ROTARY FACE SEAL WITH MAGNETIC REPELLING LOADING

Abstract

The rotary face seal with magnet loading replaces known spring mechanisms with magnetic technology that provides a consistent load with minimal variation, which is not affected by natural frequency and material fatigue due to cyclic loading. This improves seal performance and service life by eliminating the issues that compromise the effectiveness of conventional spring mechanisms. The repelling pusher magnetic technology is advantageous because it replaces the spring mechanism within a self-contained stationary cartridge with a pusher type magnetic assembly configuration that enable exact drop-in replacement of existing seal configurations.

Description

BACKGROUND OF THE INVENTION

The invention relates generally to mechanical rotary face seals. Such mechanical rotary face seals are typically used to seal media (gas or fluid) between the shaft and the housing where one is stationary and the other is rotating. These seals are used in the aerospace industry, commercial industry, nuclear industry, and other high reliability industries, such as, test equipment and race car engines and transmissions or the like.

There are a number of problems and concerns typically associated with known mechanical rotary face seals. Standard mechanical rotary face seals use a spring mechanism for the mechanical load that provides positive contact against the rotary mating surface that is either a separate ring attached to shaft, shaft flange or end face, or a bearing inner race. The loading of the spring mechanism can have a large variation caused by operating range (stroke) length, compromised when it's natural frequency is reached during operation from shock and vibration, and load reduction (weakening) due to material fatigue under cyclic loading and temperature extremes.

There have been a number of attempts in the prior art to address these common problems.

For example, U.S. Pat. No. 3,708,177 for Magnetic Seal for a Rotary Shaft and Magnet Therefor addresses the well-known eddy current issue but it is unknown if the design was commercially feasible. U.S. Pat. No. 4,795,168 for a Magnetic Seal Assembly does not address the eddy current issue because the magnet inserts rotate. U.S. Pat. No. 5,078,411 for Variable Magnetic Rotary Seal does not address the eddy current issue because the magnet inserts rotate. U.S. Pat. No. 5,730,447 for Self-Aligning Magnetic Rotary Seal also does not address the eddy current issue because the magnet inserts rotate. U.S. Pat. No. 6,805,358 for Magnetic Seal also does not address the eddy current issue because either the magnet inserts rotate or the magnetically attractive member is exposed to continuously changing north and south poles during rotation.

FIGS. 1 and 2 show an example of such a prior art rotary face seal 10 in detail. It includes an anti-rotation design that uses two (2) tangs 12 on the seal case 16 that engage slots 14 in the cup 18 which permits fluid movement in this area. It has a removable “take apart” cartridge design that facilitates repair, replacement and inspection of internal parts. It has a solid outside diameter cup option with internal milled tangs 12 and seal case slots 14. FIG. 1 shows an embodiment with outward radial tangs 24 on the seal case 16 that engages slots in the cup 18. As a further variation, FIG. 2 shows a solid outer diameter option with internal radial tangs 26 in the cup 18 that engages the slots in the seal case 16.

High pressure, low pressure and reverse pressure capability is achieved within the same cartridge by adjusting the diameters of the seal ring 20. Since it does not employ magnets, there is unrestricted selection of materials for construction. However, the slotted OD design is not practical for all applications with the majority using the internal milled tangs 12 with slots 14 in the seal case 16. There is spring load variation due to operating range and the spring load decreases as the seal ring 20 wears compromising re-seating. A wave spring 22 resides between the seal case 16 and the cup to spring-bias them apart. Also, the natural frequency of wave spring 22 is unknown and could cause loading issues under shock and vibration conditions. Moreover, the rotary mating surface which bears against the seal ring 20 mating surface 20a is not always part of the seal design, namely, the bearing inner race face, integral with the shaft (not shown) and the mating ring (not shown) obtained from multiple suppliers.

These solutions are not enough. In view of the foregoing, there is a demand for a rotary face seal that combines the best features of a magnet rotary seal with a non-magnetic seal to avoid the shortcomings associated with prior art rotary face seals.

SUMMARY OF THE INVENTION

The present invention preserves the advantages of prior art rotary face seals. In addition, it provides new advantages not found in currently available rotary face seals and overcomes many disadvantages of such currently available rotary face seals.

The invention is generally directed to the novel and unique rotary face seal that has magnetic repelling loading. The rotary face seal with magnetic loading of the present invention replaces a conventional mechanical spring mechanism with opposing/repelling magnets where the magnetic technology provides a spring-like biasing effect to provide a consistent load with minimal variation, which is not affected by natural frequency and material fatigue due to cyclic loading. This improves seal performance and service life by eliminating the issues that compromise the effectiveness of the spring mechanism. The magnetic technology replaces the mechanical spring mechanism preferably within a stationary cartridge with a “pusher” type magnetic assembly design. As a result, such a stationary cartridge of the present invention is an exact exchange or “drop-in” solution to replace known seal that use mechanical wave springs.

It is therefore an object of the present invention to provide improved rotary face seal that overcomes the shortcomings associated with the prior art and provides vastly improved performance compared to such prior art designs.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features which are characteristic of the present invention are set forth in the appended claims. However, the invention's preferred embodiments, together with further objects and attendant advantages, will be best understood by reference to the following detailed description taken in connection with the accompanying drawings in which:

FIG. 1 is a cross-sectional view of a first known prior art rotary seal construction that uses conventional wave springs;

FIG. 2 is a cross-sectional view of a second known prior art rotary seal construction that uses conventional wave springs;

FIG. 3 is a cross-sectional view of a first embodiment of the invention;

FIG. 4 is a cross-sectional view of a second embodiment of the invention with hydrodynamic lift-off grooves in the seal face of the rotating mating ring; and

FIG. 5 is an end view of the seal face of the rotating mating ring showing the hydrodynamic lift-off grooves.

DESCRIPTION OF THE INVENTION

The rotary face seal 100 of the present invention with magnet repelling loading replaces the mechanical spring mechanism with magnetic technology to provide a consistent load with minimal variation, which is not affected by natural frequency and material fatigue due to cyclic loading. This will improve seal performance and service life by eliminating the issues that compromise the effectiveness of the spring mechanism. The present invention, with its magnetic “spring” technology, replaces the mechanical spring mechanism of the prior art of FIGS. 1 and 2 with the stationary cartridge of the present invention with a pusher type magnetic assembly design that results with the stationary cartridges being an exact exchange.

Referring to FIG. 3, of the rotary face seal 100 of the present invention is shown to include a basic cartridge rotary face seal that is comprised of a cup 102, seal case 104 with inserted seal ring 106 that fits into the cup 102 with an anti-rotation feature that includes a retaining ring 108 that resides in a groove 110 in the cup 102. The cup 102, in turn, resides in a stationary housing 120 to complete the drop-in cartridge configuration. This anti-rotation structure prevents the seal case 104 from rotation when the seal ring 106 contacts a rotating mating face of a rotating mating ring 112 that is rotates with shaft 114 due to being held in place by O-ring 116 in seat 112c. Such rotation is prevented as well relative to the shaft end face 114a or integral flange face, bearing inner face (not shown).

Any type of configuration may be used for attaching the rotating mating ring 112 to the shaft 114, such as the use of O-rings, as shown. In addition, there may be a positive drive with an internal O-ring as secondary seal engagement the shaft with either radial of axial tangs that engage slots in the shaft. Or, there may be the reverse engagement with slots in the mating ring engaging tangs on the shaft. Also, there may be a positive drive with an internal O-ring as secondary seal engagement with the shaft with either radial of axial pins that engage the shaft. Further, there may be a reverse engagement with pins in the shaft engaging with the mating ring. Further, there may be a positive drive with an internal O-ring as secondary seal by using an axial clamping sleeve or a positive drive without an internal O-ring as secondary seal by using an axial clamping sleeve.

Also, an internal O-ring 118 resides in the cup 102 which interfaces with the seal case 104 to provide a secondary seal while allowing axial movement of the seal case 104 within the cup 102 along the shaft axis 114b. The seal case 104 is preferably a metal alloy, as is well-known in the art. Known 0-ring designs and materials may be used, which are known in the art for the purposes indicated herein. For example, various elastomers may be used, which may or may not be pre-swollen. An internal retaining ring 108 in the cup 102 that prevents the seal case 104 from becoming disengaged from the cup 102.

Preferably, a pair of magnets 120a and 120b are provided in the cavity defined by the space between the cup 102 and the seal case 104. The pair of magnets are a magnetic pusher assembly that is in the cup 102 and contacts the adjacent flange 104a of the seal case 104 when the seal ring 106 is mated to the mating face 112a of the rotating mating ring 112 while carrying out operation of the seal with a range of motion indicated as B in FIG. 3. The magnets 120a and 120b are preferably a pair of magnets that repel each other. The magnets 120a and 120 are each preferably of a unitary annular shape to reside within the annular-shaped cavity defined between the cup 102 and seal case 104 discussed herein. In the alternative, the opposing/repelling magnets may each be made of a number of separate magnet members to suit the application at hand to provide the designed magnetic field and circuit. The repelling magnet force may also be a drop-in repelling magnetic cartridge-like solution offered by the Polymagnet company under the mark POLYMAGNET, for example as an alternative, which can maintain the seal case 104 in the cup 102 thereby eliminating the internal retaining ring and provide the mechanical load in the spring when the seal case 104 is mated against the rotary mating face 112a during operation. Further, the force, travel and the repelling profile of the magnets may be further modified to suit the application at hand. The seal ring 106 may be any material suitable for the application at hand, such as carbon graphite, and the like. The magnets 120a and 120 provide an outwardly directed spring-biasing, as shown by arrows A in FIG. 3.

Therefore, the rotary face seal of the present invention eliminates the risks associated with prior art designs.

Turning now to FIGS. 4 and 5, an alternative embodiment 200 of the first embodiment 100 of the present invention of FIG. 3 is shown. The alternative embodiment 200 is similar to the first embodiment except that the rotating mating ring 212 has a bearing surface 212a which incorporates lift-off technology using hydrodynamic grooves 250, as can be best seen in FIG. 5, which is an end view of the bearing face 212a of the rotating mating ring 212. It should be noted that the configuration of the grooves 250 is shown by way of example, and it should be understood that any type, configuration and array of grooves 250 may be used in connection with the alternative embodiment 200 to provide the benefits of such hydrodynamic lift-off grooves.

The alternative embodiment 200 has all of the same other components as the first embodiment, such as a cup 202, seal case 204, with seal ring 206 that is pushed outwardly by magnets 220a, 220b. The seal ring 206 bears against the rotating mating ring 212. The entire seal assembly 200 receives a shaft 214 to be sealed.

It would be appreciated by those skilled in the art that various changes and modifications can be made to the illustrated embodiments without departing from the spirit of the present invention. All such modifications and changes are intended to be covered by the appended claims.

Claims

1. A rotary face seal with magnetic loading which sealingly couples a shaft to a housing, comprising: a stationary housing having a seat;a cup, having an inwardly facing groove and a central bore, residing the housing; a shaft located in the bore;a seal case residing between the cup and the shaft;an O-ring residing in the inwardly facing groove of the cup to sealingly interface the cup with the seal case providing a secondary seal and allowing axial movement of the seal case within and relative to the cup;a retaining ring connecting the cup to the seal case thereby preventing the seal case from becoming disengaged from the cup;a seal ring in communication with the seal case;a rotating mating ring, having a seal face in communication with the seal ring; the rotating mating ring rotating with the shaft;a mechanical load pusher assembly residing between the cup and the seal case thereby urging the seal case toward the rotating mating ring and the seal ring into sealing communication with the seal face of the rotating mating ring.

2. The rotary face seal of claim 1, further comprising: further comprising complementary structures on the seal case and the cup to prevent rotation of the cup relative to the seal case when the seal ring contacts a rotating mating face.

3. The rotary face seal of claim 1, wherein the mechanical load pusher assembly is magnetic.

4. The rotary face seal of claim 3, wherein the mechanical load pusher assembly are two repelling magnets.

5. The rotary face seal of claim 1, wherein the rotary face seal is configured and arranged as a self-contained cartridge.

6. The rotary face seal of claim 1, wherein the rotating mating ring further includes a groove with an O-ring residing therein with the O-ring in communication with the shaft to secure the rotating mating ring to the shaft to effectuate rotation of the rotating mating ring with the shaft.

7. The rotary face seal of claim 1, wherein the seal face of the rotating mating ring further includes a plurality of hydrodynamic grooves.