GB1095085A - Leaf springs - Google Patents

Abstract

1,095,085. Laminated leaf springs. FORD MOTOR CO. Ltd. July 29, 1966, No. 34083/66. Heading F2S. In manufacturing a laminated leaf-spring, e.g. of the semi-elliptic, quarter-elliptic, &c. kind, as light as possible with a constant fibre stress throughout the length of each leaf at the maximum load on the spring, the overhang b and thickness t of each leaf is ascertained, assuming the width w constant for all leaves, to give the maximum surface fibre stress S which is to be apportioned to each leaf of the spring, S being proportional to b where w and t are the width and wt<SP>2</SP> thickness respectively of the main part a 1 , a 2 &c., of a leaf and b is the length of the overhang portion b 1 , b 2 &c., and then the deflection Ya, Yb, Fig. 2, from a fully laden state to a free state of no load is calculated from conventional bending beam theory, the datum line from which 7a and 7b are measured being straight as shown, or curved if the spring has a curvature when fully loaded. The fully laden state is the static load required to produce a full jounce deflection. In the assembled state there may be some interference or some " gapping " between the leaves at no load, and, since a thicker leaf suffers more from fatigue than a thinner leaf, the maximum desired stress in a thicker leaf may be slightly less than in a thinner leaf. To ensure that the leaves only contact at the desired pressure points buttons can be interposed between the leaves, interference between the leaves can also be overcome by making the overhang stiffness ratio k equal to <SP>2</SP>/ 3 and forming all the leaves of the arc of a circle radius R in the unstressed state, k being the ratio of the actual stiffness of the tapered overhang to the stiffness if it were of constant thickness equal to the main part of the spring, there being no need to taper the main leaf.