US Patent 7131203 Safety razors

A safety razor blade unit is provided including at least one blade with a sharp cutting edge extending lengthwise of the blade unit, the blade being carried by a blade assembly, a support structure to which the blade assembly is pivotally joined by a hinge running the length of the blade, the support structure including first spring elements, disposed along the length of the blade assembly, configured to resiliently oppose local deformation of the blade unit under shaving forces encountered in regions where the first spring elements act, and second spring elements, interposed between the support structure and blade assembly, configured to resiliently bias the blade assembly toward a normal position with respect to the support structure.