A packaging device is disclosed for forming packaging cushions of the type that include a plastic bag filled with a solid foam, and wherein the cushions are initially formed of a plastic bag filled with a foamable material that reacts and then hardens to form solid foam. The device comprises means for advancing a sheet of plastic film material that has been center-folded to form a doubled web with one closed edge defined by the center fold and one open edge defined by the adjacent edges of the sheet. Means are included for injecting a foamable composition into the center-folded web between the two folded portions of the sheet, as are means for forming a substantially linear seal along the open edge and substantially parallel to the open edge to thereby longitudinally seal the open edge of the web. The invention further includes means for periodically interrupting the linear seal to provide an unsealed portion along the otherwise sealed edge, and means for transversely sealing the web after foamable composition has been injected, and for concurrently separating a formed and filled bag from the advanced film material.