Patent Application
20110103051
This invention relates to lighting fixtures and, more particularly, to methods of assembling lighting fixtures of the type having LED emitters.
In recent years, the use of light-emitting diodes (LEDs) for various common lighting purposes has increased, and this trend has accelerated as advances have been made in LEDs and in LED-array bearing devices, often referred to as “LED modules.” Indeed, lighting applications which have been served by fixtures using high-intensity discharge (HID) lamps and other light sources are now increasingly being to be served by LED modules. Such lighting applications include, among a good many others, roadway lighting, parking lot lighting and factory lighting. Creative work continues on development of lighting fixtures utilizing LED modules. It is the latter field to which this invention relates.
High-luminance light fixtures using LED modules as light source present particularly challenging problems. High costs due to high complexity becomes a particularly difficult problem when high luminance, reliability, and durability are essential to product success. Keeping LEDs and LED-supporting electronics in a water/air-tight environment may also be problematic, particularly when, as with roadway lights and the like, the light fixtures are constantly exposed to the elements. Use of a plurality of LED modules presents further challenges.
Yet another cost-related challenge is the problem of achieving a high level of adaptability in order to meet a wide variety of different luminance requirements. In other words, providing a fixture which can be adapted to give significantly greater or lesser amounts of luminance as deemed appropriate for particular applications is a difficult problem. Light-fixture adaptability is an important goal for LED light fixtures.
The product safety of lighting fixtures creates an additional area of difficulty, and such fixtures are most often required to comply with standards put forward by organizations such as Underwriters Laboratories Inc. (UL) in order to gain acceptance in the marketplace. One such set of standards deals with the accessibility of the electrically-active parts of a fixture during operation, and, more importantly, during periods of stress on the fixture such as in a fire situation during which some elements of the lighting fixture are compromised. The UL “finger test” mandates that a human finger of certain “standard” dimensions (defined in NMX-J-324-ANCE, UL1598, Dec. 30, 2004, FIG. 19.22.1, page 231) should not be able come in contact with any electrically-live parts of the fixture under such circumstances. The standards also establish certain material limitations on the enclosures of such products, all of which are dependent on the voltages and power levels within the fixtures.
Increased product safety can be costly to achieve and reduced optical efficiency in many cases may be a result of improving product safety. For example, placing a fixture behind a sheet of glass to provide increased safety can result in an optical efficiency loss of up to 10%.
For LED-based lighting fixtures, the cost of the power supply is an important part of the overall fixture cost. When a large number of LEDs are used to provide the necessary level of illumination, it is advantageous to use a single power supply providing higher voltages and higher power levels, which, in turn, requires more stringent safety standards. In particular, power supplies with a Class 2 power supply rating are limited to 100 watts at a maximum of 60 volts (30 volts if under wet conditions). LED-based lighting fixtures with a large number of LEDs can benefit (both by cost and efficiency) by using a Class 1 power supply, in which both the power and voltage limitations of a Class 2 power supply are exceeded. If power requirements for a lighting fixture are higher than the Class 2 limits, then multiple Class 2 power supplies are required (which can be costly) unless the more stringent safety standards which using a Class 1 supply brings about can be achieved.
As mentioned above, such more stringent requirements include satisfying the “finger test” under certain fire conditions during which it is possible that lighting module elements such as lenses made of polymeric materials may be removed. For example, in an LED device with a primary lens made of glass and a secondary lens made of polymeric material, it is necessary to provide enclosure barriers over the entire electrical portion of the module (on which the LED devices are mounted) except over the primary lenses. It is assumed that under these circumstances, the polymeric secondary lenses will be destroyed in the fire, leaving the primary lenses exposed. Also for example, if a single polymeric lens is used in place of both the primary and secondary lenses, then the enclosure barriers must prevent “standard finger” access to the electrical elements in situations in which the single lens is no longer in place.
Thus there is a need for improved LED lighting fixtures which can better serve the requirements of general-illumination lighting fixtures and which can provide both the safety and cost-effectiveness which the marketplace requires and/or prefers.
In short, there is a significant need in the lighting industry for an improvement in manufacturing lighting fixtures using LEDs, addressing the problems and concerns referred to above.
It is an object of the invention to provide an improved method for assembly of high-efficiency LED modules for use in lighting fixtures, such improved method overcoming some of the problems and shortcomings of the prior art, including those referred to above.
Another object of the invention is to provide a reduced-cost LED apparatus with high-efficiency LED-light distribution.
Yet another object of this invention is to provide an efficient and accurate assembly of the LED apparatus.
Still another object of the present invention is to provide a reduced-cost method of manufacturing of LED-apparatus with high-efficiency LED-light distribution.
Another object of this invention is to provide a method of reduced-cost manufacturing LED apparatuses providing a variety of different types of LED-light distribution.
How these and other objects are accomplished will become apparent from the following description and the drawings.
The present invention is an improvement in LED apparatuses of the type having an LED device defining a light-emission axis and a lens member positioned over the LED device and establishing a light path therebetween. The LED device is on a mounting board having an LED-supporting surface.
Prior LED devices had LED packaging of the type including reflectors and primary lenses surrounding LEDs. Such packaging may add material costs to manufacturing LED apparatus. The presence of the reflector in packaged LED devices may also reduce light-output efficiency due to added complexity in controlling orientation of reflected LED light. On the other hand, when the reflector is an a form of an aluminum ring which surrounds the LED, such reflector may serve as a reference for aligning the lens member over the LED device.
The LED apparatus of the present invention provides an important advantage in that it can utilize very small LED devices which include an LED configured for illuminating substantially white light and preferably without reflectors or substantial primary lenses. Some examples of LED devices have one or multiple number of light-emitting LEDs. Such multiple LEDs may emit light with the same wave length and produce a common-color light. Alternatively, multiple diodes may emit light of different waive lengths thus of different colors which may be blended to achieve a desired-color light. Persons skilled in the art would appreciate a broad variety of available LED devices.
The inventive LED apparatus includes a lens-aligning member having front and back surfaces and defining an aperture. The aperture is preferably configured to receive the LED device therethrough such that the LED device protrudes beyond the front surface. The lens member preferably includes a lens portion and a flange thereabout. The flange of the lens member is attached to the front surface of the lens-aligning member such that the lens portion substantially surrounds the protruding LED device. The lens-aligning member preferably has a first mating feature which is positioned and arranged for mating engagement with a second mating feature of the mounting board. The first and second mating features accurately align the lens member over the LED device by accurately aligning the lens-alignment member with the mounting board.
In preferred embodiments, the back surface of the lens-aligning member abut the LED-supporting surface of the mounting board. The first mating feature is preferably a protrusion extending from the back surface of the lens-aligning member. The second mating feature is a complementary hollow formed in the LED-supporting surface of the mounting board and receiving the protrusion. Each of the back surface of the lens-aligning member and the LED-supporting surface of the mounting board may have a pair of the mating features.
The lens-aligning-member front surface preferably has guide projections which extend from the front surface and have lateral surfaces engaging the edge of the lens-member flange.
The front surface of the lens-aligning member preferably includes a recess configured to snugly receive the flange therein. The guide projections preferably extend from the front surface with their lateral surfaces along the wall of the recess. The recess wall and the lateral surfaces are preferably engaging the edge of the lens-member flange.
Preferred embodiments of the inventive LED apparatus further include a cover which defines an opening aligned with the light path. A gasket is preferably pressed with the lens-aligning member between the cover and the mounting board thereby securing the lens member over the LED device. Such embodiments may further include a base member. The base member and the cover together preferably define an LED-apparatus interior which encloses and compresses the gasket with the lens-aligning member and the mounting board between the cover and the base member. Such gasket arrangement preferably provides a weather-proof seal about the LED device. The base member is preferably a heat sink providing heat dissipation from the LED device during operation.
In some embodiments, the inventive LED apparatus provides electrical safety by satisfying a set of stringent safety standards for the enclosures in which such LED apparatus are encased, and doing so in a cost-effective manner. In such embodiments, the lens-aligning member is a fireproof safety barrier having sufficient thickness for enclosure of electrical elements on the mounting board. The aperture is sized to permit light from the LED device to pass therethrough and through the lens portion of the lens member over such LED device to prevent finger-contact of electrical elements on the mounting board when the lens portion is not present.
In some embodiments of the LED apparatus, the barrier includes a metal layer, while in more preferred embodiments, the barrier also includes an insulating layer positioned between the mounting board and the metal layer. In some of these embodiments, the metal layer and the insulating layer form a laminate.
The safety barrier preferably includes a metal layer and an insulating layer. Such layers may be laminated together, forming the laminate. Alternatively, such layers may also be separate layers. Under certain UL standards, the metal layer may be made of a flat, unreinforced aluminum sheet having a thickness of at least 0.016 inches. The minimum thickness requirements of such metal layer depends on the structure and composition of the metal layer as set forth in the specific UL standards referred to above. If the lens-aligning-member safety barrier is a laminate, the different layers of the laminate may or may not have the same width and length dimensions.
The insulating layer may serves to electrically isolate the metal layer from the electrical elements on the mounting board. In some embodiments, these electrical elements may be isolated from the metal layer by a conformal coating on the mounting board. Such conformal coating may be any of a number of available coatings, such as acrylic coating 1B73 manufactured by the HumiSeal Division of Chase Specialty Coatings of Pittsburgh, Pa.
The lens-alignment-member safety barrier may also be made of a single layer of polymeric material having a minimum thickness as set forth by the UL standards. Acceptable polymeric materials include BASF 130FR (polyethylene terephthalate with glass fiber reinforcement) supplied by the Engineering Plastics Division of BASF Corporation in Wyandotte, Mich. The layer has a minimum thickness of 0.028 inches. Other acceptable polymeric materials must satisfy certain detailed specifications related to material behavior such as hot-wire ignition, horizontal burning, and high-current arcing resistance, all of which are set forth in the UL standards referred to above. The safety barrier may be of the type disclosed in the above mentioned U.S. patent application Ser. No. 11/774,422, entire contents of which are incorporated herein by reference. However, any other known safety-barrier configuration may also be used.
The inventive LED apparatus may include a plurality of the LED devices spaced from one another on the mounting board and a plurality of lens members each establishing a light path with a respective one of the LED devices. In such embodiments, the lens-aligning member defines a plurality of apertures each of which receives a respective one of the LED devices therethrough such that the LED devices protrude beyond the front surface. Each lens member is attached to the front surface of the lens-aligning member with the lens portion substantially surrounding the respective one of the LED devices.
In some preferred embodiments, at least a subset of the lens members includes lens members configured such that each of them refracts light emitted by its respective LED device in a predominantly off-axis direction. In some of such embodiments, the lens members of such subset are arranged on the lens-aligning member to refract light in a common off-axis direction. In different embodiments with of such type, the lens members of such subset are arranged on the lens-aligning member such that at least two are oriented to refract the light in substantially different off-axis directions.
Another aspect of the present invention is a method for assembly of the inventive LED apparatus. The method includes the steps of providing the lens member, the lens-aligning member with and the mounting board. The lens-aligning member and the mounting board having the first and second mating features positioned and arranged for engagement with one another.
The lens-member flange is attached to the front surface of the lens-aligning member. The attaching may be by way of mechanical bond such as with a glue. It is preferred that the flange is attached to the lens-aligning member with a chemical bond, preferably by ultrasonic welding. The lens-aligning-member front surface preferably has guide members. The attaching step preferably includes a prior step of positioning the lens-member on the lens-aligning-member front surface such that the guide-projections' lateral surfaces engage the edge of the lens-member flange.
The lens-aligning member is placed over the mounting board such that the LED device protrudes through the aperture beyond the front surface. The first and second mating features are engaged to accurately align the lens member over the LED device by accurately aligning the lens-aligning member with the mounting board. The lens portion substantially surrounds the protruding LED device establishing a light path therebetween. The lens member is preferably secured over the LED device by securing the lens-aligning member with respect to the mounting board.
Preferred embodiments of the inventive method include further steps of powering the LED device and imaging the LED apparatus to test light-output characteristics. When the LED apparatus is fully assembled, a power is provided to the LED emitter. An image of the powered LED apparatus is then taken to test light-output characteristics. In preferred embodiments, the image of the LED apparatus is utilized to test intensity, light distribution and color temperature of the LED device(s).
The inventive method preferably includes further steps of providing a gasket member, a cover and a heat sink. The cover defines an opening aligned with the light path. The heat sink and the cover together define an LED-apparatus interior. The step of securing the lens-aligning member with respect to the mounting board is preferably by compressing the gasket with the lens-aligning member and the mounting board between the cover and the heat sink. This preferably provides a weather-proof seal about the LED device within the LED-apparatus interior. The inventive method preferably includes the further step of vacuum testing the seal for water-air/tightness of the LED-apparatus interior.
In the embodiments for assembling LED apparatuses with a plurality of spaced-apart LED devices, the lens-aligning member includes a plurality of apertures each configured for receiving a respective one of the LED devices therethrough; and a plurality of lens members are provided. In such embodiments, at least a subset of the lens members include lens members configured such that each of them refracts light emitted by its respective LED device in a predominantly off-axis direction. Prior to the attaching step, a specific type of the lens member is selected. Such selected lens members are positioned on the front surface of the lens-aligning member. The type of each lens member and its orientation are preferably verified.
In some of such embodiments the lens members of the subset are arranged on the lens-aligning member to refract light in a common off-axis direction. In different ones of such embodiments, the lens members of the subset are arranged on the lens-aligning member such that at least two are oriented to refract the light in substantially different off-axis directions.
Still another aspect of this invention is a method for manufacturing custom high-efficiency LED lensing for LED-array modules of the type including a mounting board having a plurality of LED devices spaced from one another thereon. During manufacturing of an individual separate lens member certain high-precision technologies are used to make an accurate shape of outer and/or inner surfaces of the lens portion. This is critical in achieving high-efficiency light output and distribution. Application of some of such high-precision technologies is limited when multiple lens portions are formed together in a single-piece lensing such that each of the multiple lens portions lacks some of the desired high-efficiency characteristics. This results in a loss efficiency of light-output and distribution. The inventive method allows to achieve the high accuracy of the individually-made lens portions which are securely arranged together for their placement over an LED-array module.
Such inventive method also allows to lower manufacturing costs by reducing an inventory of custom lensing. Such reduced inventory is also possible because of the use of individual lens members which may be positioned in various orientations and arrangements to accommodate different light-distribution patterns. Furthermore, based on the side of the LED-array module and the number of the LED devices on the mounting board, the inventive method allows for different number of the lens members to be arranged together. In other words, there is no need for having a special matrix-mold for making each specific lens configuration for each specific light-distribution pattern. Thus, there are cost savings on tooling for manufacturing each of the multitude of such special matrix-molds and the resulting specific lensing as well as the storage for the tooling, the molds and the multi-lens-portion lensing.
In such inventive method a plurality of separate individual lens members are provided. Each lens member includes a lens portion and a flange thereabout. It is highly preferred that the lens portion is made by using a precision technology which permits precise forming of each lens-member refracting surfaces for a specific type of high-efficiency light distribution. Also provided is a lens-support member which has front and back surfaces and defines a plurality of apertures each configured to receive a respective one of the LED devices therethrough. The lens-support member is placed over the mounting board such that each LED device protrudes through the respective aperture beyond the front surface.
The method includes the step of determining a desired light distribution of the LED-array module. Such determination may be based on the requirements for an area illumination or the desired illumination characteristics of an individual lighting fixture. According to the determined the desired light distribution, specific type(s) of the individual lens members are selected. The selected lens members are positioned on the front surface of the lens-support member to achieve such desired light distribution. The lens portion of each lens member is positioned to substantially surround a respective one of the LED devices. It is preferred that the type and orientation of each lens member are verified. It is further preferred that each lens member includes a machine-identifiable lens-indicia. In such embodiments, the steps of verifying the type and orientation of the lens members are accomplished by a vision system reading the machine-identifiable lens-indicia.
Each lens-member flange is substantially permanently attached to the front surface of the lens-support member. It is preferred that the attachment is by a substantially permanent chemical bond formed by ultrasonic welding of the flange with the lens-support member.
The lens-support member is preferably secured with respect to the mounting board to secure the lens members over the respective one of the LED devices. Such securement may be by compressing a gasket between the mounting board and a cover. Alternatively, the lens-support member may be secured to the mounting board by other suitable means available in the art.
In some preferred embodiments, the cover includes a plurality of screw holes. Prior to the step of vacuum testing, the method preferably includes the steps of inserting a screw into all but one of the plurality of screw holes. The cover preferably also includes a power connection which may be in various forms such as an electrical connector or a wireway opening. One example of the wireway opening is disclosed in commonly-owned U.S. Pat. No. 7,566,147(Wilcox et al.). When the power connection is in the form of the wireway opening, such wireway opening is sealed prior to the step of vacuum testing. The vacuum-testing step preferably utilizes the screw hole without a screw therein as an access point for the vacuum testing. It is highly preferred that the screws are inserted by using an automated screwdriver capable of controlling the torque utilized during the screw insertion for controlled pressure applied between the cover and the base member. The term “base member,” while it might be taken as indicating a lower position with respect to the direction of gravity, should not be limited to a meaning dictated by the direction of gravity.
Some embodiments of this method are performed in such a way that the cover is initially positioned with a cover inner surface facing up. The gasket is preferably in a form of a gasket layer with a plurality of apertures each aligned with a respective aperture in the cover and the respective one of the light paths. In such embodiments, the gasket is placed on the cover inner surface. The lens-support member with the lens members attached to the front surface is placed with on the gasket the front surface being against the gasket. The mounting board oriented with the LED devices facing down is placed on the back surface of the lens-support member such that the first and second mating features are engaged to accurately align the LED devices with the lens members by accurately aligning the mounting board with the lens-support member.
It is preferred that at least the steps of positioning the selected lens members on the front surface of the lens-support member and verifying the type and orientation of each lens member are performed by a robot incorporating the vision system. For example, an ABB IRB340 FlexPicker Robot with IRC5 Controller can be utilized. The robot may also perform all other steps to complete assembly of the LED apparatus, including the step of imaging the LED apparatus to test light-output characteristics and the step of vacuum testing to verify the water-air/tight seal about the LED devices. Such robot is preferably present only at a single first location.
Further steps of incorporating the LED-apparatus assembly into light fixtures may be performed at multiple locations each of which is remote from the first location. Therefore, the inventive method allows to further lower manufacturing costs by eliminating the need for the robot at the multiple manufacturing locations.
In any of the described embodiments, it is preferred that the method further includes the step of providing a central database, whereby the central database provides assembly and testing parameters. It is also preferred that the method of the present invention is performed by an automated system receiving instructions from the central database for each particular step preformed by automated tool(s). The central database collects and stores data related to all or at least one of: the LED device and LED lens-member type, selection and orientation of the lens member, screw torque, vacuum testing parameters, light output and color testing procedures.
It is further preferred that the LED apparatus includes a unique machine-identifiable module-marking. Such machine-identifiable marking can be in any suitable form. Some examples of such marking may include a text, a set of symbols, a bar code or a combination of these marking types. The steps of the inventive method are preferably repeated multiple times to create a plurality of LED apparatuses. The method preferably includes a further step of reading the unique machine-identifiable module-marking. The data of each unique machine-identifiable module-marking is associated with a specific individual LED apparatus. Such data relates to that LED apparatus' LED devices(s), the type of the lens member(s) such as selection and orientation of the lens member(s), as well as light-output and color-testing procedures.
As best seen in
Inventive LED apparatus 10 includes a lens-aligning member 40 having a front surface 41 and a back surface 42 and defining an aperture 43.
In
FIGS. 10 and 14-17 illustrate LED apparatuses 10B, D and E with lens members 24 configured such that each of them refracts light emitted by its respective LED device 11 in a predominantly off-axis direction.
Another aspect of the present invention is a method for assembly of inventive LED apparatus 10. As seen in
Lens-aligning member 40 is placed over mounting board 30, as seen in
As seen in
The method schematically shown in
In the embodiments for assembling LED apparatuses 10 with a plurality of spaced-apart LED devices 11 and a plurality of lens members 20, prior to attaching step 80, a specific type of lens member 20 is selected. Such selected lens members 20 are positioned on front surface 41 of lens-aligning member 40. The type of each lens member 20 and its orientation are verified in step 82.
When a plurality of LED apparatuses are assembled, each apparatus may require different lens members 20 placed in different locations and in different orientations. Data related to a specific lens members 20 to be utilized is received by the robot from database 15 and identified lens members 20 are placed into interior 13. Each lens member 20 is then verified to be the correct type of lens member and to be positioned in specified orientation. For such identification and verification, lens member 20 may include a machine-identifiable lens-indicia which can be in a form of a bar code, text or a specific shape which indicates a specified orientation. One example of automated devices used for step 82 is a Cognex Insight 5603 Digital Vision Camera which is associated with the FlexPicker Robot. After lens member 20 is put into place, the camera can read the indicia. The data from such reading is sent back to database 15 for storage.
Cover 50 also includes a power connection 53 shown in the form of a wireway opening 54 which allows passage of wires (not shown) from a lighting fixture to LED apparatus 10 for powering LED devices 11.
One remaining screw hole 52 is used for vacuum testing 84 to ensure water/air-tight seal of interior 13. One example of a vacuum testing apparatus is a Uson Sprint IQ Multi-Function Leak & Flow Tester which can be utilized in vacuum-testing step 84. In step 84, wireway opening 54 is temporarily sealed and a vacuum is applied via the open screw hole 52. The vacuum is applied according to data from database 15. Actual vacuum-test results are sent back to database 15 for storage. After vacuum testing 84, final screw 14 is secured in same manner as described above.
The inventive method includes further step 83 of powering LED device 11 and imaging LED apparatus 10 to test light-output characteristics. When LED apparatus 10 is fully assembled, a power is provided to LED emitter 11 through electrical connections which may be printed or otherwise provided on mounting board 30. An image of powered LED device 10 is then taken to test light-output characteristics. The image of LED apparatus 10 is utilized to test intensity, light distribution and color temperature of the LED device(s).
The imaging and analysis of LED apparatus 10 are done through an automated system. One example of such system is a National Instruments Digital Vision Camera utilizing LabView Developer Suite software which can be utilized to complete digital-imaging step 83. A digital image of powered LED apparatus 10 is taken. From this image the software can analyze light output, color characteristics, intensity and light distribution. Data related to these parameters are then sent to database 15 for storage.
Through the described inventive method, individual results can be tracked in a mass-production setting. In such mass-production setting, each individual LED apparatus 10 can include a unique machine-identifiable module-marking which may be a combination of a text with a set of symbols and a bar code. Data related to each individual LED apparatus 10 from each automated step (lens-member positioning and verification 80 and 81, screw installation 85, vacuum testing 84 and digital imaging 83) is then associated in database 15 with the unique machine-identifiable module-marking.
While the principles of this invention have been described in connection with specific embodiments, it should be understood clearly that these descriptions are made only by way of example and are not intended to limit the scope of the invention.
This application relates to U.S. application Ser. Nos. 11/744,807, filed May 4, 2007, 11/744,422, filed on Jul. 6, 2007, and 12/473,017, filed on May 27, 2009. The contents of each of these applications are incorporated herein by reference.
