Browse Prior Art Database

Thermoforming of Thin Polyurethane Films

IP.com Disclosure Number: IPCOM000074735D
Original Publication Date: 1971-Jun-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Brown, AB: AUTHOR

Abstract

A thin-walled polyurethane convoluted diaphragm can be thermoformed by vacuum drawing a flat sheet of polyurethane down onto a hot three-dimensional mold and then subsequently cooling the mold.

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Thermoforming of Thin Polyurethane Films

A thin-walled polyurethane convoluted diaphragm can be thermoformed by vacuum drawing a flat sheet of polyurethane down onto a hot three-dimensional mold and then subsequently cooling the mold.

Mold 1 includes an annular insert 2 whose raised surface defines the convolution 3 of the finished diaphragm shown in View B. The insert is spaced from the surrounding portion of the mold by small concentric annular air openings 4 and 5 which are connected to a source of vacuum, not shown. These openings are in the range of 0.001 to 0.002 inch wide and are small enough to prevent the polyurethane from deforming into the openings due to the vacuum force.

The mold is first heated to about 195 degrees F. Passages, not shown, can be formed in the mold to receive a liquid, such as hot oil, to heat the mold. A thin flat sheet of polyurethane, in the range of from 0.001 to 0.015 inch thick, is placed adjacent the top face of the mold. The sheet is then drawn down onto the face of the mold by a vacuum force of from 20 to 30 inches of mercury, to cause the sheet to conform to the shape of insert 2. With vacuum force applied, the mold is cooled by circulating a cool fluid through the passages. When the mold is cool, the vacuum force is removed, the polyurethane sheet is removed, and the finished diaphragm, View B, is cut from the sheet.

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