CA1129905A - Fluid seal with lubricated sealing surfaces - Google Patents
Fluid seal with lubricated sealing surfacesInfo
- Publication number
- CA1129905A CA1129905A CA337,932A CA337932A CA1129905A CA 1129905 A CA1129905 A CA 1129905A CA 337932 A CA337932 A CA 337932A CA 1129905 A CA1129905 A CA 1129905A
- Authority
- CA
- Canada
- Prior art keywords
- seal
- elastomer
- sealing
- rigid
- sealing surface
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Sealing With Elastic Sealing Lips (AREA)
Abstract
ABSTRACT
A fluid seal (10) for sealing against leakage be-tween relatively moving machine elements (12, 14) is capable of establishing a lubricant film between ad-jacent sliding sealing surfaces (24, 26) of the elements (12, 14) without affecting sealing between the surfaces and while establishing pressure balancing of the seal so that the pressure between the sealing surfaces is substantially less than the sealed pressure, includes as its essential elements an elastomer seal member (16) having a sealing surface (26) in sliding contact with a rigid opposed sealing surface (24). Shaped rigid members (18) enable formation and continued generation of the lubricant film and pressure balancing of the seal by controlling the deformation of the elastomer surface (26) when the latter is subjected to the sealed pressure and sliding friction between the sealing surfaces (24, 26).
The seal can be formed both as a radial type seal with annular sealing surfaces (24, 26) and as an axial type seal with flat sealing surfaces.
A fluid seal (10) for sealing against leakage be-tween relatively moving machine elements (12, 14) is capable of establishing a lubricant film between ad-jacent sliding sealing surfaces (24, 26) of the elements (12, 14) without affecting sealing between the surfaces and while establishing pressure balancing of the seal so that the pressure between the sealing surfaces is substantially less than the sealed pressure, includes as its essential elements an elastomer seal member (16) having a sealing surface (26) in sliding contact with a rigid opposed sealing surface (24). Shaped rigid members (18) enable formation and continued generation of the lubricant film and pressure balancing of the seal by controlling the deformation of the elastomer surface (26) when the latter is subjected to the sealed pressure and sliding friction between the sealing surfaces (24, 26).
The seal can be formed both as a radial type seal with annular sealing surfaces (24, 26) and as an axial type seal with flat sealing surfaces.
Description
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FLUID SEAL WITH LUBRICATED SEALING SURFACES ~ -.
FIELD OF THE INVENTION
The invention relates to sealing devices used to prevent leakage of fluid between relatively moving , ~ machine elements.
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~ BACKGROUND OF PRIOR ART
., ` " ~ `
i ~Sealing devlces in common use for sealing against ; fluid leakage between relatively moving machine elements have performance limitations and operational disadvantages.
; The elastomeric radial type 11p seal utilizes an extremely ~ narrow lip contact area and a tight fit around a shaft i circumference in order to effectively seal. The seal pressuré increases the tightness of the fit. The result-i~ inghigh pressure loadings at the sealing surfaces prevents , ~
- the~formation of a lubricant film. High sealed pressures ~ and sliding speeds are severely limited, as the sliding '~f friction causes rapid destruction of the sealing ~ i .
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surfaces. Mechanical axial flat -face seals have relatively large sealing areas that eEfectively seal. However, the combination of the flat face and the large sealing area prevents the entrance of the sealed fluid between -the seal-ing surfaces to form a lubricant film adequate for highsealed pressures and sliding speeds. The sliding friction generated by these operating conditions would destroy the sealiny surfaces by wear and overheating. Low viscosity sealed fluids, such as water, are particularly deleterious to both the radial lip and~axial face seals.
Open path labyrinth and externally pressurized seal-ing devices are used when the operating requirements are beyond the capability of sliding surface c~osed path seals.
These seals also have performance limitations and disadvan-tages. The labyrinth seal requires an excessively longlength to seal substantial pressures and is limited to applications where continuous leakage is acceptable and where a means for collectlng and disposing of the leakage ', fluid is convenient and available. The externally pres-surized seallng device blocks fluid leakage by admittance of a fluid pressurized by an external source into the leakage path. The pressurized fluid leaks both internally and externall~. The~fluid must be compatible with the system fluid and a means~for disposing of the external leakage must be provided. The requirement for an external pressure source and the energy consumption are obviously undesirable , ... , . ~ . . , - : .
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What is needed is a closed path fluid seal that can operate over an unlimited ranye of sealed pressures, speeds, and sealed fluid viscosity. It is the object of this in-~ vention to provide such a fluid seal.
.1 ) ` SUMMARY OF THE INVENTION
. .
In accordance with the invention, a sealing device , for sealing against fluid leakage between two relatively moveable machine elements is provided which comprises a uniquely constructed elastic (elastomer) sealing surface attached to one of the machine elements in sliding contact with a rigid sealing surface attached to the other machine ' element for the purpose of blocking the leakage path.
`I The unique aspect of the construction of the elastomer .~ . , sealing surface is'the embeddment therein below and parallel to theslidlng surface of a consecutive series of relatlvely rigid members particular]y shaped to control ' the deformation of the~elastomer surface when it is sub-jected to the sealed pressure~ and the~frlction forces at the sliding contact area so as to form a hydrodynamically pressuriz d~lubrlcant film between~the slldlng~surfaces and to reduce the pressure at the sealing surfaces substan-tially below that of the sealed~pressure.
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The seal assembly comprises a relatively thick ring of elastomer material bonded to a structural rigid member that is attached to the machine assembly in a manner to align the sealing surface of the elastomer material with the mating rigid sealing surface similarly supported by the machine assembly. The consecutive series of shaped rigid members are embedded in the elastomer material be-` tween its sealing surface and structural support members.
The surfaces of the shaped members are bonded to the elas-tomer material so that no leakage path e~ists around the ; members.
The shape of the embedded rigid members is as follows.
The surface of the members facing the sealing sliding sur-face of the elastomer (front surface) parallels the sealing surface. The surface of the members facing away from the ,~
; elastomer sealing surface (back surface) is spherically or compound curved, with the center of curvature being -located in the direction~of the sèaling surfaceO The - , ; sides of the members are normally straight (they can be ~ ~ 20 curved), formlng a-square or rectang1e~ The surface of ; the structural support member adjacent the spherically curved surfaces on the shaped members is similarly curved, and the two surfaces are separated by-a thin layer of elastically deformable material. An alternate embodiment .
~ 25 utilizes extremely ~hin, alter~ate, curved lamunates of elastomer and a .
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.,, ~, , relatively rigid material (metal) between the surfaces, the purpose of which will be explained later herein.
In accordance with the invention, the seal device can be formed as a radial type seal with an annular seal-ing surface or as an axial -type seal with a flat sealing surface.
By this unlque sealing surface construction, as explained in detail below, a virtually indestructible i lubricant film is formed between the sealing surface while maintaining effective sealing. As a result, the seal can operate over an unli~ited range of sealed pres-sures, speeds, and sealed fluid viscosity with extended endurance. The invention is a~major advancement in the state-of-the-art of sealing devicesO
The invention can better be understood by reference to the appended drawings which illustrate the radial and axial form of the invention, and which are explained in ~-the following detailed description.
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BRIEF DESCRIPTION OF THE DRAWINGS
FIGU~E 1 is a side elevation in cross-section of a presently preferred form of the radial seal embodying the invention;
FIGURE lA shows an enlarged detail of an alternate embodiment of the seal;
FIGURE 2 is a fragmentary vertical sectional view taken along line 2-2 in FIGURE l; -FIGURE 3 is an enlarged detail view of the seal show- . --ing how it responds to the sealed pressure;
FIGURE 4 is an enlarged detail view of the seal show-ing how it responds to the sliding friction forces at the ~ -sealing surfaces; and FIGURE 5 i5 a side elevation view in cross-section of an alternate embodiment of the seal in the form of an -15 axial type seal. . : :
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.~. DETAILED DESCRIPTION OF PREFERRED EMBODI~NT
With reference to the appended drawings, Figures 1 and 2, the radial form of the seal embodying the present invention is shown at 10 supported by housing of.the machine 14 in sealing alignment with a rotating shaft 12, the shaft sealing surface 24 sliding on the elastomer sealing surface 26 of the seal 10. Figures 1 and 2 show the seal l0 at rest, that is, the shaft not rotating and no sealed pressure exists. .
The.seal 10 consists of a relatively thick, contin-uous elastomer seal member in the form of a ring 16 with shaped rigid members 18 embedded in the ring between the elastomer sealing surface 26 and a structural support ~ .
member 20 for the elastomer seal 16, the shaped members 18 being circumferentially spaced within the elastomer seal 16 (see Figure 2) along the direction of relative motion betwèen the shaft 12 and the housing 14. The surface 36 of the shaped members 18 facing the elastomer sèaling surface 26 parallels the sealing~surface:26.
: The surfaces 38 of the shaped members facing the~struc-tural support members 20 are convex spherically curved (they may be aompound curved about different centers of curvatuxe in planes normal to~each other), with their ~; respective centers of curvature 22 being located in the directlon of the seallng surface 26 (on the same side of ~: 25 the seal 16 as the shaft 12), preferably between the , ~
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-~?~ 5 rotational axis of rhe shaft 12 and the sealing surface 24. The surface 40 on the structural support ring 20 facing the spherical surface 38 on the shaped members 18 is concave spherically curved concentric with the convex spherically curved surface 38 on the shaped members 18, the surfaces 38 and 40 being separated by a thin section of elastically deformable material 32 that is part of (e.g., integral with) the elastomer seal 16. An alternate construction for this thin section of material is shown by Figure lA, wherein the thin elastomer section is di-vided into a number of thinner sections 28 spaced aparat and bonded to rigid laminates 30. The elastomer seal 16 extends between the shaped members 18 to form a solid sealing member. All the surfaces of the rigid members 20, 18, and 30 in contact with the elastomer seaI 16 are bonded thereto.
The operation of the invention shown in Figures 1 .
and 2 is represented ln Figures 3 and 4, It is based on the natural physical properties of elastic materials '~
such as elastomers, and the control of its deformation by the embeddment o rigid members in the material. Similar to most engineering materials, elastomers are v irtually incompressible, but deformable similar to springs (the modulus of elasticity of materials is actually a spring rate). Peculiar to elastomers is that the bulk compres-sion stiffness is much greater than bulk shear stiffness . .
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,. : .; .,, and that for small deformations, the shear stiffness is independent of the compression stress. The compression/
shear stiffness ratio is further increased by shaping the elastomer material so that thebul~e area is small compared to the compression load area.
In the operation of the invention, the elastomer is deformed solely in the shear mode and, as the value of the shear deformation is minute (as described later herein~, the shear stiffness forces resisting the deformation can be ignored during operation. As to control of the elas-tomer deformation in the invention, note in Figures 1 and 2 that the bulk area of the thin elastomer section 32 supporting the shaped rigid members 18 is small compared to the spherically curved area. Thus, the shaped members 18 are constrained from displacing in the radial (compres--sion) directions, but can readily displace in the elas-tomer shear direction, that is, a swing-like motion around the center of the spherical curvature 22.
The gaps 42 and 34 ~ormed by the displacement of the shaped members 18 is shown greatly exaggerated for clarity .: .
in Figures 3 and 4. These gaps represent the lubricant .
film that is formed betwçen the sealing surfaces. Lub-ricant films formed between sliding surfaces are actually unperceptible, less than 103 inch thick (.254 mm) for ;~ 25 viscous fluids such as oils, and less than 104 inch thick (.025 mm) for low viscosity fluids such as water.
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Likewise, the deformation of the elastomer to form these gaps is unperceptible, and thus the elastomer shear forces resisting the formation of the gaps can be iynored in the operation of the invention.
It is important to clarify the nature and character of a lubricant film between sliding surfaces. The lub-ricant film need not be any thicker than a boundary film to prevent surface contactunder lightly loaded conditions.
A few drops of lubricant is sufficient to form a boundary film and the leakage of a ~fluid between two surfaces in sliding contact with boundary lubrication is negligible.
However, when the sliding velocity is high, the heat generated by the viscous shear can destroy the lubricant film and the surfaces. The simplest method for prevent-15 ing overheatin~ is to flush the sliding surfaces with -cool lubricant. This normally results in substantial leakage between sealing surfaces. Furthermore, high loadings between the surfaces makes it difficult to admit the coollng lubrlcant. - ~
Proceeding with the description of the operation of the invention, Flgure 3 shows how the sealed pressure simultaneoulsy activates sealing and the admission of the sealed fluid for lubrication purposes between the sealing .. -surfaces. The sealed pressure moment cPl causes the shaped member 18 to swing in direction to simultaneously lift the internal edge of the sealing surface admitting ~'' .
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the sealed fluid between the sealing surfaces and compres-sing the e~ternal edge to ac-tuate sea]ing. The fluid pressure profile in the gap ~2 (exaggerated for clarity in Figure 3) is a function of the value of sealed pres-sure and the gap geometry~ Pressure moments aP2 withinthe gap will add to the swing motion o~ member 18. Pres-sure moments bP3 and the moments of the forces at the sealing surfaces will substract from the swing mo-tion. ,-;
The shaped member 18 will stabilize in the sealing posi-tion when the moments are in equilibrium. The compression of the elastomer surface and the sealing area between the sealing surfaces (elastomer area in contact with shaft) both increase with increasing sealing pressures, thus increasing sealing and decreasing the pressure loading at the sealing area~ This method of "pressure balancing"
in the invention is unique.
Figure 4 shows how the slidin`g friction at the seal-ing surfaces actuates-the formation of an adequate lubri-cation film between the sealing surfaces under operating conditions of high sealed pressures and rotational speeds.
The drag from the friction forces displace the elastomer sealing surface 26 in the dixection of motion, forcing the shaped members to swing about their respective centers of-curvature 22 and to deform the sealing surface 26 from a smooth cylindrical surface into a wavy cylindrical sur-~ace pattern, the crests of the waves occurring at the side of each shaped member 18 in the cirection of motion, : ' ' , ' ' ' ~ ,: , .
.
.. . .
. : ~ ' ' . ' forming a lubricant film consisting of a consecutive series of wedge shapes 46 converging in the direction of relative movement of the adjacent sealing surface 24.
Hydrodynamic action generates pressure in the lubricant film, thus maintaininy the film when the sealed pres-sures are high, and rotation circulates the lubricant for cooling. The combined deformation of the sealing surface 26 from the action of ~he sealed pressures and the friction forces results in fluid lubrication at the internal edge of the sealing surface (towards the pressure source) tapering to boundary lubrication at the external edge. Leakage is negligible~ The motion of the shaft sealing surface 26 can be a combined rotating and axial motion without affecting sealing, a feature unique to the invention. The sealing surfaces can be reversedi that is, the elastomer sealing surfaces can be attached to the shaft and the rigid sealing surfaces fixed to the machine housing. The wedge shapes 46 are shown exaggerated in Figure 4 for clarity.
An alternate form of the invention is an axial seal with flat sealing surfaces as shown in Figure 5. The basic principle of operation will not be repeated as it is identical to that of radial form of the invention, shown in--Figures 3 and 4, except the lubrication film is formed between flat sealing surfaces in lieu of cylindrical sur-faces. In Figure 5, the sealing surface 26 lies in a ., .- . .
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~ 13 -.~ single plane and is normally ur~ed by spring 52 against the cooperating sealing surface on opposite member 50 fixed to machine housing 14. The seal assembly 10 in this embodiment may or may not rotate with shaft 54, and may or may not be slidable longitudinally along shaft 54.
Various forms of the inven~ion and modifications to the illustrated specific exemplary embodiments can be made within the scope and spirit of the invention. The I -invention is not intended to be limited except by the scope of the claims.
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.
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FLUID SEAL WITH LUBRICATED SEALING SURFACES ~ -.
FIELD OF THE INVENTION
The invention relates to sealing devices used to prevent leakage of fluid between relatively moving , ~ machine elements.
. - .
'I ' .
~ BACKGROUND OF PRIOR ART
., ` " ~ `
i ~Sealing devlces in common use for sealing against ; fluid leakage between relatively moving machine elements have performance limitations and operational disadvantages.
; The elastomeric radial type 11p seal utilizes an extremely ~ narrow lip contact area and a tight fit around a shaft i circumference in order to effectively seal. The seal pressuré increases the tightness of the fit. The result-i~ inghigh pressure loadings at the sealing surfaces prevents , ~
- the~formation of a lubricant film. High sealed pressures ~ and sliding speeds are severely limited, as the sliding '~f friction causes rapid destruction of the sealing ~ i .
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, . . .
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surfaces. Mechanical axial flat -face seals have relatively large sealing areas that eEfectively seal. However, the combination of the flat face and the large sealing area prevents the entrance of the sealed fluid between -the seal-ing surfaces to form a lubricant film adequate for highsealed pressures and sliding speeds. The sliding friction generated by these operating conditions would destroy the sealiny surfaces by wear and overheating. Low viscosity sealed fluids, such as water, are particularly deleterious to both the radial lip and~axial face seals.
Open path labyrinth and externally pressurized seal-ing devices are used when the operating requirements are beyond the capability of sliding surface c~osed path seals.
These seals also have performance limitations and disadvan-tages. The labyrinth seal requires an excessively longlength to seal substantial pressures and is limited to applications where continuous leakage is acceptable and where a means for collectlng and disposing of the leakage ', fluid is convenient and available. The externally pres-surized seallng device blocks fluid leakage by admittance of a fluid pressurized by an external source into the leakage path. The pressurized fluid leaks both internally and externall~. The~fluid must be compatible with the system fluid and a means~for disposing of the external leakage must be provided. The requirement for an external pressure source and the energy consumption are obviously undesirable , ... , . ~ . . , - : .
.
,, ~ , .
:
~: ' ', ' ~ ' .
What is needed is a closed path fluid seal that can operate over an unlimited ranye of sealed pressures, speeds, and sealed fluid viscosity. It is the object of this in-~ vention to provide such a fluid seal.
.1 ) ` SUMMARY OF THE INVENTION
. .
In accordance with the invention, a sealing device , for sealing against fluid leakage between two relatively moveable machine elements is provided which comprises a uniquely constructed elastic (elastomer) sealing surface attached to one of the machine elements in sliding contact with a rigid sealing surface attached to the other machine ' element for the purpose of blocking the leakage path.
`I The unique aspect of the construction of the elastomer .~ . , sealing surface is'the embeddment therein below and parallel to theslidlng surface of a consecutive series of relatlvely rigid members particular]y shaped to control ' the deformation of the~elastomer surface when it is sub-jected to the sealed pressure~ and the~frlction forces at the sliding contact area so as to form a hydrodynamically pressuriz d~lubrlcant film between~the slldlng~surfaces and to reduce the pressure at the sealing surfaces substan-tially below that of the sealed~pressure.
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The seal assembly comprises a relatively thick ring of elastomer material bonded to a structural rigid member that is attached to the machine assembly in a manner to align the sealing surface of the elastomer material with the mating rigid sealing surface similarly supported by the machine assembly. The consecutive series of shaped rigid members are embedded in the elastomer material be-` tween its sealing surface and structural support members.
The surfaces of the shaped members are bonded to the elas-tomer material so that no leakage path e~ists around the ; members.
The shape of the embedded rigid members is as follows.
The surface of the members facing the sealing sliding sur-face of the elastomer (front surface) parallels the sealing surface. The surface of the members facing away from the ,~
; elastomer sealing surface (back surface) is spherically or compound curved, with the center of curvature being -located in the direction~of the sèaling surfaceO The - , ; sides of the members are normally straight (they can be ~ ~ 20 curved), formlng a-square or rectang1e~ The surface of ; the structural support member adjacent the spherically curved surfaces on the shaped members is similarly curved, and the two surfaces are separated by-a thin layer of elastically deformable material. An alternate embodiment .
~ 25 utilizes extremely ~hin, alter~ate, curved lamunates of elastomer and a .
~, f ~ ' '' , , . . .
~`
.,, ~, , relatively rigid material (metal) between the surfaces, the purpose of which will be explained later herein.
In accordance with the invention, the seal device can be formed as a radial type seal with an annular seal-ing surface or as an axial -type seal with a flat sealing surface.
By this unlque sealing surface construction, as explained in detail below, a virtually indestructible i lubricant film is formed between the sealing surface while maintaining effective sealing. As a result, the seal can operate over an unli~ited range of sealed pres-sures, speeds, and sealed fluid viscosity with extended endurance. The invention is a~major advancement in the state-of-the-art of sealing devicesO
The invention can better be understood by reference to the appended drawings which illustrate the radial and axial form of the invention, and which are explained in ~-the following detailed description.
.
.
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L'~
BRIEF DESCRIPTION OF THE DRAWINGS
FIGU~E 1 is a side elevation in cross-section of a presently preferred form of the radial seal embodying the invention;
FIGURE lA shows an enlarged detail of an alternate embodiment of the seal;
FIGURE 2 is a fragmentary vertical sectional view taken along line 2-2 in FIGURE l; -FIGURE 3 is an enlarged detail view of the seal show- . --ing how it responds to the sealed pressure;
FIGURE 4 is an enlarged detail view of the seal show-ing how it responds to the sliding friction forces at the ~ -sealing surfaces; and FIGURE 5 i5 a side elevation view in cross-section of an alternate embodiment of the seal in the form of an -15 axial type seal. . : :
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.~. DETAILED DESCRIPTION OF PREFERRED EMBODI~NT
With reference to the appended drawings, Figures 1 and 2, the radial form of the seal embodying the present invention is shown at 10 supported by housing of.the machine 14 in sealing alignment with a rotating shaft 12, the shaft sealing surface 24 sliding on the elastomer sealing surface 26 of the seal 10. Figures 1 and 2 show the seal l0 at rest, that is, the shaft not rotating and no sealed pressure exists. .
The.seal 10 consists of a relatively thick, contin-uous elastomer seal member in the form of a ring 16 with shaped rigid members 18 embedded in the ring between the elastomer sealing surface 26 and a structural support ~ .
member 20 for the elastomer seal 16, the shaped members 18 being circumferentially spaced within the elastomer seal 16 (see Figure 2) along the direction of relative motion betwèen the shaft 12 and the housing 14. The surface 36 of the shaped members 18 facing the elastomer sèaling surface 26 parallels the sealing~surface:26.
: The surfaces 38 of the shaped members facing the~struc-tural support members 20 are convex spherically curved (they may be aompound curved about different centers of curvatuxe in planes normal to~each other), with their ~; respective centers of curvature 22 being located in the directlon of the seallng surface 26 (on the same side of ~: 25 the seal 16 as the shaft 12), preferably between the , ~
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-~?~ 5 rotational axis of rhe shaft 12 and the sealing surface 24. The surface 40 on the structural support ring 20 facing the spherical surface 38 on the shaped members 18 is concave spherically curved concentric with the convex spherically curved surface 38 on the shaped members 18, the surfaces 38 and 40 being separated by a thin section of elastically deformable material 32 that is part of (e.g., integral with) the elastomer seal 16. An alternate construction for this thin section of material is shown by Figure lA, wherein the thin elastomer section is di-vided into a number of thinner sections 28 spaced aparat and bonded to rigid laminates 30. The elastomer seal 16 extends between the shaped members 18 to form a solid sealing member. All the surfaces of the rigid members 20, 18, and 30 in contact with the elastomer seaI 16 are bonded thereto.
The operation of the invention shown in Figures 1 .
and 2 is represented ln Figures 3 and 4, It is based on the natural physical properties of elastic materials '~
such as elastomers, and the control of its deformation by the embeddment o rigid members in the material. Similar to most engineering materials, elastomers are v irtually incompressible, but deformable similar to springs (the modulus of elasticity of materials is actually a spring rate). Peculiar to elastomers is that the bulk compres-sion stiffness is much greater than bulk shear stiffness . .
, . . . . .
: :, . -,. . . .
,, - . ;
,. : .; .,, and that for small deformations, the shear stiffness is independent of the compression stress. The compression/
shear stiffness ratio is further increased by shaping the elastomer material so that thebul~e area is small compared to the compression load area.
In the operation of the invention, the elastomer is deformed solely in the shear mode and, as the value of the shear deformation is minute (as described later herein~, the shear stiffness forces resisting the deformation can be ignored during operation. As to control of the elas-tomer deformation in the invention, note in Figures 1 and 2 that the bulk area of the thin elastomer section 32 supporting the shaped rigid members 18 is small compared to the spherically curved area. Thus, the shaped members 18 are constrained from displacing in the radial (compres--sion) directions, but can readily displace in the elas-tomer shear direction, that is, a swing-like motion around the center of the spherical curvature 22.
The gaps 42 and 34 ~ormed by the displacement of the shaped members 18 is shown greatly exaggerated for clarity .: .
in Figures 3 and 4. These gaps represent the lubricant .
film that is formed betwçen the sealing surfaces. Lub-ricant films formed between sliding surfaces are actually unperceptible, less than 103 inch thick (.254 mm) for ;~ 25 viscous fluids such as oils, and less than 104 inch thick (.025 mm) for low viscosity fluids such as water.
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Likewise, the deformation of the elastomer to form these gaps is unperceptible, and thus the elastomer shear forces resisting the formation of the gaps can be iynored in the operation of the invention.
It is important to clarify the nature and character of a lubricant film between sliding surfaces. The lub-ricant film need not be any thicker than a boundary film to prevent surface contactunder lightly loaded conditions.
A few drops of lubricant is sufficient to form a boundary film and the leakage of a ~fluid between two surfaces in sliding contact with boundary lubrication is negligible.
However, when the sliding velocity is high, the heat generated by the viscous shear can destroy the lubricant film and the surfaces. The simplest method for prevent-15 ing overheatin~ is to flush the sliding surfaces with -cool lubricant. This normally results in substantial leakage between sealing surfaces. Furthermore, high loadings between the surfaces makes it difficult to admit the coollng lubrlcant. - ~
Proceeding with the description of the operation of the invention, Flgure 3 shows how the sealed pressure simultaneoulsy activates sealing and the admission of the sealed fluid for lubrication purposes between the sealing .. -surfaces. The sealed pressure moment cPl causes the shaped member 18 to swing in direction to simultaneously lift the internal edge of the sealing surface admitting ~'' .
. :
- :
the sealed fluid between the sealing surfaces and compres-sing the e~ternal edge to ac-tuate sea]ing. The fluid pressure profile in the gap ~2 (exaggerated for clarity in Figure 3) is a function of the value of sealed pres-sure and the gap geometry~ Pressure moments aP2 withinthe gap will add to the swing motion o~ member 18. Pres-sure moments bP3 and the moments of the forces at the sealing surfaces will substract from the swing mo-tion. ,-;
The shaped member 18 will stabilize in the sealing posi-tion when the moments are in equilibrium. The compression of the elastomer surface and the sealing area between the sealing surfaces (elastomer area in contact with shaft) both increase with increasing sealing pressures, thus increasing sealing and decreasing the pressure loading at the sealing area~ This method of "pressure balancing"
in the invention is unique.
Figure 4 shows how the slidin`g friction at the seal-ing surfaces actuates-the formation of an adequate lubri-cation film between the sealing surfaces under operating conditions of high sealed pressures and rotational speeds.
The drag from the friction forces displace the elastomer sealing surface 26 in the dixection of motion, forcing the shaped members to swing about their respective centers of-curvature 22 and to deform the sealing surface 26 from a smooth cylindrical surface into a wavy cylindrical sur-~ace pattern, the crests of the waves occurring at the side of each shaped member 18 in the cirection of motion, : ' ' , ' ' ' ~ ,: , .
.
.. . .
. : ~ ' ' . ' forming a lubricant film consisting of a consecutive series of wedge shapes 46 converging in the direction of relative movement of the adjacent sealing surface 24.
Hydrodynamic action generates pressure in the lubricant film, thus maintaininy the film when the sealed pres-sures are high, and rotation circulates the lubricant for cooling. The combined deformation of the sealing surface 26 from the action of ~he sealed pressures and the friction forces results in fluid lubrication at the internal edge of the sealing surface (towards the pressure source) tapering to boundary lubrication at the external edge. Leakage is negligible~ The motion of the shaft sealing surface 26 can be a combined rotating and axial motion without affecting sealing, a feature unique to the invention. The sealing surfaces can be reversedi that is, the elastomer sealing surfaces can be attached to the shaft and the rigid sealing surfaces fixed to the machine housing. The wedge shapes 46 are shown exaggerated in Figure 4 for clarity.
An alternate form of the invention is an axial seal with flat sealing surfaces as shown in Figure 5. The basic principle of operation will not be repeated as it is identical to that of radial form of the invention, shown in--Figures 3 and 4, except the lubrication film is formed between flat sealing surfaces in lieu of cylindrical sur-faces. In Figure 5, the sealing surface 26 lies in a ., .- . .
.
. ' ' . ,' - , , . ' '. . . :
~ 13 -.~ single plane and is normally ur~ed by spring 52 against the cooperating sealing surface on opposite member 50 fixed to machine housing 14. The seal assembly 10 in this embodiment may or may not rotate with shaft 54, and may or may not be slidable longitudinally along shaft 54.
Various forms of the inven~ion and modifications to the illustrated specific exemplary embodiments can be made within the scope and spirit of the invention. The I -invention is not intended to be limited except by the scope of the claims.
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Claims (7)
1. A seal for sealing against fluid leakage between a pair of relatively moving machine elements comprising a con-tinuous elastomer seal connected in sealing relationship to one of the machine elements for movement therewith, the seal having a continuous elastomer layer including an elastomer sealing surface adapted to slidably engage a continuous rigid sealing surface on the other machine element; a plurality of shaped rigid members embedded ionized elastomer layer beneath the elastomer sealing surface in a consecutive, closely spaced arrangement along the direction of relative movement between the machine elements; a support means for the elastomer layer; said support means including individual support surfaces located directly behind each of the shaped rigid members, each rigid member having a rear surface each support surface and one adjacent rear surface of a rigid member defining a surface pair, each surface pair being curved about a mutual center or centers of spherical curvature that is or are located on a radius line extending towards the other machine element.
2. A seal according to Claim 1, including a thin layer of substantially incompressible elastically deform-able material between each of said surface pairs, said material forming part of said seal member and providing a substantially rigid connection between each surface pair in a direction along the respective radius line of the pair in a compressive direction, while providing a resilient connection between each surface pair in direc-tions parallel to the surfaces defining the surface pair.
3. A seal according to Claim 2, said elastically deformable material comprising alternate thin layers of elastomer and relatively rigid material bonded together and extending parallel to the surface pairs, with a layer of elastomer material adjacent each support and rear surface, the support and rear surface each being bonded to the adjacent layer of elastomer material.
4. A seal as claimed in Claim 3, characterized in that each rigid member is of greater thickness from.
front to rear than the respective thickness of elastic-ally deformable material located between the surface pairs, and the portion of seal member that includes the sealing surface that lies between the rigid member and the opposed rigid sealing surface.
front to rear than the respective thickness of elastic-ally deformable material located between the surface pairs, and the portion of seal member that includes the sealing surface that lies between the rigid member and the opposed rigid sealing surface.
5. A fluid pressure seal in accordance with Claim 1, wherein said rear surface of each rigid member is compound curved about two centers of curvature in planes normal to each other.
6. A fluid pressure seal in accordance with Claim 5, said elastomer sealing surface being annular shaped.
7. A fluid pressure seal in accordance with Claim 5, said elastomer sealing surface lying in a single plane.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA337,932A CA1129905A (en) | 1979-10-18 | 1979-10-18 | Fluid seal with lubricated sealing surfaces |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA337,932A CA1129905A (en) | 1979-10-18 | 1979-10-18 | Fluid seal with lubricated sealing surfaces |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1129905A true CA1129905A (en) | 1982-08-17 |
Family
ID=4115381
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA337,932A Expired CA1129905A (en) | 1979-10-18 | 1979-10-18 | Fluid seal with lubricated sealing surfaces |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1129905A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113236782B (en) * | 2021-04-29 | 2023-11-17 | 西安航天精密机电研究所 | High-pressure-resistant low-friction dynamic sealing structure |
-
1979
- 1979-10-18 CA CA337,932A patent/CA1129905A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113236782B (en) * | 2021-04-29 | 2023-11-17 | 西安航天精密机电研究所 | High-pressure-resistant low-friction dynamic sealing structure |
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| Date | Code | Title | Description |
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| MKEX | Expiry |