CA1116223A - Multiple applicator roller toner station, multiple roller dryer station for page printing system - Google Patents
Multiple applicator roller toner station, multiple roller dryer station for page printing systemInfo
- Publication number
- CA1116223A CA1116223A CA305,630A CA305630A CA1116223A CA 1116223 A CA1116223 A CA 1116223A CA 305630 A CA305630 A CA 305630A CA 1116223 A CA1116223 A CA 1116223A
- Authority
- CA
- Canada
- Prior art keywords
- recording medium
- liquid
- roller
- toning
- printing system
- Prior art date
- 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
Links
Classifications
-
- 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
- G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
- G03G15/10—Apparatus for electrographic processes using a charge pattern for developing using a liquid developer
- G03G15/101—Apparatus for electrographic processes using a charge pattern for developing using a liquid developer for wetting the recording material
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S101/00—Printing
- Y10S101/37—Printing employing electrostatic force
Abstract
ABSTRACT
A method and apparatus for developing an electrographic-latent image on a pre-treated paper medium, by utilizing multiple rollers partially dipped in a liquid carrier.
A pre-treated paper medium comprised of a conductively treated paper base supporting a plastic dielectric coating on each of its sides, is positioned of a plurality of styli-which receive variable information in the form of electronic signals from a data processor, or other equipment and by selectively changing the plurality of styli generating a latent electrographic image of alphanumeric characters or paper which is retained by the coating.
The latent image is developed, i.e. made visible, by subjecting the paper medium to charged toning particles sus-pended in a liquid toning carrier. Multiple rollers, one each at predetermined locations, are partially submerged in a liquid toning carrier and pick up sufficient toning so as to form a meniscus between the upper portions of each roller and the paper medium. The image is then fixed i.e. made permanent by vaporizing the liquid carrier with heat.
A method and apparatus for developing an electrographic-latent image on a pre-treated paper medium, by utilizing multiple rollers partially dipped in a liquid carrier.
A pre-treated paper medium comprised of a conductively treated paper base supporting a plastic dielectric coating on each of its sides, is positioned of a plurality of styli-which receive variable information in the form of electronic signals from a data processor, or other equipment and by selectively changing the plurality of styli generating a latent electrographic image of alphanumeric characters or paper which is retained by the coating.
The latent image is developed, i.e. made visible, by subjecting the paper medium to charged toning particles sus-pended in a liquid toning carrier. Multiple rollers, one each at predetermined locations, are partially submerged in a liquid toning carrier and pick up sufficient toning so as to form a meniscus between the upper portions of each roller and the paper medium. The image is then fixed i.e. made permanent by vaporizing the liquid carrier with heat.
Description
RELAT~D ARTICLES AND PATENTS
1. "A Two-Sided Non-Impact Printing System", by R.F. ~orelli and K.M. Lakhani, U.S. Patent No. 4,165,686 issued August 28, 1979 and assigned to the same assignee as the instant application.
1. "A Two-Sided Non-Impact Printing System", by R.F. ~orelli and K.M. Lakhani, U.S. Patent No. 4,165,686 issued August 28, 1979 and assigned to the same assignee as the instant application.
2. '`Two-Side Multi Roller Toner Applicator Station for Electrographic Non-Impact Printer", by K.M. Lakhani, U.S. Patent No. 4,161,141 issued July 17, 1979 and assigned to the same assignee as the instant application.
3. "A Non-Impact Page Printing System", by R.F. Borelli, R.B. Bayless and E.R. Truax, published in the ~Ioneywell Computer Journal, Volume 8, No. 2, pp 67-80 in 1974.
4. "A Non-Impact Page Printing System", by R.F. Borelli, R.B. Bayless and E.R. Truax, published in Computer Magazine of the Institute of Electrical and Electronic Engineers, 5855 Haples Plaza, Long Beach, California, in September 1975. (Con-densed version of the article of Item 3). ~ i
5. U.S. Patent No. 3,687,107, issued 8/29/72, entitled "Printing System", and assigned to Honeywell Inc., the parent corporation of the instant assignee.
6. U.S. Patent No. 3,624,661, issued 11/30/71, entitled "Electrographic Printing System With Plural Staggered Electrode ; ~
Rows, and assigned to Honeywell Inc., the parent corporation ;
of the instant assignee. ~-
Rows, and assigned to Honeywell Inc., the parent corporation ;
of the instant assignee. ~-
7. U.S. Patent No. 3,958,251, issued 5/18/76, entitled -~
'`Electrographic Printing System Utilizing Multiple Of~set Styli", and assigned to Honeywell Information Systems Inc., the same assignee as the instant invention.
.
~ `~
'`Electrographic Printing System Utilizing Multiple Of~set Styli", and assigned to Honeywell Information Systems Inc., the same assignee as the instant invention.
.
~ `~
8. U.S. Patent No. 3,~12,78~, issued 5/28/74, entitled "Electrographic Forms Prin~ Station", and assigned to the same assignee as the instant invention.
9. U.S. Patent No~ 3,839,071, issued 10/1/74, entitled "Printing Method", and assigned to Hone~well Inc., the parent corporation of the instan~ assignee.
10. U.S. Patent No. 3,983,815, issued 10/5/76, entitled "Apparatus and Method for Printing on Plain Paper", and assigned to the same assignee as the ins~ant invention.
11. U.S. Patent No. 3,569,982~ issued 3/9/71, entitled "Electrostatic Printer with Scanning Dielectric Segment", ~nd assigned to Honeywell Inc., ~he parent corporation of the instant assignee.
12. U.S. Patent No. 3,52~,880, issued 7/28/70, entitlted "Processing Station with Document Handling and Aligning Means", and assigned to Honeywell Inc., tne parent corporation of the instant assignee.
BACKGROU~ID OF THE INVENTION
Field of the Invention l'he invention relates to an apparatus and method for printing upon a recording medium and more particularly to an apparatus for printing permanent images electrographically upon a paper medium at comparatively high speeds as is required in a computer print-out apparatus.
_ scription of the Prior Art It had long been reco~lized that computer peripherals, particularly computer print-out apparatus, were bottlenecks in the total performance of a computer system. The majority of hard copy output devices for computer systems were and still are comprised of printers which impact the paper medium with print hammers. The movement of such print hammers not only limits the speed of which read-out can be accomplished, but are noisy and difficult to maintain. In order to increase the speed, facili-tate maintenance, and still maintain print quality, a system was developed and is now being marketed commercially by Honeywell Information Systems Inc. utilizing electrographic techniques to accomplish non-impact printing. Such a printing system is disclosed in the related articles, applications and patents cited supra.
One main problem in the design of such an electrographic printing system arises at the toner station where the latent electrographic image is developed, i.e. made visible by subject-ing the paper medium to charged toning particles suspended in liquid toning carrier. The problem is to increase the variable print densities greater than a reflective print density of 0.85 yet not substantially increase the speed of the paper medium in excess of 30 inches per second. There~ are several methods of attack to this problem as will be discussed later.
Another major problem in developing the latent electro-graphic image is print contrast. This problem is at the opposite pole of the previous problem in that what is required is that the background density i.e. the density of the toner particles on the portion of the paper not selectively charged, should be kept as low as possible. Yet another problem related to the second problem is that of background staining of the paper as it passes through the transport. These and ather problems encountered do not offer trivial solutions in developing the latent electrographic image with clarity, high print density, low background density of toner particles, and minimization of background staining.
OBJECTS OF THE INV_TION
It is a primary object of the invention to provide an improved non-impact printing system.
It is another object of the invention to provide an improved method and apparatus for developing latent electro-graphlc lmages.
It is another abject of the invention to provide im-proved apparatus and a method for developing the latent electro-graphic images.
It is still a further object of the instant invention to increase the time that a latent electrographic image spends in the development zone.
Further object of the instant invention is to provide a multiple applicator roller toner station for developing latent electrographic images.
A further object of the invention is to provide multiple applicator multiple dryer roller station for an electrographic printing system.
S UMMARY OF THE INVENTION
The foregoing objects of the instant invention are achieved by a method and apparatus for developing latent electrographic images utilizing multiple toner applicator rollers, multiple roller dryer stations in combination with positive bias rollers.
A pre-treated paper medium comprised of a conductively treated paper base supporting a plastic dielectric coating on one of its two sides, which has been selectively charged on the dielectric side by a plurality of styli, is developed by subjecting the paper medium to charged toning particles suspended in a liquid toning carrier. The toning liquid is applied to the-moving dielectric paper by a plurality of rollers which are submerged in a toning liquid. To minimize toning particles being retained on the surface of the dielectric paper in areas where it has not been selectively charged, a positive charge is applied on the non-dielectric side of the coated paper via the positive bias rollers.
The residual electrostatic field of the dielectric surface of the paper attracts the particles suspended on the toner liquid and holds ~-them, thus making the images visible. Subsequent vaporization of the liquid carrier removes the vapor leaving the particles behind, which harden and make a permanent bond with the plastic coated surface.
Thus, in accordance with one broad aspect of the invention, there -~
is provided, in an electrographic printing system wherein a recording ~ `
medium moves along a predetermined path, said printlng system including a print station for applying a latent electrostatic charge to a recording medium and a toner station for applying to the recording medium a toning liquid comprised of a suspension of colored particles in a volatile carrier, the improved apparatus for applying the toning liquid to the recording medium and for removing the volatile carrier from the recording medium for fixing the colored particles permanently to the recording medium comprising in combination: a receptacle for containing the toning liquid comprised of a suspension of colored particles in a volatile carrier; a first roller-applicator rotatably mounted on said receptacle adjacent to the predetermined .. ~ ' L~
: . . . . , ..................... -:~
. .
2~3 path of said recording medium and partially submerged in said toning liquid, for applying toner liquid to one side of said recording medium; a second roller-applicator rotatably mounted to said receptacle in tandem to said first roller-applicator and adjacent to the predetermined path of said recording medium, and also partially submerged in said toning liquid, for ; applying additional toner liquid to said one side of said recording medium;
and, at least one bias roller located adjacent to the path of the recording medium and situated on the opposite side of the recording medium and offset along the path of the recording medium in relation to said first and second roller applicators.
According to another broad aspect of the invention there is provided, in an electrographic printing system wherein a recording medium moves along a predetermined path, said printing system including a print station for applying a latent electrostati.c charge to a recording medium and a toner station for applying to the recording medium a toning liquid comprised of a suspension of colored particles in a volatile carrier, the improved apparatus for applying the toning liquid to the recording medium . .
and for removing the volatile carrier from the recording medium for fixing the colored particles permanently to the recording medium comprising in combination: a receptacle for containing the toning liquid comprised of a suspension of colored particles in a volatile carrier; a plurality of roller-applicators rotatably mounted in tandem on said receptacle and adjacent to the predetermined path of said recording medium, and with each roller partially submerged in said toning liquid, for applying toner liquid ~ :
to one side of said recording medium; at least one bias roller located adjacent to the path of the recording medium and situation on the opposite side of the recording medium and offset at one end and along the path of the .
recording medium in relation to said plurality of roller applicators; and, a plurality of dryer-rollers adjacent to the predetermined path of the recording medium and situated after said plurality of roller-applicators, - 6a - ~ :
2~
said plurality of dryer-rollers for squeezing out the excess toning liquid from the recording medium.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates the basic principles of applying toner solution to a dielectric coated paper.
Figure 2 is a schematic diagram of one embodiment of the invention utilizing two applicator rolls.
Figure 3 is a schematic diagram of another embodiment of the invention having two toner applicator rolls and multidrying rolls.
~i 10 Figure 4 is still another embodiment of the invention having multiple toner application rollers and multiple drying :
.' - ':
- 6b -J~J
rollers.
_eneral Referring to Figure 1 some approaches will be discussed ; to the problem mentioned on page 4 of increasing the variable print densities greater than 0.85 while not substantially increasing the speed of the paper medium in excess of 30 inches per second. Figure 1 shows a toning station 100 which is com-prised of a toning reservoir 105 containing toning liquid 106.
Toning liquid is comprised of positive charged toner particles : 10 which are dispersed in a liquid carrier typically Isopar-L
(a trademark of Exxon Corporation). A paper medium 103 pre-treated with dielectric 104 travels to the toner station in the direction of arrow 107. The dielectric face 104 has negative electrical charges in a pattern determined by previous operations thereon as described in the above-related references and in par-ticular references 1-7. At the toner station a transfer roll comprised of any suitable conductive materials such as wear resistance steel is partially submerged in the toner liquid 106 and rotates counter cloc~wise at a constant speed and picks up toner liquid 106 and carries it to the meniscus 102 formed by the gap between the transfer roll 101 and the dielectric coded paper 103, 104. Since there are negative charges in a selected pattern on the dielectric 104 of the paper 103, the positively charged toner particles suspended in the meniscus 102 will travel to the dielectric surface 107 where they will be captured by the negative charges thereon and adhere thereto. It is obvious that the more toner particles deposited on the dielectric sur-face 104, the greater will be the print density. One way of depositing more toner particles is to decrease the gap between the transfer roll 101 and the dielectric surface 104. Since the field E from the grounded transfer roll 101 to the dielectric surface 107 is inversely proportional to the gap between the ~' ~
transfer roll and the dielectric coded paper (i.e. the closer the transfer roll to the dielectric surface the greater the e /~1/
-fccl) more particles would be deposited on the paper. However, by making the gap between the transfer roll 101 and the dielectric surface 104 smaller, the meniscus 102 is reduced and accordingly will hold less toner particles. Hence this would tend to decrease the print density. This could be remedied somewhat by increasing the speed of the transfer roll 101 but there is a maximum rotational speed which is determined by the centrifugal force at the outer rim of the transfer roll 101.
The greater the speed, the greater will be the centrifugal force at the rim of the transfer roll 101 and would cause splattering of the toner mix onto the dielectric surface 104 which is undesirable. Another way of increasing the print density is to make the toner meniscus 102 longer; hence it will have more toner particles and also the dielectric coded paper 103 will remain in the meniscus for a longer period of time.
One way to make the meniscus 102 longer is to make the transfer roll 101 larger. ~lowever, this would require a deeper reser-voir and the slowing down of the revolutions per minute of the roll in order not to exceed the peripheral speed; hence some ;
form of gear reduction would be necessary. Moreover, there is a limit to increasing the size of the meniscus using this technique. ~ -~
In an electrographic printing system a pre-treated paper medium comprised of a conduc-tively treated paper base supporting ~ , , ~ , , `\ -Z~
a plastic dielectric coatinq on at leas~ one of its sides, is positioned between a~ least two electrode assemblies each assembly compri~ed of a matrix o~ styli which receive variable information from a data processor, or other apparatus. By S selectively charging the plurality of styli, a latent image of alphanumeric characters or other type of variable printing is generated by the electrosta~ic discharge on the paper which is retained by the plastic coating. The latent image i5 then developed by subjecting the paper medium to charged toning particles suspended in liquid toning carrier.
; In developing these latent images-there are two general prior art techniques of applying the toning particles suspended in a liquid toning carrier to the paper medium. One technique .j is to dip the paper into the liquid toner medium which caxries the toner carriers~ Another technique is to bring the toner c~XC e s~
liquid to the paper and subsequently vacuum the acc~ew~ toner the paper. These prior art techniques suffer rom low print densities, poor contrast and low speed. These problems have been discussed in part supra utilizing Figure 1. The instant invention offers some solutions to these problems as ~ollows:
1. Toner solution is applied only on the dielectric side of the papar minimizing the amount of t~ner absorbed by the paper.
2. Multiple toner applicator rollers are used to apply the toner solution thus increasing the amount of toner applied to the dielectric coated paper and also increasing the dwell - time of the dielectric coated paper in the toner medium;
additionally the use o multiple toner-applicator rolls serves f ' ~ t ~"~'75~1.P
to prevent depletion of charged toner particles from the carrier liquid by replenishing the toner carrier liquid at each revolution.
Paper scrapers remove the depleted toner mix from the surface of the dielectric which otherwise would tend to impede the flow of charged toner particles to the dielectric which is freshly supplied by each toner-applicator roll.
Bias rollers at some electric potential between plus 40 volts to 100 vol~s produce a weak bias field which opposes the attraction o toner particles to any weak triboelectric charge on the paper produced by the passage of the paper web ovex the transport rollers~ thus minimizing the background staining of the paper as it passes through the transport.
TH~ TWO ROLL~R_TONER APPLICATOR EMBODIMENT
lS Referring to Figures 2 and 3 the dielectric coated paper 200, 300 traveling in the direction of the arrows A, A', at a typical speed of about 30 inches per second passes over guide roller 20, 301 to enter the developing station where the latent electrographic images on the surface of the dielectric paper are to be developed. (For a more detailea description of a typical dielectric paper utilized by the invention, see references 1 through 6 supra)~ The dielectric coated paper 200 is then guided under the first bias roller 202, 302 where a positive potential of between 40 to 100 volts is applied.
This potential produces a weak bias field which opposes the attraction of toner partioles to weak static charges on the paper which are produced by the passage of the paper over the transport rollers, yet this field i~ not strong enough to oppose the attraction of toner particles to the selectively charged areas on the paper. Thus background staining of the paper as it passes through the transport is reduced, and hence the contrast between the desired electrographic image and the background is heightened.
; The treated paper 200 then passes over transfer rollers 203, 204 and 303, 3Q4 respectively. The distance between the treated paper 200 and the transfer rollers is typically 0.005 inches. The transfer rollers rotate counter clockwise at a typical speed of 400 revolutions per minute so that their cir-cumerfence travels in the same relative direction as the paper - 10 medium. Liquid toner 207~ 307 which is pumped through inlet 208, 307 is carried by the partially submersed rollers to the -~
dielectric side of the treated paper medium, and forms a meni-scus 205, 206 and 305, 306 with the dielectric base of the paper medium. As previously described with respect to Figure 1, positively charged toner particles 102 under the influence of field E created by the selective negative charges on the surface of the dielectric 104 with respect to the grounded transfer roller 101, are deposited on the negatively charged portions of the dielectric surface 104 of the paper medium 103. As the paper 200 travels from transfer roller 203, 303 to transfer roller 206, 306 a scraper 210, 310 scrapes off excess toner liquid from the dielectric surface of paper medium and scrapers 203a, 206a, scrape the surface of rollers 203 and 2Q4 respec-tively. This permits the application of fresh toner liquid via the second toner applicator roll 206, 306 without being -diluted by the depleted liquid whose positively charged partic-les have been removed by the negative charges on the dielectric surface at the first toner applicator roll 203, 303. This assures a greater concentration of toner particles at the second meniscus 206, 306 and thus greater print density.
-11- ~ :`,.
.:
,:, .~ , ~ , :,.
: ' . . ... ~ !
' As the paper medium 200, 300 emerges from the toner ~ applicator station 200A, 300A it enters the dryer station 2003, - 300s on Figures 2 and 3 respectively where i~ is applied to dry-ing rollers 211, 213, 214, 311, 313, 315 and 316 respectively.
Dryer rollers are of approximately the same size as the toner applicator of about 1.75 inches in diameter. At the drying station 200B, 300B the paper 200, 300 is scraped of excess `: toner liquid by scrapers 210, 218, 219, 318, 318a and 319, and is squeezed dry by the dryer rollers 211, 213, 214, 311, 313, 315 and 316. (It should be noted that these rollers are sup-ported on some means of support such as the casting 215).
One of the problems of the drying station of Figure 2 is that the liquid toner carried out by the paper was excessive and in addition to making the paper difficult to handle, carried out excessive liquid which could otherwise be salvaged via the toner station 200B and the outlet 209. Accordingly, a larger ~;
number of transfer and idler rolls 300-316 were incorporated with scrapers 317, 319 before selected ones of the dryer rolls.
The developing station of Figure 3 is thus more efficient than 2C that of Figure 2 and produces greater print density with greater contrast.
ANOTHER EMBODIMENT OF THE INVENTION `~
_ _ _ _ _ _ _ _ , Referring to Figure 4 there is shown a schematic dia-gram of a multi-roller toner applicator multi-dryer station including a hot air dryer. The inven-tion is essentially the same in concept as previously described. However, because of multiple roller application, the paper medium has a greater dwell time in the toner solution and accordingly picks up a greater number of charged particles resulting in greater image density. Furthermore, the increased number of drying rollers and the hot air drying station further increase the efficiency of recycling the toner liquid and erase the efficiency of ~. .-.
~ ! ' recycling the toner liquid and furthermore produce greater con-trast. Referring to Figure 4 treated paper medium 400 is guided over a guide roll 4al and over transfer rollers ~03-409. These transfer rollers are about .75 inches in diameter as compared to the transfer rollers of Figures 1 and 2 which are typically 1.75 inches in diameter. The treated paper 400 also passes over a greater number of scraping operations via scrapers 411, 412 and 413 respectively thus enhancing the print density in accordance with the principles discussed supra. The positive bias rollers 402 and 414 serve the same function as previously described to prevent background staining of the dielectric surface of the treated paper medium.
The first drying station 425 is comprised of drying and idler rollers 418, ~19, 420, 421 and 422, and scrapers 417, 426, 426a and 427. Additionally there is another drying station 424 comprised of outlets 424a wherein hot air is guided over the treated paper ~00. Thus with this number of drying rollers, scrapers and a hot air station any liquid which would tend to remain on the paper with its toner particles would be substan-tially completely removed. Hence no liquid toner carrier wouldremain behind upon completion of the evaporation of the liquid which causes background problems and gives poor contrast because of smudging the developed images. Additionally, the evaporated liquid may be rerouted back to the tank 105, contain~
ing the toning liquid where it would condense when introduced into the cooler liquid.
While the present invention has been described in con-nection with particle embodiments thereof, it is to be under-stood that modification of these embodiments, as well as other embodiments utilizing the underlying principle of the invention are included with the spirit and scope of the invention which is to be limited only by the accompanying claims.
BACKGROU~ID OF THE INVENTION
Field of the Invention l'he invention relates to an apparatus and method for printing upon a recording medium and more particularly to an apparatus for printing permanent images electrographically upon a paper medium at comparatively high speeds as is required in a computer print-out apparatus.
_ scription of the Prior Art It had long been reco~lized that computer peripherals, particularly computer print-out apparatus, were bottlenecks in the total performance of a computer system. The majority of hard copy output devices for computer systems were and still are comprised of printers which impact the paper medium with print hammers. The movement of such print hammers not only limits the speed of which read-out can be accomplished, but are noisy and difficult to maintain. In order to increase the speed, facili-tate maintenance, and still maintain print quality, a system was developed and is now being marketed commercially by Honeywell Information Systems Inc. utilizing electrographic techniques to accomplish non-impact printing. Such a printing system is disclosed in the related articles, applications and patents cited supra.
One main problem in the design of such an electrographic printing system arises at the toner station where the latent electrographic image is developed, i.e. made visible by subject-ing the paper medium to charged toning particles suspended in liquid toning carrier. The problem is to increase the variable print densities greater than a reflective print density of 0.85 yet not substantially increase the speed of the paper medium in excess of 30 inches per second. There~ are several methods of attack to this problem as will be discussed later.
Another major problem in developing the latent electro-graphic image is print contrast. This problem is at the opposite pole of the previous problem in that what is required is that the background density i.e. the density of the toner particles on the portion of the paper not selectively charged, should be kept as low as possible. Yet another problem related to the second problem is that of background staining of the paper as it passes through the transport. These and ather problems encountered do not offer trivial solutions in developing the latent electrographic image with clarity, high print density, low background density of toner particles, and minimization of background staining.
OBJECTS OF THE INV_TION
It is a primary object of the invention to provide an improved non-impact printing system.
It is another object of the invention to provide an improved method and apparatus for developing latent electro-graphlc lmages.
It is another abject of the invention to provide im-proved apparatus and a method for developing the latent electro-graphic images.
It is still a further object of the instant invention to increase the time that a latent electrographic image spends in the development zone.
Further object of the instant invention is to provide a multiple applicator roller toner station for developing latent electrographic images.
A further object of the invention is to provide multiple applicator multiple dryer roller station for an electrographic printing system.
S UMMARY OF THE INVENTION
The foregoing objects of the instant invention are achieved by a method and apparatus for developing latent electrographic images utilizing multiple toner applicator rollers, multiple roller dryer stations in combination with positive bias rollers.
A pre-treated paper medium comprised of a conductively treated paper base supporting a plastic dielectric coating on one of its two sides, which has been selectively charged on the dielectric side by a plurality of styli, is developed by subjecting the paper medium to charged toning particles suspended in a liquid toning carrier. The toning liquid is applied to the-moving dielectric paper by a plurality of rollers which are submerged in a toning liquid. To minimize toning particles being retained on the surface of the dielectric paper in areas where it has not been selectively charged, a positive charge is applied on the non-dielectric side of the coated paper via the positive bias rollers.
The residual electrostatic field of the dielectric surface of the paper attracts the particles suspended on the toner liquid and holds ~-them, thus making the images visible. Subsequent vaporization of the liquid carrier removes the vapor leaving the particles behind, which harden and make a permanent bond with the plastic coated surface.
Thus, in accordance with one broad aspect of the invention, there -~
is provided, in an electrographic printing system wherein a recording ~ `
medium moves along a predetermined path, said printlng system including a print station for applying a latent electrostatic charge to a recording medium and a toner station for applying to the recording medium a toning liquid comprised of a suspension of colored particles in a volatile carrier, the improved apparatus for applying the toning liquid to the recording medium and for removing the volatile carrier from the recording medium for fixing the colored particles permanently to the recording medium comprising in combination: a receptacle for containing the toning liquid comprised of a suspension of colored particles in a volatile carrier; a first roller-applicator rotatably mounted on said receptacle adjacent to the predetermined .. ~ ' L~
: . . . . , ..................... -:~
. .
2~3 path of said recording medium and partially submerged in said toning liquid, for applying toner liquid to one side of said recording medium; a second roller-applicator rotatably mounted to said receptacle in tandem to said first roller-applicator and adjacent to the predetermined path of said recording medium, and also partially submerged in said toning liquid, for ; applying additional toner liquid to said one side of said recording medium;
and, at least one bias roller located adjacent to the path of the recording medium and situated on the opposite side of the recording medium and offset along the path of the recording medium in relation to said first and second roller applicators.
According to another broad aspect of the invention there is provided, in an electrographic printing system wherein a recording medium moves along a predetermined path, said printing system including a print station for applying a latent electrostati.c charge to a recording medium and a toner station for applying to the recording medium a toning liquid comprised of a suspension of colored particles in a volatile carrier, the improved apparatus for applying the toning liquid to the recording medium . .
and for removing the volatile carrier from the recording medium for fixing the colored particles permanently to the recording medium comprising in combination: a receptacle for containing the toning liquid comprised of a suspension of colored particles in a volatile carrier; a plurality of roller-applicators rotatably mounted in tandem on said receptacle and adjacent to the predetermined path of said recording medium, and with each roller partially submerged in said toning liquid, for applying toner liquid ~ :
to one side of said recording medium; at least one bias roller located adjacent to the path of the recording medium and situation on the opposite side of the recording medium and offset at one end and along the path of the .
recording medium in relation to said plurality of roller applicators; and, a plurality of dryer-rollers adjacent to the predetermined path of the recording medium and situated after said plurality of roller-applicators, - 6a - ~ :
2~
said plurality of dryer-rollers for squeezing out the excess toning liquid from the recording medium.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates the basic principles of applying toner solution to a dielectric coated paper.
Figure 2 is a schematic diagram of one embodiment of the invention utilizing two applicator rolls.
Figure 3 is a schematic diagram of another embodiment of the invention having two toner applicator rolls and multidrying rolls.
~i 10 Figure 4 is still another embodiment of the invention having multiple toner application rollers and multiple drying :
.' - ':
- 6b -J~J
rollers.
_eneral Referring to Figure 1 some approaches will be discussed ; to the problem mentioned on page 4 of increasing the variable print densities greater than 0.85 while not substantially increasing the speed of the paper medium in excess of 30 inches per second. Figure 1 shows a toning station 100 which is com-prised of a toning reservoir 105 containing toning liquid 106.
Toning liquid is comprised of positive charged toner particles : 10 which are dispersed in a liquid carrier typically Isopar-L
(a trademark of Exxon Corporation). A paper medium 103 pre-treated with dielectric 104 travels to the toner station in the direction of arrow 107. The dielectric face 104 has negative electrical charges in a pattern determined by previous operations thereon as described in the above-related references and in par-ticular references 1-7. At the toner station a transfer roll comprised of any suitable conductive materials such as wear resistance steel is partially submerged in the toner liquid 106 and rotates counter cloc~wise at a constant speed and picks up toner liquid 106 and carries it to the meniscus 102 formed by the gap between the transfer roll 101 and the dielectric coded paper 103, 104. Since there are negative charges in a selected pattern on the dielectric 104 of the paper 103, the positively charged toner particles suspended in the meniscus 102 will travel to the dielectric surface 107 where they will be captured by the negative charges thereon and adhere thereto. It is obvious that the more toner particles deposited on the dielectric sur-face 104, the greater will be the print density. One way of depositing more toner particles is to decrease the gap between the transfer roll 101 and the dielectric surface 104. Since the field E from the grounded transfer roll 101 to the dielectric surface 107 is inversely proportional to the gap between the ~' ~
transfer roll and the dielectric coded paper (i.e. the closer the transfer roll to the dielectric surface the greater the e /~1/
-fccl) more particles would be deposited on the paper. However, by making the gap between the transfer roll 101 and the dielectric surface 104 smaller, the meniscus 102 is reduced and accordingly will hold less toner particles. Hence this would tend to decrease the print density. This could be remedied somewhat by increasing the speed of the transfer roll 101 but there is a maximum rotational speed which is determined by the centrifugal force at the outer rim of the transfer roll 101.
The greater the speed, the greater will be the centrifugal force at the rim of the transfer roll 101 and would cause splattering of the toner mix onto the dielectric surface 104 which is undesirable. Another way of increasing the print density is to make the toner meniscus 102 longer; hence it will have more toner particles and also the dielectric coded paper 103 will remain in the meniscus for a longer period of time.
One way to make the meniscus 102 longer is to make the transfer roll 101 larger. ~lowever, this would require a deeper reser-voir and the slowing down of the revolutions per minute of the roll in order not to exceed the peripheral speed; hence some ;
form of gear reduction would be necessary. Moreover, there is a limit to increasing the size of the meniscus using this technique. ~ -~
In an electrographic printing system a pre-treated paper medium comprised of a conduc-tively treated paper base supporting ~ , , ~ , , `\ -Z~
a plastic dielectric coatinq on at leas~ one of its sides, is positioned between a~ least two electrode assemblies each assembly compri~ed of a matrix o~ styli which receive variable information from a data processor, or other apparatus. By S selectively charging the plurality of styli, a latent image of alphanumeric characters or other type of variable printing is generated by the electrosta~ic discharge on the paper which is retained by the plastic coating. The latent image i5 then developed by subjecting the paper medium to charged toning particles suspended in liquid toning carrier.
; In developing these latent images-there are two general prior art techniques of applying the toning particles suspended in a liquid toning carrier to the paper medium. One technique .j is to dip the paper into the liquid toner medium which caxries the toner carriers~ Another technique is to bring the toner c~XC e s~
liquid to the paper and subsequently vacuum the acc~ew~ toner the paper. These prior art techniques suffer rom low print densities, poor contrast and low speed. These problems have been discussed in part supra utilizing Figure 1. The instant invention offers some solutions to these problems as ~ollows:
1. Toner solution is applied only on the dielectric side of the papar minimizing the amount of t~ner absorbed by the paper.
2. Multiple toner applicator rollers are used to apply the toner solution thus increasing the amount of toner applied to the dielectric coated paper and also increasing the dwell - time of the dielectric coated paper in the toner medium;
additionally the use o multiple toner-applicator rolls serves f ' ~ t ~"~'75~1.P
to prevent depletion of charged toner particles from the carrier liquid by replenishing the toner carrier liquid at each revolution.
Paper scrapers remove the depleted toner mix from the surface of the dielectric which otherwise would tend to impede the flow of charged toner particles to the dielectric which is freshly supplied by each toner-applicator roll.
Bias rollers at some electric potential between plus 40 volts to 100 vol~s produce a weak bias field which opposes the attraction o toner particles to any weak triboelectric charge on the paper produced by the passage of the paper web ovex the transport rollers~ thus minimizing the background staining of the paper as it passes through the transport.
TH~ TWO ROLL~R_TONER APPLICATOR EMBODIMENT
lS Referring to Figures 2 and 3 the dielectric coated paper 200, 300 traveling in the direction of the arrows A, A', at a typical speed of about 30 inches per second passes over guide roller 20, 301 to enter the developing station where the latent electrographic images on the surface of the dielectric paper are to be developed. (For a more detailea description of a typical dielectric paper utilized by the invention, see references 1 through 6 supra)~ The dielectric coated paper 200 is then guided under the first bias roller 202, 302 where a positive potential of between 40 to 100 volts is applied.
This potential produces a weak bias field which opposes the attraction of toner partioles to weak static charges on the paper which are produced by the passage of the paper over the transport rollers, yet this field i~ not strong enough to oppose the attraction of toner particles to the selectively charged areas on the paper. Thus background staining of the paper as it passes through the transport is reduced, and hence the contrast between the desired electrographic image and the background is heightened.
; The treated paper 200 then passes over transfer rollers 203, 204 and 303, 3Q4 respectively. The distance between the treated paper 200 and the transfer rollers is typically 0.005 inches. The transfer rollers rotate counter clockwise at a typical speed of 400 revolutions per minute so that their cir-cumerfence travels in the same relative direction as the paper - 10 medium. Liquid toner 207~ 307 which is pumped through inlet 208, 307 is carried by the partially submersed rollers to the -~
dielectric side of the treated paper medium, and forms a meni-scus 205, 206 and 305, 306 with the dielectric base of the paper medium. As previously described with respect to Figure 1, positively charged toner particles 102 under the influence of field E created by the selective negative charges on the surface of the dielectric 104 with respect to the grounded transfer roller 101, are deposited on the negatively charged portions of the dielectric surface 104 of the paper medium 103. As the paper 200 travels from transfer roller 203, 303 to transfer roller 206, 306 a scraper 210, 310 scrapes off excess toner liquid from the dielectric surface of paper medium and scrapers 203a, 206a, scrape the surface of rollers 203 and 2Q4 respec-tively. This permits the application of fresh toner liquid via the second toner applicator roll 206, 306 without being -diluted by the depleted liquid whose positively charged partic-les have been removed by the negative charges on the dielectric surface at the first toner applicator roll 203, 303. This assures a greater concentration of toner particles at the second meniscus 206, 306 and thus greater print density.
-11- ~ :`,.
.:
,:, .~ , ~ , :,.
: ' . . ... ~ !
' As the paper medium 200, 300 emerges from the toner ~ applicator station 200A, 300A it enters the dryer station 2003, - 300s on Figures 2 and 3 respectively where i~ is applied to dry-ing rollers 211, 213, 214, 311, 313, 315 and 316 respectively.
Dryer rollers are of approximately the same size as the toner applicator of about 1.75 inches in diameter. At the drying station 200B, 300B the paper 200, 300 is scraped of excess `: toner liquid by scrapers 210, 218, 219, 318, 318a and 319, and is squeezed dry by the dryer rollers 211, 213, 214, 311, 313, 315 and 316. (It should be noted that these rollers are sup-ported on some means of support such as the casting 215).
One of the problems of the drying station of Figure 2 is that the liquid toner carried out by the paper was excessive and in addition to making the paper difficult to handle, carried out excessive liquid which could otherwise be salvaged via the toner station 200B and the outlet 209. Accordingly, a larger ~;
number of transfer and idler rolls 300-316 were incorporated with scrapers 317, 319 before selected ones of the dryer rolls.
The developing station of Figure 3 is thus more efficient than 2C that of Figure 2 and produces greater print density with greater contrast.
ANOTHER EMBODIMENT OF THE INVENTION `~
_ _ _ _ _ _ _ _ , Referring to Figure 4 there is shown a schematic dia-gram of a multi-roller toner applicator multi-dryer station including a hot air dryer. The inven-tion is essentially the same in concept as previously described. However, because of multiple roller application, the paper medium has a greater dwell time in the toner solution and accordingly picks up a greater number of charged particles resulting in greater image density. Furthermore, the increased number of drying rollers and the hot air drying station further increase the efficiency of recycling the toner liquid and erase the efficiency of ~. .-.
~ ! ' recycling the toner liquid and furthermore produce greater con-trast. Referring to Figure 4 treated paper medium 400 is guided over a guide roll 4al and over transfer rollers ~03-409. These transfer rollers are about .75 inches in diameter as compared to the transfer rollers of Figures 1 and 2 which are typically 1.75 inches in diameter. The treated paper 400 also passes over a greater number of scraping operations via scrapers 411, 412 and 413 respectively thus enhancing the print density in accordance with the principles discussed supra. The positive bias rollers 402 and 414 serve the same function as previously described to prevent background staining of the dielectric surface of the treated paper medium.
The first drying station 425 is comprised of drying and idler rollers 418, ~19, 420, 421 and 422, and scrapers 417, 426, 426a and 427. Additionally there is another drying station 424 comprised of outlets 424a wherein hot air is guided over the treated paper ~00. Thus with this number of drying rollers, scrapers and a hot air station any liquid which would tend to remain on the paper with its toner particles would be substan-tially completely removed. Hence no liquid toner carrier wouldremain behind upon completion of the evaporation of the liquid which causes background problems and gives poor contrast because of smudging the developed images. Additionally, the evaporated liquid may be rerouted back to the tank 105, contain~
ing the toning liquid where it would condense when introduced into the cooler liquid.
While the present invention has been described in con-nection with particle embodiments thereof, it is to be under-stood that modification of these embodiments, as well as other embodiments utilizing the underlying principle of the invention are included with the spirit and scope of the invention which is to be limited only by the accompanying claims.
-13-,, . " .
.-
.-
Claims (10)
1. In an electrographic printing system wherein a recording medium moves along a predetermined path, said printing system including a print station for applying a latent electrostatic charge to a recording medium and a toner station for applying to the recording medium a toning liquid comprised of a suspension of colored particles in a volatile carrier, the improved apparatus for applying the toning liquid to the recording medium and for removing the volatile carrier from the recording medium for fixing the colored particles permanently to the recording medium com-prising in combination:
a receptacle for containing the toning liquid comprised of a suspension of colored particles in a volatile carrier;
a first roller-applicator rotatably mounted on said receptacle adjacent to the predetermined path of said re-cording medium and partially submerged in said toning liquid, for applying toner liquid to one side of said recording medium;
a second roller-applicator rotatably mounted to said receptacle in tandem to said first roller-applicator and adjacent to the predetermined path of said recording medium, and also partially submerged in said toning liquid, for applying additional toner liquid to said one side of said recording medium; and, at least one bias roller located adjacent to the path of the recording medium and situated on the opposite side of the recording medium and offset along the path of the recording medium in relation to said first and second roller applicators.
a receptacle for containing the toning liquid comprised of a suspension of colored particles in a volatile carrier;
a first roller-applicator rotatably mounted on said receptacle adjacent to the predetermined path of said re-cording medium and partially submerged in said toning liquid, for applying toner liquid to one side of said recording medium;
a second roller-applicator rotatably mounted to said receptacle in tandem to said first roller-applicator and adjacent to the predetermined path of said recording medium, and also partially submerged in said toning liquid, for applying additional toner liquid to said one side of said recording medium; and, at least one bias roller located adjacent to the path of the recording medium and situated on the opposite side of the recording medium and offset along the path of the recording medium in relation to said first and second roller applicators.
2. The electrographic printing system as recited in Claim 1 including a first scraper between said first and second roller applicators adjacent to the predetermined path, for scraping excess liquid from the recording medium.
3. The electrographic printing system as recited in Claim 2 including a third roller-applicator rotatably mounted to said receptacle in tandem with said first and second roller-applicators and adjacent to the predetermined path of said recording medium and also partially submerged in said toning liquid, for applying additional toner liquid to said one side of said recording medium.
4. The electrographic printing system as recited in Claim 3 including a second scraper between said first and second roller applicators adjacent to the predetermined path, for scraping excess liquid from the recording medium.
5. The electrographic printing system as recited in Claim 4 wherein a bias voltage of at least plus 40 volts is applied to said bias roller.
6. The electrographic printing system as recited in Claim 4 including a plurality of dryer-rollers adjacent to the predetermined path of said recording medium and located after said first and second applicator rollers, said dryer-rollers for squeezing out excess toning liquid from said recording medium.
7. The electrographic printing system as recited in Claim 6 including at least one scraper after each dryer-roller for scraping off excess toning liquid from said recording medium.
8. The electrographic printing system as recited in Claim 7 including evaporation means after said dryer rollers positioned on each side of the recording medium for evaporating the volatile liquid carrier adhering to the recording medium.
9. The electrographic printing system as recited in Claim 8 including means for rerouting the volatile liquid to said receptacle.
10. In an electrographic printing system wherein a recording medium moves along a predetermined path, said printing system including a print station for applying a latent electrostatic charge to a recording medium and a toner station for applying to the recording medium a toning liquid comprised of a suspension of colored particles in a volatile carrier, the improved apparatus for applying the toning liquid to the recording medium and for removing the volatile carrier from the recording medium for fixing the colored particles permanently to the recording medium comprising in combination:
a receptacle for containing the toning liquid comprised of a suspension of colored particles in a volatile carrier;
a plurality of roller-applicators rotatably mounted in tandem on said receptacle and adjacent to the predetermined path of said recording medium, and with each roller partially submerged in said toning liquid, for applying toner liquid to one side of said recording medium;
at least one bias roller located adjacent to the path of the recording medium and situation on the opposite side of the recording medium and offset at one end and along the path of the recording medium in relation to said plurality of roller applicators; and, a plurality of dryer-rollers adjacent to the predetermined path of the recording medium and situated after said plurality of roller-applicators, said plurality of dryer-rollers for squeezing out the excess toning liquid from the recording medium.
a receptacle for containing the toning liquid comprised of a suspension of colored particles in a volatile carrier;
a plurality of roller-applicators rotatably mounted in tandem on said receptacle and adjacent to the predetermined path of said recording medium, and with each roller partially submerged in said toning liquid, for applying toner liquid to one side of said recording medium;
at least one bias roller located adjacent to the path of the recording medium and situation on the opposite side of the recording medium and offset at one end and along the path of the recording medium in relation to said plurality of roller applicators; and, a plurality of dryer-rollers adjacent to the predetermined path of the recording medium and situated after said plurality of roller-applicators, said plurality of dryer-rollers for squeezing out the excess toning liquid from the recording medium.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/839,715 US4141317A (en) | 1977-10-05 | 1977-10-05 | Multiple applicator roller toner station |
| US839,715 | 1977-10-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1116223A true CA1116223A (en) | 1982-01-12 |
Family
ID=25280467
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA305,630A Expired CA1116223A (en) | 1977-10-05 | 1978-06-16 | Multiple applicator roller toner station, multiple roller dryer station for page printing system |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US4141317A (en) |
| JP (1) | JPS5455441A (en) |
| AU (1) | AU516109B2 (en) |
| CA (1) | CA1116223A (en) |
| DE (1) | DE2842747A1 (en) |
| FR (1) | FR2405506A1 (en) |
| GB (1) | GB2005568B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| PL425002A1 (en) * | 2018-03-23 | 2019-10-07 | Uniwersytet Jagielloński | Device for exerting an influence on liquid in a meniscus moved on a bed and method for conducting the reaction |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4595276A (en) * | 1982-07-30 | 1986-06-17 | Photon Chroma, Inc. | Inclined toner flow control system for developing an electrostatic latent image upon a roll cassette, aperture card, or microfiche type electrophotographic film element |
| US4461561A (en) * | 1982-07-30 | 1984-07-24 | Photon Chroma, Inc. | Apparatus for imaging and developing electrophotographic microformats |
| US4454833A (en) * | 1983-07-25 | 1984-06-19 | Xerox Corporation | Liquid developer apparatus |
| EP0204774A4 (en) * | 1984-12-13 | 1988-07-04 | Cameronics Techn Corp Ltd | Method of and means for developing electrophotographic images. |
| JPS631514U (en) * | 1986-06-23 | 1988-01-07 | ||
| US4733273A (en) * | 1986-07-01 | 1988-03-22 | Xerox Corporation | Liquid developing apparatus |
| US5414498A (en) * | 1993-09-14 | 1995-05-09 | Delphax Systems | Liquid/dry toner imaging system |
| US5701561A (en) * | 1995-09-26 | 1997-12-23 | Minnesota Mining And Manufacturing Company | Method and apparatus for applying liquid toner to a print medium using multiple toner applicators for each liquid toner |
| US6183079B1 (en) | 1998-06-11 | 2001-02-06 | Lexmark International, Inc. | Coating apparatus for use in an ink jet printer |
| US6706118B2 (en) * | 2002-02-26 | 2004-03-16 | Lexmark International, Inc. | Apparatus and method of using motion control to improve coatweight uniformity in intermittent coaters in an inkjet printer |
| US7111916B2 (en) * | 2002-02-27 | 2006-09-26 | Lexmark International, Inc. | System and method of fluid level regulating for a media coating system |
| US6955721B2 (en) * | 2002-02-28 | 2005-10-18 | Lexmark International, Inc. | System and method of coating print media in an inkjet printer |
| JP5884932B1 (en) * | 2015-05-27 | 2016-03-15 | 千住金属工業株式会社 | Liquid applicator |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3256855A (en) * | 1962-04-02 | 1966-06-21 | Australia Res Lab | Machine for applying liquids |
| US3367791A (en) * | 1966-07-11 | 1968-02-06 | Addressograph Multigraph | Liquid development of electrostatic images |
| US3596635A (en) * | 1967-03-16 | 1971-08-03 | Bell & Howell Co | Electrostatographic office copier |
| JPS5122821B1 (en) * | 1970-12-10 | 1976-07-13 | ||
| US3817212A (en) * | 1972-01-10 | 1974-06-18 | Xerox Corp | Electrostatographic liquid development apparatus |
| US3816114A (en) * | 1972-03-03 | 1974-06-11 | Xerox Corp | Electro-photographic method |
| US3893417A (en) * | 1974-01-17 | 1975-07-08 | Eastman Kodak Co | Apparatus for liquid development of electrostatic images |
-
1977
- 1977-10-05 US US05/839,715 patent/US4141317A/en not_active Expired - Lifetime
-
1978
- 1978-05-02 JP JP5239578A patent/JPS5455441A/en active Pending
- 1978-06-16 CA CA305,630A patent/CA1116223A/en not_active Expired
- 1978-08-21 FR FR7824303A patent/FR2405506A1/en not_active Withdrawn
- 1978-09-28 AU AU40292/78A patent/AU516109B2/en not_active Expired
- 1978-09-30 DE DE19782842747 patent/DE2842747A1/en not_active Withdrawn
- 1978-10-04 GB GB7839222A patent/GB2005568B/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| PL425002A1 (en) * | 2018-03-23 | 2019-10-07 | Uniwersytet Jagielloński | Device for exerting an influence on liquid in a meniscus moved on a bed and method for conducting the reaction |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2842747A1 (en) | 1979-04-19 |
| AU4029278A (en) | 1980-04-03 |
| JPS5455441A (en) | 1979-05-02 |
| GB2005568A (en) | 1979-04-25 |
| US4141317A (en) | 1979-02-27 |
| FR2405506A1 (en) | 1979-05-04 |
| GB2005568B (en) | 1982-02-10 |
| AU516109B2 (en) | 1981-05-14 |
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