JPH042391Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Field of Application) The present invention relates to a resin tube heating furnace used for continuous thermoforming of resin tubes.

(Prior art) When attempting to heat and expand a thin-walled resin tube with a wall thickness of, for example, 10 to 300μ and an outer diameter of approximately 270 to 320 mm to an outer diameter of 900 to 1020 mm, conventionally a vertical tube with open upper and lower surfaces is used. A type cylindrical heating furnace is used. However, in such a heating furnace, convection occurs in the furnace, making the upper part of the furnace hotter than the lower part, making it difficult to uniformly heat the resin tube. This had the disadvantage of large dissipation and large energy loss.

(Problems to be solved by the invention) The present invention was completed with the aim of solving the above-mentioned conventional problems and creating a resin tube heating furnace that can heat the resin tube uniformly and thermally efficiently. It is.

(Means for Solving the Problems) The resin tube heating furnace of the present invention has a vertical cylindrical furnace body with open upper and lower surfaces, and a large number of infrared heaters arranged on the inner surface of the furnace body. This device is characterized by having a plurality of infrared heating devices stacked vertically in multiple stages, the infrared heating devices each having an air injection port that injects air obliquely downward at the inner peripheral edge.

(Embodiments) Next, the present invention will be described in detail with reference to illustrated embodiments.

FIG. 1 is an enlarged view of the infrared heating device that constitutes the resin tube heating furnace of the present invention.
In the figure, reference numeral 1 denotes a vertical cylindrical furnace body with open upper and lower surfaces, and the inner surface of the furnace body is lined with a stainless steel plate 2 having a high infrared reflectance. Furnace body 1
As shown in FIG. 1, it is preferable to have a structure in which it is divided into upper and lower halves, and a portion thereof can be opened and closed by a hinge 3 so that maintenance can be easily performed. A large number of infrared heaters 4 are arranged on the inner surface of the furnace body 1 over the entire circumference. These infrared heaters 4 are arranged so that the watt density is greater in the lower stage than in the upper stage, so that temperature balance between the upper and lower parts of the furnace body 1 can be easily obtained. Reference numeral 5 denotes a ring-shaped manifold provided on the upper part of the furnace body 1, and a large number of air intake ports 6 are provided on the upper surface of the manifold 5. A facing slit-shaped air injection port 7 is provided all around the circumference. Compressed air is supplied to the inside of this manifold 5 from a blower, and from air injection ports 7 to 4 to
Air is jetted diagonally downward at a speed of 20 m/s. In addition to providing the air injection port 7 at the top of the furnace body 1 as shown in the figure, for example, a large number of nozzles may be provided downward between the infrared heaters 4 on the inner surface of the furnace body 1.
Air may be injected from these nozzles.

Figure 2 shows a resin tube heating furnace of the present invention in which such infrared heating devices are vertically stacked in multiple stages, and the resin tube is continuously moved inside each furnace body 1 from the upper end to the lower end. During this time, the resin tube can be heated from room temperature to approximately 80 to 180°C. In this case, the inside of the upper infrared heating device may be heated to a low temperature of, for example, 300°C.
The inside of the middle infrared heating device is set to a medium temperature of, for example, 320℃, and the inside of the bottom infrared heating device is set to a medium temperature of, for example, 350℃.
The temperature can be set to a high temperature.

(Function) With this configuration, if the resin tube is inserted from above into the furnace body 1 of the infrared heating device stacked vertically in multiple stages and moved continuously downward, the furnace body Infrared rays are radiated from an infrared heater 4 disposed on the inner surface of the heater 1 to uniformly heat the object to be heated from the entire circumference. At the same time, air is injected diagonally downward from the air injection port 7 provided at the inner peripheral edge of the furnace body 1, so that the rising hot air current that is generated inside the furnace body 1 due to convection is directed downward. This is suppressed by the injected air, and as a result, the temperature distribution above and below the furnace body 1 becomes uniform. For example, a resin tube with an outer diameter of 300 mm and a wall thickness of 100 μ
When moving the inside of the furnace body 1 at a speed of 27 m/min to expand the outer diameter to 1020 mm, if the temperature of the infrared heater 4 is set to 350°C, the atmospheric temperature inside the furnace body 1 will be approximately 250°C. At this time, the temperature variation in the circumferential direction and vertical direction inside the furnace is about 1%, which is less than half of the conventional temperature. Moreover, the air injected diagonally downward from the air injection port 7 prevents outside air from entering from the bottom surface of the furnace body 1, and also prevents heat dissipation from the top surface of the furnace body 1, resulting in good thermal efficiency and extremely economical performance. be.

In this way, the resin tube heating furnace of the present invention is a vertical stack of multiple infrared heating devices that can individually control the temperature, so if you pass the resin tube inside it, you can create an ideal temperature rise curve. Moreover, the resin tube can be heated evenly. Moreover, since each infrared heating device is provided with an air injection port 7 that injects air diagonally downward at the inner peripheral edge of the furnace body 1, the infrared heating device of each stage is heated by the intrusion of convective heat from the adjacent stage. Thermal efficiency is improved and high temperature accuracy can be maintained without being affected.

It goes without saying that if the furnace body 1 is of a split type as in the embodiment, maintenance will be easy, and if the furnace body 1 is provided with a heat insulating layer, the thermal efficiency will be further improved.

(Effects of the invention) As is clear from the above description, the invention consists of an infrared heating device that has an air injection port that injects air diagonally downward at the inner peripheral edge of a vertical cylindrical furnace body. Therefore, while passing through the inside of each infrared heating device, the resin tube can be efficiently heated by the radiant heat from the infrared heater and the hot air generated inside the furnace body. In addition, the air injected diagonally downward from the air injection port suppresses convection inside the furnace, making it possible to reduce the variation in temperature inside each infrared heating device to about 1%, less than 1/2 of the conventional one. Thermal efficiency can be increased by minimizing energy loss through the openings on the top surface of each furnace body. Furthermore, the air injected diagonally downward from the air injection port prevents the infrared heating devices in each stage from being affected by convection heat intrusion from adjacent stages, and high temperature accuracy can be maintained.

Therefore, the present invention has extremely great practical value as a resin tube heating furnace that solves the problems of the conventional method.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view showing an enlarged infrared heating device constituting a resin tube heating furnace of the present invention, and FIG. 2 is a partially cutaway front view showing an embodiment of the present invention. 1...Furnace body, 4...Infrared heater, 7...Air injection port.

Claims (1)

[Scope of utility model registration request] A large number of infrared heaters 4 are arranged on the inner surface of a vertical cylindrical furnace body 1 with open upper and lower surfaces, and
A resin tube heating furnace characterized in that infrared heating devices each having an air injection port 7 for injecting air diagonally downward at the inner peripheral edge of the furnace body 1 are vertically stacked in multiple stages.