| 摘要 |
<p>The brake operating mechanism has a service braking chamber, and a spring-operated auxiliary braking chamber which has a mainly cylindrical and cup-shaped head (26) of a first metal, and an emergency piston (38) of the same metal sliding axially in it. The piston has a first flat surface at right angles to the head axis and towards its open end, and a second surface with a circular hub, opposite the first and extending along the axis, its min. dia. being at the free end. A coil-type pressure spring (39) acts between the hub and the base of the head. A thin-walled guide of a second metal of tubular shape fits coaxially inside the spring and against a part of the hub, and can bear at one end against the base and at the other extends away from it. The hub is accommodated in the guide when the spring is compressed.</p> |
