US3507252A

US3507252A - Combination of a container for a liquid and means for dispensing the liquid

Info

Publication number: US3507252A
Application number: US640564A
Authority: US
Inventors: Marvin A Leedom
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1967-05-23
Filing date: 1967-05-23
Publication date: 1970-04-21
Anticipated expiration: 1987-04-21
Also published as: SE331422B; NL6807256A; DE1772486A1; GB1186947A; BE715538A; JPS5018781B1; FR1566001A

Description

| 3 Sheets-Sheet 1 Aprll 21, 1970 M. A. LEEDOM COMBINATION OF A CONTAINER FOR A LIQUID, AND MEANS FOR DISPENSING THE LIQUID Fued May 23 1967 INVENTOR MAR V/A/ A. ZEEDOM B), M J

A TTORNE Y Apnl 21, 1970 M. A. LEEDOM 3,507,252

COMBINATION OF A CONTAINER FOR A LIQUID AND MEANS FOR DISPENSING THE LIQUID Filed May 23, 1967 5 Sheets-Sheet 2 INVEN 70R 7 M4 V/A/ 4. 15500114 y lrrofi'f 3,507,252 COMBINATION OF A CONTAINER FOR A LIQUID AND MEANS FOR DISPENSING THE LIQUID Marvin A. Leedom, Warminster, Pa., assignor to RCA Corporation, a corporation of Delaware Filed May 23, 1967, Ser. No. 640,564 Int. Cl. B05b 5/02 US. Cl. 118-637 14 Claims ABSTRACT OF THE DISCLOSURE An apparatus for applying a liquid developer to the surface of a recording medium to develop the latent image thereon. The apparatus consists of a container having a plurality of side walls defining a reservoir for the liquid developer, a manifold on one of the side walls for dispensing the liquid, and a pump for circulating the liquid between the reservoir and the manifold. The manifold has an exit slit therein which communicates with the interior of the manifold and applies the liquid developer to the recording medium adjacent the slit. A trough member surrounds the manifold and collects any excess liquid developer which may issue from the exit slit. The trough member is in fluid communication with the reservoir for returning the excess liquid developer to the reservoir so that it may be recirculated. A portion of the exit slit is made up of an electrically conductive member which has a source of voltage connected thereto. The pump consists of a cavity which is in fluid communication with the reservoir and the manifold, an impeller of magnetic material rotatably mounted in the cavity, and a rotating magnet adjacent the cavity for actuating the pump.

Background of the invention This invention relates generally to an improved combination of a container for a liquid and means to dispense the liquid. More particularly, the invention relates to an improved combination of a container for a liquid developer and means to provide a flow of the liquid developer to a latent image on a surface of a recording medium when the latter is disposed adjacent to the container. The improved combination of a container and liquid dispensing means there-for is particularly useful as a developing system for storing a liquid developer of the type used in the electrophotographic arts and for providing means to dispense the liquid developer to the surface of a recording medium to develop an electrostatic charge pattern on the surface as the recording medium is moved adjacent to, and slightly spaced from, the container.

It has been proposed to develop a latent electrostatic image on a photoconductive surface of a recording medium by guiding the recording medium through an open container or tray filled with a liquid developer. While such open containers or trays are satisfactory for some electrophotographic apparatus, the liquid developer in the open containers tends to evaporate at a relatively fast rate. The liquid developer in such apparatus also tends to get onto some parts of the apparatus, such as the rollers and bearings employed for moving and guiding the recording medium, and eventually interferes with the proper operation of the apparatus.

In electrophotographic apparatus where a liquid developer is pumped onto a Web of a recording medium to develop a charge pattern thereon, the apparatus usually contains open containers or trays for the liquid developer and external plumbing for circulating the liquid developer. If any of the liquid developer is accidentally spilled onto certain parts of the apparatus, the apparatus usually must United States Patent 0 "ice be dismantled for proper cleaning. Also, the fluid pressure of the liquid developer in such apparatus tends to vary with the amount of liquid developer available and with the speed of the pump, and such variations in pressure tend to cause uneven developing of the charge pattern.

Summary of invention Briefly stated, the improved combination of a container for a liquid and means to dispense the liquid comprises a manifold on a wall of the container. The manifold has an exit slit therein for dispensing the liquid to a body adjacent to the exit slit. Pump means is adapted to pump the liquid from the container to the interior of the manifold and out through the exit slit of the manifold. A trough surrounds the manifold to collect any liquid that is not consumed by the body and to return it to the interior of the container.

In a preferred embodiment of the improved combination, a standpipe extends a predetermined height above the exit slit of the manifold. The lower end of the standpipe communicates with the pump means so that the liquid can be pumped through the standpipe at the same time the liquid is pumped through the manifold. The liquid that spills over the top of the standpipe is returned to the interior of the container. The height of the liquid in the standpipe provides a head which, in turn, provides the flow of the liquid through the exit slit of the manifold with a substantially constant desired pressure. The exit slit of the manifold may be defined by electrically conductive material which may be electrically biased to function as a developing electrode.

It is an object of the present invention to provide, as a complete compact unit, a refillable or disposable, easily transportable, safe container for a liquid and means for dispensing the liquid, at a substantially constant desired pressure, to the surface of a body adjacent to the container.

Brief description of the drawings FIG. 1 is a perspective view, viewed from the front, left side, and top of one embodiment of the improved combination of a container for a liquid and dispensing means therefor, showing a cover for the container outlined in phantom;

FIG. 2 is a cross-sectional view of the improved combination taken along the line 2-2 in FIG. 4, showing a portion of a rotary magnetic drive magnetically coupled to magnetic pump means within the container of the improved combination;

FIG. 3 is an enlarged, fragmentary, cross-sectional view of the improved combination taken along the line 33 in FIG. 2, showing, in addition, the path of a recording medium, along charging, exposing, and developing stations in its association with the improved combination;

FIG. 4 is a cross-sectional view of the improved combination taken along the line 4-4 in FIG. 2;

FIG. 5 is a plan view of the improved combination, showing, in addition, a contact electrode;

FIG. 6 is a cross-sectional view of the improved combination taken along the line 6-6 in FIG. 5; and

FIG. 7 is a fragmentary, cross-sectional view of the improved combination taken along the line 7-7 in FIG.

Description of the preferred embodiment Referring particularly to FIGS. 1 and 3 of the drawings, there is shown a preferred embodiment of the improved combination of the container 10 for a liquid 12 and means for dispensing the liquid 12. The improved combination will be described as a developing system for applying the liquid 12, as an electroscopic liquid developer, to a charge pattern on a photoconductive surface 14 (FIG. 3) of a recording medium 16 to develope the charge pattern as the recording medium 16 is moved adjacent to, but slightly spaced from, the container 10.

The container of the improved combination comprises a refillable or disposable reservoir (interior space 32) for the liquid 12. The container 10, in combination with the liquid dispensing means associated therewith, forms a complete compact unit that may be used to transport the liquid 12 safely, that is, without spilling the liquid and without any undue evaporation of the liquid. To this end, the container 10 comprises a bottom wall 20, a front wall 22, a rear wall 24, a pair of

side walls

26 and 28, and a top wall 30. The walls 20-30 of the container 10 are made of a material that is chemically inert to the liquid 12 which they will contact. Where the liquid 12 is an electroscopic liquid developer, for example, such as particles of pigment dispersed in a liquid carrier of trichlorotrifluoro ethane, the walls 20-30 may be of a plastic material, such as Lucite. The walls 20-30 of the container 10 may be fastened together by any suitable plastic cement or adhesive, or a plurality of the walls 20-30 may be molded simultaneously and the remaining wall or walls may be fastened to the molded walls in a manner well known in the art, forming an interior space 32, a reservoir of prismatic shape to store the liquid 12.

The liquid 12 is inserted into the interior space 32 of the container 10 through a bore 34 (FIG. 6) in the top wall 30. The bore 34 is threaded and plugged with a slotted removable plug 36. A vent bore 38 of relatively small cross-section (about 0.050 inch) is also formed in the top wall 30 to facilitate. the filling and emptying of the container 10.

The container 10 may be sealed by a removable cover 40, shown in phantom in FIG. 1. The cover 40 may be a plastic strip or adhesive tape that is secured, as by a suitable glue, over a portion of the top Wall 30, covering the openings therein that communicate with the interior space 32, so that the container 10 may be transported without spilling the liquid 12.

Means are provided to dispense the liquid 12 from an exit slit 42 (FIG. 3) of a manifold 44 on the top wall 30. Thus, the liquid 12 can be applied to the photoconductive surface 14 of the recording medium 16. The recording medium 16 is guided adjacent to, and slightly spaced (about 0.040 inch) from, the exit slit 42 by a roller 46, disposed parallel to the exit slit 42, so that the photoconductive surface 14 may come in contact with the liquid 12 when the liquid 12 is caused to issue from the exit slit 42.

The manifold 44 comprises an elongated island-like structure on the top wall 30 surrounded by a relatively wide groove, drain, or trough 47. The manifold 44 is formed with an elongated interior slot 48 that opens on the top surface 50 of the top wall 30 and extends almost to the narrow ends of the manifold 44. The exit slit 42 of the manifold 44 is defined between a pair of oppositely disposed, parallel,

metal electrode members

52 and 54, fixed by any suitable means to the top surface 50 of the top wall 30, for the purpose hereinafter appearing. The width of the exit slit 42 of the embodiment illustrated herein is about 0.040 inch.

Means are provided to pump the liquid 12 into the in-.

terior slot 48 of the manifold 44, from where it issues through the exit slit 42 and spills over the electrode members S2 and 54 into the trough 47. The liquid 12 can be returned to the interior space 32 of the container 10 through a pair of bores 56 and 58 (FIG. 3) in the top wall 30. A pair of

tubes

60 and 62 communicate with the

bores

56 and 58, respectively, and extend into the interior space 32 of the container 10 to points just above the top surface 63 (FIG. 7) of the bottom Wall 20. This structure exposes a minimum of the liquid 12 to the ambient above the container 10 and helps to retard the evaporation of the liquid 12 into the ambient.

Pump means, comprising a magnetic impeller 64, are provided in a pump cavity 66 in the side wall 26 to pump the liquid 12 from the interior space 32 to the exit slit 42 of the manifold 44. The impeller 64 is substantially rectangular, flat, magnetic member pivoted for rotation about its center by means of a pin 68. One end of the pin 68 is fixed to the center of the impeller 64, and the other end is journaled in the bottom wall 20, as shown in FIG. 2. The pump cavity 66 is inclosed in the wall 26 and communicates with the interior space 32 of the container 10 via a conduit 70 formed in portions of the side wall 26 and bottom wall 20, as shown in FIG. 2. The conduit 70 comprises input means to the pump chamber 66. Output means from the pump chamber 66 to the interior slot 48 in the manifold 44 is provided by a continuous passageway for the liquid 12, formed by a conduit 72 in the side wall 26 and a bubble trap 74 and a conduit 76 formed in the top wall 30, as shown in FIGS. 2 and 4. The bubble trap 74 is an enlarged portion of the passageway and provides a space to which any bubbles from the liquid 12 may rise and become trapped therein, as shown in FIGS. 2 and 4.

The impeller 64 is actuated, that is, rotated, by a magnetic member 80 (FIG. 2) which is similar to, and magnetically coupled to, the impeller 64. The magnetic member 80 is mounted on one end of a pin 82 for rotation about its center. The pin 82 is supported by a bushing 83 in a wall 85. A pulley 84 is mounted on the other end of the'pin 82 for rotation by a belt '86 and a suitable motor .(not shown). Thus, the impeller 64 can be rotated in synchronism with the magnetic member 80 to which it is magnetically coupled. The magnetic member 80 does not physically touch the side wall 26, it being spaced about inch from the side wall 26. By utilizing only a magnetic coupling to drive the impeller 64, the combination of the container 10 and the liquid dispensing means therefor can be removed easily from any apparatus in which it is employed, as for refilling or replacing it with another similar combination.

Portions of the impeller 64 and the magnetic member 80 that are not directly magnetically coupled to each other are magnetically shielded, that is, covered, with a coating of a magnetic material, such as iron, to prevent stray magnetic fields. Thus, a coating 88 (FIG. 2) of iron, or nu-metal, is on the back and sides of the impeller 64. The portion of the pump cavity 66 that is opposite the coating 88 on the impeller 64 is also coated with a coating 90 of magnetic material. Portions of the magnetic member 80 that are not directly magnetically coupled to the impeller 64 are coated with a coating 92 of a magnetic material, and a shield 94 of a magnetic material is disposed about, and slightly spaced from, the coating 92. The magnetic shielding of the impeller 64 and the magnetic member 80 is desirable if the container 10 is to be employed in apparatus where stray magnetic field can adversely affect the operation of certain components, such as a cathode ray tube, for example.

The operation of the improved combination of the container 10 and liquid dispensing means therefor, as thus far described, will be explained as a developing system for applying the liquid 12, an electroscopic liquid developer, to the photoconductive surface 14 of the recording medium 16, as shown in FIG. 3. The recording medium 14 is moved, in the direction of the arrows 95 and 97 past a charging station 96 where a negative electrostatic charge is applied to the photoconductive surface 14 and a positive electrostatic charge is applied to the backing 98 (FIG. 3) of the recording medium 16 by corona discharge devices 100 and 102 of the double corona type known in the art. The voltage between the discharge devices 100 and 102 is unidirectional or pulsed and preferably in the neighborhood of at least 6,000 volts. Next, the recording medium 16 moves past an exposing station 104 where the charged photoconductive surface 14 is exposed to a light image,

as from the face 106 of a thin-window, cathode ray tube 108, to form an electrostatic latent image on the charged photoconductive surface 14. The light image on the face 106 of the cathode ray tube 108 may be formed by a character generator 110 or by any other .suitable signal generator or signal translator, such as a television receiver, for example.

The latent electrostatic image on the recording medium 16 is now moved to a developing station 112 disposed directly opposite, and spaced (about 0.040 inch) from, the developing

electrodes

52 and 54 that define the exit slit 42 of the manifold 44.

The liquid 12 is dispensed from the exit slit 42 to develop the electrostatic latent image on the photoconductive surface 14 in the following manner: The magnetic member 80 is rotated at a substantially constant speed (about 1200 rpm.) by a suitable electric motor (not shown) mechanically coupled to the belt 86. The impeller 64, magnetically coupled to, but spaced from, the magnetic member 80, is now rotated synchronously with the magnetic member 80. The liquid 12 from the interior space 32 enters the pump chamber 66 through the conduit 70 and is pumped by the impeller 64 through the exit conduit 72, the bubble trap 74, the conduit 76, the interior slot 48 in the manifold 44, and out through the exit slit 42. The liquid 12, an electroscopic liquid developer in this embodiment, now comes in contact with the electrostatic latent image on the photoconductive surface 14 to develop the latent image. The liquid 12 that is not used to develop the latent image on the photoconductive surface 14 spills over the

electrode members

52 and 54 into the trough 47. The liquid 12 in the trough 47 is returned to the interior space 32 through the

holes

56 and 58 and the

tubes

60 and 62, connected to the

holes

56 and 58, respectively. Glass wool or stainless steel W001 116, inert to the liquid 12, is disposed within a portion of the interior slot 48, adjacent to the conduit 66, for controlling and distributing the flow of the liquid 12 substantially evenly through the exit slit 42 of the manifold 44.

The

metal electrode members

52 and 54 that define the exit slit 42 are electrically connected to each other and to an electrical feed-through electrode 118- (FIGS. 2 and for biasing the

electrode members

52 and 54 with a suitable voltage with respect to the electrically conductive roller 46, in a manner known in the electrophotographic art. The

electrode members

52 and 54 may also be formed from an integral strip of metal having the exit slit 42 formed therein.

The feed-through electrode 118 may be connected to a suitable source of electrical energy through an electrically conductive contact plate 120 (FIG. 5) secured to the top wall 30 of the container 10, as by

screws

122 and 124. The feed-through electrode 118 is electrically connected to the contact plate 120 by an electrical conductor 126. A source of electrical energy can be applied to the contact plate 120 when the container is inserted in suitable apparatus 130 by means of a resilient contact 128 fixed to the apparatus 130, only a fragmentary portion of which is shown in FIGS. 5 and 6.

Although the improved combination of the container 10 and liquid dispensing means therefor, as thus'far described, has been satisfactory for certain purposes to apply liquids to a body, it has been found that the pressure of the liquid 12 through the exit slit 42 tends to vary with the speed of the impeller 64 and with the level of the liquid 12 within the interior space 32. Such variations in the pressure of the flow of the liquid 12 are undesirable in certain developing apparatus. A substantially constant pressure of the flow of the liquid 12 through the exit slit 42 is provided in the improved combination by means including a standpipe 132 (FIGS. 2 and 4) on the top wall 30 of the container 10, regardless to the speed of the impeller 64 and the level of the liquid 12 in the container 10. The standpipe 132 has a lower open end 134 (FIG. 4)

that communicates with the bubble trap 74 in the top wall 30. An upper open end 136 (FIG. 2) of the standpipe 132 communicates with a trough, or drain 138, in the form of a channel, into which the liquid 12 that overflows from the standpipe 132 falls. The drain 138 communicates with the interior space 32 through a hole 140 in the top wall 30, as shown in FIG. 2. The hole 140 is disposed near the (right) side wall 28, a relatively great distance from the standpipe 132 which is in the (left) side wall 26, so that the liquid 12 returning to the interior space 32 can be mixed adequately with the liquid 12 in the interior space 32 before it is recirculated, thereby providing good mixing of the liquid 12. This arrangement is advantageous for mixing (stirring) a liquid solution of pigment particles dispersed in a carrier fluid wherein such particles tend to settle, such as in an electroscopic liquid developer.

The space above the upper end 136 of the standpipe 132 and the drain 138 is enclosed, that is, covered, with a permanent cover 144 (FIG. 2) to prevent any of the I liquid 12 from spilling when the improved combination of the container 10 and the liquid dispensing means there for is moved.

The operation of the improved combination of the container 10 and liquid dispensing means therefor, utilizing the pressure regulating standpipe 132, will now be described: The impeller 64 is rotated by means of its magnetic coupling to the rotating magnetic member as previously described. Liquid 12 from the interior space 32 is pumped through the exit slit 42 of the manifold 44 in the manner also previously described. At the same time that the liquid 12 is pumped through the exit slit 42, the liquid 12 is also pumped through the standpipe 132 via the conduit 72 and bubble trap 74. The liquid 12 spills over the open end 136 of the standpipe 132 and falls into the drain 138. The liquid 12 is returned from the drain 138 to the interior space 32 through the hole in the top wall 30.

Since the upper open end 136 of the standpipe 132 is a fixed distance above the exit slit 42, a fixed head of the liquid 12 is always maintained within the standpipe 132 when the impeller 64 is actuated, and it is this fixed head that determines the pressure of the flow of the liquid 12 through the exit slit 42. The impeller 64 is so proportioned that it will always pump the liquid 12 through the standpipe 132 at the lowest speed for which it is designed to operate. With the arrangement of the standpipe 132 in the improved combination, it has been found that the flow of the liquid 12 through the exit slit 42 is maintained substantially constant, regardless of the speed of rotation of the impeller 64 and the level of the liquid 12 in the interior space 32.

The improved combination of the container 10 for the liquid 12 and the dispensing means therefor functions as an improved developing system for developing charge patterns on a surface adjacent to the exit slit 42 with a substantially even, relatively quiescent flow of the liquid 12. Such a system of development is necessary for good results in certain electrophotographic apparatus of the type utilizing some of the components shown and described in FIG. 3 of the drawings.

Thus, there has been described an improved combinationof a container for a liquid and dispensing means for the liquid by means of which a complete refillable or disposable compact unit can be easily and safely transported and by means of which the liquid can be applied to the surface of an adjacent body at a substantially constant pressure. While certain liquid dispensing means of the improved combination, such as the manifold and the standpipe, have been described as parts formed on the top wall of the container, these parts may be originally separable from the container and may be disposed on the container by any suitable means. Also, while the pump means, including the impeller 64, have been described as being disposed within a side wall, it may be within another wall, or inside of the container itself. By returning the liquid from the trough through tubes that extend well into the interior space, only a relatively very small portion of the surface of the liquid is exposed to the ambient so that the loss of the liquid within the container by evaporation is markedly retarded.

What is claimed is:

1. In apparatus comprising a container for a liquid, said container having a plurality of walls, including a top wall, defining an interior space, the improved combination therewith of liquid dispensing means comprising:

an elongated manifold on said top wall, said manifold having an exit slit communicating with the interior of said manifold,

a trough on said top wall surrounding said manifold,

pump means within one of said walls,

intake conduit means communicating with said pump means and with said interior space of said container,

output conduit means communicating with said pump means and with said interior of said manifold, whereby said pump means can pump said liquid from said interior space through said interior of said manifold and out through said exit slit when said pump means are actuated, and

return conduit means communicating with said trough and said interior space to return said liquid flowing into said trough to said interior space,

said manifold comprising an electrically conductive member,

at least a'portion of said exit slit being defined by said member, and

said member comprising means to apply a source of voltage thereto.

2. In apparatus as defined in claim 1,

said elongated manifold is an integral part of said top wall,

said trough is a groove in said top wall that surrounds said elongated manifold, and

said return conduit comprises a hole through said top wall.

3. A developing system for applying a liquid developer to a latent image on the surface of a recording medium to develop said latent image, said developing system comprising, in combination:

a container comprising a plurality of walls defining a reservoir for said liquid developer,

a manifold on one of said walls, said manifold having an exit slit therein communicating with the interior of said manifold,

trough means substantially surrounding said manifold and adapted to collect any of said liquid developer that may issue from said exit slit,

return conduit means communicating with said trough means and with said reservoir,

pump means supported by said container,

intake conduit means communicating with said pump means and with said reservoir,

output conduit means communicating with said pump means and with said interior of said manifold, whereby said liquid developer can be circulated from said reservoir, through said exit slit, and back to said reservoir when said pump means are actuated, and said liquid developer is applied to said surface to develop said latent image thereon when said recording medium is disposed adjacent said exit slit,

said one wall being a top wall of said container,

a metal member on said manifold and definin at least a portion of said exit slit, and

electrical connecting means connected to said metal member to apply a voltage thereto.

4. A developing system as described in claim 3, wherein said one wall is a top wall of said container, said manifold and said trough means are on said top wall,

8 i i said return conduit comprises a hole in said top wall,

and

a tube communicates with said hole and extends into said reservoir.

5. In electrostatic printing equipment, apparatus for feeding a liquid developer to a recording medium which is adapted to be moved adjacent to and past said apparatus for the purpose of developing a latent electrostatic image thereon, said apparatus comprising:

a container having a reservoir for said liquid developer;

a manifold which is adjacent said reservoir and which has an exit slit in a wall thereof for the purpose of passing said liquid developer to said recording medium, said apparatus being adapted for operation with said exit slit in an upwardly facing direction;

trough means substantially surrounding said exit slit;

liquid passageway means communicating between said trough means and said reservoir and adapted to permit gravity flow of liquid developer from said trough means into said reservoir;

pump means including liquid passageways for pumping liquid developer upwardly from said reservoir to said manifold, whereby in operation said apparatus circulates liquid developer from said reservoir through said pump means to said manifold and upwardly through said exit slit onto said recording medium, and wherein the liquid developer fed through said exit slit which is in excess of that retained by said recording medium spills over into said trough means and is returned to said reservoir,

a standpipe, an upper open end of which is above the level of said exit slit and a bottom open end of which communicates with said pump means and said manifold, said pump means being adapted to pump liquid developer upwardly through said standpipe and out the open upper end thereof, and

liquid passageway means to return the liquid developer overflown from said standpipe to said reservoir.

6. In apparatus comprising a container for a liquid adapted to be applied to the surface of a body, said container having a plurality of walls defining a reservoir, the improved combination therewith of liquid dispensing means comprising:

pump means,

intake conduit means communicating with said reservoir and with said pump means,

output conduit means communicating with said pump means and with said manifold, whereby said liquid from said reservoir can be pumped through said manifold and out through said exit slit when said pump means are actuated,

trough means surrounding said manifold for collecting said liquid flowing through said exit slit,

conduit means communicating with said trough means and said reservoir to return said liquid to said reservoir,

an electrode member on said manifold, said electrode member defining at least one edge of said exit slit of said manifold, and

means to apply a source of voltage to said electrode member.

7. In apparatus comprising a container for a liquid adapted to be applied to the surface of a body, said container having a plurality of walls defining a reservoir, the improved combination therewith of liquid dispensing means comprising:

pump means,

trough means surrounding said manifold for collecting said liquid flowing through said exit slit, and

pump means,

trough means surrounding said manifold collecting said liquid flowing through said exit slit,

said intake conduit means and said output conduit means comprising passageways in at least some of said plurality of walls,

said output conduit means having an enlarged portion disposed to trap any bubbles in said liquid before said liquid reaches said manifold,

means to apply a source of voltage to said electrode member.

9. In apparatus comprising a container for a liquid adapted to be applied to the surface of a body, said container having a plurality of walls defining a reservoir, the improved combination therewith of liquid dispensing means comprising:

pump means,

output conduitmeans communicating with said pump means and with said manifold, whereby said liquid from said reservoir can be pumped through said manifold and out through said exit slit when said pump means are actuated,

said conduit means communicating with said trough means and said reservoir comprises:

a hole formed in said one wall,

a tube communicating with said hole and extending into said reservoir, whereby said tube exposes only a small surface of said liquid in said reservoir to the ambient above said trough means to retard the evaporation of said liquid in said ambient,

10 an electrode member on said manifold, said electrode member defining at least one edge of said exit slit of said manifold, and means to apply a source of voltage to said electrode member. 10. In apparatus comprising a container for a liquid adapted to be applied to the surface of a body, said container having a plurality of walls defining a reservoir, the improved combination therewith of liquid dispensing means comprising:

pump means,

conduit means communicating with said trough means and said reservoir to return said liquid to said reservoir, and

a standpipe having a lower open end communicating with said manifold and an upper open end disposed above said exit slit, whereby said pump means can pump said liquid through said standpipe and maintain a head in said standpipe to provide the flow of said liquid through said exit slit with a substantially constant pressure.

11. In apparatus comprising a container for a liquid, said container having a plurality of walls, including a top wall, defining an interior space, the improved combination therewith of liquid dispensing means comprising:

a trough on said top wall surrounding said manifold,

pump means within one of said walls,

intake conduit means communicatin with said pump means and with said interior space of said container, output conduit means communicating with said pump means and with said interior of said manifold, whereby said pump means can pump said liquid from said interior space through said interior of said manifoldand out through said exit slit when said pump means are actuated,

return conduit means communicating with said trough said interior space to return said liquid flowing into said trough to said interior space,

a standpipe on said top wall, said standpipe having a lower open end, and

conduit means communicating with said interior of said manifold and with said lower open end,

said standpipe having an upper open end disposed a predetermined distance above said exit slit, whereby said pump means, when actuated, can pump said liquid through said standpipe to maintain a constant head of said liquid therein and to provide the flow of said liquid through said exit slit with a substantially constant pressure.

12. A developing system for applying a liquid developer to a latent image on the surface of a recording medium to develop said latent image, said developing system comprising, in combination:

pump means supported by said container,

output conduit means communicating with said pump means and with said interior of said manifold, whereby said liquid developer can be circulated from said said intake conduit means and said output conduit means comprising passageways formed in at least some of said walls.

14. A developing system for applying a liquid developer to a latent image on the surface of a recording medium to develop said latent image, said developing system comprising, in combination:

a manifold on one of saidwalls, said manifold having reservoir, through said exit slit, and back to sa d an exit slit therein communicating with the interior reservoir when said pump means are actuated, and of said manifold, said liquid developer is applied to said surface to trough means substantially surrounding said manifold develop said latent image thereon when said recordand adapted to collect any of said liquid developer ing medium is disposed adjacent said exit slit, 15 that may issue from said exit slit,

said one wall being a top wall of said container, return conduit means communicating with said trough said trough means being a groove in said top wall, means and with said reservoir, said manifold being an elongated structure integral pump means supported by said container,

with said top wall, intake conduit means communicating with said pump a pair of parallel, metal, spaced-apart members fixed means and with said reservoir,

to said manifold, adjacent edges of Said m m output conduit means communicating with said pump defining the width of said exit slit, and means and with said interior of said manifold, wherea wool-like material inert to said liquid developer in by said liquid developer can be circula ed from Sa a portion of said interior of said manifold to disre r oir, through aid exit lit, and back to said tribute the flow of said liquid developer through said reservoir when said pump means are actuated, and

exit slit when said pump means are actuated. 13. A developing system for applying a liquid developer said liquid developer is applied to said surface to develop said latent image thereon when said recordto a latent image on the surface of a recording medium to develop said latent image, said developing system coma ing medium is disposed adjacent said exit slit, standpipe on said container, said standpipe having develop said latent image thereon when said recording medium is disposed adjacent said exit slit,

said pump means comprising a cavity in one of said walls, an impeller of magnetic material within said cavity, and means mounting said impeller for rotation within said cavity, whereby said impeller may be magnetically coupled to a rotating magnet for synchronous rotation therewith, and

prising, in combination: a lower open end communicating with said interior a container comprising a plurality of walls defining a of said manifold, said standpipe having-an upper reservoir for Said liquid developer, open end disposed a predetermined height above a manifold on one of said walls, said manifold having said xit slit,

an exit slit therein communicating with the interior d ain an adjacent t said standpipe, and of said manifold, return conduit means communicating with said drain trough means substantially surrounding said manifold means d id reservoir, whe eby aid pump means and adapted to collect any of said liquid developer n pump aid liquid developer through said standthat may issue from said exit slit, pipe at the same time said liquid developer is pumped return conduit means communicating with said trough through said exit slit, said liquid in said standpipe means and with said reservoir, at said predetermined height providing a head which pump means supported by said container, provides the How of said liquid developer through intake conduit means communicating with said pump said exit slit with a substantially constant pressure.

means and with said reservoir, output conduit means communicating with said pump References Cited means and with said interior of said mlanifold, where- UNITED STATES PATENTS by said liquid developer can be circu ated from said reservoir, through said exit slit, and back to said 2 2 f g reservoir when said pump means are actuated, and gi gg 3/1965 ig 355:1) said liquid developer is app ied to said surface t 3,392,706 7/1968 Lloyd 89 XR NORTON ANSHER, Primary Examiner F. L. BRAUN, Assistant Examiner US. Cl. X.R. 95-89; 118-410,