JPH0571153B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a roots blower for a carbon dioxide laser beam oscillator. The present invention relates to a roots blower equipped with a sealing mechanism that very effectively blocks outside air from entering the casing.

(Prior art) A Roots blower for a carbon dioxide laser beam oscillator has a suction pressure of approximately 30 Torr and a discharge pressure of approximately 180 Torr, and applies this differential pressure to force the passage of carbon dioxide into the laser beam oscillator. When using a vacuum pump such as a piston pump or oil-sealed rotary pump to apply this differential pressure, oil droplets may get mixed into the carbon dioxide gas and cause trouble to the lens surface in the laser beam oscillator. Roots-type blowers are attracting attention because they are capable of dry operation and can generate a powerful vacuum despite their small size.

However, conventionally, as shown in FIG. 3, a rotor shaft f of a roots blower a is passed through a housing c from a casing b in which a roots rotor is fitted, supported by a bearing e within the housing, and projected into a timing gear chamber d. An oil seal h is provided inside the bearing e of the housing c, or an oil stopper g is further provided in the housing chamber c in contact with the timing gear chamber d as shown in FIG.
Alternatively, a mechanical seal is used instead of the oil seal h shown in FIGS. 3 and 4.

(Problems to be Solved by the Invention) When the Roots blower having the above configuration is used by interposing it in the closed pipe line described above, the inside of the Roots blower a is evacuated by the vacuum pump p, and then carbon dioxide gas is injected. However, the oil seal h or mechanical seal cannot completely prevent minute oil from flowing from the oil bath type or grease bath type bearing e to the rotor shaft f and getting wet on the low-pressure casing b. Oil is mixed into the circulating carbon dioxide gas and adheres to the lens of the carbon dioxide laser beam oscillator i, causing a chemical reaction and causing the expensive lens to be replaced. In order to prevent such accidents, the Roots blower is overhauled regularly, but the overhaul cycle is about three months at most, so it cannot last long.
Moreover, it is impossible to stop supplying oil and grease to bearing g during that time. In addition, when grease is used as a lubricant, the lifespan of the grease is much shorter than the periodic period of overhaul, and if the grease is not replaced and replenished, dry operation will occur, and rubber particles due to the wear of the rubber lip of the oil seal h will be scattered. There is a risk that fine powder will enter casing b and mix with carbon dioxide gas. In addition, when using a mechanical seal, the conditions for maintaining the seal are difficult, so the above-mentioned troubles are more likely to occur sooner than when using an oil seal, and this increases maintenance costs.
There are many problems that need to be improved.

(Means for Solving the Problems) To solve the problems mentioned in the previous section, there are the following methods: Preventing oil from leaking from bearing lubrication, Strengthening the sealing means, etc., but the present invention specifically solves the problems. The purpose of this system is to feed low-pressure carbon dioxide, which is a mixture of several gases, from the suction side of a roots blower from which air has been expelled, apply a differential pressure with the blower, and discharge it from the discharge side. In the Roots blower, a circulation is created in a closed pipe in which carbon dioxide gas is supplied to the inlet of a carbon dioxide laser beam oscillator, and the carbon dioxide returned to a low pressure and discharged from the outlet is sent to the suction side. A labyrinth corresponding to the inner periphery of the shaft insertion hole is provided, an annular chamber groove surrounding the rotor shaft is formed in the housing following the shaft insertion hole, and a four-way groove is further formed between the bearing supporting the rotor shaft and the chamber groove. The rotor shaft is characterized in that a lip-shaped sealing material made of ethylene chloride resin is installed in contact with the rotor shaft.

(Function) On the Roots rotor shaft protruding into the housing, in the Roots blower that corresponds to the inner surface of the shaft hole of the housing, the rotor shaft has a 0.1 mm diameter on the inner surface of the shaft hole of the housing.
It is normal to provide a labyrinth close to each other to produce a shaft sealing effect, but in addition to this normal effect, the labyrinth of the present invention has an annular chamber groove surrounding the rotor shaft of the housing following the shaft hole. This has a direct relationship with the formation of the rotor shaft, and it also has a correlation with the lip-shaped sealing material made of a specific material called ethylene tetrafluoride resin that is in contact with the rotor shaft between the bearing and the chamber groove. , produces effects unique to the present invention. The above-mentioned unique action is a synergistic action, and to explain the details, when there is a fine object that tries to enter the casing from the rotor shaft through the seal material, the inner space of the chamber groove expands. The purpose of this is to cause fine particles to fall to the bottom of the groove and be removed, preventing them from being sucked into the carbon dioxide gas that applies a differential pressure inside the casing. What hinders this is the pulsation that occurs in the chamber groove, and this pulsation is directly related to the rotational fluctuation of the circumferential surface of the Roots rotor rotating within the casing between the suction side and the discharge side. However, the labyrinth has the normal function of suppressing the pressure flowing into the casing to less than 2/3, and also prevents pulsation from occurring in the chamber groove, thereby completely eliminating the drop. In addition, the sealing material made of tetrafluoroethylene resin brings the lip into contact with the rotor shaft, preventing pulsation in the chamber groove and preventing sideways movement, and the above material further reduces wear on the lip. This suppresses the dust generation rate and enhances the sealing effect.

In addition, although it is outside the scope of the present invention, silicone grease was used to lubricate the bearing. Since this grease generates oil mist at temperatures above 65°C, it is not suitable for use as roots blowers for carbon dioxide laser beam oscillators, but in general roots blowers, it is common to suppress the temperature to below 65°C using a water cooling jacket, etc. Therefore, the present invention solves the oil mist generation problem by using such a cooling device.

(Example) FIG. 1 is a layout diagram of a carbon dioxide laser beam generator using a Roots blower according to the present invention, and FIG. 2 is a cutaway side view of main parts of the present invention.

In Figures 1 and 2, 1 is the built-in motor 2
This is a sealed Roots blower for a carbon dioxide laser beam generator, which is equipped with a rotor shaft 4 driven by a rotor 3 of a motor 2, which projects into a timing gear chamber 7 through a casing 5 and housings 6, 6 on both sides thereof. , the timing gear 8 is installed in the timing gear chamber 7. Although the rotor shaft, which is not directly driven by the motor but is interlocked by the timing gear 8, is not shown in the figure, the sealing mechanism is the same.

The rotor shaft 4 protruding into the housing 6 is made of tetrafluoroethylene resin and has a labyrinth 2 on its outer periphery.
The labyrinth pipe 21 provided with the screws 2 is fitted in a non-rotatable manner and passed through the shaft hole 9 provided in the housing 6. Reference numeral 10 denotes an annular chamber groove provided in the housing 6 following the shaft hole 9 and wrapped around the rotor shaft 4 passing through the center. A mirror-finished sleeve 23 made of a metal tube is fitted and fixed to the chamber groove 10.
cross it. (A cannula is not always necessary)
The chamber groove 10 has a width of about 10 mm and a depth from the mantle tube 23 to the inner circumference of about 10 mm. The housing 6 is provided with a seal fitting hole 11 and a bearing fitting hole 12 following the chamber groove 10. The fitting hole 12
The bearing 25, which is fitted in and passed through the rotor shaft 4, is
The ball 25a is lubricated with silicone grease. Specifically, Toshiba GE Silicon TSK−
I used the product with the product name 5401L. It was found that this grease does not evaporate at a temperature of 1×10 ^-3 Torr from room temperature to 65°C, and evaporates at around 30 Torr when the temperature exceeds 65°C. For this reason, the bearing 25 must maintain a temperature of 65° C. or less.

24 is a tetrafluoroethylene resin seal which is fitted into the seal fitting groove 11 between the bearing 25 and the chamber groove 10 and whose lip is in contact with the sleeve 23; I used something.

An oil separating member 26 is installed around the rotor shaft 4 at the boundary between the housing 6 and the timing gear chamber 7, and a rubber oil seal 27 seals off the oil in the timing gear chamber 7.

As shown in FIG. 1, the roots blower 1 of the above embodiment connects the closed pipe line 32 on the outlet side of the carbon dioxide laser beam oscillator 31 to the suction port of the casing 5, and connects the closed pipe line 33 on the discharge side to the inlet of the oscillator 31. Connect to the end. The closed pipe line 33 is cooled by an intercooler 34. Roots blower 1 and closed pipe line 3
2 and 33 are evacuated by a vacuum pump P before filling with carbon dioxide gas, and then filled with carbon dioxide gas mixed with several types of gas and circulated.The holding pressure of closed pipes 32 and 33 is as described above. It is as follows. In the past, during operation, the pressure in the timing gear chamber was pulled by a vacuum pump to maintain a vacuum, but this is not necessarily necessary in the present invention. This is due to the synergistic effect of the related formation of the labyrinth and the chamber groove and the parallel arrangement of the labyrinth, the chamber groove, and the seal made of tetrafluoroethylene resin, and is unique to the present invention.

(Effects of the Invention) The present invention provides a roots blower for a special purpose such as a carbon dioxide laser beam oscillator, in which a roots rotor shaft protruding from a housing is provided with a labyrinth corresponding to the inner periphery of the shaft insertion hole in the housing, and a shaft insertion hole is provided in the housing. Subsequently, an annular chamber groove is formed surrounding the rotor shaft, and a lip-shaped sealing material made of tetrafluoroethylene resin is placed in contact with the rotor shaft between the bearing that supports the rotor shaft and the chamber groove. As mentioned above, it has a special configuration in which it is installed in a similar manner, and as mentioned above, it has a synergistic effect and effect adapted to the intended use, and has an extremely advantageous effect for a carbon dioxide laser beam oscillator.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention, FIG. 1 is a layout diagram of a carbon dioxide laser beam generator using a roots blower of the present invention, and FIG. 2 is a cutaway side view of essential parts of the present invention. 3 and 4 are explanatory diagrams of the conventional example. 4...Rotor shaft, 5...Casing, 6...Housing, 9...Shaft hole, 10...Chamber groove,
22... Labyrinth, 24... Tetrafluoroethylene resin seal.

Claims (1)

[Claims] 1. Low-pressure carbon dioxide, which is a mixture of several gases, is sent from the suction side of the Roots blower from which air has been expelled, and the blower applies a differential pressure to discharge it from the discharge side, and the discharged gas is supplied to the entrance of the carbon dioxide laser beam oscillator. In a Roots blower that generates circulation in a closed pipe in which the carbon dioxide gas returned to a low pressure and discharged from the same outlet is sent to the suction side, a Roots rotor shaft protruding into the housing corresponds to the inner periphery of the shaft insertion hole of the housing. A labyrinth is provided, an annular chamber groove surrounding the rotor shaft is formed in the housing following the shaft insertion hole, and a lip-shaped chamber groove made of tetrafluoroethylene resin is formed between the bearing supporting the rotor shaft and the chamber groove. A roots blower for a carbon dioxide laser beam oscillator, characterized in that a sealing material is installed in contact with a rotor shaft.