JPH0326638Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of application of the invention) This invention is an electric resistance heating element that houses an electric resistance heating element in a stainless steel tube and radiates the heat of the electric resistance heating element into the furnace through the stainless steel tube. used for.

(Prior art and its problems) When an electric resistance heating element used in a furnace that heats objects in various atmospheres is placed in direct contact with the furnace atmosphere, the heating element is affected by the furnace atmosphere. The material changes and its properties deteriorate. For this reason, electric radiant tube heaters are often used in which an electric resistance heating element and a fire-resistant guide plate that supports it are housed in a stainless steel tube. The electric resistance heating elements used in this type of heater are multiple rod-shaped rods with the tips bent into a U-shape, and these are held by a fire-resistant guide plate, but if used for a long time at high temperatures, the stainless steel Thermal expansion and deformation occur in the tube and rod-shaped electric resistance heating elements, and this expansion and deformation forms the free end U.
It may appear at the U-shaped portion and bend the tip U-shaped portion toward the inner circumferential wall surface of the stainless steel tube. This deformation creates contact between the electrical resistance heating element and the stainless steel tube, creating an electrical spark. This electrical spark may disconnect the electrical resistance heating element or melt the stainless steel tube, creating a hole in the tube and rendering the heater unusable.

An example of holding a heater in a stainless steel tube is disclosed in Japanese Utility Model Application No. 59-103394, provided by the present applicant. In this example, the heater is held by a rectangular guide plate and a cylindrical tube part connected together. Even in this configuration, there is a high risk that the U-shaped portion at the tip of the heater will come into contact with the stainless steel tube.

One proposal to eliminate this danger is
-23813 publication, Japanese Patent Application Laid-open No. 52-53541, and Jichikoaki
As shown in Japanese Patent Application No. 35-2553, contact between the heater and the tube is prevented by filling a stainless tube with non-conductive powder around the heater to restrict thermal deformation of the heater.

Another example, as disclosed in Japanese Patent Application Laid-Open No. 51-51028, is to bake a glass tube onto the inner wall surface of the tube to prevent direct contact between the heater and the tube.

The former means for avoiding direct contact between the heater and the tube fills the inside of the heater with powder, resulting in extremely poor heat dissipation effect and causing problems such as thermal damage to the heater. Further, in the latter case, the work of baking the glass on the tube is expensive and cannot be said to be an easy work.

(Technical problem of the present invention and its means) The technical problem of the present invention is to eliminate the problems of the conventional example mentioned above, and the means used to solve the problem are electric resistance A cylindrical body is placed inside the stainless steel tube at the part where the U-shaped portion at the tip of the heating element is located, and this cylindrical body is non-conductive and fire-resistant, so
This will protect the stainless steel tube from deformation of the U-shaped portion at the tip of the electric resistance heating element.

(Example) The electric radiant tube heater 1 has a rod-shaped tube inside the austenitic stainless steel tube 2.
It has a structure in which a plurality of Fe-Cr-Al (ferrite) electrical resistance heating elements 3 are arranged. Electric resistance heating element 3
has a U-shaped bent shape at its tip 4, and is electrically contacted with the adjacent electric resistance heating element 3 at an end (not shown).

Electric resistance heating element 3 inside stainless steel tube 2
is held apart from the inner circumferential wall surface of the stainless steel tube 2 by a fireproof and non-conductive guide plate 5. The guide plate 5 is formed into a square shape,
The chamfered portion 6 of the corner portion contacts the inner circumferential wall surface of the stainless steel tube 2. The guide plate 5 has a hole 7 through which the electric resistance heating element 3 passes, and further has a hollow cylindrical portion 8 projecting to one side. As shown in FIG. 2, by inserting the cylindrical portion 8 of another guide plate 5 into the hollow of one cylindrical portion 8, the guide plates 8 are successively connected.

A fireproof and non-conductive cylindrical body 9 is disposed on a guide plate 5 that holds the U-shaped tip portion 4 of the electric resistance heating element 3. The cylindrical body 9 extends along the inner circumferential wall of the stainless steel tube 2 toward its distal end, and covers the distal end portion 4 of the electrical resistance heating element 3.

As shown in FIGS. 3 and 4, the cylindrical body 9 is
The end portion thereof has a notch 10 for receiving the corner portion of the rectangular guide plate 5. A guide plate 5 is seated on an end surface 11 of the notch 10, and a chamfered portion 6 of the guide plate 5 runs along the outer peripheral wall surface of the cylindrical body 9.

As shown in FIG. 2, a cover 1 is attached to the tip of the cylindrical body 9.
You may add 2. The cover 12 is made of non-conductive refractory material and has a grooved protrusion 13 in its center. By inserting the cylindrical part 8 of the guide plate 5 into the groove of the protrusion 13, the cylindrical body 9 and the guide plate Connect to 5. In this case, the cover 12 comes into contact with the tip of the stainless steel tube 2 and positions the guide plate 5 within the stainless steel tube 2. The guide plate 5 may be positioned within the stainless steel tube 2 by bringing the cylindrical body 9 and the tip of the cylindrical portion 8 of the guide plate 5 into direct contact with the tip of the stainless steel tube 2 without using the cover 12. .

In the example shown in FIG. 2, the cylindrical portion 8 of the guide plate 5 is
Although the stainless steel tube 2 is connected toward the distal end thereof, when the cylindrical portion 8 is disposed in the direction opposite to that shown in FIG. 2, the cylindrical body 9 is connected to the guide plate 5 as shown in FIG. It may be molded in one piece.

When a guide plate 5 as shown in FIG. 2 is used, the tip of the cylindrical body 9 may be brought into contact with a cover 12 without a protrusion, or may be brought into direct contact with the end of a stainless steel tube. . If necessary, the cylindrical body 9, guide plate 5, and cylindrical portion 8 shown in FIG. 2 may be integrally molded, and the cylindrical body 9 does not necessarily have to be made separately from the guide plate 5. Further, the cross-sectional shape of the cylindrical portion 8 does not matter.

(Effect) When a heater is used in a furnace at high temperatures for a long period of time, thermal expansion and deformation occurs in the electric resistance heating element and the stainless steel tube.This expansion and deformation causes the U-shaped tip of the electric resistance heating element to break down into the stainless steel tube. Accidents of contact with the tube may occur, but in this invention, the U-shaped tip of the electric resistance heating element is protected by a cylindrical body provided around it, so even if it is deformed, it will not come into contact with the stainless steel tube. Never.

In the present invention, since the cylindrical body is simply placed on the U-shaped portion at the tip of the electric resistance heating element, manufacturing is easy. High-temperature air around the U-shaped portion flows backwards, providing a uniform heat dissipation effect from the stainless steel tube, and preventing local thermal damage to the heating element.

[Brief explanation of drawings]

Fig. 1 is a partial perspective view showing an embodiment of the present invention, Fig. 2 is a side view showing the combination of the guide plate and the cylindrical body, Fig. 3 is a side view of the cylindrical body, and Fig. 4 is a side view of the cylindrical body. A front view and FIG. 5 are front views showing an example of a guide plate with a cylindrical body. In the figure, 2... Stainless steel tube, 3... Electric resistance heating element, 4... U-shaped tip, 5... Guide plate, 9... Cylindrical body.

Claims (1)

[Scope of utility model registration request] A structure in which a plurality of non-conductive and fire-resistant rectangular guide plates arranged in a stainless steel tube and a cylindrical part protruding from the center of the guide plates are connected;
In an electric radiant tube heater in which the corner portion of the guide plate is in contact with the inner wall surface of the stainless steel tube and holds an electric resistance heating element, the guide plate in the portion where the tip U-shaped portion of the electric resistance heating element is located is: An electric radiant tube heater characterized by having a non-conductive, fire-resistant cylindrical body surrounding a cylindrical portion and extending along an inner circumferential wall surface of the stainless steel tube.