1. Field of the Invention
The present invention relates to a self-tightening type sealing device and an isotropic pressing apparatus.
2. Description of the Related Art
A self-tightening sealing device is known as a device based on the technique of sealing fluid in a high-temperature ultra-high pressure apparatus with use of such a movable member as a piston. According to this known self-tightening sealing technique, a higher seal is created on a sealing surface by utilizing an internal pressure. Those described in “Isotropic Pressing Technique” (written by Mitsue KOIZUMI, et al., The Nikkan Kogyo Shinbun, Ltd., published Apr. 13, 1988, p. 287˜296) and Japanese Utility Model Laid Open Publication No. 170766/1986 are publicly known.
According to the conventional technique described in the above “Isotropic Pressing Technique,” in a self-tightening type sealing device in which a sealing member is tightened with an internal pressure, a tightening force imparting device for tightening the sealing member is used separately from the internal pressure. A tightening nut has been adopted as the said tightening force imparting device.
According to the technique described in the above Japanese Utility Model Laid Open Publication No. 170766/1986, a spring mechanism is attached to the tightening nut to compensate for the abrasion of the sealing member.
In the above conventional techniques, in order to obtain an initial seal in a low pressure region stably, it is necessary to manually tighten the tightening nut strongly. However, if the strongly tightened state is left as it is, it becomes very difficult to insert or remove the self-tightening type sealing device into or from a pressure vessel or a cylinder.
According to the above conventional techniques, in view of the point just mentioned above, the tightening nut is loosened manually in the device inserting or removing operation. However, in an isotropic pressing apparatus or the like in which the above inserting and removing operations are performed frequently, adjustment of the tightening force of the tightening nut by manual operation is very troublesome.
Further, in the type wherein a lowering of the tightening force caused by wear or deformation is compensated for using a spring mechanism, the range of the compensation is narrow and therefore, in the case of occurrence of wear or the like exceeding the compensation limit, it is necessary to make adjustment again using a tightening nut.