JPS6233529B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotating shaft support structure suitable for application to liquid level gauges and the like.

Conventionally, the rotating shaft of a liquid level gauge that converts the vertical movement of a float into rotational displacement is usually supported as shown in FIG. That is, reference numeral 1 denotes a rotating shaft, and one end of a connecting rod 2 extending in a direction orthogonal to the shaft 1 is connected and fixed to one end of the large diameter portion 1A of the rotating shaft 1. The other end of the connecting rod 2 is rotatably supported by a connecting tool 3, and a float 4 floating in the liquid is disposed on the connecting tool 3 via a connecting rod 5. Therefore, a rotational force in the direction of arrow A about the axis is constantly applied to the rotating shaft 1 by the float 4.

The rotating shaft 1 is made of stainless steel, Inconel,
It is inserted and held in a cylindrical tube 6 made of Monel, Hastelloy, etc., and one end opening of the tube 6 fits into the large diameter portion 1A and is fixed by welding over the entire circumference. The other end of the cylindrical tube 6 is fitted into an inner hole 8 of a cylindrical fitting 7 and fixed by welding over the entire circumference. The mounting fitting 7 is fitted and fixed into a fitting mounting hole of the meter body 9 from the inside via a gasket 10. One end of an internal arm 11 is fixed to a protruding end 1B that protrudes from the mounting bracket 7 of the rotating shaft 1 into the instrument body 9.
A nozzle 12 as a sensor for detecting the rotational displacement of the rotating shaft 1 is disposed at the tip of the rotating shaft 1 so as to be close to each other and face each other. The cylindrical tube 6 has a thin wall and is flexible so that it can rotatably hold the rotating shaft 1 and at the same time seal and protect the inside of the instrument body 9 by welding.

In such a configuration, when the liquid level 13 changes, the height of the float 4 changes, so the load applied to the large diameter portion 1A of the rotating shaft 1 changes, causing it to rotate in the direction of arrow A or in the opposite direction. When this rotating shaft 1 rotates, the internal arm 11 also rotates together, changing the gap with the nozzle 12, which changes the nozzle back pressure, which is amplified by the amplifier 14 and then output as an output signal P _0. Transmit to the outside world.

By the way, when the rotating shaft 1, the cylindrical tube 6, and the mounting bracket 7 are integrally joined by welding, the welded portions of the cylindrical tube 6 and
The strength of B and its vicinity, that is, the weld heat-affected zones C and D, decreases (due to the annealing effect), which reduces the restoring force of the tube 6 against torsion and impairs its function as a torsion spring. Ta.

The present invention has been made in view of the above-mentioned points, and includes a rotating shaft to which rotational force is constantly applied in one direction around the axis, and a rotating shaft whose both ends are welded and fixed to mounting brackets. By applying twist in the same direction as the rotational force to the welded portion of a cylindrical tube made of a thin flexible membrane that is rotatably supported and its vicinity, and work-hardening it, the decrease in strength of the cylindrical tube during welding is offset. Alternatively, the present invention provides a shaft support structure that reduces the stress and restores the function as a torsion spring.

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

FIG. 2 is a partially cutaway perspective view of essential parts showing an embodiment in which the rotary shaft support structure according to the present invention is applied to the rotary shaft of a liquid level gauge. Components in the figure that are the same as those in FIG. 1 are designated by the same reference numerals, and their explanations will be omitted. After welding, the welded parts A and B at both ends of the cylindrical tube 6 and the weld heat-affected zones C and D in the vicinity are twisted in the same direction as the rotational force (direction of arrow A) applied to the rotating shaft 1 at room temperature after welding. This results in work hardening.

This twisting work is performed using a lathe 21 as shown in FIG. That is, the chuck 23 attached to the main shaft 22 allows the large diameter portion 1A of the rotating shaft 1 to be
chuck 2 which is clamped and attached to the tailstock 24
5, clamp the flange 7A of the mounting bracket 7,
The chuck 23 on the main shaft 22 side is fixed, and the chuck 25 moves the mounting bracket 7 in the direction opposite to the arrow A direction.
That is, it is rotated by a predetermined angle in the direction of arrow B. As a result, the cylindrical tube 6 is twisted in the direction of arrow A. Then, the welded parts A and B and their surrounding parts C and D, whose strength has decreased during welding, are plastically deformed and twisted, and are partially work-hardened.

The extent of this torsion can be clearly seen by marking a straight line 26 on the circumferential surface of the cylindrical tube 6 in advance, as shown in FIG. Alternatively, the determination may be made using a torque wrench, or the fixed chuck 23 may be configured to slip when a torsional moment exceeding a certain level is applied thereto.

Next, the effects of work hardening in the present invention will be explained in general.

Work hardening is a property that appears when plastic deformation occurs at room temperature.

In other words, for metal materials, compression at room temperature,
Permanent deformation is caused by applying stress such as tension. As a result, strain occurs inside the metal, and the resistance to deformation against newly applied stress increases. This property is work hardening. Work hardening achieves an increase in yield point and elastic limit.

Therefore, as in the present application, it is more effective for the cylindrical tube 6, which is a member to which twist is applied and elastic deformation is desired. Cylindrical tube 6 of the present application
is originally formed into a cylindrical shape by cold working, and the entire cylinder has an elastic limit above a certain value. However, after that, there is a process of welding the edges, and in this process heat is applied near the edges, which eliminates the internal strain that would have occurred due to cold working, resulting in a loss of work hardenability. The strength against stress, that is, the elastic limit, is lower than that of other parts (the middle part of the cylinder). As a result, when torsion is applied to the portion during use, plastic deformation, that is, permanent deformation occurs, and the torsion spring cannot function satisfactorily.

The present invention solves this problem. In other words, after welding, the welded part is work-hardened by simply twisting at room temperature, raising the lowered elastic limit again and expanding the area where elastic deformation occurs in response to stress applied during use. By suppressing the occurrence of plastic deformation, the torsion spring can fully function as a torsion spring.

As explained above, according to the support structure for the rotating shaft according to the present invention, the rotating shaft is provided with a support structure at and around the welded portion of the cylindrical tube made of a thin-walled flexible membrane whose strength has been reduced due to annealing during welding. By applying torsion in the same direction as the rotational force, the welded part and its vicinity are work-hardened, thereby offsetting or reducing the decrease in strength due to welding and restoring the function as a torsion spring relative to the rotating shaft. be able to. Moreover, the twisting work is easy, and the effect is very large.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a support structure for a rotating shaft in a level gauge, and FIG. 2 is a partial view showing an embodiment in which the rotating shaft support structure according to the present invention is applied to a rotating shaft of a level gauge. The cutaway perspective view, FIG. 3, is a diagram for explaining the work of twisting the cylindrical tube. 1... Rotating shaft, 6... Cylindrical tube, 7...
Mounting brackets, A, B...Welded parts.

Claims (1)

[Claims] 1. A rotating shaft to which rotational force is constantly applied in one direction around the axis, and this rotating shaft is inserted through the shaft, and the opening at one end is welded and fixed to the outer peripheral surface of the rotating shaft over the entire circumference. The cylindrical tube is provided with a cylindrical tube made of a thin flexible membrane that rotatably supports the shaft, and a mounting fitting in which the other end of the cylindrical tube is fitted into an inner hole and fixed by welding. A rotary shaft support characterized in that the welded portions and the vicinity thereof are work-hardened by applying torsion in the same direction as the rotational force applied to the rotary shaft to the welded portions at both ends of the tube and their vicinity. structure.