Page:The Kinematics of Machinery.djvu/468

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KINEMATICS OF MACHINERY.

function in every case is the formation of kinematic links, these links having the form C + ...\ ...G+.

FIG. 300.

FIG. 301.

Moveable couplings subdivide themselves into those which are moveable axially, radially, and angularly. Sharp's claw coupling,

Fig. 301, is an illustration of the first kind. It is formed as a prism pair PP~, for the claws of the piece A and B are prismatic, and are so formed that relative motion can take place between them only in tl e direction of the axis of the shafts a and ~b. We may suppose the pieces A and B to be connected to a and b by key-fastenings.*

Oldham's coupling, Fig. 302, is one which is moveable radially. We have already examined this mechanism fully ( 72), and have found it to be a turning cross-block, having the special formula

FIG. 302.

The universal joint, Fig. 303, is an example of a coupling having angular motion. We have in our earlier investigations repeatedly spoken of this train, and in 62 pointed out that it was a conic turning cross-block ((7J<7 t )r. It must not be forgotten that the link C~...L...C~ is omitted from our figure, as is usually the case in representations of the joint.

These examples are sufficient to show that in the moveable

axially without disturbing the transmission of rotation.
 * This coupling is not intended for use as a clutch, but for allowing a or b to move