Electrostatic copying system having monitoring devices

A plurality of electrostatic copying machines (12), (13), (14), (16) are interconnected by bus lines (19), (21), (22). Each copying machine (12), (13), (14), (16) is provided with a sensor unit (23) for sensing various status parameters of the copying machine (12), (13), (14), (16) such as whether the copying machine (12), (13), (14), (16) is available for use, the copy sheet size, the number of copies made, the number of copy sheets remaining, etc. Each copying machine (12), (13), (14), (16) is further provided with a display unit (17) for displaying the status parameters of all of the copying machines (12), (13), (14), (16). A microcomputer (31) is provided at one of the copying machines (12) for storing and processing the status parameters and producing a hard copy.

BACKGROUND OF THE INVENTION 
The present invention relates to an electrostatic copying apparatus 
comprising a plurality of interconnected copying machines. 
In large business and government organizations it is necessary to provide 
an electrostatic copying facility which can produce various types of 
copies at high speed. One approach to the problem is to provide a single 
high speed copying machine which can achieve all functions such as copying 
on various sizes of copy paper at various magnification ratios. This 
approach has two serious drawbacks, one being the extremely high cost of 
such a copying machine and the second being the fact that only one person 
can make copies at any given time. 
A second approach is to provide several copying machines which are 
constructed to enable different functions such as copying on different 
sizes of copy paper. The copying machines are preferably located at 
different places in an office building for employee convenience. 
Generally, several single function copying machines may be purchased at a 
lower total cost than a single all-function copying machine. 
Although the second approach overcomes the disadvantages of the first 
approach, it introduces other problems. For example, a person at one 
location has no way of knowing which copying machines are in use or 
broken. Also, more work is required in supplying different sizes of copy 
paper, toner etc. for the several copying machines. It is also more 
difficult, where an organization has a number of sections, to determine 
how many copies are made by each section and of what size for cost 
allocation purposes. 
SUMMARY OF THE INVENTION 
An electrostatic copying apparatus embodying the present invention includes 
a plurality of electrostatic copying machines. A plurality of sensor means 
are connected to the copying machines respectively for sensing at least 
one copying machine status parameter. Display means are connected to the 
copying machines respectively. Interconnection means interconnect all of 
the sensor means and display means in such a manner that each display 
means displays the status parameters of all of the copying machines. 
It is an object of the present invention to provide an electrostatic 
copying apparatus comprising a plurality of electrostatic copying machines 
and means by which a user at one copying machine can determine the status 
of all of the copying machines. 
It is another object of the present invention to provide an electrostatic 
copying apparatus comprising a plurality of electrostatic copying machines 
and means for automatically collecting data indicating the status of all 
of the copying machines. 
It is another object of the present invention to provide a generally 
improved electrostatic copying apparatus. 
Other objects, together with the foregoing, are attained in the embodiments 
described in the following description and illustrated in the accompanying 
drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
While the electrostatic copying apparatus of the present invention is 
susceptible of numerous physical embodiments, depending upon the 
environment and requirements of use, substantial numbers of the herein 
shown and described embodiments have been made, tested and used, and all 
have performed in an eminently satisfactory manner. 
Referring now to FIG. 1 of the drawing, an electrostatic copying apparatus 
embodying the present invention is generaly designated by the reference 
numeral 11 and comprises electrostatic copying machines 12, 13, 14 and 16. 
Each of the copying machines 12, 13, 14 and 16 comprises a display unit 17 
and a code input unit 18. The copying machines 12, 13, 14 and 16 are 
preferably provided at different locations in an office building (not 
shown) and are interconnected by an address bus or bus line 19, a data bus 
line 21 and a control bus line 22. 
Typically, the copying machine 12 is a high speed unit capable of copying 
on B4 size paper. The copying machine 13 is a normal speed unit capable of 
copying on B4 size sheets. The copying machine 14 is capable of copying on 
A3 size paper at reduced magnification. The copying machine 16 is provided 
with an automatic feed mechanism for original documents and capable of 
aligning the images on copy sheets. 
The display units 17 are capable of displaying various copying machine 
status parameters of all of the copying machines 12, 13, 14 and 16. In 
other words, a copying machine operator or user may determine the status 
of all of the copying machines 12, 13, 14 and 16 merely by observing the 
display unit 17 at any one of the copying machines 12, 13, 14 and 16. 
The status parameters may be divided into two general types. The first type 
includes parameters which are of interest to a copying machine user, such 
as: 
1. Whether a particular copying machine is available for use or whether it 
is unavailable because it is being used by another user, broken, etc. 
2. The size of the copy sheets used in each copying machine. 
The second type of parameter is of interest to maintenance or accounting 
personal who service the apparatus 11. These include: 
3. The number of copies made by a certain copying machine, and the person 
or section who made the copies. 
4. The number of copy sheets remaining in each copying machine and/or 
supply cabinet. 
5. The amount of toner remaining in each copying machine and/or supply 
cabinet. 
6. The amount of deterioration of the photoconductive element of each 
copying machine. 
With reference also being made to FIGS. 2 to 4, each of the copying 
machines 12, 13, 14 and 16 comprises a sensor unit 23 including a 
plurality of various sensors 231, 232 . . . 23n for sensing n parameters. 
These sensors 231, 232 . . . 23n are connected to the bus lines 19, 21 and 
22 through a programmable input-output interface (I/O) 24. 
The sensors for sensing parameter number (1) above function to, for 
example, sense the status of a main switch which is maintained in a 
certain position only during copying (busy indication). Other sensors may 
sense the position of a keep relay which is energized in response to a jam 
condition and remains energized even though a main power switch is opened 
(jam condition). Other sensors may sense the position of an alarm switch 
which a user presses when the copying machine malfunctions in some way, 
runs out of paper or toner, etc. (inoperative condition). 
Sensors for sensing parameter number (2) above may be embodied by 
microswitching provided to a cassette holder of a copying machine at 
different positions. Copy sheet cassettes of different sizes are in this 
example provided with lugs at different positions to engage and actuate 
only one of the microswitches corresponding to the paper size. 
Parameter number (3) above may be sensed by means of the code input unit 18 
and a copy counter. Each copy machine user or section is provided with a 
numeric code indicating his identity. Where a user wishes to make copies 
he inputs his code number into the particular copying machine by means of 
the code input unit 18. Preferably, the copy machine may not be operated 
unless it is verified that the code number is valid and that the user is 
authorized to use the copying machine. The code input unit 18 may be 
embodied by any means known in the art such as a keyboard, magnetic card 
reader, etc. In the latter case, each user is provided with a magnetic 
card for insertion into the code input device 18 on which his code number 
is magnetically imprinted. 
Parameter number (4) above may be sensed by means of the copy counter which 
counts the number of copies made after a full cassette is inserted into 
the copying machine. The number of remaining sheets is equal to the number 
of sheets in a full cassette minus the number of copies made. Where a 
supply cabinet is provided with individual compartments for storing 
individual boxes of copy paper, microswitches may be provided to the 
compartments to sense for the presence or absence of each box of copy 
sheets. 
Parameter number (5) may be sensed by means of any device capable of 
measuring the amount of toner in a hopper in the particular copying 
machine. Alternatively, sensor means may be provided to measure the amount 
of toner which has flowed through a passageway leading from the hopper to 
a developing unit of the copying machine since the hopper was filled. 
Where individual compartments are provided for toner bottles or boxes in a 
supply cabinet, microswitches may be provided to sense for the presence or 
absence of the toner bottles. 
The amount of deterioration of a photoconductive member such as a drum, 
parameter number (6), may be determined by counting the number of copies 
made since a new drum was installed in the copying machine. 
Each display unit 17 comprises a keyboard 26 connected to the bus lines 19, 
21 and 22 through an interface 27 and a display 28 which is connected to 
the bus lines 19, 21 and 22 through a display drive unit 29. The display 
28 may be embodied by a cathode ray tube (CRT) device capable of 
displaying one or more lines of data, a light emitting diode (LED) display 
device capable of displaying characters in 7-segment or dot matrix 
configuration, an incandescent light display (indicator lamps), etc. 
Although it is within the scope of the present invention for the display 28 
of any of the copying machines 12, 13, 14 and 16 to display all of the 
parameters of all of the copying machines 12, 13, 14 and 16 
simultaneously, it is preferable from the viewpoint of reducing the size 
and cost of the display 28 to selectively view only certain parameters or 
even only one parameter at one time. For example, the user might wish to 
display parameter (1) for all of the copying machines 12, 13, 14 and 16 to 
determine which, if any, are available for use. Alternatively, the user 
may wish to determine the entire status of any particular copying machine 
12, 13, 14 or 16. In order to accomplish this objective, the keyboard 26 
is provided with a number of keys (not shown) by means of which the user 
may indicate what parameters he wishes to display and for what copying 
machine(s). 
Generally, only parameters (1) and (2) are of interest to copying machine 
users. Therefore, the display unit 17 may be adapted to be capable of 
displaying only these parameters, thus simplifying the design and reducing 
the size and cost of the display unit 17. It is desirable, however, to 
provide means by which maintenance and accounting personnel may have 
access to parameters (3) to (6), etc., in addition to the parameters (1) 
and (2). 
In accordance with the advancement of electronic technology, it is becoming 
popular in the art of electrostatic copying to provide a computer such as 
a microcomputer to a copying machine which can optimally control the 
operation of the copying machine. Such computers control the exposure of a 
photoconductive drum in accordance with the density and contrast of an 
original document being copied, the amount of deterioration and/or fatigue 
of the drum, ambient temperature and humidity, etc. The computer may also 
perform other functions such as controlling the toner replenishment rate, 
etc. Since the functions which the computer performs are determined by the 
operating program stored in memory, new functions may be provided merely 
by adding additional software. In accordance with an important feature of 
the present invention, it is necessary to provide a computer to only one 
of the copying machines 12, 13, 14 and 16, for example the copying machine 
12. The computer is designated as 31 and connected to monitor the 
parameters of and control all of the copying machines 12, 13, 14 and 16 
through the bus lines 19, 21 and 22. 
The computer 31 comprises a central processing unit (CPU) 32 which is 
connected to the bus lines 19, 21 and 22 through line buffers 33, 34 and 
36 respectively. A memory 37 is provided for the CPU 32 which comprises a 
read-only memory (ROM) 38 for storing the operating program. A 
non-volatile random access memory (RAM) 39 is provided to store the 
parameters for all of the copying machines 12, 13, 14 and 16 in addition 
to other data for exposure control, intermediate results, etc. A control 
unit 41 is provided to enable the RAM 39 for read-write operations when 
power is available and to render the RAM 39 non-volatile when power is 
turned off. Further provided to the copying machine 12 are a control panel 
42 and a printer 43 which are connected to the CPU 32 through an 
input-output interface 44. 
Depression of suitable keys (not shown) on any of the keyboards 26 causes 
data signals to be fed to the computer 31 for display of the required 
parameters (1) and/or (2) on the respective display 28. The control panel 
42 comprises keys, switches or the like (not shown) which maintenance or 
accounting personnel may operate to cause the desired parameters (3) to 
(6) to be printed by the printer 43. 
Referring now to FIG. 4, the copying machine 12 comprises a photoconductive 
drum 46 which is rotated clockwise at constant speed. An original document 
47 is placed face down on a transparent glass platen 48 and illuminated by 
a light source 49. A light image of a linear portion of the document 47 is 
reflected by plane mirrors 51 and 52 to a lens 53 which has a reflecting 
rear surface. The light image is converged twice by the lens 53 and 
reflected via another plane mirror 54 onto the drum 46. The mirror 51 is 
moved relative to the document 47 at the same surface speed as the drum 46 
for scanning the document 47. The mirror 52 is moved along with the mirror 
51 but at one-half the surface speed of the drum 46. 
Prior to imaging of the drum 46 a charger 56 applies a uniform 
electrostatic charge to the drum 46. The light image causes the formation 
of an electrostatic image through localized photoconduction. A developing 
unit 57 applies toner to the drum 46 to produce a toner image. A feed 
roller 58 feeds the top copy sheet 59 from a stack into engagement with 
the drum 46. A transfer charger 61 applies an electrostatic charge to the 
back of the copy sheet 59 to transfer the toner image thereto. Fixing 
rollers 62 fix the toner image to the copy sheet 59 and feed rollers 63 
feed the finished copy into a discharge tray 64. 
In accordance with the present invention the printer 43 may be a separate 
thermal, impact printer or the like. However, it is preferable to 
partially embody the printer 43 using various components of the copying 
machine 12. Illustrated in FIG. 4 is an imaging unit 66 disposed adjacent 
to the drum 46 upstream of the developing unit 57. The imaging unit 66 
comprises a liquid crystal overlay 67 which is connected to the unit 44. 
The overlay 67 is normally transparent but becomes locally opaque in 
response to applied electrical signals from the computer 31. The overlay 
67 is designed so that the opaque areas form characters corresponding to 
the status parameters of the copying machines 12, 13, 14 and 16. 
The imaging unit 66 further comprises a strobe light 68 such as an xenon 
tube which produces a brief but intense flash of light. Condensors 69 make 
the light from the light 68 parallel for transmission through the overlay 
67. 
To produce a hard copy of the status parameters for maintenance or 
accounting, the corresponding keys on the control panel 42 are depressed 
and the computer 31 disables the ordinary scan operation of the copying 
machine 12. Signals are fed to the imaging unit 66 to form the 
corresponding pattern on the overlay 67. Then, the strobe light 68 is 
fired to radiate a light image of the pattern on the overlay 67 onto the 
drum 46. This causes the formation of an electrostatic image corresponding 
to the pattern in such a manner that the opaque areas of the pattern on 
the overlay 67 produce dark areas in the resulting toner image. The toner 
image is transferred to a copy sheet in the normal manner. If desired, the 
overlay 67 may only produce one line of data. In this case, lines of data 
are fed to the overlay 67 in a sequential manner and the strobe light 68 
fired once for each line to sequentially produce electrostatic images of 
the lines of data. 
Further illustrated in FIG. 4 are a discharge unit 71 for discharging the 
drum 46 prior to recharging and a cleaning unit 72 for removing residual 
toner from the drum 46. 
It will be noted that since the strobe light 68 produces a very brief flash 
of light which is made parallel by the condensors 69, it is unnecessary to 
stop rotation of the drum 46 or dispose the imaging unit 66 extremely 
close to the drum 46. 
In summary, it will be seen that the present invention provides an improved 
electrostatic copying apparatus comprising a number of inexpensive copying 
machines and means for electronically interconnecting the copying 
machines. A user at any of the copying machines can determine the status 
of any of the other copying machines. In addition, means are provided for 
optimally controlling all of the copying machines using a single computer 
and print out various maintenance and accounting data. 
Various modifications will become possible for those skilled in the art 
after receiving the teachings of the present disclosure without departing 
from the scope thereof. For example, the display units 17 may be 
constituted by means such as a TMS 1967 Keyboard Interface unit 
manufactured by Texas Instruments Incorporated of Dallas, Texas USA. Such 
a device comprises a transparent electrode which is touched by the user's 
finger to input data. The device is actuated by a capacitance change 
resulting from proximity of the user's finger. It is also possible to 
eliminate the printer 43 and obtain soft copy of the maintenance and 
accounting data through the display device 17. It is also within the scope 
of the present invention to use as a parameter the type of copy the 
various copying machines are adapted to make; for example plain paper 
copies, diazo copies or masters for offset painting.