Yarn suction device in textile machines

Device for the suction of yarn in a textile machine, of the type comprising a main yarn suction and transport conduit maintained in a vacuum, an external mouth for trapping the yarn connected to said main vacuum conduit, and means of controlling suction of the yarn arranged between said trapping mouth and said main suction conduit, wherein said means of controlling suction of the yarn comprise a cylinder having an internal surface defining an internal chamber of the cylinder, and having a first transverse opening connected to said trapping mouth and a second transverse opening connected to said main yarn suction conduit, and a piston for controlling suction moving longitudinally in said chamber of said cylinder in the form of an elongated body having an internal transverse hole open at its ends designed to connect said first and said second openings in the transverse wall of the cylinder for suction of the yarn, means also being provided for driving the movement of said piston between a first yarn suction position wherein said through hole is positioned between, and connects, said first and said second openings of the cylinder and at least one second position of closure wherein said piston closes the passage between said first and said second openings, and wherein means are provided for guiding the sliding of the piston inside said chamber to maintain said through hole of the piston aligned with said first and second openings.