Cutting/sealing device for plastic bag making machines

In a cutting/sealing device for plastic bag making machines of the type having upper and lower machine sections which are aligned vertically and are adapted to move toward and away from each other in a guillotine-like manner responsive to the action of machine cams, whereby the device may cut and seal a plastic film passing between the machine sections horizontally to produce plastic bags, said upper and lower machine sections including upper and lower sealing bars secured to heating bars in turn connected to upper and lower support members, said sealing bars being provided in their opposing faces with channel members of irregular cross section and in their opposite faces adjacent to the heating bars with semi-circular cross section channels, said semi-circular cross section channels being juxtaposed to like channels of the heating bars to provide upper and lower ducts adapted to receive electrical heating resistances to heat spaced forward and rear sealing surfaces of the upper and lower sealing bars immediately adjacent to said channel members of irregular cross section which seal the lateral sides or bottom of a plastic bag immediately following cutting of the plastic film, the improvement comprising said upper and lower channel members of irregular cross section each having flat parallel spaced wall sections defining mouths of the channel members, opposing intermediate concave wall sections leading from said flat parallel wall sections, short spaced parallel wall sections extending from the concave sections and being aligned with said flat parallel wall sections and flat bottom portions extending orthogonally between the ends of the short straight wall sections remote from the mouths of the channel members.