US2404454A - Beading projection screens - Google Patents

Description

July 23, 1946. J. H. OWENS 2,404,454

BEADING PROJECTION SCREENS Filed Jan. 8, 1943 Ill lhwentor James Owens (Ittorneg Patented July 23,1946

BEADING, PROJECTION SCREENS 'James H. Owens, Camden, N. J'., assignor'to Radio Corporation of America, a corporation of Delaware Application January 8, 1943, Serial No. 411,737.-

1 This invention relates to an improved method of and apparatus for applying glass beads to projection screens, particularly the type of projec tion screens used in conjunction with 'the'projection of motion pictures. with sound.

The invention involves the provision of a .rotatable drum which is adapted to support" the screen during the operations thereon. in con- I junction with means for applyin adhesive and a novel device for distributing the beads over the adhesive surface of the screen.

One object of the invention is to. provide .an improved apparatus for applying beads to projection screens.

Another object of the invention is to provide an improved method of and apparatus for applying beads to the adhesive surface of a screen.

Another object of the invention is toprovide an improved apparatus for distributing adhesive uniformly over the surface of the screen.

Another object of the invention is to provide an improved apparatus for distributing beads evenly over the surface of a projection screen.

Another object of the invention is to Provide an improved method and apparatus for embedding the beads to a uniform depth with the adhesive or reflecting surface material on the face of the screen.

Another object of the invention is to allow the use of the smallest size beads, that is, beads having a smaller diameter than those in common use.

Another object of the invention is to provide a method and apparatus for holding the screen in a uniform plane or shape during the entire operation of applying adhesive, applying beads, and removing excess beads.

Another object of my invention is to provide a method and means for immediately removing the excess beads almost instantly after they have been deposited on the screen.

Another object of the invention is to provide an improved method of and apparatus for causing beads to adhere more securely to the surface of the screen than has heretofore been possible.

Other and incidental objects of the invention will be apparent from a reading of the following specification and an inspection of the accompanying drawing, in which:

The single figure of drawing is an end view, partly in section, of my improved apparatus and serves to illustrate the manner of performance of the method.

In the apparatus illustrated, the frame Ill supports the drum H, which may be a hollow sheet metal drum, through the bearings I4 and the 2 Claims. (01. 9118') 2 trunnions I5. The drum should be sufficiently large in both length and diameter to'support' the largest screen to be treated without folding or overlapping. The drum II is provided with appropriate means l2 for securing the screen l3 thereto under sufficient tension to keepit smooth.

An appropriate spray-gun I6 is provided for applying the adhesive, which is referably an appropriate clear paint or clear lacquer or paint or lacquer pigmented with titanium dioxide. The type of vehicle used depends upon the speed with which the operation is to beperformed, the flexibility required in the finished. screen, andsimilar factors." The spray gun I6 maybe supported upon the track I! byan appropriate carriage 18; for manipulation in either of the several fashions hereinafter described.

An appropriate trough or hopper I9 is provided above the drum II. The trough l9 may be supported from the frame I!) by appropriate brackets 20. An appropriate slot is provided at 2| to permit the beads 24 to flow from the trough. This slit may be of fixed dimensions, or it may be made adjustable. For example, the front side of the trough [9 may be made to slide up or down to adjust the size of the opening, or other equivaoutlet of the trough l9, and sometimes emerging through the slot in bunches. Both of these effects are eliminated by heating the beads and, in addition, the heated beads adhere more firmly to the surface of the screen. The improved ads herence of the heads is apparently due to several different effects: The dry surface of the beads accepts the adhesive more readily than if it had a layer of adsorbed moisture, the warm beads soften the adhesive when they strike it and thereby become more firmly lodged therein, and the warmth of the beads causes the surrounding adhesive to dry quite rapidly thereby preventing their displacement.

If so desired, the beads may be heated separately, but the heater in the trough presents advantages, particularly'in damp weather.

A baflle board 22 is provided, appropriately supported on the frame ID. This baflle board is located at such an angle that the beads emerging from the slot 2| strike it and bounce off onto the surface of the screen. This serves two purposes. If there are any clumps Of beads they are broken up by the impact, and the beads are caused to strike the screen surface practically perpendicularly at a higher velocity than if they were merely poured thereon from the trough.

The beads which :do, not adhere to the screen fall into the trough 26, whence they may be re moved and replaced in the trough l9. beadswill, of course, tendto bounce, and these Some V are caught by the screen 25, which may be of 7 any appropriate material, such as cloth, for ex:

ample, and caused to fall into the trough 26. In the operation of heading a screen the screen is first stretched on the drum and secured at I2 as above described. The adhesive paint is then applied by the spray gun l6. Starting at one end of the screen the paint may be applied in a single stripe longitudinally of the drum, the drum then rotated the proper amount, a second stripe applied, and so on until the entire screen is cov-, ered. Alternatively; the drum may be rotated continuously whilethe spray-gun is moved slowly along. Either of these methods will provide a sufliciently uniform coatingv if properl used, but I prefer the method first described for the reason that the portion of the drum. not protected by the screen does not become smeared with ad hesive and the uniformity of the coating is less afiected by air currents. i 1

After the adhesive coating has been applied 7 and, if. necessary, beenpermitted to dry to an appropriate tacky consistency, the beads are ap'-' plied; The application of the beads i vstarted further drying.

Having now described my invention, I claim: 1. Apparatus for delivering beads in a uniform spray to an adhesive-surfaced projection screen comprising a trough for supplying the beads, said trough having an extending lip and a slot adjacent thereto to flow the beads over said lip,

and a baflie mounted in spaced relation with respect to said trough atan angle to the path of beads flowing from said -lip for redirecting said beads in a uniform spray'to the projection screen. 2.'Apparatus for making beaded projection screens including. a drum having an axis of rotation, means for supporting the screen 'upon the outer surface of said drum,'spray means for applying. an adhesive coating, to'the, screen supported'on the drum, a trough havinga slot and an extending lip for uniformly supplying beads along a path'substantially parallel to a tangent to the drum, a baffle mounted in aplane substantially normal to said tangent inthe path ofsaid beads for redistributing said beadsanddirecting them into a path substantially radial to said drum, and means for rotatingsaid drum. l

] JAMES owans.-

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