JPH0469788B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to a device for mixing granules. Such devices are particularly, but not exclusively, useful in magnetic brush development devices for developing electrostatic latent images on imaging surfaces. Such devices generally use a two-component developer consisting of magnetically attractable carrier particles and toner particles triboelectrically attached thereto.

PRIOR ART The type of mixing device to which this invention relates and which is often used in magnetic brush development systems is known as a cross mixer. This cross mixer has multiple sets of chambers arranged in parallel, each chamber receiving granules at an inlet at the top of the device and discharging granules through an outlet at the bottom, and each chamber receiving granules from a position vertically below the inlet. having staggered outlets, and the inlets and outlets further comprising: a base quantity of particulate material being continuously recirculated through the apparatus;
The arrangement is such that systematic movement of the particles from one end of the device to the other occurs.

In one type of magnetic brush development device, in order to develop an electrostatic latent image on the imaging surface, developer material is conveyed by a magnetic brush development roll into development contact with the imaging surface, and then transferred by the magnetic brush transport roll to the development roll. It is transported upwards from Near the top of the transport roll, the magnetic field that attached the developer material to the roll disappears.
The developer material is separated from the roll and transported or ejected toward the top of the cross mixer as described above. A magnetic brush developing device of this type including a cross mixer is described in British Patent No. 1372731 (corresponding to Japanese Patent Application Laid-Open No. 47-28934). The cross-mixing device of the same patent includes two rows of parallel chute-like chambers, where all the chute in one row moves the developer material to the left and all the chute in the other row moves the developer material to the right. let Although such cross mixers provide good mixing properties, in some cases it is desirable to obtain more thorough mixing. Furthermore, this type of cross-mixing equipment is not only susceptible to tilting of the equipment;
There is a tendency for the amount of developer material that falls into the chute of the column to be unbalanced. Both of these tendencies create a pumping effect that concentrates a large portion of the developer material at one end of the device, resulting in a shortage at the other end.

(Object and Structure of the Invention) The present invention aims to solve the above-mentioned problems, and the granular material mixing device of the present invention is disposed in a state where it is completely buried in the granular material, and when used, It is characterized in that the demand of the granules in the area adjacent to the outlet causes the granules to flow through the device under the action of gravity.

In the following, a mixing device according to the invention for a magnetic brush developer will be described by way of example with reference to the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, there is shown a xerographic reproduction machine incorporating the present invention. The reproduction apparatus includes a photoreceptor drum 1 rotatably mounted (clockwise in FIG. 1) for transporting the photoconductive imaging surface of the drum to a series of successive xerographic processing stations:
A charging station 2, an imaging station 3, a developing station 4, a transfer station 5 and a cleaning station 6.

The charging station 2 consists of a corotron that forms a uniform electrostatic charge on the photoreceptor. The original to be copied is placed on a platen 13 and scanned by a moving optical scanning system to produce a flowing optical image on the drum 3. The light image selectively discharges the photoreceptor according to the shape of the image, thereby providing an electrostatic latent image of the object on the surface of the drum. At development station 4, the electrostatic latent image is developed into a visible image by contacting the electrostatic latent image with toner particles and depositing the toner particles onto the charged areas of the photoreceptor.
The cut sheet of paper is moved synchronously with the image on the drum surface to a transfer station 5, and the developed image is transferred to the copy paper at the transfer station 5, where a transfer corotron 7 assists in the transfer of toner particles. Give an electric field. The copy paper is then peeled off from the drum 1, and this separation is facilitated by an electric field applied from the separating corotron 8. Thereafter, the copy sheet with the developed image is conveyed by a transport belt system 9 to a fusing station 10.

After transfer of the developed image from the drum, some toner particles usually remain on the drum and these are removed at a cleaning station 6. After cleaning, the static charge remaining on the drum is completely removed by the erasing corotron 11. The photoreceptor is now ready to be charged again by the charging corotron 2 as the first step of the next copying cycle.

The optical image at the image forming station 3 is formed by an optical system 12.
formed by. An original to be copied (not shown) is placed on a platen 13 and illuminated by a lamp 14 mounted on a movable scanning table 15 holding a mirror 16. The mirror 16 is a full speed scanning mirror for full speed and half speed scanning systems. Full-speed scanning mirror 16 reflects a band-shaped image of the original to be copied onto half-speed scanning mirror 17 . The image is focused onto the drum 1 by a lens 18, and is deflected by a fixed mirror 19 in the middle. In operation, full speed mirror 16 and ramp 14 move across the apparatus at a constant speed, while at the same time half speed mirror 17 moves in the same direction at half speed. At the end of the scan, each mirror is in the position indicated by the dashed line on the left side of FIG. This movement of each mirror maintains a constant optical path length and maintains a sharp focused image on the drum throughout the scan.

In the developing station 4, a magnetic brush developing system 2 is installed.
0 develops the electrostatic latent image. Toner is dispensed from hopper 21 into developer housing 23 by rotating foam roll distributor 22 . Housing 23 contains therein a two-component developer mixture of magnetically attractive carrier and toner, which mixture is brought into development contact with drum 1 by a three-roll magnetic brush developer mechanism 24.

The developed image is transferred to the transfer station 5, and the paper feed system 25
The image is transferred from the drum to a sheet of copy paper (not shown) which is contacted by the drum. Each copy sheet is stored in two paper trays, an upper main tray 26 and a lower auxiliary tray 27. The top sheet in either tray is brought into feeding contact with a feeder 28 at a common fixed location, if desired. A feeder 28 feeds the paper along a curved guide 29 for registration at registration point 30 . After alignment, the paper is advanced into contact with the drum in synchronous relationship with the image and receives the image at transfer station 5.

The copy paper with the transferred image is transferred to the vacuum conveyor belt 9
Then, the image is transported to a fixing device 10, which is a heated roll type fixing device. The image is sandwiched between two rolls of the fuser and fixed onto the copy paper using heat and pressure. The final copy is conveyed by fuser rollers along an exit guide 31 to a receiving tray 32, which is preferably of the offset type.

After transferring the developed image from the drum to the copy paper,
The drum surface is cleaned at a cleaning station 6.
In the cleaning station, the housing 33 forms a closed space together with the drum 1, and a scraping plate 34 is mounted inside the space. A scraper plate 34 wipes residual toner particles from the drum and the wiped particles fall to the bottom of the housing where they are removed by an auger.

Referring now to FIGS. 2 and 3, the development system 20 consists of a non-conductive magnetic brush developer, the main components of which are upper and lower developer rolls 41, 42, a single transport roll 43, and a cross mixer 44. The developer mixture consists of magnetizable carrier particles and toner particles. The carrier particles are recycled in the developer housing 33 and the toner particles, some of which are consumed during development, are replenished from a source in the toner hopper 21.
It is dispensed from the hopper by a foaming roller 22 which rotates as required.

The developer housing 23 consists of a lower extrusion 45 and an upper extrusion 46. In FIG. 2, the left end 47 of the lower extrusion 45 and the lower end 48 of the front extrusion 46 define an opening adjacent the photoreceptor drum 1. In FIG. Both extrudates 45, 46 are mounted between the front and rear end plates (not shown) of the device, and the entire assembly forms a substantially sealed chamber closed at the top by the toner hopper 21 and negative pressure chamber 49. ing.

Mounted within the housing 23 are three magnetic brush rolls 41, 42 and 43. roll 41,
42 is a developing roll, and a roll 43 located above the upper developing roll 41 is a transport roll. These rolls 41, 42, and 43 are flow-molded or extruded cylinders made of aluminum or aluminum alloy, and surround fixed multipolar rubber magnets 51, 52, and 53, respectively. Each magnet is held in place on the flat of its respective spindle about which the rolls 41-43 rotate via bearings in the end caps.

Next, referring to FIG. 3, the operation of the three-roll developing mechanism of the present invention will be described in more detail. The upper and lower developing rolls 41 and 42 are rotatably mounted in opposite directions as shown by arrows 54 and 55. The developer material is transferred to the lower developer roll 42 in an intake area 56 near the bottom of the housing 33 and adjacent to the cross mixer 44.
picked up by. As shown by the arrow in FIG. 3, the developer material is carried upward at the part of the lower developer roll 42 that is farthest from the photoreceptor drum 1, and reaches the gap between the lower developer roll 42 and the upper developer roll 41. . The upper developing roll 41 is the lower developing roll 4
2, the top of the lower roll and the bottom of the upper roll are moving in the same direction, that is, towards the photoreceptor drum 1. fixed magnet 51,
The magnetic poles in 52 are arranged to divide the developer material flow into substantially equal segmented streams, one stream being carried upwardly to the photoreceptor surface by the upper developer roll 41 and the other stream being carried downwardly. Side developing roll 4
2 in a downward direction relative to the photoreceptor. During the passage of the developer material over the photoreceptor surface in close proximity to both developer rolls, development of the electrostatic latent image on the photoreceptor occurs by electrostatic deposition of some toner particles in the developer material. After developing the latent image on the photoreceptor, the developer material on the upper developer roll 41 is transported upward toward the transport roll 43. The transport roll 43 is rotatably mounted in the same direction as the upper developing roll 41,
The magnetic poles of the magnet 51 of the upper developer roll 41 are arranged so that its magnetic field substantially disappears in the nip between the upper developer roll 41 and the transport roll 43, thereby preventing developer material from entering the nip between the rolls. Virtually prevented. Therefore, the transport roll 43 transports the developer material upwardly from the photoreceptor drum and into the housing 23.
carry it towards the rear. Since the magnetic field of the magnet 53 contained within the transport roll 43 substantially disappears just beyond the top of the transport roll 43, the developer material leaves the transport roll there and is transferred to the cross mixer 44.
The developing material falls into the developer reservoir 58, which is always filled with the developer material. A depending body 60 separates the area of the housing 23 containing the magnetic brush roll from the area containing the cross mixer 44. The upper edge 61 of the depending body helps deflect the developer material into its reservoir 58, while the lower edge 62 of the depending body helps to deflect the developer material into its reservoir 58.
2 defines a feed gap adjacent to 2 through which the developer material picked up by lower developer roll 42 from region 56 passes.

The developer material circulates within the developer housing and makes development contact with the photoreceptor at two separate locations, as shown schematically in FIG. 3 by the dots representing the developer material and the accompanying arrows. A first development occurs near the upper developer roll 41 when the developer material is conveyed in a direction opposite to the direction of photoreceptor movement. The second development occurs near the lower developer roll 42, where the developer material is carried in the same orientation as the photoreceptor. The different development characteristics obtained in each of these two modes of development depend on their combination.
It has been found that this method provides a significant improvement in the quality of the developed image compared to development obtained with a single magnetic brush developer roll or two developer rolls rotating in the same direction.

During development, the developer material loses some of its toner particles, and this loss is compensated for by adding new toner particles. The addition of toner particles takes place in the upper region of the housing 23 by means of a foaming roller 22 arranged to rotate according to the demand for more toner, and by means of a transport roll 43 it is added to the reservoir 5.
The toner particles are allowed to fall onto the carrier particles which are being conveyed to 8.

In order to contain the developer material within the housing 23,
A magnetic strip seal 77 is provided along the edge of the housing formed by the lower tip 48 of the forward extrusion 46. That is, a groove or protrusion is provided along the edge of tip 48 to receive a magnetic piece having a rectangular cross section. This magnetic piece is a flexible piece of ferromagnetic material, and the desired length of the piece may be adhered to the groove or protrusion of the tip 48 with an adhesive. The magnetic poles of the magnetic strip 77 are arranged such that the surface thereof adjacent to the photoreceptor is of one polarity, and this polarity is carried so as to repel carrier particles carried towards the magnetic strip by the upper developer roll 41. It will be done.
A similar magnetic strip seal (not shown) may be provided along the edge of the housing formed by the left tip 47 of the lower extrusion 45.

A toner hopper 21 is located at the top of the housing 23.
A negative pressure chamber housing 49 is attached to the right side of the housing. The top outlet 63 of this chamber is connected via a barrel to a vacuum system, creating a small negative pressure within the developer housing. This negative pressure causes an air flow from the area of the photoreceptor drum toward the housing, thereby preventing toner fumes from being emitted from the housing;
Reduces contamination within equipment.

Toner housing 21 is a relatively tall, narrow container with a generally horizontal lid 64 on its top surface.
is accessible from the top of the device. The housing 21 is formed to fit the right-hand part of the optical system of the device, and its lower end is formed to accommodate a foam roll 22. The neck of the hopper is configured to pinch the foam roll and help direct the toner away from the roll and into the housing 23. A stirrer 65 is placed directly above the roll 22.
is attached so that the toner in the hopper 21 flows smoothly to the roll 22.

The cross mixer 44 has a hanging body 60 and a housing 2.
The lowest part of the cross mixer is located between the lower extrudates 45 of 3 and adjacent the developer uptake area 56. A cross mixer consists of three rows of parallel chambers, which are
They are a front row 71 closest to the developing roll, a middle row 72, and a back row 73 furthest from the developing roll. The three rows of chambers are formed by each set of vanes projecting from the dividing wall, and in the preferred embodiment the cross mixer consists of two components, suitably cast, for example, from an aluminum alloy. The front casting 74 (closest to the developer roll) has vanes projecting from both sides of the plate 75, whereas the rear casting 7
6 consists of a plate 77 having vanes protruding only from its rear surface. The vanes of both castings are formed such that the front projecting vane of the front casting comes into contact with the depending body 60, and the rear projecting vane comes into contact with the plate 77 of the rear casting. The rear protruding vane of the rear casting is located at the lower end 45 of the housing 23.
comes into contact with the inner surface of In this way, three rows of chambers are formed between the pendant body 60 and the lower tip 45, each row being mutually divided by the plates 75, 77, and each chamber being defined by a vane projecting from the plates 75, 77. and are mutually divided.

Each chamber formed by the vanes on the front and rear castings has an inlet at the top and an outlet at the bottom, each outlet offset to either the left or right of the vertical downline of the inlet. These chambers constitute the main chamber for the passage of developer material through the apparatus, as further described below. Each chamber is divided into pairs, and between one pair of chambers a vane defines an open-topped hopper with a small outlet at the bottom. Thus, while the main stream of developer material passing through the cross mixer occurs via the main chamber, a much smaller side stream thereby occurs through the intervening hopper.

In each row of chambers, adjacent chambers direct developer material alternately to the left or right of their respective entrances. Thus, in a given row, a small amount of developer material entering one of the chambers is moved to the left or right during its passage downward through the cross mixer and to the top of the device, which is a nearly vertical movement. During recirculation by the magnetic brush roll, a small amount of developer material reenters the top of the cross mixer and during its first pass its position is shifted to the left or right. Furthermore, the main chamber is also configured to shift the developer material from row to row during successive recirculations, as will become clear from the description below.

As an example of the configuration of the chamber and hopper, the fourth,
5 and 8 and in particular the central portion of the back row chamber.
The schematic view of the vane shown in FIG. 5 corresponds to the view of the rear casting 76, which is the lower of the two castings shown in FIG. However, whereas the schematic diagram in FIG. 5 shows a cross section of the developing device housing as seen from the front, it is a diagram as seen in FIG. 8 and from the rear. A chamber 8 is provided between the inclined vane 83 and the vertical vane 84 and between the vertical vane 84 and the inclined vane 85.
1 and 82 are formed, respectively. Entrance 1 of room 81
16 is defined by the upper edges of both vanes 83, 84, as well as by the plate 77 and the lower end 45 of the housing. Similarly, the inlet 104 of the chamber 82 is formed by the upper edges of both vanes 84, 85, as well as by the plate 77 and the lower tip 45. The bottoms of the chambers 81, 82 are substantially horizontal and are formed by vanes 88, 89.
A main outlet 90 of the chamber 81 is formed at a position offset to the left (in FIG. 5) from a position vertically below the inlet 116. Similarly, the main outlet 91 of the chamber 82 is the inlet 104.
It is formed at a position shifted to the right from the vertically lower position of. The developer material that entered the entrance 116 of the chamber 81 is sent to the exit 9.
0 to form the main flow path for the developer material. A horizontal vane 8 adjacent to a vertical vane 84 prevents the formation of a static amount of developer material in each chamber.
Small outlets 92 and 93 are formed at 8 and 89, respectively.

The walls forming the inclined vanes 83, 85 and the main chambers 81, 82 further form the inclined floor surfaces of the hoppers 94, 95. Another sloped floor surface of each hopper is formed by sloped vanes of the main chamber such as vane 96. To prevent static amounts of developer material from forming in the hopper, small openings, such as openings 97 and 98, are formed on each side of the lower hopper directly above the outlet of the main chamber.

To illustrate how the cross mixer achieves thorough mixing of developer material, the movement of a small sample amount of developer material is next tracked throughout the cycle. For ease of understanding, the cross mixer inlets followed by the sample volume sequentially are numbered sequentially in Figures 4, 5, 6, and 7, starting with 101 and ending with 118. Referring first to FIGS. 4 and 5, the starting point is the leftmost entrance 101 of the back row. After the developer material falls into this first chamber, it exits through an outlet 120 at the bottom of the cross mixer. When passing through the first chamber and the cross mixer, the developer material is shifted to the right side. The developer material is then recirculated, carried vertically upward by the magnetic brush roll, as described above, and reintroduced into the cross mixer directly above outlet 120. Therefore, some of the developer material enters the hoppers 94 in the rear row, some enters the inlet 102 (FIG. 6) in the middle row, and further part enters the hoppers 121 in the front row.
Enter. Hoppers 94, 121 have only small outlets and thus provide a slow flow reservoir of developer material. The main flow route at this point is then given by the middle row of chambers with inlets 102.

During the next recirculation, the developer material shifts to the right from the inlet 102, ie, falls into the cross mixer at a position corresponding to the front row inlet 103 (FIG. 7). Again at this point the developer material falling into the rear and middle row hoppers forms a very small portion of the flow, with the majority of the flow passing through the inlet 103. The recirculation then produces a main stream through the back row inlet 104;
Subsequent recirculation is carried out sequentially through inlets 105 (middle row), 1
06 (front row), 107 (back row), 108 (middle row)
and 109 (front row). Entrance 1
09 is the last entrance that moves the developer material to the right.
Recirculation at this location (i.e., rightmost of the cross mixer) allows the developer material to pass through the rightmost inlet of the back row.
Enter 10. The next main stream entrance is front row entrance 111
and the subsequent recirculation is at the inlet 112 (middle row),
113 (back row), 114 (front row), 115 (middle row), 116 (back row), 117 (front row) and 118
(middle row) and continue moving to the left.
After passing through the left end chamber of the middle row (inlet 118), the developer material is again in a position for recirculation and enters inlet 101 to repeat the cycle described above. Of course, since the developer material passes through all the entrances at any given point in time,
From the left side of the cross mixer to the right side and from row to row,
and the simultaneous movement of developer material from right to left and from row to row.

(Effects of the Invention) According to the present invention, each chamber of the granular material mixing device is always fully filled with granular material, and when granular material is required, the granular material comes out from the chamber outlet and enters the device. The ideal mixing automation is achieved, in which granular materials are constantly supplied to the chamber, moved through the chamber, and discharged to the outlet, and the mixing of the granular materials is always ensured according to the demand for the granular materials. Even if the position of the mixing device is not horizontal, the mixing action of the particulate matter is performed well and the mixing effect is high, and the mixing device itself can be made smaller, and the developing device and the like can also be made smaller.

In the above embodiments, the cross mixer has been described as having three rows of chambers, but it is clear that the same mixing principle can be applied to a cross mixer having two or more rows of chambers.

The material forming the cross-mixer occupies a minimal volume, there are no cavities or chambers that cannot be accessed by the developer material, and the walls of the cross-mixer casting are all relatively thin.
This allows for a maximum amount of developer material to be present within the development device, thereby reducing wear and tear on each carrier particle and extending the useful life of the developer material.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a xerographic copying apparatus incorporating the present invention; FIG. 2 is a sectional view of a magnetic brush developing device used in the apparatus of FIG. 1;
The figure is an enlarged sectional view of a part of the apparatus shown in FIG. 2; FIG. 4 is a plan view of the cross-mixing device in the developing device; FIGS. 5, 6, and 7 are views from the front of the developing device housing. 8 is a schematic cross-sectional view along the front, middle and rear row chambers of the cross mixer, respectively, for explaining the operation of the cross mixer; FIG. 8 is a perspective view of two components of the cross mixer separated from each other; FIG. FIG. 9 is a view of the two components shown in FIG. 8 as viewed from the front of the developer housing. 20...Magnetic brush development system, 23...Developer housing, 44...Cross mixing device, 71...Front row, 72...Middle row, 73...Rear row, 75, 77
...Divided plate, 81, 82... Chamber, 83, 8
5, 96... Inclined vane, 84... Vertical vane,
88, 89...Horizontal vane, 90, 91, 120
...Main exit, 94, 95, 121...Hopper,
97,98...Hopper small exit, 101-118
……entrance.

Claims (1)

[Claims] 1. A plurality of chambers arranged in parallel, each chamber being formed to receive particulate matter at an inlet at the top of the device and discharging the particulate matter from an outlet at the bottom end of the device; The outlet at the lower end of the chamber is offset from the vertically downward position of the inlet, and these inlets and outlets allow for systematic movement of a base quantity of particulates from one end of the device to the other as they are continuously recirculated through the device. a particulate mixing device arranged to produce a particulate matter, the device being arranged to be completely embedded in the particulate matter so that, in use, the particulate matter is mixed into an area adjacent to the chamber outlet; A mixing device, characterized in that, on demand, the granules are flowed through the device under the action of gravity.