US2812690A - Skylights - Google Patents

Description

Nov. 12, 1957 Filed June 26, 1952 SOUTH R. A. BOYD 2,812,690

SKYLIGHTS 4 Sheets-Sheet 1 SUN NORTH INVENTOR: 2052122" A. B0103 ATTYS.

Nov. 12, 1957 R. A. BOYD 2,812,690

. SKYLIGHTS Filed June 26, 1952 4 Sheets-Sheet 2 H0525?" A. BUYD.

t IN V EN TOR:

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ATTYS.

Nov. 12, 1957 Filed June 26, 1952 Sadr k R. A. BOYD 2,812,690

SKYLIGHTS 4 Sheets-Sheet 4 TIE-1Z- INVENTOR: EJ019212 T A. Bum- TTY'S.

United States Patent SKYLIGHTS Robert A. Boyd, Ann Arbor, Mich., assignor to Owens- Illinois Glass Company, a corporation of Ohio Application June 26, 1952, Serial No. 295,730

11 Claims. (Cl. 88-59) This invention relates to the utilization of daylight for lighting the interior of buildings through an opening in a roof or ceiling.

A major problem in utilization of daylight through an opening in a roof or ceiling is that the direct sunlight from high altitudes provides an excessive amount of light and heat. This condition is especially present during the summer months when the sun is at the higher altitudes. It is, of course, well known that the altitudes of the sun vary with the seasons of the year and also with the various latitudes.

It is therefore an object of this invention to provide a skylight which rejects direct sunlight from high altitudes and transmits light from the low altitudes and the northern sky.

Other objects of the invention will appear hereinafter.

Basically my invention comprises controlling the transmission of daylight by using four air-glass interfaces such as are present in a hollow glass block or in two spaced sheets of glass. In such a structure the interfaces are con ventionally termed Faces 1, 2, 3, and 4Face 1 being the exterior interface, Faces 2 and 3 being the interior interfaces, and Face 4 being the interface nearest the interior of the room. According to my invention, Face 1 is provided with a smooth surface or a series of longitudinal ribs extending in a generally north-south direction. Face 2 is provided with a series of parallel prisms extending in a generally east-west direction. Faces 3 and 4 are provided with ribs or are opalescent in order to diffuse the transmitted light into the interior being lighted.

The prisms on Face 2 are so constructed and arranged that direct sunlight at high altitudes from a southerly direction is rejected whereas light from the low altitudes and the northern sky is transmitted.

Referring to the accompanying drawings:

Fig. 1 is a cross sectional elevational view of a room showing the excessive sunlight from the sun at the higher altitudes;

Fig. 2 is a plan view of a skylight made of glass blocks;

Fig. 3 is a sectional view of a hollow block at the line 3--3 on Fig. 2;

Fig. 4 is a cross sectional view of a skylight comprising two sheets of glass and incorporating my invention;

Fig. 5 is a fragmentary cross sectional view of Faces 1 and 2 on a greatly enlarged scale, showing the path of light rays from high altitude angles;

Fig. 6 is a fragmentary cross sectional view of Faces 1 and 2 on a greatly enlarged scale, showing the path of light rays from various angles in the sky;

Fig. 7 is a cross sectional view on a greatly enlarged scale of a modified form of the prisms on Face 2, showing the path of the light rays from various angles in the y;

Fig. 8 is a curve of great circle transmission obtained by testing the form of the invention shown in Fig. 6;

Fig. 9 is a cross sectional view on a greatly enlarged scale of another form of the prism on Face 2, showing the path of the light rays from various angles in the sky;

Patented Nov. 12, 1957 Fig. 10 is a cross sectional view on a greatly enlarged scale of another form of the prism on Face 2;

Fig. 11 is a cross sectional view on a greatly enlarged scale of another form of the prism on Face 2, showing the path of the light rays from various angles of the sun and;

Fig. 12 is a cross sectional view on a greatly enlarged scale of a modified form of the prisms on Face 2, showing the path of the light rays from various angles of the sun.

The problem of illumination through an opening in a ceiling or roof may be illustrated by referring to a typical room. As shown in Fig. 1, sunlight passing through a vertical opening 20 in ceiling 21 emanates from a southerly direction (in the northern hemisphere). At high altitude angles of the sun, the amount of light and heat emanating therefrom is excessive and undesirable. This is shown more clearly by the following table of meteorological data representing conditions at 42 N. latitude.

TABLE I Horizontal Surface Maximum Normal Illumination Day of Year Sun Alti- Sun Intude, tensity degrees (tt..-c.) Sun Only Clear (ft.c.) Sky June 21 71% 9, 180 8, 700 1,600 May 21 and July 21. 68% 9, 070 8, 400 1, 500 Apr. 21 and Aug. 21. 60 8, 900 7, 700 1, 400 Mar. 21 and Sept. 21 48% 8, 800 6, 600 1, 200 Feb. 21 and Oct. 21 37% 8, 250 5, 000 1, 000 Jan. 21 and Nov. 21 28 7, 500 3, 500 800 Dec. 21 24% 7, 000 2, 900 800 As shown in Table I, the sun altitude and the normal sun intensity vary throughout the year, the maximum occuring during the months from April through August. Table I further indicates that the greater portion of the horizontal surface illumination is due to light from the sun and a small portion is due to the clear (northern) sky.

I have found that the desired control of illumination through a vertical opening may be obtained by interposing four air-glass interfaces between the light source and the interior. Referring to Fig. 2, the skylight 23 may consist of a series of blocks 24.

As shown in Figs. 3 and 4, the four air-glass interfaces may be found in a glass block 24 or in two spaced sheets of glass 25, 26. In such structures the interfaces are conventionally referred to as Faces 1, 2, 3, and 4Face 1 being the exterior interface, Faces 2 and 3 being the interior interfaces, and Face 4 being the interface nearest the interior of the room.

According to my invention as shown in Figs. 3 and 4, Face 1 is provided with a smooth surface 27 or a series of longitudinal ribs. Face 2 is provided with a series of parallel prism shaped ribs 28, hereinafter called prisms, having particular configurations as hereinafter described and having their axes extending in a generally east-west direction. Faces 3 and 4 may be provided with a series of ribs 29 and 30 respectively at right angles to each other. The ribs 29 and 30 have a configuration such that daylight transmitted thereto is diiiused into the interior of the room.

According to my invention, sunlight from high altitude angles is refracted by Face 1 and totally internally reflected at Face 2 and thereby rejected. More specifically, as shown in Fig. 5, the prisms 28 on Face 2 extend in an east-west direction and have surfaces 31, 32 at an included angle P. I have determined the most satisfactory included angle P is As shown in Fig. 5 the surface 31 is at an angle b to a horizontal plane. The surface 32 faces a southerly direction.

A light ray L1 at sun altitude angle a, is refracted at Pace 1, transmitted to and reflected at surface 31 to surface 32, and finally reflected to Face 1 and refracted out to the atmosphere. Similarly a light ray L2, at an angle a,., is refracted, totally internally reflected, and finally refracted to the atmosphere. In a similar .manner,,light rays at angles a and a, striking the northern slope or surface 32 are totally internally reflected. This is represented on Fig. by the double arrows. Altitude angles of the sun less than a or greater than a. are not totally internally reflected. It may be observed from Fig. 5 that the particular configuration of'the prisms on Face 2 provides a range of angle, a through a at high altitudes from which sunlight is completely and entirely rejected.

The in corporation of the prism structure shown in Fig. 5 in a skylight construction may be more clearly represented by referring to Fig. 6. It may be observed that a rayof sunlight L3 from a low altitude angle a is refracted at Pace 1, reflected at surface 31 to surface 32, and refracted out of surface 32. Similarly a light ray L4 at the same altitude angle a is refracted at Face 1 and again refracted at surface 32. A light ray L5, representing light from the northern sky at an angle a is refracted at Pace 1 and at surface 31 toward the interior. A similar light ray L6 is refracted at Face 1, reflected at surface 32, and refracted at surface 31 toward the interior.

As shown in Fig. 6, the construction of the prisms on Face 2 rejects the sunlight from the high altitude angles and permits sunlight from the low altitude angles and light from the northern sky to be transmitted toward the interior.

I have determined that for a latitude of 42 N. the angle b, which the surface 31 forms with a horizontal plane, is preferably 29. After constructing a skylight in accordance with my invention, with the angle P equal to 90 and the angle b equal to 29, and conducting illumination tests thereon the curve of great circle illumination shown in Fig. 8 is obtained. This curve rep resents the percent of light transmitted at various sun altitudes for the construction, measured along a great circle.

As shown in Fig. 8, there is an area or zone ranging between approximately 59 to 72 of sun altitude at which maximum rejection of the direct sunlight is obtained. This zone of rejection extends for approximately 13 when P=90. It may be noted that this range of approximately 13 is slightly greater than the range of the high altitude angles of the sun which are present from April through August as shown in Table I, namely, 71 /260=1l%.

The effectiveness of my invention may be more clearly shown by referring to the following table'representing the results obtained by testing the construction shown in Fig. 6, the angle P being equal to 90 and the angle b equal to 29.

TABLE II Horizontal Surface Lumens Trans-' mitted,

per sq.ft.

Percent J Transmission Sun Altitude Illumination, Sun

Only

tit

4 nation from the northern sky, as shown in the right hand column in Table I. V

A modified form of the prisms on Face 2 is shown in Fig. 7. In this form the surfaces of the prisms, 33, 34, have been changed in slope, thus in effect shifting or rotating the position of the prism about its east-west axis. The surface 33 forms an angle b with a horizontal plane, the angle b being greater than the angle b in the form of the invention shown in Fig. 6. By such a construction a light ray L9 at an altitude angle a is refracted and totally internally reflected. in the prism and finally rejected to the atmosphere. In a similar manner a light ray L10 at an altitude angle a, is rejected. These light rays as in the previous form of the invention may first strike either the surface 33 or the surface 34. This condition is indicated by the double arrows. Light rays L7, L8 from low altitude angles and light rays L11, L12 from the northern sky are subjected to substantially the same action as in the form of the invention shown in Fig. 6.

Contrasting the construction in Fig. 7 with that in Fig. 6, it is found that a is greater than a and d i5 greater-than a This indicates that by increasing the angle b, which one surface, the southern slope, of the prism makes with a horizontal plane, the area or zone of rejection of light rays from high altitude angles of the sun may be changed and shifted to include higher altitude angles. If the construction shown in Fig. 7 were made, for example, with the angle b equal to 3l it would be found that the zone of rejection of light rays would range from a '=62 /2 to a,=75 /2. If the curve of great circle illumination similar to that shown in Fig. 8 were drawn, it would be found that the zoneof maximum rejection would be shifted to the right by this increase in the angle b. Moreover a reference to the standard meteorological table indicates that the mum sun altitude of 75 /2 which is rejectedby the construction in Fig. 7, is comparable to the maximum sun altitude at a latitude of 37 N. g Y j It may thus be seen that a change in the angle b cause a shifting or change in the 13 area of rejection of high sun altitudes. In accordance with invention a' prism construction may be designed for any particular latitude; by increasing the angle b the maximum altitude of rejection may be increased, this being necessary to compensate for the lower latitudes; by decreasing the angle b the maximum altitude of rejection may be" less ened, this being necessary in thehigher latitudes;

The concepts of my invention may be utilized to pro vide a structure which is universally applicable to various latitudes. Such result may be obtained by a construction having a series of 90 prisms in which the angle b varies for each prism in a series. In Fig. 9, eachserie's consists of three prisms, prism 35 being at the angle b prism 36 at the angle b andpri'sm 37 at the angleb rb" being greater than b, which in turn is greater than 12,. According to my invention as heretofore discussed, the maximum altitude angle of rejection of prism 35 willlb'e less than that of prism 36, which in turn will be less than that ofp rism 37. I I, j j V More specifically, lightrays L13 and L14 at altitude angles a,', a are rejected by prism 35; light rays L15 and L16 at altitude angles q aga re rejected bypri'sm 36,: and light rays L17, L18 at altitude angles a a are rejected by prism 37. The relationshipof' the altitude angles would be as follows: a, greater'than a,, which in turn is greater than a,; a, greater than a, which in turn is greater tha'nfla The prism 35 would reject sunlight from lower altitudes, such as are found in the higher latitudesjp'risiri 36 would reject sunlight from intermediate sun altitudes, such as are fo iiiidinint e'rmediate latitudes; and prism 37 would' reject" sunlight at the highest sun'altitudes'such as are'fo'und in" thelower latitudes. It' may thus be seen that a series of pr'i sins at varying angles may be stiucted to reject the sunlight over a' broadra'ng'e of This table indicates that by specifying the angles b b and b as indicated, the zone of rejection of sun altitudes may be in effect broadened and thereby extend from 58 /2 to 75 /2". Table III shows that there will be total rejection of sunlight at altitude angles 62 /z-7l /z and partial rejection of sunlight at altitude angles 58%. "-62% and 7l /275 /2. It should be thus noted that the effect of having a series of prisms at various angles will be to diminish the amount of light rejected for any particular sun altitude. Thus, although the range of sun altitude partially rejected may increase, the range of altitude of sun totally rejected will be less than that which would be rejected if all the prisms were at the same angle. Specifically the range would be approximately 9 instead of approximately 13".

It should be pointed out that the series as shown in Fig. 9 is only representative. It is within the scope of my invention to have a series consisting of any number of prisms having different angles b, with each arranged in accordance with my invention to reject sunlight from predetermined altitude angles.

The concepts of the invention as exemplified in Fig. 9 may be incorporated into a single prism as shown in Fig. 10. In this. construction portions of the prism surfaces are at various angles. The portion 38 on the southern slope at an angle b has a corresponding portion 39 on the northern slope at right angles thereto. Similarly the portion 40 at the angle b has a corresponding portion 41 at right angles thereto, and the portion 42 at the angle b has a corresponding portion 43 at right angles thereto. The action of the prism in Fig. 10 would be equivalent to that of the series shown in Fig. 9, namely to broaden or increase the range of angles of sun altitude at which partial rejection will take place, at the expense of lessening the range of angles which is totally rejected.

It is within the scope of my invention to have a series or multiplicity of surfaces such that the prism faces become curved surfaces. Each increment of the surface on one slope would have a complementary increment of sur face on the other slope of the prism.

Fig. 11 shows another construction of the prism wherein the range or zone of rejection of sun altitudes is broadened providing the same results as shown in Figs. 9 and 10. In this construction the surfaces of the prism 44, 45 do not form an included angle of 90. The surface 44 forms an angle [2 with a horizontal plane and the surface 45 forms an angle with a vertical plane. 12, is not equal to c in this case being greater than c A light ray L19 at an altitude angle a and light ray L20 at angle [1 are totally reflected from the southern slope 44. However, a light ray L21 at angle a which is greater than a and a is not totally reflected by the southern slope 44. Thus the maximum range of rejection of sun altitudes by surface 44 is a to a A light ray L22 at altitude angle a and light ray L23 at altitude angle a are totally reflected from the northern slope 45. However, a light ray L24 at angle a which is less than a and a is not totally reflected by the northern slope 45. Thus the maximum rejection of sun altitudes by surface 45 is 01 to a This analysis of the rays in Fig. 11 shows that total rejection of the sunlight occurs for altitudes a to a 6 Thus this construction may be used to partially reject sunlight over a broad range of sun altitudes. The following table represents the resultant areas of rejection of sun altitudes which may be obtained by a typical construction.

TABLE IV Sun altitude rejected (b =29, c =31 Southern slope a -a =5 8 7 1 /2 Northern slope a a =6278 Total rejection a, a =6271 /2 Table IV shows that for 1),:29" and c =31, total rejection of sunlight (rejection on both surfaces) occurs at altitude angles of 62 7l /2, whereas partial rejection (rejection on one surface only) occurs at altitude angles of 5S-62 and 71 /2-78.

I have determined that the inclined angle p of the prisms on Face 2 in any of the forms of my invention may range from 82 to 98, the angle of being preferred since it is the angle which produces the largest range of altitude angles wherein complete rejection of sunlight occurs.

A further modification of the prisms on Face 2 is shown in Fig. 12. In this form, a third surface 46 at angle 1 is placed between the surface 47 and surface 48 of the adjacent prism. Such a surface serves to shorten the length of the surface 47 from that in the other forms, and to thereby transmit the sunlight from low altitude angles, which might otherwise be reflected. For example, light ray L25 would normally be reflected out of the prism but by the construction shown is refracted toward the interior. Thus, the amount of light transmitted is greater than the amount transmitted in the other forms of the invention.

I have found that the angle which the surface 46 forms with a horizontal plane is preferably greater than the largest altitude angle of sunlight which is to be rejected by the prism.

It is considered to be within the scope of my invention that the axes of the prisms may extend in a generally east-west direction and not necessarily in a precise eastwest direction.

In addition, it is within the scope of my invention to accomplish the equivalent of shifting or rotating the prisms about an east-west axis by changing the slope of the entire glass block panel, e. g. by varying its position slightly from the horizontal.

It is also within the scope of my invention that light transmitting materials other than glass might be used, embodying the teachings of my invention, with such modifications as might be necssary as apparent to those skilled in the art.

Modifications may be resorted to within the spirit and scope of the appended claims.

I claim:

1. The combination of a ceiling having an opening therethrough, and a skylight interposed in said opening and comprising a series of four air-glass interfaces interposed in a horizontal position between the daylight and the interior being lighted, the second interface from the light source having a series of parallel unsymmetrical prisms formed thereon extending in a generally east-west direction, each said prism having surfaces forming an included angle of approximately ninety degrees, one said surface of each prism forming an angle of approximately 30 degrees with a horizontal plane, said 30 degree surface extending upwardly in a southerly direction such that sunlight from high altitude angles is totally rejected by total internal reflection within a single prism and sunlight from low altitude angles and light from the northern sky are transmitted by refraction through the prisms toward the interior being lighted, said third and fourth interfaces having light difiusing means formed thereon for diffusing the light passing therethrough into the interior.

'2. The combination of a ceiling having an opening therethrough and a skylight interposed in said opening and comprising a series of four air-glass interfaces interposed in a horizontal position between the daylight and the interior being lighted, the second interface from the light source having a series of parallel unsymmetrical prisms formed thereon extending in a generally east-west direction, each said prism having surfaces forming an included angle ranging from '82 to 98 degrees, one said surface of each prism formingan angle of approximately 30 degrees with a horizontal plane, said 30 degree surface extending upwardly in a southerly direction such that sunlight from high altitude angles is totally rejected by total internal reflection within a single prism and sunlight from low altitude angles and light from the northern sky are transmitted by refraction through the prisms toward the interior being lighted, said third and fourth interfaces having light diffusing means formed thereon for diffusing the light passing therethrough into the interior.

'3. In a structure for controlling daylight, the combination comprising a ceiling having an opening therethrough and a skylight interposed in said opening and comprising at least one sheet of light-transmitting material interposed in a generally'horizontal position between the daylight and the interior being lighted, said sheet having a series of unsymmetrical parallel prisms on the face thereof nearest the interior, the axes of said prisms extending in a generally east-west direction, each said prism having a first surface extending upwardly in a southerly direction and a second surface extending upwardly in a northerly direction, said second surface form-' ing a greater angle with a horizontal plane than the angle which said first surface forms with a horizontal plane, said angles which said surfaces form with a horizontal plane, and the included angle between said surfaces ranging from 82 to 98 such that sunli ht from high altiture angles is totally rejected by total internal reflection within said prisms and sunlight from low altitude angles and light from the northern sky are transmitted by refraction through the prisms toward the interior being lighted.

4. The combination set forth in claim 3 wherein the included angle between said first and second surfaces of each said prism is approximately 90, the angle which said first surface forms with the horizontal plane being approximately 30, and the angle which said second surface forms with a horizontal plane being approximately 60.

5. The combination set forth in claim 3, the angle which said first surface forms with a horizontal plane being approximately 30.

6. The combination set forth in claim 3 including a second sheet of light-transmiting material positioned between said first sheet and the interior being lighted, said second sheet being formed with light-diffusing means thereon for diffusing the light transmitted thereto to the interior being lighted.

7. The combination set forth in claim 3 wherein said sheet of light-transmitting material comprises one of the walls of a glass block.

8. The combination set forth in claim 3 wherein each said prism has a third surface between the first surface of said prism and the second surface of the adjacent prism, the angle which said third surface forms with a horizontal plane being greater than the angle which said first surface forms with the horizontal plane.

9. The combination set forth in claim 3 wherein the included angle between said first and second surfaces of each said prism is approximately the first surface ofat least one of said prisms forming an angle of approximately 30 with a horizontal plane, the first surface of at least one other prism forming an angle of greater than 30 with a horizontal plane, and the first surface of at least one other prism forming an angle of less than 30 with a horizontal plane.

10. The combination set forth in claim 3 wherein the surfaces of each said prism are curved.

11. The combination set forth in claim 3 wherein the surfaces of each said prism are curved and form an included angle of approximately 90, the first surface of each said prism having portions thereof forming angles equal to, greater than and less than 30, respectively, with a horizontal plane, the second surface of each said prism having portions thereof forming angles of approximately 90 with corresponding portions of the first surface of said'prism.

References Cited in the file of this patent UNITED STATES PATENTS 650,209 White Q 'May 22, 1900 1,949,898 Cochrane et al Mar. 6, 1934 2,097,738 Oita Nov. 2, 1937 2,099,534 Richards Nov. 16, 1937 2,179,863 Rolph Nov. 14, 1939 2,419,267 Lenke Apr. 22, 1947 2,665,610 Harrison Jan, 12, 1954 FOREIGN PATENTS 16,560 Great Britain of 1897 355,297 France of 1905 20,046 Great Britain of 1906

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