Method and apparatus for forming a flexible thermoplastic resin foam article using an RF field
First Claim
1. A process of forming a flexible, thermoplastic foam article using a mold with a mold cavity, a pair of electrodes across which an RF field may be impressed and compressing means, said process comprising the steps of:
- inserting a preform of the foam material into the mold;
compressing the foam material with the compressing means;
applying an RF heating field while maintaining the foam material compressed to heat the foam material to a temperature below the temperature at which the foam material would become permanently deformed into its compressed state;
withdrawing the compressing means; and
permitting the foam material to expand to conform to and in substance fill said mold cavity as the material cools to cause the foam material to permanently deform to assume the general shape and size of the mold cavity.
1 Assignment
0 Petitions
Accused Products
Abstract
A process and associated apparatus for forming a foam plastic article using a mold with a mold cavity and a pair of electrodes across which an RF field may be impressed. The foam material that is to be processed is inserted into the mold and is then compressed. The compression may be at least on the ratio of 2 to 1 and perhaps as high or higher than 8:1. An RF heating field is applied while maintaining the foam material compressed and after the heat is terminated, the foam material is permitted to expand to conform to a mold shape as the material cools. This pre-compression step enables substantial reduction in processing time.
69 Citations
15 Claims
-
1. A process of forming a flexible, thermoplastic foam article using a mold with a mold cavity, a pair of electrodes across which an RF field may be impressed and compressing means, said process comprising the steps of:
-
inserting a preform of the foam material into the mold; compressing the foam material with the compressing means; applying an RF heating field while maintaining the foam material compressed to heat the foam material to a temperature below the temperature at which the foam material would become permanently deformed into its compressed state; withdrawing the compressing means; and permitting the foam material to expand to conform to and in substance fill said mold cavity as the material cools to cause the foam material to permanently deform to assume the general shape and size of the mold cavity. - View Dependent Claims (2, 3, 4, 5, 6, 7)
-
-
8. An apparatus for forming a flexible, thermoplastic foam article comprising:
-
a mold having a predetermined shape and size mold cavity; a pair of electrodes, one on each side of the mold; means for compressing a preform of the foam material in the mold cavity from a condition in which the foam material in substance fills said mold cavity, to a condition in which the foam material fills only a fraction of the volume of the mold cavity; and means for applying an RF heating field across the pair of electrodes while maintaining the foam material compressed over a heating period to heat the foam material to a temperature below the temperature at which the foam material would become permanently deformed into its compressed state; and means for withdrawing said compressing means to permit said foam material to expand after termination of the heating period to allow it to conform to and in substance fill said mold cavity as the material cools, the foam material being permanently deformed to assume the general shape and size of the mold cavity. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
-
Specification