US 3342164 A
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Sept. 19, 1967 A. M. LEWIS ELECTROSTATIC TONER HEAD AND SYSTEM 2 Sheets-Sheet 1 Filed Nov. 4, 1964 INVENTOR. ARTHUR M.LEWI$ BY 540%Wi ATTORNEY Sept; 19, 1967 A. M. LEWIS 'ELECTROSTATIC TONER HEAD AND SYSTEM File d Nov. 4, 1964 2 Sheets-Sheet P,
ARTHUR M LEWIS ATTOEY United States Patent 3,342,164 ELECTROSTATIC TONER HEAD AND SYSTEM Arthur M. Lewis, Shaker Heights, Ohio, assignor to Clevite Corporation, a corporation of Ohio Filed Nov. 4, 1964, Ser. No. 408,894 7 Claims. (Cl. 118-637) This invention pertains to a system and apparatus for applying liquid toner to a record medium to develop the latent electrostatic image thereon.
Liquid toners have been used to develop latent electrostatic images but have not generally been highly acceptable compared to dry powder developers because of the presence of excess liquid toner on the record and because of the time necessary to dry the record.
Liquid toners, if the extended drying time can be reduced, have some advantages over the dry powder toners.
In the past attempts have been made to reduce the time necessary to dry the liquid toners by squeezing excess liquid off the record with rollers, or by spraying a controlled small amount of liquid toner on the record, followed in both instances by final drying in hot air. While these systems have already achieved some commercial success in devices for copying whole sheets of records, neither system is sufiiciently rapid to permit its use in direct writing oscillograph devices.
A direct writing oscillograph should be able to drive the record medium past the recording stylus at selected speeds between very low speeds and very high speeds, and it must develop the latent image sufficiently rapidly that the record becomes almost immediately visible.
It is an object of the present invention to provide an applicator system for applying liquid toner to a record member on which a latent electrostatic image has been recorded, wherein relatively large quantities of toner are applied to the record, and wherein all excess toner is quickly removed after the image has been developed to facilitate rapid drying of the record.
Another object of the invention is to provide a liquid toner system for rapidly developing and substantially drying a moving record chart.
Still another object of the invention is to provide a toner head for applying liquid toner to a rapidly moving electrostatic record chart and for removing the excess liquid toner therefrom.
For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.
The broad term electrostatic recording may embrace xerography, electrographic recording and other systems. The present invention deals with those electrostatic systems wherein a latent or invisible record is made on a record member, which latent image is thereafter developed by the application of toner.
An example of the xerographic process is described in Carlson Patent 2,297,691, issued in 1942. Liquid toner development of a stationary record is described in Patent 3,129,115 issued to Clark et al. in 1964.
An aspect of the present invention lies in the provision of an applicator system and a toner head therefor, for applying liquid toner to a record medium on which a latent electrostatic record has been recorded. A housing forms with the record medium a developer compartment through which quantities of liquid toner are circulated in contact with the surface of the record medium. One or more cleaning nozzles are adjacent the surface of the record medium, and preferably the cleaning nozzles are adjacent the developer compartment, for withdrawing 3,342,164 Patented Sept. 19, 1967 from the surface of the record medium all excess liquid toner.
With respect to the drawings there is shown in:
FIGURE 1 a view of a direct writing oscillograph embodying the present invention.
FIGURE 2 is a view of the toner head.
FIGURE 3 is a view of the toner head with a front plate removed to show the interior thereof.
FIGURE 4 is a sectional view taken along line 44 of FIGURE 2.
FIGURE 5 is a sectional view taken along line 55 of FIGURE 2.
FIGURE 6 is a view of a modified type of a toner head with its front plate removed.
FIGURE 7 is a side view of the device shown in FIG- URE 6, and
FIGURE 8 is a sectional view taken along line 88 of FIGURE 7.
With reference to FIGURE 1 there is shown a direct writing oscillograph mounted on a base 10, the cover therefor being removed. The oscillograph comprises an electromagnetic device 12 which oscillates a recording stylus 13 in accordance with an electric signal applied from a source 14 to terminals 15, 16, as is known in the art. The stylus 13 applies an electrostatic latent image to a moving strip of record medium 17 which is driven at any one of a large number of selected speeds by motor means, gears and the like, the details of which form no part of this invention.
The stylus 13 is connected to a source 20 to provide the recording voltage. For example, the source 20 may apply 500700 volts DC. of either negative or positive polarity.
After the latent signal image has been applied to the moving record medium 17 the strip passes under a toner head 21 where liquid toner is applied to the surface of the record medium to make the latent image visible. Liquid toners per so are well known to the art.
The toner head 21 preferably is mounted in a closed liquid circulating system which comprises a reservoir 25 containing the liquid toner 26. An outlet pipe 23 from the reservoir 25 is connected to the inlet 27 of the toner head 21, and the outlet 28 of the toner head 21 is connected by hose 29 to the inlet of pump 30 which is driven by motor 31. The outlet of pump 30 is connected by hose 32 to the reservoir 25 for returning the excess liquid toner and any air picked up by head 21 thereto. A vent 24 is provided in reservoir 25 to vent the excess air which may be pumped into the reservoir along with excess liquid toner.
It 'is important that the pump 30 be connected to the outlet side 28 of the toner head 21 so that it applies a partial vacuum to the toner head 21. The record medium 17 is directly under the toner head 21, and, as shown best by FIGURE 4, the record medium effectively seals several openings 33 and a developer compartment 34 in one face 35 of the toner head 21. The partial vacuum established by pump 30 pulling the liquid toner 26 through the toner head 21 holds the record member 17 up against the underneath face 35 of the toner head. This effectively seals the openings 33 and 34 therein, and it prevents the liquid toner which is within the toner head from escaping from the toner head.
The toner head is show in detail in FIGURES 2 to 8. In FIGURES 2 and 3 it is upside down compared to its position in the instrument shown in FIGURE 1, and in FIGURE 3 a plate has been removed to show the interior. An advantage of the present system and head is that it will operate in any position.
The toner head 21 is comprised of a housing 40- which is hollow and which has an opening 41 at its face 35.
Within the housing 40 there is a small chamber 52 formed by walls 44, 45 spaced from the side walls 46, 47 of the housing. As shown in FIGURE 4 the walls 44, 45 do not extend as far down as do the side walls 46, 47. A face plate 50 having an opening 53 is secured by screws 51 in the opening 41 so that it encloses the chamber 52 and provides communication with the developer compartment 34. The face plate 50 has two small openings 54 at its end opposite to the opening 53. Inlet pipe 27 communicates with chamber 52 so that liquid toner flows through chamber 52. Opening 53 in plate 50 permits toner fluid in chamber 52 to flow into the developer compartment 34 located between the record medium 17 and the face plate 50, and the liquid toner flows through the two small openings 54 back into a passageway 60', and from there it flows out the outlet pipe 28 to the pump 30. Thus only a very small volume of toner is actually against the surface of the record medium at any given time so that if the supply of paper is exhausted virtually no toner is spilled if the liquid surface in the reservoir is at a level below the head. This avoids a siphon action which otherwise might take place. Because of the crosssectional area of the compartment 34 and because of the flow of toner through it, the surface of the record medium 17 under the head 21 is in intimate contact with a sufficient volume of continually replaced toner.
Face plate 50 preferably is made of metal and compartment 34 is very shallow so that its side 36 is close to the surface of the record medium 17 while developing the latent image. This closely spaced conducting surface 36 acts as a developing electrode to speed up development.
The face plate 50 almost, but not completely, closes the opening 41 in the face 35 of the toner head 21, thereby forming with the side walls of the housing one or more long narrow openings or nozzles 33. Preferably a long narrow opening 33 is located at each side of the developer compartment 34 where toner is applied to the record medium, though it is possible to satisfactorily operate the toner head with only one such slot 33 if it is located to the side of the head toward which the record medium is moving; i.e. to the right hand side in FIGURE 4. Compartment 60 is in communication with these slots 33, and compartment 60 is connected to the outlet pipe 28 so that pump 30 establishes a negative pressure therein. Excess liquid toner that escapes from the developer compartment 34 is vaccumed up into the compartment 60 and is then returned to the reservoir 25 together with any air which leaks in between the walls 46, 47 and the record medium 17. This negative pressure or partial vacuum at the slots 33 to either side of the head 21 assures that the record medium Will engage the face 35 of the head to minimize liquid leakage from the developer compartment 34. Thus the partial vacuum in compartment 60 and in the slots 33 serve a dual purpose-4o hold the record medium against the face 35 of the head 21 and to vacuum up any excess liquid toner.
Holes 54 are deliberately made restrictive to toner flow thereby to establish a pressure differential between compartments 34 and 60. This pressure differential prevents :air from leaking into the developer compartment 34, and assures that during normal operation the developer compartment 34 will at all times be full of toner liquid.
The developed record is in an essentially dry state as 'it leaves the head since the liquid toner contacts only one face of the record for an extremely short interval of time and since excess liquid toner is immediately vacuumed up from the surface of the record medium. The record is made visible almost immediately, and the oscillograph does not have to provide a long loop in which the record is heated to facilitate drying.
An alternative head is shown in FIGURES 6 to 8. In this embodiment the toner head 21 has an inlet pipe 27' and an outlet pipe 28'. Liquid toner and air are pulled out of outlet pipe 28' by a pump 39 thereby establishing the essential partial vacuum within the head, and liquid toner is pulled into the inlet pipe 27. Additionally a pipe 65 is connected to the pump 30 to circulate the spent liquid toner and return it to the reservoir. The pipe 65 extends through the head 21' and through the face plate into the compartment 34 where the developing process takes place. The compartment 60 which is formed in the head 21', and grooves 68 in the side walls of the head communicate at a number of locations with the slots 33'. Any excess liquid on the record is vacuumed up by slots 33' and passes through grooves 68 into the compartment 60 and is then returned through pipe 28 to the reservoir.
Pipe 65 is connected to the pump 30 through restrictive means which establish the pressure differential between compartments 34' and 60'. The restrictive means may merely be a long, small pipe or it may include a throttle valve.
The flow path of the liquid toner, as best shown in FIG- URE 7, is from inlet pipe 27 into compartment 52', thence through orifice 53' into the developer compartment 34', and then out through pipe 65 to the pump 30, as shown by the arrows 67. Any liquid tone-r which escapes from the developer compartment 34 is vacuumed up by nozzles 33' and passes through grooves 68 into compartment 60', together with any air which flows into the head between the record 17 and the side walls 46', 47' (as shown by arrows 69), and the mixture is exhausted out through pipe 28 by pump 30 and is returned to the reservoir.
While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.
1. An applicator system for applying liquid toner to a record medium on which a latent electrostatic record has been applied, comprising, a housing forming with said record medium a substantially closed developer compartment, circulator means for circulating liquid toner through said compartment and against a surface of said record medium to develop said latent record, said circulator means including a reservoir for said liquid toner, means connecting said reservoir to said housing in a closed liquid circuit, means for circulating said toner through said closed circuit and for applying a partial vacuum to said compartment, air suction means including cleaning nozzle means separated from said developer compartment and within said housing and adjacent the surface of said record medium for withdrawing from the surface of said record medium excess liquid toner, and means connecting said air suction means to said circulator means for returning said air and said excess liquid toner to said reservoir.
2. An applicator system for applying liquid toner to a record medium on which a latent electrostatic record has been applied thereby to develop said record, comprising, in combination, a housing, means for moving said record medium in engagement with said housing to establish a substantially closed developer compartment, a reservoir of liquid toner connected to said compartment, pump means connected to said housing and also connected to said reservoir for withdrawing said liquid toner from said compartment and for returning it to said reservoir and thereby establishing in said compartment a partial vacuum which tends to hold said record medium against said housing, and air suction means including cleaning nozzle means operated below ambient pressure located adjacent the surface of said record medium and within said housing for withdrawing from the surface of said record medium excess liquid toner, said cleaning nozzle means being separated from said developer compartment and being to the side of said compartment toward which said record medium moves after it has been developed.
3. An applicator system for applying liquid toner to a record medium according to claim 2, further characterized by means connecting said air suction means to said liquid pump means whereby said excess toner and air is returned to said reservoir.
4, An applicator system for applying liquid toner to a record medium according to claim 2, further characterized by cleaning nozzle means adjacent the surface of said record medium and adjacent both sides of said compartment.
5. A toner head for applying liquid toner to a record medium on which a latent electrostatic record has been applied, comprising, a housing having an opening adapted to be closed by said record medium to establish a developer compartment, means admitting liquid toner to said developer compartment, means for withdrawing said liquid toner from said developer compartment thereby establishing within said compartment pressure below ambient and air suction means including a nozzle forming part of said housing, said nozzle being separated from said developer compartment and within said housing and adjacent said record medium for withdrawing from said record medium excess liquid toner.
6. A toner head as set forth in claim 5 further characterized by said means for withdrawing said liquid toner and said air suction means for withdrawing said excess liquid toner being connected to the same vacuum pump.
7. A toner system for applying liquid toner to a moving record medium on which a latent electrostatic record has been applied, comprising, a housing forming With said record medium a substantially closed developer compartment, means for moving liquid toner through said housing and in engagement with said record medium to develop the latent image thereon, and cleaning nozzle means separated from said developer compartment and Within said housing and adjacent said record medium at a location where said latent image has been developed, said nozzle operating below ambient pressure at the surface of said record medium to remove excess liquid toner therefrom by vacuuming up the excess liquid.
References Cited UNITED STATES PATENTS 2,242,182 5/1941 McCann 118-415 X 3,027,821 4/1962 Wright 11841O X 3,038,442 6/1962 Jones et a1. 118-637 3,081,687 3/1963 Takats -89 3,122,453 2/1964 Montgomery 118---637 3,176,653 4/1965 Hansen 118-637 3,196,832 7/1965 Zin 118-637 3,238,921 3/1966 Engelstad et al 118637 3,277,493 10/ 1966 Fyler.
FOREIGN PATENTS 649,949 10/1962 Canada.
CHARLES A. WILLMUTH, Primary Examiner. PETER FELDMAN, Assistant Examiner.