JPS6314372Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an exhaust system using a turbo-molecular pump or a cryopump in an electron microscope or the like.

Turbo molecular pumps (hereinafter abbreviated as molecular pumps) or cryopumps are used to evacuate electron microscopes, etc., but molecular pumps have a high-speed rotation mechanism, and cryopumps are driven at high speed. When these pumps are used, various measures have been taken to mount them so that vibrations from these pumps are not transmitted to the electron microscope. Among these, one in which the pump is suspended from a main exhaust pipe fixed to a frame via a bellows is practical because the device can be assembled compactly.

FIG. 1 is for explaining such a conventional exhaust system. Reference numeral 1 indicates a mirror body of a transmission electron microscope, and the mirror body is attached to a pedestal 2. The pedestal 2 has four pillars 4a, 4b, 4 equipped with vibration isolating springs 3.
c and 4d (4c and 4d are not shown) on the floor 5. 6 is placed behind the mirror body 1, and sub-exhaust pipes 7a, 7 are provided in each chamber of the mirror body.
The main exhaust pipe 6 is connected to the pedestal 2 via b and 7c, and the lower end 6a of the main exhaust pipe 6 protrudes from the lower surface of the pedestal 2. 8 is a molecular pump, and the suction port 9 side of the molecular pump is connected to the lower end 6a of the main exhaust pipe 6 via a bellows 10 made of stainless steel, for example. In this case, the lower end of the molecular pump 8 is floating above the floor 5. In other words, the molecular pump has a bellows of 10
It is supported so as to be suspended from the main exhaust pipe 6 via the main exhaust pipe 6. Although not shown, an oil rotary pump is connected to the discharge port 11 of the molecular pump 8 via a pipe. A protective member 12 is made of an elastic material such as rubber or plastic.

In such an evacuation system, when the inside of the mirror is evacuated, the molecular pump 8 is sucked upward by back pressure, and as a result, the bellows 10 receives a force in the direction of compression. 8 and applies an opposite force to the bellows 10 to prevent the bellows 10 from being significantly compressed. Therefore, since the bellows 10 is not compressed, it is possible to avoid a situation where large vibrations of the pump are transmitted to the electron microscope.

However, in the conventional apparatus as described above, vibrations from the molecular pump 8, especially sound waves, are transmitted to the exhaust pipe side through the protective member 12, which is a factor that hinders improvement of image quality in an electron microscope or the like.

This proposal was made to solve such conventional drawbacks, and includes a mirror, an exhaust pipe connected to the mirror, and a bellows connected to the exhaust pipe to evacuate the interior of the mirror. A device comprising a turbo molecular pump or a cryopump and an elastic body inserted between an exhaust pipe and a pump body to prevent the bellows from being compressed when evacuated, through the elastic body. In order to reflect the sound waves transmitted from the pump side to the exhaust pipe, a member or layer made of a material having a higher density than the elastic body is provided in the middle of the elastic body, as shown in the drawings below. An embodiment of the present invention will be described in detail based on this figure, but some components that are the same as those in FIG. 1 are given the same numbers and their explanations will be omitted.

In FIG. 2 showing the main part of an embodiment of the present proposal,
The cylindrical protective member made of rubber is different from the conventional one.
It is divided into two protection members, a and 13b.
In between, an intermediate body 14 made of a material having a higher density than the material of the protective member, such as iron, is inserted into both the protective members 13.
It is glued and interposed between a and 13b. This intermediate body 14 is also integrally connected to the bellows 10 at its annular inner surface.

In such a configuration, since the density of iron, which is the material of the intermediate body 14, is extremely high compared to the density of the rubber, which is the material of the protective member 12, the impedance of the intermediate body 14 for sound wave conduction is equal to the impedance of the protective member. It becomes extremely large in comparison. Therefore, the sound waves generated by the molecular pump 8 and transmitted to the protection member 13a are reflected at the interface between the protection member 13a and the intermediate body 14 at a high rate, and are hardly transmitted to the exhaust pipe 6 side.

FIG. 3 shows another embodiment of the present invention. In this embodiment, the diameter of the cylindrical protection member 13a is made larger than the diameter of the protection member 13b, and the bellows 10 is divided into two bellows 10a, 10b. Divide into
The diameter of the bellows 10a is made larger than the diameter of the bellows 10b.

In this way, the protective member 13a, the intermediate body 1
4. In order for the sound waves to be transmitted sequentially through the protection member 13b, the sound waves must be bent at right angles at the two boundaries where the intermediate body 14 and both protection members 13a and 13b contact, so that the sound waves are further transmitted to the exhaust pipe side. The proportion of sound waves that are emitted can be reduced.

In the above-described embodiments, the case where a molecular pump is used as the pump has been described, but the present invention can be similarly applied to the case where a cryopump is used.

Further, in the above-mentioned embodiment, only one stage of the intermediate body was provided, but the effect can be further enhanced by increasing the number of stages.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional example, FIG. 2 is a diagram showing one embodiment of the present invention, and FIG. 3 is a diagram showing another embodiment of the present invention. 1: Mirror body, 2: Frame, 3: Spring, 4a, 4b:
Pillar, 5: Floor, 6: Main exhaust pipe, 8: Molecular pump,
10: Bellows, 12, 13a, 13b: Protective member, 14: Intermediate.

Claims (1)

[Scope of utility model registration request] a mirror body, an exhaust pipe connected to the mirror body, a turbo molecular pump or a cryopump connected to the exhaust pipe via a bellows for evacuating the mirror body, and the bellows when evacuated. In a device consisting of an elastic body inserted between an exhaust pipe and a pump body to prevent the pump from being compressed, the device reflects sound waves transmitted from the pump side to the exhaust pipe via the elastic body. An exhaust system for an electron microscope or the like, characterized in that a member or layer made of a material having a higher density than the elastic body is provided in the middle of the elastic body.