FIG. 46.]

[Illustration: FIG. 45.]

[Illustration: FIG. 47.]

[Illustration: FIG. 48.]

[Illustration: FIG. 49.]

[Illustration: FIG. 50.]

[Illustration: FIG. 51.]

The plunger is loaded with a spiral spring, and has a ball valve, as
shown. Intermediate between this small reservoir and the main oil tank
is another set of valves, shown in fig. 49. It will be seen that the
suction of the pump will draw the oil up, the small and lower ball
valve, of course, allowing it to pass freely. On the down stroke the
lower valve will be automatically closed, and the oil will be put under
pressure, this being determined by the load on the plunger valve, which
is adjustable by means of the screw S, fig. 48. When the required
pressure in the pipe P, figs. 45 and 49, has been attained, the plunger
valve lifts on each stroke and the surplus oil flows through the plunger
into the small reservoir R. The latter is at about the same level as
another still smaller reservoir M (shown in figs. 47 and 50), a flow of
oil being established between the two by means of a pipe Q (see figs. 48
and 50). In the reservoir R is fitted an overflow pipe, so that the oil
cannot rise beyond a certain level; hence the head of oil in the smaller
one M is always constant. On the suction stroke a partial vacuum is
formed in the engine cylinder, consequently the pressure in the
vapouriser drops somewhat below that of the atmosphere, and this small
difference in pressure is enough to cause the oil to rise in the small
passage X, fig. 45, beyond its normal level, and overflow into the
vapourising chamber, as previously described. The valve or nipper N is
shown open in the diagram, fig. 45, and all that is required to stop the
engine when running is to drop the small handle L, fig. 45, when the
valve will close, due to the spring S. The air vessel shown in fig. 49
is in communication with the pipe leading to the blow lamp. A pressure
gauge can also be fitted, although it is not in any way a necessity.

The ratchet wheel and pawl shown in fig. 48 are part of the lubricator.
The wheel drives a brass or gun-metal plug, producing an intermittent
rotary motion. The plug has a small hole in its periphery, which becomes
filled with oil when it is at the upper part of its travel, and empties
the oil out into a discharge pipe T, when it is inverted, and is then
led away and applied to the piston at the required spot. Fig. 51 shows
this arrangement in section.