Magnetic seal

Abstract: A magnetic seal for rotating shafts having a first and second annular members (11,12). Each of said annular members having a source of magnetic force (16) with the lines of magnetic force (16) being axially aligned with the shaft (10). A stationary insert (13) positioned in said housing (19) and having a sealing face (21) adjacent said annular members. The first and second annular rings (11,12) being rotatively connected with the second ring (12) being sealed to the shaft (10) and a face related to said second member for sealing contact with the face of the insert (13). The first of said rings (11,12) secured to the shaft (10) for annular rotation.

Description: Background of the Invention For many years, hermetic sealing of enclosed bearing housings has been the goal for the efficient operation of rotating equipment. Minimum maintenance of rotating equipment is of increasing importance to operators because of the necessity to improve efficiency. Minimum maintenance is difficult to obtain because of the extreme equipment duty cycles, the lessening of service factors in design and the lack of spare rotating equipment in many processing plants. Various forms of shaft sealing devices have been utilized to try to protect the integrity of the bearing environment including rubber lip seals, clearance labyrinth seals and attraction magnetic seals. Rubber lip seals were first utilized to connect the bearing frame to the rotatable shaft in an attempt to isolate the bearings from exterior contamination. Such lip seals are subject to premature wear and are short-lived. Lip seals also have been known to permit excessive amounts of moisture and other contaminants to become present in the oil reservoir of the bearing frame of the operating equipment. Labyrinth-type seals involving closely related stator and rotor rings which do not contact each other, but define labyrinth passages between them, have been devised and utilized and are illustrated in U.S. Patent No. 4,706,968. This type of seal also allowed a certain amount of axial separation of the fixed ring and the rotating ring to prevent contact and wear between sealing members and thus enhance the sealing characteristics. Labyrinth seals also allowed free transfer of humid vapors in and out of the bearing frame. Mechanical shaft seals of the non-magnetic type have also been utilized as shaft sealing devices. This type of seal employs the use of metallic springs of the coil design or welded metal bellows design to effect the closure of the sealing faces. The metal springs of either design are subject to corrosion, fatigue, product fouling and stress over time and are linear in response to opening and closing of the sealing faces. This linear response does not adequately maintain the sealing surfaces as wear or corrosion continues to occur. Attraction magnetic sealing systems have also been utilized as sealing devices. In this case, the attraction magnetic seal systems rely upon magnetic attraction to maintain face closure integrity and these seals are exemplified and described in U.S. Patent No. 4,795,168 and the references cited therein. These attraction magnetic sealing systems are subject to exterior system forces that tend to separate the relatively rotating sealing faces. This works against the principle of magnetic attraction. When the sealing faces are separated, the forces of the magnetic field are weaker and the tendency for failure in operation by further separation and further weakening is pronounced. If there is wear between the sealing surfaces, then the magnetic forces are pulled closer together and the wear rate increases exponentially. This also increases the failure rate due to the increased torque required as the magnetic field increases. Magnetic or magnetised components of the attraction-type magnetic seals are typically attempted to be insulated from ferrous bearing housings to isolate the magnetic field from the bearings and/or housing. However, there are no true insulators against magnetism and the attempts to insulate the magnetic fields have greatly increased the structural complexity and cost without any benefits. It is also known from EP 0105616 to provide a magnetic rotary seal, in accordance with the first part of claim 1, in which the magnetic orientation is designed to seal by repelling one of the sealing components. In this case, the alleged disadvantages of earlier arrangements in which magnets are mounted on the rotating component are overcome by mounting the magnets on non-rotary components of the seal. The structure so provided is complex in design in that it requires a large number of seals between rotary and non-rotary components and is therefore likely to be unreliable in use. It is an object of the invention to provide a rotating shaft seal in which sealing is achieved by mutual magnetic repulsion of seal components while obviating or mitigating the disadvantages of the seal of EP 0105616 and the prior art referred to therein. According to the present invention there is provided a rotating shaft seal comprising a housing, a rotating shaft extending through the housing, a first annular member surrounding the shaft and including a source of magnetic force secured therein with the magnetic force applied axially, a second annular member surrounding the shaft and including a source of magnetic force secured therein with the magnetic force being of like polarity to said magnetic force in the first annular member and applied axially such that the annular members are repelled by each other, and a sealing face surrounding the shaft on the side of the second annular member opposite to the first annular member, characterised in that a stationary insert is positioned surrounding the shaft and sealed to the housing, the insert defining a face perpendicular to the shaft and aligned with the sealing face of the second annular member such that the repelling magnetic forces force the sealing face into compressive contact with the face of the stationary insert to seal the housing, the first annular member is secured to the shaft, the second annular member is sealed around the shaft, and the first and second annular members are interconnected by drive means such that the second annular member is driven in rotation by the first annular member. Brief Description of the Drawings Fig. 1 is a sectional view showing the improved sealing structure with a shaft. Fig. 1a is an end view of the second rotating ring of the present invention. Fig. 1b is an end view of the first rotating ring of the present invention. Fig. 2 is a sectional view showing another embodiment of the improved sealing structure. Fig. 3 is an exploded perspective view of the two rotating rings of the improved sealing structure. Fig. 4 is a sectional view showing another embodiment of the invention. Fig. 5 is a sectional view showing yet another embodiment of the present invention. Fig. 6 is a sectional view of the embodiment of the invention shown in Fig. 5 but utilized internally. Fig. 7 is a sectional view of a pump showing various embodiments of the invention in place in the pump. Detailed Description of a Preferred Embodiment of the Invention Referring first to Fig. 1, there is shown an early arrangement of the sealing structure of the present invention. The sealing rings of the present invention are shown mounted in vertical cross sections on shaft 10. The sealing rings are first ring 11 and the second ring 12. The shaft 10 is shown extending through the bearing housing 19 and includes the insert member 13. The first sealing member 11 is shown in greater detail in Fig. 1b and comprises the ring member or rotor 11a. This rotor and the rotor 12a should be made of non-magnetic, heat-conducting materials such as bronze, 300 series stainless steel or aluminum. However, in certain cases, chemically inert plastics, such as Teflon®, may be used if conditions require or permit their use. Rotors 11 and 12 have inserted in each rotor magnetic forces 16, which comprise plug magnets in the preferred embodiment. These plug magnets are inserted so that the like polarities of the magnets face each other to repel the two rotors. There is also a means for securing the first rotor 11 to the shaft which is shown in Fig. 1b as the set screw 18a which screws into the threaded hole 18. This is only one method of securing the first ring to the shaft and other methods may be used which will still conform to the principles of the invention. Drive pins 17 in the first rotor fit into the holes 17a in the second rotor 12 to align the rotors and cause the rotors to rotate together. In Fig. 1 there are shown two sealing members 14 or O-rings to seal the rotors to the shaft. These sealing members 14 may be made of any normal conventional O-ring material. The drive pins 17 should also be made of heat conducting material so as to assist in carrying the frictional heat generated by the rotating sealing members away from the sealing members and dissipate the heat into the surrounding air or liquid. Fig. 2 shows another embodiment of the invention wherein the first rotating member or rotor 11 is pinned to the shaft 10 in a conventional manner (not shown). The sealing face 21 is now embedded in the insert member 13 rather than being flush with the exterior face of the housing member 19. In this case, there is no conventional O-ring associated with the first rotor because it has been found that such O-ring or sealing is not required with most embodiments of this invention. The pins and magnets are similar to those shown in Figs. 1a and 1b and the operation of the embodiment is essentially similar. Flange members 22, which abut the housing member 19 to securely hold the insert from lateral or axial motion. There is also in some embodiments an O-ring 20 or other sealing devices when required for proper sealing which provides a seal between the housing member 19 and the insert or stationary member 13. The sealing face in Fig. 2 is shown as 21, and comprises the same sealing face as in Fig. 1. The only difference is the configuration of the seal face which can be modified to meet various static and dynamic considerations in the required embodiment. Fig. 3 is an exploded view showing rotors 11 and 12 having more plug magnets 16 than the embodiment shown in Fig. 1. These two rotors in Fig. 3 include the driving pins 17 and holes 17a in the second rotor. There is also provided means for securing the first rotor to the shaft similar to the means 18 and 18a described in Fig. 1. One way to increase the magnetic force between the two rotors and the repelling force is by increasing the number of magnets. This repelling force can also be increased by having magnets of larger diameter or possessing increased magnetic force. The positioning of the first rotor on the shaft determines the force depending on the strength of magnets of the second rotor against the sealing face of the stator. Thus, by changing the axial position of the first rotor on the shaft, it is possible to vary the sealing force between the second rotor face and the face of the insert member 13 or stator. Fig. 4 shows another embodiment of this invention where the sealing face associated with the rotor is not attached to the rotor, but rather comprises a separate member 22. This member is forced by the same repelling magnetic force between rotors 11 and 12 to mate at the sealing face 21. The same magnets 16 and securing member 17a are shown as are the O-rings or sealing devices 20 and 14. Figs. 5 and 6 show another embodiment of the invention. In this embodiment, the rotors 11 and 12 are constructed similarly to those in Fig. 1, however, there is a new element 22 similar to the ring element 22 in Fig. 4 placed between the stator member 13 and the second rotor member 12. This element 22 may or may not be attached to the rotor 12, Preferably, it is not physically a part of rotor 12. This element 22, however, is forced against the sealing face of the stator 13 to form the seal at face 21. This configuration of member or element 22 can be modified as necessary to insure an adequate sealing face 21 between the stator 13 and the rotor 12. In Fig. 5, the stator member 13 is external to the housing member 19 and is secured from lateral motion by the flange 24 which abuts against the housing member 19. All of the members as shown in Fig. 1 and described previously, such as the seals 14 and 20, the magnets 16 and the securing means 18, 18a, are present in the embodiment of Figs. 5 and 6. Fig. 6 shows the same embodiment of the invention as in Fig. 5 except that the sealing unit of this invention is internally mounted and runs inside the pump or housing rather than external to the housing as shown in Fig. 5. The same magnetic repelling forces act to force the second stator against member 22 to seal the stator 13 at sealing face 21. In this case, the flange 24 is used to prevent axial motion of the sealing unit of this invention and is assisted by a member 25 which may be a clamp to secure the sealing unit from movement in the axial direction. As has been demonstrated, the present invention has many embodiments which will permit a plurality of uses including the use of this novel repelling magnetic sealing invention in pump stuffing boxes, sealing chambers to keep pump fluid from escaping along the shaft, and other instances where a differential pressure of fluid must be maintained. The seal components may be assembled in various configurations including right to left, left to right, inward to outward, etc. It is also possible to double or multiply these assemblies when conditions call for such configurations. It may also be desirable to encapsulate sealing member components and magnets against corrosive environments and thus insure longer life of the sealing unit. It is also possible to utilize this invention in the form of a cartridge wherein the seal assembly is mounted on a sleeve cartridge which will fit over the shaft and support the seal assembly. Fig. 7 is illustrative of some of the many configurations described above. The first embodiment 7a is similar to that shown in Fig. 1. 7a is illustrated on the left side of Fig. 7 and includes the first and second rotors 11, 12 and the stator means 13. A second embodiment 7b, similar to that shown as 7a in Fig. 4., is illustrated in the middle of Fig. 7 and includes the first rotor 11 and second rotor 12 and the stator 13. The last embodiment 7c is similar to the embodiment shown in Fig. 6 and is illustrated on the right center. This embodiment also includes rotor 11, rotor 12 and stator 13 and face member 22.

Claims: A rotating shaft seal comprising a housing (19), a rotating shaft (10) extending through the housing, a first annular member (11) surrounding the shaft and including a source of magnetic force (16) secured therein with the magnetic force applied axially, a second annular member (12) surrounding the shaft and including a source of magnetic force (16) secured therein with the magnetic force being of like polarity to said magnetic force in the first annular member and applied axially such that the annular members are repelled by each other, and a sealing face surrounding the shaft on the side of the second annular member (12) opposite to the first annular member (11), characterised in that a stationary insert (13) is positioned surrounding the shaft and sealed to the housing (19), the insert (13) defining a face perpendicular to the shaft and aligned with the sealing face of the second annular member (12) such that the repelling magnetic forces force the sealing face into compressive contact with the face of the stationary insert to seal the housing, the first annular member (11) is secured to the shaft, the second annular member (12) is sealed around the shaft, and the first and second annular members are interconnected by drive means such that the second annular member (12) is driven in rotation by the first annular member (11). A seal according to claim 1, wherein said sealing face is fixed to said second annular member (12). A seal according to claim 2, wherein said first annular member (11) is formed from non-magnetic material. A seal according to claim 3, wherein said first annular member (11) is formed from non-ferrous metal. A seal according to claim 4, wherein said first annular member (11) includes a recessed area with said source of magnetic force (16) secured in said recessed area. A seal according to claim 5, wherein said source of magnetic force (16) is a plurality of plug magnets (16). A seal according to claim 1, wherein said second annular member (12) is formed of non-magnetic material. A seal according to claim 7, wherein said second annular member (12) is a non-ferrous metal. A seal according to claim 8, wherein said second annular member (12) has a recessed area wherein said source of magnetic force (16) is secured. A seal according to claim 9, wherein said source of magnetic force (16) is a plurality of plug magnets (16). A seal as in claim 1, wherein said sealing faces comprise smooth, flat, mating, non-magnetic surfaces. A seal according to claim 1, wherein said means for sealing said second annular member (12) around said shaft is an elastomeric member (14). A seal according to claim 1, wherein said drive means is a plurality of pins (17) engaging said first and second annular members (11, 12). A seal as in claim 1, wherein said insert (13) is formed from non-magnetic material. A seal according to claim 1, wherein said means for securing said first annular member (11) to said shaft (10) includes means for adjusting the axial position of said first annular member (11) ) on said shaft (10). A seal according to claim 1, wherein the compressive sealing force is varied by the axial position of the first annular member (11) on said shaft (10) relative to said second annular member (12). A seal according to claim 1, wherein the magnetic force of the repelling magnets (16) controls the compressive sealing force.

Inventors: BLOCH HEINZ P, ORLOWSKI DAVID C, BLOCH, HEINZ P., ORLOWSKI, DAVID C.
Applicants: INPRO CO INC, INPRO COMPANIES, INC.
Application year: 1992
Main classification: F16J15
IPC codes: F16J15