Charging apparatus for electro-photographic copying device

Claim 2

An electrophotographic apparatus for the production of positive prints from positive and from negative originals with the same developer, including: a. means for providing actinic light from an original to be copied; b. a photoconductor for receiving said actinic light; c. a charging electrode positioned near to the photocondutor, for charging the photoconductor; d. electrical circuit means for providing said charging electrode with a charging potential, including a transformer having a primary winding connectable with an alternating voltage source, and a secondary winding connected with the charging electrode via a charge polarity reversing switch to enable the photoconductor to be charged selectively with a first polarity when a postive original is to be copied and with the opposite polarity when a negative original is to be copied, said primary winding having a tapping point thereon; e. charge potential adjusting means including a switch actuable by said charge polarity reversing switch adapted to connect the alternating voltage source selectively across the whole winding or part of the winding via said tapping point for adjusting said charge potential when said charge polarity is reversed by said reversing switch.

Claim 3

An electrophotographic apparatus for the production of positive prints from positive and from negative originals with the same developer, including: a. means for providing actinic light from an original to be copied; b. a photoconductor for receiving said actinic light; c. a charging electrode positioned near to the photoconductor, for charging the photoconductor; d. electrical circuit means for providing said charging electrode with a charging potential, including a transformer having a primary winding connectable with an alternating voltage source, and a secondary winding connected with the charging electrode via a charge polarity reversing switch to enable the photoconductor to be charged selectively with a first polarity when a positive original is to be copied and with the opposite polarity when a negative original is to be copied; e. charge potential adjusting means comprising a change-over switch connected between the secondary winding and the charging electrode actuable by said charge polarity reversing switch and a resistive element connectable between the secondary winding and the charging electrode by said change-over switch whereby said change-over switch effects connection of the secondary winding selectively with the charging electrode either directly or via the resistive element for adjusting said charge potential when said charge polarity is reversed by said reversing switch.

Claim 4

An electrophotographic apparatus for the production of positive prints from positive and from negative originals with the same developer, including: a. means for providing actinic light from an original to be copied; b. a photoconductor for receiving said actinic light; c. a charging electrode positioned near to the photoconductor, for charging the photoconductor; d. electrical circuit means for providing said charging electrode with a charging potential, including a transformer having a primary winding connectable with an alternating voltage source, and a secondary winding connected with the charging electrode via a charge polarity reversing switch to enable the photoconductor to be charged selectively with a first polarity when a positive original is to be copied and with the opposite polarity when a negative original is to be copied; e. charge potential adjusting means comprising a change-over switch connected between the secondary winding and the charging electrode actuable by said charge polarity reversing switch and a resistive element connectable between the secondary winding and the charging electrode by said change-over switch whereby said change-over switch effects connection of the secondary winding selectively with the charging electrode either directly or via the resistive element for adjusting said charge potential when said charge polarity is reversed by said reversing switch.

Claim 5

An electrophotographic apparatus for the production of positive prints from positive and from negative originals with the same developer, including: a. means for providing actinic light from an original to be copied; b. a photoconductor for receiving said actinic light; c. charging means positioned near to the photoconductor, for charging the photoconductor; d. electrical circuit means for providing said charging means with a charging potential, including a charge polarity reversing switch connected with the charging means to enable the photoconductor to be charged selectively with a first polarity when a positive original is to be copied and with the opposite polarity when a negative original is to be copied; e. light adjusting means associated with said means for producing actinic light and coupled to said charge polarity reversing switch for adjusting said actinic light when said charge polarity is reversed by said reversing switch.

Claim 6

An electrophotographic apparatus for the production of positive prints from positive and from negative originals with the same developer, including: a. means for providing actinic light from an original to be copied; b. a photoconductor for receiving said actinic light; c. charging means positioned near to the photoconductor, for charging the photoconductor; d. electrical circuit means for providing said charging means with a charging potential, including a charge polarity reversing switch connected with the charging means to enable the photoconductor to be charged selectively with a first polarity when a positive original is to be copied and with the opposite polarity when a negative original is to be copied; e. light adjusting means associated with said means for producing actinic light and coupled to said charge polarity reversing switch for adjusting said actinic light when said charge polarity is reversed by said reversing switch.

Claim 7

An apparatus according to claim 3, wherein the electrical circuit means includes a transformer having a primary winding connectible with an alternating voltage source and a secondary winding, said polarity reversing switch being connected with the secondary winding and said charging means comprising a charging electrode connected with the secondary winding via said polarity reversing switch.

Claim 8

An apparatus according to claim 3, wherein the light adjusting means comprises a Grey filter coupled with the polarity reversing switch and movable into and out of the path of actinic light by operation of said polarity reversing switch.

Claim 9

An apparatus according to claim 3, wherein said means for providing actinic light includes a light source connectible with a source of supply potential and arranged to illuminate the original, a resistive element connectible between the light source and said source of supply potential and a change over switch actuable by said polarity reversing switch and adapted to selectively connect the light source with the soUrce of supply potential directly or via the resistive element whereby the intensity of illumination of the subject is changed to effect adjustment of actinic light.