Note: Descriptions are shown in the official language in which they were submitted.
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PRINT WHEEL FOR MULTI HAMMER IMPACT PRINTER
The invention relates to a print wheel for serial
printing devices and particularly to high-speed serial printers
having multiple print characters arranged on beams of a disc
member.
There are two types of systems known wherein multiple
characters are arranged in concentric circles on the disc. In the
first, the disc is caused to move up or down relative to a
horizontal line of printing depending on whether a character on
lo the inner row or a character on the outer row of characters is to
be printed. In the second, multiple print hammers are provided,
one for each row of characters, and the axes of the characters in
each row differ so that they are aligned correctly for printing at
different rotational positions. This invention relates to an
improvement in print wheels for the multiple hammer system.
The invention as claimed is intended to provide a
multi character row print wheel which is relatively easy to mold as
a one-piece plastic wheel, and wherein each row of characters and
corresponding pads is formed to align accurately with the Face of
the printer platen when impacted by its associated hammer.
An aspect of this invention is as follows:
A printwheel for a multi hammer impact printer having
a platen, the printwheel comprising:
a disc hub,
beams extending radially outwardly in a single common
plane from said hub,
at least two concentric circular rows of characters
formed on said beams, each character having a pad portion and
a printing surface portion,
said pad portion of each character of at least one
of said rows being oriented relative to said beams by a first
angle and said printing surface portion of each character of
said at least one of said rows lying in a first plane, and
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said pad portion of each character of at least one
other row being oriented relative to said beams by a second
angle disposed at an angle X relative to said first angle and
said printing surface portions of each character of said at
least one of said rows lying in a second plane disposed at an
angle Y to said first plane.
One way of carrying out the invention is described
in detail below with reference to the drawing, which illustrates
only one specific embodiment in which:
Figure 1 shows prior art character-beam relationships.
Figure 2 shows a partial plan view of a print wheel
in accordance with this invention.
Figure 3 is a cross-sectional side view of the print
wheel of Figure 2 taken along line 3-3.
Figure 4 is a top view of the print wheel of Figure
2 taken along line 4-4.
Figure PA is a top view showing greatly enlarged
the relationship between the inboard and outboard print wheel
hammers, characters and platen at rest, in dashed lines, and
at the moment of printing.
Figure 5B is a top view showing greatly enlarged
the relationship between the outboard print wheel hammer, outboard
character and platen at rest, in dashed lines, and at the moment
of impact.
Figure 6 is a side view showing an inboard character greatly
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enlarged at the moment of printing.
Figure 7 is a side view showing on outboard character greatly
enlarged at the moment of printing.
Figure 8 shows a further character-beam relationship in
5 accordance with this invention.
The Figures ore not drown to scale, and certain features ore
exaggerated in size for purposes of explanation.
Referring now to Figure 1, there are shown three prior art
character bearing beams. Berm I is the standard print wheel beam that
10 carries one character 11 per beam. Beam 2 has two concentric circular rows
of characters on it, the axis of each of the characters being aligned with the
long axis of the berm. To print using a beam 2 type print wheel, a single print
hummer is used, end the print wheel is Leonard or raised depending on whether
a character from the inner (I lay or outer (I IBM row of characters is desired to
15 be printed. A print wheel with character bearing spokes such as beam 3 utilize
two print hammers. The print wheel is rotated into the position shown in
Figure I where the lower or inner character is to be printed. The print wheel
is rotated in the plane of the disc until the outer character is aligned with the
line of printing to print the outer character. The centers of characters I It
20 and I It are aligned on the long axis of the beam on which they are mounted.
An explqnqtion of how this print wheel can be used in a dual-hammer print
wheel system is disclosed in US. Patent 4,û69,907, issued January 24, 1978.
Referring now to Figures 2-4, there is seen a print wheel disc
designated generally as 5, which is made up of a hub 7 and extending
25 therefrom, a plurality of radially extending beams 9. Formed on beams 9 are
inboard character pads I I a and outboard character pads I I b. It can be seen
that beams 9 ore straight end that outboard character pads I It are formed at
on angle to the beams 9. Structurally, it is preferred to have character pods
I lo and I It formed such that their centers ore on the center of a straight
30 beam 9, but they may also have the arrangement shown in the above-
mentioned potent or generally con be placed on a berm of any non-linear
shape.
Drive means 13 is provided for rotating print wheel 5. Drive means
13 may be driven, for example, by a servo or stepper motor for rotating print
35 wheel 5 to align the desired character pad ha or fib as desired on line of
printing 15. Print hammers aye and 17b shown as dashed circles in Figure 2
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are provided to impact inboard character pods aye and outboard character
pads l lb in line with line of printing 15, respectively. A platen 19 is provided
against which printing occurs.
In operation, as print wheel S is moved along the line of printing 15
5 by carriage means (not shown), a controller (not shown) activates drive means
13, which rotates print wheel 5 unit! preselected character pad ha or fib is
aligned with line of printing 15. The appropriate print hammer aye, 17b is
then activated moving in the direction shown by arrow 21 toward the platen,
impacting the preselected character pad ha or fib and driving it toward
lo platen 19. A wedge back is provided on the pads carrying characters l lo and
fib, and the hammers aye and i7b are V-notched correspondingly to ensure a
proper capture even in the case of misalignment shammer to pad) due to
manufacturing tolerances accumulation or print-on-the-fly technique.
Conventionally, a print ink ribbon (not shown) and a print receiving
5 member such as paper (not shown) are placed between the print wheel and
platen 19 to effect printing. Depending on how much distance there is
between hammers aye and 17b, it may be necessary to move the print wheel 5
relative to the platen 19 to space the printed characters evenly. Also, the
controller can be programmed to type outboard characters out of sequence
20 since outboard characters are printed a number of spaces away from inboard
characters so that print wheel 5 movement relative to platen 19 would proceed
conventionally without the necessity for rapid back and forth movement.
While printing the inboard character l lay pure bending stress is
induced in the beam 9. It has been found in this system that the beams 9 are
25 subject to either pure bending or bending and twisting during operation when
the outboard character pads fib are printed, depending on the shape of the
beam. The straight beam shown in Figure 2 is subject to bending only; and the
beam 3, shaped as shown in Figure 1, is subject to both bending and torsion.
When outboard character pad l lb is impacted against platen 19~ because of its
30 offset position from the vertical centerline of the print wheel and also due to
the bend or twist of bearing beam, the character 23b does not meet platen 19
exactly flush but meets instead at an angle, which can cause shaded printed
characters.
In order to overcome the problem recited above, the outboard
35 character pads l lb and characters 23b formed thereon are designed to meet
the platen 19 flush and yet allow the print wheel beams to be formed in a
aye
single plane, confining complex cutting angles to the character pads l lb and
characters 23b only.
Referring now to Figures PA and 6, there is shown an inboard
character pad I I a having character aye formed thereon. rho face of
5 character pad ha, which contacts print hammer aye, is formed as a male
dihedral aye, which is shaped to mate with female dihedral aye in inboard print
hammer aye. The purpose of the dihedral mating surfaces is to align and
stabilize the character aye with reference to the platen 19 at the time of
printing. The character pad 11 a and print hammer aye shown in dashed lines
10 represent the position of the character pad l lo and print hammer 17s~ in the"at rest" position; the solid lines represent the character pad ha and print
hammer aye at the moment of printing.
It can be seen in connection with Figure PA that, as print hammer
aye moves forward in direction 21, character 19 will be flush or strike at a
IS right angle in relation to a radius of platen 19 at the time of impact as shown
in Figures PA and 6. The impact surface aye is formed with a surface
curvature to match the curve of the platen. It can be seen, however, that,
where for example, the outboard character pad fib was seen in Figure) is
driven toward the platen, the right hand and lower portions of character pad
20 1 by will impact the platen 19 first, causing a shaded printed character and
beam 9 either bending (in the case of straight beam in Figure 2) or bending and
twisting (when the beam has the shape of beam 3 depicted in Figure 1).
Referring now to Figures SUB and 7, there is shown, in accordance
with this invention, a character pad l lb and character 23b designed to allow
25 character 23b to be presented flush to platen 19 at the moment of printing as shown in Figure 7.
Figure 5B shows in dashed lines the relationship between outboard
character pad fib and outboard print hemmer 17b in the at rest position.
Outboard character pad l lb is provided with male dihedral 25b, and outboard
3û print hammer 17b is provided with female dihedral form 27b for alignment and
stabilization of character 23b at the time of impact with platen 19. In order
for the surface 29b of character 23b to be aligned with the platen 19
horizontally at the time of impact, character printing surface 29b is formed
such that at rest it is aligned at a predetermined angle Y relative to platen
35 surface 19. For convenience in molding, outboard character pad l lb surface
31b is formed in the same plane as inboard character pad l lo surface aye.
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This plane is perpendicular to the axis of rotation of print wheels. The
character pad i It is, however, formed it angle Y to the surface 31b. Then as
print wheel 5 is moved toward platen 19 and constrained in an arc by berm 9,
printing surface 29b wit! meet platen 19 flush as shown in solid line in
Figure 5B. The bisecting line 33 of mule dihedral 25b of outboard pad l lb is
formed also at angle Y to the axis of rotation of print wheel 5. This will
enable the V-surface 27b of outboard hammer I It to properly engage the pod
l lb at rest end drive it towards the platen 19 when printing so that the
bisecting line 33 takes the final position 34 perpendicular to platen 19 at the
lo moment of contact as shown in Figure EYE. Also, in order to have outboardcharacter surface 29b meet platen 19 flush vertically, it is necessary to
provide a slant of printing surface 29b of angle X versus the surface 31b us
shown in Figure 7. The superposition of cutting angles X, Y defines the spatial
position of a plane tangent to the curved print surface of the character at restsuch that when impacting the platen, this surface will uniformly comply with
the curvature of platen 19.
In a particularly preferred embodiment, the beams are spaced at
3.6 from one another providing room for Lou berms 9 on the circumference of
hub 7. In Figure 2, the angular span 30 between two spokes 9 bearing pads 11 a
2û and l lb and aligned with line of printing 15 is 32.4. From the center of the
hub 7 to the center of the character pads l lo on the inner character row is
1.4789 inches. The outer character fib centers are 1.7516 inches from the
center of the disc. The outer characters fib are placed further out than
geometrically required since the berms 9 become, in effect, shorter when bent
by hummer 17 impact. Also, us shown in Figure 5B, the axis 33 of character
pad l lb is offset from the axis 35 of print hammer 17b on angle Y of bout
4.05. This also is the angle Y that print surface 29b is formed in relationshipto surface 31b of character pad l lb us shown in Figure 5B. The angle shown
in Figures 6 and 7 is designed to be 11.2; the angle X, 3.05; and the angle
to be 8.15. The outboard hammer 17b is spaced nine intervals (or ten spokes)
away from inboard print hammer aye, equivalent to 32.4 on the print wheel 5.
Referring now to Figure 8, the concept is subject to generalization
to a print wheel with snore than two rows of characters and two printing
hammers. In Figure 8 is depicted a print wheel with three rows. The three
characters carried by the some berm are formed at different angles with the
long axis of the berm. These Jingles along with the diameter of etch row,
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ensure the proper spicing between characters when all three rows are used to
print on the same line. Also, each row will hove its own Y and X angles built
on fonts and pad wedge buck and, consequently, its own hammer angle 0.
Depending on design constraints (e.g., distance between print wheel and platen
5 19), either both angles I Y or Only one of them can be equal to zero or a
given row.
While the principles of the invention have been made clear in the
illustrative embodiments, there will be many modifications in structure,
arrangement, proportions, etc., which will occur to those skilled in the art.
10 For example, although this invention was described in connection with two
character rows and two print hammers, obviously more than two character
rows end print hammers could be used employing the same principles. Further,
although the preferred print wheel beam in accordance with this invention is
straight, the same principles of this invention would apply to the print wheels
having beams such as shown in US. Patent 4,069,907 or of any other shape.
The appended claims are, therefore, intended to cover and embrace any such
modifications within the scope and spirit of the invention.
