A closure device for a conduit for removably closing a first free end of a conduit to form a closed thrust chamber defined by said closure device and by a shuttle sliding in said conduit so that said shuttle can be pushed towards a second end of the conduit by means of a pressurized air flow introduced in said closed thrust chamber through said closure device, said shuttle dragging a dragging rope, said closure device comprising: - an elastic sealing member having a continuous annular tubular shape, having a first base end and an opposite second base end, said sealing member defining a longitudinal axis (L-L), said sealing member having an inner surface and an outer surface; - a first compression member couplable to said first base end; - a second compression member couplable to said second base end; - wherein the first compression member and the second compression member comprise respective inner faces (85, 86) which are operatively mutually facing and parallel; - compression means suitable to compress said sealing member between said first compression member and said second compression member, so that the sealing member deforms radially expanding outwardly, thus increasing the diameter thereof; - wherein said compression means comprise a tubular connection member having a first end orthogonally and centrally secured to the first compression member, and a second threaded end (58"), and said second compression member comprises a central through hole slidably couplable in the longitudinal direction with said connection member, said second compression member being able to be brought near to the first compression member by screwing a nut on said second threaded end (58"); - a pressurized air inlet passing through the compression means of the closure device; - a through opening passing through the first compression member and through the second compression member of the closure device to allow the passage of the dragging rope; - wherein said through opening; comprises: - a first hole passing through said first compression member, and a groove passing through said first compression member, which is open radially outwardly and starting from said first hole; - a second hole passing through said second compression member, and a groove passing through said second compression member, which is open radially outwardly and starting from said second hole; - said first hole and said second hole being arranged so as to be operatively mutually alignable to allow the dragging rope passing longitudinally through the closure device; characterised in that - the outer surface of the sealing member is free from interruptions and grooves and extends with continuity; - the first compression member, the sealing member, and the second compression member mutually define a free space between them, defined by said inner faces (85, 86) and by the inner surface of the sealing member; - the through opening is configured as to allow the dragging rope operatively passing through the free space. - an elastic sealing member having a continuous annular tubular shape, having a first base end and an opposite second base end, said sealing member defining a longitudinal axis (L-L), said sealing member having an inner surface and an outer surface; - a first compression member couplable to said first base end; - a second compression member couplable to said second base end; - wherein the first compression member and the second compression member comprise respective inner faces (85, 86) which are operatively mutually facing and parallel; - compression means suitable to compress said sealing member between said first compression member and said second compression member, so that the sealing member deforms radially expanding outwardly, thus increasing the diameter thereof; - wherein said compression means comprise a tubular connection member having a first end orthogonally and centrally secured to the first compression member, and a second threaded end (58"), and said second compression member comprises a central through hole slidably couplable in the longitudinal direction with said connection member, said second compression member being able to be brought near to the first compression member by screwing a nut on said second threaded end (58"); - a pressurized air inlet passing through the compression means of the closure device; - a through opening passing through the first compression member and through the second compression member of the closure device to allow the passage of the dragging rope; - wherein said through opening; comprises: - a first hole passing through said first compression member, and a groove passing through said first compression member, which is open radially outwardly and starting from said first hole; - a second hole passing through said second compression member, and a groove passing through said second compression member, which is open radially outwardly and starting from said second hole; - said first hole and said second hole being arranged so as to be operatively mutually alignable to allow the dragging rope passing longitudinally through the closure device; - the outer surface of the sealing member is free from interruptions and grooves and extends with continuity; - the first compression member, the sealing member, and the second compression member mutually define a free space between them, defined by said inner faces (85, 86) and by the inner surface of the sealing member; - the through opening is configured as to allow the dragging rope operatively passing through the free space.