Page:The Kinematics of Machinery.djvu/486

 464

KINEMATICS OF MACHINERY.

motion of the clockwork by compelling its wheels to move through equal angles in equal times.

Graham's well-known anchor escapement (Fig. 333) may serve us for an example of this. In it two free click-trains are united in such a way that the two clicks \ and 6 2, the one being a pull- and the other a push-click, form parts of the same piece, here called

FIG. 332.

FIG. 333.

an anchor. The motion of the pendulum causes the regular alternate lifting and engagement of the clicks. If the click \ be lifted, & 2 falls into one of the spaces and arrests the motion of the escape-wheel, upon which the driving force acts continually in the same direction. As the anchor swings back, 6 2 is disengaged and the escape-wheel is held by 6 r Each time the wheel moves through a distance corresponding to half the pitch. Each tooth of the wheel, as it slips past the ends q or m of the anchor, exerts some outward pressure upon it, and slightly accelerates