Page:The Kinematics of Machinery.djvu/370

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KINEMATICS OF MACHINERY.

Plate XIV. 4. Pattison's pump. This arrangement, patented in England in 1857, is simply a mechanism $$( C''_3 P^\bot )^{d}$$ in which the coupler I is used as the driving link, being shaped as a piston and paired with a chamber forming part of the frame d ; ( F) = b, d. The chamber is a hollow cylinder conaxial with the cylinder 1, while the piston I, so much of it at least as is required to make a tight joint with d, is formed as a cylinder conaxial with 2. The block c forms, as in the last case, a piston working in the prism 4. Its motions, however, are not utilised, for the necessary valves are omitted. The piston 6 encircles the expanded pin 2 of the crank a, drawing the water into the chamber upon one side and discharging it from

shown in the annexed figure, is an example of this form of chamber gear which is now very familiar. It is a treble train, having for its' special formula $$( C''_3 P^\bot )^{\frac{d}{c}}$$ The form given to the pair 2 is worth noting, it is so arranged that the one crank pin serves as an element in three completely closed pairs. The end of each of the couplers b is formed as a sector of a revolute conaxial with 2 and having both internal and external profiles. The former works upon the crank pin (2) proper,

and the latter is always in contact with the ring 2' which is concentric with 2. The form of the element carried by the crank a at 2 has thus become an open circular channel, while that of its partner element in the coupler b is a corresponding sector. The closed pair (It) or (C) is thus replaced by the pair (A), a change the nature of which was considered at some length in 71, p. 311. The pair at 3 is a closed pair, although the closure is not seen in the section shown in the figure.
 * Propagation Industrielle, 1869, p. 178.