Abstract: The tractor comprises a frame, a drive roller carried by the frame, a pressure roller and a carrier therefor. The pressure roller is biased against the drive roller. The pressure roller can be moved to be spaced slightly from the drive roller to enable paper adjustment or it can be moved to a storage position. The friction feed tractor has a paper edge guide which is automatically moved to a storage position when not in use. In their storage positions the friction feed tractor and paper edge guide act as paper supports for pin feed tractor operation.

Abstract: A solenoid-type print wire actuator includes a unitary one-piece bobbin formed of a magnetically permeable material and having two axially spaced-apart annular grooves in the outer surface thereof. An electromagnetic coil is wound on the bobbin. A dumbbell-shaped armature is disposed coaxially within the bobbin and is connected to the print wire for axial movement thereof, the armature having two cylindrical piston portions respectively disposed adjacent to the bobbin grooves. The ends of the bobbin are respectively supported in bores in the leg portions of a U-shaped member, the leg portions being interconnected by another piece to form a frame of magnetically permeable material to define a flux path.

Abstract: A dot matrix printer has a programmable interval counter which produces motion control pulses for stepping the stepper motor of a print head carriage and/or of a paper advance system. The same motion control pulse which is used to control the carriage step motor is also input to a microprocessor, in an open loop fashion, to request further print head data for driving the wire array(s) of the dot matrix print head. A programmed time delay may be introduced between the programmable interval counter and the carriage step motor to compensate for wire flight time of the print head wires in a manner which is substantially independent of carriage velocity. A variable delay may also be introduced between the programmable interval counter and the microprocessor to compensate for carriage motor shaft lag/lead.