Apparatus for monitoring developer mixture

Claim 2

In an electrostatographic reproduction machine comprising means for contacting an electrostatic image-bearing surface with a developer mixture of toner and carrier particles to apply toner to such surface to render the electrostatic image visible, an improved toner concentration monitor comprising: a resistive element in heat transfer contact with a toner composition; means for passing electrical current through said resistive element whereby said resistive element is heated and transfers heat to its surroundings at a rate dependent upon the heat transfer characteristics of said surroundings; and means for measuring the electrical power into said resistive element, whereby said power is a function of toner concentration.

Claim 3

A toner concentration monitor as set forth in claim 1 wherein said resistive element is a hot wire.

Claim 4

A toner concentration monitor as set forth in claim 2 wherein said hot wire is coated with insulating material.

Claim 5

A toner concentration monitor as set forth in claim 1 wherein said resistive element is a thermistor.

Claim 6

A toner concentration monitor as set forth in claim 1 wherein said means for passing electrical current through said resistive element comprises a constant current source electrically connected to said resistive element.

Claim 7

A toner concentration monitor as set forth in claim 1 wherein said means for passing electrical current through said resistive element comprises a constant voltage source electrically connected to said resistive element.

Claim 8

In an electrostatographic reproduction machine comprising means for contacting an electrostatic image-bearing surface with a developer mixture of toner and carrier particles to apply toner to such surface to render the electrostatic image visible, an improved toner concentration monitor comprising: a resistive element which exhibits a property wherein its electrical resistance is characteristic of the temperature of said resistive element; means for contacting said resistive element by a toner composition; and means for passing electrical current through said resistive element whereby said resistive element is heated and transfers heat to its surroundings at a rate dependent upon the heat transfer characteristics of said surroundings; and means for measuring the electrical power into said resistive element, whereby said power is a function of toner concentration.

Claim 9

In an electrostatographic reproduction machine comprising means for contacting an electrostatic image-bearing surface with a developer mixture of toner and carrier particles to apply toner to such surface to render the electrostatic image visible, an improved toner concentration monitor comprising: a resistive element which exhibits a property wherein its electrical resistance is characteristic of the temperature of said resistive element; means for contacting said resistive element by a toner composition; and means for passing electrical current through said resistive element whereby said resistive element is heated and transfers heat to its surroundings at a rate dependent upon the heat transfer characteristics of said surroundings; and means for measuring the electrical power into said resistive element, whereby said power is a function of toner concentration.

Claim 10

A toner concentration monitor as set forth in claim 7 wherein said resistive element is a thermistor.

Claim 11

A toner concentration monitor as set forth in claim 7 wherein said means for passing electrical current through said resistive element comprises a constant current source electrically connected to said resistive element.

Claim 12

A toner concentration monitor as set forth in claim 7 wherein said means for passing electrical current through said resistive element comprises a constant voltage source electrically connected to said resistive element.

Claim 13

A toner concentration monitor as set forth in claim 7 wherein said means for passing electrical current through said resistive element comprises: a constant voltage source electrically connected to said resistive element; and a current limiting resistor in series with said constant voltage source and said resistive element.

Claim 14

A toner concentration monitor as set forth in claim 11 further comprising means for monitoring the voltage across said current limiting resistor.

Claim 15

In an electrostatographic reproduction machine comprising means for contacting an electrostatic image-bearing surface with a developer mixture of toner and carrier particles to apply toner to such surface to render the electrostatic image visible, an improved toner concentration monitor comprising: a resistive element which exhibits a property wherein its electrical resistance increases inversely with temperature; means for suspending said resistive element in a developer mixture of unknown toner concentration; and an electrical power source for passing electrical current through said resistive element whereby said resistive element is heated and transfers heat to the developer mixture at a rate dependent upon the toner concentration of the mixture; and means for measuring the electrical power into said resistive element, whereby said power is a function of toner concentration.

Claim 16

In an electrostatographic reproduction machine comprising means for contacting an electrostatic image-bearing surface with a developer mixture of toner and carrier particles to apply toner to such surface to render the electrostatic image visible, an improved toner concentration monitor comprising: a resistive element which exhibits a property wherein its electrical resistance increases inversely with temperature; means for suspending said resistive element in a developer mixture of unknown toner concentration; and an electrical power source for passing electrical current through said resistive element whereby said resistive element is heated and transfers heat to the developer mixture at a rate dependent upon the toner concentration of the mixture; and means for measuring the electrical power into said resistive element, whereby said power is a function of toner concentration.

Claim 17

A toner concentration monitor as set forth in claim 13 further comprising means for determining the toner concentration of the developer mixture from the electrical power consumed by said power source to just replace the heat lost from said resistive element.

Claim 18

A toner concentration monitor as set forth in claim 13 further comprising means for maintaining said resistive element at a temperature less than the fusing temperature of the, toner.

Claim 19

In an electrostatographic reproduction machine comprising means for causing the nap of a magnetic brush to contact an electrostatic image-bearing surface with a developer mixture of toner and carrier particles to apply toner to such surface to render the electrostatic image visible, an improved toner concentration monitor comprising: a resistive element in contact with the nap of the magnetic brush; and means for passing electrical current through said resistive element whereby said resistive element is heated and transfers heat to the developer mixture of the magnetic brush until it attains a steady state temperature dependent upon the flow rate of the developer mixture in the magnetic brush, whereupon the resistive heating of said resistive element is balanced by the heat transfer from said resistive element.

Claim 20

In an electrostatographic reproduction machine comprising means for causing the nap of a magnetic brush to contact an electrostatic image-bearing surface with a developer mixture of toner and carrier particles to apply toner to such surface to render the electrostatic image visible, an improved toner concentration monitor comprising: a resistive element in contact with the nap of the magnetic brush; and means for passing electrical current through said resistive element whereby said resistive element is heated and transfers heat to the developer mixture of the magnetic brush until it attains a steady state temperature dependent upon the flow rate of the developer mixture in the magnetic brush, whereupon the resistive heating of said resistive element is balanced by the heat transfer from said resistive element.

Claim 21

A toner concentration monitor as set forth in claim 16 wherein said resistive element is suspended at about the mid depth of the magnetic brush nap.

Claim 22

A toner concentration monitor as set forth in claim 16 wherein said resistive element is positioned in the region of approximate maximum flux of the magnetic brush.

Claim 23

A toner concentration monitor as set forth in claim 16 wherein said resistive element is heated to a temperature greater than the fusing temperature of the toner particles.

Claim 24

A toner concentration monitor as set forth in claim 16 wherein said resistive element is heated to approximately 130° F.

Claim 25

A toner concentration monitor as set forth in claim 16 wherein said resistive element is in a high magnetic flux region of the magnetic brush.

Claim 26

In an electrostatographic reproduction machine comprising means for causing the nap of a magnetic brush to contact an electrostatic image-bearing surFace with a developer mixture of toner and carrier particles to apply toner to such surface to render the electrostatic image visible, an improved toner concentration monitor comprising: a resistive element which exhibits a property wherein its electrical resistance is characteristic of the temperature of said resistive element; means for contacting said resistive element by the nap of the magnetic brush; and means for passing electrical current through said resistive element whereby said resistive element is heated and transfers heat to the developer mixture of the magnetic brush until it attains a steady state temperature dependent upon the flow rate of the developer mixture in the magnetic brush, whereupon the resistive heating of said resistive element is balanced by the heat transfer from said resistive element.

Claim 27

In an electrostatographic reproduction machine comprising means for causing the nap of a magnetic brush to contact an electrostatic image-bearing surFace with a developer mixture of toner and carrier particles to apply toner to such surface to render the electrostatic image visible, an improved toner concentration monitor comprising: a resistive element which exhibits a property wherein its electrical resistance is characteristic of the temperature of said resistive element; means for contacting said resistive element by the nap of the magnetic brush; and means for passing electrical current through said resistive element whereby said resistive element is heated and transfers heat to the developer mixture of the magnetic brush until it attains a steady state temperature dependent upon the flow rate of the developer mixture in the magnetic brush, whereupon the resistive heating of said resistive element is balanced by the heat transfer from said resistive element.

Claim 28

A toner concentration monitor as set forth in claim 22 wherein said resistive element is suspended at about the mid depth of the magnetic brush nap.

Claim 29

A toner concentration monitor as set forth in claim 22 wherein said resistive element is positioned in the region of approximate maximum magnetic flux of the magnetic brush.

Claim 30

A toner concentration monitor as set forth in claim 22 wherein said resistive element is heated to a temperature greater than the fusing temperature of the toner particles.

Claim 31

A toner concentration monitor as set forth in claim 22 wherein said resistive element is heated to approximately 130° F.

Claim 32

A toner concentration monitor as set forth in claim 22 wherein said resistive element is in a high magnetic flux region of the magnetic brush.

Claim 33

In an electrostatographic reproduction machine comprising means for contacting an electrostatic image-bearing surface with a developer mixture of toner and carrier particles to apply toner to such surface to render the electrostatic image visible, an improved toner monitor comprising: a resistive element in heat transfer contact with a toner composition; and means for passing electrical current through said resistive element whereby said resistive element is heated and transfers heat to its surroundings until it attains a steady state temperature dependent upon the heat transfer characteristics of said surroundings, whereupon the resistive heating of said resistive element is balanced by the heat transfer from said resistive element.

Claim 34

In an electrostatographic reproduction machine comprising means for contacting an electrostatic image-bearing surface with a developer mixture of toner and carrier particles to apply toner to such surface to render the electrostatic image visible, an improved toner monitor comprising: a resistive element in heat transfer contact with a toner composition; and means for passing electrical current through said resistive element whereby said resistive element is heated and transfers heat to its surroundings until it attains a steady state temperature dependent upon the heat transfer characteristics of said surroundings, whereupon the resistive heating of said resistive element is balanced by the heat transfer from said resistive element.

Claim 35

In an electrostatographic reproduction machine comprising means for contacting an electrostatic image-bearing surface with a developer mixture of toner and carrier particles to apply toner to such surface to render the electrostatic image visible, an improved toner monitor comprising: a resistive element which exhibits a property wherein its electrical resistance is characteristic of the temperature of said resistive element; means for contacting said resistive element by a toner composition; and means for passing electrical current through said resistive element whereby said resistive element is heated and transfers heat to its surroundings until it attains a steady state temperature dependent upon the heat transfer characteristics of said surroundings, whereupon the resistive heating of said resistive element is balanced by the heat transfer from said resistive element.

Claim 36

In an electrostatographic reproduction machine comprising means for contacting an electrostatic image-bearing surface with a developer mixture of toner and carrier particles to apply toner to such surface to render the electrostatic image visible, an improved toner monitor comprising: a resistive element which exhibits a property wherein its electrical resistance is characteristic of the temperature of said resistive element; means for contacting said resistive element by a toner composition; and means for passing electrical current through said resistive element whereby said resistive element is heated and transfers heat to its surroundings until it attains a steady state temperature dependent upon the heat transfer characteristics of said surroundings, whereupon the resistive heating of said resistive element is balanced by the heat transfer from said resistive element.

Claim 37

In an electrostatographic reproduction machine comprising means for contacting an electrostatic image-bearing surface with a developer mixture of toner and carrier particles to apply toner to such surface to render the electrostatic image visible, an improved toner concentration monitor comprising: a resistive element which exhibits a property wherein its electrical resistance increases inversely with temperature; means for suspending said resistive element in a developer mixture of unknown toner concentration; and an electrical power source for passing electrical current through said resistive element whereby said resistive element is heated and transfers heat to the developer mixture until it attains a steady state temperature dependent upon the toner concentration of the mixture, whereupon the resistive heating of said resistive element is balanced by the heat transfer from said resistive element to the developer mixture.

Claim 38

In an electrostatographic reproduction machine comprising means for contacting an electrostatic image-bearing surface with a developer mixture of toner and carrier particles to apply toner to such surface to render the electrostatic image visible, an improved toner concentration monitor comprising: a resistive element which exhibits a property wherein its electrical resistance increases inversely with temperature; means for suspending said resistive element in a developer mixture of unknown toner concentration; and an electrical power source for passing electrical current through said resistive element whereby said resistive element is heated and transfers heat to the developer mixture until it attains a steady state temperature dependent upon the toner concentration of the mixture, whereupon the resistive heating of said resistive element is balanced by the heat transfer from said resistive element to the developer mixture.