GB2412969A

GB2412969A - Pressure sensing apparatus

Info

Publication number: GB2412969A
Application number: GB0406828A
Authority: GB
Inventors: David Lee Sandbach; Stuart Mark Walkington; John Burkitt
Original assignee: Eleksen Ltd
Current assignee: Eleksen Ltd
Priority date: 2004-03-26
Filing date: 2004-03-26
Publication date: 2005-10-12
Anticipated expiration: 2024-03-26
Also published as: GB2412969B; GB0406828D0

Abstract

Pressure sensing apparatus comprising a cushion having an inflatable cell, an inflation channel leading to the inflatable cell and an air pressure sensor located inside the inflation channel. Two conductive layers are disposed on opposed inner surfaces of the inflatable cell. The pressure sensing apparatus may be used to generate data representing pressure within a region of deformation of the cushion caused by an occupant. From this data, a a pressure profile map may be derived and the peak interface pressure between the occupant and the cushion may be derived.

Description

24 1 2969 Pressure Sensing The present invention relates to pressure

sensing apparatus. The pressure sensing apparatus may be used to generate data representing pressure within a region of deformation of a medical cushion caused by an occupant, from which a pressure profile map may be derived.

Written Description of the Best Mode for Carrying Out the Invention Figure 1 A multiplexed fabric detector of the type described in United Kingdom Patent Publication No GB 2 365 134 A is shown in Figure 1.

Sensor 101 defines four zones arranged to be multiplexed to provide four sets of XYZ data, the data representing centre of pressure (XY), and a signal relating to force and area of contact (Z).

Figure 2 Figure 2 shows a cross-section through a four cell inflatable cushion.

The cushion includes a sensor of the type shown in Figure 1, but in this example the separator mesh is not present. Instead, the unidirectional conductive fabric layers 201 and 202 are attached to the inside surfaces of the cushion, and are insulated from each other at the contact points by an insulating mask 203. In other, active regions, an air gap forms the separation until closed, thus making electrical contact between the conductive layers 201, 202 upon flattening the cushion, or 'bottomingout'.

Adhesive 204 bonds the layers together, forming cells, which can be inflated or deflated via air channels (not shown). Since no separator mesh is used in the construction, with smooth upper and lower conductive fabric layers Z does not increase greatly in response to greater applied force, but does increase significantly in response to force applied over a greater area.

Thus, the Z reading becomes closely related to the area of the conductive sheets 201, 202 in electrical contact. The fabric layers may be pierced to accommodate the cellular construction, or may form multiple individual strips running along the cell. The principles described also apply to such structures.

Jo In a first embodiment, an air pump is connected to the air channels of the cushion in a manner that allows the pressure in the whole cushion only to be varied. In addition, a piezo-electric air pressure sensor is placed in the air channel. Alternatively, as discussed separately below, the inflation system may be arranged to allow the air pressure in separate cells, or chambers, or groups of cells, or chambers, to be varied.

Figure 3 Figure 3 shows a display 301 of four sets of XYZ data, Z1, Z2, Z3, Z4 corresponding to the four sensor zones of the four cell inflatable cushion described above with reference to Figure 2. Display 302 indicates the level of air pressure present in the cushion, measured from the air pressure sensor.

The data shown indicates an example of data derived from an occupant sitting on the cushion with no significant air pressure. The vertical and lateral positioning of Z1, Z2, Z3 and Z4 show the XY value for each sector, indicating the position of the centre of applied pressure within the sector; while the size of Z for each sector, illustrated by the size of the circle, indicates the area of conductive fabric in contact within that sector of the cushion.

Figures 4, 5 & 6 Figures 4, 5 and 6 each show a different set of displayed data, to corresponding to readings from the cushion at low, medium and higher pressures respectively. The data shown in Figure 6 represents the position on the sensor adjacent to the ischeal tuberosities of the occupant, these being the two points on the pelvis immediately above the highest pressure loading on the cushion.

At air pressure slightly greater than that shown in Figure 6, the signal from the sensor disappears altogether, indicating an absence of electrical contact within the sensor. At this point the air pressure is measured by the pressure sensor; this pressure indicating the peak interface pressure between the occupant and the cushion surface. This measurement from a standard air pressure sensor is precise and reliable, representing a significant improvement over known interface pressure measurement and monitoring systems.

Combinations of data shown in Figures 3, 4, 5 and 6 may be superimposed over each other and shown in a coloured 'contour' map, for example to assist healthcare professionals in configuring the cushion for best therapeutic effect.

in a second, preferred embodiment, the cushion includes four chambers capable of containing independent air pressures. The sensor is advantageously used in conjunction with such a system, for example to control the pressure in each chamber in order to provide and maintain a pressure for each chamber that is slightly greater than the peak interface pressure over that chamber. Thus, the occupant is immersed as deeply as 0 possible in the cushion; providing maximum surface area of support from the cushion and thereby minimising the interface pressure as far as possible.

Claims

Claims 1. Pressure sensing apparatus comprising: a cushion having an

inflatable cell; an inflation channel leading to said inflatable cell; a first conductive fabric layer and a second conductive fabric layer on opposed inner surfaces of said inflatable cell, and an air pressure sensor located within said air inflation channel.
2. Apparatus according to claim 1 in which said cushion has a plurality of inflatable cells.
3. Apparatus according to claim 2 comprising a plurality of inflation channels, wherein each cell is arranged to be independently s inflated via one inflation channel only.
4. Apparatus according to claim 2 comprising a plurality of inflation channels, wherein a group of cells is arranged to be independently inflated via an inflation channel.