US2349613A - Porous resilient printing plate - Google Patents

Description

May 23, 1944l f R. G. cHoLLAR 2,349,513

POROUS RESILIENT PRINTING PLATE Filed Feb. l2, 1942 Robert G. Chollar Inventor His Attorney PatentedlMay 23, 1944 POROUS RESILIENT PRINTING PLATE Robert G. Chollar, Dayton, Ohio, assignor to The National Cash Register Company,

Dayton,

Ohio, a corporation of Maryland Application February 12, 1942, Serial No. 430,661

(Cl. IGI-401.1)

36 Claims.

This invention relates to resilient micro-porous printing plates and the method of making them, and more particularly relates to such micro-porous resilient printing plates in which the resilient body acts as a reservoir and as a conductor for ink which is supplied to the type face through the pores.

It is known in the art of printing that porous printing members may be made of various materials more or less hard in structure to be used to absorb and conduci-l ink to a printing surface inscribed thereon. These porous substances have been non-resilient, so that printing qualities characteristic of a resilient surface equivalent to that of rubber could not be obtained. Heretofore, an

ink-resistant porous printing plate of suiicientl strength for commercial use and of the fine surface porosity necessary to give even printing has not been produced.

This invention relates to a printing member or plate made of porous rubber or rubber-like material either of a single layer or of laminated structure, as will be described, said porous rubber and the process for making it being described in my co-pending application for United States Letters Patent Serial No. 427,326, illed on the 19th day of January, 1942.

The printing member which is the subject of this invention is a consolidated laminated member, the main body 'of which is coarsely microporous and the printing surface of which is nely micro-porous, the two layers being bonded together in such a fashion that ink passes readily from one layer to another. Said coarser layer of the laminated structure is re-supplied with ink by means of a wick-like backing, which backing may be of porous metal, of woven fabric, of felted ber, or of any other capillarily conducting substance.

Therefore, the principal object of this invention is to provide a resilient micro-porous printing member.

Another object of the invention is to provide a resilient micro-porous printing member having a surface lai/er `for printing which is more iinely micro-porous than the principal body ci the member.

Another object of the invention is to provide a resilient porous printing member with a nonresilient porous backing.

Another object of the invention is to provide a printing member made of micro-porous rubber-like material which is supplied withink through a coarsely micro-porous body structure by means of a wick-like structure.

Another object of the invention is to provide a process for making the aforesaid objects.

With these and incidental objects in view, the invention includes certain novel featuresof construction and combinations of parts, the essential elements of which are set forth in appended claims and a preferred form or embodiment of which is hereinafter described with reference to the drawing which accompaniesy and forms a part of this specication.

In said drawing:

Fig. 1 is a cross-sectional view, in diagrammatic form. of the novel laminated resilientI porous structure and means for supplying ink thereto.

Fig. 2 is a diagrammatical perspective view, partly broken away, of a typical porous resilient laminated printing plate and of the inking means therefor.

'. General description The laminated printing member is made up of a finely porous layer I0 formed of particles of raw material passing a screen of less than 325 mesh to the inch in size, and of another layer Il, which is a coarser backing layer made up-of particles of raw material passing a screen of from less than 25 to 100 mesh to the inch in size, as will .be described. The two layers merge into one another at their juncture in such a fashion that the pores of one layer intorcommunicate with the pores of the adjacent layer, so that whatever iiuid recording material is contained in the layer Il is transmitted by capillary action to the layer IU. The porous layer lll is made with fine pores because it makes a more even impression, as the individual pores therein are not discernible by reason. of the mark deposited from 4the pore openings on recording material.

A method of making the porous rubber, although adequately described in my co-pending application to which reference has been made, will be summarized brieily herein.

Rubber or synthetic rubber nely comminuted to the proper mesh size, said synthetic rubber being preferably of the butadiene co-polymer type, containing ordinary vulcanizing ingredients, is mixed parts by volume with 45 parts by volume of a nely comminuted ller. One such mixture is made of particles approximately less than the 325 mesh size, and one mixture is made with particles approximately less than the `25 to 100 mesh size. The ner mix is made into afluid mass, like a rubber cement, by the addition of a volatile solvent such as methyl-ethylketone and is applied to one surface of a i000- inch thick-water-soluble poly-vinyl alcohol sheet, said coating being made thick enough so that when vdry it is approximately 2%000 of an inch in thickness as a maximum. sheet with the coating thereon is placed in a die against a matrix of the printing surface to be formed, which matrix may be of Bakelite or other material that will withstand pressure and heat and will not adhere to the POU-vinyl alcohol. 'I'he uncoated side of the poly-vinyl alcohol sheet is placed next to the matrix. On top of this coating, preferably when dry, is placed the powder mix of the coarser variety so as to give the coarser layer, when molded, a maximum thickness of between 3%000 of an inch and 12%000 of an inch. 'Ihe whole mass in the mold is compressed between the matrix and a ram with a pressure of between 250 pounds to the square inch and 6000 pounds to the square inch, as the material requires, and then is vulcanized. The butadiene co-polymers require a temperature of about 307 degrees Fahrenheit for vulcanizing, which may be applied either in or out of the mold. The molded plate is removed from the mold, and the ller, which preferably is sodium nitrate. is dissolved out by washing in a solvent which has no eect upon the resilient material used. Sodium nitrate may be washed out with hot water containing a wetting agent, suchas soap or one of the aliphatic penetrants. Other iillers suggested are powdered metals, including powdered zinc; sodium carbonate; ammonium sulphate; or powdered water-soluble poly-vinyl alcohol.

'Ihe sodium nitrate may be washed out of a printing plate one-tenth of an inch thick in about two hours, if it is agitated in hot water. The water in the pores after a washing process is preferably replaced with ink by immersing the plate. in ink above the boiling point of water, thus preventing possible adhesions of the pore surfaces. For the zinc, the carbonates, and the nitrates, acids may also be used, hydrochloric acid and dilute nitric acid being suggested. With the percentage of ingredients named, the porosity of the printing plate as a unit is about 45% by volume and will absorb by volume about 45% ink. A dye ink of the oleic acid vehicle type is suitable for use with the particular synthetic rubber mentioned.

The back of the printing plate may have bonded thereto by molding it with the rubber mix, as a third and last layer in the mold, fabric, felt. ribbon, blotting paper, or a porous metal plate I2 to act as a strengthening support for the porous rubber and as a means to re-ink the porous rubber by means of a wick Il inserted therein.

It is to be understood that the particular materials suggested are not to limit the scope of the invention. The particular size of the particles in the mix are specified as being best adapted for dye inks having an oil base. 'Ihe butadiene copolymers are resistant to corrosion by such inks.

The polyvinyl alcohol The sodium nitrate is preferred as a filler, as it may be washed out of the molded material with hot water, which will also dissolve any of the polyvinyl alcohol sheet that cannot be removed by peeling. For other inks, for thicker plates, or for different molding temperatures, the ingredients must be selected on the basis of their suitability. It is within the intended scope of this invention to make such laminated plates with more than two layers.

In Fig. 1, the portion i4 represents a character molded in the web, the cross-sectioned portion Il showing the effect on the two layers after being forced into the matrix of the character.

'I'he use of water-soluble poly-vinyl alcohol in the process described makes it possible to wash the polyvinyl alcohol sheet off the molded mass as the filler is washed out to make the rubber porous.

The printing plate described is very compressible, and printing made from such a plate should be by very light contact, which can be assured by surrounding the printing plate by non-resilient stops, preventing compression of the printing plate by contact with the record material. 'Ihe supply of lnk available at the type surface is so copious that a light and fast contact is all that is necessary to make a well-defined impression. Therefore, the printing plate, not being subjected to severe hammering and pressure, will last indefinitely as compared with ordinary printing plates, even though lthe porous structure is rather fragile as compared with solid printing plates.

It is obvious that the laminated structure shown may be used for illtering or for separating liquids or for separating solid material either in gases or in liquids, or may be used for wicks for various purposes. The laminated structure for printing plates is, however, most important if ilne printing is to be combined with high ink capacity and rapid recovery of the printing qualities after an impression. The preferred embodiment described produces a printing plate that will accommodate itself to impressions less than a second apart for extended periods.

While the process and the product made in accordance therewith are admirably adapted to fulfill the objects primarily stated, it is to be understood that the invention is directed particularly to the laminated structure and the process for making it. It is not intended to conne the invention to the preferred form or embodiment herein disclosed, for it is susceptible of embodiment in various forms by varying ingredients and processing steps, all coming within the scope of the claims which follow.

What is claimed is:

1. The method of making a molded resilient web, including the step of finely comminuting rubber containing vulcanizing ingredients; the step of comminuting to the same flneness a solid filler substance soluble by solvents not appreciably affecting the rubber; the step of intimately mixing the rubber and the filler substance in a lvolatile fluid to form a fluid mass; the step of applying a thin coating of the fluid mass onto a supporting web and allowing it to dry; the step of placing the supporting web in a mold with the uncoated side of said web next to a printing matrix; the step of preparing a coarser dry mix of the rubber and filler; the step of applying a layer of the dry coarser mix over the coating previously applied on the supporting web; lthe step of applying molding pressure to the layers of substances in the mold; the step of vulcanizing the molded product; the step of removing the supporting web from the rest of the molded product; and the step of dissolving the filler from the rubber.

2. The method recited in claim 1 wherein the rubber used is one of the butadiene co-polymers.

3. The method recited in claim 1 wherein the rubber used is one of the butadiene co-polymers and the filler used is sodium nitrate.

4. I'he method recited in claim 1 wherein the filler used is sodium nitrate.

5. The method recited in claim 1 wherein approximately 55% of the rubber by volume is mixed with enough of the filler by volume to make 100%.

6. The method recited in claim 1 wherein the rubber used is a butadiene co-polymer mixed 55% by volume with sodium nitrate 45% by volume.

7. The method recited in .claim 1 wherein the volatile fluid is methyl-ethyl-ketone.

8. The method recited in claim 1 wherein the rubber used is a butadiene co-polymer and the volatile fluid is methyl-ethyl-ketone.

9. The method recited in claim 1 wherein the supporting web used is a sheet of poly-vinyl alcohol.

10. The method recited in claim l wherein the supporting web used .is a sheet of water-soluble poly-vinyl alcohol.

11. 'Ihe method recited in claim 1 wherein the supporting web used is approximately 1A000 of an inch thick.

12. The method recited in claim 1 wherein the particles oi' the finer mix pass through a screen of 325 mesh to the inch.

13. The method recited in claim 1 wherein the particles of the coarser mix pass through a screen o! between 25 and 100 mesh to the inch.

14. The method recited in claim 1 wherein the particles of the finer mix pass through a screen of 325 mesh to the inch and the particles of the coarser mix pass through a screen of between 25 and 100 mesh to the inch.

15. 'I'he method recited in claim 1 wherein the thickness of the film left on the supporting web after the volatilization of the volatile fluid 1s approximately 295000 of an inch.

16. 'Ihe method recited in claim 1 wherein the coarser mesh after being molded is of a thickness between approximately 895000 of an inch and 125A000 of an inch.

17. The method recited in claim 1 wherein the molding pressure used is between 250 and 6000 pounds to the square inch.

18. The method recited in claim 1 wherein the matrix is of a thermo-setting plastic.

19. The method recited in claim 1 wherein the matrix is of molded Bakelite.

20. 'Ihe method recited in claim 1 wherein the vulcanizing is done while molding pressure is applied.

2l. The method recited in claim 1 wherein the vulcanizing is done after the molding pressure has been released.

22. The method recited in claim 1 wherein the vulcanizing is done after removal of the object from the mold.

23. The method recited in claim 1 wherein the nller is sodium nitrate and the solvent therefor is hot water.

24. The method recited in claim 1 wherein the illler is dissolved in acid.

25. The method recited in claim 1 wherein the supporting web is removed by peeling.

26. The method recited in claim 1 wherein the supporting web is removed by dissolving.

27. The method recited in claim 1 wherein the coarse mix is applied to the coating before it is dry.

28. The method of making a molded resilient porous web, including the step of forming a laminated web of comminuted vulcanizable rubber containing a comminuted soluble solid tlller, the particle size of one outside layer of the web being finer than of other layers, and molding a printing face on the side having the ilner layer: the step of vulcanizing the rubber; and the step of removing the fiilr by dissolving.

29. The method recited in claim 28 wherein the rubber is a butadiene co-polymer.

30. The method recited in claim 28 wherein the ller is sodium nitrate.

31. The method recited in claim 28 wherein the ller is sodium nitrate and the solvent is water.

32. The method recited in claim 28 wherein the particles of the tlner layer will pass a screen of 325 mesh or more to the inch.

33. The method recited in claim 28 wherein the tlller is soluble in acids not aiecting the rubber.

34. The method recited in claim 28 wherein the molded product is bonded to a porous backing material.

35. 'Ihe method recited in claim 28 wherein the web after removal oi' theiiller is impregnated with ink.

36. The method recited in claim 28 wherein the web is placed in contact with a wick conductor of ink.

ROBERT G. CHOLLAR.

-JERTIFI GATE 0F CO RREC TI ON.

Patent No. 2,5h9,615. May 2.5, 19h14.

ROBERT G. CHOLLAR.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correctiones follows: Page 1, second column, vline 22, strike out the words "passing s. Screen of less than" and insert instead --snall enough to pass a screen of; line 25, strike out in size; iines 26 and 27., for "from less than 25 to lOO mesh to the inch in size" read --25 to 100 mesh to the inch or finern; page 2, second column, line )49, after "to'l insert --substantially--g and that the said Letters Patent should be read vdth this correction therein that the same may conform to the record of the case 1n the Patent Office.

signed and sealed this 8th day of August, A. n. 191m.

Leslie Frazer v(Seel) Acting Commissione: of {fes-.liften

Images