Automatic screen printing process and apparatus

An automatic screen printing process comprising the steps of continuously driving an endless belt to apply and stick a material to be printed onto the endless belt along a predetermined length smaller than one travelling circle of the endless belt, then driving the endless belt intermittently to feed the material to be printed to a printing operation zone and a drying operation zone, while repeating the cycle of the printing operation during stoppage of the endless belt and the operation of travelling the endless belt along a repeat length during stoppage of the printing operation, thereby to print the entire surface of the material applied to the endless belt and dry the printed material, and repeating said printing step until a pattern of a predetermined number of colors is obtained is disclosed. According to this automatic screen printing process, since a pattern of a predetermined number of colors is printed while turning round an endless belt on which a material to be printed is applied, color pastes are gradually applied to already dried preceding color pastes, bleeding of colors or mingling of color pastes can be prevented, and a printed product having a pattern having sharp contours and very clear colors can always be obtained. Further, since a color paste applied to a material to be printed is immediately dried in drying zone and a subsequent color paste is then applied to the dried color paste, even if a color paste is applied in a considerable thickness or amount, disfiguration of a printed pattern or mingling of colors can be effectively prevented, and as a result, multi-color printing becomes possible with good coloring effects and high printing precision.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an automatic screen printing process and 
apparatus. More particularly, the invention relates to a process and 
apparatus for manufacturing various kinds of high quality printed products 
in small lots automatically and stably without performing troublesome 
manual operations. 
2. Description of the Prior Art 
According to the conventional manual printing method, a fixed printing 
stand of a horizontal or inclined type having a length of 25 to 60 m is 
employed, stencil frame positioning fixtures are attached to the stand at 
intervals corresponding to the repeat length of a design for moving the 
stencil frames in the lengthwise direction precisely along the same 
length, and the operation of moving the stencil frames and the printing 
operation are carried out in sequence manually based on these positioning 
fixtures. 
In this method, a plain cloth is applied to the surface of the printing 
stand while manually moving the cloth, and the printed cloth is dried on 
the printing stand or the printed cloth is once peeled from the printing 
stand and is then dried in the state hung from a ceiling. After peeling of 
the printed cloth, the top face of the printing stand is manually washed 
with water or it is washed with water by means of a simple movable 
water-washing machine, and after removal of water and application of a 
paste, a subsequent plain cloth is applied to the surface of the printing 
stand and the printing operation is then conducted. By repeating such 
cycle of operations certain times, printing of one lot is completed. 
According to the conventional screen-running type semiautomatic printing 
method, a printing stand similar to the printing stand used in the manual 
printing method is employed and rails are laid out on both the sides of 
the printing stand for travelling printing unit-running stands, and 
fixtures for travelling the running stands in the lengthwise direction of 
the printing stand in parallel to said rails and precisely positioning the 
running stands having stencil frames attached thereto are attached to the 
printing stand at intervals corresponding to the repeat length of a design 
and a roll of a plain cloth is applied to the surface of the printing 
stand. Thus, the running stands travel automatically or manually to 
perform the printing operation, and after completion of the printing 
operation, the printed cloth is dried on the surface of the printing stand 
by a movable drying machine or the printed cloth once is peeled from the 
surface of the printing stand and is then dried in the state hung from a 
ceiling. 
Then, the surface of the printing stand is washed with water manually or by 
using a movable water washing machine, and after removal of water, a 
subsequent plain cloth to be printed is applied to the surface of the 
printing stand. Thus, the above procedures are repeated certain times and 
printing of one lot is completed. 
As will be apparent from the foregoing illustration, not only the manual 
printing method but also the screen-running type printing method involves 
a number of manual operation steps and the efficiency of the printing 
operation is very low. Further, since plain cloths are separately applied 
every time one cycle of the printing operation is completed, deviations of 
the quality are conspicuous in printed products of one lot and various 
disadvantages are caused by such deviation of the quality. 
OBJECTS OF THE INVENTION 
It is therefore a primary object of the present invention to provide an 
automatic screen printing process and apparatus in which a variety of high 
quality printed products of small lots, which have heretofore been 
manufactured by manual printing or screen-running type printing methods, 
can be manufactured automatically at a high efficiency stably without 
deviations of the quality. 
Another object of the present invention is to provide an automatic screen 
printing process and apparatus in which the printing operation can always 
be accomplished under constant cloth-applying and printing conditions even 
if a worker is not experienced. 
Still another object of the present invention is to provide an automatic 
screen printing process and apparatus in which application of a material 
to be printed to an endless belt is performed by continuously driving the 
endless belt and the material is applied entirely along the peripheral 
face of the endless belt, whereby the material to be printed can always be 
applied under a certain tension, the printing operation can be performed 
at a high precision even on a flexible material, and a maximum applicable 
length of a material to be printed can be prolonged to the length of one 
travelling circle (circumference) of the endless belt and therefore, the 
equipment space of the printing apparatus can be reduced to 1/2 of the 
equipment space necessary for the conventional fixed type printing stand. 
A further object of the present invention is to provide an automatic screen 
printing process and apparatus in which a predetermined number of colors 
are printed while an endless belt to which a material to be printed is 
applied turns round through printing and drying zones repeatedly, so that 
color pastes are applied on already dried preceding color pastes, whereby 
bleeding of colors and mingling of color pastes can be prevented and 
printed products having clear colors and sharp pattern contours can always 
be obtained. 
SUMMARY OF THE INVENTION 
In accordance with one fundamental aspect of the present invention, there 
is provided an automatic screen printing process which comprises the steps 
of: 
(A) continuously driving an endless belt travelling through a pasting 
operation zone, a printing operation zone, a drying operation zone and a 
washing operation zone, thereby to apply a material to be printed onto the 
endless belt along a predetermined length smaller than one travelling 
circle of the endless belt, and cutting the material to be printed into 
said predetermined length according to need, 
(B) travelling said endless belt onto which the material to be printed has 
been applied, to a position for starting the printing operation, 
(C) intermittently driving the endless belt to deliver the material to be 
printed to the printing operation zone and drying operation zone and 
thereby repeating the cycle of operations of performing printing during 
stoppage of the endless belt and feeding the endless belt along a repeat 
length during stoppage of the printing operation, whereby the entire 
surface of the material to be printed, which has been applied to the 
endless belt, is printed and the printed material is dried, 
(D) repeating said steps (B) and (C), according to need, to print a 
desirable number of colors on the entire surface of the material to be 
printed, which has been applied to the endless belt, and 
(E) continuously driving said endless belt to peel off the printed and 
dried material as a printed product from the endless belt and washing the 
endless belt in the washing operation zone. 
In accordance with the other fundamental aspect of the present invention, 
there is provided an automatic screen printing apparatus comprising an 
endless belt laid out to travel through a pasting operation zone, a 
printing operation zone, a drying operation zone and a washing operation 
zone by means of a pair of pulleys, a servo drive mechanism for driving 
said endless belt intermittently and continuously through said pulleys, a 
pasting mechanism disposed in the pasting operation zone so that it can 
engage with and separate from the endless belt, a mechanism for feeding to 
the endless belt a material to be printed and applying and sticking the 
material to the endless belt, a printing unit disposed in said printing 
operation zone, said printing unit including a screen, a squeegee capable 
of scanning on the screen and a squeegee driving mechanism, a lift 
mechanism for driving and moving the printing unit in the vertical 
direction between a lowermost printing position and an uppermost 
non-printing position, a drying device disposed in said drying operation 
zone, a mechanism for peeling off a printed product from the endless belt, 
a washing mechanism disposed in the washing operation zone so that it can 
engage with and separate from the endless belt, a positioning mechanism 
for correctly registering the material to be printed with a position for 
starting the printing operation, and a drive control mechanism for 
continuously driving said servo drive mechanism for applying the material 
to be printed onto the endless belt along a predetermined length and 
intermittently driving said servo drive mechanism for travelling the 
endless belt intermittently by a predetermined repeat length along the 
entire surface of the material to be printed, wherein said pasting 
mechanism and washing mechanism are connected to said drive control 
mechanism so that the pasting and washing mechanisms are allowed to fall 
in agreement with the endless belt only when the endless belt is 
continuously driven, and wherein said lift mechanism and squeegee driving 
mechanism are connected to said drive control mechanism so that dropping 
of the printing unit to the lowermost position is performed on 
confirmation of the repeat length feeding of the material to be printed, 
scanning movement of the squeegee is performed on confirmation of 
completion of dropping of the printing unit to the lowermost position, 
elevation of the printing unit to the uppermost position is performed on 
confirmation of completion of scanning movement of the squeegee and 
driving of the endless belt is performed on confirmation of elevation of 
the printing unit to the uppermost position. 
In accordance with one preferred embodiment of the above-mentioned 
automatic screen printing process of the present invention, prior to or 
simultaneously with printing of a first color, marks for respective 
feedings are printed on the surface of the endless belt and at printing of 
each of subsequent colors, the corresponding feeding mark is detected to 
control the feed length of the endless belt. 
In accordance with one preferred embodiment of the above-mentioned 
automatic screen printing apparatus of the present invention, the printing 
unit further includes a mechanism for printing marks for respective 
feedings on the surface of the endless belt prior to or simultaneously 
with printing of a first color, a detecting mechanism is disposed in the 
printing operation zone or in an area adjoining to the printing operation 
zone to detect said marks and a control mechanism is disposed to stop said 
servo drive mechanism in response to a signal issued from said mark 
detecting mechanism to control the feed length of the endless belt. 
In the conventional automatic printing process and apparatus in which an 
endless belt to which a material to be printed has been applied is 
intermittently fed to a printing operation zone by intermittent movement 
of pulleys, the intermittent feed length of the belt is naturally 
determined by the rotation angle of the pulleys and the precision of this 
feeding is influenced by errors of the thickness, hardness and elongation 
of the endless belt, changes of properties of the belt caused by changes 
of the ambient temperature and humidity, especially the thermal influence 
of an annexed drying device, and expansion and contraction of the driving 
pulleys caused by changes of the ambient temperature, rather than by the 
degree of the mechanical precision at driving or stopping of a driving 
roller. Accordingly, in the conventional automatic screen printing process 
and apparatus, it is very difficult to always maintain a high precision in 
the feed length of the endless belt. 
Further, in the conventional automatic screen printing process and 
apparatus of this type, the endless belt travels and turns round several 
times according to the number of colors to be printed, and since there is 
present a considerable lapse of time between the point of printing of a 
first color and the point of printing of a last color, the feed length of 
the endless belt is gradually changed during this time because of the 
above-mentioned various influences and it is very difficult to maintain a 
precise feed length of the endless belt throughout the printing operation. 
In contrast, according to the above-mentioned preferred embodiments of the 
present invention, the foregoing defects involved in the above-mentioned 
conventional automatic screen printing technique utilizing pulleys for 
intermittent feeding of the endless belt can be completely eliminated, and 
multi-color printing can be performed always at a high feed precision 
irrespectively of the above-mentioned factors having influences on the 
feed length of the endless belt and this high precision in the feeding of 
the endless belt can be maintained even to the step of printing of a final 
pattern. 
In accordance with an especially preferred embodiment of the present 
invention, the feed length (repeat length) of the endless belt is set as a 
pulse number, the actual fed length of the endless belt is detected as a 
number of pulses, digital control is performed so that reduction of the 
speed of the endless belt and stopping of movement of the endless belt are 
performed depending on the difference between the set pulse number and the 
number of the actually detected pulses according to a program and this 
digital control is combined with the above-mentioned mark-detecting feed 
length control for performing reduction of the speed of the endless belt 
and stopping of movement of the endless belt on detection of marks printed 
on the surface of the endless belt, whereby a very high precision can 
always be maintained in the feed length of the endless belt. 
The present invention will now be described in details by reference to the 
accompanying drawing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIGS. 1 and 2, a driven pulley 2 and a driving pulley 3 are 
mounted on both the ends of a machine frame 1, and an endless belt 4 is 
stretched between these pulleys so that the belt 4 travels through a 
pasting operation zone A, a printing operation zone B, a drying operation 
zone C and a washing operation zone D. 
A printing unit 5 having a known structure is disposed on the upper side of 
the belt 4 in the printing operation zone B and a stool (not shown) as a 
printing stand is disposed on the lower side of the belt 4 in the printing 
operation zone. This printing unit 5 includes a screen 6, a stencil frame 
7 for supporting the screen 6, a squeegee 10 disposed scannably on the 
screen 6 through guide rail 8 and carrier 9, and a squeegee driving 
mechanism 11 (motor). The screen-supporting stencil frame 7 is easily 
dismountably attached to a printing unit supporting stand 12, and a 
plurality of squeegees 10 are arranged so that they are moved to scan on 
the screen and the moving direction is reversed on both the ends of the 
screen by the carrier 9. 
A lift mechanism having a known structure is disposed to move the printing 
unit 5, namely the supporting stand 12, in the vertical direction between 
the lowermost printing position (the position shown in FIG. 1) and the 
uppermost non-printing position, and this lift mechanism includes a fluid 
cylinder 13 and a series of a link mechanism 14. 
The drying operation zone C is located subsequently to the above-mentioned 
printing operation zone B on the running passage of the endless belt 4, 
and a known drying mechanism 15 such as a hot air drier, an infrared lamp 
or an electric heater is disposed in the drying operation zone C. 
In order to tightly support the endless belt 4 in portions other than the 
portion supported by the stool, a plurality of guide rolls 16 may be 
arranged on the running passage of the belt 4. 
A servo driving mechanism 17 (motor) having a known structure is disposed 
to drive the driving pulley 3 to thereby drive the endless belt 4 
intermittently and continuously around the driving pulley 3. The driving 
force of the servo drive mechanism 17 is transmitted to the driving pulley 
3 through a reduction gear 18 and a spur gear 19. 
On the side of the machine frame 1 where the driven pulley 2 is located, 
the pasting operation zone A is formed, and a pasting device 20 having a 
known structure is disposed in the pasting operation zone A so that it can 
engage with and separate from the endless belt 4. 
On the side of the machine frame 1 where the driven pulley 2 is located, a 
feed mechanism 21 having a known structure is disposed to feed a plain 
cloth 22 to be printed, and the cloth 22 is fed onto the paste-applied 
belt 4 and the fed cloth 22 is caused to adhere to the belt 4 by means of 
a sticking roller 23. 
On the side of the machine frame 1 where the driving pulley 3 is located, 
the washing operation zone D is formed, and a washing device 24 having a 
known structure is disposed in this washing operation zone D so that the 
washing device 24 can engage with and separate from the endless belt 4. 
Further, on the side of the machine frame 1 where the driving pulley 3 is 
located, a guide roll 25 is disposed to peel off a printed product 22' 
from the belt 4 and guide it to a known winding device (not shown). 
A mechanism 26 for registering the printing-starting end of the material 22 
to be printed with the standard (leading) end of the screen on the endless 
belt 4 is mounted on the machine frame 1. 
A drive control switch 28 is mounted on an operation panel 33 (see FIG. 1) 
attached to the machine frame 1 to drive the servo drive mechanism 17 
continuously for applying a predetermined length of the material 22 to be 
printed to the endless belt 4 and also to drive the servo drive mechanism 
17 intermittently for feeding the endless belt 4 by a predetermined repeat 
length toward the printing operation zone along the entire surface of the 
material to be printed. 
The pasting mechanism 20 and washing mechanism 24 are electrically 
connected to the drive control switch 28 so that these mechanisms are 
allowed to fall in contact with the belt 4 only when the belt 4 is 
continuously driven. 
The lift mechanism 13 and squeegee driving mechanism 11 can be operated 
only when the belt 4 is driven intermittently, and they are electrically 
connected to the drive control mechanism 28 so that by using known limit 
switch means (not shown), dropping of the printing unit 5 to the lowermost 
position (printing position) is performed on confirmation of feeding of 
the material 22 along the repeat length, scanning driving of the squeegee 
10 is performed on confirmation of dropping of the printing unit 5 to the 
lowermost position, elevation of the printing unit 5 is performed on 
confirmation of completion of the scanning movement of the squeegee 10 and 
driving of the endless belt 4 is performed on confirmation of elevation of 
the printing unit 5 to the uppermost position (non-printing position). 
In the present invention, it is especially preferred that prior to or 
simultaneously with printing of a first color, marks for respective 
feedings be printed on the surface of the endless belt and at printing of 
each of subsequent colors, the corresponding feeding mark be detected to 
control the feed length of the endless belt. For embodying this feature, a 
mechanism 27 for printing marks for respective feedings on the surface of 
the endless belt prior to or simultaneously with printing of a first color 
is mounted on the printing unit 5. This mechanism 27 comprises, for 
example, a small screen device and marks 28' are printed on the surface of 
the belt 4 by a known squeegee device (not shown). The marks 28' are 
printed directly on the belt surface, and the intended detection can be 
sufficiently attained if the size of these marks is one that can be 
detected by, for example, a photoelectric device. In case of an endless 
belt having a surface portion composed of a black material, such as an 
ordinary endless belt, an aqueous or oily ink of a bright color such as a 
white ink or yellow ink for ordinary printing is used for printing of 
these marks. Of course, when marks 28' are printed on a white background 
of an endless belt, a black or brown ink may be used for printing of these 
marks. Instead of the small screen device 27 disposed independently from 
the printing screen 6, a stencil pattern may be formed only on the screen 
6 of a first color for printing marks on the belt surface so that by 
reciprocative scanning movements of the squeegee 10 and a flood doctor 
(not shown), printing of marks can be accomplished simultaneously with the 
printing operation. Further, if there is a margin in the material to be 
printed, these marks may be printed on such margin of the material to be 
printed. 
At the subsequent printing operation, namely at the operation of printing a 
first color or second color and subsequent colors in the above-mentioned 
preferred embodiment, these marks 28' are detected by detecting mechanisms 
29 and 30 disposed in the printing operation zone or in the vicinity of 
the printing operation zone. For example, such detecting mechanism 
comprises a photoelectric device for detecting marks 28' by reflection of 
rays, and it is preferred that such detecting mechanism be constructured 
by a pair of a detecting device 29 located in the front to issue signals 
for reduction of the speed and a detecting device 30 located in the rear 
to issue stopping signals. 
These indicating devices 29 and 30 are disposed on a shaft 31 of the 
machine frame 1 so that they can slide on the shaft 31, if necessary 
together with the abovementioned positioning mechanism 26 and their 
positions can be adjusted with respect to the direction of advance of the 
belt. The distances L.sub.1 and L.sub.2 from the center of the printing 
screen 6 can optionally be adjusted according to the belt feed length L 
(repeat length) or the belt feed velocity (in the embodiment shown in FIG. 
2, a relation of L.sub.2 =2L is established but establishment of this 
relation is not an indispensable requirement in the present invention). 
In the present invention, it is especially preferred that the feed length 
of the endless belt be controlled by a combination of (i) pulse control 
where the repeat length (feed length) of the endless belt is set as a 
pulse number, the actual fed length of the endless belt is detected as a 
number of pulses and reduction of the speed of the endless belt and 
stopping of movement of the endless belt are performed depending on the 
difference between the set pulse number and the number of the actually 
detected pulses and (ii) mark-detecting control where marks on the belt 
surface are detected and reduction of the speed of the endless belt and 
stopping of movement of the endless belt are performed on detection of 
these marks. 
In a digital drive control mechanism preferably employed in the present 
invention, which is diagrammatically illustrated in FIG. 3, a direct 
current electric motor 17 for driving the endless belt 4, a switch 32 for 
setting the repeat length as a pulse number, a repeat length detecting 
mechanism 34 for detecting the actual fed length of the endless belt 4 as 
a number of pulses, a digital control mechanism 35 and an electric motor 
control mechanism 36 for controlling an electric input to the direct 
current electric motor 17 are arranged so that specific relationships 
described hereinafter should be established among these members. 
In order to drive the endless belt 4 strictly according to an electrically 
controlled program, it is preferred to use the direct current electric 
motor 17. 
The switch 32 is mounted on an operation panel of the digital control 
mechanism 35, and the repeat length of the endless belt 4 is set to a 
desirable value as a pulse number. 
The repeat length detecting mechanism for detecting the actual feed length 
of the endless belt 4 comprises a pulse generator 34 connected directly to 
a driving shaft 42 of the electric motor 17. This pulse generator 34 is 
capable of generating signals of a predetermined pulse number precisely in 
correspondence to the displacement angle of a rotation shaft (not shown) 
thereof. Of course, instead of this method in which the pulse generator 34 
is directly connected to the driving shaft 42, there may be adopted a 
method in which the linear displacement (feed length) of the endless belt 
is converted to an angular displacement and this angular displacement is 
transmitted to the rotation shaft of the pulse generator 34 or the angular 
displacement of the pulley 3 is directly transmitted to the rotation shaft 
of the generator 34. 
Pulse signals from the pulse generator 34 are transmitted to the digital 
control mechanism 35 through a line 37. Such pulse signal is displayed as 
an actual feed length on a digital display area 38 formed on an operation 
panel of the digital control mechanism 35. 
In the digital control mechanism 35, subtraction is conducted between the 
pulse number set by the switch 32 and the pulse number detected through 
the pulse generator 34, and a speed reduction signal is generated so as to 
stop the direct current electric motor 17 at the set pulse number. 
The electric motor control mechanism 36 ordinarily comprises a thyristor 
panel, and a speed reduction signal from the digital control mechanism 35 
is supplied as an SCR gate signal to the thyristor panel 36 through a line 
39. An electric input applied from a power source 40 to the direct current 
electric motor 17 through the thyristor panel 36 and line 41 is controlled 
based on the abovementioned SCR gate signal (speed reduction signal) to 
reduce the velocity of the electric motor 17 and stop the electric motor 
17 at the set pulse number. A tachometer 43 for detecting the actual 
rotation speed of the direct current electric motor 17 as a voltage is 
connected to the driving shaft 42 of the direct current electric motor 17, 
and a detection signal from the tachometer 43 is fed to a digital 
regulator 35 through a line 45 and fed back to the electric motor control 
mechanism 36 through a line 46. 
It is advantageous that driving of the direct current electric motor 17 is 
performed after arrival of the printing unit 5 at the uppermost position 
has been confirmed. For embodying this feature, a projection 47 is formed 
on the lifting frame driving mechanism 14 so that when the printing unit 5 
is located at the uppermost position, this projection 47 is detected by a 
limit switch 48. A detection signal of the limit switch 48 is fed to the 
digital control mechanism 35 through a line 49. 
Referring to FIG. 4 illustrating the relation between the belt feed 
velocity and the time at the step of printing of marks, the feed stroke of 
the belt 4 comprises an acceleration driving region AB, a constant speed 
driving region BC and a speed reduction-stopping region CD, and the 
stoppage period DA follows this feed stroke and both such feed stroke and 
stoppage period constitute one cycle of the printing operation. In FIG. 4, 
the area surrounded by lines AB, BC, CD and DA corresponds to the feed 
length of the belt. 
In the relation illustrated in FIG. 4, the feed length L (m) of the belt is 
represented by the following formula: 
##EQU1## 
wherein .DELTA.t.sub.1 stands for the time (sec) of the acceleration 
driving, t stands for the time (sec) of the constant speed driving, 
.DELTA.t.sub.2 stands for the time (sec) of the speed reduction-stopping, 
and V stands for the velocity (m/sec) of the belt at the constant speed 
driving. 
In the foregoing formula (1), values of V, .DELTA.t.sub.1 and 
.DELTA.t.sub.2 are determined by the mechanical structure of the printing 
apparatus and the capacity of the direct current electric motor 17. 
In the printing apparatus of the present invention, at the step of printing 
of marks on the belt surface prior to or simultaneously with printing of a 
first color, the digital control mechanism 35 and electric motor control 
mechanism 36 (thyristor panel) are set so that the endless belt 4, namely 
the direct current electric motor 17, is driven according to the diagram 
of FIG. 4. More specifically, the repeat length is set as a pulse number 
by the switch 32, and in the digital control mechanism 35, pulse numbers 
corresponding to the respective operation times .DELTA.t.sub.1, t and 
.DELTA.t.sub.2, namely N.DELTA.t.sub.1, Nt and N.DELTA.t.sub.2 in which N 
designates the pulse number per unit time (Hz/sec), are set. 
Control of the driving of the endless belt at the mark-printing step is 
performed according to the following procedures. 
(i) On receipt of the detection signal from the limit switch 48, the 
digital control mechanism 35 emits an acceleration signal to the electric 
motor control mechanism 36 and an acceleration current is supplied to the 
direct current electric motor 17 based on this signal. Accordingly, the 
endless belt 4 is driven and accelerated along the line AB in FIG. 4. 
(ii) The digital control mechanism 35 counts the pulse number 
.DELTA.t.sub.1 N and/or confirms from the detection signal from the 
tachometer 34 that the rotation speed of the electric motor 17 arrives at 
a level corresponding to the velocity V of the constant speed driving of 
the belt. At this point, the digital control mechanism 35 emits a constant 
speed driving signal to the electric motor control mechanism 36, and on 
receipt of this signal, the electric motor control mechanism 36 supplies a 
constant speed driving electric current to the direct current electric 
motor 17 to drive at a constant speed the direct current electric motor 
17, namely the endless belt 4, along the line BC in FIG. 4. 
(iii) The digital control mechanism performs subtraction between the pulse 
number (N.sub.S) set by the switch 32 and the pulse number (N.sub.D) 
detected by the feed length detecting mechanism, and when the difference 
(N.sub.S -N.sub.D) corresponds to the value represented by the following 
formula: 
EQU N.sub.S -N.sub.D =.DELTA.t.sub.2 N (2) 
in which N.sub.S is equal to N.DELTA.t.sub.1 +Nt+N.DELTA.t.sub.2, the 
digital control mechanism 35 emits a speed reduction signal to the 
electric motor control mechanism 36. On receipt of this signal, the 
electric motor control mechanism 36 supplies a speed reduction electric 
current to the direct current electric motor 17. Accordingly, the speed of 
the electric motor 17, namely the endless belt 4, is reduced along the 
line CD in FIG. 4 and the electric motor 17 is stopped to stop the endless 
belt 4. Speed reduction and stopping of the direct current electric motor 
are performed by reference to the detected pulse signal from the feed 
length detecting mechanism 34 and the voltage signal from the tachometer 
43 so that the endless belt 4 is stopped precisely at the repeat length 
corresponding to the set pulse number. The speed reduction current may be 
supplied in the form of so-called electric brake to the electric motor. 
Any of known mechanisms can be used as the digital control mechanism 35 in 
the present invention, and preferred examples are Digital DC Servo Model 
DDS-P manufactured by Nippon Reliance Kabushiki Kaisha and Position Pack 
Model 300, each of which is easily commercially available. 
From the operation facility and the simplicity of the mechanism, it is 
preferred that the adjustment of the repeat length of the belt 4 be 
performed by changing the feed time of the belt, especially the constant 
speed driving time (t). Further, this adjustment can be accomplished by 
changing the velocity (V) of the constant speed driving by keeping the 
total feed time (.DELTA.t.sub.1 +t+.DELTA.t.sub.2) substantially constant. 
At the step of printing of a first color or second color or any subsequent 
color, driving of the endless belt is controlled by detection of marks. 
For accomplishing this control, the detecting device 29 for generating 
speed reduction signals is connected to the digital control mechanism 35 
through a line 50 and the detecting device 30 for generating stopping 
signals is connected to the digital control mechanism 35 through a line 
51. 
Referring to FIG. 5 illustrating the relation between the belt feed 
velocity and the time at the step of printing of a first or second color 
or any of subsequent colors, the feed stroke of the endless belt 4 
comprises an acceleration driving region AB, a constant speed driving 
region BC.sub.1 and the speed reduction-stopping region C.sub.1 C.sub.2 
C.sub.3 D.sub.1. The acceleration driving and constant speed driving of 
the belt are performed in the same manner as described above by reference 
to FIG. 4. When the detecting device 29 for generating speed reduction 
signals detects a mark 28' [the feed length Lo of the belt 4 corresponds 
to 
##EQU2## 
the digital control mechanism 35 emits a speed reduction signal to the 
electric motor control mechanism 36 based on the detection signal from the 
detecting device 29. Accordingly, the electric motor control mechanism 36 
supplies a speed reduction electric current to the direct current electric 
motor 17, and the speed of the electric motor 17, namely the belt 4, is 
reduced along the line C.sub.1 C.sub.2 in FIG. 5 and the belt 4 is then 
driven at a very slow constant speed V.sub.2. 
When the detecting device 30 for generating stopping signals then detects 
the mark 28', based on the detection signal from the detecting device 30, 
the speed of the electric motor 17, namely the endless belt 4, is reduced 
and the endless belt 4 is stopped by the digital control mechanism 35 and 
the electric motor control mechanism 36 as indicated by the line C.sub.3 
D.sub.1 in FIG. 5. 
The speed reduction driving time .DELTA.t.sub.3 of the belt 4 is set so 
that the relation represented by the following formula: 
##EQU3## 
wherein L stands for the set feed length of the belt, .DELTA.L designates 
a maximum contraction error of the belt and t.sub.1, .DELTA.t.sub.1 and 
.DELTA.t.sub.1 and .DELTA.t.sub.3 are as defined above, is established. By 
this arrangement, it is made possible to perform feeding of the endless 
belt at a high precision by detecting the marks. 
In the printing apparatus illustrated in FIGS. 1 to 3, the printing 
operation is performed according to the following procedures. 
(A) Step of Printing Marks 
At first, the drive control switch 28 on the operation panel 33 is turned 
over for continuous driving, thereby to drive the endless belt 4, and by 
the positioning mechanism 26, the printing-starting end of the endless 
belt 4 is registered with the standard end of the printing unit 5. 
Subsequently, the switch 28 is turned over for intermittent driving, and an 
intermittent driving switch 52 (see FIG. 1) on the operation panel 33 is 
turned over for digital control. 
At the point of starting printing of marks, a compression fluid is supplied 
to the fluid cylinder 13 and by the operation of the fluid cylinder 13, 
the printing unit 5 is brought down and is stopped at the lowermost 
printing position. In this state, an ink is applied to the surface of the 
belt 4 through the mark-printing stencil to print marks 28' on the surface 
of the belt 4. 
This operation of printing of marks 28' may be performed automatically or 
manually by using a known squeegee mechanism (not shown). When the 
squeegee operation is carried out automatically, the printing unit 5 is 
operated in the following manner as described in detail hereinafter. 
Namely, on confirmation of dropping of the printing unit 5 by a limit 
switch (not shown), the squeegee is driven to perform to scanning 
movement, and on confirmation of completion of the scanning movement of 
the squeegee by a limit switch (not shown), elevation of the printing unit 
5 and initiation of driving of the endless belt are performed. When 
printing of marks is manually conducted, it is possible to drive the belt 
4 intermittently after a certain stoppage time. 
On confirmation of elevation of the printing unit 5 to the uppermost 
position by a limit switch 48 (see FIG. 3), the endless belt 4 is 
intermittently fed by the set feed length (L) according to the program 
described in detail hereinbefore by reference to FIGS. 3 and 4. Every time 
feeding of the belt 4 is stopped, one mark is printed on the belt surface. 
Thus, a great number of detecting marks 28' are formed at intervals L 
along the entire peripheral surface of the belt 4. 
(B) Step of Preparation for Printing 
When the drive control switch 28 on the operation panel 33 is then turned 
over for continuous driving, the endless belt 4 is continuously driven 
through the direct current electric motor 17 and reduction gear 18, and 
simultaneously, the pasting mechanism 20 is operated to apply a paste to 
the belt surface. A material 22 to be printed is fed under an appropriate 
tension onto the endless belt 4 and is applied and stuck to the belt 4 by 
the sticking roll 23. The material 22 is applied to the endless belt 4 
continuously along a necessary printing length which is smaller than one 
travelling circle of the endless belt 4. Stopping of continuous driving of 
the endless belt 4 can be done after it has been confirmed that the 
material 22 to be printed has been applied and stuck to the belt along a 
predetermined length. This confirmation is accomplished by visual 
observation of a worker or by putting off the above-mentioned 
cloth-sticking switch or drive control switch, or the confirmation can be 
automatically accomplished by detecting the rear end of the material 22 
having a predetermined length. The material 22 to be printed may be cut 
into a predetermined length in advance and then fed onto the belt, or the 
material 22 may be cut by an appropriate cutting mechanism (not shown) 
when it is applied onto the belt 4 along a predetermined length. Of 
course, cutting of the material 22 to be printed may be done by a manual 
operation using scissors, a knife or the like. 
According to the printing process of the present invention, since 
application of a paste and sticking of a material 22 to be printed are 
performed while continuously driving the endless belt 4, uneven 
application of the paste or occurrence of uneven tension is not caused. 
Therefore, it is possible to apply and stick a material to be printed onto 
the endless belt under a constant tension stably in a constant state, and 
the printing operation can be accomplished at a very high precision. This 
advantage is especially prominent when the material to be printed is a 
cloth or fabric having a high flexibility. Of course, a tension to be 
applied to a cloth or the like may be adjusted by means for a known feed 
device, or a cloth or the like may be expanded or subjected to a special 
treatment for correcting meandering. Further, the amount applied of a 
paste or the paste-applying width may optionally be adjusted by means of 
the pasting device. 
Then, the endless belt 4 is further driven continuously, and the 
printing-starting end of the material 22 applied onto the endless belt 4 
is registered with the standard end of the printing unit 5 by the 
positioning mechanism 26. 
At initiation of the printing operation, the stencil frame 7 provided with 
the screen 6 having a predetermined stencil pattern is attached to the 
printing unit and a predetermined color paste (not shown) is fed onto the 
screen 6. 
(C) Printing Step 
In the above-mentioned state, the intermittent drive switch 52 is turned 
over for detection of marks, and the printing operation is started. 
On initiation of the printing operation, a compression fluid is supplied to 
the fluid cylinder 13 to actuate the cylinder 13 to bring down the 
printing unit 5 and stop the unit 5 at the printing operation position. 
Then, dropping of the printing unit 5 to the printing operation position 
is confirmed by a limit switch (not shown), and the squeegee driving motor 
11 is operated to drive the squeegee 10 attached to the squeegee carrier 9 
and cause the squeegee 10 to make scanning movement, whereby the printing 
operation is performed. Arrival of the squeegee 10 at the position of 
completion of scanning movement is confirmed by a limit switch (not shown) 
or the like, and the squeegee 10 is stopped or the squeegee 10 and doctor 
(not shown) are changed over or returned. Further, the printing unit 5 is 
lifted up by the fluid cylinder 13. Arrival of the printing unit 5 at the 
uppermost position is confirmed by a limit switch (not shown) or the like, 
and then, driving of the endless belt 4 is started through the motor 17 
and reduction gear 18. 
The intermittent feeding of the endless belt 4 is performed by the control 
mechanism described in detail hereinbefore by reference to FIGS. 3 and 5, 
and the endless belt 4 is stopped precisely at the position where the mark 
28' on the belt is detected by the detecting device 30 and the printing 
operation of the subsequent cycle is carried out in succession. The 
foregoing printing procedures are repeated along the entire length of the 
material 22 applied to the endless belt 4. 
With the intermittent feeding of the endless belt 4, the printed material 
is intermittently fed to the drying operation zone C adjoining to the 
printing operation zone B, and the applied color paste is dried by the 
drying device 15. 
At the point when printing of a first color and drying are completed to the 
terminal end of the material 22 applied to the endless belt, the 
intermittent driving of the endless belt 4 is stopped. Then, the stencil 
frame and squeegee of the printing unit 5 are exchanged for those for 
printing of a second color, and if necessary, the drive control switch 28 
is turned over for continuous driving to register the printing-starting 
end of the material 22 on the endless belt 22 with the standard end of the 
screen 6. 
Then, the drive conrol switch 28 is turned over for intermittent driving 
and the printing operation and drying operation are automatically 
performed even to the terminal end of the material 22 by the intermittent 
feedng of the endless belt in the same manner as in case of printing of 
the first color. 
After completion of printing of the second color, printing of a third 
color, a fourth color and subsequent colors of a predetermined number is 
performed according to the foregoing procedures while circulating the 
endless belt 4 in the state where the material to be printed is applied 
and stuck to the endless belt 4. 
According to the present invention, since printing of a predetermined 
number of colors is performed while circulating the belt 4 having the 
material 22 applied and stuck thereto, color pastes are sequentially 
applied to already dried preceding color pastes, and hence, bleeding or 
mingling of color pastes is prevented and printed products having clear 
colors and sharp contours can always be obtained. Further, since a color 
paste applied to a material to be printed is immediately dried in the 
drying operation zone and a subsequent color paste is applied thereto, 
even if color pastes are applied on a material to be printed in a large 
quantity and a considerable thickness, disfiguration of patterns or 
mingling of colors can be effectively prevented, and multi-color printing 
can be advantageously accomplished with good coloring effects at a high 
printing precision. 
Moreover, according to the preferred embodiments of the present invention, 
by controlling the feeding of the endless belt at the printing step by 
detecting marks printed on the surface of the belt, even if there is 
present a long lapse of time between the point of printing of a first 
color and the point of printing of a last color or the belt is influenced 
by the heat applied at the drying step, a very high feed precision can 
always be maintained and occurrence of such troubles as shear in colors 
can be effectively eliminated. 
(D) Post-Treatment Step 
When printing of a predetermined number of colors is completed, the drive 
control switch 28 is turned over for continuous driving to drive the 
endless belt 4 continuously. 
A printed product 22' is peeled off from the belt 4 below the guide roll 25 
and wound by a winding device (not shown). 
The belt washing mechanism 24 is actuated by the operation of the drive 
control switch 28 to wash the belt 4 with water. 
After water washing and removal of water, the endless belt 4 is subjected 
to the paste-applying operation in the pasting operation zone A in the 
same manner as described above, and a subsequent material to be printed is 
fed onto the paste-applied endless belt 4 by the sticking roller 23. 
In order to enhance the operation efficiency and simplify the operation, it 
is preferred that peeling of the printed product 22', washing and pasting 
of the endless belt 4 and application of the material to be printed be 
sequentially conducted while the endless belt 4 is continuously driven. If 
desired, however, these operations may be conducted separately by 
continuously driving the endless belt independently for these operations 
respectively. 
In the foregoing embodiments, printing of one color is accomplished while 
the endless belt 4 makes one circle of travel. In the present invention, 
however, there may be adopted a method in which a plurality of printing 
units 5 are arranged along the lengthwise direction of the apparatus in 
the printing operation zone and printing of a plurality of colors is 
performed while the belt 4 makes one circle of travel. In this case, the 
endless belt 4 is intermittently driven and rotated at the number of times 
corresponding to the ratio of predetermined print color number/number of 
printing units. This embodiment is especially advantageous for applying a 
plurality of color pastes onto a material to be printed in such 
arrangement that mingling of colors is not substantially caused. 
Moreover, there may be adopted a modification in which a combination of a 
rotary screen and a squeegee is used as the printing unit and the printing 
operation is carried out while continuously driving the endless belt 4. 
This printing operation using a rotary screen is especially advantageous 
for printing of plain cloth, resist printing, discharge printing and 
printing of continuous patterns such as stripe patterns. If necessary, the 
rotary screen may be used in combination with a flat screen for the 
manufacture of printed products. 
In the present invention, printing of marks can be performed simultaneously 
with printing of a first color. In this case, the above-mentioned step (B) 
for preparation is first conducted, and the mark-printing step (A) and the 
step of printing of a first color are then conducted simultaneously while 
driving the belt under digital control. Then, printing of second and 
subsequent colors is carried out in the same manner as described above 
with respect to the printing step (C).