Note: Descriptions are shown in the official language in which they were submitted.
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Ti t e_o~ the Invention
ROT~TABI,E FOCUSING MEANS
FOR
VARIABLF MAGNIFICATION
ELECTROPHOTOGRAPHIC COPIER
sackgr _nd of the Invention
My invention relates to electrophotographic copiers
and, more particularly, to variable magnification elec-tro-
photogra~hic copiers using movable focusing means.
In electrophotographic copiers of khe prior ar-t
movable focusing means are used to vary the magnification
of the light image focused upon a photoconductive surface.
However, the focusing means is translated along its optical
axis, in a same manner as the lens of a camera. To produce
this translational movement of the focusing means is
mechanically complex and expensive in view of the precision
with which it must be accomplished to achleve accurate focus
at various magnifications. In my inven-tion, variable
magnification is obtained by rotating the focusing means
about an axis orthogonal to its optical axis, resulting in
a mechanically simpler, more accurate, and less expensive
construction.
The problem of changing magnification in an
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electrophographic copier is particularly clifficult in
copiers having focusing means of fixed focal len~th. In
such copiers a change of ma~ni~ication requires not only
a change in the ratio of the object distance to -the image
distance but also a change in the sum of the object and image
distances.
SUMMARY OF THE INVENTION
One object of my invention is to provide a variable
magnification electrophotographic copier having focusing means
which rotates about an axis orthogonal to its optical axis.
Another object of my invention is to provide a
variable magnification electrophotographic copier which is
mechanically simple and inexpensive.
Other and further objects of my invention will appear
from the following description.
- With the present invention the above objects are met
by providing electrophotographic copying apparatus incIuding
in combination a photoconductive surface, focusing means
having an optical axis, means mounting the focusing means for
rotation about a fixed axis of rotation which is generally
orthogonal to the optical axis, in a first angular position
the focusing means providing a focused image of a first
magnification on the surface~ in a second angular position the
focusing means providing a focused image of a second magnifica-
tion on the surface, and means for selectively rotating the
focusing means back and forth between the first and second
angular positions, the angular difference between the first and
second positions being relatively large, and the focusing means
providing no focused image at any angular position intermediate
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the first and second positions.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings which form part of
the instant specification and which are to be read in conjunc-
tion therewith and in which like reference numerals are used
to indicate like parts in the various views.
FIGURE 1 is a fragmentary side elevation of a
first embodiment of my invention showing the optical paths
for different magnifications.
FIGURE 2 is a side elevation of the first embodiment
showing the details of mechanism for driving the vaxious optical
elements.
FIGURE 3 is a side elevation of an electrophoto-
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graphic copier employing -the first embodiment oE F.CGURES
1 ancl 2.
FIGURE 4 is a side elevation of a second
embodimen-t of my lnvention showing -the optical paths
for various magnifica-tions.
FIGURE 5 is a fra~mentary plan view of the
second embodiment showing the details oE mechanism
for driving the various optical elements.
Descri~tion of the Preferred Embodiment
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FIGURES 1 through 3 show the first embodiment
of my invention. ~n object documen-t 2 to be copied is
placed upon tranSparen.t platen 4, which is mounted
in the top of housing 6 of an electrophotographic copier.
Light from lamp 8 is re:Elected hy a semi-elliptical
reflector 10 and a planar mirror 12 to illuminate a
lateral strip of the document. Light from the illuminated
strip of document 2 is directed to a reflex lens 20 .
after sequential reflection from full-rate scanning
mirror 14, half-rate scanning mirror 16, and a mirror 18.
Reflex lens 20 includes a double convex lens 22 and a
planar mirror 24, and is mounted on shaft 26 for rotation
about an axis which orthogonally intersec-ts the optical
axis of lens 20.
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Li~ht from reElex lens 20 is Eocused upon a charged
pho-toconductive surEace 3~ aEter sequen-tial reflections
from mirrors 28 and 30. The pho-toconductive layer 32
is mounted on a drum 34.
The magnification of the image formed by re:Elex
lens 20 upon surface 32 is equal to the ratio of the
image distance to the object clistance. For a magnification
of unity, the image on -the photoconductive surface is
the same size as the documen-t; and the object and image
distances from the lens are equal. If the image is to
be smaller than the objec-t document 2, so that -the
magnification is less -than unity, then the object distance
must be increased and the image distance decreased.
This reduction in magnification is made by moving mirror
18 to the al-ternate position 18A, by ro-tating reflex
lens 20 so -that its lens and mirror are in the alternate
positions 22A and 24A, by moving mirror 28 to -the alternate
positions28A, and by rotating mirror 30 on its shaft 31
to the alternate position 30A.
As shown in FIGURE 2, a magnification-changing
crank 36 provided with a crank handle 37 is attached to a
rotatable drum 38, about which flexible cable 40 is
wrapped. Cable 40 passes over tensioning pulley 42, which
is mounted on a lever ~4 journalled on a fixed shaft 46.
Lever 4~ is biased by spring 48 -toward spring anchorage
50 to take up slack in cable 40. Cable 40 further passes
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over pullcys 52, 5~, and 56 before beiny returned -to
drum 38.
One end of spring 58 is a-ttached to cable 40~
and -the other is secured to a housing 60, in which reflex
lens 20 is mounted. Benea-th housin~ 60 are fixed stops
62 and 64. Stop 62 limits counterclockwise rotation of
housing 60 to the angular orientation for unity magnifica-tion;
and stop 64 limits clockwise ro-ta-tion of housing 60 to
-the alternate angular orientation 60A for reduced
magnification.
Onè end of sprin~ 66 is a-t-tached to cable 40,
and the other is secured to a lever 68, journalled at
one end on a shaft 70. The other end of lever 68 rota-tably
mounts a shaft 72 to which is secured mirror 18. Stops
74 limit counterclockwise rota-tion of lever 68 and hold
mirror 18 in the positio~ and angle for unity magnification.
Stops 76 limit clockwise rotation of lever 68 and hold
mirror 18 in the alternate position and angle 18A for
reduced magnifica-tion.
One end of spring 78 is attached to cable 40,
and the other is secured to a lever 80, journalled at one
end on a fixed shaft 82. The other end of lever 50
rotatablv mounts a shaft 84 to which is secured mirror 28.
Stops 86 limit clockwise rotation of lever 80 and hold
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mirror 28 in the position and angle for un:ity magniflcation.
S-tops 88 limit counterclockwise ro-tation of lever 80 and
hold mirror 28 in -the al-ternate position and angle 28A
for reduced magnification.
One end of spring 90 is a-t-tached to cable 40,
and the other is secured -to mlrror 30. Stop 92 limits
clockwise rotation of mirror 30 -to the angular orien-tation
for uni-ty magnifica-tion. Stop 94 limi-ts counterclockwise
rotation of mirror 30 to the alterna-te angular orien-tation
30A for reduced magnification.
When magnifica-tion-changing crank 36 is in the
position shown in FIGURE 2, the op-tical sys-tem produces
unity magnification. Cable 40 is moved counterclockwise
along its path, -thus moving the attached ends of springs
58, 66, 78, and 90 to the posi-tion shown. Spring 58
biases housing 60 agains-t stop 62 spring 66 biases
mirror 18 against stops 74; spring 78 biases mirror 28
against stops 86; and spring 90 biases mirror 3Q against
stop 92. Thus, the optical elements oE the system are in
the proper position for unity magnifica-tion. Crank 36
is maintained in the position shown by a detenting member-
98 which cooperates wi-th a first de-ten-t 101 in the surface
of drum 28. Member 98 is provided with a hemispherical
head secured to a shaft which telescopes within a ~ixed
casing 96, and is biased toward engagement wi-th the drum
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by a coil sprin~ 100.
A recluction in magnification is obtained by
rotating crank 36 clockwise -to the alternate position 36~.
Sufficient manual force must be initially applied to
crank h~ndle 37 to cause head 98 to ride ou-t of detent
101 to the surface of drum 38 against the biasing force
of spring 100. Thereaf-ter the crank 36 may be easlly
rotated to its alternate position 36A, where spring 100
forces head 98 into a second detent 102 in the surface
of drum 38, to maintain the crank in -the alternate
position. Cable 40 is moved clockwise along its path,
thus moving springs ~8, 66, 78, and 90 to the alternate
positions shown in FIGURE 2. Spring 58 now biases -.
housing 60 to the alternates angular orientation 60A
against stop 64; spring 66 now biases mirror 18 to the
alternate ~osition and angle 18A against stops 76;
spring 78 now biases mirror 28 to the alternate position
and.angle 28A against stops 88; and spring 90 now biases
mirror 30 to the alternate angular orientation 30A
against stop 94. All of the op-tical elements are now
- in the proper position for reduced magnification.
Referring now to FIGURE 3, lamp 8, reflector
10, illuminating mirror 12, and scanning mirror 14 are
all mounted on a full-rate carriage 120. Mirror 16 is mounted
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on a half-rate carriac~e 122. Bo-th the full and half-rate
carriages ride upon laterally spaced rails 124 (only one
of tihich is shown). Full~rate carriage 120 and half-rate
carriaye 122 each move between the positions shown and
the alternate positions 120~ a:nd 122A.
Carriages 120 and 122 are moved by a flexible
cable 126. Cable 126 is attached to a fi.xed anchorage
132. Cable 126 passes half-way around one groove of a
two-groove sheave 130, which is ro-tatably mounted on
half-ra-te carriage 122, and is then secured to full-ra-te
carriaye 120 by clamp 128. From clamp 128, cable 126
passes over pulley 134 to drum 136, which is mounted upon
the output shaft of a two speed transmission 138. Cable
126 is wound around drum 136 and -then passes over tensioning
pulley 140, journalled at one end of lever 142. The
other end of lever 142 is journalled on a fixed shaft 144.
Lever 142 is biased by a spring 146 attached to anchorage
148. Cable 126 then passes over pulley 150, passes
half-way around the other groove of sheave 130, and is
attached to a fixed anchorage 152.
The portion of cable 126 from clam,p 128 to
sheave 130 is parallel to the portion of cable from sheave
130 to anchorage 132. Since cable 126 is fixedly -
attached to both clamp 128 and anchoraye 132, the sum
of -thelengths of these two cable portions is constan-t.
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When carria~e 122 moves toward anchorage 132, the lenyth
of cable from sheave 130 to anchorage 132 decreases, while
the length of cable from sheave 130 toclamp 128 incre~ses.
The movement of clamp 128 is the sum of the movement of
clamp 128 relative to sheave 130 and the movement of
carriage 122. Thus, carriage 120 moves twice as fast
as carriage 122.
As the full-rate carriage moves from position
120A to the position 120 shown in solid lines, the
half-rate carriage moves from position 122A to the position
122 shown in solid lines. Movement of carriage 120 to
the right increases the objec-t distance by the amoun-t
of such movement. Movement of carriage 122 to the right
decreases the object dis-tance by twice the amount of
such movement. Since carriage 120 moves a-t twice the
the rate of carriage 122, the object distance remains
eonstant; and scanning of document 2 does not alter the
foeus of the image upon surface 32.
As mirror 14 scans the object field of document
2, the image field upon pho-toconductive surface 32
likewise moves. To prevent blurring of the image, surface
32 must move at a velocity which is equal to the produe-t
of the seanning speed of mirror 14 and the magnifieation
of the image focused upon surface 32.
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FIG~RE 3 shows a mechanlsm for synchronizing
the motion of photoconductive surface 32 wlth tha-t of
scanning mirror 14 at two differen-t magnifications.
Motor 162 rotates a sprocket 164 which drives a chain
166. Chain 166 rotates a first sprocket 168 mounted
on an input shaft of two speed transmission 138 and a
second sproc~e-t 170 mounted on the supporting shaft of
drum 34. Rotation of sprocket 168 causes transmission
138 to rotate drum 136. This moves cable 126 and
causes the full-rate and half-rate carriages to scan
document 2. Rotation of sprocke-t 170 causes drum 34
to rotate, moving photoconduc-tive surface 32 in
synchronism with carriage 120.
- Also wound par-tially around drum 38 and attached
thereto is a cable 154. Cable 154 passes over pulley
156 to a gear shifting lever 158 of two speed transmission
138. With handle 36 in the position shown cable 154`
maintains gear shift lever 158 in the position shown,
which provides the proper gear ratio for unity
magnification. With this gear ratio, the peripheral
velocity of the photoconductive surface 32 of drum 34
is equal to the velocity of carriage 120 When handle
36 is ro-tated clockwise to the position 36A shown in
FIGURE 2 ! cable 154 unwinds from drum 38, permitting
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spring 160 to pull shift lever 158 to the right and
se-t transmission 138 -to the proper gear ratio for
reduced magnification. If the reduced magnification
is one-half, for example, then the gear ratio must be
doubled to ensure that carriage 120 moves at a velocity
which is -twice -that of the peripheral surf~e 32 of the drum 34.
FIGURES 4 and 5 show an al-ternate embodiment of
my invention. Document 200 to be copied is placed upon
transparen-t platen 202 mounted in the top of housing
204 of an electrophotographic copier. Light from lamp
206 is reflected from reflector 208 and mirror 210 to
illuminate a narrow strip of document 200. Light from
this illuminated strip is direc-ted to reflex lens 216
after sequential reflection from full-rate scanning
mirror 212 and half-rate mirror 214. Reflex lens 216
is of fixed focal length and comprises lens 218 and
mirror 220, both moun-ted to ro-tate as a unit about the
axis 228 of a shaft 238 (FIGU~E 5). Light from lens
216 is focused upon the photoconductive surface 224 of
drum 226 after reflection from mirror 222 to produce
an image the magnification of which is u~it~, for example.
If a reduced magnification is desired, reflex
lens 216 is rotated about axis 228 to the posi-tion 216A~
Since the rotational axis 228 is orthogonal to, but
appreciably displaced from, the optical axis of reElex lens
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216, there results an appreciable displacement of the
optical cen-ter of lens 216.
The rotation oE reflex lens 216 to the position
216A unmasks a mirror 230; and light from half-rate
mirror passes to lens 216A onl~7 aE-ter reflec-tion from
mirror 230. This increases the object dis-tance. Light
from lens 216A is now focused on pho-toconductive surface
22~ after sequential reflection from mirrors 232~ and 234.
Mirror 232 is mounted on a rotatable shaft 233. For
unity magnification, mirror 232 is in the position shown
where it does not intercept -the light path from mirror
222 to photoconductive surface 22~. For reduced
magnification, mirror 232 is rotated by shaft 233 to the
alternate position 232~. The increased ra-tio of o~ject
distance to image distance reduces the magnification
while maintaining a properly focused image.
FIGURE 5 shows a mechanism for moving the optical
elements 216 and 232 of FIGURE 4 to change the
magnification. By moving magnification-changing crank
handle 236 from the position shown to the alternate
position 236A, shaft 238 is rotated. Shaft 238 comprises
two sections disposed on either side of an eccentric or
yoke 2~0 on which reflex lens 216 is mounted. The two
sections of sha~t 238 are coaxial with ro-tational axis 228.
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Shaft 238 is mountecl :Eor both rotc~-tion and translation
by bearings 242 and 246. Bearing 242 is formed with a
helical cam slot 248 in which rides a pin 250 mounted
in the upper section of shaft 238. ~s shaft 238 is
rotated clockwise from above by crank 236, pin 250 moves
upwardly in cam slo-t 248, thus moving shaft 238 upwardly.
When crank 236 is moved to the position 236A, pin 250
will be moved -to posi-tion 250A. Hence yoke 240 will
not only be rotated approximately 180 about axis
228, but it will also be shifted upwardly. It will be
understood that upward movement in the plan view of
FIGURE 5 actually represents horizon-tal movement. This
horizontal movement causes images produced at reduced
magnifica-tion to have a common margin with images produced
at unity magnification. This shifting of the reflex
lens perpendicular to itsoptical axis to achieve a common
margin at various magnifications may also be applied
in the first embodiment of my invention.
Pulley 252 is mounted on the lower section of
shaft 238 inboard of bearing 246. The lower sec-tion of
shaft 238 is provided with an elongated slot 264, and
pulley 252 is provided with a pin or key (not shown)
which rides in slot 264.
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Thus rotational movement of shaft: 238 causes rotational
movement of pulley 252; but translational movement of
shaft 238 rela-tive to pulley 252 is accolllmoda-ted.
Secured to bearing 246 is an arm 245 which mounts a
keeper or thrust bearing 244 preventing axial motion
of pulley 252.
Flexible belt 254 couples pulley 252 to another
pulley 256, which is mounted on shaft 233. Shaft 233 is
rotatably supported by bearings 260 and 262. Thus
rotation of crank 236 rotates shaft 233 and mirror 232
which is secured thereto. Pulley 256 is nearly -twice
the diameter of pulley 252 since the rotatio.n. of mirror
232 for a change o magnification is only slightly greater
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than 90.
The ends of cam slot 248 serve as stops accurately
to fix the position of yoke 240, and hence mirror 232,
- for each magnification. Gravity acting on the eccentrically
mounted reflex lens 216 biases pin 250 against the inboard
end of slot 248 in the position shown. In the alternate
position, gravity biases pin 25OA against the outboard
end of slot 2~8.
It will be seen that I have accomplised the
object of my invention. I have provided a variable
magnifica ion electrophotographic copier wherein the focusing
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means rotates about an axis orthoyc)nal to i-ts optical
axis. The rotational axis may substantially intersect
the op-tical axis as in FIGURI` 1 or may be appreciably
displaced from the optical axis as in FIGURE ~. Since
no translation of the focusing means along its optical
axis is needed, the construction is simple and inexpensive
while providing accura-te focusing at various
magnifications.
It will be understood that certain features
and subcombinations are of utility and may be employed
without reference to other features and s~ co~binations.
This is contemplated by and is within the scope of my
claims. It is further obvious that various changes
may be made in details wi-thin the scope of my claims
without departing from -the spirit of my invention.
It is, therefore, to be unders-tood that my invention
is not to be limited to the specific details shown and
described.
Haviny thus described my invention, what I
claim is:
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