US3540412A

US3540412A - Electrographic apparatus having an inking slot bearing against a web pulling roller

Info

Publication number: US3540412A
Application number: US661871A
Authority: US
Inventors: William A Lloyd
Original assignee: Varian Associates Inc
Current assignee: Varian Medical Systems Inc
Priority date: 1967-08-21
Filing date: 1967-08-21
Publication date: 1970-11-17
Anticipated expiration: 1987-11-17
Also published as: FR1576164A; GB1228972A; DE1797111A1

Description

rUnited States Patent Primary Examiner-Bernard Konick [72] Inventor William A. Lloyd Assistant Exam iner-Gary M. Hoffman San Jose, California AppLNo. 661,871

Attorneys-William J. Nolan and Leon F. Herbert [22] Filed Aug.21, 1967 [45] Patented Nov.l7,1970

346/74 resilient material to allow foreign particles to pass with the 11S/410x recording web across the slot without destroying the seal or 101/366X tearing the web.

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ANALOG T0 DIGITAL CONVERTER Patented' Nov. 17, 1970 V4/////,/7//y /////v///,///C

INVENTOR. WILLIAM A. LLOYD DESCRIPTION OF THE PRIOR ART Heretofore, electrographic recorders have been disclosed employing aninking channel having an inking slot formed in one side thereof and bearing against a flat plate over which a recording web is pulled by means of a friction drive roller. Such a recorder apparatus is disclosed and claimed in copending U.S. application Ser. No. 578,801 filed Sept. l2, 1966 now U.S. Pat. No. 3,392,401 and assigned to the same assignee as the present invention.

The problem with such a prior art recorder paper drive apparatus is that the friction drive wheels pull on the electrogiraphic recording paper downstream ofthe liquid inker. Thus, the drive wheels pull on a wet surface or bear against a wet surface ofthe web which can result in nonuniform paper drive speeds and the printing of ghost images on the recording web due to the transfer of ink from the images on the web to an idler roller and then back to a subsequent portion of the web. In addition` the provision of the flat plate opposite `the inking slot allows the recording paper to deform into the inking slot, due to atmospheric pressure, resulting in uneven wear on the edges of the slot. Uneven wear can make it difficult to form an initial seal with the paper. If the inking channel is pushed into engagement with the plate then small foreign particles carried along with the web are caught at the marginal edges ofthe inking slot resulting in tearing of the electrographic recording paper.

Therefore, a need exists for an electrographic recording paper drive mechanism and inking channel arrangement wherein the frictional paper drive is not performed on the wet paper and means are provided for pressing the recording paper against the marginal edges of the slot to facilitate formation of a seal in such a manner that foreign particles carried along with the recording paper do not result in loss of the seal with the inking slot or tearing of the recording paper.

SUMMARY OF THE PRESENT INVENTION v The principal object of the present invention is the provision of an improved electrographic inking apparatus.

One feature ofthe present invention is the provision` in an electrographic 'inking apparatus, of an inking channel disposed facing a 'drive roller which pulls the electrographic paper past the inking slot in the inking channel and wherein the marginal edges of the inking slot are curved to conform to the curved surface of the drive roller to facilitate forming a liquid seal between the inking slot and the recording web.

Another feature of the present invention is the same as the preceding feature wherein the curved surface of the drive roller, which faces the recording web, has a substantial coefficient offriction and is made ofa compressible resilient material to facilitate sealing between the web and the marginal edges ofthe inking slot.

Another feature of the present invention is the same as any one or more of the preceding features including means for providing a spring bias force for urging the paper drive roller and inking channel toward each other to sandwich the recording paper therebetween to facilitate formation of the liquid seal between the paper and the inking slot.

Other features and advantages of the present invention will become apparent upon a perusal of the following specification taken in connection with the accompanying drawing wherein:

BRIEF DESCRIPTION OF THE DRAWING The drawing is a perspective view, partly schematic and partly in block diagram form, depicting an electrographic recorder incorporating features ofthe present invention.

2 DESCRIPTION oF THE PREFERRED EMBODIMENTS Referring now to the drawing there is shown an electrographic recorder l incorporating features of the present invention` The recorder 1 includes a pair of input terminals 2 and 3 to which an input signal E,- is applied to be measured and recorded. The input signal was fed to a preamplifier 4 wherein it is amplified and fed to the input of an analog-todigital converter 5 The analog-to-digital converter tracks the input signal E,- and produces a binary data output 6 representative of the input signal 12,. The binary data output signal 6 is fed to an array of electrographic writing electrodes 7 extending crossA wise of an electrographic recording paper 8 having a conductive paper backing and a thin dielectric charge retentive surface facing the array of writing electrodes 7.

A cylindrical frictional drive roller 9, more fully described below, frictionally grips the paper 8 and pulls the paper 8 past the array of writing electrodes 7 from a supply ll. A takeup roll l2 takes up the recording paper 8 after it has passed over the drive roller 9.

The writing electrode array 7 has selected one of its electrodes energized by the output 6 of the analog-to-digital converter 5 for laying down a line charge image on the charge retentive surface of the recording paper 8. The line charge image is a signal trace representative of the input signal E,- to be recorded. Signal writing electrodes 7 cooperate with a second writing electrode plate I4 disposed on the conductive side of the recording paper 8 and operated at a suitable potential such that the writing potential applied to the selected electrode of the array 7 produces approximately minus 500 to 4minus 900 volts relative to the electrode plate 14.

An electrographic recorder employing an array of writing electrodes energized by the output ofan analogtodigital converter is disclosed and claimed in copending U.S. application Ser. No. 582,767 filed Sept. 28, 1966 now U.S. Pat. No. 3,394,383 and assigned to the same assignee as the present invention.

An electrographic inking channel 15 is disposed facing the drive roller9. The inking channel 15 includes an inking slot 16 cut through the side wall ofthe channel I5 and having its marginal edges curved to conform to the curved cylindrical surface of the drive roller 9. Liquid electrographic toner (ink) is supplied to the inking channel l5 from a reservoir 17 by means of a liquid ink line 18A A vacuum pump 19 draws a suitable vacuum on the top of the inking channel l5, as of minus l5 inches of water, by means ofa vacuum line 2l. The vacuum head drawn on the inking channel l5 causes the liquid ink within the reservoir 17 to be drawn via the liquid line 18 into the inking channel l5 to a predetermined level within the inking channel above the inking slot I6. A float valve controls v the conductance ofa vacuum bypass line to the reservoir, not

shown, for maintaining the liquid level within the inking channel 15 at the desired height. An inking channel supplied with a vacuum head and interconnected to a reservoir and including a bypass float controlled liquid level means is disclosed and claimed in copending U.S. application Ser. No. 577,443 filed Sept. 6, l966 now U.S. Pat. No. 3,392,706 and assigned to the same assignee as thc present invention.

A spring bias force, schematically indicated by a tension spring 23 interconnecting the inking channel l5 and the drive roller 9, causes the drive roller 9 to press the recording paper 8 against the marginal edges of the inking slot 16 to assure formation of a liquid seal therebetween such that a vacuum head may be pulled on the inking channel 15 to draw the ink into the channel 15 and inking slot 16.

The drive roller 9 is preferably made of a compressible resilient material such as a synthetic elastomer as of urethane elastomer or neoprene, which also provides a substantial coefficient of friction between the roller and the conductive backing of the paper 8 to permit frictional drive of the paper 8. The material should also be chemically inert to the liquid toner. The compressible resilient characteristic of the drive roller 9 facilitates formation of the liquid seal between the I paper 8 and the marginal edges of the inking slot 16 and, in addition,'permits small foreign particles carried on the surface of the paper 8 to pass the slot 16 without breaking the fluid seal between the paper 8 and the marginal edges of the slot 16. ln addition the compressibility of the roller 9 prevents these particles from being lodged between the paper 8 and the marginal edges of the inking slot 16. Trapping of the particles could result in tearing of the paper and loss of therfluid seal. An advantage of frictionally driving the recording paper 8 at the inking slot l5 is that the frictional drive of the paper is obtained on dry paper without the need of an idler roller riding on the wet side of the lpaper. ThisA avoids transfer of ghost images from the idler roller to the recording paper. ln other words, the prior artidler roller is replaced by the inking channel 15.

The drive'roller 9 is rotationally driven by means of.a belt 25 and a pair of pulleys 26 and 26'. Drive pulley 26' is driven from the shaft of a motor 27, only partially shown. A pair of

idler rollers

28 and 29 are disposed on the conductive side of the web on opposite sides of the writing electrode array 7 to assure that the electrographic paper 8 is properly positioned with respect to the writing array 7.

Since many Changes could be made in the above construction and many apparently widely different 'embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

l claim:

l. ln an electrographic apparatus for reproducing an image onto a recording'medium, the combination comprising:

a rotating drive roller for engaging and moving the recording medium; means for rotating the drive roller;

inking means mounted proximate the drive roller and provided with an inking chamber having an inking slot therein for applying inkl from the ink chamber -to the recording medium, the marginal edges of the inking slot being curved to conform to the contourofthe drive roller with the recording medium positioned therebetween; biasing means between the drive roller andthe inking means for engaging the recording medium between the drive rollerand the marginal edges of the inking slot to deter ink leaks and permit the rotating drive roller t'o move the recording medium; and vacuum means for establishing a lower than atmospheric pressure in the ink chamber the surface. further deterring ink fromleaking out ofthe ink chamber between the marginal edges of the inking slot and the recording medium. 2. The electrographic apparatus `of claim l wherein the coefficient of friction of th'e surface of the drive roller is higher than the coefficient of friction of the marginal edges of the inkingslot for permitting the drive roller to frictionally engage and move the recording medium.

3. The electrographic apparatus of claim l whereinl the vacuum means additionally functions to transport and circulate the ink to and through the inking chamber.

4, The electrographic apparatus of claim l wherein the bias v means is a resilient spring member for urging the drive roller and the marginal edges of the inking slot into sealing engagement with the recording medium positioned therebetween.

5. The electrographic apparatus of claim l wherein the curved surface of the drive vroller is a compressible resilient material to'faeilitate sealing between the drive roller and the marginal edges of the inking slot with the recording medium therebetween while permitting foreign particles on the recording medium toy compress the curved surface of the drive roller and to pass with the recording medium across the marginal edge ofthe inking slot.

6. The electrographic apparatus of claim 5 wherein the compressible resilient surface of the drive rolleris made of a synthetic elastomer.