US3608792A - Apparatus for dispensing finely divided particulate material - Google Patents

Abstract

Method and apparatus for dispensing a finely divided particulate material in which a resilient member having a textured outer surface of cell-like cavities being adapted to receive and support particulate material therein is passed through a quantity of the particulate material to load said member and the member then transported to a discharge station where the member is deformed sufficiently to force the particulate material from the surface of said member.

Description

United States Patent [72] inventor Frederick W. Hudson West Henrietta, N.Y. [21] Appl. No. 796,965 [22] Filed Feb. 6, 1969 [45] Patented Sept. 28, 1971 [73] Assignee Xerox Corporation Rochester, N.Y.

[54] APPARATUS FOR DISPENSING FINELY DIVIDED PARTICULATE MATERIAL 3 Claims, 4 Drawing Figs.

[52] US. Cl 222/407, 222/414,222/D1G. 1 [51] Int. Cl (10 11/00 [50] Field of Search 222/414, 410, 408, 407, 406, 403, DIG. 1,311, 312, 315

[5 6] References Cited UNITED STATES PATENTS 2,965,266 12/ 1960 Rutkus, Jr. et al 222/D1G. 1 3,399,652 9/1968 Gawron 22/D1G. 1

1,855,214 4/1932 Alton 222/414 1,894,058 1/1933 Rice 222/414 UX 2,237,504 4/1941 Roath 222/414 UX 2,329,666 9/1943 Syverud.. 222/414 X 3,128,015 4/1964 Wallis 222/414 X 3,172,574 3/1965 Hiler et a1. 222/414 X 3,221,938 12/1965 Yonkers et a1 222/D1G. 1

Primary Examiner-Samuel F. Coleman Assistant Examiner-David A. Scherbel Attorneys-Norman E. Schrader, James J. Ralabate and Michael J. Colitz, Jr.

ABSTRACT: Method and apparatus for dispensing a finely divided particulate material in which a resilient member having a textured outer surface of cell-like cavities being adapted to receive and support particulate material therein is passed through a quantity of the particulate material to load said member and the member then transported to a discharge station where the member is deformed sufficiently to force the particulate material from the surface of said member.

'PATENTED ssrza nan sum 1 or INVENTOR. FREDERICK W. HUDSON BY '7 A TTORNEY APPARATUS FOR DISPENSING FINELY DIVIDED PARTICULA'IE MATERIAL The invention invention relates to method and apparatus for dispensing finely divided particulate material and, in particular, to an improvement in xerographic toner dispensing.

More specifically, this invention relates to method and apparatus for unifonnly dispensing finely divided toner material evenly across a xerographic developing apparatus. In the art of xerography, a plate formed of the photoconductive material such as selenium, is placed over a conductive substrate and the surface of the plate charged uniformly. The plate is then exposed to a light image of an original to be reproduced. The photoconductive surface becomes conductive under the influence of the light image so as to selectively dissipate the charge found thereon to form an electrostatic latent image. In the xerographic process, a pigmented resin material, commonly referred to as toner, is electrostatically attracted to the latent electrostatic image on the photoconductive surface is proportion to the amount of charge found thereon. Areas of small charge concentration become areas of low toner density while areas of greater charge concentration become proportionally more dense. The fully developed image isyusually transferred from the photoconductive plate to a final support material, as for example, paper, and the image fixed thereto to form a permanent record of the original.

The most widely accepted method of developing a latent electrostatic in automatic xerographic reproducing apparatus is by the conventional cascade development method. In a cascade system, a two-component developer material is employed to develop the latent electrostatic image. Two-component developer comprises a toner blended from finely subdivided materials to yield a fine powder composition and a course carrier material to which the toner is electrostatically bonded. The toner and carrier materials are triboelectrically remote and interact when brought into rubbing contact to assume oppositely charged polarities. The charged toner material is electrostatically attracted to the carrier surface to which it remains bonded in a charged state. During the developing process, the two-component material is poured or cascaded over an image-bearing photoconductive surface where the carrier gives up its toner to the charged image areas thus making the latent image visible.

As can be seen, the toner supply in the development system becomes deplete as the toner is used up in the development process and must therefore be replaced periodically within the system in order to maintain the toner to carrier ratio in the automatic equipment at a level sufficient to sustain continuous operation. The addition of new toner into a developing system has not been heretofore a problem in the xerographic art. However, with the advent of new xerographic developing apparatus and techniques, particularly those for developing solid areas and half-toned images, it is now extremely important that the dispensing apparatus be able to rapidly and accurately deliver a uniformly distributed quantity of particulate material to the development system upon demand. It has been found that dispensing devices which pour or gravity feed toner from a container into a developing system cannot provide the degree of accuracy or uniformity of dispensing required by these newer systems.

It is therefore an object of this invention to improve apparatus for dispensing a finely divided particulate material.

It is a further object of this invention to improve xerographic image development.

Yet another object of this invention is to accurately dispense an evenly distributed quantity of finely divided particulate material from a storage container.

A still further object of this invention is to improve the operation of xerographic toner-dispensing apparatus wherein accurately metered amounts of toner material 'can be uniformly added to a xerographic development system.

These and other objects of the present invention are attained by means of a resilient member having an outer surface made up of open-celled cavities which are capable of receiving and holding therein finely divided particulate material,

brought in contact therewith, means to transport the resilient member from a first loading station when particulate material is brought into contact with the open-celled member and a second discharge station at which is positioned deforming means biasing the resilient member sufficiently to force the particulate material from the surface of said member.

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

FIG. 1 illustrates schematically a preferred embodiment of a xerographic apparatus adapted for continuous and automatic operation and incorporating a toner dispenser in accordance with the present invention;

FIG. 2 is a side elevation in partial section showing the toner dispenser of the present invention mounted in operative relation with the xerographic developer housing illustrated in FIG.

FIGS. is an end view of the toner dispenser of the present invention taken along lines 33 of FIG. 2;

FIG. 4 is a partial side elevation of a second embodiment of the toner dispenser of the present invention partially broken away to illustrate various elements of the dispensing device in which the dispensing element is an endless belt.

Referring now to FIG. 1, there is shown an embodiment of the instant invention within a suitable environment such as an automatic xerographic reproducing machine having a xerographic plate including a photoconductive layer or lightreceiving surface I1 placed on a conductive backing and formed in the shape of a drum. The drum 10 is mounted to a shaft which is joumaled for rotation in the machine frame so as to rotate the drum in the direction indicated by the arrow thus causing the drum surface to sequentially pass a plurality of xerographic processing stations.

For the purposes of the present disclosure, the several xerographic processing stations in the path of movement of the drum surface will be described functionally as follows:

a charging station A, at which a uniform electrostatic charge is deposited on the photoconductive layer of the drum surface;

an exposure station B, at which a light or radiation pattern of an original document support on platen 8 is projected onto the drum surface to dissipate the charge found thereon in the exposed areas thereby forming a latent electrostatic image;

a development station C, at which xerographic developing materials including toner particles having electrostatic charge opposite to the electrostatic image on the drum surface are cascaded over the drum wherein the toner particles adhere to the electrostatic latent image to make the latent image visible in configuration of the original document to be reproduced;

a transfer station D, at which the xerographic powder image is electrostatically transferred from the drum surface to a final support material; and

a drum-cleaning and discharge station E, at which the drum surface is brushed to remove residual toner particles remaining thereon after image transfer and at which the drum surface is exposed to a light source to effectively complete discharge of any residual electrostatic charge found thereon.

It is believed that the foregoing description is sufficient for purposes of the present application to show the general operation of the xerographic reproducing apparatus employing a toner dispenser constructed in accordance with the present invention. Although not shown, suitable drive means are provided to drive the drum, sheet feed mechanisms for moving the final support material, developer conveyors, and other operating mechanisms at predetermined speeds relative to each other for proper machine operations. For further details concerning the specific construction of the xerographic apparatus shown herein, reference is had to US. Pat. No. 3,30 l ,126 issued in the name of Robert F. Osborne, et al.

In the specific arrangement shown, the developer conveyor system includes a plurality of transverse buckets 15 that are horizontally supported between two endless belts I6 posi-- tioned on opposite sides of the developer housing and which extend over pulleys 17 that are fixed on transverse shafts 18 and 19. For actuating the toner conveyor system, upper shaft 18 is driven through means of a belt and motor arrangement (not shown) that causes the conveyor system to rotate in the direction indicated constantly while the machine is in operation. The developer material conveyed upwardly by the conveyor system is discharged into an entrance chute (not shown) that extends transversely across the entire developing system structure, and which extends downwardly to direct the flow of developer material into contact with the xerographic drum surface. Toner particles are pulled away from the carrier components thereof and deposited on the drum surface to form a xerographic powder image. The partially denuded carrier particles pass off the drum surface are directed back into the lower sump portion of the developer housing. As toner powder images are formed, additional toner particles must be supplied to the developer material in proportion to the amount of toner deposited on the drum surface. To supply additional toner particles to the developer material, there is provided a toner-dispensing mechanism 13 that constitutes one form of the subject matter of the present invention.

Referring specifically to FIGS. 2 and 3, there is shown in detail the toner dispenser of the present invention in which toner material is stored within a hopperlike container and is dispensed directly therefrom into the developer material supported within developer housing 14. As will be explained in greater detail below, dispensing roll 20 is adapted to pick up particles of toner material stored within hopper 21 and transport the toner exterior the hopper where it is uniformly dispensed into the supply developer material which has been cascaded over the xerographic drum surface. In order to ensure uniform distribution of new toner, the toner dispenser roll extends horizontally substantially across the drum surface and functions to deliver an even quantity of toner across the entire width of the developer housing in accordance with the dispensing rate required.

In the form of the invention shown in FIGS. 2 and 3, the toner-dispensing apparatus 13 includes a rectangular-shaped hopper 21 generally formed of inwardly turned sidewalls 22, 23 and substantially parallel end walls 24, 25 (FIG. 3) that are integrally connected at their respective corners to support particulate material therein. The lower part of the sidewalls 22, 23 terminate in dependent base members 28 and 29, respectively, which cooperate to describe an opening 34 through which toner material is dispensed directly into the developer material supported within developer housing 14. The container base generally referred to as 60 extends horizontally along the length of the developer housing with left-hand base member 28, as shown in FIG. 2, secured to developer housing wall and right-hand base member 29 secured to developer housing wall 30 and right-hand base member 29 secured to the lower developer housing 31, as for example by means of spot welding.

Horizontally supported in container base 60 directly over opening 34 is dispensing roll 20 which extends transversely across the width of the developer housing. The dispensing roll is securely mounted upon shaft 26, as for example by glueing, and the shaft in turn, rotatably supported in bearing 35 provided in end walls 24, 25 (FIG. 3). The dispensing roll may be fabricated of any number of available foamed materials which are capable of being formed with a cellular structure. The dispensing roll of the present invention has an open-celled outer surface wherein the surface of the roll is made up of a series of small open cavities or cells each being capable of receiving and holding therein a substantially uniform quantity of finely divided particulate material. Typical examples of such foamable materials which can be formed in an open-cell configuration are polyurethanes, polyvinyl chloride, silicones, polystyrenes, styrene acrylonitriles, cellulose acetate, and phenolics. Foaming of these materials can be accomplished either by a mechanical frothing, a physical dissolving of a gas or liquid within the resin material, or by chemically incorporating a foaming or blowing agent directly into the material which is capable of releasing an inert gas within the resin when the temperature of the resin is increased.

A typical roll for use in the preferred embodiment of this invention is one fabricated of a urethane foam. Urethane foams are cellular plastics formed by the reaction of a polyol and an isocyanate, generally in the presence of a catalyst. The two materials react rapidly in the presence of tertiary amines, in combination with stannous or other metalic salts, to produce a material which is relatively strong but yet resilient at room temperature. The term resiliency, as herein used, is the property of the material, upon being deformed, to recover its original posture rapidly when the force of deformation is removed. It is found that by varying the ratio of raw materials and the foaming condition, it is possible to produce a flexible foam having a broad spectrum of end properties. For example, cell formation can stabilized by means of chemical forming in the presence of a surfactant which controls the size of gas bubbles thus promoting uniform cell structures. Silicones and/or organic surfactants, generally ionic, are most widely used to control the expansion of gas bubbles. By properly choosing materials and controlling the formation of the cell-like structures, it is possible to form a foamed-polyurethane-dispensing roll as herein described having high tensile strength and extremely good resiliency.

Resilient dispensing roll 20 is mounted within the base of hopper 21 to form a movable seal capable of retaining toner material within hopper 21. The parallel ends of the cylindrical roll are supported in light-biasing contact with the end walls 24, 25 of the hopper to prevent toner material from passing between the sides of the roll and the hopper wall. As illustrated in FIG. 2, the cylindrical outer surface of the roll is arranged to pass sequentially through the particulate material in the hopper and the dispensing opening 34 as the roll is rotated in the direction indicated. The individual dependent base members are each provided with an upper boss 37 and lower boss 38 which extend horizontally across the width of the hopper and which are arranged to protrude into the path of rotation of the roll. The upper boss bosses 37 are adapted to deform the roll inwardly sufficiently enough to form a seal capable of preventing toner material from escaping from the hopper around the surface area of the roll. As can be seen, the entire outer periphery of the roll is mechanically biased in contact with the interior surface of the container to form a movable seal for retaining the fine material within the container. Lower bosses 38 also deform the roll surface inwardly and provide a second seal further ensuring that there is no unwanted leakage of toner from the hopper. However, as will be explained in greater detail below, the lower bosses perform a second function. The lower bosses deform the resilient roll sufficiently so that the toner material being transported on the roll surface is forced from the surface of the roll and dispensed through openings 34.

Referring now to FIG. 3, the left-hand portion of shaft 26 passes through hopper end wall 24 and has securely affixed to the end thereof a gear 40. Gear 40 is mated to any suitable drive means for rotating the dispensing roll in the direction indicated at a speed to produce the desired dispensing rate.

As previously noted, the resilient roll cooperates with the internal surface of the container to provide a movable seal for preventing unwanted toner from escaping from the container. In operation, the roll also functions to deliver a substantially uniform and even quantity of particulate material across the dispensing opening. It has been found that the individual cell like cavities on the roll surface become loaded with toner particles when the particulate material is brought in contact with the roll surface as for example when the roll is rotated through a 'quantity of such material. Although the exact loading mechanism is not clearly understood, it is believed that the individual cavities fill themselves in a scooplike manner as they are moved through the fine granular material much as an open-mouthed container would fill itself if brought first through a quantity of sand. Because the walls of the cavities are resilient, the cavities also have the unique quality of grasping or holding the particulate material that is received therein. By forming the cavities to a substantially uniform size, each individual cell is capable of supporting approximately an equal amount of particulate material. Furthermore, the formation of a unifonn cell size ensures that the material is evenly dis tributed across the surface of the roll. In effect, the foamed elastomeric roll as herein disclosed is not only a self-loading device but also has the capability of storing and holding a load that is evenly distributed across the surface of the member.

After moving through the supply of particulate material in the container, the toner-ladened roll surface is then moved sequentially past upper boss 37, the interior surface 61 of the container and lower boss 38 before passing into dispensing opening 48. As noted above, the roll surface is compressed slightly by upper boss 37 to P event the supply of material in the container from escaping. However, the mechanical biasing pressure is insufficient to destroy the rolls unique loading and toner'holding properties. Although some toner may be dislodged as the deformed roll surface is moved past the upper protruding surface, the amount of toner lost is evenly distributed over the roll surface. In effect, the relative distribution of toner across the roll remains unchanged. After moving past boss 37, the resilient roll recovers slightly and comes in sliding contact with the interior surface 61 of the container. The curved wall surface acts to constrain the roll surface and to further hold the particles in the cells as the roll is forwarded toward the dispensing opening.

It has been found that two distinct mechanisms, used alone or in combination, can be employed to remove particulate material from the surface of the open-celled elastomeric roll. The first method is to defonn the resilient roll surface just prior to its entering the dispensing opening so that further rotation of the roll causes the roll surface to spring back to its original posture as it passes into the opening. It should be understood that the roll is sufficiently deformed prior to entering the opening so that the toner in or on the roll surface is mechanically thrown into the opening as the roll recovers. Secondly, the particulate material can also be mechanically pushed from the roll surface by means of a stationary compressing member or the like placed in interference with the roll surface. As the roll moves toward the stationary compressing member, the surface of the roll is deformed to enlarge the cavity openings. Further movement of the roll towards the member causes the granular material to be pushed or forced from the surface of the roll.

in the instant embodiment of the present invention, both methods of removing toner material from the roll surface are employed. However, it should be quite clear that either of these two methods could be used along or in combination thereof to dispense material from the roll surface without departing from the teachings of the present invention. Referring now specifically to FIG. 3, two bosses which protrude into the path of movement of the roll surface are located on the sidewalls of the container adjacent to container opening 34. As the roll is rotated in the direction indicated the right-hand boss, as shown in FIG. 2, acts to compress the roll prior to its entrance into opening 48. Further rotation of the roll surface into opening 34 allows the deformed roll to spring back to its original shape to mechanically throw the toner from the surface thereof. Further rotation of the roll through the opening brings the roll surface into biasing contact with the left-hand lower boss. This seconding member protruding into the path of travel of the roll pushes against the upwardly moving surface to cause the cell to open and also acts to scrape or push any toner remaining on the roll surface back into dispensing oiehing 34. By employing this two step toner removal technique, a complete and thorough dispensing of material is accomplished.

Referring now specifically to FIG. 4, there is shown a second embodiment of the present invention in which the dispensing member is formed in the shape of an endless belt. A

resilient open-celled elastomer material 42, as herein disclosed, lS cast on a brass substract 43 to form a belt 44. The

belt is suspended between pulleys 47 and 48 and is driven over idler pulleys 49 and 50 wherein the belt moves continually through the openings provided between toner container 45 and developer housing 14. Drive pulley 47 is mounted on a transverse shaft 52 which, in turn, is driven by motor means 53 to move the belt in the direction indicated. In operation, belt 44, which extends horizontally across the width of developer housing 14, is brought into contact with the supply of toner material supported within container 45. The open-celled cavities on the resilient belt surface become uniformly loaded with toner and are carried upwardly into the developer housing 14. A back deflector plate 58 mounted in the container protects the surface of the belt and permits new toner to be added to the container without disturbing the operation of the dispensing unit. As the belt continues to rotate around pulley 48 the surface of the belt is inverted over the developer material supported within the housing. A deforming member 55 is securely affixed to sidewall 56 of the housing and is positioned to compress a portion of the belt surface in this inverted region. As the belt is moved through the inverted zone over the developer mix, the deforming member both compresses the belt surface sufficiently to open the cell cavities and to push or force the toner from the surface of the belt into the developer mix.

While the invention has been described with reference to the structure disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modification or changes as may come within the scope of the following claims.

1. Apparatus to dispense finely divided particulate xerographic toner material including a resilient cylindrical member having an outer surface formed of opened-celled cavities being of such a size as to be capable of holding therein toner material for being transported thereby, the open-celled cavities also being of such a size that when expanded they are capable of permitting the discharge of toner material therefrom,

a loading station adjacent said cylindrical member,

a discharge station adjacent said cylindrical member,

a pair of first boss members projecting into said cylindrical member along spaced-apart lines to define said loading station therebetween, said first boss members projecting into said cylindrical member sufficiently to cause the expansion of the celled cavities at said loading station for the reception of toner material therein,

a pair of second boss members projecting into said cylindrical member along spaced-apart lines to define said discharge station therebetween, said second boss members projecting into said cylindrical member sufficiently to cause the expansion of the celled cavities at said discharge station for the discharge of toner material therefrom,

means for rotating said cylindrical member whereby sequential portions of the surface thereof move between said loading station whereat toner material may be received into the expanded celled cavities thereof and said discharge station whereat toner material may be discharged from the expanded celled cavities thereof and side members in contact with the end faces of said cylindrical member to prevent toner material from passing between said loading station and said discharge station thereadjacent.

.2. The apparatus as set forth in claim 1, and further including curved surfaces, each connecting a first and a second boss member for maintaining said opened-celled cavities compressed thereadjacent.

3. The apparatus as set forth in claim 1, wherein said cylindrical member is made of a foamed open-celled urethane material.

Claims (3)

1. Apparatus to dispense finely divided particulate xerographic toner material including a resilient cylindrical member having an outer surface formed of opened-celled cavities being of such a size as to be capable of holding therein toner material for being transported thereby, the open-celled cavities also being of such a size that when expanded they are capable of permitting the discharge of toner material therefrom, a loading station adjacent said cylindrical member, a discharge station adjacent said cylindrical member, a pair of first boss members projecting into said cylindrical member along spaced-apart lines to define said loading station therebetween, said first boss members projecting into said cylindrical member sufficiently to cause the expansion of the celled cavities at said loading station for the reception of toner material therein, a pair of second boss members projecting into said cylindrical member along spaced-apart lines to define said discharge station therebetween, said second boss members projecting into said cylindrical member sufficiently to cause the expansion of the celled cavities at said discharge station for the discharge of toner material therefrom, means for rotating said cylindrical member whereby sequential portions of the surface thereof move between said loading station whereat toner material may be received into the expanded celled cavities thereof and said discharge station whereat toner material may be discharged from the expanded celled cavities thereof and side members in contact with the end faces of said cylindrical member to prevent toner material from passing between said loading station and said discharge station thereadjacent.

2. The apparatus as set forth in claim 1, and further including curved surfaces, each connecting a first and a second boss member for maintaining said opened-celled cavities compressed thereadjacent.

3. The apparatus as set forth in claim 1, wherein said cylindrical member is made of a foamed open-celled urethane material.

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