JPH0729799B2 - How to join glass tubes - Google Patents

Description

The present invention relates to a method for joining glass tubes, and is suitable for manufacturing glass tubes for compact fluorescent lamps that are bent in a U shape.

[Prior Art] In recent years, a low-pressure discharge tube covered with a ball-shaped globe called a compact fluorescent lamp has been recommended. As a glass tube for this purpose, there is one in which one long glass tube is bent into a double U-shape, and one in which two U-tubes are joined and integrated. The former has a drawback that since the whole is finished in a compact size, the bending is complicated and it is easily damaged during processing. The latter is proposed as an improvement on the above-mentioned drawbacks, in which the side portions of the U-shaped glass tubes are arranged side by side with a burner applied from the inside of the glass tube to the planned communication hole of the glass tube, and the communication hole is formed by the wind pressure of the frame. At the same time, the meat is extruded to the outer peripheral edge of the communication hole to join them together.

[Problems to be Solved by the Invention] According to such a conventional method, since the communication hole for joining two U-shaped tubes is formed by piercing the side portion by the wind pressure of the burner, a sharp frame is formed. It is not possible to obtain a large opening diameter by the method of melting by applying one point. For example, when the inner diameter of the glass tube has a size of 15 mmφ, the inner diameter of the communication hole requires a dimension of about 10 mmφ, and a large amount of heat power is required to pierce this with the frame of the burner. However, if the burner frame has a size corresponding to an opening of 10 mmφ, the glass near the opening position will soften and deform, and it will be difficult to obtain an opening shape with a perfect circle. Further, there is a problem that the inner surface of the glass tube is contaminated with the frame.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a novel joining method that solves the above-mentioned problems and obtains an opening shape having a desired size on a side portion of a glass tube.

[Means for Solving the Problems] The present inventor has variously studied methods alternative to the direct processing by the frame of the burner, and opened the side portion of the glass tube by using a molding member to bulge it into a desired shape. Then, a method of welding two glass tubes to each other to obtain a communication hole is conceived.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. Generally, the discharge tube has a longer shape because the luminous efficiency thereof is improved as the length of the discharge path is increased.
On the other hand, it is necessary to make the shape compact. The compact fluorescent lamp glass tube shown in FIG. 1 satisfies the above conditions by joining two U-shaped glass tubes 1 and 2 by a projecting annular portion 3 so as to communicate with each other.

As is apparent from FIG. 2, the molding member 10 to be inserted into the glass tube 1 (or 2) is provided so as to protrude from one of the two parallel insertion rods 11 and 12, and the outer diameter of the molding member 10 is The protrusion height, which is equal to the opening size, is set to be approximately half the distance between two U-shaped tubes adjacent to each other. The insertion rods 11 and 12 are integrally fixed to the mold 13 and are made of a carbon material that withstands high temperatures and does not adhere to glass. The thickness of the insertion rods 11 and 12 is set to be slightly smaller than the inner diameter of the glass tube minus the protruding height of the molding member 10.

As shown in FIG. 3, the bent side of the glass tube 1 is chucked with a gripping tool 20 and fixed to a work table (not shown), and the insertion rods 11 and 12 are fully inserted until the mold 13 abuts on the tube end. And then set. The molding member 10 presses the predetermined position of the opening from the inside of the side portion by the weight of the insertion rods 11 and 12 and the mold 13 in the glass tube 1. In this state, the burner 30 is arranged downward, and when the position of the side of the forming member 10 to be pressed is heated from the outside, the side part which is softened eventually swells as shown in FIG. Form part 3.

Next, FIG. 5 shows an example of a method for forming an opening on the top surface of the protruding protruding annular portion 3. A tungsten rod 31 with a diameter of several mm is prepared, and the tip of this rod 31 is burned.
At 32, heat to red heat and insert a small hole into the top surface.
Then, the glass tube 1 is brought to a position orthogonal to the frame of the burner 32, and the top surface is heated, so that the melting spreads from the small holes and an opening equal to the inner diameter of the protruding annular portion 3 is obtained.

In the same procedure, an opening is formed in the glass tube 2 at a position symmetrical to the glass tube 1, and thereafter, the glass tubes 1 and 2 are joined by butting the protruding annular portions 3 to each other and welding them together. . FIG. 6 shows the joining process, and a burner 33 having a large number of gas holes radially provided in the tip end portion in the axial direction of the glass tube is used. As shown in (a) of the figure, the burner 33 is inserted into the tube end of the glass tube with the openings of the glass tubes 1 and 2 being slightly separated from each other, and the frame of the burner 33 has a protruding annular portion. To heat. When both openings began to soften and melt over the entire circumference,
Both are brought close to each other and welding is completed as shown in FIG.

[Effect] As described above, according to the method of the present invention, since the shape of the opening is obtained by inserting the molding member into the glass tube and using the molding member, the shape of the opening is accurate and the shape of the perfect circle is easily formed. can get. The protruding annular portion formed by the molding member is U
Since the member of the connecting pipe that joins the U-shaped pipe and the U-shaped pipe is configured, a separate connecting pipe is not required, which contributes to cost reduction.

[Brief description of drawings]

The drawings are examples for explaining the method of the present invention.
The figure shows a glass tube for a compact fluorescent lamp, (a) is a front view, (b) is a side view, and (c) is a plan view. FIG. 2 is a perspective view of the molding member, FIG. 3 is a cross-sectional view of the glass tube in the process of heating the position of the pressing side portion of the molding member from the outside, and FIG. 4 projects to the side portion by the pressing force of the molding member. FIG. 5 is a sectional view of the glass tube in the step of forming the annular portion, FIG. 5 is a perspective view of the glass tube showing a step of forming an opening in the top surface of the protruding annular portion, and FIG. 6 is welding two U-shaped tubes. It is sectional drawing of the glass tube which shows the process to do. Reference numerals 1 and 2 are U-shaped glass tubes, 3 is a protruding annular portion, 10 is a molded member, and 30, 32 and 33 are burners.

Claims (1)

[Claims] 1. In a method of joining side portions of glass tubes arranged in parallel to each other through a communication hole, a molding member is inserted from the inside of the glass tube into the communication hole opening portion of the glass tube side portion, and then the planned opening portion is formed. The glass tube is heated and softened from the outside and pressed by a molding member to bulge, and then the bulging top surface is opened to form a protruding annular portion, and then two of the glass tubes are juxtaposed to each other to form a protruding annular shape. A method for joining glass tubes, characterized in that parts are butted and welded.