| 摘要 |
A cover plate (12) with cushioned mat (18) is rotatably mounted on a bottom plate (16). The cushioned mat (18) is fixed on the cover plate (12) by an integral, rigid retention ring (20), an inner bead (34) of the retention ring (20) engaging clampingly under an outer bead (26) of the cover plate (12). An annular groove (22) near the outer edge of the cover plate (12) causes the remaining annular wall (24) with the marginal bead (26) to be connected to the rotating plate (12) only via a thin web, this web representing a bending zone (28), so that when the retention ring (20) is lifted off the annular wall (24) acts as a resilient tongue and can be moved elastically inwards. <IMAGE> |
