BRIEF DESCRIPTION OF THE DRAWINGS
In the detailed description of the preferred embodiment of the invention presented below, reference is made to the accompanying drawings, in which:
FIG. 1 is an end view, partly in cross-section, of a reproduction apparatus magnetic brush development station;
FIG. 2 is an end view, partly in cross-section and on an enlarged scale, of the developer roller and metering skive, according to this invention, of the magnetic brush development station of FIG. 1;
FIG. 3 is a bottom plan view, partly in cross-section and on an enlarged scale, of a portion of the developer roller and metering skive of FIG. 2;
FIG. 4 is a view in perspective of the metering skive of FIG. 2, according to this invention, including the cam actuator for selectively moving the metering skive;
FIG. 5 is a top plan view of the actuator for moving the metering skive according to this invention; and
FIG. 6 is a schematic end view of the developer roller and movable metering skive, according to this invention, showing the action on contaminates when the metering skive is moved to the remote position.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the accompanying drawings, FIG. 1 shows a reproduction apparatus magnetic brush development station, designated generally by the numeral 10. The magnetic brush development station 10 includes a housing 12 forming, in part, a reservoir for developer material. The development station housing 12 is locatable in a reproduction apparatus in operative association with a dielectric support member (DSM) adapted to carry latent image charge patterns, and have developer material images formed of such latent image charge patterns, which are thereafter transferred to receiver sheets to form desired reproductions. Since this arrangement forms no part of the instant invention, and is well known in the art, the overall reproduction apparatus is not shown in 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 FIG. 1) fourteen-pole core magnet 16 inside a rotating (clockwise in FIG. 1) shell 18. Of course, the core magnet 16 and the shell 18 can have any other suitable relative rotation, which causes developer material to be transported to a development zone 20 into operative association with the dielectric support member DSM to develop latent image charge patterns thereon.
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 FIG. 3). The core magnet 16 does not extend the entire length of the developer roller 14. As such, the developer nap on the shell 18 does not extend to the end of the developer roller 14.
At each end of the developer roller 14, a single-pole permanent ceramic magnet 24 is used (one end shown in FIGS. 2 and 3) as a seal to prevent leakage of developer material from the ends of the development roller. The magnet 24 is selected to provide a magnetic field with a strength in the range of 400 to 1200 gauss, and preferably 900 gauss. One end 24a of the magnet 24 is approximately flush with the end of the developer roller 14 and extends along the longitudinal axis of the developer roller such that an overlap (approximately 10 mm) exists with the developer roller. The single pole magnet 24 is secured to the underside of the metering skive 22 by a metal plate 26a and fastener 26b, with the active pole of the magnet 24 in close proximity to the developer roller circumference. The metal plate 26a functions to shunt the magnetic field, except in the area of the magnet 24, which faces the developer roller 14.
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 FIG. 2) in operative association with the developer roller 14 to accurately set a predetermined developer material metering gap, and a second position remote from the first position (shown in FIG. 6).
To provide for selective movement of the metering skive 22, as shown in FIG. 5, the metering skive 22 is supported on a member 21, mounted in the development station housing 12, for movement perpendicular to the longitudinal axis of the developer roller 14. The support for the metering skive 22 is provided by a plurality of guide pins 31 (only one is shown in FIG. 5) spaced along the length of the metering skive 22. The guide pins 31 extend from the member 21 and are respectively received within a plurality of bores 32 defined in the metering skive 22 for sliding movement relative thereto. A plurality of adjusting screws 34 (again, only one is shown in FIG. 5) are threadably received respectively in webs 36 formed in the metering skive 22. The adjusting screws 34 respectively capture springs 38 between the webs 36 and the member 21. The springs 38 urge the adjusting screws 34 threaded into the webs 36 in a direction toward the developer roller 14 until the heads 34a of the adjusting screws engage the member 21, thus positioning the metering skive 22 in a desired first operative location relative to the developer roller 14 to accurately set the metering gap at a desired predetermined spacing location for delivery of developer material therethrough. Turning of the adjusting screws 34 serves to respectively change the distance between the webs 36 and the screw heads 34a so as to enable the metering gap to be accurately adjusted when necessary to change the predetermined spacing location for setting the metering gap.
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 34 an 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 FIG. 5 to the left, the ramp member 44 urges the screw 46 in a direction perpendicular to, and away from, the member 21. This in turn moves the metering skive 22 to a second position remote from the aforementioned first position to enable contaminate removal in the manner discussed below. The actuator arm 48 may be moved manually to rotate the cam member 52 about the pin 50, or may be selectively actuated by any suitable electrical or mechanical mechanism such as a motor (not shown). An extension piece 58 is connected to the actuator arm 48 and is urged by a suitable spring member 60 in a direction to position the cam member 52 to set the slide plate 42 such that the metering skive 22 is located in the first (operative) position.
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 FIG. 6) from the developer material due to centrifugal force and/or lower particle charge. This removes the contaminate particles CP from the developer material such that when operation of the development station 12 is again desired, the actuator arm 48 under the urging of spring member 60 can readily move the metering skive 22 back to the first (operative) position to accurately reset the metering gap between the metering skive 22 and the developer roller 14.
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.
PARTS LIST
10 Magnetic brush development station
12 Housing
12
a Reservoir
14 Developer roller
16 Core magnet
18 Shell
20 Development zone
21 Member
22 Metering skive
24 Single pole magnet
24
a End
26 Metal plate
26
b Fastener
28 Augers
30 Transport roller
31 Guide pins
32 Bores
34 Adjusting screws
34
a Screw heads
36 Webs
38 Capture springs
40 Actuator mechanism
42 Slide plate
42
a Groove
44 Ramp member
46 Screw
48 Actuator arm
50 Pin
52 Cam member
54 Opening
56 Feature
58 Extension piece
60 Spring member
Patent Application
20080056773
