[0001] The invention relates to serial printers and, more particularly, to high-speed serial
printers having print fonts arranged upon a disc member, which rotates the fonts past
an impacting printing hammer at a print station generally designated as 2.
[0002] In such printing systems, it is necessary to accurately position the print head as
the print head contacts the print ribbon so that the.printed characters will be aligned
and spaced evenly. One method for assuring alignment of the print characters is shown
in U.S. Patent 3,840,105. In that patent there is disclosed the use of a male shaped
surface on the back of the print fonts, which is made to fit into a corresponding
shaped female surface on the print hammer. As the print hammer moves into contact
with the type font at a print station, the font is forced by the shaped surfaces to
align with the print hammer resulting in aligned printed characters. This system is
referred to herein as detent alignment. Because of room constraints around the print
wheel circumference, character slugs must be placed immediately adjacent to one another,
sometimes resulting in as little as several mils separation between adjacent characters.
The detent alignment technique, however, requires a fairly wide hammer to ensure capture
of the character slug. It can be seen accordingly that the print hammer can strike
or at least cause a twisting torque to character slugs or type fonts adjacent the
desired font. This is undesirable not only because of the damage the twisting impact
can cause the adjacent font support beam,but because of the interference that can
occur between the adjacent beam and the desired font support beam causing adjacent
character printing and print misalignment.
[0003] The invention as claimed is intended to provide a remedy. It solves the problem of
how to design an alignment print hammer for aligning type fonts that will work satisfactorily
even when the type fonts are relatively close together. This is accomplished by tapering
the sides of the print hammer or type slugs or both. Both is preferable as explained
below.
[0004] One way of carrying out the invention is described in detail below with reference
to the drawings, which illustrate only one specific embodiment, in which:
Figure 1 is a perspective view of the disc print wheel, hammer and motor drive of
this invention.
Figure 2 is a top view representation of the prior art detent alignment system showing
a print hammer and two character slugs.
Figure 3 is a top view representation of the detent alignment print hammer and two
character slugs in accordance with this invention.
[0005] The Figures show a serial printing apparatus including a print wheel disc generally
designated as 1, a motor 5 for driving the print wheel and a print hammer 15 for striking
and aligning the type font or character slugs 11. The print wheel 1 is mounted for
rotation on shaft 3 of motor 5. Motor 5 can move wheel 1 in either a clockwise or
counterclockwise direction as indicated by arrows 7. Print wheel 1 contains a plurality
of outward extending beams or spokes 9 having print heads 11 formed thereon. On one
face of print heads 11 are formed characters 13. The face of print heads 11 facing
detent alignment hammer 15 is dihedral alignment surface 17 shaped to mate with the
dihedral alignment opening 19 in alignment print hammer 15. The beams or spokes are
bonded in hub 21, which is fitted to shaft 3 of motor 5.
[0006] The prior art hammer and print heads are shown in Figure 2. As seen in Figure 2,
the print hammer 15 is roughly aligned with the type slug lla. It can be seen that
as hammer 15 is moved by, for example, a solenoid towards the type font lla in direction
27 and engages surface 17, that further movement in direction 27 towards the print
ribbon (not shown) will cause hammer 15 to strike edge 28 of print head llb causing
interference with the smooth flight of print head lla and causing a twisting torque
of the beam supporting head llb and undesirable adjacent character printing.
[0007] Referring now to Figure 3, there is seen a detent alignment print hammer 15 and type
fonts or character slugs lla and llb in accordance with this invention. A portion
of the sides of print hammer 15 has been removed to form tapered portion 29. It can
be seen that when hammer 15 is moved forward in direction 27, character slug llb,
the adjacent slug, will be swept aside by print hammer taper surface 29 instead of
being directly impacted. A further improvement in operation is obtained where the
type slugs are also tapered as shown in Figure 3. Here the sides of the larger type
slugs represented by slug llb in Figure 3 are removed to form slanted surface 31.
Not only has it been found that by tapering the surface of slugs ll,a greater misalignment
between print hammer 15 and type slug lla can be tolerated, but it has been found
that print wheel 1 can be rotated in a direction 7 while the print hammer 15 is in
a forward position, which could increase printing speed. Obviously, surfaces 29 and
31 could be made in other shapes, for example, fillet, bevel, flute, etc.
[0008] As will be obvious to one skilled in the art, there are many modifications to the
invention, which will present themselves. All such modifications as naturally occur
to those skilled in the art are deemed to fall within the scope of the attached claims.
The illustrative embodiment depicted in the attached drawings is considered merely
as an exemplary representation of one of the ways of practicing the invention.
1. A serial printer in which character slugs(11) having shaped alignment surfaces(17)
are mounted on print wheel (1) and are rotated through a print station(2), and a detent
alignment print hammer(15)having a corresponding shaped alignment surface(19)is positioned
to strike slugs (11) at the print station (2), characterized in that the print hammer
(15) is shaped (29) to cause adjacent character slugs(11)to be swept aside.
2. The serial printer of Claim 1 wherein at least a portion of said character slugs(11)
have tapered sides (31).
