US3360652A - Fail safe photoelectric sheet sensing machine control circuit - Google Patents

Fail safe photoelectric sheet sensing machine control circuit Download PDF

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Publication number
US3360652A
US3360652A US403844A US40384464A US3360652A US 3360652 A US3360652 A US 3360652A US 403844 A US403844 A US 403844A US 40384464 A US40384464 A US 40384464A US 3360652 A US3360652 A US 3360652A
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United States
Prior art keywords
photocell
light
paper
machine
drum
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Expired - Lifetime
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US403844A
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English (en)
Inventor
Bernous Tayeb
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Xerox Corp
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Xerox Corp
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Filing date
Publication date
Application filed by Xerox Corp filed Critical Xerox Corp
Priority to US403844A priority Critical patent/US3360652A/en
Priority to GB43036/65A priority patent/GB1121099A/en
Priority to DE1522805A priority patent/DE1522805C3/de
Priority to FR34921A priority patent/FR1455478A/fr
Application granted granted Critical
Publication of US3360652A publication Critical patent/US3360652A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/70—Detecting malfunctions relating to paper handling, e.g. jams
    • G03G15/706—Detecting missed stripping form xerographic drum, band or plate

Definitions

  • This invention relates to an electrical circuit and, particularly, to an electrical circuit to control a machine in response to three different levels of illumination on a photoconductive cell.
  • this invention relates to a circuit for use with a photoconductive cell which detects the presence or absence of a sheet of paper on a rotating drum in a xerographic apparatus and further acts as a fail safe device in that it detects functional inoperativeness of the photocell itself.
  • a rotating drum having a photoconductive surface is used to create an electrostatic latent image on its surface.
  • a powder image in the configuration of the electrostatic latent image is developed on the drum surface and transferred to cut sheets of paper by means of an electrostatic charge applied to the back of the paper. Since there is a latent electrostatic charge on the surface of the drum and an electrostatic charge is applied-on the paper during the transfer operation, the paper tends to adhere to the surface of the xerographic drum.
  • the sheets of paper are stripped from the surface of the drum after transfer, usually by a putter which blows a sharp stream of air between the paper and the drum and physically forces the sheet of paper away from the drum surface.
  • a sheet of paper will adhere to the drum surface past the position at which it should be removed. This occurs when, for any reason, the puffer mechanism fails to operate or the paper is not aligned in the proper position on the drum to be removed from the drum. When this situation occurs it of paper on the drum surface and immediately shut downthe machine before subsequent copies are reproduced or the paper is jammed within the machine.
  • the present-invention permits the utilization of alight source directed against the surface of the xerographic drum with the light reflected into a photoconductive cell to detect the presence or absence of paper on the drum surface and to shut down the machine upon the detection of a sheet of paper. It also functions to shut down the machine when the photoconductive cell itself becomes inoperative as, for example, the glass on the housing of the photoconductive cell becomes too dusty or dirty to pass adequate light or the light source fails.
  • a light source is directed at an angle against the xerographic plate so that a portion of the light is deflected off the surface of the plate into the photoconductive cell, the surface of the plate having a smooth reflective surface.
  • the intensity of the light reaching the photoconductive cell varies partially because the paper is usually of lighter color than the xerographic plate and thus reflects a larger amount of light, but also because of the diffusive nature of the surface of the paper as opposed to the reflective surface of the xerographic drum. Thus, various colored papers may be used and the photocell responds in the same manner as when white paper is used. When, for any reason, the amount of light reaching the photoconductive cell is reduced below that reflected from the surface of the xerographic drum, the photoconductive cell responds to change the characteristics of the circuit and shut down the machine.
  • the photocell responds to three conditions or modes of operation; that is, when the machine is operating normally, the xerographic drum reflects light to the photocell and energizes a control relay which allows the machine to function in its normal manner.
  • the photocell will detect the sheet of paper and, accordingly, change the characteristics of the electrical circuit and deenergize the control relay, shutting down the machine.
  • the third mode of operation occurs when the photocell assembly fails to operate for any reason It is, therefore, an object of this invention to control a machine in response to increases intensity reaching a photocell;
  • lit is a further object of this invention to detect sheets paper which adhere to a rotating xerographic drum; It is a further object of this invention to detect misfed sheets of paper in a xerographic apparatus;
  • FIG. 1 is an isometric view of a xerographic drum with a light source and a photocell mounted adjacent thereto with portions broken away to show hidden structure;
  • FIG. 2 is an isometric view of the light source and photocell shown in FIG. 1 with portions broken away to show internal structure;
  • FIG. 3 is a schematic front view of the xerographic drum and sensing box with one removed to show the internal arrangements of parts;
  • FIG. 4 is a schematic wiring diagram of a circuit for use with the photocell shown in FIG. 1.
  • a xerographic drum 10 is shown in FIG. 1 in the position that it would be mounted in an automatic xerographic machine.
  • the drum is rotatably mounted on a shaft, not shown, extending through bearing 12 in the middle of the drum.
  • the drum is held on the shaft by means of a hand nut 14, which cooperates with threads on the end of the shaft to secure the drum in place.
  • the drum rotates in the direction shown by the arrow.
  • Sheets of paper are fed by the conveyor 16 into surface contact with the drum cover of the sensing box and electrostatically tacked to the drum surface by transfer corotron 18. At this point xerographic powder images which have previously been developed on the drum surface are transferred to the surface of the sheet of paper by the transfer corotron 18.
  • the conveyor 20 is a vacuum conveyor which will hold the paper on the surface of the belt and draws the paper away from the drum surface after the sheet has contacted the surface of the conveyor.
  • a puffer tube 22 directs a series of sharp streams of air through nozzles 24 between the drum surface and the sheet of paper.
  • the nozzles 24 extend across the length of the drum and effectively deflects the sheet of paper from the surface of the drum down against the surface of the belt 20.
  • the stream of air in the putter tube 22, emerging from the nozzles 24, is produced by a small air pump, not shown, and controlled and timed by electrical circuitry, not shown, to puff at the proper time to deflect the sheet of paper onto the conveyor belt 20.
  • the puffer mechanism fails to strip the sheet of paper from the surface of the drum, the sheet of paper would continue to rotate around the drum surface interfering with the operation of other mechanisms about the periphery of the drum. Also, with the sheet of paper on the surface of the drum, further xerographic images cannot be produced or developed; therefore, it is desirable to immediately stop the machine and manually remove the sheet of paper from the drum surface.
  • a photocell and lamp housing 26 is mounted adjacent to the xerographic drum immediately after the puffer tube 22 and before a precleaned corotron 28.
  • the photocell and lamp housing, or sensing box, 26 is seen in FIG. 2 with portions broken away to show the lamp 30 mounted in a socket 32 in one compartment of the housing 26.
  • the lamp is angled to direct its rays through a clear or polarized glass covered opening 34 in the top of the housing against the surface of the xerographic drum 10.
  • a second compartment 36, in the housing 26, is separated from the lamp 30 by a partition 38 and houses a photocell 40.
  • a second opening in the top of the housing 26 immediately above the photocell 40 is covered by a clear or polarized glass 42 and permits the entrance of light rays into the housing and into the photo cell 40, as seen in FIG. 3.
  • the light rays from the lamp 30 are directed through the glass 34 against the surface of the drum 10, as shown by the dotted lines. Light is reflected from the surface of the drum and a portion of that light enters through the glass 42 to the photocell 40.
  • a sheet of paper is on the surface of the drum 10
  • larger amounts of light are reflected from the surface of the paper, which is rougher than the surface of the drum, through the glass 34 to the photocell 40.
  • the changes in light intensity reaching the photocell 40 changes the characteristics of a circuit having a control relay CR-1, as shown in the schematic wiring diagram in FIG. 4.
  • the relay CR-1 controls the operation of the automatic xerographic machine.
  • FIG. 4 shows a schematic wiring diagram of the circuit for the photocell 40 and the control relay CR-1.
  • the circuit is connected to a 110-volt A.C. source.
  • a rectifier 44 converts the current to DC.
  • Direct current passes through a pair of resistors R1 and R2 to the photocell 40 and the control relay CR1.
  • the photocell 40 is set for a normal mode of operation when light reflected from the surface of the xerographic drum is reflected into the photocell.
  • a silicon controlled rectifier 46 or other threshold switching means is connected in the circuit in series with the control relay CR-l, and its gate is connected to the photocell to be controlled thereby in accordance with the current passing through the photocell.
  • a zener-diode 50 is connected in the circuit parallel to the control relay CR-l and the photoconductive cell 40 to maintain the voltage in the circuit at a predetermined level. Since the rectifier 44 allows current to pass on each half cycle, a condenser 52 is mounted in parallel with the control relay CR-l to provide uniform current flow through the relay on the half cycles during which no current is passing through the rectifier. A pair of silicon diodes 54 or other diodes having negative resistance conducting characteristics are connected in the triggering circuit to the gate of the silicon controlled rectifier 46 to bypass current in excess of the amount required to trigger the silicon controlled rectifier 46.
  • the photoconductive cell 40 is adjusted for the normal mode of operation, that is, when the normal amount of light being reflected off the surface of the xerographic drum enters the photoconductive cell the voltage and current to the gate of the silicon controlled rectifier 46 is sufficient to trigger the rectifier and permit current to pass, energizing the control relay CR-1. With the relay CR-l energized, its contacts located in the circuitry to the automatic xerographic machine are closed permitting operation of the machine.
  • the resistance in the photoconductive cell 40 increases to a point wherein the voltage drop across the photoconductive cell 40 is so great that the voltage at point A is too low to trigger the silicon controlled rectifier 46.
  • the silicon controlled rectifier opens cutting off current flow to the relay CR-l and the contacts of the relay CR-l open, shutting down the automatic xerographic machine.
  • a fail safe detecting device for use in detecting misfed sheets of paper in an automatic xerographic machine including:
  • control means adapted to permit operation of the machine when energized and to shut down the machine when deenergized
  • a threshold switching means connected in series with the control means to control current flow through the control means, a limited current power supply connected to said threshold switching means and said control means,
  • a photocell electrically coupled to said threshold switching means and said power supply to trigger said threshold switching means and thereby energize said control means at a photocell response of a predetermined value
  • diode means coupled to said photocell and said power supply to short said power supply in response to a photocell response of higher than said predetermined value
  • a light source positioned in the automatic xerographic machine to reflect a predetermined amount of light into the photocell under normal operative conditions and to reflect an increased amount of light into the photocell when a sheet of paper is misfed in the machine thereby producing a photocell response of higher than the above mentioned predetermined value
  • the photocell having a resistance when exposed to light
  • a fail safe device for use in xerographic reproducing machines to detect the presence of paper on a Xerographic drum and to detect its own failure to perform in the desired manner including:
  • a light source mounted to direct rays of light against the surface of a Xerographic drum
  • a photocell mounted adjacent to the surface of a Xerographic drum in a position to receive a portion of the light rays reflected from the drum surface
  • control circuit including a control relay electrically coupled with the photocell
  • control relay being adapted to permit operation of 3,278,754 3,284,787 12/1966 Voigt et al 307-885 the Xerographic machine upon energization and to shut down the machine upon deenergization,
  • said circuit also having a threshold switching means the photocell being adapted to pass sufficient current to fire the threshold switching means and actuate the control relay when light is reflected from the light source ofl? the surface of the xerographic drum into the photocell and to limit the current necessary to fire the threshold switching means and thus deenergize the control relay when sufficient light fails to reach the photocell and to pass more than a predetermined amount of current upon the occurrence of a greater amount of light at the photocell than that reflected from the xerographic drum, and diode means coupled to said photocell actuated by said current of more than a predetermined amount to draw sufiicient current through the photocell to decrease the current flow through the control relay and thus deenergize said control relay so as to shut down the machine.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Controlling Sheets Or Webs (AREA)
  • Control Or Security For Electrophotography (AREA)
  • Paper Feeding For Electrophotography (AREA)
US403844A 1964-10-14 1964-10-14 Fail safe photoelectric sheet sensing machine control circuit Expired - Lifetime US3360652A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US403844A US3360652A (en) 1964-10-14 1964-10-14 Fail safe photoelectric sheet sensing machine control circuit
GB43036/65A GB1121099A (en) 1964-10-14 1965-10-11 Sheet sensing device in xerographic machines
DE1522805A DE1522805C3 (de) 1964-10-14 1965-10-13 Vorrichtung zur Steuerung des Betriebes einer Kopiermaschine
FR34921A FR1455478A (fr) 1964-10-14 1965-10-14 Dispositif servant à détecter la présence d'une feuille sur le tambour d'une machine xérographique

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US403844A US3360652A (en) 1964-10-14 1964-10-14 Fail safe photoelectric sheet sensing machine control circuit

Publications (1)

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US3360652A true US3360652A (en) 1967-12-26

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US403844A Expired - Lifetime US3360652A (en) 1964-10-14 1964-10-14 Fail safe photoelectric sheet sensing machine control circuit

Country Status (4)

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US (1) US3360652A (de)
DE (1) DE1522805C3 (de)
FR (1) FR1455478A (de)
GB (1) GB1121099A (de)

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3501635A (en) * 1968-05-01 1970-03-17 Scripto Inc Portable thermographic copying machine with photoelectric means to activate the heat lamp thereof upon insertion of a specimen into the machine
US3521060A (en) * 1967-08-24 1970-07-21 Xerox Corp Method for detecting the misrouting of transparencies during the process of imaging thereon
DE1935616A1 (de) 1969-07-14 1971-02-04 Canon Kk Fotokopiergeraet
US3593065A (en) * 1969-07-14 1971-07-13 Xerox Corp Sheet detection apparatus
US3650617A (en) * 1971-02-01 1972-03-21 Xerox Corp Switching detector
US3650616A (en) * 1971-02-01 1972-03-21 Xerox Corp Mispuff detector
US3650619A (en) * 1971-02-01 1972-03-21 Xerox Corp Switching detector
US3650618A (en) * 1971-02-01 1972-03-21 Xerox Corp Switching detector
US3791729A (en) * 1972-07-11 1974-02-12 Xerox Corp Apparatus for monitoring a sheet transport mechanism
US3832065A (en) * 1973-03-23 1974-08-27 Xerox Corp Drum track detector
US3835300A (en) * 1971-11-24 1974-09-10 Kleindienst & Co Web-reading system with replaceable drum
US3901607A (en) * 1974-02-21 1975-08-26 Xerox Corp High aperture reflection photodetector apparatus
JPS5123347Y1 (de) * 1975-03-10 1976-06-15
JPS5461938A (en) * 1977-10-27 1979-05-18 Konishiroku Photo Ind Co Ltd Copy concentration controller/paper clogging detector
US4320961A (en) * 1980-01-28 1982-03-23 Nashua Corporation Jam detecting apparatus and method for electrostatic copier
US4365894A (en) * 1979-05-31 1982-12-28 Konishiroku Photo Industry Co., Ltd. Method for controlling toner concentration
DE1967317C2 (de) * 1969-07-14 1983-11-10 Canon K.K., Tokyo Meß- und Steuervorrichtung für wenigstens einen Funktionsablauf in einem Gerät
US4925174A (en) * 1987-05-29 1990-05-15 Am International Incorporated Method and apparatus for controlling a collator
US20050201808A1 (en) * 2004-03-11 2005-09-15 Barry Raymond J. Combined paper and transparency sensor for an image forming apparatus

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3278754A (en) * 1964-09-16 1966-10-11 Ibm Photosensitive double document detector
US3284787A (en) * 1964-02-24 1966-11-08 Aseco Inc Multi-purpose alarm system

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3284787A (en) * 1964-02-24 1966-11-08 Aseco Inc Multi-purpose alarm system
US3278754A (en) * 1964-09-16 1966-10-11 Ibm Photosensitive double document detector

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3521060A (en) * 1967-08-24 1970-07-21 Xerox Corp Method for detecting the misrouting of transparencies during the process of imaging thereon
US3501635A (en) * 1968-05-01 1970-03-17 Scripto Inc Portable thermographic copying machine with photoelectric means to activate the heat lamp thereof upon insertion of a specimen into the machine
DE1935616A1 (de) 1969-07-14 1971-02-04 Canon Kk Fotokopiergeraet
US3593065A (en) * 1969-07-14 1971-07-13 Xerox Corp Sheet detection apparatus
DE1967317C2 (de) * 1969-07-14 1983-11-10 Canon K.K., Tokyo Meß- und Steuervorrichtung für wenigstens einen Funktionsablauf in einem Gerät
US3650617A (en) * 1971-02-01 1972-03-21 Xerox Corp Switching detector
US3650616A (en) * 1971-02-01 1972-03-21 Xerox Corp Mispuff detector
US3650619A (en) * 1971-02-01 1972-03-21 Xerox Corp Switching detector
US3650618A (en) * 1971-02-01 1972-03-21 Xerox Corp Switching detector
US3835300A (en) * 1971-11-24 1974-09-10 Kleindienst & Co Web-reading system with replaceable drum
US3791729A (en) * 1972-07-11 1974-02-12 Xerox Corp Apparatus for monitoring a sheet transport mechanism
US3832065A (en) * 1973-03-23 1974-08-27 Xerox Corp Drum track detector
US3901607A (en) * 1974-02-21 1975-08-26 Xerox Corp High aperture reflection photodetector apparatus
JPS5123347Y1 (de) * 1975-03-10 1976-06-15
JPS5461938A (en) * 1977-10-27 1979-05-18 Konishiroku Photo Ind Co Ltd Copy concentration controller/paper clogging detector
US4239372A (en) * 1977-10-27 1980-12-16 Konishiroku Photo Industry Co., Ltd. Transfer type electrophotographic copying machine
US4365894A (en) * 1979-05-31 1982-12-28 Konishiroku Photo Industry Co., Ltd. Method for controlling toner concentration
US4320961A (en) * 1980-01-28 1982-03-23 Nashua Corporation Jam detecting apparatus and method for electrostatic copier
US4925174A (en) * 1987-05-29 1990-05-15 Am International Incorporated Method and apparatus for controlling a collator
US20050201808A1 (en) * 2004-03-11 2005-09-15 Barry Raymond J. Combined paper and transparency sensor for an image forming apparatus
US7018121B2 (en) 2004-03-11 2006-03-28 Lexmark International, Inc. Combined paper and transparency sensor for an image forming apparatus

Also Published As

Publication number Publication date
DE1522805A1 (de) 1969-10-30
FR1455478A (fr) 1966-10-14
DE1522805C3 (de) 1974-12-05
GB1121099A (en) 1968-07-24
DE1522805B2 (de) 1974-04-18

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