| 摘要 |
A programmer timer (10) having motor driven cams (61, 64, 62, 66) for operating electrical switching mechanisms (102, 116, 144, 138, 126). The motor comprises a pair of spaced stator plates (24, 26) with a coil (34) and permanent magnet rotor (36) therebetween, received in a walled chamber (28) in the timer housing. Motor reduction gears (44) drive a shaft (48) for driving the ratchet wheels (72, 68) and rotary cams. The motor, gear train cams and electrical switching mechanisms are contained in a single integral housing (12). Separate concentric fast and slow ratchet wheels (72, 68) are driven by a single eccentric driven pawl (14). The center of rotation of the eccentric is positioned so that drive pawl contacts the ratchet wheel at an angle at least 10 DEG greater than a tangent at the contact point, for all eccentric positions, to provide ratchet wheel advance in the event of reverse rotation of the eccentric. A bifurcated anti-reverse pawl (84) is biased against the fast and slow ratchet wheels by a spring arm (88) integral therewith. The center of rotation of the eccentric is spaced from the fast and slow ratchet wheel centers and optionally has a subinterval cam (148) provided thereon for affecting switching. The anti-reverse pawl may optionally be pivoted about the center of rotation of the drive eccentric. The motor stator plates optionally include integrally therewith a striker arm (178, 180) and anvil (176) for cam controlled operation of a buzzer. The ratchet drive pawl alternatively is biased by a spring arm (154) formed integrally therewith. The ratchet wheel may also optionally employ wiper contacts (200) for contacting a stationary printed circuit board. |
