Ozone and Chemical Resistant Coating for Railway Line Elastomeric Components

Abstract

Elastomeric pads are shown for positioning on top of railroad ties. Pre-cast concrete panels that are commonly provided at railway grade crossings between and alongside the rails rest on the pads. The pads may be extruded from a variety of natural or synthetic elastomeric materials. The pads include a panel or body formed of the elastomeric material with an exterior surface. A synthetic, polymeric coating is applied to at least selected portions of the exterior surface of the elastomeric body. The coating provides improved properties which allow more standard elastomers to be utilized for the main body of the component. The coatings can also be applied to railroad tie boots to provide increased ozone resistance.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] The present application claims priority from the earlier filed provisional application, serial number 60 / 776,380, filed Feb. 24,2006, entitled “Impact, Abrasion and Chemical Resistant Coating For Railway Line Pads and Boots.”BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to surface coatings which provide enhanced performance properties for elastomeric components used in railway line emplacements including railway line pads and boots and to goods produced with such coatings. Specifically preferred coatings are used to provide improved weathering, anti-vibration, abrasion and oil and chemical resistance characteristics for such goods. The invention also relates to assemblies of rails, pads, boots and rail foundation members when secured together in a railway line emplacement. [0004] 2. Description of the Prior Art [0005] A variety of rubber or elastomeric type goods are used in the railro...

AI Technical Summary

Benefits of technology

[0016] It is an object of the present invention to provide a railway pad, boot or other elastomeric component used in a rail pad assembly which component has improved weatherability, ozone, impact, abrasion and oil and chemical resistance characteristics when in place in a railway installation.

[0018] Another particularly preferred coating is manufactured by Lord Chemical Products, as the LORD HPC-5C™ coating. This coating is a one-part, room temperature curing hydrogenated nitrile butadiene rubber. In use, the base rubber material, such as styrene butadiene rubber, is provided with a single coat of CH7701™ primer plus a single coat of HPC-5C™ topcoat. The addition of the HPC-5C™ coating allows styrene butadiene rubber to meet ozone requirements, meet tensile strength and elongation after aging requirements, minimize flame propagation, decrease fume toxicity, and increase oil and fluid resistance.

Problems solved by technology

Despite having been engineered to withstand the weight of vehicular traffic, these panels are subject to wear and can fail prematurely.

When a heavy truck passes over the crossing, the panels are subjected to bending stresses, tending to deflect downward where the tires of vehicles pass over areas of the panels that are not directly supported by the ties.

Rather, it is the fact that the undersurface of the panel is in tension as it repeatedly strikes against the upper surface of the tie so that tiny chips are broken away from the bottom surface of the panel, leading to eventual surface cracks and propagation of the cracks.

Premature failure of a panel in such railway crossings is most likely to occur when the ties are unusually uneven.

However, the panels still do fail, and in order to counter premature failure of the concrete panels, pads of rubber or rubberlike materials have been used atop the ties to distribute the loads of motor vehicle traffic more evenly.

However, natural rubber or other existing elastomer compounds are not satisfactory to meet the requirements in all applications.

The raw SBR materials which have been used in the past will not meet the new standards for ozone resistance.

Images