US3110919A - Fluid spreader - Google Patents

Description

Nov. 19; 1963 D. w. BARNBY FLUID SPREADER Filed April 12, 1961 I N VEN TOR. Eon/440 #59246) SPENCER L.- BLAYL w. A. SCHA/CH United States Patent 3,110,919 FLUTE STREADER Donald W. Earnhy, Woodbury, N..l., assignor to Owenslilinois Glass Company, a corporation of (lhio Filed Apr. 12, 1961, Ser. No. 102,436 1 Qlaim. (ill. 15236) This invention relates generally to fluid spreaders and more particularly to an apparatus for use in preparing stencil screens.

Stencil screens for the application of inks, colors, plastisols and the like are well known. They are woven with fine metal, silk, nylon or other similar materials to a fine mesh size, for example, 150 to 175 meshes per linear inch. Such screens are prepared for printing by closing all of the interstices between the wires or threads except those which define thedesign which is intended to be printed. The design is printed on a surface by forcing semi-fluid or pasty material through the remaining open meshes by means of a squeegee.

The screens are prepared by coating the entire screen with a film of a photo-sensitive material which is dried in complete darkness and then exposed to strong light through a positive photographic film of the desired design to be printed. After exposure the film protected by the design on the photograph remains soluble and may be washed from the screen with a liquid, usually water, thus forming the open meshes of the screen. The remaining portions of the film are rendered insoluble by the actinic rays, thus forming the closed screen meshes.

In the use of these screens for stenciling, the particular thickness of the photo-sensitive.rnaterial is an important factor because the amount of ink, etc. transferred to the pintinrg surface is normally determined by the thickness of the photo-sensitive material on the screen. This is due to the fact that the squeegee fills to the brim the open meshes and thus when the screen is removed the ink will remain on the printed surface. The deeper the cavities, the greater will be the deposit of ink, etc.

In the prior art, it was customary to spread the photosensitive material over the screen by hand or with a scraper or other similar device. This produced thick and thin portions in the screen with the result that an uneven pattern was produced which tended to have varying and inaccurate shades of color and color gradations. In addition, the screen or other surface to be coated in many instances is of an uneven contour with the result that with presently available equipment, the fluid mate-rial or photo-sensitive emulsion is not evenly applied. This obviously lowers the quality of the coated article or the article printed by such a screen and often results in rejection of the article.

It is therefore an object of the present invention to provide a stencil screen which has a uniform depth of photo-sensitive material on its surface. Another object of this invention is to provide an apparatus which will uniformly apply the photo-sensitive material to the stencil screen.

A further object of this invention is to provide a simple and inexpensive apparatus for applying a fluid material or coating to a non-flat surface.

Another object of this invention is to provide an apparatus for applying photo-sensitive materials to a stencil screen which apparatus readily adapts itself to irregular surfaces of the screen.

These and other objects of this invention will become apparent from a reading of the following detailed description taken in conjunction with the drawing in which:

FIGURE 1 is a top plan view of the upper portion "ice of a stencil screen with a diagrammatic illustration of the apparatus of my invention;

FlGURE 2 is a longitudinal view partly in section taken along lines 22 of FIGURE 1 showing the apparatus of this invention diagrammatically in operating position against the stencil screen;

FIGURE 3 is a fragmentary perspective view partly in section of the photo-sensitive material applying apparatus of my invention; and

FIGURE 4 is a perspective view partly in section of another embodiment of my invention.

in brief, the apparatus embodying my invention comprises a support member, a flexible helically wound spring mounted in said member, and a resilient backing means in the support member for the spring. A portion of the periphery of said spring extends beyond the support member and is adapted to apply said material to said screen. The axis of the spring is transverse to the direction of movement of this apparatus when it is being used.

Referring now to the drawing, reference numeral 10 denotes a metal screen, the surface of which is to receive a coating of a photo-sensitive material 12. In the illustrated embodiment the screen is constructed of fine wires of stainless steel. it should be understood that the screen material may also be nylon, silk or other suitable material, the selection of which depends upon the nature of the printing fluid and desires of the operator.

One or more coatings of the photo-sensitive material 12 may be applied to the screen 10. Their number, composition and drying times are conventional and form no part of this invention.

The screen it is stretched tight on a frame 11, which frame serves as a carrier for the screen when it is used on a stencil screen type printing machine. Suitable clamping means (not shown) are used to retain the screen 16.

The photo-sensitive material 12 is spread over the metal screen 10 by the photo-sensitive material applying apparatus or coater 13 which will be described more fully hereinafter. The coater 13 is illustrated as being carried over md in contact with the screen 19 by a support 1d. If desired, the coater 13 may also be hand operated which normally is the method of operation. The support 14 has been illustrated diagrammatically inasmuch as the same forums no part of this invention. If hand operated, the screen could be tilted or retained flat, as illustrated, and the operator would merely take the place of the support 14. The material 12 is shown as being applied to the underside of the screen it). It should be understood that the material 12 is also applied to the top side of the screen it by merely inverting the screen.

The coater l3 embodying my invention is best illustrated in FIGURE 3 and a second embodiment of the same is shown in FIGURE 4. As illustrated in FIGURE 3, it comprises a support member 15 which may be constructed of any suitable material such as steel or cast iron. Specifically this member comprises an elongated rectangular sheet metal bent along longitudinal lines to provide a member of generally inverted U-shaped crosssection. The support member 15 includes a longitudinal channel 16 consisting of a top 17 and side walls 18. The lower margin of each of the latter having narrow inwardly directed flanges '20. A pair of opposed parallel flat arms 21 depend from the inner margin of said flanges 20.

The lower end of said member 15 is, of course, opened to receive therein, a helically wound spring 22. The is held in place by a pin 23 which passes through the side wall 19 of the member 15 and the spring has a 3 working portion or edge 22a for projecting below the free ends of the arms 21 for engagement with the stencil screen 16.

The spring 22. is closely and evenly wound so as to form a flexible but steady Working edge 22a. The longitudinal axis of the spring 2 2 is parallel to the long axis of the support member and transverse to the direction of movement of the center 2'13 when the same is being used. The pin 23 holds the spring in the support member but permits relatively free vertical movement therein. A resilient or spongy backing member 24 is slidably received between the arms 31 of the support member 15 and is immediately adjacent to the upper edge of the spring 22. Through a pin and slot connection between the arms 21 and the backing member 24, the latter is permitted to float vertically throughout its length or in any localized area as may be required by irregularities in the surface being coated and transmitted through the spring 22.

Such pin and slot connection comprises a longitudinal series of vertical transverse slots 25 in the backing member 24 and corresponding bolts 26 extending through holes in the arms 21 and the slots 25 in said backing member. Nuts (not shown) are threaded on one end of the bolts 26, thus the backing member 24 is secured against accidental displacement. The slots 25 are formed in such a fashion that the backing member 24 is permitted relatively free vertical movement in relation to bolts 26.

For the purpose of yieldingly urging the backing member 24 and spring 22 downwardly relative to the supporting arms 21, a resilient backing means 27 is carried by the support member 15. This backing may assume various forms and preferably is housed within the aforementioned channel 16 of the upper part of the support member. The backing means 27 may be constructed of any suitable solid resilient or spongy substance such as sponge rubber or as shown may be an elongated sealed hollow bladder of suitable deformable material such as rubber. The hollow bladder may be partially or completely filled with a fluid such as air or .water. This resilient backing means 27 for the backing member 24 always maintains the backing member 24 and the spring 22 under substantially equal pressure and in equal contact with the screen irrespective of the variations and contour of the screen. Such will insure that the photo-sensitive material will be applied evenly and to the desired thickness on the screen.

In the illustrated embodiment, especially FIGURE 3, the spring 22 and backing member 24 are shown in the position which they will assume upon being placed on the screen 10. Thus the upper portion of backing member 24 comes into contact with the backing means 27 and yieldably deforms the same in the manner shown. This provides the floating pressure which insures that an even application of photo-sensitive material is applied to metal screen 10. When the coater 13 is raised vertically to a non-operating position, the backing member 24 may move out of contact with the backing means 27. The upper ends of slots 25 then come to rest against bolt housings (not shown) thereby preventing complete removal of the backing member 24 from the coater 13.

It is preferred but not necessary that a plurality of vertical parallel slots 3t} be provided in the body of the backing member 24. These slots 30 extend from the bottom of the backing member 24 to within a short distance of the upper end of the same. These slots improve the vertical flexibility of backing member 24-.

The above described coater was utilized to spread a photo-sensitive composition over a stainless steel screen. This coater reduced by approximately one-half the variations in thickness of the coating over that which had been heretofore obtained by the conventional methods.

Referring now to FEGURE 4 wherein an alternate embodiment of this invention is illustrated, reference number 31 denotes a support member which may be constructed of any suitable material such as steel or cast iron. This member comprises an elongated rectangular sheet metal bent along longitudinal lines to provide a member of generally inverted U-shaped cross-section. It includes a longitudinal channel 32 consisting of a top 33 and side walls 34. The lower margin of each of the latter having inwardly directed flanges 35.

The lower end of said support member 31 is open to receive therein a helically wound spring 36 similar to the spring 2?; in FIGURE 3. The spring is held in place by the inwardly directed flanges 35 and has a working portion or edge 37 which projects below the flanges 35 for engagement with the screen ill. The flanges 35 are formed in such a fashion that the spring 36 is permitted to float vertically throughout its length or in any localized area as may be required by irregularities in the screen. They also secure the spring 36 in the support member 31 against accidental displacement.

For the purpose of yieldingly urging the spring 36 downwardly relative to the side walls 34 and against the flanges 35, a resilient backing means 38 is carried by the support member 31. The backing may assume various forms and preferably is housed within the aforementioned channel 32 or" the upper part of the support member 31. This backing means is constructed of the same material and in the same manner as the backing means 2 7 illustrated in FIGURE 3. it also operates in the same manner and performs the same function as that backing means except that it is in direct contact with the spring 36 rather than in contact with the backing member 24.

If only a substantially uniform coating is desired, the springs 22 and 37 may be eliminated. in their place a flexible bar of suitable material such as hard rubber or a plastic material may be provided. The flexible bar would then be provided with a series of grooves around its circumference similar to the helically wound spring. The flexibility of the bars will apply a substantially uniform coating, but the uniformity of the coating may be less than that obtainable by the utilization of the respective springs hereinbefore described.

It can thus be seen from the foregoing that this new and novel coater will insure that a photo-sensitive material is evenly applied to the surface of the stencil screen irrespective of the variation in the contour of the same. This device may also be used to spread \a fluid material over any desired surface wherein an even coating is desired.

It will also be apparent that various modifications may be made in this invention Without departing from the spirit and scope as defined in the appended claim.

I claim:

An apparatus for applying photo-sensitive materials to a screen for use with a stencil screen type printing machine comprising a hollow rectangular support member, a flexible helically 'Wound spring mounted in said member, the axis of said spring being parallel to the longitudinal axis of said support member, a resilient intermediate backing means for said spring received within a portion of said support member, said intermediate backing means having a plurality of vertical parallel slots therein adjacent said spring, means for mounting said intermediate backing means for vertical movement in said support member, a portion of the periphery of said spring extending beyond said member and adapted to apply said material to said screen, and a fluid backing means-re-- ceived in said support member for said intermediate backing means.

References Cited in the file of this patent UNITED STATES PATENTS 1,566,358 White Dec. 22, 1925 1,956,561 Coates May 1, 1934 3,029,779 Hornbostel Apr. 17,. 1962

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