Paper feeder of a label printer

A paper feeder of a label printer makes printing successively on a continuous printing paper on which a multiplicity of label papers are affixed. The paper feeder includes a control device for moving back the continuous printing paper by a length obtained by adding a fixed length capable of continuously making the next printing subsequently to a final printing position of the printing paper upon resumption of the printing operation when the movement of the printing paper is stopped by completion of the printing operation to an adjustment length for settling a printing position and makes printing successively from a fixed position of the label paper upon resumption after the printing operation is stopped. In this case, the adjustment length is set to a sum of a length from the printing start position of the printing paper upon resumption of the printing operation to a label position detection sensor disposed ahead in the backward direction and a length required to cause the printing paper to reach a constant speed upon resumption of the printing operation.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a paper feeder of a label printer using an 
electronic photographic system which makes printing on a continuous 
printing paper on which a multiplicity of label papers are successively 
affixed. 
2. Description of the Relative Art 
There is known a label printer which can make printing successively on a 
continuous printing paper on which a multiplicity of label papers are 
successively affixed. When an electronic photographic system is adopted to 
this kind of label printer, toner attached on the label paper is thermally 
pressed by a fixing device using a heat roller. Accordingly, when the 
printing operation is stopped on the way, it is necessary to feed the 
printing paper forward by a predetermined length until a final printing 
position passes through the fixing device. Thereafter, when the printing 
operation is resumed, a process for the printing is made newly so that a 
blank portion is formed between the final printing position and the next 
printing start position on the printing paper, resulting in unused portion 
of the printing paper from the position of the heat roller to the position 
of the main charger being left blank. 
A paper feeder of a non-impact transfer type printer disclosed in Japanese 
Patent Publication No. 56-5993 comprises a photosensitive drum which is 
applied with information to be printed, a retractor mechanism which causes 
the photosensitive drum to be brought into contact with the printing paper 
or be separated from the printing paper, a control circuit which controls 
to make equal the rotational speed of the photosensitive drum to the 
feeding speed of the paper when the photosensitive drum is in contact with 
the paper, and control means for moving back the printing paper by a 
predetermined distance in order to make the distance between the transfer 
completion end and the next transfer start end of the printing paper to a 
predetermined value when the photosensitive drum is separated from the 
printing paper, whereby the occurrence of blank printing paper is avoided 
when the printing is resumed. 
In the label printer which makes the printing on the label paper having a 
fixed length in the longitudinal direction of the printing paper, it is a 
matter of course that it is necessary to move back the printing paper to a 
target position to eliminate blank paper and it is further necessary to 
set the printing resumption position to a predetermined position of the 
label paper exactly. In addition, since many functional portions including 
a roller mechanism for moving the paper, a fixing device, a transfer 
charger and the like are disposed in the traveling path of the printing 
paper and a length of the paper to be moved back is relatively long, it is 
very important to control the backward movement of the paper to a target 
position stably and exactly. 
However, in the paper feeder of the non-impact transfer type printer 
disclosed in the above publication, since it is merely performed that the 
paper is moved back by a predetermined value in order to eliminate the 
vain paper, it can not be adopted in the label printer requiring high 
accuracy, reliability and stability. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a paper feeder of a 
label printer which can obtain original continuous printing quality 
without printed state on a continuous printing paper being interrupted 
even when printing operation is interrupted on the way while the printing 
is effected on label papers affixed on a continuous printing paper 
successively and can eliminate unused portion of the continuous printing 
paper to avoid blank printing paper and further can control to set a 
printing position exactly with high accuracy upon resumption of the 
printing so that high printing quality can be attained. 
Further, it is another object of the present invention to provide a paper 
feeder of a label printer which can effect prevention of wear of a 
photosensitive drum by a continuous printing paper due to the control and 
prevention of deterioration of the printing paper by a heat roller and can 
prevent occurrence of jam such as loosening of paper and paper jam in the 
backward movement of the printing paper so that the printing paper can be 
moved back to a target position exactly and stably. 
In order to achieve the above objects, the paper feeder 1 of the label 
printer according to the present invention comprises a main charger 3 for 
charging a photosensitive drum 2, a printing head 4 for applying printing 
information, a developer 5 for attaching toner, a transfer charger 6 for 
transferring the toner on the photosensitive drum 2 to label papers S 
affixed on a continuous paper R constituting a continuous printing paper 
P, and a fixing device 7 for fixing the toner by causing the continuous 
printing paper P to pass through the fixing device 7. The paper feeder 1 
of the label printer using the electronic photographic system capable of 
making printing successively on the label papers S comprises a control 
device W for moving back the continuous printing paper P by a lenth Lt+Lg 
where Lt is a fixed length capable of continuously making the next 
printing subsequently to the final printing position Mf of the printing 
paper upon resumption of the printing operation when the movement of the 
printing paper is stopped by completion of the printing operation and Lg 
is an adjustment length for settling a print start position. In this case, 
the fixed length Lt is a length corresponding to a distance between a 
printing position Mn for printing subsequently to the final printing 
position Mf on the printing paper P passing through the fixing device 7 
and the position of the printing head 4, and the adjustment length Lg is a 
length obtained by adding a length Ls from the printing start position of 
the printing paper P upon resumption of the printing operation to a label 
position detection sensor 10 disposed ahead in the backward direction to a 
length Lh required until the moving speed of the printing paper P reaches 
a fixed speed upon resumption of the printing operation. On the other 
hand, drive roller mechanism 11a and 11b are disposed ahead in the 
backward direction to rotate in the reverse direction upon the backward 
movement so that the printing paper P is moved back. Thus, the backward 
speed of the printing paper P is set to a lower speed (for example, about 
1/2 to 1/3) than the printing speed. Further, the fixing device 7 is 
provided with a fixer displacement mechansim 14 for separating heat 
rollers 12 and 13 from the printing paper P upon the backward movement. In 
this case, the fixer displacement mechanism 14 displaces one of the pair 
of heat rollers 12 and 13 and the pair of heat rollers 12 and 13 are 
disposed so that both of the heat rollers 12 and 13 are separated from the 
printing paper P when one of the heat rollers is displaced. Further, a 
guide mechanism 15 which separates the printing paper P from the 
photosensitive drum 2 in the backward movement is provided in a transfer 
charger displacement mechanism 16 which separates the transfer charger 6 
from the photosensitive drum 2. 
When the movement of the continuous printing paper P is stopped, the 
printing paper P is moved back by a length of the fixed length Lt plus the 
adjustment length Lg. In this case, while the length for the backward 
movement is relatively long, the printing paper is moved back to the 
target position stably and exactly and the printing start position is set 
exactly upon resumption of the printing operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A preferred embodiment of the present invention is now described with 
reference to drawings. 
In order to facilitate understanding of the present invention, the whole 
configuration of the label printer K using an electronic photographic 
system is described with reference to FIG. 9. 
A machine body 70 is provided with a supply reel 71 and a take-up reel 72 
mounted to reel shafts disposed in front and rear ends of the machine body 
70. The take-up reel 72 and a cutter 73 can be provided selectively. On 
the other hand, a photosensitive drum 2 is disposed in the middle of the 
machine body 70. A continuous printing paper P supplied from the supply 
reel 71 is wound on a take-up reel 72 through a traveling path N 
consisting of a guide post 75, a plurality of drive roller mechanisms 11a, 
11b and 76 each including a pair of drive roller and driven roller, a 
plurality of guide plates 77, a guide post 78 and the like. In this case, 
the printing paper P comes into contact with the periphery of the 
photosensitive drum 2. 
Further, a transfer charger 6 is disposed opposite to the photosensitive 
drum 2 in the traveling path N. Disposed in the traveling path N near the 
take-up reel between the photosensitive drum 2 and the take-up reel are a 
suction device 80 utilizing a belt which sucks the printing paper P fed 
from the photosensitive drum 2 by a negative pressure so as to take out 
the printing paper P stably and a fixing device 7 which fixes the toner 
attached on the printing paper P guided by the suction device 80 by means 
of a pair of heat rollers 12 and 13. 
On the other hand, disposed successively around the photosensitive drum 2 
before the transfer in opposing relationship thereto are a main charger 3 
which charges the photosensitive drum 2, a printing head 4 which applies 
information such as figures and characters to be transferred to the 
photosensitive drum 2 and a developer 5 which attached the toner to the 
information portion of the photosensitive drum 2. Disposed successively 
around the photosensitive drum 2 after the transfer in opposing 
relationship thereto are a peel-off nail 81 which peels off the printing 
paper P from the photosensitive drum 2, a cleaner (toner collector) 84 
including a blade 82 and a magnetic roller 83 and an eraser 85 which 
erases charges on the photosensitive drum 2. Numerals 10 and 86 denote 
label position detection sensors which detect an edge of the label paper 
and numeral 87 denotes a paper sensor which detect the presence of the 
printing paper P. 
Accordingly, the photosensitive drum 2 is charged by the main charger 3 and 
is applied with the printing information by the printing head 4. Then, the 
photosensitive drum 2 is attached with the toner by the developer 5. The 
toner is transferred to the label paper S of the printing paper P from the 
photosensitive drum 2 by the transfer charger 6 and the printing paper P 
passes through the fixing device 7 to fix the toner on the label paper S. 
The configuration of the paper feeder 1 according to the present invention 
is described with reference to FIGS. 1 to 8. 
First, the configuration of a controller for the paper feeder 1 is 
described with reference to FIG. 1. 
As shown in FIG. 1, each of drive axes for a plurality of roller mechanisms 
11a, 11b and 76 which moves the printing paper P and reel axes for the 
supply reel 71 and the take-up reel 72 is provided with an electromagnetic 
clutch not shown. Thus, the electromagnetic clutches can be turned on and 
off so that the movement of the printing paper P can be switched in the 
direction of printing movement (forward direction) and in the backward 
direction. 
Further, a controller W includes the function of generating commands such 
as a start command C1 for starting the printing operation, a stop command 
C2 for stopping the printing operation, a forward command C3, a 
preparation command C4, a return or backward movement command C5 and the 
like and comprises a command supply unit 25, a clutch controller 26, a 
running or moving motor controller 27, a functional motor controller 28 
and a driving circuit 29. Functions of each portion of the controller W 
will be described later. 
On the other hand, a fixing device 7 suitable for use in the paper feeder 1 
is configured as shown in FIG. 3. The fixing device 7 includes a pair of 
heat rollers 12 and 13, and one heat roller 12 thereof constitutes a drive 
roller which is fixedly mounted to the machine body 70. The heat roller 12 
is a hollow roller made of, for example, aluminum and in which a lamp 
heater is provided. Further, the other heat roller 13 is supported by a 
fixer displacement mechanism 14 and constitutes a driven roller which is 
moved forward and backward with respect to the heat roller 12. The fixer 
displacement mechanism 14 includes a movable plate 32 which is swingably 
supported by a shaft 31. The heat roller 13 is mounted to the movable 
plate 32 which is urged to be moved to the heat roller 12 by a spring or 
the like. The heat roller 13 can be formed of a hollow roller made of, for 
example, aluminum and an outer periphery of which is covered with silicone 
rubber and in which a lamp heater is disposed. An engagement member 33 is 
integrally formed in the movable plate 32 and is operated to or abutted 
against an eccentric cam 34 which is rotated by a drive portion 35. 
Numeral 36 denotes a limit switch which detects the position of the 
eccentric cam 34. Thus, the movable plate 32 can be swingably displaced 
over a predetermined angular range so that the heat roller 13 can be 
pressed onto or separated from the heat roller 12. In this case, when the 
heat roller 13 is separated from the heat roller 12, a gap G is produced 
between the heat rollers 12 and 13 and the disposition of the heat rollers 
12 and 13 (or the relative disposition of the drive roller mechanism 76) 
is selected so that the printing paper P is positioned intermediate of the 
gap G. 
The fixing device 7 may by structured as shown by another embodiment of 
FIGS. 4 to 6. 
As shown in FIG. 4, the heat roller 12 is rotatably mounted through a 
horizontal axis 12s to a stationary frame 41 disposed in the normal 
direction. 
On the other hand, a movable frame 43 is rotatably mounted through a 
horizontal axis 43a in the stationary frame 41 positioned under the heat 
roller 12 and the heat roller 13 is rotatably supported to the movable 
frame 43 through an axis 13s. The heat roller 13 is disposed under the 
heat roller 12 so that the heat roller 13 can abut against the heat roller 
12, while in the natural state the movable frame 43 is angularly moved and 
displaced by its own weight about the axis 43s so that the heat roller 13 
is separated from the heat roller 12. 
One end of the movable frame 43 is bent at a right angle thereto to form 
therein an engagement piece 44. Further, a rotation drive portion not 
shown is provided on the side of the stationary frame 41 (on this side of 
the drawing) and an eccentric cam 46 of which rotation is controlled by a 
rotary shaft 45 of the rotation drive portion is disposed so that the 
periphery of the cam 46 can abut against the engagement piece 44. 
As shown in FIGS. 5 and 6, the eccentric cam 46 has a predetermined 
thickness and is formed with a D cut plane 47 formed in a peripheral 
portion 46s separated farthest from the rotary shaft 45. A cavity or 
hollow container 48 is formed in substantially the middle of the D cut 
plane 47 and a pair of opposed stoppers 49a and 49b are integrally formed 
on open edges of the container 48 so that the stoppers are protruded 
toward each other. Further, a pushed portion 40 having a round end is 
slidably disposed in the container 48. In this case, the pushed portion 40 
is formed with slits 51a and 51b formed over a predetermined length from 
an upper end to a lower end of the pushed portion 40 and through which the 
stopper 49a and 49b pass. Thus, the stopper 49a and 49b are engaged with 
engagement portions 52a and 52b formed on the lower end of the pushed 
portion 40 so that the pushed portion 40 is prevented from going out from 
the container 48 and the pushed portion 40 is guuided by the stoppers 49a 
and 49b. A compression coil spring 53 is disposed in the container 48 so 
that the upper end of the pushed portion 40 can be protruded from the D 
cut plane 47 (peripheral portion 46s) by a predetermined length in the 
natural state and the pushed portion 40 can be pushed into the container 
48 against the resilience of the coil spring 53. 
Accordingly, in the printing operation, the eccentric cam 46 is displaced 
to the position shown by the solid line in FIG. 4. Thus, the eccentric cam 
46 pushes up the engagement piece 44 and is stopped in the state in which 
the upper end of the pushed portion 40 abuts against the engagement piece 
44. More particularly, in this state, the pushed portion 40 is slightly 
pushed into the container 48 and accordingly the heat roller 13 is moved 
to a set position (pressurizing position F1) shown by a solid line. Thus, 
the heat roller 13 is urged to abut against the heat roller 12 by the coil 
spring 53 to exhibit the ordinary toner fixing function. On the other 
hand, when the eccentric cam 46 is rotated, the engagement piece 44 of the 
movable frame 43 is displaced downward by its own weight while the 
engagement piece 44 is put on the eccentric cam 46. The eccentric cam 46 
is stopped to be rotated 180.degree. and in this state the engagement of 
the eccentric cam 46 and the engagement piece 44 is released. The movable 
frame 43 is engaged with a stopper not shown in a position shown by 
phantom line and the heat roller 13 is positioned in a release position 
(release position F2) shown by phantom line so that the heat rollers 12 
and 13 are maintained to be separated from each other. Even in this case, 
the continuous printing paper P is positioned so that the printing paper P 
does not come into contact with both of the heat rollers 12 and 13. 
The transfer charger 6 suitable for use in the paper feeder 1 is structured 
as shown in FIGS. 7 and 8. The transfer charger 6 includes a transfer 
charger body 6a and a transfer charger displacement mechanism 16 which 
supports the body 6a. The displacement mechanism 16 includes a movable arm 
61 having a rotary fulcrum 61A disposed at one end as shown in FIG. 7 and 
the body 6a is mounted to the other end of the movable arm 61. The movable 
arm 61 is driven by a drive portion 62 to cause the body 6a to approach 
the photosensitive drum 2 so that the movable arm 61 is selectively moved 
to a set position Hs in which the function thereof is exhibited and to a 
release position Hr in which the movable arm 61 is separated from the 
photosensitive drum 2. 
The drive portion 62 comprises a drive unit 63 including a motor 62a and a 
gear mechanism 62b and an eccentric position of an output gear 62c of the 
drive unit 63 is rotatably coupled through a link 64b to a bracket 64a 
disposed behind the movable arm 61. Thus, when a rotating angle of the 
motor 62a is controlled, the body 6?a of the transfer charger can be 
selectively moved to the set position Hs or the release position Hr. 
On the other hand, the movable arm 61 is formed into a U-letter shape in 
section and the arm is disposed so that an opening thereof is opposed to 
the photosensitive drum 2. A guide mechanism 15 is disposed in the middle 
of the movable arm 61. The guide mechanism 15 is provided with a first 
guide roller 65 which guides the continuous printing paper P and position 
restriction rollers 67a and 67b are rotatably supported to shaft portions 
65a and 65b formed integrally at both sides of the first guide roller 65. 
Further, ends of the shaft portions 65a and 65b are rotatably supported to 
the movable arm 61 as shown in FIG. 8. Consequently, the first guide 
roller 65, the position restriction rollers 67a and 67b can be rotated 
with regard to the movable arm 61. The position restriction rollers 67a 
and 67b have a diameter larger than that of the first guide roller 65. 
Thus, the printing paper P is moved smoothly by the first guide roller 65 
and is brought into contact with the photosensitive drum 2 stably. 
Further, since the position restriction rollers 67a and 67b can be rotated 
while the restriction rollers come into contact with and follow the 
periphery of the photosensitive drum 2, the rollers 67a and 67b can 
restrict the relative position of the movable arm 61 and the 
photosensitive drum 2. In this case, since the body 6a of the transfer 
charger always follows the periphery of the photosensitive drum 2, the 
distance between the body 6a and the photosensitive drum 2 is always 
constant. Further, a second guide roller 68 is disposed in the middle of 
the movable arm 61 and in the opposite side of the body 6a, as viewed from 
the printing paper P. The positional relation of the movable arm 61 and 
each portion of the guide mechanism 15 in the transfer charger 6 is as 
follows. 
First, in the printing operation in which the movable arm 61 is positioned 
in the set position Hs, the printing paper P is guided by the drive roller 
mechanism 11b, the first guide roller 65 and the photosensitive roller 2 
as shown by P1 of FIG. 7 and is not in contact with the second guide 
roller 68. On the other hand, when the movable arm 61 is positioned in the 
release position Hr, the first guide roller 65 and the second guide roller 
68 are both moved back by the backdown of the movable arm 61 to engage the 
second guide roller 68 with the printing paper P so that the printing 
paper P is separated from the periphery of the photosensitive drum 2 as 
shown by P2 of FIG. 7. 
In this manner, the guide mechanism 15 is provided in the movable arm 61 so 
that the printing paper P can be separated from the photosensitive drum 2 
without deteriorating the positional accuracy of the transfer charger body 
6a. 
Operation of the paper feeder 1 according to the present invention is now 
described with reference to FIGS. 1 and 2. 
First, the start command C1 is produced from the controller W in the 
printing operation and is supplied through the command supply unit 25 to 
the clutch controller 26, the running motor controller 27, the fixing 
device 27 and the functional motor controller 28 of the transfer charger 
6. Thus, the drive unit 29 is driven to set each portion to the printing 
operation state. That is, the electromagnetic clutch of the take-up reel 7 
can be turned on to wind the printing paper P and the electromagnetic 
clutches for the drive roller mechanisms 11a, 11b and 76 are turned on the 
rotated in the normal direction. Further, the heat roller 13 of the fixing 
device 7 is pressed against the heat roller 12 by the fixer displacement 
mechanism 14 and becomes the state in which the fixing operation can be 
made. The movable arm 61 of the transfer charger displacement mechanism 16 
in the transfer charger 6 is rotated clockwise so that the printing paper 
P is brought into contact with the photosensitive drum 2 to set the state 
in which the transfer operation can be made. The electromagnetic clutch of 
the supply reel 71 is turned off but applies a predetermined back tension 
to the printing paper P. 
Accordingly, in the printing operation, the printing paper P is moved in 
the direction of arrow V1 and is wound on the take-up reel 72. 
On the other hand, when the printing operation is stopped (interrupted) on 
the way, the stop command C2 is produced and the forward command C3 is 
produced to move the printing paper P forward until the final printing 
position Mf passes through the heat rollers 12 and 13 as shown in FIG. 2. 
An amount of forward movement according to the forward command C3 is set 
on the basis of the distance between the transfer charger 6 and the fixing 
device 7. 
If the forward movement of the printing paper P has been completed and the 
movement of the printing paper P is stopped, the printing paper P is moved 
back io the direction of arrow V2. In the backward movement, the heat 
roller 13 is separated from the heat roller 12 in the fixer displacement 
mechanism 14 in response to the preparation commnand C4. Consequently, the 
printing paper P is separated from both of the heat rollers 12 and 13. 
Thus, burning and deterioration of the printing paper P due to heat (about 
150.degree. to 190.degree. C.) left in the heat rollers are prevented. 
Further, the transfer charger displacement mechanism 16 in the transfer 
charger 6 is angularly moved counterclockwise in response to the 
preparation command C4 so that the printing paper P is separated from the 
photosensitive drum 2. Thus, wearing of the photosensitive drum 2 by the 
printing paper P in the backward movement is avoided. The completion of 
the above processing of the fixing device 7 and the transfer charger 6 is 
detected by the limit switch 36 or the rational angle of the motor 62a and 
the return command C5 is produced. Consequently, the electromagnetic 
clutch of the supply reel 71 is turned on so that the reverse rotation is 
controlled and further the electromagnetic clutch of the take-up reel 72 
is turned off. At this time, the two sets of drive roller mechanism 11a 
and 11b disposed between the photosensitive drum 2 and the supply reel are 
rotated reversely for the backward movement while the electromagnetic 
clutches are on, while the drive roller mechanism 76 disposed behind the 
fixing device 7 is served as an idler by turning off the electromagnetic 
clutch. The movement of the suction device 80 is stopped. 
The feeding speed of the backward movement is set to a speed lower than 
that in the printing operation. The speed of the backward movement depends 
on the tensile strength for the printing paper P but is preferably set to 
a speed as large as a half or one third of the speed in the printing 
operation. The reason why the speed of the backward movement is low is 
that since the printing paper P is released from being held between the 
heat rollers 12 and 13 of the fixing device 7 and from being pressed to 
the photosensitive drum 2, the moving resistance is made small and 
accordingly the printing paper P becomes loose so that a jam occurs easily 
if the speed of the backward movement is high. The speed of the backward 
movement is provided in the command value of the return command C5. 
Further, the length for the backward movement is set to the length of the 
fixed length Lt capable of making printing continuously subsequently to 
the final printing position Mf of the printing paper P plus the adjustment 
length Lg for settling the printing position. That is, the fixed length Lt 
is equal to a sum (L1+L2) of the length L1 from the printing position Mn 
for continuous printing subsequently to the final printing position Mf to 
the transfer position Ms in the photosensitive drum 2 and the length L2 
from the position Ms to the position Mcc immediately after the printing 
head 4. The adjustment length Lg is set so that the printing paper P which 
has been moved back is not deviated from the printing start position in 
the resumption of the next printing operation. The adjustment length Lg is 
equal to a sum of the length Ls for setting the printing position and the 
length Lh for compensation upon start. The length Ls is equal to a 
distance between the position Mcc corresponding to the printing position 
on the printing paper P upon the resumption of printing and the label 
position detection sensor 10 for detecting the edge of the label paper. 
The length Lh is equal to a distance between the label position detection 
sensor 10 and the leading edge of the label paper S on which the printing 
is first made upon the resumption of the printing operation. Accordingly, 
upon the resumption of the printing operation, a transient acceleration 
upon the start is absorbed in the forward movement for the length Lh and 
the speed of the forward movement is constant when passing through the 
label position detection sensor 10. The leading edge of the label paper P 
is detected by the label position detection sensor 10 and accordingly the 
normal printing position Mcc on the label paper S is set by the timer in 
the movement of the length Ls. Thus, the exact printing position is 
settled by setting the length Lg. The actual backward length Lr, the 
adjustment feeding command and the stop command are provided in the return 
command C5 and each of the distances can be set using the timers on the 
basis of the time and speed. 
As described above, the embodiment of the present invention has been 
described, although the paper feeder of the label printer according to the 
present invention is not limited the embodiment and can be modified in 
detailed configuration and operation without departing from the spirit of 
the present invention.