Patent Grant
7502581
This invention relates in general to a development station for a reproduction apparatus, and more particularly to a movable metering skive for a reproduction apparatus magnetic brush development station, for contamination control at such metering skive.
In typical commercial reproduction apparatus (electrographic copier/duplicators, printers, or the like), a latent image charge pattern is formed on a uniformly charged charge-retentive or photoconductive member having dielectric characteristics (hereinafter referred to as the dielectric support member). Pigmented marking particles are attracted to the latent image charge pattern to develop such image on the dielectric support member. A receiver member, such as a sheet of paper, transparency or other medium, is then brought directly, or indirectly via an intermediate transfer member, into contact with the dielectric support member, and an electric field is applied to transfer the marking particle developed image to the receiver member from the dielectric support member. After transfer, the receiver member bearing the transferred image is transported away from the dielectric support member, and the image is fixed (fused) to the receiver member by heat and/or pressure to form a permanent reproduction thereon.
One type of development station commonly utilized in electrographic reproduction apparatus is the magnetic brush development station, such as shown in U.S. Pat. No. 6,385,415, issued on May 7, 2002, in the names of Hilbert et al. The magnetic brush development station includes a housing providing a reservoir for a supply of developer material. The developer material may be, for example, two-component material including magnetic carrier particles and relatively smaller pigmented marking particles. A mechanism, such as a paddle wheel, auger, or ribbon blender, is located in the reservoir and serves to stir the carrier particles and marking particles to triboelectrically charge the particles so that the marking particles adhere to the surface of the carrier particles. A transport mechanism brings the developer material into the field of a plurality of magnets within a sleeve (commonly referred to as a developer or toning roller). The plurality of magnets and the sleeve are caused to rotate relative to one another such that the magnetic field of the magnets causes the marking particles to be brought into the vicinity of the latent image charge patterns on the dielectric support member. The marking particles are thus applied to the latent image charge patterns in order to adhere to, and thereby develop such patterns.
While magnetic brush development stations of the above-described type are generally suitable for operation in present commercial reproduction apparatus, improvements in speed and range of use escalate the demands on all of the systems of the reproduction apparatus, especially the development station. For example, reliability of the magnetic brush developer station can be affected when marking particles contaminate drive components, seals, and circuit boards. Increased customer and/or service personnel time to clean these components reduces the available up-time and productivity of the equipment. Contaminates are especially disturbing to the magnetic brush developer station performance at the point where developer material is metered onto the developer roller. Metering is necessary to provide a layer of developer material of only that thickness which will serve to optimally develop the image charge pattern on the dielectric support member. Any developer material flow disturbances lead to image quality artifacts in the finished permanent reproduction. Contaminants tend to collect on the metering skive, particularly when the contaminants are larger than the skive spacing from the developer roller. Collected contaminants then impede uniform flow of developer material to the developing zone into association with the dielectric support member, and generate the noted artifacts by, for example, causing incomplete image development. It is therefore desirable to prevent build up of contaminates at the metering skive.
In view of the above, this invention is directed to a magnetic brush development station for a reproduction apparatus with a movable metering skive so as to enable such metering skive to control and prevent contamination build up at such metering skive. The magnetic brush development station includes a housing forming, at least in part, a reservoir for developer material. A developer roller is mounted within the housing for delivering developer material to a development zone. The developer roller includes a core magnet inside a shell, the core magnet and the shell having relative rotation. A transport mechanism is provided for delivering developer material from the reservoir to the developer roller. A metering skive is provided for controlling the quantity of developer material delivered from the reservoir portion of the housing to the developer roller and then to the development zone. The metering skive is positioned parallel to the longitudinal axis of the developer roller at a location upstream in the direction of shell rotation prior to the development zone, and establishes a predetermined spacing, or metering gap, between the metering skive and the developer roller. A mechanism is provided for selectively moving the metering skive between an operative position relative to the developer roller and a position remote from the developer roller, wherein build up of contamination at the entrance to the metering gap between the metering skive and the developer roller is substantially prevented.
The invention, and its objects and advantages, will become more apparent in the detailed description of the preferred embodiment presented below.
In the detailed description of the preferred embodiment of the invention presented below, reference is made to the accompanying drawings, in which:
Referring now to the accompanying drawings,
As described above, the developer material may be composed of two-part material. As such, a plurality of augers 28 is provided, which have suitable mixing paddles for stirring the developer material within the reservoir 12a of the housing 12. A developer roller 14, mounted within the development station housing 12, includes a rotating (counterclockwise in
The quantity of developer material delivered from the reservoir portion of the housing 12, by a transport roller 30, to the developer roller 14, and then to the development zone 20, is controlled by a metering skive 22. The metering skive 22 is positioned parallel to the longitudinal axis of the developer roller 14, at a location upstream in the direction of shell rotation prior to the development zone 20. The metering skive 22 extends the length of the developer roller 14 (see
At each end of the developer roller 14, a single-pole permanent ceramic magnet 24 is used (one end shown in
It is apparent that the magnet 24 as described above therefore provides an effective seal preventing developer material from escaping from the ends of the developer roller 14. Since this seal does not have any moving parts, there is no wear, and there is no mechanical friction, which would generate heat and create undesirable developer material flakes. Moreover, there is no seal material, which would wear and contaminate the developer material.
There have been many different attempts at controlling developer nap thickness on the developer roller 14 as a way to decrease sensitivity to developer roller/dielectric support member spacing. If the developer nap is too thick, developer material can leak away from the magnetic core of the developer roller resulting in contamination of other areas of the electrographic reproduction apparatus. If the developer nap is too thin, there may not be enough developer material present in the developer material transported to the development zone 20 to enable high quality image development. Past attempts at controlling the developer nap thickness on the developer roller (like developer roller 14) have included slots in tubes or plates and metering skives. The slot width or developer material skive metering gap (the distance between the metering skive 22 and the developer roller 14), and its relationship to the developer roller, must be tightly controlled if the developer nap is to be adequately and effectively controlled.
Extreme sensitivity of developer nap height to skive metering gap in prior development stations has been well documented. However, placing the skive metering gap in the region of lowest possible magnetic field from the developer roller's magnetic core 16 decreases that sensitivity by a factor of two to four times. This makes the skive-metering gap easier to setup in manufacturing and less sensitive to differences in the skive-metering gap along the length of the developer roller 14. Still, larger particles in the developer material mixture, and other contaminates, can block the developer material flow at the metering gap between the metering skive 22 and the developer roller 14. This may impede flow of the developer material to the developer roller 14, which in turn can cause artifacts in the development of the image to be reproduced. Therefore, according to this invention, the metering skive 22 is mounted for selective movement to a first position (shown in
To provide for selective movement of the metering skive 22, as shown in
An actuator mechanism 40 (best seen in FIG. 5)is provided to selectively move the metering skive 22 to a second position remote from the developer roller 14 so as to enable contaminates to be removed from the metering gap between the metering skive 22 and the developer roller 14. The actuator mechanism 40 includes a slide plate 42 supported on the member 21. A groove 42a in the slide plate 42 accommodates the head 34a of the adjusting screw and enables the slide plate to move in a direction substantially parallel to the longitudinal axis of the developer roller 14. The slide plate 42 includes a ramp member 44, which moves integrally with the slide plate. The ramp member 44, and slide plate 42 are coupled to the metering skive 22 by a screw 46.
Movement of the slide plate 42, and thus the ramp member 44, is selectively effected by an actuator arm 48. The actuator arm 48 is coupled to a cam member 52 eccentrically mounted on a pin 50. The cam member 52 is received in an opening 54 of a feature 56 extending from the slide plate 42. When the actuator arm 48 is rotated about the axis of the pin 50, the lobe of the cam member 52 engages the walls of the opening 54 and moves the slide plate 42 in the direction parallel to the axis of the developer roller 14. When the slide plate 42 (and ramp member 44) move from the location shown in
During operation of the development station 12, when images are to be developed to form desired reproductions, the lobe of the cam member 52 is set in a location by urging of the spring member 60 in the position to locate the slide plate 42, and thus the metering skive 22, in the first operative position relative to the developer roller 14. This sets the metering gap between the metering skive 22 and the developer roller 14 at the desired predetermined location such that developer material of ideal thickness will be transported through the metering gap to the development zone 20 to optimally develop desired electrostatic images on the dielectric support member DSM.
During non-operative times, the actuator arm 48 may be selectively rotated by any suitable means (manually or mechanically) to position the cam member 52 to set the lobe of the cam member in the position where the metering skive 22 is moved to the second position remote from the first position. In the second position for the metering skive 22, the metering gap between the metering skive 22 and the developer roller 14 is substantially expanded so as to enable any contaminates, which would otherwise disrupt flow in the metering gap, to flow through such expanded gap. The size (weight) of the contaminate particles CP causes such particles to be jettisoned (see
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4624545 | Yasuda et al. | Nov 1986 | A |
| 6385415 | Hilbert et al. | May 2002 | B1 |
| Number | Date | Country | |
|---|---|---|---|
| 20080056773 A1 | Mar 2008 | US |
