JPH07235698A - Heat-insulating load supporter for superconducting magnet - Google Patents

Abstract

PURPOSE:To facilitate assembly and disassembly at the normal temperature, and to obtain firm clamping at a low temperature by a method wherein the tangent of a taper angle is made larger than a friction coefficient between an FRP rod and metal fittings, at the normal temperature both the rod and the metal fittings are not fixed, the friction coefficient between both the rod and the metal fittings is made larger than the tangent of the taper angle at the low temperature and both the rod and the metal fittings are clamped by high clamping force. CONSTITUTION:Fitting tapered sections 6 and FRP tapered sections 7 having taper angles 5 deg. mutually are formed to an FRP rod I, a cryostat fitting 2 and a vacuum tank fitting 3. A PTFE lubricant 7 is atomized and applied to the fitting taper 6 and the FRP tapered section 7, a PTFE film is formed, frictional resistance is reduced and axial tension is applied to the FRP rod 1, and the cryostat fitting 2 and the vacuum tank fitting 3 are clamped. The displacement of the end sections of the FRP rod 1 is constrained by the bolts 6. When tensile force is lowered when both the fitting 2 and the fitting 3 are disassembled, frictional coefficients among the FRP rod l, the cryostat fitting 2 and the vacuum tank fitting 3 are made smaller than the tangent of the taper angles, thus mutually sliding both the fitting 2 and the fitting 3 in the tapered sections, then resulting in natural disassembly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended for a load carrier for a superconducting magnet, and in particular, it is easy to assemble and disassemble at a fastening portion of a FRP rod and a metal fitting, and can hold a strong fastening force at a low temperature for a long time. A load support fastening portion.

[0002]

2. Description of the Related Art In a load carrier for a superconducting magnet, a low temperature tank holding a superconducting coil and a refrigerant and a vacuum chamber at room temperature are adiabatically held by the load carrier. As an example of this load support, as shown in FIG. 3 (Japanese Patent Laid-Open No. 63-36503), a central leg portion of a T-shaped pulling fitting 18 is attached to a fitting 15 attached to a cryogenic container and a vacuum container, respectively. The nut 16 is tightened and fixed, and a cap nut 17 is mounted on the top of the nut 16. Both ends of the support member 13 are inserted into the cap nut 17, and the truncated cone-shaped taper is engaged by the two-piece pieces 14. And fix it.

However, in this case, the support member 13 and the top 1
If the taper angle of 4 is small, the two adhere to each other due to friction, and therefore a compressive load in the axial direction is required to disassemble at room temperature after assembly, which may break the rod.
On the other hand, if this taper angle is large, both taper portions will slip at low temperatures and firm fastening cannot be obtained.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a load support which can be easily assembled and disassembled at room temperature and which can be firmly fastened at a low temperature.

[0005]

In order to achieve this object, the present invention provides a load support for adiabatically supporting a cryostat, which has an FRP rod having a taper at its end and a taper inside. A structure in which a lubricant whose friction coefficient increases at a low temperature is applied between metal fittings fixed to the low temperature tank and a high surface pressure is held between both tapers by applying an axial tensile force to the FRP rod is used. The tangent of the taper angle is larger than the friction coefficient at the fastening temperature and smaller than the friction coefficient at the low temperature.

[0006]

In this structure, since the tangent of the taper angle is larger than the friction coefficient between the FRP rod and the metal fitting at room temperature, they are not fixed to each other and can be easily assembled and disassembled. Further, at low temperature, the friction coefficient between the two is larger than the tangent of the taper angle, so both are fixed and stably fastened with a high fastening force.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an assembled and disassembled state of an embodiment of the present invention.
FIG. 2 shows a superconducting magnet using one embodiment of the present invention. Figure 2
In, the load support 9 adiabatically holds the superconducting coil 10, the low temperature tank 11 for holding the refrigerant, and the vacuum tank 12 at room temperature. In FIG. 1, a load support 9 is a unidirectional strengthened FRP rod 1, a low temperature tank metal fitting that is held at a liquid helium temperature and is wrapped around a superconducting coil 10 and fixed to a low temperature tank 11, and a vacuum tank metal fitting that is maintained at ambient temperature. It consists of three. In manufacturing this load support, the conical core 4 is inserted from both ends of the fiber bundle to match the taper shape of the low temperature tank fitting 2 and the vacuum tank fitting 3 having a taper angle of 5 °, and the resin is impregnated to mold the support. Perform molding. As a result, the FRP rod 1, the low temperature tank fitting 2, and the vacuum tank fitting 3 can be provided with the fitting taper portion 6 and the FRP taper portion 7 having a taper angle of 5 °, and the taper portion can maintain a uniform surface pressure. The conclusion is made. After fastening, creep of FRP rod 1, FRP
Since the load acting on the rod 1 and the fastening force reduction due to cooling heat shrinkage are considered, it is desired that the fastening portion be firmly fastened in consideration of these fastening force reduction. Therefore, PTF dissolved in a solvent is used for the metal fitting taper portion 6 and the FRP taper portion 7.
Spray and apply E-based lubricant 7 and dry to make thin and strong PT
An FE film is formed. This PTFE film has a friction coefficient of 0.01 at room temperature, and when friction resistance is reduced and axial force (tensile tightening force) is applied to the FRP rod 1, the PTFE film is firmly bonded to the low temperature tank fitting 2 and the vacuum tank fitting 3. The conclusion is made. Further, the bolt 6 is screwed into the end portions of the low temperature tank fitting 2 and the vacuum tank fitting 3 under the axial load condition to restrain the displacement of the end portion of the FRP rod 1 and prevent the fastening force from decreasing.

Further, when disassembling the both, the bolt 6 is removed with the tensile axial force similarly applied. Next, when the tensile force is reduced, the friction coefficient between the FRP rod 1, the low temperature tank fitting 2 and the vacuum tank fitting 3 is the tangent tan θ (θ = 5 °) of the taper angle θ.
Since tan θ is less than 0.087), the two parts are naturally disassembled by sliding at the taper parts. This state is shown in FIG. 4 as the relationship between the axial force and the axial relative displacement at room temperature.

The friction coefficient of PTFE lubricant 7 at 4.2K is 1.2, which is larger than the tangent of the taper angle of 0.087. Therefore, both are fixed by the increase of the friction coefficient. FIG. 5 shows the relationship between the axial tensile force at 4.2K and the axial relative displacement between the FRP rod 1 and the cold bath fitting 2. In this case, as described above, the two are fixed due to the increase in the friction coefficient, and the displacement is hardly changed even after the axial load is applied, and the strong fastening is performed.

[0010]

According to the present invention, the FRP rod and the metal fitting can be easily assembled and disassembled at room temperature, both are firmly fastened at a low temperature, and frictional heat generation due to vibration is suppressed.

[Brief description of drawings]

FIG. 1 is a sectional view showing an assembled and disassembled state of an embodiment of the present invention.

FIG. 2 is a sectional view of a superconducting magnet using an embodiment of the present invention.

FIG. 3 is a sectional view of a conventional example.

FIG. 4 is a characteristic diagram showing the relationship between axial force and axial relative displacement at room temperature.

FIG. 5 is a characteristic diagram showing the relationship between axial force and axial relative displacement at 4.2K.

[Explanation of symbols]

1 ... FRP rod, 2 ... low temperature tank fitting, 3 ... vacuum tank fitting,
4 ... Conical center, 5 ... Bolt, 6 ... Tapered part of metal fitting, 7 ... FR
P taper portion, 8 ... PTFE-based lubricant, 9 ... Load support.

Claims (1)

[Claims] 1. A load support for adiabatically supporting a cryostat of a superconducting magnet, wherein an FRP rod having a taper at its end and a metal fitting fixed to the cryostat rubs at a low temperature. Applying a lubricant whose coefficient increases,
It is a structure in which a high surface pressure is held between both the tapers by applying an axial tensile force to the P rod to fasten the taper, and the tangent of the angle of the taper is larger than the friction coefficient at the fastening temperature.
An adiabatic load support for a superconducting magnet, which has a friction coefficient smaller than that at a low temperature.