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(11) | EP 2 357 402 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | LED fluorescent lamp |
| (57) The invention provides a LED fluorescent lamp (10), comprising a lamp cap (800),
a bulb shell (100), a control circuit (600), at least two LED light sources (400),
at least two light source panels (300) on which the at least two LED light sources
are secured, respectively, heat-conducting means (500) and cover (700) means. The
heating-conducting means (500) comprises at least two thermally conductive base plates
which are disposed at an angle oblique to a longitudinal central axis of the heat-conducting
means, and on which base plates the at least two light source panels are secured in
a thermally conductive manner, the base plates extending downward from their bottom
ends to form a receiving chamber. The cover means (700) comprises a casing, and a
hollow barrel (710) for accommodating the control circuit, the casing is engaged snugly
with the heat-conducing means such that the heat-conducting means is coupled thermally
to the cover means. The cover means have a plurality of radiating fins (721) on its
outer surface. A path having good thermal conduction and thermal dissipation is created
along the light source panels - the heat-conducting means ― the casing of the cover
means ― the radiating fins. The LED fluorescent lamp exhibits excellent thermal conduction
and thermal dissipation to provide a solution to the problem associated with the thermal
dissipation of the LEDs.
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FIELD OF THE INVENTION
[0001] The present invention is generally in the field of lighting fixtures. More specifically, the present invention concerns a LED fluorescent lamp used as a lighting fixture with high luminous efficiency and good thermal dissipation characteristics.
BACKGROUND OF THE INVENTION
[0002] As a solid state light source, LEDs (light-emitting diodes) emerged in the sixties of the 20th century and are a product with long life span, firm structure, low power consumption and flexible dimension such that they are becoming to take the place of conventional high pressure halide lamps in a wide range of lighting applications. However, LEDs would generate comparatively high heat energy, with a result of their high light fades and shortened life span. This leads to limited applications of LEDs to some extent.
[0003] A currently available LED lamp, which is used for the purpose of illumination, usually comprises a plurality of LED light sources to form a LED array in order to reach the required illuminance and power, because a single one LED light source has relatively low illuminance and power. The greater the number of the LED light sources is, the more luminous and efficacious the LED lamp is. The LED array structure may satisfy the requirement for illuminance, but it causes several problems including heat concentration, high temperature at local positions, and adverse influence on the stability of the circuit control system. Because of the absence of specialized means for heat conduction and heat dissipation, the heat energy generated by the plurality of LED light sources cannot be effectively dissipated, such that the temperature of the housing of the lamp is so high to the extent that people would get scalded and that this lamp is vulnerable to get burned out.
[0004] Presently, great efforts have been made to provide various solutions in an attempt to tackle the heat dissipation of the LED lighting fixtures. However, these solutions are either less effective to dissipate the heat, or are expensive and structurally complicated though being effective on heat dissipation. For example, Chinese Utility Model patent No. 200910011246.8 with the title "LED illuminating lamp with a radiator having looped heat tubes" discloses a LED illuminating lamp which utilizes a radiator having looped heat tubes for heat dissipation. Although the problem of LED heat radiation is effectively solved by using the structure of the looped heat tubes-based radiator and the principle of the low heat resistance and the high heat conduction coefficient of the heat tubes, the method to dissipate heat disclosed in this patent is very expansive and structurally complicated.
[0005] Therefore, there is a need for improving the currently available LED lamps used for the purpose of illumination in terms of their thermal dissipation, in order for enhanced luminous efficiency, reduced energy consumption, decreased light fade, and increased luminous flux.
SUMMARY OF THE INVENTION
[0006] An object of the invention is to address the drawbacks in the prior art mentioned above by providing a novel LED fluorescent lamp which has good characteristics of thermal conduction and thermal dissipation. The LED fluorescent lamp can also have a prolonged service life, reduced energy consumption and decreased light fade.
[0007] The above object can be attained by providing a LED fluorescent lamp comprising a lamp cap received in a cap holder and connected to a power source, a bulb shell and a control circuit, the LED fluorescent lamp further comprises:
at least two LED light sources connected to the control circuit;
at least two light source panels on which the at least two LED light sources are secured, respectively;
heat-conducting means comprising at least two thermally conductive base plates which are disposed at an angle oblique to a longitudinal central axis of the heat-conducting means, and on which base plates the at least two light source panels are secured in a thermally conductive manner, the base plates extending downward from their bottom ends to form a receiving chamber having an annular interface at a bottom edge thereof;
cover means comprising a casing, and a hollow barrel for accommodating the control circuit, wherein the casing is engaged with the bulb shell, and has on its inner wall an annular interface which is engaged snugly with the annular interface of the heat-conducting means such that the heat-conducting means is coupled thermally to the cover means; and the hollow barrel is fixed at its bottom to the casing, and the hollowing barrel and the control circuit together are received within the receiving chamber.
[0008] In one preferred embodiment of the invention, the LED fluorescent lamp comprises:
three LED light sources;
three light source panels on which the three LED light sources are secured, respectively;
wherein the heat-conducting means comprises three thermally conductive base plates which are disposed at an angle oblique to the longitudinal central axis of the heat-conducting means at equal angular interval, the base plates each comprise a lower portion and an upper portion formed by extending obliquely upward and inward from a top end of the lower portion, all the three upper portions forming a triangular structure atop the heat-conducting means, and the triangular structure has a through hole on its top surface for allowing passage of electric wires connecting the LED light sources to the control circuit.
[0009] The heat-conducting means further comprises three lower partitions arranged respectively between the lower portions of the base plates, and three upper partitions formed by extending obliquely upward and inward from top ends of the lower partitions, respectively, the lower portions of the base plates and the lower partitions are set against each other to surround a conical surface; and the three light source panels with the LED light sources are secured on the base plates, respectively.
[0010] Preferably, each of the lower portions of the base plates has a spring bore for snap fitting one end of the spring, the other end of the spring is fixed on the light source panel, such that the light source panel is firmly secured on the base plate.
[0011] According to the invention, the LED light sources may be secured on the light source panels by glue dispensing or mechanically; and the light source panels may be secured on the thermally conductive base plates by fasteners, glue dispensing or viscous radiating oils. Advantageously, a layer of radiating oil may be arranged between the light source panel and the thermally conductive base plate.
[0012] To increase the dissipation efficiency, the casing may have on its outer surface a plurality of radiating fins that are disposed in a spaced manner.
[0013] The bottom of the hollow barrel of the cover means may be snap-fitted or screwed into the casing, which would be within the ability of a person skilled in the art.
[0014] In order to enhance the thermal dissipation, the light source panels, the heat-conducting means, and the casing of the cover means are formed with a thermally conductive material selected from the group consisting of aluminium, aluminium alloy and ceramic.
[0015] It is known that a LED light source in a LED lighting fixture is a prominent heating element that generates heat. The heat energy generated would have adverse influence on the stability of the control circuit of the LED lighting fixture, which in turn affects the lumination of the LED light source. In the LED fluorescent lamp of the invention, the light source panels, on which the LED light sources are secured, are in intimate contact with the heat-conducting means which is also in intimate contact with the cover means having radiating fins, thus creating a good path for thermal conduction and thermal dissipation. This path allows the heat energy generated from the LED light sources to dissipate successfully through the light source panels - the heat-conducting means - the cover means ― the radiating fins, and the temperatures of the LED light sources and thus the temperature of the interior of the lamp are therefore decreased greatly. Consequently, the temperature of the control circuit inside the lamp would not be too high, to ensure the stability of the control circuit. According to the invention, the path for thermal conduction and thermal dissipation is effective to ensure the LED light sources not to overheat. This prolongs the service life of the LED fluorescent lamp, and accordingly solves the problem of heat generation in a high power LED fluorescent lamp.
[0016] In addition, modifying the design of the thermally conductive base plates positioned in the heat-conducting means to cater for mounting of more LED light sources and light source panels allows the manufacturing of a series of high power LED fluorescent lamps.
[0017] The objects, characteristics, advantages and technical effects of the invention will be further elaborated in the following description of the concepts and structures of the invention with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018]
Fig.1 is a front view of a LED lamp fluorescent lamp constructed according to an embodiment of the invention.
Fig. 2 is a sectional view taken along line A-A of Fig. 1.
Fig. 3 is a perspective exploded view of the LED fluorescent lamp of Fig. 1.
Fig. 4 is a perspective top view of the heat-conducting means in the LED fluorescent lamp of Fig. 1.
Fig. 5 is a perspective exploded bottom view of the heat-conducting means of Fig. 4.
Fig. 6 is a front view of the heat-conducting means of Fig. 4.
Fig. 7 is a top view of the heat-conducting means of Fig. 4.
DETAILED DESCRIPTION OF THE INVENTION
[0019] While this invention is illustrated and described in preferred embodiments, the LED fluorescent lamps may be produced in many different configurations, sizes, forms and materials.
[0020] Referring now to the drawings, Figs. 1 to 3 provide a LED fluorescent lamp 10 constructed consistent with a preferred embodiment of the present invention. In this embodiment, the LED fluorescent lamp 10 comprises a glass bulb shell 100, three LED light sources 400, three light source panels 300, heat-conducting mean 500, a control circuit 600, cover means 700 and a lamp cap 800.
[0021] The glass bulb shell 100 may be transparent, or selected from the group consisting of glass bulb shell with injected silicon coating, glass bulb shell with torsional lines, and frosted glass bulb shell according to the actual needs. The lamp cap 800 may be of various sizes according to the actual needs, for instance, the lamp cap 800 may be selected from the group of E11, E12, E14, E17, E26 and E27 lamp caps. The control circuit 600 is not the essence of the invention and therefore not described in detail herein.
[0022] The LED light source can consist of one or more LEDs. In this embodiment, each of the three LED light sources 400 consists of 3 chip LEDs which are secured on the respective light source panel 300. The LED light sources 400 can be secured on the light source panels 300 by glue dispensing or mechanically or any means known in the art.
[0023] As shown in Figs. 4 to 7, the heat-conducting means 500 has a generally triangular upper portion and a generally cylindrical lower portion. In this embodiment, the heat-conducting means 500 comprises three thermally conductive base plates which are disposed at an equal angular interval and are inclined to a longitudinal central axis of the heat-conducting means. The inclined arrangement of the base plates relative to the longitudinal central axis of the heat-conducting means ensures that the light from the LED light sources emits directly. Each of the three thermally conductive base plates comprises a lower portion 510 and an upper portion 530 formed by extending obliquely upward and inward from a top end of the lower portion 510, and the light source panel 300 with the LED light source 400 is secured on the upper portion 530. All of the three upper portions 530 are abutted together to form a triangular structure on the top of the heat-conducting means 500. This triangular structure has a flat top surface 560 having a through hole 561 at its center for allowing passage of the wires which electrically connect the LED light sources 400 and the control circuit 600.
[0024] A layer of radiating oil can be coated between the light source panel 300 and the thermally conductive base plate for better heat transfer. Of course, the light source panel 300 may be secured on the thermally conductive base plate by any method known in the art, provided that heat conduction and heat dissipation therebetween are achieved. For example, a viscous radiating oil can be used to directly attach the light source panels 300 onto the sides of the base plates, respectively. In the present embodiment, a spring 200 is used to further reinforce the securing of the light source panels onto the upper portions 530 of the base plates. In particular, each of the lower portions 510 of the base pates has a spring bore 511 in which one end of the spring 200 is snap-fitted, the other end of the spring 200 is fixed on the light source panel 300. Because the spring is in compressed condition, the light source panel 300 is firmly maintained by the force of the spring to be fixed intimately on the upper portion 530 of the base plate.
[0025] The heat-conducting means 500 further comprises three lower partitions 520 arranged respectively between the lower portions 510 of the base plates and three upper partitions 540 formed by extending and being inclined upward and inward from top ends of the lower partitions 520, respectively. The lower portions 510 of the base plates and the lower partitions 520 are abutted against each other to surround a conical surface, as shown in Figs. 4 and 7. The inclined arrangement of the upper partitions 540 and the lower partitions 520 ensures that the light from the light sources 400 can emit effectively and sufficiently in various directions and are not blocked.
[0026] The conical surface surrounded by the lower portions 510 of the base plates and the lower partitions 520 extends downward from its bottom end to form a receiving chamber 550 having an annular interface at a bottom edge thereof. In this embodiment, the annular interface is formed as a step 551 by bending the bottom edge of the receiving chamber 550.
[0027] The cover means 700 is of annular configuration, and comprises a casing 720 and a hollow barrel 710. The hollow barrel 710 is fixed at its bottom to the casing 710 by any method known in the art. The casing 720 has an upper end which is engaged with the glass bulb shell 100 by any method known in the art, for example snap-fit or screws. The upper side of the inner wall of the casing 720 protrudes outward to form a step which is engaged snugly and intimately with the step 551 of the heat-conducting means 500, such that the heat-conducting means 500 is coupled thermally to the cover means 700 to create an excellent thermally conductive contact. The hollow barrel 710 is fitted in dimension into the receiving chamber 550 of the heat-conducting means 500.The control circuit 600 is placed into the hollow barrel 710, and then they are together received in the receiving chamber 550.
[0028] The casing 720 has on its outer surface a plurality of radiating fins 721 that are parallel to the longitudinal central axis thereof and disposed in a spaced manner. The arrangement of the radiating fins 721 further boosts the dissipation of heat energy transmitted from the heat-conducting means 500.
[0029] The light source panels 300, the heat-conducting means 500 and the casing 720 of the cover means are preferably formed with a thermally conductive material selected from the group consisting of aluminium, aluminium alloy and ceramic.
[0030] According to the invention, the light source panels secured with the LED light sources lie tightly against the thermally conductive base plates of the heat-conducting means which is in thermally intimate contact with the cover means having an outer surface with a plurality of radiating fins, thereby creating a path having good characteristic of thermal conduction and thermal dissipation along the light source panels - the heat-conducting means ― the casing of the cover means ― the radiating fins. The heat energy generated by the LED light sources is allowed to dissipate rapidly through this path, which facilitates the reduction in the temperature of the LED light sources. Thus, the problem associated with the thermal dissipation of the LED lighting fixtures is successfully resolved.
[0031] The number of the LED light sources may be 2 or more, for example, 3 or 4 and even more, as long as the number of the thermally conductive base plates of the heat-conducting means 500 is adjusted accordingly to cater for the number of the LED light sources. Hence, a higher power LED fluorescent lamp, which has low energy consumption and decreased light fade, can be manufactured, because the problem associated with the thermal dissipation of the LED is successfully resolved.
[0032] Thus, the present invention provides a LED fluorescent lamp which effectively solves the problem of thermal dissipation associated with LED lamps and which exhibits characteristics of high luminous efficiency and increased luminous flux.
[0033] Having sufficiently described the nature of the present invention according to some preferred embodiments, the invention, however, should not be limited to the structures and functions of the embodiments and drawings. It is stated that insofar as its basic principle is not altered, changed or modified it may be subjected to variations of detail. Numerous variations and modifications that are easily obtainable by means of the skilled person's common knowledge without departing from the scope of the invention should fall into the scope of this invention.
at least two LED light sources connected to the control circuit;
at least two light source panels on which the at least two LED light sources are secured, respectively;
heat-conducting means comprising at least two thermally conductive base plates which are disposed at an angle oblique to a longitudinal central axis of the heat-conducting means, and on which base plates the at least two light source panels are secured in a thermally conductive manner, the base plates extending downward from their bottom ends to form a receiving chamber having an annular interface at a bottom edge thereof;
cover means comprising a casing, and a hollow barrel for accommodating the control circuit, wherein the casing is engaged with the bulb shell, and has on its inner wall an annular interface which is engaged snugly with the annular interface of the heat-conducting means such that the heat-conducting means is coupled thermally to the cover means; and the hollow barrel is fixed at its bottom to the casing, and the hollowing barrel and the control circuit together are received within the receiving chamber.
three LED light sources;
three light source panels on which the three LED light sources are secured, respectively;
wherein the heat-conducting means comprises three thermally conductive base plates which are disposed at an angle oblique to the longitudinal central axis of the heat-conducting means at equal angular interval, the base plates each comprise a lower portion and an upper portion formed by extending obliquely upward and inward from a top end of the lower portion, all the three upper portions forming a triangular structure atop the heat-conducting means; the heat-conducting means further comprises three lower partitions arranged respectively between the lower portions of the base plates, and three upper partitions formed by extending obliquely upward and inward from top ends of the lower partitions, respectively, the lower portions of the base plates and the lower partitions are set against each other to surround a conical surface; and
wherein the three light source panels with the LED light sources are secured on the base plates, respectively.
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.
Patent documents cited in the description