Contamination control device for an electrostatographic development station

A development station for an electrostatographic reproduction apparatus wherein pigmented marking particles from a particulate material mixture of pigmented marking particles and magnetic carrier particles are utilized to develop latent image charge patterns on a dielectric member. The development station has a housing adapted to be located adjacent to a dielectric member. The housing defines a reservoir for a particulate material mixture, and an opening facing such dielectric member. A mixer for mixing particulate material, a magnetic brush for applying pigmented marking particles from such particulate material mixture to a latent image charge pattern to develop such charge pattern, and a transport for transporting such particulate material from the mixer to the magnetic brush are located within the housing. A device is provided for collecting contaminating airborne particulate material contamination. The contamination collecting device includes an elongated tube, located externally of the housing. The tube defines an opening communicating through the wall of the tube with the interior thereof. Passages are defined by the housing between the magnetic brush and the mixer, communicating with the opening of the tube, and a vacuum is supplied to the interior of the tube to substantially prevent contamination of the reproduction apparatus and its environment.

BACKGROUND OF THE INVENTION 
The present invention relates in general to control of contamination within 
the environment of electrostatographic reproduction apparatus, and more 
particularly to a contamination control device for the development station 
of the reproduction apparatus. 
In typical commercial reproduction apparatus (for example, 
electrostatographic copier/duplicators, printers, or the like), a latent 
image charge pattern is formed on a uniformly charged dielectric member. 
Pigmented marking particles, contained in a development station, are 
attracted to the latent image charge pattern to develop such image on the 
dielectric member. A receiver member is then brought into contact with the 
dielectric member, and an electric field is applied to transfer the 
marking particle developed image to the receiver member from the 
dielectric member. After transfer, the receiver member bearing the 
transferred image is transported away from the dielectric member, and the 
transferred image is fixed to the receiver member by heat and/or pressure 
to form a permanent reproduction thereon. 
One type of development station commonly used in electrostatographic 
reproduction apparatus is referred to as a magnetic brush development 
station. An exemplary magnetic brush development station, such as shown in 
US Pat. No. 4,878,089 (issued Oct. 31, 1989, in the name of Gustlits et 
al), includes a housing providing a reservoir for a supply of developer 
material. The developer material may be, for example, a two component 
material comprising 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 the marking particles to triboelectrically charge the 
particles so that the marking particles adhere to the surfaces of the 
carrier particles. A transport mechanism brings the developer material 
mixture into the field of a plurality of magnets which, in turn, apply the 
marking particles to the latent image charge pattern on the dielectric 
member to adhere to the pattern forming the developed image. 
It is well known that while the magnetic brush development station has been 
perfected to the point where, in general, it is quite efficient in 
developing latent image charge patterns, it still tends to generate 
considerable airborne particulate matter. This is due to the high 
turbulence during mixing and, at least in part, to the fact that during 
mixing certain particles remain uncharged, receive only a low charge, or 
acquire a wrong sign charge. These particles readily become airborne 
rather than flowing with the remaining developer material mixture via the 
transport mechanism into the magnetic development field. 
Such airborne particulate matter, if left uncontrolled, may escape from the 
developer station and cause the interior of the reproduction apparatus to 
become contaminated. This can adversely effect the reproduction apparatus 
causing operating problems and/or degraded copy output. Moreover, the 
contamination may eventually escape to the environment surrounding the 
reproduction apparatus and unduly contaminate such environment. 
Accordingly, certain electrostatographic reproduction apparatus have 
provided contained exhaust systems operatively associated with the 
respective development stations. While such systems have been shown to 
reduce airborne particulate contamination associated with magnetic brush 
development stations, they are not completely efficient, and thus allow 
adverse contamination to build up in the reproduction apparatus and its 
environment. 
SUMMARY OF THE INVENTION 
In view of the foregoing discussion, this invention is directed to a device 
for efficiently controlling contamination in a magnetic brush development 
station for an electrostatographic reproduction apparatus wherein 
pigmented marking particles from a particulate material mixture of 
pigmented marking particles and magnetic carrier particles are utilized to 
develop latent image charge patterns on a dielectric member. The 
development station has a housing adapted to be located adjacent to a 
dielectric member. The housing defines a reservoir for a particulate 
material mixture, and an opening facing such dielectric member. A mixer 
for mixing particulate material, a magnetic brush for applying pigmented 
marking particles from such particulate material mixture to a latent image 
charge pattern to develop such charge pattern, and a transport for 
transporting such particulate material from the mixer to the magnetic 
brush are located within the housing. A device is provided for collecting 
contaminating airborne particulate material contamination. The 
contamination collecting device comprises an elongated tube, located 
externally of the housing. The tube defines an opening communicating 
through the wall of the tube with the interior thereof. Passages are 
defined by the housing, between the magnetic brush and the mixer, 
communicating with said opening of the tube, and a vacuum is supplied to 
the interior of the tube to substantially prevent contamination of the 
reproduction apparatus and its environment. 
The invention, and its objects and advantages, will become more apparent in 
the detailed description of the preferred embodiment presented below.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the accompanying drawings, FIGS. 1 and 2 show a typical 
magnetic brush development station (such as the development station shown 
and described in the aforementioned US Pat. No. 4,878,089), designated 
generally by the numeral 10, for an electrostatographic reproduction 
apparatus. The development station 10, described herein to the extent 
necessary for a full understanding of the instant invention, includes a 
housing 12 having intercommunicating portions 12a-12c including a lower 
portion 12a which serves as a reservoir for developer material. The 
developer material is, for example, a two-component material having 
magnetic carrier particles intermixed with relatively smaller pigmented 
marking particles. The upper portion 12b of the housing 12 contains a 
magnetic brush 14 for applying the pigmented marking particles to latent 
image charge patterns respectively formed on a dielectric member 16 moving 
along a path in juxtaposition to an opening 18 in the upper housing 
portion 12b. 
The magnetic brush 14 includes a core 20 having a plurality of magnets 
spaced around the peripheral surface of the core. A nonmagnetic 
substantially cylindrical shell 22 surrounds the core 20 and has its 
longitudinal axis offset from the longitudinal axis of the core. Such 
offset has the effect of decreasing the field strength of the core magnets 
over the area of the shell 22 spaced farther from the magnets so that the 
particulate developer material mixture has less propensity to adhere to 
the shell in that area and returns to the reservoir. Of course, in other 
magnetic brush development station arrangements, the core and shell may be 
concentrically aligned. 
As is well known in the art, the core and/or shell can be fixed or 
rotatable as long as the particular arrangement causes the particulate 
developer material mixture to move in the fields of the core magnets into 
contact with the dielectric member 16. In the exemplary magnetic brush 
development station 10 as illustrated in FIG. 1, the core 20 (and the 
magnets) rotates clockwise, while the shell 22 rotates counterclockwise. A 
latent image charge pattern on the dielectric member attracts marking 
particles from the developer material mixture into adhering relationship 
with the charge pattern to develop such pattern. The developed pattern can 
then be subsequently transferred to a final receiver sheet and fixed 
thereto by heat and/or pressure, or may be fixed directly on the 
dielectric member. 
The particulate developer material mixture within the reservoir formed by 
the housing portion 12a is stirred by a mixer 24. The mixer 24 is, for 
example, a ribbon blender. The ribbon blender includes an inner helical 
ribbon 28a and an outer helical ribbon 28b connected by means of rods 30 
to a shaft 32. The shaft 32 is supported in the housing 12 for rotation 
about the longitudinal axis of such shaft. The pitch of the respective 
ribbons 28a, 28b are of opposite hand so that, as the shaft 32 rotates the 
ribbons, the particulate developer material mixture is moved in opposite 
directions along the length of the blender, and the material is agitated 
to provide a triboelectric charge which causes the marking particles to 
adhere to 0the carrier particles. Of course, other types of mixers, such 
as paddle wheels or augers for example, are suitable for use with this 
development station. 
The mixer 24 also moves the particulate developer material mixture radially 
with respect to the mixer so that the material is moved into the portion 
of the housing 12 designated by the numeral 12c. A transporting mechanism 
34 is located within the housing portion 12c. The mechanism 34, which 
serves to transport developer material into the field of the magnets of 
the core 20 of the magnetic brush 14, includes a roller 36. The roller 36 
is mounted on a shaft 38 which is, in turn, rotatably supported in the end 
portions of the housing 12 (only one end shown in FIG. 1). A plurality of 
pickup members 40 are supported by the roller 36. The pickup members 40, 
which are located about the periphery of the roller 36 and extend 
respectively along the full length thereof, are in the general shape of 
buckets. As the roller 36 is rotated, the pickup members move through the 
particulate developer material mixture and pick up material. Such material 
is held until the developer material is in the magnetic field of the 
magnets of the core 20 of the brush 14. The material is then readily 
attracted to the shell 22 of the magnetic brush. The particulate developer 
material mixture is then moved by the magnetic brush 14 in an airstream 
flow (designated by the letter F in FIG. 2) into applying relation with 
the charge pattern bearing member 16 in the well known manner to develop 
the latent image charge pattern on such member. 
As noted above, magnetic brush development stations, such as the exemplary 
station 10, tend to promote the formation of airborne particulate 
material, in part in the form of uncharged, low charged, and wrong sign 
toner particles. One prior art device directed at preventing contamination 
by particulate material from a typical magnetic brush development station 
is shown in FIG. 3. Such device, designated by the numeral 50, includes an 
elongated tube 100 attached to the outer portion of the housing 12 of the 
development station 10. The tube 100 has a plurality of ports 102 (only 
one shown in FIG. 3) communicating with the interior of the tube, and 
located at spaced intervals along a longitudinal element of the tube. The 
tube is coupled to a vacuum source (not shown) to draw air into the tube 
through the ports. The ports 102 are directed toward the dielectric member 
16 downstream, in the direction of travel of the dielectric member, of the 
toning zone T where development of the latent image charge pattern takes 
place. The airstream of particulate material flow for this arrangement is 
particularly shown in FIG. 3 as designated by the letter F'. As can be 
readily appreciated, particulate material in the airstream flow F' has 
already left the confines of the development station housing 12 prior to 
the attempt at capture of the particulate material provided by the vacuum 
supplied to the tube 100. Accordingly, while a considerable amount of 
particulate material is captured and removed through the tube, a 
significant portion may still escape with the airstream into the 
reproduction apparatus and its environment. 
It has been unexpectedly found that acting on the airstream flow in the 
area of the mixer 24 much more effectively and efficiently removes 
airborne particulate material from the airstream. The airstream of 
particulate material flow for this arrangement is particularly shown in 
FIG. 2 as designated by the letter F. A contamination control device 60 is 
provided, as best shown in FIGS. 2, 4, and 5. The contamination control 
device 60 includes an elongated tube 110 attached to the outer portion of 
the housing 12 of the development station 10 (similar to the arrangement 
of FIG. 3). The tube 110 has a plurality of ports 112 communicating with 
the interior of the tube. The ports 112 are located at spaced intervals 
along a longitudinal element of the tube (see FIG. 5). A vacuum source V 
(see FIG. 1) is coupled to the tube 110 to draw air into the tube through 
the ports 112. The coupling of the tube 110 to the vacuum source V may be 
accomplished via a conduit 114 terminating adjacent to the end 110a of the 
tube. The conduit is located relative to the development station 10, when 
the station is properly operatively positioned within the reproduction 
apparatus, so as to automatically connect the conduit (and thus the vacuum 
source) to the tube when the development station is installed in the 
reproduction apparatus. 
In contradistinction to the arrangement of the prior art, the ports 112 are 
directed toward the mixer 24. The housing 12 of the development station 
includes openings 116 communicating with the ports 112. Accordingly, the 
vacuum source V is effective to draw air from the area of the mixer 24 
through the openings 116 and the ports 112 into the tube 110 where it can 
be directed via the conduit 114 to a downstream contained collection 
chamber (not shown) to capture the particulate material. Since the air in 
the area of the mixer 24 is the portion of the airstream flow F most laden 
with particulate material, the described arrangement of the contamination 
control device 60 is the most effective and efficient at capturing and 
removing the particulate material. Thus, when the airstream flow F reaches 
the toning zone T (and beyond), after being subjected to the contamination 
control collection device 60 of this invention, it is more uniformly clean 
than with any arrangement previously found in the prior art. Therefore, 
the reproduction apparatus and its environment remain substantially 
uncontaminated. 
The invention has been described in detail with particular reference to 
preferred embodiment thereof, but it will be understood that variations 
and modifications can be effected within the spirit and scope of the 
invention as set forth in the claims.