JPS6132789B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sheath heater in which a heat generating wire is housed in a sheath filled with an inorganic insulating material, and a sheath heater is equipped with a thermocouple for detecting the temperature of the sheath.

When using this type of heater, it is necessary to detect the temperature at which the heater itself generates heat. In particular, for heaters with explosion-proof construction used in dangerous locations where explosive gases are present, it is desirable to directly detect and control the surface temperature of the heater itself. For this purpose, thermocouples have conventionally been placed on the surface of the sheath, but if the thermocouple is simply inserted into a groove carved in the axial direction, an air layer will exist between the thermocouple and the sheath surface. Not only will the temperature of the sheath surface itself not be detected, but the thermocouple may become detached from the sheath. Therefore, in this invention, a thermocouple is attached to the sheath, housed in an exterior tube, and the exterior tube is compressed and reduced in diameter over its entire length to bring the thermocouple into close contact with the sheath.The temperature of the sheath surface itself can be accurately measured. The purpose is to detect and firmly hold the thermocouple to the heater.

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings.

As shown in FIGS. 1 and 2, a long sheath-like metal sheath 1 is densely filled with an inorganic insulating material 2 such as magnesium oxide MgO, and heating wires 3 are housed therein. Next, a groove 4 having a semicircular cross section is carved in the axial direction on the outer circumferential surface of the sheath 1, and a thermocouple 5 is fitted into the groove 4 at the upper side as shown in FIG. 2, and a displacement prevention member 6 is fitted at the lower side.
The anti-displacement member 6 is fixed by welding or the like, and the sheath 1 is housed in an exterior tube 7 whose inner wall has no axial grooves, with the thermocouple 5 inscribed therein in a concentric manner. Thereafter, the outer tube 7 housing the thermocouple 5 and sheath 1 therein is squeezed and reduced in diameter by cold rolling such as drawing with a die, as shown in FIG. The groove 4 on the outer peripheral surface of the sheath 1 is formed to match the circular cross section of the thermocouple 5, the displacement prevention material 6 has the same cross section as the thermocouple 5, and the squeezing direction of the sheath tube 1 is upward in FIG. The positional displacement of the thermocouple 5 is corrected by the presence of the displacement prevention material 6. Exterior pipe 1
The degree of diameter reduction is such that the outer circumferential surface of the sheath 1 and the inner circumferential surface of the sheath tube 1 are in close contact with each other and the thermocouple 5 can be firmly held.

The present invention provides a sheath heater in which the sheath is filled with an inorganic insulator to accommodate a heating wire, in which an axial groove is carved on the outer peripheral surface of the sheath, a thermocouple is fitted into the groove, and a thermocouple is inserted into the sheath. A misalignment prevention material with the same cross section as the thermocouple is placed in series with the thermocouple, fitted and welded, and the thermocouple and misalignment prevention material are concentrically inscribed within the exterior tube, which has no axial grooves cut into the inner wall. This is a sheath heater that is stored in a state where the outer tube is compressed to reduce its diameter over its entire length, and the surface temperature of the sheath heater itself can be directly detected and controlled. In addition, since the thermocouple is attached by squeezing the outer tube, there is no air layer between the thermocouple and the sheath, and the surface temperature of the heater itself can be accurately detected. Strongly held. Furthermore, since the thermocouple is attached by squeezing the outer tube, a high-quality sheath heater can be provided with extremely simple processing. In the groove on the outer circumferential surface of the sheath, a misalignment prevention material with the same cross section as the thermocouple is placed in series with the thermocouple and welded, so that even if the diameter is squeezed and reduced, it remains fixed in the axial direction of the outer circumferential surface of the sheath. The temperature sensing portion of the thermocouple can be positioned at a fixed location, and displacement of the temperature sensing portion in the axial direction can be prevented.

The inner wall of the sheath tube is not machined with any axial grooves or other things that are difficult to machine, making it extremely easy to machine, and as a result, the sheath heater can be provided at low cost.

[Brief explanation of the drawing]

Figures 1 and 2 show the sheath heater according to an embodiment of the present invention before the thermocouple is compressed and attached to the sheath heater. FIG. FIG. 3 is a plan view showing a state in which the outer tube is squeezed and reduced in diameter and a thermocouple is attached. DESCRIPTION OF SYMBOLS 1...Sheath, 2...Inorganic insulator, 3...Heating wire, 4...Groove, 5...Thermocouple, 6...Displacement prevention material, 7...Exterior tube.

Claims (1)

[Claims] 1. In a sheath heater in which the sheath is filled with an inorganic insulator to house a heating wire, a groove in the axial direction is carved on the outer circumferential surface of the sheath, a thermocouple is fitted into the groove, and the same cross section as the thermocouple is prevented from shifting. The material is placed in series with the thermocouple, inserted and welded, and the thermocouple and misalignment prevention material are housed concentrically in an exterior tube with no axial grooves cut into the inner wall, and the exterior A sheath heater made by squeezing and reducing the diameter of a tube over its entire length.