A calliper is a device that pinches brake discs with arbitrary force to create braking force. RTRI developed a pneumatic floating calliper that offered simplicity and outstanding maintainability without requiring the use of a pneumatic-hydraulic conversion device (i.e. a booster cylinder) and was interchangeable with the existing lightweight and compact hydraulic calliper used on Shinkansen vehicles.
In this device, an elliptical diaphragm-pressing mechanism, free from parts such as levers and gears, works to directly transmit large forces and is used as an operating actuator. The diaphragm operates simply to convert air pressure into pressing force, and is characterised by a high level of freedom in terms of the shape of its fabrication because it uses a thin and airtight rubber membrane. It is therefore possible to configure it with the same size as a hydraulic calliper (Fig. 1).
Testing on a braking test bench confirmed that the pneumatic floating calliper offered a level of brake performance equivalent to that of the hydraulic calliper (Fig. 2), and that the increase in temperature of the diaphragm could be suppressed to a level that did not adversely affect its lifespan thanks to the adiabatic piston arrangement within the brake lining (Fig. 3).