Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
Printing Apparatus
Technical Field
This invention relates to a 'printing apparatus, particularly
to a device for preventing display character fouling in a printing
apparatus installed in portable label printing and of Fixing
apparatus (hand labeler) or the like.
Background Art
The printing apparatus of a hand labeler generally has
selector wheels supported on a shaft at one end portion of
a printer frame and a type bearing member section at the
other end portion of the frame. Endless printing bands
made of a flexible material such as rubber or synthetic
resin and formed on their outer surfaces with types and
display characters are wound around the selector wheels and
the type bearing member section. The selector wheels are
rotated to rotate the endless printing bands to locate
desired types on the outer surfaces of the type bearing
member section where they can be printed, ink is applied to
the types by an ink roller or the like, and the types can
then be impressed on a label or the like.
Each endless printing belt is formed with types
around one half its perimeter and display characters around,
the other half of its perimeter, the arrangement being
defined so that the display character at the position
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viewable through a display window section provided in the
printer frame corresponds to the type positioned at the
type bearing member section.
Prescribed types can therefore be positioned at
the type bearing member section by using a type select
operating shaft to rotate the selector wheels while viewing
the display characters through the display window section.
However, if an endless printing band is rotated
beyond the prescribed rotation range when it is rotated by
operating the type select operating shaft, the display
characters may be rotated as far as the type bearing member
section and be fouled by application of ink thereto by the
ink roller. This leads to such problems as that the
display characters become hard to see when selecting
prescribed types while viewing the display characters
through the display window section.
Various proposals have been made for preventing
this fouling of the display characters (by ink application
prevention means). In the "printing band structure" of
Japanese Patent Publication No. Sho 62(1987)-33080, for
example, a projection is provided on a rotating disk for
rotating the endless printing band and a stop is provided
in the vicinity of the rotation range region of the endless
printing band. Owing to abutment of the projection on the
stop, the rotating disk can rotate only within the
prescribed region.
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However, this device involves problems such as
that the projection interferes with the display characters
and that if the rotating disk is rotated with excessive
force after the projection strikes on the stop, the endless
printing band may elongate, causing it to print improperly
or fall off.
Further, in the "printer" of Japanese Patent
Application Laid-open No. Hei 6(1994)-155878, a
protuberance is formed on the outer peripheral surface of
the endless printing band to be engageable with a stop and
the crest surface of a drive projection engaging with an
indentation provided on the periphery of the selector wheel
is formed as a slanted surface. When a selector wheel is
forcibly rotated after the endless printing band has
reached the limit position, the endless printing band
slips.
Iri this printing apparatus,however, the problem arises that
the slipping at the time the endless printing band is
rotated with excessive force wears, cracks and otherwise
damages the slanted surface of the endless printing band.
Moreover, since the outer peripheral surface of
the endless printing band is formed with the protuberance,
the problem arises that the number of type that can be
provided on the. endless printing band decreases.
Further, in the "device for preventing fouling of
printer display characters" of Japanese Utility Model'
Application Laid-open No. 6(1994)-71146, the rotation range
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of the endless printing band is limited by abutment of a
sectionally thick type portion formed on the outer
perimeter of the endless printing band with a leg portion
of an indicator.
Damage of the indicator and damage of the endless
printing band by cracking and the like when excessive
rotational force are also a problem in this device.
Another problem is that the endless printincJ band may pass
.. beneath the indicator.
In "printer" of Japanese Patent Publication No.
Hei 4(1992)-34951, on the other hand, rotation of the
endless printing band is limited by engagement between a
tooth formed on the endless printing band and a stop
shoulder.
This printing apparatus also has problems in that
application of excessive rotational force elongates the
endless printing band and causes wear, cracking and other
damage.
Thus in all of these configurations the attempt
to prevent fouling of the display characters by limiting
rotation of the endless printing band to a prescribed
region makes it difficult to avoid the direct or indirect
action of large external forces on the endless printing
band. They therefore encounter the problems of elongation
and damage, the problem that the original purpose cannot be.
achieved because the projections ride over the stops, and
other problems.
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This invention was accomplished in the light of
the aforesaid problems and has as an abject to provide a printing
apparatus which prevents fouling of the display characters on
an endless printing band by keeping them from being
positioned at the type bearing member section, i.e., from
being brought opposite the ink roller.
Another object of the invention is to provide a Prnting
apparatus wherein the rotation o f a n end 1 a s s p r i n t i ng b a nd i s
limited in a manner that keeps excessive rotational force
from acting on the endless printing band itself, thereby
avoiding wear, cracking and other damage.
Another object of the invention is to provide a printing
apparatus which minimizes the reduction in number of type
caused by formation of a projection for limiting rotation
of an endless printing band.
Another object of this invention is to provide a printing
apparatus wherein forcible rotation of an endless printing
band at its rotation limit causes idle rotation of the
selector wheel and puts only moderate load on the endless
printing band.
Another object of this invention is to provide a Printing
apparatus wherein the tension (degree of tautness) of an
endless printing band can be regulated within a prescribed
range.
Bisclosure of the Invention ,
A first aspect of the invention is directed to
enabling idle rotation of the selector wheels by adopting
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selector wheel rotation restricting members (movable stop
members) of a movable type having elastic sections,
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enabling the movable stop members to move when excessive
force acts on the selector wheels or the endless printing
bands, and allowing the engaged state of the endless
printing bands with the selector wheels to become a
partially engaged state therewith to produce slack.
According to this first aspect of the invention, a printer
having at least one endless printing band formed on its
outer peripheral surface with multiple types and display
characters and wound about a selector wheel and a type
bearing member section and enabling selection of a desired
type of the endless printing band is characterized in
comprising a movable stop member provided between the
selector wheel and the type bearing member section and
formed at one end portion with at least one regulating boss
portion for engaging the-selector wheel and provided at
another end portion thereof with an elastic section having
at least one engagement piece, a stop bearing member for
restricting movement of the movable stop member by abutting
on the elastic section of the movable stop member, and at
least one drive projection provided on an inner peripheral
surface of the endless printing band to be engageable with
the engagement piece of the elastic section of the movable
stop member, engagement between the drive projection and,
the engagement piece with movement of the endless printing
band causing movement of the movable stop member to enable
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release of the engagement between the selector wheel and
the regulating boss section.
To stabilize the moving action of the movable
stop member, the printer can be provided with a stop guide
for guiding the movable stop member in its movement
direction.
The elastic section can have a bifurcated
engagement spring section. Since the bifurcated engagement
spring section can elastically deform laterally with
movement of the movable stop member in the vertical
direction, for example, the engagement between the drive
projection of the endless printing band and the elastic
section can be further strengthened acid the movable stop
member can effect smooth elastic movement.
The stop bearing member can have a slanted
bearing surface for bearing the elastic section. Since the
elastic section is elastically deformed along the slanted
bearing surface when the movable stop member moves, the
engagement between the drive projection of the endless
printing band and the elastic section can be further
strengthened and the movable stop member can effect smooth
elastic movement.
The endless printing band can have at least one
blank section with no types on its peripheral surface and
the inner peripheral surface at least one display
character adjacent to the side of the blank section in the
direction of rotation can be made a flat section.
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Specifically, the~inner peripheral surface at
least one display character adjacent to the side of the
blank section in the direction of rotation can be formed
without projections capable of engaging with the selector
wheel, thereby avoiding engagement between the selector
wheel and the endless printing band and facilitating idle
rotation of the selector wheel.
According to a second aspect of the invention, a printing
apparatus having at least one endless printing band formed on
its outer peripheral surface with multiple types and
display characters and wound about a selector wheel and a
type bearing member section and enabling selection of a
desired type of the endless printing band is characterized
in comprising a stop member provided between the selector
wheel and the type.bearing member section and at least one
drive projection provided, on an inner peripheral surface of
the endless printing band to be engageable with the stop
member, engagement between the drive projection and the
stop member with movement of the endless printing band
producing slack in the endless printing band to enable idle
rotation of the selector wheel.
In the device for preventing display character
fouling in a printer according to this invention, the
regulating boss portion and the elastic section are formed
on the movable stop member, the regulating boss portion,
engages with the selector wheel, and the elastic section
elastically deforms. As a result, regulation of the
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endless printing band type selection operation (appropriate
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set states of individual types at the type bearing member
section and differentiation of the set states) can be
secured.
Therefore, while types and display characters of
the endless printing band can be selected as desired by
rotating the selector wheel to rotate the endless printing
.. band thereabout, a drive projection of the endless printing
band engages with the elastic section of the movable stop
member just before a display character strikes (contacts)
the ink roller to produce a sensation of resistance
(resistance action) tending to once halt the rotation.
When an attempt is made to rotate the selector
wheel beyond the point of this resistance action, the
elastic section elastically deforms and the movable stop
member itself moves slightly toward the type bearing member
section side.
In this way, the rotational traction between the
regulating boss portion of the movable stop member and the
selector wheel decreases below that in the normal type
selection state and, in addition,,the endless printing band
slackens from its engagement point with the selector wheel
to its engagement point with the elastic section of the
drive projection, thereby releasing its engagement with the
selector wheel and allowing the selector wheel to rotate
idly.
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Since the display characters are therefore not
rotated to and positioned at the rotation region of the ink
roller, fouling thereof can be prevented. Moreover, any
excessive force acting to rotate the selector wheel further
is transferred through the endless printing band and a
drive projection thereof to the elastic section of the
movable stop member, whereafter it acts in the direction of
producing idle rotation between the regulating boss portion
of the movable stop member and the selector wheel and does
not damage the endless printing band.
Since the drive projection is provided on the
inner peripheral surface of the endless printing band and
made engageable with the elastic section of the movable
stop member, thare is no reduction of the numbers of types
and display characters on the peripheral surface of the
endless printing band.
In the second aspect of the invention, slack
is produced in the endless printing band when its rotation
is prevented by its engagement with the stop member, the
selector wheel and the endless printing band are put in a
released state or in a state .in which, even if they
contact, rotation of the selector wheel does not act on the
endless printing band, the selector wheel rotates idly, the
endless printing band does not move to move the display
characters as far as the type bearing member section, and
the possibility of the display characters being fouled by
contact with the ink roller is eliminated.
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A third aspect of the invention is characterized
in that a cam member whose rotational position can be
adjusted is provided within the endless printing band to be
rotatable into and out of contact with the inner peripheral
surface of the endless printing band. In this case, the
tension of the endless printing band can be adjusted by
rotating the cam member to vary the degree of contact
between the cam member and the endless printing band.
Brief Description of Drawings
Figures 1 is a sectional view of a printer
according to the first aspect of the invention; Figure 2 is
a sectional view taken along line II-II in Figure 1; Figure
3 is a sectional view showing an endless printing band of
the printer shown in Figure 1 when rotated to the rotation-
prevented state; Figure 4 is a sectional view showing the
idle rotation state of a selector wheel; Figure 5 is
sectional view of a printer according to the second aspect
of the invention; Figure 6 is a sectional view taken along
line VI-VI in Figure 5; Figure 7 is a side view of an
endless printing band in the second aspect; Figure 8 is a
sectional view showing the rotation-prevented state of
endless printing bands and the idle rotation state of
selector wheels; Figure 9 is a sectional view of a printer
according to the third aspect of the invention; Figure 10
is a sectional view taken along line II-II in Figure 9;
Figure 11 is a side view of an adjuster; Figure 12 is a
partially cut-away enlarged side view of an essential
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portion of a printer frame and an adjuster section; Figure
13 is a sectional view showing an endless printing band of
the printer shown in Figure 9 when rotated to the rotation-
prevented state; and Figure 14 is sectional view showing
the idle rotation state of a selector wheel.
Best Mode for Carrying out the Invention
In Figures 1 and 2, one end portion of a printer
frame 3 of a printer 1 is provided with multiple selector
wheels 5 which are selectively rotatable by an operating
shaft 4 for type selection, the other end portion thereof
is provided with a type bearing member section 6 of T shape
section extending parallel to the operating shaft ~1 for
type selection, and endless printing bands 7 are wound
about the selector wheels 5 and the type bearing member
section 6 under prescribed tension. That is, multiple rocas
of the endless printing bands 7 are wound about the
selector wheels 5 and the type bearing member section 6.
A display window 8 is formed as an opening in the printing
apparatus frame 3 at an end surface portion thereof facing
the selector wheels 5 and the end surface portion provided
with the type bearing member section 6 is formed with an
ink roller access opening 9. An ink roller R can move into
contact with the endless printing bands 7 at the ink roller
.access opening 9.
The operating shaft 4 is used to select specific
types of the endless printing bands 7 by moving it in the
axial direction to select (locate) a desired row of the
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endless printing bands 7 and rotating the selector wheel 5
of the located row. The operating shaft is mounted with
respect ~ ~ painting apparatus frame 3 to be movable in the
direction of its axis and to be rotatable about its axis.
Its outer peripheral surface is formed with multiple
locator grooves 4A spaced regularly in the axial direction
and a rotary pin 1l is formed to project for near its tip.
On the other hand, the printing apparatus frame 3 is formed
with a vertical hole 3A for accommodating a steel locator
ball 12 and the steel locator ball 12 accommodated in the
vertical hole 3A is urged toward the locator grooves 4A by
a locator spring 13 to engage the steel locator ball 12
with one of the locator grooves 4A.
Thus when the operating shaft ~k is moved axially,
the steel locator ball 12 successively engages with the
locator grooves 4A. At this time, the rotary pin 11
successively moves to the positions of corresponding
selector wheels 5 to engage with internal engagement
recesses 5A formed at the inner peripheral surfaces of the
selector wheels 5. Thus the selector wheel 5 of the
desired row can be located by axially moving the operating
shaft 4.
The printer frame 3 is further equipped cnith an
indicator 10 movable along the display window B in parallel
with the axis of the operating shaft ~k. The indicator 10
is connected to the operating shaft 4 to be only rotatable
relative thereto and to move integrally with the operating
k
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shaft 4 in the axial direction. The indicator 10 is formed
with a pointer 10A which projects into the display window
8. The pointer ,0A points to the selector wheel 5 of the
desired row selected by the operating shaft 4.
Each endless printing band 7 is formed at
separate regions on its outer peripheral surface with
prescribed numbers of types 7A and display characters 7B.
Specifically, half of the outer periphery of each endless
printing band 7 is formed with a plurality of types 7A and
the other half of the outer periphery thereof is formed
with a plurality of display characters 7B. A blank section
7C is formed at each boundary region between the group of
types and the group of display characters and, as explained
later, the blank sections 7C face the display window 8 and
the ink roller access opening 9 when the endless printing
band 7 is at, the terminal portion of its movement range.
The portion of the inner peripheral surface of
the endless printing band 7 opposite the types 7A is made
flat and the portion thereof opposite the display
characters 7B is formed with low drive projections 7D and
high drive projections 7E each engageable with peripheral
engagement notches 5B of the selector wheel 5.
The high drive projections 7E are provided at
portions opposite display characters 7B located
substantially in the middle of the plurality of display,
characters 7B. The number thereof can be freely set in
light of the numbers of the types 7A and the display
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characters 7B and the like to extend over a prescribed
region on the inner peripheral surface of the endless
printing band 7.
When the selector wheel 5 is rotated, the low
drive projections 7D and the high drive projections 7E
engage with the peripheral engagement notches 5B of the
selector wheel 5 to rotate the endless printing band 7 and
enable a desired type 7A to contact the ink roller R at the
ink roller access opening 9.
Plural movable stop members 14 associated c~rith
the respective selector wheels 5 are mounted on the ,printing apparatus
frame 3 between the selector wheels 5 and the type bearing
member section 6 and inside the endless printing bands 7
wound about the selector wheels 5 and the type bearing
member section 6.
Specifically, a stop guide 3B is provided to
proj ect fr~n the printing apparatus frame 3 and t h i s s t o p g a i d a 3 B
fits into elongate guide windows 14C formed at the center
portions of the movable stop members 14. The movable stop
members 14 can move to some degree in the directions of
approaching and separating from the selector wheels 5.
Each movable stop member 14 is formed at one end
with a pair of regulating boss portions 14A for engaging
the peripheral engagement notches 5B of the selector wheel
5 and at the other end thereof with an elastic section 148.
The elastic section 14B has a bifurcated
engagement spring section 14D. The bifurcated engagement
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spring section 14D is formed at its tip portion with
outward projecting engagement pieces 14E. The tip surfaces
of engagement pieces 14E are formed as slanted surfaces 14F
that splay toward the tip end. A stop bearing member 15 is
disposed between the movable stop members 14 and the type
bearing member section 6. As shown in Figure 2, the stop
bearing member 15 is formed integrally with the printing apparatus
frame 3. The surfaces of the stop bearing member 15 facing
the movable step members 14 are formed as bearing member
side slanted surfaces 15A which abut on the slanted
surfaces 14F of the engagement pieces 14E. The movement of
the movable stop members 14 is restricted by the abutment
of the slanted surfaces 14F and the bearing member side
slanted surfaces 15A.
In the normal selectable state, the movable stop
members 14 are individually urged toward the selector
wheels 5 by the action of the elastic sections 14B. An
upper gap S1 is formed between the elongate guide windows
14C and the stop guide 3B so that the movable stop members
14 can move downward in the drawings and also return.
The printing apparatus frame 3,is provided between the
selector wheels 5 and the type bearing member section 6
with presser frames 3C, 3D for preventing outward deviation
of the endless printing bands 7. As shown in Figures 1 and
2 , in the normal type selectable state of the printing apparatus 1
configured in this manner, a desired row can be selected by
moving the operating shaft 4 in the axial direction,
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whereafter a desired type 7A can be selected by rotating
the operating shaft 4 either clockwise or counterclockwise
at that row so as to rotate the endless printing band 7 via
the selector wheel 5 and stopping the rotation of the
operating shaft 4 at the position where the desired display
character 7B of the endless printing band 7 can be seen
through the display window 8.
In this selected state, the type 7A corresponding
to the selected display character 7B is set on the type
bearing member section 6 and exposed at the ink roller
access opening 9. Printing can be effected by turning the
ink roller R to apply ink to this type 7A and pressing the whole
printing appratus 1 onto a label by, for example, operating a
hand lever (not shown) or the like.
Figure 3 is a sectional view showing an endless
printing band 7 when rotated clockwise in the dracaing to
the rotation-prevented state. This is an example where the
operating shaft 4 was operated to rotate the selector wheel
until the endless printing band 7 rotated clockwise by an
amount causing the blank sections 7C to come opposite the
display window 8 and the ink roller access opening 9 and a
high drive projection 7E of the endless printing band 7 to
engage with one engagement piece 14E (right side of the
drawing) of the elastic section 14B of the movable stop
member 14.
The engagement between the high drive projection
7E and the engagement piece 14E therefore prevents the
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selector wheel 5 from rotating even if an attempt is made
to rotate the selector wheel 5 further, whereby positioning
of display characters 7B of the endless printing band 7 at
the ink roller access opening 9 is avoided and fouling of
display characters 7B by the ink roller R is prevented.
Figure 4 is a sectional view showing the idle
rotation state of a selector wheel 5. In the foregoing
rotation-prevented state, if an attempt is made to forcibly
rotate the selector wheel 5 further, the peripheral
engagement notches 5B of the selector wheel 5 escape from
the regulating boss portions 14A of the movable stop
members 14 to ride thereon in the illustrated state.
Specifically, the movable stop member 14 moves
downward in the drawing guided by the stop guide 3B,
whereby a lower gap S2 occurs between the elongate guide
window 14C and the stop guide 3B, the slanted surfaces 14F
of the elastic section slide on the bearing member side
slanted surfaces 15A, the legs of the bifurcated engagement
spring section 14D of the elastic section 14B spread
laterally outward, and the engagement between the
engagement piece 14E and the high drive projection 7E of
the endless printing band 7 is strengthened.
In this state, the selector wheel 'S rotates idly
because slack develops in the endless printing band 7
between the portion of the blank section 7C on the upper,
side and the portion of the engagement piece 14E so that
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the low drive projections 7D escape from the peripheral
engagement notches 5B of the selector wheel 5.
Since the engagement portion between the
engagement piece 14E and the high drive projection 7E is
located downstream in the direction of rotation of the
selector wheel 5 and the endless printing band 7 and,
further, the presser frames 3C and 3D restrain the endless
.. printing band 7 and keep it from bulging outward, the
amount of slack developed between the selector wheel 5 and
the endless printing band 7 is sufficient to ensure idle
rotation of the selector wheel 5.
The selector wheel 5 can therefore rotate idly
when an excessive external force acts thereon. Moreover,
while the selector wheel 5 rotation itself acts more on the
regulating boss portions 14A of the movable stop member 14
than on the endless printing band 7, no hindrance to type
selection arises owing to wear of the movable stop member
14 since the movable stop member 14 is harder than the
endless printing band 7.
If the selector wheel 5 is rotated in the
opposite (counterclockwise) direction, the engagement
between the peripheral engagement notches 5B and the
regulating boss portions 14A is reestablished and the
elasticity of the movable stop member 14 restores it to its
original position shown in Figure 1.
Figures 5 and 6 are sectional views of a dual
printer 20 according to the second aspect of the invention.
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Figure 6 is a sectional view taken along line VI-VI in
Figure 5. The printer 20 is constituted by combining two
printers 21 of substantially the same structure. Like
portions to those of the printer 1 are assigned like
reference symbols in the drawings and will not be explained
in detail. Only structural features differing from those
of the printer 1 will be explained.
A first presser frame 23A and a second presser
frame 23B of the printer frame 23 of the printer 20 are
formed substantially laterally symmetrical and a guide
plate 24 is provided midway between them, thereby ensuring
smooth movement of endless printing bands 7.
Sleeves 25 are fitted in the printer frame 23 to
be rotatable about their axes. Selector wheels 5 are
supported on the sleeves 25 and operating shafts 4 are
inserted into the sleeves 25. The sleeves 25 are formed in
the axial direction with slits 25A (Figure 6). Rotary pins
11 erected on the operating shafts 4 are inserted into the
slits 25A and the tips of the rotary pins 11 engage with
internal engagement recesses 5A of the selected selector
wheels 5. ,
On the other hand, the operating shafts ~1 are
fitted with co-rotation prevention rods 26 rods for
permitting rotation of only the selected selector wheels 5.
Each co-rotation prevention rod 26 is fitted on the'
associated operating shaft A to be rotatable only in
parallel with and relative to the operating shaft. It is
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mounted to be movable relative to the printing apparatus frame 23 only
in its axial direction and engages with a single peripheral
engagement notch 5B of each associated selector wheel 5.
The co-rotation prevention rod 26 is formed at a location
facing the rotary pin 11 with a notch 26A for permitting
rotation of the selector wheel 5 engaged by the rotary pin
11.
Therefore, since only the specific selector wheel
selected by the operating shaft 4 can rotate and the
peripheral engagement notches 5B of the other selector
wheels 5 are engaged with the co-rotation prevention rod
26, the selector wheels 5 adjacent to the specific selector
wheel 5 being rotated are prevented from rotating so that
no endless printing band 7 other than the selected and
operated endless printing band moves.
Figure 7 is a side view of an endless printing
band 7. The number of low drive projections 7D formed on
the inner peripheral surface of the endless printing band
7 is two less than in the case of the printing apparatus 1 (Figure 1 ) .
Specifically, the inner peripheral surface
portions at the display characters 7B adjacent to the blank
sections 7C on the downstream side thereof in the direction
of rotation of the endless printing band 7 are not formed
with low drive projections 7D but are formed as flat
portions 7F.
Although the illustrated example shows a pair
(two) of flat portions 7F on the inner peripheral surface
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of the endless printing band 7, insofar as the ability to
rotationally drive the endless printing band 7 by the
selector wheel 5 can be maintained, it is possible to
further facilitate the occurrence of idle rotation by
providing the inner peripheral surface of the endless
printing band 7 with two sets of two side-by-side flat
portions 7F (total of four).
Since the dual printer 20 of this configuration
provides the same effects as that shown in Figure 1 and
other figures, in can reliably prevent fouling of the
display characters 7B by the ink roller R without damaging
the endless printing bands 7.
Specifically, as shown in Figure 8, taking the
printer 21 on the right side by way of example, when a high
drive projection 7E of the endless printing band 7 engages
one of the engagement pieces 14E of the movable stop member
14 owing to rotation of the selector wheel 5 in the
clockwise direction, further rotation of the selector wheel
is prevented (rotation-prevented state).
If the selector wheel 5 of the.printing apparatus 21 on the
right side of Figure 8 is rotated clockwise in an attempt
to cause further clockwise rotation from the rotation-
prevented state, the selector wheel 5 rides up on the
regulating boss portions 14A and assumes an idly rotating
state owing to separation of the outer peripheral surface
of the selector wheel 5 in the direction of rotation from
the inner peripheral surface of the endless printing band
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7 including the flat portions 7F (with no drive
projections). In other words, as is clear from the
drawings, the endless printing band 7 exhibits a slack
state relative to the selector wheel 5, giving rise to idle
rotation.
To be more specific, since the inner peripheral
surface at the display character 7B immediately to the
right in the figure from the blank section 7C positioned at
the display window 8 is a flat portion,7F with no low drive
projection 7D, engagement between the selector wheel 5 and
the endless printing band 7 easily releases, whereby slack
tends to develop in the endless printing band 7 to enable
ready transition to the idle rotation state.
Since the other operations and effects are the
same as those of the first aspect, they are not described
in detail here.
Like the printer according to the second aspect
described in the foregoing, that according to the first
aspect shown in Figures 1 to 4 can also be configured to
facilitate the development of slack in the endless printing
bands 7 so as to enable ready transition of the selector
wheels 5 to the idle rotation state.
When the diameter of the selector wheels 5
according to the first aspect are made smaller than the
selector wheels according to the second aspect, the '
development of slack in the endless printing bands 7 and
the transition of the selector wheels 5 to the idle
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rotation state can be facilitated by defining the height of
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the low drive projections 7D at positions corresponding to
the flat portions 7F to fall within a prescribed range.
Further, when these selector wheels 5 are larger
than in the second aspect (Figure 5), the idle rotation
state is readily exhibited if the flat portions 7F formed
on the inner peripheral surfaces of the endless printing
bands 7 are made equivalent to two characters to the left
and right of the blank sections 7C.
Figures 9 and 10 are sectional views of a printing apparatus
according to the third aspect of the invention. A tension
adjustment mechanism 30 for the endless printing bands is
disposed within the endless printing bands 7 at a location
between the stop bearing member 15 and the type bearing
member section s. The tension adjustment mechanism 30 has
an adjuster 31 (cam member). As shown in Figure 11, the
adjuster 31 is integrally formed of a sectionally
elliptical main body 31A, cam adjustment rotary shafts 31B,
an adjustment arm 31C and an engaging ridge 31D.
Specifically, the sectionally elliptical main
body 31A is provided on opposite end surfaces with cam
adjustment rotary shafts 31B. The sectionally elliptical
main body 31A is rotatably supported on the printing apparatus frame
3 by the cam adjustment rotary shafts 31B. When the
sectionally elliptical main body 31A is rotated, its outer
peripheral portion makes and breaks contact with the inner
peripheral surfaces of the endless printing bands 7.
G CA 02234427 1998-04-08
One end surface of the sectionally elliptical
main body 31A is formed with the adjustment arm 31C
extending perpendicular to the cam adjustment rotary shaft
31B, and the engaging ridge 31D is provided on the tip
portion of the adjustment arm 31C to face the printer frame
3.
On the other hand, as shown in Figure 12, a
surface of the printer frame 3 lying perpendicular to the
drawing sheet is formed with multiple radially extending
cam adjustment grooves 32 with which the engaging ridge 31D
can engage. Other points are the same as shown in Figures
1 and 2.
At the time assembly of the printer at the
factory, for example, the attitude or relative position of
the sectionally elliptical main body 31A with respect to
the endless printing bands 7 can be adjusted by rotating
the sectionally elliptical main body 31A about the cam
adjustment rotary shafts 31B to bring the engaging ridge
31D of the adjustment arm 31C into engagement with a
desired one of the cam adjustment grooves 32 of the printer
frame 3.
As shown in Figure 9, for example, the tension of
the endless printing bands 7 can be increased by
positioning the sectionally elliptical main body 31A to
thrust toward the endless printing bands 7 since this
causes the sectionally elliptical main body 31A to abut
CA 02234427 1998-04-08
26
relatively strongly on the inner peripheral surfaces of the
endless printing bands 7.
Otherwise, if the sectionally elliptical main
body 31A is rotated to the attitude shown in Figures 13 and
14, the adjuster 31 does not contact the inner peripheral
surfaces of the endless printing bands 7, whereby the
tension of the Pndless printing bands 7 can be reduced.
Adjustment of the rotation angle of the adjuster
31 thus enables adjustment of the tension of the endless
printing bands 7 for ensuring their proper rotation and
further enables the condition of slackening of the endless
printing bands 7 in the idle rotation state shown in Figure
14 and the effect of the idle rotation of the selector
wheel 5, which is related to the slackened condition, to be
brought within the desired ranges.
The set angular position of the adjuster 31 can
also be adjusted to readjust the tension of the endless
printing bands 7 in response to elongation or slackening of
the endless printing bands 7 during use of the printing apparatus.
Since, as explained in the foregoing, the
invention provides the stop members, each having regulating
boss portions and an elastic section, and further provides
the stopper bearing member on which the elastic sections
abut to restrict movement of the movable stopper members,
it enables the selector wheels to ride up and rotate idly,'
thereby preventing fouling of the endless printing bands by
~ CA 02234427 1998-04-08
27
the ink roller and reducing the load on the endless
printing bands 7.
Further, since an attempt to rotate a selector
wheel from its rotation-prevented state causes it to rotate
idly owing to separation between the outer peripheral
surface of the selector wheel in the direction of rotation
and the inner peripheral surface of the endless printing
band, no load arises owing to contact friction between the
two surfaces.
When the tension adjustment mechanism is provided
within the endless printing bands, moreover, the degree of
endless printing band tensioning can be simply adjusted by
rotating the adjuster within a prescribed range.
