publication_number US 4389037 A abstract a gate valve includes a pair of identically shaped tapered discs defining a tapered self locking axially translatable gate wherein each disc has an annular hardened seating surface which engages the mating surfaces on the valve body adjacent the flow ports tongues on the sides of the discs ride in vertical grooves on the valve body as the gate travels between a raised open and a lowered closed position the discs are separated by an annular spacer ring of substantially smaller diameter than the seating surfaces surrounding an interlocking segmented hub formed on the inner juxtaposed surfaces of the discs the arrangement being such that the spacer ring can be sized to establish an overall gate width which will ensure that the seating surfaces are making proper sealing engagement with the valve seats with the diametral differences increasing the disc flexibility the spacer ring can be replaced by an appropriately sized spacer ring to compensate for thickness reduction in resurfacing the seating surfaces application_number US 15901780 A description referring to fig1 there is shown a gate valve 10 made in accordance with the present invention of the type used for high pressure fluid applications such as electric power generation systems of either the fossil or nuclear type such a gate valve is usable in a product line ranging between nominal sizes of 11 2 inches and 42 inches and in ansi pressure classes of 600 900 1500 2500 and 4500.