US3873002A

US3873002A - Toner dispenser logic control

Info

Publication number: US3873002A
Application number: US351741A
Authority: US
Inventors: James R Davidson; Carol A Walter
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1973-04-16
Filing date: 1973-04-16
Publication date: 1975-03-25
Anticipated expiration: 1992-03-25
Also published as: BR7403036D0; CA1008915A; DE2408411A1; AU6791674A; IT1009837B; BE813798A; FR2225782B1; FR2225782A1; GB1457565A; JPS5031829A; JPS544853B2; NL7404416A

Abstract

A control device which regulates the dispensing of predetermined quantities of particles from a storage container to a mix for maintaining the concentration thereof substantially at a preselected level. The foregoing abstract is neither intended to define the invention disclosed in the specification, nor is it intended to be limiting as to the scope of the invention in any way.

Description

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ABSTRACT A control device which regulates the dispensing of predetermined quantities of particles from a storage container to a mix for maintaining the concentration thereof substantially at a preselected level. The foregoing abstract is neither intended to define the invention disclosed in the specification, nor is it [56] References Cited UNITED STATES PATENTS intended to be limiting as to the scope of the invention Vw a W y n a .m 3 B w 2 2 WM ee LET. 5 No CD oo 66 99 H 4] Mm v w 8O 7O 23 12 Claims, 10 Drawing Figures PAIENIIED MIR? 5 5 3, 873 00?.

SHEET 2 [IF 3 F l I I I I 1 I 62 I I Voltage I 2 l I 17?? Control Oscillator LOgiC Motor T P I I I l I Detector V Binary Counf Log:

Counter Detector Memory Dispense I r\ Timer 72 f 74 I gag Dispense Increment Identification Binary Count Logic coumer Detector Memory A 7 7 25639 f'\ J\ f\ II I I Dispense Increment Low-Toner Defeco Identification v {94 n02 {/M M n f 99 Binary Count Lag/c f er c unt Detector Memory Dispense Timer 96 ;.98 Dispense Increment Low-Toner I Defecfor Identification I TONER DISPENSER LOGIC CONTROL BACKGROUND OF THE INVENTION This invention relates generally to an electrophotographic printing machine, and more particularly concerns a control device which meters predetermined quantities of toner particles from a toner particle storage container to a developer mix utilized in the printing machine development system.

Various types of systems have been devised to regu late the addition of toner particles to the developer mix. These systems are generally arranged to monitor the concentration of toner particles in the developer mix and furnish additional toner particles thereto as required. By maintaining toner particle concentration within the developer mix at about a preferred value, the image density of the copy produced by the printing machine remains substantially constant.

Heretofore, dispensing systems metered substantially constant quantities of toner particles into the developer mix of the development system. The control system sensed the concentration of toner particles within the developer mix and produced an electrical signal indicative thereof. One such system is disclosed in copending application Ser. No. 213,056 filed in 1971 now Pat. No. 3,754,821. As disclosed therein, an electrically biased transparent electrode disposed on a photoconductive surface passes through the developer mix. While in the development Zone, the transparent electrode attracts toner particles thereto. Subsequently, the electrode is illuminated and the density of toner particles attracted thereto is indicated by the intensity of light passing therethrough. A photosensor detects the intensity of light rays passing through the transparent electrode and develops an electrical signal proportional thereto. The electrical signal is compared with a reference and a control signal is developed actuating the toner particle storage container if the detected density is below the control point. Each excitation signal results in the actuation of the toner particle storage container for a prescribed length of time during the next successive development cycle. In this manner, a relatively fixed guantity of toner particles are dispensed into the developer mix of the development system when required. This type of system is known in the art as an ON-OFF system. By

this, it is meant that the concentration of toner particles in the developer mix is sensed, and an electrical signal generated which energizes the toner particle storage container. Thus, if the concentration of toner particles in the developer mix is beneath a specified level, additional toner particles are supplied thereto. However, if the toner particle concentration is adequate, no electrical signal is generated and the toner particle storage container remains quiescent. In a system of this type, the amount of toner particles dispensed into the developer mix during each development cycle must be maintained within narrow limits. At the lower limits sufficient toner particles must be added to the developer mix to maintain satisfactory image density when toner particle demand is at a maximum. Contrawise, superfluous quantities of toner particles must not be added to the developer mix during any one development cycle as this would produce excessive image density. It is, therefore, apparent than an ON-OFF system of this type has a narrow latitude in order to attain the foregoing requirements.

Accordingly, it is a primary object of the present invention to improve the control device for regulating the dispensing of toner particles from a toner particle storage container to the developer mix of a development system utilized in an electrophotographic printing machine.

SUMMARY OF THE INVENTION Briefly stated, and in accordance with the present invention, there is provided a control device for regulat' ing the dispensing of predetermined quantities of particles from a storage container to a mix.

Pursuant to the present invention, the control device includes detecting means and summing means. The detecting means senses the concentration of particles in the mix. In addition, the detecting means produces an electrical signal indicating that the sensed particle concentration in the mix is beneath a predetermined level. Summing means are provided to develop a plurality of output signals corresponding to a discrete number of detecting means electrical signals. Each summing means output signal actuates the storage container to dispense differing quantities of pazrticlesinto the mix.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the draw ings in which:

FIG. I is a schematic perspective view of a multicolor electrophotographic printing machine embodying the features of the present invention thereinz:

FIG. 2 is a block diagram of the control device of the present invention employed in association with the FIG. 1 printing machine;

FIG. 3 is a functional block diagram of the FIG. 2 control device;

FIG. 4 is a logic diagram of one of the blocks in the FIG. 3 functional block diagram;

FIG. 5 is a logic diagram of another of the blocks of the FIG. 3 functional block diagram;

FIG. 6 is a logic diagram of another of the blocks of the FIG. 3 functional block diagram;

FIG. 7 is a logic diagram of another of the blocks of the FIG. 3 functional block diagram;

FIG. 8 is a logicdiagram of another of the blocks of the FIG. 3 functional block diagram;

FIG. 9 is a logic diagram of another of the blocks of the FIG. 3 functional block diagram; and

FIG. 10 is a logic diagram of another of the blocks of the FIG. 3 functional block diagram.

While the present invention will be described in connection with a preferred embodiment thereof, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION For a general understanding of the disclosed multicolor electrophotographic printing machine in which the present invention may be incorporated, continued reference is had to the drawings. In the drawings, like reference numerals have been used throughout to des ignate like elements. Turning now to FIG. 1, the various components of the multi-color printing machine are illustrated schematically therein. Although the control device of the present invention is particularly well adapted for use in this type of electrophotographic printing machine, it should become evident from the following discussion that it is equally well suited for use in a wide variety ofelectrostatographic printing machines, and is not necessarily limited in its application to the particular embodiment shown herein.

As depicted in FIG. 1, the electrophotographic printing machine utilizes a drum having a photoconductive surface 12 secured to the exterior circumferential surface thereof. Drum 10 is mounted rotatably on the machine frame and driven at a substantially constant angular velocity, in the direction of arrow 14, by a drive motor (not shown). As drum 10 rotates, photoconductive surface 12 passes sequentiallythrough a series of processing stations. The drive motor rotates drum 10 at a predetermined speed relative to the other operating mechanisms of the printing machine. The machine logic coordinates the timing of the various operations with the rotation of drum 10 to produce the proper sequence of events at the respective processing stations.

Initially drum 10 rotates photoconductive surface 12 through charging station A. At charging station A, a co-' rona generating device, indicated generally at 16, extends longitudinally in a transverse direction across photoconductive surface 12. This readily enables corona generating device 16 to spray ions onto photoconductive surface 12 to produce a relatively high, substantially uniform charge thereon. Preferably, corona generating device 16 is of a type described in US. Pat. No. 2,778,946 issued to Mayo in I957.

After photoconductive surface 12 is charged to a substantial uniform potential, drum 10 is rotated to exposure station B. At exposure'station B, a color filtered light image of original document 22 is projected onto charged photoconductive surface 12. Exposure station B includes a moving lens system, generally designated by the reference numeral 18, and a color filter mechanism shown generally at 20. A suitable moving lens system is disclosed in U.S. Pat. No. 3,062,108 issued to Mayo in 1962, and a suitable color filter mechanism is described in copending application Ser. No. 830,282 filed in I969. Original document 22, such as a sheet of paper, book, or the like is placed face down upon transparent viewing platen 24. As shown in FIG. 1, lamps 26 are adapted to move in a timed relationship with lens 18 and filter mechanism 20 toscan successive incremental areas of original document 22 disposed upon platen 24. In this manner, a flowing light image of the original document 22 is projected onto photoconductive surface 12. During the exposure process, filter mechanism 20 interposes selected color filters into the optical light path of lens 18. The appropriate filter operates on the light rays transmitted through lens 18 to record an electrostatic latent image on photoconductive surface 12 corresponding to a preselected spectral region of the electromagnetic wave spectrum, hereinafter referred to as a single color electrostatic latent image.

Drum 10 next rotates to a development station C. At development station C, three individual developer units, generally indicated by the

reference numerals

28, and 32, respectively are arranged to render visible the electrostatic latent image recorded on photoconductive surface 12. Preferably, the developer units are all of a type generally referred to in the art as magresponding to the complement of the'spectral region of the wave length of light transmitted through filter 20. For example, a green filtered electrostatic latent image is developed by depositing green absorbing magenta toner particles thereon, blue and red filtered latent images are developed with yellow and cyan toner particles, respectively. A typical development station employing a plurality of developer units, as disclosed in FIG. 1, is described in copending application Ser. No. 255,259, filed in 1972.

Pursuant to the present invention, additional toner particles are added to the respective developer mixes when the concentration thereof is reduced beneath a specified level. The toner particle concentration is determined by detecting means, indicated generally at 34. Detecting means 34 includes a transparent electrode assembly 36 mounted on photoconductive surface 12 of drum 10 in the non-image area thereof. A light source 38, in cooperation with

fiber optics

40 and 44, transmits the light rays through transparent electrode assembly 36 to photosensor 42. As the electrostatic latent image recorded on photoconductive surface 12 is developed, toner paricles are deposited on transparent electrode 36. The intensity of the light rays passing through transparent electrode 36 is indicative of the density of toner particles deposited thereon. Photosensor 42 disposed in oven 46, receives the light rays transmitted through transparent electrode 36. The logic elements, indicated generally at 60, of the present invention are adapted to process the electrical output signal from photosensor 42. Logic elements 60 will be described hereinafter in greater detail with reference to FIGS. 2 through 10, inclusive. The output from logic elements 60 actuate the respective toner particle storage container for dispensing toner particles into the developer mix of the appropriate developer unit when the concentration thereof is beneath a prescribed level.

Proceeding now with the-various processes associated with the multi-color electrophotographic printing machine depicted in FIG. 1, after development, the now visible image is advanced to transfer station D. At transfer station D, the toner powder image adhering electrostatically to photoconductive surface 12 is transferred to a sheet of final support material 50. Final support material 50 may be amongst others, plain paper or a sheet of thermoplastic polysulfone material. A transfer roll, shown generally at 52, secures support material 50 releasably thereto for movement in a recirculating path therewith. Transfer roll 52 is adapted to rotate in synchronism with drum 10 (in this case at substantially the same angular velocity therewith). Hence, a plurality of toner powder images may be transferred from photoconductive surface 12 to support material 50, each toner powder image being superimposed in registration with the prior one. Image transfer is achieved by electrically biasing transfer roll 52 to a potential having sufficient magnitude and the proper polarity to attract electrostatically toner particles from the latent image recorded on photoconductive surface 12 to support material 50. US. Pat No. 3,612,677 issued to Langdon et al. in 1971 describes a suitable electrically biased transfer roll. Transfer roll 52 includes a recess therein arranged to prevent photoconductive surface 12 from moving into contact with the toner particles deposited on transparent electrode 36. Thus, the toner particles are not disturbed by the transfer process and represent a true indication of the toner particle concentration within the developer mix.

After a plurality of toner powder images have been transferred from photoconductive surface 12 to support material 50, support material 50 is separated from the surface of transfer roll 52 and advanced to the fusing station (not shown). At the fusing station, the toner powder image is permanently affixed to support material 50. One type of suitable fuser is described in US. Pat. No. 3,498,592 issued to Moser etal. in 1970 Support material 50, with the toner powder image affixed thereto, is, thereupon, advanced by conveyors (not shown) to a catch tray (not shown). The catch tray is arranged to permit the machine operator to readily remove the completed copy from the printing machine.

The last processing station in the direction of rotation of drum 10, as indicated by arrow 14, is cleaning station E. As heretofore indicated, a preponderance of the toner particles are tranferred .to support material 50, however, some residual toner particles remain on photoconductive surface. 12. Cleaning station E removes these residual toner particles from photoconductive surface 12. The residual toner particles are initially brought under the influence of a cleaning corona generating device (not shown) adapted to neutralize the remaining electrostatic charge. Thereafter, the neutralized toner particles are cleaned from photoconductive surface 12 by arotating fibrous brush 56. Brush 56 is positioned in contact with photoconductive surface 12. One type of suitable brush cleaning device is described in U.S. Pat. No. 3,590,412 issued to Gerbasi in 1971.

lt is believed that the foregoing description is sufficient to illustrate the general operation ofa mul'ti-color electrophotographic printing machine utilizing the teachings of the present invention therein.

FIG. 2 depicts a system to meter a predetermined quantity of toner particles into the developer mix of the corresponding developer units. As shown in FIG. 2, dashed lines represent a signal path within the printing machine of FIG. 1, whereas solid lines refer to control logic signals. Detecting means 34 develops an output voltage which is compared to a reference voltage indicative of the desired toner concentration within the corresponding developer mix. Comparator 58 determines the differences between the reference voltage developed by voltage source 57 and the voltage generated by detecting means 34. This difference becomes an error signal which actuates control logic 60.

Control logic 60 will be described hereinafter with reference to FlGS. 3 through 10, inclusive. One output from control logic 60 is an electrical signal indicating that toner particles are depleted from the respective toner particle storage container. This signal in turn gencrates a signal actuating oscillator motor 62 of the toner particles storage container to develop either a full or partial (in this case half) dispense of toner particles therefrom. Another signal therefrom indicates the time 6 in the print cycle that the'signal actuating the appropri ate toner particle storage container should be on or off. The toner particles dispensed from the respective toner particle storage container increase the concentration of toner particles in the developer mix and modify the density sensed by detecting means 34 on subsequent development cycles. Thus, the control system depicted in FIG. 2 is arranged to regulate the concentration of toner particles within the developer mix of the corresponding developer unit. However, the particular invention disclosed herein is directed to the detailed structural configuration of contro logic 60. This will be described hereinafter in greater detail with reference to FIGS. 3 through 10, inclusive.

FIG. 3 illustrates a functional block diagram of control logic 60 comprising three independent logic channels associated therewith.'Logic channel 63 is associated with the cyan toner particles, logic channel 64 is associated with the magenta toner particles, and logic channel 66'is associated with the yellow toner particles. An electrical output signal from detecting means 34 is transmitted on line 68 to binary counter 70 of the appropriate logic channel, in this case, the cyan logic channel. Binary counter 70 sums the number of electrical output signals from detecting means 34. lf the total number of electrical signals exceeds the binary number 10, i.e., 1010, low-toner detection block 72 is actuated generating a signal which causes the printing machine to stop after completion of the print-cycle. 1f the toner door (or in lieu thereof, the machine door) is opened and closed to add additional toner particles to the container, the low-toner condition is removed and binary counter 70 reset to zero so that printing may resume.

In addition, an electrical output from binary counter 70 actuates dispense increment indentification block 74. This, in turn, actuates dispense time block 76, which determines the length of time that the oscillator motor is vibrated, thereby defining the length of the next toner dispense therefrom. Thus, if identification block 74 indicated that from one to three electrical output signals have been obtained from detecting means 34, i.e., 0001., 0010, or 0011, the left two binary numbers being even (00), the toner dispense time will be a partial dispense, whereas if identification block 74 indicates that the number of electrical outputsignals from detecting means 34 ranges from four to ten, i.e., 0100, 0101, 0110, 0111,1000,1001, or 1010, the left binary number being odd (01 or 10), the toner dispense time will be a full dispense time.

The output signal from binary counter also actuates count detector block 78, which in turn energizes memory of a count block 80. Counter detector 78 verities that there has been a request for toner particles, and logic memory 80 provides a toner dispense signal. Logic memory 80 is energized by a toner dispense signal from toner dispense time element 76 and from count detector 78. When the electrical signals from count detector 78 and element 76 are both present memory element 80 is actuated. Element 80 develops a toner dispense signal of the appropriate length which energizes the oscillator motor of the appropriate toner particle storage container, in this case the cyan toner particle storage container. Developer length block is interconnected with cyan developer unit 32 and determines the length of time that cyan developer unit 32 is actuated.

Channels

64 and 66 are essentially the same as that of logic channel 63. Logic channel 64 actuates the magenta toner particle storage container and includes binary counter 82 adapted to count the number of electrical output signals from detecting means 34. When binary counter 82 indicates that the total number of electrical output signals from the detection means exceeds 10, low-toner detector 84 inhibits toner particle dispensing. Toner dispensing increment identifier 86 indicates when the total number of electrical counts is intermediate four and ten. The signal therefrom ener giz'es toner dispense time block 88 which permits a full dispense to be developed. Count detector 90 is actuated by binary counter 82, and in association with a signal from dispense time 88 actuates binary memory 92. If, however, from one to three electrical output signals have been summed from detecting means 34, element 88 will reduce the dispense time in half. Thus, the toner particle storage container oscillator motor will be energized for about one-half the time and about one-half the number of toner particles will be dispensed into the magenta developer unit. Development length block 87 is interconnected with magenta developer unit 30, and determines the length of time that magenta developer unit 30 is actuated.

In a similar fashion, logic channel 66 develops a full or partial dispense signal for the yellow toner particle storage container. As depicted in FIG. 3, binary counter 94 sums the number of electrical output signals from detecting means 34. If binary counter 94 indicates that ten electrical output signals have been produced by detecting means 34, low-toner detection block 96 is actuated. Low-toner detection block 96 thereupon inhibits yellow toner particle dispensing. The output signal from binary counter 94 also actuates the dispense increment identification block 98 which determines whether binary counter 94 is indicating an electrical output signal from detecting means 34 that is less than three or ranges from four to ten. Dispense increment identification block 98 actuates dispense timer 100. The output signal from binary counter 94 actuates count detector 102. The signal from dispense timer 100 and count detector 102 actuates memory counter 104. Element 104, in turn, energizes the yellow toner particle storage container oscillator motor for the time prescribed. Thus, if one to three electrical output signals have been sensed, the yellow logic channel oscillator motor is energized for a half dispense cycle. However, if four to ten electrical output signals have been sensed from detecting means 34, the oscillator motor of the yellow toner particle storage container is actuated for a full dispense cycle. Developer length block 99 is interconnected with yellow developer unit 28, and determines the length of time that yellow developer unit 28 is actuated.

The present invention has been described in connection with a pair of output signals for energizing the oscillator motor such that the toner particle storage container discharges two differing quantities of toner particles into the developer mix. However, one skilled in the art will appreciate that a plurality of output signals may be used for energizing the oscillator motor such that the toner particle storage container discharges a plurality of differing quantities of toner particles into the developer mix.

Referring now to FIGS. 4 through 10, inclusive, the detailed logic elements utilized to form'the blocks of FIG. 3 will be discussed. The logic elements used to formulate the blocks of FIG. 3 are substantially identical for each channel. Accordingly, the following description will describe the logic elements of the blocks for channel 62 of FIG. 3, the blocks for the remaining channels being the same. 7

Turning initially to FIG. 4, the logic elements of developer length logic block will be described. The de-- veloper signal generated by logic block 75 determines the length of time that developer unit 28 is in operation. As shown in FIG. 1, control 60 is interconnected with developer unit 28, i.e., logic block 75 of control logic 60 is interconnected therewith. Developer unit 28 remains operative for an 8% inch by l 1 inch long image one predetermined time interval, and for an 11 inch by 14 inch long image a second predetermined time interval. Preferably, developer length logic block 75 includes NAND gate 106, NAND gate l08, and NAND gate 110. The output signals from the foregoing NAND gates energize NAND gate 112. The output from NAND gate 112 energizes developer unit 28 for the requisite time duration.

With reference now to FIG. 5, toner dispense time block 76 is energized by developer lengthblock 75. Toner dispense time block 76 is implemented so as to provide the other logic functions with the pulse duration of the developer signal. It provides a long dispense signal, e.g., when the binary count ranges from 4 to 10, and a short dispense signal, e.g., when the binary count ranges from 1 to 3. When the binary count is O the toner particle storage containers are inhibited from dispensing toner particles therefrom. Block 76 includes NAND gate 114 which, in conjunction with an external signal energizes NAND gate 116. Inverter 118 inverts the external signal and with two other external signals actuates NAND gate 120. The output signals from NAND gate 116 and NAND gate 120 energize NAND gate 122. AND gate 124 is actuated by the output signal from NAND gate 122, the output of block 75, and an external signal. The output signal from AND gate 124 is utilized as an input signal to memory of a count block 80.

Turning now to FIG. 6, binary counter of dispense request block 70 is depicted in detail therein. A count of O in binary, on the output thereof indicates that no toner particles are dipensed from the toner particle storage container. A binary count ofl through 3, inclusive, indicates a half dispense, and a binary count of 4 through 10 inclusive, indicates a full dispense. A lowtoner shut down occurs in the printing machine cycle following the tenth request to dispense toner particles. The count of the binary counter is enabled when the output from comparator 58 (FIG. 2) indicates that toner particles are not being deposited on transparent electrode 36 (FIG. 1), and a low-toner condition does not exist. The binary counters are reset to zero count when the door for the housing of the toner particle storage container or in lieu thereof, the machine door, is opened and closed, or by an initializing function obtained by turning the printing machine OFF and ON. Preferably, logic block 70 includes AND gate 126 connected to binary counter 128. The appropriate output signals from binary counter 128 actuate low-toner detector block 72, dispense increment identification block 74 and detection of a count block 78.

Low-toner detection block 72 will now be described with reference to FIG. 7. Low-toner detection logic block 72 decodes the binarysignal from the output signal of binary counter 128. If a count of 10 is decoded, a low toner signal is generated. However, when the door to the housing of the toner particle storage'container is opened and closed, i.e., additional toner particles are added to the toner particle storage container, the low toner condition is removed since binary counter 128 is reset to zero. Low-toner detection block 72 includes inverter 130 and inverter 132. The inputs to

inverters

130 and 132 are output Signals from counter 128. The output signals from

inverters

130 and 132, in conjunction with the output signals from binary counter 128, energized NAND gate 134. A negative output signal from NAND gate 134 inhibits further dispensing of toner particles from the toner particle storage container when a low-toner condition exists.

Turning now to FIG. 8, detection of a count block 78 will be described in detail. Detection of acount block 78 includes inverter 136, inverter 138, inverter 140 and inverter 142. The output signals from the foregoing inverters actuate NAND gate 144. The input signals to

inverters

136, 138, 140and 142 are the outputs from binary counter 128.

Inverters

136, 138, 140 and 142 in association with NAND gate 144 operate in conjunction with one another as an OR function to verify that there has been a request for toner particles. The output signal from NAND gate 144, and the output signal from AND gate 124 (FIG. energize memory of a count block 80.

FIG. 9 illustrates the logic element utilized to form dispense increment block 74. Preferably, dispense increment block 7.4 includes EXCLUSIVE OR 146. EX- CLUSIVE OR 146 is actuated by the two left binary digits of binary counter 128. The output signal from EXCLUSIVE OR 146 is 0 when the two left binary digits are even, i.e., 00. However, the output signal from EXCLUSIVE OR 146 is 1 when the two left binary digits are odd, i.e., 01 or 10. A 0 output from EXCLU- SIVE OR 146 indicates a half dispense signal, whereas a 1 output from EXCLUSIVE OR 146 indicates a full dispense signal. The output signal from EXCLUSIVE OR 146 actuates toner dispense time block 76.

Finally, FIG. illustrates memory of a count block 80. Block 80, preferably, includes FLIP-FLOP 148 and AND gate 150. FLIP-FLOP 148 has the output thereof toggled i.e., set at 1, whenever both a toner dispense time signal from block 76 and a count signal from block 78 are present. FLIP-FLOP 148 will remain at 1 until a 0 is toggled in by the toner dispense time block 76 when there is no count signal from block 78, or FLIP- FLOP 148 is reset by the printing machine logic. AND gate 150 is used as the final pulse width determination of the toner dispense signal.

In recapitulation, it is apparent that the control device'of the present invention meters a predetermined quantity of toner particles to the developer mix so as to maintain the concentration thereof at a substantially constant level. This is achieved by logic circuitry which totals the number electrical signals from the photosen sor to generate either a full or partial dispense signal dependent upon number of signals received. In this manner, a predetermined quantity of toner particles are dispensed into the developer mix over a predetermined time interval. If the electrial output signal is such as to require a partial dispense, the time interval is reduced, whereas if the electrical output signal is such as to require a full dispense the time interval is maintained at the full increment.

It is, therefore, apparent that there has been provided, in accordance with this invention, a control device for metering predetermined quantities of toner particles into the developer mix of a printing machine development system that fully satisfies the objects, aims and advantages set forth above. While this invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

What is claimed is:

1. A control device for regulating the dispensing of predetermined quantities of particles from a storage container to a mix, including:

means for detecting the concentration of particles in the mix, said detecting means being arranged to provide an electrical signal indicating that the particle concentration within the mix is beneath a predetermined level; and

means for summing said detecting means electrical signals and providing a plurality of output signals each corresponding to a predetermined number of electrical signals, each output signal from said summing means being adapted to actuate the storage container for dispensing predetermined differing quantities of particles therefrom into the mix. said summing means provides a first output signal when the number of electrical signals from said detecting means is less than a first pre-selected sum, the first output signal being adapted to actuate the storage container for dispensing a first predetermined quantity of particles therefrom, and a second out put signal when the number of electrical signals from said detecting means is intermediate the first pre-selected sum and a second pre-selected sum, the second output signal being adapted to actuate the storage container for dispensing a second predetermined quantity of particles therefrom.

2. A device as recited in claim ll, further including means for actuating the storage container, in response to the signal from said summing means, to dispense an amount of particles from the storage container corre sponding to the output signal furnished thereto 3. A device as recited in claim 2, wherein said summing means includes:

means for counting the number of electrical signals from said detecting means;

means for generating the first output signal in response to said counting means indicating that the number of electrical signals from said detecting means is less than the first pre-selected number of electrical signals; and

means, responsive to said counting means indicating that the number of electrical signals from said detecting means is intermediate the first and second preselected number of electrical signals, for developing'the second output signal.

4. A device as recited in claim 3, further including means, responsive to said counting means indicating that the number of electrical signals from said detecting means is greater than the second preselected number thereof, for producing a signal adapted to prevent said actuating means from energizing the storage container for dispensing particles therefrom.

5. A device as recited in'claim 4 further including means for resetting saidcounting means to zero in response to said counting means indicating that the number of electrical signals from said detecting means is greater than the second preselected number of electrical signals.

6. A device as recited in claim 5, wherein the second predetermined quantity of particles dispensed from the storage container is greater than the first predetermined quantity of particles dispensed therefrom, the second predetermined quantity of dispensed particles being preferably about twice the amount of the first predetermined quantity of dispensed particles.

7. An electrophotographic printing machine of the type having a toner particle storage container arranged to dispense predetermined quantities of toner particles therefrom into a developer mix utilized in a development system thereof, including:

means for detecting the concentration of toner particles in the developer mix, said detecting means being arranged to provide an electrical signal indicating that the toner particle concentration'within the developer mix is beneath a predetermined level; and

means for summing said detecting means electrical signals and providing a plurality of output signals each corresponding to a predetermined number of electrical signals, each output signal from said summing means being adapted to actuate the toner particle storage container for dispensing predetermined differing quantities of toner particles therefrom into the developer mix, said summing means provides a first output signal when the number of electrical signals from said detecting means is less than a first pre-selected sum, the first output signal being adapted to actuate the toner particle storage container for dispensing a first predetermined quantity of toner particles therefrom, and a second output signal when the number of electrical signals from said detecting means is intermediate the first pre-selected sum and a second pre-selected sum, the second output signal being adapted to actuate the toner particle storage container for dispensing a second predetermined quantity of toner particles therefrom.

8. A printing machine as recited in claim 7, further including means for actuating the toner'particle storage container, in response to the signal from said summing means to dispense an amount of toner particles from the toner particle storage container corresponding to the output signal furnished thereto.

9. A printing machine as recited in claim 8, wherein said summing means includes:

means for counting the number of electrical signals from said detecting means;

means for generating the firstoutput signal in response to said counting means indicating that the number of electrical signals from said detecting means is less than the first preselected number of electrical signals; and

means, responsive to said counting means indicating that the number of electrical signals from said detecting means is intermediate the first and second preselected number of electrical signals, for developing the second output signal.

10. A printing machine as recited in claim 9, further including means, responsive to said counting means indicating that the number of electrical signals from said detecting means is greater than the second preselected number thereof, for producing a signal adapted to pre' vent said actuating means from energizing the toner particle storage container for dispensing toner particles therefrom.

11. A printing machine as recited in claim 10, further including means for re-setting said counting means to zero in response to said counting means indicating that the number of electrical signals from said detecting means is greater than the second preselected number of electrical signals.

12. A printing machine as recited in claim 11, wherein the second predetermined quantity of toner particles dispensed from the toner particle storage container is greater than the first predetermined quantity of toner particles dispensed therefrom, the second predetermined quantity of dispensed toner particles being preferably about twice the amount of the first predetermined quantity of dispensed toner particles.

Claims

1. A control device for regulating the dispensing of predetermined quantities of particles from a storage container to a mix, including: means for detecting the concentration of particles in the mix, said detecting means being arranged to provide an electrical signal indicating that the particle concentration within the mix is beneath a predetermined level; and means for summing said detecting means electrical signals and providing a plurality of output signals each corresponding to a predetermined number of electrical signals, each output signal from said summing means being adapted to actuate the storage container for dispensing predetermined differing quantities of particles therefrom into the mix, said summing means provides a first output signal when the number of electrical signals from said detecting means is less than a first pre-selected sum, the first output signal being adapted to actuate the storage container for dispensing a first predetermined quantity of particles therefrom, and a second output signal when the number of electrical signals from said detecting means is intermediate the first pre-selected sum and a second pre-selected sum, the second output signal being adapted to actuate the storage container for dispensing a second predetermined quantity of particles therefrom.

2. A device as recited in claim 1, further including means for actuating the storage container, in response to the signal from said summing means, to dispense an amount of particles from the storage container corresponding to the output signal furnished thereto.

3. A device as recited in claim 2, wherein said summing means includes: means for counting the number of electrical signals from said detecting means; means for generating the first output signal in response to said counting means indicating that the number of electrical signals from said detecting means is less than the first pre-selected number of electrical signals; and means, responsive to said counting means indicating that the number of electrical signals from said detecting means is intermediate the first and second preselected number of electrical signals, for developing the second output signal.

4. A device as recited in claim 3, further including means, responsive to said counting means indicating that the number of electrical signals from said detecting means is greater than the second preselected number thereof, for producing a signal adapted to prevent said actuating means from energizing the storage container for dispensing particles therefrom. Pg,24

5. A device as recited in claim 4 further including means for resetting said counting means to zero in response to said counting means indicating that the number of electrical signals from said detecting means is greater than the second preselected number of electrical signals.

7. An electrophotographic printing machine of the type having a toner particle storage container arranged to dispense predetermined quantities of toner particles therefrom into a developer mix utilized in a development system thereof, including: means for detecting the concentration of toner particles in the developer mix, said detecting means being arranged to provide an electrical signal indicating that the toner particle concentration within the developer mix is beneath a predetermined level; and means for summing said detecting means electrical signals and providing a plurality of output signals each corresponding to a predetermined number of electrical signals, each output signal from said summing means being adapted to actuate the toner particle storage container for dispensing predetermined differing quantities of toner particles therefrom into the developer mix, said summing means provides a first output signal when the number of electrical signals from said detecting means is less than a first pre-selected sum, the first output signal being adapted to actuate the toner particle storage container for dispensing a first predetermined quantity of toner particles therefrom, and a second output signal when the number of electrical signals from said detecting means is intermediate the first pre-selected sum and a second pre-selected sum, the second output signal being adapted to actuate the toner particle storage container for dispensing a second predetermined quantity of toner particles therefrom.

8. A printing machine as recited in claim 7, further including means for actuating the toner particle storage container, in response to the signal from said summing means to dispense an amount of toner particles from the toner particle storage container corresponding to the output signal furnished thereto.

9. A printing machine as recited in claim 8, wherein said summing means includes: means for counting the number of electrical signals from said detecting means; means for generating the first output signal in response to said counting means indicating that the number of electrical signals from said detecting means is less than the first preselected number of electrical signals; and means, responsive to said counting means indicating that the number of electrical signals from said detecting means is intermediate the first and second preselected number of electrical signals, for developing the second output signal.

10. A printing machine as recited in claim 9, further including means, responsive to said counting means indicating that the number of electrical signals from said detecting means is greater than the second preselected number thereof, for producing a signal adapted to prevent said actuating means from energizing the toner particle storage container for dispensing toner particles therefrom.