Self-indexing label marking gun

An improved adhesive label printer of the type which operates in combination with pre-cut adhesive labels carried on a separable backing tape with regularly spaced apart perforations, the printer having trigger operated tape transport means for transporting the backing tape and labels through the printer and for sequentially separating the labels from the backing tape, the tape transport means having non-trigger operated portions which exert a retarding frictional force against the movement of the backing tape through the printer, and a printing head with a plurality of selectable characters for imprinting the labels, wherein the improvement comprises

• a drive drum, the drive drum being rotatably mounted in the printer to contact the backing tape, and having a plurality of circumferentially spaced apart, radial projections for mating with the spaced apart perforations in the backing tape, the drive drum being selectively rotatable by the trigger operated means,
• spring loaded pressure roller means mechanically interengaged to rotate with the drive drum and to resiliently press the backing tape against the drive drum, the roller means and drive drum together initially exerting a frictional pulling force on the label backing tape which is less than the retarding frictional force exerted by the tape transport means on the backing tape and labels which must be overcome to pull the backing tape and labels through the printer, whereby self-indexing is accomplished when the initial rotation of the drive drum and pressure roller means causes the backing tape to slip over the drive drum projections until the projections of the drive drum mate with the spaced apart perforations in the backing tape upon initial operation of the trigger operated tape transport means.