Unit for the magnetic brush development of latent electrostatic images

Claim 2

A developer apparatus for the development of a latent image of electrostatic charges on an electrically non-conductive support, produced in an electrostatic printing or copying machine, by means of a mixture of carrying magnetic particles and of electrostaticly chargeable developer particles, comprising: a container containing said mixture and having in the bottom a discharge trap for the mixture, a tubular cylinder of non-magnetic material rotatably mounted in said first container, a magnet mounted in said tubular cylinder capable of setting up a magnetic field having zones of density of flux which are relatively different and adapted to assume selectively two operative positions of development fixed with respect to said first container and a third emptying position fixed with respect to said first container wherein the zone of least flux density of the magnet is downwards in correspondence with said trap for emptying the container from the mixture, and means for cyclically, in synchronism with the cycle of the machine, advancing and retracting said container towards and from said surface bearing said latent image.

Claim 3

A developer apparatus having a development section and a supply section for the development of a latent image of electrostatic charges on an electrically non-conductive support, produced in an electrostatic printing or copying machine, by means of a mixture of carrying magnetic particles and of electrostatically chargeable developer particles, comprising: a first container for the developing section containing said mixture, a first tubular cylinder of non-magnetic material rotatably mounted in said first container, a first magnet mounted in said tubular cylinder capable of setting up a magnetic field having zones of density of flux which are relatively different and adapted to assume selectively two operative positions of development, fixed with respect to said first container, and a third accessory position fixed with respect to said first container, a second container for the supply section containing said mixture in concentrated form and having an aperture communicating with said first container, a second tubular cylinder of non-magnetic material rotatably mounted in said second container, a second magnet mounted in said second tubular cylinder for rotation therewith for feeding concentrated mixture on the surface of said second cylinder towards said aperture, means at said aperture for scraping concentrated mixture from said second cylinder into said first container, and means for cyclically, in synchronism with the cycle of the machine, advancing and retracting said development and supply sections towards and from said surface bearing said latent image.

Claim 4

A developer apparatus having a development section and a supply section for the development of a latent image of electrostatic charges on an electrically non-conductive support, produced in an electrostatic printing or copying machine, by means of a mixture of carrying magnetic particles and of electrostatically chargeable developer particles, comprising: a first container for the developing section containing said mixture, a first tubular cylinder of non-magnetic material rotatably mounted in said first container, a first magnet mounted in said tubular cylinder capable of setting up a magnetic field having zones of density of flux which are relatively different and adapted to assume selectively two operative positions of development, fixed with respect to said first container, and a third accessory position fixed with respect to said first container, a second container for the supply section containing said mixture in concentrated form and having an aperture communicating with said first container, a second tubular cylinder of non-magnetic material rotatably mounted in said second container, a second magnet mounted in said second tubular cylinder for rotation therewith for feeding concentrated mixture on the surface of said second cylinder towards said aperture, means at said aperture for scraping concentrated mixture from said second cylinder into said first container, and means for cyclically, in synchronism with the cycle of the machine, advancing and retracting said development and supply sections towards and from said surface bearing said latent image.

Claim 5

An apparatus in accordance with claim 2 wherein the second tubular cylinder accomplishes A predetermined angular rotation in correspondence with each cycle of approach and retraction of the development and supply sections.

Claim 6

An apparatus in accordance with claim 3, wherein a dosing roller contained in the first container has a roughened surface effecting a pre-levelling on the mass of the development mixture and the predisposition of the mass itself to the formation of a magnetic brush.

Claim 7

An apparatus in accordance with claim 4, wherein a single command, in correspondence with the development cycle of the machine, sets in motion a cam device which, in its programmed displacements, commands in sequential manner the approach to the surface carrying the electrostatic image of the magnetic brush which forms on the surface of the first cylinder the circulation of the mixture through the movement of the dosing roller and of a mixing roller, the lowering of the development and supply sections with simultaneous predetermined angular rotation of the second tubular cylinder and the stoppage of the developer apparatus in the position of rest.