embodiment, in a hot plate having two heating surfaces and which is invertible to utilize the second heating surface when the first is worn to the point of replacement. Parallel stream transfer channels through the plates in the cross machine direction are formed in the fabrication process and each embodiment of the hot plate may utilize the same steam supply and condensate collecting manifolds (25) and underlying plate supporting system. Each of the plates may be made of relatively thin material making the hot plates thermally responsive to rapid heating and/or cooling.

Description

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 350°F. (177°C) 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 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 280-290°F (136-143°C). 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.
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.
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.

Summary 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 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 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 interfaces between 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 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 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 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 with the 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 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 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 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 20 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 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 38 by an insulating layer 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 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 other convenient connecting mechanism, and the bottom plate 40 is similarly secured to the upper edges or faces of the members 41 and 42.
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 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 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 a lower 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 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 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 500°F (260°C) 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 adhesive of the type generally described herein may also include a suitable metal filler material to enhance heat transfer. As shown in FIG. 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.

Claims

A fabricated hot plate for use in supporting and heating of a web of material traveling over and in contact therewith, said hot plate comprising:
a series of elongate metal members (17, 18, 20, 84, 51, 52, 78, 80, 81) having angular cross sectional shapes, each of said members positioned with respect to an adjacent member along abutting contact portions (22, 85, 54, 65) to define an internal heating fluid channel (21, 60, 82) and a flat external surface portion; and

fluid-tight molten metal connecting seams joining the abutting contact portions to form a continuous flat heating surface from said external surface portions and a series of parallel heating fluid channels underlying said heating surface.
The hot plate as set forth in claim 1 wherein said elongate metal members comprise:
upper and lower rectangular plates (17, 18) of substantially the same shape, area and thickness, each of said plates providing a flat heating surface; and

separator bars (20) disposed in parallel spaced relation between said plates, each bar providing a contact portion with each of said plates.
The hot plate as set forth in claim 1 wherein said elongate metal members comprise:
upper and lower rectangular plates (51, 52) of substantially the same shape, area and thickness, each of said plates providing a flat heating surface; and

integral separator ribs (53) formed in spaced parallel relation on the side of each plate opposite the heating surface, each rib on one plate aligned with a rib on the other plate to provide a contact portion.
The hot plate as set forth in claim 1 wherein said elongate metal members comprise:
T-section members (70, 72, 68), each having a face plate (70) having parallel opposite face plate edges and an integral leg plate (72) centered on and extending perpendicularly to the face plate and having a leg plate edge parallel to said face plate edges; and,

each of said T-section members being inverted with respect to the adjacent member; and,

face plate edges from alternate adjacent members and the leg plate edge from the inverted member intermediate said alternate adjacent members providing the contact portions for one connecting seam.
The hot plate as set forth in claim 1 wherein the elongate metal members comprise:
C-section members (56), each including upper and lower face plates (61, 62) having parallel face plate edges and an integral leg plate (63) extending perpendicularly to and having upper and lower edges inter-connecting the face plates; and

the face plate edged of one C-section member and the upper and lower edges of the leg plate of the adjacent member providing the abutting portions for the connecting seams.
The hot plate as set forth in claim 1 comprising a pair of heating fluid distribution manifolds (25), each manifold connecting the open ends of the fluid channels along one edge of the hot plate.
A hot plate assembly for supporting and heating a paper web traveling over and in contact with a plate surface comprising:
upper and lower rectangular metal plates (17, 18) of substantially the same shape, area and thickness, each of said plates having a smooth outer surface;

a series of metal separator bars (20) disposed in parallel spaced relation between and in contact with said plates for form therewith a series of heating fluid channels (21) extending, in use, through the hot plate assembly in a direction transverse to the direction of web travel;

means for providing a permanent fluid-tight connecting seam along the contact interfaces between each separator bar and the plates.
The hot plate assembly as set forth in claim 7 wherein the seams are selected from welded and brazed and adhesive connections.
The hot plate assembly as set forth in claim 7 comprising:
a pair of heating fluid distribution manifolds (25) each connecting the open ends of the heating fluid channels along one lateral edge of the hot plate assembly;

a lower supporting frame (38) including a bottom frame member (40) adapted to underlie the hot plate assembly in parallel vertically spaced relation thereto;

anchoring means (43) rigidly interconnecting the hot plate assembly and the bottom frame member midway between the manifolds; and,

vertical holddown means interconnecting 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.
A fabricated hot plate for use in supporting and heating a web of material traveling over and in contact therewith, said hot plate comprising:
a pair of generally rectangular plates (78, 80) of substantially the same shape, each of which is formed to a similar arcuate shape in the direction of web travel to provide an upper plate (78) defining a convex upper web contact surface and a lower plate (80) defining a concave lower outer plate surface;

separator bars (81) of generally rectangular cross section disposed in spaced relation between said plates, each bar providing an abutting contact surface with the inner faces of each of said plates (78, 80); and,

fluid-tight molten metal connecting seams joining the abutting contact portions.
The hot plate as set forth in claim 6 comprising:
a lower supporting frame (38) including a frame member (40) adapted to underlie the hot plate in parallel vertically spaced relation thereto;

anchoring means (43) rigidly interconnecting the hot plate and the frame member midway between the manifolds; and,

vertical holddown means interconnecting the manifolds and the lateral edges of the support frame to restrain the lateral edges of the hot plate against vertical movement and to allow horizontal lateral movement thereof.
The apparatus as set forth in claim 11 wherein said lower supporting frame includes a bottom plate (40) underlying said hot plate in parallel vertical spaced relation thereto; and,
further including a layer of insulation (39) between said bottom plate and said hot plate.
A fabricated hot plate for use in supporting and heating of a web of material traveling over and in contact therewith, said hot plate comprising:
a series of elongate metal members (17, 18, 20, 84, 51, 52, 78, 80, 81, 70, 71, 63) having angular cross sectional shapes, each of said members positioned with respect to an adjacent member along abutting contact portions to define internal heating fluid channels (21, 82, 60) and a flat external surface portion; and,

connecting means for joining the abutting contact portions to form a continuous flat heating surface from said external surface portions and a series of parallel heating fluid channels underlying said heating surface.
The hot plate as set forth in claim 13 wherein said connecting means comprises epoxy adhesive joints.
The hot plate as set forth in claim 13 wherein said elongate metal members comprise square section tubes (84).