Abstract:
A projection screen apparatus comprises a support blank of a lightweight, rigid material defining a front face surface having a smooth concave curvature in two orthogonal directions. The front face surface terminates at a mounting rim skirting the front face surface peripherally. A projection screen is fixed to the front face surface of the support blank thereby assuming its doubly concave curvature. A box-like fixture supports the blank while suction is drawn between the front face of the blank and the screen material so as to draw the screen material into intimate contact with the surface of the blank in order to bond the screen to the blank.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to projection screens and more particularly to a double concave screen system and method of assembly. 
     2. Description of Related Art 
     Images projected onto compound curved reflective surfaces are optically pleasing and more akin to reality. The illusion of size of image is increased, the depth of perception is enhanced and edge distortion is reduced. Projecting images onto curved surfaces is not new, but because of complex problems, such display screens have been limited to cylindrical shapes. It also has been difficult to produce a compound curved display surface that is reflectively dynamic and affordable. Recent technology has advanced the composition of the screen surface, greatly reducing the light bounce problem inherent to curved screens. Advances in the molding process and molding materials have also advanced to a point where compound curved screens are practical and affordable. It is desirable to provide a relatively large compound curved display screen for mass audiences that can be easily and inexpensively fabricated. It is further desirable for the large compound curved screen to occupy a minimum amount of space and to be installed with the least amount of interference with existing structures. There is a further need to provide a compound curved screen for the smaller audience such as the school or home that can be inexpensively molded, occupy a minimum amount of space, be lightweight and easily portable. 
     Yamashita, U.S. Pat. No. 3,964,822 describes a projection screen including a substrate having a metallic aluminum surface and a transparent film overlay. The metallic aluminum surface is provided with a pattern of directional irregularities and a pattern of craters. The projection screen is produced by subjecting an aluminum surface to a mechanical surface treatment to form a dense pattern of fine irregularities, etching the treated surface to form a crater pattern thereon and coating the resulting surface with a protective transparent film. 
     Holzel, U.S. Pat. No. 3,998,522 describes a screen such as those generally used for exhibiting projected images. A boxlike frame has a rim formed about its front. A membrane (the projection screen) covers the front with its margin extending to the vicinity of the rim. A cover encloses the back of the frame and is connected in sealed engagement to the margin of the membrane so as to form a plenum. Gas is withdrawn from the plenum whereby the membrane forms a concave image receiving surface curved in a relatively constant degree about a single point so that the image receiving surface takes on a spherical shape. 
     Rain, U.S. Pat. No. 4,022,522 describes a tailored membrane supported solely by a peripheral frame forms the front panel of a chamber. A source of vacuum or an air blower maintains a pressure in the chamber which differs from that of the ambient atmosphere. As a result, the tailored membrane is either drawn forward or pushed taut to provide a concave or convex viewing surface having a configuration determined solely by its tailoring. 
     Schudel, U.S. Pat. No. 4,089,587 describes an improved projection screen. The screen includes a film which is constructed of at least partially deformable, resilient material. One surface of the film has in combination a random matte texture and a substantially unidirectional striated texture. A layer of reflective material is deposited on the above-mentioned surface of the film to provide a high gain, damage resistant reflective surface. In one embodiment of the present invention, the layer of reflective material is located on the back surface of the film, and the front surface has a matte texture so that light from a projector or other source passes through the matte surface of the film to be reflected by the layer of reflective material on the back surface thereof. In another embodiment of the present invention, the layer of reflective material is located on the front surface of the film so that light projected on the screen is reflected by the layer of reflective material without passing through the film. 
     Nash et al., U.S. Pat. No. 4,750,808 describes a projection screen including a rectangular film having a back surface, a front surface and a periphery, a support frame and chamber connected to the periphery of the film for defining the shape of the periphery of the film, a device for creating a pressure differential between the front surface and the back surface of the film, a sensor for sensing the position of the film and indirectly sense the pressure differential on the film and a controller for controlling the device for creating the pressure differential in response to the sensor such that the position of the film is a predetermined position as a result of some pressure differential whereby the shape of the film is set by the shape of the frame which is connected to the periphery of the film and by the predetermined position of the film resulting from the pressure differential. 
     Zobel, Jr. et al., U.S. Pat. No. 5,128,130 describes a projection screen formed from a plurality of translucent fabric panels joined along overlapping peripheral edge portions to produce a reflective, curved front screen surface. Overlapping peripheral edge portions extend outwardly from the back surface of the screen and are configured to be substantially less reflective than the front or projection surface of the screen. Accordingly, the visibility of seams between adjacent fabric panels to a viewer viewing images projected onto the screen is diminished. 
     The prior art teaches the use of curved projection screens but does not teach a double concave screen mounted onto a lightweight and rigid blank and a method of assembly using vacuum suction. The present invention fulfills these needs and provides further related advantages as described in the following summary. 
     SUMMARY OF THE INVENTION 
     The present invention teaches certain benefits in construction and use which give rise to the objectives described below. 
     The present invention addresses the above described needs by providing a compound curved display screen of sufficient dimensions for commercial theaters, conventions, trade shows, etc. The present invention further addresses these needs by providing a compound curved display screen of sufficient dimensions for home theaters, instruction classes, sports lounges, etc. The invention comprises a molded unit having a surface of a toroid. The molded unit is comprised of a material such as polyurethane for both strength and lightweight. Placed on and bonded to the concave surface of the molded component is a reflective screen material with an anti-light bounce feature. The screen is mounted to the peripheral edges of the blank and then stretched and bonded to the toroidal surface of the blank using vacuum suction. 
     A primary objective of the present invention is to provide an apparatus and method of use of such apparatus that provides advantages not taught by the prior art. 
     Another objective is to provide such an invention method capable of mounting a flexible screen material to a double concave surface. 
     A further objective is to provide such an invention capable of preventing light bounce on the surface of the screen. 
     A still further objective is to provide such an invention comprising a fixture for holding a support blank with a screen stretched across it, and for providing vacuum suction between the support blank and the screen to enable stretch mounting the screen onto the blank. 
     Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings illustrate the present invention. In such drawings: 
     FIG. 1 is a perspective view of a support blank of a preferred embodiment of the invention; 
     FIG. 2 is a cutaway perspective view of the support blank with screen stretched across it, mounted in a fixture of the invention; 
     FIG. 3 is a section view thereof taken along line  3 — 3  in FIG. 2; and 
     FIG. 4 is perspective view of an inner gasket, screen, outer gasket, fascia strip and mounting frame thereof wherein the gaskets and fascia strip are shown as each comprising a set of four separate pieces. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The above described drawing figures illustrate the invention in at least one of its preferred embodiments, which is further defined in detail in the following description. 
     A projection screen apparatus comprises a rectangular support blank  10  of a lightweight, rigid material, preferably molded polyurethane, defining a front face surface  12  and a rear surface  14  as shown in FIGS. 1 and 3. The front face surface  12  has a smooth concave curvature in two orthogonal directions, i.e. from top to bottom and from left to right, and both are preferably arcs of a sphere, but may alternately be aspherical. The radius of curvature in the horizontal direction is generally greater than that in the vertical as is clear from FIG.  1 . This surface  12  terminates at a mounting rim  16  skirting the front face surface  12  peripherally, i.e., as shown in FIG. 1, running along the top, bottom and both side edges. A projection screen  20  of polyvinyl chloride or similar material which is stretchable and gas impermeable, is bonded to the front face surface  12  of the support blank  10  so that it intimately assumes the concave curvature of the front face surface  12 . This intimate contact is shown in FIG.  3 . An anti-light-bounce coating  26 , well known to one of skill in the art, is placed on an outfacing surface  22  of the projection screen  20  for reducing light reflection or bounce which tends to wash-out the images projected onto the screen  20  because it is curved. 
     Preferably, an inner gasket seal  30 , of a rubber or similar material, is placed between the projection screen  20  and the mounting rim  16  and is bonded to both the screen  20  and the mounting rim  16 . An outer gasket seal  40 , similar to the inner seal  30 , is placed and bonded between the screen  20  and a peripheral facia  50 . The facia  50  may be made in one piece or in separate pieces as is shown in FIG.  4 . When made in separate pieces, the facia  50  comprises  4  plastic or wood strips of a flexible nature so as to be able to conform to the surfaces of the mounting rim  16 . The seals  30  and  40  also may be made in one piece (not shown) each forming a four sided frame structure, or, as shown in FIG. 4, they may be madeup of separate top, bottom and side portions. The facia  50  is preferably strips of wood, plastic or metal placed in congruence with the mounting rim  16  as shown in FIG.  2 . Preferably 3M Co., Fast Bond 30-NF® adhesive, or its equivalent, is used to bond items  20 ,  30 ,  40  and  50  together., These seals  30 ,  40 , prolong the life of the apparatus and prevent separation of the screen  20  from the blank  10 . 
     Preferably, the invention further comprises, in combination with the above described projection screen apparatus  5 , a blank supporting structure  60  made up, as shown in FIGS. 2 and 3, of a back panel  62  fastened to top panel  64 , bottom panel  65 , and left and right side panels  66 ,  67 . Such panels may comprise solid surfaces or framework construction. Those of skill in the art will know how to construct structure  60  in the foregoing or alternative ways. The supporting structure  60  has a double concave, open rectangular front edge  70  corresponding in shape to the mounting rim  16  of the support blank  10  and it is positioned peripherally adjacent thereto when the blank is cradled within the structure  60 . The supporting structure  60  also provides a strut network configured and engaged within the structure  60  for the purpose of supporting the blank  10  and rigidizing the structure  60 . The box strut network is made up of a plurality of ribs  92  positioned in mutually parallel juxtaposition horizontally, and a plurality of stringers  94  positioned in mutually parallel juxtaposition vertically. The ribs  92  and stringers  94  are mutually engaged for common support, and are further engaged with the structure  60  as shown in FIG. 2 in the broken section, and also in FIG.  3 . The ribs  92  and stringers  94  provide contour surfaces  96  which are positioned for contact with the rear surface  14  of the support blank  10  for physical support when the blank  10  is mounted within the support structure  60 , preferably with the surface  12  facing upwardly. 
     The present invention defines a method of manufacturing the projection screen apparatus  5  using the supporting structure  60 . The support blank  10  defined above is molded with the double concave front face surface  12  and with the mounting rim  16 , where the rim skirts the front face surface  12  peripherally as shown in FIG.  1  and previously described. Next, the inner sealing gasket  30  is bonded to the rim  16  of the support blank  10  and the projection screen  20  is laid across and bonded to the inner sealing gasket  30 . The outer sealing gasket  40  and the fascia  50  are then bonded to the outer surface  22  of the screen  20 . The outer sealing gasket  40  is fastened over the screen  20  and fasteners are driven into the mounting rim  16  of the support blank  10  so that the projection screen  10  encloses the front face surface  12  of the support blank  10  and the volume covered by the screen  10  is closed and sealed. the support blank  10  is then mounted within the blank supporting structure  60  with the facia  50  positioned adjacent peripherally to the open rectangular front edge  70  of the supporting structure  70 , and in a position contiguous thereto. The rear surface  14  of the blank  10  rests against the contoured surfaces  96  of the ribs  92  and spars  94  and preferably the front surface  12 , and the screen both face upwardly. Flat straps  100 , which are made of a rigid metal, or equivalent, are then fastened in place as shown in FIG. 2 using common fasteners driven into the mounting rim  16 , through inner and outer sealing gaskets as well as the screen  20 , and also into the front edge  70  of structure  60 , so that the blank  10  with the screen  20  in place, is secured within structure  60 . The infacing surface of the projection screen and/or the front face surface  12  of the support blank is coated with a bonding agent of a suitable type. Suction is applied to the space between the projection screen  20  and the support blank  10  so as to draw the projection screen  20  into close and intimate contact with the front face surface  12  of the support blank  10  and enable bonding of the screen  20  to the blank  10 . This is achieved through the reduction of air pressure within the enclosure so that standard atmospheric pressure, (approximately 14.8 pounds per square inch) is applied to the exterior surface of the projection screen  20 , thereby pressing it inwardly into contact with the front face surface  12  of the support blank  10 . Suction is maintained until the bonding of the screen to the blank is completed. 
     An important aspect of the structure of the present invention which enables the screen  20  to be sealed, is the use of the two gaskets  30 ,  40  as defined above, so that placement and engagement of these gaskets is a necessary part of the present method to assure a tight peripheral seal to hold suction. Application of suction, the methods and means of such being very well known in the art, is applied through plural tubes  110  mounted peripherally in the blank  10  as shown in FIG.  3 . Peripheral suction has been discovered to provide an improved result as the screen  20  is stretched from a starting position where its four edges describe arcs, and the screen material laying between these four edges is stretched between the edges and the final position where the screen is bonded to the surface  12 . Air pressure forces the screen material to stretch and move into contact with the surface  12  of the blank  10  in an even and wrinkle free condition. 
     While the invention has been described with reference to at least one preferred embodiment, it is to be clearly understood by those skilled in the art that the invention is not limited thereto. Rather, the scope of the invention is to be interpreted only in conjunction with the appended claims.