Windscreen wiper with elongated, curved backbone

A windscreen wiper which includes

• an elongate backbone which is curved in a plane, is of a resiliently flexible material and which has a connecting formation at a portion intermediate its length for connection to a displacing and force applying member;
• and
• a wiper blade attached to the backbone;
• the backbone having first and second longitudinal ends and a mounting surface defined along the length thereof from said first longitudinal end to said second longitudinal end, said backbone being secured to said wiper blade, said curved backbone being substantially coextensive with said wiper blade, said backbone having a transverse cross-sectional profile defining a thickness and a width thereof, the thickness of said backbone being greatest at said intermediate portion and gradually decreasing along at least a first portion of said backbone, which is defined between said connecting formation and said first longitudinal end,
• the backbone having a free-form curved profile in a plane, whereby the backbone defines an x-y plane, a z-axis extending perpendicularly from the x-y plane;
• the backbone having a suitably varying cross-sectional profile along its length and a suitable free-form curvature, such that a double integral Z.sub.T is less than 1.0 mm, where ##EQU6## where l is a cantilever length of the backbone from the connecting formation to the first longitudinal end of the backbone and I.sub.zz (x) is the moment of inertia about the z-axis at a position x along the backbone from the connecting formation, R(x) is the radius of curvature of the backbone at position x expressed in metres, and I.sub.yy (x) is the moment of inertia about the y-axis at position x.