Line printer hammer banks

1. A hammer bank, comprising:

a back plate;

a plurality of elongated pole pieces coupled to the back plate and extending forwardly from a front surface thereof, each pole piece having an electrical coil disposed about a circumfery thereof;

a permanent magnet having a back surface coupled to the front surface of the back plate;

a shunt fret defining a plurality of elongated, downwardly extending shunts and having a back surface coupled to a front surface of the permanent magnet; and

a hammer fret having a back surface coupled to the front surface of the back plate and defining a plurality of elongated, upwardly extending hammers, each hammer being interdigitated between a pair of adjacent shunts and including an elongated spring portion having a hammer head disposed at an upper end thereof, each hammer head having a printing tip projecting forwardly therefrom.

2. The hammer bank of claim 1 , further comprising:

a flux bar interposed between the front surface of the permanent magnet and the back surface of the shunt fret; and

a hammer fret mounting bar interposed between the front surface of the back plate and the back surface of the hammer fret.

3. The hammer bank of claim 2 , wherein at least one of the back plate, the flux bar, the shunt fret and/or the hammer fret is made of a magnetically permeable material.

4. The hammer bank of claim 2 , wherein the back plate comprises a generally flat plate.

5. The hammer bank of claim 4 , wherein the back plate comprises a stamping.

6. A line printer incorporating the hammer bank of claim 2 .

7. The hammer bank of claim 1 , wherein the back plate comprises a stamping.

8. The hammer bank of claim 1 , wherein at least one of the pole pieces comprises a generally flat, rectangular bar.

9. The hammer bank of claim 8 , wherein the at least one pole piece comprises a stamping.

10. The hammer bank of claim 1 , wherein a back end of each of the pole pieces is coupled to the front surface of the back plate with a magnetically permeable coupling.

11. The hammer bank of claim 10 , wherein the coupling comprises a press fitting, a stake, a rivet, a brazed joint, a welded joint or an adhesive joint.

12. The hammer bank of claim 1 , further comprising a cover disposed over a front face of the hammer bank, the cover including a plurality of openings, each corresponding to and through which a respective one of the printing tips of the hammers can project.

13. A line printer incorporating the hammer bank of claim 1 .

14. A line printer, comprising:

a shuttle mechanism; and

a hammer bank coupled to the shuttle mechanism for horizontal reciprocating movement by the shuttle relative to a vertically moveable print medium, wherein the hammer bank comprises:

a back plate;

a plurality of elongated pole pieces extending forwardly from a front surface of the back plate, each pole piece having an electrical coil disposed about a circumfery thereof;

a permanent magnet having a back surface coupled to the front surface of the back plate;

a shunt fret having a back surface coupled to a font surface of the permanent magnet and defining a plurality of elongated, downwardly extending shunts; and

a hammer fret having a back surface coupled to the front surface of the back plate and defining a plurality of elongated, upwardly extending hammers, each hammer being interdigitated between a pair of adjacent struts and including an elongated spring portion having a hammer head disposed at an upper end thereof, each hammer head having a printing tip projecting forwardly therefrom.

15. The line printer of claim 14 , wherein the hammer bank further comprises:

a flux bar interposed between the front surface of the back plate and the back surface of the shunt fret; and

a hammer shunt mounting bar interposed between the front surface of the back plate and the back surface of the hammer fret.

16. The line printer of claim 14 , wherein:

the shuttle mechanism comprises a moveable hammer bank carrier frame; and

the hammer bank is removably coupled to the carrier frame by one or more fasteners.

17. A method for making a hammer bank for a line printer, the method comprising:

attaching a back end of each of a plurality of elongated pole pieces to a front surface of a back plate such that the pole pieces extend forwardly therefrom and are arranged in a line and disposed generally parallel to one another,

disposing an electrical coil about a circumfery of each of the pole pieces;

coupling a back surface of a permanent magnet to the front surface of the back plate;

coupling a back surface of a shunt fret to a font surface of the permanent magnet, the shunt fret defining a plurality of elongated, downwardly extending shunts; and

coupling a back surface of a hammer fret to the front surface of the back plate, the hammer fret defining a plurality of elongated, upwardly extending hammers, each hammer being interdigitated between a pair of adjacent shunts and including an elongated spring portion having a hammer head disposed at an upper end thereof, each hammer head having a printing tip projecting forwardly therefrom.

18. The method of claim 17 , further comprising:

interposing a flux bar between the front surface of the back plate and the back surface of the shunt fret; and

interposing a hammer fret mounting bar between the front surface of the back plate and the back surface of the hammer fret.

19. The method of claim 17 , wherein the providing comprises stamping the back plate from a generally flat sheet of material.

20. The method of claim 17 , wherein the attaching comprises a staking, riveting, press fitting, brazing, welding or adhesive bonding process.