U.S. patent number 3,684,890 [Application Number 05/006,622] was granted by the patent office on 1972-08-15 for photosensitive misfeed detector.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to Thomas F. Hayne, Charles A. Whited.
United States Patent |
3,684,890 |
Hayne , et al. |
August 15, 1972 |
PHOTOSENSITIVE MISFEED DETECTOR
Abstract
A misfeed detector for sensing the presence of a properly fed
sheet of support material prior to the sheet being conveyed to the
photoconductive surface of a xerographic machine for transfer of a
developed image thereto. A photocell system utilizes two
reflections from an area where both a sheet should be located and a
gripper member is situated to determine whether a sheet is
correctly positioned to be conveyed for an image transfer. If a
misfeed of the sheet is detected by the photocells, a shutdown of
the xerographic machine is effected.
Inventors: |
Hayne; Thomas F. (Fairport,
NY), Whited; Charles A. (Fairport, NY) |
Assignee: |
Xerox Corporation (Rochester,
NY)
|
Family
ID: |
21721786 |
Appl.
No.: |
05/006,622 |
Filed: |
January 28, 1970 |
Current U.S.
Class: |
250/223R;
271/261; 250/559.4 |
Current CPC
Class: |
G03G
15/70 (20130101) |
Current International
Class: |
G03G
15/00 (20060101); G06m 007/00 () |
Field of
Search: |
;250/223,204,219DQ,219F
;101/284,408-410 ;271/53,57,60 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Stolwein; Walter
Claims
WHAT IS CLAIMED IS:
1. An apparatus for detecting the non-feed and mis-feed of
positioning of a sheet material supported on a conveying surface
including
energy beaming means to direct a plurality of energy beams against
a conveying surface adapted to convey a sheet material to a
utilization station,
energy sensing means to sense the plurality of levels of energy
produced by the plurality of energy beams directed against the
conveying surface,
control means responsive to the plurality of levels of energy
sensed by the energy sensing means to indicate the feed and
non-feed of positioning of a sheet material on the conveying
surface upon the plurality of levels of energy being substantially
equal to each other, and
said control means further including a timing means to measure a
pre-determined time interval beginning upon the application of
power to said control means and again recommencing upon the sensing
of an unequal energy level whereby the control means is conditioned
prior to the beginning of each sensing cycle.
2. The apparatus of claim 1 wherein the energy beaming means
directs two beams of radiant energy against the conveying surface
and a non-reflective member positioned thereon.
3. The apparatus of claim 2 wherein the energy sensing means senses
the reflective level of the two beams of radiant energy from the
conveying surface and the non-reflective member.
4. A detector apparatus for detecting the improper positioning of a
sheet member on a conveying surface having a sheet securing means
comprising
a first energy means to direct a first beam of energy against the
conveying surface,
a second energy means to direct a second beam of energy against the
sheet securing means,
energy sensing means to sense the magnitudes of the energy produced
by the first beam of energy and the second beam of energy directed
against the conveying surface and the sheet securing means
respectively,
control means responsive to the relative magnitudes of energy
sensed by the energy sensing means to indicate the improper
positioning of a sheet material on the conveying surface upon the
magnitudes of energy remaining balanced for a predetermined time
interval.
5. The apparatus of claim 4 wherein the first energy means and the
second energy means each direct a beam of radiant energy.
6. The apparatus of claim 4 wherein the magnitude of energy
produced by the second beam of energy is unequal to the magnitude
of energy produced by the first beam of energy directed against the
conveying surface having a properly positioned sheet material.
7. The apparatus of claim 4 wherein the time interval is measured
by a timing circuit.
8. The apparatus of claim 4 wherein the conveying surface
supporting a sheet member moves relative to the detector apparatus
to produce unbalanced magnitudes of energy during the time interval
upon the sensing of a properly positioned sheet.
9. A method of sensing the presence of a properly positioned sheet
of material being conveyed by a conveying surface including a sheet
securing means comprising the steps
directing a first beam of energy against a conveying surface having
a first energy reflective level to produce a first magnitude of
energy,
directing a second beam of energy against a sheet securing means
having a second energy reflective level to produce a second
magnitude of energy,
moving the surface and sheet securing means relative to the first
and second energy beams, and
sensing the proper positioning of a sheet of material on the
conveying surface upon at least one of the first magnitude of
energy and the second magnitude of energy changing value during a
predetermined time interval.
Description
BACKGROUND OF THE INVENTION
This invention relates in general to the proper handling of a sheet
of material and in particular to a detecting device for sensing the
proper feeding of a sheet of support material for transfer of a
developed electrostatic image thereto.
More specifically, this invention relates to a misfeed detector
wherein a photocell system detects whether a sheet of support
material is properly positioned prior to being fed to a utilization
station. A photolamp directs two beams of light through a fiber
optic means to reflect off the surface supporting the sheet
material and the gripper member gripping the paper being fed
thereon. If a sheet of support material is properly fed to the
surface supporting the sheet material, the beam of light striking
the gripper finger and the beam striking the paper produce
unbalanced reflective values to thereby indicate a sheet is
properly fed. However, if the two beams of light are reflected in a
substantially balanced condition, a misfeed of a sheet is indicated
and a control signal is produced to effect a discontinuation of the
operation of the particular machine utilizing the sheet. Further,
to insure the accurate detection of the feeding of a sheet
material, a light sensitive element is positioned within the light
producing housing to sense whether a proper beam of light is
present.
Although not intended to be so limited, for convenience of
illustration the misfeed detector of the present invention is
described for use in an automatic xerographic reproducing machine.
In the process of xerography a xerographic plate comprising a layer
of photoconductive material on a conductive backing is given an
uniform electrostatic charge on its surface and is then exposed to
the subject matter to be reproduced by various projection
techniques. This exposure discharges the plate in accordance with
the light intensity reaching it thereby creating a latent
electrostatic image on or in the plate. Development of the image is
effected by developers which may comprise, in general, a mixture of
suitable, pigmented or dyed, resin base powder, hereinafter
referred to as toner, which is brought into contact with the plate
by various well-known development techniques. During such
development of the image, the toner powder is brought into surface
contact with the photoconductive coating and is held there
electrostatically in a pattern corresponding to the latent
electrostatic image. Thereafter, the developed xerographic image
may be transferred to the support material to which it may be fixed
by any suitable means such as heat fusing.
Several techniques are employed in the prior art to produce the
aforementioned transfer of the developed toner image from the
photoconductive surface to a support material. One well-known
method utilizes the use of a web of support material such as paper
which is positioned against the photoconductive drum by means of
two rollers offset from the point of actual transfer of the image
to the material. The transfer of the developed material to the web
is effected by use of a corotron which applies an electrostatic
charge to the back side of the support material to effect transfer
of the toner image thereto. However, in such a system it is usually
necessary to cut the web support material into sheets after the
toner image has been fused thereto in order to produce convenient
reproductions. Therefore, a suitable cutting system must be
employed in the xerographic machine which will accurately meter the
web of support material past a cutter to provide the correct
correspondence of the cut sheets to the original image.
The precise indexing of the web to produce an accurately cut sheet
is difficult to achieve as well as increases the complexity of the
xerographic machine. In addition to the difficulties presented by
the necessity of the web of support material being properly
indexed, the use of a web is also economically wasteful since the
support material must carry the transferred image to the fusing
means thereby not utilizing material between the image at the
fusing area and the subsequent image to be transferred. Therefore,
it has become advantageous in many xerographic applications to
utilize sheets of support material to receive developed toner
images.
An example of a toner image transfer system utilizing a support
material in sheet form is disclosed in the copending application,
Ser. No. 830,426 by Michael Langdon filed June 4, 1969, now
abandoned. Such a particular system may be, for example, utilized
in a color xerographic reproducing machine and includes the use of
an electrical bias potential applied to a conductive transfer
roller to effect efficient transfer of the image thereto. The
conductive roller is mounted adjacent the photoreceptor drum to
rotate at the same surface speed. A sheet of paper from a paper
feeder is moved to the conductive roller and is gripped by a
gripper member so as to be carried to the transfer station adjacent
the drum surface. Such a transfer system overcomes the problems of
registration caused by the required cutting of sheets after
transfer and fusing and further prevents the waste of support
material inherent in web systems.
However, unlike a web of support material which generally does not
misfeed unless the supply roll of material is depleted, the
utilization of support material in individual sheets frequently
encounters improper feeding situations. The sheets often physically
jam in the paper feeder or in other areas and do not reach the
position of transfer as required. Such a failure of a sheet of
paper to be located between the transfer roller and the
photoconductor drum results in the failure of a duplicate being
produced by the machine. Further, an absence of a sheet between the
transfer roller and the photoconductive drum causes the developed
image to transfer to the surface of the roller which allows toner
from the mistransferred image to be applied to subsequently fed
sheets and thus damage their quality. Also, toner not properly
transferred to a support material hinders the proper operation of
the xerographic machine by contaminating it with excess particles
which tend to interfere with the elements of the apparatus.
In order to overcome the problems of a misfed sheet of material in
a xerographic machine, it becomes desirable to provide a detection
device which accurately and quickly determines whether a sheet of
support material has been properly fed to the transfer device. Such
a detection system must be compatible with a xerographic machine to
effectively cooperate in its operation and still be relatively
inexpensive and have good operational reliability. Further, the
sheet detection system must accurately determine whether a sheet
has been properly fed by the paper feeding mechanism and desirably
indicate whether the sheet of paper is properly gripped by the
member carrying in on the transfer means. As a further precaution
to prevent the misfeed of a sheet, it is important to utilize a
misfeed detector which includes a fail safe mechanism to insure
that the system is continuously operating to detect the presence of
a sheet of support material. Therefore, it is advantageous to
utilize in a xerographic machine employing support material in
sheet form, a misfeed detection device which clearly indicates the
correct positioning of a sheet of material for reception of an
image from a photoconductive surface.
SUMMARY OF THE INVENTION
It is, therefore, an object of this invention to improve the
transfer of a developed image from a photoconductive surface to a
sheet of support material.
Another object of this invention is to improve the detection of the
proper feeding of a sheet of support material to a transfer
device.
A further object of this invention is to detect the proper feeding
of a sheet material by means of a photocell system.
Still another object of this invention is to improve the detection
of whether a gripper member has properly gripped a sheet of
material being conveyed by a roller.
A still further object of this invention is to detect the failure
of a photolamp to operate in a detection system.
These and other objects are obtained in accordance with the present
invention wherein there is provided a misfeed detector that
reliably detects the presence of a sheet of paper or other support
material as, for example, being fed to a photoconductor drum to
receive a developed electrostatic image therefrom. The detection
system includes a photolamp which directs two beams of light upon
the surface supporting the sheet material and a gripper member for
conveying the sheet member, and according to the detected
reflective outputs of the beams, a control signal to the machine
utilizing the sheet is effected. If a sheet of material is properly
fed and the proper reflective signal is detected, the machine is
given a go signal to continue its normal sequence of operations.
However, if the reflective value of the light beams indicates that
a misfeed of a sheet material has occurred or that the gripper
member is not properly in position, then the detection system
produces a signal to discontinue the operation of the machine to
prevent further damage to the apparatus. As a further protection
the detection system includes a photocell means to detect the
presence of a light beam to insure that the detecting device is
properly operating.
The novel misfeed detection system of the present invention
produces a reliable indication of the proper feeding of a sheet of
support material. Not only does the detection device disclosed
herein improve the prior art detection of sheets of material, but
also further gives an indication of the proper positioning of the
gripper member which conveys the support material. Further, the
inclusion of a fail safe light detection system makes the present
detection system extremely reliable, since the light emanating from
a lamp does not need to be periodically checked until the fail safe
detection system detects the presence of an inoperable lamp. Also,
the detection unit of this application is both compact and
non-complex and readily cooperates with various types of sheet
feeding mechanisms. Therefore, the present invention presents a
novel and accurate misfeed detection system having high reliability
not heretofore provided by the prior art.
DESCRIPTION OF THE DRAWINGS
Further objects of the invention together with additional features
contributing thereto and advantages accruing therefrom will be
apparent from the following description of one embodiment of the
invention when read in conjunction with the accompanying drawings
wherein:
FIG. 1 is a schematic illustration of a transfer device for a
xerographic machine utilizing the misfeed detector of the present
invention.
FIG. 2 is a side schematic illustration of the misfeed detector of
the present invention.
FIG. 3 is a schematic illustration of the illuminator for the
misfeed detector of the present invention.
FIG. 4 is a front schematic illustration of the misfeed detector of
the present invention.
FIG. 5 is a schematic illustration of the positioning of a properly
fed sheet of support material on the conductive roller of the
transfer device.
FIG. 6 illustrates the electrical circuit in the detection device
of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, there is shown a schematic illustration of an
example of transfer device 2 mounted adjacent a photoconductive
drum 1 and utilizing the misfeed detector of the present invention.
The transfer device 2 comprises a conductive transfer roller 3
coupled to a suitable electrical bias potential and the roller is
rotated by a suitable motor means (not shown) in a clockwise
direction at the surface speed of the drum 1. The bias potential
connected to the conductive roller 3 produces an electric field
which effects transfer of the developed toner image from the
photoconductive drum 1 to a sheet 4 of support material which is
positioned between the confronting faces of the drum and the
roller. The sheet 4 of support material is fed at the proper
sequence to the bottom of the conductive roller by feeder mechanism
5 at a faster speed than the speed of the surface and the sheet is
then gripped by gripper member 6 mounted on the roller.
A series of gripper fingers are provided to swing down onto the
properly positioned sheet of support material by suitable means
(not shown) and grasp the sheet in order to carry it in the upward
direction on the conductive roller to be in a transfer position.
For a more detailed description of the transfer device 2 utilizing
the conductive roller herein described, reference is made to the
aforementioned copending application Ser. No. 830,426.
Still referring to FIG. 1, the position of the misfeed detector
according to the present invention is illustrated generally at 10.
A detector plate 11 is mounted in close vicinity to the transfer
roller at the point after the sheet of support material is supplied
to the transfer roller and is gripped by the gripper members 6. The
detector plate is mounted by a suitable screw means 12 onto a
V-shaped bracket 13, wherein the vertical extending portion 14 of
the bracket extends a greater width than the horizontal support
portion 15 as best shown in FIG. 2. Again, referring to FIG. 1, the
bracket 13 is supported on a support member 16 which rests on the
housing of the xerographic machine. The plate 11 extends from the
vertical portion of the bracket 13 along the conductive roller to
be at least in confrontation with the first gripper member as best
shown in FIG. 3.
Referring in particular to FIG. 2, the plate of the misfeed
detector includes two angularly directed holes 17 and 18 drilled
at, for example, identical complementary angles with respect to a
normal direction from the plate surface, although dissimilar angles
can be utilized if desired. Two fiber optical light guide members
19 and 20 are mounted respectively in holes 17 and 18 and both
light guides extend to a common illuminator housing (to be
explained in detail later). The fiber optics light guide comprises
any suitable conventional fiber optical material as, for example, a
plastic. The plate 11 further includes two holes 21 and 22 drilled
in a perpendicular direction to the surface of the plate which
supports two conventional photocell elements 23 and 24 capable of
detecting light intensity. Alternatively, the photocells may be
remotely located wherein a fiber optic light guide directs light
reaching the holes 21 and 22 to a respective photocell element. The
holes 21 and 22 may also be drilled at a selected angle other than
normal as shown. The photocells 23 and 24 are coupled by suitable
electrical connectors (not shown) to the electrical circuit of the
present invention (to be illustrated later).
Referring now to FIG. 4, there is illustrated the illuminator
housing 30 which transmits light through the fiber light guide
members 17 and 18. The illuminator housing is mounted in any
convenient remote location from the detector plate, and within the
housing 30 a lamp 31 of any conventional type is mounted on a
bracket 32. The lamp 31 is connected by suitable electrical leads
to a low voltage power supply (not shown) for illumination of the
lamp. The light from the lamp is directed to the receiving end 33
of the fiber optics light guide which is mounted in suitable
brackets 34 directly adjacent the light beam of the lamp 31 to
receive the rays therefrom. The end 33 of the fiber optics light
guide receives the light from the lamp and divides it up into two
beams which are directed through the two separate fiber optics
guide members 19 and 20. The light in the two fiber optics light
guide members is directed to their respective ends mounted in holes
17 and 18 in the detector plate 11 to form two beams which are
directed onto the transfer roller. Also a light sensitive element
35 such as, for example, a phototransistor used as a photodiode is
mounted within the illumination housing 30 and is responsive to the
level of light within the illuminator housing to cause a shutdown
of the xerographic machine in the event that the lamp fails to
illuminate. The cooperation of the photodiode 35 within the circuit
of the detector to effect a fail safe type sensing function will be
explained later in conjunction with the description of FIG. 6.
Referring now to FIG. 5, there is illustrated a schematic view of
the transfer roller 3 wherein a properly fed sheet of paper being
gripped by the gripper fingers is illustrated. The roller 3 is
shown with a properly inserted sheet 4 of support material which is
gripped by three gripper fingers 6. The gripper finger which is
used as a reflective surface is painted black whereby when a beam
of light is directed upon it, no reflection will occur. Therefore,
the light emanating from the fiber optic member 19 is directed upon
the location where the gripper finger should be when properly
gripping a sheet of paper. The light being directed by the other
fiber optic member 20 is directed to a location on the roller
directly adjacent to the gripper finger which is reflective if a
white support member is properly present, but the roller surface in
the vicinity of the gripper is selected to be non-reflective in
absence of a sheet.
Therefore, if a properly fed sheet is attached to the roller by the
gripper, an unbalanced reflective value is produced by the gripper
finger and the sheet surface. However, it can also be seen that if,
for example, a sheet of paper is not properly fed to the gripper,
light will not reflect off the transfer roller and a balanced black
or very low level reflection is detected by the photocells.
Similarly, if a sheet covers the black gripper finger and thereby
being improperly attached to the roller, a substantially balanced
reflective value is detected by the two photocells, since both
beams of light are directed against the sheet.
Referring now to FIG. 6, the electrical circuit is illustrated
which cooperates with the photocell system of the misfeed detector
of the present invention. The two sensing photocells 23 and 24 in
the detection plate 11 form two arms of a bridge circuit which
includes a resistor R1 and a tap element and the bridge is coupled
to a suitable DC power source. The bridge circuit is connected to
the base of a suitable PNP transistor 60 and through a resistor R2
to the emitter of the PNP. A suitable bias resistance R3 is further
coupled to the base of transistor 60. The base of a second
identical PNP transistor 61 is connected to the emitter of the
transistor 60 and the collector of transistor 61 is coupled to the
collector of the first PNP. The photodiode 35 shown in FIG. 4 is
connected in the circuit block 63 to effect a control signal to
discontinue operation of the xerographic machine in the event of a
burn out of the lamp (as will be described in detail later).
The circuit of the invention further includes a timing means which
comprises a capacitor C1 and resistors R4 and RT that control the
firing of a unijunction transistor UJT. The transistor UJT is
suitably biased by resistances RT, R4, R5, and R6 wherein RT
provides thermal compensation for the unijunction due to ambient
variations in the machine environment. The output of the
unijunction is connected to the collector of a silicon controlled
rectifier SCR which includes a relay 64 in series therewith. The
logic circuit of the xerographic machine is coupled to the timing
circuit to apply and subsequently remove power from the detector
timing circuit to determine proper feeding of a sheet during the
appropriate interval. In this manner proper feed or lack of proper
feed is determined and the machine is allowed to continue or
commanded to begin a shutdown sequence.
In operation, the detector circuit effects a control of the
xerographic machine by the particular timing sequence of the timing
means. The power source of the detector circuit is actuated by he
machine logic circuit to begin the charging of capacitor C1 of the
detector to commence a timing sequence by the timing means. If the
bridge becomes unbalanced before the triggering of the UJT
transistor by the capacitor as in the case where the photocell 23
does not sense reflected light while the photocell 24 does sense
illimination, then the two PNP transistors will both conduct to
discharge the capacitor C1 whereby the capacitor has not reached a
level sufficient to trigger the UJT and therefore a new timing
cycle is begun by the timing circuit. In order to achieve a precise
start time for the timing means and to improve photocell stability,
a test pattern 65 is mounted a predetermined distance ahead of the
gripper fingers on the transfer roller as best shown in FIG. 5. At
a time after the power is applied to the circuit in its proper
sequence of operation, the light beams strike the black and white
pattern 65 on the roller to produce the aforementioned discharge of
the capacitor C1 because of the unbalance of the photocells and a
new timing interval is then again commenced, since the capacitor
has not reached a level sufficient to trigger the UJT.
After the new time interval has been started by the renewed
charging of the capacitor C1, the gripper fingers and sheet on the
conductor roller 3 are rotated past the detecting light beams
produced by lamp 31. If the photocells 23 and 24 detect a correctly
fed sheet and the darkened gripper finger is in the correct
position to carry the paper to the transfer station, the capacitor
again is discharged to effect a new timing cycle since photocells
sense an unbalanced light condition. However, if the photocells
detect a balanced black condition, then a sheet of support material
has been misfed and both transistors 60 and 61 will not fire to
reset the timer as in the unbalanced light situation. Thereafter,
the timing circuit after a balanced detection continues its normal
time interval by the capacitor C1 being charged by the power
source. When the capacitor is then charged to the required level,
the unijunction UJT is triggered to instantaneously fire the SCR
switch and the relay 64 is energized. If the relay 64 is energized
the machine circuit will receive a signal to effect a shutdown
sequence of the xerographic machine. Similarly, if the photocells
detect the condition where a sheet of paper is present but the
sheet covers the gripper finger, a balanced light condition is
sensed which will likewise not discharge the capacitor to reset the
timer and thus a shutdown sequence is also effected. On the other
hand, if an unbalanced light pattern is sensed by the photocells
due to a properly fed sheet of material as stated previously, the
timer is reset and the relay is not energized whereby the machine
logic circuit continues normal operation of the apparatus.
If an improper fed sheet is detected, the shutdown of the operation
of the xerographic machine may involve a sequence of operations
such as, for example, fusing of a prior transferred image, a
movement by the transfer charged away from the photoreceptor drum,
or other desirable events needed before a satisfactory shutdown
should be effected. Further, the photodiode 35 mounted in the
illuminator housing possesses a low resistance when lighted and
upon the lamp being burned out, the diode immediately acquires a
high resistance. The resulting high resistance makes it impossible
for the PNP transistors to discharge the capacitor C1 to reset the
timing circuit for a new sequence which is necessary for a go
situation for the machine. Therefore, the UJT triggers at the next
interrogation interval as the capacitor C1 becomes charges to the
necessary level to energize the relay and cause the machine to
discontinue operation in a manner similar as in the case of a
misfed sheet of support material as previously described.
In the above description there has been disclosed an improved
misfeed detection device for insuring the correct feeding of a
sheet of support material to the transfer station of a xerographic
apparatus. The misfeed detection device of the present invention
may be utilized in conjunction with other image transfer mechanisms
and xerographic machines other than the one herein disclosed.
Further, the novel detection device disclosed herein was described
for convenience of illustration for use in a xerographic machine,
but the invention may be utilized in any system where it is desired
to detect the misfeeding of sheet material. Also the sensor may be
used to test the efficiency of grip (percentage of area of paper
gripped) by relating the relative effectiveness of an ideal grip in
the form of the test pattern to the actual grip by observation of
the capacitor discharge curve.
While the invention has been described with reference to the
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the true
spirit and scope of the invention. In addition, many modifications
may be made to adapt a particular situation or material to the
teaching of the invention without departing from its essential
teachings.
* * * * *