Note: Descriptions are shown in the official language in which they were submitted.
103754~ .
~ACKGROUND_OF T~E INVENTION
This invention relates to an electrosta~ic reproduc-
tion machine having an endless ~lt assembly, ~ut more parti-
! cularly to means ~or tracking the movement of an endless
S photoconductive belt within the machine, and means for sensing
when the lateral deviation of a belt reaches a predetermined
position on one side or the other of the normal course of the
belt, and for causing the movement of the belt to cease in
response thereto. The invention also includes means for
easily adjusting the sensing means when the belt assembly is
initially moved into the machine cabinet.
In the practice of xerography as described in U. S.
Patent ~o. 2,297,691 to Chester F. Carlson, a xerographic
surface comprising a layer of photoconductive insulating material
affixed to a conductive backins~ is used to support electrosta~c
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imagesO In the usual method of carrying out the process, the
` xerographic plate is electrostatically charged uniformly over
its surface and then exposed to a light pattern o the imaye
; being` reproduced to thereby discharge the charge in the areas
where light strikes the layer. The undischarged areas of th
layer thus form an electrostatic charge pattern in conformity
, with the configuration of the original light pattern.
-i The latent electrostatic image may then he developed
by contacting it with a finely divided electrostatically
a~tractable material, such as a resinous powder. The powder
is held in the image areas by the electrostatic fields on the
lay~r~ Where~the field is greatestt the greatest amount of ;
material is deposited; and where the field is least, litt1e
or not material is deposited. Thus, a powder image is produced
in conformity with the light image of the copy being reproduced.
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The powder is su~scqucntly t~ans~erred to a she~t of paper
or other surfacc and suitably fixed to thereby form a permanent
print.
` - The latest machine concept or copiers utilizes
high speed flash exposure of a document and an endless belt
having a photoconductive area thereon, the belt being mounted
for movement around a closed path past various processing
;; stations.
Photoconductor belts are v~ry delicate, are easily ~ -
damaged, and the movement thereof through processing stations ~ ~ -
in the reproduction machine must be accomplished with high ~-~
precision and with as little irregular movement as possible. ~-~
Additionally, should the tracking of the photoconductive belt
become irregular and uncorrectable by the tracXing mechanism
of the machine, the machine must be placed in an inoperative
mode as quickly as possible to prevent irreparable damage to
the photoconductive belt as well as the machine.
To place the machine in this inoperative mode, a
fail-safe mechanism utilizing switches is normally used, a
portion of the mechanism being in contact with the belt or a
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sensing ring during its movement. One of the problems with
such arrangements is that of initially adjusting the mechan-
, ism when the belt assembly or module is moved into the cabinet
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of the reproduction machine. The belt assembly is mounted on
at leas~ one shaft so that it can be moved into and out of th~
cabinet. Because of mechanical tolerances within the belt
assembly and the other parts of the machine, it may be necessary ~
~' to make so~e initl~l ~djustments on the fail-safe ~echanism. ~;
Because the rear interior of the cabinet is relatively dark ~;
and inaccessible, however, it is very difficult to make any
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~0375~
major adjustments. Thus, what is needed is an accurate fail-
~aft mechanism which will shut the machine off aq quickly as ~ -
possible should the tracking of the belt become irregular and
uncorrectable, but one which also can ~fe easily adjusted while
mounted on the rear of the machine cabinet. The switches are
mounted on the rear of the cabinet as opposed to the belt
module so as to eliminate the need to make or disconnect
electrical connections each time the belt module i ff moved into
or out of the cabinet.
-~ 10 SUMMARY OF THE INVENTIO~
~, The present invention is directed to a fail-sa~e
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mechanism for stopping the movement o~ an endless photoconductive -~
belt in an electrostatic reproduction machine in the event that
the tracking of the belt becomes irregular and uncontrollable.
The fail-safe mechanism has two mercury switches, and mounted ~
to the rear wall of the machine cabinet so as to be contacted ~'
by the sensing ring of the belt module as the latter is moved
, into the cabinet. When contacted, the, mechanism has a rod
'l, having indicia which rod is movable withrespect to the
remainder of the mechanism for registering the position o~
,, the mechanism when the belt is at one extreme limit of the
' permissible deviation from its normal course. When the belt
~ module i9 pulled out from the cabinet, a reading can be taken ;~
'`! fr~m the rod indicia, and a pointer on the mechanism then can
l 25 be set at a corresponding reading on a second indicia on the ~'
!
,~ mechanism. This operation sets the attitude of the switches
~,, with respect to the photoconductive belt for two extreme '
positions o~ th~ belt ~rom its normal course. When the be~
module is pushed back into the machine cabinet so as to once
again contact the fail-safe mechanism, the mechanism is ready
, for operation.
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1~37S4~1
Thus, in accordance with the present teachings,
r there is provided an improved electrostatic reproduction machine
` which has a framework, an endless bel~ assembly which i mounted
- for movement between an operative position within the framework ~ ~-
~' to an inoperative position remote from the framework with the
belt assembly having a plur~lity of rollers which are adapted
1l to support and move an endless belt which has a photoconductive
; ~ area thereon. The improvement comprises means which include
switch means mounted to the framework for sensing a lateral
deviation of the belt from its normal course of movement during
operation and for opening a circuit in response to sensing a
predetermined deviation. Means are provided mounted so as to
contact the belt assembly when the latter has been moved into
its opera'cive position for indicating how the position of the
~'"r switch means with respect to the belt assembly should be -
adjusted with means for adjusting t:he position of the switch
means as indicated.
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9 ~37S4f~
BRIEF DEscRIr?~oi~ OF T~ DR~WIl~GS
A better understanding of the present invention
as well as other objects and further features thereof will
become apparent upon consideration c the following detailed
; 5 disclosure thereof, especially when taken with the accompanying
drawings, wherein like numerals designate like parts throughout.
Figure 1 is a schematic sectional view of an elec-
trostatic reproduction machine embodying the principles of
the invention; and
Figure 2 is a top view of a portion of the belt
assembly, and of the fail-safe mechanism;
Fi~ure 3 is an isometric view showing the fail-sae
mechanism mounted to the rear wall of the machine cabinet.
l DETAILED DESCRIPTION OF THE I~VE~TION
;l 15 For a general understanding o~ the illustrated copier
reproduction machine in which the invention may be incorporated,
reference is had to Figure 1 in which the various system com-
pon~nts for the machine are schematically illustrated. A
document to be copied is placed upon a transparent support
pla~en P ixedly arranged in an illumination assembly, generally
indicated by the reference numeral 10, positioned at the left -
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end of the machine. Li~ht rays from an illumination system
a~e flashed upon the document to produce image rays corres~
, ponding to the informational areas. The image rays are pro~i 2S jected by means of an optical system onto the photosensitive
surface of a xerographic plate in the form of a flexible photo~
conductive belt lZ ~rran~e~ on a belt assembly, generally i~di-
cated by the rsference numeral 14.
The belt is comprised o a photoconductive layer of
se~snium which is the light receiving sur~ace and imaging mediur.
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~3754~^ ~
for the appara~us formcd on a conductive backing. The surfa~e -~
of the photoconductLve belt is made photosensitive by a previous
step of uniformly charging the same by means of a corona
generating device or corotron 13.
S The belt is journaled for continuous movement upon
three rollers 20, 21, and 22 positioned with their axes in
parallel. The photoconductive belt assembly 14 is slidably
mounted upon two support shafts 23 and 24 with the roller 22
rotatably supported on the shaft-23 which is secured to the
1~ frame of the apparatus and i5 rotatably driven by a suitable
;~ motor and drive assembly (not shown) in the direction of the ~ ~-
~! arrow at a constant rate. During exposure of the belt I2,
the portion exposed is that portion of the belt running
between rollers 20 and 21. During movement of the belt 12 `~
~ 15 the reflected light image of the original document positioned
`~, on the platen on the surface of the belt to produce an electro-
static latent image thereon at exposure station A. ~ `
As the beLt surface continues its movement, the
electrostatic image is passed through a developing station B
in which there is positioned a developer assembly, generally
indicated by the reference numeral 15, and which eff~cts
development of the electrostatic image by means of multiple
magnetic brushes 16 as the image moves through the development
. zone.
, 25 The developed electrostatic image i5 transported ;~
`, by the belt to a transfer station C where a sheet of copy paper
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is moved between a transfer roller 29 and the belt at a speed
in synchronism with the moving belt in order to accompl~sh
transier of the developed image by an electrical bias on the - -~
~ 30 transfer roller. There is provided at this station a sheet -~ -
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~37~4~
transport mechanism, generally indicated at 17, adapted to
transport sheets of paper from a paper handling mechanism,
generally indicated by the reference numeral 18, to the deve-
lopsd imaye on the belt at the station C.
After the sheet is stripped from the belt 12, it is
conveyed into a fuser assembly, generally indicated by 19,
wherein the developed and transferred xerographic powser image
on the sheet material is pexmanently fixed thereto. After
fusing, the finished copy is discharged from the apparatus at a
.
1~ suitable point for collection externally of the apparatus. The
toner particles remaining as residue on the developed image,
background particles and those particles otKerwise not trans-
f~rred are carried by the belt 12 to a clearing apparatus 26
positioned on a course of the belt between rollers 20 and 22
adjacent to charge device 25.
; Further details xegarding the structure of the belt
j as~embly 14 and its relationship with the machine and support
.l therefor may be found in U. S. Patent 3,730,623 assigned to
- the same assignee.
2~ Referring now to Figure 2, thera is illustrated a
~ tracking assembly~ generally indicated as 30 including the upper
i~ roller 20 and the tracking roller 21. The upper roller 20 is
; rotatably supported on a hollow shaft journaled for rotation in
bearings disposed in side plates such as described in U. S.
patent 3,702,131 to David Roth Stokes, et al entitled "Belt
Tracking System", assigned to the same assignee. The trackins
roller 21 ~s secured to a shaft ~ournaled for rotation in
bearings secured to 'he ends of the parallel legs of a yoke
member. The tracking mechanism is described in Canadian
~¦ 30 application 185,436.
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~37548
It is sufficient for present purposes to say that ;~;
the tracking mech~nism includes a flat plastic sensing ring
32 which contacts the belt 12 udring movement of the latter
ovex the roller 20. The sensing ring is mounted for rotation
about a bearing, and is supported on a support plate 34. Thus,
lateral movement of the belt 12 results in lateral movement
o both the sensing ring 3~ and support plate 34 which in
turn causes rotation of a shaft 36 about its axis to efect
the correction necessary to move the belt back to its normal
course of movement. It is only when the tracking mechansim
- 30 does not satisfactorily correct the movement of ~he belt
that the fail-safe mechanism 38 (Fi~ure 2) of the present
invention operates to stop the movement of the belt.
Referring to Figures 2 and 3, the operation of the
mechanism 38 will be described in more detail. When on its
normal course, the belt 12 overlaps each end of roller 20 by
a distance "a", which in the present example is 1/8 inch. If
t~e belt deviates 1/8 inch in either direction during operation
; of the machine, the mechanism operates to stop the movement
of the belt to prevent damage to the machine and the belt. It
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does this by opening (or closing) one of two mercury switches
40 or 42 depending upon the direction of the deviation of the ` ~;
.
b~elt~
To sèt the mechanism up for operation, the belt
assembly 14 (without a belt) is moved into the machine cabinet
away from the reader as viewed in Fiqure l, and to the left
as viewed in Figure 2) until the sensing pin 44 of the mechanism
38 is contacted by either the sensing ring 32 or the support
plate 34 of the belt assembly as shown. As can be seen, the
mechanism 38 is mounted to the rear wall 46 of the machine-
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1~3754~
cabinet. The mechanism 38 has a setting rod 48 which is
slidably mounted in an opening 50, the setting rod contacting
the rear wall 46 prior to the time the sensing pin 44 is con-
tacted by the belt assembly 14. The setting rod has color
coded markings 46 on one end thereof, and as the belt assembly
applies a linear force against the sensing pin ~4, the housLng
52 moves inwardly toward the rear wall 46 while simultaneously
rotating in a countclockwise direction via the action of
flexure legs 49. As the housing 52 moves inwardly, more of
the setting rod 48 is exposed. Thus, when the belt asse~bly
14 (without the belt) is initially moved completely into t~e
cabinet, the setting rod 48 will indicate via the color coded
markings 46 how the mechanism 38 should be adjusted. This
inward position o the mechanism will correspond to one of the
limits of the permissible deviation of the belt 12, because
1 without a belt on the belt assembly 14, the sensing ring will
'¦ be resting against the end of the roller 20.
After the belt assembly 14 has thus been moved into
-~ the machine cabinet, it is then pulled out o~ the cabinet, and
a reading is taken of how far the setting rod 48 is prot~uding.
It is apparent that as the ho~sing 52 moves outwardIy from ~he
rear wall 46 as the belt assembly 14 is being withdrawn from
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t~e cabinet, the setting rod 48 will move along with it.
The sensing pin is normally held in a fixed position
with respect to the housing 52 by a locking screw 54. After the -~
belt assembly has been withdrawn from the cabinet, ho~ever, ~he
locking screw 54 is loosened so that the sensing pin 44 Gan be ~ ~
'~! rotated so that its pointer 56 points to one of the color coded ~-
markings 58 which corresponds to the reading obtained on th~
markings 46 on the setting rod 48: as can be seen, when the
sensing pin is rotatcd, both switches 40 and 42 are a1so r ~ ed.: -:
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37S4~3
By the above procedure, tlle attitude of the s~itches
40 and 42 has now been set, and when a belt is placed onto the
rollers 20, 21, and 22, and the belt assembly moved back into
' the machine cabinet, the mechanism 38 is properly adjusted and
ready for operation.
As should now be apparent, the belt 12 is in its
normal position in Figure 2, each end of the belt overlapping
the roller 20 by 1/8 inch in the present example. Thus, the ~ ;-
- belt can deviate a total of 1/4 inch during its movement and
- 10 1~8 inch in either direction from that shown in Figure 2. If
~ it does deviate 1/8 inch in either direction, the mechanism ;
.
38 will act to stop the movement of the belt by opening the ~`
, circuit to the motor driving the belt assembly 14. It does
this by rotating either clockwise or counterclockwise from the
position shown in Figure 2 depending ~pon the direction of the ~;
deviation of the belt 12 from its normal course. The attitude
of the switches having been initially adjusted, one of the ,;~
sw1tches will open (or close) to open the motor circuit drivlng
the belt assembly, depending upon which direction the mechanism
38 rotates.
As can be seenj the above arrangement provides for a
fail-safe mechanism which is very accurate, but yet provides for
easy adjustment so as to accommodate itself to belt assemblies -
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or machines having varying tolerances. In the present embodi~
, 25 ment, a suitable mechanism was formed from plastic. Other ; ;~
materials might also be used, however, the modules of the
material and t~e cross-sectional area of th~ flexure legs
being taken into consideration to get the degree of movement
desired.
While the invention has been describ~d with refer-
ence ~o the 6tr~ture ~ losed, it is not confined to the
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~)375~4~1 -
~ details sct forth, but i5 intencled to cover such modifications
;~ or changes as may come within the scope of the following
claims: ~;
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