Measured Feed for Upper-cylinder Lubricant
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IF it is conceded that upper-cylinder 1 lubricant should be provided only on starting up a cold or partially cold engine, the Drok lubricator, introduced by Drok Lubricators, Ltd., 208 Bath Road, Slough, Bucks, should fulfil its purpose. The lubricator, which is piped up to the inlet manifold, depends upon the depression in the manifold for its operation. When the engine is stationary, the air in the manifold, the piping and all internal passages in the lubricator is at atmospheric pressure.
The oil in a container (L) enters' through an air-oil vent (A) in the base. chamber (K) and percolates by gravity
through a porous ceramic disc (B) into a metering chamber (C).
This chamber has a capacity of approximately 4 c.c.. and the metering disc is so calibrated that it takes approximately two hours for the metering chamber to fill. Immediately the engine is rotated, the air pressure in the manifold drops, the oil being drawn up passage 13 and so into the engine.
The place of the oil in the chamber is -taken by air which is drawn down passage E from the air space at the top of the container. Filler cap M has an airtight seal and the resulting drop in pressure in this air space causes. air. to enter through the felt air filter H, down passage F and so into the base chamber. There it displaces the oil through the air-oil vent, bubbling up
through the oil into the air spaco in the top of the container.
This condition obtains all the time the engine is running, and by a suitable restrictor in passage F, the rate of air flow. .whilst being sufficient to prevent the entry of oil into the base chamber, is insufficient to affect carburation.
As disc B has air on both sides, no further oil can pass into chamber C. Immediately the engine stops. however, pressure in the whole system returns to atmospheric and oil begins to percolate through disc B to charge the chamber for the next start.
The -quantity of oil which can enter the engine at any one time is limited to the capacity of the metering chamber. and the frequency with which this can deliver a full charge is again limited to the rate at which the oil can pass through the porous disc.
As the full 4 c.c. takes approximately tw6 hours to pass through the disc, at no time can an excessive quantity of oil enter the combustion chambers.
Other than the non-return valve (N) in the pipe from the lubricator to the manifold, there are no moving parts, and as the main components are constructed in phenolic resins and extruded plastics, maintenance should he negligible. The container is made of glass.