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.

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 defined or otherwise carried by so called "primary" and "mating rings. " 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/primary ring. 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 non-collapsible flexible sealing membrane for incorporation in a mechanical seal assembly and use in rotary shaft equipment, in which the sealing membrane includes a substantially radially outward extending first flange portion, which can be urged into an axially shiftable ring by a biasing mechanism, and a substantially axially outboard extending second coaxial portion, substantially radially inward of the balance diameter of the seal and that is held fixed to a stub sleeve by an annular band.

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 flexible sealing membrane for incorporation in a mechanical seal assembly and use in rotary shaft equipment. The mechanical seal assembly of the invention is defined in claim <NUM>.

The flexible sealing membrane can be implemented, generally, as a ring that includes an outer, substantially radially extending portion, which can be urged into an axially shiftable ring by seal components such as a plurality of axially spaced springs. This first portion is generally non-collapsible and surrounds an inner portion that is generally thinner than the outer portion. In operation, movement of the primary ring relative to the shaft will result in deflection of the outer portion relative to the inner portion and in some cases, the rotating shaft of the rotary shaft machine.

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

In one embodiment, a mechanical seal assembly adapted for arrangement around a rotating shaft of a rotating device is disclosed. The mechanical seal assembly includes a first seal ring that, in operation, is axially shiftable relative to the rotating shaft and a second seal ring that, in operation, is axially fixed relative to the rotating shaft. The assembly also includes an annular carrier having a base and a removable end portion configured to be affixed to a housing of the rotating device. The axially shiftable first seal ring is proximate and axially shiftable relative to the annular carrier in response to axial movement of the rotating shaft and the axially fixed second seal ring and the axially shiftable first seal ring has an axially shiftable seal face that interfaces with an axially fixed seal face of the axially fixed second seal ring. Also includes is a biasing mechanism that urges the axially shiftable first seal ring toward the axially fixed second seal ring to engage the axially shiftable seal face to the axially fixed seal face with a closing force and an annular flexible sealing membrane.

The sealing membrane can be any membrane disclosed herein. For example, the sealing membrane can include an outer portion arrangeable between the axially shiftable first seal ring and the biasing mechanism and that is axially shiftable relative to the rotating shaft. The membrane can also include an inner portion surrounded by the outer portion and positioned between the base and the removable end portion of the annular carrier. In at least one embodiment, the base and the removable end portions hold the inner portion fixed relative to the annular carrier as the outer portion shifts relative to the rotating shaft.

In any prior embodiment, the base can have an upper surface with a depression formed therein that is arranged proximate the outer portion of the annular flexible sealing membrane.

In any prior embodiment or alternatively, the removable end portion can have an upper surface with a depression formed therein that is arranged proximate the outer portion of the annular flexible sealing membrane.

In any prior embodiment or alternatively, the outer portion presents a thicker cross-section than a cross-section of the inner portion.

In any prior embodiment or alternatively, the biasing mechanism comprises an axially shiftable annular retainer proximate the outer portion and a plurality of radially spaced spring members arranged between the annular carrier and the retainer.

In any prior embodiment or alternatively, the assembly can further comprise a rotating sleeve operably coupled to the rotating shaft for rotation therewith and wherein the axially fixed second seal ring is operably coupled to the sleeve. In any prior embodiment or alternatively, wherein the axially fixed second seal ring is operably coupled to the sleeve by a plurality of pins.

In any prior embodiment or alternatively, the sealing membrane can comprise a flexible elastomer.

In any prior embodiment or alternatively, the seal assembly can further comprise an anti-extrusion ring within a groove of the axially shiftable first seal ring.

In any prior embodiment or alternatively, the anti-extrusion ring can comprise a material of a greater hardness than the flexible elastomer of the sealing membrane.

In any prior embodiment or alternatively, the seal assembly can further comprise a gland plate adapted to connect to the housing and the carrier can be connected to the gland plate.

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

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 falling within the scope of the subject matter as defined by the claims.

<FIG> is a cross-sectional views depicting a portion of a seal assembly <NUM> including a flexible 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> (e.g., a body of a rotary machine) coaxial of the shaft <NUM>. Various stationary (or non-rotating) components of seal assembly <NUM> can be operably coupled to the housing <NUM> or another element such as a gland plate generally indicated by reference number <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>.

An axially fixed seal ring <NUM> (or mating ring) is mounted on the face of the annular flange formation <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>.

In the following discussion, direction A shall be referred to as the outboard direction (with the opposite direction being inboard direction) and direction B shall be referred to as the radially outward direction).

The sealing membrane <NUM> presents a generally dumbell-shaped cross-section, comprising an outer portion <NUM> and an inner portion <NUM> surrounded by the outer portion <NUM>. An inboard face of outer portion <NUM> can abut outboard face of the axially shiftable seal ring <NUM>, creating a pressure tight seal. The outer portion <NUM> can tilt or otherwise move relative to the inner portion as the axially shiftable ring <NUM> moves. As shown in <FIG>, the inner portion <NUM> can present a thinner cross section than the outer portion <NUM> to enable such relative movement.

The inner portion <NUM> is fixed to and held by an annular carrier <NUM>. In more detail, the annular carrier <NUM> can be connected to the housing <NUM> or the gland plate <NUM> and a provides a stable and generally non-moveable base for a biasing mechanism <NUM> discussed below.

The illustrated annular carrier <NUM> is illustrated as including two portions, a primary or base portion <NUM> and a removable end portion <NUM> that can be attached to the base portion <NUM> by, for example, a fastener <NUM>. The annular carrier <NUM> and the fastener <NUM> can comprise steel or stainless steel in embodiments.

The base portion <NUM> and the removable end portion <NUM> can be sized and arranged such that hold the sealing membrane <NUM>. As illustrated, the inner portion of the sealing membrane is disposed between the base portion <NUM> and the removable end portion <NUM> in such a manner that the inner portion <NUM> does not move relative to the base portion <NUM> or the housing <NUM>. More details of the sealing membrane <NUM> are discussed below.

An annular anti-extrusion ring <NUM> can be present in an annular groove of axially shiftable seal ring <NUM> and abut or be proximate to the outer portion <NUM> or other portions of the sealing member <NUM> and the annular carrier <NUM>. The 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). In one embodiment, 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 assembly <NUM>.

The biasing mechanism <NUM> can abut the outer portion <NUM> of the sealing member <NUM>. Biasing mechanism <NUM> can comprise an axially shiftable annular retainer <NUM>, the fixed carrier <NUM>, and one or more biasing members <NUM> spanning therebetween. The retainer <NUM> can be arranged proximate to the outer portion <NUM>. The retainer <NUM> can present a protrusion <NUM>, extending axially inboard outside the outer diameter of outer portion <NUM>. The protrusion <NUM> can be radially spaced from the outer face of outer portion <NUM>. The primary base portion of the fixed 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. The 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 the base portion <NUM> can include bores adapted to house at least part of each biasingmember <NUM>, such that biasing members <NUM> are partially located within retainer <NUM> and base portion <NUM>.

Those of ordinary skill in the art will appreciate that the arrangement depicted in <FIG> includes 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 the shaft <NUM> can drive sleeve member 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 <NUM> provided in housing <NUM> to lubricate the 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 the sealing faces <NUM> and <NUM> can result in an opening force, urging axially shiftable seal ring <NUM> axially outboard (direction A) from the axially fixed seal ring <NUM>. Similarly, a closing force can be provided by the 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>.

The outer portion <NUM> can shift (or otherwise translate) 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 outer portion <NUM>.

<FIG> show an example sealing member <NUM> according to one embodiment and a cross-section thereof, respectively. The sealing member <NUM> includes the outer portion <NUM> and the inner portion <NUM>. The inner portion <NUM> has a first thickness T1 and the inner portion <NUM> has a second thickness T2. T1 is greater than T2 in one embodiment. In one embodiment, T1 is three times larger than T2.

As discussed above and with further reference to <FIG>, motion of the shiftable seal ring <NUM> will cause the outer portion <NUM> to move axially inboard/outboard. The difference in thickness between the inner and outer portions <NUM>, <NUM> will allow for such flexion while the inner portion is held axially fixed relative to the housing <NUM> by the fixed/annular carrier <NUM>.

With reference to <FIG> and <FIG>, the annular carrier <NUM> can include one or more depressions formed radially outward surfaces thereof that allow for the movement of the outer portion <NUM> of the sealing member <NUM>. In particular, the base <NUM> of the annular carrier <NUM> includes an outer surface <NUM> that has a depression 210a formed therein that is arranged, in operation, near the outer portion <NUM>. Similarly, the removable end portion <NUM> of the annular carrier <NUM> includes an outer surface <NUM> thathas a depression 208a formed therein that is arranged, in operation, near or proximate the outer portion <NUM>. These depressions are optional but may allow for easier relative movement of the outer portion <NUM> relative to the inner portion <NUM> as the primary ring <NUM> moves. The depressions 208a/210a can, individually or collectively, define a flange travel region <NUM>. Further, in some embodiments, only one of the depressions may be provided.

For example, with reference to <FIG>, the outer portion <NUM> can move axially inboard (direction A) relative to the inner portion <NUM> as shown in FIG. 4B shows a situation where the outer portion <NUM> has moved axially outboard (direction A') relative to the inner portion <NUM>. In both cases, the inner portion <NUM> is held in a substantially constant location due to it being captivated between the base portion <NUM> and the removable end portion <NUM> of the annular carrier <NUM> (see <FIG>).

Referring back to <FIG>, the sealing member <NUM> includes a central hole <NUM> formed in the inner portion <NUM>. This central hole <NUM> can be sized and arranged such that surrounds the shaft <NUM> and, optionally, the sleeve member <NUM>. The sealing member <NUM> can include one or more fastener holes <NUM> through which the fasteners can pass to join the base and removable end portions <NUM>, <NUM> of the annular carrier <NUM>. It shall be understood that the base and a removable end portions <NUM>, <NUM> hold the inner portion <NUM> fixed relative to the annular carrier <NUM> as the outer portion <NUM> shifts. Such shifting can be relative to the rotating shaft <NUM>. Of course, end regions of the inner portion <NUM> may slightly shift with the outer portion <NUM> but the vast majority is held immovable and herein shall be included when describing the inner portion <NUM> as immovable, fixed, or otherwise not shifting.

As discussed above, the depressions 208a/210a are optional and can be omitted as shown in <FIG>. Further, the extrusion ring <NUM> can be omitted in some embodiments as shown in <FIG>. It should be noted that the extrusion ring can be omitted in cases without and without the depressions.

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 outer portion <NUM> of sealing membrane <NUM> moves inboard. Biasing mechanism <NUM> can be used to set the working height of the seal and compress outer 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. In some embodiments, due to the depressions, the vertical force may not be 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 outer portion <NUM> and retainer <NUM> can be defined by a gap provided between an outboard face of retainer <NUM> and an inboard face <NUM> of carrier <NUM>, or by the compression limit of biasing members <NUM>. In embodiments, translation of outer portion <NUM> can be limited to prevent folding over, or other collapsing of sealing member <NUM>.

In addition, because outer portion <NUM> is held in a radially extending orientation by axially shiftable seal ring <NUM> and retainer <NUM>, inner portion <NUM> is held in an axially extending orientation the base and removable end portions <NUM>, <NUM> of the annular carrier <NUM>, the sealing member <NUM> is non-collapsible.

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 invention, the scope of the invention being only limited by the appended claims. It should be appreciated, moreover, that the various features of the embodiments thathave been described may be combinedin 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 (<NUM>) adapted for arrangement around a rotating shaft (<NUM>) of a rotating device, the mechanical seal assembly (<NUM>) comprises:
a first seal ring (<NUM>) that, in operation, is axially shiftable relative to the rotating shaft (<NUM>);
a second seal ring (<NUM>) that, in operation, is axially fixed relative to the rotating shaft;
an annular carrier (<NUM>) having a base (<NUM>) and a removable end portion (<NUM>) configured to be affixed to a housing (<NUM>) of the rotating device, wherein the axially shiftable first seal ring (<NUM>) is proximate and axially shiftable relative to the annular carrier (<NUM>) in response to axial movement of the rotating shaft (<NUM>) and the axially fixed second seal ring (<NUM>), and wherein the axially shiftable first seal ring (<NUM>) has an axially shiftable seal face (<NUM>) that interfaces with an axially fixed seal face (<NUM>) of the axially fixed second seal ring (<NUM>);
a biasing mechanism (<NUM>) that urges the axially shiftable first seal ring (<NUM>) toward the axially fixed second seal ring (<NUM>) to engage the axially shiftable seal face (<NUM>) to the axially fixed seal face (<NUM>) with a closing force; and
an annular flexible sealing membrane (<NUM>) comprising:
an outer portion (<NUM>) arrangeable between the axially shiftable first seal ring (<NUM>) and the biasing mechanism (<NUM>), the outer portion (<NUM>) being axially shiftable relative to the rotating shaft (<NUM>);
an inner portion (<NUM>) surrounded by the outer portion (<NUM>) and positioned between the base (<NUM>) and the removable end portion of the annular carrier,
wherein the annular flexible sealing membrane (<NUM>) comprises a central hole (<NUM>) formed in the inner portion (<NUM>) and arranged to surround the shaft (<NUM>), the inner portion (<NUM>) extends radially outward from the central hole (<NUM>), and the outer portion (<NUM>) extends radially outward from the inner portion (<NUM>),
wherein the annular flexible sealing membrane (<NUM>) presents a generally dumbell-shaped cross-section, comprising the outer portion (<NUM>) and the inner portion (<NUM>) surrounded by the outer portion (<NUM>);
wherein the base (<NUM>) and the removable end portions (<NUM>) hold the inner portion (<NUM>) fixed relative to the annular carrier (<NUM>) as the outer portion (<NUM>) shifts relative to the rotating shaft (<NUM>).