Magnetic toner transfer method and apparatus

A transfer method for magnetic toner particles arranged in an image configuration on a magnetic medium corresponding to a latent magnetic image, comprising:

• (a) effecting in succession relatively perpendicular approaching movement at first and second velocities with the first velocity magnitude greater than the second, contact and relative perpendicular separating movement at third and fourth velocities with the third velocity magnitude less than the fourth between at least respective parallel portions of the facing surfaces of a toned magnetic medium and a toner receiving medium without disturbing the toner particle arrangement;
• (b) subjecting the toner particles to a first electrostatic field, at least during the period of relative approaching movement, beginning with a predetermined first separation distance being reached between said magnetic and receiving mediums, said first electrostatic field having a predetermined magnitude and a direction which urges the toner particles substantially toward the magnetic medium and away from the receiving medium;
• and
• (c) discontinuing the first electrostatic field and subjecting the toner particles to a second electrostatic field having a direction which urges the toner particles substantially toward the receiving medium and away from the magnetic medium, for a predetermined time period following contact between said magnetic and receiving mediums and continuing after separation of the last mentioned mediums at least until a predetermined second separation distance between the last mentioned mediums is reached on relative separating movement thereof, said second electrostatic field having a predetermined minimum magnitude at least when separation of the first and second medium portions is effected.

A method of high-speed transfer of magnetic toner particles which are predeterminably arranged on a surface of an endless first magnetic medium of pre-selected width to a receiving medium comprising establishing a toner attracting force including electrostatic and magnetic field forces for attracting the toner to the magnetic medium:

• selecting a maximum variable first rate and a maximum variable second rate of relative approaching, generally perpendicular movement between the magnetic and receiving mediums, which rates are defined at least in part by the instantaneous separation between the magnetic and receiving mediums, the width of the magnetic medium and the toner attracting force associated with the magnetic medium, said second rate being substantially less than the first rate;
• selecting a first separation distance between the magnetic and receiving mediums;
• effecting relative, generally perpendicular, approaching movement between the magnetic and receiving mediums at or below the maximum of said variable first rate until said first separation distance is reached;
• and
• therefollowing, effecting relative approaching movement between the magnetic and receiving mediums at or below the maximum of said second rate such that the magnetic and receiving mediums are brought into contact without disrupting the toner, said first separation distance and the maximums of said variable first and second rates being selected such that relative approaching movement between the magnetic and receiving mediums is achieved substantially without degradation of the toner particle arrangement on the magnetic medium.

Magnetic toner particle transfer apparatus comprising:

• a movably mounted, magnetic medium capable of having a magnetic toner carried thereby arranged to correspond to a magnetic field associated with the magnetic medium, said magnetic field defining a latent magnetic image,
• a platen positioned adjacent the magnetic medium on the non-toner bearing side thereof,
• a transfer electrode spaced from and generally parallel to the platen and toner particle bearing surface of the magnetic medium and adapted to have a receiving medium positioned between the electrode and the magnetic medium,
• electrical bias means coupled to the transfer electrode for establishing an electric field for retaining toner to the magnetic medium prior to contact of the magnetic medium with a receiving medium,
• drive means coupled to at least either the platen or transfer electrode for moving the platen and electrode relative to each other along a path that is generally perpendicular to their parallel surfaces at or below a first variable velocity until a selected relatively small separation distance between the magnetic medium and a receiving medium is reached and thereafter at a second variable velocity until contact occurs between the magnetic medium and a receiving medium,
• said first and second variable velocities being equal to or less than maximum rates below which the toner particle image on the magnetic medium remains substantially undisturbed by air currents created between the magnetic medium and a receiving medium.