Automatic crankcase oil change and makeup system

A system for changing oil in the lubricating oil circuit of an internal combustion engine while the engine is running, which comprises:

• a source of fresh lubricating oil,
• used oil displacement means having a fixed volume and having an input connected to said circuit and an output, said used oil displacement means being operable to periodically receive a series of small increments of used lubricating oil from said circuit according to said fixed volume so as to periodically remove such increments from said circuit;
• first sensing means operatively associated with said used oil displacement means for sensing completion of said receiving of each of said increments of used oil from said circuit, and in response to each such sensing to cause removal of such increment just received from said displacement means;
• and
• fresh oil displacement means having an input connected to said fresh oil source and an output connected to said circuit and being operable to periodically receive and deliver a series of small increments of fresh oil to said circuit at substantially the same periodicity as said used oil displacement means removes used oil increments from said circuits;
• each said fresh oil increment being volumetrically not substantially less than a corresponding said used oil increment and being delivered to said circuit not substantially later than said removal of such corresponding used oil increment, whereby the volume of oil in said circuit is not materially reduced by said removing of each of said used oil increments.

The method of changing oil in the lubricating oil system of an internal combustion engine while the engine is running, and wherein said lubricating oil system includes oil sump means containing a portion of the lubricating oil in said system, said method comprising the steps of:

• periodically removing a series of small increments of used lubricating oil from said system, and
• not later than said removing of each of said increments of used oil, delivering a small increment of fresh lubricating oil into said system which is volumetrically not substantially less than such increment of used oil;
• whereby the volume of oil in said system is not materially reduced by said removing of each of said increments of used oil;
• sensing the level of oil in said sump means at least each time a said successive increment of used oil is removed from said system by sensing the oil levels at a plurality of spaced apart locations in fluid communication with said sump means to generate a plurality of signals, and developing an average of said signals representative of said oil level in said sump means;
• if the oil level so sensed is not substantially below a predetermined satisfactory operating level when a said successive increment of used oil is removed, then delivering that removed increment of used oil to receptacle means;
• but if the oil level so sensed is substantially below said predetermined level when that increment of used oil is removed, then delivering that removed increment of used oil to said system, whereby the corresponding increment of fresh oil that is delivered to said system constitutes makeup oil.