Fur Brush Developing Apparatus

Abstract

Fur brush developing apparatus for developing a latent electrostatic image on an electrostatic member with toner by simultaneously contacting the member to a toner cloud and toner-laden fur brush including a container to hold toner having a portion of its surface covered by a fur brush, the fur brush and the portion of the container covered thereby having a plurality of apertures, and means to oscillate the container while the fur brush is in contact with the electrostatic member so that toner in the container that is maintained in a mobile, agitated condition passes through the apertures onto and between the fibers of the fur brush and is deposited on the electrostatic member by the fur brush. The fur brush apparatus can be oscillated in an orbital manner so that it gives a multidirectional effect to the developing process producing developed images free of directional marks and background.

Description

BACKGROUND OF THE INVENTION

This invention relates to developing latent electrostatic images, and more particularly, to depositing toner on an electrostatic member by the combined effect of simultaneously contacting the member to a toner cloud and a toner-laden fur brush.

In reproduction apparatus such as those employing the xerographic process, a latent electrostatic image conforming to the information to be reproduced is first formed on an electrostatic member and then developed by the application of an electroscopic pigmented, resinous, finely divided powder called toner. A known method of developing the latent image is by applying toner to the electrostatic member with a suitable toner-laden developing brush such as a fur brush having a plurality of fibers protruding from a backing material. Toner is loaded onto the fibers of the developing brush and then the brush is brought into contact with the electrostatic member to develop the latent image thereon.

There are several methods by which toner can be placed on the fibers of a fur brush. One method of accomplishing this is to pass the brush through a toner reservoir. In this technique, the toner particles are picked up and held by the fibers of the brush as it passes through the reservoir by mechanical forces and/or forces of electrostatic attraction. Although this method of loading is relatively simple in theory, there is inherent difficulty associated with it in actual operation since a cavity develops in the toner reservoir as the brush rotates making it extremely difficult to continue to load the brush. The toner particles in the reservoir tend to become packed and stuck together especially at high humidities, and, as a result, once the toner particles immediately adjacent the brush are removed from the reservoir the fibers on the brush no longer contact the remaining toner particles in the reservoir. An auger or other types of mixing apparatus can be placed in the reservoir to prevent the toner from packing but it has been found that such cavities still occur in the toner reservoir resulting in inefficient loading of the brush over a period of continuous operation.

A second loading technique is to distribute toner particles onto a brush through a screened hopper. The hopper can be vibrated and placed over the brush so that the toner held inside the hopper falls through the screen, usually of a fine mesh, and onto the fibers of the brush. This type of loading device has a serious problem in that it is difficult to achieve uniform placement of toner on the fibers and the nonuniformity of toner greatly impairs the developing process. In addition, it is important to place a charge of desirable polarity and uniform intensity on the toner particles before they reach the plate and this is difficult to achieve in a hopper loading system.

In addition to the loading problems associated with known fur brush development systems, the quality of the toner images produced by fur brush development process is not always the highest due to directional marks in the toner image and the spurious deposition of toner in the nonimage areas of the electrostatic member. A common manner in which fur brush is utilized in continuous reproduction equipment is to make the brush cylindrical in shape and rotate it continuously in one direction to deposit toner on the electrostatic member. Since the fibers always interfere with the member in one direction, directional marks, or perceivable nonuniformities in the toner image over the areas of equal potential, result in the developed image. These marks can appear as streaks, discrete lines, untrue edges, etc., and generally degrade the appearance and quality of the toner images. The casual deposition of toner in nonimage areas of the member accompanied by toner images of too little density can also result when a cylindrical fur brush is used for development.

The present invention is a fur brush developing apparatus adapted to eliminate the problems of the prior art devices. The apparatus disclosed herein carries out development by simultaneously contacting the latent electrostatic image to a toner cloud and a toner-laden fur brush which together produce dense toner images free of background toner and directional marks. The apparatus includes an oscillatable toner container covered with a fur brush which contacts the electrostatic member and applies toner thereto. The container and fur brush contain apertures so that when they are oscillated an agitated cloud of toner particles passes through the apertures onto and between the fibers of the brush. The fibers of the brush, in turn, control the deposition of toner on the electrostatic member through a multidirectional movement.

Accordingly, it is an object of this invention to improve fur brush apparatus used in developing electrostatic images.

It is another object to improve fur brush developing apparatus by loading the toner on the brush with an agitated, mobile cloud of toner particles.

It is another object of this invention to load fur brush development apparatus by forming a mobile, agitated cloud of toner particles within the brush enabling the toner particles to pass through apertures to fibers on the brush.

It is another object of this invention to develop a latent electrostatic image on an electrostatic member by simultaneously contacting the member with a toner cloud and a toner-laden fur brush.

It is another object of this invention to develop a latent electrostatic image on an electrostatic member by applying toner to the member in a multidirectional action.

SUMMARY

This invention relates to a fur brush developing apparatus having a oscillatable toner container covered by a fur brush. As the container oscillates, the toner within it in a mobile, agitated mass passes from the container through a plurality of apertures in the container and brush onto and between the fibers of the fur brush. The toner particles are deposited on an electrostatic member bearing the latent image by fur brush development as the brush fibers interfere with the member and by toner cloud development as the mobile, agitated mass of toner between the fibers contacts the member.

One embodiment of the invention takes the form of an oscillatable toner container having one side covered with a fur brush which is oscillated in an orbital path. A second embodiment of the invention is a hollow, cylindrical container having a fur brush wrapped about its periphery which is rotated.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be used in conjunction with the accompanying drawings; wherein:

FIG. 1 is a schematic illustration of the invention.

FIG. 2 is a schematic illustration of the multidirectional movement of the invention.

FIG. 3 is a schematic illustration of an alternate embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention can be used for the developing step in any reproduction system wherein toner particles are applied to an electrostatic member bearing a latent electrostatic image. Although the invention is described within the environment of a xerographic copier, for the purpose of this disclosure, it is not intended that it be limited to use in this type of reproduction system.

Referring to FIG. 1, a schematic illustration of a xerographic copying machine is shown which utilized the invention. The principle element of the machine is electrostatic member 60. Member 60 has five processing stations arranged about its periphery which carry out the operational steps of the xerographic process. These stations include charging station 10, exposing station 20, developing station 30, transfer station 40, and cleaning station 50. Member 60 is supported by rotatable drum 63 which is driven about the shaft 64 by motor M-1. The peripheral surface of the drum 63 is covered with layer 62, an electrically conductive material, which, in turn, is covered on its outer surface with layer 61, a photoconductive material such as vitreous selenium.

An latent electrostatic image is formed on the member 60 by passing it through charging station 10 and exposing station 20. The charging station includes any suitable means of placing uniform charge on layer 61 such as corona charging device 11. Exposing station 20 comprises any suitable projector 21, or the like, which forms and focuses a light image on the member conforming to the information being reproduced. The movement of the light image projected onto the electrostatic member 60 is synchronized with the rotation of the electrostatic member causing selective charge dissipation on elemental areas of layer 61 to form a latent electrostatic image thereon.

After the formation of the latent electrostatic image, electrostatic member 60 passes through developing station 30. At the developing station toner particles are applied to the surface of the drum by a developing brush having fibers 35. Fur brush 37 comprises a unified structure including a backing material 36 and fibers 35 protruding from the backing material. The fur brush is attached to container 32 and the whole assembly is oscillatable by any suitable mechanism 34 which produces such motion. The oscillating means is connected to the container by arm 33. The arrows showing the directions of oscillation of the developing brush are indicative of only one oscillatory motion that can be used and may not necessarily be the most optimum for all copier configurations. When the developing brush is oscillated, toner particles 31 inside container 32 form a mobile, agitated mass of toner which moves through apertures 39 and onto and between the fibers of the fur brush. The fibers then, in conjunction with the toner cloud therebetween, deposit the toner particles on the surface of member 60. Toner particles which are applied to the surface of the member by developing brush adhere to the drum surface according to the configuration of the latent electrostatic image formed beforehand. Various aspects of the structure and operation of the fur brush developing apparatus shown at station 30 will be described in more detail below.

Following the development step, the toner image is brought through transfer station 40 where the image is transferred from the drum surface to support material 41. Transfer of the toner image to the support material is carried out by corona device 42 which forms an electrostatic field between the support material and member 60. Transfer takes place between guide rollers 45 which act to the position the support material against the electrostatic member in the transfer station. Support material 41 is fed from reel 43 before transfer and is rewound on reel 44 after transfer takes place. If support material 41 is the permanent substrate upon which the toner image is to be fixed, fusing device 46 is desirable to make the toner image permanent and can be placed along the path of the support material between the point where the toner image is transferred to the support material and the point where the support material is rewound on reel 44. The fusing device is positioned to heat the toner particles and fuse them to the support material.

The final station shown in FIG. 1 is cleaning station 50 which includes a cylindrical fur brush 51 which contacts the surface of the electrostatic member. The cleaning station is desirable to remove any residue toner particles from the electrostatic member after transfer occurs and before the surface begins a new cycle.

It is intended that various moving elements be driven and controlled by any suitable means (not shown) so that the copier operates as described above.

It is within the confines of development station 30 that the present invention is utilized. As shown in FIG. 1, the developing brush includes oscillatable container 32 having fur brush material secured to one of its sides, the side of the container facing the electrostatic member 60. The container may be made of any suitable material which is adapted to hold toner. The container should be relatively airtight save the apertures since it is undesirable for the toner particles to escape from the container in any other manner than through the apertures intended for this purpose.

The side of the container immediately adjacent the electrostatic member is covered with fur brush 37. The fur brush consists of a unitary structure having backing material 36 with fibers 35 protruding therefrom and is mounted so that the fibers are readily engageable with the surface of the member. The fur brush can be made of any suitable synthetic or natural material; for example, natural materials such as rabbit fur, fox fur, camel hair, etc., can be used, or in the alternative, synthetic materials such as dynel (a synthetic fiber of 40 percent acrylon nitrile and 50 percent vinyl chloride), velvet, nylon, etc., can be used.

The side of the container to which the fur brush is securely mounted has a plurality of apertures 39. The size of the apertures can vary from 0.0025 to several square inches depending on the amount of toner desired to flow to the fibers and member. The purpose of these apertures is to enable the mobile, agitated mass of toner created within the container to pass from the container onto and between the fibers of the fur brush material as the apparatus oscillates. If the apertures are made in the vicinity of 0.0025 square inch, the flow of toner to the fibers is small, and the developing brush is more adaptable to low-speed copiers. It has been found that when sizes much below 0.0025 square inch are used there is a chance of clogging the apertures and restricting the action of the toner as a single, agitated mass.

On the other hand, apertures may be used which extend to several square inches in area. The limiting factor on the overall size of the apertures is the amount of fibers retained on the fur brush to carry out brush development. As the aperture size increases the amount of fibers decrease proportionally. Thus, the size of the apertures in any given development system will depend on a balance between the amount of toner flow desired and the amount of fibers necessary to carry out adequate brush development.

The character of the oscillations of the developing brush may be such as to produce either a powder cloud or a fluidized bed of toner. In the powder cloud situations, the toner forms a cloudlike mass which is controlled by the fur brush and either toner alone or a developer mixture of toner plus a granular material called carrier beads can be used in the toner container. In the case of a fluidized bed, a developer mixture of both carrier beads and toner is used at all times in the container and the oscillations are such that the entire mass of developer expands and takes on some of the characteristics of a fluid. In this situation the toner between the fibers of the brush is also controlled by the movements of the brush.

FIG. 2 shows the fur brush apparatus being oscillated in an orbital path to achieve a multidirection effect in development. The movement of the toner container 32 and brush 37 is controlled by any suitable mechanism 38 which is joined to the container by arm 33. Mechanism 38 can be a cam and follower apparatus or any other suitable apparatus which causes the developing brush to move in an orbital path such as the path shown in arrows in FIG. 2. The term "orbital path" herein is meant to be a generic term to include all movement which gives the fur brush a multidirectional action relative to the member 60 being developed and can include simple back-and-forth oscillation, circular motion, elliptical motion, etc.

The multidirectional brush movement is desirable since it tends to eliminate directional marks in the toner image which are common in unidirectional brush development. In addition, multidirectional brush development forms denser toner images and leaves nonimage areas free from the casual deposition of toner due to the sweeping action of the fibers during development. The sweeping action sweeps any spuriously deposited toner from the nonimage areas into the image areas where it is desired thereby producing reproductions of high quality.

The present apparatus carries out development through the combined effects of toner cloud development and fur brush development. The toner which reaches the fibers of the brush is deposited on the electrostatic member by the wiping action of the brush fibers on the member. As mentioned above, this development technique eliminates incidental deposit of toner in nonimage areas and directional marks. The toner which remains mobile in toner cloud form between the fibers of the brush is deposited on the electrostatic member as the member becomes exposed to the toner cloud. The toner cloud is particularly advantageous for dense solid area coverage and the formation of images of good resolution.

The toner cloud is controlled by the fibers so that it remains within the development area and any incidental deposit of toner in nonimage areas caused by the toner cloud is swept into the image areas by the fibers of the fur brush. The result of the combined action of simultaneous toner cloud and fur brush development is dense solid area coverage with good resolution together with little or no directional marks and no background toner. To insure that a high degree of control is maintained on the powder cloud and that the powder cloud does not escape the fur brush, those fibers on the fur brush which are located at its edges can be made slightly longer than the rest of the fibers. In this manner, the powder cloud and/or toner particles on the fur brush tend to be sealed within the edge or boundary fibers of the brush.

In addition to the oscillations produced by mechanism 38, a low air pressure can be introduced into the toner container by any suitable source 53 to aid the creation of the toner cloud and urge it to pass freely through the apertures and onto the fibers. As the toner particles pass onto the fibers and drum and are eventually used to develop the latent image, means can be provided to replenish the supply of toner particles within the container. For example, additional toner particles can be brought into the container with the blast of low air pressure introduced into the container to produce the toner cloud, by passing the air through a toner reservoir 52.

Referring to FIG. 3, there is shown an alternative embodiment of the developing brush. In this embodiment, container 132 assumes the shape of a rotary, hollow container. Wrapped about its periphery is fur brush 137 comprised of a backing material 136 having a plurality of fibers 135 protruding therefrom. The developing brush is surrounded by housing 138 which contains any particles which may escape from the developing brush completely. The container and fur brush have a plurality of apertures 139 which serve the same function as the apertures described in conjunction with FIG. 1. Housing 138 surrounds the developing brush on every side except in the area where the fibers interfere with drum 60; that is, the area where development takes place.

The operation of the rotary developing brush is similar to the developing brush described in conjunction with the FIG. 1, except that the developing brush in FIG. 2 rotates rather than oscillates. As the developing brush rotates, toner particles 131 held within the brush form a mobile, agitated mass of toner or toner cloud. The toner cloud passes through the apertures and onto and between the fibers of the developing brush.

Housing 138 can be biased as shown in FIG. 2 to keep the toner cloud among the fibers of the developing brush. This result is accomplished if the polarity of the bias placed on the housing were the same polarity as the triboelectric charge existent on the toner particles being used for development. Since like charges repel, the toner particles are repelled from this housing area and are urged into and among the fibers of the fur brush. Although the bias on the housing is optional, the presence of the housing itself about the developing brush is desirable to maintain the toner particles in among the fibers of the brush.

While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this disclosure is intended to cover such modifications as will become apparent to those skilled in the art upon reading the disclosure.

Claims

What is claimed is:

1. An apparatus for developing an electrostatic image on an image-bearing member with toner by simultaneously contacting the member with a toner cloud and toner-laden fur brush comprising:

a. a fur brush having fibers protruding from a backing material supported adjacent the member with its fibers interfering with the member;

b. means to load toner particles on the fibers;

c. means to move the fibers relative to the member to develop the electrostatic image on the member with toner particles on the fibers of the fur brush; and

d. means to form a toner cloud between the fibers on the fur brush to simultaneously develop the electrostatic image on the member with toner particles in the toner cloud.

2. The apparatus in claim 1 wherein means to load the toner particles on the fibers and means to form a toner cloud between the fibers are the same means.

3. An apparatus for developing an electrostatic image on an image-bearing member with toner particles by simultaneously contacting the member with a toner cloud and toner-laden fur brush comprising:

a. an oscillatable toner container adjacent the member adapted to hold a quantity of toner particles;

b. a fur brush having fibers protruding from a backing material covering at least a portion of the container; the fur brush being located on the side of the container facing the member with its fibers interfering with the member;

c. a plurality of apertures in the fur brush and the portion of the container covered thereby, the apertures being of sufficient size to enable toner particles to pass from the container to the fibers on the fur brush; and

d. means to oscillate the container to form a cloud of toner therein whereby as the container is oscillated the toner particles pass through the apertures and onto and between the fibers of the fur brush.

4. The apparatus in claim 3 wherein the means to oscillate the container includes means to move the container and fur brush in an orbital path whereby the movement of the fibers on the fur brush is multidirectional as development of the electrostatic image is carried out.

5. The apparatus in claim 3 wherein the fibers located in the edge areas on the fur brush are longer than the other fibers on the fur brush whereby the toner cloud formed between the fibers on the fur brush is contained within the edges of the fur brush.

6. The apparatus in claim 3 further including means to supply additional toner particles to the toner container as development is carried out whereby toner particles can be placed on the member continuously.

7. The apparatus in claim 3 further including means to introduce air pressure into the toner container whereby the toner cloud is urged through the apertures onto and between the fibers on the fur brush.