Flow indicator for train pneumatic brakes - with loose fit piston moved into wide duct for low impedance

摘要

The main supply duch (4) for the train pneumatic brakes is fitted with a monitoring piston which operates on the pressure difference across it to determine the flow, and to operate a set of electric contacts (19). These indicate to the driver if the brakes are still being filled. The monitoring piston (10) has a loose fit in the valve set (9), or is fitted with a slot. This allows a minimum airflow. - For larger airflows the piston is displaced onto a wider section of the duct so as to impede the flow, and to enable the brake lines to be filled rapidly. Different sizes of valve seating can be fitted to cope with different capacities of brake line. The system enables the driver to see when the brakes are fully filled, so that he can pull away without danger of the hold-off brakes operating.