KR20100068638A - Bellows type mechanical seal assembly - Google Patents

Abstract

A bellows type mechanical sealing assembly is disclosed for preventing fluid from leaking in the sliding sealing surface between the rotor and the stator. The mechanical sealing assembly includes a pair of sealing rings mounted to the shaft, a bellows disposed between the pair of sealing rings to elastically press at least one of the pair of sealing rings, and fastening on the shaft. And a stator fixed by the means and rotating mutually with the shaft and in slidable contact with any one of the pair of sealing rings.

Description

Bellows type mechanical sealing assembly {BELLOWS TYPE MECHANICAL SEAL ASSEMBLY}

The present invention relates to a mechanical sealing assembly for sealing fluids of high pressure or fluctuating pressure, and more specifically, to a bellows type mechanical to prevent leakage of fluid in the sliding sealing surface between the rotor and the stator. A sealing assembly.

Sealing devices, in particular bellows-type mechanical sealing assemblies, are sometimes used to prevent the outflow of relatively high pressure process fluid to the motor driving the pump along the pump shaft.

This mechanical sealing assembly has a pair of sealing rings having opposing sliding surfaces and a metal bellows surrounding the shaft. The bellows is coupled with a cylindrical member having one end coupled to one of the pair of sealing rings and the other end connected to the shaft. The bellows not only separates the high pressure chamber from the low pressure chamber, but also elastically presses against the sealing ring opposite the sealing ring associated therewith.

Bellows-type mechanical sealing assemblies are well known in the art as disclosed in US Pat. Nos. 3,372,939, 3,776,560, 4,163,563, 4,365,816, and 4,453,722. The patent shows a metal bellows in which a plurality of annular members or diaphragms are stacked and the ends of which are welded to each other, the metal bellows being coupled to a sealing assembly.

Referring to Figure 1 will be described in more detail with respect to the conventional bellows type mechanical sealing assembly. 1 shows a mechanical sealing assembly disposed inside a housing 11 and enclosing a shaft 14 passing through the housing 11.

This mechanical sealing assembly has a stator (or insert) 16 and a rotor, the stator and the rotor having sliding sealing surfaces 20 and 22 in sliding contact with each other. The rotor is secured by an adapter 42 supported by a bearing 36 and is configured to rotate with the shaft 14.

The rotor includes a metal cylindrical support member 24 fixed by an adapter 42, a bellows 28 having one end coupled to the support member 24, and a metal ferrule having the other end of the bellows 28 coupled thereto. a metal ferrule 30 and a sealing ring 18 coupled with the metal ferrule 30. The sealing ring 18 has a sliding sealing surface 22 in sliding contact with the sliding sealing surface 20 of the stator 16. The bellows 28 elastically presses the sealing ring 18 toward the stator 16.

The bellows 28 has a plurality of laminated and rippled corrugated annular diaphragms which are welded at the inner and outer ends to form a series of inner and outer joints. The end diaphragm has an inner distal end without a joint, which is joined to the support member 24 by welding at one end and to one end of the ferrule 30 at the other end. Thus, the end diaphragms take the form of interacting or non-operating in the bellows structure.

The mechanical sealing assembly includes a first O-ring 32 to prevent high pressure sealed fluid from leaking along the shaft 14, and lubricant stored between the housing 11 and the mechanical sealing assembly leaks to the right in the drawing. A second o-ring 34 is provided to prevent it from becoming.

The above structure provides support for the closest diaphragm of the bellows, increasing the pressure capacity of the bellows. With this structure, all diaphragms of the bellows perform substantially the same mechanical support function.

However, since the bellows of the rotor moves in the vertical direction by the high speed rotation of the shaft, the bellows does not rotate at a constant radius but rotates at an irregular radius. As a result, the sliding sealing surface 22 of the rotor does not come into contact with the sliding sealing surface 20 of the stator 16 in an irregular pattern, but in an irregular pattern, whereby the coating of the sliding sealing surface 20 of the stator is broken. Cases often occur.

In particular, when such a mechanical sealing assembly is applied to a screw type high vacuum pump, the following problems arise.

Since the screw type high vacuum pump has a pair of screws installed in parallel to rotate in contact with each other, when the pump is operated, a high temperature of about 270 to 370 ° C is generated therein. Therefore, the stator 16 of the mechanical sealing assembly mounted on the input shaft side of the vacuum pump is exposed to the high temperature generated inside the vacuum pump as it is.

More specifically, since the stator 16 is made of metal, the high temperature heat generated by the vacuum pump is transferred to the stator 16 as it is. Therefore, the sliding sealing surface 20 of the stator 16 is deformed by the heat of high temperature, and a problem arises that the roughness of the sliding sealing surface falls. If the roughness of the sliding sealing surface falls, the life of the mechanical sealing assembly is shortened.

In addition, when the vacuum pump is operated, fluid flows into the gap between the stator 16 and the shaft. At this time, the fluid enters while pushing the diaphragm of the bellows 26 to the rear (left side in the drawing), so that the bellows 28 which has pushed the sealing ring 18 toward the stator 16 is compressed. Thus, a gap is created between the sealing ring 18 and the stator 16, so that the lubricant of the mechanical sealing assembly is introduced into the vacuum pump through the gap.

Although such a screw type high vacuum pump was developed about 20 years ago, although the mechanical sealing assembly used in such a high vacuum pump has the above-mentioned problems, no solution has been proposed. In particular, the expensive mechanical seal assemblies used in such screwed high vacuum pumps are being replaced at a cycle of about six months.

Accordingly, an object of the present invention is to provide a bellows type mechanical sealing assembly which can maintain the roughness of the sliding sealing surface by preventing centrifugal force from acting on the bellows.

Another object of the present invention is to provide a bellows type mechanical sealing assembly in which the contact force of the sliding sealing surface between the rotor and the stator can be increased when hydraulic pressure is applied to the bellows.

Still another object of the present invention is a bellows type mechanical seal that can prevent the transfer of high temperature heat generated inside the pump to the sliding sealing surface between the rotor and the stator when the mechanical sealing assembly is applied to a screw type high vacuum pump. It is to provide an assembly.

In order to achieve the above and other objects of the present invention, in accordance with an aspect of the present invention, a mechanical sealing assembly disposed inside the housing to seal a gap between the housing and the shaft, the pair of sealing rings mounted to the shaft And a bellows disposed between the pair of sealing rings to elastically press at least one of the pair of sealing rings, and fixed by the fastening means on the shaft to mutually rotate with the shaft. A mechanical sealing assembly is provided that includes a stator in slidable contact with any one of the sealing rings of.

The mechanical sealing assembly also includes a metal ferrule disposed between the bellows and the sealing ring in contact with the stator of the pair of sealing rings.

The bellows has a plurality of annular diaphragms, the inner and outer end portions of the annular diaphragm being joined by welding, respectively, and the outermost disposed diaphragm is welded with the metal ferrule and the other of the pair of sealing rings. The bellows functions as a compression spring to press the sealing ring in either direction.

Preferably, the sealing surface of the sealing ring sliding with the stator is coated with carbon, and the sealing surface of the support member opposite to the sealing surface of the sealing ring is coated with tungsten carbide. Carbon has a property of absorbing heat, and tungsten carbide has a property of dissipating heat, so that heat generated between sliding sealing surfaces can be effectively controlled.

The sealing ring sliding with the stator is movable in the axial direction of the shaft on the shaft, and the stator is immovable with respect to the shaft. Thus, the sealing ring can be pressed towards the stator by the bellows.

According to the above-described configuration, the bellows is disposed on the stator to prevent centrifugal force from acting on the bellows, thereby maintaining the roughness of the sliding sealing surface constantly.

When hydraulic pressure is applied to the bellows, the contact force of the sliding sealing surface between the rotor and the stator may increase.

When the mechanical sealing assembly is applied to a screw type high vacuum pump, it is possible to prevent the high temperature heat generated inside the pump from being transferred to the sliding sealing surface between the rotor and the stator.

Hereinafter, a bellows type mechanical sealing assembly according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a cross-sectional view showing a bellows type mechanical sealing assembly according to the present invention.

The mechanical sealing assembly of the present invention is disposed inside the housing 111 and surrounds the rotating shaft 114 passing through the housing 111, thereby sealing a gap between the housing 111 and the shaft 140.

The mechanical sealing assembly includes a stator and a rotor 124. The stator includes a first sealing ring 116 mounted to the housing 111, a bellows 128 having a plurality of laminated and rippled corrugated metal annular diaphragms, a metal ferrule 130 welded to a portion of the diaphragm, And a second sealing ring 118 fixed to the metal ferrule 130.

The first sealing ring 116 is axially displaceable with respect to the shaft 140, and the second sealing ring 118 is axially movable with respect to the shaft 140. The first sealing ring 116 is coupled with the second sealing ring 118 by a cylindrical bellows 128 and a cylindrical metal ferrule 130.

Bellows 128 includes a plurality of laminated and rippled corrugated annular diaphragms. The annular diaphragm is welded at the inner and outer distal ends to form a series of inner and outer joints, and of the plurality of annular diaphragms, the leading diaphragm 128a is joined by welding to the flange portion of the first sealing ring 116. The end diaphragm 128b is joined to the flange portion of the metal ferrule 130 by welding. The bellows not only functions like a compression spring, but also compensates for the eccentricity between the rotor and the stator.

The metal ferrule 130 is fixed to a part of the outer circumferential surface of the second sealing ring 118 and presses the second sealing ring 118 toward the rotor 124. The rotor 124 is firmly fixed to the shaft 114 by the adapter 142 and rotates with the shaft 114.

According to one aspect of the invention, the second sealing ring 118 and the support member 124 are arranged to be in contact with each other at sliding sealing surfaces 120 and 122 oriented perpendicular to the shaft 114. . The second sealing ring 118 is axially movable relative to the shaft, while the support member 124 is not axially movable relative to the shaft.

Preferably, the sealing surface 120 of the second sealing ring 118 is coated with carbon having endothermic properties, and the sealing surface 122 of the supporting member 124 is coated with tungsten carbide having exothermic properties.

In addition, the mechanical sealing assembly includes a first O-ring 132 to prevent high pressure sealed fluid from leaking along the shaft 114, and a sealed joint between the housing 111 and the first sealing ring 116. A second o-ring 134 is provided to prevent leakage of the fluid or lubricant.

It is common for the mechanical sealing assembly of the present invention to simultaneously apply a high pressure internal pressure. By the internal pressure applied to the mechanical sealing assembly, the second sealing ring 118 is pressed toward the support member 124 by the bellows 128.

Hereinafter, the operation of the assembly will be described taking as an example the case where the mechanical sealing assembly according to the present invention is applied to a shaft of a screw type high vacuum pump.

The mechanical sealing assembly of the present invention includes a first sealing ring 116, a bellows 128, a metal ferrule 130, a second sealing ring 118, and a rotor 124 as a stator, and rotates with the stator. The chair is mounted on the shaft of the vacuum pump.

In the case where the mechanical sealing assembly of the present invention is mounted on the shaft of the vacuum pump, the first sealing ring 116 is mounted on the input shaft side of the vacuum pump. Thus, since the bellows 128 does not rotate when the vacuum pump is operating, no rotational force acts on the bellows 128. Therefore, since the sliding sealing surface 120 of the second sealing ring 118 is in contact with the sliding sealing surface 122 of the rotor 124 in a constant orbit, the roughness of the sliding sealing surface of the rotor 124 is constant. Can be maintained.

In addition, since the rotor 124 is constituted by a ring, even if the rotor 124 rotates at a high speed with the shaft 114, the sliding sealing surfaces 120 and 122 have no influence. In addition, since the sliding sealing surfaces 120 and 122 contact each other while forming a circle of a constant diameter, no noise is generated in the mechanical sealing assembly, so that quietness can be maintained.

Since the O-ring 134 is installed between the stator and the housing 111, the vibration generated in the vacuum pump is absorbed by the O-ring 134 without being transmitted to the bellows 128. Therefore, vibration of the bellows itself is minimized, maximizing the stability of the mechanical sealing assembly.

In addition, a high heat of about 270 to 370 ° C. is generated inside the screw type high vacuum pump, so that the sealing sliding surfaces 20 and 22 are disposed at a position far from the vacuum pump. Therefore, since the sealing sliding surface is protected from high heat, there is no problem such as deformation by high temperature.

In addition, when fluid flowing inside the high vacuum pump is applied to the bellows 128 through a gap between the first sealing ring 116 and the outer circumferential surface of the shaft 114, the contact of the sliding sealing surface between the rotor and the stator increases. To prevent leakage of the fluid.

Although the present invention has been described with reference to the above embodiments, the protection scope to be protected is not limited by the above embodiments. The protection scope of the present invention is determined by the following claims.

1 is a cross-sectional view of a conventional bellows type mechanical sealing assembly.

2 is a cross-sectional view of a bellows type mechanical sealing assembly according to a preferred embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

111: housing

114: rotating shaft

116: first sealing ring

118: second sealing ring

124: stator

128: bellows

130: metal ferrule

Claims (6)

A mechanical sealing assembly disposed inside a housing to seal a gap between the housing and the shaft, A pair of sealing rings mounted to the shaft, A bellows disposed between the pair of sealing rings to elastically press at least one of the pair of sealing rings; And a stator fixed on the shaft and interrotating with the shaft, the stator in slidable contact with any one of the pair of sealing rings. The method of claim 1, And a metal ferrule disposed between the bellows and the sealing ring in contact with the stator of the pair of sealing rings. The method of claim 2, The bellows has a plurality of annular diaphragms, wherein the inner and outer ends of the annular diaphragm are each welded, and the outermost diaphragm is welded to the other of the metal ferrule and the pair of sealing rings. Mechanical sealing assembly. The method of claim 1, And the sealing surface of the sealing ring sliding with the stator is coated with carbon, and the sealing surface of the support member opposite the sealing surface of the sealing ring is coated with tungsten carbide. The method of claim 4, wherein And the sealing ring sliding with the stator is movable in the axial direction of the shaft on the shaft, the stator being immovable relative to the shaft. The method of claim 1, And a sealing member installed in the sealing ring in contact with the housing of the pair of sealing rings, and a sealing member provided in the stator to seal the interface between the stator and the shaft.

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