The present invention relates to apparatus for storing and dispensing particulate material and in particular to a toner or developer cartridge for electrostatographic printing machines.
In an electrostatographic reproducing apparatus commonly in use today, a photoconductive insulating member is typically charged to a uniform potential and thereafter exposed to a light image of an original document to be reproduced. The exposure discharges the photoconductive insulating surface in exposed or background areas and creates an electrostatic latent image on the member which corresponds to the image areas contained within the usual document. Subsequently, the electrostatic latent image on the photoconductive insulating surface is made visible by developing the image with developing powder referred to in the art as toner. Most development systems employ a developer material which comprises both charged carrier particles and charged toner particles which triboelectrically adhere to the carrier particles. During development the toner particles are attracted from the carrier particles by the charge pattern of the image areas in the photoconductive insulating area to form a powder image on the photoconductive area. This image may subsequently be transferred to a support surface such as copy paper to which it may be permanently affixed by heating or by the application of pressure. Following transfer of the toner image to a support surface, the photoconductive insulating member is cleaned of any residual toner that may remain thereon in preparation for the next imaging cycle.
As the toner particles are depleted from the developer material it is necessary to dispense additional toner particles into the developer mixture. Further, the carrier has a limited life due to a variety of problems occurring with continued use. For example, the carrier may become impacted with toner thereby altering its triboelectric properties or if the carrier is coated with the material to enhance triboelectric properties the coating may deteriorate with time. U.S. Pat. No. 4,614,165 to Folkins et al. describes a developing process involving the addition of both toner particles and carrier particles to the developer in the developer housing to insure that the usable life of the developer material in the chamber at any point in time is at least equal to the life of the photographic printing machine. To accommodate the addition of further carrier and toner material, waste or spent developer is removed from the developer housing when it seems to exceeds a predetermined quantity. Thus, in most commercial embodiments the concentration of toner particles within the developer mixture is maintained substantially constant. To achieve this particulate material containers for toner and/or developer which discharge the toner and/or developer into the development system have been used. In replenishing the toner particles in an electrostatographic printing machine, it is important to minimize any spillage which may result in contamination of otherwise uncontaminated areas. Further, the toner particles being very finely ground may become airborne carrying this contamination to other areas but immediately adjacent the development system. In addition, the spilled toner particles have a tendency to cling to an operator's hands or to the surrounding environment. Accordingly, there is a need to provide a toner and/or developer storing and dispensing device which may be used to periodically replenish the toner and/or developer in an automatic printing machine and which can avoid the above difficulties thereby overcoming a dirty and messy operation.
While the desire to minimize contamination by the toner or developer and provide for "white glove" machine operator involvement during the replenishment activity of the toner or developer is of paramount importance it is also noted that the toner and/or the developer container must be capable of containing the toner and/or developer during periods of storage and/or shipment under conditions which may go from one extreme to another by way of temperature, pressure and/or impact. A common approach to sealing a toner container or cartridge has been to seal the dispensing opening with a breathable plastic film of polyvinyl chloride, for example, which has a pressure and heat actuated adhesive on one side which upon the application of heat and pressure forms a very good seal with the dispensing opening. When necessary for use, the dispensing opening can be opened and particulate materials emptied into the developer housing. A principle difficulty, however, associated with this type of sealing arrangement is the preciseness required for pressure, temperature and time in sealing the toner cartridge. For example, if a hot iron is left on to long, it may burn or melt through the plastic film. Accordingly, it has been found that the plastic film is generally too time temperature dependent. In addition, the adhesive is frequently applied unevenly and with the uneven application of the adhesive in trying to manually peel or remove the film from the opening the force that may have to applied may be uneven and an ineffective seal may be formed in areas where too little adhesive is applied. Further, once this plastic film seal is broken and upon exhaustion of the supply of toner and/or developer in the cartridge so that it must be removed and replenished with a full cartridge, there is really effectively no seal to protect the user from toner spillage and contamination upon loading the cartridge from the machine.