JPH0429198B2 - - Google Patents

Description

Detailed Description of the Invention Technical Field The present invention relates to a cylindrical inner plate that surrounds an object to be heated, a cylindrical outer plate that surrounds the inner plate, and a mica film disposed between the inner plate and the outer plate. The present invention relates to a band heater having heating wires electrically insulated by a plate or the like.

Prior Art This band heater works to heat an object surrounded by an inner plate using heat generated from a heating wire. A band heater as shown in FIG. 1 is known. In the same figure,
A band heater 4 having a heater 1 and a band 3 carrying the heater 1 and provided with a tightening screw 2 is attached tightly to the object to be heated 5 under the tightening action of the tightening screw 2. Heated object 5
is heated by the heater 1 which generates heat by supplying power from the lead wire 6. however,
As shown in the figure, this band heater 4 has a threaded portion 7.
Since it has a protruding part such as the lead cover part 8 and the lead cover part 8, a corresponding space is required for installation. However, in recent years, it has become necessary for objects to be heated, such as plastic injection molding machines or molds, to occupy as little space as possible around the object. The above-mentioned conventional band heaters cannot be said to be suitable for use.

As a heater that solves this problem, a cylindrical heater as shown in FIG. 2 is conventionally known. As shown in the figure, this heater 9 does not require a threaded portion, and the lead cover portion 8' does not protrude excessively, so it can be used even in a narrow space. However, since this heater 9 is used by being inserted into the object to be heated from the side, its adhesion to the object to be heated is poor. Furthermore, when the temperature rises due to energization, the adhesion further deteriorates due to thermal expansion. In this case, since the heater is in a dry state, the thermal efficiency deteriorates and at the same time the life of the heater is shortened.

Purpose In view of the above points, an object of the present invention is to provide a heater that can be used even in a narrow space and has good thermal efficiency.

Structure This purpose is to make the thermal expansion coefficient of the cylindrical outer plate that constitutes the heater larger than the thermal expansion coefficient of the cylindrical inner plate that also constitutes the heater, and to This can be achieved by providing a gap in the axial direction and between both ends so that the heater contracts inward due to thermal expansion when heated with electricity.

EMBODIMENT OF THE INVENTION Hereinafter, the present invention will be described in detail based on drawings showing embodiments thereof.

In Figure 3, bandless band heater 1
1 has a cylindrical inner plate 12 and a cylindrical outer plate 13, and between these side plates is a heating wire 1 wound around a core mica plate 14, as shown in FIG.
5 is placed. A portion of the cylindrical body formed by the inner plate 12 and the outer plate 13 is provided with a gap in the axial direction and extending to both ends. Heating wire 15 and side plate 1
A mica plate 16 as an insulator is placed between 2 and 13.
is placed. The heating wire 15 generates heat by being supplied with power from the lead wire 6. Outer plate 13
is made of a material having a coefficient of thermal expansion larger than that of the inner plate 12. Therefore, when the heating wire 15 generates heat, the inner plate 12 and the outer plate 1
Due to the difference in thermal expansion between the heater 11 and the heater 11, the heater 11 contracts inward.

Bandless band heater 11 according to this embodiment
is made of the above-mentioned structure, so when an object to be heated is inserted inside the inner plate 12 and then energized, the object to be heated is heated by the heat generated by the heating wire 15.
At this time, since the heater 11 contracts inward as described above, the adhesion between the inner plate 12 and the object to be heated is improved. Therefore, heating can be performed extremely efficiently without worrying about dry baking. Furthermore,
As is clear from FIG. 3, the heater 11 does not require any protruding parts such as threaded parts found in conventional band heaters, so it can be used even in narrow spaces. Furthermore, since the band 3 having the tightening screw 2 is not required, it can be produced economically and at low cost.

The above embodiment is a case in which the present invention is applied to a so-called mica heater using a mica plate as an electrical insulator, but as shown in FIG. It goes without saying that the present invention can be applied to other heaters.

Effects As described above, according to the present invention, since the coefficient of thermal expansion of the outer plate of the band heater is made larger than that of the inner plate, the entire band heater contracts inward when heating an object. Therefore, the band heater and the object to be heated come into close contact with each other, thereby greatly improving thermal efficiency.

In addition, since there is no need for fastening means such as tightening screws to ensure tight contact, manufacturing costs are reduced accordingly, and there is no protruding portion, which is advantageous in terms of space.

[Brief explanation of drawings]

Figure 1 is a front view of a conventional band heater.
Fig. 2 is a perspective view showing a conventional cylindrical heater, Fig. 3 is a perspective view of a bandless band heater showing an embodiment of the present invention, and Fig. 4 is a cross-sectional view taken along line A-A of the heater shown in Fig. 3. FIG. 5 is a sectional view of a main part of another heater in which the present invention can be practiced. 5... Heated object, 12... Cylindrical inner plate, 13
... Cylindrical outer plate, 15 ... Heating wire, 11 ... Bandless band heater.

Claims (1)

[Claims] 1. A band heater having a cylindrical inner plate surrounding an object to be heated, a cylindrical outer plate surrounding the inner plate, and an electrically insulated heating wire disposed between the inner plate and the outer plate, A bandless band characterized in that the thermal expansion coefficient of the outer plate is larger than that of the inner plate, and a part of the cylindrical body formed by the inner and outer plates is provided with a gap in the axial direction and between both ends. heater.