Page:Motors and motor-driving (1902).djvu/155

Rh misses. Consequently, instead of the valve being raised, it remains shut.

We shall now explain how this is accomplished. The arm, commonly known as the hammer, is the direct medium through which this change is effected. It will be seen in fig. 14

that it rests on a perfectly circular collar,, whereas in fig. 15 it has mounted on to a cam, , which is fixed eccentrically on to the shaft. This cam is so mounted on shaft, that when the protruding portion of cam  is pushing up the roller , the hammer  rests on cam , at the maximum