Abstract: The invention describes a machine (10) for producing bags of flexible material, comprising a reel-holder group (12) that removably supports at least one reel (14, 16) capable of supplying at least one said flexible material, a welding group (18) provided with at least one upper welding plate (20) and at least one corresponding lower welding plate (22) that are heated and provided with corresponding linear welding tracks, such upper (20) and lower (22) welding plates acting on the film according to a vertical alternate movement, and at least one cutting group (24, 26) that separates from each other the single bags that have just been obtained further to the welding operation on the film. The lower welding plate (22) is made integral with a base (30), whereas the upper welding plate (20) is mobile with an alternate motion along a plurality of vertical guiding columns (32).

Abstract: An improved performance welding bar placed in a welding machine for the welding of thermoplastic material of low and high density, suitable for both the lower welding bar (11) and the upper welding bar (12) among which bars (11, 12) the material is moved along by at least one pair of lower (14) and upper (15) supply rollers, placed on top of each other, the two welding bars (11, 12) moved backwards and forwards between themselves by a control group (20), wherein each welding bar (11, 12) is made from a magnesium-zinc aluminum alloy, within which the percentage of zinc to be found is between 5.0-6.5% and the percentage of magnesium to be found is between 2.0-3.0%. According to the invention the use of a magnesium zinc aluminum alloy is provided for, for a welding bar in a welding machine of thermoplastic material, wherein the bar is continually activated by a forward and/or backward movement with regards to a second similar welding bar.

Abstract: An improved-efficiency welding device in a plastic bag production machine, of the type including an upper welding bar and a lower welding bar, at least one of which is driven with reciprocating vertical movement between a position separated from The plastics material to be welded and a position in contact with the plastics material and the lower or upper other bar, the movement of the at least one welding bar being imparted by a pair of vertically guided rods driven by a first eccentric linkage to which they are connected by a pin, the first linkage obtaining its movement from a central shaft, there being provided a second eccentric between the rod and the first eccentric linkage and driven by an additional motion transmission system which rotates it to cause the at least one welding bar to undergo a further lowering and/or raising movement at a predetermined stage, with resultant welding engagement between the an least one welding bar and the other welding bar.