Patent Description:
This invention relates to rotary shaft equipment having mechanical seal assemblies providing a seal between a housing and rotatable shaft of the rotary shaft equipment. More particularly, it relates to such rotary shaft equipment and seal assemblies that include a secondary sealing membrane such as a bellows.

Mechanical seals are used to provide a seal between a rotating shaft and a stationary housing of a pump, compressor, turbine, or other rotating machine. End face mechanical seals generally include a primary seal interface comprising two relatively rotatable seal faces. Frictional wear between the seal faces can cause a gap to form therebetween, leading to excessive leakage. Accordingly, some end face seals require regular adjustment in order to maintain the appropriate or axial position of an axially shiftable seal member (also known as "seal height") in order to account for such wear.

Various biasing mechanisms have been contemplated to provide a closing force to automatically accommodate wear. Such biasing mechanism have included single and multiple coil springs, and metal bellows.

Pusher seal assemblies comprise a dynamic secondary seal (such as an o-ring) to provide a seal between the shaft and the seal members themselves. The dynamic secondary seal of pusher seals is generally configured to move axially with the axially shiftable seal member. This axial movement relative to the shaft can cause fretting or shredding of the secondary seal due to friction.

Non-pusher seals generally feature a secondary shaft seal that is not intended to move axially relative to the shaft, such as an o-ring (generally used with metallic bellows seals), or an elastomeric bellows, an example of which is provided in <FIG>. The depicted mechanical seal comprises an elastomeric bellows that is driven to rotate with the shaft relative to the housing. This non-pusher seal can reduce torque stress on the bellows, which are intended to contract and expand to balance the opening and closing forces on the seal faces. At high pressures, such as gauge pressures above about <NUM> bar(g), however, the shaft itself can translate axially. This can create an axial load on the elastomeric bellows which can cause the elastomer to rigidly collapse, as shown in the detail view (where lighter areas are those with higher pressure). This axial rigidity prevents the bellows from effectively counteracting the closing force provided by the biasing members, leading to excess face pressure, frictional wear, and eventual seal failure.

<CIT> discloses a mechanical seal comprising a mating ring that includes a sliding portion having a sliding surface that slides against a sealing ring within an end surface on an atmosphere side thereof in an axial direction of a shaft, and a retained portion that extends from a radially outward end portion of the sliding portion toward a sealed-fluid side in the axial direction and is retained by a sleeve. The mechanical seal includes an annular holder that is fixed to the sleeve and receives pressure from an O-ring that receives, from the sealed-fluid side in the axial direction, a fluid pressure of a fluid to be sealed that flew into a space created by a flange portion of the sleeve and the retained portion of the mating ring.

Ongoing demand for improved productivity, reliability, durability and changing envelope requirements for pumps and other rotary shaft equipment dictate continued effort for new developments in seal assemblies. In particular, a need exists for mechanical seals that can operate to seal higher internal pressures. The present disclosure relates to an advance in seal technology that addresses these needs.

Embodiments of the present disclosure meet the need for mechanical seals that can operate to seal higher internal pressures by providing a non-collapsible flexible sealing membrane (or bellows) for incorporation in a mechanical seal assembly and use in rotary shaft equipment.

According to the invention there is provided a mechanical seal assembly in accordance with claim <NUM>. Preferred features are set out in dependent claims <NUM> to <NUM>.

The flexible sealing membrane includes a first, substantially radially extending portion, which can be urged into an axially shiftable ring by seal components including a plurality of axially spaced springs. The flexible sealing membrane further includes a second, substantially axially extending portion, substantially radially inward of the balance diameter of the seal, and oriented generally orthogonally to the first portion. The second portion is advantageously held fixed to a stub sleeve by an annular band. The angle between the first portion and the second portion of sealing membrane can provide for directional control of the forces acting on the stub sleeve. The flexible sealing membrane can reduce the effects on seal performance caused by axial shifting of the rotating shaft at high pressures.

The mechanical seal assembly is adapted for arrangement around a rotating shaft and comprises an axially shiftable seal ring arranged axially outboard of a axially-fixed seal ring, and a flexible sealing membrane. The flexible sealing member includes a flange portion arrangable between the axially shiftable seal ring and a biasing mechanism, the flange portion being axially shiftable relative to the rotating shaft by forces transmitted to the flange portion by the biasing mechanism and the axially shiftable seal ring. The flexible sealing member further includes a coaxial portion extending axially from a flexible connection portion at a radially inward extent of the flange portion. The coaxial portion is held axially fixed relative to the rotating shaft by an annular band at an outer diameter and an annular stub sleeve at an inner diameter whereby the closing force applied to the stationary seal ring by the flange portion remains fixed regardless of the axial position of the flange portion.

In embodiments, the coaxial portion is arrangable at a diameter within the balance diameter of the seal and the connecting portion presents a thinner cross section than the flange portion and the coaxial portion.

Axially inward translation of the rotating shaft urges the flange portion to shift axially inboard and radially inward against the stub sleeve. Axially outboard directed forces (such as the outward translation of the rotating shaft) can urge the flange portion to shift axially outboard and radially outward relative to the coaxial portion.

In an embodiment, the mechanical seal system further comprises an anti-extrusion ring receivable within a groove of the axially shiftable seal ring.

In an embodiment, the stub sleeve is axially fixed to the biasing mechanism by a snap ring.

In an embodiment, the biasing mechanism comprises an axially shiftable annular retainer proximate the flange portion, an annular carrier, axially fixed to a gland plate, and a plurality of radially spaced spring members arranged therebetween.

In an embodiment, a rotating sleeve is operably coupled to the rotating shaft for rotation therewith and the axially fixed seal ring is operably coupled to the sleeve by a plurality of pins.

In an embodiment, an annular flexible sealing membrane is adapted for arrangement within a mechanical seal assembly, and comprises a coaxial portion including a radially inboard directed face, an axially outboard directed face, and a radially outward directed face. The member further comprises an axially shiftable flange portion extending radially outward from the coaxial portion and including an axially inboard directed face, a radially outward directed face, and an axially outboard directed face. In an embodiment, the axially outboard directed face of the flange portion is coupled to the radially outward directed face of the coaxial portion by a flexible connecting portion comprising an axially inboard and radially inward facing facet. The facet can include a first segment extending axially outboard from the axially inboard directed face of the flange portion and a second segment extending axially outboard and radially inward from the first segment to the radially inboard directed face of the coaxial portion.

In an embodiment, the sealing membrane comprises a flexible elastomer.

Subject matter hereof may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying figures.

While various embodiments are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the claimed inventions to the particular embodiments described. On the contrary, the intention is to cover all modifications and alternatives falling within the scope of the subject matter as defined by the claims.

<FIG> and <FIG> are broad and detail (respectively) cross-sectional views depicting a portion of a seal assembly <NUM> including a flexible, non-collapsible, sealing membrane <NUM> depicted in conjunction with an article of rotary shaft equipment such as a pump, mixer, blender, agitator, compressor, blower, fan, or the like, according to an embodiment of the present disclosure.

As is common for seal assemblies of this type, seal assembly <NUM> can seal a rotating, axially extending, shaft <NUM> of an article of rotary shaft equipment. Seal assembly <NUM> can provide a seal for the process chamber <NUM> at the inboard extent of the seal assembly <NUM> with respect to the ambient surroundings <NUM>.

The seal assembly <NUM> can be arranged coaxial of the shaft <NUM> in a bore defined by an annular housing <NUM> coaxial of shaft <NUM>. Various stationary (or non-rotating) components of seal assembly <NUM> can be operably coupled to housing <NUM>, or a gland plate <NUM>, which is in turn also operably coupled to housing <NUM>.

Various rotating components can be operably coupled to shaft <NUM>, for rotation therewith. An annular sleeve member <NUM> is secured to the shaft <NUM> for rotation therewith. An annular flange formation <NUM> extends radially outwardly of the sleeve member <NUM> at the end thereof adjacent the process chamber <NUM>. A plurality of annularly spaced pins <NUM> can extend axially through bores in sleeve flange <NUM>.

An axially fixed seal ring <NUM> (or mating ring) is mounted on the face of sleeve flange <NUM> remote from the process chamber <NUM>, for rotation therewith. Annular o-ring <NUM> provides a resilient secondary seal between sleeve member <NUM> and axially fixed seal ring <NUM>. In embodiments, more or fewer secondary sealing o-rings may be present. Axially fixed seal ring <NUM> includes outboard sealing face <NUM>.

An axially shiftable seal ring <NUM> (or primary ring) is arranged outboard and adjacent to axially fixed seal ring <NUM>. Axially shiftable seal ring <NUM> includes inboard sealing face <NUM>. Inboard sealing face <NUM> abuts outboard sealing face <NUM>.

While, as depicted and described, axially shiftable seal ring <NUM> is stationary and axially fixed seal ring <NUM> is rotatable, in embodiments, the relative axial movement can be provided by either the rotating or stationary seal ring.

Inlet <NUM> can be defined within housing <NUM> and/or gland plate <NUM> to provide a sealing lubricant (not shown) to sealing faces <NUM> and <NUM>.

Annular bellows, or sealing membrane <NUM> can present a generally L-shaped cross-section, comprising a first, generally radially outward extending, flange portion <NUM> and a second, generally axially outboard extending, coaxial portion <NUM>. Flange portion <NUM> and coaxial portion <NUM> can be operably coupled by a flexible connecting portion <NUM>. An inboard face of flange portion <NUM> can abut outboard face of axially shiftable seal ring <NUM>, creating a pressure tight seal. Coaxial portion <NUM> is substantially or entirely radially inward of the balance diameter of the seal, where the pressure differential across the seal is the greatest. Flexible connecting portion <NUM> can present an angular facet <NUM> at a radially inward side and a connecting angle θ between flange portion <NUM> and coaxial portion <NUM> at a radially outward side. In embodiments, angle θ can be approximately ninety degrees, though other angles may also be used. Flexible connecting portion <NUM> can present a thinner cross section than flange portion <NUM> or coaxial portion <NUM> to enable stretching and compression.

Angular facet <NUM> can terminate at corner <NUM> at a radially inward extent of flexible connecting portion <NUM>. Facet <NUM> can present an angle ϕ, relative to the axial axis of between about <NUM>° to about <NUM>°. Sealing member <NUM> is non-collapsible and can comprise a flexible material. Example flexible materials include elastomers such as nitrile, fluroreslastomer, and ethylene propylene rubbers, though other materials can be used.

Coaxial portion <NUM> is fixed to an annular stub sleeve <NUM> by annular band <NUM>. Radially outward directed faces of stub sleeve <NUM> can abut coaxial portion <NUM>, facet <NUM>, and axially shiftable seal ring <NUM>. Stub sleeve <NUM> can present groove <NUM> to receive snap ring <NUM> to locate stub sleeve axially relative to carrier <NUM> (discussed below). In embodiments, stub sleeve <NUM> can be located radially by snap ring <NUM>, hydraulic pressure, or interference fit with carrier <NUM> (discussed below) or other components of seal assembly <NUM>. Stub sleeve <NUM>, band <NUM>, and snap ring <NUM> can comprise steel or stainless steel in embodiments.

Annular anti-extrusion ring <NUM> can be present in an annular groove of axially shiftable seal ring <NUM> and abut axially shiftable seal ring <NUM>, stub sleeve <NUM>, and sealing member <NUM>. Annular anti-extrusion ring <NUM> can comprise a harder elastomer than sealing membrane <NUM>, such as a <NUM> to <NUM> (Shore D) durometer carbon filled polytetrafluoroethylene (PTFE). Because extrusion is most likely at the balance diameter of the seal, the inner diameter of anti-extrusion ring <NUM> can be arranged at the balance diameter of the seal.

Biasing mechanism <NUM> can abut flange portion <NUM>. Biasing mechanism <NUM> can comprise an axially shiftable annular retainer <NUM>, axially fixed carrier <NUM>, and one or more biasing members <NUM> spanning therebetween. Retainer <NUM> can be arranged proximate flange portion <NUM>. Retainer <NUM> can present protrusion <NUM>, extending axially inboard outside the outer diameter of flange portion <NUM>. Protrusion <NUM> can be radially spaced from the outer face of flange portion <NUM>. Carrier <NUM> can be axially and rotationally fixed to gland plate <NUM> by one or more pins <NUM>, though other fixation mechanisms can be used. Biasing members <NUM> can comprise one or more radially spaced springs, though other biasing mechanisms known in the art can be used. In embodiments, one or both of retainer <NUM> and carrier <NUM> can include bores adapted to house at least part of each biasing member <NUM>, such that biasing members <NUM> are partially located within retainer <NUM> and carrier <NUM>.

Those of ordinary skill in the art will appreciate that the arrangements depicted in <FIG> and <FIG> include components that may be altered or eliminated in other seal assembly embodiments. In addition more or fewer components may be incorporated in other embodiments of seal assemblies according to the present disclosure.

In operation, rotation of shaft <NUM> can drive sleeve member <NUM> and axially fixed seal ring <NUM> to rotate relative to axially shiftable seal ring <NUM>. Seal lubricant (not shown) can be provided to seal <NUM> through one or more inlets provided in housing <NUM> to lubricate seal sealing faces <NUM> and <NUM> and to create a pressure gradient across sealing faces <NUM> and <NUM>.

The pressure gradient and hydraulic pressure created by the relative rotation of sealing faces <NUM> and <NUM> can resulting in an opening force, urging axially shiftable seal ring <NUM> axially outboard from axially fixed seal ring <NUM>. Similarly, a closing force can be provided by biasing mechanism <NUM>, urging axially shiftable seal ring <NUM> inboard toward axially fixed seal ring <NUM>.

Those of ordinary skill in the art will appreciate that the closing force at a seal face interface can be calculated from the closing area (AC), the opening area (AO), the outer diameter of the stationary ring face (OD), the inner diameter of the stationary ring face (ID) and the balance diameter (BD), as detailed below: <MAT> where <MAT>.

Flange portion <NUM> can shift axially and radially based on the relative closing and opening forces, and the axial translation of the shaft itself, such that the closing force applied to axially shiftable seal ring <NUM> is constant, regardless of the position of flange portion <NUM>.

<FIG> are detail views of an embodiment of a seal assembly, in which some effects of axial movement on sealing membrane <NUM> can be seen. An axially outward translation of the shaft can be transmitted to flange portion <NUM> via sleeve <NUM>, axially fixed ring <NUM>, and axially shiftable seal ring <NUM>. This movement can cause flange portion <NUM> to compress slightly and distort at an angle, preventing any changes in the opening and closing forces at the seal interface. In particular, as depicted, axially outboard translation of axially shiftable seal ring <NUM> can transmit the opening force to flange portion <NUM>, causing flange portion <NUM> to be translated axially outboard and radially outward away from stub sleeve <NUM> as depicted in <FIG>. Conversely, an axially inward translation of the shaft can relieve pressure on flange portion <NUM>, enabling flange portion <NUM> to translate axially inboard and radially inward against stub sleeve <NUM>. This contact between sealing membrane and stub sleeve <NUM> can further minimize leakage.

A high pressure gradient across sealing faces <NUM> and <NUM> can encourage partial extrusion of flexible sealing membrane <NUM> between stub sleeve <NUM> and axially shiftable seal ring <NUM>. This can be resisted by the harder material of anti-extrusion ring <NUM>.

Over the life of the seal, sealing faces <NUM> and <NUM> will wear relative to each other. Because sealing membrane <NUM> can move inboard, toward process chamber <NUM>, and outward, away from process chamber <NUM>, over the life of the seal, it can help to maintain an appropriate seal gap. Hydraulic pressure can keep the axially shiftable seal ring <NUM> from contacting axially fixed seal ring <NUM> while the flange portion <NUM> of sealing membrane <NUM> moves inboard. The hydraulic pressure can keep the other components, such as stub sleeve <NUM>, in place. Further, because coaxial portion <NUM> is below the balance diameter of the seal, the hydraulic pressure applied to coaxial portion <NUM> will not affect the closing force, or the balance diameter itself. Biasing mechanism <NUM> can be used to set the working height of the seal and compress flange portion <NUM> of sealing membrane <NUM> against an end of the axially shiftable seal ring <NUM> (distal in relation to the process chamber, and opposite sealing face <NUM>) of the axially shiftable seal ring <NUM> (creating a seal) when no hydraulic pressure is present. Because the vertical force is not altered by the axial movement of sealing membrane <NUM>, and the closing force at the interface of sealing faces <NUM> and <NUM> is not affected.

The maximum axially outboard translation of flange portion <NUM> and retainer <NUM> can be defined by a gap provided between an outboard face of retainer <NUM> and an inboard face of carrier <NUM>, or by the compression limit of biasing members <NUM>. In embodiments, translation of flange portion <NUM> can be limited to prevent bunching, folding over, or other collapsing of sealing member <NUM> at connecting portion <NUM>. In one embodiment, translation of flange portion <NUM> can be limited to maintain angles θ or ϕ.

In addition, because flange portion <NUM> is held in a radially extending orientation by axially shiftable seal ring <NUM> and retainer <NUM>, coaxial portion <NUM> is held in an axially extending orientation by stub sleeve <NUM> and band <NUM>, sealing member <NUM> is non-collapsible.

As can be seen in <FIG>, the angle θ between flange portion <NUM> and coaxial portion <NUM> of sealing membrane <NUM> provides for directional control of the forces acting on stub sleeve <NUM> and axially shiftable seal ring <NUM>. Coaxial portion <NUM> allows flexibility of flange portion <NUM> and connecting portion <NUM> while flange portion <NUM> is under pressure at the balance diameter of the seal.

Various embodiments of systems, devices, and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the claimed inventions. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the claimed inventions.

Persons of ordinary skill in the relevant arts will recognize that the subject matter hereof may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features of the subject matter hereof may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the various embodiments can comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. Moreover, elements described with respect to one embodiment can be implemented in other embodiments even when not described in such embodiments unless otherwise noted.

Claim 1:
A mechanical seal assembly adapted for arrangement around a rotating shaft, the mechanical seal assembly having a first and a second seal ring, the first seal ring axially shiftable relative to the rotating shaft (<NUM>) and the second seal ring (<NUM>) axially-fixed relative to the rotating shaft (<NUM>), the mechanical seal assembly comprising:
a biasing mechanism (<NUM>) that urges the axially shiftable first seal ring (<NUM>) toward the axially fixed second seal ring (<NUM>);
an annular flexible sealing membrane (<NUM>) comprising:
a flange portion (<NUM>) arrangeable between the axially shiftable first seal ring (<NUM>) and the biasing mechanism, the flange portion (<NUM>) being axially shiftable relative to the rotating shaft (<NUM>) by forces transmitted to the flange portion (<NUM>) by the biasing mechanism, and the first seal ring (<NUM>);
a flexible connection portion (<NUM>) at a radially inward extent of the flange portion (<NUM>), wherein the flexible connection portion (<NUM>) presents an angular facet (<NUM>) at a radially inward side;
a coaxial portion (<NUM>) extending axially from the flexible connection portion (<NUM>), the coaxial portion (<NUM>) held axially fixed to a stub sleeve (<NUM>) by an annular band at an outer diameter and the stub sleeve (<NUM>) at an inner diameter, wherein the stub sleeve (<NUM>) abuts the coaxial portion (<NUM>) and the axially shiftable first seal ring (<NUM>);
characterised in that the stub sleeve (<NUM>) abuts the angular facet (<NUM>), and the flexible connecting portion (<NUM>) is configured such that it flexes in response to axial movement of the axially shiftable first seal ring (<NUM>) and the flange portion (<NUM>) such that the closing force applied to the axially shiftable first seal ring (<NUM>) is not affected; and
such that axially inward translation of the shaft (<NUM>) causes the flange portion (<NUM>) to translate axially inboard and radially inward against the stub sleeve (<NUM>).