Protective tube structure for thermometer

Abstract

There is provided a protective tube structure for a thermometer in which a gap between an anti-vibration strip and a surface of a protective tube is eliminated to prevent corrosion of the protective tube, and the anti-vibration strip can be easily formed. The protective tube structure for a thermometer includes: a cylindrical portion 2; and one or more projected rims 3 formed into a spiral on an outer wall of a barrel of the cylindrical portion 2, and the projected rim 3 is formed by cutting an outer surface of a barrel of a cylindrical member.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side view, partially in section, of a configuration of a protective tube structure for a thermometer according to the present invention;

FIG. 1B is a cross sectional view taken in the direction of arrow A-A;

FIG. 2 is an enlarged view of a portion B in FIG. 1B;

FIG. 3 is a side view of a conventional protective tube structure that prevents generation of a Karman vortex;

FIG. 4 is an enlarged view of essential portions in FIG. 3;

FIG. 5A is a side view, partially in section, of another example of a conventional protective tube structure; and

FIG. 5B is a cross sectional view taken in the direction of arrow C-C.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of a protective tube structure for a thermometer according to the present invention.

In FIG. 1A, the right half from the centerline C.L. shows a protective tube 1 in section, and the left half shows an appearance of the protective tube 1.

In FIGS. 1A and 1B, the protective tube 1 of the thermometer of the embodiment is made of SUS304, and includes a closed-end cylindrical portion 2, and projected rims 3 formed on an outer wall of a barrel of the cylindrical portion 2.

As shown in FIG. 1B, three projected rims 3 are circumferentially spaced at equal spaces, and formed into spirals in parallel with each other toward the tube axis direction of the cylindrical portion 2.

A cylindrical hole S is formed in the center of the cylindrical portion 2 (along the tube axis) to a predetermined depth so that a temperature sensor such as a thermocouple or a resistance temperature sensor is inserted therein.

The outer wall of the barrel of the cylindrical portion 2 is tapered (an outer diameter D₂ of a rear end of the cylindrical portion is larger than an outer diameter D₁ of a tip of the cylindrical portion) and narrowed toward the tip. This allows the cylindrical portion 2 to be smoothly mounted to or removed from a pipe (not shown in the figure).

The projected rim 3 corresponds to a wire wound around an outer wall of a barrel of a cylindrical portion in a conventional structure, and in the present invention, the spiral projected rim 3 is formed by cutting. The projected rim 3 functions as an anti-vibration strip that prevents generation of a Karman vortex.

Specifically, the protective tube 1 is formed into a cylindrical shape which is closed at one end by drilling a round rod, and in a barrel of the protective tube 1, an area between the projected rims 3 is cut into a groove using an end mill on a milling machine to form the projected rims 3 in streaks.

In the protective tube 1 thus formed by cutting, the projected rim 3 is formed integrally with the protective tube 1, and thus no gap is created between the protective tube and the wire as in the conventional wire mounting method by welding.

Further, as shown in an enlarged view in FIG. 2, the bottom 3a of the projected rim 3 is connected to an outer wall surface 1a of the barrel of the protective tube 1 with a radius 4 to form a smooth surface without a welding bead placed in a gap at a contact portion between the protective tube 1 and the wire as in the conventional all-around welding, thereby completely solving the problem of the conventional protective tube that adhesion of impurities causes corrosion.

On the other hand, on a top of the projected rim 3, opposite corners 3b and 3b are formed substantially at a right angle, and thus an irregular flow for preventing a Karman vortex is more effectively formed than the protective tube to which the wire having a circular section is welded.

EXAMPLE

A round rod was drilled to form a protective tube 1 as a cylindrical member, and an outer wall of a barrel of the protective tube 1 was cut into a groove by an end mill to form projected rims 3 into spirals.

An outer diameter of the formed protective tube 1 (except the projected rim 3) was about φ20 mm (D), and a height of the projected rim 3 was 2 mm (about 0.1 D).

The projected rims 3 were formed into three spiral windings in parallel with each other, and a winding pitch was about 100 mm (about 5 D).

The protective tube 1 thus obtained was mounted to a pipe to be measured in a perpendicular to a flow of a fluid, a thermocouple was inserted into a cylindrical hole S in the protective tube 1, and the temperature of the fluid was measured.

It was confirmed that no impurity adheres to the projected rim 3 according to the protective tube 1 of the thermometer having the above described configuration.

In the embodiment, the protective tube 1 is made of SUS304, but not limited to this, the protective tube 1 may be made of, for example, SUS316, SUS316L, or other heat-resistant and corrosion-resistant steel or the like according to the use.

The foregoing description of at least one preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings.

Claims

1. A protective tube structure for a thermometer comprising: a cylindrical portion; andone or more projected rims formed into a spiral on an outer wall of a barrel of the cylindrical portion,wherein said projected rim is formed by cutting an outer surface of a barrel of a cylindrical member.

2. The protective tube structure for a thermometer according to claim 1, wherein said cylindrical member is formed in tapered shape which is narrowed toward a tip.

3. The protective tube structure for a thermometer according to claim 1, wherein opposite corners on a top of said projected rim are formed substantially at a right angle, and a bottom of said projected rim and the outer wall surface of the barrel of said cylindrical portion are connected with a radius.

4. The protective tube structure for a thermometer according to claim 2, wherein opposite corners on a top of said projected rim are formed substantially at a right angle, and a bottom of said projected rim and the outer wall surface of the barrel of said cylindrical portion are connected with a radius.