Developing Material Applicator

The present invention relates to an applicator for use in presenting a powdered developing material against the surface of an article for application thereto and, more particularly, to a magnetically responsive powder applicator for use in a photoelectrostatic copying machine for applying finely divided particles over the photoreceptor surface to cause the particles to electrostatically adhere to the photoreceptor surface to form a powdered image in the configuration of an electrostatic latent image previously developed on the photoreceptor surface.

In most photoelectrostatic copying machines, there is employed an applicator for applying a finely divided electroscopic developing material, known as "toner", over the photoreceptor surface. The applicator is generally positioned at a developing station at which the toner particles having an electrostatic charge opposite in polarity to that of the electrostatic latent image previously formed on the photoreceptor surface are applied over said photoreceptor surface whereby the toner particles adhere to the electrostatic latent image to form a powdered image in the configuration of the original to be copied. The photoreceptor surface may be in the form of either a rotary drum or a substantially endless belt.

The known toner applicator comprises a substantially box-like container or tank positioned above the developing station for accommodation of a mass of toner particles therein and has a slit, or a like opening, formed at the bottom thereof above and in spaced relation to the photoreceptor surface. The toner tank includes a rotary dispenser housed for rotation within the toner tank and extending in parallel relation to the slit or the like opening at the bottom of said toner tank. The rotary dispenser is in the form of either a rotary brush or a screwed stud similar in shape to a screw conveyor and, during operation thereof, acts to dispense the toner particles from the interior of the toner tank over the photoreceptor surface through the slit or the like opening in the form of cascading flow.

The toner applicator of the known construction referred to above has various disadvantages. For example, because of the particular construction of the toner applicator, it cannot be disposed anywhere as desired other than above the photoreceptor surface and, in addition, the toner particles downwardly flowing from the toner tank through the bottom slit tend to catch up with foreign particles which may ultimately constitute a cause for stains which may appear on the finished, or reproduced, recording sheet. Moreover, since adjustment of the amount of toner particles to be dispensed has been carried out by adjusting the rotation of the rotary dispenser, the amount of the toner particles to be applied by the dispenser tends to vary depending on the condition of the developing material within the toner tank. This often prevents uniform development in relation to the electrostatic charge carried by the latent image and, accordingly, the resultant image reproduced on the recording sheet lacks a sharp contrast.

Accordingly, an essential object of the present invention is to provide a magnetically responsive powder applicator for use in a photoelectrostatic copying machine which applicator is capable of applying magnetically responsive, finely divided particles over the photoreceptor surface in a substantially uniform and stable amount, with substantial elimination of the foregoing disadvantages inherent in the conventional applicator of a similar kind.

Another object of the present invention is to provide a magnetic powder applicator, which can, therefore, uniformly deposit thermally fusible resinous particles on the photoreceptor surface to ensure formation of a sharp powdered image thereon.

A further object of the present invention is to provide a magnetically responsive powder applicator, which can be disposed in any position as desired relative to the photoreceptor surface.

In order to accomplish the foregoing objects of the present invention, the present invention features magnetic attraction utilized in transporting the developing material which is a mixture of magnetizable carrier beads and toner particles. The toner tank is, according to the present invention, divided into two compartments communicating with each other through an opening formed adjacent the bottom thereof in a partition wall; one compartment adapted to accommodate a mass of the developing material and the other compartment adapted to operatively accommodate means for transferring the developing material onto the photoreceptor surface.

These and other objects and features of the present invention will become apparent from the following description taken in conjunction with preferred embodiments thereof with reference to the accompanying drawings, in which:

FIG. 1 is a schematic sectional elevational view of a magnetically responsive powder applicator according to one embodiment of the present invention, and

FIGS. 2 and 3 are similar views to FIG. 1, showing other embodiments of the present invention.

Before the description of the present invention proceeds, it should be noted that like parts are designated by like reference numerals throughout the accompanying drawings.

Referring now to FIG. 1, there is shown a developing assembly comprising a substantially box-like housing H having the interior divided into two compartments 1 and 4 by means of a partition wall Ha, which compartments 1 and 4 are in communication with each other through a substantially rectangular opening Hb adjacent the bottom of the housing H. The opening Hb may either be formed in the partition wall Ha or be provided by making the partition wall Ha terminate adjacent the bottom of the housing H. Alternatively, the housing H may comprise separate casings corresponding to the compartments 1 and 4, respectively.

The compartment 1 serves as a powder tank for accommodating a mass of finely divided toner particles while the compartment 4 serves as a chamber for accommodating mutually associated operative elements of the developing assembly as will be described in more details.

Within the compartment or powder tank 1, there is an impeller 3 supported for rotation in the direction as shown by the arrow and extending sidewise in parallel to the plane of a known photoreceptor surface 12, and a magnetic roll 5 having a consecutive portion of the outer periphery thereof situated within the compartment 4 through the opening Hb, which magnetic roll 5 is positioned adjacent the bottom of the housing H and also the opening Hb for rotation in the direction shown by the arrow and extends in parallel relation to the impeller 3. While the details of the magnetic roll 5 will subsequently be described, the impeller 3 is positioned so as to carry and throw the developing material within the powder tank 1 toward the magnetic roll 5 during rotation thereof.

The developing material employed in association with the applicator of the present invention is a mixture of known magnetizable carrier beads and known toner particles. However, it is to be noted that, as will be understood from the subsequent description of the present invention, while the toner particles are consumed during use of a copying machine and, therefore, must be supplied into the powder tank 1 each time the level of the toner particles within the powder tank 1 falls below a predetermined level, the carrier beads can be cycled within the housing and, therefore, need not be supplied as frequently as the toner particles. Accordingly, once the compartment 4 is supplied with the sufficient amount of mixture of carrier beads or iron beads and toner particles, only the toner particles need to be replenished thereafter.

The magnetic roll 5 comprises an elongated shaft 5a around which a plurality of alternately magnetically polarized elongated members, each having a substantially sector-shaped section, are rigidly positioned for rotation together with the shaft 5a coupled to a suitable drive motor (not shown) through a reduction gear train (not shown). Accordingly, it will readily be seen that, during rotation of the magnetic roll 5, magnetizable carrier beads magnetically attracted to the magnetic roll 5 and standing on the outer peripheral surface of said roll 5 as magnetic brush bristles 6 contact toner particles under friction and electrostatically attract the toner particles, as indicated by 7, whereby the toner particles are carried by the magnetic roll 5 along with the carrier beads for transference from one position within the powder tank 1 to another position within the compartment 4 through the opening Hb.

Rotatably positioned within the compartment 4 in the vicinity of that portion of the magnetic roll 5 which is exposed towards said compartment 4 through the opening Hb is a clipping roll 8 having a plurality of clipping blades 9 secured to the outer periphery of said roll 8 in equally spaced relation to each other and outwardly extending therefrom in a substantially tangential direction and in a substantially opposite manner to the direction of rotation of the roll 8 shown by the arrow. More specifically, assuming that the magnetic roll 5 is adapted to rotate counterclockwise as indicated by the arrow, the clipping roll 8 is preferably rotated in the same direction so that the clipping blades 9 can, during rotation of the clipping roll 8, successively clip the magnetic bristles 7 formed by the carrier beads and the toner particles on the outer peripheral surface of the magnetic roll 5.

Though the magnetic bristles and, therefore, the developing material, which have successively been clipped by the clipping blades 9 on the clipping roll 8 tend, as the clipping roll 8 continues to rotate counterclockwise, to fall by gravity onto the bottom of the compartment 4, continued rotation of the clipping roll 8 causes the clipping blades 9 to successively scoop the developing material from the bottom of the compartment 4 towards an intermediate transfer sleeve assembly 10 which is positioned substantially above the clipping roll 8.

The intermediate transfer sleeve assembly 10 comprises a hollow cylinder or sleeve 10a made of nonmagnetizable material supported within the compartment 4 for rotation in the direction shown by the arrow and counter to the direction of rotation of the clipping roll 8. For rotating the sleeve 10a, a drive pulley (not shown) which may be coupled to the drive motor common to the magnetic roll 5 and the clipping roll 8 through the same or a different reduction gear train (not shown) may be contacted connected to the outer peripheral surface of said sleeve 10a adjacent one end thereof for transmitting a rotational force of said pulley to said sleeve 10a.

Within the sleeve 10a, there is mounted a plurality of alternately polarized magnetic bars 10b rigidly mounted on a non-rotatable shaft 10c in spaced relation to each other. These magnetic bars 10b are positioned relative to the sleeve 10a such that the developing material successively transferred from the bottom of the compartment 4 to a position substantially immediately below the sleeve assembly 10 is picked up by the sleeve 10a by the effect of magnetic attraction exerted by one of the magnetic bars 10b positioned close to said clipping roll 8 and, then transferred, during rotation of the sleeve 10a, towards a position adjacent an applicator roll assembly 11 while the particles constituting the developing material tumble on the outer peripheral surface of the sleeve 10a under the effects of the changing directions of the magnetic fields respectively produced by the magnetic bars 10b. The particles constituting the developing material form magnetic brush bristles on the outer peripheral surface of the sleeve 10a even during transference thereof towards the position adjacent the applicator roll assembly 11. More specifically, in the illustrated embodiment of FIG. 1, since the applicator roll assembly 11 is positioned adjacent a developing window Hc formed in a wall member of the housing H in opposite relation to the partition wall Ha and at a position laterally adjacent the intermediate sleeve assembly 10 while the latter is positioned substantially intermediate between the partition wall Ha and said applicator roll assembly 11, two of the magnetic bars 10b are approximately 180.degree. spaced from each other about the axis of the shaft 10c while the other magnetic bar 10b is positioned approximately 90.degree. spaced from one of said two magnetic bars 10b, which is the closest to the clipping roll 8, and preceding the other of said two of the magnetic bars with respect to the direction of rotation of the sleeve 10a.

The applicator roll assembly 11 is constructed in a substantially similar manner as the intermediate sleeve assembly 10 and comprises a sleeve or hollow cylinder 11a of nonmagnetizable material supported for rotation in the direction as indicated by the arrow and in a direction counter to the direction of rotation of the sleeve 10a. For effecting rotation of the sleeve 11a, the drive pulley, which has hereinbefore been described as used to rotate the intermediate sleeve 10a in contact therewith, may also be contacted to the outer peripheral surface of said sleeve 11a. Alternatively, while the drive pulley referred to above is drivingly engaged to one of the sleeves 10a and 11a, the other sleeve 11a or 10a may be arranged so as to receive a rotational force of said drive pulley as transmitted through said one of said sleeves 10a and 11a. In any event, the sleeve 11a is positioned such that a portion of the outer peripheral surface of said sleeve 11a is exposed to the outside of the compartment 4 through the developing window Hc and terminates in the close vicinity of the photoreceptor surface 12, which is in the illustrated embodiment of FIG. 1 a portion of a substantially endless belt movable in the direction indicated by the arrow.

Within the sleeve 11a, there is at least one magnetic bar 11b rigidly mounted on a non-rotatable shaft 11c supported in position within the compartment 4. The magnetic bar 11b is positioned relative to the sleeve 11a such that the developing material carried by the sleeve 10a being rotated in the manner as hereinbefore described can be picked up by the sleeve 11a by the effect of magnetic attraction exerted by said magnetic bar 11b forming magnetic brush bristles on the outer peripheral surface of the sleeve 11a in a substantially identical manner as those formed on the outer peripheral surface of the sleeve 10a. The developing material thus transferred onto the sleeve 11a is carried past the developing window Hc to a point where the carrier beads will no longer be held under the influence of the magnetic field developed by the magnetic bar 11b and, consequently, drop off the sleeve 11b and back to the bottom of the housing H in a manner as indicated by 6.

As is well known to those skilled in the art, the magnetic brush bristles carried on the sleeve 11a contact, as they pass in front of the developing window Hc, consecutive portions of the photoreceptor surface 12 having an electrostatically charged latent image opposite in polarity to that of the toner particles so that the latter can be attracted to the photoreceptor surface 12 to develop a powdered image in the configuration of the latent image and, hence, the original to be copied. At this time, the carrier beads remain attracted to the outer peripheral surface of the sleeve under the influence of the magnetic field developed by the magnetic bar 11b until they reach the point where they come out of said magnetic field.

In the embodiment shown in FIG. 2, the developing assembly within the compartment 4 of the housing H is designed so as to apply developing material in a cascading flow over the photoreceptor surface. For this purpose, a known bucket conveyor 13 is employed. Since the construction of the bucket conveyor 13 itself is well known, the structural details thereof are herein omitted and the bucket conveyor 13 will now be described in terms of its function within the compartment 4.

During operation of the bucket conveyor 13 moving in the direction indicated by the arrow in FIG. 2, the magnetic brush bristles formed on the outer peripheral surface of the magnetic roll 5 are successively clipped by buckets 13a of the conveyor 13 in a substantially similar manner as they are clipped by the clipping blades 9 in the foregoing embodiment of FIG. 1. The carrier beads and toner particles (the developing materials) are carried by the buckets 13a upwardly and, as the buckets turn around one of the support rolls 13b which is positioned above the other of the support rolls 13b, are thrown through the developing window Hc onto the photoreceptor surface which, in the embodiment of FIG. 2, is a portion of the peripheral surface of a photoreceptor drum 14. The developing material which has been cascaded over the photoreceptor surface 14 flows in contact with the outer peripheral surface of the photoreceptor drum 14 and, at this time, the toner particles are attracted to the electrostatically charged latent image on the photoreceptor surface in the known manner while the carrier beads are recovered in the bottom of the housing H.

Positioned in the vicinity of the photoreceptor surface 14 and substantially in the plane of the developing window Hc is an elongated plate electrode 15 of arched shape in section to which an electrical potential having a polarity opposite to the electrostatic charge carried by the latent image on the photoreceptor surface is to be applied thereby cancelling an electrical potential carried by the other portion of the photoreceptor surface than the latent image. Application of the electrical potential to the plate electrode 15 is advantageous in that sharp reproduction of the image of the original to be copied can ultimately be obtained on a web of sheet, for example, recording paper.

Referring to FIG. 3, shown there is an embodiment of the present invention wherein the developing material carried by the clipping roll 8 is directly transferred to the applicator roll assembly 11. More particularly, in the embodiment of FIG. 3, the intermediate sleeve assembly 10 employed in the foregoing embodiment of FIG. 1 is omitted.

In the embodiment of FIG. 3, the applicator roll assembly 11 has three magnetic bars 11x rigidly mounted on the fixed shaft 11c in spaced relation to each other about said shaft 11c. It should be noted that a similar considration as has been paid in connection with the positioning of the magnetic bars 10b in the embodiment of FIG. 1 should be paid in connection with positioning of the magnetic bars 11x relative to the sleeve 11a. Moreover, due to the orientation of the clipping blades 9 on the clipping roll 8, the sleeve 11a in the embodiment of FIG. 3 is adapted to be rotated counterclockwise as indicated by the arrow while the photoreceptor surface 12 is correspondingly adapted to be moved downwards as indicated by the arrow and in a direction counter to the direction of the rotation of the sleeve 11a.

A magnetic cylinder 15, which corresponds to the magnetic roll 5 of FIG. 1 and is constructed in a substantially similar manner as said magnetic roll 5 of FIG. 1, is non-rotatably supported by the housing within the compartment 1. Positioned around said magnetic cylinder 15 is a rotatable sleeve 16 supported in a similar fashion to the sleeve 11a. The assembly including the magnetic cylinder 15 and the sleeve 16 functions in a manner substantially similar to the magnetic roll 5 employed in any of the embodiments of FIGS. 1 and 2.

From the foregoing full description of the present invention, it has now become clear that, since a rotatable supply means, such as the magnetic roll 5 or the magnetic cylinder 15, is employed, the developing assembly can be arranged in any position lateral, above or below the powder tank 1. It is also clear that the magnetizable carrier beads are so circulated within the housing H that a fresh mass of carrier beads need not be frequently supplied into the housing H.

From the foregoing description and with reference to the accompanying drawings, it is also clear that various changes and modifications are apparent to those skilled in the art. By way of example, the magnetic roll 5 which has been described as employed in the embodiments of FIGS. 1 and 2 may be replaced by the assembly including the magnetic cylinder 15 and the sleeve 16 which has been described as employed in the embodiment of FIG. 3. Alternatively, the assembly including the magnetic cylinder 15 and the sleeve 16 of FIG. 3 may be replaced by the magnetic roll 5 of FIGS. 1 and 2. Furthermore, the sleeve 16 may be fixed, in which case the magnetic cylinder 15 should be designed so as to rotate with the shaft.

Accordingly, these changes and modifications are to be understood as included within the true scope of the present invention unless they depart therefrom.