Component tray for electrical fixture housing

An assembly for an electrical fixture housing, the housing of the type enclosing ballasts, the housing including top and rear walls, first and second side walls, and two heat sink pads orthogonally disposed respecting one another, the assembly including a component tray having a longitudinal axis between first and second ends, a middle portion, and a ballast secured to the middle portion, and first and second tray attachments structured for quickly-detachable attachment of the respective first and second ends of the component tray to the respective first and second side walls of the housing, where the attachment effects direct and snug engagement of the ballast with the two heat sink pads.

FIELD OF THE INVENTION

The invention relates generally to housings for electrical fixtures and, more particularly, to a system for securing a ballast in such a housing.

BACKGROUND OF THE INVENTION

Many lighting systems use lamps which are powered by electrical and/or electronic circuits that include transformers for changing a line voltage to meet the needs of a particular type of lamp(s) being powered. Such transformers may be identified simply as being “ballasts,” although that term may also refer to the entire circuit being used to power the lamp(s). In a lighting fixture, a ballast can also assist in regulating power. For example, when such a ballast is used in conjunction with a capacitor, a power factor of the circuit is controlled. When a ballast transformer is used, for example, in an HID lighting application, the transformer may act as an inductor for limiting power. Conventional ballasts often use an open core and coil construction, in which a core of laminated steel, iron, or similar material has wire windings.

Lighting fixtures create heat as a result of its lamp(s) converting electrical energy into light. The heat inside such a lighting fixture is made greater when a ballast is also included inside the lighting fixture housing because the ballast also consumes energy and generates heat. Heat can be very damaging to lighting components, causing compromised performance or failure. It is therefore important to reduce the amount of such heat inside the lighting fixture in order to extend the life of the various lighting fixture components, for safety, and for other reasons. For example, a failing ballast can get extremely hot and become a fire hazard. While some ballasts include a safety device which shuts the ballast off in case of extreme thermal conditions, such safety devices are not infallible and, in any event, such problems may be reduced by simply reducing the heat within the fixture.

It is known to transfer heat from the ballast to the lighting fixture housing for dissipating such heat. For example, a double-wall ballast engagement and ballast mounting method is disclosed in U.S. Pat. No. 6,867,959, incorporated herein in its entirety and having the same assignee and inventors as the present invention. The '959 patent discloses a housing where screws are used for directly attaching the ballast to two walls of the fixture. However, such a structure is not adapted for easily servicing the lighting fixture, such as when it becomes necessary to replace any of the various components of the ballast circuit. There is a need for a lighting fixture that provides for transferring heat from the ballast while also providing for ease of ballast circuit servicing.

OBJECTS OF THE INVENTION

It is an object of the invention to provide an improved electrical fixture housing overcoming some of the problems and shortcomings of the prior art, including those referred to above.

Another object of the invention is to provide an electrical fixture housing having a component tray adapted for easy servicing of an enclosed ballast circuit.

Another object of the invention is to provide a component tray for electrical fixtures where a ballast mounted on the component tray is positioned for efficient heat transfer between at least one side of the ballast and at least one wall of the fixture housing.

Still another object of the invention is to provide a component tray for electrical fixtures that provides snug engagement of a ballast and two walls of an electrical fixture housing by use of an urging mechanism for positioning the component tray in the housing.

Yet another object of the invention is to provide a component tray for electrical fixtures that is configured for either of a closed position forcing a ballast snugly against at least one wall of a housing and an open position semi-detaching the tray from the housing for servicing the component tray.

Another object of the invention is to provide a configuration for a component tray of an electrical fixture whereby the component tray swings into or out of a position of snug engagement of a ballast with at least one wall of a housing of the electrical fixture along an arc-shaped path.

Another object of the invention is to provide apparatus for first positioning a ballast tray in a location where adjacent walls of a ballast become close to corresponding walls of a heat sink, and then snugly fastening the ballast against the heat sink so that maximum heat transfer takes place between the two ballast walls and the heat sink.

Another object of the invention is to provide a method of snugly seating a ballast against heat sink wall(s) of an electrical fixture, where a self-adjusting attachment structure allows the ballast to be fastened into flush abutment with the heat sink wall(s) or unfastened to be easily moved to a servicing position.

Another object of the invention is to provide a component tray for lighting fixtures that is adapted for easy servicing and for snugging a ballast of the component tray against a heat sink surface of a housing of the lighting fixture, with a self-adjusting of the snugging mechanism.

How these and other objects are accomplished will become apparent from the following descriptions and drawing figures.

SUMMARY OF THE INVENTION

According to an aspect of the invention, in a housing for electrical lighting fixtures, the housing of the type enclosing ballasts, the housing including top and rear walls and first and second side walls, an improvement includes a ballast being secured to a component tray and being directly and snugly engageable with at least one heat sink surface of the housing by a quickly-detachable attachment of the component tray to the first and second side walls.

According to another aspect of the invention, an assembly is disclosed for an electrical fixture housing, the housing of the type enclosing ballasts, the housing including top and rear walls, first and second side walls, and at least one heat sink pad, the assembly including a component tray having a longitudinal axis between first and second ends, a middle portion, and a ballast secured to the middle portion, and, first and second tray attachments structured for quickly-detachable attachment of the respective first and second ends of the component tray to the respective first and second side walls of the housing, where the attachment effects direct and snug engagement of the ballast with the at least one heat sink pad.

According to a further aspect of the invention, apparatus includes a housing for electrical lighting fixtures, the housing of the type enclosing ballasts, the housing including two heat sink pads, a ballast tray having a ballast disposed thereon, hinge means for moving the ballast tray to and from a position of snug engagement with the two heat sink pads, and fastening means for securing the ballast tray to the housing.

According to another aspect of the invention, a method of engaging a ballast of a component tray with at least one heat sink surface of an electrical fixture housing, includes swinging the ballast to a position proximate and essentially parallel to the heat sink surface, and snugging the ballast against the heat sink surface by fastening the component tray to the electrical fixture housing.

As a result of various implementations of the invention, an improved construction of an electrical fixture overcomes certain problems of the prior art by providing optimized heat sinking for ballast transformer(s) of the electrical fixture, while also providing improved serviceability for a ballast circuit of the fixture that includes the ballast transformer.

The foregoing summary does not limit the invention, which is instead defined by the attached claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a perspective view of a lighting fixture10of a preferred embodiment. A ballast tray20is shown having a hook21that is being lifted over and dropped onto a mounting rod31that is secured to a portion of the housing40. Ballast tray20is adapted for mounting a ballast transformer50thereon. Ballast transformer50has opposite long-dimension surfaces51,53and a top surface52. When hook21is placed onto rod31, ballast tray20hangs from rod31and may be swung up into housing40by pushing up on the distal end28of ballast tray20. When distal end28of ballast tray20is thus moved into position, a shaft61of a fastening portion60is placed into a notch26of fastening end28, whereby an angled portion27of fastening end28is caused to be held up by a fastening surface62. A knob63is threaded onto shaft61, so that when knob63is turned, fastening surface62is urged against an outside surface of angled portion27and ballast tray20is thereby pressed up and into housing40. In particular, such installation of ballast tray20into housing40causes top surface52of ballast50to be pressed against an upper heat sink pad42, and causes rear-facing long-dimension surface53of ballast50to be pressed against a rear heat sink pad43. Preferably, ballast50and ballast tray20are configured so that surfaces52,53of ballast50are respectively parallel with heat sink pads42,43when ballast tray20is in the closed and fastened position, thereby optimizing a transfer of heat from ballast50to housing40.

A ballast50may have an “open core and coil” construction, in which a core of laminated steel, iron, or similar material has windings of coils of wire. An exemplary ballast transformer suitable for preferred embodiments is an autotransformer ballast available from Advance Transformer Co. of Rosemont, Ill. and has a part number 71A6091A. A dry film capacitor is used in series between the secondary of such a transformer and a lamp (not shown), the capacitor also being available from Advance and having a part number 7C240P40-R. Such a capacitor is shown with a reference character57and is secured to ballast tray20with a capacitor holder22.

Typical housings for electrical lighting fixtures are constructed from aluminum, steel, composites or other metals and are commonly designed in view of size concerns as well as a variety of factors including separation of the ballast from other heat-sensitive components, aesthetic appeal, etc. Rear heat sink pad43is preferably fully attached to housing40around at least three of its four perimeter sides, thereby distributing heat from heat sink pad43to adjacent heat conductive portions of housing40.

FIG. 2is a perspective view andFIGS. 3A–Care respective top, side, and end views of a component tray20according to an exemplary embodiment. A wire routing hole24is provided on a top surface25of ballast tray20for passing wires (not shown) therethrough, such as for electrically connecting primary windings of ballast transformer50with a line voltage and connecting secondary windings of ballast transformer50together with leads from capacitor57and a lamp socket (not shown), etc. Various other components may be mounted to component tray20, such as power transistors and other heat-generating components, capacitors and other non-heat-generating components, etc. The components may include a starter/ignitor (not shown) which may include electronic components in a small case, acting, for example, to increase lamp voltage from approximately 280 VAC to approximately 3000 volt pulses, for a short time until a lamp strikes. After the lamp strikes, in this example, the starter deactivates and normal 280 VAC operation resumes. A grounding terminal hole35is provided in top surface25of ballast tray20for attachment of a grounding terminal (not shown) in order to connect earth ground of an electrical service. Opposing rear mounting holes36are provided on a rear transformer mounting bracket33and front mounting holes37are provided on a front transformer mounting bracket34, for mounting ballast50to ballast tray20using two long machine screws32or the like that pass through corresponding holes54,55formed in ballast transformer50. A nut plate (not shown) or the like is preferably used for securing ballast transformer50to ballast tray20, whereby threaded holes of the nut plate are engaged by machine screws32, causing ballast transformer50to be tightly secured against the inside surface of brackets33,34. Distal ends of screws32pass through the opposite holes36,37of the respective hole pairs to provide additional structural integrity.

In the exemplary embodiment ofFIG. 3C, three separate pairs of ballast front mounting holes37are provided. This allows one of a number of different size ballasts to be selectively installed in component tray20for various different applications. For example, the illustrated configuration of tray20provides for three different ballast lengths, shown as respective distances between mounting hole36and one of the three mounting holes37. Any width less than or equal to the maximum width distance, between the pair of rear transformer mounting brackets33along rear tray wall76, may be used. Any ballast transformer height less than or equal to the maximum height, for example the distance between ballast tray20and rear heat sink pad43when tray20is in a fastened-down state, may be used.

FIG. 13shows an alternative embodiment where a ballast transformer150has a short height. An extension151, formed of a metal having a high heat conductivity, is attached to a bottom surface of ballast transformer150, the overall total height of ballast150with the added extension151is approximately the same as the height of ballast transformer50. Extension151may be a conductive spacer, a set of bracket(s) for attaching ballast150at a distance from the inside surface of ballast tray20, or the like. As a result, when ballast tray20is fastened in place, a top surface152of ballast150engages rear heat sink pad142in the same manner as when ballast transformer50is used, so that heat of ballast transformer150is transferred to heat sink pad142. It is also possible to use a shorter transformer150without using extension151. In such a case, only a long side153of ballast transformer engages a heat sink surface143of housing140, and heat sink pad142is not used for heat conduction. A smaller transformer150generally produces less heat and the use of only one surface for heat sinking may be acceptable.

Ballast tray20is formed with hook21being angled away from a rear tray portion76to a front tray portion77. That is, an acute angle A is formed between the longitudinal axis70of tray20and a longitudinal axis71of hook21. InFIG. 4, a rod31having a longitudinal axis81is shown mounted near a rear corner of housing40using rear rod mounting bracket47and front rod mounting bracket48. An acute angle X is formed between rod longitudinal axis81and tray longitudinal axis70when component tray20is installed. As shown inFIG. 5, rod31is mounted onto a rear post45and a front post46of housing40. Front post46extends to a distance further from a well portion49of housing40, compared with rear post45. This height difference of posts45,46causes rod31to be tilted towards the rear of housing40and toward rear heat sink pad43. In an alternative embodiment, shown by example inFIG. 12, a rod bracket96is a cast unitary structure that provides another way of mounting rod31.

The amount of tilt is shown as an angle Z between a plane83, normal to rear heat sink pad43, and rod longitudinal axis81. Although not mandatory, angle Z is preferably from one to ten degrees. Since the combination of the individual orientations of components of fixture10is designed to achieve a positioning of a ballast50in a location where a side53of ballast50is essentially parallel and in close proximity to a heat sink pad43, angle Z may be selected to be zero or greater than ten degrees, but a corresponding alteration may then be necessary for other dimensions of the fixture. Since angle X causes tray20to swing away from heat sink pad43when tray20is being lowered away from its attached location, angle Z allows the arc of travel of tray20to have a two-dimensional nature, whereby tray20simultaneously rotates while moving in a downward angle.

As a result of angles A, X, and Z, tray20may be caused to swing away from rear heat sink43when ballast tray20is being swung down or when ballast tray20is being closed into housing40, as shown inFIGS. 6A–6C. For mounting rod31, the combination of angles X and Z allows a directionality of ballast tray travel into the heat sink “corner” of the housing formed by the intersection of heat sink pads42,43. In particular,FIG. 10shows an arc of travel for a long side53of ballast transformer50as it is placed into position by closure of ballast tray20. This is also shown byFIGS. 8 and 9, respective cross-sectional views ofFIGS. 6B and 6Ain successive stages of such closure. The arced travel acts to prevent interference of ballast tray20and its various components with portions of housing40. The arced travel is optimized by the specific angles A, X, and Z, so that long side53of ballast transformer50is positioned to be essentially parallel with heat sink pad43at a position where fastener60is engaged with fastening end28of ballast tray20.

At the fastening end28of ballast tray20, an angle B is formed between the tray longitudinal axis70and a plane72of angled portion27. When fastening shaft61is placed into notch26of tray20, fastening surface62is caused to rest atop a fastening surface30of angled portion27. Fastening shaft61is arranged to be approximately orthogonal to fastening surface30when shaft61is engaged with notch26. That is, the attachment and length of shaft61causes shaft61to be approximately perpendicular to plane72, in two dimensions. However, shaft61is also angled from rear to front of housing40, which causes ballast tray20and long ballast side53to be pulled toward rear heat sink pad43when knob63is tightened down. The tightening of knob63also causes ballast tray and long ballast surface53to be forced tighter against top heat sink pad42. Thereby, ballast transformer50is tightened in a manner where it is forced into the heat sink corner.

The tightening of knob63further causes a longitudinal stretching force to be exerted on tray20due to the force of fastening surface62on fastening surface30. This longitudinal force acts to slightly bend tray20and pull against mounting rod31, there being at least some elasticity in tray20for a slight springing action. A tray stop99is formed on an interior surface of housing40near fastener60. Tray stop99is dimensioned for abutting a top surface (ballast side surface) of ballast tray20near fastening end28, when ballast tray is in the fastened position ofFIG. 7and knob63has been fastened to a predetermined point. At the abutment point, knob63is able to be further turned to increase the fastening force of fastening surface on angled portion27. As knob63is further tightened to force ballast tray20against tray stop99, the tightening of knob63becomes increasingly more difficult until a point is reached where additional tightening requires great strength and would not be attempted by the service person or installer. At such a point, the deformation or slight stretching of tray20caused by the force of fastening surface62on angled portion27, and the orthogonally-oriented force on tray20caused by tray20being deformed by being over-tightened against the already-snugged ballast50, are each limited by tray stop99. Such a state causes ballast tray20to be securely fixed at each end and by additional fulcrums established by the aforementioned tray stop99and ballast50each pushing against middle portions of tray20. Such use of ballast50and tray stop99adds additional locations that act as spring members with respect to tray20and that contribute to the self-adjustment of tray20into its position of alignment of ballast50with the heat sink corner of housing40. This adds to the structural integrity by efficiently distributing the holding forces being exerted on tray20and by securing tray20at multiple locations. When a short ballast150is alternatively used, a ballast extension151may be used to provide the ballast fulcrum or, when such extension151is not used, tray stop99acts to limit the above-described deformation of tray20and over-tightening by fastener60. However, the full benefit of the fastening structure vis-a-vis ballast tray20, where such ballast acts as a spring member in the self-adjustment of tray20, is achieved when a ballast of ballast tray20is in abutment with top heat sink pad42. It is noted that during tightening, angle B acts to direct force vectors at rod31, at heat sink pad42, and at heat sink pad43.

Front and rear rod mounting brackets47,48are attached to side wall41and fastener60is attached to side wall44. It is understood that the term “side wall” as used herein can refer to portions of housing40other than those portions literally on the sides and may refer to portions that are not opposed to one another. For example, posts such as rear and front posts45,46are considered parts of adjacent wall41, and a given side wall may include curved portions and portions that are angled with respect to top wall98.

FIG. 10shows generally the arc of travel of long side53of ballast50, also shown by the example ofFIGS. 8 and 9. One end result is placement of long side53at a position where a subsequent engagement and fastening of fastening end28causes long side53to be tightened against rear heat sink43with essentially the entire surface area of long side53being in contact with rear heat sink43. Another end result is placement of top side52of ballast50at a position where the subsequent tightening of fastener60also causes essentially the entire surface area of top side52to contact upper heat sink pad42. As shown inFIG. 11, the tightening of fastener60acts to snug ballast50into the heat sink corner by forcing sides52,53against respective heat sink pads42,43. In addition, it is noted that the structures of hook21, fastener60, and notch26each allow for some “slop” due to a loose fit at each of these tray attachment locations, whereby the natural tendency of sides52,53to seat themselves against respective heat sink walls42,43causes each of such attachment structures to adjust slightly during the placement stage ofFIG. 10and the fastening stage ofFIG. 11. Accordingly, a highly efficient heat transfer is effected by the snug, tight abutment of sides52,53with respective heat sink pads42,43. For example, fastener60has a base portion69where shaft61is loosely attached to housing40by a bracket68. Shaft61preferably has an angled portion (not shown) between bracket68and housing40, which keeps shaft61from falling out and which becomes pressed against an underside of bracket68when shaft61is engaged with notch26and knob63is tightened onto shaft61. Such a tension type securement of fastener60into a tightened position also facilitates the self-adjusting action of the tray attachments due to their loose fit, which increases the ballast placement accuracy and efficiency in snugly seating ballast50.

When servicing of the lighting fixture10becomes necessary, a service person may first turn off the corresponding circuit breaker and remove an outer lens cover (not shown) from the fixture, thereby exposing the inside portion. The service person may then remove any lamp(s) requiring replacement or just leave them in if they are still good and are not likely to be damaged by accessing ballast tray20. Then, knob63may be turned counter-clockwise to loosen fastener60and reduce the force being exerted on tray20by fastening surface62. When knob63has been adequately backed out, the service person may then carefully lift up slightly on fastening end28of tray20to relieve the force of gravity being exerted onto fastening surface62. Such allows fastener60to be disengaged from notch26and moved near the adjacent side wall of housing40, out of the way of ballast tray20, which then can be lowered to hang from rod31for servicing as shown inFIG. 6C. A handle (not shown) may be attached to ballast tray20for assisting in opening and closing ballast tray20and for lifting ballast tray20up and over rod31when removing or attaching ballast tray20to rod31. It is noted that fixture10may be serviced without any tools being required. For example, a cover plate (not shown) is typically used for attaching a glass or similar lens type structure to housing40so that light may be transmitted therethrough. Such cover plate may be provided with fasteners that require no tools. Similarly, knob63of fastener60is preferably easily gripped and rotated by hand, and is formed of a non-conductive material to reduce the possibility of electric shock to the service person. Component tray20may be provided with wire connectors, so that component tray20may be loosened using knob63, lowered, disconnected from wires of fixture10, un-hinged, and then removed from fixture10, all without the use of any tools. This provides additional safety in an industrial type ballast installation.

The exemplary housing40has mounting holes91at a rear portion, for optional mounting of light fixture10to a post, wall, or other supporting structure. A feed-thru hole92is provided for allowing electrical service connections to ballast tray20and to one or more lamp sockets. For example, an electrical cord may be secured at feed-thru92using a strain relief, grommet, or the like, or a conduit fitting or other suitable structure may be attached for safely providing electrical service. A connection compartment95is provided between the curved rear walls93,94of housing40and the rear side of rear heat sink pad43. Such connection compartment95provides a convenient space for connecting, for example, individual jumper assemblies (not shown) using twist-on wire connectors and the like, and for installation of an earth ground connection to housing40, and for other electrical connections.

FIG. 12shows a housing40formed by casting or similar process, although other processes such as welding may be used. A rod mounting bracket base96is formed as a portion of a cast housing40, bracket base96having grooves for receiving rod31and having tapped holes for receiving mounting hardware for holding rod31in its intended location. In a preferred embodiment, bracket brace96has an upper portion having a same height at each end thereof, where one or more rod holders may be attached such as by being secured to threaded receptacles in bracket96. Such a bracket96has a rod-holding portion with an angle Z formed therein for holding rod31at the required angle with respect to heat sink pad43. A fastener bracket base97has a groove for receiving a hooked bottom portion of fastener60and has a tapped hole for receiving mounting hardware for attaching fastener60so that it does not fall out of housing40.

Heat sink pads42,43are preferably arranged perpendicularly with respect to one another. As shown inFIGS. 8 and 9, top heat sink pad42is a separate surface from well portion49of housing40because the well portion49curves away from the flat surface of top heat sink pad42. Rear heat sink pad43, as shown inFIG. 1, is formed as a separate surface that is, for example, joined to housing40by welding or other structure. Housing40is a heat sink and heat from ballast50is transferred to the two respective engaged walls of integral heat sink pads42,43.

The heat generated in a lighting fixture typically causes components to have a shortened life. A general rule of thumb is that, for every ten degrees Celsius you remove from the lighting fixture, you double the life of individual components. The mounting of a ballast within the enclosure of a lighting fixture housing, for dissipating the generated heat by conduction and radiation, is therefore important to its operation. As a result of implementing the double heat-sinking structure of fixture10, as much as ten to fifteen degrees Celsius may be removed. Otherwise, ballast heat would be trapped and damage would result.

In conventional structures, heat transfer, from the ballast to the fixture housing which encloses the ballast, lamp and other electrical lighting fixtures, is facilitated by the application of grease, gel, resin and the like to a single surface of the ballast case connected with respect to the housing. Mounting plates have also been used to provide a medium for heat transfer from one surface of the ballast to one surface of the housing. While heat transfer is a major concern in housing design, the housing must also provide free access to ballast components and wiring so that maintenance can be performed. Such an advantage is provided by implementation of the present invention. In addition, the present invention may be applied to situations where a large heat dissipation is not required, but where serviceability and at least some heat reduction is desired, such as for heat sinking protection of heat-sensitive components of a component tray. For example, when a scale is small, a space savings may result from being able to package components in a smaller footprint because heat is conducted to an adjacent housing rather than being accumulated at the heat generation location.

Although the illustrated exemplary embodiments each include a ballast tray20being disposed in the same housing as a lamp, it is also possible to enclose lamps and ballasts in separate housings. In such a case, it is desirable to install a lighting fixture in close proximity to a ballast housing, so that high voltage wiring between the two structures is minimized. Such a ballast housing (not shown) is preferably provided with a pair of heat sink pads disposed orthogonally with respect to one another, so that a ballast of the housing may be snugly engaged with the corresponding heat sink corner by attachment of ballast tray20, as for the embodiment ofFIG. 1and others described herein. The same serviceability is thereby provided while optimizing heat sinking of the ballast. Similarly, the invention may be implemented in electrical fixtures used in applications other than lighting. For example, a component tray may be attached with a quickly-detachable mechanism for use in any application where a transformer of the component tray becomes hot and it is desired to transfer the heat by conduction to the walls of a housing or other heat sinking structure.

While the principles of the invention have been shown and described in connection with specific embodiments, it is to be understood that such embodiments are by way of example and are not limiting. Consequently, variations and modifications commensurate with the above teachings, and with the skill and knowledge of the relevant art, are within the scope of the present invention. The embodiments described herein are intended to illustrate best modes known of practicing the invention and to enable others skilled in the art to utilize the invention in such, or other embodiments and with various modifications required by the particular application(s) or use(s) of the present invention. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.