The present invention pertains to means and method for manufacturing multiwalls. More particularly, the present invention pertains to systems and methods for converting transversely to vertically oriented cores of multiwalls.
Multiwalls are commonly used in the construction of different types of plastic furniture. Their basic structure is sandwich having skin surfaces on top and bottom that enclose a core in the middle. The core is usually formed of transversely extending flutes along the length or width of the multiwall relative to the top and bottom skins. The core provides the multiwall the strength to bear loads, particularly, when used in shelf systems, closets, cupboards and the like. To increase the strength of multiwalls the core is oriented upright relative to the skins. Several technologies have been developed for manufacturing a core that is 90° oriented relative to the top and bottom skins. These technologies essentially manufacture hollow vertical poles on the bottom surface then laminated from top with the upper surface, which evidently leads to complicated, time consuming and expensive process, resulting in a more expensive product.
There is, therefore, a need to provide cost-effective, relatively simple, faster and cheaper method for forming vertically oriented core of multiwalls and multiwall comprising such core.
Further, there is a need to provide relatively simple means for manufacturing such vertically oriented core of multiwalls and multiwall comprising such core.
The present invention responds to these objectives as detailed in the following description with exemplary reference to the accompanying drawings.
In one aspect, the present invention provides a method of manufacturing vertically oriented core of multiwall and multiwall comprising such core. The manufacture of multiwalls with a core that contains vertical flutes is more complicated and time consuming than a core with a smaller number of transversely oriented flutes. This is due to the need to produce a larger number of shortened vertical flutes relative to a smaller number of transverse flutes to cover the same area. The method of the present invention essentially uses available materials, constructions and devices that make it technologically simple and cost-effective relative to current technologies to obtain the same product.
Therefore, the method comprises a method for the manufacture of vertically oriented multiwall core, namely a core of a multiwall that comprises vertically oriented flutes relative to top and bottom skins that cover them. Such method comprises the following:
(a) providing fluted multiwall or fluted core of multiwall that comprises at least one array of transversely oriented flutes;
(b) providing at least one cutting means configured for slicing the array of transversely oriented flutes of the fluted multiwall or fluted core of multiwall;
(c) placing the cutting means in contact at selected distance from first longitudinal edge of the fluted multiwall or fluted core of multiwall;
(d) cutting through a selected thickness of the fluted multiwall or fluted core of multiwall with the cutting means;
(e) generating a slice of the fluted multiwall or fluted core of multiwall;
(f) folding the slice relative the fluted multiwall or fluted core of multiwall or a slice previously cut off from said fluted multiwall or fluted core of multiwall;
(g) packing the folded slice with the previous folded slice;
(h) repeating steps (c)-(g) until reaching second longitudinal edge parallel the first longitudinal edge of the fluted multiwall or fluted core of multiwall.
Optionally, adjacent slices are heat-welded or heat-fused to each other after folding. Optionally, adjacent slices are arranged in contact with each other by pressing them together, for example with a press applied on the two extreme slices of the pack of slices formed.
The folding of the slices after cutting may be done 90° clockwise relative to the currently forming vertically oriented multiwall, 90° counterclockwise relative to the previously cut slice or 180° clockwise relative to the origin multiwall. In the last option of folding, the slices are packed one above the other in stack formation, where the last slice cut is positioned on top of the stack
To form the multiwall of the present invention, further step is required of thermal treatment for leveling the open bases of the shortened vertical flutes formed. A further step of laminating the top and bottom surfaces of the core completes the process of manufacturing the multiwall. Therefore, the method as detailed above further comprises:
(i) stabilizing the upper and lower surfaces of the vertically oriented core multiwall; and
(j) covering the upper and lower surfaces of the vertically oriented core multiwall.
In one particular non-limiting embodiment, the slicing of the origin multiwall with transversely oriented flutes half- or part-thickness essentially creates accordion configuration of the slices that may be folded 90° relative each other clockwise or counterclockwise around the newly formed axis between them. To achieve that the slicing may be carried out with at least one knife that cuts through the thickness of the origin multiwall and along the longitudinal length perpendicular to the flutes between the first and second transverse edges of the origin multiwall. This slicing is done at a selected distance from the longitudinal edges of the multiwall or previous cuts. Thus an array of slices is obtained that may be folded one upon the other in an accordion configuration. The slicing may be done down to the bottom layer of the multiwall, leaving only the bottom layer that connects between adjacent slices and stretched when folding them.
In another particular embodiment, the slices are folded 180° relative to the origin multiwall in stack formation, where they are packed one above the other, the last slice being on top. The multiwall is cut down to its bottom layer that connects between adjacent slices and stretched when folding them.
When the slicing is carried out in only one direction from one surface to the opposite surface, then the slices may be completely cut and separated from the origin multiwall or partly cut down to the bottom layer of the origin multiwall and folded 180° as described above. The slices may be folded by rotating them 90° clockwise one over the other, then welded to each other, for example by heat-welding or heat-fusion, or mechanically pressed together, thereby forming the core of vertically oriented shortened flutes of the multiwall of the present invention. Slicing in opposite directions from the top and bottom surfaces may be done for partial slicing down to the bottom layer of the origin multiwall, keeping the slices connected to each other. In the general case, a selected horizontally measured distance is set between the cutting means placed on each surface of the origin multiwall. One cutting means, for example a roller knife or a blade, cuts through the multiwall in opposite direction relative the other cutting means. This opposite cutting is required to enable the folding of adjacent slices over each other in 90° alternating clockwise and counterclockwise directions, where the slices are still connected to each other in alternating upper and lower connecting lines.
The number of cutting means may be one or more. In one particular non-limiting example, when the origin multiwall is mounted, for example, on conveyor belt, then it is transported relative to a cutting means placed in fixed position. The cutting means is moved down to cut a slice off of the multiwall, then moved up and the multiwall transported the distance selected for creating another slice. The slicing repeats itself until reaching the longitudinal edge of the multiwall.
In an alternative, cog-wheel with blades between neighbor teeth constantly rolls over the surface of the multiwall or core of multiwall, enabling the blades to cut through its thickness and throughout the length. For example, top and bottom cog-wheels with blades between their teeth may be used to continuously cut slices off from a multiwall or core of multiwall traveling between them. The distance between the cog-wheels provides sufficient space to allow a multiwall or core of multiwall to pass through while being cut part-, half- or full-way through their thickness.
In still another alternative, a plurality of cutting means may simultaneously cut through the thickness of the origin multiwall either completely or partially from the two surfaces.
The folding step may be simultaneous with the cutting step, where every slice formed is folded over a previously cut slice and welded, fused or pressed to it, for example by heat-welding or heat-fusion or with use of a press, while a new slice is formed. Thus, a continuous process for manufacturing vertically oriented multiwalls or cores of multiwalls is obtained.
Stabilizing with thermal treatment for leveling the top and bottom surfaces of the core and covering or lamination are done when completing the slicing and folding as described above. In particular, the covering or lamination may be carried out by heat-welding, heat-fusion or gluing.
In one particular embodiment, the covering step is done with extruded sheets, where each sheet comprises at least two layers, where the layers are distinguished one from the other according to their MFIs (Melt Flow Index).
The covering with such sheets that form the covers comprises:
placing the covers on the upper and lower surfaces of the slices formed from cutting the transversely oriented flutes of the fluted multiwall or fluted core of multiwall;
applying heating means over these covers; and
heating the covers.
The heating is configured to turn at least part of the bottom layer of the covers to adhesive, where that adhesive bonds the laminates to the upper and lower surfaces of the slices. It should be noted that the MFI of the bottom layer is sufficient to at least partly melt and bond it to the slices.
In one particular embodiment, the upper and lower surfaces of the slices are wavy, indented and/or textured, where the adhesive formed from the bottom layer of the cover is configured to form mechanical and/or physical bond with the upper and lower surfaces of the slices. The top layer of the cover forms the skin of the multiwall and is bonded to the multiwall core upon melting the adhesive that is obtained from the bottom layer of the cover.
In one particular embodiment, the bottom layer of the cover is foamed with increased free volume within to enable better spreading on and adhering to the top and bottom surfaces of the slices.
The method of manufacturing the multiwall with vertically oriented shortened flutes is not limited to a particular shape of flutes. Particular non-limiting examples of cross sections of the flutes in the origin multiwall may be selected from circular, rectangular, pentagonal, hexagonal, octagonal, parallelogram and diamond. The number of layers of flutes in the origin multiwall may also be more than one. Such example is illustrated in
The material from which the origin fluted multiwall or fluted core of multiwall is made is also not limited. In particular, the material may be selected from polypropylene (PP), polyethylene (PE), polyethylenterphthalate (PET), polystyrene (PS) and polycarbonate (PC).
In another aspect, the present invention provides a machine configured for manufacturing vertically oriented multiwall core, where the system comprises:
conveyor belt configured for conveying fluted multiwall or fluted core of multiwall that comprises at least one array of transversely oriented flutes;
at least one cutting means configured for cutting through the fluted multiwall or fluted core of multiwall; and
positioning means configured for positioning the at least one cutting means in contact with upper and lower surfaces of the fluted multiwall or fluted core of multiwall.
Further, the machine may comprise:
thermal treatment means configured for heat-welding or heat-fusing neighbor slices cut off from the origin multiwall to each other;
pressing means configured for pressing the slices to each other;
thermal treatment means configured for leveling the upper and lower surfaces of the newly formed core; and
laminating means configured for laminating these upper and lower surfaces.
In still another aspect, the present invention provides vertically oriented multiwall manufactured according to the method or with the machine as described above.
The following will describe particular and non-limiting examples of the present invention with exemplary reference to the drawings without departing from the scope and spirit of the present invention.
The following describes different aspects of the method and machine of the present invention and in further detail and for demonstration purposes without departing from the scope and spirit of the present invention. It is understood that the configuration(s) and mode(s) of operation described herein do not limit the present invention to the particulars detailed below.
The first step of converting transversely to vertically oriented core of multiwall can be carried out in two exemplary methods as illustrated in
The (b/c) indication in
In a particular embodiment, the bottom surface of the extruded sheet, that is the bottom surface of layer (a) that comes in contact with the surfaces of the slices (5), is not smooth. For example, such surface may be wavy, indented and/or textured to match waviness, indentation and/or texture of the surfaces of the slices (5) that result in the process of cutting the transverse flutes to form perpendicular flute core. In such case, layer (a) may better function as adhesive upon melting and optionally slightly pressing, due to the plurality of crevices and holes at the slices surfaces into which the adhesive can infiltrate and form a stronger bond, mechanical and/or physical.
The vertically oriented multiwall core (1′) is shown in different perspectives in
Heat may be applied also to relieve tension built in the core as in the cutting and folding process.
Vertically oriented core multiwall can be essentially done with any shape of flutes and/or any form of packing.
Double layer core of hexagonal flutes (9) is demonstrated in
It should be noted, that the cross sectional shapes of the flutes described above and illustrated in the accompanying drawings are only examples of the possible shapes of flutes that may be used to form vertically oriented flute core. Therefore, rectangular, circular, parallelogram, octagonal and diamond shapes are other examples that may be used to manufacture vertically oriented cores of multiwalls. Further, transversely oriented cores with more than one layer may be used to manufacture the vertically oriented core of multiwall.
Those skilled in the art to which this invention pertains will readily appreciate that numerous changes, variations and modifications can be made without departing from the scope of the invention mutatis mutandis.