Patent ID: 7461721

Claim:
An elevator comprising a hoisting rope set having hoisting ropes of a substantially round cross-section, a counterweight and an elevator car suspended from the hoisting ropes and at least one rope pulley provided with rope grooves having a predetermined depth and a cross section having an upper portion with a predetermined radius of curvature and a lower portion with a different radiius of curvature, the at least one rope pulley being a traction sheave coated with a layer of material increasing the coefficient of friction, the coating layer being located in the upper portion of the grooves with the predetermined radius of curvature to form an auxiliary grooving space without a coating between a bottom of the coating layer and the lower portion of the groove with the different radius of curvature, said traction sheave being driven by a drive machine to move the hoisting rope set, wherein in the auxiliary grooving space and the shape of the auxiliary grooving space provide an increased coefficient of friction between the hoisting rope and the rope grooves relative relative to that provided by a pully groove without the predetermined shape of the auxiliary grooving that allows the hoisting rope to bite into the traction sheave after the coating on the surface of the traction sheave has been lost wherein the elevator is usable when the coating on the surface of the fraction sheave has been lost.