CA1042196A - Device for the development of an electrostatic charge image - Google Patents
Device for the development of an electrostatic charge imageInfo
- Publication number
- CA1042196A CA1042196A CA222,033A CA222033A CA1042196A CA 1042196 A CA1042196 A CA 1042196A CA 222033 A CA222033 A CA 222033A CA 1042196 A CA1042196 A CA 1042196A
- Authority
- CA
- Canada
- Prior art keywords
- cylinder
- powder
- rear wall
- tray
- magnet
- 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
- G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
- G03G15/09—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer using magnetic brush
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G2215/00—Apparatus for electrophotographic processes
- G03G2215/08—Details of powder developing device not concerning the development directly
- G03G2215/0802—Arrangements for agitating or circulating developer material
- G03G2215/0816—Agitator type
- G03G2215/0827—Augers
- G03G2215/083—Augers with two opposed pitches on one shaft
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Dry Development In Electrophotography (AREA)
- Magnetic Brush Developing In Electrophotography (AREA)
Abstract
A B S T R A C T
A device for developing an electrostatic charge image by means of a developing powder comprising magnetizable carrier particles and toner particles comprises a reservoir which contains a quantity of the powder and a cylinder mounted for rotation near a rear wall of the reservoir. The cylinder cooperates with a first permanent magnet disposed above the cylinder to form a magnetic brush. A support sheet carrying the electrostatic image is transported over a portion of the cylinder where the electrostatic image is converted into a powder image by the magnetic brush. A second magnet is mounted on or close to the outside of the rear wall of the reservoir.
A device for developing an electrostatic charge image by means of a developing powder comprising magnetizable carrier particles and toner particles comprises a reservoir which contains a quantity of the powder and a cylinder mounted for rotation near a rear wall of the reservoir. The cylinder cooperates with a first permanent magnet disposed above the cylinder to form a magnetic brush. A support sheet carrying the electrostatic image is transported over a portion of the cylinder where the electrostatic image is converted into a powder image by the magnetic brush. A second magnet is mounted on or close to the outside of the rear wall of the reservoir.
Description
10~'~19~
This invention relates to a device for the development of an electrostatic charge image by means of a developing powder, comprising magnetizable carrier particles and toner particles.
Such a device is known from United States Patent No. 3,639,051;
which issued on February 11, 1972 in the name of Savin Business Machines Corporation.
This device is provided with a reservoir having a bottom, two side walls and a front and rear wall, which reservoir can contain a quantity of the developing powder mentioned, a cylinder rotatably mounted near the rear wall between the side walls of the reservoir and a magnet cooperating with this cylinder to a magnetic brush, means for transporting the support bearing the charge image along this cylinder, one or more mixing members mounted in bearings near the bottom of the reservoir between its side walls and means for replenishing the amount of developing powder in the reservoir.
Such teveloping devices are for instance applied in electro-photo-graphic copying devices, and thereby serve to bring the developing powder on to a photoconductive material, provided with a latent charge image. For that purpose the cylinder, situated with its lower side in the developing powder, is causet to rotate, by which a certain amount of developing powder, which has been mixed as homogeneously as possible by the rotating mixing members in the reservoir, and thereby has also been brought to the desired tribo-olectric charge height, is transported upwards through the space between the cylinter and the rear wall of the reservoir as a result of the magnetic attraction by the cylinder. When the developing powder has arrived near the oagnet, the oagnetizable carrier particles of the developing powder are caused to raise. In this way a kind of brush is formed on the cylinter wall. This brush comes into contact with the photoconductive material which, preferably in a direction opposite to the direction of rotation of the cylinder, is guid-ed along the upper site of the cylinter. Thereby toner particles are attract-ed from the developing powder by the latent charge image on the photoconduct-~' ; . .
104;~9~;
ive material, which charge image has a charge which is opposite to that which is given to the toner particles by the triboelectric charging in the reservoir by which the charge image is converted into a visible powder image.
The magnetizable particles of the developing powder and the toner particles which were not attracted by the latent charge image, come loose from the cylinder when they have arrived out of the magnetic field and are then again fed back into the reservoir. Of course the developing powder in the reser-voir must be replenished regularly with toner particles to replace the amount of toner particles consumed. If necessary, also the iron particles are refreshed regularly. When the device is in operation, the magnetizable particles and the toner particles in the reservoir are continuously mixed by the mixing members, in order to ensure that the developing powder taken upwards from this reservoir by the cylinder has an optimally homogeneous composition and the triboelectric charge height required for a good develop-ment.
Conventional developing devices do not appear to be fully satis-factory. When after a long period of non-use the copying device is again set into operation, the triboelectric charge height of the developing powder initially often is rather low, so that the copies made during that initial period are not strong enough. In addition, for instance as a result of the conditions of operation, which may highly vary, the composition of the develop-ing powder in the reservoir often differs too much from place to place, and therefore also the triboelectric charge height, as a consequence of which the quality of the copies made with such a developing powder shows great fluctuations or may sometimes even become insufficient.
The object of the invention is to provide a developing device in which the above-mentioned disadvantages are obviated or mitigated, in that upon leaving the reservoir the developing powder always has a very homogen-eous composition and an amply sufficient triboelectric charge height. -A -2- ~ ~
' . ' ~ ' ' '' ' ', - .' ' ,. ~ ,,, According to the present invention, there is provided, in apparatus for developing an electrostatic charge image on a support by applying thereto a powder mixture of magnetizable carrier particles and toner particles, comprising a tray for holding a quantity of said mixture, said tray having a bottom wall, two side walls, a front wall and a rear wall, magnetic brush forming means including a cylinder mounted for rotation between said side walls in bearings thereon near said rear wall and a permanent magnet disposed above said cylinder, means for transporting said support over said cylinder through a magnetic field between said cylinder and said magnet, at least two mixing elements mounted for rotation between said side walls in bearings thereon near said bottom wall, and means for replenishing a deficiency of toner particles in the powder mixture in the tray, the improvement which comprises said rear wall having an overflow edge over which an excess of powder approaching the apex of said cylinder will escape at a level between said apex and the axis of the cylinder, and said replenishing means compris-ing means for supplying a fresh m;~ture of magnetizable particles and toner particles for admixture with the mixture returning to said tray from said magnetic field and the mixture in said tray.
The invention will now be described in detail with the aid of the accompanying drawings in which:-Figure 1 i9 a cross-sectional view of a device according to the invention; and ~:
Figure 2 is an exploded perspective view of the most important parts of the device shown in Figure 1.
The device for the development of an electrostatic charge image, consists of a reservoir 1 with a bottom 2, a front wall 3, a rear wall 4 and two side plates 5 and 6 forming the side walls (Figure 2). Between the plates 5 and 6 a cylinder 7 is rotatably installed in bearings, the cylinder cooperating with a permanent magnet 8 to form a so-called magnetic brush.
~A~` ~ ~3~
, . ' ~, ' . .
lU4219~
A belt 13 of photoconductive material guided along the upper side of the cylinder 7 by means of rolls 9 and 10 and guides 11 and 12 is formed with a charge image which is converted by the magnetic brush into a so-called powder image. A channel-shaped trough 14 is installed between the plates 5 and 6 and a screwlike transporting or feed member lS is disposed along the member 14 between bearings in the plates 5 and 6. The feed member 15 is formed by a shaft 16, round which two coaxial helical coils 17 and 18 are arranged which coils are fixed to the shaft 16 at their extremities. The member 14 is provided with an opening 21 in one of the walls of the channel.
Mixing members 23, 24 and 25 are installed in bearings between the plates 5 and 6. A permanent magnet 53 is installed against the rear wall 4 of the reservoir 1. The magnet is mounted in a holder 54 which has an elongate side 55 which projects into engagement with the under surface of the reservoir 1.
When the device described above is in operation, the cylinder .. . . ,. ~
~ ".... .. . .....
P~ ' - . : - . . .
rotates into the direction, indicated by the arrow A in Figure 1, as a result of which a part of the developing powder in the reservoir 1, which powder consists of a mixture of magnetizable carrier particles and toner particles, is transported upwards. This developing powder thereby passes the permanent magnet 53 and undergoes an additional and extra strong mixing in the magnetic field formed between this magnet 53 and the cylinder 7. Subsequently the developing powder arrives in the field of the permanent magnet 8, where there is formed on the surface of the cylinder 7 a so-called magnetic brush, which brushes against the belt of photoconductive material moving in the direction of the arrows B. In this way the latent charge image on this belt is convert-ed into a powder image. The opposite directions of movement of the cylinder 7 and the belt 13 produce an accumulation of the developing powder near 50 (Figure 1), but since the edge 51 of the rear wall 4 lies at a height of a point intermediate the highest point and the centre of the cylinder 7, the developing powder can freely escape outwards over this edge 51, by which this accumulation is eliminated. The projecting side 55 of the magnet sup-port 54 prevents this powder from reaching the magnet 53.
After the developing powder has left the magnetic field of the permanent magnet 8, the magnetizable carrier particles and the remaining toner particles fall from the cylinder 7 into the trough 14, after which these particles are transported by the screwlike transporting member 15 to the opening 21 and arrive into the reservoir 1 through this opening. In addition, during the operation of the device a fresh mixture of magnetizable carrier particles and toner particles is brought into the trough 14 by means which are not shown but which lead into the trough 14 near the shortest part of the trough adjacent the opening 21. When the device is in operation, the developing powder is continuously mixed by the mixing members 23, 24 and 25.
The concentration of the toner particles in the developing powder is measured optically via a window 33 in the bottom of the reservoir 1 by a device 52.
The window 33 is swept clean by a brush 32 which is fixed to the mixing ' ' ' ': ' . - , :::
104;~196 member 24.
The details of the mixture replenishing device and the various mixing members form no part of the present invention but for a fuller under-standing of these details reference should be made to copending Canadian application ser.no. 216,253, filed on December 17, 1974, in the name of Mathias Jacobus Johannus Maria Vola et al.
The exact position of the magnet 53 outside the rear wall of the reservoir can be chosen within very wide limits. However, it appears that the best results are obtained, when the magnet is situated on or close to the position where the distance between the rear wall and the rotatable cylinder is a minimum. It is thought that the successful effect of the magnet 53 mounted according to the invention must be ascribed to consequent magnetic compression of the developing powder between the rear wall of the reservoir and the rotating cylinder, by which a very intensive additional mixing of the developing powder is effected, shortly before this powder leaves the reservoir.
Surprisingly it has appeared, that the magnet 53 also effects the ~ -formation of a higher magnetic brush having a very uniform meniscus between the rotating cylinder and the other magnet 8 cooperating with it, which is favourable for the quality of the copies made.
Although in principle the type of magnet is irrelevant and, for example, an electromagnet coult be used, a permanent magnet will be preferred for economical reasons. ~ ~
In general, the length of the magnet 53 will a~tcorrespond with -the length of the rotatable cylinder. The width may amount to, for example, one or re centimetres. The magnet may for instance have a rectangular section or be shapet in accordance with the shape of the rear wall of the reservoir at the place of its installation.
Particularly good results are obtained using the embotiment des-cribet. However, the invention can be applied to similar embodiments which 1~4~196 do not have the described means for replenishing the developer mixture or the rear edge for preventing accumulation of mixture.
The presence of the magnet 53 in the developing device described above not only appear to have the intended further improvement with regard to homogeneity and triboelectric charge height of the developing powder leaving the reservoir, but also appeared to have resulted in a considerable improvement in the mixing in the trough 14. This is probably caused by the fact that the additional magnet 53 eliminates or strongly reduces the lines of force created by the magnet which forms the powder brush. -: . - ~ . : ~ , . ~ .
- .
This invention relates to a device for the development of an electrostatic charge image by means of a developing powder, comprising magnetizable carrier particles and toner particles.
Such a device is known from United States Patent No. 3,639,051;
which issued on February 11, 1972 in the name of Savin Business Machines Corporation.
This device is provided with a reservoir having a bottom, two side walls and a front and rear wall, which reservoir can contain a quantity of the developing powder mentioned, a cylinder rotatably mounted near the rear wall between the side walls of the reservoir and a magnet cooperating with this cylinder to a magnetic brush, means for transporting the support bearing the charge image along this cylinder, one or more mixing members mounted in bearings near the bottom of the reservoir between its side walls and means for replenishing the amount of developing powder in the reservoir.
Such teveloping devices are for instance applied in electro-photo-graphic copying devices, and thereby serve to bring the developing powder on to a photoconductive material, provided with a latent charge image. For that purpose the cylinder, situated with its lower side in the developing powder, is causet to rotate, by which a certain amount of developing powder, which has been mixed as homogeneously as possible by the rotating mixing members in the reservoir, and thereby has also been brought to the desired tribo-olectric charge height, is transported upwards through the space between the cylinter and the rear wall of the reservoir as a result of the magnetic attraction by the cylinder. When the developing powder has arrived near the oagnet, the oagnetizable carrier particles of the developing powder are caused to raise. In this way a kind of brush is formed on the cylinter wall. This brush comes into contact with the photoconductive material which, preferably in a direction opposite to the direction of rotation of the cylinder, is guid-ed along the upper site of the cylinter. Thereby toner particles are attract-ed from the developing powder by the latent charge image on the photoconduct-~' ; . .
104;~9~;
ive material, which charge image has a charge which is opposite to that which is given to the toner particles by the triboelectric charging in the reservoir by which the charge image is converted into a visible powder image.
The magnetizable particles of the developing powder and the toner particles which were not attracted by the latent charge image, come loose from the cylinder when they have arrived out of the magnetic field and are then again fed back into the reservoir. Of course the developing powder in the reser-voir must be replenished regularly with toner particles to replace the amount of toner particles consumed. If necessary, also the iron particles are refreshed regularly. When the device is in operation, the magnetizable particles and the toner particles in the reservoir are continuously mixed by the mixing members, in order to ensure that the developing powder taken upwards from this reservoir by the cylinder has an optimally homogeneous composition and the triboelectric charge height required for a good develop-ment.
Conventional developing devices do not appear to be fully satis-factory. When after a long period of non-use the copying device is again set into operation, the triboelectric charge height of the developing powder initially often is rather low, so that the copies made during that initial period are not strong enough. In addition, for instance as a result of the conditions of operation, which may highly vary, the composition of the develop-ing powder in the reservoir often differs too much from place to place, and therefore also the triboelectric charge height, as a consequence of which the quality of the copies made with such a developing powder shows great fluctuations or may sometimes even become insufficient.
The object of the invention is to provide a developing device in which the above-mentioned disadvantages are obviated or mitigated, in that upon leaving the reservoir the developing powder always has a very homogen-eous composition and an amply sufficient triboelectric charge height. -A -2- ~ ~
' . ' ~ ' ' '' ' ', - .' ' ,. ~ ,,, According to the present invention, there is provided, in apparatus for developing an electrostatic charge image on a support by applying thereto a powder mixture of magnetizable carrier particles and toner particles, comprising a tray for holding a quantity of said mixture, said tray having a bottom wall, two side walls, a front wall and a rear wall, magnetic brush forming means including a cylinder mounted for rotation between said side walls in bearings thereon near said rear wall and a permanent magnet disposed above said cylinder, means for transporting said support over said cylinder through a magnetic field between said cylinder and said magnet, at least two mixing elements mounted for rotation between said side walls in bearings thereon near said bottom wall, and means for replenishing a deficiency of toner particles in the powder mixture in the tray, the improvement which comprises said rear wall having an overflow edge over which an excess of powder approaching the apex of said cylinder will escape at a level between said apex and the axis of the cylinder, and said replenishing means compris-ing means for supplying a fresh m;~ture of magnetizable particles and toner particles for admixture with the mixture returning to said tray from said magnetic field and the mixture in said tray.
The invention will now be described in detail with the aid of the accompanying drawings in which:-Figure 1 i9 a cross-sectional view of a device according to the invention; and ~:
Figure 2 is an exploded perspective view of the most important parts of the device shown in Figure 1.
The device for the development of an electrostatic charge image, consists of a reservoir 1 with a bottom 2, a front wall 3, a rear wall 4 and two side plates 5 and 6 forming the side walls (Figure 2). Between the plates 5 and 6 a cylinder 7 is rotatably installed in bearings, the cylinder cooperating with a permanent magnet 8 to form a so-called magnetic brush.
~A~` ~ ~3~
, . ' ~, ' . .
lU4219~
A belt 13 of photoconductive material guided along the upper side of the cylinder 7 by means of rolls 9 and 10 and guides 11 and 12 is formed with a charge image which is converted by the magnetic brush into a so-called powder image. A channel-shaped trough 14 is installed between the plates 5 and 6 and a screwlike transporting or feed member lS is disposed along the member 14 between bearings in the plates 5 and 6. The feed member 15 is formed by a shaft 16, round which two coaxial helical coils 17 and 18 are arranged which coils are fixed to the shaft 16 at their extremities. The member 14 is provided with an opening 21 in one of the walls of the channel.
Mixing members 23, 24 and 25 are installed in bearings between the plates 5 and 6. A permanent magnet 53 is installed against the rear wall 4 of the reservoir 1. The magnet is mounted in a holder 54 which has an elongate side 55 which projects into engagement with the under surface of the reservoir 1.
When the device described above is in operation, the cylinder .. . . ,. ~
~ ".... .. . .....
P~ ' - . : - . . .
rotates into the direction, indicated by the arrow A in Figure 1, as a result of which a part of the developing powder in the reservoir 1, which powder consists of a mixture of magnetizable carrier particles and toner particles, is transported upwards. This developing powder thereby passes the permanent magnet 53 and undergoes an additional and extra strong mixing in the magnetic field formed between this magnet 53 and the cylinder 7. Subsequently the developing powder arrives in the field of the permanent magnet 8, where there is formed on the surface of the cylinder 7 a so-called magnetic brush, which brushes against the belt of photoconductive material moving in the direction of the arrows B. In this way the latent charge image on this belt is convert-ed into a powder image. The opposite directions of movement of the cylinder 7 and the belt 13 produce an accumulation of the developing powder near 50 (Figure 1), but since the edge 51 of the rear wall 4 lies at a height of a point intermediate the highest point and the centre of the cylinder 7, the developing powder can freely escape outwards over this edge 51, by which this accumulation is eliminated. The projecting side 55 of the magnet sup-port 54 prevents this powder from reaching the magnet 53.
After the developing powder has left the magnetic field of the permanent magnet 8, the magnetizable carrier particles and the remaining toner particles fall from the cylinder 7 into the trough 14, after which these particles are transported by the screwlike transporting member 15 to the opening 21 and arrive into the reservoir 1 through this opening. In addition, during the operation of the device a fresh mixture of magnetizable carrier particles and toner particles is brought into the trough 14 by means which are not shown but which lead into the trough 14 near the shortest part of the trough adjacent the opening 21. When the device is in operation, the developing powder is continuously mixed by the mixing members 23, 24 and 25.
The concentration of the toner particles in the developing powder is measured optically via a window 33 in the bottom of the reservoir 1 by a device 52.
The window 33 is swept clean by a brush 32 which is fixed to the mixing ' ' ' ': ' . - , :::
104;~196 member 24.
The details of the mixture replenishing device and the various mixing members form no part of the present invention but for a fuller under-standing of these details reference should be made to copending Canadian application ser.no. 216,253, filed on December 17, 1974, in the name of Mathias Jacobus Johannus Maria Vola et al.
The exact position of the magnet 53 outside the rear wall of the reservoir can be chosen within very wide limits. However, it appears that the best results are obtained, when the magnet is situated on or close to the position where the distance between the rear wall and the rotatable cylinder is a minimum. It is thought that the successful effect of the magnet 53 mounted according to the invention must be ascribed to consequent magnetic compression of the developing powder between the rear wall of the reservoir and the rotating cylinder, by which a very intensive additional mixing of the developing powder is effected, shortly before this powder leaves the reservoir.
Surprisingly it has appeared, that the magnet 53 also effects the ~ -formation of a higher magnetic brush having a very uniform meniscus between the rotating cylinder and the other magnet 8 cooperating with it, which is favourable for the quality of the copies made.
Although in principle the type of magnet is irrelevant and, for example, an electromagnet coult be used, a permanent magnet will be preferred for economical reasons. ~ ~
In general, the length of the magnet 53 will a~tcorrespond with -the length of the rotatable cylinder. The width may amount to, for example, one or re centimetres. The magnet may for instance have a rectangular section or be shapet in accordance with the shape of the rear wall of the reservoir at the place of its installation.
Particularly good results are obtained using the embotiment des-cribet. However, the invention can be applied to similar embodiments which 1~4~196 do not have the described means for replenishing the developer mixture or the rear edge for preventing accumulation of mixture.
The presence of the magnet 53 in the developing device described above not only appear to have the intended further improvement with regard to homogeneity and triboelectric charge height of the developing powder leaving the reservoir, but also appeared to have resulted in a considerable improvement in the mixing in the trough 14. This is probably caused by the fact that the additional magnet 53 eliminates or strongly reduces the lines of force created by the magnet which forms the powder brush. -: . - ~ . : ~ , . ~ .
- .
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In apparatus for developing an electrostatic charge image on a support by applying thereto a powder mixture of magnetizable carrier part-icles and toner particles, comprising a tray for holding a quantity of said mixture, said tray having a bottom wall, two side walls, a front wall and a rear wall, magnetic brush forming means including a cylinder mounted for rotation between said side walls in bearings thereon near said rear wall and a permanent magnet disposed above said cylinder, means for transporting said support over said cylinder through a magnetic field between said cylinder and said magnet, at least two mixing elements mounted for rotation between said side walls in bearings thereon near said bottom wall, and means for replenishing a deficiency of toner particles in the powder mixture in the tray, the improvement which comprises said rear wall having an overflow edge over which an excess of powder approaching the apex of said cylinder will escape at a level between said apex and the axis of the cylinder, and said replenishing means comprising means for supplying a fresh mixture of magnetizable particles and toner particles for admixture with the mixture returning to said tray from said magnetic field and the mixture in said tray.
2. In apparatus according to claim 1, the further improvement which comprises another permanent magnet that is mounted on or close to the outside of said rear wall at a location opposite a lower portion of the surface of said cylinder so that powder being moved by said cylinder from said tray is passed through the field of this other magnet.
3. Apparatus according to claim 2, said other magnet being mounted at or close to the location where the distance between said rear wall and said cylinder is the smallest.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7404121A NL7404121A (en) | 1974-03-27 | 1974-03-27 | Toner powder developer for photocopier - having magnet to control carrier and toner mixt. and meniscus to control rate of application |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1042196A true CA1042196A (en) | 1978-11-14 |
Family
ID=19821050
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA222,033A Expired CA1042196A (en) | 1974-03-27 | 1975-03-13 | Device for the development of an electrostatic charge image |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1042196A (en) |
| NL (1) | NL7404121A (en) |
-
1974
- 1974-03-27 NL NL7404121A patent/NL7404121A/en not_active Application Discontinuation
-
1975
- 1975-03-13 CA CA222,033A patent/CA1042196A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| NL7404121A (en) | 1975-09-30 |
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