US3851229A

US3851229A - Current measuring device

Info

Publication number: US3851229A
Application number: US00372436A
Authority: US
Inventors: T Hayne; R Schroll
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1973-06-21
Filing date: 1973-06-21
Publication date: 1974-11-26
Anticipated expiration: 1991-11-26
Also published as: CA1005525A

Abstract

A current measuring device in which the current flow produced by a corona generating device is detected. The device measures the spatial distribution of the current flow from the corona generating device.

Description

United States Patent [191 Hayne et a1.

[451 Nov. 26, 1974 CURRENT MEASURING DEVICE [75] Inventors: Thomas F. Hayne, Fairport; Ross E.

Schroll, Rochester, both of NY.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: June 21, 1973 [2]] Appl. No.: 372,436

[52] US. Cl. 317/262 A, 324/32, 324/725 [51] Int. Cl. H01t 19/00 [58] Field of Search 317/262 A; 324/32, 33, 324/72, 72.5

[5 6] References Cited UNITED STATES PATENTS 3,358,378 12/1967 Downs 324/32 3,739,246 6/1973 Haas 317/262 A Primary Examiner-J. D. Miller Assistant E.raminerHarry E. Moose, Jr.

Attorney, Agent, or FirmH. Fleischer; J. J. Ralabate; C. A. Green [57] ABSTRACT A current measuring device in which the current flow produced by a corona generating device is detected. The device measures the spatial distribution of the current flow from the corona generating device.

18 Claims, 4 Drawing Figures CURRENT MEASURING DEVICE BACKGROUND OF THE INVENTION This invention relates generally to a multi-color electrophotographic printing machine, and more particularly concerns a current measuring device adapted to detect the spatial distribution of the current flow from a corona generating device utilized in the electrophotographic printing machine.

In a typical electrophotographic printing machine, a photoconductive surface is electrostatically charged to a substantially uniform potential over the entire surface thereof, and then exposed to a light image of the original document being reproduced. The light image selectively discharges the photoconductive surface in the irradiated areas to form an electrostatic latent image thereof. The electrostatic latent image is then developed by contacting it with finely divided electrostatically attractable material, such as toner particles. Thereafter, the developed image is transferred to a suitable sheet of support material, such as paper, amongst others. The powder image transferred to the support material is subsequently suitably affixed thereon to form a permanent copy of the original document.

In multi-color electrophotographic printing successive electrostatic latent images are formed on the photoconductive surface, each image representing a particular color in the original. In this type of printing, a plurality of single color toner powder images are transferred to the sheet of support material in superimposed registration with one another. Hence, multi-color electrophotographic printing requires a plurality of tonerpowder images whereas black and white or single color printing requires only a single toner powder image. It is, therefore, evident that the amount of toner particles used in the formation of a multi-color copy is significantly greater than that required for the production of a single color copy. The increased amount of toner powder used in a multi-color electrophotographic printing machine substantially increases the contamination from dust and toner particles. In any electrophotographic printing machine there is a need to make sim ple and repeatable measurements of the effect of dirt on the corona generating device. This is particularly true in the case of a multi-color electrophotographic printing machine wherein large amounts of dust or toner particles are formed due to the large amount of toner powder utilized therein.

The corona generating device develops a spray of ions which is deposited on the photoconductive surface to provide a substantially uniform charge thereon. However, as dirt or toner particles are deposited on the coronode wires or grid wires of the corona generating device, the current flow from the corona generating device to the photoconductive surface varies as a function of the contamination thereon. Hence, the uniformity of the charge deposited on the photoconductive surface will vary along the length of the coronode wire depending upon the extent of the contamination thereon.

Accordingly, it is the primary object of the present invention to improve detection of the spatial distribution of the current flow from a corona generating device utilized in an electrophotographic printing machine.

SUMMARY OF THE INVENTION Briefly stated, and in accordance with the present invention, there is provided a device for measuring the spatial distribution of the current flow from a corona generating device.

In the present instance, the device includes corona generating means, accumulating means and current sensing means. The corona generating means forms a spray of ions which are deposited on the accumulating means. Pursuant to the present invention, the accumulating means has a plurality of substantially equally spaced electrically conductive portions insulated from one another. The sensing means is in electrical communication with the accumulating means. In this manner, the sensing means measures the current flow at each electrically conductive portion of the accumulating means. This determines the spatial distribution of the current flow from the corona generating device in the longitudinal direction thereof.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which:

FIG. 1 is a schematic perspective view of a multicolor electrophotographic printing machine incorporating a corona generator which requires the spatial distribution of the current flow therefrom to be measured;

FIG. 2 is a schematic perspective view of the FIG. 1 corona generator associated with the current measuring device of the present invention;

FIG. 3 is an elevational view of the FIG. 2 current measuring device; and

FIG. 4 is a schematic electrical diagram of the FIG. 2 current measuring device.

While the present invention will be described in connection with a preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION For a general understanding of the disclosed multicolor electrophotographic printing machine having a corona generator incorporated therein for utilization in conjunction with the current measuring device of the present invention, continued reference is had to the drawings. In the drawings, like reference numerals have been used throughout to designate like elements. Turning now to FIG. l,'the various components of the multicolor printing machine are depicted schematically therein. Although the current measuring device of the present invention will be described in conjunction with the corona generator of the FIG. 1 printing machine, it is particularly well adapted for use with any type of corona generator. Hence, it will become evident from the following discussion that the current measuring device is well suited for use with a wide variety of corona generators, and is not necessarily limited to the particular embodiment shown herein. Initially, the multi-color electrophotographic printing machine will be described in its normal process mode. Thereafter, the printing machine will be described with the photoconductive drum removed therefrom and the current measuring device of the present invention incorporated therein in association with the corona generator thereof so as to determine the spatial distribution of the current flow therefrom.

The normal process mode of the multi-color electrophotographic printing machine disclosed in FIG. 1 will now be described. The electrophotographic printing machine utilizes a drum having a photoconductive surface 12 secured to and entrained about the exterior circumferential surface thereof. Drum 10 is mounted rotatably on the machine frame and driven at a substantially constant angular velocity, in the direction of arrow 14, by a drive motor (not shown). As drum 10 rotates, photoconductive surface 12 advances sequentially through a series of processing stations. The drive motor rotates drum 10 at a predetermined speed relative to the other operating mechanisms of the printing machine. A timing disc mounted in the region of one end of the shaft of drum 10 cooperates with the machine logic to synchronize the various machine operations with the rotation of drum 10. In this manner, the proper sequence of events is produced at the respective processing stations.

Initially, drum 10 rotates photoconductive surface 12 through charging station A. At charging station A, a suitable corona generator, indicated generally at 16, extends longitudinally in a transverse direction across photoconductive surface 12. Corona generator 16 is designed to spray ions onto photoconductive surface 12 to produce a relatively high, substantially uniform charge thereon. The charge distribution or the current profile produced by corona generator 16 is, preferably, subustantially uniform in the longitudinal direction to generate a substantial uniform charge on the photoconductive surface in the longitudinal direction. However, frequently the accumulation of dirt or toner particles on corona generator 16 will degradate the current flow therefrom producing deviations in charge across photoconductive surface 12. The foregoing charge deviations may also result if the corona generator is not aligned such that it is substantially parallel to and spaced from the photoconductive surface 12. Occasionally corona generator 16 is skewed relative to photoconductive surface 12 resulting in a non-uniform charge across photoconductive surface 12. The current measuring device of the present invention is adapted to determine the current flow distribution in the longitudinal direction of corona generator 16. Corona generator 16 will be described hereinafter in detail with reference to FIG. 2.

- After photoconductive surface 12 is charged to a substantially uniform potential, drum 10 rotates to exposure station B. At exposure station B, a color filtered light image of original document 18 is projected onto charged photoconductive surface 12. Exposure station B includes a moving lens system, generally designated by the reference numeral 20, and a color filter mechanism shown generally at 22. A suitable moving lens. system is disclosed in U.S. Pat. No. 3,062,108 issued to Mayo in 1962. Original document 18, such as a sheet of paper, book, or the like is disposed face down upon transparent viewing platen 24. As shown in FIG. 1, lamps 26 are adapted to move in a timed relationship with lens 20 and filter mechanism 22 to scan successive incremental areas off original document 18 disposed upon platen 24. This produces a flowing light image of original document 18 which is projected onto charged photoconductive surface 12. Filter mechanism 22 is arranged to interpose selected color filters into the optical light path of lens 20. The filter operates on the light rays transmitted throughlens 20 to record an electrostatic latent image on photoconductive surface 12 corresponding to a preselected spectral region of the electromagnetic wave spectrum, hereinafter referred to as a single color electrostatic latent image.

After the electrostatic latent image is recorded on photoconductive surface 12, drum 10 rotates to development station C. At development station C, three individual developer units, generally indicated by the

reference numerals

28, 30 and 32, respectively, render visible the electrostatic latent image recorded on photoconductive surface 12. Preferably, the developer units are all of a type generally referred to as magnetic brush developer units. Each of the developer units contain appropriately color toner particles corresponding to the complement of the spectral region of the wave length of light transmitted through filter 20. By way of example, a green filtered electrostatic latent image is developed by depositing green absorbing magenta toner particles thereon. Similarly, blue and red filtered latent images are developed with yellow and cyan toner particles, respectively.

After development, the now visible toner powder image is advanced to transfer station D. At transfer station D, the toner powder image adhering electrostatically to photoconductive surface 12 is transferred to a sheet of final support material 34, Final support material 34 may be, plain paper or a sheet of thennoplastic polysulfone maten'al, amongst others. A transfer roll, shown generally at 36, secures support material 34 releasably thereon for movement in a recirculating path therewith. Transfer roll 36 is adapted to rotate in synchronism with drum 10, in the direction of arrow 38, at substantially the same angular velocity therewith. This readily enables a plurality of toner powder images to be transferred from photoconductive surface 12 to support material 34 in superimposed registration with one another. U.S. Pat. No. 3,612,677 issued to Langdon et al. in 1971 describes a transfer roll electrically biased to a sufficient magnitude and the proper polarity to attract toner particles from photoconductive surface 12 to support material 34.

Prior to proceeding with the description of fusing apparatus 58 disposed at fixing station E, the sheet feeding path will be briefly discussed. A stack 40 of sheet material 34 is disposed on tray 42. Feed roll 44 cooperating with retard roll 46 separates and advances successive uppermost sheets from stack 40. The advancing sheet moves into chute 48 which guides it into the nip of register rolls 50. Register rolls 50 forward the advancing sheet to transfer roll 36 where gripper fingers 52 secure the sheet thereon. After a plurality of toner powder images have been transferred to support material 34 gripper fingers 52 space support material 34 from transfer roll 36 permitting stripper bar 54 to be interposed therebetween. In this manner, support material 34 is stripped from transfer roll 36 and advanced on endless conveyor 56 to fixing station E.

At fixing station E, fuser 58 permanently affixes the multi-layered toner powder image to support material 34. The toner powder image is generally heat settable and one type of suitable fuser arranged to fix the toner powder image is described in US. Pat. No. 3,493,592 issued to Moser et al. in 1970. After the toner powder image is fused to support material 34, support material 34 is advanced by

endless conveyors

60 and 62 to catch tray 64. Catch tray 64 is suitably arranged to permit the machine operator to readily remove the completed multi-color copy from the printing machine.

The last processing station in the direction of rotation of drum 10, as indicated by arrow 14, is cleaning station F. As previously indicated, a preponderance of the toner particles are transferred to support material 34, however, some residual toner particles remain on photoconductive surface 12. Cleaning station F removes these residual toner particles from photoconductive surface 12. The residual toner particles are initially brought under the influence of a corona generating device (not shown) adapted to neutralize the remaining electrostatic charge on photoconductive surface 12 and the residual toner particles. Thereafter, the neutralized toner particles are cleaned from photoconductive surface 12 by rotating fibrous brush 66. One type of suitable brush cleaning device is described in US.

- Pat. No. 3,590,412 issued to Gerbasi in 1971. It should be noted that in addition to removing the toner particles, cleaning station F levels the charge remaining on photoconductive surface 12 so that corona generator 16 may recharge photoconductive surface 12 to the requisite desired potential. In this manner, photoconductive surface 12 may be repeatedly charged to substantially the same level for each successive single color electrostatic latent image. Hence, it is of paramount importance to have corona generator 16 adapted to charge photoconductive surface 12 to a substantially uniform level. Any degradation in charge produced by corona generator 16 must be identified. As heretofore indicated, degradations in charge may be used by an accumulation of dirt on corona generator 16 or the skewness thereof relative to photoconductive surface It is believed that the foregoing description is sufficient to illustrate the general operation of a multi-color electrophotographic printing machine. Moreover, the foregoing discussion has indicated a need for determining the spatial distribution of the current flow developed by corona 16 so as to evaluate the uniformity of the charge deposited on photoconductive surface 12. FIGS. 2 through 4, inclusive, will be discussed hereinafter to provide a detailed description of the current measuring device utilized in conjunction with corona generator 16 to insure that the charge or current flow produced therebyis substantially uniform in a longitudinal direction.

Referring now to FIG. 2, drum is removed from the FIG. 1 printing machine and current measuring device 68 placed therein in lieu thereof. Coronagenerator 16 is described in detail in FIG. 2. As depicted therein, corona generator 16 includes an elongated shield 70 preferably made from a conductive material such as an aluminum extrusion. Elongated shield 70 is substantially U-shaped'and may be grounded or, in lieu thereof, biased to a suitable electrical voltage level. A

pair ofdischarge electrodes

72 and 76 are mounted in the chamber defined by U-shaped shield 70.

Discharge electrodes

72 and 76 are, preferably, coronode wires approximately 0.0035 inches in diameter and extend longitudinally along the length of shield 72.

Coronode wires

72 and 76 are made preferably from a suitable platinum material.

Coronode wires

72 and 76 are suitably excited to produce a flow of ions therefrom. The ion flow is adapted to be deposited on current measuring device 68 so that the current flow along the longitudinal axis of

coronode wires

72 and 76 may be evaluated. Grid means or a plurality of substantially parallel, spaced, fine conductive wires 74 extend in a longitudinal direction from one end of shield to the other end thereof and across about three fourths of the open end of the chamber therein.

Coronode wires

72 and 76 are secured to an insulating plate (not shown) mounted on the ends of shield 70. As depicted in FIG. 2, coronode wire 72 is positioned in the portion of the chamber of shield 70 that is covered vby grid wires 74. Coronode wire 76 is disposed in the open portion of the chamber of shield 70, Le, the portion not covered by grid wires 74. As heretofore indicated, current measuring device 68 replaces photoconductive drum 10 in the electrophotographic printing machine of FIG. 1. Current measuring device 68 is located such that the surface thereof is spaced substantially the same distance from corona generator l6as photoconductive surface 12. Current measuring device 68 includes current sensing means 78 and accumulating means 80. Accumulating means 80 includes a plurality of substantially equally spaced electrically conductive portions 82 insulated from one another. Electrically conductive portions 82 are mounted on an elongated surface 84. Elongated surface 84 is illustrated in detail in FIG. 3. In the preferred embodiment of the present invention twenty three electrically conductive portions 82 are mounted on elongated surface 84. Preferably, elongated surface 84 may be formed from a printed circuit wiring board with 22 guage wire electrically connected to each electrically conductive portion 82 and to current sensing means 78. Current sensing means 78 includes switch and ammeter 92. A sheet of insulating material 86, preferably made from 0.005 inches thick polyester, e.g., Mylar, extending about l0 inches in length and 2 inches in width is interposed between elongated surface 84 and arcuate member 88. Arcuate member 88 is preferably made from a substantially rigid, conductive material such as aluminum. The curvature of arcuate member 88 duplicates that of photoconductive drum 10. In this manner, accumulating means 80 simulates photoconductive surface 12. Switch 90 is electrically connected to the 23 conductive portions 82 of accumulating means 80. A suitable 24 point switch is Model No. 53 MY 21070 made by Grayhill, Inc. of Le Grange, Ill. Switch 90 in turn, is connected to a suitable ammeter 92. By rotating knob 91, switch 90 connects successive electrically conductive portions 82 to ammeter 92 to register the current flow from each of the electrically conductive portions 82 independently determining the current distribution in the longitudinal direction of

coronode wires

72 and 76, respectively. In this manner, the charge distribution on photoconductive surface 12 may be evaluated and the uniformity thereof defined. This permits the ready determination of whether or not corona generator 16 must be readjusted or cleaned.

Referring now to FIG. 3, there is shown a printed circuit representation of elongated surface 84. As shown therein 23 electrically conductive portions 82 are spaced from one another by insulating means 94. Printed circuit board 84 may be fabricated by suitable means such as by having both sides of an insulating board, e.g., glass reinforced epoxy, coated with a thin metal sheet, e.g., a thin sheet of copper. A chemical etching process removes the copper in all areas except conductive portions 82. In order to connect the electrical lead wires, i.e., 22 guage wire, to board 84, each conductive portion 82 extends to a row of uniformly spaced edge contacts 81 arranged to connect with the 22 gauge external lead wires.

Turning now to FIG. 4, the operation of the present invention will be briefly described. A portion of accumulating means 80 is depicted in FIG. 4 and includes a plurality of electrically conductive portions 82 spaced from one another and electrically insulated from one another. In addition, accumulating means 80 includes a polyester sheet of insulating material 86 entrained about conductive arcuate number 88. In FIG. 4, one lead from switch 90 is electrically connected to ammeter 92. The other lead is electrically grounded. In this way, only the electrically'conductive portion 82 connected to the lead in communication with ammeter 92 will record a reading thereon. The remaining electrical portions 82 will be grounded and not produce a reading on ammeter 92. Hence, by rotating knob 91 (FIG. 2) each electrically conductive portion 82 may have the current flow thereon read by ammeter 92 so as to determine the current flow distribution produced thereon by corona generator 16.

An alternate electrical arrangement may be employed to measure the current uniformity of a biased or simulated charged surface. In this type of arrangement, a first resistor is connected in series with ammeter 92 and electrically conductive portion 82 being meausred. The remaining electrically conductive portions 82 are connected to an electrical common, which, in turn, is connected to an electrical ground through a second series resistor. The voltage across the econd series resistor acts as a biasing potential. Similarly, the voltage across the first resistor is known by measuring the current passing therethrough, i.e., the current measured by LII modifications, andvariations as fall within the spirit and broad scope of the appended claims.

What is claimed is: 1. A current measuring device, including: corona generating means arranged to form a spray of ions; means, closely spaced to said corona generating means, for accumulating the ions formed by said corona generating means to produce a current flow, said accumulating means comprising a plurality of substantially equally spaced electrically conductive portions insulated from one another; and means, in electrical communication with said accumulating means, for sensing the current flow on each portion of said accumulating means to detect the spatial distribution of the current flow produced by said corona generating means. 2. A device as recited in claim 1, wherein said current sensing means includes:

switch means in electrical communication with said accumulating means; and current measuring means in electrical communication with said switch means, said switch means being adapted to electrically connect each portion of said accumulating means to said current measuring means to detect the current flow thereon. 3. A device as recited in claim 2, further including a pair of resistance elements, one of said resistance cleammeter 92. This enables the current uniformity of the biased surface to be evaluated. By way of example, the first resistor, in series with ammeter 92, is preferably about 60 meg ohms, while the second resistor, in series with the grounded electrically conductive portions 82, is about 600 meg ohms.

In recapitulation, the current measuring device of the present invention determines the spatial distribution of the current flow produced by a corona generator. This enables the performance of the corona generator to be evaluated. In multi-color electrophotographic printing, the corona generator must produce a substantially uniform current flow on the photoconductive surface to develop a substantially uniform charge thereon. The foregoing is hindered by the accumulation of dust or the skewness of the corona generator relative to the photoconductive surface. The utilization of the current measuring device of the present invention simulates the photoconductive surface to determine the current flow distribution thereon.

Thus, it is apparent there has been provided, in accordance with the present invention, a current measuring device that fully satisfies the objects, aims and advantages set forth above. While this invention has been described in connection with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives,

ments being electrically connected in series between said current measuring means and the portion of said accumulating means in electrical communication therewith, the other of said resistance elements being electrically connected in series between the other portions of said accumulating means and an electrical ground.

4. A device as recited in claim 2, wherein said corona generating means includes:

an elongated shield defining an open ended chamber;

and

a corona discharge electrode disposed in the open ended chamber of said shield.

5. A device as recited in claim 4, wherein said discharge electrode includes at least a pair of spaced substantially parallel conductive coronode wires, said pair of coronode wires extending substantially in a longitudinal direction along the length of said shield.

6. A device as recited in claim 5, further including grid means comprising a plurality of spaced substantially parallel grid wires mounted in said shield and extending substantially in a longitudinal direction along the length thereof, said plurality of grid wires partially enclosing the open end of said shield with one of the coronode wires being disposed in the chamber thcrebeneath, the other of said coronode wires being disposed in the unenclosed portion of the chamber of said shield.

7. A device as recited in claim 6, wherein said accumulating means includes an elongated surface having the electrically conductive portions thereof arranged along discrete regions of the longitudinal axis thereof, said elongated surface being closely spaced to said pair of coronode wires with the longitudinal axis of said elongated surface being closely spaced from and substantially parallel to the longitudinal axes of said pair of coronode wires, said elongated surface being arranged such that each electrically conductive portion detects the current flow from the discrete region opposed therefrom along the longitudinal axes of said coronode wires.

8. A device as recited in claim 7, wherein said accumulating means includes:

a conductive arcuate member; and

an insulating sheet mounted on the exterior peripheral surface of said arcuate member, said elongated surface being mounted on said insulating sheet such that each electrically conductive portion extends from one marginal region of said arcuate member to the other marginal region thereof with each electrically conductive portion being located on a discrete region of said arcuate member in the longitudinal direction thereof.

9. A device as recited in claim 8, wherein said elongated surface includes a printed circuit board.

10. A device simulating a photoconductive surface forsensing the current distribution thereon in an electrophotographic printing machine of the type having corona generating means spraying ions to create a charge on the photoconductive surface, including:

means, closely spaced to the corona generating means, for accumulating the ions formed by the corona generating means to produce a current flow, said accumulating means comprising a plurality of substantially equally spaced electrically conductive portions insulated from one another; and

means, in electrical communication with said accumulating means, for sensing the current flow on each portion of said accumulating means to detect the spatial distribution of the current flow produced by the corona generating means.

11. A device as recited in claim 9, wherein said current sensing means includes:

switch means in electrical communication with said accumulating means; and

current measuring means in electrical communication with said switch means, said switch means being adapted to electrically connect each portion of said accumulating means to said current measuring means to detect the current flow thereon.

12. A device as recited in claim 11, further including a pair of resistance elements, one of said resistance elements being electrically connected in series between said current measuring means and the portion of said accumulating means in electrical communication therewith, the other of said resistance elements being electrically connected in series between the other portions of said accumulating means and an electrical ground.

13. A device as recited in claim 11, wherein the corona generating means of the electrophotographic printing machine includes:

an elongated shield defining an open ended chamber;

and

a corona discharge electrode disposed in the open ended chamber of said shield.

14. A device as recited in claim 13, wherein said discharge electrode includes at least a pair of spaced substantially parallel conductive coronode wires, said pair of coronode wires extending substantially in a longitudinal direction along the length of said shield.

15. A device as recited in claim 14, further including grid means comprising a plurality of spaced substantially parallel grid wires mounted in said shield and extending substantially in a longitudinal direction along the length thereof, said plurality of grid wires partially enclosing the open end of said shield with one of the coronode wires being disposed in the chamber therebeneath, the other of said coronode wires being disposed in the unenclosed portion of the chamber ofsaid shield.

16. A device as recited in claim 15, wherein said accumulating means includes an elongated surface having the electrically conductive portions thereof arranged along discrete regions of the longitudinal axis thereof. said elongated surface being closely spaced to said pair of coronode wires with the longitudinal axis of said elongated surface closely spaced from and substantially parallel to the longitudinal axes of said pair of coronode wires, said elongated surface being arranged such that each electrically conductive portion detects the current flow from the discrete region opposed therefrom along the longitudinal axes of said coronode wires.

17. A device as recited in claim 16, wherein said accumulating means includes:

a conductive arcuate member; and

18. A device as recited in claim 16, wherein said elongated surface includes a printed circuit board.

Claims

1. A current measuring device, including: corona generating means arranged to form a spray of ions; means, closely spaced to said corona generating means, for accumulating the ions formed by said corona generating means to produce a current flow, said accumulating means comprising a plurality of substantially equally spaced electrically conductive portions insulated from one another; and means, in electrical communication with said accumulating means, for sensing the current flow on each portion of said accumulating means to detect the spatial distribution of the current flow produced by said corona generating means.

2. A device as recited in claim 1, wherein said current sensing means includes: switch means in electrical communication with said accumulating means; and current measuring means in electrical communication with said switch means, said switch means being adapted to electrically connect each portion of said accumulating means to said current measuring means to detect the current flow thereon.

3. A device as recited in claim 2, further including a pair of resistance elements, one of said resistance elements being electrically connected in series between said current measuring means and the portion of said accumulating means in electrical communication therewith, the other of said resistance elements being electrically connected in series between the other portions of said accumulating means and an electrical ground.

4. A device as recited in claim 2, wherein said corona generating means includes: an elongated shield defining an open ended chamber; and a corona discharge electrode disposed in the open ended chamber of said shield.

6. A device as recited in claim 5, further including grid means comprising a plurality of spaced substantially parallel grid wires mounted in said shield and extending substantially in a longitudinal direction along the length thereof, said plurality of grid wires partially enclosing the open end of said shield with one of the coronode wires being disposed in the chamber therebeneath, the other of said coronode wires being disposed in the unenclosed portion of the chamber of said shield.

8. A device as recited in claim 7, wherein said accumulating means includes: a conductive arcuate member; and an insulating sheet mounted on the exterior peripheral surface of said arcuate member, said elongated surface being mounted on said insulating sheet such that each electrically conductive portion extends from one marginal region of said arcuate member to the other marginal region thereof with each electrically conductive portion being located on a discrete region of said arcuate member in the longitudinal direction thereof.

10. A device simulating a photoconductive surface for sensing the current distribution thereon in an electrophotographic printing machine of the type having corona generating means spraying ions to create a charge on the photoconductive surface, including: means, closely spaced to the corona generating means, for accumulating the ions formed by the corona generating means to produce a current flow, said accumulating means comprising a plurality of substantially equally spaced electrically conductive portions insulated from one another; and means, in electrical communication with said accumulating means, for sensing the current flow on each portion of said accumulating means to detect the spatial distribution of the current flow produced by the corona generating means.

11. A device as recited in claim 9, wherein said current sensing means includes: switch means in electrical communication with said accumulating means; and current measuring means in electrical communication with said switch means, said switch means being adapted to electrically connect each portion of said accumulating means to said current measuring means to detect the current flow thereon.

13. A device as recited in claim 11, wherein the corona generating means of the electrophotographic printing machine includes: an elongated shield defining an open ended chamber; and a corona discharge electrode disposed in the open ended chamber of said shield.

15. A device as recited in claim 14, further including grid means comprising a plurality of spaced substantially parallel grid wires mounted in said shield and extending substantially in a longitudinal direction along the length thereof, said plurality of grid wires partially enclosing the open end of said shield with one of the coronode wires being disposed in the chamber therebeneath, the other of said coronode wires being disposed in the unenclosed portion of the chamber of said shield.

16. A device as recited in claim 15, wherein said accumulating means includes an elongated surface having the electrically conductive portions thereof arranged along discrete regions of the longitudinal axis thereof, said elongated surface being closely spaced to said pair of coronode wires with the longitudinal axis of said elongated surface closely spaced from and substantially parallel to the longitudinal axes of said pair of coronode wires, said elongated surface being arrangEd such that each electrically conductive portion detects the current flow from the discrete region opposed therefrom along the longitudinal axes of said coronode wires.

17. A device as recited in claim 16, wherein said accumulating means includes: a conductive arcuate member; and an insulating sheet mounted on the exterior peripheral surface of said arcuate member, said elongated surface being mounted on said insulating sheet such that each electrically conductive portion extends from one marginal region of said arcuate member to the other marginal region thereof with each electrically conductive portion being located on a discrete region of said arcuate member in the longitudinal direction thereof.