Rotary plug valve

Claim 1

In a rotary plug valve including: a valve body member having a through bore constituting a fluid passage and a vertical through bore which crosses the fluid passage at a right angle, said vertical bore being formed with a plug seat surface in which the ports of said fluid passage open; a plug member adapted to be received by said vertical bore of said valve body member and having a fluid passage including ports capable of being aligned with the ports in said plug seat, the peripheral surface of said plug member opposing said plug seat being formed with at least its central portion including said ports having a seat surface which can make a sealing contact with said plug seat; circumferential grooves formed in either one of the seat surfaces of said valve body member and said plug member at both longitudinal end portions so as to sandwich the central region of said one of said valve body member and said plug member, each of said circumferential grooves having a bottom wall and opposing end walls; elastically deformable packing "O" rings received in said circumferential grooves so as to be pressed between the bottom walls of said circumferential grooves and the seat surface of the other of said valve body member and said plug member thereby to form tight seals therebetween; a plurality of channels formed in the seat surface of either one of said valve body member and said plug member so as to extend longitudinally at both sides of each port of said either one of said valve body member and said plug member in such a manner as to provide communication between said circumferential grooves thereby forming a closed lubrication system; and means including a passage connected to at least one of said channels and adapted for allowing a lubricant to be charged therethrough into said closed lubrication system; wherein the improvement comprises that said bottom wall of each of said circumferential grooves is inclined toward said central region relative to said opposing seat surface so that the distance between said bottom wall and the opposing seat surface is greater at the end of said circumferential groove proximate said central region than at the end of said circumferential groove distant said central region, whereby during charging of the valve with lubricant, the "O" rings are caused to deform elastically by being wedged into the portions of the respective grooves distant said central region thereby providing a more effective seal and storing pressure energy therein.