Escalator having yieldable primary and non-yieldable secondary transverse guide points on one side thereof

Claim 1

An escalator, comprising: an endless belt having first and second sides; a plurality of steps attached to said endless belt; means for driving said endless belt in a loop which includes load-bearing and return runs for said steps; skirt means disposed to provide substantially vertical side walls adjacent to said steps, with a predetermined running clearance therebetween having a normal dimensional range which includes a normal minimum dimension; a plurality of guide wheels rotatably mounted on the first side of said endless belt; said guide wheels having a compressible tread portion; said guide wheels having a substantially incompressible hub portion; said tread portion having a flat cross-sectional configuration at its outer periphery, inner and outer side wall portions, and outwardly curved inner and outer edges which interconnect the outer periphery with the inner and outer side wall portions, respectively; said hub portion being a tubular structure having first and second ends which extend outwardly past the inner and outer edges, respectively, of said tread portion; a guide track on the first side of said endless belt; said guide track having a flat support portion for supporting the flat outer periphery of the tread portion of said guide wheels, and inner and outer primary guide surfaces which extend upwardly from the flat support portion, said inner and outer primary guide surfaces being spaced to cooperate with the inner and outer edges, respectively, of the tread portion of said guide wheels, to define first and second primary guide points, respectively, which guide the endless belt within a first predetermined dimensional range from a desired tracking centerline when the endless belt is subjected to normal side thrust forces; said guide track having portions which continue upwardly from both the inner and outer primary guide surfaces to define inner and outer secondary guide surfaces; said inner and outer secondary guide surfaces being spaced to cooperate with the first and second ends, respectively, of said hub portion to define first and second secondary guide points, respectively; said first and second secondary guide points becoming operative after abnormal side thrust forces compress an edge of said tread portion to force the endless belt beyond one of the first and second primary guide points, but before the endless belt and its connected steps move laterally by a dimension equal to the minimum normal running clearance, to provide positive limits on the lateral movement of said endless belt and steps which preclude contact between said steps and said skirt means on either side of said endless belt, while guiding said endless belt solely from the first side thereof.