US3253540A - Method of printing - Google Patents

Description

May 31, 1966 K. G. LUSHER 3,253,540

METHOD OF PRINTING Filged April 19, 1963 5 Sheets-Sheet l ,QTTQRNEYS May 31, 1966 K. G. LUSHER 3,253,540

METHOD OF PRINTING 'Filed April 19, 1965 5 Sheets-Sheet 2 INVENTOR. KENNETH G. LuHE/zl ,ClrroRA/EVS May 31, 1966 K. G. I UsHl-:R

METHOD OF' PRINTING 5 Sheets-Sheet Z Filed April 19, 1963 1 N VENTOR, /fEN/VErH G. LujHE/z United States Patent O The present invention relates to a method of printing and more particularly to a method of forming a printing image for transfer to a surface to be printed.

In my copending, earlier Ifiled application Serial No. 242,229, filed December 4, 1962, now Patent No. 3,150,- 547, and in the earlier filed application of William H.

- Wood, Serial No. 242,230, yfiled December 4, 1962, both of said applications being assigned to the assignee of the instant invention, there have been disclosed various methods for the formation of an image to be printed upon a surface, the image being formed of printing particles transferred to the surface to be printed (preferably by electrostatic means), and cured thereon in any desired manner, such as by heating, vapor fusing, covering with a transparent coating, or the like.

As particularly disclosed in my own above-identified application, the particles are formed to the image to be printed by a silk screen process wherein the particles are superimposed upon and brushed or otherwise forced through a foraminous screen or the like onto an offset printing plate.

The present invention provides a method of image formation in which the printing particles are adhered to the screen, rather than being displaced therethrough.

More specifically, the present invention contemplates the utilization of a foraminous carrier element, such as a silk screen or the like, having an open image-defining pattern thereon. Conventional silk screening processes may be utilized to -form the open image-defining pattern; eg. the pattern may be photographically developed on the screen utilizing a conventional photo-sensitive gelatin or the pattern may be pierced or chemically etched in a metallic sheet or foil. In any event, the term screen is used generically herein to denote a foraminous carrier element having openings corresponding to and defining, preferably in mirror-image form, the pattern to be printed.

The screen, after its formation, is provided with apertures which are smaller than the particles to be printed. A plurality of randomly oriented printed particles are formed into a gaseous suspension, e.g. air-floated, and are directed against the surface of the foraminous screen by differential gaseous pressure. The gaseous medium, of course, passes freely through the screen, while the particles are screened out at the screen surface at locations corresponding to the location of the screen apertures. The thickness of the resultant particle layers can be easily regulated, e.g. by varying the concentration of the suspension, the suspension flow rate, or the time of exposure of the screen to the suspension. By maintaining the differential gaseous pressure, the particles are adhered to the screen surface until such time as they are transferred to the surface to be printed.

In a preferred embodiment of the invention, the screen is positioned adjacent a body of randomly oriented printing medium particles in a tray-like container, and a vacuum head or box is fitted to the screen and evacuated to create a vacuum at the screen openings. The pressure differential thus created between the screen and the supply body of particles will cause some of the particles `of the body to migrate through the screen surface, Since the particles are larger than the screen spacing, the particles will become adhered to the screen and will remain in place so long as the-vacuum is maintained. Thus, there Patented May 31, i966 is provided, at the screen surface, a plurality of printing particles oriented on the surface in accordance with the openings therein dening the pattern to be printed.

IFinally, the screen or foraminous surface bearing the particles at the openings therein is positioned adjacent the surface to be printed, and the particles are transferred to the surface to `be' printed in the same pattern `and in the same orientation as the particles existed at the screen. This transfer can be accomplished in several different ways, e.g. by electrically attracting the particles from the screen to the surface to be printed, by blowing the particles onto the surface to be printed, by contacting the particles with a heated surface to be printed so that the particles fuse to the surface, or in any other desired manner.

Additionally, multi-colored printing -can be accomplished by utilizing individual screens for each of the colors to be printed and individually transferring particles .from the individual screens to a composite screen, which serves as an offset medium from which the differently colored particles are transferred to the surface to be printed in any of the different ways set forth above.

It is, therefore, an important object 'of the present invention to provide a new and improved method of printing utilizing printing particles which are oriented into a desired pattern at a foraminous screen by creating a pressure differential between a body of the particles and the screen to transfer particles from the body to the Screen to define thereon the pattern to be printed.

Another important object of the present invention is to provide a method of printing wherein a `body of randomly oriented printing medium particlesand a foraminous screen having openings corresponding to the pattern to be printed are superimposed and the screen is evacuated to attract to and adhere at the screen a layer of the particles, the particle layer being subsequently transferred to and affixed on the article to be printed.

It is a still further object of this invention to provide a method of forming an image to be printed by transferring to and adhering at a foraminous transfer medium a pluarity of printing particles subjected to a pressure differential, maintaining the pressure differential while superimposing the transfer medium on the article to be printed, and `finally transferring the particles to the surface to be printed.

Yet another, and no less important, object of this invention is the provision of a method of making a multicolored image to be printed by attracting to and adhering at different foraminous surfaces the appropriately differently colored printing particles and sequentially transferring the differently colored particles to a common carrier element by evacuating the carrier element.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

On the drawings:

FIGURE 1 is a diagrammatic representation of an initial step of the present invention, utilizing a foraminous screen fitted with a vacuum head and superimposed over a body of printing particles;

FIGURE 2 is a view similar to FIGURE l illustrating the transfer of the printing particles to the screen by air floatation of the particles;

FIGURE 3 is a view illustrating the transfer ofthe particles from the screen to a surface to be printed by electrical means;

FIGURE 4 illustrates a modied method of the present invention wherein a continuous foraminous screen is utilized and the printing particles are tr-ansferred from 3 the screen to the surface to be printed by mechanical pressure alone;

FIGURES 5 through 9 illustrate the method of the present invention as adapted to the formation of multicolored printing images simultaneously transferred elec'- trostatically to the article to be printed from a composite offset image. v

Before explaining the present invention in detail, it 1s to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

As shown on the drawings:

In FIGURE 1, reference numeral refers generally to a foraminous carrier element comprising a screen 11 formed of Woven stainless steel wire or the like mounted in a surrounding, perimetric frame 12. Applied to the screen 11 is a conventional gelatin coating 13.

As explained in my earlier led applications, such screens are generally referred to as silk screens, although the screen element thereof may be formed of fine wire, such as stainless steel wire, or by punching, etching or otherwise forming small apertures in a metallic plate or the like. The screen 11 is coated with and invested within the non-metallic coating 13 which is substantially thicker than the thickness of the wire 11 and which is generally va gelatinous material, such as a bichromated gelatin applied to the metallic screen 11 as a solution and allowed to dry in the absence of light. The dried gelatinous rnaterial is sensitive to light, and the gelatin will become insoluble in water upon exposure to light. The light sensitive resultant screen 10 may have images readily reproduced thereon by various well known photographic techniques. In that embodiment of the invention illustrated in FIGURE l of the drawings, it will be seen that the screen 10 is provided with a medial, coating-free aperture 15.

In air-tight contact with the frame 12 of the screen 10 is a vacuum head indicated generally at 16 and having an interior air passage 17 connected to a suitable source of vacuum or reduced pressure, the evacuation of the space 17 being illustrated by the directional arrow 18. The evacuation of the space 17 encompassed by the head 16 will, of course, induce a current of air through the opening in the screen 10.

The screen 10 is superimposed over an open-topped tray or container 20 containing a supply of particulate printing medium 21 of the type described in my earlier iled application. Several specific particle compositions are disclosed in my earlier filed application and the earlier filed application of William H. Wood (both of which are above-identified), and it is unnecessary to repeat these compositions in the instant application.

However, it will be appreciated that the particle size of the particulate material 21 in the container 20 is greater than the openings of the Wire 11. Thus, by way of example, particles of the type and composition set forth in my earlier led application having a particle size of from 13 to 26 microns can be utilized in conjunction with a 325 by 325 mesh screen 11.

As illustrated in FIGURE 2 of the drawings, the continued evacuation of the space 17 will induce a draft of air upwardly through the screen opening 15 and particles from the container 20 will be air-floated upwardly against the undersurface of the screen to be deposited thereon in a layer indicated at 25. The air in which the particles are dispersed will pass freely into the vacuum head 16, while the particles will be screened out at the aperture 15. So long as the vacuum indicated by the directional arrow 18 is maintained, the layer 25 of the particles will remain in place. Further, it has been found that the longer the vacuum is maintained and the relative positions of the supply of particles 21 and the screen remains fixed, the thicker `the layer 25 will become. By varying the degree of evacuation of the vacuum head 16 and by varying the length of time that the relationship of FIG- URES 1 and 2 is maintained, the various thicknesses of particles can be built up on the undersurface of the screen 10.

After the desired layer 25 of particles has been built up upon the undersurface of the screen 10, the screen 10 and the container 20 are relatively moved, and the screen is positioned adjacent'a surface 30 to be printed. f

Where the surface being printed is non-conductive, e.g. a paper surface, the surface may be backed up by a conductive metallic plate 31 connected to one side of a high voltage source, as by lead line 32, the other side of the high voltage source, either A.C. or D.C.,.being connected by lead line 33 to the metallic screen 11. By applying a relatively high voltage, e.g. on the order of 200 to 20,000v

volts, across the space between the screen 11 and the conductive plate 31, the particle layer 25 adhered to the undersurface of the screen by the vacuum 18 will be transferred to and deposited upon the interposed surface 30 to be printed.

The electrical transfer of the particle layer 25 to the surface 30 is, of course, due to the fact that the particles at the screen 11 will pick up the charge of the screen and will be transferred to the surface 30 by virtue of the relative opposite polarity of the conductive plate 31. Depending upon the actual operating conditions, the vacuum 18 may be maintained during the electrostatic transfer, in which case the electrostatic attraction must be greater than the differential pressure urging the particles against the screen 11, or the vacuum may be interrupted during the electrostatic transfer. Subsequent to their transfer to the surface of the article 30, the particles are adhered thereto by techniques well known in the art, as above explained.

In that embodiment of the invention illustrated in FIG- URE 4 of the drawings, an endless, belt-type foraminous element 40 is utilized, this belt having openings therethrough defining the pattern or a mirror image of the pattern to be printed. The belt 40 is trained about a pair of guide rolls 41, 42, one of which is driven, to provide a lower effective horizontal reach 43 underlying a vacuum head 4S of the type heretofore described and evacuated as indicated by the directional arrow 46. The vacuum head 45 is continuously evacuated and serves to transfer to the undersurface of the reach 43 of the belt 40 printing particles from a supply 47 of such particles in a container or tray 48. The particles adhered to the undersurface of the belt reach 43 are indicated `generally at 49, such particles being oriented in conformity to the pattern of openings in the belt reach 43.

The surface to be printed preferably constitutes a web 50 trained about a pair of rolls 51 and traveling in the same direction as the belt reach 43, i.e. in the direction of directional arrows 53. The web 50 to be printed is heated to a temperature less than its kindling point by suitable means, as by a fuel fired burner emitting a llame 56 contacting that surface of the web 50 which is subsequently moved into facing relationships to the undersurface of the reach 43 of the belt 40.

The location of the upper roll 51 is such that the web 50 is in pressure contact with the particles 49 adhered to the undersurface of the web 43 and the vacuum head 45 is of such size and configuration that at the time of initial contact between the web 50 and the belt reach 43 the particles 49 are still subjected to the inuence of the vacuum indicated by the directional arrows 46.

Thus, the vacuum head 45 serves to adhere particles 49 from the supply 47 of such particles on the undersurface of the foraminous belt 40 and serves to retain these particles on the belt until, and preferably after, pressure contact exists between the particles 49 and the web or surface 50 to be printed. Since the web 50 is heated, as by the burner 55, the pressure and heat of contact between the particles 49 and the web 50 will effectively transfer the particles to the web 50.

In that embodiment of the invention illustrated in FIG- URES 5 through 9, substantially the same operations as performed in FIGURES 1 through 3 are repeated for different colors or particles.

More particularly, in FIGURE 5 of the drawings, the screen indicated generally at 60 is conveXo-concave in configuration and is secured to a vacuum head 61 which is evacuated, as at 62, so that particles 63 from a container 64 are adhered to the open portions of the screen surface, as at 65. Subsequently, the vacuum head 61 and the screen 60 bearing the adherent particles 65 are positioned immediately adjacent a second screen 66 carried by a separate Vacuum head 67, the screen 66 being concavo-conveX and of matching configuration to the screen 60 after the screens 60, 66 are juxtaposed, as illustrated in FIGURE 6, the vacuum in the head 61 is released and a Vacuum is applied to the head 67, as indicated by directional arrow 68 to transfer the particles 65 from the screen 60 to the screen 66. The screen 66 has openings 69 registering with the openings 65 in the screen 60 and additional nonregistering openings 70 therein.

A third screen 71 having a different aperture pattern therein defined by openings 76 and provided with a vacuum head 72 is evacuated, as indicated at 73, to transfer particles 74 of a different coloration from a different container 75 to the screen 71, as at 76. Preferably, the particles transferred to the screen 71, as at 76, are of a different coloration than the particles applied to the screen 60. After transfer of the particles from the screen 60 to the screen 66, the screen 60 is removed from its position over the screen 66, and the screen 71 is positioned in juxtaposition to the screen 66, as illustrated in FIG- URE 8. Upon now interrupting the vacuum in the vacuum head 72 while retaining the vacuum in the vacuum head 67, the particles 76 are transferred from the screen 71 to the screen 66.

Thus, the screen 66, of concavo-convex configuration, is provided with layers of particles 65 and 76 of different coloration. Finally, the screen 66 bearing the two different colors of particles is positioned adjacent the article to be printed, i.e. a glass container of generally cylindrical configuration, indicated generally at 80. By heating the surface of the glass article 80 to an elevated temperature (as disclosed in the above-identified application of William H. Wood) and impressing a high volta-ge on the screen 66 and the surface of the article 80, the differently colored particles 65, 76 can be readily electrically transferred at the same time to the surface to be printed.

Thus, the embodiment of the invention illustrated in FIGURES 5 through 9 provides a means for separately forming partial images of different coloration (at screens 6 60, 71), transferring these partial images to a composite screen 66 to form a complete multi-color image, and then concurrently imposing the multi-color image particles from the screen 66 onto the article 80.

I claim:

1. In a method of printing utilizing a particulate printing medium, the steps of superimposing separate supplies of randomly oriented printing medium particles of distinct coloration and separate foraminous screens with apertured masks to define different open patterns thereon, respectively, creating a vacuum at each said open screen pattern to attract to and adhere at said screen a layer of said particles from the corresponding supply of particles, thus forming a plurality of differently colored partial pattern layers at the separate screens, sequentially transferring the partial pattern layers in registry with each other to a single composite evacuated screen masked to define the complete pattern in a layer upon said composite screen, and finally transferring said complete pattern layer from said composite screen to a surface to be printed.

2. In a method of printing a desired multi-colored imageutilizing printing medium particles of different colors, the steps of superimposing upon separate supplies of randomly oriented printing medium particles of distinct coloration a plurality of separate foraminous screens each having an apertured mask to define different open patterns thereon corresponding, respectively, to different portions of the image to be printed, creating a vacuum at each said open `screen pattern to attract to and adhere at said screen a layer of particles from the corresponding supply of particles, thus forming a plurality of differently colored partial pattern layers on the separate screens, separately l transferring the individual partial pattern layers to a single composite evacuated screen in Iregistry with each other to define the complete multicolor pattern to be printed, and finally electrically transferring said complete multicolored pattern from said composite screen to a surface to form said desired multicolor image upon said surface.

lll

References Cited by the Examiner UNITED STATES PATENTS 1,668,322 5/1928 Kessler 101-116 X 2,239,619 4/1941 Murgatroyd et al. 101-129 X 2,525,135 10/1950 Huff 210-404 2,590,321 3/1952 Huebner. 2,787,556 4/ 1957 Haas. 3,093,039 6/ 1963 Rheinfrank.

ROBERT E. PULFREY, Primary Examiner'.

WILLIAM B. PENN, Examiner.

PAUL R. WOODS, Assistant Examiner.

Claims (1)

1. IN A METHOD OF PRINTING UTILIZING A PARTICULATE PRINTING MEDIUM, THE STEPS OF SUPERIMPOSING SEPARATE SUPPLIES OF RANDOMLY ORIENTED PRINTING MEDIUM PARTICLES OF DISTINCT COLORATION AND SEPARATE FORAMINOUS SCREENS WITH APERTURED MASKS TO DEFINE DIFFERENT OPEN PATTERNS THEREON, RESPECTIVELY, CREATING A VACUUM AT EACH SAID OPEN SCREEN PATTERN TO ATTRACT TO AND ADHERE AT SAID SCREEN A LAYER OF SAID PARTICLES FROM THE CORRESPONDING SUPPLY OF PARTICLES, THUS FORMING A PLURALITY OF DIFFERENTLY COLORED PARTIAL PATTERN LAYERS AT THE SEPARATE SCREENS, SEQUENTIALLY TRANSFERRING THE PARTIAL PATTERN LAYERS IN REGISTRY WITH EACH OTHER TO A SINGLE COMPOSITE EVACUATED SCREEN MASKED TO DEFINE THE COMPLETE PATTERN IN A LAYER UPON SAID COMPOSITE SCREEN, AND FINALLY TRANSFERRING SAID COMPLETE PATTERN LAYER FROM SAID COMPOSITE SCREEN TO A SURFACE TO BE PRINTED.

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