US 3359663 A
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Dec. 26, 1967 J. A. BLACK STENCIL SCREEN FRAME Filed Feb. 23, 1967 n/I/I 1N VENTOR. /4/766 19. 3146/ United States Patent 3,359,663 STENCIL SCREEN FRAME James A. Black, 13700 Sparta NW., Kent City, Mich. 49330 Filed Feb. 23, 1967, Ser. No. 617,886 1 Claim. (Cl. 38-10291) ABSTRACT OF THE DISCLOSURE A stencil screen frame assembly having elongated, interfitting and interconnected bars and channels forming peripheral screen clamping means, adjustably fitted within and secured to a peripheral rigid channel support, in a manner to stretch and secure a stencil screen over an upwardly projecting planar edge surface of the support.
Background of the invention This invention relates to a ste'ncil screen assembly for stencil printing, and more particularly to a multiple component stencil screen assembly having positive holding, controlled tensioning action on a stencil screen.
Prior art stencil screen frames largely employ a rigid peripheral frame member having a groove in its surface into which the screen periphery is depressed by a rubber ring squeezed into the groove. The amount of tension put on the screen is difiicult to control. Also, the rubber ring sometimes pops out of the groove, allowing the screen to slip and become slack. Both factors constitute significant disadvantages, particularly in trying to maintain accurate registry. Variations of such constructions have similar or other disadvantages.
Summary of the invention It is an object of this invention to provide a stencil screen frame assembly that (a) has positive screen holding action, eliminating possible slippage of the stencil screen, (b) has controlled, adjustable screen tensioning capacity, (0) has a relatively simple structure capable of relatively inexpensive manufacture, and (d) is simple to employ, assemble, and disassemble. Additional objects and advantages will become apparent upon studying the following specification in conjunction with the drawings.
The assembly, briefly, includes a rigid peripheral screen support having a co-planar surface over which the screen is tensioned, and screen periphery positive clamping means secured to the support and adjustable with respect to the support to effect controlled tension over the coplanar surface.
Drawing FIG. 1 is a plan view of the novel stencil screen frame assembly, without the screen attached;
FIG. 2 is a sectional enlarged view of a portion of the apparatus in FIG. 1 taken on plane II-II;
FIG. 3 is an enlarged sectional view taken on plane IIIIII of FIG. 1; and
FIG. 4 is a fragmentary enlarged perspective view of the portion of the apparatus in FIG. 1.
Detailed description The complete stencil screen frame assembly basically includes a rigid peripheral support frame member 12, and clamping means 14. Clamping means 14 includes a plurality of elongated interfitting channel members 16, and a plurality of elongated bar members 18, with interfitting connectors 20 securing clamping members 16 and 18 together. A plurality of connectors 22 secures the clamping means in an adjustable fashion to support 12.
More specifically, rigid peripheral support member 12,
normally of metal, is a channel shaped member in cross section, including a bottom 12a, and side walls, specifically inner side wall 12b and outer side wall 12c, both integrally connected with bottom 12a. The upper edge portion 12b of peripherally inner side wall 12b and outer side wall 120, both integrally connected with bottom 12a. The upper edge portion 12b of peripherally inner side wall 12b includes a surface area in one plane around member 12 for engaging a stencil screen 26 secured to the frame assembly.
Stencil screen 26 may be made of any of conventionally employed materials, including metal, polymeric materials, or the equivalent, woven in a pattern to have a porous construction. It is provided with a desired pattern by conventional coating techniques, to block out certain areas, and leave certain other areas porous in a desired print pattern. The screen has suflicient flexibility to bend on the assembly.
The height of wall 12b, or expressed in other terms, the depth of the slot or channel in channel member 12 is substantially larger than the height of clamping means 14, so that, by controlla'bly pulling the clamping means downwardly with respect to upper edge 12d, increased tension is provided on screen 26.
The elongated, channel shaped, outer members 16 of clamping means 14, along all peripheral edges of the assembly, have an inner U-shaped configuration matching that of the outer configuration of elongated bar elements 18 which slidably fit there within, with a small space being left between these members to receive the peripheral edge of screen 26. A plurality of fasteners such as threaded studs 20 are threadably interconnected with member 18 through openings in the base of member 16, so that the periphery of the screen can be tightly and positively secured between these members in the manner illustrated in FIG. 2. (For convenience, members 20 are shown in FIG. 1 as small open circles, while fastener members 22 are shown in dark circles for diiferentiation therebetween.) The enlarged heads of bolts 20 may be recessed into either member 16 or member 12 to allow them to be tightly interfitted, as by having countersink recesses 12c as in FIG. 2.
The plurality of fastener members 22 extend through openings 12 in the base of 12a of frame 12 to secure clamping means 14 to member 12. In FIG. 3, clamping means 14 is shown pulled into engagement with the bottom of channel 12, applying maximum tension to screen 26. In actual use, the tension on screen 26 can be varied Widely merely by adjusting the plurality of bolts 22, to pull it a varied amount toward the bottom of channel 12. It will be noted that, in the preferred construction shown, the width of the channel in member 12 is substantially greater than the width of clamping means 14. Preferably, the openings 12 for adjusting bolts 22 are provided immediately adjacent the peripheral inner wall 12b so that the wall of member 16 of the clamping means will engage and be retained in sliding relationship with wall 12b for stability and vertical alignment of the clamping means when applying increased tension on screen 26.
Manufacture of the assembly is relatively inexpensive since bar members 18 can be cut from bar stock, drilled and tapped, members 16 can be severed from extruded channel stock and drilled, and members 12 can be formed by cutting extruded channel stock on the diagonal, drilling and countersinking, and welding the corners together.
Use of the novel assembly, attaching, or removing a stencil screen are also relatively simple. Specifically, to attach a selected stencil screen to the frame assembly, first the peripheral edges of the stencil screen are secured to the clamping means by pressing the screen down between members 18 and 16 with insertion of members 18 into members 16-, then threading fasteners 20 between the members to tighten and lock the screen positively. Then, the plurality of clamping means 14 are inserted into the sides of channel member 12, and adjustable securing fasteners 22 are threadably engaged through the two channels and into the bar members. By adjusting members 22, the tension applied to the stencil screen is controlled, to place and maintain it in a controlled co-planar relationship for optimum printing action and accurate registry. The frame is then mounted to suitable clamping means (not shown) on a printing mechanism, for traversing of the screen by a typical squeegee assembly. It will be realized that, although the frame assembly is shown in an upright position, it can be inverted, or used in other- Wise oriented positions, depending upon the equipment with which it is employed.
It is conceivable that certain minor deviations in construction may be employed within the concept of the invention, and hence, the invention is intended to be limited only by the scope of the appended claim, and the reasonable equivalents thereto.
A stencil screen frame assembly comprising: rigid peripheral support means configurated to form a central open area. including peripheral surface means defining a plane of screen support and a peripheral channel opening toward said surface; screen periphery clamping means in said peripheral channel comprising closely interfitting elongated bars and elongated channels secured together by removable fasteners for positively clamping the screen therebetween whether or not the screen is under tension; and threaded members extending between said peripheral channel and said clamping means in a manner to forcefully shift said clamping means away from said plane to apply controlled tension to the screen.
References Cited UNITED STATES PATENTS 1,895,309 1/1933 Boomershine 38102.91 3,255,540 6/1966 Gilman 38-10291 FOREIGN PATENTS 519,040 4/1953 Belgium. 171,104 8/ 1934 Switzerland.
PATRICK D. LAWSON, Primary Examiner.