(under the class definition) Devices comprising means specially adapted for use in the operation of placing a mass of filter material, e.g., gravel, in final position in the well.
(1) Note. Means for merely lowering a preformed screen or bed of filter material into the well is not included. Such filter beds may have means aiding to form them above ground or a contiguous reservoir for filter material which is intended to fall down to replenish the main filter bed. Also means for merely supporting filter material placed into the well are not included. See subclass 228 for all these devices.
SEE OR SEARCH THIS CLASS, SUBCLASS:
228, for screens comprising filter material.
278, for processes of placing a bed of filter material.
