JPH0222950B2 - - Google Patents

Description

Claim 1: An electrostatic toner and dust repulsion device for an electrophotographic printing device, wherein a magnetic toner deposit brush roller creates a specific toner and dust atmosphere, comprising: a first electrostatic toner repulsion means; and a second electrostatic toner repulsion means. an electrostatic toner repelling means, the first and second repelling means being disposed at both ends of the toner adhering brush roller and adjacent to a peripheral surface of the light receiving drum; further comprising means for applying an electrical potential to each of the repelling means, the electrical potential effectively repelling the toner from areas proximate to the repelling means and preventing the magnetic toner from adhering to adjacent surfaces of the drum. further comprising means for shunting and grounding an electric field from a charging coctron, of a polarity similar to that of the toner, which causes the roller to concentrate the toner, and is located adjacent to one of the electrostatic repulsion means. Equipped with an electrostatic toner and dust repulsion device.

2. The device according to claim 1, wherein the means for shunting and grounding the electric field includes a longitudinal conductive member extending parallel to the light-receiving drum, with means for installing the member on the frame of the device. invention.

3. The means for shunting and grounding the electric field is a substantially V-shaped thin flat copper member bent to match the radius of curvature of the light-receiving drum. invention of.

4. The first and second electrostatic repulsion means are each a thin, flat plate-like copper member, and each repulsion means is longitudinally supported within a groove of a respective insulating member. The invention described in item 1.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to electrophotographic apparatus and to automatic means for preventing migration of toner dust from a developer station to other parts of the apparatus.

2 BACKGROUND OF THE INVENTION Electrophotographic printing devices that use two-component toners, that is, toner and carrier particles, typically use a magnetic brush or toner deposition roller at a faster speed than devices that use single-component toners. Rotate at speed. This is because the amount of toner is small in a two-component system. All toner materials consist of ultra-fine powder materials that can be airborne. The toner particles in single component systems are heavier and therefore are not easily blown away in the air;
In contrast, two-component toner particles are lighter and non-magnetic, whereas the two-component toner particles are lighter and non-magnetic. The problem of toner migration due to air turbulence caused by the movement of toner carrier particles therefore poses a particular problem.

Brush-like seals at the edges of the rotatable receiver drum serve to limit ambient dust to a certain extent. Nevertheless, toner dust can migrate considerably to other parts of the device, cause undesirable adhesion to moving parts such as bearings, gear trains, etc., and adhere to the copy itself, making it unreliable and relatively dirty. A device.

To date, no electrostatic adhesion means have been commercially available that are designed to economically overcome this problem.

If the carrier particles create friction and thus reduce the charge/mass ratio (Q/M), this is a particular problem in high speed printers, where the magnetic rolls supporting the so-called magnetic brushes rotate at high rotational speeds.
A low Q/M reduces the attraction between the toner particles and the carrier particles, resulting in free toner particles moving with the airflow within the device. Therefore, these airborne dust particles are quite a nuisance.

SUMMARY OF THE INVENTION As is known in the reproduction art, triboelectric charges are generated when a toner material is mixed with a carrier material (usually non-conductive particles) to form a developer body.
Usually, carrier particles are charged (positively) +Ve,
The toner particles, on the other hand, are (negatively) charged -Ve. However, some toner particles are mechanically dislodged, resulting in the dust problem described above. Electrostatic attraction and repulsion are well known phenomena. Electrostatic adhesion is
It is used industrially to capture and remove all aspects of waste products from deposits and effluents.

This invention utilizes this repulsive effect of static electricity.

Even if a member is charged with -V (negative) charge, a pair of members that have substantially the same conductivity and are charged with static electricity will be separated from the light-receiving recording drum of the electrophotographic device. and placed. The charged member is positioned across the width of the drum and adjacent the developer section (or developer unit) within the apparatus. The insulating support member keeps the charged electrostatic element in close proximity to (but not in contact with) the drum surface. A few tens of thousandths of an inch of space is sufficient to effectively seal the area adjacent the drum and toner portion from dust. Applying a negative potential to the electrostatically charged members causes the fully negatively charged toner dust to be repelled from the area adjacent each electrostatic member.

More particularly, the invention includes a pair of elongated thin strips of electrically conductive material (e.g., made of copper) attached to each insulative molded member. The two parts are placed adjacent to, but separated from, the periphery of the photoreceptor drum of the electrophotographic printing device. A grounded conductive member fixed to the lowermost of the two electrostatic repellent members prevents the electric field generated by the adjacent positively charged corotron from attracting toner dust. A shaped shunt member or grounding member effectively shunts or grounds the electric field lines from the corotron and prevents negatively charged toner from being attracted to the corotron.

This arrangement completely eliminates the toner dust problem and leaves the area around the photoreceptor drum cleaner and ensures a more readable copy.

[Brief explanation of drawings]

FIG. 1 is a side view partially drawn with imaginary lines, showing a part of an electrophotographic apparatus embodying the present invention.

2 is a front view (partially cut away) of a portion of the apparatus of FIG. 1; FIG.

FIG. 3 is a (partially cutaway) view of the electrostatic repulsion member of FIGS. 1 and 2;

FIG. 4 is a (partially cut away) view of the shunt means of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention is directed to "Toner Concentration Sensor For Electrophotographic Apparatus", a commonly assigned application.
Richard, C. Fedder (Richard C.Fedder)
429,861, filed September 30, 1982.

For example, the formation of lines that are generally acceptable to the eye as normal or standard printing.
In order to form clean, clear black prints (copies) on white paper, dry copying machines require the following:
It is necessary to use a very fine dry powder toner material. The apparatus of this application also utilizes a two-component developer, characterized by a developer consisting of very fine powdered toner and larger carrier particles.

When toner and carrier particles are mixed to form a so-called developer body, triboelectric charges are generated. The carrier particles acquire a positive (+Ve) charge and the toner material acquires a negative (-Ve) charge. inevitably,
Some toner particles remain uncharged, ie, free, creating environmental dust that moves randomly into the surrounding atmosphere and into all parts of the device.

Physical seals cannot be placed along the cylindrical surface of the photosensitive drum for obvious reasons.
Anything that comes into contact with the polished surface of the drum will interfere with the charging of the drum surface, thus interfering with printing.

This problem is solved by exploiting attraction and repulsion phenomena, ie repulsion of charges rather than mutual attraction.

Referring to FIG. 1 of the drawings, it can be seen that the invention includes a rotatable photoreceptor drum 10 having a photosensitive surface 12 for receiving a visible image of information or data on the photosensitive surface. Below and slightly to the left (off center) is one of the two corotrons 14. (The corotron on the other side of the first right hand side is not shown as it does not form part of this invention.) Immediately to the upper left of the corotron 14 is a protruding device frame 18. There is an L-shaped lower bar member 20 made of glass-filled nylon that is secured by bolts 16 to the lower bar member 20 . The member 20 is attached to the drum 1
0, but without contact, is arranged to extend across the drum 10 (from one side to the other). Adjacent to the lower bar member 20, but separated above, is an upper L-shaped glass-filled nylon bar member 22. Each bar member 20 and 22 includes
There is an elongated, fairly wide channel or groove 24 extending from one end of each member to the other end. A substantially square opening 26 is provided at one end of each member 20 and 22;
6 will be explained later. Each bar member 2
The integral portion opposite 0 and 22 includes a plurality of bonding holes 28 arranged in a separated relationship on a thickened or raised land portion 30.
is provided. The former portion 30 extends from one end of each bar to the other and connects the connecting bolt 16.
Strengthen the elements to hold. The two mounting support members 20 and 22 differ only in their physical orientation and are otherwise identical in cross-section. Upper member 22 is angled as shown in FIG. 1 to take advantage of the available equipment portion to which upper member 22 is physically attached. Similarly, the lower member 20
is adapted to allow joining to available device structures. Since no corotron is used above member 22, there is no need to use a second shunt member (described below) as was used in lower member 20.

An elongated, relatively thin conductive copper strip 32 is provided with an integral bent tongue 34 at one end and includes a mating hole 36 in FIG. It is seated within a directional groove or channel 24. Bent tongue portion 34
is received within the square opening 26. 2
The physical mounting structure of the members 20 and 22 is as follows:
The flat planar opposing portions of each copper strip 32 are
It faces generally towards the surface of the drum 10 so that the strip 32 of the lower member 20 is generally parallel to the drum surface. Two (upper and lower) electrostatic repulsion devices 20 and 22 are located in close proximity to the drum 10, as shown in FIG.
However, it is positioned relative to the magnetic brush developer roller member 38 which is mounted without contact. As members 10 and 38 are rotated during operation of the machine, outer shell 39 of member 38 rotates past a plurality of internally disposed stationary magnets (not shown) and absorbs developer material 40 (toner and A carrier) is conveyed upwardly from a source (not shown) by a rotatable magnetic member 38 to a surface in contact with the drum 10. Lines of force are generated on the surface between the member 38 and the drum 10 due to the arrangement of magnets inside the member 38 and the static electricity on the drum 10, and the lines of force are generated in the plane between the member 38 and the drum 10 in parallel to the axis of rotation of the member 38. During the periphery of
A longitudinally extending ridge, land or magnetic brush 42 is received. The shell of member 38 supports a charge of approximately 300 volts of B ⁺ potential. On drum 10,
A potential of B ⁺ of 750-800 volts is given. The two electrostatic repulsion devices are each provided with a negative potential of approximately -1200 volts across lead 44 from a source (not shown). The corotron 14, located below and to the right of the roll 38, receives 4500 Hz from a source (not shown) by means of a lead 48.
maintained at a B ⁺ potential of ~6000 volts.

Since a high voltage is applied to the corotron 14,
The electric field lines generated by this element extend outwardly from there and into the area adjacent to the magnetic brush 42 . Normally, this would result in negatively charged toner developer being attracted from the brush area to the corotron 14. However, the present invention utilizes a shunt member 46, such as a copper strip, whose major surface is bent in a V-shape, as shown in FIG. Joining notches 4 are provided along the length of the member 46 to secure the member 46 to the lower member 20 by the bolt 16.
8 is provided. The shunt member 46 is coextensive with the lower repulsion member 32 and is joined to the frame 18, which is at ground potential as shown.

In operation, toner developer dust generated during operation of the apparatus described herein is transferred to drum 10 and members 20 and 22 when voltage is applied to each member as described above. and,
It is confined in the area between the brush generating member 38 and the brush generating member 38. No toner is allowed to escape into the surroundings or atmosphere.

This arrangement of structures directs or shunts the field lines from the corotron 14 to ground, thus preventing ambient toner dust from spreading outward from the brush area 42, thus overcoming the dust problem.

An additional advantage derived from this combination of structures is that the optical density of the print is enhanced by the toner concentration adjacent the print area on drum 10.