Patent Application
20060285340
1. Field of the Invention
The present invention relates to a luminaire, more specifically to a vented luminaire with a potentially flammable diffuser.
2. Description of Related Art
Luminaires are commonly used in office buildings and the like. The luminaire may be a recessed luminaire that is mounted so as to be flush with the ceiling and provides the needed illumination. To improve the light distribution pattern, most luminaires include a diffuser. The diffuser acts to modify the light distribution of the light bulbs and helps prevent the formation of hot spots and undesirable glare that would be distracting to the occupants working in the vicinity of the luminaire. While the diffuser could be made of a variety of materials, the diffuser may be made of a perforated basket with a translucent plastic inlay. Plastic is light as compared to glass, is unlikely to shatter into sharp pieces when dropped, and can be readily made with desired properties so as to provide the type of light transmission that corresponds to the design requirements of the luminaire.
As is known, many office buildings have ceilings that use what is known as a drop ceiling design. The drop ceiling may provide a space between the visible ceiling and a structurally supportive ceiling and this space may be referred to as a plenum. The use of drop ceilings allows electrical and ventilation systems to be run in the plenum so that an electrical and a ventilation system can direct electricity and air where needed. Some buildings also use the plenum as a return air source for the ventilation system. While the primary function of a luminaire is to provide light, as most rooms include at least one luminaire, the luminaires can also provide ventilation. To do so, the luminaire may be coupled to the ventilation system so that air can enter or exit the ventilation system through the one or more vents in the luminaire. The coupling may simply be a vent that provides a passageway so as to fluidly connect the room to the plenum and may also be a connection between a booted luminaire and a duct that is connected to the ventilation system. Thus, the luminaire can provide light and also provide an air return and/or an air supply for the room. This has the benefit of minimizing the need for additional vents in the ceiling and therefore can provide a cleaner and more attractive appearance.
One potential drawback with the use of plastic diffusers, or other materials similar to plastic, is that they are flammable. Generally speaking, plastic will burn when subjected to sufficient heat or flame. The response of most plastics varies from sustaining the flame once the plastic is ignited to merely burning while the flame is applied, however both examples are considered flammable for the purpose of this invention. Thus, the use of a plastic diffuser is potentially problematic because, in the event of a fire, the diffuser may burn even if the plastic material does not sustain the fire.
The problem may become exacerbated when vented luminaires with potentially flammable diffusers are connected to the ventilation system. In addition, as the luminaire is often recessed, the provision of fire extinguishing equipment, such as sprinklers in the ceiling, may not direct fire suppressing materials onto the luminaire. In the event of a fire, the diffuser may burn and, because of the close proximity to the vents in the luminaire, the burning diffuser may cause smoke to enter the ventilation system or spread fire to adjacent luminaires. To address these potentially life threatening problems, the Underwriters Laboratory provides standard UL 1598. This standard requires, among other things, that a flammable diffuser drop away from the luminaire in the event of a fire. To ensure the plastic diffuser drops away, one method is to use a deformable support made of two different metals. When subjected to heat, the different rates of expansion of the two different metals causes the support to deform and allows the diffuser to drop. Unfortunately, such a method is unduly restrictive because it limits how the support can hold the diffuser. Therefore, an improvement is needed so that the support holding the diffuser can be designed as needed while still meeting the requirements of UL 1598.
In an aspect of the present invention, an air handling luminaire includes a potentially flammable diffuser supported at both ends by fusible links, the links supported by a housing. When subjected to sufficient heat, at least a portion of the fusible links will soften and allow the diffuser to drop away. In an embodiment, the diffuser may include a plastic material and be supported by four fusible links.
The present invention is illustrated by way of example and not limited in the accompanying figures in which like reference numerals indicate similar elements and in which:
Luminaires for use in buildings, such as office buildings, have a number of requirements. The luminaires preferably are both attractive and functional. Furthermore, to save money it is beneficial to maximize the functionality of the luminaire by using it as part of the ventilation system. In addition, the luminaires may also protect against the possibility of an emergency, such as a fire.
The housing 20 may be made out of a 20-gauge cold rolled steel alloy and may be coated with a white reflective paint such as a polyester powder coat applied over a 5-stage process with a resultant reflectance of 94% or more. Other colors, such as silver, may also be provided.
In an illustrative embodiment, the diffuser 30 includes a perforated basket (not shown) along with a frosted acrylic configured to minimize visibility of the underlying linear light sources while maximizing the efficiency of the luminaire. In an embodiment, the diffuser 30 may include a perforated metal basket with a plastic inlay (not shown), which may be configured to have the desired light transmission properties corresponding to the configuration of the luminaire. While the perforated basket (which may be made of metal) aids in supporting the plastic portion of the diffuser 30, in an embodiment the perforated basket may be omitted and a sufficiently robust plastic material may be used instead.
The diffuser 30 is supported by one or more fusible links 40 mounted near the corners of the diffuser 30. When sufficient heat is applied to the one or more fusible links 40, the diffuser can drop away from the housing 20 and the one or more vents 25.
It should be noted that, depending on how the diffuser 30 and the means for supporting it are configured, one fusible link 40 may be sufficient to support the diffuser 30. For example, if the diffuser 30 was primarily supported by the fusible link 40 but also was partially supported by non-fusible links (not shown), when the fusible link 40 softened the diffuser 30 could still drop.
As can be appreciated, various known electrical components typically used in luminaires are required. These components are known in the art and, therefore, will not be described. The housing 20 may additionally include one or more holes suitable for accepting wires and/or allowing various electrical components to be installed within or connected (either directly or indirectly) to the housing in a known manner.
As depicted, the first bracket 50 is mounted to the housing 20. The mounting may include known methods of mounting, such as interlocking components, fasteners or adhesives, to name a few. As depicted, the first bracket 50 is inserted into a hole 22 in the housing 20 and the second bracket 60 is inserted into a hole 35 in the diffuser 30. In this manner, the first bracket 50 and the second bracket 60 will securely support the diffuser 30. A potential benefit of providing the hole 22 in the housing 20 is that the hole 22 can be used as a positioning feature for the installation of the bracket 50 so as to aid in the assembly of the luminaire 10 (
As is known, office spaces are intended to be kept within a range of temperatures. When the temperature significantly exceeds the expected range of temperatures, the temperature may be considered elevated. For example, but without limitation, a temperature of 202 degrees Fahrenheit may be considered elevated. When subjected to the appropriate elevated temperature, a low temperature compound, such as a low temperature compound 70 (
It should be noted that the term softening means that at least part of the material supporting the diffuser 30 plastically yields, melts, gives way, or releases in some other manner. In the case of a low temperature compound 70 made of a lead-based solder, for example, the softening may be referred to as melting. For some low temperature compounds, the softening may be relatively abrupt while in other low temperature compounds, the softening may be more gradual and may even occur over a range of temperatures.
Referring back to
The low temperature compound 70 is provided and joins the edges 58 and 64 of the brackets 50 and 60, respectively. The low temperature compound 70 may be a low temperature solder configured to hold the first and second brackets 50, 60 together. For example, the low temperature compound 70 may be a solder alloy having a compensation of 52% Bismuth, 30% Lead and 18% Tin. Such a solder would typically have a melting point around 202 degrees Fahrenheit or about 94.4 degrees Celsius. Naturally, a low temperature solder could be configured to melt at a higher temperature such as 220 or 300 degrees Fahrenheit or even some temperature below 200 degrees Fahrenheit. Thus, the term low temperature refers to a temperature below the burning point of the diffuser 30. Thus, depending on the material properties of the diffuser 30, the composition of the low temperature compound 70 can vary as desired.
While depicted as provided on the edge of the fusible link 40, it may be useful to place the low temperature compound 70 within a fusing hole 62 of bracket 60. The fusing hole 62, which may be shaped as depicted or of any other shape such as triangular or some irregular shape, can provide a mating surface area that helps allow the two brackets 50, 60 to become fastened together. Furthermore, locating the low temperature compound 70 near the middle of the mating surfaces of the bracket 50 and bracket 60 helps minimize unwanted stresses on the low temperature compound 70.
Turning to
It may be useful to configure the fusible link 40 so that it blends in with the housing 20. In an illustrative embodiment, both brackets 50, 60 may be formed out of 22-gauge cold rolled steel. Once the two brackets are combined together by the low temperature compound 70 (not shown), the fusible link 40 may be painted white. For example, the fusible link 40 may be spray painted or dipped. Of course, depending on the materials and the design of the fusible link 40, the painting step may not be necessary.
Turning to
It should be noted that numerous other configuration are possible. Thus, the design of the fusible link 40 is only limited by the packaging constraints of the luminaire 10 (
The present invention has been described in terms of preferred and exemplary embodiments thereof. Numerous other embodiments, modifications and variations within the scope and spirit of the appended claims will occur to persons of ordinary skill in the art from a review of this disclosure.
