Device employing multicolor toner particles for generating multicolor images

Device for generating multicolor images which employs a latent electric charge pattern and development of this on an information carrier (21) using toner particles (16) of different colors. Separate developers (10-13) are used for each color. Each developer (10-13) is individually provided with a toner carrier, preferably a conductive developer roll (14) and a back electrode (23) which cooperates with the developer roll by attraction forces. An electrode unit (29) is arranged between the conductive developer roll and the back electrode 23. The electrode unit (29) includes at least one electrode layer/direction (22), essentially including relative parallel electrodes, which are common for all developers (10-13), and a plurality of apertures (27). The apertures (27) are opened and closed respectively by signals from at least one driving device (25). The toner carriers (14) and/or the back electrode/electrodes (23) is/are arranged to have applied a potential difference with respect to the colour selection, which results in attraction forces between the toner carrier (14) and the back electrode (23). A possible second electrode layer/direction (33), which includes electrodes (33) which are essentially parallel and formed at an angle to the first electrode layer (22), is provided to be controlled individually by at least a second driving device (31).

The present invention relates to a device for presenting multicolour 
images, by means of a latent electric charge pattern and development of 
this on an information carrier by means of toner particles of different 
colours, by using separate developers for each colour, each developer is 
arranged with a toner carrier, preferably a developer roller cooperative 
with a back electrode by means of attraction forces as well as an 
electrode means arranged between these, provided with pervious apertures 
which are opened and closed respectively by means of signals from at least 
one control device. 
BACKGROUND OF THE INVENTION 
The present invention is a further development of the method and device 
described in Swedish patent 8704883 for development of images and text by 
means of monochromatic toner particles on an information carrier, by using 
computer generated signals. According to the patent an information 
carrier, for example paper, is brought in electric cooperation with at 
least one screen or lattice-shaped electrode means, which through control 
in accordance to the desired pattern configuration opens and closes 
passages through an electrode matrix, by galvanic connection of the 
electrodes of the matrix to at least one voltage supply. Through 
consequently opened passages, an electric field is exposed for attracting 
the toner particles towards the information carrier. Further, through the 
international patent application PCT/SE90/00398 it is known, that the 
electrode matrix consists of a weave, where the weave wires consist of 
electrodes and where each mesh is surrounded by double electrodes. Through 
SE-90000631 it is known that a back electrode can be screen-shaped, ie. 
divided in a number of individual electrodes, and placed in front of the 
meshes of the electrode matrix. 
THE OBJECT AND THE IMPORTANT FEATURES OF THE INVENTION 
The object of the invention is to provide a device of the above described 
type, which gives high quality multicolour prints by means of a 
constructive simple and thereby a cheap device. These tasks have been 
solved by means of an electrode means including at least one electrode 
layer, essentially including relative parallel electrodes, which are 
common for all developers; that the toner carriers and/or the back 
electrode(s) is (are) arranged to have applied, with respect to the colour 
selection, with a potential difference, which results in attraction forces 
between the toner carrier and the back electrode; and/or that another 
electrode layer including essentially parallel electrodes forming an angle 
to the electrodes of the first electrode layer is provided to be 
controlled individual by at least a second driving device.

DESCRIPTION OF THE EMBODIMENTS 
FIGS. 2 and 3 show a device consisting of a number, for instance four, 
separate developers 10-13, each including a toner carrier 14, preferably a 
conductive developer roller and a container 15 for toner particles 16, 
even called toner. Each developer contains a colour, for instance magenta, 
cyan, yellow and black (M, C, G and B). A special scrape device 17, 
so-called "doctor blade" is provided to produce a uniform layer of toner 
particles 16 on the toner carrier 14. Each toner carrier 14 includes a 
core, consisting of a number of permanent magnets 20 with different 
polarity. These are provided to attract the toner particles 16 to the 
roller 14. Each of these rollers is individually connectable to a voltage 
supply by means of switches 18a-18d, which means that the toner carriers 
14 can be supplied by different potentials. The toner particles 16 are 
transferred to an information carrier 21, which can be a paper sheet, via 
an opening 19, arranged in the toner container 15, facing the information 
carrier 21. The transfer occurs by means of attraction forces, which are 
produced between the toner carrier 14 and at least a back electrode 23. An 
electrode means 29, consisting of a lattice-shaped electrode layer 22 is 
arranged between the toner carriers 14 and the back electrodes 23. In this 
embodiment the electrode layer 22 consists of electrodes 24 of thin 
conductors, according to FIG. 4, supported on an insulating carrier 26, in 
which the conductor and the carrier are provided with pervious apertures 
27, to act as passages for said attraction forces. The electrodes 24 in 
the electrode layer are common for all developers 10-13 and connected to a 
driving device 25. 
In the shown embodiment, the switching unit 18b is connected to V.sub.1 
(=330), whereby only one toner carrier 14 with one type of toner particles 
16, ie. cyan, receives necessary potential, so that the electric field 
attracts the particles from the toner carrier 14 to the information 
carrier 21. By means of the signals from the driving device 25, the 
electrodes 24 are controlled, so that passages for the attraction force in 
the apertures 27 are opened or closed between the back electrode 23 and 
the toner carrier 14. By bringing an information carrier 21, eg. a paper 
sheet, between the developer 10-13 and the back electrodes 23, cyan toner 
particles 16 are transported on the information carrier 21. In FIG. 3 the 
embodiment is elucidated, where cyan is transported from the toner carrier 
14 to the information carrier 21, whereby the switch 18 for the cyan 
developer is connected to V.sub.1. By connecting the electrodes 24 to 
different voltages, henceforth called ON or OFF-voltage, the toner 
particles 16 are guided to the information carrier 21. An ON-voltage is a 
voltage resulting that an "opening" is obtained in the electrode apertures 
27 and that the attraction force between the back electrodes 23 and to 
V.sub.1 connected toner carrier 14 causing toners to be applied on the 
information carrier, while an OFF-voltage prevents the attraction force to 
reach the toner particles. Through the remaining electrode apertures 
appurtenant to the developers, which are provided on same signal line 28, 
according to FIG. 4, connected to the ON-voltage, no toners pass when non 
sufficient field strength is obtained between the developer, connected to 
V.sub.0 (=for example 0V), and the back electrodes 23. A connection of the 
electrode 24 to an ON-voltage, results in cyan being transported to the 
information carrier. Pervious apertures 27 in electrodes 24, which are not 
connected to the same signal line 28 of driving device 25, are "closed" by 
means of OFF-voltage. This is also applied for the remaining electrode 
apertures belonging to the other developers, which are provided on the 
same signal line 28. 
"Electrographic printing" particles are used in an embodiment according to 
FIGS. 5 and 5a. In this case the electrode matrix is substituted by a 
"particle modulator", which consists of slit-formed apertures 27 arranged 
on an insulating plate 34, adjacent to which is a first electrode layer 
22, so-called signal electrodes, on one side of the plate and another 
electrode layer 33, so-called base electrodes on the other side of the 
plate. Consequently, the electrodes 22 and 33 are outdistanced by means of 
the plate 34. According to this principle, if the toner particles 16 have 
negative (-) charge, the signal electrode 22 is connected to a positive 
(+) voltage by means of the driving devices 25 and the driving device 31 
connects the base electrode to a negative (-) voltage, while the back 
electrode 23 is connected to a positive voltage. This causes an attraction 
force between the back electrode 23 and the toner carrier 14, with 
direction towards the back electrode is produced. By connecting the 
above-mentioned voltages to the electrodes 22 and 33, a field between the 
electrodes 22 and 33 (from 33 towards 22) is obtained, so that the toner 
through the aperture 27 can be modulated. If the voltage of, eg. the 
signal electrode 22, is changed so that the field between the electrodes 
22 and 33 changes direction, the aperture 27 is closed, ie. no toner 
particles are transferred from the toner carrier 14. By using a common 
back electrode 23 for all developers 10-13, all signal electrodes on a 
longitudinal line are connected to the same control signal and the toner 
carriers 14 are connected to different voltages by means of the switches 
18a-18d. 
Those in FIG. 6 and 6a shown embodiments of electrode means 29, according 
to the invention, consist of inter-woven electrodes 24 and 30 forming an 
angle with each other, configuring a net with open meshes, which 
constitute said apertures 27. The information carrier 21 is located 
between the electrode means 29 and the back electrode 23. A number of 
driving devices 25 and 31 are provided to control the apertures 27 of the 
electrode means 29. Different colours are applied by the toner carriers 14 
being commonly connected to, for instance earth and the back electrodes 23 
to V.sub.2 or V.sub.3, at which connection to V.sub.2 blocks the 
attraction forces between the back electrode and the toner carrier, while 
the connection to V.sub.3 produces a field of force. By connecting the 
electrodes 24 to different voltages, ie. ON or OFF-voltages, passages in 
the electrode means 29 are opened, through which toner particles 16 are 
attracted to the information carrier 21. To obtain attraction through 
proper passage, a back electrode, arranged in front of the passage, is 
connected to potential (V.sub.3) which produces an attraction force, while 
the other back electrodes are connected to other potential (V.sub.2). 
When generating images and text, different resolutions are used. A 
character, consisting of, eg. a number of black points, can have a lower 
resolution than an image consisting of, eg. different colours with higher 
dot density. According to the principal diagram in FIG. 7, the electrode 
means can consist of different numbers of apertures with varying sizes for 
different colours, for example area 35 is arranged with lower aperture 
density, eg. 150 dpi (dots/inch) for black toner particles and area 36 
with higher aperture density, for example 300 dpi for toner particles of 
other colours. By reducing the number of signal conductors 28, which 
passes between the electrodes 24, ie. the shortest way to the next 
electrode group, also the production of the electrode means can be 
simplified. This method can also be applied when an electrode means of 
"particle modulator" type is used. 
An embodiment of the developer units 10-13, comprising toner containers and 
particle carriers, are shown uppermost in FIG. 8. The developer units are 
mounted in a cartridge 37, having spacer means 38 and holders 39 with 
seats for holding the developer means 10-13 in correct distance relative 
each other and the electrode means 29. Channels are arranged for driving 
means, such as gearwheels, belts or the like (not shown), which drive the 
particle carriers of the developers 10-13. 
The bottom portion of the cartridge 37 is open for exposing the particle 
carriers 14 to electrode means 29. Preferably, the electrode means 29 is 
arranged at the bottom portion of the cartridge 37, connected to a driving 
unit 25 and a retainer 40, which are arranged on both short ends of the 
cartridge. 
According to this embodiment, the back electrode is arranged as a transport 
belt 41, comprised of flexible conductive or semi-conductive material 
suspended between two rotatable rollers 42 and 43, one of which is rotated 
by means of rotation devices 44. 
The belt 41 is arranged with a plurality of pervious holes 45. Under the 
belt and between the rollers 42 and 43, a sucking or vacuum apparatus 70, 
comprising a chamber 46 and with this through a nozzle communicating fan 
47 is arranged. A filter device 48 is provided in communication with the 
fan 47. The chamber 46 is provided with the grind smoothed bars 50. 
All or some parts of the belt 41 are arranged with curved flock pads 49 of 
insulating or conducting material, which pads have larger holes 51 
(compared to holes 45) at the curve points, preferably partly surrounded 
by pointed peak of the flock pad 49 in the belt movement direction, see 
FIG. 9. 
The belt 41 has several functions. Besides operating as the back electrode, 
it is designed for conveying the information carrier, eg. paper sheet or 
the like, and cleaning the electrode means 29. When a paper sheet is 
delivered to the transport part of the belt having sucking holes 45, the 
paper sheet is fixed gradually on the belt by means of the sucking forces. 
The bars 50 support and attract the belt (and the paper), and due to the 
sucking the paper is attached to the belt with high precision, whereby the 
distance between the paper and the electrode means is determined exactly. 
The high precision attachment of the paper to the belt is desirable when 
the paper is conveyed a longer distance, where several colours are applied 
on the paper than in a monochromatic printer unit having only one 
developer. 
The electrode means must be cleaned after each or several printing 
operations due to the congregation around the apertures of the electrode 
means by the toner particles. The congregation results in obstruction of 
the apertures 27 and deterioration of the printing quality. 
Some coloured toner particles consist of material, having non or very 
little magnetic or electric properties, which means that cleaning the 
electrode means using, for example magnets will not work properly. By 
using the flock pads 49 on the belt 41, the adhesive toner particles 67 
adhered to the electrode means 29 are brushed off and some wasted toners 
68 are sucked to the chamber 46 via holes 51, as shown in FIG. 9. If 
conductive flock pads 49 are used, the surface of the electrode means 29 
can be charged or neutralized by flock pads delivering charges. 
The back electrode 23 in the belt 41 is energized through the bars 50, 
rollers 42 or 23, or by means of a sliding contact (not shown). 
A printer unit 52 shown in FIG. 10, comprises the developers 10-13, 
arranged in a developer compartment in the cartridge 37. The electrode 
unit 29, which in this case consists of flexible material, such as thin 
insulating film provided with conductive electrodes, is flexibly suspended 
by means of stretch/suspension means 53, to provide accurate distance to 
the back electrode and the particle carrier. The electrode means 29 is 
connected to driver means, ie. driver IC's 25. The printer 52 is provided 
with a detachable paper cassette, shown inserted in a space under the 
printer 52 in its working position and partly drawn out for loading with 
the paper (hatched lines). 
A stack of paper 54 is so arranged that a friction pick up roller 69 feeds 
a paper sheet towards an U-shaped wall 56, which guides the paper sheet in 
front of a registration roller 55, which senses the presence of the paper 
sheet and by cooperation with the roller 43 guides the paper onto the 
combined belt and back electrode 23. In this embodiment the flock pads 49 
are arranged only on one part of the belt, and a surface of the belt 
having suction holes 45 and having at least the same dimensions of the 
paper sheet is arranged to convey the paper. The paper sheet is 
transported by the developers 10-13, gradually under the electrode means, 
at which the desired toner colour is transferred on the paper. After toner 
transfer procedure the paper is guided through fusing means 57 and by the 
delivery rollers 58 to a paper delivery tray 59. 
As shown in FIG. 9, after paper sheet output or during the printing, after 
paper sheet passing by each developer 10-13, the flock pads 49 pass by the 
electrode means 29, preferably in front of each developer and the 
remaining toner on the electrode means is brushed off, some adhered to the 
flocks of the flock pad and some sucked out to the vacuum chamber 46 and 
thus to the filter. 
If the toner particles, which are used in the developers 10-13 have 
electrical or magnetic property, they can charge the surface of the 
electrode means and increase the adherence and disturb the transportation 
of the toner from the toner carrier onto the paper, the flocks can contain 
conductive material to charge or neutralize the surface of the electrodes 
and the adhesive toners in the print zone 60. One or more cleaning rollers 
65 are arranged in communication with a toner waste container 66. When the 
flock pads 49 pass by the mentioned cleaning rollers 65, the toner 
particles adhered to the flocks are brushed off by means of the cleaning 
rollers 65 and the wasted toner is delivered to the container 66. 
A manual feeding tray 61 is arranged to feed the paper sheet or the like 
manually. The functions of the printer unit 52 are controlled and 
displayed by means of a display and keyboard unit 62 arranged in front 
portion 63 of the printer. The power is supplied to the different parts by 
means of a power supply 64. 
The invention is not limited to above described embodiments and other 
devices in the scope of claims can occur, for example the toner carrier 
can consist of gas- or airflows and the back electrode can be replaced 
with a conducting information carrier. 
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List of referencal numbers 
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10-13 developer 
14 toner carrier, preferably a developer roll 
15 toner container 
16 toner particles 
17 doctor blade 
18 switching unit 
19 opening in container 
20 permanent magnet 
21 information carrier 
22 first electrode layer/direction 
23 back electrode 
24 electrode 
25 driving device 
26 insulating carrier 
27 aperture 
28 signal line 
29 electrode means 
30 transversal electrode 
31-32 driving device 
33 second electrode layer/direction 
34 insulating layer 
35 area with low aperture density 
36 area with high aperture density 
37 cartridge 
38 spacer 
39 holder 
40 retainer 
41 belt 
42, 43 roller 
44 rotation device 
45 pervious hole 
46 vacuum chamber 
47 fan 
48 filter 
49 flock pad 
50 bar 
51 pervious hole 
52 printer unit 
53 suspension means 
54 stack of paper 
55 registration roller 
56 guide wall 
57 fusing means 
58 feeding roller 
59 paper delivery tray 
60 print zone 
61 manual paper feed tray 
62 display and keyboard unit 
63 front portion 
64 power supply 
65 cleaning roller 
66 waste toner container 
67 jammed toner 
68 wasted toner 
69 pick-up roller 
70 vacuum/suction means 
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