US2998802A - Electrostatic developing apparatus - Google Patents

Description

Sept. 5, 1961 G. A. HARRIS ETAL 2,998,802

ELECTROSTATIC DEVELOPING APPARATUS Filed Jan. 2s, 1G59 ...W vf

`27 74/\ F f9.3 u 21 23 51* 5 JNVENToRs 2 G GEORGE A. HARms "\\`$1 BY EL GOD I MONTGOMERY 8 0 I V832 AGENT United States Patent O 2,998,802 ELECI'ROSTATIC DEVELOPING APPARATUS George A. Harris, Malvern, and Elwood T. Montgomery, Drexel Hill, Pa., assignors to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Filed Jau. 28, 1959, Ser. No. 789,725 6 Claims. (Cl. 118-637) The invention hereinafter described and claimed has to do with electrostatic apparatus and more particularly to apparatus for visibly developing information electrostatically recorded on a recording medium.

The electrostatic recording process consists broadly of three steps. The first step comprises establishing, or printing, electrically charged areas on selected portions of a recording medium, which are representative of information. The second step consists of developing such charged areas on the recording medium by means of an inking powder thus to make them visible. The third step, which is optional, consists in xing, or rendering such developed areas substantially permanent. In the electrostatic recording process, these three steps take place sequentially and at physically separate locations.

The recording medium is preferably made of a backing layer, or web of paper, on one side of which is bonded a thin layer of high resistivity, or dielectric material. The web of paper is moved through the printing apparatus where the electrostatically charged areas are established and from this station it passes to the inking and fixing stations sequentially.

During the developing or inking of the latent electrostatic image, developing powder or ink will adhere to the electrostatically charged areas, thus to make them visible. Unfortunately under some conditions powder will also adhere to the background or uncharged portions of the recording material. This is au undersirable condition as it tends to obscure the desired information.

Therefore, it is an important object of the present invention to provide novel apparatus for developing or inking electrostatically recorded information or images in a manner overcoming this disadvantage.

More specifically, it is an object of the present invention to provide a novel inking device for images electrostatically recorded on a record medium whereby ink adhering to the uncharged or background areas of the recording medium is removed.

Another object of the invention is to provide such apparatus which will recover Ithe ink removed from the noncharged or background areas of the recording medium.

ln accordance with the above objects and first briefly described, the invention comprises apparatus through which an electrostatically charged web of recording material may be passed for developing the charged areas with inking powder which is maintained in contact with the charged side of the web. The inking powder is housed in a chamber including suction cleaning apparatus for causing air to sweep across the inked surface thus to remove excess ink which is returned to the ink supply.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered with the accompanying drawings wherein:

FIG. l is a perspective view of apparatus embodying the invention, with parts removed better to show the interior of the apparatus;

FIG. 2 is a sectional view of the apparatus, taken along line 2-2 of FIG. 3; and

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2.

Referring now to the drawing illustrating the preferred form of the invention, and first to FIGS. 1 and 3, it will be seen that the apparatus comprises a housing 10, somewhat triangular in cross-section, and formed by a bottom wall 11, a back wall 12, a top Wall 13, side walls 14, and a front wall 15. The forward or right hand ends of bottom and top walls 11 and 13 terminate short of front wall 15 thus to provide an inlet opening or slot 16 and an outlet opening or slot 17 respectively, both of which extend across the housing to points adjacent the side walls 14, and together provide means whereby a record medium may be threaded through the housing. While other types of record medium may be used, in the presently described embodiment of the invention it is a web of paper 18 of the type described above. It will be understood that the web of paper may be fed through the housing continuously or incrementally step-by-step, by means not shown. In the latter case the speed may be such that it can be described as being substantially constant.

Front wall 15 is provided with a curved inner surface 19 over which the web 18 is tightly held as it is fed through the chamber 20 enclosed by the housing 10. Feeding of the web may be by any suitable well known means, such as rollers, not shown.

A strip of exible material 21, such as felt, is secured by suitable means, along the front edge of bottom Wall 11. The forward edge 22 of the felt member is turned upwardly and maintained flexed against the web 18, or wall 15 if no web is present, by a spring leaf 23 also suitably secured to the front edge of bootom wall 11 and terminating adjacent the front edge of the felt member 21. lnlet opening 16 thus is sealed in a manner preventing ink from spilling out of the housing.

With reference to FIGURES 1 and 2, it will be seen that the upper portion of curved surface 19 of front wall 15 is spanned by the ink removing apparatus indicated generally by the numeral 24 and secured upon spaced abutments 25, projecting from surface 19, as by screws 26, thus to provide a slot 27 through which web 18 is threaded.

The ink removing device is a suction cleaner formed by a plurality of elongated members 32, 33, 34, 35, 36 and 37 secured together in stacked relationship, as by screws 38. Member 32 is formed with a pair of aligned elongated recesses 39 and 39a in its upper face, as seen in FIG. 2, which are enclosed by member 33 to form a pair of aligned elongated chambers 40 and 40a. A pair of aligned recesses or chambers 41 and 41a in the outer or curved right hand face 42 of member 32 (FIG. 3) are in open communication with chambers 40 and 40a respectively as by apertures 43a spaced along the length of wall 43 separating the chambers. The wall 41h separating chamber 41 and 41a is tapered to a thin leading edge facing web 18 so as not to block air from sweeping over this portion of the web. Member 33 is formed with two spaced recesses 44 and 45 which are formed into elongated chambers 46 and 47 by plate members 34 and 36 respectively, which chambers are in communication with chambers 40 and 40a as by apertures 48 and 49 respectively. Valves 50 and 51 normally maintain apertures 48 and 49 in closed condition, but are responsive to low pressure in chambers 46 and 47 to open the apertures.

`Chamber 46 is in open communication with one chamber 52 of a diaphragm pump 53 by means of pipe 54 and conduit 55, the latter being formed by aligned holes through wall 15 and members 32 land 33. In like manner, chamber 47 at the right hand side of the ink removing device, is connected to chamber 56 of pump 53 by pipe 57 and conduit 58, the latter being `formed in the same manner as conduit `55 on the left hand side of the apparatus.

Members 35 and 37 `are 4formed with recesses 59 and 60 respectively on their undersides, as seen in FIGURE 2, and cooperate with plates 34 yand 36 to ` form conduits 61 and 62 which communicate with chambers 46 and 47 by means of apertures 63 and 64 respectively. the latter being normally closed by pressure responsive valves 65 and `66. The outlet ends 67 and 68 of these conduits are in open communication with `housing chamber 20 containing ia supply of ink 69.

Pump S3 may be of any suitable kind but for the purpose of illustration. is shown asbeing of the type wherein a flexible diaphragm 70 serves both as the pumping or air displacing means, and the means for dividing the pump housing into the two chambers 52 and 56 mentioned above, thereby effecting double action for each pump cycle, as described below. The diaphragm is normally urged to the left. as seen in FIGURE 2, by coil spring 72 positioned on one side thereof, and is provided on its other side with an actuating rod 73 which extends through the wall 74 into the path of rotation of a cam 75 mounted on a shaft 76 driven by a motor 77.

In the operation of the apparatus, motor 77 is energized by suitable means, not shown, to rotate cam 75. During the iirst half-rotation of the cam to the broken line position 78a. its high point 78 will move rod 73, and diaphragm 70 to the right, as seen in FIGURE 2, to the lbroken line position 70a against the pressure of coil spring 72. Continued rotation returns the cam to `its full line position whereby spring 72 is effective to return the diaphragm to its full line position as the end of rod 73 follows the periphery of cam 75 to its low point. It is seen, therefore, that each reciprocatory cycle of plunger 73 and consequently diaphragm 70 effect both a pressure and a sucking action through pipes 54 and 57 and their associated conduits and chambers, as more fully described below.

Considering first the movement of diaphragm 70 from its full line position to its broken line position. as illustrated in FIG. 2, air will be displaced from chamber 56 and forced through pipe 57, conduit 58 and into chamber '47. causing valve 51 to close aperture 49 and valve 66 to open aperture 64 permitting the high pressure air to ow through the aperture into conduit 62 and through outlet opening 68 into housing 20. Simultaneously the chamber 52 of the pump is enlarged, creating a low pressure in this chamber causing air to be sucked through pipe 54, conduit 55 and chamber 46, thus to reduce the pressure in the latter chamber. In response to this lowered pressure in chamber 46 valve 65 closes aperture 63 |and valve 50 opens aperture 48. Chamber 40 thus is opened to the sucking action of. the pump causing air to be sucked at high velocity from chamber 20 to sweep through the left hand half of slot 27 through chamber 41. apertures 43a. chamber 40. aperture 48. into chamber 46, conduit 55, pipe 54 and pump chamber 52.

On its retum stroke to the full line position the abovedescribed pumping action is reversed. Chamber 52 becomes the high pressure side and chamber 56 the low pressure side. 'From chamber 52 air is forced through pipe 54. conduit 55. chamber 46. aperture 63 (valve 65 being opened and valve 58 closed by the pressure difr["erential across them), conduit 61, and through outlet 67 into housing chamber 20. The low pressure created in chamber 56 by this stroke of diaphragm 70 sucks air into the chamber through pipe 57. conduit 58, chamber 47, aperture 49 (valve 66 being closed and valve 51 opened by the pressure differential across them) to reduce the pressure in chamber 40a. Thus air from housing chamber 20 is caused to sweep at high velocity through the right hand half of slot 27, through chamber 41a, apertures 43a, chamber 40a, aperture 49, and into chamber 47, conduit 58. pipe 57 and pump chamber 56. Thus it is seen that each complete cycle of pump 53 effects a sweep of air from chamber 20 at high velocity through the full width of slot 27, and the return of the air to chamber 20.

Web 18 previously fed through inlet opening 16, slot 27 and out of the housing through slot 17 is drawn tightly against curved surface 19 offront wall 15,` as it moves through the apparatus, either continuously or incrementally as described' above. Information is electrostatically charged or printed on the web by the apparatus shown at 80, which includes at least one, but preferably a row ofv printing heads 81, as seen in FIG. 1, and a back-up electrode 82, all in accordance with the lapparatus described in the copending application of Epstein et al., Serialv No. 714,767, filed February l2, 1958, and assigned to the assignee of the present invention. Incidentally, a suitable ink for use in the apparatus is also described in this copending application.

As the charged paper moves through the lower portion of the housing, ink particles adhere to the latent image on the charged portion of web 18', thus visibly developing these images. Unfortunately, as mentioned above, some of the ink Imay also adhere to the background or uncharged areas of the web. However, in particular accordance with the present invention, as the web passes through slot 27, the high velocity air passing through the slot, as described above, sweeps across the paper yand forcibly removes the unwanted ink adhering to the web. The ink entrained in the iair on the suction stroke of the pump is returned to lhousing chamber 20 on the pressure stroke.

To facilitate inking of the web, van ink agitator is positioned in the ink supply 69. The agitator is rotated by its mounting shaft 86 in a counterclockwise direction whereby its agitator vanes 87 urge the particles of ink toward the web as it passes through the housing. Rotation of the agitator 85 may be effected in any convenient manner such as by the pulley 88 secured to the end of shaft 86 and driven yby belt 89 shown in FIG. l, it being understood, of course, that belt 89 can be driven by any well known means, not shown, `but which may be motor 77, if desired.

Thus it is seen that the invention provides apparatus which will develop a clean copy of information electrostatically recorded on the web 18, and iat the same time recover the excess ink removed from the web.

We claim:

l. Apparatus for visibly developing images electrostatically recorded on one side of a recording medium comprising, a housing for holding a supply of inking powder. said housing having inlet and outlet openings through which said record medium may be passed through said housing, the electrostatically charged side of said record ing medium being in contact with said inking powder as the record medium passes through said housing thus to develop the images recorded thereon, suction cleaning means within said housing, said suction cleaning means including a chamber having an opening extending across and closely adjacent said developed surface of said record medium, means for reducing the pressure within said chamber whereby air is drawn from within said housing to sweep across said developed surface of said record medium and into said chamber, thereby to remove excess ink from said record medium, and means for exhausting the air and the excess ink from said chamber into said housing.

2. A construction according to claim l wherein said pressure reducing means includes a pump, means between said pump and said chamber permitting said pump on its suction stroke to draw air from said chamber thus to reduce the pressure therein, but preventing air from entering said chamber on the pressure stroke of said pump, and means effective to discharge air from said pump into said housing on said pressure stroke of said pump.

3. A construction in accordance with claim 1 wherein said pressure reducing means includes a pump, conduit means connecting said pump to said chamber, first valve means between said conduit and said chamber permitting said pump on its suction stroke to draw air from said chamber thus to reduce the pressure therein, but preventing air from entering said chamber from said conduit on the pressure stroke of said pump, and second valve means in said conduit effective to discharge air from said conduit into said housing on said pressure stroke of said pump.

4. A construction according to claim 3 and including a second chamber aligned with said first mentioned chamber and separated therefrom hy a medial wall, said combined chambers spanning said record medium, and wherein said conduit means includes first and second conduits, each conduit including first and second valve means, and said pump includes first and second ports each alternating as suction and pressure ports, said first conduit connecting said first mentioned chamber to said first port, and said second conduit connecting said second chamber to said second port, whereby each cycle of said pump effects both a suction and a pressure condition through its associated conduits alternately to remove air from said chambers and move it into said housing.

5. Apparatus for visibly developing images electrostatically recorded on one side of a recording medium comprising, a housing for holding a supply of inking powder, said housing having inlet and outlet openings through which said record medium may be passed through said housing, the electrostatically charged side of said recording medium being in contact with said inking powder as the record medium passes through said housing thus to develop the images recorded thereon, suction cleaning means within said housing, said housing including a wall over which said record medium moves during its passage through said housing, said suction cleaning means including an elongated member with one face closely adajacent said wall thereby to form a narrow slot through which said record medium moves in passing through said housing, a pair of aligned recesses in said one face of said member forming chambers therein, said chambers facing said wall and each Spanning approximately one half the Width of said record medium, and means alternately to reduce the pressure within said chambers thus to cause housing air to sweep through said slot at high velocity and across said record medium, first across the half spanned by one of said chambers and then the half spanned by the other of said compartments, thus to remove excess ink from the developed surface of said record medium.

6. Apparatus in accordance with claim 5 wherein said last means includes a pump having first and second ports each alternating as suction and pressure ports on each cycle of said pump, and conduit means connecting one of said ports to one of said chambers and to the interior of said housing, and the other of said ports to the other of said chambers and to the interior of said housing, and valve means in said conduits effective to open said conduits to said chambers only on the suction stroke of said pump relative to a given port, and to the interior of said housing only on the pressure stroke of said pump relative to a given port.

References Cited in the file of this patent UNITED STATES PATENTS 2,732,775 Young et al. Jan. 31, 1956 2,842,456 Carlson July 8, 1958 2,851,373 Tregay et al. Sept. 9, 1958 2,862,472 Carlson Dec. 2, 1958 2,892,446 Olden June 30, 1959

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