There are various uses for elongated flexible assemblies such as for elevator load bearing members or roping arrangements, drive belts for machines such as a passenger conveyor and handrails for passenger conveyors, for example. Such assemblies may be designed with a plurality of cords covered by a polyurethane jacket. For example, U.S. Pat. Nos. 6,295,799 and 6,739,433 show belts for use in suspending an elevator car and counterweight within an elevator system. An example passenger conveyor handrail construction is shown in U.S. Pat. No. 4,982,829. An example passenger conveyor drive belt is shown in U.S. Pat. No. 6,540,060.
One aspect of such assemblies is that the jacket could burn when in an environment that could instigate combustion such as exposure to flames. Providing an ability to resist or minimize any burning of the jacket would be useful. One challenge when considering making such a jacket flame-resistant is keeping the desired qualities of the jacket material. The examples mentioned above all need a certain flexibility to follow a path of movement while the assembly is in use. It is also desirable to have proper surface characteristics for the intended use of the assembly.
Flame retardant polyurethane compositions have been suggested. For example, U.S. Pat. No. 4,542,170 uses a pentate salt and a phosphate combination to provide flame retarding properties. Not all flame retardants are compatible with the requirements for the example assemblies mentioned above.
USPTO Backgrounds
USPTO Backgrounds