Apparatus for controlling the amount of charge applied to a surface

Claim 2

In a xerographic reproducing apparatus having a coronagenerating device with at least one corona wire positioned in closely spaced relation to a xerographic plate for applying an electrostatic charge onto the xerographic plate, said corona wire being supported in and substantially enclosed by a conductive shield and wherein the charging current to the xerographic plate is produced by the potential applied to the corona wire whereby an increase in potential on this wire will effect an increase in potential charging current and the decrease in this potential will affect a decrease in charging current, apparatus for controlling the potential applied to said corona wire comprising; corona-detecting means approximately the length of and parallel to said corona wire and positioned adjacent said conductive shield for detecting a portion of the charging current, a comparator for comparing signals applied thereto, first means for applying a reference current to said comparator, second means for connecting the output of said coronadetecting means to said comparator, voltage-producing means operatively connected to the output of said comparator and responsive to the variations in the charging current from said reference current for producing a voltage whose magnitude relative to an initial value changes in a direction inversely proportional to said charging current variations, and means connecting the output of said voltage-producing means to said corona wire to correct for the variations in the charging current.

Claim 3

The apparatus as defined in claim 1 wherein said corona-detecting means comprises a wire approximately the length of and parallel to said corona wire.

Claim 4

In a corona-generating device having at least one corona wire positioned in closely spaced relationship to a recipient surface for applying an electrostatic charge onto said surface, said corona wire being supported in and substantially enclosed by a conductive shield, apparatus for controlling the potential applied to said corona wire comprising: corona-detecting means positioned adjacent said conductive shield for detecting a portion of the generAted corona, comparator means for comparing the detected portion of the generated corona with a source of reference current, said comparator means generating an output signal proportional to the variations of the detected corona from said reference current, means operatively connected to the output of said comparator means for producing a voltage whose magnitude varies in a direction which is inversely proportional to said detected corona variations, said voltage-producing means including a variable frequency oscillator operatively connected to the output of said comparator means, the outside pulse width of said oscillator being a function of the current input to said comparator means, and a modulator coupled to the output of said variable frequency oscillator, the modulator operating on a DC voltage supplied thereto for producing a voltage whose average value is proportional to the output pulse width of said variable frequency oscillator, and means for connecting said voltage-producing means to said corona wire to correct for variations in the detected corona.

Claim 5

In a corona-generating device having at least one corona wire positioned in closely spaced relationship to a recipient surface for applying an electrostatic charge onto said surface, said corona wire being supported in and substantially enclosed by a conductive shield, apparatus for controlling the potential applied to said corona wire comprising: corona-detecting means positioned adjacent said conductive shield for detecting a portion of the generAted corona, comparator means for comparing the detected portion of the generated corona with a source of reference current, said comparator means generating an output signal proportional to the variations of the detected corona from said reference current, means operatively connected to the output of said comparator means for producing a voltage whose magnitude varies in a direction which is inversely proportional to said detected corona variations, said voltage-producing means including a variable frequency oscillator operatively connected to the output of said comparator means, the outside pulse width of said oscillator being a function of the current input to said comparator means, and a modulator coupled to the output of said variable frequency oscillator, the modulator operating on a DC voltage supplied thereto for producing a voltage whose average value is proportional to the output pulse width of said variable frequency oscillator, and means for connecting said voltage-producing means to said corona wire to correct for variations in the detected corona.

Claim 6

In a xerographic reproducing apparatus having a corona-generating device with at least one corona wire positioned in closely spaced relation to a xerographic plate for applying an electrostatic charge onto the xerographic plate, said corona wire being supported in and substantially enclosed by a conductive shield and wherein the charging current to the xerographic plate is produced by the potential applied to the corona wire whereby an increase in potential on this wire will effect an increase in charging current and the decrease in this potential will affect a decrease in charging current, apparatus for controlling the potential applied to said corona wire comprising, corona-detecting means approximately the length of and parallel to said corona wire and positioned adjacent said conductive shield for detecting a portion of the charging current, a comparator for comparing signals applied thereto, first means for applying a reference current to said comparator, second means for connecting the output of said corona-detecting means to said comparator, voltage-producing means operatively connected to the output of said comparator and responsive to the variations in the charging current from said reference current for producing a voltage whose magnitude relative to an initial value changes in a direction inversely proportional to said charging current variations, said voltage-producing means including a variable frequency oscillator operatively connected to the output of said comparator, the output pulse width of said oscillator being a function of the current input to said comparator, and a modulator coupled to the output of said variable frequency oscillator, said modulator operating on a DC voltage applied thereto for producing a voltage whose average value is proportional to the output pulse width of said variable frequency oscillator, and means connecting the output of said voltage-producing means to said corona wire to correct for the variations in the charging current.

Claim 7

In a xerographic reproducing apparatus having a corona-generating device with at least one corona wire positioned in closely spaced relation to a xerographic plate for applying an electrostatic charge onto the xerographic plate, said corona wire being supported in and substantially enclosed by a conductive shield and wherein the charging current to the xerographic plate is produced by the potential applied to the corona wire whereby an increase in potential on this wire will effect an increase in charging current and the decrease in this potential will affect a decrease in charging current, apparatus for controlling the potential applied to said corona wire comprising, corona-detecting means approximately the length of and parallel to said corona wire and positioned adjacent said conductive shield for detecting a portion of the charging current, a comparator for comparing signals applied thereto, first means for applying a reference current to said comparator, second means for connecting the output of said corona-detecting means to said comparator, voltage-producing means operatively connected to the output of said comparator and responsive to the variations in the charging current from said reference current for producing a voltage whose magnitude relative to an initial value changes in a direction inversely proportional to said charging current variations, said voltage-producing means including a variable frequency oscillator operatively connected to the output of said comparator, the output pulse width of said oscillator being a function of the current input to said comparator, and a modulator coupled to the output of said variable frequency oscillator, said modulator operating on a DC voltage applied thereto for producing a voltage whose average value is proportional to the output pulse width of said variable frequency oscillator, and means connecting the output of said voltage-producing means to said corona wire to correct for the variations in the charging current.