Apparatuses and methods for determining performance parameters of a flexible surface

1. A method for determining a characteristic of a flexible surface, the method comprising:

providing a test device at least part of which having a bottom area and side area, the test device comprising a plurality of sensing points extending from the bottom upwardly toward the side, wherein the test device has a substantially hemispherical shape and the sensing points are arranged on the substantially hemispherical shape in a plurality of spaced, parallel rings that are centered on a radius of the hemispherical shape passing through an apex of the substantially hemispherical shape with at least two sensing points being arranged on each concentric ring;

pressing the test device into a flexible surface;

measuring pressures at the sensing points; and

determining an envelopment parameter of the surface based on the pressures, wherein the determining operation comprises:

determining a contact area of the test device using the sensing points, and the immersed area of the test device using a distance that the test device has been pressed into the flexible surface.

2. The method as recited in claim 1 , wherein the determining operation comprises:

determining a contact depth based upon the highest location of a sensing point where a nominal pressure is sensed.

3. The method as recited in claim 1 , wherein the determining operation comprises:

determining percent envelopment by dividing the contact area by the immersed area.

4. The method as recited in claim 1 , wherein the test device comprises a flexible material adjacent the sensing points.

5. The method as recited in claim 4 , wherein the test device comprises a hemispherical shell, wherein the flexible material comprises a gel adhered to an exterior of the shell, and wherein the sensing points comprise concentric rings of sensors spaced along the exterior of the shell.

6. A method for determining a characteristic of a patient support surface, the method comprising:

pressing a test device into a patient support surface, wherein at least part of the test device has a generally rounded shape having a bottom area and a side area, the test device comprising a plurality of sensing points extending from the bottom upwardly toward the side, wherein the rounded shape of the test device comprises a substantially hemispherical shape and the sensing points are arranged on the substantially hemispherical shape in a plurality of spaced, parallel rings that are centered on a radius of the hemispherical shape passing through an apex of the substantially hemispherical shape with at least two sensing points being arranged on each concentric ring;

measuring pressures at the sensing points;

transmitting signals representing the pressures from the sensing points to a data device;

storing pressure data representing the pressures in the data device; and

determining an envelopment parameter of the surface based on the pressure data; wherein the envelopment parameter is determined by dividing a contact area (CA) by an immersion area (IA), wherein CA and IA are calculated by the following formulas:

CA =2*π* r *(contact depth)

IA =2*π* r *(immersion depth),

wherein r is the radius of the generally rounded shape.

7. The method as recited in claim 6 , wherein an immersion depth is calculated by measuring how far down the test device has been pressed into the support surface.

8. The method as recited in claim 6 , further comprising:

measuring an immersion depth that the test device has been pressed into support surface, wherein the envelopment parameter is further based on the immersion depth.

9. The method as recited in claim 6 , wherein the pressing operation is carried out at a controlled force by a measuring device.

10. The method as recited in claim 9 , wherein the measuring device comprises a force displacement measuring device.

11. The method as recited in claim 9 , wherein the measuring device presses the test device into the patient support surface at a known force and records displacement data indicating how far the test device has been pressed into the patient support surface.

12. A method for determining a characteristic of a patient support surface, the method comprising:

pressing a test device into a patient support surface, wherein at least part of the test device has a generally rounded shape having a bottom area and a side area, the test device comprising a plurality of sensing points extending from the bottom upwardly toward the side, wherein the rounded shape of the test device comprises a substantially hemispherical shape and the sensing points are arranged on the substantially hemispherical shape in a plurality of spaced, parallel rings that are centered on a radius of the hemispherical shape passing through an apex of the substantially hemispherical shape with at least two sensing points being arranged on each concentric ring;

measuring pressures at the sensing points;

transmitting signals representing the pressures from the sensing points to a data device;

storing pressure data representing the pressures in the data device; and

determining an envelopment parameter of the surface based on the pressure data;

wherein the pressing operation is carried out at a controlled force by a measuring device; wherein the measuring device presses the test device into the patient support surface at a known force and records displacement data indicating how far the test device has been pressed into the patient support surface; wherein the envelopment parameter is determined based on a contact area determined from the pressure data and an immersion parameter determined from the displacement data.

13. The method as recited in claim 6 , wherein the contact depth is determined by a height from the bottom of the test device of the sensing point that measures a pressure exceeding a nominal pressure.

14. A method for determining a characteristic of a patient support surface, the method comprising:

pressing a test device into a patient support surface, wherein at least part of the test device has a generally rounded shape having a bottom area and a side area, the test device comprising a plurality of sensing points extending from the bottom upwardly toward the side, wherein the rounded shape of the test device comprises a substantially hemispherical shape and the sensing points are arranged on the substantially hemispherical shape in a plurality of spaced, parallel rings that are centered on a radius of the hemispherical shape passing through an apex of the substantially hemispherical shape with at least two sensing points being arranged on each concentric ring;

measuring pressures at the sensing points;

transmitting signals representing the pressures from the sensing points to a data device;

storing pressure data representing the pressures in the data device;

determining an envelopment parameter of the surface based on the pressure data; and

measuring the immersion depth that the test device has been pressed into support surface, wherein the envelopment parameter is further based on the immersion depth; wherein the envelopment parameter is an envelopment percentage (EP) determined by the following equation:

(2*π* r *(contact depth))/(2*π* r *(immersion depth)).

15. The method as recited in claim 14 , wherein the contact depth is determined by a distance to a highest sensing point that senses a pressure that is greater than a nominal value, and the immersion depth is determined by measuring a distance that the test device has been pressed into the patient support surface.

16. The method as recited in claim 15 , wherein the distance that the test device has been pressed into the patient support surface is determined by a force displacement measuring device that automatically carries out the pressing step until a predetermined pressure is reached.