CA1052634A - Method and apparatus for developing an electrostatic latent image on an electrophotographic film - Google Patents
Method and apparatus for developing an electrostatic latent image on an electrophotographic filmInfo
- Publication number
- CA1052634A CA1052634A CA223,990A CA223990A CA1052634A CA 1052634 A CA1052634 A CA 1052634A CA 223990 A CA223990 A CA 223990A CA 1052634 A CA1052634 A CA 1052634A
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- chamber
- toner
- film
- toner particles
- developing
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Abstract
ABSTRACT OF THE DISCLOSURE
Disclosed is a method and apparatus for developing an electrostatic latent image on an electrophotographic film through use of a special developing chamber forming a passageway through which electrostatically charged toner particles are conducted to contact the film. The chamber has an opening bordered by a mask against which the film is placed to form a seal, an inlet through which toner particles and drying air enter the chamber, and an outlet through which toner particles and drying air leave the chamber. The apparatus further includes supply means for pro-viding toner particles to the chamber, toner flow-control means for permitting a predetermined quantity of toner particles to flow through the developing chamber at predetermined times, air supply means for supplying drying air to the inlet of the chamber, and vacuum means connected to the outlet of the chamber for drawing the toner particles and air through the chamber. The vacuum means creates a sub-atmospheric pressure within the chamber to prevent leakage of toner particles from the chamber around the film.
Disclosed is a method and apparatus for developing an electrostatic latent image on an electrophotographic film through use of a special developing chamber forming a passageway through which electrostatically charged toner particles are conducted to contact the film. The chamber has an opening bordered by a mask against which the film is placed to form a seal, an inlet through which toner particles and drying air enter the chamber, and an outlet through which toner particles and drying air leave the chamber. The apparatus further includes supply means for pro-viding toner particles to the chamber, toner flow-control means for permitting a predetermined quantity of toner particles to flow through the developing chamber at predetermined times, air supply means for supplying drying air to the inlet of the chamber, and vacuum means connected to the outlet of the chamber for drawing the toner particles and air through the chamber. The vacuum means creates a sub-atmospheric pressure within the chamber to prevent leakage of toner particles from the chamber around the film.
Description
~ * *
The present invention is described, but not claimed in commonly assigned co-pending Canadian Application 223,992.
The present invention relates generally to electrophoto-graphy and more particularly to improvements in developing an image on an electrophotographic element.
In electrophotography, it is common to apply a uniform electrostatic charge to the surface of a photoconductive layer.
The charge is then selectively dissipated in a pattern by expo-sing the surface to a light image. The resulting pattern of charges produces an electrostatic latent image on the photo-30 conductive layer, which is rendered visible by applying to it --1-- .
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5~34 electrostatically charged toner particles which adhere to the sur-face o~ the photoconductive layer by electro~tatic attraction. A
permanent visible image can be obtained by using toner particles which can be heat ~used to the photoconductive layer and subject-S ing them to a heat application step.
In the conventional developing method using liquid developer, which is a liquid carrier for finely divided electro-static particle~ such as carbon particles, the image exposed film is dipped in the liquid developer to produce a visible image corresponding to the latent image thereon. While this method o developing is satis~actory for some types of system~ and film, it is not satisfactory for the type of system in which imaging and developing takes place automatieally within a single apparatus.
In that mlcrophotographie eopying maehine, data from sueeessive aocuments i~ sequentially recorded on individual frames of a multi-~rame miGrofiehe. Because it i8 desirable to image and develop eaeh frame quickly beforo ropeating the proeess for the next frame, the proeess for developing the images must be one which ean be carried out quiekly and eonveniently to a mierofiehe fixed within a holder within tho reproduction apparatus. Additionally, the developing system must bo eapable of quickly applying the eorreet amount of developer, or toner partieles ~whieh are preferably ~u~pended in a liquid carrier) to the imaged area of the film and removing the toner particles from the film without permitting ~5 leakage of the toner partieles into the interior of the reprodue-tion apparatus. The system must also be eapa~le of quickly evap-orating any of ~he toner carrier liquid remaining on the film to immo~ilize the toner partieles remaining on the film and prevent ~mearing of the toned imaged.
~herefore, it is an object of the invention to provide ~5~3*
a method and appar us for quickly applying a mea~ured ~uantity of liquid toner to an imaged area of a film without permitting leak-age of the liquid toner beyond the imaged area of the film. A
further object of the invention i~ to quickly evaporate residual S toner carrier liquid remaining on the film after toning. And a further object of the invention is to provide a method and apparatus for accomplishing the above ob~ects while the film is held in a carrier within a microphotographic reproduction apparatus.
According to one aspect o~ the invention there is pro-vided an apparatus for developing an electrostatic latent imageon an electrophotographic film comprising: a developing chamber forming a passageway through which electrostatically charged toner particles are conducted to contact the film, the chamber having an opening bordered by a mask agains~ which the film is placed to lS form a seal, an inlet through which toner partiales and air enter the chamber, and an outlet through which toner particles and air leave the chamber; supply means for providing toner particles to be passed through the chamber; toner flow control means for permitting a predetermined quantity of toner particles to flow through the developing chamber at predetermined times; air supply means for - supplying drying air to the inlet of the chamber; and vacuum means connected to the outlet of the chamber for drawing the toner par-ticles and the air through the chamber, the vacuum means creating sub-atmospheric pressure within the chamber to prevent leakage of toner particles from the chamber around the film.
According to another aspect of the invention there is provided a method of developing an electrostatic latent image on an electrophotographic film comprising the steps of: positioning the film against an opening in a developing chamber; drawing toner particles through the chamber with a vacuum source which creates a .:
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lC~S'~;34 sub-atmospheric pressure within the chamber to prevent leakage of the toner particles from the chamber around the film.
In its preferred form, the invention includes control means operably connected to the vacuum means for providing a high vacuum level and a low vacuum level, the low vacuum level being used to draw the toner particles through the developing chamber, and the high vacuum level being used to draw the drying air through the chamber. The preferred form of the apparatus further includes a development electrode forming one wall of the passageway for con-ducting the toner particles through the developing cham~er in a position close to the opening through which the toner particles contacts the film.
The invention will now be described by way of example with reference to the accompanying drawings in which:
Fig. 1 i8 a diagrammatic view of the developing apparatus of the invention.
Fig 2 is an enlarged cross-sectional view of the developing chamber illustrated in Fig. 1, taken along lines 2-2.
Fig. 3 is a diagrammatic view of the pre~erred embodiment of the developing apparatus of the invention, and Fig. 4 is an enlarged _ross-sectional view of the developing chamber illustrated in Flg. 3.
Referring to Fig. 1, the toner supply network in accor-dance with one embodiment of the present invention i8 in the form of a closed systein and include~ a suitable toner reservoir 11 con-taining a su~ply of liquid toner 30. Liquid toner 30 may be of any suitak~e type well known in the art, but preferably consist-ing of ~lack colored electro3copic particles colloidally suspended in a iiquid vehicle. A four-part connector block communicates in~eriorly of the reser~oir 11 and support~ a toner pickup tube 14 which is connectea to a toner pump 13.
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~(~5'~34 The pump 13 supplies toner via line 15 to a pressure relief or bypass valve 23 having first and second outlet ports communi-cating respectively with reservoir 11 via tube 24, and with the processing assembly via tube 16. Tube 16 feeds first solenoid valve 19 through a suitable filter element 25. Solenoid valve 19 is vented to the atmosphere through tube 21 and has its out-~
let port connected to the inlet of a second solenoid valve 20 by a short length of tube 16. Tube 16 between the first and second solenoid valves 19 and 20 has an internal volume corresponding to the amount of toner necessary to effectuate the development of a single frame on a microfiche.
Solenoid valve 20 communicates with the fluid reservoir 11 by conduit 22 and has its outlet port coupled by a fluid line 17 to the inlet port 31 (Fig. 2) of the developing chamber 10. Out-~.~
let port 32 of the toner module is connected via conduit 18 to a toner vacuum separator 26 which separates unused toner and con-ducts it back to the reservoir 11 by gravity. A vacuum line 28 is also connected to the toner vacuum separator 26 and applies a negative pressure to the system through a two stage regulator 29.
; 20 Regulator 29 may be of any suitable construction known to those skilled in the art and is electrically controlled to selectively provide low and high vacuum levels to the toner vacuum separator . ~
~ 26. A vacuum pump 12 operably communicates with the two-stage . ~
-~ regulator to complete the system.
Fig. 2 illustrates a microfiche 37 in position against the developing chamber 10 with the photoconductive surface of the micxofiche facing the developing chamber 10. The developing ~, I
chamber 10 includes an inlet 31, a passageway 33, and an outlet 32. Within the passageway 33 is an opening 34 formed by rect-angularly shaped flange or mask means 35. The frame of the ., ,: . . .
~o5,~f~34 microfiche 37 to be toned (or developed) is placed against the opening 34 which is the same size as the frame, whereby toner particles flowing through the passageway 33 will contact that frame of the microfiche 37. Forming one wall of the chamber passageway 33 opposite the opening 34 is a development electrode 36, provided by a thin plate of electrically conductive material such as copper. The development electrode 36 is beneficial in toning the image on the frame in a manner well known in the art.
The development electrode 36 is preferably positioned close to the opening 34 to create a strong electric field between the electrode 36 and microfiche 37 and to force liquid toner flowing through the passageway 33 against the microfiche 37.
~ The developing chamber 10 is placed against the surface of ; the microfiche 37, and solenoid valve 19 of the toner supply circuit is opened, causing toner fluid to be pumped from ~ reservoir 11 through solenoid valve 19 and tube 16 to the closed solenoid valve 20. Fluid thus circulates through tube 16 and solenoid valves 19 and 20 and is returned through tube 22 to the : reservoir 30. In this manner, the portion of tube 16 between - 20 solenoid valves 19 and 20 is filled with toner fluid in the precise amount necessary for effectuating the development of the latent image on a single frame of the microfiche 37. Solenoid valve 19 is thereafter closed, opening vent tube 21, and ~ solenoid valve 20 is simultaneously opened, closing off conduit ~ 25 22, whereby the metered amount of toner fluid contained within ~ tube 16 is conducted through tube 17 to the inlet port 31 of the '~:
developing chamber 10. Toner fluid is drawn through the develop-ing chamber 10 by the vacuum at a low vacuu~evel setting by proper actuation of the two-stage-regulator 29.
The two-stag~ regulator 29 is then switched to its high ; -6-.
105'~634 vacuum mode, thereby precluding the leakage of toner fluid from the developing chamber 10 around the microfiche 37 and pulling drying air through vent tube 21 to effect a substantial drying of the developed microimage.
In a preferred embo~diment, the drying step also includes separating the microfiche 37 slightly from the mask means 35 to draw additional drying air into the developing chamber 10 from around the frame being developed for more effective drying. The use of vacuum creates an effective seal between the chamber 10 and the microiche 37 for purposes of preventing toner fluid from leaking out.
Referring to Figs. 3 and 4, the preferred embodiment of the invention is disclosed (with the indicating numerals which are identical to indicating numerals in Figs. 1 and 2 representing ; 15 system components which are identical to the system components , .
in Figs. 1 and 2). The preferred system includes toner reservoir 11 containing liquid toner '30, and from which toner fluid is drawn through conduit 14, through solenoid valve 38 and line 17 into the inlet 41 of developing chamber 40 by way of orifice needle 42. The liquid toner 30 is drawn through chamber passageway 33, through the developing chamber outlet 32, and into the toner vacuum separator 26 by way of conduit 18. Tonex vacuum separator 26 is a conventional liquid/gas separator and is connected by way of conduit 28 to vacuum pump 12 through two-:~ , stage regulator 29. Leading from the bottom of toner vacuum 1 separator 26 is toner return line 27, which conducts the toner ;' .
'J, ~ fluid back into the toner reservoir 11.
Drying air is conducted through solenoid valve 44 and con-duit 39 into developing chamber inlet 41. Developing chamber 40 includes an opening 34 communicating with the chamber passageway 105;~34 33 and formed by rectangularly shaped mask means 35. The frame of the microfiche 37 to be toned is placed against opening 34 to form a seal with mask means 35. Of course, the photoconductive layer of the microfiche 37 is faced lnward into the developing chamber 40. One wall of the chamber passageway 33 is formed by development electrode 36 positioned opposite the opening 34 and very close to the opening to create a strong electric field be-tween the electrode 36 and the microfiche 37 and to f~rce the liquid toner flowing through the chamber passageway 33 against the microfiche 37. The development electrode can be ~rovided by a very thin electrically conductive plate, and functions in a manner well known to those skilled in the art. Covering develop-ment electrode 36 is a finely woven fabric 43, such as silk, which is saturated by the toner fluid during the toning process.
The fabric 43 retains enough of the liquid carrier to remain moist during the drying step which will be.described subsequent-; ly. In this way, permanent deposition of toner particles upon - the development electrode 36 is prevented. The fabric 43 also can cover other portions of the passageway 33 walls to prevent ~- 20 permanent deposition of toner on them.
- The operation of the preferred form of the invention will now be described. As soon as an imaged frame of a microfiche 37 is placed against opening 34 in the developing chamber 40, the vacuum pump 12 applies a low-level vacuum, controlled by a two-stage regulator 29, through conduit 28, toner vacuum separator 26, conduit 18, developing chamber 40, conduit 17, solenoid valve 38, and conduit 14 to draw toner particles 30 through the :
chamber passageway 33 of the developing chamber 40. During this operation the solenoid valve 38 is opened, and the solenoid valve 43 is closed to prevent air from being pulled through the conduit 16)5'~;34 39. The needle orifice 42 is sized to meter the liquid toner 30 through at a predetermined rate. A timer closes solenoid valve 38 when the desired quantity of toner fluid 30 has been pulled through the developing chamber 40. ~Immediately upon closing of solenoid valve 38, solenoid valve 43 opens, permitting drying air to be drawn through conduit 39 into the chamber passageway 33. At the same time the two-stage regulator 29 is switched to the high-vacuum level stage to draw air through at a fast rate.
The air being drawn through at a fast rate assures quick evapora-; 10 tion of residual toner carrier liqui~ remaining on the microfiche 37, as well as drawing air in from any opening which might exist - between the microfiche 37 and the mask means 35, thereby prevent-- ing toner fluid from flowing along the microfiche beyond the frame being toned or into the interior of the reproduction apparatus. Pulling the toner liquid 30 through the solenoid by ,vacuum means also creates a pressure within the passageway chamber 33 that is lower than the pressure of the outside air and draws air through any opening inadvertently formed between mask means 35 and the microfiche 37, thereby forming an air seal to prevent the liquid toner from leaking from the developing chamber 40.
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The present invention is described, but not claimed in commonly assigned co-pending Canadian Application 223,992.
The present invention relates generally to electrophoto-graphy and more particularly to improvements in developing an image on an electrophotographic element.
In electrophotography, it is common to apply a uniform electrostatic charge to the surface of a photoconductive layer.
The charge is then selectively dissipated in a pattern by expo-sing the surface to a light image. The resulting pattern of charges produces an electrostatic latent image on the photo-30 conductive layer, which is rendered visible by applying to it --1-- .
~.:
. . : : - :
~ . - .; .- .. . .: , ~: - - , . : , - . ...
,: ~ . . : . . -~, . . .. ... . . ..
5~34 electrostatically charged toner particles which adhere to the sur-face o~ the photoconductive layer by electro~tatic attraction. A
permanent visible image can be obtained by using toner particles which can be heat ~used to the photoconductive layer and subject-S ing them to a heat application step.
In the conventional developing method using liquid developer, which is a liquid carrier for finely divided electro-static particle~ such as carbon particles, the image exposed film is dipped in the liquid developer to produce a visible image corresponding to the latent image thereon. While this method o developing is satis~actory for some types of system~ and film, it is not satisfactory for the type of system in which imaging and developing takes place automatieally within a single apparatus.
In that mlcrophotographie eopying maehine, data from sueeessive aocuments i~ sequentially recorded on individual frames of a multi-~rame miGrofiehe. Because it i8 desirable to image and develop eaeh frame quickly beforo ropeating the proeess for the next frame, the proeess for developing the images must be one which ean be carried out quiekly and eonveniently to a mierofiehe fixed within a holder within tho reproduction apparatus. Additionally, the developing system must bo eapable of quickly applying the eorreet amount of developer, or toner partieles ~whieh are preferably ~u~pended in a liquid carrier) to the imaged area of the film and removing the toner particles from the film without permitting ~5 leakage of the toner partieles into the interior of the reprodue-tion apparatus. The system must also be eapa~le of quickly evap-orating any of ~he toner carrier liquid remaining on the film to immo~ilize the toner partieles remaining on the film and prevent ~mearing of the toned imaged.
~herefore, it is an object of the invention to provide ~5~3*
a method and appar us for quickly applying a mea~ured ~uantity of liquid toner to an imaged area of a film without permitting leak-age of the liquid toner beyond the imaged area of the film. A
further object of the invention i~ to quickly evaporate residual S toner carrier liquid remaining on the film after toning. And a further object of the invention is to provide a method and apparatus for accomplishing the above ob~ects while the film is held in a carrier within a microphotographic reproduction apparatus.
According to one aspect o~ the invention there is pro-vided an apparatus for developing an electrostatic latent imageon an electrophotographic film comprising: a developing chamber forming a passageway through which electrostatically charged toner particles are conducted to contact the film, the chamber having an opening bordered by a mask agains~ which the film is placed to lS form a seal, an inlet through which toner partiales and air enter the chamber, and an outlet through which toner particles and air leave the chamber; supply means for providing toner particles to be passed through the chamber; toner flow control means for permitting a predetermined quantity of toner particles to flow through the developing chamber at predetermined times; air supply means for - supplying drying air to the inlet of the chamber; and vacuum means connected to the outlet of the chamber for drawing the toner par-ticles and the air through the chamber, the vacuum means creating sub-atmospheric pressure within the chamber to prevent leakage of toner particles from the chamber around the film.
According to another aspect of the invention there is provided a method of developing an electrostatic latent image on an electrophotographic film comprising the steps of: positioning the film against an opening in a developing chamber; drawing toner particles through the chamber with a vacuum source which creates a .:
....
lC~S'~;34 sub-atmospheric pressure within the chamber to prevent leakage of the toner particles from the chamber around the film.
In its preferred form, the invention includes control means operably connected to the vacuum means for providing a high vacuum level and a low vacuum level, the low vacuum level being used to draw the toner particles through the developing chamber, and the high vacuum level being used to draw the drying air through the chamber. The preferred form of the apparatus further includes a development electrode forming one wall of the passageway for con-ducting the toner particles through the developing cham~er in a position close to the opening through which the toner particles contacts the film.
The invention will now be described by way of example with reference to the accompanying drawings in which:
Fig. 1 i8 a diagrammatic view of the developing apparatus of the invention.
Fig 2 is an enlarged cross-sectional view of the developing chamber illustrated in Fig. 1, taken along lines 2-2.
Fig. 3 is a diagrammatic view of the pre~erred embodiment of the developing apparatus of the invention, and Fig. 4 is an enlarged _ross-sectional view of the developing chamber illustrated in Flg. 3.
Referring to Fig. 1, the toner supply network in accor-dance with one embodiment of the present invention i8 in the form of a closed systein and include~ a suitable toner reservoir 11 con-taining a su~ply of liquid toner 30. Liquid toner 30 may be of any suitak~e type well known in the art, but preferably consist-ing of ~lack colored electro3copic particles colloidally suspended in a iiquid vehicle. A four-part connector block communicates in~eriorly of the reser~oir 11 and support~ a toner pickup tube 14 which is connectea to a toner pump 13.
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~(~5'~34 The pump 13 supplies toner via line 15 to a pressure relief or bypass valve 23 having first and second outlet ports communi-cating respectively with reservoir 11 via tube 24, and with the processing assembly via tube 16. Tube 16 feeds first solenoid valve 19 through a suitable filter element 25. Solenoid valve 19 is vented to the atmosphere through tube 21 and has its out-~
let port connected to the inlet of a second solenoid valve 20 by a short length of tube 16. Tube 16 between the first and second solenoid valves 19 and 20 has an internal volume corresponding to the amount of toner necessary to effectuate the development of a single frame on a microfiche.
Solenoid valve 20 communicates with the fluid reservoir 11 by conduit 22 and has its outlet port coupled by a fluid line 17 to the inlet port 31 (Fig. 2) of the developing chamber 10. Out-~.~
let port 32 of the toner module is connected via conduit 18 to a toner vacuum separator 26 which separates unused toner and con-ducts it back to the reservoir 11 by gravity. A vacuum line 28 is also connected to the toner vacuum separator 26 and applies a negative pressure to the system through a two stage regulator 29.
; 20 Regulator 29 may be of any suitable construction known to those skilled in the art and is electrically controlled to selectively provide low and high vacuum levels to the toner vacuum separator . ~
~ 26. A vacuum pump 12 operably communicates with the two-stage . ~
-~ regulator to complete the system.
Fig. 2 illustrates a microfiche 37 in position against the developing chamber 10 with the photoconductive surface of the micxofiche facing the developing chamber 10. The developing ~, I
chamber 10 includes an inlet 31, a passageway 33, and an outlet 32. Within the passageway 33 is an opening 34 formed by rect-angularly shaped flange or mask means 35. The frame of the ., ,: . . .
~o5,~f~34 microfiche 37 to be toned (or developed) is placed against the opening 34 which is the same size as the frame, whereby toner particles flowing through the passageway 33 will contact that frame of the microfiche 37. Forming one wall of the chamber passageway 33 opposite the opening 34 is a development electrode 36, provided by a thin plate of electrically conductive material such as copper. The development electrode 36 is beneficial in toning the image on the frame in a manner well known in the art.
The development electrode 36 is preferably positioned close to the opening 34 to create a strong electric field between the electrode 36 and microfiche 37 and to force liquid toner flowing through the passageway 33 against the microfiche 37.
~ The developing chamber 10 is placed against the surface of ; the microfiche 37, and solenoid valve 19 of the toner supply circuit is opened, causing toner fluid to be pumped from ~ reservoir 11 through solenoid valve 19 and tube 16 to the closed solenoid valve 20. Fluid thus circulates through tube 16 and solenoid valves 19 and 20 and is returned through tube 22 to the : reservoir 30. In this manner, the portion of tube 16 between - 20 solenoid valves 19 and 20 is filled with toner fluid in the precise amount necessary for effectuating the development of the latent image on a single frame of the microfiche 37. Solenoid valve 19 is thereafter closed, opening vent tube 21, and ~ solenoid valve 20 is simultaneously opened, closing off conduit ~ 25 22, whereby the metered amount of toner fluid contained within ~ tube 16 is conducted through tube 17 to the inlet port 31 of the '~:
developing chamber 10. Toner fluid is drawn through the develop-ing chamber 10 by the vacuum at a low vacuu~evel setting by proper actuation of the two-stage-regulator 29.
The two-stag~ regulator 29 is then switched to its high ; -6-.
105'~634 vacuum mode, thereby precluding the leakage of toner fluid from the developing chamber 10 around the microfiche 37 and pulling drying air through vent tube 21 to effect a substantial drying of the developed microimage.
In a preferred embo~diment, the drying step also includes separating the microfiche 37 slightly from the mask means 35 to draw additional drying air into the developing chamber 10 from around the frame being developed for more effective drying. The use of vacuum creates an effective seal between the chamber 10 and the microiche 37 for purposes of preventing toner fluid from leaking out.
Referring to Figs. 3 and 4, the preferred embodiment of the invention is disclosed (with the indicating numerals which are identical to indicating numerals in Figs. 1 and 2 representing ; 15 system components which are identical to the system components , .
in Figs. 1 and 2). The preferred system includes toner reservoir 11 containing liquid toner '30, and from which toner fluid is drawn through conduit 14, through solenoid valve 38 and line 17 into the inlet 41 of developing chamber 40 by way of orifice needle 42. The liquid toner 30 is drawn through chamber passageway 33, through the developing chamber outlet 32, and into the toner vacuum separator 26 by way of conduit 18. Tonex vacuum separator 26 is a conventional liquid/gas separator and is connected by way of conduit 28 to vacuum pump 12 through two-:~ , stage regulator 29. Leading from the bottom of toner vacuum 1 separator 26 is toner return line 27, which conducts the toner ;' .
'J, ~ fluid back into the toner reservoir 11.
Drying air is conducted through solenoid valve 44 and con-duit 39 into developing chamber inlet 41. Developing chamber 40 includes an opening 34 communicating with the chamber passageway 105;~34 33 and formed by rectangularly shaped mask means 35. The frame of the microfiche 37 to be toned is placed against opening 34 to form a seal with mask means 35. Of course, the photoconductive layer of the microfiche 37 is faced lnward into the developing chamber 40. One wall of the chamber passageway 33 is formed by development electrode 36 positioned opposite the opening 34 and very close to the opening to create a strong electric field be-tween the electrode 36 and the microfiche 37 and to f~rce the liquid toner flowing through the chamber passageway 33 against the microfiche 37. The development electrode can be ~rovided by a very thin electrically conductive plate, and functions in a manner well known to those skilled in the art. Covering develop-ment electrode 36 is a finely woven fabric 43, such as silk, which is saturated by the toner fluid during the toning process.
The fabric 43 retains enough of the liquid carrier to remain moist during the drying step which will be.described subsequent-; ly. In this way, permanent deposition of toner particles upon - the development electrode 36 is prevented. The fabric 43 also can cover other portions of the passageway 33 walls to prevent ~- 20 permanent deposition of toner on them.
- The operation of the preferred form of the invention will now be described. As soon as an imaged frame of a microfiche 37 is placed against opening 34 in the developing chamber 40, the vacuum pump 12 applies a low-level vacuum, controlled by a two-stage regulator 29, through conduit 28, toner vacuum separator 26, conduit 18, developing chamber 40, conduit 17, solenoid valve 38, and conduit 14 to draw toner particles 30 through the :
chamber passageway 33 of the developing chamber 40. During this operation the solenoid valve 38 is opened, and the solenoid valve 43 is closed to prevent air from being pulled through the conduit 16)5'~;34 39. The needle orifice 42 is sized to meter the liquid toner 30 through at a predetermined rate. A timer closes solenoid valve 38 when the desired quantity of toner fluid 30 has been pulled through the developing chamber 40. ~Immediately upon closing of solenoid valve 38, solenoid valve 43 opens, permitting drying air to be drawn through conduit 39 into the chamber passageway 33. At the same time the two-stage regulator 29 is switched to the high-vacuum level stage to draw air through at a fast rate.
The air being drawn through at a fast rate assures quick evapora-; 10 tion of residual toner carrier liqui~ remaining on the microfiche 37, as well as drawing air in from any opening which might exist - between the microfiche 37 and the mask means 35, thereby prevent-- ing toner fluid from flowing along the microfiche beyond the frame being toned or into the interior of the reproduction apparatus. Pulling the toner liquid 30 through the solenoid by ,vacuum means also creates a pressure within the passageway chamber 33 that is lower than the pressure of the outside air and draws air through any opening inadvertently formed between mask means 35 and the microfiche 37, thereby forming an air seal to prevent the liquid toner from leaking from the developing chamber 40.
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., _9_ '
Claims (8)
1. An apparatus for developing an electrostatic latent image on an electrophotographic film comprising:
a developing chamber forming a passageway through which electrostatically charged toner particles are conducted to contact the film, the chamber having an opening bordered by a mask against which the film is placed to form a seal, an inlet through which toner particles and air enter the chamber, and an outlet through which toner particles and air leave the chamber;
supply means for providing toner particles to be passed through the chamber;
toner flow control means for permitting a predetermined quantity of toner particles to flow through the developing chamber at predetermined times;
air supply means for supplying drying air to the inlet of the chamber; and vacuum means connected to the outlet of the chamber for drawing the toner particles and the air through the chamber, the vacuum means creating sub-atmospheric pressure within the chamber to prevent leakage of toner particles from the chamber around the film.
a developing chamber forming a passageway through which electrostatically charged toner particles are conducted to contact the film, the chamber having an opening bordered by a mask against which the film is placed to form a seal, an inlet through which toner particles and air enter the chamber, and an outlet through which toner particles and air leave the chamber;
supply means for providing toner particles to be passed through the chamber;
toner flow control means for permitting a predetermined quantity of toner particles to flow through the developing chamber at predetermined times;
air supply means for supplying drying air to the inlet of the chamber; and vacuum means connected to the outlet of the chamber for drawing the toner particles and the air through the chamber, the vacuum means creating sub-atmospheric pressure within the chamber to prevent leakage of toner particles from the chamber around the film.
2. Apparatus according to claim 1, further including control means attached to the vacuum means for providing a high vacuum and a low vacuum, the low vacuum being used to draw the toner particles through the developing chamber, and the high vacuum being used to draw drying air through the chamber.
3. Apparatus according to claim 1, wherein the developing chamber includes a development electrode forming one wall of the passageway for conducting the toner particles through the developing chamber and being positioned close to the opening through which the toner particles contact the film.
4. Apparatus according to claim 1, including separating means for separating the toner and the air conducted through the developing chamber and return conduit means for returning the separated toner to the toner supply means for recirculation.
5. Apparatus according to claim 1, wherein the toner flow control means is provided by, a pair of solenoid operated valves through which the toner particles pass in route from the toner supply means to the developing chamber;
a predetermined length of conduit for conducting the toner particles from the first solenoid to the second solenoid; and means for opening and closing each of the solenoids alter-natingly at predetermined times to permit a predetermined quantity of the toner particles to be stored in the predetermined length of conduit between the solenoid valves for passage to the devel-oping chamber at a predetermined time.
a predetermined length of conduit for conducting the toner particles from the first solenoid to the second solenoid; and means for opening and closing each of the solenoids alter-natingly at predetermined times to permit a predetermined quantity of the toner particles to be stored in the predetermined length of conduit between the solenoid valves for passage to the devel-oping chamber at a predetermined time.
6. Method of developing an electrostatic latent image on a portion of an electrophotographic film, comprising the steps of:
A. positioning the film against a mask bordering an opening in a developing chamber with the mask bordering the portion of the film being developed and forming a seal against fluid flow;
B. drawing toner liquid through the chamber and into contact with the portion of the film with a vacuum source which creates a sub-atmospheric pressure within the chamber to prevent leakage of the toner liquid from the mask beyond the portion of the film being developed; and C. after step B, drawing drying air through the chamber with a vacuum source which creates a sub-atmospheric pressure within the chamber to prevent toner liquid from leaking past the mask beyond the portion of the film during drying.
A. positioning the film against a mask bordering an opening in a developing chamber with the mask bordering the portion of the film being developed and forming a seal against fluid flow;
B. drawing toner liquid through the chamber and into contact with the portion of the film with a vacuum source which creates a sub-atmospheric pressure within the chamber to prevent leakage of the toner liquid from the mask beyond the portion of the film being developed; and C. after step B, drawing drying air through the chamber with a vacuum source which creates a sub-atmospheric pressure within the chamber to prevent toner liquid from leaking past the mask beyond the portion of the film during drying.
7. Method according to claim 6, wherein the toner liquid is drawn through the chamber at a low vacuum level in step B and the drying air is drawn through the chamber at a high vacuum level in step C.
8. Method according to claim 6, wherein step C further includes separating the film slightly from the developing chamber and drawing additional drying air into the chamber from around the film through the opening.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US459195A US3916828A (en) | 1973-04-09 | 1974-04-08 | Apparatus for developing an electrostatic latent image on an electrophotographic film |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1052634A true CA1052634A (en) | 1979-04-17 |
Family
ID=23823789
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA223,990A Expired CA1052634A (en) | 1974-04-08 | 1975-04-07 | Method and apparatus for developing an electrostatic latent image on an electrophotographic film |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1052634A (en) |
-
1975
- 1975-04-07 CA CA223,990A patent/CA1052634A/en not_active Expired
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