Another system that is half splash, and half force feed, is the pump circulated system much used in automobiles.
THE SPLASH FEED SYSTEM is the simplest of all, as the bearings are lubricated by the oil spray caused by the connecting rod end splashing through an oil puddle located in the bottom of the closed crank case. The piston and cylinder are lubricated by the spray, as well as the bearings, as the lower end of the piston projects into the crank chamber at the moment that the connecting rod end strikes the oil puddle.
To maintain constant lubrication, it is necessary that the oil in the puddle be kept at a constant height, or as in some cases be varied in such a way that the surface of the puddle is raised and lowered in proportion to the load on the engine. In the average engine the oil level is maintained by overflow pipes or openings that allow any excess of oil over the fixed level to flow back to the pump. In the Knight engine the puddles are formed in movable cups which are connected with the throttle in such a way that the opening of the throttle raises the oil level and supplies more oil to the engine at the greater load, or speed.
Oil in splash systems is supplied by a low pressure pump, usually of the rotary type, in the base of the engine. Oil from the pump passes to the bearings, drops into the puddle, overflows through the overflow opening, and returns to the pump through a filter, the same oil being used over and over again until exhausted. This strainer should be removed occasionally and the dirt removed, for should it be allowed to collect it is likely to obstruct the oil supply. The oil should be replaced before it becomes too black or foul, the crank case and bearings thoroughly cleaned with kerosene, and new oil replaced. The supply may be interrupted by the failure of the pump, caused by sheared keys or leakage of air in the suction line due to cracks. It would be well to run the engine for a few minutes with the kerosene in the crank case, in order that all of the oil may be removed. See that the drain cock is closed at the bottom of the cylinder or all of the oil will be lost. Lock the valve handle carefully so that it cannot jar open. If light colored smoke appears in intermittent puffs with a multiple cylinder engine, it indicates that one cylinder is receiving too much oil.
(117) Force Feed Lubricating System.
The force feed system is by far the most reliable of all oiling systems, as it feeds uniformly and continuously at almost any temperature, and against the pressure of practically any obstruction in the pipe.
The oil is supplied by a small pump driven from the engine, the pump being incased in the oil tank housing. Frequently a hand pump is used in combination with the power pump when starting the engine, or at times when the power pump is out of service. A single pump is used with any number of leads, each lead, or feed, having an independent regulating valve and sight feed, or a pump unit may be provided for each lead, depending on the size of the engine.
(118) Bosch Force Feed Oiler.
The force feed of the Bosch Oiler is so positive in character, that the flow of oil is not affected by heavy back-pressure due to elbows and the diameter of the conducting pipes. Springs, valves and other devices, which would check the flow of oil, are fundamentally eliminated. The amount of oil fed may be accurately and permanently regulated. Glands and other packings and bushings are eliminated. Connecting rods and all links are eliminated by the direct application of the movements of the oscillating cam disks to the pump plungers and piston valves.
Each feed of this oiler is provided with a separate pump element consisting of a pump body plunger and a piston valve, the suction and feed ducts connecting directly with the pump body of their respective elements. With this construction, pump elements may be replaced or added. The oiler requires no attention other than to be supplied with oil; and the opening and closing of the valves, pet cocks, etc., on starting and stopping the machine is rendered unnecessary. The correct and regular operation of the elements may be verified by observation of the reciprocating movements of the regulating screws.