Patent Application
20060227536
The invention relates generally to housings for electrical fixtures and, more particularly, to a system for securing a ballast in such a housing.
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.
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.
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.
A ballast 50 may 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 character 57 and is secured to ballast tray 20 with a capacitor holder 22.
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 pad 43 is preferably fully attached to housing 40 around at least three of its four perimeter sides, thereby distributing heat from heat sink pad 43 to adjacent heat conductive portions of housing 40.
In the exemplary embodiment of
Ballast tray 20 is formed with hook 21 being angled away from a rear tray portion 76 to a front tray portion 77. That is, an acute angle A is formed between the longitudinal axis 70 of tray 20 and a longitudinal axis 71 of hook 21. In
The amount of tilt is shown as an angle Z between a plane 83, normal to rear heat sink pad 43, and rod longitudinal axis 81. Although not mandatory, angle Z is preferably from one to ten degrees. Since the combination of the individual orientations of components of fixture 10 is designed to achieve a positioning of a ballast 50 in a location where a side 53 of ballast 50 is essentially parallel and in close proximity to a heat sink pad 43, 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 tray 20 to swing away from heat sink pad 43 when tray 20 is being lowered away from its attached location, angle Z allows the arc of travel of tray 20 to have a two-dimensional nature, whereby tray 20 simultaneously rotates while moving in a downward angle.
As a result of angles A, X, and Z, tray 20 may be caused to swing away from rear heat sink 43 when ballast tray 20 is being swung down or when ballast tray 20 is being closed into housing 40, as shown in
At the fastening end 28 of ballast tray 20, an angle B is formed between the tray longitudinal axis 70 and a plane 72 of angled portion 27. When fastening shaft 61 is placed into notch 26 of tray 20, fastening surface 62 is caused to rest atop a fastening surface 30 of angled portion 27. Fastening shaft 61 is arranged to be approximately orthogonal to fastening surface 30 when shaft 61 is engaged with notch 26. That is, the attachment and length of shaft 61 causes shaft 61 to be approximately perpendicular to plane 72, in two dimensions. However, shaft 61 is also angled from rear to front of housing 40, which causes ballast tray 20 and long ballast side 53 to be pulled toward rear heat sink pad 43 when knob 63 is tightened down. The tightening of knob 63 also causes ballast tray and long ballast surface 53 to be forced tighter against top heat sink pad 42. Thereby, ballast transformer 50 is tightened in a manner where it is forced into the heat sink corner.
The tightening of knob 63 further causes a longitudinal stretching force to be exerted on tray 20 due to the force of fastening surface 62 on fastening surface 30. This longitudinal force acts to slightly bend tray 20 and pull against mounting rod 31, there being at least some elasticity in tray 20 for a slight springing action. A tray stop 99 is formed on an interior surface of housing 40 near fastener 60. Tray stop 99 is dimensioned for abutting a top surface (ballast side surface) of ballast tray 20 near fastening end 28, when ballast tray is in the fastened position of
Front and rear rod mounting brackets 47, 48 are attached to side wall 41 and fastener 60 is attached to side wall 44. It is understood that the term “side wall” as used herein can refer to portions of housing 40 other 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 posts 45, 46 are considered parts of adjacent wall 41, and a given side wall may include curved portions and portions that are angled with respect to top wall 98.
When servicing of the lighting fixture 10 becomes 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 tray 20. Then, knob 63 may be turned counter-clockwise to loosen fastener 60 and reduce the force being exerted on tray 20 by fastening surface 62. When knob 63 has been adequately backed out, the service person may then carefully lift up slightly on fastening end 28 of tray 20 to relieve the force of gravity being exerted onto fastening surface 62. Such allows fastener 60 to be disengaged from notch 26 and moved near the adjacent side wall of housing 40, out of the way of ballast tray 20, which then can be lowered to hang from rod 31 for servicing as shown in
The exemplary housing 40 has mounting holes 91 at a rear portion, for optional mounting of light fixture 10 to a post, wall, or other supporting structure. A feed-thru hole 92 is provided for allowing electrical service connections to ballast tray 20 and to one or more lamp sockets. For example, an electrical cord may be secured at feed-thru 92 using 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 compartment 95 is provided between the curved rear walls 93, 94 of housing 40 and the rear side of rear heat sink pad 43. Such connection compartment 95 provides a convenient space for connecting, for example, individual jumper assemblies (not shown) using wire nuts and the like, and for installation of an earth ground connection to housing 40, and for other electrical connections.
Heat sink pads 42, 43 are preferably arranged perpendicularly with respect to one another. As shown in
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 fixture 10, 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 tray 20 being 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 tray 20, as for the embodiment of
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.
