Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to magnetic developer
transport systems and magnetic brusn ~evelopment s~ste~s.
More specifically, this invention relates to
~ magne~ic developer transport system which controls the
S developer band width during transport thereof.
One application of the inven~ion is for magnetic
developer ~ransport sys~ems for a cascade developmer
system.
Another application of the invention is for
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a magnetic transport system for a magnetic brush aeveloper
system.
5till another application of the invention is
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~ox a transport assembly which transports developer rom -~
one magnetic brush develo~er roll to another magnetic
;15 brush developer roll. `
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-- It is usually desirable to have as much
~deYeloper capacity as possible in a developer sump since
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the more capacity that a sump has, the less fxe~uent
- that a copying machine must be serviced to rep}ace old
developer with ne-w developer.
~ It is an object o this invention to provide
: a developer transpoxt system which will permit the use
of large capacity developer su~ps.
A problem with a magnetic brush development
system has been spreading of a toner band on the mag~tic
brush when the developer is passed between a nip formed
by the mag netic brush and a pho~orecept~ve surfacè and
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also between the nip of a magnetic brush and a transport roll
in a multi-roll developer brush system whereby some of the
developer is forced out of the development zone and is therefore
no longer available for developing an image during that cycle.
It is another object of this invention to provide a
multi-magnetic developer roll system with means which will
allow for spreading of a developer band on a magnetic developer
roll and on an intermediate transport roll and yet retain all of
the developer and transport the same at a proper width to another
magnetic developer brush so that all of the developer may be
used for developing an image during that cycle.
Thus~ in accordance with the present teaching a
developer system is provided which includes developer particles ~;
which are ferromagnetic properties, an endless rotatable
member which has the developer thereon with means being provided
for rotating the member about a given axis. Magnetic means
are provided for attracting and holding the developer on the ,~
member for a given degree of rotation with the magnetic means
including at least two permanent stationary magnets extending ;`~
in a generally axiaI direction surrounded by the rotatable
member. One of the magnets is longer than the other with the
ends of the longer magnet extending in an axial direction beyond
the ends of the shorter magnet, whereby the developer within
the field of the longer of the magnets will extend an axial
width on the rotatable member corresponding substan~ially to
the width of the longer magnet and the developer within the
field of the shorter magnet will extend an axial width on ;
the rotatable member corresponding substantially to the width of
the shorter magnet.
Other objects of this invention will become apparent
from the following description with reference to the drawings ~;
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wherein~ 4 ~ ~5 9
Figure 1 is a schematic view of a xerographic copying
system illustrating in particular a magnetic roll transport
system;
Figure 2 is a view of the transport system of Figure
1 flattened out to illustrate a developer transport path and
the relative width of magnet members in the transport sy6tem;
Figure 3 is a view along section line 3-3 of Figure::.
l; and :~
Figure 4 is a view of a schematic brush developer
system in which the concept of the invention is incorporated.
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- . This invention rela~es to well~no~n ~erograDhic
copier syst~ms. Such systems ut.ilize a pho~oconductive ~ -
drum or b~lt having arranged around it an ima~ing station, .
a developing station, a transfer station, a fusing
station, and a cieaning station, all of ~hich are well-
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known to those s~illed in the art.
~. Referring to Figure 1, there is illustrated .
a development station which ~omprises a drum 10, :~
: - having a photoconductive sur~ace 11 thereon, a developer
sump 12 having developer particles 14 therein, a pair . -:
of rotatable cylindrical transport rolls 16 and 18, and
a development electrode 20~ The term "developer" as . . . ~:~
.~ used in this specification and in the claims refer to
. e~ther xerographic carrier particles having ferromagnetic . :~
properties mixed with xerographic toner particles or -
: : xerographic toner particles per se having ferromagnetic
. ~roperties. Located within the transport roll 16
are a plurality of stationary circumferentially arranged
. permanent magnets 22, 24, 26 and 28 trhich are fixed to . ::.
the developer housing. ; . . .
. Located within the transport roll 18 aré
stationary circumferentially arranged per~anent magnets
30, 32 and 34. These permanent magnets are in the foxm
of bars which e~tend generally parallel to the ~Xi5
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.2S about ~r~ich its respzctive transport roll rotates.
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Referring to Fiyure 2, the rolls 16 and 18 are
depicted in a flattened out position to illustxate the
develop2r band ~Jidth during transport thereof. The rolls
have also been partially cut away ~o sho~r the xelative
lengths of the permanent magnets surrounded thereby. It
can be seen tha~ magnets 22 and ~4 are the longest and are
~ the same length, magnet 26 is shorter, magnets 28 and 30
are ~he same length but shor~er than magnet 26 and magnets
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- - 32 and 34 are the s~me length but shorter than magnets
~ 28 and 30 and correspond to the development zone width.
The magnets are positioned in such a manner and are of such
a strength relative to each other tha~ the developer -
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particles will form a width corresponding to substa~tially
the length of the magnet when the toner particles are
-~5 txansported by their respecti~e roller to a position - ~ -
ad~acent to the particular m~gnet. This means that toner ~ ,
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paxticles on transport roller 16 which are adjacent to ~ -~
the magnet 22 will have a band width equal to the length
of the ~agnet 22 and as the roller carries that band
into the field of magnet 24 the-band will remain the
same width. When the roller 16 carries the same developer
band within the field of magnet 2G the band width will
narrow to the length of ~agne~ 26 and then as the band
is transported within the field of magnet ~8 the band
width ~lill narrow to the 1 ngth of the magnet 28. As
the band is transported across the magnet 28 into th~
~ield of magnet 30, the band or toner particles will be
. attractcd to the roller 18 from~the roller 16 where~the
- toner. particles assum~ a band width on the roLler 18 ~.
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equivalent to the length of the magnet 3~ ~hich is the
same length as magn~t 28. T.lereafter the roller 18
txansports the same toner band to the field of magnet 32
~herein the toner band width narro~7s to the lenyth of
magnet 32 and thereaf~er the toner particle layer is
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` ~arried within the field of magnet 34 and remains the
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same width since magnet 34 is the same length as magnet
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32~ T~e transport roller 18 continues to rotate the band
o developer out of ~he field of magnet 34 to a release
point 35 whereby the developer is no longer held onto
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, ~he roll 18 by the magnet 3a cnd then falls b~ centrifugal
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orce and gra~ity into the space bet~een the electrode
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20 and the photoreceptor 10 wher~by the developer will
cascade over the phoLoconductor surface 11 to de~Jelo~
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~15 an electrostatic latent image thereon.
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- Magnet 22 is positioned in such a manner that
it ~ill attract the residual magnetic de~eloper to -~
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- ~ - the roll 16 thereby acting as a pickoff magnet. Magnet
24 is positioned to attract additional developer to
the roll 16 from the developer sump while the remaining
magnets are positioned for transporting the developér ~ ~
to the release point 35. --` ~ -
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As the~dPvelop~r;band decreasesl the layer OL
toner at the edges of the band builds up to a thickness
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~ greater than the layer bettleen the~edges as sho~n in
Figure 3. A scxaper blade~36 is positioned adjacent the
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roller 18 in such a manner to scrape off the excess
developer from the edges whereby a uni~orm layer is
ca~rie~ to the r~lease point 35. The edg~ layer ~hich
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`~ i5 scraped o~f by th~ scraper 36 falls bac~ into the
developer S~lp at a position which corresponds
axially with th~ ends of the magnets 34. From this it
. can be seen that develo~er which was picked up in an
;~ S axial position which corresponds with the ends of the
magnets 22 and 24 has now been moved inwardly to an axial
- position wh~'ch corresponds ~ith the develvpment zone
width. Thus, this syste~ keeps developer moving from . ~`
. the axiai ends o~ the sump housing to a position where
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10 . it can be utilized i~ image development. : . :
n cascade development, it is known that . .
; d~veloper is dumped onto the photoconductive surface
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~ ove~ a width that corresponds to the develo~ment zone
,~- . but as the developer cascades downwar~s over tne photo-
lS conductive surface, the developer ~idth expands beyond
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the width of the development zone thus requiring a sump .
which is wider than the deve~opment zone~ The developer
which is lscated in the end of the housing, which corres~
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: : . .ponds to a dLmension beyond the width of the development
zone, must he mixed and kept moving in~o the develop~ent
zone in order that the maximum capacity of the sump or
~ developer sump is utilized. It follows that ~ith the
-~. system of ~his invention, it is possible to cons~ruct
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. developer sumps which are much wider than development
zones since one can~construct and design thQ magnets
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to be of such lengths and 5trengths to narrow ~he
developer band ~o the width of the developmen~ zone at ~ :
the release point. With this additional developer sump
capacity, a copier m~y be op~rated.for a ~uch lon~er : ;
~30. p~riod of ti~e without ha~i.n~ to replenish developer~
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Re~erring to Figure 4, there is illustrated
a maqnetic brush development s~stem comprising a photo~
: conductor belt 100, 2 develop~r sump 102 containing
magnetic develop r particles 104 therein, transport
rolls 106 and 108, a irst development roll 110 and an
upper development roll 112, and a transport roll 114 .
~hich is located between the development rolls. Located
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. within the transport roll 106 are permanent magnet
I`~ bars 116, 118 and 120. Located within the transport
roll 108 are permanent magnet bars 122, 124, and 126 and
.-. . locat~d within the developer roll 110 are stationary
.. permanent magnet bars 128, 130 and 132. Stationary
:-. permanent magnet bars 134, }36 and 138 are located -
~ithin the transport roll 114 and stationary permanent
15 .magnet bars 140, 142 and 144 are iocated ~lithi.n
: . the developer roll 112. A scraper memb~r 146 is located
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. adjacent the developer roll 112 and a scraper member :. .
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148 is located adjacent the de~eloper roll 110 to
scrape off excess developer on the re pectiYe rolls : .:
and direct the same back to the sump 102. The transport
:. rolls 106 and 108 operate in the~same manner as the ro~ls
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16 and 18 in the e~bodimen~ of Figure 1. The ma~n~t 116 ~ :
is p~sitioned to attract developer from the sump to the
surface of the roll 10~6 and is of a length which is
~25 greater than the width of the development zone. lYagnets
: 129, 122, 124 and 126 are progressiYe].y shorter than
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magne~ llG to narrow the developer ~nd attr~cted to -~he
ro}l 106 by the magnet 116 to a wid~h equal to the
development zone ~hich~is th~ wldth of magnet bar 125. -
The developer band is~transferr~ to the:~a~netic brush .
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as it comes within the field of the magnet 128 and
since the band h~s already b~en reducPd to the devalop-
ment zone wi~l~h, the ma~nets 128 and 130 may be of
;~ equal ~ength. . .
l S As described previously, develo~er builds up
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at the ends of the developer band as it becomes narro~ed
.and therefore the scraper 148 is utilized to scrape off
~he ~xcess developer at the edges Gf the developer band
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. which falls back into the developer 5ump. .: :~
10 ~ When developer passes through a nip bet~7een two .
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rol1s such as betueen the photoconductor ]00 and developer
. roll 110, the developer roll 110 and transport roll 114,
and the transport roll 114 and the development roll 112,.
the developer band widens whereby developer is forced
eithex out of the development zone or off the ends . . ~ :
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of the developer rolls. In order to compensate for - .
: and prevent this from happening, the magnets 132 and
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~ : 134 may be longer than the development zone ~idth to keep
-: ~ the developer on the: rolls . ~agnets 136 and 138 may be
:20 decreasingly shorter in length than magnet 134 so when
~he developer band is passed through the nip between
the transport roll 114 and the developer roll 112 the
. developer band will spread to the width of the dev~loper
~ zone thus retaining all the developer for presentation ~.
by the developer roll 112 to the latent image. :~ :
. If transport roll 114 is utilized as a ,~
developer roll instead of a ~.ransport roll, the wid~
o~ the magnets of each roll could be adjusted to com~
. pensate for widening of the developer band as ~he band ~:
paSSQS through the ni~ be~ween the photoconductor 100 ~ ~
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- and the respcctive developer roll to avoid dcvelop~r
loss and thus r~tain all the developer for presentation
to the latent ima~e.
In sum~ary, it can be s~en that in accordance ~with the
~5 principles of this invention, the developer band w.idth
can be con~rolled by varying ~he sizes of the magnets
$` to keep the developer at the outer edges o the developer
.
- sump moving in~ards to the developer æone~ I~ can
also be ùtilized to compe~sate for spreading of the
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developer band and thereby loss of developer ~hen the
d~veloper bana is transpor~ed 'rom one development roll
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t in a magnetic brush system to another development roll
` either directly or by~an intermeliary transport roller.
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~ ' It is obvious that the concept of this lnvention
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' 15 may be applied to continuous webs rather than the trans~
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port or developer rollexs described.
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~ - It should be understood that to carr~ out ~ ~-:: '
~- ~ the principles of ~he invention the ~.agnets can be
d signed to be any length and adjacent magnets ma~ either
vary in length or be ~the same length depending on the
xesults desir~d and the space available to obtain such
results. The main criteria is to design the magnets
in such a manner to shape-the developer band width in
accordance ~ith desired results.
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