US3593065A - Sheet detection apparatus - Google Patents

Sheet detection apparatus Download PDF

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Publication number
US3593065A
US3593065A US3593065DA US3593065A US 3593065 A US3593065 A US 3593065A US 3593065D A US3593065D A US 3593065DA US 3593065 A US3593065 A US 3593065A
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United States
Prior art keywords
machine
threshold switching
photocell
control means
switching means
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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English (en)
Inventor
Robert A Domalski
Donald J Quant
Richard C Kahler
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Xerox Corp
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Xerox Corp
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Publication date
Application filed by Xerox Corp filed Critical Xerox Corp
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Publication of US3593065A publication Critical patent/US3593065A/en
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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

  • SHEET 1 BF 2 By DONALD ATTORNEY SHEET 2 UF 2 PATENIED JUL 1 3 1971 L L 2m mm mm 8 L Em 2m m I -16 3% Nam mmom mo w 95 90 5 mum 21 ME mwm mmm w 9m wmm mm omm NEW 8 1 mum SHEET DETECTION APPARATUS
  • This invention relates to apparatus for inactivating a machine in response to an improper condition and in particular to a circuit including a photoconductive cell which detects the presence of a sheet of paper on a rotating xerographic surface and inactivates the apparatus upon the sheet being at an undesired location.
  • 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 or other support material by means of an electrostatic charge applied to 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 puffer which blows a sharp steam of air between the paper and the drum and physically forces the sheet of paper away from the drum surface.
  • the present invention permits the utilization of a light source directed against the surface of the xerographic drum with the light reflected into a photocell 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.
  • a light source is directed against the xerographic plate so that a portion of the light is received by the photocell.
  • the light source reflects light from the drum to the photocell to retain a control relay deenergized and the machine running.
  • the photocell When a sheet of paper adheres to the surface of the drum beneath the photocell, the light is reflected from the paper to rapidly increase the light reaching the photocell.
  • the associated circuitry is designed such that when the amount of light reaching the photocell varies significantly, the photoconductive cell responds to rapidly change the characteristics of the circuitry and shuts down the machine.
  • H6. 1 is an isometric view of part of a xerographic machine including a xerographic drum with a light source and a photocell mounted adjacent thereto;
  • HO. 2 is an isometric view of the light source and photocell shown in FIG. 1;
  • FIG. 3 is an electrical schematic diagram of the circuit including the photocell sown in FIG. 1.
  • a xerographic member in the shape of a drum 10 is shown 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.
  • Sheets of paper are fed by the conveyor 16 into surface contact with the drum and electrostatically tacked to the drum surface by transfer corotron 18.
  • 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 nozzle 24 between the drum surface and the sheet of paper.
  • the noules 24 extend across the length of the drum and effectively deflect the sheet of paper from the surface of the drum down against the surface of the belt 20.
  • the stream of air in the puffer 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 into the conveyor belt. Further details of the puffer and other portions of the xerographic machine may be had by reference to US. Pat. No. 3,301,126 issued to Osborne et al.
  • 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 and causing leakage of developer from its housing. Also, with the sheet of paper on the surface of the drum, further xerographic images cannot be produced or developed. It is, therefore, desirable to immediately stop the machine and manually remove the sheet of paper from the drum surface.
  • a photocell and light source support 26 is mounted adjacent to the xerographic drum 10 immediately after the puffer tube 22 and before a precleaned corotron 25.
  • the support 26 is a bracket which retains an electroluminescent panel 28 and photocell 30 in proper orientation with respect to each other and with respect to the xerographic drum.
  • the panel has a transparent window 32 in the center thereof to permit light, reflected from the drum, to be received by the photocell, which is located behind the window portion of the panel.
  • the support 26 is formed with a lip 34 for holding the electroluminescent panel in place, a central plate section 36 for holding the photocell in place and an apertured support section 38 to permit its mounting in the machine. Electrical leads 40 and 42 couple the photocell to its associated circuit and the panel to a source of potential.
  • the electrical circuit of which the photocell 30 is a part and which may be considered element PC] of the circuit, is shown in FIG. 3.
  • the circuit also includes a main DC power source PS1 for supplying the powerto the circuit and a control relay Kl which, when deenergized permits the xerographic reproducing machine to run,'and which, when energized, inactivates the machine.
  • the circuit may be considered as being made up of four major sections, the misspuff section, the clear section, the startup timer section and the dark history section.
  • the first section, the misspuff section includes the control relay Kl, a threshold switching means in the form of silicone controlled rectifier SCR1, transistors Q2 and Q4, capacitor C4 and the photocell PCl.
  • the purpose of this section is to pennit the normal operation of the machine when the control relay K1 is in a first or deenergized state but to switch the control relay to a second or energized state to stop the machine upon the sensing of a misspuff by the photocell.
  • R15 is to provide temperature compensation for Q6. Once Q6 fires, this will provide a signal through R14 and across R16 to the gate of SCRZ and once SCR2 fires it will provide current through R12 and R13 to the base ofQS which will turn on Q5. This will thus now allow the circuit to detect paper on the drum.
  • CR1] is to provide the system with a one shot capability such that the unijunction transistor, once it has fired, will not free run and fire again. This prevents any false triggering on a rapid startup.
  • the second timer is the dark history timer.
  • the presence of this section is needed due to the fact that when the photocell is dark for any prolonged period of time, as for example several hours, it has a memory to the dark and requires a long length of time to stabilize its resistance. This time is in excess of the time allowed by the startoff timer section thus necessitating the need for reducing this stabilizing time for the photocell.
  • the input capacitors C3 and C4 are charged up to a high voltage very quickly by the circuit section.
  • the charging network is switched out and the photocell is switched in. More particularly, the starting up of the machine causes C10 to charge up to the PS1 potential through R23 24, 25.
  • Toner banding is a strip of toner located axially on the drum surface and occurs after a jam. This would normally come around under the photocell after the jam was cleared at which time the photocell would view the dark band which would cause a sudden increase in resistance such that it would allow current to flow through C3 which would turn on the Q1 and Q3. This would cause the relay to trigger through 05, relay K1, R26 03. This would provide a parallel holding path for the relay. Under this condition, the relay would pull in but then drop out. The relay, however, would have been held in for a sufficient time to cause the machine to shut down.
  • Relay 2K2 is in the circuit to prevent such false shutdowns. This contact is normally closed but is opened during machine printing times so that the control relay cannot be energized by current flowing through this path. In this manner, the problem of toner banding is overcome.
  • Apparatus for use in detecting misfed sheets in an automatic xerographic reproducing machine and for inactivating the machine in response to detected misfed sheets including,
  • control means adapted to pennit the o era on of the machine when said control means is in a first state and to shut down the machine when said control means is in a second state
  • threshold switching means coupled with said control means to control current flow through said control means
  • a light source positioned in the xerographic reproducing machine
  • photocell means electrically coupled with said threshold switching means and positioned in the xerographic reproducing machine to receive light from said light source
  • capacitor means coupled to said threshold switching means and said photocell means to prohibit the flow of current to said threshold switching means during normal operatons of the reproducing machine so that the control means may be held in its first state
  • the capacitor means also being adapted, when the resistance of said photocell means is rapidly decreased by the sensing of a misfed sheet in the xerographic reproducing machine to cause a flow of current to said threshold switching means whereby said threshold switching means conducts current to render said control means in its second state to thereby inactivate the xerographic reproducing machine.
  • a circuit for use in detecting mist'ed sheets in an automatic machine including adapted, when said photocell means changes resistance through the detection of a misfed sheet, to cause a circuit imbalance and flow current through said capacitor whereby said threshold switching means is energized to reverse the state of said control means,
  • transistor means in series with said control means and said threshold switching means, said transistor means being in a nonconducting state prior to activation of the circuit and means to energize said transistor means a predetermined time after the energization of the circuit to thereafter permit current flow through said control means.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Control Or Security For Electrophotography (AREA)
  • Controlling Sheets Or Webs (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
US3593065D 1969-07-14 1969-07-14 Sheet detection apparatus Expired - Lifetime US3593065A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US84151669A 1969-07-14 1969-07-14

Publications (1)

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US3593065A true US3593065A (en) 1971-07-13

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US3593065D Expired - Lifetime US3593065A (en) 1969-07-14 1969-07-14 Sheet detection apparatus

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US (1) US3593065A (en))
CA (1) CA923544A (en))
CS (1) CS151559B2 (en))
DE (1) DE2034965C3 (en))
GB (1) GB1322794A (en))
HU (1) HU168207B (en))
SU (1) SU365085A3 (en))

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3676691A (en) * 1970-10-05 1972-07-11 Copystatics Mfg Corp Automatic shut-off circuit for copying machine
US3878398A (en) * 1973-09-13 1975-04-15 Itek Corp System for detecting given changes in monitored light intensity
US4237466A (en) * 1979-05-07 1980-12-02 The Mead Corporation Paper transport system for an ink jet printer
US4753430A (en) * 1987-05-29 1988-06-28 Am International Incorporated Method and apparatus for controlling a collator
US4757984A (en) * 1987-05-29 1988-07-19 Am International Incorporated Method and apparatus for controlling a collator
US4925174A (en) * 1987-05-29 1990-05-15 Am International Incorporated Method and apparatus for controlling a collator
US4936562A (en) * 1987-05-29 1990-06-26 Am International Incorporated Method and apparatus for controlling a collator

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4332462A (en) * 1979-05-25 1982-06-01 Canon Kabushiki Kaisha Feed control device

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2859960A (en) * 1956-06-07 1958-11-11 Purdy Frederick A Electrical control responsive to successive circuit interruptions
US3360652A (en) * 1964-10-14 1967-12-26 Xerox Corp Fail safe photoelectric sheet sensing machine control circuit
US3393604A (en) * 1965-08-13 1968-07-23 Gen Time Corp Condition responsive process timer

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2859960A (en) * 1956-06-07 1958-11-11 Purdy Frederick A Electrical control responsive to successive circuit interruptions
US3360652A (en) * 1964-10-14 1967-12-26 Xerox Corp Fail safe photoelectric sheet sensing machine control circuit
US3393604A (en) * 1965-08-13 1968-07-23 Gen Time Corp Condition responsive process timer

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3676691A (en) * 1970-10-05 1972-07-11 Copystatics Mfg Corp Automatic shut-off circuit for copying machine
US3878398A (en) * 1973-09-13 1975-04-15 Itek Corp System for detecting given changes in monitored light intensity
US4237466A (en) * 1979-05-07 1980-12-02 The Mead Corporation Paper transport system for an ink jet printer
US4753430A (en) * 1987-05-29 1988-06-28 Am International Incorporated Method and apparatus for controlling a collator
US4757984A (en) * 1987-05-29 1988-07-19 Am International Incorporated Method and apparatus for controlling a collator
US4925174A (en) * 1987-05-29 1990-05-15 Am International Incorporated Method and apparatus for controlling a collator
US4936562A (en) * 1987-05-29 1990-06-26 Am International Incorporated Method and apparatus for controlling a collator

Also Published As

Publication number Publication date
GB1322794A (en) 1973-07-11
HU168207B (en)) 1976-03-28
DE2034965B2 (de) 1979-07-26
DE2034965C3 (de) 1980-03-27
SU365085A3 (en)) 1972-12-28
DE2034965A1 (de) 1971-02-04
CA923544A (en) 1973-03-27
CS151559B2 (en)) 1973-10-19

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