order to allow the bed 1 of hook needles to be driven at a work speed equal to the one of the bars and the side plates the two ends of the bar and the bed 1 as shown in fig7 are supported by the upper ends of the two parallel arms 57 extending in a substantially vertical position of which only one is visible both arms have a considerable length and are pivotably connected at the lower end thereof to pins 58 fixed to the frame due to the increased lenght of the arms 57 and the limitation of the range of their pivotal movement determined by the operational displacement of the hook needles the latter draw an arc which can practically be considered rectilinear near the bed of the hook needles the arms 57 are caused to swing by a respective connecting rod 59 operated by an eccentric 60 the eccentricity being such as to induce the hook needles to a reciprocated movement having a displacement sufficient for their work also in this case the introduction of the connecting rod eccentric mechanism allows high work speed it has still to be noted that the novel features of the bars namely their circular cross section with their guide and stiffening means the mechanism operating the same bars or the mechanism operating the side plates 10 and 11 and the mechanism operating the bed of the hook needles must necessarily work in concert with each other to obtain high work speed rates because the lack of one of them would not.