Abstract: A wrapping machine comprises a tube former for a forming a web of wrapping material into a tube with a longitudinal seal, a variable speed feeding mechanism for feeding the web continuously to the tube former, an infeed conveyor for feeding articles in succession into the tube former so that they become entubed in the tube of wrapping material, and crimping dies situated beyond the tube former which are operative to form transverse seals in the tube of wrapping material between the articles. The machine includes an adjustable modulating device for matching the speed of movement of the dies to substantially the speed of advance of the tube during formation of the transverse seals. An adjustable control mechanism is provided for so controlling the dies that they will form, by appropriate adjustment, transverse seals at either every revolution, during alternate revolutions only, or during every 3rd, 4th . . . or nth revolutions of a constant speed driving shaft.