FIELD OF INVENTION

The present invention relates to a tubular solid state light emitting lighting device, and more particularly to a lighting device comprising a tube, which is elongate and light transmissive, and which includes a light diffuser; electrical contacts arranged at the ends of the tube; and an elongate solid state light emitting member extending along the tube and being connected with the electrical contacts.

TECHNICAL BACKGROUND OF INVENTION

Tubular lighting devices having a solid state light source are typically constructed as a replacement lighting device which is useful in existing luminaries, which have been used with conventional fluorescent light tubes (TL tube). A typical solid state light emitting element is a LED (Light Emitting Diode), as disclosed in US 2010/0103673. These so called retrofit LED light tubes have many advantages in comparison with the conventional fluorescent light tubes, as is well known within the art. However, the manufacture of the LED light tubes is cumbersome since the LED members are inserted into the tube and attached to the inner wall thereof, and the diameter of the tube is small and the length is long. Typical dimensions of the tube are more than one meter long and an inner diameter of less than 25 mm. BRIEF DESCRIPTION OF THE DRAWINGS

It is an object of the present invention to provide a simplified construction of the tubular solid state light emitting lighting device and a simplified manufacture thereof.

The object is achieved with a lighting device according to the present invention as defined in the appended claims.

Thus, according to one aspect of the invention, there is provided a lighting device comprising a tube, which is elongate and light transmissive, and which includes a light diffuser. The lighting device further comprises electrical contacts arranged at the ends of the tube, and an elongate solid state light emitting member extending along the tube and being connected with the electrical contacts. The solid state light emitting member is attached to an outer surface of the tube and emits light through the tube. According to another aspect of the invention, there is provided a method of manufacturing a lighting device, comprising:

- providing a tube, which is elongate and light transmissive, and which includes a light diffuser;

- providing the tube with electrical contacts at the ends thereof; and

- attaching an elongate solid state light emitting member to an outer surface of the tube, such that the solid state light emitting member extends along the tube and emits light through the tube.

Thus, by arranging the solid state light emitting member on the outer surface of the tube, the difficult interior mounting is avoided. The illumination properties of the lighting device are however maintained, since the light output of the light emitting member is directed through the tube.

It is to be noted that, as understood by the person skilled in the art, the feature "solid state light emitting member" includes different kinds of solid state light emitters, such as for example LEDs, and OLEDs.

Furthermore, it should be noted that outside mounting of LED members has been proposed in US patent application No. 2006/0028837. However, in that case the elongate part that the LED unit was mounted on was a solid rod of transparent material, and not a tube, which is clearly different as understood by the person skilled in the art. Thus, obvious advantages with the present invention, such as using a slightly modified current manufacturing line for conventional fluorescent tubes, are not obtained in that prior art solution.

According to an embodiment of the lighting device, the tube wall has been bent inwards to form a recess, and wherein the solid state light emitting member has been received in the recess, wherein the outer surface of the solid state light emitting member is embraced by the circumference of the rest of the tube. The advantage of this embodiment is that the outer periphery of the lighting device can be kept fully circular.

According to an embodiment of the lighting device the light emitting member is attached to the tube by means of an adhesive. This is a simple yet reliable attachment, avoiding any mechanical working of the tube.

According to an embodiment of the lighting device, the light emitting member is covered with an electrically insulating encapsulation material. Thereby protection from external impact as well as electrical safety are obtained. According to an embodiment of the lighting device, the solid state light emitting member comprises multiple solid state light emitters arranged in a row.

According to an embodiment of the method of manufacturing a lighting device, wherein the elongate solid state light emitting member comprises a elongate lead frame, the lead frame is arranged on a mounting support, and said attaching an elongate solid state light emitting member to an outer surface of the tube comprises mounting the tube on the solid state light emitting member while carried by the mounting support. The outer surface mounting of the solid state light emitting member opens for using more flexible members than those mounted by inserting them into the tube. In this embodiment, due to usage of a support for assembling the member and mounting the tube on the member while the member is still supported, additional elements making the member more rigid.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail and with reference to the appended drawings in which:

Fig. 1 is a cross-sectional view of an embodiment of a lighting device

according to the present invention;

Fig. 2 is a side view of the lighting device shown in fig. 1;

Fig. 3 is a cut out view of another embodiment of the lighting device; and Figs. 4A-4D illustrate the manufacture of a lighting device according to this invention.

DESCRIPTION OF EMBODIMENTS

A first embodiment of the lighting device 100 according to this invention, as shown in Figs.1 and 2, comprises a tube 102, which is elongate and light transmissive. The tube 102 includes a glass tube 104 and a tubular light diffuser 106 arranged inside of, and concentrically with, the glass tube 104. The light diffuser 106 is a diffusing layer deposited on the inner surface of the glass tube 104. Alternatively, the diffuser can be an individual element arranged in the glass tube 104. An elongate solid state light emitting member 108 is attached to an outer surface 114 of the tube 102, and emits light through the tube 102. In this embodiment the solid state light emitting member 108 is a LED member, which has been attached to the tube 102 by means of an adhesive, which partly consisted of an encapsulation material, and partly consisted of glue, as will be explained in more detail below in conjunction with the description of an embodiment of the manufacturing method. The LED member 108 extends along the length of the tube 102. The LED member comprises a lead frame 110 and several LEDs 112 arranged in a row along the length of the tube 102. The LED member 108 is electrically connected with electrical contacts comprised in end caps 116, which are arranged at each respective end of the tube 102. In this embodiment the end caps 116 are conventional end caps used at fluorescent light tubes as well. Each end cap has electrical terminal pins 120, which are arranged to be fitted into corresponding reception means of a luminaire.

According to a second embodiment of the lighting device 200, having the same basic structure as the first embodiment, i.e. an elongate tube 202 including a glass tube 204 and a diffuser 206; and a LED member 208, comprising a lead frame 210 and a plurality of LEDs 212. However, according to this second embodiment, a portion 214 of the wall of the tube 202 has been bent inwards to form a recess 216. The recess 216 extends along the tube 202. The LED member 208 has been received in the recess 216, such that the outer surface 218 of the LED member 208 is embraced by the circumference of the rest of the tube 202.

Referring to Figs. 4A-4D, according to an embodiment of a method of manufacturing the lighting device, it is manufactured as follows. On a general level, an elongate and light transmissive tube including a light diffuser is provided with electrical contacts at its ends, and it is engaged with an elongate solid state light emitting member at the outer surface of the tube, such that the solid state light emitting member extends along the tube and emits light through the tube. More particularly, firstly, at SI, a LED member 400 comprising a lead frame 402 having LEDs 404 arranged thereon, is provided. Furthermore, the lead frame 402 is provided with bond pads 406 arranged in the vicinity of the LEDs 404, and alignment holes 408. Then, as shown at S2, the LED member 400 is arranged on a mounting support 410, such as a mounting table, and the LED member 400 is aligned by means of receiving fixed protrusions 412 of the mounting support 410 in the holes 408. Next, as shown at S3, the lead frame 402 is divided, e.g. by cutting it, into several individual lead frame parts 414, each carrying at least one LED 404 and/or at least one bond pad 406. Each cut 416 is made between a LED 404 and a bond pad 406. Thus, the LED 404 and the bond pad 406 become located close to an end of their respective lead frame part 414. In this embodiment the LEDs 404 are to be series connected. Therefore, as shown at S4, at each cut, the separated LED 404 and bond pad 406 are then wire bonded 418. As a last measure of preparing the LED member 400 before attaching it to the tube, at S5, dots of optical glue 420 are dispensed on the LEDs 404, and dots 422 of another, less expensive, adhesive, such as an encapsulation material, are dispensed at predetermined spaced locations on the lead frame 402. Then, at S6, the tube 424 is mounted on top of the LED member 400 and connecting therewith by means of the adhesive, i.e. the dots of optical glue 420 and the dots of encapsulation material 422. After curing the adhesive (S7) the assembly is removed from the mounting support 410 and rotated 180 degrees (S8), such that the LED member 400 is on top. Finally, at S9, the LED member 400 is covered with encapsulation material 426, and the encapsulation material 426 is cured (S10). The encapsulation material 426 is electrically insulating. The encapsulation material can be any appropriate material, as understood by the person skilled in the art, such as an epoxy or silicone.