US1890828A - Projection screen - Google Patents

Description

DBG 13, 1932. F. H. mcHARDsoN-ETAL 1,890,828

PROJECTION SCREEN Filed Feb. 18. 1928 3 sheets-sheet 1 D- 13', 1.932 nF. H. RICHARDSON ETAL 1,890,828

` PROJECTION SCREEN Filed Feb. 18. 192e '3 sheets-sheet 2 Dec. 13, 1932. -F.H.-1cl-|ARDsoN E'rAL 1,890,328

, PROJECTION SCREEN Filed Feb.' 18, 1928 5 Sheets-Sheet 3 zo l/ 1 ummm 45u? ga/Z 46 Patented Dec. 13, 1932 UNITED STATES PATENT ori-"ICE FRANK HERBERT RICHARDSON, OF SOUTH LYME, CONNECTICUTpAND JAY CLEIS KBOESEN, OF BELLEVILLE/NEW JERSEY PROJECTION scREEN Application filed February 18, 1928. Serial No. 255,280.

This invention relates to motion picture projection, and especially to a new and improved composite screen which is characterized by a high visibility at extreme angles,

and an exceptionally low cost.

Heretofore, considerable diiiiculty has been experienced in securing motion picture,

screens which were susceptible of use under varying conditions obtaining in moving picture theatres. This difficulty has been due to the fact that optimum refiectivity from the screens hitherto available is confined to a relatively narrow area on either side of a line representing the axis of projection of the rays of light from the projector. This area is, for the average good screen, comprised within an area whose outer limits are bounded by lines varying some 30 from the axis of projection. Various expedients have been tried to secure an extension of the angle of visibility, but such results are secured at the expense of the depth of reiection of the projected picture.

A further disadvantage of the screens hithv erto used, resides intheir high initial cost and their gradual deterioration due to the deposition of atmospheric dust and, dirt in the fibres of the screen.

Itis an object of the present invention to provide a screen which is at one and the same time characterized by high refiecting power` and a wide range of diffusion characteristics.

It is a further object of the present invention to provide a screen of the type designated which is relatively cheap in cost and readily replaceable, whereby optimum projecting conditions may be maintained Without undue expense.

Yet another object of the present invention is the provision of such a readily replaceable screen, which may optionally be comprsed of a plurality of' separate units.

Still another object of the invention is the provision of an improved projection `screen apparatus which is designed .to afford maximum service coupled with ease of replacement of the screen member proper.

A further object of this invention is the provision of a plurality of improved screen members, so constituted and arranged as to occupy a minimum of space and thus afford considerable savings in transportation charges.

These and other important objects and advantages of this invention will be described in this specification and illustrated in the accompanying drawings, it being understood thatA they-are given by way of illustration only, as the underlying features maybe incorporated in a variety of devices without departing from the spirit and scope of the invention.

In the drawings, like numerals refer to similar parts throughout the several views of which n Figs. 1, 2 and 3 are enlarged cross-sections of screens suitable for use in the present invention;

Fig. 4 is a front view of a frame for-supporting the composite screen;

0 Fig. 5 is a cross-section of the frame show- 1ng the clamping or retaining means 'for the screen; f

Fig. 6 is a horizontal section of a clamping device;

Fig. 7 is a. front view of a compositeframe with one end broken away;

Fig. 8 is a cross-section taken on line 8-8 of Fig. 7

Fig. 9 is a showing partly in section and 80 partly in elevation of a screen mounting with a plurality of screen members Fig. 10 is a cross-section taken on line 10-10 of Fig. 9;

Fig. 11 is a perspective view of a pack of 85 screen sheets and protecting opaque'sheets;

Fig. 12 is a schematic showing of a method of joining a plurality of screen members to form a large screen;

Fig. 13 is a schematic showing of the re- 90 lection characteristics of a screen of thepresent invention in comparison with screens of the lprior art; and

Fig. 14 is a graphical representation of the curves illustrated in Fig. 13.v

As intimated hereinbefore, projection screens vary in their optical properties `to such an extent, that in any given installation, the particular type of reflecting surface used must be carefully figured out beforehand in 10u Order to secure optimum visibility on the part of spectators seated invarious parts of the auditorium and at diverse angles from the axis of projection.

The screens of the prior art show a remarkable variation in reflection characteristics, ranging from surfaces which almost completely diffuse the incident light to screens of a very specular nature, having very high' reflecting powers on the projection axis and very low values in directions departing by .relatively small amounts from the normal.

flects a large proportion of the incident light within a relatively narrow angle` thus effecting considerable economy in operation. Where sucli a specular reflecting type of screen is employed in a room whose length is relatively small compared with its width` a light source of high power would not assure sufficient visibility for those seated at a considerable angle from the axis of projection. While those seated more nearly in the center of the house or room are 'subjected to an uncomfortable brightness or high glare due to the almost direct reflection of the intense light rays. j

' These difficulties are overcome bythe present inventon in which an efficient reflecting surface of such suitable diffusing characteristics, is provided by a surface of manganese carbonate or like substance. This material has a. diffuse reflecting characteristic which combines the good properties. of specular. metallic reflecting surfaces, and the diffusing, pigment surfaced screens. Referring to Figs. 13 and 14, there is shown graphically the optical characteristics of a screen A of the present invention compared, for purposes of illustration, with a screen of each of the specular B and diffuse C types.

As shown in the figures referred to, the visibility of screen A is very high at an angle of from the axis of projection, the drop in visibility or reflecting power, (on a basis of magnesium oxide having an arbitrary re' fleeting power of 100), is from approximate ly 98 at 0 angle to approximately 70 at 70 angle. Screen B, which is of the reflecting type. is characterized by an extremely high reflecting power within an angle of 20 from the axis of projection, which rapidly decreases with slight increases in the angular variation to a low value of at 40 angle and by successive decrements to 20 at 7 0 angles.

Such a type of screen is, therefore, of necesf surfaces is characterized by an initial reflecting power of about 15,0, which drops sharply to a. value of about 60 at 20 from the axis of projection, and at 70 has a nominal value of 25, which is approximately that of screen B at such an angle. It is to be noted that screen A has a higher reflecting power for all angles greater than 30 from the axis of projection than the typical screens considi ered.

The optimum areas of visibility for the three types of screens'are diagrammatically shown in Fig. `13, in which the axis of projection is designated generally by the line X-Y, the screen being placed at X and the motion picture projector at Y. It will be seenfrom this showing that screen A is characterized by an extreme power of diffusibility of incident light, together with a reflecting power which approximates that of the true specular or reflecting type of screen.

The foregoing optical considerationshave been predicated upon the use, for' example, of finely divided magnesium carbonate, ground to a fineness of 200 mesh or more, and

associated with or incorporated in a fibrous material in a manner now to be described.

In 4Fig. 1, there is shown a section of a screen, comprising a fibrous body 1, of 'pa er, or the like, which may or may not be bac ted up with a reinforcing cloth or other support, desired. A layer of suitable adhesivey material 2, is applied to one surface of sheet 1, and over this is sprinkled a layer of finely divided magnesium carbonate 3. The carbonate layer may be applied to the adhesive in any other manneras by placing an excess of the material on the adhesive, removing the excess, and applying pressure to the surface to smoothen it out.

In place of applying magnesium carbonate to the adhesive layer, as described, it may be ,incorporated in the body of the paperl by adding it to the pulp in the beating engine, and then subjecting the resultant pulp to the usual steps in the papermaking process. Such a magnesium carbonate impregnated paper is shown in section in Fig. 2 and is designatedgenerally by the numeral 4. In addition to incorporating a light reflecting and diffusing component, such ls-magnesium carbonate, in the paper sheet, pigments may be added for a purpose which will now be described.

As is well known, certain portions of the spectrum of the projected beam are undesirable, and it is customar to filter out such undesirable components y interposing tinted screens between the source of light and the projection screen. Such filters create a loss of eective projecting power at the projector. By the use of appropriate pigments in the paper, in conjunction with the carbonate or other reflecting material, certain undesirable portions' of the spectrum of the projected beam are absorbed and the remainder is reflected back to the audience as a rectified light, whichresults in creating a more desirable appearing screen. By this means there is secured a more efficient utilization of the initial projected light, which enables the production of results much superior to the ones now obtained. Where it is not desired to expend the money necessary to produce an impregnated sheet of the type described, the procedure described in relation to the showing in Fig. 1 may be modified as designated in Fig. 3. Here the base sheet of heavy paper of any appropriate strength desired, is coated with an adhesive in which has been incorporated a sutiicient quantity of themagnesium carbonate, or its equivalent. Any desired pigment may be associated with the carbonateadhesive composition, for the purposes above designated. l

By the use of the paper screens of the present invention, the initial cost of installing a reflecting surface is very considerably cheapened', and in addition, the replacement cost is so low that relatively frequent renewals of the screen surface are possible without being inhibited by the uneconomical high costs of Y the screens now in use.

CTI

In adapting the improved screens of the present invention to standard installations, it is sometimes necessary to combine two or more paper screens in order to secure the requisite size. This is due to the fact that the width of paper normally available for the purposes described is not sufficient for large screens, the present constructions being composed of a plurality of interwoven sheets of fabric prepared without seams.

Referring now to Figs. 4 and 5, there is shown a suitable frame comprising top and bottom pieces 6 and 7 and side pieces 8 and 9,l together with an intermediate cross piece 10. These members are joined together to form a firm, integral structure by any suitable means well known to those skilled in the art.

The several members are provided with iii-- wardly curved surfaces 11, which, in effect, assures a single line support around the periphery of t'h'e frame and across the crosspiece. The function of this singleline lsupport feature will be discussed more in detail hereinafter.A

` The screen sections 12 and 13, Fig. 5, are brought Aaround the members 6 and 7 respectively, the ends 14 and 15 being he1 d tight by means of clamps 16 acting throughsupports 17. The. previously beveled ends 18, 18 of sections 12 and 13 are coated on their adjacent portions with a suitable adhesive and held in position during setting by a special clamp comprising a frame member-19 and removable end clamps 20, 21 adapted to fit over the ends of the member 19 and hold it in cooperating relation to side pieces 8 and 9. lVing screws 22, 23, are tapped into angle portions 24, 250i the clamps and serve to hold the latter in position', asabove noted. lll/*hen the adhesive has set, the clamp structure is removed and the joint 18. 18 smoothed by a roller or any other suitable means. if necessary.

By the process set forth, a projection screen of any desired size can be made up in situ, with a minimum of labor and expense, and susceptable otr easy replacement at low cost.

IVliile the edge portions 18, 18. have been spoken of as being both beveled, it is obvious that one edge only, e. g., 18, need be beveled orskivedl to secure the desired result. .It isl also to be noted, that while the screen sections have been joined with the top section overlapping the bottom. the condition may be reversed. or the sections may be secured together with a longitudinal joint instead of a horizontal one, the frame and its associated parts' lending themselves readily to such transposition. The position of the seam in the conipleted screen will be determined by the relation of the projector thereto.

The sheets of magnesium carbonate coated or impregnated paper may be wound on rolls, positioned respectively at the top and bottom ot the frame, or they may be placed to one side of the screen in a light proofbox, which construction being a preferred one for large installations, will be described in detail later In Figs. 7 and 8 is shown an optional con-` struction of the frame members, where the completed frame is ,too large to be conveniently shipped, and a knockdown or collapsible construction is desired. As shown, the im' proved frame comprises a plurality of frame units 30, 31, composed otquarter-round frame members 32, joined' as already described under Fig. 4. At the abutting faces 33, 34 of the units there is provided a plurality of pins 35 joined'to the top ot the lower frame unit in any suitable manner, and in register with a plurality of .sockets 3G in the lower frame member of the upper unit. This construction assures the proper register of the several units. which may then be clamped, or otherwise held to form a rigid frame.

In the frame structures shown, it will be noted thatthe paper of the screen contacts therewith at the edges of the quarter-round members around the periphery of the frame' i and across the center-piece. Such a condi-A I the present invention has as its primary funcprovision of a large screen surface which may be readily replaced at 'a low cost and with'a i minimum of time andv labor. Referring now l I- 'mf-.to Figs. 9 and 10, there is shown a stage drop or support comprising top, side and bottom members 40, 41 and 42 respectively. These members are recessed, as at 43 to receive a ,v 1.5 frame44, l,constructed as above described.

This frame is held in position in the recesses of the'. support by any suitable means, as by screws 45, 46. At one side of the support,

or at the top o r bottom -as desired, is a lightproof magazine comprising front and back Walls 47, 48, and an end door 49 attached to the back Wall by hinges 50. A suitable.1atch` not shown, may be provided to hold the door closed.l I

Inside the light-proof cabinet are posi- .tionedthe roll supports 51, 52, 53 and 54. The supports are secured to the cabinet in any desired manner. Supports 53, 54 are provided with removable and adjustable clamping jaws 55, held in coacting relationship to theshafts 57 of the rolls 58.59 by wing bolts 56. The fabric on the rolls overlaps for an ap# .preciable amount as shown at 60, to permit the formation of ascreen joint, previously described. When it is desired to prepare a new screen or replace an old one, the fabric on the rolls is drawn across the frame from out of the light-proof box and the joint is prepared in the manner previously described, the far edge of the composite sheet being clamped to the frame. The sheets of fabric, instead of overlapping, may merely abut or be adjacent to each other, and the desired joint between them readily secured by superposing a relatively narrow strp of the fabric over the edges, and then clamping the Whole assembly in the usual manner. Both edges of the intermediate strip are beveled, which feature involves further savings in installation and replacement costs. The necessary tension on the roll end of the fabric is secured j by the coaction of the braking clamps 55, and the tension roll 61 journalled in sockets 62,

at either end of the light-proof chamber.l If desired, the rolls may be provided with arewinding mechanism, not shown, for the purpose of securing the necessary tension of the screen after assembly.

.The aperture 68 1n the support member abutting and forming part of the light-proof chamber, serves to keep dust out of the chamber as well as to prevent the penetration of' the light rays'from the projector.

AWhere an exceptionally large screen surface is desired, or Where,-from reasons of economy, narrower fabric is to be used, any

Lacasse number of rolls may be positioned within the light-proof chamber without departing from ized by a series ofl reflecting surfaces 70,

separated by sheets of opaque material 71. These surfaces are designed'` for use in small or temporary installations, where a standard 'si ze screen is not needed or the space available does not permit its use.

These packs of alternately disposed screen surfaces and opaque sheets can be made up at a central plant and shipped to outlying districts at a minimum .of cost both for manufacture and expressage as Well as for installation.

When they are received` it is merely necessary to support the pack in a suitably p0- sitioned frame, tear off the protecting opaque sheet, and the first screen is ready for use. lVhen the first screen surface has deteriorated through use or age, it and its underlying protecting sheet are torn off and a fresh surface is immediately available. The

opaque protecting sheets are used to prevent-v deteriorati-on of the underlying screensurfaces, as the projecting arcs and lamps now in use are sufficiently powerful to project light ofsuch intensity, that ordinary fabric, either paper or cloth. even when heavily loaded or sized, is readily penetrated'.

In Fig. 12 there is di agrammatically shown a method of joining several sheets to form a screen.4 The members 7 0a and 7 0b are joined alongV their lateral edges, the edge of sheet 701) being shown folded back to show the relative position of the sheets, as are members 700 and 70d, l and the resulting composite sheets are joined together along the line M-N to form a screen vof the desired size. This form of association of small sheets of the type suitable for use in a pack, renders available the new and improved motion picturescreen of the present inventionin any locality, and.is especially adapted for emergency or large temporary installations.

While it has been stated herein thatpaper or another commodity maybe used as the base or support for the manganese carbonate or other preferred coating, itgwill be understood that thisbase or supportinay be of nondesirable fire proofing agents. lWhen material otheri thanjpaper maybe used for thez bas'eor supportitv may be treated by any suitable material to obtain the non-Hammable condition.

While the improvements comprehended within the spirit and scope of the present invention have been discussed in relation to their use in motion picture projection, it is lto be understood that the underlying features may be incorporated in other optical instruments, such as photometers and light measuring instruments generally.

It will now be appreciated that there has been provided a new and improved motion picture screen which is suited for use in any type of room, or location, so as to be universally available for such purposes. It will also be appreciated that the screen pack disclosed is a' notable advance in the art, and renders the improvements of the present invention generally available, and particularly 2 br small or temporary installations, such as may be Yused in home-movies. There has also been provided a mechanism adapted to make the screens .of the present invention readily replaceable at a low cost and a minimum expenditure of labor.

What is claimed'is:

1. A projection screen comprising a plu- "rality of strips of carbonate coated paper joined at their adjacent edges by integral skived portions thereofin overlapping relation to form a substantiallyinvisible seam.

2. A projection screen comprising a plurality of strips of fabric having a reflecting surface characterized by a high light-diii'using capacity, said strips being joined at their adjacent edges by integral, bevelled portions thereof in overlapping relation, to form substantially invisible seams.

"3. A projection screen housing, including in combination,a frame, a guide member on the frame, and a' plurality of screen rolls journaled on the frame adjacent the guide member.

4.n A projection screen assembly, including in combination, a frame, a guide roller on the frame, a pair of screen rolls journalled on the frame adjacent the guide roller `and inl staggered relation to, each other, iibrous'screenv so material on the rolls and adapted to be withlap' sur ace.

5. A projection screen assembly, including in'combination, a frame, a guide roller on the frame, a plurality of screen rolls journalled on the' frame adjacent the guid roller and in staggered relation to each other, Y- fibrous screen material on the rolls and adapted to be withdrawn therefrom across the frame in overlapping relation to form a continuous screen surface.

6. As an article of manufacture, a composite projection screen, including fin' combihavingre ecting surfaces having the optical nation, a lurality of opaque flexible strips characteristics of magnesium carbonate, said strips being separate and positioned in overlying relatlon to each other whereby to provide a continuous screen surface.

7. As an article of manufacture, a composite projection screen, including, in combination, a plurality of opaque flexible strips having reiiecting surfaces having the optical characteristics of magnesium carbonate, said strips being separate and positioned in overlying relation whereby to provide a continuous screen surface, a rame for said com osite screens, said frame including top, ottom, side, and back members and a laterally pos'tioned roll chamber, a guide member between the chamber and the frame, and means` in the chamber for operatively mounting a plurality of -rolls of the aforesaid iiexible screen strips.

F RANKn HERBERT RICHARDSON. JAY CLEIS KROESEN.

drawn therefrom across the frame in overmg relation vtoform la contlnuous screen

Images