| 摘要 |
<p>The motor unit for operating a railway signal includes a frame housing, the motor assembly and operating arm. Electric switch detectors sense the movement of the arm to indicate that it has moved fully. The motor assembly comprises an hydraulic system including a sealed reservoir (6), a filter (7) and a pump (8) driven by an electric motor (9). There is a pressure limiter (10) and a three position valve (11) controlling the operation of a double acting piston (12). The piston is connected to a lever which is rigidly attached to the axle on which the operating arm is mounted. On this axle there are also two fingers which operate the switch detectors. The signal is operated by switching on the pump motor to create the necessary hydraulic pressure to move the signal arm. Alternative arrangements may use either a pneumatic system or an electromagnet system.</p> |
