U.S. patent number 3,789,794 [Application Number 05/212,155] was granted by the patent office on 1974-02-05 for apparatus for developing electrostatic images.
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 |
3,789,794 |
Smith , et al. |
February 5, 1974 |
APPARATUS FOR DEVELOPING ELECTROSTATIC IMAGES
Abstract
An electrostatic copier includes means to recirculate developer,
comprising a diluent carrier and a tacky toner, between a developer
supply tank and a developer station. A recirculation system
communicates a mechanical mill with the supply tank. Means
monitoring developer level in the supply tank and opacity of the
developer material control the respective feeds of carrier and
toner to the mill.
Inventors: |
Smith; Ian Edward (Lockleys,
South Australia, AU), Hastwell; Peter John (Elizabeth
Grove, South Australia, AU), Vermeulen; Marinus
Cornelius (Valley View, South Australia, AU) |
Assignee: |
Savin Business Machines
Corporation (Valhalla, NY)
|
Family
ID: |
22789776 |
Appl.
No.: |
05/212,155 |
Filed: |
December 27, 1971 |
Current U.S.
Class: |
118/694; 399/57;
118/602; 399/61; 137/93 |
Current CPC
Class: |
G03G
15/104 (20130101); Y10T 137/2509 (20150401) |
Current International
Class: |
G03G
15/10 (20060101); G03g 013/10 () |
Field of
Search: |
;117/37LE,102
;118/602,612,DIG.23,637,7 ;137/93 ;259/4,8,DIG.30 ;355/10 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kaplan; Morris
Attorney, Agent or Firm: Shenier & O'Connor
Claims
1. In an electrostatic copier utilizing a liquid developer having a
diluent constituent and a tacky toner constituent which is
insoluble in said diluent, a container for holding a quantity of
said developer, mechanical mill means for subjecting developer
passing therethrough to shear stresses sufficiently great to
maintain an emulsion of said toner and said diluent, means
including a pump for circulating said developer from said container
through said emulsifying means and back to said container, a
developer unit, and means for supplying developer to said developer
unit from said
2. Apparatus as in claim 1 including means for holding a supply of
toner, means for monitoring the opacity of said developer liquid
and means responsive to said monitoring means for feeding said
toner from said
3. Apparatus as in claim 1 including means for holding a supply of
said diluent, means for sensing the level of developer in said
container and means responsive to said sensing means for feeding
diluent from said
4. Apparatus as in claim 1 including means for holding a supply of
said toner, means for holding a supply of said diluent, means for
monitoring the opacity of said developer, means for sensing the
level of said developer in said container, means responsive to said
monitoring means for feeding toner from said toner supply to said
mill means, and means responsive to said sensing means for feeding
diluent from said diluent
5. In an electrostatic copier utilizing a liquid developer having a
diluent component and a tacky toner component apparatus including a
tank for holding a supply of said liquid developer, a developer
unit, means including a first pump for circulating developer liquid
from said tank through said developer unit and back to said tank,
mechanical mill means for subjecting developer passing therethrough
to shear stresses sufficiently great to maintain an emulsion of
said toner and said diluent, and means including a second pump for
circulating developer liquid from
6. Apparatus as in claim 5 including means for holding a supply of
said toner, means for monitoring the opacity of said developer
liquid and means responsive to said monitoring means for feeding
toner from said supply to
7. Apparatus as in claim 6 in which said toner holding means
comprises
8. Apparatus as in claim 5 including means for holding a supply of
said diluent, means for sensing the level of liquid in said tank
and means responsive to said sensing means for feeding diluent from
said supply to
9. Apparatus as in claim 5 in which said mill means comprises a
stator member, a rotor, means forming a narrow space between said
rotor and said stator, means for directing material fed to said
mill means into said space, and means for moving said rotor
relative to said stator to apply
10. Apparatus as in claim 9 in which said space forming means
comprises an annular vane on said stator and an annular vane on
said rotor, said rotor vane being disposed adjacent said stator
vane to form an annular space, said directing means comprising
openings in said rotor vane, and means for
11. Apparatus as in claim 5 in which said mill means comprises a
rotor and a stator, a plurality of concentric annular vanes on said
rotor and on said stator, said stator and rotor vanes cooperating
to form a plurality of narrow annular spaces, means for directing
material fed to said mill means to said rotor, means forming
openings in said vanes for directing material fed to said rotor to
said spaces and means for rotating said
12. Apparatus as in claim 11 in which said stator vane openings are
generally radial and in which said rotor vane openings extend from
inlet to outlet in a direction slanted opposite to the direction of
rotation of the rotor.
Description
BACKGROUND OF THE INVENTION
In our co-pending application, Ser. No. 155,108, filed June 21,
1971, we disclose a novel method for contact transfer of liquid
toner developed electrostatic images. The latent electrostatic
image, formed on a photoconductive surface is developed by a novel
liquid toner which comprises a volatile liquid which suspends a
high molecular weight resin. This resin has the property of
becoming tacky, so that it can be transferred from the
photoconductive surface to a carrier such as plain paper by
contacting the paper with the developed image. The resin is admixed
with pigment and is normally insoluble in the volatile diluent or
carrier component of the developing liquid. Accordingly, we form an
organosol by dissolving the high molecular weight resin in a
solvent and then emulsify the resultant organosol with the volatile
liquid carrier within which the resin is insoluble. As developer
liquid is used the toner component becomes depleted and must be
replenished. The size of the equipment which would be necessary to
furnish an adequate developer liquid source for extended operation
would render it impractical. Attempts to replenish the organosol by
direct addition to the diluent result in coagulation and
flocculation rendering the developing liquid unsuitable for proper
development of the image. That is, the resin upon contact with the
volatile liquid vehicle tends to segregate and isolate itself
within the resulting mixture.
Moreover, since the organosol tends to precipitate and settle to
the bottom of the developer tank, the organosol dispersion requires
continual agitation when the machine is not being operated. If this
is not done, copies made after a prolonged period of machine
idleness will be of inferior quality.
Not only is it advantageous to agitate the developer liquid but it
is necessary to disperse the toner organosol with the diluent
vehicle when either diluent or toner is added to the developer
liquid.
SUMMARY OF THE INVENTION
One object of our invention is to provide a continuous supply of
tacky toner liquid developer of correct composition.
Another object of our invention is to provide an efficient
apparatus for replenishing the components of a tacky toner liquid
developer.
A further object of our invention is to provide a liquid developer
supply system of reduced volume.
Still a further object of our invention is to provide a completely
self-regulating developer supply system capable of continually
supplying a developer fluid of proper composition to
electrophotographic apparatus.
Other and further objects of our invention will appear from the
following description:
In general, we provide for a continuous and homogenous supply of
tacky toner developer liquid to a developer station in an
electrophotographic apparatus by providing two independent paths of
developer liquid circulation each of which includes a common toner
supply tank. One path continually circulates toner from the toner
supply tank to an emulsifying mill, the discharge of which returns
to the toner supply tank. The other path continually circulates
toner liquid taken from the toner supply tank to the developer
zone, the discharge of which returns to the toner supply tank.
Mixing of the independently circulating rings occurs in the toner
supply tank. We thus assure an uninterrupted flow of developer
liquid of the proper composition to the developing station to
develop the latent electrostatic image. We employ separate pumps in
our two circulating rings.
We may continuously monitor the toner concentration by measuring
the light transmissibility of the fluid at any desired point such,
for example, as that at which liquid leaves the developer station.
When the toner concentration is sufficiently low a photosensor
receives a greater flux of light due to the reduced opacity of the
developer fluid. When enough light strikes the sensor a solenoid
valve opens to add toner concentrate to the circulating ring
through the emulsifying mill.
We employ a mechanical impingement mill to apply high shear
stresses to the viscous toner organosol. The injection of the
concentrate into the emulsifying mill is intermittent, depending
upon the rate of toner depletion in the developer zone.
The level of fluid in the apparatus is monitored by a level
indicator positioned at an appropriate point such as in the toner
supply tank. When the level of fluid in the supply tank reaches a
predetermined low another solenoid valve activates to supply
diluent carrier liquid to the emulsifying zone. The toner is
maintained at a proper consistency and a supply of developer liquid
is available without the necessity of employing a large and
cumbersome developer liquid supply tank.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings which form part of the instant
specifications 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 showing electrostatic copying
apparatus employing a liquid developer and incorporating one
embodiment of our invention.
FIG. 2 is a fragmentary sectional view, drawn on an enlarged scale,
of an impingement mill used in our invention.
FIG. 3 is a fragmentary sectional view drawn on an enlarged scale
showing one of the control valves of our invention.
FIG. 4 is a sectional view drawn on an enlarged scale taken along
the line 4-4 of FIG. 2.
FIG. 5 is a diagrammatic view showing the control circuitry
operating the valves controlling admission of the toner concentrate
and the diluent liquid.
DESCRIPTION OF THE PREFERRED EMBODIMENT
More particularly, referring now to FIG. 1 of the drawings a copy
machine incorporating our developer supply system includes a drum
88 provided with a photoconductive surface 87. The drum 88 is
supported on a shaft 90 which rotates in the direction of the arrow
when the machine operates. Light source 93 insures that any
residual electrical charge remaining on surface 87 from a previous
exposure is reduced by conduction to ground. Preparatory to forming
a latent image on surface 87 an electrostatic charging device 92
charges the surface 87 of the drum, which is enclosed in a
lightproof casing (not shown) as is known in the art. An exposure
system 94 focuses an image of the original to be copied on the
charged photoconductive surface thus producing a latent
electrostatic image on the surface of the drum. As the drum
rotates, this latent image moves to the developer zone indicated
generally by reference numeral 96 at which a tray and applicator
means 98 subjects the latent image to the action of the developer
liquid. The tacky developed image is carried by the drum into
contact with paper 112 which is heated by a heater 116 as it leaves
a supply roll 114. Although the tacky toner is attracted to the
photoconductive drum surface in accordance with the light or dark
areas of the original, the toner, owing to its composition,
exhibits a greater affinity for the paper surface 112 than it does
for the drum surface 87. After picking up the developed image the
paper 112 passes to delivery rolls 118.
To assure uniformity of this process, a developer supply pump 75
driven by a motor 76 draws developer liquid from the toner supply
tank 64 and discharges it through pipe 84 into developer tray 98. A
developer applicator in tray 98 applies developer fluid to the
surface 87. Excess developer liquid leaving the photoconductive
surface 87 collects in a trough 86. A pipe 74 conducts liquid from
trough 86 through the toner monitoring system indicated generally
by reference numeral 66 and back to supply tank 64. As successive
images are developed toner in the developer liquid is depleted at a
relatively rapid rate and carrier liquid is depleted at a
relatively slower rate so that the makeup of the liquid changes
slightly on each operation of the machine.
Our apparatus includes another loop of circulating fluid including
the toner supply tank 64. This second system includes a developer
recirculating pump 77 driven by a motor 78. Pump 77 continually
withdraws developer fluid from the toner supply tank 64 through
pipe 70 and pumps it through a pipe 80 into an impingement mill
body 14. From the body 14 liquid passes back to tank 64 through
pipe 62 to complete the loop.
Now referring to FIGS. 1 and 2, it can be seen that the fluid
discharging from recirculating pump 77 passes through pipe 80 and
is then tangentially injected into the impingement mill body 14
where it mixes with developer fluid 15 in the mill body. The
combined fluids whirl about in the direction of the arrows and exit
through pipe 62 after passing through a space 51 formed by mounting
a disc-shaped cap 56 on spacers 58 carried by a flange 59 on an
extension 60 from pipe 62. The emulsion thus formed in mill 14
flows back to toner supply tank 64 through pipe 62.
As with the circulation through supply pump 75 the consistency of
the developer fluid 15 in each succeeding cycle through pump 77 is
of a slightly different makeup than that in the preceding cycle.
This change in fluid consistency in succeeding cycles through
supply pump 75 and through recirculation pump 77 occurs during
development of the successive latent electrostatic images. As has
been pointed out hereinabove, there will unavoidably be some slight
evaporation of the diluent during each cycle as well as depletion
of toner from the developer liquid. That is, the concentration of
toner in a given volume of fluid entering tray 98 will be slightly
greater than that collected in return trough 86 for that same
volume owing to development of the image.
Referring now to FIGS. 1, 2, and 3, a container 4 holds a supply of
toner concentrate liquid 2. A pipe 12, fixed in a cap 6,
communicates with a source fluid under pressure (not shown) which
supplies pressure to piston 5 to push toner concentrate through
supply pipe 10. The cap 6 of container 4 is removable so that toner
paste 2 can be replenished. The pipe 10 is normally closed by a
valve 25 operated by a solenoid 16. Valve 25 which normally engages
seat 27 has a stem 24 connected to the armature 18 of a solenoid
16. Operation of solenoid 16 controls the admission of toner paste
into the mill. Stuffing box 19 seals the commutating stem 24 and
valve chamber 22. The operation of solenoid 16 is controlled by a
toner monitoring system indicated generally by reference numeral
66. Actuation of solenoid 16 lifts valve 25 from its seat 27. When
this occurs paste 2 from the valve chamber 22 flows into a rotor
intake chamber 42.
Now referring to FIGS. 1 and 5, the monitor 66 is similar to the
toner monitoring system described in U.S. Pat. No. 3,354,802. We
position the toner monitoring unit 66 in pipe 74. It is to be
understood, however, that the location of monitor 66 in pipe 74 is
shown by way of illustration only and not by way of limitation, as
the monitor may be positioned elsewhere, for example, in supply
pipe 84. Monitor 66 includes an incandescent source 66a and a
photosensor 66b. When the toner liquid has the proper or desired
concentration the voltage at the anode of photosensor 66b is equal
to that at the junction of resistors 67b and 67c so that the net
input to differential amplifier 100 is zero. When toner pigment is
depleted the illumination of the photosensitive element 66b by lamp
66 increases because of the reduction of opaqueness of the
developer liquid 15. This reduces the resistance of the
photosensitive element 66b and hence reduces the voltage there
across. The voltage to the "minus" input of differential amplifier
100 becomes more negative than the voltage at its "plus" input.
Differential amplifier 100 accordingly, provides a positive output
which is coupled forwardly through diode 100a to energize solenoid
winding 16. The negative terminal of battery 110 is grounded. Lamp
66a is connected between the positive terminal of battery 110 and
through a resistor 67a to the anode of photosensor 66b, the cathode
of which is grounded. Positive terminal of battery 110 is further
serially connected through resistors 67b and 67c to ground. The
junction of resistors 67b and 67c is connected to the plus input of
a differential amplifier 100. The anode of photosensor 66b is
connected to the minus input of differential amplifier 100. We
apply the output of differential amplifier 100 to the anode of
diode 100a, the cathode of which is connected through solenoid
winding 16 to ground.
The amount of light striking photodetection element 66b is a
function of the light transmissibility of developer liquid 15. When
the toner concentration is increased the opacity of fluid 15
increases. The illumination of photosensor 66b decreases when the
toner concentration increases. When this occurs, the voltage at the
anode of photosensor 66b rises and the output of differential
amplifier 100 decreases so that solenoid 16 is de-energized thereby
closing valve 25.
Referring now to FIGS. 1 and 2, a supply of volatile carrier liquid
43 is stored in container 82. Cap 83 is removable from container 82
so that diluent liquid 43 may be added as needed. Pipe 44 is
normally closed by a valve 25a operated by a solenoid 16a. The
volatile liquid 43, under the influence of gravity, fills valve
chamber 22a and is retained therein in its normally closed position
of valve 25a.
Valve 25a, adapted to seat on seat 27a, is operated by a solenoid
16a through its armature 18a and the valve stem 24a, thereby
regulating the admission of volatile diluent into the mill. We
provide stuffing box 19a at the top of chamber 22a to seal the
valve stem. The solenoid 16a is controlled by the opening and
closing of a microswitch 106 actuated by a float 104 in tank 64.
Actuation of solenoid 16a lifts valve 25a from its seat 27a. The
diluent in chamber 22a then flows into the rotor intake chamber
42.
Referring now to FIG. 5, the normally closed microswitch 106 is
connected in series with diluent control solenoid 16a across
battery 110. Float 104 slides vertically on a guide 105 so that
when the fluid level reaches a predetermined point, the switch 106
opens and de-energizes winding 16a, permitting the valve 25a to
close.
Referring again to FIGS. 1, 2, and 3, an electric motor 53 having a
shaft to which sprocketed wheel 53a is keyed is energized to drive
a chain 51 which drives a sprocket wheel 52 on impingement mill
shaft 54. Shaft 54 is positioned concentrically within housing 50
and is free to rotate therein on bearings 48. A key 23 secures the
hub 33 of the mill rotor 32 to shaft 54. Rotor 32 has apertures 40
and a pair of cylindrical vanes 36 formed with apertures 38 as can
be more clearly seen in FIG. 3. As shown in FIG. 2, underbody vanes
34 are formed on the underside of rotor 32. We position rotor 32
adjacent to stator body 26 which forms the top of mill casing 14.
Stator 26 supports both valve chambers 22 and 22a. These chambers
extend through stator 26 so as to be positioned in the space
between the first rotor vane and rotor hub 33, which space forms
rotor intake chamber 42. Stator 26 is formed with vanes 28 having
apertures 30. The entire rotor assembly is sealed about shaft 54 by
means of packing 47.
When the photocopying apparatus is actuated, motor 53 through the
chain drive described above will spin rotor 32. When this occurs
the fluid in the rotor intake chamber 42 accelerates outwardly
circulating through apertures 40. When valves 25 and 25a are closed
the developer fluid in the impingement mill body 14 circulates
through the spaces between and through the openings in rotor vanes
36 and stator vanes 28. On command from the tonor monitor toner
paste flows into chamber 42. On command from developer liquid level
sensor diluent 43 flows into the impeller intake chamber 42. These
fluids either singly or in combination are accelerated outwardly of
chamber 42.
Referring now to FIG. 4, the outward movement of the fluids occurs
through apertures 38 in rotor vanes 36, and through apertures 30 in
stator vanes 28. Some of the fluid traverses the narrow annular
spaces or interstices between stator vanes 28 and rotor vanes 36 as
well as the interstices between rotor body 32 and stator body 26.
The juxtaposed relation of these vanes causes violent shear
stresses which emulsifies and homogenizes the traversing fluids.
The effluent mixes with developer liquid 15 in mill casing 14.
Underbody vanes 34 aid the circulation of the fluids.
It is to be understood that the injection of toner paste 2 or
volatile diluent 43 or both is made only when required. However,
the homogenizing process is continuous while the machine is
operating. After the machine has been in operation for some time,
some precipitation may occur. To clear the system of precipitates,
we provide tap pipe 61 controlled by valve 63, in the lower portion
of mill body 14, permitting removal of any accumulated
coagulants.
In use, when the electrostatic copier is energized, motors 76, 78,
and 53 operate and rotate continuously while the machine is
operating. Motor 76 drives pump 75 to discharge developer liquid
through pipe 84 to the developing tray 98. Developing liquid
returns through pipe 74 to the toner supply tank 64 from which it
passes through pipe 68 for continuous circulation around the
circulating ring comprising the toner supply tank 64 and the
developing tray 98. Energization of motor 78 operates pump 77 which
draws developer liquid from toner supply tank 64 through pipe 70
and discharges it through pipe 80 into the homogenizer 14. The
discharge from the homogenizer 14 through pipe 62 returns the
homogenized developing fluid to the toner supply tank 64. The
operation of motor 53 drives the homogenizer rotor 32 through the
chain drive 51. The organosol components of the developing fluid
are thoroughly homogenized in the carrier liquid by the interaction
of the stationary vanes and rotary vanes of the homogenizer, as
well as by the agitation which takes place in the homogenizer body
14. When the high molecular weight components of the tacky toner
composition become reduced in quantity, the optical control system
66 will insure their replenishment. This occurs when valve 25 opens
allowing the air pressure upon piston 5 to deliver the toner
concentrate to the homogenizer. When the concentration reaches the
proper consistency, the optical control system permits valve 25 to
seat. Some toner liquid adheres to the revolving drum surface 87
and evaporates. This reduces the liquid level within the toner tank
64. When this occurs microswitch 106, held open by float 104,
closes energizing solenoid 16a and operating valve 25a permitting
diluent from the diluent storage tank 82 to flow through pipe 44
into the homogenizing zone.
It will be seen that we have accomplished the objects of our
invention. We have provided a system for maintaining the developer
liquid in proper condition. We have provided a continuous supply of
tacky toner liquid of correct composition to a developer station.
We have provided a novel means and method for replenishing our
tacky toner component of the developer liquid. Our machine is of
reduced size. We have provided a self-regulated toner developer
supply system which continually supplies toner fluid of proper
composition to the developing zone.
It will be understood that certain features and sub-combinations
are of utility and may be employed without reference to other
features and sub-combinations. 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.
* * * * *