NATURAL LIGHTING APPARATUS

Abstract: A natural lighting apparatus including: a mirror (12) having a mirror face for reflecting light; a supporting mechanism (4, 8) for supporting the mirror (12) to be rotatable about both a first axis and a second axis perpendicular to the first axis; a first sensing mechamsim (44) for sensing a first direction of the light source about the first axis for generating a first signal representative of the first light source direction about the first axis; a second sensing mechanism (46) for sensing a second direction of the light source about the second axis for generating a second signal representative of the second light source direction about the second axis; an attitude control mechanism (30, 34) for angularly moving the mirror about the first axis according to the first signal from the first sensing mechanism (44) and about the second axis according to the second signal from the second sensing mechanism, thus controlling the attitude of the mirror to reflect light from the light source in a predetermined direction.

Description: The present invention relates to a natural lighting apparatus which introduces natural light, such as sunlight, in a desired direction. The natural lighting apparatus is conventionally used for lighting with sunlight shade places of a building, street, etc. Such a conventional natural lighting apparatus is controlled by means of a computer system to follow the sun for enhancing its lighting efficiency. For this control the locus of the sun is calculated according to information as to latitude, etc at the installation place. This prior art lighting apparatus is disadvantageous in that it must be adjusted to the latitude and the like according to change in the installation site with a relatively high accuracy, and in that the computer program must be also changed. These disadvantages result in considerable rise in installation cost. Accordingly, it is an object of the present invention to provide a natural lighting apparatus which necessitates no substantial adjustment, such as latitude adjustment, to change in the installation place, thus reducing installation cost. A natural lighting apparatus permitting rotation of a mirror about first and second mutually perpendicular axes according to the preamble of claim 1 is known from US-A-2 135 997. In the known device a light source following lever is constituted by a secondary mirror forming part of a contact maker. This secondary mirror is mounted to an inner mirror-supporting frame for pivotal movement about an axis parallel to, but displaced from, the second main-mirror pivot axis. A pulley system linking the two axes ensures that the main mirror rotates at half the angular rate of the secondary mirror. It is a further object of the present invention to provide a natural lighting apparatus having a simpler mechanical construction. The above and other objects are achieved by a natural lighting apparatus in accordance with claim 1. In particular, the light source following lever of the invention pivots about the same axis as the main mirror, and the pulley system of the prior art is replaced by a crank mechanism. Further advantageous embodiments of the invention are defined in the dependent claims. The invention will now be described by way of example with reference to the accompanying drawings in which like reference numerals designate similar parts throughout the figures: FIG. 1 is a side view, partly broken away, of a natural lighting apparatus according to the present invention; FIG. 2 is an enlarged side view of the light introducing unit 3 in FIG. 1; FIG. 3 is an enlarged plan view of the light reflecting unit in FIG. 1; FIG. 4 is one side view of the light reflecting unit in FIG. 3; FIG. 5 is another side view of the light reflecting unit in FIG. 3; FIG. 6 is a perspective view of an enlarged coarse control sensor in FIG. 2; FIG. 7 is a perspective view of an enlarged fine control sensor in FIG. 2; FIG. 8 is a side view with a reduced scale of the fine control sensor in FIG. 7; FIG. 9 is a front view of the fine control sensor in FIG. 8; FIG. 10 is a modified form of the natural lighting apparatus in FIG. 1; FIG. 11 is a front view of a modified form of the light introducing unit in FIG. 2; FIG. 12 is a rear view of the light introducing unit in FIG. 11; FIG. 13 is a perspective view of a modified form of the fine control sensor in FIG. 7; FIG. 14 is a side view with a reduced scale of the fine control sensor in FIG. 13; and FIG. 15 is a front view of the fine control sensor in FIG. 14. Detailed Description of the Preferred Embodiments Referring to FIGS. 1 to 9, a natural lighting apparatus, constructed according to the present invention, includes a light introducing unit 3 for introducing sunrays S vertically downwards and a light reflecting unit 20 for reflecting sunrays S' in a predetermined position. The light introducing unit 3 has a cubic outer frame 4 mounted to a side wall 2 of a building with a supporting frame 6. Each of the five faces of the outer frame 4 except the bottom face are covered with a transparent cover 56 made of acrylic resin although the latter are not shown in FIG. 1. A rectilinear inner frame 8 is mounted to the outer frame 4 to pass through it. The inner frame 8 is supported on the outer frame 4 for rotation about a vertical axis Z with its center axis placed along the vertical axis Z. Upper and lower frame members of the inner frame 8 have an upper journal 21 and lower journal 22 respectively. The upper journal 21 passes rotatably through an arcuate supporting member 24, of which opposite ends are attached to the outer frame 4, while the lower journal 22 is rotatably supported on a thrust bearing 26 which is mounted to the supporting frame 6. The upper journal 21 has a spur gear 27 mounted at its top. The spur gear 27 meshes with a pinion 28 which is mounted on an output shaft of a driving unit 30 including an electric motor and fixed to the arcuate supporting member 24. The spur gear 27, pinion 28 and the drive unit 30 constitute a frame rotating mechanism 10. The spur gear 27 has a coarse control sensor 44 mounted on its top face. The arcuate supporting member 24 has a limit switch 45 for limiting the horizontal rotation range of the frame 8. The limit switch 45 is actuated by actuating rods (not shown) mounted to the spur gear 27. The inner frame 8 has a rectilinear plane mirror 12 mounted with pins 42 and 42 to its side frame members 8B and 8B, only one of which is shown, for rotation about a horizontal axis. The mirror 12 is placed between the side frame members 8B and 8B with its mirror face 32 directed a front direction. The mirror 12 is provided with a mirror rotating mechanism 14 which includes an drive unit 34 including an electric motor and pivotably connected through a bracket 36 to the back of the mirror 12 for angular movement about a horizontal axis. The output shaft of the drive unit 34 is coaxially jointed to a screw rod 38 which is threaded to a horizontal strip member 41 of which opposite ends are mounted to the inner frame 8 through both horizontal stays 40 and inclined stays 43. By actuating the motor of the drive unit 34 the mirror 12 is angularly moved about the pins 42. One side frame member 8B of the inner frame 8 is provided with a limit switch 145 for limiting the lower limit of the dip angle ϑ of the mirror 12 and another limit switch 47 for limiting the upper limit of the dip angle ϑ of the mirror 12. These limit switches 145 and 47 are actuated when the rear face 33 of the mirror 12 impinges upon them. The inner frame 8 has a pair of generally L-shaped sun following levers 16 and 16, only one of which is shown. Each of the sun following levers 16 and 16 are pivotally attached to a corresponding side frame member 8B through the pin 42 to be located between the mirror 12 and the side frame member 8B. Each sun following lever 16 has a fine control sensor 46 at the free end of one arm 16A nearer to the mirror face 32. The other arm 16B of each sun following lever 16 is connected to a corresponding side edge 13 of the mirror 12 through a slider crank mechanism 18, which includes a slider 50. Each slider 50 has a dovetail groove (not shown) and slidably fits around an elongated dovetail tenon 54 formed in the corresponding side edge 13 to extend along the latter. Two link members 48 and 52, equal in length, are pivotally connected at their one ends to a corresponding slider 50. The other ends of the link members 48 and 52 are also pivotally connected to the other arm 16B of a corresponding sun following lever 16 through a pin 49 and to a corresponding side frame member 8B through a pin 53, respectively. Thus, the dip angle ϑ is held a half of an angle contained between the one arm 16A and the side frame members 8b about the horizontal axis. The reflecting unit 20 is more clearly shown in FIG. 3-5, in which it includes a rectilinear tubular frame 58. A multiplicity of upper parallel plane mirror strips 60 are rotatably supported to the inside of the frame 58 to form an upper louver. Further, the frame 58 has a multiplicity of lower parallel plane mirror strips 64 rotatably mounted to the inside thereof at a lower level than the upper plane mirror strips 60. The lower plane mirror strips 64 are perpendicular to the upper plane mirror strips 60, thus forming a grid in a plan view. The upper and lower plane mirror strips 60 and 64 are mounted to the frame 58 respectively through journals 62, 62 and 66, 66. In this embodiment, the angles of plane mirror strips 60 and 64 to the horizontal plane are individually controlled by angularly moving them. However, they may be simultaneously adjusted by providing a sprocket to, for example, one journal 62 of each of the upper plane mirror strips 60 and by connecting the sprockets with a chain. As illustrated in FIG. 6, the coarse control sensor 44 has a generally T-shape and includes a rectangular parallelopiped base portion 70 and a rectangular parallelopiped body portion 78 perpendicularly extending from the base portion 70. The body portion 78 has a pair of photosensors 74 and 74 attached to its opposite side walls 78A and 78A at positions near to the base portion 70 and symmetric to the centre line C1 of the body portion 78. The photosensors 74 and 74 are disposed so that electric signals supplied from them are equal in amplitude when the center axis C1 of the body portion 7B is directed toward the sun. When the center axis C1 crosses the direction of the sunrays S, the shadow of the body portion 78 falls one one of the photosensors 74 and 74, thus causing the difference in quantity of received sunrays between the photosensors 74 and 74. The coarse control sensor 44 is mounted on the gear 27 so that the centre axis C1 of the body portion 78 is directed perpendicular to and fowards of the mirror faces 32 of the mirror 12, Each of the fine control sensors 46 includes a square base plate 76 and an body portion 178 attached at its one end to the base plate 76 at a right angle. The body portion 178 has a generally square tubular shape and has a longitudinal groove 80 formed in each side face 179 thereof over its length, the groove 80 having a semicircular cross-section. Each of the longitudinal grooves 80 is formed to extend at the center of the corresponding side face 179 of the body portion 178 so that they are symmetric to the center axis C2 of the body portion 178. Four photosensors 82 which are a half in diameter of the grooves 80 are attached to the base plate 76 so that a half of each of them fits into the corresponding groove 80 as illustrated in FIG. 7. Thus, the photosensors 82 are disposed at regular angular intervals of 90° about the center axis C2. The center axis of the light receiving face of each photosensor 82 is directed toward the top of the body portion 178 and in parallel with the center axis C2. With such a construction, shadows 178A of the body portion 178 as illustrated in FIG. 9 falls on at least one of the photosensors 82 when the center axis C2 of the body portion 178 crosses the direction of sunrays S. Another photosensor 84 is attached to the top end of the body portion 178 with its light receiving face placed concentric with the body portion. This photosensor 84 may be omitted. The base plate 76 of each of the two fine control sensors 46 and 46 is mounted to the distal end of the one arm 16A of the corresponding sun following lever 16 so that its center axis C2 is directed forwards in parallel with the longitudinal axis of the one arm 16A as illustrated in FIG. 2. The photosensors 74, 74, 82, 82, 82, 82 and 84, and limit switches 45, 47 and 145 are electrically conncented to a conventional electric control unit 55 (FIG. 2). The drive units 30 and 34 are electrically connected to a power source (not shown) through the control unit 55. When the centre axis C1 of the coarse sensor 44 crosses the direction of sunrays S, there occurs a difference in quantity of received sunrays between the photosensors 74 and 74. Electric signals representing a quantity of received sunrays are supplied from the photosensors 74 and 74 to the control unit 55 where comparison between received light quantities of the photosensors 74 and 74 is made to generate a drive signal which drives the driving unit 30 for turning the inner frame 8 about the vertical axis Z to minimize the difference in received light quantities of the photosensors 74 and 74, so that the center axis C1 of the coarse sensor 44 is brought generally in parallel with the direction of sunrays S in a horizontal plant. Thus, the mirror face 32 is directed toward the sun with an initial dip angle ϑ. This coarse control operation is completed when the difference in received light quantities of the photosensors 74 and 74 drops to a predetermined level. In the fine control sensors 46, electric signals representative of received light quantity are supplied from the photosensors 82 and 82 to the control unit 55 where comparison between received light quantities of the photosensors 82 and 82 is also made to generate a drive signal which drives the driving unit 34, so that the screw rod 38 is rotated for turning the mirror 12 about the pins 42 or the horizontal axis. Thus, the sun following levers 16 and 16 are rotated about pins 42 and 42 through slider crank mechanisms 18 to minimize the difference in received light quantities of the photosensors 82 and 82, so that the center axis C2 of each fine sensor 46 is directed to sunrays S as illustrated in FIG. 2. In this event, the dip angle ϑ is automatically set to (90° - α) with the slider crank mechanisms 18 where the angle α is a half of the angle formed between each one arm 16A and the inner frame 8 about the horizontal axis. Thus, sunrays S are reflected by the mirror face 32 downward along the vertical axis Z. The control unit 55 may supply a drive signal, according to output signals from photosensors 82 and 82 horizontally disposed, to the drive unit 30 so that fine control of rotation of the inner frame 8 is made. In this manner, the natural lighting apparatus follows the sun so that it reflects light downwards. The mirror 12 is kept stationary at night or on a cloudy day since output signals from the photosensors in each of the sensors 44, 46 balance. The limit switch 45 is actuated by the actuating rods off the spur gear 27 to provide inner frame limit position signals to the control unit 55, which then stops and reverses the motor of the drive unit 30. Thus, the mounting positions of the actuating rods define the range of the rotation angle of the inner frame 8. When the mirror 12 is rotated to a substantially vertical position, it actuates the lower limit dip angle limit switch 145, which provides a lower limit dip angle signal to the control unit 55, which then revereses the motor of the drive unit 34. When the upper dip angle limit switch 47 is actuated by the mirror, which is placed substantially horizontal, it provides an upper limit dip angle signal to the control unit 55, which according to this signal reverses the motor of the drive unit 34. Thus, the range of the dip angle ϑ is determined by these limit switches 47 and 145. A modified form of the natural lighting apparatus in FIG. 1 is illustrated in FIG. 10, in which the reflecting unit 20 is supported by the supporting frame 6 to be located just below the light introducing unit 3. This lighting apparatus is used for lighting a shade place 88 of a building. FIGS. 11 and 12 illustrate a modified form of the light introducing unit 3 from which this modification is generally distinct in that it has a pair of semicircular plane mirror 90 and 92 jointed through four channel shaped joints 94, 94, 94 and 94 to the opposite side edges of the mirror 32 to form an assembled plane mirror having a generally ellipse shape. The two semicircular mirrors 90 and 92 are connected to the side frame members 8B and 8B of the inner frame 8 respectively through shafts 96 and 98, which are horizontally fixed to corresponding side frame members 8B, for rotation about the horizontal axis H. In this modification, the mirror 12 is not directly connected to the side frame members 8B and 8B. Further, sun following levers 100 and 102, to each of which the fine control sensor 46 is mounted, are connected to the side frame members 8B and 8B through pins 106 and 108, respectively. The rear ends of the sun following levers 100 and 102 are jointed with a horizontal connecting rod 104. The inner frame 8 is provided at its lower frame member 8A with a pair of introduced light sensors 120 and 120 of the same structure as the fine control sensors 46. The introduced light sensors 120 and 120 are mounted to the lower frame member 8A so that their body portions 178 are directed vertically upwards. These introduced light sensors 120 and 120 are electrically connected to the control unit 55 for more precisely controlling the angles of the mirror about the vertical and horizontal axes Z and H. However, the introduced light sensors 120 and 120 may be omitted. Further, they may function as fine control sensors without providing of the fine control sensors 46 and 46. A modified form of the fine control sensors 46 is illustrated in FIGS. 13 to 15, in which it includes a base disc 132 and a cylindrical body portion 134 erected on the base disc 132. The body portion 134 has four parallel rectangular fin plates 136 mounted to it at regular angular intervals of 90° about its center. Four photosensors 140, 140, 140 and 140 are mounted to the base disc 132 between adjacent two fin plates 136 at regular angular intervals of 90° about the centre of the body portion 134. The body portion 134 has another photosensor 138 mounted at its top although this sensor 138 may be omitted. Each groove defined by the body portion 134 and adjacent two fin plates performs the same function as the semicircular groove 80 of the fine control sensors 46 in FIG. 7 as shown in FIG. 15. The rotation axis of the inner frame 8 may be inclined to the vertical axis Z in which case the horizontal axis H is perpendicular to the included rotation axis. In a specific form, the outer frame 4 may be placed so that the rotation axis of the inner frame is horizontal. While the invention has been disclosed in specific detail for purposes of clarity and complete disclosure, the true scope of the invention is defined by the appended claims.

Claims: A natural lighting apparatus comprising: (a) a mirror (12) for reflecting light from a light source (S) towards a predetermined direction parallel to a first axis; (b) supporting means for supporting the mirror (12) to be rotatable about both the first axis and a second axis perpendicular to the first axis, the supporting means comprising an outer frame (4) and an inner frame (8) supported on the outer frame (4) for rotation about the first axis, the mirror (12) being supported on the inner frame (8) to be rotatable about the second axis; (c) first sensing means (44) for sensing a first direction of the light source about the first axis for generating a first signal representative of the first light source direction about the first axis; (d) second sensing means (46, 130) for sensing a second direction of the light source about the second axis for generating a second signal representative of the second light source direction about the second axis; (e) attitude control means (14, 30, 34) for angularly moving the mirror about the first axis according to the first signal from the first sensing means and about the second axis according to the second signal from the second sensing means; (f) a light source following lever (16), pivotally mounted to the inner frame (8); and (g) means, connecting the mirror (12) to both the inner frame (8) and the light source following lever (16), for maintaining the angle between the mirror (12) and the inner frame (8) about the second axis, to be one half of the angle between the inner frame (8) and the light source following lever (16); characterized by (h) said light source following lever (16) being pivotally mounted on said second axis; (i) said second sensing means (46, 130) being mounted on said light source following lever (16); and (j) said means for maintaining including a crank mechanism (18) comprising first (48) and second (52) link members, first ends of which are pivotally mounted on a slider (50) which slides along a plane of the mirror (12), the second end of the first link member (48) being pivotally mounted on an end of the light source following lever (16) and the second end of the second link member (52) being pivotally mounted on the inner frame (8) at a position below the second axis, whereby the angle between the mirror (12) and the inner frame (8) about the second axis is held equal to one half of the angle between the inner frame (8) and the direction to the light source. An apparatus according to claim 1, characterized by the mirror (12) comprising a central substantially rectangular plane mirror (32) and semicircular plane mirrors (90, 92) mounted on the same plane and opposite sides of the central mirror (32) to form together a generally elliptical planar mirror surface. An apparatus according to claim 1 or 2, characterized by a reflecting unit (20) for reflecting light reflected from the mirror (12) towards a second predetermined direction said reflecting unit (20) including a plurality of upper plane mirror strips (60), both ends of each of the upper plane mirror strips (60) being movably pivoted on respective parallel members of a frame (58), and a plurality of lower plane mirror strips (64), both ends of each of the lower plane mirror strips (64) being movably pivoted on the other respective parallel members of the frame (58) so that the lower plane mirror strips (64) are perpendicular to the upper plane mirror strips (60). An apparatus according to any of claims 1 to 3 wherein the first sensing means (44) is mounted on the top of the first axis and the first sensing means (44) comprises an elongated body portion (78) having a rectangular cross-section and a central longitudinal axis and at least two first photosensors (74), disposed on opposite sides of the central axis of the body portion (78) for receiving light from the source and generating the first signals. An apparatus according to claim 4, wherein the elongated body portion (78) has an end for extending towards the light source and a rectangular cross-section and the first photosensors (74) are mounted on opposite exterior surfaces of the elongated body portion away from the end for extending toward the light source. An apparatus according to any of claims 1 to 5, wherein the second sensing means (46, 130) comprises: a base (132, 76); an elongated body portion (134, 178) extended from the base and having a rectangular or circular cross-section and a central longitudinal axis; and at least two second photosensors (82, 132) disposed on the base on opposite sides of the central axis of the body portion (134, 178) for receiving light from the source and generating the second signals. An apparatus according to claim 6, wherein the elongated body portion (178) has axial grooves (80) extending along its outer surface, each groove extending from one of the second photo-sensors (82) towards the end of the elongated body portion (178) opposite the base (76). An apparatus according to claim 7 wherein the elongated body portion (178) has a rectangular cross section and the grooves (80) extend along the side faces (179) of the body portion (178). An apparatus according to claim 6, wherein the elongated body portion has a cylindrical body portion (134) and rectangular fin plates (136) extending radially outwards from the body portion (134) along its length at regular intervals and wherein the photosensors (140) are mounted between the fin plates. An apparatus according to claim 6, 7, 8 or 9 further comprising a photosensor (84, 138) mounted on the end of the elongated body portion (178, 134) opposite the base (76, 132). An apparatus according to any one of the above claims, wherein the attitude control means comprises: a first rotation unit (10) for rotating the mirror (12) about the first axis; and a second rotation unit (14) for rotating the mirror (12) about the second axis. An apparatus according to claim 11, wherein the first rotation unit (10) rotates the inner frame (8) with respect to the outer frame (4) and the second rotation unit (14) rotates the mirror (12) with respect to the inner frame (8). An apparatus according to claim 12, wherein the second rotation unit (14) comprises a drive unit (34) pivotably connected to the mirror (12) which drives a screw rod (38) the end of which engages a member (41) connected to the inner frame. An apparatus according to any of the above claims, wherein the attitude control means further comprises a control unit (55) for comparing the first signals from the first photosensors (74) to control the first rotation unit (10) to direct the mirror (12) in the first light source direction and for comparing the second signals from the second photosensors (82) to control the second rotation unit (14) to direct the mirror (12) in the second light source direction. An apparatus according to any one of the above claims, wherein the first axis is a vertical axis and the second axis is a horizontal axis.

Inventors: HANE, TADASHI C/O SHIMIZU CONSTRUCTION CO., LTD.
Applicants: SHIMIZU CONSTRUCTION CO., LTD.
Application year: 1987
Main classification: F21S11
IPC codes: F24J2, F21S11