| 摘要 |
<p>There is provided a timing device of the type suitable for controlling the cycling of appliances and the like. The timing device employs a known type of switching cam and switch elements. A drive is provided for the switching cam which provides for slow or normal advance of the cam. More specifically, the drive system employs two pawls each of which is advanced independently by means of drive cams. The pawls are provided with short and normal strokes. Each pawl engages separate ratchet teeth in the switching cam. At the time it is desired to have the shorter stroke pawl assume the function of advancing the switching cam, the ratchet teeth for the large advance parl are omitted from the switching cam and this longer stroke pawl then merely moves on the surface of the cam until ratchet teeth are again provided for it to function.</p> |
