Liquid filtration system with level-responsive contaminant removal and air flow control for vacuum producer

A system for optimizing operation of liquid filtration equipment having a first electric motor for periodically removing the layer of solid contaminants on the filter media through which the liquid passes, and a second electric motor which drives a centrifugal vacuum producer to remove air from an enclosed space beneath the filter media. The filtration system is of the type wherein contaminated liquid is supplied to a tank open to the atmosphere for passage through the media, whereon solid contaminants are collected, into the underlying, enclosed space. A drop in the level of liquid in the tank, e.g., in response to removal or reduction of the layer of contaminants, allowing excess air to enter the enclosed space below the media, causes a like drop in the position of a float which is connected by a linkage means to a throttling valve interposed between the enclosed space and the vacuum producer. The throttling valve is carried on a shaft which moves in response to changes in liquid level to control the rate at which air is removed from the enclosed space beneath the media, thereby controlling the horse-power required from the vacuum producer motor. The same shaft carries a pair of cams, the selectively set rotational position of which actuate limit switches for starting and stopping of the motor which effects removal of the contaminants.