Method and Apparatus for Molding and Replicating Minute Surface Characteristics

It is well known to use wax to make impressions of surfaces to be later molded in other materials, such as in denistry and in the making of electrotype. The use of heat to soften the wax and use of vacuum to cause the wax to conform to the surface being molded are both broadly old in the art.

The present invention is primarily intended to reproduce in fine detail, surfaces of ships underwater so that their degree of roughness and drag may be determined. The apparatus is designed to be hand positioned by a diver and applied to selected submerged and exposed areas of a ship hull. The apparatus utilizes a vacuum and heat in a novel way to achieve the accurate reproduction of the surface of a ship hull.

FIG. 1A is a schematic view of the invention in cross-section in it's initial position on the ship's hull.

FIG. 1B is a view similar to FIG. 1A showing the heating circuit closed.

FIG. 1C is a view similar to FIG. 1A showing the elements in position for taking the impression of the surface.

Referring to the drawings for a more detailed description of the invention wherein corresponding parts are numbered the same, there is shown in FIG. 1A, a body 10 having upper and lower parts 11 and 12 respectively. Carried within the body 10 in sliding relation thereto is a member 13. The member 13 carries the wax or other molding material 14 which is removable and replacably, member 13 also has mounted therein a heating element 16. A piston member 13a may be connected to element 13. Separating the chamber formed by the housing 10 into two parts, subchambers 18 and 19, is a diaphram 17 which is attached between the parts 11 and 12 of the housing 10 and to the sliding element 13. Along the exposed edge of the lower housing 12 is attached a resilient gasket 21 which may be of magnetic material or constructed to function like a suction cup to facilitate attachment of the device to the ship hull 27 and to provide a watertight seal between the device and the ship hull 27.

There is provided in body 10 for each of its parts, or subchambers 18 and 19, ports 22, 23, 24 and 25 connected to suitable valving (not shown) to permit selective evacuation and flooding of the subchambers. Such valving may consist of a simple valve for each of the ports or a more complex four-way valve may be used. By proper selection of valves, air can be selectively admitted to the subchambers to aid in removing water while the subchambers are being exhausted or the subchambers can be selectively flooded.

Also a suitable switch 26 is mounted in the housing 10 and connected through a suitable electrical circuit to the electrical heating element, which for thermo plastic materials is embedded in the molding material or is mounted in close proximity to the surface of the molding material to permit the softening of the material.

Examples of such materials would be a mixture of 40% carnauba wax with 40% rosin, 10% beeswax, and 10% paraffin but other suitable waxes and some plastics, both thermo setting and thermo plastics can be used as molding materials. Also the molding material may incorporate mold release agents such as silicone oil, or may incorporate conductive metal colloids to improve heat transfer.

As depicted in the successive drawings, the device is first positioned against a section of the hull of a ship to be replicated as is shown in FIG. 1A with the element 13 retracted from the surface. The water is then evacuated from both subchambers 18 and 19 leaving an equalized partial vacuum, as shown in FIG. 1B. Then, depending on the selected molding material, the switch 26 is then closed for sufficient time to soften, but not melt, the molding material. When the material is sufficiently soft, the switch 26 is opened to cut off the heat and then water at ambient pressure is rapidly admitted to subchamber 18, above the diaphram 17, which due to its resilience normally holds element 13 retracted from the surface being replicated. This hydrostatic pressure causes the element 13 to move into contact with and forces the molding material into molding relationship with the surface being replicated as shown in FIG. 1C. If the molding material is thermo-setting, then the switch is not closed until after the molding material has been forced against the surface. The molding material unless it is thermo-setting solidifies upon contact with the ship hull which serves as a heat sink. As a slight modification to the recited procedures, the application of heat may be delayed until the replicating material is in contact with the surface to be replicated. Such a change in operating procedure might be useful with particular replicating materials. The final step is that of readmitting water at ambient pressure to the subchamber 19. If necessary to separate the replicating material from the surface, the water in subchamber 18 can be withdrawn. The water serves to further cool any thermo plastic molding material and helps separate the replicating material from the surface.

It is to be understood that within the state-of-the-art positive replications can be made from the negatives produced by the described apparatus and method.

Obviously many modifications and variations of this invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the following claims the invention may be practiced otherwise than as specifically described.