Downhole flow control device

A downhole choke mechanism comprises an inner (432, fig 32) and an outer (404, fig 32) cylindrical housing, the inner housing having helical grooves 418 cut into its outside surface and encloses the tubing cavity. The outer housing has a number of lower ports (406, figure 34) and a number of upper ports (410, figure 30). Fluid is transmitted from the upper and lower ports through the helical grooves 418 into the tubing cavity through ports (429, 431 when aligned in figure 32) in the upper key body 422 and inner housing. A key 426 is provided in a slot in the key body 422 which can be actuated to variably obscure the flow through the helical grooves.