Method of making multilayer product having honeycomb core of improved strength

A process of making a multilayered product having an interior honeycomb layer or core. The interior layer is formed by extruding a generally corrugated web of material. The corrugated web is cut and folded to create the honeycomb core. Outer protective skins are applied to exterior surfaces of the interior layer to create a multilayered material which is then cut to size.

FIELD OF THE INVENTION

This invention relates generally to a product for structural, packaging, and other applications and the process of making the product.

BACKGROUND OF THE INVENTION

In the aerospace industry, honeycomb products have been used as a core component for sandwich panels and boards that are resistant to buckling and bending. These honeycomb products each comprise a plurality of cells which, in cross-section, have a generally hexagonal shape. Such products may be fabricated from aluminum, fiber paper or plastic, among other materials. A sandwich structure may be prepared having two cover layers or skins which are welded, adhesively bonded or otherwise secured to the honeycomb product to create a multilayered or multi-laminate material. Interest expressed in other industrial sectors concerning the use of lightweight sandwich structures is continually growing, due at least in part to the realization of its high strength properties while maintaining a relatively low structural weight per volume of product.

A multilayered or multi-laminate material having a honeycomb product as the core thereof may be used in the packaging industry. However, in automobile part packaging and comparable markets, such a product must compete with corrugated paperboard or corrugated plastic or like materials which may be produced quickly and relatively inexpensively.

U.S. Pat. No. 6,183,836 discloses a honeycomb core for use in a sandwich material in which the material of the honeycomb core is cut and then folded to create a plurality of hexagonal cells. Due to the process used to make the honeycomb product, including the complex folding of the cut sheet, the resultant structure may be expensive to manufacture.

A process for producing a folded honeycomb core for use in sandwich materials from a continuous uncut web is disclosed in U.S. Pat. No. 6,726,974. U.S. Pat. No. 6,800,351 discloses another process for producing a folded honeycomb core which includes scoring a corrugated material before rotating interconnected corrugated strips. The honeycomb core resulting from using either of these methods may have material which adds to the weight of the honeycomb core, but may not significantly improve the strength of the honeycomb core.

Regardless of which method is used to manufacture a honeycomb core, the resultant core may have a compressive strength in one direction which is higher than the compressive strength in another direction. Often the compressive strength in one direction is higher due to several layers of the material being overlapped; all the overlapped portions extending in the same direction. Accordingly, there is a need for a multilayered product which has an interior honeycomb layer having equal strengths in multiple directions.

There is further a need for a process for manufacturing a product, such as a honeycomb product, for use in a multilayered material which is less expensive and more efficient than heretofore known processes.

SUMMARY OF THE INVENTION

The present invention comprises a process for producing a sandwich-like or multilayered product having an interior layer, including a honeycomb core. The invention also includes the resultant product made by the method(s). The product may have any number of layers; the product is not intended to be limited to three layers. The processes of the present invention may be used to make products for use in any desired environment or industry, including but not limited to, packaging materials.

According to one aspect of this invention, a process of making a multilayered product comprises moving a web of material in a first direction. The web of material has a cross-section of regions of varying thickness, the regions extending in the first direction. These regions of increased thickness compared to other portions or regions of the web may be any desired width and/or height. The web or webs may be heated to any desired temperature and of any desired widths at the start of the process and at any stage in the process. In addition, the web or webs may be any desired material including, but not limited to, plastic.

The next step comprises treating the web of material with a tool to produce a corrugated web of material having a generally corrugated profile with interrupted flattened peaks and flattened valleys joined by connecting portions of the web, the flattened peaks and flattened valleys extending in the first direction or direction of travel of the web. An additional step comprises folding the corrugated web to create a honeycomb core. Another step comprises applying or securing outer skins to the honeycomb core. In order to obtain a product of a desired size, the last step in the process may comprise cutting the multilayered material, including the honeycomb core and the outer skins to create the finished product.

According to another aspect of the invention, the process comprises making a multilayered product, including an interior layer having a honeycomb core. The process includes applying outer skins to the interior layer and cutting the combined layers to a desired size. The process of making the interior layer comprises extruding a web of material in a first direction. The web has a generally corrugated profile with continuous flattened peaks and flattened valleys joined by connecting portions of the web, the flattened peaks and flattened valleys extending in the direction of travel of the web. The next step in the process comprises cutting the continuous corrugations of the corrugated web. The next step in the process comprises folding the corrugated web to create a honeycomb core. Another step in the process comprises applying outer skins to the honeycomb core.

According to another aspect of the invention, the process comprises making a multilayered product, including an interior layer having a honeycomb core. One step in the process comprises extruding a web of material to produce a corrugated web of material having continuous flattened peaks and flattened valleys joined by connecting portions of the web. The flattened peaks and flattened valleys extend in the direction of travel of the web. Another step in the process comprises cutting portions of the corrugated web. Another step in the process comprises folding the corrugated web to create a honeycomb core. Another step in the process comprises applying outer skins to the honeycomb core.

According to another aspect of the invention, the extrudate is shaped so that some of the connecting portions of the continuous corrugations are thicker than the peaks or valleys of the continuous corrugations due to the configurations of the extruder. Alternatively or additionally, some of the connecting portions of the continuous corrugations are thicker than other of the connecting portions of the continuous corrugations due to the configuration of the extruder.

Regardless of the method used to create the multilayered product, one advantage of the process is that a lightweight, strong product having a large strength-to-weight ratio may be quickly and easily manufactured in a desired size or height. The product of this invention, which may be produced according to any of the processes described herein, has a relatively high strength-to-weight ratio, and may be made from many different materials quickly and inexpensively. The strength-to-weight ratio may be improved by strategic removal of material from the web at some time in the process of fabricating the product. The multilayered product may be incorporated into any desired product, or used in any desired manner.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to the drawings and, particularly toFIGS. 1 and 2, a flexible web or membrane of material10is shown entering an apparatus12for producing a continuous flow of multilayered or sandwich-like material14which is cut to size to produce a finished multilayered product16shown inFIG. 5. The web of material10may come from any source including, but not limited to, a roll18shown inFIG. 1. Alternatively, the web10shown in cross-section inFIG. 3may be stacked or otherwise stored. Once unwound or unrolled, the web of material10is generally flat. However, as shown inFIG. 3, web10is not planar; rather it has portions of differing thicknesses across its width, defined as the linear distance between its opposed edges20. The web10is pulled or moved in the direction of arrows19in any conventional manner, including being helped by a rotational, moving roller21shown inFIG. 1. The direction of travel of the web10during this process is indicated by arrows19, as shown inFIGS. 1 and 2. Although only one moving roller21is shown inFIG. 1, the web10may pass around or between several rollers before being treated or deformed by a movable tool22, shown in detail inFIG. 2, into a generally corrugated shape as shown and described below.

The flexible web of material10may be solid or may have openings formed therethrough at any stage in the process, as illustrated and/or described in U.S. patent application Ser. No. 11/535,623, which is fully incorporated herein.

The next step in the process is to plastically deform or treat the web of material10with a movable tool22, which may be cooled or heated to any desired temperature. Alternatively, the moving web of material10shown inFIG. 3may be heated before being plastically deformed via the tool22. Although only one tool22is illustrated, any number of similar tools may be used together or in any desired order at any desired temperature. Although one design or configuration is shown in the tool22, other similar designs or generally corrugated patterns may be on tool22to impart generally corrugated designs onto the movable web10.

After the web10has been plastically deformed into a generally corrugated web24by use of the tool22, the generally corrugated web24is folded along the edges of the transversely extending flats26to create a continuous honeycomb core40, as described in U.S. Pat. No. 6,726,974, which is fully incorporated by reference herein.

The configuration or shape of the tool22imparts a specific configuration to the web10passing downstream in the direction of arrows19. As shown inFIGS. 1 and 2, the treatment or deformation caused by the tool22creates an uncut generally corrugated web24having a generally corrugated profile with interrupted (as opposed to continuous) flattened peaks28and flattened valleys30joined by connecting portions32, all extending in the direction of travel of the web10shown by arrows19. The tool22plastically deforms or shapes the unrolled web of material10from a generally flat orientation shown inFIG. 3to a generally corrugated orientation having spaced flattened peaks28and flattened valleys30joined by connecting portions32, all extending in the direction of travel of the web10shown by arrows19and interrupted by flats26. SeeFIG. 4.

FIG. 3shows a cross-section of the unrolled web10before it is treated with tool22. The web10has a series of spaced, raised portions or regions34of increased thickness “T” compared to the thickness “T1” of the remainder of the web10. These raised portions34extend in the direction of travel19of the web10or longitudinally. The width W4of each of the raised portions34is identical to the sum of three widths W1, W2and W3as shown inFIG. 3. Therefore, when the web10shown inFIG. 3is plastically deformed or treated as described herein and shown inFIGS. 1 and 2to create the corrugated web24shown inFIG. 2, the corrugated web24has flattened valleys28and flattened peaks30of reduced thickness “T1”. Every other one of the connecting portions32has an increased thickness “T” greater than the thickness “T1” of the peaks30, valleys28and other connecting portions32, as shown inFIG. 4.

As shown inFIG. 2, the next step in the process is applying or securing outer skins36(shown in phantom for clarity) to upper and lower surfaces38,39of the folded continuous honeycomb core40in the direction of travel19of the web10. As shown inFIGS. 1 and 2, this process described above with the steps being performed as described herein creates a continuous strip of material14having a sandwich-like or trilaminate composition, the outer skins36being outside and secured to the continuous interior layer40. As shown inFIG. 5, the continuous interior layer40comprises a honeycomb core made up of honeycomb cells42, each having a hollow interior44, which reduces the weight of the final product16without compromising the strength of the product16.

As illustrated inFIG. 2, the continuous multilayered material14may be cut to size via a cutter46to create a finished product16. As shown inFIG. 5, the finished product16has a honeycomb interior layer40sandwiched between outer skins36. Although one size product16is illustrated inFIG. 5, the product16may be any desired size, i.e., length, width and/or height.

FIG. 2shows two outer or protective skins36being placed over and under the continuous honeycomb core40to create a three-layered continuous product14. The outer skins36may be applied from rolls of material (not shown), or may be supplied in any known manner. The cutter or cutting device46shown inFIG. 2cuts the three-layered continuous product14to a desired size having a longitudinal dimension or length L in the direction of travel of the materials and a transverse dimension or width W perpendicular to the direction of travel of the materials, as shown inFIG. 5. The result is a finished product16having a honeycomb interior layer40and outer skins36. This process enables the product16to weigh less than comparable products having a solid honeycomb core without compromising strength or integrity.

FIG. 5illustrates a finished multilayered product16made in accordance with the method shown inFIGS. 1-4having a pair of opposed side edges50, the distance between which defines the width W of the product16. Similarly, product16has a pair of end edges52, the distance between which defines the length L of the product16. The product16has a middle layer or honeycomb core48covered on top and bottom with outer or protective skins or layers36.

One of the results of having every other one of the connecting portions32of the corrugated web24thicker than the peaks28and valleys30of the corrugated web24(shown inFIGS. 1 and 2) is that the strength of the honeycomb core40of product16shown inFIG. 5is the same in the transverse and longitudinal directions. As shown inFIG. 4, because the thickness of “T” of every other one of the connecting portions32of the corrugated web24is approximately the same as the thickness “T1” of two peaks28or valleys30of the corrugated web24contacting each other, after the process of manufacture is completed, resulting in product16, the strength of the honeycomb core40of product16is the same in both the transverse and longitudinal directions. This resulting product16is similar to the product(s) disclosed in U.S. patent application Ser. No. 13/024,838, which is fully incorporated herein.

Referring toFIG. 6, a flexible, generally corrugated web of material54is shown exiting an extruder56. The flexible web of material54is similar, but not identical in configuration, as the corrugated web24shown inFIG. 4. The corrugations in the web54are continuous, rather than interrupted as they are in corrugated web24shown inFIGS. 1 and 2. As shown inFIGS. 7 and 7A, extruder56is specifically configured to produce a generally corrugated web or extrudate54having continuous flattened valleys57and flattened peaks58of the same thickness “T2” and every other one of the connecting portions60being of an increased thickness “T3”, as shown inFIG. 7A. The thickness “T3” is greater than the thickness “T2”.

As shown inFIG. 8, the extruder56creates an uncut generally corrugated web54having a generally corrugated profile with continuous flattened peaks58and continuous flattened valleys57joined by continuous connecting portions60, all extending in the direction of travel of the web54shown by arrows19. As shown inFIGS. 8 and 9, the next step in the process is to cut portions of the uncut corrugated web54using upper and lower cutters62,64which may or may not be heated. The drawings show cutters62,64of one particular configuration. As shown inFIG. 9, arrows41are used to represent that the cutters62,64may be heated. However, the cutters used in any of the processes of this invention may be other sizes, shapes or configurations and may be moved by any conventional means, such as a pneumatic power drive or any other driver (not shown).

As shown inFIG. 9, the group of upper cutters62may be joined together by one or more joiners66(one being shown in phantom inFIG. 9) and move together in the direction of arrows67. In order to cut the generally flattened peaks58and the connecting portions60of the uncut corrugated web54, the cutters62are moved downwardly, as shown inFIG. 9, a specific distance without cutting the generally flattened valleys56of the uncut corrugated web54.

Similarly, as shown inFIG. 9, the group of lower cutters64may be joined together by one or more joiners68(one being shown in phantom inFIG. 9) and move together in the direction of arrows69. In order to cut the generally flattened valleys56and the connecting portions60of the uncut corrugated web54, the cutters64are moved upwardly, as shown inFIG. 9, a specific distance without cutting the generally flattened peaks58of the uncut corrugated web54. Although the number and size of the cutters62,64ofFIGS. 8 and 9do not equal one another, one skilled in the art may appreciate that any number of cutters of any desired size may be used in accordance with the present invention.

The location of the cutters62,64may be changed to change the distance between the upper cuts70made by the upper cutters62and the lower cuts72made by the lower cutters64. The distance between adjacent cuts70,72determines the height “H” of the cells74of the honeycomb core or layer52as shown inFIGS. 10 and 11. As a result of the cutting process shown inFIGS. 8 and 9, a continuous cut corrugated web78is formed.

As shown inFIG. 10, the next step in the process is to fold the continuous cut corrugated web78along scored portions80to create fold lines82. Each fold line82is defined by a plurality of aligned, spaced upper cuts70or a plurality of spaced, aligned lower cuts72and spaced scored portions80. If desired, the scored portions80may be omitted. Fold lines82extend transversely from one side edge84of the continuous cut corrugated web78to the opposing side edge84in a direction generally perpendicular to the direction of travel of the continuous cut corrugated web78. As shown inFIG. 10, after being folded in an accordion fashion, the continuous cut corrugated web78shortens and becomes a continuous honeycomb core or layer76. The folding step is disclosed schematically by the box86inFIGS. 8 and 12.

As shown inFIGS. 10 and 11, the fold lines82alternate between the upper and lower planes P1and P2of the continuous cut corrugated web78. The honeycomb core76has a height H defined as the distance between the upper and lower planes P3, P4of the honeycomb core76after the continuous cut corrugated web78has been folded, as shown inFIGS. 10 and 11. As shown inFIG. 11, each of the cells74of the honeycomb core76has a hollow interior88. As shown inFIGS. 8 and 11, when the continuous cut corrugated web78is folded, the touching or contacting portions of the continuous peaks58and continuous valleys57may be joined together in any known manner.

As shown inFIG. 8, the next step in the process is applying or securing outer skins90to upper and lower surfaces92,94of the continuous honeycomb core76in the direction of travel of the web54. As shown inFIG. 8, this process described herein creates a continuous strip of material95having a sandwich-like or trilaminate composition, the outer skins90being outside and secured to the continuous interior layer76. The continuous interior layer76comprises the honeycomb core made up of honeycomb cells74, each having a hollow interior88, which reduces the weight of the final product96without compromising the strength of the product96.

As illustrated inFIG. 12, the continuous multilayered material95may be cut to size via a cutter98to create a finished product96having a honeycomb interior layer. Although one size product96is illustrated inFIG. 12, the product96may be any desired size, i.e., length, width and/or height.

FIG. 8shows two outer or protective skins90being placed over and under the continuous honeycomb core76to create a three-layered continuous product95. The outer skins90may be applied from rolls of material (not shown), or may be supplied in any known manner. The cutter or cutting device98cuts the three-layered continuous product95to a desired size having a longitudinal dimension or length L in the direction of travel of the materials and a transverse dimension or width W perpendicular to the direction of travel of the materials, as shown inFIG. 12. The result is a finished product96having a honeycomb interior layer100and outer skins102. This process enables the product96to weigh less than comparable products having a solid honeycomb core without compromising strength or integrity.

FIG. 13illustrates the finished multilayered product96. Multilayered product96has a pair of opposed side edges104, the distance between which defines the width “W” of the multilayered product96. Similarly, multilayered product96has a pair of end edges106, the distance between which defines the length “L” of the product96. The multilayered product96has a middle layer or honeycomb core100covered on top and bottom with outer or protective skins or layers90.

Referring toFIGS. 1,7and7A, one of the results of having one of the connecting portions60of the extruded corrugated web54thicker than the peaks58and valleys57of the corrugated web54(shown inFIG. 7A) is that the strength of the honeycomb core100of product96shown inFIG. 13is the same in the transverse (between opposed side edges104) and longitudinal (between opposed end edges106) directions. As shown inFIG. 7A, because the thickness “T3” of alternative connecting portions60of the corrugated web54is approximately the same as the thickness of two peaks58or two valleys56of the corrugated web54contacting each other, after the process of manufacturing multilayered product96is complete, the strength of the honeycomb core100of product96is the same in both the transverse and longitudinal directions.

FIGS. 14-16illustrate another aspect of the invention.FIG. 14illustrates a flexible, generally corrugated web of material110exiting an extruder112. The flexible web of extruded material110is similar to, but not identical in configuration, as the continuous corrugated web54shown inFIG. 7. Both have continuous, as opposed to interrupted, corrugations. However, all of the connecting portions118of the continuous corrugations in the web110are thicker than the peaks and valleys, unlike in extruded corrugated web54shown inFIGS. 6,7and7A. As shown inFIG. 15, extruder112is specifically configured to produce a generally corrugated web or extrudate110having continuous flattened valleys114and flattened peaks116of the same thickness “T4” with each of the connecting portions118being of an increased thickness “T5”. The thickness “T5” is greater than the thickness “T4”.

As shown inFIG. 14, the extruder112creates an uncut generally corrugated web110having a generally corrugated profile with continuous flattened peaks116and continuous flattened valleys114joined by continuous connecting portions118, all extending in the direction of travel of the web110shown by arrow19.

As shown inFIG. 16, the extruded corrugated web110, after being cut and folded as described herein, has two outer skins120applied.FIG. 16illustrates a finished multilayered product122made in accordance with this aspect of the invention (after the extruded corrugated web110has skins applied and is cut to a desired size). Multilayered product122has a pair of opposed side edges124, the distance between which defines the width “W” of the multilayered product122. Similarly, multilayered product122has a pair of end edges126, the distance between which defines the length “L” of the product122. The multilayered product122has a middle layer or honeycomb core128covered on top and bottom with outer or protective skins or layers120.

One of the results of having each of the connecting portions118of the corrugated web110thicker than the peaks116and valleys114of the corrugated web110(shown inFIG. 15) is that the strength of the honeycomb core128of product122shown inFIG. 16is the same in the transverse (between opposed side edges124) and longitudinal (between opposed end edges126) directions. As shown inFIG. 15, because the thickness “T5” of each connecting portion118of the corrugated web110is approximately the same as the thickness of two peaks116or valleys114of the corrugated web110contacting each other, after the process of manufacturing multilayered product122is complete, the strength of the honeycomb core128of product122is the same in both the transverse and longitudinal directions.

FIGS. 17-19illustrate another aspect of the present invention.FIG. 17illustrates a flexible, generally corrugated web of material130exiting an extruder132. The flexible web of extruded material130is similar to, but not identical, in configuration as the continuous corrugated web54shown inFIG. 7. Both have continuous, as opposed to interrupted, corrugations. However, every fourth connecting portion138of the continuous corrugations in the web130are thicker than the peaks136and valleys134, unlike in extruded corrugated web54shown inFIGS. 6,7and7A. As shown inFIG. 17, extruder132is specifically configured to produce a generally corrugated web or extrudate130having continuous flattened valleys134and flattened peaks136of the same thickness “T6” with every fourth one of the connecting portions138being of an increased thickness “T7”. The thickness “T7” is greater than the thickness “T6”.

As shown inFIG. 17, the extruder132creates an uncut generally corrugated web130having a generally corrugated profile with continuous flattened peaks136and continuous flattened valleys134joined by continuous connecting portions138, all extending in the direction of travel of the web130shown by arrow19.

As shown inFIG. 18, the extruded corrugated web130, after being cut and folded as described herein, has two outer skins140applied.FIG. 18illustrates a finished multilayered product142made in accordance with this aspect of the invention (after the extruded corrugated web130has skins applied and is cut to a desired size). Multilayered product142has a pair of opposed side edges144, the distance between which defines the width “W” of the multilayered product142. Similarly, multilayered product142has a pair of end edges146, the distance between which defines the length “L” of the product142. The multilayered product142has a middle layer or honeycomb core148covered on top and bottom with outer or protective skins or layers140.

One of the results of having every fourth connecting portion138of the corrugated web130thicker than the peaks136and valleys134of the corrugated web130(shown inFIG. 17) is that the strength of the honeycomb core148of product142shown inFIG. 19is the same in the transverse (between opposed side edges144) and longitudinal (between opposed end edges146) directions. As shown inFIG. 17, because the thickness “T7” of every fourth connecting portion138of the corrugated web110is approximately the same as the thickness of two peaks136or valleys134of the corrugated web130contacting each other, after the process of manufacturing multilayered product142is complete, the strength of the honeycomb core148of product142is the same in both the transverse and longitudinal directions.

FIG. 20illustrates an extruder150which extrudes a continuous honeycomb core152. The continuous honeycomb core152may assume any of the configurations described or shown herein. A cutter154is moved downwardly in the desired location to create a middle or interior honeycomb layer156of a multi-layered product158shown inFIG. 21. After the desired size, middle or interior honeycomb layer156is cut from continuous honeycomb core152, outer skins160are applied as described above.

FIG. 21illustrates a finished multilayered product158made in accordance with this aspect of the invention (after the extruded and cut corrugated core152has skins applied). Multilayered product158has a pair of opposed side edges162, the distance between which defines the width “W” of the multilayered product158. Similarly, multilayered product158has a pair of end edges164, the distance between which defines the length “L” of the product158. The multilayered product158has a middle layer or honeycomb core156covered on top and bottom with outer or protective skins or layers160.

While I have described several preferred embodiments of the present invention, persons skilled in the art will appreciate changes and modifications which may be made without departing from the spirit of the invention. For example, although one configuration of a cell is illustrated and described, the cells of the present invention may be other configurations, such as cylindrical in shape. Therefore, I intend to be limited only by the scope of the following claims and equivalents thereof.