Source: http://www.google.com/patents/US5825384?dq=5,912,661
Timestamp: 2015-07-01 17:19:22
Document Index: 484694177

Matched Legal Cases: ['art 2', 'art 2', 'art 33', 'art 31', 'art 32', 'art 33', 'art 31', 'art 32', 'art 33', 'art 31', 'art 32', 'art 33', 'art 31', 'art 32', 'art 33', 'art 33', 'art 33', 'art 31', 'art 31', 'art 32', 'art 32', 'art 31', 'art 32', 'art 31', 'art 32', 'art 11', 'art 202', 'art 203', 'art 202', 'art 203', 'art 203', 'art 202', 'art 11', 'art 11', 'art 11', 'art 11', 'art 202', 'art 202', 'art 11', 'art 202', 'art 202', 'Application No. 104769', 'Application No. 3972']

Patent US5825384 - Image forming apparatus including means for controlling the flight of toner ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsAn image forming apparatus of the present invention includes a toner carrier, a counter electrode, and a control electrode, which have the same potential as a ground potential of the image forming apparatus during a non-operational period while a flight electric field-use operational voltage and control...http://www.google.com/patents/US5825384?utm_source=gb-gplus-sharePatent US5825384 - Image forming apparatus including means for controlling the flight of toner or visualizing particles in accordance with an image signalAdvanced Patent SearchPublication numberUS5825384 APublication typeGrantApplication numberUS 08/715,514Publication dateOct 20, 1998Filing dateSep 18, 1996Priority dateSep 22, 1995Fee statusLapsedAlso published asDE69629338D1, DE69629338T2, EP0764540A2, EP0764540A3, EP0764540B1Publication number08715514, 715514, US 5825384 A, US 5825384A, US-A-5825384, US5825384 A, US5825384AInventorsHirokazu FujitaOriginal AssigneeSharp Kabushiki KaishaExport CitationBiBTeX, EndNote, RefManPatent Citations (19), Non-Patent Citations (2), Referenced by (3), Classifications (9), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetImage forming apparatus including means for controlling the flight of toner or visualizing particles in accordance with an image signal
US 5825384 AAbstract
1. An image forming apparatus comprising:a visualizing particle carrier for carrying visualizing particles; a counter electrode provided vis-a-vis said visualizing particle carrier; a control electrode provided between said visualizing particle carrier and said counter electrode; power supply means for applying a flight electric field-use voltage across said visualizing particle carrier and said counter electrode so that an electric field for causing the visualizing particles to fly from said visualizing particle carrier toward said counter electrode is generated; control voltage applying means for applying a control voltage to said control electrode so that the flight of the visualizing particles is controlled in accordance with an image signal; and control means for controlling said power supply means and said control voltage applying means, so that during an operational period while the flight electric field-use voltage and control voltage are applied, said visualizing particle carrier, said counter electrode, and said control electrode are first respectively set to have a bias potential, the bias potential being set to have the electric potential of said counter electrode and a polarity of said counter electrode during application of the flight electric field-use voltage. 2. An image forming apparatus as set forth in claim 1, wherein, during a non-operational period while the flight electric field-use voltage and the control voltage are not applied, said control means causes each of said visualizing particle carrier, said counter electrode, and said control electrode to have a ground potential of said image forming apparatus.
3. An image forming apparatus as set forth in claim 1, further comprising:cleaning means for removing foreign material adhering to a surface of said counter electrode; and cleaning process control means for causing a foreign material flying electric field to be generated at least either before image formation starts or after the image formation ends, the electric field causing foreign material adhering to said control electrode to fly toward said counter electrode. 4. The image forming apparatus as set forth in claim 3, wherein said cleaning process control means applies an alternating voltage to said counter electrode so that the electric field is generated.
5. The image forming apparatus as set forth in claim 4, wherein the alternating voltage has a peak value set to the potential of said counter electrode when the flight electric field-use voltage is applied, and a bottom value set not higher than a ground potential of the image forming apparatus.
6. The image forming apparatus as set forth in claim 3, wherein, when the foreign material flying electric field is generated both before and after the image formation, said cleaning process control means controls the foreign material flying electric field so that the electric field is generated for a longer period after the image formation than before the image formation.
7. An image forming apparatus as set forth in claim 1, further comprising:a recording medium transport route through which a recording medium is transported while being in contact with said counter electrode, the recording medium transport route being provided between said control electrode and said counter electrode, the visualizing particles adhering to the recording medium; and charging removing means for removing electric charges of said control electrode. 8. The image forming apparatus as set forth in claim 7, wherein said charge removing means removes the electric charges before the image formation.
9. The image forming apparatus as set forth in claim 7, wherein:said control electrode includes an insulating layer, a plurality of gates provided in said insulating layer, and a plurality of electrode sections, each electrode section being provided around each gate, visualizing particles being allowed to pass through said gates, the control voltage being applied to said electrode sections; said charge removing means includes a resistive layer and a connecting circuit, said resistive layer being provided on at least one surface of said insulating layer, said connecting circuit electrically connecting or disconnecting said resistive layer to an object so that electric charges of said resistive layer are released through the object during connecting; and said resistive layer has a limited resistance such that a surface resistance of said resistive layer is smaller than that of said insulating layer and that a time constant derived from the surface resistance of said resistive layer and a capacitance between the electrode sections is greater than a voltage control cycle of said control electrode. 10. The image forming apparatus as set forth in claim 9, wherein said connecting circuit connects or disconnects said resistive layer to said visualizing particle carrier.
11. The image forming apparatus as set forth in claim 9, wherein said connecting circuit connects or disconnects said resistive layer to a ground terminal of said image forming apparatus.
12. The image forming apparatus as set forth in claim 9, wherein said resistive layer is provided in contact with said electrode sections.
13. The image formation apparatus as set forth in claim 7, wherein:said control electrode includes an insulating layer, a plurality of gates in said insulating layer and a plurality of electrode sections, each electrode section being provided around each gate, visualizing particles being allowed to pass through said gates, the control voltage being applied to said electrode sections; said charge removing means includes a resistive layer, said electrode sections being provided on said resistive layer; and said resistive layer has a limited resistance such that a surface resistance of said resistive layer is smaller than that of said insulating layer and that a time constant derived from the surface resistance of said resistive layer and a capacitance between the electrode sections is greater than a voltage control cycle of said control electrode. 14. The image forming apparatus as set forth in claim 7, wherein:said control electrode includes an insulating layer, a plurality of gates provided in said insulating layer, and a plurality of electrode sections, each electrode section being provided around each gate, visualizing particles being allowed to pass through said gates, the control voltage being applied to said electrode sections; and said charge removing means includes: a photoconductive layer provided on at least one surface of said insulating layer, said photoconductive layer having a resistance decreasing upon receipt of light, a connecting circuit for electrically connecting or disconnecting said photoconductive layer to an object so that electric charges of said photoconductive layer are released through the object during connecting, and a light source for projecting the light on said photoconductive layer. 15. The image forming apparatus as set forth in claim 14, wherein said connecting circuit connects or disconnects said photoconductive layer to said visualizing particle carrier.
16. The image forming apparatus as set forth in claim 14, wherein said photoconductive layer is provided in contact with said electrode sections.
17. The image forming apparatus as set forth in claim 7, wherein:said control electrode includes a plurality of gates and a plurality of electrode sections, each electrode section being provided around each gate, visualizing particles being allowed to pass through said gates, the control voltage being applied to said electrode sections; and said charge removing means includes a photoconductive layer on which said electrode sections are provided, and a light source for projecting light on said photoconductive layer. 18. An image forming apparatus as set forth in claim 1, further comprising:a connecting circuit for connecting said visualizing particle carrier to a ground terminal of said image forming apparatus through a resistor with a limited resistance; and switching means, provided in said connecting circuit, for switching said connecting circuit so as to connect said visualizing particle carrier to the ground terminal when no voltage is applied to said visualizing particle carrier, while disconnecting when a voltage is applied to said visualizing particle carrier. 19. An image forming apparatus as set forth in claim 1, further comprising:a connecting circuit for connecting said visualizing particle carrier to said counter electrode through a resistor with a limited resistance; and switching means, provided in said connecting circuit, for switching said connecting circuit so as to connect said visualizing particle carrier to said counter electrode when said flight electric field-use voltage is not applied to said visualizing particle carrier, while disconnecting when said flight electric field-use voltage is applied to said visualizing particle carrier. 20. The image forming apparatus as set forth in claim 1, wherein said control means controls said power supply means and said control voltage applying means, so that during an operational period while the flight electric field-use voltage and the control voltage are applied, a flight suppressing voltage in the control voltages is first applied to said control electrode, the flight suppressing voltage for suppressing the flight of the visualizing particles, and thereafter the flight electric field-use voltage is applied across said visualizing particle carrier and said counter electrode.
21. The image forming apparatus as set forth in claim 20, wherein said control means control said power supply means and said control voltage applying means, so that, when the application of the flight electric field-use voltage and the control voltage is suspended, the flight suppressing voltage as the control voltage is applied to said control electrode, then the application of the flight electric field-use voltage is suspended, and thereafter the application of the flight suppressing voltage is suspended.
22. An image forming apparatus as set forth in claim 1, further comprising a recording medium transport route through which a recording medium is transported while being in contact with said counter electrode, the recording medium transport route being provided between said control electrode and said counter electrode, the visualizing particles adhering to the recording medium.
FIG. 1(a) is a timing chart of potentials of respective members of an image forming apparatus as one embodiment example, and FIG. 1(b) is another timing chart of potentials of respective members of the image forming apparatus.
FIG. 2 is a schematic front view illustrating the arrangement of the whole image forming apparatus.
FIG. 3 is an enlarged view illustrating an image forming unit illustrated in FIG. 2.
FIG. 4 is an enlarged view illustrating a portion around an image forming head illustrated in FIG. 3.
FIG. 5(a)is a perspective view illustrating an example of a control electrode illustrated in FIG. 4, and FIG. 5(b) is a cross-sectional view illustrating the control electrode illustrated in FIG. 5(a).
FIG. 6 is a perspective view illustrating a control electrode which has the same configuration as that illustrated in FIG. 5(a) but utilizes a different type of wires.
FIG. 7(a) is a perspective view illustrating another example of the control electrode illustrated in FIG. 5(a), and FIG. 7(b) is a cross-sectional view illustrating the control electrode illustrated in FIG. 7(a).
FIG. 8 is an enlarged perspective view illustrating control grids of the control electrode illustrated in FIG. 7(a).
FIG. 9(a) is a perspective view illustrating another example of the control electrode illustrated in FIG. 5(a), and FIG. 9(b) is a cross-sectional view illustrating the control electrode illustrated in FIG. 9(a).
FIG. 10 is an enlarged perspective view illustrating plate electrodes of the control electrode illustrated in FIG. 9(a).
FIG. 11 is a block diagram illustrating voltage applying parts for applying voltages to the image forming unit of the image forming apparatus illustrated in FIG. 2, and a control unit for controlling the voltage applying parts.
FIG. 12 is a schematic front view illustrating a structure of an image forming unit provided in an image forming apparatus in accordance with another embodiment of the present invention.
FIG. 13 is a timing chart of potentials of respective members of the image forming unit illustrated in FIG. 12, the potentials thereof during the image forming operation including the cleaning process.
FIG. 14 is a view illustrating a waveform of a voltage applied to the counter electrode during the cleaning process illustrated in FIG. 13.
FIG. 15 is a perspective view illustrating a control electrode provided in an image forming apparatus in accordance with another embodiment of the present invention.
FIG. 16 is a circuit diagram of a switching circuit illustrated in FIG. 15.
FIG. 17 is a timing chart of potentials of respective members of the image forming apparatus provided with the control electrode illustrated in FIG. 15, the potentials thereof during the image forming operation including the charge removing process for removing charges from the control electrode.
FIG. 18 is a perspective view illustrating another example of the control electrode illustrated in FIG. 15.
FIG. 19 is a perspective view illustrating still another example of the control electrode illustrated in FIG. 15.
FIG. 20 is a perspective view illustrating still another example of the control electrode illustrated in FIG. 15.
FIG. 21 is a schematic front view illustrating a structure of an image forming unit provided in an image forming apparatus in accordance with another embodiment of the present invention.
FIG. 22 is a perspective view illustrating the control electrode illustrated in FIG. 21.
FIG. 23 is a timing chart of potentials of respective members of the image forming unit illustrated in FIG. 21, the potentials thereof during the image forming operation including the charge removing process for removing charges from the control electrode.
FIG. 24 is a circuit diagram illustrating a charge removing circuit for a toner carrier provided in an image forming apparatus in accordance with still another embodiment of the present invention.
FIG. 25 is a circuit diagram illustrating a charge removing circuit for a counter electrode provided in an image forming apparatus in accordance with still another embodiment of the present invention.
FIG. 26 is a view illustrating an arrangement of a whole image forming apparatus in accordance with still another embodiment of the present invention.
FIG. 27 is a schematic front view illustrating the arrangement of the image forming unit provided in the image forming apparatus illustrated in FIG. 26.
FIG. 28 is a block diagram illustrating voltage applying parts for applying voltages to the image forming unit of the image forming apparatus illustrated in FIG. 26, and a control unit for controlling the voltage applying parts.
FIG. 29 is a schematic front view illustrating an arrangement of an image forming unit provided in an image forming apparatus in accordance with another embodiment of the present invention.
FIG. 30(a) is a perspective view illustrating a portion of the control electrode illustrated in FIG. 29, and FIG. 30(b) is a cross-sectional view of the portion illustrated in FIG. 30(a) when it is sectioned along the A--A arrow line.
FIG. 31 is a schematic front view illustrating an arrangement of an image forming unit provided in an image forming apparatus in accordance with still another embodiment of the present invention.
FIG. 32(a) is an enlarged view of a portion of the counter electrode illustrated in FIG. 31, and FIG. 32(b) is an equivalent circuit schematic of the portion of the counter electrode illustrated in FIG. 32(a).
FIG. 33 is a graph illustrating potential gradation in the portion of the counter electrode illustrated in FIG. 32(a).
FIG. 34 is a graph illustrating strength gradation of an electric field around the counter electrode illustrated in FIG. 32(a).
FIG. 35 is a schematic front view illustrating an arrangement of an image forming unit provided in an image forming apparatus in accordance with still another embodiment of the present invention.
FIG. 36 is an enlarged view illustrating the counter electrode illustrated in FIG. 35.
FIG. 37 is a front view illustrating another example of the counter electrode illustrated in FIG. 36.
FIG. 38 is a front view illustrating still another example of the counter electrode illustrated in FIG. 36.
The following description will explain one embodiment of the present invention referring to FIGS. 1 through 11.
As shown in FIG. 2, an image forming apparatus of the present embodiment includes an image forming unit 1 provided with a toner supplying part 2, an image forming head 3, and a counter electrode 4. The image forming unit 1 forms an image in accordance with image signals on a sheet 5 which is a recording medium, by using toner 18 which is visualizing particles.
As shown in FIG. 3 illustrating the image forming unit 1, the toner supplying part 2 is equipped with a toner storing tank 17 which stores toner 18 as visualizing particles. Inside the toner storing tank 17, there are provided an agitating roller 19 for agitating the toner 18 thereby charging it, and a toner carrier 20, which is a visualizing particle carrier in a cylindrical shape, for carrying the toner 18 by electric force, magnetic force, or both of them. The toner carrier 20 carries the toner 18 on the circumferential surface thereof and transports while rotating. The toner storing tank 17 has an opening 17a through which the toner 18 is supplied. The opening 17a is disposed between the toner carrier 20 and the counter electrode 4.
The counter electrode 4 is provided vis-a-vis the toner carrier 20, and the image forming head 3 is provided between the counter electrode 4 and the toner carrier 20. The sheet 5 is transported between the image forming head 3 and the counter electrode 4 so that the sheet 5 is in contact with the surface of the counter electrode 4. Note that though the counter electrode 4 illustrated in FIG. 3 is in a plate-like shape, the counter electrode 4 may have any shape, such as the plate-like shape, or a cylindrical shape as shown in FIG. 2.
The control electrode 22, as shown in FIG. 4, has gates 22a, which are a plurality of holes for allowing the toner 18 to pass through the control electrode 22. The image forming unit 1 controls a voltage to be applied to the control electrode 22 and a voltage applied across the counter electrode 4 and the toner carrier 20, thereby controlling an electric field around the image forming head 3. With this arrangement, the toner 18 carried by the toner carrier 20 is caused to selectively fly in the direction to the counter electrode 4, so that a toner image is directly formed on the sheet 5 on the counter electrode 4. Note that the electric field around the image forming head 3 is exerted on at least the toner carrier 20, the control electrode 22, the sheet 5 on the counter electrode 4, and the counter electrode 4.
The control electrode 22 may have any of the arrangements shown in FIGS. 5(a) and 5(b), FIG. 6, FIGS. 7(a) and 7(b), FIG. 8, FIGS. 9(a) and 9(b), and FIG. 10. A control electrode 22 shown in FIGS. 5(a) and 5(b) is arranged so that a plurality of conductive wires 24 are provided in parallel on the both sides of an insulating substrate 23 as an insulating layer, the conductive wires 24 on one side and those on the other side being provided in directions perpendicular each other, thereby forming a net-shaped matrix. Note that FIG. 5(b) is a cross-sectional view of the control electrode 22 shown in FIG. 5(a) . The wires 24 on one side and those on the other side form, at intersections thereof, a plurality of control grids 25 which are electrode sections. Each wire 24 is connected to a leader line 26, through which control voltages are supplied from a control voltage applying part 33 shown in FIG. 11 to each wire 24, therefore, to each control grid 25. A toner passing hole is formed in the insulating substrate 23 in each portion surrounded by the control grids 25. The toner passing holes are equivalent to the above-mentioned gates 22a, thereby being hereinafter referred to as gates 22a.
A control electrode 22 shown in FIG. 6, like the electrode 22 described above, has two-layered wires 27 forming a net-shaped matrix. Between the layers of the wires 27, there is provided an insulating substrate 23 as described above (not shown). The wires 27 are folded at the edges of the insulating substrate 23, and gates 22a are formed in portions surrounded by the wires 27 of the two layers.
A control electrode 22 shown in FIGS. 7(a) and 7(b) is arranged so that a plurality of control grids 25 composed of conductive rings are regularly provided on one side of an insulating substrate 23. A control electrode 22 shown in FIG. 8 is arranged likewise. Note that FIG. 7(b) is a cross-sectional view of the electrode 22 shown in FIG. 7(a). Control grids are respectively connected to leader lines 26, through which a control voltage is supplied to each control grid 25. Gates 22a as described above are formed in the insulating substrate 23.
A control electrode shown in FIGS. 9(a) and 9(b) is arranged so that a plurality of conductive plate electrodes 28 are provided in parallel on the both sides of an insulating substrate 23. A control electrode 22 shown in FIG. 10 is arranged likewise. Note that the insulating substrate 23 is omitted in FIG. 10. The plate electrodes 28 on one side and those on the other side are provided in respective directions perpendicular each other. There are provided holes 28a in line on each plate electrode 28, so that holes 28a on the plate electrodes 28 on one side are provided vis-a-vis those on the other side, whereby a plurality of control grids 25 are formed. Note that gates 22a as mentioned above are formed in the insulating substrate 23.
An image forming apparatus in accordance with the present embodiment is provided with a toner carrier power supply part 31 and a counter electrode power supply part 32 which compose power supply means, and a control voltage applying part 33 which is control voltage supplying means, as shown in FIG. 11. Operations conducted by the toner carrier power supply part 31, the counter electrode power supply part 32, and the control voltage applying part 33 are controlled by the control unit 16. The toner carrier power supply part 31 supplies a bias potential E1 (see FIG. 1(a)) and others to the toner carrier 20. The counter electrode power supply part 32 supplies an operating potential E2 and others to the counter electrode 4. The control voltage applying part 33 supplies a flight suppressing voltage E3, a toner flight voltage E4 (see FIG. 1(a)), and others to the control electrode 22.
The following description will depict a motion sequence for image formation of the image forming apparatus in accordance with the above-mentioned arrangement of the present embodiment. In the image forming apparatus shown in FIG. 2, when a motor (not shown) of the image forming apparatus is actuated in response to an image formation start signal sent from a host computer (not shown), one of the sheets 5 in the sheet cassette 6 is sent out by the feed roller 7. When the sheet detecting member 8 is pushed up by the sheet 5 thus sent out, the feed sensor 9 detects a sheet feeding state, thereby issuing a detection signal. With the detection signal, the control unit 16 is informed of that the sheet 5 has been supplied in a normal state.
The transportation of the sheet 5 is once suspended when the sheet 5 reaches the register roller 10 not in motion. On the other hand, in response to the detection signal from the feed sensor 9, the control unit 16 starts issuing an image signal to be used in the image formation, in accordance with an image formation signal sent from the host computer. In the next stage, the control unit 16 converts the image signal to an electric signal to be sent to the control electrode 22 provided in the image forming head 3. After converting a predetermined quantity of image signals, the control unit 16 actuates a motor which drives the register roller 10, so that the register roller 10 transports the sheet 5 to the position of the control electrode 22, namely, the image forming region 21 shown in FIG. 12. Note that the quantity of image signals to be converted is predetermined depending on the arrangement of the image forming apparatus.
During the image formation, after a power switch is turned on, the potentials of the respective parts in the image forming unit 1 are controlled at timings as shown in FIG. 1(a). To be more specific, on turning on the power switch, the control unit 16 is actuated, thereby causing the toner carrier power supply part 31, the counter electrode power supply part 32, and the control voltage applying part 33 to stand by. In this state, the counter electrode 4, the control electrode 22, and the toner carrier 20 have the same potential as that of a ground terminal of the image forming apparatus (the potential is hereinafter referred to as ground potential (GND)). Therefore, the toner 18 carried by the toner carrier 20 is by no means caused to fly toward the counter electrode 4.
Subsequently the flight suppressing voltage E3 for suppressing the flight of the toner from the toner carrier 20 to the counter electrode 4 is applied to the control electrode 22, which is followed by setting the potential of the counter electrode 4 to the operating potential E2. Note that the operating potential E2 causes an electric field to be generated between the toner carrier 20 an d the counter electrode 4 so that the electric field causes the toner 18 to fly from the toner carrier 20 toward the counter electrode 4. Thus, the potential of the counter electrode 4 is set to the operating potential E2 after the flight suppressing voltage E3 is applied to the control electrode 22 as described above. As a result, inappropriate flight of the toner 18 from the toner carrier 20 toward the counter electrode 4 is suppressed in the image forming apparatus of the present embodiment, even while the counter electrode 4 has the operating potential E2.
As described above, after the respective potentials of the counter electrode 4, the control electrode 22, and the toner carrier 20 are switched from the ground potential (GND) to the bias potential E1 of the toner carrier 20, the image forming process is carried out by using the bias potential E1 as a reference potential during the image formation. With the image forming process thus arranged, images of higher quality are yielded compared with the case where, as shown in FIG. 1(b), the respective potentials of the above three members are not switched to the bias potential E1 of the toner carrier 20. This has been confirmed by experiments. Note that it is possible to carry out the image forming process by setting the potentials as shown in FIG. 1(b) so as to prevent inappropriate flight of the toner 18, though it results in that the quality of obtained images may somewhat fall.
The following description will discuss another embodiment of the present invention, referring to FIGS. 12 through 14. The members having the same structure (function) as those in the above-mentioned embodiment will be designated by the same reference numerals and their description will be omitted.
An image forming apparatus in accordance with the present embodiment includes an image forming unit 1 shown in FIG. 12. The image forming unit 1 has a counter electrode 4 in a cylindrical shape, which is driven by a driving system (not shown) and rotates in a direction (indicated by an arrow in the figure) of transportation of a sheet 5 in synchronization with the transportation of the sheet 5 during image formation. The counter electrode 4 is provided with a cleaning blade 41, which is cleaning means for removing from the surface of the counter electrode 4 foreign material adhering thereto. The cleaning blade 41 is provided so that one edge thereof contacts the surface of the counter electrode 4.
FIG. 13 illustrates a cleaning process which is conducted in the image forming apparatus of the present embodiment before and after the image forming process. The cleaning process is controlled by the control unit 16 as cleaning process control means. The cleaning process is carried out by applying an alternating voltage shown in FIG. 14 to the counter electrode 4 in the state before and after the image forming process, the state wherein the counter electrode 4 has the bias potential E1. The reason why the alternating voltage is employed is that the charged toner 18 does not have a fixed polarity, either positive or negative. The alternating voltage has a peak value set to the operating potential E2 and a bottom value set to the ground potential (GND) of the image forming apparatus. Note that the voltage applied to the counter electrode 4 during the cleaning process is not restricted to the voltage shown in FIG. 14, but it may be an AC voltage having a sinusoidal waveform.
Here, it is possible to cause the foreign material 42 adhering to the control electrode 22 to fly and adhere to the counter electrode 4 by applying the alternating voltage shown in FIG. 14 to the counter electrode 4 during the above-described cleaning process. The foreign material 42 on the counter electrode 4 is removed by the cleaning blade 41, as mentioned above. It is thus possible to prevent such foreign material 42 on the control electrode 22 from adversely affecting the flight of the toner 18, and therefore images of high quality are obtained.
The following description will discuss still another embodiment of the present invention, referring to FIGS. 3, 15 through 20. The members having the same structure (function) as those in the above-mentioned embodiment will be designated by the same reference numerals and their description will be omitted.
An image forming apparatus in accordance with the present embodiment has an image forming unit 1, for example, as shown in FIG. 3, and an image forming head 3 provided therein is provided with a control electrode 51 shown in FIG. 15. The control electrode 51 is composed of a insulating substrate 23, ring-shaped control grids 25, and two resistive layers 52. The control grids 25 are regularly provided on one surface of the insulating substrate 23, and one resistive layer 52 is provided on the same surface so that the control grids 25 are buried under the resistive layer 52. The other resistive layer 52 is provided on the other side of the insulating substrate 23. Therefore, the control electrode 51 has the same configuration as the control electrode 22 shown in FIGS. 7(a) and 7(b), and FIG. 8, except that the control electrode 51 is provided with the resistive layers 52. The resistive layers 52 are realized by using insulating plastics such as polyimide whose resistivity is reduced by diffusing carbon thereon.
Regarding the requisite (1), in the case where the resistance of the resistive layers 52 is greater than the surface resistance of the insulating substrate 23, the resistive layers 52 hinder the unnecessary electric charges accumulated on the surface of the control electrode 51 from coming off, thereby causing an adverse effect. Therefore, such an adverse effect is avoided by satisfying the requisite (1). Generally, an insulating substance has a surface resistance of 1014 Ω through 1017 Ω. Therefore, the requisite (1) is satisfied by setting an upper limit of the resistance of the resistive layers 52 to around 1010 Ω through 1012 Ω, which is 3 through 4 orders below the surface resistance of the insulating substance. On the other hand, the lower limit of the resistance of the resistive layers 52 depends on the capacitance between the control grids 25, the voltage control cycle of the control electrode 51, and the like.
Here, from a viewpoint of the time constant, the following description will examine a lower limit of the resistance which the resistive layers 52 are required to have so that the unnecessary electric charges are not caught by the resistive layers 52 and released in a time span sufficiently longer than the control cycle of the control electrode 51, under conditions described below. A capacitance of control grids 25 in a control electrode for use in an apparatus with a resolution of 600 dpi is substantially not more than 1 pF. When the control electrode 51 has a voltage control cycle of 40 kHz, the resistance which the resistive layers 52 are required to have is 2.5�107 Ω. Therefore, the lower limit of the resistance of the resistive layers 52 is set to around 1010 Ω through 1011 Ω, which is satisfactorily great, being 3 through 4 orders above the resistance derived from the capacitance of the control grids 25 and the voltage control cycle of the control electrode 51. Therefore, under the above conditions, the surface of the control electrode 51 is discharged in accordance with the function EXP(-t/a), by setting the resistance of the resistive layers 52 to around 1010 Ω through 1011 Ω.
With the described arrangement, a process for removing electric charges from the control electrode 51 is carried out under the control of the control unit 16 before and after the image forming process, as shown in FIG. 17. Note that voltages for the image formation applied to the counter electrode 4, the control electrode 51, and the toner carrier 20 are controlled as described above with reference to FIG. 1.
When the charged toner and dust adhere to the control electrode 51, the surface potential of the control electrode 51 changes, as shown in FIG. 17. Therefore, the charge removing process is carried out before the image forming process, when the control electrode 51 has a potential set to the bias potential E1 of the toner carrier 20. During the charge removing process, the voltage applied to the control line 56 is switched from a low level to a high level and is kept to the high level for a predetermined period of time, thereby turning on the lead switch 54 and causing the resistive layers 52 of the control electrode 51 to be connected to the toner carrier 20. Here, the electric charges adhering to the control electrode 51, which have spread over the resistive layers 52, are caused to move from the resistive layers 52 to the toner carrier 20. As a result, electric charges of the control electrode 51 are removed. Therefore, accurate control of the voltage applied to the control electrode 51 can be achieved, ensuring that images of high quality are obtained.
Note that the control electrode 51 may have the same configuration as that of a control electrode 61 shown in FIG. 18, which is arranged so that only one resistive layer 52 is applied on a surface of the insulating substrate 23 where the control grids 25 are not provided, though the control electrode 51 shown in FIG. 15 has the two resistive layers 52 provided on both sides of an insulating substrate 23. In the case of the control electrode 61, it is not necessary to satisfy the requisite (2) since the resistive layer 52 is not in contact with the control grids 25.
Furthermore, a control electrode 71 shown in FIG. 19 may substitute for the control electrode 51. The control electrode 71 has the same configuration as that of the control electrode 51 shown in FIG. 15 except that the surface of the insulating substrate 23 where the control grids 25 are not provided does not have the resistive layer 52. In short, the control electrode 71 is arranged so that the resistive layer 52 is in contact with the control grids 25. Therefore, the unnecessary electric charges adhering to the insulating substrate 23 reach the control grids 25 through the resistive layer 52, and are released through the circuits connected to the control grids 25, for example, the control voltage applying part 33, thereby resulting in that the unnecessary electric charges are removed from the control electrode 71. In this case, the control grids 25 are connected to, for example, a ground terminal of the image forming apparatus through the control voltage applying part 33 in the stand-by state prior to the image forming operation, as shown in FIG. 1(a). This simplifies the arrangement, since it is not necessary to connect the resistive layer 52 to the toner carrier 20 through the switching circuit 53.
Furthermore, a control electrode 81 shown in FIG. 20 may substitute for the control electrode 51. The control electrode 81 is arranged so that the control grids 25 are formed over the resistor layer 52 as a substrate, instead of the insulating substrate 23.
Moreover, the control electrodes 51, 61, 71, and 81 may have the control grids in accordance with any of the arrangements shown in FIGS. 5(a) and 5(b), and FIG. 6 wherein the wires 24 and 27 are employed respectively, and the arrangements shown in FIGS. 9(a) and 9(b), and FIG. 10 wherein the plate electrodes 28 are employed.
The following description will discuss still another embodiment of the present invention, with reference to FIGS. 21 through 23. The members having the same structure (function) as those in the above-mentioned embodiment will be designated by the same reference numerals and their description will be omitted.
An image forming apparatus of the present embodiment is provided with, for example, an image forming unit 1 shown in FIG. 21, which has an image forming head 3 provided with a control electrode 91 shown in FIG. 22. The control electrode 91 is composed of an insulating substrate 23, ring-shaped control grids 25, and two photoconductive layers 92. The control grids 25 are regularly provided on one surface of the insulating substrate 23, and one of the photoconductive layers 92 is formed so that the control grids 25 are buried under the photoconductive layer 92. The other photoconductive layer 92 is formed on the other surface of the insulating substrate 23. In short, the control electrode 91 has the same configuration as that of the control electrode 22 shown in FIGS. 7(a) and 7(b), and FIG. 8, except that the control electrode 91 is provided with the photoconductive layers 92. The photoconductive layers 92, for example, have insularity in an ordinary state, while the same have a smaller resistance when light is projected thereon. The photoconductive layers 92 are respectively connected to a toner carrier 20 through a switching circuit 53.
As shown in FIG. 21, there are provided, for example, four light sources 93 in the vicinity of the control electrode 91, so that light is projected on the photoconductive layers 92. The turning on/of f of the light sources 93 is controlled by the control unit 16. Note that the number and positions of the light sources 93 are not specified, provided that the photoconductive layers 92 are irradiated by the same.
With the described arrangement, a charge removing process for the control electrode 91 is carried out under the control of the control unit 16 before and after the image forming process, as shown in FIG. 23. Note that voltages shown in the figure which are applied for image formation to the counter electrode 4, the control electrode 91, and the toner carrier 20 are controlled as described above with reference to FIG. 1.
Note that the control electrode 91 may also have any of the following configurations: the same configuration as that of the control electrode 61 shown in FIG. 18 except that the photoconductive layer 92 substitutes for the resistive layer 52; the same configuration as that of the control electrode 71 shown in FIG. 19 except that the photoconductive layer 92 substitutes for the resistive layer 52; the same configuration as that of the control electrode 81 shown in FIG. 20 except that the photoconductive layer 92 substitutes for the resistive layer 52.
The following description will discuss still another embodiment of the present invention, with reference to FIGS. 3 and 24. The members having the same structure (function) as those in the above-mentioned embodiment will be designated by the same reference numerals and their description will be omitted.
An image forming apparatus of the present embodiment has an image forming unit 1, wherein a toner carrier 20 is connected to a toner carrier power supply part 31 and a ground terminal of the image forming apparatus through a switching circuit 101 as a connecting circuit shown in FIG. 24. Note that the switching circuit 101 is applicable in the case where the bias potential E1 to be supplied to the toner carrier 20 has a negative polarity. The switching circuit 101 is provided with a relay 102 as switching means, which is composed of a normally closed contact 102a, a normally opened contact 102b, and a electromagnetic coil 102c.
With the foregoing arrangement, when the power switch of the image forming apparatus is turned on thereby actuating the toner carrier power supply part 31, the transistor 104 is turned on and the contact 102a is opened, while the contact 102b is closed. As a result, the toner carrier 20 is caused to have the bias potential E1 as shown in FIG. 1.
The following description will discuss still another embodiment of the present invention, with reference to FIGS. 3 and 25. The members having the same structure (function) as those in the above-mentioned embodiment will be designated by the same reference numerals and their description will be omitted.
An image forming apparatus of the present embodiment has, for example, an image forming unit 1 shown in FIG. 3, and the image forming unit 1 includes a switching circuit 111 shown in FIG. 25 as a connecting circuit. The switching circuit 111 is composed of a relay 112 which is switching means having the same configuration as that of the relay 102, resistors 113 and 115, a transistor 114 of an NPN type, and the above-described switching circuit 101. Note that the switching circuit 111 is applicable in the case where the toner 18 is negatively charged.
The relay 112 includes a normally closed contact 112a, a normally opened contact 112b, and an electromagnetic coil 112c. One terminal of the contact 112a is connected to a counter electrode 4 while the other terminal thereof is connected to a toner carrier 20 through the resistor 113. One terminal of the contact 112b is connected to a counter electrode power supply part 32 while the other terminal is connected to the counter electrode 4. One terminal of the electromagnetic coil 112c is connected to the counter electrode power supply part 32 while the other terminal thereof is connected to a corrector of the transistor 114. The transistor 114 has an emitter connected to the toner carrier power supply part 31 and a base connected to the counter electrode power supply part 32 through the resistor 115. The toner carrier 20 is connected to the toner carrier power supply part 31 through the switching circuit 101, as shown in FIG. 24.
With the described arrangement, when a voltage for causing the counter electrode 4 to have the operating potential E2 shown in FIG. 1 is outputted from the counter electrode power supply part 32, the transistor 114 is turned on, wherein the contact 112a is opened while the contact 112b is closed, thereby causing the counter electrode 4 to have the operating potential E2.
The following description will discuss still another embodiment of the present invention, with reference to FIGS. 26 through 28. The members having the same structure (function) as those in the above-mentioned embodiment will be designated by the same reference numerals and their description will be omitted.
An image forming apparatus of the present embodiment has a plate-shaped counter electrode 4 as shown in FIGS. 26 and 27. A control electrode 22 and the counter electrode 4 are provided so that the surfaces thereof are parallel. A sheet 5 is transported along a sheet transport route 29 between the control electrode 22 and the counter electrode 4 so that the sheet 5 contacts the surface of the counter electrode 4.
The control electrode 22 may have any of the configuration shown in FIG. 6, that shown in FIG. 8 and FIG. 7(b) which is a cross-sectional view of the configuration of FIG. 8, and that shown in FIG. 10 and FIG. 9(b) which is a cross-sectional view of the configuration of FIG. 10. Note that a cross-sectional view of the configuration shown in FIG. 6 is shown in FIG. 5(b). Furthermore note that insulating substrates are omitted in FIGS. 6, 8, and 10. The configurations of the control electrode 22 are as described above.
The counter electrode 4 includes an extension section 4a, as shown in FIG. 27. The extension section 4a is provided at least on the downstream side of a portion facing the image forming region 21 of the sheet transport direction, and extends in the sheet transport direction. In the present embodiment, the extension section 4a is provided only on the downstream side of the sheet transport direction, with a downstream-side section of the counter electrode 4 longer than an upstream-side section of the same. The extension section 4a is arranged so as to have a length two times as long as that of a main section of the counter electrode 4, the main section being a section from the upstream-side end of the counter electrode 4 to the point indicated by the broken line in the figure. The downstream-side end portion of the extension section 4a reaches in the vicinity of the fixing part 11. Besides, the downstream-side end portion of the extension section 4a extends farther in the sheet transport direction than the downstream-side end portion of the control electrode 22, so that it is prevented that an electric field generated by the control electrode 22 adversely affects the condition of the toner 18 held on a sheet 5. Note that the downstream-side end portion of the control electrode 22 is a portion including the leader lines 26 connected to the control grids 25, namely, a portion to which the control voltage is applied. In the present embodiment, the foregoing downstream-side end portion of the control electrode 22 is shown as an end portion of the image forming head 3 in FIG. 27. The length of the counter electrode 4 is set longer as the image forming apparatus has a higher speed of the image forming process.
The image forming apparatus of the present embodiment is provided with a control unit 201, a flight electric field-use power supply part 202, and a control voltage applying part 203, as shown in FIG. 28. The flight electric field-use power supply part 202 applies a voltage across the toner carrier 20 and the counter electrode 4, the voltage for generating an electric field which causes the toner 18 to fly from the toner carrier 20 to the counter electrode 4. The control voltage applying part 203 applies a control voltage to the control electrode 22 in accordance with an image signal. The operations of the described two members are controlled by the control unit 201.
The following description will discuss the image formation conducted by the image forming apparatus of the present embodiment which has the described arrangement, with reference to FIGS. 26 and 27. The sheet 5 is transported to the image forming region 21, as described in the first embodiment. In the next stage, the control voltage in accordance with the image signal is applied by the control voltage applying part 203 to the control electrode 22. At the same time, a voltage is applied by the flight electric field-use power supply part 202 across the toner carrier 20 and the counter electrode 4, thereby generating an electric field in a direction such that the toner 18 is caused to fly from the toner carrier 20 toward the counter electrode 4. As a result, the electric field in the vicinity of the image forming head 3 is controlled in accordance with the image signal, thereby causing a toner image to be formed, in accordance with the image signal, on the sheet 5. The sheet 5 is transported over the counter electrode 4 to the fixing part 11, by which the toner image on the sheet 5 is fixed thereto.
According to the arrangement shown in FIG. 27, the extension section 4a is provided on the downstream side of the image forming region 21 of the sheet transport direction and reaches in the vicinity of the fixing part 11 thereby not allowing the electric charges held by the sheet 5 to decrease but increasing the supply of electric charges to the sheet 5. Therefore, the toner 18 caused to adhere to the sheet 5 in the image forming region 21 is maintained thereon until the toner 18 is fixed on the sheet 5 by the fixing part 11. Thus, the ability of keeping the toner 18 on the sheet 5 is enhanced.
The following description will discuss another embodiment of the present invention, with reference to FIGS. 29 and 30. The members having the same structure (function) as those in the above-mentioned embodiment will be designated by the same reference numerals and their description will be omitted.
An image forming apparatus in accordance with the present embodiment has an image forming unit 1, which, as shown in FIG. 27, includes a shield plate 204 as a conductive shield member. The shied plate 204 is provided on the downstream side of an image forming region 21 in the sheet transport direction along the surface of an image forming head 3 which faces a counter electrode 4. The portion of the image forming head 3 facing the shield plate 204 corresponds to, for example, the portion where leader lines 26 are provided, the leader lines 26 for supplying a voltage to control grids 25 on the control electrode 22. The portion is shown in FIG. 30(a), and FIG. 30(b) which is a cross-sectional view obtained by cutting the image forming head 3 shown in FIG. 30 along the A--A line. Therefore, the voltage applied to the control grids 25 is also applied to the above-mentioned portion. Note that the shield plate 204 is provided on a surface of an insulating substrate 23, which is opposite to the surface where the control grids 25 are provided.
With the above arrangement wherein the shield plate 204 is provided in addition to the configuration shown in FIG. 27, the movements of the toner 18 on the sheet 5 is further surely prevented.
The following description will discuss another embodiment of the present invention with reference to FIGS. 31 through 34. The members having the same structure (function) as those in the above-mentioned embodiment will be designated by the same reference numerals and their description will be omitted.
As shown in FIG. 31, an image forming apparatus of the present embodiment has an image forming unit 1 provided with a counter electrode 211 instead of the above-mentioned counter electrode 4. The counter electrode 211 has a conductive area 211a which is provided vis-a-vis the control electrode 22, and a high-resistive area 211b which is provided on the downstream side of the conductive area 211a in the sheet transport direction. An end portion of the high-resistive area 211b reaches in the vicinity of the fixing part 11. The other end portion of the high-resistive area 211b is electrically connected to the conductive area 211a. The conductive area 211a is connected to the flight electric field-use power supply part 202, while the downstream-side end portion of the high-resistive area 211b is connected to the ground terminal of the image forming apparatus. A view zooming in the arrangement around the counter electrode 211 is shown in FIG. 32(a), and an equivalent schematics of FIG. 32(a) is shown in FIG. 32(b).
More specifically, during the transport of the sheet 5 along the sheet transport route 29, electric charges are supplied to the rear surface of the sheet 5 by the counter electrode 211, and the toner 18 on the surface of the sheet 5 is held thereon, without moving, due to the electric charges. When a predetermined voltage is applied to the counter electrode 211 by the flight electric field-use power supply part 202, the conductive area 211a of the counter electrode 211 has a predetermined potential in accordance with the predetermined voltage. On the other hand, the high-resistive area 211b has a potential which, as shown in FIG. 33, gradually decreases as the voltage decreases from the upstream-side end to the downstream-side end, finally falling to the ground potential of the image forming apparatus at the downstream-side end portion. With such a gradation of the potential of the counter electrode 211, the electric field of the counter electrode 211 has a strength greater than that of the flight electric field in the image forming region 21, and the strength gradually falls from the upstream-side end to the downstream end of the high-resistive area 211b, as shown in FIG. 34. Therefore, when the sheet 5 comes off from the counter electrode 211 and is fed to the fixing part 11, an electric discharge does not occur between the sheet 5 and the counter electrode 211, thereby ensuring that movement of the toner 18 on the sheet 5 due to the shock of the discharge is avoided.
To be more specific, the electric charges applied by the counter electrode 211 to the rear surface of the sheet 5 contribute in keeping equilibrium with the electric charges of the toner 18 adhering to the surface of the sheet 5, and the potential of the sheet 5 as a whole becomes 0 V under the condition that sufficient electric charges are supplied to the sheet 5. Therefore, in the case where the downstream-side end portion of the high-resistive area 211b has the ground potential, which is 0 V, no potential difference occurs between the sheet 5 and the downstream-side end portion of the high-resistive area 211b, thereby causing no discharge between the two when the sheet 5 comes of f from the high-resistive area 211b. When a drastic change occurs in the potential of the counter electrode 211 thereby causing the downstream-side end portion of the counter electrode 211 to have a ground potential, a discharge may possibly occur due to the drastic change in the potential. In contrast, in the case where the potential of the conductive area 211a gradually decreases in the high-resistive area 211b, finally to the ground potential at the downstream-side end portion of the high-resistive area 211b, namely, the downstream-side end portion of the counter electrode 211, such a problem as described above by no means occurs.
The following description will discuss still another embodiment of the present invention with reference to FIGS. 35 through 38. The members having the same structure (function) as those in the above-mentioned embodiment will be designated by the same reference numerals and their description will be omitted.
As shown in FIG. 35, an image forming apparatus of the present embodiment has an image forming unit 1, which is provided with a counter electrode 221 instead of the counter electrode 4 of the foregoing embodiments. The counter electrode 221 is provided with an endless resistive belt 222, and first through third conductive rollers 223 through 225 which support the conductive belt 222. The first through third conductive rollers 223 through 225 are lined up in the sheet transport direction. The first conductive roller 223 is disposed on the upstream side of the sheet transport direction, while the second conductive roller 224 on the downstream side, so as to rotatably support the resistive belt 222. The third conductive roller 225 is provided between the first conductive roller 223 and the second conductive roller 224, so that the third conductive roller 225 contacts the rear surface of the resistive belt so that a section between the first and third conductive rollers 223 and 225 faces the region where the sheet transport is carried out (hereinafter referred to as sheet transport section). A part of the sheet transport section of the resistive belt 222 which is between the first conductive roller 223 and the third conductive roller 225 is provided parallel to the control electrode 22, while the other part of the sheet transport section of the resistive belt 222, which is between the third conductive roller 225 and the second conductive roller 224, is inclined so that the second conductive roller 224 is lower than the third conductive roller 225.
As shown in FIG. 36, the first and third conductive rollers 223 and 225 are connected to the flight electric field-use power supply part 202 of the above-described embodiments, while the second conductive roller 224 is connected to the ground terminal of the above-described embodiments, which is provided in the image forming apparatus. Therefore, when a predetermined counter electrode voltage is applied to the first conductive roller 223 and the third conductive roller 225 by the flight electric field-use power supply part 202 during the image formation, the part of the resistive belt 222 between the first conductive roller 223 and the third conductive roller 225, namely, the part corresponding to the image forming region 21, becomes a uniform potential section 221a, which has a uniform potential causing the flight electric field. On the other hand, the part between the third and second conductive rollers 225 and 224 becomes a potential decreasing section 221b, which has a potential gradually decreasing from the third conductive roller 225 to the second conductive roller 224 and finally falling to the ground potential.
Note that the counter electrode 221 may have the same arrangement as that of the counter electrode 61 of FIG. 37. In the counter electrode 61, the first and second conductive rollers 223 and 224 have the same diameter, while the third conductive roller 225 has a smaller diameter. With the described arrangement, it is not necessary to incline the resistive belt 222 in the potential decreasing region. It is possible to dispose the resistive belt 222 horizontally through the uniform potential section and the potential decreasing section.
Furthermore, the counter electrode 221 may have the same arrangement as that of the counter electrode 241 of FIG. 38. A conductive brush 242 is provided in the counter electrode 2 41 in t he place of the third conductive roller 225, so that the conductive brush 242 is provided in contact with the rear surface of the resistive belt 222.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS4751532 *Apr 24, 1987Jun 14, 1988Fuji Xerox Co., Ltd.Thermal electrostatic ink-jet recording headUS4860036 *Jul 29, 1988Aug 22, 1989Xerox CorporationDirect electrostatic printer (DEP) and printhead structure thereforUS5036341 *Nov 30, 1988Jul 30, 1991Ove Larsson Production AbMethod for producing a latent electric charge pattern and a device for performing the methodUS5095322 *Oct 11, 1990Mar 10, 1992Xerox CorporationAvoidance of DEP wrong sign toner hole clogging by out of phase shield biasUS5128695 *Apr 5, 1991Jul 7, 1992Brother Kogyo Kabushiki KaishaImaging material providing deviceUS5214451 *Dec 23, 1991May 25, 1993Xerox CorporationToner supply leveling in multiplexed DEPUS5329307 *Feb 12, 1993Jul 12, 1994Mita Industrial Co., Ltd.Image forming apparatus and method of controlling image forming apparatusUS5374949 *Jul 26, 1993Dec 20, 1994Kyocera CorporationImage forming apparatusUS5404155 *Nov 8, 1993Apr 4, 1995Brother Kogyo Kabushiki KaishaImage forming apparatus having an aperture electrode with controlled image potentialUS5477250 *Nov 15, 1993Dec 19, 1995Array Printers AbDevice employing multicolor toner particles for generating multicolor imagesUS5497175 *Jul 12, 1994Mar 5, 1996Brother Kogyo Kabushiki KaishaImage forming apparatus having aperture electrodes with lubricating layer thereonUS5504509 *Jul 12, 1994Apr 2, 1996Brother Kogyo Kabushiki KaishaImage forming apparatus with specific aperture electrode unitUS5523777 *Mar 18, 1994Jun 4, 1996Brother Kogyo Kabushiki KaishaAperture electrode with overlying charge memberUS5614932 *Apr 23, 1996Mar 25, 1997Brother Kogyo Kabushiki KaishaImage forming apparatusUS5625392 *Mar 4, 1994Apr 29, 1997Brother Kogyo Kabushiki KaishaImage forming device having a control electrode for controlling toner flowUS5659344 *Apr 7, 1995Aug 19, 1997Brother Kogyo Kabushiki KaishaImage forming apparatus having a plurality of aperature electrodes and intermintent openings forming an electrostatic fieldUS5708464 *Nov 4, 1996Jan 13, 1998Agfa-Gevaert N.V.Device for direct electrostatic printing (DEP) with "previous correction"DE4038083A1 *Nov 29, 1990Jun 27, 1991Kyocera CorpImaging system for copier or laser printer - has electromagnetically controlled toner slits controlling transfer of toner to copy sheetDE4338992A1 *Nov 15, 1993May 26, 1994Array Printers AbVorrichtung zur Darstellung mehrfarbiger Bilder* Cited by examinerNon-Patent CitationsReference1 *Published Unexamined Japanese Patent Application No. 104769/1983, Published Jun., 1983.2 *Published Unexamined Japanese Patent Application No. 3972/1994, Published Jan., 1994.* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS6042220 *Mar 2, 1998Mar 28, 2000Sharp Kabushiki KaishaImage forming device forming an image on a recording medium using flying developerUS6257709 *Jun 9, 1998Jul 10, 2001Sharp Kabushiki KaishaImage forming apparatusUS7506974 *Sep 27, 2005Mar 24, 2009Fujifilm CorporationImage forming apparatus* Cited by examinerClassifications U.S. Classification347/55, 399/55, 399/291International ClassificationB41J2/415, G03G15/34Cooperative ClassificationB41J2/4155, G03G15/346European ClassificationB41J2/415B, G03G15/34S1Legal EventsDateCodeEventDescriptionSep 18, 1996ASAssignmentOwner name: SHARP KABUSHIKI KAISHA, JAPANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:FUJITA, HIROKAZU;REEL/FRAME:008267/0916Effective date: 19960904Mar 28, 2002FPAYFee paymentYear of fee payment: 4Mar 22, 2006FPAYFee paymentYear of fee payment: 8May 24, 2010REMIMaintenance fee reminder mailedOct 20, 2010LAPSLapse for failure to pay maintenance feesDec 7, 2010FPExpired due to failure to pay maintenance feeEffective date: 20101020RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services