Toner concentration detector

Claim 2

In a printing apparatus for rendering visible a latent electrostatic image carried on a recording medium by applying to the medium at a toning station a working toner solution comprising a suspension of toner particles in a volatile carrier, improved means for maintaining a predetermined concentration of toner particles in the working toner solution comprising, in combination: a reservoir of toner particles; measuring means for continuously measuring the concentration of toner particles in the working toner solution, said measuring means including a light source, a transparent chamber spaced apart from the light source to receive a continuously flowing stream of working toner solution, first light detection means sensitive to light in the near infrared region of the light spectrum for measuring light intensity from the light source passing through the chamber, and means for transmitting light from the light source through the transparent chamber to the first light detection means along a first path having a first predetermined length; second light detection means for detecting the intensity of light passed to said chamber from said light source; means for providing current to the light source; means for adjusting the current to the light source in response to said second light detection means to maintain a predetermined constant light intensity from the light source; transfer means for transferring toner particles from the reservoir to the working toner solution at a predetermined rate; and operation means responsive to the measuring means for operating the transfer means when the toner particle concentratiOn decreases below a first predetermined value and for terminating the operation of the transfer means when the toner particle concentration increases to the first predetermined value.

Claim 3

In a printing apparatus for rendering visible a latent electrostatic image carried on a recording medium by applying to the medium at a toning station a working toner solution comprising a suspension of toner particles in a volatile carrier, improved means for maintaining a predetermined concentration of toner particles in the working toner solution comprising in combination: a reservoir of toner particles; measuring means for continuously measuring the concentration of toner particles in the working toner solution, said measuring means comprising a light source, a transparent chamber holding a portion of the working toner solution, first light detection means having a positive terminal and a negative terminal for generating a first current signal flowing from the negative terminal to the positive terminal in response to light, first positioning means for positioning the first light detection means to receive light from the light source that is passed through the chamber, second light detection means having a positive terminal and a negative terminal for generating a second current signal flowing from the negative terminal to the positive terminal in response to light, and second positioning means for positioning the second light detection means to receive light from the light source before the light has passed through the working toner solution; transfer means for transferring toner particles from the reservoir to the working toner solution at a predetermined rate; and operating means responsive to the measuring means for operating the transfer means when the toner particle concentration decreases below a first predetermined value and for terminating the operation of the transfer means when the toner particle concentration increases to the first predetermined value, said operating means comprising amplifier means having a first output and a second output for amplifying and inverting the first current signal with respect to the second current signal to produce a first amplified signal having a first voltage on the first output corresponding to the first current signal and to produce a second amplified signal having a second voltage on the second output corresponding to the second current signal so that the ratio of the first voltage to the second voltage remains constant irrespective of the changes in the intensity of the light produced by the light source, said amplifier means comprising a first operational amplifier having an inverting input, a noninverting input and an output comprising said first output; means for operatively connecting the positive terminal of the first light detection means to the noninverting input of the first operational amplifier and for operatively connecting the negative terminal of the first light detection means to the inverting input of the first operational amplifier; a second operational amplifier having an inverting input, a noninverting input and an output comprising said second output; and means for operatively connecting the positive terminal of the second light detecting means to the inverting input of the second operational amplifier and for operatively connecting the negative terminal of the second light detecting means to the noninverting input of the second operational amplifier.

Claim 4

In a printing apparatus for rendering visible a latent electrostatic image carried on a recording medium by applying to the medium at a toning station a working toner solution comprising a suspension of toner particles in a volatile carrier, improved means for maintaining a predetermined concentration of toner particles in the working toner solution comprising in combination: a reservoir of toner particles; measuring means for continuously measuring the concentration of toner particles in the working toner solution, said measuring means comprising a light source, a transparent chamber holding a portion of the working toner solution, first light detection means having a positive terminal and a negative terminal for generating a first current signal flowing from the negative terminal to the positive terminal in response to light, first positioning means for positioning the first light detection means to receive light from the light source that is passed through the chamber, second light detection means having a positive terminal and a negative terminal for generating a second current signal flowing from the negative terminal to the positive terminal in response to light, and second positioning means for positioning the second light detection means to receive light from the light source before the light has passed through the working toner solution; transfer means for transferring toner particles from the reservoir to the working toner solution at a predetermined rate; and operating means responsive to the measuring means for operating the transfer means when the toner particle concentration decreases below a first predetermined value and for terminating the operation of the transfer means when the toner particle concentration increases to the first predetermined value, said operating means comprising amplifier means having a first output and a second output for amplifying and inverting the first current signal with respect to the second current signal to produce a first amplified signal having a first voltage on the first output corresponding to the first current signal and to produce a second amplified signal having a second voltage on the second output corresponding to the second current signal so that the ratio of the first voltage to the second voltage remains constant irrespective of the changes in the intensity of the light produced by the light source, said amplifier means comprising a first operational amplifier having an inverting input, a noninverting input and an output comprising said first output; means for operatively connecting the positive terminal of the first light detection means to the noninverting input of the first operational amplifier and for operatively connecting the negative terminal of the first light detection means to the inverting input of the first operational amplifier; a second operational amplifier having an inverting input, a noninverting input and an output comprising said second output; and means for operatively connecting the positive terminal of the second light detecting means to the inverting input of the second operational amplifier and for operatively connecting the negative terminal of the second light detecting means to the noninverting input of the second operational amplifier.

Claim 5

In a printing apparatus for rendering visible a latent electrostatic image carried on a recording medium by applying to the medium at a toning station a working toner solution comprising a suspension of toner particles in a volatile carrier, improved means for maintaining a predetermined concentration of toner particles in the working toner solution comprising in combination: a reservoir of toner particles; measuring means for continuously measuring the concentration of toner particles in the working toner solution, said measuring means comprising a light source, a transparent chamber holding a portion of the working toner solution, first light detection means having a positive terminal and a negative terminal for generating a first current signal flowing from the negative terminal to the positive terminal in response to light, first positioning means for positioning the first light detection means to receive light from the light source that is passed through the chamber, second light detection means having a positive terminal and a negative terminal for generating a second current signal flowing from the negative terminal to the positive terminal in response to light, and second positioning means for positioning the second light detection means to receive light from the light source before the light has passed through the working toner solution; transfer means for transferring toner particles from the reservoir to the working toner solution at a predetermined rate; and operating means responsive to the measuring means for operating the transfer means when the toner particle concentration decreases below a first predetermined value and for terminating the operation of the transfer means when the toner particle concentration increases to the first predetermined value, said operating means comprising amplifier means having a first output and a second output for amplifying and inverting the first current signal with respect to the second current signal to produce a first amplified signal having a first voltage on the first output corresponding to the first current signal and to produce a second amplified signal having a second voltage on the second output corresponding to the second current signal so that the ratio of the first voltage to the second voltage remains constant irrespective of the changes in the intensity of the light produced by the light source, first analog means for algebraically adding and scaling the first amplified signal and the second amplified signal to produce a first switching voltage which varies with the toner particle concentration and which has a first predetermined voltage value corresponding to said first predetermined value of the toner particle concentration; signal generating means for operating the transfer means; and first switching means for enabling the signal generating means in response to a first switching voltage less than the first predetermined voltage value and for disabling the signal generating in response to a first switching voltage greater than the first predetermined voltage value.

Claim 6

In a printing apparatus for rendering visible a latent electrostatic image carried on a recording medium by applying to the medium at a toning station a working toner solution comprising a suspension of toner particles in a volatile carrier, improved means for maintaining a predetermined concentration of toner particles in the working toner solution comprising in combination: a reservoir of toner particles; measuring means for continuously measuring the concentration of toner particles in the working toner solution, said measuring means comprising a light source, a transparent chamber holding a portion of the working toner solution, first light detection means having a positive terminal and a negative terminal for generating a first current signal flowing from the negative terminal to the positive terminal in response to light, first positioning means for positioning the first light detection means to receive light from the light source that is passed through the chamber, second light detection means having a positive terminal and a negative terminal for generating a second current signal flowing from the negative terminal to the positive terminal in response to light, and second positioning means for positioning the second light detection means to receive light from the light source before the light has passed through the working toner solution; transfer means for transferring toner particles from the reservoir to the working toner solution at a predetermined rate; and operating means responsive to the measuring means for operating the transfer means when the toner particle concentration decreases below a first predetermined value and for terminating the operation of the transfer means when the toner particle concentration increases to the first predetermined value, said operating means comprising amplifier means having a first output and a second output for amplifying and inverting the first current signal with respect to the second current signal to produce a first amplified signal having a first voltage on the first output corresponding to the first current signal and to produce a second amplified signal having a second voltage on the second output corresponding to the second current signal so that the ratio of the first voltage to the second voltage remains constant irrespective of the changes in the intensity of the light produced by the light source, first analog means for algebraically adding and scaling the first amplified signal and the second amplified signal to produce a first switching voltage which varies with the toner particle concentration and which has a first predetermined voltage value corresponding to said first predetermined value of the toner particle concentration; signal generating means for operating the transfer means; and first switching means for enabling the signal generating means in response to a first switching voltage less than the first predetermined voltage value and for disabling the signal generating in response to a first switching voltage greater than the first predetermined voltage value.

Claim 7

An apparatus according to claim 3 wherein the operating means further comprises: second analog means for algebraically adding and scaling the first amplified signal and the second amplified signal to produce a second switching signal having a voltage which varies with the toner particle concentration and which has a second predetermined voltage value corresponding to a second predetermined value of the toner particle concentration less than the first predetermined value of toner particle concentration; and second switching means for altering the signal generating means to operate the transfer means at an increased rate in response to a second predetermined voltage less than the second predetermined voltage value.

Claim 8

An apparatus according to claim 4 wherein the first analog means comprises a first resistor connected to the first output and a second resistor connected to the second output.

Claim 9

An apparatus according to claim 4 wherein the signal generating means comprises a pulse generator having a control gate for producing pulses at a predetermined repetition rate.

Claim 10

An apparatus according to claim 6 wherein the first switching means comprises a transistor connected between the first analog means and the control gate.

Claim 11

An apparatus according to claim 7 wherein the second switching means comprises means for increasing the predetermined repetition rate of the pulses produced by the pulse generator.