US Patent 7941883 Therapeutic mattress

A mattress (2) which in plan view comprises an inner portion (4) and an outer portion (6), and the mattress (2) being such that the inner portion (4) is of a size for being slept on by at least one person, the outer portion (6) extends at least partially around the inner portion (4), and the inner portion (4) has a lower compression rate than the outer portion (6) whereby the weight of the person on the inner portion (4) is distributed over a greater area than would be the case if the inner portion (4) had the same compression rate as the outer portion (6), and whereby the outer portion (6) constrains the inner portion (4) and controls lateral expansion of the inner portion caused by the weight of the person on the inner portion (4).