BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates an embodiment of the two dispenser system of this invention.
FIG. 2 illustrates a typical electrostatic marking system that can be used with the two dispenser system of this invention.
DETAILED DISCUSSION OF DRAWINGS AND PREFERRED EMBODIMENTS
FIG. 1 depicts an embodiment of the two dispenser system 129 of this invention. The two dispenser system includes two open-ended hoppers 106 and 107, each having a dispensing regulator such as a foam roller 108 and 109, respectively, positioned in the open ends thereof. A supply of toner or replenisher material (comprising toner particles or a mixture of carrier particles and toner particles wherein the majority of mixture by weight is toner particles), referred to generally as material 110 is stored in hopper 106. A supply of developer material (comprising a mixture of carrier particles and toner particles wherein the majority of mixture by weight is carrier particles), referred to generally as material 111 is stored in hopper 107. As rollers 108 and 109 rotate the materials 110 and 111 are discharged from the hoppers 106 and 107 into the developer housing 101 and reservoir 112 shown in FIG. 2. The dispensing regulators 108 and 109 may be individually adjusted and controlled to regulate the dispense rates of materials 110 and 111 from hoppers 106 and 107. As rollers 108 and 109 rotate, materials 110 and 111 are discharged from dispensers 106 and 107 into a developer housing 101 and reservoir 112 shown in FIG. 2. These materials can be transported to the housing 101 and reservoir 112 by any suitable means such as a conveyor channel 104 using an auger 105 or a conveyer belt or any other suitable means. A sensor or control may be used in each dispenser 1 (106) and dispenser 2 (107) to regulate and control the flow of materials 110 and 111 out of dispensers 106 and 107.
Referring now to FIG. 2, there are shown the details of an Hybrid scavengeless development (HSD) developer which is one system where the two dispenser system of this invention can be used. Obviously, the two dispenser system of FIG. 1 can be used with any other suitable marking or development system other than that shown in FIG. 2. Briefly, HSD technology deposits toner onto the surface of a donor roll via a conventional magnetic brush. The donor roll generally consists of a conductive core covered with a thin (50 to 200 micron) partially conductive layer. The magnetic brush roll is held at an electrical potential difference relative to the donor core to produce the field necessary for toner development. Applying an AC voltage to one or more electrode wires spaced between the donor roll and the imaging belt provides an electric field which is effective in detaching toner from the surface of the donor roll to produce and sustain an agitated cloud of toner particles about the wires, the height of the cloud being such as not to be substantially in contact with the belt. Typical AC voltages of the wires relative to the donor are 700-900 Vpp at frequencies of 5 15 kHz and may be applied as square waves, rather than pure sinusoidal waves. Toner from the cloud is then developed onto the nearby photoreceptor by fields created by a latent image. However, in another embodiment of the hybrid system, the electrode wires may be absent. For example, a hybrid jumping development system may be used wherein an AC voltage is applied to the donor roll, causing toner to be detached from the donor roll and projected towards the imaging member surface.
Continuing with FIG. 2, marking apparatus or development station 100 comprises a reservoir 112 containing original developer material 113 and receives the materials 110 and 111 from the dispensers 106 and 107 when practicing the present invention. Typically, the developer material may be either of the one component or two component type. For use in the present invention, developer material 113 is of the two component type, that is it comprises carrier granules and toner particles. The two-component developer material 113 may be of any suitable type. The use of an electrically conductive developer can eliminate the possibility of charge build-up within the developer material on the magnetic brush roll which, in turn, could adversely affect development at the second donor roll. In one embodiment, the two-component developer consists of 5-5 micron insulating toner particles, which are mixed with 50-100 micron conductive magnetic carrier granules such that the developer material comprises from about 90% to about 99% by weight of carrier and from 10% to about 1% by weight of toner. By way of example, the carrier granules of the developer material may include a ferromagnetic core having a thin layer of magnetite overcoated with a non-continuous layer of resinous material. The toner particles may be made from a resinous material, such as a vinyl polymer, mixed with a coloring material.
In FIG. 2, the reservoir or developer housing 101 comprises within the housing reservoir or housing auger or augers, indicated at 114, which are rotatably-mounted in the reservoir chamber. Augers 114 serve to transport and to agitate the material within the reservoir and encourage the toner particles to charge and adhere triboelectrically to the carrier granules. Magnetic brush roll 115 transports developer material 113 from the reservoir 112 to loading nips 116, 117 of donor rolls 118, 119. Magnetic brush rolls are well known, so the construction of roll 115 need not be described in great detail. Briefly the roll comprises a rotatable tubular housing within which is located a stationary magnetic cylinder having a plurality of magnetic poles impressed around its surface. The carrier granules of the developer material are magnetic and, as the tubular housing of the roll 115 rotates, the granules (with toner particles adhering triboelectrically thereto) are attracted to the roll 115 and are conveyed to the donor roll loading nips 116, 117. Metering blade 120 removes excess developer material from the magnetic brush roll 115 and ensures an even depth of coverage with developer material before arrival at the first donor roll loading nip 116.
At each of the donor roll loading nips 116, 117, toner particles are transferred from the magnetic brush roll 115 to the respective donor roll 118, 119. The carrier granules and any toner particles that remain on the magnetic brush roll 115 are returned to the reservoir 112 as the magnetic brush continues to rotate. The relative amounts of toner transferred from the magnetic roll 115 to the donor rolls 118, 119 can be adjusted, for example by applying different bias voltages to the donor rolls; adjusting the magnetic to donor roll spacing; adjusting the strength and shape of the magnetic field at the loading nips and/or adjusting the speeds of the donor rolls. Sensors can be used where suitable.
Each donor roll 118 and 119 transports the toner to a respective development zone 121, 122 through which the photoconductive belt 103 passes. At each of the development zones 121, 122, toner is transferred from the respective donor roll 118, 119 to the latent image on the photoconductor belt 103 to form a toner powder image on the belt 103. Various methods of achieving an adequate transfer of toner from a donor roll to a latent image on a imaging surface are known and any of those may be employed at the development zones 121, 122. Transfer of toner from the magnetic brush roll 115 to the donor rolls 118, 119 can be encouraged by, for example, the application of a suitable D.C. electrical bias to the magnetic brush and/or donor rolls. The D.C. bias (for example, approximately 70 V applied to the magnetic roll) establishes an electrostatic field between the donor roll 118 and 119 and magnetic brush rolls 115, which causes toner particles to be attracted to the donor roll 118 and 119 from the carrier granules on the magnetic brush roll 115.
In the device of FIG. 2, each of the development zones 121, 122 is shown as having a pair of electrode wires 127, 128 disposed in the space between each donor roll 118, 119 and belt 103. The electrode wires may be made from thin (for example, 50 to 100 micron diameter) stainless steel wires closely spaced from the respective donor roll. The wires are self-spaced from the donor rolls by the thickness of the toner on the donor rolls and may be within the range from about 5 micron to about 20 micron (typically about 10 micron) or the thickness of the toner layer on the donor roll.
For each of the donor rolls 118 and 119, the respective electrode wires 127 and 128 extend in a direction substantially parallel to the longitudinal axis of the donor roll. An alternating electrical bias is applied to the electrode wires by an AC voltage source 123. The applied AC establishes an alternating electrostatic field between each pair of wires and the respective donor roll, which is effective in detaching toner from the surface of the donor roll and forming a toner cloud about the wires, the height of the cloud being such as not to be substantially in contact with belt 103. The magnitude of the AC voltage in the order of 200 to 500 volts peak at frequency ranging from about 8 kHz to about 16 kHz. A DC bias supply (not shown) applied to each donor roll 118, 119 establishes electrostatic fields between the photoconductive belt 103 and donor rolls for attracting the detached toner particles from the clouds surrounding the wires to the latent image recorded on the photoconductive surface of the belt.
After development, excess toner may be stripped from donor rolls 118 and 119 by respective cleaning blades (not shown) so that magnetic brush roll 115 meters fresh toner to the clean donor rolls. As successive electrostatic latent images are developed, the toner particles within the developer material 113 are depleted. A developer dispenser 129 such as those generally described with reference to FIG. 2, stores a supply of toner particles, with carrier particles. The dispenser 129 is in operative communication with reservoir 112 and, as the concentration of toner particles in the developer material is decreased (or as carrier particles are removed from the reservoir as in a “trickle-through” system or in a material purge operation as discussed below), fresh material (toner and/or carrier from dispensers 106 and 107) are furnished to the developer material 113 in the reservoir 112. The auger 114 in the reservoir chamber mixes the fresh material with the remaining developer material so that the resultant developer material therein is substantially uniform with the concentration of toner particles being optimized. In this way, a substantially constant amount of toner particles is in the reservoir with the toner particles having a constant charge; this is an important aspect of the present invention. Developer housing 101 may also comprise at least one outlet 124 for removing developer material from the housing 101 in accordance with a developer material purge operation. The rectangle indicated as element 129 in the upper left portion of FIG. 2 represents the total structure of FIG. 1. The dispenser outlets 130 feed materials 110 and 111 directly or indirectly into reservoir 112 by any suitable means. Outlet 124 may further comprise a regulator (not shown) such as an auger or roller to assist in removing material from the housing.
Various sensors and components within developer apparatus 100 are in communication with system controller 102 which monitors and controls the operation of the developer apparatus to maintain the apparatus in an optimal state. In addition to voltage source 123, donor rolls 118 and 119, magnetic brush roll 115, augers 114, dispenser 129 and outlet 124, system controller 123 may, for example, communicate with a variety of sensors, including, for example, sensors to measure toner concentration, toner charge, toner humidity, the voltage bias of the developer material, bias of the magnetic brush roll, the bias of the donor roll, and image quality determined by sensor 125 adjacent imaged photoconductor layer 103.
In summary, the embodiments of the present invention provide an electrostatic marking system and a development station in operative relationship with other stations in said system. This development station comprises a developer housing enabled to hold toner and carrier. The housing is enabled to accommodate replenishing in the housing of the toner by a first dispenser with a replenishing material wherein a majority of the material by weight is toner particles, and enabled to accommodate the developer by a second dispenser with a replenishing material wherein a majority of the material by weight is carrier particles.
In this marking system the image quality of marks on a receiving medium is periodically gauged by a sensor to determine image quality and activation of at least one of the first and second dispensers. The first and second dispensers are independently controlled when adding contents to the housing or reservoir 112. Activation of the first and second dispenser is provided when image low area coverage of marks on a receiving medium results after extended periods of time.
This system is enabled to provide improved image quality and reduce developer waste over extended periods of use. At least the second dispenser is activated when a system sensor or actuator reaches a critical value in the housing.
Embodiments of this electrostatic marking system comprise, as above noted, a development station operatively connected to other stations in the system. The development station comprises a developer housing enabled to hold toner, carrier and at least one first sensor. The housing is also enabled to accommodate replenishing of materials in the housing by a first and second dispenser. The first dispenser is enabled to replenish toner in the housing. The first and second dispensers are enabled to be actuated when a system sensor or actuator in the housing reaches a predetermined critical value. This critical value is measured by at least one first sensor which is operatively connected to an actuation component which actuates either or both first and second dispensers.
The system is enabled to reduce a level of scheduled maintenance required for the system. The second dispenser is enabled to add and accept new developer to the housing and the system is enabled to dispense old developer for removal from the system. The first dispenser is enabled to dispense a material to the housing wherein a majority of said material by weight is toner particles. The second dispenser is enabled to dispense a material into the housing wherein a majority of the material by weight is carrier particles.
In this system, toner dispensed into the housing by either the first or second dispenser comprises toner that may be optimized for high developability, thereby allowing the developability of material in the housing to recover at a rate faster than if normal toner was dispensed therein. Fresh carrier dispensed or replenished to the housing is at a much lower amount, thereby minimizing a total amount of carrier dispersed into said system to minimize the quantity of developer waste generated by the printer.
As noted, the first and second dispensers are independently controlled. The development station is enabled to be retrofitted into existing electrostatic marking apparatus and reduced developer waste is provided by this novel development station.
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
Patent Application
20080044190
