ORIGINAL AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Invention title: "ADJUSTABLE DOWNLIGHT FITTING" Applicant: RADIANT LIGHTING PTY LTD The following statement is a full description of this invention, including the best method of performing it known to me: -2 "ADJUSTABLE DOWNLIGHT FITTING" Field of the Invention The present invention relates to an adjustable downlight fitting suitable for 5 flush mounting in a ceiling. Background to the Invention Many home and office environments now have downlights installed to provide improved illumination or to create a particular ambience that cannot be achieved with conventional fluorescent or incandescent lighting. Downlight 10 fittings using 12 volt halogen bulbs are quite common, mounted flush with the ceiling. There are many existing examples of 12 volt downlight fittings which include the facility to rotate or tilt the bulb housing, thereby moving the axis of illumination. In fittings where the overall size is large relative to the bulb size, the mechanism used may be a gimballed mount or similar mounting. 15 In fittings where the overall size is compact in relation to the bulb size there is not the space to use more elaborate mounting mechanisms such as gimbals. In such instances alternative prior art downlight mounting structures have been developed. In one example, the bulb housing is a rotationally symmetrical shroud attached to a mounting bezel by a pair of simple brackets 20 which allow the bulb housing to pivot about an axis defined by the fixing rivets. This approach has several shortcomings. In order to conceal the pivot brackets, the pivot axis is located behind the plane of the mounting bezel and usually midway between the centreline of the bulb and the inner diameter of the mounting bezel. To enable the bulb housing to rotate there must be a 25 substantial annular gap between the bulb housing and the mounting bezel. This gap allows entry of dust and debris from the ceiling cavity. The location of the pivot axis also leads to the rotational movement partly obscuring the light beam when in the rotated position. Furthermore, as the pivot axis is also offset from the centre of gravity of the 30 bulb housing, there is an inherent rotational force acting to make the bulb -3 housing fall to its most rotated position. The only thing holding the bulb housing in any desired position is the friction of the rivet fixings which hold the pivot brackets. With repeated movements over time there is a tendency for this friction to reduce and consequently positional control is reduced or lost 5 completely. The present invention was developed with a view to providing a downlight fitting with a compact pivot mechanism that overcomes at least some of the problems of the prior art. References to prior art in this specification are provided for illustrative 10 purposes only and are not to be taken as an admission that such prior art is part of the common general knowledge in Australia or elsewhere. Summary of the Invention According to the present invention there is provided an adjustable downlight fitting for flush mounting in a ceiling, the downlight fitting comprising: 15 a mounting frame for mounting the downlight in a ceiling; an adjustable bulb housing pivotably mounted in the mounting frame about a pivot axis which is off-centred with respect to the bulb housing, the bulb housing having a shroud with a curved external surface, the radius of curvature of said external surface being substantially equal to a width 20 dimension of said bulb housing; and a pressing means mounted on said mounting frame adjacent to said external surface and adapted to press against said external surface so as to apply a holding force against said bulb housing substantially perpendicular to the pivot axis in whatever position the bulb housing is pivoted wherein, in use, 25 said bulb housing can be pivoted to a desired angle about the pivot axis, which is on the opposite side of the bulb housing to that of the pressing means, and will be held at that angle by said pressing means. Preferably said pressing means is a compressible roller rotatably mounted on said mounting frame adjacent to said external surface. Preferably said -4 compressible roller comprises a cylinder of compressible material such as rubber, rotatably mounted on a transverse axle. The transverse axle is preferably supported between a pair of axle mounts provided on an inner 5 edge of the mounting frame. Preferably said pivot axis is defined by a pair of specially shaped tabs provided on an edge of the shroud of the bulb housing, diametrically opposite the point at which the pressing means presses against the shroud. Preferably the tabs rest on the inner edge of the mounting frame, either side of a 10 protrusion provided on the edge of the mounting frame. Advantageously the interaction of the pivot tabs with the edge of the mounting frame, and guided by the protrusion, result in a hinge-like pivoting action of the bulb housing about the pivot axis. A fastening means prevents the tabs from lifting off the protrusion. 15 Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. Likewise the word "preferably" or variations such as "preferred", will be understood to imply that 20 a stated integer or group of integers is desirable but not essential to the working of the invention. Brief Description of the Drawings The nature of the invention will be better understood from the following detailed description of several specific embodiments of the invention, given by 25 way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a prior art downlight fitting flush mounted in a ceiling as it would typically be seen from below; Figure 2 is a side perspective view of the prior art downlight fitting of Figure 1 showing the bulb housing in a rotated position; -5 Figure 3 is a top perspective view of the prior art downright fitting of Figure 1 showing the pivot mechanism for the bulb housing; Figure 4 is a bottom perspective view of a first embodiment of a 5 downlight fitting according to the present invention; Figure 5 is a top perspective view of the downlight fitting of Figure 4; Figure 6 is another top perspective view of the downlight fitting of Figure 4 showing the pivot mechanism from a different angle; Figure 7 is bottom perspective view of the downlight fitting of Figure 1 10 showing the bulb housing in a rotated position; Figure 8 is a top perspective view of the downlight fitting of Figure 7; Figure 9 is a bottom perspective view of a second embodiment of a downlight fitting according to the present invention; and, Figure 10 is a top perspective view of the downlight fitting of Figure 9. 15 Detailed Description of Preferred Embodiments Figures 1 to 3 illustrate a prior art downlight fitting 10 of the type described above in the Background to the Invention. A bulb housing 12 has a rotationally symmetrical shroud 14 attached to a mounting bezel 16 by a pair of simple brackets 18 which allow the bulb housing to pivot about an axis 20 20 defined by the fixing rivets. As noted above, in order to conceal the pivot brackets 18, the pivot axis 20 is located behind the plane of the mounting bezel 16. To enable the bulb housing 12 to rotate there must be a substantial annular gap 22 between the bulb housing 12 and the mounting bezel 16. This gap 22 allows entry of dust and debris from the ceiling cavity. The location of 25 the pivot axis also leads to the rotational movement partly obscuring the light beam when in the rotated position as shown in Figure 2. Also, as noted above, with repeated movements there is a tendency for the friction of the rivet fixings which hold the pivot brackets 18 to reduce over time and consequently positional control is compromised.
-6 A first embodiment of a downlight fitting 30 according to the invention, as illustrated in Figures 4 to 8, comprises a mounting frame 32 for mounting the downlight in a ceiling. An adjustable bulb housing 34 is pivotably mounted in 5 the mounting frame 32 and has a shroud with a curved external surface 36. The radius of curvature of the external surface 36 is substantially equal to a width dimension of the bulb housing 34. In this embodiment the bulb housing 34 is of circular configuration and the radius of curvature of the external surface 36 is substantially equal to the diameter of the bulb housing 34. 10 A pressing means 38 is mounted on the mounting frame 32 adjacent to the external surface 36, and is adapted to press against the external surface 36, (as can be seen most clearly in Figure 6), so as to apply a holding force against the bulb housing 34 in whatever position the bulb housing is pivoted. The bulb housing 34 can be pivoted to a desired angle about a pivot point 40, 15 located on the opposite side of the bulb housing 34 to that of the pressing means 38, and will be held at that angle by the pressing means 38, as shown in Figures 7 and 8. In this embodiment the pressing means 38 is in the form of a compressible roller 42 rotatably mounted on the mounting frame 32 adjacent to the curved 20 external surface 36. As can be seen most clearly in Figures 6 and 8, the compressible roller 42 comprises a wheel or cylinder 44 of compressible material such as rubber, rotatably mounted on a transverse axle 46. The axle 44 is supported between a pair of axle mounts 48 provided on an inner edge of the mounting frame 32. The diameter of the cylinder 42 and the position of 25 the axle 44 is selected so as to partially compress the cylinder 42 against the curved external surface 36 of the bulb housing 34. In this embodiment the bulb housing 34 has a shroud which opposite the pivot point 40 is of partially toroidal surface, and is adapted to pivot about the pivot point 40, defined by a pair of specially shaped tabs 50, as can be seen most 30 clearly in Figure 5. The pivot tabs 50 are provided on the edge of the shroud of the bulb housing 34, diametrically opposite the point at which the compressible roller 42 presses against the shroud. The tabs 50 rest on the -7 inner edge of the mounting frame 32, either side of a protrusion 52 provided on the edge of the mounting frame 32. The interaction of the pivot tabs 50 with the edge of the mounting frame 32, and guided by the protrusion 52, 5 result in a hinge-like pivoting action of the bulb housing 34 about the pivot point 40. The protrusion 52 prevents the tabs 50 from being moved away from a position opposite the compressible roller 42. The pressure of the compressible roller 42 against the shroud of the bulb housing 34 effectively holds the pivot tabs 50 against the inner edge of the 10 mounting frame 32 in the region of the pivot point 40. The rotatable mounting of the cylinder 44 allows the bulb housing to be pivoted about the pivot point, to a desired angle as shown in Figures 7 and 8, without in any way compromising the holding force of the compressible roller 42 acting on the shroud of the bulb housing 34. Since the pivot axis at the pivot point 40 is 15 tangential to the edge of the bulb housing 34, the light beam from the light bulb in the bulb housing is not obscured when the housing is pivoted. The toroidal element in the shape of the shroud of the bulb housing 34 maintains a consistent degree of contact with the cylinder 44 at all positions through its range of motion. 20 The compressive force resulting from the deformation of the cylinder 44 is constant and is of sufficient magnitude to result in a resistance to rotation of the bulb housing 34 that is greater than the torque applied by the force of gravity acting on the bulb housing. Hence the bulb housing is held at the desired angle without slippage. The arrangement of the pivot mechanism and 25 the geometry of the bulb housing 34 also remove the need for a substantial annular gap between the bulb housing and the mounting frame. When the bulb housing 34 is pivoted to its fully horizontal position as shown in Figure 4, the bulb housing completely closes off the aperture in the mounting frame 32. Figures 9 and 10 illustrate a second embodiment of the downlight fitting 60 in 30 accordance with the present invention. This embodiment is similar to the first embodiment except that instead of the mounting frame and bulb housing -8 having a circular configuration, they have a rectangular or square shape. The geometry of the shroud of the bulb housing is modified to suit the rectilinear profile, but the principles of operation remain the same. A bulb housing 64 is 5 pivotably mounted in a mounting frame 62 and has a shroud with a curved external surface 66. The radius of curvature of the external surface 66 is substantially equal to a width dimension of the bulb housing 64. A pressing means 68 is mounted on the mounting frame 62 adjacent to the external surface 66, and is adapted to press against the external surface 66, 10 (as can be seen most clearly in Figure 10), so as to apply a holding force against the bulb housing 64 in whatever position the bulb housing is pivoted. The bulb housing 64 can be pivoted to a desired angle about a pivot point 70, located on the opposite side of the bulb housing 64 to that of the pressing means 68, and will be held at that angle by the pressing means 38, as shown 15 in Figure 10. In this embodiment the pressing means 68 is in the form of a compressible roller 72 rotatably mounted on the mounting frame 62 adjacent to the curved external surface 66. The arrangement and operation of the compressible roller 72 is similar to that of the first embodiment and will not be described again in detail. The arrangement and operation of the pivot tabs in 20 this embodiment, (not visible in the drawings), are also similar to that of the first embodiment and will not be described again in detail. Now that preferred embodiments of the downlight fitting in accordance with the present invention have been described it will be apparent that it provides a number of advantages including the following: 25 (i) It provides a compact construction using a simple pivot mechanism; (ii) The pivot mechanism provides constant and reliable positional control of the bulb housing at any desired angle; (iii) The beam of light is never obstructed by any parts of the downlight fitting no matter at what angle the bulb housing is pivoted; and, 30 -9 (iv) The downright fitting is of simple design and is therefore relatively inexpensive to manufacture and install. It will be readily apparent to persons skilled in the relevant arts that various 5 modifications and improvements may be made to the foregoing embodiments, in addition to those already described, without departing from the basic inventive concepts of the present invention. For example, the pressing means may not be in the form of a compressible roller but could be in the form of a resilient arm that presses against the curved external surface of the 10 shroud. Therefore, it will be appreciated that the scope of the invention is not limited to the specific embodiments described and is defined by the appended claims. 15 20 25 30 35 40