Link 7 is connected by turning pair B to bellcrank 1 and by turning pair C to latch 2 which slides in fixed guide a. Links 2 and 7 are connected by turning pair C to link 3 which, in turn, is connected by turning pair D to latch 4, sliding in guide b of link 5. Link 5 and wheel 6, having slots c, turn independently of each other about a fixed axis (not indicated). When latch 2 enters a slot c of wheel 6, the wheel is held stationary. When bellcrank 1 is turned counterclockwise, latch 2 is withdrawn from engagement with wheel 6 and, by means of link 3, latch 4 simultaneously enters another slot of the wheel. At this, point C coincides with the axis of rotation of wheel 6 and link 5. Link 5 then turns wheel 6 about its axis through the required angle. After this, bellcrank 1 is turned clockwise to withdraw latch 4 from engagement with wheel 6. Simultaneously, latch 2 is inserted into the corresponding slot c and locks wheel 6.
$1836$LR,SE$