Butterfly valve

Claim 1

A butterfly valve particularly suitable for connection with synthetic resin pipes and for underground installations, said butterfly valve being characterized by: A. a body of synthetic plastic having (1) a main portion defining (a) a central annular valve casing and (b) a pair of tubular mouthpieces that are coaxial with said valve casing and project in opposite axial directions therefrom, and (2) a cylindrical chamber portion projecting laterally from said valve casing at one side thereof, said chamber portion having its axis normal to that of said main portion; B. a metal driven shaft extending diametrally across said valve casing coaxially with said chamber portion and having an end portion projecting into said chamber portion, said driven shaft being rotatably journaled in coaxial bearings in the wall of said valve casing; C. a cylindrical actuating member axially slidably and rotatably confined in said chamber portion, said actuating member (1) having a helix connection with said chamber portion whereby axial motion of said actuating member is accompanied by rotation thereof, and (2) surrounding said end portion of the driven shaft and having a splined connection therewith whereby the actuating member is axially movable relative to said shaft but said shaft is constrained to rotate with the actuating member; D. a drive shaft journaled in an outer portion of said chamber, said drive shaft (1) being coaxial with the driven shaft, (2) being confined to rotation relative to said body, (3) having an outer end portion that is accessible at the exterior of said chamber for rotational actuation and (4) having an inner end portion in said chamber that is surrounded by said actuating member and has a threaded connection therewith whereby rotation of the drive shaft imparts axial motion to the actuating member; and E. a disc-like valve element secured to said driven shaft to be turned flatwise between open and closed positions by rotation of the driven shaft.