CA2008050A1 - Radial shaft seal - Google Patents
Radial shaft sealInfo
- Publication number
- CA2008050A1 CA2008050A1 CA002008050A CA2008050A CA2008050A1 CA 2008050 A1 CA2008050 A1 CA 2008050A1 CA 002008050 A CA002008050 A CA 002008050A CA 2008050 A CA2008050 A CA 2008050A CA 2008050 A1 CA2008050 A1 CA 2008050A1
- Authority
- CA
- Canada
- Prior art keywords
- shaft
- groove
- seal
- disk
- radial
- 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.)
- Abandoned
Links
Landscapes
- Sealing Devices (AREA)
- Sealing With Elastic Sealing Lips (AREA)
Abstract
Abstract In a radial seal for a shaft projecting from a space to be sealed, a seal disk has parallel front and rear faces and is affixed to a reinforcement ring. The seal disk is made of an elastic deformable material and at its inner edge, is axially drawn in the direction towards its front face, thereby becoming flared to a frustoconical shape, with its rear face slidably engaging the shaft. The rear face has a helical first groove which encompasses the shaft to provide for retrograde transport of leaking fluid back into the space to be sealed. The front face has a helical second groove which extends substantially parallel to and coaxially with the first groove and is intermediately positioned to the first groove thereby providing increased surface area for the front face. This gives better radiation of frictionally produced heat and increases the service life of the seal.
Description
~ ~ 20080S0 RADIAL SHAFT SEAL
The present invention relates to a radial seal for a shaft, as used for example with the crankshaft for a two stroke internal combustion engine.
Such a radial seal is known from British Patent GB-A-2036196. In producing the seal disk shown there it is first formed as an annular disk of PTFE (polytetrafluoroethylene) which is then widened at its inner edge to a frustoconical shape so that after installation of the radial seal, mutual contact between the shaft and the rear face of the radial seal is provided along the surface of a section of the shaft. The rear face of the seal has a helical groove which surrounds the shaft to return leaking fluid to the sealed chamber. The front face of the seal disk is smooth. A disadvantage of that radial seal is that the oil becomes carbonized due to the high temperatures reached caused by friction in contact area between the seal and shaft. The accumulation of such oil-carbon as a deposit in the region of contact reduces the reliability of the seal. Elevated temperatures at the seal which adversely affect the integrity of its material and reduce the service life are a further drawback.
It is an object of the presen~ invention to provide a radial seal with a longer service period.
In the following description reference will be made to the drawing, which shows the upper part only of an axial cross section of a radial seal embodying the invention.
In accordance with the invention there is provided, a radial seal for a shaft projecting from a space to be sealed and defining an axial direction and comprising:
a seal disk of an elastic deformable material, having an inner and an outer edge and substantially parallel front and rear faces, a reinforcement ring fixed to the rear face of said disk, the disk being drawn out in the axial direction at its inner edge toward sald front face for slidably engaging said shaft, said rear face having a first helical groove providing for retrograde transport toward said sealed space of fluid leaking along said shaft, said front face having a second helical groove, said æecond groove being positioned coaxially with and intermediate to said first groove.
,,. ~ i , - ~
~,- ~ ' ' ' :. ' :
The second groove yields an increase in surface area of the front face thereby providing better heat radiation than in prior art seals. Heat is produced during operation by friction between the rotating shaft and the rear surface of the seal disk. The amount of lubricant, generally an oil, which is located in the dynamic sealing region is therefore better protected from - overheating and subsequent degradation. The original lubrication of an unused radial seal therefore subsists over extended periods, and wear of the seal during operation is substantially reduced. The turns of the second groove are intermediately positioned to the turns of the first groove so that the disk is not substantially weakened by the second groove. The thickness of the seal disk may be the same as in seals of the prior art.
The first and second groove may be produced by press forming or machining processes. When the disk is made of PTFE it is preferred to press form the disk and to apply elevated temperatures while doing so to achieve stability of the shape and size of the grooves. Increased depth of the second groove results in an increase of the front surface area. It is preferred to produce the second groove such that its depth is at least 0.25 times the thickness D of the seal disk, which is generally less than one millimeter.
The first and second grooves of respective pitch Tl and T2 may be dimensioned in such a way that their depth profiles A1 and A2 respectively at least to some extent overlap in the radial direction. That is to say, the bottom of the first groove is at a greater radial distance from the shaft surface than is the bottom of the second groove. The area of the front face available for heat radiation thereby is maximized. Likelihood of formation of carbon deposits from overheated oil in the region of the first groove is thus greatly reduced.
The webs between the turns of the second groove may have a radially ;
outvardly rounded profile. Although the second groove is quite small in such an embodiment, the groove generally has a cross sectional area of less than 0.25 mm , and an efficient, continuous exchange of the volume of liquid contained in the groove and that in the adjacent sealed space is achieved and therefore a further improved removal of heat is achieved. Radially inwardly the groove has a rounded profile as well. Notch effects which otherwise would lead to premature destruction of the seal from radially angular displacements of the sealed shaft are therefore prevented. The first and second grooves are .S,'',, , ~ : ; ,~ . , ~`
` ^ 2008050 preferably provided in the dynamic sealing region of the seal disk only. Thegrooves may be omitted outside that region, especially in that part of the seal disk which is used to fix it to an appropriate housing. The flexibilities of the regions which include grooves and those without are very different. To avoid breaking the seal disk, it is preferred to construct the first and second groove in such a way that their profiles do not include any sudden directional changes and gradually taper into the remaining surface of the front and rear faces of the seal disk respectively. The transition zone between the two regions is therefore smoothly constructed and the flexibilities of both regions gradually blend into each other.
A radial seal embodying the invention generally defined at 7 and shown in the figure includes a metallic mounting and reinforcement ring 1 with a substantially angular profile. An intermediate ring 10 of elastic rubber material is vulcanized onto the radially inwardly projecting flange of the reinforcement ring and is adhesively affixed to the radially outwardly projecting part of a seal disk 2. Intermediate ring 10 is continuous and includes a dust excluding lip 11 and a statically active seal ring 12 which annularly encloses the reinforcement ring 1 on its outside in the left half of the figure. Seal disk 2 is firstly manufactured as an annular, flat disk of PTFE having substantially parallel front and rear faces 3, 4. The disk is subsequently positioned in a heatable stamping tool and axially drawn forward at its inner edge towards the front face during the closing of the tool and flared to a frustoconical shape. Simultaneously with the forming of the disk, the front and rear faces are plastically deformed in an embossing step where a single spiral groo~e is shaped into each of the front and rear faces ~ respectively. The grooves are staggered and embossed to sufficient radial depth that mutual overlap of the depth of the profiles is effected. The ; actual shape of the profiles~ the dimensions and relative mutual positioning of the first and second grooves 6, 8, are shown in the drawing. The grooves remain substantially unchanged with respect to shape, dimension and positioning, e~en after removal, cooling and reheating, if the holding time in the heat and embossing die is sufficiently long. Seven test seal disks were manufactured as described above.
P.AT 14063-1 ~0~5~) For comparison purposes seven radial seals of corresponding shape and size but having no second groove 8 have also been made. Both sets of radial seals were subsequently tested for comparison under the same conditions.
Motor oil of viscosity grade lOW-40 was used as the sealed medium. The test period was separated into twenty-one cycles each of twenty-four hours duration. ~uring each cycle the conditions were periodically changed according to the following schedule:
In a first phase of fourteen hours duration, the temperature of the sealed medium was at 150 C and the sealed shaft rotated at 7,500 Rpm;
In a second phase of six hours duration, the temperature of the medium was at 130 C and the shaft rotation was unchanged: and, In a third phase of four hours duration, the heating of the sealed medium was switched off and the shaft was held stationary.
The results of the tests were as follows:
None of the radial seals embodying the invention leaked. The radial seals without the second groove all leaked. Good improvement, in absence of oil-carbon deposits, was achieved using a radial seals embodying the invention. No deposits were found in the dynamic sealing zone of the novel radial seals, having a second groove, after completion of the above mentioned tests, whereas small to large deposits were found in the dynamic sealing zone of the corresponding known seals having no second groove. Furthermore the -sealing lips of the conventional seals showed strong changes in surface ~;~ colour, also indicating elevated temperatures during the test. Thus, the new radial seals provided for better dissipation of heat and extended service life.
~, ~O ~
~ ~ .
PAT 1406~-1 ,~ ", ~
.:. ~ : . .', .. . :.. ~:: . ' : - ' . " , .
~` "' ~ . ' '":'' ', '.:' ~": " ,.,. ' . :~' :..
~:~ f : ' ; ~ ~''" ' ; .
The present invention relates to a radial seal for a shaft, as used for example with the crankshaft for a two stroke internal combustion engine.
Such a radial seal is known from British Patent GB-A-2036196. In producing the seal disk shown there it is first formed as an annular disk of PTFE (polytetrafluoroethylene) which is then widened at its inner edge to a frustoconical shape so that after installation of the radial seal, mutual contact between the shaft and the rear face of the radial seal is provided along the surface of a section of the shaft. The rear face of the seal has a helical groove which surrounds the shaft to return leaking fluid to the sealed chamber. The front face of the seal disk is smooth. A disadvantage of that radial seal is that the oil becomes carbonized due to the high temperatures reached caused by friction in contact area between the seal and shaft. The accumulation of such oil-carbon as a deposit in the region of contact reduces the reliability of the seal. Elevated temperatures at the seal which adversely affect the integrity of its material and reduce the service life are a further drawback.
It is an object of the presen~ invention to provide a radial seal with a longer service period.
In the following description reference will be made to the drawing, which shows the upper part only of an axial cross section of a radial seal embodying the invention.
In accordance with the invention there is provided, a radial seal for a shaft projecting from a space to be sealed and defining an axial direction and comprising:
a seal disk of an elastic deformable material, having an inner and an outer edge and substantially parallel front and rear faces, a reinforcement ring fixed to the rear face of said disk, the disk being drawn out in the axial direction at its inner edge toward sald front face for slidably engaging said shaft, said rear face having a first helical groove providing for retrograde transport toward said sealed space of fluid leaking along said shaft, said front face having a second helical groove, said æecond groove being positioned coaxially with and intermediate to said first groove.
,,. ~ i , - ~
~,- ~ ' ' ' :. ' :
The second groove yields an increase in surface area of the front face thereby providing better heat radiation than in prior art seals. Heat is produced during operation by friction between the rotating shaft and the rear surface of the seal disk. The amount of lubricant, generally an oil, which is located in the dynamic sealing region is therefore better protected from - overheating and subsequent degradation. The original lubrication of an unused radial seal therefore subsists over extended periods, and wear of the seal during operation is substantially reduced. The turns of the second groove are intermediately positioned to the turns of the first groove so that the disk is not substantially weakened by the second groove. The thickness of the seal disk may be the same as in seals of the prior art.
The first and second groove may be produced by press forming or machining processes. When the disk is made of PTFE it is preferred to press form the disk and to apply elevated temperatures while doing so to achieve stability of the shape and size of the grooves. Increased depth of the second groove results in an increase of the front surface area. It is preferred to produce the second groove such that its depth is at least 0.25 times the thickness D of the seal disk, which is generally less than one millimeter.
The first and second grooves of respective pitch Tl and T2 may be dimensioned in such a way that their depth profiles A1 and A2 respectively at least to some extent overlap in the radial direction. That is to say, the bottom of the first groove is at a greater radial distance from the shaft surface than is the bottom of the second groove. The area of the front face available for heat radiation thereby is maximized. Likelihood of formation of carbon deposits from overheated oil in the region of the first groove is thus greatly reduced.
The webs between the turns of the second groove may have a radially ;
outvardly rounded profile. Although the second groove is quite small in such an embodiment, the groove generally has a cross sectional area of less than 0.25 mm , and an efficient, continuous exchange of the volume of liquid contained in the groove and that in the adjacent sealed space is achieved and therefore a further improved removal of heat is achieved. Radially inwardly the groove has a rounded profile as well. Notch effects which otherwise would lead to premature destruction of the seal from radially angular displacements of the sealed shaft are therefore prevented. The first and second grooves are .S,'',, , ~ : ; ,~ . , ~`
` ^ 2008050 preferably provided in the dynamic sealing region of the seal disk only. Thegrooves may be omitted outside that region, especially in that part of the seal disk which is used to fix it to an appropriate housing. The flexibilities of the regions which include grooves and those without are very different. To avoid breaking the seal disk, it is preferred to construct the first and second groove in such a way that their profiles do not include any sudden directional changes and gradually taper into the remaining surface of the front and rear faces of the seal disk respectively. The transition zone between the two regions is therefore smoothly constructed and the flexibilities of both regions gradually blend into each other.
A radial seal embodying the invention generally defined at 7 and shown in the figure includes a metallic mounting and reinforcement ring 1 with a substantially angular profile. An intermediate ring 10 of elastic rubber material is vulcanized onto the radially inwardly projecting flange of the reinforcement ring and is adhesively affixed to the radially outwardly projecting part of a seal disk 2. Intermediate ring 10 is continuous and includes a dust excluding lip 11 and a statically active seal ring 12 which annularly encloses the reinforcement ring 1 on its outside in the left half of the figure. Seal disk 2 is firstly manufactured as an annular, flat disk of PTFE having substantially parallel front and rear faces 3, 4. The disk is subsequently positioned in a heatable stamping tool and axially drawn forward at its inner edge towards the front face during the closing of the tool and flared to a frustoconical shape. Simultaneously with the forming of the disk, the front and rear faces are plastically deformed in an embossing step where a single spiral groo~e is shaped into each of the front and rear faces ~ respectively. The grooves are staggered and embossed to sufficient radial depth that mutual overlap of the depth of the profiles is effected. The ; actual shape of the profiles~ the dimensions and relative mutual positioning of the first and second grooves 6, 8, are shown in the drawing. The grooves remain substantially unchanged with respect to shape, dimension and positioning, e~en after removal, cooling and reheating, if the holding time in the heat and embossing die is sufficiently long. Seven test seal disks were manufactured as described above.
P.AT 14063-1 ~0~5~) For comparison purposes seven radial seals of corresponding shape and size but having no second groove 8 have also been made. Both sets of radial seals were subsequently tested for comparison under the same conditions.
Motor oil of viscosity grade lOW-40 was used as the sealed medium. The test period was separated into twenty-one cycles each of twenty-four hours duration. ~uring each cycle the conditions were periodically changed according to the following schedule:
In a first phase of fourteen hours duration, the temperature of the sealed medium was at 150 C and the sealed shaft rotated at 7,500 Rpm;
In a second phase of six hours duration, the temperature of the medium was at 130 C and the shaft rotation was unchanged: and, In a third phase of four hours duration, the heating of the sealed medium was switched off and the shaft was held stationary.
The results of the tests were as follows:
None of the radial seals embodying the invention leaked. The radial seals without the second groove all leaked. Good improvement, in absence of oil-carbon deposits, was achieved using a radial seals embodying the invention. No deposits were found in the dynamic sealing zone of the novel radial seals, having a second groove, after completion of the above mentioned tests, whereas small to large deposits were found in the dynamic sealing zone of the corresponding known seals having no second groove. Furthermore the -sealing lips of the conventional seals showed strong changes in surface ~;~ colour, also indicating elevated temperatures during the test. Thus, the new radial seals provided for better dissipation of heat and extended service life.
~, ~O ~
~ ~ .
PAT 1406~-1 ,~ ", ~
.:. ~ : . .', .. . :.. ~:: . ' : - ' . " , .
~` "' ~ . ' '":'' ', '.:' ~": " ,.,. ' . :~' :..
~:~ f : ' ; ~ ~''" ' ; .
Claims (8)
1. A radial seal for a shaft projecting from a space to be sealed and defining an axial direction and comprising:
a seal disk of an elastic deformable material, having an inner and an outer edge and substantially parallel front and rear faces, a reinforcement ring fixed to the rear face of said disk, the disk being drawn out in the axial direction at its inner edge toward said front face for slidably engaging said shaft, said rear face having a first helical groove providing for retrograde transport toward said sealed space of fluid leaking along said shaft, said front face having a second helical groove, said second groove being positioned coaxially with and intermediate to said first groove.
a seal disk of an elastic deformable material, having an inner and an outer edge and substantially parallel front and rear faces, a reinforcement ring fixed to the rear face of said disk, the disk being drawn out in the axial direction at its inner edge toward said front face for slidably engaging said shaft, said rear face having a first helical groove providing for retrograde transport toward said sealed space of fluid leaking along said shaft, said front face having a second helical groove, said second groove being positioned coaxially with and intermediate to said first groove.
2. A radial seal for a shaft as defined in claim 1, wherein at least one of said first and second grooves are produced by a press forming process.
3. A radial seal for a shaft as defined in claim 1, wherein at least one of said first and second grooves are produced by a machining process.
4. A radial seal for a shaft as defined in claims 2 or 3, wherein said second groove has a depth of at least 0.25 times the thickness of the seal disk.
5. A radial seal for a shaft as defined in claim 4, wherein depth profiles of said first and second grooves overlap in the radial direction of the shaft.
6. A radial seal for a shaft as defined in claim 5, wherein webs located between the turns of said second groove have a radially outwardly rounded profile.
7. A radial seal for a shaft as defined in claim 6, wherein said second groove gradually merges to the undrawn front face of the seal disk without any sudden directional change.
8. A radial seal for a shaft as defined in claim 7, wherein said seal disk is substantially PTFE.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3901738 | 1989-01-21 | ||
| DEP3901738.9 | 1989-01-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2008050A1 true CA2008050A1 (en) | 1990-07-21 |
Family
ID=6372525
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002008050A Abandoned CA2008050A1 (en) | 1989-01-21 | 1990-01-18 | Radial shaft seal |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPH02225884A (en) |
| BR (1) | BR9000150A (en) |
| CA (1) | CA2008050A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10117881A1 (en) * | 2001-04-10 | 2002-11-21 | Freudenberg Carl Kg | Radial shaft seal |
| US7100924B2 (en) * | 2004-01-15 | 2006-09-05 | Federal-Mogul Worldwide, Inc. | Elastomeric hinged seal |
| JP6622059B2 (en) * | 2015-11-02 | 2019-12-18 | 株式会社荒井製作所 | Oil seal |
-
1990
- 1990-01-16 BR BR909000150A patent/BR9000150A/en unknown
- 1990-01-18 CA CA002008050A patent/CA2008050A1/en not_active Abandoned
- 1990-01-19 JP JP9010473A patent/JPH02225884A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPH02225884A (en) | 1990-09-07 |
| BR9000150A (en) | 1990-10-23 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |