LED LIGHT FIXTURE

Abstract

A light fixture includes a housing and an LED light assembly provided on the housing. A visor extends from the housing at least partially around the LED light assembly. A heater element is connected to the visor.

Description

TECHNICAL FIELD

The present invention is directed to an LED light fixture that may be exposed to weather, and more specifically, to an LED light fixture having a heater element provided on a visor for helping to improve visibility of the LEDs.

BACKGROUND

Light Emitting Diodes (LED) are becoming the primary lighting source for traffic signals due to the energy savings, performance, and lifespan. Energy savings alone, which is as high as 90%, would be enough reason to use LED lights. Additionally, traditional incandescent bulbs, that were widely used prior to the introduction of LEDs, are rated for two years of traffic use. Changing the bulbs is challenging and costly. Lastly, LEDs are becoming brighter and more energy efficient every year.

LEDs may not generate enough heat to melt snow that accumulates inside the visor of the traffic light and covers the LED lens, not allowing light to penetrate through. It is known to include a heater directly on the surface of the LED lens, which have been ineffective at eliminating the snow buildup inside the visor. Some municipalities have made the decision not to replace the incandescent bulbs with LEDs because of the snow buildup issues. Other municipalities have changed back from LED to incandescent lights. Traffic signals, pedestrian signals, pre-emption receiver sensors, and railroad crossings may also have LEDs and can be impacted by snow and ice buildup.

SUMMARY

In one example, a light fixture includes a housing and an LED light assembly in the housing. A visor extends from the housing at least partially around the LED light assembly. A heater element is connected to the visor.

Other objects and advantages and a fuller understanding of the invention will be had from the following detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic illustration of a light fixture including an example heater system.

FIG. 1B is a front view of the light fixture of FIG. 1 with a door opened.

FIG. 2 is a top view of a heater element for the light fixture of FIG. 1.

FIG. 3 is an exploded view of the heater element of FIG. 2.

FIG. 4 is a schematic illustration of a module for the heater system.

FIG. 5 is a wiring schematic for the light fixture.

FIG. 6 is a schematic illustration of another example light fixture including solar panels.

FIG. 7 is a top view of another example heater element.

DETAILED DESCRIPTION

The present invention provides a light fixture heating system that is cost effective, easy to integrate, and will provide heat in and around the light fixture visor/LED efficiently while providing significant energy savings over traditional technology. The heating system shown and described herein can be very effective at melting snow that has built up within the visor/light assembly and can help prevent ice and snow from building up in the first place. In one example, the heating system includes a self-regulating heater element provided on the light fixture visor that at least partially surrounds the LED light assembly. A supplemental heater element can optionally be added around the perimeter of the LED light assembly.

The heater element can be formed as a fixed wattage heater or a positive temperature coefficient (PTC) heater element. In the latter case, the PTC heater element contains conductor particles, e.g., a conductive carbon black filler material, dispersed in a polymer base or matrix having a crystalline structure. The crystalline structure of the matrix densely packs the conductor particles into its boundary so they are close enough together at room temperature to form chains and allow conductive paths of current to flow through the polymer insulator via these carbon chains.

When the resistive layer is at room temperature, there are numerous carbon chains forming conductive paths through the matrix. In some embodiments, there are two conductive buses with each having a corresponding terminal connected to the resistive layer. When a voltage is applied across the resistive layer from the conductive buses, the layer carries a current via the conductor particles. As a result, the temperature of the resistive polymer layer rises until it exceeds the polymer's transition temperature, causing the polymer to change from its initial crystalline phase to an amorphous phase. In the amorphous phase, the conductor particles are spaced further apart from one another [relative to the crystalline phase] and, thus, the electrical resistance of the resistive polymer layer increases until current is prevented from passing through the resistive layer. This, in turn, prevents current from passing through the conductive buses to prevent further heating thereof.

An insulating layer on the heater element can be configured to work in relation to the heat generated by the resistive layer to direct heat in a direction or to block heat flow emanating towards a region. The insulating layer can be positioned as a layer over or under the resistive layer.

The present technology provides a low profile, e.g., flat, and highly adaptable/flexible device that can be integrated into LED light fixtures while providing heating at the same or similar level to an incandescent bulb for a similar application. The heater system can be adapted to fit the LED light fixture. This allows end users to conveniently retrofit the heater element to existing light fixtures and eliminate the cost of purchasing and replacing an entirely new light fixture.

With this in mind, FIGS. 1A-1B illustrate an example light fixture 10 having a series of LED light assemblies 20. As shown, the light fixture 10 is a traffic light having three round/circular LED light assemblies 20 for helping to control or direct vehicle traffic. To this end, the respective light assemblies 20 can provide red/“stop” indication, yellow/“warning” indication, green/“go” indication or turn indication. Alternatively, the light fixture 10 and light assemblies 20 can be configured as pedestrian/cross-walk lights, pre-emption receiver sensors, railroad crossing lights or other roadway signaling or indicating lights (not shown). Regardless, it will be appreciated that the light fixture of the present invention can use any number of LED light assemblies 20, including one, in any number of shapes and sizes.

The housing 12 shown includes one to five doors 14 (three doors shown) on which the respective light assemblies 20 are mounted. The doors 14 are removably and pivotably connected to the housing 12 and selectively close an interior space 16 thereof. Each light assembly 20 includes an enclosure 22 having a lens 26 connected thereto that faces away from the housing 12. The enclosure 22 is secured to the door 14 along a sealed interface 23. In one example, the periphery of the enclosure 22 includes a gasket (not shown) for sealing the interface 23.

The lens 26 can be round, square, etc. An LED circuit board assembly (not shown) is provided within the enclosure 22 behind the lens 26. A series of LEDs 24 is mounted to the LED board assembly so as to emit light through the lens 26.

A shroud or visor 30 is connected to and extends from each door 14. The visor 30 can be, for example, ball-cap or visor-shaped. In any case, the visor 30 includes an inner surface 34 and an outer surface 32. The inner surface 32 defines a passage 36 extending away from the door 14 along a centerline 38. The visor 30 can partially (as shown) or fully (not shown) encircle/surround the centerline 38. Consequently, the visor 30 can partially or fully encircle/surround the respective light assembly 20. As shown, a notch 40 extends radially through the bottom of the visor 30 to the passage 36. The notch 40 can allow for rain, snow, melted snow, etc. to flow out of the passage 36 and away from the lens 26. In any case, the visor 30 helps to focus light emitted by the LEDs 24 along the passage 36, thereby increasing the visibility of the LEDs.

A heater system is provided on the visor 30 for helping to prevent/reduce the buildup of snow, ice, etc. on the lens 26. The heater system includes at least one heater element formed as a composite 50. One or more of the composites 50 can be secured to the inner surface 34 of each visor 30 (as shown) and/or the outer surface 32 (not shown). Consequently, the composite(s) 50 can cover a portion of the inner surface 34 and/or the outer surface 32 or the entirety of either/both surfaces. In any case, the composite 50 can be flexible or rigid.

In one example, the composite 50 is a positive temperature coefficient (PTC) heater element. Alternatively, the heater element can be formed as a fixed wattage heater (not shown). Referring to FIGS. 2-3 the PTC composite 50 includes a first or carrier layer 51 made of an electrically insulating material, e.g., Mylar®, that can be impervious to water and other debris to extend the service life of the products. The carrier layer 51 includes a tab 49 and can be made the same color as the inner surface 34 of the visor 30, e.g., painted black, to prevent altering the light output of the LEDs 24.

The composite 50 further includes a polymer base layer 52 formed from a conductive material. The polymer base layer 52 can be, for example, a screen printed, flexible polymeric ink. The polymer base layer 52 includes a first bus 54 and second bus 56 spaced from each other. The first bus 54 includes a base 58 and finger portions 60 extending away from the base. The second bus 56 includes a base 64 and finger portions 66 extending away from the base. The finger portions 60, 66 extend towards one another and can be interdigitated. That said, the finger portions 60, 66 are spaced from one another. The polymer base layer 52 includes a tab 59 aligned with and overlying the tab 49 on the carrier layer 51.

A resistive layer 70 is connected to, e.g., screen printed on, the polymer base layer 52 and can be modified or formed in desired shapes to electrically connect the first bus 54 to the second bus 56. The resistive layer 70 can be formed in one or more pieces. The resistive layer 70 includes a tab 71 aligned with and overlying the tabs 49, 59 in the carrier and polymer base layers 51, 52.

The resistive layer 70 can be positioned between the polymer base layer 52 and the carrier layer 51 (not shown) or on top of the polymer base layer to sandwich the same between the layers 51, 70 (as shown). In any case, the resistive layer 70 can have a higher electrical resistance than the polymer base layer 52 and experience a PTC effect when heated by current.

That said, the resistive layer 70 will ultimately reach a designed steady-state temperature in which current is restricted/slowed from passing through the resistive layer and, thus, restricted/slowed from passing through the buses 54, 56. The resistive layer 70 will thereafter draw a reduced amperage required to maintain the steady state temperature, thereby self-regulating its temperature and helping to prevent overheating. The resistive layer 70 will stay “warm”—remaining in the high electrical resistance state as long as power is applied.

On the other hand, removing power will reverse the phase transformation—causing contraction of the matrix—and allow the carbon chains to re-form as the polymer matrix re-crystallizes. The electrical resistance of the resistive layer 70 (and therefore of the composite 50) thereby returns to its original value. In other words, the resistive layer 70 is electrically conductive at room temperature but heating the resistive layer reduces its electrical conductivity until current is restricted/slowed from passing therethrough.

An interface layer 80 helps to connect the composite 50 to the inner surface 34 of the visor 30 and completely seals the composite. In one example, the interface layer 80 directly engages the inner surface 34. The interface layer 80 can be directly connected to at least one of the polymer base layer 52 and the resistive layer 70. The interface layer 80 can be, for example, a double-sided adhesive, e.g., acrylic adhesive or thermally conductive foam adhesive.

The interface layer 80 can include a peelable adhesive liner or backing including, for example, paper, vinyl or mixtures thereof (not shown). Alternatively or additionally, mechanical fasteners (not shown) can connect the composite 50 to the visor 30. The composite 50 can also be provided in the visor 30 via overmolding, heat staking or by welding the composite between the surfaces 32, 34 (not shown). Regardless, when the composite 50 is assembled (FIG. 2), the components 51, 52, 70, 80 are oriented such that the respective tabs 49, 59, 71, 81 are aligned with one another, thereby collectively forming a composite tab or connector tail 90.

The heater system further includes a riveted or crimped first terminal 84 connected to the first bus 54. A rivet or crimped second terminal 82 is connected to the second bus 56. In one example, the terminals 82, 84 are secured to the connector tail 90 in a manner that electrically connects the terminals to the respective buses 54, 56. The terminals 82, 84 can be generally planar (as shown) or angled, e.g., 90° terminals (not shown).

Referring to FIG. 4, the heater system further includes a control module 98 for connecting each composite 50 to a power source and regulating the power distribution to each composite. To this end, the module 98 includes a printed circuit board (PCB) 100 having a controller and being connected to a power source via a connector 102. The voltage input to the module 98 can be, for example, 48 VDC or 120 VAC.

A series of connectors 104, 106, 108, 110, 112 are also provided on the circuit board 100 to enable one or more of the composites 50 to be connected to the module 98 via the terminals 82, 84. One or more sensors 118, e.g., temperature sensor, humidity sensor, and/or snow sensor, can be connected to a connector 113 on the circuit board. The sensors 118 can be positioned inside or outside the visor 30 and monitor the environmental conditions in/around each lens 26. The connectors 102-113 can be standard wire-to-board connectors, e.g., PID connectors, GEZ connectors, HYV connectors and the like. More or fewer of the connectors 104-113 are contemplated.

The module 98 can include a thermostat 140 associated with each connector 104, 106, 108, 110, 112 to control power flow between the module and the respective connector. Alternatively, a separate thermostat 140 can be associated with each connector 104, 106, 108, 110, 112 (not shown). Regardless, the thermostat 140 controls power flow between the module 98 and each composite 50. In one example, the thermostat 140 enables current flow from the module 98 to the corresponding composite 50 when the temperature around the corresponding LED light assembly 20 falls below a predetermined value, e.g., about 0° C. On the other hand, the thermostat 140 prevents current flow from the module 98 to each composite 50 when the temperature is above the predetermined value.

It will be appreciated that the thermostat 140 can be omitted entirely. In this construction, the module 98 can be connected to or provided with a breaker (not shown) that either continuously enables or continuously prevents current flow to the connectors 104-112 regardless of environmental conditions. In other words, the composites 50 are either always on or always off depending solely on whether the user has activated the breaker.

The module 98 is secured to the traffic light housing 12 within the interior space 16 (see also FIG. 1B). To this end, fasteners can extend through mounting openings 114 in the module 98 to secure the module to existing screw holes/standoffs within the housing 12 (not shown). Alternatively, the module 98 can be secured to the housing 12 with mounting tape/foam, Velco®, etc. Regardless, a single module 98 can be used for all the light assemblies 20 in the light fixture 10 or each light assembly can have its own module associated therewith.

FIG. 5 illustrates a schematic diagram of a circuit for the traffic light 10 in which two composites 50 are secured to the inner surface 32 of the visor 30 associated with one lens 26. Wiring 151 connects the LED light assemblies 20 to a common voltage supply device or power supply 196. The wires 120 electrically connects the terminals 82, 84 from each composite 50 to the corresponding connector 104, 106 on the module 98. Wiring 120 also connect any sensor(s) 118 to the module 98. Wiring 130 connects the power supply 196 to the connector 102 on the module 98 to power the module.

When the composites 50 are installed, the tabs 90 extend through the sealed interface 23 between the LED light assembly 20 and the associated door 14 (see FIG. 1B). This positions the tabs 90—and therefore the terminals 82, 84 connected thereto—within the interior space 16. The wires 120 then connect the module 98 to the terminals 82, 84. Once the door 14 is closed, the tabs 90 and terminals 82, 84 are sealed within this housing 12 away from wind, rain, snow, dirt, etc. It will be appreciated that the doors 14 of the traffic light 10 can be removable, thereby enabling a maintenance technician to install/inspect the light assemblies 20 and associated composites 50 on the doors at a more desirable location, e.g., on the ground, in a vehicle, at a facility, etc.

During operation of the traffic light 10, the thermostat 140 passively monitors the temperature around each lens 26. When the temperature falls below the predetermined value on one or more of the lenses 26, the thermostat 140 automatically closes to initiate/enable current flow to the composites 50 associated with the cold lenses. As the temperature of the composites 50 rise and cause the PTC effect, the heat is transferred to the visors 30, which thereby helps to prevent, reduce or remove snow and ice accumulation on the lens 26 associated therewith. Heat from the composite 50 can also directly heat the associated lens and snow thereon. In other words, the lenses 26 can be directly and indirectly heated by the composites 50 associated therewith.

The thermostat 140 can continue enabling current flow to the composites 50 so long as the air temperature around the visor 30 is below the predetermined value, thereby helping to ensure light from the LEDs 24 is visible through the lens 26 despite inclement weather. Any melted snow can flow along the inner surface 32 and composite 50 and out of the visor 30 through the notch 40. Once the air temperature around the visor 30 reaches the predetermined value the thermostat 140 automatically opens to cut off power supply to the composites 50.

Alternatively or additionally, the sensor(s) 118 can monitor the temperature, humidity, onset of snow and/or accumulation thereof around the lenses 26 and send signals to the module 98 indicative thereof. The module 98 controller can evaluate the signals and selectively supply current to the composites 50 in response thereto.

In one example, the module 98 controller is configured to initiate supplying power to the composites 50 when the air temperature around the visor 30 falls below about 38° F. and subsequently cut power to the composites when the air temperature reaches about 42° F. Alternatively or additionally, the module 98 controller can also take humidity into account, e.g., supply power to the composites 50 when the air temperature around the visor 30 falls below about 38° F. and the relative humidity is above 50%. The module 98 controller can also selectively power the composites 50 when the snow sensor 118 detects an amount of snowfall on/around the lens 26 that exceeds a predetermined amount. Other factors that can be used to determine composite 50 activation, including when and how long, include a timer circuit and/or battery backup sensor.

The module 98 can be controlled wirelessly by a web-based application or app that allows a user to directly control individual heating of the composites 50 regardless of the sensed environmental conditions. In other words, the app allows a user to override or ignore any signals received by the module 98 from the sensors 118 or thermostat 140.

In another example shown in FIG. 6, solar panels or cells 170 can be secured to the outer surfaces 32 of the visors 30 for powering the heater system, including the module 98 and components 50, 118 connected thereto. The solar panels 170 can also power the light assemblies 20. A rechargeable battery (not shown) can be electrically connected to the solar panels 170 and mounted in the interior space 16 of the housing 12 to protect the battery from the elements. The battery can replace or supplement the power supply 196. When the composites 50 are in use, heat therefrom radiates outward through the visor 30 and heats the solar panels 170, thereby helping to keep snow and ice from building thereon.

Another example composite 250 is illustrated in FIG. 7. Features in the composite 250 that are similar those in FIGS. 2-3 are given reference numbers 200 higher. The composite 250 includes the carrier layer (not shown) and base layer 252 with corresponding busses 254, 256 having interdigitated fingers 260, 266. The resistive layer 270 is provided over, e.g., printed on, the base layer 252 in a manner that resembles a checkboard pattern. More specifically, the resistive layer 270 is formed as a series of conductive portions 272 spaced apart from one another by non-conductive portions, i.e., voids or empty spaces 274, arranged collectively in a checkboard pattern. In this manner, the resistive layer 270 does not cover every portion of the base layer 252, i.e., there are discontinuities in the printing pattern.

The checkerboard pattern exemplifies how the resistive layer can be provided in the composite in any desirable configuration, e.g., symmetric, asymmetric, random, patterned, variable density, etc. This flexibility allows the resistive layer to have a desired watt density at each and every position on the composite. Consequently, a specific heating profile can be provided depending on the application where the heating system will be used.

The heater systems shown and described herein, e.g., heater elements formed as fixed wattage heaters or phase-changing composites, are advantageous in helping to avoid a hazardous condition as a result of snow buildup on LED lights, such as traffic lights, pedestrian crosswalk lights, railroad crossings, and pre-emptive receiver sensors.

The PTC heater element may be installed without the need for sensors, thermostats, or other feedback electronics. The PTC heater element is efficient and runs at very low steady state current. Current draw increases as temperatures decrease or snow attempts to stick to the surface, returning to steady state after melting. The PTC heater element is configurable to many different shapes, contours, and sizes of visors. Custom shapes ensure proper assembly and flexibility.

What have been described above are examples of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims.

Claims

1. A light fixture comprising: a housing;an LED light assembly provided on the housing;a visor extending from the housing at least partially around the LED light assembly; anda heater element connected to the visor.

2. A light fixture as set forth in claim 1, wherein at least a portion of the heater element is screen printed directly onto the visor.

3. A light fixture as set forth in claim 1, wherein the heater element is mounted to an inner surface of the visor.

4. A light fixture as set forth in claim 1, further comprising a solar panel mounted to an outer surface of the visor for powering the heater element.

5. A light fixture as set forth in claim 1, further comprising a solar panel mounted to an outer surface of the visor for powering the LED light assembly.

6. A light fixture as set forth in claim 1, wherein the heater element is a PTC heater element.

7. A light fixture as set forth in claim 1, wherein the heater element is a fixed wattage heater element.

8. A light fixture as set forth in claim 1, wherein the heater element includes a connector tail on which electrical terminals are mounted, the connector tail extending through an interface between the LED light assembly and the housing to an interior space of the housing.

9. A light fixture as set forth in claim 1, wherein the heater element is connected to the visor with adhesive.

10. A light fixture as set forth in claim 1, wherein the heater element is heat staked to the visor.

11. A light fixture as set forth in claim 1, wherein the heater element is overmolded to the visor.

12. A light fixture as set forth in claim 1 wherein the heater is welded between the inner surface and an outer surface of the visor.

13. A light fixture as set forth in claim 1, further comprising a temperature sensor for determining when the heater element should be energized.

14. A light fixture as set forth in claim 1, further comprising a humidity sensor for determining when the heater element should be energized.

15. A light fixture as set forth in claim 1 wherein the heater resistance is used to determine when the heater should be energized.

16. A light fixture as set forth in claim 1, wherein the housing and the visor are formed as part of a traffic light.

17. A light fixture as set forth in claim 1 wherein the heater element is the same color as the inner surface of the visor.

18. A light fixture as set forth in claim 1, further comprising a control module connected to the heater element for controlling the temperature of the heater element.

19. A light fixture as set forth in claim 18, further comprising a solar panel secured to an outer surface of the visor for supplying power to the control module.

20. A light fixture as set forth in claim 1, further comprising a solar panel secured to an outer surface of the visor for recharging a battery in the housing.

21. A light fixture as set forth in claim 1, wherein a timer circuit is used to determine when the heater element should be energized.

22. A light fixture as set forth in claim 1, wherein a battery backup sensor is used to determine when the heater element should be energized.

23. A light fixture as set forth in claim 1, wherein the functionality of the heater element can be monitored and controlled wirelessly.

24. A light fixture as set forth in claim 1, wherein only a single heater element is connected to the visor.

25. A light fixture as set forth in claim 1, further comprising a second heater element connected to the visor.