JPH0463494B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing annular fluorescent lamps, and particularly aims to reduce the occurrence of cracks caused by bending of a straight glass bulb. Generally, this type of annular fluorescent lamp is manufactured by sealing a straight glass bulb A with a stem B provided with electrodes at both ends, and using a mold near the sealing part to create a node. It is manufactured by forming a glass bulb A in a heat-softened state and bending the glass bulb A into an annular shape by holding this joint C with a chuck D of a bending roller. By the way, the joint C of the glass bulb A and the tip of the chuck D are formed in the same shape with a curved surface with a radius of about 0.7 to 0.8 mm, and the joint C and the chuck D are in close contact with each other and are stable. A grasping state is obtained. For this reason, the bending operation can be performed reliably. However, when the glass bulb A begins to be bent by the upward rolling of the bending roller, the gripping position of the chuck D relative to the joint C shifts as shown by the dotted line in the figure. Lower Ca is check D
is strongly pressed. As a result, cracks are likely to occur at the joint C during bending work or after the product is completed.
Particularly in the case of glass bulbs A made of soda glass and stem B made of lead glass, there is a problem in that crack failures occur by as much as 3%. In view of these points, the present invention provides a method for manufacturing an annular fluorescent lamp that can significantly reduce cracking accidents at joints during bending of glass bulbs with a simple configuration. This will be explained with reference to FIGS. 2 and 3. First, as shown in FIG. 2, a stem 2 equipped with electrodes at both ends of a straight glass bulb 1 is sealed, and at the same time, on the outer periphery of the glass bulb 1 near the sealed portion,
The lower portion 3 forms a concave joint portion 4 which is flat over a width of 1 to 3.5 mm in the axial direction of the glass bulb 1. After heating and softening the glass bulb 1 in a heating furnace, the lower end of the glass bulb 1 is supported by the mount pin 5, and the positional relationship of the joint 4 with respect to the chuck supporting the upper end joint is determined. Become constant. Next, as shown in FIG. 3, the central portion of the flat bottom 3 of the joint 4 is gripped with a chuck 6 having a curved surface with a radius of 0.7 to 0.8 mm at the tip, for example. After the mount pin 5 is lowered to the dotted line position shown in the figure, a bending roller (not shown) is rolled upward to bend it into an annular shape. An annular fluorescent lamp is then manufactured by a conventional method. Since the flat bottom part 3 is formed in the joint part 4 of the glass bulb 1 in this way, when the glass bulb 1 is bent, the position of the chuck 6 with respect to the joint part 4 is at the third position.
Even if the transition is as shown by the dotted line in the figure, the joint 4
The lower side 4a of is not pressed strongly. Therefore, cracks occurring during bending work or after the product is completed can be significantly reduced. It is particularly effective when the length of the flat bottom part 3 is within the range of 1 to 3.5 mm, and a remarkable improvement effect can be obtained when soda glass is used as the glass bulb 1, but when it is less than 1 mm, cracking defects may occur. Moreover, if it exceeds 3.4 mm, the shape of the knot 4 becomes large and it becomes difficult to attach the base, which is not preferable. Next, specific examples will be described. The total length is
A straight glass bulb made of soda glass with a diameter of 546 mm, a wall thickness of 1.1 mm, and an outer diameter of 29 mm is sealed with a stem made of lead glass at both ends, and a low part of 0.5 to 4.0 mm is placed near the sealed part. FCL30 was manufactured by forming a concave joint that is flat in the axial direction of the glass bulb, and gripping it with a chuck with a curved surface with a radius of 0.7 to 0.8 mm at the tip and bending it into an annular shape, as shown in the table below. The crack occurrence situation as shown is obtained.

[Table] As is clear from the table above, when the length of the flat bottom of the joint is 1 mm or more, the incidence of cracks is extremely low, but when it is less than 1 mm, the incidence is high. This is thought to be because when the thickness is 1 mm or more, the pressure (tension) on the joint by the chuck is reduced. However, if the diameter exceeds 3.5 mm, the knot becomes large and it becomes difficult to attach the base. We also confirmed that the length of the flat bottom has little to do with the size of the annular fluorescent lamp. In addition, in the present invention, the glass bulb may be made of lead glass or low lead glass in addition to soda glass. As described above, according to the present invention, cracks caused by bending of the glass bulb can be avoided by forming the joint part in a concave shape with the lower part being flat with a predetermined width along the axial direction of the glass bulb. Defects can be effectively reduced.

[Brief explanation of the drawing]

Figure 1 is a side sectional view for explaining the conventional method;
FIG. 2 to FIG. 3 are explanatory diagrams of the method of the present invention, and
FIG. 2 is a side sectional view showing a state in which a knot is formed near the sealing portion of the glass bulb, and FIG. 3 is a side sectional view showing a state in which the knot is gripped by a chuck.

Claims (1)

[Claims] 1 The stem 2 is sealed at the end of the straight glass bulb 1, and a concave shape is formed near the sealing part so that the lower part 3 is flat over a width of 1 to 3.5 mm in the axial direction of the glass bulb 1. An annular fluorescent lamp characterized in that it includes a step of forming a knot 4, and a step of gripping the flat lower part 3 of the knot 4 and bending the heated softened glass bulb 1 into an annular shape. Production method.