| 摘要 |
PURPOSE:To maintain the decending speed of a carriage automatically constant with a simple device by connecting the brushes of a permanent magnet field DC motor provided to the carriage through semiconductor switching elements which are conducted by the application of voltage higher than prescribed values. CONSTITUTION:When a carriage 3 mounted thereon with a welding torch 16 begins to descend by gravity along rails 5 in parallel with a weld line 10, the spur gear 21 meshed with a rack 11 provided to the rails 5 begins to rotate, by which a motor shaft 18 is rotated. Therefore, a permanent magnet field DC motor 17 operates as a power generator, thereby generating electric power. On the other hand, the lead wires 24, 25 of the brushes of the motor 17 are connected through constant voltage diodes which are semiconductor switching elements 27, 28, 29. Then, when the carriage 3 tries to descend fast, the generating voltage of the motor 17 rises higher than the Zener voltage of the constant voltage diodes; therefore, the braking force acts and the descending speed is dropped. When the generating voltage drops lower than the Zener voltage, the braking force does not act any more and the speed increases, thus the speed is controlled constant. |
