218,446. Martin, J. C. May 23,1923. Plug cocks.-A plug cock is pressed to its seating by spring or like mechanical resilient means, and is provided with packing on the smaller end, and with lubricating-passages having a non-return valve at the inlet. The casing 10 is closed at the lower end by the cap 14 which encloses the spring &c. 13 to press the plug 12 against its seating. Fibrous packing rings 20 are provided, and are pressed against the smaller end of the conical surface by a gland ring 28. The upper end of the plug is provided with shoulders 34 coacting with a stop on the gland ring, to limit the rotation. The plug is lubricated by means of channels 37, 38, connected with a central chamber 42. A hollow member 48 screws into the upper end of the plug and carries a nipple 50 provided with a non-return valve 47. The device is filled with lubricant, which is forced into the passages 37, 38 by screwing down the member 48. Alternatively, the non-return valve may be provided in the member 48, the upper end of which is then screw-threaded externallv to receive a grease gun. In a modification, the packing 20 may surround the cylindrical stem of the valve.