JPS62228691A - Roots type vacuum pump - Google Patents

Abstract

PURPOSE:To prevent production of gas due to vacuum of an insulating material for covering the wire material of a stator and to shut off suction of the gas to the interior of a casing, by a method wherein a can is inserted in the inner periphery of a stator for securing, and outer gas is prevented from mixing in vacuum atmosphere in a casing. CONSTITUTION:A can 21 is engaged in a manner to make contact with the inner peripheral surface of a stator 17, an insertion end 22 is pressed against a rubber plate 28 engaged with the inner surface of a motor case 6, and outer end 23 is pressed against an outer peripheral ring 30 of a bearing 16. this constitution enables prevention of production of outer gas to the inner periphery of the stator 17 resulting from suction of the negative pressure of the insulating material of the stator 17 and mixing of the outer gas in vacuum atmosphere in the casing 1. This constitution is adapted for the peculiar action of a root type vacuum pump with a built-in motor, prevents final arrival at a vacuum desired value and mixing of outer gas, being impure gas, in, for example, the carbonic acid gas circulating circuit of a carbonic acid gas laser oscillator, and enables production of an effect in that purity of carbonic acid gas is prevented from being damaged.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to roots-type vacuum pumps and has a particular field of application in which carbonic acid is adapted for use in laser beams.

(Prior art) Vacuum pumps are widely used for carbon dioxide applications such as laser beam oscillators, food products, and other vacuum equipment applications. No blower has ever noticed that outer gas is generated from the insulating material of the motor stator and taken measures against it.

Figure 3 shows a conventionally used, completely sealed, high-vacuum roots-type pump with a built-in motor, and the inner periphery of the stator a of the built-in motor is open toward the rotor. It is something.

However, the windings of the stator a'I are made of extremely thin conducting wires covered with insulating materials such as plastics made fluid by a solvent, and although the solvent is evaporated and dried, the It remains and is contained in.

Of course, a motor that loosens will not cause any actual damage under normal usage conditions and will not be considered a problem. On the other hand, in vacuum pumps, especially vacuum pumps for carbon dioxide laser beam oscillators, in order to force carbon dioxide gas through the oscillator and circulate it, a casing is inserted in the gas circulation circuit to create a differential pressure between the suction side and the discharge side. If a vacuum pump such as an oil-sealed rotary pump is used to generate a Roots-type vacuum pumps with a built-in motor that are operable, can provide a strong vacuum even though they are small, and do not impair the purity of the circulating carbon dioxide by introducing foreign gases into the circulating carbon dioxide gas have attracted attention and have been put into practical use. ing.

However, in the conventional motor-built-in roots-type vacuum pump shown in FIG. 3, the inventors have found that a small amount of 7 terps is mixed into the circulating carbon dioxide gas.

In other words, the volume expansion of liquid gas can be expressed by a simple calculation formula, so the vaporization outer of ice is
When rr, Q is 760 cc, and it is calculated that an unexpected expansion of the body M occurs. The inventors of the present invention have found that the main source of these 7 turbulences is the solvent remaining in the insulating material covering the wires of the stator. This is clear from the fact that the present invention completely shuts off the outer gas.

However, if the above-mentioned gas enters the casing C, which is made up of a vacuum atmosphere, the achievement of the target degree of vacuum will be significantly delayed, and if the carbon dioxide is inserted into the carbon dioxide gas circulation path of the laser beam oscillator, the carbon dioxide The outer gas mixes with the carbon dioxide gas, impairing its purity, and as in the case of oil droplets, it causes problems with the lens, etc. as described in 1itf.・As shown in the figure, one rotor d protrudes into the atmosphere, is connected to the output shaft e of an external motor m-, by a coupling f, and the outer periphery of the coupling r etc. is sealed with a boar body 9. A pressure difference is created between the inside of the casing C-, and the inside of the casing 9, so that the outside air is in a negative pressure atmosphere in the casing c-.
1, and even if measures are taken to prevent the leakage with mechanical seals, oil seals, etc., it is difficult to sustain the sealing action that can withstand large differential pressures.6 In addition, as shown in Figure 5, the motor built-in fluid In the motor ITL-, which is used for a medium pump or a liquid-lubricated land pump, the inner periphery of stator-1 is used to prevent liquid from entering from the rotation-Tj side and stator l from being exposed to moisture. It is known that the f'7+ configuration is cut off by can K, but
These pumps are in casing C↓′! Sky does not occur,
There is no suction of outer gas ν1.

(Problems to be Solved by the Invention) As explained with reference to FIG. 3, the present invention is effective in preventing outer busses generated from the stator and entering the negative pressure casing in a built-in roots type vacuum pump. The problem is to be able to prevent this from happening.

(Means for Solving the Problems) The present invention aims to solve the problems mentioned above, and the gist of the invention is to house a pair of roots-shaped rotors in a casing, and to connect the rotor shafts to one another. A timing gear is attached to each rotor shaft on the outside of the housing, and a timing gear is installed on each rotor shaft on the outside of the housing. In a closed roots vacuum pump connected to the rotor of a built-in motor, a fixed The inner circumference of (
This is characterized in that a can for cutting off the outer gas described in item 11 is inserted and fixed to prevent the mixture of outer gas into the vacuum atmosphere inside the casing.

A preferred embodiment of the invention will now be described.

(Example) FIG. 1 is a longitudinal side view, and FIG. 2 is a perspective view of the can.

In the figure, reference numeral 1 denotes a casing 1 having a suction port (not shown) and a discharge port 2, and a housing 3.4 constituting an end portion is provided on both sides of the casing 1. Reference numeral 5 designates a timing gear cover that is bonded and fixed to the outside of one housing 3, and 6 is a motor casing that is bonded and fixed to the outside of the other housing 4.

A pair of roots-shaped rotors 7.9 are housed in the casing 1,
The rotor shaft 8.10 protruding on both sides is supported by the bearing 11.12 of the housing 3 on the left side in FIG. housing 4
The rotor shaft 10 is supported by bearings 15, 16 of
is a shaft 19 of a rotor 18 which is formed into a large shape and rotates around the center of a circumferential rotor 17 attached to the motor casing 6, and the shaft 1
The two ends are supported by bearings 20 of the motor casing 6.

The present invention has a configuration as described in +iir.The can 21 shown in FIG. Insert it into! #i O-ring 24 fitted on the outer periphery of one end 23
is pressed onto the inner peripheral wall of the fitting groove 29 of the bearing 16, and its outer end 23 is inserted into the outer peripheral ring 30 of the bearing 16, and the integrally formed end [26
The rotor shaft 10 is warmly passed through the center hole 27 provided in the center hole 27.

(Operations and Effects of the Present Invention) As described in the section of Means for Solving Problems and the section of Examples, the present invention provides an outer periphery of the fixed f by negative pressure suction of the insulating material of the stator. To prevent the generation of busses and the intrusion of the after gas into the vacuum atmosphere inside the casing, a can is inserted and fixed on the inner periphery of the stator to prevent the generation and intrusion of busses. This configuration is adapted to the specific action of a roots-type vacuum pump equipped with a built-in motor, and is designed to prevent impurities from reaching the final vacuum target value and, for example, from impurities in the carbon dioxide bus circulation circuit of the carbon dioxide 7Y thread laser beam oscillator.
This has the end effect of not impairing the purity of the carbonated bath by mixing in some outer gas.

[Brief explanation of drawings]

1.2 shows an embodiment of the present invention, with FIG. 1 being a longitudinal sectional front view and FIG. 2 being a perspective view of the can. Figure 3 is a cut-away side view of a conventional roots-type vacuum pump with a built-in motor.
FIG. 4 is a partially cutaway side view of a conventional roots-type vacuum pump with an external motor, and FIG. 5 is a sectional view of a conventional water pump with a built-in motor. Applicant 7 Co., Ltd. Represented by Patent Attorney Yu Sonobe Figure 5 C-2i

Claims (1)

[Claims] A pair of Roots-shaped rotors are housed in a casing, the rotor shafts are supported through the housing, a timing gear is attached to each rotor shaft on the outside of one housing, a motor casing is provided on the outside of the other housing, and one rotor shaft is In a closed roots vacuum pump which is connected to the rotor of a built-in motor attached to the casing, in order to block the generation of outer gas and suction into the casing due to the vacuum of the insulating material covering the wire of the stator, A roots-type vacuum pump characterized in that a can for blocking the outer gas is inserted and fixed on the inner periphery of the stator to prevent the outer gas from being mixed into the vacuum atmosphere inside the casing.