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United States Patent 3,600,083
Leedom August 17, 1971

ELECTROSTATIC PRINTING SYSTEM EMPLOYING A REPLACEABLE CARTRIDGE TO PROVIDE A SUPPLY OF A RECORDING ELEMENT AND PROCESSING MEANS THEREFOR

Abstract

A replaceable cartridge, adapted to be removably installed in an electrostatic printing system, provides a supply of a recording element and charging, developing, and cutting means therefor. Means are provided to convey and to guide the recording element through the cartridge along a path including charging, image exposing, developing, and cutting stations.


Inventors: Leedom; Marvin A. (Warminster, PA)
Assignee: RCA Corporation (
Appl. No.: 04/799,391
Filed: February 14, 1969


Current U.S. Class: 399/111 ; 399/385
Current International Class: G03G 15/00 (20060101); G03G 15/26 (20060101); G03G 15/28 (20060101); G03g 013/10 ()
Field of Search: 355/3,10,13,16,4,6,7,10--12

References Cited

U.S. Patent Documents
2826168 March 1958 Grant, Jr.
3319546 May 1967 Magnusson
Primary Examiner: Matthews; Samuel S.
Assistant Examiner: Bero; E. M.

Claims



I claim:

1. A replaceable cartridge for an electrostatic printing system of the type wherein a recording element is moved, by drive means disposed in said system and external to said replaceable cartridge along a continuous path through said cartridge, said path including at least an image exposing station and a developing station, said cartridge comprising:

a storage section comprising means to store a supply of said recording element,

guide means disposed in said cartridge and engageable with said recording element and said drive means for cooperating therewith to guide and to move said recording element along said path only when said cartridge is installed in said system, whereby charge patterns can be formed on said recording element at said image exposing station,

said drive means being separate and detached from said recording element and said guide means when said cartridge is removed from said system, and

a developer section comprising means to develop said charge patterns at said developing station.

2. A replaceable cartridge as described in claim 1, wherein

said path through said cartridge comprises, in addition, a charging station,

a portion of said path including said charging station being in said storage section,

a wire disposed in said storage section adjacent said charging station,

a source of voltage disposed in said system but external to said cartridge, and

means on said cartridge and connected to said wire for applying said source of voltage to said cartridge only when said cartridge is installed in said system, whereby to cause a corona discharge about said wire to charge said recording element at said charging station.

3. A replaceable cartridge as described in claim 1, said path through said cartridge including, in addition, a cutting station located past said developing station, and

said cartridge comprising, in addition,

cutting means disposed between said storage section and said developer section for cutting said recording element at said cutting station after said recording element has been developed.

4. A replaceable cartridge as described in claim 1, said path through said cartridge including, in addition, a charging station and a cutting station,

said storage section including said charging station and having a wire adjacent to said charging station for providing a corona discharge at said charging station,

said cutting station being located along said path, past said developing station and between said storage section and said developer section, and

cutting means disposed between said storage section and said developer section to cut said recording element at said cutting station after said recording element has been developed.

5. A replaceable cartridge for an electrostatic printing system comprising:

a developer section, and a recording-element storage section disposed on, and removably fastened to, said developer section,

said storage section comprising a compartment for a recording element,

said developer section comprising a reservoir compartment for a liquid developer and pump means disposed in said cartridge for pumping, when actuated, said liquid developer to said recording element, and

said pump means comprising means to couple power drive means disposed in said system and external to said cartridge to said pump means to actuate said pump means only when said cartridge is installed in said system.

6. A replaceable cartridge as described in claim 5, comprising, in addition:

at least one roller being disposed in said storage section for guiding said recording element along a processing path,

said storage section having a rear wall with an opening therein adjacent said roller, whereby to expose a portion of said recording element for providing charge patterns thereon, and

said processing path of said recording element extending between said storage and said developer sections.

7. In an electrostatic printing system of the type wherein a recording element is moved along a continuous path, through said cartridge, including a charging station, an exposing station, and a developing station, the improvement comprising, in combination:

a replaceable cartridge adapted to be removably installed in said system,

said cartridge having a storage section for storing a supply of said recording element,

said cartridge including said path and said stations,

drive means in said system, external to said cartridge, adapted to engage said recording element, for moving it along said path, only when said cartridge is installed in said system,

exposure means in said system adapted to expose said recording element to provide charge patterns thereon at said exposure station only when said cartridge is installed in said system,

said cartridge having a developer section for developer and means, when actuated, for developing said charge patterns on said recording element, and

said drive means being adapted to be coupled to said means for developing said charge patterns only when said cartridge is installed in said system.

8. In an electrostatic printing system of the type described in claim 7, said combination comprising, in addition:

charging means disposed in said storage section of said cartridge for charging said recording element when energized from an energy source in said system and external to said cartridge.
Description



BACKGROUND OF INVENTION

This invention relates generally to an electrostatic printing system employing a replaceable cartridge to provide a supply of a recording element and processing means therefor. More particularly, the invention relates to a replaceable cartridge adapted to be removably installed in an electrostatic system of the type providing electrostatic charge patterns on an electrically insulating surface of a recording element. The replaceable cartridge is particularly useful for providing a replenishing supply of a recording element and processing means therefor in an electrophotographic printing system wherein charge patterns are formed on a previously uniformly charged recording element by exposing the uniformly charged recording element with light images from a cathode-ray tube.

In most prior art electrophotographic printing systems of the type wherein a recording element is moved sequentially along a path to electrostatic charging, image exposing, developing and cutting stations, it is customary to include all of the recording-element processing and conveying means in one relatively large housing or cabinet. Such prior art apparatus requires periodic servicing. For example, a relatively thin wire that is used for electrostatic charging usually gets dirty, arcs, and may break with use. Where liquid toners are used for developing, the recording element guide means may become coated with developer and require periodic cleaning. The cutting means get dull with use and must either be replaced with new blades or sharpened. Where pumps are used for conveying liquid developers, the pump seals tend to become dry, causing the developer to leak through, and the developer reservoir requires periodic cleaning. Also the supply of the recording element has to be replenished periodically. Most of the aforementioned servicing requires the services of skilled personnel and takes the apparatus out of use during the servicing.

The aforementioned disadvantages of the prior art apparatus are substantially overcome by the replaceable cartridge of the present invention in that each replaceable cartridge provides a fresh supply of the recording element and either new or reserviced charging, developing, and cutting means. Thus, a new or reserviced replaceable cartridge can be used to replace an exhausted one, and the latter can be either discarded or reserviced at will, thereby eliminating the servicing and down time of the electrostatic printing system.

SUMMARY OF INVENTION

A replaceable cartridge is adapted to be removably installed in an electrostatic printing system of a type wherein a recording element is moved along a path including at least an exposing station and a developing station. The replaceable cartridge has means to hold a supply of the recording element and developer therefor, and includes the aforementioned path and stations.

In one embodiment, the replaceable cartridge comprises an electrostatic charging station, an image exposing station, a developing station, a cutting station, and means for processing the recording element at these stations. The replaceable cartridge has the advantage of providing a replenishing supply of the recording element, fresh charging means, fresh developing means, and sharp cutting means in one unit which, when exhausted or inoperative for any reason, can be replaced with a similar cartridge. The exhausted replaceable cartridge can be serviced and replenished for reuse.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of an embodiment of the replaceable cartridge, viewed from the top, front, and right side, the top cover being cut away;

FIG. 2 is a rear view of the replaceable cartridge, disposed against drive means (not a part of the replaceable cartridge) for moving the recording element, some parts of the cartridge being broken away;

FIG. 3 is a top view of the replaceable cartridge, showing the recording-element drive means, cutter drive means, and pump drive means, the replaceable cartridge being disposed against a cathode-ray tube for receiving light images therefrom;

FIG. 4 is a fragmentary, cross-sectional view of the replaceable cartridge and cathode-ray tube, taken along the line 4-4 in FIG. 3, showing the recording-element drive means;

FIG. 5 is a top view of the lower developer section of the replaceable cartridge with the upper recording-element storage section of the replaceable cartridge removed;

FIG. 6 is a cross-sectional view of the replaceable cartridge, taken along the line 6-6 of FIG. 5, showing the removable cartridge positioned against a cathode-ray tube for receiving light images therefrom; and

FIG. 7 is a cross-sectional view of the removable cartridge taken along the line 7-7 of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1 of the drawing, there is shown a replaceable cartridge 10 comprising a lower developer section 12 and an upper recording-element storage section 14 disposed on the developer section 12 and secured to the latter by any suitable means, such as screws 16 and 18 (FIG. 5). The two sections 12 and 14 are separable from each other to facilitate both the construction of the cartridge 10 and its servicing when necessary. The cartridge 10 is of substantially rectangular cross section, both horizontally and vertically, having a front wall 20, a rear wall 22, a floor 23, a pair of right and left sidewalls 24 and 26, respectively, and a removable top cover 27. The cartridge 10 is constructed preferably of plastic sheet material that is relatively opaque to light or is painted to provide a relatively light-tight container.

Referring now to FIGS. 2 and 6, there is shown a supply roll 28 of a web of a recording element 30 of the type used in an electrophotographic printing system. In FIG. 6, the web of the recording element 30 is shown defining a path through which it is moved. The path includes a charging station 32, an image exposing station 34, a developing station 36, and a cutting station 38 for processing the recording element 30 in a process of printing information derived from light images on a thin-window, cathode-ray tube 40. The cathode-ray tube 40 is adapted to cooperate with the cartridge 10, as shown in FIGS. 3, 4, and 6. It is within the contemplation of the invention, however, to provide electrostatic charge patterns on the recording element at the image exposing station by means other than the cathode-ray tube 40.

The recording element 30 comprises, for example, a web of relatively electrically conductive paper, having a resistivity preferably between 10.sup.3 ohm-cm. and 10.sup.7 ohm-cm., coated with a thin, relatively electrically insulating layer (not shown) of photoconductive zinc oxide in a resin binder, in a manner well known in the electrophotographic printing art. The photoconductive zinc oxide layer of the recording element 30 is disposed against the face 42 of the cathode-ray tube 40. A thin sheet of a transparent plastic material (not shown) may be disposed between the face 42 of the cathode-ray tube 40 and the recording element 30 to prevent frictional wear of the tube 40, if necessary.

The supply roll 28 of the recording element 30 is disposed within a compartment 44 in the storage section 14 of the cartridge 10, as by supporting the supply roll 28 by a mandrel 46 whose ends are disposed in inner slots 48 and 50 in the pair of right and left sidewalls 24 and 26, respectively, as shown in FIG. 1 and 2. The web of the recording element 30 is threaded initially along the path, within the cartridge 10, including the charging station 32, the image exposing station 34, the developing station 36, and the cutting station 38. The recording element 30 emerges from the cartridge 10 through a slot 52 in the front wall 20 between the sections 12 and 14, as shown in FIGS. 1, 6, and 7. For example, as shown in FIG. 6, the web of the recording element 30 is threaded in a path leading from the supply roll 28, then under a guide roller 54, over roller means, such as a pair of metal rollers 56 and 58, between the top of the lower developer section 12 and the bottom of the upper storage section 14, and finally out through the relatively narrow slot 52 in the front wall 20.

The rollers 54, 56, and 58 are parallel to each other and are journaled for free rotation in bearings in the sidewalls 24 and 26 of the cartridge 10. The rollers 54, 56, and 58 comprise guide means for guiding the recording element 30 along its path to its aforementioned processing stations. Also the roller 56 comprises part of the charging means, and the rollers 56 and 58 comprise part of the image exposing means, as will hereinafter be described in detail.

Electrode means within the cartridge 10 is provided to electrostatically charge the insulating (photoconductive layer) surface of the recording element. To this end, there is provided a relatively thin wire 60, of about 4 mils diameter, disposed within the compartment 44, between the sidewalls 24 and 26, and parallel to, and slightly above, the roller 56 with which it cooperates to provide a corona discharge. The ends of the wire 60 are secured to lugs 62 and 64 on the sidewalls 24 and 26, respectively, for connection to a source of voltage (not shown) of sufficient amplitude (about 6,000 volts DC) to provide the wire 60 with a corona discharge of desired polarity between the roller 56 and the wire 60, whereby to charge the surface of the recording element 30 uniformly as it is moved past the charging station 32. The metal roller 56 is also adapted to be connected to the aforementioned source of voltage and comprises a portion of the electrode means for charging the recording element 30.

The rear wall 22 of the cartridge 10 is formed with an opening 66 to permit the thin-window, cathode-ray tube 40 to substantially contact the charged recording element 30 at the exposing station 34, as shown in FIG. 6. When the uniformly charged recording element 30, disposed over (usually grounded) rollers 56 and 58, is exposed by light images from the cathode-ray tube 40, electrostatic latent images are formed thereon in a manner well known in the art. These latent images are developed at the developing station 36 (FIG. 7) by liquid developer 68 within the lower developer section 12 of the cartridge 10, in a manner to be hereinafter described in detail.

After the recording element 30, with the developed information thereon, is moved through the slot 52 in the cartridge 10, a portion of the developed recording element 30 may be cut off by actuating a cutter 70 at the cutting station 38, in a manner also hereinafter to be described in detail.

Recording-element drive means, external to the replaceable cartridge 10 and not a part thereof, are employed to move the recording element 30 along the path including the charging station 32, the image exposing station 34, the developing station 36, and the cutting station 38. The external recording-element drive means comprise a pair of parallel, spaced-apart, first-class levers 72 and 74 disposed to receive the cartridge 10 between them, as shown in FIG. 3. The levers 72 and 74 are pivoted about separate pins 76 and 78, supported by parallel, vertical members 80 and 82, respectively, as shown in FIG. 3. The rear ends of the levers 72 and 74 are biased downwardly by springs 84 and 86, respectively, as shown in FIGS. 3 and 4.

A shaft 88, adapted to be rotated by a motor 90, is journaled in the levers 72 and 74 adjacent the front ends thereof, and gears 92 and 94 are fastened to the shaft 88, adjacent opposite ends thereof, for rotation therewith, as shown in FIG. 3. A pair of gears 96 and 98, disposed to mesh with the gears 92 and 94, are fixed on ends of separate short shafts 100 and 102, respectively. The short shafts 100 and 102 are also journaled in the proximal ends of the levers 72 and 74, respectively. A pair of rubber drive wheels 104 and 106 are fixed to the other ends of the shafts 100 and 102, respectively, for rotation therewith. With this arrangement, the recording element 30 can be moved along its processing path by merely positioning the cartridge 10 so that the lateral, parallel, opposite edges of the recording element 30 are disposed between the rubber drive wheels 104 and 106 and the idler roller 58 of the cartridge 10. Hence, when thus positioned, energizing the motor 90 causes the recording element 30 to unwind from the supply roll 28 and move through its processing path, within the cartridge 10, and out through the elongated slot 52. The recording-element drive means are not part of the replaceable cartridge 10, and it is within the contemplation of the present invention to employ drive means other than those described above. The cathode-ray tube 40 is also disposed between the levers 72 and 74 so that the horizontal center of the tube 40, which is the image forming portion thereof, can be positioned adjacent the image exposing station 34 of the cartridge 10.

The cartridge 10 is formed with guide means adjacent the floor 23 thereof so that it can be correctly anchored in an electrophotographic system to receive the light images from the cathode-ray tube 40 and the drive means for moving the recording element 30. For example, a plurality of parallel bar guides 108, 110, 112, and 114 extend downwardly to the floor 23 of the cartridge 10, and a pin 116 is disposed between the parallel bar guides 110 and 112 for engaging a mating hook 118 in the base 120 of an electrophotographic system for anchoring the cartridge 10, as shown in FIG. 6.

The lower developer section 12 comprises means to develop the recording element 30 at the developing station 36 during the movement of the recording element 30 along its processing path. Referring now particularly to FIGS. 6 and 7 of the drawing, the developing station 12 is shown comprising a plurality of reservoir compartments, such as a main compartment 122, a pressure compartment 124, a bubble-filter compartment 126, and a developer-return compartment 128. All of the compartments in the developer section 12 communicate with each other through ducts, such as ducts 130 and 132 between the main compartment 122 and the pressure compartment 124, for example, and function as a combined reservoir for the liquid developer 68. The pressure compartment 124 communicates with the filter compartment 126 through a narrow inlet 136 to remove any bubbles in the developer 68. The developer-return compartment 128 also communicates with the main compartment 122, as shown in FIGS. 6 and 7.

A pump 140 is provided within the developer section 12 to pump the liquid developer 68 from the reservoir compartments to the developing station 36. For example, a pump shaft 142 is journaled in top and intermediate horizontal walls 144 and 146 of the developer section 12 for rotation therein. A pump drive wheel 148 is fixed to the upper end of the pump shaft 142, and an impeller 150 is fixed to the lower end of the pump shaft 142 within the pressure compartment 124. A circular plate 152, to prevent vortex formations in the liquid developer 68, is disposed around, and spaced from the pump shaft 142 within the main compartment 122. The plate 152 is fixed to, and spaced from, the intermediate wall 146 by spacers 153. The horizontally disposed pump drive wheel 148 extends beyond the right wall 24 of the container 10 through a slot 154 therein.

The pump 140 is driven by means of a rubber friction wheel 156 coupled to a motor (not shown) external to the cartridge 10, when the cartridge 10 is in the position for receiving light images from the tube 40 and the drive means to drive the recording element 30, as shown in FIG. 3. The rubber friction wheel 156 and driving means therefor are not part of the cartridge 10 but cooperate with the cartridge 10 when the latter is positioned in an electrophotographic printing system adapted to receive it.

The developer 68 is introduced into the reservoir compartments of the developer section 12 through an opening 58 in the top wall 144. The opening 158 is fitted with a removable plug 160. A flattened tubular member 162 (FIG. 6) communicates with, and extends from, the filter compartment 126 and terminates in an elongated slit 164 which, in effect, is substantially adjacent the developing station 36. A metallic member 166 (FIG. 5) substantially covers the upper portion of the tubular member 162 so that a bias voltage may be applied thereto to cause it to function as a developing electrode, in a manner well known in the electrostatic printing art. A plurality of holes 168 are formed in the top wall 144 of the developer section 12 on opposite sides of the metallic member 166 to provide a return path for the liquid developer 68 into the developer return compartment 128. A stand pipe 170, extending to a greater height than that of the tubular member 162, communicates with the pressure chamber 124 to provide a constant head of pressure for the liquid developer 68 emerging through the slit 164 at the developing station 36.

When the pump 140 is operated, as by coupling the pump drive wheel 148 to the rubber friction wheel 156, the impeller 150 forces the liquid developer 68 through the narrow inlet 136 between the pressure chamber and the filter chamber 126, thereby preventing bubbles from entering the filter chamber 126. Also, the circular plate 152 prevents a vortex formation in the liquid developer 68 and thereby prevents the formation of excess bubbling. The pressurized liquid developer 68 is also pumped through the stand pipe 170 so that it overflows and returns through communicating ducts to the main and developer-return compartments 124 and 128. The pressurized liquid developer 68 is also forced through the tubular member 162. The pressure of the liquid developer 68 emerging through the elongated slit 164, adjacent the developing station 36, is substantially constant and is determined primarily by the pressure head provided by the difference in the height of the stand pipe 170 with respect to the height of the tubular member 162. The arrows in FIGS. 6 and 7 indicate the flow path of the liquid developer 68 under the influence of the pressure provided by the pump 140.

Referring now particularly to FIG. 5, the top wall 144 of the developer station 12 is shown as being formed with short raised side portions 172 and 174 adjacent the sidewalls 24 and 26, respectively, and long flattened portions 176 and 178 intermediate the short raised side portions 172 and 174. This construction provides the cartridge 10 with guide means for supporting the recording element 30 adjacent its lateral parallel side edges and preventing wet developed images on the recording element 30 from touching the top wall 144, thereby preventing smearing of the developed images. The liquid developer 68 may contain a highly volatile carrier fluid and a chemical fixer to dry and fix the developed image on the recording element 30 in a matter of seconds, in a manner well known in the art. The cutter 70 is disposed between the developer section 12 and the storage section 14 to cut off a portion of the recording element 30 from the web, as desired. To this end, the top wall 144 of the developer section 12 is formed with a slot 180 for engaging a cutter bar 182 slidably therein. The right and left sidewalls 24 and 26 of the cartridge 10 are also formed with slots for receiving the cutter bar 182 slidably therein, as shown in FIGS. 1 and 5.

The cutter bar 182 has a sharpened knife blade 184 extending upwardly therefrom and disposed so as to cut through the web of the recording element 30 at the cutting station 38 when the cutter bar 182 is moved slidably within the slot 180. The cutter bar 182 may be actuated manually or it may be coupled to an arm 186 (FIG. 3) for actuation by any suitable means in the electrophotographic printing system in which the cartridge 10 is to be employed.

Before the replaceable cartridge 10 is inserted into an electrophotographic printing system for cooperation therewith, it is furnished with a fresh supply roll 28 of the recording element 30 threaded along the predetermined path including the charging station 32, the image exposing station 34, the developing station 36, and the cutting station 38, as shown in FIG. 1. The wire 40 is new and smooth to provide an even corona discharge when suitably energized. The rollers 54, 56, and 58 are clean, the blade 184 of the cutter 70 is sharp, and the liquid developer is fresh. The supply of the liquid developer 68 is sufficient to develop all the electrostatic images to be formed on the recording element 30. Thus, when the supply of the recording element 30 is exhausted by use, the liquid developer 68 is also substantially exhausted. The operation of the electrophotographic printing system can continue, however, by replacing the exhausted cartridge 10 with a new or reserviced replaceable cartridge 10, thereby insuring substantially continuous and efficient functioning of the electrophotographic printing system.

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