(under the class definition) Devices comprising piston means adapted to be inserted from the top of the well into an already placed well conduit and to be driven down by fluid pressure acting directly on the piston.
(1) Note. The piston must closely contact the wall of the casing or tubing as it moves down or be close enough to function as a scraper.
SEE OR SEARCH THIS CLASS, SUBCLASS:
170+, for brushing, scraping, cutting or punching cleaners adapted to fall down a well by gravity.
177.3, for wiping means adapted to fall by gravity down the well.
193+, for plugs of the dropped ball type.
291, for processes of cementing using piston separators. SEE OR SEARCH CLASS
92, Expansible Chamber Devices,
172+, for pistons for an expansible chamber device.
