EP0098509A2 — Electrostatic field control method and apparatus

Claim 1

Independent Claim 94 words

A method for controlling the electrostatic field charge on a photoconductive surface of an electrophotographic recording member applied thereto by a corona generator, characterized by the steps of applying an electrostatic surface charge on the photoconductive surface, at least partially discharging regions of said charged surface by exposing same to radiation to provide exposed regions and blocking other regions of said surface to provide unexposed regions, generating signals representative of the comparison of said exposed and unexposed regions on the same photoconductive surface and controlling said corona generator in response to said comparison signals.

Claim 2

Independent Claim 94 words

A method for controlling the electrostatic field charge on a photoconductive surface of an electrophotographic recording member applied thereto by a corona generator, characterized by the steps of applying an electrostatic surface charge on the photoconductive surface, at least partially discharging regions of said charged surface by exposing same to radiation to provide exposed regions and blocking other regions of said surface to provide unexposed regions, generating signals representative of the comparison of said exposed and unexposed regions on the same photoconductive surface and controlling said corona generator in response to said comparison signals.

Claim 3

Dependent Claim 58 words

The method according to claim 1 characterized by the additional step of generating a predetermined signal, detecting the electrostatic field charge in each of the exposed and unexposed regions and comparing at least said electrostatic charge signal to said predetermined signal to provide the comparison signal and directing said comparison signal to the corona generator for controlling same.

Claim 4

Dependent Claim 97 words

The method according to claim 1 characterized in that the photoconductive surface is charged in a succession of levels extending from at least a lesser to a greater level, the exposed and unexposed regions produced by illuminating a region of successive charge levels of said surface, the electrostatic field charge being detected in each of the successive charge levels of the exposed and unexposed regions of the photoconductive surface, and the further step of generating a predetermined signal, at least said detected electrostatic field charge signal being compared to the predetermined signal to provide said comparison signals.

Claim 5

Independent Claim 61 words

The method according to any one of claims 1, 2 or 3 characterized in that the step of applying the charge to the photoconductive surface includes moving one of the photoconductive surface and a corona generating device relative to the other and controlling the corona level output of said corona generating device in a predetermined sequence related to said relative movement.

Claim 6

Independent Claim 72 words

The method according to any one of claims 1, 2 or 3 characterized in that the step of applying the charge to the photoconductive surface includes moving one of the photoconductive surface and a corona generating device relative to the other and controlling the corona level output of said corona generating device in a predetermined sequence related to said relative movement, said predetermined sequence of corona level output including a staircase pattern.

Claim 7

Independent Claim 28 words

The method according to any one of claims 1, 2 or 3 characterized in that the step of producing unexposed regions includes shielding said unexposed region from illumination.

Claim 8

Independent Claim 30 words

The method according to any one of claims 1 to 4 characterized in that the step of detecting the electrostatic field charge includes moving the photoconductive surface across sensing device.

Claim 9

Independent Claim 40 words

The method according to claims 2 or 3 characterized in that the-step of generating a predetermined signal includes generating a signal for a predetermined charge level and which is representative of the profile of the characteristics of an exposure lamp.

Claim 10

Independent Claim 27 words

The method according to any one of claims 1 to 6 characterized in that the comparison signals are employed to control the intensity of an exposure lamp.

Claim 11

Independent Claim 29 words

The method according to any one of claims 1 to 6 characterized in that the comparison signals are employed to control the duration of operation of an exposure lamp.

Claim 12

Independent Claim 28 words

The method according to any one of claims 1 to 10 characterized by the provision of ramp-like average surface voltage wrought by the charge and partial discharge cycle.

Claim 13

Independent Claim 31 words

The method according to any one of claims 1 to 11 characterized in that the average surface voltage of the photoconductive surface is independent of the specific choice of photoconductive surfaces.

Claim 14

Dependent Claim 237 words

The method according to claim 1 in which the exposure is effected by an exposure lamp and the charge detected by an electrometer; characterized in that the photoconductive surface being positioned in facing relationship with the corona generator means, the exposure lamp and the electrometer, the photoconductive surface is moved past said corona generator and a charge potential applied to the surface, the corona level output of said corona generator is controlled in a predetermined sequence related to the movement of the photoconductive surface, the photoconductive surface is moved over said exposure lamp and selected regions thereof are shielded from illumination to produce the unexposed and exposed regions, said exposure lamp being excited for a predetermined period of time to illuminate said exposed region of the photoconductive surface, the photoconductive surface is moved across said electrometer, the charge on the photoconductive surface related to said movement of the photoconductive surface is detected to provide the detected charge signal output, and further characterized by the steps of storing said detected charge signal in memory means, correlating the detected charge signals to said predetermined sequence of corona outputs, comparing the detected charge signal for said unexposed region of the photoconductive surface with the predetermined stored signal to provide a compared signal for a first control task, comparing said compared signal and the predetermined signal for said exposed region, and providing a second compared signal for a second control task.

Claim 15

Dependent Claim 28 words

The method according to claim 11 characterized in that one of the photoconductive surface and the corona generating means is reciprocated at least once relative to the other.

Claim 16

Dependent Claim 24 words

The method according to claim 11 characterized by the step of effecting a time delay prior to detecting the charge on the photoconductive surface.

Claim 17

Dependent Claim 142 words

Apparatus for controlling the electrostatic field charge of a photoconductive surface of an electrophotographic member for practicing the method according to claims 1 to 15 characterized by a charging device for charging the photoconductive surface in a succession of levels extending from at least a lesser to a great level, an illuminating device for partially discharging by illuminating a region of successive charge levels of the surface to produce an exposed region and an unexposed region, a sensor for detecting the electrostatic field charge in each of the successive charge levels of the exposed and unexposed regions of the photoconductive surface, a signal generator producing a predetermined signal, a comparator for comparing at least said detected electrostatic field charge signal to a predetermined signal and providing said compared signals for control tasks in accordance with said detected signal and said predetermined signal.

Claim 18

Dependent Claim 187 words

In an electrophotographic imaging apparatus which includes a platen having an electrophotographic member secured thereto, the electrophotographic member including an exposed photoconductive surface, a drive for moving the photoconductive surface, a charging device for charging the photoconductive surface and an exposure device for exposing the photoconductive surface to radiant energy pattern to form a latent electrostatic image of the pattern on the exposed surface; an electrometer for detecting the electrostatic charge on a moving photoconductive surface characterized by: A. a housing having a aperture therein and disposed adjacent the photoconductive surface, B. a sensor head enclosed in said housing and mounted to coincide with said aperture, C. a rotatable member having a plurality of equispaced apertures therein and mounted on said housing such that said member apertures coincide with said housing aperture and disposed between said sensor head and the photoconductive surface, D. a drive mechanism coupled to said rotatable member for repetitively interrupting and coupling said sensor head at a frequency related to the rotation speed of said member and the number of equispaced apertures therein, and E. an amplifier circuit coupled to said sensor head.

Claim 19

Dependent Claim 187 words

In an electrophotographic imaging apparatus which includes a platen having an electrophotographic member secured thereto, the electrophotographic member including an exposed photoconductive surface, a drive for moving the photoconductive surface, a charging device for charging the photoconductive surface and an exposure device for exposing the photoconductive surface to radiant energy pattern to form a latent electrostatic image of the pattern on the exposed surface; an electrometer for detecting the electrostatic charge on a moving photoconductive surface characterized by: A. a housing having a aperture therein and disposed adjacent the photoconductive surface, B. a sensor head enclosed in said housing and mounted to coincide with said aperture, C. a rotatable member having a plurality of equispaced apertures therein and mounted on said housing such that said member apertures coincide with said housing aperture and disposed between said sensor head and the photoconductive surface, D. a drive mechanism coupled to said rotatable member for repetitively interrupting and coupling said sensor head at a frequency related to the rotation speed of said member and the number of equispaced apertures therein, and E. an amplifier circuit coupled to said sensor head.

Claim 20

Dependent Claim 22 words

The apparatus according to claim 17 characterized in that said frequency is removed from a harmonic frequency of a power line freqaency.

Claim 21

Dependent Claim 20 words

The apparatus according to claim 17 characterized in that said sensor head produces signal for direction for a control task.

Claim 22

Dependent Claim 123 words

An electrometer for detecting the electrostatic charge on a moving photoconductive surface characterized by: A. a housing having an aperture therein and disposed adjacent the photoconductive surface, B. a sensor head enclosed in said housing and mounted to coincide with said aperture, C. a rotatable member having a plurality of equispaced apertures therein and mounted an said housing such that said member apertures coincide with said housing aperture and disposed between said sensor head and the photoconductive surface, D. a drive mechanism coupled to said rotatable member for repetitively interrupting and coupling said sensor head at a frequency related to the rotation speed of said member and the number of equispaced apertures therein, and E. an amplifier circuit coupled to said sensor head.

Claim 23

Dependent Claim 123 words

An electrometer for detecting the electrostatic charge on a moving photoconductive surface characterized by: A. a housing having an aperture therein and disposed adjacent the photoconductive surface, B. a sensor head enclosed in said housing and mounted to coincide with said aperture, C. a rotatable member having a plurality of equispaced apertures therein and mounted an said housing such that said member apertures coincide with said housing aperture and disposed between said sensor head and the photoconductive surface, D. a drive mechanism coupled to said rotatable member for repetitively interrupting and coupling said sensor head at a frequency related to the rotation speed of said member and the number of equispaced apertures therein, and E. an amplifier circuit coupled to said sensor head.

Claim 24

Dependent Claim 22 words

The apparatus according to claim 20 characterized in that said frequency is removed from a harmonic frequency of a power line frequency.

Claim 25

Dependent Claim 20 words

The apparatus according to claim 20 characterized in that said sensor head produces signal for direction for a control task.

Electrostatic field control method and apparatus

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