(1) Field of the Invention
The present invention relates to fluorescent lamps having meandering discharge paths and manufacturing methods of the same, particularly to a technique for improving handleability of fluorescent lamps especially during the installation process.
(2) Description of the Related Art
In recent years, single-based fluorescent lamps, or so-called compact fluorescent lamps, have been popularly used for their advantages in long lives and low electricity consumption.
In a compact fluorescent lamp, in order to keep it compact, a plurality of constituent tubes that each have a U-shaped discharge path are connected together, so as to form a tube with one meandering discharge path. More specifically, in order to form one meandering discharge path, the discharge paths of the constituent tubes are connected by one or more bridges, in such a way that an area in the vicinity of an end of a constituent tube is connected to an area in the vicinity of an end of another constituent tube, wherein each of these ends connected is one of the ends that are positioned opposite to the turning portion of each constituent tube. Also, in a compact fluorescent lamp, the constituent tubes connected in such a manner are disposed on a case so that the bridged portions are positioned close to the lamp base, and the turning portions are away from the lamp base. (For example, see the Japanese Unexamined Patent Application Publication No. 62-278749.) In the disclosure, on the turning portion side of the lamp, it is arranged so that the constituent tubes are disposed with a gap interposed therebetween.
When this kind of compact fluorescent lamp is to be inserted into a socket, people normally hold the vicinity of the turning portions of the constituent tubes (the side opposite to the case) by the hand. At this time, a compressive force is applied to the constituent tubes on the turning portion side of the lamp, and the distance between the constituent tubes becomes smaller at the areas with no bridge. Also, since a force is applied to the bridge provided on the base side, the bridge may be distorted, and there may be cracks between the bridge and the constituent tubes at their boundaries. In some cases, the constituent tubes themselves may be damaged or, for example, cracked.
In order to keep the lamps from being damaged during an installation process, the Japanese Unexamined Patent Application Publication No. 62-90844 discloses a technique for keeping the constituent tubes apart even when a compressive force is applied, by having an arrangement wherein (i) spacers are inserted between the constituent tubes at the tube extremities just for the purpose of installation, (ii) the fluorescent lamp is inserted into a socket while the spacers are still attached, and (iii) the spacers are taken out after the lamp is installed and before the lamp is driven for light emission.
The Japanese Unexamined Utility Model Application Publication No. 63-128662 discloses a technique for disposing tubes so that they lean toward each other when two or more V-shaped constituent tubes are attached to an installation base.
With the arrangement disclosed in the Japanese Unexamined Patent Application Publication No. 62-90844, although it is possible to keep the fluorescent lamp from being damaged during the process of inserting the lamp into a socket, it is necessary to provide the spacers, which are the parts that do not contribute to the original function of the fluorescent lamp i.e. to emit light. As a result, there are problems that the quantity of light is reduced, or the costs of the lamps become high.
With the arrangement disclosed in the Japanese Unexamined Patent Application Publication No. 63-128662, since the bridge is stored below the surface level of the case, the lamp is free from the problem of having the bridge damaged; however, since the V-shaped constituent tubes are used, it is required that the surface area of the holder to which the constituent tubes are attached should be large, and the fluorescent lamp is less advantageous in terms of its compactness. It is inevitable that the vessel in which the fluorescent lamp is to be disposed also has large capacity, and it is disadvantageous in terms of the cost. In addition, since the only arrangement made is that the constituent tubes are disposed so that they lean toward each other, it is not possible to completely keep the bridge and the constituent tubes from being damaged.
Further, with the arrangement disclosed in the Japanese Unexamined Patent Application Publication No. 63-128662, since the bridge is stored inside the case, parts of the tubes in the vicinity of the bridge are also stored in the case. As a result, the quantity of light is reduced as much.