JPH08261963A - Sample heating device for thermal analyzer - Google Patents

Abstract

PURPOSE: To improve the cooling characteristic without reducing the heating characteristic so much by winding a heater wire round the outer periphery of a protective tube, and circulating air between the space around the protective tube and the external space. CONSTITUTION: A current is fed to a heater wire 12 wound round a protective tube 10 at the time of heating, and the protective tube 10 and a sample in it are heated. Since air holes are bored on the upper and lower heat insulating plates 22, 24, the heating efficiency is inevitably reduced. The heater wire 12 is wound directly round the outer face of the protective tube 10, its heating efficiency is excellent, and the reduction of the heating efficiency is supplemented. The heater current is tuned off for cooling the sample, and the protective tube 10 and the sample in it are cooled. The air in the space 26 around the protective tube 10 is replaced with the external air by natural convection, and the cooling of the protective tube 10 is accelerated. When air is forcibly fed by a fan 34, the cooling efficiency is further improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample heating device for a thermal analyzer, and more particularly to a sample heating device adapted to heat a sample inside a protective tube from the outside of the protective tube.

[0002]

2. Description of the Related Art A conventional sample heating device of a thermal analyzer is used for heating to a high temperature or for rapidly raising the temperature.
As much heat as possible does not escape from the heater to the external space,
The circumference of the heater is covered with heat insulating material. The space between the heater and the heat insulating material is substantially a closed space so that the closed space does not communicate with the external space.

[0003]

The conventional sample heating apparatus described above has the following problems. Although there is little heat escape, it is advantageous when raising the temperature, but it takes a very long time to cool the sample from a high temperature to room temperature. Therefore, the measurement cycle of the sample becomes long and the measurement efficiency decreases. If the air is simply circulated around the heater in order to solve such a problem, then it takes time to raise the temperature or the sample cannot be heated to a desired high temperature.

The present invention has been made in order to solve the above-mentioned problems, and an object thereof is a sample in which the temperature rising characteristics are not significantly deteriorated and the cooling characteristics are significantly superior to those of the conventional samples. It is to provide a heating device.

[0005]

According to the present invention, there is provided a thermal analysis device comprising a cylindrical protective tube defining a space around a sample, and heating a sample inside the protective tube from the outside of the protective tube. In the sample heating device, the heater wire is wound around the outer peripheral surface of the protective tube, a heat insulating material is arranged around the protective tube, and the space around the protective tube between the protective tube and the heat insulating material and the external space of the sample heating device. To communicate with each other to allow air to flow between the space surrounding the protective tube and the external space. In this case, air circulation can be achieved by forming air holes that open to the outer peripheral surface side of the protective tube in both heat insulating plates that define both axial ends of the protective tube surrounding space. A fan for blowing air into the space around the protective tube may be provided.

The present invention is not particularly limited with respect to the sample to be placed inside the protective tube and the measuring method thereof, and the present invention is a sample heating device for various thermal analyzers such as thermogravimetric measurement, differential thermal analysis and thermomechanical analysis. Can be used as

As an additional feature of the present invention, one of the both heat insulating plates is elastically fixed in the axial direction of the protective tube by a spring-loaded pressing claw provided on the outer cylinder of the sample heating apparatus. You can It is also possible to arrange a safety cover around the casing of the sample heating device and form a large number of air circulation holes in this safety cover.

[0008]

Function The sample heating device has the following functions.
When the sample is cooled from a high temperature to room temperature, air is circulated in the space around the protective tube by natural convection or forced ventilation to promote cooling. Thereby, the cooling time is remarkably shortened as compared with the conventional closed space type. On the other hand, when the temperature of the sample is raised, the heating wire is directly wound around the protective tube, so that the heating efficiency is excellent, and the decrease in heating efficiency due to air circulation is compensated.

Further, by fixing the heat insulating plate with the pressing claws having the spring property, the expansion and contraction of the shield tube can be absorbed by the pressing claws, so that no gap is required between the elastic plate and the shield tube. Further, when the safety cover is provided around the casing, the surface temperature of the safety cover can be kept low, which is safe for the operator.

[0010]

1 is a front sectional view of a sample heating apparatus according to an embodiment of the present invention. A sample for thermal analysis is arranged inside the cylindrical protection tube 10, and a heater wire 12 is spirally wound directly on the outer peripheral surface of the protection tube 10. Around the protective tube 10 made of alumina, a heat insulating material 14, a shield cylinder 16 made of stainless steel, an outer cylinder 18 made of stainless steel, and a casing 20 made of stainless steel punch metal are arranged. There is. The heat insulating material 14 is formed of a cylindrical material mixed with alumina.

The heat insulating material 14 and the shield cylinder 16 are sandwiched in the axial direction by a pair of heat insulating plates 22 and 24 made of alumina. Since air holes are formed in the heat insulating plates 22 and 24, the protective tube surrounding space 26 between the protective tube 10 and the heat insulating material 14 communicates with the external space of the sample heating device, and the protective tube surrounding space 26. Air flows between the outside space and the outside space.
Not only the heat insulating plates 22 and 24 but also the upper heat insulating plate 22
Air holes for air circulation are also formed in the support 23 above, the metal plate 42 below the lower heat insulating plate 24, and the bottom plate 21 of the casing 20.

FIG. 2 is a plan view of the heat insulating plate 22. The shape of the other heat insulating plate 24 is also the same. The heat insulating plate 22 has a circular shape, and a circular hole 28 through which the protective tube 10 passes is opened in the center thereof. The heat insulating plate 22 further has five air holes 3
0 is open evenly. The air holes 30 are circular holes 2
It is open to the 8 side. Therefore, the air hole 30 faces the outer peripheral surface of the protection tube 10. Also, this heat insulating plate 2
Two slits 32 are formed in No. 2 in order to prevent deformation cracking when alumina is sintered.

Next, the temperature rising / cooling characteristics of this sample heating apparatus will be described. In FIG. 1, when the temperature is raised, an electric current is passed through the heater wire 12 wound around the protective tube 10 to heat the protective tube 10 and the sample therein. The periphery of the protective tube 10 is thermally insulated from the outside by the heat insulating material 14, the shield cylinder 16, and the outer cylinder 18, so that heat during heating is unlikely to escape. However, since air holes are opened in the upper and lower heat insulating plates 22 and 24, outside air flows into the protection pipe surrounding space 26 from below through the air holes, and the air in the protection pipe surrounding space 26 is moved upward. Go out from. Therefore, it is unavoidable that the heating efficiency is reduced as compared with the conventional case in which the space 26 around the protective tube is closed. However, since the heater wire 12 is wound directly on the outer surface of the protective tube 10, the heating efficiency is excellent. Further, since it is not necessary to dispose a conventional heater bobbin between the protection tube 10 and the heat insulating material 14, the heating efficiency is excellent even when the sample heating device is downsized. As described above, the decrease in heating efficiency due to the air flowing through the space 26 around the protective tube is compensated for by the improvement in heating efficiency due to the direct winding of the heater wire around the protective tube. The decrease is not so noticeable.

On the other hand, when cooling the sample, the current supplied to the heater wire 12 is turned off. As a result, the protective tube 10 and the sample inside thereof are naturally cooled. In this embodiment, as described above, the air in the protective tube surrounding space 26 is replaced with the external air by natural convection, and the cooling of the protective tube 10 is promoted. Further, if the fan 34 is used to forcefully send air, the cooling efficiency is further improved.

FIG. 5 is a graph showing a temperature change curve when the sample is cooled. The curve of the prior art example in which the space around the protective tube is substantially sealed, the natural cooling curve of the present invention, and the curve of forced cooling by a fan from the middle of natural cooling are shown. In this graph, the vertical axis is the temperature of the sample and the horizontal axis is time, both of which are shown on a logarithmic scale. Taking the case of cooling the sample temperature from 1500 ° C to room temperature as an example,
If the heater power is turned off at time t1, it takes about 2 hours to drop to 50 ° C. in the conventional closed space type.
On the other hand, with the natural cooling of the present invention, it takes about 50 minutes in about 30 minutes.
It goes down to ℃. Furthermore, if forced cooling is performed midway (time t2), the temperature drops to 50 ° C. in about 15 minutes (time t3). As described above, in the present invention, the cooling efficiency is remarkably improved as compared with the conventional example. This significantly shortens the measurement cycle of the sample and improves the measurement efficiency.

By the way, the reason why forced cooling is not performed from the beginning is as follows. Even in the case of natural cooling, the temperature is rapidly lowered in a region where the temperature is relatively high, so that the effect of shortening the time by forced cooling is not so remarkable. Rather, if forced cooling is performed at a high temperature, there is a concern that the protective tube may crack due to a sudden temperature change. Forced cooling after the temperature has dropped to a certain extent is effective in shortening the time.

FIG. 3 shows an example of a so-called horizontal type sample heating device in which a protective tube is horizontally arranged. The structure of the sample heating device itself is the same as that in the case of FIG. 1, but the circulation of air by natural convection is as shown by the arrows in the figure. The cooling efficiency by natural convection is slightly lower than that of the vertical type shown in FIG. FIG.
This is an example of forced cooling by a fan in a horizontal sample heating apparatus. In the horizontal type, the effect of forced cooling is remarkable because the effect of natural convection is not so great.

Next, a method of fixing the heat insulating plates 22 and 24 in FIG. 1 will be described. The lower heat insulating plate 24 is pressed upward by the three spring holding claws 44 via the metal plate 42. The base end of the pressing claw 44 is fixed to the outer peripheral surface of the outer cylinder 20. The three pressing claws 44 are arranged at equal intervals on the circumference. By the heat insulating plate 24 pushed upward, the heat insulating material 14 and the shield tube 16 are pushed upward, and finally the upper heat insulating plate 22 is supported by the support member 23.
Pressed to. In this way, the two heat insulating plates 22 and 24 are fixed in the sample heating device without any play. Even if the shield tube 16 or the like expands or contracts in the axial direction during heating and cooling of the sample, the pressing claws 44 having a spring property absorb the expansion and contraction, and the heat insulating plates 22 and 24 are held without play.

By the way, in the conventional sample heating apparatus, since the heat insulating plate is fixed by using the screw without using the spring-holding claw, the heat insulating plate and the shield tube are considered in consideration of expansion and contraction of the shield tube. There was a gap in between. In such a case, when transporting the sample heating device, the heat insulating plate shook and collided with the shield tube or the like, and the sintered heat insulating plate was broken. On the other hand, when the pressing claw having the spring property is used as in the embodiment of FIG. 1, the heat insulating plate is always held firmly, and the accident that the heat insulating plate collides with the shield cylinder is eliminated.

FIG. 6 is a view showing a safety cover put on the outside of the casing 20 of the sample heating apparatus shown in FIG.
A front view (A), a side view (B) and a plan view (C) are shown. The safety cover 36 is an example applied to a sample heating apparatus including a protection tube 10 of a type in which a gas flow tube 38 extends upward. A large number of air circulation holes 40 are opened in the side surface, front surface, and back surface of the safety cover 36, and the safety cover 36 is effectively cooled by natural convection of air. Thereby, even if the sample is heated to 1500 ° C., for example, the surface temperature of the safety cover 36 can be suppressed within 60 ° C. Therefore, even if the operator accidentally touches the safety cover 36 while heating the sample at a high temperature, it is safe without being burned.

[0021]

The sample heating apparatus of the present invention has the following advantages. When the sample is cooled from a high temperature to room temperature, air flows in the space around the protective tube, and the cooling time is shortened.
On the other hand, when the temperature of the sample is raised, the heating wire is directly wound around the protective tube, so that the heating efficiency is excellent, and the decrease in heating efficiency due to air circulation is compensated. Further, by fixing the heat insulating plate with the pressing claws having spring properties, the expansion and contraction of the shield tube can be absorbed by the pressing claws, and no gap is required between the elastic plate and the shield tube. Further, when the safety cover is provided around the casing, the surface temperature of the safety cover can be kept low, which is safe for the operator.

[Brief description of drawings]

FIG. 1 is a front sectional view of a sample heating apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view of a heat insulating plate.

FIG. 3 is an example of natural convection in a horizontal sample heating apparatus.

FIG. 4 is an example of forced cooling of a horizontal sample heating apparatus.

FIG. 5 is a graph showing a temperature change curve during cooling of a sample.

FIG. 6 is a front view, a side view, and a plan view of a safety cover.

[Explanation of symbols]

 10 Protective Tube 12 Heater Wire 14 Insulation Material 16 Shield Tube 18 Outer Tube 20 Casing 22, 24 Insulation Plate 26 Protective Tube Surrounding Space 30 Air Hole 34 Fan 44 Holding Claw

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akifumi Akiyama 3-9-12 Matsubara-cho, Akishima-shi, Tokyo Rigaku Denki Co., Ltd.

Claims (5)

[Claims] 1. A sample heating device of a thermal analysis device, comprising: a cylindrical protective tube defining a space around a sample; and heating a sample inside the protective tube from the outside of the protective tube. Is wound around the outer peripheral surface of the protection tube, a heat insulating material is arranged around the protection tube, and the space around the protection tube between the protection tube and the heat insulating material is communicated with the external space of the sample heating device to protect the protection tube. A sample heating device, characterized in that air is allowed to flow between the space around the tube and the external space. 2. The sample heating apparatus according to claim 1, further comprising a fan for blowing air into the space around the protective tube. 3. The sample heating according to claim 1, wherein air holes that open to the outer peripheral surface side of the protective tube are formed in both heat insulating plates that define both ends in the axial direction of the protective tube surrounding space. apparatus. 4. One of the two heat insulating plates is elastically fixed in the axial direction of the protective tube by a spring holding claw provided on the outer cylinder of the sample heating device. The sample heating device described. 5. The sample heating apparatus according to claim 1, wherein a safety cover is arranged around the casing of the sample heating apparatus, and a large number of air circulation holes are formed in the safety cover.