CN214466101U

CN214466101U - Magnetic Fluid Seals with Pin Sleeves

Info

Publication number: CN214466101U
Application number: CN202023333220.6U
Authority: CN
Inventors: 李德才; 赵文曦
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2020-12-31
Filing date: 2020-12-31
Publication date: 2021-10-22
Anticipated expiration: 2030-12-31

Abstract

The utility model discloses a magnetic liquid sealing device with a pin shaft sleeve. The magnetic liquid sealing device with a pin shaft sleeve comprises: a casing, a shaft, a shaft sleeve, a connecting component and a sealing component. It has a first end and a second end, the shaft is pivotally arranged in the chamber, at least one end of the shaft protrudes from the chamber, the shaft is sleeved in the casing and sleeved on the shaft, and one end of the shaft sleeve is provided with a shaft along the shaft. The radially extending positioning portion of the sleeve, the positioning portion is in contact with the end face of the first end of the shaft, the connecting assembly is used to connect the positioning portion with the first end of the shaft, and the sealing assembly is arranged in the chamber and sleeved on the shaft sleeve . The magnetic liquid sealing device with the pin bushing of the utility model has the advantages of simple structure, convenient installation, good sealing effect and the like.

Description

Magnetic liquid sealing device with pin shaft sleeve

Technical Field

The utility model belongs to the sealed field of mechanical engineering, specifically, relate to a take magnetic liquid sealing device of pin axle sleeve.

Background

The magnetic liquid sealing technology is that a closed magnetic loop is formed by a permanent magnet, a pole shoe, a pole tooth and a magnetic conduction shaft, magnetic liquid is limited in a sealing gap, and novel non-contact sealing of a plurality of O-shaped liquid sealing rings is formed. The leakage-free high-reliability high-pressure-resistant sealing ring has the advantages of zero leakage, no mechanical abrasion, long service life, high reliability and the like, and is used by more and more industries.

In the related art, in the sealed occasion of major diameter, high load, magnetic fluid seal structure requires to use magnetic material to make the axle, is unfavorable for using under the operating condition, consequently uses the mode of plus magnetic conduction axle sleeve to realize magnetic fluid seal frequently, but because there is the hole in the position of being connected between axle sleeve and the axle, under the strong magnetic force effect, the axle sleeve is the skew of easy atress and the assembly degree of difficulty is high, has the eccentric possibility of installation simultaneously, influences magnetic fluid seal device's sealed effect.

SUMMERY OF THE UTILITY MODEL

The present invention aims at solving at least one of the technical problems in the related art to a certain extent.

Therefore, the embodiment of the utility model provides a simple to operate, assembly are simple, sealed effectual magnetic liquid sealing device who takes pin axle sleeve.

According to the utility model discloses take magnetic liquid sealing device of pin axle sleeve, include: a housing having a chamber; a shaft having a first end and a second end, the shaft being pivotably disposed within the chamber, at least one end of the shaft extending from within the chamber; the shaft sleeve is arranged in the cavity and sleeved on the shaft, one end of the shaft sleeve is provided with a positioning part extending along the radial direction of the shaft sleeve, and the positioning part is opposite to the end face of the first end of the shaft; a coupling assembly for coupling the locating portion to a first end of the shaft; and the sealing assembly is arranged in the cavity and sleeved on the shaft sleeve.

According to the utility model discloses take magnetic liquid sealing device of pin axle sleeve links to each other location portion and the first end of axle through coupling assembling to the material of no longer counter shaft has limited to some extent, has effectively reduced the assembly degree of difficulty of axle sleeve with the axle, has guaranteed axle and axle concentricity, thereby has guaranteed the magnetic liquid sealing device's of taking the pin axle sleeve sealing performance.

In some embodiments, the connecting assembly includes positioning pins and fastening members, the positioning pins and the fastening members are spaced apart from each other in a radial direction of the shaft sleeve, the positioning portion is provided with a first pin hole penetrating through the positioning portion in an axial direction of the shaft sleeve, a second pin hole aligned with the first pin hole is provided in an end surface of the first end of the shaft, and the positioning pins are fitted in the first pin hole and the second pin hole.

In some embodiments, the fastening member is a screw or a bolt, a threaded hole is formed in an end surface of the first end of the shaft, the positioning portion is provided with a connecting through hole penetrating through the positioning portion in the axial direction of the shaft sleeve, the connecting through hole is a countersunk hole, and the fastening member penetrates through the connecting through hole and is in threaded fit in the threaded hole.

In some embodiments, the connecting assembly is a plurality of connecting assemblies, and the connecting assemblies are arranged at intervals along the circumferential direction of the shaft sleeve.

In some embodiments, a blind bore is provided in the end face of the shaft extending in the axial direction of the shaft.

In some embodiments, the magnetic liquid sealing device with the pin shaft sleeve further comprises an end cover, the end cover is sleeved on the shaft sleeve, and the end cover is detachably mounted on the shell and located on one side, protruding from the cavity, of at least one end of the shaft.

In some embodiments, the seal assembly comprises: the pole shoes are arranged in the cavities and sleeved on the shaft sleeve, the pole shoes are arranged at intervals along the axial direction of the shaft sleeve, gaps are formed between the inner circumferential surfaces of the pole shoes and the outer circumferential surface of the shaft sleeve in the radial direction of the shaft sleeve, and magnetic liquid is filled in the gaps; the permanent magnet is arranged in the cavity and sleeved on the shaft sleeve, and the permanent magnet is positioned between the adjacent pole shoes.

In some embodiments, the magnetic liquid sealing device with the pin shaft sleeve further includes a magnetism isolating ring disposed in the cavity and surrounding the shaft sleeve, an inner circumferential surface of the magnetism isolating ring is spaced apart from an outer circumferential surface of the shaft sleeve, the pole shoes include two outer pole shoes located at outermost sides in an axial direction of the shaft sleeve, and the magnetism isolating ring is respectively disposed between the outer pole shoes and the housing.

In some embodiments, the magnetic liquid sealing device with the pin shaft sleeve further comprises a sealing member arranged between the outer peripheral surface of the pole piece and the shell, the outer peripheral surface of the pole piece is provided with an annular groove, and the sealing member is matched with the annular groove.

In some embodiments, the inner circumferential surface of the pole piece is provided with a plurality of pole teeth, the plurality of pole teeth are arranged at intervals in the axial direction of the shaft sleeve, and the gap is formed between the inner circumferential surface of the pole teeth and the outer circumferential surface of the shaft sleeve.

Drawings

Fig. 1 is a schematic structural view of the magnetic fluid sealing device with a pin shaft sleeve of the present invention.

Fig. 2 is a partially enlarged view of a in fig. 1.

Reference numerals:

a magnetic liquid sealing device 100;

a housing 1; a chamber 11;

a shaft 2; a threaded hole 21; the connection through-hole 22; a blind hole 23;

a shaft sleeve 3; a positioning portion 31;

a connecting assembly 4; positioning pins 41; a fastener 42;

a seal assembly 5; a pole piece 51; the pole teeth 511; a permanent magnet 52; a magnetism isolating ring 53; a first magnetism isolating ring 531; a second magnetism isolating ring 532; a seal 54;

and an end cap 6.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining the present invention, and should not be construed as limiting the present invention.

A magnetic fluid seal device with a pin bush according to an embodiment of the present invention will be described with reference to fig. 1 to 2.

As shown in fig. 1-2, a magnetic fluid seal device 100 with a pin shaft sleeve according to an embodiment of the present invention includes a housing 1, a shaft 2, a shaft sleeve 3, a connecting assembly 4, and a sealing assembly 5.

The housing 1 has a chamber 11. The shaft 2 has a first end (right end in fig. 1) and a second end (left end in fig. 1), the shaft 2 is pivotably disposed within the chamber 11, at least one end of the shaft 2 protrudes from the chamber 11, and the left end of the shaft 2 protrudes from the chamber 11 in fig. 1.

The shaft sleeve 3 is arranged in the shell 1 and sleeved on the shaft 2, the shaft sleeve 3 is fixed relative to the shaft 2 so as to rotate along with the shaft 2, one end of the shaft sleeve 3 is provided with a positioning part 31 extending along the radial direction of the shaft sleeve 3, the positioning part 31 is opposite to the end face of the first end of the shaft 2, and preferably, the positioning part 31 and the end face of the first end of the shaft 2 are contacted and attached with each other.

The coupling assembly 4 couples the positioning portion 31 to the first end of the shaft 2. The sealing assembly 5 is arranged in the cavity 11 and sleeved on the shaft sleeve 3.

According to the utility model discloses take magnetic liquid sealing device 100 of pin axle sleeve is used for linking to each other location portion 31 with the first end of axle 2 through coupling assembling 4, from this, install axle sleeve 3 and axle 2 together through coupling assembling 4, reduced the installation and the assembly degree of difficulty between axle sleeve 3 and the axle 2, axle 2 can choose for use non-magnetic material to make, effectively reduced magnetic liquid sealing device 100's magnetism and leaked, guaranteed the sealed effect of taking the magnetic liquid sealing device 100 of pin axle sleeve.

In use, casing 1 accessible bolt mounting is on reation kettle's the cauldron body or on the cell body of stirred tank, and the axle links to each other with agitating unit (for example stirring paddle) to the material of drive agitating unit in to reation kettle or stirred tank stirs, and seal assembly prevents that the material in reation kettle or stirred tank from leaking moreover.

In some embodiments, the connecting assembly 4 includes positioning pins 41 and fastening members 42, the positioning pins 41 and the fastening members 42 are spaced apart in the radial direction of the sleeve 3, the positioning portion 31 is provided with a first pin hole penetrating the positioning portion 31 in the axial direction of the sleeve 3, a second pin hole aligned with the first pin hole is provided in the end surface of the first end of the shaft 2, and the positioning pins 41 are fitted in the first pin hole and the second pin hole.

Specifically, as shown in fig. 1, the positioning portion 31 of the boss 3 is provided with a first pin hole penetrating the positioning portion 31 in the left-right direction, the right end face of the shaft 2 is provided with a second pin hole aligned with the first pin hole, and the positioning pin 41 is inserted and fitted in the first pin hole and the second pin hole. When the shaft 2 and the shaft sleeve 3 are connected by the fastener 42, the shaft sleeve 3 is positioned relative to the shaft 2 by the positioning pin 41, so that the shaft sleeve 3 cannot rotate relative to the shaft 2 and the concentricity of the shaft sleeve 3 and the shaft 2 is ensured, and the rotation of the shaft sleeve 3 relative to the shaft 2 and the eccentricity of the shaft sleeve 3 relative to the shaft 2 caused by the strong magnetic force action of the sealing assembly 5 are avoided.

In some embodiments, the fastening member 42 is a screw or a bolt, the end face of the first end of the shaft 2 is provided with a threaded hole 21, the positioning portion 31 is provided with a connecting through hole 22 penetrating through the positioning portion 31 in the axial direction of the shaft sleeve 3, the connecting through hole 22 is a countersunk hole, and the fastening member 42 is threaded in the threaded hole 21 through the connecting through hole 22.

Specifically, as shown in fig. 1, the right end face of the shaft 2 is provided with a threaded hole 21, the positioning portion 31 is provided with a counter bore penetrating the positioning portion 31 in the left-right direction, and the counter bore is aligned with the threaded hole 21, the fastening member 42 is passed through the counter bore to be engaged with the threaded hole 21, thereby fixing the boss 3 to the right end of the shaft 2, and the head of the screw or bolt is located in the large bore section of the counter bore, i.e., the screw or bolt does not protrude from the right surface of the positioning portion 31.

In some embodiments, the connecting assembly 4 is plural, and the plural connecting assemblies 4 are arranged at intervals along the circumferential direction of the sleeve 3. Therefore, the stability between the shaft sleeve 3 and the shaft 2 is increased, and the shaft sleeve 3 is more stably fixed at the right end of the shaft 2.

In some embodiments, a blind bore 23 is provided in the end face of the shaft 2, extending in the axial direction of the shaft 2. According to the utility model discloses magnetic liquid sealing device 100 of area pin axle sleeve is through being equipped with the blind hole 23 along axle 2's axial extension in the terminal surface of axle 2 to saved the material of axle 2, alleviateed the weight of axle 2, effectively improved the antitorque ability of axle 2, and then improved the life of axle 2.

In some embodiments, the magnetic fluid seal apparatus 100 with pin shaft sleeve further comprises an end cap 6, the end cap 6 is sleeved on the shaft sleeve 3, and the end cap 6 is detachably mounted on the housing 1 and located at a side of at least one end of the shaft 2 extending from the chamber 11. Specifically, as shown in fig. 1, the end cap 6 is sleeved on the left end of the shaft sleeve 3, and the end cap 6 is disposed on the left side surface of the housing 1 through a screw, so as to protect the sealing assembly 5 in the housing 1, thereby improving the service life of the magnetic liquid sealing device 100 with the pin shaft sleeve.

In some embodiments, the seal assembly 5 comprises: a plurality of pole pieces 51 and permanent magnets 52. The plurality of pole shoes 51 are arranged in the cavity 11 and sleeved on the shaft sleeve 3, the plurality of pole shoes 51 are arranged at intervals along the axial direction of the shaft sleeve 3, and a gap is formed between the inner circumferential surface of the plurality of pole shoes 51 and the outer circumferential surface of the shaft sleeve 3 in the radial direction of the shaft sleeve 3, and the gap is filled with magnetic liquid.

The permanent magnet 52 is arranged in the cavity 11 and sleeved on the shaft sleeve 3, and the permanent magnet 52 is positioned between the adjacent pole shoes 51. The permanent magnet 52, the pole shoe 51 and the shaft sleeve 3 form a closed magnetic circuit, and the pole shoe 51 generates a non-uniform magnetic field with alternate intensity in the gap by using the permanent magnet 52, so that the magnetic liquid is absorbed between the pole teeth 511 and the shaft sleeve 3, and the magnetic liquid is filled in the gap, thereby achieving the purpose of sealing.

In some embodiments, the magnetic fluid sealing device 100 with pin shaft sleeve further comprises a magnetism isolating ring 53, the magnetism isolating ring 53 is arranged in the cavity 11 and surrounds the shaft sleeve 3, and the inner circumferential surface of the magnetism isolating ring 53 is spaced apart from the outer circumferential surface of the shaft sleeve 3. The pole shoes 51 comprise two outer pole shoes 51 which are positioned at the outermost sides in the axial direction of the shaft sleeve 3, and the magnetism isolating rings 53 are respectively arranged between the outer pole shoes 51 and the shell 1. Specifically, as shown in fig. 1, the magnetism isolating ring 53 includes a first magnetism isolating ring 531 and a second magnetism isolating ring 532, the first magnetism isolating ring 531 is disposed on the left side of the plurality of pole shoes 51, and the second magnetism isolating ring 532 is disposed on the right side of the plurality of pole shoes 51, so that the first magnetism isolating ring 531 and the second magnetism isolating ring 532 can prevent magnetic lines of force generated by the permanent magnet 52 from leaking from the left side and the right side of the plurality of pole shoes 51, and the sealing effect of the magnetic liquid sealing device 100 with the pin shaft sleeve is further improved.

In some embodiments, the magnetic liquid sealing device with pin bushing 100 further includes a sealing member 54 disposed between the outer circumferential surface of the pole piece 51 and the housing 1, the outer circumferential surface of the pole piece 51 is provided with an annular groove, and the sealing member 54 is fitted in the annular groove. According to the embodiment of the present invention, the magnetic liquid sealing device 100 with a pin shaft sleeve is provided with the sealing member 54 through the annular groove, thereby improving the sealing performance between the outer circumferential surface of the pole shoe 51 and the inner circumferential surface of the housing 1.

The sealing member 54 may be a sealing ring, and it is understood that the present invention has no limitation on the size, material, and sealing grade of the sealing ring, and can be selected according to actual needs.

In some embodiments, the inner circumferential surface of the pole piece 51 is provided with a plurality of pole teeth 511, the plurality of pole teeth 511 are provided at intervals in the axial direction of the sleeve 3, and a gap is formed between the inner circumferential surface of the pole teeth 511 and the outer circumferential surface of the sleeve 3. The pole teeth 511 increase the magnetic field intensity between the pole shoe 51 and the shaft sleeve 3, so that the magnetic liquid can be more firmly adsorbed between the pole shoe 51 and the shaft sleeve 3 by arranging the plurality of pole teeth 511, thereby further improving the sealing effect of the magnetic liquid sealing device 100 with the pin shaft sleeve.

Some specific examples of the magnetic fluid seal apparatus 100 with a pinned sleeve of the present invention are described below with reference to fig. 1.

According to the utility model discloses specific example take magnetic fluid seal device 100 of pin axle sleeve includes: housing 1, shaft 2, shaft sleeve 3, coupling assembly 4 and seal assembly 5.

The housing 1 has a chamber 11, and the right end of the shaft sleeve 3 is provided with a positioning portion 31 extending along the radial direction of the shaft sleeve 3, and the shaft sleeve 3 is sleeved on the shaft 2. The left end surface of the positioning portion 31 is fitted to the right end surface of the shaft 2. The sealing assembly 5 comprises two pole shoes 51, a permanent magnet 52, a first magnetism isolating ring 531, a second magnetism isolating ring 532 and magnetic liquid.

The two pole shoes 51 are arranged in the cavity 11 and sleeved on the shaft sleeve 3, the two pole shoes 51 are arranged at intervals along the axial direction of the shaft sleeve 3, a gap is arranged between the inner circumferential surfaces of the two pole shoes 51 and the outer circumferential surface of the shaft sleeve 3 in the radial direction of the shaft sleeve 3, and magnetic liquid is filled in the gap.

The permanent magnet 52 is arranged between the two pole shoes 51, the first magnetism isolating ring 531 is arranged on the left side of the left pole shoe 51, the second magnetism isolating ring 532 is arranged on the right side of the right pole shoe 51, annular grooves are formed in the peripheral surfaces of the two pole shoes 51, sealing pieces 54 are arranged in the annular grooves, accordingly, the sealing performance of the magnetic liquid sealing device 100 with the pin shaft sleeve is guaranteed, the end cover 6 is arranged on the left side of the shell 1, the end cover 6 is sleeved on the shaft sleeve 3, and the left end of the shaft 2 penetrates through the end cover 6 and extends out of the cavity 11.

The number of the connecting assemblies 4 is multiple, two connecting assemblies 4 are shown in fig. 1, the connecting assemblies 4 are arranged at intervals along the circumferential direction of the shaft sleeve 3, each connecting assembly 4 comprises a positioning pin 41 and a screw, a first pin hole penetrating through the positioning portion 31 along the thickness direction of the positioning portion 31 is formed in the positioning portion 31, a second pin hole aligned with the first pin hole is formed in the right end face of the shaft 2, the positioning pin 41 is inserted into and matched with the first pin hole and the second pin hole, the shaft sleeve 3 and the shaft 2 are positioned relative to each other, a threaded hole 21 is formed in the right end face of the shaft 2, a counter bore penetrating through the positioning portion 31 along the left-right direction is formed in the positioning portion 31 and is aligned with the threaded hole 21, and the fastening piece 42 penetrates through the counter bore to be matched with the threaded hole 21.

Therefore, the magnetic liquid sealing device 100 with the pin shaft sleeve according to the example of the present invention has the advantages of simple assembly, good sealing effect, long service life, etc.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like, indicate the orientation or positional relationship indicated based on the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be construed as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," and "fixed" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally formed; may be mechanically coupled, may be electrically coupled or may be in communication with each other; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

In the present application, unless expressly stated or limited otherwise, the first feature may be directly on or directly under the second feature or indirectly via intermediate members. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the present disclosure, the terms "one embodiment," "some embodiments," "an example," "a specific example," or "some examples" or the like mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art without departing from the scope of the present invention.

Claims

1. A magnetic liquid sealing device with a pin shaft sleeve is characterized by comprising: a housing having a chamber; a shaft having a first end and a second end, the shaft being pivotably disposed within the chamber, at least one end of the shaft extending from within the chamber; the shaft sleeve is arranged in the cavity and sleeved on the shaft, one end of the shaft sleeve is provided with a positioning part extending along the radial direction of the shaft sleeve, and the positioning part is opposite to the end face of the first end of the shaft; a coupling assembly for coupling the locating portion to a first end of the shaft; and the sealing assembly is arranged in the cavity and sleeved on the shaft sleeve.

2. The magnetic fluid seal device with a pin shaft sleeve of claim 1, wherein the connection assembly comprises positioning pins and fastening pieces, the positioning pins and the fastening pieces are arranged at intervals along a radial direction of the shaft sleeve, the positioning portion is provided with a first pin hole penetrating through the positioning portion along an axial direction of the shaft sleeve, a second pin hole aligned with the first pin hole is arranged in an end face of the first end of the shaft, and the positioning pins are fitted in the first pin hole and the second pin hole.

3. The magnetic fluid seal device with a pin shaft sleeve according to claim 2, wherein the fastening member is a screw or a bolt, a threaded hole is formed in an end surface of the first end of the shaft, the positioning portion is provided with a connecting through hole penetrating through the positioning portion in an axial direction of the shaft sleeve, the connecting through hole is a counter bore, and the fastening member penetrates through the connecting through hole and is in threaded fit in the threaded hole.

4. The magnetic-fluid seal apparatus with a pin sleeve according to claim 1, wherein said connecting members are plural, and said plural connecting members are provided at intervals in a circumferential direction of said sleeve.

5. The magnetic fluid seal with a pin bushing of claim 1, wherein a blind bore extending in an axial direction of the shaft is provided in an end face of the shaft.

6. The magnetic fluid seal apparatus with a pin shaft sleeve of claim 1, further comprising an end cap, wherein said end cap is sleeved on said shaft sleeve, said end cap is detachably mounted on said housing and located on a side of said shaft where at least one end of said shaft protrudes from said chamber.

7. The magnetic-fluid seal apparatus with a pin bushing of claim 1, wherein said seal assembly comprises:

the pole shoes are arranged in the cavities and sleeved on the shaft sleeve, the pole shoes are arranged at intervals along the axial direction of the shaft sleeve, gaps are formed between the inner circumferential surfaces of the pole shoes and the outer circumferential surface of the shaft sleeve in the radial direction of the shaft sleeve, and magnetic liquid is filled in the gaps;

the permanent magnet is arranged in the cavity and sleeved on the shaft sleeve, and the permanent magnet is positioned between the adjacent pole shoes.

8. The magnetic fluid seal apparatus with a pin bushing of claim 7, further comprising a magnetism isolating ring disposed in said chamber and surrounding said bushing, an inner circumferential surface of said magnetism isolating ring being spaced apart from an outer circumferential surface of said bushing, said pole shoes including two outer pole shoes located at outermost sides in an axial direction of said bushing, said magnetism isolating ring being respectively disposed between said outer pole shoes and said housing.

9. The magnetic fluid seal apparatus with a pin bushing of claim 7, further comprising a seal disposed between an outer circumferential surface of the pole piece and the housing, the outer circumferential surface of the pole piece being provided with an annular groove, the seal being fitted in the annular groove.

10. A magnetic fluid seal with a pin bush according to any of claims 7 to 9, wherein an inner peripheral surface of the pole piece is provided with a plurality of pole teeth which are arranged at intervals in an axial direction of the bush, and the gap is formed between the inner peripheral surface of the pole teeth and an outer peripheral surface of the bush.