Vehicle suspension member designed to divert crack propagation

#This invention relates generally to a vehicle suspension member and method for making same exemplary of which is a leaf spring comprising a singular or plurality of leafs or plates of which at least one has at least one discontinuity therewithin that is substantially parallel to the longitudinal axis extending between opposite ends thereof and effective to redirect or divert crack propagation in a direction generally parallel thereto.

#Although coil springs have recently come into favor for passenger car suspension systems, leaf springs remain in favor for use particularly in truck suspension systems and are likely to for many years to come because of the load capacity, packaging and axle location advantages associated therewith. Although described herein with particularity to leaf springs, the present invention includes any vehicle suspension member subject to torsional or bending loads and having a longitudinal axis extending between opposite ends such as torque rods (also called trailing arms) for axle control; traction bars (keep axle from twisting during braking); and track rods (keep axle from shifting laterally).

#Leaf springs generally comprise a singular leaf or plate or a plurality of leafs or plates of substantially constant or tapered thickness most commonly made from steel and secured together and operative to support the frame of the vehicle on the wheel axle. As might be expected, the number of leafs or plates employed in the leaf spring is based on allowable design stress for a given load capacity and deflection range.

#FIG. 1 is a side view of a vehicle suspension leaf spring 50 showing the redirected crack propagation;

#FIG. 2 is a schematic block diagram of a method of making a leaf or plate 22 from a billet 10 having a central void or from a tubular section 14;

#FIG. 3 is a schematic block diagram of a method of making a plate or leaf from a billet having a plurality of voids or cavities 28;

#Leaf spring 50 in FIG. 1 comprises singular leaf or plate 2 that extends between opposite ends thereof (not shown) that are adapted such as by being formed into eyelets to secure plate 2 to a vehicle frame. Commonly, only one plate in a stacked plurality of spring leaf plates need have eyelets at one or both its opposite ends. In some instances it may be preferable to omit eyelets. Although shown in FIG. 1 as tapering in a direction towards its opposite ends to provide the thickest section at its center, plate 2 may also have a substantially constant thickness throughout its entire length as previously described and well known to those skilled in leaf spring art.

#As earlier described, plate 2 may be just one of a plurality of stacked leafs or plates that are secured together to provide the suspension system for a vehicle.

#Plate 2 is commonly made from a suitable spring steel alloy and has a substantially rectangular cross-section and a longitudinal axis "L/A" referenced by numeral 4 that extends therealong between its opposite ends.