Measuring and testing – Dynamometers – Responsive to multiple loads or load components
Reexamination Certificate
2000-07-31
2001-09-18
Noori, Max (Department: 2856)
Measuring and testing
Dynamometers
Responsive to multiple loads or load components
Reexamination Certificate
active
06289747
ABSTRACT:
The invention relates to a pressure-sensitive area sensor.
Sensors of this type are currently used e.g. to detect occupation or record a pressure profile in car seats in order to control the tripping of an air bag. In this case they are placed on deformable seat upholstery or integrated in the latter and are designed to detect whether and if necessary how the seat is under load. The body size and sitting posture of the seated person, for example, can then be derived from the determined pressure profile.
Already known sensors of this generic type comprise a sheet-type supporting structure, over the area of which several pressure-sensitive switching elements are distributed. The latter form the pressure-sensitive areas. To permit adaptation of the two-dimensional supporting structure to a three-dimensional supporting area, it is already known to use a supporting structure which consists only of strip-type connecting paths held together by an outer frame. The pressure-sensitive switching elements are integrated in the strip-type approximately 2 cm wide connecting paths.
It has bee n established that the response behaviour of the switching elements is affected by deformations of the supporting structure in these already known area sensors.
Hence the present invention is based on the task of improving the response behaviour of the switching elements in the pressure-sensitive area sensors described above.
According to the invention this problem is solved by an area sensor according to claim
1
.
A pressure-sensitive area sensor of this type comprises a two-dimensional supporting structure, which consists substantially of flexible connecting paths, and several pressure-sensitive switching elements, which are distributed over the area of the supporting structure. According to the invention the pressure-sensitive switching elements are supported by free-standing projections on the connecting strips at least where the supporting structure is subjected to larger three-dimensional deformations.
Compared to already known pressure-sensitive area sensors, in which the switching elements are integrated in the connecting paths, the effect of deformations of the supporting structure on the switching elements is attenuated in the area sensors according to the invention. The switching elements on the free-standing projections of the connecting strips are in fact mechanically disconnected from the supporting structure to a certain degree. This means that the two-dimensional supporting structure can adapt to a three-dimensional supporting area (such as seat upholstery) and to its deformations without causing larger parasitic loads on the switching elements. In other words the switching elements are no longer pre-loaded by mechanical stresses in the connecting paths, which are caused by deformations of the supporting structure. Consequently their response behaviour is substantially improved. Furthermore, it should be noted that compared to already known area sensors, in which the switching elements are integrated in the connecting strips, the width of the connecting strips may be far smaller than the width (or diameter) of the switching elements in the area sensor according to the invention. In other words the width of the connecting strips is determined solely by their connection function and not by the dimension of the switching elements in the sensor according to the invention. Narrower connecting strips are less resistant to deformation, so that three-dimensional deformations of the supporting structure produce smaller mechanical stresses, which may impair the response behaviour of the switching elements. The adaptation of the two-dimensional area sensor to a three-dimensional supporting area is, of course, also improved by better three-dimensional deformability of the area sensor. When the area sensor is used in an upholstered seat, e.g. to detect occupation of the seat or record a pressure profile, the area sensor according to the invention produces more comfortable sitting by improved deformability and smaller coverage of the seat area.
In an advantageous embodiment of the area sensor the narrow connecting strips incorporate deformation loops or deformation curves. These deformation elements also improve the deformability of the connecting strips and thus produce even better adaptation of the two-dimensional supporting structure of the sensor to a three-dimensional supporting area. As the resistance of the connecting strips to deformation is thus greatly reduced, the latter do not transmit any significant bending moments or torsional moments, which cause parasitic loads in the switching elements.
The deformation loops are advantageously each arranged in a connecting strip between two projections, so that a compressive force acting locally on a switching element in a first projection does not cause a mechanical load on the switching element in the adjacent projection. By arranging the deformation element immediately in front of a projection it is ensured that no significant bending and torsional moments are transmitted to the projection.
The projections advantageously comprise a head section, which carries the switching element, and a connecting link, which connects the head section to the connecting path. The dimension of the connecting link perpendicular to the connection direction should preferably be smaller than the corresponding dimension of the head section. This tapering of the projection in the area of the connecting link ensures that the latter is more flexible than the head section, with the result that residual deformations are essentially absorbed by the connecting link and have no significant effects on the switching element. In addition the connecting link of the projection can be perpendicular to the connecting path, with the result that the mechanical uncoupling between head section and connecting strip is further improved.
The supporting structure advantageously comprises connecting strips arranged like a grid, which are connected to each other via deformation loops or curves. This grid-type arrangement of the connecting strips permits uniform distribution and advantageous connection of the switching elements. In addition the grid-type supporting structure has essentially the same deformability in two perpendicular directions. Consequently more uniform adaptation of the area sensor to a three-dimensional supporting surface is achieved.
The pressure-sensitive switching elements advantageously have electrical connecting leads which are integrated in the connecting paths. In a preferred embodiment the supporting structure consists of two sheets glued together, connecting leads and switching elements being arranged between the two sheets.
The area sensor preferably comprises pressure-sensitive resistance sensors, which are known inter alia by the name “Force Sensing Resistors (FSR)”. The resistance of an FSR sensor of this type is dependent on the compressive force acting on it. Resistance sensors of this type comprise, for example, a planar electrode, an area coated with semi-conductor material, which is opposite the planar electrode, and a spacer. The spacer ensures that the planar electrode and the semi-conductor material are not contacted when the switching element is not actuated. In the case of a compressive load on the FSR sensor the contact resistance diminishes with increasing compressive force. The planar electrode of the FSR sensor can be mounted on a first sheet and the semi-conductor material surface on a second sheet, the first and second sheet being separated by a spacer sheet.
An area sensor according to the invention is used advantageously, e.g. in an upholstered seat to detect occupation or to record a pressure profile, the area sensor resting on the upholstery or being integrated in the latter. The high flexibility of the supporting structure and the small width of the connecting strips ensure more comfortable sitting compared to already known pressure-sensitive area sensors.
The high flexibility of the supporting structure and the fact that the individual swi
Billen Karl
Federspiel Laurent
Knecht Reinhard
Theiss Edgard
I.E.E. International Electronics & Engineering S.A.R.L.
Noori Max
Spencer George H.
Venable
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