| 摘要 |
An improved process for cell opening of cellular polyurethane molded foam using timed partial pressure release (TPPR) reduces pinch deformation and contour lines by releasing the internal mold pressure in a curing cellular molded polyurethane foam product in a controlled manner which allows gas to escape from the mold, but which prohibits relative movement of the mold sealing surfaces by more than an imperceptible amount. The regulated air supply is not shut off, and the venting of the air bag is such as to only lower the pressure to the extent that a virtually imperceptible parting at the seal areas of the mold occurs, at which time the internal pressure is released, cell walls rupture, and gas (23) escapes through the seal area (3). Although the gap between the upper and lower tools is sufficient to allow for the escape of air, it does not allow for the escape of polyurethane material to any appreciable extent. Moreover, at the point in time where the pressure of the polyurethane foam again approaches atmospheric pressure, the remaining pressure of the air bag, which is maintained greater than the weight of the tool, again seals the tool at the sealing surfaces, thus preventing any egress of the green polyurethane foam. |
