GB608346A - Improvements in or relating to torsion spring systems - Google Patents

Abstract

608,346. Torsion-bar springs. MENSFORTH, T., and FIRTH & J. BROWN, Ltd., T. Feb. 20, 1946, No. 5339. [Class 108 (iii)] Means are provided in a torsion spring system whereby the stiffness of the spring is automatically and continuously varied throughout a part or whole of its deflection. In the construction shown, the torsion rod 12 is rotatable at the outer end 16 in a bearing carried by a concentric casing 10, the inner end of the rod 12 being anchored to the casing. The casing which may be in two parts, bolted together as shown by bolts 11 or alternatively may be broached from a solid tube, has two abutments 21, Fig. 3; diametrically spaced and extending axially along the bore of the casing 10. Faces 18 are machined on opposite sides of the bar 12 in such a way that the angle formed between the faces and a reference plane containing the longitudinal axis of the bar varies progressively along the bar. Each face is arranged to engage the extreme inner end portion of the respective abutment 21 as shown in Fig. 3. On deflection of the bar 12 by an operating arm 15, the point of contact of the faces 18 with their respective abutments 21 progress from the inner to the outer end of the bar. The space 23 between the rod 12 and casing 10 may be sealed by a bush 22 and filled with oil or grease. In an alternative arrangement, not shown, the torsion rod may be of circular section and provided with one or more longitudinally disposed ribs or splines adapted to engage one or more similar ribs or splines arranged on the bore of the casing, the point of engagement being caused to vary progressively on deflection of the bar by disposing the casing ribs and/or the torsion bar ribs helically in relation to the longitudinal arms of the assembly. The pitch of the helically arranged ribs may be made to vary along the length of the casing or bar. In both constructions, the casing may be anchored at both ends to the respective member of the parts between which the spring assembly is mounted. Alternatively, the casing may be anchored at one end or at an intermediate position, in which case it will be stressed in torsion and will contribute to the resilience of the assembly. In the latter case, the cross-sectional area of the casing may be varied to influence the deflection characteristic. The cross-sectional area of the torsion bar may also be varied in relation to its length. The variation in angular disposition between the faces or ribs on the bar and the abutments on the sleeve may be made zero for part of the length at the outer end of the bar so that the assembly has a constant rate over a given range of operation.