Stationary light source electrophotographic copier

A stationary light source electrophotographic copier wherein collimated light from the source is directed to a scanner having upper and lower document illuminating reflectors comprising thin members of negligible mass maintained under tension. The lower reflector includes a plurality of generally horizontal slats disposed in a generally vertical array. Heat from the stationary light source is used to dry or fix copies.

BACKGROUND OF THE INVENTION 
My invention relates to electrophotographic copiers having a stationary 
light source. In some prior art copiers, the light source for illuminating 
the original document to be copied is mounted on the scanner. This 
construction results in scanners of high mass and consequent limited speed 
of operation. As shown by Hildenbrandt in U.S. Pat. No. 3,758,774, the 
scanner mass may be greatly decreased by using a stationary light source 
having a parabolic cylindrical collimating reflector in conjunction with 
an upper and a lower parabolic cylindrical reflector mounted on the 
scanner to illuminate the document from widely differing angles and 
prevent shadowing of three dimensional objects. The upper reflector is 
mounted more remote from the light source than the illuminated region; and 
since the angles of incidence and reflection are less than 45.degree., the 
upper mirror assumes a general orientation of less than 45.degree. from 
the vertical. The lower reflector is mounted closer to the light source 
than the illuminated region; and since the angles of incidence and 
reflection exceed 45.degree., the lower mirror assumes an orientation of 
less than 45.degree. from the horizontal. Because of the favorable 
geometry of the upper reflector, it can illuminate the document over a 
range of angles from the normal approaching 90.degree. without 
substantially increasing the length of the scanner. However, because of 
the unfavorable geometry of the lower reflector, it can illuminate the 
document only over a limited range of angles; and the length of the 
reflector and hence the scanner increases as the tangent of the angle of 
illumination from the normal. The two illuminating reflectors constitute 
an appreciable portion of the total mass of the scanner. 
SUMMARY OF THE INVENTION 
One object of my invention is to provide a stationary light source copier 
wherein the illuminating reflectors have negligible mass. 
Another object of my invention is to provide a stationary light source 
copier wherein the lower reflector illuminates the document over a wide 
range of angles including large angles from the normal. 
Still another object of my invention is to provide a stationary light 
source copier wherein the illuminating reflectors comprising extremely 
thin members maintained under sufficient tension to prevent appreciable 
distortion from air loads and inertial forces. 
A further object of my invention is to provide a stationary light source 
copier wherein the lower document illuminating reflector comprises a 
plurality of generally horizontal reflectors disposed in a generally 
vertical array. 
A still further object of my invention is to provide a stationary light 
source electrophotographic copier wherein heat generated by the light 
source is used to dry or fix copies. 
Other and further objects of my invention will appear from the following 
description. 
In general, my invention contemplates an electrophotographic copier having 
a stationary light source directing collimated light to a scanner provided 
with an upper and a lower document illuminating reflector. The reflectors 
each comprise thin members of negligible mass which are maintained under 
tension to provide rigidity. The lower reflector comprises a plurality of 
generally horizontal reflectors disposed in a generally vertical array. 
The lower reflector is thus disposed in a louvered manner, as the slats of 
an open venetian blind. Heat from the stationary, light source is used to 
dry or fix copies.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, elongated lamp 6 and a parabolic cylindrical reflector 
8 are mounted within housing 4 of an electrophotographic copier. 
Collimated light from reflector 8 is directed horizontally to full-rate 
scanning carriage 12 which moves from the position shown to the position 
12A in scanning a document 24 positioned on glass plate 22. Mounted on 
carriage 12 is a curved upper illuminating reflector 20 and a lower 
illuminating reflector 14. The lower reflector comprises two curved 
elements or slats 16 and 18 mounted in the fashion of a louver or open 
venetian blind. 
Reflector 20 and slats 16 and 18 of reflector 14 bring the collimated light 
beam to at least a partial focus to illuminate a narrow strip of document 
24 from a plurality of angles, reducing shadows from surface projections 
of the document or object to be copied. Since the extent of focusing 
provided by the illuminating reflectors is not critical and is variable 
within fairly wide limits, these reflectors do not require a high degree 
of optical precision. 
Light from the illuminated strip of document 24 is reflected by a planar 
mirror 26 mounted on carriage 12. Light from mirror 26 is reflected from a 
half-rate mirror 28 and directed to a reflex lens 31 comprising lens 30 
and mirror 32. Light from lens 31, after reflection from mirror 34, passes 
through a slit 35 between aperture plates 36 and is focused on the 
photoconductive surface 38 of drum 40. 
As drum 40 rotates counterclockwise (in FIG. 1), surface 38 is charged by 
corona conductor 42, exposed to light through aperture slit 35, and 
developed by a liquid developer 46 in tank 44. A sheet of copy paper 48 
from a stack 50 is fed by a drive roller 52 and by guide rollers 54 into 
contact with the developed photoconductive surface 38. Transfer corona 
conductor 56 charges paper 48, causing toner particles of the developer to 
be transferred from surface 38 to paper 48. 
Collimating reflector 8 is formed in a conductive heat sink 57 which is 
provided with a semi-circular cylindrical recess in which is mounted a 
knurled heating roller 60 driven in synchronism with surface 38. Roller 60 
is provided with an electrical resistance winding 61. Mounted beneath 
roller 60 is a dished plate 66 provided with an electrical resistance 
winding 67. An electrical resistance winding 58 is mounted in heat sink 
57. 
As shown in FIG. 2a, winding 67 is energized from wall plug 69 through 
regulator 68 to maintain plate 66 at a constant elevated temperature. Plug 
69 also energizes winding 58 through regulator 59 to maintain heat sink 57 
at a constant elevated temperature. Plug 69 is connected to brushes 64 and 
64a which engage respective slip rings 63 and 63a to energize winding 61 
through regulator 62 and maintain roller 60 at a constant elevated 
temperature. Plug 69 selectively excites lamp 6 through switch 7. 
Heat from lamp 6 is conducted through sink 57 and is radiated to roller 60. 
Heat from sink 57 and roller 60 is also radiated to plate 66. The 
electrical energy dissipated in resistance windings 58, 61, and 67 to 
maintain heat sink 57, roller 60, and plate 66 at elevated temperatures is 
thus reduced. It will be appreciated that members 57, 60, and 66 tend to 
reach the same temperature because of heat radiation therebetween. It will 
also be appreciated that any two of the three resistance windings may be 
omitted. To insure rapid attainment of regulated temperature of members 60 
and 66 after the copier is first started, I preferably provide windings 67 
and 61, and omit only winding 58 and regulator 59. 
Paper 48 is guided by rollers 55 between the heated plate 66 and the heated 
roller 60 which dry the paper and fix the developed image thereon. 
Thereafter copy paper 48 passes to tray 70. 
FIG. 3 shows the machanism for moving carriage 12 and half-rate mirror 28. 
Cable 320 extends from cable anchorage 304 half-way around one grove of a 
two-groove sheave 306 journalled on half-rate carriage 308 which mounts 
mirror 28. Carriage 308 rides upon rails 310 (only one of which is shown). 
Cable 302 extends from sheave 306 to a clamp 310 mounted on full-rate 
carriage 12. Carriage 12 also rides upon rails 310 and mounts louvered 
lower reflector 14, upper reflector 20 and scanning mirror 26. From clamp 
310, cable 302 passes over pulley 314 and over roller 316 to drum 318. 
Mounted coaxially with drum 318 is a pulley 320, which is driven by a belt 
322 engaging a pulley 324 on the shaft of a motor 326. Cable 302 is wound 
around drum 318 and then passes over a tensioning pulley and over roller 
316 again to a pulley 338. From pulley 338, cable 302 passes half-way 
around the other groove of sheave 306 to cable anchorage 340. Tensioning 
pulley 328 is journalled at one end of lever 330 which is rotatably 
mounted on fixed shaft 332. Lever 330 is biased by a spring 334 toward 
spring anchorage 336 to take up slack in cable 302. 
As is well known to the art, carriage 12 and mirror 26 move at twice the 
speed of half-rate carriage 308 and mirror 28. This causes the object 
distance or length of the optical path from document 24 to lens 31 to 
remain constant so that the image on surface 38 is always in proper focus. 
FIG. 4 shows a document illumination system similar to that of FIG. 2, 
except that the lower reflector 402 comprises six planar elements or slats 
404 through 414 mounted in the fashion of a louver or an open venetian 
blind. The slats are disposed in a generally linear array; and each slat 
extends generally orthogonal to the line of the array. Because louvered 
reflector 402 is comprised of planar slats, no one slat acting alone 
provides any focusing or light concentrating effect. However, the slats 
acting in conjunction with one another bring light to a partial focus, 
since each slat illuminates the same narrow strip of document 24. 
The louvered reflectors 14 and 402 are advantageous because the uppermost 
slat 18 or 414 is mounted nearest the document and can thus illuminate it 
at a relatively large angle from the normal without greatly increasing the 
length of scanning carriage 12. The advantage may be illustrated by 
constructing in FIG. 4 an equivalent single lower reflector 422 which 
illuminates document 24 over the same range of angles as louvered 
reflector 402. Reflector 422 would extend from point 419 to point 420. 
Point 419 is the intersection of the horizontal light ray 415 from beam 
reflector 8 and the light ray 416 from the lowermost slat 404. Point 420 
is the intersection of projections of the horizontal light ray 417 from 
beam reflector 8 and the light ray 418 from the uppermost slat 414. The 
initial slope of reflector 422 at point 419 would be the same as slat 404, 
or slightly less than 45.degree.; and the final slope of reflector 422 at 
point 420 would be the same as slat 414, or appreciably less than 
45.degree.. The inordinate length of reflector 422 would require a 
corresponding increase in the length and weight of carriage 12 to support 
such reflector. 
FIGS. 5 and 6 illustrate a lightweight curved reflector suitable for the 
upper reflector 20 and the curved slats of lower reflector 14. A thin 
flexible reflective strip 502 formed for example of aluminum foil or of a 
plastic sheet provided with a reflective coating on one surface is secured 
at its ends to mountings 504 and 506. Mounting 504 comprises two curved 
members 512 and 514 between which one end of flexible strip 502 is clamped 
by screws 516. Rods 518 and 520 extend from the ends of clamp 512; and rod 
522 extends from the center of clamp 514. Rods 518, 520, and 522 pass with 
a sliding fit through corresponding bores in side 508 of carriage 12. Each 
rod is provided with a head 526 and a coil spring 524 which bears against 
such head and against the outboard surface of side 508. Mounting 506 
comprises curved members 528 and 530 between which the other end of 
flexible reflector 502 is clamped by screws 532. Clamp 528 is affixed to 
side 510 of carriage 12. Springs 524 maintain strip 502 in tension 
providing it with sufficient rigidity to resist appreciable distortion 
under air loads and inertial forces. It will be understood that members 
512, 514, 528, and 530 may be straight instead of curved. With such 
construction, strip 502 will be a planar reflector suitable for the slats 
of louvered reflector 402. 
FIGS. 7, 8, and 9 show an alternate reflector construction suitable 
especially for planar reflectors, as the louvered reflector 402. Flexible 
reflecting strips 404, 406 408, 410, 412, and 414 are mounted at one end 
on respective cylindrical pegs 704, 706, 708, 710, 712, and 714 secured to 
member 716 of carriage 12. Each peg is provided with a longitudinally 
extending cavity 718 having a narrow mouth. Each strip is provided with 
enlarged ends 902 and 903. Ends 902 are received and retained in cavities 
718. Ends 903 are received and retained in similar cavities 812 in six 
corresponding cylindrical members, such as 804 and 806. Each cylindrical 
member, such as 806, is journalled on a corresponding shaft, such as 808, 
mounted on member 810 of carriage 12. Each cylindrical member, such as 
806, is biased counterclockwise, in FIG. 9, by a corresponding helical 
spring, such as 814, the ends of which are mounted in members 806 and 810 
and which surrounds shaft 808. Each cylindrical member, such as 806, is 
retained on its shaft by a corresponding washer 816 and a lock nut 818 
threaded upon the end of shaft 808. Spring 814 biases cylinder 806 axially 
against washer 816 to maintain strip 406 positioned a proper distance from 
carriage member 810. The rotational bias of spring 814 maintains strip 406 
in tension, providing it with sufficient rigidity to resist significant 
distortion under air loads and inertial forces. This tension is maintained 
despite some creep or gradual elongation of strip 406 in the event it is 
formed of a plastic having a reflective coating on one surface. 
It will be seen that I have accomplished the objects of my invention. I 
have provided a stationary light source electrophotographic copier wherein 
the document illuminating reflectors mounted on the scanner have 
negligible mass and comprise thin members maintained under tension. The 
lower reflector illuminates the document over a wide range of angles 
including large angles from the normal and comprises a plurality of 
generally horizontal slats disposed in a generally vertical array. Heat 
from the stationary light source is coupled by conduction and radiation to 
dry and fix copies. 
It will be understood that certain features and subcombinations are of 
utility and may be employed without reference to other features and 
subcombinations. This is contemplated by and is within the scope of my 
claims. It is further obvious that various changes may be made in details 
within the scope of my claims without departing from the spirit of my 
invention. It is, therefore, to be understood that my invention is not to 
be limited to the specific details shown and described.