Patent ID: 7415875

Claim:
A belt force measuring device with a measuring spring ( 12 ), which spring is arranged in the flux of a force and a strain of which spring is a measure of the belt force, wherein the measuring spring ( 12 ) is formed in such a way and arranged by means of a first mounting and a second mounting in the flux of force such that, depending on the belt force, the spring extends between the first and second mountings, the force measuring device further comprises a strain measuring structure ( 23 ) being arranged at or on the measuring spring ( 12 ), the measuring spring being formed as a tension spring, and wherein the measuring spring ( 12 ) is arranged such that it is integrated in a housing ( 2 ) of a belt buckle (l); and wherein the strain measuring structure ( 23 ) is a strain gauge, the measuring spring ( 12 ) has two regions ( 20 , 21 ) with lower spring rigidity, which two regions are connected by means of a portion ( 22 ) of higher spring rigidity, and there is at least one of said strain measuring structure ( 23 ) arranged in the portion ( 22 ) of higher spring rigidity.