The present invention relates to a fuel-lubricating oil proportioning and mixing device, more particularly for use on a boat powered by internal combustion engine of the two-cycle type using a mixture of fuel and lubricating oil, for withdrawing from a lubricating oil reservoir a predetermined quantity of lubricating oil required to be mixed with a given quantity of fuel.
Dry sump internal combustion engines, such as two-cycle engines, require a fuel-oil mixture to be supplied to the engine when the engine is operated. In some installations, as is often the case for motorcycles, a variable discharge oil pump supplies a measured flow of lubricating oil from a separate reservoir into the carburetor inlet, the oil being automatically mixed with the fuel atomized in the carburetor. The pump is controlled so as to supply a variable flow of lubricating oil as a function of the throttle opening. Lubricating systems of this type present many inconveniences, such as requiring a separate oil injection pump which is subject to deterioration, wear and malfunction, the discharge rate of which must be calibrated with precision so as to supply neither too much nor too little lubricating oil at every throttle opening.
In other installations, wherein a mixture of fuel and lubricating oil is drawn directly from the fuel tank by gravity or by the engine fuel pump, a measured quantity of lubricating oil must be poured into the fuel tank every time the fuel tank is refilled with a known quantity of fuel. Although, with present-day lubricating oil compounded for mixing with fuel, such as gasoline, effective mixing of the oil with the gasoline requires no stirring in view of the fact that the oil is readily dissolved by the gasoline, such a task of pouring a proportionate amount of lubricating oil into the fuel tank may easily be overlooked, is time-consuming, unpleasant, and delicate to effectuate with precision when the oil is obtained from small capacity cans. To mix a proper proportion of lubricating oil with a given quantity of fuel in the fuel tank of high power two-cycle engines, of the type presently used in high speed power boats, is particularly important as too much oil in the fuel may lead to excessive smoke in the exhaust and fouling of the spark plugs, while insufficient lubricating oil, or complete lack of oil, will immediately result in damaging or completely wrecking a very expensive engine. Fast modern power boats are often powered by a pair, or even by three or four, two-hundred or more horesepower outboard engines which draw a fuel-oil mixture from a large capacity fuel tank mounted at a convenient location in the hull of the boat. When several hundred gallons of fuel are taken in during refueling, the task of pouring down the fuel tank filter several gallons of lubricating oil is time-consuming, especially in the course of a pit stop while racing, subject to errors as to the quantity of lubricating oil used, and somewhat messy, especially when the lubricating oil is poured from pint and quart cans.
Fuel-lubricating oil mixing devices have been designed in the past, such as disclosed in U.S. Pat. Nos. 2,908,289, 2,926,695 and 4,069,835, for example, which are adapted to automatically measure a predetermined quantity of lubricating oil from a separate reservoir, or a separate compartment in the fuel tank, and automatically mix the lubricant with the fuel as a function of the amount of fuel poured into the fuel tank, sometimes during the refueling operation itself. Such automatic mixing devices may on first glance appear to be convenient but, like any other mechanical devices, they are subject to deterioration and malfunction, more particularly if they fail to discharge into the fuel tank a sufficient quantity of lubricating oil, or if the lubricating oil reservoir has run dry.