A valve comprising a resiliently expansible and compressible plug movable in a valve chamber to open and close a flow passage intersected by the chamber. The plug has a sealing portion which is expanded outwardly against the walls of the chamber, e.g., by being compressed in a different direction to maintain a fluid type seal when the plug is moved in a chamber between open and closed positions of the valve. In a preferred embodiment, the plug is provided with 1) a valve stem and includes 2) an inner elastomeric portion in the upper portion of which is embedded 3) a rigid plate-like member or disc, preferably formed integral with the valve stem, 4) a non-elastomeric ring-shaped anti-extrusion member, preferably formed of two or more complementary arcuate portions, suitably two semi-cylindrical ring portions, surrounding the lower portion of the inner elastomeric portion of the plug below the plate member, and 5) an outer elastomeric cover portion which completely surrounds the anti-extrusion ring member or members and preferably includes a base portion which covers the bottom of the inner elastomeric plug portion.

A valve comprising a resiliently expansible and compressible plug movable in a valve chamber to open and close a flow passage intersected by the chamber. The plug has a sealing portion which is expanded outwardly against the walls of the chamber, e.g., by being compressed in a different direction to maintain a fluid type seal when the plug is moved in a chamber between open and closed positions of the valve.

A remotely movable carriage is described. The carriage finds particular utility in serving as a mobile platform from which remotely initiated and controlled inspection and work operations might be performed on the tubes in a nuclear steam generator. The carriage includes a stepping mechanism which interacts with a member, such as a tube sheet, relative to which the carriage moves in generally parallel relationship. The stepping mechanism may employ selectively extensible fingers for lateral engagement with openings in the member. Some of the fingers may be movable transversely of their longitudinal extent in a curvilinear direction, relative to the remainder of the carriage, to effect a "stepping" of the carriage. The carriage may be supported adjacent, and generally below, the member across which it is intended to step, preferably by means for grippingly engaging the member against relative vertical motion. Such gripping means may be expandable, high friction sleeves associated with the stepping fingers for insertion into gripping engagement with the tubes of a steam generator.

A valve comprising a cylindrical valve chamber, having an inlet leading into said chamber, and at least one outlet leading from said chamber and out of axial alignment with said inlet to provide a cylindrical chamber wall portion therebetween. Disposed coaxially within the chamber is at least one accordian-like resilient valve member adapted on longitudinal contraction to fold and expand radially outwardly into engagement with the cylindrical chamber wall portion to effect a seal between the inlet and the outlet and on longitudinal expansion to unfold and contract radially inwardly out of engagement with the cylindrical chamber wall portion to provide a flow passage therearound between the inlet and the outlet, and means are provided for operating the valve member.

In a valve for controlling fluid flow, the spindle comprises a flexible polymeric sheath, preferably PTFE, around the end of a stem, the sheath having a tubular portion suspended clear of the stem and having an oversize external ridge which is accommodated within the bore by flexing of the tubular portion, resistance to this flexing serving to bias the external ridge against the surrounding body to provide a gland seal.