SPECIFICATION
Tractor unit, conveyance device, and printer
BACKGROUND
1. Technical Field
[0001]
The present invention relates to a tractor unit for conveying
fanfold paper or other continuous paper having sprocket holes, to a
conveyance device including the tractor uni t , and to a printer having
the conveyance device.
2. Related Art
[0002]
Japanese Unexamined Patent Appl. Pub. JP-A-2006-8265 describes
a conveyance device for conveying continuous paper. The conveyance
device disclosed in JP-A-2006-8265 has a paper feed roller, and a
tractor unit disposed on the upstream side of the paper feed roller
in the conveyance direction of the continuous paper. The tractor unit
in JP-A-2006-8265 has a first tractor, a second tractor, a support
shaft, and a clamping mechanism. The first tractor has first tractor
pins that can engage first sprocket holes formed along one side of
the width of the continuous paper. The second tractor has second
tractor pins that can engage second sprocket holes formed along the
other side of the width of the continuous paper. The support shaft
supports the first tractor and second tractor so that both tractors
can move in a transverse direction perpendicular to the conveyance
direction of the continuous paper. The clamping mechanism holds the
second tractor in a fixed position on the support shaft.
Continuous paper is set in the conveyance device described in
JP-A-2006-8265 by engaging the first sprocket holes in the continuous
paper with the tractor pins of the first tractor set to a reference
position, then sliding the second tractor along the support shaft to
a position appropriate to the width of the continuous paper and
2
engaging the second sprocket holes of the continuous paper on the
tractor pins of the second tractor, and then clamping the second
tractor to the support shaft.
[0003]
The conveyance device described in JP-A-2006-8265 conveys
continuous paper that has already been printed on by an
electrophotographic printer. When continuous paper is printed on
using an electrophotographic process, the continuous paper may shrink
widthwise due to the heat used to fuse the toner image formed on a
photoconductive element to the continuous paper. Because the distance
between the sprocket holes formed on one side of the continuous paper
width and the sprocket holes formed on the other side changes when
the continuous paper shrinks widthwise, the sprocket holes of the
continuous paper sometimes separate from the tractor pins of the first
tractor or the tractor pins of the second tractor while the continuous
paper is conveyed.
To prevent this, the tractor unit disclosed in JP-A-2006-8265
has a stop affixed to a position corresponding to the reference
position on the support shaft, and disposes the first tractor to the
reference posi tion by pushing the first tractor towards the stop (in
the direction separating the first tractor from the second tractor)
using a spring member so that the first tractor contacts the stop.
The tractor unit can therefore prevent sprocket holes in the
continuous paper from disengaging the tractor pins when the width of
the continuous paper shrinks because the first tractor moves toward
the second tractor in resistance to the spring member and reduces the
gap between the first tractor and the second tractor.
[0005]
Separation of the sprocket holes from the tractor pins while the
continuous paper is conveyed by a paper feed device using a tractor
u.nit is not limited to when the width of the continuous paper shrinks
as a result of the printing method. For example, when the conveyance
3
direction of the continuous paper by the paper feed roller and the
conveyance direction of the continuous paper by the tractor unit do
not match precisely due to the dimensional precision of the paper feed
roller and parts of the tractor unit, or the installation precision
of the paper feed roller and tractor unit in the printer, the
continuous paper may travel in a direction intersecting the
conveyance direction due to the conveyance force of the paper feed
roller, causing the sprocket holes to separate from the tractor pins.
Using the tractor unit disclosed in JP-A-2006-8265 to avoid this is
conceivable.
[0006]
However, when the continuous paper is set in the tractor unit
disclosed in JP-A-2006-8265, the user can apply too much tension
across the width of the continuous paper. More specifically, the
continuous paper becomes easily skewed as it is pulled to the
downstream side by the conveyance force of the paper feed roller if
there is slack across the width of the continuous paper between the
first tractor and the second tractor when the continuous paper is set
in the tractor unit. As a result, after engaging the tractor pins of
the second tractor with the sprocket holes of the continuous paper,
the user commonly pulls the second tractor in the direction away from
the first tractor and applies tension across the width so that there
is no slack in the continuous paper, and then clamps the second tractor
to the support shaft.
If the user pulls the second tractor with such force that the
first tractor moves toward the second tractor side when pulling the
second tractor away from the first tractor, tension will be applied
to the continuous paper by both the excess tension applied by the user
and the urging force of the spring member, and the second tractor will
be clamped to the support shaft wi th excessive tens ion on the paper.
However, the continuous paper conversely separates from the sprocket
holes more easily if the continuous paper moves in a direction
4
intersecting the conveyance direction when excessive tension is
applied across the width of the continuous paper by the pair of
tractors.
SUMMARY
[0007]
The present invention is directed to solving the foregoing
problem, and provides a tractor unit that maintains appropriate
tension across the width of the continuous paper and prevents the
sprocket holes in the continuous paper from disengaging the tractor
pins of the tractor, a conveyance device having the tractor uni t, and
a printer having the conveyance device.
[0008]
One aspect of the invention is a tractor unit having: a first
tractor that sequentially engages first tractor pins in first
sprocket holes formed in continuous paper in the paper conveyance
direction along one side of the paper width; a second tractor that
sequentially engages second tractor pins in second sprocket holes
formed in the continuous paper in the conveyance direction along the
other side of the paper width; a support shaft that extends in a
transverse direction perpendicular to the conveyance direction of the
continuous paper, and supports the first tractor and second tractor
movably in the transverse direction; a frame that supports the support
shaft movably in the transverse direction; an elastic member that can
apply pressure pushing the support shaft in the transverse direction;
and a clamping member that fixes the second tractor on the support
shaft. The first tractor is disposed to a predetermined reference
position in the transverse direction. The elastic member exerts
(applies) an urging force (pressure) urging (pushing) the support
shaft in a second direction opposite a first direction when the
support shaft moves in the first direction from the second tractor
side to the first tractor side.
5
[0009]
In this aspect of the invention the support shaft to which the
second tractor is clamped is supported by the frame movably in the
transverse direction. Therefore, when the continuous paper moves in
a direction intersecting the conveyance direction on the tractor unit,
the second tractor holding the other edge of the continuous paper
tracks the movement of the continuous paper and moves in the
transverse direction wi th the support shaft. As a resul t , the sprocket
holes of the continuous paper can be prevented from separating from
the first tractor pins or second tractor pins while the paper is being
conveyed. Furthermore, because the elastic member exerts urging force
urging the support shaft and does not exert urging force urging the
tractor directly, the urging force of the elastic member does not work
on the continuous paper when the user sets the continuous paper in
the tractor unit and then pulls the second tractor in the direction
away from the first tractor with the second sprocket holes of the
~ontinuous paper engaged on the second tractor pins. Applying both
the excess tension applied by the user to the continuous paper and
t.he urging force of the elastic member at the same time when the second
tractor is clamped to the support shaft can therefore be avoided.
[0010]
By appropriately setting the elastic constant of the elastic
member, the second tractor can be moved together with the support
shaft in the first direction (the direction toward the first tractor)
and set to a position where the urging force (pressure) of the elastic
member and the tension on the continuous paper are balanced when
excessive tension is applied to the continuous paper by the pulling
force of the user after the second tractor is clamped to the support
shaft. Because the excess tension on the continuous paper can be
relieved if the second tractor moves to the position where the urging
force (pressure) of the elastic member and the tension on the
continuous paper are balanced, the sprocket holes in the continuous
6
paper will not easily separate from the first tractor pins or second
tractor pins when the continuous paper moves in a direction
intersecting the conveyance direction.
Furthermore, because the continuous paper is appropriately
tensioned across the width, skewing of the continuous paper while the
paper is being conveyed can be prevented.
Yet further, because the second tractor set to the posi tion where
the urging force (pressure) of the elastic member and the tension on
the continuous paper are balanced can move easily in both the first
direction and the second direction, the second tractor can track and
follow the continuous paper when the continuous paper moves in the
transverse direction. The sprocket holes in the continuous paper can
therefore be prevented from disengaging the first tractor pins or
second tractor pins while the paper is being conveyed.
[0011]
Preferably, the support shaft can move between a first position
and a second position separated from the first position in the second
direction; and the elastic member supports the support shaft in the
second position when in the initial state not exerting pressure.
Further preferably, the elastic member is a spring member, and
supports the support shaft in the second position when the spring
member is at its natural length.
[0012]
Further preferably, the frame has a support part that supports
the support shaft rotatably with the second direction end of the
support shaft passing through the support part i and the elastic member
is a coil spring disposed with the spring axis in the transverse
direction, one axial end of the elastic member connected to the
support part at a position beside the support part in the second
direction, and the other end connected to the support shaft.
In this aspect of the invention the support part can separate
the spring member from the conveyance path of the continuous paper.
7
[0013]
Another aspect of the invention is a conveyance device including
the tractor unit described above; a conveyance roller disposed
parallel to the support shaft on the downstream side of the tractor
unit in the conveyance direction; and a drive source that rotationally
drives the conveyance roller. The continuous paper is conveyed by
rotationally driving the conveyance roller, and the tractor unit
tracks and follows movement of the continuous paper.
[0014]
The conveyance direction of the continuous paper by the paper
feed roller and the conveyance direction of the continuous paper by
the tractor unit may not match precisely due to the dimensional
precision of the paper feed roller and parts of the tractor uni t , or
the installation precision of the paper feed roller and tractor unit
in the printer. When this happens, the continuous paper may move in
a direction intersecting the conveyance direction on the tractor uni t
due to the continuous paper conveyance force of the conveyance roller,
and the sprocket holes can easily separate from the first tractor pins
or second tractor pins.
The conveyance device of this aspect of the invention solves this
problem by keeping the sprocket holes in the continuous paper and the
tractor pins of the tractor engaged on the tractor unit side.
[0015]
Another aspect of the invention is a conveyance device including
the tractor unit described above; a conveyance roller disposed
parallel to the support shaft on the downstream side of the tractor
unit in the conveyance direction; and a drive source that rotationally
drives the conveyance roller. The tractor uni t has a drive shaft that
drives the first tractor and the second tractor, and a drive power
transfer mechanism that transfers rotational drive power from the
drive source to the drive shaft; and the drive power transfer
mechanism transfers rotation for conveying the continuous paper in
8
the conveyance direction through a one-way clutch to the drive shaft.
[0016]
The conveyance speed of the conveyance roller may be set greater
than the conveyance speed of the tractor uni t in a conveyance device
that drives both a conveyance roller and tractor unit to convey the
continuous paper in the paper feed direction. Even when the conveyance
speed of the conveyance roller is not set greater than the conveyance
speed of the tractor unit, the conveyance speed of the conveyance
roller may exceed the conveyance speed of the tractor unit for some
reason while the continuous paper is being conveyed. Because
excessive tension is applied by the conveyance force of the conveyance
roller to the continuous paper being conveyed when this happens, the
sprocket holes in the continuous paper can easily separate from the
first tractor pins or second tractor pins if the continuous paper
moves in a direction intersecting the conveyance direction on the
tractor unit.
The conveyance device of this aspect of the invention solves this
problem by keeping the sprocket holes in the continuous paper and the
tractor pins of the tractor engaged on the tractor unit side.
[0017]
In another aspect of the invention the conveyance roller has a
friction layer formed on the surface by a dispersion of inorganic
particles. This increases the continuous paper conveyance force of
the conveyance roller because there is substantially no slipping
between the continuous paper and the conveyance roller. As a result,
the continuous paper may be held with too much tension while being
conveyed, and the sprocket holes in the continuous paper can easily
disengage the first tractor pins or second tractor pins if the
continuous paper moves in a direction intersecting the conveyance
direction.
The conveyance device of this aspect of the invention solves this
problem by keeping the sprocket holes in the continuous paper and the
9
tractor pins of the tractor engaged on the tractor unit side.
[0018]
Another aspect of the invention is a printing device including
the conveyance device described above; and a print unit that is
disposed downstream in the conveyance direction from the conveyance
device, and prints on continuous paper conveyed by the conveyance
device.
[0019]
This aspect of the invention prevents or suppresses separation
of the sprocket holes in the continuous paper from the tractor pins
of the tractors of the tractor unit while the continuous paper is
conveyed. As a result, consistent print quality can be achieved
because conveyance of the continuous paper is stable.
A printhead that ej ects ink droplets onto the continuous paper,
for example, can be used as the print unit in this aspect of the
invention.
Fanfold paper can be used as the continuous paper.
Effect of the Invention
[0020J
The invention prevents or suppresses separation of sprocket
holes in continuous paper from the first tractor pins or second
tractor pins during continuous paper conveyance.
Other objects and attainments together with a fuller
understanding of the invention will become apparent and appreciated
by referring to the following description and claims taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows an inkjet printer according to at least of one
embodiment of the invention.
FIG. 2 is a plan view showing part of the conveyance device in
the inkjet printer.
10
FIG. 3 is a side view showing the power transfer mechanism in
the conveyance device.
FIG. 4A is a side Vlew showing part of the tractor-side drive
power transfer mechanism.
FIG. 4B is an oblique view showing part of the tractor- side drive
power transfer mechanism.
FIG. 5 is a schematic side view showing the roller-side drive
power transfer mechanism and the forward rotation transfer mechanism.
FIG. 6 is a schematic side view showing the roller-side drive
power transfer mechanism and the reverse rotation transfer mechanism.
FIG. 7A shows the second tractor just before being clamped to
the tractor support shaft.
FIG. 7B shows the second tractor clamped to the tractor support
shaft.
DESCRIPTION OF EMBODIMENTS
[0022]
At least of one preferred embodiment of the present invention
is described below with reference to the accompanying figures. In the
accompanying figures, arrow X indicates the conveyance direction to
eh continuous paper through the conveyance path, arrow Xl indicating
forward (normal paper feed direction) and arrow X2 indicating reverse
in the conveyance direction X. Arrow Y indicates the device width
direction (transverse direction) Y perpendicular to the conveyance
direction, arrow Yl indicating a first direction Yl from the second
tractor to the first tractor of the tractor unit in the device width
direction Y, and arrow Y2 indicating a second direction Y2 from the
first tractor to the second tractor of the tractor unit in the device
width direction Y.
[0023]
General configuration
FIG. 1 shows the overall configuration of an inkjet printer
11
according to this embodiment of the invention. FIG. 2 is a plan view
showing part of the conveyance device.
The inkjet printer (printing device) 1 pulls continuous paper
2 through the supply opening 4 disposed in the back of the printer
case 3, prints on the continuous paper 2 with the print unit 5, and
discharges the continuous paper 2 from a paper exit 6 disposed in the
front of the printer case 3. The continuous paper 2 is, for example,
fanfold paper, and has first sprocket holes 2a and second sprocket
holes 2b formed at a uniform pitch along the length of both sides of
the paper width as shown in FIG. 2.
[0024]
The print unit 5 includes a printhead 7, carriage 8, and carriage
moving mechanism 9. The printhead 7 has a plurality of nozzles 7a that
eject ink droplets onto the continuous paper 2. The printhead 7 is
carried on the carriage 8 wi th the nozzles 7a facing down on the z-axis
shown in FIG. 1, that is, facing the continuous paper 2.
[0025]
The carriage 8 is supported movably along a carriage shaft 11
that extends in the device width direction Y, and is moved
bidirectionally in the device width direction Y by the carriage moving
mechanism 9. The carriage moving mechanism 9 includes a carriage motor
12 and a timing belt 13 driven by the carriage motor 12. The carriage
8 is affixed to the timing belt 13, and is moved bidirectionally in
the device width direction Y according to the operation of the
carriage motor 12.
[0026]
The inkj et printer 1 also has a conveyance device 20 that conveys
the continuous paper 2. FIG. 3 is a side view of the conveyance device
20.
As shown in FIG. 1, the conveyance device 20 includes a
conveyance path 21, tractor unit 22, first conveyance mechanism 23,
and second conveyance mechanism 24. As shown in FIG. 3, the conveyance
12
device 20 also has a conveyance motor 25 that drives the tractor unit
22, first conveyance mechanism 23, and second conveyance mechanism
24; a drive power transfer mechanism 26 that transfers rotational
drive power from the conveyance motor 25 to the tractor unit 22 and
first conveyance mechanism 23; and a drive power transfer wheel train
27 that transfers the rotational drive power transferred to the first
conveyance mechanism 23 from the conveyance motor 25 to the second
conveyance mechanism 24.
[0027]
The conveyance path 21 extends in the direction of arrow X in
FIG. 1, starting from the supply opening 4, passing the printing
position A of the printhead 7 of the print unit 5, and ending at the
paper exit 6. The tractor unit 22, first conveyance mechanism 23,
print unit 5, and second conveyance mechanism 24 are disposed in this
order along the conveyance path 21 from the supply opening 4 side to
the paper exit 6 side.
[0028]
Tractor unit
The tractor unit 22 is disposed near the supply opening 4. As
shown in FIG. 2, the tractor unit 22 includes a first tractor 31 and
a second tractor 32 that hold the continuous paper 2 on opposi te sides
of the paper width; a tractor drive shaft 33 (drive shaft) and a
tractor support shaft 34 (support shaft) supporting the first tractor
31 and second tractor 32 movably in the device width direction Y; a
frame 35 that supports the tractor drive shaft 33 and tractor support
shaft 34; and a coil spring 36 (elastic member; spring member) that
can apply an urging force (pressure) urging (pushing) the tractor
support shaft 34 in the device width direction Y of the continuous
paper 2. The tractor drive shaft 33 and tractor support shaft 34 extend
parallel to each other in the device width direction Y. The tractor
drive shaft 33 is on the side of the tractor support shaft 34 closer
to the first conveyance mechanism 23, or more specifically is on the
13
downstream side of the tractor support shaft 34 in the conveyance
direction.
[0029]
As shown in FIG. 1 and FIG. 2, the first tractor 31 includes a
first tractor belt 31b (first endless belt) with multiple first
tractor pins 31a disposed on the outside surface, and a first drive
pulley 31c and first follower pulley 31d on which the first tractor
belt 31b is mounted.
The second tractor 32 includes a second tractor belt 32b (second
endless belt) with multiple second tractor pins 32a disposed on the
outside surface, and a second drive pulley 32c and second follower
pulley 32d on which the second tractor belt 32b is mounted.
The first drive pulley 31c and second drive pulley 32c are
supported coaxially by the tractor drive shaft 33 and rotate in unison
with the tractor drive shaft 33. The first follower pulley 31d and
second follower pulley 32d are supported coaxially and rotate freely
on the tractor support shaft 34.
The first tractor pins 31a can engage the first sprocket holes
2a on one side of the continuous paper 2 width, and the second tractor
pins 32a can engage the second sprocket holes 2b on the other side
of the continuous paper 2 width. The first tractor 31 and second
tractor 32 also have a tractor cover (not shown in the figure) that
partially covers the part holding the continuous paper 2 after the
continuous paper 2 is set and held with the sprocket holes 2a and 2b
engaged on the respective tractor pins 31a, 32a.
[0030]
The frame 35 includes a main frame portion 35a extending in the
device width direction Y below the tractor drive shaft 33 and tractor
support shaft 34, and a first support panel 35b and second support
panel 35c on opposite sides of the device width direction Y with the
conveyance path 21 therebetween.
The first support panel 35b supports the first direction Yl ends
14
of the tractor drive shaft 33 and tractor support shaft 34 (that is,
the ends on the first tractor 31 side) I and the second support panel
35c supports the second direction Y2 ends of the tractor drive shaft
33 and tractor support shaft 34 (that is, the ends on the second
tractor 32 side).
The tractor drive shaft 33 can rotate on its axis supported by
the first support panel 35b and second support panel 3 5c. The tractor
support shaft 34 is supported movably in the device width direction
Y by the first and second support panels.
[0031J
A bearing hole 35d for supporting the tractor support shaft 34
is disposed in the second support panel 35c. The second direction Y2
end of the tractor support shaft 34 passes through the bearing hole
35d and is supported by the second support panel 35c. A support shaft
stop 37 that limits the range of support shaft movement is disposed
to the tractor support shaft 34 at a position separated a specific
distance in the first direction Y1 from the second tractor 32 side
end. The support shaft stop 37 is disposed on the inside side (the
conveyance path 21 side) of the second support panel 35c.
A coil spring 36 that expands and contracts in the device width
direction Y is disposed around the outside of the end of the tractor
support shaft 34 protruding to the outside (the opposite side as the
conveyance path 21) from the second support panel 35c. The coil spring
36 is disposed at a position near the outside of the second support
panel 35c with one end in the spring axis direction connected to the
second support panel 3 5c, and the other end connected to the tractor
support shaft 34. This other end of the coil spring 36 and the tractor
support shaft 34 are connected through an E-ring 38 fixed on the
tractor support shaft 34. The coil spring 36 is separated from the
conveyance path 21 by the second support panel 35c.
[0032]
The tractor support shaft 34 can move between a first position
15
34A and a second position 34B that are separated in the device width
direction Y. The second position 34B indicated by a solid line in FIG.
2 is the position at which the coil spring 36 supports the tractor
support shaft 34 in the initial position when continuous paper 2 is
not set in the tractor unit 22.
When the tractor support shaft 34 is held in the second posi tion
34B, the coil spring 36 is at its natural length, and the support shaft
stop 37 is in contact with the second support panel 35c. When the
tractor support shaft 34 moves in the first direction Y1, the coil
spring 36 exerts an urging force urging the tractor support shaft 34
in the second direction Y2, that is, opposite the first direction Y1.
The first position 34A is a position separated in the first
direction Y1 from the second position 34B, and is denoted by the
imaginary double-dot dash line in FIG. 2. The first position 34A is
where the tractor support shaft 34 is located when the coil spring
36 is fully compressed.
[0033J
The tractor unit 22 includes a positioning stop 39 that positions
the first tractor 31 at a predetermined reference position H in the
device width direction Y, and a clamping mechanism 40 that clamps the
second tractor 32 to the tractor support shaft 34.
The positioning stop 39 is a flat member that protrudes up from
the main frame portion 35a, and has a through-hole in which the tractor
drive shaft 33 is inserted and rotates, and a through-hole in which
the tractor support shaft 34 is inserted and can move in the device
width direction. The first tractor 31 is attached to the first
direction Y1 side surface of the positioning stop 39, and thereby set
to the reference position H.
[0034]
The clamping mechanism 40 is known from the literature and in
this embodiment is mounted on the second tractor 32. The clamping
mechanism 40 includes, for example, a plastic member that can move
16
between a clamping position pressed against the tractor support shaft
34 and an open position separated from the tractor support shaft 34,
and a lever that sets the plastic member to the clamping posi tion or
the open position. The clamping mechanism 40 clamps the second tractor
32 to the tractor support shaft 34 when the lever is operated to move
the plastic member from the open position to the clamping position.
When the second tractor 32 is clamped to the tractor support shaft
34 by the clamping mechanism 40, the second tractor 32 is disposed
perpendicularly to the axis of the tractor drive shaft 33 and the axis
of the tractor support shaft 34, and the plural second tractor pins
32a are aligned with the conveyance direction X. When the second
tractor 32 is clamped to the tractor support shaft 34 by the clamping
mechanism 40, the second tractor 32 can also move in the device width
direction Y in unison with the tractor support shaft 34.
[0035]
First conveyance mechanism
The first conveyance mechanism 23 is disposed between the
tractor unit 22 and the printing position A on the conveyance path
21, and more specifically close to the printhead 7. The first
conveyance mechanism 23 includes a paper feed roller 41 and a pressure
roller 42. The paper feed roller 41 includes a metal roller 43 and
a roller shaft 44, and is disposed transverse to the conveyance path
21 at a position below the conveyance path 21 on the z-axis. The
pressure roller 42 is rubber or other elastic material, and is
disposed to press the continuous paper 2 conveyed through the
conveyance path 21 against the paper feed roller 41 from above on the
z-axis.
[0036]
As shown in FIG. 2, the surface of the roller 43 has a friction
coating 45 formed by a dispersion of inorganic particles. The friction
coating 45 is formed by dispersing inorganic particles of aluminum
oxide (alumina, A1203), silicon monoxide (SiO), or silicon dioxide
17
(Si02), for example, In a layer of polyester resin. This embodiment
uses crushed alumina as the inorganic particles. Alumina is relative
inexpensive and does not interfere with reducing cost, is relatively
hard, and desirably improves friction resistance. The crushing
process also produces alumina particles with sharp corners, resulting
in high friction force.
[0037]
Second conveyance mechanism
The second conveyance mechanism 24 is disposed between the
printing position A on the conveyance path 21 and the paper exit 6,
and more specifically near the printhead 7. The second conveyance
mechanism 24 includes a discharge roller 46 and a pressure roller 47.
The discharge roller 46 includes a roller 48 and a roller shaft 49,
and is disposed transverse to the conveyance path 21 at a position
below the conveyance path 21 on the z-axis. The pressure roller 47
is disposed to press the continuous paper 2 conveyed through the
conveyance path 21 against the discharge roller 46 from above on the
z-axis.
[0038]
Drive power transfer mechanism and drive power transfer wheel train
As shown in FIG. 3, the drive power transfer mechanism 26 has
a roller-side drive power transfer mechanism 61 and a tractor-side
drive power transfer mechanism 62.
The roller-side drive power transfer mechanism 61 transfers
forward rotation for conveying the continuous paper 2 forward (in the
direction of arrow Xl) through the conveyance path 21, and reverse
rotation for conveying the paper in reve~se (the direction of arrow
X2), from the conveyance motor 25 to the paper feed roller 41 of the
first conveyance mechanism 23.
The tractor-side drive power transfer mechanism 62 transfers
rotation from the conveyance motor 25 to the tractor drive shaft 33
of the tractor unit 22.
18
The drive power transfer wheel train 27 causes the discharge
roller 46 of the second conveyance mechanism 24 to turn synchronously
to the paper feed roller 41 of the first conveyance mechanism 23 at
the same conveyance speed in the same direction. The drive power
transfer wheel train 27 is denoted by a dotted line in FIG. 3.
[0039]
The tractor-side drive power transfer mechanism 62 includes a
forward transfer mechanism 63 and a reverse transfer mechanism 64.
As described below wi th reference to FIG. 4A and FIG. 4B, the forward
.t r ans f e r mechanism 63 transfers forward rotation from the conveyance
motor 25 through a one-way clutch 77 to the tractor unit 22, and the
reverse transfer mechanism 64 transfers reverse rotation from the
conveyance motor 25 through a torque limiter 79 (torque clutch) to
the tractor unit 22.
[0040]
When conveying the continuous paper 2 forward in this embodiment,
the conveyance speed of the continuous paper 2 conveyed by the paper
feed roller 41 driven through the roller-side drive power transfer
mechanism 61 is greater than the conveyance speed of the continuous
paper 2 conveyed by the first tractor 31 driven through the forward
transfer mechanism 63. The speed reduction ratios of the wheel trains
in the transfer mechanisms are set to achieve this relationship.
Conversely, when conveying the paper in reverse, the conveyance
speed of the continuous paper 2 conveyed by the first tractor 31 driven
through the reverse transfer mechanism 64 is greater than the
conveyance speed of the continuous paper 2 conveyed by the paper feed
roller 41 through the roller-side drive power transfer mechanism 61.
The speed reduction ratios of the wheel trains in the transfer
mechanisms are set to achieve this relationship.
[0041]
The roller-side drive power transfer mechanism 61 includes a
drive sprocket 60 fixed coaxially to the output shaft of the
19
conveyance motor 25, a drive gear 66 fixed coaxially to the end part
of the roller shaft 44 of the paper feed roller 41 in the first
conveyance mechanism 23, and a timing belt 67 mounted on the drive
sprocket 60 and drive gear 66.
[0042]
FIG. 4A is a side view showing main parts of the tractor-side
drive power transfer mechanism 62, and FIG. 4B is an oblique view of
the same. The configuration of the tractor-side drive power transfer
mechanism 62 that transfers power driving rotation of the tractor unit
22 forward and reverse is described next with reference to FIG. 3,
FIG. 4A, and FIG. 4B.
[0043]
The tractor-side drive power transfer mechanism 62 has a
rotating shaft 70, a transfer gear 71 is fixed coaxially to the
rotating shaft 70, and the timing belt 67 is mounted on the transfer
gear 71. A forward sun gear 72 and a reverse sun gear 73 are fixed
coaxially on the rotating shaft 70. A planetary carrier 74 is
supported freely pivotably on the rotating shaft 70 between the sun
gears 72, 73.
[0044 ]
The planetary carrier 74 has two arms 74a, 74b extending radially
with a specific angle therebetween from the rotating shaft 70. A
forward planetary gear 75 is supported freely rotationally on the end
part of the one arm 74a. The forward planetary gear 75 meshes with
the forward sun gear 72. A reverse planetary gear 76 is supported
freely rotationally on the end part of the other arm 74b. The reverse
planetary gear 76 meshes with the reverse sun gear 73.
[0045 ]
A forward transfer gear 78 is coaxially attached through the
one-way clutch 77 to the end part of the tractor drive shaft 33. The
one-way clutch 77 could be either a sprag or cam clutch. The one-way
clutch 77 transfers forward rotation, but turns freely and interrupts
20
transfer of reverse rotation when reverse rotation for feeding the
paper in reverse is received. The one-way clutch 77 therefore turns
freely and the power transfer path is also interrupted while
transferring forward rotation if a transfer member on the downstream
side of the one-way clutch 77 on the transfer path tries to turn faster
in the forward rotation direction than the transfer member on the
upstream side of the transfer path. When the one-way clutch 77 rotates
freely, that is, when the transfer path is interrupted, the first
tractor 31 and second tractor 32 follow the movement of the continuous
paper 2 conveyed through the conveyance path 21 by the paper feed
roller 41.
[0046]
The forward transfer gear 78 is a gear that can mesh with the
forward planetary gear 75, and is disposed to a position opposite the
forward planetary gear 75. A reverse transfer gear 80 is disposed
beside the forward transfer gear 78. The reverse transfer gear 80 is
affixed coaxially to the end of the tractor drive shaft 33 through
the torque limiter 79. The reverse transfer gear 80 is a gear that
can mesh with the reverse planetary gear 76, and is disposed to a
position opposite the reverse planetary gear 76. The torque limiter
79 slips when the transferred torque exceeds a specific limit, and
limits transferring torque exceeding the limit.
[0047]
In the tractor-side drive power transfer mechanism 62 thus
comprised, the forward transfer mechanism 63 is the part of the
transfer mechanism that sequentially transfers rotation from the
timing belt 67 through the rotating shaft 70, forward sun gear 72,
planetary carrier 74, forward planetary gear 75, forward transfer
gear 78, and one-way clutch 77 to the tractor drive shaft 33. The
reverse transfer mechanism 64 is the part that sequentially transfers
rotation from the timing belt 67 through the rotating shaft 70,
reverse sun gear 73, planetary carrier 74, reverse planetary gear 76,
21
reverse transfer gear 80, and torque limiter 79 to the tractor drive
shaft 33.
j0048]
FIG. 5 is a side view showing the roller-side drive power
transfer mechanism 61 and forward transfer mechanism 63. FIG. 6 is
a side view showing the roller-side drive power transfer mechanism
61 and reverse transfer mechanism 64.
[0049]
When transferring forward rotation, the rotating shaft 70 turns
counterclockwise as indicated by arrow CCW in FIG. 4B. This rotation
causes the planetary carrier 74 to also turn in the same direction.
As a result, the forward planetary gear 75 meshes with the forward
transfer gear 78. The other reverse planetary gear 76 disengages the
reverse transfer gear 80. As a result, the tractor-side drive power
transfer mechanism 62 is positioned as shown in FIG. 5.
In this position, forward rotation from the conveyance motor 25
is transferred through the roller-side drive power transfer mechanism
61 to the paper feed roller 41 and discharge roller 46. The forward
rotation is also transferred through the tractor-side drive power
transfer mechanism 62 to the first tractor 31 and second tractor 32.
The continuous paper 2 is therefore fed forward.
[0050]
When transferring reverse rotation, the rotating shaft 70 turns
clockwise as indicated by arrow CW in FIG. 4B. This rotation causes
the planetary carrier 74 to also turn in the same direction. As a
result, the forward planetary gear 75 separates from and disengages
with the forward transfer gear 78 (the drive power transfer path is
interrupted). The other reverse planetary gear 76 approaches and
engages the reverse transfer gear 80 (completing the drive power
transfer path) . As a result, the tractor-side drive power transfer
mechanism 62 is positioned as shown in FIG. 6.
In this position, reverse rotation from the conveyance motor 25
22
is transferred through the roller-side drive power transfer mechanism
61 to the paper feed roller 41 and discharge roller 46. The reverse
rotation is also transferred through the tractor-side drive power
transfer mechanism 62 to the first tractor 31 and second tractor 32.
The continuous paper 2 is therefore fed in reverse (reversed).
[0051]
Continuous paper conveyance operation
Operation of the inkjet printer 1, and particularly the
continuous paper 2 conveyance operation of the conveyance device 20,
is described next. FIG. 7A and FIG. 7B describe setting the continuous
paper 2 in the tractor unit 22, and show the tractor unit 22 from the
back in the conveyance direction X. FIG. 7A shows immediately before
clamping the second tractor 32 to the tractor support shaft 34, and
FIG. 7B shows after the second tractor 32 is clamped to the tractor
support shaft 34.
[0052]
To set the continuous paper 2 in the tractor unit 22, the first
sprocket holes 2a on one side of the continuous paper 2 width are
placed on the first tractor pins 31a of the first tractor 31 disposed
to the reference position H in the transverse direction. Next, the
second tractor 32 is slid to a position on the tractor support shaft
34 matching the width of the continuous paper 2, and the second tractor
pins 32a of the second tractor 32 are engaged with the second sprocket
holes 2b on the other side of the continuous paper 2 width. When the
second tractor pins 32a of the second tractor 32 have engaged the
second sprocket holes 2b in the continuous paper 2, the tractor
support shaft 34 is held at the second posi tion 34B by the coil spring
36 as shown in FIG. 7A. The second tractor 32 is then clamped to the
tractor support shaft 34 by the clamping mechanism 40.
[0053]
If there is slack in the continuous paper 2 between the first
tractor 31 and second tractor 32 when the continuous paper 2 is set
23
in the tractor unit 22, the continuous paper 2 can easily become skewed
when the continuous paper 2 is pulled downstream by the conveyance
force of the paper feed roller 41. To avoid or suppress skewing, the
user pulls the second tractor 32 away from the first tractor 31 to
apply tension to the width of the continuous paper 2 after engaging
the second sprocket holes 2b of the continuous paper 2 on the tractor
pins of the second tractor 32, and then clamps the second tractor 32
to the tractor support shaft 34. However, if the user clamps the second
tractor 32 to the tractor support shaft 34 while applying strong
tension to the continuous paper 2, the continuous paper 2 may be held
with too much tension. When this happens, the sprocket holes in the
continuous paper 2 can easily disengage the first tractor pins 31a
or second tractor pins 32a if the continuous paper 2 moves in a
direction intersecting the conveyance direction X while the
continuous paper 2 is conveyed.
[0054]
To solve this problem, when excess tension is applied to the
continuous paper 2 when the second tractor 32 is clamped to the tractor
support shaft 34 in this embodiment, the second tractor 32 moves with
the tractor support shaft 34 in the first direction Y1 (the direction
in which the coil spring 36 stretches) to a position where the urging
force of the coil spring 36 and the tension on the continuous paper
2 are balanced (FIG. 7B).
In other words, the spring constant of the coil spring 36 is set
appropriately so that the second tractor 32 and tractor support shaft
34 move and the tractor support shaft 34 stops between the first
position 34A and second position 34B. Because the excess tension on
the continuous paper 2 is relieved by the second tractor 32 moving
to a position where the urging force of the coil spring 36 and the
continuous paper 2 tension are balanced, the sprocket holes in the
continuous paper 2 will not easily separate from the first tractor
pins 31a or second tractor pins 32a even if the continuous paper 2
24
moves in a direction intersecting the conveyance direction X while
the continuous paper 2 is conveyed. Skewing of the continuous paper
2 can also be prevented because the tension across the width of the
continuous paper 2 is appropriately maintained by the second tractor
32 being disposed to where the urging force of the spring member and
the tension on the continuous paper 2 are balanced.
[0055]
The coil spring 36 disposed to the tractor unit 22 in this
embodiment exerts urging force on the tractor support shaft 34, and
does not exert urging force that directly urges the first tractor 31
or second tractor 32. Therefore, when the user pulls the second
tractor 32 away from the first tractor 31 after engaging the second
tractor pins 32a wi th the second sprocket holes 2b in the continuous
paper 2 when setting the continuous paper 2 in the tractor unit 22,
the urging force of the coil spring 36 does not work on the continuous
paper 2 or the second tractor 32 that pulls the continuous paper 2.
The second tractor 32 can therefore move easily in the device width
direction Y (direction Y2), and the continuous paper 2 can be easily
loaded in the tractor unit 22. In addition, when the user pulls the
second tractor 32 away from the first tractor 31, the first tractor
31 moves toward the second tractor 32 while compressing the coil
spring 36, and the second tractor 32 is not clamped to the tractor
support shaft 34 with both the excess tension applied by the pulling
force of the user and the urging force of the coil spring 36 applied
to the continuous paper 2.
[0056]
The conveyance motor 25 then drives forward. As a result, the
tractor-side drive power transfer mechanism 62 goes to the position
shown in FIG. 5, the first tractor 31 and paper feed roller 41 are
rotationally driven forward, and the continuous paper 2 is conveyed
through the conveyance path 21 toward the paper feed roller 41. The
continuous paper 2 conveyed by the first tractor 31 is then nipped
25
between the rotating paper feed roller 41 and pressure roller 42, and
conveyed further to a specific indexing position (the start position
of the printing operation) .
[0057]
When the continuous paper 2 is conveyed in the Xl direction, the
forward conveyance speed of the paper feed roller 41 is greater than
the forward conveyance speed of the first tractor 31. The paper
holding force of the paper feed roller 41 is increased by the friction
coating 45, but is lower than the paper holding force of the tractor
31 whereby the first tractor 31 engages the sprocket holes 2a. The
continuous paper 2 is therefore conveyed while being pulled with
constant tension from the paper feed roller 41 side. As a result, even
when fanfold paper supplied from a stack of folded paper is used as
the continuous paper 2, the paper can reach the indexing position with
folds and slack appropriately removed.
[0058]
The printhead 7 then prints while the paper feed roller 41
conveys the cont inuous paper 2 through the conveyance path 21. Because
the coefficient of friction of the friction coating 45 is extremely
high, the continuous paper 2 is held by the paper feed roller 41 and
pressure roller 42 with substantially no slipping, and the continuous
paper 2 can be conveyed with high precision. The tractor 31 feeds the
continuous paper 2 forward at a slower speed than the paper feed roller
41. The continuous paper 2 can therefore be constantly conveyed wi th
specific tension applied thereto.
[0059]
When the conveyance direction of the continuous paper 2 by the
paper feed roller 41 and the conveyance direction of the continuous
paper 2 by the tractor unit 22 do not precisely match due to the
dimensional precision of the paper feed roller 41 and parts of the
Lractor unit 22, or the installation precision of the paper feed
roller 41 and tractor uni t 22 in the inkj et printer 1, the continuous
26
paper 2 may travel in a direction intersecting the conveyance
direction X due to the conveyance force of the paper feed roller 41,
and the sprocket holes 2a, 2b can separate from the first tractor pins
31a or second tractor pins 32a.
To solve this problem, the second tractor 32 holding the second
direction Y2 edge part of the continuous paper 2 in this embodiment
follows the movement of the continuous paper 2 and moves with the
tractor support shaft 34 in the device width direction Y when the
continuous paper 2 moves in the tractor unit 22 in a direction
intersecting the conveyance direction X. The sprocket holes 2a and
2b of the continuous paper 2 can therefore be prevented from
separating from the first tractor pins 31a or second tractor pins 32a
while the continuous paper 2 is being conveyed.
[0060]
vJhen the continuous paper 2 is set in the tractor unit 22 in this
embodiment, the second tractor 32 moves to a position where the urging
force of the coil spring 36 and the tension on the continuous paper
2 are balanced as shown in FIG. 7B. As a result, the second tractor
32 and tractor support shaft 34 can move easily in both the first
direction Y1 and second direction Y2 of the device width direction
Y even though the urging force of the coil spring 36 is working on
the tractor support shaft 34. The second tractor 32 therefore
desirably follows movement of the continuous paper 2 in the devic.e
width direction Y. The sprocket holes 2a and 2b of the continuous paper
2 therefore do not easily separate from the first tractor pins 31a
or second tractor pins 32a.
[0061]
Furthermore, because the conveyance speed of the paper feed
roller 41 is faster than the conveyance speed of the tractor unit 22,
excess tension is applied by the conveyance force of the paper feed
roller 41 while conveying the continuous paper 2, and the sprocket
holes 2a and 2b of the continuous paper 2 can easily separate from
27
the first tractor pins 31a or second tractor pins 32a when the
continuous paper 2 moves on the tractor unit 22 in the device width
direction Y intersecting the conveyance direction X of the continuous
paper 2.
By using a one-way clutch 77 in the tractor-side drive power
transfer mechanism 62, this embodiment of the invention solves this
problem and prevents the conveyance force of the paper feed roller
41 from applying excess tension while conveying the continuous paper
2. More specifically, when the tension on the continuous paper 2 due
to the conveyance force of the paper feed roller 41 exceeds a specific
limit, the first tractor pins 31a of the first tractor 31 and the
second tractor pins 32a of the second tractor 32 are forcibly pulled
in the forward rotation direction by the paper feed roller 41, thus
causing the one-way clutch 77 to turn freely and allow movement of
the first tractor pins 31a and second tractor pins 32a. In other words,
because the first tractor 31 and the second tractor 32 can simply
follow movement of the continuous paper 2, the tension on the
continuous paper 2 does not increase. The sprocket holes 2a and 2b
of the continuous paper 2 can be prevented from easily separating from
the first tractor pins 31a or second tractor pins 32a during paper
conveyance. High print quality can also be achieved because the
one-way clutch enables conveying the continuous paper 2 forward in
a consistent, desirably tensioned state.
[0062]
The continuous paper 2 conveyed by the paper feed roller 41
passes the printing position A of the print unit 5 and is printed on
by the printhead 7. The continuous paper 2 then passes between the
rotating discharge roller 46 and pressure roller 47. The continuous
paper 2 is then further conveyed through the conveyance path 21 by
the discharge roller 46, and discharged from the paper exit 6 into
the discharge tray 16.
[0063]
28
When the continuous paper 2 must be conveyed in the reverse
direction, the conveyance motor 25 is driven in the reverse rotation
direction. This reverse rotation is transferred through the
roller-side drive power transfer mechanism 61 to the paper feed roller
41, and through the tractor-side drive power transfer mechanism 62
to the first tractor 31. This causes the tractor-side drive power
transfer mechanism 62 to disengage the forward transfer mechanism 63
and engage the reverse transfer mechanism 64 as shown in FIG. 6.
[0064]
As described above, the conveyance speed of the continuous paper
2 by first tractor 31 is greater than the conveyance speed of the
continuous paper 2 by the paper feed roller 41 when the continuous
paper 2 is conveyed in reverse. The continuous paper 2 is therefore
reversed with specific tension, and paper jams due to slack or creases
in the paper, for example, are prevented. The reverse rotation is also
transferred through the torque limiter 79 to the tractor drive shaft
33. The torque limiter 79 releases and turns freely (slips) when the
transferred torque exceeds a specific limit, and torque transfer is
limited to less than the torque limit. The torque limiter 79 also slips
when excess torque is applied to the continuous paper 2, and tension
on the continuous paper 2 is therefore limited to less than the
specific limit. Problems such as excessive torque causing the
sprocket holes 2a and 2b of the continuous paper 2 to disengage the
first tractor pins 31a or second tractor pins 32a can therefore be
prevented.
[0065]
Tractor unit variation
In the embodiment described above the first tractor 31 is
attached to the positioning stop 39 disposed to the frame 35 and
thereby fixed in the reference position H, but the first tractor 31
can be disposed to the reference position H while able to move within
a limited range in the device width direction Y. If the positioning
29
member in this configuration has a first stop disposed on one side
of the first tractor 31 in the device width direction Y with a small
gap to the first tractor 31, and a second stop on the opposite side
of the first tractor 31 with a small gap to the first tractor 31, the
first tractor 31 can be disposed to the reference position H while
being able to move in the device width direction Y between the first
stop and the second stop. If the first tractor 31 is disposed to the
reference position H while being able to move in a specific range in
the device width direction Y, the sprocket holes 2a and 2b of the
continuous paper 2 can also be prevented from disengaging the first
tractor pins 31a or second tractor pins 32a by movement (chatter) of
the first tractor 31 in the device width direction Y.
[0066]
The invention can also be applied to a conveyance device 20 that
conveys the continuous paper 2 by driving the paper feed roller 41,
and is configured so that the tractor unit 22 can track and follow
movement of the continuous paper 2 conveyed by the paper feed roller
41. The invention can also prevent or suppress disengagement of the
sprocket holes 2a and 2b of the continuous paper 2 from the first
tractor pins 31a or second tractor pins 32a in the tractor unit 22.
Desirable tension on the continuous paper 2 can also be maintained
during media conveyance.
The invention being thus described, it will be obvious that it
may be varied in many ways. Such variations are not to be regarded
as a departure from the spirit and scope of the invention, and all
such modifications as would be obvious to one skilled in the art are
intended to be included within the scope of the following claims.

lihat is claimed is:
1. A tractor unit comprising:
a first tractor that sequentially engages first tractor pins in
first sprocket holes formed in continuous paper in the paper
conveyance direction along one side of the paper width;
a second tractor that sequentially engages second tractor pins
in second sprocket holes formed in the continuous paper in the
conveyance direction along the other side of the paper width;
a support shaft that extends in a transverse direction
perpendicular to the conveyance direction of the continuous paper,
and supports the first tractor and second tractor movably in the
transverse direction;
a frame that supports the support shaft movably in the transverse
direction;
an elastic member that can apply pressure pushing the support
shaft in the transverse direction; and
a clamping member that fixes the second tractor on the support
shaft;
the first tractor being disposed to a predetermined reference
position in the transverse direction, and
the elastic member applying pressure pushing the support shaft
in a second direction opposite a first direction when the support
shaft moves in the first direction from the second tractor side to
the first tractor side.
2. The tractor unit described in claim 1, wherein:
the support shaft can move between a first position and a second
position separated from the first position in the second direction;
and
the elastic member supports the support shaft in the second
position when in the initial state not exerting pressure.
31
3. The tractor unit described in claim 2, wherein:
the elastic member is a spring member, and supports the support
shaft in the second position when the spring member is at its natural
length.
4. The tractor unit described in claim 1, wherein:
the frame has a support part that supports the support shaft
rotatably with the second direction end of the support shaft passing
through the support part; and
the elastic member is a coil spring disposed wi th the spring axis
in the transverse direction, one axial end of the elastic member
connected to the support part at a position beside the support part
in the second direction, and the other end connected to the support
shaft.
5. A conveyance device comprising:
a tractor unit;
a conveyance roller disposed parallel to a support shaft on the
downstream side of the tractor uni t in the conveyance direction; and
a drive source that rotationally drives the conveyance roller;
the tractor unit including
a first tractor that sequentially engages first tractor
pins in first sprocket holes formed in continuous paper in the paper
conveyance direction along one side of the paper width,
a second tractor that sequentially engages second tractor
pins in second sprocket holes formed in the continuous paper in the
conveyance direction along the other side of the paper width,
a support shaft that extends in a transverse direction
perpendicular to the conveyance direction of the continuous paper,
and supports the first tractor and second tractor movably in the
transverse direction,
a frame that supports the support shaft movably in the
32
transverse direction,
an elastic member that can apply pressure pushing the
support shaft in the transverse direction, and
a clamping member that fixes the second tractor on the
support shaft,
the first tractor being disposed to a predetermined
reference position in the transverse direction, and
the elastic member applying pressure pushing the support
shaft in a second direction opposite a first direction when the
support shaft moves in the first direction from the second tractor
side to the first tractor side;
wherein the continuous paper is conveyed by rotationally driving
the conveyance roller, and the tractor unit tracks and follows
movement of the continuous paper.
6. The conveyance device described in claim 5, wherein:
the conveyance roller has a friction layer formed on the surface
by a dispersion of inorganic particles.
7. The conveyance device described in claim 5, wherein:
the support shaft of the tractor unit can move between a first
position and a second position separated from the first position in
the second direction; and
the elastic member of the tractor unit supports the support shaft
in the second position when in the initial state not exerting
pressure.
8. The conveyance device described in claim 7, wherein:
the elastic member of the tractor unit is a spring member, and
supports the support shaft in the second position when the spring
member is at its natural length.
33
j
9. The conveyance device described in claim 5, wherein:
the frame of the tractor unit has a support part that supports
the support shaft rotatably with the second direction end of the
support shaft passing through the support part; and
the elastic member of the tractor unit is a coil spring disposed
with the spring axis in the transverse direction, one axial end of
the elastic member connected to the support part at a position beside
the support part in the second direction, and the other end connected
to the support shaft.
10. A conveyance device comprising:
a tractor unit;
a conveyance roller disposed parallel to a support shaft on the
downstream side of the tractor unit in the conveyance direction; and
a drive source that rotationally drives the conveyance roller;
the tractor unit including
a first tractor that sequentially engages first tractor
pins in first sprocket holes formed in continuous paper in the paper
conveyance direction along one side of the paper width,
a second tractor that sequentially engages second tractor
pins in second sprocket holes formed in the continuous paper in the
conveyance direction along the other side of the paper width,
a support shaft that extends in a transverse direction
perpendicular to the conveyance direction of the continuous paper,
and supports the first tractor and second tractor movably in the
transverse direction,
a frame that supports the support shaft movably in the
transverse direction,
an elastic member that can apply pressure pushing the
support shaft in the transverse direction, and
a clamping member that fixes the second tractor on the
support shaft,
34
the first tractor being disposed to a predetermined
reference position in the transverse direction, and
the elastic member applying pressure pushing the support
shaft in a second direction opposite a first direction when the
support shaft moves in the first direction from the second tractor
side to the first tractor side;
wherein the tractor uni t has a drive shaft that drives the first
tractor and the second tractor, and a drive power transfer mechanism
that transfers rotational drive power from the drive source to the
drive shaft, and
the drive power transfer mechanism transfers rotation for
conveying the continuous paper in the conveyance direction through
a one-way clutch to the drive shaft.
11. The conveyance device described in claim 10, wherein:
the conveyance roller has a friction layer formed on the surface
by a dispersion of inorganic particles.
12. The conveyance device described in claim 10, wherein:
the support shaft of the tractor unit can move between a first
position and a second position separated from the first position in
the second direction; and
the elastic member of the tractor unit supports the support shaft
In the second position when in the initial state not exerting
pressure.
13. The conveyance device described in claim 12, wherein:
the elastic member of the tractor unit is a spring member, and
supports the support shaft in the second position when the spring
member is at its natural length.
14. The conveyance device described in claim 10, wherein:
35
the frame of the tractor unit has a support part that supports
the support shaft rotatably with the second direction end of the
support shaft passing through the support part; and
the elastic member of the tractor unit is a coil spring disposed
with the spring axis in the transverse direction, one axial end of
the elastic member connected to the support part at a position beside
the support part in the second direction, and the other end connected
to the support shaft.
15. A printing device comprising:
a conveyance device; and
a print unit that is disposed downstream in the conveyance
direction from the conveyance device, and prints on continuous paper
conveyed by the conveyance device;
~he conveyance device including
a tractor unit,
a conveyance roller disposed parallel to a support shaft
on the downstream side of the tractor unit in the conveyance direction,
and
a drive source that rotationally drives the conveyance
roller;
the tractor unit including
a first tractor that sequentially engages first tractor
pins in first sprocket holes formed in continuous paper in the paper
conveyance direction along one side of the paper width,
a second tractor that sequentially engages second tractor
pins in second sprocket holes formed in the continuous paper in the
conveyance direction along the other side of the paper width,
a support shaft that extends in a transverse direction
perpendicular to the conveyance direction of the continuous paper,
and supports the first tractor and second tractor movably in the
transverse direction,
36
;
a frame that supports the support shaft movably in the
transverse direction,
an elastic member that can apply pressure pushing the
support shaft in the transverse direction, and
a clamping member that fixes the second tractor on the
support shaft,
the first tractor being disposed to a predetermined
reference position in the transverse direction, and
the elastic member applying pressure pushing the support
shaft in a second direction opposite a first direction when the
support shaft moves in the first direction from the second tractor
side to the first tractor side;
wherein the continuous paper is conveyed by rotationally driving
the conveyance roller, and the tractor unit tracks and follows
movement of the continuous paper.
16. A printing device comprising:
a conveyance device; and
a print unit that is disposed downstream in the conveyance
direction from the conveyance device, and prints on continuous paper
conveyed by the conveyance device;
the conveyance device including
a tractor unit,
a conveyance roller disposed parallel to a support shaft
on the downstream side of the tractor uni t in the conveyance direction,
and
a drive source that rotationally drives the conveyance
roller;
the tractor unit including
a first tractor that sequentially engages first tractor
pins in first sprocket holes formed in continuous paper in the paper
conveyance direction along one side of the paper width,
37
a second tractor that sequentially engages second tractor
pins in second sprocket holes formed in the continuous paper in the
conveyance direction along the other side of the paper width,
a support shaft that extends in a transverse direction
perpendicular to the conveyance direction of the continuous paper,
and supports the first tractor and second tractor movably in the
transverse direction,
a frame that supports the support shaft movably in the
transverse direction,
an elastic member that can apply pressure pushing the
support shaft in the transverse direction, and
a clamping member that fixes the second tractor on the
support shaft,
the first tractor being disposed to a predetermined
reference position in the transverse direction, and
the elastic member applying pressure pushing the support
shaft in a second direction opposite a first direction when the
support shaft moves in the first direction from the second tractor
side to the first tractor side;
wherein the tractor unit has a drive shaft that drives the first
tractor and the second tractor, and a drive power transfer mechanism
that transfers rotational drive power from the drive source to the
drive shaft, and
the drive power transfer mechanism transfers rotation for
conveying the continuous paper in the conveyance direction through
a one-way clutch to the drive shaft.