| 摘要 |
Hot-box signalling devices are disclosed for indicating the presence of overheated bearings in vehicles such as rail cars. The device includes means defining a closed compartment containing a fluid and pressure-sensitive means communicating with the compartment. The compartment is arranged in thermal communication with a bearing of the vehicle so that increases in the temperature of the bearing cause increases in the pressure exerted by the fluid. The pressure-sensitive means is adapted to produce a signal when the pressure exerted by the fluid exceeds a predetermined threshold representing an over-temperature condition in the bearing. Preferably, the pressure-sensitive means takes the form of a plug normally closing an opening in the compartment, and a marker material, the plug and marker material being expelled when the pressure in the compartment reaches said predetermined threshold. In one aspect of the invention, provision is made to compensate for ambient temperature. The invention also provides a system for detecting a signal produced by a hot-box signalling device.
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