A
coolant filter for use in filtering a
coolant solution which flows through the
coolant filter includes a filter housing
assembly which is made up of an outer housing which is crimped to a nutplate which defines an internally threaded flow outlet. A generally cylindrical
filter element is positioned inside of the filter housing
assembly and a first endplate is bonded to the end of the
filter element which is adjacent to the nutplate. An endplate member is provided for attachment to the opposite end of the
filter element and is configured in such a way so as to define an interior chamber where supplemental coolant additive
pellets are stored. A closing plate is applied across the open end of the interior chamber so as to create an enclosed chamber for the supplemental coolant additive
pellets. A slow release mechanism is provided for controlling the rate of release of the supplemental coolant additive from the enclosed chamber into the coolant solution. In one embodiment of the present invention, the slow release mechanism includes a
diffusion tube which defines a
diffusion orifice. In another embodiment of the present invention, the slow release mechanism includes a semipermeable (or osmotic) membrane
wafer. In both instances, the slow release mechanism is positioned between the source of supplemental coolant additive and the flow outlet in the nutplate.