| 摘要 |
1532637 Optical projectors S BESANCENOT 21 Oct 1975 [21 Oct 1974] 43119/75 Heading G2J [Also in Division F2] Slide-changing mechanism for a projector, of the kind in which the mechanism is operated by a push-rod (1), Fig. 3, (not shown) pivoted to the end of a crank arm fixed to a shaft 2 which is continuously driven by an electric motor (not shown) through two stages of gearing, includes an arm 11 which disengages the two stages in turn. In operation, a gear-wheel 10 fast on shaft 2 engages a pinion 9 fast with a gear-wheel 7, both of which are freely mounted on a shaft 8 fixed to an arm 11 pivoted at 12. Gear-wheel 7 engages a pinion 6 continuously driven by the motor. One end 14 of lever 11 is spring-urged against the armature 15 of an electromagnet. When the electromagnet is not energized, the armature 15 takes up the position shown in faint lines, and lever 11 rocks about its pivot to disengage gear wheel 7 from pinion 6, and pinion 9 from gear-wheel 10. When a slide change is to be made, the operator presses a button which energizes the electromagnet for a short time. The armature 15 moves to its full-line position, pivoting lever 11 so that first gear-wheel 7 engages pinion 6, then pinion 9 engages gear-wheel 10, and the motor drives shaft 2 through the gears. At the same time a stud 13 at the other end of lever 11 enters a gap 19 formed in a flange 18 of the gear-wheel 10, pushing back a shoe 20 against action of a spring 21. When the electromagnet is de-energized, the gear-wheel 10 has turned so that stud 13 is trapped by flange 18, until the gear-wheel has completed one revolution, during which the push-rod (1) makes a complete excursion. At the end of the revolution, spring- loaded shoe 20 ejects stud 13 from the flange 18, and the gears are disengaged once more. |
