Patent Application
20100061762
This invention relates to electrophotographic systems and, more specifically to customer photoreceptor replacement units or (CRU).
By way of background, in a typical electrophotographic printing process, a photoconductive member, either a belt or drum, is charged to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photoconductive member is exposed to a light image of an original document being reproduced. Exposure of the charged photoconductive member selectively dissipates the charge thereon in the irradiated areas. This records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. Generally, the developer material is made from toner particles adhering triboelectrically to carrier granules. The toner particles are attracted from the carrier granules to the latent image forming a toner powder image on the photoconductive member to a copy sheet. Heat is applied to the toner particles to permanently affix the powder image to the copy sheet.
After extended use and contact with elevated heat and somewhat abrasive materials such as carrier granules and toner and passing through the various process stations, the photoconductive member becomes worn and in need of replacement. Care must be taken in removing the old photoconductive unit and in installing the new replacement unit so that the photoconductive unit and surrounding machine components are not seriously damaged.
Generally, drum photoreceptor replaceable units have a plastic shroud for physical protection and light damage to the light-sensitive unit. However, it is typical, in order to remove the drum unit from the protective housing, a gap in the plastic housing must be made for a handle or other type of drum removal device. This gap is often covered with a pull strip, an opaque, adhesive-backed paper strip, which is stuck over the gap to the plastic housing and must be removed from the housing before the drum unit can be removed. Once the light-blocking strip has been removed, the light-blocking protection for the drum unit is gone. Additionally, if the adhesive fails on the strip then small pieces of the adhesive could end up on the drum unit causing serious image quality defects.
This invention includes a new system for covering the gap in the plastic shroud which continues to provide light protection to the drum unit while the drum unit is being removed from the shroud. This invention also eliminates the chance of failed adhesive flaking off the pull strip and falling into the drum unit. The invention provides utilizing two flexible gap-covering strips, each having adhesive on one edge attached to the shroud that would overlap approximately 1-5 mm directly over the gap in the shroud. This would provide light protection to the photoreceptor until installed while eliminating the chance of adhesive-caused contamination of the photoreceptor and the need for the customer to entirely remove the strip prior to inserting the CRU into the marking machine.
Preserving the full functionality of the photoreceptor is important especially considering the complexity of today's high speed marking machines and their imaging. The photoreceptor or photoconductive surface is especially key to a proper functioning especially of today's high speed color and monochrome electrophotographic printers. The shroud of this invention preserves the effectiveness of the photoconductive drum surface by minimizing surface damage and the effects of light on this surface. This invention, in particular, provides a new system involving covering the gap in the plastic shroud for drum photoreceptor replaceable xerographic units. An embodiment of the invention is to utilize two strips, each having adhesive on one edge that would overlap approximately 1-5 mm directly over the gap. These two overlapping strips will cover the gap in the customer replaceable unit (CRU) shroud while being flexible enough to bend when the handle unit passes therethrough upon installing the CRU. As earlier noted, this invention importantly provides improved (A) light protection to the drum unit while it is being removed from the shroud and installed, (B) it eliminates a failure mode whereby the adhesive flakes off the pull strip and falls into the drum unit and contaminates the photoreceptor causing image quality defects and (C) it also eliminates the customer step of removing the adhesive strip from the shroud.
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There are two advantages of this design in comparison to the existing prior art pull strip. The first advantage of this two-part light shield 2 is that the customer does not need to remove it from the plastic shroud 1 which decreases the likelihood of light shock occurring on the photoreceptor drum (not shown located in shroud 1). A second advantage of this design relative to the original pull strip is in the action of the adhesive. An actual situation occurred where the adhesive structure of the original pull strip was not functioning properly. As the customer removed the light shield strip from the CRU shroud, the adhesive broke free and small globs of adhesive material fell onto the photoreceptor drum causing print defects at failure level at the beginning of the cartridge life. The new design eliminates that possibility by not having the light shield strips 2 removed. The photoconductive drum is pushed out of the shroud 1 at shroud exit 7 and installed in the marking apparatus without undue exposure to light. The handle 4 is in movable contact with the photoconductive drum and, as the handle moves toward exit 7, the drum is also moved; i.e. in the direction of arrow 5. One side of each strip 2 is adhered to the shroud at a location 8. The strips 2 may be made from any flexible electrically-insulating material such as plastic, rubber, paper, cloth or mixtures thereof. It is only important that one end 8 of both strips adhere to the shroud at one horizontal edge of the gap 3 and that the overlapping strip ends 6 are flexible enough to allow the handle 4 to be pushed therebetween. The shroud 1 is made from conventional prior art materials, usually a relatively rigid plastic provided it protects the integrity of the enclosured photoconductive drum.
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In the present invention, the handle 4 could stay with the drum 12 after installation or can be easily removed if desired. In one embodiment, a 1 cm gap 3 would have a strip overlap of about from 1-5 mm. In a larger shroud having a larger gap (about 18 mm), there would be a strip overlap of about 1-7 mm. The strips 2 of this invention must be light blocking and could be any suitable material such as plastic, paper, cloth, wood or a brush-like configuration.
In summary, the present invention provides a shroud for housing a replacement photoconductive drum. This shroud comprises an elongated housing configured to house a photoconductive drum. The housing is entirely enclosed except for an exit open portion and a gap on its top portion which extends throughout substantially the length of the housing and terminating at the exit.
Positioned over the gap are at least two separate light-blocking, overlapping flexible strips. These strips are configured to permit a movable handle structure to travel therebetween to the shroud exit when removing the photoconductive drum from the shroud. These flexible strips overlap approximately 1-5 mm directly over the gap and are flexible enough to bend upon installation of the replacing photoconductive drum. The strips are configured to provide light protection to the drum while it is removed from the shroud.
The movable handle is configured to move the drum toward the shroud exit during the drum replacement procedure. The shroud has on one first end portion a closed structure and on an opposite second end portion an open end to act as a shroud exit location for the drum.
The strips are constructed of a flexible material selected from the group consisting of plastic, rubber, paper, cloth and mixtures thereof. The strips extend through substantially the entire length of the gap and one side of the strips is attached to the shroud and at the opposite side overlaps at a center gap location with the other strip. The strips are configured to allow passage of the handle at the overlapping portions of the strips.
In a specific embodiment, the shroud comprises an elongated housing configured to house the photoconductive drum. The housing is entirely enclosed except for an exit open portion and a gap on its top portion which extends throughout substantially the length of the housing and terminating at the exit.
It will be appreciated that variations 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.
