WO1999024249A1

WO1999024249A1 - Corrugated paperboard manufacturing apparatus and method for enhancing heat transfer to an advancing corrugated paperboard sheet

Info

Publication number: WO1999024249A1
Application number: PCT/US1998/023926
Authority: WO
Inventors: Anthony J. Sissons; David Alan Thomas
Original assignee: Interfic, Inc.
Priority date: 1997-11-10
Filing date: 1998-11-10
Publication date: 1999-05-20
Also published as: AU1315399A

Abstract

An apparatus and method for manufacturing corrugated paperboard includes a heating section such as a plurality of steam heat chests (62) used in a double-facer for defining a heating surface. A take-up mechanism (35) is positioned downstream from the heating surface for advancing a corrugated paperboard sheet along a predetermined path of travel adjacent the heating surface. The take-up mechanism draws the corrugated paperboard sheet along the path of travel adjacent the heating surface (31). A plurality of flexible sheets (34) are positioned in side-by-side relation opposite the heating surface and transversely across the predetermined path of travel and longitudinally along the path of travel for slidably contacting and applying pressure to urge the advancing corrugated paperboard sheet against the heating surface so that heat is transferred from the heating surface to the advancing corrugated paperboard sheet. A support structure supports the plurality of flexible sheets in the position above the path of travel and includes movable support frames that carry the flexible sheets. The movable support frames are movable in a vertical direction to control the pressure applied onto each of the respective flexible sheets against the advancing corrugated paperboard sheet.

Description

CORRUGATED PAPERBOARD MANUFACTURING APPARATUS AND METHOD FOR ENHANCING HEAT TRANSFER TO AN ADVANCING CORRUGATED PAPERBOARD SHEET

Field of the Invention

The present invention relates to the field of corrugated paperboard manufacturing, and more particularly, to an apparatus and method for enhancing heat transfer from the heating surface of a double- facer to an advancing corrugated paperboard sheet . Background of the Invention

Corrugated paperboard is widely used as a material for fabricating containers and for other packaging applications. Corrugated paperboard is strong, lightweight, relatively inexpensive, and may be recycled. Conventional corrugated paperboard is constructed of two opposing liners and an intervening fluted sheet secured together using an adhesive. The adhesive is typically a starch-based adhesive applied as a liquid. Accordingly, heat is transferred to the paperboard to dry or set the adhesive during the manufacturing of the paperboard.

A conventional so-called double-facer for setting the adhesive includes a series of steam heating chests over which the paperboard is advanced. A conveyor belt engages the upper surface of the board and advances the board along the heating chests. A series of rolls is typically used to provide backing pressure to the back side of the conveyor belt.

Accordingly, the paperboard is pressed into contact with the underlying steam heating chests.

Unfortunately, the steam heating chests have a tendency to bow or deflect due to temperature differences thereby producing low quality paperboard. This problem is explained in greater detail in U.S. Patent No. 5,456,783 to Sissons. The Sissons patent discloses a significant advance in the art of corrugated paperboard manufacturing wherein a series of contact assemblies provide backing pressure to the conveyor (or traction) belt rather than conventional backing rolls. The contact assemblies include independently mounted and biased contact shoes, mounted in side-by-side relation. The contact shoes can readily conform to any bowing of the steam heating chests. The contact assemblies are readily installed, and operated with greatly reduced maintenance, especially compared to conventional backing rolls and their associated bearings. Because heat transfer to the paperboard is also increased, fewer heating chests may be used and ambient energy losses reduced further.

A conveyor belt is not always desirable, however, for advancing the paperboard over the heating surface defined by the heating chests. The conveyor belt often absorbs much heat and moisture creating production difficulties, and increasing maintenance costs .

U.S. Patent No. 5,256,240 to Shortt discloses a plurality of fluid filled bladders for applying the backing pressure to a conveyor belt of a double-facer . The Shortt patent discloses that in certain applications the conveyor belt may be omitted; however, the patent fails to disclose how to advance the corrugated paperboard sheet along its path of travel against the heating chests without a conveyor belt. Also, the disclosed bags can bear upon a thin steel plate that is loosely pivotable about a transverse rod at its upstream end in relation to the direction of travel of the board. This system provides some flexibility in pressure application against the advancing paperboard sheet, but the amount of applied pressure is limited by the pivoting motion about the one transverse rod positioned at the upstream end.

Other prior art systems disclose improved pressure application systems, but they have limited control and sometimes work in conjunction with an undesirable conveyor (or traction) belt. For example, U.S. Patent No. 5,466,329 to Marschke discloses a variable load ballast in a double-facer where hold-down ballast members are positioned in side-by-side relation transversely across the belt. The rows are divided into longitudinal segments controlled by a vertical actuator, which moves the segments between a full-load ballast position on the belt and an upper no-load position. The various ballast members are formed from rollers or a flexible membrane, which varies the load on the hold-down belt. Thus, forces are generated from the ballast members onto the hold- down belt and then onto the corrugated paperboard, adding to the complexity of the process. This undesirable hold-down belt further adds to the problems described above because the use of a moving belt increases maintenance costs .

U.S. Patent No. 5,561,918 to Marschke discloses another double- facer for securing the adhesive in a corrugated paperboard manufacturing system where no driven hold-down belt or similar conveyor belt is used. The paperboard sheet is pulled through the double-facer by a downstream conveyor section formed from transport belts. The apparatus discloses longitudinal strips extending the length of the heating section of the double- facer . Each of the strips is attached at the upstream end to a rotatable drum, which is supported for rotation on a horizontal axis extending in the cross machine direction. The drums are unrolled to lengthen each strip. Although this system discloses no hold-down belt, the strips are limited in use by the pressure applied along the entire strip at individual sections. Also the mechanism used for unrolling the strips and the associated controls for operating the strips can be complicated.

Summary of the Invention It would be advantageous if a double-facer used no conveyor system over the heating surface, and also allowed greater control over the pressure applied onto the advancing corrugated paperboard sheet .

In view of the foregoing background, it is therefore an object of the present invention to enhance heating uniformity in the double facer for setting the adhesive without the drawbacks of elongate strips that extend across the entire length of the heating section, while also providing adequate pressure control without undue system complexity.

It is another object of the present invention to provide an apparatus and associated method for manufacturing corrugated paperboard having a pressure application mechanism that is relatively straight- forward in design and slidably contacts and applies pressure to urge the advancing corrugated paperboard sheet against a heating surface in the heating section of a double-facer.

These and other objects, features and advantages of the present invention are provided by an apparatus and associated method for manufacturing corrugated paperboard, which includes a heating means for defining a heating surface, such as typically found with a double-facer in corrugated paperboard manufacturing. A take-up means is positioned downstream from the heating surface for advancing a corrugated paperboard sheet along a predetermined path of travel adjacent to the heating surface. A leading portion of the corrugated paperboard sheet is initially fed along a predetermined path of travel adjacent the heating surface and pulled by the take-up means positioned downstream from the heating surface. A plurality of flexible sheets are positioned opposite the heating surface and positioned transversely in side-by-side relation across the predetermined path of travel and longitudinally along the path of travel for slidably contacting and applying pressure to urge the advancing paperboard sheet against the heating surface so that heat is transferred from the heating surface to the advancing corrugated paperboard sheet. The plurality of flexible sheets are supported by appropriate support means, and pressure means applies pressure onto each of the respective flexible sheets and against the advancing corrugated paperboard sheet .

In one aspect of the present invention, the flexible sheets include edge portions transverse to the predetermined path of travel and the support means comprises means for supporting the flexible sheets along the transverse edge portions. The support means can include a fixed frame, and a plurality of movable support frames carrying the flexible sheets. Drive means is supported by the fixed frame and connected to the movable support frames for vertically moving the movable support frames and, in turn, changing the applied pressure of the flexible sheets against the advancing corrugated paperboard sheets. The movable support frames can be spaced apart about the distance of one flexible sheet in the longitudinal direction so that a flexible sheet will be supported between two movable support frames . In still another aspect of the present invention, the drive means includes a motor supported by the fixed frame and a transmission interconnecting the motor and the movable support frames. The transmission can include vertical drive shafts for raising and lowering the movable support frames. In yet another aspect of the present invention, weight means applies pressure against the flexible sheets . Such weight means can include a plurality of weight plates that engage the flexible sheets . The support means also can include a chain and a fastener means such as bolts carried by the chain for supporting the weight plates against the flexible sheets .

In still another aspect of the present invention, the heating surface defining means comprises at least one steam heating means, such as a steam chest, and at least one infrared heating means, such as an infrared heater. The take-up means can comprise first and second opposing traction belts and an associated drive for engaging and pulling the corrugated paperboard sheet along the path of travel . The associated method for manufacturing corrugated paperboard in accordance with the present invention comprises the steps of advancing a corrugated paperboard sheet along a predetermined path of travel adjacent a heating surface in a double-facer by drawing the corrugated paperboard sheet from a take-up mechanism positioned downstream from the heater surface. A plurality of flexible sheets are supported opposite the heating surface so that the flexible sheets are positioned transversely in side-by-side relation across the predetermined path of travel and longitudinally along the path of travel. In accordance with the present method, flexible sheets are positioned against the advancing corrugated paperboard sheet and slidably contact and apply pressure on the advancing corrugated paperboard sheet to press the sheet against the heating surface so that heat is transferred from the heating surface to the advancing, corrugated paperboard sheet .

Brief Description of the Drawings Other objects, features and advantages of the present invention will become apparent from the detailed description of the invention which follows, when considered in light of the accompanying drawings in which:

FIG. 1 is a schematic side view diagram of the apparatus in accordance with the present invention; FIG. 2 is a side elevation view showing the steam chest section, the advancing corrugated paperboard sheet, and the fixed frame holding a movable support frame, which carries a flexible sheet;

FIG. 3 is a sectional view taking along line 3-3 of FIG. 2 showing a movable support frame and the interconnection of a support chain and flexible sheet to the movable support frame;

FIGS. 4a-4c are schematic side elevational diagrams, illustrating how pressure can be applied to various flexible sheets and onto the advancing corrugated paperboard, while the pressure applied onto other flexible sheets could be reduced;

FIGS. 4d-4f are schematic elevational diagrams, illustrating how pressure could be varied on a flexible sheet by raising or lowering the movable support frame so that the amount of weight generated by the weight members on a flexible sheet can vary; and

FIG. 5 is a perspective view of a portion of the apparatus illustrating how the support chain is connected to the weight members and resting on a flexible sheet.

Detailed Description of The Preferred Embodiments

The present invention will now be described more fully with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, like numbers refer to like elements throughout .

The corrugated paperboard apparatus 20 in accordance with the present invention is initially explained with reference to FIG. 1. The apparatus 20 includes one or more preheaters 22 positioned upstream from a double-facer 25. A glue or adhesive station 23 is positioned between the preheaters 22 and the double- facer 25. The glue station 23 applies glue to the flute tips of the single-faced sheet 21 and joins the single-faced sheet to the liner 24. The formed corrugated paperboard sheet 28 advances along the predetermined path of travel 29 over the heating section 30, where the corrugated paperboard sheet is pressed against the heating surface 31 for setting the adhesive. Backing pressure is provided by the series of schematically illustrated flexible sheet means, which includes a plurality of flexible sheets 34 that are aligned transverse in side-by-side relation (FIG.2) and longitudinally along the path of travel 29, described in greater detail below. In one embodiment, five flexible sheets 34 are positioned in side-by-side relation transverse across the path of travel .

Take-up means 35 is provided downstream from the double-facer 25 to draw the corrugated paperboard sheet 28 along the predetermined path of travel through the double- facer . The take-up means includes the illustrated set of upper rolls 37, 40, and 41 over which the upper traction belt 43 is guided. A lower traction belt 45 is similarly guided over the illustrated lower rolls 46,47 , and 50. A motor 52 drives the lower traction belt 45, and may also drive the upper belt 43 in synchronization with the lower belt, and under the control of the illustrated controller 53 as would be readily understood by those skilled in the art. To enhance take-up, the traction belts in the take-up means preferably are formed to have a high coefficient of friction surface coating to enhance the ability of the belts to grasp the corrugated paperboard sheet .

The preheater 22 typically may include an electrically powered infrared heater (not shown) for heating the preheater body so that heat is transferred to a liner contacting a first surface portion of the body as the liner is advanced along the path of travel to the double-facer 25. Further details of the preheater and its structure can be found in the above identified and incorporated by reference co-pending patent application serial number 08/731,534, filed October 16, 1996, assigned to the assignee of the present inventor and the entire disclosure of which is incorporated herein by reference. As further illustrated in FIG. 1, the beltless operation of the double-facer 25 is shown in detail . Because the conventional conveyor belt is not used to advance the paperboard sheet 28 over the heating section 30, the present invention provides the take-up means 35 downstream from the heating section 30 for advancing the corrugated paperboard sheet along its desired path of travel adjacent the heating surface 31 of the heating section 30.

Typically, the paperboard sheet can be advanced manually to the take-up means 35. However, as disclosed in Figures 5-8 of the incorporated by reference '534 application, an initial sheet feeding means can initially feed a leading portion of the corrugated paperboard sheet 28 along the path of travel. The initial sheet feeding means may be provided in one embodiment by a pair of opposing upper and lower rolls and an associated drive motor. The rolls are positioned upstream of the heating surface 31 for initially engaging and advancing the leading portion of the corrugated paperboard sheet into the double-facer. The leading edge is first manually advanced and a power cylinder is lowered to bring the upper roll into an engagement with the sheet . The lower roll is rotated to advance the leading edge of the sheet to the take-up means.

In yet another embodiment of the initial sheet feeding means as disclosed in the incorporated by reference '534 application, a board engaging mechanism is provided for engaging the leading portion of the corrugated paperboard sheet. A board engaging mat is positioned in overlying relationship with the leading portion of the corrugated paperboard sheet and frictionally engages the sheet to advance the sheet to the take-up means 35. The mat is advanced to a raised or storage position, after the initial feeding is completed.

Referring again to FIG. 1, the heating section 30 further comprises a steam chest section 80 formed from a plurality of serially aligned steam chest 82, followed by an infrared heating section 84, which includes an infrared heater that generates greater heat typically than a steam chest 82. It should be understood by those skilled in the art that the infrared heating section 84 can be placed downstream or upstream of the steam chest section 80 or between steam chests .

As further illustrated in FIG. 1, a plurality of flexible sheets 34 are positioned opposite the heating surface 31 as defined by the steam chest section 80 and infrared heating section 82 and positioned transversely in side-by-side relation across the predetermined path of travel and longitudinally in series along the path of travel (FIGS. 1, and 4a-4c) . The flexible sheets 34 slidably contact the advancing corrugated paperboard sheet and apply pressure to urge the advancing corrugated paperboard sheet against the heating surface 31 so that the heat is transferred from the heating surface to the advancing corrugated paperboard sheet . The flexible sheets are formed from thin sheet steel or similar material, which has flexibility, appropriate heat transfer characteristics, and strength to apply pressure to the advancing corrugated paperboard sheet without weakening.

Support means, indicated generally at 88, supports the plurality of flexible sheets in a position above the path of travel. Pressure means, indicated generally at 89, applies pressure against the respective flexible sheets and, in turn, applies pressure against the advancing corrugated paperboard sheet (FIG.2) . The pressure means 89 can vary the amount of pressure applied by one flexible sheet 34 against the advancing corrugated paperboard sheet by raising or lowering the flexible sheet as shown in FIGS. 4d-4f. Additionally, the total pressure applied by one flexible sheet can be increased, while the total pressure applied by another flexible sheet can be reduced so that the pressure applied against various portions of the advancing corrugated paperboard sheet is varied as shown in FIGS. 4a-4c. It is also possible to change the pressure applied at one end of a respective flexible sheet with respect to the other end by lowering one end or raising the other end along the longitudinal direction. In general, the pressure is uniform across the width of each shee . In some instances, side-by-side adjustment could also be varied to change the pressure applied from one side of a flexible sheet to another. The illustrated embodiment shows a structure where the sheets move vertically.

Referring now to FIGS. 2, 3, and 5, details of the support means 88 and its supporting connection to a flexible sheet, and the pressure means 89, are shown in detail. A fixed frame 90 is formed of longitudinally extending opposing supports 90a and extends longitudinally along the heating section 31.

Fixed frame cross-piece members 90b (shown in dashed lines in Figure 2) extend across the longitudinally extending supports, forming an open, rectangular support structure . In one aspect of the present invention, the fixed frame supports a plurality of movable support frames 92, which are spaced apart from each other in the longitudinal direction about the distance of one flexible sheet 34. The movable support frames are formed from opposing cross-piece members 92a, 92b extending transverse to the path of travel, and longitudinally extending support members 93 connected to the cross-piece members. The movable support frames form an open frame unit having opposing transverse ends formed by the cross-piece members 92a,

92b.

Each cross-piece member of the fixed frame 90 forms a rectangular configured fixed frame spaced a vertical distance over the rectangular configured movable support frame. Each rectangular configured fixed frame supports opposing drive motors 94, 94a positioned on central portions of the cross-piece members 90b and a horizontal output shaft 98 interconnecting the motors 94, 94a. The motors 94, 94a connect via respective transversely extending shafts 96 to gear boxes 100 positioned at each corner of the rectangular configured fixed frame 90. Vertical drive shafts 99 extend from respective gear boxes 100 downward and connect into the top portion of the movable support frame 92 at respective corners adjacent the transverse cross-piece members 92a, 92b. An appropriate fastener means, such as a threaded opening 104 receives threaded ends of the vertical drive shafts

99.

The controller 53 allows operator control over the drive motors 94, 94a to control vertical movement of the respective transverse ends formed by the cross-piece members 92, 92b so as to vary the pressure applied by the flexible sheets 34 against the advancing corrugated paperboard sheet . Although drive motors 92, 92a are illustrated for moving a respective movable support frame 92, it should be understood that various drive means and transmission systems can be used as known by those skilled in the art, so that fewer drive motors are required, for example.

As shown in FIG. 2, flexible sheets 34 also include longitudinal ends 110 extending transverse to the path of travel. The first flexible sheet in the longitudinal series, and also in the last in the series, the ends 110 are connected to one cross-piece member 92a of a respective movable support frame by a respective fastening means 112, such as bolts 112a,

112b. The same flexible sheet is connected at its other end to the opposing transverse cross-piece member 92b of the movable support frame 92 by a pivotally mounted connecting member 114 carried by the movable support frame 92. The movable support frames 92 are spaced about the distance of one flexible sheet so that opposing transverse ends formed by the cross-piece members 92a, 92b of those movable support frames that oppose each other have pivotally mounted connecting members 114 located at their ends. Thus, the number of movable support frames used in the apparatus is reduced. Weight means, indicated generally at 116, applies pressure against the flexible sheets 34 so that as a movable support frame 92 is lowered, the amount of pressure borne against the advancing corrugated paperboard sheet is varied (FIG. 2 and 5) . The weight means 116 comprises a plurality of weight plates 118 that engage a respective flexible sheet. The weight plates 118 are illustrated as thin, substantially rectangular (illustratively shown as square) weight plates, preferably formed from steel or other similar heavy material. The weight plates 118 are positioned against the flexible sheet and held by a chain 120 carried by a respective movable support frame 92, and held thereto by the fastening means 121, bolts 121a and fastener 121b (FIG.3). Although only substantially rectangular weight plates are illustrated, other weight means similar to weight plates can be used as known to those skilled in the art.

The chain 120 is fastened at its chain end to one transverse cross-piece of the movable support frame and to the pivotal connecting member 114 as shown in

FIG. 2. Appropriate bolt fasteners 122 as shown in

FIG.5 extend through the chain links 124 into respective weight plates 118. The weight plates 118 press freely against the flexible sheet, but are not connected thereto. Other fastening means can be used as suggested to those skilled in the art.

In operation, the machine operator observes the corrugated paperboard sheet manufacturing operation and through appropriate controlled feedback or visual observation, will lower or raise an appropriate movable support frame 92 so that pressure can be varied against a particular area along the heating surface 31 and onto the advancing corrugated paperboard sheet. Adjustments will be made as required during the manufacturing process so that individual flexible sheets are varied, changing the applied pressure, as necessary. In some instances, an automatic computer controller can accept feedback from a sensor or other control means (not shown) and make appropriate adjustments to the manufacturing process as necessary.

The use of flexible sheets and weighted members are advantageous because the "cookie pan" type of sheet arrangement has limited moving parts as compared to the endless conveyor belt and backing pressure rolls, and is simple in design, and cost effective. This design also is efficient in greatly varying the desired amount of pressure that can be applied to selected sections of the heating surface so that the necessary pressure can be applied to the advancing corrugated paperboard sheet at the proper positions on the heating surface to counter any warpage or "bow" on the heating surface.

Many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that the modifications and embodiments are intended to be included within the scope of the appended claims .

Claims

THAT WHICH IS CLAIMED IS:

1. An apparatus for manufacturing corrugated paperboard, said apparatus comprising: heating means for defining a heating surface; take-up means positioned downstream from the heating surface for advancing a corrugated paperboard sheet along a predetermined path of travel adjacent the heating surface; a plurality of flexible sheets positioned opposite the heating surface and positioned transversely across the predetermined path of travel and longitudinally along the path of travel for slidably contacting and applying pressure to urge the advancing corrugated paperboard sheet against the heating surface so that heat is transferred from the heating surface to the advancing corrugated paperboard sheet ; support means for supporting the plurality of flexible sheets; and pressure means for applying pressure onto each of the respective flexible sheets against the advancing corrugated paperboard sheet .

2. An apparatus according to claim 1 wherein said flexible sheets include edge portions transverse to the predetermined path of travel, and said support means comprises means for supporting said flexible sheets along said edge portions in side-by- side relation.

3. An apparatus according to claim 1 wherein said support means includes a fixed frame, a plurality of movable support frames, and means connecting said flexible sheets to said movable support frames .

4. An apparatus according to claim 3 wherein said movable support frames are spaced apart the distance of one flexible sheet in the longitudinal direction.

5. An apparatus according to claim 3 wherein said pressure means includes a motor supported by said frame, and transmission means interconnecting said motor and said movable support frames for vertically moving said movable support frames and changing the applied pressure of the flexible sheets against the corrugated paperboard sheet .

6. An apparatus according to claim 5 wherein said transmission means comprises vertical drive shafts for raising and lowering the movable support frames.

7. An apparatus according to claim 1 wherein said pressure means includes weight means for applying weight against the flexible sheets .

8. An apparatus according to claim 7 wherein said weight means comprises a plurality of weight plates that engage the flexible sheets.

9. An apparatus according to claim 8 including a chain and fastening means for fastening said weight plates to said chain.

10. An apparatus according to claim 9 wherein said fastening means further comprises bolts for engaging and fastening said weight plates to said chain.

11. An apparatus according to claim 1 wherein said take-up means comprises at least one traction belt and an associated drive for engaging and pulling the corrugated paperboard sheet along the path of travel .

12. An apparatus according to claim 11 wherein said traction belt has a coefficient of friction to aid in engaging and pulling the corrugated paperboard sheet along the path of travel .

13. An apparatus according to claim 11 further comprising at least one air bearing positioned adjacent said at least one traction belt for providing backing pressure thereto.

14. An apparatus according to claim 1 wherein said heating surface defining means comprises at least one steam heating chest.

15. An apparatus according to claim 1 wherein said heating surface defining means comprises at least one infrared heater.

16. An apparatus according to claim 1 wherein said take-up means comprises first and second opposing traction belts and associated drives for engaging and pulling the corrugated paperboard sheet along the path of travel .

17. An apparatus for manufacturing corrugated paperboard, said apparatus comprising: heating means for defining a heating surface; means for advancing a corrugated paperboard sheet along a predetermined path of travel adjacent the heating surface; a plurality of flexible sheets positioned opposite the heating surface and positioned transversely across the predetermined path of travel and longitudinally along the path of travel for slidably contacting and applying pressure to urge the advancing corrugated paperboard sheet against the heating surface so that heat is transferred from the heating surface to the advancing corrugated paperboard sheet ; support means for supporting the plurality of flexible sheets; and pressure means for applying pressure onto each of the respective flexible sheets against the advancing corrugated paperboard sheet .

18. An apparatus according to claim 17 wherein said means for advancing a corrugated sheet along a predetermined path of travel further comprises take-up means positioned downstream from the heating surface for advancing a corrugated paperboard sheet along a predetermined path of travel adjacent the heating surface.

19. An apparatus according to claim 17 wherein said flexible sheets include edge portions transverse to the predetermined path of travel, and said support means comprises means for supporting said flexible sheets along the transverse edge portions in side-by-side relation.

20. An apparatus according to claim 17 wherein said support means includes a frame, a plurality of movable support frames and means connecting said flexible sheets to said movable support frames .

21. An apparatus according to claim 20 wherein said movable support frames are spaced apart the distance of one flexible sheet in the longitudinal direction.

22. An apparatus according to claim 20 wherein said pressure means includes a motor supported by said frame, and transmission means interconnecting said motor and said movable support frames for vertically moving said movable support frames and changing the applied pressure of the flexible sheets against the corrugated paperboard sheet .

23. An apparatus according to claim 22 wherein said transmission means includes drive shafts for raising and lowering the movable support frames.

24. An apparatus according to claim 17 wherein said pressure means includes weight means for applying weight against the flexible sheets.

25. An apparatus according to claim 24 wherein said weight means comprises a plurality of weight plates that engage the flexible sheets.

26. An apparatus according to claim 25 including a chain and fastening means for fastening said weight plates to said chain.

27. An apparatus according to claim 26 wherein said fastening means further comprises bolts for securing said weight plates to said chain.

28. An apparatus according to claim 17 including take-up means comprising at least one traction belt and an associated drive for engaging and pulling the corrugated paperboard sheet.

29. An apparatus according to claim 28 further comprising at least one air bearing positioned adjacent said at least one traction belt for providing backing pressure thereto.

30. An apparatus according to claim 28 wherein said traction belt has a coefficient of friction to aid in engaging and pulling the corrugated paperboard sheet along the path of travel.

31. An apparatus according to claim 17 wherein said heating surface defining means comprises at least one steam heating chest.

32. An apparatus according to claim 17 wherein said heating surface defining means comprises at least one infrared heater.

33. An apparatus for manufacturing corrugated paperboard, said apparatus comprising: heating means for defining a heating surface; take-up means positioned downstream from the heating surface for advancing a corrugated paperboard sheet along a predetermined path of travel adjacent the heating surface; a plurality of flexible sheets positioned opposite the heating surface and positioned transversely across the path of travel and longitudinally along the path of travel for slidably contacting and applying pressure to urge the advancing corrugated paperboard sheet against the heating surface so that heat is transferred from the heating surface to the advancing corrugated paperboard sheet; support means for supporting the flexible sheets opposite the heating surface; weight means for applying downward pressure against the flexible sheets; and means for controlling the pressure applied onto each of the respective flexible sheets by the weight means against the advancing corrugated paperboard sheet .

34. An apparatus according to claim 33 wherein said weight means comprises a plurality of weight plates that engage the flexible sheets .

35. An apparatus according to claim 34 including a chain and fastening means carried by said chain for fastening said weight plates to said chain.

36. An apparatus according to claim 35 wherein said fastening means further comprises bolts for securing said weight plates to said chain.

37. An apparatus according to claim 33 wherein said means for advancing a corrugated sheet along a predetermined path of travel further comprises take-up means downstream from the heating surface for advancing a corrugated paperboard sheet along a predetermined path of travel adjacent the heating surface .

38. An apparatus according to claim 33 wherein said flexible sheets include edge portions transverse to the predetermined path of travel, and said support means comprises means for supporting said flexible sheets along the transverse edge portions.

39. An apparatus according to claim 33 wherein said support means includes a fixed frame, and a plurality of movable support frames supporting said flexible sheets, and including drive means supported by said frame and connected to said support plates for vertically moving said support plates and changing the applied pressure of the flexible sheets against the advancing corrugated paperboard sheet .

40. An apparatus according to claim 39 wherein said movable support frames are spaced apart the distance of one flexible sheet in the longitudinal direction .

41. An apparatus according to claim 39 wherein said means for controlling the pressure comprises at least one motor supported by said fixed frame, and transmission means interconnecting said motor and said movable support frames for vertically moving said movable support frames and changing the applied pressure of the flexible sheets against the corrugated paperboard sheet .

42. An apparatus according to claim 39 wherein said transmission means comprises vertical drive shafts for raising and lowering the movable support frames .

43. An apparatus for manufacturing corrugated paperboard, said apparatus comprising: heating means for defining a heating surface; take-up means downstream from the heating surface for advancing a corrugated paperboard sheet along a predetermined path of travel adjacent the heating surface; a fixed frame positioned adjacent the predetermined path of travel; a plurality of movable support frames positioned opposite the heating surface and transverse to and longitudinally with the predetermined path of travel ; drive means supported by said fixed frame and interconnecting said movable support frames for moving said movable support frames in a vertical direction; and a plurality of flexible sheets carried by each of said plurality of movable support frames and positioned opposite the heating surface for slidably contacting and applying pressure to urge the advancing corrugated paperboard sheet against the heating surface so that heat is transferred from the heating surface to the advancing corrugated paperboard sheet, wherein said drive means vertically moves said movable support frames and associated flexible sheets to change the pressure applied against the advancing corrugated paperboard sheet .

44. An apparatus according to claim 43 wherein said flexible sheets include edge portions transverse to the predetermined path of travel, and said movable support frames further comprise means for supporting said flexible sheets along the edge portions so that the flexible sheets are supported in side-by- side relation.

45. An apparatus according to claim 43 wherein said movable support frames are spaced apart in the longitudinal direction the length of a flexible sheet, and wherein at least one flexible sheet is carried by two spaced movable support frames .

46. An apparatus according to claim 43 wherein said drive means comprises at least one motor supported by said fixed frame, and transmission means interconnecting said motor and movable support frames.

47. An apparatus according to claim 46 wherein said transmission means includes vertical drive shafts for raising and lowering the movable support frames.

48. An apparatus according to claim 43 including a plurality of weight plates carried by each of said movable support frames for applying pressure against the flexible sheets.

49. An apparatus according to claim 43 including a chain carried by each said movable support frames, and fastening means interconnecting said chain and said weight plates.

50. A method for manufacturing corrugated paperboard comprising the steps of: advancing a corrugated paperboard sheet along a predetermined path of travel adjacent a heating surface in a double-facer by drawing the corrugated sheet from a take-up mechanism positioned downstream from the heating surface; supporting a plurality of flexible sheets opposite the heating surface so that the flexible sheets are positioned transversely in side-by-side relation across the predetermined path of travel and longitudinally along the path of travel; and slidably contacting and applying pressure on the advancing corrugated sheet by the flexible sheets and against the heating surface so that heat is transferred from the heating surface to the advancing corrugated paperboard sheet .

51. A method according to claim 50 wherein said flexible sheets include edge portions transverse to the predetermined path of travel, and including the step of supporting the flexible sheets along the edge portions of the flexible sheets.

52. A method according to claim 50 including the step of supporting the flexible sheets by a plurality of movable support frames positioned over the predetermined path of travel, and moving the movable support frames in a vertical direction by an associated motor and transmission.

53. A method according to claim 52 including the step of spacing the movable support frames the distance of one flexible sheet in the longitudinal direction along the predetermined path of travel.

54. A method according to claim 52 including the step of raising and lowering the movable support frames by drive shafts.

55. A method according to claim 50 including the step of applying pressure against the flexible sheets by engaging the flexible sheets with weight plates .

56. A method according to claim 55 including the step of supporting the weight plates on a chain.

57. A method according to claim 56 including the step of suspending the chain, weight plates and flexible sheets from a movable support frame.

58. A method according to claim 57 including the step of spacing the movable support frames longitudinally a distance of about one flexible sheet, and suspending a flexible sheet, and weight plates between two spaced movable support frames .

59. A method for manufacturing corrugated paperboard comprising the steps of: advancing a corrugated paperboard sheet along a predetermined path of travel adjacent a heating surface of a double-facer, by drawing the corrugated sheet from a take-up mechanism positioned downstream from a heating surface; supporting a plurality of flexible sheets opposite the heating surface so that the flexible sheets are positioned transversely across the predetermined path of travel and in series along the path of travel; engaging each flexible sheet with a plurality of weight plates; and lowering the flexible sheets and then slidably contacting and applying pressure on the flexible sheets and against the advancing corrugated sheet so that heat is transferred from the heating surface to the advancing corrugated paperboard sheet .

60. A method according to claim 59 wherein said flexible sheets include edge portions transverse to the predetermined path of travel, and including the step of supporting the flexible sheets along the transverse edge portions of the flexible sheets.

61. A method according to claim 59 including supporting the flexible sheets by support frames, and moving respective movable support frames in a vertical direction for changing the pressure of the flexible sheets against the advancing corrugated sheet.

62. A method according to claim 59 including the step of spacing the movable support frames the distance of one flexible sheet in the longitudinal direction along the predetermined path of travel so that at least one flexible sheet is carried between two movable support frames .

63. A method according to claim 62 including the step of raising and lowering the movable support frames by drive shafts driven from a motor and transmission .

64. A method according to claim 62 including the step of supporting the weight plates on a chain.

65. A method according to claim 64 including the step of suspending the chain, weight plates and flexible sheets from a movable support frame.

66. A method according to claim 65 including the step of spacing the movable support frames longitudinally a distance of one flexible sheet, and suspending a flexible sheet and associated weight plates between the spaced movable support frames .