Electrophotographic copying machine

An electrophotographic copying machine of a transfer type has a capability of reproducing an image on a copying paper selectively at a plurality of magnifications and also a capability of feeding copying papers of different sizes. The machine comprises a plurality of timers of a first group operable in common to all of modes of operation of the machine and a plurality of timers of a second group operable during a particular mode of operation, these timers of the first and second groups being sequentially controlled by a microcomputer.

BACKGROUND OF THE INVENTION 
The present invention generally relates to a copying machine and, more 
particularly, to an electrophotographic copying machine of slit exposure 
type having a plurality of sequence modes of operation. 
With recent advancement in integrated circuit technology, low-cost and 
versatile micro-computers have largely been developed and some of them are 
currently employed in machines for use in promotion of the public welfare. 
This trend applies even in the field of copying machine and, in reality, a 
diversity of copying machines are currently available and/or suggested. 
Of the copying machines now available in the commercial market, a copying 
machine utilizing a micro-computer, especially a computerized 
electrophotographic copying machine of either slit exposure type or powder 
image transfer type which had generally been considered complicated in 
sequence of control, has now been developed to such an extent that a 
variety of functions can automatically be controlled accurately and 
efficiently in sequence. This type of computerized, or 
computer-controlled, copying machine involves numerous advantages. 
On the other hand, diversification of the available functions has posed 
numerous problems. In other words, the programmed sequence control 
performed by a micro-computer is the sequence control wherein desired 
control signals are generated when counted values of clock pulses which 
are generated in the micro-computer and which have been counted and/or 
divided to attain programmed numerical data each determined for a 
particular control objective, the programmed numerical data being, 
however, correlated to each other as a whole so that the control 
objectives can be controlled in a predetermined sequence. In view of this, 
where the sequence control by the digital timer is desired to be performed 
in exact and accurate unison with operation of the machine with respect to 
the whole control objectives, not only are timers of different preset 
times one for each of the control objectives required, but also the number 
thereof is many. 
In an electrophotographic copying machine, where it is desired to have a 
number of functional capabilities of, for example, reproducing an image in 
one of a plurality of magnifications and on a copying paper of a size 
selected from a plurality of sizes of papers with which the machine can 
work, and yet, where those functional capabilities are required to be 
controlled in sequence, not only is the available combination thereof 
many, but also a corresponding number of timers are required. In addition 
thereto, a difficulty is involved in carrying out a check as to whether or 
not the sequence control being performed ensures an exact and correct 
operation of the copying machine. Especially, where repeated reproduction 
of the same image on two or more copying papers is to be carried out, this 
should not be a mere repetition of the sequence that is performed during 
the reproduction of an image on one copying paper and, in order to 
increase the copying speed, measures must be taken to enable the machine 
to be ready for the next succeeding reproduction of the image half-way 
during the sequence for the preceding reproduction of the image being 
currently performed. Heretofore, in order for the next succeeding copying 
operation, specifically the scanning of the image to be reproduced, to be 
initiated during the repeated copying operation of the machine, a complete 
return of the optical scanner to the original position after having been 
moved to the opposite, scanned position has generally been required and so 
is evidenced by the fact that a timing signal generated upon the complete 
return of the optical scanner to the original position has long been 
utilized. 
However, with the diversification of the sequence modes, it has been found 
the timing at which the optical scanner returns to the original position 
is too early to provide a starting point at which the next succeeding 
copying operation is initiated in view of the position of a copying paper 
being supplied and also the operation of a paper jamming detector. In 
order to eliminate this inconvenience, it may be possible to use a timer 
of a preset time long enough to provide a delay before the start of the 
next succeeding copying operation so that the machine can be programmed so 
as to initiate the next succeeding copying operation after the lapse of 
the preset time of the timer. However, where the timer of the type 
referred to above is actually employed, the stand-by time during which the 
machine is held standstill is unnecessarily prolonged, resulting in a 
relatively large loss of time and also hampering the high speed operation 
of the copying machine. 
Although the use of a timer for multi-copying for each sequence mode can be 
contemplated to eliminate the above described disadvantages, this in turn 
results in the increased number of timers employed. Yet, in the case where 
the timer for multi-copying is set at the mode at which the next 
succeeding copying operation can be initiated immediately after the 
complete return of the optical scanner to the original position, it is in 
practice difficult to coincide the timing at which the timing signal is to 
be generated from the timer with the timing at which the optical scanner 
completes its return movement to the original position. Even in this case, 
the timer must have a sufficiently long preset time and a loss of time is 
involved accordingly. 
SUMMARY OF THE INVENTION 
The present invention has been developed with a view to substantially 
eliminating the above described disadvantages and inconveniences and has 
for its essential object to provide an improved electrophotographic 
copying machine having a plurality of sequence modes of operation wherein 
a plurality of timers are employed so as to operate in timmed relation to 
each other to enable an efficient continued copying operation of the 
machine. 
Another object of the present invention is to provide an improved 
electrophotographic copying machine of the type referred to above, which 
is reliable in performance and employs a minimized number of component 
parts. 
The present invention is directed to an electrophotographic copying machine 
of transfer type which comprises an electrophotographic member supported 
for rotation in one direction, a support for the support of an original to 
be copied thereon, a scanning means supported for reciprocal movement 
between start and scanned positions relative to the original support to 
scan the original on the support, means for designating one of a plurality 
of image forming conditions for determing a particular mode of operation, 
means for driving the scanning means, means for detecting that the 
scanning means is held at the start position, means for transporting a 
copying paper, and control means operatively correlated with at least said 
scanning means, said designating means, said driving means, said detecting 
means and said transferring means for generating a control signal during 
the mode of operation based on the image forming condition designated by 
the designating means. 
The objects of the present invention discussed above can be accomplished by 
providing the electrophotographic copying machine of the above described 
construction with a first group of timer means utilizable in common to all 
of the modes irrespective of said particular mode of operation, means for 
determining the particular mode of operation on the basis of an output 
signal generated from the designating means, a second group of timer means 
having their preset times determined in correspondence to the mode of 
operation determined by the determining means, and a processing means for 
generating, in response to the lapse of the preset time of each timer 
means of the first and second groups, a control signal necessary to 
control said scanning means, said driving means and said transferring 
means and also for performing a process incident to completion of one 
copying operation when both of the condition in which the preset time of 
one particular timer means of the second group has been passed and the 
condition in which the detecting means has detected the complete return of 
the scanning means to the start position after having been moved to the 
scanned position are fulfilled. 
By constructing the electrophotographic copying machine in the manner 
described above, not only can the copying operation be carried out 
efficiently, but also a plurality of copies can be made in rapid 
repetitive succession.

DETAILED DESCRIPTION OF THE EMBODIMENT 
Before the description of the present invention proceeds, it is to be noted 
that like parts are designated by like reference numerals throughout the 
accompanying drawings. It is also to be noted that, for facilitating an 
easy and better understanding of the present invention, the latter will be 
described under separate headings. 
Copying Machine and Operation 
Referring to FIG. 1, an electrophotographic copying machine to which the 
present invention is applied comprises an electrophotographic member which 
is shown in the form of a photoreceptor drum 1 made of metal such as 
aluminum and having its outer peripheral surface deposited, either by 
coating or by vapor deposition, with a photoconductive layer of, for 
example, selenium. This photoreceptor drum 1 is supported within the 
machine housing for rotation in one direction, for example, in a 
counterclockwise direction as viewed in FIG. 1, in any known manner. 
Around the photoreceptor drum 1, there are arranged in a given order, an 
electrostatic charger 2, an exposure filter 3, a side eraser 4, a 
developing unit 5, a transfer charger 6, an AC eraser 7 for facilitating 
separation of a copying paper from the photoreceptor drum 1, an air nozzle 
assembly 8 for separating the copying paper from the photoreceptor drum 1, 
an AC eraser 9, a cleaning unit 10 and an eraser lamp 11, each of these 
components 2 to 11 being so arranged as to work on the photoreceptor drum 
1 as it rotates in the counterclockwise direction. 
The outer peripheral surface of the photoreceptor drum 1 after residual 
powder and residual electrostatic charge have already been removed in 
seccession by the cleaning unit 10 and the eraser lamp 11 is uniformly 
charged with an electrostatic charge by the charger 2 and is subsequently 
exposed through the filter 3 to an optical image of an original indicia to 
be reproduced, which original is scanned by an optical scanning system as 
will be described later. By this way, an electrostatic latent image 
complemental in shape to the image of the original can be formed on the 
photoreceptor drum 1. 
The side eraser 4 is operable to dissipate an unwanted portion of 
electrostatic charge, deposited on an end portion of the photoreceptor 
drum, when the machine is set to operate so as to reproduce the original 
image on a copying paper on a reduced scale and, for this purpose, this 
side eraser 4 is operatively associated with a magnification selector. 
The electrostatic latent image so formed on the photoreceptor drum 1 in the 
manner as described above is developed by the developing unit 5 into a 
visible powder image, which powder image is subsequently transferred onto 
the copying paper 12 which has been transported from a paper feed 
mechanism, as will be described later, in synchronism with the rotation of 
the photoreceptor drum 1. Shortly before the transfer of the powder image 
onto the copying paper 12, the latter is electrostatically charged by the 
transfer charger 6 so that the powder image can be attracted onto the 
copying paper as it contacts the photoreceptor drum 1 being rotated. The 
electrostatic attractive force developed between the copying paper 12 and 
the photoreceptor drum 1 during the transfer of the powder image onto the 
copying paper 12 is removed by the AC eraser 7 and, thereafter, the 
copying paper 12 bearing the transferred powder image is separated from 
the photoreceptor drum 1 by the aid of air jets blown off from the air 
nozzle asssembly 8. The copying paper 12 so separated from the 
photoreceptor drum 1 is then transported by a conveyance belt 13 towards a 
fixing device whereat the powder image on the copying paper 12 is fixed by 
the application of both heat and pressure. The copying paper having the 
powder image fixed thereon is finally ejected out of the machine housing 
and onto a storage tray 16 by means of an ejecting roller assembly 15. 
During the continued rotation of the photoreceptor drum 1 and after the 
copying paper bearing the powder image has been separated from the 
photoreceptor drum 1 in the manner described above, the electrostatic 
charge is again erased by the AC eraser 9, followed by the cleaning of the 
photoreceptor drum 1 which is performed by the cleaning unit 10 to remove 
the residual powder. Thereafter and shortly before completion of one 
complete rotation of the photoreceptor drum 1, rays of light are radiated 
by the eraser lamp 11 onto the photoreceptor drum 1 to completely remove 
the residual electrostatic charge in readiness for the next succeeding 
reproduction. 
While the details of the paper feed mechanism will be described later, the 
copying machine to which the present invention is applied has upper and 
lower paper supply units one positioned above the other, each of the paper 
supply units being adapted to receive a paper cassette containing copying 
papers in stacked state. The stacked copying papers 12 in the respective 
paper cassettes loaded in the paper supply units are held in contact with 
associated feed roller R1 and R2 which are selectively rotated one at a 
time to supply the copying papers 12 from the upper and lower cassettes C1 
and C2. It is to be noted that, in FIG. 1, the upper cassette C1 is shown 
as containing the copying paper of small size whereas the lower cassette 
C1 though shown as empty is adapted to contain the copying papers of a 
size larger than that in the cassette C1. 
Where each copying paper is supplied from the upper cassette C1, the 
copying paper so supplied is temporarily held standstill by a timing 
roller 20 which is driven in response to a synchronizing signal, necessary 
to synchronize the paper feed with the rotation of the photoreceptor drum 
1, to feed the copying paper towards a transfer station whereby the powder 
image on the photoreceptor drum 1 is transferred onto such copying paper. 
On the other hand, where each copying paper is supplied from the lower 
cassette C2, the supply of the copying paper is initiated earlier than 
that from the upper cassette C1 and the copying paper so supplied is held 
standstill by an intermediate feed roller assembly 25. This intermediate 
roller assembly 25 is driven in response to the application of a suitable 
timing signal so as to feed the copying paper towards the timing roller 20 
whereby the copying paper is again held stationary until the synchronizing 
signal is applied to a drive for the timing roller 20. 
Hereinafter, the details of each of the operating mechanisms of the copying 
machine and the sequence of operation thereof will be described. 
Paper Feed Mechanism: 
As hereinbefore described, the copying machine to which the present 
invention is applied can be loaded with the two cassettes one above the 
other. However, since paper feed mechanisms one for each paper cassettes 
C1 and C2 are of identical construction, only one of them will be 
described in details for the sake of bravity. 
Referring to FIG. 2 wherein the paper feed roller assembly is schematically 
shown, the feed roller R is rigidly mounted on a shaft 30 for rotation 
together therewith at a position substantially intermediate of the length 
of the shaft 30, which shaft 30 is adapted to receive a rotary drive 
necessary to rotate the roller R through a clutch unit of a construction 
as will be described later. A generally U-shaped lever 31 is supported at 
31a for pivotal movement in a plane perpendicular to the shaft 30 and is 
normally biased counterclockwise as viewed in FIG. 2 by a spring 31b. The 
lever 31 has a dispatching stand 32 rigidly mounted thereon in alignment 
with the feed roller R and protruding therefrom towards the roller R. This 
dispatching stand 32 has a friction member 32a lined on one surface of the 
dispatch stand 32 facing the roller R1 which friction member 32a is 
normally held in contact with the roller R because of the lever 31 being 
biased counterclockwise by the spring 31b. The roller R is cooperable with 
the dispatching stand 32 in such a manner that the copying papers can be 
drawn out of the associated paper cassette one at a time in succession and 
then fed towards the processing station through a nipping area between the 
roller R and the friction member 32a during rotation of the roller R. 
The lever 31 can be pivoted clockwise against the spring 31b to disengage 
the dispatching stand 32 from the roller R in response to the removal of 
the paper cassette C from an associated cassette holder 40. For this 
purpose, as best shown in FIGS. 3(a) and 3(b), a release mechanism is 
employed, which release mechanism comprises a release lever 33 supported 
at a substantially intermediate portion thereof for pivotal movement 
between engaged and disengaged positions and a torsion spring 34 for 
biasing the release lever 33 to assume the disengaged position as shown in 
FIG. 3(b), one end 33a of said release lever 33 being normally engaged to 
the lever 31. This release mechanism is so designed that, when the paper 
cassette C is loaded into the cassette holder 40, the release lever 33 is 
pivoted from the disengaged position as shown in FIG. 3(b) towards the 
engaged position as shown in FIG. 3(a) against the torsion spring 34 with 
the other end of said release lever 33 held in contact with the paper 
cassette being loaded into the cassette holder 40, and when the paper 
cassette is removed from the cassette holder 40, the release lever 33 is 
pivoted from the engaged position towards the disengaged position by the 
action of the torsion spring 34 with the end 31a pressing the lever 31 to 
pivot clockwise against the spring 31b. Therefore, it is clear that, as 
the cassette C is removed from the cassette holder 40, the dispatching 
stand 32 is disengaged from the feed roller R as best shown in FIG. 3(b) 
to allow the copying paper, which would be held in a position sandwitched 
between the feed roller R and the dispatching stand 32, to be removed 
together with the removal of the cassette C from the holder 40. This is 
advantageous in that there is no possibility of the copying paper being 
left unremoved from the machine during the replacement or replenishment of 
the paper cassette. 
The details of the clutch unit are best shown in FIG. 4. This clutch unit 
comprises a clutch drum 41 rigidly mounted on the shaft 30 for rotation 
together therewith and also comprises a brake drum 42, a kick spring 43 
and a sprocket wheel 44, all mounted on the shaft 30 for rotation 
independently of the rotation of the shaft 30. The kick spring 43 is so 
mounted on the shaft 30 as to selectively fasten the clutch drum 41 
together with a boss portion of the sprocket wheel 44 and unfasten or 
release it therefrom and is positioned inside the brake drum 41 in such a 
manner that one end 43a is engaged in a notch 42a in the brake drum 42. 
The sprocket wheel 44 is operatively associated with a solenoid unit SL1 
through a clutch lever 45. The clutch lever 45 is supported at one end by 
means of a pin 46 for pivotal movement between operative and inoperative 
positions and has a pawl portion 45a defined at the opposite end thereof 
remote from the pin 46 as best shown in FIGS. 5(a) and 5(b). The brake 
drum 42 has its outer peripheral surface formed with a plurality of 
circumferentially equally spaced ratchet teeth 42b with which the pawl 
portion 45a of the clutch lever 45 is engaged one at a time during 
deenergization of the solenoid unit SL1 as shown in FIG. 5(a) to interrupt 
rotation of the brake drum 42. When the rotation of the brake drum 42 is 
interrupted in this way with the pawl portion 45a of the clutch lever 45 
engaged to one of the ratchet teeth 42b as shown in FIG. 5(a), the kick 
spring 43 is loosened thereby interrupting the transmission of a drive 
force of the sprocket wheel 44 to the shaft 30. 
On the other hand, when and so long as the solenoid unit SL1 is energized 
with its plunger retracted as shown in FIG. 5(b), the pawl portion 45a of 
the clutch lever 45 is disengaged from any one of the ratchet teeth 42b to 
allow the kick spring 43 to fasten the boss portion of the sprocket wheel 
44 and the clutch drum 41 together, resulting in the transmission of the 
drive force of the sprocket wheel 44 to the shaft 40 to rotate the latter. 
While the present invention utilizes the clutch unit of the type employing 
the kick spring, the prior art has long employed a one-way, one-revolution 
clutch mechanism of a construction wherein the brake drum 42 has only a 
ratchet tooth defined thereon, which ratchet tooth is engaged by a pawl 
member, coupled to a solenoid unit or any other actuator, each time the 
brake drum 41 completes its 360.degree. rotation. On the other hand, the 
paper feed roller R is so operable as to urge a stack of copying paper 
upward from bottom and also to feed each copying paper in frictional 
contact therewith when it is rotated. In view of this, if the diameter of 
the paper feed roller R is too small, the surface area of contact of the 
roller R to each copying paper is reduced with consequent reduction in 
both paper feeding capability and effect and, therefore, the timing at 
which the copying papers are fed in succession will be adversely affected. 
If the diameter of the roller R is made too large with a view to 
substantially eliminating the disadvantages and inconveniences caused by 
the use of a roller R of reduced diameter, plural copying papers tend to 
be supplied at one time and/or the copying paper fed and temporarily held 
standstill at either the intermediate roller assembly or the timing roller 
tends to warp or loop to such an extent that it results in jamming of the 
copying papers inside the machine housing or wrinkling the copying paper. 
Accordingly, it has long been considered extremely difficult to determine 
a suitable diameter of the paper feed roller R. 
In view of the above, in the present invention, the brake drum 42 is so 
designed as to have a plurality of ratchet teeth 42b as described 
hereinbefore and, at the same time, the paper feed roller R of a 
relatively large diameter is employed to increase the paper feeding 
capability. Specifically, the brake drum 42 having the ratchet teeth 42b 
is so designed that the pawl portion 45a of the clutch lever 45 can be 
engaged to any one of the ratchet teeth 42b before the brake drum 42 
completes its 360.degree. rotation, thereby avoiding any possible feed of 
plural copying papers at one time. For this purpose, in the embodiment of 
the present invention so far illustrated, the brake drum 41 is formed with 
six ratchet teeth 42b on the outer peripheral surface thereof in 
circumferentially equally spaced relation to each other on the one hand 
and, on the other hand, the solenoid unit SL1 being energized is so 
designed as to be deenergized each time the brake drum 42 undergoes 4/6 to 
5/6 of one complete rotation, the engagement of the pawl portion 45a of 
the clutch lever 45 to one of the ratchet teeth 42b stops the brake drum 
42 when the brake drum 42 completes 5/6 of one complete rotation. It is, 
however, to be noted that the number of the ratchet teeth 42b and the time 
at which the engagement of the pawl portion 45a to one of the ratchet 
teeth 42b takes place actually may be determined in consideration of the 
diameter of the paper feed roller R, the pressing force of the stacked 
copying papers and the distance to the timing roller. 
A manual paper feed mechanism employed in the machine embodying the present 
invention is shown in FIG. 6. Where a copying paper is desired to be 
manually supplied, a manual feed table C3 should be mounted and inserted 
in the machine at a position above the upper supply unit shown in FIG. 1. 
The feed table C3 has a magnet M1 rigidly secured to a front lateral 
portion thereof, which magnet M1 is operatively associated with a detector 
switch SW1. This switch SW1 detects the presence of the magnet M1, when 
the feed table C3 is inserted in the machine in readiness for the manual 
paper feed, not only to set the machine to work under a sequence control 
mode for manual paper feed but also to energize an indicator (not shown) 
for indicating to that effect. The feed table C3 has an elongated roller 
support 48 having one end pivotally connected at 48a to the table C3 and 
the other end 48b protruding outwards therefrom. This support 48 has a 
substantially intermediate portion on which a roller 49 is rotatably 
mounted in alignment with and immediately below the paper feed roller R. A 
connecting rod 51 having one end rigidly connected to an angle member 50 
for pivoting the support 48 so as to engage and disengage the roller 49 to 
and from the roller R is rotatable supported by a machine framework and is 
normally biased counterclockwise by a torsion spring 52. The other end of 
the connecting rod 51 remote from the angle member 50 is coupled to a 
plunger of a solenoid unit SL2 by means of an L-shaped relay lever 53 and 
an intermediate lever 54. 
In this construction, when a copying paper is manually inserted in between 
the rollers R and 49, a paper feed detector as will be described later is 
activated to energize the solenoid unit SL2 with the plunger consequently 
retracted. The retraction of the plunger of the solenoid unit SL2 results 
in the pivotal movement of the roller support 48 in a direction with the 
roller 49 engaged to the roller R to sandwitch the copying paper between 
the rollers R and 49. Simultaneously therewith, the clutch unit of the 
construction described hereinbefore is operated to cause the roller R to 
be driven to feed the copying paper into the machine. As the trailing edge 
of the copying paper so fed by the rotation of the roller R in cooperation 
with the roller 49 is moved past the paper feed detector, the solenoid 
unit SL2 is deenergized with the plunger thereof consequently projected, 
so that the roller support 48 is pivoted in the opposite direction with 
the roller 49 disengaged from the roller R. It is to be noted that, when 
the plunger of the solenoid unit SL2 is projected in a direction counter 
to the direction shown by the arrow in FIG. 6, one end of the relay lever 
53 remote from the intermediate lever 54, which lever 53 is rotatable 
together with the connecting rod 51, is engaged to a stopper 55 to prevent 
further rotation of the relay lever 53 and, hence, the connecting rod 51. 
This stopper 55 is so adjustably secured to the machine framework that 
both the pressure of contact of the roller 49 to the roller R and the 
spacing between the rollers R and 49 which is established during 
disengagement of the roller 49 from the roller R can be adjusted. 
The paper feed detector is best shown in FIGS. 7(a) and 7(b) and comprises 
an ultrasonic wave generator S and a wave sensor D which are arranged on 
respective sides of the path of travel of the copying paper. This paper 
feed detector is so designed that, when and so long as the wave sensor D 
detects an ultrasonic wave generated from the generator S as shown in FIG. 
7(b), the sensor D can provide an electric signal indicative of the 
absense of the copying paper. 
Reference numeral 35 shown particularly in FIG. 2 represents a tuning fork 
secured to the lever 31 for absorbing, and thereby minimizing, noises 
which would be generated as a result of friction between the roller R and 
the dispatching stand 32. 
In the present invention, the stacked copying papers with the cassette C 
are so designed as to be upwardly shifted to contact the roller R by an 
upwardly biased bottom plate operatively placed at the bottom of the 
cassette as the weight of the stacked copying papers reduces as a result 
of successive feed of the papers one at a time out of the cassette into 
the machine. This arrangement is advantageous in that the pressure of 
contact of the copying papers to the paper feed roller R can be maintained 
at a constant value irrespective of the reduction of the weight of the 
copying papers which would take place as the copying papers are 
successively consumed. In addition thereto, arrangement is made such that 
the upward shifting force exerted by the bottom plate on the stack of the 
copying papers can be adjustable depending on the size of the stacked 
copying papers in a particular paper cassette. Since the details of the 
above described arrangement are disclosed in the Japanese Patent 
Application No. 54-26544 filed in 1979 in Japan, by the same assignee of 
the present invention, they will not be described herein for the sake of 
brevity. 
Paper Separating Mechanism: 
In the present invention, as a means for separating the copying paper from 
the photoreceptor drum 1 shortly after the powder image has been 
transferred from the drum 1 onto such copying paper, a row of air jets 
blown from a nozzle assembly 8 is utilized. This will now be described 
with particular reference to FIGS. 8 and 9. 
The nozzle assembly 8 is shown as comprising a pipe 60 having a row of 
perforations 61 defined therein in a direction lengthwise thereof and 
supported in position in parallel relation to, and also in the vicinity 
of, the photoreceptor drum 1, the position of said pipe 60 being however 
adjustable relative to the photoreceptor drum 1. While one end of the pipe 
60 is closed, the other end of the same pipe 60 is fluid-connected to an 
air pump 63 through a flexible hose 62. The air pump 63 is of a 
construction, as best shown in FIGS. 9(a) and 9(b), comprising a hollow 
cylinder 63a having a piston 63b housed therein for reciprocal movement in 
an axial direction of the cylinder 63a with its outer periphery held 
slidingly in contact with the inner peripheral wall of the cylinder 63a, 
said piston 63b being in turn connected to an actuating mechanism 64 by 
means of a connecting rod 65. A free end of the connecting rod 65 remote 
from the piston 63b extends through a slot 66a defined in a charge lever 
66 and is then pivotally connected to a link 67 connecting a pin 68 and a 
charging shaft 69 together, which pin 68 is supported in slots 66b, 
defined in respective lateral opposed walls of the charge lever 66, for 
movement in a lengthwise direction along the slots 66b. The charging shaft 
69 is rotatably supported in position by the charge lever 66 and extends 
in parallel relation to the pin 68. The charge lever 66 is in turn 
pivotally supported by a pin 70 on the machine framework and is normally 
biased counterclockwise about the pin 70 by the action of a spring 72 with 
the charging shaft 69 consequently held in contact with a cam wheel 71, 
whereby when the cam wheel 71 rotated in a manner as will be described 
subsequently, the shaft 69 undergoes a rocking motion about the pin 70 to 
reciprocately move the piston 63b inside the cylinder 63a. The charge cam 
wheel 71 is mounted through a clutch (not shown) on a drive shaft 73 
having a driven gear 74 rigidly mounted thereon and adapted to be driven 
by an endless transmission chain 75. 
The cam wheel 71 is normally held in such a condition as shown in FIG. 
9(a). In this condition of FIG. 9(a), the cam wheel 71 is in position to 
urge the charge lever 66 in a direction counterclockwise about the pin 70 
with the piston 63b displaced to the left as viewed in FIG. 9(a). At a 
predeterminded timing subsequent to the start of the copying operation, 
the clutch is coupled to rotate the cam wheel 71 in a direction 
counterclockwise about the shaft 73, permitting the charge lever 66 to 
pivot clockwise about the pin 70 as biased by the spring 72 with the 
charging shaft 69 slidingly contacting and following the contour of the 
cam wheel 71. However, shortly after the cam wheel 71 has been rotated 
counterclockwise, the lever 66 is rapidly pivoted clockwise by the action 
of the spring 72 with the charging shaft 69 falling in a step defined in 
the cam wheel 71 and, as a consequence thereof, the connecting rod 65 
rapidly pulls the piston 63b in a direction towards the right as shown. 
The rapid displacement of the piston 63 b to the right as shown in FIG. 
9(b) permits air contained in the cylinder 63a to be discharged to the 
pipe 60 through the hose 62, with the pipe 60 producing air jets through 
the perforations 61. The continued rotation of the cam wheel 71 in the 
counterclockwise direction results in the return of the piston 63b to the 
left as shown in FIG. 9(a) and is brought to a halt when such a condition 
as shown in FIG. 9(a) is established. 
The air jets so produced from the pipe 60 are applied in between the 
photoreceptor drum 1 and the copying paper to separate the latter from the 
drum 1 and being then rotated. 
Optical Scanning System: 
The details of the optical scanning system are shown in FIGS. 10 to 14. 
The original to be copied, which has been placed on an original support 80, 
is scanned by a scanner 82, including an illuminating lamp 81 and a first 
reflective mirror m.sub.1, as the scanner is moved towards the left as 
viewed in FIG. 10 along a guide rail 83. Rays of light reflected from the 
original and, therefore, carrying the image of the original are reflected 
by the first reflective mirror m.sub.1 towards a second reflective mirror 
m.sub.2 movable along the guide rail 83 in pursuit of the scanner 82, 
which second reflective mirror m.sub.2 reflects the light rays towards a 
third reflective mirror m.sub.3 through a lens unit L. The light rays are, 
after having been reflected by the third reflective mirror m.sub.3 and 
then by a fourth reflective mirror m.sub.4, projected onto the 
photoreceptor drum 1. It is to be noted that the scanning velocity V1 is 
expressed by the equation, V1=V/M, wherein V represents the speed of 
transportation of any one of the photoreceptor drum 1 and the copying 
paper and M represents a magnification power of the lens unit L while the 
second reflective mirror m.sub.2 is moved in pursuit of the scanner 82 at 
a speed V2 which is expressed by the equation, V2=V/2M. 
As best shown in FIG. 11, the scanner 82 has the lamp 81 stationarily 
mounted thereon and is supported by a holder 82a mounted on the guide rail 
83 for movement therealong. Although the second reflective mirror m.sub.2 
is supported by a holder 84 slidingly movable along the guide rail 83, two 
supporting portions 84a of the holder 84 are located on respective sides 
of the scanner 82 and spaced from each other a distance sufficient to 
prevent the movement of the scanner 82 from being hampered. The third and 
fourth reflective mirrors m.sub.3 and m.sub.4 are mounted on the same 
holder 85 which is adjustably supported by the machine framework. The lens 
unit L is fixedly mounted on a lens holder 86 mounted on a guide rail 87 
for movement therealong, a force necessary to move the lens holder 86 
along the guide rail 87 being transmitted thereto by means of a cable 88. 
The lens holder 86 carries a magnet 89 rigidly secured thereto, which 
magnet 89 is operatively associated with reed switches SW2, SW3 and SW4. 
These reed switches SW2, SW3 and SW4 are so arranged along the path of 
movement of the lens holder 86 as to be actuated by the magnet 89 one at a 
time when the lens unit L is set to any one of different magnifications. 
The cable 88 is connected to the lens holder 86 by means of a tension 
spring 94 and, while it is turned around idler pulleys 90, 91, 92 and 93, 
is adapted to be driven by a drive pulley (not shown), operatively coupled 
to a drive motor 95, to move the lens unit L selectively to any one of the 
positions of the different copying magnifications, which positions are 
respectively represented by the positions of the reed switches SW2, SW3 
and SW4. The movement of the lens unit L to any one of the magnification 
positions is carried out by driving the motor 95 in either direction by 
the utilization of a signal which is generated incident to selection of 
one of the copying magnifications to which the image of the original is 
desired to be enlarged or reduced, the drive of the motor 95 being also 
transmitted through an endless belt 96 to a cam wheel 98 to adjust the 
position of both of the third and fourth reflective mirrors m.sub.3 and 
m.sub.4 so that change in conjugate distance resulting from the movement 
of the lens unit L can be compensated for. The details of a position 
adjusting mechanism including the cam wheel 98 will be described later 
with particular reference to FIGS. 13 and 14. A drive mechanism for the 
scanner 82 and the second reflective mirror m.sub.2 comprises first, 
second and third scanner clutches 101, 102 and 103, a return clutch 104, a 
drive pulley 105 and a cable 108 turned around the drive pulley 105. A 
drive during the scanning is transmitted to gears (not shown) fasten onto 
respective shafts of the second and third clutches 102 and 103 through 
timing belts (not shown), the driving force thereof actuating one of the 
scanner clutches, corresponding to the selected copying magnification, to 
drive the pulley 105 at a predetermined velocity. This predetermined 
driving velocity is determined by a gear ratio so selected as to cause the 
scanner 82 and the first reflective mirrors can be moved at the respective 
velocities of V/M and V/2M described hereinbefore. Reference numeral 106 
represents a braking device operable during the scanning to impose a 
suitable load on the drive system to prevent the moving velocity from 
being adversely affected by mechanical noises. 
The return clutch 104 is adapted to receive a driving force transmitted 
through a timing belt 107 from a motor (not shown) for the developing 
unit. This arrangement is employed for the purpose of avoiding any 
possibility that, since the velocity during the return movement is so 
selected as to be higher than that during the scanning, the return will be 
initiated during the image forming operation with the increased load 
consequently imposed on the photoreceptor drum to such an extent as to 
result in fluctuation in the speed of rotation of the photoreceptor drum 1 
if the driving force from a main motor for driving the photoreceptor drum 
1, which is utilized during the scanning, is also used even during the 
return movement. 
The cable 108 turned around the drive pulley 105 is secured to the holder 
82a for the scanner 82 through a fixed pulley 109 and is connected at one 
end to the machine framework after having been turned around a movable 
pulley 110 carried by the holder 84 for the second reflective mirror 
m.sub.2 and at the other end to the machine framework after having been 
turned around a fixed pulley 111, a fixed pulley 112, the movable pulley 
110 and a fixed pulley 113. By this arrangement, the second reflective 
mirror m.sub.2 can be moved at the velocity of V/2M while the scanner 81 
is moved at the velocity of V/M. 
In the construction shown in FIG. 11, reference numeral 111 represents a 
shock absorber operable to cushion the optical scanning system during the 
return movement. The first, second and third clutches are provided in 
association with, for example, .times.1, .times.0.7 and .times.0.8 
magnifications, respectively. 
In FIG. 12, various control reed switches SW6, SW7, SW8, SW9 and SW10 and 
their associated actuating mechanism, which are necessary to achieve a 
synchronism between the copying paper being transported and the scanning 
of the original during the movement of the optical scanning system, are 
illustrated. A magnet 115 effective to selectively actuate the reed 
switches SW6 to SW10 one at a time as it is moved past these reed switches 
SW6 to SW10 is carried rigidly by a carrier projection 82b protruding from 
the holder 82a for the scanner 82. Specifically, the reed switch SW6 is 
actuated by the magnet 115 when and so long as the optical scanning system 
is held at a start position; the reed switch SW7 is actuated by the magnet 
115 to generate a reference signal which is utilized both for generating 
operating reference signals for operating a group of timers for sequence 
control as will be described later and for detecting an abnormal operating 
condition of the optical scanning system; and the reed switches SW8, SW9 
and SW10 are timing switches which are selectively utilized when the lens 
unit L is held at the .times.1, .times.0.8 and .times.0.7 magnification 
positions, respectively. It is to be noted that, in place of the reed 
switches SW6 to SW10, either microswitches or optical sensors may be 
employed. 
The position adjusting mechanism for both of the third and fourth 
reflective mirrors m.sub.3 and m.sub.4 will now be described with 
reference to FIGS. 13 and 14. This adjusting mechanism is generally 
identified by 97 and is provided for adjusting the position of both of the 
reflective mirrors m.sub.3 and m.sub.4 to compensate for variation in 
optical conjugate distance in an optical path between the original and the 
photoreceptor drum 1 which takes place when the lens unit L is moved to 
any one of the .times.1, .times.0.8 and .times.0.7 magnification 
positions. 
The cam wheel 98 forming a part of the adjusting mechanism 97 and referred 
to hereinbefore is rotated by the motor 95 for moving the lens unit L, the 
angular distance through which said cam wheel 98 is rotated corresponds to 
the distance over which the lens unit L is moved to any one of the 
magnification positions. For this purpose, the cam wheel 98 is so designed 
as to have three cam faces A, B and C to which a roller 120 as will be 
described later is rollingly engaged when the lens unit L is moved 
selectively to the .times.1, .times.0.8 and .times.0.7 magnification 
positions, respectively. 
The mechanism 97 also comprises a mirror adjusting lever 121 positioned 
adjacent to the cam wheel 98 and supported at an upper end for pivotal 
movement, said lever 121 carrying first and second levers 122 and 123 
mounted thereon for fine adjustment. The roller 120 referred to above and 
engaged to the cam wheel 98 is provided at respective tip portions 122a 
and 123a of the first and second levers 122 and 123. The free end of the 
mirror adjusting lever 121 opposite to the point of pivot thereof is bent 
frontwardly with respect to the plane of the drawing of FIG. 13 to define 
a flange 121a, to which flange 121a a holder roller 85a rigidly secured to 
the holder 85 for the third and fourth reflective mirrors m.sub.3 and 
m.sub.4 is engaged. Since the holder 85 is normally biased towards the 
left as viewed in FIG. 13 by the action of a biasing spring (not shown), 
the roller 85a is constantly engaged to the flange 121a of the adjusting 
lever 121 so that, by changing the position of the flange 121a, the 
position of the third and fourth reflective mirrors m.sub.3 and m.sub.4 
can be adjusted. 
FIG. 13 illustrates the cam wheel 98 held in a position corresponding to 
the maximum available magnification, that is, .times.1 magnification, in 
which condition the cam face A is held in face-to-face relation to the 
roller 120. In this condition, the roller 120 is not engaged to the cam 
face A because the adjusting lever 121 is engaged against a stopper 124. 
However, when the cam wheel 98 is rotated to bring the cam face B in 
position to confront with the roller 120 incident to the change of 
magnification, since the cam face B is in a form protruding frontwardly 
with respect to the plane of the drawing of FIG. 3, the cam face B engages 
the roller 120, which is carried by the tip portion 122a of the first 
lever 122 protruding frontwardly in a manner similar to the cam face B, to 
push the roller 120 in such a manner as to cause the adjusting lever 121 
to pivot counterclockwise as shown in FIG. 14(a). By this counterclockwise 
movement of the lever 121, the holder roller 85a is displaced towards the 
right thereby to change the position of the mirrors m.sub.3 and m.sub.4. 
It is to be noted that, since the levers 122 and 123 are finely adjustably 
mounted on the lever 121 by means of respective adjustment bolts 125 and 
126, fine adjustment of one or both of the levers 122 and 123 results in 
focusing adjustment of the lens unit L at each of the magnification 
positions of said lens unit L. 
When the cam wheel 98 is further rotated until the roller 120 is brought 
into engagement with the cam face C as shown in FIG. 14(b), the roller 20 
so engaged to the cam face C is the one carried by the tip portion 123a of 
the second lever 123. Even in this condition, the adjusting lever 121 is 
pivoted in a manner similar to that described with reference to FIG. 
14(a). 
As hereinbefore described, the cam faces A, B and C are so designed and so 
shaped as to adjust the conjugate distance when the lens unit L is set 
selectively at the .times.1, .times.0.7 and .times.0.8 magnification 
positions. 
Control System 
The copying machine embodying the present invention utilizes the 
micro-computer for controlling the sequence of operation thereof. 
Hereinafter, the control scheme and controls of the component parts of the 
machine, performed by the micro-computer, will be discussed. 
[Control Scheme: Basic Concept] 
As shown in FIG. 15, the micro-computer MC basically comprises a central 
processing unit CPU including an accumulator ACC, a control and command 
decoder DE, a program counter PC, stack pointer SP composed of a group of 
registors, a timer T, and an arithmetic-logic unit ALU, a random access 
memory RAM composed of semiconductor memories, a read-only memory ROM, and 
an input/output interface I/O for receiving signals applied from and 
applying control signals to, external circuit components. Input signals to 
be received by the micro-computer are fed thereto through the input/output 
interface I/O and, likewise, control signals generated from the 
micro-computer MC are fed to external circuit components and/or 
electrically operated component parts through the input/output interface 
I/O. 
So far as the micro-computer MC is involved, since a variety of types are 
currently available, any one of them can be utilized in the present 
invention if it is selected as serviceable for the intended purpose and, 
therefore, the details thereof will not herein be described. 
The basic concept of the sequence control performed by the micro-computer 
MC in the copying machine embodying the present invention, as well as 
problems and their solutions will now be discussed. 
(a) Timer in Micro-computer 
The micro-computer MC utilizes a clock pulse generator PG1 having a quartz 
oscillator, said clock pulse generator PG1 generating a train of clock 
pulses P1 of a frequency usually in the order of KHz which provide a 
minimum operating unit of the micro-computer. By combining the clock 
pulses in a number equal to a desired number of commands, a predetermined 
program can be obtained. Let it be assumed that a train of pulses P2 is 
generated each time one routine of the program completes. 
When the sequence of operation of the copying machine is to be controlled 
by the micro-computer MC, the train of pulses P2 is further counted by a 
counter, the counted value being then compared with the numerical data 
which have been stored in said program. Each time the counted value 
coincides with the numerical date, a predetermined control signal is 
generated to control, for example, the timing of ON-OFF of the 
illuminating lamp. This is a basic concept of control performed by the 
timer built in the micro-computer. 
A flow chart explanatory of the basic concept of control performed by the 
micro-computer timer is shown in FIG. 16, reference to which will now be 
made. 
Referring to FIG. 16, the step 1 illustrates that the microcomputer has 
been fed with electric power as a result of the closure of, for example, a 
main switch of the copying machine, one routine of operation of the 
microcomputer MC has been initiated, and the counting (division) of the 
pulse train generated from the clock pulse generator PG1 has been 
initiated. At the subsequent step 2 , determination is made as to whether 
a start switch for starting operation of a device, for example, a "Print" 
switch for starting the copying operation, or a timing switch for 
synchronism subsequent to the closure of the "Print" switch has been 
closed or not. If the "Print" switch or the timing switch is found to be 
closed, the process proceeds to the step 3 at which time counters C-A 
and C-B start their counting operation. These counters C-A and C-B are 
incremented by 1 each time one routine of the program completes. 
At the step 4 , check is made as to whether or not the counter C-A should 
be incremented by 1. (So long as the request flag is 1, +1 increment is 
continued.) If the flag is found to be 1, the process proceeds to the step 
5 at which the counter C-A is increment by 1. 
At the step 6 , the counted value of the counter C-A is compared with the 
numerical data concerning the timing at which the control object to be 
controlled should be ON and, if they coincide with each other, the process 
proceeds to the step 7 at which an ON signal is generated. 
The steps 8 to 11 are similar to the above described steps 1 to 7 , 
but differ therefrom in that the timing at which the control object should 
be OFF is determined by the counted number of the counter C-B. 
The step 12 illustrates processings of one routine other than ON and OFF 
control of the control object. 
The step 13 is to determine whether or not one cycle of the pulses P2 has 
completed, that is, whether or not a predetermined number of pulse trains 
P1 generated from the clock pulse generator PG1 has been counted. If it 
has completed or been counted, the process proceeds back to the first step 
1 . 
Important to note in the foregoing description made with reference to FIG. 
16 is that the steps 1 to 13 constitute one routine of the program and 
that, where the timing signal required to hold, for example, a lamp in an 
ON state is so programmed as to be generated when the value counted by the 
counter C-A attains "100", the routine of the program is repeated 100 
times before such timing signal is actually generated. Accordingly, in 
this case, where a timing signal required to hold the lamp in an OFF state 
is so programmed as to be generated when the counted value of the counter 
C-B attains "200", such timing signal is generated after the routine has 
been further repeated 100 times subsequent to establishment of the ON 
state of the lamp. (Nevertheless, during this repetition, the ON-OFF 
states of other mechanical elements are controlled.) 
(b) Problem of Sequence Control by Timer . . . I 
As has been clarified from the foregoing description, the control signal 
generated by the timer of the microcomputer is generated exactly at a 
particular timing and gives no error so long as an operating voltage 
required to operate the microcomputer is supplied thereto without 
deviating from the rated value. 
On the contrary thereto, in a motor-driven mechanical device such as the 
previously described copying machine, since an electric power required to 
drive the motor is supplied from commercial electric power outlet, 
variation in source voltage which usually takes place within the range of 
.+-.10% renders it difficult to maintain the speed of rotation of the 
motor at a constant value. Accordingly, this variation of the source 
voltage often constitutes a cause of variation in the speed of 
transportation of the copying paper as well as the speed of rotation of 
the photoreceptor drum 1. 
When it comes to the employment of the microcomputer for controlling the 
sequence of such a copying machine as involving an uncertainty as to the 
driving speed such as discussed above, there may arise such a possibility 
that the powder image is transferred from the photoreceptor drum 1 onto 
the copying paper in a displaced manner because of the uncertainty of the 
speed of transportation of the copying paper, even though a timing signal 
required to start the transportation of the copying paper so that it can 
be synchronized with the speed of rotation of the photoreceptor drum 1 is 
generated from the microcomputer at a predetermined timing after the 
"Print" switch has been held on an ON state. The displaced transfer of the 
powder image from the photoreceptor drum 1 onto the copying paper results 
in reproduction of the image of the original on an incorrect portion of 
the copying paper. 
In the copying machine embodying the present invention, the following 
solution is employed to substantially eliminate the above discussed 
inconvenience, which will be described with reference to FIG. 17. 
Referring to FIGS. 17(a) and 17(b), a motor drive shaft 200, or any other 
shaft driven by the motor, has a disc 204 rigidly mounted thereon for 
rotation together therewith. This disc 204 has a plurality of 
circumferentially equally spaced slits 203 extending radially inwardly 
from the outer peripheral edge thereof. A lamp PD and a light receiving 
element PQ are supported in alignment with each other on respective sides 
of the disc 204 such that, during the rotation of the disc 204 together 
with the shaft, rays of light emitted from the lamp PD and passing through 
the slits 203 are received by the light receiving element PQ which 
converts the pulsating light rays detected thereby into a train of 
electric pulses P3. In this arrangement, the disc 204, the slits 203, the 
lamp PD and the light receiving element PQ constitute a pulse generator 
PG3. 
The frequency of the pulses P3 generated from the pulse generator PG3 of 
the construction described above varies according to variation in speed of 
rotation of the motor. The higher the speed of rotation of the motor, the 
smaller the duration of each pulse P3, and vice versa. Thus, the rate of 
change in duration of each pulse P3 corresponds to variation in speed of 
rotation of the motor. It is to be noted that the pitch between each 
adjacent two slits 203 is so selected that the duration of each pulse P3 
generated from the pulse generator PG3 when the motor is rotated at a 
maximum possible speed is larger than that of each pulse P2 referred to 
hereinbefore. 
The train of pulses P3 so generated from the pulse generator PG3 is 
supplied to the microcomputer, the program therefor being such that, as 
shown in FIG. 18, after one cycle of the pulses P2 has been found 
completed at the step 13 shown in FIG. 16 during each routine of the 
program, the step 13 shown in FIG. 16 is followed by the step 14 prior 
to being proceeded back to the step 1 . At the step 14 as shown in FIG. 
18, check is made as to whether or not the train of the pulses P3 has been 
generated from the pulse generator PG3 and, if it is found generated, the 
process proceeds to the step 1 shown in FIG. 16. 
The relationship between the train of the pulses P3 generated from the 
electromechanical pulse generator PG3 and the control signal from the 
microcomputer will now be described with reference to FIG. 19. 
The relationship shown in FIG. 19(a) applies where the motor is rotated at 
a standard speed. Upon generation of the first pulse P.sub.3-1 of the 
pulse train P3 in synchronism with the rotation of the motor, the program 
routine proceeds back to the step 1 shown in FIG. 16 whereat the pulse 
train P2 starts, that is, the program routine is initiated. After the 
lapse of a time to, the pulse train P2 is, at the step 13 , checked as to 
whether completed or not completed. (At this time, one routine of the 
program has already been completed.) Subsequently, generation of the next 
succeeding pulse P.sub.3-1 of the pulse train P3 is confirmed at the step 
14 and, thereafter, the process proceeds back to the step 1 to 
initiate the next succeeding routine of the program. Accordingly, assuming 
that the frequency of the pulse train P3 at this time is expressed by 
t.sub.1, the difference between t.sub.1 and t.sub.0 represents a time 
during which the microcomputer is held in a stand-by condition. 
FIG. 19(b) illustrates the relationship applicable where the motor is 
rotated at an increased speed. In this case, the frequency of the pulse 
train P3 is shown by t.sub.2 which is lower than the frequency t.sub.1. 
Accordingly, the stand-by time t.sub.2 -t.sub.0 is shortened as shown. 
However, if the frequency t.sub.2 of the pulse train P3 is set to be 
necessarily larger than the time t.sub.0, one routine processing of the 
microcomputer would not be adversely affected. In addition, since the 
timing at which the process proceeds back to the step 1 , is accelerated 
by the generation of the second pulse P.sub.3-2, the operation of the 
microcomputer can cope with variation in speed of the copying machine. 
FIG. 19(c) illustrates the relationship applicable where the frequency 
t.sub.3 of the pulse train P3 becomes higher than the frequency t.sub.1, 
that is, the motor is rotated at a reduced speed. In this case, since the 
stand-by time t.sub.3 -t.sub.0 is prolonged, the timing at which the pulse 
train P.sub.2 is initiated is delayed for a time corresponding to the 
value through which the speed of rotation of the motor has been reduced 
and, accordingly, the operation of the microcomputer can cope with the 
reduced speed of rotation of the motor. 
Important to note in connection with the foregoing description is that the 
time t.sub.0 required for the microcomputer to complete one routine of the 
program does not vary with correspondingly no change in the program being 
performed by the microcomputer and that, as previously described, each of 
the counters C-A and C-A is incremented by 1 for each routine. If the 
speed of rotation of the motor varies, the standy-by time between the time 
of completion of one routine to the start of the next succeeding routine 
varies, but no numerical data stored in the program will vary. 
(c) Problem of Sequence Control by Timer . . . II 
The problem associated with the relationship between the control signal 
from the microcomputer and variation in speed of the copying machine is 
solved in the manner as discussed under the preceding subheading (b). 
The other problem associated with the microcomputer is such as discussed 
hereinbelow. 
As shown in the flow charts of FIGS. 16 and 18, during one routine, the 
timing at which the control signal is supplied outside is determined by 
which step it is supplied to the outside. In other words, assuming that 10 
msec. is required to complete one routine, there is a delay of 10 msec. 
between the first and last steps. In the microcomputer of this type, the 
taking-in and generation of signals from and to external circuits, 
respectively, are similarly checked at predetermined steps during one 
routine. For the purpose of illustration, let it be assumed that, as shown 
in FIGS. 20(a) and 20(b), the ON-OFF state of a predetermined switch SW is 
checked at a timing T1 subsequent to the start of the processing of one 
routine. Shown in FIG. 20(a) is a case where, since the switch SW is found 
to be held in an ON state at the timing T1, a control signal Sig is 
generated at that timing to initiate a predetermined operation. FIG. 20(b) 
is the case where, since the switch SW is found to be held in an OFF state 
at the timing T1, the time at which the control signal Sig is actually 
generated is the timing T2 during the next succeeding routine. However, 
the timings at which the switch SW is held in the ON state shown 
respectively in FIGS. 20(a) and 20(b) are displaced a difference .DELTA.t 
from each other, which difference .DELTA.t usually occurs in any type of 
machines and, therefore, is considered falling within the tolerance. The 
time at which the control signal Sig is generated in the case of FIG. 
20(a) and that in the case of FIG. 20(b) are displaced from each other a 
period of time equal to that required to complete one routine, that is, 10 
msec. or more. 
Although the delay of 10 msec. discussed above appears not problematical, 
the delay of 10 msec. corresponds to or results in displacement of 2 mm in 
the case, for example, where the copying paper is transported at a speed 
of 20 cm/sec. Accordingly, if the generation of the control signal 
required to start the transportation of the copying paper is delayed 10 
msec., the image of the original reproduced on the copying paper will be 
displaced 2 mm. This may present a problem to be solved, depending on the 
application. Yet, the higher the copying speed, the larger this delay. 
In the copying machine embodying the present invention, the above discussed 
problem is solved by the following measures which will be described with 
particular reference to FIG. 21. It is to be noted that, for the sake of 
brevity, the control of the timing at which the rotation of only the 
timing roller 20 (FIG. 1) is initiated is taken into consideration in the 
description that follows with reference to FIG. 21. As hereinbefore 
described, the timing roller 20 is operable to temporarily stop the 
leading edge of the copying paper and then to transport it after having 
synchronized with the powder image on the photoreceptor drum 1. 
As shown in FIG. 21, when a switch SW which is depressed incident to the 
start of the copying operation of the copying machine, (for example, the 
timing switches SW8 to SW10,) is held in an ON state, the timing roller 20 
is rotated, and the microcomputer will control the timing at which the 
drive of the timing roller 20 should be interrupted. That is to say, if 
the rotation of the timing roller 20 is initiated in response to the ON 
state of the switch SW, irrespective of whether the ON state has a 
particular relationship with the routine of the microcomputer, there is no 
displacement. However, since the timing at which the roller 20 is brought 
to a halt is not required to be controlled accurately so much as the time 
at which the roller 20 is initiated to rotate, an arrangement is made to 
cause the microcomputer to bring the timing roller 20 to a halt. 
It is to be noted that the timer control of the microcomputer is preferred 
and advantageous since the timing at which the timing roller 20 should be 
brought to a halt varies from time to time depending on the size of the 
copying paper being used and/or a combination of copying condition during 
multi-copying operation of the machine. 
[Paper Feed Control] 
The copying machine embodying the present invention has hereinbefore 
described as having the upper and lower paper supply units accommodating 
therein the paper cassettes, the copying papers being fed one at a time 
from one of the paper cassettes by the action of the corresponding paper 
feed roller R1 or R2 which has been selectively brought into operation. 
The manual paper feed mechanism, and the mechanism for and the reason of 
feeding the copying paper by the rotation of the paper feed roller through 
an angle corresponding to 5/6 of the 360.degree. rotation have also been 
described hereinbefore. However, hereinafter the paper feed mechanism will 
be described in association with the size of the copying papers in the 
corresponding paper cassette and the sequence mode control performed by 
the control mechanism using the microcomputer. 
The control of the paper feed mechanism will first be described with 
particular reference to FIG. 22. 
Assuming that electric power is supplied to the copying machine, the 
microcomputer MC is also fed with electric power to start its control 
operation. The paper feed control performed by the microcomputer MC is 
such that, where the upper cassette is selected at the step 1 from a 
start signal section, the flag is set to "1". At the step 2 , an "Empty" 
indicator is turned off. UP represents a determination flag. When this 
flag UP is set to "1", this means that one of the paper feed rollers which 
is associated with the upper cassette in the upper supply unit, that is, 
the roller R1, is brought into operation. The selection as to which one of 
the rollers R1 and R2 should be brought into operation is determined at 
the will of the operator of the machine, and a signal thereof is supplied 
to the determination flag UP in the central processing unit CPU through 
the interface I/O. As a result of this, the following control is performed 
in accordance with the program, stored in the read-only memory ROM, in 
dependence on the contents of the determination flag UP. At the step 3 , 
the contents of the determination flag UP is discriminated by the 
accumulator ACC, and if the contents of the flag UP is found to be "1", 
the process proceeds to the step 4 during which check is made as to 
whether or not the upper cassette C1 is empty. This empty detecting system 
will be described later. 
If it is found that the upper cassette C1 is not empty, the step 4 is 
followed by the step 8 during which the flag UP is set to "1". At the 
subsequent step 9 , the contents of the flag UP is discriminated and, at 
the step 10 , a signal indicative of the supply of the copying paper from 
the upper cassette is generated. On the other hand, where the upper 
cassette C1 is found to be empty, the step 4 is followed by the step 5 
during which check is made to find whether or not the lower cassette C2 is 
empty. If the lower cassette C2 is found to be empty, the "Empty" 
indicator is turned on during the step 7 . However, if the lower cassette 
C2 is found not to be empty during the step 5 , the process proceeds to 
the step 6 at which time a check is made as to whether or not the size 
of the copying papers contained in the upper cassette C1 is the same as 
that in the lower cassette C2. Should the size of the copying papers in 
the upper cassette C1 be found not to be the same as that in the lower 
cassette C2, the step 6 is followed by the step 7 during which the 
"Empty" indicator is turned on. On the other hand, if the size of the 
copying papers in the upper cassette C1 is found to be the same as that in 
the lower cassette C2, the step 6 is followed by the step 11 at which 
time the flag UP is set to "0". After the flag UP has been set to "0", the 
process proceeds from the step 9 to the step 12 during which a signal 
indicative of the supply of the copying paper from the lower cassette C2 
is generated. Accordingly, when the upper cassette C1 is empty and the 
size of the copying papers in the lower cassette C2 is the same as that 
which have been contained in the upper cassette C1, the copying papers are 
automatically fed from the lower cassette C2 one at a time. A system for 
detecting the size of the copying paper will be described later. 
In the case where the flag UP is set to "0" during the step 1 , that is, 
where the roller R2 associated with the lower cassette in the lower supply 
unit is brought into operation, a similar process takes place. In other 
words, the step 3 is followed by the step 13 during which check is 
made as to whether or not the lower cassette C2 is empty, and then 
followed by the step 14 during which check is made as to whether or not 
the upper cassette C1 is empty. At step 15 , a check is made to find 
whether or not the size of the copying papers in the upper cassette C1 and 
that in the lower cassette C2 are identical with each other, and where 
they are found to be identical, the step 15 is followed by the step 8 
at which time the flag UP is set to "1" so that the supply of the copying 
papers one at a time from the upper cassette C1 can automatically be 
initiated. 
Hereinafter, the system of detecting the size of the copying papers and the 
empty detecting system will be described in relation to outputs from the 
microcomputer MC with reference to FIGS. 1 and 23. 
The upper and lower cassettes C1 and C2 are loaded in the copying machine 
in the manner as shown in FIG. 1. FIG. 23(a) illustrates an arrangement of 
magnets mA, mB, mC and mD selectively secured to the bottom of each of the 
cassettes C1 and C2 by the use of a bonding agent, so that they can 
cooperate with a corresponding number of reed switches (not shown) which 
are selectively actuated by one or more of the magnets mA to mD, when the 
cassette is loaded in the machine, to detect the size of the copying 
papers contained in such cassettes. For this purpose, for each size of the 
copying paper listed in the table shown in FIG. 23(b), one or a 
combination of the magnets mA to mD are secured to the bottom of the paper 
cassette in a manner as marked by the circles in the table of FIG. 23(b). 
By way of example, in the case of the A3-size copying papers, only the 
magnet mA is secured at a definite position on the bottom of the cassette 
containing such A3-size papers and in the case of the A6-size copying 
papers, all of the magnets mA to mD are secured at respective positions on 
the bottom of the cassette containing such A6-size copying papers. 
Therefore, it will readily be seen that, if one of the reed switches (not 
shown) located in the machine at a predetermined position corresponding to 
the position of, for example, the magnet mA on the bottom of the cassette 
is activated by the magnet mA, the size of the copying papers contained in 
such cassette can be detected as A3-size paper. In this way, one or a 
combination of the reed switches when activated by the presence of 
corresponding one or combination of the magnets mA to mD generate 
respective signals with which the microcomputer MC determines the size of 
the copying papers in the cassette actually loaded in the machine. 
As shown in FIG. 23(a), for enabling the detection whether or not each 
cassette loaded in the machine is empty, the bottom and the top covering 
of each cassette have respective openings defined therein for the passage 
of a beam of light therethrough. On the other hand, two combinations of 
light emitting diodes PD1 and PD2 with light sensors PC1 and PC2 are 
employed in the machine one for each of the upper and lower cassettes C1 
and C2, respectively, as shown in FIG. 1. Specifically, the light emitting 
diode PD1 and the light sensor PC1 are so positioned that, when the lower 
cassette C1 is loaded in the machine and such lower cassette is empty, a 
beam of light emitted from the diode PD1 can pass through the openings in 
the bottom and top covering of such lower cassette C2 and be then sensed 
by the light sensor PC1. Similarly, the light emitting diode PD2 and the 
light sensor PC2 are so positioned that, when the upper cassette C1 is 
loaded in the machine and such upper cassette is empty, a beam of light 
from the diode PD2 can pass through the openings in the bottom and top 
covering of such upper cassette C1 and be then sensed by the light sensor 
PC2. 
Since the control of the paper supply mechanism described above is 
disclosed in the U.S. Patent Application Serial No. 19,893 filed Mar. 12, 
1979 by the same assignee of the present invention, the details thereof 
are not herein described for the sake of brevity and reference may be had 
thereto. 
As described hereinbefore, in the copying machine embodying the present 
invention, discrimination of the size of the copying papers in the 
cassette is performed by the reed switches, installed on the machine, in 
cooperation with the combination of the magnets mA to mD, and the control 
is carried out in a manner as shown in the flow chart of FIG. 22. 
Therefore, the paper supply can be performed effectively and efficiently. 
It is to be noted that, as hereinbefore described, at the time any one of 
the paper feed rollers R1 and R2 is driven, the time during which the 
solenoid SL1 is actuated is so controlled as to enable the corresponding 
roller R1 or R2 to rotate through the angle corresponding to 5/6 of the 
360.degree. rotation. 
The signals generated from the paper size detecting system shown in FIGS. 
23(a) and 23(b) are utilized not only to control the operation of the 
paper feed mechanism, but also to control the time during which the 
optical scanning system is moved and to select the sequence mode which is 
set variable according to the size of the copying papers used and the 
selected magnification. In other words, when the size of the copying 
papers or the magnification factor is switched over to another size or 
magnification factor, the various control timers must be so set that the 
distance and velocity of movement of the optical scanning system is moved 
correspondingly or the time during which any one of the electrostatic 
charge and exposure is effected is varied to effect an efficient copying 
operation with the minimized loss of time. Accordingly, the signals from 
the paper size detecting mechanism are utilized to determine the preset 
times of the respective control timers for each sequence mode. As an 
example in which the preset time of the timer is varied for each sequence 
mode, the control of the time during which the optical scanning system 
will now be described. 
[Control of Optical Scanning System] 
A flow chart showing how the optical scanning system is controlled is shown 
in FIG. 24. 
Referring now to FIG. 24, from the start signal section, the condition of 
copying operation is determined at the step 1 . That is to say, at the 
step 1 , check is made as to whether or not the "Print" switch (not 
shown) is turned on and if it is found to be turned on, a delay timer 
TIM-1 (not shown) is actuated at the subsequent step 2 . This is for the 
purpose of securing the time necessary to cause the illuminating lamp 81 
to be lit to its maximum available intensity of light before the start of 
operation of a drive mechanism for the optical scanning system which takes 
place incident to the switching-on of the "Print" switch. It is to be 
noted that the delay timer TIM-1 has a construction similar to any one of 
the counters C-A and C-B referred to hereinbefore. At the step 3 
following the step 2 , check is made as to whether or not the timer TIM-1 
is completed, and if it is completed, the process proceeds to the step 4 
during which the size of the copying papers is checked. This checking of 
the paper size is performed by supplying the signal from the size 
detecting system to the microcomputer MC through the interface I/O. At the 
step 5 following the step 3 , based on the signal indicative of the 
magnification generated from the corresponding reed switch SW2, SW3 or SW4 
shown in FIG. 11, a predetermined number of pulses is set in view of the 
size of the copying papers detected in the manner as hereinbefore 
described. This setting of the predetermined number of pulses is carried 
out by the utilization of numerical data set by supplying the signal 
indicative of the detected paper size and the signal indicative of the 
selected magnification to the random access memory RAM through the 
interface and designating the address of the program stored in the 
read-only memory ROM on the basis of what is determined by the contents of 
the random access memory RAM. 
At the step 6 , a selection signal for selecting one of the scan clutches 
101, 102 and 103 (FIG. 11), which is also used to designate the copying 
speed, is generated in dependence on the signal indicative of the selected 
magnification (It is to be noted that the main motor has already been 
started incident to the switching-on of the "Print" switch.) and the 
optical scanning system starts its movement at a predetermined velocity. 
At the step 7 , a check is made as to whether or not a switch is actuated 
at a predetermined position by the movement of the optical scanning 
system. This switch is, for example, the reed switch SW7 which is actuated 
by the magnet 115 as shown in FIG. 12. When the reed switch SW7 is found 
to be turned on, the process proceeds to the step 8 during which the 
pulse number count flag is set to "1". This flag is obtained by previously 
designating a predetermined bit in a predetermined area of the random 
access memory RAM. 
At the step 9 , said pulse number count flag is determined and, if it is 
set to "1", the step 9 is followed by the step 10 during which "1" is 
added to the contents of the counter. This counter serves to designate an 
area of the random access memory RAM for counting which is different from 
that of the random access memory RAM used at the step 5 and is operable 
to count up the contents by an increment of "1" in response to each pulse 
of the pulse train P2, that is, each time one routine of the program 
completes. 
At the step 11 , comparison is made as to whether or not the contents of 
the random access memory RAM for counting is equal to the predetermined 
numerical value preset in the program designated by the contents stored in 
the random access memory RAM in correspondence with the size of the 
copying papers and the magnification set during the step 5 . If they are 
found to be equal to each other the step 11 is followed by the step 12 
, but skips to the step 13 if they are found to be not equal to each 
other. As a comparison means, for example, a command capable of loading 
the contents of the random access memory RAM for counting in the 
accumulator ACC and comparing the accumulator ACC and the designated 
contents of the random access memory RAM is utilized. 
If it is found as a result of the comparison made at the step 11 that the 
counted number is equal to the preset numerical value, the process 
proceeds to the step 12 at which time a signal necessary to turn off the 
scan clutches is generated followed by the generation of a signal 
necessary to turn on the return clutch which takes place delayed a certain 
time from the generation of the signal for the scan clutches. (It is to be 
noted that other timers are set even during this delay time.) While an 
electric circuitry for turning on and off the clutches by the use of an 
arbitrary signal is well known to those skilled in the art and, therefore, 
the details thereof are not herein described, it is generally connected to 
a clutch actuating circuit from the interface I/O through any suitable 
switching circuit. Completion of the return movement of the optical 
scanning system which has started the return movement is carried out in 
the process during the step 13 . (It is to be noted that, when the switch 
SW6 is turned on, this means that the return movement of the optical 
scanning system has been completed.) 
During the step 12 , not only are the signals necessary to interrupt the 
scanning and to initiate the return movement generated as hereinbefore 
described, the contents of the random access memory RAM are cleared in 
readiness for the next succeeding copying operation and also the pulse 
number count flag is reset to "0". 
After a train of synchronizing pulses P3 necessary to adjust the pulse 
interval of each pulse of the pulse train P2 has been generated at the 
step 14 , the process returns back to the initial step 1 . 
In the foregoing description, one routine of operation of the microcomputer 
MC which takes place during the duration of each pulse of the pulse train 
P2 has been described. However, in view of the fact that the scanning of, 
for example, the A-3 size or A-5 size originals at an equal magnification 
requires 2 seconds or 1 second, respectively, assuming that the designed 
value of the pulse interval of the above described synchronizing pulse is 
10 msec., the preset number in the program will read 200 or 100 in the 
case where it has been found during the step 4 that the A-3 size or A-5 
size copying paper is used, respectively. In such case, subsequent to the 
start of the scanning, and after the above described operation has been 
repeated 200 or 100 times, respectively, subsequent to the switching-on of 
the switch SW7, the determination of "YES" is carried out at the step 11 
, thereby interrupting the movement of the optical scanning system. 
Although the speed of movement of the optical scanning system may vary 
with variation of the speed of the motor of the drive system, the 
difference therebetween can be compensated for because the synchronizing 
pulse P3 can also vary with variation of the speed of the motor, and, 
therefore, the preset number need not be changed. It is to be noted that 
it is possible to design or prepare a signal necessary to turn off the 
scanning movement by continuously operating two or more timers subsequent 
to the switching-on of the switch SW7. 
Where the magnification factor is selected to be of a value other than an 
equal magnification factor and so is detected, the preset number at the 
step 5 varies correspondingly because the number corresponding to the 
time required for the optical scanning system movable at a speed 
determined in dependence on the selected magnification factor to travel a 
distance corresponding to the area to be copied has been predetermined 
beforehand and set. Even where a combination of the magnification factor 
and the size of the copying paper is selected in such a manner as to 
require the optical scanning system to travel a distance larger than the 
available length of the support 80 (FIGS. 1 and 10), care is required so 
as to avoid any possible setting of the number required for the optical 
scanning system to travel such a large distance. 
This type of control of the time required for the optical scanning system 
to undergo its scanning movement requires the setting of a complicated 
combination of times, as compared with those occasions wherein the return 
position is determined to cope only with the size of the original to be 
copied, because the speed of the scanning movement must be adjusted each 
time the magnification factor is changed. In view of this, the employment 
of a construction wherein the setting times of the timers are made 
variable according to the program by the use of the microcomputer, such as 
achieved by the present invention, is advantageous. 
Although in the flow chart of FIG. 24, the copying machine embodying the 
present invention has been shown, for the sake of brevity, as having a 
capability of reproducing the image on the copying papers of six different 
paper sizes, one at a time in contrast to the nine sizes shown in FIG. 
23(b) as available, the machine embodying the present invention is to be 
understood as having a capability of reproducing the image on the copying 
papers of the sizes specified in FIG. 23(b) one at a time. In addition, in 
an actual sequence control, an arrangement of the timers will be more 
complicated than that described for the purpose of illustration of the 
present invention, because the timing controls of the electrostatic 
charge, the exposure and other operations than the control of movement of 
the optical scanning system are also paralleled. Hereinafter, an specific 
example of sequence control will be described. 
[Sequence Control] 
As hereinbefore described, the copying machine embodying the present 
invention has a capability of reproducing the image at a plurality of 
magnifications and also a capability of reproducing the image on copying 
papers of different sizes and, therefore, has a plurality of sequence 
modes one for each selected combination of the paper sizes and the 
magnifications. 
Where different sequence control programs are employed and set one for each 
sequence mode, the copying machine would not work efficiently. 
Accordingly, in the present invention, the sequence control for the 
copying operation is carried out by selecting a suitable combination of a 
first group of timers TA common to all of the sequence modes with a second 
group of timers TB of which the setting are determined by a combination of 
the signals indicative of the magnification detected (i.e., those 
generated from the respective reed switches SW2 to SW4 as shown in FIG. 
11) with the signals indicative of the particular size of the copying 
papers (i.e., those generated from the respective reed switches 
operatively associated with the magnets mA to mD). Some specific examples 
of the sequence control for the copying operation will now be described 
with particular to FIGS. 25 to 27 in combination with FIG. 1. 
Two Repetitive Reproduction on A-5 size Paper at .times.1 Magnification 
The sequence control mode for this purpose is shown in a timer chart shown 
in FIG. 25. 
Referring to FIG. 25, when the "Print" switch is turned on after the 
electric power has been supplied to the machine and the fixing device 14 
has subsequently been heated to a predetermined temperature, the main 
motor (not shown) is driven to transmit its drive force to the 
photoreceptor drum 1 and also the other movable parts through the chains 
and the timing belts. 
Incident to the switching-on of the "Print" switch, the timers TA-1 and 
TA-3 of the timer group TA are set. The timer TA-1 serves to actuate the 
paper feed roller R2 when the lower cassette C2 is selected to be brought 
into operation whereas the timer TA-3 serves to switch on the 
electrostatic charger 2 upon the lapse of the preset time thereof. The 
timer TA-6 is set in response to the lapse of the preset time of the timer 
TA-3 to switch on the clutch 101 for the optical scanning system to 
initiate the scanning movement of the optical scanning system and, at the 
same time, the timer TA-4 for operating the roller R1 starts its 
operation. After the lapse of the preset time of the timer TA-1, not only 
is the timer TA-2 operated, but also the solenoid unit for the clutch 
associated with the paper feed roller R2 is switched on (See FIGS. 4 and 
5) for a predetermined time as hereinbefore described, thereby permitting 
the paper feed roller R2 to be brought to a halt upon completion of its 
rotation through the angle corresponding to 5/6 of one complete rotation. 
The copying paper fed by the paper feed roller R2 is temporarily brought 
to a halt by the intermediate roller 25. When the copying paper is fed 
from the upper cassette C1, it will not be brought to a halt by the roller 
25, but by the timing roller 20. As the optical scanning system moves, the 
reed switch SW7 shown in FIG. 12 is switched on by the magnet 115 when the 
optical scanning system passes the predetermined position to set the 
timers TA-5, TA-7 and TB-1. The timer TA-5 is operable to drive the 
intermediate roller 25 upon the lapse of the preset time thereof to feed 
the copying paper, which would be temporarily blocked thereby, towards the 
processing station. Although the timer TA-7 is operable to drive the 
timing roller 20 upon the lapse of the preset time thereof, the timing 
roller 20 is driven directly in response to the switching-on of the timing 
switch SW8 actuated by the optical scanning system, and the timer is used 
to bring the timing roller 20 to a halt upon the lapse of the preset time 
of the timer TA-13 as will be described later. 
The timer TB-1 belongs to the second timer group TB, the preset time of 
which varies according to the size of the copying paper and the 
magnification selected. That is to say, as is the case with the timers 
TB-2 and TB-3 described later, with respect to the control object whose 
operating time is required to be changed in dependence on change in size 
of the copying paper and magnification, the preset time of each of the 
timers of the second timer group TB is made variable by suitably and 
selectively setting the numerical data. This data has been set in the 
program, according to the external signals so that, upon the lapse of the 
preset time of the particular timer of the second timer group TB or by 
continuously setting the predetermined first timer group TA to the second 
timer group TB, the operation thereof can be switched off. 
The timer TB-1 is set during the timing of the switching-off of the 
electrostatic charger. The timer TB-2 is set upon the lapse of the preset 
time of the timer TA-5 and is kept in the set state during the timing of 
the switching-off of the drive of the intermediate roller 25. The timer 
TA-8 for switching off the clutch 101 and the timer TA-9 for switching on 
the return clutch 104, both belonging to the first timer group and being 
common to all of the sequence modes, are set at a reference time 
coinciding with the time at which the preset time of the timer TB-1 of the 
second timer group TB and, therefore, the timing at which the scanning 
completes and the return movement is initiated is variable substantially 
in dependence on the paper size and the copying magnification. 
This equally applies to the operation of the timer TA-13 which is set upon 
the lapse of the preset time of the timer TB-2 and, accordingly, the 
timing at which the timing roller 20 is switched off is also variable. 
The third timer TB-3 of the second timer group TB is adapted to be set upon 
the lapse of the preset time of the timer TB-2, the preset time of which 
is so selected as to lapse somewhat earlier than the timing at which the 
optical scanning system returns to the original position, the timing at 
which the read switch SW6 is turned on. Then, after the switching-on of 
the reed switch SW6, the timer TA-12 for switching on the electrostatic 
charger in readiness for the reproduction of the image on the next 
succeeding copying paper is actuated followed by the timer TA-6 which is 
actuated upon the lapse of the preset time of the timer TA-12 to switch on 
the scan clutch. 
During a repetitive copying operation to produce two copies according to 
this sequence mode, the supply of the next succeeding copying paper is, as 
is the case of the previous supply of the first copying paper from the 
upper cassette by the action of the paper feed roller R1, initiated by the 
action of the paper feed roller R2 during the timing at which the scan 
clutch 101 is switched off that is, upon the lapse of the preset time of 
the timer TA-8 and also during the timing at which the scan clutch 101 is 
switched on, that is, upon the lapse of the preset time of the timer TA-6. 
In this sequence mode, although the timer TB-3 does not work substantially, 
this timer TB-3 is treated as a conditional signal for initiating the 
copying operation for the reproduction of the same image on the second and 
succeeding copying papers. That is, in the sequence mode which will be 
described later, the time at which the preset time of the timer TB-3 
elapses is set to be later than the timing at which the optical scanning 
system returns to the original position so that, upon the lapse of the 
preset time of the timer TB-3. The timer TA-12 for switching on the 
electrostatic charger and the timer TA-6 for switching on the scanning 
movement can be actuated, whereby the electrostatic charging and other 
operations for the next succeeding copying operation can be initiated by 
the AND logic of two conditional signals which are respectively generated 
upon the lapse of the preset time of the timer TB-3 and the switching-on 
of the switch SW6. In other words, at the timing either at which the 
preset time of the timer TB-3 has passed or at which the optical scanning 
system returns to the original position, whichever occurs later, the 
copying operation to produce the second and succeeding copies is 
initiated. 
As hereinbefore described, during the repetitive copying operation to 
produce a plurality of copies in succession, in order to switch on the 
electrostatic charger, the scanning and others for the copying operation 
to produce the second and succeeding copies, it is at least essential that 
the optical scanning system be returned to the original position. In 
addition thereto, depending on the combination of the paper size and the 
magnification used (The length of the passage through which the copying 
paper travels is also one of factors influential on this combination, 
too.), there are various conditions to be satisfied in order for the 
second and succeeding cycles of copying operation to be initiated and the 
time required for these conditions to be satisfied varies according to the 
sequence mode. Therefore, the timer TB-3 has a preset time determined on 
the basis of the copying initiating conditions for each sequence mode and 
generates the conditional signal, the sequence mode of FIG. 25 being an 
example wherein those conditions are satisfied before the optical scanning 
system completes its return movement to the original position. 
The illuminating lamp 81 is preliminarily energized by the switching-on of 
the "Print" switch and is then energized to emit the maximum available 
light upon the lapse of the preset time of the timer TA-6. However, during 
the next succeeding cycle of copying operation to produce the second copy, 
the lamp 81 is preliminarily energized upon return of the optical scanning 
system to the original position and energized to emit the maximum 
available light upon the lapse of the preset time of the timer TA-6. The 
heater incorporated in the fixing device is electrically energized only 
during the deenergization of the illuminating lamp 81, thereby minimizing 
any possible excessive consumption of the electric power consumed on a 
whole by the copying machine. A separator clutch CL is a clutch for 
actuating the charge cam wheel 71 in the paper separating mechanism as 
described with reference to and shown in FIGS. 8 and 9 and, when this 
clutch is coupled, the cam wheel 71 is rotated to cause the nozzle 
assembly 8 to produce the jets of air in the manner as hereinbefore. 
In the timer chart for the sequence control described above, since the 
mechanical operation and the control signals from the microcomputer MC 
need not be synchronized with each other, the timers TA-1, TA-2, TA-3, 
TA-4 and TA-6 may be timers which do not utilize the pulse train P3 
generated by such a mechanical pulse generator PG3 as shown in FIG. 18, 
but which are operable with internal reference pulses PG2 generated inside 
the microcomputer MC as shown in FIG. 16. Particularly, the use of the 
internal timers for the timers TA-1 and TA-3 is preferred because the 
motor requires a certain time subsequent to the switching-on thereof until 
the rotation thereof is stabilized. Moreover, since the scan movement and 
the transportation of the copying paper must be synchronized exactly with 
each other subsequent to the switching-on of the reed switch SW7 actuated 
by the optical scanning system, the timers TA-5, TA-7, TB-1 and so on are 
operable with the pulse train P3 generated from the pulse generator PG3. 
In FIG. 25, timers for detecting the occurrence of paper jamming and for 
detecting the failure of the scanning are also shown. 
The timer TA-16 is set in response to the switching-on of the scan clutch, 
that is, upon the lapse of the preset time of the timer TA-6 and is 
operable to determine, and generate a detection signal indicative of, the 
failure of the scanner 82 to move, when the reed switch SW7 is not 
actuated during the preset time of the timer TA-16. 
The timers TA-17, TA-18 and TA-19 are operable to detect whether or not the 
copying paper, the transportation of which is initiated at the time the 
timing switch SW8 is turned on, that is, at the time the timing roller is 
switched on, has arrived at or passed through check points P1, P2 and P3 
shown in FIG. 1, respectively. The timers TA-17, TA-18 and TA-19 are 
provided in two series systems which have their starting points of 
operation respectively at the time of the switching-on of the timing 
roller and the switching-off of the timing roller (upon the lapse of the 
preset time of the timer TA-13). The timers of the system having the 
starting point coinciding with the switching-on of the timing roller are 
used to determine whether or not the copying paper being transported has 
arrived at the respective check points P1, P2 and P3 within predetermined 
times. That is, should the copying paper being transported fail to arrive 
at the check points P1, P2 and P3 by the respective times the preset times 
of the timers TA-17, TA-18 and TA-19 have passed, they generate jam 
signals indicative of the occurrence of the paper jamming. On the other 
hand, the timers of the system having the starting point coinciding with 
the switching-off of the timing roller, the reference of which is 
synchronized with the trailing or rear end of the copying paper with 
respect to the direction of transportation thereof, generate jam signals 
indicative of the occurrence of the paper jamming when the copying paper 
is present at the check points P1, P2 and P3 at the time of the lapse of 
the preset timer thereof, respectively. A method and a structure for 
detecting the occurrence of the paper jamming in the manner described 
above is are disclosed in the U.S. patent application Ser. No. 28,322 
filed Apr. 9, 1979 by the same assignee of the present invention and, 
therefore, the details thereof are not herein recited for the sake of 
brevity. 
For detecting the copying paper at each of the check points P1, P2 and P3, 
an ultrasonic sensor is employed although either a microswitch or a 
photosensor may be employed instead of the ultrasonic sensor. However, the 
use of the ultrasonic sensor at each of the check points P1, P2 and P3 is 
advantageous because it has no projecting element or actuator such as 
required in the microswitch and also it can be used with a transparent 
film as a copying paper. 
It has been described that the next succeeding cycles of copying operation 
to produce the second and succeeding copies are initiated at the timing 
either at which the preset time of the condition timer TB-3 has passed or 
at which the optical scanning system has returned to the original 
position, whichever occurs later. However, when and after the last copy 
has been produced, an autoshut timer TA-15 is actuated by this timing 
signal to enable the main motor to be brought to a halt a predetermined 
time after the completion of the repetative copying operation for 
producing the copies in succession. 
Two Repetitive Reproduction on A-4 size Paper at .times.1.4 Magnification 
A timer chart for the sequence control mode for this purpose is shown in 
FIG. 26. (It is to be noted that this is an example wherein the copying 
machine of the present invention can produce a copy at a maximum available 
magnification.) 
As can be understood from FIG. 26, the difference between the sequence 
modes shown respectively in FIGS. 25 and 26 resides in the timers TB-1, 
TB-2 and TB-3 of the second timer group TB while the preset time 
characteristics and functions of the timers of the first timer group 
remain the same. Specifically, the preset times of the respective timers 
of the second timer group TB are varied to cope with the selected paper 
size and the selected magnification so that they can work in harmony with 
the timers of the first timer group TA to achieve a systematized sequence 
control. 
In the sequence mode shown in FIG. 26, the preset time of the timer TB-3 
takes place subsequent to the return of the optical scanning system to the 
original position and, accordingly, the timer TA-12 for initiating the 
electrostatic charging is actuated upon the lapse of the preset time of 
the timer TB-3, followed by the actuation of the timer TA-6 for initiating 
the scanning of the optical scanning system. 
As regards the auto-shut timer TA-15, it is set upon the lapse of the 
preset timer TB-3. 
Although the capability of reproducing the image at .times.1.4 
magnification has not hereinbefore referred to, it is to be noted that, 
during this capability, the scanning speed is lower than that during the 
capability of reproducing the image at equal (.times.1.0) magnification 
and, accordingly, the timing switch would be on one side of the reed 
switch SW8 adjacent the reed switch SW6. 
Two Repetitive Reproduction on A-3 size Paper at .times.0.647 Magnification 
A timer chart for the sequence control mode for this purpose is shown in 
FIG. 27. (It is to be noted that this is an example wherein the copying 
machine of the present invention can produce a copy on a minimum available 
magnification.) 
As can be understood from FIG. 27, even in this sequence mode, the preset 
times of the timers of the first timer group TA remain the same while 
those of the second timer group TB are varied. In addition, in view of the 
fact that the A-3 size copying paper is a maximum possible size that the 
copying machine can accept and that the scanning speed is also the highest 
possible speed due to the minimum available magnification, the preset time 
of the condition timer TB-3 terminates later than the completion of return 
of the optical scanning system to the original position. The timing switch 
used during this sequence control is located at a position displaced 
towards the scanning direction relative to the position where the timing 
switch is located when the magnification is .times.0.7. It is to be noted 
that the magnification of .times.0.647 is the one used when the copying 
paper, the dimensions of which are measured according to the footage 
system, is used. 
It is also to be noted that, during the reproduced copying operation now 
under discussion, the side eraser 4 is lit. Since the width of the image 
projected onto the drum 1 during the reduced copying operation is smaller 
than the effective width of the photoreceptor drum 1, the side eraser 4 
serves, when lit, to dissipate some of the electrostatic charge on the 
photoreceptor drum 1 which are present on the end portions of the drum 1. 
The portion of the electrostatical charge on the drum 1 which is to be 
erased by the side eraser can be selectively controlled according to the 
magnification selected. 
Although the present invention has fully been described in connection with 
the preferred embodiment thereof with reference to the accompanying 
drawings, it is to be noted that various changes and modifications are 
apparent to those skilled in the art. Such changes and modifications are 
to be understood as included within the true scope of the present 
invention unless they depart therefrom.