End cap for a tubular light source

An end cap (104) for a tubular light source (102), the tubular light source (102) configured to be arranged in a lighting fixture (106) comprising at least one socket (108), wherein the end cap (104) comprises, a first housing portion (202), two connector pins (208) at least partly arranged on an outside of the first housing portion (202) and adapted to fit in the socket (108), and a switch assembly comprising a switch element, wherein the switch assembly being adapted to form a conductive path between the socket (108) and the tubular light source (102) through a depression of the switch element in combination with a relative rotational motion of the first housing portion (202) in relation to the tubular light source (102) as the tubular light source (102) is mounted in the fixture (106).

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is the U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/IB2012/051274, filed on Mar. 16, 2012, which claims the benefit of and priority to European Patent Application No. 11160372.6, filed on Mar. 30, 2011. These applications are hereby incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to an end cap for a tubular light source, and in particular to an end cap enabling safe installation of such a tubular light source.

BACKGROUND OF THE INVENTION

Fluorescent lighting tubes are commonly used in a large range of lighting systems as a result of advantages such as longer life time and better luminous efficiency compared to incandescent lamps. However, in the continuous effort to reduce power consumption, it is desirable to replace conventional light tubes with still more energy efficient and environmental friendly alternatives. One such alternative is to use LED tubular light sources having a plurality of LED's arranged in a tube similar to the fluorescent tube. In order to facilitate a transition from fluorescent tube lights to LED tubular light sources, the LED tubular light sources should be configured to be mounted in already existing fixtures for fluorescent light tubes. However, the electrical circuitry is different in an LED tubular light source compared to in a fluorescent light tube in that the LED tube may provide a current path between the two end caps. As a result, installation of retrofitted LED tubular light sources may be a safety hazard as it is possible to first install one end cap in the mains connected fixture while having the other end cap still exposed and carrying a live potential on the connection pins of the exposed cap. Thus, the installer may touch the exposed end cap and get an electrical shock.

US2010/018178 discloses a suggestion on how the aforementioned safety issue may be alleviated by introducing a safety switch in the end cap of the LED tubular light source. However, a push-in safety switch according to US2010/018178 may in some cases be unintentionally engaged when the installer is pushing a first end of the tubular light source as a second end is inserted into the fixture, thereby exposing the installer to potential hazard as the unconnected end cap may then have a live potential. Furthermore, the installer may gain a false sense of security as the presence of a safety switch may make the installer believe that installation is safe in all circumstances.

Therefore, there is a need for an improved safety mechanism to improve the safety for the installer when installing retrofitted LED tubular light sources.

SUMMARY OF THE INVENTION

In view of the aforementioned and other drawbacks of prior art, it is an object of the present invention to improve the safety when installing a tubular light source, in particular it is an object to provide an end cap for a tubular light source comprising LEDs, the end cap further comprising a safety switch to facilitate safe installation of the tubular light source in a fixture.

According to an aspect of the present invention, it is therefore provided an end cap for a tubular light source, the tubular light source configured to be arranged in a lighting fixture comprising at least one socket, wherein the end cap comprises a first housing portion, two connector pins at least partly arranged on an outside of the housing and adapted to fit in the socket, and a switch assembly comprising a switch element, wherein the switch assembly being adapted to form a conductive path between the socket and the tubular light source through a depression of the switch element in combination with a relative rotational motion of the first housing portion in relation to the tubular light source as the tubular light source is mounted in the fixture.

The present invention is based on the realization that a safety switch for a tubular light source may advantageously be integrated into the end cap of the tube and that the safety switch preferably is automatically closing an electrical circuit by forming a conductive path between the socket and the tubular light source during installation of such a light source. In particular, in some tubular light sources, the internal circuitry is arranged so that the light source may provide a conductive path from the connector pins in one end portion of an elongate tube to connector pins in the opposite end portion even if the light source is not active contrary to what was possible in conventional fluorescent light tubes. In other words, it is possible that mounting one end portion of the tubular light source in the socket of the lighting fixture leads to the connector pins in the opposite end portion carrying a live voltage. In particular, having a push-in mechanism arranged on the end cap may cause the installer to unintentionally push the safety mechanism, thereby engaging the electrical circuit, during installation of the tubular light source. By having a switch which automatically closes an electrical circuit only when the connector pins are out of reach for the installer, the risk for the installer of receiving an electrical shock when installing a tubular light source is significantly reduced. A further advantage of the present invention is that a double safety feature is provided which is integrated in an end cap for a tubular light source. The double safety feature is provided through a switch assembly where the electrical circuit is closed only through a combination of a push-movement of the switch element and a rotational movement of either the end cap or the tubular light source. One way to mount a tube light in a fixture is to first push the pins into the socket, thereby simultaneously engaging the push part of the safety switch. Thereafter the tubular light source may be rotated, either as a part of the mounting procedure as is the case for some fixtures or as a separate second step operative to close the electrical circuit from one end portion of the tubular light source to the other. In the first case, the circuit is closed as a part of the mounting procedure and in the second case an additional rotational motion is required, either way provides a double safety feature requiring two steps to close the electrical circuit. An additional advantage is that the end cap according to the present invention is compatible with and thereby provides safety for a plurality of different sockets. As an example, the end cap may be used in fixtures equipped with either of G5 and G13 type lamp sockets.

According to one embodiment, the end cap may advantageously comprise a second housing portion rotationally movable in relation to the first housing portion, wherein the conductive path is formed through a rotation of the second housing portion in relation to the first housing portion when the switch element is depressed.

Additionally, the second housing portion may be at least partially arranged inside the first housing portion.

Furthermore, the end cap may comprise conductive receiving means arranged in the second housing portion and configured to receive the connector pins through a rotation of the second housing portion in relation to the first housing portion, and wherein the electrically conductive receiving means are configured to be axially aligned with the connector pins only when the switch element is depressed. Consequently, the connector pins may preferably extend into the second housing portion where the connection between the pins and the receiving means is made. The electrically conductive receiving means may advantageously be arranged on a plate which in turn is mechanically connected to the axially movable switch element. The axial alignment of the electrically conductive receiving means and the connector pins thereby enables the connection between the socket and the light source as the end cap is mounted. Thus, if the rotational movement is performed without the switch element being depressed, there would be no electrical contact between the connector pins and the light source as the electrically conductive receiving means would be positioned in another axial plane. Additionally, spring means may advantageously be connected to the plate or the switch element in order to return the switch element to an un-pressed position when no external pressure is applied. The spring means may be a coil spring connected to the plate, but it may equally well be any other elastic element arranged to return the switch element to an un-pressed position.

In one embodiment, the switch element at least partly arranged on the outside of the housing may advantageously be a peg protruding in between the two connector pins. Having a peg or any similar structure protruding between the connector pins provides a simple way to depress the peg as the end cap is installed into a fixture, thereby performing the first step in the two-step process of creating a conducting path. The peg is preferably designed and configured so as to ensure that it is depressed when mounted in the intended fixture. The switch element should furthermore be activated at a relatively high force in order to reach a higher safety level as it may be possible for the installer to apply some force on the switch element during installation, thereby accidentally depressing the switch element.

In one embodiment, the second housing portion may advantageously be connected to the first housing portion by spring means acting in a rotational direction, the spring means being configured to return the relative rotational position of the first and second housing portions to an idle position. The spring means are operative to return the relative rotational position of the inner and the first housing portion in the case where the switch element is not depressed. However, the force of the electrically conductive receiving means in the rotational direction is preferably larger than the aforementioned spring force between the inner and first housing portion in order to maintain a conductive path between connector pins and the electrically conductive receiving means after a rotation has been performed while the switch element was depressed. The spring means may be coil springs, leaf springs, elastic elements or any similar structure.

Furthermore, the tubular light source is preferably mechanically fixed with the second housing portion. An advantage of fixing the tubular light source to the second housing portion is that installation is simplified as it is possible to rotate the entire tubular light source when mounting the tubular light source in a fixture.

In one embodiment of the invention, the electrically conductive receiving means may advantageously be spring clips. Furthermore, the spring clips may be adapted to the diameter of the end portions of the connector pins so that the connector pins are fixed in a rotational direction if a rotational motion has been performed and if the rotational force is sufficiently large to engage the connector pins in the spring clip. On the other hand, the spring clips should not fix the connector pins in an axial direction in the case where the switch element is depressed but released again. Thus, the axial alignment of the receiving means and the connector pins should not be maintained by a force from the spring clips acting in an axial direction. Consequently, the force of the spring means acting on the plate and switch element in an axial direction should be larger than the frictional force of the spring clips acting in the axial direction. The electrically conductive receiving means may equally well be any structure or arrangement filling the function of the spring clips described above. Furthermore, the spring clips may be equipped with caps or similar devices preferably made from an insulating material such that no electrical connection is formed in the case when the first and second housing portions are rotated in relation to each other while the switch element is not depressed.

In one embodiment, the connector pins may advantageously be cylindrical having an end portion with a larger diameter configured to connect to the electrically conductive receiving means.

According to one embodiment, at least one end cap as discussed above may advantageously be arranged on at least one end of a tubular illuminator part comprising a plurality of light emitting elements in order to form a tubular light source. Furthermore, such a tubular light source may advantageously be provided with an appropriate fixture comprising at least one socket for receiving the at least one end cap and for connecting the tubular light source to an electrical power supply, thereby forming a luminaire. Additionally, the tubular light source may advantageously comprise optics configured to mix light. Such optics may be any mixing and/or collimating means. Light mixing optics may advantageously be used if the light emitting elements comprise LEDs. However, the light emitting elements may be any light source such as a fluorescent or incandescent light source.

According to another aspect, it is provided an end cap for a tubular light source, the tubular light source configured to be arranged in a lighting fixture comprising at least one socket, wherein the end cap comprises a first housing portion, two connector pins at least partly arranged on an outside of the housing and adapted to fit in the socket, and a second housing portion rotationally movable in relation to the first housing portion, wherein a conductive path between the socket and the tubular light source is formed through a rotation of the second housing portion in relation to the first housing portion.

Effects and features of this aspect of the invention are largely analogous to those described above in connection with the first aspect of the invention. However, an additional advantage of this aspect is that an end cap providing safe installation of a tubular light source can be achieved in a simple way at a low cost. In some applications, an end cap providing single safety may be sufficient.

DETAILED DESCRIPTION

In the following, various embodiments of an end cap according to the present invention are mainly discussed with reference to an end cap for a tubular light source providing safety through a two-step mechanism including both an axial and a rotational motion. It should be noted that this by no means limits the scope of the present invention which is equally applicable to safety mechanisms for end caps where safety is provided by means of a first housing portion and a second housing portion being rotational in relation to each other.

FIG. 1schematically illustrates a luminaire100wherein a tubular light source102comprising an end cap104according to the present invention is being mounted into a mains connected fixture106. As illustrated inFIG. 1a, one end cap104is first inserted into a socket108arranged in the fixture106, thereby depressing a switch110arranged on the outside of the end cap104. Next, as depicted inFIG. 1b, the opposing end cap104of the light source102is inserted into the opposing socket104. After that, the mounting is completed by rotating the tubular light source102as illustrated inFIG. 1c. The rotation may, depending on the configuration of the socket104, be either a rotation of the tubular light source100in relation to the end cap104and/or it may be a rotation of the end cap104in relation to the socket108. Both the push and rotate motions are required to activate the safety mechanism which is operative to engage the electrical circuit of the luminaire100. It should also be noted that while the tubular light source102is currently illustrated with end caps104in both ends, the two-step safety feature will also be provided in the case where the tubular light source102is equipped with only one end cap104according to the present invention.

FIGS. 2aand 2bare exploded views in two different perspectives schematically illustrating en exemplary end cap104according to the present invention.

A currently preferred embodiment will now be described with reference toFIG. 2in conjunction withFIG. 3showing a sectional view of the end cap. The end cap comprises a first housing portion202and a second housing portion204which is axially rotatable in relation to the first housing portion202. The second housing portion204is mechanically connected to the tubular light source102. The first202and second204housing portions are further connected through coil springs206acting in an axially rotational direction so as to return the relative rotational position of the first202and second204housing portions to an idle position when no external rotational force is applied. Two electrically conductive connector pins208adapted to fit into the socket108are arranged so that a portion of the connector pins208are protruding from the outside of the first housing portion202through openings205in the first housing portion202and another portion is arranged inside the second housing portion204. In the second housing portion204, the openings207for the connector pins202are elongate to allow for a certain degree of rotation of the second housing portion204in relation to the connector pins208and the first housing portion202. Next, a peg210is arranged so as to be located in between the connector pins208on the outside of the first housing portion202, the peg210further extending into the second housing portion204where the peg201is mechanically connected to a plate212.

There are also holding pins213arranged in the second housing portion204with corresponding openings215in the plate212for receiving the holding pins213in order to fix the plate212to the second housing portion204in an axially rotational direction while allowing axial movement of the second housing portion204in relation to the plate212. The plate212further comprises elongate openings217configured to allow the plate212to be axially rotatable in relation to the connector pins208. Furthermore, spring clips214are arranged on the side of the plate212facing the tubular light source102. The end portions216of the connector pins208facing the tubular light source102have a larger diameter and are configured to engage the spring clips214upon rotation of the plate212in relation to the connector pins208. The spring clips214are configured to be axially aligned with the end portions216of the connector pins208when the peg210is depressed and where the plate212is consequently moved in an axial direction. The larger diameter of the end portions216of the connector pins208is required so as to avoid that the connector pins208are engaging the spring clips214in the case where a relative rotation is performed while the peg210is not depressed.

A coil spring218is also arranged between the plate and a holding element220. The coil spring218is configured to return the peg210and plate212to an idle position when no external force is applied. The force required to compress the coil spring218when depressing the peg210should be sufficiently high so that the peg may not easily be accidentally depressed by the installer during installation.

FIGS. 3ato 3cillustrate the end cap switch assembly more clearly in relation to the different mounting steps illustrated inFIG. 1.FIG. 3acorresponds toFIG. 1awhere the end cap120is in an idle position. InFIG. 3b, corresponding toFIG. 1b, the peg210is depressed and through the movement of the peg210and plate212in the axial direction the spring clips214on the plate212becomes axially aligned with the end portions216of the connector pins208. In the next step, as shown inFIG. 3ccorresponding toFIG. 1c, a rotation of the tubular light source102and thereby a rotation of the second housing portion204in relation to the first housing portion202and the socket108is performed. Through the rotation, the end portions216of the connector pins208engage the spring clips214thereby closing forming a conductive path between the mains connected socket108and the tubular light source102. The spring clips214may be connected to any intermediate control circuitry required to operate the tubular light source102.

FIGS. 4aand 4bschematically illustrate an alternative embodiment of an end cap402according to the present invention. The end cap comprises a first404and a second406housing portion and the first housing portion404is arranged partly overlapping the second housing portion406. The first404and second406housings may further be connected by spring means (not shown) both in the axial and in the rotational direction. One or more protrusions408at the inside of the first housing are configured to be arranged in a groove410extending along the circumference of the second housing portion406so as to connect the two housings while allowing relative rotational movement. The groove410is further configured to have an additional groove portion412extending in the axial direction and the protrusions408at the inside of the first housing portion404are configured to lock into the axially extending groove portion412by the force applied by axially oriented spring means so as to hinder rotational movement of the first housing portion404in relation to the second housing406in an “idle mode”. When the first housing portion404is pressed towards the second housing portion406, for example when the tubular light source is mounted in a fixture, the protrusions408are released from the vertical groove portions412, thereby allowing rotational movement. By rotating the first housing portion404in relation to the second housing portion406, the connector pins414make contact with conductive receiving means416which in turn are connected to the tubular light source, thereby forming a conductive path between the connector pins414and the tubular light source.

The rotational force required to engage and release the mechanical connection of the end portions216of the connector pins208to the spring clips214should be smaller than the force required to dismount the tubular light source102from the socket104, otherwise the connector pins208may still be connected to the spring clips214as the end cap104is dismounted from the socket108. Additionally, the rotational force of the coil springs206should not be so high so as to release the end portions216of the connector pins208from the spring clips214. Furthermore, the axial force of the coil spring218acting on the plate212should be larger than the force of the spring clip214acting on the end portions216of the connector pins208in the axial direction. Thereby the end portions216of the connector pins208are released from the spring clip214, thus returning the peg210to its idle axial position, when no external force is applied.

Even though the invention has been described with reference to specific exemplifying embodiments thereof, many different alterations, modifications and the like will become apparent for those skilled in the art. Also, it should be noted that parts of the disclosed end cap may be omitted, interchanged or arranged in various ways, the end cap yet being able to perform the functionality of the present invention.