parallel and in a spaced relationship to each other a carriage 24 adapted to support a print head not shown is slidably carried by the guides 20 and 22 the carriage is therefore supported for guided lateral movement in either longitudinal direction along the guide rods 20 22 which also prevent transverse movement or shifting of the carriage alignment relative to the platen and the printer generally a longitudinally extending screw shaft or lead screw 26 is disposed in a spaced parallel relationship to each of the guide rods 20 and 22 between the upstanding support ends 16 and 18 of the support 12 end shaft mounts 28 rotatably support at least one of the ends of the screw shaft 26 and if desired both such ends within apertures 30 see fig2 formed in the upstanding support ends or legs 16 of the support 12 a reversible electric motor 32 drives the screw shaft 26 through a pinion gear 34 and a driven gear 36 non rotatably secured to one end of the lead screw as will be understood the carriage 24 includes a threaded follower not shown operatively engaged by the screw shaft 26 by which the rotary movements of the shaft are translated into linear movement of the carriage along the shaft during the operation of the overall printer of which the structure shown in fig1 forms a portion the printer control and logic system actuates the electric.