Printer having a linear motor

A dot type printer comprising a printing head, a carriage carrying the head, an elongated guide rail having a high magnetic permeability, the carriage being mounted on the guide rail so the carriage can be translated longitudinally along the guide rail, a drive system for longitudinally translating the carriage along the guide rail, said drive system including:

• a yoke having high magnetic permeability portions, said yoke including the guide rail, a permanent magnet, a first magnetic pole face for the permanent magnet contacting a portion of the yoke to maintain the guide rail at the first magnetic polarity, a second magnetic pole face for the permanent magnet being spaced from all high magnetic permeability portions of the yoke, the second pole face being elongated and extending substantially throughout the distance travelled by the carriage in a direction parallel to the elongated direction of the guide rail, an air gap for magnetic lines of flux of the permanent magnet being formed between the guide rail and the second pole face whereby the magnetic lines of flux are at right angles to the direction of travel of the carriage along the elongated direction of the guide rail, a winding wound on said carriage to produce a magnetic field in the same direction as the elongated direction of the guide rail in response to current being applied to the winding, whereby the magnetic field from the winding interacts with the permanent magnetic lines of flux to produce a force to translate the carriage along the rail, wherein the printing head comprises plural printing hammers, a coil for controlling activation of each hammer, the coil controlling the activation of each hammer being disposed in the air gap so as to be permanently responsive to the magnetic lines of flux of the permanent magnet, whereby a magnetic field resulting from current being supplied to a particular coil interacts with the permanent magnetic lines of flux to produce a force to activate the hammer associated with the particular coil.

A dot type printer comprising a printing head, a carriage carrying the head, an elongated guide rail having a high magnetic permeability, the carriage being mounted on the guide rail so the carriage can be translated longitudinally along the guide rail, a drive system for longitudinally translating the carriage along the guide rail, said drive system including:

• a yoke having high magnetic permeability portions, said yoke including the guide rail, a permanent magnet, a first magnetic pole face for the permanent magnet contacting a portion of the yoke to maintain the guide rail at the first magnetic polarity, a second magnetic pole face for the permanent magnet being spaced from all high magnetic permeability portions of the yoke, the second pole face being elongated and extending substantially throughout the distance travelled by the carriage in a direction parallel to the elongated direction of the guide rail, an air gap for magnetic lines of flux of the permanent magnet being formed between the guide rail and the second pole face whereby the magnetic lines of flux are at right angles to the direction of travel of the carriage along the elongated direction of the guide rail, a winding wound on said carriage to produce a magnetic field in the same direction as the elongated direction of the guide rail in response to current being applied to the winding, whereby the magnetic field from the winding interacts with the permanent magnetic lines of flux to produce a force to translate the carriage along the rail, wherein the printing head comprises plural printing hammers and a coil for controlling activation of each hammer, the coils controlling the activation of the hammers being disposed in the air gap so as to be permanently responsive to the magnetic lines of flux of the permanent magnet, each coil comprising a metal spiral situated in a plane perpendicular to flux lines of the permanent magnet, each spiral being at least partly in the air gap, whereby a magnetic field resulting from current being supplied to a particular coil interacts with the permanent magnetic lines of flux to produce a force to activate the hammer associated with the particular coil.