Automatic toner concentrate detector and control device

Claim 2

In an electrostatic copying machine in which a recording member is imparted with an electrostatic charge and is developed by contact with a charge attractable toner powder included in a mixture of magnetically attractive carrier particles and toner powder combined in a predetermined mixture ratio of particles to powder and including a developer assembly having a quantity of said mixture for applying the latter to said image which is developed by the selective adherence of the powder, the improvement comprising: sensing means in said developer assembly including inductive reactance generating means and magnetic means for attracting said mixture to said sensing means, said generating means having a predetermined inductive reactance when the ratio of toner powder to carrier particles of said mixture is at said predetermined ratio, and control circuit means connected to said sensing means for monitoring changes in the inductive reactance of said generating means as said toner powder is depleted from said mixture and, in response thereto, for indicating a change in the toner-to-carrier ratio of said mixture.

Claim 3

A copying machine as claimed in claim 1 further including a toner powder dispensing assembly responsive to said control circuit means for dispensing toner powder to said developer assembly in response to changes in the inductive reactance of said generating means to maintain the ratio of carrier particles and toner powder at said predetermined level to provide optimum print density.

Claim 4

In an electrostatic copying machine as recited in claim 2, the improvement further comprising means responsive to said control circuit means for indicating the depletion of toner powder from said dispensing assembly.

Claim 5

In an electrostatic copying machine as recited in claim 2, the improvement further comprising means for enabling the interruption of the operation of said copying machine in response to the depletion of toner powder from said dispeNsing assembly.

Claim 6

A copying machine as claimed in claim 2 wherein said control circuit means includes an oscillator circuit having a predetermined frequency when said toner powder and carrier particles ratio is at said predetermined ratio and in response to a change in the inductive reactance of said generating means, changing said frequency, the output of said circuit controlling said toner powder dispensing assembly so that upon a predetermined change in frequency, said dispenser is actuated to deliver toner powder to said developer means.

Claim 7

A copying machine as claimed in claim 1 wherein said generating means comprises an electrical coil located in the vicinity of said developer assembly in contacting relation with at least a portion of said developer mixture.

Claim 8

In an electrostatic copying machine in which a recording member is imparted with an electrostatic charge and is developed by contact with a charge attractable toner powder included in a mixture of magnetically attractive carrier particles and toner powder combined in a predetermined mixture ratio of particles to powder and including a developer assembly having a quantity of said mixture for applying the latter to said image which is developed by the selective adherence of the powder, the improvement comprising: inductive sensing means in said developer assembly having a predetermined inductive reactance when the ratio of toner powder to carrier particles of said mixture is at said predetermined ratio, and control circuit means connected to said inductive sensing means for monitoring changes in the inductive reactance of said sensing means as said toner powder is depleted from said mixture and in response thereto, for indicating a change in the toner-to-carrier ratio of said mixture, said sensing means comprising a coil wrapped about a first end of an iron core and a magnet positioned adjacent the opposite end thereof, said magnet being of a predetermined Gauss strength to attract developer mix toward said coil wrapped end without retaining said mixture thereat permanently.

Claim 9

In an electrostatic copying machine in which a recording member is imparted with an electrostatic charge and is developed by contact with a charge attractable toner powder included in a mixture of magnetically attractive carrier particles and toner powder combined in a predetermined mixture ratio of particles to powder and including a developer assembly having a quantity of said mixture for applying the latter to said image which is developed by the selective adherence of the powder, the improvement comprising: inductive sensing means in said developer assembly having a predetermined inductive reactance when the ratio of toner powder to carrier particles of said mixture is at said predetermined ratio, and control circuit means connected to said inductive sensing means for monitoring changes in the inductive reactance of said sensing means as said toner powder is depleted from said mixture and in response thereto, for indicating a change in the toner-to-carrier ratio of said mixture, said sensing means comprising a coil wrapped about a first end of an iron core and a magnet positioned adjacent the opposite end thereof, said magnet being of a predetermined Gauss strength to attract developer mix toward said coil wrapped end without retaining said mixture thereat permanently.

Claim 10

In an electrostatic copying machine which includes developer means for applying toner from a dry developer mixture including toner and magnetizable carrier particles in a predetermined ratio to copy material having a charged image thereon, means for monitoring said developer mixture thereby to maintain the ratio of toner-to-carrier particles of said mixture substantially at said predetermined ratio, said monitoring means comprising inductive sensing means located in the vicinity of said developer means in contact with at least a portion of said developer mixture, said sensing means having a predetermined inductive reactance when the quantity of toner and carrier particles are at said predetermined ratio, the inductive reactance of said sensing means changing in accordance with the change in ratio of toner-to-carrier particles of said mix, thereby to indicate a need for replenshing toner particles to said mixture.

Claim 11

In an electrostatic copying machine which includes developer means for applying toner from a dry developer mixture including toner and magnetizable carrier particles in a predetermined ratio to copy material having a charged image thereon, means for monitoring said developer mixture thereby to maintain the ratio of toner-to-carrier particles of said mixture substantially at said predetermined ratio, said monitoring means comprising inductive sensing means located in the vicinity of said developer means in contact with at least a portion of said developer mixture, said sensing means having a predetermined inductive reactance when the quantity of toner and carrier particles are at said predetermined ratio, the inductive reactance of said sensing means changing in accordance with the change in ratio of toner-to-carrier particles of said mix, thereby to indicate a need for replenshing toner particles to said mixture.

Claim 12

In a copying machine of the type in which a recording member is imparted with an electrostatic charge and is developed by applying a mixture of carrier and toner materials combined in a predetermined mixture ratio of carrier material to toner material and including a magnetic brush assembly for forming bristles of the mixture and moving the bristles into engagement with the member to develop the electrostatic image, the improvement comprising: inductive sensing means mounted in engagement with a portion of the bristles of said magnetic brush and having a predetermined electrical inductance, and toner dispensing means connected and controlled by said inductive sensing means for selectively adding toner material to said developer mixture in dependence on the change in inductance of said sensing means due to the depletion of toner in said bristles.

Claim 13

In a copying machine of the type in which a recording member is imparted with an electrostatic charge and is developed by applying a mixture of carrier and toner materials combined in a predetermined mixture ratio of carrier material to toner material and including a magnetic brush assembly for forming bristles of the mixture and moving the bristles into engagement with the member to develop the electrostatic image, the improvement comprising: inductive sensing means mounted in engagement with a portion of the bristles of said magnetic brush and having a predetermined electrical inductance, and toner dispensing means connected and controlled by said inductive sensing means for selectively adding toner material to said developer mixture in dependence on the change in inductance of said sensing means due to the depletion of toner in said bristles.