JPH06147320A - Pressure container - Google Patents

Abstract

PURPOSE:To reduce the temperature change of inside air and promptly stabilize air pressure by accelerating the heat conduction of compressed air in a pressure container for a drive system and a capacity system. CONSTITUTION:When compressed air flows from a compressed air supply source 4 into a pressure container 1 before the measured 2 is driven, pressure in the pressure container 1 rises and the temperature of air increases but heat energy of the air is transferred to the inner wall of the pressure container 1 and radiated to the outside. The temperature of the compressed air when filled increases but the heat is radiated from the pressure container 1, so that an increase of temperature is small. When the measured 2 is driven, a great amount of compressed air flows out of the pressure container 1 and so compressed air in the pressure container 1 expands and the temperature decreases. As a result, heat supplied from a fine metal wire 3 is absorbed by the pressure container 1 from the outside and supplied to the fine metal wire 3, so that the temperature is restricted from decreasing to rapidly stabilize air pressure in the pressure container 1. Prompt measurement is therefore allowed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure vessel in which compressed air flows in and out, such as a pressure vessel used in an actuator of a pneumatic impact tool driven by pneumatic pressure, a device controlled by pneumatic pressure, a measuring instrument utilizing pneumatic pressure, Regarding

[0002]

2. Description of the Related Art Generally, when controlling a pneumatic device of this type by air pressure, a pressure change occurs inside a pressure vessel of a drive system or a capacity system when compressed air flows in and out, and the air is rapidly changed accordingly. Since it is compressed or expanded, the temperature of the internal compressed air changes, and this temperature change further causes pressure fluctuations in the container.

For example, in a pneumatic impact tool in which a fastener such as a nail is driven by using air pressure, an air chamber for storing compressed air is formed around a piston / cylinder mechanism which is a drive mechanism. The piston is shockedly driven by introducing compressed air in the chamber into the drive cylinder. Therefore, when the compressed air in the air chamber is introduced into the drive cylinder, the air in the air chamber expands rapidly, the temperature of the air in the air chamber decreases, and the resulting pressure drop also drives the piston. There is a problem that As described above, when the actuator is driven at a high speed in a state close to the adiabatic expansion, it is known that the driving output is reduced by about 30% as compared with the case where the actuator is expanded isothermally.

Similarly, in a measuring device, a precise control device, etc., when the pressure inside the pneumatic container is set to a constant value, when air is introduced into the container and filled, the temperature inside the container rises and the air temperature rises, Therefore, the pressure also rises. Therefore, there is a problem that it takes a long time until the temperature of the compressed air becomes stable and the pressure becomes constant. For example, in the case of an air cuff used to measure blood pressure, when filling the cuff with air, the air temperature rises because it is close to adiabatic compression,
There is a problem that the pressure in the cuff is not stable until the air temperature in the cuff becomes constant and accurate blood pressure measurement cannot be performed.

In order to deal with such inconvenience, for example, in a measuring instrument for measuring the flow rate, consumption amount, etc. of air, a fan is arranged in a pressure vessel filled with air of a predetermined pressure to stir the air. As a result, the air temperature is made uniform and pressure fluctuations are stabilized quickly. However, in the above method, a fan and a drive source for driving the fan must be provided in the pressure vessel, and cannot be used for a portable tool such as a nail driver or a small blood pressure measuring instrument. .

[0006]

SUMMARY OF THE INVENTION The present invention solves the above problems and provides a drive system,
It is an object of the present invention to provide a pressure vessel capable of promptly stabilizing the air pressure by reducing the change of the internal air temperature by promoting the heat conduction of compressed air in the pressure vessel of the capacity system.

[0007]

To achieve the above object, in the pressure vessel according to the present invention, a heat conductive material having a high heat conductivity and a small volume is housed so that the contact area with the internal air becomes large. It is characterized by

As the heat conducting material, a bundle of thin metal wires or a porous metal may be used.

Further, the container may be formed of a flexible material, and a heat conducting material having flexibility may be filled and housed inside the container.

[0010]

According to the above-mentioned structure, when the compressed air suddenly flows into the pressure vessel, the pressure in the pressure vessel rapidly increases, so that the air temperature rises.
However, the thermal energy of this air is transferred to the heat conducting material. Since the heat conductive material has good heat conductivity and a high heat transfer rate, the temperature rise of the air inside the pressure vessel can be small, and the air pressure can be quickly stabilized.

On the contrary, when a large amount of compressed air instantaneously flows out of the pressure vessel, the temperature is lowered due to the rapid expansion of the compressed air, but heat is supplied from the heat conducting material. Therefore, the rise in air temperature can be suppressed to a small level,
The air pressure stabilizes quickly.

If a bundle of thin metal wires or a porous metal is used, the simplest and most efficient heat conducting material can be obtained.

Further, according to the structure in which the container is made of a flexible material and the flexible heat-conducting material is filled and contained in the container, it can be used as an air cuff of a blood pressure measuring instrument. The present invention can be applied.

Therefore, according to the present invention, the rise of the air temperature in the pressure vessel of the drive system and the capacity system can be suppressed without requiring a special cooling device such as a fan or a drive source thereof. The performance of the pressure vessel can be improved without impairing the advantage of small size and light weight in tools and measuring instruments.

[0015]

Embodiment 1 FIG. 1 (a) shows an air flow rate measuring device, which is composed of a metal pressure vessel 1 of a constant volume filled with compressed air of a predetermined pressure, and an object 2 to be measured. The amount of compressed air consumed by the measured object 2 is measured by measuring the compressed air pressure in the pressure vessel 1 before and after the measured object 2 is driven.

In the pressure vessel 1, copper, aluminum,
A thin metal material having high thermal conductivity such as stainless steel is formed as the thin metal wire 3 so as to have a small volume, and is filled and housed in a rolled shape so as to have a large contact area with the internal air. In the case of steel wool, for example, the metal thin wire 3 filled in the pressure vessel 1 of 500 cc is 3
Since it can be constructed with a volume of about cc, the capacity of the pressure vessel 1 itself is not largely sacrificed. Heat conductive material is thin wire 3
Instead of being formed as, a porous metal having high thermal conductivity may be used.

According to the above construction, when the compressed air is suddenly introduced into the pressure vessel 1 from the compressed air supply source 4 before the measured object 2 is driven, the pressure in the pressure vessel 1 rapidly increases. The air temperature rises, but the thermal energy of this air is transmitted from the metal wire to the inner wall of the inner wall of the pressure vessel 1 as shown in FIG. 2 (b), and is further radiated from the pressure vessel 1 to the outside. . Since the metal thin wire 3 has good thermal conductivity and a high heat transfer rate, the temperature rise of the compressed air in the pressure vessel 1 is suppressed to an extremely low level. As described above, when the compressed air is filled, the temperature of the compressed air rises as the pressure increases, but the heat passes through the thin metal wire 3 and the pressure vessel 1
Since the heat is radiated from the device, the temperature rise in the entire device is small, and the air pressure in the pressure vessel 1 is quickly stabilized. Therefore, accurate measurement can be performed immediately.

Next, when the measured object 2 is driven, the pressure vessel 1
Since a large amount of compressed air flows out instantaneously from, the temperature of the compressed air in the pressure vessel 1 drops as the compressed air expands rapidly. In this case, heat is rapidly supplied from the thin metal wire 3 as shown in FIG. 3C, and the pressure vessel 1 absorbs heat from the outside to supply the heat to the thin metal wire 3. Pressure vessel 1 with suppressed temperature drop
The air pressure inside stabilizes rapidly. Therefore, quick measurement can be performed.

Further, if the pressure vessel 1 also has high thermal conductivity, the efficiency will be further improved.

[0020]

[Embodiment 2] Next, an example in which the pressure vessel 1 is used as an air cuff of a blood pressure measuring device will be described with reference to FIG. Fill the thin wire 3. By the way, such a pressure vessel 1 has flexibility, and is expanded by the air pressure that has flowed into the inside, or is deformed by an external pressing force or the like.
Therefore, the thin metal wire 3 is accommodated by knitting the thin wire material into a bundle so as to have springiness so as to cope with the above deformation, or by gathering it so as to form a loop or a spiral. As a result, when the pressure container 1 contracts and then expands again, the thin metal wire 3 expands due to the spring property, so that the metal wires 3 are always evenly arranged in the pressure container 1.

According to the above arrangement, when measuring blood pressure,
The heat capacity of the thin metal wire 3 absorbs the heat generated by the compressed air when the air cuff is filled with air, and the rise in the air temperature in the air cuff is suppressed to a small level. Therefore, the time required for the air pressure in the cuff to stabilize becomes short, and the blood pressure can be measured quickly and with high accuracy.

In the case of this example, since a thin metal wire is used as the heat conductive material, the flexibility of the cuff is not impaired and no trouble occurs in use.

The heat conducting material 3 is not always the pressure vessel 1.
Need not be in contact with the inner wall of the. Also, the pressure vessel 1 does not have to be made of the heat conductive material 3. In such a case, after the measurement, heat is radiated from the thin metal wire 3 that has absorbed the heat, and the temperature is stabilized in equilibrium with the ambient air temperature, so that the next measurement is prepared. Therefore, it takes a relatively long time until the next measurement. However, a measuring instrument such as a sphygmomanometer that has a long measurement interval does not hinder the measurement.

[0024]

Third Embodiment Next, the pressure vessel 1 is used for a main air chamber 8 and a piston returning air chamber 9 formed around the driving piston / cylinder mechanism 6 and inside the grip 7 in a pneumatic impact tool such as a nail driver. Example of doing Fig. 3 (a) (b)
Explained by.

The main air chamber 8 is a compressed air supply source 4.
The compressed air supplied from is stored in advance, and when the head valve 10 is opened, the compressed air is supplied into the cylinder 6b to act on the upper surface of the drive piston 6a and strike it. At this time, the air in the cylinder 6b on the lower surface side of the drive piston 6a is compressed. The piston return air chamber 9 takes in the compressed air in the cylinder 6b from the through hole 11 and closes the head valve 10 so that the supply side of the drive cylinder 6b communicates with the exhaust port 12 through the through hole 11 to drive the piston 6a. The lower surface of the drive piston 6a is raised to return to the top dead center position. Therefore, the compressed air in the main air chamber 8 and the piston return air chamber 9 is continuously expanded and compressed.

The housings a of the main air chamber 8 and the piston return air chamber 9 are made of a metal having a high thermal conductivity such as aluminum, and the inside of each chamber is made of stainless steel, copper or the like having a high thermal conductivity. A thin metal wire 3 (for example, a copper wire having a wire diameter of 0.002 mm) rolled into a bundle is filled and arranged.

In the above structure, the compressed air supply source 4 is provided in the main air chamber 8 before the pneumatic impact tool is driven.
Compressed air is supplied from and is maintained at a predetermined pressure.
When the head valve 10 is opened and the compressed air in the main air chamber 8 is introduced into the drive cylinder 6b as shown in FIG. 6B, the compressed air in the chamber 8 expands rapidly, causing a temperature drop. However, the compressed air comes into contact with the heat conducting material composed of the bundle of metal fine wires 3 and receives heat from the metal fine wires 3, so that the temperature decrease is suppressed to an extremely small level. As a result, the drop in the air pressure in the main air chamber 8 is suppressed, so that the piston 6a is driven while maintaining a high pressure. The thin metal wire 3 is in contact with the inner wall of the housing a, absorbs the heat released to the compressed air in the main air chamber 8 from the outer wall of the housing a, and changes the temperature of the compressed air supplied from the compressed air supply source 4. Is rapidly maintained at room temperature to prepare for the next shock actuation.

Similarly, when the compressed air is introduced into the piston return air chamber 9 when the piston 6a descends, the temperature of the air in the air chamber rises. Since the metal wire 3 is brought into contact with the metal wire 3 to be cooled, the increase in the air temperature is suppressed, the damping of the impact force due to the back pressure can be reduced, and the driving force can be increased. The thin metal wire 3 radiates the heat absorbed from the air in the air chamber 9 from the outer wall of the housing a,
Prepare for the next ascending return operation of the piston 6a.

[Brief description of drawings]

1 (a), (b), and (c) are an overall schematic diagram of an air flow rate measuring device, an explanatory diagram when compressed air flows into a pressure vessel, and an explanatory diagram when compressed air flows out, respectively.

FIG. 2 is a schematic sectional view of an air cuff.

3A and 3B are schematic cross-sectional views of a pneumatic impact tool before and after operation, respectively.

[Explanation of symbols]

 1 Pressure vessel 3 Heat conduction material (fine metal wire)

Claims (3)

[Claims] 1. A pressure vessel comprising a heat conductive material having a high heat conductivity and a small volume so as to have a large contact area with internal air. 2. The pressure vessel according to claim 1, wherein the heat conductive material is a bundle of thin metal wires or a porous metal. 3. The pressure vessel according to claim 1, wherein the vessel is formed of a flexible material, and a flexible heat conductive material is filled and housed inside the vessel.