US3196831A - Developing unit for photocopy machine - Google Patents

Description

A July 27, 1965 M. 1.. SUGARMAN, JR 3,

DEVELOPING UNIT FOR PHOTOCOPY MACHINE Filed July 23, 1962 4 Sheets-Sheet l I 6 3px Manx dc:

July 27, 1965 M. L. SUGARMAN, JR 3,196,83

DEVELOPING UNIT FOR PHOTOCOPY MACHINE 4 Sheets-Sheet 2 Filed July 23, 1962 a @fi z M m o E m Q: m Md o g ML fiw CATTCRMSYL/ July 27, 1965 M. L. SUGARMAN, JR 3,196,831

1 DEVELOPING UNIT FOR PHOTOCOPY MACHINE Filed July 25, 1962 4 Sheets-Sheet 3 MVEZIQTOD CjFr-rc max/- United States Patent 0 continuation-in-part of my applica- This application is a 123 filed November 16, 1959, now

tion Serial No. 653, Patent No. 3,088,386.

The present invention relates to clectrophotographic printing and more particularly to an improved means for developing a powder image on a copy sheet.

T13 electrophctcgrar 'c printing process employed in oflicphotocopying mac 'lvS and the like involves the steps of uniformly char. ng an clectrographic sheet, exposing the sheet to produce a latent image thereon with dissipation of the charge from the light-struck areas, and development of the ii. age by applying a pigmented powder or toner which tends to adhere selectively to the charged areas. The powder, which conventionally inclu es a minor portion of heat sensitive resin is subsequently fixed in place on the surface or" the sheet by radiant heat.

it is an object of the present invention to provide an improved developing unit for a photocopy machine which is capable of applying toner evenly over equally charged areas of the sheet to produce a high quality copy. It is another object of the present invention to provide a devcloping unit which is capable of producin accurate uniform copies over long periods of time and without risl; of pigment starvation where a large number of copies are required of a sheet having widely varyin toner requirements in various column positions on the sheet. More specifically, it is an object to provide a developing unit for a photocopy machine which provides a source or reservoir of toner powder extending the width of the sheet but in which means are provided for constantly equalizing the reservoir so that all column positions on the sheet are treated uniformly regardless of the length of the run. In an extreme case in wmch the left half of the sheet, for example, is heavily pi ment-ed while the right half is completely clear, toner will be supplied to the left half exclusively but without unbalancing the level of toner in the reservoir. it is an object of the invention in one of its aspects to provide a toner distributing mechanism which operates constantly and which is capable of distributing toner along the length of the reservoir from a replen or w ch deposits toner powder at a single point in the reservoir. In this connection it is an object to provide a developing unit including a novel replenishing device in which the act of replenishment has no elfect upon the uniformity of development.

it is a more specific object, related to the foregoing, to provide a novel developing roller and associated magnetic circuit for use with toner powder having a magnetic component and which is distinguished by the formation of helical tufts which are swept transversely along the copy sheet for the purpose of depositing toner thereon. It is a correlative object to provide a roller and magnetic circuit which insures deposition of toner in the charged areas in. an amount proportioned to the magnitude of the charge but which provides efficient clean-up in the white or uncharged areas. Thus, it is an object to provide a developing unit which is free from any tendency to produce streaks or blemishes on the sheet.

it is a further object of the invention to provide a developer unit for use with finely divided and highly pigmented toner powder but which has novel provisions for insuring that the powder is kept within the unit so that the sheets, sheet transport mechanism and the machine in general are kept free of contamination even after long periods of operation. In this connection it is an object to provide a developing unit having novel provision for entry of the sheets vertically through the body of toner powder with provision for immediate and positive closure. Thus, even though the developer unit is located in an elevated position in the machine, there is no risk that powder will be dusted downwardly into the transport mechanism.

It is a general object of the invention to provide a unitary developing unit which is not limited to use with the disclosed machines but which may be employed wherever it is desired to develop an electrostatically charged sheet.

In one of its aspects it is an object of the present invention to provide a novel replenishing unit for periodically replenishing the reservoir and which is ellective to positively discharge a predetermined amount of toner powder free of any packing or bridging of the powder in the discharge opening. Reliable discharge is assured even though toner powder is employed which is much finer than that which can be accommodated by conventional replenishing devices.

It is a more specific object to provide a replenishing device which is capable of accurately metering out predetermined quantities of powder in order to keep the reservoir up to rated level and in which the amount of powder which is discharged at each operation may be accurately adjusted over a wide ra ge.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:

PEGURE l is a simplified vertical section of a photocopy machine employing the present invention.

FIG. 2 is a plan view, in partial section, of a developing unit constructed in accordance with the present invention.

PEG. 3 is an end elevation of the unit shown in FIG. 2 and particularly the driving means therefor.

FIG. 4 is a horizontal broken section taken through the right hand end of the developing unit along line 4-4 in FIG. 3 to show the sealing arrangement and a portion of the magnetic circuit.

FIG. 5 is an enlarged horizontal section showing the profile of the developing roller and taken along the line 55 in FIG. 1.

FIG. 6 is an enlarged fragment showing the roller profile and associated back-up plate taken along the line 66 in FIG. 2.

FIG. 7 is a schematic diagram of a portion of the control circuit.

FIG. 8 is a vertical section taken through the replenishing device forming a part of the present invention.

PEG. 9 is an exploded View of the dispensing elements.

10 is a fragmentary section showing adjustment of the choke plate to vary the discharge of the replenisher.

While the invention has been described in connection with a preferred embodiment, it will be understood that it is not intended to limit the invention to the particular embodiment shown but it is, on the contrary, intended to cover the various alternative and equivalent constructions which may be included within the spirit and scope of the appended claims.

Turning now to FIGURE 1 of. the drawings, an electrophotographic copying machine intended for office use has a frame 11, a base 12 and a housing 1. At the front of the housing two inlet slots are provided, a first slot 14 for the original and a second slot F5 for the copy sheet, with the two sheets, indicated as 16 and 17, being fed in together face to face. The sheets are separated and the copy sheet, which has a coat of zinc oxide or similar material having the ability to dissipate a stored electric charge in areas which are selectively struck by light, passes through a charging unit 18. The original is fed into an illuminating station 21 at the same time that the copy sheet 17 is fed into an exposing station 22 and with both sheets proceeding at the same speed. Light from a source 23 illuminates the original, with the image thereof being reflected by a mirror and lens assembly 24 onto the moving copy sheet. Subsequently the original is discharged into a return chute 25 while the copy sheet is conveyed upwardly by transport rollers 26, 27 into a developing unit 3% and fixing unit 31 for discharge rearwardly onto a tray 32 recessed in the top of the machine. For the detailsof the fixing unit 31, which fixes in place the toner deposited on the sheet in the developing unit 3% reference is made to copending application Ser. 209,122, now Patent No. 3,159,735, filed July 11, 1962. It will be noted that the fixing unit includes two expeller rollers 36, 3'7 which cooperate with the input rollers 26, 27 located below the fixing unit 36. Such rollers are driven by a common motor at a constant transport speed via any desired belt or gearing arrangement.

Turning more detailed attention to the developing unit 30, it includes a generally rectangular box or bin 43 mounted between brackets 41, 42 secured to the frame of the machine by any desired means. surface 44 and a bottom 45 which are secured to end members 4-6, 47 which may be of plastic or the like. The bin is enclosed along its front surface by a barrier or guide plate 48 secured by screws 49.

For the purpose of admitting the copy sheet into the underside of the developing unit, a longitudinal opening 5% is provided immediately behind the guide plate 48. This opening is normally closed by a flap 51 of yieldable material which is so light as to be readily pushed aside by the leading edge of an advancing sheet (see 17 in FIG. 6), with immediate self closure augmented by the weight the the toner powder as soon as the sheet has gone by. The flap 51 may be held captive along one edge by a longitudinal clamping plate 52 which is secured to the bottom of the bin by screws 53.

In order to prevent any small amount of toner which might tend to escape upon passage of especially thick copy sheets from falling down to contaminate the sheet transporting mechanism, the feed rollers 26, 27 at the bottom of the entryway are inwardly offset as shown at FIG.

1 and a longitudinally extending tray 55 is provided along the lower lip of the guide plate 48. The amount of toner lost in this fashion is extremely minute so that it normally will not be necessary to clean the tray even after many hundreds of hours of operation.

For the purpose of wiping the face of the copy sheet with toner powder for adherence of the latter to the charged areas, a developing cylinder 69 is provided having stub shafts 61, 62 which are journaled in bearing blocks 63, 64 mounted in the end members of the developing unit. For rotating the cylinder the shaft 61 carries a belt pulley 65 which is engaged by a belt 66 leading to the driving motor of the machine. While the motor itself has not been shown, reference may be made application Ser. 853,123, now Patent 3,088,386 for driving details.

In carrying out the present invention the developing cylinder 60 is made of magnetic material having a pattern of upraised ridges or projections and means are provided for establishing a magnetic flux substantially at right angles thereto and through the copy sheet so that magnetic tufts or brushes of toner mix are formed on the ridges for wiping across the surface of the copy sheet. The composition of the toner mix is outside of the scope of the present application and it will suflice to say that such mix consists of a mixture of pigmented toner particles and magnetic particles, with the toner particles adhering to the magnetic particles as a result of triboelectric effect and leaving the magnetic particles when the toner particles are brushed in contact with the surface of the copy sheet. The tufts result from thefact that the flux tends to be concentrated at the high points of the cylinder.

The bin has a back More specifically, in accordance with the present invention' the surface of the developing cylinder is formed into a pattern of helical ridges so that the tufts take the form of continuous helices which sweep laterally across the face of the sheet as the sheet is advanced longitudinally through the developing unit. Thus referring to FIG. 5 the individual helical ridges indicated at '76 are in the form of a 60 V thread having sharply defined ridges 71 and forming tufts or brushes 72. For the purpose of increasing the amount of lateral sweep per revolution of the developing cylinder, a multiple thread is preferably employed. Thus in a practical case twelve interleaved threads may be used having a half inch lead to produce twenty-four ridges per lineal inch of the cylinder. Thus where the cylinder is rotated at a rate of 68 revolutions per minute the helical brushes 72 sweep'laterally over the copy sheet at the rate of 34 inches per minute. It is found that this sweeping motion not only conveys toner to each unit of charged area of the copy sheet but in addition produces a cleaning or scrubbing action so that the wiped or uncharged areas on the sheet are swept clear to produce a clean white background. Thus any contaminating particles on an uncharted area of the sheet are reattracted to the magnetic particles in the mix by triboelectric action.

For the purpose of guiding the sheet about the periphery of the developing cylinder 64 the barrier or guide plate 43 is spaced parallel to the surface of the cylinder by an amount suificient to accommodate well defined brushes 72. In a practical case such spacing, indicated at '75, may be on the order of 0.035 inch. Moreover, the guide plate 43 is preferably bent into an arcuate profile so as to follow the surface of the cylinder and so that the sheet is acted upon uniformly over a substantial portion of the cylinder 7 periphery.

For the purpose of establishing magnetic flux at right angles to the developing cylinder, the bearing blocks 53, 64; are made of magnetic material and are bridged by an elongated magnetic pole member which extends parallel to the cylinder outside of the barrier or guide member 43 and with permanent magnets being provided in the circuit so that the developing cylinder is at one polarity and the cooperating pole piece at the opposite polarity. In the present instance (see especially FIGS. 2-4) the elongated pole piece indicated at St) is joined to the magnetic bearing blocks by permanent magnets 81, 82 which are polarized in parallel with one another, i.e., with same polarity so that the fiux, indicated at 85', is distributed more or less uniformly to the surface of the cylinder 60. The barrier or guide plate 43 is made of aluminum or other non-magnetic material so that it does not obstruct or distort the flux flowing to the cylinder.

In accordance with one of the aspects of the invention longitudinal transport elements are provided adjacent the cylinder in the toner bin for transporting the toner mix continuously in opposite directions so that the level of the toner in the bin is constantly balanced. In the present instance the transport elements are in the form of augers 91, 92 mounted upon shafts 93, Q4 and so pitched and rotated that they tend to transport the powder oppositely with respect to one another. In the present instance this is achieved by employing augers of the same hand and with the drive shafts being coupled together by directly meshing gears d5, 96 for rotation in opposite directions. As shown in FIG. 3 the latter gears are coupled to the shaft of the cylinder 68 by means of a drive gear 97 at the right hand end of the shaft and an interposed idler gear 98.

While the angers 91, 92 may take various forms, it is 7 preferred to use a simple strip of metal twisted into auger shape and with the ends being fitted into hubs 91a, 92a respectively.

It is found that the transport and leveling arrangement described above is particularly advantageous when used in combination with the developing cylinder 6% which has a unidirec ional helical pattern of ridges and which therefore acts, of itself, to urge the toner mix down to one end, in this case the left hand end, of the toner bin. In carrying out the present invention the augers are preferably operated only partly submerged, with the level of the toner mix being indicated at 1th) in FIG. 1. Thus, any tendency toward pile up of the toner mix, for example, at the left hand end of the bin tends to submerge the augers thereby increasing the efficiency of the return auger so that it transports a larger amount of material away from the region where the mix has tended to collect. It sometimes happens that many copies are desired of a single original which has a greater amount of solidly pig mented area at certain column positions across the width of the sheet than at others. This tends to cause depletion of the toner powder at the highly pigmented positions. However, any tendency toward starvation at any column position is prevented in the present machine, regardless of the number of copies, by the fact that the angers tend to maintain the balance or level of toner mix constant from one end of the bin to the other. Thus perfect uniformity is assured, as a result of which the developing unit may be employed in completely automated copying machines of the electrostatic type where hundreds of co may be run off in a single run.

Means are provided for preventing leakage of the toner mix along the shafts which penetrate the bin. In the case of the developing cylinder do this function is provided by a sealing assembly 11% at ea 11 end of the cylinder. As shown in FIG. 4 the sealing assembly is in the form of a face seal having a stator ill and a rotor 112. Such sealing assembly is the same as that usually employed in the sealing of liquids and hence well known to those skilled in the art. It will suffice to say that the rotor 112, which is seated in an annular retainer 1'13, rotates with the shaft. The cooperating stator element includes a biasing spring (not shown) to keep the sealing surfaces in engagement. The shafts 93, 94 are sealed by use of resilient lip-type seals 115, 11s: mounted in suitable recesses in the brackets 41, 42 as shown.

In accordance with one of the aspects of the present invention replenishing means are provided at the top of the developing unit for depositing measured amounts of toner from time to time concentrated at a single position at the rear of the augers for immediate longitudinal distribution by the augers. The replenishing unit 120 is preferably mounted upon a supporting or base plate 521 which forms the top plate for enclosing the toner bin and which is preferably secured to the side members 41, 42 of the developing unit as shown in FIG. 2. A spring-closed inspection cover 122 is provided in the plate for checking the operation in the level of the toner bin when desired.

.iounted on tle plate 121 is a magazine 1255 in the form of a hollow vertical cylinder. At the bottom of the cylinder and secured to the plate 121 is a stationary disc 126 in the form of a shallow inverted cup having ports or openings 127, 128 and a mounting flange 129. For metering toner powder from the magazine a metering disc 133 having peripheral notches 131, 132 is interposed in the cup between the stationary disc 126 and the supporting plate 121, and the discharge opening 135 is angularly offset from the ports 127, 128 of the stationary disc. Thus rotating the disc serves to rotate a trapped quantity of toner into position for discharge.

To oscillate the metering disc 13 the disc is connected to a vertical shaft 149 to which it is secured by a pin 1dr. At the lower end of the shaft 14-) an arm is provided having a pin 143 which engages the shaft. The arm 142 is coupled to a solenoid 145 by a link 146, and a coil spring 147, anchored to the frame plate, which provides power for the return stroke. Outboard support for the shaft l 'lil is supplied by a bracket 148. The stroke of a sc-lenoi is preferably such that on the forward stroke the notch 132 of the metering disc rotates between d a position under the port 128 of the stationary disc to a position over a discharge port in the supporting plate. On the return stroke the remaining notch 131 performs a similar function rotating from under the port 127 to a position over the discharge port. Thus where both the notches 131, 132 are utilized the replenisher is capable of depositing two measured doses of toner powder each time the solenoid is energized. It order to cut the dis charge in half, one of the notches on the metering disc may simply be omitted.

in accordance with one of the aspects of the invention the size of the dose is made adiustable by providing a choke plate secured to the magazine and above the stationary disc and having ports which may be adjusted into register with the ports in the disc. The magazine is rotatable with respect to the mounted or base plate and provided with suitable calibrated indicia so that adjustment is effected simply by rotating the magazine. in the present instance the choke pla e indicated at 15% has openings 151, 152'; which correspond to the openings 127, in the stationary disc. For securing the choke plate to the magazine suitable tabs 1c 15$ are provided. The magazine is made rotatable with respect to the supporting plate by forming the base portion with an annular groove 155 engaged by lugs 25 A st onary pointer 157 cooperates with a scale whicn is rotatable with the magazine.

it Will be apparent, then, that when the magazine is adjustably rotated relative movement will take place between the ports choking down the area through which toner may enter the notches in the metering disc and thereby determining the quantity of toner which is ejected during each operation.

For the purpose of agitating the finely divided toner and for thereby preventing packing or bridging, agitators I161, 162 are secured to the upper end of the shaft The agitators are preferably spaced from one another as shown with the lowermost agitator bein mounted more or less directly over the choke plate so that it tends to sweep toner into the metering space. It is found that this construction produces a high degree of reliability and metering accuracy even when used with toner powder having a particle dimension measured in terms of microns.

For the purpose of keeping the magazine 1255 at a safely low temperature, a heat shield 165 is provided which is spaced from the wall of the magazine on posts 166. Windows 157 at the lower edge of the shield upward movement of cooling air. Thus there is no possibility that the magazine will be heated to the point that fusion of the toner powder will tend to take place.

In spite of the fact that the toner is deposited in a concentrated dose at one point along the length of the developin cylinder, the action of the transporting angers, previously mentioned, is such that the added material is immediately distributed over the width of the cylinder so that addition of toner does not affect copy-to-copy uniformity.

In accordance with one of the aspects of the present invention means are provided for actuating the dispenser once for each copy made. The actuating signal derived from a switch 168 responsive to the leading edge of the original and which is used in the overall control circuitry disclosed in detail in my copending application. Referring to FIG. 7, a simple series connection 16?" is made heween the switch and the solenoid 145 of the replenisher. Since the replenisher may, because of its novel design, be adjusted for low consistent output per cycle, it is found that the toner is maintained at a desired level 0* er long periods of time without further care or attention.

If desired, and without departin' from the invention, means may be provided for actuating the replenishing unit 120 after a predetermined number of copies have been processed. Thus, a timer 17% may be used having input terminals 171 and output terminals 172. The timer has been indicated diagrammatically since timers are well known to those skilled in the art capable of producing an output pulse upon receipt of a predetermined, counted, number of input pulses. When using the timer the regular lead (FIG. 7) 169 is broken. The input terminals are connected to the switch 163 and the output terminals are connected to the solenoid, just as shown by the dotted lines. Thus after a predetermined, preferably adjustable, number of counts the counter 17G triggers an impulse to the solenoid to deposit a predetermined amount of toner powder in the bin.

It will be seen from the above description that a developing unit has been provided which meets all of the requirements of reliable production in an office type machine, providing clear, uniform copies regardless of the distribution of light and dark on the sheet and regardless of the length of the run. The above developing unit while shown in a preferred embodiment is not limited to use in a particular machine but may be employed wherever it is desired to develop a latent image on an electrostatically charged sheet.

N e claim as our invention:

1. In a developing unit for a photocopy machine capable of developing a copy sheet having an electrostatic latent image thereon, the combination comprising a toner bin for containing a quantity of toner mix including toner powder and magnetic carrier particles therefor, a magnetic developing cylinder rotatably mounted in said bin, means for transporting the copy sheet through the bin, said toner bin having a side wall in the form of a sheet of nonmagnetic material of curved contour to conform to the shape of the cylinder and spaced therefrom to define a passage of uniform width for admission of the copy sheet, a longitudinally extending magnetic pole arranged on the opposite side of the non-magnetic sheet for establishing lines of flux extending through the non-magnetic sheet and copy sheet, the surface of the cylinder having well defined helical ridges thereon for concentrating the magnetic flux and for forming helical tufts of toner mix which are swept laterally across the surface of the sheet as the developing cylinder is rotated thereby to deposit toner powder in the charged areas for sweeping toner powder clear of the non-charged areas.

2. In a developing unit for a photocopy machine capable of developing a copy sheet having an electrostatic latent image thereon, the combination comprising a toner bin having bottom and side Walls and extending the width of the sheet, a supply of toner mix in said bin including pigmented toner particles and magnetic particles for carrying the same, a magnetic developing cylinder in said bin and having a shaft, means for transporting the copy sheet through the bin, magnetic bearing blocks for mounting the cylinder for rotation, permanent magnets magnetically coupled to said bearing blocks and bridged by a magnetic pole which extends the length of the cylinder and spaced parallel thereto, a non-magnetic barrier interposed between the cylinder and the magnetic pole and arranged closely adjacent the cylinder to define a path for the sheet, the magnetic cylinder being formed with a series of helical ridges for concentration of magnetic flux and for formation of tufts of toner mix which are swept across the copy sheet as the sheet is advanced adjacent said guide, and means forsealing the shaft against escape of powder into said bearing blocks.

References Cited by the Examiner UNITED STATES PATENTS 2,779,306 1/57 Dunn 117-175 X 2,786,439 3/57 Young 118-637 2,796,258 6/57 Beck 271-29 2,890,968 6/59 'Giaimo 118-637 X 2,892,446 6/59 Olden 118-637 2,904,000 9/59 Fisher et al. 117-175 2,910,964 11/59 Stavrakis et al 117-175 X 2,979,026 4/61 Reuter 118-637 3,003,462 10/61 Streich -118-637 3,081,737 3/63 Frantz et al. 118-637 3,088,386 5/63 Sugarman 95-17 CHARLES A. WILLMUTH, Primary Examiner.

WILLIAM MARTIN, Examiner.

Who-1.,

Claims (1)

1. IN A DEVELOPING UNIT FOR A PHOTOCOPY MACHINE CAPABLE OF DEVELOPING A COPY SHEET HAVING AN ELECTROSTATIC LATENT IMAGE THEREON, THE COMBINATION COMPRISING A TONER BIN FOR CONTAINING A QUANITY OF TONER MIX INCLUDING A TONER POWDER AND MAGNETIC CARRIER PARTICLES THEREFOR, A MAGNETIC DEVELOPING CYLINDER ROTATABLY MOUNTED IN SAID BIN, MEANS FOR TRANSPORTING THE COPY SHEET THROUGH THE BIN, SAID TONER BIN HAVING A SIDE WALL IN THE FORM OF A SHEET OF NONMAGNETIC MATERIAL OF CURVED CONTOUR TO CONFORM TO THE SHAPE OF THE CYLINDER AND SPACED THEREFROM TO DEFINE A PASSAGE OF UNIFORM WIDTH FOR ADMISSION OF THE COPY SHEET, A LONGITUDINALLY EXTENDING MAGNETIC POLE ARRANGED ON THE OPPOSITE SIDE OF THE NON-MAGNETIC SHEET FOR ESTABLISHING LINES OF FLUX EXTENDING THROUGH THE NON-MAGNETIC SHEET AND COPY SHEET, THE SURFACE OF THE CYLINDER HAVING WELL DEFINED HELICAL RIDGES THEREON FOR CONCENTRATING THE MAGNETIC FLUX AND FOR FORMING HELICAL TUFTS OF TONERS MIX WHICH ARE SWEPT LATERALLY ACROSS THE SURFACE OF THE SHEET AS THE DEVELOPING CYLINDER IS ROTATED THEREBY TO DEPOSIT TONER POWDER IN THE CHARGED AREAS AND FOR SWEEPING TONER POWDER CLEAR OF THE NON-CHARGED AREAS.

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