Note: Descriptions are shown in the official language in which they were submitted.
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POLYTETRAFLUOROETHYLENE AND ELASTO ER SEAL
Background of the Invention
1. Fieid of the Invention:
The present invention relates to seals in general and in particular to shaft
seals for use at low
temperatures.
2. Description of Related Art:
Shaft seals made of a composite material or bi-material have been known for
many years in
the art. Prior art shaft seals have been designed for sealing against
lubricant leakage along shafts
such as engine crank shafts and motor vehicle drivetrain shafts. It is known
in the art to create seals
in a composite manner using both polytetrafluoroethylene and elastomer. These
composite seals
usually do not have substantially uniformed thickness. The PTFE and ehastomer
of the seals are
usually separately manufactured and molded. Furthermore, many of the prior art
seals create bending
effects in the PTFE portion of the seal which reduces shaft followability and
sealabihity thus
resulting in leaks along the shaft through the seal member. There have been
particular problems in
PTFE seals being used in low temperature environments.
Therefore, there is a need in the art for a combination PTFE elastomer shaft
seal that has
greater flexibility and permits the PTFE to achieve better followability and
sealability along the shaft
particularly at low temperatures.
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Su~mmal-y of the Invention:
One object of the present invention is to provide a new
polytetrafluoroethylene and elastomer
seal.
Another object of the present invention is to provide a shaft seal where the
polytetrafluoroethylene retains its hoop stiffness and rigidity while having
its bending effects
reduced.
Another object of the present invention is to provide a shaft seal that has a
flexible elastomer
hinge which allows polytetrafluoroethylene to better follow an eccentric
shaft.
Still a further object of the present invention is to provide a shaft seal
which is particularly
suited for use at low temperatures.
To achieve the foregoing objects a shaft seal for use on a shaft includes a
rigid case. The
shaft seal further includes a hinge member connected to the rigid case. The
shaft seal also includes
a resilient sealing element bonded to the hinge member. The sealing element
includes a notch that
extends through to the hinge member.
One advantage of the present invention is that it provides a new and improved
polytetrafluoroethylene and elastomer shaft seal.
A further advantage of the present invention is that it provides a shaft seal
that uses a
polytetrafluoroethylene sealing element which retains its hoop stiffness and
rigidity while bending
effects are reduced.
Yet another advantage of the present invention is that it provides a shaft
seal with a flexible
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hinge which allows for better followability and sealability along an eccentric
shaft particularly at low
temperatures.
Other objects, features and advantages of the present invention will become
apparent from
the subsequent description and appended claims, taken in conjunction with the
accompanying
drawings.
brief Description of the Drawings:
Fig. 1 shows a cross section of the present invention.
Fig. 2 shows a cross section of an alternate embodiment of the present
invention.
Fig. 3 shows a cross section of an alternate embodiment of the present
invention.
Sest lVlode of CarrXing Out the Invention and Description of the Preferred
Embodiment(sl:
Referring to the drawings, a polytetrafluoroethylene (PTFE) and elastomer
shaft seal 10 is
shown. A composite shaft seal is for use on shafts of all types and allows for
better followability
of the PTFE on an eccentric shaft particularly at low temperatures. The PTFE
will provide stiffness
and rigidity but will not display bending effects as had been seen in previous
shaft seal designs. An
elastomer portion of the shaft seal 10 will act as a hinge which will be very
flexible and will permit
the PTFE to better follow and seal an eccentric shaft. The shaft seal 10 is
particularly suited for low
temperature environments but it should be noted the shaft seal 10 provides
advantages at all
temperatures but particularly low temperatures.
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The shaft seal 10 includes a rigid case 12 which generally has an L-shaped
cross section. In
the preferred embodiment the rigid case 12 is made of metal however, it should
be noted that any
other rigid material such as ceramics, hard plastics, or any other rigid
material known may be used.
The shaft seal 10 also includes a hinge member 14 which is connected to an
outside surface
of the rigid case 12. The hinge member 14 is connected via bonding to the
rigid case 12 however,
it should be noted that any other type of connection may be used such as
gluing, chemical bonding,
mechanical bonding or the like. The hinge member 14 is preferably made of an
elastomer material
however, it should be noted that any other type of flexible plastic or rubbers
may be used depending
on the operating environment of the seal. The hinge member 14 has a generally
ring like appearance
but is flexible. The flexibility of the hinge member 14 allows for the sealing
element 16 to better
follow an eccentric shaft which particularly occurs at low temperatures.
The shaft seal 10 also includes a sealing element 16 which is bonded directly
to the elastomer
hinge member 14 on its outside edge opposite the side bonded directly to the
case 12. The sealing
element 16 is preferably made of a polytetrafhuoroethylene material however,
any other material that
exhibits the same stiffness and rigidity as that of PTFE made be used
depending on the needs of the
operating environment. The PTFE sealing element 16 retains its hoop stiffness
and rigidity while
any bending effects are reduced because of the bond to the elastomer member
14. Furthermore, the
PTFE sealing element 16 is cut through to the ehastomer 14 at a critical
diameter or diameters
depending on the sealing application. Flowever, there is at least one notch 18
cut into the sealing
element 16. The first notch 18 cut into the sealing element 16 is located near
an end of the metal
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case 12 which creates a bending moment where the notch 18 appears at the
elastomer 14 such that
the seal element 16 will have better followability on an eccentric shaft 20
because of the notches 18
in the sealing element 16 through to the elastomer hinge member 14. The
sealing element 16 may
also have another notch 22 on its outer surface which is cut through to the
hinge member 14 such
that the end of the sealing element 16 will even further follow the
eccentricities of the shaft 20
during normal operation. Any type of sealing unit which is bi-directional or
uni-directional may be
used with the notched or cut through sealing element. A third notch 24 may
also be used on the
inside surface of the sealing element such that the third notch 24 is adjacent
to the end of the
elastomer hinge member 14. Thus, creating a bending moment such that the PTFE
sealing element
16 will stay in complete contact with the eccentricities of a shaft 20.
Therefore, with the notches 18
cut through to the sealing element to the elastomer hinge member 14 the
sealing element 16 has
better followability on an eccentric shaft particularly at low temperatures.
Figure 2 shows an alternate embodiment of the present invention. It includes a
single notch
218 in the sealing element 216. The notch 218 extends through to the hinge
member 214.
Figure 3 shows a shaft seal 310 where there is a single notch 318 in the seal
element 3I6
through to the hinge member 314. The hinge member 314 also comes into contact
with the shaft
320. The sealing element 316 also includes a plurality of notches 326 which do
not extend through
to the hinge member 314.
The present invention has been described in an illustrative manner, it is to
be understood that
the terminology which has been used is intended to be in the nature of words
of description rather
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than of limitation.
Many modifications and variations of the present invention are possible in
light of the above
teachings. Therefore, within the scope of the appended claims, the present
invention may be
practiced otherwise than as specifically described.
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