Patent ID: 7493810

Claim:
A mechanical load bearing indicator for producing signals to a user when the user applies more than selected amounts of load between an extremity of the use and a surface, comprising: a base plate adapted to establish a frame of reference with the surface; a load plate mounted for movement toward and away from the base plate and adapted to receive loads from the user's extremity; at least two snap domes stacked one above the other, and mechanically engaged between the base plate and the load plate for generating two signals when more than two different respective and selected loads are applied to the load plate by the extremity, the snap domes each being physically separate pieces of material from each other, each snap dome having a stable position and a snap-through unstable position; and an intermediate plate between the at least two snap domes, and when a first lower one of the loads is applied to the load plate, a first one of the snap domes collapses and when a second higher one of the loads is applied to the load plate, a second one of the snap domes also collapses; the at least two snap stacked domes being engaged in series between the base plate, the intermediate plate and the load plate, the first one of the snap domes being of a type to collapse at the first lower one of the loads and the second one of the snap domes being of a type to collapse at the second higher one of the loads so that when the first lower one of the loads is applied to the load plate, the first one of the snap domes collapses from its stable position and snaps-through to its unstable position, and when the second higher one of the loads is applied to the load plate, the second one of the snap domes also collapses from its stable position and snaps-through to its unstable position.