GB990734A - Improvements in rubber spring suspensions - Google Patents

Abstract

990,734. Rubber springs. MOULTON DEVELOPMENTS Ltd. May 11, 1962 [May 11, 1961], No. 17257/61. Heading F2S. A method of reducing primary creep in rubber springs comprises the steps of deflecting a spring to a strain corresponding at least to its fully loaded condition and holding the deflection for a significant time, e.g. 30 minutes, at this strain and then releasing the strain to a value corresponding to the static deflection of the spring during its service life the spring being prevented from ever reverting back into its free, undeflected, condition. The spring as described, e.g. in Specification 848,996, is first subjected to an hydraulic pressure for approximately 30 minutes of about 400 p.s.i. which corresponds to the bump position, the pressure being subsequently reduced to about 200 p.s.i. to correspond to the static deflection of the spring during its service life, provision being made, e.g. stops, for preventing the spring from adopting its free, undeflected, condition even when the vehicle is jacked and the sprung structure no longer bears upon the spring. In the case of cone spring suspensions as described in Specification 763,432, the spring is deflected to its bump condition and held there for 30 minutes, the strain then being released to a value corresponding to the normal static strain and held there by a bolted tie-piece until it is required for installation on the vehicle. Alternatively, the unrestrained spring may be assembled to the suspension linkage of a car and then compressed and held for 30 minutes at the full bump position before being released to adopt the static condition, stops being provided to prevent the spring from going into its free undeflected position. A comparable technique is adopted for torsional rubber shear springs of the kind described in Specification 676,190, Specifications 676,098, 813,259, 870,489. 914,166, 914,167 and 942,829 also are referred to.