Method of Treating Springs

Author:  Paul Otto Friedrich Vorwerk
Source:  US Patent 1,947,927
Doc ID:  1930004
Year of Publication:  1930
Abstract:  
It is generally known that the number of oscillations up to fatigue or fracture of springs, particularly leaf springs, is related with the properties of the surface of the springs. It is also known that small scores in the surface of springs such as occur due to rolled-in scales or grooves and small crevices of other types, give rise to points of incipient premature fatigue or fracture. It is further known that by etching or sand blasting such crevices can be flattened out whereby the fatigue and fracture of the springs is delayed and the life is thus somewhat extended. The invention resides in the utilization of the knowledge that by increasing the tensile strength of a very thin superficial layer of springs, the number of oscillations up to fatigue can be increased by 600-1000% and that for this purpose a compacting suffices by impacts which are so small that they can be effected by a sand blast.