The Evolution of the Positive Locking Mechanism in End Release Buckles

Abstract

Crash tests conducted by Ford, General Motors, and other automakers have shown that localized accelerations on various objects, including seatbelt buckles, can experience many multiples of the center of gravity acceleration (sometimes exceeding 500 g's) due to contact with other objects within the vehicle or from elastic and plastic deflections of the vehicle structure. In March of 1959, the Cummings [18] pivoting cover buckle patent recognized that the moving parts should be so balanced that "the buckle will not open under the influence of inertia." This paper follows the development of the modern lock for the latch buckle design concept through its evolution. After a discussion of the realization of the inertial potential for unlatching of the buckle from numerous patents and testing, seatbelt locking mechanisms will be discussed by category, followed by a short summary of the inertial blocking mechanisms. These designs will be described, patents for each listed, examples given of vehicles where they have been installed, and the inertial capability of each buckle type catalogued. From this discussion, the reader should have a clear understanding of the capabilities of the modern lock for the latch seatbelt buckle and the roots from whence it has been developed.