| 摘要 |
An electrical switching contact (Figure 3), especially for an arcing contact of a tap changer switch, comprises a roller 31 rotatably mounted on a shaft 32. The shaft also has reaction means 36 between which and the roller a helical spring 35 extends coaxially with the shaft to bias the roller into electrical contact with a shoulder 34. The spring is a light frictional fit on the shaft and keyed at one end to the roller for rotation therewith. Attempted rotation of the roller in one direction winds the spring onto the shaft by increasing frictional pressure thereby preventing further rotation, while rotation in the opposite direction takes place freely. Alternatively, a spring 57 may be a light frictional fit both on a roller 51 and a sleeve 55, fitted on a shaft 52, and will also wind tight in one direction of roller movement to prevent further such movement (Figure 5). The spring 35 or 57 provides a simple method of providing both axial bias and ratchet effects. <IMAGE> |
