The present invention relates generally to a method of attaching an LED module to a housing using lance and form sheet metal features to create a spring clip and an additional lance and form feature used as a backstop.

The invention allows the LED module to expand and contract relative to the housing and thereby allow for small movements (and thereby alleviate buckling). This feature allows the LED module to remain flat to maximize surface contact area with the housing to thereby maximize conduction and heat dissipation.

As used herein the term “lancing” refers to a piercing or slitting operation in which the workpiece (sheet metal) is sheared and bent to create a pocket-shaped opening in the metal sheet. Lancing modifies the geometry of the workpiece without removing any material. “Forming” is a general term used to describe the process of converting a blank, featureless workpiece into a specific three-dimensional part.

The lance and form features of the current invention are sufficiently small to be used with existing Zhaga compliant LED module geometry typically reserved for screws or rivets for a standard Zhaga compliant LED module (Zhaga being a worldwide consortium aiming to standardize the LED modules used in LED lighting fixtures). Further, with the current invention, the luminaire would comply with the Single Lighting Regulation (SLR) of the EU.

Most LED indoor troffer luminaires for office, schools, hospitals, and other commercial spaces incorporate one or more LED modules. An LED module typically consists of a Printed Circuit Board (PCB) containing LEDs and other components to provide light for the luminaire. Some luminaries, which may include back lit panels, may use six or more LED modules. In the prior art, LED modules are typically secured to the luminaire by screws, rivets, glue, or double-sided tape. These methods can be costly and make it difficult to disassemble. They can also be attached via a lance and form feature like a spring clip stamped into the sheet metal when fabricating the luminaire housing. Further, they require a relatively large space on the LED module.

Fig. 1 depicts an exploded view of an exemplary prior art luminaire having a Zhaga compliant LED module secured with screws. As illustrated, item 10 depicts the luminaire housing, to which an LED module 20 is mounted using screws 30. Also illustrated is an LED driver 40 and a diffuser 50.

Fig. 2 illustrates a typical LED module 20 (e.g., a Zhaga compliant “Fortimo LED Strip VO LV3” manufactured by Signify). As illustrated, the LED module contains a plurality of cutouts or recesses 200 (hereinafter referred to as “recesses”) along its lateral edges. Fig. 3 depicts the prior art method of using screws 30 in conjunction with these recesses 200 to secure the LED module.

Typically LED modules so mounted are not easy to disassemble. The invention makes for easy removal of LED modules for recycling or replacement at the end of life of the LED module or replacement due to an LED module failure — without the need to replace the entire luminaire. The Single Lighting Regulation (SLR) for the European Union (EU) now requires that lighting products in the EU comply with the eco design requirements established in three directives: (EC) No 244/2009, (EC) No 245/2009 and (EU) No 1194/201. Generally, LED-based products must adhere to certain removability and replaceability requirements. The current invention readily meets these requirements.

Further, the cost of securing an LED module can be relatively high with respect to the total cost of the luminaire. These securing costs include the cost of the prior art fastener (e.g., screw, rivet, glue, tape, etc.) plus the cost to assemble (typically labor cost). By way of example using fastening with screws: Cost = cost of the screw + cost of labor and/or machine cost. Material costs can vary depending on the type of screw, geometry etc. Labor cost can vary dramatically depending on where it is assembled (high vs. low-cost region), cost of automation equipment if used, etc. Use of the current invention realizes savings on both materials and labor.

Previous methods of securing an LED module also include the use of a prior art lance and form. The current invention realizes several advantages over this prior art. One such advantage is that it requires the use of less space on the LED Module. That is, a standard lance and form feature commonly used on prior art LED modules are typically very large and take up a lot of space on the LED module which increases cost significantly. It is preferable to utilize smaller LED modules as the smaller the LED module, the lower the cost to manufacture. However, a typical lance and form 400 shown in Figs. 4a and 4b positioned on a Philips Evokit Gen5 LED module 410 requires a large amount of space. As illustrated, this lance and form requires a space of 20x10 mm which includes the keep out area which must be free of circuitry. Moreover, a bigger problem illustrated in Fig. 4b is that this method requires a custom LED module and cannot be used with an LED module with a standard Zhaga compliant footprint. Accordingly, this increases costs and limits replacement options.

Another advantage of the current invention is that it allows for increased surface contact area of the LED module to the housing. This increases heat dissipation via conduction and heat spreading to maximize cooling of the module and in turn the LEDs. The higher the operating temperatures of the LEDs the shorter the life of the module and can cause premature failures, color shift, and lower efficacies.

By way of example, a standard 44 inch LED module, which is typically used in a 2x4 ft. luminaire, heats up and cools down when the power is cycled. This results in the LED module and the housing expanding and contracting at different rates. This is due to the differences in thermal expansion of steel or aluminum housing vs. a typical CEM3 PCB material for the LED module. Buckling can occur in response to the stresses resulting from the mounting screws not allowing for free movement of the LED module. The invention allows the LED module to expand and contract relative to the housing and allow for small movements. This will allow the LED module to remain flat to maximize surface contact area to the housing to maximize conduction and heat dissipation.

The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

Fig. l is a perspective view of a prior art luminaire having an LED module secured with screws;

Fig. 2 is a perspective view of an exemplary LED module containing a plurality of recesses along its lateral edges;

Fig. 3 is a perspective view of a prior art embodiment in which screws are used in a plurality of the LED module recesses;

Figs. 4a - 4b are perspective views of a standard prior art lance and form feature used in securing LED modules;

Fig. 5 provides perspective views of the lance and form clip feature of the present invention;

Figs. 6a - 6c illustrate assembly of an LED module to a luminaire housing utilizing the present invention. Fig. 7 is a perspective view of the lance and form backstop feature of an embodiment of the present invention;

Figs. 8a - 8c illustrate operation of the lance and form backstop feature in attaching the LED module to the luminaire housing; and,

Fig. 9 is a perspective view illustrating an embodiment of the invention in which a screw is used in lieu of the backstop.

It is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings.

Referring now in detail to the drawings, wherein like numerals indicate like elements throughout the several views, there are shown in Figure 5 various aspects of the lance and form clip feature of the present invention. In particular, the sheet metal luminaire housing 520 has been sheared and bent to create a pocket-shaped opening in the metal sheet. Further, the bent material has been further shaped to create the lance and form clip feature 510 of the present invention.

Figs. 6a - 6c illustrate assembly of an LED module to the luminaire housing utilizing the present invention. Fig. 6a depicts the LED module 20 about to be placed onto a surface of the luminaire housing 520. As illustrated, the luminaire housing 520 contains a plurality of lance and form clips 510. As illustrated in Fig. 6b, two recesses 200 on the LED module are positioned adjacent to two of the lance and form clips. Lastly, the LED Module is moved relative to the luminaire housing 520 in a direction substantially parallel to the surface of the luminaire housing 520.

The arrow labelled “D” indicates this direction of the movement of the LED Module 20 (and its recesses 200) relative to the luminaire housing 520 (and its lance and form clips 510). The lance and form clips 510 are sufficiently flexible to allow for LED module 20 to easily be slid manually without tools in the D direction (or lateral direction) to engage the lance and form clips, and thereby at least partly secure the LED module to the luminaire housing 520.

It should be noted that in a standard 44 inch LED module, which is typically used in a 2 x 4 ft. luminaire, there are a total of 28 recesses 200 on the LED module. Typically, not all need to used — maybe half or less is typical depending on how hot the module is running. The more power/lumens required, the more heat will need to be dissipated and thus more lance and form clips would be employed to maximize surface contact and conduction.

In one embodiment of the invention, a minimum of three lance and form clips (at least one on each opposing side of the LED module) are employed to sufficiently secure the LED module to the housing in all directions except in the X direction. An additional lance and form feature can be used as a backstop to constrain the LED module in the X direction. An example of such an additional lance and form backstop is depicted as item 710 in Fig. 7. As with the lance and form clip feature 510 discussed above, item 710 is formed from the luminaire housing 520 in a similar manner.

Figs. 8a - 8c illustrate operation of item 710 in the assembly process. In particular, as illustrated in Fig. 8a, the LED module 20 is positioned vertically above the luminaire housing 520 such that the lance and form clip feature 510 aligns with an LED module recess 200. The LED module is then moved downward in the Z direction as indicated by the arrow. The backstop 710 is sufficiently flexible in the Z direction to be easily temporarily flexed downward (as shown in Fig. 8b) and to spring back up after the LED module 20 is slid in the D direction. Fig. 8c illustrates this final position of the LED module 20 with backstop 710 constraining the LED module 20 in the X direction, and other lance and form clips constraining the LED module in all other directions.

In a further embodiment of the invention, a gap (not illustrated) of approximately 1-2 mm exists between the end of the LED module 20 and the surface 720 of item 710. This gap allows for standard manufacturing tolerance stack up between the LED module and the sheet metal relative to item 710, and for thermal expansion and contraction induced movement of the LED module 20 relative to the luminaire housing as discussed above. It should be noted that only one backstop 710 is needed at an end of the LED module to secure movement of the LED module in the X direction.

In the above described embodiment, the assembly and disassembly can be performed very quickly without tools or fasteners. In alternative embodiments a single screw can be employed in place of the lance and form backstop. One such embodiment is illustrate in Fig. 9 in which item 30 depicts the screw in a recess 200 of the LED module. In one further embodiment of the current invention, the screw would be positioned at one end of the LED module to thereby prevent movement of that end of the LED module (and thus the entire LED module structure) in the X direction, but allow the LED module to expand in the X direction.

The lance and form clips 510 and backstop features 710 are manufactured with standard sheet metal fabrication processes and do not add cost of the piece part due to the nature of the sheet metal stamping process. While the features will add a one-time cost to the fabrication of the stamping die, the cost will be sufficiently small when amortized into production volumes for the life of the product.

In addition, the lance and form clips 510 and backstop features 710 of the present invention are sufficiently small, approximately 3.6mm x 1.5mm, thereby permitting use with the existing Zhaga compliant LED module geometry typically reserved for screws or rivets for a standard Zhaga compliant LED module. Further, with the invention the luminaire would comply with the Single Lighting Regulation (SLR) for the EU.

The foregoing description of several methods and an embodiment of the invention has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise steps and/or forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the claims appended hereto.

While there has been shown, described, and pointed out fundamental and novel features of the present invention as applied to preferred embodiments thereof, it will be understood that various omissions and substitutions and changes in the apparatus described, in the form and details of the devices disclosed, and in their operation, may be made by those skilled in the art without departing from the spirit of the present invention.

It is expressly intended that all combinations of those elements that perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Substitutions of elements from one described embodiment to another are also fully intended and contemplated.

Any reference signs in the claims should not be construed as limiting the scope of the claims or the invention described by the subject matter claimed.