NL2011782C2

NL2011782C2 - Profile for a led tube, led tube comprising said profile and method for assembling a led tube.

Info

Publication number: NL2011782C2
Application number: NL2011782A
Authority: NL
Inventors: Paul Steffens; Jürgen Honold
Original assignee: Silicon Hill B V
Priority date: 2013-11-11
Filing date: 2013-11-11
Publication date: 2015-05-13
Also published as: WO2015069104A1

Abstract

The invention relates to a profile (10) for a LED tube (2), LED tube comprising said profile and method for assembling a LED tube (2). The profile (10) comprises an elongated base section having a substantially U-shaped cross section and a supporting section (24) extending from the base section for supporting a printed circuit board, PCB (12), wherein each of the arms of the base section is provided with a protrusion (27) for retaining the PCB between the supporting section and the protrusions, wherein the supporting section is formed by a resilient member.

Description

Profile for a LED tube, LED tube comprising said profile and method for assembling a LED tube

The invention relates to a profile for a LED tube. A LED tube is a tubular lighting, wherein the light source is formed by light emitting diodes, LEDs. LED tubes are often used as one to one replacement of fluorescent tubes, as LEDs provide many advantages in terms of energy efficiency and product life time. LED tubes comprise a profile for mounting the printed circuit board (PCB) with the LEDs in the tube.

In most cases, the LED tube profile serves as a heat conductor to transfer the heat generated by the LEDs to the outside of the LED tube. A profile for a LED tube according to the preamble of claim 1 is known in the art. A problem of conventional profiles for LED tubes is that a gap is present between the supporting section and the PCB in order to take into account deviations in the dimensions of the PCB or the profile. This gap deteriorates the heat transfer from the PCB to the profile. Therefore, a heat conducting paste is usually applied between the PCB and the profile. However, this solution is not optimal in terms of heat transfer. Furthermore, applying the heat conducting paste increases the number of process steps for assembling the LED tube.

An object of the invention is to overcome or at least reduce the above disadvantages and to provide a profile for a LED tube allowing an improved heat transfer to the profile from a PCB mounted to the profile.

This goal is achieved with the profile for a LED tube according to the invention, the profile comprising - an elongated base section having a substantially U- shaped cross section; and - a supporting section (24) extending from a first arm (22) of the base section towards a second arm (20) of the base section for supporting a printed circuit board (12), PCB, wherein each of the arms (20, 22) of the base section is provided with a protrusion (26, 28) for retaining the PCB between the supporting section and the protrusions, characterized in that the supporting section is formed by a resilient member.

By forming the supporting section as a resilient member, the supporting section presses against the PCB, thereby improving the contact between the PCB and the profile. The improved mechanical contact between the PCB leads to an improved heat transfer between these parts. Therefore, heat produced by LEDs of the PCB is effectively transferred to the profile. As build up of heat is avoided, the life time of a LED tube comprising the profile according to the invention is increased. A heat conducting paste may no longer be required. Therefore, the number of steps to assemble a LED tube is reduced. However, it is noted that a heat conducting paste may still be applied if desired.

Moreover, if a heat conducting paste is applied, the layer of conducting paste will be less thick due to a higher and equally distributed clamping force of the PCB against the supporting section. Therefore, heat transfer from the PCB to the profile is improved.

An additional advantage of embodiments of the profile according to the invention is that it enables a new way of assembling a LED tube. In conventional LED tubes, the front of the PCB is inserted from a short side of the profile and between the supporting section and the retaining protrusions. The PCB is then slid along the profile until it is completely positioned within the profile. Due to the typical length of LED tubes, this way of assembling is cumbersome. Furthermore, the sliding movement may damage the PCB. The profile according to the invention overcomes this disadvantages by enabling the PCB to be mounted in the profile from the top. One end of the PCB is inserted between the protrusion of the first arm of the base section and the supporting section, after which the other end of the PCB is pressed down, thereby snapping the PCB into place. The snapping or clicking operation is possible because the resilient member allows some movement of the arms of the U-shaped base section with respect to each other. This way of assembling the LED tube is faster and leads to less damage to the PCB.

For example, the profile is made of or comprises a metal or metal alloy, such as aluminium, copper or steel. In another example, the profile is made of or comprises thermal conductive plastic.

For example, the profile is produced by extrusion.

The profile is preferably made of a material having a good thermal conductivity, e.g. a thermal conductivity higher than 50 W m_1 K-1, 100 W πΓ1 KT1, higher than 120 W m_1 K_1, higher than 150 W m_1 K_1 or higher than 200 W πΓ1 K_1.

The supporting section may for example be provided with resilience by choosing an appropriate shape of the supporting section. For example, a part of the supporting section comprises a zigzag or undulating shape. In another example the supporting section comprises a zone with a reduced thickness to provide resilience.

In a preferred embodiment according to the invention the resilient member is a tab having a free end, thus defining a gap between the second arm of the base section and the free end of the tab.

The tab provides resilience to the supporting section, while still allowing production of the profile in one piece and by means of extrusion.

In a further preferred embodiment according to the invention the tab is moveable between a retaining position wherein the PCB is placed between the tab and the protrusions and a resting position wherein the tab extends at an angle a with respect to the plane defined by the PCB in the retaining position.

In other words, when placing the PCB the tab is displaced from its resting position, thus providing a spring force against the PCB when the PCB is locked in the retaining position, wherein the PCB is positioned between the tab and the protrusions of the base section of the profile. The supporting section of the profile is thus pressed tightly against the PCB, resulting in a firm contact between the PCB and the profile. Therefore, the heat transfer is improved and thus the lifetime of the LEDs is increased.

In a further preferred embodiment according to the invention, the second arm of the base part comprises an abutment member arranged to limit the movement of the tab.

When assembling a LED tube based on the profile of the invention, the PCB is pressed down on the supporting section. As the supporting section exhibits resilience, it will also move in a downward direction, i.e. towards the base section. To avoid bending the tab too far and thereby deforming the tab, the abutment member limits the movement of the tab.

In a preferred embodiment according to the invention, the protrusion of the second arm of the base section is a resilient protrusion. This further improves the ease of assembly of the LED tube, as the PCB can be moved past the protrusion of the second arm more easily, even if the arms of the U-shaped base section only show a limited ability to move with respect to each other.

Additional or alternatively, the protrusion of the second arm is formed on a resilient end zone of the second arm of the base section. In this embodiment, the outer end region of the second arm can be bent in an outward direction with respect to the profile. When the PCB is inserted by inserting one end between the supporting section and the retaining protrusion of the first arm and subsequently pushing the other end downwards past the protrusion of the second arm, the end zone of the second arm moves outwardly, i.e. away from the first arm. This allows for a quick and easy assembly of a LED tube. Furthermore, when the PCB is moved past the protrusion of the second arm, the end zone of the second arm will exert an inwardly directed force on the PCB, i.e. a clamping force, leading to a rigid fixation of the PCB in the profile.

In an exemplary embodiment one or both of the retaining protrusions may be movable between a first position wherein said protrusion does not obstruct the path of the PCB when placing the PCB on the supporting section, and a second position wherein said protrusion extends over the supporting section such that the PCB is positioned between the supporting section and said protrusion when the PCB has been placed on the supporting section. For example, the first position may be a substantially upright position, i.e. substantially perpendicular to the plane defined by the supporting section. For example, the second position may be a position wherein said protrusion is substantially parallel to the supporting section. For example, the one or both protrusions can be moved back and forth between the first and second position. The PCB can be placed on the supporting section easily when one or both protrusions are in the first position as they do not extend over the supporting section. When the PCB has been placed, the one or both protrusions can be moved to the second position, e.g. by a snapping or bending movement, thereby retaining the PCB between the supporting sections and the protrusions. Preferably, at least the protrusion of the second arm is movable between the first position and second position as described above.

In a preferred embodiment according to the invention, the supporting section is provided with a groove near the first arm of the base part for inserting a side of the PCB. The groove provides room to tilt the PCB after one end is inserted in the profile. As the flexibility of PCB' s may vary, the groove ensures that also relatively stiff PCB can be positioned between the supporting section and the protrusion of the first arm of the base section by the tilting movement.

In a preferred embodiment according to the invention the base section is provided with a longitudinal recess having a substantially flat surface for stably positioning the profile on an assembly bench. Preferably, the recess is provided in a bottom portion of the base section, such as substantially opposite to the supporting section of the profile. Conventional profiles for LED tubes often have a cylindrical shape, making it difficult to position these tubes on an assembly bench. The flat surface of the recess enables stable positioning of the profile during assembly.

The invention further relates to a LED tube comprising the profile as described above, wherein the LED tube further comprises : - a PCB positioned between the supporting section and the protrusion of the arms of the base section; and — a cover for covering the PCB, wherein the profile comprises a first attachment means and the cover comprises a second attachment means engaging with the first attachment means for attaching the cover to the profile .

The same advantages and effects as described above for the profile apply to the LED tube according to the invention .

As mentioned above the profile enables an improved attachment of the PCB to the profile as well as a faster and easier assembly. The cover covers the PCB with the LEDs. The cover is transparent or translucent, i.e. light passes through the cover. For example, the cover is made of a plastic, such as polycarbonate (PC), poly(methyl methacrylate) (PMMA) or polystyrene.

The first attachment means and second attachment means enable mechanically connecting the profile and the cover.

Due to this mechanical connection, thermal expansion of the components of the LED tube can be absorbed. This is especially relevant in view of the large amount of heat generated by LEDs and the fact that the cover and the profile are usually made of different materials having a different thermal expansion coefficient. It is noted that this advantage also relates to the attachment of the PCB to the profile, which is also a mechanical connection.

Preferably, the first attachment means and second attachment means are arranged to form a snap connection, which enables an easy assembly of the LED tube.

In a preferred embodiment of the LED tube according to the invention, the support section is less stiff than the PCB. This has the advantage that the resilient supporting section will not deform the PCB.

In a preferred embodiment according to the invention the LED tube further comprises a phosphor element and the cover comprises a protruding member for clamping the phosphor element between said protruding member and at least one of the PCB and the supporting section. A phosphor is a luminescent material, such as a phosphorescent or fluorescent material. Phosphors are used in LED lighting to adjust the light spectrum with respect to the spectrum of the light emitted by the LEDs. The light emitted by the LEDs excites the phosphor, which re-emits light with a different wavelength (often a longer wavelength, i.e. more towards the red part of the visible spectrum).

The phosphor element may be provided from any suitable material, such as glass provided with a phosphor layer. By providing the protruding member to the cover, the phosphor element can be mechanically attached to the profile/PCB.

The mechanical connection of the phosphor element to the profile and/or the PCB has the advantage that thermal expansion of the components is taken into account, in contrast to other forms of connecting such as gluing.

The wavelength shifting process of phosphors generates heat. Therefore, a phosphor is preferably placed remotely to the LEDs. This configuration is called a remote phosphor. Preferably, the phosphor element according to the invention is a remote phosphor element. For example, the phosphor element is an elongated element having a substantially U-shaped cross section, wherein the arms of the U-shape are positioned on the PCB or the supporting section.

In a further embodiment the phosphor element comprises at least one flange for clamping the flange between the protruding member of the cover and at least one of the PCB and the supporting section. For example, the phosphor element is an elongated element having a U-shaped cross section wherein the flanges are attached to the ends of the arms of the U-shape.

In a preferred embodiment according to the invention the protrusions for retaining the PCB are integrally formed with the first attachment means of the profile. In other words, the profile comprises a section which functions both as a protrusion for retaining the PCB as first attachment means for attaching the cover. For example, a protrusion for retaining the PCB and a first attachment means are formed by a single element having a substantially T-shaped cross section.

The invention further relates to a method for assembling a LED tube, wherein the method comprises: - providing a profile as described above; - positioning a printed circuit board, PCB, between the supporting section and the protrusions; and - connecting a cover to the profile to cover the PCB.

The same advantages and effects as described above for the profile and the LED tube apply to the method of the invention .

In a preferred embodiment the step of positioning the PCB comprises: - inserting one end of the PCB between the supporting section and the protrusion of the first arm of the base section; and - tilting the PCB while keeping said one end between the supporting section and the protrusion of the first arm of the base section thereby pressing the other end of the PCB past the protrusion of the second arm and thus mechanically locking the PCB between the supporting section and the protrusions of the base section.

Further advantages, features and details of the invention will be elucidated on the basis of exemplary embodiments thereof, wherein reference is made to the accompanying figures.

Figure 1 shows a first embodiment of a LED tube according to the invention;

Figure 2 shows a cross section of the first embodiment according to line II-II in figure 1;

Figure 3 shows an exploded view of the components of the first embodiment of the LED tube;

Figures 4A-4C show in a front view cross section the assembly of the LED tube of the first embodiment;

Figures 5A-5B show a front view of a cross section of a first embodiment of a profile for a LED tube according to the invention;

Figures 6A-6C show a front view of a cross section of a second embodiment of a profile for a LED tube according to the invention; and

Figures 7A-7C show a variant according to the invention of the embodiment of figures 4A-4C. LED tube 2 comprises end caps 4, 6 and body 8 (figure 1). End caps 4, 6 are used for placing LED tube 2 in a fixture, wherein end cap 4 is provided with electrical contacts to provide the LED tube 2 with electrical power.

Body 8 (figure 2) comprises a profile 10 which in this example is an extrusion profile of aluminium. Body 8 further comprises a printed circuit board (PCB) 12 on which the LEDs 18 of the tube 2 are provided. Optionally a remote phosphor element (14) is provided. Body 8 further comprises a cover 16. Cover 16 is transparent or translucent, i.e. it allows light to pass through. In the example shown cover 16 is made of polycarbonate (PC). As can be seen most clearly in figure 3, the LEDs 18 are provided on PCB 12 in the form of a LED-strip .

The profile 10 of tube 2 has a substantially U-shaped cross section, defining a first arm 22 and a second arm 20 (figure 4A). The profile 10 further comprises a section 24 for supporting the PCB, wherein the supporting section 24 extends from first arm 22 towards second arm 20. The supporting section 24 forms a resilient tab with a free end. The free end of tab 24 is provided at a distance of second arm 20, such that a gap 25 is formed between second arm 20 and the tab 24. Alternatively, the tab may be connected to the second arm 20 via a flexible part, e.g. a part having a zigzag shape or undulating shape, thus providing resilience to the tab 24.

The arms 20, 22 of the U-shape base of the profile 10 comprise protruding ribs 26, 28 for retaining PCB 12 between tab 24 and these ribs 26, 28. The second arm 20 of the base of the profile 10 is provided with a further protrusion 27 which serves as a abutment member which in this exemplary embodiment serves as an additional supporting surface such that PCB 12 is retained between ribs 26, 28 and supporting surfaces 24, 27. The protrusion 27 takes the form of a rib in this exemplary embodiment.

Supporting section 24 of the profile 10 comprises a groove 30, which is provided near the zone where section 24 is connected to the first arm 22. Groove 30 enables insertion of PCB 12 under an angle with respect to supporting section 24, after which the opposing end of the PCB can be pressed down to the position between ribs 26 and rib 27.

Profile 10 preferably comprises a mounting element 32 which has an opening for receiving a screw to mount the end caps 4, 6 to the body 8 of the tube 2. Profile 10 further comprises a recess 34 on its lower end which provides a flat surface, instead of continuing the substantially semi circular shape of the profile. The flat surface thereby allows stably placing profile 10 on an assembly bench for assembling the tube 2.

Cover 16 is provided with ribs 36, 38 (figure 4B). Ribs 36, 38 can engage with ribs 40, 42 of the profile 10. Cover 16 can be pressed down on profile 10 to form a mechanical connection by means of the ribs 36, 38 and ribs 40, 42.

In the case a phosphor element is provided, such as remote phosphor element 14, cover 16 preferably comprises protruding ribs 44, 46 to clamp the phosphor element against the PCB or supporting section 24. In the exemplary embodiment the remote phosphor element 14 comprises flanges 48, 50 which engage with the ribs 44, 46 of cover 16.

Tab 24 may be provided at an angle a with respect to the horizontal plane, as shown in figure 5A. In other words, in its resting position the free end of tab 24 is positioned further away from the base section than in the situation wherein the PCB 12 is placed on top of tab 24 (figure 5B). Therefore, when the PCB 12 is placed in the profile 10, the tab 24 exerts a force B from below to the PCB 12. The PCB 12 is retained by ribs 26, 28, which will exert a reaction force A on the PCB 12. Therefore, a tight contact between tab 24 and PCB 12 is ensured, improving heat transfer and improving the mechanical stability of the assembled tube.

In another exemplary embodiment (figures 6A-6C), the tab 24 has a thickness such that it is more flexible than the PCB 12. In the embodiment shown the abutment member 27 serves to limit the movement of tab 24 in the downward direction. The retaining rib 26 of profile 10 is resilient to accommodate an easy positioning of the PCB 12 in the profile 10 .

The assembly of a LED tube according to the method of the invention will now be explained with reference to the figures 4A-4C. Firstly, profile 10 is extruded from aluminium. The profile is place on a assembly bench, wherein elongated recess 34 is placed over a matching part of the assembly bench. One side of the PCB with the LEDs is inserted in groove 30. The PCB is tilted such that its other end is moved past retaining rib 26, thereby mechanically locking PCB 12 in profile 10. Remote phosphor element 14 may be placed subsequently on PCB 12. Alternatively, PCB 12 has been provided with a remote phosphor element 14 before inserting it is profile 10. In another embodiment, no phosphor element is placed on the PCB. After fitting the PCB in profile 10 the cover 16 is attached to profile 10 by engaging ribs 36, 38 with ribs 40, 42 of the profile. In case a remote phosphor element 14 is provided, the ribs 44, 46 of cover 16 will engage with the flanges 48, 50 of the remove phosphor element 14. This completes the body of LED tube 2. Subsequently the end caps 4, 6 can be attached to body 8 using the attachment means 32.

Protrusion 26' (figure 7A-7C) is provided under an angle, e.g. under an acute angle greater than zero degrees with respect to the plane defined by supporting section 24. This enables an easy placement of PCB 12 in profile 10. Preferably, protrusion 26' is resilient, such that it can be pressed against the PCB by cover 16, as shown in figure 7C.

The present invention is by no means limited to the above described exemplary or preferred embodiments thereof. The rights sought are defined by the following claims, within the scope of which many modifications can be envisaged.

Claims

A profile (10) for an LED tube (2), comprising: an elongate base member with a substantially U-shaped cross-section; and a support member (24) extending from a first arm (22) of the base member to a second arm (20) of the base member for supporting a printed circuit board (12), PCB, in which each of the arms (20, 22 of the base part is provided with a protrusion (26, 28) for holding the PCB between the support part and the protrusions, characterized in that the support part is formed by a resilient element.

The profile of claim 1, wherein the resilient member is a lip with a free end so that it defines an opening (25) between the second arm of the base member and the free end of the lip.

Profile according to claim 2, wherein the lip is movable between a holding position in which PCB is placed between the lip and the protrusions and a rest position in which the lip extends at an angle (a) with respect to the plane that the PCB places in the holding position is defined.

Profile according to claims 2 or 3, wherein the second arm of the base part comprises a stop element (27) which is adapted to limit the movement of the lip.

The profile of any one of the preceding claims, wherein the protrusion of the second arm of the base member is a resilient protrusion.

The profile of any one of the preceding claims, wherein the protrusion of the second arm is formed at a resilient end zone of the second arm of the base member.

Profile according to one of the preceding claims, wherein the support part is provided with a groove (30) near the first arm of the base part for insertion of a side of the PCB.

Profile according to one of the preceding claims, wherein the base part is provided with a longitudinal recess (34) with a substantially flat surface for stable positioning of the profile on an assembly table.

An LED tube comprising the profile of any one of the preceding claims, wherein the LED tube further comprises: a PCB positioned between the support member and the protrusions of the arms of the base member; and a cover (16) for covering the PCB, wherein the profile comprises first fastening means (40, 42), and the hood comprises second fastening means (36, 38) which engage with the first fastening means for fastening the hood to the profile.

10. LED tube according to claim 9, wherein the first fixing means and the second fixing means are adapted to form a snap connection.

11. LED tube according to claim 9 or 10, wherein the support part is less rigid than the PCB.

The LED tube of claims 9, 10 or 11, wherein the LED tube further comprises a luminescent element (14), wherein the cap comprises a protruding element (44, 46) for clamping the luminescent element between the protruding element of the cover and at least one of the PCB and the support part.

The LED tube of claim 12, wherein the luminescent element comprises at least one flange (48, 50) for clamping the flange between the protruding element of the cap and at least one of the PCB and the support member.

LED tube according to any of claims 9-13, wherein the projections for holding the PCB are integrally formed with the first fixing means of the profile.

A method for assembling an LED tube, the method comprising: providing a profile according to any of claims 1-8; positioning a printed circuit board, PCB, between the support member and the projections; and connecting a cap to the profile to cover the PCB.

The method of claim 15, wherein the step of positioning the PCB comprises: inserting one end of the PCB between the support member and the protrusion of the first arm of the base member; and tilting the PCB while holding one end between the support member and the protrusion of the first arm of the base member, the other end of the PCB being pushed past the protrusion of the second arm, so that the PCB is mechanically confined between the support member and the protrusions of the base member.