Cutting – Other than completely through work thickness or through work... – Splitting
Reexamination Certificate
1999-05-18
2003-12-30
Dexter, Clark F. (Department: 3724)
Cutting
Other than completely through work thickness or through work...
Splitting
C083S019000, C264S163000, C264S284000, C264S321000
Reexamination Certificate
active
06668698
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to continuous methods for shaping the surface of a slab of compressible or cellular polymer material, such as polyurethane foam, by cutting portions of the material from the slab with a blade after the slab has been compressed between a compression roller and a patterned surface of a moving platform, preferably at a region where the platform is adjacent to or driven by a drive roller.
Several methods and apparatus for cutting slabs of cellular polymer materials have been disclosed in the prior art. For example, U.S. Pat. No. 4,700,447 to Spann discloses convolute-cutting slabs of polyurethane foam by compressing a slab or pad of foam between a pair of rolls with opposed spaced projecting fingers arranged in a pattern and cutting the foam with a saw blade transversely just as it emerges from the rolls. The cut slab is then separated into two pads each with convolute-cut surfaces forming a series of peaks separated by valleys. The valleys formed on one pad are formed by slicing away foam which becomes a mating peak or projection on the other pad. Spann then shaves the peaks to form a more planar top surface. As noted in Spann, convolute cutting alone produces only rounded peaks and rounded valleys, and it is difficult, if not impossible, to produce a cut surface with peaks having substantially flat top surfaces or with recesses having substantially straight side walls. The convolute usually is intended to form the classic symmetrical and repeating “egg crate” pattern of peaks and valleys. To achieve a planar upper surface at other than the recessed portions, the tops of the peaks must be cut or shaped in a second step.
Compressible cellular polymer materials may also be cut using a hot wire cutter. A slab of such material is cut by moving the slab relative to one or more hot wires as shown, for example, in U.S. Pat. No. 4,683,791 (Demont). Only straight cuts in regular or symmetrical patterns may be formed using a hot wire cutter. See also U.S. Pat. No. 4,915,000 (MacFarlane) and U.S. Pat. No. 5,573,350 (Stegall).
Shapes may be cut into the surface of a slab of cellular polymer material using a punch cutting apparatus, such as disclosed in U.S. Pat. No. 5,299,483 (Ber-Fong). A block of the cellular material is pressed against a template so that a portion of the material is forced through an opening in the template. The exposed material is then cut by a blade and removed, leaving a recess or cavity in the slab. This method cuts one block of material at a time, and only one surface at a time.
U.S. Pat. No. 4,351,211 (Azzolini) compresses a block of foam material against a template or die having an aperture therein using a pair of plates with concave and convex portions. The compressed foam is transversely cut along the template as it is held between the plates. More complex cut regions may be obtained than when using a template without the plates with raised and depressed portions, but only one block is cut at a time. Other template or pattern cutting methods are shown in U.S. Pat. No. 3,800,650 (Schroder) and U.S. Pat. No. 3,653,291 (Babcock).
The surface of a cellular polymer material may be shaped by molding or embossing, as opposed to cutting. U.S. Pat. No. 4,383,342 (Forster), for example, discloses injecting the foam-forming composition in a mold cavity. After sufficient curing time, the individual foamed article is removed from the mold. Other one-shot molding techniques are known to persons of skill in the art. The molded cellular polymer product generally forms a tough skin at the surfaces that were in contact with the mold.
Continuous and semi-continuous molding processes are also known. These processes have the same drawbacks associated with one-shot molding techniques. For example, U.S. Pat. Nos. 4,128,369 and 4,290,248 (Kemerer, et al.) disclose an apparatus and method for impression molding thermoplastic products. The thermoplastic material in a liquid state is injected between compressed traveling belt molds. As the belt molds travel away from the point of introduction of the thermoplastic, they are cooled, which in turns cools the thermoplastic material. The hardened molded thermoplastic material is removed from between the belts to form the finished product. Kemerer does not show a method for cutting or shaping a cellular polymer material, such as polyurethane foam.
A method of embossing a foam surface using a patterned metallic embossing belt or band is shown in U.S. Pat. No. 4,740,258 (Breitscheidel). The foam is heated and then pressed against the embossing belt. The belt is removed after the foam surface cools. The embossed surface by design has a hardened skin. No method for cutting or shaping the foam is disclosed.
U.S. Pat. No. 5,534,208 (Barr) discloses a continuous rotary method for surface shaping synthetic foams in which the foam is compressed between a compression roller and a die roller having raised and recessed portions. The portions of the foam extruded into the recesses in the die roller are cut away. The compressed foam portions return to an uncompressed state after passing through the rollers. As a result, a mirror-image pattern to the pattern on the surface of the die roller is cut on the surface of the foam. The diameter of the die roller limits the length of the shaped foam article that may be formed.
The prior art does not disclose a continuous method for shaping a compressible or cellular polymer material by cutting to form recesses of various depths and various symmetrical and non-symmetrical shapes. Nor does the prior art disclose a method for shaping a slab of compressible or cellular polymer material of unlimited length using a movable patterned platform, such as an endless belt, as the template for cutting the surface of the slab. Nor does the prior art disclose a method for forming a profile cut product without the hardened skin or hard spots associated with molded or embossed products.
SUMMARY OF THE INVENTION
A continuous method for shaping a compressible or cellular polymer material, such as polyurethane foam, by cutting and removing portions of the material is disclosed. A slab of cellular polymer material is compressed between a compression roller and a surface of a moving patterned platform. The moving patterned platform is interposed between the compression roller and a cooperating surface, such as the surface of a drive roller. Because the moving patterned platform may be formed from a flexible material, the compression force preferably is applied at a region where the platform is adjacent to a solid surface of the drive roller. In a less preferred embodiment, the moving patterned platform is interposed between the compression roller and a follower roller and the compression force is applied at a region where the platform is adjacent to a solid surface of the follower roller. A knife blade is positioned downstream from the compression roller and the point at which the compression force is applied, preferably with the blade interposed between the compression roller and the patterned platform. The slab surface is cut transversely by the blade just as the slab emerges from between the compression roller and the moving patterned platform, thus trimming off portions of the cellular material that filled the recesses or voids in the patterned platform. In an alternate embodiment, the blade is positioned so that it shaves a fine scrim layer of foam from the slab surface, and makes deeper cuts into the slab in the regions in which the polymer material has filled the recesses or voids in the patterned platform. If the patterned platform defines upstanding projections, instead of or in addition to recesses, the projections force a portion of the foam material away from the blade and less material is cut from the slab surface in those regions.
The patterned platform may be an endless belt or a series of movable panels or plates or any other structure that may travel in a continuous circuit or path. Where the patterned platform is an endless belt, the belt is placed over a series o
Connolly Bove & Lodge & Hutz LLP
Dexter Clark F.
Foamex L.P.
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