From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
The flexibility, design possibilities, and air conditioning properties of foamed latex for use in cushioning.
| Identifier | ExFiles\Box 132\3\ scan0232 | |
| Date | 9th January 1939 guessed | |
| - 5 - Flexibility of Material in Design The density or load carrying capacity of foamed latex is varied primarily by the quantity of air combined with the latex. A wide range of hardness is possible with the only limitation being the lightness of foam that will be stable in production. Additional flexibility is possible in the molding operation by changing the size, shape, or spacing of the base coring. By this means, different degrees of support may be obtained in portions of the same cushion. Practically any requirement in cushioning can be obtained by these two methods and sufficient process control is possible to provide uniform production results. Air Conditioning Like many modern structures, foamed latex is air conditioned. The problem of heat is generally implied when rubber is closely associated with the human anatomy. This has been true to a large extent as most rubber products are impervious to air and, since rubber is not a rapid conductor, the body heat and moisture are retained at the areas of contact. It has been shown previously by Elden (1) that the actual flexure of the material under operating conditions does not generate heat sufficient to increase the cushion temperature. The problem then is one of removing body heat from the contact area by ventilation. The manufacturing process of foamed latex provides a completely porous mass. After vulcanization, the material is thoroughly saturated with the curing medium and drying is accomplished by centrifugal action followed by the circulation of hot air around and through the cushion. The results obtained from these operations would be impossible without complete inter-connection of cells to and through the surface of the structure. Each flexure of foamed latex produces a forced circulation of air which equalizes temperature and evaporates body moisture. Tests have been made to check the rate of temperature change in different cushion materials. Temperatures were recorded by means of a thermo-couple placed directly underneath the trim fabric. The trim fabric was identical on all cushions. Test results are shown graphically in Fig. #8. Three cushions were heated for a sufficient period to bring them all to a uniform temperature of 135°F.{Mr Friese} This temperature was selected as a possible one for the inside of a closed car under certain summer conditions. The cushions were removed individually and allowed to cool to a constant temperature of 106°F.{Mr Friese} The time in minutes required for this change in the three materials is shown in the left-hand graph of Fig. #8. At the temperature of 106°F, a passenger was seated on the cushion, remaining still for eight minutes, and then flexing the cushion for two minutes. The resultant temperatures at the cushion surface are shown in the right-hand graph of Fig. #8. Such results are proof of the change of air in the foamed latex structure. Further indication of the ventilating properties of this material is the use in the surgical field for dressings and cast padding to eliminate irritation and blistering of skin areas which are covered for long periods. | ||