Continuous direct electrophotographic recorder
US 2732775 A
Description (OCR text may contain errors)
1956 c. J. YOUNG ETAL CONTINUOUS DIRECT ELECTROPHOTOGRAPHIC RECORDER Filed Feb. 11, 1953 2 Sheets-Sheet l INVENTOR. CHARLES J.YOUNG,8\
ROGER G. OLDEN ATTORNEY Jan. 31, 1956 c. J. YOUNG ET AL 3 CONTINUOUS DIRECT ELECTROPHOTOGRAPHIC RECORDER Filed Feb. 11, 1953 2 Sheets-Sheet 2 INVENTOR. CHARLES J. YOUNG, a ROGER G. OLDEN ATTORNEY United States Patent 2,732,775; CONTINUOUS DIRECT ELECTROPHOTOGRAPHIC RECORDER Charles J. Young and Roger G. Olden, Princeton, N. .L,
assignors to Radio Corporation of. America, a corporation of Delaware Application February 11, 1953, Serial No. 336,342 3 Claims. (Cl. 95,-1.7)
The invention relates to photographic apparatus and particularly, although not necessarily exclusively, to an apparatus for the developmentv of electrophotographic images.
In electrophotography the latent electrostatic image on the material having a photoconductive surface is developed by dusting this latter material with developing powder of suitable triboelectric properties. This operation can be performed by cascading a carrier loaded with developing powder over the electrostatically charged and photo graphically exposed photoconductive surface or by bringing the material into intimate contact with the powder particles in the form of a powder cloud. The powder cloud should consist of very small powder particles inasmuch as the definition of the copy deteriorates withthe inclusion of larger particles. The powder cloud should contain particles of only one polarity, which polarity should be opposite to the polarity of the unexposed p01" tions on the photoconductivesurface,
It is, therefore, an object of the present invention to provide a novel continuous system and apparatus for the production and development of electrophotographic images.
It is also an object of the invention to provide a novel powder cloud generator for use withthe above mentioned electrophotographic apparatus.
It is a still further object of the inventionto provide a novel means for continuously exposing, developing and printing electrophotographic. images of good overall definition.
In accordance with the invention, thereis provided a continuous electrophotographic recorder including a powder cloud generator and feed system therefor. The recorder comprises a drive mechanism and a series of idler rollers in contact with the drive mechanism through; the medium of a continuous web of material having a photoconductive surface. The photoconductive. surface is caused to be drawn from a supply reel or other means over a grounded drum in such fashion that the uncoated side of the Web contacts the drum. The web passes beneath an electrostatic charging unit and over the grounded drum to an exposure area where the web is exposed to light. Developing powder stored in one part of the novel powder cloud generator, is caused to form a powder cloud which arises to contact the passing paper. An image is caused to be formed by means ofthe powder particles adhering according to its polarity to either the unexposed or exposed portions of the web. The web is then passed over a heating unit which fuses the powder into the web and thus causes the recorded copies to be permanent.
The novel features which are considered characteristic of the invention are set forth with particularity in the appended claims, but for a better understanding of the invention itself, both as to itsorganization and method of operation together with other and further objects and advantages, reference may be had to the following description of certain specific embodiments shown merelyfor 2,732,715 Ice Patented Jan. 31, 1956 illustration taken in connection with the accompanying drawings, in which:
Figure 1 is a schematic view of the continuous electrophotographic recorder;
Figure 2 is a view in perspective, of the powder container for the powder cloud generator, partially cut away to show the filling aperture and contents thereof;
Figure 3 is an elevational view of the complete powder cloud generator; and
Figure 4 is a view of Figure 3 along the line 4-4, showing the internal operation of the powder container shown in Figure 2.
Referring to the complete electrophotographic recorder and particularly to Figure 1, there is shown an illustrative embodiment of the composite apparatus noW to be described. A large cylinder or recording drum 10, which maybe made of some conventional conductive material is conveniently positioned so as to be in continuous intimate contact with a web 12 of photosensitive material, for example, paper coated to provide a photoconductive surface. Drive means in the form of a roller 14 is positioned near the drum 10. The driving means may be actuated by a motor (not shown) against the pressure of the idler roller 16 in the direction indicated by the arrows 18 and 20, respectively. The aforementioned direction of movement will thus cause the web 12 to be withdrawn from a supply reel 22 over the idler roller 24 in the direction indicated by the arrow 26. The coated web 12 is threaded around the recorder drum 1%) so that its uncoated side is in contact with the drum 10. An electrostatic charging unit 28, which may, for example, consist of a number of fine corona wires 30, 31 and 32 and a grounded cover 34, is positioned adjacent the idler roller 24 and in the general area where the web 12 first contacts the drum 10. Application of a charging voltage from a source not shown, to the charging unit 28, causes a corona discharge to appear around the corona wires. Due to this electrostatic charge, the web is locked to the freely turning drum 10.
In the general area 36 exposure to light, by means of a projector, not shown, takes place. The direction of the light beam from the projector is indicated by the arrow 38.
A powder cloud generator 39 is disposed beneath the drum 10 and parallel to the drum. Developing powder 40 is stored in the hopper 42 within the plush covered powder cloud generator 39. A predetermined portion of the developing powder 40 drops from the hopper 42 to the hollow plush covered roller 44. The plush covered roller 44 picks up a predetermined small quantity of powder 40 and carries it in the direction of the arrow 45, to a set of spring fingers 46 which are disposed under tension from the support 48 against the plush covered roller. The powder 40 thus carried to the spring fingers 46 tends to be flicked by means of the vertically disposed plush fibers in a forward direction, thus generating a powder cloud 50 which rises towards the passing web 12. At this point, the powder particles adhere to portions of the web 12 thus developing a latent electrostatic image.
Some of the developing powder 49 will tend to adhere also, to the background portions of the web 12. This condition is undesirable. A hollow cylinder or tube 52 is or may be provided, with a fine, longitudinal saw-cut 54 therein. The tube 52 is disposed and supported so that the saw-cut 54 is directed slantingly toward the forwardly moving web 12. The tube 52 is or may be connected to the discharge side of a vacuum cleaner, for example, or other device for forcing a stream of air into the tube. The stream of air coming out of the tube 52 strikes the moving web 12 and blows the undesirable powder 40 off the background of web 12. A second tube 56; having a larger longitudinal opening 58 therein, is or may be connected to the suction side of the vacuum cleaner, before mentioned. The tube 58 is disposed and supported opposite the drum 1% in such a position that the excess developing powder 49 blown off by means of the tube 52 can be sucked up and retained for later reuse.
Adjacent the large drum is a fixing unit as which may be a heater lamp (not shown) or a series of fine resistance wires 62 which may be connected to a voltage source (not shown). The heating unit 60 fuses the developing powder into the web 12 and thus makes the recorded copy permanent.
Reference will now be made to Figure 3 of the drawing which shows an elevational view of the novel powder cloud generator described in connection with Figure 1. There is shown in Figure 3 a view of the hollow plush covered roller d4 which surrounds the developing powder hopper 42 of the novel powder cloud generator 39. The hollow cylinder 44 is provided with alternate helices consisting of a plush tape 64 wound there around and a series of perforations 65 in the cylinder. The plus tape 64 is cemented or otherwise secured around the drum 44 between the helical rows of perforations 65 longitudinally of the drum. Both ends of the hollow drum 44 are covered. The end cover 66 is or may be a solid member of Bakelite or other similar material having a shaft 68 on one side thereof and integral therewith and a bearing seat 7 0 opp 0- site the shaft 68. The opposite end of the drum 44 has an end cover 72 fastened therein. The cover 72 is drilled to receive the shaft 74. Shaft 74 is retained in the support member 76 by means of the screw '78 in such fashion that the shaft '74 is not permitted to be rotated or moved. The shaft 6-? is rotatably disposed in the support 81 through the aperture 82 therein and is connected to a driving means 84 which may, for example, be a pulley or other well known driving mechanism (not shown). Drive means 84 is operated by suitable transmission means from the drive roll 14. A series of bolts 86 retain the end covers 66 and 72 to the cylinder 44. Adjacent the lower portion of the rotatable cylinder 44 is a shield member 88 which prevents excess developing powder from being otherwise scattered beyond the confines of the recorder.
The hopper 42, shown in detail in Figure 2, is disposed within the hollow cylinder 44. A shaft end 96 is adapted to be retained within the bearing seat 79 so that the hopper 42 may be adjustably disposed within the cylinder 44. The opposite end of the hopper 42 has the shaft 74 associated therewith. The hopper 42 is supported Within the hollow cylinder 44 with the slotted open portion 92 thereof, rigidly fixed vertically, adjacent the shield member 88.
Figure 2 is a perspective view of the hopper 42 shown schematically in the drawing of Figure 1. The hopper 42 is or may be fabricated of suitable material, for example, sheet metal. The hopper is roughly horseshoe-shaped and is sealed at either end by the wedge-shaped covers 93 and 94. A slit 92 is maintained in the hopper so that the hopper may be filled with the developing powder 40.
Adjacent one side of the hopper 42, is a rigid longitudinal member 96 which is the support means for a longitudinal brush 98. The brush 9% is the means for preventing clogging of the helical holes in the cylinder 44 by the powder 49. The hopper 42 is shown in the loading position in Figure 2. The end cover 93 is cut away to show the powder as contained therein.
As shown in the view of Figure 4, the hopper member 42 of the powder cloud generator 39 is disposed in stationary relationship to the plush covered drum 44. The helically disposed alternate rows of plush and perforations on the drum 44 cause a relatively small amount of the powder 46 to be discharged through the holes 65 to the inside of the shield 38 and to be picked up by the plush 64. The shield member 88 is disposed in very close relation to the outer ends of the plush fibers so that the plush tends to retain a certain portion of the developing powder as the plush helix rotates over the shield 88. The brush 98 provides a sweeping action over the internal area of the drum 44 and thus, as before mentioned, tends to prevent the powder 40 from clogging the helically disposed holes 65 while permitting suflicient powder to penetrate the perforated drum and be retained on the plush 64. As the drum 44 is caused to rotate in the direction of the arrow 100, the fibers of the plush are bent or depressed downwardly by the spring fingers 46. As the plush fibers are pressed against the spring fingers, the fibers are flicked forwardly so that a dusty cloud 50 of developing powder 40 of predetermined density tends to form and to rise into the area above the roller 44 and adjacent the drum 10.
The generation of the powder cloud 56 is automatically controlled by means of the size of the holes 65 in drum 44 and the speed of the plush covered roller 44. The powder cloud 50 thus generated is steady, and of the proper proportion to provide sufficient density on the recorded copy.
A reference to Figure 3 of the drawing will show that the hopper member 42 may be simply and easily loaded with fresh developing powder 40. The end cover 66 for the plush covered roller or cylinder 44 is readily removable by removing the bolts 86 therefrom. This operation exposes one end of the hopper member 42. By loosening the bolt 78, the shaft 74 will allow the hopper to be rotated through 180 thus bringing the slit 92 therein, into a vertical position. After removing the support with members 84, 68 and 66, the hopper 42 can be withdrawn from within the plush covered roller 44 and refilled.
Operation of the electrophotographic recorder is continuous, simple and efficient. A supply of photosensitive material, which, in the illustrative embodiment shown, is or may be coated paper, is drawn from the supply roll or reel 22. The paper web is caused to circle around the idler 24 and over the drum 10 beneath the unit 28 where it is electrostatically charged. The paper web 12 is exposed in the area 36, thence passed through the powder cloud 50 where the latent electrostatic image is developed. EX- cess powder is removed by means of the associated air blast and vacuum, and the exposed paper web is then drawn over a fixing unit 60 where the powder on the paper 12 is fused and a permanently recorded copy is made.
7 The paper may then be passed to a take-up reel, not shown.
There has thus been described a novel continuous direct electrophotographic recorder which can be used for the continuous development and printing of a wide variety of objects and materials which it is desired to make into permanent copy.
What is claimed is:
l. A continuous direct electrophotographic recorder comprising, in combination, means for feeding a continuous web of material having a photoconductive surface along a predetermined path, electrostatic charging means for applying an electrostatic charge to said surface, means for exposing said electrostatically charged surface to a light image to produce a latent electrostatic image on said surface, means for developing said latent image and means for fixing said developed image, and said developing means comprising an electroscopic developing powder cloud generating means including, a hollow cylinder mounted for rotation about its longitudinal axis, said cylinder having alternate rows of perforations and of strips of brush-like material, a hopper positioned within said cylinder for carrying and dispensing a quantity of developer powder, said powder being applied through said perforations to said brush-like material, and means for causing said brush-like material to project said powder into space to form a cloud.
2. A continuous direct electrophotographic recorder comprising, in combination, means for feeding a continuous web of material having a photoconductive surface along a predetermined path, electrostatic charging means for applying an electrostatic charge to said surface, means for exposing said electrostatically charged surface to a light image to produce a latent electrostatic image on said surface, latent image and means for fixing said developed image, and said developing means comprising an electroscopic developing powder cloud generating means including, a hollow cylinder mounted for rotation about its longitudinal axis, said cylinder having alternate rows of perforations and of strips of brush-like material, a hopper positioned within said cylinder for carrying and dispensing a quantity of developer powder, said powder being applied through said perforations to said brush-like material, means for causing said brush-like material to project said powder into space to form a cloud, and shield means for directing said cloud into intimate contact with said surface bearing said latent image.
3. A continuous direct electrophotographic recorder comprising, in combination, means for feeding a continuous web of material having a photoconductive surface along a predetermined path, electrostatic charging means for applying an electrostatic charge to said surface, means for exposing said electrostatically charged surface to a light image to produce a latent electrostatic image on said surface, means for developing said latent image and means for fixing said developed image, and said developing means comprising an electroscopic means for developing said developing powder cloud generating means including, a hollow cylinder mounted for rotation about its longitudinal axis, said cylinder having alternate rows of perorations and of strips of brush-like material, a hopper positioned within said cylinder for carrying and dispensing a quantity of developer powder, said powder being applied through said perforations to said brush-like material, a friction member carried by said hopper and positioned to engage the inner surface of said cylinder to prevent said dispensed powder from fouling said perforations and means for causing said brush-like material to project said powder into space to form a cloud.
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