| 摘要 |
A program switching mechanism comprises a programmer (1) advanced stepwise by a pawl (7) engaging a ratchet wheel (5) and reciprocated by a rocking lever (15), driven by a cam (31) on a driving disc (29) which also advances a dwell timing ratchet wheel (35) via a striker (33). The ratchet wheel (35) carries dwell timing cams (61, 57) which engage a time control lever (47) which holds the pawl (7) out of engagement with the teeth of the ratchet wheel (5) during the dwell phases and displace the lever to release the pawl (7) to enable it to reengage the ratchet wheel (5). The lever (47) has a sensing tip (43) which drops into recesses of two different depths in a cam disc (3), rotated with the programmer, to move the lever (47) into the path of one or other of the timing cams (61, 57) and displace the pawl (7) to its inoperative dwell position. A pin-and-slot pivot (49) of the lever (47) enables the programmer to be rotated manually. An alternative embodiment with axially acting ramps on the ratchet wheel (35) is described. <IMAGE> |
