Patent Application
20080045393
In the embodiments discussed below, each will be understood to be formed by the technique known in the art as ‘spiral winding’.
In one preferred embodiment, the invention provides a rigid concrete form tube constructed from multiple sub-layers of material, wherein each said sub-layer consists of a woven HDPE mesh disposed in between one or more layers of kraft paper. Similar results may be obtained with PP mesh. The kraft paper may be bonded to the mesh in a conventional manner according to the art, but it is particularly preferred that the paper is bonded to the mesh via an intermediate layer of poly-ethylene (PE).
An example of the preferred kind of mesh material is that supplied by Insulation Solutions, of 127 Dandenong-Frankston Road, Dandenong, Victoria 3175, Australia, under the name of “Metal Wrapping”, item no. 1625.
This material has properties as outlined in Table 1.
Typically, the HDPE material is supplied in the form of a scrim cloth having between 8 and 10 strands per inch in any direction. This material is particularly suited to this application due to its very high tensile strength, and in particular to its very high resistance to any level of stretching. The HDPE is then laminated with 40 gsm kraft paper via low-density polyethylene (LDPE) via conventional methods known in the art.
The general type of concrete form tubes to which the invention may be applied are described in detail in U.S. Pat. No. 5,376,316 discussed above, and the following description is made with reference to the general kind of structures described therein.
An ideal structure for a rigid casting tube incorporating this material would consist of between four and six of the above described sub-layers, bonded together by a conventional paper-paper adhesive, such as PVA. The material may be constructed using conventional spiral winding apparatus well known in the art, which involves gluing or otherwise affixing multiple layers of paper (typically, Kraft paper or similar fibrous paper) to each other whilst winding each layer around a steel mandrel of a given diameter.
Further layers of polyethylene may be affixed to the outer surfaces of the material to provide a desired surface texture for the casting. In particular, it is preferred that there be sufficient layers of polyethylene bonded to the inside surface of the tube to ensure a smooth surface of the casting. The overall thickness of the tubing material should be between 2.5 mm and 5 mm in order to provide sufficient rigidity to stand up without the assistance of a rigid superstructure.
Where different surface finishes are required, the person skilled in the art will be aware of other alternative materials which are available to achieve various finishes or surface properties.
It will be appreciated by those skilled in the art that the invention is not only applicable to tubing constructed predominantly from kraft paper, and that this is merely one of the more common materials used in this industry and whose properties are likely to be enhanced by the invention.
For example, it would be possible to construct a casting tube by incorporating the HDPE mesh within multiple layers of another polymer material such as polyethylene. In such a case, it would be preferable to bond the layers together by direct heat treatment or by using a hot-melt glue.
An ideal structure for a flexible casting tube incorporating this material would consist of one or two of the above-described sub-layers, with optionally further layers of a single sided paper/mesh composite affixed to the outer surface of the tube material to provide a desired surface texture, but having an overall thickness of less than 4 mm in order to provide sufficient flexibility to lay flat when not in use.
It will further be apparent to those skilled in the art that the invention provides an improved construction of multi-layer tubes for a variety of different applications, notwithstanding the preferred embodiments addressed above are addressed to concrete forming. It is apparent that the improved tensile strength of the tubing material provided by the invention will afford improved performance in many other applications where such properties are desirable.
For example, a tube of similar construction to that described above for the rigid form-work tube might equally be applied as a packaging material for metal components. A tube wall structure having four or five of said inventive sub-layers, the walls of the tube having a thickness of between about 3 mm and about 4 mm, is anticipated to allow the tubing material sufficient tensile strength to resist tearing or puncturing when hard or sharp components come into the kind of violent contact with the inner surface of the tube as may be expected during transport.
It is also anticipated that a tube of improved crush resistance may be provided where the inventive tube wall structure is applied, as the improved tensile resistance of the wall is likely to assist in preventing deformation of a thicker version of such tubes. As described above, the improved tensile strength achieved throughout the tube wall is likely to assist in preventing differential buckling of the tube, of the kind where one side of the wall, for example the outer side, is placed under compression and the immediately adjacent and corresponding section of the wall, for example the inner side, is placed under tension. The portion of the wall placed under tension is accordingly less likely to yield to the crush force.
Preferably, when used as a core of this kind, a tube wall structure is provided having 10 to 15 sub-layers, and an overall thickness of about 20 mm.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003903948 | Jul 2003 | AU | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/AU04/01017 | 7/30/2004 | WO | 00 | 5/10/2007 |
