U.S. patent number 3,741,643 [Application Number 05/200,433] was granted by the patent office on 1973-06-26 for pneumatic assembly for removing excess developer liquid from photoconductive surfaces.
This patent grant is currently assigned to Savin Business Machines Corporation. Invention is credited to Peter John Hastwell, Ian Edward Smith, Marinus Cornelius Vermeulen.
United States Patent |
3,741,643 |
Smith , et al. |
June 26, 1973 |
PNEUMATIC ASSEMBLY FOR REMOVING EXCESS DEVELOPER LIQUID FROM
PHOTOCONDUCTIVE SURFACES
Abstract
Our invention contemplates a pneumatic assembly for removing
excess developer liquid from photoconductive surfaces.
Electrophotographic apparatus for exposing an electrostatically
charged photoconductive surface to a pattern of light and shade to
produce a latent electrostatic image and then toning that image
with a liquid toner is known to the art. In order that such
electrophotographic apparatus may operate over extended periods of
time and produce copy without soiled background, it is necessary to
remove excess liquid toner from the photoconductive surface. It has
been suggested that the excess toner be removed with an elongated
jet of air or air knife. We have discovered that the angle of
incidence of the air jet is significant and that advantageous
results are obtained by positioning the air knife so that the air
jet is substantially normal to the moving photoconductive surface.
We have provided means for removing an accumulation of toner
contained in the developer liquid from the air knife nozzle and
from the photoconductive surface adjacent the nozzle. The removal
of excess toner liquid evaporates the light components of the
liquid, such as light hydrocarbon liquids, and creates some air
pollution. We have provided means for preventing the discharge of
evaporated hydrocarbon vapors into the atmosphere. We accomplish
this by a hood around the air knife assembly into which sufficient
air is bled. An amount of polluted air, equivalent to that bled
into the system, is passed into a filter such as one formed of
activated charcoal before being discharged into the atmosphere to
remove the light hydrocarbon vapors from the discharged air.
Inventors: |
Smith; Ian Edward (Lockleys,
AU), Hastwell; Peter John (Elizabeth Grove,
AU), Vermeulen; Marinus Cornelius (Valley View, South
Australia, AU) |
Assignee: |
Savin Business Machines
Corporation (Valhalla, NY)
|
Family
ID: |
22741707 |
Appl.
No.: |
05/200,433 |
Filed: |
November 19, 1971 |
Current U.S.
Class: |
399/249; 355/27;
239/597 |
Current CPC
Class: |
G03G
15/107 (20130101); G03G 15/11 (20130101) |
Current International
Class: |
G03G
15/10 (20060101); G03G 15/11 (20060101); G03g
015/10 () |
Field of
Search: |
;355/10,3,27
;118/637,DIG.23 ;239/595,597,598 ;96/1LY ;117/37LE |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Greiner; Robert P.
Claims
Having thus described our invention, what we claim is:
1. In an electrophotographic machine, a member having a
photoconductive surface, means for producing a latent electrostatic
image on said surface, means for applying liquid developer to said
surface, an air knife for removing excess developer from said
surface, means for moving said member in a direction to carry said
image sequentially past said developer applying means and said air
knife, said air knife being formed with an elongated air nozzle
slot defining a pair of side walls, means for positioning said air
knife normal to said photoconductive surface, one of said walls
terminating in an outwardly extending lip adjacent to the edge of
said nozzle outlet which is leading with respect to said direction
of movement, said lip being positioned below the terminus of the
other nozzle side wall.
2. An electrophotographic machine as in claim 1 in which said lip
carries a porous metal overlay.
3. In an electrophotographic machine as in claim 2, a baffle
carried by said overlay and extending into said nozzle slot.
4. In an electrophotographic machine as in claim 1, a baffle, and
means for positioning said baffle in said nozzle slot, said baffle
being provided with a portion spaced from and extending in the
direction of said lip.
5. In an electrophotographic machine, a member having a
photoconductive surface, means for producing an electrostatic
latent image upon said surface, a liquid developing station for
developing said image, an air knife for removing excess developer
liquid from said surface, means for moving said image first past
said developing station and then past said air knife, a metering
roller positioned between said developing station and said air
knife closely adjacent said photoconductive surface, means for
rotating said roller, and means for wiping developing liquid from
the surface of the roller.
6. An electrostatic photographic machine as in claim 5 in which
said air knife is positioned to direct a sheet of air normal to
said photoconductive surface.
7. An electrostatic photographic machine including in combination a
member having a photoconductive surface, means for producing an
electrostatic latent image upon said surface, a developing station
for developing said latent image, an air knife for removing excess
developer from said surface, means for moving said image first past
said developing station and then past said air knife, a hood
surrounding said air knife and said developing station, a blower, a
first duct taking suction from inside said hood communicating with
the inlet of said blower, and a second duct providing communication
between the outlet of said blower and said air knife.
8. A machine as in claim 7 in which said hood is spaced from said
photoconductive surface and a bleeder duct providing communication
between the atmosphere and said second duct, the construction being
such that some circumambient air is drawn into the hood by the
blower and some air drawn from the hood is discharged to the
atmosphere.
9. A machine as in claim 8 including means for controlling the flow
of air through said second duct and through said bleeder duct.
10. A machine as in claim 8 including absorption means positioned
to absorb vaporized liquid passing through the atmosphere through
said bleeder duct.
11. An electrostatic photographic machine including in combination
a member having a photoconductive surface, means for producing an
electrostatic latent image upon said surface, a liquid developing
station for developing said latent image, an air knife, means for
moving said image first past said developing station and then past
said air knife, means for positioning said air knife normal to said
photoconductive surface to cause said air knife to remove excess
developer from said surface, a hood, means for positioning said
hood about said air knife, and means for reducing the air pressure
within the hood to remove vaporized developer.
Description
BACKGROUND OF THE INVENTION
In our co-pending application, Ser. No. 155,108, filed June 21,
1971, we have disclosed a novel method of contact transfer of
liquid toner developed electrostatic images. In our method, a
photoconductive surface is exposed to a pattern of light and shade
as usually done in electrophotographic processes and the image
developed by a toner. Our toner is not a dry one, but a novel
liquid developer which carries a component adapted to assume a
state of tackiness so that the developed image can be transferred,
while the toner is in a tacky state, from the photoconductive
surface to a carrier such as paper or the like. The photoconductive
surface may be mounted on a drum or on a belt which is adapted to
be moved through a zone in which it is wet with the developing
toning liquid. The amount of liquid picked up by the drum or belt
is a function of the speed at which the belt passes through the
developing zone. For example, at a rate of about forty feet per
minute, an area of one square foot of photoconductive surface will
pick up about seven grams of developing liquid. Since the
developing liquid comprises not only the tacky toner component but
a diluent such as a light hydrocarbon, this diluent must be
evaporated either from the photoconductive surface or from the
paper during the reproducing process. This requires energy and the
evaporation of fumes which, if allowed to pass into the atmosphere,
pollute it. We recognized this problem in our above-identified
co-pending application and have provided an air knife for removing
excess toner from the surface of the photoconductive drum or
belt.
We first discovered that the angle of incidence of the air jet
impinging upon the photoconductive drum or belt was significant.
Contrary to what one might believe, a tangential direction of the
air jet or air of the air knife against the surface of the drum did
not give the best results. Surprisingly, an angle of incidence
normal to the surface of the belt or along a radius of the drum
gives an improved removal of excess toner liquid from the
photoconductive surface. The direction of a sheet of air normal to
the surface of the photoconductor, while giving better results than
a nozzle directed tangentially to the surface, did produce
turbulence. This turbulence caused an accumulation of toner
components on the surface adjacent the relative leading edge of the
nozzle in its relative motion to the drum or belt. In practice, the
nozzle is stationary while the drum or belt moves, so that, when we
use the term "relative leading edge," we consider the drum
stationary and the nozzle moving. It is the area of the drum or
belt adjacent the relative leading edge of the nozzle at which the
build-up occurs. When this build-up becomes thick, part of it will
detach itself from the drum and may clog a part of the nozzle. If
this occurs, it will produce a line on the image being reproduced.
In order to relieve the accumulation adjacent the relative leading
edge of the nozzle, we provide an area along its leading edge at
which some material of the nozzle is removed. This will form a
configuration in which the lagging edge of the nozzle is higher
than its leading edge. This produces an area between the leading
edge of the nozzle and the surface of the drum through which air
flows in a direction substantially at right angles to the exit
direction of the sheet of air from the air knife nozzle. The
direction of flow, furthermore, is toward the relative leading edge
of the nozzle which serves to reduce the thickness of the toner
build-up adjacent the leading edge of the nozzle, which would
otherwise form owing to the relative motion and the turbulence
described above.
While this form of the invention is operative, we found over
extended periods of time, as for example after 3000 copies, a
significant build-up of toner deposit takes place at the relative
leading edge of the nozzle. We were successful in removing the
excess toner from the photoconductive surface but were now faced
with another problem, that of the build-up just mentioned. We were
able to eliminate this build-up by providing the area of the nozzle
adjacent its relative leading edge with a porous structure so that
air would pass through the porous structure to the blind surface of
the leading edge of the air knife nozzle at which a dead air area
tends to exist. We also solved this problem by the use of a baffle
to direct a sheet of air over the relative leading edge of the
nozzle to eliminate the dead air space.
After we had solved the problem of build-up in the manner just
described, we found that we had introduced another problem, namely,
that the air stream would divide and part of it would pass along
the direction of travel of the drum while the other part of the air
stream would pass in the opposite direction. The portion of the air
stream passing in the same direction as the travel of the drum or
belt produced pollution and contamination of the paper and machine
parts. By this we mean that the atmosphere adjacent the transfer
point was laden with evaporated toner liquid and in some cases the
liquid would condense on the drum, machine parts and paper adjacent
the transfer station. This problem was solved by providing a hood
or manifold around the nozzle area. The air for the air knife takes
suction from the manifold and passes to the center of the
centrifugal blower, the outlet of which furnishes air to the air
knife. In passing through the blades of the centrifugal blower,
entrained toner particles are thrown out of the air by centrifugal
force. We found the inner casing of the centrifugal fan coated with
toner after a period of operation. The removal of toner particles
prevents the nozzle of the air knife from becoming clogged by the
recirculation of the removed toner particles. The interior of the
air knife remains clean.
Since it is undesirable to pass the vapors of the diluent into the
atmosphere especially at high reproduction rates, we provide a hood
completely about the toner tank and the air knife. This hood is
such that air from the atmosphere can be continuously bled into the
toner and air knife area hood and passed to the inlet of the
centrifugal blower. At a rate of flow of eighteen cubic feet per
minute to the air knife, we find that we can operate the blower to
discharge twenty-two cubic feet per minute. The discharge of the
blower is provided with a bleeder outlet which passes through a
filter of activated charcoal or the like. About four cubic feet per
minute, for example, are drawn into the hood from the outside air.
This is controlled by the spacing of the hood from the surface of
the drum. It will be seen that sufficient fresh air is being fed to
the system and sufficient polluted air is being removed from and
purified by the filter, so that the air circumambient of the
machine is pollution-free.
If a higher boiling diluent is employed, the build-up of toner
liquid on the drum is much heavier than with a lighter hydrocarbon
diluent. This will require the use of a higher velocity air knife
which requires the employment of a higher air pressure as the air
supply to the air knife. In order to avoid using the higher
pressure which requires bigger and more expensive equipment to
achieve, we reduce the thickness of the film of developing liquid
on the photoconductive surface mechanically through a roller. This
roller is positioned relatively upstream from the air knife and is
spaced adjacent the drum and out of contact with it so that it acts
as a film thickness metering means. It is driven by appropriate
means at the same linear velocity as the photoconductive surface.
The excess developing liquid which is removed mechanically from the
surface of the photoconductor is scraped from the metering roller
by means of a wiper or doctor blade and re-passed into the toner
tank. By driving the roller at the same speed and in the same
direction as the surface of the photoconductor, no shear is
introduced and the liquid is carried around on the surface of the
roller to a position where it can be wiped therefrom.
SUMMARY OF THE INVENTION
One object of our invention is to provide a novel pneumatic
assembly for removing excess developer liquid from photoconductive
surfaces.
Another object of our invention is to provide an improved air knife
which will remove excess toner from a photoconductor surface in an
efficient manner.
Another object of our invention is to provide an air knife which
will remove liquid toner from a photoconductive surface without
permitting clogging of its nozzle after use over long periods of
time.
A further object of our invention is to provide a pneumatic
assembly for removing excess developer liquid from photoconductive
surfaces without contaminating the air circumambient to the
electrophotographic apparatus.
Other and further objects of our invention will appear from the
following description:
In general, our invention contemplates the provision of an air
knife disposed to eject a sheet of air normal to a photoconductive
surface which may be carried by a drum or moving belt or the like.
This surface is adapted to carry a latent electrostatic image which
has been developed by exposure to a liquid toner which may
advantageously be toner particles or a toner organosol suspended or
emulsified in a light hydrocarbon liquid in which the toner
particles or organosol are insoluble. The configuration of the air
knife is such that it will produce a secondary sheet of air
directed toward the relative leading edge of the air knife nozzle.
The main sheet of air prevents a build-up of toner on the
photoconductive surface. This auxiliary sheet of air prevents
accumulations of toner upon the nozzle itself. A hood surrounds the
air knife assembly. Air from the air knife takes suction from
within the hood and delivers air to a centrifugal blower, the
output of which feeds the air knife. A volume of air equivalent to
that passing into the hood from the outside air is bled from the
discharge of the centrifugal blower and passed through means for
absorbing the hydrocarbon vapors such as a bed of activated
charcoal or the like.
Where higher boiling hydrocarbons are used, it becomes desirable,
in order to avoid increasing the velocity of the air in the air
knife, to use an auxiliary roller mechanically to reduce the film
thickness before subjecting the film of liquid toner on the
photoconductive surface to the action of the air knife
assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, which form part of the instant
specification and which are to be read in conjunction therewith,
and in which like reference numerals are used to indicate like
parts in the various views:
FIG. 1 is a diagrammatic view of an electrostatic copying machine
employing a rotary drum carrying a photoconductive member and
showing the relative position of the air knife, with respect to the
drum and the toning zone.
FIG. 2 is an enlarged view with parts in section showing one form
of an air knife.
FIG. 3 is a side elevation taken along line 3--3 of FIG. 2 (with
parts removed) showing the air knife per se.
FIG. 4 is a diagrammatic view illustrating one defect in the form
of the air knife as shown in FIG. 2.
FIG. 5 is a diagrammatic view with parts in section showing the
manner in which a modified form of air knife tends to correct the
defect of the air knife shown in FIG. 2.
FIG. 6 is a fragmentary sectional view showing an improved form of
an air knife.
FIG. 7 is a fragmentary sectional view showing another embodiment
of an improved air knife construction.
FIG. 8 is a fragmentary sectional view showing the improved air
knife of FIG. 7 in conjunction with an auxiliary roller for use
with toners employing higher boiling hydrocarbon diluents.
FIG. 9 is a diagrammatic view showing our improved air knife in
combination with an anti-pollution system.
DESCRIPTION OF THE PREFERRED EMBODIMENT
More particularly, referring now to the drawings, we have shown a
diagrammatic view of an electrostatic copying machine in FIG. 1, in
which the drum 2 is formed with a photoconductive surface and is
adapted to revolve about a supporting shaft 4 in the direction of
the arrow. An electrostatic charging device 6 is employed to charge
the surface of the drum with an electrostatic charge, it being
understood that the drum is used in a light-proof casing (not
shown). An image of an original to be copied is focused upon the
charged photoconductive surface by an exposure device 8, as is well
known to the art, to leave a latent electrostatic image represented
by the pattern of electrons 10 shown on the drum. The charged image
is then developed by a liquid toner such as is described in our
co-pending application above identified The liquid toner is stored
in a tank 12 from which it is adapted to be pumped by pump 14 which
takes suction from the tank 12 through pipe 16. The toner is
discharged though pipe 18 into a developing zone 20 in which it is
applied to develop the latent image. The excess toner passes from
the developing zone through pipe 22 back to the tank 12.
The excess toner on the developed image and the photoconductive
surface is removed by an air knife indicated generally by the
reference numeral 24. A roll of paper or other web material 26 is
drawn over roller 28 in contact with the developed image and
remains in contact with the drum until it reaches roller 30 where
it passes over guide roller 32 and is pulled to a cutting station
by appropriate means (not shown since these are known to the art).
The hood 34 is adapted to heat the back of the paper 26 by hot air
furnished to the hood 34 from manifold 36 to which the hot air is
supplied from an appropriate source (not shown). It will be
observed that the air knife 24 is positioned normal to the
photoconductive surface.
Referring now to FIG. 2, the air knife 24 is formed of a pair of
elongated members 40 and 42 clamped together by bolts 44, as can be
seen more readily by reference to FIG. 3. A gasket 46 performs the
dual function of spacing member 44 from 42 to provide an elongated
nozzle 48. We provide end plates 50 and 52 which are secured to the
members 40 and 42 by means of machine screws 54, as can be seen by
reference to FIG. 3. The end plates also serve to fix the spacing
between the members 40 and 42 so that the width of the nozzle is
predetermined. The bottom of the nozzle thus formed is closed by a
plate 56 to which an air distributor manifold 58 is secured. The
air distributor manifold 58 terminates in an air duct 60 to which
an air hose 62 is affixed. Air is supplied to the assembly by the
air hose 62, as will be pointed out more fully hereinafter. A hood
70', which may be placed under reduced pressure by applying a
suction hose to the duct 72', surrounds the air knife assembly.
Toner blown from the drum 2 by the air knife passes into the
developing zone 20 to return to the system.
We have discovered that air velocity normal to the drum surface
dries the surface much more effectively than air flowing in the
direction tangentially to the drum. The rotation of the drum, in
moving the web of paper at a rate of about 40 feet per minute, will
coat a drum twelve inches in width with 320 grams of developer
liquid per minute.
In using a light hydrocarbon diluent such as a hydrocarbon liquid
sold under the trademark of "ISOPAR G" by Humble Oil & Refining
Company, we require a volume of air of about seventeen and one-half
cubic feet per minute through an air knife having a slot 6 inches
long and 0.02 inches in width. The speed of the air jet to
accomplish the evaporation of the ISOPAR G is about 240 miles per
hour. ISOPAR G has a specific gravity of 0.75 at 60.degree. F. It
has a flash point of 105.degree. F. and a kauributanol number of
27. Its initial boiling point is 157.degree. C. Its final boiling
point is 177.degree. C. It is a substantially pure isoparaffin.
The toner is a solution of a high molecular weight resin
substantially insoluble in the ISOPAR G suspended in or emulsified
in the ISOPAR G. As the light hydrocarbon diluent evaporates, the
film of residual toner liquid increases in thickness and in
specific gravity. It collects on the drum adjacent the nozzle as
shown in FIG. 4. This causes deflection of the air from the nozzle
in a forward direction. Furthermore, drops of the thickened toner
containing a high proportion of the high molecular weight resin may
drop from the drum on the air knife and accumulations of resin thus
formed tend to clog the air knife nozzle.
Since the drum moves in a clockwise direction and the nozzle of the
air knife is stationary, the relative motion of the nozzle with
respect to the drum is to the right as viewed in the drawings.
Stated otherwise, the right-hand side of the nozzle is the relative
leading edge of the nozzle, considering its relative motion with
respect to the drum. It will be observed in FIG. 2 that the
relative leading edge of the nozzle has been extended and is wider
than the trailing edge of the nozzle. We have found that we can
correct the tendency of the high molecular weight resin components
of the toner liquid which are not evaporated by the air knife to
accumulate on the drum adjacent the air knife by increasing the
clearance between the drum and the leading edge of the nozzle of
the air knife. This is shown diagrammatically in FIG. 5. This
entails removing a portion of the top surface of the member 42 of
the air knife. An improved embodiment of the air knife is shown in
FIG. 6. In this embodiment, a portion of the leading edge of the
air knife, namely, the upper surface of the member 42 adjacent the
drum 2, has been removed and capped with a sintered bronze plate
70. The trailing edge of the sintered bronze plate carries a baffle
72 extending into the air knife nozzle passage 48. This baffle
directs air through the pores of the sintered bronze plate 70. The
arrangement is such that the trailing member 40 of the nozzle,
which extends above the upper surface of the sintered bronze plate
70 will direct air to the right as shown by the arrow in FIG. 5.
The air directed by the baffle 72 through the pores of the sintered
bronze plate 70 will ensure that there is no collection of toner
resin on the leading edge 43 of the nozzle member 42.
We have found that we can also prevent the accumulation of resinous
toner materials at the leading edge 43 of the nozzle member 42 by
inserting a different baffle 74 as shown in FIG. 7. This baffle has
a portion 76 extending in the direction of the leading edge of the
nozzle to direct air over the surface 41 of nozzle member 42.
It will be observed that, in the nozzle shown in FIGS. 5, 6 and 7,
a component of the air jet is directed to move toward the leading
edge of the nozzle. This component smooths the toner layer upon the
drum and eliminates turbulence introduced by the jetting of high
velocity air against the drum in a direction normal to it. The
spacing between the upper surface 41 of the leading member 42 of
the nozzle assembly from the drum is about 0.125 inches. In FIG. 4,
the accumulation is designated by the reference numeral 39. The
smoother build-up shown in FIGS. 5 and 7 is designated by the
reference numeral 37.
In the form of the nozzle shown in FIGS. 6 and 7, no gasket is
employed. Instead, the nozzle assembly is completed by the end
plates 50 and 52.
Referring now to FIG. 8, in some environments, it is desirable to
employ somewhat higher boiling hydrocarbon diluents in the toner
formulation. For example, ISOPAR L has an initial boiling point of
188.degree. C. and a final point of 210.degree. C.; while ISOPAR M
has an initial boiling point of 240.degree. C. and a final point of
249.degree. C.
The specific gravity of ISOPAR M is 0.78 and it has a flash point
of 180.degree. F. Because of its higher distillation range, more
energy is required to evaporate it from the photoconductive
surface. This will require higher air pressure and a greater
velocity in the air knife. This in turn requires a higher pressure
output from the air blower. In order to reduce the amount of air
required by the air knife, we have shown an arrangement in FIG. 8
for use with higher boiling isoparaffin diluents in the toner
formulations. Adjacent the toning station casing 20, we provide a
roller 100 driven by appropriate means (not shown) so the linear
velocity of the surface of the roller 100 is equal to that linear
velocity of the drum 2. The roller is mounted for rotation about a
shaft 102 and is spaced from the surface of the drum 2 by a
distance of 0.005 inches. The film 35 formed by ISOPAR M on the
surface of drum 2 has a thickness of 0.012 inches. This film is
mechanically reduced in thickness by the roller 100 so that the
balance of the film 37 can readily be removed by the air knife
assembly 24 as shown in FIG. 8. A wiper plate 104 maintains the
roller 100 substantially free of a thick film of toner. The excess
toner being wiped from the roller 104 passes back into the toner
system.
Referring now to FIG. 9, we have shown our air knife in combination
with an anti-pollution system. The toning zone 20 and the air knife
assembly 24 are mounted in a casing 200 which is spaced from the
surface of the drum 2. The centrifugal blower 202 takes suction
from the duct 72' communicating with the interior of the casing
200. The blower discharges air through duct 204. The main body of
the air passes through pipe 208 controlled by valve 206 and is
discharged through hose 62 to air knife distributor manifold 58 to
the air knife 24. A portion of the air passes through branch duct
210 controlled by valve 212 to a light hydrocarbon absorption unit
214. The speed of the blower 202 is such that it will draw about 22
cubic feet per minute of air from inside the casing 200. The valve
206 is so positioned that about eighteen cubic feet of air per
minute will be furnished to the air knife. About four cubic feet of
air per minute are drawn from the outside atmosphere, as shown by
the arrows between the drum and the edges of the casing or hood
200. Since 22 cubic feet per minute are being drawn from the hood
and only 18 feet per minute bled to it, about four cubic feet of
air will be drawn from the outside circumambient atmosphere into
the hood. The light hydrocarbon vapors evaporated from the surface
of the drum by the action of the air knife will pass into the
centrifugal blower and be recirculated. The position of valve 212
is such that about four cubic feet of air per minute will pass
through the absorption unit. The absorption unit is filled with
activated charcoal 218 which is prepared by dry distillation of
coconut shells followed by treatment with very high temperature
steam. The charcoal will absorb the light hydrocarbon vapors so
that the air passing to the atmosphere through discharge pipe 216
will be substantially free of pollution. About two and one-half
cubic feet of activated charcoal will weigh about forty pounds and
is capable of absorbing about a gallon of the light hydrocarbon
diluent evaporated by the air knife. No air is discharged from the
system except that which passes through the absorbent bed of
activated charcoal. In this manner, our machine can be used in
closed spaces for long periods of time without danger of
contaminating the air by evaporation of the light hydrocarbon used
as a diluent in the liquid toner.
The absorption unit 214 is so positioned that it can be easily
removed and replaced by a new absorption unit when the activated
charcoal 218 becomes saturated with hydrocarbons. The bolts 220
which attach the lower flange 222 to the duct 211 and the bolts 224
which attach the flange 223 to the upper flange of the unit 214 may
be easily removed for quick replacement of a fresh absorption unit.
The diluent collected by the absorption unit can be recovered, if
desired, by stripping the absorbed ISOPAR from the activated
charcoal by steam. The steam containing the ISOPAR vapor can then
be condensed and passed to a separating zone where the water is
drawn off and the ISOPAR recovered.
It will be seen that we have accomplished the objects of our
invention. We have provided a novel pneumatic assembly for removing
excess developer liquid from photoconductive surfaces. We have
provided an improved air knife for accomplishing this in an
efficient manner. The construction of the air knife is such that it
can be used for long periods of time without having its nozzle
become clogged by the residue or the heavy components in the liquid
toner formulation. The arrangement is such that the circumambient
air is not polluted.
It will be understood that certain features and subcombinations are
of utility and may be employed without reference to other features
and subcombinations. This is contemplated by and is within the
scope of our claims. It is further obvious that various changes may
be made in details within the scope of our claims without departing
from the spirit of our invention. It is, therefore, to be
understood that our invention is not to be limited to the specific
details shown and described.
* * * * *