the movement of the flapper valve assembly does two things first it uncovers lower cone ports 209 allowing fluid communication between the inside of the drill string and the volume inside the expandable casing and outside of the duplex cone assembly the second thing movement of the flapper assembly does is to remove inward support for the first dogs 211 the first dogs are supported on fingers extending from a cylinder section of the assembly mandrel the fingers are flexible enough to bend inward when the support of the flapper assembly is removed the inward movement of the first dogs can be improved by providing that the surfaces between the dogs and the lower cone rest are at a slight angle from normal to the centreline of the duplex cone apparatus further the fluid pressure within the flow path will exert a force on the lower cone tending to urge the lower cone away from the assembly mandrel when the first dogs are disengaged the second dogs 212 will catch support surfaces 901 to permit recovery from the wellbore of the lower cone with the rest of the duplex cone assembly referring now to fig1 the top end of the expandable casing is shown configured for upward expansion of the expandable casing 101 for upward expansion of the expandable casing the slidable section 406 is pulled back upward to engage the slidable section shoulder 407 with the flow path seal 409 thus the drill string and the flow path are.