LAMP COMPRISING AN ELONGATED LIGHT SOURCE, PARTICULARLY A ROD-SHAPED FLUORESCENT LAMP, AND SHADE OF TRANSPARENT MATERIAL
United States Patent 3716710
A lamp comprising an elongated light source, such as a rod-shaped fluorescent lamp, and a lamp shade of transparent material. The lamp shade has its surface provided with a first set of grooves defining ridged elevations between them and extending parallel to the axis of the elongated light source, and two sets of diagonal grooves symmetrically crossing said first set of grooves in such a manner that the vertex lines defining the bottoms of the troughs formed by the diagonal grooves intersect on the lines of the ridges between neighboring longitudinal grooves and thereby divide the surface into panels of which each contains a prismatic center configuration having a face on each side of a longitudinal ridge, two quarter faces divided by a hip at each end of the ridge and a triangular base pyramid adjoining the foot of the face on each side of the ridge.
US Patent References:
LIGHT FITTING HAVING AT LEAST ONE TUBULAR LAMP AND A TRANSPARENT COVERING OF SYNTHETIC RESIN GLASS WITH A PRISMATIC SURFACE
Muller et al. - October 1970 - 3532876
Light refractor
Winkler et al. - September 1961 - 3001062
Control of daylighting
Boyd - October 1956 - 2768556
LIGHT FITTING HAVING AT LEAST ONE TUBULAR LAMP AND A TRANSPARENT COVERING OF SYNTHETIC RESIN GLASS WITH A PRISMATIC SURFACE
Muller et al. - October 1970 - 3532876
Light refractor
Winkler et al. - September 1961 - 3001062
Control of daylighting
Boyd - October 1956 - 2768556
Inventors:
Clostermann, Friedrich (Hagen, DT)
Richter, Han-joachim (Neheim-Husten, DT)
Richter, Han-joachim (Neheim-Husten, DT)
Application Number:
05/029088
Publication Date:
02/13/1973
Filing Date:
04/16/1970
View Patent Images:
Export Citation:
Assignee:
Trilux-Lenze KG (Neheim-Husten, DT)
Primary Class:
Other Classes:
362/330
International Classes:
F21V5/00; F21V5/00
Field of Search:
240/106,51.11,9.5,92,93,41.4 161/2,3.5,123 350/259
Primary Examiner:
Queisser, Richard C.
Assistant Examiner:
Snee III, Charles E.
Claims:
What is claimed is
1. A lamp comprising an elongated light source, such as at least one rod-shaped fluorescent lamp, and a lamp shade of transparent material, one surface of said shade having a plurality of spaced parallel longitudinal V-shaped grooves extending in a direction substantially parallel to the said elongated light source and forming parallel ridges between adjacent pairs of said longitudinal grooves, and two sets of equally spaced parallel V-shaped grooves extending diagonally to said longitudinal grooves, one of said sets being transverse to said other set and the vertex lines of said diagonal grooves having points of intersection which are in a vertical plane with said ridges between the longitudinal grooves, the edges of both sets of adjacent parallel diagonal grooves being spaced from each other by a flattened ridge area, whereby configurations on hexagonal bases surrounded by pyramids on triangular bases are formed within each zone of the surface of the shade defined by adjacent pairs of diagonal grooves of both sets, said configurations on the hexagonal bases are elongated prisms with a ridge line extending parallel to the elongated light source, have inclined side faces defined by said longitudinal grooves and have inclined quarter faces defined by said diagonal grooves.
2. A lamp according to claim 1 wherein the vertex lines of said diagonal grooves form squares, each square containing one of said configurations on the hexagonal base and two of said pyramids on triangular bases, said longitudinal grooves extending diagonally across each of said squares parallel to said elongated light source and the vertex lines of adjacent longitudinal grooves passing through opposite corners of each of said squares define isosceles, right angled triangles, the legs of which are half the length of a side of the square.
3. A lamp according to claim 1 wherein the diagonal grooves intersect the longitudinal grooves at an angle of less than 45° .
4. A lamp according to claim 1 wherein the diagonal grooves and longitudinal grooves include discontinuity lines at the same level with respect to the surface of the shade.
5. A lamp according to claim 1 wherein the angle at the ridge of the prismatic configuration is approximately 90° .
6. A lamp according to claim 1 wherein the vertex angle of both said longitudinal and diagonal grooves is about 90° .
7. A lamp according to claim 1 wherein the angle of the ridge of the prismatic configurations is approximately 130° .
8. A lamp according to claim 1 wherein the vertex angle of said longitudinal and diagonal grooves is approximately 130° .
9. A lamp according to claim 1 wherein the surface of the lamp shade comprises depressions corresponding to the elevations.
1. A lamp comprising an elongated light source, such as at least one rod-shaped fluorescent lamp, and a lamp shade of transparent material, one surface of said shade having a plurality of spaced parallel longitudinal V-shaped grooves extending in a direction substantially parallel to the said elongated light source and forming parallel ridges between adjacent pairs of said longitudinal grooves, and two sets of equally spaced parallel V-shaped grooves extending diagonally to said longitudinal grooves, one of said sets being transverse to said other set and the vertex lines of said diagonal grooves having points of intersection which are in a vertical plane with said ridges between the longitudinal grooves, the edges of both sets of adjacent parallel diagonal grooves being spaced from each other by a flattened ridge area, whereby configurations on hexagonal bases surrounded by pyramids on triangular bases are formed within each zone of the surface of the shade defined by adjacent pairs of diagonal grooves of both sets, said configurations on the hexagonal bases are elongated prisms with a ridge line extending parallel to the elongated light source, have inclined side faces defined by said longitudinal grooves and have inclined quarter faces defined by said diagonal grooves.
2. A lamp according to claim 1 wherein the vertex lines of said diagonal grooves form squares, each square containing one of said configurations on the hexagonal base and two of said pyramids on triangular bases, said longitudinal grooves extending diagonally across each of said squares parallel to said elongated light source and the vertex lines of adjacent longitudinal grooves passing through opposite corners of each of said squares define isosceles, right angled triangles, the legs of which are half the length of a side of the square.
3. A lamp according to claim 1 wherein the diagonal grooves intersect the longitudinal grooves at an angle of less than 45° .
4. A lamp according to claim 1 wherein the diagonal grooves and longitudinal grooves include discontinuity lines at the same level with respect to the surface of the shade.
5. A lamp according to claim 1 wherein the angle at the ridge of the prismatic configuration is approximately 90° .
6. A lamp according to claim 1 wherein the vertex angle of both said longitudinal and diagonal grooves is about 90° .
7. A lamp according to claim 1 wherein the angle of the ridge of the prismatic configurations is approximately 130° .
8. A lamp according to claim 1 wherein the vertex angle of said longitudinal and diagonal grooves is approximately 130° .
9. A lamp according to claim 1 wherein the surface of the lamp shade comprises depressions corresponding to the elevations.
Description:
BACKGROUND OF THE INVENTION
This invention relates to a lamp comprising an elongated light source, particularly a rod-shaped fluorescent lamp, and a shade of transparent material having a surface bearing a set of grooves extending parallel to the elongated light source and intersected by further grooves crossing them at an angled. The intersecting sets of grooves thus give rise to the formation between them of prismatic configuration having a central crest and a sloping face on each side.
In a known arrangement continuous strip-shaped prismatic configurations resembling cylinder lenses are formed on the surface. One objection of such lamp shades is that they are too transparent and that the light sources and installational fittings inside the lamp can be seen through the shade.
It has already been proposed to eliminate this defect by providing a shade made of a transparent plastics material with prismatic surface configurations. In this arrangement the longitudinal grooves are intersected by transverse grooves crossing the lamp axis at right angles, but more widely spaced than the longitudinal grooves. If both sets of grooves are of Vee-shaped cross section the crossing grooves define prismatic configurations resembling hipped roofs with their ridges running parallel to the lamp.
SUMMARY OF THE INVENTION
The principal object of the invention is to distribute the light of the lamp primarily in the broadside direction, a further object being to render the interiors of the lamps less visible than through the shades already known in the art. Moreover, it is also intended that the lamp shades and the tools needed for making the shades should be producible at an economical price.
For achieving these objects the present invention provides a lamp comprising an elongated light source, such as a rod-shaped fluorescent lamp, and a lamp shade of transparent material having a surface provided with a first set of grooves defining ridged elevations between them and extending parallel to the axis of the elongated light source, and two sets of diagonal grooves symmetrically crossing said first set of grooves in such a manner that the vertex lines defining the bottoms of the troughs formed by the diagonal grooves intersect on the lines of the ridges between neighboring longitudinal grooves and thereby divide the surface into panels of which each contains a prismatic center configuration having a face on each side of a longitudinal ridge, two quarter faces divided by a hip at each end of the ridge and a triangular base pyramid adjoining the foot of the face on each side of the ridge.
According to the angle of strike of the diagonal grooves these will define square or diamond panels in which the prismatic configurations rise in the center. Pyramids on a triangular base are formed at the base of each side of the central prismatic configurations. Moreover, the diagonal grooves cutting across the elevations between neighboring longitudinal grooves give rise to the quarter faces formed between the hips and a crest descending from the end of the ridge to the point of intersection of the vertices of the troughs of the diagonal grooves.
That this arrangement destroys the clear view through the shade is due to the creation of the multiplicity of relatively small surfaces, such as of the pyramid faces, which have a flashing effect like that of a cut diamond. The directed useful light is principally transmitted through the sloping side faces of the prismatic center configurations. The idea which underlies the invention comprises a large number of possibilities of directing the light into given directions by selecting the pitch of the side faces.
The invention further proposes that the cross sections of the diagonal grooves should be Vee-shaped. This cross section of the diagonal grooves can be combined with any desired cross sectional contour of the longitudinal grooves and the latter may for instance have the form of symmetrical or asymmetrical cylinder and like rod-shaped lenses. The diagonal grooves should be so disposed that the vertex lines defining the bottoms of the grooves intersect on the lines of the ridges between the longitudinal grooves when viewed from above.
For refracting the light into given directions the pitch of the sides of the longitudinal grooves may be varied. More particularly the side faces may include a discontinuity where the pitch abruptly changes.
The invention further proposes that such a discontinuity line should also appear on the quarter faces at the ends of the prismatic center configurations. For this purpose the sides of the diagonal grooves must likewise be divided by a discontinuity line dividing the sides into faces of different pitch. The quarter faces of the prismatic configuration can thus also be used for directionally controlling the emitted light.
The flashing cut-diamond effect of the pyramids which prevents the interior of the lamp from being seen can be improved if, according to the invention, the faces of the pyramids are also divided by discontinuity lines. This can be achieved if the discontinuity lines on the side of the longitudinal and diagonal grooves are at a sufficiently low level.
Furthermore, according to another feature of the invention the angle of intersection between the longitudinal and diagonal grooves may be less than 45°. In such a case the panels defined by the intersecting diagonals will be diamond-shaped, causing the side faces of the prismatic center configurations to be more elongated. This effect can also be utilized for controlling the direction of emission of light from the lamp.
BRIEF DESCRIPTION OF THE DRAWINGS
Several embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which:
FIG. 1 is a plan view of a lamp with a shade provided with the proposed groovings;
FIG. 1A is a side view of the lamp shown in FIG. 1;
FIG. 1B is a partial end view of the lamp shown in FIG. 1 indicating the configuration of the grooves;
FIG. 2 is a plan view, on a larger scale, of several square panels defined by grooves provided in the lamp shade surface, the cross sections of the intersecting grooves being triangular;
FIG. 2A is a section on the line 2A--2A of FIG. 2;
FIG. 2B is a section on the line 2B--2B of FIG. 2;
FIGS. 3, 3A and 3B show cross sections of a second embodiment with a pitch descontinuity forming a salient angle in the section;
FIGS. 4, 4A and 4B show a third embodiment comprising triangular-base pyramids having faces divided by discontinuity lines;
FIGS. 5, 5A and 5B show a fourth embodiment of a groove cross section having a pitch discontinuity forming a reentrant angle in the section;
FIG. 6 is a plan view of a fifth embodiment having a configuration obtained by diagonal grooves intersecting the longitudinal grooves at an angle of less than 45°; and
FIGS. 7, 7A, 7B, 7C, 7D, 7E and 7F illustrate other possible groove configurations of the cylinder lens type.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference first to FIGS. 1, 1A, and 1B, 15 is a lamp casing, 10 is the associated shade of transparent material. The undersurface of the shade 10 has the configuration proposed by the invention. It is provided with a set of parallel longitudinal grooves 11 extending parallel to the lamp or lamps. In cross section these grooves 11 are triangular. The elevations 12 between neighboring grooves are likewise triangular in cross section. The grooves are diagonally intersected at angles of 45° by two further sets of grooves 13, also of triangular cross section.
The vertex lines of the troughs formed by the two sets of diagonal grooves intersect on the lines of the crests of the elevations 12.
This will be understood more particularly from FIG. 2, which is a plan view of several squares defined by the intersecting diagonal grooves and shows sections taken on the diagonal line A--A and on the transverse line B--B.
20 are the triangular section longitudinal grooves (section B--B), 21 being the vertex lines of the troughs formed by these grooves. The elevations 20a between the grooves 20 are likewise triangular in cross section and form ridges 22.
The section A--A shows the diagonal grooves 23 which are likewise triangular in cross section and form sharp-angled troughs 24. The edges 23a of adjacent diagonal grooves 23 are spaced from each other. The intersecting diagonal grooves 23 run at angles of 45° and define a system of squares having corners at the intersection points 27 where the vertex lines 24 of the troughs or grooves 23 intersect. The intersection points 27 are located on the projections of the lines of the ridges 22.
A portion of the prismatic elevation 20a, resembling a faceted surface, remains in the center of each square. From each end of the ridge 22 of this elevation a hip 22a leads to the intersection points 27.
The bottom end of the side face 26 on each side of the central prismatic elevation is adjoined by a pyramid 28 on a triangular base. These pyramids 28 complete the square.
The utilized light is emitted in desired directions at the calculated optical angles, particularly from the side faces 26. Light is also emitted through the quarter faces 25. By appropriately selecting the angles of the diagonal grooves the same emission effect can be imparted to these quarter faces 25. The interior of the lamp is obscured particularly by the joint effect of the pyramids which surround each prismatic center elevation and generate the flashing effect of a cut diamond.
In the embodiment according to FIGS. 3, 3A and 3B the cross section of longitudinal grooves 30 includes a Vee angle 31 of 90° in the trough, whereas the angle at the ridge 32 is about 130°, due to the pitch of the sides including a discontinuity 33. These angles are governed by the desired directional emission of the light. In this embodiment the diagonal grooves 34 are likewise of triangular cross section forming an angle in the troughs at 35 of 90°, and they also have a similar discontinuity at 36. The view of the surface in plan shows that the discontinuities 33 and 36 extend around the center elevation in a plane parallel to the base. The quarter faces as well as the side faces are thus divided into component faces 36a, 36b of different pitch at the same angles of refraction. The prismatic elevation has the appearance of being faceted. 38 are lateral pyramids.
In the embodiment according to FIGS. 4, 4A and 4B the discontinuity 43 respectively 46 in the longitudinal grooves and the diagonal grooves are at a lower level. Consequently a discontinuity line 49 also cuts the faces of the pyramids 48 and these pyramids therefore likewise appear as if they were bevelled. The cut diamond effect of the pyramids is thus increased.
In the embodiment according to FIGS. 5, 5A and 5B the angle at the ridge 52 is 90°. It has been found that when this is the case some reflection occurs in the neighborhood of the ridge and that this contributes to preventing the interior of the lamp from being seen, as intended by the invention. If the vertex angle in the trough 51 of the grooves is 130° a discontinuity forming a re-entrant dihedral angle appears at 53.
In the embodiment according to FIG. 6 the angle 63 between longitudinal grooves 61 and diagonal grooves 65 is less than 45° when seen in plan. The squares are therefore changed to diamonds and the side faces 62 are more elongated and enlarged.
Instead of the longitudinal grooves having flat sides these may be arched, forming elongated cylinder lenses, possibly of differing cross sections, as illustratively indicated in FIGS. 7, 7A, 7B, 7C, 7D, 7E and 7F. The arched surfaces may be concave as at 72, convex as at 70, symmetrical as at 71 or asymmetrical as at 73, 74 and 76. They may also be combined with flat faces 75.
In association with all these longitudinal grooves Vee-section diagonal grooves may be provided and so disposed that the lines of intersection, i.e. the hips, adjoin the ridges and the vertex lines of the troughs. The diagonal grooves may also have arched sides, care being taken to see that the discontinuity lines where the pitch changes abruptly are also contour lines.
The invention is applicable to lamps having elongated light sources of all kinds, particularly rod-shaped fluorescent lamps, but also to linear arrays of incandescent lamps and so forth.
The invention is further applicable to trough-shaped, tubular or disc-shaped lamp shades made of silica glass or transparent plastics.
In all the illustrated embodiments the prismatic and pyramidal configurations are elevations. However, the same effect can be achieved by inverting the geometries in such a manner that the elevations become depressions.
The invention can be carried into effect by simple production methods because the longitudinal and diagonal grooves are quite easily producible on conventional machine tools, for instance by cutting the grooves into steel platens which may then be used as dies for pressing the shade if the configurations are to be depressions. On the other hand, if the configurations are to be elevations, as in the described embodiments, then the tools required for pressing must be negative copies of the machined matrices.
As may be required, the proposed configurations may be provided on the insides or outsides of the shades.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive.
This invention relates to a lamp comprising an elongated light source, particularly a rod-shaped fluorescent lamp, and a shade of transparent material having a surface bearing a set of grooves extending parallel to the elongated light source and intersected by further grooves crossing them at an angled. The intersecting sets of grooves thus give rise to the formation between them of prismatic configuration having a central crest and a sloping face on each side.
In a known arrangement continuous strip-shaped prismatic configurations resembling cylinder lenses are formed on the surface. One objection of such lamp shades is that they are too transparent and that the light sources and installational fittings inside the lamp can be seen through the shade.
It has already been proposed to eliminate this defect by providing a shade made of a transparent plastics material with prismatic surface configurations. In this arrangement the longitudinal grooves are intersected by transverse grooves crossing the lamp axis at right angles, but more widely spaced than the longitudinal grooves. If both sets of grooves are of Vee-shaped cross section the crossing grooves define prismatic configurations resembling hipped roofs with their ridges running parallel to the lamp.
SUMMARY OF THE INVENTION
The principal object of the invention is to distribute the light of the lamp primarily in the broadside direction, a further object being to render the interiors of the lamps less visible than through the shades already known in the art. Moreover, it is also intended that the lamp shades and the tools needed for making the shades should be producible at an economical price.
For achieving these objects the present invention provides a lamp comprising an elongated light source, such as a rod-shaped fluorescent lamp, and a lamp shade of transparent material having a surface provided with a first set of grooves defining ridged elevations between them and extending parallel to the axis of the elongated light source, and two sets of diagonal grooves symmetrically crossing said first set of grooves in such a manner that the vertex lines defining the bottoms of the troughs formed by the diagonal grooves intersect on the lines of the ridges between neighboring longitudinal grooves and thereby divide the surface into panels of which each contains a prismatic center configuration having a face on each side of a longitudinal ridge, two quarter faces divided by a hip at each end of the ridge and a triangular base pyramid adjoining the foot of the face on each side of the ridge.
According to the angle of strike of the diagonal grooves these will define square or diamond panels in which the prismatic configurations rise in the center. Pyramids on a triangular base are formed at the base of each side of the central prismatic configurations. Moreover, the diagonal grooves cutting across the elevations between neighboring longitudinal grooves give rise to the quarter faces formed between the hips and a crest descending from the end of the ridge to the point of intersection of the vertices of the troughs of the diagonal grooves.
That this arrangement destroys the clear view through the shade is due to the creation of the multiplicity of relatively small surfaces, such as of the pyramid faces, which have a flashing effect like that of a cut diamond. The directed useful light is principally transmitted through the sloping side faces of the prismatic center configurations. The idea which underlies the invention comprises a large number of possibilities of directing the light into given directions by selecting the pitch of the side faces.
The invention further proposes that the cross sections of the diagonal grooves should be Vee-shaped. This cross section of the diagonal grooves can be combined with any desired cross sectional contour of the longitudinal grooves and the latter may for instance have the form of symmetrical or asymmetrical cylinder and like rod-shaped lenses. The diagonal grooves should be so disposed that the vertex lines defining the bottoms of the grooves intersect on the lines of the ridges between the longitudinal grooves when viewed from above.
For refracting the light into given directions the pitch of the sides of the longitudinal grooves may be varied. More particularly the side faces may include a discontinuity where the pitch abruptly changes.
The invention further proposes that such a discontinuity line should also appear on the quarter faces at the ends of the prismatic center configurations. For this purpose the sides of the diagonal grooves must likewise be divided by a discontinuity line dividing the sides into faces of different pitch. The quarter faces of the prismatic configuration can thus also be used for directionally controlling the emitted light.
The flashing cut-diamond effect of the pyramids which prevents the interior of the lamp from being seen can be improved if, according to the invention, the faces of the pyramids are also divided by discontinuity lines. This can be achieved if the discontinuity lines on the side of the longitudinal and diagonal grooves are at a sufficiently low level.
Furthermore, according to another feature of the invention the angle of intersection between the longitudinal and diagonal grooves may be less than 45°. In such a case the panels defined by the intersecting diagonals will be diamond-shaped, causing the side faces of the prismatic center configurations to be more elongated. This effect can also be utilized for controlling the direction of emission of light from the lamp.
BRIEF DESCRIPTION OF THE DRAWINGS
Several embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which:
FIG. 1 is a plan view of a lamp with a shade provided with the proposed groovings;
FIG. 1A is a side view of the lamp shown in FIG. 1;
FIG. 1B is a partial end view of the lamp shown in FIG. 1 indicating the configuration of the grooves;
FIG. 2 is a plan view, on a larger scale, of several square panels defined by grooves provided in the lamp shade surface, the cross sections of the intersecting grooves being triangular;
FIG. 2A is a section on the line 2A--2A of FIG. 2;
FIG. 2B is a section on the line 2B--2B of FIG. 2;
FIGS. 3, 3A and 3B show cross sections of a second embodiment with a pitch descontinuity forming a salient angle in the section;
FIGS. 4, 4A and 4B show a third embodiment comprising triangular-base pyramids having faces divided by discontinuity lines;
FIGS. 5, 5A and 5B show a fourth embodiment of a groove cross section having a pitch discontinuity forming a reentrant angle in the section;
FIG. 6 is a plan view of a fifth embodiment having a configuration obtained by diagonal grooves intersecting the longitudinal grooves at an angle of less than 45°; and
FIGS. 7, 7A, 7B, 7C, 7D, 7E and 7F illustrate other possible groove configurations of the cylinder lens type.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference first to FIGS. 1, 1A, and 1B, 15 is a lamp casing, 10 is the associated shade of transparent material. The undersurface of the shade 10 has the configuration proposed by the invention. It is provided with a set of parallel longitudinal grooves 11 extending parallel to the lamp or lamps. In cross section these grooves 11 are triangular. The elevations 12 between neighboring grooves are likewise triangular in cross section. The grooves are diagonally intersected at angles of 45° by two further sets of grooves 13, also of triangular cross section.
The vertex lines of the troughs formed by the two sets of diagonal grooves intersect on the lines of the crests of the elevations 12.
This will be understood more particularly from FIG. 2, which is a plan view of several squares defined by the intersecting diagonal grooves and shows sections taken on the diagonal line A--A and on the transverse line B--B.
20 are the triangular section longitudinal grooves (section B--B), 21 being the vertex lines of the troughs formed by these grooves. The elevations 20a between the grooves 20 are likewise triangular in cross section and form ridges 22.
The section A--A shows the diagonal grooves 23 which are likewise triangular in cross section and form sharp-angled troughs 24. The edges 23a of adjacent diagonal grooves 23 are spaced from each other. The intersecting diagonal grooves 23 run at angles of 45° and define a system of squares having corners at the intersection points 27 where the vertex lines 24 of the troughs or grooves 23 intersect. The intersection points 27 are located on the projections of the lines of the ridges 22.
A portion of the prismatic elevation 20a, resembling a faceted surface, remains in the center of each square. From each end of the ridge 22 of this elevation a hip 22a leads to the intersection points 27.
The bottom end of the side face 26 on each side of the central prismatic elevation is adjoined by a pyramid 28 on a triangular base. These pyramids 28 complete the square.
The utilized light is emitted in desired directions at the calculated optical angles, particularly from the side faces 26. Light is also emitted through the quarter faces 25. By appropriately selecting the angles of the diagonal grooves the same emission effect can be imparted to these quarter faces 25. The interior of the lamp is obscured particularly by the joint effect of the pyramids which surround each prismatic center elevation and generate the flashing effect of a cut diamond.
In the embodiment according to FIGS. 3, 3A and 3B the cross section of longitudinal grooves 30 includes a Vee angle 31 of 90° in the trough, whereas the angle at the ridge 32 is about 130°, due to the pitch of the sides including a discontinuity 33. These angles are governed by the desired directional emission of the light. In this embodiment the diagonal grooves 34 are likewise of triangular cross section forming an angle in the troughs at 35 of 90°, and they also have a similar discontinuity at 36. The view of the surface in plan shows that the discontinuities 33 and 36 extend around the center elevation in a plane parallel to the base. The quarter faces as well as the side faces are thus divided into component faces 36a, 36b of different pitch at the same angles of refraction. The prismatic elevation has the appearance of being faceted. 38 are lateral pyramids.
In the embodiment according to FIGS. 4, 4A and 4B the discontinuity 43 respectively 46 in the longitudinal grooves and the diagonal grooves are at a lower level. Consequently a discontinuity line 49 also cuts the faces of the pyramids 48 and these pyramids therefore likewise appear as if they were bevelled. The cut diamond effect of the pyramids is thus increased.
In the embodiment according to FIGS. 5, 5A and 5B the angle at the ridge 52 is 90°. It has been found that when this is the case some reflection occurs in the neighborhood of the ridge and that this contributes to preventing the interior of the lamp from being seen, as intended by the invention. If the vertex angle in the trough 51 of the grooves is 130° a discontinuity forming a re-entrant dihedral angle appears at 53.
In the embodiment according to FIG. 6 the angle 63 between longitudinal grooves 61 and diagonal grooves 65 is less than 45° when seen in plan. The squares are therefore changed to diamonds and the side faces 62 are more elongated and enlarged.
Instead of the longitudinal grooves having flat sides these may be arched, forming elongated cylinder lenses, possibly of differing cross sections, as illustratively indicated in FIGS. 7, 7A, 7B, 7C, 7D, 7E and 7F. The arched surfaces may be concave as at 72, convex as at 70, symmetrical as at 71 or asymmetrical as at 73, 74 and 76. They may also be combined with flat faces 75.
In association with all these longitudinal grooves Vee-section diagonal grooves may be provided and so disposed that the lines of intersection, i.e. the hips, adjoin the ridges and the vertex lines of the troughs. The diagonal grooves may also have arched sides, care being taken to see that the discontinuity lines where the pitch changes abruptly are also contour lines.
The invention is applicable to lamps having elongated light sources of all kinds, particularly rod-shaped fluorescent lamps, but also to linear arrays of incandescent lamps and so forth.
The invention is further applicable to trough-shaped, tubular or disc-shaped lamp shades made of silica glass or transparent plastics.
In all the illustrated embodiments the prismatic and pyramidal configurations are elevations. However, the same effect can be achieved by inverting the geometries in such a manner that the elevations become depressions.
The invention can be carried into effect by simple production methods because the longitudinal and diagonal grooves are quite easily producible on conventional machine tools, for instance by cutting the grooves into steel platens which may then be used as dies for pressing the shade if the configurations are to be depressions. On the other hand, if the configurations are to be elevations, as in the described embodiments, then the tools required for pressing must be negative copies of the machined matrices.
As may be required, the proposed configurations may be provided on the insides or outsides of the shades.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive.