Wheelchair cushion utilizing foams of different stiffnesses

摘要

A polyurethane foam wheelchair cushion comprises first, second, third and fourth elements. The first element extends across the front portion of the cushion and is made of a relatively stiff foam. The second element is centered near the back portion of the cushion and is made of a foam with a lower stiffness than the first element. Third and fourth elements are on either side of the second element and are made of a foam having an intermediate stiffness between the first element and the second element. Transition surfaces between the second and third and fourth elements are angled relative to a vertical plane. Such an angled transition surface provides a gradual change in stiffness in the vertical direction between materials of different stiffnesses. The top surface of the first element is oriented relative to the second element so that the user's ischial tuberosities will be located approximately 1.5 inches lower than the back surface of the user's thighs when the user is sitting in the wheelchair cushion.