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Easing the stress on mechanical face seals
Patents
Patents T h i s is a l i s t of r e c e n t l y p u b l i s h e d patents covering designs and i n v e n t i o n s of r e l e v a n c e to S e a l i n g Technology readers. Countries can be identified by the code in f r o n t of t h e n u m b e r : AT Austria BE Belgium CA Canada CH Switzerland EP European Patent FR France HU Hungary IR Eire JP J a p a n LI Liechtenstein NL Netherlands RO Romania SE Sweden WO World Patent
US United States AU Australia BR Brazil D Germany ES Spain FI Finland GB Britain IL Israel IT Italy KP North Korea LU Luxembourg NO Norway SU Former Soviet Union
Full c o p i e s of t h e o r i g i n a l p a t e n t d o c u m e n t s c a n b e o b t a i n e d from t h e following:
The British Library P a t e n t Express, 2 5 S o u t h a m p t o n Buildings, L o n d o n WC2A lAW, UK. Fax: + 4 4 171 4 1 2 7 9 3 0 T h e B r i t i s h L i b r a r y will also s u p p l y a list of l i b r a r i e s i n c l u d e d in t h e P a t e n t I n f o r m a t i o n Network.
US P a t e n t Office S c i e n t i f i c Library 1 5 t h a n d E a s t S t r e e t s , NW W a s h i n g t o n , DC 2 0 2 3 1 , USA The J a p a n e s e P a t e n t Office 43 K a k s l l m l g a s e k i 3 - c h o m e Chiyoda-ku, Tokyo I00, Japan
Sliding contact excludes contamination Title: S e a l i n g d e v i c e Patent number: US5678828 Date: 2 1 s t O c t o b e r 1 9 9 7 Inventor: Yasunari H a m a y a A s s i g n e e : NOK C o r p o r a t i o n C o n v e n t i o n a l oil s e a l s in applications such as iron-steel rolling mills, h a v e a seal lip f o r m e d of a n e l a s t i c r u b b e r m a t e r i a l . T h e s e a l is u s u a l l y fitted b e t w e e n a h o u s i n g a n d a r o t a t i o n a l shaft, supported through a bearing such t h a t t h e s e a l lip c o n t a c t s t h e shaft. However foreign m a t e r i a l s u c h a s i r o n p o w d e r or s h a r p d u s t c a n i n v a d e t h e seal, d a m a g i n g t h e s e a l lip. A p r e v i o u s a t t e m p t to n e g a t e t h i s p r o b l e m h a s p r o v i d e d a n oil s e a l w h i c h r e m o v e s foreign m a t e r i a l s u p p l y i n g a flow of g r e a s e p e r i o d i c a l l y to t h e s e a l lip. A l t h o u g h t h i s m a y p r o t e c t the seal, c o n s u m p t i o n of g r e a s e is excessive. Another solution proposes a compound-type packing, which comprises a hard resin material sealing against the shaft and a r u b b e r - l i k e e l a s t i c m e m b e r fixed to t h e b a c k of t h e r e s i n . T h e p a c k i n g is fitted into a groove in t h e h o u s i n g . S i n c e t h e p a c k i n g is f o r m e d of a h a r d r e s i n , it m a y b e
i
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Figure 1. T h e slidIng t w o p i e c e d e s i g n b l o c k s foreign particles.
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l e s s s u s c e p t i b l e to d a m a g e . It is, however, i n f e r i o r in i t s a b i l i t y to s e a l t i g h t l y on t h e s h a f t . In a d d i t i o n , s i n c e t h e groove h a s to b e f o r m e d b y c u t t i n g into t h e h o u s i n g to p r o v i d e a r e c t a n g u l a r cross-section, an unstable sealing p e r f o r m a n c e will r e s u l t a t t h e c u t surface. Thus, there are problems w i t h t h i s m e t h o d a s well. T h i s p a t e n t (Figure 1) describes a seal which addresses t h e s e flaws. T h e d e v i c e c o m p r i s e s a n a n n u l a r first s e a l m e m b e r m a d e of a r u b b e r - l i k e e l a s t i c p i e c e a n d a m e t a l r i n g for reinforcement. A second seal m e m b e r c o n s i s t s of a s l i d i n g m e m b e r m a d e of r e s i n a n d a rubber-like elastic member. The first m e m b e r h a s a s e a l lip on t h e fluid side, in c o n t a c t w i t h the shaft. A r e c e s s in t h i s m e m b e r receives the second member, and t h e p e r i p h e r a l p o r t i o n s of e a c h a r e in s l i d i n g c o n t a c t , This arrangement blocks foreign m a t e r i a l s u c h a s d u s t from i n v a d i n g t h e seal. E v e n if fluid l e a k s t h r o u g h t h e s e a l lip of t h e frst s e a l m e m b e r , o u t - f l o w c a n be prevented by the sliding m e m b e r of t h e s e c o n d s e a l member. Hence the sealing p e r f o r m a n c e is i m p r o v e d . S e v e r a l p r o j e c t i o n s on t h e o u t e r s u r f a c e of t h e e l a s t i c s e c t i o n of t h e s e c o n d s e a l m e m b e r a r e also r e c o m m e n d e d . T h e s e c o n t a c t t h e i n s i d e of t h e m e t a l ring, c r e a t i n g a n even b e t t e r seal.
Easing the stress on mechanical face seals assembly Including a gasket Patent number: US5676382 Date: 1 4 t h O c t o b e r 1 9 9 7 Inventor: J D a h l h e i m e r A s s i g n e e : F r e u d e n b e r g NOK General P a r t n e r s h i p A m e c h a n i c a l face s e a l a s s e m b l y n o r m a l l y i n c l u d e s a s e a l ring a n d a m a t i n g ring. T h e m a t i n g ring r o t a t e s w i t h t h e s h a f t while t h e seal r i n g r e m a i n s s t a t i o n a r y . T h e seal ring is axially l o a d e d , u r g i n g it into e n g a g e m e n t w i t h t h e m a t i n g ring to provide t h e fluid seal.
Sealing Technology No. 48
Patents
Figure 2. The g a s k e t is p l a c e d b e t w e e n m a t i n g ring and h o u s i n g , f o r m i n g a s e a l by axial c o m p r e s s i o n . Previous arrangements have described a mating ring which i n c l u d e s a s t a t i c s e a l in t h e l b r m of a g a s k e t fitted b e t w e e n t h e h o u s i n g a n d t h e ring. T h i s c o m p r e s s e s t h e m a t i n g r i n g to minimize tensile stresses. The p o t e n t i a l lor c r a c k i n g a n d h e n c e m a t i n g r i n g f a i l u r e is r e d u c e d . However, o n e d i s a d v a n t a g e of t h i s a r r a n g e m e n t is t h a t t h e g a s k e t substantially covers and insulates t h e o u t e r s u r I a c c of t h e m a t i n g ring. I n s u l a t i n g t h e m a t i n g r i n g r e d u c e s or i m p e d e s h e a t t r a n s f e r to the s e a l e d fluid r e s u l t i n g in increased t h e r m a l s t r e s s on the seal. It h a s also b e e n s u g g e s t e d t h a t a g a s k e t be fitted in c o m p r e s s i o n on the i n s i d e d i a m e t e r b e t w e e n t h e i n n e r s u r f a c e of t h e m a t i n g ring a n d the s h a f t . To a s s u r e long t e r m s t a t i c s e a l i n g , t h e force n e c e s s a r y to c o m p r e s s t h e g a s k e t m u s t be sufficie ~t to o v e r c o m e potential problems such as e l a s t o m e r c o m p r e s s i o n sel, c r e e p , stress rel~xation and any s h r i n k a g e of t h e g a s k e t d u e to fluid e x p o s u r e . A d d i t i o n a l l y , t h e g a s k e t m a y lose its c o m p r e s s i v e s e a l i n g force w h e n u s e d in a low t e m p e r a t u r e e n v i r o n e n t d u e to t h e r m a l c o n t r a c t i o n . Finally, t h e t o l e r a n c e s of t h e i n s i d e d i a m e t e r of t h e m a t i n g ring, t h e o u t s i d e d i a m e t e r of the s h a f t a n d the size of t h e g a s k e t itself m a y r e s u l t in an u n s a t i s f a c t o r y v a r i a n c e in t h e c o m p r e s s i v e lorce e x e r t e d to a c h i e v e a p r o p e r s t a l i c seal.
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In p r a c t i c e , p r o v i d i n g c o m p r e s s i v e force sufficient to ensure long-term static sealing m a y a p p l y a r a d i a l force to t h e i n s i d e d i a m e t e r of the m a t i n g r i n g which may cause cracking r e s u l t i n g in failure. Accordingly, t h e p r e s e n t i n v e n t i o n (Figure 2) is a seal a s s e m b l y with a g a s k e t p o s i t i o n e d between the mating ring and h o u s i n g or sleeve s e c u r e d to t h e s h a f t s u c h t h a t t h e seal is l b r m e d b y axial c o m p r e s s i o n of t h e g a s k e t . T h e axial force is a p p l i e d to the m a t i n g ring b y the seal ring. The seal d o e s n o t u s e r a d i a l c o m p r e s s i o n of t h e g a s k e t to p r o v i d e a s t a t i c seal. The p r o p o s e d seal a s s e m b l y i n c l u d e s a n i n n e r sleeve s e c u r e d to t h e shaft. T h e i n n e r sleeve i n c l u d e s a side p o r t i o n e x t e n d i n g r a d i a l l y o u t w a r d . The i n n e r sleeve also h a s a n i n n e r c i r c u m f e r e n t i a l flange. T h e i n n e r s u r f a c e e n g a g e s t h e s h a f t so t h e sleeve r o t a t e s with t h e shaft. A m a t i n g ring, l y p i c a l l y f o r m e d of a h i g h - s t r e n g t h c e r a m i c m a e r i a l , is p o s i t i o n e d a b o u t t h e i n n e r sleeve. T h e m a t i n g ring i n c l u d e s a n i n n e r c i r c u m f e r e n t i a l s u r f a c e , an o u t e r c i r c u m f e r e n t i a l s u r f a c e , a n axially facing side s u r f a c e a n d a n axially lacing mating surace. An axial l o a d a p p l i e d to t h e m a t i n g s u r f a c e of t h e m a t i n g ring c o m p r e s s e s t h e flange p o r t i o n of t h e g a s k e t to form t h e s t a t i c s e a l b e t w e e n t h e i n n e r sleeve a n d
m a t i n g r i n g a n d p r e v e n t loss of a s e a l e d fluid c o n t a i n e d w i t h i n a housing area. Further. the axially e x t e n d i n g t u b u l a r p o r t i o n of t h e g a s k e t is p o s i t i o n e d b e t w e e n t h e m a t i n g r i n g a n d i n n e r sleeve s u c h t h a t a g a p or c l e a r a n c e e x t e n d s a l o n g a t l e a s t a p o r t i o n of t h e tubular section/mating ring and t u b u l a r p o r t i o n / i n n e r sleeve i n t e r f a c e s so tlhat a s i g n i f i c a n t l y r e d u c e d r a d i a l m o u n t i n g force is a p p l i e d to t h e i n s i d e d i a m e t e r of the m a t i n g ring. Additionallv. the clearance proxrides a n o p e n c h a n n e l to d e t e c t a n y l e a k a g e b e t w e e n the flange p o r t i o n of t h e g a s k e t a n d m a t i n g r i n g even a t m i n i m a l p r e s s u r e s . The c l e a r a n c e b e t w e e n the tubular portion and inner sleeve allows t h e d e t e c t i o n of a n y l e a k a g e b e t w e e n t h e flange p o r t i o n of t h e ~ a s k e t a n d the i n n e r s u r t a c e of t h e i n n e r sleeve. O n e a d v a n t a g e of t h e p r e s e n t i n v e n t i o n is t h a t b e c a u s e t h e s e a l o c c u r s a t axial s u r f a c e s , t h e seal m a y be t e s t e d p r i o r to u s a g e . A d d i t i o n a l l y , the s e a l allows t h e u s e of c e r a m i c m a t i n g r i n g s a s t h e y a r e n o t s u b j e c t e d to h i g h tensile stresses. Thus, the invention provides a reliable static axial s e a l b e t w e e n t h e m a t i n g r i n g a n d t h e s h a f t while e l i m i n a t i n g the p r o b l e m s t y p i c a l l y o c c u r r i n g with r a d i a l c o m p r e s s i o n m o u n t e d m e c h a n i c a l face seals.
Environmental groove k e e p s contact pressure under control Title: H y d r o d y n a m i c a l l y lubricated rotary shaft seal with environmental-side groove Patent number: US5678829 Date: 2 1 s t O c t o b e r 1 9 9 7 I n v e n t o r s : M Kalsi, W C o n r o y Assignee: Kalsi E n g i n e e r i n g Inc This d e s c r i b e s a h y d r o d y n a m i c a l l y lubricated, interference type r o t a r y s h a f t seal w h i c h incorporates self-lubrication and c o n t a m i n a n t e x c l n s i o n in a m u c h simplified embodiment. F i g u r e 3 i l l u s t r a t e s a seal whose interfacial contact pressure
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Patents T h i s is a l i s t of r e c e n t l y p u b l i s h e d patents covering designs and i n v e n t i o n s of r e l e v a n c e to S e a l i n g Technology readers. Countries can be identified by the code in f r o n t of t h e n u m b e r : AT Austria BE Belgium CA Canada CH Switzerland EP European Patent FR France HU Hungary IR Eire JP J a p a n LI Liechtenstein NL Netherlands RO Romania SE Sweden WO World Patent
US United States AU Australia BR Brazil D Germany ES Spain FI Finland GB Britain IL Israel IT Italy KP North Korea LU Luxembourg NO Norway SU Former Soviet Union
Full c o p i e s of t h e o r i g i n a l p a t e n t d o c u m e n t s c a n b e o b t a i n e d from t h e following:
The British Library P a t e n t Express, 2 5 S o u t h a m p t o n Buildings, L o n d o n WC2A lAW, UK. Fax: + 4 4 171 4 1 2 7 9 3 0 T h e B r i t i s h L i b r a r y will also s u p p l y a list of l i b r a r i e s i n c l u d e d in t h e P a t e n t I n f o r m a t i o n Network.
US P a t e n t Office S c i e n t i f i c Library 1 5 t h a n d E a s t S t r e e t s , NW W a s h i n g t o n , DC 2 0 2 3 1 , USA The J a p a n e s e P a t e n t Office 43 K a k s l l m l g a s e k i 3 - c h o m e Chiyoda-ku, Tokyo I00, Japan
Sliding contact excludes contamination Title: S e a l i n g d e v i c e Patent number: US5678828 Date: 2 1 s t O c t o b e r 1 9 9 7 Inventor: Yasunari H a m a y a A s s i g n e e : NOK C o r p o r a t i o n C o n v e n t i o n a l oil s e a l s in applications such as iron-steel rolling mills, h a v e a seal lip f o r m e d of a n e l a s t i c r u b b e r m a t e r i a l . T h e s e a l is u s u a l l y fitted b e t w e e n a h o u s i n g a n d a r o t a t i o n a l shaft, supported through a bearing such t h a t t h e s e a l lip c o n t a c t s t h e shaft. However foreign m a t e r i a l s u c h a s i r o n p o w d e r or s h a r p d u s t c a n i n v a d e t h e seal, d a m a g i n g t h e s e a l lip. A p r e v i o u s a t t e m p t to n e g a t e t h i s p r o b l e m h a s p r o v i d e d a n oil s e a l w h i c h r e m o v e s foreign m a t e r i a l s u p p l y i n g a flow of g r e a s e p e r i o d i c a l l y to t h e s e a l lip. A l t h o u g h t h i s m a y p r o t e c t the seal, c o n s u m p t i o n of g r e a s e is excessive. Another solution proposes a compound-type packing, which comprises a hard resin material sealing against the shaft and a r u b b e r - l i k e e l a s t i c m e m b e r fixed to t h e b a c k of t h e r e s i n . T h e p a c k i n g is fitted into a groove in t h e h o u s i n g . S i n c e t h e p a c k i n g is f o r m e d of a h a r d r e s i n , it m a y b e
i
2,° 22 .,, I
3
21d 23
32 .
.._T2 .
.
.
Figure 1. T h e slidIng t w o p i e c e d e s i g n b l o c k s foreign particles.
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l e s s s u s c e p t i b l e to d a m a g e . It is, however, i n f e r i o r in i t s a b i l i t y to s e a l t i g h t l y on t h e s h a f t . In a d d i t i o n , s i n c e t h e groove h a s to b e f o r m e d b y c u t t i n g into t h e h o u s i n g to p r o v i d e a r e c t a n g u l a r cross-section, an unstable sealing p e r f o r m a n c e will r e s u l t a t t h e c u t surface. Thus, there are problems w i t h t h i s m e t h o d a s well. T h i s p a t e n t (Figure 1) describes a seal which addresses t h e s e flaws. T h e d e v i c e c o m p r i s e s a n a n n u l a r first s e a l m e m b e r m a d e of a r u b b e r - l i k e e l a s t i c p i e c e a n d a m e t a l r i n g for reinforcement. A second seal m e m b e r c o n s i s t s of a s l i d i n g m e m b e r m a d e of r e s i n a n d a rubber-like elastic member. The first m e m b e r h a s a s e a l lip on t h e fluid side, in c o n t a c t w i t h the shaft. A r e c e s s in t h i s m e m b e r receives the second member, and t h e p e r i p h e r a l p o r t i o n s of e a c h a r e in s l i d i n g c o n t a c t , This arrangement blocks foreign m a t e r i a l s u c h a s d u s t from i n v a d i n g t h e seal. E v e n if fluid l e a k s t h r o u g h t h e s e a l lip of t h e frst s e a l m e m b e r , o u t - f l o w c a n be prevented by the sliding m e m b e r of t h e s e c o n d s e a l member. Hence the sealing p e r f o r m a n c e is i m p r o v e d . S e v e r a l p r o j e c t i o n s on t h e o u t e r s u r f a c e of t h e e l a s t i c s e c t i o n of t h e s e c o n d s e a l m e m b e r a r e also r e c o m m e n d e d . T h e s e c o n t a c t t h e i n s i d e of t h e m e t a l ring, c r e a t i n g a n even b e t t e r seal.
Easing the stress on mechanical face seals assembly Including a gasket Patent number: US5676382 Date: 1 4 t h O c t o b e r 1 9 9 7 Inventor: J D a h l h e i m e r A s s i g n e e : F r e u d e n b e r g NOK General P a r t n e r s h i p A m e c h a n i c a l face s e a l a s s e m b l y n o r m a l l y i n c l u d e s a s e a l ring a n d a m a t i n g ring. T h e m a t i n g ring r o t a t e s w i t h t h e s h a f t while t h e seal r i n g r e m a i n s s t a t i o n a r y . T h e seal ring is axially l o a d e d , u r g i n g it into e n g a g e m e n t w i t h t h e m a t i n g ring to provide t h e fluid seal.
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Patents
Figure 2. The g a s k e t is p l a c e d b e t w e e n m a t i n g ring and h o u s i n g , f o r m i n g a s e a l by axial c o m p r e s s i o n . Previous arrangements have described a mating ring which i n c l u d e s a s t a t i c s e a l in t h e l b r m of a g a s k e t fitted b e t w e e n t h e h o u s i n g a n d t h e ring. T h i s c o m p r e s s e s t h e m a t i n g r i n g to minimize tensile stresses. The p o t e n t i a l lor c r a c k i n g a n d h e n c e m a t i n g r i n g f a i l u r e is r e d u c e d . However, o n e d i s a d v a n t a g e of t h i s a r r a n g e m e n t is t h a t t h e g a s k e t substantially covers and insulates t h e o u t e r s u r I a c c of t h e m a t i n g ring. I n s u l a t i n g t h e m a t i n g r i n g r e d u c e s or i m p e d e s h e a t t r a n s f e r to the s e a l e d fluid r e s u l t i n g in increased t h e r m a l s t r e s s on the seal. It h a s also b e e n s u g g e s t e d t h a t a g a s k e t be fitted in c o m p r e s s i o n on the i n s i d e d i a m e t e r b e t w e e n t h e i n n e r s u r f a c e of t h e m a t i n g ring a n d the s h a f t . To a s s u r e long t e r m s t a t i c s e a l i n g , t h e force n e c e s s a r y to c o m p r e s s t h e g a s k e t m u s t be sufficie ~t to o v e r c o m e potential problems such as e l a s t o m e r c o m p r e s s i o n sel, c r e e p , stress rel~xation and any s h r i n k a g e of t h e g a s k e t d u e to fluid e x p o s u r e . A d d i t i o n a l l y , t h e g a s k e t m a y lose its c o m p r e s s i v e s e a l i n g force w h e n u s e d in a low t e m p e r a t u r e e n v i r o n e n t d u e to t h e r m a l c o n t r a c t i o n . Finally, t h e t o l e r a n c e s of t h e i n s i d e d i a m e t e r of t h e m a t i n g ring, t h e o u t s i d e d i a m e t e r of the s h a f t a n d the size of t h e g a s k e t itself m a y r e s u l t in an u n s a t i s f a c t o r y v a r i a n c e in t h e c o m p r e s s i v e lorce e x e r t e d to a c h i e v e a p r o p e r s t a l i c seal.
Sealing Technology No. 48
In p r a c t i c e , p r o v i d i n g c o m p r e s s i v e force sufficient to ensure long-term static sealing m a y a p p l y a r a d i a l force to t h e i n s i d e d i a m e t e r of the m a t i n g r i n g which may cause cracking r e s u l t i n g in failure. Accordingly, t h e p r e s e n t i n v e n t i o n (Figure 2) is a seal a s s e m b l y with a g a s k e t p o s i t i o n e d between the mating ring and h o u s i n g or sleeve s e c u r e d to t h e s h a f t s u c h t h a t t h e seal is l b r m e d b y axial c o m p r e s s i o n of t h e g a s k e t . T h e axial force is a p p l i e d to the m a t i n g ring b y the seal ring. The seal d o e s n o t u s e r a d i a l c o m p r e s s i o n of t h e g a s k e t to p r o v i d e a s t a t i c seal. The p r o p o s e d seal a s s e m b l y i n c l u d e s a n i n n e r sleeve s e c u r e d to t h e shaft. T h e i n n e r sleeve i n c l u d e s a side p o r t i o n e x t e n d i n g r a d i a l l y o u t w a r d . The i n n e r sleeve also h a s a n i n n e r c i r c u m f e r e n t i a l flange. T h e i n n e r s u r f a c e e n g a g e s t h e s h a f t so t h e sleeve r o t a t e s with t h e shaft. A m a t i n g ring, l y p i c a l l y f o r m e d of a h i g h - s t r e n g t h c e r a m i c m a e r i a l , is p o s i t i o n e d a b o u t t h e i n n e r sleeve. T h e m a t i n g ring i n c l u d e s a n i n n e r c i r c u m f e r e n t i a l s u r f a c e , an o u t e r c i r c u m f e r e n t i a l s u r f a c e , a n axially facing side s u r f a c e a n d a n axially lacing mating surace. An axial l o a d a p p l i e d to t h e m a t i n g s u r f a c e of t h e m a t i n g ring c o m p r e s s e s t h e flange p o r t i o n of t h e g a s k e t to form t h e s t a t i c s e a l b e t w e e n t h e i n n e r sleeve a n d
m a t i n g r i n g a n d p r e v e n t loss of a s e a l e d fluid c o n t a i n e d w i t h i n a housing area. Further. the axially e x t e n d i n g t u b u l a r p o r t i o n of t h e g a s k e t is p o s i t i o n e d b e t w e e n t h e m a t i n g r i n g a n d i n n e r sleeve s u c h t h a t a g a p or c l e a r a n c e e x t e n d s a l o n g a t l e a s t a p o r t i o n of t h e tubular section/mating ring and t u b u l a r p o r t i o n / i n n e r sleeve i n t e r f a c e s so tlhat a s i g n i f i c a n t l y r e d u c e d r a d i a l m o u n t i n g force is a p p l i e d to t h e i n s i d e d i a m e t e r of the m a t i n g ring. Additionallv. the clearance proxrides a n o p e n c h a n n e l to d e t e c t a n y l e a k a g e b e t w e e n the flange p o r t i o n of t h e g a s k e t a n d m a t i n g r i n g even a t m i n i m a l p r e s s u r e s . The c l e a r a n c e b e t w e e n the tubular portion and inner sleeve allows t h e d e t e c t i o n of a n y l e a k a g e b e t w e e n t h e flange p o r t i o n of t h e ~ a s k e t a n d the i n n e r s u r t a c e of t h e i n n e r sleeve. O n e a d v a n t a g e of t h e p r e s e n t i n v e n t i o n is t h a t b e c a u s e t h e s e a l o c c u r s a t axial s u r f a c e s , t h e seal m a y be t e s t e d p r i o r to u s a g e . A d d i t i o n a l l y , the s e a l allows t h e u s e of c e r a m i c m a t i n g r i n g s a s t h e y a r e n o t s u b j e c t e d to h i g h tensile stresses. Thus, the invention provides a reliable static axial s e a l b e t w e e n t h e m a t i n g r i n g a n d t h e s h a f t while e l i m i n a t i n g the p r o b l e m s t y p i c a l l y o c c u r r i n g with r a d i a l c o m p r e s s i o n m o u n t e d m e c h a n i c a l face seals.
Environmental groove k e e p s contact pressure under control Title: H y d r o d y n a m i c a l l y lubricated rotary shaft seal with environmental-side groove Patent number: US5678829 Date: 2 1 s t O c t o b e r 1 9 9 7 I n v e n t o r s : M Kalsi, W C o n r o y Assignee: Kalsi E n g i n e e r i n g Inc This d e s c r i b e s a h y d r o d y n a m i c a l l y lubricated, interference type r o t a r y s h a f t seal w h i c h incorporates self-lubrication and c o n t a m i n a n t e x c l n s i o n in a m u c h simplified embodiment. F i g u r e 3 i l l u s t r a t e s a seal whose interfacial contact pressure
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