JPH0412595Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] The present invention relates to a core wire used for coiling a square filament, and more particularly to a core wire (hereinafter referred to as a mandrel) that can prevent wire breakage during coiling of a tungsten wire. [Prior Art] Tungsten W filaments used in incandescent bulbs generally have a round shape or a square shape. Square filaments are used in halogen lamps such as OHPs and projectors. Conventionally, in coiling for manufacturing a square filament, a square mandrel (core wire) made of brass or molybdenum having a rectangular cross-sectional shape is used, and a W wire is coiled along the mandrel. The square mandrel prevents springback, maintains the coil shape, and adjusts the recrystallized structure of the W wire (improves non-sagging properties).
Heat treatment must be performed at a temperature range of 800 to 1600°C, and generally a mandrel made of molybdenum, which has a high melting point, is used. After the heat treatment, a rectangular W filament coil having a predetermined shape is obtained by melting the mandrel using acid or the like. [Problems to be solved by the invention] However, in the conventional square mandrel, the molybdenum plate is cut with a sliver or the like and formed into a square shape. The shape of the W filament is such that stress is concentrated at the locations of burrs, etc. generated by the parts and slits, and back tension is likely to be applied. When coiling is performed while bending the filament at right angles, the filament often breaks due to the phenomenon of notching, resulting in a poor yield. Furthermore, as shown in JIS H4460, it suggests a method of weakening the bending strength of coiling by increasing the wire diameter of the mandrel relative to the wire diameter of W, but due to the design of the filament, the mandrel At present, it is not possible to increase the diameter. Therefore, in view of the above-mentioned drawbacks, the purpose of the present invention is to improve the cross-sectional shape of the square mandrel, thereby alleviating the stress concentration that occurs at the right angles of the square mandrel during coiling of the W wire. To provide a mandrel without wire breakage during coiling. [Means for Solving the Problems] According to the present invention, the transverse contour consists of two parallel straight lines facing each other with an interval, and an outer side connecting one end of these straight lines and the other end thereof, respectively. A core wire used for coiling a rectangular filament is obtained, which is characterized by being composed of two curved lines extending out in a curved shape. [Example] An example of the present invention will be described. Core wire used for coiling the square filament according to the present invention (hereinafter referred to as deformed mandrel)
By tape rolling molybdenum wire,
It could be easily molded. Here, a test was conducted to compare the number of coiling breakages using the deformed mandrel according to the present invention and a conventional square mandrel. First, as shown in Fig. 1, a square mandrel 1 (A-1) of a conventional example is made by cutting a rolled molybdenum plate with a thickness of 1 mm into a rectangular shape using a sliver to form a square shape of 1t x 5w x l. By tape rolling the molybdenum wire drawn to φ, the dimensions are 1t x 5w x
Modified mandrel 2 (B
-1) Prepare. As shown in Fig. 2, a W wire 3 for filament with a wire diameter of 0.18φ is attached to the rectangular mandrels A-1 and B-1 and the deformed mandrels 1 and 2 at a tension of 10% of the tensile strength of the W wire 3. While playing the song,
Coiling was performed at a rotation speed of 500 rpm, tightly wound for 1 meter, and the number of wire breaks was counted. Next, a square mandrel 1 (A-2) of a conventional example cut and formed with a sliver to a size of 3□×l and a modified mandrel 2 (B-2) of an embodiment of the present invention that was tape rolled to the same size. A W wire 3 for filament with a wire diameter of 0.18φ was prepared and coiled under the same conditions as above, and the number of wire breaks at this time was counted. Similarly, a square mandrel 1 (A-3) of the conventional example cut and formed with a slitter to have dimensions of 1□×l and a modified mandrel 2 (B-3) of the embodiment of the present invention which was tape rolled to the same dimensions. A W wire 3 for filament with a wire diameter of 0.1φ was prepared and coiled under the same conditions as above, and the number of wire breaks at this time was counted. The coiling disconnection results are shown in Table 1.
The number of disconnections is the average value of the 10 tests above. As a result, as shown in FIG. 3, the tape-rolled deformed mandrel 2 according to the present invention can coil the W wire without bending it at right angles, and can relieve stress concentration during coiling, resulting in coiling breakage. are all gone.

[Table] It is clear that the same effect can be obtained even when the cross-sectional shape of the deformed mandrel according to the present invention is a plate drawn through a die or a die-forged plate. [Effects of the invention] According to the invention, by improving the cross-sectional shape of the square mandrel, stress concentration that occurs at the right angle part of the square mandrel during coiling of W wire is alleviated, and wire breakage during coiling can be prevented. A protected mandrel can be provided.

[Brief explanation of the drawing]

Fig. 1 is a comparative perspective view of a deformed mandrel according to the present invention and a conventional square mandrel, Fig. 2 is a front view of a mandrel coiled with W wire, and Fig. 3 is a comparison perspective view of the deformed mandrel according to the present invention and a conventional square mandrel. FIG. 3 is a sectional view showing a wrapped state. 1... Square mandrel, 2... Deformed mandrel, 3... Tungsten wire.

Claims (1)

[Claims for Utility Model Registration] 1. The transverse contour consists of 2 parts facing each other with an interval between them.
A core wire used for coiling a rectangular filament, characterized in that it consists of parallel straight lines of a book and two curved lines extending outwardly connecting one end and the other end of these straight lines, respectively. 2. A core wire used for coiling a square filament according to claim 1 of the utility model registration, characterized in that the material is molybdenum or an alloy thereof.