Picture Screen Roller Fabric Attachment

Abstract

A projection screen having a spring roller with a fabric-locking groove comprised of opposed side walls stepped on the roller periphery to the thickness of the fabric for producing safe mounting and flat hanging of picture surfaces, the side walls of which groove outwardly converge on a gap in the roller periphery of width equal to about twice the thickness of the screen fabric forming an inwardly-bent, wedging channel for locking on a metal strip clamped to the inner edge of the fabric screen and inserted therein so that the more the fabric is pulled, the tighter and more uniformly the screen will be held and the flatter the fabric will hang during use.

Description

BACKGROUND OF THE INVENTION

The spring-loaded roller on which a picture screen fabric sheet is wound almost invariably has been made of wood or hollow metal tube. Accordingly, the inner edge of the screen fabric has been attached by staples to the periphery of the wood roller on a recessed ledge running along the roller length at a depth equal to the thickness of the screen fabric. This method of attachment has not been too secure in the safe mounting nor too flat in the hanging of picture surfaces. When color slides or film are projected on a screen surface, it should be smooth and taut and hang flat without unsightly deformations in order to present a clear, undistorted picture.

In order to have the picture surface hang flat from a hollow metal tube roller, clips, keys, keepers and snap-in bars in conjunction with fabric-locking grooves have been used. Hartshorn, U.S. Pat. No. 444,832, shows a snap-in bar in a fabric-locking groove arrangement which suffers from the disadvantage that as an attachment, it is not secure. Kampas, U.S. Pat. No. 1,807,535, shows a keeper for clamping on the end of the fabric slidably installed in the fabric-locking groove which differs from the attachment of the present invention in the absence of a wedging action, which makes the attachment more secure the tighter it is pulled. Yeates, U.S. Pat. No. 1,834,669, shows a fabric groove with interlocking key which lacks the positive lock-up feature that is characteristic of this invention. Anderson, U.S. Pat. No. 3,018,824, shows a clip arrangement for attachment of the fabric to the roller which is complicated and expensive to assemble.

There is thus a need for an improved roller for a roll-up projection screen which is low in cost and without a substantial hanging deformation of the viewing surface of the screen, and which is easily replaceable. Also, it was to overcome the foregoing described deficiencies that the present invention was conceived.

SUMMARY OF THE INVENTION

The invention relates to projection screens of the type which, when not in use, are stored would up on a roller. One essential concept of this invention involves a metallic tubular roller formed from a single rectangular flat piece of heavy gauge sheet metal containing a screen fabric locking groove and a stepped portion adjacent one side of the groove to substantially eliminate hanging deformations in the viewing surface of the screen and give a secure and safe mounting of the screen. The groove is of inwardly-bent, channel-shaped cross-section having side walls disposed inwardly of the roller periphery but in outwardly-converging relation running the full length of the roller for locking on and wedging in a folded metal strip clamped along the full length of the inner edge of the screen fabric which is inserted in the groove. Diametrically opposite the groove, the free edges of the tube are integrally formed by an outwardly-extending male tongue and female groove locking joint.

It is thus an object of this invention to provide an improved low-cost roller for a roll-up projection screen which is formed from a single rectangular flat piece of heavy gauge metal containing a screen fabric locking groove and a stepped portion adjacent one side of the groove, whereby to substantially reduce hanging deformation in the viewing surface of the screen when in use.

Other objects and important features of the invention will be apparent from a study of the following specification taken with the drawings, which together describe and illustrate a specific embodiment of the invention, and what is now considered to be the best mode of practicing the principles thereof. Other embodiments may be suggested to those having the benefit of the teachings herein, and such other embodiments are intended to be reserved especially as they fall within the scope and spirit of the subjoined claims.

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of this invention is shown in the accompanying drawings, in which:

FIG. 1 is a reduced, perspective view of a slide and movie projection screen incorporating the present invention;

FIG. 2 is an enlarged transverse section substantially taken on the line 2--2 of FIG. 1 but showing the several convolutions of successive layers of screen fabric wound around the roller in rolled-up position;

FIG. 3 is an enlarged fragmented section of the fabric groove in the spring roller and illustrating the locking of the fabric on the folded metal strip;

FIG. 4 is an enlarged transverse section of the roller showing the fabric unwound from the roller and extended for use; and

FIG. 5 is an enlarged fragmented perspective view illustrating the method of assembly of the roller fabric attachment and showing one of the end plugs.

DESCRIPTION OF THE PREFERRED EMBODIMENT

This invention concerns the design and construction of slide and movie projection screen which are designated in general by the reference numeral 10 on FIG. 1 in which the housing or case 11 carries projection screen fabric 12 attached to and would up on roller 13 under the usual spring tension (the spring not being shown) in successive layers 14 for storage. The fabric 12 extends out slot 15 in case 11 drawn by slat 31 during use. As clearly shown in the drawing, the screen fabric 12 has opposite front and back faces, vertical side edges, an outer edge secured to suspension bar 31 and an inner edge secured to locking strip 25, as described more fully below.

Eccentric hollow spring roller 13 incorporates a fabric locking groove 16 extending within the interior of the roller having outwardly converging side walls 17 and 28, of which wall 17 is radially stepped below wall 18 an amount equal to the thickness of the fabric adjacent where the groove opens to roller periphery walls 13' and 13", respectively. Radius R of roller peripheral wall 13" in FIG. 3 differs from radius [R-(t/2)] of roller peripheral wall 13' by an amount equal to one-half the fabric thickness t/2 and each of these radii are centered on a common diameter of roller 13 passing through groove 16 separated by an amount equal to one-half the fabric thickness t/2 (about 0.008 inches). Translating in figures, the thickness of the fabric t is preferably 0.016 inches while the radius R is preferably 0.689 inches, and the radius [R-(t/2)] is preferably 0.681.

Tubular shaped roller 13 incorporating fabric-locking groove 16 is formed from a single rectangular flat sheet of heavy gauge metal (about 0.021 inches) having first and second sides 19 and 19', first and second edges 19a and 19a', and a first end 20 and a second end (not shown). Edges 19a and 19a' of the rectangular sheet are formed tongue and groove in a conventional manner so that upon circumferentially extending side 19 along radius [R-(t/2)] of peripheral wall 13' and side 19' along radius R of wall 13" (and side 19') to meet on the far side of the roller from groove 16 according to the geometry of FIG. 3, there engaging flush lock seam joint 21 so formed at the juncture of the two sides circumferentially extended, and there closing the open tubular section the structural integrity of the tubular form of roller 13 as shown in FIG. 5 is completed. The seam 21 lies diametrically opposite the groove 16.

Fabric groove 16 in FIG. 3 has outwardly converging side walls 17 and 18 terminating in gap 27 at roller periphery 13' and 13", respectively, with side wall 19 stepped inwardly of side wall 19' adjacent of gap 27 by an amount equal to the thickness t of the fabric. The width of the gap is equal to about twice the thickness of the fabric. Side wall 17 is smoothly faired into juncture with periphery 13' of roller 13 by external radius r.sub.s (preferably about 0.052 inches) with side wall 18 similarly smoothly faired into periphery 13". Both side walls 17 and 18 are inwardly bent to internal radii r.sub.a (preferably about 0.031 inches) at their junctures with base 24 and are connected thereacross by base 24 forming fabric-locking groove 16. Folded metal strip 25 clamped along inner edge 26 of fabric 12 wedges in fabric-locking groove 16 attaching the fabric to the roller with uniform fit-up along its full length so that during use the fabric hangs flat without substantial deformation in its picture-viewing area. The angle of side wall 17 is preferably about 38.degree. while the wall 18 is preferably about 42.degree., both converging outwardly from the base 24.

Fit-up of the metal strip 25 in fabric-locking groove 16 for attachment of fabric to roller is shown in FIG. 3. Metal strip 25 is wider than the perpendicular distance from apex 22 to opposite side wall 17 of fabric groove 16 so that a pull on fabric 12 wedges end 25' of strip 25 and the adjacent fabric 12 into the side wall 17 of groove 16. Thus, the more the pull on fabric 12, the greater the wedging action of metal strip 25 into groove 16.

The width of the metal strip 25 is narrower than the distance from apex 22 to apex 23 across base 24 of groove 16 so that metal strip 25 can easily be hand-slid in groove 16 in the assembly of fabric-attaching elements shown in FIG. 4. Simultaneous with the sliding assembly of strip 25 in groove 16 that portion of fabric 12 adjacent thereto is also inserted in gap 27 and slid therealong to complete the attachment of fabric to roller. Metal strip 25 may be optionally slid in groove 16 with fold 25" adjacent apex 22 as shown in FIG. 3 or, in the reverse sense, with fold 25" adjacent apex 23 (not shown).

The wedging action of metal strip 25 in fabric groove 16 with a completely unreeled screen is shown in FIG. 4. This configuration imposes the most critical condition under which attachment of fabric to roller must function without hanging deformation of the screen in the picture-viewing area. Metal strip lock-up in groove 16 here results in a flatter screen fabric hang than for conventional means of attachment because fabric 12 is maintained straight along its inner edge 26 by the straightness of the fold in metal strip 25, and also maintained flat along its full length by the fit-up of strip 25 wedging in longitudinal groove 16 against side wall 17 or 18. As very clearly shown in FIG. 3, the tension force transmitted by screen 12 to unroll the screen causes strip 25 to be wedged in groove 16 with one longitudinal edge of the strip forced into the apex 22 and the other longitudinal edge of the strip forced towards wall 17 to wedge or grip fabric 12 between the edge of the strip and the wall so that the more the fabric is pulled, the tighter the screen will be held.

Spring roller 13 is rotatably mounted in case 11 on end gudgeons or end plugs 32, one of which is slip-fitted in the end 20 of roller 13 shown in exploded view in FIG. 5. Plug 32 is a cup-shaped sheet metal stamping having back face 32a and flange 29 for slip-fitting in the inside diameter of tubular roller 13. Spindle 28 is axially mounted to said back face for rotatably carrying the roller. Flange 29 has specially formed cutouts 30 circumferentially spaced therein, each cutout of which can slip over the inward protrusions of either fabric groove 16 or lock seam 21 selectively for locking up and supporting end plug 32 in the end 20 of tubular roller 13. Plug 32 so installed in end 20 also prevents the spreading apart of sides 17 and 18 of groove 16 under the wedging action of metal strip 25 or the accidental opening of the lock seam 21. A second end plug (not shown) slips in the opposite end (not shown) of roller 13 in a similar manner performing the same general purpose but rotatably carrying an axially-mounted, flat-sided shaft attached in a conventional manner to the usual spring (not shown).

Although but one embodiment of this invention has been herein shown and described, it will be understood that numerous details of the construction shown may be altered or omitted without departing from the spirit of the invention as defined by the following claims.

Claims

I claim:

1. In a projection screen including a housing, a tubular roller having end caps and a peripheral wall rotatably mounted within said housing and a screen fabric having opposite faces, side edges, an inner edge and an outer edge and a suspension slat secured to said screen fabric at its outer edge, the improvement in roller structure and means for attaching the inner edge of said fabric to said roller so that the fabric will hang flat during use comprising:

a. a groove formed in the interior of said tubular roller, said grove comprising a bottom wall and side walls converging from the opposite edges of said bottom wall towards the periphery of said tubular roller to form a narrow gap at the periphery of said roller extending longitudinally thereof, one of said side walls being offset below the other side wall at the periphery of said roller an amount substantially equal to the thickness of the fabric and the peripheral wall of the tubular roller in the region of the groove being offset the same amount, the side walls being smoothly faired into the periphery of the tubular roller and the peripheral surface of the roller making a smooth transition from one side of said gap to the other side, and

b. a folded strip clamped to the inner edge of the fabric, said strip extending longitudinally in the groove and being of a width such that when the fabric is subjected to a tension force between its inner and outer edges said strip is positioned at an angle to the base of the groove with one of the longitudinal edges of the strip disposed in the corner formed by said base and one of said converging walls and the other longitudinal edge of the strip being adjacent the other of said converging walls with the fabric disposed between said other longitudinal edge and said other converging wall, an increasing tension on the fabric causing said strip and the interposed fabric to bear more strongly against said other wall.

2. In a projection screen as claimed in claim 1, the further improvement wherein the tubular roller has a longitudinal locking seam circumferentially spaced from said gap and end caps are mounted in the ends of said roller, each of said caps comprising:

a. a back face,

b. a flange element circumferentially mounted to one side of said back face slip-fitted within said tubular roller peripheral wall,

c. a spindle element centrally mounted to said back face extending in a direction opposite to that of said flange, and

d. cutouts circumferentially spaced in said flange for sliding over the fabric locking groove means and the locking seam.