Liquid Development Apparatus

Abstract

A liquid developing station is provided in a copying device for developing electrostatic images on receivers in a manner such that distribution of developing liquid across the receiver is very uniform. A liquid reservoir for the development liquid is provided which is adapted to receive separate containers for supplying additional carrier or developing liquid and toner particles. The liquid is dispensed directly into the reservoir by inserting a container thereof into a first receptacle in the top of the reservoir. Toner particles are supplied in an aerosol can which may be positioned in a second receptacle with the nozzle thereof adjacent an inlet to a liquid pump within the reservoir. To add toner, the operator may energize a circuit which upon the next operation of the copying device will cause the aerosol can to dispense a measured quantity of toner particles into the pump inlet so that it is immediately circulated and mixed in the developing liquid for the next print. After each print cycle, developing liquid quickly drains from the developing station into the reservoir.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

Reference is made to my commonly assigned copending U.S. Pat. application Ser. No. 29,742 filed Apr. 24, 1970.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to liquid development of electrostatic images and more particularly to means for evenly distributing such liquid and for replenishing the liquid and toner particles as they are depleted.

2. Description of the Prior Art

In one conventional electrophotographic process, a receiver material having a photoconductive coating thereon is charged, as by a corona device, to provide a generally uniform electrostatic charge thereon which is selectively dissipated by exposure to a radiation pattern to form an electrostatic image. This image may then be developed by passing the receiver sheet through a medium containing toner particles having a charge thereon of opposite polarity to the charge of the electrostatic image. Thus, the particles are attracted to the receiver to form a visible toner image which may be subsequently fused to make it permanent. The development medium may be either a powder or a liquid. In the case of liquid, the carrier liquid, such as Isopar contains toner particles suspended therein.

These particles are selectively drawn out by the electrostatic image on the receiver to form a toner image. As successive prints are made, the toner particles become depleted from the liquid, subsequently reducing the contrast of the prints being made. Also, variations in contrast may exist if the liquid developer is not evenly distributed across the surface of the receiver to assure that all parts of the electrostatic image have substantially equal access to the toner particles so that development will be complete and uniform.

Various attempts have been made to accomplish uniform development. These include spraying liquid against the receiver sheet; applying liquid by means of rollers; and immersing the receiver in liquid. However, each of these prior art methods has certain disadvantages. If the developer liquid is sprayed, the spray must be carefully controlled so that it does not get on unwanted parts of the copier. Also, it is difficult to maintain an even spray from each orifice. Application rollers may not be truly uniform, so that uneven pressure is exerted against the receiver, resulting in uneven application of developer. When the receiver is immersed in liquid it tends to become saturated therewith and requires substantial drying time before the print is ready for use. Other devices provide a shallow pool through which the receiver is passed but even distribution of developer liquid across the pool is difficult to accomplish. Furthermore, developing liquid is often retained in the developing station between print cycles, thereby increasing the possibility of spillage due to bumping or jarring of the printer.

In addition, prior art devices either do not provide means for replacing developing liquid and toner particles or do so in such a manner that the quality of prints varies over an undesirably wide range. In most instances, it is inconvenient and difficult to replace developer liquid, usually resulting in shutdown of the entire machine and sometimes substantial disassembly must be accomplished before additional liquid can be added. Attempts have been made to replenish the depleted toner particles, such as shown in U.S. Pat. No. 3,416,860 to Mihojevich et al. However, in this device no convenient way is provided for replenishing carrier liquid and toner concentrate is dispensed into a reservoir at an opposite end thereof from the pump so that dispersion of the toner particles through the liquid may take some time. Thus, additional prints may be made which have low contrast even after the operator has caused additional toner particles to be added.

SUMMARY OF THE INVENTION

The above enumerated problems are substantially overcome by the present invention wherein a reservoir for developer liquid is positioned to one side of a developing station. Developing liquid is pumped from the reservoir by a pump through a manifold arrangement at the developing station so that developer is spread evenly across a receiver sheet as it passes through the developing station. Between print cycles, the liquid in the developing station is drained back into the reservoir. This substantially reduces the possibility of spillage, should the printer be jarred or moved. In addition, the reservoir is mounted for sliding movement along tracks so that it may be withdrawn for replenishing the carrier liquid and/or the toner particles. In this connection, the reservoir is provided with two receptacles, one for receiving a rupturable container of carrier liquid and the other for receiving an aerosol can of toner particles. The receptacle for the carrier liquid is provided with an impaling means which causes the liquid in the container to immediately be dispensed into the reservoir, but also includes valve means for discontinuing flow of liquid into the reservoir if the level of the reservoir reaches a predetermined height. The aerosol can may be activated periodically by means of a solenoid which is energized in the first cycle of the machine subsequent to the operator pressing a switch to indicate that more toner is needed. The aerosol can dispenses concentrate toner particles into a pump inlet so that toner is immediately available for developing the next print.

Additional features and advantages of the invention will be apparent from the description which follows, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal offset section through the developing station and replenishing station showing the developer path from the reservoir to the developing station and how toner concentrate and carrier liquid are added;

FIG. 2 is a fragmentary vertical section, taken along line 2--2 of FIG. 1, showing flow of developing liquid into a manifold;

FIG. 3 is a partially exploded, perspective view of the developer station showing the arrangement of the trays therein;

FIG. 4 is a diagrammatical circuit diagram illustrating a portion of the circuitry used in connection with this invention;

FIG. 5 is a fragmentary, exploded, perspective view of a drain tray and connecting parts to the replenishing station;

FIG. 6 is an exploded view of the manifold and developing tray used in the developing station illustrated in FIGS. 1-3;

FIG. 7 is a fragmentary perspective view of a portion of the replenishing station showing the manner in which the replenishing station may be withdrawn for adding toner; and

FIG. 8 is a vertical section of an alternative developing station which may be used in connection with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with this invention, a receiver, such as receiver 10 of FIG. 1 having a photoconductive surface, is charged with an electrostatic charge exposed to a radiation pattern to form an electrostatic image and then fed image side down through developing station D. The charging and exposure steps could take place in the manner illustrated in my commonly assigned U.S. Pat. application Ser. No. 829,615 to Clyde P. Glover entitled, "Charging Device" and filed June 2, 1969, now abandoned.

Developing station D includes an upper arcuate tray 11 and a lower arcuate tray 12 positioned to provide a passageway therebetween through which receiver 10 is fed by drive rollers 13 and 14. Developing liquid is fed into lower tray 12, in a manner to be described, and evenly distributed across the receiver so that the electrostatic image on the receiver attracts toner particles from the developing liquid to create a toner image. As the receiver leaves the developing station, it passes through a pair of squeegee rollers 15 and 16 which remove excess developing liquid therefrom. Conveniently, upper tray 11 includes an arcuate surface 17 and is provided with a curved guard 18 which extends over squeegee roller 15 to prevent splashing of any developing liquid which may be carried off of roller 15. In addition, tray 11 is provided with lateral side walls 19 and diagonally extending ribs 21 which serve to space receiver 10 from the bottom of surface 17 so that it does not stick thereto. Conveniently, bottom tray 12 is provided with arcuate bottom wall 22 having diagonally extending ribs 23 which are conveniently spaced between ribs 21 as best seen in FIG. 2. Ribs 23 serve to support the image side of receiver 10 should the liquid in the developing station not be sufficient to do so. Conveniently, the developing liquid is provided through a plurality of slots 24 and extending between adjacent ribs. The liquid which is pumped up through slots 24 spills over the leading and trailing edge of bottom tray 12 into a drain tray 25 which has bottom walls 26 sloping toward an outlet 27 which is generally rectangular in shape and is adapted to receive a sleeve 28 which will be described more fully below. Conveniently, bottom tray 12 has a pair of outwardly extending flanges 22' shown in FIG. 3, which engage ledges 26', shown in FIG. 5, to support tray 12 over tray 25.

The developing liquid is supplied from a replenishing or liquid supply station R which holds a supply of liquid developer 29 in a generally box-like reservoir 30. Within reservoir 30 is a pump 31, driven by a motor 32, which pump draws liquid from the reservoir through inlet 33 and discharges it into a flexible tube or pipe 34. This pipe extends around a pin 35 and terminates in a slidable block 36 to which is connected a tube 37 extending into a central hole 38 in sleeve 28. The liquid then passes through an angular pipe 39 connected to manifold 40, as best seen in FIG. 6, having a lower half 41 and upper half 42, the upper half being formed integrally with bottom tray 12. Thus, the lower half 41 includes an elongated passageway portion 43 communicating with a large enclosed portion 44. Within portion 44 is a baffle 45 which deflects liquid developer toward each end of the manifold. Lower half 41 mates with upper half 42 so that a passageway portion 46 in upper half 42 is aligned with passageway portion 43 to form a single passageway. Also, upper half 42 includes a large portion 47 which cooperates with portion 44 to form a large enclosure and includes a baffle 48 spaced further from the passageway than baffle 45 to further assist in distribution of developing liquid across the manifold so that a substantially equal amount flows evenly through slots 24. Pump 31 runs continuously throughout the print cycle so that developer liquid is continuously pumped through slots 24 filling bottom tray 12 and overflowing the leading and trailing edges thereof whereupon it falls into drain tray 25 and is drained through outer openings 49 in sleeve 28 back into reservoir 30. Thus, the space between upper tray 11 and lower tray 12 is completely filled with liquid and the flow of this liquid through the slots tends to support receiver 10 above ribs 23 so that the image side thereof does not actually touch the lower tray or the ribs at all under normal operation. Advantageously, streaking of the image due to contact with ribs 23 is minimized.

As seen in FIG. 4, a print cycle is initiated by depressing normally open start switch 51 which is held in the closed position by a time delay circuit 52 so that pump motor 32 runs continuously for a predetermined length of time sufficient for a receiver sheet to be charged, exposed and developed. After a print cycle is completed, the toner in developer station D drains out through slots 24 back into reservoir 30.

When the developer liquid 29 in reservoir 30 becomes depleted, a float switch 54 will close a circuit to lamp 53, shown in FIG. 4, so that the operator will know that additional developing fluid should be added. To accomplish this, reservoir 30 may be slid out of the machine, as along track 54, shown in FIGS. 1 and 7, so that it is accessible outside of machine housing 55. Movement of reservoir 30 is permitted by flexible tube 34 which moves from the dotted line position shown in FIG. 7 to the solid line position adjacent pin 35. To facilitate this, block 36 is frictionally mounted between a pair of parallel guides 56 and 57. Conveniently, reservoir 30 is provided with a top 58 having an elongated slot 59 covered by a slidable panel 60 which is movable within flanges 61 best seen in FIGS. 1 and 3. Conveniently, panel 60 is provided with an opening 62, best seen in FIG. 5, through which sleeve 28 extends. Thus, when reservoir 30 is removed from the housing as by sliding it along track 54 to the left, as viewed in FIGS. 1 and 7, panel 60 will be caused to slide along top 58 so that the hose connections may remain stationary.

Top 58 is provided with a first receptacle 63 for receiving a rupturable bottle or container 64 of developing liquid and a second receptacle 65 for receiving an aerosol can 66. When reservoir 30 is withdrawn from housing 55 the receptacles are accessible so that the developer container 64 and aerosol can 66 may be replaced. When the operator notes that light 53 is lit due to depletion of the developing liquid, reservoir 30 may be withdrawn and any empty bottle 64 may be removed and a new one placed therein. Conveniently, these containers or bottles are made of a rupturable material, such as polyethelene, and may be urged downwardly in receptacle 63 so that the end thereof is impaled by a piercing tube 67 to permit developing liquid in container 64 to be drained into reservoir 30. After inserting the bottle the reservoir may be slid back to its initial position in the machine, as shown in FIG. 1. Conveniently, the piercing tube comprises an enlarged tubular end 68. End 68 is provided with a plurality of holes 69 through which the fluid is dispersed from container 64 into reservoir 30. If desired, a filter, not shown, may be provided in end 68 to prevent lint from entering the reservoir. A float valve 71 is provided within end 68 which closes off piercing tube 67 should be level of fluid rise to a predetermined level, thereby preventing overflow of the developing liquid.

Aerosol can 66 is provided with a metering nozzle 72 and is supported by a flange 72' that rests against the bottom of receptacle 65.

When it is noticed that the prints are losing their contrast, switch 73, seen in FIG. 4, is closed by the operator to cause a memory circuit 74 to momentarily energize solenoid 75 and the next time copy button 51 is closed. As seen in FIG. 1, solenoid 75 is connected to an arm 76, having an end which engages the bottom of aerosol can 66 and which is pivoted about a pin 77 on housing 55. Thus, upon energization of solenoid 75 the arm 76 will be rotated in a counterclockwise direction as viewed in FIG. 1 causing can 66 to be depressed so that metering valve 72 discharges a measured quantity of toner particles into the constricted space in reservoir 30 formed by a shroud 78. Thus, the toner particles are immediately directed into inlet 33 of pump 31 which pumps them along with toner liquid drawn into the shroud through an opening 79 so that a more concentrated developing liquid is presented at the developing trays for the very next print. After the momentary energization, solenoid 75 is returned to its initial position, as by coil spring 81 so that the right hand end of arm 76 rests on stop pin 82 extending from housing 55.

An alternative developer station D' is shown in FIG. 8 wherein upper and lower trays 85 and 86, respectively, provide a path for receiver sheet 10' to be fed therebetween, as by feed rollers 87 and 88. After development the excess developer liquid is removed from the sheet by squeegee rollers 89 and 91. The development trays are positioned within a drain tray 92 for returning the liquid to a reservoir station. Conveniently, the development liquid is pumped through an inlet 93 at the bottom of tray 86 and through a second inlet 94 adjacent the leading end of tray 86. Developing liquid is supplied to these inlets by pipes 95 and 96, respectively, from a tee 97 attached to pump 98. Such as arrangement creates a waterfall effect at inlet 94 since the developer liquid flows down the arcuate surface of tray 86. However, rapid filling of the tray is assured since liquid is also introduced through inlet 93. As the tray fills, the liquid is discharged from tray 86 through a series of openings 99 adjacent the leading end of the tray and then drains through an inlet 100 of drain tray 92 and back into the reservoir. At the end of a print cycle, liquid drains out through inlet 93 into the reservoir.

From the foregoing, the advantages of the present invention are readily apparent. A developer station for developing an electrostatic image is provided wherein even distribution of developing liquid across a developer tray and hence across a receiver sheet bearing the electrostatic image is assured. This is accomplished in one embodiment by providing a manifold having a series of baffles which cause the liquid to be distributed so that it is introduced evenly through a series of slots across the bottom of the tray. In another embodiment, liquid is introduced adjacent the leading edge and at the bottom of the tray. Also, the developing liquid and toner concentrate can easily be replaced in the reservoir since the reservoir is conveniently removable from the housing for selective insertion of a container of developing liquid when the liquid level is low or for insertion of an aerosol can containing concentrate toner particles when the toner supply is low. During operation, when the operator notices the contrast of the prints is no longer satisfactory, a button may be pressed to energize a memory circuit so that during the next cycle of the machine a solenoid is momentarily energized to discharge a metered amount of toner particles from the aerosol can into an area adjacent the inlet to the pump so that a developing liquid enriched in toner particles is provided to the development station for the very next print. Also, at the end of each cycle the developing liquid is drained from the developing station thereby reducing the possibility of spillage if the printer is moved or jarred.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Claims

I claim:

1. A liquid toner supply station for use in electrophotographic apparatus for supplying toner to a developing station, said supply station comprising:

a reservoir for containing a body of liquid developer;

a pump, having an inlet in said reservoir and being cyclically operable for pumping development liquid from said reservoir to the developing station;

first support means for receiving a container of developing liquid for replenishing developing liquid in said reservoir and including means defining a developing liquid passage from a received container into said reservoir;

second support means for receiving a container of toner and including means defining a toner passage from a received toner container into said reservoir;

shroud means, extending from said toner passage to said pump inlet, for limiting dispersion of toner during movement from said toner passage into said pump inlet;

means for dispensing toner from a received toner container;

means for selectively signalling actuation of said dispensing means; and

control means for delaying a signalled actuation of said dispensing means until the next operative cycle of said pump.